UNITED STATES ENVIRONMENTAL PROTECTION AGENCYREGION III

- 841 Chestnut Building; Philadelphia, Pennsylvania 19107

SUBJECT: Record of Decision - Transmittal Memo' DATE: Jun* 28, 1990

FROM: Thomas C. Voltaggio, Associate DirOffice of Superfuhd (3HW02) /

TO: Edwin B. EricksonRegional Administrator (3RAOO)

Attached is the Record of Decision (ROD) for the East Mt. Zion

Superfund Site. The decision outlines all necessary remedial

actions which must be performed in order to be protective of

the public health and the environment. There were no significant

changes from the Proposed Plan to the ROD. I recommend that you

sign the attached document. The Commonwealth of Pennsylvania

has concurred with this decision.

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DECLARATIONFOR THE

RECORD OF DECISION

Site Name and Location

East Mt. Zion LandfillSpringettsbury Township/ York County, Pennsylvania

Statement of Basis and Purpose

The decision document presents the selected remedial actionfor the East Mt.'. Z ion site in Springettsbury Township,Pennsylvania, which was chosen in accordance with the ComprehensiveEnvironmental Response, Compensation and Liability Act of 1980(CERCLA), as amended by the Superfund Amendments andReauthorization Act of 1986 (SARA) and, to the extent practicable,the National Oil and Hazardous Substance Pollution Contingency Plan(NCP). This decision is based upon the contents of theadministrative record for the East Mt. Zion site.

The United States Environmental Protection Agency (EPA) andthe Pennsylvania Department of Environmental Resources (PADER)agree on the selected remedy.

Assessment of the Site

Actual or threatened release of hazardous substances from thissite, if not addressed by implementing the response action selectedin this Record of Decision (ROD) , may present an imminent andsubstantial endangerment to public health, welfare, or theenvironment. ;

Description of the Remedy

This remedy addresses remediation of ground watercontamination by eliminating or reducing the risks posed by thesite through engineering and institutional controls.

The selected remedy includes the following major components:

o Installation and maintenance of an impermeable cap andgas vents over the 10-acre landfill

o Installation and maintenance of surface water controlsystems for the cap

o Installation and maintenance of a fence around the site

o Monitoring ground water contaminant attenuation afterinstallation of the cap

o Initiation of a deed restriction regarding futureactivities at the site.

Declaration

The selected remedy is protective of human health and theenvironment, complies with Federal and State requirements that arelegally applicable or relevant and appropriate to the remedialaction, and is cost-effective. This remedy utilizes permanentsolutions and alternative treatment (or resource recovery)technologies , to the maximum extent practicable for the site .However, because treatment of the principal threats of the site wasnot found to be practicable, this remedy does not satisfy thestatutory preference for treatment as a principal element. As thisremedy will result in hazardous substances remaining onsite abovehealth based levels, a review will be conducted within five yearsafter the initiation of the remedial action to ensure that theremedy continues to provide adequate protection of human health andthe environment.

Ericks n Dategional Administrator

Region III

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Site Description and Summary ofRemedial Alternative Selection for the

East Mt. Zion Superfund Site.York County, Pennsylvania

SITE LOCATION AND DESCRIPTION

The East Mount Zion site is located in SpringettsfauryTownship, York County, Pennsylvania, upon a wooded ridge east ofMount Zion and approximately 15 miles southeast of Harrisburg.It is located along the south side of Deiningei- Road just beforethe entrance to Rocky Ridge County Park. The site location isshown in Figure 1. .- - -

The site is situated on 10 acres atop an 860-ft-highforested ridge. Bounding the site to the east, north, and southis the York County Recreation Park, Rocky Ridge; Doersam Woodssubdivision bounds the site to the immediate west. Alsodispersed among the woodlands areas and at lower elevations tothe south (Ridgewood Road), west (Mount Zion Road), and north(Deininger Road and Druck Valley Road) are numerous privatedwellings.

On the southern side of the property, the height of thelandfill gradually increases from east to west until, at thesouthwestern end, there is a steep rise culminating with anapproximately 70 percent toe slope. The toe slope averages 70-80percent along the southern edge of the landfill. The northernhalf of the landfill, which bounds Deininger Road, is flatter andgradually approaches the grade of the roadway. Exposed refuse islocated on the steep side slopes. Figure 2 shows the sitetopography and approximate fill boundary.

The East Mount Zion site is located in the Conestoga ValleySection of the Piedmont Physiographic Province. The ConestogaValley Section includes a relatively flat central valley and twoprominent hill areas on the northwest edge of the section—thePigeon Hills north of Hanover and the Hellam Hills northeast ofYork. The hill areas coincide with the outcrops of hardquartzite and conglomerate.

The predominant bedrock underlying the site has been mappedas the Hellam Member of the Lower Cambrian Chickies Formation.The Chickies Formation is typically a massive, prominentlybedded, white arkosic quartzite and quartz pebble conglomerate ina sericitic, arkosic matrix. Structurally, the site is situatedon the upper plate of the Glades Overthrust on the northwest limbof the Mount Zion Anticline, which strikes east-northeast tosouth-southeast. Bordering the site to the southeast is the

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Highmount Overthrust. In the vicinity of the site, bedding planestrike and dip is approximately 32 degree E, 29 degree SE. Fieldmeasurements indicate the orientation of the primary joint set tobe N66 degree SW with joint spacings on the order of 10-15 ft(Lloyd and Growitz 1977). The site is situated at an averageelevation of 860 ft mean sea level (MSL), just north of the ridgecrest of 880 ft MSL. The topography primarily slopes to thenorthwest, west-southwest and southeast.

The in situ soil underlying the site consists of highlypermeable Edgemont Channery stoney loam which ranges in thicknessfrom <2 to 15 ft. The soil is well drained. Much of the in situsoil was stripped away and redistributed over the site duringwast© disposal operations. Additionally, other soil from offsitelocations may have been utilized for the final cover fill.

The site is situated within the Susquehanna River Basin andlies at the divide of the Codorus and Kreutz Creek watersheds toth© west and southeast, respectively. Subsurface drainage ischanneled via two tributaries. Both drainage density andpatterns are controlled by geologic features (i.e., topography,bedding, and jointing). Near the site, the dominant drainagepattern is semirectangular to the south and east, and semiradialto the west. Surface runoff exits the site to the west along anadjoining intermittent stream which turns south toward thetownship of East York. Surface runoff exiting the southern and©astern slopes of the landfill enters an unnamed intermittentstream which flows south to Kreutz Creek. A leachate seepemanating from the southeast corner of the site previouslydischarged to the intermittent stream at the southeast boundaryof the site; however, recent regrading of a dirt access road hasdammed the seep and formed a small leachate pond.

The Chickies Formation, Hellam Member, constitutes the majoraquifer beneath the site. Secondary porosity in the form offractures and joints control both the storage and flowcharacteristics of the aquifer. Ground water flow is typicallycontrolled by surface topography (i.e., recharge topographic highareas, discharge adjacent low-lying streams and springs). Datafrom the existing Doersam Woods test well adjacent to thenorthwest property boundary indicate bedrock aquifer water levelsare on the order of 100-120 ft below the surface. Typical ofthis type of ground water regime, fluctuations of 20-30 ft arenot uncommon, especially in the recharge zones (i.e., hills).Water-bearing zones (open fractures and joints) are reported tooccur with consistent frequency to about 200 ft below thesurface. The average specific capacity of a well drilled in theChickies Formation is 0.34 gpm/ft* Average well yields are about8 gpm with 50 ft of drawdown after 1 day of pumping. The maximumreported well yield for the Chickies Formation is 100 gpm.

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Typically, fracture density and aperture decrease withincreased depth. Below 250-300 ft, fracture apertures are smalland few; water contribution from these deeper fracture sets isusually negligible.

Since the initiation of Pennsylvania Department ofEnvironmental Resources (PADER) investigations pertinent to thesite, Springettsbury Township has installed municipal watersupply lines along portions of Mount Zion, Deininger, DruckValley, and Ridgewood roads. As a result, many of the residencesthat were once dependent on private supply wells are now usingthe township water supply. However, the water line installationis incomplete along Druck Valley and Ridgewood roads and someresidences along portions of these roads are still using groundwater obtained from private wells that withdraw from the ChickiesAquifer. As part of the RI, the private wells of residences onDruck Valley and Ridgewood roads not serviced by the municipalwater line were sampled. Since these samples were taken, theseresidences have also been hooked up to the township water supply.

SITE HISTORY AND ENFORCEMENT ACTIVITIES

Over the course of its active life (approximately 1955 to1972), the site was a repository for domestic and industrialwastes. It operated as an area-type landfill in which areas forfilling were excavated (at times to nonrippable bedrock), filled,and covered with native materials. There is evidence that thesite was operated as an open-burning dump at some period in itshistory. The site presently exists as an open field on whichweeds and small woody plants grow. The cover placed on the siteat and since closure of the site is thin, and in some locationswaste materials, such as tires, are protruding.

The site was purchased in January 1952 by Charles H. Fetrow.Mr. Fetrow used the property as a nonpermitted disposal site forresidential and industrial wastes. The date when disposaloperations commenced is unknown; however, a 1955 aerialphotograph shows signs of some excavation activity at the site.Early 1963 PADER inspection reports on the landfill indicateimproper disposal of residential and industrial wastes. Notes ofinterviews conducted by PADER personnel indicate that paintthinner, paint filters, and metal sludge wastes were disposed atthe site.

Throughout 1969 and 1971 PADER personnel completed numerousSanitation Establishment Inspections on the site. Discrepancieswere frequently cited, pointing out that garbage and trash werebeing placed directly on bedrock in open trenches, and thatproper cover was not being applied on a daily basis, as required.Litter control was also inadequate. The landfill was closed in1972 by court order and has remained inactive since* Someadditional grading, covering, and seeding was conducted by the

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site owner under court order from 1974 to 1976. Since 1974 theproperty has changed owners several times.

In 1983 EPA conducted a Preliminary Assessment and SiteInspection (PA/SI) at the site. The site inspection revealedtrace levels of trichloroethylene (TCE) in ground water samples.Benzene was reported in a leachate sample, and dichlorobenzenewas found in a leachate and pond sediment samples. Previousinvestigations by the Pennsylvania Department of EnvironmentalResources (PADER) indicated low level contamination of onemonitoring well and surface water samples. A test well near thenorthwest boundary of the site was reported by PADER to containtrace levels of several organic compounds including vinylchloride and benzene. PADER also sampled wells serving RockyRidge County Park. No organic pollutants were detected in thesesamples. The landfill was listed on the Superfund NationalPriorities List (NPL) in September 1984. An RI/FS was conductedto quantify any contamination which might be attributable to thesite; to assess any risks to human health and the environment;and to develop a set of alternatives which could be used toaddress any risks posed by the site.

Eleven potentially responsible parties (PRPs) have beenidentified as being associated with the site. These PRPS weresent General Notice Letters in April 1989 to come forward andtak© responsibility for part, if not all, of the RI/FS. Due toinadequate interest on the part of the PRPs to perform the RI/FS,the State of Pennsylvania took the lead for performing the RI/FSunder a Cooperative Agreement with EPA. Field work for the RI/FScommenced in February 1988 and was completed by April 1989.

COMMUNITY RELATIONS

Pursuant to section 300.67(c) of the National ContingencyPlan (NCP) , a Community Relations Plan was developed for theProposed Plan that was based on the RemedialInvestigation/Feasibility Study (RI/FS) . In compliance withSections 113 (k) (2) (i-v) and 117 of SARA, the AdministrativeRecord, including the Proposed Remedial Action Plan, was placedfor public viewing at the Springettsbury Township Building onFriday, May 18, 1990.

An announcement of the availability of the AdministrativeRecord was placed in the York Daily Record on May 18, 1990. TheAdministrative Record contained the Draft RemedialInvestigation/Feasibility Study Reports which listed thealternatives developed as part of the Feasibility Study. Aperiod for public review and comment on the Proposed RemedialAction Plan was held from May 18, 1990 to June 18, 1990. Apublic meeting was held on May 30, 1990, at the Springettsbury

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Township Building regarding EPA and PADER selection of thepreferred alternative. Approximately 25 people were inattendance at the meeting.

SCOPE AND ROLE OF RESPONSE ACTIONS

The scope and role of the response action _for the East Mt.Zion landfill is to prevent further contamination of the deepground water aquifer by controlling or eliminating the source ofcontamination to the aquifer. The response action addresses theground water contamination at the site which is the principalthreat posed by the site.

SUMMARY OF SITE CHARACTERISTICS

Waste Fill Characterization

The areal extent and volume of the fill material wereestimated using geophysical survey results and identifying highconductivity anomalies of the fill that may be associated withhigh concentration of metallic constituents. The results of theterrain conductivity survey indicated a relatively heterogeneous,moderately high to very high conductive fill. The surveyestimated the approximate thickness of the fill to be typicallyless than 15 ft thick in the east to a maximum thickness greaterthan 45 ft along the southwest and west portions of the site.The results of the soil vapor contaminant assessment (SVCA)indicated significant levels of methane gas in the soil vapor atthe site. In general, the northern portion of the site containsthe highest levels of methane. Organic compounds (benzene andtoluene) were also detected during the SVCA in the fill. Thehighest organic compound concentrations occurred in the easternand northeastern portions of the fill.

