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NORTH PENN AREA 1PHASE II FEASIBILITY STUDY REPORTWork Assignment No. 03-3LW8.0Contract No. 68-W8-0090June 1994
Prepared for
Environmental Protection AgencyRegion III
841 Chestnut StreetPhiladelphia, Pennsylvania 19107
This document has been prepared for the Environmental Protection Agency under Contract No. 68-W8-0090. Thematerial contained herein is confidential and is not to be disclosed to, discussed with, or made available to any person orpersons for any reason without the prior express approval of a responsible official of the Environmental ProtectionAgency.
WDCR675/028.51
CONTENTS
Section Page
I Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1Purpose and Organization of Report . . . . . . . . . . . . . . . . . . . . . 1-1Facility Background Information ....................... 1-2Nature and Extent of Contamination . . . . . . . . . . . . . . . . . . . . . 1-4Fate and Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Baseline Risk Assessment ........................... 1-8
2 Remedial Action Objectives and ARARs ....................... 2-1General Remedial Action Objectives ..................... 2-1Site-Specific Remedial Action Objectives .................. 2-2ARARs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3Determination of ARARs and Guidelines To Be Considered ...... 2-6
3 Identification, Screening, and Evaluation of RemedialAlternatives ....................................... 3-1
General Response Actions ........................... 3-1Ground water Well Yields and Area of Contaminated Media ...... 3-1Initial Identification and Screening of Remedial Alternativesand Process Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
Evaluation of Remedial Alternatives and Process Options ........ 3-6Media-Specific Remedial Alternatives . . . . . . . . . . . . . . . . . . . . 3-8
4 Detailed Analysis of Media-Specific Remedial Alternatives ........... 4-1Introduction .................................... 4-1Evaluation Criteria . .............................. 4-1Analysis of Media-Specific Alternatives . . . . . . . . . . . . . . . . . . . 4-3Description of Groundwater Remedial Alternatives ............ 4-4Comparative Analysis of Groundwater Alternatives ............ 4-11Description of Soil Alternatives ........................ 4-13Comparative Analysis of Soil Alternatives ................. 4-16
5 Works Cited ....................................... 5-1
Appendix A. Preliminary Remediation Goals
Appendix B. Estimation of Aquifer Remediation Time
Appendix C. Costs
Appendix D. Estimation of Soil Remediation Time
WDCR753/027.51 ii
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CONTENTS (cont.)
Follows ^Figures Page
1-1 Site Map .......................................... 1-21-2 PCE Concentrations from CLP Analyses (Gentle Cleaners) ........... 1-51-3 PCE Concentrations from CLP Analyses (Granite Knitting Mills) ....... 1-51-4 PCE Concentrations from CLP Analyses (Parkside Apartments) ........ 1-5
Tables
1-1 Site Chronology ...................................... 1-41-2 Analytical Results of Organic Compounds Detected in Groundwater
Samples Obtained from Residential, Industrial, andMunicipal Wells ................................. 1-4
1-3 Contaminants of Concern ................................ 1-81-4 Exposure Pathways Addressed ............................. 1-91-5 Summary of Risk Characterization Results (Residential
Groundwater Use) ................................ 1-101-6 Summary of Risk Characterization Results (Potential Future
Contact with Subsurface Soil) ......................... 1-10 -^
2-1 Preliminary Remediation Goals—Subsurface Soil .................. 2-12-2 Preliminary Identification of Potential Action-Specific ARARs
For North Penn Area 1 ............................. 2-7
3-1 Initial Screening of Technologies and Process Options forGroundwater ................................... 3-2
3-2 Initial Screening of Technologies and Process Options for Soil ......... 3-23-3 Evaluation of Remedial Process Options for Groundwater ............ 3-73-4 Evaluation of Remedial Process Options for Soil . . . . . . . . . . . . . . . . . . 3-73-5 Remedial Action Alternative Screening—Groundwater ............... 3-83-6 Remedial Action Alternative Screening—Soil .................... 3-8
4-1 Summary of Alternatives Evaluated for Groundwater ............... 4-34-2 Summary of Alternatives Evaluated for Soil ..................... 4-34-3 Summary of Costs of Groundwater Alternatives 1 Through 4 .......... 4-114-4 Summary of Costs of Soil Alternatives 1, 2, and 3 ................ 4-17
WDCR753/027.51
OWDCR753/027.51 iii
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Section 1Introduction
A feasibility study (FS) was performed for the North Perm Area 1 site located inMontgomery County, Pennsylvania. The site is one of 12 Superfund sites in the NorthPenn Water Authority (NPWA) area that have been or are being investigated underSuperfund. Six of these sites have been listed on the National Priorities List on the basisof volatile organic compound (VOC) contamination in groundwater. For this FS, thecandidate remediation technologies were developed to reduce the toxicity, volume, ormobility of contaminants in groundwater and soil. Each technology was evaluated inaccordance with the National Contingency Plan (NCP). Remedial alternatives for ground-water and soil were evaluated separately, as directed by the remedial project manager(RPM), to allow added flexibility in the selection of the final remedy. The remedialalternative will be selected by the United States Environmental Protection Agency (EPA)using the results of the detailed analysis of the media-specific remedial alternatives.
The FS was performed for the EPA under work assignment No. 03-3LW8.0.
Purpose and Organization of Report
The purpose of the FS was to evaluate remedial technologies as the basis for selection of aremedial action for North Penn Area 1. This FS report has been prepared in accordancewith the requirements of the NCP and the Comprehensive Environmental ResponseCompensation and Liability Act (CERCLA), as amended by the Superfund Amendment andReauthorization Act (SARA). The FS was performed using the methodology outlined inthe Guidance for Conducting Remedial Investigations and Feasibility Studies UnderCERCLA, Interim Final, USEPA, September 1988, except that media-specific alternativeswere carried through the detailed analysis rather than complete multi-media remedialalternatives.
This report is divided into four sections and is formatted to follow the process ofidentifying and evaluating potential remedial technologies.
Section 1 presents background data on the site and summarizes the results of previousinvestigations.
Section 2 presents the remedial action objectives, potential contaminant pathways, health-based criteria, and applicable or relevant and appropriate requirements (ARARs).
Section 3 describes development of the general response actions and identifies potentialremedial alternatives under each action.
1-1«R3QI323
Section 4 identifies and describes the screening of the media-specific remedial alternativesagainst the seven NCP criteria appropriate for the FS.
Facility Background Information
Site Description
The North Penn Area 1 site is located in the town of Souderton in Montgomery County,Pennsylvania. The boundaries of the site are shown in Figure 1-1. The site has beeninvestigated by the EPA on the basis of a 1989 listing of the site on the National PrioritiesList (NPL). The site is one of 12 that EPA identified in the North Penn area hi 1986(NUS, 1986) on the basis of contamination of groundwater in production wells by VOCs.The contamination at the Area 1 site was first noted in NPWA well S-9. The well wasdecommissioned in 1979 because of high tetrachloroethene (PCE) levels in thegroundwater. The EPA's subsequent searches for the potentially responsible party (PRP)identified five facilities in the area that may have contributed to the groundwatercontamination. These facilities and the groundwater contamination were investigated in theremedial investigation (RI).
Site History
Five facilities that used PCE or other solvents and may have contributed to contaminationof the groundwater were identified at the site: Gentle Cleaners, Granite Knitting Mills,Parkside Apartments, Lexco Engineering and Manufacturing Corp., and the formerStandard Terry Mills. The location of each facility is shown in Figure 1-1. Figure 1-1also shows the estimated limits of the site on the basis of locations of the facilities and theapproximate distribution of contaminated groundwater in the bedrock aquifer.
Gentle Cleaners
Gentle Cleaners began operating before 1953 (Versar, 1988; Techlaw, 1987). It is knownthat between 1953 and 1983, the company used 70 to 100 gallons of PCE per month andsmall amounts of 1,1,1-trichloroethane (1,1,1-TCA) and other chlorinated solvents. After1983, the facility continued to use about 50 gallons per month of PCE. The PCE wasstored onsite in an aboveground storage tank or drums. An underground storage tank(UST) also may have been used to store PCE at the facility. However, no evidence of theUST was found during the RI.
At Gentle Cleaners, Musheno (1980) documented a spill of 75 gallons of PCE thatoccurred in the early 1970s. PCE reportedly flowed out the rear door onto a grassy areabehind the building. In addition, discharge of PCE to a sink that drained into the samegrassy area may have contributed to soil contamination.
3R30I321*
LEGEND600 1200 1800
NPWA WELL
GRANITE KNITTING MILLS WELLsCALE: f-w
BOROUGH AND TOWNSHIPBOUNDARIES
PRELIMINARY BOUNDARY OFAREA 1 (NUS, 1986a)
REVISED BOUNDARY OFAREA 1 (1991)
POTENTIALLY RESPONSIBLE K1/s .K _DADTV IDOB\ North Penn Area 1PARTY (PRP) Pnase n RI/FS
Granite Knitting Mills ^DGranite Knitting Mills (GKM) has operated a knitting mill since the early 1960s. From
1967 to 1979, a dry-cleaning machine using PCE was maintained at the facility. Use ofthe machine may have stopped by 1979. PCE for the machine was stored in a tank insidethe building. Wastes generated from the machine were estimated to contain about2 percent PCE and were stored inside in drums on the southwest side of the building(Versar, 1988).
Property owners in the area have reported discharges from the facility into the alley thatruns along the southeast side of the building. These discharges were described as solventsand dyes, but their point of origin along the building was not identified. Reportedly,drums containing waste oil with some solvent contamination were stored outside, along thesouthwest side of the building, before disposal.
Parkside Apartments
The Parkside Apartments property once included a dry-cleaning establishment. ThreeUSTs containing petroleum hydrocarbon fuels were once located on the property butallegedly were removed around 1980 (personal communication, P. Stoudt, 1989). AnotherUST that may have been at the south corner of the facility (Musheno, 1980) could not belocated during onsite activities. Area residents reported that part of the facility may havebeen landfilled with dirt and construction debris. gh
Lexco Engineering
Lexco Engineering and Manufacturing Corporation (Lexco) has used 1,1,1-TCA at itsfacility since 1979. The facility purchases 110 gallons annually and generates 10 gallons aswaste annually. The 1,1,1-TCA is used in a trough and may have spilled or leaked ontothe floor. Operations at the facility have been ongoing since before 1960 (LoganDeposition, 1991). The facility uses one UST for oil storage. A second UST in whichgasoline was stored is located along the side of the building but is no longer in service.
Standard Terry Mills
The former Standard Terry Mills building previously was occupied by a trolley repairshop, supermarket, gas station, knitting mill, and other activities. These operations couldhave used solvents and chemicals and may have contributed to local groundwatercontamination.
The former Standard Terry Mills facility was in operation until May 1991, when a fireoccurred at the facility; the buildings were later razed. The facility has undergone aPhase I property assessment, during which the site was primarily evaluated for poly-chlorinated biphenyl contamination; a report indicated that the facility was uncontaminated(personal communication, P. McManus, 1992). Two USTs were identified at the facility. 4lk
1-3 flR30!326
John Crawford, current owner of the former Standard Terry Mills, reported that one USTwas removed about 7 years ago and that two fuel oil tanks were removed around January1991.
A chronology of site activities is presented in Table 1-1.
Summary of Past Remedial Actions
No remedial actions have been taken at North Penn Area 1. Water from NPWA wells S-8and S-10 is not treated but is blended with water from other wells to meet drinking waterquality standards. Well S-9 has been shut down.
Nature and Extent of Contamination
In fall 1986, groundwater samples were collected and analyzed for VOCs. The results ofthe sampling indicated contamination of the GKM well and of well S-9. Other local wellsalso exhibited contamination. On the basis of these results, the site was scored andproposed for the NPL.
RI activities were conducted in the spring of 1992. Investigations performed during the RIincluded a well inventory, soil boring, soil sampling and analysis, aquifer testing, andgroundwater sampling and analysis. The soil sampling and analysis defined soil character-istics and levels of VOC contamination of the soil at the facilities. The aquifer testingcharacterized aquifer hydraulics and provided information needed to evaluate remedialoptions. The groundwater sampling defined the nature and extent of VOC contamination ofthe bedrock aquifer at the site, to the extent possible using existing wells. No monitoringwells were installed during the investigations. Historical data and data collected during theRI indicate that PCE is the primary contaminant of concern.
Groundwater Contamination
Table 1-2 shows the results of VOC analysis of groundwater samples collected fromresidential wells and municipal and industrial wells at and near the site.
The highest levels of contamination occur in wells at the center of the site, including theGKM well, NPWA wells S-9 and S-10, and the Souderton Borough well (679).Comparison of historical data with the results of the RI groundwater analyses indicate that,although some VOC contamination still exists, it appears to have declined over time. PCEwas detected at the maximum concentration limit (MCL) of 5 /xg/1 in NPWA well S-9.PCE was detected in discrete zone samples from well S-9 at concentrations from 8 to 17/ig/1, which suggests that PCE levels in the aquifer around S-9 may exceed the MCL. PCEwas detected at a lower concentration in well S-10 and was not detected at all in well S-8.Contamination from the Area 1 plume may have affected a residential well west of the site.The well (designated R-2 in the RI report) is reportedly 250 feet deep and is presumably
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WDCR669/024.51
Table 1-1SITE CHRONOLOGY
1979
June 1986
July 1986
August 1986
September 1986
January 1987October 1987
June 1988
August 1988
March 1989
April to June 1992
The NPWA discovers PCE contamination in well S-9;sampling of wells S-9 and S-10 is initiated
EPA Region III requests information from PRPs underCERCLA Section 104(e)104(e) information is provided by Parkside Apartments104(e) information is provided by Granite Knitting Mills,Inc., and by Gentle Cleaners, Inc.
NUS Corporation completes the Site Discovery
An EPA contractor samples residential and other wells at thesiteThe site is scored using the Hazard Ranking System
The site is proposed for the NPL
Techlaw completes the Final Facility ReportATSDR completes a Preliminary Health Assessment
The Versar Technical Evaluation Report is completed
The North Penn Area 1 NPL listing becomes finalCH2M HILL performed RI activities at site
flR30!328
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cased from the surface to bedrock. The concentration in this well was low, estimated at0.1
VOC contaminants are still entering the groundwater. During packer sampling at the GKMwell, the highest concentration of PCE (330 /zg/1) was found entering through a fracture inthe top interval of the well, above the water level. Video logging showed water enteringthe well above the water table from fractures at a depth of about 22 feet below grade.
There is no direct definitive evidence that dense non-aqueous phase liquids (DNAPLs) arehi the groundwater at the site. Even a PCE concentration of 330 tg/1 detected in packersampling at the GKM well is only 0.2 percent of the solubility of PCE. However, it isknown that 75 gallons of PCE were spilled at Gentle Cleaners and probably introducedDNAPLs to the subsurface. The presence of DNAPLs would explain why PCE wasdetected at all depths of the GKM well (total depth of 190 feet) and of well S-9 (total depthof 300 feet), although at concentrations that are only a small fraction of the solubility ofPCE.
Soil Contamination
Soil sampling locations and PCE results are shown in Figures 1-2, 1-3, and 1-4 for GentleCleaners, Granite Knitting Mills, and Parkside Apartments, respectively. Detectable levelsof VOCs (particularly PCE) hi soil were identified in the 6- to 10-foot interval at GentleCleaners, Granite Knitting Mills, and Parkside Apartments. PCE at an estimated concen-tration of 7 /ig/kg was found at one location at Standard Terry Mills. No VOCs weredetected at Lexco. A concentration of PCE of 300,000 ig/kg detected at Gentle Cleanerssuggests the presence of DNAPLs in the soil, at least at some tune in the past; this isconsistent with the reported spill of 75 gallons of PCE at the facility.
Fate and Transport
This discussion addresses the Gentle Cleaners, GKM, and Parkside Apartments properties.On the basis of the results of the sampling, which showed little or no contamination, theLexco and Standard Terry Properties will not be discussed further. The potential transfor-mation and transport of the contaminants of concern were evaluated through surface soil,subsurface soil, groundwater, and surface water. Because the migration pathways of con-cern are subsurface soil and groundwater, the fate and transport evaluation of these mediais summarized below.
Soil
Soil sampling indicated decreasing concentrations with increasing distance from potentialsources and lower concentrations at the surface, as is typical for VOCs. It is likely thatconcentrations are, in fact, decreasing as the contaminants move through the soil and away
1-5HR3GI33Q
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DISCHARGE HOLE t AIR VENTDOORWAY
STONEWALL
LEGENDy SOIL BORINGA LOCATIONS -.ND NOT DETECTED
ALL UNITS IN po/ka FIGURE 1-2
LIMIT PCE CONCENTRATIONSFROM CLP ANALYSESGENTLE CLEANERSNorth Perm Area 1Phase II RI/PS
HR3GI33I
ill
AR30I332
313311S7.agn
UNNAMED TRIBUTARY OF SK/PPACK CREEK
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ALL UNITS IN pa/kg, VALUE ESTIMATEDJ BELOW DETECTION LIMIT
FIGURE 1-4PCE CONCENTRATIONSFROM CLP ANALYSESPARKSIDE APARTMENTSNorth Perm Area 1Phase II RI/FS
HR30I33X
from their original sources. Causes of this reduction are dilution, dispersion, and possibly ^biodegradation. flp
At Gentle Cleaners, the contamination is likely to be migrating to the groundwater. AtGKM, the potential rate of PCE migration is slowed because the contaminated soil iscovered by asphalt. At the Parkside Apartments, the contamination probably is migratingtoward the intermittent stream to the northwest.
Groundwater
PCE was detected in three of the tested wells: S-9, the Granite Knitting Mills (GKM)well, and a Souderton Borough well. The levels in these wells ranged from 1 to 5 j*g/l.The wells also contained TCE (0.2 jig/1) and cis-l,2-DCE at 1 jtg/1. One well showed0.9 jtg/1 of 1,1,1-TCA.
These levels indicate that at least some contamination has leached through the soil and intothe aquifer. All of the compounds detected are soluble in water and are expected to betransported fully dissolved hi the groundwater. However, if they enter the aquifer as non-aqueous liquids, they can travel downward rapidly because of their high density and lowviscosity. Soil data from Gentle Cleaners suggest that such liquids probably were presentin the soil at some tune, although no evidence was found in the groundwater.
The analyses of groundwater indicate that contamination has reached the aquifer below thesite. Pumping from the GKM well appeared to dilute the concentrations in the well, whichindicates that the groundwater surrounding the well is less contaminated. Contaminatedsoil was detected at both the Gentle Cleaners and the GKM facilities; the source of thecontamination in the aquifer has not been definitively determined from this investigation.The contamination at Gentle Cleaners is upgradient of the GKM well, and it is possible thatcontamination from this source has traveled downgradient to the well via surface runoff andgroundwater movement.
