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Work Plan to Determine Background Metals inSurface Soils at the Aerojet Super-fund Site

Main Plant Sacramento, California

Prepared By:

Robert S Borch, Ph.D.GeoSyntec Consultants, Inc

Scott L. Neville, R,G.Aerojet Environmental Operations

July 2005Aerojet Document Conlml No.. SRI0119962.

Aerojet Background Soiis Metals Work Plan

INTRODUCTION AND BACKGROUND

The 1994 Sitewide Background Levels of Soil Trace Elements (the Background Study)was conceived and executed as a response to a concern with screening level soilsmetals data obtained from previous investigations (prior to the 1991 Stage 1 RemedialInvestigation) at the Aerojet site. These early investigations suggested that large areaswere contaminated with trace metals such as cadmium and thallium, even thoughhistoric site use information indicated that these metals had never been handled orreleased at the site.

Given the size of the Aerojet facility, including the Inactive Rancho Cordova Test Site,the Off-Highway Vehicle Park, and Sites 40 and 41, we felt that the appropriateapproach to determining background metals was to follow the procedures utilized inregional studies, with the proviso that the facility size was still sufficiently small to coverthe site with a uniform grid.

Aerojet's model was the Shacklette and Boerngen (1984), USGS Professional Papernationwide study of background levels of trace elements. This study sampled the top12 inches of soil, sieved and ground the samples, and performed a total digestionprocedure using hydrofluoric acid (HF) to assist in digesting silicate minerals prior toanalyzing the samples by ICP. It should be noted that the use of a total digestionprocedure is universal in the widely-used regional studies of background levels of traceelements in soils. In order to maximize the number of samples that could be analyzedwithin our budget, we elected to use a laboratory (Chemex, now ALS Chemex)specializing in exploration geochemistry (for a total cost of approximately $15 persample including sample preparation). Although the Chemex procedure differed insome respects from the EPA's comparable total digestion procedure (EPA Method3052), the results should be comparable, as the critical step is the use of hydrofluoricacid to dissolve silicate minerals. This laboratory was demonstrably superior with regardto analytical accuracy as measured by recoveries on National Institute of Standards andTechnology Standard Reference Material (NIST SRM) soils submitted as blind qualityassurance samples, but it was not an EPA certified laboratory. Additionally, theChemex data are such that conventional data validation analysis cannot be made whichwas a recent request by regulatory agencies.

The 1994 Sitewide Background Metals study successfully demonstrated that theapparent widespread levels of suspect metals were in fact analytical artifacts. However,the use of the 1994 data set has been questioned by the Regulatory Agencies, primarilywith regard to the more aggressive sample digestion procedure and the level ofcomparability of the 1994 data set and any new soil metal data. Some deficiencies withregard to the level of statistical analysis included in the background report were also

Aerojet Document Control # SR 10119962 July 2005Page 1

Aerojet Background Soils Metals Work Plan

noted. Regulatory Agencies also expressed concern that the 1994 analytical resultscould not be validated and hence cannot be used for Risk Assessment As a resultAerojet will collect new soil samples to be analyzed by a certified environmentallaboratory subject to up-to-date data validation methodology.

APPROACH

Regulatory Agencies have stated that the Site Wide Background Metals Work Planmust include sampling of all three major soil types encountered at the Aerojet MainPlant as well as offsite areas such as Area 41. These soil types are: Xerorthents(Dredge Tailings), the Redding-Corning-Red Bluff soil complex and the Auburn-WhiteRock-Argonaut soil complex. For this work plan we will focus on developingbackground data for the Xerorthents and the Redding-Corning-Red Bluff soil based onthe schedule for Operable Units (OUs) which are focused on the main 8,500 acre facility(see Figure 1). Aerojet will conduct the work necessary to compile a background dataset for the Auburn-White Rock-Argonaut soil type prior to the implementation of theRI/FS for the Area 41 Soil and Groundwater OU (OU 4). Since the schedule for OU 4has not been determined, the actual date of when the background data set for theAuburn-White Rock-Argonaut soil type cannot be specified. Once the schedule for theOU 4 RI/FS has been determined, a date for the development of this background dataset will be included in the subsequent Program Plan Modification Report (PPMR)Annual Update.

