SDMS US EPA REGION V -1

SOME IMAGES WITHIN THISDOCUMENT MAY BE ILLEGIBLE

DUE TO BAD SOURCEDOCUMENTS.

Declaration For the Record of Decision

SITE NAME AND LOCATION

Main Street Well FieldElkhart, Indiana

STATEMENT OF BASIS AND PURPOSE

This decision document presents the selected remedial action forthe Main Street Well Field site in Elkhart, Indiana, developed inaccordance with CERCLA, as amended by SARA and, to the extentpracticable, the National Contingency Plan. This decision isbased on the administrative record for this site.

The State of Indiana concurs with the selected remedy.

ASSESSMENT OF THIS SITE

Actual or threatened releases of hazardous substances from thissite, if not addressed by implementing the response actionselected in this Record of Decision (ROD) , may present animminent and substantial endangerment to public health, welfare,or the environment.

DESCRIPTION OF THE

This operable unit is the second for this site. The firstoperable unit provided an alternate water supply by selecting airstripping as the cost effective remedy. The function of thissecond operable unit is to provide remediation of soil and groundwater contamination in areas of known contamination on the Eastside of the well field and well field restoration by interceptingthe plume from undefined sources on the West side of the wellfield. A third operable unit may be required if additionalsources are identified.

The major components of the selected remedy include:

In-Situ Vacuum Extraction of VOCs in contaminated soil;- Removal of a small paint layer and off-site disposal in

accordance with the Soil and Debris Treatability Variance;Installation of new interceptors on the West side of the wellfield to prevent continued plume migration into the well fieldand provide well field restoration;Continued use of the existing air stripper to assure a cleandrinking water supply;Ground water monitoring to assure adequate performance of theair stripper and attainment of ground water standards;Deed restrictions on East Side property with contaminated soiluntil the soil and ground water cleanup standards are met.

DECLARATION

The selected remedy is protective of human health and theenvironment, complies with Federal and State requirements thatare legally applicable or relevant and appropriate to theremedial action, and is cost-effective. This remedy utilizespermanent solutions and alternative treatment technologies to themaximum extent practicable for this site. This remedy satisfiesthe statutory preference for treatment as a principal element ofthe remedy.

Because this remedy may result in hazardous substances remainingon-site above health based levels, a review will be conductedwithin five years after commencement of remedial action to ensurethat the remedy continues to provide adequate protection of humanhealth and the environment.

Regional Administrator Date*

Record of Decision SummaryMain Street Hell Field

Elkhart, Indiana

I. SITE NAME. LOCATION AND DESCRIPTION

The well field:

The Main Street Well Field (MSWF) is located in the City ofElkhart, Elkhart County, Indiana, at 942 N. Main St. It coversapproximately 48 acres. The Elkhart Water Works (EWW) maintainsthree well fields currently and a fourth well field will go on-line in 1991 to supplement the city's demand. MSWF is theprimary water supply for the city and supplies approximately 80percent of EWW's production capacity for a city of approximately44,000 people. The well field currently contains 17 productionwells, two existing interceptors used as production wells, two 2-million gallon storage tanks, an air stripping facility, sixrecharge ponds and a treatment/pumping station (See figure 1).

Geology/Hydrology:

The aquifer system in northwest Elkhart County consists of coarsesand and gravel deposits averaging 175 feet in thickness. In theMSWF area, sand and gravel (glacial outwash) occurs to depthsranging from 42 to 58 feet. These deposits consist of mixedsands and sands and gravels. Regionally, below the outwash is agray and hard to very dense silty clay layer which separates theunconfined aquifer from a deeper aquifer. The lower aquiferranges from 0 to 120 feet thick within the city boundaries. Theconfining layer is at least 10 to 160 feet thick in the vicinityof Miles Laboratory. The Miles investigative data, inconjunction with data collected during all phases of the RI,indicates that the lower aquifer interfingers with the till layerand eventually pinches out locally northwest of and beneath thewell field. The till is continuous throughout the study area andthe lower aquifer appears to be absent beneath the MSWF. Thistill layer acts as an aquitard or confining layer in the studyarea. Beneath the clay and silt till lie bedrock units of theColdwater and Ellsworth Shales of Mississippian age and theSunbury Shale of Devonian age. See figure 2.

The regional aquifer, inclusive of MSWF, is part of a designatedsole source aquifer. The direction of regional ground water flowis generally south, toward the St. Joseph River and itstributary, Christiana Creek. This southerly flow is morepredominant east of the well field. In the area west of the wellfield, the ground water flow tends from northwest to southeasttoward the well field. The ground water flow in this area issubject to influence by natural factors, such as Christiana Creekand by ground water pumpage and recharge. The effect of MSWF onground water flow patterns is dependent upon ground water levels;the number, location and rate of pumping of the supply wells; the

recharge from Christiana Creek and other industrial ground wateruse and recharge.

Horizontal gradients in the unconfined aquifer measured in thedirection of ground water flow, range from .003 to .020 ft/ft.These gradients do not represent natural gradients because of thedraw-down induced by various pumping wells and pumping rates.Similarly, the pumping and recharge significantly affects theground water velocity. The regional velocity is approximately102 ft/year. However, near the well field it can besignificantly higher - 470 ft/yr measured west of the well field,and 820 ft/yr measured southeast of the well field.

The water-table configuration is dramatically influenced byartificial recharge, draw-down from the MSWF, and draw-down fromthe industrial wells in the study area. The response of thewater-table is directly related to the number of wells pumpingand the rates at which they are pumped. Subsequently, the groundwater flow patterns are also impacted and change on a daily, oreven an hourly basis. Therefore, the dynamic nature of theunconfined aquifer and impact of the pumping-wells induces apotential for ground water mixing and rapid fluctuations in flowvelocities.

II. Site History and Enforcement Activities:

Contamination History:

The first known incident of ground water contamination at theMSWF was in the mid-50's. Ground water was contaminated withphenols as a result of releases from a fuel tank farm east of thewell field. The contamination problem was mitigated byexcavating six recharge ponds in the well field and divertingwater to those ponds from Christiana Creek. EWW acquired thewater rights to Christiana Creek from the Indiana-Michigan stateline to MSWF.

In 1981, MSWF was sampled as part of U. S. EnvironmentalProtection Agency's (EPA's) National Ground water Supply Survey.The well field was found to be contaminated with trichloroethene(TCE) at 94 ppb, 1,2-dichloroethene (1,2-DCE) at 33 ppb, 1,1,1-trichloroethane (TCA) at 5 ppb and 1,1-dichloroethane (DCA) at 2ppb. Observation wells were installed near and on the Excel andDurakool properties located on the East side of the well field.The results of this sampling program indicated that bothindustries were likely sources of ground water contaminationaffecting the MSWF. The city installed two interceptor wells inthe well field on the eastern edge of the property and tookproduction wells near that area out of service. The interceptorwells were discharged to Christiana Creek under an NPDES permit.

TCE levels in the finished water supply and production wells

N

S C A L E : 1 :24000SOURCE:USGS TOPO MAP

E L K H A R T IND

FIGURE 1Site Location Map

WELL FIELD-

r- 0"

— 90"

- 100"

-150'

•—200'

1S TW56 TW38

A'

DSB3

SANO AND QftAVEL

3 «ILTV CLAY/CLAY

S3 »HALE

F IGURE 2Generic-schematic Geologic Cross-sectionof the Main Street Well Field Site

dropped significantly following installation of the interceptorwells. However, in 1984, TCE levels on the west side of the wellfield began to increase. One well increased from 14 to 75 ppb ofTCE. EPA suspected that a separate plume had reached or beendrawn into the well field. In 1985, all 15 production wellsshowed measurable TCE levels.

First Operable Unit:

MSWF was proposed for inclusion on the National Priorities List(NPL) in December 1982, and was placed on the NPL in September,1983. In April 1985, EPA began a Phased Feasibility Study (PFS)to address alternatives for an alternate water supply. In August1985, USEPA signed a Record of Decision (ROD) recommending airstripping. The facility is designed to obtain removalefficiencies of 99.1 percent of TCE. Seven production wells plusthe two east side interceptors were piped to the air stripper.The facility has a capacity of 6.45 million gallons per day. Theair stripping facility consists of three stripping units(towers); each has a diameter of 10 feet, a tower height of 30feet and a total stack height of 55 feet. The air stripper wenton-line in September 1987.

Previous Studies:

1. East Side

Two companies operating on the East side of the well field havebeen present since the 1920s and 1930s. Over the years, bothhave expanded their operations at that location and thus, theirbuildings have seen several additions and changes. Excelmanufactures automobile and truck sash and window assemblies.Durakool manufactures relay and tilt switches. Both industrieshave used TCE and other chlorinated solvents for degreasing intheir processes. In 1983, Excel and Durakool retained the sameconsultant to conduct a voluntary investigation of theirproperties. TCE concentrations in soil on the Excel propertyranged from 0 to 570,000 ppb. On the Durakool property,concentrations ranged from 0 to 5,000 ppb. In 1984, the Stateand EPA determined that the investigative work done by Excel andDurakool was not adequate to meet the requirements of an RI/FS.Federal funds were authorized in 1984 for a federal-lead RI/FS,beginning with a PFS. Special notice was issued after EPAcompletion of the PFS and signing of the ROD to Excel andDurakool offering these companies the opportunity to implementthe air stripper remedy and complete the RI/FS. The response wasnot acceptable and was therefore, rejected. EPA and the IndianaDepartment of Environmental Management (IDEM) funded constructionof the air stripper and continued the RI/FS as federally fundedresponse activities.

2. West Side

Little was known about why the western production wells werecontaminated in 1984. The idea of a western plume was stillonly a theory in 1984. This seemed a likely scenario given thehighly industrial nature of the area west of the well field.However, without more specific information, there was no one tonotice or provide the opportunity to undertake the RI/FS.

Identification of sources of the West side contaminated plume ismore challenging than the East or North side of the well fielddue to the diversity of industry, the higher building tenantturn-over and the almost ubiquitous use of chlorinated solvents,many related to metal finishing operations. Several privateresponse actions have been performed on the West side, however,and these source areas are likely contributors.

