PB98-963109
EPA 541-R98-040
September 1998
EPA Superfund
Explanation of Significant Difference
for the Record of Decision:
Fort Lewis Logistics Center
Tillicum, WA
9/9/1998
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RECEIVED
opp i 1 iQQfl
EXPLANATION OF SIGNIFICANT DIFFERENCE OC A
Environmental Cleanup Office
for the
DEPARTMENT OF THE ARMY
LOGISTICS CENTER
FORT LEWIS, WASHINGTON
I. Introduction
This document presents an Explanation of Significant Difference (ESD) from the Record of
Decision (ROD) for the Logistics Center at Fort Lewis. Washington. The ROD was signed by
the U.S. Army (Army), the U.S. Environmental Protection Agency (EPA), and the Washington
State Department of Ecology (Ecology) in September 1990.
Site Name and Location:
Logistics Center
Fort Lewis, Washington
The Fort Lewis Logistics Center was placed on the National Priorities List (NPL) in December
1989 under the Comprehensive Environmental Response. Compensation, and Liability Act
(CERCLA) of 1980. as amended by the Superfund .Amendments and Reauthorization Act
(SARA) of 1986. The lead agency for the Logistics Center studies and cleanup is the Army. An
installation-wide Federal Facilities Interagency Agreement (FFA) between the Army. EPA. and
Ecology became effective in January 1990. This FFA provides the framework for management.
investigation, and remediation of releases of hazardous substances on Fort Lewis as necessary to
protect public health, welfare, and the environment.
This ESD. prepared in accordance with section 117tc > of CERCLA and 40 CFR 300.435c(2)(i),
is necessary to document changes to the selected remedy outlined in the ROD. The Army and
EPA support the need for this ESD and participated in the decision-making. In accordance with
the October 14. 1994 EPA/Ecology agreement. Ecology was provided with a milestone briefing
on this ESD.
The selected remedy described in the ROD for the Logistics Center primarily addresses the
potential risks posed by volatile organic compound r'VOC) contamination in groundwater by
reducing the site contamination to levels that are protective of human health and the
environment. The goal of the selected remedy is to restore groundwater to its beneficial use.
which is a drinking water source. The major components of the selected remedy are:
1. Install groundwater extraction wells capable of capturing the groundwater
contaminant plume in the unconfined aquifer.
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2. "Install on-site groundwaier treatment facilities to remove contaminants from the
collected groundvvater.
3. To expedite groundwater remediation, install groundvvater extraction wells near areas
of highest concentration of contaminants and discharge treated groundwater
upgradient of these extraction wells to facilitate flushing secondary sources from the
groundwater.
4. Monitor the groundwater contaminant plume and the extraction/treatment system
during groundwater remediation activities to ensure that both groundwater and
surface water remediation goals are achieved.
5. Implement administrative and institutional controls that supplement engineering
controls and minimize exposure to releases of hazardous substances during
remediation.
6. Investigate the lower aquifer(s) to determine the presence of contamination and to
evaluate the extent of contamination, if necessary. If contamination is found, a
groundwater extraction system will be installed, which is capable of capturing the
contaminant plume, with subsequent treatment of the extracted groundwater in the on-
site treatment facility. The remediation goals specified for the unconfmed aquifer
will also apply to any contaminated lower aquifers.
7. Perform confirmational soil sampling to ensure that all remaining sources of soil
contamination have been identified and characterized.
Items 1 through 3 were completed by installing two grour.i\vater extraction and treatment
systems in the unconfmed aquifer that became fully operational in August 1995. Items 4 and 5
are ongoing.
To address item 6. an investigation was conducted in 19^-^4 to better determine the nature and
extent of contamination in the lower aquifer (Salmon Springs aquifer)" :>. The study concluded
that trichloroethylene (TCE) was the only contaminant to exceed ROD remediation goals, but
that the contamination was more widespread than previousiy thought. An annual monitoring
report for 1998 '•'* confirmed these findings, and found :h.v. TCE concentrations in some lower
aquifer wells are actually increasing with time.