Contaminant Fate and Transport
Contaminants percolate or are leached through the soil layer (which is thin at the site),enter the fractures hi the rock, and move down to the water table. At the water table, thecontaminants enter the groundwater system. If the water table is a subdued representationof the surface topography and no pumping influences the groundwater flow, groundwaterand dissolved contamination move in a generally south-to-southeast direction from GentleCleaners and Granite Knitting Mills and in a northwest direction from Parkside Apartmentstoward the unnamed tributary to Skippack Creek. The amount of fracturing of the bedrockand the extent to which these fractures are interconnected determines the extent to whichthe water table assumes a subdued representation of the surface topography. The tendencyfor groundwater to move in these directions would be influenced by pumping at NPWAwells S-8 and S-10, the generally northeast-to-southwest trend of fractures in the bedrock inthe area, and the course of the unnamed tributary. Pumping of local domestic wells may jflk
1-6
influence the direction of flow to some degree, but this is not believed to occur.Contaminated groundwater either is removed from the hydrogeologic system by pumpingwells or by discharge into the unnamed tributary.
It is possible that some biological degradation is taking place in the groundwater. Althoughlevels of organic carbon hi bedrock are extremely low, microbes are known to beindigenous to groundwater environments. Measuring the dissolved organic carbon and thedissolved oxygen concentration in the groundwater would aid in determining whether bio-degradation is occurring. If conditions are anaerobic, then the degradation products ofPCE would be TCE and DCE. The more chlorinated the compound, the more oxidized thecompound is, and anaerobic dechlorinations are more favored. As the degree of chlori-nation decreases, so does the driving force for anaerobic dechlorination. PCE is thechlorinated ethene most likely to degrade in anaerobic conditions. Under aerobicconditions, PCE will not biologically degrade.
Transport Modeling
The model commonly known as the "Summers" model (Summers et al., 1980) was usedfor simulating mixing of contaminated soil water in the aquifer. On the basis of thecalculations using the Summers model, residual PCE contamination at Gentle Cleaners andParkside Apartments of approximately 260 to 270 /*g/kg will result hi contamination of theunderlying aquifer to a concentration on the order of 5 jtg/1, the MCL for PCE. At GKM,soil contamination on the order of 820 /xg/kg would contaminate groundwater underlyingthe site to 5 jtg/1. The application of the Summers model is discussed in Appendix A.
There is, of course, considerable uncertainty about the groundwater concentration estimatedby the model. In addition to the uncertainty associated with the assumptions of the model,there is uncertainty in the hydraulic parameters such as recharge and hydraulic conductivityused in the model. Therefore, in this application, the Summers model represents only ascreening approach that indicates the approximate level of groundwater contamination thatmight be derived from residual soil contamination.
In summary, all of the contaminants that were detected have similar fate and transportproperties: relatively high water solubilities, high Henry's Law Constants, and low K ,,which reflects their mobility in soil and water. The concentration of the VOCs in soil isexpected to fall over tune as the contaminants volatilize and move downward. The highestdegree of contamination is in the subsurface soil, generally at the greater depths.Subsurface soil has been and probably continues to be the source of the groundwatercontamination. Contaminants hi the groundwater may be undergoing anaerobic biologicaldegradation.
RR301335
Baseline Risk Assessment —^
The risk assessment was performed in accordance with the following guidance andadvisories:
• EPA Risk Assessment Guidelines (EPA, 1986a,b,c).
• Exposure Factors Handbook (EPA, 1989a)
• Risk Assessment Guidance for Superfund, Volume I, Human HealthEvaluation Manual, Part A. Interim Final. (EPA, 1989b).
• Human Health Evaluation Manual, Supplemental Guidance: StandardDefault Exposure Factors (EPA, 1991)
The results of the risk assessment were used to help determine whether remediation isnecessary, to help provide justification for performing remedial action, and to assist indetermining what exposure pathways need to be remediated. The following presents asummary of the results of the assessment.
Selection of Contaminants of Concern
The risk from only VOCs was quantified because there were no data on any other potentialcontaminants. The 14 contaminants identified as primary contaminants of toxicological orenvironmental concern and selected for baseline risk assessment are listed in Table 1-3.The chemicals of concern were selected on the basis of the following criteria:
• The frequency of detection in soil and water (if a contaminant was detectedin fewer than 5 percent of the samples, it was dropped as a contaminant ofpotential concern.)
• Estimated concentrations of certain compounds
The soil at the site was separated into three distinct areas, specifically: Gentle Cleaners,Parkside Apartments, and Granite Knitting Mills. The groundwater, however, was treatedthe same for the entire site.
Toxicity Assessment
In general, toxicity assessment has two steps. The first step, hazard identification, is theprocess of determining what adverse health effects, if any, could result from exposure to aparticular chemical. The second step, dose-response evaluation, quantitatively examinesthe relationship between the level of exposure and the incidence of adverse health effects inan exposed population. In the case of North Penn, toxicity values were obtained from EPAdatabases, including IRIS (1992), HEAST (1992), and EPA Region Ill's "Risk-based con-
1-8 AR3QI336
Table 1-3CONTAMINANTS OF CONCERN
AcetoneBenzeneBromodichloromethaneCarbon disulfideChloroformChloromethane1,1-DichloroethaneCis/trans-1,2-DichloroetheneEthylbenzeneMethylene chlorideTetrachloroetheneToluene1,1,1-TrichloroethaneTrichloroethene
TOCR667/01L5I/3 BR30I337
centration tables, Third quarter 1992." The toxicity values for trichloroethylene werebased on the levels established before its withdrawal from IRIS.
Exposure Assessment
On the basis of RI data, pathways were identified through which human population may beexposed now or in future to the contaminants of concern. These pathways were evaluatedhi the baseline risk assessment under current and potential land-use conditions. A numberof potential human exposure pathways have been identified at the site. These include:
• Soil—Existing and potential future ingestion and dermal absorption ofcontaminants from surface and subsurface soil
• Groundwater—Potential future residential use with ingestion, dermalabsorption, and inhalation of volatilized compounds
• Air—Existing and potential future inhalation of volatiles from contaminatedsoil
Table 1-4 presents the exposure pathways addressed in the baseline risk assessment,highlighting which pathways will have a quantitative assessment and which will be assessedqualitatively. Subsurface soil is included as a potential exposure pathway for futureresidents because excavation of soil, such as for the installation of home foundations, couldoccur. Such excavation could bring subsurface soil to the surface, allowing direct exposureto the contaminants that have been detected in subsurface soil.
Quantification of Exposure
Exposure pathways for current and future use were evaluated separately.
Current Use
In reviewing the data on surface soil (0 to 2 feet) for Granite Knitting Mills, GentleCleaners, and Parkside Apartments, it was noted that the Granite Knitting Mills facility hasasphalt or buildings covering all available surface soil and, therefore, no potential for directcontact with surface soil at the facility. Therefore, the potential risks associated withcurrent direct contact with surface soil were discussed in a qualitative rather than quanti-tative manner.
The air pathways represented by outdoor exposure to VOCs in soil or from VOCs in soilentering the home are being treated in a qualitative manner because of the relatively lowVOC concentration in surface soil and the statement in Risk Assessment Guidance forSuperfund (RAGS) Part B (EPA, 1991), specifically: "for many undisturbed sites withvegetative cover such as those found in areas of residential land use, air pathways arerelatively minor contributors of risk.'' Jtb
&R3G1338
Table 1-4EXPOSURE PATHWAYS ADDRESSED
Receptor(Onsite) Media Exposure Route
QuantitativeAssessment
QualitativeAssessment
Current Land Use
Residents— Onsite
Residents— Offsite
Workers— Onsite
Surface Soil
Air (outdoors)(indoors)
Groundwater
Surface Soil
Air (outdoors)
IngestionDermal Absorption
InhalationInhalation
IngestionDermal AbsorptionInhalation (IndoorVolatile)
IngestionDermal Absorption
Inhalation
XXX
XX
XX
XX
X
Future Land Use
Residents — Onsite Groundwater
Subsurface Soil
IngestionDermal AbsorptionInhalation (IndoorVolatile)
IngestionDermal Absorption
XXX
XX
WDCR665/024.51
flR30!339
Residential use of contaminated groundwater for drinking water would lead to exposure ^through direct ingestion of water and drinks made from water; inhalation of vapors during VVshowers, baths, and washing; and dermal absorption during showers and baths. Onlyreasonable maximum (or upper-bound) exposure assumptions were used for the residential-use-of-groundwater scenario because of the limited range of the parameters needed tocalculate -intake. The upper boundary of intake-factor values for the ingestion rate,exposure frequency, exposure duration, body weight, and averaging tune were used tocalculate reasonable maximum exposure.
Another potential exposure pathway under current land use is the outdoor inhalation ofVOCs from contaminants in surface soil and the indoor inhalation of VOCs entering thehome. The low levels of VOCs in surface soil imply that this is not a viable source ofeither ingestion or inhalation of VOCs outdoors. The potential might exist for subsurfaceVOCs to migrate into homes along fractures in the soil and through cracks in homefoundations. Again, the relatively low levels of VOCs in subsurface soil indicate that thisis not a potential pathway of great concern.
Future Use
Table 1-4 shows that for future land use, residents potentially could be exposed to ground-water on the site and to subsurface soils following excavation of soil. New guidance inPart B of RAGS was used to calculate an age-adjusted soil ingestion factor.
Risk Characterization
Summary tables of risk characterization results are shown in Table 1-5 for residentialgroundwater (current and future) and in Table 1-6 for subsurface soil (future only).Included hi the tables are estimates of central tendency (or average) exposure as well asreasonable maximum exposure.
Residential Groundwater Use
As can be seen in Table 1-2, from the maximum concentrations detected, none of theVOCs are above their MCLs; most are near their detection limit. These low concentrationsequate to low risk levels.
The contribution of dermal and inhalation risk is about the same as that of ingestion. Therisks associated with the potential future onsite residential use of groundwater are roughlythree tunes the levels seen for current offsite use of groundwater.
Table 1-5 also presents the risks associated with the potential future onsite residential useof groundwater from the shallow aquifer, although it is unlikely that the shallow aquiferwill ever have a residential well installed. A grab sample showed a very high concentra-tion of PCE (330 jtg/1). It can be seen that the excess lifetime cancer risks of 2 x 10"4 fora child and 3 x 10"4 for an adult are at the upper end of the target risk level established by Jttk
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EPA. The noncarcinogenic hazard index is greater than the target risk level of 1 (8 for achild and 3 for an adult).
Direct Contact with Subsurface Soil
Table 1-6 gives the summary of risk characterization results for potential future contact byonsite residents with subsurface soil following excavation. The assumptions used to predictrisk from this scenario are very conservative.
Results of Risk Assessment
For groundwater, the overall result is that the relatively low concentrations of VOCs equateto low risk levels. The excess lifetime cancer risk for current offsite residential use for achild calculated using reasonable maximum exposure assumptions and upper-bound concen-trations is about 1 x 10"6. For potential future onsite residential use, the excess lifetimecancer risk for a child is 2 x 10~6, while for an adult it is 3 x 10'6. Potential future onsiteresidential use was also calculated for groundwater infiltrating through the soil. Thisshallow groundwater scenario yielded an excess lifetime cancer risk of 2 x llT4 for a childand 3 x 10"4 for an adult.
For soil, the excess lifetime cancer risks for both a child and an adult at ParksideApartments are well below EPA's target risk level. The excess lifetime cancer risk fromingestion and dermal contact with subsurface soil at Granite Knitting Mills is at or nearEPA's target level for an adult and a child.
The excess lifetime cancer risk for Gentle Cleaners is at least 10 times higher than that ofthe other two facilities. PCE (found at 300,000 //g/kg at the 8- to 10-foot interval) is theprimary contaminant, leading to an excess lifetime cancer risk of 4 x 10"6 for a child and1 x 10"6 for an adult. However, the average risks calculated are about an order ofmagnitude lower than the calculated reasonable maximum risk levels.
WDCR754/015.51
Section 2Remedial Action Objectives and ARARs
This section presents remedial action objectives and corresponding ARARs for the NorthPenn Area" 1 site. Remedial action objectives include general objectives as defined by theNCP and CERCLA as well as site-specific objectives. Site-specific objectives relate tospecific contaminated media, such as groundwater and soil, and to potential exposure routesand are used to identify target areas of remediation and contaminant concentrations.Establishing site-specific objectives requires an understanding of the contaminants in theirrespective media and is based upon the evaluation of risk to the public health and theenvironment and upon ARARs. These goals are as specific as possible without undulylimiting the range of technologies that can be developed for detailed evaluation.
General Remedial Action Objectives
The NCP states that the national goal of the remedy selection process is to select remediesthat are protective of human health and the environment, that maintain protection overtime, and that minimize untreated waste (40 CFR, Part 300.430).
The statutory scope of CERCLA, as amended by SARA, includes the following generalgoals for remedial action at all CERCLA sites:
• The objectives for the degree of remedial action cleanup shall be refinedsuch that remedial actions "shall attain a degree of cleanup of hazardoussubstances, pollutants, and contaminants released into the environment andof control of further releases at a minimum which assures protection ofhuman health and the environment." [Section 121(d)]
• Selection of remedial actions "in which treatment that permanently andsignificantly reduces the volume, toxicity, or mobility of the hazardoussubstances, pollutants, and contaminants is a principal element" shall bepreferred. [Section 121(b)] An explanation must be published if a perma-nent solution using treatment or recovery technologies is not selected.
• It is required that the selected remedy comply with or attain the level of any"standard, requirement, criteria, or limitation under any Federal environ-mental law ... or any promulgated standard, requirement, criteria, orlimitation under a State environmental or facility siting law that is morestringent than any Federal standard, requirement, criteria, or limitation."[Section 121(d)(2)(A)]
2-1
IR3013U6
Site-Specific Remedial Action Objectives jm±
For the contaminants of concern at the site, the preliminary remediation goals (PRGs) forsoil were developed by two methods. The first method used the EPA's Risk AssessmentGuidance for Superfund: Volume 1—Human Health Evaluation Manual, Pan B. The totalrisk from a medium is set equal to the combined risk from all exposure pathways. Thistotal risk is then set equal to a target risk, and the concentration that produces this risk isderived by back calculation. In the second method, the PRGs were developed byestimating the effects of contaminated soil on groundwater.
For North Penn Area 1, the risk-based PRGs were developed assuming that the (future)exposure pathways of concern are ingestion of and dermal contact with subsurface soil.The chemical of concern that yields greater than 99 percent of both carcinogenic andnoncarcinogenic risk is PCE. The risks for a child for both pathways are greater thanthose for an adult.
PRGs for the subsurface soil were calculated using the exposure parameters from thebaseline risk assessment and the process from the risk assessment guidance. Table 2-1shows the results.
Table 2-1PRELIMINARY REMEDIATION GOALS— SUBSURFACE SOIL
Risk for IngestionRisk for Dermal Contact
PRG Concentration forTarget Risk of 10'6PRG Concentration forTarget Risk of 10'5PRG Concentration forTarget Risk of 104
Carcinogenic Risk5.7 x 10'8 x Concentration3.3 x 10'7 x Concentration
2.6 mg/kg
26 mg/kg
260 mg/kg
Noncarcinogenic Risk
1.28 x 10'3 x Concentration7.25 x 10'3 x Concentration
114 mg/kg
1,140 mg/kg
11,400 mg/kg
As indicated by the table, the PRG for PCE as a noncarcinogen is higher than the PRG forPCE as a carcinogen. Therefore, the recommended PRG for PCE in subsurface soil is thatfor PCE as a carcinogen.
If a PRG range of 2.6 mg/kg to 26 mg/kg is imposed, only the Gentle Cleaners andGranite Knitting Mills would be affected. The maximum volume of affected soil was .calculated to be 98 cubic yards and 457 cubic yards, respectively, at these two facilities. ••
8R3QI3U
PRGs were also developed based on the effects of residual soil contamination migratingdown to the water table and contaminating the underlying groundwater. Details of how thePRGs were estimated are provided in Appendix A. The following PRGs were estimatedfor each of the three facilities: 0.27 mg/kg at Gentle Cleaners, 0.26 mg/kg at GraniteKnitting Mills, and 0.82 mg/kg at Parkside Apartments. These PRGs assume that ground-water cannot be contaminated by the residual soil contamination above the MCL of PCE of5 fjig/l. Applying these PRGs, the maximum volume of affected soil at Gentle Cleanerswas calculated to be 115 cubic yards; at Granite Knitting Mills, 400 cubic yards; and atParkside Apartments, 95 cubic yards.
Because these PRGs are more protective than the values based on ingestion and dermalexposure, the ground water-based values were used as the cutoff points for determiningappropriate remedial action objectives (RAOs). These RAOs were then used to identifyremedial technologies for soil at the site.
ARARs
As required by Section 121 of CERCLA, remedial actions carried out under Section 104 orsecured under Section 106 must attain the levels or standards of control for hazardoussubstances, pollutants, or contaminants specified by the ARARs of federal environmentallaws and state environmental and facility siting laws, unless waivers are obtained.According to EPA guidance, remedial actions must also take into account nonpromulgated"to be considered" criteria or guidelines if the ARARs do not address a particularsituation.
Definition of ARARs
ARARs are distinguished by EPA as being either applicable to a situation or relevant andappropriate to it. These distinctions are critical to understanding the constraints imposedon remedial alternatives by environmental regulations other than CERCLA. The defini-tions of ARARs below are from EPA guidance (EPA 1988).
Applicable Requirements
Applicable requirements are standards, standards of control, and other substantive environ-mental protection requirements, criteria, or limitations promulgated under federal or statelaw that specifically address a hazardous substance, pollutant, contaminant, remedialaction, or other circumstance as defined in the NCP, 40 CFR 300.5.
For a requirement to apply, the remedial action or the circumstances at the site must satisfyall the jurisdictional prerequisites of that requirement. For example, the land disposalrestrictions (LDRs) under RCRA would be "applicable" to a response action involvingonsite land disposal.
&R30I3U8
Relevant and Appropriate Requirements ^
Relevant and appropriate requirements are standards, standards of control, and othersubstantive environmental protection requirements, criteria, or limitations promulgatedunder federal or state law that, while not applicable to a hazardous substance, pollutant,contaminant, remedial action, or other circumstance at a CERCLA site, address problemsor situations sufficiently similar to those encountered at the CERCLA site so that their useis well suited to the particular site. Relevant and appropriate requirements are defined inthe NCP, 40 CFR 300.5. For example, while RCRA regulations do not apply to closingin-place hazardous waste that was disposed of before 1980, RCRA regulations for landfillclosure with hazardous substances in place may be deemed relevant and appropriate.
The NCP, 40 CFR 300.400(g)(2) specifies factors to consider in determining what require-ments of other environmental laws are relevant and appropriate:
• The purpose of the requirement relative to the purpose of CERCLA
• The media regulated by the requirement
• The substance regulated by the requirement
• The actions or activities regulated by the requirement
• Variations, waivers, or exemptions of the requirement
• The type of place regulated and the type of place affected by the release orCERCLA action
• The type and size of facility or structure regulated by the requirement oraffected by the release or contemplated by the CERCLA action
• Consideration of use or potential use of affected resources in the requirement
In some circumstances, a requirement may be relevant to the particular site-specific situa-tion but not appropriate because of differences in the purpose of the requirement, theduration of the regulated activity, or the physical size or characteristic of the situation it isintended to address. There is more discretion involved in the judgment of relevant andappropriate requirements than in the determination of applicable requirements. EPArecognizes that it is possible for only part of a requirement to be relevant and appropriate.For example, MCLs under the Safe Drinking Water Act (SDWA) may not be appropriatefor evaluating groundwater that has no potential use as drinking water. However, arequirement may be "relevant and appropriate" even if only part of it is implemented.
