502S5

COMMODORE SEMICONDUCTOR GROUPa division of Commodore Business Machines, Inc.

F Work Plan for the

* REMEDIAL INVESTIGATION ANDI FEASIBILITY STUDYf of the CSG Facility at

950 Rittenhouse Road" Norristown, Pennsylvania

ii

* January 1989

L "~Li Prepared By:

m 2>0S5ffi>0 AR30008I^ t r ttmton k— ^ M'WTBiTOMB.nDfn

L Roy F. Weston, Inc.West Chester, Pennsylvania

RECEIVEDI- " GERM REMEDIAL ENFORCEMENT SECHflU

JAN 311989

' EPA- Region III

1

WORK PLAN

for the

REMEDIAL INVESTIGATION ANDFEASIBILITY STUDY

of the4

CSG FACILITY

at 950 Rittenhouse Road,. Norristown, Pennsylvania

Prepared By:

ROY F. WESTON, Inc.. Weston WayI West Chester, Pennsylvania 19380

AR3Q00824053B

PROJECT PARTICIPANTS

The following staff members of Commodore Semiconductor Grouphave participated in the planning and preparation of this WorkPlan:

G. Giansanti, andR. Ng.

The following staff members of Roy F. Weston, Inc. have parti-cipated in the planning and preparation of this Work Plan:

R. Alexander,S. Jakatt, P.G.,J. Kesari,C. Kufs, P.G.,J. Marks, P.E.,D. Messinger, P.G.,S. Schuyler, P.E.,K. Sheedy, P.G.,C. Stratton, andJ. Yang, Ph.D., P.E.

AR3000834053B

TABLE OF CONTENTS

Section Title

1 INTRODUCTION

1.1 Site Location1.2 Site History1.3 Work Plan Organization

2 SITE CONDITIONS 2-1

2.1 Site Facilities 2-12.1.1 History of Underground Waste

Solvent Storage Tanks at CSGFacility 2-3

2.1.2 French Drain/Air Stripper System 2-42.1.3 Monitor and Extraction Wells/

Air Strippers 2-42.2 Waste Streams 2-7

2.2.1 Elementary Neutralization System 2-72.2.2 Solvent 2-72.2.3 Spent Photo Resist 2-72.2.4 Used Oil 2-72.2.5 Arsenic* Waste 2-72.2.6 Carbon 2-8

2.3 Environmental Setting 2-82.3.1 Physiographic Setting 2-82.3.2 Climate 2-102.3.3 Surface Drainage 2-122.3.4 Ecological Setting 2-122.3.5 Hydrogeology 2-13

2.3.5.1 Overburden Hydrogeology 2-132.3.5.2 Bedrock Hydrogeology 2-13

2.3.6 Groundwater Quality 2-242.3.6.1 Overburden Groundwater

Quality 2-242.3.6.2 Bedrock Groundwater

Quality 2-242.4 Summary 2-35

3 RI/FS STRATEGY AND OBJECTIVES 3-1

3.1 Contaminant Transport Mechanisms 3-13.2 Contaminant Exposure Rates 3-23.3 Applicable Remediation Technologies 3-23.4 RI/FS Objectives 3-43.5 RI/FS Data Requirements 3-53.6 RI/FS Strategy 3-5

4053B

TABLE OF CONTENTS(continued)

Section Title Page4 RI/FS SCOPE 4-1

4.1 RI/FS Overview : 4-14.2 Task 1 — Planning ; ^ r 4-1

4.2.1 Subtask 1.1 — Prepare andSubmit Work Plan 4-1

4.2.2 Subtask 1.2 — Assess ExistingWells 4-1

4,2.3 Subtask 1,3 —Evaluate Fracture•- ---•""-- ^ • races: 1-. .- v< - '• - - 4-2

4*2.4 Subtask a,4 — Evaluate Historicalf Ae r i a1 Photogr aphs 4 2

: ......r- 4.2.5 Subtask 1.5 ;r~? Identify ARARs 4-24.2,6 EPA Review of Work Plan 4-2

-'.--* 4,2.7 Subtask 1,6 — Collect WaterLevel Measurements 4-3

4,2.8 Subtask 1.7—— Performance Area•< Reconnaissance , 4-3

4,2.9 Subtask 1;8 — Quantify SiteModel .-•; = - ;;. - 4-3

4.2.10 Subtask*1.9 ~ Prepare RemedialInvestigation Site OperationsPlan - .- -. . 4-5

- 4.2.11: Subtask 1.10 — Revise Work Plan 4-6^ 4.2.12 EPA Review of Revised Work Plan 4-6

4 .2.13 EPA Review of RISOP ;. , 4-64,2.14 Subtask l.ll— Prepare Base Maps 4-74,2.15 Subtask 1.12; Revise RISOP 4-74,2.16 EPA Review of Revised RISOP 4-7

4v3 -Task 2 -*• Source Characterization 4-7^ 4.3.1 Subtask 2»!•*- Obtain Site Access 4-7

-4.3.2 -Subtask 2.2 — Mobilize Equipment 4-84.3.3 Subtask 2.3 — Mobilize Driller

for Soil Borings: 4-84.3.4 Subtask 2,4 — Conduct a Soil-

Gas Survey , 4-84.3.5 Subtask 2.5 — Sample Soil and

Install^Vapor Probes ^ 4-84.3.6 Subtask 2.6 — Analyze Soil: : fSamples ': / T; ••..> • 4-94.3.7 Sxibtask 2.7 -Monitor Vapor

;- ^Probes/Piezometers ; 4-94.4 Task 3 — Focused Feasibility Study : 4-10

4.4.1 S\ibtask 3.1 - - Conduct FocusedFeasibility Study on In SituVolatilization 4-10

;' - -: :•'-"> . vi4053B

AR30008M

TABLE OF CONTENTS(continued)

Section Title Page

4.4.2 Subtask 3.2 — Meet with EPA toDiscuss FFS 4-10

4.4.3 Subtask 3.3 — Plan ISV Test(Optional) 4-11

4.4.4 Subtask 3.4 — Conduct ISV Test(Optional) 4-11

4.5 Task 4 — Site Characterization 4-114.5.1 Subtask 4.1 — Mobilize Driller

for Well Installation 4-114.5.2 Subtask 4.2 — Mobilize Eguipment 4-124.5.3 Subtask 4.3 — Conduct Ecological

Assessment 4-124.5.4 Subtask 4.4 — Collect Surface

Water Samples 4-124.5.5 Subtask 4.5 — Install New Wells 4-144.5.6 Subtask 4.6 — Log Wells (Bore-

hole Geophysics) 4-154.5.7 Subtask 4.7 — Test Wells

(Hydrologic) 4-154.5.8 Subtask 4.8 — Survey Wells 4-164.5.9 Subtask*4.9 — Sample Wells 4-164.5.10 Subtask 4.10 — Analyze Water

Samples (First Round) 4-174.5.11 Subtask 4,11 — Sample Wells

(Second Round) 4-174.5,12 Subtask 4.12 — Analyze Ground-

water Samples (Second Round) 4-174.6 Task 5 — Residential Well Sampling 4-17

4.6.1 Subtask 5.1 — Sample ResidentialWells 4-17

4.6.2 Subtask 5.2 — Sample ResidentialWells 4-18

4.7 Task 6 — Data Evaluation 4-184.7.1 Subtask 6.1 — Validate Sample

Analyses 4-184.7.2 Subtask 6.2 — Re-Evaluate

Groundwater Model 4-184.7.3 Subtask 6.3 — Conduct Risk

Assessment 4-184.7.4 Subtask 6.4 — Set Response

Levels 4-194.7.5 Subtask 6.5 — Develop Remedial

Alternatives 4-19

AR300085vii

4053B

REFERENCES

viii4053B

TABLE OF CONTENTS(continued)

Section ' ' ' Title -. ;;;4.8 Task 7 —Feasibility Study 4-19

4.8.1 Subtask 7.1 -—Meet With EPA toDiscuss FS , 4-19

4.8.2 Subtask 7.2 --Evaluate Remedial^Alternatives / ; : • 4-19

4.8.3 -"Subtask" 7.3 •— Prepare RI/FS- Report: - '"•-•-• -- -- 4-20

4.8.4 EPA Review of Draft RI/FS Report 4-204.8.5 'Subtask 7.4 — Revise RI/FS

. . _Report - •; : .-: -~- 4-204.8.6 EPA Review-of Revised Report 4-204,8.7 Public-'Comment Period 4-204,8.8 Subtask 7.5-*- Prepare:for Public

•- • • Meeting 4-20

5 SCHEDULE AND REPORTING 5-1

5.1 RI/FS Schedule - ; 5-15.2.. .Reporting f ; 5-3

R-1

LIST OF FIGURES

Figure No. Title Page

1-1 Location of CSG Site 1-2

1-2 CSG French Drain and Stormwater Detention/Drainage Systems 1-4

2-1 CSG Site, Operations Building with Expan-sion, and Locations of the UndergroundTanks and Monitor Wells at the CSG Site 2-2

2-2 Locations of Wells Monitored onand near the CSG Site 2-6

2-3 Physiographic Provinces in the MiddleAtlantic States 2-9

2-4 Topography and Drainage in the Vicinity ofthe CSG Site 2-11

2-5 Contour Map of the Elevation of the Top ofBedrock 2-14

2-6 Overburden Water Table, March 20, 1980 2-16

2-7 Locations of Cross-Sections AB, AC, and BC 2-17

2-8 Cross-Section AB, Valley Forge CorporateCenter 2-18

2-9 Cross-Section AC, Valley Forge CorporateCenter 2-19

2-10 Cross-Section BC, Valley Forge CorporateCenter 2-20

2-11 Bedrock Water Level Fluctuations 2-22

2-12 Site Well Locations with the ApproximateAreas of Influence of Deep Recovery Wells 2-23

2-13 Chemical Signatures of Water SamplesCollected at CSG Site, July 1987 2-26

2-14 Chemical Signatures of Water SamplesCollected at CSG Site, October 1987 2-27

2-15 Time-Series Model for Well AUD-3 2-32

2-16 Time-Series Model for Well VFCC-4 A R J 0 Oa-i-Ss)

ix4053B

LIST OF FIGURES(continued)

Figure No. Title

2-17 Time-Series Model for Well MOS-11 2-344-1 Probable Surface Water-Sampling Locations 4-13

5-1 Schedule of Tasks for .the RI/FS of the CSGSite on Rittenhouse Road , , 5-2

4053B

LIST OF TABLES

Table No. Title Page

2-1 Commodore/MOS Wells Installationand Completion Data 2-5

2-2 Commodore/MOS Technology, Inc.Depth to Water (feet) Shallow Wells 2-15

2-3 Relative Influence of Well Location, Timeof Sampling, and Sampling/Analysis Error onTCE Concentrations in Groundwater between1982 and 1987 2-29

3-1 Summary of Data Needs for the CSG RI/FS 3-6

AR300087xi

4053B

SECTION 1

INTRODUCTION

This Work Plan describes the objectives, the scope of activi-ties, and the schedule for a Remedial Investigation and Feasi-bility Study (RI/FS) of a facility owned by Commodore Semicon-ductor Group (CSG), a subsidary of Commodore Business Machines(CBM). This section describes the location, the recent historyof the site, and the overall objectives of the RI/FS.

1.1 SITE LOCATION

The CSG site is located in southeastern Pennsylvania in thesouthwestern portion of Montgomery County, approximately 15miles northwest of downtown Philadelphia (see Figure 1-1). The14-acre site is situated on the northwestern border of the Val-ley Forge Corporate Center at 950 Rittenhouse Road, approxi-mately 1 mile north of the Schuylkill River. The site is bor-dered on the northwest by Rittenhouse Road and the GeneralWashington Country Club and on all other sides by commercialand industrial facilities of the Valley Forge Corporate Center.Private residences exist approximately 0.5 mile in all direc-tions from the site.

1.2 SITE HISTORY

The facility was originally constructed in 1970 by MOS Technol-ogy, Inc., a subsidiary of Alien Bradley Corporation. At thetime the building was constructed (1970), an underground con-crete tank was installed for storing waste trichloroethene(TCE) that had been used in manufacturing semiconductor chips.In 1974, the concrete tank was reported to have leaked. MOSlater installed a steel tank next to the concrete tank anddiscontinued use of the concrete tank.

In 1978, TCE was detected in water from Audubon Water Companywells 3 and 5, located approximately 1,000 feet southwest ofthe facility on Rittenhouse Road. During that period, thePennsylvania Department of Environmental Resources (PADER)identified the site as a possible TCE source. MOS then exca-vated and removed both tanks and approximately 30,000 cubicfeet of TCE-contaminated soil. The tanks were replaced with afiberglass-lined concrete vault.

In October 1979, SMC Martin, Inc. was retained to delineate theextent and magnitude of the TCE occurrence and to assess thehydrogeologic setting beneath the site. In addition, the use

AR3000881-1

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1-2

of TCE in the semiconductor chip manufacturing process waseliminated. TCE had been used in the semiconductor chip clean-'ing process and was replaced by hydrochloric acid. In 1980, CBMpurchased the facility from MOS Technology, Inc.