I) "Fort Lewis Logistics Center Lower Aquifer Groundwaicr Sru;; rinal Technical Memorandum. Ebasco
Environmental. Prepared for Seattle District. Army Corps ot'Er..; reers. 1993.
2) "Fort Lewis Logistics Center Lower Aquifer Study" Final Adccr.-m to Final Technical Memorandum. ::.b;isco
Environmental. Prepared for Seattle District. Army Corps of Er.i..~;srs. 1994.
3) "Fort Lewis Logistics Center Remedial Action Monitoring - Se-v-d Year Monitoring Report" Woodward-
Clyde. Prepared for U.S. Anny Corps of Engineers. Seattle Dii~;:. 1998.
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Confirmational soil sampling and other investigation activities were completed in 1993-94 to
address item 7 <4 ". These studies were aimed at identifying and characterizing hazardous or
toxic soil constituents at the East Gate Disposal Yard (EGDY). the Battery Acid Pit, and the
Defense Reutilization and Marketing Office (DRMO). Results indicate that the EDGY is the
primary source of chlorinated solvent contamination at the Logistics Center.
In 1998. additional wells were installed to the southwest of the EGDY to further delineate the
lateral extent of the TCE plume in this area, and to determine whether any additional sources of
contamination exist in this area.
New site characterization studies, limited system performance data, and recent information
concerning the effectiveness of pump and treat systems have resulted in a reevaluation of the
current remediation strategy set forth in the ROD (see detailed discussion in section III).
This ESD addresses enhancements to be implemented in the overall strategy for remediating the
site and will become part of the Administrative Record file pursuant to Section 300.825(a)(2) of
the National Oil and Hazardous Substance Pollution Contingency Plan (NCP).
II. Summary of Site History, Contamination Problems, and Selected Remedy
investigations and Findings
In 1985. the Army identified traces of TCE and cis-1,2 dichloroethyiene (DCE) in several
monitoring wells installed in the unconfined aquifer beneath the Logistics Center. A limited site
investigation was performed in 1986 under the Defense Environments: Restoration Program
DERP). During 1986 and 1987, EPA performed a groundwater investigation in and near the
city of Tillicum and found that groundwater contamination beneath Tiilicum appeared to
originate from the Logistics Center. As a result, the Army agreed to :?jdy the groundwater
rlume off the installation as part of the Logistics Center Remedial Investigation (RI). The RI
••vas conducted in 1987-88 and included a field investigation to determine the nature and extent
of contamination in soil, groundwater, surface water, and sediments.
The Feasibility Study (FS). completed in May 1990. evaluated remeciai action alternatives. The
?J and ROD determined that the shallow, unconfined aquifer beneath :he Logistics Center is
contaminated \vith VOCs. primarily TCE and DCE. and presents an .-acceptable risk to human
r.ealth and the environment. The source of the VOC contamination v-.^s thought to be in or near
:he EGDY. The individual source sites within the EGDY, however, vere not precisely
delineated.
"Fort Lewis Logistics Center Limited Field Investigation Confirmational Soil jimpling. Fon Lewis. WA" Final
Technical Memorandum. Woodward-Clyde. Prepared for Seattle District. L.S \rrny Corps ot"Engineers. 1993.
"Fon Leu is Logistics Center Limited Field Investigation Confirmational Soil Sampling, Fort Lewis. WA" Final
Addendum Technical Memorandum. Woodward-Clyde, Prepared for Seattle D:.-trict, U.S. Army Corps of
Ensineers. 1995.
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The EGDY is located just outside the east gate of the Logistics Center and was used between
1946 and 1960 as a disposal site for waste generated by the Mount Rainier Ordinance Depot.
Aerial photograph interpreters estimate 24 trenches were excavated in the yard. The trenches
reportedly were used for the disposal of waste TCE and petroleum, oil, and lubricants (POL)
from equipment cleaning and degreasing activities. The trenches were subsequently backfilled .
and are not currently evident.