2"4 flR30l31»9
A requirement judged to be relevant and appropriate must be complied with to the samedegree as if it applied. Relevant and appropriate requirements that are more stringent thanapplicable requirements take precedence over the applicable requirements.
Substantive vs. Administrative Requirements
Another factor in determining which requirements must be complied with is whether therequirement is substantive or administrative. Onsite CERCLA response actions mustcomply with substantive requirements but not with administrative requirements of environ-mental laws and regulations as specified in the NCP, 40 CFR 300.5 definitions of ARARsand as discussed in 55 FR 8756. Substantive requirements pertain directly to actions orconditions in the environment. Administrative requirements facilitate the implementation ofthe substantive requirements of an environmental law or regulation. In general, adminis-trative requirements prescribe methods and procedures such as fees, permitting, inspection,and reporting requirements by which substantive requirements are made effective forpurposes of a particular environmental or public health program.
In summary, onsite CERCLA response actions must meet the intent of other environmentallaws but need not conform with all the applicable administrative rules. This distinctionapplies only to onsite actions. Offsite response actions are subject to the full requirementsof applicable standards or regulations, including administrative requirements such aspermits.
ARAR Waivers
Section 121 of CERCLA also identifies six conditions under which waivers to ARARs canbe granted:
• The selected remedial action is only part of a total remedial action that willattain ARARs (this is an "interim remedy").
• Compliance with ARARs would result hi greater risk to human health andthe environment than a noncompliant alternative.
• Compliance with the ARAR is not practicable from an engineeringperspective.
• The selected remedial action would attain equivalent performance orstandard of control by alternative methods.
• The ARAR is a state requirement that is not consistently applied (nor hasthere been any demonstrated intent to apply) in similar circumstances.
flR301350
• In cases of actions under Section 104, compliance with the ARAR will notresult in a balance of available CERCLA funds with the protection of humanhealth and the environment; i.e., compliance with the ARAR will be tooexpensive relative to benefits that could be attained at other sites.
Where remedial actions are selected that do not attain ARARs, the lead agency mustpublish an explanation in terms of these waivers.
Other Criteria or Guidelines To Be Considered
In addition to the legally binding requirements established as ARARs, many federal andstate programs have developed criteria, advisories, guidelines, or proposed standards thatmay provide useful information or recommend procedures for consideration if no ARARsaddress a particular situation or if existing ARARs do not provide protection. In suchsituations, these "to be considered" criteria or guidelines should be considered in settingremedial action levels.
Determination of ARARs and GuidelinesTo Be Considered
Three classifications of requirements are defined by EPA in the ARAR determinationprocess: chemical-specific, location-specific, and action-specific. Each classification isdiscussed below. Potential ARARs and other criteria that are important in the developmentof remedial actions for the North Penn Area 1 site are also presented.
Chemical-Specific ARARs
Chemical-specific ARARs regulate the release to the environment of hazardous substanceshaving certain chemical or physical characteristics or materials containing specifiedchemical compounds. They are important in determining the extent of soil and ground-water remediation as well as in determining the residual levels allowed for hazardoussubstances after treatment.
Chemical-specific ARARs associated with the North Penn Area 1 FS are concerned withcleanup standards for groundwater and soil because remedial objectives address theremediation of contaminated media. Chemical-specific ARARs for soil and groundwatertypically include RCRA LDRs, MCLs, and other cleanup-related requirements. The RCRAFacility Investigation Guidance document (EPA 1989c) sets action levels for PCE in soil at64 mg/kg and in water at the MCL. The rate proposed in Corrective Action for SolidWaste Management Units (SWMUs) at Hazardous Waste Management Facilities (55 FR30789, July 27, 1990) revised the action levels to 10 mg/kg in soil and 0.7 /zg/l in water.These are the concentrations that trigger RCRA facility investigations.
2-6 flR30!35l
The RCRA LDRs for PCE (spent solvents—F001-F005, discarded commercial chemicalproduct—U210, and multisource leachate—F039) establish treatment requirements of56 jug/1 in "wastewater" and 5.6 mg/1 in "nonwastewater." Wastewater is defined asliquids with less than 1 percent by weight total organic carbon (TOC) and less than1 percent total suspended solids (TSS) for U210 and F039 wastes. For F-listed solvents,wastewater is defined as a solvent-water mixture with less than 1 percent TOC or less than1 percent by weight of the solvent constituents for an F-listed solvent.
At the North Penn Area 1 site, it is assumed that the groundwater has less than 1 percentTOC; therefore, the most applicable RCRA ARAR is 5.6 jug/1.
For North Penn Area 1, the PRGs were established on the basis of the potential effects ofsoil contamination on groundwater. The MCL of 5 /*g/l for PCE in groundwater and thePRGs of 0.26 mg/kg to 0.82 mg/kg for PCE in soil are to be considered. These criteriameet the promulgated LDRs that are relevant and appropriate to the site.
Location-Specific ARARs
Location-specific ARARs are restrictions on the concentration of hazardous substances orthe conduct of activities solely because they are in specific geophysical locations. Someexamples of special locations include floodplains, wetlands, historic places, and protectedhabitats. No known location-specific ARARs exist for this phase of the remedial activitiesat the North Penn Area 1 Superfund site. The site properties are not located in floodplains;wetlands; protected habitats; or in areas of scientific, historic, or archaeologicalsignificance.
Action-Specific ARARs
Action-specific ARARs set performance, design, or other controls for particular activitiesinvolving the management of hazardous substances or pollutants. An example of an action-specific requirement is the design requirement for landfilling hazardous waste, establishedin RCRA Section 264.301. RCRA provides the most action-specific requirements becauseit regulates the management of hazardous waste. Potential action-specific ARARs,including RCRA's LDRs for the North Penn Area 1 site, are discussed below. These andother action-specific ARARs are summarized by remedial technology in Table 2-2.
RCRA Land Disposal Restrictions. RCRA LDRs, 40 CFR 268, prohibit land disposal oflisted wastes unless constituents in the waste or in the toxicity characteristic leachingprocedure (TCLP) extract are below the maximum allowable concentrations.
Other RCRA Requirements. RCRA Part 264 outlines requirements for remedial alter-natives involving onsite treatment, storage, or disposal of hazardous wastes. RCRASubtitle C requirements will be potential ARARs for remedial alternatives that involvetransportation, treatment, storage, and/or disposal of hazardous wastes. The Hazardousand Solid Waste Amendments (HSWA) prohibit beyond specified dates the continued land
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1 performance
standard requires minimization of
T fur
ther m
aintenance an
d con
trol; minimization
ination of
post-closure e
scape of ha
zardous
hazardous con
stitue
nts, leachate, contaminated
or ha
zardous waste d
ecomposition
products.
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The RCRA
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specified levels or by
specified technologies. T
he RCRA
requirements won
be considered relevant an
d appropriate to wastes
that are not RCRA
hazard
wastes, but which are similar (
same
constituents) as RCRA
wastes.
RCRA
Lard Disposal
Restrictions re
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wastes to
specified levels or
by specified te
chnologies be
fore land disposal.
If tr
eatm
to the sp
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r by the sp
ecified technology
is not ac
hievable or
appropriate, a variance must
be obtained from
the EPA. If th
e wastes ar
edetermined to
be RCRA
wastes, these requirements would be
applicable.
In the ev
ent tha
t the wastes
being removed
are determined to be hazardous
wastes, the requirements of
this section would
be applicable.
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contaminated co
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liners, dikes), contaminated su
bsoils, and structu
and equipment c
ontaminated with waste an
d leac
and management
of th
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In the event
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stes being removed
are determined
to be hazardous
wastes, the requirements of
this section would
be applicable.
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environmental factors are being considered.
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If Pe
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state
regulations ar
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stringent than federal water quali
standards, th
e Pennsylvania
standards will be applicable to
direct di
scharge.
The sta
te has
authority under 4
0 CFR 131 to implement
direct di
scharge
requirements
within th
e sta
te, and should be contacted on
a case-by-case ba:
when
direc
t discharges are contemplated.
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If tr
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quiremf
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Permitting and reporting requirements wil
l be ap
plicabll
only
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discharged at an
offsi
te lo
cation.
The permitting
authority and should be contacted on a case-by-case basis to determine
efflu
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Use of
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ollutants. U
se of b
est c
onvent
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ontrol technology (BCT) is required to
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llutants.
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ng st
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^
Exact limitations are based on re
view of the proposed
treatment system and
receiving water characteristics, and ar
e usually determined on
a case-by-cas
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rmitting au
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contacted to determine effluent
limita
tions.
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at levels
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technc
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Detailed
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disposal of hazardous wastes without treatment. Wastes treated in accordance with the ^treatment standards set by EPA pursuant to RCRA Section 3004(m) are not subject to the ••prohibitions and may be disposed of in a RCRA landfill.
DOT Regulations. Department of Transportation Rules for Hazardous Materials Transport(49 CFR Parts 107 and 171 through 179) regulate the transport of hazardous materials,including packaging, shipping equipment, and placarding. These rules apply to wastesshipped off the site for laboratory analysis, treatment, or disposal.
OSHA Regulations. Occupational Safety and Health Administration regulations (29 CFRParts 1904, 1910, and 1926) outline requirements that apply to workers engaged in onsiteinvestigative and remedial activities.
Pennsylvania State Regulations. Offsite Transportation Requirements (25 PA CodeChapter 263) applies to wastes shipped off the site.
The following state regulations apply to air strippers and soil decontamination units:
• 25 PA Code Section 123.1 prohibits the emission of fugitive aircontaminants. This section also regulates emissions during constructionactivities.
• 25 PA Code Section 123.2 prohibits fugitive air emissions from crossing the -facility's property line. ••
• 25 PA Code Section 123.31 prohibits malodorous air emissions fromcrossing the property line.
• 25 PA Code Section 123.41 prohibits visible emissions of greater than20 percent capacity.
• 25 PA Code Section 127.1 requires the use of the best available technologyfor any new source. Air stripping with its subsequent liberation of VOCscan be considered a new source
WDCR754/013.51
2-8 4R30I359
Section 3Identification, Screening, and Evaluation
of Remedial Technologies
This section presents general response actions to address the remedial action objectivesoutlined in Section 2. Potential remedial technologies and specific process options areidentified under each response action. The technologies and process options undergo aninitial screening followed by a more in-depth evaluation to determine their suitability aspart of a remedial alternative.
General Response Actions
General response actions (GRAs) were developed separately for groundwater and soil tosatisfy the remedial action objectives. For groundwater, the GRAs included:
• No action• Extraction/treatment• Disposal
For soil, the GRAs included:
• No action• In situ treatment• Excavation and ex situ treatment• Excavation and landfilling
Groundwater Well Yields and Area of Contaminated Media
Groundwater
Two existing groundwater wells could be used for extraction of contaminated groundwaterat the site; the GKM well and NPWA well S-9. The volumetric flow rate of contaminatedgroundwater that would be generated by pumping one of these wells was estimated usingdata from the site RI. Two different extraction approaches were evaluated for the GKMwell and one for NPWA well S-9.
GKM Well
One option is for only the upper part of the GKM well to be pumped. PCE was detectedat a maximum concentration of 330 /*g/l in water during a packer test from the upper partof the well (above the water level). (Note: Although the water in the fracture above the
flR30!360
water table is technically in the vadose zone, it will be termed groundwater in this FSreport because groundwater remediation methods such as pump and treat are applicable.)This approach would involve setting a packer at some point near but below the fracturethrough which the contaminated groundwater is entering and collecting the groundwaterabove the packer. The maximum flow rate that could be sustained from this fracture isprobably less than 1 gallon per minute (gpm). Another option would be for the entireGKM well to be pumped continuously. On the basis of the pumping test for this well, theflow rate would most likely be approximately 13 gpm. The expected concentration of PCEfor this scenario would be 6 /ttg/1, based on the historical values.
NPWA Well S-9«,
In this approach, NPWA well S-9 would be pumped. Well S-9 reportedly has a yield ofapproximately 80 gpm. The expected concentration of PCE for this scenario would be10 pig/1, based on the historical values.
Soil
Data presented in the Phase II RI Report, and the PRG of 0.26 mg/kg to 0.82 mg/kg ofPCE in soil, were used to estimate the volume of contaminated soil at the site. Accordingto the RI data the areas of contamination above the PRGs at each facility are small. AtGentle Cleaners the volume of soil to be removed is estimated at 115 cubic yards for aPRG of 0.27 mg/kg; at Granite Knitting Mills, 400 cubic yards for a PRG of 0.26 mg/kg;and at Parkside Apartments, 95 cubic yards for a PRG of 0.82 mg/kg.
Initial Identification and Screening ofRemedial Technologies and Process Options
A preliminary list of treatment technologies was developed to meet the GRAs. The prelim-inary technologies were selected on the basis of existing site data. The number of poten-tially applicable technology types was reduced by evaluating the response action withrespect to technical implementability. The preliminary screening of the remedial tech-nologies for groundwater and soil is shown in Tables 3-1 and 3-2, respectively.
Groundwater Treatment Technologies
Since the primary contaminant at the North Penn Area 1 site is PCE, only technologies thataddress treatment of volatile organics will be considered. These technologies are naturalattenuation, groundwater extraction with physical/chemical treatment using either airstripping, activated carbon adsorption, or oxidation of the extracted water. Where thetreated water is to be discharged usually determines the required level of treatment. Thethree potential discharge options for the treated water are:
• Discharge to a publicly owned treatment works (POTW) ••
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Table 3-1
HNOLOGIES AND PROCESS OPT
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• Discharge to a local surface water body• Recharge or reinjection into the groundwater
Since .each of these discharges typically has different quality standards, this selection canhave a significant impact on treatment requirements. Evaluation of these discharge optionsneeds to be performed hi order to assess the applicability and effectiveness of potentialtreatment technologies.
Table 3-1 summarizes the advantages and disadvantages of the potential treatmenttechnologies. These technologies are described in the following paragraphs.
Natural Attenuation
Natural attenuation or passive remediation relies on natural processes to decontaminatecontaminated soil and groundwater. The only activity undertaken is continual monitoringof the contaminants of concern within the subject area. The natural processes that con-tribute to attenuation include:
• Biodegradation• Volatilization• Adsorption• Dispersion/dilution• Hydrolysis
Natural attenuation is most likely responsible for the observed decrease in contaminantconcentrations at the North Penn Area 1 site. It is most applicable at sites where the effecton the environment and health and safety considerations are limited.
Air Stripping
Air stripping is a mass transfer process in which VOCs in groundwater are transferred tothe vapor phase. It is an efficient treatment method for water contaminated with volatile,low solubility organic constituents, including chlorinated hydrocarbons such as PCE andTCE.
Activated Carbon Adsorption
In activated carbon adsorption, groundwater is pumped through a fixed bed of carbon thathas been thermally activated to increase its surface area. The activated carbon selectivelyadsorbs constituents hi the waste by surface attraction, in which organic molecules areattracted to the internal pore surfaces of the carbon granules. Activated carbon can adsorbvolatile organics present in the groundwater.
Chemical Oxidation *
Chemical oxidation usually is considered for dilute aqueous wastes. Constituentssusceptible to chemical oxidation include some volatile and semivolatile organics.
Oxidation-reduction reactions are those in which electrons are transferred from one con-stituent ion to another. Hazardous constituents can be converted by this process toconstituents with less toxic oxidation states. Oxidation of some organic constituents canproceed readily to CO2 and water. However, the reaction is dependent on the dosage ofthe oxidizing agent (oxidant), pH, oxidation potential, and formation of stable inter-mediates. Some common oxidants include ozone, permanganate, and hydrogen peroxide.
Ultraviolet Light Oxidation
Ultraviolet light oxidation is a process in which water contaminated with organics isexposed to ultraviolet light (UV) in combination with an oxidant such as ozone or hydrogenperoxide. The UV and oxidant act synergistically to oxidize the organics present in thewater. A potential drawback of this process is that it cannot selectively oxidize a givencompound from a mixture of oxidizable compounds.
If compounds or properties of the water cause the contaminant to absorb the UV light, thenthis process may not be as efficient. Scaling inside the UV system may cause thisproblem. Pretreatment may reduce potential scaling.
EPA's SITE program has evaluated an oxidation system developed by Ultrox International.The system consists of three processes used in combination: hydrogen peroxide treatment,ozone treatment, and ultraviolet radiation. The site at which this system was evaluated hasgroundwater contaminated by VOCs. Removal efficiencies as high as 90 percent for thetotal volatiles present were achieved. EPA concluded that Ultrox International's system hasbeen demonstrated to be effective hi removing chlorinated and nonchlorinated organics.
Soil Treatment Technologies
As with the groundwater, PCE in soil is of primary concern at the North Penn site.Therefore, only treatment technologies that address treatment of volatile organics will beconsidered. These are soil vapor extraction, soil washing, solvent extraction, incineration,and low temperature thermal treatment. Excavation of contaminated soils with disposal atan offsite landfill is also considered. Table 3-2 presents the initial screening of thetreatment technologies.
Natural Attenuation
Natural attenuation may be used to treat contaminated soil. As when used to treat ground-water, the only activity undertaken is continual monitoring of the subject area to make sure
3"4 SR301365
that the natural remediation processes are working to decrease the contaminantconcentrations and that the contamination is not spreading.
These natural remediation processes include:
• - Biodegradation• Volatilization• Desorption• Leaching• Photolysis
Soil Vapor Extraction
Soil vapor extraction (SVE) may be used to remove volatile contaminants from soils insitu. In the process, a vacuum is drawn on one or more extraction points in the soil. Thisvacuum draws the soil gases and any volatile contaminants out of the soil and to thesurface. If resulting air emissions pose a risk to human health or the environment, then anactivated carbon collection vessel may be used to adsorb the contaminants from theextracted gases before they are discharged to the atmosphere.
Soil Washing
In soil washing, excavated soils are mixed in a reaction vessel with a washing solution.The soil-washing fluid typically is an aqueous solution containing compounds that increasethe solubility of the specific contaminant that is adsorbed to the soil. For example, asurfactant may be used for hydrophobic constituents. The pH of the washing solution alsomay be adjusted to enhance the movement of the constituents into the water. Once thesolution has moved the constituents from the soils to the water phase, the solids aredewatered and the effluent is treated in a wastewater treatment process. Soil washing is awell-developed technology that has been used extensively in Europe and at a number ofSuperfund sites in the United States. Soil washing is an appropriate technology for water-soluble and water-mobile contaminants. It is not appropriate for soils with a high claycontent; the North Penn Area 1 soils do not have a high clay content but are very silty andhave low permeability. In addition, the North Penn Area 1 soils contain a wide range ofparticle sizes that may need to be screened before washing to separate the soil by particlesize. Bench- and/or pilot-scale treatability studies, using contaminated soils from a site,are usually required to determine the proper chemistry of the washing solution.
