semspub.epa.gov · version 1.3. technical activities work plan remedial investigation/feasibility...

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davis

Version 1.3

GRIGGS AND WALNUT GROUNDWATER PLUME SITE

RI/FS TECHNICAL ACTIVITIES WORK PLAN

GWP_TWP_VER1.2.WPD DECEMBER 2001

[This page intentionally left blank.]

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Version 1.3

Technical Activities Work PlanRemedial Investigation/Feasibility Study

Griggs and Walnut Avenue Groundwater Plume SiteLas Cruces, Doña Ana County, New Mexico

EPA ID NM0002271286

Response Action Contract No. 68-W6-0036EPA Work Assignment No. 961-RICO-06HZ

CH2M HILL Project No. 164462DCN 01-2830

Prepared for:U.S. Environmental Protection Agency

Prepared by:CH2M HILL, INC

March 2002

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GWP_TWP_VER1.3_PREFACE.WPD FEBRUARY 2002

Preface This work plan was prepared for the US Environmental Protection Agency Region 6 (EPA) for the

purpose of setting forth the technical activities to be conducted under a Remedial Investigation/

Feasibility Study (RI/FS) for the Griggs and Walnut Avenue Groundwater Plume Site located in Las

Cruces, Doña Ana County, New Mexico (EPA ID NM0002271286). This work plan was prepared under

the Response Action Contract No. 68-W6-0036 and EPA Work Assignment Number 961-RICO-06HZ to

meet in part the requirements of EPA’s Statement of Work for this project (EPA, 2001) as defined in the

Work Assignment Work Plan dated April 3, 2001 (CH2M HILL, 2001). Incorporated by reference are

the RI/FS Field Sampling Plan, (CH2M HILL, 2002a), the Quality Assurance Project Plan (CH2M

HILL, 2002b), the Site Management Plan (CH2M HILL, 2002c), and the Health and Safety Plan

(CH2M HILL, 2002d), which provide detailed procedures for performance of the work. This Technical

Activities Work Plan, Version 1.3, is an update to Version 1.2, date December 2001, with the replaced

pages indicated by the February 2002 date and Ver1.3 in the footers of the changed pages.

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GWP_TWP_VER1.2_CONTENTS.WPD DECEMBER 2001i

Contents

List of Acronyms

1.0 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

2.0 Site Background and Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.1 Site Description and Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12.1.1 Site Investigation History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12.1.2 Site Environmental Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

2.2 Source, Nature, and Extent of Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-82.2.1 Source of Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-82.2.2 Nature and Extent of Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

3.0 Site Conceptual Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

4.0 Data Quality Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.1 State the Problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14.2 Identify the Decision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24.3 Identify Inputs to the Decision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-44.4 Define the Study Boundaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

5.0 Site Characterization Tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.1 Available Data Collection and Site Reconnaissance . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15.2 Field Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

5.2.1 Site-Specific Plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-45.2.2 Civil Survey and Access Agreements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-45.2.3 Private Water Supply Well and Monitoring Well Search . . . . . . . . . . . . . . . . 5-55.2.4 Sampling Effort Mobilization/Demobilization . . . . . . . . . . . . . . . . . . . . . . . . 5-55.2.5 Drilling/Well Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-65.2.6 Soil Vapor Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-75.2.7 Soil Sample Collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-85.2.8 Aquifer Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-95.2.9 Sample Collection and Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-105.2.10 Surveying of Sample Locations and Site Features . . . . . . . . . . . . . . . . . . . . . 5-105.2.11 Management of Investigation-Derived Waste . . . . . . . . . . . . . . . . . . . . . . . . 5-11

5.3 Data Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-115.3.1 Data Validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-115.3.2 Data Reduction, Tabulation and Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . 5-115.3.3 Data Evaluation Technical Memorandum . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11

5.4 Risk Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-125.5 Remedial Investigation Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-125.6 Project Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-13

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GWP_TWP_VER1.2_CONTENTS.WPD DECEMBER 2001ii

6.0 Feasibility Study Tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6.1 Compilation of ARARs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16.2 Development of Remedial Action Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26.3 Development of General Response Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26.4 Identification and Screening of Remedial Technologies . . . . . . . . . . . . . . . . . . . . . . . . 6-26.5 Development and Screening of Remedial Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . 6-36.6 Evaluation of Remedial Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-46.7 Feasibility Study Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4

7.0 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

List of Tables

Table 2-1 PCE Concentrations in Wells Located in the Vicinity of the Griggs and WalnutGroundwater Plume Site

Table 4-1 Data Quality Objectives

Table 5-1 Proposed Monitoring Well Locations and Rationale for Selected LocationsTable 5-2 Overview of RI/FS Schedule

List of Figures

Figure 1-1 Site Location Map

Figure 2-1 Well Location MapFigure 2-2 Soil Vapor Concentrations at 8 ft. bgs at the DACTD Maintenance YardFigure 2-3 Historical PCE ConcentrationsFigure 2-4 Depth of Well Screen Intervals - Cross-Section A-A’Figure 2-5 Depth of Well Screen Intervals - Cross-Section B-B’Figure 2-6 Depth of Well Screen Intervals - Cross-Section C-C’Figure 2-7 Location of Potential Sources of PCE

Figure 3-1 Initial Site Conceptual Model

Figure 5-1 Historical PCE Concentrations and Proposed New Monitor Well Location MapFigure 5-2 Locations of Proposed New Monitor Wells & Previously Identified Potential Sources of

PCE

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List of Acronyms

GWP_TWP_VER1.3_ACRONYMS.WPD FEBRUARY 2002iii

ARARs Applicable or Relevant and Appropriate Requirementsbgs below ground surfaceCERCLA Comprehensive Emergency Response and Comprehensive Liability ActCLC City of Las CrucesDACTD Doña Ana County Transportation Department1,2-DCA 1,2-Dichloroethanecis-1,2-DCE cis-1,2-DichloroetheneDNAPL Dense non-aqueous phase liquidDPT Direct-Push TechnologyDQOs Data Quality Objectives EPA US Environmental Protection Agency FSI Focused Site InspectionFSP Field Sampling Plan GWP Griggs and Walnut Ground Water Plume Superfund SiteHRS Hazard Ranking SystemHSP Health and Safety PlanIDW Investigation Derived WasteLUST Leaking Underground Storage TankMCL Maximum Contaminant LimitNCP National Contingency PlanNMED New Mexico Environment DepartmentNPL National Priorities ListPA Preliminary AssessmentPCE tetrachlorothene, or perchloroethenePID Photoionization Detectorppb-v parts per billion by volume QAPP Quality Assurance Project PlanRI/FS Remedial Investigation/Feasibility StudySAP Sampling and Analysis PlanSDWA Safe Drinking Water ActSMP Site Management PlanSSSR Superfund Site Strategy RecommendationSVE Soil Vapor ExtractionTAWP Technical Activities Work PlanTCE TrichloroetheneTPH Total Petroleum Hydrocarbonsug/L Micrograms per Literug/Kg Micrograms per KilogramUSTB Underground Storage Tank BureauVOCs Volatile Organic Compounds

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Section 1Introduction

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GWP_TWP_VER1.3_SECT01_INTRO.WPD MARCH 20021-1

Section 1

IntroductionThe Remedial Investigation/Feasibility Study (RI/FS) is a process by which the nature and extent of risks

posed by a hazardous waste site are quantified and potential remedial options are evaluated sufficient to

support an informed risk management decision regarding remedial action for the site. This RI/FS

Technical Activities Work Plan (TAWP) has been prepared to describe the tasks to be conducted under a

RI/FS for the Griggs and Walnut Avenue Groundwater Plume (GWP) site in Las Cruces, Doña Ana

County, New Mexico. Specific details regarding how the task activities are to be conducted are

presented in site-specific plans presented under separate cover (as described below). The overall project

schedule is described in Section 5.

The GWP site is a plume of groundwater contaminated with tetrachloroethylene (also known as

perchloroethylene, commonly referred to as PCE). The extent of the plume is currently defined by

groundwater samples from four municipal supply wells, sixteen monitor wells, and one private well

meeting observed release criteria (EPA, 2000b). The plume is currently known to be at least 8,000 feet

long and 2,000 feet wide, however, the precise horizontal and vertical extent of the plume has yet to be

confirmed. Figure 1-1 shows the location of the site within the City of Las Cruces.

A specific source of the contamination has not yet been identified, but several potential sources of the

contamination have been identified based on their proximity to the groundwater plume and the potential

use of PCE at those locations (PCE is the only known contaminant associated with the site), and these

will be reviewed during the RI. The Hazard Ranking System (HRS) Documentation Record, released by

the U. S. Environmental Protection Agency (EPA) in November 2000, states that the potential sources

include dry cleaning facilities, leaking underground storage tank (LUST) sites, the Las Cruces Landfill,

the Old Las Cruces Landfill, and vehicle and equipment maintenance yards. After the HRS package

was released, it was identified that the City of Las Cruces Fleet Maintenance Yard operation included a

PCE tank, handled by Safety Kleen. Because PCE use at the site has been documented, the Fleet

Maintenance yard is added to the list of potential sources for the site. The HRS documentation record

also indicated that there is currently not enough information to identify these facilities as the source of

the contamination. The site is currently considered a contaminated groundwater plume with an

unidentified source (EPA, 2000b). The RI/FS will address these various sources of contamination, first

through literature searches, aerial photograph evaluation, plume definition data, and then with physical

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GWP_TWP_VER1.3_SECT01_INTRO.WPD FEBRUARY 20021-2

sampling as warranted. In several situations, the extent of the plume beneath the potential sources has

not yet been confirmed; this will be done prior to focused sampling at any particular potential source.

Based on the results of the HRS scoring, the site was proposed to EPA’s National Priorities List (NPL)

on January 1, 2001.

Routine compliance sampling conducted by the New Mexico Environment Department (NMED)

Drinking Water Bureau first identified PCE in municipal supply Wells No. 21 and No. 27 in August

1993. The concentration of PCE in both wells was below the EPA maximum contaminant level (MCL)

of 5 micrograms per liter (ug/L). PCE was first detected by the NMED Drinking Water Bureau in Well

No. 18 in January 1995, at a concentration of 32 ug/L. Resampling in February indicated a concentration

of 1.5 ug/L, below the MCL. The initial sample result of 32 ug/l was eventually rejected because the

result could not be reproduced and there were concerns that, since the well had been turned off prior to

sampling, the sample was not representative of water in the aquifer. The NMED Drinking Water Bureau

conducts sampling and analysis for most public water supply systems in the State of New Mexico and

submits samples for analysis to Safe Drinking Water Act (SDWA) certified laboratories. Samples are

collected using a standard set of procedures by someone who is certified to collect compliance samples

for meeting the requirements of the SDWA. Volatile organic compound (VOCs) samples are analyzed

using EPA method 524.2 (the test approved by the Safe Drinking Water Act).

The NMED Drinking Water Bureau conducted subsequent sampling of Well No. 18 which showed PCE

concentrations of about 1 ug/L in multiple sampling events until January 1996, when PCE was again

detected above the MCL, this time at 6.4 ug/L. The sampling and analytical methods associated with

these sampling events are not specifically documented in the record, but typical procedures applied by

the NMED are standardized. Quality assurance/quality control (QA/QC) procedures are reported to be

handled by the laboratories, which are certified. Since January 1996, the concentration of PCE detected

in samples collected by the NMED Drinking Water Bureau, the City of Las Cruces (CLC), and the

NMED Superfund Oversight Section from this well have ranged from not detected to 47.0 ug/L. PCE

has also been detected in samples from municipal supply Well No. 19. (See Figure 1-1 for the locations

of the municipal wells in relation to the site). All detected concentrations of PCE in Wells Nos. 19, 21,

and 27 have been below the MCL, but concentrations in samples collected from CLC Well Nos. 21 (up to

3.4 ug/L) and 27 (up to 4.9 ug/L) have been increasing somewhat with time. Municipal Well No. 18 was

removed from the city water supply system in September 1996 due to both operational issues and the

presence of PCE (EPA, 2000b). Municipal Well No. 27 was taken offline in February 2001 due to a

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GWP_TWP_VER1.3_SECT01_INTRO.WPD FEBRUARY 20021-3

mechanical problem which was repaired. The well was put back online during a short time in the early

summer of 2001, but conveyance of water from this well to the water supply system was discontinued

after sampling conducted by the CLC confirmed the continued presence of PCE at concentrations near

the MCL.

The NMED Superfund Oversight Section initiated a groundwater investigation of the plume in May 1997

(EPA, 2000b). Also, beginning in June 1997, an investigation was being conducted at a LUST site at the

Doña Ana County Transportation Department (DACTD) maintenance yard, within which Well No. 18 is

located, to comply with New Mexico Underground Storage Tank Regulations, which are overseen by the

Underground Storage Tank Bureau (USTB) of the NMED. Another LUST investigation was also

conducted during December 1997 at the Gas Card site, located approximately 0.6 miles northwest of

Well No. 18 (SMA, 1997a, SMA, 1997b, and SMA, 1998). The NMED also had samples collected from

monitor wells at another LUST site, the Circle K #1603, located approximately 0.3 miles north of the

Gas Card site, analyzed for PCE in March 2001 (PCE was not detected in any of the Circle K site wells).

As a result of these investigations, twenty-five monitor wells have been installed in the vicinity of the

GWP site.

The purpose of this RI/FS is to determine the nature and horizontal and vertical extent of the groundwater

contamination associated with the GWP Site (specifically related to PCE detected at munipal wells 18,

19, 21, and 27). Determination of the nature and extent of contamination will be supported by the soil

vapor and groundwater sample analytical data and the locations of potential sources identified during the

site assessments/site inspections conducted at the site from 1997 through 2000. RI data collection

activities will be limited to data gaps identified in the existing database. New monitor wells will be

installed at locations appropriate for documenting the horizontal and vertical extent of the plume, and for

confirming potential source areas. Site characterization tasks will be conducted only as necessary to

support an informed risk-based decision for remedial action at the site, including delineation of source

areas as necessary to prevent continuing contamination. The relationship of the contamination detected

in Well No. 24 to the GWP site will also be confirmed.

This document, the Technical Activities Work Plan, provides an overview of the RI/FS objectives and

the activities to be conducted. The site-specific plans which describe how each task activity is to be

conducted are the Sampling and Analysis Plan (SAP), the Site Management Plan (SMP), and the Health

and Safety Plan (HSP). The SAP is composed of the Field Sampling Plan (FSP) and the Quality

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GWP_TWP_VER1.3_SECT01_INTRO.WPD DECEMBER 20011-4

Assurance Project Plan (QAPP); these plans detail the sampling and analysis procedures to be followed

by the field and laboratory personnel, respectively, as well as the data management procedures to be

followed throughout the sampling and analysis activities. The SMP describes handling of site access,

security, contingency procedures, management responsibilities, and investigation-derived waste (IDW);

procedures specified in the SMP will ensure contaminants are not released offsite as a result of RI/FS

activities. The HSP describes CH2M HILL-specific employee training requirements, protective

equipment requirements, medical surveillance requirements, standard health and safety operating

procedures, and contingencies applicable to performance of the RI/FS activities. These site-specific

plans are provided under separate cover and are referenced as appropriate throughout the TAWP.

