USW
HAZARDOUS
SITE CONTROL
DIVISION
Remedial
Planning/
Field
Investigation
Team
(REM/FIT))
ZONE II
CONTRACT NO.
68-01-6692
CH2MBHILL
Ecology&
Environment
Executive Summary
Feasibility Study for
Subsurface Cleanup
Western Processing
Kent Washington
EPA 37 OL16.2
March 6,1985
-------
i
UJ
O
'/
HAZARDOUS
SITE CONTROL
DIVISION
Remedial
Planning/
Field
Investigation
Team
(REM/FIT)
ZONE II
CONTRACT NO.
68-01-6692
CH2MKHILL
Ecology &
Environment
Executive Summary
Feasibility Study for
Subsurface Cleanup
Western Processing
Kent, Washington
EPA 37 OL16.2
March 6,1985
-------
W60816.F5
EWB
-------
PREFACE
This volume of the Western Processing Subsurface Cleanup
Feasibility Study contains only the Executive Summary.
Volume I contains Chapters 1 through 7, and Volume II
contains Appendixes A through G.
111
-------
CONTENTS
Page
Preface iii
Background S-l
Nature and Extent of Contamination S-5
Endangerment Assessment S-18
Description of Example Remedial Action
Alternatives S-21
Alternatives Evaluation S-37
v
-------
TABLES
Page
S-l Indicator Contaminants Used at Western
Processing S-7
S-2 Location of Chemicals Within the Soil
Profile S-7
S-3 Concentrations of Dissolved Metals in
Mill Creek Upstream and Downstream of
Western Processing S-17
S-4 Excess Lifetime Cancer Risk Resulting
From Ingestion of Contaminated Soil or
Groundwater at Western Processing S-20
S-5 Contaminants at Western Processing
Occurring in Concentrations That Could
Result in Exceedance of ADI's S-20
S-6 Technologies Available for Use in Example
Remedial Action Alternatives S-22
S-7 Remedial Action Components S-23
S-8 Summary of Components Included in
Example Alternatives S-25
S-9 Summary of Public Health, Environmental,
and Technical Evaluations S-41
VII
-------
FIGURES
Page
S-l Location Map S-2
S-2 Vicinity Map S-3
S-3 Western Processing Site, December 31, 1984 S-6
S-4 Summary of Nature and Extent, Indicator
Metals in Soils 0 to 9 Feet Below Ground
Surface S-8
S-5 Summary of Nature and Extent, Indicator
Volatiles in Soils 0 to 9 Feet Below Ground
Surface S-9
S-6 Summary of Nature and Extent, Indicator Acid
Extractables in Soils 0 to 9 Feet Below
Ground Surface S-10
S-7 Summary of Nature and Extent, Total PAH
Compounds in Soils 0 to 9 Feet Below Ground
Surface S-ll
S-8 Summary of Nature and Extent, Total Phthalates
in Soils 0 to 9 Feet Below Ground Surface S-12
S-9 Summary of Nature and Extent, Indicator
Metals in Groundwater S-15
S-10 Summary of Nature and Extent, Organic Priority
Pollutants in Groundwater S-16
S-ll Conceptual Site Plan for Example
Alternative 2 S-27
S-12 Conceptual Site Plan for Example
Alternative 3 S-29
S-13 Site Plan for Example Alternative 4 S-33
S-14 Conceptual Site Plan for Example
Alternative 5 S-35
S-15 Plan View of Mill Creek Diversion Berms and
Temporary Pipeline S-39
S-16 Analysis Areas S-47
IX
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EXECUTIVE SUMMARY
OF THE
FEASIBILITY STUDY FOR SUBSURFACE CLEANUP
WESTERN PROCESSING
KENT, WASHINGTON
This Executive Summary presents the major findings of the
Feasibility Study for Subsurface Cleanup, Western Processing,
Kent, Washington (March 6, 1985). The Feasibility Study was
prepared by U.S. Environmental Protection Agency (USEPA) and
their contractor, CH2M HILL, under the authority of the
Comprehensive Environmental Response, Compensation and Lia-
bility Act (CERCLA) of 1980 (also known as the "Superfund"
legislation).
The overall goal of the Feasibility Study is to provide rel-
evant technical and other information about the Western Pro-
cessing site and surrounding area in order for USEPA to select
"...the lowest cost alternative that is technologically feas-
ible and reliable and that effectively mitigates and minimizes
damage to, and provides adequate protection of, public health,
welfare or the environment" [40 CFR 300.68 (j)].
To accomplish this goal, the following process was undertaken:
1. The nature and extent of contamination at the site
was assessed using soil, sediment, surface water,
and groundwater samples.
2. On the basis of the nature and extent assessment,
an endangerment assessment was prepared that
addressed the risks presented by the site to pub-
lic health and the environment.
3. Example remedial action alternatives for mitigating
the problems identified by the nature and extent
and endangerment assessments were then developed.
4. The example remedial action alternatives were eval-
uated and compared to determine their relative
cost, technical feasibility and effectiveness in
remedying site problems, mitigating public health
and environmental impacts, and complying with govern-
ment standards and policies.
BACKGROUND
The Western Processing property is a 13-acre area located in
the Green River Valley at 7215 South 196th Street, Kent,
Washington. Figures S-l and S-2 show the general location
and site vicinity. The Western Processing Company, Inc.,
conducted industrial waste processing, reclamation, and
S-l
-------
FIGURE S1
LOCATION MAP
S-2
-------
WESTERN
PROCESSING
SITE
FIGURE S-2
VICINITY MAP
S-3
-------
storage activities on 11 of those acres between 1961 and
1983. These activities resulted in contamination of site
soil and, subsequently, of groundwater and surface water on
and near the Western Processing property.
Since the early 1970's, several agencies including the
USEPA, Washington Department of Ecology (WDOE), Metro, and
the Kent Fire Department have investigated problems at the
site. Actual cleanup of the site began in 1983, when USEPA
issued an administrative order pursuant to CERCLA instruc-
ting Western Processing to cease all operations at the site
and to begin cleanup of the contaminated areas. Since then,
there have been three major remedial activities undertaken
to mitigate the hazards posed by the site.
First, in June 1983, a $1.4 million emergency removal action
was undertaken by USEPA using CERCLA funds. Drums and im-
pounded liquids that presented the greatest hazard were re-
moved from the site. This removal action was completed in
July 1983.
Second, from September through December 1983, WDOE undertook
measures to control stormwater run-on and run-off at the
site. These measures included: (1) removing the bottom
material from a former surface impoundment (the reaction
pond) and storing this material in a pile onsite; (2) cov-
ering the pile with an impermeable, flexible cover; (3) re-
grading and paving portions of the site to promote drainage;
and (4) installing berms at the perimeter of the paved area
to control run-on and run-off.
Third, in July 1984, Chemical Waste Management (CWM), Inc.,
under contract to the potentially responsible parties, began
a surface cleanup of the site costing about $9 million. The
cleanup included: (1) removal of wastes and structures from
the surface of the site; (2) grading and construction of a
lined impoundment to provide stormwater collection; and
(3) treatment of collected stormwater. The removal activi-
ties were completed in November 1984, with the exception of
about 3,000 gallons of dioxin-contaminated liquid that had
The potentially responsible parties are the individuals or
companies that operated the Western Processing facility or
who generated or transported the materials brought to the
site. They are potentially responsible under CERCLA for
funding or conducting the cleanup of the site. There are
about 300 potentially responsible parties associated with
Western Processing. In 1984 some of the generators and
transporters formed a group called the Western Processing
Coordinating Committee to negotiate the surface cleanup of
the site with USEPA. In this executive summary, the term
potentially responsible parties refers to this group.
