SFUND RECORDS CTR

2085609

Aerojet Site

Field Sampling Plan for

Validation of the Johnson and Ettinger Model

Prepared by

Aerojet

Sacramento, California

June 2005

SR10119861

Table of Contents

1.0 Introduction 1

1.1 Purpose 1

1.2 Areas of Responsibility 1

1.3 Statement of Problem 2

2.0 Background 2

2.1 Site Description 3

2.2 Operational History 3

2.3 Previous Investigations 4

2.4 Hydrogeology 4

3.0 Project Data Quality Objectives 5

3.1 Project Objectives 5

3.2 Decision Statement 5

3.3 Input Parameters 6

3.4 Data Review and Validation 6

3.5 Data Management 6

3.6 Assessment Oversight 7

4.0 Sampling 7

4.1 Sample Collection 7

4.2 Sampling Locations 8

4.3 Field Methods 8

5.0 Schedule 10

6.0 References 11

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List of Tables

Table

3-1 Methods TO-14A and 8021B Detection Limits

4-1 Sampling Locations

5-1 Schedule to Conduct Validation of the Johnson & Ettinger Model

List of Figures

Figure

2-1 Study Area Map

2-2 Well Locations

2-3 Layer B Potentiometric Surface Map April 2004

2-4 Layer C Potentiometric Surface Map April 2004

2-5 Layer B TCE Isoconcentration Contours 2000-2005

2-6 Layer C TCE Isoconcentration Contours 2000-2004

2-7 Hydrostratigraphic Cross Section A - A'

4-1 Proposed Sample Locations

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1.0 Introduction

This Field Sampling Plan (FSP) is submitted as a RemedialInvestigation/Feasibility Study (RI/FS) deliverable pursuant to the Aerojet SitePartial Consent Decree (PCD) to the United States Environmental ProtectionAgency (EPA), the California Regional Water Quality Control Board (RWQCB),and the California Department of Toxic Substances Control (DTSC). This Planresponds to the US EPA letter dated 16 November 2004 requesting a Tier 3 Site-Specific Pathway Assessment for the lands downgradient of the Central DisposalArea (CDA) and to the Agency comments received on the February 2005, "FinalPerimeter Groundwater Operable Unit RI/FS" (PGOU RI/FS).

The vapor intrusion pathway has been identified as a potentially completepathway at this site. The vapor intrusion model developed by Johnson andEttinger (1991) is frequently used to evaluate this pathway. However, for a Tier 3Site-Specific Pathway Assessment, a combination of site measurements andmodel predictions using the Johnson & Ettinger model (J&E model) will be usedto estimate potential risks due to the vapor intrusion pathway. The data collectedpursuant to this FSP may be used to characterize the vapor intrusion model inputassumptions.

1.1 Purpose

This document describes the sampling, analysis, and reporting tasks Aerojet andits contractors will conduct for a site-specific validation of the J&E model. Thepurpose of this evaluation is to assess the efficacy of the model to predictsubsurface contaminant vapor migration incorporating Aerojet site conditions andsupport its application to evaluate potential vapor intrusion from volatile organiccompounds in groundwater at the Aerojet site. Once the validation has beencompleted and Aerojet has received Agency approval of the validation, Aerojetwill conduct the Tier 3 site-specific vapor intrusion pathway evaluation requestedfor the lands downgradient of the Central Disposal Area. Once validated, Aerojetwill also use the J&E model, in concert with available soil-vapor and groundwaterdata, to respond to Agency comments on the PGOU RI/FS as well as to conductthe evaluation of vapor intrusion from VOCs in groundwater during the sourcearea operable unit RI/FS'.

1.2 Areas of Responsibility

This project is being conducted by Aerojet and its contractors. In accordancewith the provisions of the PCD, the project will be overseen by EPA, DTSC, andRWQCB personnel. The following table lists the project personnel and areas ofresponsibility:

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EPA Project Manager (PM) Charles Berrey EPA ReviewRWQCB PM Alex MacDonald RWQCB ReviewDISC PM Ed Cargile DISC ReviewAerojet PM Cindy Caulk Project ManagerAerojet technical Steve Costello Coordinate field activities,

Aerojet QA ManagerConsultant GeoSyntec Robbie Ettinger Vapor intrusion pathway

evaluation and technicalanalysis of data

Consultant ERM Bruce Lewis, et. al., Perform field workConsultant LDC TBD Third Party Quality