Soil Flushing
Soil flushing uses the same principles as soil washing, but instead of excavating the soils,soil flushing removes the contaminants in situ. In soil flushing, the washing solution isapplied to the soil and allowed to percolate through the contaminated area. The solution isthen recovered using down-gradient extraction wells and treated in a wastewater treatment
3-5flR30!366
process to remove the contaminants. The treated solution may then be recycled and reusedas the washing solution.
The effectiveness and rate of cleanup by soil flushing depend on the specific contaminantand site. Soil flushing is appropriate for water-soluble or water-mobile contaminants. It isinappropriate for soils with low or variable permeability. The hydrogeology of the sitemust be sufficiently characterized to successfully design a soil flushing system. This mayinvolve computer modeling of the groundwater flow at the site. Column studies usingcontaminated soils may be appropriate to estimate the application and pumping rates andthe chemistry of the washing solution.
Thermal Treatment
Thermal treatment technologies include incineration and low temperature thermal treatment.Incineration is a proven treatment technology for soil contaminated by a wide range oforganic contaminants. In this process, the soil is deposited in a rotary kiln or other type ofincinerator. The incinerator heats the soil to temperatures greater than 800°F so that thecontaminants are broken down to nonhazardous products. However, if the combustionprocess is incomplete, hazardous by-products may be generated.
In low temperature thermal treatment, excavated solids are deposited in a heat transfer unitand an air stream is induced. As the soil is heated to greater than SOOT, the soil moistureand organic constituents are volatilized and carried by the air stream to an off-gas handlingsystem. The volatilized constituents are then either condensed or adsorbed onto activatedcarbon; if condensed, the condensate is incinerated. The volume of material requiring finaltreatment also is reduced.
Low temperature thermal treatment is an appropriate technology for organic contaminantsthat have boiling points less than 500°F. However, this technology is not appropriate forsoil with a high clay content; the North Penn Area 1 soil does not have a high clay contentbut is very silty. Bench- or pilot-scale tests on the contaminated soil may be appropriate toevaluate process applicability and operating parameters.
Disposal
Treated soil can be backfilled or disposed of on the site. Treated or untreated soil can bedisposed of at an offsite landfill. The soil would be tested to determine if it is a RCRAhazardous waste. If the soils is determined to be a RCRA hazardous waste, land disposalrestrictions would be considered.
Evaluation of Remedial Technologies and Process Option
The technologies mat were not eliminated hi the preliminary screening process wereevaluated hi greater detail in order to eliminate nonviable technologies and simplify the «k
3"6 /IR3G1367
development and analysis of remedial alternatives. The technologies were evaluated usingthe criteria of effectiveness, implementability, and relative cost.
Effectiveness
In the screening process, effectiveness pertains to:
• The ability of a technology or process option to handle the estimated areasor volumes of media and to prevent or minimize the release of hazardoussubstances to potential receptors
• The degree of protection afforded to human health and the environmentduring construction and implementation of the technology or process option
• The reliability and performance of the technology or process option withrespect to the site conditions
Implementability
Implementability pertains to:
• The availability and capacity of treatment, storage, and/or disposal servicesor vendors
• The constructibility of the technology or process option under site conditions
• The time needed to implement the technology or process option, to achievebeneficial results, and to satisfy the remedial action objectives
Cost
For the relative cost screening, general capital and operations and maintenance (O&M)costs for the process options were considered. Detailed, site-specific cost estimates werenot developed. The relative cost of process options was considered only if the cost of anoption was believed to be significantly higher than the cost for other process options havingcomparable effectiveness or implementability.
Where possible, a single process option was selected as representative of a GRA. In somecases, more than one process option was selected because the options could not be differen-tiated in terms of effectiveness, implementability, or relative cost. Tables 3-3 and 3-4present the process option evaluations for groundwater and soil, respectively.
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Media-Specific Remedial Alternatives
The remaining process options that were not screened out during the process option evalua-tion were assembled into potential media-specific remedial action alternatives for the site.The statutory preferences contained in the CERCLA amendments, Section 121 (b), wereused in assembling these alternatives. The positive and negative preferences are asfollows:
• Remedial actions that involve treatment that permanently and significantlyreduces the volume, toxicity, or mobility of the contaminants or hazardoussubstances are preferred over remedial actions not involving such treatment.
• Off-facility transport and disposal of hazardous substances or contaminatedmaterials without treatment is considered the least-favored remedial action.
• Remedial actions using permanent solutions, alternative treatmenttechnologies, or resource-recovery are preferred.
Tables 3-5 and 3-6 list the remedial alternatives that were developed to address the site'ssoil and groundwater contamination. The soil and groundwater alternatives were not com-bined into site-wide remedial alternatives to allow for greater flexibility in developingalternatives and to simplify the analysis of the sitewide alternatives.
Groundwater
The following factors guided the development and selection of groundwater remedialalternatives for the site:
• The contamination at the site is migrating to the southwest.
• The only wells sampled during the RI with PCE concentrations near theMCL of 5 fj.g/1 are the GKM well and well S-9, with maximum concentra-tions of 3 and 5 /zg/1, respectively.
• Discrete intervals in both well S-9 and the GKM well have PCE concentra-tions greater than the MCL. Samples collected from 0 to 28 feet deep in theGKM well and 245 to 265 feet deep in well S-9 had maximum concentra-tions of 330 and 17 /xg/1 PCE, respectively.
• Well S-9 is within the zone of influence of the GKM well when the GKMwell is being pumped at its maximum yield (about 13 gpm).
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Groundwater Alternative 1: No Action
The no-action alternative, required by the NCP, is the baseline alternative against whichthe effectiveness of other remedial alternatives would be judged. Under this alternative, nocontrol or remediation would take place. This alternative was retained for further analysis.
Groundwater Alternative 2: Natural Attenuation
Alternative 2 relies on natural processes to decontaminate groundwater. These processesinclude biodegradation, volatilization, adsorption, dispersion, and photolysis. The onlyactivity undertaken during natural attenuation is quarterly monitoring of the contaminants ofconcern in the subject area. The results of the monitoring activities would be used todetermine if natural attenuation was decreasing the concentrations of the contaminants andproviding sufficient protection to human health and the environment. The monitoringwould include obtaining groundwater samples from the GKM well and well S-9. Themonitoring would continue until the 5-year review, at which time a decision would bemade by EPA to either continue or cease the monitoring activities. If at any time duringthe monitoring period the groundwater concentrations at well S-9 begin to increase to thepoint where they could affect the drinking water wells to the southwest, then a contingencyplan (extraction/treatment) would be implemented. Natural attenuation is a viable alter-native because groundwater concentrations of PCE have decreased over time. Thisalternative was retained for further analysis.
Groundwater Alternative 3: Extraction from GKM Well and Air StrippingTreatment
Alternative 3 includes pumping the entire GKM well, treating the extracted water using anair stripper, and discharging the treated water to the local sewer system or a nearby stream.The discharge option should not significantly affect the effectiveness, implementability, orcost. The discharge option will be chosen following discussions with the Commonwealthof Pennsylvania and EPA regarding site ARARs. This alternative also includes the moni-toring of wells S-9 and S-10 to ensure that contamination is not spreading towards themunicipal drinking water wells.
The air stripper would be sized to treat the extracted water to below the required dischargelimit. This limit will be determined from discussions with the appropriate regulatoryauthorities. For this cost estimate, it was assumed that off-gas treatment using vapor-phaseactivated carbon would not be required because of the very low concentrations of VOCsthat would be in the off-gas. The anticipated flow rate of extracted groundwater is13 gpm.
Pumping the GKM well should be effective in controlling the migration of contaminantstowards the municipal drinking water wells. The contamination is currently less than1 /ig/1 PCE in well S-10 and downgradient of this well. Well S-9, which is upgradient ofS-10 and downgradient of the GKM well, is in the radius of influence of the GKM well.
3-9 flR301378
Therefore, the groundwater that has contaminant concentrations near the MCL would bepulled back to the northeast by the pumping of the GKM well.
One potential disadvantage of alternative 3 is that much of the extracted groundwater couldhave a PCE concentration near or below 5 /ig/1. Pumping test data from the RI reportindicate that after 24 hours of pumping, the PCE concentration in the extracted ground-water decreased over time. The sample sent to the CLP had a concentration of 3 /xg/1.Alternative 3 could therefore be treating water that already meets the MCL.
This alternative was retained for further analysis.
Groundwater Alternative 4: Extraction from GKM Well and ActivatedCarbon Treatment
Alternative 4 is the same as alternative 3 except that activated carbon would be used totreat the extracted groundwater instead of air stripping. Activated carbon is sometimesmore cost-effective than air stripping in treating low concentrations of volatile organics ifthe costs to regenerate the spent carbon are low. Both of the technologies should be ableto meet the discharge limits, assuming that the limits are somewhere around the MCL of 5/Ltg/1. Both technologies also can be automated, so little operator attention would berequired. This technology would generate spent carbon that would require treatment and/ordisposal. It could generate a large volume of spent carbon because it would remove bothvolatile and nonvolatile organic compounds from the groundwater.
This alternative was screened out because it provided the same effectiveness as alter-native 3 and was more expensive because of the volume of carbon that would requireregeneration (assuming off-gas treatment is not required).
Groundwater Alternative 5: Extraction from GKM Well and Well S-9 andAir Stripping Treatment
Alternative 5 includes pumping the upper part of the GKM well, where groundwater wasdetermined to have a high concentration of PCE, and well S-9. The extracted groundwaterwould be treated hi a dedicated air stripper for each well. The total flow rate from theGKM well is anticipated to be less than 1 gpm, and the flow rate for well S-9 should beabout 80 gpm.
Alternative 5 would extract the contaminated water sampled during the packer test in theupper part of the GKM well and prevent any contaminated groundwater from migratingpast well S-9 into the municipal drinking water wells. Because of the small volume ofcontaminated groundwater that is entering the GKM well through the upper part of thewell, the groundwater would have to collect over a period of tune and then be periodicallypumped out. A water-level sensor would be needed to start the discharge pump whensufficient water has collected and another to shut off the pump when the groundwater hasbeen removed.
AR30I379
Alternative 5 has the advantage that only a small amount of contaminated groundwaterfrom the GKM well would need to be removed and treated. The disadvantage is that onlyperiodic pumping is feasible of the upper part of the well, and this makes treatmentoperations difficult. Another disadvantage is that well S-9 will produce a large volume(80 gpm) of relatively clean groundwater that was assumed to need treatment beforedischarge to a sewer or nearby stream. This assumption may be revised once the ARARsare evaluated and a discharge method and concentration limit are determined.
Alternative 5 was retained for further analysis.
Groundwater Alternative 6: Extraction from GKM Well and Well S-9 andActivated Carbon Treatment
Alternative 6 is the same as alternative 5 except that the extracted groundwater would betreated using activated carbon. Alternative 6 was not retained because it is more expensivethan alternative 5 and about equally effective.
Soil
The following factors guided the development and selection of soil remedial alternatives forthe site:
• The contamination is in small areas at three locations. There are 115 cubicyards of soil with PCE concentrations greater than 0.27 mg/kg at GentleCleaners, 95 cubic yards of soil at Parkside Apartments greater than0.82 mg/kg, and 400 cubic yards of soil at GKM with PCE concentrationsgreater than 0.26 mg/kg.
• The contamination is relatively shallow. The soil contamination is assumedto be approximately 10 feet deep at Parkside Apartments and GKM and 6 to12 feet deep at Gentle Cleaners; this is the depth to bedrock at the facilities.
• The soil has low permeability. The soils at Gentle Cleaners are silts withlittle clay and a trace of gravel. At GKM and Parkside Apartments, thesoils are fine sandy silts with variable sand, silt, clay, and shale fragments.
• The soil at GKM is covered with asphalt or well-packed gravel.
Soil Alternative 1: No Action
The no-action alternative, required by the NCP, is the baseline alternative against whichthe effectiveness of other remedial alternatives would be judged. Under this alternative, nocontrol or remediation would take place. Alternative 1 was retained for further analysis.
ftR3Qi380
Soil Alternative 2: Natural Attenuation
Alternative 2 relies on natural processes to decontaminate soil. These processes includebiodegradation, volatilization, adsorption, dispersion, and photolysis. The only activityundertaken during natural attenuation is quarterly monitoring of the contaminants of con-cern in the subject area. The results of the monitoring activities would be used to deter-mine if natural attenuation were decreasing the concentrations of the contaminants andproviding sufficient protection to human health and the environment. The monitoringwould include soil sampling from the areas with PCE concentrations greater than PRGs atthe facilities. The monitoring would cease when all soil PCE concentrations were less thanPRGs. Alternative 2 was retained for further analysis.
Soil Alternative 3: Treatment of Soils to Less Than PRGs for PCE
Alternative 3 involves the excavation and treatment of all soil with PCE concentrationsgreater than PRGs. This includes approximately 115 cubic yards of soil at GentleCleaners, 400 cubic yards at GKM, and 95 cubic yards at Parkside Apartments. The treat-ment method would be low temperature thermal treatment (LTTT). The treated soil wouldthen be backfilled onsite. Alternative 3 was screened out because of the high cost.
Soil Alternative 4: Offsite Disposal of Soils With Greater Than PRGs forPCE
Alternative 4 includes the excavation and offsite disposal or treatment of all soils with PCE ^concentrations greater than PRGs. This includes approximately 115 cubic yards of soil atGentle Cleaners, 400 cubic yards at GKM, and 95 cubic yards at Parkside Apartments.Alternative 4 was retained for further analysis.
WDCR754/014.51
3-12 SR30I38I
Section 4Detailed Analysis of Media-Specific Remedial Alternatives
Introduction
The detailed analysis of the media-specific remedial alternatives provides the informationrequired to select the remedy for the North Penn Area 1 site. Alternatives that passed thescreening described in Section 3 have been developed into remedies for soil and ground-water at North Penn Area 1. Each alternative contained in this section addresses potentialthreats posed by soil or groundwater at the site. All of the media-specific alternatives areevaluated against nine criteria defined in the NCP. The first seven criteria were applied inthis FS. The last two criteria will be applied by EPA in the record of decision (ROD).The nine criteria are:
• Protection of human health and environment• Compliance with ARARs• Long-term effectiveness and permanence• Reduction of toxicity, mobility, and volume• Short-term effectiveness• Implementability• Cost• State acceptance• Community acceptance
Evaluation Criteria
The detailed analysis is the means for assembling and evaluating technical and policyconsiderations to develop the rationale for selecting a remedy. The following paragraphsdefine the nine criteria.
Protection of Human Health and Environment
Under this evaluation criterion, the alternative is assessed in terms of how well it achievesand maintains adequate protection of human health and the environment. The overallappraisal of protection draws on the assessments conducted under other evaluation criteria,especially long-term effectiveness and performance, short-term effectiveness, and com-pliance with ARARs.
Compliance with ARARs
Under this evaluation criterion, the alternative is assessed in terms of how well it meetsfederal and state ARARs that have been previously identified. Significant ARARs wouldbe identified for each alternative, and descriptions of how they are met would be given.
When an ARAR is not met, the basis for justifying one of the six waivers allowed underCERCLA would be discussed. A discussion of the compliance of each alternative withchemical- and action-specific ARARs is included.
Long-Term Effectiveness and Permanence
Under this criterion, the alternative is assessed in terms of the risk remaining at the siteafter response objectives have been met. The focus of this criterion is the effectiveness ofthe controls in managing risks posed by treatment residuals or untreated wastes.
Reduction of Toxicity, Mobility, and Volume
Under this criterion, the alternative is assessed in terms of how permanently and signif-icantly it reduces toxicity, mobility, and volume of the hazardous substance. The statutorypreference for such technologies is satisfied when treatment reduces the principal threats atthe site through destruction of toxic contaminants, irreversible reduction in contaminantmobility, or reduction of total volume of contaminated media.
Short-Term Effectiveness
Under this criterion, the alternative is assessed in terms of its effects during theconstruction and implementation phase, up until remedial action objectives are met.Alternatives are evaluated with respect to their effects on human health and the environ- ••ment during implementation of the remedial action, until protection is achieved. ™
Implementability
Under this criterion, the alternative is assessed in terms of the technical and administrativefeasibility of executing it and the availability of various services and materials requiredduring its implementation. Technical feasibility includes construction, operation, reliabilityof technology, ease of undertaking additional remedial action, and monitoring.Administrative feasibility includes activities required by other offices and agencies (e.g.,local permits). Availability of services and materials includes availability of adequateoffsite treatment, storage capacity, and disposal services; necessary equipment andspecialists; services and materials; and prospective technologies.
Cost
Under this criterion, the alternative is assessed in terms of its capital costs, annualoperation and maintenance (O&M) costs, and total present worth. The cost estimates areconsidered order-of-magnitude level and are expected to be accurate within +50 to -30percent for the identified scope of the remedial action. The actual cost of the projectwould depend on the final scope and design of the selected remedial action, the schedule ofimplementation, competitive market conditions, and other variables. Most of these factors ^do not affect the ranking by cost of the alternatives. ••
4"2 HR3QI383
State Acceptance
Under this criterion, the alternative is assessed in terms of technical and administrativeissues and concerns the state may have regarding it. This criterion is not discussed in thisreport but will be addressed in the ROD once comments on the RI/FS reports have beenreceived.
Community Acceptance
Under this criterion, the alternative is assessed in terms of issues and concerns the publicmay have regarding it. As with state acceptance, this criterion is not discussed in thisreport but will be addressed in the ROD once comments on the RI/FS reports have beenreceived.
Analysis of Media-Specific Alternatives
In Section 3, media-specific alternatives are evaluated on the basis of effectiveness,implementability, and cost. Here, each alternative is described and evaluated on the basisof the seven criteria previously discussed. A summary of this evaluation is presented inTable 4-1 and Table 4-2. The media-specific alternatives to be evaluated are as follows:
Groundwater
• Alternative 1—no action
• Alternative 2—natural attenuation
• Alternative 3—extraction from entire GKM well and air stripping treatment
• Alternative 4—extraction from upper part of GKM well and air strippingtreatment
• Alternative 5—extraction from well S-9 and air stripping treatment
Soil
• Alternative 1—no action
• Alternative 2—natural attenuation
• Alternative 3—excavation and offsite disposal of soil that has greater thanPRGs of PCE
4"3
MO
OD
B:
|Q
§UKg
g
Table 4-1
rES EVALUAT
»>•
1
MMARY OF ALTER!
a
<t %V) u•M C•3 |
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U -o c<u c cjQ. M eo. £•»=>•« 2|||HS § o B.^ t3 'j; ~£1?SB!:?
£ 1•c 1e -a Sfj W e «III*
s** "ll|l^li*
M Uw 3
BM t3V 3
is H•< s
aZ
cj C
2 z
«
Ue.*«8
S
m>'•§E15
w
rn
E«13800
8« 'o•5 .Si,^ S10 0
•§ §81u j!S roll3i
_ ws o•3 e.
