VOLUME I
\
FEASIBILITY
STUDY FOP.
SUBSURFACE CLEAK7UP
WESTERN PROCESSING
KENT, WASHINGTON
EPA 37.0L16.2
March 6, 1985
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Chapter 4
ENDANGERMENT ASSESSMENT
4.1 INTRODUCTION
The objective of this endangerment assessment is to determine
the potential for human health and environmental impacts if
no action is taken on the Western Processing site. The as-
sessment that follows contains a brief description of the
site; the land use of the site and the surrounding area; a
description of the contaminants present in all environmental
media; and a toxicology summary of compounds characteristic
of site contamination. The exposure scenarios and resulting
quantitative risks are discussed separately for each envi-
ronmental medium.
4.2 SITE DESCRIPTION
The Western Processing site is located approximately 4 miles
north of the central business district of the City of Kent,
Washington. The site is currently zoned M-2, limited indus-
trial district, by the City of Kent. M-2 zoning requires a
minimum lot size of 20,000 square feet, maximum site
coverage of 65 percent, and building height may not exceed
35 feet. Principal uses allowed in an M-2 industrial zone
include: manufacturing, processing, treating, assembling
and packaging of products; printing, publishing, and allied
industries; warehousing and distribution; crop and tree
farming; scientific laboratories; administrative or exec-
utive offices; and warehousing with retail sales. Accessory
uses include: repair operations and commercial sales inci-
dental to the principally permitted use; dwelling units for
maintenance and security personnel; employee recreation fa-
cilities; restaurants or cafeterias in conjunction with the
principally permitted use; and temporary buildings for use
during construction of permanent buildings. Conditional
uses may include: commercial office, retail, and service
uses intended to serve the M-2 district; utilities and com-
munication facilities; and public facilities.
The properties to the north and south of the site are also
zoned M-2. Properties to the west are zoned M-l, industrial
park district, and those to the east are zoned M-3, general
industrial district. In general, uses allowed in each of
the industrial districts are similar except that M-3 zones
may include industrial uses such as sawmills, truck storage
yards, electroplating, and transit terminals. Development
standards are most restrictive in the M-l zone and least
restrictive in the M-3 zone (City of Kent, 1974).
The Western Processing site is bounded on the south by an
empty lot, sparsely vegetated by disturbed area species. On
4-1
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the western edge, Mill Creek runs across the northwestern
corner of the site in a northerly direction. A vacant
residence lies adjacent to the northwestern corner, west of
Mill Creek. Slightly further west is the Century Industrial
Park, which contains 15 businesses. The Fairway Building
lies just west of the industrial park and contains 10 busi-
nesses, including a truck and equipment storage center and
repair lot for a major communications firm. Directly north
of the site are vacant residences and an open vegetated lot.
The Interurban Trail lies east of the site on a former
railroad right-of-way that is adjacent to the Burlington
Northern Railroad tracks. A Weyerhaeuser complex, an unpaved
car lot for South Seattle Auto Auction, and a storage lot
for semis and tank trucks of Matlack are found east of the
railroad tracks. Figure 4-1 shows the site and surrounding
properties.
4.3 CONTAMINATION
Environmental media contaminated at the Western Processing
site include:
o Soils—both surface and at depth
o Groundwater
o Mill Creek water and sediments
Eighty-three USEPA priority pollutants were found in onsite
soils and 57 were found in onsite groundwater monitoring
wells. Surface waters are contaminanted primarily with
inorganics, all of which are USEPA priority pollutant
metals.
Chapter 3 described the nature and extent of contamination
in each medium. It also discussed the issue of tentatively
identified compounds in the environmental samples. Because
of the high uncertainty in the identity and concentrations
of these tentatively identified compounds, it has not been
possible to include them in this endangerment assessment.
Appendix D discusses the fate and transformation of the
indicator compounds or classes.
4.4 TOXICOLOGY AND EXPOSURE TO SITE CHEMICALS
The human health risk from exposure to chemicals at Western
Processing will result from the compound effects of exposure
to the multiple chemicals present. Simultaneous exposure to
a variety of chemicals could lead to a wide range of effects.
The potential for synergistic or potentiating effects exists.
In this endangerment assessment, however, risk is assumed to
be additive because the toxicological data are not adequate
to describe the synergisms or antagonisms of multiple chemi-
cal exposures. A total of 29 compounds known or suspected
to be human carcinogens were among the priority pollutants
(Table 4-1).
4-2
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COMMERCIAL SHEARING INC.
PRODUCTION SUPPLY CO.
, K6 SYSTEMS, INC.
CENTURY INDUSTRIAL PARK
Pacific Northwest Bell
Forbes
Cullen Bindery
T&E MFC
Industrial Screen Print
Hamilton Enterprises
Hose & Coupling Inc.
CNC Precision Machining
Coast Line Cabinets
Master Grinders
Century Battery Co.
Century Development
Wood World
Cascade Sawing and Drilling
S&S Amusement Co.
FAIRWAY BUILDING
Glen Supply Co
Puget Sound Woodworks
National Truck and Print Specialist
Law Office
Pacific Northwest Bell Truck and
Equipment Center
Evergreen Sign Co.
Thermal Tec.
Fairway Corp.
N.W Trailer and Equipment
C.W Grove & Son
SOUTH SEATTLE ,
AUTO AUCTION
MATLACK
TRUCK STORAGE
LOT
OFFICE/WAREHOUSE SPACE
FIGURE 4-1
EXISTING LAND USE
4-3
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Table 4-1
KNOWN AND SUSPECTED CARCINOGENS ON
EPA PRIORITY POLLUTANT LIST
Known Carcinogens
Found Onsitea
Arsenic
Benzene
Benzidine
Chromium
Vinyl chloride
Suspected Carcinogens
Found Onsite3
Aldrin
y-Benzene hexachloride(y-BHc)
b,c
Benzo(a)anthracene
Benzo(k)fluoranthene
Benzo(a)pyrene
Beryllium
Cadmium^
Chloroform
Chrysene
1,2-Dichloroethane
1,1-Dichloroethene
Dieldrin
2,4-Dinitrotpluene
Fluoranthene 'c
Hexachlorobutadiene ,
Indeno(l,2,3~cd) pyrene
N-nitrosodiphenylamine
Nickel
PCB
1,1,2,2-Tetrachloroethane
Tetrachloroethene
1,1,2-Trichloroethane
2,4,6-Trichlorophenol
Trichloroethene
dIARC, 1982.
bSax, 1984.
°Equivocal tumorigenic agent.
No evidence that the chemical is a human carcinogen via the
ingestion route, but a carcinogenic potential has been
associated with other routes.
eClayton and Clayton, 1981.
4-4
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Human exposure to contaminants onsite is dependent on the
environmental media in which the contaminant is present and
the present and future land uses of the site and surrounding
areas. Exposure may occur from ingestion, inhalation, or
dermal contact with soils; ingestion or contact with ground-
water; or ingestion or contact with surface waters, sedi-
ments, or organisms living in surface waters. The expo-
sure scenarios and resulting risks in each environmental
medium are discussed separately below.
4.5 SOILS
Data used for the assessment of risk from soil contamination
are presented in Chapter 3, Section 3.5, and all soil con-
taminant data are reported in dry weight concentrations un-
less otherwise indicated. Extensive regrading of the site
occurred during late 1984. The effect on surface soil con-
centrations and the reported depths for samples below the
surface are not known. For this assessment, it is assumed
that the concentrations reported in Chapter 3 are represen-
tative of the depths reported there. A listing was made of
all compounds that had reported concentrations greater than
the detection limit at onsite sampling points. Mean concen-
trations of inorganic compounds were screened against concen-
trations of each compound in the Kent Valley or in local
sediments (see Table 3-5). Compounds were not used in this
assessment of health and environmental impacts unless site
concentrations exceeded these expected background
concentrations.
Mean surface concentrations were then calculated for com-
pounds that were present in at least three surface sampling
points spread over the site, using the detection limit for
the concentration reported as non-detects. For some sample
concentrations that were not quantified, the concentrations
were reported as between the detection limit and five times
the detection limit. Doses were calculated using both con-
centrations to derive means.
Maximum concentrations were also used in the health risk
assessment and were obtained for both the surface soils and
from soils 0 to 12 feet deep. The maximum concentration for
soils at depth was used on the assumption that excavation of
the site during construction of structure foundations could
occur if no remedial action is taken on the site. This could
bring contaminated soil to the surface and it was assumed
that this soil would be left at the surface. It was further
assumed that the soil concentrations remain constant as a
worst case.
4-5
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The exposure scenario used in this assessment of risk from
soil contamination assumed soil ingestion and no change in
current land use patterns in the area. One scenario assumed
worker exposure only, as the site is presently industrial
and future use was assumed to be the same.
Although no study has shown adult soil ingestion during out-
door work or play (USEPA, November 1984) , Kimbrough et al.
(1983) estimated an adult soil ingestion rate of 0.1 gm/day.
This value has been used in this study, although it may be
an upper bound estimate. This provides a lifetime average
soil ingestion rate of 0.00082 gm soil per kilogram body
weight per day for exposure to carcinogens for a 70-kg person
with a 40-year exposure period and a 70-year lifetime. To
estimate the dose, this rate was multiplied by the ratio of
expected workdays with less than 0.01 inch of rainfall (148)
to the number of days in the year (NOAA, 1979-1983) because
it was assumed that soil ingestion could only occur on those
days. For noncarcinogens, the daily soil ingestion rate of
0.1 gm/day for adults was used.
A residential scenario for carcinogens was also considered.
Although it is unlikely that a zoning change to residential
would ever take place for the site, current zoning allows
dwelling units for maintenance and security personnel. Three
lifetime soil ingestion rates were developed for the resi-
dential scenario for exposure to carcinogens: 0.00048 g
soil per kilogram body weight per day (assumes child inges-
tion of 0.1 g/day for ages 2 to 6 and zero at all other
ages); 0.024 g/kg/day (assumes child ingestion of 5 g/day
for ages 2 to 6 and zero at all other ages); and 0.028 g/kg/
day (assumes soil ingestion rates from Kimbrough et al.,
1983). A soil ingestion rate of 0.1 g/day for adults and
one gram per day for children was used for noncarcinogens
(see Appendix E for the derivations). These rates were mul-
tiplied by the ratio of the expected days with less than
0.01 inch of rainfall (217) to the number of days in the
year to estimate the dose.
The risk assessment for carcinogens and dose estimate for
noncarcinogens were calculated using both the mean onsite
surface soil concentration and the maximum onsite surface
soil and soil-at-depth concentrations. The average concen-
trations were estimated using an area-weighted average of
the measured surface concentrations, based on Thies,sen poly-
gons. The estimated excess lifetime cancer risk, R, was
With the Thiessen polygon method, each point of the surface
is assigned the concentration of the closest sampling point.
2The excess lifetime cancer risk is the incremental increase
in the probability of getting cancer compared to the
background probability.
4-6
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calculated with the following model:
R = 1 - e'pd (4-1)
where
p = cancer potency (kg-day/mg)
d = dose (mg/kg/day)
Cancer potencies were obtained from USEPA's Carcinogen As-
sessment Group. These are derived from the upper limit of
cancer risk associated with a given exposure, and the actual
risk may be less.
The results of this analysis for the worker scenario are
shown in Tables 4-2 and 4-3 for the carcinogens found onsite
for surface soil and soils at depth, respectively. Ingestion
of site soil is estimated to lead to an excess lifetime can-
cer risk of 5 x 10~ using.the maximum concentrations in
surface soils, and 2 x 10 using the maximum concentrations
in soils at depth. The mean concentrations of surface soils
yield an excess cancer risk of 5 x 10~ . The prime con-
tributor to the cancer risk is PCB's. For the ingestion
rate of 0.00048 g/kg/day in the residential scenario, th|
excess lifetime cancer risks are estimated to be 1 x 10
for thefimaxinmm concentrations in soils 0 to 12 feet deep,
4 x 10 for the maximum observed surface concentrations,
and 4 x 10~ for the mean observed surface concentrations.
For the residential scenario with 0.024 g/kg/day soil intake,
the excess lifetime cancer risks are estimated to be
7 x 10 , 2 x 10 , and 2 x 10 , respectively. For the
residential scenario with 0.028 gm/kg/day intake, the excess
lifetime cancer risks are 8 x 10 , 2 x 10 , and 2 x 10 ,
respectively. These estimated cancer risks would increase
if all contaminants could be used in the derivation of risk,
but cancer potency values do not exist for the PAH compounds
found at Western Processing. Also potency values available
for benzene and vinyl chloride are derived on the basis of
worker inhalation exposure and animal inhalation studies,
respectively, and are not directly applicable to the inges-
tion pathway. Use of five times the detection con-
centrations for the trace compounds did not alter the total
cancer risk.
PCB's (reported here as the sum of concentrations of
reported mixtures) were also detected in six off-property
areas. Areas II and III had single reported sediment
concentrations of 3,510 and 1,170 ug/kg, respectively. Two
samples had detected concentrations in Area V (with 270 and
1,900 yg/kg). Of the six detected concentrations reported
in Area VI, four were reported in terms of wet weight (500,
1,000, 4,300, and 24,800 yg/kg) and two in terms of dry
weight (28.6 and 4,100 pg/kg). One sample of the Mill Creek
sediment near 196th Street had a reported PCB concentration
4-7
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Table 4-2
SUMMARY OF ONSITE SURFACE SOIL CONTAMINATION AND CANCER POTENCIES
FOR CARCINOGENS, WORKER SCENARIO
Fraction
Contaminant of Concern
Volatile Organics Trichloroethene
Base/Neutral
Benzo(a)anthracene
PCB
Chrysene
Fluoranthene
Maximum Observed Level
Cancer Potency
(kg-day/mg)
d
0.019
4.34
Concentration
(ug/kg)
37
884,000
3,300e
1,210,000
234,000
Lifetime
b
Average Dose
(pg/kg/day)
0.000012
0.30
0.0011
0.41
0.079
Mean Observed Level"
Cancer Risk Concentration
(x 10" ) (ug/kg)
0.0002 4.2
38,000
5 3106
50,000
25,000
Lifetime
b
Average Dose
(ug/kg/day)
1.4 x lo"6
1.1 x 10
1.0 x 10~
1.6 x lo"
7.1 x 10"
Cancer Risk
(x lo"6)
0.00001
0.5
I
oo
TOTAL 5 0.5
aU3EPA, December 1984..
b
Dose calculated from lifetime average soil ingestion rate of 0.00082 g/kg/day and exposure fraction = 0.41.
Mean concentrations calculated using detection limit for nonquantifiable but detected concentrations.
International Agency for Research on Cancer believes that there is inadequate evidence for classifying trichloroethene as a human carcinogen.
Sum of all PCBs.
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Table 4-3
SUMMARY OF ONSITE SOIL CONTAMINATION TO A DEPTH OF 12 FEET
AND CANCER POTENCIES FOR CARCINOGENS, WORKER SCENARIO
Maximum Observed Level
Fraction
Contaminant of Concern
Volatile Organics Benzene
Base/Neutral
Chloroform
Trichloroethene
Benzo (a) anthracene
PCB
Chrysene
Fluoranthene
Fluorene
a
Cancer Potency Concentration
(kg-day/mg) (yg/kg)
6,500
0.007 18,000
0.019 580,000
884,000
4.3 114,000
1,210,000
234,000
8,600,000
Lifetime
Average Dose Cancer Bisk
(pg/kg/day) (xlO~ )
0.0022
0.0061 0.04
0.19 4
0.29
0.038 200
0.41
0.079
2.9
TOTAL
200
USEPA, December 1984.
°Dose calculated from lifetime average soil ingestion rate of 0.00082 mg/kg/day and exposure fraction = 0.41.
"Mean concentrations calculated using detection limit for nonquantifiable but detected concentrations.
International Agency for Research on Cancer believes that there is inadequate evidence for classifying
trichloroethene as a human carcinogen.
2Sum of all PCBs.
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of 690 yg/kg. In Area IX, two sediment samples had reported
concentrations (2,000 and 37,200 yg/kg) and two detected
concentrations were reported in one bore hole: 13,900 yg/kg
at the surface and 121 yg/kg at 34 feet in depth. With the
same industrial use scenario as in Tables 4-2 and 4-3, the
excess lifetime cancer risks for the maximum_and mean observed
surface concentrations in Area VI are 4 x 10~ and 9 x 10~ ,
respectively, and in Area IX are 5 x 10~ and 3 x 10~ , re-
spectively. The excess lifetime cancer risks from the two
residential scenarios would be between 0.8 times (for the
0.00048 g/kg/day case) and 50 times (for the 0.028 g/kg/day
case) these risks. It should be noted that the sampling
locations in Area VI were not chosen randomly, but by proxi-
mity to stained surface soils without vegetation.
The calculated daily doses for noncarcinogenic compounds at
0.1 g soil per day are shown in Table 4-4 and Table 4-5 for
mean and maximum concentrations of surface soil and maximum
concentration of soils at depth. The daily doses of lead
and chromium (assuming hexavalent) exceed their acceptable
daily intakes (ADI). At one gram of soil per day, the cad-
mium concentration also exceeds its ADI. Because the ana-
lytical method that measured the inorganics in the soil
involved a total digest, it is not clear how much of the
inorganics are bioavailable. Several of the compounds
listed on Tables 4-4 and 4-5 do not have ADI values.
The maximum observed off-property, surface lead concentra-
tions are 1,300 mg/kg in Area II; 260 mg/kg in Area V;
270 mg/kg in Area VI; and 3,850 mg/kg in Area VIII (average
of duplicate samples). The 95th percentile on local back-
ground soil lead concentrations was 76 mg/kg. With the same
assumptions as in Table 3-5, the lead intake with these
maximum concentrations would be 0.13, 0.026, 0.027, and
0.38 mg/day, respectively. Areas II and VIII exceed the
lead ADI with the maximum soil concentrations. However,
assuming a higher ingestion rate of one gram per day.- the
ADI for lead is exceeded in all four areas.
Exposure pathways of dust inhalation, dermal contact with
contaminated soils, and inhalation of volatiles released
from soils were not examined quantitatively in this endan-
germent assessment. Determining the impact on humans from
dust inhalation requires data on a variety of factors, such
as particle size, wind speed, direction and pattern, and
Cancer risks were calculated only for those areas with
three or more reported surface detections.
4-10
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Table 4-4
SUMMARY OF ONSITE SURFACE SOIL CONTAMINATION AND CRITERIA FOR NONCARCINOGENS
Base/Neutrals Bis(2-ethylhexyl)phthalate
Acids
Inorganics
2,4-Dimethylphenol
Phenol
Antimony
Boron
Cadmium
Chromium
Copper
Cyanide
Lead
Nickel
Zinc
Acceptable
Daily
Intake
(mg/day)
42
7
0.29
b
0.17
0.175 (VI)
125 (III)
_..
7.6
0.1
1.5
Maximum Observed Level
Soil
Concentration
(mg/kg)
860
11
19
98
90
420
1,210
880
15
31,000
740
81,000
Calculated Dose at
0.1 g Soil /Day
(mg/day)
0.086
0.0011
0.0019
0.0098
0.009
0.042
0.12
0.088
0.0015
3.1
0.074
8.1
Soil Calculated Dose at
Concentration 0.1 g Soil/Day
(mg/kg) (mg/day)
120
4.4
4.8
13
65
48
310
320
3.1
5,700
150
12,000
0.012
0.00044
0.00048
0.0013
0.0065
0.0048
0.031
0.032
0.00031
0.57
0.15
1.2
Mean concentrations calculated using detection limit for nonquantifiable but detected concentrations.
Oral threshold effect level for smokers.
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Table 4-5
SUMMARY OF ONSITE SOIL CONTAMINATION TO A DEPTH
OF 12 FEET AND CRITERIA FOR NONCARCINOGENS
Fraction
Volatile Organics
Base/Neutrals
Acids
Inorganics
Contaminant of Concern
1 , 1-Dichloroethane
Etbylbenzene
Toluene
1,1, 1-Trichloroethane
Trichlorofluorome thane
Bis (2-ethylhexyl)phthalate
1 , 2-Dichlorobenzene
Di-n-butyl phthalate
Di-n-octyl phthalate
2 ,4-Dicblorophenol
2 ,4-Dimethylphenol
Pentachlorophenol
Phenol
Antimony
Boron
Cadmium
Chromium
Copper
Cyanide
Lead
Nickel
Selenium
Zinc
Acceptable
Daily
Intake
(mg/day)
___
1.6
30
38
42
___
88
7
—
2.1
7
0.29
0.173
0.175 (VI)
125 (III)
__.
7.6
0.1
1.5
— _
— — —
Maximum Observed Level
Soil
Concentration
(mg/kg)
18
37
394
174
0.073
860
565
2.6
29
7.9
11
17
27
130
240
420
7,600
5,700
179
141,000
1,900
30.5
81,000
Calculated Dose at
0.1 g Soil/Day
(mg/day)
0.0018
0.0037
0.0394
0.0174
0.0000073
0.086
0.0565
0.00026
0.0029
0.00079
0.0011
0.0017
0.0027
0.013
0.024
0.042
0.76
0.57
0.0179
14.0
0.19
0.00305
8.1
Oral threshold effect level for smokers.
4-12
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distance to receptors. These data were not available. Risk
would increase to persons who spend most of their working
day out of doors and downwind of the site (prevailing wind
direction is from the south). Dermal contact with contami-
nated soils would be expected also to increase the potential
public health risk.
Inhalation of volatiles from disturbance of soils below the
surface would be expected to increase the overall exposure
from the site. Many of the volatile compounds, however, are
present only in soils at depth. During the remedial inves-
tigation, site personnel measured air organic concentrations
above background (about one ppm with the HNU) in the breathing
zone only when near drums. All surface drums have been re-
moved from the site. HNU readings of split-spoon samples,
which approximate the condition of freshly exposed soil,
were as high as 1,500 ppm, but more generally were below
10 ppm.
4.6 GROUNDWATER
Data used for the groundwater contamination assessment are
presented in Chapter 3, Section 3.6. No known major water
supplies are currently affected by the site. The nearest
municipal wells, serving the City of Kent, are approximately
6,500 feet to the southeast, hydraulically upgradient. Two
domestic wells (T23NR4E36N and T22NR4E2H1), whose condition
and use are unknown, are located about 2,000 feet regionally
downgradient at the site (Hart Crowser, 1984). Based on the
current conceptual model of the groundwater flow system
(Section 3.3), contaminated groundwater from Western Pro-
cessing does not move to the west beyond Mill Creek. If
contaminants do move under the creek, then the two domestic
wells, if still in use, may eventually become contaminated.
Data used in this assessment are from onsite monitoring wells
only. Site averages were calculated for each compound that
was present in at least 5 of the 32 monitoring stations
(28 well stations with four stations having two wells). The
concentrations for samples at which non-detects were
reported were assumed to be the detection limit in computing
the mean. For some compound concentrations that were not
quantified, the concentrations were reported as between the
detection limit and five times the detection limit. Doses
were calculated using both concentrations to derive means.
The scenario used to assess risk from exposure to onsite
groundwater is ingestion of water. One case assumed inges-
tion of onsite groundwater as a result of industrial devel-
opment of the site and use of groundwater as the potable
water source. Another case assumed a lifetime of daily
residential exposure that estimates a "worst case" risk
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through consumption of groundwater. Currently, no onsite
wells or contaminated off-property wells are known to be
used for potable water. If new wells are ever constructed
in this aquifer, they will probably be screened below
50 feet in the more permeable fine to medium sand. As a
worst case, it was assumed that the chemicals in the ground-
water would reach this depth undiluted. Therefore, the mean
groundwater concentration (0- to 30-foot depth) was used in
this assessment. It was also assumed that contaminants in
the groundwater remained at a constant concentration for the
entire exposure period, 70 years for the residential and
40 years for the worker scenarios.
For carcinogens, the worker exposure scenario assumed 0.017 L
of water per kg body weight per day over a 40-year period,
250 days per year, to determine the daily intake of each
contaminant. The residential exposure scenario assumed a
lifetime average water intake of 0.035 L of water per kg
body weight per day over a 70-year period. (See Appendix E
for the derivation of both intake values.) Risk was assumed
to be additive, as stated previously, and Equation 4-1 was
used to estimate the excess lifetime cancer risk. For non-
carcinogens, a daily ingestion rate of 2 liters of water per
day was assumed for derivation of the daily dose of each
compound.
The results of the worker exposure analysis are presented on
Table 4-6. Ingestion of site groundwater over a 40-year,
5-day work week period is estimated to lead to an excess
lifetime cancer risk of 0.2 using maximum concentrations and
0.008 using mean concentrations at the detection limit for
compounds detected but not quantified. Use of mean values
calculated with trace contaminants at five times their de-
tection limit does not alter the cancer risk. Prime contri-
butions to the cancer risk come from exposure to arsenic,
1,2-dichloroethane, chloroform, and trichloroethene.
The results of the residential exposure analysis are shown
in Table 4-7. Exposure to site groundwater for the residen-
tial scenario is estimated to lead to an excess lifetime
cancer risk of 0.5 using maximum concentrations and 0.03
using mean concentrations with the detection limit for
compounds detected but not quantified. Use of mean concen-
trations at five times the detection limit for the trace
concentrations did not alter the cancer risk. Major con-
tributors to the cancer risk with both maximum and mean con-
centrations are arsenic, 1,2-dichloroethane, chloroform, and
trichloroethene. The estimated cancer risks would increase
if cancer potency values for ingestion were available for
benzene and vinyl chloride. It should be emphasized that
the cancer risks represent potential but not current situa-
tions, as there are no water production wells onsite. High-
4-14
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Table 4-6
SUMMARY OF ONSITE GROUNDWATER CONTAMINATION AND CANCER POTENCIES
FOR CARCINOGENS, WORKER SCENARIO3
Maximum Observed Level
Mean Observed Level
Fraction
Volatile Organics
Inorganic
Contaminant of Concern
1 , 2-Dichloroethane
Benzene
Chloroform
Tetrachloroethene
1 , 1 ,2-Trichloroe thane
Trichloroethene
Vinyl chloride
Arsenic
b
Cancer Potency
(kg-day/mg)
0.069
0.07
0.035e
e
0.573
0.0196
—
15
Concentration
(yg/L)
16,000
2,200
27,000
1,800
45
210,000
360
600
Lifetime
Average Dose
(yg/kg/day)
170
24
290
20
0.49
2,300
3.9
6.5
Cancer Risk Concentration
(xlO )
10,000
20,000
1,000
30
40,000
100,000
(yg/L)
300
43
2,100
47
8.3
18,000
23
17
Lifetime
Average Dose
(yg/ /kg/day)
3.3
0.47
22
0.51
0.090
200
0.25
0.18
Cancer Risk
(xlO~6)
200
2,000
20
5
4,000
3,000
I
I—>
<_n
TOTAL
200,000
As described in the text, these risks represent potential exposure scenarios, not current ones. There are no production wells onsite.
Cancer risks have been rounded off to one significant figure.
USEPA, December 1984.
CDose calculated from lifetime average water ingestion rate of 0.016 L/kg/day and exposure fraction = 0.68.
Mean concentrations calculated using detection limit for nonquantifiable but detected concentrations.
International Agency for Research on Cancer believes that there is inadequate evidence for classifying chemical as a human carcinogen.
8,000
-------
Table 4-7
SUMMARY OF ONSITE GROUNDWATER CONTAMINATION AND CANCER POTENCIES
FOR CARCINOGENS, LIFETIME RESIDENTIAL SCENARIO3
Maximum Observed Level
Mean Observed Level
Fraction Contaminant of Concern
Volatile Organics 1,2-Dichloroethane
Benzene
Chloroform
Tetrachloroethene
1 , 1 , 2-Tr ichloroethane
Trichloroethene
Vinyl chloride
Inorganic Arsenic
1
M TOTAL
-------
capacity production wells downgradient of the site are drilled
near the valley margins. They penetrate a different aquifer
that discharges to the upper aquifer. Thus, contamination
from Western Processing is not probable.
Daily intakes for the noncarcinogenic compounds are shown on
Table 4-8. With the maximum onsite observed levels, ADI's
are exceeded for toluene, 1,1,1-trichloroethane, bis(2-ethyl-
hexyl)phthalate, phenol, cadmium, chromium, cyanide, lead,
and mercury. With the mean onsite contaminant concentration
level, phenol, cadmium, chromium (assuming hexavalent), lead,
and nickel intakes exceed the ADI's. Intake of mercury and
1,1,1-trichloroethane represent 75 and 60 percent, respec-
tively, of their ADI's.
Using the mean concentration calculated for the nonquanti-
fiable but detected compounds at five times the detection
limit does not change the results. All other compounds
listed on Table 4-8 do not have ADI's.
Scenarios using dermal contact or inhalation of volatiles as
the exposure pathway were not assessed quantitatively in
this endangerment assessment. Cancer risks would be expected
to increase if these pathways were quantified and the dose
added to the chemical intakes via ingestion calculated above
(Andelman, 1984; Brown et al. 1984).
4.7 SURFACE WATER—MILL CREEK
Groundwater movement from the site and the influence of ground-
water on surface waters of Mill Creek are discussed in Sec-
tion 3.3 of this report. This section examines the impacts
of the groundwater discharge in the creek.
4.7.1 HUMAN HEALTH
Mill Creek is not known to be a source of potable water.
Contamination of Mill Creek does not appear to pose a hazard
to human health because the primary contaminants (several
metals) do not have large bioconcentration factors and are
not particularly toxic to humans. With an upper limit con-
sumption of 2 liters per day, dissolved metal concentrations
in Mill Creek near and downstream of Western Processing in
1984 samples would lead to metal intakes less than the ADI's
for cadmium, hexavalent chromium, lead, and nickel. With
total mercury, the daily intake would also be less than its
ADI. Table 3-49 summarizes the maximum organic concentra-
tions found in Mill Creek. Assuming an ingestion rate of
2 L/day for those chemicals with ADI's, bis(2-ethylhexyl)
phthalate, di-N-butylphthalate, 2,4-dichlorophenol, phenol,
ethylbenzene, and toluene all result in daily intakes less
than their ADI's. With the lifetime water intake rate of
4-17
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Table 4-8
SUMMARY OF ONSITE GROUNDWATER CONTAMINATION AND CRITERIA FOR NONCARCINOGENS
Fraction Contaminant of Concern
Volatile Organics 1,1-Dichloroethane
Ethylbenzene
Toluene
Trans-l,2-dichloroethene
1,1, 1-Trichloroethane
Acids 2,4-Dimethylphenol
Phenol
Inorganics Boron
Cadmium
Chromium
Cobalt
Copper
Cyanide
Iron
Lead
Manganese
Mercury
Nickel
Zinc
Acceptable
Daily
Intake
(rag/day)
...
1.6
30
...
38
___
7
0.17b
0.175 (VI)
125 (III)
...
7.6
0.1
...
0.02
1.5
— — —
Maximum Observed
Concentration 2
(yg/L)
33,000
95
22,000
390,000
340,000
10,000
270,000
110,000
60,000
65,000
5,500
13,000
35,000
480,000
3,300
480,000
46
280,000
510,000 1
Level
Dose at
L water/day
(mg/day)
66
0.19
44
780
680
20
540
220
120
130
11
26
70
960
6.6
960
0.092
560
,000
Mean Observed
a
Concentration 2
(yg/U
620
8.6
570
14,000
7,600
930
75,000
5,900
1,100
1,500
420
740
190
85,000
210
89,000
7.7
11,000
93,000
Level
Dose at
L water/day
(mg/day)
1.2
0.017
1.1
28
15
1.9
150
12
2.2
3.0
0.84
1.5
0.38
170
0.42
180
0.015
22
190
°Hean concentrations calculated using detection limit for nonguantifiable but detected concentrations.
b
Oral threshold effect level for smokers.
-------
0.035 L/kg/day, exposure to suspected carcinogens 1,2-di-
chloroethane, tetrachloroethane, and trichloroethane lead to
excess lifetime cancer risks of about 10 to 10 . The
same exposure to the chloroform and 1,1,2-trichloroethane in
Mill Creek would lead to an excess lifetime cancer risk of
about 10 . The total cancer risk from these five suspected
carcinogens in Mill Creek would be 2 x 10 . These intake
rates represent potential scenarios only, however, and it
would be expected that creek water ingested during recrea-
tional activities would be much less than the above assumed
rates.
Some organics that are known or suspected carcinogens were
observed in creek sediments. However, their occurrence was
not consistent and their concentrations were low (see Ta-
ble 3-49). Concentrations of halogenated volatile organic
compounds in sediment were measured on more than one occa-
sion. Concentrations were lower in 1984 than in 1983, pos-
sibly as a result of loss to the atmosphere or movement
downstream.
4.7.2 AQUATIC ORGANISMS
The Municipality of Metropolitan Seattle (Metro) has done
biological sampling at stations E317 and 0317 (Plate 1),
both downstream of Western Processing. The results are re-
viewed by GCA (Yake, 1985; Draft Report). Metro staff con-
cluded that the biota from the two locations in Mill Creek
(actually Mill Creek and the Black River) indicated poorer
water quality than is representative of the region. How-
ever, the lack of an upstream reference station precludes
reaching direct conclusions about the impacts of Western
Processing on Mill Creek. The absence of normal biota in
areas upstream of Western Processing has been noted by
Yake (1985).
Lacking direct biological evidence, conclusions about the
effects of Western Processing on aquatic life must be based
on water-quality information. The concentrations of several
pollutants increased several fold in Mill Creek in the vi-
cinity of Western Processing. Cadmium, copper, and zinc
dissolved in Mill Creek waters at and below Western Process-
ing, however, routinely exceed USEPA ambient water quality
criteria for the protection of aquatic life. Concentrations
of dissolved cadmium always exceed the criteria for 24-hour
exposure, and usually exceed the maximum-exposure criteria
in areas adjacent to and downstream of Western Processing.
Concentrations of dissolved copper exceeded the 24-hour cri-
teria for aquatic organisms on four of five occasions when
measured by WDOE (Table 3-38) and also when measured by USEPA
in January 1984. The maximum allowable concentration of
copper was exceeded once in the WDOE data and probably in
4-19
-------
the USEPA sampling (Table 3-44). Water hardness, necessary
for the calculation of a maximum allowable concentration,
was not reported by USEPA, but the hardness values from the
WDOE samples indicate a range of 52 to 140 mg/L as CaCO-.
The 24-hour criteria for copper were also exceeded upstream
of Western Processing in January 1984 (Table 3-38).
Concentrations of dissolved zinc always exceeded the 24-hour
average criteria for aquatic organisms of 47 ppb, and
usually exceeded the maximum allowable concentrations (based
on hardness). On occasions when hardness was not measured,
concentrations of zinc were much higher than the criteria
calculated for the highest hardness value observed by WDOE
(Table 3-38). It is highly likely that the maximum allow-
able concentrations of zinc were exceeded on all but one
occasion when dissolved concentrations were measured.
Concentrations of dissolved lead were often below limits of
detection. However, occasionally the 24-hour criteria for
aquatic organisms were exceeded both upstream and downstream
of Western Processing.
Current USEPA criteria for hexavalent and trivalent chromium
were used for comparison with concentrations in Mill Creek.
Chromium could be present in either the +6 or +3 valence
state in Mill Creek depending on the valence state discharged
to the creek. Unfortunately, the limits of detection for
dissolved chromium were always in excess of the 24-hour cri-
terion for freshwater aquatic life for hexavalent chromium
(WDOE samples, Table 3-38), and concentrations of chromium
upstream of Western Processing were rejected for quality
control reasons (USEPA samples, Table 3-44). It is therefore
difficult to determine whether criteria values were exceeded
upstream of Western Processing. Hexavalent chromium, while
soluble, has a high affinity for reducing agents such as
organic particles, and typically is bound to particulate
matter in aerobic water. Concentrations of chromium in Mill
Creek were always far below the maximum allowable concentra-
tion for trivalent chromium. There is no 24-hour average
criterion for trivalent chromium.