Provided in Section 2 of this Work Plan is a brief description of the site background and environmental

setting. Section 3 describes the current view of the site conceptual model, used as a basis for outlining

RI/FS activities. Data Quality Objectives for use in defining the level of investigation and depth of

evaluation for the RI/FS are described in Section 4. Section 5 outlines the site characterization tasks

defined to supplement the existing database of information available from historic sampling and

analytical activities conducted for the site. Section 6 outlines the tasks defined to complete a feasibility

study for the site. References are listed in Section 7.

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##

#

# #

#

#

#

#

#

#

#

(

CLC Well 27

CLC Well 18

CLC Well 21

CLC Well 54

CLC Well 28

CLC Well 26

CLC Well 19

CLC Well 57

CLC Well 10

CLC Well 20

CLC Paz Park Well

CLC Well 61

CLC Well 24

N

Interstate Highway

Legend

City of Las Cruces (CLC) Supply Wells#

1000 0 1000 2000 3000 Feet

.-,

RIO GRANDE

.-,10

GWP_TWP_Ver1.2_Figure1-1.pdf

Figure 1-1

Site Location Map

Griggs & Walnut Ground Water Plume Site

Las Cruces, New Mexico

.-,25

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Section 2Site Background and Setting

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GWP_TWP_VER1.3_SECT02_SITEBACKGROUNDANDSETTING.WPD DECEMBER 20012-1

Section 2

Site Background and SettingA summary of the available data on the physical and historical characteristics of the GWP site has been

compiled from the previous investigative record. This section provides a description of this information

as well as a summary of the nature and extent of contamination documented to-date.

2.1 Site Description and BackgroundThe GWP site is a contaminated groundwater plume centered near the intersection of Griggs Avenue and

Walnut Street in Las Cruces, Doña Ana County, New Mexico. The geographic coordinates at this

location are approximately 32"18' 56.0" north latitude and 106"45' 36.0" west longitude. Four municipal

drinking water supply wells within the site are affected (EPA, 2000b), although only one, Well No. 18

(out of service since 1996), has demonstrated concentrations of PCE above the MCL. This well is

located at the DACTD maintenance yard, near the intersection of Griggs and Walnut. A fifth well, CLC

Well No. 24 located south of the site, has demonstrated detections of PCE in recent sampling events

beginning in June 2001; this detection may or may not be related to the GWP site (wells in between this

well and the site are not affected). A brief description of the site investigative history and environmental

setting is provided in the following paragraphs. A map of the site is provided as Figure 1-1.

2.1.1 Site Investigation History

The NMED Superfund Oversight Section began investigating the groundwater contamination at the GWP

site in May 1997. A Preliminary Assessment (PA) Report for the site was issued by NMED on October

30, 1997. The report concluded that the threat to human health through the groundwater pathway is

likely significant. The report also stated that the source of the contamination had not been identified, and

therefore the surface water, soil, and air pathways could not be characterized at that time (NMED, 1997).

The conclusions of the PA led the EPA to issue a Superfund Site Strategy Recommendation (SSSR) for

the site. The SSSR recommended that NMED conduct a Focused Site Inspection (FSI) to determine the

extent of the contamination and determine the location of potential sources (EPA, 1998b). In December

1997, a LUST investigation was conducted under the authority of the USTB of the NMED at the Gas

Card LUST site (identified in NMED documents as the Shook Well). The Gas Card Site is located

approximately 0.6 miles northwest of Well No. 18 at the intersection of Solano Drive and Augustine

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GWP_TWP_VER1.3_SECT02_SITEBACKGROUNDANDSETTING.WPD FEBRUARY 20022-2

Avenue. Five soil borings were drilled, and one monitor well, MW-1 ( the Gas Card well), was installed.

Groundwater was encountered at 102 feet below ground surface (bgs). Two soil samples were collected

from each boring, and one groundwater sample was collected from the well, for analysis of petroleum-

related constituents. PCE was not analyzed in any of these samples. The analytical results showed

elevated concentrations of Total Petroleum Hydrocarbons (TPH) in one soil boring. No petroleum-

related constituents were detected in the groundwater sample (SMA, 1997b). The NMED Superfund

Oversight Section collected groundwater samples from the Gas Card well in June 1998 and July 1999.

The analytical results revealed the presence of PCE in the groundwater at concentrations exceeding the

MCL (EPA, 2000b).

Beginning in June 1997, a separate investigation was conducted at another LUST site at the DACTD

maintenance yard. This investigation was conducted in response to a fuel spill at the site. The first phase

of the investigation involved the drilling of one soil boring and the installation of one monitor well, MW-

1. Groundwater was encountered at 187 feet bgs. Two soil samples and one groundwater sample were

collected for analysis of petroleum-related constituents. The soil samples, collected at 165 and 195 feet

bgs, and the groundwater sample revealed the presence of gasoline-related constituents (SMA, 1997a).

The presence of contamination led to further investigation at the site in February and March 1998. The

NMED Superfund Oversight Section participated in this investigation as part of their groundwater

investigation of the PCE contamination in CLC Well No. 18. Five additional monitor wells, MW-2

through MW-6, were installed at the site (see Figure 2-1 for well locations at the site), and soil samples

were collected during drilling for analysis of petroleum-related hydrocarbons (SMA, 1998). NMED

representatives collected split soil samples for analysis of volatile organic compounds (VOCs).

Of the samples analyzed, PCE was detected at 241 micrograms per kilogram (ug/Kg) in only one soil

sample, from MW-5, at 135 feet bgs (EPA, 2000b). Groundwater samples collected from MW-2 through

MW-6 in March 1998 showed no hydrocarbon-related contamination, but PCE was detected in samples

from wells MW-2 through MW-5. The MCL was exceeded in samples from wells MW-2 and MW-4

(SMA, 1998). Because of the PCE detections, the NMED Superfund Oversight Section performed

additional monitoring at these wells in April 1998, July 1999, March 2000, and July 2000. In each event,

the PCE concentration detected exceeded the MCL in samples from wells MW-2 through MW-4. The

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PCE concentration exceeded the MCL in samples from MW-5 in March and July 2000, and the PCE

concentration exceeded the MCL in the sample from MW-1 in July 2000. Table 2-1 shows the sample

analytical results for the wells that have been sampled during the site’s investigation history. The HRS

Documentation Record indicates that the site references consider the PCE contamination detected in the

monitor wells to be unrelated to the fuel spill at the DACTD LUST site (EPA, 2000b).

The findings of the SSSR led the NMED Superfund Oversight Section to conduct additional

investigations at the GWP site. These investigations were conducted in a phased approach between 1997

and 2000. Part of this investigation included the groundwater sampling from the wells at the DACTD

site and the Gas Card Site. Also, two surface water samples were collected from drainage sumps located

near the diesel shop at the DACTD facility in October 1998. PCE was detected in one of these surface

water samples at 3.3 ug/L. In July 1999, the NMED Superfund Oversight Section also conducted a

shallow soil vapor investigation at the DACTD yard, with soil vapor samples collected to 8 feet bgs.

PCE concentrations in the shallow soil vapor ranged from non-detect up to 12 parts per billion by volume

(ppb-v), with the highest concentrations occurring in the northeast corner of the yard. Figure 2-2 shows

the results of the soil vapor investigation.

The results of the soil vapor study led the NMED Superfund Oversight Section to install additional

monitor wells (MW-SF1 through MW-SF10) between February and June 2000. These wells were

located within the vicinity of Well No. 18, the DACTD maintenance yard, and the Gas Card Site.

Groundwater samples collected from these wells in March and July 2000 revealed the presence of PCE in

samples from nine of the wells (MW-SF1 through MW-SF8 and MW-SF10), and the PCE concentration

exceeded the MCL in samples from eight of the wells (MW-SF1 through MW-SF5, MW-SF7, MW-SF8,

and MW-SF10). Four of the wells were installed at the DACTD maintenance yard. The PCE

concentrations detected in these wells ranged from 19 to 52 ug/L.

The NMED Superfund Oversight Section also sampled two additional municipal water supply wells

(CLC Well Nos. 10 and 54), an additional city-owned well (the Paz Park Well), and two private wells

(identified as wells LRG-3191 and LRG-7375) as part of their investigation. Well LRG-3191 was

sampled during March and June 1998. LRG-7375 was sampled in January and June 1998. CLC Well 10

003851




was sampled in July 1999. CLC Well 54 was sampled in July 1999 and April 2000, and the Paz Park

Well was sampled April and June 1998, and July 1999. Of these wells, PCE was only detected in the

sample from private well LRG-3191, at a concentration of 1.0 ug/L. Monitor well MW-SF8, located on

Santa Fe Street between Pinion Avenue and Picacho Avenue, represents the furthest upgradient detection

of PCE (EPA, 2000b).

In March 2001, a soil investigation and groundwater sampling was conducted at another LUST site, the

Circle K Store #1306, located approximately 0.3 miles north of the Gas Card site and 0.2 miles east of

CLC Well No. 10. The Circle K #1306 site has been monitored by the USTB since a petroleum product

release was identified at the site in 1991. The March 2001 investigation was conducted to support a risk

assessment for the site. During this investigation, the eight monitor wells at the site were sampled, and

one soil boring was completed. Five soil samples were collected from the soil boring. At the request of

the NMED USTB, all the samples were analyzed for a wide range of VOCs, and PCE was not detected in

any of the soil or groundwater samples (CDM, 2001).

In May 2001, the NMED Drinking Water Bureau began monthly sampling of the municipal supply wells

that contained PCE to determine if PCE concentrations were approaching the MCL. This sampling

included only those wells that were being used to supply drinking water to the system, which included

CLC Wells Nos. 19 and 21, and beginning in June, CLC Well No. 27. The sampling and analytical

method associated with these sampling events is not specifically documented for this effort, although

standard NMED procedures would have been followed; no QA/QC samples were collected as part of

these sampling efforts. Based on the analytical results, the PCE concentration has risen in all the wells

previously known to be affected by PCE, and PCE was detected in another well, CLC Well No. 24, at a

concentration of 1.5 ug/L, during a compliance sampling event in June 2001. It is important to note,

however, that three wells located between Well No. 24 and the GWP Site wells do not demonstrate the

presence of PCE (CLC Wells Nos. 20, 26, and 61). As a result, the PCE contamination in Well No. 24

may or may not be related to the GWP Site. Other than Well No. 18 (which is out of use), the affected

supply wells have not yet demonstrated detections above MCLs.

003852




During the June 2001 sampling round, samples from Well No. 27 demonstrated a PCE concentration of

4.5 ug/L, samples from Well No. 21 demonstrated a PCE concentration of 3.4 ug/L, and samples from

Well No. 19 demonstrated a PCE concentration of 1.4 ug/L. A sample collected from Well No. 27

during August 2001 revealed a PCE concentration of 4.9 ug/L. As a result of the continued elevated

concentrations in Well No. 27, the CLC discontinued pumping from this well into the water supply

system. The CLC continued to pump the well four hours a day, discharging the water to the sanitary

sewer. The continued pumping will help keep the PCE contaminant plume from migrating toward other

pumping wells. The June 2001 sampling round also showed detection of PCE at 1.5 ug/L in a sample

from CLC Well No. 24, a previously unaffected well (Figure 1-1 shows the location of each City well

mentioned above).

To date, PCE has been detected in five municipal supply wells (Nos. 18, 19, 21, 24, and 27), 16 monitor

wells (the six wells at the DACTD facility, the Gas Card well, and nine of the ten monitor wells installed

by the NMED Superfund Section), and one private well used for irrigation (LRG-3191). The furthest

upgradient well known to contain PCE, MW-SF8 (located on Santa Fe Street between Pinion Avenue and

Picacho Avenue), is located over 4,000 feet west-northwest of the DACTD facility. Figure 2-1 shows

the locations of each well discussed in the HRS documentation. The location of the Circle K #1306 is

also shown on this map (where monitor wells showed no detections of PCE). Table 2-1 shows the

concentrations of PCE detected in the wells associated with the site. The historical PCE concentrations

in groundwater at the site are also shown on Figure 2-3. It should be noted that the monitor wells are

screened at the water table, which occurs at a much shallower depth than the well screens for the city’s

municipal water supply wells. Figures 2-4, 2-5, and 2-6 are cross-sections that show the depths where

wells at the site are screened relative to the water table, the ground surface, and each other (for some

wells, elevations are not precise due to a lack of surveyed elevations, and the screened interval(s) for

Well No. 21 is unknown). The locations of each cross-section are shown on Figure 2-1.

In November 2000, EPA Region 6 prepared the HRS Documentation Record for the GWP site to evaluate

whether the site should be placed on the NPL. The HRS score for the site was 50, which was well above

the 28.5 score used to determine if a site should be placed on the NPL (EPA, 2000b). The site was

003853




proposed for inclusion on the NPL in January 2001 (66 FR 2380, January 11, 2001), and added to the

NPL in June 2001 (66 FR 32235, June 14, 2001).

2.1.2 Site Environmental Setting

This section describes physical characteristics of the site vicinity in terms of potential pathways. This

information has been compiled from the HRS Documentation Record (EPA, 2000b).

Regional Geology. Las Cruces is located in the Mexican Highlands section of the Basin and Range

physiographic province. In general, the physiography of the area consists of uplifted fault-block

mountain ranges and intermontane basins. The intermontane basins are structurally depressed areas that

have been displaced downward with respect to the mountains. The mountain ranges and intermontane

basins generally have a north-south trend. Other mountain types in the area include broad domal uplifts

and erosional remnants of igneous intrusive bodies. The major physiographic features in the Las Cruces

area are the entrenched Rio Grande and two intermontane basins, the Jornada del Muerto and the Mesilla

Bolson. The City of Las Cruces is located in the Mesilla Valley (located within the Mesilla Bolson) east

of the Rio Grande. The Jornada del Muerto is located north and east of Las Cruces (King, et al., 1971).

The regional geology is comprised of the Quaternary-aged flood plain alluvium and the Miocene to

Middle Pleistocene Santa Fe Group. The flood plain alluvium was deposited by the Rio Grande. It

generally consists of a thick basal sand and gravel channel unit overlain by finer-grained flood plain

deposits. The unit is generally about 4 miles wide and 80 feet thick. The Santa Fe Group is a rock

stratigraphic unit composed of sequences of unconsolidated to moderately consolidated sedimentary

deposits and volcanic deposits consisting of basalts and minor ash-fall deposits that have partially filled

the intermontane basins along the Rio Grande depression from the San Luis Valley of Colorado to the

lower El Paso Valley of Texas and Chihuahua, Mexico. The Santa Fe Group occurs at thicknesses up to

4,000 feet (Frentzel, et. al, 1990).

