THIRD EXPLANATION OF SIGNIFICANT DIFFERENCES (ESD ... · Contact: Kenneth Richards, NHDES Remedial...

THIRD EXPLANATION OF SIGNIFICANT DIFFERENCES (ESD)

Tinkham Garage Superfund Site

EPA ID NHD062004569

Londonderry NH

2016

Tinkham Garage

Superfund Site

ESD AREA

waterline

Tinkham Garage Superfund Site Londonderry NH

Third Explanation of Significant Differences (ESD) Tinkham Garage Superfund Site

February 2016

TABLE OFCONTENTS

I INTRODUCTION page 1

II SUMMARY OF SITE HISTORY CONTAMINATION PROBLEMS

AND SELECTED REMEDY page 6

III DESCRIPTION OF SIGNIFICANT DIFFERENCES AND page 11 THE BASIS FOR THESE DIFFERENCES

IV SUPPORT AGENCY COMMENTS page 15

V STATUTORY DETERMINATIONS page 15

VI PUBLIC PARTICIPATION page 16

VII DECLARATION page 17

ATTACHMENTS

Attachment 1 - Site Location Map of the Tinkham Garage Superfund Site

Attachment 2 - Site Map - current Groundwater Management Zone boundaries and Wells

Attachment 3 - Site Plan showing drawdownin bedrock during1983 and 1986 pump tests

Attachment 4 - Isoconcentration Map showing contours of total VOCs in bedrock (2008)

Attachment 5 -Contour Map showing Total VOC and 14-dioxane concentrations(2014)

Attachment 6 - 2014 Bedrock Investigation fracture sampling results and Map of well locations

Attachment 7 - Historical Contaminant Comparison Table

Attachment 8 - Table of Applicable or Relevant and Appropriate Requirements (ARARs)

2016

THIRD EXPLANATION OFSIGNIFICANT DIFFERENCES

TINKHAM GARAGE SUPERFUND SITE

I INTRODUCTION

A SITE NAME amp LOCATION

Site Name Tinkham Garage

Superfund Site (Site) Site

Location Londonderry NH

The 375 acre Site is generally bounded by Route 102 to the north Gilcreast Road to

the east Ross Drive to the southeast and an unnamed tributary to Beaver Brook to

the west (See Attachment 1)

B LEAD amp SUPPORT AGENCIES

Lead Agency United States Environmental Protection Agency (EPA)

o Contact Cheryl Sprague EPA Remedial Project Manager Spraguecherylepagov (617) 918-1244

Support Agency New Hampshire Department of Environmental Services (NHDES)

o Contact Kenneth Richards NHDES Remedial Project Manager

KennethRichardsdesnhgov (603) 271 ndash 4060

C Legal Authority for ESD

Section 117(c) of the Comprehensive Environmental Response Compensation and

Liability Act (CERCLA) 42 USC Section 9617(c) requires that if the US

Environmental Protection Agency (EPA) determines that the remedial action being

undertaken at a site differs significantly from the Record of Decision (ROD) for that

site EPA 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 Section 300435(c)(2)(i) of the National

Contingency Plan (NCP) and EPA guidance (OSWER Directive 92001-23P)

indicate that an ESD rather than a ROD amendment is appropriate where the

adjustments being made to the ROD are significant but do not fundamentally alter

the overall remedy with respect to scope performance or cost EPA has determined

that the adjustments to the 1986 ROD 1989 Amended ROD and subsequent ESDs as

provided in this ESD are significant but do not fundamentally alter the overall

remedy for the Tinkham Garage Superfund Site with respect to scope performance

or cost Therefore this ESD is being properly issued

1

In accordance with Section 117(d) of CERCLA and Section 300825(a) of the NCP

EPA voluntarily chose to hold a public comment period on the draft ESD document

from October 9 2015 to October 30 2015 to ensure that all interested parties had an

opportunity to provide input to EPA before a final decision was made on this

modification to the remedy at the Site

D SUMMARY OF CIRCUMSTANCES NECESSITATING THIS ESD

In late 1982 residential drinking water supplies including the primary water supply

well (LGSW) serving the Londonderry Green Apartments complex southwest of the

Site were found to be contaminated Bottled water was supplied and Point of Entry

(POE) water treatment systems were installed in nearby residential homes The State

of New Hampshire issued a health order in early 1983 advising residents not to drink

their well water Following an analysis of feasible water supply alternatives EPA

initiated an early action in the fall of 1983 to provide an alternative water supply line

to approximately 400 impacted residences relying on groundwater for their drinking

water supply EPA listed the Site on the NPL in September 1983

A Remedial Investigation (RI) conducted from 1984 to 1986 documented widespread

contamination from volatile organic compounds (VOCs) in both the overburden and

bedrock aquifers as well as in surface water and in soils located in the field behind

the Tinkham Garage and at the Londonderry Green Apartment Complex (now the

Woodland Village Condominium Complex) Pumping tests conducted as part of the

RI at the supply well (LGSW) documented that bedrock groundwater flow occurs

primarily through fracture zones that are interpreted to strike (trend) in a NESW

direction across the Site (see Attachment 2- Site Map and Attachment 3 ndash Pump test

drawdown map) The pumping of the LGSW well indicated a significant (29 feet)

drawdown in water level 1500 feet to the northeast in monitoring well FW-11D

which is located down gradient of the primary source area near the Tinkham Garage

This bedrock drawdown was seen primarily in monitoring wells along a narrow

2600rsquo long zone however the northeastern and southwestern extent of this influence

was not fully delineated

Following the completion of a Feasibility Study in 1986 EPA issued a ROD for the

Site Based on conclusions presented in a July 1988 Pre-Design Study Report the

ROD was amended in 1989 as well as in 1992 and 2003 through the issuance of two

ESDs as described later in this document

In 2009 as part of the Five Year Review required for the Site concerns were raised

about elevated concentrations of 14- dioxane and its mobility in groundwater at the

Site Subsequently EPA required additional investigations to evaluate the long-term

protectiveness of the existing groundwater monitoring program Specifically

existing monitoring wells utilized to monitor bedrock water quality at the Site are

constructed as continuous open-hole completions in bedrock and therefore span and

connect multiple fracture zones in each well The additional investigations were

conducted to evaluate contaminant concentrations in three select bedrock monitoring

2

wells (one source area and two down gradient) to characterize discrete fracture zones

water flow and water quality From April through October 2014 these investigations

were conducted at the Site and the results indicated elevated concentrations (up to

760 ugl) of 14-dioxane within discrete fractures in bedrock intercepted by

monitoring well FW-11D This well is considered to represent bedrock conditions

immediately down gradient of the former Tinkham Garage source area In addition a

14-dioxane concentration of 32 ugl was identified in a water sample collected from

a discrete fracture zone in monitoring well FW-28D which is located in an area

considered to represent the southsouth-east boundary conditions for the Site and at 48

ugl in monitoring well FW-21 which represents the southwest boundary conditions

Overall these additional bedrock investigations supported previous conclusions

regarding contaminant distribution VOCs were solubilized from soils to groundwater

in the former Tinkham Garage source area and dissolved VOCs migrated in

overburden groundwater from the source area towards the east southeast and south

into the nearby wetlands VOCs migrated through the overburden and entered

bedrock fractures within and down gradient from the former source area behind the

Tinkham Garage and flowed within fractures which strike from northeastsouthwest

and that 14 dioxane is found with varying concentrations within the conductive

fractures that extend across the Site (See Attachments 5 -2014 Groundwater Sampling

Results and Attachment 6- 2014 Bedrock Investigation Results) These investigations

also demonstrated that the current horizontal and vertical extent of groundwater

contamination has not been fully delineated

In November 2014 the NHDES MtBE Remediation Bureau as part of an

investigation conducted by the Department designed to evaluate the potential

presence of MtBE in residential water supply wells provided the NHDES Hazardous

Waste Remediation Bureau and EPA with data which indicated that residential wells

in the Site vicinity are contaminated with chemical constituents similar to those found

in groundwater at the Site at levels which exceed drinking water standards These

residences utilize deep bedrock wells as their source for drinking water and are

located approximately 1500 feet northeast of the major contaminant source area at the

Site where levels of contaminants remain at concentrations greater than drinking

water standards See Attachment 2 for residential locations and Table 1 below for

chemical constituents found at the Site in excess of drinking water standards and those

found in the nearby residential properties

The residential wells that were found to be impacted northeast of the Site appear to be

clustered in a location that would fall within the fracture zone of influence shown on

