to I t

57 EAST MAIN ST SUITE 205 WESTBOAO MA 01581 bull SOS 366-8033 FAX 508 366-5442

PO BOX 2199 PRINCETON NJ 08543-2199 bull 609 530-0003 FAX 609 530 -1084

September 27 1991

Ms Diana Kina US Environmental Protection Aaency Waste Hanaaement Division (HSN-CAN5) 90 Canal Street Boston HA 02203

RE Tinkhams Garaae Site Londonderry New Hampshire Terra Vac Project No 42-0002 Interia Discharae Alternative Analysis

Dear~ Terra Vac has coapleted development and evaluation of alternatives for the interim discharae of aroundwater recovered durinl the source-control remedial action at the Tinkhaaa site

We have prepared this letter report for your use in preparina the Explanation of Sianificant Differences (ESD) for the proposed interim diacharae alternative This letter presents a discussion of the alternatives evaluated and auary of the costa effectiveness and impleaentability aspects of each alternative

PROJECT BACKGROUND

The Cannons Sites Group contracted Terra Vac in 1988 to iapleaent the source-control remedial action aa specified in the Tinkhaaa Garaae Site (the Site) Record of Decision (ROD) The sourceshycontrol remedial action at the Tinkhaas Site incorporated the uae of the Terra Vac Dual Vacuum Extraction Process for soil and aroundwater remediation

I I

I I

TERRAVACMs Diana King September 27 1991 Page 2

As part of the source-control remedial action contaminated aroundwater at the Site is to be recovered in conjunction with the soil remediation process and treated above-ground usingconventional treatment technologies

The ROD tor the Site specified that the groundwater recovered from the source area (the Garage Area) would be treated if necessary to achieve a pretreatment discharge standard of 5 parts per million (ppm) Total Toxic Organics (TTO) and would be discharged to a proposed combined stormsanitary sewer that was to be constructed on the Site Groundwater recovered as part of the Management of Migration (MOM) remedial action was also to be discharaed to the proposed sewer The proposed sewer was to be connected to the Town of Derry wastewater treatment plant

Since approval of the ROD the schedule for installation and operation of the new sewer has been protracted As a result an evaluation ot alternatives for discharge of aroundwater duringthe source-control remediation has been performed so that this action can be implemented in a timely manner

The evaluation of alternatives for interim groundwater dischargebaa included the identification screening and detailed analysisof alternatives for treatment and discharge on-site Several alternatives have been identified and evaluated for cost implementability and effectiveness An evaluation of these alternatives is presented below

DESCRIPTION QE SIGNIFICANT DIFFERENCES

In general alternatives for discharge to on-site surface waters and 1roundwater were evaluated The costs implementability and effectiveness of several alternatives were evaluated as presented below to select one option for iapleaentation

The preferred interim discharge alternative (Option 1 below)consists of treatinl 1roundwater recovered from the Gara1e Area via aeration and carbon adsorption prior to dischar1e to an existing storm drainaae channel adjacent to the Gara1e Area Groundwater will be treated to a dischar1e standard of the applicable Maximum Contaminant Levels (HCLs) for the volatile oraanic compounds (VOCs) ot concern in the Garaae Area

While the groundwater discharae alternative selected in the ROD ampilht not have required treatment for the duration of the source remediation to meet the required dischar1e limitation of 5 ppmTTO the proposed alternative interim di charge will likely require treatment throughout the remediation

TERRAVACMs Diana King September 27 1991 Page 3

The proposed interim discharge alternative will allow commencement and completion of source remediation in a timely manner when compared to the time required to approve design and implement the proposed sewer connection The proposed interim discharge incorporates conventional groundwater treatment and conveyance technologies and complies with all appropriate Federal and State environmental requirements

Furthermore the recommended alternative is an on-site solution which requires no subsurface disturbance or installations and is otherwise easily implemented We believe that the selected option is the most coat-effective alternative evaluated to the sewer discharge selected in the ROD

DEVELOPMENTINITIAL SCREENING QE ALTERNATIVES

The objective of aelectina an alternative tD the ee~er discharae selected in the ROD is to provide a tempp~~ry on-site bulleana of discharaing treated groundwater from the Garage Area The selected option should be one that can be ibullplemented in a timely manner at minimal capital and operating expense and which satisfies the requirements of Federal and State regulations for on-site discharges

Baaed upon the results of previous pilot teat work at the site it is anticipated that the initial groundwater pumping rates will be 50 to 60 ~allons per minute with equivalent resultant diacbarae flow rates

The alternatives which were developed consist of several components the treatbullent system conveyance method and diacharse location Initially two potential cateaoriea of discharae options were considered discharae to aroundwater and discharge to surface water

The first step in the development process was to evaluate the aeneral catesories of surface water and around water discharges to bulleet the objectives of the interim discharae Once a discharae option (surface water or around water) was selected locations of specific diacharae points conveyance bullethoda and required treatment were identified assembled into specificalternatives and t e alternatives evaluated

Groundwater Discharge Options

With ~ the broad category of groundwater discharse are several options to discharge directly to ground via infiltration

~ salleries or trenches to allow direct infiltration to the sroundwater table

bull

shy

Ms Diana King TERRAVAC September 27 1991 Page 4

In consideration of the generally shallow wat er table throughoutthe site and the objective of implementing a least cost temporaryalternative the option of discharging to groundwater was eliminated from further consideration