Regional Hydrogeology. The regional hydrogeology is largely controlled by the structure of the

geology. Groundwater basins are situated in the intermontane basins between the uplifted fault-block

mountain ranges. The major groundwater basins in the Las Cruces area are the Mesilla Groundwater

003854




Basin and the Jornada del Muerto Groundwater Basin. Las Cruces is located within the Mesilla

Groundwater Basin, and the Jornada del Muerto Basin is further to the north and east. The two basins

are separated by a subsurface high in the less permeable bedrock (King, et al., 1971).

The Rio Grande flood plain alluvium and the Santa Fe Group are the two major groundwater reservoirs

in the area. In the Mesilla Groundwater Basin, the two units form a complex aquifer system.

Groundwater recharge is primarily from the Rio Grande into the flood plain alluvium. The groundwater

then migrates downward through the shallow alluvium to the upper Santa Fe Group through a series of

interconnected gravel, sand, and clay lenses. Vertical flow within the system is restricted by thin,

interbedded clay lenses in the lower part of the flood plain alluvium and the upper portion of the Santa Fe

Group. This vertical heterogeneity results in the horizontal permeability generally exceeding the vertical

permeability by several orders of magnitude. Groundwater occurs under unconfined conditions within

the flood plain alluvium and under unconfined to semi-confined conditions within the Santa Fe Group.

Groundwater flow within the Mesilla Groundwater Basin is generally to the southeast (King, et al.,

1971).

The Mesilla Groundwater Basin aquifer has excellent recharge, transmission, and storage capacity.

These characteristics make the aquifer system capable of producing large quantities of high quality water

for agricultural, municipal, and industrial uses. The CLC Municipal Water System is a blended system

supplying water from 28 wells to approximately 67,900 people. The well field is located on the east side

of the Rio Grande within inter-tonguing sand and gravel layers in the Santa Fe Group. No single well

supplies more than 40% of the total water within the system, and the system produces on average

approximately 8 million gallons per day (EPA, 2000b).

Site Hydrogeology. In the vicinity of the GWP site, groundwater occurs under unconfined conditions in

unconsolidated to semi-consolidated fine sands with some gravel and clay. The aquifer is within the

Santa Fe Group. Groundwater flow is typically towards the east, away from the Rio Grande and towards

the City’s well field. Groundwater flow direction at the site is influenced by the recharge zone at the Rio

Grande and the pumping in the City’s well field. The depth-to-water at the site is approximately 185 feet

bgs (as measured at the DACTD maintenance yard) (EPA, 2000b).

003855




Climate. Surface water in the Las Cruces area is very limited. The climate in the area is arid. In the

Mesilla Valley, temperatures reach 90" F or greater an average of 101 days a year. In January, the

coolest month, the average daily maximum temperature is 57" F and the average daily minimum

temperature is 25" F. Precipitation amounts in the valley range between 8.0 and 9.0 inches per year, with

most precipitation being in the form of rain. Most rain is limited to brief, intense thunderstorms that

occur between July and September. Potential evaporation and transpiration greatly exceeds rainfall.

Potential evaporation rates measured in an evaporation pan average about 97 inches per year. Potential

evaporation and transpiration rates limit the amount of surface water available in the area. This also

limits the amount of recharge the aquifer receives from rainfall (King, et al., 1971).

2.2 Source, Nature, and Extent of ContaminationSite investigation activities were conducted by the NMED Superfund Oversight Section between 1997

and 2000 to identify the source and extent of the PCE contaminated groundwater plume. Several

potential sources were identified as a result of this investigation, but attribution to a specific source or

sources of the contamination was not identified or confirmed. In addition, the extent of contamination

was not completely defined by the locations of the wells installed. A summary of the NMED Superfund

Oversight Section’s findings regarding the source, nature, and extent of contamination is described in the

following paragraphs.

2.2.1 Sources of Contamination

The NMED Superfund Oversight Section attempted to identify the source of the contamination by

locating nearby facilities that potentially used PCE as part of their operations. PCE was first developed

in the early 1900's in Europe in an attempt to develop chemical commodities produced from acetylene.

Commercial production in the United States began in 1925, and widespread use of PCE in the dry

cleaning industry began in the 1930's (IRAC, 1979). PCE is widely used in dry cleaning. Other uses of

PCE include textile processing, metals cleaning, vapor degreasing, rubber coatings, solvent soaps,

printing inks, adhesives and glues, sealants, polishes, lubricants, silicones, and in the electronics industry

as a photoresist stripper (ATSDR, 1991).

003856




Facilities that may have used or managed PCE in the vicinity of the affected groundwater include the

following (the locations of these facilities are illustrated on Figure 2-7):

• DACTD Maintenance Yard (where Well No. 18 is located).

• The former Crawford Airport (formerly located near the northeast corner of Hadley Avenue and

Solano Drive, until the 1960s) (EPA, 2000b)

• The former National Guard Armory (formerly located near the northeast corner of Hadley

Avenue and Solano Drive, until 1990) (EPA, 2000b).

• Private dry-cleaning facilities

• Old Las Cruces Landfill (located east of the GWP affected area) and the Las Cruces Landfill (not

shown on Figure 2-7, but located approximately 1 mile further to the east).

• The City of Las Cruces Fleet Maintenance Yard, located at 1501 East Hadley (located within the

boundary of the former Crawford Airport).

The difficulty in finding the specific source of the PCE contamination is not unexpected; multiple

sources may be contributing to the contamination (EPA, 2000b). PCE use is likely to have occurred at

each of these facilities, but whether or not any have contributed to the PCE-affected groundwater has not

been confirmed. The RI will include further field investigation where PCE has been detected in soil

and/or soil vapor to verify whether there is a link to the groundwater plume, and use delineation of the

horizontal extent of the plume to determine what further investigation is warranted at other potential

sources.

2.2.2 Nature and Extent of Contamination

The investigation activities conducted by the NMED Superfund Oversight Section resulted in limited soil

sampling at select locations, limited surface water sampling at select locations, a soil vapor survey, and

groundwater sampling. These activities identified PCE in one soil and one surface water sample at the

DACTD facility. The soil vapor survey identified PCE in the soil vapor at the DACTD facility. The soil

vapor survey measured soil vapor concentrations at 8 feet bgs, and PCE concentrations ranged from non-

detect to 12 ppb-v (NMED, 1999). PCE was detected in groundwater samples at various locations.

003857




The monitor wells installed by the NMED Superfund Oversight Section provided good information about

the horizontal extent of the plume and concentrations at the water table, but the full horizontal and

vertical extent is not completely defined by these wells. PCE in its original form is a dense non-aqueous

phase liquid (DNAPL). To-date, only dissolved phase concentrations have been detected (no DNAPL).

Dissolved PCE was detected both upgradient and downgradient from the affected municipal supply

wells. Currently, the plume is known to be at least 8,000 feet long and approximately 2,000 feet wide,

and extend vertically from the water table to the depth of the water supply wells. See Figures 2-4, 2-5,

and 2-6 for the depths where wells at the site are screened relative to the water table, the ground surface,

and each other. These cross-sections also show the most recent sample analytical result for PCE for each

well..

The MCL is exceeded in one municipal supply well and 14 monitor wells, based on analytical data

collected by the NMED Superfund Oversight Section, the CLC, and the NMED Drinking Water Bureau.

Of the wells sampled, PCE concentrations ranged from non-detect to 53 ug/L (this high concentration

was detected in monitor well MW-SF3). The PCE concentrations appear to be stable over time in some

wells and increasing with time in others (see Figure 2-3 for the historical PCE concentrations in

groundwater at the site). Figures 2-4, 2-5, and 2-6 show in cross-section view the depth of the wells’

screened intervals and most recent PCE concentration for each well illustrated). Low concentrations of

1,2-dichloroethane (1,2-DCA), at MW-1 (at the DACTD facility), and trichloroethene (TCE), in MW-

SF10, were detected during the July 2000 sampling event (both 1,2-DCA and TCE are degradation

products of PCE). No other PCE-related VOCs have been detected. Currently, exposure through

ingestion of the groundwater is the only known exposure pathway potentially affected by the

contamination (EPA, 2000b), although there may also be some potential for exposure to PCE in soil

vapor at the DACTD maintenance yard. The PCE in soil vapor at the DACTD maintenance yard is due

to a currently unidentified surface source, and is not a result of soil vapor migration from the affected

groundwater that occurs at about 180 feet beneath the yard.

003858

Table 2-1PCE Concentrations in Wells Located in the Vicinity of the Griggs and Walnut Groundwater Plume SiteGriggs and Walnut Avenue Groundwater Plume SiteLas Cruces, New Mexico

Well IDWell Screened

Interval (ft) Aug-933 Feb-943 Jun-943 Oct-943 Jan-953 Feb-953 Apr-953 Jun-953 Aug-953 Oct-953 Jan-963 Feb-963 Apr-963 Jul-963 Jan-973 Jul-973

Well 10 3654 - 3554 NDWell 18 3730 - 3464 32.0 1.5 0.5 0.6 ND 6.4 0.8 0.8 1.0Well 19 3712 - 3457 0.3 0.3 ND ND ND ND ND 0.6 NDWell 21 unknown 0.9 0.8 1.0 1.0 0.7 1.3 1.2 1.2 1.1 1.3Well 24 unknownWell 27 3624 - 3339 1.4 0.7 0.6 0.8 ND 0.8 1.0 1.8Well 54 275 - 4791 ND NDPaz Park 260 - 3701

LRG-3191 130 - 1501

LRG-7375 unknownGas Card 3864 - 3854MW-1* 3856 - 3846MW-2* 3847 - 3842MW-3* 3854 - 3844MW-4* 3856 - 3846MW-5* 3856 - 3846MW-6* 3856 - 3846MW-SF1 3853 - 3838MW-SF2 3850 - 3835MW-SF3 3851 - 3836MW-SF4 3856 - 3841MW-SF5 3856 - 3841MW-SF6 3860 - 3845MW-SF7 3866 - 3851MW-SF8 3868 - 3853MW-SF9 3843 - 3828MW-SF10 3843 - 3833MW-1# 75 - 951

MW-2# 75 - 951

MW-3# 74 - 941

MW-4# 108 - 1131

MW-5# 82 - 921

MW-6# 80 - 901

MW-7# 75 - 851

MW-8# 85 - 951

units - ug/Lblank - not sampledND - non-detectJ - estimated concentration

- indicates an exceedance of the MCL* - Well Located at the DACTD Transportation Yard# - Well Located at the Former Circle K Store #1306**- Two samples collected, result is the average value of the two.Well screen intervals are in feet above mean sea level, except where no surveyed elevations were available1 - depth of well screen interval is in feet below ground surface2 - Sampling event conducted by the NMED Superfund Oversite Section3 - Sampling event conducted for compliance sampling by NMED Drinking Water Bureau4 - Sampling event conducted by Souder Miller and Associates (private consultant) as part of LUST investigation5 - Sampling event conducted by CDM (private consultant) as part of LUST investigation

GWP_TWP_Ver1.2_Table2-1.xls\Table2-1_PCEinWells Page 1 of 2 December 2001

003859

Table 2-1PCE Concentrations in Wells Located in the Vicinity of the Griggs and Walnut Groundwater Plume SiteGriggs and Walnut Avenue Groundwater Plume SiteLas Cruces, New Mexico

Well IDWell Screened

Interval (ft) Jan-982 Mar-982 Apr-982 May-984 Jun-982 Aug-984 Oct-982 Dec-984 Mar-984 Jul-992 Mar-002 Apr-002 Jul-002 Mar-015 Jun-013

Well 10 3654 - 3554 NDWell 18 3730 - 3464 15.0 18.0 17.0 20.1 7.0 47.0 (J)Well 19 3712 - 3457 1.1 0.8 (J) 1.2 1.4Well 21 unknown 2.0 2.0 2.3 2.0 3.4Well 24 unknown 1.5Well 27 3624 - 3339 1.4 2.0 4.5 4.0 4.5Well 54 275 - 4791 ND ND NDPaz Park 260 - 3701 ND ND ND NDLRG-3191 130 - 1501 1.0 2 0.9LRG-7375 unknown ND NDGas Card 3864 - 3854 15.0 17.0 11.0MW-1* 3856 - 3846 3.0 4.4 ND 1.6 3.0 7.0MW-2* 3847 - 3842 52 4 23.0 35.0 40.0 44.0 40.0 26.0 32.0MW-3* 3854 - 3844 20 4 15.0 10.0 11.0 21.0** 22.0 24.0 14.0 (J)MW-4* 3856 - 3846 8.1 4 9.0 7.0 5.0 5.0MW-5* 3856 - 3846 2.3 4 3.0 2.5 1.0 0.5 3.0 6.0 8.0MW-6* 3856 - 3846 ND 4 3.0 1.4 1.1 1.5MW-SF1 3853 - 3838 52.0 41.0 (J)MW-SF2 3850 - 3835 42.0MW-SF3 3851 - 3836 43.0 53.0MW-SF4 3856 - 3841 19.0 17.0MW-SF5 3856 - 3841 7.0MW-SF6 3860 - 3845 3.0MW-SF7 3866 - 3851 13.0MW-SF8 3868 - 3853 13.0MW-SF9 3843 - 3828 NDMW-SF10 3843 - 3833 31.0MW-1# 75 - 951 NDMW-2# 75 - 951 NDMW-3# 74 - 941 NDMW-4# 108 - 1131 NDMW-5# 82 - 921 NDMW-6# 80 - 901 NDMW-7# 75 - 851 NDMW-8# 85 - 951 ND

units - ug/Lblank - not sampledND - non-detectJ - estimated concentration

- indicates an exceedance of the MCL* - Well Located at the DACTD Transportation Yard# - Well Located at the Former Circle K Store #1306**- Two samples collected, result is the average value of the two.Well screen intervals are in feet above mean sea level, except where no surveyed elevations were available1 - depth of well screen interval is in feet below ground surface2 - Sampling event conducted by the NMED Superfund Oversite Section3 - Sampling event conducted for compliance sampling by NMED Drinking Water Bureau4 - Sampling event conducted by Souder Miller and Associates (private consultant) as part of LUST investigation5 - Sampling event conducted by CDM (private consultant) as part of LUST investigation

GWP_TWP_Ver1.2_Table2-1.xls\Table2-1_PCEinWells Page 2 of 2 December 2001

003860

Figure 2-1

Well Location Map



Legend

GWP_TWP_Ver1.2_Figure2-1.pdf

# City of Las Cruces (CLC) Supply Wells(Screen Intervals Range From 3730 to 3325 MSL)

'W Private Wells(Screen Interval For LRG-3191 From 130 - 150 bgs)(Screen Interval For LRG-7375 Is Unknown)

$ Monitor Wells (Screen Intervals Range From 3867 to 3827 MSL)

N

500 0 500 1000 Feet

#

#

#

# #

#

#

#

#

#

#

'W

'W

$$$

$ $$

$$$

$

$$$

$

$

$

$

#

(

CLC Well 27

CLC Well 18CLC Well 19

CLC Well 21

CLC Well 57

CLC Well 10

CLC Well 54

CLC Well 28

CLC Well 26

CLC Well 20

CLC Paz Park Well

LRG-7375

LRG-3191

MW-1MW-2

MW-3

MW-4 MW-5

MW-6

MW-SF2

MW-SF3

MW-SF4

MW-SF5MW-SF6MW-SF7

MW-SF8

MW-SF9

MW-SF-1

MW-SF10

Gas Card Well

#

Circle K# 1306

C

C'