Between October 1979 and November 1981, SMC Martin conducted ahydrogeologic assessment that involved additional excavationand soil analyses in the vicinity of the underground storagetanks and the installation of wells to monitor and test thewater-bearing zones in the bedrock and overburden. Several ofthose wells have since been abandoned. The hydrogeologicassessment determined that TCE contamination of the bedrockaquifer exists both on and off the site at concentrations inexcess of the Safe Drinking Water Act standard of 5 parts perbillion (ppb). Exposure to TCE at high parts per million (ppm)concentrations can cause central nervous system depression,resulting in mental confusion, incoordination, and insomnia(Doull, et al., 1980).

Recovery of TCE-contaminated groundwater began in 1981 withpumpage of well VFCC-4. At that time the water was treated byspray irrigation. This spray irrigation system is described ina letter dated 2 October 1981 from W. Jolly (PADER) to R.Fuller (Commodore-MOS). The letter states "The treatmentscheme is to use air stripping of sprayed water pumped fromwell No. 4 through two spray nozzles at an approximate rate of140 gallons per minute. The spray site will be a 5-acre areato the southwest of your building and will include a portion ofthe Lee Carpet property." By 1984, the spray irrigation systemwas replaced by an air stripper system. In addition, a Frenchdrain with an air stripper was installed to collect and treatshallow groundwater as part of a 100,000-sguare foot buildingexpansion (see Figure 1-2). In 1987, a stripper column wasin- stalled in connection with AUD-3 as part of the groundwaterremediation system.

The soil from the 1978 removal and the 1984 facility expansionwas spread on MOS property south of the building, aerated, andvegetated under the direction of PADER.

In 1985, CSG initiated testing of the drinking water from resi-dential wells not on a public supply system. Fourty-four homeswere orginally tested for VOCs; 23 of the residential wellssampled had more than l ppb TCE. Whole-house carbon filterswere installed by CSG at these 23 residences. Well water fromthese residences is monitored quarterly, and the carbon filtersare changed annually.

In February 1984, the EPA performed a site investigation of theCSG facility, scored the facility on the Hazard Ranking System(HRS), and ranked the site for proposed inclusion on the Na-tional Priorities List (NPL) . This was followed by a Pennsyl-vania CERCLA Remedial Enforcement investigation in Ai

1-34053B

M II I IMI I II I I I It IM M II I I I I I M M I M HI M I

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In January 1987, the EPA proposed the Rittenhouse Road site forinclusion on the NPL. In March 1987, CSG initiated an appealof the HRS score and the status of the CSG facility as aproposed NPL site.

Between November 1987 and July 1988, Commodore Business Ma-chines (the parent company of CSG) and EPA negotiated anAdministrative Order by Consent (Consent Order) requiring aRemedial Investigation and Feasibility Study of the site. ThisWork Plan describes the specific scope of activities that willbe undertaken pursuant to that Consent Order.

1.3 WORK PLAN ORGANIZATION

The remainder of this Work Plan consists of four additionalsections. Section 2 presents an overview of site conditionsbased upon data collected between 1978 and 1987. Section 3 de-scribes the most likely routes of contaminant migration andsite remediation strategies, specific data requirements toevaluate possible remediation alternatives, and the overallobjectives of the RI/FS. Section 4 describes the 7 generictasks and 47 subtasks to be undertaken during the RI/FS.Section 5 describes the schedule of subtasks for the RI/FS.

Specific protocols for field and laboratory data generationwill be detailed in the Remedial Investigation Site OperationsPlan (RISOP), which will be developed prior to initiation ofsite activities.

AR3000901-5

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SECTION 2

SITE CONDITIONS

Section 2 describes current conditions at the CSG site, includ-ing interpretations of data collected between 1978 and 1987.Key findings are that:

• Groundwater in both the bedrock and the overburden arecontaminated with volatile organic compounds (VOCs)from one on-site source and possibly several off-sitesources.

• The existing remediation program is improving ground-water quality even though on-site soil may still becontaminated with VOCs.

• The existing monitoring data are not adequate to eval-uate completely the complexities of groundwater andcontaminant migration.

• Air and surface waters do not appear to be significantroutes of contaminant migration from the CSG site.

This section consists of four subsections:

• Subsection 2.1; Site Facilities — Describes the for-mer and present underground storage tanks, the Frenchdrain system, the wells used for groundwater monitor-ing, and the air strippers used to treat contaminatedgroundwater.

• Subsection 2.2: Waste Streams — Describes chemicalwastes currently being generated at CSG.

• Subsection 2.3: Environmental Setting — Describes thephysiographic setting, climate, surface drainage, hy-drogeology, and groundwater quality.

• Subsection 2.4: Summary — Provides a summary of thekey details and concepts described in Section 2.

2.1 SITE FACILITIES

Operations at the CSG site are housed within one 160,000-squarefoot building (see Figure 2-1). The building consists of a60,000-square foot facility originally constructed in 1970 anda 100,000-square foot expansion added to the original buildingin 1984-85. Currently, all manufacturing, testing, researchand development, and administrative activities ar e. conductedwithin the original 60,000-square foot building A RllidUloC^boo-square foot addition is currently used for storage, shippingand receiving, and utility support systems. Plans are underway

2-14054B

2-2

to equip the expansion with state-of-the-art facilities formanufacturing semiconductor chips.

Behind the building there are various utility and supply sys-tems housed in a fenced area. These include a 40,000-cubicfoot nitrogen generating system, dual 33-kilovolt power distri-bution systems, a specialty gas cylinder vault, a 100-gpm pro-cess wastewater treatment system, a. 12,000-gallon fuel storagevault, and a 2,000-gallon bulk waste solvent collection system.

The present bulk waste solvent collection system is stored un-derground, with its base at a depth of approximately 8 feet be-low ground surface. The system consists of a 2,000-gallon fi-berglass tank inside a fiberglass-lined concrete vault. Thefiberglass lining contains an alarm-equipped, solvent-levelmonitoring system for immediate leak detection. The contentsof the tank, which are reported to consist of 90 percent water,are removed from the site at roughly 6-week intervals foroff-site disposal.

The southwestern corner of the property contains a stprmwaterdetention basin. The purpose of the stormwater detention sys-tem is to contain runoff from heavy rains for a short period toallow the VFCC stormwater sewers time to carry the excess dis-charge. This system drains to the VFCC surface water drainagesystem, which flows westward along Rittenhouse Road and emptiesinto Lamb Run.

The remainder of the CSG property consists of asphalt parkinglots separated by grassy areas.

2.1.1 History of Underground Waste Solvent Storage Tanks atCSG Fac iIi ty

The original underground waste solvent storage tank was in-stalled in 1970 during the construction of the original 60,000-square foot building by MOS Technology. That tank was locatedadjacent to the southeastern side of the building as shown inFigure 2-1. The tank was constructed of concrete and was un-lined. The volume of that tank and the schedule for periodicremoval and disposal of tank contents are not known.

In 1974, the use of that concrete tank was discontinued due tosuspected leakage. An unlined steel tank was installed under-ground in a location adjacent to the concrete tank. The volumeof the steel tank and the schedule for removal of tank contentsare not known.

In 1978, TCE was detected in local groundwater, and PADER iden-tified MOS as a potential source of contamination. In 1979,following soil analysis for TCE in the tank vicinity, the ori-ginal concrete tank, the subsequently installed steel tank, and

AR3000932-3

4054B

30,000 cubic feet of contaminated soil were excavated and re-moved from the site. A new underground waste solvent collec-tion system was installed. That system consisted of a steeltank within a concrete vault (SMC Martin, Inc., 1984).

In 1983, CSG removed the steel tank from the concrete vault.The vault was then lined with fiberglass, was equipped with amonitoring system for leak detection, and a 2,000-gallon fiber-glass tank was placed within the vault. This is the presentwaste solvent collection system (SMC Martin, Inc., 1984).

2.1.2 French Drain/Air Stripper System

Prior to the construction of the 100,000-square foot buildingexpansion in 1984-1985, a 30,000-square foot French drainsystem was installed for recove.ry of perched groundwater at adepth of approximately 25 feet beneath the new building addi-tion. The effluent from the French drain system is routed toan air stripper to remove volatile organic compounds prior todischarge into the Valley Forge Corporate Center stormwatersystem. Permission to treat TCE-contaminated water with theCSG air stripper and to discharge the water to an on-sitedrainage swale was originally granted in a letter from W.Stanley (PADER) to Commodore/MOS dated 9 December 1983. Theoutfall of the storm sewer is at the southern boundary of thesite. Tests of air emissions from the stripper columns havenot identified VOC concentrations above acceptable dischargelimits (SMC Martin, Inc., 1986). The CSG air discharge permitnumber is 46-399-057.

2.1.3 Monitor and Extraction Wells/Air Strippers

Since 1979, nine overburden groundwater monitor wells (MOS-2through -9 and -12) and five bedrock groundwater monitor wells(MOS-10, -11, -13, -14, and -15) have been installed on the CSGfacility (see Figure 2-1 and Table 2-1). Many of those wellswere abandoned during the facility expansion. The procedurefor abandonment is not available, although presumably at leastsome of the wells were removed during deep excavation for thebuilding foundation. Currently, the only remaining wells arebedrock wells MOS-11, -13, and -15. These three wells aremonitor wells and are currently not used for groundwaterrecovery (SMC Martin, Inc., 1986). ,<•"* •"/ <- *

Off-site wells installed as part of prior site assessments in-clude MOS-17 and MOS-18 (see Figure 2-2). Both of these wells,in addition to all other off-site wells that have been utilizedin the CSG site assessment to date, are bedrock wells. MOS-17has since been abandoned. The method and date of abandonmentare not known. No shallow overburden wells exist off site. Ad-ditional off-site wells include the Valley Forge Co rpor-ateq Cen-ter production wells VFCC-2, -3, and -4; Audubon saj:U Companyproduction wells AUD-3 and -5; Audubon Water Company monitorwells AUD MW-1 and AUD MW-2; and the General Washington CountryClub production wells GW-i, GW-2, and GW-3 (see Figure 2-2),

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CSG Former TankOMOS-13

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LegendFormer LeakingUnderground Storage TankLocationPublic Supply Well

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FIGURE 2-2 LOCATIONS OF WELLS MONITORED ON AND NEAR THE CSG SITE

2-6

Since 1984, well VFCC-4 has been pumping groundwater throughair stripper columns to reduce groundwater VOC concentrations.A stripper column was added to well AUD-3 in 1987. Tests ofair emissions from the stripper columns have not identified VOCconcentrations above acceptable discharge limits (SMC Martin,Inc., 1986).

2.2 WASTE STREAMS

CSG currently generates six waste streams on a regular basis.These waste streams are described in the following subsections.

2.2.1 Elementary Neutralization System

Process wastewater containing mixtures of acids and causticsand effluent water from wet impingment fume exhaust scrubbersis piped to an elementary neutralization system. The pH of thesolution waste is adjusted to neutral (6.0 to 9.0) in the neu-tralization system, and the neutralized wastewater is dis-charged to the publicly owned treatment works (POTW).

Analytical testing helps to ensure that the neutralization sys-tem's effluent meets all Federal, state, and local requirements.

2.2.2 Solvent

A mixture of solvents, consisting mainly of acetone, isopropylalcohol, and freons, is piped or manually dumped into the un-derground storage tank.

Waste analytical results determine how and where the wastestream is disposed.

2.2.3 Spent Photo Resist

Photo resist is accumulated in 55-gallon drums. Chemical con-stituents are xylenes, n-butyl acetate, mineral spirits, and2-ethoxyethyl acetate.

Analytical results determine how and where the waste stream canbe disposed.

2.2.4 Used OiI

Used oil is not regulated as a hazardous waste by Federal orPennsylvania state law; however, analytical testing is per-formed to ensure that the oil does not contain any hazardouscharacteristics.

2.2.5 Arsenic Waste

Manufacturing uses arsenic in its process. Arsenicgenerated when preventive maintenance is performed oncess equipment. The waste is mainly rags, gloves, paper, and

2-74054B

other debris contaminated with a small amount of arsenicaldust. Analytical testing is necessary to determine how mucharsenic is in the waste, thereby, determining disposal methodand location.

2.2.6 Carbon

Waste carbon is generated from three sources:

• An activated carbon filtration system is incorporatedin the potable water system. This is to eliminatecontaminants in the drinking water.

• The deionized water system utilizes carbon filtrationto inhibit solvent contaminants from entering the pro-cess water and contaminating the product.

• The outside air intake on HVA/C No. 1 uses a carbonfiltration system to control the quality of air enter-ing the building.

Waste analysis is necessary to determine which contaminantshave been absorbed by the carbon and how much. This determinesthe method of disposal and the disposal facility for the waste.

