FOR THE

LOWELL MASSACHUSETTS

SEPTEMBER 2003

IJLS Environmental Protecton Agency

Description of the Signiifica nt Difference 10

Supporting Agency Comments 13

Statutory Delerrn inatio ns 13

Public Participation 14

Declaration 14

Site Name Silresirn Chemical Corporation Superfund Site

Site Location City of Lowell Middlesex County Massachusetts

B Lead and Support Agenciies

Suppoirt Agency Masssichusetl s Deparlrnent o Environinnenlal IPirotection (MADEP)

C Legal Aotlhioritv

Under Section 117(lt) of the Comprehensive Environmenial Response Compensation and Liability Act (CEIRCLA) 42 USC sect 9617 (c) Section 300435(c) of the Nalional Contingency Plan (INCIP) 40 CF R sect 300435(c)2)(l) and EPA guidance Office of Solid Wasle and Ennieirgency Response (OSVVEiR) Directive 9355 3-02 if EPA detennines that differences in the iremedral action significantly change but do not fundamentally alller the remedy selected in Ihe Record of Decision (ROD) with respect to scope performance or cost ERA shall publish an Explanation of Significant Differences (ESD) between the remedial action being undertaken and the remedial action set forth in the ROD and the reasons such changes are being made

0 Sumirnairy of Qrcuinstances Necessitating this Explaini-iilion of Significant Differences

This ESD documents a change to the remedy for the Silresirn Chemical Corporation Superlund Site (Site)that was originally selected in I he 1991 ROD The change is to present revised risk-based clean-up goals (CIJGs) for the Site In addition although not a significant change EPA is also creating a second Operable Unit (OU) to facilitate documenting clean-up activities atthe Siile

Revseel Clean-up Goals

The 1991 ROD included both source control and nnianagemienl of migration components to obtain a comprehensive remedy for the Site The source control component of the remedy called for in-situ soil vapor extraction (SVE) of approximately 137000 cubic yards of contaminated soil Following treatment soil with residual contamination would be excavated stabilised and capped on the Silresirn property The remedy also included active restoration of the overburden and bedrock aquifers by pumping and lirea ling I he conta riniin ated groundwater

At the lime the ROD was written I he aquifer bellow the Site was classified by the Federal Government as a Class 118 aquifer and by the Connirnoinwealllh of Massachusetts as a Class I aquifer Ground waters assigned to these classes are defined as being fresh waters found in I he saturated zone of unconsolidated deposits or consolidated rock and bedrock and are designated as a source of potable wateir supply (potential drinking water) Therefore the future installation of drinking water wells in residential areas

ndeirlain by the contaminated ground wateir could resull nn a potential human healllh risk

ground water might be used as drinking water exposure to contaminants might occur in ough ingeslion dermal absorption or inhalalion of vapors

order to support the 1991 KOI) a nsk assessment was conducted CGiTiputedl based on average concentrations of contaminants in conjunction with the correspondinci polenlial receptors The calculaled risks included a scenario whereby ground water could be used in I he future as clrinkimg water in the vicinity ol the Site

1998 Ml AD El P cornpleled a Giroundwater Use and Value Determination which resulted in a recommendation of low use and value for the ground water beneath the Site MADE IF has stipulated that groundwater would not be used as drinking water in the future Thus delerrn mail ion constituted a significant change from I he previous drinking water classification thai was used togt establish clean-up levels in the 1991 ROD As a result M AIDER has reel ass ified this aquifer as a N on -Potential Drinking Water Source Area

Following ground water reclassification the impact of this change on the existing clean-shyup levels for the Site was evaluated The results of I his evaluation were surnrnaiiiied in the January 2002 Final Additional Site Investigation and Revision of Site Clean-up Goals Report Revised risk-based CUGs were calculated based on I he groundwater reclassification additional data revised exposure pathways and current land use assumptions and Site conditions These CUGs were further modified nn 2003 to ref lect current El PA risk assessment guidance and protocols

Additional Operable Units

At the time of the 1991 ROD the Site consisted of only one Oil to address bolh source control and management of migration components The term operable unit is used lo define a discrete portion ogtr phase of the overall clean-up plan at a Site and facilitates

source conlrol aclivitii

LI S lnvrironirnenlal Prelection Agency Reco r ds C en ler One Congress Street Bos ton MA 02114 Monday Ihirough Fnday firorn 1000 am to 1 00 p rn and

from 200 pm to 500 p in

Pollard Memorial Library 401 IVIerriinmaclk Street Lowell IVIassachuseIts 01852 Ph 9 78970 4120 Monday Ihirough Thursday from 9 00 a rn lo 9 GOp rn and Friday from 9 00 a rn lo 5 00 p rn

11 bull SU MMARY PF STE H j TORY CQNTAM NA T1P_N lfi RQBLEM S AND SEJJCTEDJyEMEDY

A Si I e H istory Hiiri d C on I aim iinu-i lion Fir oIblliE rnsi

The Site is composed of appiroximately 16 acres of land in an induslrial area of Lowell Massachusetls juampl south of the Ciilys central business district (Figure 1 and Figuire 2) The Site includes a 4 5 acre property foirmeirly owned and operated by the Silresirn Chemical Corporation (Silresimi) at 136 Tanner Street and soil and groundwaler co nl animal ion lhal extends to olher nearby properties

The 45 acre SiI re si in properly is bordered by I he Lowell Iron and SI eel properly lo the norlh I he BampIVI railroad yard and I racks to the easlAnortheast the Lowell Used Aulo Paris and Tucci properties lo the soulh and Tanneir Stireet lo I he west Residential areas are located south easl and northeast of I he Silireampim property with the closest residences located on Canada Main and Maple Streets roughly 300 lo 500 feet from I he Silresirn properly boundary River Meadow Brook lies approximatelyAGD feet west of the Silresirn property and flows northeasl into I he Concord River The Concord River joins I he Meinriinack River approximately 1 mile northeast of the Site iiiast Pond a small surlace water body is located about 300 feel to I he east of I he Silresirn properly

An 8-foot high chain link fence secures the Silresirn properly Most of the land surface will him the fence is covered with a lernporary clay cap Crushed stone has been placed on runoff areas along I he northern and southern perimeleir of I he Silresinn property lo

lipiing vapor extraction vent piping natural gas potable water and sewer lines power lines and process control wiring

ltlaquo Overhead and underground high voltage power lines and I An interim passive cap venting system

The Site and its surrounding areas have been used for industrial activities since the early 1900s From 1916 to 1971 several petroleum companies used I he Silresiirn property as an oil and fuel storage deoot From 1971 through 1977 Silresirn operated its chernical waste reclamation facility The facilitys primary operations included recycling and reclaiming various chemicals and consolidating wastes for off-site disposal

The Massachusetts Division of Water Pollution Control (DWPC) now Ml AD El P granted I he facility a hazardous waste colled ion and disposal permit in 1973 Wastes were accepted at the facility in drums tank trucks railiroac tanker cars and other containers These substances included halogenated solvents oi y wasles alcohols plaling wastes metal sludge and pesticide wastes Although exact figures do not exist it is estimated I hat the facility handled sipproxirnalely 3 million gallons of waste per year

I he air and sampled soils and found contamination bolh on and oil the Sliilresim property In 1984 EPA raised the height of the fence from 6 to 8 feet and covered highly contaminated areas with 9 inches of crushed gravel and a lernpoirary day cap In 1986 damage to the original fence was repaired Subsequenl sampling revealed an additional area of soil contamination that EPA enclosed In 1986 EPA discovered dioxin the fence was relocated to prevent public access and a temporary gravel cover was placed over the dioxin-cointaminated soil to prevent contact

of soil coiTlarnination The Rl identified approximately 100 individual contiaririiinanls in on-site groundwateir and soils Volatile oirganic compounds (VOCs) were the primary co ntannin an I type identified Semi-volatile orga nic compounds (SVOCs) polychlorinated biphenyls (PCBs) metals herbiciides pesticides and dioxin were also identified

In September 1991 EPA issued the ROD for the Site The remedy selected in the ROD called for in-situ SVE of contaminated soil Soils with residual contamination would be excavated stabilized and capped on-site Contaminated groundwater would be extracted and treated by nnietals removal air stripping and vapor treatment prior 1o discharge to the City sewer system

In early 1993 a Consent Decree between EPA and a group of potentially responsible parties (IPRPs) was executed Under this Consent Decree the PRPs provided approximately $40 million in clean-up funding for the Site

Management of Migration

Construction of the GWTF began in rrnid-1994 and groundwater extraction and treatment has been underway since November 1996 Initial actions to fence the Silresirn property and cap or cover areas of contamination have reduced the potential for accidental exposure and further migration of contaminated soils The temporary cap has subsequently been upgraded These actions have eliminated the immediate threats posed by the Site while final clean-up activities are underway The operation of the GWIT has several objectives as outlined in the ROD

raquo Manage the migration of contaminated groundwater toward downgradient receptors of local building basements IRiver Meadow Brook and East Pond

laquo Capture as much of the contaminated plume as possible and raquo Drawdown the groundwateir across the Site lo support the source control remedy

To date the groundwater extraction system has been unable lo achieve the drawdown objective across the Site The extraction well array and GWTF have removed a significant amount of VOCs from the groundwater plume (over 50 tons) however plume

migration has shown some increased cone en liral ions of VOCs in cerlain areas downgradient erf the Silresirn property

on ducted using three techniques conventional SVEi healed imiphase SvE In general extracted vapor flow rates

standlaird cubic leet per minute)1 and radii of influence (lt 7-lt

the additional removal of an estimated 12 Ions of VOCs from the subsurface however the effectiveness of the SVE system was limited because the Site was not sufficiently de-watered soil moisture content was very high and very low permeability soils were encountered The overall conclusion of these SVE activities was that despite the removal of relatively significant quantities of VOCs it would be unlikely I hat conventional SVE would be able to reach I he original clean-up levels for the Site

The results ol these tests are summarized in the following conclusions

laquobull SVE has the potential for significant subsurface VOC mass removal however it is not likely to reduce soil contamination to I he ROD clean-up levels within the ROD established lime frame

raquo Site conditions (high soil moisture and low soil permeability) limited SVE effectiveness in removing contaminants from the subsurface soil

laquobull High vacuum SVE and multiphase extraction were found to be ineffective technique- for removing VOCs from the soil at I he Site and

raquo Heated air injection with SVE has the potential to increase I he rale of contanminant removal fro inn the subsurface soil

ai c reatrnent alternatives was performed iipplicability for the remediation of VOCs at the Site were considered Weighing idvantages and disadvantages for each remedial option resulted in the selection of the ileclrical resistance heating (ERH) technology as the only viable option for a pilot test at

I RH is an in-situ thermal remediation technology that uses electrical heating to enhance The ERH pilot test was designed lo evaluate applicability of Site conditions reveal

itial technical difficulties and determine the effectiveness of the technology for removing subsurface contaminants to targeted levels Results of the pilot test will be used lo evaluate the ability of ERH lo overcome the limitations observed during the SVE operations and ultimately allow an effective and cost efficient scale-up lo full-scale I reatrnent The pilol test began in October 2002 and continued through early January 2003 A final report is being prepared and will be evaluated lo determine the technologys effectiveness for removing contamination on a wide area of the Site

B Summary of the Record of Decision

The ROD (signed September 19 1991) discussed the alternatives evaluated for remediating contamination at the Site and described in detail the selected remedy for I he Site The selected remedy includes a management of migration alternative (giroundwa-ter extraction metals prelreatrnent air stripping aqueous phase carbon adsorption vapor phase carbon adsorption or thermal oxidation) and a source control alternative (SVE excavation stabilization and capping on the Silresim property) lo address all contannination at the Site A detailed description of the clean-up levels and the selected remedy is presented in Section X of the ROD

To date some success has been achieved through the implementation of a number of the remedial activities inn anda led by the ROD In particular SVE has been evaluated via pilot tests and implemented in a limited area on the Site Management of migration remedial components for ground water extraction and treatment were successfully in stalled and continue to operate Operation of the GWTF and extraction wells has resulted in some VOC contaminant concentration reduction in the groundlvvater plume although the extent of the reduction varies significantly depending on the specific area of the Site In some areas ol the Site VOC concentrations have increased However it should be noted that the extraction wells and GWTF were not designed for overall plume rernediation The main objective of the GWTF and extraction wells was lo contain the groundwater plume and lo de-water the Site sufficiently to allow for remediation of soils utilizing traditional SVE

significant change EPA is also creating a second OU to bullfacilitate clocunnienling clean-up activities at I he Site The basis for modifying the 1991 ROD cl Ban-up levels is described below

chieve remedial objectives I he ROD Remedy Review recommended several changes These recommendations took inlo consideration the changes in Site cc (reclassification of groundwateir under the Site) the inability of the irnplerne lechnologies to achieve the objectives stated in the ROD sine the use of some revislt

control activities to achieve remedial objectives ol ha migration removing the contaminant source term and reducing hurnan heal ecological risk at the Site the rive-Year Review supported the recommendations ouIlliinied in the ROD Remedy Review

laquo Inability of the extraction well system to contain contaminant plume migration towards identified downg rad ie nl receptors

ii Inability of the extraction well system and GW7T to meet ROD clean-up levels within the foreseeable future

raquo Results of the 8V operations indicating thai SVE alone would not be able to reduce subsurface soil contamination to meet ROD clean-up levels within the time frame established in the ROD

ltbull Risk assessment assumptions that no longer appeared appropriate for the Site and

igt The change in the groundwater classification for the aquifer below the Site by IvIAIDEP to low use and value from its prior classification as drinking water

The first step of the Action IPIIan included an investigation focusing on strategies to control the continued migration of contaminated groundwater and to irnpilement innovative technologies to remiediale VOC-contanrninated soils The second step of the Action Plan involved a comprehensive investigation to identify and compile existing data collect new data and revise clean-up levels Investigation activities have been completed (implementation of innovative technologies to address VOC-contarninated soils is ongoing as ERH pilot test results are still being evaluated

The following activities were identified to evaluate existing clean-up levels based on the new groundwater classification and to revise clean-up levels where necessary

in Review Site groundwater reclassiiliication bull Evaluate recent monitoring data and current Site conditions igt Identify reimiainirig or newly identified exposure pathways raquo Develop response objectives to coincide with remaining or newly identified

exposure pathways bull Evaluate the appropriateness of the groundwater leaching model and subsequent

development or application of new soil-to-groundwater modeling parameters or data as necessary and

raquo Develop revised risk-based CIJGs for aII impacted media (principally groundwaler and unsaluraled zone soils)

In order to support I he development of revised risk-based CUGs field activities were conducted at the Site between November 2000 and July 2001 These activities also helped to delineate areas of soil excavation and the size and extent of the VOC source area The results of these field activities showed heterogeneous groundwater and soil

contamination consisting of VUCs SVUUs RGBs metals polycydic aromatic Tyclrocarbons (PAHs) and diogtunfurans on and oft the Silresirn property

The risk-based CUGs do not show an overall increasing or decreasing trend as compared to the 1991 ROD clean-up levels because some exposure pathways were eliminated (direct ingestion of ground mailer) while others were added (indoor inhalation ofVOCs)

In June 2003 the revised risk-based CUGs were further modified to reflect cuinrent EPA risk assessment guidance and protocols Specifically the carcinogenic risk goal was chaned from 10 to 10 gt and the non-carcinoeiniic hazard index was changed from 01

ecological impacts from qroundwateirl and the MADEiP Method 3 Upper ( Linrii its for soil and groundwaler The modified CUGs are identified as the

e com mended Clean-Lip Goals in Appendix A

EPA and MADEP consider the modified CUGs to be adequately protective health and the environment Additionally although not a significant change tlh of a second OLI will facilitate documenting clean-up activities at the Site

4 Revised Clean-up Gosils

tequireirnenis iuch as Dninkiino Wai or MlaxiiiTiurn ConlaiTiinant Levels and Non-zero inninant Level Goals

i I he 1999 ROD Remedy Review it was determined that certain ROD clean-up levels were based on assumptions thai were no longer appropriate and therefore required

ground water needed to be reviewed Future use exposure scenarios needed to be evaluated

raquo Changes in exposure pathways bullbullbull The extern I of the contaminated groundwater plume needed to be evaluated because il was moving faster than originally projected Potential off-property subsurface soil con lamina ion needed to be evaluated

gt Evolution of the technical approaches for Supeirfund risk assessment - The vapor rni grain on model and the methodology for selecting COPCs were no longer currenl and

raquo Specific technical issues relating to toxicily estimates - The use of toxicity surrogates for PAHs and dioxin was no longer recommended or necessary

Necessary updates for calculating revised CUGs included

ltgt Evaluating the subsurface soil to indoor air pathway for the commercialindustrial worker

ltbull Evaluating additional chemicals the inhalation palhways and igt Evaluating a child recreational receptor in the event thai I he Silresirn property or

adjacent properties are redeveloped for recreational use (eg soccer field) The potenlial exists for this type of development however since the area is currently

are summarized below Overall the chainpes in risk assumptions regarding groundwaler soil and air exposures at the Site significantly impact the CIJGs for a ariely of contaminants

Current Land Use and Site Conditions The approximate 16-acre Site is located in a heavily industrialized section of Lowell

storage facilities tractor-trailer storage light industrycommercial corido minium bull and open industrial land As a result oi MADEPs Ground water Use andl Value Deteinrimiriation IvIADEP has stipulated that ground water in the area would not be used as a drin king water source in I he failure This determination constitutes a significant change from the drinking water classification used to establish the 1991 ROD clean-up levels

The reasonaby foreseeable future land use designation for the Site is coinnnTiercialindustrial Soils with residual contamination above the CUGs will be excavated stabilized and capped on the Silresirn property Future exposures to soil or exposed groundwateir are considered possible even though the cap will likely extend over the entire Siliresim property A potential future recreational use scenario was also evaluated

The commercial industrial properties surrounding the Silresirn properly also are expected to continue to be used for cornnnieircialindustrial purposes in the foreseeable future However future renovation or redevelopment of these properties is considered possible including construction of new buildings with basements The BSIVI railroad coinridor adjacent to the Siliresim property on the eastern side is also assumed to remain a railroad corridor for the foreseeable future Ground water is assumed to remain unused for consumptive and non-consumptive uses in the future (ie for drinking or induslriaJ process uses) due to MADEPs Groundwateir Use and Value Determination coupled with the relatively low yield of the shallowest water bearing layers While this assumption appears reasonable given this classification no formal restrictions or institutional controls have been established to ensure thai the ground water us not used for consumptive or non-consumptive purposes or that future land use does not involve contact with potentially contaminated soils

An exposure pathway describes the physical linkage between the source of a COPC and a current or projected future exposed receptor The potential human receptors that have been identified at this Site (under cuinrent and reasonably anticipated future exposure scenarios include com mercia Iindustrial workers railroad workers construction worke rs (eg new facility construction or uliilrry installlatiionrnaintenance workers) and

12

trespassers These potential human receptors may come in contact with surface soil (0 1 fl bgs) exposed subsurface soil as a result of excavation (unsaturated soil gtl ft bg and lt 10 fl bgs) groundwater and ambient or indoor air containing contaminant origin calling from the Sule The potential routes of exposure are incidental iingestiioi inhalation of partioulales or wolallies and dermal absorption These exposure route were also evaluated for a potential future recreational use scenario II should be note that leaching from soil to g round water is no longisir conside1 red a risk becauslt groundwater us no longer a potential drinking water source The pathway of most concern is through VOC emissions from contaminated giroundwater and subsequent diffusion upward into ambient and indoor air

now rrsK-oaseci nuiiiDers

WiOiMl CitiiribJii Units

Under this BSD I he Site will be divided into two Oils to facilitate docuinnentinq clean-up activities as defined below

approximately 12 Ions of subsurface VUC conlarninalicri However operalion of the SVE svsterin was placed on hold because it was unlike v that it would be able to reac Site CUGs

comply wnlh Federal and Slate requirement that are applicable or relevant and appropriate and are co si-effective The revised remedy utilizes permanent solutions

This E gt[) and supporting in formal ion are available for public review at the location lentiHied within this document In addition a notice of availability of the BS

piwided to a local newspaper of general circulation

or the foregoing reasons by my signature below I approve the iissuance of lt= llxplainiation oi Significant Differences tor the Silresirn Chemical Corporation Supeirfunc Site in Lowell Massachusetts and the changes and conclusions staled1 therein

Sus^h Studlieri Acting Director Office of Site Remediation and Restoration USE PA Region I

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(IJ f rgt 3 I-shy shy rtl -r-i bull bull 11 -13 i bull shy 3 gtbull iamp bullbullbull gt (IJ S l 4l - rr bull TI i shy ni -- bullbullbull |= SJ b iii -5 L J $ ij ij i-iP J1 S sL e3 1 1 laquo laquo E Qlt1) E ii i ii-1 p MI ishy j t shy

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FOSTE R WH E E L E R E N VI RON M ENTA L CO R PORATI ON

The purpose of t h i s memorandum is to sinnraariltltbull I be re corn mended Clean-Dp GoEils (CUGs) f o r the s u r f a c e soil subsurface soi l and groundwater related to i he Si l res im Superfund Site im support of an Explanation of Significant Difference (BSD) The r isk-based ( LGs were or ig inal ly presented in the FniEil Add il lona I Site ID vesl igat ion and Re v is ion o f Si te C lean-Up (ioal s (Eosler Wheel er 2002) T hese CIJG s ivere discussed r e f ined ar id then compared to site da ta Appl icable or Relevant and Appropr ia te Requirements (ARARs) and curreni ROD cleanup levels fhe fo l lowing presents the c r i l e n a used lo develop the recommended CUGs (as cogtrnpairedto the current KOI) c l e a n u p levels)

bulli An updated IJSEPA COC screening and se lec t ion process was used (USEPA 1989 1 9 9 5 1999)

laquo The evaluat ion of the carcinogenic and non-cEireinogeriic polycyclic aromatic hydrocarbon (PAH) conipounds vas performed individually i n s t e a d of as EI g-roup ( U S E P A 1994 200 I a)

bulli T he upda ted cle rma I ris k asse ssrnenl guidance (FAGS Pa rt E) wa s applied (USE PA 2 GO1 b)

laquo The USE A Adult Lead Model was used to calculate soil lead c o n c e n t r a t i o n s associated with a (Ei rge t blood lead level and exposure parameter (USKPA 1996)

laquo The updated guidance for r isk assessment o f lt Eire moge n ic polyclhlorinated biphenylsi (PC Eh) wasiised(NCEA 1996)

Updated lox ico log ica l factors and parameters were usedl (USEPA 1997a 200la and MADEP 1 9 9 4 )

i A target r i sk goal of 1 E-5 and a target haard mdelt of 1 was used for each chernncal (d i rec t ion from USE PA Region 1 Site Manager)

laquo An assumption was made l l i E i t suirface soil consists of the soil between () -shy 1 ft bgs and lhal subsurface ur isa tura ted soil consists of the soil between 1 shy 10 fit bgs (USE PA I99 i )

laquo The Site ground w a t e r was reclassified as being low use and va lue nn a MA13EP Groun d w aie r Use and Val ue Detenminail ion (1VIA DEiF 1998)

laquo Leaching f rom s u b s u r f a c e (unsaturated) soil to ground wa te r was not considered EI critical consideration in setting sub- u r fE ice sioil CUGs (Fo- kT Wheeler 1999 2002)

laquo Commercial industr ia l l a n d use was assumed instead of r e s iden t i a l land use (foster Wheeler 19992002)

laquo The subsur face vapor in t rus ion to indoor air was e v E i l u a t e d as EI primary mbalEi t ion exposure ran te (Foste r W bee ler 2002 D SEP A 1997b)

ltbull Potential exposures to a construction worker w e r tr^aluated for soil and Birouridwater (Foster W h e e l e r 2002)

laquo Potential exposures to a trespasser were evaluated for so i l (Foster Wheeler 2 0 0 2 )

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

Description of the Signiifica nt Difference 10

Supporting Agency Comments 13

Statutory Delerrn inatio ns 13

Public Participation 14

Declaration 14

Site Name Silresirn Chemical Corporation Superfund Site

Site Location City of Lowell Middlesex County Massachusetts

B Lead and Support Agenciies

Suppoirt Agency Masssichusetl s Deparlrnent o Environinnenlal IPirotection (MADEP)

C Legal Aotlhioritv

Under Section 117(lt) of the Comprehensive Environmenial Response Compensation and Liability Act (CEIRCLA) 42 USC sect 9617 (c) Section 300435(c) of the Nalional Contingency Plan (INCIP) 40 CF R sect 300435(c)2)(l) and EPA guidance Office of Solid Wasle and Ennieirgency Response (OSVVEiR) Directive 9355 3-02 if EPA detennines that differences in the iremedral action significantly change but do not fundamentally alller the remedy selected in Ihe Record of Decision (ROD) with respect to scope performance or cost ERA shall publish an Explanation of Significant Differences (ESD) between the remedial action being undertaken and the remedial action set forth in the ROD and the reasons such changes are being made

0 Sumirnairy of Qrcuinstances Necessitating this Explaini-iilion of Significant Differences

This ESD documents a change to the remedy for the Silresirn Chemical Corporation Superlund Site (Site)that was originally selected in I he 1991 ROD The change is to present revised risk-based clean-up goals (CIJGs) for the Site In addition although not a significant change EPA is also creating a second Operable Unit (OU) to facilitate documenting clean-up activities atthe Siile

Revseel Clean-up Goals

The 1991 ROD included both source control and nnianagemienl of migration components to obtain a comprehensive remedy for the Site The source control component of the remedy called for in-situ soil vapor extraction (SVE) of approximately 137000 cubic yards of contaminated soil Following treatment soil with residual contamination would be excavated stabilised and capped on the Silresirn property The remedy also included active restoration of the overburden and bedrock aquifers by pumping and lirea ling I he conta riniin ated groundwater

At the lime the ROD was written I he aquifer bellow the Site was classified by the Federal Government as a Class 118 aquifer and by the Connirnoinwealllh of Massachusetts as a Class I aquifer Ground waters assigned to these classes are defined as being fresh waters found in I he saturated zone of unconsolidated deposits or consolidated rock and bedrock and are designated as a source of potable wateir supply (potential drinking water) Therefore the future installation of drinking water wells in residential areas

ndeirlain by the contaminated ground wateir could resull nn a potential human healllh risk

ground water might be used as drinking water exposure to contaminants might occur in ough ingeslion dermal absorption or inhalalion of vapors

order to support the 1991 KOI) a nsk assessment was conducted CGiTiputedl based on average concentrations of contaminants in conjunction with the correspondinci polenlial receptors The calculaled risks included a scenario whereby ground water could be used in I he future as clrinkimg water in the vicinity ol the Site

1998 Ml AD El P cornpleled a Giroundwater Use and Value Determination which resulted in a recommendation of low use and value for the ground water beneath the Site MADE IF has stipulated that groundwater would not be used as drinking water in the future Thus delerrn mail ion constituted a significant change from I he previous drinking water classification thai was used togt establish clean-up levels in the 1991 ROD As a result M AIDER has reel ass ified this aquifer as a N on -Potential Drinking Water Source Area

Following ground water reclassification the impact of this change on the existing clean-shyup levels for the Site was evaluated The results of I his evaluation were surnrnaiiiied in the January 2002 Final Additional Site Investigation and Revision of Site Clean-up Goals Report Revised risk-based CUGs were calculated based on I he groundwater reclassification additional data revised exposure pathways and current land use assumptions and Site conditions These CUGs were further modified nn 2003 to ref lect current El PA risk assessment guidance and protocols

Additional Operable Units

At the time of the 1991 ROD the Site consisted of only one Oil to address bolh source control and management of migration components The term operable unit is used lo define a discrete portion ogtr phase of the overall clean-up plan at a Site and facilitates

source conlrol aclivitii

LI S lnvrironirnenlal Prelection Agency Reco r ds C en ler One Congress Street Bos ton MA 02114 Monday Ihirough Fnday firorn 1000 am to 1 00 p rn and

from 200 pm to 500 p in

Pollard Memorial Library 401 IVIerriinmaclk Street Lowell IVIassachuseIts 01852 Ph 9 78970 4120 Monday Ihirough Thursday from 9 00 a rn lo 9 GOp rn and Friday from 9 00 a rn lo 5 00 p rn

11 bull SU MMARY PF STE H j TORY CQNTAM NA T1P_N lfi RQBLEM S AND SEJJCTEDJyEMEDY

A Si I e H istory Hiiri d C on I aim iinu-i lion Fir oIblliE rnsi

The Site is composed of appiroximately 16 acres of land in an induslrial area of Lowell Massachusetls juampl south of the Ciilys central business district (Figure 1 and Figuire 2) The Site includes a 4 5 acre property foirmeirly owned and operated by the Silresirn Chemical Corporation (Silresimi) at 136 Tanner Street and soil and groundwaler co nl animal ion lhal extends to olher nearby properties

The 45 acre SiI re si in properly is bordered by I he Lowell Iron and SI eel properly lo the norlh I he BampIVI railroad yard and I racks to the easlAnortheast the Lowell Used Aulo Paris and Tucci properties lo the soulh and Tanneir Stireet lo I he west Residential areas are located south easl and northeast of I he Silireampim property with the closest residences located on Canada Main and Maple Streets roughly 300 lo 500 feet from I he Silresirn properly boundary River Meadow Brook lies approximatelyAGD feet west of the Silresirn property and flows northeasl into I he Concord River The Concord River joins I he Meinriinack River approximately 1 mile northeast of the Site iiiast Pond a small surlace water body is located about 300 feel to I he east of I he Silresirn properly

An 8-foot high chain link fence secures the Silresirn properly Most of the land surface will him the fence is covered with a lernporary clay cap Crushed stone has been placed on runoff areas along I he northern and southern perimeleir of I he Silresinn property lo

lipiing vapor extraction vent piping natural gas potable water and sewer lines power lines and process control wiring

ltlaquo Overhead and underground high voltage power lines and I An interim passive cap venting system

The Site and its surrounding areas have been used for industrial activities since the early 1900s From 1916 to 1971 several petroleum companies used I he Silresiirn property as an oil and fuel storage deoot From 1971 through 1977 Silresirn operated its chernical waste reclamation facility The facilitys primary operations included recycling and reclaiming various chemicals and consolidating wastes for off-site disposal

The Massachusetts Division of Water Pollution Control (DWPC) now Ml AD El P granted I he facility a hazardous waste colled ion and disposal permit in 1973 Wastes were accepted at the facility in drums tank trucks railiroac tanker cars and other containers These substances included halogenated solvents oi y wasles alcohols plaling wastes metal sludge and pesticide wastes Although exact figures do not exist it is estimated I hat the facility handled sipproxirnalely 3 million gallons of waste per year

I he air and sampled soils and found contamination bolh on and oil the Sliilresim property In 1984 EPA raised the height of the fence from 6 to 8 feet and covered highly contaminated areas with 9 inches of crushed gravel and a lernpoirary day cap In 1986 damage to the original fence was repaired Subsequenl sampling revealed an additional area of soil contamination that EPA enclosed In 1986 EPA discovered dioxin the fence was relocated to prevent public access and a temporary gravel cover was placed over the dioxin-cointaminated soil to prevent contact

of soil coiTlarnination The Rl identified approximately 100 individual contiaririiinanls in on-site groundwateir and soils Volatile oirganic compounds (VOCs) were the primary co ntannin an I type identified Semi-volatile orga nic compounds (SVOCs) polychlorinated biphenyls (PCBs) metals herbiciides pesticides and dioxin were also identified

In September 1991 EPA issued the ROD for the Site The remedy selected in the ROD called for in-situ SVE of contaminated soil Soils with residual contamination would be excavated stabilized and capped on-site Contaminated groundwater would be extracted and treated by nnietals removal air stripping and vapor treatment prior 1o discharge to the City sewer system

In early 1993 a Consent Decree between EPA and a group of potentially responsible parties (IPRPs) was executed Under this Consent Decree the PRPs provided approximately $40 million in clean-up funding for the Site

Management of Migration

Construction of the GWTF began in rrnid-1994 and groundwater extraction and treatment has been underway since November 1996 Initial actions to fence the Silresirn property and cap or cover areas of contamination have reduced the potential for accidental exposure and further migration of contaminated soils The temporary cap has subsequently been upgraded These actions have eliminated the immediate threats posed by the Site while final clean-up activities are underway The operation of the GWIT has several objectives as outlined in the ROD

raquo Manage the migration of contaminated groundwater toward downgradient receptors of local building basements IRiver Meadow Brook and East Pond

laquo Capture as much of the contaminated plume as possible and raquo Drawdown the groundwateir across the Site lo support the source control remedy

To date the groundwater extraction system has been unable lo achieve the drawdown objective across the Site The extraction well array and GWTF have removed a significant amount of VOCs from the groundwater plume (over 50 tons) however plume

migration has shown some increased cone en liral ions of VOCs in cerlain areas downgradient erf the Silresirn property

on ducted using three techniques conventional SVEi healed imiphase SvE In general extracted vapor flow rates

standlaird cubic leet per minute)1 and radii of influence (lt 7-lt

the additional removal of an estimated 12 Ions of VOCs from the subsurface however the effectiveness of the SVE system was limited because the Site was not sufficiently de-watered soil moisture content was very high and very low permeability soils were encountered The overall conclusion of these SVE activities was that despite the removal of relatively significant quantities of VOCs it would be unlikely I hat conventional SVE would be able to reach I he original clean-up levels for the Site

The results ol these tests are summarized in the following conclusions

laquobull SVE has the potential for significant subsurface VOC mass removal however it is not likely to reduce soil contamination to I he ROD clean-up levels within the ROD established lime frame

raquo Site conditions (high soil moisture and low soil permeability) limited SVE effectiveness in removing contaminants from the subsurface soil

laquobull High vacuum SVE and multiphase extraction were found to be ineffective technique- for removing VOCs from the soil at I he Site and

raquo Heated air injection with SVE has the potential to increase I he rale of contanminant removal fro inn the subsurface soil

ai c reatrnent alternatives was performed iipplicability for the remediation of VOCs at the Site were considered Weighing idvantages and disadvantages for each remedial option resulted in the selection of the ileclrical resistance heating (ERH) technology as the only viable option for a pilot test at

I RH is an in-situ thermal remediation technology that uses electrical heating to enhance The ERH pilot test was designed lo evaluate applicability of Site conditions reveal

itial technical difficulties and determine the effectiveness of the technology for removing subsurface contaminants to targeted levels Results of the pilot test will be used lo evaluate the ability of ERH lo overcome the limitations observed during the SVE operations and ultimately allow an effective and cost efficient scale-up lo full-scale I reatrnent The pilol test began in October 2002 and continued through early January 2003 A final report is being prepared and will be evaluated lo determine the technologys effectiveness for removing contamination on a wide area of the Site

B Summary of the Record of Decision

The ROD (signed September 19 1991) discussed the alternatives evaluated for remediating contamination at the Site and described in detail the selected remedy for I he Site The selected remedy includes a management of migration alternative (giroundwa-ter extraction metals prelreatrnent air stripping aqueous phase carbon adsorption vapor phase carbon adsorption or thermal oxidation) and a source control alternative (SVE excavation stabilization and capping on the Silresim property) lo address all contannination at the Site A detailed description of the clean-up levels and the selected remedy is presented in Section X of the ROD