S-4
-------
to be placed in special temporary storage trailers located
on the property until a long-term storage and/or disposal
location could be identified. Treatment of the contaminated
surface water will continue until the spring of 1985. Nego-
tiations are underway with the potentially responsible parties
to continue this activity until the next stage of cleanup
begins. Figure S-3 shows the condition of the site in
December 1984.
These remedial activities were primarily designed to allevi-
ate the obvious and immediate environmental hazards and human
health risks posed by the site. Further investigation of
site contamination was undertaken as part of the feasibility
study to provide data for better defining the existing and
potential hazards posed by the site and for identifying final
solutions to the problems.
NATURE AND EXTENT OF CONTAMINATION
The nature and extent of contamination at Western Processing
was analyzed using soil, sediment, surface water, and ground-
water samples collected on and off the Western Processing
property between 1982 and 1984. The samples were tested to
determine the presence of organic and inorganic contaminants,
primarily the USEPA priority pollutants. Priority pollutants
are chemicals that USEPA considers to be of particular con-
cern when found in the environment above background levels.
In all, approximately 90 of the 126 priority pollutants were
found in Mill Creek or in the soil or groundwater on and off
the Western Processing property.
In order to simplify the analysis of the nature and extent
of contaminantion at Western Processing, 16 indicator com-
pounds were used to characterize the contamination on and
off the Western Processing property. Table S-l lists the
indicator contaminants selected. They are the compounds
that were frequently detected, are relatively mobile, or are
highly persistent and toxic,
SOILS CONTAMINATION
In total, 81 of the USEPA priority pollutants (including all
indicator compounds) were found in soils samples taken on
the Western Processing property. Fifty-six of the priority
pollutants were found in samples taken off the property.
Some contaminants were found at low concentrations at depths
to 80 feet, but most contamination occurred within 15 feet
of the surface. Table S-2 and Figures S-4 through S-8
summarize the location of the indicator compounds within the
The Western Processing property is not the source of con-
tamination for all off-property contamination. Some areas
across Mill Creek were contaminated by a separate source.
S-5
-------
i
WESTERN PROCESSING
FIGURE S-3
WESTERN PROCESSING SITE
DECEMBER 31, 1984
-------
Table S-l
INDICATOR CONTAMINANTS USED AT WESTERN PROCESSING
Organics
Volatile Organics:
1,1,1-Trichloroethane
Trans-1,2-Dichloroethene
Tetrachloroethene
Trichloroethene
Toluene
Chloroform
Acid Extractable Compounds:
2,4-Dimethylphenol
Phenol
Base/Neutral Compounds:
Total PAH's
Total Phthalates
Other Organics:
PCB's
Oxazolidone
Inorganics
Metals:
Cadmium
Chromium
Copper
Nickel
Lead
Zinc
Total priority pollutant polycyclic aromatic hydrocarbons
(PAH's).
Table S-2
LOCATION OF CHEMICALS WITHIN THE SOIL PROFILE
Indicator
Compounds
Metals
Volatile Organics
Acid Extractables
Base/Neutrals
Total PAHs
Phthalates
PCB's
Depth Below the Surface
Where Compounds Were
Most Frequently Found
0 to 9 feet
6 to 9 feet
9 to 21 feet
0 to 3 feet
0 to 9 feet
Surface soil
Depth Below the
Surface Where Compounds
Were Found in the
Highest Concentrations
0 to 9 feet
6 to 9 feet
9 to 21 feet
0 to 3 feet
Surface soil
10 feet (on-property)
Surface soil (off-
property)
S-7
-------
= 1 — 1.000 mg/kg
= 1.000 - 10.000 mg/kg
= > 10.000 mg/kg
S-8
FIGURE S-4
SUMMARY OF NATURE AND EXTENT
INDICATOR METALS IN SOILS
0 TO 9 FEET BELOW GROUND SURFACE
-------
= i — 1.000 pg'kg
= 1.000-10.000 jug/kg
100 200
72ND AVE.
FIGURE S-5
SUMMARY OF NATURE AND EXTENT
INDICATOR VOLATILES IN SOILS 0 TO 9 FEET
BELOW GROUND SURFACE
S-9
-------
1 — 1.000pg/kg
1.000 —10,000 pg/kg
> 10.000 fjg/ kg
FIGURE S-6
SUMMARY OF NATURE AND EXTENT
INDICATOR ACID EXTRACTABLES IN SOILS
0 TO 9 FEET BELOW GROUND SURFACE
S-10
-------
INTERURBAN TRAIL
OLD SANlTJUtV
DISCHARGEIWH
= 0 — i.OOO*jg/Kg
- 1.000 — 10.000 /ug/ kg
- 10.000 — 100,000 /ug/kg
= 100.000 — 1.000.000 (ug/kg
= > 1.000,000 /ug'kg
5-11
SUMMER? OF NATURE AND EXTENT
TOTAL PAH COMPOUNDS IN SOILS
0 TO 9 FEET BELOW GROUND SURFACE
-------
= 0 — 1,000
-------
soil profile on and off the Western Processing property.
The information contained in the table and figures is briefly
described below.
Figure S-4 shows the concentrations of the indicator metals
found in the soil down to 9 feet below the surface. The
highest concentrations of the indicator metals were found in
soils on the property- Lower levels (but still above back-
ground levels) were found in off-property soil samples.
Metal concentrations are greatest between the surface and
9 feet below. Priority pollutant metals concentrations above
background do not appear to extend beyond about 20 feet below
the ground surface.
Figure S-5 shows the extent of contamination from the vola-
tile organic contaminants listed in Table S-l. They are
most widespread in soil on the property at depths less than
9 feet. Within this depth range, they were found most fre-
quently and in higher concentrations in soil from 6 to 9 feet
below the surface.
Contamination by the acid extractable compounds is depicted
in Figure S-5. Acid extractable contamination was found
mostly in subsurface soil on the Western Processing property
between 9 and 21 feet beneath the surface.
Base/neutral compounds as represented by total PAH's and
total phthalates (Figures S-7 and S-8) were most frequently
detected in soil on the property. PAH contamination was
most widespread between 0 to 3 feet below the surface, with
the highest concentrations also occurring between 0 and 3 feet.
Phthalate contamination was most widespread between the sur-
face and 9 feet. The highest concentrations of phthalates
were found in surface soil.
PCB' s were found onsite at depths up to 15 feet. Off the
property, the majority of the PCB contamination was found in
the surface soil. The maximum detected concentration was
found onsite at 9 feet below the surface.
GROUNDWATER CONTAMINATION
Groundwater samples were taken from wells on and off the
Western Processing property. The samples were tested for
all USEPA priority pollutants. Fifty-six of the priority
pollutants were identified in groundwater samples taken on
The determination of background concentrations is discussed
in Chapter 2 of the Feasibility Study. For soil, indicator
metals are assumed to have a total background concentration
of 350 mg/kg. For groundwater, indicator metals are assumed
to have a total background concentration of 525 yg/L.
S-l 3
-------
the property and 53 in off-property wells. The greatest
frequency of occurrence and the highest concentrations of
all indicator compounds were found in shallow wells (0 to
15 feet).
Figures S-9 and S-10 show the locations and concentrations
of the indicator compounds. Metals concentrations in ground-
water were highest in shallow wells located on the northern
end of the site. Total indicator metals in these wells often
exceeded 100,000 mg/L. Total indicator metals concentrations
in intermediate wells (16 to 57 feet deep) and in deep wells
(60 to 135 feet deep) were highest in on-property wells and
decreased off the property.
Volatile organic and acid extractable contaminant concentra-
tions were highest in shallow wells on the property. Acid
extractables were found in concentrations exceeding
10,000 mg/L in shallow wells only.
Base/neutrals, PAH's, and phthalates were detected infre-
quently in wells on or off the property- When they were
detected, base/neutrals were found most frequently in on-
property shallow wells in concentrations of less than 20 mg/L.
