United States Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R10-92/049
July 1992
f/EPA Super-fund
Record of Decision:
Fort Lewis (Landfill No. 5),
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NOTICE.
The appendices listed in the index that are not found in this document have been removed at the request of
the issuing agency. They contain material which supplement. but adds no further applicable information to
the content of the document. All supplemental material is, however, contained in the administrative record
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50272-1 01
REPORT DOCUMENTATION I t. REPORT NO. I~ 3. Recipienfs Accession No.
PAGE EPA/ROD/R10-92/049
4. Title and Subtitle 5. Report Date
SUPERFUND RECORD OF DECISION 07/10/92
Fort Lewis (Landfill No. 5), WA
First Remedial 6.
Action - Final
7. Author(s) 8. Performing Organization Rept No.
9. Performing Orgalnlzation Name and Address 10. ProjecVTaskIWork Unit No.
11. Contract(C) or Grant(G) No.
(C)
(G)
1~ Sponsoring Organization Name and Address 13. Type 01 Report & Perfod Covered
U.S. Environmental Protection Agency
401 M Street, S.W. 800/000
washington, D.C. 20460 14.
15. Supplementary Notes
PB93-964607
16. Abstract (Umlt: 200 words)
The 180-acre Fort Lewis (Landfi 11 No. 5) site is located on the west side of the
86,000-acre Fort Lewis Military Reservation in Pierce County, Washington. GrO\md water
is used as the source of the municipal water supply; however, supply wells are not
affected by the site. From 1967 to 1990, the landfill accepted 77,000 tons per year of
mixed municipal, industrial, commercial, and residential waste and 188,000 cubic yards
per year of demolition waste from the Fort Lewis Military Reservation, the VA Medical
Center, and McChord Air Force Base. Dewatered sludge from the Fort Lewis Sewage
Treatment Plant was also disposed onsite. Ini tially, waste was placed in trenches
running north to south, which were covered with soil in 1971. Subsequently, until 1990,
site trenches running east to west were used for disposal. In 1985, as part of the
closure procedures for the inactive portions of Landfill No. 5, the Army covered the
east-west trenches with a multi-layer cap. Ground water modeling conducted from 1980 to
1984 revealed that contaminant conce~ntrations in the ground water did not exceed
regulatory standards and will decrea.se over time because the cap will reduce leachate
production. This ROD addresses a final remedy for the inactive portions of thE~
(See Attached Page)
17. Document Analysis a. Descriptors
Record of Decision - Fort Lewis (Landfill No. 5), WA
First Remedial Action - Final
Contaminated Media: None
Key Contaminants: None
b. IdentltJeralOpen-Ended Terms
.. ..
c. COSA TI ReldfGroup
18. Availability Statement 19. Security Class (This Report) 21. No. of Pages
None 62
20. Security Class (This Page) ~ Price
Nnnp
OPTIONAL FORM 272 4-77)
(See ANSI-Z39.tB)
See Instructions on Reverse
(Formerly NTiS-35)
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EPA/ROD/R10-92/049
Fort Lewis (Landfill No.5), WA
First Remedial Action - Final
Abstract (Continued)
landfill. Recent investigations by the Army indicate that conditions at
currently pose no unacceptable risks to human health or the environment;
are no primary contaminants of concern affecting this site.
the site
therefore, there
The selected remedial
water monitoring will
operating and closure
remedy.
action for thii~ site is no further action; however, onsite ground
continue in accordance with state and local solid waste landfill
requirements. There are no costs associated with this no action
PERFORMANCE GOALS/STANDARDS:
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, , '
. . ,. . . .
RECORD OF DECISION,
..
,'.
FORT LEWIS MILITARY RESERVATION, WASHINGTON
Fort Lewis Landfill No.5
u.s. Environmental Protection Agency, Region X
U.S. Department of the Anny
Washington State Department of Ecology
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~~
RECORD OF DECISION
for the
UNITED STATES ARMY
FORT LEWIS LANDFILL NO.5
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TABLE OF CONTENTS
Declaration of the Record of Decision
Decision Summary
page
Introduction.
I.
Site Name, Location, and Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1
II.
Site History and Enforcement Activities. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2
m.
Community Relations. . . , . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . .. 4
IV.
Scope and Role of Response Action Within Site Strategy. . . . . . . . . . . . . . . . .. 5
v.
Summary of Site Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . .. 6
VI.
Sununary of Site Risks. . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10
VII.
Selected Remedy. . . . . . . . . ,. . . . . . , . . . . . . . . . . . . . . . . . . .. . . . . . . . . . .. 19.
VIII.
Documentation of Significant Changes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 20
Responsiveness Summary. . . . ; . . . , . . . . . . . . . . . . . .. . . . . . .. . . . .. . . . . .. . . . . . ... 21
Appendices
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DECLARATION OF THE RECORD OF DECISION
SITE NAME AND LOCATION
Landfill No.5
Fort Lewis Military Reservation, Pierce County, Washington
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected fmal remedial action for Fon Lewis Landfill No.
5 in Pierce County, Washington. The selected remedy was chosen in accordance with
CERCLA, as amended by SARA, and, to the extent practicable, the National Oil and
Hazardous Substances Pollution Contingency Plan (NCP). This decision is based on the
Administrative Record for the site.
The lead agency for this decision is the U.S. Army. The U.S. Environmental Protection
Agency (EPA) approves of this decision and, along with the State of Washington Department
of Ecology (Ecology), has participated in the scoping of the site investigations and in the
evaluation of remedial investigation data. The State of Washington concurs with the selected
remedy.
DESCRIPTION OF THE SELELIED REMEDY
The Department of the Army has determined that no further remedial action is necessary at
Fort Lewis Landfill No.5 to ensure protection of human health and the environment. This
decision is based on the results of the human health and ecological risk assessments, which
detennined that conditions at the site pose no unacceptable risks to human health or the
environment. The Army will continue to implement the operating and closure requirements
of Landfill No.5 under a permit administered by the Tacoma-Pierce County Health
Department. The closure complies with State Minimum Functional Standards for Solid Waste
Handling, pursuant to Washington Administrative Code (WAC) 173-304, including the
construction of a cover over Zones 1 through 4 of the landfill, a surface water management
system to control runoff from the covered landfill, and a passive gas ventilation system to
collect and burn landfill gas. As part of the closure and operation of Landfill No.5, the
Army will continue to monitor groundwater to assist in confIrming the prediction of
decreasing contamination. If monitoring does not confurn the prediction of decreasing
contamination, the Army will evaluate the need to perlotm additional response action in
accordance with all applicable laws and regulations. Administrative controls will.be
implemented to' restrict future development and use of the landfIll as identified under an
operating or closure permit issued at the landfIll.
DECLARATION
The selected remedy is protective of human health and the environment. Consistent with
Section XIX of the Federal Facility Agreement, the Department of the Army will conduct a
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Signature sheet for the foregoing Fort Lewis Landfill No.5 Record of Decision between the
Department of the Army and the U.S. Environmental Protection Agency, with concurrence by
the Washington State Department of Ecology.
rllaAAQ 0. ~
D na Rasmussen
Regional Administrator, Region X
U.S. Environmental Protection Agency
7 -/0 ~ &1 J-
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Signature sheet for the foregoing Fort Lewis Landfill No.5 Record of Decision between the
Department of the Army and the U.S. Environmental Protection Agency, with concurrence by
the Washington State Department of Ecology.
~ tJiJ~
Lewis D. Walker
Deputy Assistant Secretary of the Army (I, L, & E)
Environment, Safety and Occupational Health
7 /2'-1 /92-
Date
"" Carmen J. ez
~'" Lieutenant Gen a, U.S. Army
Commander, I Corps and Fort Lewis
).6 j~ \(t't~
Date
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Signature sheet for the foregoing Fort Lewis LandfiU No.5 Record of Decision between the
Department of the Army and the U.S. Environmental Protection Agency, with concurrence by
the Washington State Department of Ecology. .
~J..~ i-~
CarQI Fleskes, Program Director
Toxics Cleanup Program
Washington State Department of Ecology
1/1/9:1
.
Date
~.~fi:~1 A.M.
Attorney Generalis wftce.
State of Washington
rl+ } 1'/'1~
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DECISION SUMMARY
INTRODUCTION
Fort Lewis Landfill No.5 was listed on the National Priorities List (NPL) in 1987 under the
Comprehensive Environmental Response. Compensation, and Liability Act of 1980
(CERCLA, or Superfund). as amended by the Superfund Amendments and Reauthorization
Act of 1986 (SARA). .
In accordance with Executive Order 12580 (Superfund Implementation) and the National Oil
and Hazardous Substances Pollution Contingency Plan (NCP), the Department of the Anny
perfonned a Remedial Investigation for Fort Lewis Landfill No.5. The Remedial
Investigation (RI) characterized the nature and extent of contamination in groundwater.
surface water. sediments, and air near the landfill. A Baseline Risk Assessment and an
Ecological Risk Assessment were conducted in 1991 to evaluate potential effects of the
landf1l1 contaminants on human health and the environment, respeCtively.
I.'
SITE NAME, LOCATION, AND DESCRIPTION
Fort Lewis Landfill No.5 is located adjacent to the Dupont-Steilacoom Highway on the west.
side of the Fort Lewis Military ReselVation in Pierce County, Washington (see Figures 1 and
2). It is approximately 1.5 miles north of Dupont and 3.5 miles south of Steilacoom. The
western edge of the landfill is approximately 1 mile from Puget Sound. The study area of the
RI included Landfill No.5 and portions of Weyerhaeuser and Lone Star- property west from
the Fort Lewis boundary to Puget Sound, south to Sequalitchew Creek, and north to near Solo
Point
The Landfill No.5 property encompasses approximately 180 acres. It is surrounded by a
chain link fence. and the entrance gate at the northeast corner of the landfill is secured at the
end of each work day. A 60 acre parcel within the landfill property was initially deflfled as
Landfill No.5 on the National Priorities List (NPL) (see Figure- 3).
Landfill No.5 is located adjacent to the northeastern portion of the City of Dupont The
predominant land use in the area is the Fort Lewis Military ReselVation, which encompasses
approximately 86,000 acres and fonns the northeastern, east and southeastern boundaries of
the City. The portion of the City west of Landfill No.5 is now undeveloped, but the area is
zoned for future industrial development. South of Landfill No.5, the zoning changes to
mixed-use, whiG.h allows a mix of office/commercial and residential uses. Land uses which
might eventually be developed in this area mclude warehouse and office park developments,
with some commercial uses concentrated near 1-5 and the Dupont-Steilacoom Highway. The
only proposed commercial development in the City at present is a sand and gravel mine at the
Pioneer Aggregates site (see Figure 4).
Groundwater is the source of the municipal water supply for the City of Dupont. There are
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"
Figure 2), and one at El Rancho Madrona. The Bell Hill wells are the primary water supply
for the City of Dupont These wells are intended to serve as the primary water supply for
new developments in the commercial/ industrial zone west of Landfill No.5. EI Rancho
Madrona, a small residential subdivision in southwestern Dupont outside of the Landfill No.5
RI study area, is served by its own water supply well. None of these municipal water supply
wells lie within or near the plume of groundwater contamination west of Landfill No.5.
The primary source of drinking water for Fort Lewis is Sequalitchew Springs, which is
located near the east end of Sequalitchtew Lake approximately 4,000 feet upgradient of
Landfill No.5. Alternate source and emergency backup wells are, also located upgradient of
Landfill No.5.
Surface water features are shown on Figure 5. These featill'es include storm water draims.ge
channels on the noIth, south and west sides of the landfill; Sequalitchew Lake and marshy
areas to the southeast; Sequalitchew Creek and Edmond Marsh about 112 mile to the south
and southwest; an ephemeral pond in a kettle to the west; and Puget Sound to the north and
west. In addition, springs are present during the wet season along lower. Sequalitchew Creek
at the locations designated as 88-9-SW and 88-1O-SW on Figure 5. Sequalitchew Lake and
Sequalitchew Creek support populations of cold-water and warm-water fish species. Fishing
activity on Sequalitchew Creek: downstream of Landfill No.5 is believed to be low because
this area is private property that is not open to the public. Similarly, the lack of public access
is believed to limit hunting activity in the area west of Landfill No.5.