Soil sampling and removal of contaminated soil was conducted byMiles Laboratory between 1984 and 1985 after exposingunderground degreasing tanks during demolition of old buildingson the old Adams & Westlake property which it had purchased.Miles removed over 900 yards of soil containing TCE and 1,1,1-TCA.

TCE contamination of the ground water was discovered on anotherpart of the Miles Laboratory property in 1984. Investigationsinto the likely source of contamination suggested that the sourceof the TCE contaminated ground water was west of Miles (atElkhart Products). TCE is reportedly not used by Miles at thisfacility. In 1985, an additional release of 180 gallons ofmethylene chloride, ethyl alcohol and acetone occurred at theMiles facility. Contaminated soil was removed and ground waterrecovered. This area is currently undergoing a RCRA FacilityInvestigation (RFI).

TCE spill events occurred at the Elkhart Products Corporation(EPC) site located west of Miles Laboratory. EPC is amanufacturer of copper fittings and custom fabricated tubularproducts. EPC investigated their own property from August 1985through February 1986. They are currently vapor extractingcontaminated soil and treating contaminated ground water usingair stripping.

III. Community Participation;

EPA and IDEM have been conducting community relations activitiesat the site since 1985. Fact sheets were issued periodically toinform the community of air stripper construction and RI/FSprogress. In addition, an availability session was held toprovide the community, including the potentially responsibleparties, an opportunity to have their questions answered.

The Remedial Investigation Report was released to the public inMay, 1989. The Phase III Technical Memorandum and FeasibilityStudy was released to the public in January, 1991. Thesedocuments were made available to the public in both theAdministrative Record maintained at the EPA Region 5 office andat the Elkhart Public Library and at the information repositoryin the City Engineer's Office. The notice of the availability ofthese two documents was published in the Elkhart Truth on January18, 1991. A public Comment period was held from January 23, 1991through March 22, 1991. In addition, a public meeting was heldon February 7, 1991. At this meeting, representatives from EPAand IDEM answered questions about site risks and the remedialalternatives under consideration. A response to the commentsreceived during this period is included in the ResponsivenessSummary, which is part of this Record of Decision. This decisiondocument presents the selected remedial action for the MSWF sitein Elkhart, Indiana, chosen in accordance with CERCLA, as amendedby SARA, and, to the extent practicable, the National ContingencyPlan. The decision for this site is based on the AdministrativeRecord.

IV. Scope and Role of Operable Unit:

Main Street Well Field is a multi-source, multi-plume Superfundsite. It is more complex than most sites. As a result, EPAorganized the work into operable units (OUs). These are:

- OU One: Alternate Water Supply.- OU Two: East Side Source Control- OU Three: Additional Source Control action (if required)

EPA has already selected a remedy for OU One (Alternate WaterSupply) as described in the previous section. The contaminatedground water is a principal threat at this site because of thedirect ingestion of drinking water from a municipal system andpotential unrestricted use of an aquifer that containscontaminants above health-based levels.

The purpose of this OU response action is to prevent current orfuture exposure to the contaminated soils and contaminantmigration into the ground water East of the well field, and toprevent current and potential future contaminant migration intothe well field from the West, thus restoring the well field toits highest beneficial use.

Since significant uncontrolled "hot spots" have not beenidentified West of the well field, it is uncertain how long theplume will continue to exist. If additional sources areidentified in other parts (west or north) of the study area, anadditional OU may be completed in the future.

6

V. s r a r v of site Characteristics

Soil investigations at this site were limited to suspected "hotspot" areas. Volatile Organic Compounds (VOCs) were thecontaminants of primary concern for identification of hot spots.However, co-disposal with other contaminants needed to beevaluated so that remedial action alternatives could address theentire hot spot. Contaminants selected for investigativepurposes were selected based on suspected material disposed of.Where knowledge of possible disposed material was too limited,full chemical scan was conducted.

The study area, or site boundary, was defined by the ground watercapture zone of the well field and by the total area of groundwater contamination within the capture zone. These boundarieswere measured several times over the course of the RI/FS due tothe dynamic nature (rapid and frequent changes) of the capturezone, and because its extent defined how far west EPA's responseauthorities extended under this CERCLA site. This capture zoneis shown on Figure 3. Ground water is uncontaminated upgradientof Elkhart Products Co. on the west side and upgradient of Excelon the east side. South of these locations ground water iscontaminated and constitutes the ground water study area. Thisarea is over 300 acres, approximately half of which isindustrial. In conducting this RI/FS, no attempt was made toprovide a comprehensive RI/FS on each property. Instead, areasof known or suspected disposal were the focus of investigativeefforts. Priority was given to those areas which remainedunremediated or where remediation was completed, but residualcontamination concentrations were unknown. This approachprioritized efforts and resources to provide the highest amountof contaminant reduction for the effort expended.

All media were sampled, including air, soil, surface water andground water. Figure 4 shows the distribution of TCE in the hotspot areas on the East Side of the well field. TCE ranged from 0to 88,000 ppb on the Excel property and from 0 to 29,000 ppb onthe Durakool property. Although other VOCs are present, TCE isthe most wide spread and present in the highest concentrations.The distribution of other VOC contaminants is discussed in theRI report. Chemicals detected in a least one soil or groundwater sample are shown on Tables 1 and 2. Significantconcentrations of VOCs were not detected in West Side soil(generally below 50 ppb) , therefore, hot spots could not bedefined. While other contaminants, such as inorganics andPolynuclear Aromatic Hydrocarbons (PAHs) were present on the WestSide, their presence was not associated with VOCs, therefore,this operable unit RI/FS did not evaluate the extent of suchcontamination .

Figure 5 shows TCE ground water concentration contours from bothEast Side and West Side plumes. The East Side plume was measured

Bl-a -nc cn-s c:

o3n>

Approximate Distance North (feet)

Hi- M•o r« s

M MM < f10 > fliO HO H 1J

O HZ PI

8s

1

t

c

'A- -ACKJ ^ £14^

...„-.-,

DURAKOOL!̂ 8f

, 13

"

-A-*rr

ITEXCEL

*•.„

FIGURE 4TCE on Eastside Properties

¥

TABLE 1 CHEMICALS DETECTED IN AT LEAST ONE SOIL SAMPLE IN THE EAST SIDE OPERABLEUNIT OF THE MAIN STREET WELL FIELD OR IN A BACKGROUND SAMPLE

Frequency of Detection Range of Detected Values, ing/kgChemical

AcenaphtheneAcenaphthyleneAcetoneAlpha-chordaneAluminumAnthraceneAntimonyArsenicBariumBenzeneBenzo (a) anthraceneBenzo(a)pyreneBenzo (b)fluorantheneBenzo (g , h , i) peryleneBenzo (k) f luoran theneBenzole acidBerylliumBeta-BHCBis(2-Ethylhexyl)phthalate2-ButanoneBucylbenzylphthalateCadmiumCalciumCarbon disulfideCarbon tetrachlorideChlorobenzeneChloromethane

(methyl chloride)ChromiumChrysenecis-1 , 3-dichloropropene

East

10/1666/16685/1822/61138/13828/16649/138128/138137/1383/18240/16631/16636/16628/16629/1664/16667/1386/6141/1664/1703/16654/138138/1386/1823/1822/1821/116

138/13842/1661/116

Well Field

0/140/143/150/156/60/140/66/66/60/150/140/140/140/280/142/140/6om10/140/150/141/66/60/150/150/150/15

6/60/140/15

Background

0/60/65/100/59/90/67/96/98/90/101/61/61/61/61/60/66/92/51/60/50/63/99/90/100/100/100/4

9/91/60/4

East

0.034-0.370.052-0.190.003-1000.011-0.015740-9,2700.05-1.31.1-51.80.41-26.53-1760.002-0.330.033-3.60.037-3.10.039-2.60.049-3.40.037-2.10.11-0.750.21-1.70.0013-0.130.41-400.005-0.120.048-0.820.46-6.3512-124,0000.001-0.0660.001-0.430.005-0.41.1

2.7-63.80.035-40.005

Well Field

_-0.076-0.14-1,110-2,580--1.9-3.65.4-14.4------0.071-0.1--0.11-0.27--1.729,900-51,700----

4.1-9.1--

Background

..-0.026-0.79-1,260-5,720_0.47-301.09-3.18.65-186-0.0630.0820.0960.0760. 12-0.21-0.670.013-0.030.048--0.85-4.7841-58,900—-——

2.9-120.1-

continued-

Table 1 - continued

Frequency of Detection Range of Detected Values, mg/kgChemical

CobaltCopperCyanideA, A -DOTDi-N-butyl phthalateDi-N-octyl phthalateDibenzo (a, h) anthraceneDibenzofuran1 , 2-Dichlorobenzene1 , 3-Dichlorobenzene1 , A-Dichlorobenzene1 , 1-Dichloroethane1,2-Dichloroethene (total)1 , 2-DichloropropaneDieldrinDiethyl phthalateDimethyl phthalate2,4-DinitrophenolEthylbenzeneFluorantheneFluoreneGamma-chlordaneHexachlorobenzeneHexachloroe thaneIndeno (1 ,2, 3-CD) ,pyreneIronLeadMagnesiumManganeseMercuryA-Methyl-2-pentanone

East

131/138137/1388/1389/6156/1661/16611/16616/1661/1662/1661/1031/1822A/1821/1822/613/1660/1661/16622/18251/16611/166A/611/1031/16625/166138/138138/138138/138138/138A3/1380/182

Well Field

6/66/60/60/1510/1A0/1A0/1A0/1A0/1A0/140/140/150/150/150/150/141/140/1A0/150/140/1A0/150/1A0/140/1A6/66/66/66/60/60/15

Background

6/99/90/92/50/60/60/60/60/60/60/30/100/100/101/50/60/60/60/101/60/60/50/30/61/69/99/99/99/92/91/10

East

1.2-17.62.A-2300.53-3100.00089-0.030.042-0.760.610.043-0.530.046-0.250.010.061-0.350.0960.0020.001-580.0010.003-0.0040.05-0.61-1.70.001-3900.038-7.50.047-0.560.0022-0. 0410.130.0990.065-2.21.820-2A.7001.2-1,0506A7-A6.200A3. 6-9860.1-195-

