HMM A S S O C I A T E S , INCLETTER*

fNC . INEFRS FNVIKONMFM M C ONSU I \MS \ PI ANNFRS

DATE: May 24,1991

TO: Richard GoeMertU.S. EPA90 Canal StreetHSN-CAN-5Boston, MA 02203

FROM: Mark O. HeubergerHMM Associates, Inc.196 Baker AvenueConcord, MA 01742

JOB NO.: 2176-160

SUBJECT: Drait of Final Revisions for Feasibility Study - Section 2.0

XFor Your InformationPer Your Request X

For Your Review/CommentsFor Your Authorization

REMARKS:

Enclosed is a draft of the revisions for Section 2.0 of the FS, in accordance with EPA's 4/25/91comment letter. Also enclosed is a comment/response letter indicating the changes that havebeen made. The new text is indicated by bold italics and the deleted text is underlined. Therevisions are also keyed to the numbered EPA comments.

Please contact me at (508) 371-4120 if you have any questions or comments.

t—

Signature

COMMENTS:

Date

Signature Date

2176-160/HAZ/5338 - 5/24/91

196 Baker Avenue • Concord • Massachusetts • 01742 • (508) 371-4000 • FAX: (508) 371-2468Three F x e c u t i v e Park Dnvo • Bedford • Nou Hampshire • 0 5 1 0 2 • (60!) 647-1010 • FAX (605) 626-4642

2.0 IDENTIFICATION AND SCRHKNIWi OP TECHNOLOGIES

2.1 INTRODUCTION

The purpose of Section 2.0 of the Savage Well Site FS is to identify, screen, and select the

most appropriate remedial technologies which can be subsequently combined into remedial

action alternatives. The selection process is performed pursuant to current EPA RI/FS guidancer

(Guidance for Conducting Remedial Investigations and Feasibility Studies under CERCLA -

Interim Final OSWER Directive 9355.3-01. October. 1988^ and the National Contingency Plan

as revised and reported in the March 8r 1990 Federal Register.

The development of remedial alternatives consists of six general steps which are discussed

• Develop remedial action objectives specifying the contaminants and media of

interest, exposure pathways, and remediation goals that permit a range of treatment

and containment alternatives to be developed. The objectives developed are based

on contaminant-specific ARARs. when available, and risk related factors.

• Develop general response actions that address the objectives for each medium of

interest.

• Identify volumes or areas of media to which general response actions might be

ftpplfcd, taking into account the requirements for protectiveness as identified in the

remedial action objectives.

• Identify and screen the technology categories applicable to each general response

action to eliminate those that cannot be implemented technically at the Savage

Well site or would not be effective in treating site contaminants.

1 Identify and evaluate technology options to select a representative process for each

technology category retained for consideration. Although specific processes are

selected for alternative development and evaluation,, these processes are intended

to represent the broader range of process options within a general technology type.

• Assemble the selected representative technologies into alternatives representing a

range of treatment and containment combinations, as appropriate.

2176-160/HAZ-5254 2-1

The selection process emphasizes sorting of technologies to achieve a reliable remedy

which acknowledges the practical limitations of the use of treatment. Furthermore, this processis undertaken with the flexibility necessary and appropriate to ensure that remedial actions

selected are reliable solutions for the identified site problems.

The following sections of the Feasibility Study follow a site-specific analysis and one that

is biased toward action. This approach is focused on the alternatives that are available to

effectively address DNAPLs and the alternatives that are practical given the extent and nature of

the contamination and the unprotected, unconfined nature of the aquifer. In addition, many

identifiable alternatives are inappropriate because the risk assessment has demonstrated that

groundwater is the only medium of concern at the Site. Therefore, the alternatives that are

developed in ensuing sections of the Feasibility Study are those that are appropriate for the

specific conditions of the Site.

The National Contingency Plan provides several other criteria and conditions that

emphasize that a site-specific selection process is warranted. The groundwater at the Site is not

currently used as a drjnKfog water source. In addition, adequate drinking water supplies are

currently available to replace the supply formerly provided by Savage Well. New Hampshire

regulations may proscribe future use of the aquifer as a municipal supply because the current and

foreseeable future use of the land area that is contributory to the aquifer includes incompatible

uses such as industrial, commercial and agricultural. Therefore, remediation of the active

aquifer to the 10^ to 1CP* human health criteria levels may not be appropriate.

MCLs may be achievable in those portions of the aquifer where there are dilute

contaminants but on the basis of current scientific evidence they may not be achievable for the

concentrated plume where contaminants likely exist as separate phase, or dense non-aqueous

phase liquids (DNAPLs).

Subsequent evaluations of groundwater treatment options will examine the benefits and

costs of various alternatives including recovery and treatment of concentrated plume and

recovery and treatment of the extended plume along with natural attenuation. The time frames

will be assessed in the context of what the NCP considers to be rapid restoration, one to five

the water supplies, which were drawn from the Site aquifer, has been for the most part

implemented.

The benefits of natural attenuation will be examined in conjunction with groundwater

recovery and treatment and protection of environmental receptors. Natural advection,

biodegr^dation. flispcrsion. dilution and absorption mav effectively reduce the level of

contaminants in the portions of the aquifer outside the soui

2176-160/HAZ-5254 2-2

concentrations protective of human health and the environment in a time frame that is

sufficiently rapid. Institutional controls may be necessary to ensure that the groundwater is not

used for potable purposes during the time period in which the CERCLA regulated contaminantsare naturally attenuated.

Clearly in the case of the concentrated plume where contaminants may exist as separatephase (DNAPL)f restoration of the groundwater may be impractical. The Feasibility Study will

consider options for the extraction and treatment of groundwater from the concentrated plume to

prevent migration to downgradient portions of the aquifer.Based on the existing information regarding the nature and extent of contamination, and

the risks posed to public health and the environment, two general response categories have been

developed for the Savage Well site: 1) Source Control; and 2) Management of Migration.These categories are identified and explained in Section 2.2. Remedial Action Objectives.

22 KHMHnTAL ACTION OBJECTIVES

This Feasibility Study develops and evaluates remedial alternatives for Source Control

and Management of Migration measures. Source Control alternatives focus on mitigating

residual contaminants in soils and sediments to the extent that such contamination posesunacceptable risks to human health or the environment. Management of Migration alternatives

are developed to address contamination in two types of areas, specifically.

• areas where contaminants exist as a separate phase, free product, or above their

solubility units (concentrated plume); and

• areas where contaminants exist primarily as ? dissolved phase (extended plume).

The concentrated plume areas are likely to result in continued long-term release and

contamination of downgradient groundwater. Based on recent research and experience at othersites, the concentration of VOCs detected downgradient of O.K. Tool indicate that it is likelythat VOCs exist in the aquifer beneath O.K. Tool as separate phase, dense non-aqueous phaseliquid (DNAPL). Remedial alternatives should place strong emphasis on controllingcontaminant migration from the concentrated plume areas. The existence of DNAPL at the

Savage Well Site hflS be,e,n inferred from the following!

2176-160/HAZ-5254 2-3

• historical materials management practices:

• concentrations of dissolved chlorinated hydrocarbons in groundwatcr immediately

downgradient from O.K. Tool and in groundwater sampled during source-removal

excavations at 0,K. Tool;

• calculations based upon concentrations of chlorinated hydrocarbons in soils

removed during excavations at O.K. Tool; and

• contaminant behavior and site geology and hydrogeology, which provide for

unrestricted downward vertical migration of denser-than-water contaminants

through highly permeable overburden.

Because of the typical occurrence of DNAPLs in discontinuous lenses and pools, and because of

the low miscibility of PCE and other chlorinated solvents, the DNAPLs present a persistent

long-tern source of solvents. While it may not be technically feasible to isolate and recover the

DNAPL accumulations,, removing or containing volumes or masses of contaminants in the

concentrated plume will reduce the overall extent of contamination and the time frame required

to return the balance of the aquifer to its beneficial use.

The Management of Migration alternatives focus on remediating the concentrated plumeand contaminated off-site groundwater east of the trailer park and preventing further migration

of contaminated groundwater to downgradient receptors including fish hatcheries, the Souhegan

River and other potential water users (see Figure 2-1). There currently exists a discharge of

contaminated groundwater from the aquifer to the Souhegan River. There is also evidence that

there is limited migration of contaminated groundwater to the north of the Souhegan River

including migration to production wells used by a private fish hatchery (Souhegan Valley

Aquaculture). Remedial alternatives should be developed and evaluated as to the feasibility of

mitigating any environmental or health impact posed by this migration of contaminated

groundwater.

Due to the potential future demands for groundwater and surface water resources in the

Milford area, remedial action objectives should include consideration of returning the aquifer toa level of water quality which is consistent with its most beneficial use in the future. Althoughthe majority of the land area overlying the contaminated portion of the aquifer is currently and

for the foreseeable future zoned for industrial user only a portion of it has been developed as

such. The zoning as of March. 1990 is illustrated on Figure 2-1. Depending upon subsequent

growth and municipal needs, portions of the industrially zoned portion of the aquifer may at

some point be reclassified as commercial.

2176-160/HAZ-5254 2-4

Some portion of the contaminated aquifer may be excluded from full remediation due totechnical feasibility and cost considerations. However, remedial alternatives should be

developed and evaluated which would over some time frame restore a portion of the aquifer tosome practical level of beneficial usefulness.

The Monk 8,1990, National Contingency Plan (NCP) identifies Ike objectives of andgeneral procedures to follow when conducting a feasibility study (tee 40 CFR 3O0.43O(e)).The NCP states that the primary objective of a feasibility study (FS) is to: "-. ensure thatappropriate remedial alternatives are developed and evaluated such that relevant informationconcerning ike remedial action options can be presented to a decision maker and anappropriate remedy selected" (40 CFR 300.430(e)(l)). The national goal of the remedyselection process, as stated in Ike NCP, is to select remedies that are: "~. protective of humanhealth and the environment, that maintain protection over time, and that minimize untreatedwaste" (40 CFR 3O0.43O(a)(lXi)). In developing remedial alternatives, the NCP requiresthat: 1) remedial action objectives are established, 2) potentially suitable technologies areidentified and evaluated, and 3) suitable technologies are assembled into alternativeremedial actions. The remedial action objectives developed must address each of thecontaminated media present on-sOe. The remedial alternatives developed to address eachobjective must be protective of human health and the environment.

Feasibility Studies Under CERCLAf Chapter 4, Interim Final (EPA/540/G-89/004, pg. 4-1),"The FS may be viewed (far explanatory purposes) as occurring in three phases: thedevelopment of aJtematives, the screening of the alternatives, and the detailed analysis of thealternatives." The objective of Section 2.0 of the Savage Municipal Water Supply SiteFeasibility Study is to assist in the first phase of the feasibility study process which is todevelop alternatives.

23 VRMKnjAL ACTION OBJECTIVES

Prior to the development and evaluation of remedial alternatives, the remedial actionobjectives far the site must be established. The NCP is very specific on the basis upon whichthese remedial action objectives are to be developed.

The primary objective for establishing Aese cleanup objectives is to protect humanhealth and the environment. Therefore, where appropriate, standards which currently &jmi(such as Maximum Contaminant Levels (MCLs) or Maximum Contaminant Level (Souls(MCLGs) will be the target cleanup levels in instances where they are considered to beApplicable or Relevant and Apm vpt into Requirements (ARARs). tf no such standards exist,

2176-160/HAZ-5254 2-6

the cleanup level* an based on concentrations which result m exposure levels that anprotective of human health and the environment. If the contaminant for which no regulatorycleanup standard exists is a known or suspected carcinogenic compound, then the cleanuplevel is based on a concentration level in the medium which results in an excess upper bound

lifetime cancer risk to an individual of between 1.0 x Iff* and IjO x Iff*, or a concentration

corresponding to a Hazard Quotient, also known as a Hazard Index (HI), of 1.0 for

compounds with non-carcinogenic effects.The preliminary remediation goals established in the feasibility study process an based

on available data and information. In accordance with the NCP, preliminary remedialcleanup objectives may be subject to change as more information regarding technology

treatment limitations, equipment detection capabilities and other impacting ate conditionsbecomes available. Final remediation goals an determined at the time of remedy selection.

Remedial action objectives specify contaminants and media of concern, potentialexposun pathways, and remediation goals for each impacted medium at the site. Thefallowing sections identify contaminants detected in the various affected media, set allowableexposures based on the human health risk assessment and ARARs, and develop pnuminary

remediation goals. Remedml action objectives an summarised at the eml of && section,

2.2.1 Contaminant* «rf lntt***t

Contaminants have been detected at the Savage Well Site in groundwater, surface water,

sediments, soil, and air. The overall objectives of remediating the site are to reduce the risks to

public health and welfare and to the environment protect human health and the environment.

This is done by identifying die contaminants posing unacceptable risk in each medium, thenevaluating remedial alternatives to address tike contaminants in the affected media. Thefollowing sections discuss the contaminants of interest for each medium at the Savage WeUSite. Specific remedial response objectives for the Savage Well Site are based on the exposure

levels and associated risks posed by the nature and extent of contaminants- These exposurelevels, risks and supporting documentation are identified in the Remedial Investigation (RD. in

the bageliune risk assessment, and in the Applicable or Relevant and Appropriate Requirements

(ARARs) for remedial alternatives.

2176-160/HAZ-5254 2-7

Groundwatcr

i/The primary remedial action objectives for the site focus on groundwater. The specific 3,5" d

objectives are to return the groundwater to some level of beneficial uses in a reasonable time

frame consistent with the current land-use of the site: the nature and distribution of

contaminants: the physical/technological constraints to removing contaminants; and the sources

of the on-site contamination.

Contaminants of interest in developing remedial action objectives for groundwater were

determined based on the frequency of occurrence as documented in the RI, their intrinsic :?/;toxicological properties, their pretence im large quantities, their potential far mowing into

critical exposure pathway*, the results of the baseline risk assessment, and the

chemical-specific ARARs as identified in Section 2.2.2. The remedial response action objective 3 C—•* ^^

for groundwater to protect human health is to prevent future ingestion and household use of

groundwater. For groundwater, the compounds of interest were identified at levels which

exceed Maximum Contaminant Levels (MCLs); exceed a total excess lifetime cancer risk range

of 1.0 x 10" to 1.0 x 10"" or non-carcinogenic Hazard Index (HI) greater titan 1 (based on

the risk assessment); and/or exceed reference doses. Figure 2-1 presents the extent ofgroundwater contamination exceeding MCLs. Future use scenarios for potential exposure to

groundwater as drinking water or through ingestion and for household use produced cancer risks

or hazard indices above typically acceptable remediation target ranges for the following

compounds:

tetrachloroethylene (PCE)

trichloroethylene (TCE)

1,1 -dichloroethylene (1,1 -DCE)

trans-1,2-dichloroethylene (1,2-DCE)

IJJ-trichloroethane (TCA)

• chromunm 31lead

beryOsmm

These analytes, therefore, are selected as the contaminants of interest in groundwater for the

Savage Well Site.An additional contaminant of interest is 1.1.1-trichloroethane (TCA) since it occurs at

concentrations above the MCL. However. TCA was detected during the RI at concentrations l

above the MCL only at MI-30. adjacent to the Hitchiner plant.