The Nisqually, Puyallup, and Squaxin Tribes have treaty rights to conduct commercial sahllon
fishing in the Nisqually Reach near Fort Lewis. Nisqually tribal fishermen use gillnets and
beach seines to harvest coho and chum salmon along the Dupont shoreline between
Sequalitchew Creek and Tatsolo Point Nisqually tribal members also use the Dupont
shoreline for subsistence and recreational harvesting of non-salmonid fish and shellfISh.
II.
SITE HISTORY AND ENFORCEMENT ACTIVITIES
The Fort Lewis Landfill No.5 NPL Site Source Area operated from 1967 through July 1990.
It accepted mixed municipal solid waste (industrial, commercial, and residential) and
demolition waste (concrete, asphalt, wood, steel and other building debris) from the Fort
Lewis Military Reservation, V A Medical Center, and McChord Air Force Base. Dewatered
sludge from the Fort Lewis Solo Point Sewage Treatment Plant was also disposed at the
landfill. Based on Fort Lewis records, the annual total waste stream was approximately
77,000 toils of mixed municipal solid waste and 188,000 cubic yards of demolition waste.
Initial waste placement began in a 10 to 11 acre north-south trench along the east side of the
landfill (Figure 3). The north-south trench was covered with soil in about 1971. Subsequent
filling of the landfill with mixed municipal and demolition waste was in east-west trenches
designated Zones 1 through 4 on Figwre 3. The east-west trenches covered approximately 32
acres and had a total waste thickness of 25 to 30 feet. The base of the waste was emplaced
at 10 to 15 feet below the original ground surface. Along the west side of the landfill were a
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series of narrow pits that were used until 1978 for sewage treatment plant floatables, bar
screenings, grease trap sludges and septic system pumpings. These pits were filled and
covered with low penneability material and soil.
Fort Lewis stopped using the east-west trenches in August 1990. These trenches were
covered in four phases starting with the west end in 1987 and concluding on the east in
November 1990. The cover was constructed to comply with State of Washington Minimum
Functional Standards (MFS) for Solid Waste Handling (WAC 173-304). The cover includes a
multi-layer soil and synthetic membrane system to minimize the amount of leachate produced,
surface water collection and detention structures to control runoff from the covered landfill,
and a passive gas ventilation system to burn methane in flare stacks.
. In 1980, the Army began conducting environmental assessments at Fort Lewis under the
. Depanment of Defense Installation Restoration Program (IRP). The purpose of the program
is to evaluate past and current use of toxic and hazardous materials and assess the potential
for off-site migration of such materials. A limited groundwater sampling program was
conducted as part of the IRP in 1980. The groundwater sampling results showed elevated
iron and manganese concentrations in groundwater immediately west of Landfill No.5. The
subsequent Installation Assessment Report (1983) stated that Landfill No.5 was the probable
source of the observed iron and manganese contamination, but noted that the observed
groundwater concentrations did not exceed the water quality standards then in force.
Consequently, the Installation Assessment Report did not recommend further studies or
remedial action at Landfill No.5.
Additional groundwater monitoring wells were installed by the Army in 1983 and 1984 to
defrne the configuration of the leachate plume emanating from Landfill No.5. Groundwater
sampling results indicated that elevated levels of specific conductance extended approximately
3,000 feet west of the landfill. .
In 1985, the Army began preparations for closure of the inactive portions of Landfill No.5
and development of a new cell. A Closure and Development Plan was prepared for Landfill
No.5 to ensure compliance with applicable state regulations for solid waste landfills. -
Groundwater sampling was conducted as part of the planning effort. Sample results again
showed elevated concentrations of iron and manganese downgradient of the landfill.
As a result of the documented iron and manganese contamination of groundwater, Landfill
No.5 was added to the National Priorities List (NPL) in 1987. In 1988, the Army began a
Remedial Investigation (RI) to characterize the nature and extent of contamination and to
assess potential. risks to human health and the environment.
A.
Source Areas
Groundwater sampling conducted for the Closure and Development Plan (1985) indicated that
the east-west ttenches (Zones 1-4) and the north-south trench of Landfill No. 5 we~e the pre-
dominant sources of most of the compounds detected in groundwater samples (Figure 3). The
septage/sewage sludge pits along the west side of the landfill also were identified as potential
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sources of groundwater contamination. Computer simulations indicated that leaching of
landfill wastes was the primary mechanism for contaminant transport to groundwater.
B.
Enforcement
Under the authority of the Tacoma-Pierce County Health Department, Landfill No.5 Zones I
through 4 were closed in compliance with Washington State Minimum Functional Standards
for Solid Waste Handling (Washington Administrative Code (WAC) 173-304).
On January 29, 1990, the Army, the EPA, and the State of Washington D~partment of
Ecology (Ecology) entered into a Federal Facility Interagency Agreement (lAG). The IAG
established a procedural framework and schedule for developing, implementing, and
monitoring appropriate response actions conducted at Fort Lewis. Under the terms of the
IAG, EP A and Ecology provided oversight of subsequent RI activities and agree on the final
remedy for this Record of Decision (ROD).
Ill. COMMUNITY RELATIONS
A.
Community Relations During the RI
The Anny developed a community relations plan (CRP) in 1988 as part of the overall
management plan for the Fort Lewis Landfill No.5 RIfFS. The community relations plan
was designed to promote public awareness of the investigations and puhlic involvement in the
decision-making process.
Before the CRP was prepared, local citizens and public offichils were interviewed to identify
potential issues and concerns associated with Landfill No.5. 1bis information was used to
tailor the CRP to meet the specific needs of the local communities.
Several news releases and fact sheets were prepared and distributed for public review. The
news releases and fact sheets provided summaries of RIlFS work in progress, results t'6 date,
and upcoming activities. These are listed as follows:
Document
Date
News Release #1
Fact Sheet #1
EPA News Release
EPA Fact Sheet
Seattle Po'st- Intelligencer Article
Seattle Times article
. News Release #2
Fact Sheet #2
Proposed Plan
11/89
1/89
1/90
1/90
1/90
1/90
2/92
2/92
2/92
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To promote community awareness of RIJFS activities, infonnation repositories containing
primary site documents were established at the following tluee locations:
Tillicum Library
14916 Washington Ave. SW
Tacoma, W A 98498
(206) 588-1014
Lakewood Library
6300 Wildaire Road
Tacoma, W A 98499
(206) 582-6040
Fort Lewis Environmental and Natural Resources Division
Fort Lewis, W A 98433-5000
(206) 967-5337
Also, in accordance with section 113 of CERCLA, an administrative record was established to
provide the basis for the selected remedy. The administrative record is available for public
review at the Lakewood Library and the Fort Lewis Environmental and Natural Resources.
Division.
B.
Community Relations to Support Selection of Remedy
The public was given the opportunity to participate in the remedy selection process, in .
accordance with Sections 113 (k)(2)(B)(i-v) and 117 of CERCLA. The Proposed Plan, which
summarized the RI results and described the preferred alternative, was mailed to
approximately 300 interested parties on February 6, 1992. The Army provided public notice
through an advertisement in the Tacomil Morning News Tribune to explain the Proposed Plan, .
list the public comment period, and announce the public meeting. A news release was
provided to local media on February 26, 1992, which resulted in news coverage by 1I!e
Tacoma Morning News Tribune on February 28, 1992.
A 30-day public comment period was held from February 6 to March 9, 1992. No requests
for extension were received. Approximately 34 people attended a public meeting held in the
Dupont City HalIJCommunity Center on March 3, 1992. Oral and written comments were
considered by EP A, the Army r and Ecology in selecting the no further action alternative.
One" set of written comments, post-marked March 10, 1992, were received. Responses to
these comments are included within the Responsiveness Sumtnary.
IV. SCOPE AND ROLE OF RESPONSE ACTION WITHIN SITE STRATEGY
In keeping with standard environmental management of municipal landfills, closure of the
Landfill No.5 was initiated in 1987 before its listing on the National Priorities List and was
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conducted under the authority of the Tacoma-Pierce County Health Department The closure
complies with State Minimum Functional Standards for Solid Waste Handling (Washington
Administrative Code (WAC) 173-304) and included the consttuction of a cover over Zones 1
through 4 of the landftll, a swface wat.er management system to conn-ol runoff from the
covered landfill, and a passive gas ventilation system to collect and bum landfill gas. In
accordance with WAC 173-304, the Army will continue to perform operations~ maintenance,
and monitoring of the landfill systems with oversight provided by the Tacoma-Pierce County
Health Department
The Fort Lewis Landfill No.5 RI evaluated the nature and extent of contamination in all
potentially affected media including groundwater, surface water, soil, sediment, and air.
Based on the results of the RI, the Baseline Risk Assessment, and the Ecological Risk
Assessment, no further remedial action uGqer CERCLA is necessary to ensure protection of
human health or the environment
v.
SUMMARY OF SITE CHARACTERISTICS
A.
Site. Geology & Hydrogeology
Fort Lewis Landfill No.5 is situated on a glacial outwash plain that slopes gently to the west
toward Puget Sound. The elevation of the plain in the vicinity of the landfill is 200 to 220
feet above mean sea level (MSL). Major features of relief in the study area are the Burke
Hills to the north, the canyon cut by Sequalitchew Creek to the south, several kettles (glacial-
derived depressions) between the landfIll and Puget Sound, and the steep cliff face separating
the outwash plain from the narrow beach along Puget Sound.
Landfill No.5 is underlain by a series of glacial and interglacial deposits (see Figures 6 and
7). The uppermost formation, the Vashon Drift, is approximately 75 feet thick. It consists of
gravels, glacial till, and sand, and contains significant quantities of groundwater. Beneath the
Vashon Drift is the Kitsap Formation, which consists of about 70 feet of fine sands and silty
clays with small lenses of organic material. The Salmon Springs Formation underlies-the
Kitsap Formation. The Salmon Springs Formation consists of about 50 feet of glacial sand
and gravel deposits which contain appreciable groundwater. Beneath the Salmon Springs
Formation is the Puyallup Formation, which consists of fme-grained silt and clay with
occasional deposits of fine sand and gravel.
Approximately 3,000 feet west of Landfill No.5, the Vashon Drift, Kitsap, and Salmon
Springs Formations are replaced by the Sequalitchew Delta deposit. The Sequalitchew Delta
formation consJ.sts .of at least 220 feet of coarse-grained glacial outwash material. It cont.ains
significant amounts of groundwater.
Two distinct groundwater flow systems have been identified in the loq.l study area; a shallow
unconfined flow system in the Vashon Drift Aquifer and a deeper confined flow system in the
Salmon Springs Aquifer (see Figure 8). Aquifers deeper than the Salmon Springs Aquifer are
not believed to have been affected by landfill activities. The Vashon Drift and Salmon
Springs flow systems are interconnected due to leakage from the shallow system downward
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through the less permeable Kitsap Aquitard. Estimated groundwater travel time through the
Kitsap Aquitard is about 6 years. Groundwater in the shallow Vashon Drift Aquifer flows
west and northwest at a rate of approximately 18 - 330 feet/year. Groundwater in the
underlying Salmon Springs Aquifer flows toward the northwest at a rate of approximately 0.5
to 1300 feet/year.
The Vashon Drift and Salmon Springs Aquifers are replaced by the Sequalitchew Delta
Aquifer about 3,000 feet west of the landfill (see Figure 8). The water table within the
Sequalitche-.y Delta Aquifer is at about 10 feet above mean sea level (MSL), which is much
deeper than the water table in the Vashon Drift Aquifer (approximately 185 feet MSL).
. Groundwater in the Sequalitchew Delta aquifer flows toward Puget Sound at a rate of
approximately.4,000 to 37,000 feet/year.
Recharge to the water table flow system in the study area comes primarily from precipitation
and lateral flow within the Vashon Drift Aquifer. Upon entering the water table aquifer,
groundwater flows to the west and northwest, while a small amount moves vertically
downward through the Kitsap Aquitard. At the edge of the Vashon Drift unit, the
. groundwater flows downward to the water table in the Sequalitchew Delta Aquifer, at a
velocity of about 3 to 5 feet/day. Estimated travel time from the vicinity of the landfill
through the water table aquifers to discharge as springs along Puget Sound is in the range. of
25 to 100 years.