MILL CREEK CONTAMINATION
Contamination in Mill Creek consists primarily of high metals
concentrations in the water and the channel sediments.
Table S-3 shows the concentrations of the dissolved indicator
metals in water samples taken from Mill Creek in 1984. The
samples were taken upstream and downstream of Western
Processing.
The data show that concentrations of several dissolved metals
in downstream samples increased up to three orders of magni-
tude over the upstream samples. In Table S-3 the metals
concentrations found in Mill Creek water samples are compared
to the USEPA ambient water quality criteria for aquatic life.
The concentrations of dissolved copper, lead, cadmium, nickel,
and zinc exceeded the USEPA 24-hour ambient water quality
criteria for aquatic life in most samples taken downstream
of Western Processing. Concentrations of dissolved copper,
cadmium, and zinc exceeded the USEPA maximum ambient water
quality for aquatic life in one or more samples downstream
of Western Processing.
Twenty-five organic priority pollutants were found in Mill
Creek water. However, most were found at levels below the
USEPA ambient water quality criteria; organic contaminant
concentrations appear to have diminished since surface reme-
dial actions were taken.
S-14
-------
en
I
///////// = Background to 1,000 pg/L
V\\\V=> 1,000 wg/L
27 - Well Number
O = Well where indicator metals were
detected at or below background
levels.
0 = Well where indicator metals were
detected above background levels.
NOTE: Shaded area means that one or more
indicator metals were measured at
concentrations within the given range.
FIGURE S 9
SUMMARY OF NATURE AND EXTENT
INDICATOR METALS IN GROUNDWATER
-------
'//////// = Quantified level
to 1.000 iiig/i-
v\\\V =>1.000/ug/L
27 = Well Number
O = Well where indicator organics
were not detected
• = Well where indicator organics
were detected
NOTE: Shaded area means that one or more
organic priority pollutants were detected
at concentrations within the given range.
FIGURE S-10
SUMMARY OF NATURE AND EXTENT
ORGANIC PRIORITY POLLUTANTS
IN GROUNDWATER
-------
Table S-3
CONCENTRATIONS OF DISSOLVED METALS IN MILL CREEK
UPSTREAM AND DOWNSTREAM OF WESTERN PROCESSING
EPA Ambient Water
Quality Criteria for
Dissolved Sampling Data (yg/L) Aquatic Life (yg/L)
Metals (yg/L) Upstream Downstream 24-Hour Maximum
Chromium n.d. to 2.0 n.d. to 5 29.0 21.0
Copper n.d. to 2.0 12 to 23 5.6 18.0
Lead n.d. to 2.0 n.d. to 8 2.3 131.0
Cadmium n.d. 6.4 to 18.9 0.0354 4.3
Nickel n.d. 45 to 104C 96.0 1,844.0
Zinc n.d. to 41 113 to 936 47.0 425.0
Note: n.d. = not detectable.
Samples were taken on four different days in 1984. The values shown in
this table are the highest and the lowest sample values found. Samples
taken on a fifth day (May 22, 1984) are not included in this table be-
cause flows in the creek were unusually high on that day and the sample
data are therefore not expected to be representative of typical Mill
Creek water quality.
The criteria vary depending on the measured hardness of the water. The
criteria shown are for the hardness measured in the upstream samples
showing the highest concentration of the metals. This gives the least
strict criteria.
Hardness was not measured on the date that this sample was taken in
order to calculate the ambient water quality criteria, a hardness value
of 100 assumed.
Sediment samples from Mill Creek were also tested for metals
and organics. Concentrations of some metals in Mill Creek
sediments increased at Western Processing and remained high
downstream of the site. Sediment concentrations of cadmium,
chromium, copper, nickel, and zinc all increased ten- to
one-hundred-fold at downstream locations relative to concen-
trations upstream of Western Processing. Other metals, such
as lead, that are abundant in samples from the property did
not increase in Mill Creek sediments downstream of Western
Processing. It therefore appears that sediments in Mill
Creek become contaminated by adsorbing metals from solution
rather than from the deposition of contaminated soil via
surface water runoff.
The results of sediment analyses for organic priority pollu-
tants have been somewhat inconsistent. Contamination of
Mill Creek sediments with organic compounds attributable to
Western Processing is not clearly indicated from sediment
S-17
-------
analyses alone. The presence of phthalates, some PAH's, DDT
derivatives, and low dissolved oxygen concentrations appear
to be caused by sources upstream of Western Processing.
CONTAMINANT MIGRATION
The pattern of soil, groundwater, and Mill Creek contamina-
tion off the Western Processing property indicates that
groundwater and surface water run-off have become contami-
nated following contact with contaminated soil and have then
migrated from the property, thereby carrying contamination
to other areas. The contribution of surface water to off-
property contamination was reduced during 1983 and 1984 when
remedial measures were taken by WDOE and CWM to control
stormwater run-on and run-off. In the absence of remedial
action, soil contaminants in the unsaturated zone will con-
tinue to leach into the already contaminated shallow
groundwater.
Groundwater is the primary means by which contaminants are
transported off the property. Most of the groundwater from
beneath the Western Processing site flows toward and dis-
charges into Mill Creek. Therefore, most of the contamina-
tion moving from the site via groundwater eventually dis-
charges to Mill Creek.
ENDANGERMENT ASSESSMENT
The purpose of the endangerment assessment was to determine
the present or potential risks presented by the site to pub-
lic health and the environment. This was done by identifying
the places where, or situations under which, people and the
environment are or could be exposed to the contaminants and
by quantifying the risks associated with this exposure.
The area immediately surrounding Western Processing is not
heavily populated. Within 300 feet, the only occupied struc-
tures are roughly 160,000 square feet of single-story office,
light industrial, and storage buildings. Drinking water for
these businesses is supplied by the City of Kent. The shallow
aquifer beneath the Western Processing site is not used for
drinking or industrial water supply. The area is zoned for
general and light industrial uses and is expected to be
developed in the future in accordance with this zoning.
Residential development would be limited to caretakers'
residences permitted under the present industrial zoning.
RISK ASSESSMENT
The endangerment assessment addressed the human health risks
that would result from ingestion (eating or drinking) of
contaminated soil or water from the Western Processing pro-
perty or Mill Creek. The main factors used in determining
S-l!
-------
these risks are the concentrations of contaminants in the
soil and water, the potential rate at which the contaminants
might be ingested, and the potencies or toxicities of the
contaminants.
RISK PRESENTED BY SOILS AND GROUNDWATER
Two methods were used to determine the public health risk
presented by the contaminants at Western Processing. One
method was used to address the risks associated with contam-
inants known or suspected to be carcinogens; the other method
was used to address risks associated with toxic compounds.
For carcinogens, the risk was calculated using a mathematical
model that estimates the increased probability of getting
cancer for someone who ingests the soil or water from the
Western Processing site over a long period. This is referred
to as the excess lifetime cancer risk. Table S-4 shows the
excess lifetime cancer risk expected to result from the
ingestion of contaminated soil or groundwater from the
Western Processing site.
The concentrations of contaminants in the soil and ground-
water are high enough that regular ingestion would increase
the cancer risk for those who ingest them. In general,
Table S-4 presents an over-estimate of the human health risk
posed by the soil and water because the rates assume continu-
ing ingestion over a period of at least 40 years. The rate
of soil ingestion leading to the maximum cancer risk assumes
that people live near and ingest the soil from the property
for 70 years. Because residential development in the area
is not expected, this scenario is unlikely. Both the maximum
and minimum cancer risks presented by the groundwater are
over-estimated because both risk calculations are based on
regular consumption of the groundwater. However, the shallow
groundwater beneath Western Processing is not used as a drink-
ing water source. Other types of exposure would result in a
lower excess lifetime cancer risk.