AssuranceLab TBD Vapor analysisLab Aerojet Analytical Lab Water analysisSoils Lab Youngdahl & Assoc Soil physical properties

Analysis

1.3 Statement of Problem

The vapor intrusion pathway has been identified as a potentially completepathway at this site. This exposure pathway considers the volatilization ofchemicals from soil and/or groundwater and migration to a building near theground surface. Structures in areas far removed from contaminant sources couldhave potential risk to indoor from volatile contaminants contained in theunderlying groundwater or new structures could be constructed over existingsource areas. Potential future exposures due to vapor intrusion are typicallyevaluated through modeling. However when site-specific model inputs result invapor intrusion attenuation factors significantly different from screening-levelvalues, DTSC and USEPA guidance (DTSC, 2005 and USEPA 2002)recommend additional data collection and analysis to evaluate the validity of thesite-specific values used in the modeling. This additional analysis reduces theuncertainty in the vapor intrusion risk estimates resulting from the site-specificmodeling.

2.0 Background

By USEPA letter dated 16 November 2004 the Agencies notified Aerojet theyhad used the J&E model as a tool to evaluate potential indoor air quality basedon groundwater concentrations of trichloroethylene in two monitoring wellslocated within the CDA. The results of the Agency evaluation concluded that theJ&E model predictions exceeded acceptable indoor air risk levels for future slab-on-grade construction. Accordingly, the Agencies requested a Tier 3 reviewemploying statistically significant soil-vapor sampling data.

In addition, on 15 February 2005 Aerojet submitted the Perimeter GroundwaterOperable Unit Remedial Investigation/Feasibility Study (POOL) Rl/FS, CV'EI,

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2005). In their letter of 14 April 2005, the Agencies transmitted comments on theJ&E modeling done as part of the RI/FS and requested site-specific validation ofthe J&E model assumptions and attenuation factors. On 26 May 2005 Aerojetand the Agencies met and agreed (1) that Aerojet would validate the J&E modelwith data collected from the lands downgradient from the CDA, (2) Aerojet wouldconduct the Tier 3 site-specific vapor intrusion pathway evaluation requested forthe lands downgradient of the Central Disposal Area (3) the results of the J&Evalidation would be incorporated into modifications, as necessary to the PGOURI/FS, and (4) the validation study would support the future use of the J&E modelin the remaining source area OU RI/FS'.

2.1 Site Description

The lands downgradient of the CDA include undeveloped land and paved parkingareas, portions of which remain part of the Aerojet Superfund site (approximately20 acres) and portions of which were removed from the Aerojet Superfund site asthey were buffer lands on which no industrial activity had occurred. Historicaldredging activities were conducted on portions of the CDA and on a small part ofthe southern and most of the northern portion of the lands downgradient of theCDA. Figure 2-1 shows the extent of dredging activities in the area.

The CDA was historically used by Aerojet to dispose of waste generated throughindustrial processes. The shallow VOC plumes that originate in the CDA migratenorthwestward.

For the purposes of this plan, the term "site" includes all of the landsdowngradient of the CDA. Since Aerojet wishes to validate the model to dredgedand undredged soil types, some sampling locations will be located on the CDA.For that reason, background information for the CDA is also presented below.

The lands downgradient of the CDA, which have been owned by Aerojet sincethe early 1960's, consist of flat undeveloped land and paved areas. A railroadspur is present extending from the northern to the southern portions of the siteand extending along the southern portion of the non-Superfund land. The land tothe east, north, and west consists of additional buffer land, buildings used foroffice and light industrial, and open land. The CDA is located to the south and isundeveloped land.

2.2 Operational History

The central disposal area was used by Aerojet for disposal of inert solid waste,septage waste, and tar as well as for chemical waste burning.

The western portion of the CDA and the northern portion of the landdowngradient of the CDA were dredged for gold during the early 20th century(Figure 2-1). The dredging operation removed sediments from ahead of the

SR10119861

dredge, separated gold by washing with water, and redeposited the spoils behindthe dredge. Finer materials (less than approximately 0.375 inch) weredischarged off the stern of the dredge through a tail sluice while a mix of finesand coarser materials was discharged approximately 150 to 175 feet behind thestern by a stacker conveyer.