2176-160/HAZ-5254 2-8

The Savage Well was used as a public drinking water supply by the Town of Milford until -^ -7

1983. In May, 1988 the Savage Well was sold outright to Hitchiner Manufacturing for use in its

industrial operations.

Groundwater at the site is not currently used for Drinking water or for other household

uses. Thus, it is not a current exposure problem but only a potential for future exposure that

should be considered.

The remedial objectives for groundwater may be achieved by: 1) reducing the levels of

contaminants in groundwater; 2) preventing ingestion or household use of groundwater within

the site area through the use of institutional controls (i.e., eliminating the potential for exposure

route; 3) preventing the migration of groundwater contaminants off-site toward a potential

receptor: or 4) some combination of the above. This objective has been partially achieved by the

installation of a drinking water supply line to the site area.

An additional remedial objective for groundwater is to prevent or mitigate migration of

contaminants beyond their current extent. Concentrated plume areas have been identified at the

site and may serve as source areas for continued migration of contaminants to downgradient

achieved bv controlling migration from the concentrated plume. This action is considered to be

a form of Management of Migration.

In general, remedial objectives for groundwatei are also designed to protect the

environment. While the results from the RI for the Savage Well Site indicate that groundwater

in the area of the leading edge of the contaminant plume discharges to the Souhegan River, the

analytical results of the surface water and sediments sampled in the river do not indicate that

groundwater contaminants are adversely impacting the river.

Therefore. Ambient Water Quality Criteria (AWQO may be more appropriate as

regulatory levels and remedial target levels than the Maximum Contaminant Levels (MCLs).

The Ambient Water Quality Criteria (AWQC) levels for aquatic life are significantly higher than

MCLs (i.e., 840 ug/1 vs. 5 ug/l for PCE). Because fish in the river may be consumed, and

because of the existence of fish hatcheries to the north of the river, the Ambient Water Quality

Criteria (AWQC) standards for waters supporting fish used for human consumption as stipulated

in the Clean Water Act are appropriate as remedial action objectives for these areas. AWQC

levels for human ingestion of fish are set at 8.85 ug/1 for tetrachloroethylene and 80.7 ug/l for

trichloroethvlene. (See Table 2-4)

2176-160/HAZ-5254 2-10

As stated at the beginning of this section, the overall remedial action objective for t(£

groundwater is to return the aquifer to appropriate beneficial uses in a reasonable time framegiven the current land-use and potential future land-use of the site and the nature and extent ofcontamination. The site is characterized by a large, high-yield sand and gravel aquifer situatedin a river valley which, along its southern border, is also the site of numerous industries and

commercial operations which use and store some amounts of hazardous materials and wastes.Groundwater at the site is not currently used for drjn|qr|g w^er andr given New Hampshire

Public Water Supply Regulations for siting of public water supplies, it is anticipated that it willnot be possible for the entire aquifer at the Savage Well Site to be used as a public drinjcipgwater supply in the future, and the beneficial uses to which the aquifer should be returned may

be limited to industrial process water, irrigation, and other non-drinking \m*- Therefore. MCLs

do not seem to be appropriate remediation goals for the entire aquifer. Current New HampshireWater Supply Regulations Section WS 309.05, "Protective Radius - Chemicals",, states that nonew water supply may be located in an aquifer which has, at any tributary point to itr a facilitywhich uses, stores or disposes of significant amounts of hazardous waste. This regulation has

evidently been uniformly interpreted and applied by the State to prohibit the siting of a publicwater supply at locations similar to the Savage Well, having potential hazardous waste sources

at points tributary to them.

The State of New Hampshire currently is drafting a weUhgad protection program asrequired by Section 1428 of the 1986 Safe Drinking Water Acts Amendments (SDWAl The

provisions of this draft program confirm the increasing stringency being applied by State

regulators to the siting of public water supplies. These draft regulations would provide forgroundwater classifications.

The Savage Well Site would likely be currently classified as "GC". but no higher than

"GB". The State policy with respect to GC classified sites would be to prohibit public water

supplies in the area and contain contamination, including protection from exposure by

institutional controls.

Thus, the most likely future beneficial use of the groundwater is industrial process water,irrigation and other non-drinking water uses.

SoU

The risk assessment for exposure to soil contaminants via ingestion or dermal absorption < , ,

resulted in risk estimates within the target range for performance goals and hazard indices

below unity, i.e., reference doses were not exceeded. There are no Federal or New HampshireARARs that specify soil concentration limits. Therefore, no compounds of interest areidentified and no remedial action objectives are developed for the protection of human health.

2176-160/HAZ-5254 2-11

The Baseline Human Health Risk Assessment did not identify any current use exposurescenarios involving contact with soils or other surficial materials which could be considered aspotential source materials that produced risks above the limits typically specified by EPA inestablishing cleanup goals. Hypothetical worst-case future exposure scenarios for contact withsoils at O.K. Tool produced risks at the upper end of the acceptable range typically specified byEPAr however, these exposure scenarios are considered unlikely. It should be further noted thatthe majority of the risk associated with these hypothetical scenarios is from two compounds,

arsenic and PCBsf and that the elevated concentrations of these compounds detected in soils arelimited to an area behind the Q.K. Tool building to which access is limited.

The Baseline Healtik Risk Assessment considered potential health impacts fromexposure to chemicals in soil through ingestiou and dermal absorption. At tike HUchninerand Hendrix Areas, of the four exposure scenario considered (present industrial and futureresidential land uses for average and maximum contaminant concentrations), none of tikeindividual contaminants produced cancer risks greater than IjO x Iff* or Hazard Quotientsin excess of IJO. Under tike future residential use scenario, tike maximum concentration ofPCS (24ppm) produced a cancer risk of 33 x Iff"3. However, tikis is an area of limited accessand tike scenario is unUkely. Therefore, no contaminants of interest are identified for tikesoils at tike HuchinerfHendrix Area.

At tike OK Tool Area, under tike present industrial use and maximum contaminantconcentration scenario, no individual contaminants produced cancer risks in excess ofljO xIff* or Hazard Quotients greater thorn IJO. Under tike future residential use and maximumcontaminant concentration scenario, arsenic and lead exceed tike Hazard Quotient of IJO and,in tike case of arsenic, tike cancer risk of 1.0x1 ff* onfy for tike young child exposureassumptions when tike marhnum value detected in the soU at OK Tool is considered. Whenthe average soU concentration is considered, neither contaminant exceeds a Hazard QuotientofljOoran excess lifetime cancer risk of 1.0x10*. Based on tike low overall risks posedunder current and future scenarios, no contaminants of interest are identified for tike OKToolt

2176-160/HAZ-5254 2-12

The Ecological Risk Assessment, which was conducted independently for EPA by theCadmus Group, Inc., concluded that the only potential ecological risks posed by the site wererelated to the permitted outfalls for the Hitchiner-Hendrix discharge stream and that, given the

cessation of discharges from Hendrix (which has in fact occurred), much if not all of the

potential risk may be eliminated. The Ecological Risk Assessment concluded that theappropriate response would be continued monitoring of the site.

However, in general, it is also necessary to consider remedial action objectives for sourcecontrol and protection of the environment, i.e.. to prevent or mitigate the migration of VQC

contaminants from soil into groundwater that would result in contamination in excess of

groundwater remediation objectives, or would unreasonably lengthen the time to achievegroundwater remedial goals. In addition to evaluating contaminants for interest in soils based ondie results of die Risk Assessment, the Feasibility Study also evaluated contaminants of interestbased on the potential for impact to groundwater quality. Previous remedial actions completedat the site prior to the RI removed original sources of contaminants at OX.. Tool through soilremoval, treatment, and off-site disposal (see RI Section 1.2.3% and previous reports byNormandeau, Inc.} Analytical data collected during the RI indicate that residual VOC Aconcentrations in soils at OJt. Tool have been greatly reduced, in part as a result of theprevious remedial actions and in part as a result of volatilization and flushing ofcontaminants in th soils and that remaining residual VOC contaminants in soils are belowthe current concentrations of contaminants in the groundwater.

Actions completed at the site include the following:

L Source control through soil removal, treatment, and off-site disposal has beenaccomplished at the primary PCE source area (O.K. Tool);

2. None of the PRPs currently use PCE in their processes and the PRP's materials Cf2handling and manufacturing processes have been substantially modified to

cessation of discharge from Hendrix and the modification and reduction ofpermitted discharges from Hitchiner.

In order to determine whether residual contaminants identified in unsaturated soils are ^ icapable of leaching contaminants at a significant volume to impact groundwater conditions, theSummers model was used to determine allowable residual soil concentrations which, given

2176-160/HAZ-5254 2-13

leaching of contaminants to groundwater, would result in groundwater contaminantconcentrations below the MCLs. The model was run for the following contaminants detected atelevated levels in soils at O.K. Tool: tetrachloroethylene; PCBs (Arochlor 1254), lead, and

arsenic. Table 2-1 presents a summary of the assumptions and input parameters used in the

model and the results for each of the compounds. The complete results of the Summers Modelare included in Appendix IX.

The Appendix also includes a discussion of the parameters used as input in the modelas well as a discussion of the sensitivity of the model to changes in input values. In order toaccount for the sensitivity of the model to the parameters used as input, the model was runusing a range of values for organic carbon content (foe) and partition coefficient (Kd), as wellas a range of values for horizontal conductivity (Kh) and vertical conductivity (Kv). It wafound that varying vertical conductivity does effect the results of the model. The model wasrun using a Kh value of 234 ft/day, derived from the January, 1990 on-site pump test of theHitchiner well. The model was also run using a value of 10Q feet/day, which yielded lowerallowable residual concentrations.

An area of 200 feet by 150 feet, corresponding to the area behind the O.K. Tool buildingwhere elevated contaminants were detected, was assumed and the rate of infiltration through the

soils was assumed equal to 15 inches per year. The results of the model indicate that PCEconcentrations of 320 to 686 ug/kg (Kh = 234) and 139 to 303 (Kh = 100) value, could remain insoils without impacting the groundwater, dependent on the assumed foe value. The highest PCE

concentrations detected outside the O.K. Tool building were in the range of 130 to 440 ug/kg,below the upper range of results, and only one sample result (440 ug/kg) exceeded the lowerend of the range. Therefore, the model indicates that the existing PCE contamination inunsaturated soils should not impact groundwater.

The analysis was also performed for PCE in soils underneath the existing O.K. Tool

building, where concentrations up to 2,400 ug/kg were detected. Assuming an area of 120 x 60feet, corresponding to the length of the building from the first floor drain to the downgradientend of the building and the width across which elevated PCE levels were detected (note thatthe width does not effect the results of the model), and infiltration of 15 inches/year. Theanalysis indicates that PCE concentrations as high as 531 to 1,154 ug/kg (Kh = 234) and 229 to

498 (Kh = 100) can remain in soils without impacting the groundwater. It should be noted thatonly two of eight samples beneath the building were found to contain concentrations outside thisrange. It should be further noted that the analysis assumes that the building is not present. Inreality, due to the existence of the building, there is no infiltration, and therefore, the allowablesoil concentrations should be much higher to reflect actual site conditions.

2176-160/HAZ-5254 2-14

The results of the Summers model for PCBs in the area behind the O.K. Tool building

indicated that concentrations as high as 52,000 to 113,000 ug/kg (Kh = 234) and 23,000 to

49,000 (Kh = 100) could remain in soils without impacting groundwater. By comparison, the

highest PCBs concentration detected at O.K. Tool was 10,000 ug/kg.

The results of the analysis for lead indicated that concentrations of approximately 44,000

to 96,000 ug/kg (Kh = 234) and 19,000 to 42,000 (Kh = 100) could remain in soils without

impacting groundwater, and die results for arsenic indicated allowable concentrations ranging

from 3,800 to 32,000 ug/kg (Kh = 234) and 1,200 to 14,000 (Kh = 100). Concentrations of lead

(up to 610 mg/kg) and arsenic (up to 204 mg/kg) outside the modelled range of values were

detected in several soil samples at O.K. Tool, however, the near background concentrationsreported for lead (52 mg/kg) and arsenic (17 mg/kg) (Shaklette and Boerngen, 1984) are also

outside the modelled results. Moreover, levels of As and Pb have not been detected in

groundwater samples from monitoring wells in this area at levels above the MCLs. There is a

large amount of uncertainty involved in die use of the Summers model for metals due to die

wide range of reported Koc and Kd values for metals, and, based on die observed site conditions,

it appears that the amount of leaching of metals is less than that predicted by the model. No

contaminants of interest are identified in soils based on these results.

2176-160/HAZ-5254 2-15

TABLE 2-1

SUMMERS LEACHING MODEL RESULTS

Compound

PCE

PCBs(Arochlor

1254)

CsAllowable Soil Concentration

Areafeet

120x60(beneathO.K. Toolbuilding)

200 x 150(outsideO.K. Tool)

II

ii

Foe

.0023

.005

.0023

.005

.0023

.005

Kocml/g

364

364

364

364

29,50029,500

Kdml/g

0.84

1.82

0.84

1.82

67.8147.5

ForMCLs in Groundwaterug/kg

Kh-234ft/dav Kh-lOOft/dav

531

1,154

320

696

51,907112,841

229

498

139

303

22,57149,067

Lead

Arsenic

.0023

.005

.0023

.005

5,0005,000

NANA

11.525

18.3

43,98995,628

3,82531,749

19,12841,583

1,66313,805

2176-160/HAZ-5254 2-16

Surface Water

The Baseline Health Risk Assessment for surface water exposure scenarios produced risk

levels and hazard indices below the target ranges and therefore does indicate contaminants of

interest for surface water. Because there is a low potential for use of surface waters as a

drintqng water supply, MCLs are not applicable in developing remedial action objectives for

human health protection. Several contaminants which were detected in surface waters at levels

which exceed the Federal and New Hampshire Ambient Water Quality Criteria for protection of

aquatic life, which are applicable ARARs. These include toluene (SW-19), acrolein (SW-19), Y 5

copper (SW-4 through SW-9), lead (SW-5), nickel and chromium (SW-5). However, the

locations of the elevated levels of toluene, acrolein, lead, and chromium are all in the process

water discharge stream, at or immediately adjacent to the permitted industrial outfall from the

Hitchiner facility, and are within the limits established by the NPDES permit. Copper levels

were found to exceed AWQC levels at five points (SW-5 through SW-9) along the length of the

discharge stream, but were below the permitted discharge levels. Copper levels drop

significantly along the length of the discharge stream and are below detection limits (and below

ARAR levels) in the Souhegan River, indicating that the river is not being impacted by copper in

the discharge stream. Sampling of sediments and surface water in the Souhegan River was

performed during a period of low flow (September 5-6, 1989) such that these results are

considered as representative of levels that would occur in the stream under the typical range of

flow conditions (see Section 3.2 of the RI).