CSG's waste streams are comprised of mixtures of many chemicalconstituents; therefore, analytical parameters focus on wastestream characteristics (corrosivity, ignitability, reactivity,and toxicity). Additional analytical parameters (heat of com-bustion, percentage of water, and specific gravity) are alsomeasured to establish the disposal method and to complete thewaste profiles required by the disposal facility. The Elemen-tary Neutralization System is the only waste stream discharginginto the Lower Providence Township sewer system. The wastegenerator permit number is PAD 093 730 174.

In August 1982, a letter was received by MOS Technology fromthe Lower Providence Township Sewer Authority referencing heavymetals in Montgomery County Sewer Authority waste sludge. MOSreceived this letter as one of the possible sources. On 1September 1982, MOS submitted heavy metals test results fortheir waste streams. "The testing results were low and do notappear to be a problem." These data were accepted by the lowerProvidence Township as sufficient.

2.3 ENVIRONMENTAL SETTING

2.3.1 Physiographic Setting

The CSG facility is located in the Triassic Lowland sec ^the Piedmont Physiographic Province of southeastern BteBrtsyT1-vania (see Figure 2-3). The site is underlain by the middle

2-84054B

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arkose member of the Triassic Stockton Formation, which ischaracterized in this location by fine- and medium-grained ar-kosic (pink or reddish-gray in color, composed of angular orsubangular grains) sandstone, red shale, very fine red sand-stone, and a few beds of coarse-grained arkose. The stratahave a regional structural dip of 5 to 18 degrees to the north-west, although local warping results in a northeastern dip insome locations (Rima, et al. , 1962). To the north, overlyingthe middle arkose member, is the upper shale member of theStockton Formation. This upper member is characterized by redshale, siltstone, and very fine-grained arkosic sandstone(Rima, et al., 1962). To the south, the lower arkose memberconsists of coarse- to very coarse-grained arkosic sandstoneand conglomerate, with occasional beds of shale and fine- tomedium-grained arkose. Farther south is the Piedmont Uplandssection of the Piedmont Physiographic Province. That sectionis characterized by intensely deformed rocks of the CambrianElbrook, Ledger, Antietam, and Harpers formations (Berg, etal., 1980).

The topography of the area is strongly influenced by drainagetributaries to the Schuylkill River, which lies approximately 1mile to the south of the CSG site. Gentle ridges and valleystrending west-southwest to east-northeast are the dominant fea-tures. The typical difference in elevation between the ridgecrests and the valley floors is approximately 10 to 20 feet.Several drainage tributaries cut across the ridges to empty in-to the Schuylkill River (see Figure 2-4).

Land use in the area is a combination of residential, indus-trial, and agricultural. The northern boundary of Valley ForgeNational Park is located approximately 0.75 mile south of thesite.

2.3.2 Climate

The climatic monitoring station closest to the CSG site is lo-cated in Norristown, Pennsylvania. Annual rainfall recorded atthat station for the period beginning January 1951 and endingDecember 1980 averaged 44.45 inches, with the range for theperiod having a low of 31.24 inches in 1963 and a high of 63.27inches in 1979. Mean monthly rainfall for the same period isrelatively stable throughout the year, with a 30-year mean lowof 2.95 inches for February and a 30-year mean high of 4.46inches for August.

Temperatures ranged from a mean monthly low of 19°F in Januaryto a mean monthly high of 86°F in July for the years 1981through 1986. The average annual temperature was 53°F for thatsame period.

AR300IOO

2-104054B

0 1000 2000 3000J LScale in Feet

Source: USGS 7,5 Min Topographic Maps - Valley Forge, PA/coTfegeville, PA

FIGURE 2-4 TOPOGRAPHY AND DRAINAGE IN THE VICINITY OF THE CSG SITE

2-11

2.3.3 Surface Drainage

Regional surface drainage is toward the Schuylkill River viatributary streams. Local surface drainage in the vicinity ofthe site is to the south or west, while actual site runoff iscollected and discharged through the Valley Forge CorporateCenter stormwater system to Lamb Run, a small tributary of theSchuylkill River.

Between May 1984 and April 1985, CSG performed a building ex-pansion that included site regrading, construction of thestormwater detention basin, and parking area expansion. Theregrading and parking area paving on the southern side of thebuilding direct runoff to the stormwater detention basin.Roughly 50 percent of the building and parking lot runoff iscollected by the basin. The remainder is directed south to theVFCC stormwater system or south along Rittenhouse Road.

During wet seasons, effluent from the French drain system isalso discharged to the Valley Forge Corporate Center stormwa-ter system after it is treated in a dedicated air strippercolumn. Periodic tests of the treated effluent have not iden-tified VOCs "above detection limits. The data from the periodictesting, however, are no longer available.

2.3.4 Ecological Setting

The ecology of the area surrounding the CSG site is one of de-clining farmland and increased home and corporate construc-tion. Small wooded lots of predominantly deciduous trees lienorth and east of the Valley Forge Corporate Center. Largewooded acreage exists primarily north of the town of Audubon,over 0.5 mile northwest of the site, and south of the sitealong the Schuylkill River, also over 0.5 mile from the site.Other wooded areas are orchards and tree "lanes" on the GeneralWashington Country Club. Small farms, open fields, privatehomes, and the Valley Forge Corporate Center occupy themajoritiy of the land area. This land probably supports mostlysmall woodland mammals (e.g., rabbits, squirrels, skunks, wood-chucks, and rodents) but may also support a small deer popula-tion.

Aquatic environments are restricted to the Schuylkill River andPerkiomen Creek, which are 1 mile from the site at their clos-est. Tributaries and intermittent streams, such as Mine Run,Lamb Run, and Indian Creek, direct surface drainage to the twomajor tributaries. Of these, only Lamb Run's northern inter-mittent extension touches the site. These aquatic areasprobably support waterfowl, reptiles, and small freshwaterspecies of fish.

AR300I02

2-124054B

2.3.5 Hydrogeology

Bedrock beneath the CSG site consists of the middle arkosefeldspathic sandstone and red shale and sandstone members ofthe Triassic Stockton Formation, which is overlain by up to 25feet of unconsolidated material (SMC Martin, Inc., 1984).Groundwater in the bedrock is stored and transmitted throughboth primary intergranular pores and secondary fractures.Groundwater in the overburden is stored and transmitted onlythrough intergranular pores during seasonally wet periods.

2.3.5.1 Overburden Hydrogeology

Based upon data collected from the overburden wells before theywere abandoned, the overburden consists primarily of reworkedmaterial from site grading performed during construction of theMOS facility, and little surface material remains in situ. Theoverburden consists of sand, sandy or silty clay, and clay andranges from 10.5 to 25 feet in thickness. The overburden/bed-rock interface (depicted in Figure 2-5) is an undulatory sur-face with a general dip to the southwest.

Groundwater in the overburden occurs seasonally. Water eleva-tions tend to be highest in the late spring and lowest in thelate summer-fall. Depth to water measurements collected be-tween October 1979 and November 1981 are provided in Table 2-2.Depth to groundwater varies from about 5 feet on the northernside of the site (near wells MOS-4 and -15) to 10 to 20 feet onthe southern side of the site (near wells MOS-2, -3, and -12).Flow is to the south, presumably following the slope of theground surface. Figure 2-6 is a contour map of the water tablein.the overburden based upon data collected on 20 March 1980.

VOCs have been found in the overburden north of the removedleaking tanks. There are several possible explanations forthis. SMC Martin (1984) suggests that drought conditions inthe fall of 1980 may have caused a short-term reversal in thegroundwater gradient which would account for VOCs migratingnorthward. A second possibility is that dense VOCs may followlocal variations in the elevation of the bedrock surface. Ifthe first hypothesis is correct, VOC concentrations will prob-ably have decreased considerably since 1980. If the secondhypothesis is correct, VOC concentrations will be as high orhigher than in 1980. New overburden wells proposed for instal-lation during Subtask 4.5 will identify the correct transportmechanism.

2.3.5.2 Bedrock Hydrogeology

Bedrock stratigraphy along the three cross-sections identifiedin Figure 2-7 is depicted in Figures 2-8, 2-9, and 2-10,five sandstone layers interbedded with shale and sil"been identified beneath the CSG site. Some strata appear to be

2-134054B

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GENFRALASH ING TON..•'NTR> CLUB

22°

>- ,-198.07 13" ',J/ XVCOMMODORE //\ >•y \ v/-/ i

200 * VFCC 2

LegendHI Residential Well

With Street Address% Public Supply WellO Monitoring Well

Irrigation WellAbandoned Well

\N^ Based on Data From SMC Martin, 1984

FIGURE 2-5 CONTOUR MAP OF THE ELEVATION OF THE TOP OF BEDROCK

2-14

________________________________I

Table 2-2

Commodore/MOS Technology, IncDepth to Water (feet)

ShaI Iow We I Is

Well NumberDate 2

10/17/79 9.9210/23/79 10.6510/26/7912/11/79 11.6512/12/79 11.4612/13/79 7.9003/04/80 12.8103/11/8003/12/80 11.3003/18/8003/20/8004/15/8005/01/8006/06/8011/06/8007/06/81 10.2911/11/8111/16/8111/17/81

3

10.6711.30

13.0013.1413.3515.76

15.78

10.5711.6814.63

14.77

4

5.676.456.46

10.25

10.01

7.024.404.848.85

7.21

5 6

4.13 6.214.64 8.204.77 6.66

8.82 11.25

8.65 8.14*

8.366.365.46

10.12

5.28

7

5.43

9.80

9.35

6.054.604.908.33

6.93

8 9

12.0211.58

15.77 9.959.40

15.70 9.498.60

14.84 9.4611.48 6.4512.63 5.6714.56 9.51

14.48 6.20

12

32.8517.7817.2110.4412.2416.67

16.7020.6819.3518.02

*Well destroyed

Source: SMC Martin, Inc. (July 1984).

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V 13COMMODORE

Legend_ Residential Well• With Street Address• Public Supply Well

Irrigation WellAbandoned Well

O Monitoring Well

Scale in Feet

FIGURE 2-7 LOCATIONS OF CROSS-SECTION AB, AC AND BC

2-17

r«-350'-*i K—-460'—M f<——500'—**w—————————1470'-

A230-220-210-200-

AUDAUD MW-2 VFCC-4 MOS-15MW-1 20779 209.42 214.28199.24

150-

100-

•?_-_-_-_-_-_-_-_-_- _-_-!.-_- -210

-50-

-100-

TD 405'Elev-=-195-58

Source: Based on Data From SMC Martin, 1986

-W Water EntryDuring Drilling

-50

-100

FIGURE 2-8 CROSS-SECTION ABVALLEY FORGE CORPORATE CENTER

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lithologically continuous across the area, while others appearto grade laterally into coarser or finer lithologies. TheStockton Formation has a maximum thickness of approximately2,000 feet in the vicinity of the site.

Dip of bedding appears to be less than 5 degrees to the north-east in this area. This is in contrast to the regional dip of5 to 18 degrees to the northwest and is probably attributableto localized undulations.

The Stockton Formation is a dual-porosity hydrogeologic system;it stores and transmits groundwater through both primary inter-granular pore spaces and secondary fractures (Rima, etal. , 1962). Most of the bedrock wells penetrate multiple waterentry zones. The majority of those zones have been encounteredin sandstone strata, with the remainder occurring in fracturedsiltstones and shales.

The deep bedrock wells in the area penetrate multiple water en-try zones — as many as nine in VFCC-4. It is possible thatmany of these zones are not in hydraulic communication with ad-jacent zones and that only the uppermost zone or zones actuallycontain elevated VOC concentrations. However, groundwater ele-vations monitored between 1981 and 1983 in six deep wells (seeFigure 2-11) suggest that there is at least a partial verticalconnection between the various stratigraphic units. Neverthe-less, because of the complex nature of groundwater flow throughfractured bedrock, it is possible that discrete zones of flowmay exist. If this is the case, the water from these wellswould be a combination of affected and unaffected groundwater.It would then be possible to design a more efficient ground-water extraction and treatment system that would draw waterfrom only those zones with elevated VOC concentrations; how-ever, conclusive data concerning the presence of discretewater-bearing zones within the bedrock system and the distri-bution of contaminants from zone to zone are lacking.

The groundwater flow direction in the bedrock is presumed to beto the south toward the Schuykill River. It is presumed thatgroundwater flow is controlled predominantly (but not exclu-sively) by fractures and that regional flow will be towardmajor surface water bodies (i.e., the Sckuylkill River). Thepresumption of fracture flow is based upon previous studies(Rima et al., 1962; Newport, 1971; and SMC Martin, Inc., 1984and 1986). The presumption of regional groundwater flow towardmajor surface water bodies is the conventional assumption ap-plied to hydrogeologic systems in humid climates. Localizedpumping, however, will divert flow directions within the conesof influence of pumping wells (see Figure 2-12).