Recharge to theconfmed aquifer flow system in the study area comes primarily from vertical
migration through the Vashon Drift Aquifer.and leakage through the Kit.~p Formation or
lateral flow within the Salmon Springs Aquifer. Upon entering the confined aquifer, .
groundwater flows to the west and northytest. A small, but unquantifiedamount may move
vertically downward through the Puyallup Aquitard. At the edge of the Salmon Springs
Formation, the groundwater flows downward to the water table in the Sequalitchew Delta
Aquifer, under a gradient estimated as 0.05 and a velocity of about 7 to 18 feet/day. Using
the hydraulic parameters estimated in the RI, the travel time from the vicinity of the landfill
vertically through the Vashon Drift Aquifer and Kitsap Aquitard, then laterally to discharge as
tidal or subtidal springs along Puget Sound is in the range of six to seventy-five year~
B.
Nature and Extent of Contamination
1.
Groundwater
For the RI, groundwater samples were collected from 25 monitoring wells on four occasions
between February 1989 and January 1990. Two additional wells were installed in. January
1990 and samp~~din January and May 1990. Rl well locations are shown in Figure 9.
Groundwater samples were analyzed for a broad range of chemical and physical parameters.
Tables I through 4 summarize the analytical results for groundwater samples collected during
the RI.
Water samples were collected from the Yashon Drift, Salmon Springs and Sequalitchew Delta
Aquifers to evaluate the presence of landfill-derived contaminants in groundwater. At the
time of sample collection, the temperature, pH, Eh and specific conductance of the water were
-------
measured. In general, pH and specific conductance show spatial trends that could be
considered indicative of contamination from the landfill. Laboratory analysis of the water
samples provided data on the presence of inorganic and organic contaminants in the
groundwater. Of the inorganic compounds measured, only iron, manganese, chloride and,
perhaps, barium appear to be related to the landfill. Several volatile organic compounds
(vinyl chloride; chloroethane; l,l-DCA; 1,2-DCE; 1,2-DCA; TCE; PCE; 1,1,2,2-PCA;
benzene; toluene; ethylbenzene and xylenes) and base/neutral and acid-extractable (BNA)
organic compounds (naphthalene; diethylphthalate, bis(2-ethylhexyl)phthalate; 4-methyl
phenol; 1,4-dichlorobenzene; acenaphthene and di-n-octyl phthalate) were detected in
monitoring wells primarily near the downgradient edge of the landfill. Neither organochlorine
pesticides nor PCBs were detected in any of the water samples. A summary of groundwater
contamination in each of the aquifers follows.
The Vashon Drift Aquifer immediately underlies the landfill and shows the highest levels and
extent of contamination. The specific conductance, manganese and chloride levels in
groundwater aI'e elevated relative to background as much as 3,000 feet downgradient of the
landfill. Near the landfill, the groundwater pH appears to be slightly lower than the
background values, and iron and manganese are 3 to 4 orders of magnitude higher. than
background. . Elevated manganese concentrations extend farther downgradient than the high
iron values. The barium concentration is elevated near the landfill in the Vashon Drift
Aquifer; however, none of the other trace inorganic compounds (arsenic, cadmium,
chromium, lead, mercury, selenium, silver and zinc) evaluated in this study were detected at a
level or with a pattern of occurrence that suggest that the landfill is the source of these
compounds in the groundwater.
The only wells that showed moderately consistent detections of volatile organic compounds
(VOCs) in water samples from the Vashon Drift Aquifer were those nearest the landfill. The
maximum concentration of any of these compounds detected is 16 micrograms per liter
(pg/L). The VOCs with the greatest areal distribution are l,l-DCA and 1,2-DCE. Because
VOCs were not analyzed in water samples collected from some of the wells completed in the
Vashon Drift Aquifer, the westerly extent of contamination of 1,I-DCA and 1,2-DCE is
uncertain. As with the VQCs, the majority of the BNA compounds detected were fOlffid in
the cluster of wells adjacent to the western (downgradient) edge of the landfill.
Diethylphthalate is the only BNA compound that appears to be present beyond the margin of
the landfill, but its distribution is limited.
The Salmon Springs Aquifer occurs beneath the Vashon Drift Aquifer, and the two aquifers
are separated by the Kitsap Formation Aquitard. The affected area in the Salmon Springs
Aquifer, as sho.wn by elevated specific: conductance of the groundwater, is limited to
approximately),OOO to 2,500 feet from the landfill. At monitoring well 88-5-SS nearest the
landfill in this aquifer, the specific conductance and chloride concentrations of water samples
are elevated and the pH is slightly depressed, as was the case with samples from the
overlying Vashon Drift Aquifer. In addition, barium, iron and manganese concentrations m
groundwater collected from the Salmon Springs Aquifer are elevated in the zone near the
landfill. -
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Water samples from monitoring well 88-5-SS contained the VOC compounds vinyl chloride,
chloroethane, l,l-DCA, 1,2-DCE, TCE, 1,1,2,2-TCA, benzene, toluene and xylenes. These
compounds were also found in water from the overlying Vashon Drift Aquifer and probably
represent landfill contamination. The wells in the Salmon Springs Aquifer adjacent to 88-5-
SS did not contain detectable quantities of any of these compounds, therefore the VOC plume
in the Salmon Springs Aquifer is much more restricted than that in the Vashon Drift Aquifer.
Water samples from monitoring well 88-5-SS contained naphthalene and diethylphthalate, but
they were not detected in any other Salmon Springs Aquifer monitoring wells.
The Sequalitchew Delta Aquifer is the water table aquifer that is present between the western
edge of the Vashon Drift/Salmon Springs Aquifers and Puget Sound. The primary inorganic
parameters that have been identified as indicators of the presence of contamination in
groundwater at this site (specific conduc~nce, iron and manganese levels) were not found to
be elevated in groundwater samples collected from the Sequalitchew Delta Aquifer. Three
VOCs (l,1,2,2-PCA; 1,1,2-trichloro 1,2,2-trifluoroethane; and toluene) were found at low
concentrations and in random patterns in a few water samples. These compounds were not
consistently detected, and the few detections were assumed to be sampling or analysis.
artifacts. There were no confirmed detections of any BNA compounds in. water samples
collected from any of the Sequalitchew Delta Aquifer monitoring wells.
To assess contaminant fate and transport, the .results of the RI groundwater sampling program
were incorporated in the U.S. EPA's Multi-Media Model. The model estimated that .
contaminant concentrations would decrease over time because the multi-layer cap installed at
Landfill No. 5' during 1987-1990 would reduce leachate production. Figures 10 through 14 .
show the model-calculated trends in concentrations of several key contaminants. .
Supplemental groundwater sampling was conducted after completion of the RI. Six
monitoring wells were sampled in April, June, and S~ptember 1991 to monitor spatial and
temporal trends in the contamination plume. As shown in Figure 15, generally contaminant
concentrations of most contaminants are decreasing with time, which is consistent with the
results of the RI contaminant transpon model.
-
2.
Surface Water Contamination
The surface water quality sampling program included the following water quality parameters:
field measurements (temperature, specific conductance, pH and Eh), organic compounds
(VOCs, BNAs, pesticidesIPCBs), inorganic compounds (primarily metals), and conventional
water quality parameters. Surface water sampling locations are shown in Figure 5. Sampling
results are summarized in Table 5.
.~. ..
In general, the chemical data indicate that the landf1l1 is not affecting surface water quality at
the site. Very few organic compounds were measured in any of the surface water samples.
Of the twelve metals analyzed (Ag, As, Ba, Cd, Cr, Fe, Hg, Mn, Na, Pb, Se and Zn), five
(Ag, As, Cr; Pb and Se) were not measured above their detection limits and of the remainder
all, except for Na, had low concentrations or levels similar to background. The sodium
concentration in water collected from the beach seep was high compared to groundwater and
other surface water values, but this is due to the impact of seawater on the beach seep. None
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of the conventional water quality parameters show values that would indicate the presence of
contamination from the landfill. .
3.
Sediment Contamination
SedIment samples were collected from the surface water monitoring stations and an
infiltration basin on the landfIll. A few VOCs, BNAs and several inorganic constituents were
detected (see Table 6). Most of the inorganic compounds were found at sampling stations
upstream as well as downstream of the landfill; therefore, it was determined that Landfill ~\jo.
5 is not a source of sediment contamination. The Army is studying past and current waste
disposal practices in the vicinity of the drainage channel under a separate investigation to
determine the likely source of sediment contamination.
4.
Air Contamination
Landfill gases emitted from Landfill No.5 are collected by a network of perforated
underground pipes and directed to 10 flare stacks for burning. Gas emissions are too low to
keep the flare stacks burning continuously. Therefore, the flare stacks often act as vents.
Landfill gas emissions were sampled at 3 of the 10 flare stacks on the landfill. Several
VOCs, including toluene, benzene, vinyl chloride, and methylene chloride, were detected (see
Table 7). To estimate impacts on ambient air quality, the landfill gas sampling results were
incorporated in U.S. EPA's Industrial Source Complex-Long Tenn computer model. This
model provides conservative results, typically predicting ambient concentrations that are twe
to three times higher than actual measured concentrations. The maximum predicted VOC
concentrations are several orders of magnitude lower than the stack concentrations and are
well below the Puget Sound Air Pollution Control Agency's Acceptable Source Impact Levels.
VI. SUMMARY OF SITE RISKS
The baseline risk assessment for Fort Lewis LandfIll No.5 considered human health and
ecological risks. The risk assessments were conducted in accordance with EPA's Risk
Assessment Guidancefor Superfund, Volume I: Human Health Evaluation Manual and
Volume II: Environmental Assessment Manual and EPA national guidance. The risk
assessment methods and results are summarized in the following sections.
A.
Human Health Risks
The human health risk assessment evaluated potential risks associated with exposure to
chemical conurrunants from Landfill No.5. The assessment considered potential exposure to
landfill contaminants in groundwater, surface water, sediment, and air. Soil was not included
in the quantitative risk assessment because the landfill cap precludes direct exposure to
underlying contaminated soil. Both carcinogenic (i.e., causing the development of cancer;
and non-carcinogenic (i.e., direct toxic effects on organ systems, reproductive and -
developmental effects) risks were evaluated. Risks were estimated for current and future land
uses in the vicinity of Landfill No.5. The assessment estimated hypothetical risks for people
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residing or working adjacent to the west edge of the landfill and at the edge of the
contaminated groundwater plume approximately 3,000 feet west of the landf1l1. The risks are
hypothetical because no one resides or works in these areas at this time. Risks also were
estimated for workers at the landfill and trespassers adjacent to the landfill.
To ensure that potential health risks would not be underestimated, a conservative approach
was used as recommended in EPA's Risk Assessment Guidance for Superfund, Volwne I:
Hwnan Health Evaluation Manual and EPA national guidance. Reasonable conservative
estimates and assumptions were used to enhance confidence in the conclusions of the risk
assessment Key steps in the risk assessment are outlined below.
1.
Identification of Chemicals of Concern
Potential chemicals of concern are those that are released to the environment from waste
sources at Landfill No.5 and that may pose health risks to humans who come into contact
with them. In the Landfill No.5 risk assessment, chemicals of concern were identified
through evaluation of RI sampling Tesults for groundwater. surface water. sediments. and
landfill gas emissions. . Groundwater was sampled at more than 22 monitoring w~lls on a
quarterly basis over a IS-month period. Surface water and sediments in nearby waterways
were also sampled quarterly. Landfill gas emissions were sampled once at three locations;
All chemical analytes for the sampled media were included in the risk assessment except the
following: (1) chemicals that were not detected in groundwater. surface water, sediment, or
landfiil gas; (2) chemicals for which toxicity reference values, such as cancer slope .valuesor
reference doses (RIDs) have not been developed; and (3) chemicals identified as essential
nutrients. In addition, compounds determined to be unrelated to the landfill source were
excluded from the risk assessment Tables 1, 2,3, 4, and 6 list.the potential chemicals of
concern included in the risk assessment for Landfill No.5.