The Logistics Center is located on an extensive upland glacial drift plain. Investigations have
shown that the hydrostratigraphy of the area is quite complex. Generally, the geology consists of
sand and gravel deposits with till layers (Vashon Drift) overlying a finer-grained, nonglacial
deposit (Kitsap Formation). The Vashon Drift is mostly permeable and contains the unconfmed
aquifer. The base of the aquifer is the Kitsap Formation, which separates the unconfined aquifer
from the Salmon Springs aquifer (also known as the lower aquifer). The unconfined aquifer is
continuous across the site. Depth to the water table varies between 7 and 35 ft below land
surface near the Logistics Center and groundwater flow is to the west-northwest.
The Salmon Springs aquifer generally lies between 100 and 200 ft below land surface, and in
turn, overlies the deeper Puyallup Formation. The Salmon Springs aquifer acts largely as a
confined aquifer contained within the Salmon Springs Drift, a sequence of recessional and
advance glacial sediments. Groundwater within the aquifer moves generally in the direction of
Puget Sound at an average velocity of about 3 ft/day.
Contamination appears to enter the unconfined aquifer at or near the source area and migrates
downgradient as a plume, along the axis of the Logistics Center (see Figure I'61). TCE
concentrations near the source area generally range from 500 to >50,000 micrograms per liter
(u.g/L). Throughout the main body of the plume, TCE concentrations range from 100 to 200
ug/L. The TCE concentration at the definable leading edge of the plume, adjacent to Interstate
Highway 5 (1-51. is 50 jug L. The leading edge of the plume downgradient (under Tillicum) is
not well defined.
DCE concentrations near the source area generally range from 100 to >500 |.ig/L. and from 10 to
50 ng/L throughout the main body of the plume. Vinyl chloride concentrations in the unconfined
aquifer have been below detection in all but two source area wells. LC-134 and LC-162.
'Remedial Actions
Remedial desigr, and conitruction for items I through 3 of the selected remedy (see pages 1-2)
took place in two phases. Phase I included design and placement of the well fields. The Phase I
Design Analysis was completed in May 1992. Placement of the well fields was completed in
May 1993. Phase II included design and placement of the treatment and recharge systems, and
piping. The Phase II Design Analysis was completed in August 1993. Construction of the
treatment systems was completed in 1995.
6) "Fort Lewis Logistic Center Remedial Action Monitoring First Annual Monitoring Report" \Voodward-Clyde.
Prepared for U.S. Army Corps of Engineers. Seattle District. 1997.
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Two extraction and treatment systems were constructed, one at each end of the Logistics Center.
The dovvngradient system, known as the 1-5 system because of its proximity to the Interstate, \vas
designed to halt further flow of contaminated groundwater across the installation boundaries.
This system contains 15 extraction wells located along a line from 150'" Avenue to the south end
of Tacoma Drive. Recharge occurs through four infiltration galleries (trenches) downgradient of
the extraction wells, along the Logistics Center boundary. The upgradient system, known as the
East Gate system was designed to remove contaminants directly from the probable source areas.
This system is divided into primary and secondary extraction fields. The primary field contains
four wells and is located near the intersection of Rainier Drive and East Lincoln Drive; the
secondary field contains two wells and is located approximately 1500 ft downgradient of the
primary field. Recharge occurs through two infiltration galleries and two recharge wells, located
approximately 1000 ft upgradient of the primary extraction field.
Lower Aquifer Study
*
The lower aquifer study(l<:>, required pursuant to item 6 of the selected remedy, was conducted
during the same time period as the remedial design and construction activities. This study
confirmed the presence of TCE contamination in the lower aquifer. Groundwater movement
from the unconfined aquifer to the lower aquifer through a window, or windows, in the
intervening confining layer (Kitsap Formation) was determined to be one source of the lower
aquifer contamination. Improperly completed wells may also be a conduit for contaminant
migration into the lower aquifer, although the lower aquifer study concluded that this was not a
significant source of contamination.