Provides
suffi
cient
protection of h
uman
he
and environment when
concentrations are
decreased.
No ve
rifica
tion of
protection from
contamination.
8E o2 .3£ >s*-. m° -a1 5P u0.3C
m"
E11
n
1^COuon
•ag
1.2J2•§ <4= O0 Sj= 3
Sir"S c
ll
S ,
Ultimately
will achieve
MCL for PCE.
Action
specific ARARs
are no
applicable.
"co * EZ•— 28
o | . < .S
'c5 j,1 2 '§ "I 3tg § < S. .0 S
Hip!Z C to < C M
f?us^iO Cfiu <
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l_ gn ™ u cS U 3 3 SO "° rt ra *O u
rn -0 JJ .S §
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lll£llQ "O U w tn
o 1 '•= S |•b > o o .—
*-• *
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w ^^ 2 OT .£ «jljlijl
o
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u u uhr -S §Q JtZJ tU CU
en(U
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c uO 00 U 'Q ES *°
iElllllllI=g
1 co id« n J; 5 .£
iiflii£! 00 o g oo "
1 1 i 1 1 i.C 2 fl,) 13 4) tO
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tf
rt ®
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td
|
Table 4-1
ES EVALUATED FOR GROUN
ij>
^g£a§u.OOS<'£.SDen
ON —VI cj
"> £ 8> B H* £ "e "E* Sss g a«* t
co «!
1 =3
I- -U L!u c tjg- ce E
1 S 1 I
lilt^ 1= s2 -en
x cc "-w a. .3!
Alternative 3
Extraction from
Entire
GKM Well and
Air Stripping Treatment
B_O
r) «' - iii<a ~s< 3
«
»•*
^ §
• SB <V O
^
£
UcoCO5W
emission
rate
woul
ID"4 Ib/hr of PCE,
s very low and
red insignificant.
•1 <§ i .-§0 M ._i g£ u •= §t— J2 ? 0
•oIs .«j <« c §III!if b.l*£ > *o
•- ° ~ -§«o ~ •-: c£ u > oH *o ? o
The emission
rate
from the air
stripper would
be 1.95xlO'5
Ib/hr of PC
E which is very
low and considered
insignificant.
C3vt£'cO
^•a«isw „t: gJ g00 0
.1'5E2 „••in u~ sli2 fcon M
1 gp .>
II00 U
3 1 ' "
£ > S s a 1g 0 E .£3 CO S.S oo I; g j t
™ X ^ 00 _S M
llllll
Q. W
„ M eS O
»•!••= §ing 0 H M~ ° |=C3 O t. >TO u CL •*->
« *C B. C Q.C/3 O 3 *w tifi
§ .Is2 I * j, S» (/) p ro Q j£ 3g. « -5 S c§ -o g ,;0 s * •« tT"0 " || | 1 I -f E1 |
u -1 j? M S x .I1 1till nilc/)F n.i= 3 rau-S
S = •«' = J3-<*. C *•- S u ®o g '5 ,., M -o o
. o i J e O ' 3 i g c P c o o
" 'B "o g g""§^ °.|
•i | -| —. | | * g J 5 .|
WO u5P"C3 2 t3 W U CO
1)
1.0"H.o.CQ
Z
1"1iEt
OO
0o
ooVJ
$417,000
$367,620
0
to"c<ugD.
tn5
oiOQ
HR30I386
Table 4-2
iLTERNATIVES EVALUATED
FOR SOI
•to.OI*&2*2aC/3
enAlternative 3
Excavation and
ite Disposal of
Soils >PRG
O
Alternative 2
Natural Attenuation
^ —
O B.1 .2™ *•CO Us<Is
•c*cue
ec"«U
S3.—O
ch of t
he remedial action ob
ed<u8
•o
Provides
suffi
cient pr
otection of h
uman
health and environment.
Cleanup time
estimated at 8 to 25 ye
ars.
1C (A
•S "iw —o csS..2b* to=> .S° 1S §S
o w
iJ-
"5£
X
11« io Pu •—
Cu U
•*«
PCE of at
each
facili
ty wil
lvariance to the LDRs
may 1
J
illallT3
The PRGs
for PCE in
soil
will be
achieve^
Action-specific ARARs
are not applicable.
Cleanup time estimated at 8 to 25.
8.9 '5>
>. 0 JU
OJ) . O
'§ .£ 0,c CSB <; o
IliaUS!ill!z-g li
SL<;5;|
S.2"S.£5
i
ing-term exposure to contam
reating VOCs
in
soil.
o *-— Eto •—
•i '1•— ieW tx]
. S"•o 5:
Eliminates long-term exposure to
contaminants
after
natural processes degra
contaminants to PRGs.
Effective in remoi
VOCs
from
soil.
2c1"c
g rfcs n
11rt > »
U 4)Cfl >
•oisgillh* cW) Cc S0 uJ cu
•a(U3•a
tentia
l of so
il contaminants
iiff
site.
llS "*"
•a3
The res
ults of th
e monitoring
activ
ities wo
be used to determine
if na
tural attenuation
were
decreasing the concentrations of t
hecontaminants.
c2. Bra o i-c^l-8o & 3 n•O -75 -0 =U M U •« >< ctf *• s ^J • "~
.£ 1 5
ilihIfljlZ3 111
B.6"Jo;'5'g|2
IIO «i
S •g -oci ci
'5<" CJ•o >o -a= 1
nd tr
ansportation of c
ontami
icreases vo
latile emissions,
flikelihood of a
ccidents.
ra c <oc 'r -so.S'-a
1151^1
tf)
1
o"5Vi
10
t:o00
„g3CJ
"cotoC'co
a.V
i5 J3o «
Sg>1£
1|S•eo00
a
1 =
line c
onstruction
activi
ties.
nd materials needed
are avai
uire treatment
at di
sposal
fai
regulations.
0 ™ 1> "§"~ c >. !£ 1 2 ;>,— .& "3-£ tefiS 3
o 52 ?hft . . fl> O
Easily implemented.
Continual monitorinj
the contaminants of co
ncern in the subject
area is required.
The monitoring would
c<
when
all so
il PCE concentrations were
bel
PRGs.
u
1CL1
.1?ic4>"5.j=
$429,516
$150,744
o
to£c
fc.tina
<-*» irnp*om•nr-u
o
O
Description of Groundwater Remedial Alternatives
Groundwater Alternative 1: No Action
Under the no-action scenario, no control or remediation would take place. The no-actionalternative, required by the NCP, is the baseline remedial alternative against which theeffectiveness of other remedial alternatives will be judged.
Protection of Human Health and Environment
The no-action alternative would not protect human health or the environment from presentcontamination levels. The risk posed by the facilities would not be decreased. The risk ofpotential exposure would continue from the contaminated media.
Compliance with ARARs
The no-action alternative would not meet any chemical-specific ARARs. Action-specificARARs are not applicable because no action occurs.
Long-Term Effectiveness and Permanence
The no-action alternative would not provide long-term effectiveness and permanence. Therisk currently associated with the facilities would not be decreased and may be increasedthrough migration of contaminants. This alternative would provide no control of thecontaminants. Because contaminants would be left at the facility, a review of the siteconditions would be required every 5 years.
Reduction of Toxicity, Mobility, and Volume
The no-action alternative would not provide any reduction of toxicity, mobility, or volumeand would not meet the statutory preference for treatment.
Short-Term Effectiveness
Because no action would occur under this alternative, the level of risk to human health andthe environment remains at current levels.
Implementability
This alternative does not have a monitoring or construction component associated with it;therefore, there are no issues concerning implementation.
4-4 HR30I388
Cost ±
Taking no action would require no expenditure of money for capital purposes. As part ofthe 5-year review process, samples may be required and time could be expended onpreparing a report detailing the risk associated with the facility; however, these costs havenot been included in the FS.
Groundwater Alternative 2: Natural Attenuation
This alternative is the no-action alternative with monitoring to determine if naturalprocesses are achieving the PRGs. The natural processes include biodegradation,volatilization, adsorption, dispersion, and hydrolysis. Quarterly monitoring of thecontaminants of concern would be conducted in the subject area to determine if naturalattenuation was decreasing the concentrations of the contaminants and providing sufficientprotection to human health and the environment. The monitoring would include obtaininggroundwater samples from the GKM well and well S-9. The monitoring would continueuntil the 5-year review, at which tune a decision would be made by EPA to continue orcease the monitoring activities. If at any time during the monitoring period the ground-water concentrations at well S-9 begin to increase to the point where the drinking waterwells to the southwest could be affected, then a contingency plan (extraction/treatment)would be implemented.
Protection of Human Health and Environment
Alternative 2 would provide sufficient protection to human health and environment when allgroundwater PCE concentrations are decreased. It may take up to 91 years for the processof natural attenuation to reduce the contamination in groundwater to the background con-centration if the contaminated soil is not treated or removed from the site. Up to 76 yearswould be required if the contaminated soil is removed. These times assume cleanup to thebackground concentration, which is probably zero. Less time would be required to cleanup to below the MCL. A conservative modeling effort was conducted to estimate timerequired for cleanup; this modeling effort is described in Appendix B.
Compliance with ARARs
Alternative 2 would achieve the MCL for PCE. Action-specific ARARs are not applicablebecause the only activity taken during natural attenuation is quarterly monitoring of thecontaminants of concern.
Long-Term Effectiveness and Permanence
This alternative would eliminate long-term exposure to contaminants because naturalprocesses would reduce contaminant concentrations.
BR30I389
Reduction of Toxicity, Mobility, and Volume
Alternative 2 would reduce the toxicity, mobility, and volume of the contaminatedgroundwater through natural processes. The monitoring results would be used to verifythat natural attenuation was decreasing the concentrations of the contaminants.
Short-Term Effectiveness
Under alternative 2, the level of short-term risk to human health and the environmentwould remain at current levels. On the other hand, alternative 2 would not affect humanhealth during implementation.
Implementability
Alternative 2 would be easy to implement. Periodic monitoring of the contaminants ofconcern in the subject area would be required to verify the effectiveness of naturalattenuation. A contingency plan (extraction/treatment) would be developed for implemen-tation if the sampling data indicated that contamination was posing a threat to human orenvironmental receptors.
Cost
The capital cost would be $0. The O&M costs would be $11,140 per year. The totalpresent worth cost based on monitoring over a 30-year period would be $367,620.
Groundwater Alternative 3: Extraction from Entire GKM Well andAir Stripping Treatment
Alternative 3 includes pumping the entire GKM well, treating the extracted water using anair stripper, and discharging the treated water to the local sewer system. Alternative 3 alsoincludes the monitoring of wells S-9 and S-10 to ensure that further contamination is notspreading towards the municipal drinking water wells.
The air stripper will be sized to treat the extracted water to below the required dischargelimit. This limit will be determined in discussions with the appropriate regulatoryauthorities. For the cost estimate, it was assumed that off-gas treatment using vapor-phaseactivated carbon would not be required because of the very low concentrations of VOCsthat would be in the off-gas. The anticipated flow rate of extracted groundwater is13 gpm.
Protection of Human Health and Environment
Alternative 3 would provide protection to both human health and environment.Groundwater extraction and air stripping treatment would reduce the threat to human healthposed by ingestion of contaminated groundwater and would reduce the possibility of further
4-6
HR3Q1390
environmental degradation. The remediation tune estimated for transport only using thistechnology is estimated to be more than 500 years because the GKM well is at the head ofthe contaminant plume, and only a part of the plume would be affected by pumping thewell. Also, there would be much more clean water pumped from upgradient and side-gradient of the well (see Appendix B). Natural processes are estimated to achieve cleanupin 76 to 91 years as described under alternative 2. Relying solely on pumping, the GKMwell appears to not be effective; however, the value in pumping from this well is tointercept and remove the more highly contaminated groundwater assumed to be present inand entering the aquifer in the vicinity of Gentle Cleaners. Contaminated groundwaterdowngradient from the pumping influence of the GKM well would continue to migratetoward pumping well S-10.
Compliance with ARARs
Alternative 3 would meet the MCL for PCE (5 /xg/1). To meet action-specific ARARs, thegroundwater treatment system would be designed to meet the pretreatment standards orNPDES criteria for discharge of treated water to a POTW. The air treatment systems forthis technology, if required, would be designed to comply with federal and stateregulations.
Long-Term Effectiveness and Permanence
Alternative 3 would eliminate long-term exposure to contaminants because human healthrisks posed by ingestion of groundwater in the future would be reduced commensurate withthe reduction of PCE to less than 5 (ig/l by the pump and treat systems.
Reduction of Toxicity, Mobility, and Volume
Pumping the GKM well should be effective in controlling the migration of contaminantstowards the municipal drinking water wells from the upgradient part of the contaminantplume. The PCE contamination is currently less than 1 jug/1 in well S-10 and downgradientof well S-10. Well S-9, which is upgradient of S-10 and downgradient of the GKM well,is in the radius of influence of the GKM well. Therefore, the groundwater that hascontaminant concentrations near the MCL would be pulled back to the northeast by thepumping of the GKM well. The air stripper would be sized to treat the extracted water tobelow the required discharge limit.
Short-Term Effectiveness
The air stripper would produce the off-gas at a very low emission rate of 1.95 x 10"5 Ib/hrof PCE, which is considered insignificant. Once the groundwater extraction and treatmentsystems are installed, the contaminant plume would begin to recede from its currentposition.
O4-7 BR30I39I
Implementability
Alternative 3 is implementable. It involves the use of proven technologies. All equipmentand materials exist and are readily available in modular, off-the-shelf packages. Operationwould require monitoring of the groundwater and the air to assess the effectiveness of thegroundwater extraction and treatment systems. One potential disadvantage of alternative 3is that much of the extracted groundwater could have a PCE concentration near or below5 /Ltg/1. Pumping test data from the RI report indicate that, after 24 hours of pumping, thePCE concentration in the extracted groundwater decreased over time and the sample sent tothe CLP had a concentration of 3 jwg/1. Alternative 3 could therefore be needlessly treatingwater that already meets the MCL.
Cost
It has been estimated that the present worth cost of alternative 3 would be $417,000 with acapital cost of $7,586 (the cost of vapor-phase activated carbon for the off-gas treatmentwas not included) and an annual O&M cost of $13,593 (see Appendix C).
Groundwater Alternative 4: Extraction from Upper Part of GKM Welland Air Stripping Treatment
Alternative 4 includes pumping the upper part of the GKM well, where groundwater wasdetermined to have a high concentration of PCE. The extracted groundwater would betreated in an air stripper and then discharged to the local sewer system. The flow rate ofextracted groundwater is anticipated to be less than 1 gpm.
Under alternative 4, the contaminated water sampled during the packer test in the upperpart of the GKM well would be extracted. Contaminated groundwater would be preventedfrom migrating past well S-9 into the municipal drinking water wells. Because the volumeof contaminated groundwater entering the GKM well through the upper part of the well issmall, the groundwater would have to collect over a period of time and then periodically bepumped out. A water-level sensor would be needed to start the discharge pump whensufficient water has collected, and another to shut off the pump when the groundwater hasbeen removed.
Protection of Human Health and Environment
Overall protection of both human health and environment would be similar to that ofalternative 3. The remediation tune is estimated to be less than the cleanup tune foralternative 2 (91 years if the contaminated soil is not removed or 76 years if thecontaminated soil is removed) because the highly contaminated groundwater carryingthrough the fractures above the water level into the well would be intercepted and pumpedoff (see Appendix B).
4"8 flR30!392
Compliance with ARARs ^
Alternative 4 would be similar to alternative 3 with regard to ARARs.
Long-Term Effectiveness and Permanence
The long-term effectiveness and permanence of alternative 4 would be similar to that ofalternative 3.
Reduction of Toxicity, Mobility, and Volume
All effects would be the same as those of alternative 3.
Short-Term Effectiveness
Implementation of alternative 4 would have some possibility of risk, similar to that ofalternative 3. The emission rate is estimated at 1.5 x 10"6 Ib/hr of PCE.
Implementability
The implementation of alternative 4 would be the same as that of alternative 3, except onlyperiodic pumping of the upper part of the well is feasible because it will generate only1 gpm. Alternative 4 has an advantage in that only a small amount of contaminatedgroundwater from the GKM well would need to be removed and treated. The disadvantageis that only periodic pumping of the upper part of the well is feasible, which makestreatment operations difficult.
Cost
The total present worth cost is estimated to be $381,000 (which reflects a period of30 years of operation) based on a capital cost of $7,586 and an annual O&M cost of$12,417 (see Appendix C).
Groundwater Alternative 5: Extraction from Well S-9 and Air StrippingTreatment
Alternative 5 includes pumping of the entire screened portion of well S-9. The extractedgroundwater would be treated in an air stripper and then discharged to the local sewersystem or a nearby stream. The flow rate of extracted groundwater is anticipated to beabout 80 gpm.
O4"9 BR30I393
Protection of Human Health and Environment
Overall protection of both human health and environment would be similar to that ofalternative 3. The remediation time is estimated to be 116 years if the contaminated soilremains at the site, or 101 years if the soil is removed. The length of time required forcleanup would vary depending on removal of the contaminated soil (source). A conser-vative modeling effort was conducted to estimate time required for the cleanup; thismodeling is described in Appendix B.
Compliance with ARARs
Alternative 5 would be similar to alternative 3 with regard to ARARs. In addition, thegroundwater treatment system also would be designed to meet federal and state limitationsto prevent exceedances of the water quality standards for discharge of treated water to thecreek.
Long-Term Effectiveness and Permanence
The long-term effectiveness and permanence of alternative 5 would be similar to that ofalternative 3, except that this technology would not prevent the migration of contaminatedgroundwater from the GKM well.
Reduction of Toxicity, Mobility, and Volume
All effects would be the same as those of alternative 3, except that alternative 5 would notreduce toxicity, mobility, or volume of contaminated groundwater from the GKM well.
Short-Term Effectiveness
Implementation of alternative 5 would have some possibility of risk, similar to that ofalternative 3. The emission rate is estimated at 2.0 x 10"4 Ib/hr of PCE.
Implementability
The implementation of this alternative would be the same as that of alternative 3, exceptthat only the contaminated groundwater from well S-9, and not from the GKM well, wouldbe extracted and treated. Alternative 5 has a disadvantage in that well S-9 will produce alarge volume (80 gpm) of relatively clean groundwater that may have to be treated anyway,before discharge to a sewer or nearby stream.
Cost
The total present worth cost is estimated to be $695,000 (which reflects 30 years ofoperation). The capital cost is $8,586, and the annual O&M cost is $22,829 (seeAppendix C).
4-10
Comparative Analysis of Groundwater Alternatives ^
The five groundwater alternatives were compared on the basis of the seven evaluationcriteria to identify the relative benefits of each alternative.