To date some success has been achieved through the implementation of a number of the remedial activities inn anda led by the ROD In particular SVE has been evaluated via pilot tests and implemented in a limited area on the Site Management of migration remedial components for ground water extraction and treatment were successfully in stalled and continue to operate Operation of the GWTF and extraction wells has resulted in some VOC contaminant concentration reduction in the groundlvvater plume although the extent of the reduction varies significantly depending on the specific area of the Site In some areas ol the Site VOC concentrations have increased However it should be noted that the extraction wells and GWTF were not designed for overall plume rernediation The main objective of the GWTF and extraction wells was lo contain the groundwater plume and lo de-water the Site sufficiently to allow for remediation of soils utilizing traditional SVE

significant change EPA is also creating a second OU to bullfacilitate clocunnienling clean-up activities at I he Site The basis for modifying the 1991 ROD cl Ban-up levels is described below

chieve remedial objectives I he ROD Remedy Review recommended several changes These recommendations took inlo consideration the changes in Site cc (reclassification of groundwateir under the Site) the inability of the irnplerne lechnologies to achieve the objectives stated in the ROD sine the use of some revislt

control activities to achieve remedial objectives ol ha migration removing the contaminant source term and reducing hurnan heal ecological risk at the Site the rive-Year Review supported the recommendations ouIlliinied in the ROD Remedy Review

laquo Inability of the extraction well system to contain contaminant plume migration towards identified downg rad ie nl receptors

ii Inability of the extraction well system and GW7T to meet ROD clean-up levels within the foreseeable future

raquo Results of the 8V operations indicating thai SVE alone would not be able to reduce subsurface soil contamination to meet ROD clean-up levels within the time frame established in the ROD

ltbull Risk assessment assumptions that no longer appeared appropriate for the Site and

igt The change in the groundwater classification for the aquifer below the Site by IvIAIDEP to low use and value from its prior classification as drinking water

The first step of the Action IPIIan included an investigation focusing on strategies to control the continued migration of contaminated groundwater and to irnpilement innovative technologies to remiediale VOC-contanrninated soils The second step of the Action Plan involved a comprehensive investigation to identify and compile existing data collect new data and revise clean-up levels Investigation activities have been completed (implementation of innovative technologies to address VOC-contarninated soils is ongoing as ERH pilot test results are still being evaluated

The following activities were identified to evaluate existing clean-up levels based on the new groundwater classification and to revise clean-up levels where necessary

in Review Site groundwater reclassiiliication bull Evaluate recent monitoring data and current Site conditions igt Identify reimiainirig or newly identified exposure pathways raquo Develop response objectives to coincide with remaining or newly identified

exposure pathways bull Evaluate the appropriateness of the groundwater leaching model and subsequent

development or application of new soil-to-groundwater modeling parameters or data as necessary and

raquo Develop revised risk-based CIJGs for aII impacted media (principally groundwaler and unsaluraled zone soils)

In order to support I he development of revised risk-based CUGs field activities were conducted at the Site between November 2000 and July 2001 These activities also helped to delineate areas of soil excavation and the size and extent of the VOC source area The results of these field activities showed heterogeneous groundwater and soil

contamination consisting of VUCs SVUUs RGBs metals polycydic aromatic Tyclrocarbons (PAHs) and diogtunfurans on and oft the Silresirn property

The risk-based CUGs do not show an overall increasing or decreasing trend as compared to the 1991 ROD clean-up levels because some exposure pathways were eliminated (direct ingestion of ground mailer) while others were added (indoor inhalation ofVOCs)

In June 2003 the revised risk-based CUGs were further modified to reflect cuinrent EPA risk assessment guidance and protocols Specifically the carcinogenic risk goal was chaned from 10 to 10 gt and the non-carcinoeiniic hazard index was changed from 01

ecological impacts from qroundwateirl and the MADEiP Method 3 Upper ( Linrii its for soil and groundwaler The modified CUGs are identified as the

e com mended Clean-Lip Goals in Appendix A

EPA and MADEP consider the modified CUGs to be adequately protective health and the environment Additionally although not a significant change tlh of a second OLI will facilitate documenting clean-up activities at the Site

4 Revised Clean-up Gosils

tequireirnenis iuch as Dninkiino Wai or MlaxiiiTiurn ConlaiTiinant Levels and Non-zero inninant Level Goals

i I he 1999 ROD Remedy Review it was determined that certain ROD clean-up levels were based on assumptions thai were no longer appropriate and therefore required

ground water needed to be reviewed Future use exposure scenarios needed to be evaluated

raquo Changes in exposure pathways bullbullbull The extern I of the contaminated groundwater plume needed to be evaluated because il was moving faster than originally projected Potential off-property subsurface soil con lamina ion needed to be evaluated

gt Evolution of the technical approaches for Supeirfund risk assessment - The vapor rni grain on model and the methodology for selecting COPCs were no longer currenl and

raquo Specific technical issues relating to toxicily estimates - The use of toxicity surrogates for PAHs and dioxin was no longer recommended or necessary

Necessary updates for calculating revised CUGs included

ltgt Evaluating the subsurface soil to indoor air pathway for the commercialindustrial worker

ltbull Evaluating additional chemicals the inhalation palhways and igt Evaluating a child recreational receptor in the event thai I he Silresirn property or

adjacent properties are redeveloped for recreational use (eg soccer field) The potenlial exists for this type of development however since the area is currently

are summarized below Overall the chainpes in risk assumptions regarding groundwaler soil and air exposures at the Site significantly impact the CIJGs for a ariely of contaminants

Current Land Use and Site Conditions The approximate 16-acre Site is located in a heavily industrialized section of Lowell

storage facilities tractor-trailer storage light industrycommercial corido minium bull and open industrial land As a result oi MADEPs Ground water Use andl Value Deteinrimiriation IvIADEP has stipulated that ground water in the area would not be used as a drin king water source in I he failure This determination constitutes a significant change from the drinking water classification used to establish the 1991 ROD clean-up levels

The reasonaby foreseeable future land use designation for the Site is coinnnTiercialindustrial Soils with residual contamination above the CUGs will be excavated stabilized and capped on the Silresirn property Future exposures to soil or exposed groundwateir are considered possible even though the cap will likely extend over the entire Siliresim property A potential future recreational use scenario was also evaluated

The commercial industrial properties surrounding the Silresirn properly also are expected to continue to be used for cornnnieircialindustrial purposes in the foreseeable future However future renovation or redevelopment of these properties is considered possible including construction of new buildings with basements The BSIVI railroad coinridor adjacent to the Siliresim property on the eastern side is also assumed to remain a railroad corridor for the foreseeable future Ground water is assumed to remain unused for consumptive and non-consumptive uses in the future (ie for drinking or induslriaJ process uses) due to MADEPs Groundwateir Use and Value Determination coupled with the relatively low yield of the shallowest water bearing layers While this assumption appears reasonable given this classification no formal restrictions or institutional controls have been established to ensure thai the ground water us not used for consumptive or non-consumptive purposes or that future land use does not involve contact with potentially contaminated soils

An exposure pathway describes the physical linkage between the source of a COPC and a current or projected future exposed receptor The potential human receptors that have been identified at this Site (under cuinrent and reasonably anticipated future exposure scenarios include com mercia Iindustrial workers railroad workers construction worke rs (eg new facility construction or uliilrry installlatiionrnaintenance workers) and

12

trespassers These potential human receptors may come in contact with surface soil (0 1 fl bgs) exposed subsurface soil as a result of excavation (unsaturated soil gtl ft bg and lt 10 fl bgs) groundwater and ambient or indoor air containing contaminant origin calling from the Sule The potential routes of exposure are incidental iingestiioi inhalation of partioulales or wolallies and dermal absorption These exposure route were also evaluated for a potential future recreational use scenario II should be note that leaching from soil to g round water is no longisir conside1 red a risk becauslt groundwater us no longer a potential drinking water source The pathway of most concern is through VOC emissions from contaminated giroundwater and subsequent diffusion upward into ambient and indoor air

now rrsK-oaseci nuiiiDers

WiOiMl CitiiribJii Units

Under this BSD I he Site will be divided into two Oils to facilitate docuinnentinq clean-up activities as defined below

approximately 12 Ions of subsurface VUC conlarninalicri However operalion of the SVE svsterin was placed on hold because it was unlike v that it would be able to reac Site CUGs

comply wnlh Federal and Slate requirement that are applicable or relevant and appropriate and are co si-effective The revised remedy utilizes permanent solutions

This E gt[) and supporting in formal ion are available for public review at the location lentiHied within this document In addition a notice of availability of the BS

piwided to a local newspaper of general circulation

or the foregoing reasons by my signature below I approve the iissuance of lt= llxplainiation oi Significant Differences tor the Silresirn Chemical Corporation Supeirfunc Site in Lowell Massachusetts and the changes and conclusions staled1 therein

Sus^h Studlieri Acting Director Office of Site Remediation and Restoration USE PA Region I

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(IJ f rgt 3 I-shy shy rtl -r-i bull bull 11 -13 i bull shy 3 gtbull iamp bullbullbull gt (IJ S l 4l - rr bull TI i shy ni -- bullbullbull |= SJ b iii -5 L J $ ij ij i-iP J1 S sL e3 1 1 laquo laquo E Qlt1) E ii i ii-1 p MI ishy j t shy

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FOSTE R WH E E L E R E N VI RON M ENTA L CO R PORATI ON

The purpose of t h i s memorandum is to sinnraariltltbull I be re corn mended Clean-Dp GoEils (CUGs) f o r the s u r f a c e soil subsurface soi l and groundwater related to i he Si l res im Superfund Site im support of an Explanation of Significant Difference (BSD) The r isk-based ( LGs were or ig inal ly presented in the FniEil Add il lona I Site ID vesl igat ion and Re v is ion o f Si te C lean-Up (ioal s (Eosler Wheel er 2002) T hese CIJG s ivere discussed r e f ined ar id then compared to site da ta Appl icable or Relevant and Appropr ia te Requirements (ARARs) and curreni ROD cleanup levels fhe fo l lowing presents the c r i l e n a used lo develop the recommended CUGs (as cogtrnpairedto the current KOI) c l e a n u p levels)

bulli An updated IJSEPA COC screening and se lec t ion process was used (USEPA 1989 1 9 9 5 1999)

laquo The evaluat ion of the carcinogenic and non-cEireinogeriic polycyclic aromatic hydrocarbon (PAH) conipounds vas performed individually i n s t e a d of as EI g-roup ( U S E P A 1994 200 I a)

bulli T he upda ted cle rma I ris k asse ssrnenl guidance (FAGS Pa rt E) wa s applied (USE PA 2 GO1 b)

laquo The USE A Adult Lead Model was used to calculate soil lead c o n c e n t r a t i o n s associated with a (Ei rge t blood lead level and exposure parameter (USKPA 1996)

laquo The updated guidance for r isk assessment o f lt Eire moge n ic polyclhlorinated biphenylsi (PC Eh) wasiised(NCEA 1996)

Updated lox ico log ica l factors and parameters were usedl (USEPA 1997a 200la and MADEP 1 9 9 4 )

i A target r i sk goal of 1 E-5 and a target haard mdelt of 1 was used for each chernncal (d i rec t ion from USE PA Region 1 Site Manager)

laquo An assumption was made l l i E i t suirface soil consists of the soil between () -shy 1 ft bgs and lhal subsurface ur isa tura ted soil consists of the soil between 1 shy 10 fit bgs (USE PA I99 i )

laquo The Site ground w a t e r was reclassified as being low use and va lue nn a MA13EP Groun d w aie r Use and Val ue Detenminail ion (1VIA DEiF 1998)

laquo Leaching f rom s u b s u r f a c e (unsaturated) soil to ground wa te r was not considered EI critical consideration in setting sub- u r fE ice sioil CUGs (Fo- kT Wheeler 1999 2002)

laquo Commercial industr ia l l a n d use was assumed instead of r e s iden t i a l land use (foster Wheeler 19992002)

laquo The subsur face vapor in t rus ion to indoor air was e v E i l u a t e d as EI primary mbalEi t ion exposure ran te (Foste r W bee ler 2002 D SEP A 1997b)

ltbull Potential exposures to a construction worker w e r tr^aluated for soil and Birouridwater (Foster W h e e l e r 2002)

laquo Potential exposures to a trespasser were evaluated for so i l (Foster Wheeler 2 0 0 2 )

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

Site Name Silresirn Chemical Corporation Superfund Site

Site Location City of Lowell Middlesex County Massachusetts

B Lead and Support Agenciies

Suppoirt Agency Masssichusetl s Deparlrnent o Environinnenlal IPirotection (MADEP)

C Legal Aotlhioritv

Under Section 117(lt) of the Comprehensive Environmenial Response Compensation and Liability Act (CEIRCLA) 42 USC sect 9617 (c) Section 300435(c) of the Nalional Contingency Plan (INCIP) 40 CF R sect 300435(c)2)(l) and EPA guidance Office of Solid Wasle and Ennieirgency Response (OSVVEiR) Directive 9355 3-02 if EPA detennines that differences in the iremedral action significantly change but do not fundamentally alller the remedy selected in Ihe Record of Decision (ROD) with respect to scope performance or cost ERA shall publish an Explanation of Significant Differences (ESD) between the remedial action being undertaken and the remedial action set forth in the ROD and the reasons such changes are being made

0 Sumirnairy of Qrcuinstances Necessitating this Explaini-iilion of Significant Differences

This ESD documents a change to the remedy for the Silresirn Chemical Corporation Superlund Site (Site)that was originally selected in I he 1991 ROD The change is to present revised risk-based clean-up goals (CIJGs) for the Site In addition although not a significant change EPA is also creating a second Operable Unit (OU) to facilitate documenting clean-up activities atthe Siile

Revseel Clean-up Goals

The 1991 ROD included both source control and nnianagemienl of migration components to obtain a comprehensive remedy for the Site The source control component of the remedy called for in-situ soil vapor extraction (SVE) of approximately 137000 cubic yards of contaminated soil Following treatment soil with residual contamination would be excavated stabilised and capped on the Silresirn property The remedy also included active restoration of the overburden and bedrock aquifers by pumping and lirea ling I he conta riniin ated groundwater

At the lime the ROD was written I he aquifer bellow the Site was classified by the Federal Government as a Class 118 aquifer and by the Connirnoinwealllh of Massachusetts as a Class I aquifer Ground waters assigned to these classes are defined as being fresh waters found in I he saturated zone of unconsolidated deposits or consolidated rock and bedrock and are designated as a source of potable wateir supply (potential drinking water) Therefore the future installation of drinking water wells in residential areas

ndeirlain by the contaminated ground wateir could resull nn a potential human healllh risk

ground water might be used as drinking water exposure to contaminants might occur in ough ingeslion dermal absorption or inhalalion of vapors

order to support the 1991 KOI) a nsk assessment was conducted CGiTiputedl based on average concentrations of contaminants in conjunction with the correspondinci polenlial receptors The calculaled risks included a scenario whereby ground water could be used in I he future as clrinkimg water in the vicinity ol the Site

1998 Ml AD El P cornpleled a Giroundwater Use and Value Determination which resulted in a recommendation of low use and value for the ground water beneath the Site MADE IF has stipulated that groundwater would not be used as drinking water in the future Thus delerrn mail ion constituted a significant change from I he previous drinking water classification thai was used togt establish clean-up levels in the 1991 ROD As a result M AIDER has reel ass ified this aquifer as a N on -Potential Drinking Water Source Area

Following ground water reclassification the impact of this change on the existing clean-shyup levels for the Site was evaluated The results of I his evaluation were surnrnaiiiied in the January 2002 Final Additional Site Investigation and Revision of Site Clean-up Goals Report Revised risk-based CUGs were calculated based on I he groundwater reclassification additional data revised exposure pathways and current land use assumptions and Site conditions These CUGs were further modified nn 2003 to ref lect current El PA risk assessment guidance and protocols

Additional Operable Units

At the time of the 1991 ROD the Site consisted of only one Oil to address bolh source control and management of migration components The term operable unit is used lo define a discrete portion ogtr phase of the overall clean-up plan at a Site and facilitates

source conlrol aclivitii

LI S lnvrironirnenlal Prelection Agency Reco r ds C en ler One Congress Street Bos ton MA 02114 Monday Ihirough Fnday firorn 1000 am to 1 00 p rn and

from 200 pm to 500 p in

Pollard Memorial Library 401 IVIerriinmaclk Street Lowell IVIassachuseIts 01852 Ph 9 78970 4120 Monday Ihirough Thursday from 9 00 a rn lo 9 GOp rn and Friday from 9 00 a rn lo 5 00 p rn

11 bull SU MMARY PF STE H j TORY CQNTAM NA T1P_N lfi RQBLEM S AND SEJJCTEDJyEMEDY

A Si I e H istory Hiiri d C on I aim iinu-i lion Fir oIblliE rnsi

The Site is composed of appiroximately 16 acres of land in an induslrial area of Lowell Massachusetls juampl south of the Ciilys central business district (Figure 1 and Figuire 2) The Site includes a 4 5 acre property foirmeirly owned and operated by the Silresirn Chemical Corporation (Silresimi) at 136 Tanner Street and soil and groundwaler co nl animal ion lhal extends to olher nearby properties

The 45 acre SiI re si in properly is bordered by I he Lowell Iron and SI eel properly lo the norlh I he BampIVI railroad yard and I racks to the easlAnortheast the Lowell Used Aulo Paris and Tucci properties lo the soulh and Tanneir Stireet lo I he west Residential areas are located south easl and northeast of I he Silireampim property with the closest residences located on Canada Main and Maple Streets roughly 300 lo 500 feet from I he Silresirn properly boundary River Meadow Brook lies approximatelyAGD feet west of the Silresirn property and flows northeasl into I he Concord River The Concord River joins I he Meinriinack River approximately 1 mile northeast of the Site iiiast Pond a small surlace water body is located about 300 feel to I he east of I he Silresirn properly

An 8-foot high chain link fence secures the Silresirn properly Most of the land surface will him the fence is covered with a lernporary clay cap Crushed stone has been placed on runoff areas along I he northern and southern perimeleir of I he Silresinn property lo

lipiing vapor extraction vent piping natural gas potable water and sewer lines power lines and process control wiring

ltlaquo Overhead and underground high voltage power lines and I An interim passive cap venting system

The Site and its surrounding areas have been used for industrial activities since the early 1900s From 1916 to 1971 several petroleum companies used I he Silresiirn property as an oil and fuel storage deoot From 1971 through 1977 Silresirn operated its chernical waste reclamation facility The facilitys primary operations included recycling and reclaiming various chemicals and consolidating wastes for off-site disposal

The Massachusetts Division of Water Pollution Control (DWPC) now Ml AD El P granted I he facility a hazardous waste colled ion and disposal permit in 1973 Wastes were accepted at the facility in drums tank trucks railiroac tanker cars and other containers These substances included halogenated solvents oi y wasles alcohols plaling wastes metal sludge and pesticide wastes Although exact figures do not exist it is estimated I hat the facility handled sipproxirnalely 3 million gallons of waste per year

I he air and sampled soils and found contamination bolh on and oil the Sliilresim property In 1984 EPA raised the height of the fence from 6 to 8 feet and covered highly contaminated areas with 9 inches of crushed gravel and a lernpoirary day cap In 1986 damage to the original fence was repaired Subsequenl sampling revealed an additional area of soil contamination that EPA enclosed In 1986 EPA discovered dioxin the fence was relocated to prevent public access and a temporary gravel cover was placed over the dioxin-cointaminated soil to prevent contact

of soil coiTlarnination The Rl identified approximately 100 individual contiaririiinanls in on-site groundwateir and soils Volatile oirganic compounds (VOCs) were the primary co ntannin an I type identified Semi-volatile orga nic compounds (SVOCs) polychlorinated biphenyls (PCBs) metals herbiciides pesticides and dioxin were also identified

In September 1991 EPA issued the ROD for the Site The remedy selected in the ROD called for in-situ SVE of contaminated soil Soils with residual contamination would be excavated stabilized and capped on-site Contaminated groundwater would be extracted and treated by nnietals removal air stripping and vapor treatment prior 1o discharge to the City sewer system

In early 1993 a Consent Decree between EPA and a group of potentially responsible parties (IPRPs) was executed Under this Consent Decree the PRPs provided approximately $40 million in clean-up funding for the Site

Management of Migration

Construction of the GWTF began in rrnid-1994 and groundwater extraction and treatment has been underway since November 1996 Initial actions to fence the Silresirn property and cap or cover areas of contamination have reduced the potential for accidental exposure and further migration of contaminated soils The temporary cap has subsequently been upgraded These actions have eliminated the immediate threats posed by the Site while final clean-up activities are underway The operation of the GWIT has several objectives as outlined in the ROD

raquo Manage the migration of contaminated groundwater toward downgradient receptors of local building basements IRiver Meadow Brook and East Pond

laquo Capture as much of the contaminated plume as possible and raquo Drawdown the groundwateir across the Site lo support the source control remedy

To date the groundwater extraction system has been unable lo achieve the drawdown objective across the Site The extraction well array and GWTF have removed a significant amount of VOCs from the groundwater plume (over 50 tons) however plume

migration has shown some increased cone en liral ions of VOCs in cerlain areas downgradient erf the Silresirn property

on ducted using three techniques conventional SVEi healed imiphase SvE In general extracted vapor flow rates

standlaird cubic leet per minute)1 and radii of influence (lt 7-lt

the additional removal of an estimated 12 Ions of VOCs from the subsurface however the effectiveness of the SVE system was limited because the Site was not sufficiently de-watered soil moisture content was very high and very low permeability soils were encountered The overall conclusion of these SVE activities was that despite the removal of relatively significant quantities of VOCs it would be unlikely I hat conventional SVE would be able to reach I he original clean-up levels for the Site

The results ol these tests are summarized in the following conclusions

laquobull SVE has the potential for significant subsurface VOC mass removal however it is not likely to reduce soil contamination to I he ROD clean-up levels within the ROD established lime frame

raquo Site conditions (high soil moisture and low soil permeability) limited SVE effectiveness in removing contaminants from the subsurface soil

laquobull High vacuum SVE and multiphase extraction were found to be ineffective technique- for removing VOCs from the soil at I he Site and

raquo Heated air injection with SVE has the potential to increase I he rale of contanminant removal fro inn the subsurface soil

ai c reatrnent alternatives was performed iipplicability for the remediation of VOCs at the Site were considered Weighing idvantages and disadvantages for each remedial option resulted in the selection of the ileclrical resistance heating (ERH) technology as the only viable option for a pilot test at

I RH is an in-situ thermal remediation technology that uses electrical heating to enhance The ERH pilot test was designed lo evaluate applicability of Site conditions reveal

itial technical difficulties and determine the effectiveness of the technology for removing subsurface contaminants to targeted levels Results of the pilot test will be used lo evaluate the ability of ERH lo overcome the limitations observed during the SVE operations and ultimately allow an effective and cost efficient scale-up lo full-scale I reatrnent The pilol test began in October 2002 and continued through early January 2003 A final report is being prepared and will be evaluated lo determine the technologys effectiveness for removing contamination on a wide area of the Site

B Summary of the Record of Decision

The ROD (signed September 19 1991) discussed the alternatives evaluated for remediating contamination at the Site and described in detail the selected remedy for I he Site The selected remedy includes a management of migration alternative (giroundwa-ter extraction metals prelreatrnent air stripping aqueous phase carbon adsorption vapor phase carbon adsorption or thermal oxidation) and a source control alternative (SVE excavation stabilization and capping on the Silresim property) lo address all contannination at the Site A detailed description of the clean-up levels and the selected remedy is presented in Section X of the ROD

To date some success has been achieved through the implementation of a number of the remedial activities inn anda led by the ROD In particular SVE has been evaluated via pilot tests and implemented in a limited area on the Site Management of migration remedial components for ground water extraction and treatment were successfully in stalled and continue to operate Operation of the GWTF and extraction wells has resulted in some VOC contaminant concentration reduction in the groundlvvater plume although the extent of the reduction varies significantly depending on the specific area of the Site In some areas ol the Site VOC concentrations have increased However it should be noted that the extraction wells and GWTF were not designed for overall plume rernediation The main objective of the GWTF and extraction wells was lo contain the groundwater plume and lo de-water the Site sufficiently to allow for remediation of soils utilizing traditional SVE

significant change EPA is also creating a second OU to bullfacilitate clocunnienling clean-up activities at I he Site The basis for modifying the 1991 ROD cl Ban-up levels is described below

chieve remedial objectives I he ROD Remedy Review recommended several changes These recommendations took inlo consideration the changes in Site cc (reclassification of groundwateir under the Site) the inability of the irnplerne lechnologies to achieve the objectives stated in the ROD sine the use of some revislt

control activities to achieve remedial objectives ol ha migration removing the contaminant source term and reducing hurnan heal ecological risk at the Site the rive-Year Review supported the recommendations ouIlliinied in the ROD Remedy Review

laquo Inability of the extraction well system to contain contaminant plume migration towards identified downg rad ie nl receptors

ii Inability of the extraction well system and GW7T to meet ROD clean-up levels within the foreseeable future

raquo Results of the 8V operations indicating thai SVE alone would not be able to reduce subsurface soil contamination to meet ROD clean-up levels within the time frame established in the ROD

ltbull Risk assessment assumptions that no longer appeared appropriate for the Site and

igt The change in the groundwater classification for the aquifer below the Site by IvIAIDEP to low use and value from its prior classification as drinking water

The first step of the Action IPIIan included an investigation focusing on strategies to control the continued migration of contaminated groundwater and to irnpilement innovative technologies to remiediale VOC-contanrninated soils The second step of the Action Plan involved a comprehensive investigation to identify and compile existing data collect new data and revise clean-up levels Investigation activities have been completed (implementation of innovative technologies to address VOC-contarninated soils is ongoing as ERH pilot test results are still being evaluated

The following activities were identified to evaluate existing clean-up levels based on the new groundwater classification and to revise clean-up levels where necessary

in Review Site groundwater reclassiiliication bull Evaluate recent monitoring data and current Site conditions igt Identify reimiainirig or newly identified exposure pathways raquo Develop response objectives to coincide with remaining or newly identified

exposure pathways bull Evaluate the appropriateness of the groundwater leaching model and subsequent

development or application of new soil-to-groundwater modeling parameters or data as necessary and

raquo Develop revised risk-based CIJGs for aII impacted media (principally groundwaler and unsaluraled zone soils)

In order to support I he development of revised risk-based CUGs field activities were conducted at the Site between November 2000 and July 2001 These activities also helped to delineate areas of soil excavation and the size and extent of the VOC source area The results of these field activities showed heterogeneous groundwater and soil

contamination consisting of VUCs SVUUs RGBs metals polycydic aromatic Tyclrocarbons (PAHs) and diogtunfurans on and oft the Silresirn property

The risk-based CUGs do not show an overall increasing or decreasing trend as compared to the 1991 ROD clean-up levels because some exposure pathways were eliminated (direct ingestion of ground mailer) while others were added (indoor inhalation ofVOCs)

In June 2003 the revised risk-based CUGs were further modified to reflect cuinrent EPA risk assessment guidance and protocols Specifically the carcinogenic risk goal was chaned from 10 to 10 gt and the non-carcinoeiniic hazard index was changed from 01

ecological impacts from qroundwateirl and the MADEiP Method 3 Upper ( Linrii its for soil and groundwaler The modified CUGs are identified as the

e com mended Clean-Lip Goals in Appendix A

EPA and MADEP consider the modified CUGs to be adequately protective health and the environment Additionally although not a significant change tlh of a second OLI will facilitate documenting clean-up activities at the Site

4 Revised Clean-up Gosils

tequireirnenis iuch as Dninkiino Wai or MlaxiiiTiurn ConlaiTiinant Levels and Non-zero inninant Level Goals

i I he 1999 ROD Remedy Review it was determined that certain ROD clean-up levels were based on assumptions thai were no longer appropriate and therefore required

ground water needed to be reviewed Future use exposure scenarios needed to be evaluated

raquo Changes in exposure pathways bullbullbull The extern I of the contaminated groundwater plume needed to be evaluated because il was moving faster than originally projected Potential off-property subsurface soil con lamina ion needed to be evaluated

gt Evolution of the technical approaches for Supeirfund risk assessment - The vapor rni grain on model and the methodology for selecting COPCs were no longer currenl and

raquo Specific technical issues relating to toxicily estimates - The use of toxicity surrogates for PAHs and dioxin was no longer recommended or necessary

Necessary updates for calculating revised CUGs included

ltgt Evaluating the subsurface soil to indoor air pathway for the commercialindustrial worker

ltbull Evaluating additional chemicals the inhalation palhways and igt Evaluating a child recreational receptor in the event thai I he Silresirn property or

adjacent properties are redeveloped for recreational use (eg soccer field) The potenlial exists for this type of development however since the area is currently

are summarized below Overall the chainpes in risk assumptions regarding groundwaler soil and air exposures at the Site significantly impact the CIJGs for a ariely of contaminants

Current Land Use and Site Conditions The approximate 16-acre Site is located in a heavily industrialized section of Lowell

storage facilities tractor-trailer storage light industrycommercial corido minium bull and open industrial land As a result oi MADEPs Ground water Use andl Value Deteinrimiriation IvIADEP has stipulated that ground water in the area would not be used as a drin king water source in I he failure This determination constitutes a significant change from the drinking water classification used to establish the 1991 ROD clean-up levels

The reasonaby foreseeable future land use designation for the Site is coinnnTiercialindustrial Soils with residual contamination above the CUGs will be excavated stabilized and capped on the Silresirn property Future exposures to soil or exposed groundwateir are considered possible even though the cap will likely extend over the entire Siliresim property A potential future recreational use scenario was also evaluated

The commercial industrial properties surrounding the Silresirn properly also are expected to continue to be used for cornnnieircialindustrial purposes in the foreseeable future However future renovation or redevelopment of these properties is considered possible including construction of new buildings with basements The BSIVI railroad coinridor adjacent to the Siliresim property on the eastern side is also assumed to remain a railroad corridor for the foreseeable future Ground water is assumed to remain unused for consumptive and non-consumptive uses in the future (ie for drinking or induslriaJ process uses) due to MADEPs Groundwateir Use and Value Determination coupled with the relatively low yield of the shallowest water bearing layers While this assumption appears reasonable given this classification no formal restrictions or institutional controls have been established to ensure thai the ground water us not used for consumptive or non-consumptive purposes or that future land use does not involve contact with potentially contaminated soils

An exposure pathway describes the physical linkage between the source of a COPC and a current or projected future exposed receptor The potential human receptors that have been identified at this Site (under cuinrent and reasonably anticipated future exposure scenarios include com mercia Iindustrial workers railroad workers construction worke rs (eg new facility construction or uliilrry installlatiionrnaintenance workers) and

12

trespassers These potential human receptors may come in contact with surface soil (0 1 fl bgs) exposed subsurface soil as a result of excavation (unsaturated soil gtl ft bg and lt 10 fl bgs) groundwater and ambient or indoor air containing contaminant origin calling from the Sule The potential routes of exposure are incidental iingestiioi inhalation of partioulales or wolallies and dermal absorption These exposure route were also evaluated for a potential future recreational use scenario II should be note that leaching from soil to g round water is no longisir conside1 red a risk becauslt groundwater us no longer a potential drinking water source The pathway of most concern is through VOC emissions from contaminated giroundwater and subsequent diffusion upward into ambient and indoor air

now rrsK-oaseci nuiiiDers

WiOiMl CitiiribJii Units

Under this BSD I he Site will be divided into two Oils to facilitate docuinnentinq clean-up activities as defined below

approximately 12 Ions of subsurface VUC conlarninalicri However operalion of the SVE svsterin was placed on hold because it was unlike v that it would be able to reac Site CUGs

comply wnlh Federal and Slate requirement that are applicable or relevant and appropriate and are co si-effective The revised remedy utilizes permanent solutions

This E gt[) and supporting in formal ion are available for public review at the location lentiHied within this document In addition a notice of availability of the BS

piwided to a local newspaper of general circulation

or the foregoing reasons by my signature below I approve the iissuance of lt= llxplainiation oi Significant Differences tor the Silresirn Chemical Corporation Supeirfunc Site in Lowell Massachusetts and the changes and conclusions staled1 therein

Sus^h Studlieri Acting Director Office of Site Remediation and Restoration USE PA Region I

ADFIII si LOCS Draquo

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=i bull - 1 -shyj 3 iij shy| IS |i i i = gt|i |igt D e~ ti bull bull bull (3pound

- jj ^3 -3 sshy (i i- ~ S = a ]=shy s= 7 lttrade ==

(IJ f rgt 3 I-shy shy rtl -r-i bull bull 11 -13 i bull shy 3 gtbull iamp bullbullbull gt (IJ S l 4l - rr bull TI i shy ni -- bullbullbull |= SJ b iii -5 L J $ ij ij i-iP J1 S sL e3 1 1 laquo laquo E Qlt1) E ii i ii-1 p MI ishy j t shy

= s ^ i = t t = i i pound t1

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FOSTE R WH E E L E R E N VI RON M ENTA L CO R PORATI ON

The purpose of t h i s memorandum is to sinnraariltltbull I be re corn mended Clean-Dp GoEils (CUGs) f o r the s u r f a c e soil subsurface soi l and groundwater related to i he Si l res im Superfund Site im support of an Explanation of Significant Difference (BSD) The r isk-based ( LGs were or ig inal ly presented in the FniEil Add il lona I Site ID vesl igat ion and Re v is ion o f Si te C lean-Up (ioal s (Eosler Wheel er 2002) T hese CIJG s ivere discussed r e f ined ar id then compared to site da ta Appl icable or Relevant and Appropr ia te Requirements (ARARs) and curreni ROD cleanup levels fhe fo l lowing presents the c r i l e n a used lo develop the recommended CUGs (as cogtrnpairedto the current KOI) c l e a n u p levels)

bulli An updated IJSEPA COC screening and se lec t ion process was used (USEPA 1989 1 9 9 5 1999)

laquo The evaluat ion of the carcinogenic and non-cEireinogeriic polycyclic aromatic hydrocarbon (PAH) conipounds vas performed individually i n s t e a d of as EI g-roup ( U S E P A 1994 200 I a)

bulli T he upda ted cle rma I ris k asse ssrnenl guidance (FAGS Pa rt E) wa s applied (USE PA 2 GO1 b)

laquo The USE A Adult Lead Model was used to calculate soil lead c o n c e n t r a t i o n s associated with a (Ei rge t blood lead level and exposure parameter (USKPA 1996)

laquo The updated guidance for r isk assessment o f lt Eire moge n ic polyclhlorinated biphenylsi (PC Eh) wasiised(NCEA 1996)

Updated lox ico log ica l factors and parameters were usedl (USEPA 1997a 200la and MADEP 1 9 9 4 )

i A target r i sk goal of 1 E-5 and a target haard mdelt of 1 was used for each chernncal (d i rec t ion from USE PA Region 1 Site Manager)

laquo An assumption was made l l i E i t suirface soil consists of the soil between () -shy 1 ft bgs and lhal subsurface ur isa tura ted soil consists of the soil between 1 shy 10 fit bgs (USE PA I99 i )

laquo The Site ground w a t e r was reclassified as being low use and va lue nn a MA13EP Groun d w aie r Use and Val ue Detenminail ion (1VIA DEiF 1998)

laquo Leaching f rom s u b s u r f a c e (unsaturated) soil to ground wa te r was not considered EI critical consideration in setting sub- u r fE ice sioil CUGs (Fo- kT Wheeler 1999 2002)

laquo Commercial industr ia l l a n d use was assumed instead of r e s iden t i a l land use (foster Wheeler 19992002)

laquo The subsur face vapor in t rus ion to indoor air was e v E i l u a t e d as EI primary mbalEi t ion exposure ran te (Foste r W bee ler 2002 D SEP A 1997b)

ltbull Potential exposures to a construction worker w e r tr^aluated for soil and Birouridwater (Foster W h e e l e r 2002)

laquo Potential exposures to a trespasser were evaluated for so i l (Foster Wheeler 2 0 0 2 )