The criteria for aquatic organisms are generally based on
total recoverable metals (USEPA, March 1979). If suspended
matter is present in the water sampled, total recoverable
metals would exceed concentrations of dissolved metals, but
be less than total metals. Comparison of concentrations of
dissolved metals with the USEPA criteria for protection of
aquatic life is likely to underestimate the actual exposure
and risk. Comparison with concentrations of total metals
could substantially overestimate the risk. When concentra-
tions of dissolved metals exceed the criteria, a clear threat
to aquatic life exists.
4-20
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The criteria to protect aquatic life are based on toxicity
to a large number of species. Two salmonid fish of commer-
cial or recreational importance presently inhabit or previ-
ously inhabited portions of the Mill Creek-Springbrook Creek
drainage. Those species are coho salmon (Williams, Laramie,
and Ames, 1975) and cutthroat trout (Rick Tosper, Washington
Department of Fisheries, personal observation). Juvenile
coho salmon are planted upstream of Western Processing as
part of a salmon rehabilitation program by the Washington
Department of Fisheries and must migrate past Western Pro-
cessing to reach the sea. Toxicity of copper and zinc to
both species and toxicity of cadmium to coho salmon have
been measured in test systems. Table 4-9 shows the ranges
of acute toxicities and the chronic toxicity data available
from the USEPA criteria documents (USEPA, October 1980).
Toxicity of the three metals for two other salmonids with
similar habitat requirements is also shown. One of these
species (rainbow trout) has also been reported to use Mill
Table 4-9
SUMMARY OF TOXICITY VALUES FOR CADMIUM, COPPER, AND
ZINC TO FOUR SALMONID FISH
Metal Species Chronic
and Species Acute Values (yg/L) Values (ug/L)
Cadmium
Coho Salmon — 7.2 (44)
Rainbow Trout 1-7 (23)
Chinook Salmon 1.8-3.5 (23)
(Juveniles)
Copper
Coho Salmon 46-70 (20-99)
Cutthroat Trout 15.7-367 (26-205)
Rainbow Trout 19.9-890 (30-290) 19 (45.4)
Chinook Salmon 10-130 (13-359)
Zinc
Coho Salmon 905-4,600 (25-94)
Cutthroat Trout 90 (-)
Rainbow Trout 90-7,210 (20-333) 277 (26)
Chinook Salmon 97-701 (24-24) 371 (25)
Notes: Coho salmon and cutthroat trout are species of concern
likely to inhabit Mill Creek, and rainbow trout and
Chinook salmon are similar representative species.
Associated hardness values in mg/L are shown in
parentheses.
4-21
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Creek, but its presence has not been confirmed by the Wash-
ington Department of Fisheries. Concentrations of dissolved
cadmium, copper, and zinc in Mill Creek are sufficient to
cause mortalities over a few days to the species shown. It
is reasonably certain that the species listed could not re-
main in Mill Creek in the immediate vicinity of Western Pro-
cessing without being killed or otherwise adversely affected.
Based on data in the criteria documents, the water in Mill
Creek is likely to be toxic to a wide variety of aquatic
organisms. However, there are also aquatic organisms that
might survive in Mill Creek because of relative insensitiv-
ity to toxicity of metals.
Metals draining into Mill Creek appear to be adsorbed by
sediment in suspension and the streambed. Suspended and
bedload transport of metals was discussed in Section 3.7.3.
In general, metals adsorbed to sediment are not readily re-
moved. However, extraction procedure (EP) toxicity tests
(45 Federal Register, 33127) performed by the USEPA (1984)
on Mill Creek sediments indicate that relatively large
amounts of soluble cadmium, copper, and zinc are present in
Mill Creek sediments, either adsorbed or as pore water.
Sediment collected at or downstream of Western Processing
gave EP concentrations that exceeded the maximum allowable
concentrations of those three metals for aquatic organisms
in the extraction volume (USEPA, May 1982 and January 1984).
Sediment elutriate from upstream of Western Processing
exceeded the maximum allowable concentration for copper, but
by a lesser amount than sediment from near or downstream of
Western Processing. In the creek, leaching volumes would be
much greater, the pH would be higher, and the concentrations
of metals in Mill Creek from sediment leachate would be lower
than observed during EP toxicity tests.
Dissolved lead exceeded criteria values upstream, adjacent
to, and downstream of Western Processing. Similar values
were observed at all three locations.
If the EP toxicity samples were filtered prior to analysis,
as confirmed by USEPA (Gahler, personal communications,
1984), contaminated sediment in Mill Creek is a potential
source of soluble metals in toxic concentrations.
With the exception of one measured value of bis(2-ethylhexyl)
phthalate, the concentrations of organic compounds detected
in Mill Creek sediment were well below concentrations that
pose a hazard to aquatic life. The highest concentration of
bis (2-ethylhexyl) phthalate in sediment was observed upstream
of Western Processing. Sediment samples collected most recent-
ly contained low concentrations of volatile organics but
were not tested for other organic compounds (Schmidt and
Vandervort, 1984).
4-22
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4.8 LIMITATIONS OF THE METHODOLOGY
Uncertainties inherent in the calculation of excess lifetime
cancer risk may act to either increase or decrease risk,
depending on the source of the uncertainty. Factors that
may have led to an underestimate of the human health risk
include:
o Not all known or suspected human carcinogens have
estimated cancer potencies, or potencies are only
available for exposure pathways not used in this
assessment. Therefore, the estimated total cancer
risk will not include their contributions.
o Chemical doses may act synergistically rather than
additively.
o Dermal and inhalation doses were not calculated,
and these would add to the total body burden.
o Higher concentrations may be present, although not
measured.
o Environmental transformation and degradation of
chemicals may produce products with increased tox-
icities compared to their parent chemicals.
Factors that may have led to an overestimate of the human
health risk include:
o The intestinal absorption rate from ingestion has
been assumed to be 100 percent.
o Cancer potencies from USEPA's Carcinogen Assess-
ment Group are established as an upper bound
estimate.
o The true value for an adult soil ingestion rate
may be closer to zero rather than the 0.1 g/day
estimated by Kimbrough et al. (1983) and used in
this endangerment assessment.
o This assessment assumed that the environmental
chemical concentrations do not change with time,
whereas some can be expected to decrease over time
through biological and chemical degradation.
o Exposure times of 40 and 70 years for the worker
and residential scenarios were assumed, whereas
employment and residential turnover would be ex-
pected to lead to shorter exposure periods.
o Chemical doses may act antagonistically rather
than additively.
4-23
-------
o Concentrations for nondetected chemicals may be
less than the detection limits and therefore the
estimated mean concentrations may be high.
A factor that may lead to an over- or underestimate of the
human health risk is that regrading the site in late 1984
may either have increased or decreased surface soil
concentrations.
4.9 SUMMARY AND CONCLUSIONS
Implementation of the no-action alternative on the Western
Processing site may result in the following impacts from
each environmental medium:
o Soils—There is.-a potential excess lifetime cancer
risk of 5 x 10 , principally from PCB contamina-
tion, associated with the ingestion of onsite
surface soils with site mean concentrations in a
future worker scenario. An estimated potential
cancer risk of 5 x 10~ is associated with the
ingestion of soils if the maximum surface concen-
trations are used. This increases to an estimated
2 x 10 risk if maximum concentrations from zero
to 12 feet deep are used. Excess lifetime cancer
risks in three potential future residential sce-
narios ranged from about 0.8 times to 50 times
greater. Ingestion of soils could lead to an
exceedance of the acceptable daily intake for lead.
Soils in six off-property areas (II, III, V, VI,
and IX and Mill Creek sediments) also had detected
PCB's. Areas VI and IX had at least three reported
detections in the surface soils, which was the
criterion for calculating a cancer risk for an
area. With the mean and maximum concentrations
and the worker scenario, the potential excess life-
time cancer risks associated with ingestion of
soil are 9 x 10 and 4 x 10 ,_respectively, in
Area VI and 3 x 10 and 5 x 10 , respectively.-
in Area IX. Excess lifetime cancer risks in the
three residential scenarios would be 0.8 times to
50 times greater. Ingestion of surface soil in
Areas II and VIII could lead to an exceedance of
the acceptable daily intake for lead.
o Groundwater—No known water supplies are currently
affected by the site. Use of onsite groundwater
as a potable water source for a work place, however,
would present an estimated excess lifetime cancer
risk of 0.2 using maximum onsite concentrations
and 0.008 using mean onsite concentrations. Cancer
4-24
-------
risk would increase to an estimated 0.5 if a resi-
dential scenario is used with maximum concentra-
tions and 0.02 if mean onsite concentrations are
used. It is emphasized, however, that these expo-
sure scenarios represent only potential exposures,
as contaminated groundwater is not now being used.
Surface water (Mill Creek)—Mill Creek is not cur-
rently known to be used as a source of potable
water. Even assuming that Mill Creek is the sole
source for someone's potable water, no ADIs were
exceeded and the potential excess lifetime cancer
risks were about 10 with maximum reported organic
concentrations. Endangerment to aquatic life in
Mill Creek is in the form of toxic concentrations
of cadmium, chromium, copper, and zinc that are
presently occurring in Mill Creek water and sedi-
ment as a result of groundwater flow from Western
Processing. Organic contaminants from Western
Processing do not appear to pose a threat to
aquatic life because concentrations are well below
those known to cause harm.
4-25
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Chapter 5
REMEDIAL ACTION TECHNOLOGIES
Remedial action technologies were identified through the
following process:
1. A list of site-specific problems was derived from
a review of Chapter 3 (Nature and Extent of
Contamination).
2. General responses addressing site problems were
determined and categorized as "technology groups."
3. Specific technologies were identified within the
technology groups.
5.1 SITE PROBLEMS
This section provides an overview of existing site problems
previously identified in Chapter 3. They can be classified
in the following categories:
o Surface water contamination and runoff
o Leachate generation and contaminated groundwater
o Contaminated soils and underground debris
o Contaminated groundwater discharge to Mill Creek
o Contaminated sediments
o Underground utilities within the zone of
contamination
These problems are discussed below as they pertain to the
subsurface cleanup at Western Processing.
5.1.1 SURFACE WATER CONSIDERATIONS
Mill Creek (also called King County Drainage Ditch No. 1)
runs in a northerly direction along the northwest corner of
the site. Before stormwater drainage improvements were
implemented in 1983, Mill Creek was a receptor of both con-
taminated surface water and groundwater from Western Proces-
sing. Berms and an asphalt cover were constructed by DOE to
control stormwater; they have minimized the amount of conta-
minated surface water reaching Mill Creek. More recently, a
stormwater collection system has collected stormwater for
discharge to the Metro sewer system. However, groundwater
flow from Western Processing into Mill Creek still occurs.
In addition, Mill Creek sediments are contaminated and these
contaminated materials contact the stream flow.
5-1
-------
A similar situation exists in a small drainage ditch along
the east side of the site. The contaminated sediments pres-
ent within the ditch could contaminate the water flowing
through the ditch.
5.1.2 LEACHATE GENERATION AND CONTAMINATED GROUNDWATER
Leachate from the contaminated soils on the Western Proces-
sing site has contaminated the groundwater under the site.
There is also some evidence of off-property migration of
contaminated groundwater locally in all directions. This is
believed to be due to a groundwater mound located beneath
the site. Mill Creek is the major discharge point for con-
taminated groundwater.
5.1.3 CONTAMINATED SOILS AND UNDERGROUND DEBRIS
The soils of the Western Processing site have been found to
be grossly contaminated with metals and organics, as described
in Chapter 3. The contaminated soils are documented as the
source of groundwater contamination and must be considered a
major site problem. In addition, buried drums have been
found on the Western Processing site. The magnitude of this
problem is unknown and will remain unknown until either
additional subsurface exploration (such as magnetometer or
ground penetrating radar) or an excavation is done.
Other underground materials that may be encountered during
remedial action include underground septic tanks, abandoned
underground piping and utilities, and old foundations and
footings.
5.1.4 CONTAMINATED SEDIMENTS
The sediments of Mill Creek have been found to be contam-
inated with the metals cadmium, chromium, copper, and zinc,
as described in Chapter 3. At present, Mill Creek waters
contact contaminated sediments. As described in Chapter 3,
the metals probably have saturated the ion-exchange sites in
the sediments at the points of entry to the creek, so these
sediments may not be contributing more metal ions than are
already in the groundwater. However, as water with lower
metal concentrations or with a low pH contacts these sedi-
ments, metal ions will leach from them.
5.1.5 UNDERGROUND UTILITIES IN THE ZONE OF CONTAMINATION
Underground utilities that pass near the site include power
cables, sewer and water lines, telephone ducts, an oil line,
and a natural gas line. The presence of utilities within or
near the zone of contamination represents additional path-
ways for contaminant migration. Other unidentified utility
lines may be located on or near the site, and they may pre-
sent problems during a subsurface cleanup.
5-2
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5.2 TECHNOLOGY GROUPS
This section evaluates several technology groups for their
applicability to the site problems at Western Processing.
Technologies applicable to V7estern Processing fall into one
or more of the following technology groups:
o Surface water controls
o Leachate and groundwater controls
o Waste and soil excavation and removal
o Contaminated sediments removal or containment
o In situ treatment methods
o Disposal of groundwater
o Direct waste treatment
o Disposal of excavated soils
o Mitigation of problems caused by underground util-
ities within the zone of contamination
Each technology group is discussed below in terms of its
applicability to Western Processing.
5.2.1 SURFACE WATER CONTROLS
Surface water controls are designed to prevent the migration
of contaminated surface water off-property and to prevent
the contamination of bodies of surface water. Surface water
controls may also be used to prevent surface water from in-
terfering with other remedial actions. They are also used
to prevent surface water from running on or running off the
area of contamination or to collect contaminated runoff for
treatment and disposal.
5.2.2 LEACHATE AND GROUNDWATER CONTROLS
Leachate and groundwater controls are designed to prevent or
to minimize the contamination of groundwater by leachate
generation as well as contaminant migration via groundwater.
Leachate and groundwater controls can include the use of
caps, containment barriers, and/or groundwater removal and
treatment.
5-3
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5.2.3 WASTE AND SOIL EXCAVATION AND REMOVAL
Excavation and removal of waste and contaminated soils may
be implemented to eliminate or reduce the source of ground-
water pollution, to reduce the threat of direct exposure to
contaminated soils, and/or to aid in the implementation of
another remedial action, such as the installation of a
slurry wall. The removal of underground debris is included
in this technology group.
5.2.4 CONTAMINATED SEDIMENTS REMOVAL OR CONTAINMENT
This technology group is designed to prevent contact between
contaminated sediments and Mill Creek surface water flow.
The primary problem caused by the presence of contaminated
sediments in Mill Creek is that contaminants can dissolve
into the stream flow from those contaminated sediments.
5.2.5 IN SITU TREATMENT METHODS
In situ treatment methods are designed to mitigate contami-
nation problems without moving contaminated materials. Meth-
ods include contaminant destruction, treatment, and fixation.
In situ treatment is usually used in more homogeneous situa-
tions than those found at Western Processing. Individual in
situ treatment technologies are examined later in this chapter
to determine if any are applicable to Western Processing
site problems.
5.2.6 DIRECT WASTE TREATMENT
Direct waste treatment can be implemented to destroy contam-
inants in, to remove contaminants from, or to stabilize and
in some instances to fixate contaminants within solid, liquid,
or gaseous waste streams. Incineration can completely decom-
pose many types of organic contaminant molecules. Treatment
systems can remove contaminants from liquid and gaseous waste
streams. Solids treatment systems can remove contaminants
from homogeneous solid areas. Direct waste treatment may be
applicable to many of the Western Processing site problems,
including contaminated groundwater and possibly contaminated
soils.
5.2.7 DISPOSAL OF GROUNDWATER
This technology group is designed to dispose of groundwater
once the water has been removed from the aquifer. Ground-
water can be disposed after or in lieu of treatment. The
range of disposal options is affected by the degree of
groundwater treatment implemented prior to disposal.
5-4
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5.2.8 DISPOSAL OF EXCAVATED SOILS
This technology group becomes applicable to Western Processing
site problems if and when contaminated soils are removed
from the site. Excavated soils may be disposed of or treated
onsite or offsite.
5.2.9 MITIGATION OF PROBLEMS CAUSED BY UNDERGROUND
UTILITIES WITHIN THE ZONE OF CONTAMINATION
As discussed in Chapter 3, there may be problems with contami-
nants leaving the site in or adjacent to utility conduits.
Since it is a rather minor task to seal the utilities leaving
the site, each example alternative assumes that all utility
trenches and conduits leaving the site will be sealed to
block the transport of contamination, and all utilities
passing through the contamination zone will be checked for
leak potential and/or rerouted.
5.2.10 SUMMARY OF TECHNOLOGY GROUPS
Table 5-1 summarizes the existing site problems that would
be significantly affected by the selection of a particular
technology group. The table shows that a particular tech-
nology group will sometimes apply to more than one site
problem.
After the technology groups were identified they were assessed
in preparation for assembling and screening example remedial
action alternatives. Each technology group was assessed
separately without consideration of positive or negative
effects when used in combination with other technologies.
The preliminary assessment procedure considers only major
impacts of the identified technologies. The procedure uses
available data to allow preliminary conclusions to be drawn
about effects and to facilitate comparisons between tech-
nologies before detailed analysis is performed. It also
permits identification of sensitive general issues. This
procedure catalogs only major impacts and does not rely on
quantification since it is a preliminary screening procedure
for identifying and eliminating infeasible technologies.
The feasible technologies were available for use in the
example remedial action alternatives discussed in Chapter 6.
5-5
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Table 5-1
IMPACT OF TECHNOLOGY GROUPS
ON EXISTING AND POTENTIAL SITE PROBLEMS
Soil
and Mill
Under- Creek
Technology ground Sedi- Ground-
Groups Debris ments water
Surface Water Controls X X
Leachate and Groundwater
controls X X
Waste and Soil Excava-
tion and Removal X XX
Contaminated Sediments
Removal or Containment X
In Situ Treatment XXX
Direct Waste Treatment X X
Disposal of Groundwater X
Disposal of Excavated
Soils X X
Note: "X" indicates that site problem would be positively
affected by implementation of the technology group.
5.3 ASSESSMENT CRITERIA
The technologies found to be potentially applicable to
Western Processing are listed in Table 5-2. Selection of
the potential applicable remedial technologies was based on
the following general conditions:
o Physical site conditions that preclude, restrict,
or promote the use of a specific technology
o Chemical and physical characteristics of contami-
nation that affect the effectiveness of a remedial
technology
o Inherent nature of a technology, such as perfor-
mance record, reliability, and operating problems
5-6
-------
Table 5-2
TECHNOLOGIES POTENTIALLY APPLICABLE AT WESTERN PROCESSING
Surface Water Controls
o Capping
Sprayed asphalt membrane
Portland cement concrete
Bituminous concrete (asphalt)
Gravel over geotextile over clay
Loam over clay
Loam over synthetic membrane over sand
Loam over sand over synthetic membrane over
clay
o Diversion and Collection Systems (Mill Creek
Diversion)
Piped gravity bypass
Ditches and trenches (new channel)
Pump and pipe system with diversion dam
Groundwater Controls
o Containment or Diversion Barriers
Soil-bentonite slurry wall
Cement-bentonite slurry wall
Vibrating beam-asphalt wall
Grout curtains
o Groundwater Pumping
Well points
(a) Suction wells
(b) Jet ejector wells
(c) Submersible wells
Deep wells
Waste and Soil Excavation and Removal
Contaminated Sediments Removal and Containment
o Mechanical Dredging
o Hydraulic Dredging
o Pneumatic Dredging
In Situ Treatment Methods
o Hydrolysis
o Oxidation
o Vitrification
o Reduction
o Soil aeration
5-7
-------
Table 5-2
(continued)
o Solvent flushing
o Neutralization
o Polymerization
o Bioreclamation
o Permeable treatment beds
o Solidification
Direct Waste Treatment
o Onsite Treatment of Aqueous and Liquid Waste Streams
Biological Treatment Techniques
(a) Aerobic Biological Treatment Systems
Activated sludge
Trickling filters
Aerated lagoons
Waste stabilization ponds
Rotating biological discs
Fluidized bed bioreactors
(b) Anaerobic Biological Treatment Systems
Chemical Treatment Techniques
Neutralization
Precipitation
Cyanide oxidation
Organic chemical oxidation
Hydrolysis
Reduction
Organic chemical dechlorination
Molecular chlorine removal
Physical Treatment Techniques
(a) Flow equalization
(b) Coagulation/flocculation
(c) Sedimentation
(d) Activated carbon
(e) Ion exchange
(f) Membrane processes
Reverse osmosis
Electrodialysis
Ultrafiltration
(g) Liquid/liquid extraction
(h) Oil-water separator
(i) Steam distillation
(j) Air stripping
(k) Steam stripping
(1) Filtration
(m) Dissolved air flotation
o Off-property Treatment
5-8
-------
Table 5-2
(continued)
Disposal of Groundwater
o Discharge to a publicly owned treatment works
o Discharge to Mill Creek
o Discharge to Green River
o Spray irrigation
o Shallow reinjection
o Deep well injection
Disposal of Excavated Soils
o Offsite landfill disposal at a RCRA-permitted
facility
o Onsite landfill disposal
o Incineration at an offsite facility
5-9
-------
To refine the relative applicability of each technology.- the
following additional criteria were applied:
o Technical Feasibility. Technical feasibility
includes a general assessment of reliability,
implementation capability, and safety. Reliabi-
lity is assessed in categories of effectiveness,
durability, and whether or not the technology is
proven. Implementation capability is assessed in
the categories of ease of installation, applica-
bility to site conditions, time required to imple-
ment, and monitoring requirements. The safety
category addresses the relative safety of a
technology during operation and in the event of
failure of the technology.
o Environmental, Public Health, and Institutional
Impacts. The evaluation and screening of remedial
technologies from an environmental perspective
addresses both short-term (construction-related)
and long-term (operation-related) effects on the
natural and manmade environment. Short-term
effects considered during technology screening
include odor, noise, air pollution, groundwater
pollution, surface water pollution, wildlife habi-
tat alteration, disposal of construction mate-
rials, and disruption of households, businesses,
and services. Long-term effects considered during
technology screening include odor, noise, air pol-
lution, surface water pollution, groundwater pol-
lution, and wildlife habitat alteration; effect on
any threatened and endangered species, or on the
use of natural resources; alteration of parks,
transportation, and urban facilities; relocation
of households, businesses, or services; and aes-
thetic changes. Public health evaluations for
each technology were made by judging exposure
(short- and long-term) for each alternative.
Institutional impacts were evaluated relative to
political jurisdiction; surface water and ground-
water standards; air quality, odor, and noise
standards; land acquisition, land use restrictions,
and zoning; and federal, state, or local laws or
policies.
o Cost. Costs were compared for each technology.
The comparison reflects relative rather than
absolute costs and, wherever possible, considers
life-cycle as well as capital costs. A negative
assessment indicates that a technology is more
expensive relative to other technologies, and a
positive assessment indicates that a technology is
less expensive relative to other technologies.
5-10
-------
The applicable technologies were individually rated by as-
sessing them with regard to the above criteria. The fol-
lowing scale was used for rating the technologies on the
summary tables:
Rating Definition
Extremely negative effects, even with
mitigating measures; technology not
worth further consideration
Negative effects that are not strong
enough or certain enough to be sole
justification for eliminating a
technology; only moderate negative
effects
o Of very little apparent positive or
negative effect, but inclusion can be
justified for some special reason;
little change from existing conditions
+ A positive or moderately positive benefit
++ An extremely positive benefit
* Inappropriate to draw conclusions at this
point in the evaluation process
5.4 DISCUSSION OF ASSESSED APPLICABLE REMEDIAL TECHNOLOGIES
Applicable technologies have been organized by technology
group. Each technology by itself does not address all
public health impacts of the site. To allow consistent
ratings, each technology is rated relative to its impact or
effectiveness in application to a specific hazard. This
assumes that concerns regarding site hazards not addressed
by a single action can potentially be mitigated through
implementation of other technologies. The effect of combin-
ing technologies will be considered in Chapter 6. Because a
complete analysis of the effectiveness of a technology
requires that its interaction with other technologies be
examined, this chapter contains only general assessments of
the remedial action technologies.
5.4.1 SURFACE WATER CONTROLS
5.4.1.1 Capping
The following capping technologies assume no soil removal,
treatment, or other containment. Table 5-3 shows the
results of the preliminary assessment of capping technol-
ogies. Capping is used to eliminate human or animal contact
5-11
-------
Table 5-3
PRELIMINARY ASSESSMENT OF SURFACE CAP TECHNOLOGIES
Evaluation
Technology
Environmental, Public
Technical Health, and Institutional Cost
comment a.) (see comment b.) (see comment c.)
Loam Over
Synthetic
Membrane Over
Sand
Loam Over Clay
Loam Over Sand
Over Synthetic
Membrane Over
Clay
Comments
Sprayed
Asphalt
Portland
Cement
Concrete
Bituminous
Concrete
(Asphalt)
Gravel Over
Geotextile
Over Clay
o o a. Asphalt membrane is not durable.
+ - a. Concrete cap is relatively difficult
to install properly.
b. Concrete cap would allow limited future
site use.
c. Capital costs for this type of cap are
high.
+ o a. Susceptible to cracking.
b. Asphalt cap would allow limited
future site use.
o o a. Requires three passes to construct.
Technology has little proven, long-
term experience .
a. Time consuming and difficult to
implement. "Self-healing" capacity of
clay is not present.
Although construction is difficult and
time consuming, this cap is more
durable than other types of caps.
This capping technology is compliant
with RCRA regulations.
Capital costs for this type of cap are
high.
-------
with contaminated soils, to reduce water infiltration
through contaminated soils, and to eliminate contaminant
transport by surface water runoff and airborne emissions.
5.4.1.1.1 Sprayed Asphalt Membrane
This technology involves surface grading and spray applica-
tion of a 1/4- to 1/2-inch-thick layer of asphalt to reduce
infiltration and eliminate volatile and particulate emis-
sions from the soil surface. It requires minimal material
handling and a small labor force, and is easy to implement.
However, the membrane is not very durable because it is
photosensitive, has poor weather resistance, becomes brittle
with age, and is susceptible to severe progressive cracking.
5.4.1.1.2 Portland Cement Concrete
This technology involves surface grading and placement of a
base course and a concrete slab with steel mesh to minimize
infiltration and reduce emissions of volatiles and particu-
lates from the surface soil. The technology is durable and
resistant to chemical and mechanical damage. However, Port-
land concrete is susceptible to cracking from settlement and
shrinkage. Installation requires the placement of forms and
steel and the making of expansion joints. It has very high
capital costs although proper design and installation gen-
erally result in relatively low maintenance costs.
5.4.1.1.3 Bituminous Concrete (Asphalt)
This technology involves surface grading and placement of a
base course and bituminous (asphalt) pavement to minimize
infiltration and reduce emissions of volatiles and particu-
lates from the soil surface. The technology has proven
effective. However, as with the other more rigid materials,
bituminous concrete is susceptible to cracking from settle-
ment and shrinkage. Bituminous concrete is photosensitive
and tends to weather more rapidly than Portland concrete.
This weathering generally contributes to operation and main-
tenance expenses that are greater than for Portland con-
crete. An asphalt cap is presently in place over the area
of the site used as a solids reaction pond.
5.4.1.1.4 Gravel Over Geotextile Over Clay
This technology involves surface grading and compaction of
native materials to minimize infiltration and reduce partic-
ulate emissions from the soil surface. A clay layer is then
placed and compacted over the surface. The clay is covered
with a geotextile and compacted gravel to provide a flexible
surface course that can withstand heavy vehicular traffic.
5-13
-------
5.4.1.1.5 Loam Over Clay
This technology involves surface grading and the placement
of compacted clay to minimize infiltration and eliminate
volatile and particulate emissions from the soil surface.
The clay is covered with loam (topsoil) to control moisture,
protect the integrity of the clay layer, and allow revege-
tation. The clay has some self-healing properties but is
subject to cracking due to desiccation and will not carry
vehicular traffic.
5.4.1.1.6 Loam Over Synthetic Membrane Over Sand
This technology involves grading and covering site soils
with a blanket of sand overlaid with an impermeable synthetic
membrane that is covered by loam (topsoil) to protect the
synthetic liner and allow revegetation. The synthetic mem-
brane is susceptible to punctures, cracking, and chemical
degradation, and will not carry vehicular traffic.
5.4.1.1.7 Loam Over Sand Over Synthetic Membrane Over Clay
(RCRA Cap)
This technology involves grading and covering site soils
with compacted clay and an impermeable synthetic membrane
that is covered by sand. Overlying this sequence of mate-
rials is loam (topsoil) to protect the membrane and allow
revegetation. The technology takes advantage of the self-
healing properties of clay and the impermeable nature of
synthetic membrane at correspondingly higher capital cost.
The cap complies with RCRA requirements for site closure.
The cap requires difficult construction techniques and will
not withstand vehicular traffic.
5.4.1.2 Diversion and Collection Systems (Mill Creek
Diversion)
The following technologies may be used should a diversion of
Mill Creek be implemented. Preliminary assessments of Mill
Creek diversion technologies are shown in Table 5-4. Since
Mill Creek is being relied upon to capture groundwater and
minimize westward migration of the contamination, any di-
version may increase the area in which contaminated ground-
water flows.
5.4.1.2.1 Piped Gravity Bypass
This technology would involve installing a large conduit
pipe around Mill Creek as it passes Western Processing.
This action would eliminate any hydraulic connection between
the site and Mill Creek. To avoid flooding, the system would
have to be sized to carry the maximum anticipated seasonal
creek flow. This action could be used as a temporary or a
permanent response. Local groundwater discharging to the
creek would have to be managed in the area of the
excavation.
-------
Table 5-4
PRELIMINARY ASSESSMENT OF MILL CREEK DIVERSION TECHNOLOGIES
Evaluation
ui
I
Technology
Piped Gravity
Bypass
Ditches and
Trenches
(New Channel)
Pump and Pipe
System with
Diversion Dam
Technical
(see comment a.)
Environmental, Public
Health, and Institutional
(see comment b.)
Cost
(see comment c.)
c.
c.
Comments
If permanent, destroys any biolo-
gical use of Mill Creek. May
alter local groundwater
gradients.
Expensive to implement.
c.
Diversion of creek may alter local
groundwater gradients. New channel
will involve an excavation through
potentially hazardous areas.
Expensive to implement.
Pumping increases versatility of
the diversion system.
Diversion of creek may alter
local groundwater gradients.
Expensive to implement.
-------
5.4.1.2.2 Ditches and Trenches (New Channel)
This technology involves digging a new creek channel farther
from the Western Processing site. The creek flow would be
dammed and diverted to the new channel. This new channel
would probably be located north and west of the present creek
location. The diversion could be made permanent or used
only for the period of time necessary to implement some other
remedial action.
5.4.1.2.3 Pump and Pipe System with Diversion Dam
This technology involves the use of a diversion dam with a
low-head pump to divert the Mill Creek flow. The water would
be pumped through a pipe to an alternate stream bed or would
be pumped to a different section of Mill Creek. The diversion
could be made permanent or used only for the period of time
necessary to implement some other remedial action.
5.4.2 GROUNDWATER CONTROLS
5.4.2.1 Containment or Diversion Barriers
The following containment or diversion technologies assume
that capping would also be employed. Table 5-5 summarizes
the preliminary assessment of containment or diversion barrier
technologies. Containment or diversion barrier technologies
are assessed assuming that complete containment is the goal
of the remedial response. Discussion of other uses for barri-
ers is presented in Chapter 6.
5.4.2.1.1 Soil-Bentonite Slurry Wall
This technology involves excavation of a trench using benton-
ite slurry for temporary stabilization. Backhoes can be
used to excavate a trench to depths of up to 50 to 60 feet.
The trench is then backfilled with a soil-bentonite mixture
to provide a low permeability confining wall. Cost-effec-
tiveness of this technology is greatly enhanced where native
soil can be used in the soil-bentonite mixture. The suita-
bility of native soil for use in the soil-bentonite mixture
depends upon texture, grain size distribution, moisture con-
tent, and permeability- The effectiveness of this technol-
ogy has been proven in other hazardous waste applications.
However, the heterogeneity of the subsurface materials and
extreme depth to bedrock (or other relatively impermeable
strata) at the Western Processing site make complete con-
tainment difficult.
5.4.2.1.2 Cement-Bentonite Slurry Wall
This technology involves the excavation of a trench using
bentonite slurry for temporary stabilization. The trench is
5-16
-------
Table 5-5
PRELIMINARY ASSESSMENT OF CONTAINMENT BARRIER TECHNOLOGIES
Evaluation
Ul
I
Technology
Soil-Bentonite
Slurry Wall
Technical
(see comment a.)
Environmental, Public
Health, and Institutional
(see comment b.)
Cost
(see comment c.)
Cement-
Bentonite
Slurry Wall
Vibrating Beam
Asphalt Wall
Comments
a. Aquiclude is approximately 150 feet
beneath Western Processing site.
Possibility of chemical degrada-
tion of slurry wall.
b. Due to deep aquiclude, complete
containment is very difficult.
a. Aquiclude is approximately 150 feet
beneath Western Processing site.
Cement-bentonite is simpler to install
than soil-bentonite. Possibility
of chemical degradation of slurry
wall.
b. Due to deep aquiclude, complete
containment is very difficult.
c. More expensive then soil-bentonite
slurry wall.
a. Membrane is thin. Effectiveness
of seal is difficult to determine.
Susceptible to chemical attack.
Possibility of chemical degrada-
tion of wall.
Grout Curtain
c.
Determining effectiveness of grout
curtain at the Western Processing site
would be difficult. Possibility
of chemical degradation of curtain.
Due to the depth of the aquiclude,
complete containment is very
difficult.
Relatively high material costs.
-------
then backfilled with cement-bentonite mixture to displace
the slurry and provide a confining wall. The technology has
proven effective and durable in other hazardous waste appli-
cations. However, the extreme depth to bedrock (or other
relatively impermeable strata) at the Western Processing
site makes complete containment difficult. A cement-
bentonite slurry wall technology requires less operating
space and involves a less complicated construction operation
but is more permeable than a soil-bentonite slurry wall.
5.4.2.1.3 Vibrating Beam-Asphalt Wall
This technology involves using vibratory force to advance a
steel beam into the ground and injecting a relatively thin
wall of asphalt (or cement, bentonite, or both) as the beam
is withdrawn. The wall is constructed by successive place-
ment of adjacent segments. The technology is most applic-
able to clean fine to medium sands and has the inherent
problem of maintaining beam alignment and the continuity of
adjacent segments. The extreme depth to bedrock (or other
relatively impermeable strata) at the Western Processing
site make complete containment difficult.
5.4.2.1.4 Grout Curtain
This technology involves the injection of cement grout (with
bentonite) through vertical pipes installed into the ground.
Typically, a minimum of three rows of pipes is required at
staggered spacing. This technology is more expensive than
the slurry wall technologies, and grout curtains are usually
used in porous or fractured rock. The major difficulty with
grouting for water cut-off is the inability to control where
grout actually ends up and, therefore, the integrity of the
containment cannot be assured.
5.4.2.2 Groundwater Pumping
The assessment of the following groundwater pumping tech-
nologies assumes that the effluent will undergo proper
treatment and/or disposal. Table 5-6 summarizes the
assessment.
5.4.2.2.1 Well Points
Well points are a common method of dewatering excavations
and are used in groundwater pumping networks. A well point
system generally consists of a series of closely spaced
small-diameter wells, usually interconnected by a header
pipe or a manifold. Pumps commonly used in well point
systems include suction pumps, jet ejector pumps, and sub-
mersible pumps. Well points are best suited for use in low-
permeability soils. Well points can be used at a variety of
depths, depending upon the type of pump used.