Data from the geophysical survey and SVCA were used to picklocations for the waste characterization borings. The results ofsoil borings performed in the fill indicated that the fill rangesfrom 11 to 33 ft in thickness and may be up to 50 ft thick in thesouthwest and west-central portions of the site* The wastematerial, which was saturated at some borings, typicallyconsisted of general household and municipal refuse, includingwire, paper, cloth, brick, wood, glass, plastic,, and cans, with amatrix of silty sand. Significant decomposed organic debrisapparently accounts for much of the methane generated. Samplelocations are shown in Figure 3.

Eighteen waste samples were obtained at varying depths fromsix waste characterization boring locations. Additionally, onewaste material sample was observed and then collected at thesurface near the toe of the fill. Analytical results show thattrace metals concentrations were elevated in the majority ofsamples. Trace metal concentrations are shown in Table 1. In

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general, the concentrations ranged from 2 to 500 timesconcentrations normally found as an average in background soilsamples. In general, the greatest number of trace metals weredetected in boring B-5. However, the highest concentrations ofseveral trace metals (i.e., copper and aluminum) contaminationwere detected in the exposed waste sample. The metals observedare generally consistent with known past disposal practices atthe site and metals such as cadmium, chromium, and zinc werepreviously sampled in sludges that were reportedly disposed of atth© site.

Various volatile organic compounds (VOCs) and semivolatilecompounds were detected in the waste. The volatile organiccompounds which were observed at significant levels in the fillincluded acetone, 2-butanone, toluene, chlorobenzene,ethylbenzene, and xylenes. Although the soil vapor indicated thepresence of TCE and PCE, those chlorinated compounds were notobserved during the waste sampling.

Pesticides were detected in a total of four of the compositesamples from waste borings B-l through B-4. PCBs were detectedin several soil boring samples collected. Two borings, B-3 andB-5, had concentrations above Ippm (although estimated values) ofArochlor 1016 and 1254.

Ground Water

Ground water was sampled from each of ten monitoring wellsduring three different sampling rounds conducted 19-20 April, 24-25 May, and 15 September 1988. Analytical results for groundwater samples from the monitoring wells around the perimeter ofthe site reflected low level contamination from the fill. Thepopulation at risk were area residents that were still usingground water as a drinking water source.

The majority of the ground water trace metal concentrationswere less than the drinking water standards or at naturallyoccurring concentration levels, as defined by the literaturevalue ranges. The only trace metal contaminants consistently(for two or more sampling events) detected above the literatureconcentration ranges and/or drinking water standard MCLs invarious wells were cobalt, iron, magnesium, and manganese.

There were no PCBs detected in any of the ground watersamples. Also, with the exception of a relatively low level ofendosulfan sulfate detected in Well EA-5D during the May samplinground, no pesticides were detected.

There were only a few monitoring well samples containingrelatively low concentrations of a small group of volatile andsemivolatile compounds. Almost all organics observed were notconsistently measured in more than one sampling round. Also, all

were observed at low concentrations. A few compounds (volatileand semivolatile) were consistently detected during all threesampling rounds. The volatile compounds consistently detected inall three sampling rounds included 1,1, dichloroethane, benzene,and chlorobenzene. The semivolatile compounds detected in allthree sampling rounds at low concentrations were 1,4dichlorobenzene and bis(2ethylhexyl)phthalate.

Also, vinyl chloride concentrations in EA-4D and EA-6D were6 and 7 ug/L, respectively, during only the April sampling event.Also, since TCE was detected during the SVCA and since vinylchloride is a degradation product of TCE (and PCE) the observedvinyl chloride concentrations may be a direct result of leachategeneration during the spring months.

Figure 3 presents reasonable worst case averageconcentrations of detected compounds for the monitoring wells.As illustrated in Figure 3, vinyl chloride and benzeneconcentrations marginally exceed their primary maximumcontaminant levels (MCLs) in the deep aquifer zone at the siteperimeter. The MCLs for vinyl chloride and benzene are 2 ug/Land 5 ug/L, respectively. Manganese also exceeded the secondarymaximum contaminant level (SMCL) in the majority of samples atthe site perimeter.

Ground water samples were also obtained on 28-29 August 1988from 14 residential wells, two wells on the Rocky Ridge Parkproperty, and one well on a lot for Doersam Woods. The locationsof the residential, Doersam Woods test and park wells in relationto the East Mount Zion site are shown in Figure 4.

The trace metal concentrations for the residential wells(Table 2) were within the acceptable levels as defined by MCLsand SMCLs. The iron and manganese concentrations exceeded theSMCLs for seven and three residential locations, respectively.No elevated levels of cadmium, chromium, or zinc were observed.The Old Park Well had a high lead concentration (68.6 ug/L);however, since no monitoring wells showed high levels, theconcentration is not believed to be related to the site.Furthermore, the water in the Old Park Well was stagnant for along period of time. This may also be a reason why lead levelsin this well were elevated.

No detectable levels of PCBs, pesticides, or volatileorganics were observed during any sampling events. Onesemivolatile compound, di-n-butylphthalate, was detected at 6ug/L at one residence, which may be a result of laboratorycontamination, since (1) the compound was also detected in themethod blank, and (2) it was not detected in any other domesticor ground water samples (di-n-butylphthalate is a knownlaboratory contaminant).

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The ground water flow patterns identified at the siteinclude several interrelated regimes. The flow regimes include ashallow water-bearing zone, which is seasonal in nature, anintermediate zone, and a deep water-bearing zone. The depth toground water is generally less than 20 ft. The shallow zone isin intimate hydraulic communication with the saturated portion ofthe landfill. Based on the waste characterization data, shallowwater-level data, and surface topography, a radial flow patternfrom the fill is inferred. Outside the radial flow influences,the shallow water flows predominantly in a westerly andsoutheasterly direction where it discharges into intermittentstreams. The intermediate zone is also seasonal in occurrenceand serves as a transitional zone from the shallow to the deepzone.

The deep water zone is the regional aquifer and exists underunconfined conditions. Ground water flow in this zone is throughfractures, joints, and weathered seams. Based on the seasonalnature of the shallow and intermediate zones and the contaminantlevels observed in the deep wells, it is believed that theprimary zone of ground water transport of contamination is thedeep water-bearing zone. Ground water flow in the deep aquiferis to the north-northwest. Linear ground water velocities in thedeep zone are relatively high-9 ft/day. Therefore, residenceslocated along the linear fracture traces would have receivedground water that passed under the site within a 9-month period.This fact also points out the dilution of leachate infiltrationto the deep-flow zone. The relatively high transmissivity rangecalculated for the aquifer ranges from 4,840 to 8,470 gpd/ft.

The resultant average concentrations observed in themonitoring wells at the site are presented in Figure 3. Theaverage concentrations of the most soluble/mobile constituentsare at or below the contract required detection limits (CRDLs)for those compounds. These constituents also averagedconcentrations marginally above the MCLs. Therefore, minimalground water dilution will result in concentrations below MCLs.Based on the low concentrations, no offsite ground water modelingwas conducted, and concentrations observed in the monitoringwells at the site were used for input to the risk assessment.

It is EPA's Superfund policy to use EPA's GroundwaterProtection strategy and Groundwater Classification Guidelines toassist in determining the appropriate type of remediation for aSuperfund site. Three classes of ground water have beenestablished on the basis of ground water value and vulnerabilityto contamination. The deep aquifer at the site is a Class IIaquifer. A Class II aquifer is one which is a current orpotential source of drinking water and water having otherbeneficial uses.

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Surface Water and Sediment

Surface water and sediment samples are grouped togetherbecause of the close association between the two groups.Populations at risk are wildlife and aquatic life that may beimpacted by the surface water and sediment contamination.

The site is situated within the Susquehanna River Basin andlies at the divide of the Codorus and Kreutz Creek watersheds tothe west and southeast, respectively. Subsurface drainage ischanneled via two tributaries. Both drainage density andpatterns are controlled by geologic features (i.e., topography,bedding, and jointing). Near the site, the dominant drainagepattern is semirectangular to the south and east and semiradialto the west. Figure 5 shows the general surface water flowpatterns at the site.

Surface water runoff and seepage of leachate from theeastern portion of the fill are currently channeled to aperimeter ditch along the southwestern boundary, which in turnempties into a surface water/leachate collection pond at thesoutheastern corner of the site.

Surface water runoff and seepage of leachate from thewestern portion of the fill are collected along the southwesternsite boundary by a shallow ditch and channeled to a largediameter corrugated pipe, which in turn is connected to theDoersam Woods Subdivision storm sewer system. Surface waterrunoff from the central portion of the fill is directed toward adepression near the center of the fill where, during the laterwinter months, it remains ponded.

Analytical results for surface water samples collected atthe seeps at the southeast and western portions of the fillshowed limited contribution of contaminants from the waste fill.The only detected organics in the leachate seep were acetone,benzoic acid, lindane, xylenes, and bis(2-ethylhexyl)phthalate,all at very low levels.

The metals concentrations for the west leachate seep weregenerally higher than the southeast leachate seep. Elevatedinorganics included copper, manganese, and mercury. Thepotential impacts, however, appear minimal based on thefollowing:

copper Perennial upstream concentrations were higherthan downstream concentrations

manganese downstream concentrations, from both seeps,were the same relative concentrations as thebackground upstream

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mercury no detectable levels were observed downstream

Also to assess potential partitioning of contaminants intoth© sediments at the leachate seeps and possible downstreamwaters, samples were collected at observed seeps and localsurface waters. Since background sediment concentrations werenot available, the sediment samples were compared to backgroundsoil concentrations and average soil concentrations forSoutheastern Pennsylvania. Comparison of average sedimentconcentrations to regional background levels show that, with theexception of cadmium in the southeast leachate sediment sample,all average sediment concentrations were within or below therange of regional concentrations. For cadmium, concentrationsabove 1.8 mg/kg were observed in the leachate watercoursesediment and the southeast leachate pond.

No pesticides or PCBs found in the fill were detected in anyof the surface water samples. One pesticide, 4,4-DDE, wasdetected in a composite sediment sample from the southeastleachate pond watercourse. No other pesticides were identifiedin the sediment samples. PCBs were identified in two sedimentsamples. Arochlor 1016 was detected in two composite sedimentsamples from the southeast leachate pond watercourse at 100 ppb(a very low level).

Surficial Soil

The results of the samples indicate the presence of onlybackground levels of metals, and levels of volatile andsemivolatile contaminants were less than the contract requiredquantification limits.

SUMMARY OF SITE RISKS

The purpose of the risk assessment performed for the EastMount Zion landfill site was to evaluate the human health riskposed by any releases from the site. In order to estimate thehuman health risk, the risk assessment focused on the following:(1) the contaminants detected during the remedial investigationat the site; (2) the potential environmental pathways by whichpopulations might be exposed to compounds released from the site;(3) the estimated exposure point concentrations of the compoundsof concern; (4) applicable or relevant and appropriaterequirements (ARARs), criteria, and advisories; (5) the estimatedintake levels of the compounds of concern; and (6) the toxicityvalues of the compounds of concern. The level of risk that thesite poses to human health was then quantified.

It was determined that the number of compounds detected atthe site was small enough that a subset of the constituents did

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11not need to be selected for use in the risk assessment, i,e.,selection of indicator chemicals was not necessary. Therefore,all compounds that could be quantitatively evaluated wereincluded.

Exposure Assessment ;

This step in the risk assessment process involvesdetermining the potential routes of exposure to the humanpopulation, the estimated concentrations to which the populationis exposed, and the population at risk. The baseline riskassessment at the East Mount Zion site considered the potentialexposure routes, including ground water (drinking water), surfacewater (and sediment), air, and direct contact. Of these routesof exposure, ingestion of ground water (drinking water) was theonly significant human health exposure route identified.

Exposure Point Concentrations

As indicated in previous sections ground water samples werecollected from monitoring wells onsite, from nearby offsiteresidential wells, and from two offsite nonresidential wells(i,e., the Abandoned Park Well and the Old Park Well).

The ground water data from the wells located at the site(Figure 3) are indicative of releases occurring to ground waterfrom the contamination at the site, but are not indicative of thecontamination to which the population is currently being exposedgiven that there are no domestic wells at the site. Thesemonitoring well data, however, will be used to evaluate thepotential risk associated with hypothetical ingestion of groundwater at the site. Data from the residential wells (Table 3) arethe best available indicators of current risk to the neighboringpopulation. The two nonresidential wells (the Abandoned ParkWell and the Old Park Well) can be used as potential indicatorsof offsite migration, but neither is an actual monitoring wellbuilt to current construction specifications and neither iscurrently used as a source of drinking water. These two wellscould, potentially be used as drinking water sources. However,PADER has notified the well owners that these wells need to beabandoned. Therefore, the exposure of individuals ingestingwater from these wells is not expected, and the data must beevaluated within this context.

For the monitoring Wells, two exposure cases, an averagecase and a reasonable worst-case, were considered based on theaverage and reasonable worst-case concentrations detected inthese wells. To calculate these two exposure pointconcentrations, the average individual well concentration overthe time period sampled (April to September in most cases) wascalculated first. One-half the instrument detection limit (IDL)was used in these calculations when a chemical was not detected.

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An arithmetic mean was then calculated using the individual wellaverage concentrations to obtain an estimate of the most likelyconcentration of chemicals in onsite monitoring well groundwater. The reasonable worst-case concentration of chemicals inthe monitoring wells was defined for the purpose of this riskassessment as the highest average individual well concentration.Average and reasonable worst-case monitoring well concentrationsare presented in Tables 4 and 5.

