Independent Design Review:
 Grants Chlorinated Solvents Plume
            Super fund Site
Grants, Cibola County, New Mexico
            EPA Region 6
          Report of the Independent Design Review
  Site Visit Conducted at the Grants Chlorinated Solvents Plume Superfund Site
                August 1, 2007

               Revised Report
                June 4, 2008

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           Solid Waste and          EPA-542-R-11-005
           Emergency Response        May 2011
           (5203P)              www.epa.gov
    Independent Design Review:
 Grants Chlorinated Solvents Plume
           Superfund Site
Grants, Cibola County, New Mexico
           EPA Region 6

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                                         NOTICE
Work described herein was performed by GeoTrans, Inc. (GeoTrans) for the U.S. Environmental
Protection Agency (U.S. E.P.A). Work conducted by GeoTrans, including preparation of this report, was
performed under Work Assignment #57 of EPA contract 68-W-02-034 Tetra Tech EM, Inc., Chicago,
Illinois. Mention of trade names or commercial products does not constitute endorsement or
recommendation for use.

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                                EXECUTIVE SUMMARY
An Independent Design Review (IDR) involves a team of expert hydrogeologists and engineers that are
independent of the site, conducting a third-party peer review of remedy selection, remedy design, or re-
design of an existing remedy. It is a broad review that considers the goals of the remedy, site conceptual
model, available site data, performance considerations, protectiveness, cost-effectiveness, and closure
strategy. The review includes reading site documents, visiting the site for one day, discussing the site
with the site team, and compiling a report that includes findings and a discussion regarding remedial
options and/or items for consideration during design.  Consideration is given to stakeholder input to the
degree that input is provided in site documents or during interviews with the site team, but because the
review is technical in nature, no separate meetings are held with each stakeholder.  The purpose of the
review is to gain a thorough understanding of the site conceptual model and drivers for the site and to
provide findings and analysis that are of value to the site team in making decisions regarding remedy
selection and design. The findings and analysis presented in the IDR report are based on the information
provided and the discussions with the site team and  could change if additional information were made
available. Because of the limited scope of the IDR process, the information used in the analysis is
assumed to be accurate unless errors in the information are discovered during the IDR.  The IDR is
intended to be a constructive process and is not intended to criticize past  actions or to simply document
site details.

The findings are the opinions of the IDR team and the discussion is intended to help the  site team identify
opportunities for improvements.  In many cases, further analysis, beyond that provided in the IDR report,
may be needed prior to implementing items presented in the discussion.  The considerations provided in
the IDR report are the opinions of the IDR team and do not constitute requirements for future action, but
rather are provided for the consideration by the Region and other site  stakeholders.

The Grants Chlorinated Solvents Plume Superfund Site in Grants, Cibola County, New Mexico was
selected by EPA OSRTI based on a nomination from EPA Region 6.  The remedy is in the early design
stage and has an estimated cost of $29.5 million. Several pre-design activities, including additional
subsurface investigation and pilot tests, are ongoing and will be evaluated prior to the preliminary design
(expected Fall/Winter 2008) and the final design.  Results from activities conducted after the IDR site
visit are not included in this report and are reserved  for future discussion between the IDR team and the
site team.

The IDR team notes some of the following findings and interpretations regarding the site conceptual
model and remedial strategy to date.

    •   Ground water is present beneath the site in thin (approximately 1 foot thick) sand and silt lenses
        within competent clay. A relatively long, continuous lens with a thickness of approximately 1
        foot is present approximately 8 feet to 16 feet bgs. Water quality data suggest that the highest
        concentrations  and most significant horizontal transport of site-related contamination occur
        within this lens.

    •   A ground water concentration of tetrachloroethene (PCE) as high as 3,400 ug/L  was detected as
        deep as 60 feet during direct-push sampling. Limited data at the site suggest an  upward hydraulic
        gradient, which means that dense non-aqueous phase liquid (DNAPL) was likely present as free
        product at one point to allow for substantial vertical contaminant migration.

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•   The abundance of silt and clay in the subsurface, the presumed vertical migration of
    contamination through these low permeability materials, and the age of the plume (perhaps dating
    back to the 1970s), suggests to the IDRteam that aquifer restoration could be diffusion limited,
    resulting in a longer than expected time frame for remediation.

•   Ground water data suggest to the IDR team that the majority of contamination may have already
    migrated from the source area.

•   Lithologic and water quality data with depth is limited.

•   Concentrations of trichloroethene and cis-l,2-dichloroethene (PCE degradation products) are 10
    times higher near the Allsup underground storage tank site than elsewhere in the plume indicating
    the hydrocarbons in the subsurface are providing a food source for microbes in the area and
    promoting reductive dechlorination.  However, concentrations of vinyl chloride are not as high,
    suggesting that reductive dechlorination is not complete and that bioaugmentation (i.e.,
    introducing appropriate microorganisms) may be appropriate.

•   Limited soil data to date indicate that the area and volume for source remediation is likely much
    smaller than indicated in the Record of Decision (ROD), and the smaller volume for remediation
    may change the cost-effectiveness of some remedial options that have a high capital cost
    component.

•   Because of contaminant migration and perhaps limited water quality and lithologic information
    with depth, the zone defined as the source area and targeted for thermal remediation does not
    appear to coincide with the  zone of highest detected contamination and vertical migration.  The
    zone that seems more appropriate based on existing data for source zone remediation appears to
    be on the downgradiet portion  of the Holiday Cleaners property, First Avenue, and properties
    downgradient of First Avenue.

•   The site team prefers a source area remedy that allows Holiday Cleaners to continue operating. If
    the area requiring source area treatment is actually downgradient of the building and parking lot,
    then this may be feasible. However, if thermal treatment is required beneath and immediately
    around the property, this may be logistically difficult both during construction and operation due
    to the small property and the limited access to customers.

•   Other options for source area remediation discussed in the ROD and Feasibility Study include
    limited excavation followed by in-situ chemical oxidation (ISCO) with enhanced reductive
    dechlorination (ERD) polishing or ERD alone. Injections of oxidants or nutrients will
    preferentially enter the sand lenses, which occupy only a percentage of the aquifer volume within
    the source area. As a result, the amount of oxidant and nutrient required may have been
    significantly overestimated by  using the entire volume of the source area.

•   Based on the finding that only  a portion of the Holiday Cleaners site is contaminated and the role
    of the sand lenses in controlling oxidant/nutrient delivery, the IDRteam believes that the
    effective volume of the source  area that would be treated by ISCO or ERD would  be almost an
    order of magnitude smaller than the volume  assumed in the Feasibility Study. Based on available
    data, the amount to be injected and the number of injection points may therefore be high by
    almost an order of magnitude if all other factors remain unchanged.
                                       in

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    •   The assumed treatment depth for the shallow plume core and hot spot is from 8 feet to 20 feet,
       and the injection of oxidants and nutrients is based on the total pore volume for this depth
       interval.  However, the majority of the mass and ground water flow appears to be in a thin sand
       lens that is approximately 0.5 to 1  foot tick.  As a result, the injection quantities needed may be an
       order of magnitude lower than what the site team has calculated if all other parameters and
       assumptions remain unchanged.

    •   The IDR team notes that diffusion of contaminant mass out of the lower permeability layers over
       time (as is assumed by the site team for the source area) may also contribute to extending remedy
       time frames in the  shallow plume core and hot spot such that the remedial time frame might be
       longer than the 5 to 6 year time frame that is estimated for the ISCO/ERD approach.

    •   The results and lessons learned from the pre-investigation and the pilot tests may help better
       estimate  the volumes that require treatment and the amount of oxidant or nutrient that is
       appropriate. The IDR team believes that the findings from the pilot tests could result in revisiting
       the selected remedy for the source area.

    •   Reported relatively high sulfate concentrations in site ground water may accelerate electron donor
       consumption  and may become a limiting factor for successful reductive dechlorination.
       Furthermore, in the absence of sufficient alkalinity, the  pH may decrease, inhibiting bacterial
       growth, and limiting reductive dechlorination.

    •   Significantly  fewer injection points may be required for establishing the biobarriers for the
       shallow plume periphery and deep plume if preferential injection into thin but highly permeable
       zones occurs.

    •   Some of the direct-push ground water samples that have helped define the deep plume may be the
       result of contamination that was brought down to deeper intervals during sampling rather than
       contamination that has migrated under natural conditions. As a result, the vertical and horizontal
       extent of the deep plume may have been overestimated. Installation and sampling of deep
       monitoring wells can help determine if the plume is accurately delineated.

Based on the above findings, the IDR team presents a discussion on remedial strategy and remedy
implementation.  The discussion highlights the following items.

    •   The results from the pre-design investigation and pilot studies could have substantial affect on the
       remedy design and could warrant revisiting the selected remedy for the source zone. The IDR
       team suggests reviewing the data from these studies and revisiting the remedy selection process
       before proceeding with design of the selected remedy. The IDR team can assist with reviewing
       the data and provide a valuable third-party, technical perspective.

    •   Injection of oxidants or nutrients for the shallow plume  core and hot spot remedy might be
       efficiently accomplished through trenches or horizontal wells. In addition, the amount of oxidant
       or nutrient that might be needed is likely less than estimated in the Feasibility Study due to
       preferential flow through the thin sand lenses.  The estimated costs for injections (both materials
       and labor) may be higher than needed. Depending on the outcome of the pilot studies, ERD
       rather than ISCO with ERD polishing, may be more appropriate for remediating this zone.

    •   The preferred flow of water, contamination, and injected nutrients through the thin sand lenses
       could substantially reduce the estimated amount of nutrients and the number of injection points
                                           IV

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       for implementing ERD in the shallow plume periphery and deep plume. This could affect remedy
       cost, but it can also affect remedy performance. The injection of too much donor can also result
       excessive organic acids that could lower the pH and inhibit ERD.

    •   The IDR team believes that the remediation time estimates presented in the ROD appear
       optimistic for a heterogeneous subsurface with clays and may bias remedial decisions. PCE and
       its degradation products have diffused into clay material for nearly 40 years. Based on
       experience at other sites, the  IDR team believes that contamination that has diffused into the clay
       will continue to contribute dissolved contamination to the more transmissive zones for decades.
       The IDR team suggests that the site team adjust its expectations for the remedy time frame to
       avoid the potential for moving away from an ERD biobarrier remedy that is working.

    •   The cost for the ERD biobarrier remedy will be highly dependent on how long the biobarrier lasts
       between injections.  The site  team has estimated that injections will be needed every 15  months.
       The pilot study  results will help determine if this frequency is appropriate.

    •   The cost for the ERD biobarrier remedy will also be highly dependent on the true extent of the
       deep plume. Results from the pre-design investigation will help define the true extent of the deep
       plume and volume that requires remediation.

In addition to the above strategy-related recommendations, the IDR team provides the following items for
consideration with respect to implementation.

    •   Given the heterogeneous nature of the site and the importance of stratigraphy for interpreting the
       site conceptual model, use rotosonic drilling during pre-design activities to obtain better cores for
       analysis.