Any groundwater discharge option would involve significantconstruction activity to install a leachinginfiltration system to accommodate the anticipated discharge tlowrates and would potentially result in surface FO~dt~J a~ thbull dibullchbullrse ~oint The estimated cost to coastruct anmiddot inmiddotfi~ trat1on systeaa was 50 000

Surface Water Discharge Options

Within the seneral category of surface water discharges are two overall options Options include discharging directly to an on-site wetland area or to a receiving stream such as the existing drainage channel which flows adjacent to the site in a southeasterly direction from Route 102 to a major wetland network downgradient of the site

There are numerous potential locations for discharge outfallbull in the vast wetland area that abuts the Site to the south and the existing drainage channel adjacent to the Site which flows to these wetlands These two options for discharse to a wetland area and to the existing drainage area were developed into four alternatives with different discharge locations and conveyancemethods These four alternatives were evaluated based upon their general suitability from a permitting perspective and their implementation from a construction and cost perspective

Discharge Locations --shy

Three options are available for discharge to the existins drainase channel These include (1) discharge overland directly to the existing drainage channel (2) construction of and discharse to a new subsurface drain immediately dovngradient of the garage area and (3) discharge to the existing subsurface drain (curtain drain) immediately upgradient of the 1arase area The fourth option is to discharge to some downsradient wet area on the property via overland or subsurface drai n These four options are shown on Figure 1

In all cases the discharged water primari ly flows to the wetland areas on the property A portion of the discha rge wate r wi ll naturally recharge the aquife r downgradient of the s ite

I

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I -- EXCLUSION ZONE 1 ~ OfIDamp TWO

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I I

I I

TERRAVACMs Diana King September 27 1991 Page 2

As part of the source-control remedial action contaminated aroundwater at the Site is to be recovered in conjunction with the soil remediation process and treated above-ground usingconventional treatment technologies

The ROD tor the Site specified that the groundwater recovered from the source area (the Garage Area) would be treated if necessary to achieve a pretreatment discharge standard of 5 parts per million (ppm) Total Toxic Organics (TTO) and would be discharged to a proposed combined stormsanitary sewer that was to be constructed on the Site Groundwater recovered as part of the Management of Migration (MOM) remedial action was also to be discharaed to the proposed sewer The proposed sewer was to be connected to the Town of Derry wastewater treatment plant

Since approval of the ROD the schedule for installation and operation of the new sewer has been protracted As a result an evaluation ot alternatives for discharge of aroundwater duringthe source-control remediation has been performed so that this action can be implemented in a timely manner

The evaluation of alternatives for interim groundwater dischargebaa included the identification screening and detailed analysisof alternatives for treatment and discharge on-site Several alternatives have been identified and evaluated for cost implementability and effectiveness An evaluation of these alternatives is presented below

DESCRIPTION QE SIGNIFICANT DIFFERENCES

In general alternatives for discharge to on-site surface waters and 1roundwater were evaluated The costs implementability and effectiveness of several alternatives were evaluated as presented below to select one option for iapleaentation

The preferred interim discharge alternative (Option 1 below)consists of treatinl 1roundwater recovered from the Gara1e Area via aeration and carbon adsorption prior to dischar1e to an existing storm drainaae channel adjacent to the Gara1e Area Groundwater will be treated to a dischar1e standard of the applicable Maximum Contaminant Levels (HCLs) for the volatile oraanic compounds (VOCs) ot concern in the Garaae Area

While the groundwater discharae alternative selected in the ROD ampilht not have required treatment for the duration of the source remediation to meet the required dischar1e limitation of 5 ppmTTO the proposed alternative interim di charge will likely require treatment throughout the remediation

TERRAVACMs Diana King September 27 1991 Page 3

The proposed interim discharge alternative will allow commencement and completion of source remediation in a timely manner when compared to the time required to approve design and implement the proposed sewer connection The proposed interim discharge incorporates conventional groundwater treatment and conveyance technologies and complies with all appropriate Federal and State environmental requirements

Furthermore the recommended alternative is an on-site solution which requires no subsurface disturbance or installations and is otherwise easily implemented We believe that the selected option is the most coat-effective alternative evaluated to the sewer discharge selected in the ROD

DEVELOPMENTINITIAL SCREENING QE ALTERNATIVES

The objective of aelectina an alternative tD the ee~er discharae selected in the ROD is to provide a tempp~~ry on-site bulleana of discharaing treated groundwater from the Garage Area The selected option should be one that can be ibullplemented in a timely manner at minimal capital and operating expense and which satisfies the requirements of Federal and State regulations for on-site discharges

Baaed upon the results of previous pilot teat work at the site it is anticipated that the initial groundwater pumping rates will be 50 to 60 ~allons per minute with equivalent resultant diacbarae flow rates

The alternatives which were developed consist of several components the treatbullent system conveyance method and diacharse location Initially two potential cateaoriea of discharae options were considered discharae to aroundwater and discharge to surface water

The first step in the development process was to evaluate the aeneral catesories of surface water and around water discharges to bulleet the objectives of the interim discharae Once a discharae option (surface water or around water) was selected locations of specific diacharae points conveyance bullethoda and required treatment were identified assembled into specificalternatives and t e alternatives evaluated