For the residential wells and nonresidential (i.e., the OldPark Well and the Abandoned Park Well) offsite wells, each ofwhich had one valid sample, exposure point concentrations wereconsidered to be the concentrations of chemicals detected in eachwell (i.e., each well was evaluated separately). Theseconcentrations (corrected for blank contamination and samplesconsidered invalid) are presented in Table 3. The reasonableworst-case concentrations of chemicals in any residential wellwere also determined and are presented in Table 6.

Comparison to Applicable or Relevant and Appropriate Requirements

In the case of ground water concentrations, the appropriateARARs are the Drinking Water Standards and Health Advisories,given that the ground water is used as a source of drinking waterin the area. The pertinent standards are the Primary MaximumContaminant Levels (MCLs), the Secondary Maximum ContaminantLevels (SMCLs) and the Lifetime Health Advisories (HAs). TheMCLs are based upon health, technological feasibility and costconcerns, and carry regulatory authority for public water supplysystems. They have also been considered in many cases to beappropriate standards for ground water that is used for drinkingwater* SMCLs have been established based upon aestheticqualities, i.e., odor and taste. They do not carry regulatoryauthority, but are meant to serve as reasonable goals fordrinking water quality. The Lifetime HAs are based upon healthconcerns and have been established for many compounds which donot have MCLs. They do not have regulatory authority and aremeant to serve as guidelines for government officials responsiblefor protecting public health in the case of spills orcontamination situations.

Concentrations of compounds detected in the ground water atthe site and in wells in the neighboring vicinity of the site,and MCLs, SMCLs, and Lifetime HAs are presented in Tables 4 and7. In the case of ground water in monitoring wells at the siteonly reasonable worst case concentrations of vinyl chloride andbenzene marginally exceeded their MCLs. Average concentrationsof these two chemicals were less than their respective MCLs.Average and reasonable worst-case iron and manganeseconcentrations exceeded the aesthetically-based SMCLs.

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Estimation of Daily Intake

Because there are not health-based ARARs for eachcontaminant of toxicplogical concern detected in the groundwater, the daily intake of each contaminant was estimated inorder to be used in conjunction with appropriate risk values todetermine the total potential risk posed by the site to thesurrounding population. In order to calculate the estimateddaily intake levels (EDIs) , the U.S. EPA's standard assumption ofingestion of 2 L of drinking water per day for an adult with abody weight of 70 kg was used in the following equation (U.S. EPA1986a and 1988a)

EDI (mg/kg/day) = fC)(BW)

WhereC = concentration of contaminant in ground water (mg/L)IR = daily drinking water ingestion rate (L/day)BW = body weight (kg)

The EDIs for the contaminants of concern are presented in Tables5 and 6. It should also be noted that it was not necessary tocalculate exposure to the residential population viavolatilization of constituents from their well water (e.g., whileshowering) given that no volatiles were detected in anyresidential water samples.

Toxicitv Assessment

Cancer potency factors (CPFs) have been developed by EPA'sCarcinogenic Assessment Group for estimating excess lifetimecancer risks associated with exposure to potentially carcinogenicchemicals. CPFs, which are expressed in units of (mg/kg-day) -1,are multiplied by the estimated intake of a potential carcinogen,in mg/kg-day, to provide an upper-bound estimate of the excesslifetime cancer risk associated with exposure at that intakelevel. The term "upper bound" reflects the conservative estimateof the risks calculated from the CPF. use of this approach makesunderestimation of the actual cancer risk highly unlikely.Cancer potency factors are derived from the results of humanepidemiological studies or chronic animal bioassays to whichanimal-to-human extrapolation and uncertainty factors have beenapplied.

Reference doses (RfDs) have been developed by EPA forindicating the potential for adverse health effects from exposureto chemicals exhibiting noncarcinogenic effects* RfDs, which areexposure levels for humans, including sensitive individuals, thatis not likely to be without an appreciable risk of adverse healtheffects. Estimated intakes of chemicals from environmentalmedia (e.g., the amount of a chemical ingested from contaminateddrinking water) can be compared to the Rfd. Rfds are derived

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from human epidemiological studies or animal studies to whichuncertainty factors have been applied (e.g., to account for theuse of animal data to predict effects on humans). Theseuncertainly factors help ensure that the RfDs will notunderestimate the potential for adverse noncarcinogenic effectsto occur.

The carcinogenic potency factors for carcinogenic compoundsand RfDs for noncarcinogenic compounds are presented in Tables 5and 6.

Excess lifetime cancer risks are determined by multiplyingthe intake level with the cancer potency factor. These risks areprobabilities that are generally expressed in scientific notation(e.g., 1x10-6 or IE-6). An excess lifetime cancer risk of IE-6indicates that, as a plausible upper bound, an individual has aone in million chance of developing cancer as a result of site-related exposure to a carcinogen over a 70-year lifetime underth© specific exposure conditions at a site.

Potential concern for noncarcinogenic effects of a singlecontaminant in a single medium is expressed as the hazardquotient (HQ) (or the ratio of the estimated intake derived fromthe reference dose). By adding the HQs for all contaminantswithin a medium or across all media to which a given populationmay reasonable be exposed, the Hazard Index (HI) can begenerated. The HI provides a useful reference point for gaugingthe potential significance of multiple contaminant exposureswithin a single medium or across media.

In the case of contaminants detected in the monitoring wellsat the site, the total HI exceeds one, i.e., 1.5, only underreasonable worst-case exposure conditions (Table 5). Cadmium andmanganese are the compounds having the greatest impact on the HI,i.e., 3.4E-1 and l.OE+0, respectively. The estimated dailyintake of either compound does not exceed respective RfD,although manganese is clearly at its RfD. Risks are assumed tobe additive within type of critical effect. The critical toxiceffects for cadmium are renal effects, and for manganese, nervoussystem effects. Therefore, additivity is not assumed for thesecompounds. Based on this, the only noncarcinogen of potentialconcern is manganese, which under reasonable worst-caseconditions is just at a concentration which would result in adaily intake equal to its RfD.

For carcinogens detected in the monitoring wells, the totalcarcinogenic risks under average and reasonable worst-caseexposure conditions were 1.7E-4 and 3.8E-4, respectively (Table5). These values are just outside the target range of IE-4 toIE-6 which is used by the U.S. EPA for selecting remedies atCERCLA sites. Arsenic and vinyl chloride are the contaminantsmost significantly contributing to total cancer risk estimates.

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There is some concern, however, about the certainty of thedata and the concentrations used to calculate the carcinogenicrisks. In the case of arsenic, it should be noted that themaximum concentration of 1.8 ug/L is well below the currentdrinking water standard of 50 ug/L. In reviewing the data onarsenic, one sees that arsenic was detected in only one validsample in only one well, EA-4D. On the other two samplingoccasions at EA-4D, ho arsenic was detected. It should also benoted that for the one sampling event in which arsenic wasdetected at EA-4D, the analyte was detected below the contractrequired detection limit (CRDL), but above the instrumentdetection limit (IDL). In evaluating the metals detected in theonsite and surficial soil at East Mount Zion, arsenic levels donot appear to be of concern in soil.

In reviewing the vinyl chloride data, this compound wasdetected in only two wells, EA-4D and EA-6D, and only during thefirst of three sampling rounds at each well. Both times thatvinyl chloride was detected, it was at a level below the CRDL,but above the IDL. Therefore, the concentration was estimatedeach time. It should also be noted that vinyl chloride was notdetected in the waste or surficial soil samples at the site.

Two other compounds that potentially contribute in a lesssignificant manner to the total carcinogenic risk are 1,1-dichloroethane and bis(2-ethylhexyl)phthalate, which wereassociated with carcinogenic risks of 1.4E-5 and 2.7E-6,respectively, at reasonable worst-case concentrations, and 2.5E-6and 6.2E-6, respectively, for average concentrations. Inevaluating the monitoring well data, these compounds wereconsistently detected in the waste samples (Figure 3).

Benzene at reasonable worst-case concentrations marginallyexceeds its MCL, i.e., 5,3 ug/L versus 5 ug/L. The averagebenzene concentration of 1.1 ug/L, however, is well below theMCL. The only well where benzene was consistently detected wasEA-4D (Figure 3). Benzene was also detected during the soilvapor survey. ,

In the case of residential wells, risk values were availableonly for the noncarcinogenic effects associated with the detectedcompounds. Therefore, potential carcinogenic effects could notbe quantified. The total HI for all compounds, regardless ofcritical effect, was less than one for each individualresidential well. Using the maximum concentration of chemicalsdetected in any residential well, the HI was still less than one(i.e., 4.2E-1) (Table 6). Therefore, no deleterious effectsassociated with the residential wells are expected.

In the case of the two nonresidential wells, neither ofwhich is used as a source of drinking water, all the compoundsfor which risk values were available were associated with

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. _ ..the Old Park Well were 2E-1 and 6.7E-2, respectively, which areless than 1. Therefore, no deleterious effects associated withingestion of ground water in the area of each well are expectedbased on the compounds evaluated. However, as indicatedpreviously, lead in the Old Park Well was detected at aconcentration which exceeds the existing and proposed drinkingwater standards. This does not appear to be related to thelandfill given that lead was detected in only one monitoring wellat the site at a concentration well below the existing MCL andjust equal to the proposed MCL. Also, the levels of leaddetected in waste and surficial soil samples did not indicatethat lead was a contaminant of concern at the site.

In summary? exposure pathways quantitatively evaluated inthis risk assessment were for ingestion of ground water fromonsite monitoring wells, residential wells, and non-residentialwells. Evaluation of the monitoring well data indicates thatthere would be potential risk associated with ingestion of groundwater onsite and at the site perimeter. The noncarcinogeniccompound of greatest concern is manganese. The carcinogeniccompounds potentially of concern are arsenic, vinyl chloride,benzene, 1,1,-dichloroethane, and bis(2-ethylhexyl)phthalate. Aspreviously noted, arsenic was detected in only one well (belowthe CRDL) and only during one of three sampling rounds in thatwell. In one shallow monitoring well, the concentration of leadwas less than its MCL and just equal to the proposed MCL.

Evaluation of the residential and nonresidential wells inthe neighboring area indicates that there is no significant riskbeing posed to the population ingesting ground water based on thesamples, chemicals and exposure pathways evaluated. Forresidential ground water, the hazard index was less than one evenunder reasonable worst case conditions. No carcinogenicchemicals of concern were identified. Lead concentrations in allresidential wells were less than the MCL, although levels in somewells exceeded the proposed MCL. The only compound of concern inthe nonresidential wells was lead detected in the Old Park wellsample. The source of the lead problem in the well is unknown,but it does not appear to be associated with the contamination atthe site based on the sample results of the RI. It should alsobe noted that the Old Park well is not used as a source ofdrinking water. No carcinogenic chemicals of concern wereidentified in the nonresidential wells.

Environmental Assessment

Surface water samples were collected from the southeast andwest leachate seeps, east and west intermittent streams, and theeast and west perennial streams. The samples collected wereanalyzed for metals and organics. The observed concentrationswere compared to Pennsylvania Water Quality Criteria for Toxic

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Substances and the Federal Ambient Water Quality Criteria.Analytical results for surface water samples collected at thesoutheast and western leachate seeps showed limited contributionof contaminants from the waste fill. Comparison of the inorganicdata to the appropriate criteria resulted in the identificationof two compounds that exceeded acute and chronic water criteria.These compounds were copper and mercury. However, thesecompounds were not found in elevated levels downstream of thesite.

In evaluating the surface water organics data, only thosecompounds with established Pennsylvania or EPA water qualitycriteria were reviewed (Table 8). This evaluation indicated thatnone of the organics identified were observed to exceed anyaquatic life criteria.

Sediment samples were collected within the leachate seepsand analyzed for metals and organics. There were no organicsdetected in the sediment that were of concern. Comparison ofaverage sediment concentrations to Regional backgroundconcentrations show that, with the exception of cadmium in thesoutheast leachate sediment samples, all average sedimentconcentrations were within or below the range of regionalconcentrations, For;cadmium, concentrations above 1.8 mg/kg wereobserved in the southeast leachate pond and watercoursesediments. The southeast leachate watercourse sediment had thehighest concentration of cadmium at 6.5 mg\kg. No aquatictoxicological significance is known to be associated with theseelevated levels of cadmium sediment values.

In summary, several compounds were observed to exceedidentified water quality or sediment quality criteria, thesecompounds are not expected to adversely impact aquatic systemsbecause of the flow restrictions placed on the leachate seeps.The west leachate seep flows into the Doersam Woods stormdrainage system where it is impounded in a sediment pond.Extensive dilution is expected within this system prior to itseventual discharge during storm events. Similarly, leachate fromthe southeast portion of the landfill is impounded in the surfacewater/leachate collection pond. Any flow from the southeastleachate pond is expected to be diluted prior to combining withKreutz Creek, thereby minimizing any aquatic life impacts.

In assessing potential impacts to terrestrial life which mayuse surficial waters in the site vicinity as drinking water,health and risk based calculations have revealed that theutilization of surficial waters associated with the site by localpopulations of wild or feral vertebrate animals would not elicitany cancerous risk or noncancerous health threat to theseanimals. These calculations assumed combined impacts fromcontaminants found in the surface waters and the sediments andemployed health-based criteria normally used in risk calculations

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in humans. Except for occasional transient species, no federallylisted or proposed threatened or endangered species are known toexist in the East Mt. Zion site area.