Attachment 3 if that zone were extended another 1500rsquo further northeast (in the

same SWNE strike direction) Many households also located within the residential

area immediately northeast of the Site have previously connected to the existing

waterline This fact along with the 1983 removal from service of the original

groundwater pumping wells southwest of the Site source area may have made it

possible that this group of residential wells located furthest northeast of the source

area have drawn the contaminant plume through bedrock in that direction

3

Table 1- Groundwater Constituents found in exceedance of Drinking Water Standards

Site Source Area

Overburden Groundwater

Site ndash Bedrock Groundwater

down gradient of Source Area

Residential Bedrock Water Supply

Wells located northeast of the source

area (Boston and Charleston

Avenues)

14- dioxane 14-dioxane 14 -dioxane

TCE TCE TCE

VC VC VC

12 -DCA 12-DCA

PCE

Cis 12-DCE

Benzene

Source Haley and Aldrich Annual Groundwater Quality Monitoring Report for 2014

for the former Tinkham Garage Site located in Londonderry New

Hampshire March 20 2015

Source NHDES MtBE Bureau sampling data 20142015

Upon notification of this residential well contamination the NHDES Waste Management

Division took immediate action to address risks posed by exposure to contaminants in

drinking water by installing POE treatment systems in three households where

concentrations were found to exceed drinking water standards Because conventional

(carbon filtration) POE systems can be generally unreliable for 14-dioxane removal all

properties where the NH AGQS standard of 3 ugl was exceeded were provided with

bottled water in addition to POE treatment systems

Therefore for the reasons described above this ESD includes the following

o Obtaining necessary approvals and designs for the connection andor extension of the

existing waterline in the area to reach all impacted or potentially impacted

residences still relying on private wells (current data indicate that at a minimum

five bedrock wells are impacted by Site contaminants along Charleston and Boston

Avenues)

o Installation of all water line extension andor connection infrastructure to all Site

impacted or potentially impacted residences

o Proper abandonment of any existing potable water well that is not utilized for long-term groundwater monitoring per EPArsquos direction and

4

O Required monitoring of residential water supply wells to establish a further

understanding of the area of Site impacts or potential future impacts through continued use of residential water supply wells not connected to the waterline

EPA in consultation with NHDES believes that connection to a waterline (which is

already present in the area) for those residents whose wells have been impacted by the

Site or may be impacted in the future from continued use of their well is an acceptable

and sustainable alternative for preventing human exposure to contaminated groundwater

with concentrations above drinking water standards

In addition this ESD addresses the groundwater remedy set forth in the 1986 ROD as

amended and specifically addresses a recently identified Contaminant of Concern (COC)

at the Site namely 14-dioxane

Therefore this ESD

o Formally incorporates 14-dioxane as a Site COC with the NH Ambient

Groundwater Quality Standard (AGQS) of 3 ugl in groundwater as a cleanup level

that shall be met at the completion of the remedy

o Requires a review and revision of the institutional controls (Groundwater Management

Zone-GMZ and deed restrictions) as needed as well as implementation of additional

bedrock investigations to evaluate the contaminant extent fate transport and

timeframe for attainment of the groundwater cleanup level due to the addition of 14-

dioxane

Therefore this ESD also includes

o Clarification on the approach that will be utilized to determine that groundwater

Cleanup Levels have been attained the groundwater remedy is protective and

support for a determination that groundwater restoration is complete

E AVAILIBILITY OF DOCUMENTS

EPA will consider and respond to all formal comments received during the comment

period before issuing a final ESD EPArsquos response to these public comments will be

attached as a Responsiveness Summary to the final ESD The ESD the supporting

documentation for the ESD and the Administrative Record are available to the public

at the following locations and may be reviewed at the times listed below

5

US Environmental Protection Agency Office of Site Remediation and Restoration Records Center 5 Post Office Square Suite 100 Boston MA 02109-3912 Phone (617) 918-1440 Monday-Friday 900 am - 500 pm

Leach Library 276 Mammoth Road Londonderry NH 03053 Phone (603) 432-1132 Monday-Thursday 900 am ndash 800 pm Friday 1000 am ndash 200 pm Saturday 900 am ndash 500 pm

This ESD and the Administrative Record are available for public review at the

locations and times listed above as well as on the internet at

httpwwwepagovsuperfundtinkham Adobe Reader is required to review the

documents on-line

Notice of the release of the final ESD will be published in the Derry News

II SUMMARY OF SITE HISTORY SELECTED REMEDY AND RECENT CONTAMINATION

A SITE HISTORY AND RISKS

History

This Site is located approximately one mile southwest of the intersection of Interstate

Route 93 and State Route 102 in Londonderry New Hampshire

Initial complaints of foam and odors occurring in a small unnamed brook crossing

Ross Drive led the Londonderry Health Department to Tinkham Garage in April

1978 Their investigation concluded that liquids and sludge from tank truck washings

had been dumped behind the Tinkham Garage directly to the ground surface A

subsequent citizen complaint to the New Hampshire Water Supply and Pollution

Control Commission (NHWSampPCC) now the NHDES resulted in ordering a cleanup

involving removal of surface contamination Additionally a diversion trench was

excavated to divert surface water run-off from behind the garage area away from

Ross Drive

6

EPA completed a Preliminary Assessment in August 1981 which showed that the

groundwater used as a potable water supply as well as soil and surface water were

contaminated with VOCs In January 1983 the drinking water supply well servicing

the Londonderry Green Apartments (presently Woodland Village Condominiums) and

several residential supply wells along Mercury and McAllister Drive were taken out of

service because of documented and potential organic chemical contamination These

residents were temporarily supplied bottled water and POE treatment systems until a

feasibility study was completed and a permanent water line was installed by the

NHWSampPCC under a cooperative agreement between the State and the EPA in

November 1983

The Site was put on the National Priorities List (NPL) in September 1983 The

Remedial Investigation (RI) was completed in January 1986 The investigation

documented contamination from volatile organic compounds in both the overburden

and bedrock aquifers as well as in surface water and in soils located in the field

behind the Tinkham Garage and at the Woodland Village Condominium Complex

Risk

The 1986 ROD indicated that the greatest potential risk presented by the Site is from

ingestion of groundwater contaminated with VOCs including benzene chloroform

12-dichloroethane methylene chloride tetrachloroethylene trichloroethylene and

vinyl chloride Groundwater from the fractured bedrock served as the primary source

of drinking water prior to 1983 when use of wells onsite ended and the alternate water

supply (waterline) was provided Groundwater is contaminated primarily by volatile

organic compounds and their degradation products including recently detected 14-

dioxane Based on the current understanding of exposure pathways and contaminants

found at the Site additional risks would include inhalation from exposure to TCE

while showering or via vapor intrusion and ingestion of groundwater contaminated

with 14-dioxane Groundwater from fractured rock still provides drinking water to

residents living outside the current GMZ to the east northeast and southeast of the

Site

At the time of the 1986 ROD contaminants ranged from approximately 1 ugl to 6700 ugl total VOCs and the upper limit lifetime cancer risk was estimated at

2 x l0-2 As a result the bedrock aquifer presented unacceptable risks and was

undrinkable Also in 1986 given the active pumping and the short distance to the

former condominium supply wells as well as geological factors EPA concluded that

the disposal area behind the Tinkham Garage was the primary source of contaminants

found in the nearby residential supply wells While the plume of groundwater

contaminants has dispersed across much of the Site and the concentrations have

decreased AGQS exceedances remain highest within and near the former source area

behind the Tinkham Garage

7

B RECENTCONTAMINATION

2014 Bedrock Investigations

Included as part of the Groundwater Management Permit a network of seven bedrock

monitoring wells with long open-borehole intervals which intersect multiple water-

bearing fracture zones have been part of the long term monitoring program Bedrock

investigations were conducted in 2014 to assess the long term protectiveness and

adequacy of this groundwater monitoring program Because concentrations of

contaminants (VOCs and 14-dioxane) can vary between individual fracture zones

monitoring data results may reflect contaminant concentrations from individual

fractures which then are potentially diluted by clean water entering the borehole from

more transmissive fractures in the bedrock The 2014 bedrock investigations

included packer testing to ascertain contaminant concentrations within discrete

fracture zones within the boreholes at three bedrock monitoring wells FW11D

FW28D and FW-21D

The results indicated that concentrations of total VOCs and 14-dioxane found in the

deepest intervals studied were higher than the shallowest intervals by a factor of

roughly an order of magnitude of 12 to 5 respectively The total VOC and 14-

dioxane concentrations measured in the individual fracture zones tested support the

conceptual site model and previous conclusions regarding contaminant distribution

wherein the highest concentrations are found in bedrock well FW11D immediately

down gradient of the former Tinkham Garage source area lower concentrations are

found farthest down gradient in bedrock FW21D which is located in an aquifer

discharge area and that higher contaminant concentrations are found in the

conductive fractures that extend between these two wells Under pumping and

ambient conditions the majority of the water would be produced from fractures

between 70 and 110 feet below ground surface and the highest concentrations of total