All compounds detected in landfill gas emissions were identified as chemicals of concern and
included in the quantitative risk assessment No site-related chemicals of concern were found
in surface waters and springs, and RI hydrologic data showed that surface waters and.springs
were unlikely to be affected in the future. Consequently, surface water was not evaluated in
the quantitative risk assessment
Potential chemicals of concern in groundwater and sediments were subjected to a risk-based
screening process in order to identify chemicals to be included in the quantitative risk
assessment The maximum detected concentration of each potential chemical of concern was
compared to risk-based and regulation-based screening concentrations. For groundwater, the
risk-based screening concentrations were those that would result in an estimated incremental
lifetime cancer -risk: greater than 1 x 10-6 (I in 1,000,000) or a hazard quotient greater than
0.1. For sediments, the risk-based screening concentrations were those that would result in an
estimated incremental lifetime cancer risk greater than 1 x 10-7 (1 in 10,000,000) or a hazard
quotient greater than 0.1. Chemicals which exceeded the risk-based screening concentrations
were included in the quantitative risk assessment. Table 8 lists the chemicals of concern that
passed the screen and were evaluated in the quantitative risk assessment
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2.
Exposure Assessment
a.
Exposed Populations
Exposure pathways were evaluated for the following receptors:
Current Use:
Worker at Landfill No.5
Trespasser visiting the drainage channel adjacent to the landfill
Futw.e Use:
Future resident living adjacent to the western edge of the landfill
Future resident living at the edge of the groundwater plume, approXimately 3,000 feet
west of the landfill
Worker ata future industrial site adjacent to the western edge of the landfill for 30
years
\\Torker at a future industrial site at the edge of the groundwater plume, approximately
3,000 feet west of the landfill
b.
Exposure Pathways
The following exposure pathways were evaluated:
Ingestion of groundwater by hypothetical future residents and industrial workers
Inhalation of landfill gas emissions by hypothetical future residents and industrial
workers and current landfill workers
Inhalation of VOCs released from groundwater during domestic use by hypothetical
future residents
. Dermal absorption of organic compounds in groundwater by hypothetical future
residents .~~ng showering
Ingestion of sediments by regular visitors to the drainage channel
Dermal absorption of organic compounds in sediments by hypothetical visitors to the
drainage channel -
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c.
Exposure Point Concentrations
Groundwater: Average and reasonable maximum exposure concentrations were estimated
based on transport and dispersion modeling and/or field measurements. Groundwater
transport modeling was used to estimate concentrations of chemicals of concern at potential '
exposure points over 10- and 30-year periods. Average estimated groundwater exposure
concentrations are listed in Table 9. These are considered reasonable maximum
concentrations for the following reasons:
,.
Estimated future chemical concentrations at the well closest to the landfill source, well
LS-Ax- VD, were used as potential exposure point concentrations for the residential
scenario. Well LS-Ax- VD had the highest chemical concentrations measured in
groundwater during the RI. Groundwater sample results from this well were used to
back-calculate the landfill source concentrations used in the contaminant transport
model.
Concentrations at well 89-17- VD were used to represent potential exposure point
concentrc1tions for the Sequalitchew Delta Aquifer, which is the likely source of
groundwater for the future industrial development scenario. Well 89-17-VD is located
in the Vashon Drift Aquifer at the leading edge of the plume, approximately 3,000 feet
west of Landfill No.5. Chemical concentrations found in the Sequalitchew Delta
Aquifer were significantly lower than those found in the Vashon Drift- Aquifer.
Concentrations decrease with time because of declining concentrations within the landfill
and reduced leachate production because of the landfill cover. As .noted in Figure 15,
groundwater sampling. conducted after the RI was completed appears to validate the
model-calculated decline in contaminant concentrations.
Air: Air dispersion modeling of flare vent stack einissions was performed to identify the
points of maximum impact of landfill gas emissions both onsite and offsite. The ISCL T
model used for this. assessment typically predicts chemical concentrations that are two or three
times higher than actual concentrations in ambient air. A conservative estimate of landfill gas
flow rates was used to further reduce the chance of under-predicting ambient air
concentrations. Estimated exposure point concentrations are listed in Table 10.
Average sediment exposure concenttations were estimated by taking the average
concenttations of the chemicals of concern measured at the two sampling locations
downstteam of Landfill No.5. The highest concenttation of each chemical was used as the
maximum exposure concentration. For comparison purposes, average and maximum exposure
concenttations also were calculated for the two sampling stations located upstream of the
landfill. The average and maximum concentrations at the two sediment exposure points are
listed in Table 11.
d.
Chemical Intake by Exposure Pathway
Chemical intakes for each exposure pathway were calculated based 00 the exposure point
concenttations and other exposure parameters such as water and sediment ingestion rates,
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inhalation rates, dennal absorption rates, body weights, exposure frequencies and durations..
Reasonable maximum exposure calcula.tions for the Fort Lewis Landfill No.5 risk assessment
used values from the Standard Default Exposure Factors document (OSWER Directive No.
9285.6-03).
3.
Toxicity Assessment
The toxicity assessment addresses the potential for a chemical of concern to cause adverse
effects in exposed populations and estimates the relationship between extent of exposure and
extent of toxic injury (i.e., dose-response relationship). Qualitative and quantitative toxicity
information for the chemicals of concern is acquired through evaluation of relevant scientific
literature. The most directly relevant data come from studies in humans. Most of the useable
information on the toxic effects of chemicals comes from cOIluolled experiments in animals.
Table 12 lists the toxicity values for the chemicals of concern.
Slope factors (SFs) have been developed by EPA for estimating excess lifetime cancer rish
associated with exposure to potential carcinogens. SFs, which are expressed in units of
(mg/kg-day)-l, are multiplied by the estimated intake of a potential carcinogen, in mg/kg-day,
to provide an upper-bound estimate of the excess lifetime cancer risk associated with
exposure at that intake level. The tenn "upper bound" reflects the conservative estimate of
the risks calculated from the SF. Use of this approach makes underestimation of the actual
cancer risk highly unlikely. Slope factors are derived from the results of human
epidemiological studies or chronic anirnal bioassays to which mathematical extrapolation frem
high doses to low dose has been applied (e.g., to account for the use of animal data to predict
effects on humans).
Reference doses (RIDs) have been developed by EPA for indicating the potential for adverse
health effects from exposure to chemicals exhibiting noncarcinogenic effects. RfDs, which
are expressed in units of mg/kg-day, are estimates of lifetime daily exposure levels for
humans, including sensitive individuals which are likely to be without risk of adverse effect
Estimated intakes of contaminant(s)of concern from environmental media (e.g., the amount
of a contaminant(s) of concern ingested from contaminated drinking water) can be compared
to the RID. RIDs are derived from human epidemiological studies or animal studie,s to which
uncertainty factors have been applied (e.g., to account for the use of animal data to predict
effects on humans).
4.
Risk Characterization
Carcinogenic risk is estimated as the incremental probability of an individual developing
cancer above the normal background population incidence over a lifetime of potential
exposure to a chemical known or suspected to cause cancer. To estimate cancer risk, slope
factors are combined with site exposure information to estimate the incremental cancer risk;
i.e., the increase in the probability of contracting cancer. An excess lifetime cancer risk of I
x 10-1 indicates that an individual has up to a one in ten thousand chance of devel~ping
cancer over a lifetime of exposure to a site-related carcinogen.
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Table 13 lists the estimated health risks for each receptor and pathway. The total excess
cancer risk for reasonable maximum residential exposures to groundwater and landfill gas at
the landf1l1 boundary is 1.4 x 10-5 (approximately 1 in 100,000). This risk level is within the
EPA Superfund acceptable risk range of 1 x 10-4 to 1 X 10-6 (1 in 10,000 to 1 in 1,000,000).
All other exposure scenarios (residential on plume axis and industrial at boundary and at
plume axis) resulted in lower cancer risks. Noncarcinogenic health hazards are not expected
from exposures resulting from Landfill No.5. Orlly one exposure pathway resulted in a
hazard index near I (reasonable maximum ingestion of groundwater by a hypothetical resident
located at the landfill fenceline).
The chief contributors to the estimated cancer risk' are ingestion of vinyl chloride in '
groundwater and inhalation of vinyl chloride and 1,l,2,2-PCA released from groundwater,
during domestic use. The cancer rislr...s may be overestimated because, although the maximum
detected concentration of 1,l,2,2-PCA exceeded the screening level, the chemical analytical
results suggest that its actual presence in groundwater is questionable. Nevertheless,
including it in the risk assessment is a conservative approach that will result in risk estimates
that are unlikely to be exceeded under actual exposure conditions. '
The sediment exposure scenario is a special case that was included to assess potential health
threats that may be associated with exposure to compounds in sediments in the drainage
channel adjacent to the landfill. The landfill has not been identified ,as a source of the
compounds detected in the sediments because the channel drains a large area upstream and ,
the same compounds are detected both upstream and adjacent to the landtill. Ingestion of
channel sediments under a trespasser exposure scenario results in an estimated excess cancer
risk of 6 x 10'6, due entirely to the presence of arsenic, a common constituent of herbicides
that may have had widespread use in the area.
Human Health Risk Characterization Summary
The results of the base1ine'human health risk assessment support the following conclusions
concerning the potential health hazards associated with exposures to groundwater, landfill gas
emissions, and sediments in the drainage channel:
.
The total excess cancer risk for reasonable maximum residential exposures to
groundwater and landfill gas at the property fenceline is 1.4 x 10'5 (approximately 1 in
100,000). This risk level is within the EP A Superfund acceptable risk range of 1 x 10-4
to 1 x 10,6 (1 in 10,000 to 1 in 1,000,000). The exposure assumptions are extremely
conservative, and it is unlikely that the estimated risk level would be exceeded under
any likely. exposure conditions.
.
The chief .contributors to the estimated cancer risks are ingestion of vinyl chloride in
groundwater and, in the residential scenarios, inhalation of vinyl chloride and 1,1,2,2-
PCA released from groundwater into indoor air. Because 1,I,2,2-PCA was detected
only twice in 50 samples, inclusion of this compound in the risk assessment is a
conservative approach that may result in overestimation of cancer risk. -
-------
Reasonable Maximum Exposure (RME) excess cancer risks for hypothetical industrial
receptors at the downgradient wen 89-17- VO and at the fenceline are 1 x 10-6 and 2 x
10-6, respectively. The assumed exposure conditions are very conservativ~, and it is
unlikely that these risk levels would be exceeded under any likely exposure conditions.
.
Noncarcinogenic health hazards are not expected from exposures to groundwater or
landfill gas. Only one exposure pathway resulted in a hazard index near 1.0 (reasonable
maximum ingestion of manganese-contaminated groundwater by a hypothetical resident
located. at the landfill fenceline). However, this exposure scenario is unlikely to occur
because the area west of the landfill is uninhabited, the area is zoned for industrial
development, and future residential development is planned for locations distant from
the landfill and away from the plume of contaminated groundwater.
.
No health threats are posed to CWTent landfill workers by inhalation of landfill gas
emissions.
.
Incremental. cancer risk due to RME exposures to sediments in the drainage channel
range are approximately 1 in 1,000,000 (l X 10-6 upgradient of landfill and 6 x 10-0
adjacent to the landf1lI). The landfill has not been identified as a source of the
compounds in the channel sediments; and therefore the health risks mayor may not be
landfill-derived. The incremental cancer risk is almost entirely attributable to ingestion
of arsenic in the sediments.
.
The results of the risk assessment indicate that exposure to chemicals of concern in
groundwater and air near the landfill is not likely to result in a public health hazard.
5.
Uncertainty
The primary sources of uncertainty for this risk assessment are associated with the estimates
of exposure point concentrations and the assumptions regarding human exposure scenarios.
Conservative assumptions were used so that risks would not be underestimated. Chenricals of
concern were selected using a health-risk-based screen and included all compounds present in
concentrations ~at might pose potential health risks. The groundwater transport and air
dispersion models estimate exposure point concentrations that are not likely to be exceeded
and, as a result, may overstate the concentrations to which individuals may be exposed. A
reasonable worst-case exposure scenario at the landfill fenceline was addressed. The
ingestion rates, inhalation rates, and exposure times used in estimating daily intakes are
conservatively high and, as such, are not likely to be exceeded. Toxicity factors used to
assess potential health risks are derived from studies in sensitive animal species and the
application of'safety factors and conservative relationships between dose and response.
The results of the risk assessment provide an upper-bound estimate of potential risk under
reasonable y.'orst-case exposure conditions. The results indicate that exposures to
groundwater, air, and sediments near the landfill are not likely to have adverse effects on
public health-
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B.
Ecological Risk Assessment
An ecological risk assessment was conducted to evaluate the potential impacts on biota of
chemical constituents in groundwater, surface water, or sediment that may have been released
from Fort Lewis Landfill No.5. The primary objective of the ecological risk assessment was
to perform a screening-level analysis to estimate the potential for adverse effects to plants and
animals that may result from exposures to hazardous compounds. The results of the
ecological risk assessment were intended to support management decisions on whether
remedial action is required for environmental protection.