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WASHINGTONCOUNTRY O.U8

Source: March 20,1987 Letter to R.H. Wyer,U.S. EPA from S. King, Attorney for Commodore Buanesfe

FIGURE 2-12 SITE WELL LOCATIONS WITH THE APPROXIMATE AREAS OFINFLUENCE OF THE DEEP RECOVERY WELLS

2-23

Aquifer tests on well VFCC-4 were conducted in 1981 and 1983and yielded estimates of average hydraulic conductivity of 0.54feet/day and 0.22 feet/day, respectively (SMC Martin, Inc.,1984). The average velocity of groundwater migration was sub-sequently calculated to be approximately 32 feet/year (SMC Mar-tin, Inc., 1984). Based upon these estimates of groundwaterflow and assuming no retardation, the maximum distance thatgroundwater and contaminants from the site may have migratedsince 1970 (when the tank was installed) is less than 600 feet.Significantly different flow rates may exist, however, in areasthat are well fractured or are pumped at substantial rates.

2.3.6 Groundwater Quality

Groundwater in both the overburden and bedrock has been sampledand analyzed for volatile organic compounds since 1979. Bothzones have been shown to contain elevated VOC concentrations.In 1984, monitoring efforts in the overburden were curtailedbecause the wells were removed as part of the buildingexpansion and the regrading of the site. Few analyses ofgroundwater from the overburden wells were conducted between1980 and 1984 because the wells were usually dry. Bedrockmonitoring was expanded in 1986 to include selected residentialwells within 1 mile of the site. This monitoring programcontinues on a quarterly basis.

2.3.6.1 Overburden Groundwater Quality

Groundwater in the overburden was analyzed for VOCs between1979 and 1984. During that period, concentrations ranged frombelow detection limits to 100,000 micrograms per liter (ppb).Overburden well MOS-4 was sampled on 10 August 1984 andmeasured 1,500 ppb TCE. No other overburden wells have beensampled since 1981. In general, the highest VOC concentrationswere near the former location of the underground storage tank(wells MOS-9 and -12) and in the northern corner of the site(wells MOS-4, -8, and -7). This suggests that the migration ofdense VOCs may be influenced by the topography of the bedrocksurface or by groundwater movement that has not been defined todate.

2.3.6.2 Bedrock Groundwater Quality

Existing analytical data show bedrock groundwater to have ele-vated concentrations of trichloroethene (TCE), 1,1,1-trichloro- 1ethane (TCA), trans-l,2-dichloroethene (1,2-DCE), 1,1-dichloro- -'ethene (1,1-DCE), 1,1-dichloroethane (1,1-DCA), and tetra-chloroethene (PCE) within 1 mile of the CSG site. Those con- {stituents are found both hydraulically upgradient and ;downgradient from the CSG site.

AR300IU

4054B2-24 H

1

Using data from the residential well sampling program, the rel-ative occurrence of those VOCs was evaluated and mapped aschemical signatures. Chemical signatures for the July andOctober 1987 sampling rounds are shown in Figures 2-13 and2-14, respectively.

Chemical signatures are graphical depictions of the proportionof an individual chemical constituent relative to the totalconcentration of a chemical group. Specifically, Figures 2-13and 2-14 illustrate the percentages of 1,1-DCE; 1,1-DCA;1,2-DCE; TCA; TCE; and PCE relative to the sum of the concen-trations of all VOCs analyzed. Each vertical block of thechemical signatures in Figures 2-13 and 2-14 represents 10 per-cent of the total VOC concentration shown in the ellipse at thetop of each signature.

To construct Figures 2-13 and 2-14, existing data from the July1987 and October 1987 sampling rounds were compiled from thequarterly sampling reports. Several of the wells containedeither very low concentrations of VOCs or levels below the de-tection limits. For consistency, any well having a total VOCconcentration of less than 10 ppb was excluded from the anal-ysis. The cutoff level of 10 ppb was selected based upon de-tection limits of the individual VOCs (typically 1 or 2 ppb)and the MCLs for DCE, TCE, and PCE (7, 5, and 5 ppb, respec-tively) . Approximately two-thirds of the wells sampled hadtotal VOC concentrations less than 10 ppb.

In general, four types of chemical signatures are apparent inFigure 2-13 and 2-14:

• Predominant PCE/TCE — found only at well MOS-13.Because PCE degrades to TCE, this signature mayreflect the well's proximity to the source area or ananomaly in well construction. ' ' . ---'

• Predominant TCE/1,2-DCE — found in wells within ap-proximately 2,500 feet southwest to southeast of theCSG facility. This signature may represent TCE fromthe former underground storage tank and its primarybreakdown product 1,2-DCE.

• Predominant TCA/TCE — found northeast of the CSG fa-cility. This signature may represent a different con-taminant source given that the area is hydraulicallyupgradient and that the TCA concentrations (which arenot breakdown products of TCE) are higher than at theCSG facility. Furthermore, the greater proportion of1,1-DCE relative to 1,2-DCE may reflect a relativelynew source compared to the postulated 1970-1978 re-lease, because the rate of degradation from TCE to1,1-DCE is much faster than from TCE to J. 2-DCJ~

An J U U I2-25

4054B

PredominantTCE, TCA

PredominantTCE, 1,2-DCE1,1-DCE

1,1-DCA1,2-DCETCATCEPCE ABCDEF

GW1AUDMW2

AUDMW1

41 J= Total VOCConcentration inMicrograms/Liter

PredominantTCA

ABCDEF2622Graphs Express the Percent of

Indicator Chemical ConcentrationsRelative to the Sum of the 2618eave o e um o e 2618 >ss r^b o n n i i rConcentrations Source: Based on Data From SMC Martin, 1987 / ABCDr10UUi ID

FIGURE 2-13 CHEMICAL SIGNATURES OF WATER SAMPLES COLLECTEDNEAR THE C.S.G. SITE, JULY 1987

2-26

PredominantTCE, TCA

481French Drain

LegendA = 1,1-DCEB = 1,1-DCAC = 1,2-DCED = TCAE = TCEF = PCE

= Total VOCConcentration inMicrograms/Liter

Predominant

PredominantTCA

Scale in FeetGraphs Express the Percent ofIndicator Chemical ConcentrationsRelative to the Sum of the

fiR3Q01 17Concentrations Source: Based on Data From SMC Martin, 1987

FIGURE 2-14 CHEMICAL SIGNATURES OF WATER SAMPLES COLLECTEDNEAR THE C.S.G. SITE, OCTOBER 1987

2-27

• Predominant TCA — found 3,500 feet south of the CSGfacility in residential wells near the intersection ofAudubon and Trooper Roads. Given the absence of TCEand 1,2-DCE, this contamination is probably attribut-able to a relatively new source other than CSG.

Given that a groundwater remediation system has been in placesince 1984, an evaluation of historical sampling data was un-dertaken to assess the pumping effect. A statistical dimensionmodel (i.e., space-time model) was developed for TCE using datacollected from six wells between 1982 and 1987 (SMC Martin,Inc., 1987). Statistical dimension models combine statisticalmodels for spatial data (i.e., location-based data on region-alized variables) with models for temporal data (i.e., time-dependent data on autocorrelated variables). For this applica-tion, a trend-surface model was linked to a time-series regres-sion model to evaluate location- and time-dependent effects.

Table 2-3 summarizes the results of the model. Key interpre-tations of the model include:

• Wells relatively distant from the site and close topumping wells (e.g., AUD MW-1, AUD MW-2, AUD-3, andVFCC-3) have stable or decreasing concentrations.Figure 2-15 illustrates the relatively stable concen-trations at well AUD-3.

• Decreases in TCE concentrations are greatest near thepumping center (e.g., VFCC-4 and AUD MW-2). Figure2-16 illustrates the decreasing concentrations at wellVFCC-4.

• The only place TCE concentrations appear to be in-creasing is at MOS-11, which is located near where theformer underground storage tank was prior to its re-moval . This trend seems to indicate that contaminatedsoil that was not removed at the same time as the tankmay still be a source of TCE to the groundwater. Fig-ure 2-17 illustrates the trend of TCE concentrationsat well MOS-11.

• Seasonal effects on TCE concentrations tend to besmall, except at MOS-11. This may be attributable toflushing of the contaminated overburden during wetseasons.

• Since the model was developed for MOS-11 (last datacollected in 1986), it appears that concentrations arebeginning to decrease.

AR300I 18

2-284054B

Table 2-3

Relative Influence of Well Location, Time of Sampling,and Sampling/Analysis Error on TCE Concentrations

in Groundwater Between 1982 and 1987

Well

MOS-11

AUD MW-1

VFCC-4

LocationEffect(ug/L)*

2,214

144

537

SeasonalEffect

(ug/L/sample)

Increasing Time

+ 177

Decreasing Time

± 8±29

Long-TermTime Trend

** (ug/L/yr)**

Trend

+736

Trends

-161

-128

Error(ug/L)**

+390

+ 76

+ 112

Relatively Stable Time Trends

VFCC-3

AUD-3

AUD MW-2

72

73

616

+ 12

± 9

+92

+ 9

- 1

-42

+20

+ 14

+ 79

* - Trend-Surface Model:

[TCES] = 2,150.9 + 4.2 NX + 1.5 (Nf/1,000) - 3.6 EJ.- 3.5 (Ej;/l,000)

where:

N! = (N0 cos (10) - E0 sin (10)) - 5,354E! = (EO cos (10) + N0 sin (10)) - 235NO = Arbitrary north coordinate in feetEQ = Arbitrary east coordinate in feetSample size = 175R2 =0.83Probability = 0.0001

2-294054B

AR300I 19

Table 2-3(continued)

** - Time-Series Models:

MOS-11 [TCEt] = -9,665.4 + 2.0 t + 187.2

where:t = Number of days since 1 January 1971Sn = sin (t + 304) + cos (t + 304)Sample size = 20R2 =0.80Probability = 0.0001

AUD MW-1 [TCEt] = 195.6 - 0.04 t + 8.7 S4

where:S4 = sin (t + 91) + cos (t + 91)Sample size = 34R2 =0.08Probability = 0.2685

VFCC-4 [TCEt] = 1,734.8 - 0.4 t + 30.2 S5

where:S5 = sin (t + 122) + cos (t + 122)Sample size = 34R2 =0.70Probability = 0.0001

VFCC-3 [TCEt] = -118.9 + 0.02 t + 11.7 S10

where:S10 = sin (t + 274) + cos (t + 274)Sample size = 34R2 =0.43Probability = 0.0002

AR300I20

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Table 2-3(continued)

AUD-3 [TCEt] = 22.2 - 0.002 t + 87 S5

where:

Sample size = 28R2 =0.29Probability = 0.0137

AUD MW-2 [TCEt] = 569.7 - 0.1 t + 91.4 S5

where:

Sample size = 28R2 =0.66Probability = 0.0001

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In general, it appears that in addition to the 1970-1978 TCEleakage from the site, there are off-site sources of VOC con-tamination within approximately l mile of the CSG site. Ground-water pumpage between 1984 and 1988 appears to be lowering theVOC concentrations in the immediate vicinity of the CSG site.

2.4 SUMMARY

Key findings reported in this section are as follows:

• Between 1970 and 1978, an unlined, underground con-crete storage tank probably leaked a waste solutionof approximately 90 percent water and 10 percent TCE.This tank was replaced by an unlined steel tank in1974, which was, in turn, replaced by a single-linedsteel tank system in 1978, and then by a double-linedfiberglass tank system in 1983.

• Approximately 30,000 cubic feet of contaminated soilwas also removed when the leaking tank was removed in1978. However, some contaminated soil was probablyleft in place.

• Beginning in 1984, water from selected supply wellsowned by the Audubon Water Company and the ValleyForge Corporate Center was successfully treated by airstripping in an effort to reduce VOC concentrations inthe bedrock aguifer.

• In 1985, a French drain system was installed (as partof a building expansion) in an effort to collect VOCsin the seasonal overburden water-bearing zone.

• VOC concentrations in the air and the surface water donot appear to present a significant path for themigration of contaminants.

• The overburden water-bearing zone appears to be satur-ated only during wet seasons, during which flow tendsto be to the south or southeast. Wells that hadmonitored this zone between 1980 and 1984 have beenabandoned.

• Flow in the bedrock aguifer follows both primary andsecondary porosity channels and probably moves to thesouth or to nearby pumping wells. VOC concentrationsin the bedrock aguifer seem to be decreasing (espe-cially near the pumping wells), except at well MOS-11,near the former location of the leaking tank.

• Based upon the distribution of VOCs in the area, itappears that there are off-site sourcestion north and south of the CSG site.

2-354054B

SECTION 3

RI/FS STRATEGY AND OBJECTIVES

3.1 CONTAMINANT TRANSPORT MECHANISMS

Based upon the background information summarized in Section 2,there are a number of environmental pathways that may be impor-tant in the migration of VOCs from the CSG site.

The original leaking concrete tank and some contaminated soilwere removed in 1978. Approximately 1 to 8 feet of contaminatedsoil had to be left behind because of the proximity of the ex-cavation to the building. Over time, contaminants in that zonemay migrate downward to the bedrock, especially during wet sea-sons. This mechanism is supported by the relatively high VOCconcentrations in wells near the former tank location 10 yearsafter the leaky tank was removed.