For non-carcinogens, USEPA has identified the daily contami-
nant intake levels that, if exceeded, can cause observable
health effects in humans. This level is referred to as the
acceptable daily intake (ADI). The ADI's are used to evalu-
ate the hazard posed by non-carcinogenic contaminants found
at Western Processing. Table S-5 shows the compounds for
which the ADI levels would be exceeded, given the mean con-
centrations of contaminants found at Western Processing and
an assumed consumption of 0.1 gram of soil per day or 2 liters
of groundwater per day.
S-19
-------
Table S-4
EXCESS LIFETIME CANCER RISK RESULTING FROM INGESTION
OF CONTAMINATED SOIL OR GROUNDWATER AT WESTERN PROCESSING
Risk resulting from ingestion
of the soil on the Western Pro-
cessing property (0.1 gram per
day over a 40-year period)
Risk resulting from ingestion
of groundwater under the West-
ern Processing site (2 liters
per day over a 70-year period)c
Maximum Risk
8 people in 1,000
who ingest the soil
at the indicated
rate
5 people in 10 who
ingest the ground-
water at the indi-
cated rate
Minimum Risk
2 people in
10,000,000 who
ingest the soil
at the indicated
rate
3 people in
1,000 who ingest
the groundwater
at the indicated
rate
No one is using this water as a drinking water source.
Note: This table shows the number of people who would get cancer if
they ingested soil or groundwater from the Western Processing
site at the indicated rate. The risk level varies depending on
the concentrations of contaminants assumed to be present in the
soil or water and the amount ingested.
Table S-5
CONTAMINANTS AT WESTERN PROCESSING
OCCURRING IN CONCENTRATIONS THAT COULD RESULT IN
EXCEEDANCE OF ADI'S
Soil
Groundwater
Lead
Chromium
Cadmium
Toluene
1,1,1-Trichloroethane
Bis (2-ethylhexyl)phthalate
Phenol
Cadmium
Chromium
Cyanide
Lead
Mercury
Note: Daily intake of the above contaminants would exceed
the ADI's as calculated using the concentrations of
these contaminants measured in the soil and ground-
water on the property and an assumed ingestion rate
of 0.1 gram soil/day or 2 liters water/day.
S-20
-------
RISK PRESENTED BY MILL CREEK
The risk presented by Mill Creek to human health was evalu-
ated based on the measured levels of carcinogens and dis-
solved metals in the creek water and an assumed ingestion
rate. Given an ingestion rate of 2 liters of water per day,
none of the ADI's for metals would be exceeded by drinking
Mill Creek water. The risk presented by carcinogens in Mill
Creek was estimated assuming a lifetime use of the water as
drinking water. It was estimated that one person in 10,000
who used Mill Creek as a lifetime drinking water source would
get cancer because of the ingestion of carcinogens. Because
Mill Creek is not used as a drinking water source, the risk
is hypothetical in these scenarios. A more probable future
use of Mill Creek is recreational use. Exposure resulting
from recreational use of Mill Creek would not lead to health
risks.
Concentrations of dissolved metals in Mill Creek exceed the
water quality criteria for protection of aquatic life.
Table S-3 shows the contaminant concentrations found in Mill
Creek and compares them with the criteria for protection of
aquatic life. It is reasonably certain that some aquatic
species found in Mill Creek could not remain near Western
Processing without being adversely affected by the metals
contamination. Concentrations of organic priority pollu-
tants in Mill Creek are generally not high enough to ad-
versely affect aquatic organisms.
DESCRIPTION OF EXAMPLE REMEDIAL ACTION ALTERNATIVES
Given the nature and extent of contamination on and off the
property and the environmental and human health risks that
the contamination poses, a comprehensive list of possible
remedial action technologies that could be used to remedy
the contamination was developed. The technologies were
identified from a literature review and knowledge of remedial
actions undertaken at other uncontrolled hazardous waste
sites. An initial screening was conducted to identify the
technologies that are proven and most applicable to the prob-
lems at Western Processing. The technologies that were se-
lected through the screening process are listed in Table S-6.
The types of problems existing at Western Processing were
then categorized as follows:
o Potential direct human and animal contact with
contaminants from Western Processing
o Past and potential future contaminated surface
water runoff
S-21
-------
Table S-6
TECHNOLOGIES AVAILABLE FOR USE IN EXAMPLE REMEDIAL
ACTION ALTERNATIVES
A. Surface Caps
o Sprayed asphalt
o Portland cement concrete
o Bituminous concrete (asphalt)
o Gravel over geotextile over clay
o Loam over synthetic membrane over sand
o Loam over clay
o Loam over sand over synthetic membrane over
clay (RCRA cap)
B. Groundwater Containment or Diversion Barriers
o Soil-bentonite slurry wall
o Cement-bentonite slurry wall
o Grout curtain
C. Groundwater Pumping
o Well points
o Deep wells
D. Soil Excavation
E. Sediment Removal
o Mechanical dredging
F. Groundwater Treatment
o Aerobic treatment systems
o Neutralization
o Precipitation
o Cyanide oxidation
o Organic chemical oxidation
o Reduction
o Organic chemical dechlorination
o Molecular chlorine removal
o Flow equalization
o Activated carbon
o Ion exchange
o Membrane processes
o Liquid/liquid extraction
o Filtration
o Air stripping
o Steam stripping
o Offsite treatment at a commercial facility
G. Groundwater Disposal
o Discharge to a publicly owned treatment works
(Metro)
o Discharge to Mill Creek
o Discharge to the Green River
o Shallow reinjection
H. Soil Disposal
o Offsite landfill
o Onsite landfill
o Offsite incineration
I. Mill Creek Diversion
o Piped gravity bypass
o Ditches and trenches (new channel)
o Pump and pipe system with diversion dam
S-22
-------
o Infiltration and subsequent leaching of contami-
nants from the unsaturated zone into the
groundwater.
o Contaminated groundwater quality beneath the
Western Processing site.
o Contamination of Mill Creek via groundwater migrat-
ing from the site to levels that exceed background
or ambient water quality criteria levels.
The list of suitable technologies was then used to develop a
set of remedial action components that were determined to be
particularly suitable for these problems. The remedial action
components and the problems they address are shown in
Table S-7.
Table S-7
REMEDIAL ACTION COMPONENTS
Component
Surface cap
Excavation (and disposal)
Groundwater extraction, treatment,
and disposal
Diversion barrier
Mill Creek sediment removal
Problem Addressed
Direct contact with con-
taminants, infiltration,
contaminated runoff
Contaminant leaching
from unsaturated zone,
direct contact with con-
taminants, contaminated
runoff, source materials
below the groundwater
table
Groundwater contamina-
tion, contaminant dis-
charge to Mill Creek
Contaminant discharge to
Mill Creek
Direct contact of aquatic
organisms with chemicals
adhering to or released
from contaminated
sediments
The unsaturated zone is that subsurface area between the
land surface and the top of the groundwater table.
S-23
-------
In addition, a sixth component, monitoring, was identified
as necessary to evaluate the effectiveness of any remedial
action undertaken to mitigate problems at the Western Pro-
cessing site.
As can be seen, none of the remedial action components is
capable by itself of addressing all the problems at Western
Processing. Therefore, to provide a comprehensive remedial
action, some or all of the components must be combined.
As an example of the comprehensive actions that might be
appropriate at Western Processing, four example remedial
action alternatives were identified for evaluation as part
of the Feasibility Study by combining different remedial
action components. A remedial action plan developed and
evaluated by the potentially responsible parties was in-
cluded as part of the Feasibility Study as an additional
example alternative. The PRP plan was developed to meet a
different set of goals that included returning the site to
productive, unrestricted use (see Appendix A to this study).