DESCRIPTION OF ALTERNATIVES

The remedial action objectives for the East Mt* Zion siteare (1) to prevent ingestion of ground water which hasconcentrations (that are related to the East Mt. Zion site)greater than established MCLs and (2) protect downstream waterquality to assure concentrations of parameters that areassociated with the site meet Federal and State Water Qualitycriteria. Applicable or relevant and appropriate requirementswhich pertain to the alternatives below are listed in Table 10.There are no historical or archeological sites in the East Mt.Zion site vicinity that would be impacted by implementation ofthe following alternatives.

Based on these remedial action objectives, the alternativesdeveloped to address contamination at the East Mt. Zion site are:

Alternative #1___No Action

The Superfund program is required to evaluate the No Actionalternative. Under this alternative, no remedial action would betaken to address contaminant sources or their potential migrationpathways, and any site posed risk would remain unchanged. Thisalternative would be selected only if the site posed little or norisk to public health or the environment from hazardoussubstances as addressed in the Superfund law. Long-termmonitoring (30-years) of the ground water, surface water,sediment, and soil would be performed.

*There are no capital costs associated with the no action

alternative. The sampling costs are estimated to be $320,000 forthe first year and $80,000 for each subsequent year for.thirtyyears. Present net worth for 30 years at 8% interest would be$1,220,000.

Alternative #2___Restricted Access with EnvironmentalMonitoring

Under this alternative a chain link fence would be installedaround the landfill so that public access to the landfill wouldbe restricted. Also, a long-term (30-year) monitoring programconsisting of ground water, surface water, sediment and soilsampling would be implemented. Deed restrictions would also beimplemented to limit future use of the site.

The capital cost for installation of the fence is estimatedto be $45,000. The sampling costs are estimated to be $320,000for the first year (quarterly sampling at $80,000 per event) and

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$80,000 for each subsequent year for thirty years. Present networth cost for this alternative for 30 years at 8% interest wouldbe $1,265,000.

Alternative #3___Multilayer Cap with Methane Venting

Under this alternative, the landfill would be closed as amunicipal waste landfill under Pennsylvania Municipal WasteRegulations. This alternative consists of surface waterdiversions, methane venting through gas vents, constructing amultilayer cap consisting of a clay layer or synthetic liner,sand drainage layer, and a soil cover. In conjunction with capinstallation, regrading of the fill may be necessary due to thesteepness of the slopes on the south and west sides of the fill.This alternative would act to inhibit the mobility ofcontaminants. Ground water monitoring and deed restrictionswould be integral components of this alternative. A chain-linkfence would be installed around the site so that public access tothe site would be restricted.

The estimated capital expenditure for this alternative wouldbe $1,945,000. The operation and maintenance expenditures areestimated to be $100,000 for ground water monitoring for thefirst year (quarterly at $25,000 per event) and $25,000 annuallythereafter for thirty years. Present net worth cost for thisalternative for 30 years at 8% interest would be $2,230,000.

Alternative #4___Excavation and OffSite Incineration

This alternative would involve the excavation and disposalof the waste material at a municipal incinerator. Thisalternative would require the excavation and disposal ofapproximately 300,000 cubic yards of waste material.Incineration involves the thermal destruction of organiccompounds to a nonhazardous product. Treatability testing of thewaste may be required to determine the ability of the incineratorto handle the physical properties of the waste involved and toeffectively destroy the waste based on its chemical properties.Metal contaminants will remain in the incinerator ash and willrequire disposal in a secure offsite facility. Also large bulkitems in the fill may be unsuitable for incineration and requireoffsite landfill disposal. A staging area for the waste materialwould be required. After excavation, clean fill would beimported to bring the site back to grade. The existing covermaterial would be stripped, stockpiled, and then backfilled.

Based on existing waste characterization, the landfill wasteis not believed to be RCRA hazardous waste. This would beconfirmed prior to offsite incineration or disposal.

The estimated capital expenditure for this alternative wouldbe $12,830,000. No operation and maintenance expenditures are

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expected for this alternative. Present net worth cost for thisalternative therefore would be $12,830,000.

Alternative #5 Excavation and Off-Site Landfilling

This alternative is similar to alternative 4 with theexception that offsite disposal would be by landfilling and notincineration.

The estimated capital expenditure for this alternative wouldbe $13,260,000. No operation and maintenance expenditures areexpected for this alternative. Present net worth cost for thisalternative therefore would be $13,620,000.

Alternative #6 Rearadina

This alternative consists of regrading ares of the landfillwhich do not facilitate surface water runoff from the site. Thiswould entail importing fill material and soil from offsite andproviding slopes to promote runoff. The reduction ofinfiltration to the fill material will reduce the leachateproduction at the site thereby alleviating the ground watercontamination at the site. Ground water monitoring and deedrestrictions to limit future use of the site would also beincluded as components of this alternative. A fence would alsobe installed at the site to restrict public access.

The estimated capital expenditure for this site would be$115,000. Ground water sampling costs are estimated to be$100,000 for the first year (quarterly at $25,000 per samplingevent) and $25,000 for each subsequent year for thirty years.Present net worth cost for this alternative for 30-years at 8%interest would be $460,000.

COMPARATIVE ANALYSIS OF ALTERNATIVES

A detailed analysis was performed on the six alternativesusing the nine evaluation criteria presented in Table 9 in orderto select a remedy. The following is a summary of the comparisonof each alternatives1 strength and weakness with respect to thenine evaluation criteria.

Overall Protection of Public Health and the Environment

All of the remedial alternatives considered for the East Mt.Zion site, except for Alternative 1 (no action), 2 (restrictedaccess with environmental monitoring), and 6 (regrading) areprotective of human health and the environment by eliminating,reducing, or controlling risks through various combinations oftreatment and engineering controls and/or institutional controls.Current site conditions can be expected to persist should the noaction or restricted access with monitoring alternatives be

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chosen. Calculations for leachate reduction by regrading thefill reveal that only a 10% reductiori in leachate contaminationcan be expected. MCLs would not be achieved under the regradingalternative, therefore the remedy is not protective of humanhealth and the environment. As the no action, restricted accesswith environmental monitoring, and regrading alternatives do notprovide for protection of human health and the environment forground water at the site perimeter, they are not eligible forselection and shall not be discussed further in this document.

Alternatives 4 and 5 both involve the excavation and off-site disposal of the waste material from the landfill. However,alternative 4 requires incineration of the waste material as acomponent. Residual ash would then be disposed of in a securefacility. Under alternative 5 the excavated waste would becontainerized and transported to a secure facility without anyfurther treatment prior to disposal. Based on currentinformation, the waste in the fill is not a RCRA hazardous waste.However, prior to implementation of alternatives 4 or 5, thewaste would have to be characterized and handled appropriately.Complete removal of the waste would eliminate the risk of anyfuture ground water contamination at the site. Residual risksassociated with the site would be much less than IE-6 atcompletion.

Alternative 3 entails the installation of an impervious capat the site. The cap would effectively reduce infiltration tothe fill thereby alleviating ground water contamination at thesite and site perimeter resulting in achievement of backgroundlevels of contaminants in the ground water. Access and deedrestrictions would be components of alternative 3. If, asassumed, capping eliminates leachate generationf residual groundwater risks are estimated at much less than IE-6.

Compliance with ARARs

SARA requires that remedial actions meet applicable orrelevant and appropriate requirements (ARARs) of otherenvironmental laws. These laws may include: the Toxic SubstancesControl Act, the Clean Water Act, the Resource Conservation andRecovery Act, and any state law which has stricter requirementsthan the corresponding federal law.

A "legally applicable" requirement is one which wouldlegally apply to the response action if that action were nottaken pursuant to Sections 104, 106, or 122 of CERCLA. A"relevant and appropriate" requirement is one that, while not"applicable", is designed to apply to problems sufficientlysimilar that their application is appropriate. A list of ARARsfor each of the considered alternatives is presented in Table 10.

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Alternatives 3, 4 ,and 5 will comply with their respectiveARARs identified in Table 10, Alternatives 1, 2, and 6 would notcomply with all respective ARARs identified in Table 10 and arenot protective of human health and the environment.

Long-Term Effectiveness and Permanence

Each of the alternatives considered addresses the groundwater contamination at the site. By eliminating the source ofcontaminants to the ground water each alternative achieves acertain degree of long-term effectiveness and permanence. Thedifference between the alternatives with regard to long-termeffectiveness and permanence is directly related to how eachalternative addresses ground water contamination at the site.

Alternatives 4 and 5 provide the greatest degree ofpermanence. They both involve the excavation and offsitetransport of the fill material. Alternative 4 requires theincineration of the fill material and subsequent disposal ofresidual ash in a secure offsite landfill. Under alternative 5,the excavated material would be transported to an offsitefacility without prior treatment.

Alternative 3, while not removing the contaminants, alsooffers long-term effectiveness by reducing the mobility of thecontaminants. This alternative includes an impermeablemultilayer cap that will limit the infiltration of precipitationthrough the fill material and preclude the leaching ofcontaminants into the ground water.

Reduction of Toxicity, Mobility, or Volume through Treatment

Alternatives 4 provides for the completereduction/elimination of toxicity, mobility, and volume bycompletely removing the source of the contamination andincinerating the waste fill material. Incineration involves thethermal destruction of the organic constituents of the fillmaterial to a nonhazardous product. Alternative 5, whileeliminating the toxicity, mobility, and volume of the wastematerial at the site itself, does not provide for the overallreduction of toxicity, mobility, and volume since the waste isnot treated prior to landfilling. Alternative 3 does notprovide treatment of the waste material directly and, therefore,does not reduce the toxicity or volume. The mobility of thecontaminants in the fill, however, is significantly reduced oreliminated by the cap and thereby the site's impact to the groundwater is reduced. Assuming that infiltration to the fill is thesole source of leachate which subsequently migrates through thefill, the migration of the constituents to the ground water willbe eliminated.

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Snort-Term Effectiveness

Alternatives 4 and 5 would involve the excavation of thecover material and the waste, the removal of the waste offsite,and backfilling with clean fill. The risks associated with theexcavation are associated with potential volatilization from thewaste and potential dust emissions from the cover material. Winderosion from the cover material may cause a problem with fugitivedust emissions. The waste material, however, is expected to bepartially saturated and moist and is therefore expected to emitalmost no dust at all. These emissions are of concern (1) forworker exposure and (2) for potential migration to neighboringhousing developments.

Because portions of the fill and existing cover materialwill be significantly disturbed under alternative 3, there isalso potential for increased volatilization from the waste andfugitive dust emissions from the cover material under thisalternative also. Clearing, excavation, and redistribution ofthe waste under alternative 3 is expected to take 3 to 4 months.Short-term exposure therefore would be primarily limited to thatduration in contrast to the possible 3-4 years for totalexcavation of the waste under alternatives 4 and 5. Based onaverage waste characteristics, the daily emission rates for thevolatile compounds in the fill are very low. These emissionrates conservatively assume complete volatilization of thecompound in the waste excavated in a day which was estimated at300 yd3/day. Fugitive dust emission from the fill material isexpected to be minimal since it is currently partially saturated.

In addition to volatile emissions from the site, it is alsoexpected that short-term odoriferous emissions are extremelylikely during the exqavation. :

Implementability

While all the alternatives considered are implementable,some alternatives are technically easier to implement thanothers. .

Alternative 3 is the easiest to implement. Capping is awell established technology which is commonly used in municipaland hazardous waste site closures. Removal of the existingvegetation and regrading of the site may be necessary. Regradingof the landfill would require a cut volume of approximately20,000 cubic yards. Clearing, excavation, and redistribution ofthe waste is expected to take 3-4 months. Total cap installationis expected to be complete within a year after constructionbegins.

Alternatives 4 and 5 both involve excavation of the wastematerial currently in the fill. The quantity of waste estimated

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to be excavated is 300,000 cubic yards. Total excavation of thewaste is expected to take 3-4 years. Additional clean fill wouldhave to be hauled back to the site to bring the site back tograde. The difference between alternatives 4 and 5 is how thewaste will be disposed of once it is excavated. Underalternative 4, which includes incineration of the waste, anincinerator with adequate capacity to handle the volume of wastewould have to be found prior to implementation of thealternative. Residual ash from the incineration process wouldthen have to be taken to a secure offsite facility for disposal.Alternative 5 would involve transporting the excavated wastedirectly to an offsite facility. In order to implement bothalternatives 4 and 5, a suitable disposal facility would have to

identified prior to disposal of the waste.

This evaluation examines the estimated costs forimplementing the remedial alternatives. Capital and annual O&Mcosts are used to calculate estimated present worth costs foreach alternative. Alternative 3, multilayer cap with methaneventing, has a moderate capital cost and annual costs whichresults in an estimated present worth of $2,230,000. Alternative4, excavation and offsite incineration, has a high capital costwhich results in an estimated present worth cost of $12,830,000.Alternative 5, excavation and offsite landfilling, also has ahigh capital cost which results in a present worth cost of$13,620,000. No annual O&M costs are expected for eitheralternative 4 or 5,

State Acceptance

Pennsylvania has concurred with the selected remedialalternative*

Community Acceptance

Community acceptance is assessed in the attachedResponsiveness Summary. The Responsiveness Summary provides athorough review of the public comments received on the RI/FS andthe Proposed Plan, and U.S. EPA's and PADER's responses to thecomments received.