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

At the lime the ROD was written I he aquifer bellow the Site was classified by the Federal Government as a Class 118 aquifer and by the Connirnoinwealllh of Massachusetts as a Class I aquifer Ground waters assigned to these classes are defined as being fresh waters found in I he saturated zone of unconsolidated deposits or consolidated rock and bedrock and are designated as a source of potable wateir supply (potential drinking water) Therefore the future installation of drinking water wells in residential areas

ndeirlain by the contaminated ground wateir could resull nn a potential human healllh risk

ground water might be used as drinking water exposure to contaminants might occur in ough ingeslion dermal absorption or inhalalion of vapors

order to support the 1991 KOI) a nsk assessment was conducted CGiTiputedl based on average concentrations of contaminants in conjunction with the correspondinci polenlial receptors The calculaled risks included a scenario whereby ground water could be used in I he future as clrinkimg water in the vicinity ol the Site

1998 Ml AD El P cornpleled a Giroundwater Use and Value Determination which resulted in a recommendation of low use and value for the ground water beneath the Site MADE IF has stipulated that groundwater would not be used as drinking water in the future Thus delerrn mail ion constituted a significant change from I he previous drinking water classification thai was used togt establish clean-up levels in the 1991 ROD As a result M AIDER has reel ass ified this aquifer as a N on -Potential Drinking Water Source Area

Following ground water reclassification the impact of this change on the existing clean-shyup levels for the Site was evaluated The results of I his evaluation were surnrnaiiiied in the January 2002 Final Additional Site Investigation and Revision of Site Clean-up Goals Report Revised risk-based CUGs were calculated based on I he groundwater reclassification additional data revised exposure pathways and current land use assumptions and Site conditions These CUGs were further modified nn 2003 to ref lect current El PA risk assessment guidance and protocols

Additional Operable Units

At the time of the 1991 ROD the Site consisted of only one Oil to address bolh source control and management of migration components The term operable unit is used lo define a discrete portion ogtr phase of the overall clean-up plan at a Site and facilitates

source conlrol aclivitii

LI S lnvrironirnenlal Prelection Agency Reco r ds C en ler One Congress Street Bos ton MA 02114 Monday Ihirough Fnday firorn 1000 am to 1 00 p rn and

from 200 pm to 500 p in

Pollard Memorial Library 401 IVIerriinmaclk Street Lowell IVIassachuseIts 01852 Ph 9 78970 4120 Monday Ihirough Thursday from 9 00 a rn lo 9 GOp rn and Friday from 9 00 a rn lo 5 00 p rn

11 bull SU MMARY PF STE H j TORY CQNTAM NA T1P_N lfi RQBLEM S AND SEJJCTEDJyEMEDY

A Si I e H istory Hiiri d C on I aim iinu-i lion Fir oIblliE rnsi

The Site is composed of appiroximately 16 acres of land in an induslrial area of Lowell Massachusetls juampl south of the Ciilys central business district (Figure 1 and Figuire 2) The Site includes a 4 5 acre property foirmeirly owned and operated by the Silresirn Chemical Corporation (Silresimi) at 136 Tanner Street and soil and groundwaler co nl animal ion lhal extends to olher nearby properties

The 45 acre SiI re si in properly is bordered by I he Lowell Iron and SI eel properly lo the norlh I he BampIVI railroad yard and I racks to the easlAnortheast the Lowell Used Aulo Paris and Tucci properties lo the soulh and Tanneir Stireet lo I he west Residential areas are located south easl and northeast of I he Silireampim property with the closest residences located on Canada Main and Maple Streets roughly 300 lo 500 feet from I he Silresirn properly boundary River Meadow Brook lies approximatelyAGD feet west of the Silresirn property and flows northeasl into I he Concord River The Concord River joins I he Meinriinack River approximately 1 mile northeast of the Site iiiast Pond a small surlace water body is located about 300 feel to I he east of I he Silresirn properly

An 8-foot high chain link fence secures the Silresirn properly Most of the land surface will him the fence is covered with a lernporary clay cap Crushed stone has been placed on runoff areas along I he northern and southern perimeleir of I he Silresinn property lo

lipiing vapor extraction vent piping natural gas potable water and sewer lines power lines and process control wiring

ltlaquo Overhead and underground high voltage power lines and I An interim passive cap venting system

The Site and its surrounding areas have been used for industrial activities since the early 1900s From 1916 to 1971 several petroleum companies used I he Silresiirn property as an oil and fuel storage deoot From 1971 through 1977 Silresirn operated its chernical waste reclamation facility The facilitys primary operations included recycling and reclaiming various chemicals and consolidating wastes for off-site disposal

The Massachusetts Division of Water Pollution Control (DWPC) now Ml AD El P granted I he facility a hazardous waste colled ion and disposal permit in 1973 Wastes were accepted at the facility in drums tank trucks railiroac tanker cars and other containers These substances included halogenated solvents oi y wasles alcohols plaling wastes metal sludge and pesticide wastes Although exact figures do not exist it is estimated I hat the facility handled sipproxirnalely 3 million gallons of waste per year

I he air and sampled soils and found contamination bolh on and oil the Sliilresim property In 1984 EPA raised the height of the fence from 6 to 8 feet and covered highly contaminated areas with 9 inches of crushed gravel and a lernpoirary day cap In 1986 damage to the original fence was repaired Subsequenl sampling revealed an additional area of soil contamination that EPA enclosed In 1986 EPA discovered dioxin the fence was relocated to prevent public access and a temporary gravel cover was placed over the dioxin-cointaminated soil to prevent contact

of soil coiTlarnination The Rl identified approximately 100 individual contiaririiinanls in on-site groundwateir and soils Volatile oirganic compounds (VOCs) were the primary co ntannin an I type identified Semi-volatile orga nic compounds (SVOCs) polychlorinated biphenyls (PCBs) metals herbiciides pesticides and dioxin were also identified

In September 1991 EPA issued the ROD for the Site The remedy selected in the ROD called for in-situ SVE of contaminated soil Soils with residual contamination would be excavated stabilized and capped on-site Contaminated groundwater would be extracted and treated by nnietals removal air stripping and vapor treatment prior 1o discharge to the City sewer system

In early 1993 a Consent Decree between EPA and a group of potentially responsible parties (IPRPs) was executed Under this Consent Decree the PRPs provided approximately $40 million in clean-up funding for the Site

Management of Migration

Construction of the GWTF began in rrnid-1994 and groundwater extraction and treatment has been underway since November 1996 Initial actions to fence the Silresirn property and cap or cover areas of contamination have reduced the potential for accidental exposure and further migration of contaminated soils The temporary cap has subsequently been upgraded These actions have eliminated the immediate threats posed by the Site while final clean-up activities are underway The operation of the GWIT has several objectives as outlined in the ROD

raquo Manage the migration of contaminated groundwater toward downgradient receptors of local building basements IRiver Meadow Brook and East Pond

laquo Capture as much of the contaminated plume as possible and raquo Drawdown the groundwateir across the Site lo support the source control remedy

To date the groundwater extraction system has been unable lo achieve the drawdown objective across the Site The extraction well array and GWTF have removed a significant amount of VOCs from the groundwater plume (over 50 tons) however plume

migration has shown some increased cone en liral ions of VOCs in cerlain areas downgradient erf the Silresirn property

on ducted using three techniques conventional SVEi healed imiphase SvE In general extracted vapor flow rates

standlaird cubic leet per minute)1 and radii of influence (lt 7-lt

the additional removal of an estimated 12 Ions of VOCs from the subsurface however the effectiveness of the SVE system was limited because the Site was not sufficiently de-watered soil moisture content was very high and very low permeability soils were encountered The overall conclusion of these SVE activities was that despite the removal of relatively significant quantities of VOCs it would be unlikely I hat conventional SVE would be able to reach I he original clean-up levels for the Site

The results ol these tests are summarized in the following conclusions

laquobull SVE has the potential for significant subsurface VOC mass removal however it is not likely to reduce soil contamination to I he ROD clean-up levels within the ROD established lime frame

raquo Site conditions (high soil moisture and low soil permeability) limited SVE effectiveness in removing contaminants from the subsurface soil

laquobull High vacuum SVE and multiphase extraction were found to be ineffective technique- for removing VOCs from the soil at I he Site and

raquo Heated air injection with SVE has the potential to increase I he rale of contanminant removal fro inn the subsurface soil

ai c reatrnent alternatives was performed iipplicability for the remediation of VOCs at the Site were considered Weighing idvantages and disadvantages for each remedial option resulted in the selection of the ileclrical resistance heating (ERH) technology as the only viable option for a pilot test at

I RH is an in-situ thermal remediation technology that uses electrical heating to enhance The ERH pilot test was designed lo evaluate applicability of Site conditions reveal

itial technical difficulties and determine the effectiveness of the technology for removing subsurface contaminants to targeted levels Results of the pilot test will be used lo evaluate the ability of ERH lo overcome the limitations observed during the SVE operations and ultimately allow an effective and cost efficient scale-up lo full-scale I reatrnent The pilol test began in October 2002 and continued through early January 2003 A final report is being prepared and will be evaluated lo determine the technologys effectiveness for removing contamination on a wide area of the Site

B Summary of the Record of Decision

The ROD (signed September 19 1991) discussed the alternatives evaluated for remediating contamination at the Site and described in detail the selected remedy for I he Site The selected remedy includes a management of migration alternative (giroundwa-ter extraction metals prelreatrnent air stripping aqueous phase carbon adsorption vapor phase carbon adsorption or thermal oxidation) and a source control alternative (SVE excavation stabilization and capping on the Silresim property) lo address all contannination at the Site A detailed description of the clean-up levels and the selected remedy is presented in Section X of the ROD

To date some success has been achieved through the implementation of a number of the remedial activities inn anda led by the ROD In particular SVE has been evaluated via pilot tests and implemented in a limited area on the Site Management of migration remedial components for ground water extraction and treatment were successfully in stalled and continue to operate Operation of the GWTF and extraction wells has resulted in some VOC contaminant concentration reduction in the groundlvvater plume although the extent of the reduction varies significantly depending on the specific area of the Site In some areas ol the Site VOC concentrations have increased However it should be noted that the extraction wells and GWTF were not designed for overall plume rernediation The main objective of the GWTF and extraction wells was lo contain the groundwater plume and lo de-water the Site sufficiently to allow for remediation of soils utilizing traditional SVE

significant change EPA is also creating a second OU to bullfacilitate clocunnienling clean-up activities at I he Site The basis for modifying the 1991 ROD cl Ban-up levels is described below

chieve remedial objectives I he ROD Remedy Review recommended several changes These recommendations took inlo consideration the changes in Site cc (reclassification of groundwateir under the Site) the inability of the irnplerne lechnologies to achieve the objectives stated in the ROD sine the use of some revislt

control activities to achieve remedial objectives ol ha migration removing the contaminant source term and reducing hurnan heal ecological risk at the Site the rive-Year Review supported the recommendations ouIlliinied in the ROD Remedy Review

laquo Inability of the extraction well system to contain contaminant plume migration towards identified downg rad ie nl receptors

ii Inability of the extraction well system and GW7T to meet ROD clean-up levels within the foreseeable future

raquo Results of the 8V operations indicating thai SVE alone would not be able to reduce subsurface soil contamination to meet ROD clean-up levels within the time frame established in the ROD

ltbull Risk assessment assumptions that no longer appeared appropriate for the Site and

igt The change in the groundwater classification for the aquifer below the Site by IvIAIDEP to low use and value from its prior classification as drinking water

The first step of the Action IPIIan included an investigation focusing on strategies to control the continued migration of contaminated groundwater and to irnpilement innovative technologies to remiediale VOC-contanrninated soils The second step of the Action Plan involved a comprehensive investigation to identify and compile existing data collect new data and revise clean-up levels Investigation activities have been completed (implementation of innovative technologies to address VOC-contarninated soils is ongoing as ERH pilot test results are still being evaluated

The following activities were identified to evaluate existing clean-up levels based on the new groundwater classification and to revise clean-up levels where necessary

in Review Site groundwater reclassiiliication bull Evaluate recent monitoring data and current Site conditions igt Identify reimiainirig or newly identified exposure pathways raquo Develop response objectives to coincide with remaining or newly identified

exposure pathways bull Evaluate the appropriateness of the groundwater leaching model and subsequent

development or application of new soil-to-groundwater modeling parameters or data as necessary and

raquo Develop revised risk-based CIJGs for aII impacted media (principally groundwaler and unsaluraled zone soils)

In order to support I he development of revised risk-based CUGs field activities were conducted at the Site between November 2000 and July 2001 These activities also helped to delineate areas of soil excavation and the size and extent of the VOC source area The results of these field activities showed heterogeneous groundwater and soil

contamination consisting of VUCs SVUUs RGBs metals polycydic aromatic Tyclrocarbons (PAHs) and diogtunfurans on and oft the Silresirn property

The risk-based CUGs do not show an overall increasing or decreasing trend as compared to the 1991 ROD clean-up levels because some exposure pathways were eliminated (direct ingestion of ground mailer) while others were added (indoor inhalation ofVOCs)

In June 2003 the revised risk-based CUGs were further modified to reflect cuinrent EPA risk assessment guidance and protocols Specifically the carcinogenic risk goal was chaned from 10 to 10 gt and the non-carcinoeiniic hazard index was changed from 01

ecological impacts from qroundwateirl and the MADEiP Method 3 Upper ( Linrii its for soil and groundwaler The modified CUGs are identified as the

e com mended Clean-Lip Goals in Appendix A

EPA and MADEP consider the modified CUGs to be adequately protective health and the environment Additionally although not a significant change tlh of a second OLI will facilitate documenting clean-up activities at the Site

4 Revised Clean-up Gosils

tequireirnenis iuch as Dninkiino Wai or MlaxiiiTiurn ConlaiTiinant Levels and Non-zero inninant Level Goals

i I he 1999 ROD Remedy Review it was determined that certain ROD clean-up levels were based on assumptions thai were no longer appropriate and therefore required

ground water needed to be reviewed Future use exposure scenarios needed to be evaluated

raquo Changes in exposure pathways bullbullbull The extern I of the contaminated groundwater plume needed to be evaluated because il was moving faster than originally projected Potential off-property subsurface soil con lamina ion needed to be evaluated

gt Evolution of the technical approaches for Supeirfund risk assessment - The vapor rni grain on model and the methodology for selecting COPCs were no longer currenl and

raquo Specific technical issues relating to toxicily estimates - The use of toxicity surrogates for PAHs and dioxin was no longer recommended or necessary

Necessary updates for calculating revised CUGs included

ltgt Evaluating the subsurface soil to indoor air pathway for the commercialindustrial worker

ltbull Evaluating additional chemicals the inhalation palhways and igt Evaluating a child recreational receptor in the event thai I he Silresirn property or

adjacent properties are redeveloped for recreational use (eg soccer field) The potenlial exists for this type of development however since the area is currently

are summarized below Overall the chainpes in risk assumptions regarding groundwaler soil and air exposures at the Site significantly impact the CIJGs for a ariely of contaminants

Current Land Use and Site Conditions The approximate 16-acre Site is located in a heavily industrialized section of Lowell

storage facilities tractor-trailer storage light industrycommercial corido minium bull and open industrial land As a result oi MADEPs Ground water Use andl Value Deteinrimiriation IvIADEP has stipulated that ground water in the area would not be used as a drin king water source in I he failure This determination constitutes a significant change from the drinking water classification used to establish the 1991 ROD clean-up levels

The reasonaby foreseeable future land use designation for the Site is coinnnTiercialindustrial Soils with residual contamination above the CUGs will be excavated stabilized and capped on the Silresirn property Future exposures to soil or exposed groundwateir are considered possible even though the cap will likely extend over the entire Siliresim property A potential future recreational use scenario was also evaluated

The commercial industrial properties surrounding the Silresirn properly also are expected to continue to be used for cornnnieircialindustrial purposes in the foreseeable future However future renovation or redevelopment of these properties is considered possible including construction of new buildings with basements The BSIVI railroad coinridor adjacent to the Siliresim property on the eastern side is also assumed to remain a railroad corridor for the foreseeable future Ground water is assumed to remain unused for consumptive and non-consumptive uses in the future (ie for drinking or induslriaJ process uses) due to MADEPs Groundwateir Use and Value Determination coupled with the relatively low yield of the shallowest water bearing layers While this assumption appears reasonable given this classification no formal restrictions or institutional controls have been established to ensure thai the ground water us not used for consumptive or non-consumptive purposes or that future land use does not involve contact with potentially contaminated soils

An exposure pathway describes the physical linkage between the source of a COPC and a current or projected future exposed receptor The potential human receptors that have been identified at this Site (under cuinrent and reasonably anticipated future exposure scenarios include com mercia Iindustrial workers railroad workers construction worke rs (eg new facility construction or uliilrry installlatiionrnaintenance workers) and

12

trespassers These potential human receptors may come in contact with surface soil (0 1 fl bgs) exposed subsurface soil as a result of excavation (unsaturated soil gtl ft bg and lt 10 fl bgs) groundwater and ambient or indoor air containing contaminant origin calling from the Sule The potential routes of exposure are incidental iingestiioi inhalation of partioulales or wolallies and dermal absorption These exposure route were also evaluated for a potential future recreational use scenario II should be note that leaching from soil to g round water is no longisir conside1 red a risk becauslt groundwater us no longer a potential drinking water source The pathway of most concern is through VOC emissions from contaminated giroundwater and subsequent diffusion upward into ambient and indoor air

now rrsK-oaseci nuiiiDers

WiOiMl CitiiribJii Units

Under this BSD I he Site will be divided into two Oils to facilitate docuinnentinq clean-up activities as defined below

approximately 12 Ions of subsurface VUC conlarninalicri However operalion of the SVE svsterin was placed on hold because it was unlike v that it would be able to reac Site CUGs

comply wnlh Federal and Slate requirement that are applicable or relevant and appropriate and are co si-effective The revised remedy utilizes permanent solutions

This E gt[) and supporting in formal ion are available for public review at the location lentiHied within this document In addition a notice of availability of the BS

piwided to a local newspaper of general circulation

or the foregoing reasons by my signature below I approve the iissuance of lt= llxplainiation oi Significant Differences tor the Silresirn Chemical Corporation Supeirfunc Site in Lowell Massachusetts and the changes and conclusions staled1 therein

Sus^h Studlieri Acting Director Office of Site Remediation and Restoration USE PA Region I

ADFIII si LOCS Draquo

lti

lii

pound j2bull

LLJ

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C

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ltis

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shy

b gt

craquo i[i

i deg bullgt

fdJr 111

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-i 3 o a

i

ltgt HI

i -is D

c J

iii i ltgt

bull -3

i g

w

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3 w

j|

laquopound e

fi (I laquo gt

iii

ijj IJL

bullbullbull ID $

O

inE

ij-O

j0o

shy

S = bull

ii S lt

bull lt[

nil (L)

jii[bullbull bull -i

n|gt

tri bullF1

igtraquot

E a

ir ii III Jl

CObullar

cgt CO^j

ugt

J

Ji

b(i ltLI

u (pound lt UI upi lt

=i bull - 1 -shyj 3 iij shy| IS |i i i = gt|i |igt D e~ ti bull bull bull (3pound

- jj ^3 -3 sshy (i i- ~ S = a ]=shy s= 7 lttrade ==

(IJ f rgt 3 I-shy shy rtl -r-i bull bull 11 -13 i bull shy 3 gtbull iamp bullbullbull gt (IJ S l 4l - rr bull TI i shy ni -- bullbullbull |= SJ b iii -5 L J $ ij ij i-iP J1 S sL e3 1 1 laquo laquo E Qlt1) E ii i ii-1 p MI ishy j t shy

= s ^ i = t t = i i pound t1

o ltgt o s 2 ltN3 w J bullbull = ^j

cu CL ]

^ 0

[ fir ]bullbullbull [ ltu

(3

[ii 11 D L^tl

(LJ

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illSti

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-L

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=

iJUil ii(i

FOSTE R WH E E L E R E N VI RON M ENTA L CO R PORATI ON

The purpose of t h i s memorandum is to sinnraariltltbull I be re corn mended Clean-Dp GoEils (CUGs) f o r the s u r f a c e soil subsurface soi l and groundwater related to i he Si l res im Superfund Site im support of an Explanation of Significant Difference (BSD) The r isk-based ( LGs were or ig inal ly presented in the FniEil Add il lona I Site ID vesl igat ion and Re v is ion o f Si te C lean-Up (ioal s (Eosler Wheel er 2002) T hese CIJG s ivere discussed r e f ined ar id then compared to site da ta Appl icable or Relevant and Appropr ia te Requirements (ARARs) and curreni ROD cleanup levels fhe fo l lowing presents the c r i l e n a used lo develop the recommended CUGs (as cogtrnpairedto the current KOI) c l e a n u p levels)

bulli An updated IJSEPA COC screening and se lec t ion process was used (USEPA 1989 1 9 9 5 1999)

laquo The evaluat ion of the carcinogenic and non-cEireinogeriic polycyclic aromatic hydrocarbon (PAH) conipounds vas performed individually i n s t e a d of as EI g-roup ( U S E P A 1994 200 I a)

bulli T he upda ted cle rma I ris k asse ssrnenl guidance (FAGS Pa rt E) wa s applied (USE PA 2 GO1 b)

laquo The USE A Adult Lead Model was used to calculate soil lead c o n c e n t r a t i o n s associated with a (Ei rge t blood lead level and exposure parameter (USKPA 1996)

laquo The updated guidance for r isk assessment o f lt Eire moge n ic polyclhlorinated biphenylsi (PC Eh) wasiised(NCEA 1996)

Updated lox ico log ica l factors and parameters were usedl (USEPA 1997a 200la and MADEP 1 9 9 4 )

i A target r i sk goal of 1 E-5 and a target haard mdelt of 1 was used for each chernncal (d i rec t ion from USE PA Region 1 Site Manager)

laquo An assumption was made l l i E i t suirface soil consists of the soil between () -shy 1 ft bgs and lhal subsurface ur isa tura ted soil consists of the soil between 1 shy 10 fit bgs (USE PA I99 i )

laquo The Site ground w a t e r was reclassified as being low use and va lue nn a MA13EP Groun d w aie r Use and Val ue Detenminail ion (1VIA DEiF 1998)

laquo Leaching f rom s u b s u r f a c e (unsaturated) soil to ground wa te r was not considered EI critical consideration in setting sub- u r fE ice sioil CUGs (Fo- kT Wheeler 1999 2002)

laquo Commercial industr ia l l a n d use was assumed instead of r e s iden t i a l land use (foster Wheeler 19992002)

laquo The subsur face vapor in t rus ion to indoor air was e v E i l u a t e d as EI primary mbalEi t ion exposure ran te (Foste r W bee ler 2002 D SEP A 1997b)

ltbull Potential exposures to a construction worker w e r tr^aluated for soil and Birouridwater (Foster W h e e l e r 2002)

laquo Potential exposures to a trespasser were evaluated for so i l (Foster Wheeler 2 0 0 2 )

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

LI S lnvrironirnenlal Prelection Agency Reco r ds C en ler One Congress Street Bos ton MA 02114 Monday Ihirough Fnday firorn 1000 am to 1 00 p rn and

from 200 pm to 500 p in

Pollard Memorial Library 401 IVIerriinmaclk Street Lowell IVIassachuseIts 01852 Ph 9 78970 4120 Monday Ihirough Thursday from 9 00 a rn lo 9 GOp rn and Friday from 9 00 a rn lo 5 00 p rn

11 bull SU MMARY PF STE H j TORY CQNTAM NA T1P_N lfi RQBLEM S AND SEJJCTEDJyEMEDY

A Si I e H istory Hiiri d C on I aim iinu-i lion Fir oIblliE rnsi

The Site is composed of appiroximately 16 acres of land in an induslrial area of Lowell Massachusetls juampl south of the Ciilys central business district (Figure 1 and Figuire 2) The Site includes a 4 5 acre property foirmeirly owned and operated by the Silresirn Chemical Corporation (Silresimi) at 136 Tanner Street and soil and groundwaler co nl animal ion lhal extends to olher nearby properties

The 45 acre SiI re si in properly is bordered by I he Lowell Iron and SI eel properly lo the norlh I he BampIVI railroad yard and I racks to the easlAnortheast the Lowell Used Aulo Paris and Tucci properties lo the soulh and Tanneir Stireet lo I he west Residential areas are located south easl and northeast of I he Silireampim property with the closest residences located on Canada Main and Maple Streets roughly 300 lo 500 feet from I he Silresirn properly boundary River Meadow Brook lies approximatelyAGD feet west of the Silresirn property and flows northeasl into I he Concord River The Concord River joins I he Meinriinack River approximately 1 mile northeast of the Site iiiast Pond a small surlace water body is located about 300 feel to I he east of I he Silresirn properly

An 8-foot high chain link fence secures the Silresirn properly Most of the land surface will him the fence is covered with a lernporary clay cap Crushed stone has been placed on runoff areas along I he northern and southern perimeleir of I he Silresinn property lo

lipiing vapor extraction vent piping natural gas potable water and sewer lines power lines and process control wiring

ltlaquo Overhead and underground high voltage power lines and I An interim passive cap venting system

The Site and its surrounding areas have been used for industrial activities since the early 1900s From 1916 to 1971 several petroleum companies used I he Silresiirn property as an oil and fuel storage deoot From 1971 through 1977 Silresirn operated its chernical waste reclamation facility The facilitys primary operations included recycling and reclaiming various chemicals and consolidating wastes for off-site disposal

The Massachusetts Division of Water Pollution Control (DWPC) now Ml AD El P granted I he facility a hazardous waste colled ion and disposal permit in 1973 Wastes were accepted at the facility in drums tank trucks railiroac tanker cars and other containers These substances included halogenated solvents oi y wasles alcohols plaling wastes metal sludge and pesticide wastes Although exact figures do not exist it is estimated I hat the facility handled sipproxirnalely 3 million gallons of waste per year

I he air and sampled soils and found contamination bolh on and oil the Sliilresim property In 1984 EPA raised the height of the fence from 6 to 8 feet and covered highly contaminated areas with 9 inches of crushed gravel and a lernpoirary day cap In 1986 damage to the original fence was repaired Subsequenl sampling revealed an additional area of soil contamination that EPA enclosed In 1986 EPA discovered dioxin the fence was relocated to prevent public access and a temporary gravel cover was placed over the dioxin-cointaminated soil to prevent contact

of soil coiTlarnination The Rl identified approximately 100 individual contiaririiinanls in on-site groundwateir and soils Volatile oirganic compounds (VOCs) were the primary co ntannin an I type identified Semi-volatile orga nic compounds (SVOCs) polychlorinated biphenyls (PCBs) metals herbiciides pesticides and dioxin were also identified

In September 1991 EPA issued the ROD for the Site The remedy selected in the ROD called for in-situ SVE of contaminated soil Soils with residual contamination would be excavated stabilized and capped on-site Contaminated groundwater would be extracted and treated by nnietals removal air stripping and vapor treatment prior 1o discharge to the City sewer system

In early 1993 a Consent Decree between EPA and a group of potentially responsible parties (IPRPs) was executed Under this Consent Decree the PRPs provided approximately $40 million in clean-up funding for the Site

Management of Migration

Construction of the GWTF began in rrnid-1994 and groundwater extraction and treatment has been underway since November 1996 Initial actions to fence the Silresirn property and cap or cover areas of contamination have reduced the potential for accidental exposure and further migration of contaminated soils The temporary cap has subsequently been upgraded These actions have eliminated the immediate threats posed by the Site while final clean-up activities are underway The operation of the GWIT has several objectives as outlined in the ROD

raquo Manage the migration of contaminated groundwater toward downgradient receptors of local building basements IRiver Meadow Brook and East Pond

laquo Capture as much of the contaminated plume as possible and raquo Drawdown the groundwateir across the Site lo support the source control remedy

To date the groundwater extraction system has been unable lo achieve the drawdown objective across the Site The extraction well array and GWTF have removed a significant amount of VOCs from the groundwater plume (over 50 tons) however plume

migration has shown some increased cone en liral ions of VOCs in cerlain areas downgradient erf the Silresirn property

on ducted using three techniques conventional SVEi healed imiphase SvE In general extracted vapor flow rates

standlaird cubic leet per minute)1 and radii of influence (lt 7-lt

the additional removal of an estimated 12 Ions of VOCs from the subsurface however the effectiveness of the SVE system was limited because the Site was not sufficiently de-watered soil moisture content was very high and very low permeability soils were encountered The overall conclusion of these SVE activities was that despite the removal of relatively significant quantities of VOCs it would be unlikely I hat conventional SVE would be able to reach I he original clean-up levels for the Site

The results ol these tests are summarized in the following conclusions

laquobull SVE has the potential for significant subsurface VOC mass removal however it is not likely to reduce soil contamination to I he ROD clean-up levels within the ROD established lime frame

raquo Site conditions (high soil moisture and low soil permeability) limited SVE effectiveness in removing contaminants from the subsurface soil

laquobull High vacuum SVE and multiphase extraction were found to be ineffective technique- for removing VOCs from the soil at I he Site and

raquo Heated air injection with SVE has the potential to increase I he rale of contanminant removal fro inn the subsurface soil

ai c reatrnent alternatives was performed iipplicability for the remediation of VOCs at the Site were considered Weighing idvantages and disadvantages for each remedial option resulted in the selection of the ileclrical resistance heating (ERH) technology as the only viable option for a pilot test at

I RH is an in-situ thermal remediation technology that uses electrical heating to enhance The ERH pilot test was designed lo evaluate applicability of Site conditions reveal

itial technical difficulties and determine the effectiveness of the technology for removing subsurface contaminants to targeted levels Results of the pilot test will be used lo evaluate the ability of ERH lo overcome the limitations observed during the SVE operations and ultimately allow an effective and cost efficient scale-up lo full-scale I reatrnent The pilol test began in October 2002 and continued through early January 2003 A final report is being prepared and will be evaluated lo determine the technologys effectiveness for removing contamination on a wide area of the Site

B Summary of the Record of Decision

The ROD (signed September 19 1991) discussed the alternatives evaluated for remediating contamination at the Site and described in detail the selected remedy for I he Site The selected remedy includes a management of migration alternative (giroundwa-ter extraction metals prelreatrnent air stripping aqueous phase carbon adsorption vapor phase carbon adsorption or thermal oxidation) and a source control alternative (SVE excavation stabilization and capping on the Silresim property) lo address all contannination at the Site A detailed description of the clean-up levels and the selected remedy is presented in Section X of the ROD

To date some success has been achieved through the implementation of a number of the remedial activities inn anda led by the ROD In particular SVE has been evaluated via pilot tests and implemented in a limited area on the Site Management of migration remedial components for ground water extraction and treatment were successfully in stalled and continue to operate Operation of the GWTF and extraction wells has resulted in some VOC contaminant concentration reduction in the groundlvvater plume although the extent of the reduction varies significantly depending on the specific area of the Site In some areas ol the Site VOC concentrations have increased However it should be noted that the extraction wells and GWTF were not designed for overall plume rernediation The main objective of the GWTF and extraction wells was lo contain the groundwater plume and lo de-water the Site sufficiently to allow for remediation of soils utilizing traditional SVE

significant change EPA is also creating a second OU to bullfacilitate clocunnienling clean-up activities at I he Site The basis for modifying the 1991 ROD cl Ban-up levels is described below

chieve remedial objectives I he ROD Remedy Review recommended several changes These recommendations took inlo consideration the changes in Site cc (reclassification of groundwateir under the Site) the inability of the irnplerne lechnologies to achieve the objectives stated in the ROD sine the use of some revislt

control activities to achieve remedial objectives ol ha migration removing the contaminant source term and reducing hurnan heal ecological risk at the Site the rive-Year Review supported the recommendations ouIlliinied in the ROD Remedy Review

laquo Inability of the extraction well system to contain contaminant plume migration towards identified downg rad ie nl receptors

ii Inability of the extraction well system and GW7T to meet ROD clean-up levels within the foreseeable future

raquo Results of the 8V operations indicating thai SVE alone would not be able to reduce subsurface soil contamination to meet ROD clean-up levels within the time frame established in the ROD

ltbull Risk assessment assumptions that no longer appeared appropriate for the Site and

igt The change in the groundwater classification for the aquifer below the Site by IvIAIDEP to low use and value from its prior classification as drinking water

The first step of the Action IPIIan included an investigation focusing on strategies to control the continued migration of contaminated groundwater and to irnpilement innovative technologies to remiediale VOC-contanrninated soils The second step of the Action Plan involved a comprehensive investigation to identify and compile existing data collect new data and revise clean-up levels Investigation activities have been completed (implementation of innovative technologies to address VOC-contarninated soils is ongoing as ERH pilot test results are still being evaluated

The following activities were identified to evaluate existing clean-up levels based on the new groundwater classification and to revise clean-up levels where necessary

in Review Site groundwater reclassiiliication bull Evaluate recent monitoring data and current Site conditions igt Identify reimiainirig or newly identified exposure pathways raquo Develop response objectives to coincide with remaining or newly identified

exposure pathways bull Evaluate the appropriateness of the groundwater leaching model and subsequent

development or application of new soil-to-groundwater modeling parameters or data as necessary and

raquo Develop revised risk-based CIJGs for aII impacted media (principally groundwaler and unsaluraled zone soils)

In order to support I he development of revised risk-based CUGs field activities were conducted at the Site between November 2000 and July 2001 These activities also helped to delineate areas of soil excavation and the size and extent of the VOC source area The results of these field activities showed heterogeneous groundwater and soil

contamination consisting of VUCs SVUUs RGBs metals polycydic aromatic Tyclrocarbons (PAHs) and diogtunfurans on and oft the Silresirn property

The risk-based CUGs do not show an overall increasing or decreasing trend as compared to the 1991 ROD clean-up levels because some exposure pathways were eliminated (direct ingestion of ground mailer) while others were added (indoor inhalation ofVOCs)

In June 2003 the revised risk-based CUGs were further modified to reflect cuinrent EPA risk assessment guidance and protocols Specifically the carcinogenic risk goal was chaned from 10 to 10 gt and the non-carcinoeiniic hazard index was changed from 01

ecological impacts from qroundwateirl and the MADEiP Method 3 Upper ( Linrii its for soil and groundwaler The modified CUGs are identified as the

e com mended Clean-Lip Goals in Appendix A

EPA and MADEP consider the modified CUGs to be adequately protective health and the environment Additionally although not a significant change tlh of a second OLI will facilitate documenting clean-up activities at the Site

4 Revised Clean-up Gosils

tequireirnenis iuch as Dninkiino Wai or MlaxiiiTiurn ConlaiTiinant Levels and Non-zero inninant Level Goals

i I he 1999 ROD Remedy Review it was determined that certain ROD clean-up levels were based on assumptions thai were no longer appropriate and therefore required

ground water needed to be reviewed Future use exposure scenarios needed to be evaluated

raquo Changes in exposure pathways bullbullbull The extern I of the contaminated groundwater plume needed to be evaluated because il was moving faster than originally projected Potential off-property subsurface soil con lamina ion needed to be evaluated

gt Evolution of the technical approaches for Supeirfund risk assessment - The vapor rni grain on model and the methodology for selecting COPCs were no longer currenl and

raquo Specific technical issues relating to toxicily estimates - The use of toxicity surrogates for PAHs and dioxin was no longer recommended or necessary

Necessary updates for calculating revised CUGs included

ltgt Evaluating the subsurface soil to indoor air pathway for the commercialindustrial worker

ltbull Evaluating additional chemicals the inhalation palhways and igt Evaluating a child recreational receptor in the event thai I he Silresirn property or

adjacent properties are redeveloped for recreational use (eg soccer field) The potenlial exists for this type of development however since the area is currently

are summarized below Overall the chainpes in risk assumptions regarding groundwaler soil and air exposures at the Site significantly impact the CIJGs for a ariely of contaminants