5-1!
-------
Table 5-6
PRELIMINARY ASSESSMENT OF GROUNDWATER PUMPING TECHNOLOGIES
Evaluation
Technology
Well Points
with Suction
Pump System
Well Points
with Jet
Ejector Pump
System
Well Points
with Submer-
sible Pump
System
Environmental, Public
Technical Health, and Institutional Cost
(see comment a.) (see comment b.) (see comment c.)
Comments
a. Maximum effective lift is approximately
15 feet.
c. Less expensive than other pumping
systems.
a. Jet ejector pumps can lift water from
greater depths than can suction pumps.
a. Requires electrical power to many pumps.
c. Higher OSM and capital costs than other
well point pumping systems.
Deep Wells
-------
Suction Pumps. In a suction pump system, each well point is
connected to a central centrifugal suction pump. The well
points are usually spaced from two to six feet apart, depend-
ing on the permeability of the saturated soil and on the
desired zone of drawdown. The maximum effective lift that
can be generated by a suction pump system is approximately
15 feet.
Jet Ejector Pumps. Jet ejector pumps are used in deeper
well point systems requiring a greater lift than can be
delivered by a suction pump system. Jet ejector pumps can
lift water from depths of 100 feet or more. The jet ejector
system requires an additional unit to recirculate water
through the pump.
Submersible Pumps. Submersible pumps are centrifugal pumps
placed inside each well casing below the water level. They
generally require a 3-inch-minimum well diameter. The lift
capabilities of submersible pumps are generally limited only
by the size of the pump that will fit in a given well.
5.4.2.2.2 Deep Wells
Deep wells are generally considered to be higher capacity
single-unit wells screened at greater depths than those found
in a well point system. Submersible pumps and vertical tur-
bine pumps are commonly used in deep wells. Deep wells are
generally best suited for use in higher permeability soils
because of their higher pumping capacity.
5.4.3 WASTE AND SOIL EXCAVATION AND REMOVAL
Waste and soil excavation and removal technologies are not
categorized. No assessment is provided since the choice of
excavation methods is generally made by the contractor.
5.4.4 CONTAMINATED SEDIMENTS REMOVAL AND CONTAINMENT
The following technologies for the removal of contaminated
sediments from Mill Creek are assessed in Table 5-7. It is
assumed that the excavated sediments will be disposed of at
a RCRA-permitted landfill and that Mill Creek will be tempo-
rarily diverted around the dredging activity.
5.4.4.1 Mechanical Dredging
Mechanical dredging technologies include the use of clam-
shells, draglines, and backhoes. Mechanical dredging tech-
nologies are easier to implement than are other types of
dredging, and they do not require the treatment or disposal
of large quantities of potentially contaminated surface water.
Dewatering of the sediments may be required prior to transport
and disposal of contaminated material.
5-20
-------
Technology
Table 5-7
PRELIMINARY ASSESSMENT OF SEDIMENT REMOVAL TECHNOLOGIES
Evaluation
Technical
(see comment a.)
Environmental, Public
Health, and Institutional
(see comment b.)
Cost
(see comment c.)
Comments
1. Mechanical
Dredging
2. Hydraulic
Dredging
3. Pneumatic
<-n Dredging
a. Relatively easy to implement.
a. Results in the removal of large
quantities of potentially
contaminated surface water which
then must be treated or disposed
of.
a. Results in the removal of large
quantities of potentially
contaminated surface water which
then must be treated or disposed
of.
-------
5.4.4.2 Hydraulic Dredging
Hydraulic dredging technologies involve the pumping of sedi-
ments and some water from Mill Creek and the subsequent sep-
aration and disposal of the sediments and water. Hydraulic
dredging technologies include the use of suction devices,
cutterheads, and dustpans. These technologies would remove
the sediments; however, they would be extremely difficult to
implement because of the need for sedimentation basins and
for disposal and treatment of the water. Also some dewater-
ing of the channel may be required for complete containment
of contaminated material.
5.4.4.3 Pneumatic Dredging
Pneumatic dredging technologies involve the use of air to
induce an upward flow of air, water, and sediments. Pneu-
matic dredging technologies include the use of airlifts and
oozers. Large amounts of water are removed from the stream
along with the sediments. That water must then be treated
or otherwise disposed.
5.4.5 IN SITU TREATMENT METHODS
The following assessment of in situ soil treatment technol-
ogies assumes that the process is implemented with no soil
removal, other treatment, or containment technologies. This
simplified overview is useful in determining if the tech-
nology has any application for the site. The determination
of whether an in situ treatment technology would be func-
tionally useful for actual site cleanup requires a further
evaluation of how it can or cannot be effectively combined
with other technologies. A preliminary assessment of these
methods is presented in Table 5-8.
5.4.5.1 Hydrolysis
Hydrolysis is a chemical reaction in which water reacts with
another substance to form two or more new substances. It
involves the ionization of the water molecule as well as the
splitting of the compound hydrolyzed. It is effective in
degrading organic compounds, ionic salts, and organometallic
compounds but is not an effective treatment for metals. In
addition, some type of catalyst or heat addition is required
for many of the desired reactions. Since metals are a problem
at Western Processing this technology may not be effective.
5.4.5.2 Oxidation
Oxidation involves the transfer of electrons from contami-
nant compounds to desired oxidizing agents. Cyanide and
organic compounds such as phenols, alcohols, and pesticides
can be oxidized. Ozone, hydrogen peroxide, and chlorine are
5-22
-------
Table 5-8
PRELIMINARY ASSESSMENT OF IN SITU TREATMENT TECHNOLOGIES
Evaluation
Technology
Hydrolysis
Technical
(see comment a.)
Environmental, Public
Health, and Institutional
(see comment b.)
Cost
(see comment c.)
Oxidation
Vitrification
Reduction
Soil Aeration
Solvent
Flushing
Comments
a. Very difficult to implement without
heat or catalysis; ineffective in
treating metals.
b. May result in hazardous side re-
actions. May worsen existing ground-
water contamination problem.
a. Very difficult to implement on a heter-
ogeneous system.
b. May result in hazardous side reactions.
a. Technology is still developmental. It
has not been demonstrated on a field-
scale operation.
a. Very difficult to implement on a
heterogeneous system.
b. May result in hazardous side reactions.
a. Very difficult to implement on deep
subsurface contamination.
b. May worsen air pollution problem. May
result in a gas migration problem.
a. Solvents may not leach through the
entire zone of contamination.
b. Technology may involve the use of
potentially hazardous compounds.
Hazardous solvents may actually con-
tribute to the subsurface contamina-
tion problem.
-------
Table 5-8
PRELIMINARY ASSESSMENT OF IN-SITU TREATMENT TECHNOLOGIES
(continued)
Evaluation
Technology
Neutralization
Technical
(see comment a.)
Environmental, Public
Health, and Institutional
(see comment b.)
Cost
(see comment c.)
Polymerization
ui Bioreclamation
I
to
>£>
Permeable
Treatment
Beds
Solidification
Comments
a. Very difficult to implement on a
heterogeneous system.
b. Involves the addition of potentially
hazardous compounds to the zone of
contamination.
a. Prohibitively difficult to implement
on a heterogeneous, uncontrolled
system.
a. High levels of heavy metal contamina-
tion make implementation of biorecla-
mation prohibitively difficult.
a. Technology requires shallow
impermeable strata to be effective
(not present at Western Processing) .
a. Long-term reliability has not been
demonstrated for this application.
-------
the major oxidizing agents used to treat waste. Oxidation
is difficult to implement in the solid phase due to the need
for the diffusion of the oxidizing agent.
5.4.5.3 Vitrification
In situ vitrification involves the melting of waste and soil
in place to bind the waste in a glassy solid matrix. The
melting is done by passing an electric current through the
contaminated soils. Some organics would be destroyed by the
high operating temperature. In situ vitrification, although
still in development, is theoretically applicable to a wide
range of soil contamination problems, including inorganic
contamination. Control of air emissions and side reactions
during the heating process may be a problem.
5.4.5.4 Reduction
Reduction involves the transfer of electrons from reducing
agents to contaminant compounds. Reduction is most often
used to convert hexavalent chromium to its trivalent form.
Reduction is difficult to implement in the solid phase and
is not compatible with oxidation processes that may be
required to treat other site contaminants.
5.4.5.5 Soil Aeration
Soil aeration involves the "saturation" of soil with air or
some similar gas. It is generally used for surface or near-
surface applications. It is difficult to aerate subsurface
soils. Soil aeration is very effective treatment for vola-
tile organic contamination but is not applicable for other
types of contamination.
5.4.5.6 Solvent Flushing
Solvent flushing involves the use of a solvent to leach con-
taminants from an unsaturated zone. The elutriate is then
gathered by wells or well points and the hazardous constitu-
ents are treated and/or disposed. Typical solvents used are
water, acids, ammonia, and chelating agents. In situ solvent
extraction of hazardous wastes has not been demonstrated.
In addition, solvent flushing is difficult to implement on
nonhomogeneous wastes. Total containment of the solvent
waste stream would be extremely difficult. The chemistry of
the process in soil is not completely understood or predict-
able. Flushing times can vary depending on the pollutant
being flushed. The metals at Western Processing would
require long flushing times. Flushing has the potential to
mobilize contaminants that would otherwise be bound to the
soils. For these less mobile contaminants capture must be
complete to mitigate potentially adverse environmental and
public health impacts.
5-25
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5.4.5.7 Neutralization
Neutralization is a process used to adjust the pH of a waste
stream. It is accomplished by adding acidic material to
alkaline wastes and alkaline material to acidic wastes.
Neutralization techniques are often used to allow the use of
other treatment technologies. The technology is an appli-
cable treatment for areas of extreme pH, but would be diffi-
cult to implement on in situ soils.
5.4.5.8 Polymerization
Polymerization involves the conversion of hazardous monomer
compounds to nonhazardous and stable polymers. Polymeri-
zation is applicable to many organic compounds; however,
each compound requires a different and rather refined poly-
merizing technique. Polymerization is not an applicable
treatment for inorganic contamination, and therefore is not
applicable to many of the contaminants found at Western
Processing.
5.4.5.9 Bioreclamation
Bioreclamation involves the use of microoganisms for in situ
treatment of waste material. The microorganisms break down
compounds via metabolic activity. Bioreclamation can be
effective in treating a wide range of organic contamination
but is ineffective in treating inorganic contamination. The
microorganisms must be adapted for specific contaminants by
pilot-scale testing. Bioreclamation is very difficult to
apply to deep subsurface contamination or multi-compound
contamination.
5.4.5.10 Permeable Treatment Beds
Permeable treatment beds involve the use of trenches filled
with a reactive permeable medium to act as an underground
reactor. They are used to treat contaminated groundwater or
leachate via the precipitation process. Permeable treatment
beds are applicable in relatively shallow aquifers, since
the trench must be constructed down to an impermeable layer.
The materials used in permeable bed reactors include:
o Limestone or crushed shell for metals removal
o Activated carbon for nonpolar organics removal
o Alauconitic green sand for heavy metals removal
o Zeolites and synthetic ion exchange resins to remove
solubilized heavy metals
o Sodium hypochlorite to remove cyanide
5-26
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Because of the varied nature of the contaminants found at
Western Processing and the depth to an impermeable layer, it
would be extremely difficult to employ this technology
effectively.
5.4.5.11 Solidification/Stabilization
Stabilization is the use of chemical fixants to physically
stabilize contaminated soils. The chemical fixants are
applied through probes that can be drilled up to 45 feet
into the soil. Few chemical stabilizations have been done
and the technology is unproven. Solidification involves the
use of materials to absorb liquid and/or to solidify the
matrix. For both stabilization and solidification, testing
must be done to determine the leachability of the final
product.
5.4.6 TREATMENT OF AQUEOUS AND LIQUID WASTE STREAMS
The assessment of the following treatment technologies assumes
that no response actions other than capping and groundwater
pumping are employed. Individual treatment technology assess-
ments are based on how well the technologies remove the speci-
fic contaminants for which they are designed and on whether
they interfere with the implementation of any other technology
(see Table 5-9).
5.4.6.1 Aerobic Biological Treatment Systems
Biological treatment systems are usually classified on the
basis of whether they are aerobic or anaerobic. By defin-
ition, aerobic treatment systems require air to function
while anaerobic treatment systems function in the absence of
air.
Aerobic treatment systems include the following technologies:
o Activated sludge
o Trickling filters
o Aerated lagoons
o Waste stabilization ponds (both aerobic and
anaerobic)
o Rotating biological discs
o Fluidized bed bioreactors (may be aerobic or
anaerobic)
5-27
-------
Table 5-9
PRELIMINARY ASSESSMENT OF GROUNDWATER TREATMENT TECHNOLOGIES
Evaluation
Technology
Aerobic Treatment
Systems
Activated
Sludge
Trickling
Filters
Aerated
f Lagoon
to
CD
Technical
(see comment a.)
Environmental, Public
Health, and Institutional Operating Cost
(see comment b.) (see comment c.)
Capital Cost
(see comment c.)
Comments
Waste
Stablization
Ponds
Rotating Bio-
logical Discs
Fluidized Bed
Bioreactors
a. Well proven technology.
b. Removes many toxic
compounds.
c. Low operating, high
capital cost.
c. Low operating, high
capital cost.
a. Requires operating area
larger than site.
b. Large, open area of
hazardous materials
during operation.
c. High capital, low
operating costs.
Same comments as for
aerated lagoons.
a. Historically has had
operating difficulties.
b. Process is self-
contained. Removes
most organics.
c. Low operating, high
capital costs.
Same considerations as for
rotating biological discs.
-------
Table 5-9
PRELIMINARY ASSESSMENT OF GROUNDWATER TREATMENT TECHNOLOGIES
(continued)
Evaluation
Technology
Anaerobic Treatment
Systems
Technical
(see comment a.)
Environmental, Public
Health, and Institutional Operating Cost
(see comment b.) (see comment c.)
Capital Cost
(see comment c.)
Comments
a. Very sensitive to
heavy metals.
c. High capital, high
energy costs.
Chemical Treatment
Techniques
Neutraliza-
tion
en
ro
Precipitation
Cyanide
Oxidation
Organic
Chemical
Oxidation
Hydrolysis
a. Relatively easy to
implement. Well proven
technology.
a. Well proven for the re-
moval of heavy metals.
c. High capital, low
operating costs.
a. Well proven for the
removal of cyanide.
b. Destroys hazardous
material.
c. Low capital, high
operating costs.
a. Well proven for the re-
moval of some organics.
b. Destroys hazardous
material.
c. Low capital, high
operating costs.
a. Beneficial reactions
would have already
occurred in aqueous
environment.
-------
Table 5-9
PRELIMINARY ASSESSMENT OF GROUNDWATER TREATMENT TECHNOLOGIES
(continued)
Evaluation
Technology
Reduction
Technical
(see comment a.)
Environmental, Public
Health, and Institutional Operating Cost
(see comment b.) (see comment c.)
Capital Cost
(see comment c.)
Organic
Chemical
Dechlorination
I
U)
o
Molecular
Chlorine
Removal
Flow
Equalization
Coagulation/
Flocculation
Comments
a. Best way to destroy
hexavalent chrome.
b. Trivalent chrome less
toxic than hexavalent
chrome.
c. Low capital, high
operating costs.
a. Easy to implement.
Required for cyanide
oxidation process.
b. Degrades chlorinated
organic compounds.
c. Low capital, high
operating costs.
a. Easy to implement.
Required for some
cyanide oxidation
processes.
c. Low capital, high
operating costs.
a. Easy to implement.
Required for many
processes.
c. Low maintenance costs.
a. No suspended solids in
groundwater. Technology
is not directly appli-
cable.
-------
Table 5-9
PRELIMINARY ASSESSMENT OF GROUNDWATER TREATMENT TECHNOLOGIES
(continued)
Evaluation
Technology
Sedimentation
Technical
(see comment a.)
Environmental, Public
Health, and Institutional Operating Cost
(see comment b.) (see comment c.)
Capital Cost
(see comment c.)
(.n
I
Activated
Carbon
Comments
Technology is not ap-
plicable for Western
Processing site
problems.
NOTE: Both sedimenta-
tion and flocculation
are used as part of
precipitation tech-
nology.
Removes most organic
compounds.
Uses large amounts of
carbon.
Ion Exchange
Effectively removes
metals and boron.
Expensive to regener-
ate ion exchange resin.
Membrane Processes
Reverse
Osmosis
Electrodialysis
Expensive equipment
needed. Process is
power intensive.
Expensive equipment.
Process is power
intensive.
Ultrafiltration
c. Expensive equipment.
-------
Table 5-9
PRELIMINARY ASSESSMENT OF GROUNDWATER TREATMENT TECHNOLOGIES
(continued)
Evaluation
Technology
Liquid/Liquid
Extraction
Technical
(see comment a.)
Environmental, Public
Health, and Institutional Operating Cost
(see comment b.) (see comment c.)
Capital Cost
(see comment c.)
I
OJ
Oil-Water
Separator
Filtration
Comments
Organics concentration
too low for efficient
operation.
Process uses potenti-
ally hazardous solvents.
Requires expensive
equipment and uses large
amounts of chemicals.
No free oil expected.
Technology is not appli-
cable for site problems.
No suspended solids in
groundwater. Technol-
ogy is not directly
applicable. Required
as pretreatment.
Very low operating
costs.
Air
Stripping
a. Simple to implement.
Removes volatile or-
ganic compounds.
b. May cause air pollution
problems in ijnmediate
area.
c. Low operating costs.
-------
Table 5-9
PRELIMINARY ASSESSMENT OF GROUNDWATER TREATMENT TECHNOLOGIES
(continued)
Evaluation
Technology
Steam
Stripping
Technical
(see comment a.)
Environmental, Public
Health, and Institutional Operating Cost
(see comment b.) (see comment c.)
Capital Cost
(see comment c.)
On
I
Dissolved
Air
Flotation
Offsite Treatment
at a Commercial
Facility
Comments
a. Readily implementable.
Removes volatile organic
compounds.
b. May cause air pollution
problems in immediate
area.
c. High operating costs.
a. Not applicable for
Western Processing
site problems.
a. Nearby facilities may
require modifications to
handle contaminants.
c. User fees at commercial
facilities are usually
very high.
-------
Aerobic treatment systems remove biodegradable organic
compounds, bioadsorb a limited amount of metals and nonde-
gradable organic compounds, and oxidize reduced compounds.
Aerobic treatment systems produce sludge that may still
contain hazardous constituents. High levels of metals or
volatile organic compounds could disrupt the entire process.
Each of the aerobic biological processes will perform gener-
ally the same functions; however, each process may be more
or less efficient for a particular application.
5.4.6.1.1 Activated Sludge
This technology is an effective way to remove most toxic
organic compounds. Water containing extremely high levels
of metals may require pretreatment before activated sludge
is used. The sludge would probably require disposal as
hazardous waste.
5.4.6.1.2 Trickling Filters
Trickling filters are columns packed with media which, like
activated sludge, remove organic compounds. They will often
have lower removal efficiencies, however, and be more prone
to nonuniform loading.
5.4.6.1.3 Aerated Lagoons
Aerated lagoons are large complete-mix basins in which or-
ganic wastes are biodegraded by organisms as in an activated
sludge system. The large basin volume helps to dampen feed-
stream variations. The lagoons requires a very large land
area.
5.4.6.1.4 Waste Stabilization Ponds
Waste stabilization ponds are similar to aerated lagoons
except that air is not artificially diffused. Waste stabi-
lization ponds require the largest land area of any of the
biological systems.
5.4.6.1.5 Rotating Biological Disks
The rotating biological disk technology treats organic wastes
by fixed-film biological growth. The biological mass is
contained on a series of disks. These disks are partially
immersed in a tank containing the waste material. The disks
are then rotated, providing alternate immersion and aeration.
As with most biological treatment processes, this technology
is more effective in treating organics than inorganics, but
it is the most sensitive to feedstream variations.
5-34
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5.4.6.1.6 Fluidized Bed Bioreactors
This technology implements the processes of biological
treatment by using a fluidized bed reactor. A fluidized bed
reactor is a solid phase reactor. The reactor medium is
usually some type of finely powdered or granular material.
Air or water is passed through the reactor medium, creating
a fluidized effect. As with most biological treatment pro-
cesses, fluidized bed bioreactors are more effective treat-
ing organic contamination than inorganic contamination.
5.4.6.2 Anaerobic Biological Treatment Systems
Anaerobic treatment systems remove organic compounds by bac-
terial conversion to carbon dioxide, methane, and sometimes
hydrogen sulfide. Anaerobic treatment systems will destroy
biodegradable compounds. The methane gas produced can be
recovered for useful applications. Most anaerobic systems
are very sensitive to heavy metals. Anaerobic degradation
may be occurring at Western Processing. However, the hetero-
geneous nature of the contamination at Western Processing,
the high concentrations of heavy metals in the groundwater,
and the probably low concentration of biodegradable organics
would make the implementation of an anaerobic biological
treatment system very difficult.
5.4.6.3 Neutralization
Neutralization is used to treat waste streams that are alka-
line or acidic in order to meet pH discharge standards.
Neutralization is often used in conjunction with other treat-
ment technologies as a pre-treatment or post-treatment reme-
dial action. Neutralization is implemented by adding acidic
reagents to alkaline streams or by adding alkaline reagents
to acidic streams.
5.4.6.4 Precipitation
Precipitation is a technology by which the chemical equilib-
rium of a waste stream is altered to reduce the solubility
of undesirable components. These materials precipitate out
as a solid phase and are removed by solids removal processes.
Precipitation is often used to remove heavy metals from water,
It is assumed that the precipitation technology includes
both coagulation/flocculation and sedimentation functions.
5.4.6.5 Cyanide Oxidation
Cyanide oxidation is usually implemented via chlorination.
Chlorine and a caustic are added to the cyanide-contaminated
waste stream, producing first the less toxic cyanate ion and
then nontoxic bicarbonates and nitrogen. If organics are
present in the waste stream, potentially hazardous chlor-
inated organics may be produced.
5-35
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Another method for achieving cyanide oxidation is ultraviolet/
ozonation. Ozone is a powerful oxidizing agent and it breaks
down many refractory organic compounds not treatable with
biological treatment technologies. Ozone reacts with oxidiz-
able materials present in the waste stream. To ensure ade-
quate reaction time, large vessels called contactors are
required for the ozonation process. Ultraviolet radiation
enhances the destructive power of the ozone.
5.4.6.6 Organic Chemical Oxidation
Organic oxidation is often accomplished by using wet air
oxidation (WAO). The WAO process is a liquid-phase combus-
tion implemented through the addition of high-pressure air
and sometimes a catalyst at elevated temperatures. The
reaction products are steam, nitrogen gas, carbon dioxide,
and an oxidized liquid waste stream. Supercritical water
(water above its critical temperature and pressure) may also
be used as an oxidizing agent.
Another form of organic oxidation is chemically induced oxi-
dation, accomplished by adding an oxidizing agent to the
waste stream. Commonly used chemical oxidants include hydro-
gen peroxide and potassium permanganate. Chemical oxidation
is effective only if the reaction produces less hazardous
constituents.
As with cyanide oxidation, ultraviolet/ozonation can also be
used to achieve organic oxidation. Ozonation is an effective
treatment for chlorinated hydrocarbons, alcohols, chlorinated
aromatics, and pesticides, as well as cyanides.
5.4.6.7 Hydrolysis
Hydrolysis is a chemical reaction in which water reacts with
another substance to form two or more new substances. The
reaction involves the ionization of the water molecule as
well as the splitting of the hydrolyzed compound. Hydroly-
sis reactions may have been occurring naturally at Western
Processing and catalysis would be required to increase the
reaction rate above what is naturally occurring.
5.4.6.8 Reduction
Reduction involves the transfer of electrons from reducing
agents to contaminant compounds. Reduction is most often
used to convert hexavalent chromium to its less toxic tri-
valent form. Chrome reduction is effected by adding a
reducing agent to the waste stream under highly acidic
conditions. The trivalent chromium is then removed by
precipitation.
5-36
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5.4.6.9 Organic Chemical Dechlorination
Organic chemical dechlorination involves the degradation of
chlorinated organic compounds by breaking the carbon-
chlorine bond. Ultraviolet/ozonation is a method that has
been used to degrade chlorinated hydrocarbons and chlor-
inated aromatics through oxidation.
5.4.6.10 Molecular Chlorine Removal
Molecular chlorine removal involves the use of sulfur dioxide
gas or activated carbon to remove chlorine from a waste stream.
It may be necessary to implement this technology if cyanide
removal via chlorination is used.
5.4.6.11 Flow Equalization
Flow equalization involves the use of basins or tanks to
control and lessen flow and concentration fluctuation. The
technology is used as a pretreatment operation for many bio-
logical, chemical, and physical treatment processes. Flow
equalization can be implemented as in-line equalization, or
as off-line equalization, in which only the flow above a
specified amount is diverted to the equalization area and is
fed back into the main stream at low flow.
5.4.6.12 Coagulation/Flocculation
Coagulation/flocculation involves the combination of suspended
particles to form small clumps of solid matter. It is pro-
moted by gentle stirring with slow-moving paddles. The
technology may be used as part of a precipitation process to
remove sludges after treatment but will not be used by it-
self because of the apparent absence of suspended solids in
the Western Processing groundwater.
5.4.6.13 Sedimentation
Sedimentation is the settling out by gravity of solids par-
ticles suspended in a liquid. It is generally used with
precipitation and flocculation as a post-treatment operation
and will not be used as a main treatment process at Western
Processing.
5.4.6.14 Activated Carbon
Activated carbon is used in the granular or powdered form to
remove contaminants from aqueous wastes via carbon adsorption.
The technology is primarily used to remove those organic
compounds that are not treatable by biological treatment.
Activated carbon is often used to protect biological treat-
ment systems from being overloaded with toxic contamination.
5-37
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5.4.6.15 Ion Exchange
The ion exchange technology can be used to remove soluble
metallic elements; anions such as halides, cyanides, and
nitrates; and carboxylic acids, sulfonic acids, and some
phenols at alkaline pH. Ion exchange involves the use of
insoluble resins capable of promoting a reversible inter-
change of ions with species in the waste stream. Period-
ically, the ion exchange resins must be regenerated to main-
tain the system capacity and effectiveness.
5.4.6.16 Membrane Processes
Membrane processes involve the use of semi-permeable membranes
to remove contaminants from aqueous waste streams. Relatively
clean product water is produced, leaving behind a more concen-
trated waste stream equal to 10 to 50 percent of the original
volume which requires further treatment or disposal. Membrane
processes are highly susceptible to fouling and often require
extensive pretreatment, even with wastes that are relatively
low in contaminants. Membrane processes in use today include
reverse osmosis, electrodialysis, and ultrafiltration.
5.4.6.16.1 Reverse Osmosis
Reverse osmosis is accomplished by passing the waste stream
through a semi-permeable membrane at high pressure. Typical
membranes are impermeable to most inorganic and some organic
compounds.
5.4.6.16.2 Electrodialysis
Electrodialysis is accomplished by using an electric current
to aid in the separation of substances that ionize in solu-
tion. Semi-permeable membranes are placed between electrodes
to isolate and separate constituents as anions (-) or cations
(+). Electrodialysis is generally effective for most inor-
ganic species, but does not remove organics. Organics may
in fact degrade the electrodialysis membranes.
5.4.6.16.3 Ultrafiltration
Ultrafiltration involves the use of microscopic filters to
remove wastes from aqueous streams. The technology is
generally effective at removing all suspended solids and
some dissolved molecules with a molecular weight greater
than 1,000.
5.4.6.17 Liquid/Liquid Extraction
The liquid/liquid extraction technology involves the use of
a solvent to extract contaminants from the aqueous phase.
The solvent is vigorously mixed with the aqueous phase,
removing certain contaminants. The solvent phase is then
allowed to separate from the aqueous phase and is treated or
5-38
-------
disposed of. The technology requires the use of potentially
hazardous solvents and the disposal of the hazardous solvent
phase effluent.
5.4.6.18 Oil-Water Separation
Oil-water separation technology is used to remove free oil
from water. No free oil has been found in the groundwater
under and near the Western Processing site, so this tech-
nology was eliminated from further consideration.
5.4.6.19 Air Stripping
Air stripping removes volatile organic compounds from aque-
ous waste streams. It is effected through the use of a
stripping tower. The aqueous waste stream is pumped into
the top of the tower and allowed to cascade down. Air is
forced up the tower from the bottom. The air removes the
volatiles from the waste stream. It may be necessary to use
an emission control device to prevent the development of an
air pollution problem at the site.
5.4.6.20 Steam Stripping
Steam stripping is similar to air stripping except that steam
acts as the stripping agent. Steam stripping removes a wider
range of compounds than are ordinarily removed by air strip-
ping, including those that are less volatile. Steam strip-
ping is very energy-intensive because of the high steam usage.
5.4.6.21 Filtration
Filtration is a physical method for separating suspended
solids from liquids but is not effective for the removal of
dissolved solids. It could be used as a pre-treatment and
post-treatment operation for many of the other treatment
technologies.
5.4.6.22 Dissolved Air Flotation
Dissolved air flotation removes insoluble hazardous components
from an aqueous phase. Since suspended solids do not seem
to be a problem at Western Processing, the technology was
eliminated from further consideration.
5.4.6.23 Offsite Treatment at a Commercial Facility
An alternative to constructing an onsite treatment plant
would be to transport the contaminated groundwater to a
commercial treatment facility. There are commercial treat-
ment facilities in the region that have indicated that they
are interested in treated contaminated water from Western
5-39
-------
Processing. The transport and treatment costs of the large
quantities of water needing treatment would have to be eval-
uated against the costs of onsite treatment.
5.4.7 DISPOSAL OF GROUNDWATER
The following groundwater disposal technology assessments
assume that no other remedial action except groundwater
pumping and treatment will be used. The amount of ground-
water treatment necessary for a particular groundwater
disposal technology is considered during the technical
assessment. The preliminary assessments of groundwater
disposal technologies are shown in Table 5-10.
5.4.7.1 Discharge to a Publicly Owned Treatment Works
This technology would be implemented by discharging the
groundwater pumped from under the Western Processing site
into the Metro sewage system. High levels of contamination
make this response action institutionally unacceptable with-
out preliminary groundwater treatment. In addition, Metro
will impose a limit on the quantity of discharge.
5.4.7.2 Discharge to Mill Creek
This technology involves the discharge of groundwater into
Mill Creek under an NPDES permit. High levels of contamina-
tion make this response action institutionally unacceptable
in the absence of groundwater treatment. The treatment
requirements for the NPDES discharge permit are generally
more stringent than the requirements for a Metro discharge
permit.
5.4.7.3 Discharge to the Green River
This technology involves the discharge of groundwater into
the Green River under an NPDES permit. High levels of con-
tamination make this option institutionally unacceptable in
the absence of groundwater treatment. This option offers
greater flexibility over discharge to Mill Creek because of
the larger size and flow of the Green River; however, the
water must be pumped one to 1-1/2 miles from the site to the
Green River.
5.4.7.4 Spray Irrigation
This technology involves the use of treated groundwater to
irrigate fields in the surrounding area. The wet climate in
the Puget Sound area makes this technology virtually
infeasible.
5-40
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Table 5-10
PRELIMINARY ASSESSMENT OF GROUNDWATER DISPOSAL TECHNOLOGIES
Evaluation
Technology
Discharge to a
Publicly Owned
Treatment Works
Discharge to Mill
Creek Under an
NPDES Permit
Discharge to
Green River
Under an NPDES
Permit
Spray Irrigation
Shallow Reinjection
Technical
(see comment a.)
Environmental, Public
Health, and Institutional Cost
(see comment b.) (see comment c.)
Comments
a. Easy to implement. Requires less
pretreatment than other technologies.
b. Requires permitting to implement.
c. Must pay user fees.
a. Must meet stringent discharge
criteria.
b. Requires permitting to implement.
c. No user fees required.
a. Must meet stringent discharge cri-
teria. Must pump water from site to
Green River.
b. Requires permitting to implement.
a. Not feasible due to wet climate.
a. Similar effluent criteria as discharge
to Mill Creek.
b. Effects on local groundwater system
need evaluation; permits could be
required.
-------
5.4.7.5 Shallow Reinjection
This technology involves the reinjection of treated ground-
water into the shallow aquifer. The desirability of this
technology would depend on whether the shallow aquifer
required recharge during groundwater pumping. Reinjection
would replace the pumped groundwater with higher quality
water and would minimize drawdown of the water table. Even
with a high degree of water treatment there are strong
institutional objections to reinjection.
5.4.8 DISPOSAL OF EXCAVATED SOIL
The following soil disposal technology assessment assumes
that no other remedial action except soil excavation will be
taken (see Table 5-11).
5.4.8.1 Landfill Disposal at an Offsite Facility.
This technology involves the transportation and disposal of
hazardous wastes at a RCRA-permitted and -compliant hazard-
ous waste landfill. The hazardous materials are not removed
from the environment, only transferred to a more controlled
situation. There is a slight environmental risk involved in
the transport of the hazardous materials.
5.4.8.2 Construction of an Onsite Landfill
This technology involves the construction of an onsite, secure
hazardous waste landfill. Hazardous material is excavated
and clean backfill imported and placed so that the bottom
liner of the landfill can be located above the seasonal high
water table. A bottom liner is then installed according to
the latest available technologies. A leachate detection
system is installed between the liners and a leachate col-
lection system installed above the top liner. The landfill
would also include a gas venting system and a secure imper-
meable cover. The hazardous materials remain onsite, but in
a more controlled situation.
5.4.8.3 Incineration at an Offsite Facility
This technology involves the destruction by incineration of
the soil-contaminant matrix at an approved offsite hazardous
waste incinerator. Incineration will destroy all forms of
soil contamination with the exception of heavy metals.
Incineration may not render the soil-contaminant matrix
nonhazardous and that material may still require disposal at
a hazardous waste disposal facility -
5.4.9 SUMMARY OF PRELIMINARY TECHNOLOGY ASSESSMENT
A technology is considered to have passed through the pre-
liminary assessment procedure if it did not receive a double
negative (--) mark in any of the assessment categories. The
5-42
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Table 5-11
PRELIMINARY ASSESSMENT OF SOIL DISPOSAL TECHNOLOGIES
Evaluation
Technology
Offsite
Landfill
Technical
(see comment a.)
Environmental, Public
Health, and Institutional
(see comment b.)
Cost
(see comment c.)
Comments
Materials present at Western Process-
ing are eligible for landfill disposal.
Suitable capacity must be available
to implement. Does not remove hazar-
dous material from environment.
Disposal costs are a function of
market conditions.
Onsite
Landfill
un
I
Offsite
Incineration
a. Construction of onsite landfill is
difficult and lengthy. Requires
extensive monitoring for many years.
b. Does not remove hazardous material
from environment.
c. Costs less than offsite landfill
disposal for large volumes of
material.
a. Heavy metals are not destroyed. Some
licensed incinerators may not accept
due to heavy metal content.
b. Destroys some types of contamination.
c. Costs more than landfill disposal.
-------
preliminary assessment procedure is designed only to screen
out those technologies that appear to be infeasible for the
Western Processing site. The screened technologies generated
from this chapter may be used in example remedial action
alternatives. In developing the example remedial action
alternatives, no attempt will be made to incorporate all
possible technologies. Detailed design work may indicate
that technologies that passed preliminary assessment but
were not used in an example alternative may have technical,
environmental/institutional, or cost benefits greater than
the benefits of those technologies used in the example
alternatives. Table 5-12 is a list of all technologies that
have passed the preliminary assessment.