Groundwater Discharge Options

With ~ the broad category of groundwater discharse are several options to discharge directly to ground via infiltration

~ salleries or trenches to allow direct infiltration to the sroundwater table

bull

shy

Ms Diana King TERRAVAC September 27 1991 Page 4

In consideration of the generally shallow wat er table throughoutthe site and the objective of implementing a least cost temporaryalternative the option of discharging to groundwater was eliminated from further consideration

Any groundwater discharge option would involve significantconstruction activity to install a leachinginfiltration system to accommodate the anticipated discharge tlowrates and would potentially result in surface FO~dt~J a~ thbull dibullchbullrse ~oint The estimated cost to coastruct anmiddot inmiddotfi~ trat1on systeaa was 50 000

Surface Water Discharge Options

Within the seneral category of surface water discharges are two overall options Options include discharging directly to an on-site wetland area or to a receiving stream such as the existing drainage channel which flows adjacent to the site in a southeasterly direction from Route 102 to a major wetland network downgradient of the site

There are numerous potential locations for discharge outfallbull in the vast wetland area that abuts the Site to the south and the existing drainage channel adjacent to the Site which flows to these wetlands These two options for discharse to a wetland area and to the existing drainage area were developed into four alternatives with different discharge locations and conveyancemethods These four alternatives were evaluated based upon their general suitability from a permitting perspective and their implementation from a construction and cost perspective

Discharge Locations --shy

Three options are available for discharge to the existins drainase channel These include (1) discharge overland directly to the existing drainage channel (2) construction of and discharse to a new subsurface drain immediately dovngradient of the garage area and (3) discharge to the existing subsurface drain (curtain drain) immediately upgradient of the 1arase area The fourth option is to discharge to some downsradient wet area on the property via overland or subsurface drai n These four options are shown on Figure 1

In all cases the discharged water primari ly flows to the wetland areas on the property A portion of the discha rge wate r wi ll naturally recharge the aquife r downgradient of the s ite

I

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M t--- i l LICpoundI TRAILER

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I -- EXCLUSION ZONE 1 ~ OfIDamp TWO

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TERRAVACMs Diana King September 27 1991 Page 3

The proposed interim discharge alternative will allow commencement and completion of source remediation in a timely manner when compared to the time required to approve design and implement the proposed sewer connection The proposed interim discharge incorporates conventional groundwater treatment and conveyance technologies and complies with all appropriate Federal and State environmental requirements

Furthermore the recommended alternative is an on-site solution which requires no subsurface disturbance or installations and is otherwise easily implemented We believe that the selected option is the most coat-effective alternative evaluated to the sewer discharge selected in the ROD

DEVELOPMENTINITIAL SCREENING QE ALTERNATIVES

The objective of aelectina an alternative tD the ee~er discharae selected in the ROD is to provide a tempp~~ry on-site bulleana of discharaing treated groundwater from the Garage Area The selected option should be one that can be ibullplemented in a timely manner at minimal capital and operating expense and which satisfies the requirements of Federal and State regulations for on-site discharges

Baaed upon the results of previous pilot teat work at the site it is anticipated that the initial groundwater pumping rates will be 50 to 60 ~allons per minute with equivalent resultant diacbarae flow rates

The alternatives which were developed consist of several components the treatbullent system conveyance method and diacharse location Initially two potential cateaoriea of discharae options were considered discharae to aroundwater and discharge to surface water

The first step in the development process was to evaluate the aeneral catesories of surface water and around water discharges to bulleet the objectives of the interim discharae Once a discharae option (surface water or around water) was selected locations of specific diacharae points conveyance bullethoda and required treatment were identified assembled into specificalternatives and t e alternatives evaluated

Groundwater Discharge Options

With ~ the broad category of groundwater discharse are several options to discharge directly to ground via infiltration

~ salleries or trenches to allow direct infiltration to the sroundwater table

bull

shy

Ms Diana King TERRAVAC September 27 1991 Page 4

In consideration of the generally shallow wat er table throughoutthe site and the objective of implementing a least cost temporaryalternative the option of discharging to groundwater was eliminated from further consideration

Any groundwater discharge option would involve significantconstruction activity to install a leachinginfiltration system to accommodate the anticipated discharge tlowrates and would potentially result in surface FO~dt~J a~ thbull dibullchbullrse ~oint The estimated cost to coastruct anmiddot inmiddotfi~ trat1on systeaa was 50 000

Surface Water Discharge Options

Within the seneral category of surface water discharges are two overall options Options include discharging directly to an on-site wetland area or to a receiving stream such as the existing drainage channel which flows adjacent to the site in a southeasterly direction from Route 102 to a major wetland network downgradient of the site

There are numerous potential locations for discharge outfallbull in the vast wetland area that abuts the Site to the south and the existing drainage channel adjacent to the Site which flows to these wetlands These two options for discharse to a wetland area and to the existing drainage area were developed into four alternatives with different discharge locations and conveyancemethods These four alternatives were evaluated based upon their general suitability from a permitting perspective and their implementation from a construction and cost perspective