The window, interpreted to be a sandy deltaic sequence that filled in the western margins of a
deep trough, is located near the center of the Logistics Center and trends across the groundwater
gradient. At a minimum, the window extends from the area near well LC-66D to well LC-69D. 2
distance of about 1800 ft (see Figure 2). The plume extending into the lower aquifer from this
window is not well defined, but is at least as wide as the distance between the two wells (1800
ft), and is at least 3500 ft in length (the distance between wells LC-69D and LC-72D). TCE
concentrations in the lower aquifer immediately downgradient of the window are similar to the
concentrations in the unconfined aquifer in the area of the window (100 to 180 ug/L). DCE
concentrations in the lower aquifer are generally below 10 ug/L. Vinyl chloride concentrations
were below detection limits (0.3 and 0.6 ug/L).
Modeling conducted in 1994 indicates that the predicted hydraulic path of the contaminant plume
in the lower aquifer is generally west-northwest' ''. The predicted path passes beneath 1-5.
Camp Murray. American Lake, and North Fort Lewis, and intersects Puget Sound in the vicinir-
of Southern Cormorant Passage. The distance from the point where the contaminants enter the
lower aquifer to the point where the plume path intersects Puget Sound is approximately 5.'/ ni
The lower aquifer plume is expected to remain at least 175 ft below land surface throughout its
predicted path, beneath the Kitsap Formation.
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Since the lower aquifer study was completed, there has been one new well installed in the
downgradient plume area (LC-74). This well has provided additional water-ievel data and
gradient information, and a broader definition of the lower aquifer plume. Chemical data
collected from this and other wells since the modeling was completed, show that the
contamination is distributed along a more southerly flow path than was predic:ed by the model.
and that the plume is still not well bounded by wells along the southerly and downgradient
westerly boundaries<3). The additional water-level data also indicate a more southerly flow
direction than that modeled. Therefore, the conclusion that the lower aquifer plume will remain
beneath government property all the way to the Puget Sound must be regarded as tentative
pending further geochemical analysis and flow modeling.
III. Description of the Significant Differences and the Basis for those Differences
This ESD was determined necessary to document the reasons for enhancing the selected remedy
for the unconfmed aquifer:
from using groundwater extraction and treatment in on-site treatment facilities
to using innovative technologies to accelerate treatment and/or control of the
source area and the contaminant plume in the unconfined aquifer in addition
to utilizing groundwater extraction and treatment in on-site treatment
facilities. The extraction and treatment systems may be shut down at some
time in the future if no longer required.
and for the lower aquifer:
from extending the groundwater extraction and treatment in on-site treatment
facilities to the lower aquifer at this time
to accelerating the cleanup of the unconfined aquifer through source control at
the EGDY and the use of innovative technologies in the unconfined aquifer,
and conduct additional studies on the transport of contaminants to and
through the lower aquifer.
The factors considered in enhancing the strategy for remediation of the grour.cv.uter at the Fort
Lewis Louistics Center include:
• New site characterization data
• Performance data on the existing pump and treat systems
• New information on the effectiveness of pump and treat systems::: jeneral
• Availability of new and innovative treatment options.
These factors are discussed below.
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New Site Characterization Data
New information on both the nature and extent of the solvent contamination at the Fort Lewis
Logistics Center has become available(7). This information coupled with data in the RI has
reaffirmed the EGDY and adjacent areas as the primary source of the solvent contamination in
the groundwater. Further, the RI indicates that at least 51,000 kg of solvents (largely TCE) may
have been disposed to the trenches in the EGDY between 1946 and 1960. Given the current
performance of the pump and treat systems, which are removing approximately 650 kg/yr, the
minimum time to remediate the TCE contamination is 78 yr. This figure is considerably longer
than the 30- to 40-yr period estimated when the ROD was signed. If, in fact, the performance of
the pump and treat systems decline with time, as they have at most other sites, the time required
will be considerably longer than 78 yr.