VOCs occur in the discharge stream in part as the result of process water pumping wells

intersecting the outer fringes of the plume on the south side of Route 101. The concentrations in

the discharge stream are significantly lower than those in the aquifer to which it discharges.

Discharge of low levels of contamination to the area of the aquifer that is aJready affected by

high levels of contaminants would not increase the overall contaminant level or the time frame

required to reach remedial goals. The results of the baseline risk assessment have not shown the

discharge stream's contribution to the underlying aquifer to pose an unacceptable risk. The

Ecological Risk Assessment, which was conducted independently for EPA by the Cadmus

Group, Inc., concluded that the only potential ecological risks posed by the site were related to

the permitted outfalls for the Hitchiner-Hendrix discharge stream and that, given the cessation of

discharges from Hendrix (which has in fact occurred), much if not all of the potential risk may

be eliminated. Additionally, Hendrix has terminated its discharge and Hitchiner has made

process modifications to educe their discharge since the time of the RI sampling.

2176-160/HAZ-5254 2-17

For the reasons discussed above, no contaminants of interest have been identified and noremedial action objectives need to be developed for surface water.

The baseline risk assessment for exposures via ingestion or dermal absorption of

contaminants in sediments produced risk estimates within the target range for performance goals

and hazard indices below unity, i.e., references doses were not exceeded. There are no Federalor New Hampshire ARARs that specify sediment concentration limits for protection of humanhealth. Therefore, no compounds of interest are identified and no remedial action objectives

need to be developed for the protection of human health.Remedial action objectives for the protection of the environment should be to prevent or

mitigate releases from sediments which would result in surface water contaminant levels in

excess of AWQC. The only contaminants for which concentrations detected in sediments aresignificantly higher than AWQC levels in surface water are metals in sediments immediatelyadjacent to the NPDES-permitted industrial outfalls at the Hitchiner Facility (SW-4, SW-5, and

SW-6), at the extreme upstream end of the discharge stream. As discussed in the surface watersection, there is no indication of elevated levels of any metals in the waters of the dischargestream except copper and there is no indication of an impact to the Souhegan River from metals

in the discharge stream. The chemistry of the soils, metal and water suggest that these metals

are relatively immobile in their present location. For these reasons, no remedial actionobjectives need to be developed for sediments for protection of the environment.

Ak

Contaminants detected in air consist of acetone, methylene chloride, tetrachloroethylene,and 1,1,1 trichloroethane. All detected concentrations were below the proposed New HampshireAmbient Ak Level (AAL) guidelines. And the Risk Assessment did not identify any

unacceptable risks from inhalation exposures. Therefore, no remedial action objectives aredeveloped for air. The detected values are substantially below the Acceptable Ambient AirLevels (AALs), as obtained from the NH Air Resources Agency. The AALs are 100 to300-fold lower than the air concentration limits set for these chemicals to protect individualsin the workplace. However, the risk assessment techniques used in setting worker exposurelimits dtffer from those typically used for hazardous waste site impact assessment and the NHDivision of Public Health Services maintains that AALs are not appropriate for evaluatingthe potential risk via exposure to airborne chemicals.

2176-160/HAZ-5254 2-18

The Baseline Health Risk Assessment indicated that the oncer risk far the maximmm

exposure calculation is 7 x IV6 (within the target risk range), with tetrachtoroethylenecontributing the greatest portion of the risk. The estimated risk for the average case risk issubstantially smaller (approximately 7 x 10"^). it should be noted that the exposure scenario

constructed for this analysis is perhaps more conservative Aon others reported in this

analysis. The parameters include exposure 24 hours per day, 365 days per year and, for

maximum risks, are specific to a location at the Hitehiner-Hendrix discharge pipe. Thus, it isconsidered unlikely that anyone would be exposed for that period of time. It is also importantthat, with the cessation of discharge from time Hendrix operation, chemicals may no longer be

Att hazard indices for the air inhalation scenario are below 1, indicating that

non-cancer impact of tins exposure is extremely unSkefy.Since none of contaminants detected in air produce a cancer risk or Hazard Quotient

exceeding target risk levels, no contaminants of interest are identified for air.

2.2.2 Applicable or KffkY«lt wd Appropriate gfq!limnpna (ARARg)

In terms of health risks,, remediation goals and acceptable contaminant target action levels

are established for carcinogenic compounds by EPA target ranges for acceptable excess lifetime

cancer risks (1 x 10 to 1 x lO^X and for non-carcinogenic compounds by reference doses

established for individual contaminants. Additionally, remediation standards and target levels

for remediation are based on institutional requirements provided by The Comprehensive

Environmental Response, Compensation, and Liability Act (CERCLA) as amended by The

Superfund Amendments and Reauthorization Act (SARA). The National Contingency Plan

(NCP) includes a summary of Federal and State statutes,, regulations, etc, that are potentially

applicable or relevant and appropriate requirements (ARARs) for remedial alternatives.

1m order to develop remediation goals far the Savage Municipal Water Supply Site,

chemical and location specific AKARs were evaluated. The NCP (40 CFR Part 3OOS) definesARARs as "Applicable" or "Relevant and Appropriate Requirements". In accordance with

the NCP the following definitions an used to define "Applicable" and "Relevant andAppropriate Reautrements."

Applicable Requirements are Federal and State public health and environmentalrequirements which would be legally applicable to the response or remedial action if that action

was not undertaken pursuant to CERCLA (Federal, State, and local permits are not required forfund-financed remedial actions or remedial actions taken pursuant to Federal action underSection 106 of CERCLA).

2176-160/HAZ-5254 2-19

Relevant and Appropriate Requirements are Federal public health and environmentalrequirements that apply to circumstances sufficiently similar to those encountered at CERCLA

sites such that their application would be appropriate although not legally required.Applicable requirements mean those cleanup standards, standards of control, and other

substantive requirements, criteria, or limitations promulgated under federal environmental orstate environmental or facility siting laws that spcdficaUy address a hazardous substance,poUutant, contaminant, remedial action, location, or other circumstance found at a CERCLAsite. Only those state standards that are identified by a state in a timely manner and that aremore stringent Aon federal requirements may be applicable.

Relevant fntif ^ffropriate requiftmenfs mttm those cleanup tfmiiififf ffipufifdj ofcontrol, and other substantive requirements, criteria, or limitations promulgated underfederal environmental or state environmental or facility siting laws that, while not"applicable11 to a hazardous substance, pottutant, contaminant, remedial action, location, orother circumstance at a CERCLA site, address problems or situations sufficiently similar tothose encountered at the CERCLA site mat their use is well suited to the particular site. Onlythose state standards that are identified in a timely manner and are more stringent titanfederal requirements may be relevant and appropriate.

Section 121(d)(2)(A)(ii) of SARA now requires compliance with State environmental or

facility siting laws that are more stringent than Federal requirements. As a result, these statutes

and regulations are to be considered as potentially applicable or relevant and appropriate to theremediation of CERCLA sites. These requirements include ARARs as follows:

The determination that a requirement is relevant and appropriate involves acomparison of certain site-specific factors, including the characteristics of the remedialaction, the hazardous substances present at the site, or the physical circumstances of the site,with those requirements addressed in the statutes or regulations. In some cases, arequirement may be relevant, but not appropriate, given site-specific circumstances; such arequirement would not be an ARARJor the site. In addition, there is more discretion in thedetermination of relevant and appropriate; it is possible far onfy part of a requirement to beconsidered relevant and appropriate in a given case. When the analysis results in adetermination that a requirement is both relevant and appropriate, such a requirement mustbe complied with to the same degree as (f it were applicable.

A separate category which is considered discretionary under the NCP includesrequirements which are To Be Considered.11 This category encompasses non-promulgatedadvisories or guidance issued by federal or state governu^nt that an not legally binding anddo not have the status of potential ARARs.

2176-160/HAZ-5254 2-20

Im CERCLA Compliance with Other Lam Mammal: (Interim Ptnal, EPA 54016-891906,

August 1988), fare are three categories of ARARs identified. These three categories are:

Chemical-Specific

• Location-Specific• Action-Specific

The chemical-specific ARAR category coven contaminant concentrations in various

media (e#., MCLsfor contaminants in groundwater wonld be a potential chemical-specific

ARAR). Potential chemical-specific ARARs which relate to the contaminants and media of

concern at the Savage Municipal Water Snppfy Site are identified in Table 2-2.Location-specific ARARs address physical features of a specific sue where remedial responseactions will be carried out, (e.g^ wetlands, floodphuns and Areas of Critical EnvironmentalConcern (ACEC)). The potential location-specific ARARs that apply to Otis site are identifiedin Table 2-3. Action-specific ARARs are generally activity- or technology-based requirementsor limitations on remedial response actions which might be undertaken to address specificsite contaminants. Action-specific ARARs are used to assist in the determination of howselected alternatives must be implemented. The action-specific ARAR category identifiesARARs which may potentially apply to remedial actions at the Savage Municipal WaterSupply Site. The potential action^spec^ ARARs are identified in Table 2-4.

1. Chemical-specific ARARs govern the extent of site clean-up in terms of actual

clean-up levels and are used in the development of remedial action objectives,, as

discussed belowr in the screening of technologies and in the development of

remedial alternatives.

2.1 Location-specific ARARs govern natural site features such as wetland and

floodplains and manmade features such as existing landfill and disposal areas.

1, Action-specific ARARs are technology-based requirements that set restrictions on

particular kinds of activities related to managing hazardous wastes.

Potential chemical-specific, location-specific, and action-specific ARARs are presented in

Tables 2-2 through 2-4 respectively.

2176-160/HAZ-5254 2-21

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2.23 Development of Pjpel"»"TiaFy ^CTMrfJUtfafl Goal*

As discussed in Section 2.2.1, contaminants of interest have been identified forground water but have not been identified for other media at the site. The following section

outlines the preliminary remediation goals for groundwater.Based on the previous analysis, the two primary objectives which form the site-specific

remediation goals are source control objectives for soils and management of migration

objectives for contaminated groundwater. Each of these are discussed on the following herein.

Source Control Objectives

The NCP defines source control action as: "the construction or ins^lgtion and start-up of

those actions necessary to prevent the continued release of hazardous substances or pollutants or

contaminants (primarily from a source on top of or within the ground, or in buildings or other

structures) into the environment" (40 CFR 300.5).

Based on this definition, source control at the Savage Well Site could potentially include

sediments in the Hitchiner-Hendrix discharge stream or contaminated soils in the vicinity of the

industrial facilities as well as soils beneath the O.K. Tool. Hitchiner and Hendrix buildings.

Potential related pathways of exposure could be dermal and ingestion exposure to the soil as

well as inhalation exposure to volatile organic compounds released from the soil. Also,

contaminants in the soil can potentially be released into groundwater resulting in contamination

in excess of groundwater remediation objectives. However, as discussed previously in Section

2.2. lf none of diese potential pathways represent risks outside the acceptable range at the Savage

Well Site.

The Baseline Human Health Risk Assessment did not identify any current use exposure

scenarios involving contact with soils or other surficial materials which could be considered as

potential source materials that produced ri^y above the limits typically ffipe/cified by EPA in

establishing cleanup goals (10-4 to 10-6). Hypothetical worst-case future exposure scenarios for

contact with soils 8t O.K. Tool produced risks fit the upper end of the acceptable range typjjcajllyspecified hv EPAr however, this exposure scenario is considered unlikely. It should be further

noted that the majority of the risk associated with this hypothetical scenario is from two

compounds, arsenic and PCBsf and that the elevated concentrations of these compounds detected

in soils are limited to an area behind the O.K. Tool building to which access is limited.

2176-160/HAZ-5254 2-33

The Ecological Risk Assessment, which was conducted independently for EPA by the

Cadmus Group. Inc.. concluded that the only potential ecological risks posed by the site were

related to the permitted outfalls for the Hitchiner-Hendrix discharge stream and that, given the

cessation of discharges from Hendrix (which has in fact occurred), much if not all of the

potential risk may be eliminated. The Ecological Risk Assessment concluded that the _S (

appropriate response would be continued monitoring of the site.

However, in general, it is also necessary to consider remedial action objectives for source <c"?

control and protection of the environment, i.e.. to prevent or mitigate the migration of VQC

contaminants from soil into groundwater that would result in contamination in excess of

groundwater remediation objectives, or would unreasonably lengthen the time to achieve

groundwater remedial goals. The data for this site indicate that the original sources of

contaminants at O.K. Tool have been remediated through soil removal, treatment, and off-site

disposal, and that remaining residual contaminants in soils are below the current concentrations

of contaminants in the groundwater. Based on these findings and the results of the Summers

leaching model (discussed below), it was determined that further remediation of soils below the

building's concrete floor slab is not warranted. However, due to the high concentration of

contamination in the saturated zone beneath the building and the potential existence of Dense

Non- Aqueous Phase Liquids (DNAPLs)r the control of further release of contaminants to the

aquifer from source areas in the saturated zone will be considered as an objective of the

gtoundwater response actions.

The analysis of source control objectives also takes into consideration the significant

amount of remedial action and other activities, including source removal and modifications of

materials management practices, that have taken place to mitigate the contaminants and

potential impacts from the contaminants. Many of the remedial objectives called out in the EPA

guidance and in the NCP have for great part been achieved to date.

Actions completed at the site include the following:

It Source control through soil removal,, treatment, and off-site disposal has been ~>

accomplished at the primary PCE source area (O.K. TooDi

2± None of the PRPs currently use PCE in their processes and the PRP's materials

handing pnd manufacturing processes have been substantially modified to

minimize the potential for release of hazardous materials, including the cessation

of discharge from Hendrix and the modification and reduction of permitted

from Hitchiner.

2176-160/HAZ-5254 2-34

The data for this site indicate minimal potential for impact to human health or theenvironment posed by residual contaminants in soils and sediments as indicated by: n the

Baseline Human Health Risk Assessment; 2) the Ecological Risk Assessment: and 3)calculations of the potential impact of residual soil contamination on groundwater quality usingthe Summers leaching model. Consequently, remedial objectives for source control arecurrentl satisfied b a No-Action alternative, includin lon-term monitorin.

As discussed previously, the only potential medium of concern for management of ~> ->

migration is groundwater.

The following remedial action objectives apply to groundwater (Guidance for ConductingRemedial Investigations and Feasibility Studies Under CERCLA, p. 4-10, OSWER Directive9355.3-01, October, 1988):

1. Prevent ingestion of water having carcinogens (see Section 2.2 for list ofcontaminants of concern) in excess of target clean-up levels and a total excesscancer risk (for all contaminants) of greater than 10" to 10 .

2. Prevent ingestion of water having non-carcinogens (see Section 2.2 for list of

contaminants of concern) in excess of target clean-up levels, reference doses, or ^ -* MCLs.