SAMPLE POPULATION & STATISTICAL ANALYSIS

A discussion of statistics was incorporated in Aerojet's response to Agencies Commentsdated June 15, 2005 and concluded that a sample population of 40 per soil type wouldsatisfy Agencies statistical requirements. This number was subsequently approved bythe USEPA in their letter dated June 28, 2005. Background data collected for each soiltype will undergo a data reduction process using statistical and graphical methods toeliminate potential outlier measurements. Graphical displays of the data, includingquantile probability plots and outlier box-plots, will be evaluated for evidence ofpolymodal distributions within each data set. A probability plot partitioning techniquewill be used to identify discontinuities or inflection points in the probability-plotdistributions that could indicate the presence of contamination intermingled withbackground concentrations of chemicals (Sinclair 1974; EPA 2000; and DTSC 1997).This is an iterative process, wherein one or more measurements are trimmed, and thenthe remaining data are re-plotted and subjected to additional analysis. Formalgoodness-of-fit tests (for example, Shapiro-Wilk W, Anderson-Darling, or Cramer-vonMises W2 test) will be used in conjunction with the probability plots to determine if thedata fit a particular distribution. After this process is completed, each distribution will beidentified as normal, lognormal, gamma or, if none of the standard parametric

Aerojet Document Control # SR 10119962 July 200t>Page 2

Aerojet Background Soils Metals Work Plan

distributions provides an adequate fit, nonparametric. Tables of summary statistics willbe provided for the trimmed data sets and will indicate the number of removedmeasurements as well as the removal criteria.

A distribution-dependent approach will also be used to calculate one or more single-point threshold values to represent background concentrations for each chemical.Single-point thresholds will be calculated as simple percentiles (for example, 90th, 95th,or 99th percentiles) as well as upper or lower tolerance limits (LTL, UTL) for selectedpercentiles. The approach for calculating tolerance limits is described in EPA (1992).Selection of a best or most appropriate single-point threshold value will be made basedon a thorough evaluation of the data and on a chemical-by-chemical basis or each soiltype.

SAMPLE LOCATION AND GRID SPACING

Sample locations will be determined by placing a uniform triangular grid across the main8,500 acre facility, following the procedure used in the 1994 study. The grid spacing willbe determined by first using the Soil Conservation Service's Soil Map for the area todetermine the total areas within the facility occupied by the two soil types, thendetermining the grid spacing needed to give a total of 40 points within the Redding-Corning-Red Bluff series soils. A grid with a random starting point and orientation willthen be laid over the site, and the actual number of usable grid points (samplelocations) will be counted. Grid points lying within potential sources sites and locally inthe drainages from potential source sites will be excluded. If there are less than 40usable sample locations then the grid spacing will be decreased and the processrepeated. Xerorthents comprise the majority of the site, so that there will be more than40 grid points for this soil series. 40 grid points will be randomly selected for samplingfrom the available grid points. Sample locations will be determined in the field by acombination of aerial photographs and a hand-held GS receiver with an accuracy ofapproximately 50 feet. The exact sampling point will be selected that is the nearestpoint that is:

• Primarily soil (rather than rock, gravel, peat, etc.);

• Free of unusual odors, discoloration or non-soil materials (like trash);

• A reasonable distance from roads, pavement, structures, outfalls, drainageswales etc.