Contaminants migrating downward through the unsaturated zonemay be in the form of a concentrated phase, with flow directedgenerally to the southwest along the top of the bedrock sur-face, or as a more dilute phase whose migration is in responseto the water table gradient. During wet seasons, contaminantflow in that zone may be to the south, according to water tablemaps produced in 1979, 1980, and 1981, before the overburdenwells were abandoned.

Contamination in the bedrock aguifer will eventually flow southto the Schuylkill River, discharge as springs to the Lamb Runtributary to the Schuylkill River which drains the Valley ForgeCorporate Center, or discharge to nearby pumping wells.

Contaminants entering the environment via the air transportpathway would come primarily from the air strippers. Air emis-sions from the air stripper columns have been tested as part ofPADER permit requirements and are not considered to be sig-nificant. There is also no significant transport or exposureattributable to direct contact.

In summary, the most probable contaminant transport mechanismappears to be migration through the bedrock aquifer to pumpingwells.

Less probable transport mechanisms may include migrationthrough the bedrock aquifer or the seasonally saturated over-burden to nearby surface waters south of the site and flow inthe overburden along the top of bedrock to the southwest of thesite. The presence of undocumented off-site VOC sources maycomplicate the evaluation of these contaminant transport path-wavs- AR300I26

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3.2 CONTAMINANT EXPOSURE RATES

Given the likely contaminant transport mechanisms, the mostprobable routes of exposure to site contaminants are summarizedas follows:

• Public Supply Wells. The only public supply wellsknown to be affected are VFCC-3 , VFCC-4 , and AUD-3 .VFCC-3 has not been pumping for several years. VFCC-4and AUD-3 effluents are treated by air strippers.Tests of these strippers have been submitted to EPAand PADER in the past. The strippers are, from alltesting to date, effectively removing VOCs below 5ppb. The General Washington Country Club wells GW-l,GW-2, and GW-3 are used during the summer for irri-gation only.

• Residential Wells. Monitoring groundwater quality isa continuous part of CSG's residential well samplingprogram. Forty-four area homes on individual wellswere originally sampled in September 1984. Twenty-three of the homes were found to have VOCs in theirwell water in excess of 1 ppb, and whole-house filterswere installed in these 23 homes. Sampling and testingof these homes on a quarterly basis has been used toprevent exposure by ingestion, inhalation, or contact.

• Surface Water . Water samples from CSG's on-sitedrainage ditch have been sampled and tested. Thissampling is described in the 30 October 1985 documentprepared by NUS ("Site Inspection of Valley Forge Cor- jporate Center," Prepared Under TDD No. F3-8312-06, EPANo. PA 1431, Contract No. 68-01-6699).

The report states that "The detection of low concen-trations of trans-l,2-dichloroethylene (6 ug/L) andTCE (13 ug/L) in the downstream aqueous sample from anon-site surface water flow indicated another source of |off-site migration. No contaminants were detected in >the upstream sample. All surface water runoff fromthis site discharges into the Schuylkill River. While Ta public water supply intake is located 4 miles down- Jstream on the Schuylkill River, little or no hazardsare posed by the low concentrations of contaminants ,detected in this case. TCE and related compounds jreadily volatilize from flowing surface waters." J

3.3 APPLICABLE REMEDIATION TECHNOLOGIES

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1

Based upon data collected between 1978 and 1987, there appearto be two primary areas that will require remediation: -i

• Contaminated soil in the overburden, n D o o n i o -7AnoUU i L I

1

• Contaminated groundwater in both the overburden andthe bedrock.

The contaminated soil in the overburden includes the soil underthe former location of the leaking tank as well as any soil atthe top of bedrock which also may have been affected. Threepossible strategies for remediating the contaminated soil are:

• Excavation — Any source remediation technology re-quiring prior excavation (e.g., off-site disposal,soil washing, incineration, low-temperature thermalstripping) will be extremely difficult to implementbecause of the depth of the contaminated soil and itsproximity to buildings and major utilities. Addi-tional data on the depth and concentrations of con-taminants will be necessary to evaluate this reme-

!-~ diation strategy.

• Soil Flushing — Contaminants may be able to be flush-ed from the soil using water or surfactants. However,this strategy is likely to exacerbate groundwater con-tamination in the bedrock if not implemented properly.Data on the depth and concentrations of contaminantsas well as a calibrated groundwater flow model will beneeded to evaluate this option.

• In Situ Volatilization — VOCs may be able to be vola-tilized and removed from the soil using suctionprobes. Although this approach will not ensure totalVOC removal, it should provide some VOC removal and berelatively easy to implement.

The primary contaminated groundwater to be remediated would bethat in the bedrock aquifer. However, remediation of contami-nated groundwater in the seasonally saturated overburden willhave to be evaluated because it can act as a VOC source for thebedrock aguifer. Possible strategies for addressing contami-nated groundwater include:

• Physical Barriers — Because of the fractured natureof the bedrock, physical barriers (e.g., slurry walls)are not an appropriate groundwater remediation strate-gy-

• Groundwater Removal and Treatment — The existingpump-and-treat system has shown this approach to beeffective. However, because existing wells were usedfor convenience, it is not likely that the currentsystem is an optimal design. Data needed to improvethe design include information on the distribution andconcentration of VOCs remaining in the soil as well ascalibrated groundwater flow and contaminanmodels.

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• Well Head Treatment — Instead of remediating theaquifer, it may be preferable to provide separatetreatment systems for individual wells (e.g., airstrippers for public supply wells and carbon filtersfor private low-flow wells). This strategy can beevaluated using the same data as for the groundwaterremoval and treatment option.

• Natural Attenuation (i.e., no action) — Long-term ac-tive aquifer remediation may not be cost effective ifthe sources of contamination (both on-site and off-site) cannot be controlled. In that case, the naturalprocesses of biological and chemical degradation, di-lution, and dispersion may reduce VOC concentrationsto appropriate levels over time. In this case, find-ing an alternate source of drinking water will be nec-essary. A calibrated contaminant transport model willbe necessary to evaluate this alternative.

3.4 RI/FS OBJECTIVES

The overall goal of the RI/FS is to identify a remedial alter-native that will address contamination attributable to the CSGsite in a cost-effective manner. Specifically, this will re-quire fulfilling the following eight objectives:

I. Delineate the approximate areal extent and depth ofsoil VOC contamination as well as bedrock groundwaterVOC contamination.

II. Determine whether it is feasible to extract VOCs fromthe soil by in situ volatilization or soil flushing.

III. Determine the direction of groundwater flow in boththe overburden (if possible) and the bedrock.

IV. Determine whether nearby off-site VOC sources arecontributing to the groundwater contamination.

V. Develop a groundwater flow/contaminant transport mod-el that can be used to optimize a groundwater pump-and-treat system or other remedial action.

VI. Evaluate the risks posed to human health and/or theenvironment from exposure to VOCs migrating from theCSG site.

VII. Assess candidate remedial alternatives for mitigatingrisks posed by VOC concentrations.

VIII. Determine how the affected media will be changed bythe installation of a remedial action.

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3.5 RI/FS DATA REQUIREMENTS

A number of data elements will be required to fulfill the ob-jectives outlined in Subsection 3.3. Table 3-1 summarizes thedata needed to meet each of the eight objectives and the meth-ods proposed for obtaining the data.

3.6 RI/FS STRATEGY

Based upon the information presented in Subsections 3.1 through3.5, a seven-part RI/FS strategy has been developed. Thisstrategy consists of:

• Task 1: Planning — review and evaluation of back-ground information as well as selected field activi-ties needed to develop the Remedial InvestigationSite Operations Plan (RISOP).

• Task 2: Source Characterization — analysis of soil-gas and soil samples to determine the approximate ex-tent of VOCs in the soil on the CSG site.

* Task 3: Focused Feasibility Study — evaluation ofin situ volatilization as a possible means to fast-track a low-risk source control method prior to thefull-scale feasibility study.

• Task 4: Site Characterization — installation of newwells and testing of new and existing wells to obtaindata on groundwater flow and quality and surfacewater sampling to evaluate possible ecologic impacts.

• Task 5: Residential Well Sampling — continuation ofthe current sampling program for residential wells,with additional data analyses and validation con-ducted as input to the risk assessment.

• Task 6: Data Evaluation — development of a ground-water flow model, a risk assessment, and candidateremedial alternatives.

• Task 7: Feasibility Study — an engineering evalua-tion of the candidate remedial alternatives.

Specific activities to be undertaken as part of these sevenmajor tasks are described in Section 4.

3-54055B

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SECTION 4

RI/FS SCOPE

4.1 RI/FS OVERVIEW

This section describes the various tasks required to performthe RI/FS, the purpose or objective of each, and the manner inwhich each task will be carried out. To provide sufficient de-tail, each of the seven major tasks described in Subsection 3.6has been divided into a number of subtasks. Each of the sub-tasks is related to preceeding and succeeding subtasks in amanner that will expedite the logical completion of the RI/FS.Critical-path activities are designated in this section by anasterisk(*).

4.2 TASK 1 — PLANNING

Task 1 includes subtasks required to finalize plans (i.e., theWork Plan and the RISOP) for the RI/FS and to conduct a prelim-inary site evaluation. The preliminary site characterizationwill be accomplished through a series of stepwise subtasks be-ginning with collecting water levels and culminating with de-veloping a conceptual groundwater flow model. These subtasksare described as follows.

4.2.1 Subtask 1.1 — Prepare and Submit Work Plan*

This Work Plan represents the completion of Subtask 1.1.

4.2.2 Subtask 1.2 — Assess Existing Wells

The existing wells in the area must be assessed to determinetheir "usability" for this investigation. Existing well datawill be included in this investigation as much as possible tointegrate previous study data with new data. Existing monitorwells will be used in: (l) taking water level elevations forhydraulic gradient determinations; (2) determining the ground-water quality; (3) conducting borehole geophysical examina-tions; and (4) recovering contaminants. To perform these tasks,the well must: (1) be able to accommodate equipment; (2) be ina condition to monitor accurately a target zone; and (3) not becross-contaminating zones. These criteria were used in examin-ing wells prior to Work Plan approval as agreed upon in a meet-ing between EPA, CSG, and WESTON on 10 March 1988 at CSG. Sub-task 1.2 will be conducted in conjunction with Subtask 1.6.

The primary criteria for the usability of an existing well arewhether the well can accommodate a depth-to-water meter, wheth-er a water sample can be collected from the well, and whetherthe well can be examined with a geophysical probe or borehole

AR30QI334-1

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TV camera. If at least one of these criteria can be met, thewell will have at least some degree of usability for thisstudy. Other criteria of importance are the condition of thecasing, condition of the casing collar, and condition of thewell screen, if any. Repairs required to the surface casing ofany well owned by CSG will be effected during Subtask 4.3.

Prior to any permanent physical change to the existing wells,EPA will be notified of the intended action(s).

4.2.3 Subtask 1.3 — Evaluate Fracture Traces

Lineaments at the surface evident on aerial photographs may beindicative of subsurface faults and fractures. Those faults andfractures could be conduits for groundwater flow and for theflow of contaminants that move in the secondary openings. His-torical aerial photographs and geologic mapping were used toidentify traces of subsurface fractures.

4.2.4 Subtask 1.4 — Evaluate Historical Aerial Photographs

Historical aerial photographs from the past 40 years were com-pared to evaluate historical site development. Possible off-site sources of contamination, both past and present, wereidentified as part of this investigation. For example, the1952 USGS 7.5-minute topographic map of Valley Forge, Pennsyl-vania, indicates that an area that is now General WashingtonCountry Club used to be the Valley Forge Municipal Airport.Possible spills at a municipal airport could be contributing tothe area's VOC contamination. Gas stations, primarily south ofthe site, or dry cleaning establishments, northwest and north-east of the site, could also be contributing contaminants tothe groundwater. To the extent possible, findings from theaerial photograph survey were augmented with ground reconnais-sance in conjunction with Subtasks 1.6 and 1.7.

4.2.5 Subtask 1.5 — Identify ARARs

A complete survey of Federal, state, and local regulations/re-quirements were conducted to identify the Applicable or Rel-evant and Appropriate Requirements (ARARs) for the CSG site.This survey commenced during the project-planning phase. TheARARs will be identified in the RISOP.

4.2.6 EPA Review of Work Plan*

EPA will take no longer than 60 calendar days from the date ofsubmission to review the Work Plan. EPA may contact CSG forclarification during review.

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4.2.7 Subtask 1.6 — Collect Water Level Measurements

Collecting water levels from area wells is a critical part ofdefining the local groundwater potentiometric surface. Thechange in the potentiometric surface over distance will definethe direction and gradient of groundwater flow. Water levelshave been collected on a quarterly basis in both overburden andbedrock wells. The data will be mapped and stored on computerdisk for modeling purposes.

Data from three nearby USGS stream gauging stations will be in-corporated into this study.

To monitor long-term effects on a constant basis, a recordingdevice will be placed on a well near the suspected source ofcontamination. Data from this type of a device will aid inassessing the effects of local groundwater withdrawal (pumping).

A reconnaissance of surface water in the site vicinity has beenconducted as part of this subtask. Locations for surface waterflow and quality monitoring were identified.