Current Land Use and Site Conditions The approximate 16-acre Site is located in a heavily industrialized section of Lowell

storage facilities tractor-trailer storage light industrycommercial corido minium bull and open industrial land As a result oi MADEPs Ground water Use andl Value Deteinrimiriation IvIADEP has stipulated that ground water in the area would not be used as a drin king water source in I he failure This determination constitutes a significant change from the drinking water classification used to establish the 1991 ROD clean-up levels

The reasonaby foreseeable future land use designation for the Site is coinnnTiercialindustrial Soils with residual contamination above the CUGs will be excavated stabilized and capped on the Silresirn property Future exposures to soil or exposed groundwateir are considered possible even though the cap will likely extend over the entire Siliresim property A potential future recreational use scenario was also evaluated

The commercial industrial properties surrounding the Silresirn properly also are expected to continue to be used for cornnnieircialindustrial purposes in the foreseeable future However future renovation or redevelopment of these properties is considered possible including construction of new buildings with basements The BSIVI railroad coinridor adjacent to the Siliresim property on the eastern side is also assumed to remain a railroad corridor for the foreseeable future Ground water is assumed to remain unused for consumptive and non-consumptive uses in the future (ie for drinking or induslriaJ process uses) due to MADEPs Groundwateir Use and Value Determination coupled with the relatively low yield of the shallowest water bearing layers While this assumption appears reasonable given this classification no formal restrictions or institutional controls have been established to ensure thai the ground water us not used for consumptive or non-consumptive purposes or that future land use does not involve contact with potentially contaminated soils

An exposure pathway describes the physical linkage between the source of a COPC and a current or projected future exposed receptor The potential human receptors that have been identified at this Site (under cuinrent and reasonably anticipated future exposure scenarios include com mercia Iindustrial workers railroad workers construction worke rs (eg new facility construction or uliilrry installlatiionrnaintenance workers) and

12

trespassers These potential human receptors may come in contact with surface soil (0 1 fl bgs) exposed subsurface soil as a result of excavation (unsaturated soil gtl ft bg and lt 10 fl bgs) groundwater and ambient or indoor air containing contaminant origin calling from the Sule The potential routes of exposure are incidental iingestiioi inhalation of partioulales or wolallies and dermal absorption These exposure route were also evaluated for a potential future recreational use scenario II should be note that leaching from soil to g round water is no longisir conside1 red a risk becauslt groundwater us no longer a potential drinking water source The pathway of most concern is through VOC emissions from contaminated giroundwater and subsequent diffusion upward into ambient and indoor air

now rrsK-oaseci nuiiiDers

WiOiMl CitiiribJii Units

Under this BSD I he Site will be divided into two Oils to facilitate docuinnentinq clean-up activities as defined below

approximately 12 Ions of subsurface VUC conlarninalicri However operalion of the SVE svsterin was placed on hold because it was unlike v that it would be able to reac Site CUGs

comply wnlh Federal and Slate requirement that are applicable or relevant and appropriate and are co si-effective The revised remedy utilizes permanent solutions

This E gt[) and supporting in formal ion are available for public review at the location lentiHied within this document In addition a notice of availability of the BS

piwided to a local newspaper of general circulation

or the foregoing reasons by my signature below I approve the iissuance of lt= llxplainiation oi Significant Differences tor the Silresirn Chemical Corporation Supeirfunc Site in Lowell Massachusetts and the changes and conclusions staled1 therein

Sus^h Studlieri Acting Director Office of Site Remediation and Restoration USE PA Region I

ADFIII si LOCS Draquo

lti

lii

pound j2bull

LLJ

(o (1) -c

C

c^

(ti b a

bull|lhraquo

r1uii1ijlagt

ltis

iraquo bull-

shy

b gt

craquo i[i

i deg bullgt

fdJr 111

| raquoS-shy I- i]j

-i 3 o a

i

ltgt HI

i -is D

c J

iii i ltgt

bull -3

i g

w

(3i

3 w

j|

laquopound e

fi (I laquo gt

iii

ijj IJL

bullbullbull ID $

O

inE

ij-O

j0o

shy

S = bull

ii S lt

bull lt[

nil (L)

jii[bullbull bull -i

n|gt

tri bullF1

igtraquot

E a

ir ii III Jl

CObullar

cgt CO^j

ugt

J

Ji

b(i ltLI

u (pound lt UI upi lt

=i bull - 1 -shyj 3 iij shy| IS |i i i = gt|i |igt D e~ ti bull bull bull (3pound

- jj ^3 -3 sshy (i i- ~ S = a ]=shy s= 7 lttrade ==

(IJ f rgt 3 I-shy shy rtl -r-i bull bull 11 -13 i bull shy 3 gtbull iamp bullbullbull gt (IJ S l 4l - rr bull TI i shy ni -- bullbullbull |= SJ b iii -5 L J $ ij ij i-iP J1 S sL e3 1 1 laquo laquo E Qlt1) E ii i ii-1 p MI ishy j t shy

= s ^ i = t t = i i pound t1

o ltgt o s 2 ltN3 w J bullbull = ^j

cu CL ]

^ 0

[ fir ]bullbullbull [ ltu

(3

[ii 11 D L^tl

(LJ

U 1 I

y J

I (IDE ii

]laquo

illSti

ii z 1 9

-L

C

IJLI LLI

=

iJUil ii(i

FOSTE R WH E E L E R E N VI RON M ENTA L CO R PORATI ON

The purpose of t h i s memorandum is to sinnraariltltbull I be re corn mended Clean-Dp GoEils (CUGs) f o r the s u r f a c e soil subsurface soi l and groundwater related to i he Si l res im Superfund Site im support of an Explanation of Significant Difference (BSD) The r isk-based ( LGs were or ig inal ly presented in the FniEil Add il lona I Site ID vesl igat ion and Re v is ion o f Si te C lean-Up (ioal s (Eosler Wheel er 2002) T hese CIJG s ivere discussed r e f ined ar id then compared to site da ta Appl icable or Relevant and Appropr ia te Requirements (ARARs) and curreni ROD cleanup levels fhe fo l lowing presents the c r i l e n a used lo develop the recommended CUGs (as cogtrnpairedto the current KOI) c l e a n u p levels)

bulli An updated IJSEPA COC screening and se lec t ion process was used (USEPA 1989 1 9 9 5 1999)

laquo The evaluat ion of the carcinogenic and non-cEireinogeriic polycyclic aromatic hydrocarbon (PAH) conipounds vas performed individually i n s t e a d of as EI g-roup ( U S E P A 1994 200 I a)

bulli T he upda ted cle rma I ris k asse ssrnenl guidance (FAGS Pa rt E) wa s applied (USE PA 2 GO1 b)

laquo The USE A Adult Lead Model was used to calculate soil lead c o n c e n t r a t i o n s associated with a (Ei rge t blood lead level and exposure parameter (USKPA 1996)

laquo The updated guidance for r isk assessment o f lt Eire moge n ic polyclhlorinated biphenylsi (PC Eh) wasiised(NCEA 1996)

Updated lox ico log ica l factors and parameters were usedl (USEPA 1997a 200la and MADEP 1 9 9 4 )

i A target r i sk goal of 1 E-5 and a target haard mdelt of 1 was used for each chernncal (d i rec t ion from USE PA Region 1 Site Manager)

laquo An assumption was made l l i E i t suirface soil consists of the soil between () -shy 1 ft bgs and lhal subsurface ur isa tura ted soil consists of the soil between 1 shy 10 fit bgs (USE PA I99 i )

laquo The Site ground w a t e r was reclassified as being low use and va lue nn a MA13EP Groun d w aie r Use and Val ue Detenminail ion (1VIA DEiF 1998)

laquo Leaching f rom s u b s u r f a c e (unsaturated) soil to ground wa te r was not considered EI critical consideration in setting sub- u r fE ice sioil CUGs (Fo- kT Wheeler 1999 2002)

laquo Commercial industr ia l l a n d use was assumed instead of r e s iden t i a l land use (foster Wheeler 19992002)

laquo The subsur face vapor in t rus ion to indoor air was e v E i l u a t e d as EI primary mbalEi t ion exposure ran te (Foste r W bee ler 2002 D SEP A 1997b)

ltbull Potential exposures to a construction worker w e r tr^aluated for soil and Birouridwater (Foster W h e e l e r 2002)

laquo Potential exposures to a trespasser were evaluated for so i l (Foster Wheeler 2 0 0 2 )

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

lipiing vapor extraction vent piping natural gas potable water and sewer lines power lines and process control wiring

ltlaquo Overhead and underground high voltage power lines and I An interim passive cap venting system

The Site and its surrounding areas have been used for industrial activities since the early 1900s From 1916 to 1971 several petroleum companies used I he Silresiirn property as an oil and fuel storage deoot From 1971 through 1977 Silresirn operated its chernical waste reclamation facility The facilitys primary operations included recycling and reclaiming various chemicals and consolidating wastes for off-site disposal

The Massachusetts Division of Water Pollution Control (DWPC) now Ml AD El P granted I he facility a hazardous waste colled ion and disposal permit in 1973 Wastes were accepted at the facility in drums tank trucks railiroac tanker cars and other containers These substances included halogenated solvents oi y wasles alcohols plaling wastes metal sludge and pesticide wastes Although exact figures do not exist it is estimated I hat the facility handled sipproxirnalely 3 million gallons of waste per year

I he air and sampled soils and found contamination bolh on and oil the Sliilresim property In 1984 EPA raised the height of the fence from 6 to 8 feet and covered highly contaminated areas with 9 inches of crushed gravel and a lernpoirary day cap In 1986 damage to the original fence was repaired Subsequenl sampling revealed an additional area of soil contamination that EPA enclosed In 1986 EPA discovered dioxin the fence was relocated to prevent public access and a temporary gravel cover was placed over the dioxin-cointaminated soil to prevent contact

of soil coiTlarnination The Rl identified approximately 100 individual contiaririiinanls in on-site groundwateir and soils Volatile oirganic compounds (VOCs) were the primary co ntannin an I type identified Semi-volatile orga nic compounds (SVOCs) polychlorinated biphenyls (PCBs) metals herbiciides pesticides and dioxin were also identified

In September 1991 EPA issued the ROD for the Site The remedy selected in the ROD called for in-situ SVE of contaminated soil Soils with residual contamination would be excavated stabilized and capped on-site Contaminated groundwater would be extracted and treated by nnietals removal air stripping and vapor treatment prior 1o discharge to the City sewer system

In early 1993 a Consent Decree between EPA and a group of potentially responsible parties (IPRPs) was executed Under this Consent Decree the PRPs provided approximately $40 million in clean-up funding for the Site

Management of Migration

Construction of the GWTF began in rrnid-1994 and groundwater extraction and treatment has been underway since November 1996 Initial actions to fence the Silresirn property and cap or cover areas of contamination have reduced the potential for accidental exposure and further migration of contaminated soils The temporary cap has subsequently been upgraded These actions have eliminated the immediate threats posed by the Site while final clean-up activities are underway The operation of the GWIT has several objectives as outlined in the ROD

raquo Manage the migration of contaminated groundwater toward downgradient receptors of local building basements IRiver Meadow Brook and East Pond

laquo Capture as much of the contaminated plume as possible and raquo Drawdown the groundwateir across the Site lo support the source control remedy

To date the groundwater extraction system has been unable lo achieve the drawdown objective across the Site The extraction well array and GWTF have removed a significant amount of VOCs from the groundwater plume (over 50 tons) however plume

migration has shown some increased cone en liral ions of VOCs in cerlain areas downgradient erf the Silresirn property

on ducted using three techniques conventional SVEi healed imiphase SvE In general extracted vapor flow rates

standlaird cubic leet per minute)1 and radii of influence (lt 7-lt

the additional removal of an estimated 12 Ions of VOCs from the subsurface however the effectiveness of the SVE system was limited because the Site was not sufficiently de-watered soil moisture content was very high and very low permeability soils were encountered The overall conclusion of these SVE activities was that despite the removal of relatively significant quantities of VOCs it would be unlikely I hat conventional SVE would be able to reach I he original clean-up levels for the Site

The results ol these tests are summarized in the following conclusions

laquobull SVE has the potential for significant subsurface VOC mass removal however it is not likely to reduce soil contamination to I he ROD clean-up levels within the ROD established lime frame

raquo Site conditions (high soil moisture and low soil permeability) limited SVE effectiveness in removing contaminants from the subsurface soil

laquobull High vacuum SVE and multiphase extraction were found to be ineffective technique- for removing VOCs from the soil at I he Site and

raquo Heated air injection with SVE has the potential to increase I he rale of contanminant removal fro inn the subsurface soil

ai c reatrnent alternatives was performed iipplicability for the remediation of VOCs at the Site were considered Weighing idvantages and disadvantages for each remedial option resulted in the selection of the ileclrical resistance heating (ERH) technology as the only viable option for a pilot test at

I RH is an in-situ thermal remediation technology that uses electrical heating to enhance The ERH pilot test was designed lo evaluate applicability of Site conditions reveal

itial technical difficulties and determine the effectiveness of the technology for removing subsurface contaminants to targeted levels Results of the pilot test will be used lo evaluate the ability of ERH lo overcome the limitations observed during the SVE operations and ultimately allow an effective and cost efficient scale-up lo full-scale I reatrnent The pilol test began in October 2002 and continued through early January 2003 A final report is being prepared and will be evaluated lo determine the technologys effectiveness for removing contamination on a wide area of the Site

B Summary of the Record of Decision

The ROD (signed September 19 1991) discussed the alternatives evaluated for remediating contamination at the Site and described in detail the selected remedy for I he Site The selected remedy includes a management of migration alternative (giroundwa-ter extraction metals prelreatrnent air stripping aqueous phase carbon adsorption vapor phase carbon adsorption or thermal oxidation) and a source control alternative (SVE excavation stabilization and capping on the Silresim property) lo address all contannination at the Site A detailed description of the clean-up levels and the selected remedy is presented in Section X of the ROD

To date some success has been achieved through the implementation of a number of the remedial activities inn anda led by the ROD In particular SVE has been evaluated via pilot tests and implemented in a limited area on the Site Management of migration remedial components for ground water extraction and treatment were successfully in stalled and continue to operate Operation of the GWTF and extraction wells has resulted in some VOC contaminant concentration reduction in the groundlvvater plume although the extent of the reduction varies significantly depending on the specific area of the Site In some areas ol the Site VOC concentrations have increased However it should be noted that the extraction wells and GWTF were not designed for overall plume rernediation The main objective of the GWTF and extraction wells was lo contain the groundwater plume and lo de-water the Site sufficiently to allow for remediation of soils utilizing traditional SVE

significant change EPA is also creating a second OU to bullfacilitate clocunnienling clean-up activities at I he Site The basis for modifying the 1991 ROD cl Ban-up levels is described below

chieve remedial objectives I he ROD Remedy Review recommended several changes These recommendations took inlo consideration the changes in Site cc (reclassification of groundwateir under the Site) the inability of the irnplerne lechnologies to achieve the objectives stated in the ROD sine the use of some revislt

control activities to achieve remedial objectives ol ha migration removing the contaminant source term and reducing hurnan heal ecological risk at the Site the rive-Year Review supported the recommendations ouIlliinied in the ROD Remedy Review

laquo Inability of the extraction well system to contain contaminant plume migration towards identified downg rad ie nl receptors

ii Inability of the extraction well system and GW7T to meet ROD clean-up levels within the foreseeable future

raquo Results of the 8V operations indicating thai SVE alone would not be able to reduce subsurface soil contamination to meet ROD clean-up levels within the time frame established in the ROD

ltbull Risk assessment assumptions that no longer appeared appropriate for the Site and

igt The change in the groundwater classification for the aquifer below the Site by IvIAIDEP to low use and value from its prior classification as drinking water

The first step of the Action IPIIan included an investigation focusing on strategies to control the continued migration of contaminated groundwater and to irnpilement innovative technologies to remiediale VOC-contanrninated soils The second step of the Action Plan involved a comprehensive investigation to identify and compile existing data collect new data and revise clean-up levels Investigation activities have been completed (implementation of innovative technologies to address VOC-contarninated soils is ongoing as ERH pilot test results are still being evaluated

The following activities were identified to evaluate existing clean-up levels based on the new groundwater classification and to revise clean-up levels where necessary

in Review Site groundwater reclassiiliication bull Evaluate recent monitoring data and current Site conditions igt Identify reimiainirig or newly identified exposure pathways raquo Develop response objectives to coincide with remaining or newly identified

exposure pathways bull Evaluate the appropriateness of the groundwater leaching model and subsequent

development or application of new soil-to-groundwater modeling parameters or data as necessary and

raquo Develop revised risk-based CIJGs for aII impacted media (principally groundwaler and unsaluraled zone soils)

In order to support I he development of revised risk-based CUGs field activities were conducted at the Site between November 2000 and July 2001 These activities also helped to delineate areas of soil excavation and the size and extent of the VOC source area The results of these field activities showed heterogeneous groundwater and soil

contamination consisting of VUCs SVUUs RGBs metals polycydic aromatic Tyclrocarbons (PAHs) and diogtunfurans on and oft the Silresirn property

The risk-based CUGs do not show an overall increasing or decreasing trend as compared to the 1991 ROD clean-up levels because some exposure pathways were eliminated (direct ingestion of ground mailer) while others were added (indoor inhalation ofVOCs)

In June 2003 the revised risk-based CUGs were further modified to reflect cuinrent EPA risk assessment guidance and protocols Specifically the carcinogenic risk goal was chaned from 10 to 10 gt and the non-carcinoeiniic hazard index was changed from 01

ecological impacts from qroundwateirl and the MADEiP Method 3 Upper ( Linrii its for soil and groundwaler The modified CUGs are identified as the

e com mended Clean-Lip Goals in Appendix A

EPA and MADEP consider the modified CUGs to be adequately protective health and the environment Additionally although not a significant change tlh of a second OLI will facilitate documenting clean-up activities at the Site

4 Revised Clean-up Gosils

tequireirnenis iuch as Dninkiino Wai or MlaxiiiTiurn ConlaiTiinant Levels and Non-zero inninant Level Goals

i I he 1999 ROD Remedy Review it was determined that certain ROD clean-up levels were based on assumptions thai were no longer appropriate and therefore required

ground water needed to be reviewed Future use exposure scenarios needed to be evaluated

raquo Changes in exposure pathways bullbullbull The extern I of the contaminated groundwater plume needed to be evaluated because il was moving faster than originally projected Potential off-property subsurface soil con lamina ion needed to be evaluated

gt Evolution of the technical approaches for Supeirfund risk assessment - The vapor rni grain on model and the methodology for selecting COPCs were no longer currenl and

raquo Specific technical issues relating to toxicily estimates - The use of toxicity surrogates for PAHs and dioxin was no longer recommended or necessary

Necessary updates for calculating revised CUGs included

ltgt Evaluating the subsurface soil to indoor air pathway for the commercialindustrial worker

ltbull Evaluating additional chemicals the inhalation palhways and igt Evaluating a child recreational receptor in the event thai I he Silresirn property or

adjacent properties are redeveloped for recreational use (eg soccer field) The potenlial exists for this type of development however since the area is currently

are summarized below Overall the chainpes in risk assumptions regarding groundwaler soil and air exposures at the Site significantly impact the CIJGs for a ariely of contaminants

Current Land Use and Site Conditions The approximate 16-acre Site is located in a heavily industrialized section of Lowell

storage facilities tractor-trailer storage light industrycommercial corido minium bull and open industrial land As a result oi MADEPs Ground water Use andl Value Deteinrimiriation IvIADEP has stipulated that ground water in the area would not be used as a drin king water source in I he failure This determination constitutes a significant change from the drinking water classification used to establish the 1991 ROD clean-up levels

The reasonaby foreseeable future land use designation for the Site is coinnnTiercialindustrial Soils with residual contamination above the CUGs will be excavated stabilized and capped on the Silresirn property Future exposures to soil or exposed groundwateir are considered possible even though the cap will likely extend over the entire Siliresim property A potential future recreational use scenario was also evaluated

The commercial industrial properties surrounding the Silresirn properly also are expected to continue to be used for cornnnieircialindustrial purposes in the foreseeable future However future renovation or redevelopment of these properties is considered possible including construction of new buildings with basements The BSIVI railroad coinridor adjacent to the Siliresim property on the eastern side is also assumed to remain a railroad corridor for the foreseeable future Ground water is assumed to remain unused for consumptive and non-consumptive uses in the future (ie for drinking or induslriaJ process uses) due to MADEPs Groundwateir Use and Value Determination coupled with the relatively low yield of the shallowest water bearing layers While this assumption appears reasonable given this classification no formal restrictions or institutional controls have been established to ensure thai the ground water us not used for consumptive or non-consumptive purposes or that future land use does not involve contact with potentially contaminated soils

An exposure pathway describes the physical linkage between the source of a COPC and a current or projected future exposed receptor The potential human receptors that have been identified at this Site (under cuinrent and reasonably anticipated future exposure scenarios include com mercia Iindustrial workers railroad workers construction worke rs (eg new facility construction or uliilrry installlatiionrnaintenance workers) and

12

trespassers These potential human receptors may come in contact with surface soil (0 1 fl bgs) exposed subsurface soil as a result of excavation (unsaturated soil gtl ft bg and lt 10 fl bgs) groundwater and ambient or indoor air containing contaminant origin calling from the Sule The potential routes of exposure are incidental iingestiioi inhalation of partioulales or wolallies and dermal absorption These exposure route were also evaluated for a potential future recreational use scenario II should be note that leaching from soil to g round water is no longisir conside1 red a risk becauslt groundwater us no longer a potential drinking water source The pathway of most concern is through VOC emissions from contaminated giroundwater and subsequent diffusion upward into ambient and indoor air

now rrsK-oaseci nuiiiDers

WiOiMl CitiiribJii Units

Under this BSD I he Site will be divided into two Oils to facilitate docuinnentinq clean-up activities as defined below

approximately 12 Ions of subsurface VUC conlarninalicri However operalion of the SVE svsterin was placed on hold because it was unlike v that it would be able to reac Site CUGs

comply wnlh Federal and Slate requirement that are applicable or relevant and appropriate and are co si-effective The revised remedy utilizes permanent solutions

This E gt[) and supporting in formal ion are available for public review at the location lentiHied within this document In addition a notice of availability of the BS

piwided to a local newspaper of general circulation

or the foregoing reasons by my signature below I approve the iissuance of lt= llxplainiation oi Significant Differences tor the Silresirn Chemical Corporation Supeirfunc Site in Lowell Massachusetts and the changes and conclusions staled1 therein

Sus^h Studlieri Acting Director Office of Site Remediation and Restoration USE PA Region I

ADFIII si LOCS Draquo

lti

lii

pound j2bull

LLJ

(o (1) -c

C

c^

(ti b a

bull|lhraquo

r1uii1ijlagt

ltis

iraquo bull-

shy

b gt

craquo i[i

i deg bullgt

fdJr 111

| raquoS-shy I- i]j

-i 3 o a

i

ltgt HI

i -is D

c J

iii i ltgt

bull -3

i g

w

(3i

3 w

j|

laquopound e

fi (I laquo gt

iii

ijj IJL

bullbullbull ID $

O

inE

ij-O

j0o

shy

S = bull

ii S lt

bull lt[

nil (L)

jii[bullbull bull -i

n|gt

tri bullF1

igtraquot

E a

ir ii III Jl

CObullar

cgt CO^j

ugt

J

Ji

b(i ltLI

u (pound lt UI upi lt

=i bull - 1 -shyj 3 iij shy| IS |i i i = gt|i |igt D e~ ti bull bull bull (3pound

- jj ^3 -3 sshy (i i- ~ S = a ]=shy s= 7 lttrade ==

(IJ f rgt 3 I-shy shy rtl -r-i bull bull 11 -13 i bull shy 3 gtbull iamp bullbullbull gt (IJ S l 4l - rr bull TI i shy ni -- bullbullbull |= SJ b iii -5 L J $ ij ij i-iP J1 S sL e3 1 1 laquo laquo E Qlt1) E ii i ii-1 p MI ishy j t shy

= s ^ i = t t = i i pound t1

o ltgt o s 2 ltN3 w J bullbull = ^j

cu CL ]

^ 0

[ fir ]bullbullbull [ ltu

(3

[ii 11 D L^tl

(LJ

U 1 I

y J

I (IDE ii

]laquo

illSti

ii z 1 9

-L

C

IJLI LLI

=

iJUil ii(i

FOSTE R WH E E L E R E N VI RON M ENTA L CO R PORATI ON

The purpose of t h i s memorandum is to sinnraariltltbull I be re corn mended Clean-Dp GoEils (CUGs) f o r the s u r f a c e soil subsurface soi l and groundwater related to i he Si l res im Superfund Site im support of an Explanation of Significant Difference (BSD) The r isk-based ( LGs were or ig inal ly presented in the FniEil Add il lona I Site ID vesl igat ion and Re v is ion o f Si te C lean-Up (ioal s (Eosler Wheel er 2002) T hese CIJG s ivere discussed r e f ined ar id then compared to site da ta Appl icable or Relevant and Appropr ia te Requirements (ARARs) and curreni ROD cleanup levels fhe fo l lowing presents the c r i l e n a used lo develop the recommended CUGs (as cogtrnpairedto the current KOI) c l e a n u p levels)

bulli An updated IJSEPA COC screening and se lec t ion process was used (USEPA 1989 1 9 9 5 1999)

laquo The evaluat ion of the carcinogenic and non-cEireinogeriic polycyclic aromatic hydrocarbon (PAH) conipounds vas performed individually i n s t e a d of as EI g-roup ( U S E P A 1994 200 I a)

bulli T he upda ted cle rma I ris k asse ssrnenl guidance (FAGS Pa rt E) wa s applied (USE PA 2 GO1 b)

laquo The USE A Adult Lead Model was used to calculate soil lead c o n c e n t r a t i o n s associated with a (Ei rge t blood lead level and exposure parameter (USKPA 1996)

laquo The updated guidance for r isk assessment o f lt Eire moge n ic polyclhlorinated biphenylsi (PC Eh) wasiised(NCEA 1996)

Updated lox ico log ica l factors and parameters were usedl (USEPA 1997a 200la and MADEP 1 9 9 4 )

i A target r i sk goal of 1 E-5 and a target haard mdelt of 1 was used for each chernncal (d i rec t ion from USE PA Region 1 Site Manager)

laquo An assumption was made l l i E i t suirface soil consists of the soil between () -shy 1 ft bgs and lhal subsurface ur isa tura ted soil consists of the soil between 1 shy 10 fit bgs (USE PA I99 i )

laquo The Site ground w a t e r was reclassified as being low use and va lue nn a MA13EP Groun d w aie r Use and Val ue Detenminail ion (1VIA DEiF 1998)

laquo Leaching f rom s u b s u r f a c e (unsaturated) soil to ground wa te r was not considered EI critical consideration in setting sub- u r fE ice sioil CUGs (Fo- kT Wheeler 1999 2002)

laquo Commercial industr ia l l a n d use was assumed instead of r e s iden t i a l land use (foster Wheeler 19992002)

laquo The subsur face vapor in t rus ion to indoor air was e v E i l u a t e d as EI primary mbalEi t ion exposure ran te (Foste r W bee ler 2002 D SEP A 1997b)

ltbull Potential exposures to a construction worker w e r tr^aluated for soil and Birouridwater (Foster W h e e l e r 2002)

laquo Potential exposures to a trespasser were evaluated for so i l (Foster Wheeler 2 0 0 2 )

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

of soil coiTlarnination The Rl identified approximately 100 individual contiaririiinanls in on-site groundwateir and soils Volatile oirganic compounds (VOCs) were the primary co ntannin an I type identified Semi-volatile orga nic compounds (SVOCs) polychlorinated biphenyls (PCBs) metals herbiciides pesticides and dioxin were also identified

In September 1991 EPA issued the ROD for the Site The remedy selected in the ROD called for in-situ SVE of contaminated soil Soils with residual contamination would be excavated stabilized and capped on-site Contaminated groundwater would be extracted and treated by nnietals removal air stripping and vapor treatment prior 1o discharge to the City sewer system

In early 1993 a Consent Decree between EPA and a group of potentially responsible parties (IPRPs) was executed Under this Consent Decree the PRPs provided approximately $40 million in clean-up funding for the Site

Management of Migration

Construction of the GWTF began in rrnid-1994 and groundwater extraction and treatment has been underway since November 1996 Initial actions to fence the Silresirn property and cap or cover areas of contamination have reduced the potential for accidental exposure and further migration of contaminated soils The temporary cap has subsequently been upgraded These actions have eliminated the immediate threats posed by the Site while final clean-up activities are underway The operation of the GWIT has several objectives as outlined in the ROD

raquo Manage the migration of contaminated groundwater toward downgradient receptors of local building basements IRiver Meadow Brook and East Pond

laquo Capture as much of the contaminated plume as possible and raquo Drawdown the groundwateir across the Site lo support the source control remedy

To date the groundwater extraction system has been unable lo achieve the drawdown objective across the Site The extraction well array and GWTF have removed a significant amount of VOCs from the groundwater plume (over 50 tons) however plume

migration has shown some increased cone en liral ions of VOCs in cerlain areas downgradient erf the Silresirn property

on ducted using three techniques conventional SVEi healed imiphase SvE In general extracted vapor flow rates

standlaird cubic leet per minute)1 and radii of influence (lt 7-lt

the additional removal of an estimated 12 Ions of VOCs from the subsurface however the effectiveness of the SVE system was limited because the Site was not sufficiently de-watered soil moisture content was very high and very low permeability soils were encountered The overall conclusion of these SVE activities was that despite the removal of relatively significant quantities of VOCs it would be unlikely I hat conventional SVE would be able to reach I he original clean-up levels for the Site

The results ol these tests are summarized in the following conclusions

laquobull SVE has the potential for significant subsurface VOC mass removal however it is not likely to reduce soil contamination to I he ROD clean-up levels within the ROD established lime frame

raquo Site conditions (high soil moisture and low soil permeability) limited SVE effectiveness in removing contaminants from the subsurface soil

laquobull High vacuum SVE and multiphase extraction were found to be ineffective technique- for removing VOCs from the soil at I he Site and

raquo Heated air injection with SVE has the potential to increase I he rale of contanminant removal fro inn the subsurface soil

ai c reatrnent alternatives was performed iipplicability for the remediation of VOCs at the Site were considered Weighing idvantages and disadvantages for each remedial option resulted in the selection of the ileclrical resistance heating (ERH) technology as the only viable option for a pilot test at

I RH is an in-situ thermal remediation technology that uses electrical heating to enhance The ERH pilot test was designed lo evaluate applicability of Site conditions reveal

itial technical difficulties and determine the effectiveness of the technology for removing subsurface contaminants to targeted levels Results of the pilot test will be used lo evaluate the ability of ERH lo overcome the limitations observed during the SVE operations and ultimately allow an effective and cost efficient scale-up lo full-scale I reatrnent The pilol test began in October 2002 and continued through early January 2003 A final report is being prepared and will be evaluated lo determine the technologys effectiveness for removing contamination on a wide area of the Site

B Summary of the Record of Decision

The ROD (signed September 19 1991) discussed the alternatives evaluated for remediating contamination at the Site and described in detail the selected remedy for I he Site The selected remedy includes a management of migration alternative (giroundwa-ter extraction metals prelreatrnent air stripping aqueous phase carbon adsorption vapor phase carbon adsorption or thermal oxidation) and a source control alternative (SVE excavation stabilization and capping on the Silresim property) lo address all contannination at the Site A detailed description of the clean-up levels and the selected remedy is presented in Section X of the ROD

To date some success has been achieved through the implementation of a number of the remedial activities inn anda led by the ROD In particular SVE has been evaluated via pilot tests and implemented in a limited area on the Site Management of migration remedial components for ground water extraction and treatment were successfully in stalled and continue to operate Operation of the GWTF and extraction wells has resulted in some VOC contaminant concentration reduction in the groundlvvater plume although the extent of the reduction varies significantly depending on the specific area of the Site In some areas ol the Site VOC concentrations have increased However it should be noted that the extraction wells and GWTF were not designed for overall plume rernediation The main objective of the GWTF and extraction wells was lo contain the groundwater plume and lo de-water the Site sufficiently to allow for remediation of soils utilizing traditional SVE

significant change EPA is also creating a second OU to bullfacilitate clocunnienling clean-up activities at I he Site The basis for modifying the 1991 ROD cl Ban-up levels is described below

chieve remedial objectives I he ROD Remedy Review recommended several changes These recommendations took inlo consideration the changes in Site cc (reclassification of groundwateir under the Site) the inability of the irnplerne lechnologies to achieve the objectives stated in the ROD sine the use of some revislt

control activities to achieve remedial objectives ol ha migration removing the contaminant source term and reducing hurnan heal ecological risk at the Site the rive-Year Review supported the recommendations ouIlliinied in the ROD Remedy Review

laquo Inability of the extraction well system to contain contaminant plume migration towards identified downg rad ie nl receptors

ii Inability of the extraction well system and GW7T to meet ROD clean-up levels within the foreseeable future

raquo Results of the 8V operations indicating thai SVE alone would not be able to reduce subsurface soil contamination to meet ROD clean-up levels within the time frame established in the ROD

ltbull Risk assessment assumptions that no longer appeared appropriate for the Site and

igt The change in the groundwater classification for the aquifer below the Site by IvIAIDEP to low use and value from its prior classification as drinking water

The first step of the Action IPIIan included an investigation focusing on strategies to control the continued migration of contaminated groundwater and to irnpilement innovative technologies to remiediale VOC-contanrninated soils The second step of the Action Plan involved a comprehensive investigation to identify and compile existing data collect new data and revise clean-up levels Investigation activities have been completed (implementation of innovative technologies to address VOC-contarninated soils is ongoing as ERH pilot test results are still being evaluated

The following activities were identified to evaluate existing clean-up levels based on the new groundwater classification and to revise clean-up levels where necessary

in Review Site groundwater reclassiiliication bull Evaluate recent monitoring data and current Site conditions igt Identify reimiainirig or newly identified exposure pathways raquo Develop response objectives to coincide with remaining or newly identified

exposure pathways bull Evaluate the appropriateness of the groundwater leaching model and subsequent

development or application of new soil-to-groundwater modeling parameters or data as necessary and

raquo Develop revised risk-based CIJGs for aII impacted media (principally groundwaler and unsaluraled zone soils)

In order to support I he development of revised risk-based CUGs field activities were conducted at the Site between November 2000 and July 2001 These activities also helped to delineate areas of soil excavation and the size and extent of the VOC source area The results of these field activities showed heterogeneous groundwater and soil

contamination consisting of VUCs SVUUs RGBs metals polycydic aromatic Tyclrocarbons (PAHs) and diogtunfurans on and oft the Silresirn property

The risk-based CUGs do not show an overall increasing or decreasing trend as compared to the 1991 ROD clean-up levels because some exposure pathways were eliminated (direct ingestion of ground mailer) while others were added (indoor inhalation ofVOCs)

In June 2003 the revised risk-based CUGs were further modified to reflect cuinrent EPA risk assessment guidance and protocols Specifically the carcinogenic risk goal was chaned from 10 to 10 gt and the non-carcinoeiniic hazard index was changed from 01

ecological impacts from qroundwateirl and the MADEiP Method 3 Upper ( Linrii its for soil and groundwaler The modified CUGs are identified as the

e com mended Clean-Lip Goals in Appendix A

EPA and MADEP consider the modified CUGs to be adequately protective health and the environment Additionally although not a significant change tlh of a second OLI will facilitate documenting clean-up activities at the Site