To assist in determining exact soil type we will utilize the detailed quadrangle-scale soilmaps provided in the United States Department of Agriculture (USDA) 1993 Soil Surveyof Sacramento County. Additionally, based on previous agency comments, we may

Aerojet Document Control # SR 10119962 July 2005PageS

Aerojet Background Soils Metals Work Plan

consider (depending of actual field conditions) combining the following soil types: 1)Vleck-Mokelumne grouped with Redding-Corning-Red Bluff, 2) Urbanland-Americanos-Natomas grouped with Redding-Corning-Red Bluff; 3) Slickens grouped withXerorthents and the Pentz-Hadselville grouped with Redding-Corning-Red Bluff (seeFigure 1 - USDA General Soil Map).

SAMPLE COLLECTION

Soil samples will be collected in accordance with Aerojet's Standard OperatingProcedure, (Aerojet Document Control Number SR10119895, July 2005). The upper 12inches of soil (equivalent to the "A" Horizon) will be collected at each sample locationwith hand tools appropriated for the type of soil. The soil sample will be sieved to < 2mm size fraction and homogenized. The sample will then be run through a standardriffle splitter to split the sample into two equal parts. One sample split will be submittedfor laboratory analysis the remaining split will be archived. The location of each samplewill be logged in a manner that provides enough information to geocode the point in ageographic information system. The sampler will classify the soil as to type, and willrecord a description of the immediate area including roads, trails, structures, litter,waterways and prominent land features. The sampling area will also be photo-documented, and descriptions of each photograph will be recorded.

SAMPLE ANALYSIS

Sample analysis will be in accordance with the August 2004 Aerojet Quality AssuranceProject Plan (QAPP) (Aerojet Document Control Number SR10116065). The attachedTable 5-6 (from the Aerojet QAPP) presents the analytical methods, PQLs, MDLs formetals in soil. Note that where applicable, we will use the analytical method that hasthe lower PQL/MDL Additionally, for this investigation, we will not be analyzing thosemetals that are considered essential nutrients, specifically: calcium, magnesium,potassium and sodium.

QUALITY ASSURANCE

Quality assurance will be in accordance with the August 2004 Aerojet QualityAssurance Project Plan (QAPP) (Aerojet Document Control Number SR10116065). Forthis investigation we will be collecting 80 soil samples for analysis. We proposesubmitting 10 percent of the total (8 samples) for triplicate analysis. Data QualityObjectives are presented in Table 1.

Aerojet Document Control # SR 10119962 July 2005Page 4

Aerojet Background Soils Metals Work Plan

SCHEDULE

The proposed schedule is presented as Figure 2. Assuming a 60 day agency review /Aerojet response to comment scenario, field work would begin in late September 2005.We have allocated 30 days for laboratory analysis and 40 days for data analysis andreport generation. A report of findings would be completed by November 30, 2005.

REFERENCES

Aerojet, August 2004, Quality Assurance Project Plan, Aerojet Superfund Site, AerojetGeneral Corporation; Aerojet Document Control Number SR10116065.

Aerojet, July 2005, Standard Operating Procedures for the Aerojet Superfund Site,Aerojet General Corporation; Aerojet Document Control Number SR10109895.

Borch, R.S., 1994, Sitewide Background Levels of Soil Trace Elements, AerojetPropulsion Systems Plant and Adjacent Subsidiary Sites, Rancho Cordova, CA. AerojetDocument Control Number SR10109716.

Shacklette, H.T., and Boerngen, J.G., 1984, Element concentrations in soils and othersurficial materials of the conterminous United States: U.S. Geological SurveyProfessional Paper 1270,105 p.

United States Department of Agriculture, Soil Conservation Service, Soil Survey ofSacramento County, California, 1993.

Department of Toxic Substances Control (DTSC). 1997. "Selecting InorganicConstituents as Chemicals of Potential Concern at Risk Assessments at HazardousWaste Sites and Permitted Facilities." Final Policy. Human and Ecological RiskDivision, Department of Toxic Substances Control, California Environmental ProtectionAgency. Sacramento, CA. February.

Sinclair, A.J. 1974. "Selection of Threshold Values in Geochemical Data UsingProbability Graphs." Journal of Geochemical Exploration, 3: 129-149.