B'

BA

A'

CLC Well 61

CLC Well 24

A --- A' Locations of Cross Sections forFigures: 2-4, 2-5, & 2-6

003861





003862

Gasoline

Shop

Superfund Oversight Section

Ground Water Quality Bureau

New Mexico Environment Department

Drawn by: J. Shain 8/99Last modified by: christopher holmes 10/2000

Scale050 100 200

1 Inch Equals 100 Feet

Unpaved Parking Lot

Cottonwood Street

Willow

Street

N

Figure 5

MW-SF3

MW-SF4

Vacant Lot

MetalShed

City of Las Cruces

Well 18

Storage

Asphalt Mixing Area

Storage

Cemetery

Unpaved Parking Lot

Griggs Avenue

Diesel

Shop

Office Building

Ove

rhan

g

Wash Bay

Parking

Lot

MW-4

MW-3

MW-1

MW-2MW-SF2

MW-5

MW-SF1

Legend

fence

Results of soil vapor survey at the Doña Ana County Transportation Department,2025 East Griggs Avenue, Las Cruces, New Mexico.

monitoring well

Ground Water, Griggs and Walnut Site, CERCLIS Number: NM0002271286

MW-4

Geoprobe pointGP-1ND PCE concentration (ppb-v)

ND not detected

GP-30Trace

GP-31-2 ppb

GP-243 ppb

GP-254 ppb

GP-4ND

GP-5~1 ppb

GP-27ND

GP-31ND

GP-32ND

GP-21-2 ppb-v

GP-1ND

GP-33ND

GP-6ND

GP-7ND

GP-23ND

GP-101 ppb

GP-82-3 ppb

GP-91 ppb

GP-183 ppb

GP-111-2 ppb

GP-153 ppb

GP-126 ppb

GP-226 ppb

GP-132-3 ppb

GP-297ppb

GP-169 ppbGP-17

7 ppb

GP-26ND

GP-147ppb

GP-2112 ppb

GP-28ND

GP-19traceGP-20

ND

003863

davis

Figure 2-2 Soil Vapor Concentrations at 8 ft. bgs at the DACTD Maintenance Yard (Reproduced from NMED Figure) Griggs and Walnut Avenue Groundwater Plume Site Las Cruces, New Mexico





003864

#

#

#

# #

#

#

#

#

#

#

'W

'W

$$$$ $ $

$$$$

$$$

$

$

$$

#

(

MW-1MW-2

MW-3

MW-4

MW-5

MW-6

MW-SF2

MW-SF3

MW-SF4

MW-SF5MW-SF6MW-SF7

MW-SF8

MW-SF9

MW-SF-1

MW-SF10

Gas Card Well

CLC Well 27


CLC Well 21

CLC Well 57

CLC Well 10

CLC Well 54

CLC Well 28

CLC Well 26

CLC Well 20

CLC Paz Park Well

LRG-7375

LRG-3191

?

?

?

?

?

?

?

CLC Well 61

CLC Well 24

Legend? Estimated Extent of PCE Detections

(based on existing monitor and water supplywell sample analysis)

#(Screen Intervals Range From 3730 to 3325 MSL)City of Las Cruces (CLC) Supply Wells

'W

$ Monitor Wells(Screen Intervals Range From 3867 to 3827 MSL)

PCE concentration units are ug/L

500 0 500 1000 Feet

Figure 2-3

Historical PCE Concentrations



N

Mw-1 Pce_conc.

Date Values 03/12/1998 NS 04/15/1998 3.0 08/31/1998 4.4 12/03/1998 ND 03/02/1999 1.6 07/13/1999 3.00 07/18/2000 7.00

Mw-2 Pce_conc.

Date Values 03/11/1998 52.0 04/15/1998 23.0 08/31/1998 35.0 12/03/1998 40.0 03/02/1999 44.0 07/13/1999 40.00 03/13/2000 26.00 07/19/2000 32.00

Mw-3 Pce_conc.

Date Values 03/11/1998 20.0 04/15/1998 15.0 08/31/1998 10.0 12/03/1998 11.0 03/02/1999 18.0 03/14/1999 24.00 07/13/1999 22.00 03/14/2000 24.00 07/18/2000 14.0 (Jv)

Mw-4 Pce_conc.

Date Values 03/12/1998 8.1 04/15/1998 9.0 08/31/1998 NS 12/03/1998 NS 03/02/1999 NS 07/13/1999 7.00 03/15/2000 5.00 07/18/2000 5.00

Mw-6 Pce_conc.

Date Values 03/24/1998 ND 04/15/1998 3.0 09/01/1998 1.4 12/04/1998 1.1 03/02/1999 1.5

Mw-sf9 Pce_conc.

Date Values 07/18/2000 ND

Mw-sf2 Pce_conc.

Date Values 03/14/2000 42.0

Mw-5 Pce_conc.

Date Values 03/12/1998 2.3 04/16/1998 3.0 08/31/1998 2.5 12/03/1998 1.0 03/02/1999 0.5 07/15/1999 3.00 03/15/2000 6.00 07/19/2000 8.00

Mw-sf3 Pce_conc.

Date Values 03/14/2000 43.0 07/17/2000 53.00

Mw-sf4 Pce_conc.

Date Values 03/14/2000 19.0 07/17/2000 17.00

Mw-sf5 Pce_conc.

Date Values 07/17/2000 7.0

Mw-sf6 Pce_conc.

Date Values 07/17/2000 3.0

Mw-sf7 Pce_conc.

Date Values 07/17/2000 13.0

Mw-sf8 Pce_conc.

Date Values 07/17/2000 13.0

Mw-sf10 Pce_conc.

Date Values 07/19/2000 31.0

Mw-sf1 Pce_conc.

Date Values 03/15/2000 52.0 07/18/2000 41.0 (Jv)

Gas_Card _Well Pce_conc.

Date Values 05/05/1998 15.0 06/23/1998 17.0 07/15/1999 11.0

Well_10 Pce_conc.

Date Values 06/07/1995 ND 07/20/1999 ND

Well_18 Pce_conc.

Date Values 03/13/1994 ND 01/10/1995 32.0 02/22/1995 1.5 02/27/1995 1.2 04/12/1995 0.5 08/18/1995 0.6 10/04/1995 ND 01/09/1996 6.4 02/21/1996 0.8 04/03/1996 0.8 05/02/1996 1.0 07/23/1996 ND 04/15/1998 15.0 06/23/1998 18.0 10/20/1998 17.0 07/20/1999 20.1 04/20/2000 7.0 7/18/2000 47.0 (Jv

Paz_park Pce_conc.

Date Values 04/15/1998 ND 06/23/1998 ND 07/20/1999 ND

Well_54 Pce_conc.

Date Values 01/11/1995 ND 04/24/1996 ND 07/20/1999 ND 04/20/2000 ND

Well_21 Pce_conc.

Date Values 08/09/1993 0.9 02/17/1994 0.8 06/21/1994 1.0 10/10/1994 1.0 01/10/1995 0.7 04/05/1995 1.3 08/18/1995 1.2 10/04/1995 1.2 01/09/1996 1.1 01/22/1997 1.3 04/15/1998 2.0 04/27/1998 2.0 06/23/1998 2.0 07/20/1999 2.3 04/20/2000 2.0

Lrg-7375 Pce_conc.

Date Values 01/27/1998 ND 06/23/1998 ND

Well_19 Pce_conc.

Date Values 03/13/1994 0.3 05/16/1994 0.3 10/03/1994 ND 01/09/1995 ND 04/05/1995 ND 08/18/1995 ND 10/04/1995 ND 01/09/1996 0.6 07/23/1997 ND 04/15/1998 1.1 06/23/1998 0.80 J 07/20/1999 1.2

Well_27 Pce_conc.

Date Values 08/09/1993 1.4 05/16/1994 0.7 06/21/1994 0.7 10/03/1994 0.6 05/09/1995 0.8 08/18/1995 ND 10/04/1995 0.8 02/23/1996 1.0 07/29/1997 1.8 04/15/1998 1.4 06/23/1998 2.0 07/20/1999 4.5 04/20/2000 4.0

Lrg-3191 Pce_conc.

Date Values 03/12/1998 1.0 06/24/1998 0.9

GWP_TWPVer1.2_Figure2-3.pdf

Well_ 20 Pce_conc.


Private Wells(Screen Interval For LRG-3191 From 130 - 150 bgs)(Screen Interval For LRG-7375 Is Unknown)

Well _26 Pce_conc.


Well _61 Pce_conc.


Well _24 Pce_conc.

Date Values 06/26/2001 1.5

003865





003866

003867

CH2M HILL

Refer to Figure 2-1 for the location of this cross-section in plan view.





003868

003869

davis

davis

Figure 2-4 Locations of Potential Sources of PCE (Reproduced from NMED Figure) Griggs and Walnut Avenue Groundwater Plume Site Las Cruces, New Mexico

CH2M HILL






003870

003871

CH2M HILL






003872

Main S

treet U.S

. 70

U.S. 70PicachoAvenue

We l l 10ND( .5)

MW-SF67/00 3

We l l 184/00 7 .0 , 8 .9

MW-SF57/00 7

MW-SF77/00 6

MW-SF87/00 13

We l l 214/00 2 .0 , 2 .5

Paz Par k We l l ND( .5)

We l l 54ND( .5)

Spruce Avenue

We l l 28ND( .5)

Walnut S

treet

We l l 1912/99 0 .9

We l l 274/00 4 .0 , 4 .1

MW-SF107/00 30

Amador Avenue

Lohman Avenue

Las Cruces

Griggs Avenue

MW-SF97/00 ND(1)

Solano Drive

LR G-31916/98 0 .9 , 0 .92

Avenue

We l l 26ND( .5)

We l l 20 ND( .5)

We l l 57ND( .5)

Hadley Avenue

21

2

25

flood con t r o l dam

3

41

1

1

Explanation

We l l 214/00 2 .0 , 2 .5

Production WellDate PCE Concentration (µg/L)

MW-SF107/00 30

Monitoring WellDate PCE Concentration (µg/L)

Locations used for dry cleaning between 1955 and 1990

Poten t i a l Sour ces o f PCE

For mer Na t iona l Guard A r mor y

For mer C r aw fo r d A i r por t

Doña Ana Coun ty Tr anspor ta t i on Depar tmen tN ine mon i to r i ng we l l a r e shown i n F igu r e 3 .

O ld Las C r uces l and f i l l4

3

1

1

1sp l i t samp les2dup l i ca te samp les

Scale1,000 2,000 4,000

1Inch Equals 2,000 Feet

N

0

2

New Mexico Environment DepartmentGround Water Quality BureauSuperfund Oversight Section

Figure 1Ground Water, Griggs and Walnut Site, CERCLIS Number: NM0002271286

Production wells, monitoring wells, and potential sources of tetrachloroethene in Las Cruces, New Mexico.

Drawn by: christopher holmes 10/2000

003873

CH2M HILL

Figure 2-7 Locations of Potential Sources of PCE (Reproduced from NMED Figure) Griggs and Walnut Ground Water Plume Site Las Cruces, New Mexico





003874

Section 3Site Conceptual Model

003875





003876

GWP_TWP_VER1.3_SECT03_SITECONCEPTUALMODEL.WPD FEBRUARY 20023-1

Section 3

Site Conceptual Model Information obtained from the HRS Documentation Record and gathered during the initial site visit was

used to develop a conceptual understanding of the site in terms of potential sources and potential

migration pathways. This initial conceptual model is used to begin evaluation of potential risks to human

health and the environment, assist in identifying locations where additional sampling is necessary, and

ultimately to assist in the identification of possible remedial technologies. This understanding is

necessary to enable appropriate design of the RI/FS in the planning stage.

The initial site conceptual model for the GWP site is presented in Figure 3-1. This figure identifies

potential primary sources and release mechanisms identified through review of site documents. No

sources have yet been confirmed, but the possible sources shown on Figure 3-1 are identified as

possibilities from information presented in the site documents, and based on knowledge of potential

sources documented at other sites. These include possible routine spills, potential leaking from process

equipment and/or storage vessels, and possible improper disposal of PCE by dumping on the ground. If

such releases occurred, these activities could result in the creation of secondary sources of contamination

in the form of affected surface soil and subsurface soil. Assuming PCE release to the soil, the secondary

release mechanisms would then include volatilization into soil vapor and infiltration/leaching from the

soil to the groundwater. The potential for the presence of PCE in the form of a DNAPL in the subsurface

would also exist under these potential release scenarios. If DNAPL is present, then it would also be a

secondary source of contamination in the subsurface. Release mechanisms associated with a potential

DNAPL would include volatilization into soil vapor and dissolution into the soil and the groundwater.

As described in Section 2, various facilities have been identified in the vicinity of the affected

groundwater that would or could have used PCE in their operation (or could have managed waste PCE in

their operation) and therefore could potentially have contributed to a release of PCE to the soil and/or

groundwater (see Figure 2-3 for locations of potential sources). These facilities include the DACTD

maintenance yard, the former National Guard Armory, the former Crawford Airport (both formerly

located near the northeast corner of Hadley Avenue and Solano Drive (EPA, 2000b), various private dry

cleaning establishments located throughout the area, the City of Las Cruces Fleet Maintenance Yard, and

the Las Cruces Landfill, located east of the plume. Whether or not any one of these facilities contributed

to the PCE in the groundwater associated with Well Nos. 18, 19, 21, and 27 is not yet known;

003877




determination of whether any of these are actual sources for the contamination affecting the groundwater

in the study area will be facilitated through the collection of site characterization data.

The migration pathways for contamination originating from the potential sources include surface soil,

subsurface soil, soil vapor, and groundwater. The identification of potential receptors along these

migration pathways, and the risk to these potential receptors, will be a function of the RI/FS. Currently,

the City of Las Cruces municipal supply Well Nos. 18, 19, 21, and 27, and one private residential well

are the only potential identified link to possible receptors at the site. The site conceptual model

presented in Figure 3-1 will be refined following completion of the site characterization, described in

Section 5.

At the present time, there is no indication that indoor air is a significant migration pathway or potential

route of exposure for this site. In terms of exposure at the surface, the only location where PCE has been

detected in the vapor phase to date is in the shallow subsurface at the DACTD maintenance yard, and

further sampling of soil and soil vapor is planned there to help determine the risks associated with the

contamination (soil vapor pathway). At other areas of the site, the affected media (groundwater) occurs

at over 200 feet below ground surface, too deep to present an indoor air risk for structures located on the

ground surface above the plume from soil vapor (i.e. there is no pathway).