VOCs and 14-dioxane were also generally found in fractures at depths between 70

and 110 feet below ground surface Bedrock investigations were not extended deeper

at these locations during these investigations The bedrock fracture scope and

assessment prepared by Haley amp Aldrich is summarized in a report titled ldquoFractured-

Bedrock Evaluation Tinkham Garage Site Londonderry New Hampshirerdquo dated 24

October 2014

2014 Groundwater Monitoring Results

Former Source Area amp Areas Down Gradient Monitoring well NAI-K2 (located

within the former source area) was sampled in MarchApril and November 2014

Results of VOC and 14-dioxane analyses indicated that concentrations of

tetrachloroethylene (PCE) trichloroethylene (TCE) cis-12-dichloroethylene (cis-12-

DCE) and vinyl chloride (VC) exceeded AGQS standards for both sampling rounds

(See Attachment 5)

8

In wells located down gradient of the former source area FW20 and OW-2D

concentrations of 12-dichloroethane (12-DCA) VC and 14-dioxane exceeded the

AGQS standards for both sampling rounds

Bedrock monitoring well FW11D (located immediately down gradient of the former

source area) as well as bedrock monitoring wells LGSW ERT01 and FW21D (all

located further down gradient in the residentialcondominium area) were sampled in

MarchApril 2014 Monitoring well FW11D was sampled again in November 2014

During MarchApril 2014 VC and 14-dioxane concentrations in well FW11D

exceeded MCLAGQS standards In addition to VC and 14-dioxane concentrations

of TCE and 12-DCA were above their MCLAGQS during the sampling round in

November 2014 Detected concentrations of 14-dioxane were above the AGQS

standard of 3 ugL in monitoring wells LGSW ERT01 and FW21D in MarchApril

2014 In addition benzene exceeded the AGQS criteria in well LGSW Detected

VOC concentrations appear to be decreasing at these locations

GMZ Boundary Wells VOCs were not detected in GMZ boundary wells FW-25

ERT-04 and FW28D in the MarchApril and November sampling rounds 14-

dioxane was detected in GMZ boundary well FW28D at concentrations of 16 μgL (open borehole) in MarchApril 2014 While the borehole average concentration was

found below 2 ugl 14-dioxane was found at 32 ugl during the 2014 bedrock

investigations within a discrete fracture which is above the AGQS of 3 ugl

Surface Water Surface water locations SW-1 and SW-2 near the former source area

were sampled in MarchApril and November 2014 (See Attachment 4) Aside from

14-dioxane no other VOCs were detected at either surface water location during

both sampling events In MarchApril 2014 14-dioxane was detected 030 ugL at

SW-2 14-dioxane concentrations were 11 ugL and 13 ugL at locations SW-1 and

SW-2 respectively in November 2014

C SUMMARY OF THE SELECTED REMEDY

The 1986 ROD for the Tinkham Garage Superfund Site groundwater cleanup required

(1) removal of volatile organic compound (VOC) contaminated groundwater from the

overburden and bedrock aquifers through the use of two former bedrock supply wells

(LGSW and LGAW) and a shallow trench to be located behind the Tinkham Garage

building (2) transfer of contaminated groundwater through a force main and pump

station to the Derry Publically Owned Treatment Works (POTW) for off-site treatment

and (3) pre-treatment of extracted groundwater on-site as necessary to attain pre-

treatment standards required by the Derry POTW

The installation of the water line for private residences and the condominiums in 1983

was relied upon for the continued protection of public health in the selection of the

9

1986 remedial action as well as the extension of this water supply for residences and

commercial properties built within the boundaries of the Site since 1986

The ROD was amended in March 1989 to change the remedial approach for soils to

vacuum-enhanced extraction (VEE) which in turn allowed the shallow groundwater

extraction remedy to be modified from the planned trench behind the Tinkham

Garage building to a well system installed as part of the VEE The 1986 ROD

required that groundwater extraction would proceed for a two year period from the

date of implementation At the end of the two year period an evaluation would be

made by EPA to assess progress towards meeting the remedial objectives for the

cleanup of groundwater at the Site If steady state conditions have been reached and

it is evident remedial objectives are not achievable EPA would re-evaluate the

objectives and its remedial approach for groundwater at the Tinkham Site

The soil vacuum extraction began operations in November 1994 Groundwater

extraction was initiated in May 1995 Bedrock groundwater was extracted from the

two previous condominium supply wells LGAW and LGSW and was conveyed

back on-site via a dedicated sewer line At the source area shallow groundwater was

extracted through the vacuum extraction wells and was pretreated on-site via an air

stripper and carbon before both were discharged to the Derry POTW Following

attainment of the soil remedial goals within the former source area in November

1995 the VEE system was dismantled and the shallow groundwater extraction

system was then modified to include six independent wells pumping a combined

flow of 4500 gallons per day however reduced contaminant levels allowed

pretreatment to be discontinued prior to discharge to the POTW

In July 1996 the potentially responsible party (PRP) group requested a temporary

shutdown of the two bedrock pumping wells on the basis that VOC contamination

had reached steady-state conditions The PRPsrsquo consultant GEI prepared a report

Revised Request for Temporary Shutdown of Bedrock Pumping Systems July 8

1996 The 1986 ROD as amended in 1989 required the pumping of shallow

groundwater and contaminated bedrock aquifers for a period of up to two years until

treatment goals of 5 ugl of PCE and TCE were reached at each monitoring well or

until a decision was approved to cease pumping either following the two year period

or ifwhen steady state conditions were reached andor remedial objectives were

deemed not to be achievable In May 1997 the PRPs requested that EPA evaluate the

permanent shutdown of the complete groundwater extraction system based on

evidence of natural attenuation through active biodegradation in the shallow aquifer

attainment of steady-state conditions in the bedrock aquifer and an estimate that

drinking water standards were expected to be achieved within a 15 year period

Groundwater pumping of the two bedrock wells (former condominium supply wells)

which had a combined flow rate of 110000 gallons per day was suspended in 1997

though monitoring continued as the groundwater plume was deemed to have reached

steady state conditions The provision of the alternate drinking water source (1983

waterline) had reduced the potential for exposure to contamination at the Site and

10

protected public health while cleanup activities were being completed The 2003 ESD

documented the data collected to support the change from the 1986 cleanup to the use

of natural attenuation processes to reduce concentrations in groundwater at the Site to

remain protective of public health and the environment and in the interim relied upon

established institutional controls as part of a NHDES Groundwater Management

Permit

Construction within the Site has continued since 2003 and both a 165 unit residential

retirement development as well as several commercial properties utilize potable water

supplied through an extension of the water line installed in 1983 A five year review

was completed in 2004 as was a Reuse Assessment A Groundwater Management

Permit (Permit) was issued by the State of NH in 2007 and renewed in 2012 to ensure

that the existing groundwater monitoring and institutional controls remained in place

until cleanup levels are achieved at the Site The Permit established a Groundwater

Management Zone (GMZ) that is defined as the subsurface volume in which

groundwater contamination associated with Site is contained Both the third five year

review completed for the Site in 2009 and the fourth five year review completed in

September 2014 state that the remedy at the Site is expected to be or is protective of

human health and the environment and in the interim exposure pathways that could

result in unacceptable risks are being controlled Long-term monitoring indicates that

anaerobic degradation processes are reducing chlorinated compounds in groundwater

at the Site

As required by the Permit long-term groundwater monitoring continues at the Site

The elevated concentrations detected of 14-dioxane in the bedrock in 2014 suggest

that the time to achieve drinking water standards will be extended beyond the 15

years estimated in 1997 In light of the findings of these investigations and the

finding of nearby impacted residential water supply wells additional Site

investigations are deemed necessary to further identify the nature and extent of Site

contaminants in bedrock whether the current GMZ is adequate and whether

additional groundwater monitoring points are necessary to administer the Permit

The Permit and associated GMZ will be revised as necessary in response to the

additional data collected from these investigations The current remedy which allows

for natural attenuation at the Site to reduce the concentrations of chlorinated

compounds to below drinking water standards will be reviewed following these

investigations along with the findings of elevated concentrations of 14-dioxane

which is not known to readily undergo natural attenuation in the subsurface

III DESCRIPTION OF SIGNIFICANT DIFFERENCES AND THE BASIS FOR THESE DIFFERENCES

A Adding 14-dioxane as a Site Contaminant of Concern

14-dioxane is a clear liquid with a faint pleasant odor that mixes easily with water