CERCL (Superfund) allows expenditures only to protect public
health and the environment. "No action" alternatives for
the on- and off-property areas and for Mill Creek were also
identified for a total of seven example alternatives.
The purpose of developing these example alternatives was to
show a range of actions that could be taken at the site from
"no action" (leaving the site as it is) to one that removes
most of these contaminants. Not all possible remedial action
alternatives were identified. No one example alternative is
recommended over another, and the remedial action technologies
can be recombined to create other acceptable example alterna-
tives . Any alternative selected as the final remedial action
would be further refined during final design. The seven
example alternatives are described below. Table S-8 summa-
rizes the remedial action components included in each of the
example alternatives.
EXAMPLE ALTERNATIVE 1: NO ACTION
A no-action example alternative was evaluated because it
provides a baseline for comparison with the other alterna-
tives. This alternative consists of leaving the property as
it is and taking no further action to control or remove con-
taminants from on or off the property. Under this alter-
native, the site problems described under the nature and
extent of contamination and the endangerment assessment would
remain.
S-24
-------
Table S-8
SUMMARY OF COMPONENTS INCLUDED IN EXAMPLE ALTERNATIVES
Example
Alternative
1
2
Excavation/
Disposal
None
None
108,000 cubic
yards of on-
and off-
property soil;
disposal in
on-property
double-lined,
RCRA landfill.
75,000 cubic
yards of on-
property
soil; dis-
posal in off-
site double-
lined, RCRA
landfill.
300,000 cubic
yards of on-
and off-
property soil
disposal in
offsite
double-lined,
RCRA landfill
Groundwater Diversion Mill Creek
Extraction/Treatment Barrier Surface Cap Sediment Removal
b
None None None None
b
Well point system on None On and off None
and off-property property
b
Well point system None On and off None
around landfill peri- property
meter; on-property
treatment plant
Well point system on Around On property See Example
property; on- or off- property Alternative 7
property treatment perimeter
plant
b
Well point system None None None
around perimeter of
property and exca-
vation; on-property
treatment plant
None
None
None
None
None
None
None
None
None
1,700 cu yd
All example alternatives also include monitoring to evaluate effectiveness of the
actions.
b
It is assumed that Example Alternatives 6 and 7 would be combined with Example Alterna-
tive 1, 2, 3, or 5 to provide a complete remedial action.
S-25
-------
EXAMPLE ALTERNATIVE 2: SURFACE CAP AND GROUNDWATER PUMPING
AND TREATMENT
Figure S-ll shows a plan view of the components of this ex-
ample alternative. It includes a cap over the property and
portions of off-property Area V, and a groundwater extraction
(pumping) system and treatment plant. Example Alternative 2
would take approximately one year to construct. The ground-
water pumping and treatment system would operate for at least
30 years.
The surface cap would be approximately 5 feet thick and con-
sist of the following layers: topsoil (24 inches thick),
geotextile filter, sand (12 inches thick), impermeable syn-
thetic membrane, and compacted clay (24 inches thick). The
groundwater extraction system consists of 9 pumps withdrawing
groundwater from 340 well points located under the cap and
in an area to the north of the property. The pumped ground-
water would be collected and treated at a treatment plant
located in the northwest corner of the property. The treat-
ment system would consist of a four-step process involving
the following:
o Air stripping to remove volatile organics
o Lime precipitation to remove heavy metals and
organics
o Oxidation of organics using hydrogen peroxide
o Granular activated carbon adsorption to remove
additional organics
Following treatment, the groundwater would be discharged
into a Metro sanitary sewer.
EXAMPLE ALTERNATIVE 3; EXCAVATION WITH ONSITE DISPOSAL,
SURFACE CAP, GROUNDWATER PUMPING AND TREATMENT
Figure S-12 shows a plan view of the components of this ex-
ample alternative. It includes excavation of on-property
soil within the unsaturated zone (an average of 6 feet
deep), disposal of the excavated soil in an onsite landfill,
construction of a cap over the landfill and areas to the
east and west of the property, and a groundwater pumping and
treatment system. Example Alternative 3 would require approx-
imately 4 years to construct with the groundwater pumping
and treatment system operating for at least 30 years.
A total of about 108,000 cubic yards of soil would be exca-
vated. The landfill would have to be constructed in stages,
and soils excavated during each stage would have to be tem-
porarily stockpiled on the property before they could be
S-26
-------
DISCHARGE TO
EAST DRAIN
GROUNDWATER
EXTRACTION
SYSTEM
WESTERN PROCESSING
LIMITS OF SURFACE CAP
COLLECTION SYSTEM FOR
GROUNDWATER EXTRACTION
WELLS, ARROWS INDICATE
DIRECTION OF FLOW
- CONCRETE LINED DRAINAGE
DITCH OR DRAIN LINE,ARROWS
INDICATE DIRECTION OF FLOW
GROUNDWATER
TREATMENT
PLANT AREA
RUNOFF CATCH
BASINS
12" SANITARY
SEWER LINE
DISCHARGE TO
SEWER LINE
TIMBER UTILITY POLE
(REROUTED)
STEEL UTILITY POLE
OLD SANITARY
DISCHARGE LINE
DISCHARGE TO
MILL CREEK
AREA 1
BOUNDARY
8" SANITARY
SEWER LINE
I I
NOT TO SCALE
FIGURE S-11
CONCEPTUAL SITE PLAN
FOR EXAMPLE ALTERNATIVE 2:
SURFACE CAP/
GROUNDWATER PUMPING
AND TREATMENT
S-27
-------
INTERURBAN TRAIL
BURIED UTILITIES
(WATER, GAS, TELEPHONE)
LIMITS OF EXCAVATION,
BASE LINER, AND ONSITE
LANDFILL DISPOSAL
LIMITS OF SURFACE CAP
COLLECTION SYSTEM FOR
GROUNDWATER EXTRACTION
WELLS, ARROWS INDICATE
DIRECTION OF FLOW
GROUNDWATER
TREATMENT
PLANT AREA
CONCRETE LINED DRAINAGE
DITCH OR DRAIN LINE.ARROWS
INDICATE DIRECTION OF FLOW
DISCHARGE TO
SEWER LINE
12"
SANITARY
SEWER LINE
RUNOFF CATCH
BASINS
DISCHARGE TO
MILL CREEK
TIMBER UTILITY POLE
STEEL UTILITY POLE
OLD SANITARY
DISCHARGE LINE
8" SANITARY
SEWER LINE
AREA1
BOUNDARY
NOT TO SCALE
FIGURE S-12
CONCEPTUAL SITE PLAN
FOR EXAMPLE ALTERNATIVE 3:
EXCAVATION WITH ON-PROPERTY
LANDFILL DISPOSAL/
GROUNDWATER PUMPING AND
TREATMENT/SURFACE CAP
S-29
-------
placed in the landfill. The landfill would have a bottom
liner and a cap so that the contaminated soil would be com-
pletely isolated within the landfill. The cap would consist
of layers similar to the layers described for the cap in
Example Alternative 2. The liner system would consist of
the following components, starting from the bottom: a
24-inch clay liner overlain by a synthetic membrane, a
12-inch sand layer containing a leak detection and removal
system, a primary synthetic membrane liner, a 12-inch sand
layer containing a leachate collection and removal system,
and a geotextile fabric filter.
The groundwater pumping and treatment system would be simi-
lar to the system proposed for Example Alternative 2, except
that fewer well points would be used and would be located
around the perimeter of the landfill.
EXAMPLE ALTERNATIVE 4; POTENTIALLY RESPONSIBLE PARTIES'
REMEDIAL ACTION PLAN
Figure S-13 shows a plan view of Example Alternative 4. It
consists of six main components: a multi-depth excavation,
groundwater pumping and treatment, a subsurface diversion
barrier, a surface water infiltration system, an asphalt/
concrete cap, and removal of sediment from Mill Creek. The
remedial action proposed for Mill Creek is the same as in
Example Alternative 7. It would take approximately 8 years
to complete Example Alternative 4.