Well Field

1.8-4.14.4-10.2--0.032-0.43-----------0.19--------4,080-15,7002.5-8.76,910-17,40084.4-297--

Background

2.93-6.953-40-0.0021-0.008---__--__—0.0035----3.17-_—— '0.0565,220-18,1002.3-1,060914-17,10088.6-1,1600.18-0.340.01

continued-

Table 1 - continued

Frequency of Detection Range of Detected Values, mg/kgChemical

Methylene chloride(Dichlorome thane)

2-Methylnaphthalene2-MethylphenolN-NitrosodiphenylamineNaphthaleneNickelPCB-1248PCB-1260PentachlorophenolPhenanthrenePhenolPotassiumPyreneSilverSodiumStyrene1,1,2, 2-TetrachloroethaneTetrachloroetheneThalliumTinToluenetrans-1 ,2-Dichloroethene1,1, 1-Trichloroethane1,1, 2-TrichloroethaneTrichloroethene2,4, 6-TrichlorophenolVanadiumVinyl acetateXylenes (total)Zinc

East Well Field

74/182

27/1661/1662/16624/166130/1381/611/612/16658/1661/166135/13852/16647/13879/1382/1821/18229/1822/1382/7147/1820/6632/1825/182128/1821/166137/1380/18250/182138/138

7/15

0/140/140/140/146/60/150/150/140/140/146/60/141/60/60/150/152/150/60/610/150/152/150/1512/150/146/61/150/156/6

Background

6/10

0/60/60/61/67/90/50/50/61/60/67/91/60/99/90/100/102/100/90/64/102/62/100/102/100/68/90/101/109/9

0.

0.0.0.0.2.0.0.0.0.0.

East

001-0.26

041-2601047-0.051034-325-29514232-0.26043-7.21

104-7610.0.320.0.0.0.400.-0.0.0.0.2.-0.6.

033-7.567-3.7.7-1,200005-0.38010003-4.622-0.23

0008-690

0005-250006-0.006001-88018-33

001-2,3009-785

Well Field

0.001-0.026

----4.3-9.1-----126-220-1.1

Background

0.

---0.

004-0.

62

044

5-11.46---0.-990.-

12

.7-43317

55-334--0.001-0.002--0.001-0.005-0.001-0.002-0.001-0.065-3.9-10.40.001-11.5-29.2

--0.--0.0.0.-0.-

005-0.

0006-0001-0.004-0.

007-0.

02

.002003007

022

4-22.4-0.13002.21-1,160

TABLE 2c

CHEMICALS DETECTED IN AT LEAST ONE GROUNDWATER SAMPLfc OF THE MAIN STREET WELL FIELD SITE

Frequency oC Detection Range of Detected Values, (mg/L)Chemical

AcetoneAluminumAntimonyArsenicBariumBenzeneBis(2-Ethylheiryl) PhthalateButanone, 2-ButylbenrylphthalateCalciumCarbon DlaulfldeCarbon TetrachlorideChlorobenzeneChloroformChloroaethane (Methyl Chloride)CopperCyanideDlehloroethana, 1,1-Diehloroethane, 1,2-

-Dichloroethene(Total). 1,2-

N Dlchloroethene. 1.1-Dichloropropane, 1,2-IronLeadMagnesiumManganeseMethylene Chloride (Dichloromethane)NickelPhenolPotasalumSeleniumSilverSodiumTetrachloroethane. 1,1,2.2-TetrachloroetheneTolueneTram- 1 , 2-DlchloroetheneTrichloroethane, 1.1,1-TrlehloroetheneVanadiumVinyl ChlorideZinc

EasL

4/24

0/8

0/80/86/84/241/70/200/77/80/240/240/240/240/52/80/80/240/54/130/240/244/80/86/87/85/240/80/34/80/81/86/80/241/241/2410/194/2417/240/82/243/8

* = chemical was not included in the

West27/711/251/256/2523/258/723/296/60

2/2925/252/721/720/713/721/304/253/2529/721/3023/6013/723/7224/2511/2522/2519/2530/721/251/922/255/252/2525/251/7219/717/71

22/4227/7240/721/2510/7215/25

chemical

Wellfield1/30*AAA

1/30A

0/9

*

*2/300/301/300/300/9AA

4/300/98/300/300/30AA

*A

2/30AAAAAA

0/307/306/309/218/3019/30A

3/30A

analysis of the_

Background2/80/40/40/44/4

0/80/30/80/34/40/80/80/80/80/82/40/4

0/80/80/30/80/84/40/44/44/41/80/40/23/40/41/44/40/80/81/80/80/80/80/40/82/4sample .

East

0.007-0.023---

0.025-0.1110.001-0.00270.004--0.57-92-----

0.029-0.038---

0.039-0.044--

0.0425-0.878-

20.7-23.50.0009-0.3610.001-0.01--

1.03-1 .84

-

0.00974.72-26.1-

0. 110.00150.002-0.094

0.0016-0.0078O.OC2-0.096-

0.012-0.0150.02-0.033

West0.003-0.0390.50.0450.0019-0.00750.0033-0.1660.001-0.0250.006-0.110.002-0.0140.004-0.0070.024-1430.005-0.040.001-0.001-0.150.00070.0029-0.0390.0054-0.1930.001-0.00760.0140.002-0.410.001-0.0520.002-0.0030.0091-2.24

0.0018-0.00280.101-32.30.0067-0.560.001-0.0180.02290.0051.49-5.930.0018-0.00230.0093-0.00970.0245-7560.004

0.002-0.20.0004-0.0030.001-0.10.002-0.230.001-0.570. 104

0.002-0.110.0035-0.0652

Wellfield0.017AA

AA0.0015A-AA0.0002-0.0008-

0.0003--

AA0.002-0.022-

0.0008-0.068--

AAAA

0.001AAAAAA-

0.0007-0.0220.0001-0.00430.001-0.0050.0004-0.0160.0016-0.051A

0.002-0.007*

Background0.015-0.018--.

0.056-0.059-

---

68.9-71.9-----

0.026-0.033--.

--_

1-1.41-

22.7-24.80.231-0.2470.012--

1.29-1.84-

0.0116.68-8.56--

0.002---

-

0.017-0.021

CHRISTIANA CREEKMEASURING POINT

MONITORING VCU.S

PRODUCTION «€LLS

VALUES IN ppb

FIGURE 5TCE Concentrations in Groundwater

Phase II May, 1988

at a maximum of 300 ppb and the West Side plume was measured at amaximum of 570 ppb. The ground water contour is somewhatsimplistic since the plumes are commingled. The relationship ofTCE found in one well to another well is unknown. Analysis ofother ground water contaminants showed that several inorganicswere present above background, particularly on the West Side.These inorganics were evaluated in accordance with the riskassessment procedures.

During phase III field investigations, a small paint layer wasnoted in two of three borings taken in suspected disposal areason the Excel property. The paint layer is not well characterizedchemically or in terms of its actual extent. This layer wasfound to contain the highest level of TCE (88,000 ppb), xylene(2,300 ppm) and lead (2,900 ppm). The layer was visuallydistinct and samples taken below the layer show that thecontaminants were relatively well bound.

Air and surface water pathways were not considered significantsince no site related contamination above background was found inmonitoring data. The air pathway was modeled in the riskassessment for those chemicals which may present a potentialfuture risk if airborne.

A risk assessment was conducted in accordance with the RiskAssessment Guidance for Suoerfund (RAGS). The purpose of a riskassessment is to analyze the potential adverse health effects,both current and potential future, which may be posed byhazardous substances released from a site if no action were takento mitigate such releases. The risk assessment consists ofcontaminant identification (data evaluation and selection ofcontaminants of concern), toxicity assessment, exposureassessment, and risk characterization.

Contaminant Identification:

The risk assessment screened all the detected chemicals in orderto identify the potential chemicals of concern. Screening wasbased on data quality, frequency of detection, comparison tobackground, and toxicity in accordance with the RAGS. Thepotential chemicals of concern for the East Side soil and groundwater pathways remaining after screening are shown below.

Ground water

tetrachlorethane (C)trichloroethene (C)vinyl chloride (C)bariumcis-1,2-dichloroethene

Soil

arsenic (c)trichloroethene (C)Carcinogenic PAHs (C)antimonymercury

8

trans-1,2-dichloroethene xylene

(C) indicates carcinogens or potential carcinogens, all othersare non-carcinogens.

The risk assessment provides a characterization of the West sideplume for the purpose of identifying contaminants in addition toVOCs that may be a concern entering the well field. A summary ofrisk estimates for the West Side plume are found on page 11 ofthis decision summary.

Exposure Assessment:

The exposure assessment includes reasonable maximum scenarios forcurrent and future use. Under the no-action alternative, thecurrent exposure scenario assumes the air stripper is not inplace and therefore, a worker at the East side property hasexposure to contaminated soil and drinking water from the EastSide plume untreated for 40 years. A future scenario includesre-zoning the East side property from industrial to residentialuse. Adults and children living in the homes would be exposed tochemicals potentially remaining in site soils, and the residentswould drink the ground water untreated by the air stripper for 30years. The exposure pathways are summarized in the riskassessment.

Toxicity Assessment:

The toxicity assessment weighs available evidence regarding thepotential for particular contaminants to cause adverse effects inexposed individuals and provides, where possible, an estimate ofthe relationship between the extent of exposure to a contaminantand the increased likelihood and/or severity of adverse effects,including carcinogenic and noncarcinogenic effects.

The toxicity values used in this assessment are summarized inTable 3. Cancer potency factors (CPFs) have been developed byEPA's Carcinogenic Assessment Group for estimating excesslifetime cancer risks associated with exposure to potentiallycarcinogenic chemicals. CPFs, which are expressed in units of(mg/kg-day)~l, are multiplied by the estimated intake of apotential carcinogen, in mg/kg-day, to provide an upper-boundestimate of the excess lifetime cancer risk associated withexposure at that intake level. The term "upper bound" reflectsthe conservative estimate of the risks calculated from the CPF.Use of this approach makes underestimation of the actual cancerrisk highly unlikely. Cancer potency factors are derived fromthe results of human epidemiological studies or chronic animalbioassays to which animal-to-human extrapolation and uncertaintyfactors have been applied (e.g., to account for the use of animaldata to predict effects on humans.)