U.S. Environmental Protection Agency (EPA). 1992. "Statistical Analysis of GroundWater Monitoring Data at RCRA Facilities." Addendum to Interim Final Guidance.Office of Solid Waste, Washington, DC. July.

EPA. 2000. "Guidance for the Data Quality Assessment: Practical Methods for DataAnalysis." EPAQA/G-9. QAOO Update. EPA/600/R-96/084. July.

Aerojet Document Control # SR 10119962 July 2005Page 5

Aerojet Background Soils Metals Work Plan

Table 5-6AEL Methods and Practical Quantitation Limits

For Metals/Inorganic Elements in Soil

ANALYTE

Aluminum

Antimony

Arsenic

BariumBeryllium

BoronCadmiumCalcium

ChromiumChromium VI*

CobaltCopper

Iron

Lead

MagnesiumManganese

MercuryMolybdenum

Nickel

Perchlorate

Potassium

Selenium

SilverSodiumThalliumTitanium

VanadiumZinc

INSTRUMENTATION

ICP1

AA^furnaceICP

AAifurnaceICPICPICPICPICPICPICP

Extraction, colorimetricICPICPICP

ICP

ICPICP

AA:cold vaporICPICP

1C3

AA:flameICP

AAifurnaceICPICPICPICPICPICPICP

ANALYSISREFERENCE

METHODEPA 6010EPA 7041

EPA 6010/6020EPA 7060

EPA 601 0/6020EPA 6010EPA 6010EPA 6010EPA 6010EPA 6010EPA 6010EPA 71 96EPA 6010EPA 60 10EPA 6010

EPA 6010

EPA 6010EPA 60 10EPA 7471EPA 6010EPA 6010EPA 314.0

PAL-EA-0040EPA 76 10EPA 6010EPA 7740EPA 6010EPA 6010EPA 60 10EPA 60 10EPA 60 10EPA 6010EPA 6010

PQLSOIL

(mg/kg)20

0.3020

0.208.0

0.600.104.00.4014

0.800.100.800.6030

6.0

5.00.500.020

42.0

0.040

0.042000.20102.0805.02.00.6010

MDL4

(mg/kg)

30.0950

30.0303.50.200.05023.00.204.70.30

0.0980.300.304.0

3.0

2.00.20

0.00800.600.60

0.010

540.0603.5

0.4035

2.51.0

0.302.5

INDUSTRIALPRG5

(mg/kg)100,000

410

2601.6

67,0001900

100,000450

None45064

190041,000100,000

750

None19,000

3105100

20,000

100

None

5100

5100None

67None7200

100,000

RESIDENTIALPRG5

(mg/kg)76,000

31

220.395400150

16,00037

None21030900

310023,000

400150**None1800233901600

7.8

None

390

390None5.2

None550

23,000

11CP - Inductively Coupled Plasma-Atomic Emission Spectrometry2 AA - Atomic Absorption Spectrometry31C - Ion Chromatography4 MDL - Method Detection Limit, AEL5 PRG - Preliminary Remediation Goal, EPA Region IX (10/2002)* California Modified' Cancer Endpoint** CAL-Modified PRG

Aerojet Document Control # SR 10119962 July 2005Page6

Table 1: Data Quality Objectives for the Determination of Background Metals in Surface Soil Aerojet Main Plant Site

STEP 1 STEP 2

State the Problem Identify the Decisions

STEPS

Identify the Inputs to theDecision

STEP 4

Define Study Boundaries

STEPS

Develop Decision Rules

STEP 6

Specify Tolerable Limits onErrors

STEP 7

Optimize SamplingDesign

Establish background (non-anthropomorphic) levels of metals in surface soils at the Aerojet Superfund Site that can be used for exposure risk assessment and remedial feasibility decisions

Problem

To establish background (non-anthropomorphic) levels of

metals in surface soils at theAerojet Superfund Site that

can be used for exposure riskassessment and remedial

feasibility decisions

What are the statisticallyvalid natural ranges of

concentrations forindividual metal species in

surface soils?