Once dissolved into water it does not easily leave the water and enter into the air It is

11

used primarily as a solvent in the manufacture of other chemicals and as a laboratory

reagent 14-dioxane may also be present in trace amounts in cosmetics detergents

and shampoos

Currently there is not a federal enforceable drinking water standard for 14-dioxane

However under New Hampshire Statutes (RSA 485-C 6) the NHDES Commissioner is directed to establish and adopt an Ambient Groundwater Quality Standard (AGQS)

for contaminants which adversely affect human health or the environment Under the statute where health advisories have been established for a contaminant and where

such standards are based on a cancer risk the AGQS for a contaminant shall be equivalent to a lifetime exposure risk of one cancer in one million (1 in 1000000 or

10-6) exposed population According to NHDES regulations ambient groundwater

quality standards are also considered drinking water standards if a Maximum

Contaminant Level (MCL) standard has not been developed for a particular compound

In 2005 NHDES adopted an AGQS for 14-dioxane of 3 micrograms per Liter

(μgL) based on information provided at the time by EPArsquos Integrated Risk

Information System (IRIS) toxicological review In 2010 EPA developed a

cancer risk screening level which was updated in February 2015 for 14-dioxane

in tap water of 046 μgL using risk assessment guidance from the EPA Superfund

program This federal screening level guideline of 046 μgL is

equivalent to 1 in one million (1 in 1000000 or 10-6) cancer risk which is at the

most conservative end of EPArsquos acceptable risk range of between 10-6 ( 1 in

1000000) to 10-4 ( 1 in 10000) cancer risk The federal screening level for 10-4

(or 1 in 10000) cancer risk is 46 ugl The Hazard Quotient (HQ) equal to one is

567 ugL (child) These levels are developed for ingestion inhalation and dermal

contact with groundwater via drinking and household uses The cancer levels are

for a child and adult resident while the non-cancer level (HQ) is for a child

resident only the more vulnerable receptor These screening values are

considered by EPA to be protective of humans (including sensitive groups) over

a lifetime The NH AGQS concentrations of 3 ugL for 14-dioxane is well within

EPArsquos acceptable risk range for Superfund sites

In 2008 following the establishment of the AGQS for 14-dioxane NHDES required

that the groundwater at impacted sites be tested for 14-dioxane Subsequently in May

2008 14-dioxane was added to the list of parameters being tested for in the Sitersquos groundwater From 2008 to the present results of long-term monitoring events have

documented the presence of 14-dioxane at several Site wells with the highest

concentrations documented at well FW-11D down gradient of the former source area

behind Tinkham Garage As previously noted the highest observed 14-dioxane level

found in that well within a discrete fracture was 760 μgL during the 2014 bedrock

investigations

12

Based on these results 14-dioxane is now incorporated as a contaminant of concern in

groundwater and a cleanup level of 3 μgL is established through this ESD All future

monitoring activities and long-term monitoring plans including monitoring

performed as part of the NHDES Permit shall include sampling for 14-dioxane New

Hampshirersquos AGQS for 14-dioxane is identified as an applicable requirement and the

Statersquos fact sheet (WD-DWGB-3-24 2011) states that AGQSrsquo are considered

drinking water standards if an MCL standard has not been developed for a particular

compound All other ARARs identified in the 1986 ROD as amended remain the

same

The costs associated with this change which includes costs related to sampling for

14-dioxane are expected to be insignificant 14 dioxane is a compound that is

routinely analyzed for at the Site

B Use of an Alternative Water Supply (Waterline)

EPA has also modified the cleanup decision for the Tinkham Garage Superfund Site

to allow for the use of an existing public water supply (water line) as an acceptable

option to prevent human exposure to groundwater concentrations above drinking

water standards Use of a waterline as the permanent sustainable alternative for

potable water to residents impacted by the Site eliminates the long-term requirement

to provide bottled water and to provide maintain and monitor point of entry

treatment systems for impacted potable water wells as necessary In addition

residential wells nearby which remain in use could continue to draw contamination

from the bedrock and become contaminated thus also requiring frequent monitoring

and observation Because an alternative water source is readily available a contract

with the private utility to connect impacted properties andor extend the existing

waterline to residents as needed offers a sustainable implementable and cost

effective solution over the need for supplying bottled water and installing

monitoring and maintaining treatment systems EPA in consultation with the

NHDES has determined that connection to andor the extension of the nearby

waterline is a better long-term solution than providing potable water and the

continued use of point of entry treatment systems and has modified the cleanup

decision for the Site to acknowledge the use of this public water supply as an

acceptable option to protect human health

This ESD is therefore being issued to modify the selected remedy as set forth in the

1986 ROD for the Site as amended The modification described in this ESD is to

provide alternative water to prevent human exposure to Site-related groundwater with

contaminant concentrations above drinking water standards to residents outside of the

existing GMZ Similar actions were initiated in 1983 to address and prevent human

exposure to groundwater in residential areas south west of the source area

Potable supply wells impacted by the Site that are replaced with connections to either

an existing waterline (where present) or a new (eg extended) waterline will be

properly abandoned or decommissioned unless they need to be utilized as long-term

13

groundwater monitoring wells per EPArsquos direction and the POE treatment systems

will be removed thereby eliminating the requirement to provide maintain and

monitor such systems Potable wells that remain in use as groundwater monitoring

wells shall be secured so as to prevent other uses unless reuse of these wells

following additional site investigations is deemed otherwise to be acceptable by the

EPA and the NHDES

A routine sampling plan for the monitoring of all nearby residential properties which

continue to utilize the bedrock aquifer for a private potable water supply will be

implemented to ensure protection of public health In the future if additional potable

wells are found to contain Site-related contamination above drinking water standards

or are otherwise found to be impacted by Site contaminants the option to provide

connections to the waterline as described in this ESD will also be the remedial option

for additional impacted residents

The evaluation of historical groundwater data data generated from additional bedrock

geophysical and packer testing conducted in 2014 and the results of recent residential

well sampling has led EPA and NHDES to conclude that the extent of bedrock

groundwater contamination present at the Site is not adequately characterized

Further the recent data results indicate that the current monitoring well network is

not adequate to demonstrate the full lateral and vertical extent of groundwater impacts

associated with the Site Supplemental bedrock investigations shall be conducted that

will delineate the full lateral and vertical extent of groundwater contamination and

shall include the installation of a more robust groundwater monitoring well network

designed to support the monitoring requirements established by the Permit to support

a more robust conceptual site model and to support and demonstrate attainment of the

cleanup levels as outline below Upon completion of the investigations required by

this ESD a revised Permit will be issued that will provide an updated groundwater

monitoring program and if necessary a revised GMZ

The costs associated with this change are expected to be insignificant (less than

$500000) in comparison to the overall estimated costs expended for the Site to date

(approximately $10 million)

C Evaluation of Cleanup Level Attainment

The 1986 ROD and subsequent ESDs described a process for evaluating when

groundwater cleanup levels have been achieved Through this latest ESD the

evaluation of attainment of groundwater Cleanup Levels is being clarified and

updated as follows

The determination that groundwater Cleanup Levels have been met will now be based

on site-specific considerations In particular EPA will consider historical and current

monitoring data contaminant distribution trend analysis the appropriateness of the

compliance monitoring program (ie locations frequency of monitoring sampling

parameters etc) and attainment of cleanup levels throughout the GMZ as modified

14

At the time this determination is made EPA will provide a complete description of

this technical evaluation documenting attainment of groundwater Cleanup Levels

Because the groundwater remedial action has been on-going at this Site cleanup

levels may be achieved early in the process for some contaminants and therefore

EPA may rely on historical data such as number of years of sampling with no

detections for these contaminants whether cleanup levels were reached in every well

and statistical averages in their determination

After all groundwater Cleanup Levels have been met as determined by EPA

consistent with Agency guidance available at the time EPA will perform a risk

evaluation which considers additive risk from remaining COCs considering all

potential routes of exposure to document the residual risk based on exposure to

groundwater at the Site The residual risk evaluation will document the potential risk

associated with the concentrations of COCs remaining in groundwater at the Site (if

detected)