3. Restore the groundwater to concentrations Ami eammty with Federal mm* StateARARs. St* Tmlfo 2-2 which presents chemical-specific ARARs including Safe 5~S~<eDrinking Water Act MCLs.

Preliminary remediation goals, also known as target clean-up levels, are established toprovide exposure levels for individual or groups of significant risk contaminants in affectedmedia that are protective of human health and the environment. Individual or groups ofcontaminants associated with significant risk are identified as those which have a HazardIndex (HI) greater than the EPA guideline of 1.0 and/or an Increment Lifetime Cancer Risk(ILCR) outside the target risk range of 1.0 x W4 to 1.0 x 10"6. The significant riskcontaminants are compared to federal and state standards, guidelines, and criteria, whereavailable to select target clean-up levels.

For the Savage Municipal Water Supply Site, only ingestion and household use ofcontaminated groundwater produce His greater than 1.0 andlLCRs greater than 1 x2176-160/HAZ-5254 2-35

For each of the significant risk contaminants in groundwater, a final maximumcontaminant level (MCL) has been set under the Safe Drinking Water Act. Since an MCLhas been set for each of the significant risk contaminants in groundwater, the MCLs areselected as target clean-up levels for the significant risk inorganic and organiccontaminants. The target clean-up level (equal to the MCL) for each significant riskcontaminant in groundwater are presented below.

TABLE 2-5TARGET CLEAN-UP LEVELS FOR GROUNDWATER

Target Clean-Up LevelContaminant (ug/l)

Arsenic 50Beryllium 1Chromium 100Lead 51,1-DCE 7Trans-lJ-DCE 100PCE 51,1,1-TCA 200TCE 5

In assembling remedial process options into alternatives designed to achieve theseobjectives it is important to recognize differences in the contaminated groundwater. Asdescribed in Section 2.0, the data indicates an area of the contaminated groundwater plume

which has relatively high levels of contamination (i.e., the concentrated plume) and an area withsomewhat lower levels of contaminants (i.e., the extended plume). The analysis recognizes thatthe plume is persistent because of continued dissolution of the concentrated dissolved VOCcontamination and potential separate phase contamination below the water table at O.K. Tool.Additionally, areas of locally elevated concentrations of dissolved VOC contamination

2176-160/HAZ-5254 2-36

at Hitchiner and in the vicinity of MW-20 are also considered in the analysis as concentrated

areas of the plume that provide continued migration of contaminants to the aquifer.

It should be noted, however, that the volume of groundwater to be treated may be

substantially greater due to the possible presence of DNAPLs and to solvents being slowly

solubilized from pools and lenses into clean inflowing groundwater. Because of the presence of

this persistent contaminant source, and because of the low miscibility of PCE and other

chlorinated solvents, remedial objectives for this area are focused on prevention of further

release of contamination into the extended plume.

MCLs target levels may be achievable in those portions of the aquifer where there are

dilute contaminants, but on the basis of current scientific evidence, they may not be achievable, -^ i

at least in die short term, for the concentrated plume where contaminants likely exist as separate

phase (DNAPLs).

2.2.4 Areas *nd Volumes of Concern

The distribution of VOC contaminants in groundwater is illustrated on Figure 2-2.

Stratigraphic cross-sections oriented parallel to and transverse to the contaminant plume, along

with VOC concentrations indicated for individual well locations, are included in Section 1.0.

The observed distribution of volatile organic compounds extends from the immediate

vicinity of the O.K. Tool facility approximately 6,200 feet eastward and, at its widest point,

extends approximately 2,500 feet from the vicinity of Old Wilton Road on the south side to the

Souhegan River on the north side.

The mass of total volatile organic compounds in the plume was calculated by estimating

the volume of groundwater within the 1000 ppb total VOC contour and multiplying that by the

average concentration within that contour. The same procedure was taken for the area between

the 1000 ppb and the 100 ppb contour and the area between the 100 ppb and the 10 ppb contour.

Using an average saturated thickness of 84 feet, an area of 2.38 x 10+6 square feet and an

effective porosity of 0.35, the volume of contaminated groundwater within the 1000 ppb contour

is calculated to be 5.23 x 10+8 gallons (1.98 x 10+9 liters). The average concentration of total

VOCs within this contour is 4453 x 10-6 grams/liter. The mass of VOCs in the groundwater

within the 1000 ppb contour is calculated to be 8.82 x 10+6 grams or 19,448 pounds. Using an

average density for trichloroethylene (TCE), tetrachloroethylene (PCE), and 1,1,1

trichloroethane (TCA) of 1480 grams/liter, this mass corresponds to 5959 liters or 29 55-gallon

drums of equivalent DNAPL.

2176-160/HAZ-5254 2-37

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Between the 100 and 1000 ppb contours of the plume, the volume of contaminated

groundwater is calculated to be 7.34 x 10+8 gallons (2.78 x 10+9 liters) using an area of 4.67 x

10+6 square feet, an average saturated thickness of 60 feet, and an effective porosity of 0.35.

The average concentration of total VOCs between these contours is 324 x 10-6 grams/liter. The

mass of VOCs in the groundwater between the 100 and 1000 ppb contours is calculated to be 9.0

x 10+5 grams or 1986 pounds. This mass corresponds to 608 liters or 3 55-gallon drums of

equivalent DNAPL.

Between the 100 and 10 ppb contours of the plume, the volume of contaminated

groundwater is calculated to be 5.49 x 10+8 gallons (2.08 x 10+9 liters) using an area of 3.33 x

10+6 square feet, an average saturated thickness of 63 feet, and an effective porosity of 0.35.

The average concentration of total VOCs between these contours is 40 x 10-6 grams/liter. The

mass of VOCs between the 100 and 10 ppb contours is calculated to be 83,200 grams or 183

pounds. This corresponds to 56 liters or 15 gallons (0.3 55-gallon drum) of equivalent DNAPL.

The total volume of contaminated groundwater within the 10 ppb contour is 1.81 x 10+9

gallons (6.84 x 10+9 liters). The mass of total VOCs in the groundwater is estimated to be 9803

kilograms or 21,616 pounds. This corresponds to 6624 liters or 32 55-gallon drums of

equivalent DNAPL.

These estimates represent the volume of DNAPL equivalent corresponding to the volume

and concentration of dissolved VOC contamination in the concentrated and extended plume.

Because contaminants may exist as separate phase (DNAPL) in the concentrated plume, these

estimates represent minimum volumes.

2.3 GENERAL RESPONSE ACTIONS

General response actions describes those actions that will satisfy the remedial action

objectives outlined in Section 2.2. Based upon evaluation of Remedial Investigation data, the

remedial responses considered to be appropriate for groundwater at the Savage Well Site include:

• No Action

• Limited Action

• Diversion/Containment

• Collection/Treatment/Discharge

2176-160/HAZ-5254 2-39

General information on remedial response actions is presented in the following sections,including a definition of the response, a description of what it entails and what it accomplishes,and when the response is generally preferable. Information also is provided on compatiblesource control responses, and technologies available to enact these responses.

No Action

The NCP 300.68(f) states that to the extent it is both possible and appropriate the "NoAction" alternative shall be developed as part of the feasibility study. The no action alternative

allows migration of contaminants to continue (i.e., via contaminated groundwater). There is no

treatment or disposal involved with the no action response. The current condition and the S~*projected environmental fate are to be evaluated. Under natural conditions, the contamination inthe groundwater is expected to diminish over time due to dilution, dispersion, and to someextent, degradation and attenuation. The no action response would consist primarily ofenvironmental monitoring of the off-site migration of contaminants. This response evaluateswhether there would be any threat to public health, welfare or the environment, if no action is

taken. It provides the baseline risk against which all other responses can be compared. Thisresponse may be selected for management of migration problems where natural environmentalmechanisms will result in degradation or immobilization of the contamination concentration

within a reasonable period of time or if risks shown are acceptable by EPA standards.

A comprehensive program would be developed and conducted to monitor changes in bothgroundwater and surface water qualities. The monitoring program for groundwater includes

both on-site and off-site monitoring wells and the program for surface water includes samplingof Souhegan River. The current level of contamination in the groundwater will preclude its useas a drinking water source for a period of time.

The following technology could be used to enact this response:

• Long Term Environmental Monitoring

Limited Action

This is a response which allows the Federal, State and local governing bodies to mitigate

management of migration problems through institutional controls. This response employs therestriction of access and/or use of contaminated groundwater and surface water to sensitivereceptors. It is important to recognize that alternate drinking water supplies have been providedto the town and users by completed remedial action.

2176-160/HAZ-5254 2-40

The NCP states that "EPA expects to use institutional controls such as water use and deedrestrictions to supplement engineering controls . . . to prevent or limit exposure" tocontamination at the site. Such controls may be used "as a component of the completed

remedy." 40 C.F.R. s300. 43Q(a)(iiiKD). "EPA expects to use institutional controls such aswater use and deed restriction* to supplement engineering controls as appropriate for short-and long-term management to prevent or limit exposure to hazardous substances, pollutants,or contaminants. Institutional controls may be used during the conduct of the remedialinvestigation/feasibility study (RifFS) and implementation of the remedial action and, wherenecessary, as a component of the completed remedy. The use of institutional controls shallnot substitute far active response measures (c&, treatment and/or containment of sourcematerial, restoration of ground waters to their beneficial uses) as the sole remedy unless suchactive measures are determined not to be practicable, based on the balancing of trade-offsamong alternatives mat is conducted during the selection of remedy" (49 CFR 300.430(a)(l)(m)(D)). Examples of institutional controls include (1) installation of alternative watersupplies; (2) acquisition of real property; (3) regulatory restrictions; and (4) restrictions onproperty rights. See EPA Guidance on Remedial Actions for Contaminated Groundwater at

Superfund Sites (December 1988). According to the EPA Guidance, institutional controlsshould be implemented as part of the response action.

In keeping with the NCP and EPA Guidance, institutional controls are included as part of

the management of migration alternatives to prevent exposure to contaminated groundwater atthe Savage Well Site. Currently, much of the groundwater at the Site is available for use for

industrial or agricultural purposes in its present condition an<1 CCrfaJP controls are already in

place. Public water lines to businesses and residences surrounding the Savage Well Site havebeen constructed, thereby eliminating the use of the Savage Well aquifer as a drinking water

supply for the Town of Milford. As noted in the RIf the only place where groundwater still maybe used for drinking water purposes is seasonal use at the Miilfffrd Drive-in. Alternative watersupplies to the drive-in would be installed as part of the institutional controls at the site. Thus,

there would be no known use of the groundwater at the Savage Well Site for drinking water

purposes.

2176-160/HAZ-5254 2-41

In addition, the Savage Well itself currently is owned by Hitchiner Manufacturing

Company, for use as an industrial water supply. Again, no water from the Savage Well now or

in the foreseeable future could be used for drinking water purposes. Further, current state lawprohibits the placement of new wells in areas like the Savage Well Site where the storage,treatment or use of significant amounts of hazardous chemicals occurs "at any point tributary" to

the well. At the Savage Well Site, points tributary to the Well itself include gas stations, autobody repair shops, agricultural uses and industrial operations. In addition, state regulationsprohibit siting certain public wells in areas subject to one hundred year flooding. The Savage

Well site is located in large part within the 100 year floodplaijv Thus, state law provides anexisting additional institutional control preventing exposure to the contamination at the Site.

Local regulation provides an additional institutional control. The area where the PRPs arelocated is zoned industrial. According to the Town of Milford zoning regulations, residential

dwellings are specifically excluded from the industrial district. Thus, future residential exposure

to contaminants at the industrial sites of the PRPs is, as a practical matter, prohibited. Localzoning regulation also prohibits the siting of potable water supply wells in wetlands, which mayinclude parts of the Savage Well Site. Local zoning, however, muty change in the Jntnre as (T well as be Ofertmrned by the local zoning board of appeals.

In addition to the institutional controls already discussed, other controls are to be enacted £ ~5

are proposed to be enacted where possible to further restrict the possibility of usinggroundwater at the Savage Well Site for drinking water purposes. These controls include deedrestrictions preventing the use of groundwater for drinking water purposes. Several of the

potentially responsible parties, Hitchiner Manufacturing, Hendrix Wire and Cable, and O.K.Tool, Inc., have agreed to enter into deed restrictions preventing the use of groundwater at thepremises for drinking water purposes. In addition, the PRPs are approaching neighboring

landowners comprising the bulk of property at the Savage Well Site to purchase theirgroundwater rights for drinking water purposes. The institutional controls described above, incombination with other remedial action, significantly reduce if not eliminate the possibility for CV^ingestion of contaminants at the Savage Well Site.

Based on the development of alternatives in Section 3.0. one source control and eight ,management of migration alternatives were retained for detailed evaluation. The alternativesand a short description are presented in Table 4-1. Before a detailed evaluation was performedfor each alternative f each was further defined with respect to the volume and areas to beaddressed, the specific technologies and other assumptions to be

2176-160/HAZ-5254 2-42

used for costing, and the performance requirements of each alternative. The purpose of thisanalysis is to provide sufficient information to compare the alternatives, select an appropriate

remedy for a sitef and demonstrate its compliance with the CERCLA remedy selectionrequirements for the Record of Decision TROD).

The following activities could be used to enact a limited action response:

• Groundwater Monitoring

• Alternate Town Water Supplies

• Purchase of Groundwater Rights

• Land Use Controls• Deed Restrictions

Collection/Discharge

This response allows the groundwater that is extracted to be discharged either on or off the H£" .A

site. Qn-site disposal entails groundwater extraction or removal and discharge. On-site disposalmay include discharge to a surface water body or recharge to the aquifer by spraying, trenching,seepage ditches, or reinjection wells. Discharge to surface waters or groundwater normally £ cinvolves the National Pollution Discharge Elimination System (NPDES) program which defines

the contaminant levels to which the water must be treated prior to discharge. The on-site

disposal response enables the groundwater to be handled on site without extensive storage andoff-site transportation requirements and is therefore preferable to off-site disposal when feasible.

In addition to considering indirect containment and collection of dissolved chlorinatedsol vents f the FS will consider application of enhanced DNAPL recovery techniques that arecurrently under research. These methods would produce an effluent that would bepredominantly product, which would require handling and management pursuant to applicablewaste management regulations.

Off-site disposal may entail either piping the collected groundwater to local POTW orriver. Discharge to surface water must fall within NPDES permit standards stipulated for that

discharge. Groundwatcr discharged to PQTW must meet pretreatment standards stipulated forthat facility. The function of this response is to reduce the level of contamination by dilution,transfer to another media or Assist in hydrodynamic control of the contaminant plume.