Reference doses (RfDs) have been developed by EPA for indicatingthe potential for adverse health effects from exposure tochemicals exhibiting noncarcinogenic effects. RfDs, which areexpressed in units of mg/kg-day, are estimates of lifetime dailyexposure levels for humans, including sensitive individuals.Estimated intakes of chemicals from environmental media (e.g.,the amount of a chemical ingested from contaminated drinkingwater) can be compared to the RfD. RfDs are derived from humanepidemiological studies or animal studies to which uncertaintyfactors have been applied (e.g., to account for the use of animaldata to predict effects on humans). These uncertainty factorshelp ensure that the RfDs will not underestimate the potentialfor occurrence of adverse noncarcinogenic effects.

Risk characterization:

Tables 4 and 5 summarize the risk characterization results.Arsenic and carcinogenic PAHs were included as chemicals ofpotential concern as a result of application of the simplifiedscreening procedures described above. However, if backgroundcomparison and toxicity-concentration screens had been based onaverage concentrations instead of maximum sample concentrations,they would have been excluded as potential chemicals of concern.They are shown to contribute a risk not greater than 1x10-5.Since their site-relatedness was questionable, as was theirassociation with likely industrial processes, their presence wasthought to be within background variability. The chemicals ofconcern were reduced to VOCs only.

Excess lifetime cancer risks are determined by multiplying theintake 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 1x10-6indicates that as a plausible upper bound, an individual has onein one million chance of developing cancer as a result of site-related exposure to a carcinogen over a 70-year lifetime underthe specific exposure conditions at the 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 contaminant concentration in a given medium to thecontaminant's reference dose). By adding the HQs for allcontaminants within a medium or across all media to which a givenpopulation may reasonably be exposed, the Hazard Index (HI) canbe generated. The HI provides a useful reference point forgauging the potential significance of multiple contaminantexposures within a single medium or across media.

The baseline risk assessment yields the following conclusions:

East Side and Well Field Ground water. East Side soils

TABLE 3 SUMMARY OF ORAL AND INHALATION TOXICITY VALUES FOR CHEMICALSOF POTENTIAL CONCERN AT THE EAST SIDE,AREA

OF THE MAIN STREET WELL FIELD SITE1 ;

Oral InhalationChemical

Antimony

Arsenic

Barium

Mercury

trans-1 ,2-Dichloroethene

Tetrachloroethene

Trichloroethene

Vinyl chloride

PAHs(d)

Xylenes (Total)

RfD——— s—4E-4

IE-3

5E-2

3E-4

2E-1

IE-1

NA

NA

4E-1

4E+0

RfD

4E-4

IE-3

7E-2

3E-4

2E-2

IE-2

NA

NA

4E-1

2E+0

SF

NA(b)

1 . 8E+0

NA

NA

NA

5.1E-2(C)

1.1E-2(C)

2.3E+0(c)

1.2E-H(C)

NA

RfD—— s

NA

NA

IE-3

3E-4

NA

NA

NA

NA

NA

3E-1

RfD—— cNA

NA

IE-4

3E-4

NA

NA

NA

NA

NA

3E-1

SF

NA

1.5E+1

NA

NA

NA

3.3E-3(C)

6E-3(C)

3E-!(C)

6.1E+0(c)

NA

(a) RfD « subchronic reference dose; RfD - chronic reference dose; SF =slope factor. Source: USEPA (1990a,f)

(b) NA - Not available because chemical is not toxic by this route or has notbeen evaluated.

(c) Weight of Evidence: Cadmium, Bl; Tetrachloroethene, B2; Trichloroethene,B2; Vinyl chloride, A; 1,1-DCE, C; Benzo(a)pyrene, B2.

(d) Slope factors based on benzo(a)pyrene developed in the Health EffectsAssessment for polynuclear aromatic hydrocarbons (PAHs) (USEPA 1984). Useof this value for all carcinogenic PAHs is likely to result in anoverestimate of risk. This value is undergoing evaluation by USEPA.Reference doses based on napthalene. Use of this value for thenoncarcinogenic effects of PAHs is likely to result in an overestimate ofrisk.

TABLE 4 SUMMARY OF POTENTIAL CANCER RISKS FOR FUTURE ADULT RESIDENT

Exposure Exposure Route- , .. Chemical- ,.,. Rel. Chem. . .Medium Route Specific Risk Chemical^ ; Specific Risk^ ; Contribution, Z _

Soil Oral 7E-6 PCE 3E-9 0.04TCE 2E-8 0.28Care. PAHs 2E-6 28.48Arsenic 5E-6 71.19

Dermal IE-7 PCE 2E-8 16.67TCE IE-7 83.33

Inhalation 6E-8 PCE IE-9 1.64TCE 6E-8 98.36

Total 7E-6 PCE 2E-8 0.28TCE 2E-7 2.77Care. PAHs 2E-6 27.70Arsenic 5E-6 69.25

Groundwater Oral 3E-4 PCE 2E-5 6.12TCE 7E-6 2.14VC 3E-4 91.74

Inhalation , 5E-5 PCE IE-6 2.22TCE 4E-6 8.89VC 4E-5 88.89

Total 3E-4 PCE 9E-6 4.17TCE 7E-6 3.24

• VC 2E-4 92.59

Percentrisk due toSoil -2.74

Percentrisk due toGroundwat er

Total 3E-4

(a) PCE - Tetrachloroethene, TCE - Trichloroethene, Care. PAHs - Total carcinogenicpolynuclear aromatic hydrocarbons, VC * vinyl chloride

(b) These values are from Appendix Page A4-18(c) Relative contribution to total risk from this chemical or pathway.

TABLE 5 SUMMARY OF POTENTIAL CANCER RISKS FOR CURRENT WORKERS

ExposureMedium

Soil

ExposureRoute

Oral

Route-Specific Risk Chemical(a)

3E-7

Dermal

Inhalation

Total, Soil

7E-8

5E-6

5E-6

Groundwater Oral IE-4

PCETCECare. PAHsArsenic

PCETCE

PCETCE

PCETCECare. PAHsArsenic

PCETCEVC

Chemical-Specific Risk

5E-112E-9IE-72E-7

2E-97E-8

IE-85E-6

IE-85E-6IE-72E-7

4E-62E-6IE-4

(b)

Soil

Groundwater

Total IE-4

Rel. Chem.Contribution, I

0.020.66

33.1166.21

2.7897.22

0.2099.80

0.1994.161.883.77

3.771.8994.34

4.83

95.17

(O

100.00

(a) PCE - Tetrachloroethene, TCE - Trichloroethene, Care. PAHs - Total carcinogenicpolynuclear aromatic hydrocarbons, VC - vinyl chloride

(b) These values are from Appendix Page A4-11.(c) Relative contribution to total risk from this chemical or pathway.

10

Total estimated excess cancer risk for current workers is1x10-4 (or, 1 in 10,000). Ground water exposure accountsfor more than 99 percent of the risk. Over 98 percent ofthe risk due to ground water exposure is from contaminationby vinyl chloride and PCE.

Total estimated excess cancer risk for future residents is3x10-4. Ground water exposure contributes approximately 97percent of the total risk. Over 97 percent of the risk dueto groundwater exposure is from contamination by vinylchloride and PCE.

Arsenic and carcinogenic PAHs pose risk less than 1x10-5from ingestion of contaminated soil by hypothetical futureresidents. Contamination levels of these chemicals in eastside soils appear to be similar to background and may not besite related.

Noncarcinogenic effects in current workers or futureresidents are unlikely, since no hazard indices exceededl.O.

West Side and Well Field Ground water

Total estimated excess cancer risk for current workers is8x10-4. Over 89 percent of the risk due to ground waterexposure is from contamination by arsenic, 1,1-DCE and vinylchloride.

Total estimated excess cancer risk for future residents is6x10-4. Over 89 percent of the risk due to ground waterexposure is from contamination by arsenic, 1,1-DCE and vinylchloride.

Noncarcinogenic effects in current workers for futureresidents are unlikely, since no hazard exceeded 1.0.

Environmental Risks

Environmental receptors are thought to be Christiana Creek andthe St. Joseph River. The recharge ponds are not considered asignificant environmental receptor of contaminated ground waterdue to the hydrologic relationship between the ponds and theground water in that the gradient is from the ponds to theground water, reversal is not likely. In addition, the ponds aredredged every 2 years to ensure maximum infiltration rates.Samples taken from surface water and sediment within the wellfield showed no VOCs. The City discharged ground water from theEast Side interceptor wells into the creek under an NPDES permitprior to construction of the air stripper. Currently, the groundwater is pumped from these interceptor wells directly to the air

11stripper. The interceptor discharge to the creek was sampledprior to construction of the air stripper and found to contain 94ppb of TCE, 21 ppb of 1,2-DCE and 2 ppb of 1,1,1-TCE. Downstreamsamples were free of VOCs. As suspected, it is likely that thecontaminants discharged to the creek volatilized before movingfar downstream. One sample taken in the creek far downstreamshowed TCE at 8 ppb. The source of this contamination isuncertain.

The St. Joseph River is designated recreational use by IDEM. TheIDEM adopted water quality criteria for TCE for protection ofhuman ingestion of fish is 807 ppb. No criteria have beenestablished for protection of aquatic life. The Federal WaterQuality Criteria (WQC) for protection of aquatic organisms atchronic exposure levels for TCE is 21,900 ppb. For humaningestion of fish at a 1 x 10-5 risk, the WQC for TCE is also807 ppb. Ground water monitoring well data near the St. JosephRiver showed TCE at 12 ppb for the highest concentration. Thisis well below State and Federal WQC. VOCs were not detected insediments in the St. Joseph River.

MSWF was identified as a wetland and a floodplain. PAH andinorganic compounds were detected in creek and river sediments.These were attributed to natural and anthropogenic sourcesunrelated to the hot spots of concern in the study area. This ismore thoroughly discussed in section 5 of the RI report. It wasconcluded that the potential for environmental effects is low.