DESCRIPTION OF THE SELECTED REMEDY

The results of the RI/FS and base line risk assessment ledto the conclusion that the East Mt. Zion site has resulted in thecontamination of the ground water onsite and at the siteperimeter, and may pose an endangerment to human health and theenvironment. The deep aquifer in the site vicinity is currently

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used as a source of prinking water by some area residents. Theprinciples used to select the remedy were based on the followingand supported by the comparative analysis:

(1) excess cancer risk for ingestion of the ground water atthe site perimeter is 3.8E-4

(2) the Hazard Index associated with noncarcinogeniceffects from the ingestion of ground water at the siteperimeter is 1.5

(3) there is no current impact to aquatic life downstreamof the site and there is no current impact toterrestrial habitat using onsite surface water asdrinking water

Remedial action goals for the East Mt. zion site are (1) toprevent ingestion of ground water which has concentrations (thatare related to the East Mt. Zion site) greater than the MCL and(2) protect downstream water quality to assure concentrations ofparameters associated with the East Mt. Zion site meet Federaland State Water Quality Criteria.

Based upon consideration of the requirements of CERCLA, thedetailed analysis of alternatives, and public comments, EPA andPADER have selected alternative 3, multilayer cap with methaneventing.

A cap provides a relatively impermeable barrier thatisolates infiltration to buried wastes, thereby minimizing thepotential for the leaching of contaminants to the ground water.It will also significantly reduce leachate production and willlikely extend the periods where the leachate pond in thesoutheastern corner of the site is dry.

Construction of the cap would conform with the PADER cappingrequirements under the Pennsylvania Municipal Waste Regulations.These include, but are not limited to, the following:

a cap consisting of a l-ft clay layer or a 30-milsynthetic liner

a maximum cap permeability of 10-7 cm/sec

- a drainage layer over the cap

a 2-ft soil layer over the drainage layer

- a minimum surface slope of 3 percent

a maximum slope of 33 percent

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- minimization of soil erosion and sedimentation

- stormwater management based on a 24-hour, 25-year stormevent

The site work prior to installation of the cap is likely toinclude site and slope clearing; excavation; redistribution andcompaction; and cover with appropriate loam as required by PADERregulations. Access to clear the slopes is limited and may onlybe possible by clearing a road access through the park and/or theDoersam Woods lots adjacent to the site. Purchase of propertymay be necessary to ensure efficient access during construction.

In addition to capping, venting will be required to providemethane and/or VOC off-gassing. Emissions from the gas ventswill be monitored, and if they are over acceptable levels, acontrol system will be installed. Also, fencing and future siteuse (i.e., deed restrictions) will be required to protect thecap's integrity. Total installation is expected to be completewithin 1 year after construction begins.

The only long-term operation and maintenance costsassociated with this alternative are the inspection, maintenance,and repair of the cap. Also, ground water monitoring would berequired to monitor the natural attenuation of contaminants inthe ground water. The monitoring wells currently in place at thesite would be used for the ground water monitoring of thecontaminant attenuation. Samples would be taken quarterly thefirst year after completion of the cap and then annuallythereafter. Based on ground water velocity and the eliminationof the source, ground water concentrations at the landfillperimeter are expected to meet background levels within fiveyears through natural attenuation. Residual risk for theingestion of ground water at the site perimeter is estimated tobe much less than IE-6. Present net worth costs for thisalternative are estimated to be $2,230,000. A summary of thecapping costs is presented in Table 11.

STATUTORY DETERMINATIONS

Protection of Human Health and the Environment

The baseline risk assessment performed during the RIidentified one pathway of concern—ingestion of ground water atthe site perimeter. As previously discussed, the risksidentified in the baseline risk assessment are marginally outsidethe IE-4 to IE-6 cancer risk range for average ground waterconcentrations at the site perimeter. No significant risks wereidentified for residential water supplies as they relate to theEast Mt, Zion site. The only quantifiable risks associated withthe site are limited to the scenario that ground water at thesite perimeter would be used as a drinking water supply.

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Therefore, the risk reduction objectives and criteria are basedon reduction of those risks associated with the ingestion ofground water at the site perimeter and protection of the deepaquifer from further contamination.

Samples collected from the leachate seeps had two tracemetal concentrations (mercury and copper) which exceeded theaquatic water quality criteria. These constituents, although notdetected in downstream samples, are of concern because theyexceeded the ambient water quality criteria in the seeps.Although ambient water quality criteria in general do not applyto such seeps, which are seasonal in nature, as a conservativeapproach, the attainment of the aquatic water quality criteriafor copper and mercury were also remedial action objectives forthe East Mt. Zion site.

A cap provides a relatively impermeable barrier to isolatestormwater infiltration from buried wastes, thereby minimizingthe potential for the leaching of contaminants into the groundwater and the potential for the migration of the contaminantsoffsite. It will also reduce leachate production and will likelyextend the periods where the leachate pond in the southeasterncorner of the site will remain dry. Regrading of the site willalso promote better surface water runoff further alleviating on-site ponding and migration of the contaminants offsite. Residualrisk associated with the ingestion of ground water at the siteperimeter is estimated at much less than IE-6 once the cap iscomplete. Therefore the remedial action objectives are met withthis alternative.

There will be no unacceptable short-term risks or cross-media impacts caused by implementation of this remedy.

Compliance with Applicable or Relevant and AppropriateRequirements

The selected remedy of a multilayer cap with methane ventingand ground water monitoring will comply with all applicable orrelevant and appropriate chemical, action, and location specificrequirements (ARARs). A complete list of ARARs is presented inTable 10. RCRA land ban is not an ARAR for this alternativesince the waste is being capped in place.

The Pennsylvania ARAR for ground water for hazardoussubstances is that all groundwater must be remediated to"background" quality as specified fay 25 Pa. Code Chapter75.264(n). The Commonwealth of Pennsylvania also maintains thatthe requirement to remediate to background is also found in otherlegal authorities.

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ARARs specific to the selected remedy are presented below:

o Chemical-specific ARARs

25 Pa Code Chapter 123.l(c), Pennsylvania AirQuality Standards

- 25 Pa Code Chapter 127.12, Construction,Modification, Reactivation and Operation ofSources

25 Pa Code Chapter 93.1 et. seq.• PennsylvaniaWater Quality Standards

25 Pa Code Chapter 75.264(n), "background" qualityfor ground water remediation

o Location-specific ARARs

- none

o Action-specific ARARs

25 Pa Code Chapter 271.113, Pennsylvania MunicipalWaste Regulations

29 USC Parts 1910 and 1926 and 29 CFR Part 1910,Occupational Health and Safety Act requirementsare applicable to all response activities

All the ARARs listed above will be met by the selected remedy.

Cost-Effectiveness

The selected remedy is cost-effective because it has beendetermined to provide overall effectiveness proportional to itscosts, the net present worth value being $2,230,000. Theselected remedy is the least costly of the alternatives 3, 4, and5 which are equally protective of human health and theenvironment.

Utilization of Permanent Solutions to the Maximum ExtentPracticable

The EPA has determined that the selected remedy representsthe maximum extent to which permanent treatment technologies canbe utilized in a cost effective manner for the East Mt. Zionsite. Of those alternatives that are protective of human healthand the environment and comply with ARARs, the EPA has determinedthat the selected remedy provides the best balance in terms ofshort-term effectiveness; implementability; cost; reduction in

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toxicity, mobility, and volume; and long-term effectiveness.

The selected remedy does not offer as high a degree of long-term effectiveness as the excavation and disposal options,however, it will significantly reduce the risks to human healthand the environment posed by the contaminated ground water at thesite. The excess human cancer risk at the site has beenestimated to be 3.8E-4, which is above EPA's recommended upperbound of IE-4 to IE-6. Due to the relatively low risk associatedwith the site, EPA has determined that the use of more costlytreatment technologies at the East Mt. Zion site are notjustifiable. Because alternatives 3, 4, and 5 offer a comparablelevel of protection of human health and the environment, the EPAhas selected alternative 3, which can be implemented quickly;will have little or no adverse effects on the surroundingcommunity; and will cost considerably less than the otheralternatives.

Preference for Treatment as a Principal Element

The statutory preference for remedial alternatives thatemploy treatment as the principal element has been determined bythe EPA to be impracticable at the East Mt. Zion site. Due tothe relatively low risk to human health and the environment, andthe nature and extent of the contamination, the EPA hasdetermined that alternative 3, including monitoring, accessrestrictions, institutional controls, and installation of animpermeable multilayer cap, can be implemented more quickly andcost effectively than the other alternatives while stillproviding an adequate level of protection to human health and theenvironment.

EXPLANATION OF SIGNIFICANT CHANGES

The Proposed Plan for the East Mt. zion site was releasedfor comment in May 1990. The Proposed Plan identified EPA's andPADERfs preferred alternative. EPA reviewed all of the commentssubmitted during the public comment period. Upon review of thesecomments, it was determined that no significant changes to theremedy, as it was originally identified in the Proposed Plan,were necessary.

AR30I209

FIGURE 1

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TABLE 1 WASTE CHARACTERIZATION RESULTS

: Range Average

Trace Metals (mg/kg)

Aluminum 1,400-93,700 10,885Antimony ND-6.9 0,6Arsenic 0.34-72.1 2.04Barium 141-268 57,5Beryllium ND-0.88 0.21

Cadmium 0.61-26.5 7.9Chromium 1.8-154 26.1Cobalt 1.0-12.6 3.7Copper i ND-3,150 228Iron 656-939,000 761,546

Lead NO-490 130Manganese . 3.4-593 103Mercury 0.57-1.7 0.85Nickel ND-208 20.1Silver ND-98.8 5.6Tin ND-343 26

Vanadium 1.7-104 19Zinc ; • • 5.3-5,540 1,645

Pesticides (ug/kg)

Dieldrin ND-716.1 39.84,4'-DDE ' ND-542 61.8Endrin ND-10.2 1.14,4'-ODD ND-120 8.64,4'~DDT ND-1,380 78.2

PCBs (Ug/kg)

Aroclor 1016 ND-1,600 266Aroclor 1254 ND-1,900 273Aroclor 1260 . ND-141 27.7

Volatiles (ug/kg)

Methylene Chloride i ND-94 20Acetone ND-1,300 1952-butanone ND-1,800 2002-hexanone ND-20 1.02-methyl-2-pentanone ND-72 3.8

AR30I2I5

TABLE 1 (Cont.)

Range Average

Volatiles (Cont.)

Toluene ND-3,200 176Chlorobenzene ND-400 29Ethylbenzene ND-2,600 188Xylenes ND-12,000 885

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1 , 4-Di chlorobenzene ND-2 , 000 3454-Me thylphenol ND-1 , 600 2061,2, 4-Tr ichlorobenzene ND-700 46Naph thalene ND-2 , 400 3272-Methylnaphthalene ND-1 , 100 131Acenaphthene ND-350 18Dibenzofuran ND-280 17Diethylphthalate ND-840 39Fluorene ND-580 31N-Ni trosodiphenylaniine ND-930 49Phunanthrene ND-5,500 472Anthracene ND-1, 300 68Di-n-Butylphthalate ND-1, 400 452Fluoranthene ND-7 , 600 526Pyrene ND-6,100 469Butylbenzylphthalate ND-780 128bis(2-ethylhexyl)phthalate ND-310,000 29,330Chrysene ND-4,700 290Di-n-Octyl Phthalate ND-1 10 5.8Benzo ( b ) f luoran thene ND-4 , 000 210Benzo(k) fluoranthene ND-840 44Benzo ( a) pyrene ND-3 , 800 200Indeno(l,2,3-cd)pyrene ND-2, 400 126Benzo(g,h,i)perylene ND-2, 300 121Pen tachlorophenol . ND-9 , 300 489

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Table 9 DESCRIPTION OF EVALUATION CRITERIA

Overall Protection of Human Health and the Environment -addresses whether or not a remedy will: cleanup a site to withinthe risk range; result in any unacceptable impacts? control theinherent hazards (e.g., toxicity and mobility) associated with asite; and minimize the short-term impacts associated withcleaning up the site*

Compliance with ARAR's - addresses whether or not a remedy willmeet all of the applicable or relevant and appropriaterequirements of other environmental statues and/or providegrounds for invoking a waiver.

Long-term Effectiveness and Permanence - refers to the ability ofa remedy to maintain reliable protection of human health and theenvironment over time/ once cleanup goals have been met.

Reduction of Toxicity, Mobility, or Volume through Treatment -refers to the anticipated performance of the treatmenttechnologies that may be employed in a remedy.

Short-term Effectiveness - refers to the period of time needed toachieve protection, and any adverse impacts on human health andthe environment that may be posed during the construction andimplementation period until cleanup goals are achieved.

Implementability - describes the technical and administrativefeasibility of a remedy, including the availability of materialsand services needed to implement the chosen solution.

Cost - includes the capital for materials, equipment, etc. andthe operation and maintenance costs.

Support Agency Acceptance - indicates whether, based on itsreview of th* Rif FS and the Proposed Plan, the State concurswith, opposes, or has no comment on the preferred alternative.

Community Acceptance - will be assessed in the Record ofDecision following a review of the public comments received onthe RI, FS, and the Proposed Plan.