Also, while groundwater potentially affected with low levels of PCE may be found in the water

distribution system, concentrations that may reach water users are documented below the drinking water

MCL. To address the concern that this water may pose an inhalation risk, through the use of the water in

showers or evaporative coolers, the potential for risk through exposure to volatilized PCE in indoor air

was evaluated. A calculation was performed to determine the concentration of PCE that would have to

be present in the water supply to present an indoor air risk using the Integrated Human Exposure Model

(Foster and Chrostowski, 1987). The assumed exposure scenario was for a person taking a shower

using PCE-contaminated water (a more direct exposure than through the use of an evaporative cooler).

The calculation shows that the PCE concentration in the shower water would have to be 7,140 ug/L to

pose a 1 x 10-6 carcinogenic risk through inhalation. This concentration is over 100 times greater than the

highest PCE concentration historically detected in monitor wells at the site (53.0 ug./L at monitor well

003878




MW-SF3), and concentrations of PCE in groundwater in the distribution system are significantly lower

than that (less than 5 ug/L). Therefore, it is highly unlikely that exposure to PCE in indoor air resulting

from a shower or the use of evaporative coolers fed with water contaminated with PCE below the MCL

(5 ug/L), would pose a risk that isn’t already addressed by the pathway of direct ingestion or direct

contact with the affected water. Since the water supply system is monitored to maintain PCE

concentrations below 5 ug/l, there is no reason to add indoor air as a potential exposure pathway for the

RI at this time. This does not preclude indoor air from being added as a potential pathway if warranted

based on new data gathered during the investigation.

003879





003880

PotentialPrimary

Source(s)

PrimaryRelease

Mechanisms

PotentialSecondary

Sources

SecondaryRelease

Mechanisms

ExposurePathway

Dry Cleaning and/orother Processes

Utilizing PCE

PCE Storage(drums, containers,

tanks, etc.)

Improper Disposalof PCE or PCE-

containing materials

Leaks

RoutineSpills

Dumping DNAPL

Infiltration/LeachingAffectedSurface Soil

Volatilization

Dissolution

Soil Vapor

Groundwater

Receptor

Hum

an

Eco

logi

cal

Exposure Route

Ingestion

Direct Contact

**

**

Inhalation *

Ingestion

Direct Contact

**

DALLAS\PROJECT\163188\TASK01PP\WorkPlans_Technical\TAWP\VER1.2\FIGURES\FIG3-1.VSD

Figure 3-1Initial Site Conceptual ModelGriggs and WalnutGroundwater Plume SiteLas Cruces, New Mexico

AffectedSubsurface

Soil

003881





003882

Section 4Data Quality Objectives

003883





003884

GWP_TWP_VER1.2_SECT04_DQOS.WPD DECEMBER 20014-1

Section 4

Data Quality ObjectivesTo identify and describe the type and quality of the data needed to support future decisions regarding

remedial actions at the GWP site, general Data Quality Objectives (DQOs) have been identified. These

DQOs are qualitative and/or quantitative statements that provide a basis for the identification of the

RI/FS activities to be performed, and ensure that data collected during the RI/FS will be of sufficient and

adequate quality for their intended use. EPA guidance on the DQO process has been utilized in

developing these initial DQOs (EPA, 2000a). The DQO process outlined in the guidance is a seven-step

process which provides a systematic approach for defining the criteria to be met in the data collection

effort. The DQOs developed using this process are presented in Table 4-1, and discussion of the DQO

process as applied to this site is provided in the following paragraphs.

4.1 State the ProblemThe purpose of this first step in the DQO process is to develop an understanding of the broad context of

the problem being addressed by the investigation, and to define the issue(s) to be resolved by completing

the investigation.

An important consideration in defining the problem is identifying the involved parties who can provide

input to the planning stages of the RI/FS. For this site, these parties are:

• EPA Region 6 Superfund Division (lead Agency).

• NMED Superfund Oversight Section (technical support).

• NMED Drinking Water Bureau.

• Doña Ana County Transportation Department.

• City of Las Cruces Utilities Division.

Each of these parties are familiar with the site, can provide both technical and regulatory input to the

process, and have a stake in the outcome. The community is also a key stakeholder, and the involvement

of citizens into the process is an integral part of the Superfund program. Community involvement is

addressed through EPA’s development of a separate Community Involvement Plan and assignment of an

EPA Community Involvement Coordinator.

003885

CENTRAL WOOD PRESERVING COMPANY SITE



Based on the descriptions provided in Sections 2 and 3, including input provided by EPA, NMED,

DACTD, and CLC, what is known about the site is as follows: (1) there is one known contaminant

specifically associated with the GWP site (PCE); (2) soil vapor and groundwater within the investigation

area are known to be affected by the presence of the contaminant PCE (in gaseous and dissolved phases,

respectively) at certain sampled locations; (3) dissolved PCE is detected in groundwater in monitor wells

screened at the water table and in water supply wells open to the formation (up and downgradient from

the area where the soil vapor investigation was done); (4) concentrations of PCE in groundwater at some

locations have been shown to exceed the MCL of 5 ug/L; (5) there are potential surface sources of PCE

located within the investigation area; and (6) potential receptors exist (the users of the drinking water

supply system supplied by the groundwater).

What is known specific to the contaminant is as follows: (1) PCE was first commercially produced in the

US in 1925, and was widely used in dry-cleaning beginning in the 1930s; (2) historically, the typical uses

of PCE have been in dry cleaning, textile processing, and metal degreasing; and (3) degradation products

of PCE are TCE, cis-1, 2-dichloroethene (cis-1,2-DCE), 1,2-DCA, vinyl chloride, ethene, ethane, and

methane, and these degradation products are not typically detected in groundwater at the GWP site,

although low concentrations of 1,2-DCA, at MW-1 (at the DACTD facility), and TCE, in MW-SF10,

were detected during the July 2000 sampling event.

What is not yet known about the site is as follows: (1) confirmation of a specific source(s) definitively

linked to the PCE in soil vapor and groundwater; (2) definition of the vertical and horizontal extent of

PCE in soil, soil vapor, and groundwater; (3) confirmation that the PCE contamination in soil and

groundwater is present in gaseous and dissolved phases only and not in the liquid phase (ie. dense non-

aqueous phase liquid or DNAPL); and (4) confirmation of the potential likelihood for natural attenuation

of the PCE to occur in this hydrogeologic system.

4.2 Identify the DecisionThe purpose of this step in the DQO process is to define the decision statement which combines the key

question(s) the investigation will attempt to resolve with the alternative actions that may be taken. For

the GWP site, the principal RI-related investigation questions are:

003886




• Is (are) the primary source(s) of PCE contamination in soil vapor and groundwater still present

and acting as a continuing source(s)?

• Is (are) secondary source(s) of PCE in soil and or groundwater still present and acting as a

continuing source(s)?

• What is the vertical and horizontal extent and magnitude of PCE contamination in soil, soil

vapor, and groundwater, relative to potential receptors?

• Is the contamination detected at CLC Well No. 24 related to the contamination demonstrated at

the GWP Site [i.e. CLC Well Nos. 18, 19, 21, 27]?

• Do the affected soil, soil vapor, and/or groundwater pose an unacceptable risk to human health or

the environment?

• If a risk is confirmed, where do the contaminant concentrations exceed applicable or relevant and

appropriate regulations (ARARs) or exceed contaminant concentrations corresponding to

preliminary remediation goals that may be established for the site?

• What remedial alternatives are appropriate to address the contamination at the site, in light of the

risk to receptors?

Actions that could result from the resolution of the principal investigation questions are:

• Recommendation that no response action is required based on the lack of unacceptable risk to

potential receptors.

• Recommendation that some response action is required based on the unacceptable risk posed to

potential receptors.

• Identification and evaluation of potential response actions.

The ultimate outcome would be that the actions taken help achieve the goal of protecting human health

and the environment. The overall decision statement based on the principal investigation questions and

the possible actions is:

Determine whether or not the nature and extent of contamination and confirmed sources or secondary

sources of the PCE contamination in soil, soil vapor, and groundwater warrant response actions to protect

human health and the environment, and evaluate potential response action alternatives appropriate for the

site under the requirements of the NCP.

003887




4.3 Identify Inputs to the DecisionThe purpose of this step in the DQO process is to identify what information is required to support the

decision to be made, and specify which inputs require collection of additional data in the RI. These

inputs are outlined in Table 4-1.

4.4 Define the Investigation BoundariesThe investigation area for the RI corresponds to the extent of the Griggs and Walnut Avenue PCE

groundwater plume and surrounding areas where water wells could be adversely affected by the

contamination or its degradation products. The relationship of contamination in CLC Well No.24 to the

other affected wells will be evaluated to determine if its contamination is a part of the GWP site.

003888

OF 4GWP_TWP_VER1.2_TABLE4-1_DQOS_MAR02REVISION.WPD MARCH 2002

Table 4-1Data Quality Objectives

Media of Interest Data Quality Objective RI/FS Activity Analytes

Surface soil(0 to 6 inches bgs)

In areas where PCE is detected inshallow subsurface soil vapor,confirm presence/absence ofsurface soil contamination as apotential secondary source,sufficient to support risk-baseddecision regarding necessaryresponse actions

� Grid sampling of surface soil for PCE and related constituents.� Measure parameters necessary to evaluate potential response

actions.� Collect data adequate to support performance of human and

ecological risk assessments.

� Volatile Organics� Physical soil

parameters1

003889



PAGE 2 OF 4GWP_TWP_VER1.2_TABLE4-1_DQOS_MAR02REVISION.WPD MARCH 2002

Soil vapor(vadose zone - 0 toapproximately 200feet bgs)

In areas where PCE is detected inshallow subsurface soil vapor,confirm presence/absence of soilvapor contamination as apotential secondary source andexposure pathway, sufficient tosupport risk-based decisionregarding necessary responseactions

� Grid sampling of horizontal and vertical extent of subsurface soilvapor for PCE and related constituents (note: sampling of soilvapor will be conducted in potential source areas if determinedto be warranted based on the horizontal and vertical plumedefinition).

� Measure parameters necessary to evaluate potential responseactions.

� Collect data adequate to support performance of human andecological risk assessments, using existing data as appropriate toreduce RI data collection.

� Volatile Organics

003890




Subsurface soil(6 inches toapproximately 200feet bgs)

In areas where PCE is detected inshallow subsurface soil vapor,confirm presence/absence ofsurface soil contamination as apotential secondary source,sufficient to support risk-baseddecision regarding necessaryresponse actions

� Sampling of subsurface soil via direct push (grab) andconventional drilling methods, for both organic and inorganiccontamination

� Sampling of any non-aqueous phase liquid found, to supportfuture decisions regarding remedial options

� Characterize subsurface stratigraphy� Measure parameters necessary to evaluate potential remedial

action alternatives� Collect adequate data to perform human health and ecological

risk assessments

� Volatile Organics� Inorganics� Physical soil

parameters1

� Chemical and physicalcharacteristics ofNAPL3

Above areas where PCE isdetected in groundwater andwhere a source is suspected inoverlying soils based on eithersoil or soil vapor results, confirmpresence/absence of PCE insubsurface soil as a potentialcontinuing secondary source togroundwater, sufficient tosupport risk-based decisionregarding necessary responseactions.

003891




Groundwater(below water table -below approximately200 feet bgs)

Confirm horizontal and verticalextent of PCE in groundwatersufficient to make risk-baseddecision regarding necessaryresponse actions.

� Characterize deeper aquifer conditions via existing onsite watersupply and monitoring wells and available logs, and new wells.

� Measure parameters necessary to evaluate potential remedialaction alternatives

� Collect adequate data to perform human health and ecologicalrisk assessments

� Sample any non-aqueous phase liquid found, to support futuredecisions regarding remedial options

� Volatile Organics� Water quality

parameters2

� Chemical and physicalcharacteristics ofNAPL3

� Physicalcharacteristics ofaquifer

Characterize local aquiferproperties and flow conditionssufficient to support evaluation offate and transport of the PCEcontamination, sufficient to allowrisk-based decisions regardingnecessary response actions.

� Geophysical logging to assess deeper aquifer stratigraphy� Aquifer testing to evaluate groundwater flow conditions and

contaminant fate and transport with the aquifer� Computer modeling to evaluate groundwater flow conditions,

contaminant fate and transport, and to evaluate potentialremedial action alternatives.

Notes:1. Physical soil/sediment parameters include TOC, pH, grain size, permeability, toxicity, percent moisture, and oil & grease.2. Water quality parameters include TOC, pH, total dissolved solids, alkalinity, dissolved oxygen, total hardness, and major cations/anions.3. Chemical/physical parameters of NAPL include BTU, pH, liquid content, ash content, viscosity, density, and organic/inorganic components.Selection of initial sample locations is based on the need to confirm plume extent. Once the plume extent has been verified, investigations into potential sources will be moreeffective.

003892

Section 5Site Characterization Tasks

003893





003894

GWP_TWP_VER1.2_SECT05_SITECHARACTERIZATIONTASKS.WPD DECEMBER 20015-1

Section 5

Site Characterization TasksThis section describes the tasks to be conducted to complete the Remedial Investigation (RI) for this site,

i.e. the site characterization portion of the RI/FS. The activities described have been structured to

complement existing data available for the site from previous investigations conducted by the NMED.

Tasks to be conducted include literature review for the description of regional geographical, geological,

and hydrological characterization and receptor identification, file review of existing wells, site

reconnaissance, supplemental subsurface soil sampling and characterization, soil vapor sampling and

characterization, groundwater sampling and characterization, analytical data evaluation, assessment of

risk, and preparation of a RI Report. The focus of the investigation will be soil vapor and groundwater;

surface water and sediment are not considered exposure pathways for this site. These tasks will be

conducted in accordance with EPA’s Guidance for Conducting Remedial Investigations and Feasibility

Studies Under CERCLA (EPA, 1988). The following paragraphs address the site characterization-related

activities. Section 6 describes the work to be conducted under the Feasibility Study portion of the

RI/FS.

5.1 Available Data Collection and Site ReconnaissanceThis task will be performed to identify and confirm information available from local, regional, and

federal sources regarding site characteristics such as geology, hydrogeology, soil characteristics, and

water well users. A search of available records for the locations of private water supply wells will be

conducted. In addition, a search will be conducted to determine if any other environmental monitor wells

exist and can be used for the field investigation. All available records, including boring logs, geophysical

logs, and construction diagrams, will be obtained, if available, for all wells known to exist in the

investigation area. These records will be used to determine construction details and completion depths of

wells in the area. A literature review will be conducted to obtain information on regional hydrologic and

geologic conditions. The information of interest includes historical water level and groundwater flow

directions and regional studies on the hydrogeologic characteristics of the Rio Grande flood plain

alluvium and the Santa Fe Group. The CLC will be contacted to obtain available information about

municipal wells in the area of the plume. This information could include well construction details, water

003895




level data, pumping rates and/or volumes, and aquifer testing data. This information will be used to

determine the initial scope of the hydrogeologic investigation and to aid in refining the conceptual model.