This updated approach to evaluating attainment of groundwater Cleanup Levels

protectiveness of the groundwater remedy and completion of groundwater restoration

efforts reflects 1) acknowledgement that MCLs established under the Safe Drinking

Water Act are deemed protective by EPA 2) consideration of all potential routes of

exposure for groundwater 3) improved methods for assessing data variability and

other dynamic aquifer conditions that impact monitoring data and 4) reliance on up-

to-date technical guidance and tools This updated approach will support

determinations when groundwater at the Site has been restored for its permissible

beneficial use and that the groundwater no longer presents an unacceptable risk to

human health due to the presence of site-related contaminants

The costs associated with this change are expected to be minimal

IV SUPPORTINGAGENCY COMMENTS

The State of New Hampshire Department of Environmental Services (NHDES) has

participated with the EPA in reviewing the modifications to the remedy described

herein and supports the currently proposed changes to the 1986 ROD as amended

The NHDES has evaluated public comments on the draft ESD and concurs with this

final ESD

V STATUTORY DETERMINATIONS

In accordance with Section 121 of CERCLA EPA in consultation with NHDES has

determined that the modified remedy remains protective of human health and the

environment complies with all Federal and State requirements that are applicable or

relevant and appropriate to the remedy as modified herein and is cost-effective While

the modification for the addition of a new COC does not currently alter the Site

remedy connection to a water line would provide a permanent and sustainable

solution for residences impacted by this Site

15

VI PUBLICPARTICIPATIONCOMPLIANCE

In accordance with Section 300825(a) of the NCP EPA voluntarily chose to allow a

21-day public comment period prior to the finalization and signing of this ESD Such

comment period is designed to allow consideration of any possible concerns from the

public local municipalities andor the PRPs A draft of this ESD was issued publicly

on October 1 2015 A formal public comment period regarding the draft ESD was held

from October 9 2015 to October 30 2015 EPA accepted written and e-mailed

comments on the draft ESD which are included in the Administrative Record

Comments were submitted by October 30 2015 via mail e-mail or fax to

Cheryl Sprague Remedial Project Manager USEPA Region 1 OSRR07-1

5 Post Office Square - Suite 100 Boston MA 02109-3912

E-mail Spraguecherylepagov Fax (617) 918-0244

or

Rodney Elliot Community Involvement Coordinator USEPA Region 1 ORA01-1


E-mail Elliotrodneyepagov Fax (617) 918-0031

Public comments received are addressed in a Responsiveness Summary attached to this

final ESD

In accordance with Section 117(d) of CERCLA this final ESD and the

Administrative Record are available for public review at the locations and times

listed in Section IE above as well as on the internet at


documents

A public notice which summarizes the modification to the remedy as set forth in the

final ESD shall be published in the Derry News

16

VII DECLARATION

For the foregoing reasons by my signature below I approve the issuance of this Third Explanation of Significant Differences for the Tinkham Garage Superfund Site in Londonderry New Hampshire and the changes stated therein

Date Bryan lson Director Office of Site Remediation and Restoration US Environmental Protection Agency

Region 1 - New England

17

ATTACHMENTS

18

ATTACHMENT 1

19

ATTACHMENT 2- Site Plan ndash GMZ and Monitoring Wells

1

ATTACHMENT 3- Drawdown in Bedrock During 1983 and 1986 Pump tests

1

ATTACHMENT 4- VOCs in Bedrock 2008

1

ATTACHMENT 5 ndash 2014 Map showing Total VOC and 14-Dioxane Concentrations

1

ATTACHMENT 6 ndash

2014 Bedrock Investigation

Fracture Sampling

Results and Map of Well Locations

19 highlighted number indicates concentrations at or exceeding a drinking water standard

1

ATTACHMENT 7 Historical Data Comparison Table

1

ATTACHMENT 8- Table of Applicable or Relevant and Appropriate Requirements (ARARs)

1

1

1

Haley amp Aldrich Inc 465 Medford St Suite 2200 Boston MA 02129 6178867400

28 October 2015 File No 40814-004

Remedial Project Manager US Environmental Protection Agency OSRR07-1 Five Post Office Square - Suite 100 Boston MA 02109-3912

Attention Ms Cheryl Sprague

Subject Comments to the Draft Explanation of Significant Differences Tinkham Garage Superfund Site Londonderry NH United States of America v Cannons Engineering Corp et al

Dear Ms Sprague

On behalf of the Tinkhamrsquos Site Settling Group and the Cannons Sites Group (together the ldquoConsent Decree PRPsrdquo) we write to provide comments to the Draft Explanation of Significant Differences (ldquoESDrdquo) sent to us on October 2 2015 Overall we find that the actions proposed in the Draft ESD are consistent with Consent Decree PRPsrsquo commitments prior to its issuance As noted in the record already (see our letters dated April 27 2015 and July 13 2015) we committed to

Providing connections to the public water supply line for the five impacted homes and

Performing investigations necessary to determine whether the contamination in the impacted residences originates from the Tinkham Garage Superfund Site (ldquothe Siterdquo)

We remain committed to completing these activities In addition we note that the Consent Decree PRPs have consistently been proactive in meeting our responsibilities For example we began sampling for 14-dioxane in 2008 without notice from EPA or the New Hampshire Department of Environmental Services (ldquoNHDESrdquo) to assess the presenceabsence of this contaminant at the Site

With regards to the Draft ESD we provide the following comments

1 The phrase ldquoSimilar contaminantsrdquo is not equivalent to ldquosite-related contaminantsrdquo We concur with the language in the cover letter to the residents and at the top of page 3 of the Draft ESD that describes the contaminants detected in the five private wells as ldquosimilar to those found at the Tinkham Garage Siterdquo However we strongly disagree with any and all language throughout the Draft ESD that states that the five private wells are ldquoSite impactedrdquo ldquoimpacted by the Siterdquo have ldquosite-related contaminationrdquo or similar language

As described in our April 27 2015 letter there is significant contrary evidence that indicates that the Tinkham Garage Site may not be the source of contamination in the affected wells The

wwwhaleyaldrichcom

US Environmental Protection Agency 28 October 2015 Page 2

contaminants detected to date are common contaminants in groundwater that have been shown to potentially result from both industrial and residential sources In April the Consent Decree PRPs proposed additional investigations to assess whether or not the contamination originates from the Site

We request that the language throughout the final ESD reflect that the contaminants are ldquosimilarrdquo to those found at the Site Statements attributing the contaminants to the Site should be removed or altered to accurately reflect the uncertainty surrounding this issue

2 The Consent Decree PRPs concur that additional investigations are required to identify the nature and extent of Site-related contaminants in the bedrock and better understand whether the similar contaminants detected in water supply wells to the northeast of the Site do in fact result from releases at the Site Until these investigations are completed it is inappropriate to make conclusions that may ultimately prove to be incorrect For example the following conclusions in Section ID need to be supported by additional technical data

a The ESD suggests that a distinct fracture pattern extends approximately 1500 feet to the northeast

b The ESD suggests that the five impacted homes are all along the narrow fracture pattern that is shown to be only approximately 200 feet wide and located to the north of Boston Avenue and

c The ESD suggests that the intermittent pumping of few private wells could draw contamination from 1500 feet away

As discussed additional investigations are required to demonstrate the presence or absence of causation As stated previously given that the detected contaminants are common in groundwater similar contamination is not a basis to conclude that the Site has impacted the private wells in this area

3 It is premature for the ESD to definitively include waterline connections for all ldquopotentially impacted residencesrdquo waterline extensions to ldquopotentially impacted residencesrdquo or abandonment of unimpacted wells (Section ID -- three bullets at the bottom of p 3)

We recommend that these actions be altered to be consistent with the current precedent set by the Consent Decree PRPs First properties must be actually impacted it does not make sense to commit to connecting residences that are only ldquopotentially impactedrdquo Second waterline connections will only be made if at a minimum the data show impacts by contaminants ldquosimilar to those found at the Tinkham Garage Siterdquo Even then connections should only be provided if field investigations have not demonstrated that the impacts are not Site-related

4 It is relevant to note that in the past 10 years the PRPs have evaluated the exposures via inhalation of volatile organic compounds (VOCs) and the ingestion of 14-dioxane impacted water within the current site boundaries as well as along Ross Drive In both instances these exposure pathways were determined to be incomplete


EPA concluded that inhalation and ingestion exposures did not pose a risk and that the Site remedy was protective (Section ID Risk)

5 It is premature to assign a value of ldquoless than $500000rdquo to future activities or consider these costs to be insignificant Currently no scope of work has been proposed by EPA NHDES or the Consent Decree PRPs for bedrock investigations Furthermore the number of homes demonstrated to be impacted by Site-related contaminants has not been established (Section IIB Use of an Alternative Water Supply (Waterline))