5-44
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Table 5-12
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. Mill Creek Diversion
o Piped gravity bypass
o Ditches and trenches (new channel)
o Pump and pipe system with diversion dam.
C. Groundwater Containment or Diversion Barriers
o Soil-bentonite slurry wall
o Cement-bentonite slurry wall
o Grout curtain
D. Groundwater Pumping
o Well points
Suction pump system
Jet ejector pump system
Submersible pump system
o Deep wells
E. Soil Excavation
F. Sediment Removal
o Mechanical dredging
G. Groundwater Treatment
o Aerobic treatment systems
Activated sludge
Trickling filters
Aerated lagoon
Waste stabilization ponds
Rotating biological discs
Fluidized bed bioreactors
5-45
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Table 5-12
(continued)
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
Reverse osmosis
Electrodialysis
Ultrafiltration
o Liquid/liquid extraction
o Filtration
o Air stripping
o Steam stripping
o Offsite treatment at a commercial facility
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
5-46
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Table 5-12
(continued)
Soil Disposal
o Offsite landfill
o Onsite landfill
o Offsite incineration
5-47
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Chapter 6
EXAMPLE REMEDIAL ACTION ALTERNATIVES
6.1 INTRODUCTION
This chapter presents the description and detailed analysis
of example remedial action alternatives for Western Process-
ing. The example alternatives were developed using Chap-
ter 3—Nature and Extent of Contamination, Chapter 4—Endan-
germent Assessment, and Chapter 5—Remedial Action
Technologies.
The purpose of this chapter is to present a range of example
alternatives available to mitigate present and potential
future problems arising from contamination at Western Pro-
cessing. The example alternatives presented here are not
intended to describe the only alternatives that could be
implemented at Western Processing or to describe a preferred
alternative or a final design. Additional example alterna-
tives can be developed using data contained in this report.
The range of alternatives facilitates comparison of the
relative benefits and adverse impacts of each alternative.
Example Alternative 4 was developed and evaluated by the
Potentially Responsible Parties (PRP's).
Six remedial action components were defined and analyzed as
the first step in the development of the example alterna-
tives. The six components were excavation, capping, con-
tainment or diversion barriers, groundwater extraction and
treatment, Mill Creek remedial action, and monitoring. These
components are discussed below in Section 6.2. On the basis
of the component analysis, four source control alternatives
and two migration management (Mill Creek) alternatives were
then developed. These example alternatives and the PRP re-
medial action plan are described in Section 6.3. A detailed
discussion of the example alternatives covering technical
evaluation, environmental and public health assessments,
institutional requirements, and cost estimates is presented
in Section 6.4. Summary tables comparing the example alter-
natives are presented in Section 6.5.
The example alternatives presented in this chapter (except
the no-action alternatives) are effective in reducing risks
to public health and the environment. A major difference is
the length of time necessary to achieve the remedy. A
30-year period has been used as a reference time for compar-
ing the relative effectiveness of the example alternatives.
Performance beyond 30 years is discussed for those alterna-
tives that would not achieve criteria by that time.
6.2 COMPONENT ANALYSIS
Contaminants at Western Processing can be released via three
primary pathways: air, surface water, and groundwater.
6-1
-------
Contaminants will follow one or more of these pathways.
Contaminants may migrate at different rates along each path-
way or at different rates relative to other contaminants.
The contaminants will also present different potentials for
environmental harm or human endangerment depending on their
concentrations, the pathway followed, and the level at which
toxic or carcinogenic effects could occur.
Contamination released from the Western Processing site into
groundwater discharges to Mill Creek and the east drain.
The potential for human exposure to contaminated groundwater
is currently remote because the contaminated zone is rela-
tively small and is almost completely isolated by discharge
to Mill Creek and the east drain. There are also no potable
water wells on or in the immediate vicinity of the site.
The potential for human ingestion of contaminants in Mill
Creek is similarly remote because the creek and other down-
stream waters are not sources of potable water. Exposure
would be limited to potential recreational contact or to
ingestion of potentially contaminated aquatic organisms.
Aquatic organisms in the creek downstream of the location of
the old sanitary discharge line would be exposed to both
chronic and acute toxic levels of certain contaminants dis-
charging into the creek from the site via groundwater. This
situation is expected to continue for the foreseeable future
unless additional remedial activities, such as those describ-
ed in this chapter, are implemented.
An evaluation of contaminant release and exposure potential
at Western Processing has led to the identification of reme-
dial action technologies (Chapter 5). These technologies
have led in turn to the identification of six remedial action
components that could be used to eliminate or mitigate these
conditions. The six components are excavation, capping,
containment or diversion barriers, groundwater extraction
and treatment, Mill Creek remedial action, and monitoring.
The purpose of the following component analyses is to pre-
sent the objectives of the individual components, discuss in
general terms their merits, and discuss their relationship
to the other components.
6.2.1 EXCAVATION
Soil excavation can accomplish several objectives. It can
reduce the source of groundwater and surface water contami-
nation, reduce the potential for direct contact with the
contaminated soils by humans or animals, and reduce the need
for or extent of other remedial action components.
6.2.1.1 Discussion
The endangerment assessment examined the excess cancer risk
associated with exposure to carcinogens based upon the
6-2
-------
ingestion of on-property soils and examined the comparison
between the predicted daily doses of non-carcinogens and
their acceptable daily intake (ADI) for a number of scenar-
ios. A detailed discussion of the results is presented in
Chapter 4. The major results can be summarized as follows:
o For the worker scenario, ingestion of Area I soils
is estimated to lead to a maximum excess lifetime
cancerrisk of 2 x 10 for surface soils and
2 x 10 for soil at depths up to 12 feet.
o For the residential scenario, ingestion of Area I
soils is estimated to lead to a.maximum excess
lifetime cancer risk of 2 x 10 for surface soils
and 8 x 10 for soils at depth.
o All offrproperty areas showed a lower than
2 x 10 excess lifetime cancer risk.
o For non-carcinogens, the predicted daily doses of
chromium (assuming that all chromium is in the
hexavalent state) and lead exceed their ADI's for
the ingestion of Area I soils. For off-property
contamination, only Area VIII exceeds the ADI for
any non-carcinogen. The one ADI exceeded in
Area VIII is for lead.
In addition to present endangerment, the potential also
exists for continuing environmental degradation due to soil
contamination. In the absence of remedial action, soil con-
taminants could be transported to adjacent properties and
surface water via surface runoff and lead to further envi-
ronmental degradation. In addition, soil contaminants in
the unsaturated zone would continue to leach into shallow
groundwater thus adding to the contaminant mass already mi-
grating to and adversely affecting Mill Creek and the east
drain. Leaching and groundwater migration are major causes
of continued environmental degradation. A discussion of the
interaction between Mill Creek and the local groundwater
flow system is presented in Chapter 3.
The nature and extent of soil contamination are summarized
in Chapter 3 and Appendix F. Area I soils generally have
high levels of metal contaminants to depths of 15 feet or
less compared to near-surface soil background concentrations.
Area I organics were also found in high concentrations to
15 feet, with a few to over 30 feet. Approximately 95 per-
cent of the Area I contamination is in the upper 15 feet.
The contaminant levels in off-property soils were highest in
Areas II, V, VI, VIII, and IX. The contaminants detected in
Areas II, V, and IX probably came from Western Processing.
Contaminants in Area VI cannot be attributed to Western Pro-
cessing because a well-defined migration pathway has not
been established. Contamination in Area VIII appears to be
6-3
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confined to metals in the surface soil based on the limited
data available. Area VIII contamination may be attributed
to wind-blown dust from the South 196th Street roadway or
incidental spillage from truck traffic.
Table 6-1 shows the average soil concentrations of several
metals remaining after excavation to selected depths in
Areas I, II, V, and IX. These analyses are based on data
presented in Chapter 3 and include samples taken from soils
that have already been removed from the site. Table 6-2
shows the average remaining soil concentrations of several
organic compounds with no excavation and after excavation to
15 feet for the same areas.
A 15-foot excavation in Areas I and II would lower the site
average concentration of all indicator metals except zinc to
below background levels and would greatly reduce or elimi-
nate organic contaminants. Areas V and IX would require
less extensive excavations to reach background for metals.
A 15-foot excavation in Areas I and II and a 3-foot excava-
tion in Areas V and IX would remove about 95 percent of the
mass of all contamination in these areas. A 6-foot excava-
tion in Areas I and II combined with a 3-foot excavation in
Areas V and IX would remove about 60 percent of the contami-
nation in these areas.
The area average concentrations presented in Appendix F have
been used in this feasibility study to define contaminant
levels. The averaging process can mask small horizontal and
vertical zones of high contaminant levels (hot spots). If
excavation is part of the selected remedial action, opti-
mization based on the three dimensional distribution of
contaminants should be done prior to final design.
6.2.1.2 Relationship to Other Components
Both excavation and capping can reduce the potential for
human and animal exposure to contaminated soils. Both can
also reduce the contaminant mass released to the shallow
groundwater, which in turn reduces or prevents further en-
vironmental degradation. Excavation directly reduces the
contaminant mass, while capping reduces infiltration that
leaches contaminants from the unsaturated zone soils.
Excavation and capping can enhance the performance of diver-
sion barriers and groundwater extraction by increasing their
efficiency and/or shortening the time of active remedial
action.
6.2.1.3 Cost Considerations
The principal variables affecting excavation costs are dis-
posal method and excavation depth. For disposal of excava-
ted materials offsite in a double-lined, RCRA regulated
6-4
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Table 6-1
SITE AVERAGE METALS CONCENTRATIONS REMAINING IN SOIL
BY AREA AT SELECTED DEPTHS
Excavation
Depth
Area (feet)
I/II 0
3
6
9
12
15
V 0
3
6
9
12
15
IX 0
3
6
9
12
15
Site Average Concentrations
(pg/kg)
Cd
15,900
14,500
12,700
8,810
4,240
1,480
1,190
580
420
330
220
200
1,800
1,500
1,010
640
470
410
Cr
313,000
311,000
275,000
187,000
102,000
40,500
17,400
13,100
11,300
10,400
9,600
8,950
104,000
84,400
42,400
17,700
13,520
12,100
Cu
177,000
166,000
144,000
107,000
64,000
25,900
22,300
20,700
20,200
20,000
20,100
20,600
41,000
36,800
29,600
24,500
22,200
21,400
Ni
54,300
48,100
38,400
25,800
18,200
12,500
11,200
10,400
9,940
9,600
9,400
9,460
14,200
13,000
12,200
11,600
11,200
10,900
Remaining in Soil
Pb
2,420,000
1,900,000
968,000
325,000
105,000
12,800
40,200
13,400
6,430
6,200
5,490
2,380
17,200
11,700
5,800
2,580
2,350
2,180
Zn
1,620,000
1,130,000
844,000
616,000
392,000
227,000
207,000
94,500
68,300
63,300
51,800
32,000
252,000
230,000
172,000
120,000
89,000
63,900
As
5,000
4,750
4,160
4,080
4,180
4,390
7,200
7,050
7,100
7,300
7,670
8,130
9,090
8,760
8,240
7,640
7,090
6,600
Background at
95% Confidence
Interval (pg/kg)
(See Table 3-5)
2,900
40,000
73,000 43,000
76,000
109,000 10,600
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Table 6-2
SITE AVERAGE ORGANIC CONCENTRATIONS REMAINING IN SOIL
BY AREA AT SELECTED DEPTHS
Area
Excavation
Depth
(feet)
Site Average Concentration Remaining in Soil (yg/kg)
Methylene Tetrachloro- Trans 1,2- 1,1,1-Trichloro- Trichloro-
Chloroform Ethylbenzene Chloride Phenol ethene Toluene dichloroethane ethane ethene
I/II
0
15
270
6
465
7
950
150
3,000
1,100
601
4
3,870
55
170
5
1,200
5
9,100
46
0
15
830
1,600
520
0
26
37
11
6
IX
0
15
82
68
10
18
CTi
I
01
Area
I/II
Excavation
Depth
(feet)
0
15
Benzo(a)
anthracene
1,300
0
Site Average Concentration Remaining in Soil (yg/kg)
Bis(2-ethyl-
hexypphthalate
8,900
360
Fluoranthene
1,400
0
Naphthalene PCB
10,400
11
400
0
Phenanthrene
27,800
0
20,700
0
0
15
25
0
IX
0
15
180
340
270
0
Note: Nondetects = 0 except for Area I/II volatiles where nondetects = detection limit.
-------
hazardous waste landfill, costs were estimated to be $100 per
ton. Transportation costs were estimated at $40 per ton to
the nearer of the two existing Northwest hazardous waste
disposal facilities. The cost for double-lined, offsite
disposal is an estimate and could vary substantially from
$100 per ton. Double-lined capacity is not currently in
service at either of the Northwest facilities. It is es-
timated that this type of capacity will be available by mid-
1985. The cost for double-lined disposal is approximately
twice that for current disposal and significantly affects
the costs for any alternatives involving disposal of mater-
ials in offsite hazardous waste disposal facilities.
Disposal costsfor a new, onsite hazardous waste landfill are
discussed in Example Alternative 3. Onsite disposal has
some practical limitations due to the size of the site and
the shallow groundwater table. Based on the analyses in
this report, onsite disposal costs for soil in the unsaturat-
ed zone are approximately $110 per ton.
Excavation costs at Western Processing, including shoring
and a dewatering and treatment system where necessary, vary
substantially depending on the excavation depth and its rela-
tion to the water table. For this study, excavation above
the water table was estimated to cost approximately $13 per
cubic yard. Excavation between water table and 25 feet below
the ground surface (about 19 feet below the groundwater table)
was estimated to cost $31 per cubic yard. Deeper excavations
(to 50 feet) were estimated to cost approximately $42 per
cubic yard.
All costs could vary depending on actual construction meth-
ods and unanticipated variations in site conditions. Factors
not included in these unit costs are allowances for mobiliza-
tion, contractor overhead, health and safety systems, engi-
neering, and associated indirect costs and contingencies.
6.2.2 CAPPING
Surface caps can perform three major functions: (1) reduce
infiltration that leaches contaminants from soils to ground-
water; (2) eliminate direct contact between contaminated
soils and stormwater and thus prevent contaminated runoff to
adjacent surface water or soil; and (3) eliminate the poten-
tial for human or animal contact with contaminated surface
soils.
6.2.2.1 Discussion
The nature and extent of soil contamination are summarized
in Chapter 3. The areas of greatest concern are Areas I,
II, V, and IX. Soils in these areas contain sufficient
amounts of source contaminants to continue degrading the
environment through leaching to groundwater and through
6-7
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surface water runoff. Ingestion of on-property surface
soils Igads to maximum excess lifetime cancer risks of
5 x 10 for the worker scenario and 2 x 10 for the resi-
dential scenario.
Installation of a surface cap is probably a minimum remedial
response for the more contaminated areas. CERCLA compliance
with the Resource Conservation and Recovery Act (RCRA) may
require an impermeable multimedia cap or equivalent for those
alternatives that do not remove all contaminants to de
minimus (i.e., insignificant) or background levels.
The effectiveness of a cap depends on its intended purpose,
the area capped, the type of cap used, construction tech-
niques, and operation and maintenance procedures. If sig-
nificant amounts of source contaminants remain in the soil
above the water table, then the primary purpose of the cap
would be to reduce water infiltration and leaching. A RCRA
multimedia cap (soil over sand over a synthetic membrane
over clay) would probably be the most effective cap for this
purpose because it consists of two impermeable layers. The
use of this type of cap, however, would prohibit future site
development. If future site development is an important
consideration, then an asphalt or concrete cap would be
preferable. Because these caps are more permeable than RCRA
caps, the amount of source contaminants remaining in the
unsaturated zone becomes more important.
The caps discussed in this chapter effectively eliminate the
potential for human or animal exposure to contaminated sur-
face soils. They also effectively reduce the potential for
contaminated surface water runoff.
6.2.2.2 Relationship to Other Components
Capping can reduce groundwater contamination by reducing
infiltration and thus contaminant leaching to groundwater.
It therefore may reduce the need for source reduction by
excavation or groundwater extraction.
An effective cap would reduce the amount of contaminants
entering the groundwater and hence improve diversion barrier
performance or shorten the groundwater pumping time.
6.2.2.3 Cost Considerations
Preliminary costs were developed for multimedia (RCRA) and
asphalt caps. The cost shown below for the asphalt cap is
for flat coverage of the 503,000 square feet in Area I. The
cost of the RCRA cap is based on the design described in the
example alternatives. The cost of the RCRA cap includes
stormwater control structures; the cost for the asphalt cap
does not include stormwater control structures. These costs
would increase if it were necessary to stockpile materials
under a temporary cap or increase the area of the cap.
6-8
-------
These costs do not include contingencies and indirect costs
and should be used for comparison only.
RCRA CAP (MEMBRANE AND CLAY):
503,000 sq ft @ $5.70 = $2,867,000
ASPHALT CAP:
503,000 sq ft @ $1.20 = $604,000
6.2.3 CONTAINMENT AND DIVERSION BARRIERS
Containment barriers are subsurface structures commonly used
with capping and/or groundwater pumping to isolate a contam-
inant source from local and regional groundwater flows.
Diversion barriers are subsurface structures that modify
groundwater flow and associated contaminant migration but do
not completely isolate the source. Their objective is to
reduce the release of contaminants beyond the barrier.
6.2.3.1 Discussion
The purpose of complete containment is usually to prevent
the continued migration of contaminated groundwater and to
isolate the zone of contamination from the environment. To
accomplish this, the barrier should completely surround the
contamination zone and be extended into a relatively imper-
meable layer that underlies the entire contaminated area.
An effective surface cap should also be provided. Soil or
groundwater contamination left outside the perimeter of the
containment barrier would remain uncontrolled and could con-
tinue to degrade the environment.
The shallowest impermeable layer at Western Processing is
approximately 150 to 200 feet below the ground surface.
Constructing a barrier to this depth is not possible using
standard installation techniques.
A diversion barrier can reduce the amount of groundwater
flowing into and out of a contaminated zone, thereby reducing
the release of contaminants from the contaminated zone. The
degree of reduction is related to the hydrogeologic charac-
teristics of the site, the barrier depth, and the barrier
orientation in relation to the local groundwater flow pattern.
A diversion barrier does not need to reach an impermeable
layer or totally surround the zone of contamination to be
effective. At the Western Processing site, a diversion bar-
rier could reduce the groundwater flow rate and thus the
amount of contamination entering Mill Creek from the site.
Depending on the barrier depth, configuration, and length,
the contaminants migrating from behind the barrier could
follow the local groundwater flow pattern into Mill Creek,
enter the regional flow pattern and be carried beneath the
6-9
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creek to more distant discharge locations such as the Green
River, or follow both pathways.
6.2.3.2 Relationship to Other Components
A diversion barrier combined with a cap and/or excavation
could reduce contamination potential by reducing or elimi-
nating unsaturated zone leaching and by reducing contaminant
transport beyond the barrier.
A diversion barrier combined with a groundwater extraction
system within the barrier can increase the system's effec-
tiveness by directing groundwater up through the contami-
nated zone and by reducing or eliminating lateral inflow of
relatively uncontaminated water, particularly from Mill Creek.
Groundwater contamination beyond the barrier would remain
relatively unaffected.
6.2.3.3 Cost Considerations
Preliminary costs were developed for two depths of soil-
bentonite barriers: 160 feet (the depth to a continuous im-
permeable layer based on data from well DB-1) and 50 feet.
Both barriers were assumed to surround Area I (perimeter
length, 3,300 feet) . The costs presented below would in-
crease if the containment barrier depth or length increases.
The costs exclude contingencies and indirect costs.
50-FOOT DEPTH: 3,300 ft. @ $385 = $1,270,500
160-FOOT DEPTH: 3,300 ft. @ $2,640 = $8,712,000
6.2.4 GROUNDWATER EXTRACTION AND TREATMENT
The objectives of groundwater extraction are to reduce or
eliminate contaminant release via groundwater during pump-
ing, and to reduce the contaminant source strength to suffi-
ciently low levels so that, after the pumping stops,
subsequent contaminant releases will not present an endan-
germent to human health or the environment.
6.2.4.1 Groundwater Extraction
The shallow groundwater under the site is contaminated with
organic and inorganic priority pollutants (Chapter 3). Data
indicate that contaminant migration has occurred to the
north, west, and east of the site. Hydrogeological data
indicate that Mill Creek and the east drain together cur-
rently receive most, if not all, local groundwater flow and
associated contamination. Although the discharge to Mill
Creek limits the extent of contaminant migration, it also
results in the environmental degradation of the creek. In
general, the zone of major groundwater contamination is
bounded on the west by Mill Creek, on the east by the east
drain, on the north by Well 13, and on the south by the site
property boundary.
6-10
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The endangerment assessment examined the excess cancer risk
associated with the ingestion of carcinogens in the ground-
water and examined the predicted daily doses of non-carcino-
gens and their ADI's for a number of scenarios. A detailed
discussion of the results is in Chapter 4. The major results
are summarized below. It must be stressed that these are
potential scenarios because there are no potable water wells
at Western Processing.
o For the worker scenario, ingestion of contaminated
groundwater from under the site could to lead to a
maximum excess lifetime cancer risk of 0.2 (2 x
10"1).
o For the residential scenario, ingestion of contam-
inated groundwater from under the site could lead
to a maximum excess lifetime cancer risk of 0.5
(5 x 10" ) .
o Using maximum onsite groundwater concentrations,
ADI's would be exceeded for toluene, 1,1,1-trich-
loroethane, bis(2-ethylhexyl)phthalate, phenol,
cadmium, chromium, cyanide, lead, and mercury.
o Using mean onsite groundwater concentrations, ADI's
would be exceeded for phenol, cadmium, chromium
(assuming hexavalent), and lead.
In addition to the potential endangerment from present lev-
els of contamination in shallow groundwater, the possibility
of further environmental degradation due to groundwater con-
taminant migration also should be considered. Groundwater
from beneath the Western Processing site is discharging to
Mill Creek at a rate of approximately 0.1 to 0.15 cubic foot
per second (50 to 70 gallons per minute; see Chapter 3).
This discharge has been calculated to be a major contributor
of contamination to Mill Creek and its sediments.
Extraction systems are usually based on the extent of the
contamination plume and the type of contamination present.
Because most, if not all, of the local, shallow groundwater
and associated contamination discharges to Mill Creek and
the east drain, groundwater contamination from Western
Processing has not migrated significant distances
off-property. Extraction system pumping requirements were
based on the need to prevent contaminated groundwater from
continuing to migrate to Mill Creek and the east drain
during the pumping period. The extraction system was sized
to pump at a rate at least equal to the estimated rate of
groundwater discharge to Mill Creek.
Because of the relatively impermeable nature of the soil and
the need to maintain maximum flexibility in the extraction
6-11
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system, a well-point extraction system was chosen for use in
the example alternatives. The system configuration varies
among alternatives. The example alternative well-point ex-
traction systems have from 170 to 340 wells, with a total
pumping rate ranging from about 80 to 100 gpm.
Based on an extraction rate of 100 gpm, the pumping period
needed to meet groundwater and Mill Creek water quality cri-
teria varies widely depending on the criteria, the contami-
nant being considered, and the type and extent of other re-
medial action components. Table 6-3 shows calculated con-
centrations in groundwater beneath the site for selected
contaminants based on 30 years of pumping at 100 gpm (with
no other remedial action component in place). As this table
indicates, metal concentrations are not significantly
reduced even after 30 years of pumping. This is because
most inorganic contaminants move through the saturated zone
at a rate many times slower than water; some, like lead,
barely move at all. Organics, on the other hand, are much
more readily removed, as Table 6-3 illustrates. Higher
pumping rates may shorten the pumping period required to
achieve the percent reductions shown in Table 6-3.
The analysis results are very sensitive to assumptions re-
garding the volume of contaminated soils, porosity, pumping
rate, and contaminant distribution coefficients (among
others). The differences between these results (Table 6-3)
and the PRP's results (see Section 6.4.1.4 and Appendix A)
can be explained by the use of different assumptions related
to contaminant volume, effective pumping rate, contaminant
distribution coefficients, and the effect of other remedial
action components.
6.2.4.2 Groundwater Treatment
Extracted groundwater would be contaminated and therefore
proper disposal would be required. Applicable groundwater
disposal options were assessed in Chapter 5 and include dis-
charge to a publicly owned treatment works (Metro), dis-
charge to Mill Creek, discharge to the Green River, and
shallow reinjection/infiltration. Each option has treatment
requirements and/or limits on the amount of water that can
be discharged. Up to 100 gpm can be discharged to Metro
under the present Metro discharge permit for the Western
Processing site. The treatment requirements for discharge
to Metro are less stringent than for other disposal options
because the effluent would be subject to additional treatment
by Metro.
Discharge to Mill Creek or to the Green River must be done
in accordance with NPDES discharge limits. Potential efflu-
ent requirements for Metro discharge and for NPDES discharge
are shown in Tables 6-4 and 6-5. NPDES discharge is limited
6-12
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Table 6-3
PREDICTED CONCENTRATIONS OF SELECTED CONTAMINANTS
IN GROUNDWATER AFTER PUMPING FOR 30 YEARS9
Expected Average
Concentration (yg/L)
Initial
After 30 Years
Percent
Reduction
Volatile Organics
Methylene chloride
Trichloroethene
Trans-1,2-dichloroethene
1,1,1-Trichloroethane
Chloroform
Toluene
Tetrachloroethene
52,000
16,000
7,700
8,700
2,200
820
50
0
114
0
89
0
105
14
100
99
100
99
100
87
72
Nonvolatile Organics
Phenol
Naphthalene
Ethylbenzene
Inorganics (Background level)
Arsenic (17)
Cadmium (2.8)
Chromium (13)
Copper (75)
Nickel «40)C
Lead (23)
Zinc (74)
42,000
15
10
19
1,500
2,200
1,000
15,000
290
121,000
0
10
5
18
800
2,065
970
3,200
290
79,000
100
33
50
5
47
6
3
79
0
35
Assumes that a RCRA cap is in place (or that unsaturated zone has been
excavated to 6 feet) but that no contaminants are removed from the
saturated zone and that no diversion barrier is in place.
b
Background levels for organics are assumed to be zero.
"40 yg/L was detection level for groundwater samples used to determine
background.
6-13
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Table 6-4
POTENTIAL LIMITATIONS FOR DISCHARGE TO
METRO SANITARY SEWER SYSTEM
Compounds
Total oils and greases
Cyanide (total)
Total toxic organics (TTO)
Arsenic
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Zinc
pH range
Daily Maximum Concentration
(mg/L)
100
2.0
2.13
,0
1,
1.2
6.0
3.0
3.0
0.1
6.0
5.0
5.5-12.5
Table 6-5
POTENTIAL AMBIENT WATER QUALITY CRITERIA
FOR NPDES DISCHARGE3
Compound
Cadmium
Chromium
Copper
Lead
Nickel
Zinc
Chloroform
1,1,1-trichloroethane
Trans-1,2-dichloroethene
Tetrachloroethene
Trichloroethene
Toluene
2,4-dimethylphenol
Maximum
Allowable
Concentration
in Effluent
(yg/L)
3.02
22.
172
1,844
321
28,900
18,400
11,600
5,280
45,000
17,500
2,120
Maximum Average
Concentration
at Edge of
Mixing Zone
(yg/L)
1
0
0
5
3
96
47
,24g
.0025
.29
.6
.8
841
b
"b
Assumes hardness to be 100 mg/L as CaC03.
''These compounds have no 24-hour average criteria or chronic
toxicity information.
6-14
-------
to 15 percent of the surface water flow rate. During summer.
Mill Creek discharge would be limited to 135 gpm. A much
higher discharge rate is allowable during the winter. The
Green River can receive any anticipated groundwater treat-
ment discharge flow rate.
Due to the stringent treatment requirements and treatment
costs associated with other disposal options, discharge to
Metro appears to be the most desirable option. The dis-
charge limit of 100 gpm appears to be more than adequate for
successful operation of the extraction system and to protect
Mill Creek from further degradation during pumping.
To meet either of the contaminant discharge limits, the fol-
lowing types of treatment processes should be included in
the treatment system:
o Heavy metals removal
o Volatile organics removal
o Non-volatile organics removal
The development of an example treatment system is discussed
in Appendix G.
6.2.4.3 Relationship to Other Components
Implementation of other remedial actions could affect the
time required for groundwater extraction and treatment. An
effective containment barrier could eliminate the need for
groundwater extraction. Excavation and/or capping could
shorten the groundwater extraction time frame, as could a
diversion barrier. The Mill Creek results section of Appen-
dix F illustrates the above points by examining the effects
of no action and two other excavation/capping actions on
Mill Creek water quality.
6.2.4.4 Cost Considerations
Preliminary cost estimates for groundwater extraction and
treatment are presented in Section 6.4.
6.2.5 MILL CREEK
The focus of the Mill Creek remedial action is on the ad-
verse effects of the contamination that has migrated beyond
the source area at Western Processing. The primary con-
sideration of this action is to eliminate or reduce the
adverse effects that otherwise would not be mitigated by
source control remedial actions.
6-15
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6.2.5.1 Discussion
Mill Creek sediments and water have been contaminated, par-
ticularly with metals, as a result of contaminated surface
water and groundwater discharges from Western Processing and
other sources. As discussed in Chapter 3, concentrations of
several dissolved metals increased up to two orders of mag-
nitude in the reach adjacent to Western Processing. Concen-
trations of dissolved copper, cadmium, lead, and zinc exceeded
the maximum allowable ambient water quality criteria concen-
trations downstream of Western Processing. Organic priority
pollutants in Mill Creek water did not exceed criteria val-
ues, although volatile organics enter Mill Creek in the
Western Processing reach. Sediment concentrations of cad-
mium, chromium, copper, nickel, and zinc increased one to
two orders of magnitude over upstream values as the creek
passed Western Processing.
Data on organics in Mill Creek sediments indicate decreased
concentrations in more recent samples collected downstream
of Western Processing. The highest concentrations of some
organics were measured in samples from upstream of Western
Processing. The source of other environmental problems in
Mill Creek, such as low dissolved oxygen concentrations,
was also upstream of Western Processing (Yake 1985) .
The endangerment assessment (Chapter 4) discussed contamina-
tion in Mill Creek water and sediment as it affects both
human health and aquatic organisms. Important items in that
discussion are as follows:
o Priority pollutant contamination in Mill Creek
does not appear to pose a threat to human health
based upon realistic consumption scenarios.
o Concentrations of several dissolved metals exceeded
the maximum allowable ambient water quality crite-
ria concentrations for the protection of freshwater
aquatic organisms.
o On the basis of data in the criteria documents,
the water in Mill Creek is likely to be toxic to a
wide variety of aquatic organisms.
Once source control actions have reduced the discharge of
contaminants to Mill Creek to a level that would allow Mill
Creek water quality to meet cleanup criteria, the contami-
nated sediments in the creek would still remain as a poten-
tial source of continued adverse impacts to aquatic organ-
isms because of the following:
o Contaminants adhering to the sediments in Mill
Creek can leach into the water and potentially
degrade the water quality to levels that are toxic
to aquatic organisms.
6-16
-------
o The concentration of source contaminants in the
sediments is high enough to be toxic to bottom-
dwelling aquatic organisms, which are a food source
for other aquatic species; this reduces the poten-
tial of this portion of the creek to support a
healthy aquatic population.
o Contaminated sediment in the reach of Mill Creek
by Western Processing can be transported downstream.
Two example alternatives for the mitigation of sediment con-
tamination in Mill Creek have been selected. They are "no
action" and "sediment removal." "No action" would involve
leaving the contaminated sediments in place. After source
control measures are implemented, continued natural sediment
transport processes will gradually move these contaminated
sediments downstream of the Western Processing stream reach.
As the sediments move downstream, they could be dispersed
and diluted, which could reduce adverse impacts previously
identified. King County Drainage District No. 1 removes
sediment from Mill Creek as part of their maintenance opera-
tions. Contaminated sediment removed from the creek and
placed on the banks could be a continued source of contam-
ination to Mill Creek.
Sediments could be removed if they were determined to be
causing further environmental degradation after source con-
trols have been implemented. Sediment removal would involve
diverting and dewatering the creek for a few weeks and remov-
ing contaminated sediments. This would destroy the aquatic
habitat in the diversion reach. Also, fish may not be able
to pass through the diversion system. Diversion of the creek
may alter local groundwater migration patterns, but such
alteration would be temporary.
6.2.5.2 Relationship to Other Components
The condition of Mill Creek will be greatly affected by the
implementation of source control remedial actions. A suc-
cessful mitigation of contaminant discharge from Western
Processing to Mill Creek is necessary before any Mill Creek
remedial action can be successful.
6.2.6 MONITORING
Monitoring would be required for all alternatives to ensure
that the selected remedial action is performing as expected
and that public health and the environment are protected.
Groundwater monitoring would require the measurement of water
levels and quality at various depths, locations, and times
both on and off the property. Caps and landfill liners would
be monitored for integrity. Flow rate and quality monitoring
would be required for the groundwater extraction and treatment
6-17
-------
system. Mill Creek water and sediments also would be moni-
tored. Additional items, such as organic vapors and airborne
particulates, would be monitored during construction of any
alternative.
Monitoring system design, construction, and operating details
would be determined during detailed design. Further modifi-
cations during implementation of a particular alternative
would be likely.
Because the monitoring system would be the same for each
example alternative (except no action), it will not be ad-
dressed in either Section 6.3, Description of Example Alter-
natives, or Section 6.4, Evaluation of Example Alternatives.
6.3 DESCRIPTION OF EXAMPLE ALTERNATIVES
As previously identified, the purpose of this chapter is to
present a range of example alternatives available to miti-
gate contamination at Western Processing. The specific
example alternatives presented here are not intended to
describe the only alternatives that could be implemented at
Western Processing or to describe a preferred alternative or
a final design. Additional example alternatives can be de-
veloped using data contained in this report. The range of
alternatives facilitates comparisons of the relative bene-
fits and adverse impacts of each alternative. Example Alter-
native 4 was developed and evaluated by the Potentially
Responsible Parties (PRP's).
6.3.1 EXAMPLE ALTERNATIVE 1—NO ACTION
Example Alternative 1 is the no action alternative. Under
Example Alternative 1, no further action of any kind would
be taken at Western Processing. The cost for Example Alter-
native 1 is zero because the alternative includes no capital
or operating expenses.
6.3.2 EXAMPLE ALTERNATIVE 2—SURFACE CAP WITH GROUNDWATER
EXTRACTION AND TREATMENT
Example Alternative 2 is intended to reduce contaminated
runoff to Mill Creek from Western Processing and adjacent
soils, to reduce rainwater infiltration and leaching of con-
taminated soils, to prevent direct contact with contaminated
soils by humans or animals, to improve the groundwater qual-
ity in the shallow aquifer beneath Western Processing, and
reduce the amount of contamination migrating from Western
Processing via groundwater to a level that will eliminate
endangerment to human health and to aquatic organisms in
Mill Creek.
6-18
-------
The site plan and cross-section for Example Alternative 2
are shown in Figures 6-1 and 6-2. In general, Example Al-
ternative 2 includes a multilayer RCRA cap both on and off
the property, surface drainage control, and groundwater
extraction and treatment. A more detailed description of
Example Alternative 2 is given below, organized by
component.
6.3.2.1 Excavation
Example Alternative 2 incorporates no excavation or offsite
disposal of contaminated soils.
6.3.2.2 Capping
Example Alternative 2 includes a five-layer multimedia cap.
The cap would be constructed over Areas I and II and the
eastern portion of Area V. From top to bottom, the layers
consist of: 24 inches of loam (topsoil), a geotextile filter,
12 inches of sand, a 20- to 40-mil impermeable synthetic
membrane, and 24 inches of compacted clay. The cap would be
sloped to promote draining and would include interior and
perimeter concrete-lined surface ditches and detention basins
to provide stormwater collection and discharge. The storm-
water system would be designed to comply with the City of
Kent stormwater ordinance No. 2130. The cap would be vented
to prevent the buildup of vapors.