2.3 Previous Investigations

The Aerojet Superfund site was first investigated during the 1980s as part of theinitial site investigation (Aerojet Site-Scoping Report, ICF, 1989) and later as apart of the Remedial Investigation (Rl) for the Aerojet Site (Stage 1 RI/FS Report,ICF, 1993). Within the CDA, the focus of these investigations was on thelocation of the potential source sites. Four of the monitoring wells (Wells 3015-16, 3054, and 3468) installed during the course of investigating the CDA are inlands included in the study area (Figure 2-2).

The current aquifer designations were developed during the latest Zone 1Groundwater Extraction and Treatment Evaluation (GET D EffectivenessEvaluation Report, Aerojet, 1992). As part of the 1992 evaluation, Aerojetinstalled eight monitor wells and three extraction wells (Well 4385, 4440, and4445) in the center of the VOC plume within the study area, downgradient of theCDA, to investigate and capture the TCE migrating northwestward. Theextraction wells were not operated due to the presence of perchlorate.

Currently, Aerojet is operating a demonstration project near Well 4440 toevaluate in-situ perchlorate treatment. Fourteen additional monitor wells and twotreatment wells have been installed to characterize, remediate, and monitorremediation as part of that ongoing project.

The investigation of the non-Superfund lands downgradient of the CDA wasreported in the Final Site Assessment Report for the Candidate Carve-Out Lands(ERM, 2000). The aquifer unit designations were recently refined in the PGOURI/FS (CVEI, 2005)

2.4 Hydrogeology

Previous investigations of the Aerojet site have divided the sediments intomultiple hydrostratigraphic layers labeled A through F. Each hydrostratigraphiclayer is comprised of relatively permeable sediments with similar geologic andhydrogeologic properties that are separated by layers of sediments that are ofrelatively lower permeability. The uppermost groundwater in the site has beendesignated as layer B in the PGOU Rl. Eight monitor wells are completed inLayer B in or near the lands downgradient from the CDA and seven in the CDA.The Agencies' evaluation included data from wells in Layer C since those datarepresented the shallowest water monitored in the area. For that reason,information from Layer C is also discussed below.

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In Layer B, the depth to groundwater ranges from less than 30 feet toapproximately 35 feet below ground surface. The groundwater gradient in LayerB is northwest at 0.01 feet per foot in the lands downgradient of the CDA and0.02 feet per foot under the CDA (Figure 2-3). In Layer C, the gradient isnorthwest at 0.025 feet per foot under the CDA and varies from 0.01 feet per footin the southern portion of the lands downgradient of the CDA to approximately0.003 feet per foot in the northern portion (Figure 2-4). The flattening of thegradient in the north is due to recharge of treated groundwater from the GET Dfacility, which enters Layer C through recharge wells located northwest of thesite.

As previously mentioned, there is a VOC plume within the groundwater migratingfrom the CDA toward GET D. Figures 2-5 and 2-6 show the extent of TCE,which is the most prevalent VOC, in Layers B and Layer C, respectively. Thehighest concentrations of TCE in Layer B groundwater are detected in the CDAat Wells 3456 and 3623 (3,100 and 680 ppb, respectively, in 2004). Under thelands downgradient of the CDA, the highest concentrations of TCE are detectedat Wells 3628 and 3632 (47 and 78 ppb, respectively, in 2003). During the sameperiod, TCE at 14 ppb was detected in Well 3631, which monitors shallowergroundwater at the same location as 3632.

As the plume migrates to the northwest, it also migrates downward. Figure 2-7 isa cross section that illustrates the downward migration of TCE with bothpotentiometric data (presented as equipotential contour lines) and chemical data(presented as isoconcentration contours). This cross section is drawn roughlyparallel to the chemical plume flow direction and extends from the CDA to thecentral portion of the study area, where no TCE was detected in the shallowestgroundwater. The downward component of groundwater flow is greater in theCDA but is present throughout the study area. The TCE concentration dataindicate that the VOC plume deepens as it migrates away from the CDA.

3.0 Project Data Quality Objectives

3.1 Project Objectives

The primary objective of this field sampling effort is to collect sufficient soil vaporand groundwater data to assess the validity of the site-specific application of theJ&E model. Soil vapor and groundwater samples will be collected and analyzedfor volatile organic compounds (VOCs), and soil samples will be analyzed forphysical properties. The VOC analysis of the soil vapor and groundwatersamples will be used to characterize the soil vapor concentration profiles atvarious locations around the site. The model will be run to predict soil-vaporconcentration profiles using shallow groundwater concentrations and soilphysical properties. These modeled results will be compared to measured soil-

SR10119861

vapor concentrations collected during this study to evaluate the model validation.This model validation evaluation will support the application of the J&E model infuture soil-vapor intrusion risk assessments at the Aerojet site.