Discharge Locations --shy

Three options are available for discharge to the existins drainase channel These include (1) discharge overland directly to the existing drainage channel (2) construction of and discharse to a new subsurface drain immediately dovngradient of the garage area and (3) discharge to the existing subsurface drain (curtain drain) immediately upgradient of the 1arase area The fourth option is to discharge to some downsradient wet area on the property via overland or subsurface drai n These four options are shown on Figure 1

In all cases the discharged water primari ly flows to the wetland areas on the property A portion of the discha rge wate r wi ll naturally recharge the aquife r downgradient of the s ite

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M t--- i l LICpoundI TRAILER

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I -- EXCLUSION ZONE 1 ~ OfIDamp TWO

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Ms Diana King TERRAVAC September 27 1991 Page 4

In consideration of the generally shallow wat er table throughoutthe site and the objective of implementing a least cost temporaryalternative the option of discharging to groundwater was eliminated from further consideration

Any groundwater discharge option would involve significantconstruction activity to install a leachinginfiltration system to accommodate the anticipated discharge tlowrates and would potentially result in surface FO~dt~J a~ thbull dibullchbullrse ~oint The estimated cost to coastruct anmiddot inmiddotfi~ trat1on systeaa was 50 000

Surface Water Discharge Options

Within the seneral category of surface water discharges are two overall options Options include discharging directly to an on-site wetland area or to a receiving stream such as the existing drainage channel which flows adjacent to the site in a southeasterly direction from Route 102 to a major wetland network downgradient of the site

There are numerous potential locations for discharge outfallbull in the vast wetland area that abuts the Site to the south and the existing drainage channel adjacent to the Site which flows to these wetlands These two options for discharse to a wetland area and to the existing drainage area were developed into four alternatives with different discharge locations and conveyancemethods These four alternatives were evaluated based upon their general suitability from a permitting perspective and their implementation from a construction and cost perspective

Discharge Locations --shy

Three options are available for discharge to the existins drainase channel These include (1) discharge overland directly to the existing drainage channel (2) construction of and discharse to a new subsurface drain immediately dovngradient of the garage area and (3) discharge to the existing subsurface drain (curtain drain) immediately upgradient of the 1arase area The fourth option is to discharge to some downsradient wet area on the property via overland or subsurface drai n These four options are shown on Figure 1

In all cases the discharged water primari ly flows to the wetland areas on the property A portion of the discha rge wate r wi ll naturally recharge the aquife r downgradient of the s ite

I

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I -- EXCLUSION ZONE 1 ~ OfIDamp TWO

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Ms Diana King TERRAVAC September 27 1991 Page 5

Conveyance Methods -- shy

In all cases overland flow from the treatment system to the discharae point is the preferred option for ease of installation and minimal coat Water would be conveyed to the discharae pointvia a flexible synthetic wovenPVC hose The discharae hose would be protected from damage and inspected frequently In the cases of discharge to the existing drainage channel the carryinacapacity of the existing channel was considered The anticipatedflowrates are not expected to exceed the drainaae channel capacity

Since it is anticipated that the project would be completedbefore the winter no freeze protection is anticipated to be necessary Alternatively subsurface drainaae lines could be installed for the treatment system dischar1e However this would silnificantly increase the cost associated with these options For these reasons subsurface drainaae lines were not included in the final alternatives

Replacement hose will be kept on-site throughout the operation in case of needed repair to the discharge hose If operation does occur in the winter then new hose will replace frozen sections as needed

Groundwater Treatment -- shy

The method of treatment would be the same for each discharae Therefore the variability in costs are associated only with the discharae method The State of New Hampshire Department of nvironmental Services (NH DES) was consulted to determine PJraquolicable ~r relevant water quality discharae standards Since no state standardalixiatlr Terra Vac bas proposed a pretreatmentstandard of the applicable drinkina water Maximum Contaminant Level (MCLs) for the Gara1e Area contaminants of concern These contaminants of concern and their associated MCLs are as follows

trichloroethylene 5 bull11tetrachloroethylene 200 ag1

Preliainary desiln of the 1roundwater treatment systemincorporates diffused aeration and carbon adsorption The size of the treataent system will be deterained based upon an assessment of the present aroundwater quality in this area and flowrates

As stated pr viously the anticipated initial aroundwater pumpina rate is 50 to 60 1allons per minute Once adequate water table depre sion has been achieved the pumping rates will decline and be rou1hly equivalent to the natural aquifer recharae rate

I

TERRA VAC Ms Diana King September 27 1991 Pate 6

The proposed treatment system will operate on a continual basis throuthout the remediation project Treatment system flowratea will be controlled by the use of atorateequalization tanka between the well pumps and aerationcarbon treatment units

The treatment system will be located in the equipment area shown on Figure 1 The equipment area which will also be the location of the vacuum extraction system and vapor treatment equipment will be secured by fencing

The four alternatives developed which are described below were

Option 1 Discharge directly to existing drainage channel

Option 2 Diacharte to a new downtradient subsurface drain

Option 3 Discharte to the existing upgradient curtain drain

Option 4 Discharte to a downtradient wetland area on the property

DETAILED ANALYSIS Ql ALTERNATIVES

Alternative Description

The four alternatives retained for detailed evaluation are described below and depicted in Fiture 1