2176-160/HAZ-5254 2-43

The following technologies could be used to enact this type of response:

• Groundwater Extraction Wells• Interceptor Trenches• Discharge to Hitchiner-Hendrix Stream• Discharge to POTW

• Discharge to River

Containment/Diversion

Containment - Containment of contamination is more difficult to achieve in terms of a

management of migration response. Containing a migrating plume usually requires a greaterexpenditure of resources than containing a source due to the larger areas and volumes of water.Additionally, an impervious cover is constructed to minimize development of a hydraulic headin the contained area. Generally speaking, containment may also be employed by cappingcontaminated soils to minimize contaminant migration. Hydrodynamic control can also be usedto contain a plume.

Diversion - Diversion is a response which allows management of migration problems (i.e.,contaminated groundwater and surface water), to be controlled. This response includes the useof diversion structures, selective pumping, or conduits of high permeabilities to redirect flow ormigration patterns across a site. This response allows contaminated groundwater or surfacewater to be diverted away from sensitive areas or sensitive receptors, such as drinking water

wellfields downgradient of source areas. Another objective is to divert groundwater upgradientof source areas and reroute surface water to prevent it from flowing through the contaminationthereby reducing the migration of contaminants from source areas. Diversion of groundwaterflow is preferable when the horizontal component of groundwater flow through the overburdenis significant and easily controlled.

The following technologies could be used to enact a containment/diversion response:

• Multi-layer Cap• Permeable Cap• Grout Curtain

Slurry Walls• Sheet Piling• Bottom Seal Grouting• Injection-Well• Groundwater Interceptor Trench

2176-160/HAZ-5254 2-44

• Infiltration/Recharge Basin• Dikes and Berms

Extraction Wells

Collection/On-site Treatment/Discharge

To the extent that the collection and treatment are effective this treatment response

eliminates the potential of further migration of contaminants and exposure to receptors. Many

treatment processes create their own contaminant releases (sidestreams and/or residuals) and

these must be controlled. Treatment does, however, allow the groundwater to be discharged

locally, either via recharge to the groundwater or discharge to the surface water at a higher level

of quality.

Pretreating the groundwater followed by pumping to a local off-site facility is also an

option. Unless hookup to a sewer line is feasible, however, off-site treatment can require a

considerable transportation effort because of the large volumes typically associated with

groundwater pumping. Such large volumes are usually more appropriate for on-site treatment of

groundwater. On-site treatment of groundwater is generally preferred over containment or

diversion because it provides a more permanent, long-term solution to the groundwater

contamination problem.

The following collection/on-site treatment/discharge technologies (biological, chemical,

and physical) are consistent with 300.70 of the NCP and could be used to enact this type of

remedial response:

• CollectionExtraction Well System

• Chemical Treatment- Solvent Extraction

Coagulation/Hocculation/Precipfta/ionSequesteringIon ExchangeElectrolysis

- Steam StrippingSurfactantsUltraviolet OxidationAir StrippingOxidation/ReductionWet Air OxidationNeutralizationIn-situ Chemical Treatment

2176-160/HAZ-5254 2-45

Physical TreatmentSedimentationFiltrationCarbon AdsorptionSolvent Separation/Recovery ExtractionReverse OsmosisUltra FiltranonDissolved Air FlotationDistillationEvaporationThermal MobilizationAir StrippingSteam Stripping

Biological TreatmentRotating Biological ContactorsLagoons (Aerated-Aerobic)Lagoons (Anaerobic)Constructed WetlandsIn-situ Biode gradationPacked Bed ReactorEnzymatic Degradation

DischargeHitchiner-Hendrix Discharge Local StreamRecharge WellLeachfieldPipeline to RiverPOTWRCRA Facility

This general response action addresses residuals associated with treatment ofcontaminated groundwater. As a result of treatment, metal sludges, spent GAC, and/orbiological sludges may potentially be generated. These residuals will need to be characterizedto determine whether they are RCRA characteristic hazardous waste. This characterizationwill be determined through Toacily Characteristic Leaching Procedure (TCLP). Ifdetermined to be hazardous, the residuals would be disposed at a RCRA TSD JaeiKty. If

The fallowing technologies are appropriate far this general response action:RCRAfacOitySnbthle D, sottd wasteJaciUty

2176-160/HAZ-5254 2-46

2.4 IDENTIFICATION ANT> SfRRRMjNG OF TECHNOLOGY TYPES AND PROCESS

OPTIONS

The development of remedial alternatives begins by identifying, screening, and evaluating

potentially applicable remedial technologies and associated process options. A wide range of

potentially applicable technology types and process options have been identified for the

groundwater contamination at the Savage Well site. The technologies and process options were

screened on the basis of technical implementability, given site contaminant distribution and

local hydrologic, geologic, and hydrogeologic conditions. This process is documented in

Section 2.4.1.

Following the initial screening for technical implementability, the technologies and

process options which were carried past the screening step were evaluated against three criteria:

effectiveness, implementability, and cost, to select one representative process option for eachtechnology type. This process is presented in Section 2.4.2. Section 2.4.3 presents a summaryof the remedial technologies and process options which were determined to be the most

representative (i.e., optimum combinations of effectiveness, implementability, and cost).

2.4.1 Idwi^iQipflftiflp flpd Screciiing f»f ftcmedijil Tff^HtO^?£iiCT 8ffi} Process Options

The initial screening of technologies and process options begins by listing the universe of

potentially applicable remedial technologies and process options. Each technology and process

option is evaluated to determine if it is technically implementable at the Savage Well Site.Those technologies and process options which are determined to be technically implementableare carried through the screening process into the more detailed evaluation. Those which are

determined not to be technically implementable are screened out and dropped from further

consideration.

The identification and screening of remedial technologies and process options is discussedin this section. Remedial technologies and process options are identified in the following textunder the groundwater general response actions to which they apply. Figure 2-3 depicts thegroundwater general response actions, the technologies and process options which potentially

apply to each general response action, a brief description of the technology or process option,and a description of whether the technology or process option is potentially applicable or why it

is screened out.

2176-160/HAZ-5254 2-47

No Action

There are no remedial technologies or process options under the No Action generalresponse, other than monitoring, as described below. This general response action is

implementable at the Savage Well site and has been retained in accordance with the

requirements of NCP.

Limited Action

a. Monitoring: This option involves long-term periodic monitoring of groundwaterquality. Monitoring is retained.

2176-160/HAZ-5254 2-48

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b. Alternate Town Water Supply: An alternate water supply for residences at the

Savage Well Site has already been provided by the Town of Milford. Further

remedial actions of this type could be undertaken if necessary. Alternate water

supply is retained because this action provides a potable water supply while

eliminating or restricting the use of the contaminated water supply.

c. Industrial Water Supply: Industrial Water Supply is retained because this action

provides for a beneficial use of groundwater at the site.

c. Deed Restrictions: Restrictions would be placed on future land use andgroundwater development rights and use. This option is retained.

d. Purchase of Groundwater Rights: Purchase of groundwater rights would

prevent the future development of groundwater extraction wells for use as awater supply. This option is retained.

Collection/Discharge

a. Groundwater Extraction Wells: This option involves a series of wells to extract

contaminated groundwater,. and is retained.

k Subsurface Drains: Groundwater interceptor trenches are subsurface drains which

include any type of buried conduit used to convey and collect aqueous discharges

by gravity flow. Interceptor trenches essentially function as an infinite line ofextraction wells. They create a continuous zone of influence in which groundwater

within this zone flows towards the drain- However,, they are only implementable to

contaminated to depths of approximately 90 to 100 feet below ground surface,

drains are eliminated.

Ci Chemical and Physical EnhancementyPNAPL Mohi1'zarif>n:

•_ Steam - This option involves injection of steam into DNAPL-bearmg strata

to mobilize the DNAPL to collection/extraction points. This technology is

at a preliminary research stage and is unproven.

2176-160/HAZ-5254 2-54

Additionallyt DNAPLs are difficult to isolate, mobilize, and recovery

particularly given site-specific conditions JncHudJng the thickness of the

unconsolidated and the aquifer presence of fractured bedrock. This option

is eliminated.

Heat - This option would apply heat to the DNAPL sources to mobilize to

collection/extraction points. It is eliminated for the same reasons as steam.

Surfactants - This option would inject surfactants into the DNAPL source

to mobilize to extraction points. Therefore, it is eliminated for the same

reasons as the steam and heat options.

On-Site Discharge:

groundwater would be piped to an on-site stream. This technology is

retained for further evaluation.

Off-Site Discharge:

POTW - Under this technology, treated

would be piped to a publicly owned treatment WQiJks (POTW). A new

piping system would have to be constructed to transport the treated

the discharge before POTW would accept it. The city of Milford has a

secondary wastewater treatment facility which may accept treated

mmctmimmilMft 4 discharge. This technology is retained for further

evaluation.

Pipeline to River - is retained because of proximity to the Souhegan River.

The Souhegan River is a Class B waterway and currently receives

discharges from a number of point sources, This technology would

discharge uncontaminated water that would be combined with

presentment and treated waste would meet criteria levels established bv

the permitting authority. This technology would have to be designed to

meet the requirements of the NPDES prof

2176-160/HAZ-5254 2-55

RCRA Facility - This option would involve either bulk transport or

pumping via a pipeline to a RCRA TSD facility. This option is retained.

Containment/Diversion

a. Capping:

Multi-layer Cap - This option involves constructing a composite cap of low

permeability soil over an FML to contain source areas in the vadose zone.Since there is no well defined source area in the vadose zone, this option is

eliminated.

Permeable Cap - This option involves construction of a permeable soilcover over a source area in the vadose zone, and is eliminated for the samereason as the multi-layer cap.

b. Vertical Barriers:

Grout Curtain - This is a barrier wall created by drilling a series ofadjacent, overlapping bore holes and filling them with a relatively

impermeable material, usually a fluid which sets and hardens. These walls

are usually placed at least two or three rows deep. Grout curtains areconsidered as a possible method for containing contamination migration in

the vicinity of O.K. Tool, and are therefore retained.

Slurry Wall - Slurry walls are subsurface barriers designed to reducegroundwater flow in unconsolidated earth materials. The term slurry wall

can be applied to a variety of barriers all having one thing in common: theyare all constructed in a vertical trench that is excavated under a slurry. Thisslurry, usually is a mixture of bentonite and water, acts essentially like adrilling fluid. It hydraulicaUy shores the trench to prevent collapse, and, atthe same time, forms a filter cake on the trench walls to prevent high fluidlosses into the surrounding ground. Slurry wall types are differentiated by

the materials used to backfill the slurry trench. Most commonly, an

engineered soil mixture is blended with the bentonite slurry and

2176-160/HAZ-5254 2-56

placed in the trench to form a soil-bentonite slurry wall. In some cases, the

trench is excavated under a slurry of portland cement, bentonite, and water,and this mixture is left in the trench to harden into a cement-bentoniteslurry wall. In the rare case where great strength is required of a subsurfacebarrier, pre-cast or cast-in-place concrete panels are constructed in thetrench to form a diaphragm wall. Slurry wall is retained.

Sheet Piling - Sheet piling is a horizontal groundwater barrier technique <£. %>whereby sheets of material are driven vertically into the ground surface.Sheet piles can be made of wood, pre-cast concrete, or steel. Sheet piling iseliminated retained, for potential application in areas of the site wheredepths to bedrock are not excess and boulder zones are not present.

Bottom Seal Grouting - is eliminated because this technology is difficult toemploy and nearly impossible to ensure integrity has been accomplished.

c. Groundwater Control Barriers:

Injection Well System - This option involves the injection of water into

wells to alter the hydrodynamics of the aquifer (i.e., divert the direction andrate of groundwater flow). Injection wells are retained.

Groundwater Interceptor Trench - Groundwater interceptor trenches aresubsurface drains which include any type of buried conduit used to conveyand collect aqueous discharges by gravity flow. Interceptor trenchesessentially function as an infinite line of extraction wells. They areimplementable to depths of 25 to 30 feet below ground surface. Since theupper aquifer is contaminated to depths of approximately 90 to 100 feetbelow ground surface, this option is eliminated.

Infiltration/Recharge Basin - is retained because this technology is used fordischarge of clean surface water/groundwater flush contaminated

groundwater, or to form a hydraulic barrier.

2176-160/HAZ-5254 2-57

- it retained. The technology womU remove cleat waterto produce a hydraulic barrier and limit arigratiom of contaminatedgroundwater.

d. Surface Controls: This option involves the use of dikes and berms to protectstructural components from the 100-year flood plain. Dikes and berms arewell-compacted earthen ridges or ledges constructed immediately upslope from or

along the perimeter of disturbed areas (e.g., disposal sites). These structures aregenerally designed to provide short-term protection of critical areas by interceptingstorm run-off and diverting the flow to natural or manmade drainage ways, to

stabilized outlets, or to sediment traps. The two terms, dikes and berms, aregenerally used interchangeably; however, dikes may also have applications asflood containment levees. Therefore, dikes and berms are retained for further

evaluations.

Collection/Ire atment/Discharge

a. Groundwater Extraction Wells: This option involves a series of wells to extractcontaminated groundwater, and is retained.

b. Chemical Treatment:

• Solvent Extraction - Solvent extraction is a process involving the solution ~7(of contaminants into solvent. It involves mixing the liquid waste streamwith solvent then by raising the temperature. the contaminants

preferentially solubilize into the solvent. Water/solvent mixture isseparated into two layers in the separator and the solvent containingcontaminants continues in the process into a heat exchanger. Thetemperature of the solvent is decreased to the point where the contaminantsare no longer soluble in the mixture forming two layers. This option is notfeasible due to contaminant concentrations being too low to meet influentrequirements f and is therefore eliminated.

• Coagulation/Flocculation/Precipitation - is a series of physical treatmentprocesses which are used to enhance sedimentation or clarification andcould be used as a pretreatment technology for removal of metals ingroundwater. The waste stream is mixed while a coagulant

2176-160/HAZ-5254 2-58

is added. Coagulants adhere readily to suspended solids and with eachother (agglomerate) so that the resultant particles are too large to remain insuspension. Flocculation is primarily used to enhance precipitation of

inorganics such as metals. Slow mixing is provided by a mixing paddle.

Coagulation/Flocculation/Precipitation technologies are retained for furtherevaluation as a pretreatment process for removing metals and solids

including iron and manganese.

Sequestering - Sequestering is a process whereby chemicals are added tobind up certain constituents by forming complexes. Typically this processis targeted to soluble iron and manganese at low to moderate levels andtherefore is retained for further evaluation as a pretreatment technology.

Ion Exchange - Ion exchange is a process whereby selected contaminantions are removed from the aqueous phase and replaced by less toxic ions

held by ion exchange resins. Ion exchange resins are primarily syntheticorganic materials containing ionic functional groups. Resins with

negatively charged sites are cation exchangers because they absorbpositively charged ions. Anion exchangers contain positively charged sites

and, consequently, take up negative ions. Ion exchange is retained because

this technology is applicable to removing iron and manganese which mayfoul other operational units.

Electrolysis - In this process cathodes and anodes are immersed in a tankcontaining a waste to be oxidized, and a direct electrical current is imposed

on the system in order to decompose the contaminant material. During thedecomposition, metals present are plated out on the cathodes. Electrolysis

is used to treat high concentrations (up to 10 percent) of cyanide and toseparate metals to allow their potential recovery. This process needs aseparate arrangement for each metal.