3.2 Decision Statement

If this evaluation demonstrates that the J&E model adequately predicts the soilvapor concentration profile, the model will be used in the RI/FS to evaluate thepotential for vapor migration from VOCs in groundwater at the Aerojet site.

3.3 Input Parameters

Soil Vapor. Soil-vapor samples will be collected at multiple depths during drillingto provide a profile at each location. In order to reduce any uncertainty regardingdata quality due to drilling influences, semi-permanent vapor sampling ports willbe installed. Soil-vapor samples will be analyzed using method TO-14A. Theanalysis will target Freon-113, chlorinated ethenes, and chlorinated ethanes asthese are contaminants potentially present in soil vapor above the plumeemanating from the CDA. Table 3-1 lists the method TO-14A detection limits forthe analytes in this study.

Groundwater. Samples of groundwater will be collected just below first water.The samples will be analyzed at Aerojet's laboratory using method 8021B for theanalytes listed on table 3-1. Groundwater samples will also be collected from theexisting multiple-completion monitoring wells following Aerojet StandardOperating Procedures for groundwater samples.

Soil. Soil samples will be collected and analyzed for physical properties. Theproperties that will be reported are depth, soil moisture content, dry bulk density,organic carbon fraction, and grain size.

3.4 Data Review and Validation

Aerojet will submit 10 percent of the analytical data to their Quality Assurance(QA) consultant for Level 3 data validation. If any irregularities arise, thesepackages will be upgraded to level 4 and an additional 10% of the data will bereviewed at Level 4.

3.5 Data Management

All samples for physical or chemical analysis will be labeled after collection withthe location, date, time, depth interval, unique sample identification, requestedanalysis, and sampler's initials. The sampler will record the sample informationon a chain of custody form, which will remain with the samples at all times.Additional information for soil-vapor samples includes ambient air temperature,well air volume, purge volume, purge time, purge rate(s) sample volume, and

SR10119861 8

flow rate during sample collection. The sampler will also record the samplinginformation in a bound notebook with sequentially numbered pages for futurereferral. The notebook will also describe weather conditions, irregularities withsampling procedures, if any, and any sampler's comments. If the sample iscollected during drilling, the sample interval will be noted on the boring log withits unique sample identification and sampling media. The sampling notebook willbe utilized for repeat measurements made at semi-permanent vapor monitoringlocations.

The Laboratories utilized are audited in accordance with Aerojet's SitewideQuality Assurance Project Plan (QAPP) (Aerojet, 2004).

3.6 Assessment Oversight

The Aerojet QA manager will be present for the initiation of the project work andwill visit the site periodically as field work progresses. The field locations arewithin a mile of the Aerojet Site Remediation offices so the Aerojet QA managercan easily respond should a question arise. The Aerojet QA manager has theauthority to recommend modifications to the planned work during field work tomaintain work progress. Whenever possible, the Aerojet QA manager willattempt to resolve any question using the guidelines within this document,Aerojet's QAPP, and general industry standards. The agencies will be notified ofany change to the proposed work in this plan if any changes are made. If theAerojet QA manager determines that a proposed deviation of the workplan mayaffect data quality or usefulness, he has the authority to suspend field workpending consultation with at least one Agency representative.

4.0 Sampling

4.1 Sample Collection

Aerojet proposes to collect up to 28 undisturbed soil samples for physicalanalysis and up to 14 shallow groundwater samples for chemical analysis. Thesamples will be collected from 7 boreholes within dredged sediments and 7boreholes within undredged sediments.

Each borehole will be converted to a semi-permanent soil-vapor sampling wellwith up to five sampling ports at different depths per location. Aerojet will collecta sample from each location after at least one week of equilibration followinginstallation. The need for any additional soil vapor sampling will be determinedfollowing evaluation of the initial results.

Additional groundwater samples will be collected from monitor wells 42, 48, 3398and 3631 to obtain updated information at those locations.

4.2 Sampling Locations

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Six sampling locations are proposed to be installed within the dredged material inthe CDA and southern portion of the lands downgradient of the CDA near thehigher concentrations of TCE in Layer B. One sampling location is proposed tobe installed within the dredged material in the northern portion of the landsdowngradient of the CDA near an existing Layer B well where low concentrationsof TCE have been detected historically.