VTI. Description of Alternatives;Based on the findings of the Remedial Investigation and riskassessment, the following Remedial Action Objectives weredeveloped for the MSWF site:

Continue to provide a safe source of drinking water throughon-going use of the air stripper.

Control migration of contaminated ground water to the wellfield to minimize existing ground water contamination withinthe well field.

Minimize risk to human health and the environment fromdirect contact with contaminated soil.

Reduce migration of soil contaminants to the ground water inareas of known contamination.

The feasibility study documents technology and alternativescreening steps. The alternatives evaluated in detail include:

1. No Action

TABLE 6WASTE QUANTITY TABLE (AREA AND VOLUME)

MalnStreelW.il Field SiteElkhart, Indiana

Paint Layer Waste

Soil

Qroundwaler

Notes

1 Paint Layer Next to Building

1 Potential Paint Layer Under Building

TOTAL

Three Hot Spots Based on Rl Data

Two Potential Hot Spots Based on Previ-ous Information

TOTAL

Assume 4 ol 7 Production Well* On-Llneat Any Given Time

Area (sq. ft.)

250

250

500

1A 15.3002A 17.5004A 5.600

5A 3,3006A 5,500

47.400

Volume (cu. yds )

30

30

60

1A 8,5002A 6,5004A 2,200

5A 1,6006A 3,000

22.000

NOT APPLICABLE

Total Flow (gpm) Number ol Wells

NOT APPLICABLE

NOT APPLICABLE

2,820 7 Production2 Interceptor

14

action alternative would remain at 1x10-4 for the current workerand 3/10~4 for the potential future resident on the East Side andat 8x10-4 (current worker) and 6x10-4 (potential future resident)on the West Side. Thus, without any cleanup, the potentiallifetime excess cancer risk will exceed the acceptable risk rangeof 10-4 to 10-6.

The total present net worth of alternative 1 is presumed to benothing.

Alternative 2; In— situ Vacuum Extraction. Paint Layer Removal.Current Well System. Current Air Stripper. Deed Restrictions, and

water Monitoring

Alternative 2 incorporates the use of in-situ vacuum extraction(ISVE) to remediate the volatile organic contaminants documentedin the hot spots of soil contamination on the East side.Extraction and treatment of the contaminated ground water isaccomplished by maintaining the existing interceptor system andair stripper treatment facility.

Maintaining the operation of the existing interceptor wells andair stripper provides control of the ground water contaminantplume into the well field from the East side but does not providecontrol of contaminated ground water from the West Side.

ISVE is a process to remove or recover VOCs in vadose-zone(unsaturated) soil. A subsurface gradient is created andvaporized volatile contaminants migrate through the air spacesbetween soil particles toward extraction points where they arerecovered. If emissions control is needed, the removed VOCs areprocessed through a liquid-vapor separator and then treated by anactivated carbon bed, catalytic converter, afterburner.Implementation of ISVE would include installing at least 50extraction wells to the water table, installing blowers, pipingand a temporary support building. The duration of the treatmentrequired to attain the soil cleanup standard is estimated as 12months .

Deed restrictions are used to prevent use of ground water on theEast Side until such time as the soil and ground water standardsare met.

In addition to treatment of the TCE contaminated soils, the paintlayer will be removed, sampled for the target compound list anddisposed of off -site in accordance with RCRA. Additionalcharacterization of the paint layer will be required in thedesign phase in order to determine the primary functional groupsof concern. Based on that information, an off -site treatmenttechnology will be selected. Cost estimates are based on thermaldestruction (incineration) .

15

The present net worth of alternative 2 is estimated at $3.8Million.

Alternative 3; Low Temperature Thermal Desorption. In—situExtraction. Paint Layer Removal. Current Well System. Current AirStripper. Deed Restriction, and Ground water Monitoring

Alternative 3 addresses the soil contamination in the East Sidehot spots by means of removal, to the extent practicable,followed by thermal treatment of the soils with an on-site lowtemperature thermal desorption (LTTD) treatment system.Recognizing that excavation of large quantities of soil next toand/or beneath the buildings may not be desired or necessary,ISVE is proposed to remove the remaining VOC contamination inthese areas.

Two different LTTD systems are currently in operation. One isdirectly fired, forcing heated air counter-current to the flow ofsoils and the other system is indirectly fired using an oxygenfree atmosphere. Both systems use rotary drums and heat transferto desorb and remove volatile and semi-volatile organiccompounds. The organic compounds are removed by condensation,through carbon absorption, or through combustion and theairstream is then discharged through a stack. Process residualsinclude processed waste, condensed organic compounds, an aqueousoffstream, ash from the afterburner, spent carbon and airemissions (which may require controls, as discussed in thecompliance with ARARs section).

Excavated soil would be placed on trucks, hauled to the on-siteLTTD laydown area (0.25 miles away), preprocessed to remove anylarge boulders, then fed into the LTTD unit. The treated soilswould be stockpiled and eventually replaced in the originalexcavation. Treatment of the estimated 14,600 cubic yards wouldtake approximately 60 to 90 days after the system is set up. TheISVE portion of the remedy would require at least 17 extractionwells and the duration would still be expected to extend over 12months.

The total present net worth of alternative 3 is estimated at $8.5million.

Alternative 4; In—Situ Va

16

entering the well field.

Construction of the new interceptor wells on the West side isanticipated to decrease the average daily quantity of groundwater requiring treatment from 4.1 million gallons per day (MGD)to 1.3 - 2.5 MGD, depending on well field demand. Greater wellfield demand would require greater pumping of the interceptorwells as well. Construction of the new interceptor wells willalso necessitate the construction of approximately 3,000 linearfeet of 10-inch diameter ductile force main from the West sideinterceptor wells to the air stripper building.

Initially, the existing East side interceptors, production wellsand new West Side interceptors will be routed through the airstripper. When the production wells decrease concentrations,only the East and West interceptors will be routed to the airstripper. This is expected to take less than 5 years. As theEast side ground water cleanup standards are achieved, only theWest side interceptors will be routed to the air stripper.

The air stripper was designed for an influent concentration of310 ppb at 6.5 MGD. At this rate, emissions did not exceed 1x10-6 risk levels, nor did it exceed any State or Federal standard.The air stripper, treating water from the East and Westinterceptor wells, will emit approximately 2.02 pounds/day (737pounds/year) of VOCs. The concentration in the influent willincrease from the 15 to 20 ppb currently measured toapproximately 200 ppb. The concentration will increase becausethe new western interceptors will be located in the mostconcentrated portion of the plume and because the existingproduction wells currently routed to the air stripper will nolonger need to be routed to the air stripper. The combined airemissions from both the air stripper and the ISVE are expected tobe less than the State regulated permit amount of 25 tonsVOCs/year (326 IAC 8-1-6), the State Implementation Plan (SIP)regulated standards of 3 pounds/hour or 15 pounds/day.Therefore, emissions controls will not likely be needed.

During the design phase, estimates for air emission mass and ratewill be refined and reevaluated. The estimate for newinterceptor capacity will be refined and if an increased flow isrequired in order to achieve complete interception, the airemissions rates will be reevaluated to ensure that ARARs andprotective levels are not exceeded. And if necessary, the airstripper facility would be modified to accommodate projected flowchanges. Similarly, if soil concentrations or volume changesignificantly, air emissions controls will also be evaluated forthe ISVE system.

The total present net worth of alternative 4 is estimated at $3.4million.

17

Alternative 5; Low Temperature Thermal Desorption. In— SituVacu"?* Extraction. Paint Layer Removal. New Interceptor WellSystem. Current Air Stripper. Deed Restrictions, and Ground WaterMonitoringAlternative 5 combines the West Side ground water interceptionsystem described in Alternative 4 with the LTTD contaminatedsoils remediation approach identified in Alternative 3.

The total present net worth of alternative 5 is $8.1 million.

VTII. Comparison of Alternatives:

Table 7 summarizes the alternatives relative to the 9 criteria.

Criteria;

Overall Protection of Human Health and the Environment:

Alternative 1, no action, does not satisfy the requirement foroverall protection of human health and the environment becausethe risks posed by contaminated soils and ground water wouldremain. Alternatives 2, 3,4 and 5 are all protective since theyeach include treatment of contaminated soil and ground water.Alternatives 2 and 3 are protective in that the VOC contaminationis intercepted by the production wells and treated by the airstripper. However, the concentrations are more dilute and thewell field itself is not restored. Alternatives 4 and 5 areconsidered more protective due to the plume containment outsideof the well field. The net result is that the well field isrestored within a relatively short timeframe (a few years orless) .

Compliance with ARARs:

Section 121(d) of SARA requires that remedial actions meetlegally applicable or relevant and appropriate requirements(ARARs) of other environmental laws. These laws may include: theResource Conservation and Recovery Act (RCRA) , the Clean WaterAct (CWA) , the Clean Air Act (CAA) , the Safe Drinking Water Act(SDWA) , and any state law which has more stringent requirementsthan the corresponding Federal law. "Legally applicable"requirements are those cleanup standards, standards of control,and other substantive environmental protection requirements,criteria or limitations promulgated under Federal or State lawthat specifically address a hazardous substance, pollutant,contaminant, remedial action, location, or other circumstances ata CERCLA site. "Relevant and appropriate" requirements are thoserequirements that, while not legally applicable to the remedialaction, address problems or situations sufficiently similar tothose encountered at the site that their use is well suited tothe remedial action.

18

Non-promulgated advisories or guidance documents issued byfederal or state governments do not have the status of ARARs;however, where no applicable or relevant and appropriaterequirements exist, or for some reason may not be sufficientlyprotective, non-promulgated advisories or guidance documents maybe considered in determining the necessary level of cleanup forthe protection of human health and the environment.

Table 9 provides a summary of ARARs and other pertinent laws andregulations for the alternatives. Below, however, is adiscussion of the significant ARARs for the respectivealternatives.