Option 1 - Discharte directly to existing drainage channel

In this option water would be discharted from the treataent system to a point in the exiatint drainage channel downtradient of the site via the flexible hose By dischartint downtradient of the tara1e area there is no chance ot this water beinl rechar1ed to the lamprate area

Option 2 - Dischar1e to a new downgradient subsurface drain

In this option a subsurface drain similar to the exiatinl upgradient curtain drain would be constructed down1radient of the 1ara1e area Water will be diachar1ed directly to this drain which would diachar1e to the exiatinl draina1e channel This would be the moat expensive of the available options as it would require subsurface excavation and construction

Hs Diana King TERRAVAC September 27 1991 Page 7

Option 3 - Discharge to the existins uparadient curtain drain

Water would be discharaed directly to this xistinl curtain drain via ~ new connection made at the uparadient end of this drain This option is not desirable because the potential exists for the treated water to be recharaed into the contaminated aaraae area since the drainase pipe is perforated Also water would be discharse to the drainage channel at a point hydraulicallyupsradient of the site where it could recharae groundwater

Option 3 was eliminated in the initial screeninl of alternatives due to the poten~ial of recharse to the contaminated area

Option 4 - Discharae to a downaradient wet area on the property

In this option water would be discharaed to the surface at a point substantially downsradient of the site in a wet area on the property The exact point of discharae would be selected after a field survey of available areas The primary advantaae of thia alternative is that water would be discharsed entirelydownaradient of the aite This would also provide slower recharge to the aquifer

Effectiveness Evaluation

All of the remaininl alternatives (Options 1 2 and 4) provide a hiah-dearee of short- and lona-term effectiveness in providinl a suitable discharse alternative to the sewer discharae selected in the ROD All three alternatives convey the treated water awayfrom the source area thereby eliminatinl the potential for recharae to that a~ea

Implementabilitr Evaluation

Technical Feasibility --shy

The remaininl alternatives utilize overland pipinl to convey the water to the dischar1e location Options 1 and 4 rely solely on the installation of discharae pipeboae to the ultimate discharae location (drainase channel or wetlands) Option 2 requirebullsubsurface installation of a drainase pipe to carry water to the existinl drainaae channel

TERRAVACMs Diana KingSeptember 27 1991 Page 8

This subsurface installation requires extensive excavation (outside of the contaminated zone) and intrusiondisturbance of the natural setting Since the ultimate discharge location is to the existing drainage channel as in Option 1 this option(Option 2) was eliminated from further consideration The same effect and benefit can be achieved via the less intrusive and costly option of overland discharge directly to the drainaae channel (Option 1)

Administrative Feasibility --shy

To determine the administrative feasibility of the remainina alternatives Option 1 - Discharae overland to the existina drainage and Option 4 - Discharge to a downgradient wet area Terra Vac consulted with the NH DES Wetlands Board We presentedthe proposed alternatives and requested a determination of the applicable or relevant and appropriate requirements of surface water discharge and suitability of each alternative

A site tourwalkover was conducted with Ms Lori Sommer Wetlands Inspector on July 25th The purpose to the site tour was to examine and evaluate the drainage channel and wetland areas for discharge

After walking a substantial length of the drainage channel it was determined that it was technically appropriate to discharse to the channel that is the channel has the capacity and characteristics to accept the proposed discharae flow rate Further it was determined that there was no technical advantaae to discharsing a sianificantly areater distance to a downaradient wetland area

During the site visit a specific location in the channel was selected as the discharse location This location is at a pointin the channel with a cobble base that will serve for erosion control

Subsequent to this site tour information was received froa the NH DES Water Supply and Pollution Control Division relative to the applicable or relevant and appropriate water quality criteria Due to the absence of any specific discharae criteria Terra Vac proposes to treat the recovered aroundwater to drinkins water standards

Cost Evaluation --shy

To further support the selection of the preferred alternative coat estimates have been developed for each alternative These coat estimates are presented primarily for comparison since th preferred alternative (Option 1) was selected baaed upon technical and

TERRA VACMs Diana Kins September 27 1 1991 Pase 9

administrative feasibility Nonetheless it can be seen from these estimates that the preferred alternative is the least cout alternatives evaluated

~Evaluation

In summary the estimated coats for the interim discharae alternative retained for detailed evaluation are

Treatment - Capital costa $35000 - $45000 OlM ( 9 months) $45000 - $90000

Diacharae - Option 1 (Preferred Alternative) $1 1 500 - $2 1 500

Option 2 $25000 -$40000

Option 4 S5ooo -noooo The ranae of estiaated coats for the construction and operationof the treatment system is $80 1 000 to $135000 The ranae of estiaated costs of the discharae options includina treataent are $81 1 500 to $137 1 500 (Option 1) and $105000 to $175 1 000 (Option 2)

We trust that this report meets with your approval In any event please feel free to contact ae at (508) 366-8033 to discuss this evaluation and if you require additional inforaation Thank you in advance for your attention to this aatter

S~inc~rel~

S Ciriello n ManaaerNew Enaland

JSCdac

Attachment

cc Jia Malot Terra Vac Ed Malaanis 1 Terra Vac Diane Leber Ciba-Geiay Mike Walters Polaroid Judy Tinkham 1 Tinkhaa Realty Toa Andrews NH DES Robert Sanoff 1 Foley Hoaa amp Eliot