    •   When planning for the  ERD  injections, consider the use of extracted ground water, rather than
       potable water.

    •   The IDR team provides specific suggestions for monitoring well locations and depth intervals.
       Suggestions are also provided to conduct pumping tests in specific wells.

    •   The IDR team suggests that data validation be limited during the long-term monitoring program
       given that data collected during the  Remedial Investigation, data collected during pre-design
       activities, and a long record of long-term monitoring data will be available to help determine the
       validity of individual samples.

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                                       PREFACE
This report was prepared as part of a pilot project conducted by the United States Environmental
Protection Agency Office of Superfund Remediation and Technology Innovation (U.S. EPA OSRTI).
The objective of this pilot project is to conduct independent, third-party reviews of soil and ground water
remedies that are jointly funded by EPA and the associated  State agency.  The reviews are ideally
conducted during the pre-design, design, or re-design stage  so that independent perspectives on the
remedy are provided before costs are incurred for implementing and operating the remedies. The project
contacts are as follows:
          Organization
    Key Contact
         Contact Information
U.S. EPA Office of Superfund
Remediation and Technology
Innovation
(OSRTI)
Kathy Yager
USEPA Region 1 - New England
Regional Laboratory
11 Technology Drive
Mail Code: EGA
North Chelmsford, MA 01863-2431
phone: 617-918-8362
vager.kathleen@epa.gov
U.S. EPA Office of Superfund
Remediation and Technology
Innovation
(OSRTI)
Kirby Biggs
USEPA Headquarters
1200 Pennsylvania Avenue, N. W.
Mail Code: 5203P
Washington, DC 20460
phone: 703-299-3438
biggs.kirbv@epa.gov
Tetra Tech EM, Inc.
(Contractor to EPA)
Carla Buriks
Tetra Tech EM Inc.
1881 Campus Commons Drive, Suite 200
Reston,VA20191
phone: 703-390-0616
Carla.buriks@ttemi.com
GeoTrans, Inc.
(Contractor to Tetra Tech EM, Inc.)
Doug Sutton
GeoTrans, Inc.
2 Paragon Way
Freehold, NJ 07728
phone: 732-409-0344
dsutton@geotransinc. com
                                         VI

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                         TABLE OF CONTENTS
NOTICE	i
EXECUTIVE SUMMARY	ii
PREFACE	ii
TABLE OF CONTENTS	iii
1.0  INTRODUCTION	1
    1.1 PURPOSE	1
    1.2 TEAM COMPOSITION	2
    1.3 DOCUMENTS REVIEWED	2
    1.4 PERSONS CONTACTED	2
    1.5 BASIC SITE INFORMATION AND SCOPE OF IDR	3
2.0  SITE BACKGROUND AND CONCEPTUAL MODEL	5
    2.1 SITE LOCATION AND HISTORY	5
    2.2 SITE HYDROGEOLOGY	6
    2.3 EXTENT OF CONTAMINATION	6
       2.3.1    SOIL  	6
       2.3.2   GROUND WATER	7
    2.4 RECEPTORS	7
    2.5 REMEDY OBJECTIVES	8
    2.6 DESCRIPTIONS OF THE SELECTED REMEDIES	8
3.0  IDR FINDINGS	11
    3.1 FINDINGS RELATED TO SITE HISTORY AND SITE CONCEPTUAL MODEL	11
    3.2 FINDINGS RELATED TO DESIGN AND PRE-DESIGN ACTIVITIES	12
4.0  DISCUSSION REGARDING REMEDIAL STRATEGY AND IMPLEMENTATION ... 16
    4.1 CONSIDERATIONS REGARDING STRATEGY	16
       4.1.1    CONSIDERATIONS FOR SOURCE AREA REMEDIATION	16
       4.1.2   CONSIDERATIONS FOR SHALLOW PLUME CORE AND HOT-SPOT REMEDIATION 17
       4.1.3    CONSIDERATIONS FOR SHALLOW PLUME PERIPHERY AND DEEP PLUME
              REMEDIATION	18
       4.1.4   RECONSIDER EXPECTATIONS FOR REMEDY TIME FRAMES AND PROGRESS
              TOWARD RESTORATION	18
    4.2 CONSIDERATIONS PERTAINING TO IMPLEMENTATION	19
       4.2.1    CONSIDER ROTOSONIC DRILLING DURING PRE-DESIGN DRILLING	19
       4.2.2   USE GROUNDWATER INSTEAD OF POTABLE WATER DURING REMEDIATION
              INJECTIONS	19
       4.2.3    OTHER RECOMMENDED SITE CHARACTERIZATION DETAILS	19
       4.2.4   LIMIT DATA VALIDATION DURING LONG-TERM SITE MONITORING	20
                                 Vll

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5.0  SUMMARY	21
FIGURES

Figure 1 Cross-Section of Contaminant Distribution and Target Zones for Remediation
Figure 2 Proposed Soil Boring/Monitoring Well Locations
ATTACHMENT A

Figure 3-2 from the Final Remedial Investigation Report, 2005 (Lithologic Cross Section)
Figure 5-2 from the Final Remedial Investigation Report, 2005 (Soil Data)
Figure 5-3 from the Final Remedial Investigation Report, 2005 (Plume Map)
Figure 3-1 from the Final Remedial Investigation Report, 2005 (Cross Section Locations)
Figure 5-12 from the Final Remedial Investigation Report, 2005 (Longitudinal Cross Section)
Figure 11 from the Record of Decision (Structures with Vapor Intrusion Mitigation Systems)
Figure 12 from the Record of Decision (Extent of Source Areas)
Figure 13 from the Record of Decision (Shallow Plume Core ISCO Remedy, Conceptual Layout)
Figure 14 from the Record of Decision (Shallow Plume Core ERD Remedy, Conceptual Layout)
Figure 15 from the Record of Decision (Shallow Plume Periphery Remedy, Conceptual Layout)
Figure 16 from the Record of Decision (Deep Plume Remedy, Conceptual Layout)
                                      Vlll

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                                1.0    INTRODUCTION
1.1     PURPOSE

During fiscal years 2000 and 2001 independent reviews called Remediation System Evaluations (RSEs)
were conducted at 20 operating Fund-lead pump and treat (P&T) sites (i.e., those sites with pump and
treat systems funded and managed by Superfund and the States). Due to the opportunities for system
optimization that arose from those RSEs, EPA OSRTI has incorporated RSEs into a larger post-
construction complete strategy for Fund-lead remedies as documented in OSWER Directive No. 9283.1-
25, Action Plan for Ground Water Remedy Optimization. OSRTI has since commissioned RSEs at
additional Fund-lead sites with P&T systems.

Lessons learned from the RSEs conducted to date indicated potential value in conducting independent
reviews during the pre-design, design, or re-design stage of a remedy so that an independent perspective
from a peer review can be considered before a remedy is implemented and operated. As a result, the EPA
OSRTI Technology Innovation and Field Services Division is conducting pilot Independent Design
Reviews (IDRs) at Fund-lead sites that are nominated by the EPA Regions.  These sites are typically at
one of the following stages:

    •   Pre-design - The Region is in the process of determining the remedy for the site. The Remedial
        Investigation is typically completed and the site team is evaluating the feasibility of several
        remedial options.

    •   Design Stage - The Region has selected a remedy and documented it in a Record of Decision
        (ROD). The Region is at any phase of the Remedial Design stage.

    •   Re-Design Stage - The Region has selected, designed, and may have implemented a remedy but
        the remedy is being reconsidered. Based on data collected to date, the Region is considering new
        remedial options or is designing a new remedy for the site.

An Independent Design Review (IDR) involves a team of expert hydrogeologists and engineers that are
independent of the site, conducting a third-party peer review of remedy selection, remedy design, or
remedy  re-design. The site team is chosen based on their ability to conduct and document a thorough
evaluation and their experience with the type of contaminants, hydrogeology, and remedial technology at
the subject site. It is a broad review that considers the goals of the  remedy, site conceptual model,
available site data, performance considerations, protectiveness, cost-effectiveness, and closure strategy.
The review includes reading site documents, visiting the site for one day, discussing the site with the site
team, and compiling a report that includes findings and a discussion regarding remedial options and/or
items for consideration during design. Consideration is given to stakeholder input to the degree that input
is provided in site documents or during interviews with the site team, but because the review is technical
in nature, no separate meetings are held with each stakeholder. The purpose of the review is to gain a
thorough understanding of the site conceptual model and drivers for the site and to provide findings and
analysis that are of value to the site team in making decisions regarding remedy selection and design.  The
findings and analysis presented in the IDR report are based on the information provided and the
discussions with the site team and could change if additional information were made available. Because
of the limited scope of the IDR process, the information used in the analysis is assumed to be accurate

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unless errors in the information are discovered during the IDR.  The IDR is intended to be a constructive
process and is not intended to criticize past actions or to simply document site details.

The findings are the opinions of the IDR team and the discussion is intended to help the site team identify
opportunities for improvements. In many cases, further analysis, beyond that provided in the IDR report,
may be needed prior to implementing items presented in the discussion. The considerations provided in
the IDR report are the opinions of the IDR team and do not constitute requirements for future action, but
rather are provided for the consideration by the Region and other site  stakeholders.

The Grants Chlorinated Solvents Plume Superfund Site in Grants, Cibola County, New Mexico was
selected by EPA OSRTI based on a nomination from EPA Region 6.  The remedy is in the early design
stage and has an estimated cost of $29.5 million. This report provides a brief background on the site, a
summary of observations made during a site visit, and recommendations regarding the design of the
selected remedy. The cost impacts of the recommendations are also discussed.