4 Revised Clean-up Gosils

tequireirnenis iuch as Dninkiino Wai or MlaxiiiTiurn ConlaiTiinant Levels and Non-zero inninant Level Goals

i I he 1999 ROD Remedy Review it was determined that certain ROD clean-up levels were based on assumptions thai were no longer appropriate and therefore required

ground water needed to be reviewed Future use exposure scenarios needed to be evaluated

raquo Changes in exposure pathways bullbullbull The extern I of the contaminated groundwater plume needed to be evaluated because il was moving faster than originally projected Potential off-property subsurface soil con lamina ion needed to be evaluated

gt Evolution of the technical approaches for Supeirfund risk assessment - The vapor rni grain on model and the methodology for selecting COPCs were no longer currenl and

raquo Specific technical issues relating to toxicily estimates - The use of toxicity surrogates for PAHs and dioxin was no longer recommended or necessary

Necessary updates for calculating revised CUGs included

ltgt Evaluating the subsurface soil to indoor air pathway for the commercialindustrial worker

ltbull Evaluating additional chemicals the inhalation palhways and igt Evaluating a child recreational receptor in the event thai I he Silresirn property or

adjacent properties are redeveloped for recreational use (eg soccer field) The potenlial exists for this type of development however since the area is currently

are summarized below Overall the chainpes in risk assumptions regarding groundwaler soil and air exposures at the Site significantly impact the CIJGs for a ariely of contaminants

Current Land Use and Site Conditions The approximate 16-acre Site is located in a heavily industrialized section of Lowell

storage facilities tractor-trailer storage light industrycommercial corido minium bull and open industrial land As a result oi MADEPs Ground water Use andl Value Deteinrimiriation IvIADEP has stipulated that ground water in the area would not be used as a drin king water source in I he failure This determination constitutes a significant change from the drinking water classification used to establish the 1991 ROD clean-up levels

The reasonaby foreseeable future land use designation for the Site is coinnnTiercialindustrial Soils with residual contamination above the CUGs will be excavated stabilized and capped on the Silresirn property Future exposures to soil or exposed groundwateir are considered possible even though the cap will likely extend over the entire Siliresim property A potential future recreational use scenario was also evaluated

The commercial industrial properties surrounding the Silresirn properly also are expected to continue to be used for cornnnieircialindustrial purposes in the foreseeable future However future renovation or redevelopment of these properties is considered possible including construction of new buildings with basements The BSIVI railroad coinridor adjacent to the Siliresim property on the eastern side is also assumed to remain a railroad corridor for the foreseeable future Ground water is assumed to remain unused for consumptive and non-consumptive uses in the future (ie for drinking or induslriaJ process uses) due to MADEPs Groundwateir Use and Value Determination coupled with the relatively low yield of the shallowest water bearing layers While this assumption appears reasonable given this classification no formal restrictions or institutional controls have been established to ensure thai the ground water us not used for consumptive or non-consumptive purposes or that future land use does not involve contact with potentially contaminated soils

An exposure pathway describes the physical linkage between the source of a COPC and a current or projected future exposed receptor The potential human receptors that have been identified at this Site (under cuinrent and reasonably anticipated future exposure scenarios include com mercia Iindustrial workers railroad workers construction worke rs (eg new facility construction or uliilrry installlatiionrnaintenance workers) and

12

trespassers These potential human receptors may come in contact with surface soil (0 1 fl bgs) exposed subsurface soil as a result of excavation (unsaturated soil gtl ft bg and lt 10 fl bgs) groundwater and ambient or indoor air containing contaminant origin calling from the Sule The potential routes of exposure are incidental iingestiioi inhalation of partioulales or wolallies and dermal absorption These exposure route were also evaluated for a potential future recreational use scenario II should be note that leaching from soil to g round water is no longisir conside1 red a risk becauslt groundwater us no longer a potential drinking water source The pathway of most concern is through VOC emissions from contaminated giroundwater and subsequent diffusion upward into ambient and indoor air

now rrsK-oaseci nuiiiDers

WiOiMl CitiiribJii Units

Under this BSD I he Site will be divided into two Oils to facilitate docuinnentinq clean-up activities as defined below

approximately 12 Ions of subsurface VUC conlarninalicri However operalion of the SVE svsterin was placed on hold because it was unlike v that it would be able to reac Site CUGs

comply wnlh Federal and Slate requirement that are applicable or relevant and appropriate and are co si-effective The revised remedy utilizes permanent solutions

This E gt[) and supporting in formal ion are available for public review at the location lentiHied within this document In addition a notice of availability of the BS

piwided to a local newspaper of general circulation

or the foregoing reasons by my signature below I approve the iissuance of lt= llxplainiation oi Significant Differences tor the Silresirn Chemical Corporation Supeirfunc Site in Lowell Massachusetts and the changes and conclusions staled1 therein

Sus^h Studlieri Acting Director Office of Site Remediation and Restoration USE PA Region I

ADFIII si LOCS Draquo

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lii

pound j2bull

LLJ

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r1uii1ijlagt

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shy

b gt

craquo i[i

i deg bullgt

fdJr 111

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-i 3 o a

i

ltgt HI

i -is D

c J

iii i ltgt

bull -3

i g

w

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3 w

j|

laquopound e

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iii

ijj IJL

bullbullbull ID $

O

inE

ij-O

j0o

shy

S = bull

ii S lt

bull lt[

nil (L)

jii[bullbull bull -i

n|gt

tri bullF1

igtraquot

E a

ir ii III Jl

CObullar

cgt CO^j

ugt

J

Ji

b(i ltLI

u (pound lt UI upi lt

=i bull - 1 -shyj 3 iij shy| IS |i i i = gt|i |igt D e~ ti bull bull bull (3pound

- jj ^3 -3 sshy (i i- ~ S = a ]=shy s= 7 lttrade ==

(IJ f rgt 3 I-shy shy rtl -r-i bull bull 11 -13 i bull shy 3 gtbull iamp bullbullbull gt (IJ S l 4l - rr bull TI i shy ni -- bullbullbull |= SJ b iii -5 L J $ ij ij i-iP J1 S sL e3 1 1 laquo laquo E Qlt1) E ii i ii-1 p MI ishy j t shy

= s ^ i = t t = i i pound t1

o ltgt o s 2 ltN3 w J bullbull = ^j

cu CL ]

^ 0

[ fir ]bullbullbull [ ltu

(3

[ii 11 D L^tl

(LJ

U 1 I

y J

I (IDE ii

]laquo

illSti

ii z 1 9

-L

C

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=

iJUil ii(i

FOSTE R WH E E L E R E N VI RON M ENTA L CO R PORATI ON

The purpose of t h i s memorandum is to sinnraariltltbull I be re corn mended Clean-Dp GoEils (CUGs) f o r the s u r f a c e soil subsurface soi l and groundwater related to i he Si l res im Superfund Site im support of an Explanation of Significant Difference (BSD) The r isk-based ( LGs were or ig inal ly presented in the FniEil Add il lona I Site ID vesl igat ion and Re v is ion o f Si te C lean-Up (ioal s (Eosler Wheel er 2002) T hese CIJG s ivere discussed r e f ined ar id then compared to site da ta Appl icable or Relevant and Appropr ia te Requirements (ARARs) and curreni ROD cleanup levels fhe fo l lowing presents the c r i l e n a used lo develop the recommended CUGs (as cogtrnpairedto the current KOI) c l e a n u p levels)

bulli An updated IJSEPA COC screening and se lec t ion process was used (USEPA 1989 1 9 9 5 1999)

laquo The evaluat ion of the carcinogenic and non-cEireinogeriic polycyclic aromatic hydrocarbon (PAH) conipounds vas performed individually i n s t e a d of as EI g-roup ( U S E P A 1994 200 I a)

bulli T he upda ted cle rma I ris k asse ssrnenl guidance (FAGS Pa rt E) wa s applied (USE PA 2 GO1 b)

laquo The USE A Adult Lead Model was used to calculate soil lead c o n c e n t r a t i o n s associated with a (Ei rge t blood lead level and exposure parameter (USKPA 1996)

laquo The updated guidance for r isk assessment o f lt Eire moge n ic polyclhlorinated biphenylsi (PC Eh) wasiised(NCEA 1996)

Updated lox ico log ica l factors and parameters were usedl (USEPA 1997a 200la and MADEP 1 9 9 4 )

i A target r i sk goal of 1 E-5 and a target haard mdelt of 1 was used for each chernncal (d i rec t ion from USE PA Region 1 Site Manager)

laquo An assumption was made l l i E i t suirface soil consists of the soil between () -shy 1 ft bgs and lhal subsurface ur isa tura ted soil consists of the soil between 1 shy 10 fit bgs (USE PA I99 i )

laquo The Site ground w a t e r was reclassified as being low use and va lue nn a MA13EP Groun d w aie r Use and Val ue Detenminail ion (1VIA DEiF 1998)

laquo Leaching f rom s u b s u r f a c e (unsaturated) soil to ground wa te r was not considered EI critical consideration in setting sub- u r fE ice sioil CUGs (Fo- kT Wheeler 1999 2002)

laquo Commercial industr ia l l a n d use was assumed instead of r e s iden t i a l land use (foster Wheeler 19992002)

laquo The subsur face vapor in t rus ion to indoor air was e v E i l u a t e d as EI primary mbalEi t ion exposure ran te (Foste r W bee ler 2002 D SEP A 1997b)

ltbull Potential exposures to a construction worker w e r tr^aluated for soil and Birouridwater (Foster W h e e l e r 2002)

laquo Potential exposures to a trespasser were evaluated for so i l (Foster Wheeler 2 0 0 2 )

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

migration has shown some increased cone en liral ions of VOCs in cerlain areas downgradient erf the Silresirn property

on ducted using three techniques conventional SVEi healed imiphase SvE In general extracted vapor flow rates

standlaird cubic leet per minute)1 and radii of influence (lt 7-lt

the additional removal of an estimated 12 Ions of VOCs from the subsurface however the effectiveness of the SVE system was limited because the Site was not sufficiently de-watered soil moisture content was very high and very low permeability soils were encountered The overall conclusion of these SVE activities was that despite the removal of relatively significant quantities of VOCs it would be unlikely I hat conventional SVE would be able to reach I he original clean-up levels for the Site

The results ol these tests are summarized in the following conclusions

laquobull SVE has the potential for significant subsurface VOC mass removal however it is not likely to reduce soil contamination to I he ROD clean-up levels within the ROD established lime frame

raquo Site conditions (high soil moisture and low soil permeability) limited SVE effectiveness in removing contaminants from the subsurface soil

laquobull High vacuum SVE and multiphase extraction were found to be ineffective technique- for removing VOCs from the soil at I he Site and

raquo Heated air injection with SVE has the potential to increase I he rale of contanminant removal fro inn the subsurface soil

ai c reatrnent alternatives was performed iipplicability for the remediation of VOCs at the Site were considered Weighing idvantages and disadvantages for each remedial option resulted in the selection of the ileclrical resistance heating (ERH) technology as the only viable option for a pilot test at

I RH is an in-situ thermal remediation technology that uses electrical heating to enhance The ERH pilot test was designed lo evaluate applicability of Site conditions reveal

itial technical difficulties and determine the effectiveness of the technology for removing subsurface contaminants to targeted levels Results of the pilot test will be used lo evaluate the ability of ERH lo overcome the limitations observed during the SVE operations and ultimately allow an effective and cost efficient scale-up lo full-scale I reatrnent The pilol test began in October 2002 and continued through early January 2003 A final report is being prepared and will be evaluated lo determine the technologys effectiveness for removing contamination on a wide area of the Site

B Summary of the Record of Decision

The ROD (signed September 19 1991) discussed the alternatives evaluated for remediating contamination at the Site and described in detail the selected remedy for I he Site The selected remedy includes a management of migration alternative (giroundwa-ter extraction metals prelreatrnent air stripping aqueous phase carbon adsorption vapor phase carbon adsorption or thermal oxidation) and a source control alternative (SVE excavation stabilization and capping on the Silresim property) lo address all contannination at the Site A detailed description of the clean-up levels and the selected remedy is presented in Section X of the ROD

To date some success has been achieved through the implementation of a number of the remedial activities inn anda led by the ROD In particular SVE has been evaluated via pilot tests and implemented in a limited area on the Site Management of migration remedial components for ground water extraction and treatment were successfully in stalled and continue to operate Operation of the GWTF and extraction wells has resulted in some VOC contaminant concentration reduction in the groundlvvater plume although the extent of the reduction varies significantly depending on the specific area of the Site In some areas ol the Site VOC concentrations have increased However it should be noted that the extraction wells and GWTF were not designed for overall plume rernediation The main objective of the GWTF and extraction wells was lo contain the groundwater plume and lo de-water the Site sufficiently to allow for remediation of soils utilizing traditional SVE

significant change EPA is also creating a second OU to bullfacilitate clocunnienling clean-up activities at I he Site The basis for modifying the 1991 ROD cl Ban-up levels is described below

chieve remedial objectives I he ROD Remedy Review recommended several changes These recommendations took inlo consideration the changes in Site cc (reclassification of groundwateir under the Site) the inability of the irnplerne lechnologies to achieve the objectives stated in the ROD sine the use of some revislt

control activities to achieve remedial objectives ol ha migration removing the contaminant source term and reducing hurnan heal ecological risk at the Site the rive-Year Review supported the recommendations ouIlliinied in the ROD Remedy Review

laquo Inability of the extraction well system to contain contaminant plume migration towards identified downg rad ie nl receptors

ii Inability of the extraction well system and GW7T to meet ROD clean-up levels within the foreseeable future

raquo Results of the 8V operations indicating thai SVE alone would not be able to reduce subsurface soil contamination to meet ROD clean-up levels within the time frame established in the ROD

ltbull Risk assessment assumptions that no longer appeared appropriate for the Site and

igt The change in the groundwater classification for the aquifer below the Site by IvIAIDEP to low use and value from its prior classification as drinking water

The first step of the Action IPIIan included an investigation focusing on strategies to control the continued migration of contaminated groundwater and to irnpilement innovative technologies to remiediale VOC-contanrninated soils The second step of the Action Plan involved a comprehensive investigation to identify and compile existing data collect new data and revise clean-up levels Investigation activities have been completed (implementation of innovative technologies to address VOC-contarninated soils is ongoing as ERH pilot test results are still being evaluated

The following activities were identified to evaluate existing clean-up levels based on the new groundwater classification and to revise clean-up levels where necessary

in Review Site groundwater reclassiiliication bull Evaluate recent monitoring data and current Site conditions igt Identify reimiainirig or newly identified exposure pathways raquo Develop response objectives to coincide with remaining or newly identified

exposure pathways bull Evaluate the appropriateness of the groundwater leaching model and subsequent

development or application of new soil-to-groundwater modeling parameters or data as necessary and

raquo Develop revised risk-based CIJGs for aII impacted media (principally groundwaler and unsaluraled zone soils)

In order to support I he development of revised risk-based CUGs field activities were conducted at the Site between November 2000 and July 2001 These activities also helped to delineate areas of soil excavation and the size and extent of the VOC source area The results of these field activities showed heterogeneous groundwater and soil

contamination consisting of VUCs SVUUs RGBs metals polycydic aromatic Tyclrocarbons (PAHs) and diogtunfurans on and oft the Silresirn property

The risk-based CUGs do not show an overall increasing or decreasing trend as compared to the 1991 ROD clean-up levels because some exposure pathways were eliminated (direct ingestion of ground mailer) while others were added (indoor inhalation ofVOCs)

In June 2003 the revised risk-based CUGs were further modified to reflect cuinrent EPA risk assessment guidance and protocols Specifically the carcinogenic risk goal was chaned from 10 to 10 gt and the non-carcinoeiniic hazard index was changed from 01

ecological impacts from qroundwateirl and the MADEiP Method 3 Upper ( Linrii its for soil and groundwaler The modified CUGs are identified as the

e com mended Clean-Lip Goals in Appendix A

EPA and MADEP consider the modified CUGs to be adequately protective health and the environment Additionally although not a significant change tlh of a second OLI will facilitate documenting clean-up activities at the Site

4 Revised Clean-up Gosils

tequireirnenis iuch as Dninkiino Wai or MlaxiiiTiurn ConlaiTiinant Levels and Non-zero inninant Level Goals

i I he 1999 ROD Remedy Review it was determined that certain ROD clean-up levels were based on assumptions thai were no longer appropriate and therefore required

ground water needed to be reviewed Future use exposure scenarios needed to be evaluated

raquo Changes in exposure pathways bullbullbull The extern I of the contaminated groundwater plume needed to be evaluated because il was moving faster than originally projected Potential off-property subsurface soil con lamina ion needed to be evaluated

gt Evolution of the technical approaches for Supeirfund risk assessment - The vapor rni grain on model and the methodology for selecting COPCs were no longer currenl and

raquo Specific technical issues relating to toxicily estimates - The use of toxicity surrogates for PAHs and dioxin was no longer recommended or necessary

Necessary updates for calculating revised CUGs included

ltgt Evaluating the subsurface soil to indoor air pathway for the commercialindustrial worker

ltbull Evaluating additional chemicals the inhalation palhways and igt Evaluating a child recreational receptor in the event thai I he Silresirn property or

adjacent properties are redeveloped for recreational use (eg soccer field) The potenlial exists for this type of development however since the area is currently

are summarized below Overall the chainpes in risk assumptions regarding groundwaler soil and air exposures at the Site significantly impact the CIJGs for a ariely of contaminants

Current Land Use and Site Conditions The approximate 16-acre Site is located in a heavily industrialized section of Lowell

storage facilities tractor-trailer storage light industrycommercial corido minium bull and open industrial land As a result oi MADEPs Ground water Use andl Value Deteinrimiriation IvIADEP has stipulated that ground water in the area would not be used as a drin king water source in I he failure This determination constitutes a significant change from the drinking water classification used to establish the 1991 ROD clean-up levels

The reasonaby foreseeable future land use designation for the Site is coinnnTiercialindustrial Soils with residual contamination above the CUGs will be excavated stabilized and capped on the Silresirn property Future exposures to soil or exposed groundwateir are considered possible even though the cap will likely extend over the entire Siliresim property A potential future recreational use scenario was also evaluated

The commercial industrial properties surrounding the Silresirn properly also are expected to continue to be used for cornnnieircialindustrial purposes in the foreseeable future However future renovation or redevelopment of these properties is considered possible including construction of new buildings with basements The BSIVI railroad coinridor adjacent to the Siliresim property on the eastern side is also assumed to remain a railroad corridor for the foreseeable future Ground water is assumed to remain unused for consumptive and non-consumptive uses in the future (ie for drinking or induslriaJ process uses) due to MADEPs Groundwateir Use and Value Determination coupled with the relatively low yield of the shallowest water bearing layers While this assumption appears reasonable given this classification no formal restrictions or institutional controls have been established to ensure thai the ground water us not used for consumptive or non-consumptive purposes or that future land use does not involve contact with potentially contaminated soils

An exposure pathway describes the physical linkage between the source of a COPC and a current or projected future exposed receptor The potential human receptors that have been identified at this Site (under cuinrent and reasonably anticipated future exposure scenarios include com mercia Iindustrial workers railroad workers construction worke rs (eg new facility construction or uliilrry installlatiionrnaintenance workers) and

12

trespassers These potential human receptors may come in contact with surface soil (0 1 fl bgs) exposed subsurface soil as a result of excavation (unsaturated soil gtl ft bg and lt 10 fl bgs) groundwater and ambient or indoor air containing contaminant origin calling from the Sule The potential routes of exposure are incidental iingestiioi inhalation of partioulales or wolallies and dermal absorption These exposure route were also evaluated for a potential future recreational use scenario II should be note that leaching from soil to g round water is no longisir conside1 red a risk becauslt groundwater us no longer a potential drinking water source The pathway of most concern is through VOC emissions from contaminated giroundwater and subsequent diffusion upward into ambient and indoor air

now rrsK-oaseci nuiiiDers

WiOiMl CitiiribJii Units

Under this BSD I he Site will be divided into two Oils to facilitate docuinnentinq clean-up activities as defined below

approximately 12 Ions of subsurface VUC conlarninalicri However operalion of the SVE svsterin was placed on hold because it was unlike v that it would be able to reac Site CUGs

comply wnlh Federal and Slate requirement that are applicable or relevant and appropriate and are co si-effective The revised remedy utilizes permanent solutions

This E gt[) and supporting in formal ion are available for public review at the location lentiHied within this document In addition a notice of availability of the BS

piwided to a local newspaper of general circulation

or the foregoing reasons by my signature below I approve the iissuance of lt= llxplainiation oi Significant Differences tor the Silresirn Chemical Corporation Supeirfunc Site in Lowell Massachusetts and the changes and conclusions staled1 therein

Sus^h Studlieri Acting Director Office of Site Remediation and Restoration USE PA Region I

ADFIII si LOCS Draquo

lti

lii

pound j2bull

LLJ

(o (1) -c

C

c^

(ti b a

bull|lhraquo

r1uii1ijlagt

ltis

iraquo bull-

shy

b gt

craquo i[i

i deg bullgt

fdJr 111

| raquoS-shy I- i]j

-i 3 o a

i

ltgt HI

i -is D

c J

iii i ltgt

bull -3

i g

w

(3i

3 w

j|

laquopound e

fi (I laquo gt

iii

ijj IJL

bullbullbull ID $

O

inE

ij-O

j0o

shy

S = bull

ii S lt

bull lt[

nil (L)

jii[bullbull bull -i

n|gt

tri bullF1

igtraquot

E a

ir ii III Jl

CObullar

cgt CO^j

ugt

J

Ji

b(i ltLI

u (pound lt UI upi lt

=i bull - 1 -shyj 3 iij shy| IS |i i i = gt|i |igt D e~ ti bull bull bull (3pound

- jj ^3 -3 sshy (i i- ~ S = a ]=shy s= 7 lttrade ==

(IJ f rgt 3 I-shy shy rtl -r-i bull bull 11 -13 i bull shy 3 gtbull iamp bullbullbull gt (IJ S l 4l - rr bull TI i shy ni -- bullbullbull |= SJ b iii -5 L J $ ij ij i-iP J1 S sL e3 1 1 laquo laquo E Qlt1) E ii i ii-1 p MI ishy j t shy

= s ^ i = t t = i i pound t1

o ltgt o s 2 ltN3 w J bullbull = ^j

cu CL ]

^ 0

[ fir ]bullbullbull [ ltu

(3

[ii 11 D L^tl

(LJ

U 1 I

y J

I (IDE ii

]laquo

illSti

ii z 1 9

-L

C

IJLI LLI

=

iJUil ii(i

FOSTE R WH E E L E R E N VI RON M ENTA L CO R PORATI ON

The purpose of t h i s memorandum is to sinnraariltltbull I be re corn mended Clean-Dp GoEils (CUGs) f o r the s u r f a c e soil subsurface soi l and groundwater related to i he Si l res im Superfund Site im support of an Explanation of Significant Difference (BSD) The r isk-based ( LGs were or ig inal ly presented in the FniEil Add il lona I Site ID vesl igat ion and Re v is ion o f Si te C lean-Up (ioal s (Eosler Wheel er 2002) T hese CIJG s ivere discussed r e f ined ar id then compared to site da ta Appl icable or Relevant and Appropr ia te Requirements (ARARs) and curreni ROD cleanup levels fhe fo l lowing presents the c r i l e n a used lo develop the recommended CUGs (as cogtrnpairedto the current KOI) c l e a n u p levels)

bulli An updated IJSEPA COC screening and se lec t ion process was used (USEPA 1989 1 9 9 5 1999)

laquo The evaluat ion of the carcinogenic and non-cEireinogeriic polycyclic aromatic hydrocarbon (PAH) conipounds vas performed individually i n s t e a d of as EI g-roup ( U S E P A 1994 200 I a)

bulli T he upda ted cle rma I ris k asse ssrnenl guidance (FAGS Pa rt E) wa s applied (USE PA 2 GO1 b)

laquo The USE A Adult Lead Model was used to calculate soil lead c o n c e n t r a t i o n s associated with a (Ei rge t blood lead level and exposure parameter (USKPA 1996)

laquo The updated guidance for r isk assessment o f lt Eire moge n ic polyclhlorinated biphenylsi (PC Eh) wasiised(NCEA 1996)

Updated lox ico log ica l factors and parameters were usedl (USEPA 1997a 200la and MADEP 1 9 9 4 )

i A target r i sk goal of 1 E-5 and a target haard mdelt of 1 was used for each chernncal (d i rec t ion from USE PA Region 1 Site Manager)

laquo An assumption was made l l i E i t suirface soil consists of the soil between () -shy 1 ft bgs and lhal subsurface ur isa tura ted soil consists of the soil between 1 shy 10 fit bgs (USE PA I99 i )

laquo The Site ground w a t e r was reclassified as being low use and va lue nn a MA13EP Groun d w aie r Use and Val ue Detenminail ion (1VIA DEiF 1998)

laquo Leaching f rom s u b s u r f a c e (unsaturated) soil to ground wa te r was not considered EI critical consideration in setting sub- u r fE ice sioil CUGs (Fo- kT Wheeler 1999 2002)

laquo Commercial industr ia l l a n d use was assumed instead of r e s iden t i a l land use (foster Wheeler 19992002)

laquo The subsur face vapor in t rus ion to indoor air was e v E i l u a t e d as EI primary mbalEi t ion exposure ran te (Foste r W bee ler 2002 D SEP A 1997b)

ltbull Potential exposures to a construction worker w e r tr^aluated for soil and Birouridwater (Foster W h e e l e r 2002)

laquo Potential exposures to a trespasser were evaluated for so i l (Foster Wheeler 2 0 0 2 )

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

ai c reatrnent alternatives was performed iipplicability for the remediation of VOCs at the Site were considered Weighing idvantages and disadvantages for each remedial option resulted in the selection of the ileclrical resistance heating (ERH) technology as the only viable option for a pilot test at

I RH is an in-situ thermal remediation technology that uses electrical heating to enhance The ERH pilot test was designed lo evaluate applicability of Site conditions reveal

itial technical difficulties and determine the effectiveness of the technology for removing subsurface contaminants to targeted levels Results of the pilot test will be used lo evaluate the ability of ERH lo overcome the limitations observed during the SVE operations and ultimately allow an effective and cost efficient scale-up lo full-scale I reatrnent The pilol test began in October 2002 and continued through early January 2003 A final report is being prepared and will be evaluated lo determine the technologys effectiveness for removing contamination on a wide area of the Site

B Summary of the Record of Decision

The ROD (signed September 19 1991) discussed the alternatives evaluated for remediating contamination at the Site and described in detail the selected remedy for I he Site The selected remedy includes a management of migration alternative (giroundwa-ter extraction metals prelreatrnent air stripping aqueous phase carbon adsorption vapor phase carbon adsorption or thermal oxidation) and a source control alternative (SVE excavation stabilization and capping on the Silresim property) lo address all contannination at the Site A detailed description of the clean-up levels and the selected remedy is presented in Section X of the ROD

To date some success has been achieved through the implementation of a number of the remedial activities inn anda led by the ROD In particular SVE has been evaluated via pilot tests and implemented in a limited area on the Site Management of migration remedial components for ground water extraction and treatment were successfully in stalled and continue to operate Operation of the GWTF and extraction wells has resulted in some VOC contaminant concentration reduction in the groundlvvater plume although the extent of the reduction varies significantly depending on the specific area of the Site In some areas ol the Site VOC concentrations have increased However it should be noted that the extraction wells and GWTF were not designed for overall plume rernediation The main objective of the GWTF and extraction wells was lo contain the groundwater plume and lo de-water the Site sufficiently to allow for remediation of soils utilizing traditional SVE

significant change EPA is also creating a second OU to bullfacilitate clocunnienling clean-up activities at I he Site The basis for modifying the 1991 ROD cl Ban-up levels is described below

chieve remedial objectives I he ROD Remedy Review recommended several changes These recommendations took inlo consideration the changes in Site cc (reclassification of groundwateir under the Site) the inability of the irnplerne lechnologies to achieve the objectives stated in the ROD sine the use of some revislt

control activities to achieve remedial objectives ol ha migration removing the contaminant source term and reducing hurnan heal ecological risk at the Site the rive-Year Review supported the recommendations ouIlliinied in the ROD Remedy Review

laquo Inability of the extraction well system to contain contaminant plume migration towards identified downg rad ie nl receptors

ii Inability of the extraction well system and GW7T to meet ROD clean-up levels within the foreseeable future

raquo Results of the 8V operations indicating thai SVE alone would not be able to reduce subsurface soil contamination to meet ROD clean-up levels within the time frame established in the ROD

ltbull Risk assessment assumptions that no longer appeared appropriate for the Site and

igt The change in the groundwater classification for the aquifer below the Site by IvIAIDEP to low use and value from its prior classification as drinking water

The first step of the Action IPIIan included an investigation focusing on strategies to control the continued migration of contaminated groundwater and to irnpilement innovative technologies to remiediale VOC-contanrninated soils The second step of the Action Plan involved a comprehensive investigation to identify and compile existing data collect new data and revise clean-up levels Investigation activities have been completed (implementation of innovative technologies to address VOC-contarninated soils is ongoing as ERH pilot test results are still being evaluated

The following activities were identified to evaluate existing clean-up levels based on the new groundwater classification and to revise clean-up levels where necessary

in Review Site groundwater reclassiiliication bull Evaluate recent monitoring data and current Site conditions igt Identify reimiainirig or newly identified exposure pathways raquo Develop response objectives to coincide with remaining or newly identified

exposure pathways bull Evaluate the appropriateness of the groundwater leaching model and subsequent

development or application of new soil-to-groundwater modeling parameters or data as necessary and

raquo Develop revised risk-based CIJGs for aII impacted media (principally groundwaler and unsaluraled zone soils)

In order to support I he development of revised risk-based CUGs field activities were conducted at the Site between November 2000 and July 2001 These activities also helped to delineate areas of soil excavation and the size and extent of the VOC source area The results of these field activities showed heterogeneous groundwater and soil

contamination consisting of VUCs SVUUs RGBs metals polycydic aromatic Tyclrocarbons (PAHs) and diogtunfurans on and oft the Silresirn property

The risk-based CUGs do not show an overall increasing or decreasing trend as compared to the 1991 ROD clean-up levels because some exposure pathways were eliminated (direct ingestion of ground mailer) while others were added (indoor inhalation ofVOCs)

In June 2003 the revised risk-based CUGs were further modified to reflect cuinrent EPA risk assessment guidance and protocols Specifically the carcinogenic risk goal was chaned from 10 to 10 gt and the non-carcinoeiniic hazard index was changed from 01

ecological impacts from qroundwateirl and the MADEiP Method 3 Upper ( Linrii its for soil and groundwaler The modified CUGs are identified as the

e com mended Clean-Lip Goals in Appendix A

EPA and MADEP consider the modified CUGs to be adequately protective health and the environment Additionally although not a significant change tlh of a second OLI will facilitate documenting clean-up activities at the Site

4 Revised Clean-up Gosils

tequireirnenis iuch as Dninkiino Wai or MlaxiiiTiurn ConlaiTiinant Levels and Non-zero inninant Level Goals

i I he 1999 ROD Remedy Review it was determined that certain ROD clean-up levels were based on assumptions thai were no longer appropriate and therefore required

ground water needed to be reviewed Future use exposure scenarios needed to be evaluated

raquo Changes in exposure pathways bullbullbull The extern I of the contaminated groundwater plume needed to be evaluated because il was moving faster than originally projected Potential off-property subsurface soil con lamina ion needed to be evaluated

gt Evolution of the technical approaches for Supeirfund risk assessment - The vapor rni grain on model and the methodology for selecting COPCs were no longer currenl and

raquo Specific technical issues relating to toxicily estimates - The use of toxicity surrogates for PAHs and dioxin was no longer recommended or necessary

Necessary updates for calculating revised CUGs included

ltgt Evaluating the subsurface soil to indoor air pathway for the commercialindustrial worker

ltbull Evaluating additional chemicals the inhalation palhways and igt Evaluating a child recreational receptor in the event thai I he Silresirn property or

adjacent properties are redeveloped for recreational use (eg soccer field) The potenlial exists for this type of development however since the area is currently

are summarized below Overall the chainpes in risk assumptions regarding groundwaler soil and air exposures at the Site significantly impact the CIJGs for a ariely of contaminants

Current Land Use and Site Conditions The approximate 16-acre Site is located in a heavily industrialized section of Lowell

storage facilities tractor-trailer storage light industrycommercial corido minium bull and open industrial land As a result oi MADEPs Ground water Use andl Value Deteinrimiriation IvIADEP has stipulated that ground water in the area would not be used as a drin king water source in I he failure This determination constitutes a significant change from the drinking water classification used to establish the 1991 ROD clean-up levels

The reasonaby foreseeable future land use designation for the Site is coinnnTiercialindustrial Soils with residual contamination above the CUGs will be excavated stabilized and capped on the Silresirn property Future exposures to soil or exposed groundwateir are considered possible even though the cap will likely extend over the entire Siliresim property A potential future recreational use scenario was also evaluated

The commercial industrial properties surrounding the Silresirn properly also are expected to continue to be used for cornnnieircialindustrial purposes in the foreseeable future However future renovation or redevelopment of these properties is considered possible including construction of new buildings with basements The BSIVI railroad coinridor adjacent to the Siliresim property on the eastern side is also assumed to remain a railroad corridor for the foreseeable future Ground water is assumed to remain unused for consumptive and non-consumptive uses in the future (ie for drinking or induslriaJ process uses) due to MADEPs Groundwateir Use and Value Determination coupled with the relatively low yield of the shallowest water bearing layers While this assumption appears reasonable given this classification no formal restrictions or institutional controls have been established to ensure thai the ground water us not used for consumptive or non-consumptive purposes or that future land use does not involve contact with potentially contaminated soils

An exposure pathway describes the physical linkage between the source of a COPC and a current or projected future exposed receptor The potential human receptors that have been identified at this Site (under cuinrent and reasonably anticipated future exposure scenarios include com mercia Iindustrial workers railroad workers construction worke rs (eg new facility construction or uliilrry installlatiionrnaintenance workers) and

12

trespassers These potential human receptors may come in contact with surface soil (0 1 fl bgs) exposed subsurface soil as a result of excavation (unsaturated soil gtl ft bg and lt 10 fl bgs) groundwater and ambient or indoor air containing contaminant origin calling from the Sule The potential routes of exposure are incidental iingestiioi inhalation of partioulales or wolallies and dermal absorption These exposure route were also evaluated for a potential future recreational use scenario II should be note that leaching from soil to g round water is no longisir conside1 red a risk becauslt groundwater us no longer a potential drinking water source The pathway of most concern is through VOC emissions from contaminated giroundwater and subsequent diffusion upward into ambient and indoor air

now rrsK-oaseci nuiiiDers

WiOiMl CitiiribJii Units

Under this BSD I he Site will be divided into two Oils to facilitate docuinnentinq clean-up activities as defined below

approximately 12 Ions of subsurface VUC conlarninalicri However operalion of the SVE svsterin was placed on hold because it was unlike v that it would be able to reac Site CUGs

comply wnlh Federal and Slate requirement that are applicable or relevant and appropriate and are co si-effective The revised remedy utilizes permanent solutions

This E gt[) and supporting in formal ion are available for public review at the location lentiHied within this document In addition a notice of availability of the BS

piwided to a local newspaper of general circulation

or the foregoing reasons by my signature below I approve the iissuance of lt= llxplainiation oi Significant Differences tor the Silresirn Chemical Corporation Supeirfunc Site in Lowell Massachusetts and the changes and conclusions staled1 therein

Sus^h Studlieri Acting Director Office of Site Remediation and Restoration USE PA Region I