2176-160/HAZ-5254 2-59

Limitations on this process include the physical form of feed (solids must

be dissolved), nonselective competition with other species and long processtimes. This technology is not applicable for the contaminants present in

dilute form in groundwater at the site and is therefore eliminated fromfurther evaluation due to technical feasibility concerns.

- The iOtfox Ultravioletcombine* chemical oxidation with ultraviolet photoysis to destroy ordetoxify hazardous chemicals in aqueous solutions. Ultraviolet tightsignificantly enhances ozone or hydrogen peroxide reactMty and excitesthe organic contaminants to a higher energy level which enhances therate of transformation. This process option has Umited effects on highlyturbid solutions. This process has a high capital cost and its operationcost varies with contaminated groundwater quaSty. This option is

Surfactants - This option would inject surfactants into the sediment orbedrock to mobilize the DNAPL to cottectionlextraction points. Theoption has been retained for further review.

Steam Stripping - Steam stripping is a physical treatment which uses steam

to evaporate volatile organics from aqueous wastes. Steam stripping is

essentially a continuous fractional difttjj^jfln process carried out in apacked bed or tray tower. Steam provides direct heat to the column in

which gas flows from the bottom to the top of the tower. The resultingresiduals &re contaminated steam condensate, recovered solvent and treatedeffluent. The organic vapors are sent through a condenser in preparationfor further treatment. The bottoms require further treatment such as

incineration, carbon adsorption or land disposal.

Steam stripping will treat less volatile and more soluble wastes than airstripping will and can handle a wide concentration range (e.g., from lessthan 100 ppm to about 10 percent organics'). The steam stripping processmay require air pollution controls to eliminate toxic emissions. Thecontaminants present in Savage Well site groundwater ajg air strippable.

2176-160/HAZ-5254 2-60

Steam stripping is normally used when the organic contaminants present in

groundwater are not removable by conventional air stripping. Steam

stripping may be cost-effective if a source of steam is available. It is

retained for further evaluation.

• Air Stripping - Air stripping is a mass transfer process in which volatile

organic contaminants in groundwater are transferred to the gaseous (vapor)

phase. Factors affecting the removal of specific organics from groundwater

include temperature, pressure, air to water ratio and surface area available

for mass transfer. Air to water volumetric ratios may range from 10:1 to

300: lr and are typically 50:1. A packed column or tower with an air blower

with countercurrent flow of air to water is commonly used. The products

are the effluent and the contaminated off gas or vapor phase.

Air stripping is retained because this technology is used to treat aqueous

organic wastes with relatively high volatility, low water solubility and

aromatics. The volatilized hazardous material may tritt require subsequent ~~[ H.

treatment (carbon adsorption, for example).

• Oxidation/Reduction - Oxidation and reduction are processes which are

utilized to change the chemical form of a hazardous material in order to

render it less toxic or to change its solubility, stability, separability or

otherwise change it for handling or disposal purposes. In any oxidation or

reduction reaction the oxidation state of one compound is raised (i.e.,

oxidized) while the oxidation state of another compound is lowered (i.e.,

reduced). The reaction can be enhanced by catalysis, electrolysis or

irradiation. Common commercially available oxidants include potassium

permanganate, hydrogen peroxide, calcium or sodium hypochlorite and

chlorine gas.

This treatment may be applied to chemicals such as hexavalent chromium,

mercury and lead. It is likely that other treatment processes may be used in

conjunction with chemical reduction. The waste composition must be well

known to prevent the inadvertent production of a more toxic or hazardous

end product. This technology is not applicable for the contaminants present

at the site and is therefore eliminated from further evaluation due to

technical feasibility concerns.

2176-160/HAZ-5254 2-61

Wet Air Oxidation - This option detoxifies wastes through the addition of

oxygen, pressure and heat within a vessel. This is eliminated because theinfluent levels do not meet the minimum concentration requirements.

Neutralization - Neutralization is used to eliminate or reduce the reactivity

and corrosiveness of contaminated groundwater and/or treated groundwater

for final disposal and could be used as a pretreatment technology for

removal of metals in groundwater. Residuals include a neutral effluent

containing dissolved salts and only precipitated salts. pH adjustment is a

partial neutralization process which makes the waste stream either more

acidic or more alkaline to enhance chemical, biochemical reactions, and

precipitation. When pH is adjusted by adding C(>2 the process is called

recarbonation. During this process excess calcium present in the

groundwater will precipitate as CaCC^. Groundwater may require

neutralization prior to discharge. This process would be required as part of

chemical precipitation using excess lime and is therefore retained for

further evaluation.

In-situ Chemical Treatment - is eliminated because many techniques to

hazardous waste disposal site reclamation are conceptual or in the

developmental stage.

c. Physical Treatment:

Sedimentation - Sedimentation is the separation from water by gravitational

settling, of suspended particles that are heavier than water. This technology

must be used in conjunction with other applicable technologies to be

effective. Sedimentation is retained as a separation process only.

Filtration - Filtration may be a major treatment component to remove

precipitated metals and suspended solids. It can also be used as a polishing

step for treated waste effluent. It is retained for removing suspended solids

and dewatering sediments of sludges from other aqueous waste treatment

processes.

2176-160/HAZ-5254 2-62

Carbon Adsorption - Carbon adsorption is a physical treatment processinvolving adsorption of chemical contaminants onto activated carbon. Itinvolves contacting a liquid or vapor waste stream with the carbon, usuallyby flow through a series of packed bed reactors. The activated carbonselectively adsorbs hazardous constituents in the aqueous wastes by a

surface attraction phenomenon in which the organic molecules are attracted

to the internal probes of the carbon granules. Adsorption depends on the

strength of the molecular attraction between adsorbent and adsorbate,molecular weight, type and characteristics of adsorbent, electrokineticcharge, pH, and surface are. Once the micropore surfaces are saturatedwith organics, the carbon is "spent" and must either be replaced with fresh

carbon or removed, thermally regenerated, and replaced.

Activated carbon absorption is a well developed technology which iswidely used in the removal of the volatile and semivolatile organics.Carbon adsorption is retained because this process can be used to treatsingle-phase aqueous organic wastes with high molecular weight and

boiling point and low solubility and polarity, chlorinated hydrocarbons andaromatics. It can also be used to capture volatile organics in gaseous

mixtures.

Solvent Separation/Recovery - Solvent Separation/Recovery is eliminated

because concentrations of contaminants in the groundwater are not high

enough for this technology.

Reverse Osmosis - Reverse osmosis is a process in which water isseparated from dissolved salts in solution by filtering through asemipermeable membrane at a pressure greater than the osmotic pressurecaused by the dissolved salts in the wastewater. With existing membranesand equipment, operating pressures vary from atmospheric to 10,000

*y *ykN/m'1 (1000 lb/inz). Reverse osmosis is retained because this technologyis applicable to organic components.

Ultrafiltration - Ultrafiltration is a similar process as reverse osmosisexcept operated at a much lower pressure and therefore is retained for thesame reasons as reverse osmosis.

2176-160/HAZ-5254 2-63

Dissolved Ak Flotation - In dissolved-air flotation systems, air is dissolvedin the wastewater under a pressure of several atmospheres, followed byrelease of the pressure to the atmospheric level. In small pressure systems,the entire flow may be pressurized by means of a pump (40 to 50 Ib/in2

gage) with compressed air added at the pump suction. The entire flow isheld in a retention tank under pressure for several minutes to allow time forthe air to dissolve. It is then admitted through a pressure-reducing valve to

the flotation tank where the air comes out of solution in minute bubblesthroughout the entire volume of liquid. Dissolved air flotation is eliminatedbecause this technology is normally used for emulsified oils or organicliquids, typically found in municipal waste leachate or petroleum waste not

found at the Savage Well site.

Distillation - Distillation is a physical separation process whereby a liquidis alternately heated and then cooled to achieve separation. Distillation iseliminated because the concentration of contaminants present in

groundwater at the Savage Well Site, is too low to be effective.

Evaporation - Evaporation, like distillation, is a physical separationprocess; however, the liquid is heated and completely evaporated until only

solids remain. Evaporation is eliminated for the same reason as distillation.

Thermal Mobilization - This option would apply heat to the sediment orbedrock to mobilize the DNAPL to collection/extraction points. Thisoption has been retained.

Solvent Extraction - Solvent extraction is a process that involvesdissolving the contaminants into an injected solvent. It involves mixingthe liquid waste stream with solvent then by raising the temperature, thecontaminants preferentially solubilize into the solvent. Water/solventmixture is separated into two layers in the separator and the solventcontaining contaminants continues in the process into a heat exchanger.The temperature of the solvent is decreased to the point where thecontaminants are no longer soluble in the mixture forming two layers.This option is potentially applicable for the removal of DNAPL and istherefore retained.

2176-160/HAZ-5254 2-64

Steam Stripping - Steam stripping is a physical treatment which usessteam to evaporate volatile organics from aqueous wastes. Steamstripping is essentially a continuous fractional distillation process carriedout in a packed bed or tray tower. Steam provides direct heat to thecolumn in which gas flows from the bottom to the top of the tower. Theresulting residuals are contaminated steam condensate, recovered solventand treated effluent. The organic vapors are sent through a condenser inpreparation for further treatment. The bottoms require further treatmentsuch as incineration, carbon adsorption or land disposal.

Steam stripping will treat less volatile and more soluble wastes than airstripping will and can handle a wide concentration range (e.g., from lessthan 100 ppm to about 10 percent organics). The steam stripping processmay require air pollution controls to eliminate toxic emissions. Thecontaminants present in Savage Well site groundwater are air strippable.Steam stripping is normally used when the organic contaminants presentin groundwater are not removable by conventional air stripping. Steamstripping may be cost-effective if a source of steam is available. It isretained for further evaluation.

Air Stripping - Air stripping is a mass transfer process in which volatileorganic contaminants in groundwater are transferred to the gaseous(vapor) phase. Factors affecting the removal of specific organics fromgroundwater include temperature, pressure, air to water ratio andsurface area available for mass transfer. Air to water volumetric ratiosmay range from 10:1 to 300:1, and are typically 50:1. A packed columnor tower with an air blower with countercurrent flow of air to water iscommonly used. The products are the effluent and the contaminated offgas or vapor phase.

It is not anticipated that elevated levels of organic compounds other the 7 (-.VOCs exist in the groundwater at the site, however, there is no currentlyavailable data regarding other compounds (i.e., BOD, COD, or TOCanalyses). Should analytical data obtained during design indicateelevated levels, it is possible that the treatment system would need to bemodified.

2176-160/HAZ-5254 2-65

Air stripping is retained because this technology is used to treat aqueousorganic wastes with relatively high volatility, low water solubility andaromatics. The volatilized hazardous material may wiO requiresubsequent treatment (carbon adsorption, for example).

2176-160/HAZ-5254 2-66

d. Biological Treatment:

Rotating Biological Contactors - A rotating biological contactor (RBC)

consists of a series of closed spaced circular disks of polystyrene or

poly vinyl chloride. The disks are partially submerged in water to be treated

and rotated slowly through it. In operation, biological growths become

attached to the surfaces of the disks and eventually form a slime layer over

the entire wetted surface area of the disks. The rotation of the disks

alternately contacts the biomass with the organic material in the wastewater

and then with the atmosphere for adsorption of oxygen. The disk rotation

affects oxygen transfer and maintains the biomass in an aerobic condition.

The rotation also is the mechanism for removing excess solids from the

disks by the shearing forces it creates and maintaining the sloughed solids

in suspension so they can be carried from the unit to a clarifier. Rotating

biological contactors is generally used for secondary treatment, and they

can also be operated in the seasonal and continuous-nitrification modes.

RBC is retained.

Lagoons (Aerated-Aerobic) - Lagoons (Aerated-Aerobic) are essentially the

same as the conventional extended-aeration activated-sludge process,

except that an earthen basin is used for the reactor, and the oxygen required

by the process is supplied by surface or different aerators. Lagoons

(Aerated-Aerobic) are retained.

Lagoons (Anaerobic) - Anaerobic lagoons are primarily used for the

treatment of high-strength organic wastewater. Typically, an anaerobic

lagoon is a deep earthen pond with appropriate inlet and outlet.

Stabilization is brought about by a combination of precipitation and the

anaerobic conversion of organic wastes to CC>2, CH^, and other gaseous

end products. Lagoons (Anaerobic) are eliminated in groundwater because

the organic concentration is insufficient to maintain the biomass needed for

this process.

2176-160/HAZ-5254 2-67

Constructed Wetlands - Constructed wetlands provide an environment formicrobial treatment of VOCs under anaerobic conditions. The treatmentprocess takes place predominantly in a greenhouse where climate andvegetation control allows high level of contaminant treatment year-round.The primary mechanism for treatment is breakdown of the compounds by

naturally occurring micro-organisms in the sediments and around the plant

roots within the system. Constructed wetlands are retained.

In-situ Biodegradation - it eSmmuOed be&uue of the difficulty intiodegradmg chlorinated camfoumdtt lack of technology development

pertaining to in-situ biodegradation in the groundwater.

Packed Bed Reactor - Typically, a packed-bed reactor consists of acontainer that is packed with a medium to which nitrifying microorganismscan become attached to water to be treated is introduced from the bottom ofthe reactor and air or pure oxygen is also introduced from the bottoms.

Packed bed reactor is retained.

Enzymatic Degradation - Enzymatic degradation is a bioremediationprocess whereby specific enzymes are introduced to a reactor containingwater to be treated. The enzymes function as catalysts in breaking down

the contaminants. Enzymatic degradation is eliminated because this

technology is used primarily for degradation of pesticide diazinon.Pesticide contamination is not a problem at the Savage Well Site.

e. On-Site Discharge:

Discharge to Local Stream - Under this technology, treated groundwater

would be piped to an on-site stream. This technology is retained for further

evaluation. Discharge would be required to meet the substantiverequirements of an NPDES permit.

2176-160/HAZ-5254 2-68

Discharge to Recharge Well - A recharge well re-injects treatedgroundwater back into the on-site aquifer. This technology is beingretained for further evaluation. The substantive requirements of agroundwater discharge permit need to be met.

Discharge to Leachfield - A leachfield consists of a series of wrapped

perforated pipe laid beneath the surface in highly permeable soil, typicallycoarse sand or gravel. Treated groundwater effluent is pumped to thebackfield where the water is transmitted back into the ground through theperforated pipe. This technology is retained for further study. The

substantive requirements of a groundwater discharge permit may need to bemet.

f. Off-Site Discharge:

Discharge to POTW - Under this technology, treated groundwater would bepiped to a publicly owned treatment works (POTW). A new piping systemwould have to be constructed to transport the treated groundwater.