1. barcode 576744
2. barcodetext SDMS Doc ID 576744

TERRA VAC Ms Diana King September 27 1991 Pate 6

The proposed treatment system will operate on a continual basis throuthout the remediation project Treatment system flowratea will be controlled by the use of atorateequalization tanka between the well pumps and aerationcarbon treatment units

The treatment system will be located in the equipment area shown on Figure 1 The equipment area which will also be the location of the vacuum extraction system and vapor treatment equipment will be secured by fencing

The four alternatives developed which are described below were

Option 1 Discharge directly to existing drainage channel

Option 2 Diacharte to a new downtradient subsurface drain

Option 3 Discharte to the existing upgradient curtain drain

Option 4 Discharte to a downtradient wetland area on the property

DETAILED ANALYSIS Ql ALTERNATIVES

Alternative Description

The four alternatives retained for detailed evaluation are described below and depicted in Fiture 1

Option 1 - Discharte directly to existing drainage channel

In this option water would be discharted from the treataent system to a point in the exiatint drainage channel downtradient of the site via the flexible hose By dischartint downtradient of the tara1e area there is no chance ot this water beinl rechar1ed to the lamprate area

Option 2 - Dischar1e to a new downgradient subsurface drain

In this option a subsurface drain similar to the exiatinl upgradient curtain drain would be constructed down1radient of the 1ara1e area Water will be diachar1ed directly to this drain which would diachar1e to the exiatinl draina1e channel This would be the moat expensive of the available options as it would require subsurface excavation and construction

Hs Diana King TERRAVAC September 27 1991 Page 7

Option 3 - Discharge to the existins uparadient curtain drain

Water would be discharaed directly to this xistinl curtain drain via ~ new connection made at the uparadient end of this drain This option is not desirable because the potential exists for the treated water to be recharaed into the contaminated aaraae area since the drainase pipe is perforated Also water would be discharse to the drainage channel at a point hydraulicallyupsradient of the site where it could recharae groundwater

Option 3 was eliminated in the initial screeninl of alternatives due to the poten~ial of recharse to the contaminated area

Option 4 - Discharae to a downaradient wet area on the property

In this option water would be discharaed to the surface at a point substantially downsradient of the site in a wet area on the property The exact point of discharae would be selected after a field survey of available areas The primary advantaae of thia alternative is that water would be discharsed entirelydownaradient of the aite This would also provide slower recharge to the aquifer

Effectiveness Evaluation

All of the remaininl alternatives (Options 1 2 and 4) provide a hiah-dearee of short- and lona-term effectiveness in providinl a suitable discharse alternative to the sewer discharae selected in the ROD All three alternatives convey the treated water awayfrom the source area thereby eliminatinl the potential for recharae to that a~ea

Implementabilitr Evaluation

Technical Feasibility --shy

The remaininl alternatives utilize overland pipinl to convey the water to the dischar1e location Options 1 and 4 rely solely on the installation of discharae pipeboae to the ultimate discharae location (drainase channel or wetlands) Option 2 requirebullsubsurface installation of a drainase pipe to carry water to the existinl drainaae channel

TERRAVACMs Diana KingSeptember 27 1991 Page 8

This subsurface installation requires extensive excavation (outside of the contaminated zone) and intrusiondisturbance of the natural setting Since the ultimate discharge location is to the existing drainage channel as in Option 1 this option(Option 2) was eliminated from further consideration The same effect and benefit can be achieved via the less intrusive and costly option of overland discharge directly to the drainaae channel (Option 1)

Administrative Feasibility --shy

To determine the administrative feasibility of the remainina alternatives Option 1 - Discharae overland to the existina drainage and Option 4 - Discharge to a downgradient wet area Terra Vac consulted with the NH DES Wetlands Board We presentedthe proposed alternatives and requested a determination of the applicable or relevant and appropriate requirements of surface water discharge and suitability of each alternative

A site tourwalkover was conducted with Ms Lori Sommer Wetlands Inspector on July 25th The purpose to the site tour was to examine and evaluate the drainage channel and wetland areas for discharge

After walking a substantial length of the drainage channel it was determined that it was technically appropriate to discharse to the channel that is the channel has the capacity and characteristics to accept the proposed discharae flow rate Further it was determined that there was no technical advantaae to discharsing a sianificantly areater distance to a downaradient wetland area

During the site visit a specific location in the channel was selected as the discharse location This location is at a pointin the channel with a cobble base that will serve for erosion control

Subsequent to this site tour information was received froa the NH DES Water Supply and Pollution Control Division relative to the applicable or relevant and appropriate water quality criteria Due to the absence of any specific discharae criteria Terra Vac proposes to treat the recovered aroundwater to drinkins water standards

Cost Evaluation --shy

To further support the selection of the preferred alternative coat estimates have been developed for each alternative These coat estimates are presented primarily for comparison since th preferred alternative (Option 1) was selected baaed upon technical and

TERRA VACMs Diana Kins September 27 1 1991 Pase 9

administrative feasibility Nonetheless it can be seen from these estimates that the preferred alternative is the least cout alternatives evaluated

~Evaluation

In summary the estimated coats for the interim discharae alternative retained for detailed evaluation are