Quantitative AnalyticalLaboratory Data that has

undergone rigorousvalidation and proper

OA/nr

Generation of descriptivestatistics such as measuresof central tendency (means,medians, modes), standarddeviations and confidence

intervals

The study area boundary isthe Aerojet Main Plant 8,500acre facility. This study willfocus on two primary soiltypes present within this

area: Xerothrents and theRedding-Corning -Red Bluff

Soils. Field work andReporting will take placeSeptember 2005 throught

Novemeber 2005.

Rule 1) Use only validatedanalytical data

Rule 2) Adhere to Regulatoryand Industry-accepted

statistical analysis of data

EPA-approved samplecollection procedures and

industry standard analyticalmethods will be used

following the Aerojet QAPPand SOP Documents.

Sample locations willbe determined byplacing a uniform

triangular grid acrossthe main 8,500 acrefacility. A grid with arandom starting point

and orientation will thenbe lain over the site,

and the actual numberof usable grid points

(sample locations) willbe counted. Grid points

lying within potentialsources sites and

locally in the drainagesfrom potential sourcesites will be excluded.

SR10119962Table 1July 2005

Figure 2 Background Metals Investigation Schedule

PROJECT SCHEDULE ., , v.,.. ....„,,,.....,,...,.,..,.,,.. «.,,,-,..,. -. •. . • ; . • , .AwflbJeiOSiiEkSir ^

TASK

Submit Background Metals WorkplanAgency Review of Workplan (30 days)Aerojet Respond to Comments (30 days)Final Agency ApprovalField Work Collection of 80 Soil SamplesLaboratory AnalysisData AnalysisReport Generation & Submittal

TASK DURATION(WORKDAYS)

1

3030514302515

START DATE

07/22/0507/22/0508/21/0509/20/0509/26/0510/10/0510/25/0511/14/05

END DATE

07S3/05 '; 08/2i:'05

;09/20/0509/25/iJ5WQ/65f 1/09/05H/f^/0511/29/05

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PO Box 13222Sacramento CA 95813-6000

22 July 2005

Mr. Charles Berrey Mr. Alexander MacDonald Mr. Ed CargileU.S. EPA (SFD-7-2) California Regional Water State of California75 Hawthorne Street Quality Control Board Site Mitigation ProgramSan Francisco, CA 94105 Central Valley Region Dept. of Toxic Substances Control

11020 Sun Center Dr. #200 8800 Cal Center Drive, Suite 350Rancho Cordova, CA 95670-6114 Sacramento, CA 95826-3200

RE: Work Plan to Determine Background Metals in Surface Soils at the Aerojet Superfund SiteMain Plant Sacramento, California

Dear Messers. Berrey, MacDonald, and Cargile:

Please find enclosed the document "Work Plan to Determine Background Metals in Surface Soils at the AerojetSuperfund Site Main Plant, Sacramento, California". This work plan was prepared in response to the June 28,2005 USEPA letter which approves Aerojet's statistical approach (in terms of sample number requirements) andrequests a work plan by July 22, 2005. The work plan concentrates on determining the background metals in thetwo main soil types that are present within the main plant, 8,500 acre, facility. These soil types are the Xerothrents(dredge tailings) and the Redding-Corn ing-Red Bluff soils. The other primary soil type, Auburn-Whiterock-Argonaut, which underlies the easternmost management areas (Area 40 and Area 41), will be investigated at alater time coincident with the Operable Unit RI/FS schedule.

If you have any specific questions or comments regarding this submittal you can directly contact Scott Neville(Aerojet) at (916) 355-5500 (e-mail scott.neville@aeroiet.com ).

Sincerely,

Cindy CaulkProgram Coordinator

Cc:SL Neville, AerojetC Fennesey, AerojetG Stuesse, Weston Solutions, Inc.

Aerojet Document Control # SR10119962CL A QenCorp Company