6.3.2.3 Diversion Barriers
Example Alternative 2 does not include a diversion barrier.
6.3.2.4 Groundwater Extraction and Treatment
Groundwater would be extracted at a rate of 100 gpm by a
system of 340 well points, each 30 feet deep, with the bot-
tom 20 feet screened for water collection. Approximately
200 well points would be located in Area I, and 140 would be
located in Areas II, V, IX, and X. Groundwater would be
extracted by nine centrifugal suction pumps and would be
piped to a treatment plant located in the northwest corner
of the Western Processing property in an area formerly oc-
cupied by a residence (Area VII). The groundwater system
would be operated for at least 30 years.
Four technologies have been selected for use in the ground-
water treatment system:
o Air stripping for volatile organics
o Lime precipitation for heavy metals and organics
removal, followed by filtration
6-19
-------
o Chemical oxidation of organics using hydrogen
peroxide
o Granular activated carbon adsorption for additional
organics removal
A conceptual schematic of the groundwater treatment system
is shown in Figure 6-3.
The treated groundwater would be discharged to the Metro
sewer through the City of Kent's 8-inch sanitary sewer line
on South 196th Street. Based on discussions with Metro per-
sonnel, maximum discharge to this outlet would be 140,000
gallons per day (approximately 100 gallons per minute)
unless additional hydraulic capacity is added to the sewer
system.
6.3.3 EXAMPLE ALTERNATIVE 3—EXCAVATION WITH ONSITE
DISPOSAL, GROUNDWATER EXTRACTION AND TREATMENT, SURFACE CAP
Example Alternative 3 is intended to isolate the contamina-
ted soil in the unsaturated zone from rainwater infiltration
and leaching, to reduce contaminated runoff to Mill Creek,
to prevent direct contact with contaminated soils by humans
or animals, to improve the groundwater quality in the shal-
low aquifer beneath Western Processing, and reduce the
amount of contamination migration from Western Processing
via groundwater to a level that will eliminate endangerment
to human health and to aquatic organisms in Mill Creek.
The site plan and cross-section for Example Alternative 3
are shown in Figures 6-4 and 6-5. In general, Example
Alternative 3 includes excavation of soil from the unsatur-
ated zone of Areas I and II and placement of this soil in a
lined, onsite landfill. The landfill would be covered with
a multimedia cap. In addition, Area II and the eastern por-
tion of Area V would be capped. The capped areas would have
surface drainage controls. Groundwater would be extracted
and treated.
6.3.3.1 Excavation
The excavation component of this example alternative would
include the removal of the unsaturated zone soil (assumed to
be the top 6 feet) from Areas I and II and placement of the
soil in a double-lined landfill (see Figure 6-4) constructed
on Area I. The landfill liner would consist of (top to bot-
tom) a geotextile filter, a sand layer with leachate col-
lection and removal system, a synthetic membrane primary
liner, sand with leak detection and backup collection sys-
tem, synthetic membrane, and a 2-foot-thick clay liner.
6-20
-------
RAILROAD -i t-i i i i i i i i i i i i i i i—i
DISCHARGE TO
f ^-- DISCHARGE TO
EAST DRAIN
EAST DRAIN
x x v x.v \xx x x
BURIED UTILITIES
(WATER, GAS, TELEPHONE)
GROUNDWATER
EXTRACTION
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
NOT TO SCALE
FIGURE 6-1
CONCEPTUAL SITE PLAN
FOR EXAMPLE ALTERNATIVE 2:
SURFACE CAP/
GROUNDWATER PUMPING
AND TREATMENT
6-21
-------
w
See Detail 1 Below
Runoff to Outlet
Runoff
to Outlet
Remove Fence
Vent
Runoff
to Outlet
Mill Creek
Max 5% Slope
Max 5% Slope
Vent
-Max 5% Slope / Max5%Slope
Utility Poles
\
Railroad
Track
Regrade and Compact
Existing Surface Soils
1
2" Groundwater Extraction
Wellpoints with Collection
Headers
/
Relocated
Utility Poles
14" Pipeline
Approximate
Location
Interurban Trail
Approximate
Watertable
Surface
Groundwater
Extraction
Wellpoints
with Collection
Headers
GENERALIZED CROSS-SECTION
NOT TO SCALE
Concrete-Lined Ditch
Drain to Outlet
Primary Cap
20 mil Synthetic
Membrane (Impermeable)
Midslope
Lined Ditch
Drain to Outlet
Vent Pipe
(Locate at Crown)
Vegetative
Slope Protection
Geotextile Filter
rrrr.rriTV.-rr
=-=-•==-
Secondary Cap (Clay)
2' Clay
(10'7 Permeability)
Regraded &
^Existing Ground Surface Compacted Soils
Slotted Drain Line
DETAIL 1
TYPICAL SOIL / MEMBRANE CAP SYSTEM
NOT TO SCALE
Groundwater
Extraction
Well Point (Typ.)
FIGURE 6-2
CONCEPTUAL CROSS-SECTION OF
EXAMPLE ALTERNATIVE 2:
SURFACE CAP/GROUNDWATER
PUMPING AND TREATMENT
6-23
-------
Groundwater
From Wells
Air-
Air Stripping
(Volatile Organics
Removal)
Lime
Polymer
1 Ferric Sulphate
I
cr\
NJ
en
^S^ .X^ i — Precoat
\ >"^ \ > 01. .-!„,. »~
Surge Tank
1 Rapid M\x Flocculation Clanher | 1 Disposal
_ T Vacuum Filter
H2S04 H202
1 1 -•
\ 1 \ I
\_ \ Effluent Discharge
Filter j
s:
rocess configuration sho\
vledge of groundwater cc
U, pH Adjustment Oxidation
(Non-volatile Granular
Organics Activated
Removal) Carbon
wn is based on present (Organics
>mposition. Pilot Removal)
tests will be required to verify process selection.
It is possible that additional (or fewer) processes
will be required.
2. Sequence of processes is subject to variation
based on outcome of pilot tests.
FIGURE 6-3
GROUNDWATER TREATMENT
PROCESS FLOW CHART
-------
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
AREA 1
BOUNDARY
FIGURE 6-4
CONCEPTUAL SITE PLAN
FOR EXAMPLE ALTERNATIVE 3:
EXCAVATION WITH ON-PROPERTY
LANDFILL DISPOSAL/
GROUNDWATER PUMPING AND
TREATMENT/SURFACE CAP
6-27
-------
w
/INI Creek
See Detail 1 Below
Backfill with Onsite
Excavated Material Above Liner
Runoff to
Outlet
Remove Fence
Remove
Fence
,
— <
/ '
=====4=£=
*\. • 4 «-^ — -^
\\ Excavation
x^ Slope Surfaces to Drain
=*f
J
v - A
Leachate
Collection
System
^ Existing Ground Surface
.t
Liner/Cap System Leachate '
(See Detail 1) Collection
System
Well Point
with Collection
Header
Leachate
Collection
System
Runoff
to Outlet
Utility Poles
Relocated
Utility Poles
Railroad
Track
• Jog Path
_^v_ - ' -
Well Point
with Collection
Header
14" Pipeline
Approximate
Location
Approximate
Watertable
Surface
GENERALIZED CROSS-SECTION
NOT TO SCALE
Vent Pipe
Midslope
Lined Ditch
Drain to Outlet
Primary Cap 20 mil
Synthetic Membrane
(Impermeable)
Vegetative
Slope Protection
Concrete Lined
Ditch Drainto Outlet
T
[
>_ J (Located Along Crown)
,- — 2x2'Sand Filled Trench
Encapsulated Onsite
Materials
Slotted Leachate
Collection Pipe
-K. .-rer^SJ
Synthetic Membrane
Anchor Trench
Wellpoint
Collection
Header (typical)
Synthetic Membrane
Drainage Trench
Primary Liner 20 to 40 r
Synthetic Membrane
(Impermeable) Imported
Earthfill
Well Point
(typical)
Geotextile
Filter
/ Filter
f Synthetic Membr
±=.^~ Primary Liner
Synthetic
Secondary Liner
Leak Detection
and Collection Pipe
Drain Rock
DETAIL 1
TYPICAL LINER/CAP SYSTEM
NOT TO SCALE
6-29
FIGURE 6-5
CONCEPTUAL CROSS-SECTION
OF EXAMPLE ALTERNATIVE 3:
EXCAVATION WITH ON-SITE
LANDFILL DISPOSAL/
GROUNDWATER PUMPING AND
TREATMENT/SURFACE CAP
-------
In addition to the unsaturated zone soils in Areas I and II,
soils from a portion of Area VIII would be excavated to a
depth of one foot and placed into the onsite landfill. The
excavated area would be backfilled.
6.3.3.2 Capping
Example Alternative 3 includes a five-layer, multimedia cap.
The cap would be constructed over Areas I and II and eastern
portions of Area V. The cap design would be identical to
the cap described for Example Alternative 2.
6.3.3.3 Diversion Barriers
Example Alternative 3 does not include a diversion barrier.
6.3.3.4 Groundwater Extraction and Treatment
Groundwater would be extracted at a rate of about 85 gpm by
a system of 170 well points, each 30 feet deep with the
bottom 20 feet screened for water collection. The well
points would encircle the site on 20-foot centers in Areas I,
III, IV, V, IX, and X (see Figure 6-4). Groundwater would
be extracted by six centrifugal suction pumps and piped to
an onsite treatment plant.
The groundwater treatment system design and location and
operating period would be similar to the those described as
part of Example Alternative 2.
6.3.4 EXAMPLE ALTERNATIVE 4—PRP REMEDIAL ACTION PLAN1
The components and technologies of Example Alternative 4,
the PRP plan, were developed independently of those devel-
oped by USEPA. This alternative is intended to prevent
direct human and animal contact with contaminated materials
in Area I; to eliminate the release of contaminated runoff
from Area I; to remove buried wastes from Area I; to reduce
the amount of contamination migrating from Western Processing
via groundwater to a level that will eliminate the endanger-
ment to aquatic organisms in Mill Creek; to eliminate the
need for long-term monitoring and maintenance of the property
as a hazardous waste site; to allow future productive use of
the property; and to minimize the potential for long-term
liability for the PRP's.
A description of the process by which the PRP plan was se-
lected is provided in Appendix A. Example Alternative 4 is
illustrated in Figures 6-6 and 6-7.
This section has been provided by the PRP's.
6-31
-------
In general, Example Alternative 4 includes excavation and
offsite disposal of waste materials and soil from the unsat-
urated zone in Area I, a diversion barrier, groundwater
extraction and treatment, a surface water infiltration and
drainage control system, and an asphaltic concrete pavement
to be installed over Area I after the groundwater extraction
system has been dismantled.
The PRP plan also includes the removal of sediments from
Mill Creek. Example Alternative 7 and the Mill Creek por-
tion of the PRP plan are essentially the same. Therefore,
no further discussion of the PRP cleanup plan for Mill Creek
is included in this document.
The PRP plan does not address additional off-property con-
tamination, other than off-property contaminated groundwater
which could potentially be removed during the pumping pro-
gram. Other example alternatives in this feasibility study
address the extent of off-property contamination and pos-
sible remedial approaches. One of these approaches to off-
property contamination control may be applicable and would
be one of the subjects of negotiation.
6.3.4.1 Excavation
The excavation component of the PRP plan consists of a vari-
able-depth excavation scheme designed to remove approximately
75,000 cubic yards of waste materials and contaminated soil
from the unsaturated zone in Area I and the disposal of this
material in an offsite, double-lined, RCRA hazardous waste
landfill. Imported soil would be used to backfill the
excavations.
6.3.4.2 Groundwater Extraction and Treatment
Groundwater would be removed at a rate of approximately
100 gpm by a system of three rows of well points (see Fig-
ure 6-9) installed on the property to an average depth of
about 25 feet below the ground surface. Approximately
200 well points would be installed, with individual well
points along each row spaced about 20 feet apart. The three
rows of well points would be divided into six different
operational groups by means of valves installed on the headei
pipes leading from the well points. Three centrifugal-vacuur
pumps would be installed to run the system. All header pipes
valves, and pumps would be installed above the ground surface
The groundwater pumping system would operate for a period of
up to 5 years.
6-32
-------
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
Outfall Line to Mill Creek
To Onsite or
Off site Treatment
72nd Street
Ditch
Railroad
0 150
300
Scale in Feet
6-33
FIGURE 6-6
SITE PLAN FOR
EXAMPLE ALTERNATIVE 4
WESTERN PROCESSING
Kent, Washington
-------
EXISTING POWER POLE
WEST PROPERTY LINE
ASPHALTIC CONCRETE PAVEMENT
(INSTALLED AFTER PUMPING SYSTEM REMOVED)
GRAVEL BASE COURSE
ELEVATION 23.0' MSL
EAST PROPERTY LINE
FENCE
EXISTING DITCH
DIVERSION BARRIER PLATFORM MATERIAL
ALONG SITE PERIMETER
GENERAL SITE FILL
•WELL POINT
CATCH BASIN AND
DRAINAGE CONTROL SYSTEM
WELL POINT
CATCH BASIN AND DRAINAGE
CONTROL SYSTEM '
DIVERSION BARRIER
ELEVATION -17.0*
SECTION A-A
NOT TO SCALE
ELEVATION —17.0'-
DIVERSION
BARRIER
6-35
FIGURE 6-7
SITE CROSS-SECTION FOR
EXAMPLE ALTERNATIVE 4
WESTERN PROCESSING
Kent, Washington
-------
During operation of the groundwater pumping and treatment
system, precipitation falling on the property would be al-
lowed to infiltrate through a permeable, gravel surface cov-
er. The property would be graded to prevent overland flow
from entering or leaving the property. As precipitation
infiltrates through contaminated soil between the bottom of
the excavations and the groundwater surface, it would pick
up contaminants from the soil and transport them to the
groundwater for subsequent removal by the pumping and treat-
ment system.
Treatment of groundwater prior to discharge would be pro-
vided either by a treatment plant constructed on the prop-
erty or by an existing offsite treatment plant. If the off-
site treatment plant option is selected, the contaminated
groundwater would be transported to the plant by pipeline.
Treatment would be similar to that included in Example
Alternatives 2 and 3, consisting of metals precipitation,
air stripping, chemical oxidation of organics, and carbon
treatment. Flow through the facility would be approximately
100 gallons per minute. The treated water would be dis-
charged either to the Green River (on-property treatment
plant option only) or to the Metro sewer system (both
options).
6.3.4.3 Diversion Barrier
To prevent surface water and shallow groundwater outside the
property from being pumped preferentially into the well point
system, a diversion barrier would be constructed along the
perimeter of Area I to a depth of 40 feet. While the pumping
system is operating, this barrier would allow the cleaner,
deeper off-property groundwater to be drawn through the con-
taminated soils, thereby flushing the relatively mobile con-
taminants from a depth of at least 40 feet. Following
completion of the pumping program, the barrier would act to
lengthen the travel distance, and hence travel time, for any
residual contaminants that might migrate from the property
to Mill Creek. Increasing the travel time reduces the rate
of contaminant release via groundwater from Area I to Mill
Creek.
6.3.4.4. Capping
A relatively impermeable pavement would be installed over
the property after the groundwater extraction and treatment
program is completed and the pumping system is removed.
This system was selected to inhibit the infiltration of pre-
cipitation following completion of the groundwater pumping
and treatment program. The pavement would consist of
asphaltic concrete and would be constructed over an aggre-
gate base (see Figure 6-7). The property would be graded to
form nine drainage basins, with each basin routing runoff
6-37
-------
to an internal catch basin. The nine catch basins would be
interconnected using subsurface 12-inch pipes and would route
runoff to an oil separator and flow restrictor. Discharges
to Mill Creek from this system would be at or below the rate
permitted by the City of Kent.
6.3.5 EXAMPLE ALTERNATIVE 5—EXCAVATION WITH OFFSITE
DISPOSAL
Example Alternative 5 is intended to eliminate the potential
for discharge of contaminated surface water from the site to
Mill Creek, to prevent direct contact with contaminated soils
by humans and animals, to return groundwater quality in the
shallow aquifer beneath the site to background levels, and
to eliminate the potential for endangerment of human health
and aquatic organisms in Mill Creek, and endangerment of
human health in the groundwater.
Example Alternative 5 is shown in Figures 6-8 and 6-9. 'The
main element in this alternative is the excavation and re-
moval of on-property and certain off-property soils to an
offsite, double-lined, RCRA hazardous waste landfill. Exca-
vation is proposed below the local groundwater table for the
on-property area. A dewatering system would be needed during
this portion of the excavation. The excavated areas would
be backfilled and returned to their undeveloped state.
6.3.5.1 Excavation
Soil excavation is the main component of this alternative.
Area I and II soils would be excavated to a depth of
15 feet. Soils in portions of Areas V and IX would be ex-
cavated to 3 feet; in a portion of Area VIII, soils would be
excavated to one foot (as described in Example Alternative 3)
The old sanitary discharge line would be removed from Area V.
Fill would be imported to replace the excavated soil and
return the excavated areas to the approximate former grade.
The local groundwater table is about 6 feet below the ground
surface in Area I. A dewatering system would be needed when
the excavation depth is near or below the water table and
during the placement of clean fill. The dewatering system
would consist of well points placed around the excavated
area similar to the system described in Alternative 3. De-
pending on the actual configuration of the excavation in
Area II, the petroleum pipeline may require either stabili-
zation or relocation. The required flow rate of the dewa-
tering system cannot be accurately predicted from available
data. The effluent from the dewatering system would be
treated and discharged as described for Example Alterna-
tives 2 and 3.
6-38
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RAILROAD' i i i 11 i i i 11
BURIED UTILITIES
(WATER,GAS,TELEPHONE)
PERIMETER
DEWATERING
SYSTEM
INTERURBAN TRAIL
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
>fSEWER LINE
FIGURE 6-8
CONCEPTUAL SITE PLAN
FOR EXAMPLE ALTERNATIVE 5:
EXCAVATION ABOVE AND BELOW
GROUNDWATER TABLE WITH
OFF-SITE DISPOSAL
6-39
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w
Mill Creek
Remove Fence
- Interurban Trail
Railroad
Track
\
~~ — .^
/
Remove Fence 1
Existing Ground Surface — . y \
- Limit of Excavation \^ Backfill with /
S Imported Earth /
1 — Power Poles
1 Remain
^ + _^^- Powe
| T Rerot
\ ...
V 14" Pipeline 1
Groundwater Approximate Groundwater'
Dewatering Location Dewaterinq
. Approximate Watertable
Surface
Well Points
with Collection
Headers
Well Points
with Collection
Headers
• Localized dewatering will
be used in area of deep excavation.
GENERALIZED CROSS SECTION
Not to Scale
Excavation depth exaggerated
to show components.
FIGURE 6-9
CONCEPTUAL CROSS-SECTION
OF EXAMPLE ALTERNATIVE 5:
CONTAMINATED SOIL DISPOSAL OFFSITE
ASPHALT SURFACE CAP WITH GROUNDWATER
TREATMENT.
6-41
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For the purposes of sizing and costing, the dewatering system
flow rate was assumed to be 100 gpm. This value is consis-
tent with projected groundwater extraction flow rates from
Example Alternatives 2 and 3. However, the duration of
pumping would be limited to the time required for excavation
and fill operations (approximately 4 years).
6.3.5.2 Capping
Example Alternative 5 does not contain a capping component.
6.3.5.3 Diversion Barrier
Example Alternative 5 does not contain a diversion barrier
component.
6.3.5.4 Groundwater Extraction and Treatment
Example Alternative 5 does not contain a long-term ground-
water extraction and treatment component. The construction
dewatering system would contain a treatment system similar
to that described in Example Alternative 2. The perimeter
well array would be similar to that in Example Alternative 3
with added dewatering around the deeper excavation in
Areas I and II.
6.3.6 EXAMPLE ALTERNATIVE 6—MILL CREEK-NO ACTION
Under Example Alternative 6, contaminated sediments in Mill
Creek would be left in place. No stream diversion action
would be taken.
6.3.7 EXAMPLE ALTERNATIVE 7—MILL CREEK SEDIMENT REMOVAL
Example Alternative 7 is intended to remove contaminated
sediments from Mill Creek to prevent them from moving down-
stream and from leaching contaminants into the water of Mill
Creek. During the sediment removal process, Mill Creek would
be diverted to minimize contaminant resuspension and sediment
transport during the sediment removal operation, and to mini-
mize the amount of water that would be removed with the
sediment.
Example Alternative 7 is shown in Figures 6-10 and 6-11. In
general, Example Alternative 7 entails constructing dikes
and installing pumps and pipelines to divert Mill Creek
around the Western Processing site while contaminated sedi-
ments are being excavated.
6.3.7.1 Diversion Pipeline and Pumping
The diversion period should be between July and October, the
historical low-flow season. A maximum capacity of 15 cubic
feet per second was selected for the diversion pipeline.
6-43
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Mill Creek flow is expected to be less than this rate 99
percent of the time in any given year. An 18-inch-diameter
pipeline would be installed to transport the diverted water
downstream to about 1,000 feet north of the Western Process-
ing property line, for a total diversion of 2,300 feet.
Four 1,700-gallon-per-minute pumps would be necessary.
6.3.7.2 Diversion Dikes
Diversion dikes would be provided both upstream and down-
stream of the reach from which sediment would be removed.
These dikes, together with groundwater seepage controls,
would keep the work area dry. An example engineered struc-
ture is shown in Figure 6-11. The structure consists of a
compacted gravel core, an impermeable synthetic membrane,
sand bedding, and a geotextile covered with 4-inch-diameter
riprap. The upstream berm would be approximately 7.5 feet
tall and the downstream berm would be approximately 5 feet
tall. Other types of dikes, such as the sheet-pile dikes
proposed by the PRP's, could also be an effective means to
divert Mill Creek.
6.3.7.3 Excavation of Contaminated Sediments
Sediment would be removed from the bed and banks of Mill
Creek to a depth of from six inches to one foot. The width
of the excavation is expected to average 40 feet for the
entire length of Mill Creek between the two berms. After
the sediment has been removed, the stream bed would be reha-
bilitated with gravel riffles and the stream banks with
native vegetation.
For cost estimating, the sediment was assumed to be disposed
in an offsite, double-lined, RCRA hazardous waste landfill.
Further testing may reveal that the material qualifies for
less expensive disposal.
6.4 EVALUATION OF EXAMPLE ALTERNATIVES
The example alternatives described in Section 6.3 were eval-
uated based on technical feasibility, environmental and public
health concerns, institutional requirements, and cost esti-
mates. These evaluations are discussed in this section.
Section 6.5 summarizes the results of these evaluations.
The evaluations addressed many different aspects of the
existing and potential contaminant migration pathways and
releases from Western Processing. One aspect that received
particular attention was the contamination of Mill Creek,
especially by contaminated groundwater migrating from
Western Processing. Other factors are also important in
evaluating an example alternative's effectiveness. These
include reduction in contaminant concentrations in shallow
6-44
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CTi
I
Ul
/ /^/-"'UPSTREAM
/ J^BERM
DIVERSION
PUMP STATION
FIGURE 6-10
PLAN VIEW OF MILL CREEK
DIVERSION BERMS AND
TEMPORARY PIPELINE
-------
20
19
18
17
16
Sand
.* Rip Rap
/ 8" Layer
Bedding(6") /
/ Geotextile
Existing
Creek
Bottom
_/ - |
(
£_
(Separation Material |
Must Not Be Damaged
By Rip Rap) J
^_^^^
\ -^
-
-------
groundwater beneath and adjacent to the site (a potential
concern if either this groundwater or Mill Creek were ever
to be used as a potable water source) and elimination of the
potential hazards associated with direct human contact with
contaminated soils.
Shallow groundwater and Mill Creek water quality are closely
related because local groundwater discharges to the creek.
During summer, most of the flow in the creek is supplied by
groundwater.
Because the creek and shallow aquifer are not used for water
supply, contaminant concentrations in the groundwater and
Mill Creek were compared to USEPA ambient water quality cri-
teria (24-hour and maximum) for aquatic organisms. However,
background levels near Western Processing, particularly for
metals, were higher than the ambient criteria.
Because it is not practical to clean up contaminanted ground-
water to levels that are lower than background concentrations,
the criteria for evaluating effectiveness were modified by
replacing the criteria levels with background levels whenever
background was higher than the criteria. These site-specific
modified ambient water quality criteria (see Table F-5 in
Appendix F) were then used as the basis for evaluating the
effectiveness of example alternatives.
In the absence of Western Processing, Mill Creek would
probably meet the aquatic water quality criteria for metals,
even during the summer low flow periods, despite the rela-
tively high background groundwater metals concentrations.
Natural processes in the creek, such as adsorption on sedi-
ment and chemical precipitation, reduce the dissolved metal
concentrations after groundwater discharges into the creek.
Therefore, reducing Western Processing groundwater concen-
trations to near background concentrations should allow the
creek to achieve ambient water quality criteria.
Metals, particularly zinc, were identified as key indicators
of present and probable future impacts in Mill Creek for the
following reasons:
o Organics are not now, nor are they anticipated to
be, a problem in the creek for aquatic organisms,
whereas metals are currently above ambient water
quality criteria.
o Metals are not easy to remove from the groundwater
system.
o Zinc generally exceeds its modified ambient water
quality criterion by the largest factors.
6-49
-------
o If zinc concentrations in the groundwater were
reduced to a level that allows Mill Creek to
achieve the modified ambient water quality crite-
rion for zinc, then other indicator metals would
similarly achieve the modified criteria.
To address the remote possibility that shallow groundwater
beneath the site might be used as a source of drinking water,
contaminant concentrations in this groundwater were compared
to federal drinking water standards, acceptable daily intake
(ADI) levels (assuming an average consumption of 2 liters of
water per day), and SNARL's (for longer term use). The
federal drinking water standards cover priority pollutant
metals and a single indicator organic (chloroform); these
standards must be met by public drinking water systems. The
ADI's and SNARL's are guidelines only; however, they cover
more of the organic priority pollutants found at Western
Processing. Chapters 2 and 4 contain a discussion of these
standards and guidelines. Appendix F contains additional
information on the example alternative evaluations.
6.4.1 TECHNICAL EVALUATION
The technical evaluation addresses the areas of reliability,
implementation capability, and safety. Reliability factors
include effectiveness, durability, and demonstrated perfor-
mance. Implementation capability includes ease of installa-
tion, time required to implement, and monitoring, operation,
and maintenance requirements. Safety includes the relative
safety of an example alternative during construction and
operation and in the event of a failure of part of the exam-
ple alternative. Statements concerning the period of ground-
water extraction required to achieve a particular water
quality are presented to provide a relative assessment only
and should not be considered absolute.
6.4.1.1 Example Alternative 1—No Action
The technical evaluation of Example Alternative 1 is shown
in Table 6-6. If Example Alternative 1 were implemented, no
action would be taken at Western Processing. The contami-
nants would continue to migrate in an uncontrolled manner
via existing migration pathways. It would probably take
hundreds of years of natural groundwater flow before zinc
concentrations in Mill Creek returned to the modified
ambient water quality criterion level. Drinking water stan-
dards for cadmium, chromium, and lead would probably never
be met in the shallow aquifer beneath the site.
6.4.1.2 Example Alternative 2—Surface Cap with Groundwater
Extraction and Treatment
The results of the technical evaluation of Example Alterna-
tive 2 are shown in Table 6-7- If Example Alternative 2
6-50
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cr\
ui
Category
Table 6-6
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 1
Comments
Effectiveness
Durability
Demonstrated Performance
Ease of Installation
Time to Implement
Monitoring Requirements
Operation and Maintenance
Requirements
Safety During Construction
and Operation
Safety in the Event
of Failure
All contaminants would remain in an uncontrolled state.
Direct human and animal contact with contaminated materials
could occur.
Surface water runoff could contact contaminated soil and
could carry contaminants from the site and into Mill Creek.
Leaching of contaminants from the unsaturated zone to the
groundwater would continue. Groundwater quality beneath the
site would improve slowly. It would take hundreds of years
(if ever) to achieve target levels of metals for human
health criteria for drinking water.
It would probably take hundreds of years of natural ground-
water flow before metals levels in Mill Creek, particularly
zinc, were reduced to modified ambient water quality
criteria.
Not applicable.
Since no action would be taken at the site, this analysis is
not applicable. It is assumed that contaminant migration
would continue in a manner similar to that which has
occurred since Western Processing operations stopped and the
surface cleanup was accomplished.
Not applicable.
Not applicable.
Not applicable.
Not applicable.
Not applicable.
Not applicable.
-------
Category
Effectiveness
I
Ul
to
Table 6-7
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 2
Comments
The RCRA multimedia cap would be effective in minimizing infil-
tration and leaching of contaminants in the unsaturated zone of
Areas I and II and the eastern part of Area V, in preventing con-
tact between surface runoff and the contaminated areas, and in
minimizing potential for direct human or animal contact with con-
taminated soil.
Forty years of pumping would lower most organics to below human
health target levels for drinking water in Area I/II. Drinking
water standards would not be achieved for most indicator metals
after 30 years of pumping in Area I/II. The 100 gpm extraction
and treatment system should be sufficient to prevent contaminated
groundwater flow from Areas I, II, V, and IX to Mill Creek during
the period of pumping. Concentrations of indicator metals that
could be released to Mill Creek via groundwater (if pumping were
stopped after 30 years) would not be low enough to allow Mill
Creek water to continue to achieve the modified ambient water
quality criterion for zinc.
Even if the groundwater pumping system were operated indefi-
nitely, it would not be possible to remove lead to levels that
comply with federal drinking water standards. Reducing the zinc
released to Mill Creek via groundwater to levels that would allow
the creek to meet the modified ambient water quality criterion
would take between 60 and 120 years of pumping.
Contaminated sediments in Mill Creek would be naturally dispersed
downstream and replaced with cleaner upstream sediments; however,
the amount of contamination that would continue to enter Mill
Creek via groundwater if pumping were stopped after 30 years
could recontaminate the creek sediments. Pumping for 60 to 120
years or longer would prevent the sediments from becoming
recontaminated.
The effectiveness of the groundwater extraction system would be
confirmed by field testing and through long-term monitoring. The
system would be modified as necessary during operation.
-------
Table 6-7 (continued)
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 2
Category
Comments
Effectiveness
(continued)
Durability
Demonstrated
Performance
The effectiveness of the treatment system would be confirmed by
bench- or pilot-scale testing during detailed design, and adjust-
ments would be made as necessary during operation.
A multimedia cap can be expected to have a cost-effective life-
span of 25 to 30 years. Potential sources of degradation include
chemical reactions between contaminants and the clay or synthetic
liner, cracking and/or joint separation of the synthetic liner,
leakage of the surface runoff collection devices, and leakage
around vent pipes. These conditions could reduce the effective-
ness of the cap.
The expected life span of equipment in the groundwater extrac-
tion, treatment, and monitoring systems varies from 10 to
50 years. For costing purposes, a 15-year life span was assumed.
When a particular item reaches its actual life span, that item
would be replaced to maintain the effectiveness of this
component.
Long-term experience with multimedia caps in hazardous waste appli-
cations is limited; however, this type of cap is considered to be
the state-of-the-art technology. Testing would be required prior
to installation to determine the compatibility between the cap-
ping materials and the chemicals present in the soil. If there
is a compatibility problem, different materials or configurations
could be used.
Groundwater extraction and treatment have been used successfully
in hazardous waste applications. Because of the uniqueness of
each application, monitoring would be required to confirm the
effectiveness of any extraction and treatment system. Areas of
influence and current groundwater quality are two considerations
that would require further analyses prior to implementation.
-------
Category
Ease of Installation
CTi
I
Ul
Table 6-7 (continued)
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE
Comments
Example Alternative 2 involves the importation of a
67,900-square-yard geotextile filter, a 67,900-square-yard syn-
thetic membrane, 45,200 cubic yards of loam, 45,200 cubic yards
of clay, and 22,600 cubic yards of sand. Approximately 2,900 feet
of concrete-lined ditches and 8 catch basins would be required.
These materials have been presumed to be be available locally in
these quantities.
The cap would require careful, labor-intensive construction
around the required venting.
The surface cap would have to be designed to withstand settling
and any subsidence caused by the groundwater extraction system.
Long-term access to Areas I, II, V, and VII and temporary access
to Areas IX and X would be required. The adjacent section of the
Interurban Trail would be closed during the construction period.
The distribution power line in Area II would require relocation
to the east side of the Interurban Trail.
Construction of the groundwater extraction system treatment
plant, after pilot testing has been completed and the unit pro-
cesses selected, would involve conventional materials and equip-
ment. Only minor construction would be required to connect the
groundwater treatment plant to the sewer discharge line.
Time to Implement
Eight months would be required for the construction phase of this
example alternative, not including time for additional studies,
pilot testing, and final design.
A pumping period of 30 years has been assumed for evaluation and
costing of this example alternative.
-------
Table 6-7 (continued)
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 2
Category
Comments
Monitoring
Requirements
I
Ul
t_n
Operation and
Maintenance
Requirements
Safety During
Construction and
Operation
The surface cap would require annual inspections to ensure that
it is effectively impermeable.
The surface cap and surrounding structures would require periodic
inspections for the effects of subsidence.
The groundwater extraction and treatment system would require
daily monitoring by trained personnel.
A monitoring well system would be installed and Mill Creek
monitored to evaluate the effectiveness of the remedial action.
The groundwater extraction and treatment system would require
daily operation and maintenance by trained personnel.
The groundwater treatment system would require the following
chemical quantities in the first year: precoat—250 tons, lime—
165 tons, ferric sulfate—4 tons, hydrogen peroxide—440 tons,
polyroer--one ton, and granular activated carbon—10 tons. (These
numbers are based on the conceptual treatment system shown in
Figure 6-6 at 100 gpm.)
Approximately 1,300 tons of hazardous sludge would be generated
in the first year by the treatment system. This sludge would re-
quire disposal at a RCRA double-lined hazardous waste landfill.
This amount would be expected to decline over time.
The vegetative cover on the surface cap would require periodic
maintenance.
A health and safety plan would be prepared before any construc-
tion is undertaken at Western Processing. This plan would
include onsite monitoring and perimeter monitoring of contami-
nants .
-------
Table 6-7 (continued)
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 2
Category
Comments
Safety During
Construction and
Operation
(continued)
I
Ul
Safety in the Event
of Failure
All personnel would be properly trained in accordance with
federal, state, and local regulations.
During site grading and cap construction, dust would be controlled
by appropriate measures.
Any equipment exposed to hazardous materials would be decontami-
nated.
Federal, state, King County, and City of Kent officials would be
involved in contingency and emergency response planning.
The effluent from the groundwater treatment system would be moni-
tored to ensure that it meets discharge requirements.
During cap construction, stormwater would be controlled to pre-
vent the discharge of contaminated surface water and would be
treated as necessary.
The surface cap would be vented to prevent buildup of volatile
gases.
The surface cap would contain two relatively impermeable layers.
In the event of a failure of one of the layers or the stormwater
system, the second layer and the slope of the cap should continue
to effectively reduce water infiltration. Human contact with
contaminated soils under the cap would be unlikely even if the
cap should fail to prevent infiltration. Damaged portions of the
cap or stormwater system would be repaired.
The groundwater treatment system would include storage facilities
so that any effluent not meeting discharge limits could be
retreated.
-------
Table 6-7 (continued)
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 2
Category Comments
Safety in the Event The large number of well points in the groundwater extraction
of Failure system would provide a redundancy. The failure of individual
(continued) well points would not adversely affect the performance of the
system. Additional well points could be added to the system if
necessary.