1.2     TEAM COMPOSITION

The team IDR team consists of the following individuals:
Name
Kirby Biggs
Mike Kovacich
Peter Rich
Doug Sutton
Kathy Yager*
(not present)
Affiliation
U.S. EPA OSRTI
GeoTrans, Inc.
GeoTrans, Inc.
GeoTrans, Inc.
U.S. EPA OSRTI
Phone
703-299-3438
734-213-2204
410-990-4607
732-409-0344
617-918-8362
Email
Biggs.kirby@epa.gov
mkovacich@geotransinc.com
prich@geotransinc.com
dsutton@geotransinc.com
Yager.kathleen@epa. gov
* Project coordinator(s)
1.3     DOCUMENTS REVIEWED
The following documents were reviewed during the IDR process.  The reader is directed to these
documents for additional site information that is not provided in this IDR report.
Author
CH2M Hill
CH2M Hill
U.S. EPA
CH2M Hill
U.S. EPA
U.S. EPA
Date
12/2005
3/2006
6/30/2006
3/26/2007
3/2007
7/31/2007
Title
Final Remedial Investigation Report
Final Feasibility Study Report
Record of Decision
Remedial Design Status Memorandum
Remedial Design Fact Sheet
Analytical Data
1.4     PERSONS CONTACTED
The following individuals associated with the site were present for the visit:

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Name
Sai Appaji
Jeff Minchak
Joe Sterling
Paul Favara
Mike Perlmutter
Affiliation
U.S. EPA Region 6 (RPM)
CH2M Hill
CH2M Hill
CH2M Hill
CH2M Hill
Phone
214-665-3126




Email
appaj i. sai@epa. gov




1.5     BASIC SITE INFORMATION AND SCOPE OF IDR
The Grants Chlorinated Solvent Plume (GCSP) site is defined by an area of ground water that contains
chlorinated solvents. The chlorinated solvents in ground water are primarily a result of releases from dry
cleaning operations. Chlorinated solvents detected in ground water at the site include tetrachloroethene
(PCE), trichloroethene (TCE), cis-l,2-dichloroethene (cis-l,2-DCE), trans-1,2-dichloroethene (trans-1,2-
DCE), 1,1-dichloroethene (1,1-DCE), and vinyl chloride (VC). The site is located in a primarily mixed
commercial/residential area and encompasses approximately 12.25 acres. Several possible sources for the
release of chlorinated solvents to the ground water were identified during the Preliminary Assessment
(PA) and Site Inspection (SI) (NMED, 2001), and the RI (EPA, 2005a), most of which are dry cleaning
facilities or former dry cleaning facilities. Two primary areas are targeted as source areas by the Record
of Decision (ROD). The primary source area is the Holiday Cleaners facility at the corner of First Street
and Monroe Avenue, and a secondary source area is the abandoned dry cleaning facility at First Street and
Washington Avenue. EPA will address the site as one operable unit divided into five categories: indoor
air, source areas, shallow plume core and hot spot, shallow ground water plume periphery, and the deeper
ground water plume. The ROD specifying remedies for these five categories was signed on June 30,
2006, and at the time of the IDR site visit the site team was starting the remedial design and implementing
pre-design investigation and pilot studies. This IDR considers all five categories, but most of the focus is
placed on the soil and ground water remedy given that the indoor air remedy is underway.  Results from
pre-design activities conducted after the IDR site visit are not included in this report and are reserved for
future discussion between the IDR team and the  site team.

The IDR report provides discussion on remedial strategy and implementation for the site team to consider
during the design process of the soil and ground water remedy. Although contaminants associated with
petroleum hydrocarbons are also present in the area, they are related to other sources, are not primary
drivers for the GCSP site,  and are not a focus of this IDR.

Attachment A of this report includes ten figures from the 2005 Final Remedial Investigation that illustrate
the following:

    •   Lithologic cross-section
    •   Soil data
    •   Ground water plume map
    •   Cross-section locations
    •   Longitudinal cross section of geology
    •   Longitudinal cross section of contaminant distribution
    •   Structures with vapor mitigation systems
    •   The extent of the source areas
    •   Conceptual layout of the in-situ oxidation portion of the shallow plume core remedy
    •   Conceptual layout of the enhanced reductive dechlorination portion of the shallow plume core
       remedy

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Conceptual layout of the remedy for the shallow ground water plume periphery
Conceptual layout of the remedy for the deep ground water plume

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          2.0   SITE BACKGROUND AND CONCEPTUAL MODEL
The following description reflects the site conceptual model based on data collected during the Remedial
Investigation and early Remedial Design. Additional interpretation and commentary is provided by the
IDRteam where noted.  The discussion is limited to the aspects of the site and site conceptual model that
are relevant to the scope of the IDR.


2.1     SITE LOCATION AND HISTORY

The site location and setting is discussed in Section 1.5 of this report. A brief summary of the site history,
including enforcement activities, is as follows:

    •   Several site investigations have been performed during various phases by the New Mexico
       Environmental Department (NMED), CH2M HILL (contractor to EPA), and the U.S. Geological
       Survey (USGS).  Chlorinated solvents were first identified by NMED in 1993 during an
       investigation at a local gasoline station.  Prior to 2004, NMED completed several investigations
       related to the local gasoline station and to the initial discovery of chlorinated solvents.  The
       activities included soil and ground water sampling from up to 23  direct-push borings, sampling
       existing monitoring and inactive domestic wells, installing and sampling six additional wells,
       conducting a passive soil vapor survey, sampling water from the sediment pore space of the Rio
       San Jose Channel.

    •   The site contractor conducted four rounds of indoor, outdoor, and background air sampling to
       evaluate vapor intrusion into buildings in the vicinity of the site.  A total of 16 structures were
       evaluated.

    •   Two soil vapor sampling events were conducted to evaluate  soil vapor concentrations in the
       vicinity of buildings potentially affected by vapor intrusion.  A total of 35  soil vapor samples
       were collected for analysis.

    •   The site contractor completed a two phased direct push remedial investigation in February and
       May of 2004. A total of 34 potential source area direct push borings were completed to collect
       102 soil samples including eight duplicates. A total of 81 direct push soil borings were used to
       define the lateral extent of chlorinated solvent contamination in groundwater and four direct push
       soil borings were used to determine the vertical extent. Most of the direct push investigation was
       limited to the upper  16 feet of alluvium.

    •   Two rounds of ground water sampling of 28 existing monitoring wells and three abandoned
       domestic wells were conducted. One was conducted by the site contractor in 2004 and the other
       was conducted by the USGS in 2005. One round of water level measurements was conducted to
       determine ground water flow pattern.

    •   Slug tests were performed and analyzed by the USGS at 24 of the existing monitoring wells in the
       site vicinity in 2005.

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2.2     SITE HYDROGEOLOGY

A total of 85 shallow borings and four deeper borings were drilled and lithologically characterized during
the investigation activities. The lithology in all of these borings was dominated by clay and silt with thin
layers of sand or silty sand present at varying depths. A 6-inch to 1-ft thick sand and silty sand layer was
identified continuously from the Holiday Cleaners to at least the intersection of Washington Avenue and
Anderman Street (over 1,200 feet away) at a depth gradually increasing from approximately 8 ft below
ground surface (bgs) to approximately 16 ft bgs.

Lithologic information was also collected at deeper intervals but to a maximum of 50 feet bgs. Figure 3-2
from the Remedial Investigation (see Attachment A), illustrates the shallow send lens described above,
the presence of other sand lenses to a depth of 40 feet bgs, and the absence of lithologic information
below 40 feet.

The water table is located approximately 6  to 8 feet bgs although water is present discontinuously at
shallower intervals. From 6 feet bgs to 40 feet bgs, ground water is present in relatively thin sand and silt
lenses within competent clay.  Over a five-year period of monitoring at the site, ground water flow
directions have remained consistent. In the main portion of the site, and along the centerline of the
plume, flow is to the southeast with a hydraulic gradient of approximately 0.002 to 0.003. The vertical
gradient has only been determined at one location (GMW-1), and has consistently been upward.

The hydraulic conductivity as determined by the slug tests conducted and analyzed by the USGS ranges
from below 5 feet per day at many locations to as high as 90 feet per day at one location.  A hydraulic
conductivity of 30 feet per day was measured at one location, and a hydraulic conductivity of 20 feet per
day was measured at two locations.  Based on this information and an assumed effective porosity of 0.28,
the ground water velocity in the vicinity of the main plume ranges from approximately 10 to 350 feet  per
year.

Based on drilling conducted at the site since the Remedial Investigation, a second sand lens,
approximately 20 feet thick appears to be present below the clay from about  40 feet to 60 feet bgs.  Below
60 feet bgs, competent clay is reported.
2.3     EXTENT OF CONTAMINATION

There are two known sources of PCE at the site: the active Holiday Cleaners at the corner of First Street
and Monroe Avenue and the abandoned dry cleaning facility on First Street north of Washington Avenue.
Based on interviews during the investigation and assessment phases, the release mechanisms at the
Holiday Cleaners site were routine spills, overflows from an above ground tank at the rear of the building,
releases from a system of interior drains and disposal of impacted decant water in the sanitary sewer.  The
Holiday Cleaners facility began operation in 1969. Although the facility continues to operate, the
equipment has reportedly been updated. Release mechanisms at the abandoned facility are unknown.

2.3.1          SOIL

The soil investigations conducted to date have primarily been aimed at determining the sources of the
ground water contamination.  Figure 5-2 from the Remedial Investigation shows the results of soil

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sampling results. Extensive characterization of the unsaturated soils in the source areas was not
conducted prior to the IDR site visit and is planned as part of future activities.

2.3.2          GROUND WATER

Figures 5-3 and 5-12 from the Remedial Investigation illustrate the horizontal and vertical extent of
chlorinated solvent contamination in ground water.  The location and orientation of the cross-section in
Figure 5-12 is illustrated on Figure 3-1 of the Remedial Investigation. The main portion of the plume
extends southeast of Holiday Cleaners.  The highest detected PCE concentration in ground water (51,000
ug/L) during the Remedial Investigation is from a direct-push ground water sample collected
approximately 250 feet downgradient of Holiday Cleaners. In addition, PCE concentrations from direct-
push activities are as high as 9,900 ug/L approximately 700 feet downgradient of Holiday Cleaners and
1,900 ug/L approximately 1,200 feet downgradient of Holiday Cleaners. The above-mentioned
concentrations are present in the 0.5 to 1 foot thick sand lens that is approximately 8 to 16 feet bgs.
Contamination above the Maximum Contaminant Level (MCL) extends further downgradient and also
extends as deep as 80 feet bgs but at generally much lower concentrations.

Contamination extending downgradient from the abandoned cleaners is generally much lower in
magnitude and extent than that downgradient from Holiday Cleaners.

Indoor air sampling  indicated that one or more chlorinated solvents exceeded Tier 3 levels and required
active mitigation at three structures and exceeded Tier 2 levels and required additional evaluation at eight
additional structures.

Sampling of the ground water underlying the Rio San Jose Channel showed no detections of site
contaminants of concern.
2.4     RECEPTORS

An ecological risk assessment was not conducted for the site because the site team concluded that the
contaminants of concern would not persist in surface soils or surface waters. Therefore, the primary risks
considered by the site team are associated with human health. The Baseline Human Health Risk
Assessment for the site presents the following conclusions:

    •  Water from the shallow aquifer is not currently being used in the household due to the presence
       of a public water supply; however, this water does contain chemicals at concentrations above
       their MCLs. Additionally, property owners are not legally prohibited by the City of Grants from
       using ground water.

    •  Water from the shallow aquifer has the potential to affect both the indoor air and the drinking
       water in the area.

    •  Residential indoor air contaminants of potential concern (COPCs) for the site are benzene, PCE,
       and TCE.

    •  Ground-water COPCs for the site are benzene, bromoform, cis-l,2-DCE, ethylbenzene, PCE,
       toluene, trans-1,2-DCE, TCE, VC, and total xylenes.