Overall Protection of Human Health and Environment
All of the groundwater alternatives except alternative 1 (no action) would provide adequateprotection of human health and the environment and would address the remedial actionobjectives. Alternative 2 would require a long cleanup time, and continual monitoring alsowould be required to verify the effectiveness of natural attenuation. Alternatives 3,4, and5 (groundwater extraction and treatment) would require cleanup times of varying length,would reduce the threat to human health posed by ingestion of contaminated groundwater,and would reduce the possibility of further environmental degradation.
Compliance with ARARs
The evaluation of the ability of the alternatives to cornply with ARARs included a reviewof chemical-specific and action-specific ARARs that were presented earlier in this report.There are no known location-specific ARARs for the facilities.
Alternatives 2, 3, 4, and 5 would meet the MCL for PCE (5 /xg/1). Action-specificARARs are not applicable for alternative 2. To meet action-specific ARARs, the ground-water treatment systems for alternatives 3,4, and 5 would be designed to meet federal andstate limitations. The air emission treatment systems for these alternatives, if required,would be designed to comply with federal and state regulations.
Long-Term Effectiveness and Permanence
Alternatives 2, 3, 4, and 5 would eliminate long-term exposure to contaminants becausehuman health risks posed by ingestion of groundwater in the future would be reducedcommensurate with the reduction of PCE to less than 5 jiig/1. Alternatives 3, 4, and 5would provide a higher degree of protection from risks than would alternatives 1 and 2because of the implementation of pump and treat systems; however, alternative 4(extraction from the upper part of the GKM well and treatment) would not prevent themigration of contaminated groundwater from either well S-9 or the GKM well, and alter-native 5 (extraction from well S-9 and treatment) would not prevent the migration ofcontaminated groundwater from the vicinity of the GKM well.
Reduction of Toxicity, Mobility, and Volume Through Treatment
Alternatives 2, 3, 4, and 5 would be effective in controlling the migration of contaminants;however, alternative 5 would not provide reduction of the mobility or volume of contam-inated groundwater from the vicinity of the GKM well.
Ift4-11
Short-Term Effectiveness
There are no additional short-term risks associated with alternatives 1 and 2.Alternatives 3,4, and 5 could pose a small additional risk to the community because of theair stripper off-gas.
Implementability
Alternative 2 would require quarterly monitoring activities, which are easily implemented.Alternatives 3, 4, and'5 require groundwater extraction and air stripping treatment, whichare proven technologies. All equipment and materials are readily available.
Alternative 3 (extraction from entire GKM well at 13 gpm flow rate and treatment) wouldhave a potential disadvantage in that much of the extracted groundwater could contain PCEat a concentration near or below 5 jug/1, which means this technology could involve treat-ment of water that already meets the MCL.
Alternative 4 would involve periodic pumping of the upper part of the GKM well at 1-gpmflow rate. Thus, only a small volume of contaminated groundwater from the GKM wellwould need to be removed and treated. However, since only periodic pumping of theupper part of the well is feasible, the treatment operations would be more difficult.
Alternative 5 (extraction from well S-9 only, and treatment) would have a disadvantage inthat well S-9 would produce a large volume (80 gpm) of relatively clean groundwater thatwas assumed to need treatment before discharge to a sewer or nearby stream.
Cost
Table 4-3 summarizes the costs of the five groundwater alternatives.
Table 4-3SUMMARY OF COSTS OF GROUNDWATER ALTERNATIVES 1 THROUGH 5
Capital Costs
O&M Costs(per year)
Total PresentWorth Costs
Alternative 1(No Action)
$0
$0
$0
Alternative 2(Natural
Attenuation)
$0
$11,040
$367,620
Alternative 3(Extractionfrom GKMWell andTreatment)
$7,586
$13,593
$417,000
Alternative 4(Extractionfrom UpperPart of GKMWell andTreatment)
$7,586
$12,417
$381,000
Alternative 5ExtractionFrom WellS-9 and
Treatment)
$8,586
$22,829
$695,000
4"12 AR30I396
Description of Soil Alternatives *
Soil Alternative 1: No Action
Under the no-action alternative, no control or remediation would take place. The no-actionalternative, required by the NCP, is the baseline remedial alternative against which theeffectiveness of other remedial alternatives would be judged.
Protection of Human Health and Environment
The no-action alternative would not protect human health or the environment from presentcontamination levels. The risk posed by the facilities would not be decreased. The risk ofpotential exposure to the contaminated media would continue.
Compliance with ARARs
The no-action alternative would not meet any chemical-specific ARARs. Action-specificARARs are not applicable because no action would occur.
Long-Term Effectiveness and Permanence
The no-action alternative would not provide long-term effectiveness and permanence. Therisk currently associated with the facilities would not be decreased and may be increasedthrough migration of contaminants. This alternative provides no control of thecontaminants. Because contaminants would be left at the facilities, a review of the siteconditions would be required every 5 years.
Reduction of Toxicity, Mobility, and Volume
The no-action alternative would not provide any reduction of toxicity, mobility, and volumeand would not meet the statutory preference for treatment.
Short-Term Effectiveness
Because no action would occur under this alternative, the level of risk to human health andthe environment would remain at current levels.
Implementability
The no-action alternative does not have a monitoring or construction component associatedwith it; therefore, there are no issues concerning implementation.
O4-13 AR30I397
Cost
Taking no action would require no expenditure of money for capital purposes. As part ofthe 5-year review process, samples may be required and time expended on preparing areport detailing the risk associated with the facilities; however, these costs have not beenincluded in this FS.
Soil Alternative 2: Natural Attenuation
Alternative 2 is the no-action alternative with monitoring to determine if natural processesare achieving the PRGs. The natural processes include biodegradation, volatilization,adsorption, dispersion, and photolysis. The only activity taken during natural attenuationwould be quarterly monitoring of the contaminants of concern in the subject area. Theresults of the monitoring activities would be used to determine if natural attenuation wasdecreasing the concentrations of the contaminants and providing sufficient protection ofhuman health and the environment. The monitoring would include soil sampling in theareas at each facility where PCE concentrations are greater than PRGs (0.27 mg/kg atGentle Cleaners, 0.26 mg/kg at GKM, and 0.82 mg/kg at Parkside Apartments). Themonitoring would cease when all soil PCE concentrations were less than PRGs.
Protection of Human Health and Environment
Alternative 2 would provide sufficient protection of human health and environment whenall soil PCE concentrations were decreased. The contaminated soil may require up to16 years (see Appendix D) of natural attenuation to reach the PRGs for PCE in soil. Thedegradation time is estimated to be 8 years at the Gentle Cleaners facility, 16 years atParkside Apartments, and 11 years at GKM.
Compliance with ARARs
Alternative 2 would achieve the PRG for PCE in soil. Action-specific ARARs are notapplicable because the only activity taken during natural attenuation is quarterly monitoringof the contaminants of concern.
Long-Term Effectiveness and Permanence
Alternative 2 would eliminate long-term exposure to contaminants because naturalprocesses would reduce contaminant concentrations.
Reduction of Toxicity, Mobility, and Volume
Alternative 2 would provide reduction in the toxicity, mobility, and volume of thecontaminated soil through natural processes. The monitoring results would be used toverify that natural attenuation was decreasing the concentrations of the contaminants.
4-14
301398
Short-Term Effectiveness ^
Under alternative 2, the level of short-term risk to human health and the environmentwould-remain at current levels. On the other hand, this alternative would not affect humanhealth during its implementation.
Implementability
Alternative 2 would be easy to implement. Continual monitoring of the contaminants ofconcern in the subject area would be required to verify the effectiveness of naturalattenuation. A contingency plan would be developed for implementation if sampling dataindicated that the contamination was posing a threat to human or environmental receptors.
Cost
The capital cost would be $0. The annual O&M cost would be $13,704. The total presentworth cost based on monitoring conducted over a 10-year period would be $150,744 (seeAppendix C).
Soil Alternative 3: Excavation and Offsite Disposal of Soil HavingGreater Than PRGs for PCE
Alternative 3 includes the excavation and offsite disposal or treatment of all soil havingPCE in concentrations greater than PRGs. Soil in this category includes approximately115 cubic yards of soil at Gentle Cleaners, 400 cubic yards at GKM, and 95 cubic yards atParkside Apartments.
Protection of Human Health and Environment
Alternative 3 would provide protection of human health by preventing ingestion ofgroundwater that is contaminated above the MCL of 5 /ig/1. All soil with PCE atconcentrations above PRGs would be removed from the site and properly treated and/ordisposed of in an engineered and permitted landfill.
Compliance with ARARs
Alternative 3 would meet the PRG for PCE at each facility. The significant action-specificARARs are the MCLs.
Long-Term Effectiveness and Permanence
Alternative 3 would eliminate short- and long-term exposure to PCE in concentrationsgreater than PRGs because contaminated soil above the PRG level would be removed from
Ift
4"15 flR30!399
the site. The long-term effectiveness would be realized by properly treating thecontaminated soil before landfilling.
Reduction of Toxicity, Mobility, and Volume
Alternative 3 would reduce the mobility and migration of contaminants because thecontaminants would be disposed of in a permitted landfill offsite.
Short-Term Effectiveness
Implementation of alternative 3 would have some potentially adverse effects on humanhealth and the environment. Volatile emissions and fugitive dust could increase during theexcavation and transportation of soil around the site. In addition, trucks would be requiredto transport the contaminated soil to an offsite facility. The probability of traffic accidentson the roads between the site and the disposal facility would increase.
Implementability
Alternative 3 is implementable. Its elements are all routine construction activities. Allequipment and materials exist and are readily available. Soil may require treatment at adisposal facility to comply with regulations.
Cost
The total present worth cost of alternative 3 is estimated to be $429,516 (see Appendix C).No O&M costs are expected because the technology does not involve an extended remedia-tion period and because no long-term management, maintenance, or monitoring would berequired.
Comparative Analysis of Soil Alternatives
The three alternatives were compared on the basis of the seven evaluation criteria toidentify the relative benefits of each alternative.
Overall Protection of Human Health and Environment
All of the alternatives except alternative 1 (no action) would provide adequate protection ofhuman health and the environment and would address the remedial action objectives.Alternative 2 would require a long cleanup time, and continual monitoring also would berequired to verify the effectiveness of natural attenuation. Alternative 3 (excavation andoffsite disposal) would provide long-term protection of human health and environment atthe site by removing the contaminated soil. However, alternative 3 would present short-term risks during excavation.
4"16 flRSOUOO
Compliance with ARARs ^
The evaluation of the ability of the alternatives to comply with ARARs included a reviewof chemical-specific and action-specific ARARs that were presented earlier in this report.There are no known location-specific ARARs for the site.
Alternative 2 (natural attenuation) and alternative 3 (excavation and offsite disposal) wouldachieve the PRGs for PCE in soil. Action-specific ARARs are not applicable toalternative 2. Alternative 3 would require an evaluation of the LDRs to determine if offsitesoil treatment would be required before disposal.
Long-Term Effectiveness and Permanence
Alternative 3 would provide a higher degree of long-term protection from risks than wouldalternatives 1 and 2.
Reduction of Toxicity, Mobility, and Volume Through Treatment
Alternatives 2 and 3 would provide reduction in toxicity, mobility, and volume of thecontaminated soil.
Short-Term EffectivenessIIThere are no additional short-term risks associated with alternatives 1 and 2. For ^
alternative 3, short-term effectiveness would be affected by the required excavation andtransportation of soil.
Implementability
Alternative 2 would require quarterly monitoring activities, which are easily implemented.Alternative 3 would consist of standard construction activities (excavation and offsitedisposal). All equipment and materials are available. An LDR variance would be requiredif soil that might be hazardous is to be placed in a landfill without prior treatment.
4'" J3R30UOI
Cost
Table 4-4 summarizes the costs of the three soil alternatives.
Table 4-4SUMMARY OF COSTS OF SOIL ALTERNATIVES 1, 2, AND 3
Capital CostsO&M CostsTotal PresentWorth Costs
Alternative 1(No Action)
$0
$0
$0
Alternative 2(Natural
Attenuation)
$0
$13,704
$150,744
Alternative 3(Excavation and Offsite
Disposal of Soil >26 mg/kg)
$429,516
$0
$429,516
WDCR753/017.51
4-18 flR30U02
Section 5Works Cited
Logan, Floyd A. Deposition. September 10, 1991.
McManus, Patrick. Personal Communication. 1992.
Musheno, Michael. Lansdale Groundwater Contamination Investigation. Letter to EPAfiles. July 1980.
NUS Corporation. A Field Trip Report for North Penn Water Authority. September 8,1986.
Summers, K. et al. Methodology to Evaluate the Potential for Groundwater Contaminationfrom Geothermal Fluid Releases. Report No. EPA-600/7-80-117. IndustrialEnvironmental Research Laboratory, EPA. 1980.
Stoudt, Paul. Personal Communication. 1989.
Techlaw, Inc. Final Facility Report, North Penn Area Gentle Cleaners/Granite KnittingMills Site. October 2, 1987.
U.S. Environmental Protection Agency. Guidelines for Carcinogen Risk Assessment. 561Federal Register 33992. September 24, 1986a.
U.S. Environmental Protection Agency. Guidelines for Health Risk Assessment ofChemical Mixtures. 51 Federal Register 34014. September 24, 1986b.
U.S. Environmental Protection Agency. Guidelines for Estimating Exposure. 51 FederalRegister 34042. September 24, 1986c.
U.S. Environmental Protection Agency. CERCLA Compliance with Other Laws Manual:Draft Guidance. EPA/540/G-89/006, EPA Office of Emergency and Remedial Response,Washington, D.C. August 1988.
U.S. Environmental Protection Agency. Exposure Factors Handbook. Office of Healthand Environmental Assessment. EPA/600/8-89/043. 1989a.
U.S. Environmental Protection Agency. Risk Assessment Guidance for Superfund, VolumeI, Human Health Evaluation Manual (Pan A). Office of Emergency and RemedialResponse. Interim Final. EP A/540/1-89/001. March 1989b.
U.S. Environmental Protection Agency. RCRA Facility Investigation Guidance. EPA4fc 530/SW-89-031. May 1989c.
54 AR30U03
U.S. Environmental Protection Agency. Human Health Evaluation Manual, Supplemental ±Guidance: Standard Default Exposure Factors. Office of Solid Waste and Emergency UpResponse. 1991.
Versar, Inc. Technical Evaluation of Zone Contamination 1 (Gentle Cleaners, GraniteKnitting Mills, Parkside Apartments Site). Souderton, Pennsylvania. August 1, 1988.
WDCR753/020.51
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5"2 ftR30|ltOI»
Appendix APreliminary Remediation Goals
Introduction
Preliminary remediation goals or soil action levels (SALs) have been estimated for PCE foreach of the following facilities in North Penn Area 1: Gentle Cleaners, Granite KnittingMills, and Parkside Apartments. Facility-specific data have been used whenever available.The input data are discussed in the following section. In the next section some aspects ofthe uncertainty in the SALs estimated by this approach are presented. Finally, the resultsand conclusions are provided.
Input Data
Estimating the Dilution Factor for the Aquifer
The dilution factor of infiltrating water in the aquifer is estimated by dividing the volumeof infiltration by the sum of the volume of infiltration and volume of aquifer flow. Tocalculate these volumes values for several parameters are required.
The area of contamination for each facility was determined by outlining the area wherecontamination was detected. For sampling locations that are adjacent, one withcontamination and the other without, the boundary of the contaminated area was drawnapproximately halfway between each point. The areas are presented in the first row ofTable A-l.
The annual infiltration rate at all facilities was specified, at EPA's request, to be one-halfof the average annual precipitation rate of 45 inches (i.e., 22.5 inches or 1.9 feet). Theassumption is that the precipitation rate is equally distributed throughout the year.
The annual infiltration volume is then estimated by multiplying the area of contamination ateach facility by the annual infiltration rate, as shown hi the third row of Table A-l.
The width of the flow zone at each facility was calculated by first estimating the flowdirection of groundwater in the underlying bedrock. At Gentle Cleaners and GraniteKnitting Mills this direction is estimated to be approximately to the south; at ParksideApartments the direction is estimated to be approximately to the southwest. The width ofthe area of contamination perpendicular to the flow direction was then estimated. Thewidth of the flow zone at each facility is provided in the fourth row of Table A-l.
Table A-lESTIMATING THE DILUTION FACTORS IN THE AQUIFER FOR
INFILTRATING SOIL WATER
ParameterArea of
Contamination(ft2)
InfiltrationRate (ft/yr)
InfiltrationVolume(ftVyr)
Width of FlowZone (ft)
Depth ofAquifer (ft)
HydraulicGradientHydraulic
Conductivity(ft/yr)
Aquifer FlowVolume(ft3/yr)
AquiferDilutionFactor
Facility
Gentle Cleaners720
1.9
1,368
36
100
0.0034
1,460
17,870
0.071
GraniteKnitting Mills
6,313
1.9
11,995
205
100
0.0034
1,460
101,762
0.11
ParksideApartments
2,680
1.9
5,092
74
100
0.028
1,460
302,512
0.017
Ift
Ift
The depth of the aquifer for the purposes of the SAL calculation was assumed to be thedepth of the shallowest domestic wells at the site. Reportedly the two shallowest wells are90 and 100 feet deep. A depth of 100 feet was selected for the depth of the aquifer for thepurposes of this analysis.
OA"2 flR30|(*06
The hydraulic gradient was estimated from the hydraulic-head map provided in the RIreport. At Gentle Cleaners and Granite Knitting Mills the gradient was estimated using thewater level from the Granite Knitting Mills well and NPWA well S-19, with water levelsof 354.71 and 350.72 feet above mean sea level (msl), respectively. With a distance of1,170 feet between the wells, the gradient is estimated to be 0.0034. The gradient atParkside Apartments was estimated from the water levels in well S-19 (350.72 feet msl)and the Souderton Borough well (342.30 feet msl) located behind the Apartments. With aseparation distance of 300 feet, the gradient in this area is estimated to be 0.028. Thegradient is higher near Parkside Apartments than in the vicinity of Gentle Cleaners andGranite Knitting Mills because of the proximity of Parkside Apartments to NPWA pumpingwells S-10 and S-8. The gradients are provided in the sixth row of Table A-l.
The hydraulic conductivity of the bedrock was estimated from the data provided in the RIreport. A pumping test performed in well S-9 yielded a transmissivity of 1,200 square feetper day using drawdown data from the Souderton Borough well. Assuming an aquiferthickness of 300 feet (i.e., the depth of the pumping well) the hydraulic conductivity isestimated to be 4 feet per day, or 1,460 feet per year.
Using the data for hydraulic gradient and conductivity and aquifer thickness and width, theannual aquifer flow volume beneath each facility was estimated. These values are providedin the next to last row of Table A-l.
Using the annual volumes of infiltration and of aquifer flow the dilution factor ofinfiltrating water in the aquifer is estimated using the Summers' model (described in the RIand FS reports). The calculation is simply dividing the volume of infiltration by the sumof the volume of infiltration and volume of aquifer flow. The dilution factors are providedin the last row of Table A-l.