In the event of a complete treatment system failure, the extrac-
tion system could be turned off.
I
U1
--J
-------
were implemented, a multimedia RCRA cap would be installed
over Areas I and II and the eastern portion of Area V. The
cap should accomplish the following:
o Prevent direct contact with contaminated soils by
humans and animals
o Prevent surface water runoff from contacting con-
taminated soils
o Prevent infiltration and leaching of contaminated
materials in the unsaturated zone
A groundwater extraction and treatment system would also be
installed under Example Alternative 2. It would reduce the
concentrations of organic contaminants in the groundwater in
Area I/II to drinking water standards in less than 15 years,
and to the SNARL for longer term use in approximately
40 years. Forty years of pumping would also reduce-the
lifetime excess cancer risk for organics to 1 x 10 for the
worker scenario.
Example Alternative 2 or 3 would not be effective in achiev-
ing drinking water standards for some metals. The lead and
chromium (if hexavalent) concentrations in Area I/II ground-
water would for all practical purposes never be reduced to
drinking water standards, and cadmium would require more
than 120 years of pumping. Zinc and nickel water quality
criteria are below background groundwater concentrations.
Therefore backgrounds were used as the appropriate target
levels. Approximately 120 years of pumping would reduce
zinc and nickel concentrations to background.
During the pumping period, groundwater beneath the site
would no longer flow toward Mill Creek; therefore, contami-
nated groundwater from the site would no longer discharge
into the creek. Zinc and other contaminant concentrations
in the creek would be able to meet the modified ambient
water quality criteria after the start of pumping. If pump-
ing were stopped after 30 years, inorganic contaminants not
removed from the groundwater beneath the site would migrate
toward and into Mill Creek, and the resulting concentrations
in the creek water would exceed the modified criteria levels.
An additional 30 to 90 years of pumping would be required
before zinc and other inorganic contaminant levels in the
groundwater would be sufficiently reduced to allow Mill
Creek to meet the modified criteria.
Installation of the surface cap would require careful, labor-
intensive construction and the importation of large quanti-
ties of materials. Eight months would be required for
construction. During site grading and cap construction
there would be a potential for human exposure to airborne
contaminants.
6-58
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6.4.1.3 Example Alternative 3—Excavation with Onsite Dis-
posal, Groundwater Extraction and Treatment, Surface Cap
The technical evaluation of Example Alternative 3 is shown
in Table 6-8. The effectiveness of Example Alternative 3 in
reducing groundwater contaminant levels and in protecting
Mill Creek from zinc and other inorganic contamination is
similar to that of Example Alternative 2. Example Alterna-
tive 3 should be more reliable than Example Alternative 2
because the contaminants in the unsaturated zone of Area I
would be excavated and isolated from the environment in the
landfill. The volume of these materials is estimated to be
108,000 cubic yards.
Example Alternative 3 would be much more difficult to imple-
ment than Example Alternative 2. Installation of the land-
fill would require staged excavation and construction.
Forty-eight months would be required for the construction
phase.
This example alternative would also create safety concerns
not associated with Example Alternative 2. These concerns
are related to the excavation, stockpiling, and replacement
of contaminated soils. An advantage of Example
Alternative 3 (as well as Example Alternatives 4 and 5) is
that the excavation operation would allow drums and other
wastes known to be buried at the site in the unsaturated
zone to be removed and disposed of properly.
6.4.1.4 Example Alternative 4—PRP Remedial Action Plan
The results of the technical evaluation of Example Alterna-
tive 4 are shown in Table 6-9. If Example Alternative 4
were implemented, approximately 75,000 cubic yards of con-
taminated material would be excavated from the unsaturated
zone of Area I and transported offsite for disposal in a
double-lined, RCRA hazardous waste landfill. The excavated
areas would be backfilled with 60,000 cubic yards of imported
soil. A diversion barrier and groundwater extraction and
treatment system would be installed. Following up to five
years of groundwater pumping, the property would be capped
with an asphaltic concrete pavement.
The multi-depth excavation scheme included under Example
Alternative 4 would remove approximately 69 percent of the
total average amount of zinc and approximately 47 percent of
the total average amount of organic contaminants present in
Area I soil and groundwater. By removing contaminated sur-
face material and replacing it with imported fill, Example
This section was prepared by the PRP's.
6-59
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Category
Effectiveness
I
cn
o
Durability
Table 6-8
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 3
Comments
A total of approximately 108,000 cubic yards of contaminated
materials would be excavated from Areas I and II and a small part
of Area VIII as described in Section 6.3.3. The material would
be disposed of in an onsite, double-lined RCRA landfill. This
action would isolate approximately 60 percent of the metal con-
tamination including zinc.
The effectiveness of the RCRA multimedia cap would be similar to
the effectiveness of the cap discussed as part of Example
Alternative 2.
The effectiveness of the groundwater extraction system would be
similar to the effectiveness of the system discussed as part of
Example Alternative 2. While the landfill would further reduce
potential for leaching of contaminants compared to Example
Alternative 2 because of the excavation and isolation, Example
Alternative 3 contains fewer well points and a slightly lower
groundwater extraction rate. The 85-gpm groundwater extraction
rate should be sufficient to prevent contaminated groundwater
from flowing to Mill Creek from Areas I, II, V, and IX during the
period of pumping.
The effectiveness of the groundwater extraction and treatment
systems would be confirmed as in Example Alternative 2.
Hazardous waste landfills with double liners and leachate collec-
tion and detection systems have not been in existence long enough
to determine their useful life.
The surface cap would be expected to have a useful life similar
to the life of the cap discussed in Example Alternative 2.
The expected life span of equipment in the groundwater extraction
and treatment systems is similar to that discussed as part of
Example Alternative 2.
-------
Category
Durability
(continued)
Demonstrated
Performance
Ease of Installation
Table 6-8 (continued)
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 3
Comments
When a particular item reaches its actual life span, that item
would be replaced to maintain the effectiveness of the example
alternative. The landfill liner would require replacement if it
were determined to be vital to the continued effectiveness of
this Example Alternative at the time of failure.
Long-term experience with synthetic membrane/clay, double-lined
landfills in hazardous waste applications is limited; however,
this technology is considered to be the state of the art. Test-
ing would be required prior to installation as discussed in
Example Alternative 2.
Example Alternative 3 would involve the staged construction of a
double-lined landfill. To accomplish this, approximately 108,000
cubic yards would be excavated in stages. The excavated material
in each stage would be stored onsite temporarily prior to placing
in the landfill. Because the available area (Area I) is only 11
acres, this would be difficult, but it is expected to be feasi-
ble. All Area I underground utilities would be removed and dis-^
posed of in the landfill.
Example Alternative 3 would involve importation of approximately
122,000 square yards of geotextile filter, 122,000 square yards
of synthetic membrane material, 47,000 cubic yards of loam,
81,000 cubic yards of clay, and 58,000 cubic yards of sand.
Approximately 2,900 feet of concrete lined ditches, 8 catch
basins, and 4,200 feet of primary drainpipe would be required.
It is not known whether these materials would be available
locally in these quantities.
The bottom liner and cap would require careful, labor-intensive
construction procedures.
Clay could be handled only during the dry season.
-------
Table 6-8 (continued)
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 3
Category
Ease of Installation
(continued)
Comments
i
CTi
NJ
Time to Implement
Monitoring
Requirements
Permanent access to Areas I, II, and V would be required. Long-
term access would be required to Area VII. Temporary access to
Areas III, IV, VIII, IX, and X would be required.
The adjacent sections of the Interurban Trail would be closed
during excavation and landfill construction.
Adjacent underground utilities would require protection during
excavation activities.
Construction of the groundwater extraction system would involve
conventional materials and equipment.
Construction of the groundwater treatment plant, after pilot
testing has been completed and the unit processes selected, would
involve conventional materials and equipment. Only minor con-
struction is required to connect the groundwater treatment plant
to the sewer discharge line.
Forty-eight months would be required for the construction phase
of this example alternative, not including time for additional
studies, pilot testing, and final design. The length of the con-
struction phase is caused by the need to phase the construction
and by seasonal limitations
A pumping period of 30 years has been assumed for evaluation and
costing for this example alternative.
The monitoring requirements for Example Alternative 3 are similar
to those discussed as part of Example Alternative 2. In addi-
tion, the leachate collection and detection systems would be mon-
itored to ensure proper functioning. This would require frequent
inspections by trained personnel.
-------
Category
Operation and
Maintenance
Requirements
Safety During
Construction and
Operation
I
CTi
OJ
Table 6-8 (continued)
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 3
Comments
The operation and maintenance requirements for Example Alterna-
tive 3 would be similar to those discussed as part of Example
Alternative 2. The chemical requirements and quantity of sludge
produced by the treatment system would be slightly lower due to
the slightly lower flow rate of the extraction system (85 gpm).
If the leachate detection system showed the presence of a leak
from the primary liner, an extensive maintenance procedure could
be required.
A Health and Safety Plan would be prepared before any excavation
or construction is undertaken at Western Processing. Safety con-
siderations would include onsite and perimeter monitoring of con-
taminants. The excavation would create added safety concerns due
to the potential for airborne releases of contaminated materials
during the excavation, stockpiling, and replacement activities.
All personnel would be properly trained in accordance with fed-
eral, state, and local regulations.
Dust control measures would be implemented during the construc-
tion phase.
Equipment exposed to hazardous materials would be decontaminated.
Federal, state, King County, and City of Kent officials would be
involved in contingency and emergency response planning.
During excavation and landfill construction, stormwater would be
controlled to prevent the discharge of contaminated surface water
runoff.
-------
Table 6-8 (continued)
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 3
Category
Safety During
Construction and
Operation
(continued)
Comments
Safety in the Event
of Failure
During excavation and landfill construction, the sides of the ex-
cavated areas would be sloped to prevent collapse. The angle of
the slopes would be determined during detailed design, should
this example alternative be implemented.
If buried wastes are uncovered during excavation the material
would be evaluated for compatibility with landfill liners and
design. Certain excavated wastes such as PCB's, buried drums,
and concentrated wastes may require special handling and possibly
special disposal procedures.
The safety concerns for the groundwater extraction and treatment
systems would be similar to those discussed under Example Alter-
native 2.
The safety concerns in the event of the failure of the cap and
associated stormwater system, groundwater extraction, and treat-
ment system portions of Example Alternative 3 are similar to
those discussed for Example Alternative 2. The bottom liner con-
sists of four elements: a leachate collection system, a primary
synthetic liner, a leak detection and collection system, and a
secondary clay liner. The two collection systems and both liners
would have to fail to potentially release leachate to the local
groundwater.
Because the cap would have prevented infiltration and because
leachate from soil drainage would be captured by the leachate
collection system, contaminated soil in the landfill would be
relatively dry within a few years of landfill installation.
Consequently, the landfill cap would have to fail before complete
failure of the bottom lining system would result in the release
of leachate from the landfill.
-------
Category
Table 6-9
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 4 (PRP PLAN)*
Comments
Effectiveness
Ul
Approximately 75,000 cubic yards of buried waste materials and
contaminated soil would be excavated from Area I and be trans-
ported offsite for disposal in a double-lined RCRA landfill. The
excavated area would be backfilled with imported soil. This
action would eliminate the potential for direct contact with
contaminated soil by humans and animals, as well as prevent sur-
face water runoff from contacting contaminated soil. Approxi-
mately 69 percent of the total zinc contamination in Area I would
be removed by this action.
The groundwater pumping and treatment program would remove
approximately 7 percent more zinc from Area I and improve the
overall quality of the shallow groundwater beneath Area I. How-
ever, the analysis of indicator parameters indicates that federal
drinking water standards for certain metals would not be achieved
even if the pumping program is operated for an indefinite period
of time.
During the pumping period, the release of contaminants from
Area I to Mill Creek via groundwater would be prevented. Follow-
ing the completion of pumping, Area I would be capped with an
asphaltic concrete pavement, which would inhibit surface water
infiltration and leaching of residual contaminants from the un-
excavated soil of the unsaturated zone. In addition, the diver-
sion barrier would slow the rate of movement of contaminants that
might be released from Area I via groundwater and migrate to Mill
Creek. However, the combined effect of the excavation and pumping
program, the surface pavement, and the diversion barrier would
sufficiently reduce the amount of contamination entering Mill
Creek so that water quality within the creek could meet modified
ambient water quality criteria.
*This table prepared by the PRP's.
-------
Table 6-9 (continued)
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 4 (PRP PLAN)
Category
Comments
Effectiveness
(continued)
Durability
en
i
The effectiveness of the groundwater extraction system as mea-
sured by flow to Mill Creek would be confirmed by monitoring
during operation? the system could be modified during design and
during operation, as necessary.
The effectiveness of the treatment system would be confirmed by
bench or pilot-scale testing during detailed design, and adjust-
ments would be made as necessary during operation.
The expected life span of equipment in the groundwater extraction,
treatment, and monitoring systems varies from 10 to 50 years,
which is greater than the maximum operating period of Example
Alternative 4.
The potential life span of the diversion barrier is not known at
this time but is expected to be significantly longer than the
maximum duration of the groundwater pumping program. Factors
that could limit the durability of the diversion barrier are
chemical attack and physical disruption. These are subsequently
addressed below under the "Safety in Event of Failure" category.
The asphaltic concrete pavement that would be installed over the
site at the conclusion of the groundwater extraction and treat-
ment program would have a useful life of approximately 20 to
30 years, after which resurfacing would be required. Because the
excavation and groundwater extraction components would remove the
majority of the contamination from the site, the pavement must
only minimize rather than eliminate surface water infiltration.
Minor deterioration in the pavement would not significantly re-
duce the overall effectiveness of this component. Repavement to
control surface water infiltration may not be necessary after 20
to 30 years.
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Category
Table 6-9 (continued)
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 4 (PRP PLAN)
Comments
Demonstrated
Performance
Ease of Installation
(Tl
I
Each of the components included in Example Alternative 4 has been
used successfully in the past to perform the function for which
it would be used at the Western Processing site. Not all have
been used at a site having the physical and chemical complexity
of Western Processing, however. Therefore, field, laboratory,
and bench-scale testing would be required before final system
configurations and designs could be selected. The performance of
the installed systems would be monitored to allow further adjust-
ments, if necessary, following installation.
With the exception of the asphalt emulsion diversion barrier,
which is one of the two types of construction materials being
considered by the PRP's, all structures and facilities would be
constructed using standard techniques and equipment. Disman-
tling, where included, would also use standard techniques and
equipment.
Approximately 60,000 cubic yards of soil would be required to
backfill the excavations. This fill material would have to meet
specific design requirements related to permeability and grain
size because enhanced precipitation infiltration is a component
of Example Alternative 4 during operation of the groundwater
extraction program. Approximately 9,200 cubic yards of gravel
would be required for the permeable surface cover during the
groundwater extraction period. Other construction requirements
would include approximately 3,300 linear feet of either a soil-
bentonite slurry or an asphalt emulsion for the diversion bar-
rier; approximately 2,370 linear feet of piping and 9 catch
basins for the stormwater control system; and approximately
55,660 square yards of asphaltic concrete for the surface cover
(pavement). With the exception of the bentonite, all the con-
struction materials are expected to be available locally.
-------
Table 6-9 (continued)
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 4 (PRP PLAN)
Category
Comments
Ease of Installation
(continued)
I
CTi
00
Time to Implement
Monitoring
Requirements
During excavation and diversion barrier installation activities,
the contractor would be required to protect utilities to the
north and east of the Western Processing property. Onsite buried
utilities would be removed during the excavation process.
If a soil-bentonite type of slurry is selected to construct the
diversion barrier, large areas of the site would be required for
stockpiling soil and for slurry mixing impoundments. The instal-
lation of the barrier would need to be scheduled so that these
space requirements would not interfere with other activities.
If an asphalt emulsion system is selected to construct the di-
version barrier, special equipment would be required. More com-
plex installation procedures would be associated with this type
of barrier, and a more rigorous quality control program would
need to be implemented. However, this system would require much
less area for installation because no soil stockpiling or impound-
ments would be needed and less soil would be excavated to install
the barrier.
The adjacent sections of the Interurban Trail would be closed
during excavation of contaminated soil.
A minimum of 24 months would be required for the diversion bar-
rier installation, site excavation, groundwater extraction system
installation, and (if selected) onsite treatment plant construc-
tion. Approximately 8 years would be required for the entire
remedial action, including dismantling of structures and instal-
lation of the surface pavement assuming that the pumping program
would be operated for the full 5 years.
The groundwater extraction system would require daily monitoring
by trained personnel. Effluent from the onsite treatment plant
(if constructed) would be monitored prior to discharge.
-------
Table 6-9 (continued)
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 4 (PRP PLAN)
Category
Comments
Monitoring
Requirements
(continued)
Operation and
Maintenance
Requirements
en
I
Safety During
Construction and
Operation
A monitoring well system would be used to evaluate the
effectiveness of the remedial action.
After the remedial action is completed, inspection of the
surface pavement and stormwater control system would be the
responsibility of the site owner.
The groundwater extraction system that would be installed under
Example Alternative 4 was selected for ease and flexibility of
operation and maintenance. Routine operation and maintenance
could be performed by a properly trained individual under the
direction of an engineering professional. If an onsite treatment
plant is constructed, a qualified plant operator would be
required.
Chemical supply and treatment sludge quantities associated with
an onsite treatment plant would be similar to those identified
under Example Alternative 2.
A Health and Safety Plan would be prepared and implemented before
any activities associated with Example Alternative 4 were begun.
This plan would include onsite and perimeter monitoring for con-
taminants .
All personnel would be properly trained in accordance with fed-
eral, state, and local regulations.
Dust control measures would be implemented during construction
activities.
Any equipment exposed to hazardous materials would be decontami-
nated.
Federal, state, King County, and City of Kent officials would be
involved in contingency and emergency response planning.
-------
Table 6-9 (continued)
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 4
(PRP PLAN)
Category
Safety During
Construction and
Operation
(continued)
Comments
The safety concerns for the groundwater extraction and treatment
systems would be similar to those discussed under Example Alter-
native 2 .
During excavation and operation, stormwater would be controlled
to prevent the discharge of contaminated surface water runoff.
Trucking of excavated materials to an offsite hazardous waste
landfill would be conducted according to a transportation plan
designed to minimize potential transportation risks.
Safety in the Event
of Failure
i
-j
o
The groundwater extraction system that would be installed under
Example Alternative 4 would be expected to experience both rou-
tine and unplanned down time. The system would be designed so
that such downtime would not adversely impact the overall effec-
tiveness of the system.
Failure of the diversion barrier would potentially reduce the
effectiveness of the groundwater extraction program. Failure of
the barrier could result from disruption of the barrier by earth-
quake or from improper installation. The monitoring system that
would be installed at the site would indicate such a failure,
which could then be corrected.
The effectiveness of the barrier could be reduced if the barrier
materials were made significantly more permeable as a result of
chemical attack. However, the barrier materials would be selec-
ted on the basis of chemical compatibility testing prior to
installation. Some increase in permeability could be tolerated,
particularly after completion of the groundwater extraction pro-
gram. However, if the.permeability of the diversion barrier
increased to about 10 cm/sec, the effect of the barrier would
be essentially eliminated.
-------
Table 6-9 (continued)
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 4 (PRP PLAN)
Category
Comments
Safety in the Event
of Failure
(continued)
I
-J
Monitoring would be used to track the effectiveness of the bar-
rier during pumping system operation. Structural failure of the
barrier, or the gradually increasing permeability that would be
associated with chemical attack, would be detected by the moni-
toring system, and measures to correct the problem could be taken
as necessary.
Deterioration of the surface pavement and stormwater management
system would be expected with time. The asphaltic concrete pave-
ment is potentially more susceptible to deterioration, cracking,
or other failure than a multimedia RCRA cap but is easier to
repair and maintain. Significant deterioration of the pavement
could result in infiltration; however, because the majority of
contamination would have been removed from the unsaturated zone,
leaching of residual contamination from unexcavated soil in the
unsaturated zone is expected to be minor. The diversion barrier
would serve to slow the release of leached residual contaminants
from the property via groundwater.
Failure of the stormwater management system could cause flooding
of the property, release of stormwater to the subsurface, or more
rapid release of stormwater to Mill Creek than would be allowed
under the City of Kent stormwater management ordinance, depending
on the nature of the facility. Maintenance and repair of the
stormwater system would be the responsibility of the site owner.
-------
Alternative 4 would prevent direct contact with contaminated
soils by humans and animals. The potential for contaminated
surface water runoff would also be eliminated by the excava-
tion/backfill action; additional protection would be afforded
by the surface pavement.
The groundwater pumping and treatment program would remove
an additional 7 percent of the total average amount of zinc,
and an additional 38 to 48 percent of the total average
amount of organics estimated to be in Area I at present.
During the groundwater pumping period, surface water would
be allowed to infiltrate the contaminated soil not removed
from the unsaturated zone during the excavation program.
The water would pick up contaminants from this soil and carry
them into the saturated zone, where they would be removed by
the pumping system. This action would supplement the source
removal action provided by excavation alone.
Groundwater quality beneath the property would be signifi-
cantly improved by this alternative. However, drinking
water standards for cadmium, chromium, and lead would not be
met at the conclusion of the pumping program. It would
probably take hundreds of years of pumping before these
standards could be met, if ever.
The groundwater pumping program would prevent contaminated
groundwater from migrating from the property and discharging
into Mill Creek. Once the pumping program is completed, the
diversion barrier would continue to affect local shallow
groundwater flow patterns.
Contaminants remaining in the saturated zone following the
conclusion of the pumping program could be carried from the
property and discharged into Mill Creek via groundwater.
However, the combined effect of the following factors would
be sufficient to reduce the amount of contaminants entering
Mill Creek to a level that would allow creek water to meet
modified ambient water quality criteria:
o The surface pavement would minimize infiltration
and leaching of the residual contamination in the
unsaturated zone.
o The excavation and pumping program would have
removed approximately 76 percent of the zinc con-
tamination from the unsaturated and saturated
zones.
o The diversion barrier would slow the rate of con-
taminant release from the property and thus the
rate of discharge into Mill Creek.
6-72
-------
The following table summarizes the estimated reductions in
the zinc loading to Mill Creek just downstream of the
Western Processing site achieved by the remedial action
components of Example Alternative 4. The reductions are a
result of the actual removal of zinc mass from Area I by the
excavation and groundwater extraction programs and the
reduction in groundwater flow from the site to Mill Creek
caused by the presence of the diversion barrier.
In
In Groundwater
Soil (Ib) (Ib) Total (Ib) Reduction
1. Existing zinc mass 2,263,157 39,614 2,302,771
2. Zinc mass after
Ex. Alt. 4 665,558 39,614 705,172 69.4%
excavation
3. Zinc mass after
Ex. Alt. 4 ground-
water extraction 532,447 31,691 564,138 75.5%
The 75.5 percent reduction in Area I zinc mass is assumed to
cause an identical reduction in zinc loading to the creek.
In addition to the removal of mass, the presence of the di-
version barrier will force residual contamination migrating
from Area I to follow a longer flow path to Mill Creek and
to move vertically through zones of relatively lower hydrau-
lic conductivity. The result is a 50 to 60 percent lower
rate of release of residual contamination to the creek than
without the barrier, hence a similar reduction in loading to
the creek.
The estimated reduction in zinc loading to Mill Creek from
all of these factors is calculated as follows:
(75.5%) + (.5) (100%-75.5%) = 87.8% (or approximately 88%)
As noted above, the diversion barrier would cause residual
contaminants in the groundwater beneath Area I to migrate
vertically before they move beyond the wall. Because the
barrier depth corresponds to the depth at which regional (as
opposed to local) flow patterns begin to influence ground-
water beneath Area I, these residual contaminants could
enter the regional pattern. If this occurs, they would move
beneath, rather than into, Mill Creek and toward more
distant receptors such as the Green River. However, the
amount of contamination, if any, leaving the local flow
system would be very minor.
6-73
-------
Unlike Example Alternatives 2 and 3, Example Alternative 4
would not require long-term operation and maintenance (ex-
cept groundwater monitoring); approximately 8 years would be
involved in the construction and operation of the components.
The diversion barrier would require no maintenance. The
pavement and stormwater management system would need to be
maintained by the site owner with the same level of care
normally followed at paved industrial or commercial facili-
ties. The safety concerns of this example alternative would
be similar to those of Example Alternative 3, with the ex-
ception of the increased truck traffic associated with offsite
disposal of contaminated soil.
6.4.1.5 Example Alternative 5—Excavation with Offsite
Disposal
The technical evaluation of Example Alternative 5 is shown
in Table 6-10. Example Alternative 5 would involve the re-
moval of approximately 300,000 cubic yards of contaminated
soil and waste material from Areas I and II and portions of
Areas V, VIII, and IX, and replacement with clean fill.
Example Alternative 5 would remove approximately 95 percent
of all contaminants from Areas I, II, V, and IX, including
approximately 95 percent of the zinc contamination. By
removing all the surface soils in the excavation areas.
Example Alternative 5 prevents direct contact of stormwater,
humans, and animals with the contaminated soils in these
areas and removes most of the unsaturated zone materials in
these areas including all unsaturated zone materials from
Areas I and II. Infiltration through contaminated soil in
Areas V and IX would be minimal.
Groundwater would be extracted and treated during the con-
struction of this alternative. This action, combined with
soils removal, is expected to improve local shallow ground-
water quality. Excavation would lower the concentrations of
lead, chloroform, tetrachloroethene, toluene, and 1,1,1-
trichloroethane in Area I/II to below the federal drinking
water standards or SNARL's. Excavation and groundwater
extraction would reduce trichloroethene and trans 1,2-
dichloroethene concentrations to below the SNARL's. Cadmium
and chromium (if hexavalent) may not be reduced sufficiently
by Example Alternative 5 to achieve federal drinking water
standards. The source reduction by itself would be suffi-
cient to allow zinc and other inorganics concentrations in
Mill Creek to meet the modified ambient water quality cri-
teria after the 4-year excavation and dewatering program.
Unlike Example Alternatives 2 and 3, Example Alternative 5
would not require long-term operation and maintenance.
Forty-eight months would be required for the completion of
this example alternative. The safety concerns of this exam-
ple alternative would be similar to those of Example Alter-
native 4, except that truck traffic related to offsite
6-74
-------
Category
Effectiveness
Durability
Table 6-10
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 5
Comments
Example Alternative 5 would involve the removal of approximately
300,000 cubic yards of contaminated materials with their disposal
in a RCRA-regulated landfill and replacement of the excavated
materials with clean, compacted fill.
This alternative would remove approximately 95 percent of all
contamination in the soil. Approximately 95 percent of the
contaminated material (including zinc) would be removed from
Area I/II; 50 percent would be removed from Area V and 20 percent
from Area IX. Data are insufficient to estimate the removal
percentage from Area VIII. The soil removal program would pre-
vent human, animal, and stormwater contact with contaminated
soils in the excavated area.
In Areas I and II infiltration would be through the replacement
fill material with no leachate generation expected in Areas I
and II. Leachate generation in Areas V, VIII, and IX would be
reduced substantially.
Local shallow groundwater quality would be improved by the com-
bination of source removal and dewatering system operation.
Contaminant levels would be reduced to at or near the SNARL for
longer term use and to below federal drinking water standards for
all contaminants except cadmium and chromium. The soil removal
and dewatering program would be sufficient to allow the zinc
levels in Mill Creek to meet the modified ambient water quality
criteria.
The positive effects of the source removal may take some time to
measure in Mill Creek. All the contaminated groundwater currently
en route to Mill Creek may not be intercepted.
The dewatering and treatment systems would operate only during
the time required for excavation (about 4 years). This is much
shorter than the expected equipment life span of 10 to 50 years.
-------
Category
Demonstrated
Performance
Ease of Installation
-j
(Tl
Table 6-10 (continued)
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 5
Comments
Soil excavation and removal is a proven method for mitigating
soil contamination. The contaminated soils would be disposed of
at an offsite double-lined USEPA-permitted hazardous waste land-
fill. Long-term experience with double-lined landfills in haz-
ardous waste applications is limited; however, it can be expected
that double-lined landfills will be more protective of the envi-
ronment than are unlined or single-lined landfills. The demon-
strated performance of the dewatering and treatment systems is
similar to the groundwater extraction and treatment system.
Example Alternative 5 would involve the removal of approximately
300,000 cubic yards of contaminated soil and its replacement with
compacted, clean fill. This would create heavy truck traffic on
the surrounding roads. The availability of clean fill and of dis-
posal space at USEPA-permitted double-lined landfills has not
been confirmed.
The depth of the Area I/IT excavation (15 feet) would be well below
the groundwater table. Therefore, the excavation would require
dewatering and sheet piling for that portion of the excavation.
The excavation is anticipated to be done in stages.
Temporary access to Areas I and II and portions of V, VII, VIII,
IX, and X would be required.
The Interurban Trail would be closed adjacent to Western Process-
ing during all excavation and refilling operations.
The above-ground powerline in Area II would be relocated to
Area X.
The excavation operation would involve the use of conventional
materials and equipment; utilities in the contaminated areas
could be removed. The oil line in Area II would cause construc-
tion problems and require appropriate protection.
-------
Table 6-10 (continued)
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 5
Category
Comments
Time to Implement
Monitoring
Requirements
Operation and
Maintenance
Requirements
Forty-eight months would be required for the construction phase
of this example alternative, not including time for additional
studies, pilot testing, and final design. The approximate 4-year
implementation time presumes normal weather conditions. As with
any major earthmoving operation, prolonged adverse, wet weather
could extend the schedule beyond the 4-year period. Conversely,
an extended period of dry weather could shorten the anticipated
construction period.
During excavation, the effluent from the dewatering and treatment
system would be monitored to ensure that it meets discharge
limits.
Monitoring requirements for groundwater and Mill Creek would be
similar to Example Alternative 2.
During the construction period, the dewatering and treatment sys-
tems would require daily operation and maintenance by trained
personnel. The chemical usage requirements for the dewatering
system would be similar to those described for Example Alterna-
tive 2. Decontamination water may require additional treatment
for precipitation of fines.
Approximately 1,600 tons of hazardous sludge would be generated
per year by the treatment system. This sludge would require dis-
posal at a double-lined, RCRA hazardous waste landfill.
There would be no operation and maintenance requirements after
4 years, except monitoring.
-------
Category
Safety During
Construction and
Operation
i
~j
00
Safety in the Event
of Failure
Table 6-10 (continued)
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 5
Comments
General safety concerns and procedures would be similar to those
discussed for Example Alternative 3.
A Health and Safety Plan (including a transportation safety plan)
would be prepared before any excavation or construction is under-
taken at Western Processing.
Any equipment exposed to hazardous materials would be decontami-
nated.
Federal, state, King County, and City of Kent officials would be
involved in contingency and emergency response planning.
During excavation, the sides of the deeper excavated areas would
be supported by steel sheet piling and monitored.
Certain excavated materials such as PCB's, buried drums, and con-
centrated wastes would require special handling and possibly
disposal procedures.
The safety concerns for the dewatering and treatment systems
would be similar to those discussed for the extraction and
treatment systems in Example Alternative 2.
Should the dewatering system fail, excavation below the water
table would be suspended pending repairs.
Should the effluent from the treatment system fail to meet
discharge limits, the water would be stored for recycling through
the plant.
-------
disposal of contaminated materials would extend over a con-
siderably longer period of time.
6.4.1.6 Example Alternative 6—Mill Creek—No Action
The results of the technical evaluation of Example Alterna-
tive 6 are shown in Table 6-11. If no action were taken in
Mill Creek, the contaminated sediments would be free to
migrate downstream. No action combined with an effective
source control action (i.e., one that sufficiently reduced
groundwater contamination) would result in the gradual dis-
persal of contaminated sediments from the Western Processing
reach of the creek. There would be no installation, opera-
tion, or maintenance requirements.
6.4.1.7 Example Alternative 7—Mill Creek Sediment Removal
The results of the technical evaluation of the sediment re-
moval program that constitutes Example Alternative 7 are
shown in Table 6-12. Example Alternative 7 should effec-
tively prevent water quality degradation from, and the
continued migration of, contaminated sediments, provided the
flow of contaminated groundwater from the site to Mill Creek
is halted by a source control action.
Approximately one month would be required to complete the
sediment removal procedure. Safety concerns would be similar
to those of other soil excavation alternatives. In addition,
flooding due to an unexpectedly severe storm could cause the
release of contaminated sediments if the downstream diversion
dike is overtopped.
6.4.2 ENVIRONMENTAL EVALUATION
Each of the example alternatives was evaluated to determine
its possible effects on human health and the environment.
Tables 6-13 through 6-19 describe the impacts of the example
alternatives on all elements of the environment except the
following:
Historic and Cultural Resources: No such resources are
known to exist in the areas affected by the alternatives.
Endangered Species; No such species are known to exist in
the areas affected by the alternatives.
Wetlands; No properties that would be affected by the al-
ternatives are designated as wetlands.
Utilities: None of the alternatives would adversely affect
the availability of current public water supplies, nonhaz-
ardous solid waste disposal, telephone service, or natural
6-79
-------
I
00
O
Category
Table 6-11
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 6
Comments
Effectiveness
Durability
Demonstrated
Performance
Ease of Installation
Time to Implement
Monitoring
Requirements
Operation and
Maintenance
Requirements
Safety During
Construction and
Operation
Example Alternative 6 would not remove the contaminated sediments
from Mill Creek. The contaminated sediments in the creek would
remain in an uncontrolled state and would be moved downstream by
natural processes.
Modification of Mill Creek (e.g., dredging, detention, or re-
routing) above Western Processing as part of Kent's Drainage
Master Plan could change the effectiveness of this example alter-
native, as could the introduction of new upstream sources of
contaminants.
Without an effective source control action, contaminated ground-
water would continue to discharge from Western Processing to Mill
Creek, causing continued water quality and sediment degradation.
This process would continue for well beyond 100 years. With an
effective source control action, it would take from 5 to 10 years
for the contaminated sediments to be transported out of the local
stream reach.
Not applicable.
Not applicable.
Not applicable
Not applicable
Mill Creek would be monitored in conjunction with the implementa-
tion of the source control alternative.
Not applicable.
Not applicable.
Safety in the Event
of Failure
Not applicable.
-------
Table 6-12
TECHNICAL EVALUATION—EXAMPLE ALTERNATIVE 7
Category
Comments
Effectiveness
00 Durability
Demonstrated
Performance
Ease of Installation
Time to Implement
Example Alternative 7 would remove the contaminated sediments
(nominally estimated at one foot thick) in a 2,300-foot-long
reach adjacent to and downstream of the Western Processing site
(estimated volume 1,700 cubic yards). This action removes these
materials as a potential source of organic and inorganic (metal-
lic) pollutants to the creek. Without some source control action
(Example Alternatives 2 through 5), sediments in the creek would
become recontaminated, particularly by metals, due to the dis-
charge to the creek of contaminated groundwater from Western
Processing.
Modification of Mill Creek (e.g., dredging, detention ponds, or
rerouting) above Western Processing as part of Kent's Drainage
Master Plan could change the effectiveness of this example alter-
native, as could upstream sources of contaminants.
This example alternative would remain effective for as long as
contaminated groundwater is prevented from flowing into the
creek.
Excavation is the only component in this alternative and is a
common method of reducing contamination.
Removal of the contaminated sediments would involve the temporary
diversion of Mill Creek (diversion structure and piping) in addi-
tion to the excavation of the contaminated sediments. Depending
on the water content upon removal, the sediments may require
dewatering prior to transportation and disposal. The diversion
structure and piping should be easy to place.
Further testing can further define disposal alternatives.
Example Alternative 7 would require approximately one month to
complete and should be performed during the dry season (July to
October).