Laboratory data and field experience have suggested that dissolved TCE concentrations in excess
of about 10.000 ng/L are indicative of the existence of droplets or pools of a pure TCE phase in
the subsurface<8>. This pure phase solvent is known as a DNAPL (dense non-aqueous phase
liquid). The presence of subsurface DNAPL generally complicates the cleanup of a
contaminated site. Because dissolved aqueous TCE concentrations at well LC-136A exceed
10,000 ug/L (up to 80,000 u,g/L), it is highly likely that some DNAPL is present in the
unconfmed aquifer near the EGDY.
Performance Data on the Existing Pump and Treat Systems
The maximum concentration of TCE in groundwater near the EGDY in 1991, before
construction of the EGDY pump and treat system, was 2,400 jig/L. A concentration of 24,000
u.g/L was detected in well LC-136A. following installation in 1992. After 2 yr of operation, the
concentration has increased to as much as 80.000 ug/L in this well. This increasing
concentration is further evidence of the existence of some DNAPL at the site. The probable
existence of DNAPL coupled with the high groundwater flow rate through the source area
resulting from pumping and treating, vyill likely smear the contamination into a larger area than
that which existed before the system began operating. There is also a tendency for dissolved
aqueous TCE to diffuse from the more permeable areas of the aquifer where the groundwater
flow is occurring to less permeable areas of the aquifer. Thus, there is concern that the areal
extent of the contamination will increase as the aquifer re-equilibrates with the new higher
aqueous concentrations. This phenomenon will probably also lead to a "rebound" of TCE
concentrations in the wells to higher than original concentrations after the extraction wells are
turned off.
7) "East Gate Disposal Yard Expanded Site Investigation. Site History and Conceptual Site Model" Woodward-
Clyde, Prepared for U.S. Army Corps of" Engineers. Seattle District. 1997.
8) Feenstra S. and J. A. Cherry (1996) "Diagnosis and Assessment of DNAPL Sites"' in Dense Chlorinated
So/vents ar.J Dthcr D:\APL x in Cround\vatcr, J.F. Pankow and J.A. Cherrv, Eds. Waterloo Press. Portland. OR.
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Because purnp and treat remedies work largely on the dissolved aqueous phase, the presence of
DNAPL couid further decrease the likelihood that this pump and treat system alone can
remediate the contaminant plume. In fact, it could mean that even after pumping and treating
long enough to clean up the plume outside the source area, the EGDY system would have to
operate indefinitely to keep the plume from re-establishing itself, or to keep the EGDY
contamination from acting as a source for the lower aquifer.
The downgradient pump and treat system appears to be limiting the spread of contamination in
that direction by providing hydraulic control of the groundwater flow. However, some
movement of TCE in the downgradient direction does appear to be continuing. Because of the
relatively low concentrations of TCE at the downgradient end of the plume, mass removal rates
for TCE by this system are low.
Recent Information on the Effectiveness of Pump and Treat Svstems in General
At the time of the ROD, the Army. EPA, and Ecology believed that the selected remedy would
restore the unconfmed aquifer to its beneficial use as a drinking water source. Since that time,
however, information has become available that casts doubt on the ability of a pump and treat
system alone to restore an aquifer. The scientific and environmental communities now have a
better understanding of the limitations of pump and treat imposed by the physical, hydraulic, and
chemical conditions typical of most unconfmed aquifers. This new understanding is based on
both theoretical considerations, and on the historical performance of numerous pump and treat
systems. In most cases, these factors lead to declining performance of the pump and treat system
over time, such that the period required to achieve remediation is much longer than originally
believed0 !>.