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As noted previously, the selected remedy and the IDR focus on the contamination caused by chlorinated
solvents. With respect to drinking water, five municipal wells are located within a 4-mile radius of the
site, and another well is proposed within 1 mile of the site. Two of the municipal wells are owned by the
City of Grants, one is owned by the Village of Milan, and two are owned by the Town of San Rafael. The
proposed well would be owned by the City of Grants. All  of these municipal water wells are screened (or
will be screened) in the San Andres/Glorieta aquifer. Based on a description of regional geology, the top
of this drinking water aquifer is approximately 100 to 140 feet bgs. Ground water contamination has been
detected at approximately 80 feet bgs.
2.5     REMEDY OBJECTIVES

ROD Remedial Action Objectives

The ROD-specified Remedial Action Objectives (RAOs) for groundwater are as follows:
   •   Protection from exposure to constituents above MCLs or ARARs
   •   Restoring groundwater such that constituents are below MCLs or ARARs
   •   Preventing DNAPL from causing concentrations to exceed MCLs or ARARs
   •   Reducing concentrations to mitigate vapor intrusion

The ROD-specified RAOs for soil are as follows:

   •   Prevent groundwater from being impacted above MCLs by contaminant transport from the
       unsaturated zone
   •   Protect human health from exposure to constituents in soil
   •   Reduce concentrations to mitigate vapor intrusion

The RAO for vapor intrusion at the site is to prevent vapor intrusion resulting in exposure in excess of a
10"5 elevated cancer risk.

It is noted that the MCLs for PCE, TCE, cis-l,2-DCE, and VC are as follows:
   •   PCE - 5 ug/L
   •   TCE - 5 ug/L
   •   cis-l,2-DCE-70ug/L
   •   VC - 2 ug/L
2.6     DESCRIPTIONS OF THE SELECTED REMEDIES

The June 2006 ROD specifies the following remedies for the soil and ground water contamination.
   •   Vapor intrusion mitigation systems installed at 14 residences with either indoor air levels
       resulting in more than a 10"5 increased risk for cancer or located over underlying ground water
       with TCE or PCE concentrations higher than 1,000 ug/1.
   •   Thermal treatment (presumably electrical resistive heating) with soil vapor extraction of a 150
       foot by 100 foot by 80 foot deep volume at Holiday Cleaners and 30 foot by 80 foot by 35 foot
       deep volume at the abandoned dry cleaners. Heating and extraction is assumed to take place over

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       a 12 month period. The site team suggests that the need for polishing with another remedy may
       be needed to meet cleanup standards.  Horizontal wells may be added to enhance extraction.

    •  In-situ chemical oxidation (ISCO) with enhanced reductive dechlorination polishing in the
       shallow plume core and hot spot. This includes about 221 ISCO injection points. The targeted
       volume is 800 feet by 150 feet by 20 feet deep with injection targeted between 8 and 20 feet bgs.
       Enhanced reductive dechlorination is planned as a polishing step for the ISCO.

    •  Enhanced reductive dechlorination (ERD) barriers in the shallow plume periphery and deep
       plume including 100  shallow injection wells and 50 deep injection wells.  Recent drilling and
       injection tests in the pilot test areas indicate that a permeable zone may be consistently present at
       about 40 feet to 60 feet bgs. The treatment planned for this zone is ERD.

Figures 11 through 16 from the ROD illustrate the conceptual areas of implementation for these remedies,
and Figure 1 of this report illustrates a vertical cross-section of the target volume  for the ground water
remedies.

The site team is in the process of conducting field work  to collect data necessary for beginning the design
of these selected treatment alternatives.  The following  is a description of that field work

       Pilot Tests

       The site team is currently running pilot tests for ISCO and ERD. The ISCO pilot test includes
       injection of potassium permanganate in a well screened from 8 feet to 20 feet bgs in the shallow
       plume core. The ERD test includes injection of a lactate and emulsified soybean oil product
       provided by EOS Remediation, Inc. (EOS) at three locations, each with five depth intervals
       between 10 and 60 feet bgs. The pilot tests are ongoing through June 2008, with data expected to
       be available in August 2008.

       Source Investigation

       Further investigation is proposed on the Holiday Cleaners site  in late January 2008 to determine
       the mass to be remediated in the source zones (dry cleaner properties) and the depth of impacts.
       The investigation will include drilling boreholes up to an anticipated depth of about 80 feet.
       Groundwater samples will be taken at intervals and wells will be installed for long-term
       monitoring. A deep (200 feet bgs) upgradient well will be installed to demonstrate that impacts
       are not migrating towards deep high production water supply wells.

       Additional Monitoring Well Installation

       As mentioned above, most of the site characterization was based on shallow direct push data.
       There is no monitoring well network to indicate plume movement, concentration trends and
       remedy effectiveness. The site team plans to install about 36 monitoring wells and recognizes the
       need for several deep wells.
A preliminary design that incorporates information from the above activities is expected in the
Fall/Winter of 2008.

The total estimated cost for implementing the remedy is summarized in Table 19 of the ROD. The
following table provides a summary of the approximate cost breakdown for the various remedy
components.

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Remedy Component
Vapor intrusion mitigation systems
Thermal treatment of the source area
ISCO and ERD polishing of the shallow plume core and hot spot
ERD barriers in the shallow plume periphery
ERD barriers in the deep plume
Subtotal

Additional components (additional investigation, monitoring,
project management, Five-Year Reviews, etc.)
Total
Estimated Cost from the
ROD
$382,000
$8,018,000
$6,731,000
$3,273,000
$7,222,000
$25,626,000

$3,582,000
$29,208,000
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                                  3.0    IDR FINDINGS
The IDR team reports the following findings from the document review, site, and information
summarized in the previous section that are pertinent to the remedial strategy and implementation
discussion in the following sections of this report. These findings include opinions and interpretations
made by the IDR team based on review of the data, experience, and professional judgment and are offered
for consideration to the site team.  These opinions may differ from those of other potential reviewers and
do not necessarily reflect the opinions of U.S. EPA OSRTI, which commissioned this review.

It is noted that EPA and the site contractor plan to conduct additional investigation and are in the midst of
conducting pilot studies of the various remedial options and that the findings/interpretations presented
below by the IDR team are subject to change based on the results of this additional work.


3.1     FINDINGS RELATED TO SITE HISTORY AND SITE CONCEPTUAL MODEL

The IDR team notes the following findings and interpretations regarding the site conceptual model.

    •   Ground water is present beneath the site in thin (approximately 1 foot thick) sand and silt lenses
        within competent clay.  The relatively high hydraulic conductivity of these lenses allows for
        substantial horizontal contaminant transport, which explains how concentrations as high as 1,900
        ug/L are present approximately 1,200 feet from the source area despite the abundance of clay in
        the subsurface.

    •   A relatively long, continuous lens with a thickness of approximately 1 foot is present
        approximately 8 feet to 16 feet bgs. Water quality data suggest that the highest concentrations
        and most significant horizontal transport of site-related contamination occur within this lens.

    •   Based on water quality data, it appears that a large percentage of the contaminant mass at the site
        is present in the shallow, continuous lens at 8 feet to 16 feet bgs.  A large percentage of the
        remaining mass may be present in other, deeper lenses.

    •   A ground water concentration of PCE as high as 3,400 ug/L was detected as deep as 60 feet
        during direct-push sampling. Limited data at the site suggest an upward hydraulic gradient,
        which means that dense non-aqueous phase liquid (DNAPL) was likely present as free product at
        one point to allow for substantial vertical contaminant migration.  The presence of additional
        sand and silt lenses allow for horizontal  contaminant migration at deeper intervals.  It is also
        noted, however, that at other locations (e.g., GC-6) the IDR team believes that deep
        contamination may be the result of bringing down contamination during direct-push sampling
        rather than natural migration of contamination to this depth.  Installation and sampling of
        monitoring wells at this depth will help confirm or deny if contamination that requires
        remediation is present as deep as suggested by direct-push samples at GC-6.

    •   The abundance of silt and clay in the subsurface, the presumed vertical migration of
        contamination through these low permeability materials, and the age of the plume (perhaps dating
        back to the  1970s), suggests to the IDR team that aquifer restoration could be diffusion limited


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       given that advective processes are limited in low permeability materials.  That is, the IDRteam is
       concerned that contamination significant enough to result in continued concentrations above
       MCLs is likely present in low permeability materials (particularly near and immediately
       downgradient of the source area) that will be difficult to reach with most remedial technologies.
       As a result, although significant contaminant removal in the high permeability units may occur
       within a reasonable time frame, continued contributions of contamination diffusing from the low
       permeability materials could occur, potentially delaying the progress toward aquifer restoration.

    •   The highest ground water detected concentrations of site-related contaminants appear to be
       downgradient of the source area in the shallow lens and perhaps in deeper lenses.  This suggests
       to the IDRteam that the majority of contamination may have already migrated from the source
       area.  This migration may have occurred as dissolved contamination or as free product as
       evidenced by PCE concentrations as high as 51,000 ug/L approximately 200 feet downgradient of
       the source area downgradient boundary. The contamination at depth also appears to be
       downgradient of the source area. The highest detected  concentration of 3,400 ug/L at 60 feet bgs
       is 60 feet downgradient of the source area downgradient boundary.  Ground water samples from a
       direct-push boring within the source area (GC-11) range from less than 5 ug/L to 62 ug/L
       between 48 and 58 feet bgs.

    •   GC-11 is the only point within the source area that provides water quality data below 20 feet bgs,
       and lithologic data is only available to approximately 40 feet bgs. This one  location of vertical
       profiling within the source provides limited data to characterize the vertical extent of
       contamination and the magnitude of contamination at depth.

    •   There is a hot spot of the groundwater plume in an area unrelated to the two known sources along
       Jefferson Avenue. One potential hypothesis is that this hot-spot is due to contaminant migration
       in the bedding of the sanitary sewer line.

    •   Concentrations of PCE degradation products (TCE up to 4,800 ug/L, cis-l,2-DCE up to 1,500
       ug/L, and vinyl chloride up to 10 ug/1) are highest (over 10 times higher than elsewhere in the
       plume) in the area near the Allsup underground storage tank site indicating  the hydrocarbons in
       the subsurface are providing a food source for microbes in the area  and promoting reductive
       dechlorination.  However, the IDRteam believes that the vinyl chloride concentrations are
       sufficiently low to suggest that effective reductive dechlorination to ethene  may not be occurring
       and that bioaugmentation (i.e., introducing appropriate  microorganisms) may be appropriate to
       foster effective reductive dechlorination.


3.2    FINDINGS RELATED TO DESIGN AND  PRE-DESIGN ACTIVITIES

The IDRteam notes the following findings and interpretations regarding the various components of the
remedy.

Source Area

    •   Shallow soil borings suggest that much of the Holiday  Cleaners property is not contaminated  and
       that much of the contamination is present between the downgradient corner of the building and
       downgradient property boundary. Additional contamination is likely present beneath a portion of
       the building, but the area of shallow soils and ground water that require source treatment are
       likely substantially smaller than the 100-foot by 150-foot area indicated in the ROD, perhaps less
       than 50% of this area.  A smaller treatment volume would  likely substantially reduce the
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    estimated remedial costs for source area treatment, and may change the cost-effectiveness of
    some remedial options that have a high capital cost component.  The IDR team believes that
    additional, thorough characterization of vadose zone and saturated soils is needed before
    designing the remedy. The IDR team believes that the results of this characterization may also
    suggesting revisiting the selected remedy.