4.2.8 Subtask 1.7 — Perform Area Reconnaissance

An examination of the CSG site and surrounding area was execut-ed to locate area wells, trace local drainage patterns, identi-fy other potential contributors to groundwater contamination,and identify probable sites for soil borings and monitor wells.The location of wells for the collection of background waterquality was also evaluated.

4.2.9 Subtask 1.8 — Quantify Site Model

The key to quantifying site conditions is fully understandingthe site using the available existing data. To accomplishthis, a preliminary two-dimensional TCE transport model for theStockton bedrock aquifer at the CGS site and surrounding areawill be developed. The TCE transport model will account forthree major processes that control the movement and attenuationof TCE in groundwater: (1) movement due to the groundwater flow(advection); (2) the mixing and spreading of TCE in groundwater(dispersion); and (3) chemical reactions (adsorption).

The development of the TCE transport model will involve severalassumptions:

• Groundwater flow in the strata of sandstone is essen-tially horizontal, uniform, and two-dimensional.

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• The aquifer is homogeneous, and groundwater is ahomogeneous fluid with constant density. Therefore,aquifer properties (hydraulic conductivity, porosity,fluid density, temperature, and viscosity) aretemporally and spatially uniform.

• The effective porosity is 0.12, and the average hy-draulic gradient estimated from water level data re-presents typical groundwater conditions.

• The longitudinal dispersivity is 2 to 10 times that oflateral dispersivity.

• Dispersion is dominated by groundwater velocity varia-tions (mechanical dispersion). Molecular diffusion isnegligible compared to mechanical mixing.

• The retardation factor is used to account for retarda-tion of TCE movement relative to groundwater flowcaused by chemical reactions of TCE with the aguifermedium. If the equilibrium sorption is reached, theTCE should move at a constant average velocity equalto the groundwater velocity divided by the retardationfactor. The retardation factor, R, can be determinedfrom the distribution coefficient, K, by the followingrelation: R=l+ PK/n where P is bulk density of aguifermaterial and n is the effective porosity. The distri-bution coefficient of TCE between the solid phase andaqueous phase is calculated from: K=0.63(f) (KOw)where f is the organic content (%) of the aquifersolid matrix and Kow is octanol-water partitioncoefficient. Initial values of these parameters to beused in the solute transport modeling are:

f=0.5%, Kow=195, n=0.096, andp=2.65 g/cm3•

The actual amount of contaminant source from the leakage of theunderground solvent storage tanks is unknown. The soil wasfound to be contaminated with TCE and was removed to a depth of9 feet in the tank vicinity. The TCE loading in the model willbe estimated based upon. 30,000 cubic feet of excavated contami-nated soil and TCE concentration of 100,000 ppb measured atMOS-12 on 7 July 1981. The source strength of TCE in the start-ing simulation year (1972) will be assumed to be about two tofive times of that in 1981 during the calibration period. Thesource strength of TCE will be reduced from 0.14 pounds per dayto 0.0001 pounds per day after tank removal in 1982.

To calibrate the TCE transport model, simulated TCE concentra-tions will be compared to the actual TCE and 1,2-DCE concentra-tions measured at the site in 1987 and 1988 sapse JL,2-DCE is adaughter product of TCE with a half-life o¥'1a«<Miy / clears.

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Parameters to be adjusted during the calibration processes in-clude retardation factor, dispersivities, and source strength.

Modeling results from this study will be used to help identifylocations of additional monitor wells and other field activi-ties. These field activities will be discussed in more detailsduring preparation of the Remedial Investigation Site OperationPlan (RISOP).

4.2.10 Subtask 1.9 — Prepare Remedial Investigation SiteOperations Plan*

A Remedial Investigation Site Operations Plan will be preparedto cover all field and laboratory activities. The RISOP willconsist of four sections:

• Sampling Plan• Quality Assurance Project Plan• Health and Safety Plan• Data Management Plan

As shown in the project schedule (see Figure 5-1), the RISOP isscheduled to be submitted to EPA for review in April 1989.

The Sampling Plan will cover all soil, groundwater, surface wa-ter, and vapor sampling activities such as specifying samplelocations and explaining installation and sampling procedures.That plan will include the drilling procedures, decontaminationof drilling equipment, materials of construction, and construc-tion methods. The Sampling Plan will specify the requirementsfor compiling boring logs to document subsurface conditions. Itwill also cover procedures to develop wells and specify re-quirements for surveying activities.

A Quality Assurance Project Plan will be developed to coversample collection and handling and laboratory protocols. Samplecollection will identify the procedures for collecting samples.For groundwater this will include information on well purging,sampling devices (including materials of construction), decon-tamination, and water level measurement. For soil borings itwill specify the sampling interval, sampling devices, decon-tamination, and method of physically transferring the sample tothe sample container. For soil vapor monitoring it will includepurging procedures, sampling devices, and will specify vacuumlevel. The sampling frequency will be specified for all vaporand water samples. That plan will also specify the frequencyand procedures (if applicable) for collecting all duplicatesamples, field blanks, and QA/QC samples. Sample handling willlist all field measurements (e.g., pH) and specify sample size,container size and materials of construction, headspace, pres-ervation, transportation, storage, chain-of-custody, and sample

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management (within, the laboratory). Laboratory protocols willinclude holding times, sample preparation, analytical pro-cedures, instrument calibration, data reduction and validation,laboratory control samples, and level of QA documentation.

The Health and Safety Plan will govern all field activities.That plan will identify the nature and locations of the hazards(or potential hazards) that may be encountered in executing thefield program. It will specify the means by which personnelwill be protected, including clothing, respiratory equipment,monitoring requirements, decontamination, and contingency plan-ning.

The Data Management Plan will include necessary QA/QC proce-dures relating to data management and quality. That plan willorganize and schedule periodic data evaluations. The DataManagement Plan will summarize the objectives of the plan anddescriptions of data collection activities divided into:

• Geological data.• Chemical data.• Engineering data.

The procedures for validating, reducing, and evaluating thedata will be described.

4.2.11 Subtask 1.10 — Revise Work Plan

Following EPA's formal review of this Work Plan, EPA willtransmit its comments and questions to CSG. CSG will make aninitial appraisal of those comments and will contact EPA toclarify (as needed) the intent of the comments/questions. CSGwill then revise the Work Plan to address the comments and willre-issue it in January 1989.

4.2.12 EPA Review of Revised Work Plan

Ten copies of the revised Work Plan will be transmitted to EPAfor final review. The negotiated Consent Order does not allowfor successive iterations of the revision process. Therefore,EPA's review and approval (or disapproval) should be completedwithin 14 calendar days. Minor additional changes will beaccomplished by EPA's issuance of the revised Work Plan on an"approved-as-noted" basis.

4.2.13 EPA Review of RISOP*

Ten copies of the RISOP will be transmitted to EPA for review.After receipt of the RISOP, EPA may contact CSG for clarifica-tions. EPA's review will be completed within 60 calendar days.

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4.2.14 Subtask 1.11 — Prepare Base Maps

An overflight of the CSG site will be completed so that an ac-curate base map of the area can be developed during the firstpart of 1989. That flight will be scheduled to occur after allsnowcover has melted. This base map will have a scale of 1 inchequals 200 feet and a 2-foot contour interval.

4.2.15 Subtask 1.12 — Revise RISOP

CSG will revise the RISOP in response to EPA's comments. CSGwill make an initial review of the comments and will contactEPA if any comments are unclear. CSG will then modify the RISOPto address EPA's comments and will re-issue it within 30 calen-dar days of receipt.

4.2.16 EPA Review of Revised RISOP

As with the Work Plan, the Consent Order does not allow succes-sive iterations of the RISOP. Consequently, it is anticipatedthat EPA will be able to approve (or disapprove) of the revisedRISOP within 14 calendar days.

4.3 TASK 2 — SOURCE CHARACTERIZATION

Task 2 includes subtasks related to identifying the approximateextent of soil contamination around the area from which theleaky tank was removed and at the top of the bedrock surface.Key field activities during Task 2 will include conducting asoil-gas survey, sampling soil borings, and installing and mon-itoring vapor probes (piezometers).

4.3.1 Subtask 2.1 — Obtain Site Access

Some portion of the field activity for this investigation willtake place on properties not owned by CSG. In order to ensureproper site access, permission to work on those properties willbe sought at least 1 month in advance. Activities will be per-formed only after receiving approval from property owners.

Occasionally, work locations may have to be modified to allowfor realistic access routes. This will be a major factor duringany work on the General Washington Golf Course.

Another concern will be the use of heavy machinery adjacent tothe CSG plant itself. Microchip manufacturing requires severalvibration-sensitive steps. Drilling outside may disrupt thoseprocesses. At least 1 week advance notice must be given to pre-pare CSG for the operation.

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4.3.2 Subtask 2.2 — Mobilize Equipment

Equipment to be used during field activities will be obtainedand assembled in advance. The operating condition of all equip-ment will be' checked prior to field use.

4.3.3 Subtask 2.3 — Mobilize Driller for Soil Borings

The objective of the soil boring program is to obtain reliabledata that can be used to estimate the extent of contaminant mi-gration. This task will involve obtaining a qualified drillerfor the soil sampling. Bid specifications for qualified andHealth-and-Safety-certified drillers will be submitted to atleast three drilling companies. The most qualified company willbe chosen to perform the soil boring program at CSG from thebids received. EPA will be notified of the driller's qualifica-tions 30 calendar days prior to the beginning of the soil bor-ings .

4.3.4 Subtask 2.4 — Conduct a Soil-Gas Survey

The objective of the soil-gas survey is to examine the areaaround the site in a reasonably rapid, qualitative manner sothat the probable extent of volatile organic contaminants canbe determined. Data from the soil-gas survey will subsequentlybe utilized in the placement of soil borings and monitor wells.The soil-gas survey is to help focus the soil and groundwatersampling efforts that have been proposed.

Soil-gas probes will be driven into the unconsolidated surfacematerial to a depth of approximately 3 feet. The survey willbe initiated in the immediate vicinity of the removed tank andexpanded outward on a 100-foot grid spacing to eventually coverfour 1,000- by 1,000-foot grids surrounding the CSG site. A mapof the proposed sampling grids will be included in the RISOP.Should no VOCs be detected in the soil-gas, the survey will bediscontinued. At least 30 samples will be analyzed before adecision is made to discontinue the study if no VOCs are detec-ted. If no VOCs are detected, efforts will be made to determinewhether this represents actual environmental conditions or sometechnical difficulty. Detailed descriptions of soil-gas surveyprocedures will be found in the RISOP.

4.3.5 Subtask 2.5 — Sample Soil and Install Vapor Probes*

Soil sampling is necessary around the CSG facility to determinethe approximate extent that VOCs may have migrated along thetop of bedrock. Placement of those borings will be based uponthe topography of the bedrock surface (see Figure 2-4) and theresults of the soil-gas survey. The soil borings will be drill-ed with a decontaminated auger rig, with the augers preceededby a split-spoon sampling device. Split-spoonscontinuously below a depth of 5 feet to the top of beduse of a continuous soil corer may be substituted for

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split-spoon sampling if the equipment can be obtained withoutdisrupting the schedule.

A description of the recovered soil will be recorded in thegeologists' field notebook for later compilation. The lastsplit-spoon collected before bedrock will be sampled and sentfor VOC analysis to determine whether a contaminant layer couldbe flowing along the bedrock surface.

Given the nature of the VOC source and the possible transportmechanisms, the only soil that could be substantially contami-nated would be the few feet of saturated soil above bedrock,regardless of the number or nature of near-surface discontinu-ities. Soil samples will be scanned with a photoionizationflame inozation detector to identify the possible presence ofVOCs in the soil above bedrock. Should these instruments indi-cate a reading greater than 2 units above background, thatportion of soil will be sent for laboratory analysis (Method601) .

Once the split-spoon and augers are removed, a 2-inch PVCscreen and casing will be set in the borehole using standardmonitor well installation practices. Installed in this fashion,those probes can be used to measure water levels in the over-burden during wet periods and VOC levels in soil-gas during dryperiods. It is anticipated that up to 15 soil borings will beplaced at various locations around the CSG site and that onesample will be collected from each boring.

4.3.6 Subtask 2.6 — Analyze Soil Samples*

Historical data indicate that the contaminants of concern atthe CSG site are volatile organics. Consequently, all sampleswill be analyzed for VOCs. In addition, approximately 25 per-cent of the soil samples will be analyzed for the full TargetCompound List (TCL) of inorganics and Target Analyte List (TAL)of organics. The samples targeted for full TCL/TAL analyseswill be concentrated in the area of the removed leaking tank.Should TCL/TAL analyses of these samples indicate only volatileorganic compounds, then all subsequent analyses will be forVOCs only. If the TCL/TAL analyses indicate the presence ofcontaminants in addition to volatile organics, then approxi-mately 25 percent of all subsequent water samples will beanalyzed for the full TCL/TAL list. Specific protocols forthose analyses will be specified in the QAPP section of theRISOP.