RCRA is a significant ARAR for this operable unit. Chlorinatedsolvents were disposed of at the site prior to 1980, but the TCEand other solvents came from degreasing operations (RCRA listedprocesses). Therefore, RCRA is applicable to the treatment,storage and/or disposal of these wastes in this remedial action.In addition, any solid waste derived from the treatment, storageor disposal of a listed RCRA hazardous waste is itself a listedhazardous waste. Therefore, both prior and subsequent totreatment, the soils are considered RCRA listed hazardous wastes.The soil and ground water are also RCRA listed wastes under the"contained-in" rule. Under this rule, any mixture of a non-hazardous material with a RCRA listed hazardous waste must bemanaged as a hazardous waste as long as the material "contains11hazardous waste.

The paint layer will be removed and disposed of off-site. Thislayer consists of soil contaminated with RCRA listed hazardouswaste and, therefore, RCRA Land Disposal Restrictions (LDRs)apply to its disposal. Because the LDR treatment standards arebased on the treatment of industrial process wastes that arephysically and chemically less complex than process wastes mixedwith soil, until treatment standards for soil and debris arepromulgated, there is a presumption that a treatability variancepursuant to 40 CFR 268.44 will be used to comply with the LDRs.(See Superfund LDR Guidance #6A, OSWER Directive #9347.3-06FS,September 1990).

The guidance demonstrates that, based on their physical andchemical properties, RCRA hazardous constituents have beendivided into twelve "structural functional groups", as providedin Table 8. Each constituent in a group is treated in relationto a threshold concentration (TC) (column 3 of Table 8). If theconstituent concentration is below the TC, then the waste istreated to a level within a specific concentration range (column2 of Table 8). If the constituent concentration exceeds the TC,then the waste is treated to a level specified in terms ofpercent reduction (column 4 of Table 8).

TABLE 7COMPARATIVE EVALUATION OF FINAL ALTERNATIVES

Main Street Well Field SiteElkhart, Indiana

Page 1 of 3

Criteria Alternative 1 Alternative 2 Alternative 3 Alternative 4 Alternative 5

OVERALL PROTECTIVENESS

Human Health Protection

Contact Soil

Groundwater Ingestion

Overall Protection

COMPLIANCE WITH ARARS

No reduction In risk. 10 risk re-mains.

No reduction In risk. 10"*risk re-mains.

No protection.

Chemical-Specific ARARs

Location-Specific ARARs

Action-Specific ARARs

SHORT TERM EFFECTIVENESS

Community Protection

Does not meet ARARs.

Not applicable.

Does not meet ARARs.

Soil and groundwater path-ways provide unacceptablerisks.

Worker Protection

Time Until RAOs are Attained

Not applicable.

Not applicable.

Greater than 10"* achieved, ifneeded.

Greater than 10* risk or betterachieved.

Protective because of treat-ment of soil hot spots and treat-ment of groundwater.

Meets ARARs.

Meets ARARs.

Meets ARARs.

Potential threats include VOCreleases removal of paint layer.

Limited exposure potential dueto VOC release during ISVEconstruction

Two months for paint layer re-mediation; ISVE remediation 12months; groundwater treatmentfor ± 40 years.

Greater than 10~* achieved, Ifneeded.

Greater than 10"* risk or betterachieved.

Protective because of treat-ment of soil hot spots and treat-ment of groundwater.

Meets ARARs.

Meets ARARs.

Meets ARARs.

Higher potential for exposureand community due to airbornedischarges during soil hot spotexcavation and preprocessinghandling activities.

Greatest potential for exposuredue to VOC volatilization dur-ing excavation and treatment ofsoils.

Same as Alternative 2. How-ever, majority of soil remedia-tion accomplished within 6months.

Greater than 10* risk achieved,if needed.

Greater than 10"8 risk achieved.

Most protective because oftreatment of soli hot spots andprocess control for containingmigration of contaminatedgroundwater.

Meets ARARs.

Meets ARARs.

Meets ARARs.

Minimal adverse Impacts dur-ing short term since only con-struction activities are removalof paint layer and constructionof new extraction wells andforcemain. Potential threats In-clude VOC releases removal ofpaint layer and construction ofnew extraction wells.

Same as Alternative 2.

Two months for paint layer re-mediation; soil remediation 12months; groundwater treatmentfor ± 40 years.

Greater than 10** risk achieved,if needed.

Greater than 10"* risk achieved

Most protective because oftreatment of soil hot spot* andprocess control for containingmigration of contaminatedgroundwater.

Meets ARARs.

Meets ARARs.

Meets ARARs.

Same as Alternative 3.

Same as Alternative 3.

Same as Alternative 4. How-ever, majority of soil remedia-tion accomplished within 6months.

c

TABLE 7COMPARATIVE EVALUATION OF FINAL ALTERNATIVES

Main Street Well Field SiteElkhart, Indiana

Page 2 of 3

Criteria Alternative 1 Alternative 2 Alternative 3 Alternative 4 Alternative 5

LONG-TERM EFFECTIVENESSAND PERFORMANCE

Magnitude of Residual Risk

Adequacy and Reliability of Con-trols

Existing risk remains.

Not applicable.

Reduction of Toxlctty,Mobility, and Volume

Treatment Process Used None.

Amount Destroyed or Treated None.

Reduction of Toxicity, Mobility, orVolume

None.

Alternative treats soil hot spotsvia ISVE. Clean-up levels of 10ug/kg In soil for COC shouldbe attainable.Source control of soil hot spotsIs appropriate for providingsome control; however, exist-ing groundwater Interceptorand production wells do not op-timize groundwater plume man-agement.

Groundwater extraction by ex-isting Interceptor and produc-tion wells and treatment by airstripper. Paint layer excavated,transported off-she and Inciner-ated. Soil hot spots to betreated by ISVE\

60 c.y. of paint layer destroyedby off-she Incineration. Soli hotspots treated via ISVE ex-tracted from soil. Length ofgroundwater treatment Is ± 40years due to source control ofsoil hot spots.

ISVE reduces volume of con-taminants to groundwater. Tox-icity reduced by air stripperprocess.

Alternative treats soil hot spotsvia LTTO and ISVE. Clean-uplevels of detection limits areprojected by LTTD for COC.Same as Alternative 2.

Groundwater extraction by ex-isting Interceptor and produc-tion wells and treatment by airstripper. Paint layer excavated,transported off-she and Inciner-ated. Soil hot spots existed andtreated by LTTD on-srte. Soilsnot readily excavated to betreated by ISVE.Same as Alternative 2, exceptsoil hot spots treated via LTTDand ISVE for under buildings.Residuals requiring disposal In-clude condensate and filtercake from LTTD.

LTTD reduces volume of con-taminants to groundwater. Tox-icity reduced by air stripperprocess.

Same as Alternative 2.

Source control of soil hot spotsin conjunction with new ground-water Interceptor system pro-vides best process control ofgroundwater plume manage-ment In addition, greater flexi-bility In operating air stripperunit process.

Groundwater extraction by newInterceptor well network andtreatment by modified air strip-per. Paint layer excavated,transported off-site and Inciner-ated. Soil hot spota to betreated by ISVE.

New Interceptor system Is engi-neered for providing control ofgroundwater plume. Reducedsoil hot spots treated via ISVE.Combination of soil source con-trol and efficient extraction sys-tem decreases groundwatertreatment period to 40 years at1.28 MOD.

Same as Alternative 2.

Same as Alternative 3.

Same as Alternative 4.

Groundwater extraction by newinterceptor well network andtreatment by modified air strip-per. Paint layer excavated,transported off-site and inciner-ated. Soil hot spots excavatedand treated by LTTD on-site.Soils not readily excavated tobe treated by ISVE.Same as Alternative 4, exceptsoil hot spots treated via LTTD.

Same as Alternative 4, exceptLTTD residuals, soil volume,and mobility of contaminants.

TABLE 7COMPARATIVE EVALUATION OF FINAL ALTERNATIVES

Main Street Well Field SiteElkhart, Indiana

Page 3 of 3

Criteria Alternative 1 Alternative? Alternative 3 Alternative 4 Alternative 5

Type and Quantity of ResidualsAfter Treatment

Statutory Preference for Treatment

IMPLEMENTABILITY

Ability to Construct and Operate

Ease of Expansion

Ability to Monitor Effectiveness

Ability to Obtain Approvals andCoordinate with Other Agencies

Availability of Equipment andTechnologies

COSTS

aprtal Cost

O&M Cost

resent Worth Costs

None.

Does not satisfy.

Not applicable.

Not applicable.

Not applicable.

Not applicable.

Not applicable.

None.

Not applicable.

Not applicable.

Soil residuals.

Satisfies groundwater and soilhot spot element* for providingtreatment A principal elementto address the principal threatsat the site.

Components of alternativeshould be readily implement-able.

Same as Alternative 2, in addi-tion ISVE can be moved, ex-panded, remobllized asnecessary. Only limitation toISVE is physical/ chemical prop-erties of COC.Verification of In-sHu processesis more difficult.

Air discharge issues specific topaint layer excavation need tobe addressed.

Services and equipment avail-able. ISVE will require coordina-tion with vendors.

$1,210,000

$170,000

$3,820,000

LTTD generates condensate fil-ter cake and carbon, which re-quires disposal of soilsresiduals.Same as Alternative 2.

Same as Alternative 2.

Same as Alternative 2.

SHe constraints and permittingissues may have problems andfor delays.

Not readily adaptable.Remobillzation Is extremelycomplicated and not practical.

Soil monitoring and groundwa-ter monitoring are easily accom-plished.Same as Alternative 2, in addi-tion, will require coordinationwith local government to en-sure acceptability of LTTD.

Services and equipment avail-able. LTTD will require coordi-nation with vendors.

$5,890,000

$170,000

$8,500,000

Same as Alternative 2. In addi-tion, new Interceptor systemand modifications to air strip-per should be easy to Imple-ment.

Same as Alternative 2.

Same as Alternative 2.

Same as Alternative 2.

Same as Alternative 2.

$1,470,000

$130,000

$3,370,000

Same as Alternative 3.

Same as Alternative 3.

Same as Alternative 3. In addi-tion, new interceptor systemand modifications to air strip-per should be easy to imple-ment.

Same as Alternative 3.

Same as Alternative 3.

Same as Alternative 3.