The approach used in the risk assessment is consistent with EPA guidance for evaluating
ecological risk. The basic steps were identification of chemicals of concern, assessment of
potential exposure pathways, and characterization of threats to exposed biota. These steps are
summarized below.
1.
Identification of Chemicals of Concern
Groundwater, surface water and sediment were sampled and analyzed for a wide variety of
potentially hazardous volatile organic compounds (VOCs), base/neutral and acid-extractable
organic compounds (BNAs), pesticidesIPCBs and inorganic compounds. PCBs were not
detected in any of the media, and 4,4-DDD was the only pesticide detected (in sediment only)
in any media downgradient of the landfill. Several YOCs, BNAs and inorganic compounds
were detected in water and sediment These compounds were identified as chemicals of
concern for further evaluation in the risk assessment.
'"
2.
Exposure Assessment
a.
Exposed Populations
,I)
Potential receptors were identified as those plant and animal species likely to be exposed to
chemicals in surface water or sediments. The assessment focused on the ingestion and dermal
absorption exposure routes because these are the most likely routes for exposure to chemicals
in sediment or water. The risk assessment directly assessed potential threats to freshwater
aquatic organisms, vegetation, marine organisms and terrestrial organisms. No sensitive
resident species or habitats were identified in areas that might be affected by the groundwater
plume.
b.
Exposure Pathways
The exposure a~sessment identified potential exposure pathways from the chemical source to
the affected media, exposure points and potential receptors. Groundwater, surface water and
sediments in the surface water bodies were identified as the affected media, based on Rl data.
The primary exposure points were determined to be surface water bodies (creeks, lakes,
drainage channels) in the vicinity of the landfilL Landfill gas emissions were considered an
unlikely source of ecological risk because of the amount of dilution of the gas on mixing. with
air. Groundwater also was considered an unlikely exposure medium because the water table
is normally twenty feet or more below land surface; consequently, ecological receptors cannot
-------
come into direct contact with it. Exposure could occur only where groundwater discharges to
surface water bodies. Most of the surface water bodies located near Landfill No.5 do not
intersect a contaminant transpon pathway from the landfill. The RI demonstrated that
Sequalitchew Lake, Hamer Marsh, McKay Marsh, Edmond Marsh, Sequalitchew Creek and
the springs along Sequalitchew Creek are not hydraulically downgradient of the landfill;
consequently, these water bodies are not affected by the groundwater plume emanating from
the landfill.
Potential surface water exposure points downgradient of the landfill include the drainage
channel adjacent to the landfill, a kettle lake, beach seeps, and Puget Sound. Sediments in
the drainage channel and kettle lake were also considered potential exposure media.
Groundwater is the primary transpon mechanism from the landfill to the beach seeps and
Puget Sound. The uatural processes of dispe.rsion and mixing are expeCted to dilute
groundwater concentrations to less than detectable levels during transpon to discharge
locations along the Sound. Therefore, the beach seeps and Puget Sound are not believed to
be significant ecological exposure points.
3.
Risk Characterization
The potential for ecological threats associated with exposure to surface water and sediments
in the drainage channel and kettle were assessed by comparing the maximum concentration
ranges to normal environmental concentrations and to toxicity-based benchmarks. In the
drainage channel, bis(2-ethylhexyl)phthalate was the only compound detected in water whose
maximum concentration equalled or excee.de.d ambient water quality criteria. Maximum
concentrations of 4-methylphenol, pent.achlorophenol and 4,4-DDD in drainage channel
sediments exceeded toxicity benchmark levels; however, it is unlikely that the covered
landfill could be a current source of these compounds because refuse is not exposed and the
water table does flot appear to intersect the base of the drainage channel.
Concentrations of several inorganic compounds (arsenic, cadmium, copper, iron, lead,
manganese, mercury, nickel and zinc) were higher in drainage channel sediments than would
be expected for normal environmental conditions. The second screening of these inOl=ganics
showed that arsenic and lead concentrations exceeded toxicity-based benchmarks. Mercury
and copper had values below toxicity-based benchmarks, but above benchmarks that account
for the strong bioconcentration potential of these metals. Bioconcentration occurs when a
chemical is taken in at a faster rate than it can be metabolized or excreted, which results in
concentrations in organisms that are higher than concentrations in the organism's
surroundings. Thus, even low environmental concentrations of a chemical with strong
bioconcentra~on potential can result in deleterious concentrations in organisms.
The source(s) of the organic and inorganic potentially toxic compounds in the drainage
channel sediments have not been identified. The drainage channel collects storm water runoff
from a large portion of the Fort Lewis Military Reservation and the Village of Dupont which
are located upgradient of the landfill. Consequemly there are many possible sourc~s for these
compounds other than the landfill.
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Sediments sampled from the kettle contained levels of cadmium, lead, mercury, copper and
arsenic that were higher than nonnal environmental concentrations. Lead was the only
inorganic detected above single-species toxicity-based benchmarks. Mercury had
concentrations above values that account for bioconcentration. Exposures to lead and mercury
may pose ecological hazards to biota inhabiting the kettle. However, the hazards are not
likely to be landfill-related because these inorganic compounds were not detected in
groundwater (the only significant chemical ttanspon mechanism to this exposUre point).
Possible sources are unauthorized refuse dumping and the use of arsenical herbicides. .
Concentrations of inorganic compounds tested in kettle surface water samples were all below
toxicity benchmarks.
The approach taken in the ecological risk assessment was conservative. Maximum detected
concentrations of chemicals were compared to benchrnarks values. \Vhen ambient water
quality or sedilnent standards were. not available for a given chemical, appropriate safety
factors were used to develop toxicity-based benchmarks. Nonnal environmental ranges of
chemicals in soils of the Western United States were also used as a screening tool to compare
to measured maximum concentrations in sediment The threat to biota from nonnal .
concentration ranges of compounds was not assessed.
Few compounds had maximum concentrations that exceeded benchmarks. Generally, the
benchmarks were exceeded in only a single sample. It is unlikely that these compounds are
now being released from the landf1l1 because the refuse is not exposed to surface runoff and.
leachate-affected groundwater either does not contain the compounds or does not discharge
into the surface water bodies in question. Funhermore, there are non-landfill sources for
these compounds. The results of this ecological risk asseSSment indicate that there is little
evidence that Landfill No.5 poses any threat to ecological receptors or habitats.
VII. THE SELECTED REMEDY
The Depanment of the Army has determined that no further remedial action is necessary at
Fort Lewis Landfill No.5 to ensure protection of human health and the environment. -, This
decision is based on the results of the human health and ecological risk assessments, which
detennined tha~ conditions at the site pose no unacceptable risks to human health. or the
environment. The AI111Y will continue to implement the operating and closure requirements
of LandfLlI No.5 under a permit administered by the Tacoma-Pierce County Health
Department. The closure complies with State Minimum Functional Standards for Solid Waste
Handling, pursuant to Washington Administtative Code r.w AC) 173-304, including the
construction of a cover over Zones I through 4 of the landfill, a surface water management
system to control runoff from the covered landfill, and a passive gas ventilation system to
collect and burn landfill gas. As part of the closure and operation of Landfill No.5, the
Army will continue to monitor groundwater to assist in confirming the prediction of
decreasing contamination. If monitoring does not confmn the prediction of decreasing
contamination, the Army will evaluate the need to perform additional response acti?n in
accordance with all applicable laws and regulations. Administrative controls will be
implemented to restrict future development and use of the landfill as identified under an
operating or closure permit issued at the landfi II. .
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VIII. DOCUMENTATION OF SIGNIFICANT CHANGES
The Proposed Plan for Fort Lewis Landfill No.5 was released for public comment on
February 6, 1992. The Proposed Plan identified No Action (except continued groundwater
mo"nitoring) as the selected remedy for the site. Public comments on the Proposed Plan were
evaluated at the end of the 30-day comment period, and it was determined that no significant
changes to the Proposed Plan were necessary.
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RESPONSIVENESS SUMMARY
FORT LEWIS LANDFILL NO.5
The public comment period on the Proposed Plan was held from February 6 to
March 9, 1992. Two sets of written comments were received and are included in
. .
Appendix A. A public meeting was held on March 3, 1992 to explain the Proposed Plan
and solicit public comments. No questions were asked during the fonnal comment period
of the public meeting. The transcript of the public meeting is available in the
Administrative Record. This summary is a response to items raised in the written
comments during the public comment period.
1. Re: Page 2 of Proposed Plan - If Landfill No.5 is not a source of sediment
contamination, what is the source?
The likely source of sediment contamination is urban runoff from the drainage area
upstream of the landfill.. The upstream drainage area includes Ft Lewis as well as
portions of the City of Dupont Many compounds were found at sampling stations
upstream as weU as downstream of the landfill. A separate: investigation of past and
current waste disposal practices in the vicinity of the landfill will be conducted by the
U.S. Army to confirm the source of sediment contamination.
2. Why were the levels of benzene and dissolved manganese up in June 1991 if the
landfill was already covered?
Although the landfill was covered with a multi-layer cap in 1987-1990, the
contamination plume will continue to migrate downgradient from the landfill.
Supplemental groundwater sampling and computer modeling results indicate that
contaminant concentrations under the landfill and within the contaminant plume itself
will decrease with time. The slight increase in benzene and dissolved manganese are
within the range of data variability and water level fluctuations expected of
groundwater sampling.
-------
3. If investigative results showed no change in vinyl chloride and 1,2,dichloroethane
[concentration] between October 1989 and September 1991, bow' can the model
show the 30-year average [concentration values] down?
The investigative results did show that observed concentrations of vinyl chloride and
1,2-dichloroethane were less than detection limits in October 1989 and September
1991; the same is true for TCE and 1,1,2,2-PCA. Table I of the Proposed Plan
shows the concentration of vinyl chloride to be less than 2 pg/L on both dates. These
results should not be interpreted as indicating no change in concentration. When a
compound is not detected and/or measured at a value less than the method detection
limit (for that compound method and matrix), the concentration of the compound in
'the sample is reported as "less than detection limit." Using vinyl chloride as an
example, the actual sample concentration could be between zero and the compound
method detection limit, and will be reported the same way: <2 pg/L, the method
detection limit for vinyl chloride. The presence or absence of a trend cannot be
concluded from these results for compounds reported solely as less tha..'1 detection
limits.
The model showed that the average concentration of these compounds will decrease
over a 30-year period. This result indicates that, as leachate production is reduced at
the landfill and as'the contamination plume moves away from the landfill, the
concentrations of the compounds will decrease by dispersion and dilution. This
temporal concentration decrease trend is consistent with the results of the groundwater
sampling analyses.
4. What is the manufacturer's suggested working life for the high density
polyethylene used in capping the East-West landfill zones when the material is
used in this type of application? Are there any plans to check liner integrity
periodically?
The 60-mil high-density polyethylene (HDPE) membrane is manufactured by Gundle
Lining Systems, Inc. The expected life of the HDPE barrier layer under these
conditions is 100 years. The installation of the HDPE layer was monitored for leaks
during installation and was subject to a rigorous Quality Assurance/Quality Control
-------
program. Due to reported satisfactory installation, it is unlikely that appreciable water
currently infiltrates through the barrier. Future infIltration will have to come through
tears in the membrane. If tears were to develop, they would most likely be due to
and caused by differential settlement of the waste. Historically, the landfill has not
exhibited significant differential settlement The Landfill No.5 Operations and
Maintenance Manual requires that when a depression is observed on the landfLll and a
break is suspected in the HDPE barrier the cover must be excavated back to the
HOPE barrier and repaired per the manufacturer's recommended techniques.
Groundwater will also be monitored to check for excess infiltration to the landfill (see
item 5 below).
5. We have several questions regarding. the monitoring to be performed as part of
the landfill closure:
How frequently will samples be collected as part of the on-going site
monitoring? What. tests will be performed?
For how many years will the monitoring continue?
Where will the samples be collected? . Will the sample sites include both cross-
. .
gradient and up-gradient sites as well as the plume areas portrayed in the
documentation of the remedial investigation? We would particularly like to
see regular monitoring of groundwater in the region between the landtill and
the City of DuPont's Bell Hill well site.
Will both surface water and groundwater be sampled?