Treatment - Capital costa $35000 - $45000 OlM ( 9 months) $45000 - $90000

Diacharae - Option 1 (Preferred Alternative) $1 1 500 - $2 1 500

Option 2 $25000 -$40000

Option 4 S5ooo -noooo The ranae of estiaated coats for the construction and operationof the treatment system is $80 1 000 to $135000 The ranae of estiaated costs of the discharae options includina treataent are $81 1 500 to $137 1 500 (Option 1) and $105000 to $175 1 000 (Option 2)

We trust that this report meets with your approval In any event please feel free to contact ae at (508) 366-8033 to discuss this evaluation and if you require additional inforaation Thank you in advance for your attention to this aatter

S~inc~rel~

S Ciriello n ManaaerNew Enaland

JSCdac

Attachment

cc Jia Malot Terra Vac Ed Malaanis 1 Terra Vac Diane Leber Ciba-Geiay Mike Walters Polaroid Judy Tinkham 1 Tinkhaa Realty Toa Andrews NH DES Robert Sanoff 1 Foley Hoaa amp Eliot

1. barcode 576744
2. barcodetext SDMS Doc ID 576744

Hs Diana King TERRAVAC September 27 1991 Page 7

Option 3 - Discharge to the existins uparadient curtain drain

Water would be discharaed directly to this xistinl curtain drain via ~ new connection made at the uparadient end of this drain This option is not desirable because the potential exists for the treated water to be recharaed into the contaminated aaraae area since the drainase pipe is perforated Also water would be discharse to the drainage channel at a point hydraulicallyupsradient of the site where it could recharae groundwater

Option 3 was eliminated in the initial screeninl of alternatives due to the poten~ial of recharse to the contaminated area

Option 4 - Discharae to a downaradient wet area on the property

In this option water would be discharaed to the surface at a point substantially downsradient of the site in a wet area on the property The exact point of discharae would be selected after a field survey of available areas The primary advantaae of thia alternative is that water would be discharsed entirelydownaradient of the aite This would also provide slower recharge to the aquifer

Effectiveness Evaluation

All of the remaininl alternatives (Options 1 2 and 4) provide a hiah-dearee of short- and lona-term effectiveness in providinl a suitable discharse alternative to the sewer discharae selected in the ROD All three alternatives convey the treated water awayfrom the source area thereby eliminatinl the potential for recharae to that a~ea

Implementabilitr Evaluation

Technical Feasibility --shy

The remaininl alternatives utilize overland pipinl to convey the water to the dischar1e location Options 1 and 4 rely solely on the installation of discharae pipeboae to the ultimate discharae location (drainase channel or wetlands) Option 2 requirebullsubsurface installation of a drainase pipe to carry water to the existinl drainaae channel

TERRAVACMs Diana KingSeptember 27 1991 Page 8

This subsurface installation requires extensive excavation (outside of the contaminated zone) and intrusiondisturbance of the natural setting Since the ultimate discharge location is to the existing drainage channel as in Option 1 this option(Option 2) was eliminated from further consideration The same effect and benefit can be achieved via the less intrusive and costly option of overland discharge directly to the drainaae channel (Option 1)

Administrative Feasibility --shy

To determine the administrative feasibility of the remainina alternatives Option 1 - Discharae overland to the existina drainage and Option 4 - Discharge to a downgradient wet area Terra Vac consulted with the NH DES Wetlands Board We presentedthe proposed alternatives and requested a determination of the applicable or relevant and appropriate requirements of surface water discharge and suitability of each alternative

A site tourwalkover was conducted with Ms Lori Sommer Wetlands Inspector on July 25th The purpose to the site tour was to examine and evaluate the drainage channel and wetland areas for discharge

After walking a substantial length of the drainage channel it was determined that it was technically appropriate to discharse to the channel that is the channel has the capacity and characteristics to accept the proposed discharae flow rate Further it was determined that there was no technical advantaae to discharsing a sianificantly areater distance to a downaradient wetland area

During the site visit a specific location in the channel was selected as the discharse location This location is at a pointin the channel with a cobble base that will serve for erosion control

Subsequent to this site tour information was received froa the NH DES Water Supply and Pollution Control Division relative to the applicable or relevant and appropriate water quality criteria Due to the absence of any specific discharae criteria Terra Vac proposes to treat the recovered aroundwater to drinkins water standards

Cost Evaluation --shy

To further support the selection of the preferred alternative coat estimates have been developed for each alternative These coat estimates are presented primarily for comparison since th preferred alternative (Option 1) was selected baaed upon technical and

TERRA VACMs Diana Kins September 27 1 1991 Pase 9

administrative feasibility Nonetheless it can be seen from these estimates that the preferred alternative is the least cout alternatives evaluated

~Evaluation

In summary the estimated coats for the interim discharae alternative retained for detailed evaluation are

Treatment - Capital costa $35000 - $45000 OlM ( 9 months) $45000 - $90000

Diacharae - Option 1 (Preferred Alternative) $1 1 500 - $2 1 500

Option 2 $25000 -$40000

Option 4 S5ooo -noooo The ranae of estiaated coats for the construction and operationof the treatment system is $80 1 000 to $135000 The ranae of estiaated costs of the discharae options includina treataent are $81 1 500 to $137 1 500 (Option 1) and $105000 to $175 1 000 (Option 2)