4.3.7 Subtask 2.7 — Monitor Vapor Probes/Piezometers

Vapor probes/piezometers will be monitored periodically duringthe site investigation. During wet seasons, the water levels inthe probes will be measured as described under fiiibifeask J.. 6..H n J U U i 4 i

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During dry seasons, the air within the entire vapor probe willbe evacuated to draw gas from the soil into the probe. Soil-gaswill then be analyzed for total VOCs. Specific procedures forthis monitoring will be specified in the RISOP.

4.4 TASK 3 — FOCUSED FEASIBILITY STUDY

Task 3 includes subtasks related to determining whether in situvolatilization would be a cost-effective means of reducing soilVOC concentrations. If this technique should prove to be appro-priate, VOC source control measures could be expedited prior tothe completion of the full feasibility study.

4.4.1 Subtask 3.1 — Conduct Focused Feasibility Study on InSitu Volati Mzation

Due to the nature of the contamination, it appears that in situvolatilization (ISV) may be effective for remediating the morehighly contaminated soils at the site. Therefore, a focusedfeasibility study (FFS) will be conducted prior to preparationof the overall feasibility study. This FFS will be based upondata collected during Task 2. It will evaluate the effective-ness of ISV for removing the volatile contaminants from thesoil based upon site-specific considerations such as contami-nant location, soil type, physical constraints, water table,and emissions. Based upon those factors, the FFS will estimatethe achievable cleanup levels, the duration of the ISV activi-ty, and the impact of this activity on ambient air quality atthe property line, both with and without controls.

At the conclusion of the FFS, a report will be issued to theEPA detailing:

Method of feasibility testing.Duration of test.Chemical analyses performed.Results of testing.Conclusions/recommendations.

4.4.2 Subtask 3.2 — Meet With EPA to Discuss FFS

Because the FFS will preceed completion of the remedial inves-tigation (including the risk assessment), it will not be aimedat achieving any particular health-based target levels. Rather,it is intended solely to evaluate whether ISV would be a tech-nically viable alternative for rapidly reducing the VOC contentof the soil and thus controlling the source of groundwater con-taminants. The purpose of this meeting with EPA is to deter-mine whether there is a consensus of opinion in that regard. Inaddition, the need for pilot testing or full-scale implementa-tion will be discussed.

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4.4.3 Subtask 3.3 — Plan ISV Test (Optional)

If a decision is made during the meeting between CSG and EPAthat pilot testing is warranted, CSG will prepare an ISV TestPlan. That plan will be in the form of an addendum to theRISOP. The testing will be designed to develop actual designcriteria for an ISV system, including such factors as riserspacing, air rate, and contaminant loading. The Test Plan willestablish the location of the equipment and will specify themethodology for conducting the test. It will stipulate the op-erating procedures, identify equipment testing parameters andmonitoring frequencies, and list the chemical constituents re-quiring analysis. It would also specify the means and frequencyof sample collection, the method of laboratory analysis, thelevel of protection for operating personnel, and the means oftreating the emissions, if applicable.

4.4.4 Subtask 3.4 — Conduct ISV Test (Optional)

The ISV pilot system will be tested according to the ISV TestPlan. Because the purpose of the test is to develop designcriteria, the plan will be subject to change in response to un-expected field conditions. Any such changes will comply withthe QAPP and the Health and Safety Plan. The intent of thisflexibility is to allow the test equipment to be moved to an-other location or to increase or decrease run times. The testwill continue until enough data are available to establish de-sign criteria. To the extent possible, the work will be per-formed within the overall project schedule.

4.5 TASK 4 — SITE CHARACTERIZATION

Task 4 includes subtasks related to evaluating groundwater flowand contaminant migration and general environmental conditionsin the vicinity of the CSG site. Key activities will includesoil borings, installing new wells, and testing and samplingnew and existing wells.

4.5.1 Subtask 4.1 — Mobilize D r i l l e r for Wel l Installation

The objective of monitor well installation is to provide loca-tions for accurate depth to water measurements and to samplegroundwater for evaluating contaminant migration. Bid specifi-cations will be submitted to at least three drilling contrac-tors having Health and Safety certification. The most quali-fied company will be selected from the bids received to performthe monitor well installation. EPA will be provided the quali-fications of the driller at least 30 calendar days prior tofield mobilization.

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4.5.2 Subtask 4.2 — Mobilize Equipment

Equipment will be assembled to be sure it will be available forthe field effort and functioning properly prior to the fieldeffort. Some equipment may have to be purchased or rented forthe investigation to proceed. In this case, several weeks oflead time may be required to ensure that the necessary equip-ment is available on time.

4.5.3 Subtask 4.3 — Conduct Ecological Assessment

An ecological characterization will be conducted of the siteand the immediately surrounding area. This characterizationwill address the topography and drainage features, flora andfauna of the area, and surface waters including associatedfloodplains and wetlands. The area will be described in termsof the habitat it provides and the potential wildlife speciesthat are likely to utilize the area. The appropriate resourceagencies will be contacted to determine if any rare, threaten-ed, or endangered species, including both plants and animals,are known to occur in the project area. In addition, the areawill be assessed for the presence of critical habitats orresources that make the area unique.

The ecological characterization will be used to assess the po-tential impacts to wildlife and vegetation resulting from con-taminant migration off the project site. Information collectedfrom other study phases, including surface water and sedimentsampling results, will be integrated with the characterizationto assess the potential impacts.

4.5.4 Subtask 4.4 — Collect Surface Water Samples

The objective of the surface water sampling program is to de-termine whether surface water is a possible migration pathwayfor site contaminants. Knowing the extent to which surfacewater may be a migration pathway would also be useful forevaluating environmental and human exposure impacts. Six ofthe probable seven surface water sampling locations are shownin Figure 4-1. The locations are anticipated to be:

1 - Upgradient drainage ditch on northern side of site.

2 - Upgradient drainage ditch on eastern side of site.

3 - Stormwater detention basin.

4 - Downgradient drainage ditch on southern side of site.

5 - Stormwater outfall from surface water drainage system.

6 - Downgradient drainageway about 0.5 mile south of theCSG site.

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GW-2

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-0-GW-1

AUDMW-1

O

General WashingtonCountry Club

CSG Former TankA OMOS-13-4 MOS.-,-i

/V

AUDOMW-2

X5

LegendFormer LeakingUnderground Storage TankLocation

9 Public Supply WellO Monitor Well

Irrigation WellAbandoned Well

Sampling Location

AR300U5

FIGURE 4-1 PROBABLE SURFACE WATER SAMPLING LOCATIONS

4-13

7 - Downgradient where the drainageway becomes Lamb Run(at Audubon Road).

A single round of samples will be collected as close to theSubtask 4.9 sampling round as possible.

4.5.5 Subtask 4.5 — Install New Wells*

The objective of installing new wells is to provide the neces-sary number of data points for determining groundwater and con-taminant flow directions and gradients, as well as monitoringbackground (natural) water quality. More specifically, the ob-jectives of the drilling and installation of the monitor wellnetwork are to:

• Describe the overburden soil types and the subsurfacerock types, structure, stratigraphy, and degree offracturing.

• Provide information on the horizontal and vertical ex-tent and direction of contaminant migration,

• Provide information on the rate and direction ofgroundwater movement.

• Provide information needed to develop a groundwaterflow model of the site which can be used to design aneffective groundwater remediation plan.

Three types of monitor wells will be installed: overburdenwells to monitor groundwater perched in the overburden; shallowbedrock wells to monitor the upper 20 feet of bedrock; and deepbedrock wells to monitor deeper bedrock. The overburden wellswill be drilled to the top of the bedrock surface. Shallow bed-rock wells will be drilled so that the surface casing is set 2to 5 feet into the bedrock and 20 feet of open hole or screenedinterval exist. Deep bedrock wells will be cased to a depth ofapproximately 80 feet and will have approximately 10 to 20 feetof open hole or screened interval at their base. Up to threedeep bedrock wells will be cored from the top of bedrock to thetotal depth of the well. The annulus will then be widened andthe well completed. To the extent practical, the three typesof wells will be installed in clusters. The cored wells willbe completed first so that the deep stratigraphic informationcan be evaluated before drilling the shallow wells. Wells willbe cored first, geophysically logged, and then packer tested.Wid- ening of the annulus will be performed at the mostappropriate time (before or after geophysical logging).

It is currently anticipated that there will be a maximum ofthree deep bedrock wells, a maximum of six shallow bedrockwells at various locations in the vicinity of tfh 'ESG site, andone to four overburden wells on or relatively "61x3*9 4bfo thesite. ~

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The specific locations of the wells will be based upon the Sub-task 1.8 modeling effort, the Subtask 2.5 soil-gas survey, andthe Subtask 2.6 soil sampling. The locations will be specifiedin the RISOP together with well construction details. If thenature of groundwater and contaminant flow is still ambiguousat the conclusion of this phase of the RI, an additional roundof well installation and testing will be considered.

Part of well installation includes installing a locking cap foreach well. Previously installed monitor wells will be examinedfor security. If the wells do not have a locking cap, one willbe installed as part of this subtask.

4.5.6 Subtask 4.6 — Log Wells (Borehole Geophysics)**

Borehole geophysics will be used, as appropriate, to identifyand correlate subsurface stratigraphy, to identify zones ofwater inflow, and to identify fractures in the bedrock. Bore-hole logging will commence in the cored wells so that spon-taneous potential (SP) gamma-gamma ray, caliper, and resis-tivity log deflections can be exactly correlated to rock types.The gamma-gamma or the SP/resistivity logs will then be run inselected non-cored bedrock wells so that a correlation of thesubsurface geology can then be mapped. In addition to theSP/resistivity/gamma-gamma/caliper logs, a temperature log willalso be run in the bedrock wells. Those logs will identifyzones of different water inflow. Finally, a borehole TV logwill be taken to record the general condition of the annulus,to view fractures, and to give a cross-correlation with the SP/resistivity logs of the wells. In addition to the new wells,selected existing wells may also be logged.

It is currently anticipated that .existing wells that can phys-ically be or that are permitted to be accessed will have bore-hole geophysics run. The exceptions will be:

• Where permission to log cannot be obtained.

• Where access is impossible i.e., in a basement orunder a concrete slab (MOS MW-11).

• Where damage to the well or damage to the pump or sup-port wiring is probable.

• Where physical entry is impossible (e.g., casing col-lapse as in MOS MW-14).

• Where logging would interfere with a public water sup-ply.

4.5.7 Subtask 4.7 — Test Wells (Hydro logic)* fl R 3 0 0 I k 1

The hydrologic testing of wells will be used to determine therelative transmissivity of the formation in the site area andto determine the interconnection of water-bearing zones in the

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vicinity of the site. Groundwater flow is currently antici-pated to be predominantly influenced by fractures. Other lith-ologic discontinuities are possible, however, not probable,given the existing data and previous studies by Rima, et al.,1962 and Newport, 1971. As stated in Section 2, the StocktonFormation is currently considered a dual-porosity system.

Hydrologic testing will include packer testing of zones of in-terest. Water will be injected into the zone between packers,and the rate of pressure decline will be used to estimate thetransmissivity. If the decline curve is extremely steep, thezone that is packed-off probably represents a fractured sec-tion. The zone or zones selected for packer testing will bebased upon drilling results, water inflow, and borehole geo-physical testing. The selection of these zones in each wellwill be made in the field.

4.5.8 Subtask 4.8 — Survey Wells

The exact geographic location and elevation of every well andpiezometer will be surveyed to provide an accurate database forgroundwater modeling. New and existing wells will be surveyedto 0.01 foot. After installing the new monitor wells, a licen-sed surveyor will survey the locations and elevations to alocal bench mark. Those locations and elevations will then beused for mapping site data.

4.5.9 Subtask 4.9 — Sample Wells (First Round)*

After the new wells have been installed, developed, logged, andtested, they will be outfitted with dedicated sampling devices(e.g., bladder pumps). Those devices will prevent cross-con-tamination between wells and will ensure consistency in subse-quent sampling efforts.

All newly installed wells and wells included in the residentialwell sampling program (Subtask 5.3) will be sampled. It iscurrently anticipated that up to two sampling rounds will becollected and analyzed. Each round will be in a different sea-son, i.e., wet season or dry season, to determine possiblevariations influenced by seasons. Prior to collecting a sample,a suitable volume (e.g., three to five well volumes) of wellwater will be purged. Samples will be collected in duplicate in40-ml glass vials, coded, and transported within 12 hours ofcollection to WESTON's analytical laboratory in Lionville,Pennsylvania. The temperature, pH, and specific conductance ofthe well water will be measured in the field.

Specific protocols for groundwater sampling and testing will bespecified in the RISOP.

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4.5.10 Subtask 4.10 — Analyze Water Samples*

The groundwater samples collected during Subtasks 4.9 and 5.3will be analyzed for VOCs using Method 601. Those data will bevalidated during Subtask 6.1. Should the TCL/TAL analyses ofsoil samples show positive results for additional contaminants,a re-evaluation will be made of the groundwater sampling andanalysis program to include an appropriate number of TCL/TALanalyses. Should the soil sampling show only VOC contamina-tion, future sampling rounds will analyze only for VOC contami-nants .