Five sampling locations are proposed to be installed in undredged materialaround the northern most dredged portion of the CDA near the higherconcentrations of TCE in Layer B. Two additional locations are proposed inundredged material that is downgradient and above the TCE plumes depicted inFigures 2-5 and 2-6 near existing Layer B wells where low concentrations of TCEhistorically have been detected.

The sampling locations are shown on Figure 4-1 and listed in Table 4-1. In theevent that the field crew is unable to access a proposed location, four alternatesites (two in dredged and two in undredged material) are also located on Figure4-1 and listed on Table 4-1.

4.3 Field Methods

Boreholes will be advanced using sonic drilling technology. During drilling,continuous core will be collected for lithologic logging and to select depths forsoil-vapor probe installations. Soil samples of undisturbed sediment will becollected ahead of the borehole using a modified California sampler or similar,fitted with brass liners at the approximate depths indicated on Table 4-1. Soilsamples will be collected in brass cylinders, capped and taped upon retrieval,placed in a Ziploc bag, and stored in a chilled cooler for transport to ageotechnical laboratory.

If an attempt at collecting a soil sample is unsuccessful, the hole will beadvanced an additional 5 feet and another attempt will be made to collect a soilsample. After a sample is successfully collected, the crew will collect the nextsample at the proposed sampling depth. If field experience shows that samplerecovery in one depth range is difficult, the proposed sampling depth atremaining boreholes may be modified to compensate.

Each borehole will be advanced to groundwater and a shallow groundwatersample will be collected utilizing a Hydropunch sampler, or similar device. If anattempt at collecting a shallow groundwater sample is unsuccessful, the hole willbe advanced an additional 3 feet and another attempt will be made to collect agroundwater sample. If the second attempt is unsuccessful, the drilling casingwill be raised 1 to 2 feet to allow water to enter the borehole. The water will bebailed with a high capacity bailer to remove as much of the suspended materialas possible. Within the uppermost groundwater, it may not be possible to clarify

SR10119861 10

the water, but an attempt will be made to develop the hole as much as possibleprior to collecting a sample.

After reaching groundwater, the field geologist will select zones for soil vapormonitoring. If subsurface conditions permit, semi-permanent vapor wells will belocated near the uppermost portion of a permeable zone just below impermeableor lower permeability material. If that situation is not readily identified, thegeologist will select permeable material to monitor using Table 4-1 as a guide.

Each soil-vapor monitoring well will be constructed of %-inch diameter tubingextending from the monitored zone to the surface. At the monitoring zone, eitherthe tubing will be perforated in the field with a drill and covered with fine mesh ora commercially available vapor sampling products will be used. A 1-inchdiameter flush-joint threaded PVC pipe will be used to support the tubing duringconstruction and assure that the tubes are placed according to design. Thetubing will be fastened to the PVC pipe with zip ties. The screened end of thevapor monitoring well will be attached to the PVC pipe at the designed interval.At the time the screen is placed, the %-inch diameter tubing will be cut 3 to 5 feetlonger than the designed length and the top of the tube will be labeled with themonitored depth interval using a permanent marker.

At each monitored zone, the bore hole will be backfilled with up to one foot ofclean sand placed on 6 inches of granulated bentonite, which will be hydratedafter emplacement. A 6-inch layer of fine sand (#60) will then be placed on top ofthe filter pack. A 6-inch layer of granulated bentonite will be placed on top of thefine sand and hydrated. The intervals below, above and between eachmonitoring zone will be sealed with a thick hydrated-bentonite slurry. Allmaterials will be placed by tremmie.

The PVC pipe will extend approximately 2 feet above the ground surface and thevapor-port tubes will extend at least 1 foot beyond the PVC pipe. Each tube willbe fitted with a'T" fitting; each end of the fitting will be sealed with a threaded capto prevent direct venting to the atmosphere. A steel locking cover will be placedover the above-ground portion of the well to protect it from the elements andwildlife.

After installation, each vapor port will be purged of at least 10 well volumes. Onewell volume shall be calculated to include 40 percent pore space for the filter-pack interval as well as the tubing length. The purging will be accomplishedutilizing a portable vacuum pump fitted with a flow controller calibrated to 100ml_per minute. During the purging, the vacuum response in the other collocatedvapor ports will be monitored to test the seal between probes.