During the initial site reconnaissance, a limited door-to-door inventory of the existence of water wells

and monitor wells in the vicinity of the GWP site may be performed. The site reconnaissance will also

include a survey of the preliminary locations for monitor wells. This task will also include definition of

property boundaries, where necessary, location of utility rights of way, and identification of civil survey

data available from local and regional sources and/or within the EPA file to support performance of the

field investigation. A title search will be performed to be sure that all sample locations identified in the

RI scope of work are addressed within known property boundaries to support obtaining access

agreements under the Civil Surveying and Access Agreements task described in Section 5.2.2. A

preliminary site map will be prepared using this information as well as aerial photographs available for

the site.

Additional information concerning potential sources of the contamination will be obtained prior to the

beginning of the field investigation. The CERCLIS, RCRIS, and applicable State of New Mexico

databases will be searched to identify sites in the area of the plume that have potentially used PCE. A

Geographic Information System (GIS) will be created for the project, using the GIS data already

available from the CLC as a base. The GIS will be used to evaluate spatial relationships between

sources, wells, and contaminant data, to generate maps for the field investigation effort and the RI/FS

reports, and to support future modeling efforts. A map of identified potential sources, including those

identified by the NMED, will be generated. This information will be used to focus efforts to investigate

potential sources of the contamination.

The information gathered and reviewed during this task will be utilized to refine the site conceptual

model presented in Section 3 in terms of migration pathways and receptors, and provide a basis for the

compilation of ARARs under the Feasibility Study described in Section 6. The field investigation

program described in Section 5.2 will be refined, if necessary, based on the update to the site conceptual

model.

003896




5.2 Field InvestigationThis section describes in general the field investigation tasks to be conducted to meet the data quality

objectives defined in Section 4. The field investigation will be conducted in a phased approach. The

initial phase will include a soil vapor survey and surface soil sampling conducted using direct-push

technology (DPT) at the DACTD maintenance yard where PCE in soil vapor was detected by the NMED.

Also during the first phase, one boring will be drilled to below the water table at the DACTD

maintenance yard, and multiple soil vapor and groundwater samples will be collected during drilling in

an attempt to better define the vertical extent of contamination. In addition, water table wells will be

installed at various locations outside the perimeter of the current known detections and between potential

sources and known contamination to better define the horizontal extent of groundwater contamination

and its relationship to the potential sources. Initial well locations are illustrated on Figure 5-1 (these are

approximate and will be finalized in the field based on logistical considerations). The majority of

samples will be analyzed for PCE and/or VOCs; some geotechnical samples will also be collected to aid

in the evaluation of potential remedial alternatives.

The vertical extent of contamination is currently unknown. The contamination is known to exist as

shallow as the water table (as detected in water table monitor wells at about 200 feet bgs) and as deep as

the screened zone at CLC Well No. 27, for example (the top of the well screen for CLC Well No. 27 is

at an elevation of 3624 feet above mean sea level, or approximately 500 feet bgs). However, the effects

of pumping at the municipal wells on the vertical geometry of the plume are unknown, and it is unknown

if there are PCE concentration gradients with depth or preferential contaminant flow paths within the

aquifer. To address these issues, multi-level monitor wells will be installed as part of the investigation.

The locations of these wells will be determined during the second phase of the investigation based on the

sampling results of the water table wells. The multi-level wells will be placed in and near areas where

the PCE concentrations in the groundwater are highest.

Figure 5-2 shows the location of each potential source previously identified by the NMED, the existing

well locations (identified based on whether or not PCE has been detected in the well), and the proposed

locations for the initial wells to be installed during the first phase of the RI. Table 5-1 lists each

003897




proposed well and the reasoning for each location relative to identified potential sources and/or plume

delineation. If potential source areas are found to be suspect based on the additional data, additional

investigations may be performed in subsequent phases, potentially including soil vapor surveys, surface

and subsurface soil sampling, and/or additional groundwater well installations/sampling. Once the

contaminant plume has been defined, aquifer testing may be performed at select locations to provide data

necessary for the evaluation aquifer characteristics, contaminant fate and transport, and to identify and

evaluate potential remedial alternatives.

5.2.1 Site-Specific PlansSite-specific plans that define in detail the procedures to be followed through performance of the field

investigation are provided under separate cover. These site-specific plans are: the Sampling and Analysis

Plan (SAP), composed of the Field Sampling Plan (FSP) and Quality Assurance Project Plan (QAPP); the

Site Management Plan (SMP); and the Health and Safety Plan (HSP). Sample collection and data

management procedures are defined in the FSP; analytical methods and quality assurance/quality control

procedures are defined in the QAPP. Access, security, contingency procedures, management

responsibilities, and IDW management procedures are described in the SMP. The HSP defines CH2M

HILL-specific employee training, required personal protective equipment, medical surveillance

requirements, and standard operating procedures applicable to the field investigation tasks to be

performed.

During mobilization, these plans will be revised as necessary to take into account site-specific details not

yet identified that may affect field procedures.

5.2.2 Civil Survey and Access AgreementsUnder the Available Data Collection and Site Reconnaissance task described in Section 5.1, a title search

will be conducted to determine whether all sample locations identified in the RI scope of work are

addressed within known property boundaries. The Civil Survey and Access Agreements task will include

providing support to EPA in identifying and obtaining access agreements to complete the RI sampling

effort. Based on the legal boundary definitions, a civil survey will be performed to locate property

003898




boundaries for onsite properties to provide a reference in the field. The surveying effort will also include

the locations and reference elevations for existing water supply wells and monitor wells. This work will

be done prior to any field investigation work.

5.2.3 Private Water Supply Well and Monitor Well Search

Private water supply wells, both existing and abandoned, and existing monitor wells will be researched

(as described in Section 5.1) and located so that their locations may be surveyed as part of the civil

survey activities. In addition, this activity will include measurement of the total depth and depth to

groundwater in each existing well, and determination of the viability of each well for sampling of

groundwater (as described in Section 5.2.9).

Details regarding this activity are provided in the FSP.

5.2.4 Sampling Effort Mobilization/DemobilizationIn preparation for performance of field investigation tasks, mobilization activities will be performed.

These activities will include identification of field support equipment and necessary facilities for

performance of the field investigation tasks, procurement of all equipment and supplies, set up and

maintenance of a property inventory control system, and shipment of equipment to the site. Also included

in this task is procurement of subcontractors, filing of property access documentation (obtained in the

task described in Section 5.2.2) and distribution of access documentation to the field team, and

identification and delineation of a sampling equipment staging area and an IDW staging area. This task

will include setup of a sample team headquarters facility, whether an onsite trailer or an offsite location.

Such a facility will be necessary for phone, computer, and electrical connections during performance of

the field investigation.

At the completion of performance of the field investigation tasks, demobilization activities will be

performed. These activities will include restoration of the site to a standard determined by its prior

condition, removal of any temporary facilities placed onsite during performance of the field

investigation, preparation of a description and access procedures for any facilities remaining onsite (such

003899




as monitor wells), performance of an equipment inventory and disposition of all remaining materials and

equipment procured for the investigation.

Details regarding mobilization and demobilization procedures are defined in the FSP.

5.2.5 Drilling/Well InstallationThe groundwater investigation will be conducted using a phased approach. The initial phase will consist

of the installation of 12 monitor wells, screened at the water table, installed to identify the horizontal

extent of contamination. Also, one deep boring will be completed and a multilevel monitor well installed

at the DACTD maintenance yard. These initial proposed locations are illustrated on Figure 5-1. Actual

locations will depend on the ability to obtain access, general site conditions at each location, and the

proximity of utilities. Also, each well will be sampled after installation and development. The sample

results will be used to determine the necessity to step-out to another location in order to define the

horizontal extent of contamination. This flexibility allows for better use of resources while in the field.

Each shallow well will be drilled using a method appropriate for the depth to be attained. Soil borings

will be drilled to the water table, and completed with 15 feet of screen. The depth of the water table

varies between approximately 100 and 200 feet bgs across the site, so the depths of completion for these

wells will vary. A 15 ft screen length is proposed to account for anticipated fluctuations in the water

table and to ensure that such fluctuations do not result in a dry well during the investigation. The initial

water table wells will be installed via hollow stem auger. Each boring will be continuously cored. Soil

samples be collected during drilling using a split core barrel sampler for lithologic logging and the

collection of soil samples for analytical analysis (see Section 5.2.7 for a discussion of soil sampling). If

mud rotary or air rotary drilling is employed to drill each borehole, then the lithology will be

characterized during drilling based on observations of the soil cuttings as they are expelled from the

borehole. After installation and well development, each well will be sampled, and the results will be

used to determine additional drilling locations. During the second phase of drilling, up to 10 additional

wells may be installed at the water table to add to the delineation of the horizontal extent of

contamination.

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To determine the vertical extent of contamination, up to 6 multilevel monitor wells will be installed at

locations where the PCE concentrations in groundwater are highest. The first multilevel monitor well

will be installed at the DACTD maintenance yard early in the first phase of well installations. During

drilling, a device capable of collecting samples during drilling will be used to obtain soil vapor samples

in the unsaturated zone and groundwater samples in the saturated zone. In addition, geophysical logging

will be employed for the deep wells to better characterize the geology and hydrogeology at depth across

the site. The soil vapor and groundwater samples collected during drilling will be submitted for quick

turnaround time analysis, and the results will be used along with geophysical logging results to determine

the placement depth of individual well screen intervals. Each multilevel well will consist of 3 to 5

separate screens at different depths. Each screen will be no more than 10 feet long. The depths of

completion for the multilevel wells will vary, but it is currently anticipated that no well will be deeper

than 700 feet bgs. This depth is based on the screened interval of the deepest affected municipal supply

well, CLC Well No. 27 (refer to Figures 2-4, 2-5, and 2-6 for cross-sections that illustrate the depths of

each existing well and the vertical extent of contamination as it is currently known).

The deeper multilevel monitor wells will be installed using a drilling method capable of achieving the

desired depth, and it is anticipated that no soil samples will be collected during drilling. The lithology

will be characterized during drilling based on observations of the soil cuttings as they are expelled from

the borehole during drilling.

Details regarding drilling and well installation procedures are defined in the FSP.

5.2.6 Soil Vapor SurveyA soil vapor survey will be conducted at the DACTD maintenance yard. This survey will be conducted

to better characterize the nature and extent of PCE previously detected during NMED’s soil vapor

investigation. The investigation will focus on the two areas where PCE had previously been detected at

the DACTD maintenance yard: (1) the northeast corner of the site (paint storage area); and (2) the

northwest corner of the site (drum storage area). The initial survey will be conducted using DPT. The

sampling will be conducted on a horizontal grid established for each area, about 25 to 30 sampling points

003901




in each area. Vertically, soil vapor samples will be collected at 5 ft. intervals, initially to a depth of 20 ft.

bgs. In addition, two sampling locations will be completed to a depth of 50 ft. bgs to evaluate the

presence of PCE in deeper subsurface soil vapor. Additional samples may be collected based on the

results of the initial survey. The soil vapor sample results may indicate that the depth of investigation

needs to be increased. If a deeper investigation is required, then up to two multilevel soil vapor wells

may be installed. Each multilevel well will consist of 3 to 5 soil vapor monitoring ports, and completed

to near the water table, which occurs at 185 to 200 feet bgs at the facility.

If other potential source areas are suspected based on the results of groundwater monitoring, then a

similar soil vapor survey may be conducted at that location to evaluate the potential for such a source,

and to determine the nature, extent, and exposure potential related to soil vapor at each suspected

location.

Details regarding the soil vapor survey, drilling, and well installation procedures are defined in the FSP.

5.2.7 Soil Sample CollectionSurface soil samples will be collected at the DACTD maintenance yard during the soil vapor survey.

Additional surface soil samples will be collected where other potential source areas are suspected based

on data collected during the initial phase of the RI. Surface soil sample data will also be used to support

human health and ecological risk screenings to be performed relative to the potential soil exposure

pathway (see Section 5.4).

Subsurface soil samples will only be collected if potential source areas are identified and warrant an

investigation. Historical soil sampling data at the DACTD maintenance yard have not demonstrated the

presence of PCE in the subsurface soil, and it is not anticipated that a subsurface soil sampling program

would be successful at other areas of the site, based on the geology and nature of the contaminant. A

subsurface soil investigation will only be conducted at locations where potential sources are confirmed.

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If a subsurface soil investigation is determined to be warranted based on the initial phases of the RI, soil

borings will be advanced using a hollow stem auger and split spoon or using DPT. Each boring will be

continuously sampled for evaluation of stratigraphy, and a photoionization detector (PID) will be used to

detect the presence of any organic vapors. During installation of the shallow monitor wells, hollow stem

auger drilling techniques will be employed if feasible. All samples collected for lithologic logging

purposed will be field screened with a PID, and if warranted, soil samples will be collected where visual

and/or olfactory observations, or PID readings indicate a high probability of contamination.

Details regarding soil sampling are defined in the FSP.

5.2.8 Aquifer TestAs described in Section 5.1, available aquifer testing data will be obtained from the city for use in

analyzing fate and transport, characterization of hydraulic properties, to support the design of any

potential groundwater extraction system or help identify other potential remedial alternatives. If adequate

data is unavailable, then a five day groundwater pump test may be conducted if conditions warrant. The

presence of the CLC’s municipal well field may create non-steady state conditions in the area of the

groundwater plume. An aquifer test will only be conducted if steady-state conditions can be expected

within the expected effective area of the pump test. Information obtained from the pumping test will be

used in conjunction with any hydraulic characterization (such as pumping data or pumping rates and

volumes for individual wells, water level data, hydraulic characterization data, etc.) data available from

the city to evaluate the fate and transport of the contamination. The well used for the pump test will be

selected based on its location relative to the most contaminated portion of the plume and the proximity of

available observation wells. It is currently anticipated that CLC Well No. 18 will be used for the pump

test, if feasible considering the configuration of the wellhead and existing mechanical features.

Details regarding the pump test are defined in the FSP.

003903




5.2.9 Sample Collection and AnalysisSamples to be collected for this investigation include subsurface soil, soil vapor, and groundwater. Each

sample will be analyzed for VOCs. If soil samples are collected, a subset of samples collected will be

analyzed for total organic carbon, pH, grain size, permeability, percent moisture, and oil and grease. A

subset of groundwater samples collected via the monitor wells will also be analyzed for pH, total organic

carbon, total dissolved solids, alkalinity, dissolved oxygen, total hardness, and major cations and anions.

If PCE is encountered in a non-aqueous phase, samples will be collected for analysis of inorganic and

organic constituents, visocity, pH, liquid content, BTU, ash content, and density.

Each groundwater monitor well will be sampled after installation and development. In addition, two

subsequent groundwater sampling and water level measurement events, at approximate 4-8 week

increments, are proposed to evaluate consistency of results and temporal variations. The first event will

take place after all the wells have been installed, and the second event will take place one month after the

first.

Details regarding sample collection procedures and selected analyses are defined in the FSP. Analytical

method procedures and quality assurance/quality control procedures are defined in the QAPP.