-------
Table 6-12 (continued)
TECHNICAL EVALUATION — EXAMPLE ALTERNATIVE
Category
Comments
00
to
Monitoring
Requirements
Operation and
Maintenance
Requirements
Safety During
Operation
Safety in the Event
of Failure
Monitoring of Mill Creek waters and sediments and groundwater
quality and flow near the creek would be necessary to determine
the optimum time to remove the contaminated sediments.
Monitoring would also be done to determine the effectiveness of
the excavation.
Example Alternative 7 has no systems that would require long-term
operating and maintenance.
Example Alternative 7 would be implemented under a Health and
Safety Plan. This plan would consider general safety
precautions, the potential for overtopping the diversion
structure, and the potential for worker exposure to hazardous
materials.
Example Alternative 7 does not contain any long-term components.
Failure of the diversion structure would be the major considera-
tion during implementation. This would be considered in the
Health and Safety Plan. If creek sediment excavation did not
solve the problem, the creek could be reexcavated at some future
time.
-------
Element of the Environment
Human Health:
Soils
Table 6-13
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE 1—NO ACTION
Short-Term Effects
Same as long-term
Groundwater
Same as long-term
CTl
I
OD
U)
Surface water (Mill
Creek)
Recreational use of Mill Creek does not
pose a threat to human health. Mill
Creek is not used as a drinking water
source.
Air
Same as long-term
Long-Term Effects
Long-term health effects could result
from exposure to soils at Western Pro-
cessing. ADI's for lead, chromium (if
all chromium is in the hexavalent
state), and cadmium would be exceeded
(depending on the assumed quantity of
soil ingested and the measured contami-
nant concentrations). Exposure to
carcinogens could lead to an excess
lifetime cancer risk of from 1 x 10~ to
5 x 10 depending on the length and
frequency of exposure.
Shallow groundwater in the area is not
currently used for human consumption.
The current concentrations of organic
and inorganic contaminants in the
groundwater beneath the site exceed fed-
eral drinking water standards and the
suggested no adverse response levels
(SNARL's) for long-term use. If the
groundwater were consumed at a rate of
2 liters/day, ADI's for phenol, cadmium,
chromium (if all hexavalent), lead, and
nickel would be exceeded. For a similar
consumption rate over a 40- to 70-year
period, the excess lifetime cancer risk
would be from 5 x 10 to 8 x 10 .
Mill Creek is not used as a drinking
water source. However, if it were,
contaminants in Mill Creek could cause
an_^xcess lifetime cancer risk of about
10~ , assuming consumption of 2 L/day
for 40 years. Given the maximum con-
centrations of contaminants found and a
consumption rate of 2 L/day, the ADI's
for the metals and organics of primary
concern would not be exceeded.
Inhalation of contaminated dust could
cause health effects. This effect was
not quantified. Taking in soil via air
could add an additional exposure to the
health effects of soils described above.
-------
Table 6-13 (continued)
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE 1—NO ACTION
Element of the Environment
Aquatic Organisms in Mill
Creek:
Short-Term Effects
Groundwater:
Quantity and flow
CTl
I
00
The modified ambient water quality cri-
teria would continue to be exceeded in
Mill Creek water, which would adversely
affect aquatic life. Both chronic and
acute criteria for metals are currently
exceeded.
Groundwater would continue to flow from
the site to Mill Creek and the east drain
at the rate of approximately 50 to 70 gpm.
Regional groundwater flow (below 60 feet)
would continue to flow to the northwest
at about 50 to 100 feet per year, ulti-
mately discharging to the Green River.
Long-Term Effects
Mill Creek water quality would gradually
improve as the discharge of contaminants
to the creek via groundwater is reduced
with time. At some future date, esti-
mated to be hundreds of years, water
quality in the creek would return to
background levels.
Same as short-term impacts.
Quality
Groundwater quality would continue to
exceed federal drinking water standards
for cadmium, lead, and chromium.
Local groundwater quality would improve
gradually as contaminants are discharged
into Mill Creek and the east drain.
Many contaminants would be removed from
the groundwater naturally in less than
100 years. However, it would take hun-
dreds of years, if ever, for local
groundwater to return to federal drink-
ing water standards for cadmium, lead,
and chromium.
Stormwater:
Quantity and flow
Quality
Stormwater runoff in Area I would gener-
ally pond onsite and infiltrate into the
groundwater. Stormwater runoff in other
areas would infiltrate or run off into
Mill Creek or drainage ditches.
Contaminated surface soils would
continue to impart contaminants to
groundwater and surface waters.
The natural drainage pattern to Mill
Creek could resume in the future. Berms
would gradually deteriorate and Area I
runoff could discharge directly into
Mill Creek.
Same as short-term impacts, plus addi-
tional contaminated Stormwater may enter
Mill Creek as the berms deteriorate.
-------
Element of the Environment
Mill Creek and East Drain:
Quantity and flow
Quality
CTl
Sediment quality
Terrestrial Wildlife
Soils and Topography
(excavation, removal)
Noise
Air Quality (odor, dust)
Transportation
Flood Plains
Land Use
Table 6-13 (continued)
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE I—NO ACTION
Short-Term Effects
Long-Term Effects
No impacts to the quantity and flow
of Mill Creek.
Contaminants would continue to be dis-
charged into Mill Creek via groundwater.
Levels of zinc, chromium (if all hexava-
lent) and cadmium would greatly exceed
modified ambient water quality criteria
in Mill Creek. Surface water runoff in
Area I is controlled and would not
discharge to Mill Creek.
Dissolved contaminants discharged
via groundwater or surface water would
continue to be adsorbed by sediments.
Because of human activity and lack
of vegetation, the site has not been
significantly used by wildlife.
No impacts to soils or topography.
No noise impacts.
Contaminated dust could originate from
the site during dry periods. If vegeta-
tion becomes established, the potential
for dust generation would be reduced.
No transportation impacts.
No impacts to flood plains. Accord-
ing to FEMA maps, a 100-year flood
would inundate small areas adjacent
to Mill Creek and the east drain.
Land use might be restricted by federal,
state, or local agencies in order to pro-
tect public health. Monitoring could be
used to determine what development
restrictions should be applied to the
various analysis areas.
Same as short-term impacts.
After hundreds of years, the discharge
of heavy metals via groundwater (espe-
cially cadmium, lead, and chromium)
would be reduced to levels meeting modi-
fied ambient water quality criteria.
Past stormwater drainage patterns could
resume within several years, causing the
discharge of contaminated surface water
into Mill Creek.
Contaminant levels in Mill Creek sedi-
ments would gradually be reduced as the
source is depleted and contaminated sedi-
ments are transported downstream.
If vegetation develops, some
wildlife may be attracted to the
site. The potential for harmful
effects on wildlife resulting
from their use of the site
cannot be predicted.
Same as short-term impacts.
Same as short-term impacts.
Same as short-term impacts.
Same as short-term impacts.
Same as short-term impacts.
Same as short-term impacts.
-------
Table 6-14
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE 2—SURFACE CAP WITH GROUNDWATER EXTRACTION AND TREATMENT
Element of the Environment
Human Health:
Soils
Short-Term Effects
Exposure of workers and the general
public to contaminated soil would be
controlled by the provisions of the
Health and Safety Plan.
Groundwater
Ground-water beneath Western Processing
does not present a hazard to human health
because it is not currently a water
supply source.
I
CO
Mill Creek
Recreational use of Mill Creek does not
pose a threat to human health. Mill Creek
is not used as a drinking water source.
Air
See Soils, above.
Long-Term Effects
Placement and maintenance of the cap
would eliminate human exposure to con-
taminated soils in Areas I, II, and V.
Exposure and ingestion potential would
remain for Area VIII, where the ADI for
lead could be exceeded, and for Area IX,
where the potential excess lifetime-
cancerrisk could vary from 3 x 10 to
3 x 10 , depending on the length and
frequency of exposure.
Because of low yield, poor regional
water quality, and the presence of ade-
quate alternate water supplies, the
local shallow aquifer is not a likely
candidate for development. The proposed
well point system and cap generally pre-
clude development of a supply well in
and around Western Processing. While a
15-year groundwater extraction and
treatment operation should reduce chlor-
oform concentrations to less than the
federal drinking water standard, and
40 years of pumping should reduce other
organic concentrations to SNARL'S for
longer term use, it would take hundreds
of years, if ever, of pumping and treat-
ment to reduce cadmium, chromium, and
lead to drinking water standards.
Long-term recreational use would not
pose a threat to human health. Mill
Creek is not planned for development as
a drinking water source. If it were to
be developed, the potential lifetime
excess cancer risk would decrease over
time as the groundwater extraction sys-
tem isolated the creek from the contam-
inated groundwater and removed the
organic contaminants that contribute to
the cancer risk.
The groundwater treatment process would
release volatile organics. However, the
system would be designed and operated to
meet emissions standards, thus reducing
the potential for adverse impact from
these releases.
-------
Table 6-14 (continued)
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE 2—SURFACE CAP WITH GROUNDWATER EXTRACTION AND TREATMENT
Element of the Environment
Aquatic Organisms in Mill
Creek
Short-Term Effects
CTl
I
CD
During construction, stormwater in con-
struction areas would be collected and
treated prior to discharge to Metro.
This would minimize the potential for
discharge of contaminated stormwater run-
off into Mill Creek.
Long-Term Effects
Groundwater discharges from Areas I, II,
V, and IX into Mill Creek would be
eliminated after pumping begins, thus
improving water quality in Mill Creek.
As the water quality in Mill Creek
improves, the potential for adverse
impacts to aquatic organisms would
decrease. If groundwater pumping stops
after 30 years, groundwater from Western
Processing would again flow into Mill
Creek. With the return of groundwater
flow to the creek, metals levels
(particularly zinc) would probably
rise above modified ambient water
quality criteria. Sixty to 120 years of
pumping would be necessary to allow
metals levels in Mill Creek to stay
below modified ambient water quality
criteria.
Groundwater:
Quantity and flow
Local groundwater would continue to flow
to Mill Creek until the groundwater ex-
traction and treatment system is oper-
ating. During this time, quantity and
flow would remain unchanged.
The local groundwater would be pumped at
about 100 gpm. During that time, the
groundwater table would be drawn down an
average of 5 to 10 feet between Mill
Creek and the east drain. Shallow
groundwater flow would no longer dis-
charge to the creek or drain. Regional
flow patterns would not be significantly
affected. Pumping would not affect
water supplies in the area. After pump-
ing, groundwater would again discharge
to Mill Creek and the east drain. The
cap over Areas I, II, and V would limit
groundwater recharge from precipitation
i.ifiltration and would reduce slightly
local groundwater discharge to Mill
Creek. The creek would continue to re-
ceive groundwater from uncapped areas
and the regional system.
-------
Table 6-14 (continued)
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE 2—SURFACE CAP WITH GROUNDWATER EXTRACTION AND TREATMENT
Element of the Environment
Quality
Short-Term Effects
(Ti
I
oo
00
Stormwater:
Quantity and quality
Mill Creek:
Quantity and flow
Local groundwater quality would continue
to be controlled by natural processes
until the groundwater extraction and
treatment system was operating.
Long-Term Effects
During site regrading and cap construc-
tion, stormwater runoff patterns could be
affected. Temporary control measures
could mitigate adverse impacts. Contami-
nated stormwater in construction areas
would be collected, treated as necessary,
and discharged to Metro.
During construction. Mill Creek quantity
and flow would remain similar to existing
conditions. Groundwater would continue
to discharge to the creek. Surface water
in the construction areas would be routed
away from the creek. As portions of the
cap were completed, its stormwater system
would become operational.
During groundwater pumping, groundwater
qi/ality would gradually improve. The
contaminant levels would depend on the
length of time groundwater extraction
has been in progress and on which con-
taminant is being considered. During
pumping, contaminated groundwater would
not discharge to Mill Creek or the east
drain from Areas I, II, V, and IX. A
30-year pumping program would not reduce
cadmium, chromium, and lead concentra-
tions below federal drinking water stan-
dards. It would take hundreds of years
of pumping for the concentrations of
these metals in groundwater beneath the
site to meet the drinking water stand-
ards, if ever. As previously noted, the
shallow aquifer that flows beneath West-
ern Processing is not used as a drinking
water source.
Uncontaminated stormwater would be col-
lected off the cap in Areas I, II, and V
and discharged into Mill Creek. Storm-
water in other areas will continue to
infiltrate and/or discharge into Mill
Creek.
Groundwater extraction would intercept
groundwater that otherwise would dis-
charge to Mill Creek and the east drain.
Groundwater discharge to Mill Creek and
the east drain would resume after pump-
ing ceases. Groundwater discharge
quantity would be reduced slightly by
the presence of the cap.
-------
Table 6-14 (continued)
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE 2—SURFACE CAP WITH GROUNDWATER EXTRACTION AND TREATMENT
Element of the Environment
Quality
Short-Term Effects
During construction of Example Alterna-
tive 2, Mill Creek water quality would be
similar to current conditions.
Long-Term Effects
CTi
I
00
Sediment quality
Contaminated sediments could continue to
be a source of contamination to Mill
Creek water.
Terrestrial Wildlife
Soils and Topography
(excavation, removal)
Terrestrial wildlife and wildlife habitat
in the construction areas would be
destroyed.
No soils would be excavated. Grading and
construction of the cap over Areas I, II,
and V would change the topography of these
areas. An offsite source of about
112,000 cubic yards (total) of clay, loam,
and gravel would be necessary for the con-
struction of the cap.
During pumping, no contaminants from
Western Processing would be discharged
via groundwater to Mill Creek. The
water quality of Mill Creek would grad-
ually improve. If pumping was stopped
after 30 years, metals contamination
would be reintroduced to Mill Creek,
with the resultant levels exceeding the
modified ambient water quality criteria.
Sixty to 120 years of groundwater ex-
traction and treatment would be required
to sufficiently reduce the level of
metala contamination entering Mill Creek
from Western Processing to allow modi-
fied ambient water quality criteria to
be met in the creek.
The contaminant levels in Mill Creek
sediment would gradually decline as the
source of sediment contamination (con-
taminated groundwater) is eliminated.
If pumping were stopped after 30 years,
sediments would again be exposed to
metals contamination via groundwater.
Sixty to 120 years of groundwater ex-
traction and treatment would be required
to reduce influent groundwater metals
concentrations to levels that would
allow Mill Creek water to meet modified
ambient water quality criteria.
The vegetative cover over the cap may
provide limited habitat. Long-term
effects to wildlife inhabiting other
areas is not known. The industrial/
commercial developments around the site
are reducing wildlife habitat.
The topography of Areas I, II, and V
would be changed by the installation of
the surface cap.
-------
Table 6-14 (continued)
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE 2—SURFACE CAP WITH GROUNDWATER EXTRACTION AND TREATMENT
Element of the Environment
Noise
Air Quality
(odor, dust)
I
VD
O
Transportation
Flood Plains
Land Use
Short-Term Effects
Construction would last for 8 months.
During this time, noise levels in the
area would be increased due to grading
activities and construction of the cap,
groundwater treatment facility, and
extraction system. Additional traffic
would also generate noise. Timing and
good construction practices could miti-
gate adverse impacts.
Dust could be generated during site grad-
ing and cap construction; however, dust
control measures would be implemented to
mitigate this impact.
Truck traffic would be generated by
trucks hauling construction materials.
Employee trips would also generate addi-
tional traffic. This could cause traffic
congestion on S. 196th Street. The im-
pacts of the increased traffic could be
mitigated by staggering arrival and de-
parture times.
This alternative could involve construc-
tion on or near the designated flood
hazard areas adjacent to Mill Creek and
the east drain. Avoiding construction of
erosion-prone or flood-sensitive facil-
ities in these areas could effectively
mitigate adverse impacts.
Construction of this alternative would
limit the use of the areas where con-
struction occurs. The adjacent segment
of the Interurban Trail might have to be
closed during construction periods.
Long-Term Effects
The groundwater treatment plant would
increase noise levels slightly in the
area. Mitigation is not expected to be
necessary because the surrounding prop-
erty is under industrial use and would
not be sensitive to the minor noise
increases.
The groundwater treatment process would
release volatile organics. However, the
system would be designed and operated to
meet emissions standards that would re-
duce the potential for adverse impacts
from these releases. The long-term po-
tential for dust generation would be re-
duced by the vegetative cover over the
capped areas.
No significant long-term transportation
impacts.
No long-term impacts expected.
Future use of the capped areas would be
prohibited because of the need to main-
tain the impermeability of the RCRA cap.
Land use for areas where extraction and
treatment system components are located
would be restricted during the operating
period. Some subsidence may occur over
the pumping period in those areas where
the groundwater table has been drawn
down. Land use of areas not capped
(such as VIII and IX) could be re-
stricted by local government agencies,
depending on the soil contamination
levels.
-------
Table 6-15
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE 3—EXCAVATION WITH ONSITE DISPOSAL, GROUNDWATER
EXTRACTION AND TREATMENT, SURFACE CAP
Element of the Environment
Human Health:
Soils
Short-Term Effects
Groundwater
Mill Creek
Air
Aquatic Organisms in Mill
Creek
Groundwater:
Quantity and flow
Same as Example Alternative 2, except that more
stringent safety procedures would be necessary
during construction because there would be a
greater potential for exposure to contaminated
soils. Waste containers known to be buried
within the excavation areas would be disposed
onsite if they meet compatibility criteria.
Same as Example Alternative 2.
Same as Example Alternative 2.
See soils, above.
Same as Example Alternative 2.
Same as Example Alternative 2.
Quality
Same as Example Alternative 2.
Lonq-Term Effects
The construction of the on-property
landfill would lead to long-term im-
pacts that are similar to those
described for Example Alternative 2,
with the additional benefit that con-
taminated surface soil would be removed
from a portion of Area VIII.
Same as Example Alternative 2.
Same as Example Alternative 2.
Same as Example Alternative 2.
Same as Example Alternative 2.
Same as Example Alternative 2, except
groundwater would be pumped at a
slightly slower rate (about 85 gpm)
because there would be fewer well
points. There also would be slightly
less drawdown.
Same as Example Alternative 2, except
the rate of contaminant removal would
be slightly lower. The difference be-
tween the effectiveness of Example
Alterantives 2 and 3 in removing con-
taminants is expected to be minor and
cannot be quantified. Excavation of
the unsaturated zone soils in Areas I
and II would further reduce the poten-
tial for contaminant migration via
leaching from soils above the water
table.
-------
Table 6-15 (continued)
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE 3—EXCAVATION WITH ONSITE DISPOSAL, GROUNDWATER
EXTRACTION AND TREATMENT, SURFACE CAP
Element of the Environment
Stormwater:
Quantity and quality
cr\
I
VO
NJ
Mill Creek;
Quantity and flow
Quality
Sediment quality
Terrestrial Wildlife
Soil and Topography
(excavation and removal)
Noise
Short-Term Effects
Same as Example Alternative 2, except that the
increased soils handling and excavation would
increase the potential for erosion of uncovered
soils. Stormwater from Areas I and II would be
collected, treated as necessary, and discharged
to Metro during construction.
Same as Example Alternative 2.
Same as Example Alternative 2.
Same as Example Alternative 2.
Same as Example Alternative 2.
Approximately 108,000 cubic yards of soil would
be excavated from Areas I and II and a portion
of Area VIII and placed in an on-property land-
fill. Approximately 186,000 cubic yards (total)
of loam, sand, and clay would be needed for con-
struction of the cap and liner. The grading,
landfilling, and/or capping of Areas I and II
and a portion of Area V would change the topog-
raphy of these areas.
Construction would last for 48 months. During
that time, noise levels would be increased due
to excavation activities and construction of the
cap, liner, groundwater treatment facility, and
extraction system. Additional traffic would
also generate noise. Timing and good construc-
tion practices could effectively mitigate ad-
verse impacts.
Long-Term Effects
Same as Example Alternative 2, except
that contaminated surface soils in a
portion of Area VIII would be removed,
eliminating their potential to be a
source of Stormwater contamination.
Same as Example Alternative 2.
Same as Example Alternative 2.
Same as Example Alternative 2.
Same as Example Alternative 2.
No additional impacts. The topography
of Areas I and II and a portion of
Area V would be changed permanently.
Same as Example Alternative 2.
-------
Table 6-15 (continued)
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE 3—EXCAVATION WITH ONSITE DISPOSAL, GROUNDWATER
EXTRACTION AND TREATMENT, SURFACE CAP
Element of the Environment
Air Quality (odor, dust)
Short-Term Effects
I
kO
U)
Transportation
Flood Plains
Land Use
The impacts would be similar to Example Alterna-
tive 2 but they would be more extensive because
more soil would be moved, and contaminated soils
must be stockpiled onsite prior to placement in
the lined area. Also, the impacts would last
over a longer period because construction would
be longer. Good construction practices, cover-
ing the piles, wetting the soil, or using seal-
ants could mitigate adverse impacts. Odors may
be generated when volatile organics are released
from the soil during excavation. Organic levels
and conditions that might affect their release
would be continuously monitored, and corrective
measures would be taken if it appears that levels
might become hazardous.
Heavy truck traffic would result from hauling
construction materials to the site. Employee
trips would generate additional traffic.
Traffic generated by this alternative would be
greater than Example Alternative 2 because more
construction materials would be necessary. It
would, however, generate less traffic than
Example Alternatives 4 and 5, which involve off-
site transport of excavated soils and import of
replacement soils.
Same as Example Alternative 2.
Same as Example Alternative 2, except that the
segment of the Interurban Trail next to the site
would be closed for a longer period than under
Example Alternative 2.
Long-Term Effects
Same as Example Alternative 2.
No significant long-term transportation
impacts.
Same as Example Alternative 2.
Same as Example Alternative 2, except
that Area VIII may be analyzed to have
different restriction needs.
-------
Table 6-16
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE 4—PRP'S REMEDIAL ACTION PLAN
(This table prepared by the PRP's)
Element of the Environment
Human Health:
Soils
Short-Term Effects
Exposure of workers and the general
public to contaminated soil would be
controlled by a Health and Safety Plan.
Groundwater
Groundwater beneath Western Processing
does not present a hazard to human health
because it is not currently a water
supply source.
Mill Creek
Air
Aquatic Organisms in Mill
Creek
Same as Example Alternative 2
Same as Example Alternative 3
No increase in contaminant releases to
Mill Creek would occur during
construction.
Long-Term Effects
Following excavation, imported soil
would be placed over Area I (minimum
depth one foot) and a gravel cover would
be laid over the soil. Unexcavated
contaminated soil would thus be isolated
and the potential for direct human
exposure eliminated. The groundwater
extraction program would further reduce
residual soil contamination, and the
surface cover (pavement) would further
isolate residual contamination
following completion of the pumping
program.
Because an adequate, alternate water
supply source is present in the area,
the local, shallow aquifer is not a
likely candidate for development. While
the 5-year pumping program should reduce
chloroform concentrations to less than
the the federal drinking water standard,
the concentrations of lead, cadmium, and
chromium would not be reduced to the
levels specified by the drinking water
standards. It would take hundreds of
years of pumping before the concentra-
tions of these three contaminants in
groundwater beneath the property could
meet the drinking water standards.
Same as Example Alternative 2
Same as Example Alternative 2.
Groundwater discharges from Area I into
Mill Creek would be eliminated after
pumping begins, thus allowing water
quality in Mill Creek to achieve the
modified ambient water quality criteria.
As the water quality in Mill Creek
improves, the potential for adverse
impacts to aquatic organisms would
decrease. When groundwater pumping
stops after 5 years, contaminant
concentrations in Mill Creek would not
increase above the modified criteria
levels as a result of groundwater
discharge to the creek from Area I.
-------
Table 6-16 (continued)
ENVIRONMENTAL EVALUATION '
EXAMPLE ALTERNATIVE 4—PRP'S REMEDIAL ACTION PLAN
Element of the Environment
Groundwater:
Quantity and flow
Short-Term Effects
Construction of the diversion barrier
would alter local groundwater flow pat-
terns. The rate of groundwater discharge
to Mill Creek from the Western Processing
area would begin to be reduced.
I
UD
Ul
Quality
Onsite groundwater quality is not expected
to improve during the construction period.
Off-property groundwater quality could
begin to improve following installation
of the diversion barrier.
Lonq-Term Effects
During groundwater pumping, groundwater
levels on the property would be reduced.
Some of the groundwater immediately
around the property and below the depth
of the diversion barrier would flow
toward and into the well points. Once
the pumping program is completed, local
groundwater flow patterns would continue
to be modified by the diversion barrier.
Groundwater flow from Area I into Mill
Creek would resume, but at a slower rate
than prior to the installation of the
diversion barrier. Groundwater levels
within the confines of the diversion
barrier would stabilize and undergo
relatively little fluctuation as a
result of the inhibition of surface
water infiltration.
Effects on groundwater quality in terms
of human health and Mill Creek water and
sediment quality are discussed under the
Human Health and Mill Creek elements.
The diversion barrier would cause escap-
ing residual contamination to enter the
groundwater at a depth that could allow
some of the residual contamination to
bypass Mill Creek and be introduced into
the regional groundwater flow system.
Stormwater:
Quantity and flow
There would be no discharge of stormwater
from Area I during the construction
period.
During operation of the groundwater pump-
ing program, Area I stormwater would be
allowed to infiltrate the site as part
of the contaminant flushing process.
Following completion of the subsurface
cleanup activities, stormwater would be
collected in the stormwater management
system and discharged to Mill Creek at a
controlled rate in accordance with the
requirements of Kent stormwater ordinance
No. 2130.
-------
Table 6-16 (continued)
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE 4—PRP'S REMEDIAL ACTION PLAN
Element of the Environment
Quality
Mill Creek:
Quantity and flow
Short-Term Effects
Contaminated on-property surface water
would be collected as necessary and
appropriately treated and discharged.
The diversion barrier would reduce the
rate of groundwater flow to Mill Creek
from the site.
CTl
I
vo
Quality
Mill Creek water quality would begin to
improve before the pumping program is
initiated as a result of installing the
diversion barrier.
Long-Terro Effects
All surface water discharged from Area I
would be free of contaminants associated
with the previous use of the property as
a waste recycling facility.
No groundwater would flow to Mill Creek
from the property during operation of
the groundwater extraction system.
Following completion of the extraction
program, groundwater flows to Mill Creek
from the property would resume, but at a
lower rate than at present because of
the effect of the diversion barrier,
which will remain in place.
During the pumping period, the amount of
contaminants entering Mill Creek via
groundwater from the site would drop off
to a level that should allow Mill Creek
water quality to meet modified ambient
water quality criteria levels. The
remedial action (consisting of excava-
tion, groundwater extraction and treat-
ment, diversion barrier, and surface
pavement) would reduce overall Area I
contamination by approximately 70 per-
cent. Zinc concentrations would be
reduced 69 percent by the excavation
program and an additional 7 percent by
the groundwater pumping program. The
diversion barrier would effectively
reduce the amount of contamination en-
tering Mill Creek at any one time by at
least an additional 12 percent. The
combined zinc removal achieved by the
remedial action would be at least
88 percent.
-------
Table 6-16 (continued)
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE 4~PRP'S REMEDIAL ACTION PLAN
Element of the Environment
Sediment quality
Short-Term Effects
Green River
Terrestrial Wildlife
Soils and Topography
(excavation, removal)
No significant improvement in the amount
of contaminated sediments in Mill Creek
would occur during the relatively short
(24-month) construction period.
No impact
No wildlife are known to have previously
used the property. The property would
not be available for wildlife use during
the construction period.
Contaminated soils would be excavated and
replaced with more permeable soil from an
offsite source. The Area I surface will
be regraded to prevent surface flows from
entering or leaving the property.
Long-Term Effects
Because Hill Creek water quality should
be able to return to levels specified by
the modified ambient water quality cri-
teria as a result of Example Alterna-
tive 4, no further degradation of Mill
Creek sediments should be caused by
groundwater discharge to the creek from
Western Processing.
No impact
Because Area I will be paved, it will
remain unsuitable for wildlife use fol-
lowing completion of the groundwater
extraction program.
Following the completion of groundwater
extraction, additional grading would be
performed and the surface paved. No
significant difference between on- and
off-property topography would result.
Noise
Air Quality
(odor, dust)
Same as Example Alternative 2 but over a
construction period of 24 months.
Similar to Example Alternative 3, except
no onsite stockpiling would occur, and
the construction period would be
24 months.
Noise impacts for groundwater extraction
and treatment would be the same as for
Example Alternative 2 except that the
duration is only 5 years. Following
completion of the extraction process,
activities associated with facilities
dismantling and installation of the
surface cover (pavement) and stormw»t»r
management system would generate addi-
tional noise but for only a relatively
short (one- to 3-month) period.
Same as Example Alternative 2.
that during paving of Area I, the
characteristic asphalt odor would t«-
present during the relatively ihort
paving period. After capping, du.t
generation would not occur.
-------
Table 6-16 (continued)
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE 4—PRP'S REMEDIAL ACTION PLAN
Element of the Environment
Transportation
Short-Term Effects
I
10
oo Flood Plains
Land Use
Personal vehicle and heavy truck traffic
would significantly increase during the
construction period. Heavy truck traffic
would be associated with transporting
excavated materials from the property and
construction materials to the property.
Traffic levels would be higher than for
Example Alternatives 2 and 3 because of
the large volume of contaminated soil to
be transported offsite, but less than for
Example Alternative 5. Transportation
activities would create a volume of decon-
tamination water that could require appro-
priate treatment before either reuse or
disposal.
Same as Example Alternative 2
The property would remain unavailable for
use during the construction period.
Long-Term Effects
During the relatively brief facilities
dismantling and site paving phase, per-
sonal vehicle and truck traffic will
again increase but only slightly. No
transportation impacts will occur fol-
lowing capping of Area I.
Final grading, paving, and facilities
dismantling would have no adverse impact
on flood-prone areas along Mill Creek.
The property would remain unavailable for
redevelopment until it is paved follow-
ing completion of groundwater extraction
and treatment. Thereafter, it would be
available for redevelopment consistent
with site zoning and adjacent existing
and planned uses.
-------
Table 6-17
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE 5—EXCAVATION WITH OFFSITE DISPOSAL
Element of the Environment
Human Health:
Soils
Groundwa ter
Short-Term Effects
VD
Mill Creek
Air
Aquatic Organisms in Mill
Creek
Exposure of workers and the general public
to contaminated soil would be controlled
by the provisions of the Health and
Safety Plan.
During construction activities, the dewa-
tering system operation would draw down
the local, shallow aquifer.
Same as Example Alternative 2
See Soils, above.
The construction dewatering program would
reduce contaminated groundwater flow to
Mill Creek. Depending on the amount of
reduction, the sediments would begin to
self-clean, yielding a reduction in the
exposure of aquatic organisms to metals
contamination.
Long-Term Effects
No impacts because all contaminated sur-
face soils would be removed. No land use
limitations would be necessary.
The soil removal and dewatering actions
for Example Alternative 5 should be suf-
ficient to reduce most groundwater con-
taminant concentrations to achieve
federal drinking water standards, ADI'S,
and SNARL's except for cadmium and
chromium.
The excavation action and associated
dewatering would yield long-term
improvements similar to those indicated
for Example Alternative 2 but in a
shorter period of time.
No adverse impact because all contami-
nated surface solids would be removed.
The discharge of contaminants to Mill
Creek via groundwater originating from
Areas I, II, V, and IX would be reduced
by the removal of about 95 percent of
the contaminated soils over the 4-year
excavation period and the operation of
the dewatering system. The result of
these actions would be to allow Mill
Creek to meet modified ambient water
quality criteria.
Groundwater:
Quantity and flow
The dewatering for the 15-foot excavation
in Areas I and II would cause a localized
depression in the groundwater table.
100 gpm has been used as the baseline
estimate for dewatering.
No long-term changes are expected to the
groundwater flow system from this
alternative.
-------
Table 6-17 (continued)
ENVIRONMENTAL EVALUATION—EXAMPLE ALTERNATIVE 5
Element of the Environinent
Quality
o
o
Stormwater:
Quantity and quality
Mill Creek and East Drain:
Quantity and flow
Quality
Sediment quality
Terrestrial Wildlife
Short-Term Effects
Groundwater quality would begin to improve
as contaminated soils are removed and con-
taminated groundwater is removed by the
dewatering system. Extracted groundwater
would be treated and discharged to the
Metro system.
Same as Example Alternative 3
Mill Creek flow would be reduced by the
amount of groundwater flow diverted by
the dewatering system.
Mill Creek water quality should improve
during construction of Example Alterna-
tive 5 as groundwater is diverted.
Sediment contamination levels should de-
crease as groundwater flow is diverted
and the natural sediment transport mecha-
nisms replace contaminated sediments with
upstream sediments.
Use of Areas I, II, V, VIII, and IX by
terrestrial wildlife would be negligible
during construction activities.
Long-Term Effects
Groundwater quality would improve to
meet human health targets (except for
cadmium and chromium) with the removal
of the majority of the contaminated
soils (95 percent of the contaminated
mass). Long-term effects of groundwater
quality in terms of human health and
Mill Creek water and sediment quality
are discussed above under Human Health.
Example Alternative 5 would remove all
contaminated surface soils from Areas I,
II, V, VIII, and IX thereby eliminating
contaminated Stormwater discharge from
these areas.
Example Alternative 5 should not have a
long-term effect on Mill Creek as it in-
volves no capping or long-term ground-
water extraction or diversion barrier.
The discharge of contaminated ground-
water to Mill Creek from Western Pro-
cessing would be greatly reduced after
the soil excavation and accompanying
dewatering system are completed. Levels
of zinc in the groundwater reaching Mill
Creek would be low enough to allow the
creek to meet modified ambient water
quality criteria due to the removal of
95 percent of the zinc from the exca-
vated areas.
Because the source of inorganic contami-
nation would be removed from the local,
shallow groundwater, Mill Creek sediment
quality would be expected to improve.
Long-term impact would be a function of
ultimate use of the property.
-------
Table 6-17 (continued)
ENVIRONMENTAL EVALUATION—EXAMPLE ALTERNATIVE 5
Element of the Environment
Soils and Topography
(excavation, removal,
and backfill)
Noise
Short-Term Effects
I
H^
O
Air Quality
(odor, dust)
Transportation
Flood Plains
Land Use
Excavated areas (I, II, V, VIII, and IX)
would be disturbed for the duration of
construction activities (4 years).
Noise levels would be increased during
excavation activities. Primary sources
would be excavation equipment, truck
traffic, and the treatment plant. Timing
and good construction practices could
mitigate adverse impacts.
Same as Example Alternative 3
Approximately 40,000 truck trips would be
needed to accomplish the excavation and
fill operations. Additional trips would
be needed for workers and equipment de-
liveries. Traffic impacts could be miti-
gated by staggering arrival and departure
times and avoiding peak traffic periods.
Transportation activities would create a
volume of decontamination water that
could require appropriate treatment
before either reuse or disposal.
Same as Example Alternative 2.
Excavation and fill activities in Areas I,
II, V, VIII, and IX would restrict land
use until they are completed.
Long-Term Effects
Backfill with imported soil to approxi-
mately existing grades would be a posi-
tive benefit for these areas.
No long-term noise impacts.
Contaminated dust would not be a problem
because contaminated surface soils
would be removed.
No long-term transportation impacts.
Same as example Alternative 2.
No major long-term land use impacts
would result. The site could be re-
turned to productive use. Monitoring
wells could restrict placement of some
structures.
-------
Table 6-18
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE 6--MILL CREEK NO ACTION
o
NJ
Element of the Environment
Human Health
Aquatic Organisms in Mill
Creek
Groundwater:
Quantity and flow
Quality
Mill Creek:
Quantity and flow
Quality
Sediment quality
Short-Term Effects
Contaminants in Mill Creek sediment are
not a hazard to human health.
Toxic metals in Mill Creek water and sed-
iments would continue to pose a hazard to
aquatic organisms.