Pretreatment standards must be reached by the discharge before POTW

would accept it. The city of Milford has a secondary wastewater treatmentfacility which may accept treated discharge.

This technology is retained for further evaluation.

Discharge to River - is retained because of proximity to the SouheganRiver. The Souhegan River is a Class B waterway and currently receivesdischarges from a number of point sources. This technology would becombined with pretreatment and treated waste would meet criteria levels

established by the permitting authority. This technology would have to bedesigned to meet the requirements of the NPDES program.

Discharge to RCRA Facility - Under this technology, treated groundwaterwould be transported to a RCRA TSD facility. This option is retained.

2176-160/HAZ-5254 2-69

g. Collection of Treatment Residuals: Thjft option involves collection of treatmentresiduals for off-site disposal at a RCRA landfill. This option is retained.

RCRA Landym - The material womld be hamled to am, existing RCRASubtitle C landfill facility which is already permitted to accept hazardousmtaterials. The land disposal restrictions may impact off-ale ImdfHKng.This technology is rejamed. for father study.

Subtitle D Solid Waste FaciEtv - This option may be noble for disposal oftreatment residuals and has between reJsmfd for further study.

2.4.2 FfeaihutJCTi <?f Ricannlia1! Te^himlogjes and Prongs Option*

The technology types and process options which were carried forward from the initialimplementability screening were evaluated a second time to determine their ability to meet threenew sets of criteria. This technology evaluation compared specific technologies and processoptions within a general response action category against one another and against the threecriteria identified below. The three criteria used to conduct this second phase of the technology

evaluations were effectiveness, implementability, and cost. These criteria are defined in theNCP (40 CFR 300.430(e)(7), as follows:

• Effectiveness - This criterion focuses on the degree to which an alternative reducestoxicity, mobility, or volume through treatment, minimizes residual risks andaffords long-term protection, complies with ARARs, minimizes short-term

impacts, and how quickly it achieves protection. Alternatives providingsignificantly less effectiveness than other more promising alternatives, may beeliminated. Alternatives that do not provide adequate protection of human healthand the environment shall be eliminated from further consideration.

• Implementability - This criterion focuses on the technical feasibility and

availability of the technologies each alternative would employ and theadministrative feasibility of implementing the alternative. Alternatives that aretechnically or administratively infeasible or that would require equipment,specialists, or facilities that are not available within a reasonable period of timemay be eliminated from further consideration.

2176-160/HAZ-5254 2-70

• Cost - The costs of construction and any long-term costs to operate and maintain

the alternatives shall be considered. Costs that are grossly excessive compared to

the overall effectiveness of alternatives may be considered as one of several factors

used to eliminate alternatives. Alternatives providing effectiveness and

implementability similar to that of another alternative by employing a similar

method of treatment or engineering control, but at greater cost, may be el:minated.

Figure 2-4 presents the evaluation of remedial technologies and process options for

groundwater general response actions. Under the Collection/Discharge general response action,

off-site disposal at both a RCRA facility and POTW were eliminated due to their relatively low

implementability compared to discharge into the river. The POTW does not have the built-in

capacity to handle large flows of water anticipated from groundwater recovery and treatment.

Due to the distance of the RCRA facility from the site, this response action has low

implementability. Under Collection/Treatment/Discharge,. ion exchange was eliminated due to

low effectiveness r which is dependent on the level of ion interference, and the high capital and

Q&M COStS. _ Grout curtains and slurry walls were each eliminated due to both low

implementability and effectiveness, particularly given site-specific conditions including depth to

bedrock (greater than 80 feet) and the presence of a pervasive boulder zone at O.K. Tool. Both

reverse osmosis and ultra filtration were eliminated due to their relatively low implementability

and dependence on pre-treatment.

2.43 Selection of Repreg*^"*"'iv? T^fmnloyiey q j Process Options

Sections 2.4.1 and 2.4.2 of this report document the identification, screening, and

evaluation of potentially applicable remedial technologies and process options conducted for

groundwater at the Savage Well site. This process has resulted in the selection of a

representative group of technologies and process options for subsequent use in assembling,

screening and evaluating remedial alternatives suitable for protecting human health and the

environment. The representative technologies and process options selected for use in developing

remedial alternatives are summarized in Figure 2-5.

2176-160/HAZ-5254 2-71

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11

GROUNDWATER REMEDIALRESPONSE ACTIONS TECHNOLOGY

No Action

LimitedAction

Containment/Diversion

Collection/

Treatment/

Discharge

Coin

hm

1;1 u .

Monitoring

AlternateWater Supply

InstitutionalControls

Vertical Barriers

Control Barriers

SurfaceControls

GroundwaterExtraction Wells

/-u • i

-i

i '\

Kinued onext page

PROCESSOPTION

REFERENCEPROCESS OPTIONS NUMBER

GroundwaterMonitoring

GroundwaterMonitoring

Town WaterSupply

DeedRestrictions

Purchase ofGroundwater Rights

Sheet Piling

InjectionWell Systems

Extraction Wells

Dikes andBerms

ExtractionWells

1

2

3

4

5

6

7

8

9

10

Coagulation/Flocculation/Precipitation 1 1

Sequestering

Neutralization

Surfactants

UltravioletOxidation

12

13

14

15

2776-5/97

FIGURE 2-5 (Page 1)REPRESENTATIVE REMEDIAL TECHNOLOGIES

AND PROCESS OPTIONS GROUNDWATER

PROCESSOPTION

GROUNDWATER REMEDIAL REFERENCERESPONSE ACTIONS TECHNOLOGY PROCESS OPTIONS NUMBER

Collection/ — '

•

Discharge —

On-siteDischarge

Off-siteDischarge

Collection of Off-siteTreatment Residuals Disposal

Sedimentation

Filtration

CarbonAdsorption

Steam Stripping

Air Stripping

Solvent Extraction

Thermal Mobilization

Rotating BiologicalContactors

Lagoons(Aerobic)

ConstructedWetlands

Packed BedReactor

Local Stream

RechargeWell

Leachfield

Pipeline toRiver

RCRA Landfill

Subtitle DSolid Waste Facility

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

2776-5/97

FIGURE 2-5 (Page 2)REPRESENTATIVE REMEDIAL TECHNOLOGIES

AND PROCESS OPTIONS GROUNDWATER

SAVAGE MUNICIPAL WATER SUPPLY SITECOMMENTS ON CHAPTER TWO

33. Delete Pages 2-1, 2-2, 2-3, 2-4, and the first paragraph of 2-6. Replace it with twosections that have similar text and tone to the attached pages which are from the DoverFS. (These were furnished on April 22,1991.)

Pages have been deleted and new text added. See page 2-1.

34. If HMM needs to have a Figure 2-1, a map showing the complete extent of contaminationvs the area of the aquifer that is presently usable for drinking water can be inserted.

New Figure 2-1 has been included. See page 2-8.

35. Page 2-6, Section 2.2.1 Contaminants of Interest:

This whole section needs to be rewritten. The subject is contaminants of interest only. Itshould address the contaminants in each medium or location and not add all the extra junkof exposure scenarios, state laws, well ownership, etc. Example: the overall objectivesare "to protect human health and the environment"... delete "to reduce to public health andwelfare and to the environment."

Section has been rewritten. See page 2-7.

Page 2-6r 3rd Paragraph:

Delete the paragraph. While HMM and the PRPs attempt to place perspective on thegroundwater issue, the attempt falls far short of meeting the goal. There is no need todiscuss objectives here, especially when the objectives are not in agreement with theNCP. See guidance for full explanation. Further, the second sentence is a confusion ofthe general goal of groundwater policy and the process for developing and screeningalternatives. The examples of specific remedial action objectives can be found in Table4-1, Guidance for Conducting Remedial Investigations and Feasibility Studies underCERCLA.

Paragraph has been deleted. Seepage 2-8.

36. Page 2-6r Last Paragraph:

Add the rest of the criteria from guidance used to determine contaminants of interest.

Delete the discussion on objectives, "The remedial response... to ...exceed referencedoses." This should be stated elsewhere, and when it is stated the word "response" shouldbe changed to "action."

Discussion deleted.

Rewrite this entire section, draw from the Risk Assessment. Simply cite the contaminantsof interest, why and how selected.

Section rewritten-See Page 2-8.

2176-160/HAZ-5231 -1-

37. Page 2-7:

The top of page can be retained. Delete the paragraph which ends: "...adjacent to theHitchiner plant." The compound TCA should not treated any differently from the others.Why is this treated differently from the four above? It is irrelevant that it was found inone well, it still needs to be cleaned up. It was found above MCLs. Put it with the others.

The remaining part of the page from "The Savage well was used..." is to be deleted. Thissection deals with contaminants of interest not: ownership of a well, remediationobjectives, AWQCs which are ARARs, and other matters.

Changes and deletions made. See pages 2-8,2-10.

40. Page 2-8:

Delete the entire page. Rewrite! Present the clean up levels as MCLs! The goal of theNCP is to clean up where possible. That is the point of departure. The text should reflectthat the basis of cleanup is future residential and to restore the aquifer to drinking waterquality.

Page rewritten. See pages 2-10,2-11,2-12.

41. Page 2-9:

The first sentence is incorrect based on the existing Risk Assessment. A hazard index ofover 20 exists on the OK Tool property. A level of 24 ppm of PCB exists adjacent to theHendrix property. The section needs to be rewritten to reflect the Baseline RiskAssessment.

Sentence revised. See pages 2-11,2-12.

The report ignores future residential use scenario. Refer to the Baseline RiskAssessment. The following hazard indices exceed unity:

OK Tool, Future Residential UseArsenic -1.1Chromium -16

OK Tool, Present UseChromium - 2.9

A clean up level of about 400 ppm for chromium would reduce the hazard index to 1 (one)assuming all hexavalent chromium. If the sampling cannot be done in time for enabling abetter analysis of risk the FS will have to go forward with existing data. This would meansoil cleanup.

Second Paragraph:

This does not agree with the Baseline Risk Assessment. Read the BASELINE RISKASSESSMENT. The word "hypothetical" is not to be used.

Discussion of Risk Assessment has been revised. See page 2-12.

2176-160/HAZ-5231 -2-

42.a Page 2-9. 3rd Paragraph:

The Ecological Risk Assessment should not be concluding "any appropriate response."Delete the sentence and it will also be deleted from the Eco Risk. The response objectivesshould address the results of the Eco Risk not conclusions which the contractor should nothave made.

Sentence deleted. See Page 2-13.

42.b Page 2-9.4th Paragraph and Last Paragraph: See Page 2-13.

Delete the first sentence and rewrite it. The sentence is meaningful only in broad terms,based upon the premise that MCLs will not be applicable. Facts need to be given.Provide details on what happened at OK Tool, by who, quantities of soil, where disposedof treated, etc. What were the clean up levels, who established clean up levels and how?

Sentence deleted and rewiiueu. Revised text refers to RI and previous reports. SeePage

43. Page 2-10, Item 2:

Delete. This is not pertinent to section.

Bern deleted. See Page 2-13.

44. Page 2-10 to 2-12, Soils Discussion:

Can the Sommers model be used for Arsenic?

Based on the references for the Summers model provided by EPA, the model can be used forboth organic and inorganic compounds. HMM does not know of a reason for excluding arsenic.

How can two clean up levels be developed for same soil. It would appear that the levelsfor under the building should be same as rest of data. What if building is removed infuture?

The levels nnilff the building are different because a different area of contamination is assumed.

The tea* has been revised to more clearly explain mis. See Page 2-14.

The information on the Sommers model should be in Section 2.2.3 not here.

The discussion has been retained here because it is used to «fa*BHnmi» contaminants of interest.Some revisions to discussion have been made as requested at the 4/26/91 EPA meeting.

Last Paragraph,. First Sentence:

Correct typo - "indicted" should be "indicated."

Typo corrected. See Page 2-15.

2176-160/HAZ-5231 -3-

45. Page 2-12.2nd Paragraph:

Second sentence, delete it. The use of MCLs are not restricted just because the surfacewater has low potential for drinking water use. If the town decides in the future to usesurface water downstream of the site, MCLs would be required. There are only MCLs andAWQCs. Both would seem to have pertinent input to the evaluation of surface water. Aslong as there is potential for use as drinking water, MCLs are relevant and appropriate.

Sentence deleted. See Page 2-17.

Delete the word "applicable" before ARARs in the next to the last sentence.

"Applicable" deleted. See Page 2-17.

46. Page 2-12. Last Paragraph:

The baseline risk assessment does not have as a purpose to analyze the relationship of thedischarge stream and the aquifer. Delete the sentence. Rewrite the paragraph. Theconclusion on page 2-13 should be deleted and rewritten.

Discussion revised. Deletions made. See Page 2-17.

47. Page 2-13f Last Paragraph:

See Risk Assessment for information on air. AALs are not completely accepted by NH.Rewrite this paragraph to use info from Risk Assessment. See also comments previouslyfurnished on Ch. 1.

Paragraph revised. See Page 2-18.

48. Page 2-14. Section 2.2.2:

This should be retitled to Applicable or Relevant and Appropriate Requirements (ARARs).

Tide changed. See Page 2-19.

Delete the first paragraph. Replace with the following.

In order to develop remediation goals for the Savage Municipal Water Supply Site,chemical and location specific ARARs were evaluated. The NCP (40 CFR Part 300.5)defines ARARs as "Applicable" or "Relevant and Appropriate Requirements." Inaccordance with the NCP the following definitions are used to define "Applicable" and"Relevant and Appropriate." Please quote the NCP for the definitions.

Paragraph deleted and replaced with above text. See Page 2-19.

After the definitions a discussion on the types of ARARs, determination of relevance, etc.,TBCS, and then identifying the tables containing the ARARs should be done. See pagexiii and xiv of August 1988 draft ARARs guidance for help, CERCLA Compliance withOther Laws Vol. 1.

Discussion added. See Page 2-19.

2176-160/HAZ-5231 -4-

49. Page 2-15:

Information on Sommers model belongs here. The section should not use source controls,the focus is clean up by media or operable unit which leads into remedial actionobjectives. This would lend itself to addressing the concentrated plume and the diluteplume separately even though diey are in the same media.

The Summers model is presented in Section 2.2.1. to evaluate contaminants of interest.

It would appear the Source Control Objectives should be changed to Sediment. Use theguidance as was done in Management of Migration Objectives. Additionally if thechromium and arsenic issue at OK Tool and PCB issue at Hendrix is not resolved thenthose two locations would mean a soil medium for remediation goals.

This section has been eliminated as contaminants of interest and remedial objectives areidentified only for groondwater.

5th Paragraph:

Rewrite, the first sentence dealing with EPA cleanup goals. The point of departure is 10to the minus six. The remaining sentences are redundant. This is supposed to have to dowith goals not summations of why nothing needs to be done.

This section has been eliminated as no contaminants of interest and remedial objectives

The risk being discussed here and on page 2-27 is ecological risk. Where are die risksidentified in base line health risk assessment? Do they require remedial action objectivesfor source control in the media of concern?