Availability of New and Innovative Treatment Options
Because of the growing understanding of the limitations of standard remedies such as pump and
treat, considerable work in the scientific and environmental communities during the past several
years has focassed on developing new, more effective, and less costly alternatives. The
innovative technologies include barriers for more effectively containing the spread of
contamination. These technologies avoid the high costs of pumping for extended periods, and
are less susceptible to those properties of aquifers that lead to declining performance over time.
Because many of the new technologies are passive, there is also less danger than with active
treatments or" worsening the situation by spreading the source or contaminating larger volumes of
groundwater. Thus, they offer a better chance of protecting human health and the environment.
9) Mackay. D M. and J.A. Cherry (198')) "Groundwater Contamination: Pump and Treat Remediation", Environ.
Sci. T^cii>: ... V. 23. No. 6. 630-636.
10> MacDona'.c. J.A. and M.C. Kavanauuh (!9c)4V'Resiorinu Contaminated Groundwater. An Achievable Goal? -
The Natter..1.! Research Council's Study of Groundwater Cleanup Alternatives". Environ. Sci. TechnuL. V. 2S.
No. 3. 36IA-368A.
11) "Superfur.c: Operations and Maintenance Activities will Require Billions of Dollars" G AO Report to the
Ranking Minority Member. Committee on Commerce. House of Representatives. United States General
Accounts; Office. Washington. D.C.. GAO/RCED-95-259. September 1995.
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IV. Proposed Approach
The selected remedy in the ROD is being modified to more effectively meet the ROD goal of
restoring groundwater to a potential drinking water source. The major components of the
enhanced remedy are:
• Conduct an investigation of the EGDY (the source of contamination to the
unconfmed aquifer) and determine the feasibility of conducting source control
measures there.
• Continue to operate, maintain, and monitor the existing groundwater pump and treat
systems, and investigate/implement ways to improve the efficiency of those systems.
• Continue the groundwater monitoring program in accordance with the approved
monitoring plans; enhance the monitoring program as necessary.
• Decommission groundwater monitoring wells that are screened across water-bearing
units.
• Determine the full extent of the contaminant plume in the unconfmed aquifer, and
improve the understanding of hydrological forces influencing plume migration. This
will include adding new groundwater monitoring wells in the unconfmed aquifer to
the south of the 1-5 extraction system, adding shallow and deep well pairs located
centrally within the unconfmed aquifer plume, and investigating the impact of
irrigation practices at Clover Park Technical College. Modify the existing
groundwater capture systems as necessary to insure that the plume in the unconfined
aquifer is fully contained, or implement alternate remedial measures as needed to
mitigate the spread of contamination.
• Investigate new and innovative technologies to reduce the migration ot'or toxicity of
the dissolved contaminant plume in the unconfined aquifer, with an emphasis on
measures that may reduce the contamination reaching the lower aquifer. Perform
bench-scale, pilot-scale, and full-scale demonstrations of promising technologies.
The leading candidates presently being considered are In Situ Redox Manipulation.
Enhanced Bioremediation. and Phytoremediation.
• Adjust remedial activities for the lower aquifer to ensure both short- and long-term
protection of human health and the environment
Install additional monitoring wells to the south of the Logistics Center and other
areas as necessary to determine the extent of contamination and direction in • i: .n
the plume is moving. Add new wells, as appropriate, to the existing groundwater
monitoring program.
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Conduct a groundwater use survey and inventory covering the area downgradient
of the Logistics Center continuing to Puget Sound. Test public or private wells
found to be in or near the predicted path of the contaminant plume. If any water-
supply well is found to be impacted by the contaminant piume. the Army will
immediately implement point of use mitigation and conduct a focussed Feasibility
Study leading to a remedial or removal response to the problem.
Update and enhance, as appropriate, the groundwater model) s) to predict the fate
and transport of contaminants in both the upper and lower aquifers.
Conduct an evaluation of the effects of expedited treatment of the unconfmed
aquifer and of the EGDY on the transport of contamination to the lower aquifer.
• The Army and EPA will meet approximately once per month to discuss progress of
remedial activities at the Logistics Center.