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SUMMARY OF CAPPING COSTS

LIGHT CLEAR AND GRUB $28,000

HEAVY CLEAR AND GRUB $25,100

EXCAVATION AND REGRADING $284,000OF 20.000 CY VASTE

7.000 CY FILL- MATERIAL $38,150- DELIVERY $130,550

. - BACKFILL/COMPACT $23,870

GAS VENTING SYSTEM $7,000

30 MIL MEMBRANE $113,256

GEQNET $121,968

GEOTEXTILE • $48,400

FINAL COVER- MATERIAL $201,875- DELIVERY $602,395- BACKFILL/COMPACT $110,143

REVEGETATION $16,553

STQRMVATER MANAGEMENT $25,000

TOTAL $1,776,660i

ASSUME $1,800,000

FENCING $45,000

GROUSDVATBR MONITORING- FIRST YEAR(QUARTERLY) $100,000

GRAND TOTAL $1,945,000

GROUNDWATER MONITORING-SUBSEQUENT YEARS FOR 30 YEARS *25. 000

(ANNUALLY)

PRESENT WORTH COST FOR 30 YEARS AT 8% « $2.230.000

AR30I232

RESPONSIVENESS SUMMARY

This community relations respohsiveness summary is divided into thefollowing sections:

Section I Overview - A discussion of EPA's preferred remedialalternative and the public's response to thisalternative.

Section XX Background of Community Involvement and Concerns -A discussion of the history of community interestand concerns raised during remedial planningactivities at the East Mt. Zion Superfund Site.

Section XXX Summary of Major Comments Received During thePublic Comment Period and Agency Responses - Asummary of comments and responses categorized bytopic.

X. OVERVIEW

EPA's preferred alternative for the East Mt. Zion Site isAlternative 3 as outlined in EPA's Proposed Remedial Action Plan.

Under this alternative an impervious cap would be placed on thelandfill. The cap would provide a relatively impermeable barrierto infiltration, thereby minimizing the potential for leaching ofcontaminants into the groundwater. Surface water controls would beincluded in the cap design. This alternative would also includegroundwater monitoring to ensure the effectiveness of the cap andto monitor the natural attenuation of the contaminants in thegroundwater. Groundwater sampling will be performed and analyzedquarterly the first year, and annually thereafter. A formal reviewof the site will be conducted within five years. If during thistime, additional contamination is detected, the risk posed by thatcontamination would be determined and appropriate action taken.Deed restrictions and construction of a chain-like fence would beincluded as components of this alternative to limit future use ofthe Site and restrict access to the Site.

Based on currently available information, EPA anticipates thisalternative will be protective of human health and the environment.

During the public comment period, all written comments regardingthe selection of a remedial alternative were received from lawfirms representing potentially responsible parties. These commentsfocused on the preference for the no-action alternative and raisedspecific questions on various aspects of the RI/FS report.A public meeting was held on May 30, 1990 and comments fromresidents at the meeting centered around who was responsible for

the costs of the clean up, future use of the Site, and any possiblehealth effects to residents. Limited comments were made at thepublic meeting concerning EPA's preferred alternative. Sincethe current human health risk is negligible, several residents didquestion why action needed to be taken. EPA staff explained thatth©ir goal is also to protect the environment and that was the mainconcern at the Site.

XX. BACKGROUND O? COMMUNITY INVOLVEMENT AMD CONCERNS

Community interest in the East Mount Zion Superfund Site dates backto tha 1970's when a group of citizens first expressed concernabout the landfill to their local officials. Since that time,community concern and involvement have grown.

In 1983 EPA conducted a Preliminary Assessment and Site Inspectionat the Site. The Site Inspection revealed trace levels oftrichloroethylene in groundwater samples. Benzene was reported ina leachate sample, and dichlorobenzene was found in a leachate andpond sediment samples.

When these findings threatened to hold up the construction of theDoersam Woods housing development, residents and officials voicedtheir concerns and participated in public meetings. Major concerns©xprsssed at that time related to stagnant pools of water aroundthe landfill, debris which had worked its way to the surface of thelandfill, and contamination of the area water supply.

In 1986 Springettsbury Township installed a municipal water supply.Whil© this eased community concern to a degree, some residencesalong portions of Druck Valley and Ridgewood Roads are still usingground water obtained from private wells.

These concerns, along with comments about EPA's preferredalternative, and EPA's responses are described below.

XXX. SUMMARY OF MAJOR COMMENTS RECEIVED DURING THE COMMENT PERIODAND AGENCY RESPONSES.

Comments raised during the East Mt. Z ion Superfund S ite publiccomment period on the RI/FS and the Proposed Remedial Action Planare summarized below. The comment period was held from May 18,1990 to June 18, 1990. The comments are categorized by relevanttopic.

AR30I231*

EPA'3 Preferred Alternative

1. At the public meeting, a question was raised as to whathappens with the water that is running off the landfill andwhether or not it was getting into residents1 wells or intothe different streams in the Rocky Ridge Park.

EPA Response: While the runoff is going into the differentstreams, the contaminant levels are withinacceptable ranges. EPA's preferred alternativecalls for putting an impermeable cap over topof the landfill and thus prevent surface waterfrom getting into the landfill andcontaminating the deep aquifer. The leachateareas will be eliminated as a result ofcapping the Site.

2. A concern was raised as to whether EPA's preferred alternativewould present any dangers to residents arid what safeguardswould be in place to monitor emissions.

EPA Response: A decision will be made during the remedialdesign stage as to whether it is necessary toconstruct a cap over the entire Site orwhether a partial cap is sufficient. Inaddition, modeling has been done to estimatethe volatile emission and it is expected to beinsignificant. Nor are significant dustemissions expected. Also, monitoring will bedone during implementation of the remedialaction.

3. A question was raised on the life expectancy of the syntheticliner, the type of liner to be used and whether the cap hasbeen used before.

EPA Response: The life expectancy of the synthetic liner isin excess of 50 years. There are also claymaterials that meet the same permeabilityrequirements that synthetic materials do andthis is something that would be looked atduring the remedial design stage. Capping isan established technology which is often usedfor closing municipal and hazardous wastesites.

4. A comment was raised on the FS, specifically, would a moretechnically adequate RI reveal significant differences in thenature and extent of contamination and thus generate adifferent remedial design alternative.

EPA response: EPA feels that this RI represents atechnically adequate investigation and thatthe findings have allowed the Agency to assessthe remedial alternatives and select the bestoption. Additionally, there will becontinuing monitoring and review of dataannually to assess the performance of theselected alternative.

5. A comment was raised that the design parameters for theselected remedial alternative are not adequately supportedand, in some cases, have not been evaluated at all., i.e.methane extraction is proposed but the volume of methane gasgeneration is not discussed.

EPA response: The design parameters for the selectedalternative will be developed during thedesign phase of the remedial process.Specifics concerning methane generation andthe development of a collection and ventingsystem will be addressed during this nextphase of the process.

Remedial Alternative Preference

1. A comment was made that the recommended alternative beAlternative No. 6 due to its lowest cost or the No Actionalternative.

EPA response: See response to comment #2 below.Specifically, the regrading option wasevaluated in the detailed analysis section ofthe FS.

2. A comment was made that the recommended alternative be NoAction or Limited Action Alternative No. 1.

EPA response: All the alternative remedial action scenarioswere evaluated according to the screening anddetailed analysis requirements of the NationalContingency Plan (NCP) and the alternativethat provided the best overall acceptance ofthe nine criteria was selected. One singlecriteria is not highly weighted, but each areconsidered separately. Community and stateacceptance, implementability, long termeffectiveness, as well as cost are considered.Alternative number 3, capping and methaneventing, was selected as the alternative thatbest fulfilled all the criteria.

3. At the public meeting, a question was raised as to whether insitu treatment was considered.

EPA Response: The feasibility study did look at some in situtreatments. However, it was determined thatthey either were not feasible or insufficientevidence existed on their effectiveness; thusthey were screened out.

Remedial Investigation/Feasibility Study

1. A comment was made on the sampling results and the compoundsdriving the action.

EPA response: Anytime there is a sampling result whichindicates that the maximum contaminant level(MCL) has been exceeded, the EPA is triggeredinto taking an action to evaluate the causeand likely extent of the contamination. Atthis site the MCL was exceeded for vinylchloride and benzene, which are the compoundsthat have triggered the action.

Sampling results of specific wells over athree-round sampling period, for both arsenicand vinyl chloride were evaluated by using anaveraging technique involving identifying 1/2the detection limit when there was a non-detect during a sampling occasion.

2. A comment was made as to the ARARs (applicable or relevant andappropriate requirements), i.e., that the PennsylvaniaMunicipal Waste Management Regulations are not an ARAR as theydid not go into effect until 1988.

EPA response: Because the regulation is presently in effectall cleanup options or actions at the Sitemust consider the regulation as an ARAR. ThePennsylvania Municipal Waste Regulations arean ARAR for capping and closure due to noncompliance with the Solid Waste Regulations ineffect at the time initial closure wasordered.

3. A comment was made that the Feasibility Study does not setforth the specific monitoring requirements associated with anyof the remedial alternatives.

EPA response: Sampling costs are an important item in thepresent worth analysis of all the alternativeoptions. Specific monitoring procedures maynot have been documented in the FS butestimates were provided for the range ofassociated costs involved with monitoringprograms related to each alternative.

4. Comments were raised concerning the mismanagement of datacollection, failure to adjust to field conditions, and failureto collect an optimal amount of information via a particularmethod.

- mismanagement of data collected

EPA response: Aerial photography was used to evaluate pastwaste disposal practices and assist in scopingthe work at the Site. Specifically, a 1955image was reviewed to identify site conditionsand activities at the earliest stage.

Geophysical techniques are a standard practiceused to remotely assess subsurface siteconditions. A range of techniques are usuallyselected to provide overlapping and supportingdata that can be analyzed individually toprovide confirmation (or negative evidence) ofan evaluation. At a highly disturbed andcomplex site, such as a landfill, resistivityand conductivity surveys provide a "gross"analysis of physical aspects of siteconditions, the extent of disturbedconditions, and an approximation of thedirection or trend of potential offsitemigration of contaminated fluids. In shortgeophysics are one of the many tools used at asite for characterization, with the potentialto provide valuable data. At this site,geophysical data was used to help decide onthe location of selected soil borings.

Ground water mounding was proposed at the siteand is based on two lines of evidence: (1)contamination was identified in the deepmonitoring wells on both the "upgradient"perimeter wells and in the "downgradient"monitoring wells, and (2) professionaljudgement and evaluation that moundingcommonly occurs below saturated landfills andsurface impoundments.

Subsurface data was collected during drilling;including one rock core, that was completelydescribed, descriptions of lithology, based oncuttings and presented on boring logs, andadditional data provided by drilling rates.Fracture analysis was provided by data fromthe core description, and evaluation of thesubsurface flow characteristics. Fractureanalysis was helpful in monitoring wellplacement. Soil and borehole logs wereprepared for the report and are available.

The test borings in the fill were groutedalmost immediately after sampling to protectthe health and safety of the public. This wasnecessary because of excess methane levels,sometimes exceeding 60%.

The purpose of the pump test at the site wasto demonstrate the hydrologic interconnectionbetween the different flow zones and toidentify any potential hydrogeologic barrierthat would restrict flow at the site. Thepump test was successful in both these areas:showing the response in all three bedrock flowzones and by indicating that a barrier doesexist, that affects the amount of recharge orflow to the site, thereby defining a limitedaquifer. Specific aquifer characteristics,such as accurate storage coefficient andtrahsmissivity values, would have been anextra piece of information for the site, butthis data may not be needed with thealternative selected.

5. Comments were made concerning the development of pooranalytical data.;

EPA response: Field analytical results such as pH, specificconductivity, temperature and the results ofmethod blanks should have been included in theappendix of the RI re_port. This informationis reported in Section 2 of the report inTables 2-5, 2-6, and 2-7.

The phthalates, reported from many of thefield samples also were reported from themethod blanks, indicating possible laboratorycontamination.

All the composite sampling of the wasteindicates an iron rich metalliferous waste.Inorganic and organic analyses are presentedin the RI indicating the compounds may leachfrom the waste into the ground water.

Compositing can effect the results ofvolatiles and semi-volatiles, however, forindicating the characterization of the waste,compositing is a reliable indicator of thepotential for all compounds that may migratefrom the waste.

Detection 1imits are presented for theorganics on Table 6-2 and for inorganics inthe tables of Appendix G. Appendix G presentsthe results as they were reported while tables4-1 to 4-11 report results that are correctedfor detections in field, trip, or rinsateblanks. Modifiers, "B" and "U" are defined onmost of the tables in the Appendix and thetext.

Early in the investigation, it was decided touse the method of subtracting theconcentrations detected in field blanks fromthe sample results and reporting the finalresult. Both the raw results and the reportedresults are included in the RI report.

The lack of a QA/QC section in the RI reportis a shortcoming. The QA/QC data isavailable, and the analytical results on fieldblanks is presented in Appendix G.

6. Comments were received concerning the failure to report orcollect significant information. Examples of this include:

- decontamination procedures

EPA response: Decontamination procedures are presented inthe Field Operations Plan (FOP).

procedures for compositing

EPA response: These procedures are presented in the FOP orField Sampling Plan and in Table 2-2 of the RIfor waste characterization.

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no documentation of PID readings or how taken

EPA response: The methods for taking PID reading and thefrequency of taking the reading are in theQuality Assurance Project Plan (QAPjP) or theFOP. The results should be available in thefield logbook.

- poor detail in lithology for monitoring wells.

EPA response: Boring logs for all the wells are prepared anddetailed core log was prepared for well EA-1D.This information is available.

rock quality designation (RQD) collected but not reported

EPA response: RQD was prepared for the core from well EA-1Dand is available on the core log.

- background concentrations not cited

EPA response: Soil background concentrations are presentedin Section 4, Tables 4-8 and 4-9.

no detection limits on analyses tables

EPA response: Detection limits are presented in othersections of the report and in the Sampling andAnalysis Plan.