The purpose of the excavation program is to remove the most
highly contaminated soil. A total of about 75,000 cubic
yards of contaminated soil would be excavated to depths rang-
ing from one to 8 feet below the surface of the property.
Excavated soils would be disposed of offsite in a USEPA-
permitted, double-lined RCRA hazardous waste landfill. The
excavated areas would be filled with imported soil.
The surface water infiltration system, which would operate
during the groundwater pumping period, would allow precipi-
tation to percolate into the unexcavated soil in the unsatu-
rated zone. As it moves toward the groundwater, this infil-
trating precipitation would pick up contaminants and carry
them into the groundwater. These contaminants would then be
removed along with other contaminants in the groundwater by
the pumping system. The groundwater pumping and treatment
system would be similar to the system in Example Alterna-
tive 2 and would operate for a period of up to five years.
This alternative was developed, described, and evaluated by
the potentially responsible parties.
S-31
-------
A diversion barrier would be installed around the property
to a depth of 40 feet. The barrier would have two purposes.
During operation of the pumping system, the barrier would
prevent groundwater around the property from being drawn
directly into the well points. It would instead allow the
pumping system to draw groundwater from the deeper portions
of the aquifer up through the contaminated soil in the upper
portion of the aquifer. As this water is drawn upward
through the soil, it would flush contaminants from the soil
and allow them to be removed by the pumping system.
After the pumping system is removed, the diversion barrier
would slow the rate of any potential residual contaminant
migration from the property by 50 percent, thereby reducing
the concentration of contaminants potentially migrating from
the property. This effect is important for the protection
of Mill Creek.
After the groundwater pumping system is dismantled, an
asphaltic concrete pavement would be laid over the site.
EXAMPLE ALTERNATIVE 5; EXCAVATION WITH OFFSITE DISPOSAL,
DEWATERING, GROUNDWATER TREATMENT
Figure S-14 shows a plan view of Example Alternative 5. It
consists of soil excavation, groundwater pumping to dewater
the excavation, and subsequent groundwater treatment. The
excavation program would last four years. Soil excavation
would occur during five months of each year. The dewatering
system would operate throughout the four-year period.
About 300,000 cubic yards of contaminated soil would be re-
moved. The soil on the property would be excavated to a
depth of 15 feet below the land surface which is 9 feet
below the water table. Excavation off the property would
range to depths of from one to 3 feet. All excavated soils
would be disposed of at a USEPA-permitted, double-lined,
RCRA hazardous waste landfill, and the excavated areas would
be filled with imported soil.
Because the lower 9 feet of the 15-foot excavation would be
below the water table, groundwater would have to be prevented
from accumulating in the excavations. This water would be
removed by a well point system installed around the perimeter
of the property with localized dewatering of the excavation
and treatment in an onsite treatment plant. The treatment
system would be similar to that used in Example Alternative 2.
EXAMPLE ALTERNATIVE 6; MILL CREEK NO ACTION
Under this example alternative, no remedial action would be
taken within Mill Creek. However, the main source of water
S-32
-------
D
o
LEGEND:
Diversion Barrier to —17.0' MSL
Site Excavation (Elevation Varies).
Fill and Post-Pumping Pavement
Well Point System and Direction of Flow
Precast Catch Basin
Surge Tank
Pump
Flow Restrictor
r- Outfall Line to Mill Creek
To Onsite or
Offsite Treatment
Plant
Ditch
Railroad
150
Scale in Feet
300
s-s:
FIGURE S-13
SITE PLAN FOR
EXAMPLE ALTERNATIVE 4
WESTERN PROCESSING
Kent, Washington
-------
RAILROAD
BURIED UTILITIES
(WATER.GASJELEPHONE)
PERIMETER
DEWATERING
SYSTEM
INTERURBAN TRAIL
i
AREA OF
15' EXCAVATION
AND BACKFILL
AREA OF
3' EXCAVATION
AND BACKFILL
STEEL UTILITY POLE
DEWATERING
TREATMENT PLANT
AREA
TIMBER UTILITY POLE
(REROUTED)
AREA 1
BOUNDARY
12" SANITARY
SEWER LINE
DISCHARGE LINE
TO METRO SYSTEM
OLD SANITARY
DISCHARGE LINE
8" SANITARY
>"SEWER LINE
FIGURE S-14
CONCEPTUAL SITE PLAN
FOR EXAMPLE ALTERNATIVE 5:
EXCAVATION ABOVE AND BELOW
GROUNDWATER TABLE WITH
OFF-SITE DISPOSAL
S-35
-------
quality degradation in Mill Creek is the contaminated ground-
water discharging to the creek from Western Processing.
Therefore, measures such as those proposed in Example Alterna-
tives 2, 3, 4, and 5 that control or reduce the source of
contaminant leaching to the groundwater and improve ground-
water quality would substantially reduce contamination in
Mill Creek. After an effective source control action, how-
ever, contaminated sediments would remain in the creek and
continue to release contaminants into the creek water. Con-
taminated sediment would be present for approximately 5 to
10 years after contaminated groundwater stops discharging to
the creek.
ALTERNATIVE 7; MILL CREEK SEDIMENT REMOVAL
This example alternative involves removing the top 12 inches
of sediments from a segment of Mill Creek approximately
2,300 feet long. In all, approximately 1,700 cubic yards of
material would be removed. Construction of this alternative
would require the temporary diversion of Mill Creek. Fig-
ure S-15 shows the location of the diversion pipeline and
diversion structures (dams). The stream segment between the
point of diversion and the discharge location would be de-
watered and dredged. Costs are based on excavated materials
being disposed of in a USEPA-permitted, double-lined, RCRA
hazardous waste landfill. The channel would be rebuilt with
gravel riffles to allow natural processes to return it to
preexcavation conditions. The stream banks would be replanted
with native vegetation.
ALTERNATIVES EVALUATION
Each of the seven alternatives described above was evaluated
for the following:
o Technical feasibility and effectiveness
o Consistency with governmental laws, regulations,
and policies
o Impacts on the environment and human health
o Costs of construction and operation
Table S-9 summarizes the results of this evaluation of the
example alternatives. The areas used in this table to de-
scribe and evaluate the scope of each example alternative
are identified on Figure S-16. The example alternatives
presented in this report (except the no action alternatives)
are effective in reducing risks to public health and the
environment. A major difference is the length of time neces-
sary to achieve the remedy. A 30-year period has been used
as a reference time for comparing the relative effectiveness
S-37
-------
of the example alternatives. Performance beyond 30 years is
discussed for those alternatives that have not achieved cri-
teria by that time.
S-38
-------
cn
I
OJ
DIVERSION
PUMP STATION
FIGURE S-15
PLAN VIEW OF MILL CREEK
DIVERSION BERMS AND
TEMPORARY PIPELINE
-------
Table S-9
SUMMARY OF PUBLIC HEALTH, ENVIRONMENTAL,
AND TECHNICAL EVALUATIONS
Example
Alternative
Cost (Millions)
Present
Worth
Capital
-0-
cn
Public Health
Aspects
On-property contamination
(soils up to 12 feet deep)
would continue to have poten-
tial maximum lifetime excess
cancer risk (worker scenario)
of 5 x 10~4.
Groundwater contamination from
Western Processing would pose
no threat to City of Kent or
any other public water supply
wellflelds.
The concentrations of organic
and inorganic (metal) contam-
inants In the groundwater
Immediately below Western Pro-
cessing exceed drinking water
standards and Acceptable Dally
Intake (ADI) levels. Ingestion
of this groundwater over a
40-year period could lead to a
maximum lifetime excess cancer
risk (worker scenario) of
2 x 10 . However, the shallow
aquifer is not used for water
supply.