•   The selection of thermal remediation appears to be influenced by the need to treat vadose zone
    soils and the difficulty of treating these soils with competing technologies such as ISCO and
    ERD.  Limited excavation for the ISCO and ERD options was assumed during remedy selection,
    but demolition of the building and excavation of the vadose zone soils does not appear to be an
    option to the site team given their preference to minimize impact to the Holiday Cleaners
    business.  Depending on the extent of vadose zone contamination beneath the building, the site
    team may consider the option of demolishing the building, excavating soils, and either relocating
    the Holiday Cleaners business or constructing a new building.

•   Because of contaminant migration and perhaps limited water quality and lithologic information
    with depth, the zone defined as the source area and targeted for thermal remediation does not
    appear to coincide with the zone of highest detected contamination and vertical migration.  The
    cross-sectional view of the thermal remediation target zone from the ROD is shown in Figure 1,
    and the plan view of this target zone is presented in Figure 5-3 of the Remedial Investigation (see
    Attachment A). The zone  that seems more appropriate based on existing data for source zone
    remediation appears to be  on the downgradient portion of the Holiday Cleaners property, First
    Avenue, and properties downgradient of First Avenue. The IDR team believes that findings from
    the pre-design investigation will be important for selecting the appropriate zone for source area
    treatment and help establish the dividing line where source zone remediation ends and shallow
    plume core remediation begins.

•   The site team prefers a source area remedy that allows Holiday Cleaners to  continue operating.  If
    the area requiring source area treatment is actually downgradient of the building and parking lot,
    then this may be feasible.  However, if thermal treatment is required beneath and immediately
    around the property, this may be logistically difficult. In theory, a thermal remedy can be
    designed and implemented with below ground infrastructure, but it would likely be difficult to
    keep the business operating during the several weeks  of construction. In addition, it may be
    difficult to keep the business operating even with the  limited above-ground  foot print of the
    system, operation, and monitoring over a 12-month period.  The parking lot of the business is
    small and access for customers is already challenging, and other dry cleaners are present in the
    area to provide customers  with an alternative.

•   Other options for source area remediation discussed in the ROD and Feasibility study include
    ISCO with ERD polishing and ERD alone. These two options both included limited excavation
    (an estimated total of 638 cubic yards), with limited dewatering, and disposal of excavated soil as
    a hazardous waste.  The ISCO included injecting one and a half pore volumes into the target
    zone, and the ERD polishing or ERD-only remedies including injecting one half of a pore volume
    into the target zone  on many occasions over several years. Due to  the hydrogeology of the site,
    the predominance of silts and clays, and the existence of sand lenses, the assumption of injecting
    one pore volume or a half-pore volume may be a significant overestimate.  The injected oxidants
    or nutrients would likely preferentially migrate through the sand lenses and  bypass the tighter silts
    and clays that likely occupy the majority of the target zone. Based on a preliminary review of the
    data presented in Figure 3-2 of the Remedial Investigation, it appears that sand lenses may
    comprise approximately 25% or less of the aquifer volume near the source area.  Because the
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       sand lenses occupy only a fraction of the volume, these remedial options may be significantly
       overestimating the amount of oxidant or nutrient that would be effective at treating the source
       zone.

    •  If the smaller treatment zone (e.g., approximately 50%) discussed in the first finding of this
       section (i.e., Section 3.2) and the above-noted fraction (e.g., approximately 25%) of the source
       area aquifer that will likely readily receive oxidants or nutrients are combined, then the pore
       volume of the source area that would be treated would be approximately 1/8 of the volume
       assumed in the Feasibility Study.  That is, the number of injection points and the masses of
       oxidants and nutrients to inject may be high by a factor of approximately 8.  This could have a
       significant influence on selecting the remedy, especially given the assumed relatively high
       injection masses due to the potentially high soil oxidant demand or high sulfate concentrations
       that could negatively affect the ISCO or ERD remedies, respectively. It is also noted that the use
       of a horizontal well or injection trench, which is mentioned during the excavation portion of the
       ISCO/ERD and ERD options, does not seem to be included when calculating the number of
       injection points. The results and lessons learned from conducting the pilot tests may help better
       estimate the volumes that require treatment and the amount of oxidant or nutrient that is
       appropriate. The IDR team believes that the findings from the pilot tests could result in revisiting
       the selected remedy.

    •  All options considered for source area treatment consider the likely possibility of additional
       remediation if the original remedy does not result in achievement of cleanup standards. The site
       team suggests that thermal remediation will take no longer than 12 months but that additional
       polishing by either a passive or active remedy may be needed to reach standards.  The ISCO with
       ERD polishing suggests an approximate 5 to 6 year duration given that an five ERD injections
       will occur at 15-month intervals. The ERD-only approach suggests an approximate 15 year
       duration given that 12 ERD injections will occur at 15 month  intervals.

Shallow Plume Core and Hot Spot

    •  The selected remedy for the plume core and hot spot includes ISCO with ERD polishing.  The
       assumed treatment depth is from 8 feet to 20 feet, and the injection of oxidants and nutrients is
       based on the total  pore volume for this depth interval.  However, the majority of the mass and
       ground water flow is in a thin sand lens that is approximately  0.5 to 1 foot tick. The oxidants or
       nutrients will likely preferentially enter this thin lens; therefore, it is likely more appropriate to
       base the quantities for injection on this thin lens plus a factor of safety rather than on the whole
       volume.  As a result, the injection quantities needed may be an order of magnitude lower than
       what the site team has calculated if all other parameters and assumptions remain unchanged.

    •  The ROD states that this portion of the remedy is flexible and that the decision to implement the
       ISCO portion is dependent on pilot testing results and the presence of DNAPL. The pilot study
       results and an absence of DNAPL may suggest that implementing an ERD biobarrier approach is
       more appropriate and cost-effective than ISCO and ERD polishing. Based on the cost
       breakdowns in the Feasibility Study and information in the ROD, using the biobarrier approach
       would save approximately  $5 million. The ISCO/ERD approach was selected for this zone
       because it more rapidly removes mass than the competing approaches. The estimated time frame
       for the ISCO/ERD approach is approximately 5 to 6 years. The site team's estimated time frame
       for the biobarrier approach for the shallow plume core and shallow plume periphery (i.e., the area
       downgradient and surrounding the plume core) is approximately 20 years. The IDR team notes
       that diffusion of contaminant mass out of the lower permeability layers over time (as  is assumed
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       by the site team for the source area) may also contribute to extending remedy time frames in the
       shallow plume core and hot spot such that the remedial time frame might be longer than the 5 to 6
       year time frame that is estimated for the ISCO/ERD approach.

    •  The results and lessons learned from conducting the pilot tests may help better estimate the
       volumes that require treatment and the amount of oxidant or nutrient that is appropriate. The IDR
       team believes that the findings from the pilot tests could result in revisiting the selected remedy.
       In addition, the pre-design investigation will help further refine the volumes requiring treatment.
Shallow Plume Periphery and Deep Plume

    •   Reported relatively high sulfate concentrations in site ground water may accelerate electron donor
        consumption and may become a limiting factor for successful reductive dechlorination. If no
        naturally occurring pH buffering is present, high organic carbon loading during ERD may result
        in low pH and inhibit bacterial growth.  Evaluation of the pilot tests will be critical to the final
        design.

    •   Approximately 20,000 gallons of substrate amended water was injected into 10-foot screens in
        each of the three injection wells in the ERD pilot test area. Assuming 25% effective porosity in a
        uniform  receiving formation this quantity could result in an injection radius of influence of
        approximately 18.5 feet.  However, if most of the substrate amended water was actually injected
        into a 3 or 1 foot layer within the screen interval, the radius of influence within this layer could be
        as much  as 34 or 58 feet, respectively. Significantly fewer injection points may be required if
        preferential injection into thin but highly permeable zones occurs.

    •   The frequency of injections required to maintain the biobarriers and the true extent of the shallow
        plume periphery and deep plume have an substantial influence on the costs for this portion of the
        remedy,  and both of these parameters are relatively uncertain in the absence of information from
        the pre-design investigation and the pilot studies.
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      4.0    DISCUSSION REGARDING REMEDIAL STRATEGY AND
                                   IMPLEMENTATION
4.1     CONSIDERATIONS REGARDING STRATEGY

The following discussion pertains to determining and/or refining the remedial strategy for the site based
on the pre-design investigations that are planned or underway and other information that becomes
available during the design process. The IDR process, like the design process, is dynamic, and the IDR
team can be available to continue providing an independent perspective as additional information is
collected and the site conceptual model evolves.
4.1.1        CONSIDERATIONS FOR SOURCE AREA REMEDIATION

As discussed in Section 3.2 of this report, the IDR team believes that the pre-design investigation and
pilot studies will provide important information that may result in revisiting the selected remedy for the
source area. The IDR team offers some potential outcomes of the pre-design investigation that may result
in a significant change to design or to an alternative remedial strategy.

    •  The source area investigation confirms that the contamination in the source zones is limited to
       significantly smaller portions of the target areas assumed in the ROD and contamination in these
       zones is shallower than anticipated because the majority of vertical migration occurred
       downgradient of these zones. These findings could result in an overall smaller volume to treat
       with the selected source zone remedy. Limited excavation may become the most appropriate
       option for vadose zone  soils, and ISCO or ERD may be more cost-effective for this smaller
       volume than the thermal remediation.

    •  The pre-design investigation confirms that the majority of contaminant mass at the site has
       actually migrated downgradient from the source  zone target areas assumed in the ROD.  The
       target zones for source area remediation may therefore change.  For example, this could result in
       source zone treatment occurring under First Avenue and/or the  properties on the downgradient
       side of First Avenue rather than on the Holiday Cleaners property.

    •  The pre-design investigation may suggest little or no difference in contaminant levels for the
       source area and shallow plume core, suggesting that the same remedial strategy be implemented
       for both locations.

    •  The pilot studies may suggest that remediation of the shallow plume core, shallow plume
       periphery, and deep plume will be substantially limited by diffusion of contamination from low
       permeability zones into the more permeable sand lenses. This diffusion-limited scenario could
       substantially increase the estimates of remedy duration, and the site team may see the benefit of a
       remedial approach that allows for active remediation to occur over a longer time frame to address
       the long-term contamination. Additionally, the pilot tests may suggest that remediation of the
       shallow plume core and plume periphery is impractical with ISCO (perhaps due to a high SOD)
       or ERD (perhaps due to high sulfate levels). If this is the case,  then remediation within 1 year
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       with thermal remediation may not have a significant advantage relative to remediation within 5 to
       6 years (or longer) with ISCO and/or ERD, or an indefinite time frame for a source control
       approach.