Specific protocols for sample analysis and validation will bespecified in the RISOP.

4.5.11 Subtask 4.11 — Sample Wells (Second Round)

A second round of well sampling will be completed after a per-iod of approximately 90 days to quantify conditions during adifferent season. The sampling procedures will be the same asSubtask 4.9.

This sampling round will include wells in Subtask 4.9.

4.5.12 Subtask 4.12 — Analyze Groundwater Samples*

The groundwater samples collected during Subtask 4.11 will beanalyzed for VOCs using Method 601. Since the analyses ofsamples collected under Subtask 4.9 and 5.3 will have beenvalidated, no validation will be conducted under Subtask 4.12.

4.6 TASK 5 — RESIDENTIAL WELL SAMPLING

Task 5 represents the continuation of the quarterly residentialwell sampling program initiated in 1985. Descriptions of thenext three groundwater sampling rounds are described here toshow how the data will be integrated into the RI/FS.

4.6.1 Subtask 5.1 — Sample Residential Wells

The November 1988 round of residential well sampling tested 21wells and included monitor and supply wells, along with resi-dential wells. They were sampled and analyzed using proceduresto be documented in the RISOP. All residential and supply wellswere checked for routes of entry in order to take water levelmeasurements. Water levels were measured wherever possible. Nofurther sampling will be conducted until EPA approves the sam-pling methodology.

Samples were delivered to WESTON's laboratories and analyzedfor volatile organic compounds using a gas chromatograph (Meth-

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4.6.2 Subtask 5.2 — Sample Residential Wells

The anticipated November 1989 round of residential well sam-pling will include the same wells sampled during prior samplingrounds. Water elevations will be collected from residential andsupply wells wherever possible. Selected residential and supplywells with treatment systems will have their effluents sampledin addition to the influent (groundwater) as a check of the ef-ficiency of the treatment program. Samples will be obtained inthe same manner as the prior two rounds and will be analyzedusing a gas chromatograph (Method 601). Data from this roundwill be validated during Subtask 6.1.

4.7 TASK 6 — DATA EVALUATION

Task 6 consists of activities related to the verification, com-pilation, evaluation, and interpretation of data collected dur-ing Tasks 1, 2, 4, and 5. Key activities in Task 6 include therisk assessment and groundwater modeling.

4.7.1 Subtask 6.1 — Validate Sample Analyses*

Analytical results will be reviewed by senior analytical per-sonnel for reasonableness and validity, as well as to ensurethat the required quality control procedures were followed.Validation procedures will be included in the QAPP.

4.7.2 Subtask 6.2 — Re-Evaluate Groundwater Model*

Upon obtaining the results of the well sampling, soil-gas sur-vey, and soil sampling programs, the groundwater model will berecalibrated using the newly obtained data. Those data will in-clude the water elevations from all monitor wells, updated VOCconcentrations in the monitor wells, and the geologic logs fromthe Subtask 4.5 wells.

While the original model was used to help determine monitorwell locations, the re-evaluated model will more precisely rep-resent the aquifer properties and will be used to conduct a fi-nal risk assessment and to establish possible locations forgroundwater recovery systems.

It is currently anticipated that MODFLOW coupled with MOC orwith AT123D, TRAFRAP, or SWIFT2 will be used to model thegroundwater flow system.

4.7.3 Subtask 6.3 — Conduct Risk Assessment*

A risk assessment will be conducted to establish the extent towhich contaminants present on (or originating from) the sitemay present an imminent and substantial danger tf 9 ftftej ci>blichealth and welfare and/or the environment. It will H-ndrTsae a

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selection of contaminants of potential concern, identificationof exposure concentrations and pathways, a toxicity assessment,a comparison of projected concentrations to ARARs, and a char-acterization of potential risk to human or environmental recep-tors .

4.7.4 Subtask 6.4 — Set Response Levels*

Based upon the risk assessment, CSG will propose responselevels based on ARARs and risk levels estimated from the riskassessment for contaminants in soil and groundwater. Any con-tamination above those levels will trigger the need for remedi-al action and will be addressed in the feasibility study. Theproposed response actions and remedial alternatives will be thesubjects t)f the meeting described as Subtask 7.1.

4.7.5 Subtask 6.5 — Develop Remedial Alternatives*

Based on the nature and extent of contamination and on the re-sponse levels, CSG will develop a list of remedial alterna-tives. They will include, if possible, treatment/disposal at anoff-site facility, attainment of ARARs, exceeding ARAR require-ments, non-attainment of ARARs but protective of human healthand the environment, and no action. The list will be as exten-sive as practical.

4.8 TASK 7 — FEASIBILITY STUDY

Task 7 includes the engineering evaluation of appropriate reme-dial alternatives and the preparation of the RI/FS report.

4.8.1 Subtask 7.1 — Meet with EPA to Discuss FS*

Prior to the detailed evaluation of remedial alternatives, CSGwill meet with EPA to discuss potential remedial alternatives.The purpose will be to agree on which alternatives merit fur-ther consideration, which should be dropped, and which, if any,EPA would want added. The outcome of that meeting will be usedto establish a list of the remedial alternatives that CSG willevaluate, both through screening and detailed analysis, duringthe FS.

4.8.2 Subtask 7.2 — Evaluate Remedial Alternatives*

CSG will conduct a detailed review of the remedial alternativesbefore drafting; the RI/FS report. That review will include aninitial screening based on cost, technical feasibility, andeffectiveness. For those alternatives that remain, CSG willconduct a detailed analysis, as required under 40 CFR 300.68.The analysis will consider factors such as demonstrated relia-bility of the process, the likelihood of achieving* f I *

rcels, ease and cost of operation and maintenancavailability, and capital cost.

4-194056B

4.8.3 Subtask 7.3 — Prepare RI/FS Report*

CSG will prepare a draft report that documents the results offield work and that presents the risk assessment and the evalu-ation of remedial alternatives. The report will include calcu-lations, assumptions, analytical results, and cost estimates.The focused feasibility study noted under Task 3 will also beincorporated into the document.

4.8.4 EPA Review of Draft RI/FS Report*

EPA will review the draft RI/FS report and will issue commentswithin 60 calendar days.

4.8.5 Subtask 7.4 -- Revise RI/FS Report*

CSG will revise the RI/FS report to address EPA's comments.CSG will make an initial screening of the comments and willcontact EPA if any clarifications are required. The reportwill then be revised in accordance with EPA's comments and willbe re-issued within 45 calendar days of its initial receipt.

4.8.6 EPA Review of Revised Report*

EPA will review the revised report to ascertain that all com-ments have been satisfactorily addressed. That review will beaccomplished within 30 calendar days.

4.8.7 Public Comment Period*

Following EPA's review of the revised RI/FS report, EPA willissue it for public comment. EPA will take the lead on thepublic comment period and public meeting. The public commentperiod will be 20 calendar days.

4.8.8 Subtask 7.5 — Prepare for Public Meeting*

CSG will attend a public meeting where the findings of the re-port will be presented. Prior to the public meeting, CSG andEPA will meet to discuss the roles each organization will playin the meeting.

AR300I524-20

4056B

SECTION 5

SCHEDULE AND REPORTING

5.1 RI/FS SCHEDULE

The schedule for completing the activities described in Section4 has been forecast to extend approximately 34 months from theexecution of the Consent Order (29 July 1988). Figure 5-1 is aGANTT chart depicting that schedule.

The GANTT chart depicts anticipated start and finish dates foreach activity described in Section 4 as well- as their durationand slack. Duration is expressed in terms of working days(i.e., calendar days without weekends and holidays; 20 workingdays are approximately equal to 30 calendar days). Slack isthe number of working days that the initiation of the activitycan be delayed without delaying the overall project schedule.Activities with no slack are termed critical-path activities,because any delay in those tasks will result in an equal delayin the overall project. Delays in activities that do not fallon the critical path will not affect the overall project sche-dule as long as the delay is less than the slack.

To expedite the completion of RI activities, EPA and CSG haveagreed to undertake certain tasks prior to EPA's approval ofthe Work Plan and the RISOP. Activities scheduled to beginafter the submission of the Work Plan but before the completionof EPA's 60 calendar day review period are:

Subtask 1.2 — Assess Existing WellsSubtask 1.3 — Evaluate Fracture TracesSubtask 1.4 — Evaluate Historical Aerial PhotographsSubtask 1.6 — Collect Water Level MeasurementsSubtask 1.8 — Quantify Site Model

Subtasks 1.3, 1.4, and 1.6 will form part of the basis forSubtask 1.8. Subtasks 1.2 and 1.8 will then be used to developthe RISOP (Subtask 1.9).

Subtask 1.11 (Prepare Base Maps) is scheduled to start in lateApril so that the aerial survey can begin after the winter snowcover disappears and finish before foliage obscures land con-tours.

The schedule presented in Figure 5-1 takes into account many ofthe problems commonly encountered during RI/FS work. Unantici-pated events that may upset this schedule include:

AR300I53

5-14113B

• Access — Refusal of permission to work on adjoiningproperties and/or to utilize wells owned by others mayrequire revision of the site investigation plan ordelay its implementation schedule.

• Subcontractor Availability — Depending on the type ofdrilling required, it may be difficult to schedule adrilling subcontractor who fulfills the requirementsof the Health and Safety Plan.

• Equipment Malfunctions — Breakdowns in drilling orfield testing equipment may delay implementation ifrepairs or replacement cannot be effected expeditious-iy-

• Weather — Long-term weather anomalies may delay fieldtasks; short-term delays can be incorporated into- theexisting schedule.

• Reviews and Meetings — Reviews and meetings are typi-cally critical-path activities. Consequently, it willbe essential to schedule those events well in advance.

For the most part, the duration specified for an activity rep-resents a reasonable average duration based on experience withsimilar RI/FS projects. The activity with the greatest degreeof uncertainty is Subtask 4.5 (Install New Wells). Currently,Subtask 4.5 is scheduled to take 40 working days (approximately2 calendar months) which should be sufficient, considering typ-ical field contingencies.

As part of the focused feasibility study, it may be advisableto conduct a pilot test of an ISV system, Subtasks 3.3 and 3.4are optional tasks for planning and implementing such a test.As long as the total duration of the two tasks does not exceedapproximately 130 calendar days, the overall project schedulewill not be affected. However, if permits are required for thetest, the application and approval process may result in a sig-nificant delay.

5.2 REPORT ING

After EPA's approval of the RISOP, monthly progress reportswill be prepared and submitted by the tenth day of the follow-ing month. Progress reports will consist of:

• Activities conducted during the reporting period.

• Field data items collected (raw data will be attachedto the reports as they become available).

AR300I5I45-3

4113B

• Problems encountered or anticipated.

• Activities planned for the following month.

• Revisions to the project scope or schedule.

RR300155

5-44113B

REFERENCES

Berg, T.M., W.E. Edmunds, A.R. Geyer, et al., 1980, GeologicMap of Pennsylvania, Pennsylvania Geological Society, 4thseries, Map 1.

Doull, J., Klassen, C.D., and Amur, H.O., 1980. Casareff andDoull's Toxicology: The Basic Science of Poisons, 2nd Edition.MacMillan Publishing Co., New York, NY.

Hall, G.M., 1934, Groundwater in Southeastern Pennsylvania,Pennsylvania Topographic and Geologic Survey Water Resource Re-port, W2, 255 pp.

King, S., 1987, Commodore Semiconductor Group Proposed Listingof Site on National Priorities List, 15 pp.

Longbottom, J.E. and Lichtenberg (eds.), 1982. Methods for Or-ganic Chemical Analysis of Municipal and Industrial Wastewater.1982.

Newport, T.G. Groundwater Resources of Montgomery County, Penn-sylvania, Topographic and Geologic Survey Bulletin, 1971, W-29,83 pp.

•«

NUS Corporation, Superfund Division, October 30, 1985, SiteInspection of Valley Forge Corporate Center, Prepared under TDDNo. F3-8312-06 EPA No. PA-1431, attachments.

Rima, D.R., H, Meisler, and S. Longwill, 1962, Geology and Hy-drology of the Stockton Formation in Southeastern Pennsylvania,Topographic and Geologic Survey Bulletin, W-14, ill pp,

SMC Martin, Inc., July 1984, Investigation of TCE Contaminationat the Commodore/MOS Technology, Inc. Facility Site, Audubon,Pennsylvania, 59 pp. and appendicies. Ref: 8943-040-940 40.

SMC Martin, Inc., October 1986, Groundwater Investigation ofthe Commodore/MOS Technology Site, Norristown, Pennsylvania, 78pp. Ref: 8816-040-26016.

SMC Martin, Inc., December 1987, Results of Ground-Water Man-agement Program Third Quarter Sampling, October 1987, 5 pp. andattachments.

SMC Martin, Inc., September 1987, Results of Ground-Water Man-agement Program Third Quarterly Sampling, July 1987, 4 pp. andattachments.

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