Same as Alternative 3.

$6,160,000

$130,000

$8.050.000

T A B L E 8 ALTERNATE TREATABILTTY VARIANCE LEVELS ANDTECHNOLOGIES FOR STRUCTURAL/FUNCTIONAL GROUPS

StructuralFunctionalGroups

HalogenatedNon-PolarAromaticsDioxins

PCBs

HerbicidesHalogenatedPhenolsHalogenatedAliphaticsHalogenatedCydicsNitratedAromaticsHeterocyclics

. PclynudearAromaticsOther PolarOrganics

AntimonyArsenicBariumChromiumNickelSeleniumVanadiumCadmiumLeadMercury

ConcentrationRange(ppm)

0.5 - 10

0.00001 - 0.05

0.1 - 10

0.002 - 0.020.5-40

0.5-2

0.5-20

2.5-10

0.5-20

0.5-20

0.5-10

0.1 - 0.20.30-10.1 -400.5-60.5- 10.005

0.2-200.2-20.1-3

0.0002 - 0.008

ThresholdConcentration(ppm)

Ill̂ tî î ileilPIsslî iSVsiis/̂ ; *"K™3?

100

0.5

100

0.2400

40

200

10,000

200

400

100

210

40012020

0.0520040

3000.08

PercentReductionRange

^^Mm^MM^mmf-y^SimiimiMim:

90-99.9

90-99.9

90-99.9

90-99.990-99

95-99.9

90-99.9

99.9 - 99.99

90-99.9

95-99

90-99

90-9990-99.990-9995-99.995-99.990-9990-9995-99.999-99.990-99

Technologies that achievedrecommended effluentconcentration guidance**

PIS^Sî Sliiilt̂ IltM;:: - : f . . : . - '

Biological Treatment Low Temp. Stripping.Soil Washing. Thermal Destruction

Dechlorination, Soil Washing. Thermal Destruction

Biological Treatment Dechlorination. Soil Washing.Thermal Destruction

Thermal DestructionBiological Treatment Low Temp. Stripping.Soil Washing. Thermal DestructionBiological Treatment Low Temp. Stripping, Soil Washing.Thermal DestructionThermal Destruction

Biological Treatment Soil WashingThermal DestructionBiological Treatment Low Temp. Stripping. Soil Washing.Thermal DestructionBiological Treatment Low Temp. Stripping. Soil Washing.Thermal DestructionBiological Treatment Low Temp. Stripping. Soil Washing.Thermal Destructioni:||iillllllllllll|;:;;i |;1

19

Sampling of the paint layer indicated the presence of TCE, xyleneand lead. The sampling data, however, was limited and additionalcharacterization of the paint layer will be required in thedesign phase in order to determine the presence of additionalfunctional groups. It is expected that, at a minimum,halogenated aliphatics (e.g., TCE), halogenated non-polararomatics (e.g., xylene) and lead will be amongst the functionalgroups used to determine treatment standards and technologies.

Using the limited data available from sampling of the paintlayer, the treatability variance would be applied as follows:

Constituent Concentration TC Treatment Level

TCE 88 ppm 40 ppm 95-99.9% red.xylene 2,300 ppm 100 ppm 90-99.9% red.

(lead was not measured by TCLP, so it is not used in thisexample.)

The paint layer will be removed, sampled for the full targetcompound list and, based upon the results of that sampling, itwill be taken to a facility capable of the treatmenttechnologies and treatment standards identified in Table 8 fordisposal. Should the constituent concentrations be measured atless than the concentration range provided in column 2 of Table 8prior to any treatment, no treatment will be necessary prior todisposal in a RCRA Subtitle C facility.

The Agency intends to grant a treatability variance for the paintlayer under 40 CFR 268.44 to comply with RCRA LDRs unless publiccomment following release of this ROD overcomes the presumptionthat a treatability variance is appropriate for this waste.

Since paint layer removal is required for alternatives 2 through4, the above analysis applies to all alternatives except noaction.

With the use of LTTD, the excavation and movement of these soilsfrom their current location for treatment andreplacement/redisposal at the same location will trigger theapplicability of RCRA LDRs. The treated soils will still be RCRAlisted wastes because any solid waste derived from the treatment,storage or disposal of the RCRA listed waste is a RCRA listedwaste. LTTD treatment of the soils, however, would meet the LDRtreatment standards for TCE under 40 CFR Part 268, Subpart D and,therefore, could be disposed of at the location from which theywere removed.

The Hazardous and Sold Waste Amendments of 1984 (HSWA)established minimum technology requirements for disposal of RCRAhazardous wastes into new land disposal units. These technology

20

requirements would not be triggered upon redisposal/replacementof the LTTD-treated soils because no "new" unit would be created.

RCRA closure requirements at 40 CFR Part 264, however, would betriggered by the replacement of the soils into the pre-existingunit. Implementability of RCRA closure would be very difficultdue to the large volume of soil and restricted space at the site.The Agency would consider de-listing the waste.

This LTTD ARAR analysis applies to alternatives 3 and 5.

RCRA LDR treatment standards do not apply to soil treated in-situ. RCRA LDRs will not be triggered by alternatives 2 and 4.RCRA regulates air emissions from process vents at 40 CFR 264Subpart AA. These regulations are neither applicable norrelevant and appropriate because CERCLA waste managementactivities are considered, as a group, to be fundamentallydifferent than those RCRA regulated hazardous waste treatment,storage or disposal facilities for which the Subpart AAregulations are applicable. See 55 Fed. Reg. 25458, 25459 (June21, 1990).

Both the ISVE system and the air stripper produce emissionssubject to regulation under the Clean Air Act (CAA). Under theCAA, EPA has promulgated National Ambient Air Quality Standards(NAAQS), National Emission Standards for Hazardous Air Pollutants(NESHAPS) and New Source Performance Standards (NSPS).

NAAQS have been promulgated pursuant to Section 109 of the CAAfor particulate matter and ozone from "major" sources. Statestranslate these ambient standards into source-specific emissionlimitations in which upon US EPA approval become incorporatedinto federally enforceable State Implementation Plans (SIPs).Under the Indiana SIP any new source with a potential ofemitting 25 tons of VOCs per year must be used in conjunctionwith the best available control device to reduce emissions.Neither ISVE nor the air stripper constitute a "major source"under the CAA. Under the Indiana's SIP (APC-19, February 16,1982) and under the current Indiana air pollution regulation 326IAC-2-l-l(b)(2)(D), registration is required for sources of VOCair emissions which have the potential for emitting 3pounds/hour, 15 pounds/day, or 25 tons per year. Suchregistration requirements may result in the use of emissionscontrols on sources which exceed these limits. It is anticipatedthat implementation of any treatment alternative would fall belowthese emission standards. However, such estimates will beverified in the design phase and controls will be used ifrequired.

Pollutants for which no NAAQS exist, but that cause or contributeto air pollution that may result in serious illness have beenidentified by EPA under the CAA Subsection 112 and are called

21

NESHAPS. The only pollutant at this site for which a NESHAPSexists is vinyl chloride. See 40 CFR Part 61, Subpart F. Theemission standard for vinyl chloride plants is 10 ppm. Whilethis standard is not applicable because none of the treatmenttechnologies meets the definition of a vinyl chloride plant, itis relevant and appropriate. All treatment alternatives willsatisfy this requirement, particularly since the amount of vinylchloride at the site is very low.

The NSPS are technology-based standards which are neitherapplicable nor appropriate to the pollutants and chemicals atthis site.

Alternatives 4 and 5 require construction of a water main acrossChristiana creek. Therefore, these alternatives must assure noloss of floodplain or wetland area in accordance with ExecutiveOrders 11988 and 11990.

The SDWA requires the establishment of standards to protect humanhealth from contaminants in drinking water. Maximum ContaminantLevels (MCLs) for specific contaminants have been promulgatedunder SDWA. Additionally, SDWA maximum contaminant level goals(MCLGs), which are non-enforceable health-based goals, have beenset at levels at which no known or anticipated adverse effects onthe health of persons is likely to occur. The NCP requires thatnon-zero MCLGs shall be attained by remedial actions for waterthat are current or potential sources of drinking water, whereMCLGs are relevant and appropriate. See 40 CFR300.430(e)(2)(i)(B). More stringent standards than MCLs may beappropriate for ground water used as drinking water when multiplecontaminants and/or multiple exposure pathways may not beprotective of human health and the environment. Ground watercleanup standards for this site have been set lower than the MCLsin order to achieve a residual risk level of 1x10-5 across allmedia. See the detailed description of the selected remedy forexplanation of the ground water standards.

Balancing Criteria;

Short-term Effectiveness:

This evaluation criterion addresses the effects of thealternatives on human health and the environment duringconstruction and implementation. All of the alternatives, withthe exception of no action, involve excavation and off-sitetreatment/disposal of the paint layer waste, as well as treatmentof contaminated ground water in the existing air stripper.Alternatives 3 and 5 would have significantly greater short-termimpacts than alternatives 2 and 4, such as excavation relateddust, handling of contaminated soils and disruption of existingbusinesses. In addition, excavation of soil near the buildingswould require bracing and building support. Therefore,

22

alternatives 2 and 4 would have less short term adverse impacts.

Long-term Effectiveness and Permanence:

The evaluation of alternatives under this criterion address therisk remaining at the MSWF site at the conclusion of remedialactions. The no-action alternative provides no long-termeffectiveness and would result in continuation of the elevated10-4 risk levels that currently exist. The two treatmenttechnologies considered in alternatives 2 through 5, ISVE andLTTD, are radically different in their approach, but are capableof achieving the same cleanup standards.

In evaluating the time required until remedial action objectivesare met, consideration should be given to the time necessary toremediate individual elements of the alternatives as well as theentire site. For the MSWF site, it is impossible toquantitatively project the precise duration of the pump and treatelement of the various alternatives due to the complexinterdependence between the soils and ground water. However,qualitatively several conclusions pertaining to duration ofground water cleanup can be drawn. First, the no actionalternative would result in the indefinite, and perhapsperpetual, contamination of the MSWF aquifer. Alternatives 2 and3 will result in cleanup of the East side aquifer portion inapproximately 5 to 10 years, but the well field will remaincontaminated. Should contaminants other than VOCs become afuture problem, there would be no containment before affectingthe well field, at which point the cost of treating a moredilute, higher volume problem would be expensive. Alternatives 4and 5 provide for plume containment before reaching the wellfield, thus allowing well field restoration within a few years.