Environmental
Aspects
Priority pollutant metal con-
centrations In Hill Creek down-
strean of Western Processing
exceed chronic and acute am-
blent water quality criteria
for aquatic organisms. These
•etal concentrations probably
are and would continue to be
toxic to a wide variety of aqua-
tic organises for hundreds of
years.
Priority pollutant organic con-
centrations in Mill Creek down-
stream of Western Processing
do not exceed ambient water
quality criteria for aquatic
organisms.
Sediments In Mill Creek con-
tain high levels of priority
pollutant metals.
Technical
Aspects
Stormwater runoff would be in
contact with contaminated soils
and could carry contamination
from the site onto adjacent
areas and Into Mill Creek.
Infiltration would continue to
leach contaminants from the un-
saturated zone and carry then
into the groundwater beneath
the site.
Contaminated groundwater from
Western Processing would con-
tinue to discharge into Mill
Creek at 50 to 70 gpn. Ground-
water quality beneath the site
would Improve only very slowly
(I.e., would require well be-
yond hundreds of years to
achieve levels that would not
adversely Impact Mill Creek
water qualIty).
Other
Sine* 1983, three major re-
sponse/remedial actions at
Western Processing have
stopped the discharge of con-
taminated runoff from the pro-
perty to Mill Creek and
removed waste materials and
all structures from the sur-
face of the property. These
actions have eliminated poten-
tial hazards such as fires,
explosions, and spills or
leaks of waste materials.
Future use of the site i
restricted by local
authorities.
ay be
Recreational use of Mill Creek
would not pose a threat to hu-
man health.
Multimedia cap over
Areas I and II, and a
portion of Area V (pro-
vides two layers to pre-
vent infiltration).
Controlled stormwater
discharge from capped
areas Into Mill Creek
Groundwater pumping from
Areas I, II, V and IX,
onsite treatment and
$12.2 S30.2 Would eliminate direct human
and animal contact with contam-
inated surface soils in capped
Average areas; however, all soils
annual would remain In place.
opera-
tion & Drinking water standards and
•a Inten- ADI's for organlcs In the
ance groundwater under the site
cost/ would be met In less than
SI.67 15 years of pumping; SNAPL's*
for longer terra use would not
be met until after approxl-
Once pumping begins. Mill Creek
waters would approach ambient
water quality criteria or back-
ground (whichever is higher)
for dissolved metal contami-
nants. Contaminants adhering
to Mill Creek sediments and
gradually leaching back into
Hill Creek waters may delay
achieving ambient water qual-
ity criteria or background.
Would eliminate contaminated
The pumping system would elim-
inate discharge of contami-
nated groundwater to Mill
Creek from Areas I, II, V,
and IX during the pumping
period.
An extremely long pumping,
treatment, and systems main-
tenance period would be re-
quired before water quality
criteria, standards, or back-
ground levels could be met In
Would comply with RCRA techni-
cal requirements for closure
as an existing land disposal
facility.
The groundwater extraction rate
would be limited primarily by
sewer system capacity and se-
condarily by the permeability
of the soils.
NOTE: See Figure S-16 for locations of Areas I through X.
•Suggested No Adverse Response Level(s).
-------
Table S-9
(continued)
Example
Alternative
Cost (Millions)
Present
apltal Worth
Public Health
Aspects
Environmental
Aspects
Technical
Aspects
Other
cn
i
discharge into Metro
system (100 gpm)
Monitoring
Health and safety plans
and training prior to
construction
Excavate all unsaturated
soils (108,000 cubic
yards) In Areas I and II
and one foot in a portion
of Area VIII, with dis-
posal In new 11-acre,
double-lined, RCRA on-
slte landfill.
Multimedia cap over
landfill (Area II,
Area II, and a portion
of Area V (see Example
Alternative 2).
Controlled stonnwater
discharged from capped
areas into Hill Creek
$16.3
Average
annual
O&M
cost:
SI.69
mately 40 years of pumping.
Achieving federal drinking
water standards in the ground-
water for metal contaminants
would be much more difficult.
For example, it would require
well beyond 100 years of pump-
ing to achieve the cadraiun
standard, while the standard
for lead may never be
achieved.
Mould eliminate direct human
and animal contact with con-
taminated soils in capped
areas and in Area VIII.
Ability to achieve drinking
water standards, ADI's, and
SNARL's for organic and inor-
ganic (metal) contaminants In
groundwater beneath the site
would be essentially identical
to Example Alternative 2.
stormwater discharges from
capped area.
Approximately 60 to 120 years
of groundwater pumping would
be required to reduce the con-
centrations of metals In the
groundwoter to levels that
would not cause continued de-
gradation of Mill Creek after
the pumping system is turned
off.
Water quality problems in Mill
Creek upstream of Western Pro-
cessing, such as low dissolved
oxygen levels, could continue
to limit the habitat quality
in Mill Creek.
Mould be identical to Example
Alternative 2.
Mill Creek after the pimping
system Is turned off.
Cap would prevent infiltration
and leaching of contaminants
from the unsaturated zone in
Areas I, II, and V Into the
groundwater. Effective cap
lifetime in this application
is not known.
Would require permanent access
to some adjacent properties.
Would require a 12-month con-
struction period. Cap would
require relatively complex con-
struction techniques.
Construction impacts could be
mitigated by good construction
practices, dust and runoff con-
trols, and scheduling.
Would eliminate discharge of
contaminated groundwater from
Western Processing to Hill
Creek while the pumping system
Is operating.
Like Example Alternative 2, an
extreacly long post-construction
pumping, treatment, and site
maintenance period would be re-
quired before water quality
standards, criteria, or back-
ground levels could be met In
Mill Creek after the pumping
system is turned off.
Would require the same type of
access as In Example
Alternative 2.
Future use of the capped areas
would be prohibited.
Would comply with RCRA techni-
cal standards for construction
and closure of a new hazardous
waste landfill.
Materials to be excavated have
not yet been classified under
the WDOE Dangerous Waste Regu-
lations. No "Extremely Hazard-
ous Haste" may be landfllled
within Washington State,
Certain excavated materials
such as PCBs, burled drums,
and concentrated wastes would
require special banding and
possibly disposal procedures.
Future use of the landfill and
capped areas would be
prohibited.
-------
Table S-9
(continued)
Example
Alternative
Cost (Millions)
Present
apital North
Public Health
Aspects
Environnental
Aspects
Technical
Aspects
CO
I
Continued
GrounoVater pumping
a round 1and fill and In
portions of Areas II
and V, onslte treat-
ment, and discharge
Into Metro system
(85 gpn>
Monitoring
Health and safety plans
and training prior to
construction.
Landfill liners and leachate
collection system, when com-
bined with the cap, would pro-
vide more protection from
contaminant leaching from un-
saturated zone Into the ground-
water than Example Alterna-
tive 2. Effective landfill and
cap lifetime In this applica-
tion is not known.
The landfill would be con-
structed in phases, with the
excavated material stored on-
slte. This would be very dif-
ficult, but not impossible, to
accomplish on the limited
(11-acre) space on Area I.
Would require 48-month construc-
tion period. Cap and landfill
would require relatively com-
plex construction techniques.
The landfill and cap combina-
tion would Isolate approxi-
mately 60 percent of both the
zinc and total contamination
in the soil.
Construction Impacts could be
mitigated by good construction
practices, dust and run-off
controls, and scheduling.
The PRP Proposal*
Excavate to variable
depths (I1 to 8') in
Area I
$45,4
Average
annual
O&M
cost:
SI.9
$48.9 Would eliminate direct human
and anlnal contact with all
surface soils In Area I.