A sample will be collected after allowing the vapor well to recover from drillingeffects for at least one week. A portable vacuum pump with a flow restrictor andcontrol valve will be attached to one branch of the "T" fitting and a pre-evacuated

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Summa canister provided by the analytical laboratory will be attached to theother branch of the fitting. Each vapor port will be purged of three well volumesprior to sampling using the vacuum pump. After the purging is complete, thecontrol valve to the vacuum pump will be closed and the valve on the summacanister will be opened. The sample flow into the canister is controlled by a flowrestrictor calibrated to 100 ml_ per minute. Immediately following collection, thesample containers will be labeled, placed in a closed container, and recorded ona chain-of-custody record. Samples will be transported to the laboratory daily.

5.0 Schedule

Aerojet proposes to conduct this study in accordance with the schedule providedas Table 5-1. As shown on Table 5-1, once Aerojet receives Agency approval ofthis Field Sampling Plan, it will mobilize and begin fieldwork. Aerojet anticipatesit will submit the validation study report to the Agencies 60 days after receipt ofthe laboratory analytical results.

Once the J&E model validation report is approved, Aerojet will proceed toimplement the results of the validation into the Tier 3 site-specific vapor intrusionpathway evaluation requested for the lands downgradient of the Central DisposalArea and into the PGOU RI/FS. In addition, Aerojet will incorporate the results ofthe J&E model validation into the ongoing source area OU RI/FS'.

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6.0 References

Aerojet-General Corporation, 1992; "Aerojet Site Part 2 GET EffectivenessReport, GET D Evaluation"; December, 1992

Central Valley Environmental, Inc., 2005; "Perimeter Groundwater Operable UnitRemedial Investigation/Feasibility Study"; February, 2005

Environmental Resources Management, INC., 2000; "Final Site AssessmentReport for the Candidate Carve-Out Lands"; July, 2000

ICF Kaiser Engineers, Inc., 1989; "Aerojet Site-Scoping Report and Stage 1RI/FS Work Plan"; ICF Kaiser, December, 1989

ICF Kaiser Engineers, Inc., 1993; "Aerojet Site- Stage 1 Report Zone 1"; August,1993

John, P.C., and R.A. Ettinger, 1991; "Heuristic model for predicting the intrusionrate of contaminant vapors into buildings"; Environmental Science & Technology25, no. 8

U.S. Environmental Protection Agency, 1997-2000; "Spreadsheets for theJohnson and Ettinger Model"; Prepared by Environmental Quality Management,Inc.

SR10119861 13

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LEGEND

Carveout Lands

Carveout Lands with Special Restrictions

Dredged Areas

Scale: 1" = 1000'j

500 1000

Environmental Remediation

FIGURE 2-1

Study Area Map

6/23/05 oh SR10119860

3ttfi2" 108 V:See Detai I

•wvio-o s- -+^r.i i _~-'xr""" 'T^yi -^•4000 "42KW 7%-rOA^4067 ^^4005 ..4001'106

4150415541604165417041,75., .4180 '41854190

W , -™

4225 „<4230 f"f4235 A ;4240 f V4245 |

, 4250 / 14255" 14260* I4265 '; |

___4J

EXPLANATION

KEY TO WELL SYMBOLS

— Well Identification

— Well Type and Location103 -+ -

23.45 - - Groundwater Elevation in FeetIf Blank, No Measurement During Time Period

WELL TYPES

+ Monitor Well

A Extraction Well

V Recharge Well

50 Groundwater Elevation Contour (Feet, MSL)

N

Scale: 1" = 1600'

800 1600

Modified from PGOU Rl Report

Environmental Remediation

FIGURE 2-3

Layer BPotentiometric Surface Map April 2004

6/21/05 ah SR10119855

EXPLANATION

KEY TO WELL SYMBOLS

— Well Identification

— Well Type and Location103 •+ •

23.45- - Groundwater Elevation in FeetIf Blank, No Measurement During Time Period

WELL TYPES

+ Monitor Well

A Extraction Well

V Recharge Well

50 Groundwater Elevation Contour (Feet, MSL)

Consent Decree Boundary

Modified from PGOU Rl Report

488 83.3493497 98.9

1550 98.21551 98.115543090 98.13091 99.53100 83.43101 84.8

3102 87.43104 98.53105 98.53129 99.23137 97.83138 97.83152 103.33153 103.33156 83.63157 83.6