• Using all of the data developed about the site (including the above work),
comprehensively re-assess the remedial action and the need for additional remedial
action at the site no later than September 2000.
V. Affirmation of the Statutory Determinations
V
The modified remedies continue to satisfy the requirements of CERCLA faction 121.
Considering the new information gathered, all parties believe that the rem edies 1) remain
protective of human health and the environment, 2) comply with Federa; and State requirements
that were identified in the ROD as applicable or relevant and appropriate to this remedial action
at the time the ROD was signed, and 3) are also cost-effective with regard :o the risk imposed.
In addition, the revised remedies utilize permanent solutions and treatment technology to the
maximum extent practicable for this site.
Formal reviews of remedial actions are required to be conducted at leas; every 5 yr in cases
where hazardous substances remain on site above cleanup levels. The purpose of the 5-yr
reviews is to determine whether the remedy remains protective of human health and the
environment. A 5-yr review for the Logistics Center was last conducted :r. September 1997.
Mainly because of the appareir. increasing levels of contaminants in the .0 v-.er aquifer and the
questions regarding the direction that the contaminant plume is mo\ inc. E?A will conduct
another review no later than September 2000. This review will include ^ ,-omprehensive
assessment of the information that will be collected over the next 2 yr. and a re-evaluation of the
remedial action and of the need for additional remedial actions at the site.
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VI. Public Participation
A Community Relations Plan (CRP) was prepared in 1987 in accordance with CERCLA, as
amended by SARA. The CRP includes establishing information repositories and communication
pathways to disseminate information.
This ESD will become part of the Administrative Record File (location noted below) as required
by NCP 300.825(a)(2).
Environmental and Natural Resources Division
ATTN: AFZH-PWE-E, Building 4301
Fort Lewis, WA 98433-9500
Notice will be issued in the Tacoma News Tribune and the Northwest Guardian, that this ESD
and contents of the Administrative Record File are available for public viewing. Copies of the
ESD will be available to the public at the information repositories listed below.
Pierce County Library Pierce County Library
Lakewood Branch Tillicum Branch
6300 Wildaire Rd. SW 14916 Washington Ave. SW
Tacoma, WA 98499 Tacoma, WA 98498
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Signature sheet for the foregoing Explanation of Significant Difference for the Fort Lewis
Logistics Center between the United States Army and the L'nited States Environmental
Protection Agency, with concurrence by the Washington State Department of Ecology.
Paul T. Steucke, Jr. ^ ^\ Date
Chief, Environmental and Natural
Resources Division
Directorate of Public Works
Fort Lewis, Washington
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Signature sheet for the foregoing Explanation of Significant Difference for the Fort Lewis
Logistics Center between the United States Army and the United States Environmental
Protection Agency, with concurrence by the Washington Slate Department of Ecology.
Randall F. Smith Date f
Director, Environmental Cleanup Office
U. S. Environmental Protection Agency, Region 10
Seattle, Washington
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FXHANATION
American Lake
American Lakes
Garden Tracl
,-ll.tM
EGDY
. im
1'illicuin
..
/ Murray Creek
0500 MllfS
o 500 miOMf iFns
Fipire I. — Concentration of trichloroelhylene (TCE) measured in groundwater from the unconfined aquifer (Woodward Clyde. 1997(refercnce no.6)).
near the Logistics Center and East Gate Disposal Yard (EGDY) at Fort Lewis, Washington.
PirlimiiKWv. snhinl In rrvi^iim Pmirrlion11ITM 7mt- 10 IIS OnlnoHVtl Survrv. Water Rrsniifrr.<; Division
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OCT.I
American Lake
Tillicum
American Lakes
Garden Tract
EGDY /
,-u-.*.
Murray Creek
0.500 MltES
05OO KltOMEUnS
[•'ipiirc 2. — I..,.i i
II)
11 S (irolopirvil Siirvrv \V:iirr UrviMitcrs
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