API's, drinking water stan-
dards, and SNARL's for all
except one Indicator organic
Both during and after up to
5 years of pumping, Mill Creek
water quality should be able
to meet ambient water quality
or background levels for all
Western Processing-related
contaminants. Water quality
Once the diversion barrier Is
Installed, the discharge of
contaminated groundwater to
Mill Creek from Area I would
be reduced by approximately
50 percent.
Does not address off-property
contamination other than off-
property contaminated ground-
water (which could potentially
be removed during the pumping
program). Off-property reme-
dial actions such as those
•Summary prepared by PRPs.
-------
Example
Alternative
Continued
Cost (Millions)
Present
Capital Worth
Punlir Health
Aspects
Table S-9
(continued)
Environmental
Aspects
Technical
Aspects
Other
cn
i
Offslte disposal of all
excavated material
(75,000 cubic yards) in
a double-lined ROW
landfill
Replace excavated mater-
ial with Imported fill
Diversion wall, 40 feet
deep. Inside the perim-
eter of Area I
Groundwater pumping and
stormwater infiltration
in Area I for up to
5 years, onslte or off-
site treatment, dis-
charge to Metro or the
Green River (100 gpm)
Asphalt pavement over
Area I upon completion
of pumping
Monitoring
Health and safety plans
and training prior to
const ruction
would he met within up to
5 years of pumping. Drinking
water standards for metals
could not be met even If the
pumping program were extended
indefinitely.
problems In the creek not re-
lated to Western Processing
would continue.
Once pumping starts, the dis-
charge of all contaminated
groundwater from Area I would
be prevented.
The potential for discharge of
contaminated stornwater runoff
from Area I would be eliminated.
The Infiltration system that
would operate during the pump-
Ing program would provide addi-
tional contaminant removal from
the Area I unsaturated zone.
Would require 24-month construc-
tion period. Installation of
diversion barrier would require
relatively complex construction
techniques.
Construction Impacts could be
mitigated by good construction
practices, dust and runoff con-
trols, and scheduling.
Would remove 70 percent of con-
taminants from the unsaturated
zone including 68 percent of
the zinc contamination in
Area I.
described In the other example
alternatives would be one of
the subjects of negotiations.
The groundwater extraction
rate for this alternative Is
primarily limited by consi-
derations related to reducing
total groundwater treatment
requirements and secondarily
by soil conditions.
Double-lined landfill capacity
Is not currently available in
the Northwest but will be
available by mid-1985. The
disposal costs were estimated
to be $100 per ton, but could
vary substantially.
Property would be suitable for
future use.
Excavate 15 feet In
Areas I and II, 3 feet
in a portion of Area V
(including the old dis-
charge line), 3 fe**t in
Area IX, and 1 foot In a
portion of Area VIII.
Offsite disposal o( all
excavated material
(300,000 cubic yards)
In a double-lined RCRA
landfill
S180.3
Average
annual
06H Cost:
$0.1
Would eliminate direct human
and animal contact with all
surface soils contaminated by
Western Processing.
Would reduce concentrations of
organic contaminants In the
groundwater beneath Areas I
and II to or near drinking
water standards, ADI's, and
SNARL's for longer term use.
Lead levels will be reduced
Excavation would be suffi-
cient to allow the levels of
metals In Mill Creek, includ-
ing zinc, to permanently meet
ambient water quality criteria
or background, whichever is
higher.
Would eliminate contaminated
stornwater discharge to ground-
water and Mill Creek.
Most reliable and proven source
control alternative. Approxi-
mately 95 percent of all con-
tamination In soil would be
removed by excavation. Would
permanently eliminate contam-
inated groundwater discharges
to Mill Creek from Areas I
and II. The off-property ex-
cavations would reduce most
average metal concentrations
in soils to background.
Complies with RCRA technical
requirements for closure as a
storage facility.
Future property use would not
be restricted.
Double-lined RCRA landfill
capacity is not currently
available In the Northwest but
will be available by mid-1985.
The disposal costs were esti-
mated to be $100 per ton but
could vary substantially.
-------
Example
Alternative
Continued
Cost (Millions)
Present
apltal North
Table S-9
(continued)
Public Health
Aspects
Environmental
Aspects
Technical
Aspects
Replace excavated mate-
rial with Imported soil
Groundwater pumping for
excavation, dewatering,
onsite treatment, and
discharge to the Metro
system.
Monitoring
Health and safety plans
and training prior to
construction.
sufficiently to meet the
drinking water standard;
however, cadmium will not.
Water quality problems in Mill
Creek not related to Western
Processing would continue to
limit habitat quality.
20 months of excavation over a
4-year construction period.
Devatering and groundwater
treatment would continue dur-
ing months when excavation is
not occurring.
40,000 truck trips would be re-
quired to haul contaminated
material away from and Imported
material to the site.
Would require no operation or
maintenance activities other
than monitoring.
No permanent access would be
required.
Mill Creek No Action
(After Implementation of
Example Alternative 2,
3, 4, or 5)
None. Mill Creek sediments do
not pose a threat to human
health.
The Mill Creek sediments, which
are contaminated particularly
with metals as a result of sur-
face and groundwater discharges
from Western Processing, would
continue to be moved downstream
(and eventually dispersed and
diluted) by natural processes.
Contaminants on sediments could
adversely affect aquatic organ-
isms by leaching into the water
or by toxic effects on bottom
dwelling organisms.
Construction Impacts could be
mitigated by good construction
practices, dust and run-off con-
trols, transportation plans,
and scheduling.
With an effective source con-
trol action (such as Example
Alternative 2, 3, 4, or 5), It
would take from 5 to 10 years
for the contaminated sediments
to be transported out of the
local stream reach.
The source control would have
to remain effective for the
sediments to remain
uncontamlnated.
Modification of Mill Creek
above Western Processing as
part of Kent's drainage master
plan could change the effec-
tiveness of this example
alternative, as could the
Introduction of upstream
sources of contaminants.
Avoids the adverse impacts of
diversion and excavation.
Mill Creek Sediment
Removal (after implemen-
tation of Example Alter-
native 2, 3, 4, or 5)
SI.3
None. Mill Creek sediments
do not pose a threat to
human health.
All contaminated sediment In a
2,300-foot reach of Mill Creek
would be removed.
Monitoring of groundwater
quality and flow near the
creek would be necessary to
determine the optimal time to
Modification of Mill Creek
above Western Processing as
part of Kent's drainage master
plan could change the
-------
Alternative
Continued
Table S-9
(continued)
Cost (Millions)
Present
!apital Worth
Public Health
Aspects
Environmental
Aspects
Technical
Aspects
cn
i
Excavate and dispose of
sediment from the bed
and banks of Mill Creek
adjacent to and
1,300 feet downstream
of Western Processing.
(1,700 cubic yards)
Divert 2,300 feet of
Mill Creek into a pump-
and-plpe system during
excavation (approxi-
mately one month during
low flow season)
Rehabilitate stream bed
with gravel riffles and
natural vegetation
Monitoring
Resuspenslon and downstream
transport of contaminated sed-
iments during construction
would be prevented by divert-
ing the creek around the reach
to be excavated.
Excavation and diversion would
temporarily destroy 2,300 feet
of aquatic habitat.
Fish would not be able to pass
through this part of Mill Creek
during the one-month diversion.
After streambed excavation and
rehabilitation, water quality
problems upstream of Western
Processing, such as low dis-
solved oxygen levels, could
continue to limit habitat
quality In Mill Creek.
remove the contaminated
sediments.
The source control would have
to remain effective for the
sediments to remain
uncontamlnated.
One-month construction period.
No operation and maintenance
would be required.
effectiveness of this example
alternative, as could the
introduction of upstream
sources of contaminants.
-------
S-47
FIGURE S-16
ANALYSIS AREAS
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