3167 102.43189 99.23190 99.13193 98.03194 98.73199 83.73239 100.43269 98.63315 100.9

3607

4150415541604165417041754180418541904205

eriod

423042354240425042554270

^N

Scale: 1"= 1600'

800 1600

Environmental Remediation

FIGURE 2-4

Layer CPotentiometric Surface Map April 2004

6/21/05 ah SR10119856

4150 2804155 1904160 1004165 494170 734175 234180 184185 414190 5.1

4225 1004230 9.14235 274240 314245 324250 8.24255 684260

ANorthwest

A'Southeast

I

300-1

200-

g 100-

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-200 -1

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,-r ( jf

\

-300

-200

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mo

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-0

--100

331fl4

. 3526-83514-6 3631*3

362830^ 3519

nj oo o

CO r-

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L-200

H

EXPLANATION

0 400Horizontal Scale

V = 400'Vertical Exaggeration: 4X

Scale: 1"= 1000'i i i0 500 1000

Locator Scale

Well DesignationMultiple Completions: Depth Increasesby Ascending Well Number Order

Screened Interval

Total Borehole Depth

Approximate Direction ofGroundwater Flow

April 2004 Potentiometric Contour Line

TCE Isoconcentration Line (2000 to 2005 Data)

Geologic Contact, Dashed where Approximate

Relatively permeable sediments: Silty, poorly andwell-graded sands and gravels (GP,GW,SP,SW);silly and clayey gravels (GM/GC) and silts.Relatively lower permeability sediments:Low plasiticity clays and silts (CL.ML);silty and clayey sand (SM/SC).

Well

34

71'

30093010

3011'

3012

3015

3016"

3026"3027 '":"

3028 7

"3029 ;

30303310

3311 :

3312" :

3313";3314

3444" ;3445 ;

3446 :

"34563514

" 3515 :

3516

3519 :

3523 "i

" 35263527

3528 ;3623 :

"" 3624 :

3628

"" 3629 .

3630

36313632

3633

April 2004

Groundwater

Elevation (msl)

171.99

131.11

139.55 '

129.27

"129.15

135.65

144.04"NM167.24165.78

164.91

154.6179.07

112.7"

113.67115^54

"115.66

111.32142.43 """

138.78"\52.54

149.17

124.45124.03

130.06125.6 "

113.45

114.05114.77

115.47152.01

140.97

NM

"NM

NM

NM

NM

NM

Most RecentTCE Concentration

(ppb)49

":' < to1.279

";"" "" 16 " "NA

: 2400

NA ~NA

; NANA

NA

| NA" : 420

< 0.5' ;" < 0.5

" ^ < 0.5"

; < 1.0

: 260: NA

< 1.0"" " 3100"

12000.78NA""950 ""

: NA' " 3" ~""; < 1.0I NA" "

510""; 68

47

6001200'

". 14

78

650

Environmental Remediation

FIGURE 2-7

Hydrostratigraphic Cross Section A - A'

6/22/05 oh SRI 0119555

LEGEND

Carveout Lands

Carveout Lands with Special Restrictions

T-T- Limit of Dredged Area

• Proposed Sample Location (See Table 4-1)

+ Monitor Well Location

• Chemical Contour Line fag/L) N

Scale: 1"= 1000'|;ivigi!;-i'!»,;

Table 3-1. Methods TO-14Aand 8021B Detection Limits

Analyte

1,1,1 -Trichloroethane1 ,1 ,2,2-Tetrachloroethane1 , 1 ,2-Trichloroethane1,1-Dichloroethane1 ,1-Dichloroethylene1 ,2-Dichloroethanecis-1 ,2-Dichloroethenetrans-1 ,2-DichloroetheneChloroethaneFreon 113TetrachloroethyleneTrichloroethyleneVinyl Chloride

TO-14ADetection Limit

(ppbv)

0.500.500.500.500.500.500.500.500.500.500.500.500.50

8021 BDetection Limit

(ppb)

0.500.500.500.500.500.500.500.500.500.500.500.500.50

Modified MethodTO-14A used for soil vapor samplesMethod 8021B used for groundwater samples

SR10119862 T3-1

Table 4-1. Sampling Locations.