ADFIII si LOCS Draquo

lti

lii

pound j2bull

LLJ

(o (1) -c

C

c^

(ti b a

bull|lhraquo

r1uii1ijlagt

ltis

iraquo bull-

shy

b gt

craquo i[i

i deg bullgt

fdJr 111

| raquoS-shy I- i]j

-i 3 o a

i

ltgt HI

i -is D

c J

iii i ltgt

bull -3

i g

w

(3i

3 w

j|

laquopound e

fi (I laquo gt

iii

ijj IJL

bullbullbull ID $

O

inE

ij-O

j0o

shy

S = bull

ii S lt

bull lt[

nil (L)

jii[bullbull bull -i

n|gt

tri bullF1

igtraquot

E a

ir ii III Jl

CObullar

cgt CO^j

ugt

J

Ji

b(i ltLI

u (pound lt UI upi lt

=i bull - 1 -shyj 3 iij shy| IS |i i i = gt|i |igt D e~ ti bull bull bull (3pound

- jj ^3 -3 sshy (i i- ~ S = a ]=shy s= 7 lttrade ==

(IJ f rgt 3 I-shy shy rtl -r-i bull bull 11 -13 i bull shy 3 gtbull iamp bullbullbull gt (IJ S l 4l - rr bull TI i shy ni -- bullbullbull |= SJ b iii -5 L J $ ij ij i-iP J1 S sL e3 1 1 laquo laquo E Qlt1) E ii i ii-1 p MI ishy j t shy

= s ^ i = t t = i i pound t1

o ltgt o s 2 ltN3 w J bullbull = ^j

cu CL ]

^ 0

[ fir ]bullbullbull [ ltu

(3

[ii 11 D L^tl

(LJ

U 1 I

y J

I (IDE ii

]laquo

illSti

ii z 1 9

-L

C

IJLI LLI

=

iJUil ii(i

FOSTE R WH E E L E R E N VI RON M ENTA L CO R PORATI ON

The purpose of t h i s memorandum is to sinnraariltltbull I be re corn mended Clean-Dp GoEils (CUGs) f o r the s u r f a c e soil subsurface soi l and groundwater related to i he Si l res im Superfund Site im support of an Explanation of Significant Difference (BSD) The r isk-based ( LGs were or ig inal ly presented in the FniEil Add il lona I Site ID vesl igat ion and Re v is ion o f Si te C lean-Up (ioal s (Eosler Wheel er 2002) T hese CIJG s ivere discussed r e f ined ar id then compared to site da ta Appl icable or Relevant and Appropr ia te Requirements (ARARs) and curreni ROD cleanup levels fhe fo l lowing presents the c r i l e n a used lo develop the recommended CUGs (as cogtrnpairedto the current KOI) c l e a n u p levels)

bulli An updated IJSEPA COC screening and se lec t ion process was used (USEPA 1989 1 9 9 5 1999)

laquo The evaluat ion of the carcinogenic and non-cEireinogeriic polycyclic aromatic hydrocarbon (PAH) conipounds vas performed individually i n s t e a d of as EI g-roup ( U S E P A 1994 200 I a)

bulli T he upda ted cle rma I ris k asse ssrnenl guidance (FAGS Pa rt E) wa s applied (USE PA 2 GO1 b)

laquo The USE A Adult Lead Model was used to calculate soil lead c o n c e n t r a t i o n s associated with a (Ei rge t blood lead level and exposure parameter (USKPA 1996)

laquo The updated guidance for r isk assessment o f lt Eire moge n ic polyclhlorinated biphenylsi (PC Eh) wasiised(NCEA 1996)

Updated lox ico log ica l factors and parameters were usedl (USEPA 1997a 200la and MADEP 1 9 9 4 )

i A target r i sk goal of 1 E-5 and a target haard mdelt of 1 was used for each chernncal (d i rec t ion from USE PA Region 1 Site Manager)

laquo An assumption was made l l i E i t suirface soil consists of the soil between () -shy 1 ft bgs and lhal subsurface ur isa tura ted soil consists of the soil between 1 shy 10 fit bgs (USE PA I99 i )

laquo The Site ground w a t e r was reclassified as being low use and va lue nn a MA13EP Groun d w aie r Use and Val ue Detenminail ion (1VIA DEiF 1998)

laquo Leaching f rom s u b s u r f a c e (unsaturated) soil to ground wa te r was not considered EI critical consideration in setting sub- u r fE ice sioil CUGs (Fo- kT Wheeler 1999 2002)

laquo Commercial industr ia l l a n d use was assumed instead of r e s iden t i a l land use (foster Wheeler 19992002)

laquo The subsur face vapor in t rus ion to indoor air was e v E i l u a t e d as EI primary mbalEi t ion exposure ran te (Foste r W bee ler 2002 D SEP A 1997b)

ltbull Potential exposures to a construction worker w e r tr^aluated for soil and Birouridwater (Foster W h e e l e r 2002)

laquo Potential exposures to a trespasser were evaluated for so i l (Foster Wheeler 2 0 0 2 )

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

significant change EPA is also creating a second OU to bullfacilitate clocunnienling clean-up activities at I he Site The basis for modifying the 1991 ROD cl Ban-up levels is described below

chieve remedial objectives I he ROD Remedy Review recommended several changes These recommendations took inlo consideration the changes in Site cc (reclassification of groundwateir under the Site) the inability of the irnplerne lechnologies to achieve the objectives stated in the ROD sine the use of some revislt

control activities to achieve remedial objectives ol ha migration removing the contaminant source term and reducing hurnan heal ecological risk at the Site the rive-Year Review supported the recommendations ouIlliinied in the ROD Remedy Review

laquo Inability of the extraction well system to contain contaminant plume migration towards identified downg rad ie nl receptors

ii Inability of the extraction well system and GW7T to meet ROD clean-up levels within the foreseeable future

raquo Results of the 8V operations indicating thai SVE alone would not be able to reduce subsurface soil contamination to meet ROD clean-up levels within the time frame established in the ROD

ltbull Risk assessment assumptions that no longer appeared appropriate for the Site and

igt The change in the groundwater classification for the aquifer below the Site by IvIAIDEP to low use and value from its prior classification as drinking water

The first step of the Action IPIIan included an investigation focusing on strategies to control the continued migration of contaminated groundwater and to irnpilement innovative technologies to remiediale VOC-contanrninated soils The second step of the Action Plan involved a comprehensive investigation to identify and compile existing data collect new data and revise clean-up levels Investigation activities have been completed (implementation of innovative technologies to address VOC-contarninated soils is ongoing as ERH pilot test results are still being evaluated

The following activities were identified to evaluate existing clean-up levels based on the new groundwater classification and to revise clean-up levels where necessary

in Review Site groundwater reclassiiliication bull Evaluate recent monitoring data and current Site conditions igt Identify reimiainirig or newly identified exposure pathways raquo Develop response objectives to coincide with remaining or newly identified

exposure pathways bull Evaluate the appropriateness of the groundwater leaching model and subsequent

development or application of new soil-to-groundwater modeling parameters or data as necessary and

raquo Develop revised risk-based CIJGs for aII impacted media (principally groundwaler and unsaluraled zone soils)

In order to support I he development of revised risk-based CUGs field activities were conducted at the Site between November 2000 and July 2001 These activities also helped to delineate areas of soil excavation and the size and extent of the VOC source area The results of these field activities showed heterogeneous groundwater and soil

contamination consisting of VUCs SVUUs RGBs metals polycydic aromatic Tyclrocarbons (PAHs) and diogtunfurans on and oft the Silresirn property

The risk-based CUGs do not show an overall increasing or decreasing trend as compared to the 1991 ROD clean-up levels because some exposure pathways were eliminated (direct ingestion of ground mailer) while others were added (indoor inhalation ofVOCs)

In June 2003 the revised risk-based CUGs were further modified to reflect cuinrent EPA risk assessment guidance and protocols Specifically the carcinogenic risk goal was chaned from 10 to 10 gt and the non-carcinoeiniic hazard index was changed from 01

ecological impacts from qroundwateirl and the MADEiP Method 3 Upper ( Linrii its for soil and groundwaler The modified CUGs are identified as the

e com mended Clean-Lip Goals in Appendix A

EPA and MADEP consider the modified CUGs to be adequately protective health and the environment Additionally although not a significant change tlh of a second OLI will facilitate documenting clean-up activities at the Site

4 Revised Clean-up Gosils

tequireirnenis iuch as Dninkiino Wai or MlaxiiiTiurn ConlaiTiinant Levels and Non-zero inninant Level Goals

i I he 1999 ROD Remedy Review it was determined that certain ROD clean-up levels were based on assumptions thai were no longer appropriate and therefore required

ground water needed to be reviewed Future use exposure scenarios needed to be evaluated

raquo Changes in exposure pathways bullbullbull The extern I of the contaminated groundwater plume needed to be evaluated because il was moving faster than originally projected Potential off-property subsurface soil con lamina ion needed to be evaluated

gt Evolution of the technical approaches for Supeirfund risk assessment - The vapor rni grain on model and the methodology for selecting COPCs were no longer currenl and

raquo Specific technical issues relating to toxicily estimates - The use of toxicity surrogates for PAHs and dioxin was no longer recommended or necessary

Necessary updates for calculating revised CUGs included

ltgt Evaluating the subsurface soil to indoor air pathway for the commercialindustrial worker

ltbull Evaluating additional chemicals the inhalation palhways and igt Evaluating a child recreational receptor in the event thai I he Silresirn property or

adjacent properties are redeveloped for recreational use (eg soccer field) The potenlial exists for this type of development however since the area is currently

are summarized below Overall the chainpes in risk assumptions regarding groundwaler soil and air exposures at the Site significantly impact the CIJGs for a ariely of contaminants

Current Land Use and Site Conditions The approximate 16-acre Site is located in a heavily industrialized section of Lowell

storage facilities tractor-trailer storage light industrycommercial corido minium bull and open industrial land As a result oi MADEPs Ground water Use andl Value Deteinrimiriation IvIADEP has stipulated that ground water in the area would not be used as a drin king water source in I he failure This determination constitutes a significant change from the drinking water classification used to establish the 1991 ROD clean-up levels

The reasonaby foreseeable future land use designation for the Site is coinnnTiercialindustrial Soils with residual contamination above the CUGs will be excavated stabilized and capped on the Silresirn property Future exposures to soil or exposed groundwateir are considered possible even though the cap will likely extend over the entire Siliresim property A potential future recreational use scenario was also evaluated

The commercial industrial properties surrounding the Silresirn properly also are expected to continue to be used for cornnnieircialindustrial purposes in the foreseeable future However future renovation or redevelopment of these properties is considered possible including construction of new buildings with basements The BSIVI railroad coinridor adjacent to the Siliresim property on the eastern side is also assumed to remain a railroad corridor for the foreseeable future Ground water is assumed to remain unused for consumptive and non-consumptive uses in the future (ie for drinking or induslriaJ process uses) due to MADEPs Groundwateir Use and Value Determination coupled with the relatively low yield of the shallowest water bearing layers While this assumption appears reasonable given this classification no formal restrictions or institutional controls have been established to ensure thai the ground water us not used for consumptive or non-consumptive purposes or that future land use does not involve contact with potentially contaminated soils

An exposure pathway describes the physical linkage between the source of a COPC and a current or projected future exposed receptor The potential human receptors that have been identified at this Site (under cuinrent and reasonably anticipated future exposure scenarios include com mercia Iindustrial workers railroad workers construction worke rs (eg new facility construction or uliilrry installlatiionrnaintenance workers) and

12

trespassers These potential human receptors may come in contact with surface soil (0 1 fl bgs) exposed subsurface soil as a result of excavation (unsaturated soil gtl ft bg and lt 10 fl bgs) groundwater and ambient or indoor air containing contaminant origin calling from the Sule The potential routes of exposure are incidental iingestiioi inhalation of partioulales or wolallies and dermal absorption These exposure route were also evaluated for a potential future recreational use scenario II should be note that leaching from soil to g round water is no longisir conside1 red a risk becauslt groundwater us no longer a potential drinking water source The pathway of most concern is through VOC emissions from contaminated giroundwater and subsequent diffusion upward into ambient and indoor air

now rrsK-oaseci nuiiiDers

WiOiMl CitiiribJii Units

Under this BSD I he Site will be divided into two Oils to facilitate docuinnentinq clean-up activities as defined below

approximately 12 Ions of subsurface VUC conlarninalicri However operalion of the SVE svsterin was placed on hold because it was unlike v that it would be able to reac Site CUGs

comply wnlh Federal and Slate requirement that are applicable or relevant and appropriate and are co si-effective The revised remedy utilizes permanent solutions

This E gt[) and supporting in formal ion are available for public review at the location lentiHied within this document In addition a notice of availability of the BS

piwided to a local newspaper of general circulation

or the foregoing reasons by my signature below I approve the iissuance of lt= llxplainiation oi Significant Differences tor the Silresirn Chemical Corporation Supeirfunc Site in Lowell Massachusetts and the changes and conclusions staled1 therein

Sus^h Studlieri Acting Director Office of Site Remediation and Restoration USE PA Region I

ADFIII si LOCS Draquo

lti

lii

pound j2bull

LLJ

(o (1) -c

C

c^

(ti b a

bull|lhraquo

r1uii1ijlagt

ltis

iraquo bull-

shy

b gt

craquo i[i

i deg bullgt

fdJr 111

| raquoS-shy I- i]j

-i 3 o a

i

ltgt HI

i -is D

c J

iii i ltgt

bull -3

i g

w

(3i

3 w

j|

laquopound e

fi (I laquo gt

iii

ijj IJL

bullbullbull ID $

O

inE

ij-O

j0o

shy

S = bull

ii S lt

bull lt[

nil (L)

jii[bullbull bull -i

n|gt

tri bullF1

igtraquot

E a

ir ii III Jl

CObullar

cgt CO^j

ugt

J

Ji

b(i ltLI

u (pound lt UI upi lt

=i bull - 1 -shyj 3 iij shy| IS |i i i = gt|i |igt D e~ ti bull bull bull (3pound

- jj ^3 -3 sshy (i i- ~ S = a ]=shy s= 7 lttrade ==

(IJ f rgt 3 I-shy shy rtl -r-i bull bull 11 -13 i bull shy 3 gtbull iamp bullbullbull gt (IJ S l 4l - rr bull TI i shy ni -- bullbullbull |= SJ b iii -5 L J $ ij ij i-iP J1 S sL e3 1 1 laquo laquo E Qlt1) E ii i ii-1 p MI ishy j t shy

= s ^ i = t t = i i pound t1

o ltgt o s 2 ltN3 w J bullbull = ^j

cu CL ]

^ 0

[ fir ]bullbullbull [ ltu

(3

[ii 11 D L^tl

(LJ

U 1 I

y J

I (IDE ii

]laquo

illSti

ii z 1 9

-L

C

IJLI LLI

=

iJUil ii(i

FOSTE R WH E E L E R E N VI RON M ENTA L CO R PORATI ON

The purpose of t h i s memorandum is to sinnraariltltbull I be re corn mended Clean-Dp GoEils (CUGs) f o r the s u r f a c e soil subsurface soi l and groundwater related to i he Si l res im Superfund Site im support of an Explanation of Significant Difference (BSD) The r isk-based ( LGs were or ig inal ly presented in the FniEil Add il lona I Site ID vesl igat ion and Re v is ion o f Si te C lean-Up (ioal s (Eosler Wheel er 2002) T hese CIJG s ivere discussed r e f ined ar id then compared to site da ta Appl icable or Relevant and Appropr ia te Requirements (ARARs) and curreni ROD cleanup levels fhe fo l lowing presents the c r i l e n a used lo develop the recommended CUGs (as cogtrnpairedto the current KOI) c l e a n u p levels)

bulli An updated IJSEPA COC screening and se lec t ion process was used (USEPA 1989 1 9 9 5 1999)

laquo The evaluat ion of the carcinogenic and non-cEireinogeriic polycyclic aromatic hydrocarbon (PAH) conipounds vas performed individually i n s t e a d of as EI g-roup ( U S E P A 1994 200 I a)

bulli T he upda ted cle rma I ris k asse ssrnenl guidance (FAGS Pa rt E) wa s applied (USE PA 2 GO1 b)

laquo The USE A Adult Lead Model was used to calculate soil lead c o n c e n t r a t i o n s associated with a (Ei rge t blood lead level and exposure parameter (USKPA 1996)

laquo The updated guidance for r isk assessment o f lt Eire moge n ic polyclhlorinated biphenylsi (PC Eh) wasiised(NCEA 1996)

Updated lox ico log ica l factors and parameters were usedl (USEPA 1997a 200la and MADEP 1 9 9 4 )

i A target r i sk goal of 1 E-5 and a target haard mdelt of 1 was used for each chernncal (d i rec t ion from USE PA Region 1 Site Manager)

laquo An assumption was made l l i E i t suirface soil consists of the soil between () -shy 1 ft bgs and lhal subsurface ur isa tura ted soil consists of the soil between 1 shy 10 fit bgs (USE PA I99 i )

laquo The Site ground w a t e r was reclassified as being low use and va lue nn a MA13EP Groun d w aie r Use and Val ue Detenminail ion (1VIA DEiF 1998)

laquo Leaching f rom s u b s u r f a c e (unsaturated) soil to ground wa te r was not considered EI critical consideration in setting sub- u r fE ice sioil CUGs (Fo- kT Wheeler 1999 2002)

laquo Commercial industr ia l l a n d use was assumed instead of r e s iden t i a l land use (foster Wheeler 19992002)

laquo The subsur face vapor in t rus ion to indoor air was e v E i l u a t e d as EI primary mbalEi t ion exposure ran te (Foste r W bee ler 2002 D SEP A 1997b)

ltbull Potential exposures to a construction worker w e r tr^aluated for soil and Birouridwater (Foster W h e e l e r 2002)

laquo Potential exposures to a trespasser were evaluated for so i l (Foster Wheeler 2 0 0 2 )

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

laquo Inability of the extraction well system to contain contaminant plume migration towards identified downg rad ie nl receptors

ii Inability of the extraction well system and GW7T to meet ROD clean-up levels within the foreseeable future

raquo Results of the 8V operations indicating thai SVE alone would not be able to reduce subsurface soil contamination to meet ROD clean-up levels within the time frame established in the ROD

ltbull Risk assessment assumptions that no longer appeared appropriate for the Site and

igt The change in the groundwater classification for the aquifer below the Site by IvIAIDEP to low use and value from its prior classification as drinking water

The first step of the Action IPIIan included an investigation focusing on strategies to control the continued migration of contaminated groundwater and to irnpilement innovative technologies to remiediale VOC-contanrninated soils The second step of the Action Plan involved a comprehensive investigation to identify and compile existing data collect new data and revise clean-up levels Investigation activities have been completed (implementation of innovative technologies to address VOC-contarninated soils is ongoing as ERH pilot test results are still being evaluated

The following activities were identified to evaluate existing clean-up levels based on the new groundwater classification and to revise clean-up levels where necessary

in Review Site groundwater reclassiiliication bull Evaluate recent monitoring data and current Site conditions igt Identify reimiainirig or newly identified exposure pathways raquo Develop response objectives to coincide with remaining or newly identified

exposure pathways bull Evaluate the appropriateness of the groundwater leaching model and subsequent

development or application of new soil-to-groundwater modeling parameters or data as necessary and

raquo Develop revised risk-based CIJGs for aII impacted media (principally groundwaler and unsaluraled zone soils)

In order to support I he development of revised risk-based CUGs field activities were conducted at the Site between November 2000 and July 2001 These activities also helped to delineate areas of soil excavation and the size and extent of the VOC source area The results of these field activities showed heterogeneous groundwater and soil

contamination consisting of VUCs SVUUs RGBs metals polycydic aromatic Tyclrocarbons (PAHs) and diogtunfurans on and oft the Silresirn property

The risk-based CUGs do not show an overall increasing or decreasing trend as compared to the 1991 ROD clean-up levels because some exposure pathways were eliminated (direct ingestion of ground mailer) while others were added (indoor inhalation ofVOCs)

In June 2003 the revised risk-based CUGs were further modified to reflect cuinrent EPA risk assessment guidance and protocols Specifically the carcinogenic risk goal was chaned from 10 to 10 gt and the non-carcinoeiniic hazard index was changed from 01

ecological impacts from qroundwateirl and the MADEiP Method 3 Upper ( Linrii its for soil and groundwaler The modified CUGs are identified as the

e com mended Clean-Lip Goals in Appendix A

EPA and MADEP consider the modified CUGs to be adequately protective health and the environment Additionally although not a significant change tlh of a second OLI will facilitate documenting clean-up activities at the Site

4 Revised Clean-up Gosils

tequireirnenis iuch as Dninkiino Wai or MlaxiiiTiurn ConlaiTiinant Levels and Non-zero inninant Level Goals

i I he 1999 ROD Remedy Review it was determined that certain ROD clean-up levels were based on assumptions thai were no longer appropriate and therefore required

ground water needed to be reviewed Future use exposure scenarios needed to be evaluated

raquo Changes in exposure pathways bullbullbull The extern I of the contaminated groundwater plume needed to be evaluated because il was moving faster than originally projected Potential off-property subsurface soil con lamina ion needed to be evaluated

gt Evolution of the technical approaches for Supeirfund risk assessment - The vapor rni grain on model and the methodology for selecting COPCs were no longer currenl and

raquo Specific technical issues relating to toxicily estimates - The use of toxicity surrogates for PAHs and dioxin was no longer recommended or necessary

Necessary updates for calculating revised CUGs included

ltgt Evaluating the subsurface soil to indoor air pathway for the commercialindustrial worker

ltbull Evaluating additional chemicals the inhalation palhways and igt Evaluating a child recreational receptor in the event thai I he Silresirn property or

adjacent properties are redeveloped for recreational use (eg soccer field) The potenlial exists for this type of development however since the area is currently

are summarized below Overall the chainpes in risk assumptions regarding groundwaler soil and air exposures at the Site significantly impact the CIJGs for a ariely of contaminants

Current Land Use and Site Conditions The approximate 16-acre Site is located in a heavily industrialized section of Lowell

storage facilities tractor-trailer storage light industrycommercial corido minium bull and open industrial land As a result oi MADEPs Ground water Use andl Value Deteinrimiriation IvIADEP has stipulated that ground water in the area would not be used as a drin king water source in I he failure This determination constitutes a significant change from the drinking water classification used to establish the 1991 ROD clean-up levels

The reasonaby foreseeable future land use designation for the Site is coinnnTiercialindustrial Soils with residual contamination above the CUGs will be excavated stabilized and capped on the Silresirn property Future exposures to soil or exposed groundwateir are considered possible even though the cap will likely extend over the entire Siliresim property A potential future recreational use scenario was also evaluated

The commercial industrial properties surrounding the Silresirn properly also are expected to continue to be used for cornnnieircialindustrial purposes in the foreseeable future However future renovation or redevelopment of these properties is considered possible including construction of new buildings with basements The BSIVI railroad coinridor adjacent to the Siliresim property on the eastern side is also assumed to remain a railroad corridor for the foreseeable future Ground water is assumed to remain unused for consumptive and non-consumptive uses in the future (ie for drinking or induslriaJ process uses) due to MADEPs Groundwateir Use and Value Determination coupled with the relatively low yield of the shallowest water bearing layers While this assumption appears reasonable given this classification no formal restrictions or institutional controls have been established to ensure thai the ground water us not used for consumptive or non-consumptive purposes or that future land use does not involve contact with potentially contaminated soils

An exposure pathway describes the physical linkage between the source of a COPC and a current or projected future exposed receptor The potential human receptors that have been identified at this Site (under cuinrent and reasonably anticipated future exposure scenarios include com mercia Iindustrial workers railroad workers construction worke rs (eg new facility construction or uliilrry installlatiionrnaintenance workers) and

12

trespassers These potential human receptors may come in contact with surface soil (0 1 fl bgs) exposed subsurface soil as a result of excavation (unsaturated soil gtl ft bg and lt 10 fl bgs) groundwater and ambient or indoor air containing contaminant origin calling from the Sule The potential routes of exposure are incidental iingestiioi inhalation of partioulales or wolallies and dermal absorption These exposure route were also evaluated for a potential future recreational use scenario II should be note that leaching from soil to g round water is no longisir conside1 red a risk becauslt groundwater us no longer a potential drinking water source The pathway of most concern is through VOC emissions from contaminated giroundwater and subsequent diffusion upward into ambient and indoor air

now rrsK-oaseci nuiiiDers

WiOiMl CitiiribJii Units

Under this BSD I he Site will be divided into two Oils to facilitate docuinnentinq clean-up activities as defined below

approximately 12 Ions of subsurface VUC conlarninalicri However operalion of the SVE svsterin was placed on hold because it was unlike v that it would be able to reac Site CUGs

comply wnlh Federal and Slate requirement that are applicable or relevant and appropriate and are co si-effective The revised remedy utilizes permanent solutions

This E gt[) and supporting in formal ion are available for public review at the location lentiHied within this document In addition a notice of availability of the BS

piwided to a local newspaper of general circulation

or the foregoing reasons by my signature below I approve the iissuance of lt= llxplainiation oi Significant Differences tor the Silresirn Chemical Corporation Supeirfunc Site in Lowell Massachusetts and the changes and conclusions staled1 therein

Sus^h Studlieri Acting Director Office of Site Remediation and Restoration USE PA Region I

ADFIII si LOCS Draquo

lti

lii

pound j2bull

LLJ

(o (1) -c

C

c^

(ti b a

bull|lhraquo

r1uii1ijlagt

ltis

iraquo bull-

shy

b gt

craquo i[i

i deg bullgt

fdJr 111

| raquoS-shy I- i]j

-i 3 o a

i

ltgt HI

i -is D

c J

iii i ltgt

bull -3

i g

w

(3i

3 w

j|

laquopound e

fi (I laquo gt

iii

ijj IJL

bullbullbull ID $

O

inE

ij-O

j0o

shy

S = bull

ii S lt

bull lt[

nil (L)

jii[bullbull bull -i

n|gt

tri bullF1

igtraquot

E a

ir ii III Jl

CObullar

cgt CO^j

ugt

J

Ji

b(i ltLI

u (pound lt UI upi lt

=i bull - 1 -shyj 3 iij shy| IS |i i i = gt|i |igt D e~ ti bull bull bull (3pound

- jj ^3 -3 sshy (i i- ~ S = a ]=shy s= 7 lttrade ==

(IJ f rgt 3 I-shy shy rtl -r-i bull bull 11 -13 i bull shy 3 gtbull iamp bullbullbull gt (IJ S l 4l - rr bull TI i shy ni -- bullbullbull |= SJ b iii -5 L J $ ij ij i-iP J1 S sL e3 1 1 laquo laquo E Qlt1) E ii i ii-1 p MI ishy j t shy

= s ^ i = t t = i i pound t1

o ltgt o s 2 ltN3 w J bullbull = ^j

cu CL ]

^ 0

[ fir ]bullbullbull [ ltu

(3

[ii 11 D L^tl

(LJ

U 1 I

y J

I (IDE ii

]laquo

illSti

ii z 1 9

-L

C

IJLI LLI

=

iJUil ii(i

FOSTE R WH E E L E R E N VI RON M ENTA L CO R PORATI ON

The purpose of t h i s memorandum is to sinnraariltltbull I be re corn mended Clean-Dp GoEils (CUGs) f o r the s u r f a c e soil subsurface soi l and groundwater related to i he Si l res im Superfund Site im support of an Explanation of Significant Difference (BSD) The r isk-based ( LGs were or ig inal ly presented in the FniEil Add il lona I Site ID vesl igat ion and Re v is ion o f Si te C lean-Up (ioal s (Eosler Wheel er 2002) T hese CIJG s ivere discussed r e f ined ar id then compared to site da ta Appl icable or Relevant and Appropr ia te Requirements (ARARs) and curreni ROD cleanup levels fhe fo l lowing presents the c r i l e n a used lo develop the recommended CUGs (as cogtrnpairedto the current KOI) c l e a n u p levels)

bulli An updated IJSEPA COC screening and se lec t ion process was used (USEPA 1989 1 9 9 5 1999)

laquo The evaluat ion of the carcinogenic and non-cEireinogeriic polycyclic aromatic hydrocarbon (PAH) conipounds vas performed individually i n s t e a d of as EI g-roup ( U S E P A 1994 200 I a)

bulli T he upda ted cle rma I ris k asse ssrnenl guidance (FAGS Pa rt E) wa s applied (USE PA 2 GO1 b)

laquo The USE A Adult Lead Model was used to calculate soil lead c o n c e n t r a t i o n s associated with a (Ei rge t blood lead level and exposure parameter (USKPA 1996)

laquo The updated guidance for r isk assessment o f lt Eire moge n ic polyclhlorinated biphenylsi (PC Eh) wasiised(NCEA 1996)

Updated lox ico log ica l factors and parameters were usedl (USEPA 1997a 200la and MADEP 1 9 9 4 )

i A target r i sk goal of 1 E-5 and a target haard mdelt of 1 was used for each chernncal (d i rec t ion from USE PA Region 1 Site Manager)

laquo An assumption was made l l i E i t suirface soil consists of the soil between () -shy 1 ft bgs and lhal subsurface ur isa tura ted soil consists of the soil between 1 shy 10 fit bgs (USE PA I99 i )

laquo The Site ground w a t e r was reclassified as being low use and va lue nn a MA13EP Groun d w aie r Use and Val ue Detenminail ion (1VIA DEiF 1998)

laquo Leaching f rom s u b s u r f a c e (unsaturated) soil to ground wa te r was not considered EI critical consideration in setting sub- u r fE ice sioil CUGs (Fo- kT Wheeler 1999 2002)

laquo Commercial industr ia l l a n d use was assumed instead of r e s iden t i a l land use (foster Wheeler 19992002)

laquo The subsur face vapor in t rus ion to indoor air was e v E i l u a t e d as EI primary mbalEi t ion exposure ran te (Foste r W bee ler 2002 D SEP A 1997b)

ltbull Potential exposures to a construction worker w e r tr^aluated for soil and Birouridwater (Foster W h e e l e r 2002)

laquo Potential exposures to a trespasser were evaluated for so i l (Foster Wheeler 2 0 0 2 )

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

contamination consisting of VUCs SVUUs RGBs metals polycydic aromatic Tyclrocarbons (PAHs) and diogtunfurans on and oft the Silresirn property

The risk-based CUGs do not show an overall increasing or decreasing trend as compared to the 1991 ROD clean-up levels because some exposure pathways were eliminated (direct ingestion of ground mailer) while others were added (indoor inhalation ofVOCs)

In June 2003 the revised risk-based CUGs were further modified to reflect cuinrent EPA risk assessment guidance and protocols Specifically the carcinogenic risk goal was chaned from 10 to 10 gt and the non-carcinoeiniic hazard index was changed from 01

ecological impacts from qroundwateirl and the MADEiP Method 3 Upper ( Linrii its for soil and groundwaler The modified CUGs are identified as the

e com mended Clean-Lip Goals in Appendix A

EPA and MADEP consider the modified CUGs to be adequately protective health and the environment Additionally although not a significant change tlh of a second OLI will facilitate documenting clean-up activities at the Site

4 Revised Clean-up Gosils

tequireirnenis iuch as Dninkiino Wai or MlaxiiiTiurn ConlaiTiinant Levels and Non-zero inninant Level Goals

i I he 1999 ROD Remedy Review it was determined that certain ROD clean-up levels were based on assumptions thai were no longer appropriate and therefore required

ground water needed to be reviewed Future use exposure scenarios needed to be evaluated

raquo Changes in exposure pathways bullbullbull The extern I of the contaminated groundwater plume needed to be evaluated because il was moving faster than originally projected Potential off-property subsurface soil con lamina ion needed to be evaluated

gt Evolution of the technical approaches for Supeirfund risk assessment - The vapor rni grain on model and the methodology for selecting COPCs were no longer currenl and

raquo Specific technical issues relating to toxicily estimates - The use of toxicity surrogates for PAHs and dioxin was no longer recommended or necessary

Necessary updates for calculating revised CUGs included

ltgt Evaluating the subsurface soil to indoor air pathway for the commercialindustrial worker

ltbull Evaluating additional chemicals the inhalation palhways and igt Evaluating a child recreational receptor in the event thai I he Silresirn property or

adjacent properties are redeveloped for recreational use (eg soccer field) The potenlial exists for this type of development however since the area is currently

are summarized below Overall the chainpes in risk assumptions regarding groundwaler soil and air exposures at the Site significantly impact the CIJGs for a ariely of contaminants

Current Land Use and Site Conditions The approximate 16-acre Site is located in a heavily industrialized section of Lowell

storage facilities tractor-trailer storage light industrycommercial corido minium bull and open industrial land As a result oi MADEPs Ground water Use andl Value Deteinrimiriation IvIADEP has stipulated that ground water in the area would not be used as a drin king water source in I he failure This determination constitutes a significant change from the drinking water classification used to establish the 1991 ROD clean-up levels

The reasonaby foreseeable future land use designation for the Site is coinnnTiercialindustrial Soils with residual contamination above the CUGs will be excavated stabilized and capped on the Silresirn property Future exposures to soil or exposed groundwateir are considered possible even though the cap will likely extend over the entire Siliresim property A potential future recreational use scenario was also evaluated

The commercial industrial properties surrounding the Silresirn properly also are expected to continue to be used for cornnnieircialindustrial purposes in the foreseeable future However future renovation or redevelopment of these properties is considered possible including construction of new buildings with basements The BSIVI railroad coinridor adjacent to the Siliresim property on the eastern side is also assumed to remain a railroad corridor for the foreseeable future Ground water is assumed to remain unused for consumptive and non-consumptive uses in the future (ie for drinking or induslriaJ process uses) due to MADEPs Groundwateir Use and Value Determination coupled with the relatively low yield of the shallowest water bearing layers While this assumption appears reasonable given this classification no formal restrictions or institutional controls have been established to ensure thai the ground water us not used for consumptive or non-consumptive purposes or that future land use does not involve contact with potentially contaminated soils

An exposure pathway describes the physical linkage between the source of a COPC and a current or projected future exposed receptor The potential human receptors that have been identified at this Site (under cuinrent and reasonably anticipated future exposure scenarios include com mercia Iindustrial workers railroad workers construction worke rs (eg new facility construction or uliilrry installlatiionrnaintenance workers) and

12

trespassers These potential human receptors may come in contact with surface soil (0 1 fl bgs) exposed subsurface soil as a result of excavation (unsaturated soil gtl ft bg and lt 10 fl bgs) groundwater and ambient or indoor air containing contaminant origin calling from the Sule The potential routes of exposure are incidental iingestiioi inhalation of partioulales or wolallies and dermal absorption These exposure route were also evaluated for a potential future recreational use scenario II should be note that leaching from soil to g round water is no longisir conside1 red a risk becauslt groundwater us no longer a potential drinking water source The pathway of most concern is through VOC emissions from contaminated giroundwater and subsequent diffusion upward into ambient and indoor air

now rrsK-oaseci nuiiiDers

WiOiMl CitiiribJii Units

Under this BSD I he Site will be divided into two Oils to facilitate docuinnentinq clean-up activities as defined below

approximately 12 Ions of subsurface VUC conlarninalicri However operalion of the SVE svsterin was placed on hold because it was unlike v that it would be able to reac Site CUGs

comply wnlh Federal and Slate requirement that are applicable or relevant and appropriate and are co si-effective The revised remedy utilizes permanent solutions

This E gt[) and supporting in formal ion are available for public review at the location lentiHied within this document In addition a notice of availability of the BS

piwided to a local newspaper of general circulation

or the foregoing reasons by my signature below I approve the iissuance of lt= llxplainiation oi Significant Differences tor the Silresirn Chemical Corporation Supeirfunc Site in Lowell Massachusetts and the changes and conclusions staled1 therein

Sus^h Studlieri Acting Director Office of Site Remediation and Restoration USE PA Region I