    •  The preferred flow of water, contamination, and injected oxidants/nutrients through the thin sand
       lenses could substantially reduce the estimate amounts of oxidants/nutrients and the number of
       injection points.  The pilot test results may suggest that these changes could substantially improve
       the cost-effectiveness of these remedial approaches, making them more appropriate for the source
       zone.

    •  Further work on the Holiday Cleaners property and discussions with technology vendors may
       help the site team confirm that the selected remedy could be applied for a 12-month period
       without detriment to the Holiday Cleaners business or it could help the site team realize that these
       activities would be impractical for the business to overcome for logistical reasons.  An alternative
       remedy may be more appropriate to achieve the objective of minimizing effects on the Holiday
       Cleaners business.

This list of potential outcomes is not intended to be an exhaustive list, and it is not intended to suggest the
immediate need to reconsider the selected remedy. This list is provided to demonstrate the IDR team's
opinion that the current focus be placed on evaluating the results from the pre-design investigation and
pilot studies and then revisiting the remedy selection process to determine if the selected remedy remains
the most appropriate remedy for this portion of the site. Adhering to the selected remedy before
evaluating the information from these studies could potentially result in proceeding with a less
appropriate remedy or a mis-applied remedy. The IDR team can assist with analyzing the data from these
studies and providing a valuable third-party  perspective.
4.1.2        CONSIDERATIONS FOR SHALLOW PLUME CORE AND HOT-SPOT REMEDIATION

The current selected remedial approach includes ISCO with ERD polishing, but indicates that the selected
remedy is flexible depending on pilot study results. If pilot studies show that ISCO will not provide cost-
effective contaminant destruction then ERD injections or the use of ERD biobarriers (selected for the
plume periphery) may be used instead.  For either ISCO or ERD, the sand/silt lenses above 40 feet bgs are
within competent clays so that relatively small volumes will be available for treatment. Injection of
chemicals could be preferentially done into the lenses possibly using trenches or horizontal wells rather
then many vertical injection points.  The use of horizontal wells and trenches has its own challenges with
respect to evenly injecting mass along a long horizontal length, but also has advantages in terms of
improving coverage cost-effectively, particularly at shallow depths. Horizontal wells might also have the
added challenge of properly locating/installing the well within a thin lens.

Estimates for the labor needed for injection (ISCO and ERD) appear to be high. Based on experience
from the pilot test and from the IDR team's experience at other sites, material could be injected into the
subsurface in less than 50% of the time estimated.

Soil Oxidant Demand (SOD) may be higher than assumed during the Feasibility Study but the volume
requiring treatment is likely less. An SOD of 5 g/kg was used in the Feasibility Study but a thickness of
80 feet in the source area and about 12 feet in the shallow Plume Core and Hot Spot was used.  Actual
SOD based on bench testing is about 10 g/kg but ISCO would be concentrated on the thin transmissive
lens rather than across the soil column.  Actual chemical requirements will likely be less than projected.
However, ERD rather than ISCO may still be a more appropriate remedy for this zone to reduce
                                           17

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interferences of ISCO and ERD and take advantage of potential economies of scale for using the same
remedial approach. Pilot testing will provide key information about remedy selection for this zone.

Results from the pre-design investigation and the pilot studies should be considered to determine/refine
the appropriate volume of the aquifer to treat, the amount of oxidant/donor to inject, and the frequency
injections.
4.1.3       CONSIDERATIONS FOR SHALLOW PLUME PERIPHERY AND DEEP PLUME
            REMEDIATION

The preferred flow of water, contamination, and injected nutrients through the thin sand lenses could
substantially reduce the estimate amount of nutrients and the number of injection points for ERD. This
could affect remedy cost, but it can also affect remedy performance.  The results of the pilot tests should
be carefully analyzed to determine the appropriate amount of nutrients to inject during each event and the
appropriate interval between events. The injection of too much donor can result excessive organic acids
that could lower the pH and inhibit reductive dechlorination.

Installation and sampling of shallow and deep  monitoring wells during the pre-design investigation
should help confirm the plume delineation suggested by direct-push sampling.  Because direct-push
sampling through high levels of shallow contamination could result in introducing contamination at
deeper intervals, the plume defined by direct-push sampling may not be accurate, and the target volume
for remediation may be smaller and the cost lower.

Another factor that contributes substantially to the cost of a long-term biobarrier remedy is the frequency
that injections are required. The industry standard and the frequency suggested by the site team is
approximately one  injection every 15 months.  The pilot test results should be carefully reviewed to
determine if this frequency is appropriate for this site.  The relatively high velocities within the sand
lenses could lead to more rapid consumption of the donor and the need for more frequent injections.
 4.1.4        RECONSIDER EXPECTATIONS FOR REMEDY TIME FRAMES AND PROGRESS
             TOWARD RESTORATION

 The IDR team believes that the remediation time estimates presented in the ROD appear optimistic for a
 heterogeneous subsurface with clays and may bias remedial decisions. PCE and its degradation products
 have diffused into clay material for nearly 40 years. Based on experience at other sites, the IDR team
 believes that contamination that has diffused into the clay will continue to contribute dissolved
 contamination to the more transmissive zones for decades. Achieving MCLs for the entire plume may not
 be feasible with any technology or reasonable cost in less than several decades. The success of the
 injection-based remedies that have been proposed for the majority of the site area are based on the ability
 of the reagents to reach contamination.  The IDR team believes that diffusion will be the primary
 mechanism for transport of reagents into the impacted  clay or contaminant transport out of the impacted
 clay.  Given that diffusion has been occurring for decades, it is reasonable to assume that at least the same
 amount of time or longer will be required for remediation.

 The IDR team believes appropriate expectations for remedy time frames are important so that the site
 team does not abandon a remedy that is working and switch from remedy to remedy when the site
 conditions are the limiting factor that will also affect other remedy alternatives.
                                           18

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4.2     CONSIDERATIONS PERTAINING TO IMPLEMENTATION
4.2.1        CONSIDER ROTOSONIC DRILLING DURING PRE-DESIGN DRILLING

The complex interbedded nature of the site geology suggests that greater understanding of the vertical and
horizontal distribution of the more permeable lenses and layers is needed.  As indicated during the IDR
meeting, the IDR team strongly encourages the use of rotosonic drilling techniques at key locations at the
site.  The quality of the soil profiles generated from this drilling technique should help facilitate a greater
understanding of the local geology that could aid in completing the final remedial designs. As mentioned
above, the relatively thin high transmissive zones have can play a large role in contaminant transport, the
amount of reagent needed for remediation, and the level of effort for injection.
4.2.2        USE GROUNDWATER INSTEAD OF POTABLE WATER DURING REMEDIATION
            INJECTIONS

Municipal water from the City of Grants was used as the make-up water for the recently completed pilot
tests.  Substantially more water will be needed for full scale ERD. Recent drilling and injection work in
the ISCO and ERD pilot test areas suggested that transmissive units are present at the site. Consideration
should be given to whether one or two of the more permeable units could yield enough water to serve as
temporary extraction wells. These wells could be used to provide an alternative water source.  Site
groundwater would be a preferred alternative to municipal water for use as make-up water for three
principle reasons:


    •   Site water will be better suited geochemically. For example, it will already be reduced.

    •   Strategically placed extraction and injection wells could help sweep donor amendments or
       oxidizers into areas where access for injection is limited (e.g., under a commercial or residential
       building).

    •   Use of site water will prevent the introduction of substantial quantities of municipal water into the
       targeted injection zones and lower the chance of pushing contaminated water into other less
       impacted areas.
4.2.3         OTHER RECOMMENDED SITE CHARACTERIZATION DETAILS

The IDR team agrees with the site team that multiple new monitoring wells are needed in multiple
vertical zones.  Figure 2 proposes locations where the IDR team recommends installation of wells and the
proposed screened intervals for those wells. The monitoring well locations are intended to provide an
improved understanding of contaminant distribution and the site stratigraphy given that the thin
transmissive zones can have a significant effect on remedial design considerations. The IDR team
suggests that aquifer pumping tests be performed at PM-2S/D, PMW-4S/D and PMW-6S/D to better
determine the site hydraulic conditions and to determine whether site water could be used as an
alternative to municipal water.
                                          19

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Consistent with Section 4.2.1, some of this drilling could be conducted with rotosonic drilling because
this drilling technique provides better quality cores than direct-push technologies and will help the site
team better understand the variable stratigraphy at this site.  The IDR team proposes that the 10
monitoring well locations (shallow and deep well pairs) presented on Figure 2, be completed using
rotosonic methods. Although this drilling technique has historically been much more expensive than
hollow stem auger and other traditional drilling methods, the costs for this technology are now much
more comparable to other technologies in many parts of the country.
4.2.4          LIMIT DATA VALIDATION DURING LONG-TERM SITE MONITORING

Data validation can play an important role during investigation and site closure activities, but is often
redundant during long-term monitoring given the repetitive nature of the sampling, the long-term nature
of the monitoring, and an established record of concentrations and concentration trends. As a result, the
IDR team recommends that the site team consider limiting data validation to a small percentage of the
data once a long-term site monitoring program begins.
                                          20

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                                     5.0    SUMMARY
The IDR process included a detailed review of the site documents, a site visit, interviews with the site
team, and analysis of the information collected.  Based on this information and analysis, the IDR team
presents the following findings. These findings include opinions and interpretations made by the IDR
team based on review of the data, experience, and professional judgment and are offered for consideration
to the site team. These opinions may differ from those of other potential reviewers and do not necessarily
reflect the opinions of U.S. EPA OSRTI, which commissioned this review.

    •   Ground water is present beneath the site in thin (approximately 1 foot thick) sand and silt lenses
       within competent clay. A relatively long, continuous lens with a thickness of approximately 1
       foot is present approximately 8 feet to 16 feet bgs.  Water quality data suggest that the highest
       concentrations and most significant horizontal transport of site-related contamination occur
       within this lens.

    •   A ground water concentration of tetrachloroethene (PCE) as high as 3,400 ug/L was detected as
       deep as 60 feet during direct-push sampling.  Limited  data at the site suggest an upward hydraulic
       gradient, which means that dense non-aqueous phase liquid (DNAPL) was likely present as free
       product at one point to allow for substantial vertical contaminant migration.

    •   The abundance of silt and clay in the  subsurface, the presumed vertical migration of
       contamination through these low permeability materials, and the age of the plume (perhaps dating
       back to the 1970s), suggests to the IDR team that aquifer restoration could be diffusion limited,
       resulting in a longer than expected time frame for remediation.

    •   Ground water data suggest to the IDR team that the majority of contamination may have already
       migrated from the source area.

    •   Lithologic and water quality data with depth is limited.