The Consent Decree PRPs want to emphasize that we have worked closely and cooperatively with USEPA and NHDES since the 1980s We believe that throughout this time we have discharged fully and timely each of our obligations under the Consent Decree Furthermore in response to the impacted private wells northeast of the Site we have responded quickly and in good faith to connect these homes despite the fact that contaminant causation has not been established

Thank you for the opportunity to comment on the draft ESD

Sincerely yours HALEY amp ALDRICH INC

Ian Phillips Vice President

c Sheehan Phinney Bass + Green Attn Robert R Lucic Foley Hoag LLP Attn Seth D Jaffe

G408140042015-1028-HAI-commentsondraftexplanationdocx


2016 Explanation of Significant Differences Responsiveness Summary

General Comment received from Haley amp Aldrich (HampA) on behalf of the Consent Decree

PRPs Overall the actions proposed in the Draft ESD are consistent with Consent Decree

PRPsrsquo (or ldquoRPsrdquo) commitments prior to its issuance Haley amp Aldrich (HampA) noted the

Consent Decree PRPs commitment to providing connections to the waterline in the area for the

five households for which data indicates impacted water supply well and to performing

additional investigations

EPA Response EPA and NHDES (the Agencies) appreciate the Consent Decree PRPs

proactive approach to address these matters completely and expeditiously and their continued

commitment to complete the work required at the Tinkham Garage Superfund Site (the Site) to

protect human health and the environment

For the record the NHDES initially and immediately implemented supplies of bottled water and

point of entry treatment system on households upon receipt of data indicating that contamination

was present above drinking water standards at several properties near the Site These systems

were put in place in late 2014 and early 2015 On July 23 2015 EPA approved the request from

the RPrsquos to initiate the connection of these properties to the waterline for the five currently

impacted residential water supply wells consistent with this ESD As of January 2016 three

households have been connected to the water line and a fourth will be connected in the spring of

2016 The fifth household is currently supplied bottled water and negotiations continue to

connect this household to the waterline in 2016 A quarterly groundwater monitoring program

was implemented in the fall of 2015 and includes impacted households as well as households

where contamination was not seen previously to better understand and define the scope of the

work to be required under this ESD

Specific ESD Comments received from commenter (HampA)

Specific ESD Comment 1 The commenter noted that the phrase ldquoSimilar contaminantsrdquo was

not equivalent to ldquosite-related contaminantsrdquo The former was used in language contained in a

cover letter to the nearby residents which discussed the release of the ESD and which thanked

them for their cooperation with the Agencies while actions are undertaken to understand and

address the residential water supply well contamination issues This language was also noted at

the top of page 3 of the Draft ESD that describes the contaminants detected in the five private

wells as ldquosimilar to those found at the Tinkham Garage Siterdquo The commenter strongly disagrees

with any and all language throughout the Draft ESD that states that the five private wells are

ldquoSite impactedrdquo ldquoimpacted by the Siterdquo have ldquosite-related contaminationrdquo or similar language

The commenter asserts that as presented in a letter to the Agencies on April 27 2015 there is

significant contrary evidence that indicates that the Tinkham Garage Site may not be the source

1

of contamination in the affected wells and that the contaminants detected to date are common

contaminants in groundwater that have been shown to potentially result from both industrial and

residential sources

The commenter requested that the language throughout the final ESD reflect that the

contaminants are ldquosimilarrdquo to those found at the Site Statements attributing the contaminants to

the Site should be removed or altered to accurately reflect the uncertainty surrounding this issue

EPA Response

The Agencies have reviewed all readily available current and historical information and reports

of known or potential sources of contamination in the vicinity of the impacted residential supply

wells as well as your April 27 2015 letter Based on that review the Agencies concluded that

the Tinkham Garage Site is the most likely source of the contamination found in the impacted

residential water supply wells and this contamination is ldquosite-relatedrdquo The contaminants found

in excess of drinking water standards in these residential water supply wells (trichloroethylene

(TCE) vinyl chloride (VC) and 14-dioxane) are also found at the Site above drinking water

standards in groundwater within the source area at the Site The Consent Decree PRPs have not

provided the Agencies with specific documented information or ldquosignificant contrary evidencerdquo that suggests that the Site is not the most likely source of the contamination in these water supply

wells

The five impacted residential water supply wells are completed in the bedrock aquifer

Historical pumping tests conducted as part of the Remedial Investigations performed in 1980rsquos at

the Site have documented at least one and possibly multiple bedrock fracture sets that are

oriented in a northeastsouthwest direction These fracture sets likely act as transport pathways

for groundwater and contaminant migration from the Site The Site Conceptual Model indicates

that contaminants were historically released to the ground within the source area at the Site and

have migrated through the soil overburden into the bedrock fractures underlying the Site In the

early 1980rsquos the influence of pumping from relatively prolific bedrock water supply wells

located over 1000 feet southwest of the source area at the Site caused contamination to migrate

from the source area towards and into these water supply wells impacting hundreds of

condominium residents As a result EPA authorized the extension of a nearby water line in

1983 providing a sustainable water supply to these impacted and nearby potentially impacted

residents Similarly the residential water supplies found impacted in 20142015 are also located

over 1000 feet away from the source area at the Site in what may be the same bedrock fracture

feature and the likely migration pathway EPA has determined that the extension of and

connection to the nearby water supply line is the most sustainable permanent alternative chosen

to address this exposure pathway for these residents

Specific ESD Comment 2 The Consent Decree PRPs concur that additional investigations are

required to identify the nature and extent of Site-related contaminants in the bedrock and better

understand whether the similar contaminants detected in water supply wells to the northeast of

the Site do in fact result from releases at the Site The commenter notes that until these

investigations are completed it is inappropriate to make conclusions that may ultimately prove to

2

be incorrect The commenter noted that additional investigations should gather additional

technical data related to the following

a The ESD suggestion that a distinct fracture pattern extends approximately 1500 feet to the

northeast

b The ESD suggestion that the five impacted homes are all along the narrow fracture pattern that

is shown to be only approximately 200 feet wide and located to the north of Boston Avenue and

c The ESD suggestion that the intermittent pumping of private wells could draw contamination

from 1500 feet away

The commenter notes that additional investigations are required to demonstrate the presence or

absence of causation given that the detected contaminants are common in groundwater and that

a finding of similar contamination is not a basis to conclude that the Site has impacted the private

wells in this area

EPA Response

The Agencies agree that additional investigations as required in this ESD are necessary for

better characterization and understanding of the migration pathway of Site contaminants through

the bedrock fractures towards these residential areas In EPArsquos 2009 Third Five Year Report it

was noted that many of the monitoring wells are antiquated at the Site are constructed with long

open boreholes do not currently provide detailed information about contaminated fracture zones

and it is possible that there is a highly contaminated fracture(s) whose concentrations can be

ldquoaveraged outrdquo such that the full extent of the groundwater plume is not entirely understood

In response to this Five Year Review Report bedrock investigations were started in 2013 on the

Site by the Consent Decree PRPs to clarify potential deficiencies in the monitoring well network

and support the lack of understanding of the contaminant migration within bedrock fractures

under the Site The preliminary results of those investigations were that significantly higher

concentrations of contaminants specifically 14-dioxane are found in groundwater in the

bedrock down gradient from the source area at the Site and that the depth and extent of this

contamination within bedrock is not fully known

As noted earlier a cluster of five properties located northeast of the Site have documented ldquosite-

relatedrdquo contamination in their residential supply wells EPA and NHDES remain concerned that

continued extraction from the bedrock aquifer via these residential supply wells could exacerbate

the migration of contamination from the Site to other areas As such additional bedrock

investigations are required to more fully understand this migration potential and also minimize

or otherwise protect against future impacts from the Site towards these residential properties

Specific ESD Comment 3 The commenter noted that it is premature for the ESD to definitively

include waterline connections for all ldquopotentially impacted residencesrdquo waterline extensions to

ldquopotentially impacted residencesrdquo or abandonment of un-impacted wells (Section ID -- three

bullets at the bottom of p 3)