ADFIII si LOCS Draquo

lti

lii

pound j2bull

LLJ

(o (1) -c

C

c^

(ti b a

bull|lhraquo

r1uii1ijlagt

ltis

iraquo bull-

shy

b gt

craquo i[i

i deg bullgt

fdJr 111

| raquoS-shy I- i]j

-i 3 o a

i

ltgt HI

i -is D

c J

iii i ltgt

bull -3

i g

w

(3i

3 w

j|

laquopound e

fi (I laquo gt

iii

ijj IJL

bullbullbull ID $

O

inE

ij-O

j0o

shy

S = bull

ii S lt

bull lt[

nil (L)

jii[bullbull bull -i

n|gt

tri bullF1

igtraquot

E a

ir ii III Jl

CObullar

cgt CO^j

ugt

J

Ji

b(i ltLI

u (pound lt UI upi lt

=i bull - 1 -shyj 3 iij shy| IS |i i i = gt|i |igt D e~ ti bull bull bull (3pound

- jj ^3 -3 sshy (i i- ~ S = a ]=shy s= 7 lttrade ==

(IJ f rgt 3 I-shy shy rtl -r-i bull bull 11 -13 i bull shy 3 gtbull iamp bullbullbull gt (IJ S l 4l - rr bull TI i shy ni -- bullbullbull |= SJ b iii -5 L J $ ij ij i-iP J1 S sL e3 1 1 laquo laquo E Qlt1) E ii i ii-1 p MI ishy j t shy

= s ^ i = t t = i i pound t1

o ltgt o s 2 ltN3 w J bullbull = ^j

cu CL ]

^ 0

[ fir ]bullbullbull [ ltu

(3

[ii 11 D L^tl

(LJ

U 1 I

y J

I (IDE ii

]laquo

illSti

ii z 1 9

-L

C

IJLI LLI

=

iJUil ii(i

FOSTE R WH E E L E R E N VI RON M ENTA L CO R PORATI ON

The purpose of t h i s memorandum is to sinnraariltltbull I be re corn mended Clean-Dp GoEils (CUGs) f o r the s u r f a c e soil subsurface soi l and groundwater related to i he Si l res im Superfund Site im support of an Explanation of Significant Difference (BSD) The r isk-based ( LGs were or ig inal ly presented in the FniEil Add il lona I Site ID vesl igat ion and Re v is ion o f Si te C lean-Up (ioal s (Eosler Wheel er 2002) T hese CIJG s ivere discussed r e f ined ar id then compared to site da ta Appl icable or Relevant and Appropr ia te Requirements (ARARs) and curreni ROD cleanup levels fhe fo l lowing presents the c r i l e n a used lo develop the recommended CUGs (as cogtrnpairedto the current KOI) c l e a n u p levels)

bulli An updated IJSEPA COC screening and se lec t ion process was used (USEPA 1989 1 9 9 5 1999)

laquo The evaluat ion of the carcinogenic and non-cEireinogeriic polycyclic aromatic hydrocarbon (PAH) conipounds vas performed individually i n s t e a d of as EI g-roup ( U S E P A 1994 200 I a)

bulli T he upda ted cle rma I ris k asse ssrnenl guidance (FAGS Pa rt E) wa s applied (USE PA 2 GO1 b)

laquo The USE A Adult Lead Model was used to calculate soil lead c o n c e n t r a t i o n s associated with a (Ei rge t blood lead level and exposure parameter (USKPA 1996)

laquo The updated guidance for r isk assessment o f lt Eire moge n ic polyclhlorinated biphenylsi (PC Eh) wasiised(NCEA 1996)

Updated lox ico log ica l factors and parameters were usedl (USEPA 1997a 200la and MADEP 1 9 9 4 )

i A target r i sk goal of 1 E-5 and a target haard mdelt of 1 was used for each chernncal (d i rec t ion from USE PA Region 1 Site Manager)

laquo An assumption was made l l i E i t suirface soil consists of the soil between () -shy 1 ft bgs and lhal subsurface ur isa tura ted soil consists of the soil between 1 shy 10 fit bgs (USE PA I99 i )

laquo The Site ground w a t e r was reclassified as being low use and va lue nn a MA13EP Groun d w aie r Use and Val ue Detenminail ion (1VIA DEiF 1998)

laquo Leaching f rom s u b s u r f a c e (unsaturated) soil to ground wa te r was not considered EI critical consideration in setting sub- u r fE ice sioil CUGs (Fo- kT Wheeler 1999 2002)

laquo Commercial industr ia l l a n d use was assumed instead of r e s iden t i a l land use (foster Wheeler 19992002)

laquo The subsur face vapor in t rus ion to indoor air was e v E i l u a t e d as EI primary mbalEi t ion exposure ran te (Foste r W bee ler 2002 D SEP A 1997b)

ltbull Potential exposures to a construction worker w e r tr^aluated for soil and Birouridwater (Foster W h e e l e r 2002)

laquo Potential exposures to a trespasser were evaluated for so i l (Foster Wheeler 2 0 0 2 )

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

4 Revised Clean-up Gosils

tequireirnenis iuch as Dninkiino Wai or MlaxiiiTiurn ConlaiTiinant Levels and Non-zero inninant Level Goals

i I he 1999 ROD Remedy Review it was determined that certain ROD clean-up levels were based on assumptions thai were no longer appropriate and therefore required

ground water needed to be reviewed Future use exposure scenarios needed to be evaluated

raquo Changes in exposure pathways bullbullbull The extern I of the contaminated groundwater plume needed to be evaluated because il was moving faster than originally projected Potential off-property subsurface soil con lamina ion needed to be evaluated

gt Evolution of the technical approaches for Supeirfund risk assessment - The vapor rni grain on model and the methodology for selecting COPCs were no longer currenl and

raquo Specific technical issues relating to toxicily estimates - The use of toxicity surrogates for PAHs and dioxin was no longer recommended or necessary

Necessary updates for calculating revised CUGs included

ltgt Evaluating the subsurface soil to indoor air pathway for the commercialindustrial worker

ltbull Evaluating additional chemicals the inhalation palhways and igt Evaluating a child recreational receptor in the event thai I he Silresirn property or

adjacent properties are redeveloped for recreational use (eg soccer field) The potenlial exists for this type of development however since the area is currently

are summarized below Overall the chainpes in risk assumptions regarding groundwaler soil and air exposures at the Site significantly impact the CIJGs for a ariely of contaminants

Current Land Use and Site Conditions The approximate 16-acre Site is located in a heavily industrialized section of Lowell

storage facilities tractor-trailer storage light industrycommercial corido minium bull and open industrial land As a result oi MADEPs Ground water Use andl Value Deteinrimiriation IvIADEP has stipulated that ground water in the area would not be used as a drin king water source in I he failure This determination constitutes a significant change from the drinking water classification used to establish the 1991 ROD clean-up levels

The reasonaby foreseeable future land use designation for the Site is coinnnTiercialindustrial Soils with residual contamination above the CUGs will be excavated stabilized and capped on the Silresirn property Future exposures to soil or exposed groundwateir are considered possible even though the cap will likely extend over the entire Siliresim property A potential future recreational use scenario was also evaluated

The commercial industrial properties surrounding the Silresirn properly also are expected to continue to be used for cornnnieircialindustrial purposes in the foreseeable future However future renovation or redevelopment of these properties is considered possible including construction of new buildings with basements The BSIVI railroad coinridor adjacent to the Siliresim property on the eastern side is also assumed to remain a railroad corridor for the foreseeable future Ground water is assumed to remain unused for consumptive and non-consumptive uses in the future (ie for drinking or induslriaJ process uses) due to MADEPs Groundwateir Use and Value Determination coupled with the relatively low yield of the shallowest water bearing layers While this assumption appears reasonable given this classification no formal restrictions or institutional controls have been established to ensure thai the ground water us not used for consumptive or non-consumptive purposes or that future land use does not involve contact with potentially contaminated soils

An exposure pathway describes the physical linkage between the source of a COPC and a current or projected future exposed receptor The potential human receptors that have been identified at this Site (under cuinrent and reasonably anticipated future exposure scenarios include com mercia Iindustrial workers railroad workers construction worke rs (eg new facility construction or uliilrry installlatiionrnaintenance workers) and

12

trespassers These potential human receptors may come in contact with surface soil (0 1 fl bgs) exposed subsurface soil as a result of excavation (unsaturated soil gtl ft bg and lt 10 fl bgs) groundwater and ambient or indoor air containing contaminant origin calling from the Sule The potential routes of exposure are incidental iingestiioi inhalation of partioulales or wolallies and dermal absorption These exposure route were also evaluated for a potential future recreational use scenario II should be note that leaching from soil to g round water is no longisir conside1 red a risk becauslt groundwater us no longer a potential drinking water source The pathway of most concern is through VOC emissions from contaminated giroundwater and subsequent diffusion upward into ambient and indoor air

now rrsK-oaseci nuiiiDers

WiOiMl CitiiribJii Units

Under this BSD I he Site will be divided into two Oils to facilitate docuinnentinq clean-up activities as defined below

approximately 12 Ions of subsurface VUC conlarninalicri However operalion of the SVE svsterin was placed on hold because it was unlike v that it would be able to reac Site CUGs

comply wnlh Federal and Slate requirement that are applicable or relevant and appropriate and are co si-effective The revised remedy utilizes permanent solutions

This E gt[) and supporting in formal ion are available for public review at the location lentiHied within this document In addition a notice of availability of the BS

piwided to a local newspaper of general circulation

or the foregoing reasons by my signature below I approve the iissuance of lt= llxplainiation oi Significant Differences tor the Silresirn Chemical Corporation Supeirfunc Site in Lowell Massachusetts and the changes and conclusions staled1 therein

Sus^h Studlieri Acting Director Office of Site Remediation and Restoration USE PA Region I

ADFIII si LOCS Draquo

lti

lii

pound j2bull

LLJ

(o (1) -c

C

c^

(ti b a

bull|lhraquo

r1uii1ijlagt

ltis

iraquo bull-

shy

b gt

craquo i[i

i deg bullgt

fdJr 111

| raquoS-shy I- i]j

-i 3 o a

i

ltgt HI

i -is D

c J

iii i ltgt

bull -3

i g

w

(3i

3 w

j|

laquopound e

fi (I laquo gt

iii

ijj IJL

bullbullbull ID $

O

inE

ij-O

j0o

shy

S = bull

ii S lt

bull lt[

nil (L)

jii[bullbull bull -i

n|gt

tri bullF1

igtraquot

E a

ir ii III Jl

CObullar

cgt CO^j

ugt

J

Ji

b(i ltLI

u (pound lt UI upi lt

=i bull - 1 -shyj 3 iij shy| IS |i i i = gt|i |igt D e~ ti bull bull bull (3pound

- jj ^3 -3 sshy (i i- ~ S = a ]=shy s= 7 lttrade ==

(IJ f rgt 3 I-shy shy rtl -r-i bull bull 11 -13 i bull shy 3 gtbull iamp bullbullbull gt (IJ S l 4l - rr bull TI i shy ni -- bullbullbull |= SJ b iii -5 L J $ ij ij i-iP J1 S sL e3 1 1 laquo laquo E Qlt1) E ii i ii-1 p MI ishy j t shy

= s ^ i = t t = i i pound t1

o ltgt o s 2 ltN3 w J bullbull = ^j

cu CL ]

^ 0

[ fir ]bullbullbull [ ltu

(3

[ii 11 D L^tl

(LJ

U 1 I

y J

I (IDE ii

]laquo

illSti

ii z 1 9

-L

C

IJLI LLI

=

iJUil ii(i

FOSTE R WH E E L E R E N VI RON M ENTA L CO R PORATI ON

The purpose of t h i s memorandum is to sinnraariltltbull I be re corn mended Clean-Dp GoEils (CUGs) f o r the s u r f a c e soil subsurface soi l and groundwater related to i he Si l res im Superfund Site im support of an Explanation of Significant Difference (BSD) The r isk-based ( LGs were or ig inal ly presented in the FniEil Add il lona I Site ID vesl igat ion and Re v is ion o f Si te C lean-Up (ioal s (Eosler Wheel er 2002) T hese CIJG s ivere discussed r e f ined ar id then compared to site da ta Appl icable or Relevant and Appropr ia te Requirements (ARARs) and curreni ROD cleanup levels fhe fo l lowing presents the c r i l e n a used lo develop the recommended CUGs (as cogtrnpairedto the current KOI) c l e a n u p levels)

bulli An updated IJSEPA COC screening and se lec t ion process was used (USEPA 1989 1 9 9 5 1999)

laquo The evaluat ion of the carcinogenic and non-cEireinogeriic polycyclic aromatic hydrocarbon (PAH) conipounds vas performed individually i n s t e a d of as EI g-roup ( U S E P A 1994 200 I a)

bulli T he upda ted cle rma I ris k asse ssrnenl guidance (FAGS Pa rt E) wa s applied (USE PA 2 GO1 b)

laquo The USE A Adult Lead Model was used to calculate soil lead c o n c e n t r a t i o n s associated with a (Ei rge t blood lead level and exposure parameter (USKPA 1996)

laquo The updated guidance for r isk assessment o f lt Eire moge n ic polyclhlorinated biphenylsi (PC Eh) wasiised(NCEA 1996)

Updated lox ico log ica l factors and parameters were usedl (USEPA 1997a 200la and MADEP 1 9 9 4 )

i A target r i sk goal of 1 E-5 and a target haard mdelt of 1 was used for each chernncal (d i rec t ion from USE PA Region 1 Site Manager)

laquo An assumption was made l l i E i t suirface soil consists of the soil between () -shy 1 ft bgs and lhal subsurface ur isa tura ted soil consists of the soil between 1 shy 10 fit bgs (USE PA I99 i )

laquo The Site ground w a t e r was reclassified as being low use and va lue nn a MA13EP Groun d w aie r Use and Val ue Detenminail ion (1VIA DEiF 1998)

laquo Leaching f rom s u b s u r f a c e (unsaturated) soil to ground wa te r was not considered EI critical consideration in setting sub- u r fE ice sioil CUGs (Fo- kT Wheeler 1999 2002)

laquo Commercial industr ia l l a n d use was assumed instead of r e s iden t i a l land use (foster Wheeler 19992002)

laquo The subsur face vapor in t rus ion to indoor air was e v E i l u a t e d as EI primary mbalEi t ion exposure ran te (Foste r W bee ler 2002 D SEP A 1997b)

ltbull Potential exposures to a construction worker w e r tr^aluated for soil and Birouridwater (Foster W h e e l e r 2002)

laquo Potential exposures to a trespasser were evaluated for so i l (Foster Wheeler 2 0 0 2 )

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

are summarized below Overall the chainpes in risk assumptions regarding groundwaler soil and air exposures at the Site significantly impact the CIJGs for a ariely of contaminants

Current Land Use and Site Conditions The approximate 16-acre Site is located in a heavily industrialized section of Lowell

storage facilities tractor-trailer storage light industrycommercial corido minium bull and open industrial land As a result oi MADEPs Ground water Use andl Value Deteinrimiriation IvIADEP has stipulated that ground water in the area would not be used as a drin king water source in I he failure This determination constitutes a significant change from the drinking water classification used to establish the 1991 ROD clean-up levels

The reasonaby foreseeable future land use designation for the Site is coinnnTiercialindustrial Soils with residual contamination above the CUGs will be excavated stabilized and capped on the Silresirn property Future exposures to soil or exposed groundwateir are considered possible even though the cap will likely extend over the entire Siliresim property A potential future recreational use scenario was also evaluated

The commercial industrial properties surrounding the Silresirn properly also are expected to continue to be used for cornnnieircialindustrial purposes in the foreseeable future However future renovation or redevelopment of these properties is considered possible including construction of new buildings with basements The BSIVI railroad coinridor adjacent to the Siliresim property on the eastern side is also assumed to remain a railroad corridor for the foreseeable future Ground water is assumed to remain unused for consumptive and non-consumptive uses in the future (ie for drinking or induslriaJ process uses) due to MADEPs Groundwateir Use and Value Determination coupled with the relatively low yield of the shallowest water bearing layers While this assumption appears reasonable given this classification no formal restrictions or institutional controls have been established to ensure thai the ground water us not used for consumptive or non-consumptive purposes or that future land use does not involve contact with potentially contaminated soils

An exposure pathway describes the physical linkage between the source of a COPC and a current or projected future exposed receptor The potential human receptors that have been identified at this Site (under cuinrent and reasonably anticipated future exposure scenarios include com mercia Iindustrial workers railroad workers construction worke rs (eg new facility construction or uliilrry installlatiionrnaintenance workers) and

12

trespassers These potential human receptors may come in contact with surface soil (0 1 fl bgs) exposed subsurface soil as a result of excavation (unsaturated soil gtl ft bg and lt 10 fl bgs) groundwater and ambient or indoor air containing contaminant origin calling from the Sule The potential routes of exposure are incidental iingestiioi inhalation of partioulales or wolallies and dermal absorption These exposure route were also evaluated for a potential future recreational use scenario II should be note that leaching from soil to g round water is no longisir conside1 red a risk becauslt groundwater us no longer a potential drinking water source The pathway of most concern is through VOC emissions from contaminated giroundwater and subsequent diffusion upward into ambient and indoor air

now rrsK-oaseci nuiiiDers

WiOiMl CitiiribJii Units

Under this BSD I he Site will be divided into two Oils to facilitate docuinnentinq clean-up activities as defined below

approximately 12 Ions of subsurface VUC conlarninalicri However operalion of the SVE svsterin was placed on hold because it was unlike v that it would be able to reac Site CUGs

comply wnlh Federal and Slate requirement that are applicable or relevant and appropriate and are co si-effective The revised remedy utilizes permanent solutions

This E gt[) and supporting in formal ion are available for public review at the location lentiHied within this document In addition a notice of availability of the BS

piwided to a local newspaper of general circulation

or the foregoing reasons by my signature below I approve the iissuance of lt= llxplainiation oi Significant Differences tor the Silresirn Chemical Corporation Supeirfunc Site in Lowell Massachusetts and the changes and conclusions staled1 therein

Sus^h Studlieri Acting Director Office of Site Remediation and Restoration USE PA Region I

ADFIII si LOCS Draquo

lti

lii

pound j2bull

LLJ

(o (1) -c

C

c^

(ti b a

bull|lhraquo

r1uii1ijlagt

ltis

iraquo bull-

shy

b gt

craquo i[i

i deg bullgt

fdJr 111

| raquoS-shy I- i]j

-i 3 o a

i

ltgt HI

i -is D

c J

iii i ltgt

bull -3

i g

w

(3i

3 w

j|

laquopound e

fi (I laquo gt

iii

ijj IJL

bullbullbull ID $

O

inE

ij-O

j0o

shy

S = bull

ii S lt

bull lt[

nil (L)

jii[bullbull bull -i

n|gt

tri bullF1

igtraquot

E a

ir ii III Jl

CObullar

cgt CO^j

ugt

J

Ji

b(i ltLI

u (pound lt UI upi lt

=i bull - 1 -shyj 3 iij shy| IS |i i i = gt|i |igt D e~ ti bull bull bull (3pound

- jj ^3 -3 sshy (i i- ~ S = a ]=shy s= 7 lttrade ==

(IJ f rgt 3 I-shy shy rtl -r-i bull bull 11 -13 i bull shy 3 gtbull iamp bullbullbull gt (IJ S l 4l - rr bull TI i shy ni -- bullbullbull |= SJ b iii -5 L J $ ij ij i-iP J1 S sL e3 1 1 laquo laquo E Qlt1) E ii i ii-1 p MI ishy j t shy

= s ^ i = t t = i i pound t1

o ltgt o s 2 ltN3 w J bullbull = ^j

cu CL ]

^ 0

[ fir ]bullbullbull [ ltu

(3

[ii 11 D L^tl

(LJ

U 1 I

y J

I (IDE ii

]laquo

illSti

ii z 1 9

-L

C

IJLI LLI

=

iJUil ii(i

FOSTE R WH E E L E R E N VI RON M ENTA L CO R PORATI ON

The purpose of t h i s memorandum is to sinnraariltltbull I be re corn mended Clean-Dp GoEils (CUGs) f o r the s u r f a c e soil subsurface soi l and groundwater related to i he Si l res im Superfund Site im support of an Explanation of Significant Difference (BSD) The r isk-based ( LGs were or ig inal ly presented in the FniEil Add il lona I Site ID vesl igat ion and Re v is ion o f Si te C lean-Up (ioal s (Eosler Wheel er 2002) T hese CIJG s ivere discussed r e f ined ar id then compared to site da ta Appl icable or Relevant and Appropr ia te Requirements (ARARs) and curreni ROD cleanup levels fhe fo l lowing presents the c r i l e n a used lo develop the recommended CUGs (as cogtrnpairedto the current KOI) c l e a n u p levels)

bulli An updated IJSEPA COC screening and se lec t ion process was used (USEPA 1989 1 9 9 5 1999)

laquo The evaluat ion of the carcinogenic and non-cEireinogeriic polycyclic aromatic hydrocarbon (PAH) conipounds vas performed individually i n s t e a d of as EI g-roup ( U S E P A 1994 200 I a)

bulli T he upda ted cle rma I ris k asse ssrnenl guidance (FAGS Pa rt E) wa s applied (USE PA 2 GO1 b)

laquo The USE A Adult Lead Model was used to calculate soil lead c o n c e n t r a t i o n s associated with a (Ei rge t blood lead level and exposure parameter (USKPA 1996)

laquo The updated guidance for r isk assessment o f lt Eire moge n ic polyclhlorinated biphenylsi (PC Eh) wasiised(NCEA 1996)

Updated lox ico log ica l factors and parameters were usedl (USEPA 1997a 200la and MADEP 1 9 9 4 )

i A target r i sk goal of 1 E-5 and a target haard mdelt of 1 was used for each chernncal (d i rec t ion from USE PA Region 1 Site Manager)

laquo An assumption was made l l i E i t suirface soil consists of the soil between () -shy 1 ft bgs and lhal subsurface ur isa tura ted soil consists of the soil between 1 shy 10 fit bgs (USE PA I99 i )

laquo The Site ground w a t e r was reclassified as being low use and va lue nn a MA13EP Groun d w aie r Use and Val ue Detenminail ion (1VIA DEiF 1998)

laquo Leaching f rom s u b s u r f a c e (unsaturated) soil to ground wa te r was not considered EI critical consideration in setting sub- u r fE ice sioil CUGs (Fo- kT Wheeler 1999 2002)

laquo Commercial industr ia l l a n d use was assumed instead of r e s iden t i a l land use (foster Wheeler 19992002)

laquo The subsur face vapor in t rus ion to indoor air was e v E i l u a t e d as EI primary mbalEi t ion exposure ran te (Foste r W bee ler 2002 D SEP A 1997b)

ltbull Potential exposures to a construction worker w e r tr^aluated for soil and Birouridwater (Foster W h e e l e r 2002)

laquo Potential exposures to a trespasser were evaluated for so i l (Foster Wheeler 2 0 0 2 )

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

trespassers These potential human receptors may come in contact with surface soil (0 1 fl bgs) exposed subsurface soil as a result of excavation (unsaturated soil gtl ft bg and lt 10 fl bgs) groundwater and ambient or indoor air containing contaminant origin calling from the Sule The potential routes of exposure are incidental iingestiioi inhalation of partioulales or wolallies and dermal absorption These exposure route were also evaluated for a potential future recreational use scenario II should be note that leaching from soil to g round water is no longisir conside1 red a risk becauslt groundwater us no longer a potential drinking water source The pathway of most concern is through VOC emissions from contaminated giroundwater and subsequent diffusion upward into ambient and indoor air

now rrsK-oaseci nuiiiDers

WiOiMl CitiiribJii Units

Under this BSD I he Site will be divided into two Oils to facilitate docuinnentinq clean-up activities as defined below

approximately 12 Ions of subsurface VUC conlarninalicri However operalion of the SVE svsterin was placed on hold because it was unlike v that it would be able to reac Site CUGs

comply wnlh Federal and Slate requirement that are applicable or relevant and appropriate and are co si-effective The revised remedy utilizes permanent solutions

This E gt[) and supporting in formal ion are available for public review at the location lentiHied within this document In addition a notice of availability of the BS

piwided to a local newspaper of general circulation

or the foregoing reasons by my signature below I approve the iissuance of lt= llxplainiation oi Significant Differences tor the Silresirn Chemical Corporation Supeirfunc Site in Lowell Massachusetts and the changes and conclusions staled1 therein

Sus^h Studlieri Acting Director Office of Site Remediation and Restoration USE PA Region I

ADFIII si LOCS Draquo

lti

lii

pound j2bull

LLJ

(o (1) -c

C

c^

(ti b a

bull|lhraquo

r1uii1ijlagt

ltis

iraquo bull-

shy

b gt

craquo i[i

i deg bullgt

fdJr 111

| raquoS-shy I- i]j

-i 3 o a

i

ltgt HI

i -is D

c J

iii i ltgt

bull -3

i g

w

(3i

3 w

j|

laquopound e

fi (I laquo gt

iii

ijj IJL

bullbullbull ID $

O

inE

ij-O

j0o

shy

S = bull

ii S lt

bull lt[

nil (L)

jii[bullbull bull -i

n|gt

tri bullF1

igtraquot

E a

ir ii III Jl

CObullar

cgt CO^j

ugt

J

Ji

b(i ltLI

u (pound lt UI upi lt

=i bull - 1 -shyj 3 iij shy| IS |i i i = gt|i |igt D e~ ti bull bull bull (3pound

- jj ^3 -3 sshy (i i- ~ S = a ]=shy s= 7 lttrade ==

(IJ f rgt 3 I-shy shy rtl -r-i bull bull 11 -13 i bull shy 3 gtbull iamp bullbullbull gt (IJ S l 4l - rr bull TI i shy ni -- bullbullbull |= SJ b iii -5 L J $ ij ij i-iP J1 S sL e3 1 1 laquo laquo E Qlt1) E ii i ii-1 p MI ishy j t shy

= s ^ i = t t = i i pound t1

o ltgt o s 2 ltN3 w J bullbull = ^j

cu CL ]

^ 0

[ fir ]bullbullbull [ ltu

(3

[ii 11 D L^tl

(LJ

U 1 I

y J

I (IDE ii

]laquo

illSti

ii z 1 9

-L

C

IJLI LLI

=

iJUil ii(i

FOSTE R WH E E L E R E N VI RON M ENTA L CO R PORATI ON

The purpose of t h i s memorandum is to sinnraariltltbull I be re corn mended Clean-Dp GoEils (CUGs) f o r the s u r f a c e soil subsurface soi l and groundwater related to i he Si l res im Superfund Site im support of an Explanation of Significant Difference (BSD) The r isk-based ( LGs were or ig inal ly presented in the FniEil Add il lona I Site ID vesl igat ion and Re v is ion o f Si te C lean-Up (ioal s (Eosler Wheel er 2002) T hese CIJG s ivere discussed r e f ined ar id then compared to site da ta Appl icable or Relevant and Appropr ia te Requirements (ARARs) and curreni ROD cleanup levels fhe fo l lowing presents the c r i l e n a used lo develop the recommended CUGs (as cogtrnpairedto the current KOI) c l e a n u p levels)

bulli An updated IJSEPA COC screening and se lec t ion process was used (USEPA 1989 1 9 9 5 1999)

laquo The evaluat ion of the carcinogenic and non-cEireinogeriic polycyclic aromatic hydrocarbon (PAH) conipounds vas performed individually i n s t e a d of as EI g-roup ( U S E P A 1994 200 I a)

bulli T he upda ted cle rma I ris k asse ssrnenl guidance (FAGS Pa rt E) wa s applied (USE PA 2 GO1 b)

laquo The USE A Adult Lead Model was used to calculate soil lead c o n c e n t r a t i o n s associated with a (Ei rge t blood lead level and exposure parameter (USKPA 1996)

laquo The updated guidance for r isk assessment o f lt Eire moge n ic polyclhlorinated biphenylsi (PC Eh) wasiised(NCEA 1996)

Updated lox ico log ica l factors and parameters were usedl (USEPA 1997a 200la and MADEP 1 9 9 4 )

i A target r i sk goal of 1 E-5 and a target haard mdelt of 1 was used for each chernncal (d i rec t ion from USE PA Region 1 Site Manager)

laquo An assumption was made l l i E i t suirface soil consists of the soil between () -shy 1 ft bgs and lhal subsurface ur isa tura ted soil consists of the soil between 1 shy 10 fit bgs (USE PA I99 i )

laquo The Site ground w a t e r was reclassified as being low use and va lue nn a MA13EP Groun d w aie r Use and Val ue Detenminail ion (1VIA DEiF 1998)

laquo Leaching f rom s u b s u r f a c e (unsaturated) soil to ground wa te r was not considered EI critical consideration in setting sub- u r fE ice sioil CUGs (Fo- kT Wheeler 1999 2002)

laquo Commercial industr ia l l a n d use was assumed instead of r e s iden t i a l land use (foster Wheeler 19992002)

laquo The subsur face vapor in t rus ion to indoor air was e v E i l u a t e d as EI primary mbalEi t ion exposure ran te (Foste r W bee ler 2002 D SEP A 1997b)

ltbull Potential exposures to a construction worker w e r tr^aluated for soil and Birouridwater (Foster W h e e l e r 2002)

laquo Potential exposures to a trespasser were evaluated for so i l (Foster Wheeler 2 0 0 2 )

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

comply wnlh Federal and Slate requirement that are applicable or relevant and appropriate and are co si-effective The revised remedy utilizes permanent solutions

This E gt[) and supporting in formal ion are available for public review at the location lentiHied within this document In addition a notice of availability of the BS

piwided to a local newspaper of general circulation

or the foregoing reasons by my signature below I approve the iissuance of lt= llxplainiation oi Significant Differences tor the Silresirn Chemical Corporation Supeirfunc Site in Lowell Massachusetts and the changes and conclusions staled1 therein

Sus^h Studlieri Acting Director Office of Site Remediation and Restoration USE PA Region I

ADFIII si LOCS Draquo

lti

lii

pound j2bull

LLJ

(o (1) -c

C

c^

(ti b a

bull|lhraquo

r1uii1ijlagt

ltis

iraquo bull-

shy

b gt

craquo i[i

i deg bullgt

fdJr 111

| raquoS-shy I- i]j

-i 3 o a

i

ltgt HI

i -is D

c J

iii i ltgt

bull -3

i g

w

(3i

3 w

j|

laquopound e

fi (I laquo gt

iii

ijj IJL

bullbullbull ID $

O

inE

ij-O

j0o

shy

S = bull

ii S lt

bull lt[

nil (L)

jii[bullbull bull -i

n|gt

tri bullF1

igtraquot

E a

ir ii III Jl

CObullar

cgt CO^j

ugt

J

Ji

b(i ltLI

u (pound lt UI upi lt

=i bull - 1 -shyj 3 iij shy| IS |i i i = gt|i |igt D e~ ti bull bull bull (3pound

- jj ^3 -3 sshy (i i- ~ S = a ]=shy s= 7 lttrade ==

(IJ f rgt 3 I-shy shy rtl -r-i bull bull 11 -13 i bull shy 3 gtbull iamp bullbullbull gt (IJ S l 4l - rr bull TI i shy ni -- bullbullbull |= SJ b iii -5 L J $ ij ij i-iP J1 S sL e3 1 1 laquo laquo E Qlt1) E ii i ii-1 p MI ishy j t shy

= s ^ i = t t = i i pound t1

o ltgt o s 2 ltN3 w J bullbull = ^j

cu CL ]

^ 0

[ fir ]bullbullbull [ ltu

(3

[ii 11 D L^tl

(LJ

U 1 I

y J

I (IDE ii

]laquo

illSti

ii z 1 9

-L

C

IJLI LLI

=

iJUil ii(i

FOSTE R WH E E L E R E N VI RON M ENTA L CO R PORATI ON

The purpose of t h i s memorandum is to sinnraariltltbull I be re corn mended Clean-Dp GoEils (CUGs) f o r the s u r f a c e soil subsurface soi l and groundwater related to i he Si l res im Superfund Site im support of an Explanation of Significant Difference (BSD) The r isk-based ( LGs were or ig inal ly presented in the FniEil Add il lona I Site ID vesl igat ion and Re v is ion o f Si te C lean-Up (ioal s (Eosler Wheel er 2002) T hese CIJG s ivere discussed r e f ined ar id then compared to site da ta Appl icable or Relevant and Appropr ia te Requirements (ARARs) and curreni ROD cleanup levels fhe fo l lowing presents the c r i l e n a used lo develop the recommended CUGs (as cogtrnpairedto the current KOI) c l e a n u p levels)

bulli An updated IJSEPA COC screening and se lec t ion process was used (USEPA 1989 1 9 9 5 1999)

laquo The evaluat ion of the carcinogenic and non-cEireinogeriic polycyclic aromatic hydrocarbon (PAH) conipounds vas performed individually i n s t e a d of as EI g-roup ( U S E P A 1994 200 I a)

bulli T he upda ted cle rma I ris k asse ssrnenl guidance (FAGS Pa rt E) wa s applied (USE PA 2 GO1 b)

laquo The USE A Adult Lead Model was used to calculate soil lead c o n c e n t r a t i o n s associated with a (Ei rge t blood lead level and exposure parameter (USKPA 1996)

laquo The updated guidance for r isk assessment o f lt Eire moge n ic polyclhlorinated biphenylsi (PC Eh) wasiised(NCEA 1996)

Updated lox ico log ica l factors and parameters were usedl (USEPA 1997a 200la and MADEP 1 9 9 4 )

i A target r i sk goal of 1 E-5 and a target haard mdelt of 1 was used for each chernncal (d i rec t ion from USE PA Region 1 Site Manager)

laquo An assumption was made l l i E i t suirface soil consists of the soil between () -shy 1 ft bgs and lhal subsurface ur isa tura ted soil consists of the soil between 1 shy 10 fit bgs (USE PA I99 i )

laquo The Site ground w a t e r was reclassified as being low use and va lue nn a MA13EP Groun d w aie r Use and Val ue Detenminail ion (1VIA DEiF 1998)

laquo Leaching f rom s u b s u r f a c e (unsaturated) soil to ground wa te r was not considered EI critical consideration in setting sub- u r fE ice sioil CUGs (Fo- kT Wheeler 1999 2002)

laquo Commercial industr ia l l a n d use was assumed instead of r e s iden t i a l land use (foster Wheeler 19992002)

laquo The subsur face vapor in t rus ion to indoor air was e v E i l u a t e d as EI primary mbalEi t ion exposure ran te (Foste r W bee ler 2002 D SEP A 1997b)

ltbull Potential exposures to a construction worker w e r tr^aluated for soil and Birouridwater (Foster W h e e l e r 2002)

laquo Potential exposures to a trespasser were evaluated for so i l (Foster Wheeler 2 0 0 2 )

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

ADFIII si LOCS Draquo

lti

lii

pound j2bull

LLJ

(o (1) -c

C

c^

(ti b a

bull|lhraquo

r1uii1ijlagt

ltis

iraquo bull-

shy

b gt

craquo i[i

i deg bullgt

fdJr 111

| raquoS-shy I- i]j

-i 3 o a

i

ltgt HI

i -is D

c J

iii i ltgt

bull -3

i g

w

(3i

3 w

j|

laquopound e

fi (I laquo gt

iii

ijj IJL

bullbullbull ID $

O

inE

ij-O

j0o

shy

S = bull

ii S lt

bull lt[

nil (L)

jii[bullbull bull -i

n|gt

tri bullF1

igtraquot

E a

ir ii III Jl

CObullar

cgt CO^j

ugt

J

Ji

b(i ltLI

u (pound lt UI upi lt

=i bull - 1 -shyj 3 iij shy| IS |i i i = gt|i |igt D e~ ti bull bull bull (3pound