    •   Concentrations of trichloroethene and cis-l,2-dichloroethene (PCE  degradation products) are 10
       times higher near the Allsup underground storage tank site than elsewhere in the plume indicating
       the hydrocarbons in the subsurface are providing a food source for microbes in the area and
       promoting reductive dechlorination. However, concentrations of vinyl chloride are not as high,
       suggesting that reductive dechlorination is not complete and that bioaugmentation (i.e.,
       introducing appropriate microorganisms) may be appropriate.

    •   Limited soil data to date indicate that the area and volume for source remediation is likely much
       smaller than indicated in the Record of Decision (ROD), and the smaller volume for remediation
       may change the cost-effectiveness of some remedial options that have a high capital cost
       component.

    •   Because of contaminant migration and perhaps limited water quality and lithologic information
       with depth, the zone defined as the source area and targeted for thermal remediation does not
       appear to  coincide with the zone of highest detected contamination  and vertical migration. The
       zone that  seems more appropriate based on existing data for source  zone remediation appears to
                                           21

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    be on the downgradiet portion of the Holiday Cleaners property, First Avenue, and properties
    downgradient of First Avenue.

•   The site team prefers a source area remedy that allows Holiday Cleaners to continue operating.  If
    the area requiring source area treatment is actually downgradient of the building and parking lot,
    then this may be feasible.  However, if thermal treatment is required beneath and immediately
    around the property, this may be logistically difficult both during construction and operation due
    to the small property and the limited access to customers.

•   Other options for source area remediation discussed in the ROD and Feasibility Study include
    limited excavation followed by in-situ chemical oxidation (ISCO) with enhanced reductive
    dechlorination (ERD) polishing or ERD alone. Injections of oxidants or nutrients will
    preferentially enter the sand lenses, which occupy only a percentage of the aquifer volume within
    the source  area.  As a result, the amount of oxidant and nutrient required may have been
    significantly overestimated by using the entire volume of the source area.

•   Based on the finding that only a portion of the Holiday Cleaners site is contaminated and the role
    of the sand lenses in controlling oxidant/nutrient delivery, the IDRteam believes that the
    effective volume of the source area that would be treated by ISCO or ERD would be almost an
    order of magnitude smaller than the volume assumed in the Feasibility Study. Based on available
    data, the amount to be injected and the number of injection points may therefore be high by
    almost an order of magnitude if all other factors remain unchanged.

•   The assumed treatment depth for the shallow plume core and hot spot is from 8 feet to 20 feet,
    and the injection of oxidants and nutrients is based on the total  pore volume for this depth
    interval. However, the majority of the mass and ground water flow appears to be in a thin sand
    lens that is approximately  0.5 to 1  foot tick. As a result, the injection quantities needed may be an
    order of magnitude lower than what the site team has calculated if all other parameters and
    assumptions remain unchanged.

•   The IDR team notes that diffusion of contaminant mass out of the lower permeability layers over
    time (as is  assumed by the site team for the source area)  may also contribute to extending remedy
    time frames in the shallow plume  core and hot spot such that the remedial time frame might be
    longer than the 5 to 6 year time frame that is estimated for the ISCO/ERD approach.

•   The results and lessons learned from the pre-investigation and the pilot tests may help better
    estimate the volumes that require treatment and the amount of oxidant or nutrient that is
    appropriate.  The IDR team believes that the findings from the pilot tests could result in revisiting
    the selected remedy for the source area.

•   Reported relatively high sulfate  concentrations in site ground water may accelerate electron donor
    consumption and may become a limiting factor for successful reductive dechlorination.
    Furthermore, in the absence of sufficient alkalinity, the pH may decrease, inhibiting bacterial
    growth, and limiting reductive dechlorination.

•   Significantly fewer injection points may be required for  establishing the biobarriers for the
    shallow plume periphery and deep plume if preferential injection into thin but highly permeable
    zones occurs.
                                       22

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    •   Some of the direct-push ground water samples that have helped define the deep plume may be the
       result of contamination that was brought down to deeper intervals during sampling rather than
       contamination that has migrated under natural conditions.  As a result, the vertical and horizontal
       extent of the deep plume may have been overestimated. Installation and sampling of deep
       monitoring wells can help determine if the plume is accurately delineated.

Based on the above findings, the IDR team presents a discussion on remedial strategy and remedy
implementation. The discussion highlights the following items.

    •   The results from the pre-design investigation and pilot studies could have substantial affect on the
       remedy design and could warrant revisiting the selected remedy for the source zone. The IDR
       team suggests reviewing the data from these studies and revisiting the remedy selection process
       before proceeding with design of the selected remedy. The IDR team can assist with reviewing
       the data and provide a valuable third-party, technical perspective.

    •   Injection of oxidants or nutrients for the shallow plume core and hot spot remedy might be
       efficiently accomplished through trenches or horizontal wells.  In addition, the amount of oxidant
       or nutrient that might be needed is likely less than estimated in the Feasibility Study due to
       preferential  flow through the thin sand lenses. The estimated costs for injections (both materials
       and labor) may be higher than needed. Depending on the outcome of the pilot studies, ERD
       rather than ISCO with ERD polishing, may be more appropriate for remediating this zone.

    •   The preferred flow of water, contamination, and injected nutrients through the thin sand lenses
       could substantially reduce the estimate amount of nutrients and the number of injection points for
       implementing ERD in the shallow plume periphery and deep plume.  This could affect remedy
       cost, but it can also affect remedy performance.  The injection of too much donor can also result
       excessive organic acids that could lower the pH and inhibit ERD.

    •   The IDR team believes that the remediation time estimates presented in the ROD appear
       optimistic for a heterogeneous subsurface with clays and may bias remedial decisions. PCE and
       its degradation products have diffused into clay material for nearly 40 years. Based on
       experience at other sites, the IDR team believes that contamination that has diffused into the  clay
       will continue to contribute  dissolved contamination to the more transmissive zones for decades.
       The IDR team suggests that the site team adjust its expectations for the remedy time frame to
       avoid the potential for moving away from an ERD biobarrier remedy that is working.

    •   The cost for the ERD biobarrier remedy will be highly dependent on how long the biobarrier lasts
       between injections. The site team has estimated that injections will be needed every 15 months.
       The pilot study results will help determine if this frequency is appropriate.

    •   The cost for the ERD biobarrier remedy will also be highly dependent on the true extent of the
       deep plume.  Results from the pre-design investigation will help define the true extent of the  deep
       plume and volume that  requires remediation.

In addition to the above strategy-related recommendations, the IDR team provides the following items for
consideration with respect to implementation.

    •   Given the heterogeneous nature of the site and the importance of stratigraphy for interpreting the
       site conceptual model, use  rotosonic drilling during pre-design activities to obtain better cores for
       analysis.
                                           23

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•   When planning for the ERD injections, consider the use of extracted ground water, rather than
    potable water.

•   The IDR team provides specific suggestions for monitoring well locations and depth intervals.
    Suggestions are also provided to conduct pumping tests in specific wells.

•   The IDR team suggests that data validation be limited during the long-term monitoring program
    given that data collected during the Remedial Investigation, data collected during pre-design
    activities, and a long record of long-term monitoring data will be available to help determine the
    validity of individual samples.
                                       24

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FIGURES

-------
                         DP-79—,
                                           SHALLOW PLUME CORE TARGETED
                                           FOR CHEMICAL OXIDATION
0
   Q-
   LJ
   Q
            DP-38
        o -i
        10 -
       20 -
       30 -
       40 -
       50 -
       60 -
       70 -
       80 -
       90 -
      100
   SOURCE AREA TARGETED
   FOR THERMAL REMEDIATION
                                                                                                 SHALLOW PLUME PERIPHERY
                                                                                                 AND DEEP PLUME TARGETED
                                                                                                 FOR ERD
                                 GMW-6 DP-48/
                                        GC-4    DP-49
                                                                                                       DP-73 r 6439
                                                                                                                          - 6429
                                                                                                              - 6419
                                                                       PHASE 2 DISCRETE - DEPTH GROUND
                                                                       WATER SAMPLE
                                                                       PHASE 1 DISCRETE - DEPTH GROUND
                                                                       WATER SAMPLE

                                                                       PHASE 2 MONITORING WELL SAMPLE

                                                                       NO LITHOLOGIC RECOVERY
                                                                       LIMIT OF LITHILOGIC CHARACTERIZATION

                                                                       DIRECT-PUSH BORING

                                                                       MONITORING WELL SCREENED INTERVAL
- 6409




- 6399

         tf
         s—x
         z
- 6389   9


         Ld
         _l
         LJ
- 6379




- 6369




- 6359




- 6349
                                                                                                               6339
250
500
  HORIZONTAL SCALE IN FEET
                                              Figure 1.  Conceptual Cross-Section of Known Contaminant Extent and
                                                         Targeted Areas for Remediation Specified in the ROD.

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 LEGEND	
 _PMW— 1S/D  GEOTRANS PROPOSED goNTBOus CORE DEEP
ffl             SOteCfltlSWQSHAUjOW/CSEPMOMiTORINO
               WHi \lSHa HOTOSONIC ORU0I3 METHODS
   PMW- 11      GEOTRASS PROPOSED SHALLOW M
 >            TOU.USiJiOH5AORBOT050HPCOHILI.WG
   PMW-4.I/D  GEOTRA.MS PROPOSED OIREC'-KJSH
  p)             »KXJ«iWATER VERTICAL PBORtES
               OR CHANGE N DRILLING PRESSURE
NOTES:
    Win ! GRLATtST IMPACTS (LESS THAN 16:) THE DEEP
    MOMTOR3NG WELLS SHOtl-O BE PLACED H Thffi KTERVAL 0
    TIC DEEFE 5T KNOWN OR ASSUMED IMPACTS, A8 DELINEATED
    Cn-VERTICJL WtOFILE OROUWWATER SAMPLES
    COMPLETE 3 PRIOR TO THE INSTALLATION OF ADOTTTONW.
    MONTfORlNO WT; L S ROTOSGN1C DRlll ING METHODS
    TVICAU.Y USE WAIES AS A DRIUJNO FLUID. WHKX UN DILUTE
    OBOU13*,iTIR CONCEHTRATONS,
<.
                                                                                                                                                                        Legend

                                                                                                                                                                 Graund Wa'ar MDmlcnng Well
                                                                                                                                                                 Prrvatt Well
                                                                                                                                                                 Pliase 1 Uireat-Pust* Sa-rpling Lozat or
                                                                                                                                                                 Pliase 1 -ar^-Anger Samp hp ^ccaron
                                                                                                                                                                 PCF Concentration Greater Thar
                                                                                                                                                                               POP Concertration Rangnfj Frnrr
                                                                                                                                                                               5.000 ^H
                                                                                                                                                                 PCE Concertration Rangng Frorr
                                                                                                                                                                 503 ngt 10 <5-OCO irtyl
                                                                                                                                                                 PCE Concentration Rangng Frorp
                                                                                                                                                                 hi) jtga ID < MO ^gl
                                                                                                                                                                 PCE Conceruation Rangng From
a                                                                                                                                                                               PCE Concenitation Ranging Ftorr
                                                                                                                                                                               Lao Dstection Unit ':> <:5 p.g,'L

                                                                                                                                                                      [QQQ PCE Concentration Jug/Li

                                                                                                                                                                       Notes:
                                                                                                                                                                       ' a Vi\\us "alinsadfot ccnloLMig
                                                                                                                                                                       J = Esl' mated valua.
                                                                                                                                                                       L-Repoteclconcertratcr s be'oiwtie CRCL
                                                                                                                                                                       PCE T-iB-iaciiofosnane.
                                                                                                                                                                       PCC maximLrnccniafn'-Ent level |MC_) 's S t*g-*L
                                                                                                                                                                       C 'set-pts- sarrp'-g ocat'ois r*ot o*- B-* nap, o-s'cwi
                                                                                                                                                                       w't.'-oul 2p3Stadconcfl"l"al'ion ware r gn-getact for PCE
                                                                                                                                                                       during ihePP-asft 1 sarT$>l ngsvenL Labdatscto-1 i-n>i
                                                                                                                                                                       *as typtaly 1 Jtgifl..
                                                                                                                                                                          0     100   200    300   400


                                                                                                                                                                        Figure 1-7
                                                                                                                                                                        Shallow Zone Ground Water
                                                                                                                                                                        Detected PCE Concentrations
                                                                                                                                                                        2004 Phase 1 Sampling Event
                                                                                                                                                                       Grants Chlorinated Solvents Plume She
                                                                                                                                                                         Grants, Cibola County, New Mexico
                                                                                                                                                                                       .CH2MHILL
                                                                                                                  Figure 2.   Proposed  Soil  Boring/Monitoring Well  Locations.