3

They recommend that these actions be altered to be consistent with the current precedent set by

the Consent Decree PRPs First properties must be actually impacted it does not make sense to

commit to connecting residences that are only ldquopotentially impactedrdquo Second waterline

connections will only be made if at a minimum the data show impacts by contaminants ldquosimilar to those found at the Tinkham Garage Siterdquo Even then connections should only be provided if

field investigations have not demonstrated that the impacts are not Site-related

EPA Response The Agencies disagree that an action to protect abate or otherwise minimize

residential exposures to hazardous substances in residential water supply wells should wait until

such time that data indicates wells are impacted [EPA assumes the commenter is referring to

impacted wells as those which have contaminant concentrations in exceedance of drinking water

standards] or that an action to abate or prevent exposure to a contaminated drinking water

supply should be delayed until such time as field investigations which can take years

demonstrate that the impacts are not Site related See also the EPA response to comment 1

The National Contingency Plan (NCP) sets out in regulations that EPA has the authority to

respond to and mitigate exposures to hazardous substances The NCP regulations state that as

appropriate an action shall be undertaken by the lead agency in response to any person who is

or may be affected by a release of a hazardous substance pollutant or contaminant or when

there is a threat to public health or welfare of the United States or the environment The NCP

allows the EPA to take any appropriate action to abate prevent minimize stabilize mitigate or

eliminate the release or the threat of such a release the factors listed in the NCP to be considered

for the appropriateness of such action include both (i) Actual or potential exposure to nearby

human populations animals or the food chain from hazardous substances or pollutants or

contaminants and (ii) Actual or potential contamination of drinking water supplies or sensitive

ecosystems

The EPA Guidance on Providing Alternative Water Supplies (OSWER Directive 93553-03

dated February 1988) also indicates that provision of an alternate water supply may be

appropriate when existing supplies are contaminated or are threatened by contamination in the

near future While the data currently being collected continues to show that other nearby

households have not seen site-related impacts to their water supply wells the number of homes

which could potentially become impacted by site-related contaminants has not been fully

established A decision not to include potentially impacted households would require data which

could support and assure that remaining water supplies will not become contaminated beyond

safe use before a final remedy can be fully implemented At this Site the remedy requires

restoration of all groundwater to drinking water standards The current remedy for groundwater

at the Site to reach this criteria is Monitored Natural Attenuation (MNA) This ESD requires the

Consent Decree PRPs to determine the full horizontal and vertical extent of the contamination

and to estimate the time necessary to reach cleanup levels specifically now that 14 dioxane has

been identified at the Site (and beyond)

The Agencies believe that this ESD and the requirement for an alternative water supply via

connection to the nearby water line to impacted and potentially impacted residential properties is

appropriate and consistent with the NCP CERCLA and EPA guidance Allowance for a water

line to include potentially impacted properties via this ESD also covers all future waterline

4

connections based on a review of on-going sampling analysis bedrock investigations and

groundwater modeling which may require a similar response action to abate prevent minimize

stabilize mitigate or eliminate the release or the threat of release expeditiously

Specific ESD Comment 4 The commenter felt that it should be noted that in the past 10 years

the PRPs have evaluated the exposures via inhalation of volatile organic compounds (VOCs) and

the ingestion of 14-dioxane impacted water within the current site boundaries as well as along

Ross Drive In both instances these exposure pathways were determined to be incomplete

EPA concluded that inhalation and ingestion exposures did not pose a risk and that the Site

remedy was protective (Section ID Risk)

EPA Response To clarify our position EPA has always been concerned about the potential for

vapor intrusion into residential households because the shallow groundwater is contaminated

with volatile organic compounds which can migrate from the groundwater through the soil and

into homes above the plume The EPArsquos 2004 Second Five Year Report identified vapor

intrusion as a potential issue at the Site EPA noted that vapor intrusion into existing residences

and in residential and commercial areas yet to be built needed to be addressed to determine if

venting of structures would be appropriate

In response EPA issued a recommendation to implement a monitoring program designed to

assess the impact of TCE vapors on the health of existing residents near contaminated shallow

ground water and should unacceptable levels be found mitigation methods would then need to

be evaluated and implemented In addition the report noted that to avoid the potential for TCE

vapors to adversely impact the health of future residents living in homes above the contaminated

ground water the developer of the homes will be required to incorporate mitigation measures

into their design

As such construction of a 125-home elderly housing complex included as a precautionary

measure passive gas venting to ensure that site contaminants did not adversely affect future

homeowners The design of the venting systems was provided to EPA and NHDES for review

In addition development of the Home DepotStaples project located on the northern portion of

the site also incorporated gas venting in the design and construction

EPArsquos 2009 Third Five Year Report noted that our knowledge of vapor intrusion continues to

evolve and that additional assessment of the indoor air vapor intrusion pathway may be required

in light of updated risk based screening values and lower reporting limits

EPArsquos Fourth Five Year Report noted that groundwater samples were collected from five

monitoring wells in November 2009 and tested using test methods with lower reporting limits to

meet EPA Region Is risk based screening values for assessing vapor intrusion EPA concluded

that no further assessment of vapor intrusion was warranted and that vapor intrusion is currently

not a concern at the Site and that contaminants in excess of the MCLs and New Hampshire

Ambient Groundwater Quality Standards are within the Groundwater Management Zone

5

As noted above all new construction at the Site has employed measures to prevent exposures

related to vapor intrusion EPA continues to revise and update its standards of screening and

analysis and criteria for vapor intrusion at a site particularly and most recently for the compound

Trichloroethylene (TCE) which is found in the groundwater at the Site EPA and the NHDES

both have released recent guidance relative to vapor intrusion and have periodically lowered the

criteria for TCE exposures from vapor intrusion In addition residential water supplies were

found impacted by TCE in 20142015 located over 1000 feet away from the Site As such the

analysis of site characteristics related to vapor intrusion exposure must continually be assessed as

part of ongoing investigations and site monitoring as it simply is not considered an exposure that

is evaluated once at a site

The ESD has been revised to indicate that vapor intrusion may be a potential risk pathway at the

Site and additional assessments for vapor intrusion may be warranted The evaluation for

completed exposures to vapor intrusion are site specific and include a review of not just chemical

concentration data but also depth to water presence of vapor pathways and individual

household construction and ventilation

Residential well sampling for 14-dioxane was conducted in 2009 primarily west of the Site

along Ross Drive EPA can confirm at that time there were no impacted wells with this

contaminant which is known to migrate with water away from source areas and which does not

readily degrade The recent bedrock investigations were conducted due to concerns that the

current monitoring well network does not accurately allow for the monitoring of this chemical at

and away from the source area As required by this ESD further groundwater investigations are

warranted to better characterize the extent of this contaminant at the Site and beyond the current

GMZ boundary the fate and transport of this contaminant as it migrates through bedrock as well

as a review of the estimated timeframe until this contaminant reaches the NHDES drinking water

criteria of 3 ugl

Specific ESD Comment 5 The commenter noted that it is premature to assign a value of ldquoless than $500000rdquo to future activities or consider these costs to be insignificant Currently no

scope of work has been proposed by EPA NHDES or the Consent Decree PRPs for bedrock

investigations Furthermore the number of homes demonstrated to be impacted by Site-related

contaminants has not been established (Section IIB Use of an Alternative Water Supply

(Waterline))

EPA Response

EPA assigned a value of ldquoless than $500000rdquo to future activities associated with this ESD based

in part on the following

The ESD included connection of residential households to an existing water line The

presence of the water line nearby reduces the construction and connection costs

associated with building a new waterline At the time of this ESD five residential

properties are known to have impacted water supply wells The assigned value was

estimated as additional investigations are necessary to better understand how many

6

additional households (if any) may ultimately require connection to the existing water

line

As noted above bedrock investigations on the Site were initiated in 2013 by the Consent

Decree PRPs at the request of the Agencies who had noted deficiencies in the monitoring

well network and the lack of understanding of the contaminant migration within bedrock

fractures under the Site This ESD includes an expansion of those bedrock investigations

to facilitate a more complete understanding of contaminant migration and potential

exposure pathways from contaminated groundwater moving though bedrock from the

Site to these impacted residents

The NCP requires that the EPA estimate costs related to review and selection of a remedy

that are expected to be within +50 and -30 of the actuals costs to allow for

comparison of alternatives relative to cost effectiveness The actual costs of the

connections to the waterline were estimated at the time of the ESD based on the five

impacted households and additional bedrock investigations to support exposure pathway

analysis

7

barcode 586297

barcodetext SEMS Doc ID 586297

Third Explanation of Significant Differences (ESD) Tinkham Garage Superfund Site

February 2016

TABLE OFCONTENTS

I INTRODUCTION page 1

II SUMMARY OF SITE HISTORY CONTAMINATION PROBLEMS

AND SELECTED REMEDY page 6

III DESCRIPTION OF SIGNIFICANT DIFFERENCES AND page 11 THE BASIS FOR THESE DIFFERENCES

IV SUPPORT AGENCY COMMENTS page 15

V STATUTORY DETERMINATIONS page 15

VI PUBLIC PARTICIPATION page 16

VII DECLARATION page 17

ATTACHMENTS

Attachment 1 - Site Location Map of the Tinkham Garage Superfund Site

Attachment 2 - Site Map - current Groundwater Management Zone boundaries and Wells