Reduction of Toxicity, Mobility and Volume:

This evaluation criterion addresses the statutory preference forselecting remedial actions that employ treatment technologiesthat permanently reduce toxicity, mobility or volume of theuntreated waste. The no-action alternative provides no reductionof contaminant toxicity, mobility or volume. Alternatives 2through 5 require removal of the paint layer. Compliance withthe soil and debris variance will dictate the type of RCRAfacility which will be acceptable for treatment and/or disposal.

Both ISVE and LTTD will reduce the VOCs contamination in thesoil, thereby permanently reducing the toxicity and volume in thesoil. ISVE would be capable of treating the VOCs to the cleanupstandards in-situ with an efficiency of approximately 99.4percent. It is estimated that up to 1,000 pounds of VOCs may beextracted from the soil. The LTTD removal would achieveapproximately a 99.99 percent reduction in VOCs of the treatedsoil. In combination with ground water treatment, the treatment

23

efficiency of either technology will achieve the VOC standardsset by this ROD.

Ground water treatment can address contaminant mobility. Thewell field is not a perfect hydraulic containment system in thatcontaminated ground water does escape the capture zone and flowsouth beyond the well field. Alternatives 4 and 5 which includeWest side interceptors, would not only prevent contaminantmigration into the well field, but beyond that toward the St.Joseph River as well. Alternatives 1, 2 and 3 would allow thecontaminant migration to continue to the well field and beyond tothe river.

Implementability:

This criterion addresses the technical and administrativefeasibility of implementing an alternative, and the availabilityof various services and materials required for itsimplementation. The technologies considered, which include LTTDand ISVE, are available from commercial vendors. However, sitelimitations including confined working areas in close proximityto residential areas at the treatment site and general disruptionmake implementation of LTTD far more difficult than the ISVE soiltreatment alternative. LTTD once mobilized, must be used to thefullest extent at that time since remobilization is costly andnot as flexible. ISVE is more flexible in that it can be readilyexpanded and can be adapted to other areas if necessary*

The air stripper is already on-line and performing as designed.The additional interceptor wells on the West side are readilyimplementable.

Cost:

Alternatives are evaluated for cost in terms of capital costs,operation and maintenance cost (O&M), and present worth cost.The present worth analysis is used to evaluate expenditures thatoccur over different time periods by discounting all future coststo a common base year. For cost purposes of this project, 40years has been assumed. This is slightly over the standard 30year projection because pumping of the interceptors on the Westside and treatment via the air stripper would be required untilthe sources are identified and controlled or until they diminishthrough natural processes - an undefined timeframe. As the wellfield and East side aquifer area is restored, flow to the airstripper will be reduced and operation and maintenance (O&M)costs will be reduced. The costs assumptions for West sideinterceptors remains the same for both alternatives 4 and 5.

Cost estimates for the paint layer removal assume off-siteincineration. This is a relatively high cost per soil volumealternative relative to the ISVE cost per soil volume. Cost

24

assumptions for this element of the remedy are the same for allalternatives. Due to the uncertainty in extent of contaminationbeneath the buildings, the feasibility study costs areconsidered lower bound estimates.

Alternatives which include LTTD (3 and 5) are more costly thanthose which rely on ISVE exclusively (2 and 4). Of thealternatives which include West Side interceptors (4 and 5),alternative 4 is less costly. Capital, operation and maintenanceand present worth costs are summarized at the bottom of table 7.

Modifying Criteria:

State Acceptance:

IDEM has been involved throughout this RI/FS and supports theselected remedy.

Community Acceptance:

Community acceptance of the selected remedy is discussed in theresponsiveness summary attached.

IX. The Selected Remedy

The selected remedy will reduce the threat from contaminants atthe site such that the total excess cumulative carcinogenic riskfrom exposure to all media do not exceed 1x10-5.

Based on the RI/FS, and using the comparative analysis ofalternatives described above, USEPA has selected alternative 4 asthe most appropriate remedial action at the MSWF site. IDEM hasconcurred with selection of alternative 4. A flow chart andconceptual site diagram are shown in Figures 8 and 9respectively.

Components:

Implement ISVE for the treatment of VOCs in the contaminatedsoils in the East side hot spots.

Excavate and treat and/or dispose of the contaminated soilsassociated with the identified paint layer source area(s) atan off-site facility in compliance with State and Federalregulations.

Construct new interceptor wells (1-3 and 1-4) to the west ofthe well field to contain the plume, construct a new forcemain to connect the new interceptors to the air stripper,maintain the air stripper and its ancillary support systemand monitor.

25

Place deed restrictions on the installation and use ofpotable water supply wells on the East Side properties untilsoil and ground water goals are met and sustained.

Implement a ground water monitoring program to demonstratecompliance with the cleanup standards.

Rationale:

All alternatives, except no-action, are protective and complywith ARARs. Therefore, alternatives 2 through 5 pass thethreshold criteria. Of the alternatives involving treatment, theISVE alternatives 2 and 4, are less costly than 3 and 5 for thesame level of performance as measured by their ability to achievethe cleanup standards. ISVE requires less disruption tobusinesses and community for implementation and is more flexiblein that it can be readily expanded on-site. Given that, there isno inherent advantage in use of the LTTD technology at this site.

Alternatives 2 and 4 differ in their inclusion of West Sideinterceptors. Under alternative 2, contaminated ground watercontinues to be drawn into the well field. Although severalproduction wells are routed to the air stripper, the influentconcentration to the air stripper is low. For the same, if notlower operating cost, a lower influent flow with a highercontaminant concentration could be achieved while at the sametime preventing continued contamination of the well field. Sincehot spot areas of contamination on the West Side have not beenidentified, it is unknown how long this contamination willcontinue. In addition, the location of the well field in anindustrial area makes it vulnerable to future contamination withvery little response time should other contamination problemsdevelop. Thus, West Side interception wells provide greater longterm protection. The MSWF study area constitutes a class 2A,current use aquifer. Plume interception is consistent with theAgency's intent to restore aquifers to their highest beneficialuse in a reasonable timeframe. For these reasons, alternative 4is selected as the most protective and cost-effective remedy.

Description:

A minimum soil estimate for vapor extraction is 22,000 cubicyards. Volume estimates will be refined in the design phase.ISVE is easier to implement and does not trigger RCRA LDRsbecause the waste is treated in-situ. The paint layer isconsidered a listed waste under the RCRA derived-from rule.Additional characterization will be required during the designphase. With high concentration of xylene and lead, this wastemay also be RCRA characteristic. The paint layer volume isestimated at 60 cubic yards, assuming the disposal areaidentified beneath the building received the same waste streamsas the disposal area outside the building. ISVE is not a

26

separation technology for mixtures and will not be able to treatthis waste stream. Leaving the paint layer waste in placewould fail to satisfy RCRA closure requirements, would not meetthe cleanup standards, nor would it provide long term protection.Therefore, it will be removed and disposed of in accordance withRCRA.

The existing air stripper does not have air emissions controls onit. Existing air emissions do not exceed risk levels at designconcentrations and emissions rates. This remedy, includinghigher influent concentration as a result of the West sideinterceptors, and ISVE, is still not anticipated to exceed theState and federal regulatory levels at which control equipmentcould be required.

The remedial action objectives are translated into cleanup levelsfor soil, ground water and air as follows:

Cleanup standards for the soil, ground water and air on the EastSide are selected at a 1x10-5 level based on potential futureuse. The 1x10-5 level is very close to standard analyticaldetection limits for ground water, therefore, its achievement canbe reliably measured. At this cleanup level, the soilremediation is expected to achieve ground water protection in the10-8 range as a single pathway, prevent soils from furthercontributing to ground water contamination and is achievable withthe selected technology. The following table shows the rangefrom which the cleanup standards were selected.

Ground Water (ppb)

Current Worker Future Resident10-4 10-5 10-6 10-4 10-5 10-6

TCE 10 1.0 0.1 10 1.0 0.1PCE 5 0.5 0.05 6 0.6 0.06Vinyl Chloride 4 0.4 0.04 3 0.3 0.03

Soil (ppb)

TCE * 800 80 * 100 10PCE**Vinyl Chloride***

* TCE baseline risk not less than 10-4.** PCE baseline risk not less than 10-6.*** Vinyl Chloride not detected in soil.

Soil cleanup must achieve 100 ppb (or better) of TCE.

Interceptor wells must continue to operate until the followingground water standards are met on the East Side:

27

TCE 1.0 ppbPCE 0.6 ppbVinyl Chloride 0.3 ppb*

* The acceptable vinyl chloride standard may be modifiedslightly based on best available analytical detection limits.

The West side interceptors must continue to operate until theplume entering the well field from the west no longer poses acumulative contaminant risk of greater than 1x10-6. This isconsistent with the ROD for operable unit 1 and is appropriatefor the West Side given that without a known relationship betweensource and ground water, contaminant-specific standards cannot beselected.

It is expected that soil cleanup in combination with the existingground water treatment provided by the East Side interceptorwells will restore the ground water to the cleanup standards.Ground water monitoring is needed to ensure that cleanup levelsare met and maintained. Deed restrictions will ensure thatexposure does not occur until cleanup levels are reached.

Air pathways risks were calculated based on the percent of totalsite risk contribution from the air stripper and ISVE underassumed air flow rates. Air emissions from the air stripper andthe ISVE units were evaluated for potential impacts to receptorsand to identify whether vapor-phase carbon adsorption treatmentmay be needed on these units to reduce risks to an acceptablelevel. At assumed flow rates, emissions would be limited by thefollowing table. For example, both the air stripper and ISVEwould require state registration under the SIP for massdischarges in excess of 15 Ibs./day. Such registration may ormay not require emission control measures. If controls are notrequired by State regulation, emissions can continue uncontrolleduntil the site risk based contaminant emission mass is exceeded.The table below shows that TCE