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ATTACHMENT A

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                                                             40000/1600/1OOOLJ/1.9LJ
                                                                                                                                                                                                                      150 FT.
 10
 20
 30
 40
 50
 60
 70
 80
 90
100
                                         GC-11     GC-12/
                                      DP-02    DP-79 GMW-6
                                                                                                           DP-25  GC-6
                      48000/1 BO/<10/
-------
                  Legend
          Soil Sampling Location and Depths
          (Concentrations in mg/kg)
          GCSP Site Boundary
          Phase 1 Direct-Push Soil Sampling Location
    il sampling locations shown on the map
   ithout posted laboratory results were
  nqn-detect for the summarized analytes.
       = CLP Lab Split Sample Results.
 rPiCEtt Tetrachloroethene.
IT T1CEo= Trichloroethene.
  Cfl 2 = Cis-1,2-Dichloroethene.
     = Vinyl Chloride.
 r—B = Benzene.
 I T = Toluene.
  E = Ethylbenzene.
  X = Total Xylenes.
  Refer to Table 5-6 for soil saTnpIirijg results and
  explanation of data qualifiers.
  Figure 5-2
  Soil Sampling
   _                      mary
   ^esuTtf^" ^
        ttt^m
Graols^nlo|nated Solvents Plume Site
  Grants, Cibpla County, New Mexico
            L
                   CH2MHILL

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                Direcfl-Push Sampling Location
                     Auger Sampling Location
                   tration Greater Than
                         angmg From
                         o@g/L
      ~~l o PCE Cdncinttati
                    00 ix
                  nlratiipn panging From
                  5(D u.
                    ratibn Ranging From
                ectiorKLimit to < 5 n-g/L
  L> Reported pincsntr
  /PCE = tetrachtarpethe
/ PCE maximun contarr in:
nt Ibvd (MCL) is 5
  Direct-push sampling locations not on the map, or shown
  without a posted concentration, were non-detect for PCE
  during the Phase 1 sampling event. Lab detection limit
  was typically 1 H-g/L.
           100    200    300    400
                                   Feet
   Detected PCE Concentrations
   2004 Phase 1 Sampling Event

D Grants Chlorinated Solvents Plume Site
                   CH2MHILL

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                  onitCrfpg Well
                 cu-Push Sampling Location
               irec1(-Puen Sampling Location
         100   200   300   400


                              Feet
  Location of Lithologic

  Cross Sections
              0            o

  Grants Chlorinated Solvents Plume Site

Q
                CH2MHILL

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                                                      40000/1600/1OOOLJ/1.9LJ
                                                                                                                                                                                            150 FT.
 10
 20
 30
 40
 50
 60
 70
 80
 90
100
                                    GC-11     GC-12/
                                 DP-02   DP-79 GMW-6
                                                                                                                                           63/6/29/<2



                                                                                                                                                    \J
37000«Sa/45/<2 /
                                                                                                                                                  •   PHASE 2 DISCRETE - DEPTH GROUND WATER SAMPLE

                                                                                                                                                  A   PHASE 1 DISCRETE - DEPTH GROUND WATER SAMPLE

                                                                                                                                                  •   PHASE 2 MONITORING WELL SAMPLE
                                                                                                                                                                     ?  NO LITHOLOGIC RECOVERY
                                                                                                                                                                    — - LIMIT OF LITHOLOGIC CHARACTERIZATION
                                                                                                                                                                     L  REPORTED CONCENTRATION IS BELOW THE CRQL
                                                                                                                                                                     J  ESTIMATED VALUE
                                                                                                                                                                        DIRECT-PUSH BORING
                                                                                                                                                                        MONITORING WELL
                                                                                                                                                                        SCREENED INTERVAL
                                                                                                                                                                                  PCE CONCENTRATIONS
                                                                                                                                             PCEATCE/C12/VC (>ug/L)

                                                                                                                                                  PCE  -  TETRACHLOROETHENE
                                                                                                                                                  TCE  -  TRICHLOROETHENE
                                                                                                                                                  C12  -  CIS-1.2-DICHLOROETHENE
                                                                                                                                                   VC  -  VINYL CHLORIDE

                                                                                                                                             NOTES:
                                                                                                                                             ELEVATION IN FEET ABOVE MEAN SEA LEVEL (NAD 88)


                                                                                                                                             Figure 5-12

                                                                                                                                             Vertical Profile of PCE Contamination


                                                                                                                                                  Grants Chlorinated Solvents Plume Site

                                                                                                                                                    Grants, Cibola County, New Mexico
                                                                                                                                                                                          CH2MHILL

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             	__..,	^Location

Phase 1 Raqd/^uge^>SampfiTig4-pcatio

Residential Structure    ivy
Intrusion Mitigation System Installation P^^S

      ncentration Greater Than (  I
         o
PrkateS'
                                                                                   P CE_Qp ncefti ratio rrRarig irtaF ro m
                                                                                      E Concentrati/so Ranging
                                                                                       /L to < 50 i/g/L
                                                                                   PCE ConcentratiowRanging^Fro
                                                                                   Lab Detection Limit \.o/<^>M,d
                                                                           Notes:

                                                                           PCE = tetrachlofoethefie.
                                                                            CB-cnaximufn contaminacn lev^NMCLiis 5
                                                                           Figure 11
                                                                            tructures With Vapor
                                                                                sion Mitigation  Systems
                                                                                                        Plume Site
                                                                                             CH2MHILL

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00
32
19
                                                                                                                                                                rounc^vvater Monitori

                                                                                                                                                               Private Well

                                                                                                                                                                 ase 1 Direct-Push>6ampling Location

                                                                                                                                                               Phase 'Lhfand-Au/rfer./Sampling Location
                                        DP-440
                                                                                                                       Private 8
                                                                                                                                                           oncentration Greater Than
                                                                                                                                                           fig/L              Q
                                                                                                                                                      PCE Concentration Ranging From
                                                                                                                                                      5,000 |xg/L to < 50,000 |xg/L
                                                                                                                                                      PCE C/Wentration Ranging From
                                                                                                                                                      500 uwlto <5,000
                                                                                GMW-6
                                                                                                                                                               PCE Concentration Ranging From
                                                                                                                                                               50 |xg/L to < 500 |xg/L
                                                                                                                                                               PCE Concentration Ranging From
                                                                                                                                                               5 |xg/L to < 50 |xg/L
                                                                                                                                                               PCE Concentration Ranging From
                                                                                                                                                               Lab Detection Limit to <5 n-g/L
                                                                                   GMW-5
                                                                                                                                                        PCE maximum contaminant
                                                                                 2) Private  700
                                                                                                                                                                       00  /  150
                                                                                                                                                                   Source Area
                                                                                                                                                          ants Chtoqnated Solvents Plume Site
                                                                                                                                                           rants, CibpfevCourrty, New Mexico
   MW-
/MW-7®
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Phase 1 DirebfcPj/sli^afnpling Locatio
Phase 1 Hand-Aug^jrSamplitia Loctetio
                  n
                 Co nee nVatior> Greater Th
             PCE J^ohcentration rar^ingsErom
             PCE Concentration
              0 m/L to/< 5TO |JuafL
               loroethene.
     PCKmaxWium srantaminant'level (MCL) is
       /  /*   /       /
     I^CO/In-sijH chemical/xidation
      Rf/= EnKanced redwctive dechlorination
    Figure  13
    Conceptual Layout of
       Grants, Ci^ola County, New Mexico
       	1_CH2MHILL

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                                                                                   o
 o        • /  /

 © Private 700

& . NI

    BMW-1
     Water-JVIoni
     "V

PnVaXW


Phase 1 DirebfcPj/sli^afnpling Locatio


Phase 1 Hand-Aug^jrSampliogJ_og^itio


               n
                                                                                       Figure 14

                                                                                       Conceptual Layout of ERD
                                                                                         Grants, Ci^ola County, New Mexico


                                                                                         	1_CH2MHILL

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             Phase 1 DirecfcPi/sri^afnpling Locatio
             Phase 1 Hand-Aug^jrSampliogJ_o_g^itio
                               n
             Bib Bar>Le>for Shallow Plume
             PCE uscrcen
             500 (Jig/L to
                 Co
             5(X(Jig/l/o
                     entration Ranging
             PCE/Conoentration Rangwg From
          tetracnloroetnene.

           ximum contaminant level (MCL) is
     Shallow around water plume core bio-barrier:
        rence only, and are not included in costs for p ripher
      io-barrier
    Figure  15
    Conceptual Layout of ERD
       Grants, Ci^ola County, New Mexico

       	1_CH2MHILL

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Phase 1 DirebfcPj/sli^afnpling Locatio

Phase 1 Hand-Aug^jrSampliogJ_o_cptio

Source Treatment Area

     rrier for Treatment to 80
                  lifer for Treatment to 601ft DBS
                              A
                           ections as
                  onqentiation RangtBg From
                  oncei^Jration Ranging |R
                        0
                 Conce/ftration Rangindrrrom
               |xg/Lto /50
                    centration Ranging i-rom
                  election Limit to < 5 |xg/L
              \/
     Notes:

     PCE = tetrachloroethene.

     PCE maximum contaminant level (MCL) is 5 H-g/L

                     N
    0       100     200      300     400


    Figure  16

    Conceptual Layout of ERD
       Grants, Ci^ola County, New Mexico

       	1_CH2MHILL

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