- jj ^3 -3 sshy (i i- ~ S = a ]=shy s= 7 lttrade ==

(IJ f rgt 3 I-shy shy rtl -r-i bull bull 11 -13 i bull shy 3 gtbull iamp bullbullbull gt (IJ S l 4l - rr bull TI i shy ni -- bullbullbull |= SJ b iii -5 L J $ ij ij i-iP J1 S sL e3 1 1 laquo laquo E Qlt1) E ii i ii-1 p MI ishy j t shy

= s ^ i = t t = i i pound t1

o ltgt o s 2 ltN3 w J bullbull = ^j

cu CL ]

^ 0

[ fir ]bullbullbull [ ltu

(3

[ii 11 D L^tl

(LJ

U 1 I

y J

I (IDE ii

]laquo

illSti

ii z 1 9

-L

C

IJLI LLI

=

iJUil ii(i

FOSTE R WH E E L E R E N VI RON M ENTA L CO R PORATI ON

The purpose of t h i s memorandum is to sinnraariltltbull I be re corn mended Clean-Dp GoEils (CUGs) f o r the s u r f a c e soil subsurface soi l and groundwater related to i he Si l res im Superfund Site im support of an Explanation of Significant Difference (BSD) The r isk-based ( LGs were or ig inal ly presented in the FniEil Add il lona I Site ID vesl igat ion and Re v is ion o f Si te C lean-Up (ioal s (Eosler Wheel er 2002) T hese CIJG s ivere discussed r e f ined ar id then compared to site da ta Appl icable or Relevant and Appropr ia te Requirements (ARARs) and curreni ROD cleanup levels fhe fo l lowing presents the c r i l e n a used lo develop the recommended CUGs (as cogtrnpairedto the current KOI) c l e a n u p levels)

bulli An updated IJSEPA COC screening and se lec t ion process was used (USEPA 1989 1 9 9 5 1999)

laquo The evaluat ion of the carcinogenic and non-cEireinogeriic polycyclic aromatic hydrocarbon (PAH) conipounds vas performed individually i n s t e a d of as EI g-roup ( U S E P A 1994 200 I a)

bulli T he upda ted cle rma I ris k asse ssrnenl guidance (FAGS Pa rt E) wa s applied (USE PA 2 GO1 b)

laquo The USE A Adult Lead Model was used to calculate soil lead c o n c e n t r a t i o n s associated with a (Ei rge t blood lead level and exposure parameter (USKPA 1996)

laquo The updated guidance for r isk assessment o f lt Eire moge n ic polyclhlorinated biphenylsi (PC Eh) wasiised(NCEA 1996)

Updated lox ico log ica l factors and parameters were usedl (USEPA 1997a 200la and MADEP 1 9 9 4 )

i A target r i sk goal of 1 E-5 and a target haard mdelt of 1 was used for each chernncal (d i rec t ion from USE PA Region 1 Site Manager)

laquo An assumption was made l l i E i t suirface soil consists of the soil between () -shy 1 ft bgs and lhal subsurface ur isa tura ted soil consists of the soil between 1 shy 10 fit bgs (USE PA I99 i )

laquo The Site ground w a t e r was reclassified as being low use and va lue nn a MA13EP Groun d w aie r Use and Val ue Detenminail ion (1VIA DEiF 1998)

laquo Leaching f rom s u b s u r f a c e (unsaturated) soil to ground wa te r was not considered EI critical consideration in setting sub- u r fE ice sioil CUGs (Fo- kT Wheeler 1999 2002)

laquo Commercial industr ia l l a n d use was assumed instead of r e s iden t i a l land use (foster Wheeler 19992002)

laquo The subsur face vapor in t rus ion to indoor air was e v E i l u a t e d as EI primary mbalEi t ion exposure ran te (Foste r W bee ler 2002 D SEP A 1997b)

ltbull Potential exposures to a construction worker w e r tr^aluated for soil and Birouridwater (Foster W h e e l e r 2002)

laquo Potential exposures to a trespasser were evaluated for so i l (Foster Wheeler 2 0 0 2 )

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

lti

lii

pound j2bull

LLJ

(o (1) -c

C

c^

(ti b a

bull|lhraquo

r1uii1ijlagt

ltis

iraquo bull-

shy

b gt

craquo i[i

i deg bullgt

fdJr 111

| raquoS-shy I- i]j

-i 3 o a

i

ltgt HI

i -is D

c J

iii i ltgt

bull -3

i g

w

(3i

3 w

j|

laquopound e

fi (I laquo gt

iii

ijj IJL

bullbullbull ID $

O

inE

ij-O

j0o

shy

S = bull

ii S lt

bull lt[

nil (L)

jii[bullbull bull -i

n|gt

tri bullF1

igtraquot

E a

ir ii III Jl

CObullar

cgt CO^j

ugt

J

Ji

b(i ltLI

u (pound lt UI upi lt

=i bull - 1 -shyj 3 iij shy| IS |i i i = gt|i |igt D e~ ti bull bull bull (3pound

- jj ^3 -3 sshy (i i- ~ S = a ]=shy s= 7 lttrade ==

(IJ f rgt 3 I-shy shy rtl -r-i bull bull 11 -13 i bull shy 3 gtbull iamp bullbullbull gt (IJ S l 4l - rr bull TI i shy ni -- bullbullbull |= SJ b iii -5 L J $ ij ij i-iP J1 S sL e3 1 1 laquo laquo E Qlt1) E ii i ii-1 p MI ishy j t shy

= s ^ i = t t = i i pound t1

o ltgt o s 2 ltN3 w J bullbull = ^j

cu CL ]

^ 0

[ fir ]bullbullbull [ ltu

(3

[ii 11 D L^tl

(LJ

U 1 I

y J

I (IDE ii

]laquo

illSti

ii z 1 9

-L

C

IJLI LLI

=

iJUil ii(i

FOSTE R WH E E L E R E N VI RON M ENTA L CO R PORATI ON

The purpose of t h i s memorandum is to sinnraariltltbull I be re corn mended Clean-Dp GoEils (CUGs) f o r the s u r f a c e soil subsurface soi l and groundwater related to i he Si l res im Superfund Site im support of an Explanation of Significant Difference (BSD) The r isk-based ( LGs were or ig inal ly presented in the FniEil Add il lona I Site ID vesl igat ion and Re v is ion o f Si te C lean-Up (ioal s (Eosler Wheel er 2002) T hese CIJG s ivere discussed r e f ined ar id then compared to site da ta Appl icable or Relevant and Appropr ia te Requirements (ARARs) and curreni ROD cleanup levels fhe fo l lowing presents the c r i l e n a used lo develop the recommended CUGs (as cogtrnpairedto the current KOI) c l e a n u p levels)

bulli An updated IJSEPA COC screening and se lec t ion process was used (USEPA 1989 1 9 9 5 1999)

laquo The evaluat ion of the carcinogenic and non-cEireinogeriic polycyclic aromatic hydrocarbon (PAH) conipounds vas performed individually i n s t e a d of as EI g-roup ( U S E P A 1994 200 I a)

bulli T he upda ted cle rma I ris k asse ssrnenl guidance (FAGS Pa rt E) wa s applied (USE PA 2 GO1 b)

laquo The USE A Adult Lead Model was used to calculate soil lead c o n c e n t r a t i o n s associated with a (Ei rge t blood lead level and exposure parameter (USKPA 1996)

laquo The updated guidance for r isk assessment o f lt Eire moge n ic polyclhlorinated biphenylsi (PC Eh) wasiised(NCEA 1996)

Updated lox ico log ica l factors and parameters were usedl (USEPA 1997a 200la and MADEP 1 9 9 4 )

i A target r i sk goal of 1 E-5 and a target haard mdelt of 1 was used for each chernncal (d i rec t ion from USE PA Region 1 Site Manager)

laquo An assumption was made l l i E i t suirface soil consists of the soil between () -shy 1 ft bgs and lhal subsurface ur isa tura ted soil consists of the soil between 1 shy 10 fit bgs (USE PA I99 i )

laquo The Site ground w a t e r was reclassified as being low use and va lue nn a MA13EP Groun d w aie r Use and Val ue Detenminail ion (1VIA DEiF 1998)

laquo Leaching f rom s u b s u r f a c e (unsaturated) soil to ground wa te r was not considered EI critical consideration in setting sub- u r fE ice sioil CUGs (Fo- kT Wheeler 1999 2002)

laquo Commercial industr ia l l a n d use was assumed instead of r e s iden t i a l land use (foster Wheeler 19992002)

laquo The subsur face vapor in t rus ion to indoor air was e v E i l u a t e d as EI primary mbalEi t ion exposure ran te (Foste r W bee ler 2002 D SEP A 1997b)

ltbull Potential exposures to a construction worker w e r tr^aluated for soil and Birouridwater (Foster W h e e l e r 2002)

laquo Potential exposures to a trespasser were evaluated for so i l (Foster Wheeler 2 0 0 2 )

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

FOSTE R WH E E L E R E N VI RON M ENTA L CO R PORATI ON

The purpose of t h i s memorandum is to sinnraariltltbull I be re corn mended Clean-Dp GoEils (CUGs) f o r the s u r f a c e soil subsurface soi l and groundwater related to i he Si l res im Superfund Site im support of an Explanation of Significant Difference (BSD) The r isk-based ( LGs were or ig inal ly presented in the FniEil Add il lona I Site ID vesl igat ion and Re v is ion o f Si te C lean-Up (ioal s (Eosler Wheel er 2002) T hese CIJG s ivere discussed r e f ined ar id then compared to site da ta Appl icable or Relevant and Appropr ia te Requirements (ARARs) and curreni ROD cleanup levels fhe fo l lowing presents the c r i l e n a used lo develop the recommended CUGs (as cogtrnpairedto the current KOI) c l e a n u p levels)

bulli An updated IJSEPA COC screening and se lec t ion process was used (USEPA 1989 1 9 9 5 1999)

laquo The evaluat ion of the carcinogenic and non-cEireinogeriic polycyclic aromatic hydrocarbon (PAH) conipounds vas performed individually i n s t e a d of as EI g-roup ( U S E P A 1994 200 I a)

bulli T he upda ted cle rma I ris k asse ssrnenl guidance (FAGS Pa rt E) wa s applied (USE PA 2 GO1 b)

laquo The USE A Adult Lead Model was used to calculate soil lead c o n c e n t r a t i o n s associated with a (Ei rge t blood lead level and exposure parameter (USKPA 1996)

laquo The updated guidance for r isk assessment o f lt Eire moge n ic polyclhlorinated biphenylsi (PC Eh) wasiised(NCEA 1996)

Updated lox ico log ica l factors and parameters were usedl (USEPA 1997a 200la and MADEP 1 9 9 4 )

i A target r i sk goal of 1 E-5 and a target haard mdelt of 1 was used for each chernncal (d i rec t ion from USE PA Region 1 Site Manager)

laquo An assumption was made l l i E i t suirface soil consists of the soil between () -shy 1 ft bgs and lhal subsurface ur isa tura ted soil consists of the soil between 1 shy 10 fit bgs (USE PA I99 i )

laquo The Site ground w a t e r was reclassified as being low use and va lue nn a MA13EP Groun d w aie r Use and Val ue Detenminail ion (1VIA DEiF 1998)

laquo Leaching f rom s u b s u r f a c e (unsaturated) soil to ground wa te r was not considered EI critical consideration in setting sub- u r fE ice sioil CUGs (Fo- kT Wheeler 1999 2002)

laquo Commercial industr ia l l a n d use was assumed instead of r e s iden t i a l land use (foster Wheeler 19992002)

laquo The subsur face vapor in t rus ion to indoor air was e v E i l u a t e d as EI primary mbalEi t ion exposure ran te (Foste r W bee ler 2002 D SEP A 1997b)

ltbull Potential exposures to a construction worker w e r tr^aluated for soil and Birouridwater (Foster W h e e l e r 2002)

laquo Potential exposures to a trespasser were evaluated for so i l (Foster Wheeler 2 0 0 2 )

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

I Potential exposure - to a railroad worker on I he Damp1VI Parcel were evaluates f o r so i l ( f o s t e r W h e e l e r 2002)

Groundwatet was assumed lo encompass t h e shallow and moderate jnounclwater that are reasonably access ible ( i e within 15 f) bgs) (f o-tcr Wheeler 1999 2002)

raquo The MCP GW-3 Standard for grounidwatei lt M ( ) CMR 400974(2)) and the MCP Upper Concen t ra t ion Lirmls (UCLs) ibi soil and groundwater (310 CMR 4()0996(7))were considered for theCUG-

Based on these cnlena the following risk-based CUGs are presented for surface soil (corairneirci Eil indu sit ia I land userailroad land use) subsurface soil (cornrnercia Iindustrial land use) and groundwater (cogtmrnerc i a I indus t r i a l land use) (see Tables I t h r o u g h 3 respect ive ly) The ri sis-based CUGs shown on these tables were compared to other cleanup standards for the S i t e Eind the most stringent (lowest) was selected as the recommended CUG for each c h e m i c a l of conceinn These ogtther s tsindards were the MADEP Method I GV-1 standards (to account for e c o l o g i c a l impacts f rom I he groundwater which were not explici t ly e v a l u a t e d in the c alcylatnon of t h e r i s k - b a s e d CLGs) and the MAOlEiP Method 3 Upper ConcentTation Limi t s for oill and groandwaLeir

]SseJjerei][Cesgt

Foster Wheeler Environmental Corporation (Fosler Wheeler) W1) ROD Remedy Reviev Silresirn Superfund Site Lovell IVIassachusells February 1999

U SIB PA 1994 R isk IJ pd at es N urnbe r 2 Reg ion I Me w ampng Ian d August 1994

U SI PA 199 5 R isk IJ pd at es N u tnbe r 2 Re [fioni ][ ]sfe w En g la n d August 1995

USE PA 1996 Recommendations of the Technical Rev iew Work giroup for Lead foir an Inter im Approach to As=es=mg Risks Associated wi th Admit Exposures t o Lead in Soi l Technical R e v i e w Workgroup for Lead December 1996

I DO 1-0]

ComirrKsrdEilliKlListirial ILEind UMI

IWADEEP Method 3 Upper

ConiCEmlTHlion Liimirt (3)

Trichlcirossthene 2l-Trimethvllierizerie 35-Trimeihvllpi3rizerie

EJcnzo(a]arrtriraceiw

Elenzo(aJpgtP3riei Eienzo(o)lluorEintherie

Diberiz(Eih)amtriracene HoachiOirobenEene

24-Triehl(gtnilierizEsne 1Et Arsenic LSIEld

FVIesrcijry 7(HeiraCDigt

11C

Notes bullbull = No MADEEP Staridardi or current ROD Clean-up Level for this chemical thus TIG value shewn (1) TiBlrachlonaelhene 112-Trichlorolaquoiheme lnderio( t 23-cd)pypeiri8 Naphthalenes Thallium and

Arodor 124EI were removed from the list shown on Table 6-4(1 in Ihe Additional Site Investigation and Revisjon of Clesem-Up Goals Report (Foster Wheeler 2002) because Ihe rneixirnuni cletescted conceritralion of these criesrnicals was less than the recommended clean-up oiosal This is the same reasoning shown on Table 6-313 of tr ies report except Ihe recalculate clesan-up goals and IICts were used

(2) Rfjcommerided CUGsi eissurne a large ns goal ol IIEE-S and a laiijet hazard indes) of 1 for each chemical (3) MADEEP UCLS (310 CMFi 40 Osi96(71 Table S) wesre includecl for comparison as a possible AFiAR for Ihe sile (4) The most stnngesnt ot Ihe risk-based CUG or UCL was talkeri EIS Ihe recommended CUG for each chemical (gt) ftesnzo(a iByrene vias rerriovesd Irorri the list shown on Table S-49 in the AddiliOnal Site InvestigEition and

Filevisjon of deem-Up Goals Report (Foster Wheeler 20021 tiesciiuse the rneimrium dletssctesd concentration of this oheiriiical1 vias less than the recommended clean-iji goal This us the seinie resEisoniricj Shown on Table S-41 of fries report except the recalculated deem-up goeils and UCls were used

IS) Current Silresim Site Cleanup Level from (Record of Decision Summnary Septesmber 19 1991 I ) Current ROD Cleanup Level tor mdur dueil carcinogenic Folyaitiirriatic HgtiilrocEifboris (PAI-ls) Cun-esnt Clean-Up Level for Toteil (AI-ls

IS) Current ROD Cleanup Lesvel tor Total Polycrilorinalecl Eiiphemyls 19) The Following criesrnicals have a Surfaal Soil Clesanup Levesl under tties current ROD but did not warrant a C LJG given the updated

exposure arid risk assessment (in mglltg) Beriene (1 Ei) 1 1 -Dicrtoroesthene (0721 12-DiohloroEithane (48) Methylertes Chloride [88) arid Srvresne (14)

Chssmioals ol Concenii (1 El]

lEIenziEsrn Chlorobenzenlt Clilorofotm IZ-DichloiOEstliane bull|1-DiltfiiloroEtlierie iithylbenzerie Uethylene Chloride Styrene 1122-TEitrachloroethanE Tetraohloroethene Toluene 111l-Tiichloroelhane 1112-Tndhloroelhane Trichloroethene Vinyl Chloride 1-DiltlilorObengtene bullbulllexachlorobenzeniE Naphthalene 12 4- Tiichloro benzene Lead Mercury 237amp-TetraCDD Aroctor 1242

Curirenl SiiJresiinri Site IFiOD Cleanup Level gt[li) (rugkg]

0004 03

0(M 0001 0005

613 0 00 1 017 0 006

27 03

0003 0006

89 0034

0 i2

0001 23

C() IT

Risk-IEIaiSiiid Clean-shyUp Goal for

Suhsurlaia) Soil

lt 3)

(1111)

lt] 04 _

(Kiiiil 0031 QOOS

12 056 290 016 08) ill 13

0 12 025

00082 75 6 16

11 448 077

0005 13

iTieroiallridliisltriiil Li vi ADIp Method a

Llpipeir Cancenliraltiori

Liirnilt (4) (rncildEiJ

2000 1 0000 5000 600 90

1 0000 000 1 000

20 1 000 10000 5000 100

5000 20

5000 30

10000 10000 6 000 (300

00002 1 00

mil USE

RecoiTirvKraquoKlltxl Cleiini-Up GOall lor

Subiiurface Soil (5f (nuEiko)

(104 bull12

0015 00311 CI005

12 olaquo 290 [11Ei OIMi

111 11

(112 CI25

0006 75 6 laquo 1

ltI4EI 077

00002 13

MiliilllEi ltiraquol

IRecomiirnendtid Gleam-Up Gixil

Riiiik-lilUEKidCUCi Rilk-iii3=fiiICUCi Riiilk-lilaEied CUCi Riik-l-lasi(id ClICi Riiik-lilaised CIIG Riiik-lilaisiid CIIG Ri5k-iii=i(d CUG Riik-iiaiSi(d CUG Rik-llaisid CUG Riiik-lilaisEMJl CUG Riiik-BaisEid CUG Rigtk-llasraquoltJI CUG Riik-lli)Eraquodl CUG Riiik-l-lHSEiril CUG Rigtk-lliiSE)dl CUG Riillt-liSEd CUG Riik-lliiSEraquodl U Riik-ltiigtedi U( Riillt -l-lased AH Fiisl( -Based MJ( Fliiili-Baised MJt

MM)III uci Rlil(-BiliiEld CW

- == No curvenl ROD Cleanup Level lor I hiss chemical Ihus no value shown (1) 123TniclilaTObefi2Bne bull124-Trimiethylb(iii2ene l38-Tiirri8lJiirlbenienie lleriio(Ei)arithiraelaquorie E3erizoi[Ei)pyierie

E3enOi(b)Fluorantlierie Diben(Eih)anthraltlt5ne 14-DiHtilorobeiriieme arid Thallium wEsre removed from the liil sihovm on Table 6-50 in the Adclitionsil Site InveEitijjation and Remission of Clean-Up Goals F5epor1 (Fosgtter Wheesler 2002) because the maximum detected ooncenlralion of these cheniiicalsi was KSS than Ihe recomrneinded clean-up goal This is the SEinne nsEisoning shcwi on Table 6-46 ol the report exeepd the recalculated cPeiivupi goals and LICLs were used

(2) FlEicomiriEincled CUGEi iiissume a targEil risk goal of 1IE-5 and a large It hazard index of 1 for each chemical (3) SubiiurlaoE Soil includes only unsaturated subsurlaoEi soil iiiiiiuma lo be between 1 ft bellow (jrouncl suiirfaoEi (tigs) Eincl 10 M tigs (4]i MADEP LICLs (310 CMIFi 4fliOS)96(7) Table ( 3 1 were indiidecl hw carriparison as a possible tRhR tor (he site (5) The more stringent of the risk-based CUG or UCI was lalkan IEIS Ihe recornmended CUG lor each chemical (6) Current SiliEisim SitEi Cleanup Level from Record of Decision Summary September IE) 1991 17) Current ROD Cleanup Level loir Tolal Polychlorinatecl Eluphenls (8) The followiiricj chemicals have Ein UnsalxiratEid Soil Cleanup Level unclEir the current ROD but did no warrant a CUG given the updated

exposure and risk agtsessriieril (in rrigkg) Carbon Tetrachloiide (O()0i) EiiE((2-eihylhegtyl)phthalate (030) 12-Dichlorapropane (0 003) Individual carcinogenic PAH (10) tnans-IS-DichloroetheriE) (0067) Phenol (53) 2-IEIulanone (006) arid Xylenes [22)

bullbull

bullbull

Clwrnleals of ConiCiHiri (1 gt)

Acetone lEIenzene ChlorobenzeriiEi ChloroFoinn 12-Dioriloroethane 11-Dicriloroelhene 1--Dichforoetrini3 (lolall ciE-12-Diciriloroiithene EEthyltienzene HiEiKaehlorobulaidiEine Melhyferie Chloride 11122-THtracriloroethane Telraltlilaroe1 Inane 12i-rricrilorobiEin28ne 111 -Trie ribroethane 1l12-7richlcgtroelhane Trichloroethene Vinyl Chloride Naphthalene 1 2 4 -T rich lore benzene Arampenic Cadmium Lead

Nickel

Current SiillireSiiirn iilite ROD Cilia inup li1 til (5) (nifiil]

0006 OI OI

0006 (1007

07

ooos 0005

(12 0006 0005

0009 005

0 005 0 015 01

Fthik-Biised Gleam-Uf) 0 in ill ltin

Grotinchiialer (2| (rngri)

[1413 49 02 05

0015 120

-34

0041 14

061 59 38 120 11 14

013 0 E9 0 15

-

Commerciallndi istrial LEimjl IKE

IMIAW-P Method MADE Fgt Method 3 Upper Recommended

1 GW-3 Standard ConicenltriJtioni Clean4Jp Goal lor E3iiitigt fur (3) Limit (3) Groiindwaltssr (4]i R(iorniTiEridE(J

(rngM) jirnijiL) (irngjIL) ChE^m-Up Oiml

5M 100 i() GW-3 SUmiira 70 04EI IFiik-B SdCIJG

0 5 10 DS Ktt- il3 Kiuirij M 100 olt IFIhlk-lliiaed CUG 5M 100 IJ5 IFIIalk-IEIiiaiKl CUG 50 100 001i iiik-lllii gt(= CUG

- 10 IFIIalk-liliiaed CUG 50 100 gt() Gli1- Sn3 KiuinJ 1 100 34 IFIIiiilk-EliiaiKl CUG

(109 0 9 0041 li3k-BiieICUG 50 100 114 liii-itiel CUG 20 1100 061 Ftiraquok-BaieclCUG 5 gtlt) i GW-3Slairiilai(J - )EI Rhik-l-liiiKSCl CUG

50 100 50 GW-3Slairi[liir(J 150 100 11 Rhsk-B idCUG 20 100 14 Rlik-BEIliiCIK

41) 100 013 Rlik-BEitiiiCUG 15 60 oes Riik-Biiiji[l CUG

0 5 04

100 i

015 04

Riik-BEiltKl CUG GW-3 Stiindiirii

0 01 01 001 GWlt-3 Standanl 0 03 03 003 GW-3 Standard 0 08 1 008 GW-3Standai-d

Motes bull bull= INo MADEEF1 StandiSird or currenl ROD Cliiainup LeuEd (ltJip this chemical Hi us no vialue hovti (1) 11-Dicliloroelharie Styrerie Toluene and 12DichlorobenraquoE(rie wensi ranriioved iFrom the ligtt shoism on Tsible 6-iil in tie

Adijitioirial Site Investkiiition =ind Fiuvision ol Clean-Up Goals Report (Foster WheclEsr 2002) becauwi this iTitixirnum detoclecl agtnltltritrliiiri of lhEgti cliiernical niis ess iticin IhEi MKormnencled de=in-ijp tjc tiktwiEltE AoEitonn ciSl2Dichliiroellnsirie Araenic Cadmnurri LEI ad and Nickel wsm added to Hie Siame list because Ilie rnaxirnuirn detijclecl coiicentralion ol these chemicals was greater than the recommended clean-up goal This IEI the siarne reasoning shown on Taiblo 6-47 of the ropoit except Brte iiEicalciilcileiJI ctetiin-up goals GW-3 standairds arnl IJCLs wsire used

(2) FltiEcomnriEnltJiil (bull(ltbullbull ihiown aiE calculatiEKl wllh a tc-irget risk goail il 111- Eind si t)iQEt h^iz^nrd inijlEigt of 1 for r-ah chemk^il (3) MADEEF GW-3 Standards (310 CMR 40 0974(2) Table 1 and UCLis (310 CMR 40 0996(7) Table 61 were included loir

comparison a si possible ARAR for I he site (4) The most slriirigenl of the risk-based CUG GW-3 Slandard of UCIL was taken as Ihe recoirrirnencled CUG for each chemical (5) Current Silresirri Site Cleanup Level from Record of Decision Summary September 1 El 19911 (Egt) The following chemicals have an Inlerirn Ground Water Cleanup Level under tirie currenl ROD but did riol warrant a CUG

given the updated exposure arid nsllt asKessmerit in rncjkcj) BiEi(2-ltsithylheltyl]iprithali3le (0 004) Carbon Telrachloncle (0 C)()i) 1 2-Dichloroproparie |0005| Dioxin 150 lt 10-111 l-lfsxaoliilorobeiHBrie (0001) Individual Carcinogenic FAHS (00002] FCESs (00005) Slynarie (0101 2-Eiularione (035) Chromium [+3] (010) Copper (13) 12-Dnhloroberiene (060| lrans-12-DichloroetlienB (0 10) Pl-nariol (21] SeleniLirn 100501 Tdluene (10) and Xylenesi (10)

bullbull

bullbull

Clwrnleals of ConiCiHiri (1 gt)

Acetone lEIenzene ChlorobenzeriiEi ChloroFoinn 12-Dioriloroethane 11-Dicriloroelhene 1--Dichforoetrini3 (lolall ciE-12-Diciriloroiithene EEthyltienzene HiEiKaehlorobulaidiEine Melhyferie Chloride 11122-THtracriloroethane Telraltlilaroe1 Inane 12i-rricrilorobiEin28ne 111 -Trie ribroethane 1l12-7richlcgtroelhane Trichloroethene Vinyl Chloride Naphthalene 1 2 4 -T rich lore benzene Arampenic Cadmium Lead

Nickel

Current SiillireSiiirn iilite ROD Cilia inup li1 til (5) (nifiil]

0006 OI OI

0006 (1007

07

ooos 0005

(12 0006 0005

0009 005

0 005 0 015 01

Fthik-Biised Gleam-Uf) 0 in ill ltin

Grotinchiialer (2| (rngri)

[1413 49 02 05

0015 120

-34

0041 14

061 59 38 120 11 14

013 0 E9 0 15

-

Commerciallndi istrial LEimjl IKE

IMIAW-P Method MADE Fgt Method 3 Upper Recommended

1 GW-3 Standard ConicenltriJtioni Clean4Jp Goal lor E3iiitigt fur (3) Limit (3) Groiindwaltssr (4]i R(iorniTiEridE(J

(rngM) jirnijiL) (irngjIL) ChE^m-Up Oiml

5M 100 i() GW-3 SUmiira 70 04EI IFiik-B SdCIJG

0 5 10 DS Ktt- il3 Kiuirij M 100 olt IFIhlk-lliiaed CUG 5M 100 IJ5 IFIIalk-IEIiiaiKl CUG 50 100 001i iiik-lllii gt(= CUG

- 10 IFIIalk-liliiaed CUG 50 100 gt() Gli1- Sn3 KiuinJ 1 100 34 IFIIiiilk-EliiaiKl CUG

(109 0 9 0041 li3k-BiieICUG 50 100 114 liii-itiel CUG 20 1100 061 Ftiraquok-BaieclCUG 5 gtlt) i GW-3Slairiilai(J - )EI Rhik-l-liiiKSCl CUG

50 100 50 GW-3Slairi[liir(J 150 100 11 Rhsk-B idCUG 20 100 14 Rlik-BEIliiCIK

41) 100 013 Rlik-BEitiiiCUG 15 60 oes Riik-Biiiji[l CUG

0 5 04

100 i

015 04

Riik-BEiltKl CUG GW-3 Stiindiirii

0 01 01 001 GWlt-3 Standanl 0 03 03 003 GW-3 Standard 0 08 1 008 GW-3Standai-d

Motes bull bull= INo MADEEF1 StandiSird or currenl ROD Cliiainup LeuEd (ltJip this chemical Hi us no vialue hovti (1) 11-Dicliloroelharie Styrerie Toluene and 12DichlorobenraquoE(rie wensi ranriioved iFrom the ligtt shoism on Tsible 6-iil in tie

Adijitioirial Site Investkiiition =ind Fiuvision ol Clean-Up Goals Report (Foster WheclEsr 2002) becauwi this iTitixirnum detoclecl agtnltltritrliiiri of lhEgti cliiernical niis ess iticin IhEi MKormnencled de=in-ijp tjc tiktwiEltE AoEitonn ciSl2Dichliiroellnsirie Araenic Cadmnurri LEI ad and Nickel wsm added to Hie Siame list because Ilie rnaxirnuirn detijclecl coiicentralion ol these chemicals was greater than the recommended clean-up goal This IEI the siarne reasoning shown on Taiblo 6-47 of the ropoit except Brte iiEicalciilcileiJI ctetiin-up goals GW-3 standairds arnl IJCLs wsire used

(2) FltiEcomnriEnltJiil (bull(ltbullbull ihiown aiE calculatiEKl wllh a tc-irget risk goail il 111- Eind si t)iQEt h^iz^nrd inijlEigt of 1 for r-ah chemk^il (3) MADEEF GW-3 Standards (310 CMR 40 0974(2) Table 1 and UCLis (310 CMR 40 0996(7) Table 61 were included loir

comparison a si possible ARAR for I he site (4) The most slriirigenl of the risk-based CUG GW-3 Slandard of UCIL was taken as Ihe recoirrirnencled CUG for each chemical (5) Current Silresirri Site Cleanup Level from Record of Decision Summary September 1 El 19911 (Egt) The following chemicals have an Inlerirn Ground Water Cleanup Level under tirie currenl ROD but did riol warrant a CUG

given the updated exposure arid nsllt asKessmerit in rncjkcj) BiEi(2-ltsithylheltyl]iprithali3le (0 004) Carbon Telrachloncle (0 C)()i) 1 2-Dichloroproparie |0005| Dioxin 150 lt 10-111 l-lfsxaoliilorobeiHBrie (0001) Individual Carcinogenic FAHS (00002] FCESs (00005) Slynarie (0101 2-Eiularione (035) Chromium [+3] (010) Copper (13) 12-Dnhloroberiene (060| lrans-12-DichloroetlienB (0 10) Pl-nariol (21] SeleniLirn 100501 Tdluene (10) and Xylenesi (10)

CO MM ONW E ALT (I 0F MAS SAC HIJSETTS

Ex EC UTIVE OFFI CE oF Exvi RON M E NTA L AFF AI RS DE PA RTM EN T OF EN V]R O N M EN TA L P ROTEC TI0N 0 N E W I N T 1iR S T Ei IS E T BOSTON M A (1211) 8 (i 17 - 2 9 2 - i6 0 0

4s Su san Stuclli en A c t i n g Director pi a n EI tnon of Sigrnf i c a n t gt [(ice of Site Reirnediialiom and Restoration iiflerences lor the Silresmi S EPA Suite 1100 (H 10) heraical Corp Superfund Sitlt Ine Congress Street owe I MA Sepletnlbeir 200

BOH ton MA 02114-2023

The Department of Environmental Protection (the Depar tment ) has reviewed the proposed Explanati on of Significant DifTerenc es (ESD) daled September 2003 for the S i Ires irn Chem ical Corporation (S i l r e s im) Site This EiSD is fbir the Silresirn recoird of Decision (ROD) daled September 1991 The Department concurs with Ihe ESD lor the Si te

As stated l ine purpose of tins ESD is twofold The first is to revise the clean-nip goals for soil and groii indwater at the Site that were established in I he ROD The second is to divide the S i t e into two operable units one (br giroundwater and the soil vapor extraction pilot l e s t and the o the r lor source control actions The Depaitmem believes t h a t Ihese changes to the remedy w i l l noi affeel its overal I protee tuveness

TheDEP h as evalii ated the EFAs ESD (or consiistenc y with MLGL Chapter 21 IE and the 1VI assac husetls Cogtn lingerie y IE1 Ian (MC P) Tills BSD1 establ is h es nev clean-up goa Is based on the Departmentis 99ll Groundwater Use and Value Determination which record me ndled a low use and value for the gronirudwater beneath the Site a significanl change from the previous drinking water classif ication that was used to eslablish clean-up goals m I he 1991 ROD EPA determined that due to Site conch I i o n s and the changed gioiundwater classification some of the clean-up goals specified in the ROD were no longer appropriate f o r the S i l e The tie w cleajn-up goals were derived from the groundwaleir reclassification a rev ised conceptual site exposine model updated Lexicological pairaineLers curreirit risk assessment guidance and protocols and c u r r e n t l and use assumptions and Sile condiLions

IJfcP Loncumrice Letlei Silieirn BSD

Although there were two corn ponenl s to the ROD rnanagernenl o f rni grat iom (forgrowidwaler1) and source con tiro I (for soils) the Sile was not divided inlo separate operable units to address these two aspects This liSD now div ides the Sile in to two operable limits to address these separate components of the remedy The Department agrees t h a t I he creation ofaru additional operable unit w i l l f a c i l i t a t e docuirnenti ng clean - up a c t i v i t i e s at t h e Site

i IK luepiiriiraciiiii appreciate mie oppuniuii icy to ptovide input on this tSD and looks lorward to the cont in LI in B i rnpl e mental io n o f I he remedy i it the iilnl e If you h ave a ny qm eampl io n s pi eas e c a HI J ane t Waldroj] Projecl ]VlanaBeir for I he Site at ( 6 1 7 ) 5Si( i - l 156

1. barcode 48974
2. barcodetext SEMS Doc ID 48974

IJfcP Loncumrice Letlei Silieirn BSD

Although there were two corn ponenl s to the ROD rnanagernenl o f rni grat iom (forgrowidwaler1) and source con tiro I (for soils) the Sile was not divided inlo separate operable units to address these two aspects This liSD now div ides the Sile in to two operable limits to address these separate components of the remedy The Department agrees t h a t I he creation ofaru additional operable unit w i l l f a c i l i t a t e docuirnenti ng clean - up a c t i v i t i e s at t h e Site

i IK luepiiriiraciiiii appreciate mie oppuniuii icy to ptovide input on this tSD and looks lorward to the cont in LI in B i rnpl e mental io n o f I he remedy i it the iilnl e If you h ave a ny qm eampl io n s pi eas e c a HI J ane t Waldroj] Projecl ]VlanaBeir for I he Site at ( 6 1 7 ) 5Si( i - l 156

1. barcode 48974
2. barcodetext SEMS Doc ID 48974