Estimating Transport Parameters
The organic carbon-water distribution coefficient (K ) of PCE was defined as364 milliliters per gram (ml/gm), a value provided by,EPA. The fraction of organiccarbon (foc) for each facility was estimated from data obtained during the soil investigation.The values presented in the second row of Table A-2 are the median values from eachfacility. The product of the Koc and the f is the distribution coefficient (Kd) provided inthe third row of Table A-2. It was assumed that there is no adsorption of PCE on the sidesof fractures transmitting contaminated soil water from the top of bedrock down to the watertable, which means that the contamination will migrate at the same rate as the water in theunsaturated bedrock.
To account for degradation of PCE as it migrates through the vadose zone, the length oftime it takes for soil water contaminated with PCE to migrate from the top of bedrock tothe water table at each facility was estimated. The depth from the top of bedrock to thewater table is approximately 20 feet at Gentle Cleaners and Granite Knitting Mills andapproximately 5 feet at Parkside Apartments. The soil at the facility was assumed to be
A-3HR30U07
contaminated to a uniform concentration throughout the full depth of the soil, from the -~ground surface to the top of bedrock. ••
Table A-2ESTIMATING TRANSPORT PARAMETERS
ParameterK,,,, (ml/gm)
'•oc
Kj (ml/gm)
Soil-WaterFlow Rate(ft/yr)
Distance toTravel (ft)Travel Time
(years)Degradation-Rate Constant
(per yr)
Reduction inConcentration
Due toDegradation
Facility
Gentle Cleaners364
0.00245
0.892
9.5
20
2.1
0.693
0.23
GraniteKnitting Mills
364
0.00365
1.33
9.5
20
2.1
0.693
0.23
ParksideApartments
364
0.00529
1.93
9.5
5
0.53
0.693
0.69
Ift
Water is assumed to infiltrate through the unsaturated bedrock at a rate controlled by theinfiltration rate, the hydraulic gradient, and the effective porosity of the rock. Theinfiltration rate is estimated at 1.9 feet per year and the effective porosity of the rock isestimated at 20 percent. Dividing the infiltration rate by the effective porosity andassuming a unit hydraulic gradient provides an estimated flow rate of water in theunsaturated bedrock of 9.5 feet per year.
The distance from the top of bedrock to the water table at each facility was then divided bythe soil-water flow rate as shown in Table A-2 to obtain an estimate of the travel tune tothe water table. Based on these estimates, it takes 2.1 years at Gentle Cleaners and Granite -Knitting Mills for contaminated soil water to migrate from the top of bedrock (i.e., the ••
A-4 5R30U08
bottom of the contaminated soil) to the water table. Similarly, it takes about one-half yearat Parkside Apartments.
During the time of travel, degradation will take place. Several estimates for thedegradation rate of PCE were obtained from various sources and are listed in Table A-3.
Table A-3DEGRADATION RATES FOR PCE
DegradationHalf-Life
(yr)1 to 2
0.3 to 4.5
0.8
0.7 to 6
DegradationRate Constant
d/yr)0.69 to 0.35
2. 3 to 0.15
0.87
0.99 to 0.12
Environment
Groundwater
Aqueous anaerobicNaturally occurring
soil-groundwater system
Soil-groundwatersystem
Source
Howard etal., 1991
Howard etal., 1991Dragun, 1988
Vogel etal., 1987
These estimates apply to soil and groundwater; estimates from surface water, air, andlaboratory studies typically give somewhat higher rates of degradation. For the purposes ofthis memorandum, the median of the individual values in Table A-3 (i.e., 1 year) wastaken as the appropriate degradation half-life. The degradation-rate constant (L) was thencalculated according to:
L = 0.693 / degradation half-life
Given a degradation half-life of 1 year yields a degradation-rate constant of 0.693 per year.
The concentration of a degradable substance, assuming first-order decay, is calculatedaccording to:
C = C0 x e<-Lt>
where C = concentration after degradationC0 = initial concentrationL = degradation-rate constantt = tune
The reduction in the concentration because of degradation is provided in the last row ofTable A-2.
A"5 AR30U09
Sources of Uncertainty ^
There are several sources of uncertainty in the input data that make these soil cleanuplevels only estimates:
1. The area of contamination may not be completely defined at each facility. In mostcases the limits have been defined at least to low concentrations on the order of a few partsper billion. However concentrations may exist within the area of the investigation thatcould increase the area of contamination. This would have the effect of increasing themass of contamination reaching the groundwater and, therefore, increasing theconcentration in the groundwater.
2. The infiltration rate is estimated based on the total average precipitation in the studyarea. A higher infiltration rate carries more contaminant mass to the groundwater. Theresult of changing the infiltration rate is effectively linear; for example, increasing theinfiltration rate by 10 percent will reduce the SAL by about 10 percent. Most of theground surface at Granite Knitting Mills is covered with asphalt or with packed gravel, andinfiltration at this facility is likely less than the value used in this analysis.
3. As the area of contamination changes so may the width of the ground water-flow zone.Increasing the width increases the volume of aquifer diluting the infiltrating contamination,thus raising the SAL. However, if increasing the width increases the area then the changesin the SAL may offset because the increased area provides more contamination to thegroundwater, lowering the SAL.
4. The hydraulic gradient is only estimated because there are few water levels availablefrom the site. Increasing the hydraulic gradient increases the aquifer flow rate, increasingthe dilution potential of the aquifer and increasing the SAL. The sparsity of water-leveldata also increases the uncertainty in the distance between the top of bedrock and the watertable.
5. The hydraulic conductivity of fractured rock is difficult to define. The value used wasobtained from an aquifer test that was analyzed using methods designed for continuousporous media such as sand aquifers; therefore the actual hydraulic conductivity may behigher or lower. Varying the hydraulic conductivity has the same effect on the dilutionfactor as varying the hydraulic gradient.
6. Determining the Kj from the K . and the f is a routinely applied method. However, itmay understate the degree of adsorption by not considering, for example, such irreversibleprocesses as fixation. More-representative values for Kj can only be obtained by doingcomprehensive field or laboratory tests.
Ift
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SR30UIO
Results and Conclusions
The sequence of calculations that results in the SALs is shown in Table A-4. The MCLfor PCE of 5 ptg/1 must be met in the aquifer. Dilution of the water infiltrating from thesource soil will allow the concentration of PCE in the infiltrating water to be higher by thedilution factor. Therefore the concentration in the infiltrating water is obtained by dividingthe MCL by the dilution factor to arrive at the concentrations shown in the third row ofTable A-4. Because the source is assumed to be constant this would also be theconcentration of PCE in the soil water within the source soil if no other processes reducedthe concentration during migration.
However, assuming that degradation is occurring, the concentration in the soil water at thesource can be higher by the factor of degradation. The soil-water concentration in thecontaminated soil is then estimated by dividing the concentration of PCE in the waterinfiltrating to the water table (third row of Table A-4) by the reduction in the concentrationdue to degradation (fourth row of Table A-4) to arrive at the soil-water concentrations atthe source shown in the fifth row of Table A-4.
An example of the sequence of calculations for Gentle Cleaners follows. Because ofdilution in the aquifer by a factor of 0.071, the allowable concentration of PCE in the soilwater reaching the water table is 70 g/1. It will take 2.1 years for this PCE to reach thewater table, during which time it will degrade. Given a degradation-rate constant of0.693/yr the fraction remaining after degradation will be 0.23. Dividing the allowableconcentration at the water table of 70 /ig/1 by this fraction gives an allowable concentrationof 304 fj,g/l of PCE in the soil water within the contaminated soil.
The concentration in the soil is then calculated using the Kd and the equation:
L-s = J\.d X (_w
where Cs = concentration in the soilKd = distribution coefficientCw = concentration in the soil water.
The Kd is 0.892 ml/gm. Therefore the soil concentration of 0.271 mg/kg is the estimatedSAL.
A"7 AR30UII
Table A-4ESTIMATED ALLOWABLE CONCENTRATIONS OF PCE IN THE
SOIL WATER WITHIN THE CONTAMINATED SOIL
ParameterMCL 0*g/l)
Dilution Factor
Allowable Concentration in theSoil Water at the Water Table
(Mg/DReduction in Concentration
Due to DegradationAllowable Concentration in the
Soil Water Within theContaminated Soil
0*g/l)Distribution Coefficient
(ml/gm)
Soil Action Level(mg/kg)
GentleCleaners
5
0.071
70
0.23
304
0.892
0.27
GraniteKnitting Mills
5
0.11
45
0.23
195
1.33
0.26
ParksideApartments
5
0.017
294
0.69
426
1.93
0.82
Ift
References
Dragun, James. 1988. The Soil Chemistry of Hazardous Materials. Hazardous MaterialsControl Research Institute. Silver Spring, Maryland.
Howard, P.H., R.S. Boethling, W.F. Jarvis, W.M. Meylan, and E.M. Michalenko. 1991.Handbook of Environmental Degradation Rates. Lewis Publishers, Inc. Chelsea, Michigan.
Vogel, T.M, C.S. Griddle, and P.L. McCarty. 1987. Transformation of HalogenatedAliphatic Compounds. Envir. Sci. Technol., vol. 21, no. 8, p. 725.
WDCR838/027.WP5
Ift
OA-8 AR30UI2
Appendix BEstimation of Aquifer Remediation Time
No Action
The tune to remediate the bedrock aquifer has been estimated for the case where no actionsto expedite the groundwater remediation are taken.
The following assumptions were made:
• Wells S-10 and S-8 are pumped continuously at current discharge rates,maintaining the current groundwater-flow patterns.
• Hydrodynamic dispersion is not significant in the groundwater-flow system.
• The hydraulic gradient varies in value; a value of 8.42 feet per 300 feet or0.028, based on data from Well S-9 and the Souderton Borough well, wasused.
• The hydraulic conductivity is 1,460 feet per year, based on pumping testsperformed at the site.
• The effective porosity is 0.20.
• The bulk density of the bedrock is 1.8 gm/cm3.
• The distribution coefficient for PCE of the bedrock is 0.892 cnrVgm, basedon a normalized distribution coefficient of 364 cnrVgm (Montgomery andWelkom, 1990) and a fraction of organic matter of 0.00245, the lowestvalue measured in soil at the site.
• Gentle Cleaners is the most up-gradient source of PCE to the groundwater.
• The dimensions of the contaminant plume are basically those of the originalarea of the site shown in Figure 1-1, but the plume of concentrations abovethe MCL is narrower and extends southward from Gentle Cleaners to adistance approximately half way between wells S-9 and S-10.
• The depth to groundwater from the top of bedrock is 20 feet and the watercontent of the unsaturated zone is 0.20.
AR30IIH3
Using these assumptions, a groundwater-flow rate was calculated accordingly (seeTable B-l):
v^ = k * dh / ne
where v^- = groundwater-flow velocityk = hydraulic conductivitydh = hydraulic gradientr^ = effective porosity
Substituting the values listed in the assumptions into the equation results in a groundwater-flow velocity of 204 feet per year (ft/yr).
The rate of migration of PCE in the system is retarded by adsorption. The degree to whichretardation affects the migration rate is estimated using the retardation coefficient:
R = 1 + B * Kd * (l-iO/1
where R = retardation coefficientB = bulk density of the bedrockKd = distribution coefficient
Substituting in the values from the assumptions gives a retardation coefficient of 7.4 (seeTable B-l).
The retarded rate of migration of the contaminant is then estimated using the equation:
vr= vgw / R
The migration rate of PCE in the bedrock aquifer is then estimated at 28 ft/yr (seeTable B-l).
Under existing groundwater-flow conditions the PCE should migrate at an estimated rateof 28 ft/yr. The distance from Gentle Cleaners to Well S-10, the nearest production wellthat will remove groundwater from the aquifer, is 1,800 ft. At a rate of 28 ft/yr PCE inthe aquifer beneath Gentle Cleaners will be extracted from the aquifer within about 64 yrs(see Table B-l).
This time assumes that no additional contamination reaches the aquifer from the sourceareas. To estimate the tune added to the remediation to account for the sources, twoscenarios were considered:
• Contamination is flushed from the soil and migrates downward to theaquifer.
Ift
B"2 flR30U|l»
Table B-lESTIMATION OF REMEDIATION
TIMES FOR THE NORTH PENN AREA 1 PLUME/
Calculated Retardation CoefficientDry bulk density of the rock (B)Distribution coefficient (Kd)Effective porosity (ne)Retardation coefficient (R=l+B*Kd*(l-ne)/ne)
Anticipated Rates of Migration Under Natural ConditionsHydraulic gradient (dh)Hydraulic conductivity (k)Effective porosity (ne)Flow velocity (vgw=k*dh/ne)Retarded flow velocity (vr=vgw/R)
Time to Migrate from Gentle Cleaners to Well S-10Distance (d)Retarded flow velocity (vr)Time to migrate (tm)
Tune to Clean Up Plume with Pumping at Well S-9Length of plume (L)Width of plume (W)Area of plume (L*W*7r/4)Depth of plume (th)Effective porosity (ne)Volume of water in plume (Volp)Pumping rate at Well S-9 (QS9)Pumping rate at Well S-9 (QS9) .Time to removed one pore volumeTime to clean up plume
Time to Clean Up Plume with Pumping at Well GKMVolume of water in plume (volp*75 %)Pumping rate at Well GKM (QGKM)Pumping rate at Well GKM (QGKM)Tune to remove one pore volumeby pumping (tpo=volp*75%/QGKM)
No. of plume volumes to be removed (npo)Time to clean up plume (tpl=tpo*npo)
1.8 gm/cm30.892 3/gm
0.207.4
0.028 ft/ft1,460 ft/yr
0.20204 ft/yr28 ft/yr
1,860 ft28 ft/yr64 yr
1,860ft840 ft
1,230,000 ft2270ft0.20
66,300,000 ft380 gpm
5,621,000 ftVyr12 yr89 yr
50,000,000 ft37 gpm
492,000 ft3/yr102 yr5
510 yr
flR30l!»IS
• The contaminated soil is removed and any contamination remaining in theunsaturated part of the aquifer migrates downward to the aquifer.
For the first scenario, an average of 12 years was estimated earlier as being sufficient toremove PCE from soil at the site through natural flushing (see Appendix D). PCE thenmigrates downward through the unsaturated bedrock. The groundwater flow rate throughthe unsaturated zone is estimated by:
Vu = V; / WC
where vu = velocity of water in the unsaturated zoneVj = annual infiltration ratewe = water content
The annual infiltration rate is estimated at 1.9 ft/yr and the water content is estimated at0.20 so the soil- water flow rate in the unsaturated zone is estimated at 9.5 ft/yr and theretarded flow rate (i.e., the migration rate of PCE) is estimated to be 1.3 ft/yr using aretardation coefficient of 7.4. For the PCE to migrate the 20 ft to the water table thereforeshould take an estimated 15 yrs.
Adding the 12 years to remove the PCE from the soil and the 15 years to remove the PCEfrom the unsaturated part of the bedrock to the 64 years required for all contamination tomove downgradient to the pumping wells results in a total time of 91 years to effect acleanup by this approach.
If the soil contamination is removed, the 12 years of leaching from the soil is eliminatedand the total cleanup tune is estimated at 76 years.
Natural Attenuation
For this case, groundwater and associated contamination move under current groundwater-flow patterns. Therefore, the remediation tune is the same as for the "no action" casediscussed earlier.
Pump the Upper Part of the GKM Well at 1 GPM
In this scenario, a packer is set in the GKM well above the water level in the well andbelow the fractures carrying highly contaminated groundwater into the well. Contaminatedgroundwater then will collect on top of the packer and the contaminated groundwater isperiodically pumped off. The aquifer itself will not be pumped, and intercepting the smallamount of groundwater flow will not affect the hydraulic gradient. Therefore, thegroundwater and associated contamination will move under current groundwater-flowpatterns and the remediation tune is the same as for the "no action" and "naturalattenuation" cases discussed earlier.
B"4 AR30UI6
The difference in this scenario is that the amount of contamination entering the aquifer willbe reduced. Because it is uncertain how much of the contamination in the GKM well iscoming from the fractures in the well and how much is coming through the groundwaterfrom upgradient, it is assumed that this approach will reduce the time of remediation but byan uncertain amount.
Pump Well S-9 at 80 GPM
In this scenario, groundwater is extracted from Well S-9 at what is believed to be itsmaximum sustainable yield of 80 gpm. This will develop an elliptical cone of depressionoriented approximately northeast-southwest and coincident with the probable distribution ofthe plume.
Although the exact dimensions of the plume are unknown it is assumed to be orientedgenerally to the northeast-southwest and to extend from beneath Gentle Cleaners to thenortheast to approximately midway between wells S-9 and S-10 to the southwest. Thesouthwest limit is estimated based on their being contamination in Well S-9 but only anestimated amount .below the detection limit in Well S-10 further downgradient.
The length of the plume is estimated at 1,860 ft and the width is estimated at 840 ft.Using the formula for the area of an ellipse (i.e., Pi times the product of the semiaxes) thearea of the plume is estimated to be about 1,230,000 ft3. The depth of the plume isestimated to be 270 ft based on finding contamination at this depth in Well S-9 duringstraddle-packer tests. With an effective porosity of 0.20 the volume of groundwater in theplume is estimated to currently be about 66,300,000 ft3.
If the total volume of contaminated groundwater in the plume is 66,300,000 ft3 and well S-9 can be pumped at 5,621,000ft3 per year, then one pore volume of contaminatedgroundwater can be removed hi about 12 years. The retardation coefficient of PCE in thegroundwater system at the site is estimated at 7.4. Therefore, it should take about 7.4times longer to remove the contamination itself from the aquifer, or about 89 years. Apumping test was performed in well S-9 at a rate of 150 gpm; therefore the potentialmaximum rate of pumping this well may be much higher than 80 gpm, with acorresponding decrease in the length of tune required for remediation.
To this total time is added the two tune estimates obtained for actions to be taken with thesoil sources. In the no action and natural attenuation cases, 27 years would be added to thecleanup tune, for a total of 116 years. For the case where the soil contamination isremoved, the total cleanup tune is estimated to be 101 years.
It takes longer to clean up the aquifer pumping Well S-9 than leaving it to naturalattenuation because the expected yield of the well is less than the volume rate of flow inthe aquifer and therefore the well must be pumped longer. The advantage to pumping isthat it prevents contaminated water from reaching the drinking water wells.
AR30UI7
Pump the GKM Well at 13 GPM A
In this scenario, only the GKM well would be pumped. Because the GKM well is at thehead of the plume, only a part (estimated to be about 75 percent) of the plume would beaffected by the pumping of the well; all groundwater downgradient of Well S-9 wouldcontinue flowing under the existing groundwater-flow pattern toward Well S-10. Thevolume affected by pumping the GKM well was estimated to be about 50,000,000 ft3.
Also because the GKM well is at the head of the plume, there would be much clean waterbeing pumped from upgradient and sidegradient of the well. Therefore, only an estimated7 gpm (or about 492,000 ft3/yr) of the discharge of this well would be removingcontaminated groundwater.