5.2.10 Surveying of Sample Locations and Site FeaturesThis task will involve preparation of a topographic map of the GWP site to support the RI/FS. In

addition, all new sample location coordinates will be surveyed for inclusion on the site map. The site map

will be prepared using existing maps, existing aerial photography, and any necessary surveying

performed under this task. Specific methods to be used and criteria to be met for preparation of the site

topographic map are specified in the FSP. This task will be completed at the conclusion of sampling

activities.

Details regarding the surveying of sample locations are included in the FSP.

003904




5.2.11 Management of Investigation-Derived WasteThis task includes management, characterization and disposition of IDW associated with performance of

the field investigation. Procedures will be conducted in accordance with EPA’s Guide to Management of

Investigation-Derived Wastes (EPA, 1992a). Detailed procedures regarding management of IDW are

provided in the SMP.

5.3 Data EvaluationThe data evaluation task is included for the organization and evaluation of all new and existing data

gathered for the site. Activities include validation of laboratory analytical data, and data reduction,

tabulation, and evaluation.

5.3.1 Data ValidationThis task includes validation of the laboratory analytical results, and an evaluation of the useability of the

data. Details regarding data validation are presented in the QAPP.

5.3.2 Data Reduction, Tabulation, and EvaluationUpon validation of the laboratory analytical results, these results will be incorporated into the existing

site database. Evaluation of the data in terms of nature and extent of contamination and contaminant fate

and transport will be performed. This evaluation will support preparation of the RI Report described in

Section 5.5.

5.3.3 Data Evaluation Technical MemorandumOnce data validation, reduction, tabulation, and evaluation are complete, a draft technical memorandum

will be submitted to the EPA detailing the results of the data evaluation. Once comments are received for

the draft technical memorandum, a final technical memorandum will be prepared that incorporates the

comments and submitted to the EPA.

003905




5.4 Risk AssessmentA risk assessment will be performed to determine whether site contaminants pose a current or future risk

to human health and the environment in the absence of any remedial action. Included in this assessment

will be an identification of contaminants of concern, an assessment of exposure to those contaminants

through finalization of the site conceptual model, an assessment of the toxicity of those contaminants,

and a characterization of risk. This characterization will provide a basis for determining whether

remedial action is necessary at the site, describe for which exposure pathways remediation is necessary,

and provide justification for performance of remedial actions. Included in this assessment will be

characterization of risks to both human and ecological receptors. The risk assessment will be conducted

in accordance with EPA’s guidance, including Risk Assessment Guidance for Superfund: Volume 1 -

Human Health Evaluation Manual (Part D, Standardized Planning, Reporting, and Review of Superfund

Risk Assessments) (EPA, 1998a). Risk screening performed early in the investigation may indicate that a

full risk assessment is not required for certain pathways.

The risk assessment will be summarized in draft technical memoranda submitted for agency review as a

component of the RI report described in Section 5.5.

5.5 Remedial Investigation ReportA RI report will be prepared to document the information collected during the site characterization and

relevant data from previous sampling events. The data collected will be summarized and evaluated to

provide an assessment of key organic and/or inorganic contaminants attributable to the site and the

nature, extent, and degree of contamination by those key contaminants. The evaluation will include

preparation of cross-sections. Interpretation of the fate and transport of site contaminants will be

included. Supporting data, information, and calculations will be included as appendices. In addition, the

report will include the human health and ecological risk assessment. The report will be structured to

include the following:

003906




� Site description and background.

� Description of site characterization tasks, including field investigation activities and description

and rationale behind any deviations from the work plan or site-specific plans.

� Description of site characterization in terms of geographical and environmental setting, based on

literature sources and available site-specific data, including the final site conceptual model.

� Description of nature and extent of contamination.

� Description of applicable and site-specific fate and transport mechanisms and migration

pathways, based on the final site conceptual model.

� Description of the risk assessment.

� Summary and conclusions.

A draft report will be prepared for agency review. Upon receipt of agency review comments, a final

report which incorporates these comments will be prepared and submitted.

5.6 Project ScheduleThe overall project schedule to complete the field investigation, conduct the FS, and prepare the RI and

FS reports is included as Table 5-2. Refinements to the schedule are likely and will be communicated by

the project manager to the project team via project instruction updates.

003907





003908

GWP_TWP_VER1.2_TABLE5-1_RATIONALEFORPROPOSEDWELLLOCATIONS.WPD PAGE 1 OF 3 DECEMBER 2001

Table 5-1 Proposed Monitor Well Locations and Rationale for Selected LocationsGriggs & Walnut Groundwater Plume SiteLas Cruces, New Mexico

Initial WellIdentification

Location Reason for Selected Location

Well A North of intersection of Santa Fe Street and Fir Avenue,between MW-SF8 and CLC Well No. 10.

Investigate/determine extent of plume north andpotentially upgradient of MW-SF8

Well B Along Picacho Avenue, between North Manzanita Street andNorth Almendra Street, west of MW-SF7 and MW-SF8.

Investigate/determine extent of plume west andpotentially upgradient of MW-SF7 and MW-SF8 tohelp evaluate whether potential source(s) identifiedwest of this location should undergo furtherconsideration as potential source(s) for contaminationdetected in monitor wells MW-SF7, MW-SF8, and GasCard Well

Well C Along North Mesquite Street north of intersection with East LasCruces Avenue, west of private well LRG-3191.

Investigate/determine extent of plume west andpotentially upgradient of private well LRG-3191 to helpevaluate whether potential source(s) identified west ofthis location should undergo further consideration aspotential source(s) for the contamination detected inLRG-3191.

Well D Near the intersection of East Las Cruces Avenue and NorthVirginia Street.

Provide data to help evaluate whether contaminationobserved in private well LRG-3191 is part of the Griggsand & Walnut Groundwater Plume.

003909




GWP_TWP_VER1.2_TABLE5-1_RATIONALEFORPROPOSEDWELLLOCATIONS.WPD PAGE 2 OF 3 DECEMBER 2001

Well E Near the intersection of North Hermosa Street and East OrganAvenue.

Investigate/determine extent of plume southwest ofDACTD maintenance yard to help evaluate whethercontamination in private well LRG-3191 is part ofGriggs & Walnut Groundwater plume.

Well F Near the intersection between Palomas Avenue and Del MonteStreet.

Investigate/determine extent of plume south of DACTDmaintenance yard to help evaluate whethercontamination in private well LRG-3191 is part ofGriggs & Walnut Groundwater plume, and to helpevaluate whether potential source(s) identified south ofthis location should undergo further consideration aspotential source(s) for the Griggs & WalnutGroundwater Plume.

Well G Along South Walnut Street, south of intersection with PalomasAvenue.

Investigate/determine extent of plume south of DACTDmaintenance yard, and help evaluate whether potentialsource(s) identified southwest of this location shouldundergo further consideration as potential source(s) forthe Griggs a& Walnut Groundwater Plume.

Well H Near intersection of East Griggs Avenue and Walton Blvd,between CLC Well No. 27 and CLC Well No. 19.

Determine contaminant levels between CLC Well Nos.27 and 19

003910




GWP_TWP_VER1.3_TABLE5-1_RATIONALEFORPROPOSEDWELLLOCATIONS.WPD FEBRUARY 2002PAGE 3 OF 3

Well I Along North Telshor Blvd, east of CLC Well No. 19 Investigate/determine extent of plume east of CLC WellNo. 19

Well J Along North Telshor Blvd, east of CLC Well No. 21 Investigate/determine extent of plume east of CLC WellNo. 21

Well K Near intersection of Craig Avenue and Sumner Court, betweenCLC Well No. 21 and the Paz Park Well.

Investigate/determine extent of plume west of CLCWell No. 21 and north of MW-SF10.

Well L Northwest of intersection between Walnut Street and HadleyAvenue, between CLC Well No. 18 and the Paz Park Well.

Investigate/determine extent of plume north of CLCWell No. 18.

Initial well identifications are for discussion purposes only; actual well names will be designated during the field investigation. The rationale behind the well placement is based on the need to confirm plume extent. Once the plume extent has been verified, investigationsinto potential sources will be more effective.

003911





003912

Table 5-2Overview of RI/FS ScheduleGriggs and Walnut Avenue Groundwater Plume Superfund SiteLas Cruces, New Mexico

Activity Oct-2001 Nov-2001 Dec-2001 Jan-2002 Feb-2002 Mar-2002 Apr-2002 Jun-2002 Jul-2002 Aug-2002 Sep-2002 Oct-2002 Nov-2002 Dec-2002 Jan-2003 Feb-2003 Mar-2003 Apr-2003 May-2003

Finalize Work Plans1

Source Information Review (aerial photos, etc.)Field Investigation 2nd round 3rd roundSample Analysis and Data ValidationPrepare Data Evaluation TM and RI Report

Conduct Feasibilty Study and Prepare FS ReportFinal review and finalization of RI and FS Reports

Notes1. Consists of RI/FS Technical Activities Work Plan, RI/FS Field Sampling Plan, RI/FS Quality Assurance Project Plan, RI/FS Site Management Plan.

May-2002

GWP_TWP_Ver1.3_Table5-2_OverviewOfSchedule.xls\Overview of RIFS Schedule Page 1 of 1 February 2002

003913





003914

%

%%

%

%

%%%

%

%

%

%

#

#

#

# #

#

#

#

#

#

#

'W

'W

$$$$ $ $

$$$$

$$$

$

$

$$

#

(

MW-1MW-2

MW-3

MW-4

MW-5

MW-6

MW-SF2

MW-SF3

MW-SF4

MW-SF5MW-SF6MW-SF7

MW-SF8

MW-SF9

MW-SF-1

MW-SF10

Gas Card Well

CLC Well 27


CLC Well 21

CLC Well 57

CLC Well 10

CLC Well 54

CLC Well 28

CLC Well 26

CLC Well 20

CLC Paz Park Well

LRG-7375

LRG-3191

?

?

?

?

Well I

Well JWell K

Well L

Well H

Well GWell F

Well EWell D

Well C

Well B

Well A

?

?

?

CLC Well 61

CLC Well 24

Legend? Estimated Extent of PCE Detections

(based on existing monitor and water supplywell sample analysis)

#(Screen Intervals Range From 3730 to 3325 MSL)City of Las Cruces (CLC) Supply Wells

'W

$ Monitor Wells(Screen Intervals Range From 3867 to 3827 MSL)

PCE concentration units are ug/L

500 0 500 1000 Feet

Figure 5-1

Historical PCE Concentrations

and Proposed New Well Locations



N

Mw-1 Pce_conc.

Date Values 03/12/1998 NS 04/15/1998 3.0 08/31/1998 4.4 12/03/1998 ND 03/02/1999 1.6 07/13/1999 3.00 07/18/2000 7.00

Mw-2 Pce_conc.

Date Values 03/11/1998 52.0 04/15/1998 23.0 08/31/1998 35.0 12/03/1998 40.0 03/02/1999 44.0 07/13/1999 40.00 03/13/2000 26.00 07/19/2000 32.00

Mw-3 Pce_conc.

Date Values 03/11/1998 20.0 04/15/1998 15.0 08/31/1998 10.0 12/03/1998 11.0 03/02/1999 18.0 03/14/1999 24.00 07/13/1999 22.00 03/14/2000 24.00 07/18/2000 14.0 (Jv)

Mw-4 Pce_conc.

Date Values 03/12/1998 8.1 04/15/1998 9.0 08/31/1998 NS 12/03/1998 NS 03/02/1999 NS 07/13/1999 7.00 03/15/2000 5.00 07/18/2000 5.00

Mw-6 Pce_conc.

Date Values 03/24/1998 ND 04/15/1998 3.0 09/01/1998 1.4 12/04/1998 1.1 03/02/1999 1.5

Mw-sf9 Pce_conc.


Mw-sf2 Pce_conc.

Date Values 03/14/2000 42.0

Mw-5 Pce_conc.

Date Values 03/12/1998 2.3 04/16/1998 3.0 08/31/1998 2.5 12/03/1998 1.0 03/02/1999 0.5 07/15/1999 3.00 03/15/2000 6.00 07/19/2000 8.00

Mw-sf3 Pce_conc.

Date Values 03/14/2000 43.0 07/17/2000 53.00

Mw-sf4 Pce_conc.

Date Values 03/14/2000 19.0 07/17/2000 17.00

Mw-sf5 Pce_conc.

Date Values 07/17/2000 7.0

Mw-sf6 Pce_conc.

Date Values 07/17/2000 3.0

Mw-sf7 Pce_conc.

Date Values 07/17/2000 13.0

Mw-sf8 Pce_conc.

Date Values 07/17/2000 13.0

Mw-sf10 Pce_conc.

Date Values 07/19/2000 31.0

Mw-sf1 Pce_conc.

Date Values 03/15/2000 52.0 07/18/2000 41.0 (Jv)

Gas_Card_well Pce_conc.

Date Values 05/05/1998 15.0 06/23/1998 17.0 07/15/1999 11.0

Well_10 Pce_conc.

Date Values 06/07/1995 ND 07/20/1999 ND

Well_18 Pce_conc.

Date Values 03/13/1994 ND 01/10/1995 32.0 02/22/1995 1.5 02/27/1995 1.2 04/12/1995 0.5 08/18/1995 0.6 10/04/1995 ND 01/09/1996 6.4 02/21/1996 0.8 04/03/1996 0.8 05/02/1996 1.0 07/23/1996 ND 04/15/1998 15.0 06/23/1998 18.0 10/20/1998 17.0 07/20/1999 20.1 04/20/2000 7.0 7/18/2000 47.0 (Jv

Paz_park Pce_conc.

Date Values 04/15/1998 ND 06/23/1998 ND 07/20/1999 ND

Well_54 Pce_conc.

Date Values 01/11/1995 ND 04/24/1996 ND 07/20/1999 ND 04/20/2000 ND

Well_21 Pce_conc.

Date Values 08/09/1993 0.9 02/17/1994 0.8 06/21/1994 1.0 10/10/1994 1.0 01/10/1995 0.7 04/05/1995 1.3 08/18/1995 1.2 10/04/1995 1.2 01/09/1996 1.1 01/22/1997 1.3 04/15/1998 2.0 04/27/1998 2.0 06/23/1998 2.0 07/20/1999 2.3 04/20/2000 2.0

Lrg-7375 Pce_conc.

Date Values 01/27/1998 ND 06/23/1998 ND

Well_19 Pce_conc.

Date Values 03/13/1994 0.3 05/16/1994 0.3 10/03/1994 ND 01/09/1995 ND 04/05/1995 ND 08/18/1995 ND 10/04/1995 ND 01/09/1996 0.6 07/23/1997 ND 04/15/1998 1.1 06/23/1998 0.80 J 07/20/1999 1.2

Well_27 Pce_conc.

Date Values 08/09/1993 1.4 05/16/1994 0.7 06/21/1994 0.7 10/03/1994 0.6 05/09/1995 0.8 08/18/1995 ND 10/04/1995 0.8 02/23/1996 1.0 07/29/1997 1.8 04/15/1998 1.4 06/23/1998 2.0 07/20/1999 4.5 04/20/2000 4.0

Lrg-3191 Pce_conc.