7. Comments were received concerning specific comments in theremedial investigation report.

Page 2-19: "Each Monitoring Well Was Developed By Air SurgeMethod." Air surging when sampling for volatile or semi-volatile organics is highly inappropriate in that air couldvolatilize many of the organics in the ground water andsubsequent samples could be unrepresentative.

EPA response: Sampling of the monitoring wells took placelong after development. This time lag allowedthe wells to re-equilibrate to the surroundingground water conditions and the samples arerepresentative of those conditions. At thissite, sampling events took place severalmonths after development.

Page 2-30: "Typically, corrections are made when drawdown inthe pumping well exceed (sic) 20 percent of the total saturatedthickness..." No case was made in the text that the saturatedthickness of any of the water-bearing zones was of a definitethickness. A correction for 20 percent of the undefinedthickness is inappropriate.

EPA response: EPA agrees that 20% of an undefined thicknessis inappropriate. However, the correctionsthis statement refers to are for an unconfinedwater table condition with a known thicknessof saturated aquifer. The drawdown in thepump test at the site did not use this 20%correcting value.

Pag© 2-24 to 2-38: The analyses of the ground water and theanalytical section has many problems. Without going intodetail, the analysis presented is not sufficiently supportedby good data and the arguments and correction factors used tojustify the poor results render the results very questionable.

EPA response: EPA disagrees with the final conclusion ofthis comment. The raw results are presentedin Appendix G, including the analytical datafor the trip and field blanks.

Pag© 3-13: Re: Test borings in fill; "..., borings were notleft open a sufficient amount of time to allow for water levelstabilization ... to keep methane expulsion to a minimum.""Nonetheless, it can be assumed that the majority of the fillis saturated at least on a seasonal basis." There is no basisfor this assumption.

EPA response: EPA disagrees. The fill material waspartially saturated during the fieldinvestigation and based on projection, duringa wet season the fill would continue aspartial to fully saturated.

Page 3-14: M... a northeast-southwest trending trench isapparent in the east-central portion of the site. Thisfeature is illustrated on the isopachous map by the 10-, 15-,and 20-foot isopach contour configurations." Looking at themap, this appears to be a bench.

EPA response: The contours show the distribution ofthickness of waste as interpreted fromgeophysical soundings. The change in contoursin a northeast to southwest trend shows a

10

thickening of waste, which may represent atrench.

Page 3-15: "Ash material, incendiary in nature, is alsoprevalent throughout (the fill)." Knowing that part of theproposed remediation is exhumation and regrading, thisstatement had best be explained and proven. There is noignitability testing reported in this report. This couldpresent a significant hazard if regrading of the landfill ispart of the remediation.

EPA response: The selected alternative does not includeexcavation, nor removal of the waste materialsin the landfill. If areas of the landfillneed to be excavated during regrading, thenignitabil ity testing will be part of thedesign phase.

Page 3-18: "...Drilling cuttings and drill stem advancementrates were the only method of lithology identification forthese boreholes." Very poor methodology. This was done forall monitoring wells except one.

EPA response: The description of the drill cuttings wascompared to the detailed core descriptionprepared for well EA-1D.

"Semischist" is not a rock type.

EPA response: EPA agrees with this comment.

Page 3-21: "On the basis of this information, well EA-1D waslocated at the intersection of 2 linears just north of thesite." There is no mention of whether they thought they hadintersected these linears and there was certainly no basis forcomparison with other test borings.

EPA response: The well location was selected to test an areawith the potential for intercepting fractures.Fracture analysis of the site indicatedfractures were present and may affect the flowof ground water. One objective of welllocation EA-1D was to detect fracture and asecond obj ective was to provide a means todetermine if the flow zones wereinterconnected. The density of the fracturesencountered were reported on page 3-39 and 3-42.

i , r - 11

Pag© 3-27: This section presents a discussion of leachategeneration and the fact that landfill is unlined and in directcontact with bedrock and residual soil. Recognition of thisfact and the assumption that significant amounts of leachateis generated during wet weather periods is reasonable, but cannot be substantiated by the data generated in this report.

EPA response: EPA believes that it is reasonable to assumethat leachate is generated during wet weatherand could contact the saturated bedrock*

Page 3-20: "Based on unforeseen conditions encountered duringth© drilling and installation of EA-1D and EA-2D amodification in deep well design was implemented." Section2.1.6.2 details the drilling activities at the two wells whenit was realized that there was water cascading into the wellsfrom fractures above the zones they proposed to monitor. Anattempt was made to grout these zones, EA-1D was lost, had tob© grouted shut and was redrilled; EA-2D was converted to amedium depth well. In view of the discussion on page 3-27,cited previously, there were indications in the field thatshallow to medium depth water-bearing units existed and onlyone well was completed in order to investigate theintermediate zone. This is a very poor response to somesignificant information.

EPA response: The major aquifer in this area, and the onecommonly supplying water to the residents inthe area is the deep zone. One of the primeobjectives of the investigation was todetermine if this zone was contaminated.

Page 3-31: "...Water-bearing fractures were common throughoutthe entire cored sequence, indicative of some degree ofvertical hydraulic interconnection. It was also anticipatedthat ©ven the shallow (seasonal) perched water within theoverburden/saprolite may, in part, eventually migratevertically towards the deeper zone. If this was trulyanticipated, it went unheeded during the planning stage ofthis project.

EPA r©sponse: This information was developed after thedrilling and coring of well EA-1D. Theplanning stage of the projects was mostlycomplete at this time, however one of thereasons for drilling at location EA-1D was todetermine the interconnection provided by the

12

AR3QJ2H

proposed fractures. This obj ective wasdeveloped in the planning stage.

Page 3-33: "Deterministic characterization of the hydraulicproperties of the fracture system was not within the scope ofwork." The paragraph following this sentence goes on to makeunsupported assumptions about the fracture system for purposesof characterizing the aquifer*

EPA response: The main objective of the investigation wasnot to determine accurate hydraulic propertiesof the fracture system but to determine howthe fracture network affected the sitehydrogeology. Some of the assumptionsconcerning the fracture are based onprofessional judgement.

Page 3-34: ".. .Potentiometric level fluctuations greater than40 feet were observed." This may be due to the fact that morethan one water-bearing zone is being monitored in the deepzone. No distinct zones were shown in this report.

EPA response: This magnitude of potentiometric levelfluctuation can occur as recharge conditionschange and the levels are reaching a newequilibrium. Another explanation for thisqhange in water level is that the site islocated near a ground water divide and thereis a limited aquifer to resupply to zonebeneath the site.

Page 3-37: "Recovery data were non existent in wells EA-3D,EA-4D, and EA-5D, and incomplete in wells EA-6D, EA-7D and EA-1D." This statement gives us an indication that the pumpingwell EA-1D was over pumped and the aquifer never approached asteady state condition. As a result, calculations oftransmissivity, storativity and permeability are of doubtfulaccuracy. .

EPA response: See response to comment #4 of this section.

Page 3-40: "The shallow ground water zone is in directhydraulic communication with water mounded beneath thelandfill." This is an important concept if it is correct;there is no data to substantiate this statement.

EPA response: See response to comment #4 of this section.

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Pag© 3-41: "No effort was made to construct a water table mapof the shallow zone since waste characterization boring waterl©v©ls were inconsistent and taken at a time before theshallow wells were installed." A missed opportunity to obtaininformation that would substantiate the claim that there isradial flow to the underlying water-bearing zones below thefill. This observation hints at the possibility that thelandfill may contain distinct zones, some saturated, othersnot* This would naturally be important information tocollect, and was not done on this project.

EPA response: EPA understands that, if the fieldcircumstances concerning methane gas problemswere different, ground water elevationmeasurements of test borings in the fill atthe same time as measurements in the shallowwells would have been a good opportunity todemonstrate the potential mounding effect.The test borings in the fill had to be groutedbecause they posed a hazard. EPA alsounderstands that at any disturbed site theremight be zones of differing saturation as wellas different permeabilities. However, thisinformation does not affect the selectedremedy.

Pag© 3-43: "Intermediate depth water-bearing zones were also©ncountered during several other deep well drilling operationsat locations EA-7D, EA-6D, and EA-4D, ... intervals wereencountered at 62-72, 47, and 38 feet, respectively. EA-7 wasth© only location to exhibit a significant yield from thisintermediate zone." A second, intermediate water-bearing zoneis for all purposes encountered and ignored. Significant flowis recognized. This section does not mention the intermediatezones encountered in EA-1D and EA-2D.

EPA response: Only one of the deep wells reportedsignificant yield from the intermediate zone,well EA-7. The other four wells did not findthe important flow that would characterize amajor flow zone. One intermediate well wasinstalled in this intermediate zone, well EA-2M.

Page 3-44: "It is uncertain whether the drop in water levelin EA-2M during the 72 hours pumping test was associated withpumping or was a result of local water table lowering." Thisis an apparent effort to explain away the fact that theintermediate depth well responded better than the shalloww©lls during the pumping test. The shallow wells responded,

14

but to a lesser degree. This information reveals that EAplaced only one well in the "intermediate zone," the onehydrostatigraphic zone of greatest vulnerability.

EPA response: EPA does not agree with the last statement.There is no evidence that the intermediatezone is a major flow zone or that it is atgreatest vulnerability. This zone wasmonitored and did respond to pump tests in thelower aquifer, demonstrating someinterconnection between the two zones.

Page 3-46, 47: "The vertical flow patterns at the site arenot well defined. Vertical gradients within the deep zonewere not characterized. Vertical migration from the shallowzone to deeper zones is evident and is the primary source ofground water recharge to the deep zone." The three sentencesall occur in the same paragraph. This continues EA's patternof statements continuously being made with no information toback it up. The conclusions appear reasonable, but no effortwas made to see if they are correct.

EPA response: EPA disagrees with the format of this comment.The statements were taken out of context ofthe paragraph in which they occur. Eachstatement is followed by an explanation of themethods or limited analysis used to assess thesite conditions.

Page 5-1: "In summary, waste characteristics for organiccompounds identified include ...bis(2-ethylhexyl)phthalate(310,000 ug/kg)." This phthalate was found in method blanksand is a common laboratory contaminant. It is Remcor' sunderstanding that this phthalate was left out of thecontaminants of concern mentioned during the EPA meeting onMay 30, 1990.

EPA response: EPA agrees that phthalate is a commonlaboratory contaminant and that this highconcentration was detected in sample Comp 3REof test boring number four. EPA feels thatwhile the phthalate is of concern, it was notthe compound that triggered the site responseaction. Benzene and vinyl chloride are thetwo important compounds that have triggeredthe action.

Page 5-1: "Elevated metal concentrations were observed.. .iron(939,000 mg/kg)." Obviously a piece of metal was collected inthe sample, and the laboratory analyzed it: and found it to

15

consist of 93.9% iron. Metal fragments are to be expected inlandfill.

EPA response: EPA agrees that metal fragments are expectedin a landfill. Sampling in a complex landfillcan identify metalliferous waste.

Pag© 5-1: "...The primary mechanisms of contaminant loadinginto the surround environments is leachate generation fromwat©r percolating into the fill," There is no data availableregarding the waters in the fill nor is there any leachatederived from the fill collected.

EPA response: Water levels were observed in the test boringin the fill. There are diversion ditches andpond to control the water (leachate) thatseeps out near the border of the slope. Twoleachate seeps, one at the southeast cornerand one at the western slope of the fill, weresampled during the investigation.

Page 5-3: "The intermediate zone is not really extensive, asit was not encountered in all monitoring well borings." Thisstatement contradicts information in previous sections.

EPA response: EPA disagrees with this comment. Previoussections discuss the extent and hydrologicflow characteristic of the intermediate zoneacross the site.

Page 5-3: "The deeper water-bearing zone...is under semi-confined conditions." There is no data to substantiate thisinformation.

EPA response: EPA agrees that the word "semi-confined" maybe a misleading term.

Pag© 5-3, 4: "...The ground water transport scenario iscomposed of,..pulsed leachate generation...radial flow awayfrom the landfill...the intermediate ground waterzone.4. .appears not to be an important transportmechanism. „ .however.. .data suggests that water in theimmediate zone moves downward to deeper water zones." It isimportant in the three items characterizing the ground waterflow below the fill, not one statement can be substantiated byinformation collected during the ground water investigation.

EPA response: Water level data, boring logs, a coredescription, and hydrographs all suggest there

16

is a dominant vertically downward migration ofinfiltration.

Page 5-5: "The relative absence of volatile compounds abovedetectable levels in the shallow wells suggests that themajority of leachate is migrating vertically ratherthan...moving laterally in the shallow zone,...detailedmodeling of ground water transport is not warranted at thissite." This states the case that the monitoring of theintermediate zone is of paramount importance in determiningground water flow and comes to the conclusion that it is notimportant; when in truth there was so little significantinformation collected. No modeling is possible.

EPA response: EPA disagrees. As the report states, the low-level of volatiles detected in the monitoringwells proximal to the site, would not justifya: costly, data intensive ground water flow ortransport model*

Pages 1-9 and 1-20 - Manganese was not proven to be siterelated.

EPA response: Manganese does occur in the sample resultsfrom the waste and the groundwater. Theassociation with the site may not be provenbut seems to be indicated.

8. A comment was raised on the available technologies for siteremediation.

- Pages 2-6 and 2-7 - Permitting is discussed during theARARs presentation, but actual permit requirements forthe site were not presented.