At this discharge rate one pore volume of the available volume of the plume would beremoved in about 102 yrs. Because several pore volumes would be needed to be removedto adequately remediate the aquifer, relying solely on pumping the GKM well appears tonot be feasible. For instance, removing 5 well volumes would require an estimated510 years. The value in pumping from this well is to intercept and remove the morehighly contaminated groundwater assumed to be present in and entering the aquifer in thevicinity of Gentle Cleaners.
WDCR753/014.51
B"6 AR30HH8
Appendix CCosts
AR3QIM9
Cost Estimate for Groundwater Alternative 2: Natural Attenuation*
4 wells + duplicate + matrix spike + matrix spikeduplicate + trip blank = 8 samples for VOCs w/o TICs
8 samples x $225
8 hours of 1 person to travel to site, collect, and shipsamples
8 hrs x $65/hr
3 hours project management to prepare and write upresults
3 hrs x $75/hr2 hours clerical, laboratory scheduling, work plan
2 hrs x $45/hrShipping
$100/cooler
TravelGas and per diem
Cost Per Each Sampling EventAnnual O&M Cost (4 Sampling Events)
Total Present Worth Cost (30 Years)+ 10% Incidentals
Cost
$1,800
$520
$225
$90
$100
$50
$2,785$11,140
$334,200
$367,620
*Groundwater samples will be collected from four wells four tunes a year for30 years.
WDCR753/018.51
HR30U20
10/6/93 1:30 PM
[PRESENT WORTH (BASED ON ANNUAL CAPITAL COST] ANALYSIS \
PROJECT: NORTH PENN • AREA 1LOCATION: NORTH PENN. PAGROUNDWATER ALTERNATIVE #3: EXTRACTION FROM ENTIRE GKM WELL Q 13 GPM W / AIR STRIPPING
CAPITAL COST: $7,880SALVAGE COST: I $0
Install PumpAir StripperControl PanelPipe__
$1,000$3,986$2,200$40O
$7,586PROJNO: WDC63133.FS.R4 File: 13GPM.xls
(P/F)YR.
U1234E6789101112131415161718192021222324252627282930
ANNUAL CAP. 1 ANNUAL O&M,•«?;:: COST l j :f ; i COST :*;
$7,586$13,593$13,593$13,593$13,593
$200 $13,593$13,593$13,593$13,693$13,693
$200 $13,593$13,693$13,693$13,693$13,693
$200 $13,593$13,693$13,693$13,693$13,693
$200 $13,593$13,593$13,593$13,593$13,593
$200 $13,593$13,593$13,693$13,693$13,693
$200 $13,593
DiS.RATEf|&6b«6
1.000O1.00001.00001.00001.000O1.0OOO1.00001.00001.OOOO1.0OOO1.00001.00001.00001.00001.OOOO1.00001 .00001.OOOO1.00001.00001.00001.00001.00001.00001.00001.00001.00001.OOOO1.000O1.00001 .0000
TOTAL PRESENT • WORTHS; ; :,f, Xi>;& , ,. :.,:•• •.,.:...::' •
: :; PRESENTi|!WORTH"|l
$7,586$13,693$13,593$13,593$13,593$13,793$13,593$13,693$13,593$13,593$13,793$13,593$13,693$13,693$13,593$13.793$13,593$13,593$13,593$13,593$13,793$13,593$13,593$13,593$13,593$13,793$13,593$13,693$13,693$13,693$13,793
: .:.: $41 7.OOO
, %s?v¥ 'm; ifeSANNU. AL O&M COSTS ;. • ;. •;:. •.; •
LABOR:' : ,....:::,':;:-s.--.. ,.....• • .2HR/DY * $ 1 0/HR '365DY/YR
DIFFUSED AIR REQUIREMENTS
TOTAL LABOR PER YEAR
$7,300
$1,500
$8.800POWER: (*.08O/KWHJ
PUMP SYSTEM (3.00 HP • 24 HR/DY•1 PUMP".746KW/HP) @ 13 mgd
$1,668
POWER = HP"(HRS OF RUN TIME/DY)"(.746KW/HP-HR)•(DAYS/YR)*($/KWH)
TOTAL POWER PER YEARMATERIALS <& 5% OF LABORMONITORING (SAMPLING & TESTING)8 samples (Testing)8 samples (Labor)3 hours of PM tim2 hours Clerical, lab scheduling, work planShipping (Cooler)TravelTOTAL ANNUAL O&M:
$1,568$440
$2,785$1,800$620$225$90
$100$50
913,593
Note: Capital cost of pump includes associated piping. Assume costs of replacing motors every 5 years @ $200.
Note: The OMB Discount Rate for the October 29th, 1993 was not applied to the above figures. If they were applied to thefigures for the period of March 1993 through February 1994 the rates would be:
Nominal Rate Real Rate3-YR 5.60% 3.10%B-YR 6.00% 3.60%7-YR 6.30% 4.00%10-YR • 6.70% 4.30%30-YR 6.80% 4.50%
AR3QU2I
10/6/93 1:26 PM
[PRESENT WORTH (BASED ON ANNUAL CAPITAL COST) ANALYSIS . |
PROJECT: NORTH PENN • AREA 1LOCATION: NORTH PENN, PAGROUNDWATER ALTERNATIVE #4: EXTRACTION FROM UPPER PART OF GKM WELL @ 1 GPM W / AIR STRIPPING
CAPITAL COST: I $7,586SALVAGE COST: I $0
Install PumpAir StripperControl PanelPipe_____
$1,000$3,986$2,200$400
$7,686PROJNO: WDC63133.FS.R4 File: 1GPM.xls
(P/F)*0123456789101112131415161718192021222324252627282930
COST J COST* j$7,586
$12,417$12,417$12,417$12,417
$200 $12,417$12,417$12,417$12,417$12,417
$200 $12,417$12,417$12,417$12.417$12,417
$20O $12,417$12,417$12,417$12,417$12,417
$200 $12,417$12,417$12,417$12,417$12,417
$200 $12,417$12,417$12,417$12,417$12,417
$200 $12,417
-• <:&30JTO%|?f1 .00001.00001.00001.OOOO1.OOOO1.00001.00001.00001.0OOO1.0OOO1.00001.00001.0OOO1.000O1.0OOO1.00001.0OOO1.00001 .00001.00001.00001.00001.00001.00001.00001.00001.00001.OOOO1.00001.0OOO1.0000
TOTAL PRESENT WORTH-. ;.-.. .xv;..,,. .,,.*, , i *:,,.;..,,,,,;,;.'.,
:*WOHT'Hly|l$7,586$12,417$12,417$12,417$12,417$12,617$12.417$12,417$12,417$12,417$12,617$12,417$12,417$12.417$12,417$12.617$12,417$12,417$12,417$12,417$12,617$12,417$12,417$12,417$12,417$12,617$12,417$12,417$12,417$12,417$12,617
.•:• $381,000
•A. -r"";.v';?;™;v:5./::.:-'-,,;,i .!:;,-•..'• -LABOR: •-.;,:•-.<::• ':.. •'. . • -.
2HR/DY • $ 1 0/HR •365DY/YR(ASSUME PUMP ON - 2 HRS; OFF - 2 HRS)
DIFFUSED AIR REQUIREMENTS
TOTAL LABOR PER YEAR
$7,300
$1,500
$8,800POWER: ($.08O/KWH)
PUMP SYSTEM (1.60 HP (2 HR • 6)/DY•1 PUMP-.746KW/HP) @ 1 gpm
$392
POWER -HP'(HRS OF RUN TIME/DY)'(.746KW/HP-HR)*(DAYS/YR)*($/KWH)
TOTAL POWER PER YEARMATERIALS <& 5% OF LABORMONITORING (SAMPLING & TESTING)8 samples (Testing)8 samples (Labor)3 hours of PM tim2 hours Clerical, lab scheduling, work planShipping (Cooler)TravelTOTAL ANNUAL O&M:
$392$440
$2,785$1,800$620$225$90$100$50
$12,417
Note: Capital cost of pump includes associated piping. Assume costs of replacing motors every 5 years @ $200.
Note: The OMB Discount Rate for the October 29th, 1993 was not applied to the above figures. If they were applied to thefigures for the period of March 1993 through February 1994 the rates would be:
Nominal Rate Real Rate3-YR 5.60% 3.10%S-YR 6.00% 3.60%7-YR 6.30% 4.00%10-YR 6.70% 4.30%30-YR 6.80% 4.50%
flR30ll»22
10/6/93 1:33 PM
[PRESENT WORTH (BASED ON ANNUAL CAPITAL COST) ANALYSIS f
PROJECT: NORTH PENN - AREA 1LOCATION: NORTH PENN, PAGROUNDWATER ALTERNATIVE #5: EXTRACTION FROM WELL S-9 9 80 GPM W / AIR STRIPPING
CAPITAL COST:SALVAGE COST:
$8,586$0
Install PumpAir StripperControl PanelPipe
$2,OOO$3,986$2,200$400
$8,686PROJ NO: WDC63133.FS.R4 File: 80GPM.xls
(P/F)YR.
0123456789101112131415161718192021222324252627282930
ANNUAL CAP. (ANNUAL O&M' - ,3|C OST •';:!•'• | f !' ;;. CCSTWl
$8,686$22,829$22,829$22,829$22,829
$200 $22,829$22,829$22,829$22,829$22,829
$200 $22,829$22,829$22,829$22,829$22,829
$200 $22,829$22,829$22,829$22,829$22,829
$200 $22,829$22,829$22,829$22,829$22,829
$200 $22,829$22,829$22,829$22,829$22,829
$200 $22,829
D1S.RATEii oioo*
1.OOOO1.0OOO1.00001.00001.OOOO1.OOOO
' 1.00001.00001.OOOO1.OOOO1.00001.00001.00001.00001.OOOO1.00001.00001.00001.0OOO1.00OO1.00001.OOOO1.00OO1.00001.00001.00001.00001.00001.00001.000O1.0000
PRESENTW WORTH $H
$8,686$22,829$22,829$22,829$22,829$23,029$22,829$22,829$22,829$22,829$23,029$22,829$22,829$22,829$22,829$23,029$22,829$22,829$22,829$22,829$23,029$22,829$22,829$22,829$22,829$23,029$22,829$22,829$22,829$22,829$23,029
$696,000
•;..: ;..,•.;; . ;!.•:?: ;;..:J;;.5-i- ANNUAL O&M'. COSTS
LABOR:. ••;••:•••••• •••>.••:•• -.-•......•..."- ;•.4HR/DY * $ 1 0/HR * 365DY/YR
DIFFUSED AIR REQUIREMENTS
TOTAL LABOR PER YEAR
$14,600
$2,000
$16,600POWER; ($.080/KWH)
PUMP SYSTEM (5.00 HP * 24 HR/DY•1 PUMP".746KW/HP) @ 80 GPM
$2,614
POWER = HP*(HRS OF RUN TIME/DYP(.746KW/HP-HR)•(DAYS/YR)"($/KWH)
TOTAL POWER PER YEARMATERIALS @ 5% OF LABORMONITORING (SAMPLING & TESTING)8 samples (Testing)8 samples (Labor)3 hours of PM tim2 hours Clerical, lab scheduling, work planShipping (Cooler)TravelTOTAL ANNUAL O & M:
$2,614$830
$2,785$1,800$520$225$90
$100$50
$22,829
Note: Capital cost of pump includes associated piping. Assume costs of replacing motors every 5 years @ $200.
Note: The OMB Discount Rate for the October 29th, 1993 was not applied to the above figures. If they were applied to thefigures for the period of March 1993 through February 1994 the rates would be:
Nominal Rate Real Rate3-YR 5.60% 3.10%5-YR 6.0O% 3.60%7-YR 6.30% 4.0O%10-YR 6.70% 4.30%30-YR 6.80% 4.50%
Cost Estimate for Soil Alternative 2: Natural Attenuation*
Cost for VOCs analysis without TICs = $281 /sample
Collection:10 hrs each for 2 samplers+ travel costs+ 4 hrs project management and writeup results+ 2 hrs clerical time
$281 x 6 samples (includes QA/QC)
20 hrs x $65/hr
4 hrs x $75/hr
2 hrs x $45/hr
$20 per diem + $30 gas
Cost Per Each Sampling Event
Annual O&M Cost (4 Sampling Events)
Total Present Worth Cost (10 Years)
+ 10% Incidentals
Cost
$1,686(analyses)$1,300(labor)$300(labor)$90
(labor)$50
(travel)$3,426
$13,704
$137,040
$150,744*Soil samples will be collected from two areas four times a year for 10 years.
WDCR753/019.51
flR30ll»2l»
Cost Estimate for Excavation and Offsite Disposal (Soil Alternative 3)
Mobilization
Labor
TransportationSpotting
DisposalSubtotal+ 20% Engineering
+ 20% ContingencyTotal Present Worth Cost
Cost$1,200
$2,950 x 5 days = $14,750
$11.25/ton x 2 ton/cy x 610 cy = $13,725$200
$220/ton x 610 cy x 2 ton/cy = $268,400
(not including lab. or backfill) $298,275$357,930
$429,516
$429,516
WDCR753/021.51
AR30U25
Appendix DEstimation of Soil Remediation Time
No Action
The tune to remediate the contaminated soil has been estimated for the case where noactions to expedite the soil cleanup are taken. The PCE contaminated areas of concern atthe North Penn Area 1 site are at the Gentle Cleaners facility and Granite Knitting Mills(GKM).
The following assumptions were made:
• The source of contamination in soil is assumed to be constant over time, sothe gradual decline in the concentration in the soil at the source is notaccounted for.
• The simulated migration to the aquifer assumes no hydrodynamic dispersionor volatilization; therefore, the concentration of a contaminant reaching thewater table has not been reduced by either of these processes.
• The contamination is leached from the soil by soil water derived frominfiltrating precipitation.
• The contamination in the infiltrating soil water is assumed to be distributeduniformly over the area of the source.
• The bulk density of soil varies between facilities from 96 to 101 lb/ft3.
• The thickness of soil varies between facilities from 6 to 12 feet (ft).
• The annual rate of infiltration is 1.9 feet per year (ft/y) for all facilities.
• At Gentle Cleaners, the area containing the contaminated soil is 235 ft2 and12 ft thick. Another area is 50 ft2 with a thickness of 6 ft. The volume ofcontaminated soil is calculated to be 3,100 ft3 (see Table D-l).
• At GKM, the area containing the PCE contaminated soil is 1,080 ft2 and thecalculated volume of soil is 10,800 ft3 (see Table D-l).
• At Parkside Apartments, the area containing the contaminated soil is 250 ft2.With the thickness of soil of 10 ft, the calculated volume of soil is 2,500 ft3(see Table D-l).
D-l AR30U26
S|
11Hg
OCO
i
V.
111cuT3
I
bJDa§So>•MC5O
en
OSO)U<u73C0
Parameters
VOON
OI-H
f-ON
1
O
1"O
o
0oo0* — (
oooCN
g
|
«Ja
o
o1 — I
T-H
oVO
Thickness of un
it (ft)
oo<o
000
8en"
(4-1o
11
8oo"C
o8 — iONo
en
3"
'o(4-1Oenen03
•a-4—*
ONi— i
ONT— 1
ONi — i
s>-
Annual
rate of in
filtra
tion (ft/;
<n
<N
CN
i
Annual volume of
infil
tratio
n
8inen"
oo"
i— i»— i
?
Annual volume of
infil
tratio
n
»nd
«nd
o»n
Soil concentration (mg/kg)
enON
enent— i
SI00d
Distribution co
efficient (ml/gr
VO
d
ooend
VO
Soil-water concentration (mg/J
I
oo"s
o"enoovo"
X— N00
Total mass of contaminant (m
oinen"
es
O8OO
/•—V
1iCO3
13
13.*— »
VO
-
001 Source
duration (y) «o
oo§00ooUQ
HR30IU27
• With a KOC of 364 ml/gm and an f of 0.00245 at Gentle Cleaners, 0.00365at GKM, and an f of 0.00529 at Parkside Apartments, the K of soil atGentle Cleaners is 0.892 ml/gm, at GKM is 1.33 ml/gm, and at ParksideApartments is 1.93 ml/gm.
Using the assumptions above, the total mass of soil was calculated accordingly:
Ms = Vs * B
where Ms = Total mass of soilV, = Volume of soil' sB = Dry bulk density of soil
Substituting the values listed in the assumptions into the equation results hi the total massof soil of 300,700 Ibs at Gentle Cleaners, 1,091,000 Ibs at GKM, and 240,000 Ibs atParkside Apartments (see Table D-l).
The concentration of PCE in the soil varies, with a mean concentration of 50 mg/kg for thecontaminated soil at Gentle Cleaners and a mean concentration of 0.5 mg/kg at GKM andat Parkside Apartments. The total mass of contaminant in the soil was then calculatedusing the equation:
Mc = Cs * Ms
where Mc = Total mass of contaminantCs = Concentration of PCE in soil
The total mass of contaminant in soil is then estimated to be 6,830,000 mg at GentleCleaners, 248,000 mg at GKM, and 55,000 mg at Parkside Apartments.
The annual volume of infiltration was calculated using the equation:
V, = A * I
where V; = Annual volume of infiltrationA = Area of contaminated soilI = Annual rate of infiltration
Substituting the values from the assumptions gives the annual volume of infiltration of15,100 1/y at Gentle Cleaners, 58,100 1/y at GKM, and 13,500 1/yr at Parkside Apartments(see Table D-l).
It is assumed that the contamination is leached from the soil by soil-water derived frominfiltrating precipitation. Therefore, the PCE concentration in the soil water for eachfacility is estimated using the relationship:
BR30U28
Krt = C, / C'S
where Kd = Distribution coefficientCw = Concentration of the contamination in the water infiltrating
through the soil water
The soil-water concentrations are then estimated to be 56 mg/1 at Gentle Cleaners,0.38 mg/1 at GKM, and 0.26 mg/1 at Parkside Apartments (see Table D-l).
The total annual flushing is the amount of PCE (soil-water concentration - Cw) in theannual volume of infiltration (Vi). Thus, the total annual flushing is estimated by56 mg/1 x 15,100 1/yr = 846,000 mg/yr for Gentle Cleaners, 0.38 mg/1 x 58,100 1/yr =22,100 mg/yr for GKM, and 0.26 mg/1 x 13,500 1/yr = 3,510 mg/yr at ParksideApartments.
Based on the assumptions above and that the infiltrating contaminated soil water wasdistributed uniformly over the area of the source, with the estimated total annual flushing,the number of years for the contaminant to reach the water table was calculated using theequation:
Y = Mr / M.*-c
where Y = Source durationMw = Total annual flushing
Therefore, it would take about 8 years at the Gentle Cleaners, 11 years at GKM, and16 years at Parkside Apartments for the contaminants to migrate out of the soil (seeTable D-l). The average is 12 years.
Natural Attenuation
For this case, it is assumed that the contamination of PCE reaching the water table hasbeen reduced by natural process such as dispersion or volatilization. Therefore, theremediation tune would be less than the "no action" case discussed earlier.
Excavation and Offsite Disposal
In this scenario, the contaminated soil would be removed from the site. Therefore, therewould be no remediation tune for this alternative.
WDCR753/015.51
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