Date Values 03/12/1998 1.0 06/24/1998 0.9

Proposed Monitor Well Locations%


Well _24 Pce_conc.

Date Values 06/26/2001 1.5

Well _20 Pce_conc.


Well _61 Pce_conc.


Well _26 Pce_conc.


Private Wells(Screen Interval For LRG-3191 From 130 - 150 bgs)(Screen Interval For LRG-7375 Is Unknown)

003915





003916

Figure 5-2

Locations of Proposed New Monitor Wells

& Previously Identified Potential Sources of PCE


Las Cruces, New Mexico% Proposed Monitor Well Locations

ð Locations Where PCE Has Been Detected

r Locations Used For Dry CleaningBetween 1955 - 1990 (locations estimated)

?Legend

Locations Where PCE Has Not Been Detected#

Estimated Extent of PCE Detections (based on existing monitor and water supplywell sample analysis)


General GroundwaterGradient

#

#

#

#

#

#

%

%%

%

%

%%

%

%

%

%

%

#

ð

ð

ð

ðð

ðððð

ðððð

ðð

ððð

ð

ð

ð

#

#

r

r

r

r

rr

r

r

r

r

rr

r

#

ð

Former Crawford Airport & Current Locationof the City of Las Cruces FleetMaintenance Yard

Former NationalGuard Armory

?

?

?

?

Well I

Well JWell K

Well L

Well H

Well GWell F

Well EWell D

Well C

Well B

Well A

?

?

?

#

South Solano Drive

East Las Cruces Avenue

#

North Solano Drive

#

Spruce Avenue

#

East Hadley Avenue

#

Interstate 25

#

East Lohman Avenue

#

Walnut Street

#

South Telshor Blvd.

Dona Ana CountyTransportation DepartmentMaintenance Yard

#

Griggs Avenue

MW-1

MW-2MW-3

MW-4

MW-5

MW-6

MW-SF2

MW-SF3

MW-SF4

MW-SF5

MW-SF6MW-SF7

MW-SF8

MW-SF9

MW-SF-1

MW-SF10

GasCardWell

CLC Well 27


CLC Well 21

CLC Well 57

CLC Well 10

CLC Well 54

CLC Well 28

CLC Well 26

CLC Well 20

Paz Park CLC Well

CLC Well 61

CLC Well 24

LRG-7375

LRG-3191

Proposed Monitor Well Locations and Rationale for Selected Locations

Initial well identifications are for discussion purposes only; actual well names will be designated during the field investigation.

800 0 800 1600 Feet

N

003917





003918

Section 6Feasibility Study Tasks

003919





003920

GWP_TWP_VER1.2_SECT06_FEASIBILITYSTUDYTASKS.WPD DECEMBER 20016-1

Section 6

Feasibility Study TasksThis section describes the tasks to be conducted to address the FS portion of the RI/FS. Tasks to be

conducted include compilation of ARARs, definition of remedial action objectives, establishment of

general response actions, identification and screening of remedial technologies, description and detailed

analysis of potential remedial alternatives, performing a remedial alternatives evaluation, and preparation

of a Feasibility Study Report. These tasks will be performed in accordance with EPA’s Guidance for

Conducting Remedial Investigations and Feasibility Studies under CERCLA (EPA, 1988).

6.1 Compilation of ARARsRemedial actions selected for a site must comply with all ARARs of federal laws and more stringent state

environmental laws. Under the Comprehensive Environmental Response, Compensation, and Liability

Act (CERCLA), a requirement may be either “applicable” or “relevant and appropriate” to a specific

removal action, but not both. Definitions are as follows:

Applicable Requirements are defined as those clean-up standards, standards of control, and other

substantive environmental requirements, criteria, or limitations promulgated under federal or state

environmental or facility-siting laws that specifically address a hazardous substance, pollutant,

contaminant response action, or location at a CERCLA site.

Relevant and Appropriate Requirements are those requirements that, while not specifically applicable

to a hazardous substance, pollutant, contaminant, response action, location, or other circumstance at a

CERCLA site, address problems or situations sufficiently similar to those encountered at a CERCLA site

that their use is well-suited to the site.

Under this task, ARARs will be identified and compiled for the GWP site, and utilized in the evaluation

of remedial actions.

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6.2 Development of Remedial Action Objectives

Based on the information collected and described for the site, site-specific remedial action objectives will

be developed. These remedial action objectives will be designed to ensure protection of human health

and the environment. Each objective will include a definition of the contaminant and media of concern,

the migration pathways and exposure routes, receptors, and preliminary remediation goals. The

preliminary remediation goals will define acceptable contaminant levels or a range of levels for each

exposure route.

6.3 Development of General Response ActionsThis task will include the development of general response actions for each media of concern in terms of

treatment, excavation, pumping, etc., that would satisfy the remedial action objectives. The response

actions will account for the level of protectiveness identified by the remedial action objectives and the

chemical and physical characteristics of the site.

6.4 Identification and Screening of Remedial TechnologiesAvailable remedial technologies will be identified and screened based on the remedial action objectives

and the general response actions described for the site. Only those technologies applicable to the

contaminants of concern, their physical matrix, and the exposure pathways will be considered.

Representative process options will be selected to undergo remedial alternative development; this

selection will be based on the technology’s ability to effectively address the contamination at the site and

the technology’s implementability and potential cost.

The preferred presumptive remedy for treatment of VOCs in the vadose zone is soil vapor extraction

(SVE). EPA’s User’s Guide to the VOCs in Soils Presumptive Remedy (EPA, 1996a) and Site

Characterization and Technology Selection for CERCLA Sites with Volatile Organic Compounds in Soils

(EPA, 1993) will be used as a basis for the identification and review of technologies for soils

alternatives, as supplemented by other technologies described in literature. The presumptive remedy will

be utilized for the development and screening of alternatives portion of the feasibility study. A soil vapor

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extraction pilot study may be necessary to evaluate the effectiveness of the presumptive remedy to treat

site contaminants.

The preferred remedial alternatives for treatment of contaminated groundwater include no action,

monitored natural attenuation, and groundwater extraction and treatment. EPA’s Considerations in

Ground Water Remediation at Superfund Sites (EPA, 1992b) and Presumptive Response Strategy and

Ex-Situ Treatment Technologies for Contaminated Ground Water at CERCLA Sites (EPA, 1996b) will

be used as a basis for the identification and review of ex-situ treatment technologies for groundwater

alternatives, as supplemented by other technologies described in literature.

Data collected during the site characterization described in Section 5 will be used to evaluate the

applicability of the various technologies. Treatability study activities and/or aquifer testing may be

recommended to EPA during performance of this task if they are determined to be necessary for the

evaluation of remedial technologies.

6.5 Development and Screening of Remedial AlternativesPotential remedial alternatives will be developed based on the identification and screening of remedial

technologies and the site characterization. These media-specific or site-wide alternatives, based on

potential technologies or combination of technologies identified in the technology screening process, will

be defined with respect to size and configuration of the representative process options, time for

remediation, spatial requirements, disposal options, required permits, imposed limitations, and other

factors necessary for evaluation of the alternatives. These alternatives will be preliminarily screened for

effectiveness, implementability, and cost.

Following completion of these tasks, a draft Technical Memorandum will be prepared and submitted for

agency review. This Technical Memorandum will detail the compilation of ARARs, the remedial action

objectives, the general response actions, identification and screening of applicable remedial technologies,

and the development and screening of remedial alternatives. After incorporation of agency comments, a

final Technical Memorandum will be prepared and submitted.

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6.6 Evaluation of Remedial AlternativesThe selected alternatives that are selected based on the preliminary screening will undergo a remedial

alternatives evaluation. This evaluation will include a description of each media-specific or site-wide

alternative that outlines the remediation strategy and identifies associated ARARs and a profile of each

alternative in terms of each of the evaluation criteria. The evaluation will be presented in tabular form.

After analysis of individual alternatives, all alternatives will be compared and contrasted to one another

with respect to each evaluation criteria. A draft Technical Memorandum presenting the evaluation of

each alternative will be prepared for agency review. After incorporation of agency comments, a final

Technical Memorandum will be prepared and submitted.

6.7 Feasibility Study ReportA feasibility study report will be prepared to document the identification, screening, and evaluation of

remedial alternatives for the GWP site. This report will include a description of the remedial action

objectives and general response actions, a presentation of ARARs, a description of the technologies

screened and the results of that screening process, a description of the identified remedial alternatives,

and a description of the detailed evaluation of those alternatives.

A draft report will be prepared for agency review. Upon receipt of agency review comments, a final

report which incorporates these comments will be prepared and submitted.

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Section 7References

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GWP_TWP_VER1.3_SECT07_REFERENCES.WPD FEBRUARY 20027-1

Section 7

ReferencesAgency for Toxic Substances and Disease Registry (ATSDR), 1991. Toxicological Profile for

Tetrachloroehtylene. Draft. 1991.

CDM Engineers and Constructors Inc., 2001. Phase 5 Compliance Monitoring, QuarterlyMonitoring Report for Former Circle K Store No. 1306. May 8, 2001.

CH2M HILL, 2001. Work Assignment Work Plan, Remedial Investigation/Feasibility Study, Griggs andWalnut Groundwater Plume Site. Remedial Action Contract Work Assignment 061-RICO-06HZ. April 3, 2001.

CH2M HILL, 2002a. Field Sampling Plan, Remedial Investigation/Feasibility Study, Griggs and WalnutGroundwater Plume Site. Remedial Action Contract Work Assignment 061-RICO-06HZ. Version 1.1. February 2002.

CH2M HILL, 2002b. Quality Assurance Project Plan, Remedial Investigation/Feasibility Study, Griggsand Walnut Groundwater Plume Site. Remedial Action Contract Work Assignment 061-RICO-06HZ. Version 1.1. February 2002.

CH2M HILL, 2002c. Site Management Plan, Remedial Investigation/Feasibility Study, Griggs andWalnut Groundwater Plume Site. Remedial Action Contract Work Assignment 061-RICO-06HZ. Version 1.1. February 2002.

CH2M HILL, 2002d. Health and Safety Plan, Remedial Investigation/Feasibility Study, Griggs andWalnut Groundwater Plume Site. Remedial Action Contract Work Assignment 061-RICO-06HZ. Version 1.1. February 2002.

Cohen and Mercer, 1993. DNAPL Site Evaluation. Robert M. Cohen and James W. Mercer, GeoTrans,Inc. John Matthews, EPA Project Officer. CRC Press, Inc. 1993.

Foster, S.A., and P. C. Chrostowski. “Inhalation Exposures to Volatile Organic Contaminants in theShower.” APCA. June 1987.

Frentzel, Peter F., et. al, 1990. Geohydrology and Simulation of Ground-Water Flow in the MessilaBasin, Doña Ana County, New Mexico, and El Paso, Texas. U S Geological Survey Open-FileReport 88-305. January 1, 1990.

International Agency for Research on Cancer (IRAC), 1979. IRAC Monographs on the Evaluation of theCarcinogenic Risk of Chemicals to Humans. Vol. 20, 1979.

King, W. E., et. al, 1971. Hydrogeologic Report 1, Geology and Ground-Water Resources of Centraland Western Doña Ana County, New Mexico. New Mexico State Bureau of Mines and MineralResources, New Mexico Institute of Mining Technology. 1971.

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GWP_TWP_VER1.3_SECT07_REFERENCES.WPD FEBRUARY 20027-2

New Mexico Environmental Department (NMED), 1997. Preliminary Assessment, Las Cruces PCE,Doña Ana County, New Mexico. October 30, 1997.

New Mexico Environmental Department (NMED), 1999. Second Addendum To Site InspectionWorkplan, Las Cruces PCE. December 6, 1999.

Souder, Miller & Associates (SMA), 1997a. Onsite Investigation Report, Doña Ana CountyTransportation Department Site, Las Cruces, New Mexico. November 1997.

Souder, Miller & Associates (SMA), 1997b. Onsite Investigation Report, Gas Card Site, LasCruces, New Mexico. December 1997.

Souder, Miller & Associates (SMA), 1998. Hydrogeologic Investigation Report, Doña AnaCounty Transportation Department Site, Las Cruces, New Mexico. April 1998.

US Environmental Protection Agency (EPA), 1988. Guidance for Conducting Remedial Investigationsand Feasibility Studies Under CERCLA. Interim Final. EPA/540/G-89/004. OSWER Directive9355.3-01. October 1988.

US Environmental Protection Agency (EPA), 1992a. Guide to Management of Investigation-DerivedWastes. Fact Sheet. OSWER Directive 9345.3-03FS. January 1992.

US Environmental Protection Agency (EPA), 1992b. Considerations in Ground-Water Remediation atSuperfund Sites and RCRA Facilities - Update. OSWER Directive 9283.1-06. May 1992.

US Environmental Protection Agency (EPA), 1993. Presumptive Remedies: Site Characterization andTechnology Selection for CERCLA Sites with Volatile Organic Compounds in Soils. OSWERDirective 9355.0-48FS. September 1993.

US Environmental Protection Agency (EPA), 1996a. User’s Guide to the VOCs in Soils PresumptiveRemedy. OSWER Directive 9355.0-63FS. July 1996.

US Environmental Protection Agency (EPA), 1996b. Presumptive Response Strategy and Ex SituTreatment Technologies for Contaminated Groundwater at CERCLA Sites, Final Guidance. OSWER Directive 9283.1-12. October 1996.

US Environmental Protection Agency (EPA), 1997. EPA Requirements for Quality Assurance ProjectPlans for Environmental Data Operations. Draft Final. EPA QA/R-5. US EnvironmentalProtection Agency Quality Assurance Division, Washington, DC 20460. October 1997.

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GWP_TWP_VER1.2_SECT07_REFERENCES.WPD DECEMBER 20017-3

US Environmental Protection Agency (EPA), 1998a. Risk Assessment Guidance for Superfund: VolumeI - Human Health Evaluation Manual (Part D, Standardized Planning, Reporting, and Review ofSuperfund Risk Assessments). EPA 540-R-97-033. OSWER Directive 9285.7-01D. PB97-963305. January 1998.

US Environmental Protection Agency (EPA), 1998b. Superfund Site Strategy Recommendation. April 6,1998.

US Environmental Protection Agency (EPA), 2000a. Data Quality Objectives Process for HazardousWaste Site Investigations, EPA QA/G-4HW, Final. EPA/600/R-00/007. January 2000.

US Environmental Protection Agency (EPA), 2000b. HRS Documentation Record, Griggs and WalnutGround Water Plume Site, Las Cruces, Doña Ana County, New Mexico, CERCLIS ID. No.NM0002271286. Prepared for EPA by Roy F. Weston. November, 2000.

US Environmental Protection Agency (EPA), 2001. Statement of Work for RemedialInvestigation/Feasibility Study (Griggs and Walnut Ave Groundwater Plume, Las Cruces, NewMexico). Remedial Action Contract Work Assignment 029-RI-CO-06HZ. January 18, 2001.

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