EPA response: The discussion refers to the requirement foran NPDES permit to discharge the effluent fromonsite ground water treatment processes. Theselected alternative does not require pumpingor treating of ground water so the actualpermit requirements are not fully presented.

Pages 2-12 - The remedial objective for vinyl chlorideand benzene have been met for two of three samplingrounds. More information is required before certainbenzene and vinyl chloride concentrations become theremedial goal of the site.

; 17

EPA response: Continued monitoring of the ground water atthe site, after implementation of the selectedalternative will determine the effectivenessof the actions in reaching the remedial goals.

- Page 2-14 - Technologies are supposed to be initiallyscreened on implementability only. A second screeningthen accounts for administrative implementability,effectiveness, arid cost. This procedure was notfollowed.

EPA response: The procedures for evaluating potentialremedial alternatives is presented in theRI/FS Guidance (Oct. 1988). The initialscreening of alternatives involves threecriteria: implementability, effectiveness, andcost.

Page 2-17 - The 30-mil listed in the capping technologyis not in accordance with current guidance documents.

EPA response: The 30-mil lining is exactly what is requiredby the Pennsylvania municipal landfillregulation. A recent EPA technical guidancedocument (EPA 530-SW-89-047) lists a 20-milminimum thickness for these liners.

- Page 2-19 - Vertical and horizontal barriers are nottechnically implementable at this site.

EPA response: EPA agrees

- Page 2-26 - The excavation and disposal option for300,000 cubic yards (yd ) of material is unrealistic.

EPA response: EPA agrees.

- Page 2-26 - Cost should also include:

- Excavation- Soil erosion and sediment controls- Regrading site at completion- Site administration- Air controls- Design (engineering cost).

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AR301250

EPA response: EPA agrees that these are valid costs to beconsidered for the excavation option. Duringthe screening review of alternatives, basiccosts are considered for each option andcompared to the basic costs for the otheralternatives.

Page 2-26 - Daily cover would be required over theexcavated portion of the landfill to comply withPennsylvania municipal waste regulations.

EPA Response: EPA agrees.

Page 2-27 - Incineration did not consider sorting thewastes.

EPA Response: EPA does not agree. During the discussion ofremedial section alternatives, on page 3-5 theissue of bulk items was discussed.

- Page 2-28 - Several important points were neglected whenconsidering in-situ vitrification ISV including:

Is power available to perform this project?

The technology does not work below the water table.

- Metals in the landfill could prohibit the use ofthis technology.

The short-term hazards are high.

- The cost of in-situ vitrification is typically $400to $500 per yd and not $100 to $250 per yd , as isassumed.

EPA response: All these items are important considerationsto assess the implementability of ISV. EPArecognizes these issues and considered the ISValternative as a costly, and impracticalalternative for this site.

Page 2-31 - Ground water pumping and treatment will onlylimit the mobility of the contaminants in the fracturesystems intercepted by the wells. This will do nothingto remediate the perched ground water.

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EPA response: EPA agrees with this comment. f Ground waterpumping with either onsite J or offsitetreatment would require additional "design-phase" site assessment wells. *

* 49. A comment was made that the alternatives presented are not in

full compliance with Pennsylvania municipal landfill closureregulations unless daily cover, etc is to be included in theaction*

EPA response: EPA agrees that all alternatives would indeedrequire a daily cover placed on the exposedsite to bring the alternative into compliancewith the regulation. Some of the alternativeshave a cover already designed in the option,such as the selected alternative.

10. Alternative numbers changed identification numbers going fromChapter 3 to Chapter 4. It is difficult to follow the textdue to this detail.

EPA response: This is regrettable, EPA hopes there were nomajor problems.

11. A limited action alternative entitled regrading was added toth© list of alternatives but was not discussed in the previouschapters * I

• tEPA response: This is true; the limited action alternative

is, as the name implies, a slightly differentversion of the no action alternative. Becauseof the slight difference between the twooptions the limited action alternative wasassumed to pass the screening review and wasconsidered only under the detailed review.

12. Page 4-6 - The use of the word "sponge" is not a technicalt©rm.

EPA response: EPA agrees, but as a conceptual aid, the termdescribes the processes and occurence offluids within a landfill.

13. Page 4-8 - Costs are lower than Remcor's recent experiencewith FSs would indicate. Several factors have not beenconsidered, specifically:

20

^30/252

Wastes must be sorted prior to incineration

The longer construction schedule reducesefficiency, therefore, increases cost

- Engineering costs have not been included

- Site administration costs have not beenincluded.

EPA response: The identified costs associated with eachalternative are just estimates based on therange of acceptable cost associated withconstruction activities developed at otherSuperfund sites . The cost factor for eachalternative is one component of the selectionprocess that is evaluated in a relative senseto the other potential alternatives.

14. A comment was made that the conceptual cap grades and sectionsare not realistic for placing a multi-layer cap over thelandfill .

EPA response: EPA considers these comments to be designconsiderations and will properly address allspecific design parameters during the designphase. The final grade at the site will meetthe requirements of ^Pennsylvania municipallandfill regulations. The diagrams presentedin the FS report were presented as conceptualaid to understand the proposed remedialaction.

15. A comment was made that the assumption that the waste beingpartially saturated will lower the dust emissions is notrealistic; as soils are exposed and handled, they will dryquickly.

EPA response : The EPA agrees with this assessment . Theselected alternative ' s design andimplementation will include a plan for dustcontrol activities*

16. A comment was made that there will be increased mobility ofcontaminants, not decreased, as the landfill will be exposedfor four years, and the surface will -be irregular.

EPA response: EPA agrees that in the short term, during thefour years of excavation proposed under the

AR301Z53

source removal alternative, there would beincreased mobility of contaminants due to winderosion and ponding on the irregular surfaceof the landfill. However, the selectedalternative will not excavate materials, andcontamination will last less than two years.

17. A comment was made that the RI/FS failed to procure anadequate basis for evaluating remedial alternatives.

EPA response: EPA disagrees with this comment. The RIidentified the critical site characterizationdata needed to evaluate the potential remedialalternatives. All the criteria, referenced inthe NCP, were reviewed for each option andwith state concurrence. The best overallalternative was selected.

18. A question was raised as to what the ambient air tests showed.

EPA Response: No contamination was detected.

19. Residents asked if there was a possibility of offsitecontamination.

EPA Response: From the information currently available,there appears to be no offsite contaminationabove any kind of risk levels. The onlycontamination found was immediately adjacentto the Site and no one is drinking that water.

20. A question was raised as to whether there was any testing fordioxins and what the-results of such testing showed.

EPA Response: A high level dioxin test was done and nodioxin was found. It is not a significantconcern at this time.

Risk assessment

1. Page 1-9 - The selection of parameters and justification fortheir use in determining risks can be questioned* Use of theinstrument detection limit (IDL) has no bearing on riskassessment. Vinyl chloride and 1,l-dichloroethane do notbelong in the risk assessment because they were found in bothupgradient and downgradient wells*

22

AR3QI25U

EPA response: At this site the "upgradient" wells are most1ikely affected, at least infrequently, bycontaminants from the site because of possiblemounding of the shallow ground water. Thereare no other potential sources of contaminantsin the "upgradient" direction, that beingtowards the top of the ridge.

2. Page 1-13 - Ingestion of ground water (drinking water) was theonly significant human health exposure route identified and isnot adequately developed.

EPA response: EPA disagrees with the comment that theingestion exposure route was not adequatelydeveloped.

3. Page 1-14 - Carcinogen risks are driven by compounds that aresignificantly below maximum contaminant levels (MCLs) . Bis(2-ethylhexyl)phthalate is the only compound that belongs in therisk assessment.

EPA response: EPA feels that the compounds driving thepotential risk at this site are vinylchloride, benzene, and arsenic.

4. A comment was made on the calculation of the average and worstcase exposure concentrations and the analysis based on thosecalculations.

EPA response: In evaluating and . interpreting analyticalsampling results, it is common practice totreat non-detect or less than limit ofdetection events as 1/2 the detection limit(EPA, RCRA TEGD 1986.) Additionally thearithmetic average (or mean) of theconcentration is regarded as a reasonableestimate of the concentration likely to becontacted over the exposure period (EPA RiskAssessment Guidance Volume 1 December 1989).

5. A comment was made on the conservatism of the risk assessmentin the use of worst-case assumptions to analyze the risk tohuman health, e.g., the worst-case scenario that monitoringwells at the Site perimeter would be used for drinking waterand even if they were so used the level of consumptioncalculated was too high.

EPA response: EPA recognizes that monitoring wells will notbe used as drinking water wells, however these

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AR30I255

wells demonstrated that groundwatercontamination exists outside the landfillperimeter boundary. The assumption that theconcentration of contaminants detected belowthe site serves as a worst-case scenario forpotential risk to future use of the aquifer.

Worst case assumptions concerning ingestion ofgroundwater at a rate of 2 liter per day for70 years was the conventional standard usedfor risk assessments as of late 1988. ByMarch 1989, reasonable worst-case exposurescenarios used an average ingestion rate of1*4 liters per/day for only 30 years. This isthe average ingestion rate and length of timepeople live in a single house. This analysishas no impact on the alternative that has beenchosen for the site.

6. A comment was made on the use of the methodology for potentialaxcess cancer risk and non-carcinogenic hazard index.

EPA response: EPA accepts methodology used in this reportfor potential excess cancer risk and non-carcinogenic hazard index. The proceduresused are an acceptable method for riskassessment.

7. A comment was raised as to the accuracy of the Risk Assessmentbased on questions raised on the analytical results.

EPA response: The assumption that maximum concentrations forall contaminants are located in one well andthat on-site wells are used as a drinkingwater source is a worst-case scenario and theEPA concedes that it is unlikely to occur.However, the risk assessment worst-caseanalysis is an important step to evaluate thepotential range of possible exposure tocontaminants and groundwater intakes.

cost ....of the Remedial Action1. A question was raised at the public meeting as to who would be

paying for the cost of the remedial action.

EPA Response: EPA has identified 11 potentially responsibleparties and is continuing its efforts tonegotiate with these parties regarding the

24

cost of the actions taken at the Site. TheRI/FS was paid for-from "Superfund" through acooperative agreement with the State. Shouldthe potentially responsible parties not reachagreement with EPA for the remedial design andremedial action, Superfund money would againbe used and EPA would then attempt to laterrecover the costs from these potentiallyresponsible parties.

Future Use of the Site

1. Residents questioned how the Site could be used in the future.

EPA Response: As part of the remediation of the Site, therewould be deed restrictions placed on the Siteto limit entry and a chain link fence put upto protect the integrity of the cap.

2. A question was raised at the public meeting as to whether ornot any future construction activity in the area could haveany negative effects.

EPA Response: Future construction activity would haveminimal effect. The remedial action would dryout the landfill and thus eliminate the sourceof contamination from migrating offsite. Inaddition, the groundwater will be monitored.

3. A resident asked what the Site would look like upon completion.

EPA Response: There will be a vegetative cover on top of thecap. It will look like a field with somemethane vents.

Remaining1 Concerns

1. A comment was made that Mr. Clyde Zeigler has been improperlydesignated as a potentially responsible party.

EPA response: This is an issue that will be reviewed andevaluated at a later time. At present, thisissue does not affect the selection of anappropriate remedial alternative.

2. A comment was made that the East Mount Zion Site has beenimproperly designated as a Superfund Site on the National

25

Priorities List and requested the Site be deleted from theNational Priorities List.

EPA response: This is also an issue that will be addressedand determined at a later time. At presentthis site is on the NPL and has been properlyevaluated for remedial action.

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AR30I258

COMMONWEALTH OF PENNSYLVANIADEPARTMENT OF ENVIRONMENTAL RESOURCES

June 29, 1990Deputy SecretaryEnvironmental Protection 717-787-5028

Mr. Edwin B* BricksonRegional AdministratorUS EPA, Region III841 Chestnut BuildingPhiladelphia, PA 19107

Re: Record of Decision (ROD) ConcurrenceEast Mt. Zion, Springettsburg Twp., York Co.Final Remedy - Groundwater Remediation

Dear Mr. Erickson:

The Record of Decision for the final remedy willaddress remediation of groundwater contamination at the siteperimeter by eliminating or reducing the risks through engineeringand institutional controls.

The major components of the selected remedy include:

1. Install and maintain an impermeable cap over the 10acre landfill*

2. Install and maintain surface water control systemsfor the cap*

3, install and maintain a fence around the site,

4. Monitor groundwater contaminant attenuation afterinstallation of the cap.

5. Initiate a deed notification regarding futureactivities at the site.

I hereby concur with the EPA's proposed remedy, with thefollowing conditions:

* EPA will assure that the Department is provided anopportunity to fully participate in any negotiationswith responsible parties.

* The Department will be given the opportunity to concurwith decisions related to the design of the remedialaction, to assure compliance with DER design specificARARs *

Mr. Edwin B. Erickson - 2 - June 29, 1989Regional Administrator

* The Department's position is that its design standardsare ARARs pursuant to SARA Section 121, and we will

our right to enforce those design standards .

* The Department will reserve our right and responsibilityto take independent enforcement actions pursuant tostate and federal law.

* This concurrence with the selected remedial -action isnot intended to provide any assurances pursuant to SARASection 104(c)(3).

If you have any questions regarding this matter pleasedo not hesitate to contact me*

Sincerely,

Deputy SecretaryEnvironmental Protection

TnTftl P.12