Attachment 3 - Site Plan showing drawdownin bedrock during1983 and 1986 pump tests

Attachment 4 - Isoconcentration Map showing contours of total VOCs in bedrock (2008)

Attachment 5 -Contour Map showing Total VOC and 14-dioxane concentrations(2014)

Attachment 6 - 2014 Bedrock Investigation fracture sampling results and Map of well locations

Attachment 7 - Historical Contaminant Comparison Table

Attachment 8 - Table of Applicable or Relevant and Appropriate Requirements (ARARs)

2016



I INTRODUCTION






























1










































2












































3


Site Source Area







Avenues)


TCE TCE TCE

VC VC VC

12 -DCA 12-DCA

PCE

Cis 12-DCE

Benzene

















Avenues)




4











Therefore this ESD








dioxane











5






documents on-line




History











Ross Drive

6










November 1983






Risk













Site










7














FW28D and FW-21D


















October 2014







(See Attachment 5)

8





































9











































10






Permit















at the Site



















11



and shampoos
































investigations

12









same

































13






EPA and the NHDES





























updated as follows






14














detected)

















final ESD









15













or





final ESD





documents



16

VII DECLARATION




17

ATTACHMENTS

18

ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

US Environmental Protection Agency 28 October 2015
























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297


2016



I INTRODUCTION






























1










































2












































3


Site Source Area







Avenues)


TCE TCE TCE

VC VC VC

12 -DCA 12-DCA

PCE

Cis 12-DCE

Benzene

















Avenues)




4











Therefore this ESD








dioxane











5






documents on-line




History











Ross Drive

6










November 1983






Risk













Site










7














FW28D and FW-21D


















October 2014







(See Attachment 5)

8





































9











































10






Permit















at the Site



















11



and shampoos
































investigations

12









same

































13






EPA and the NHDES





























updated as follows






14














detected)

















final ESD









15













or





final ESD





documents



16

VII DECLARATION




17

ATTACHMENTS

18

ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom












US Environmental Protection Agency 28 October 2015













































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297











































2












































3


Site Source Area







Avenues)


TCE TCE TCE

VC VC VC

12 -DCA 12-DCA

PCE

Cis 12-DCE

Benzene

















Avenues)




4











Therefore this ESD








dioxane











5






documents on-line




History











Ross Drive

6










November 1983






Risk













Site










7














FW28D and FW-21D


















October 2014







(See Attachment 5)

8





































9











































10






Permit















at the Site



















11



and shampoos
































investigations

12









same

































13






EPA and the NHDES





























updated as follows






14














detected)

















final ESD









15













or





final ESD





documents



16

VII DECLARATION




17

ATTACHMENTS

18

ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297













































3


Site Source Area







Avenues)


TCE TCE TCE

VC VC VC

12 -DCA 12-DCA

PCE

Cis 12-DCE

Benzene

















Avenues)




4











Therefore this ESD








dioxane











5






documents on-line




History











Ross Drive

6










November 1983






Risk













Site










7














FW28D and FW-21D


















October 2014







(See Attachment 5)

8





































9











































10






Permit















at the Site



















11



and shampoos
































investigations

12









same

































13






EPA and the NHDES





























updated as follows






14














detected)

















final ESD









15













or





final ESD





documents



16

VII DECLARATION




17

ATTACHMENTS

18

ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297



Site Source Area







Avenues)


TCE TCE TCE

VC VC VC

12 -DCA 12-DCA

PCE

Cis 12-DCE

Benzene

















Avenues)




4











Therefore this ESD








dioxane











5






documents on-line




History











Ross Drive

6










November 1983






Risk













Site










7














FW28D and FW-21D


















October 2014







(See Attachment 5)

8





































9











































10






Permit















at the Site



















11



and shampoos
































investigations

12









same

































13






EPA and the NHDES





























updated as follows






14














detected)

















final ESD









15













or





final ESD





documents



16

VII DECLARATION




17

ATTACHMENTS

18

ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297












Therefore this ESD








dioxane











5






documents on-line




History











Ross Drive

6










November 1983






Risk













Site










7














FW28D and FW-21D


















October 2014







(See Attachment 5)

8





































9











































10






Permit















at the Site



















11



and shampoos
































investigations

12









same

































13






EPA and the NHDES





























updated as follows






14














detected)

















final ESD









15













or





final ESD





documents



16

VII DECLARATION




17

ATTACHMENTS

18

ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297







documents on-line




History











Ross Drive

6










November 1983






Risk













Site










7














FW28D and FW-21D


















October 2014







(See Attachment 5)

8





































9











































10






Permit















at the Site



















11



and shampoos
































investigations

12









same

































13






EPA and the NHDES





























updated as follows






14














detected)

















final ESD









15













or





final ESD





documents



16

VII DECLARATION




17

ATTACHMENTS

18

ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297











November 1983






Risk













Site










7














FW28D and FW-21D


















October 2014







(See Attachment 5)

8





































9











































10






Permit















at the Site



















11



and shampoos
































investigations

12









same

































13






EPA and the NHDES





























updated as follows






14














detected)

















final ESD









15













or





final ESD





documents



16

VII DECLARATION




17

ATTACHMENTS

18

ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297















FW28D and FW-21D


















October 2014







(See Attachment 5)

8





































9











































10






Permit















at the Site



















11



and shampoos
































investigations

12









same

































13






EPA and the NHDES





























updated as follows






14














detected)

















final ESD









15













or





final ESD





documents



16

VII DECLARATION




17

ATTACHMENTS

18

ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297






































9











































10






Permit















at the Site



















11



and shampoos
































investigations

12









same

































13






EPA and the NHDES





























updated as follows






14














detected)

















final ESD









15













or





final ESD





documents



16

VII DECLARATION




17

ATTACHMENTS

18

ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297












































10






Permit















at the Site



















11



and shampoos
































investigations

12









same

































13






EPA and the NHDES





























updated as follows






14














detected)

















final ESD









15













or





final ESD





documents



16

VII DECLARATION




17

ATTACHMENTS

18

ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297







Permit















at the Site



















11



and shampoos
































investigations

12









same

































13






EPA and the NHDES





























updated as follows






14














detected)

















final ESD









15













or





final ESD





documents



16

VII DECLARATION




17

ATTACHMENTS

18

ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297




and shampoos
































investigations

12









same

































13






EPA and the NHDES





























updated as follows






14














detected)

















final ESD









15













or





final ESD





documents



16

VII DECLARATION




17

ATTACHMENTS

18

ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297










same

































13






EPA and the NHDES





























updated as follows






14














detected)

















final ESD









15













or





final ESD





documents



16

VII DECLARATION




17

ATTACHMENTS

18

ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297







EPA and the NHDES





























updated as follows






14














detected)

















final ESD









15













or





final ESD





documents



16

VII DECLARATION




17

ATTACHMENTS

18

ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297















detected)

















final ESD









15













or





final ESD





documents



16

VII DECLARATION




17

ATTACHMENTS

18

ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297














or





final ESD





documents



16

VII DECLARATION




17

ATTACHMENTS

18

ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297


VII DECLARATION




17

ATTACHMENTS

18

ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297


ATTACHMENTS

18

ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297


ATTACHMENT 1

19


1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297



1


1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297



1


1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297



1


1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297



1

ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297


ATTACHMENT 6 ndash


Fracture Sampling



1


1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297



1


1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297



1

1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297


1

1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297


1


28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297



28 October 2015 File No 40814-004




Dear Ms Sprague








wwwhaleyaldrichcom

























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297


























































1



residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297




residential sources




EPA Response










wells























2




northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297





northeast




from 1500 feet away




wells in this area

EPA Response

























3























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297
























ecosystems



















4























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297
























into their design















5

























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297


























criteria of 3 ugl





(Waterline))

EPA Response








6


line













analysis

7

barcode 586297



line













analysis

7

barcode 586297


THIRD EXPLANATION OF SIGNIFICANT DIFFERENCES (ESD ... · Contact: Kenneth Richards, NHDES Remedial...

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Transcript of THIRD EXPLANATION OF SIGNIFICANT DIFFERENCES (ESD ... · Contact: Kenneth Richards, NHDES Remedial...