. Groundwater sampling will be conducted as part of ongoing site monitoring.
The long-term monitoring plan is being developed at this time. It will
contain specifics on sampling locations, frequency and parameters. This plan
will be made available to the public through Ft. Lewis.
-------
Will there be additional checks of future monitoring results against computer
model predictions to either verify model accuracy of point to the need for
additional study?
Future monitoring results will be reviewed and compared against computer
model predictions and against previous data observations. Large deviations
from expected future concentrations will indicate a need to reassess the
situation. Appropriate actions will be taken at that time.
Where and how will the monitoring results be reported? Will the results be
available to the public?
Results of the fIrst three rounds of supplemental groundwater sampling
program are included in Amendment No. I to the RI report and are found in
each information repository. Future monitoring results will be reported to the
Corps of Engineers and made available to the public through Fort Lewis.
Describe how additional action could be triggered by the water quality
monitoring results. Are specific groundwater contaminant concentrations the
only activating mechanism, or are there a variety of explicit warning signs
established to automatically prompt increased activity? What types of
additional action might be required in case of a further deterioration in water
quality? .
Groundwater monitoring results will be one of the mechanisms used to.
prompt renewed activity. Excessive differential settlement may also activate
additional studies to determine the cause(s) of the settlement. Additional
.. actions which may be required have been discussed in other questions in this
.. response and in the RI Amendments.
6.
Are there any provisions for on-going monitoring of groundwater level within the
landfill or in the immediate vicinity? This might allow early detection of an~'
significant additional groundwater intrusion or progressive changes in water
-------
table level which could lead to additional pulses of leachate entering the
groundwater.
Groundwater levels will be measured during the supplemental groundwater monitoring
program described in the previous item.
7. What is the status and are there any current results from the separate study of
waste disposal practices in the vicinity of the drainage channel, cited in the
summary of the proposed plan?
The work plan for the study is now in preliminary'scoping phases. Work on the
study of waste disposal practices in the vicinity of the drainage channel has not been
started. .
8. What efforts are being made today to sort and monitor the waste stream
entering the landfill? Compare current recordkeeping practices to historical
practice, as summarized in the documentation of the remedial investigation.
Currently, the landfill receives demolition waste (concrete, asphalt, wood, steel, and
other construction debris), asbestos, and mixed municipal solid waste (residential.
commercial and industrial). Separate records are maintained for each of these waste
streams. The mixed municipal wastes are soned for recyclable materials, and any
suspicious materials are removed for special handling. In this manner, the landftll is
limited to the designated types of solid wastes.
-------
Table 1: Summary of Organic Compounds Detected in Vashon Drift Wells
Concentration, ugll
Detection D.L
Compound (1) Frequem~y (2) (3) Mln (4) Max Mean (5)
Acenaphthene 1/24 1 0.7
Acetone (6) 3/38 3 <3.0 31.0 2.7
Benzene 14/38 1 0.3 7.8 1.3
Bromoform 1/38 3 - 0.4
Bis(2-e.h.)phthalate (6) 10/24 1 0.2 12.0 1.8
Chloroethane 9/38 3 0.6 2.7 1.5
Chloroform (6) 2/38 1 0.3
1 ,4-Dichlorobenzene (6) 1/24 1 0.6
1, 1-dichloroethane 28/38 1 0.4 6.8. 1.8
1 ,2-Dichloroethane (6) 4/38 2 0.6 0.8 1.0
1 ,2-Dichloroethylene 27/28 2 0.5 3.3 1.4
or-n':'octylphthalate (6) 4/24 1 <1.0 6.0 1.0
Diethylphthalate 15/24 1 <1.0 31.0 7.6
Ethylbenzene 6/38 1 0.6 9.4 1.1
Methylene chloride (6) 37/38 2 0.3 4.8 1.7
4-Methylphenol 1/24 1 <1.0 5.0 0.7
Naphthalene (6) 7/24 1 <1.0 17.0 1..9
1,1,2,2- Tetrachloroethane 1/38 2 1.0
Tetrachloroethylene 1/38 1 0.3
Toluene (6) 11/38 1 0.4 16.0 1.2
Trichl?roethylene 5/38 1 0.3 1.1 0.5-
Vinyl cliloride 7/38 2 0.8 3.2 1.2
Xylenes 8/38 2 0.4 10.0 1.5
1. Data are presented in Appendix A of Baseline Risk Assessment Report (1991).
2. Number or times detected/number of samples.
3. Detection limit, uglt
4. No minimum is shown if maximum is below detection limit.
5. Mean is carcuiatecLusifl9 one-hall the detection limit for results reported as
" non-detects. W Mean is not calculated if maximum is below detection limit.
-------
Table 2~ Summary of In.organic Compounds Detected in Vashon Drift Wells
Concentration, ug/1 (1)
Detection
Compound Frequency 2 Minimum. Maximum Mean 4)
Barium 40/40 1 5 155 32
Cadmium 1/40 2 <2 3 1
Chromium 9/40 5 5 38 4
Iron 40/40 5 34 32100 4608
Manganese 40/40 1 2 10700 221G
Mercury 1/40 0.1 <0.1 0:2 0.05
1. Concentrations are for totallnorganics.
2. Number of times detected/number of samples.
3. Detection Umit, ugJl. .
4. Mean Is calculated using one-hair the reporting limit ror results reported
-------
Table 3: Summary of Compounds Detected In Salmon Springs Welts
Concentration, ugll
Detection D.L
Compound (1) FrequenGY (2) (3) Mln (4) Max Mean (5)
Benzene 4/14 1 <1.0 3.2 1.1
Bis(2-e.h.)phthalate (6) : 2/12 1 <1.0 1.0 0.6
Chloroethane 3/14 3 0.7 1.5 1.4
1,1-dichloroethane 4114 1 0.7 1.9 0.7
1,2-Dlchloroethylene 4/14 2 0.3 1.2 0.9
Diethylphthalate 3112 1 <1.0 11.0 2.9
1,1,2,2- Tetrachloroethane. 1/14 2 0.8
Toluene (6) 1/14 (7) 1 0.2
Trichloroethylene 1/14 1 <1.0 2.5 0.6
Vinyl chloride 2/14 2 0.7 1.3 1
Xylenes 1/14 2 0.5.
Barium 10/12 1 4 102 25.6
Chromium 8/12 5 <5 136 28.7
Ircn 12/12 5 170 18900 3736
Manganese 12/12 1 19 4210 844
Mercury 1112 0.1 0.1
1. Inorganics are reported as total concentrations.
Identified laboratory contaminants are not shown.
2. Nurnber of times detected/number of samples.
3. Dete.ction limit. ugll.
4. No minimum is shown if maximum is below detection limit.
5. Mean is calculated using one-half the detection limit for results reported as
.. non-detects." Mean is not calculated if maximum is below detection limit.
6. Analyte was detected in method blanks and field blanks.
. .
7. The'single positive result for toluene is reported here. Three other
-------
-
Table 4: Summary of Compounds Detected In Sequalltchew Delta Wells
Concentration, ugll
Detection D.L
Compound (1) Frequency (2) (3) Min (4) Max
Bis(2-e.h.)phthalate 114 1 1.0
1,1,2,2- Tetrachloroethane 118 . 2 1.3
Barium 616 1 3 9
Chromium 616 5. 72 738
Iron 616 5 450 4510
Manganese 616 1 12 120
Mean (5) -
5
326
1760
48
1. Inorganlcs are reported as total concentrations.
Identified laboratory contaminants are not shown.
2. Number of times delectedfnumber of samples.
3. Detection limit, ugll.
4. No minimum is shown if maximum is below detection limit.
5. Mean Is calculated using one-half the detection limit ror results
reported as "non-detects." Mean is not calculated if maximum is
below detection limit.
-
-------
Table 5: Summary of Surface Water Sampling Results
Volatile Organic De~ctlon Umlt Range of Frequency of
Compounds (ua/l-' Concentr8t1on fuafU DetectIon
Vinyl ChJOOde 2 < 0/16
ChIoroeIhane 3 < 0/16
Melhy1ene Ct110ride 2 0.3 M8b - 2.4 Bb 15f16
Acetone 3 7.0 1116
1,1-Dlch\oc'oelhaM 1 < 0/16
Totall,2-OIc:f1\ofOelhene 2 0.311.1 1/16
Chloroform 1 < 0/16
1,2-Dlch\oc'oelhane 2 < 0/16
1,1,I-Tricf1\oc'oe1hane 1 0.4 Mb - 0.5 Jb 2116
T rich\oc'onuorornethane 5 < 0/16
Trlc:hIoroelhene 1 O.7Jb-I.5b 2116
TelTachloroelhane 1 < 0/16
Benzone 1 < 0116
Bromoform 3 < 0/16
1,1,2.2- T etracf1loroelhane 2 < 0.'16
T oIoone 1 0.3 M8b - 0.5 MBb 4116
EIhyt Benzene 1 < 0/16
Total Xylenes 2 < 0/16
1,1,2-Tric:f1loro U,2-lrIlIuoroelhane 5 < .0/16
EIhyt Elher TIC < 012
Hexane TIC. < 012
Dichloroftuoromelhane TIC < CW
BalelNeutrel and Acld-Extr8ctable De~ctlon Umlt Range of Frequency of
Com unds ull: Concentrallon u Detection
Phenol 2 < 0/16
1.".Dlchlorcbonzene 1 < 0/16
Naphthalene 1 < 0/15
DleU,ylphlhalate 1 O.2J 1/16
Acgnaphlhene 1 < 0/16
,. bIs (2-Ethylhexyt) Phthalate. 1 0.2Jb-7b ~16
DI-n-Qctyt Phthalate 1 18 1116
4-Melhy1pheno1 1 < 0/16
Benzamlde, N,N-Dielhyf-3-melhyl 11C < ciAJ
4-(I,1-Dime1hy!eIhyl}-B:enzolc Add 11C < CW
3-Methyl. Bonzolc Acid 11C < 00
Sulfur, MoIocuIar (58) 11C < 00
Ethanol, 2.Butoxy~Phosphate (3:1) TIC < CW
N~lhyl-4-methyI-Benzenesullonamldo 11C < 00
. Sullonamlde Isomer TIC < 00
Afkyl.bonzolc Acid Isomer TIC < 00
177Trlme 2.2.1 He tan-2-one TIC < 00
Inorganic Compounds Detection Umlt Range of Frequencv 01
DIssolve ufl Concentration u It: Detection
Iron (Fe) 5 8-1610b 26f33
Zinc (Zn). .. 4 - 31 20/33
Barium (Sa) . . 1 2- 45 32/33
Manganese (Mn) 1 1 - 145 26f33
Cadmium (~~) 2 2 1/33
Mereu 0.1 0.1 B 1133
< - Analyto bolow detection limit b : Analyto also found In lield blank
J : Estimated value less than M : Estimated value 01 analyte found and confirmed by analyst
specified detection limit but with low spec1r at match parameters
8 : Analyte also found In TIC: Tentatively Identili
-------
TobIe 6: Summary of SedIment Sampling R..ultli
Vol.l.. o.ganlo A8nge 0' Ft9quency 0'
00 unci c:.n-ncraUon8 Concentration DeCectlon
ChIoromoCtw>e <'4.4 - <'4S 1.11A 1/10
1Jromomo(h8ne <3.2 - tocted In an samples
B: IInotyto MO Iound In Iaboru1O<'f bllll1k
IA: Esllmmod vnluo 01 analy10 found and c:onRrmod by enalysl
-------
Table 7: Permanent Gases (%) and Volatile Organic Compound (ppb)
Concentrations In Landfill Gas Samples
Detection Flare 2 Flare 5 Flare 8 MU~
Permanent Gases Limit (4)
Oxygen 0.1 1 4 4 [7.9] 3
Nitrogen 0.1 3 16 23 [24] 14
Methane 0.1 53 44 36 [37] 44
Carbon Dioxide 0.1 43 37 35 [35] 38
.