Location

D1D2D3D4D5D6D7

DA1DA2U1U2U3U4U5U6U7

UA1UA2

Estimated Depthto Groundwater

(ft, bgs)

504550505045354540505050404025352540

Default Soil-VaporSampling Depths*

(ft, bgs)

10,20,30,40,5010,20,30,40

5, 25, 455, 15,25,35,45

5, 25, 455, 25, 4510,20,30

10, 20, 30, 4010,20,30,4010,20,30,40

10,20,30,40,505, 15,25,35,45

10, 20, 30, 405, 25, 455,15,2510,20,305,15,25

5,15,25,35

Proposed SoilSampling Depths

(ft, bgs)

25,5020,3010,3035,4535,4525,405, 15TBDTBD

25,4535,5035,4520,3025,405,1510,20TBDTBD

Sampling Rationale

Near High TCE detection at Well 3456Above upgradient plumeNear High TCE detection at Well 3015Above upgradient plumeAbove upgradient plumeNear High TCE detection at Well 3623Near Shallow Well 3398Above upgradient plumeNear moderate TCE detection at Well 34Near High TCE detection at Well 3015Above upgradient plumeAbove upgradient plumeAbove upgradient plumeAbove upgradient plumeNear Shallow Well 3631Near Shallow Well 3398Near Shallow Well 3632Near moderate TCE detection at Well 34

Proposed depth is approximate. Actual depth will be determined based on lithology encountered during drilling.Default depths will be used for locations or intervals with no significant lithology contrast.

SR10119862 T4-1

Table 5-1

Schedule to Conduct Validation of the Johnson & Ettinger Model

Task Task Duration Schedule

Prepare and submit field sampling plan to validate J&E model

Agency review and approval of Field Sampling Plan

Mobilize for fieldwork

Conduct fieldwork

Collect samples

Conduct laboratory analysis

Analyze results, prepare and submit J&E model validation report

Agency review and approval of J&E model validation report

1 month

1 month

1 month

1 month

1 month

1 month

2 months

1 month

26 May - 26 June 2005

27 June - 27 July 2005

1 - 31 August 2005

1-30 September 2005

15 September -15 October 2005

16 September -15 November 2005

16 November -15 January 2006

16 January -16 February 2006

SR10119861.xls6/27/2005

PO Box 13222Sacramento CA 95813-6000

27 June 2005

Mr. Charles Berrey Mr. Alexander MacDonald Mr. Ed CargileU.S. EPA (SFD-7-2) California Regional Water National Priority List Unit75 Hawthorne Street Quality Control Board Northern California-Central CleanupSan Francisco, CA 94105 Central Valley Region Operations Branch

11020 Sun Center Dr. #200 Site Mitigation ProgramRancho Cordova, CA 95670-6114 Department of Toxic Substances

Control8800 Cal Center Drive, Suite 350Sacramento, CA 95826-3200

RE: Transmittal of the Field Sampling Plan for Validation of the Johnson and Ettinger Model

Dear Mr. Berrey, Mr. MacDonald, and Mr. Cargile:

Please find attached the above-referenced document. As you know, this document is submitted inaccordance with our agreement at the Perimeter Groundwater Operable Unit risk assessment meetingon 26 May. It also responds to your 16 November 2004 request for a Tier 3 site-specific pathwayassessment for the lands downgradient of the Central Disposal Area (CDA), Agency commentsreceived on the Final Perimeter Groundwater Operable Unit RI/FS and to Agency comments receivedon the workplans to conduct the source area operable unit RI/FS'. We look forward to your expeditiousreview and approval so that Aerojet can proceed with collection of the site data and with validation ofthe J&E model.

As we've discussed previously, the results of this study will be incorporated into the ongoing RI/FSevaluations being conducted at the Aerojet site. Accordingly, Aerojet anticipates it will submit the Tier3 site-specific pathway assessment for the lands downgradient of the CDA no earlier than 60 daysafter written Agency approval of the J&E model validation report. Within the next week, Aerojet willseparately submit a proposed schedule modification for the PGOU RI/FS that will allow forincorporation of the J&E model validation results.

SR10119861 CL.doc 4 Qen Corp Company

Please feel free to call me if you have any questions regarding this FSP. In addition, we can schedulea discussion of this plan for our next technical meeting. I can be reached at (91 6) 355-2601 .

Sincerely,

CWJUcCindy L. CaulkPartial Consent DecreeProgram Coordinator

Attachment

cc: G. Stuesse, WestonS. Costello, AerojetR. Ettinger, GeoSyntec

SR10119861CL.doc