We trust that this report meets with your approval In any event please feel free to contact ae at (508) 366-8033 to discuss this evaluation and if you require additional inforaation Thank you in advance for your attention to this aatter

S~inc~rel~

S Ciriello n ManaaerNew Enaland

JSCdac

Attachment

cc Jia Malot Terra Vac Ed Malaanis 1 Terra Vac Diane Leber Ciba-Geiay Mike Walters Polaroid Judy Tinkham 1 Tinkhaa Realty Toa Andrews NH DES Robert Sanoff 1 Foley Hoaa amp Eliot

1. barcode 576744
2. barcodetext SDMS Doc ID 576744

TERRAVACMs Diana KingSeptember 27 1991 Page 8

This subsurface installation requires extensive excavation (outside of the contaminated zone) and intrusiondisturbance of the natural setting Since the ultimate discharge location is to the existing drainage channel as in Option 1 this option(Option 2) was eliminated from further consideration The same effect and benefit can be achieved via the less intrusive and costly option of overland discharge directly to the drainaae channel (Option 1)

Administrative Feasibility --shy

To determine the administrative feasibility of the remainina alternatives Option 1 - Discharae overland to the existina drainage and Option 4 - Discharge to a downgradient wet area Terra Vac consulted with the NH DES Wetlands Board We presentedthe proposed alternatives and requested a determination of the applicable or relevant and appropriate requirements of surface water discharge and suitability of each alternative

A site tourwalkover was conducted with Ms Lori Sommer Wetlands Inspector on July 25th The purpose to the site tour was to examine and evaluate the drainage channel and wetland areas for discharge

After walking a substantial length of the drainage channel it was determined that it was technically appropriate to discharse to the channel that is the channel has the capacity and characteristics to accept the proposed discharae flow rate Further it was determined that there was no technical advantaae to discharsing a sianificantly areater distance to a downaradient wetland area

During the site visit a specific location in the channel was selected as the discharse location This location is at a pointin the channel with a cobble base that will serve for erosion control

Subsequent to this site tour information was received froa the NH DES Water Supply and Pollution Control Division relative to the applicable or relevant and appropriate water quality criteria Due to the absence of any specific discharae criteria Terra Vac proposes to treat the recovered aroundwater to drinkins water standards

Cost Evaluation --shy

To further support the selection of the preferred alternative coat estimates have been developed for each alternative These coat estimates are presented primarily for comparison since th preferred alternative (Option 1) was selected baaed upon technical and

TERRA VACMs Diana Kins September 27 1 1991 Pase 9

administrative feasibility Nonetheless it can be seen from these estimates that the preferred alternative is the least cout alternatives evaluated

~Evaluation

In summary the estimated coats for the interim discharae alternative retained for detailed evaluation are

Treatment - Capital costa $35000 - $45000 OlM ( 9 months) $45000 - $90000

Diacharae - Option 1 (Preferred Alternative) $1 1 500 - $2 1 500

Option 2 $25000 -$40000

Option 4 S5ooo -noooo The ranae of estiaated coats for the construction and operationof the treatment system is $80 1 000 to $135000 The ranae of estiaated costs of the discharae options includina treataent are $81 1 500 to $137 1 500 (Option 1) and $105000 to $175 1 000 (Option 2)

We trust that this report meets with your approval In any event please feel free to contact ae at (508) 366-8033 to discuss this evaluation and if you require additional inforaation Thank you in advance for your attention to this aatter

S~inc~rel~

S Ciriello n ManaaerNew Enaland

JSCdac

Attachment

cc Jia Malot Terra Vac Ed Malaanis 1 Terra Vac Diane Leber Ciba-Geiay Mike Walters Polaroid Judy Tinkham 1 Tinkhaa Realty Toa Andrews NH DES Robert Sanoff 1 Foley Hoaa amp Eliot

1. barcode 576744
2. barcodetext SDMS Doc ID 576744

TERRA VACMs Diana Kins September 27 1 1991 Pase 9

administrative feasibility Nonetheless it can be seen from these estimates that the preferred alternative is the least cout alternatives evaluated

~Evaluation

In summary the estimated coats for the interim discharae alternative retained for detailed evaluation are

Treatment - Capital costa $35000 - $45000 OlM ( 9 months) $45000 - $90000

Diacharae - Option 1 (Preferred Alternative) $1 1 500 - $2 1 500

Option 2 $25000 -$40000

Option 4 S5ooo -noooo The ranae of estiaated coats for the construction and operationof the treatment system is $80 1 000 to $135000 The ranae of estiaated costs of the discharae options includina treataent are $81 1 500 to $137 1 500 (Option 1) and $105000 to $175 1 000 (Option 2)

We trust that this report meets with your approval In any event please feel free to contact ae at (508) 366-8033 to discuss this evaluation and if you require additional inforaation Thank you in advance for your attention to this aatter

S~inc~rel~

S Ciriello n ManaaerNew Enaland

JSCdac

Attachment

cc Jia Malot Terra Vac Ed Malaanis 1 Terra Vac Diane Leber Ciba-Geiay Mike Walters Polaroid Judy Tinkham 1 Tinkhaa Realty Toa Andrews NH DES Robert Sanoff 1 Foley Hoaa amp Eliot

1. barcode 576744
2. barcodetext SDMS Doc ID 576744