Volatile Organic Compounds*
Freon 12 (1) 200 4800 3100 4700 [5300] 4200
. Freon 114 (2) 200 < 170 260 [300] 177
Vinyl chloride 300 3600 1700 1100 [1200] 2133
Chloroethane 500 1100 830 760[960] 897
Freon 11 (3) 200 1200 1900 3100 [3500] 2067
cis-l,2-Dichloroelhene 300 1300 780 390 [440] 823
Freon 113 200 420 540 780 [840] 580
Methylene Chloride 200 8200 4000 4100 [4500] 5433
1,1,1- Trichloroethane 300 350 460 820 [880] 543
Benzene 200 1100 800 660 [740] 853
1,3,5- Trimethylbenzcne 200 200 220 210 [200] 210
1,4-Dichlorobenzene 100 97 140 170 [180] . 136
Toluene 200 15000 9600 9200 (8800] 11266
1,2,4- Trichlorobcnzene 200 < 420 «
-------
Table 8: ;Surntnary or Chemicals or Concern
GROUNDWATER
SEDIMENTS
"In
CarclnOQens
Carcinogens
CarclnOQons
benzene
1.2-dichloroolhane
. 1, t ,2.2-telrachloroelhane
Irlchloroethyfene
vinyl chloride
bonzo(blk)rluoranthene
chrysene
pontachlorophenol
arsenIc
benzone
molhylene chloride
. trlchlorOiJthylene
. vlnyf chloride
. .
Noncarclnooens
Noncarclnogens
Noncarclnogens
manganeso
naphlhalene
ponlachlorophonol
arsenic
1.2-dlchloroolhylone
1."-
-------
Table 9: Modeled Concentrations of Chemicals of Concern In Groundwater
(119/1)
COMPOUND 'WeU 88-LS-AX-VD Well 89-17-VD
1 0 Year Average 30 Year Average 10 Year A vera,ge 30 Year Average
Benzene 0.86 0.64 0.64 0.38
1,2- Dichloroethane 0.19 0.12 0.13 0.07
Naphthalene 1.13 1.36 0.000228 0.01
l,l,2,2.Tetrachloroethane 0.62 0.36 0.1 0.12
Trich loroelhy lene 0.12 0.09 0.09 0.05
Vinyl Chloride () ~Q 0.23 /\ '" ~ 0.1 2
V.J"" U..L't
Manganese (mgj1) 1.31 0.77 0.79 039
. .
-------
Table 10:
Maximum Ambient Air Quality Impacts from landfill Vents ISCL T
I I I I I I ONsrrE I INOU9TAIAL
I I ., I I I MAX.ANNUAlIMP~CT I ANNUAlIMP~CT I ANNUAlIMP~CT '
I I I I I AT FENCE1..1NE I AT :t2.' d'o.l\OOm I AT ~.& d'o.lOOOm
I I I I EMI9910H I .1 I
I MOl. I COHC I FlOW PATE I PATE I CHIIO I COMPOUHD 1 CHI/O I COMPOUND I CHVO 1 COMPOUHD
COMPOUHD I WT 1 (ppb) I (elin/o '.el) I (O/SEC) I COHC. I CONO. 1 COHe. I COHO. I COHO. I COHO.
I I I I I (l.40tlol~) 1 I'-IOtlol3) , (1.40/1.13) I (l.40tlol3) I 1'-I0tlol~) 1 1'-I0fI,C~)
........--.u..____nn__-- I _n-_---- I ---.--- I ----- I --- I I r 'I I I
I I I I 1 I 1 I I I
b.nune I 1' ) .~ I 11. I I I.~72E~' I I.I05E-01 I I.7IOE-08 I I.O~E-ol I I.&I~e-o. I I.~e-02 1 2.8).(e-07
I I I I I I I I I I
\.. ~Ithlorob.nll n. I 141 I 1:10 I 11.' I ~.~nE~o I 1.I05e-01 1 &.28-4e-07 I 1.0~E-01 1 ~.IfiOE-07 I I.~E-02 1 '.6IOEoO.
I I I I I I 1 I I 1
1.2~lthlo'o.th.n. I 87 I .~ I 11.1 I 1.111OE-ol I 1.105£-01 I 2.IIOe-oO I 1.029E-01 I 1.& 11 e -04 I U20e-02 I 3.~IE-07
I I I 1 I I I I I I
.thylbllUtt\l I 10& I 1600 I 11.\ 1 3.611£-05 I \.\86£-0\ I 4.203£-00 I \.028£-<'\ I 3.818£-08 1 U20e-02 I 4.173£-07
I I I I I I I I I I
Ireon t, I 137 I 2081 I 11.\ I Ue:lE-oO I \.\06£-0\ I 7.4&0£-00 I \.02ge-o\ I 0.441£-00 1 1.~E..Q1 1 1.200e-oo
I I I I . I I I I I I
11t01\,2 I 121 I ~~ I 11.\ 1 1.\24E~ I \.\06£-4>\ I U~£-ol I \.029£-0\ I \."7£-01 I \.8'2OE-02 1 2.IME-04
I I I I I I I I.' I I
mllhyhnt chloride I as) a.\.33 I ILl I '.021E~ I \.106£-01 I \.22IE-ol I 1.029E-o I I \.O~ 1 E-oO I 1.~e-02 I I.Po$7E-04
I I I I I I I I I I
IIII.Chloio-. Ihyhnl I 1M I :u3 I ILl I 1.27.IE.{JI I \.106£-01 ' \.~81£-oO I I.029E-01 I 1.266E-08 I U28E-02 I 2.306E-07
) I I ) I I I I I I
lolulh' 1 "1 1I~ I 11.\ I 2.292E~ I I.IOIE-ol I 2.1~OE-Ol I I.029E-01 I 2.300£-01 I I.~E-ot I ~.~ \6£-08
I I I I I I I I I I
\.2," .lrlchl/)tobtnun. I III I 200 I 11.1 I 1.2"E~4 I I.I06E-01 I ...&4E-07 I 1.0 29 E-o 1 I '.Q8£-o1 I 1.8'2OE-02 I 1.641E-ol
I I I I I I I I I I
1, ','-lIIChIOtC>t.lhItH I I~ I ...~ I 11.1 I 1.6~7E-ol I 1.106£-01 I UOOE-o& 1 1.029E-01 I \."'~£-o8 1 1.8'2OE-ot I 3.078E-07
I I I I I 1 I 1 I I
IllchlOt04 thyl.". I I~' I ~I II. I 1 1.2~OE-ol I I.I06E-ol I I.488E-08 1 1.020E-o\ I 1.242&-08 I 1.8'2OE-02 I 2.LOOE-01
I I I I I 1 1 I I I
vinyl chlo,ld. I ~I 21~ I 11.1 I 2.872E-ol I 1.I06E-o\ I 3.&42E-oO I I.O~E-ol I 3.066E-o& I 1.~E-02 6.12~E-07
I I I I I 1 I I 1 I
m,p-ayl.nu I 100 I 3;)4 7 I 11.1 I 7.80.4E-06 I 1.186£-01 I 0.~E-08 1 I.029E-01 I '.I2'3E-oO I I.~E-02 I '~~
I 1 I I ' 1 I I I I I
<'-I'flono I 100 1 ~7 I II. I 1 2.31~E-06 I 1.106E-01 I 2.756E-08 I I.O~E-o\ I 2.34 IE-oo I I.~Eo02 I ~.~nE-ol
I I I I I I I 1 I I
-------
Table 11: Concentrations of ChemIcals of Concern In Drainage Channel
Sedlmen.ts, mg/kg
Compound
Location
Upgradient Adjacent
SC-4,DC-1 DC-2,DC-3
Mean (1) Max Mean (1) Max
0.059 0.085 0.290 0.390
0.056 0.085 0.270 0.3!50
0.300 0.435 1.225 1.500
16.000 20.000 62.000 94.000
" 8en2o(b/k)rJuoranthene
Chrysene
Pentachlorophenol
Arsenic
-------
Table 12: Toxicity Factors for ChemiCals of Concern
Chronic Reference Dose Slope Factor
(rnglkg-d~) 1/(mg~-d~) Weight of
Evidence
Compol.nt1 Inh"l"tinn 0,.,,1 Inh"l"tion Or::tl r:1::I~!:: ~llrr.:A.
Benzene 2.9E-02 2.9E-02 A IRIS
Benzo(bIk)fluoranthene 8.4E-01 82 (1)
Chrysene 5.0E-02 82 (1)
1 ,4-Dichlorobenzene 2.0E-01 HEAST
1,2-Dichloroethane 9.1 E-02 9.1 E-02 82 IRIS
1,2-Dichloroethylene 1.0E-02 HEAST(5)
Freon 12 (2) 5.0E-02 HEAST
Ethylbenzene 2.9E -0 1 HEAST
Melhylene chloride 8.6E-01 1.6E-03 82 IRIS
Naphthalene 4.0E-03 4.0E-03 HEAST (5)
Pentachlorophenol 3.0E-02 1.2E-01 82 IRIS;HEAST
1,1,2.2-Tetrachloroethane 2.0E-01 2.0E-01 C IRIS
Tetrachloroethylene 1.0E-02 1.8E-03 82 HEAST
Toluene 6.0E-01 HEAST
1,2,4- T richlorobenzene 3.0E-03 HEAST
1.1,1-Trichloroethane 3.0E-01 HEAST
Trichloroethylene 6.0E-03 1.1E-02 82 HEAST
Freon 11 (3) 2.0E-01 HEAST
Vinyl chloride 2.9E-01 1.9E+OO A HEAST
Xylenes 8.6E-02 HEAST
Arsenic 1.0E.03 5.0E+01 1.8E+OO(4) A HEAST;IRIS
M""g"nQ<:Q 1 OF.01 11=11~
. Sources: EPA Integrated Risk Information System (IRIS), on-line database.
EPA Health Effects Assessment Summary Tables (HEAST), 1991.
1. Derived from oral slope factor for benzo(a)pyrene 01 11.5 1/(mgikg-day) (HEAST 1991).
2. Dichlorodifluoromethane
3. Trichlorofluoromethane
4. Derived from proposed unit risk 01 5E-05 1/(ugll).
-------
Table 13: Summary of Estimated Health Risks
Reasonable Maximum
AVP.r~gp- Fxro~llrp- Fxpn~lIrp-
Chronic Chronic:
Cancer Hazard Cancer Hazard
Rp-r:p-ptnr/P~thw::lY Rio::k Inrlp-x Ri<:k Intipx
Resident (fenceline, well LS-Ax-VD)
Ingestion - groundwater 1 .76E-06 0.20 6.33E-06 0.22
Inhalaticn - groundwater VOCs 1.46E-06 0 7.49E-06 0
Dermal contact - showering 2.28E-09 0.0000055 1.38E-07 0.00020
Inhalation - landfill gas 7.29E-10 0.0000055 4.86E-09 0.0000"11
3.23E-06 0.20 1.40E-05 0.22
Resident (plume edge, well 89-17-VD)
Ingestion - groundwater 9.83E-07 0.12 3.17E-06 0.11
Inhalation - groundwater VOCs 6.30E-07 0 3.39E-06 0
Dermal contact - showering 1.27E-09 0.0000000011 6.93E-G8 0.0000015
Inhalation - landfill gas 1.17E-10 0.00000088 7.83E-10 0.0000018
1.61 E-06 0.12 6.63E-06 0.11
WorKer (fenceline, well LS~Ax-VD)
Inhalation - landfill gas 1.90E-08 0.00014 7.77E-08 0.00021
Ingestion - groundwater 5.71 E-07 0.066 1.89E-06 0.079
5.91 E-07 0.066 1.96E-06 0.079
WorKer (plume edge, well 89-17-VD)
Ingestion - groundwater 3.19E-07 0.039 9.43E-07 0.038
Inhalation - landfill gas 3.06E-09 0.000023 1.25E-08 0.000034
3.22E-07 0.039 9.56E-07 0.038
Worker (onsite)
Inhalation - landfill gas 1. 64E-08 0.00012 6.70E-08 0.00018
1.64E-08 0.00012 6.70E-08 0.00018
Trespasser (upgradient drainage channel)
Ingestion - sediment 1.34E-07 0.0019 1.34E-06 0.019
Dermal contact - sediment 7.02E-12 0.000000010 1.97E-09 0.0000029 .
1.34E-07 0.0019 1.34E-06 0.019
Trespasser (adjacent drainage channel)
Ingestion - sediment 5.20E-07 0.0075 6.29E-06 0.091
Dermal contact - sediment 3.45E-11 0.000000043 8.97E-09 0.0000.1Q
5.20E-07 0.0075 6.30E-06 0.091
Resident, Subchrorilc Subchronic Hazard Index
-------
~
. ....,.-....