This section has been eliminated as no contaminants of interest and remedial objectivesare identified only for groundwater.

50. There are no comments available for the ARARs at this time. However page 2-25, NHAdministrative Code Part WS primary and secondary standards. The NH MCLs are notequivalent to SWDA MCLs. Also on the bottom of page RfDs and group potency factorswould be TBCs. Revise to EPA Cancer Potency Factors (first column). Third columnrevise to Potency Factors are developed by an EPA work group (CRAVED. Revisionsmade. See Table 2-4.

Page 2-24 is RCRA applicable to this site? RCRA is indkaitrd as applicable. See Table2-4.

Page 2-26, toluene has been lowered to 1 ,000 ppb. Previous correspondence has furnishedthe 1991 MCLs, please revise the Fed MCLs accordingly to reflect January 31, 1991revisions. Revision made. See Table 2-3.

51. Page 2-27:

The Eco Risk should not be recommending a response. Delete the sentence. The EcoRisk will be changed.

This section has been eliminated as no contaminants of interest and remedial objectivesare identified only for giuuudwalei.

2176-160/HAZ-5231 -5-

52. Page 2-27, 1st Paragraph:

This is the same as page 2-9. The subject is soils. Change the paragraph, see commentsabove, and to reiterate, this section develops clean up levels to attain remedial actionobjectives. Get rid of all the extraneous stuff included previously on page 2-9 and 2-10and rewrite concisely. Use the objectives from guidance as done for Management ofMigration.

Tins section has been eliminated as no contaminants of interest and remedial objectivesare identified only for groundwater.

53. Page 2-27. 3rd Paragraph:

The sentence on remedial objectives called out in the EPA guidance should be deleted.This is giving an incorrect impression of facts.

This section has been eliminated as no contaminants of interest and rrmetKrt objectivesare ui*Miifi«d only for groundwalei.

Item 1. Same as before, details are needed, who, what, where, what are the clean up levelsattained. Why does this have to be in two places in this chapter? It should only be in thechapter once.

This section has been rfimtMted as no contaminants of interest and remedial objectivesare identified only for groondwater.

Item 2. How is this relevant to this section?

Last paragraph. The statement concerning risk posed by the contaminants in soil ignoresthe baseline risk assessment (chromium in particular but also PCBs. This must be revisedto reflect the baseline risk assessment.

See above response.

54. Page 2-28:

First sentence regarding remedial objectives for source control: delete it.

This section has been eliminated as no contaminants of interest and remedial objectivesare identified only for gronndwater.

55. Page 2-28f 2nd Paragraph:

a. Change Management of Migration objectives to Groundwater.

Tide changed, See Page 2-35.

b. Delete the first sentence that begins: "As discussed previously..."

Sentence deleted. See Page 2-35.

c. This is an example of selective use of guidance. The guidance was not used forany other previous media. Why??

Nn mntammant* «f mten»«t «n» identified and then-fern no objective* developed far other media..

2176-160/HAZ-5231 -6-

d. Item 2. Why are MCLs left out from this item? Please insert.

MCLs have been inserted. See Page 2-35.

e. Item 3. This must be rewritten. Insert the following.

"Restore the groundwater to concentrations that comply with Federal and StateARARs, see table xxx for ARARs and table 2-4 which list MCLS." Replace xxxwith the proper table no.

Item 3 rewritten as requested. See Page 2-35.

56. Page 2-28r Last Paragraph:

This needs total rewrite. Refer to the groundwater policy in preamble to NCP page 8732.Free phase DNAPLs may extend the amount of time required for remedial activities theydo not preclude ever meeting the MCL goals.

Paragraph deleted. See Page 2-37.

57. Phase 2-29,1st Paragraph:

Same comment as directly above. The sentence should be modified to read: "they maynot be achievable, at least in the short term, for the concentrated plume wherecontaminants may exist as free phase DNAPLs."

Modification made. See Page 2-37.

58. Page 2-29, 2nd from Last Paragraph:

Change 19.448 pounds to 19,488 pounds.

Change made. See Page 2-37.

59. Page 2-32f 1st Paragraph,. 3rd Sentence:

This sentence states that the current condition and environmental fate are to be evaluated.Will this be done? Has it been done? If it is yet to be done the no action plan shouldprovide details.

Sentence deleted. See Page 2-40.

4th Paragraph:

First under Limited Action, last sentence. Delete: "by completed remedial action." Thistype of text confuses the facts by leading the reader to believe that the work was donepossibly as part of an EPA project.

Text deleted. See Page 2-40.

2176-160/HAZ-5231 -7-

60. Page 2-32. Last Paragraph:

Please delete the quote from the NCP as is and replace with entire quotation fromparagraph "(D)" on page 8846 of the NCP. The purposeful deletion of "The use ofinstitutional controls shall not substitute for active response measures..." is misleadingespecially in light of the remediation times which have recently been developed!

Quotation replaced. Sec Page 2-41.

Delete all statements that the Savage Well is not now being used for drinking waterpurposes. As long as the aquifer is a potential source of drinking water, the NCPmandates certain actions and standards.

61. Page 2-33. 1st Paragraph:

The intent here is not consistent with the NCP. Delete or revise to be consistent with theNCP. This paragraph explains how current risks were removed but not future potential.

Paragraph deleted. See Page 2-41.

62. Page 2-33T 2nd Paragraph:

a. The present ownership of the well does not in of itself preclude the future use ofthe well or of any adjacent properties. Ownership changes.

b. The 100 year flood "control" is incorrectly used. Env-Ws 373.05 states that thewell "casing" shall be above the 100 year flood. This is easily done, as it was withthe Savage Well by elevating or filling the area under the weU house. Take out thediscussion of the flood plain for the purposes of confusing the issue. Thus the PRPconclusion should be removed from the text.

Hood plain discussion deleted. See Page 2-42.

c. The Ws-309 citation is out of date. It should read Env-Ws 373.04. Citation notfound.

d. The zoning regulations can change and if water is desired enough the zoningregulations would possibly be the first item a local community would change.Thus a statement that zoning regulations can be easily changed by the localcommunity should be inserted.

Add the following to the paragraph. "Local zoning however may change in the future aswell as be overturned by the local zoning board of appeals."

Statement insetted See Page 2-42.

While the storage for treatment of hazardous materials shall be grounds for rejection, theydo not automatically result in rejection. Best management practices here in this aquifercould have involved a comprehensive monitoring program of the aquifer, identification offuture potential sources and enforcement of existing environmental laws.

Env-Ws 373.02 would also allow the Savage Well as it exists to be used with adequatetreatment, although adequate might be a difficult standard to guarantee and the existenceof other feasible sources may cause DBS to be very reluctant to grant approval. Shouldother sources become unfeasible in the future, this institutional control could cease. ThePRP Group is interpreting how an agency will decide an issue and has no authority to dothis. Thus the PRP argument should be removed from the text entirely.

2176-160/HAZ-5231 -8-

Paragraph deleted- See Page 2-42.

Env-Ws 373.04 Protective Radius - Chemicals. "The storage, treatment or use ofsignificant amounts of hazardous chemicals at any point tributary to the proposedgroundwater supply shall be grounds for rejection of the proposed source." The key wordshere would appear to be "any point tributary" and "significant." Were this aquifer in itspreexisting and natural condition, a supply could be developed in the area, perhaps at theexisting well head itself.

As HMM has pointed out in the Section 2.2.1 the industries have taken great care inreducing or eliminating the use of or disposal of hazardous materials. Please seeparagraph 1 on page 2-10, paragraphs 3 and 4 on page 2-12, and paragraph 1, 2, and 3 onpage 2-13. It would appear that from these representations that the industrial operationsdo not store, treat, or use significant amounts of hazardous materials.

The document is not to be an advocacy document. The use of partial quotes andmisleading interpretation should be stricken from the document wherever they occur.

63. Page 2-33. Noted Last Paragraph:

Change first sentence to: "...other controls proposed to be enacted where possible tofurther..."

Change made. See Page 2-42.

64. Page 2-34f Third Line:

Delete "if not eliminate."

Text deleted- See Page 2-42.

65. Page 2-34r 1st Full Paragraph:

Delete it, it is out of place.

Paragraph deleted. See Page 2-42.

66. Page 2-34r Collection Discharge:

Delete the sentence that begins: "Discharge to surface waters or..."

Sentence and entire section deleted (see comment 85b). See Page 2-43.

67. Page 2-36f Last Paragraph:

Delete the reference to the NCP, it is incorrect and not pertinent.

Reference deleted. See Page 2-45.

68. Page 2-38 r Section on Screening:

The screening out of technologies has been done to eliminate some which may be verywell used in one part of the aquifer while not able to be used in another part. For examplethe screening out of sheet piling may not be appropriate in an other part of the aquifer inwhich the depth to bedrock is less than 50 feet and there is no boulder zone. Sheet pilingthus should not be screened out except for the area of containment where the depths areexcessive.

2176-160/HAZ-5231 -9-

Sheet piling is retained. See Page 2-57.

69. Page 2-39:

The screening out of DNAPL enhancement processes is in question. It may be that theseshould not even be here so they can be included as a "to be determined" process option.These should be retained. See comments on page 2-45. It also appears inconsistent thatDNAPL technology would be screened out given the description and certainty which thePRP Group has inserted in Appendix A.

Enhanced DNAPL recovery processes have been retained under chemical and physicalCoDection/Treatment/Dischaige options. See Figure 2-3.

70. Page 2-40 r Figure 2-3. Page 2f Right Hand Column, 6th Set of Comment, Third Line,Bottom Seal Grouting:

Change "pressure" to "presence."

Change made. See Figure 2-3.

Under groundwater control barriers a new item must be added. The use of a withdrawalwell system to affect well capture zone or plume direction is possible and potentiallyapplicable to the dilute phone. The wells do not have to be in the plume itself and extractcontaminated water.

Extraction wells have been added under groundwater control barriers. See Figure 2-3.

71. Page 2-41. Solvent Extraction:

What about DNAPLs?

Solvent extraction retained as potentially applicable forDNAPLs. See Figure 2-3.

72. Page 2-42f Air Stripping:

Typo, wadste.

Correction made. See Figure 2-3.

73. Page 2-43. Figure 2-3f Page 5f Solvent Separation:

Is solvent separation/recovery not appropriate for DNAPLs or the concentrated plume?Prior to air stripping? Retained as Solvent Extraction. See Figure 2-3.

74. Page 2-44f Figure 2-3r Page 6r In Situ Biodegradation:

The screening must be site-specific.

Screened out due to difficulty of in-aim biodegradatiojLof site-specific chlorinated compounds.See Figure 2-3.

2176-160/HAZ-5231 -10-

75. Page 2-44. Figure 2-3. Page 6:

Collection of treatment residuals should include solid waste landfill for residuals. Someresiduals may not require a Hazardous waste landfill. Also a RCRA TSD facility shouldalso be included since land ban may dictate some treatment before disposal or landfill.

Solid waste landfill and RCRA facility included See Figure 2-3.

76. Page 2-45 r Top of Page. Item c:

Item c is not a remedial technology in of itself. If treatment on the well water to achieveclean up levels for surface or groundwater discharge is proposed then it could be retained.

Item deleted. See Page 2-54.

77. Page 2-45 f Bottom of Page. DNAPL Mobilization:

These should not be screened out, especially after the case is made for DNAPLs. See page416 of RI/FS guidance, right hand column, 1st full paragraph. These should be retainedbut not selected. Additionally if there is such fractured bedrock why isn't it addressed inthe RI and remediation objectives? What are the site-specific conditions HMM refers tothat make DNAPL so difficult to treat? Recovery is different from treatment.

Technologies have been retained under physical and chemical CoHectiao/Tieatmeitf/Disdiargeoptions. See Page 2-54.

78a. Page 2-46. Item d:

What about discharge to the ground?

Entire collection/discharge section has been deleted- see comment 85b. See Pages 2-54, 2-55.

78b. Page 2-46T Item e:

Is the pipeline to the river retained?

As above. See Pages 2-54, 2-55.

79. Page 2-5 lf 3rd Paragraph:

Change the last sentence to "The volatilized hazardous material will require subsequent..."

Sentence changed Airstripping has been moved to physical process section (comment 85d).See Page .

In addition, there has been no mention of total BOD, COD or TOC. What is the potentialfor other organic compounds than the VOCs of concern. This section should contain astatement to the effect that air stripping will be possible and that there are no other organicconcentration or other materials which have not been identified such that the entireproposed treatment system may not be possible. Discussion added. See Page _ .

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80. Page 2-5 lr Oxidation Reduction:

This technology may have several divergent forms. It appears that this technology isbeing used at other sites for volatile organic compounds. The ultrox system is this type oftechnology I believe. Please review and then respond as to screening.

Technology retained. Additional discussion added. See Page 2-60.

81. Page 2-57. PQTW:

If the plant has limited capacity it should be screened out here, not implementable. POTWhas been retained as a possible discharge option for a portion of the flows.

82. Page 2-58f Bottom Paragraph:

Process options are not screened out here. See page 4-16, Section 4.2.5 of RI/FSguidance. Figures and teat have been revised to reflect this comment Process options arescreened oat in Section 2.4.1.

83. Page 2-60. Figure 2-4:

Technologies should not be screened out here. This is for process options. Technologiesshould be screened out in Figure 2-3. Example, grout curtain and slurry wall should bescreened out earlier for the reasons given, but only for areas of the site where the reasonsare applicable. Where the aquifer is shallow these technologies are viable. Site-specificcan be equivalent to operable unit-specific or location-specific on a large site. Figures andtext have been revised to reflect tins comment. Technologies are screened out in Section2.4.1.

84. Page 2-60r Figure 2-4:

The "discharge" item leading to pipe to river and local stream must be screened out here ifcontaminated water is to be discharged. If being considered as an outlet for water fromwithdrawal wells that are outside the plume then they can be retained. However it must bemade clear here exactly what is meant. Dilution is not a solution. Discharge is reetainedfor treated water only. See Figure 2-4.

85. Page 2-63r Figure 2-5. Page 1:

Process options No. 3 "City Water Supply" should be 'Town water supply."

Change made. See Figure 2-5.

Entire collection discharge tree can be eliminated unless this is for discharge of cleanwater. Discharge of water without treatment is not possible thus not implementable.

Collection/Discharge tree eliminated. See Figure 2-5.

Containment Diversion. Where is the hydrodynamic controls of Alternative MM-4?Shouldn't this be here? Why can't hydrodynamic controls envelop both injection andwithdrawal wells?

Injection and extraction wells are included. See Figure 2-5.

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CollectionAreatment/discharge. The line is drawn wrong on the physical box. It shouldcome down from the chemical line.

Aii stripping is a physical process not a chemical process.

Air stripping is presented under physical process. See Figure 2-5.

86. Figure 2-5. Page 2:

Add Solid waste landfill to collection of residuals.

Solid waste landfill is added. See Figure 2-5.

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