A
-N-
~ Fort Lewis
'- ~ Landfill No.5
''-''----- Sequafilchew
. -""""'--'_.C.reek
'."''''''''''--~.......
~
Dupont
NOT TO SCALE
Project No. 8820072
Fort ,Lewis Landfill No- 5
Woodward-Clyde Consultants
Fort Lewis Landfill No.5
Location Map
Figure 1
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PrQp..\ No. 8820072
Fort Lewis Landfill No.5
Existing Land Uses in Vicinity
of Fort Lewis Landfill No.5
Figure 2
-------
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Project No. 882.0072
Fort Lewis Landfill No.5
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Site Map Figure 3
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Paul.. Gas Von' w1III III,. No. 7 600. no( ubt
~ Monl"'"'1 W.1Is (p
-------
(
(
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Project No. 8820072
Fort U!wU Landfill No.5
Plaxmed and Proposed Future Land Uses in Vicinity
of H. Lewis L~d£ill No.5
Figure 4
Woodward-Clyde Consultants e
LEGEND
""" .
::::::: Industrial Zoning
i;~;i!~it Commercial ZonIng
...., .
,'::,',\ Mlxed..Use Zoning
.
+ VIllage 01 DuPont
///// 0
/ / / / " pen Space Zoning
II1III Pioneer Aggregates
- Local Improvement District
-------
::::-;::';':';':':-;':':::::::::::::::::::::::::::::::;" Tr88tm8n~". '.' . . :: ~~~"I"" /' .~,
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:::::::::::::::::::::;:;::::;::;;;:. I : :: :: '. :.:.::::. .'::::: ;;*" \'1 \1111.1",,1 11'1, ,/ 1"'11
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-------
-
LITHOLOGY ClIMA TE
-
~
Steilacoom Gravel
Recessional Gravel
Vashon Drift- - Till - Glacial
Advance Gravel j
Colvos Sand'
'-
I
-------
225
200
150
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Woodward-C!yde Consultants
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SAUt!C« SPAIHOS TIU.
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SALMON SPAINGS OAI'"
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600
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lEGEND
,1146.531
Sequalitchew
Delta
Aquifer
50
o
(6.87)
(4A3i'~ -- - -:- -
Well
14.VD
Well
8.VD
Well
5.55
Well
2.VD
Well I
'.55
,(1 9.48)
.;. 'E' (196.871
Estimated Water labl~_'.:~!1~---------
~ -----------------
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(186.62)
,
, ~
I ,'Level 'SZ_-----------.-.---- -
'I ' {1\etC,,~~a:=-.- - -.-- (77.031 (81.58)
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Salmon Springs Aquifer
---
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V Irtical
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24X
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It'I
- Hydrog'eologic Contact Established from
Borehole Lithology. Dashed "rhere Inferred
1200'
V Water level Measured JUnI! 5. 1989
Project No. 8820072
Fort Lewis Landfill No.5
Hydrogeologic Cross Section A-A'
Woodw~rd-Clyde Consultants ~
A'
East
250
~ 200
-
...J
150 ~
-
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TR£A TM£NT OO~
PLANT
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....0000 + ..---- i)'a ~-'''' 0 '\ - .-------.------ - -. - - - Q
, g ." 'U - - - - - - - - - - - -.---.--- (J
. 691. 6-SO 90 19-55 -------------._---.-.-- - - --
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tl T8..n...~~ 0 \.11-6-- ,~_..-.---._--------:-_-
i 89-21-50 88-.118- ~~ 00"" .Ja9.-4A~., ==:::=:::~ FOR T LEWIS:':- ~
;/ 1(. 89.17-VOj6 r' ~ ~-1..~CO'T~ 89-046 va,l ----.---- LANDFILL ':-:.:
/ 88~I.S-C7VO \ 09-10-V\) ~!?~-..ct'..'O. -----.-. - NO 5 -------- '
. l ~ ~-1~ .. - - - . -. I-
/~---I . '" '.; . '. - . - -. -- -- -.
/ \ \. 88-/11-55 J 811-20-SS 88-S-SS.. . "'" 0,""" - . - - - - <:
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~ ./ ----~, .-.-.---.-:..-.---------------
.. "'" 0 O. . I - - - - - - -. - - - -.---
'-J. 69-12-VO. '-...,. - - - - - - - - -
66-7-1.1) ---::--..:. - - - - - ---
--
-----
00
00
00
FORT L~'N/S
00 NORm POST
00
~~
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~
$
.068-8-\00
~
:
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.
..
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+.H.~
--.-----------.- ..-.- - ..
..-----.- - -----"---'-"- ------
.... ..-., ----.....-.. - -
n
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r"'\.r--
. 1000"
2000'
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U:COIO
OIAT ...,0 CRAVE\. SER\ACC ROADS
Q BENCH MARl(
o VASHON oRIn AOUIF"tR
*' SAUo/ON SPRINOS AOUIF'"!:R
.6. StOUAUTCH[W OELTA AOUI~ .
o PUIJP 1t:ST \00\1.1. IN VA9iON ORIFT AOUIF"CR
..u. v.t:LLS INSTAU.£D BY WOODWARO CL'roE
CONSU\.TANTS. EXCEPT THOSt DESICNATEO
aa-LS-XX-XX. WHICH VfC:R£ INSTALLED BY
LONE STAR INDUS'lRIES.
WOODWARD CL YOt CONSUL TANTS
.c8.... ~ CV-1J [I
....... -
f£~11a ~ ,,~~ '-""'0 NnO'. If1G ~ ~ CD8.&,"'''''
Ft. Lewis Lon d fill No. 5
Ground Water Figure 9
MonltorlngLocatJons
-------
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'.
l1me'(Years)
.- .' .. .' . ...
MODELED CONCENTRATIONS: Trich1oroethene Anival Patterns
at Well 88-LS-AX-VD
Figure 12
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c
. .- 0.2
Time (Years)
Project
No. 8820072
Fort Lewis
Landfill No.5
'MODELED CONCENTRATIONS:
1,2 DicWoroelha.ne Arrival PaUerns
at Well 88-LS-AX-VD
Figure 13
-------
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L.
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TIine (Years)
MODELED CONCENTRATIONS: Vinyl Chloride Anival Patterns
at Well 88-LS-AX-VD
18
I 16
c
III
CI
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1= ~ 12
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Project
No. 8820072
20
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Spocl1c ConducMr
2
o
Milr-69
Jun-69
0c1-89
J:an-90
I\pr-91
OATE
Jun.91
Jan-92
Sep-91'
Oec-92
Fort Lewis
La.ndfill No.5
Groundwater Measurements for Benzene,
Dissolved Manganese, and Specific
Conductance for MW 88-LS-AM- VD
Fort Lewis Landfill No.5
Woodward-clyde Consultants . ~
Figure 14
2000
1800
1600 CII
"
m
1400 Q
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1200 g
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o
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800 .z
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600 ~
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200
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-------
. U.S. Army
FORT LEWIS LANDFILL NO.5
Public Meeting'
Mard1 3. 1992
COMMENT SHEET
Please use tltis form to make conunents about the Proposed Plan for Fort Lewis Landfill No.5.
. You may return this sheet (and/or additional sheets) to a study team member at this evening's
meeting, or take it. with you to fill out later. Your comments may be addressed to: I Corps and
Fort Lewis, Attn: AFZH-DEQ (paula Wofford), Fort Lewis. W A 98433-5000. Comments
must be received by March 9 to be considered.in finalizing the Proposed Plan. Thank you for
your int~cs! and comments. '.. .
. Name: fP", f~~ il "'I
U"- .0.11. tit J : "';;:<7 ?2..1tHf 17 {' /t18.M elf .
. f -
it b., ~dii~, M.-Q~.d ALe- c/'o.:y( ,
".~ "p, '~ 't ~ ~.J
. ;.:~; ~p;9J /7:; ~'dQ ". I,~. dwU./rt M-"QVJ ,r:Q.
. ' il.. 1 " "1i' arrlf.J yd- 9 I "l0-<' UJ."'rd..f' "~
jJ1/Lacf..Q~.0-;"'..t'''''(-' .c/..~ ,.-lD~i/ P.CA./y ~. rl t~.'Y71 (.p
!
-------
:1nR 17 '92 12:57
2S~ COE SEn-OIST
p.G2
~'92 16.20
ID:
DEH
TEL NO: 206 96-<:1 3289
U<135 P03
~ v.:L-
t'c&..fM~ I (J /vi ~ "
\)..'i\ \ ; ,-0 JA.. j r'\ Q~S'Jh(lS; Vt ~
Su tY1 rv~ lNT~ kl- w;\ I ~
411 a.;l- I\- \).i4$ L1.. ~ (.3\ ti, #.
9ITY OF DUPONT
Pod. omoo Box 4.S:i
Dupont.. W....Iti..stoc\ 98327
(206) 964-6Ul -fAX 964.BSM
Karch 9, 1992
HO I corp a And.Fort Lewis
ATTN: AFZH-D&Q (paula wor~ord)
Fort Lewis, WA 98433-5000
SUBJECT:
REVIEW OF ARMYrS PROPOSAL FOR NO FURTHER ACTION FOR
FORT LEWIS LANDFILL NO.5
Dear Ms. Wo!~ord:
Baaed on our reviQw of the 8uromarypropoaed plan tor Landfill No,
S, we had a nwnbQr of qu~stions. Our enqineQr visdted your
office March 6, ~992 to examine the adrninictrative record for the
5i te. We weroa able to clarify numerous lsGue.a through this
visit, but have several remaining qUastionQ. The answers may be
present in the administrativo record, but there is roors material
than could b9 rQvi~wed in detail in the several hours we had.
allowQd, We ~ould approciat~ your responses to the ~ollowing:
1.
What is the )nanufacturarfs suggested working life for the.
high dQnsity polyethylene used in capping the East-West
landfill zones wh9n the materi~l iQ used in this type or
application? Are th~ro any plans to checK liner integrity
pariodicallY?
2.
We have several qu.~tions r~qarding the monitoring tQ be
performQd as: part of t.he londrill closure:
How rrequently will oo.ropl~~ be collectsd as part. of the on-
going site monitoring? Wh3t teate will be perlormed?
For how roany years will .the monitoring c6ntinue?
Where will the samples be collected? wiil th0 &le sites
include both cross-gradient and up-gradient sites as well 86
t.he plume areas portrayed in the documentation ot the
remedial investigation? We would particularly like to seo
rogular monitoring o( groundwot.r in the region between the
landfill nnd the city of DuPont's Bell Hill well site.
will both surfaoe watGr and groundwatQr be sampled?
vi1.11 t.l1.er.,b. additional checks ot !ut:ut"c monitoring re13ults
-------
~nR J7 '92 12:SD 2S~
~'3-.g2 16'2'
COE'sen-OIST
11.J :
1'.03
uc."
t"-- .'---""'- -"-' _0'
Pago. Two.
~g~lnet comp~ter mod~l pr.dlctlon~ to either verify model
accuracy or point to the noed tor additional Btudy?
Where and how will tho monitoring reeulte be reportad?
tho. r(u~Ul tcs: be ava.ila.blo to the publio?
Hill
D..crib. how additional action oou1d bo tri9gered by the
water quality 1'Donitor.lnq re.u~ts. Are speoifio groU1'dwatcr
. cont~min~nt concentratione the only aotiv~ting mechaniem, or
arB there a variety ot explicit warning signs Gstabllshe~
to automaticallY prompt increased activity? What types of
additiona.l action might be I:equlred in ~ase 01: a turthlon or progressive
ohangeS in w~tar table level which could 1.e~d to additional
pulBea 01: leachate entering the ground~ater.
Wh~t ie the status ~nd are thsre any current results from
the aoparate et~dY of w~ste diepoasl pr~ctlce6 in the
vicinity of th~ drainage channal, cited in th~ summary or
the pro~oBed plan?
Whnt e!~orts are b6ing made today to Bort and monitor t.he
waete "treelU entering the landfi117 Compare current
recordk~Qpinq practicGS to historical prnotice, nS
summarized in the documentation of the remedial
invogtlgation.
3.
4.
5.
Thank you for the opportunity to review the plana for Landt 111
No.5 l\nd alGO for. your t~tt4ntion to our queotione-
sincerely,
CITY: OF DUPONT
~f{/A~--
WILLIAM H. G~~~EN
Mayor '
WHG/clo .
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