No effects
No effects
No effects
Contaminated sediment may continue to
leach toxic metals to Mill Creek.
There would be no short-term changes in
sediment quality.
Long-Term Effects
Terrestrial Wildlife
No effects
Same as short-term.
Over time, if onsite sources were re-
duced, levels of contamination in Mill
Creek and the potential for toxic
effects on aquatic organisms would be
reduced.
No effects
No effects
No effects
Contamination from sediment would grad-
ually decrease as contaminated sediment
is carried downstream and replaced with
cleaner material.
Over time, depending on the degree of
source control and the quality of up-
stream sediment and water, sediment
quality in Mill Creek would improve as
leachable materials are carried away by
the surface water and cleaner sediment
moves past Western Processing from up-
stream. If contaminated groundwater dis-
charge from Western Processing ceases,
it would take an estimated 5 to 10 years
for the contaminated sediments to be
dispersed.
No effects
Note: Evaluation assumes implementation of Example Alternative 2, 3, 4, or 5.
-------
Element of the Environment
Soils and Topography
(excavation, removal)
Noise
Air Quality
(odor, dust)
Transportation
Flood Plains
Land Use
Table 6-18 (continued)
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE 6—MILL CREEK NO ACTION
Short-Term Effects
Long-Term Effects
No effects
No effects
No effects
No effects
No effects
No effects
No effects
No effects
No effects
No effects
No effects
No effects
-------
Table 6-19
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE 7—MILL CREEK SEDIMENT REMOVAL
Element of the Environment
Human Health
Aquatic Organisms in Mill
Creek
I
I—"
o
Groundwater:
Quantity and flow
Quality
Mill Creek:
Quantity and flow
Quality
Sediment quality
Short-Term Effects
Sediments in Mill Creek are not a hazard
to human health.
Aquatic organisms in the reach of Mill
Creek from which sediment is removed
(about 2,300 feet) would be destroyed.
There could be adverse effects on aquatic
organisms downstream if contaminated
water and sediment were to escape the
diked-off construction area. Fish
migration would be blocked during the
time that Mill Creek flows are diverted
(about one month).
No effects
No effects
During construction (an approximately
one-month period) Mill Creek flows would
be diverted into a pipe. 2,300 feet of
Mill Creek would be dewatered during this
period.
There could be temporary decreases in the
quality of water in Mill Creek if water
draining into the construction area is
discharged downstream. In the event of a
high flow topping both diversion dams, con-
taminated water and sediment would be
carried downstream. The diversion system
would be designed to safely handle a con-
tinuous flow of 15 cfs.
Contaminated sediment could be released
to downstream areas if an extreme storm
flow overtopped the diversion dams.
Long-Term Effects
Same as short term.
Aquatic organisms would benefit from im-
proved water quality and habitat in Mill
Creek. Other, upstream, sources of
contaminants may still limit water and
habitat quality.
No effects
No effects
No effects
There would be a long-term improvement
in water quality in Mill Creek resulting
from the removal of contaminated sediment
and from revegetation of the construction
area.
Removal of contaminated sediment would
quickly improve sediment quality. The
sediment quality would continue to be
good as long as contaminated water or
groundwater does not enter Mill Creek.
Note: Evaluation assumes implementation of Example Alternative 2, 3, 4, or 5.
-------
Table 6-19 (continued)
ENVIRONMENTAL EVALUATION
EXAMPLE ALTERNATIVE 7—MILL CREEK SEDIMENT REMOVAL
Element of the Environment
Terrestrial Wildlife
Soils and Topography
(excavation, removal)
Noise
Air Quality
(odor, dust)
Transportation
Flood Plains
Land Use
Short-Term Effects
Terrestrial habitat in the construction
area would be destroyed.
The topography of Mill Creek would be
slightly altered. Approximately 1,700
cubic yards of sediment would be removed
from Mill Creek.
There would be temporary increases in
noise during diversion system construc-
tion, excavation, and pumping.
Removal of sediment from Mill Creek may
cause temporary increases in dust and
odors.
Removal of sediment would generate about
225 truck trips if the material is dis-
posed of offsite. There would also be
increases in traffic due to construction
workers and hauling equipment. There
would be short blockages of South 196th
Street during construction and removal of
the pipeline.
There would be a remote possibility of
increased flooding upstream if an
unexpectedly severe storm were to occur
during the time that Mill Creek is
diverted.
There should be no significant short-term
impacts on land use. The properties af-
fected by construction activities are
presently undeveloped.
Long-Term Effects
There would be no long-term effects be-
cause the area would be revegetated.
Gravel riffles would allow the creek bed
to agrade to its previous elevation as
sediment from upstream is deposited.
No effects
No effects
No effects
No effects
No effects
-------
gas supplies. Some alternatives will use electricity and
sewer lines.
Tables 6-13 through 6-19 describe the short-term and long-
term impacts of the example alternatives. Short-term is
defined as the construction period. Impacts expected during
and after the operation period are included in the long-term
discussions. However, for the no action alternatives,
short-term is defined as the first 5 years after selecting
this alternative. Major beneficial and adverse impacts are
summarized in Table 6-20.
6.4.3 INSTITUTIONAL EVALUATION
Institutional considerations discussed here are federal,
state, and local environmental regulations, guidelines, or-
dinances, and advisories that may be applicable to the im-
plementation of the example remedial action alternatives.
Each of the seven example alternatives identified for the
Western Processing site has different implications under the
various standards. Table 6-21 lists the laws, regulations,
and standards that are evaluated for each alternative.
The WDOE cleanup policy and the USEPA groundwater protection
strategy (GWPS) could require cleanup of the contaminated
area or groundwater to background levels or to levels that
would protect human health. However, considerations such as
technical feasibility and cost effectiveness may affect the
determination of the level of cleanup that must be achieved.
It is not known at this time what cleanup levels will be
acceptable for Western Processing and, therefore, which ex-
ample alternatives would be in compliance with these policies,
USEPA draft policy on CERCLA remedial actions requires that
feasibility studies examine alternatives that comply with
applicable sections of other federal environmental and pub-
lic health laws. It is also a USEPA policy that compliance
with state and local standards should be examined in CERCLA
feasibility studies. Factors such as fund balancing, tech-
nical impracticability, enforcement considerations, and
environmental impacts may affect the selection of the final
remedial action. State (and local) standards that are more
stringent than federal standards may form the basis for a
Superfund-financed remedy only if the remedy is (1) consis-
tent with the cost-effective remedy based on federal stan-
dards, or (2) the state pays the additional cost.
Proposed revisions to the National Oil and Hazardous Sub-
stances Pollution Contingency Plan were published in the
Federal Register on January 28, 1985. These revisions clar-
ify that, while standards must be considered, federal, state,
and local public health or environmental permits are not
6-106
-------
Table 6-20
SUMMARY OF MAJOR BENEFICIAL AND
ADVERSE ENVIRONMENTAL IMPACTS
Example Alternative 1—No Action
Beneficial
Adverse
Short-term construction
related impacts would be
avoided.
Groundwater quality beneath
the site would improve only
very slowly because of the
continued leaching of contami-
nants from soils and from the
mass of contaminants below the
water table.
Contaminated groundwater would
continue to discharge into
Mill Creek.
It would take hundreds of
years, if ever, for ground-
water quality to improve to
target levels of metals for
human health for drinking
water.
Aquatic organisms in Mill
Creek would continue to be
adversely affected by con-
taminated water and sediment.
The potential risks to human
health due to ingestion of
contaminated dust and soil
would continue.
Future land use could be
restricted because of the need
to limit contact with contam-
inated soil on and off the
property.
Without maintenance, Area I
stormwater control berms could
deteriorate, allowing contami-
nated stormwater to discharge
to adjacent areas and Mill
Creek.
6-107
-------
Table 6-20
(continued)
Example Alternative 2—Cap, Pump, and Treat
Beneficial
The surface cap over
Areas I and II and por-
tions of Area V would elim-
inate the potential for
human and stormwater con-
tact with the contaminated
soils in these areas.
The surface cap would pre-
vent leaching of contam-
inants to the groundwater
from the unsaturated zone
in Areas I, II, and V.
Groundwater pumping and
treatment for 30 years
would reduce all but one
indicator organic compound
in the groundwater to
levels below drinking water
quality criteria.
Contaminated groundwater
from Western Processing
would not discharge into
Mill Creek during the
pumping period.
Adverse
Short-term, construction
related impacts (noise,
traffic, etc.) would occur in
the area for eight months.
Most of these impacts could be
effectively mitigated.
The potential would remain for
human ingestion of contami-
nated surface soils from
Areas VIII and IX.
A 30-year pumping and treat-
ment program would not reduce
lead, cadmium, and chromium
concentrations in groundwater
beneath Area I to levels that
would meet federal drinking
water standards. Hundreds of
years of pumping would be re-
quired before these standards
could be met, if ever.
Sixty to 120 years of ground-
water pumping and treatment
would be required before modi-
fied ambient water quality
criteria for metals could be
achieved in Mill Creek after
pumping ceases. Future use of
the capped areas would be
prohibited.
Example Alternative 3—Onproperty Landfill,
Offproperty Cap, Pump, and Treat
Beneficial
The contaminated soil in
the unsaturated zone from
Areas I, II, V, and VIII
would be isolated in the
onsite landfill or capped
and thus would not be
available for leaching to
the groundwater.
Adverse
Short-term, construction re-
lated impacts would occur in
the area for 44 months. Most
of these impacts could be
effectively mitigated.
6-108
-------
Table 6-20
(continued)
Example Alternative 3, Continued
Beneficial
Adverse
The cap, liner, and excava-
tion would eliminate the
potential for human and
stormwater contact with
contaminated soils in
Areas I, II, V, and VIII.
Groundwater pumping and
treatment for 30 years
would reduce all but one
indicator organic compound
in the groundwater to
levels below drinking water
quality criteria.
Contaminated groundwater
from Western Processing
would not discharge into
Mill Creek during pumping.
See Example Alternative 2 dis-
cussion for adverse ground-
water quality effects on human
health and Mill Creek.
Future use of the property
would be prohibited because it
would be a RCRA landfill.
Future use of the off-
property, capped areas would
be similarly restricted.
Example Alternative 4—PRP Plan (Excavate, Diversion
Barrier, Pump and Treat, Cap) (Prepared by the PRP1s)
Beneficial
Approximately 70 percent of
the contamination (includ-
ing zinc) from Area I would
be removed by the excava-
tion and groundwater pump-
ing programs.
Soil excavation and back
filling with imported soil
would eliminate the poten-
tial for human and storm-
water contact with conta-
minated surface soils in
Area I.
The surface cap would in-
hibit infiltration and
leaching of residual con-
tamination from unexcavated
soil in the unsaturated
zone of Area I.
Adverse
Short-term, construction re-
lated impacts would occur dur-
ing the 24-month construction
period.
The up to 5-year pumping and
treatment program would not
reduce lead, cadmium, and
chromium concentrations in
groundwater beneath Area I to
levels that would meet federal
drinking water standards.
An indefinitely long period of
pumping would be required
before these standards could
be met, if ever.
6-109
-------
Table 6-20
(continued)
Example Alternative 4, Continued
Beneficial
Groundwater pumping for up
to 5 years would reduce all
but one indicator organic
compound in the ground-
water beneath Area I to
levels below drinking water
quality criteria.
Groundwater contamination
would be sufficiently re-
duced after up to 5 years
of pumping to allow contam-
inant concentrations in
Mill Creek to return to
modified ambient water
quality criteria levels.
The property would be avail-
able for redevelopment con-
sistent with local land uses
following the completion of
the groundwater pumping
program and paving of the
surface.
Adverse
Example Alternative 5—Excavate and Dewater
Beneficial
95 percent of the contami-
nant material, including
zinc, would be excavated
and removed from Areas I,
II, V, VIII, and IX. This
source removal would be
sufficient to allow metal
contaminant levels in Mill
Creek to meet the modified
water quality criteria.
Soil removal would elim-
inate the potential for
human and stormwater
contact with contaminated
surface soils in Areas I,
II, V, VIII, and IX.
Adverse
Short-term, construction
related impacts would occur in
the area for 5 months out of
each of the 4 years required
to complete the excavation
program. Most of these
impacts could be effectively
mitigated.
6-110
-------
Table 6-20
(continued)
Example Alternative 5, Continued
Beneficial Adverse
All of the contaminated
soils in the unsaturated
zone of Area I and
significant amounts from
Areas V and IX would be
removed. Therefore,
contaminants available for
leaching would be reduced
significantly.
Future site use of the site
would not be restricted.
Example Alternative 6—No Action in Mill Creek
Beneficial Adverse
Short-term, construction Contaminated sediment could
related impacts would be continue to leach toxic metals
avoided. into Mill Creek water for 5 to
10 years after flow of con-
taminated groundwater to Mill
Creek ceases.
Aquatic organisms in Mill Creek
could continue to be adversely
affected by contaminated water.
Example Alternative 7—Sediment Removal in Mill Creek
Beneficial Adverse
Removal of contaminated Short-term, construction re-
sediments would improve the lated impacts would occur in
quality of water in Mill the area for one month, in-
Creek, which would provide eluding the potential for
long-term benefits to resuspenion of contaminated
aquatic organisms. sediments. Fish passage could
also be blocked for one month.
Aquatic organisms in the reach
of Mill Creek from which
sediment is removed would be
destroyed.
6-111
-------
Table 6-21
LAWS, REGULATIONS, AND STANDARDS APPLICABLE TO WESTERN PROCESSING
Law or Regulation
FEDERAL
*Federal Resource Conservation
and Recovery Act (RCRA)
Federal Manifest for Trans-
port of Hazardous Waste
Toxic Substances Control Act
(TSCA)
Source of Regulation
RCRA Section 3001,
3004, 3005, 40 CFR 264,
265
RCRA Section 3002(5),
40 CFR 262
40 CFR Parts 702 to 775
Underground Injection Control
(UIC) Program: Criteria and
Standards
Permits for Structures in or
Work Affecting Navigable
Waters of the U.S
(Section 10 permit)
40 CFR Part 146
33 CFR 322
Example Alternative Affected
All example alternatives
All example alternatives
involving interstate
transport of hazardous
materials.
These regulations apply to
2,3,7,8 TCDD or PCB's at
greater than 50 ppm and
intended for disposal and
PCB's that have migrated
from the original source
of contamination. For
purposes of evaluation in
this study, it has been
assumed that only PCB
levels above 50 ppm re-
quire special disposal.
Not applicable. No under-
ground injection is
proposed.
Not applicable. Mill Creek
is not considered a navi-
gable water.
*Indicates regulations that are discussed in Appendix B.
-------
LAWS, REGULATIONS,
Law or Regulation
Permits for Discharges of
Dredged or Fill Material
Into Waters of the U.S.
(Section 404 permit)
*Response in a Floodplain or
Wetlands
*National Emissions Standards
for Hazardous Air Pollutants
Table 6-21 (continued)
AND STANDARDS APPLICABLE TO WESTERN PROCESSING
Source of Regulation
33 CFR 323
Appendix A to 40 CFR
Part 6
Clean Air Act,
Section 112; State
Implementation Plan
*National Environmental Policy
Act (MEPA)
NEPA Section 102 (2) (c)
Intergovernmental Review of
Federal Programs
40 CFR 29
Example Alternative Affected
Alternative 7 only.
All example alternatives
involving construction in
designated flood hazard
area.
These regulations would
apply to air stripping
equipment used for ground-
water treatment (adminis-
tered by Puget Sound Air
Pollution Control Agency—
PSAPCA).
CERCLA actions are exempt
because EPA's decisionmak-
ing process represents the
functional equivalency of
the analysis performed
under NEPA.
All example alternatives
requiring federal funds,
state funds, or a coopera-
tive agreement between the
state and federal agencies
*Indicates regulations that are discussed in Appendix B.
-------
Table 6-21 (continued)
LAWS, REGULATIONS, AND STANDARDS APPLICABLE TO WESTERN PROCESSING
Law or Regulation
*Relocation Assistance and
Property Acquisition
Worker Safety and Health
Protection
CTi
*National Pollutant Discharge
Elimination System (NPDES)
Permit
*Effluent Guidelines and
Standards
Federal Standards for Toxic
Pollutant Effluent
Source of Regulation
Uniform Relocation
Assistance and Real
Property Acquisition
Policies Act of 1979,
40 CFR 4
Occupational Safety and
Health Administration
(OSHA)
CWA Section 402, 40 CFR
122, 125 Subchapter N
40 CFR 400 Subchapter N,
FWPCA
40 CFR 129
Example Alternative Affected
All example alternatives
involving federal property
acquisition.
All example alternatives
involving workers on prop-
erty. Industrial safety
and health regulations are
administered under the
Washington Industrial
Safety and Health Act
(WISHA).
All example alternatives
involving discharges into
Mill Creek or the Green
River (administered by the
WDOE).
All example alternatives
involving discharge to
Metro (administered by
Metro).
All example alternatives
involving discharge into
Mill Creek or the Green
River (usually regulated
by the NPDES permit).
*Indicates regulations that are discussed in Appendix B.
-------
Table 6-21 (continued)
LAWS, REGULATIONS, AND STANDARDS APPLICABLE TO WESTERN PROCESSING
Law or Regulation
*Hazardous Materials
Regulations
*EPA Groundwater Protection
Strategy
Conservation of Wildlife
Resources
i Preservation of Scientific,
£ Historic, or Archaeological
ui Data
Preservation of Rivers on the
National Inventory
Protection of Threatened or
Endangered Species and Their
Habitats
Source of Regulation
49 CFR 170 to 179
EPA Policy Statement
Fish and Wildlife
Coordination Act
Archaeological and
Historic Preservation
Act of 1974
Wild and Scenic Rivers
Act 40 CFR Part 6.302
Endangered Species Act
50 CFR Part 402
Example Alternative Affected
All example alternatives
involving interstate
transport of hazardous
materials.
All example alternatives.
All example alternatives
except no action. This act
requires agency consulta-
tion prior to modifying any
body of water
Not applicable. No such
resources are expected to
be affected by the
alternatives.
Not applicable. No rivers
affected by the alterna-
tives are so designated.
All example alternatives
except no action. This act
requires that the agencies
request information on
endangered species in any
area affected by a proposed
action.
*Indicates regulations that are discussed in Appendix B.
-------
LAWS, REGULATIONS,
Law or Regulation
Overall Compliance With the
Clean Air Act
Federal Ocean Dumping
Requirements
STATE
*Washington State Dangerous
Waste Regulations
State Approval of Shorelines
Use
State Requirements for the
Transport of Hazardous
Substances
Table 6-21 (continued)
AND STANDARDS APPLICABLE TO WESTERN PROCESSING
Source of Regulation
Clean Air Act 40 CFR
Part 6.303
40 CFR 220-224
33 CFR 220, 224
WAC 173-303-420
Coastal Zone Management
Act of 1972
WAC 412-195
Water Quality Standards WAC 123-201
Example Alternative Affected
These regulations would
apply to air stripping
equipment used for ground-
water treatment (adminis-
tered by PSAPCA).
Not applicable. None of
the alternatives involve
ocean dumping.
All example alternatives.
All alternatives involving
construction within
200 feet of the Green
River.
All example alternatives
involving the intrastate
transport of hazardous
substances.
All example alternatives
involving discharge into
Mill Creek or the Green
River (usually regulated
by the NPDES permit).3
*Indicates regulations that are discussed in Appendix B.
-------
I
(-•
h-•
-J
LAWS, REGULATIONS,
Law or Regulation
*Hydraulics Permit
Table 6-21 (continued)
AND STANDARDS APPLICABLE TO WESTERN PROCESSING
State Environmental Impact
Statement
*State Flood Control Zone
Permit
*Washington Industrial Safety
and Health Act (WISHA)
National Pollutant Discharge
Elimination System (NPDES)
Permit
*WDOE Final Cleanup Policy
REGIONAL
*Metro Industrial Waste Dis-
charge Permit
Source of Regulation
RCW 75-20.100,
WAC 220-110
State Environmental
Policy Act (SEPA)
RCW 86.16
WAC 296-62
WAC 296-64
WAC 173-220
Policy Statement
Resolution 33774
Example Alternative Affected
All example alternatives
involving work within the
ordinary high water line
of Mill Creek or the Green
River.
The WDOE will determine
how SEPA applies to the
example alternatives.
All example alternatives
involving construction in
flood hazard areas.
All example alternatives
except no action.
All example alternatives
involving a discharge to
Mill Creek or the Green
River.
All example alternatives.
All example alternatives
involving discharge to
Metro.
*Indicates regulations that are discussed in Appendix B.
-------
Table 6-21 (continued)
LAWS, REGULATIONS, AND STANDARDS APPLICABLE TO WESTERN PROCESSING
Law or Regulation
*Puget Sound Air Pollution
Control Authority
Seattle-King County Public
Health Department
Source of Regulation
Regulations 1 and 2
Rules and Regula-
tions VIII
LOCAL
i *Land Use Approval
M
M
CO
*Stormwater and Erosion
Control Requirements
*Grade and Fill Permit
*Street Use and Street Cut
Permit
Kent Zoning Code
Kent City Code
(Reviewed by King
County)
Kent City Code,
Chapter 12
Kent City Code
Example Alternative Affected
All example alternatives
involving regulated
emissions.
Not applicable. None of
the example alternatives
involve construction of a
landfill for material not
classified as a dangerous
waste or extremely hazar-
dous waste in WAC 173-303.
All example alternatives
involving building
construction.
All example alternatives
involving construction.
All example alternatives
involving excavation and/
or construction.
All example alternatives
involving heavy street
use.
*Indicates regulations that are discussed in Appendix B.
-------
Table 6-21 (continued)
LAWS, REGULATIONS, AND STANDARDS APPLICABLE TO WESTERN PROCESSING
Law or Regulation
Stormwater Ordinance
City of Kent Surface Drainage
Utility, Drainage Master
Plan
Source of Regulation
Kent City Ordinance
No. 2130 (Reviewed
by King County)
Proposed Plan
Example Alternative Affected
All example alternatives
involving construction.
The plan is scheduled for
adoption in spring 1985.
It might affect alterna-
tives involving Mill
Creek.
*Indicates regulations that are discussed in Appendix B.
-------
required for Superfund-financed remedial actions or for
remedial actions taken pursuant to federal action under Sec-
tion 106 of CERCLA. However, storage, treatment, or dis-
posal of hazardous substances removed from CERCLA sites can
only occur at offsite facilities that are operating under
appropriate federal or state permits or authorizations.
6.4.3.1 Example Alternative 1—No Action
Table 6-22 shows how laws, regulations, and policies apply
to Example Alternative 1. Generally, the laws and regula-
tions do not apply to the no action alternative because they
primarily regulate existing facilities or proposed actions.
However, three laws and policies that address existing con-
ditions rather than proposed actions are RCRA, the USEPA
Groundwater Protection Strategy, and the WDOE Final Cleanup
Policy. These all require corrective action in the event
that hazardous materials are released into the environment.
The no action alternative proposes no corrective action, and
therefore could not be consistent with these laws and policies,
6.4.3.2 Example Alternative 2—Surface Cap with Groundwater
Extraction and Treatment
Table 6-23 shows the relationship between this example
alternative and governmental laws, regulations, and poli-
cies. In general, this alternative may comply with RCRA,
which allows surface capping and groundwater extraction and
treatment for closure of existing land disposal units if the
facilities meet certain design standards and the required
monitoring procedures are followed. A less complex cap,
such as a clay cap without a synthetic membrane, may also
comply with RCRA as long as the cap is less permeable than
the soil underneath. The WDOE Dangerous Waste Regulations
are similar to RCRA regulations in that they allow capping
of a site.
6.4.3.3 Example Alternative 3—Excavation with Onsite Dis-
posal, Surface Cap, and Groundwater Extraction and Treatment
Table 6-24 shows the relationship between this example
alternative and government laws, regulations, and policies.
Generally, the table shows that the example alternative
would be consistent with RCRA if the landfill is designed to
RCRA standards for a new land disposal facility (double
liner, leachate collection and detection systems, properly
closed and maintained). This example alternative may not be
consistent with the WDOE Dangerous Waste Regulations and
RCW 75.105, which prohibit land disposal of "Extremely Haz-
ardous Waste" (as opposed to "Dangerous Waste") anywhere in
the State of Washington (except at the Hanford landfill which
is not yet constructed). The contaminated soil at the site
has not been classified under the WDOE system. If it is
6-120
-------
Table 6-22
LAWS, REGULATIONS, AND STANDARDS APPLICABLE TO
ALTERNATIVE 1—NO ACTION
Law or Regulation
FEDERAL
Resource Conservation and Recovery Act (RCRA)
Analysis
This alternative would not be consistent with the RCRA closure
performance standard and the corrective action standard.
USEPA Groundwater Protection Strategy (GWPS)
CTl
I
This site is located over a Class II groundwater aquifer
according to the USEPA GWPS Groundwater Protection Strategy.
The GWPS states: "As a general rule, Class II aquifers will
receive levels of protection consistent with those now pro-
vided for groundwater under EPA's existing statutes....
Cleanup of contamination will usually be to background levels
or drinking water statndards but alternative procedures may be
applied for potential sources drinking water.... In these
cases the contamination may be managed in order to avoid
migration into a current source of drinking water or to avoid
widespread damage."
STATE
WDOE Final Cleanup Policy
Washington State Dangerous Waste Regulations (WAC 173-303)
WDOE's cleanup policy allows the required level of cleanup to
be defined on a site-specific basis according to established
guidelines. The WDOE would decide if this example alternative
complies with the policy.
WAC 173-303-050 provides authority to the WDOE to conduct
cleanups of dangerous waste where there is a potential for
discharge or release. Under this authority, the WDOE may
choose to agree or disagree that the no action alternative is
acceptable.
REGIONAL
PSAPCA Regulations
PSAPCA regulations would not apply if no action were taken at
the site.
LOCAL
Land Use Approval
The City of Kent and/or the Seattle-King County Health Depart-
ment may determine that future use of the site should be re-
stricted based on hazardous conditions that may continue to be
present under this alternative.
Note: See Appendix B for a discussion of some of the laws and regulations cited in this table.
-------
Table 6-23
LAWS, REGULATIONS, STANDARDS APPLICABLE TO ALTERNATIVE 2
SURFACE CAP/GROUNDWATER PUMP AND TREAT
Law or Regulation
FEDERAL
Analysis
Resource Conservation and Recovery Act (RCRA)
EPA Groundwater Protection Strategy
I
!-•
NJ
Department of Transportation (DOT)
Clean Air Act (CAA)
Floodplains and Wetlands
Relocation Assistance and Property Aquisition
Protection of Threatened and Endangered Species
Under the closure performance standard of RCRA, capping hazard-
ous waste in place is acceptable. The capped facility must be
fully maintained during the post-closure period (normally up to
30 years). Under the groundwater protection standard of RCRA,
pumping and treatment is an acceptable means to meet the correc-
tive action standard.
This site is located over a Class II groundwater according to
the USEPA Groundwater Protection Strategy. The GWPS states:
"As a general rule, Class II aquifers will receive levels of
protection consistent with those now provided for groundwater
under EPA's existing statutes.... Cleanup of contamination will
usually be to background levels or drinking water standards but
alternative procedures may be applied for potential sources of
drinking water.... In these cases the contamination may be
managed in order to avoid migration into a current source of
drinking water or to avoid widespread damage."
DOT regulations under 49 CFR 172 regulate all interstate ship-
ments of hazardous materials. This alternative may involve
transport of sludge generated by the groundwater treatment
facility. These materials must be transported according to
DOT regulations.
Air stripping equipment used for groundwater treatment would
be considered a source of air emissions and would therefore be
regulated by the CAA.
Portions of Mill Creek and
south are designated flood
has been changed since the
east and south ditches may
analysis of the impacts of
be done consistent with 40
drainage ditches to the east and
hazard areas. The eastern drainage
flood study was completed, and the
no longer be flood hazard areas. An
all construction in these areas will
CFR Part 6, Appendix A.
This regulation requires payment of just compensation to
property owners whose property is purchased by federal
agencies. This alternative could involve such a purchase.
This regulation requires that agencies request information on
endangered species in any area affected by a proposed action.
This alternative would require requesting such information
although endangered species are not expected to be present in
the area.
Note:
See Appendix B for a discussion of some of the laws and regulations
cited in this table.
-------
Table 6-23 (continued)
LAWS, REGULATIONS, STANDARDS APPLICABLE TO ALTERNATIVE 2
Law or Regulation
Analysis
STATE
WDOE Final Cleanup Policy
Washington State Dangerous Waste Regulations (WAC 173-303)
National Pollutant Discharge Elimination System (NPDES)
Permit (State Administered Program)
NJ
OJ
Washington Industrial Safety and Health Act
Flood Control Zone Permit
WDOE's cleanup policy allows the required level of cleanup to
be defined on a site-specific basis according to established
guidelines. The WDOE will decide if the cleanup achieved by
this example alternative complies with the policy.
WAC 173-303-050 provides authority to the WDOE to conduct
cleanups of dangerous waste where there is a potential for
discharge or release. Under this authority, the WDOE may
choose to agree or disagree that this alternative is
acceptable.
Although not currently proposed, the discharge of treated
groundwater into Mill Creek would require compliance with the
NPDES Water Quality Standards. The applicable standards are
those listed in the Federal Register, November 28, 1980, for
pollutants. Standards for pollutants not found in the Federal
Register would be developed by WDOE. NPDES permit standards
would have to be met for the discharge of stormwater from
capped areas.
This example alternative would require compliance with
Chapters 296-62 and 262-24 WAC, which regulate the work envi-
ronment and require a site safety plan, hazard evaluation,
worker training programs, protective equipment for workers,
and emergency equipment.
Portions of Mill Creek and drainage ditches to the east and
south are designated flood hazard areas. These standards
could apply to construction in these areas. See also Flood-
plains and Wetlands (under Federal above) for potential
changes in the designated flood hazard areas.
REGIONAL
Metro Regulations (Industrial Waste Discharge)
Puget Sound Air Pollution Control Agency (PSAPCA)
The discharge of treated groundwater to the Metro system would
require compliance with industrial waste discharge regulations
regarding quantities discharged and prohibited and restricted
substances.
Air stripping equipment for groundwater treatment is a regu-
lated source of air emissions and may require a Notice of
Construction to PSAPCA. PSAPCA will determine whether emis-
sions from the equipment or from other sources such as dust
are violating PSAPCA regulations. PSAPCA regulations in-
corporate state and federal regulations and PSAPCA is re-
sponsible for enforcing the types of air emissions standards
that apply to this site.
-------
Table 6-23 (continued)
LAWS, REGULATIONS, STANDARDS APPLICABLE TO ALTERNATIVE 2
Law or Regulation
LOCAL
Land Use Approval
Sewer Use Permit (City of Kent)
Construction Permits
I
l->
KJ
Stormwater Ordinance No. 2130
Analysis
This example alternative may require a special use permit for
construction of the surface cap and groundwater treatment
facility.
The discharge of treated groundwater into the Kent city sewer
system (which then enters the Metro sewer system) may require
a Kent sewer use permit. This permit is based on the sewer's
capacity to handle the system's discharge. Under the existing
Metro discharge permit, the maximum allowable discharge is
140,000 gpd.
Building construction may require the following permits.
o Building
o Grade and fill
o Street use and street cut
o Plumbing
o Mechanical
This ordinance requires that Stormwater detention facilities
be provided to handle stormwater volumes generated during a
25-year storm, and discharge from the site is to be limited to
the predevelopment release rate during a 10-year storm. The
stormwater control system would be designed to meet this
standard.
-------
Table 6-24
LAWS, REGULATIONS, STANDARDS APPLICABLE TO ALTERNATIVE 3
EXCAVATION WITH ONSITE DISPOSAL, GROUNDWATER PUMP AND TREAT, AND SURFACE CAP
Law or Regulation
FEDERAL
Resource Conservation and Recovery Act (RCRA)
EPA Groundwater Protection Strategy (GWPS)
to
Ui
Department of Transportation (DOT)
Clean Air Act (CAA)
Floodplains and Wetlands
Relocation Assistance and Property Acquisition
Protection of Threatened and Endangered Species
Analysis
Under the requirements of RCRA, a landfill such as that proposed
(double liner, leachate collection, properly closed and main-
tained) would be acceptable. The leachate from such a. landfill
would be considered hazardous waste and would be fully subject to
RCRA. Under the groundwater protection standard of RCRA, pumping
and treatment is an acceptable means to meet the corrective action
standard.
This site is located over Class II groundwater according to the
USEPA GWPS. The GWPS states: "As a general rule. Class II aqui-
fers will receive levels of protection consistent with those now
provided for groundwater under EPA's existing statutes.... Cleanup
of contamination will usually be to background levels or drinking
water standards but alternative procedures may be applied for
potential sources of drinking water.... In these cases the contam-
ination may be managed in order to avoid migration into a current
source of drinking water or to avoid widespread damage."
DOT regulations under 49 CFR 172 regulate all interstate shipments
of hazardous materials. This alternative may involve transport of
sludge generated by the groundwater treatment facility. These
materials must be transported according to DOT regulations.
Air stripping equipment used for groundwater treatment would be
considered a source of air emissions and would therefore be
regulated by the CAA.
See Alternative 2
This regulation requires payment of just compensation to property
owners whose property is purchased by federal agencies. This
alternative may involve such a purchase.
This regulation requires that agencies request information on
endangered species in any area affected by a proposed action.
This alternative would require requesting such information,
although it is not expected that endangered species are present in
the area.
Note: See Appendix B for a discussion of some of the laws and regulations cited in this table.
-------
Table 6-24 (continued)
LAWS, REGULATIONS, STANDARDS APPLICABLE TO ALTERNATIVE 3
Law or Regulation Analysis
STATE
WDOE Final Cleanup Policy
Washington State Dangerous Waste Regulations
(WAC 173-303)
National Pollutant Discharge Elimination System (NPDES)
Permit
Washington Industrial Safety and Health Act
Flood Control Zone Permit
REGIONAL
Metro Regulations (Industrial Waste Discharge)
Puget Sound Air Pollution Control Agency (PSAPCA)
Regulations
WDOE's cleanup policy allows the required level of cleanup to be
defined on a site-specific basis according to established guide-
lines. The WDOE will decide if the cleanup achieved by this
example alternative complies with the policy.
The WDOE prohibits the land disposal of "extremely hazardous
waste" (EHW) anywhere in the state except at the Hanford landfill,
which is not yet constructed. The classification of the wastes at
the site has not been determined and it may be possible to dispose
of "Dangerous Waste" (DW) in a landfill at the site. If the
leachate from the landfill or sludge from the treatment plant were
classified as EHW, it would face the same disposal restrictions.
If the sludge or leachate were dangerous waste of any type (DW or
EHW), it would be fully regulated.
Although not currently proposed, the discharge of treated ground-
water into Mill Creek would require compliance with the NPDES
water quality standards. The applicable standards are those
listed in the Federal Register, November 28, 1980, for 64 toxic
pollutants. Standards for pollutants not found in the Federal
Register would be developed by WSDOE. NPDES standards would also
have to be met for the discharge of stormwater from capped areas.
This example alternative would require compliance with Chap-
ters 296-62 and 296-24 WAC, which regulate the work environment and
require a site safety plan, hazard evaluation, worker training
programs, use of protective equipment by workers, and emergency
equipment on site.
See Alternative 2.
The discharge of treated groundwater to the Metro system would
require compliance with industrial waste discharge regulations
regarding quantities discharged and prohibited and restricted
substances.
Air stripping equipment for groundwater treatment is a regulated
source of air emissions and may require a Notice of Construction
to PSAPCA. PSAPCA will determine whether emissions from the
equipment or from other sources such as dust are occurring in vio-
lation of PSAPCA regulations. PSAPCA regulations incorporate
state and federal regulations and PSAPCA is responsible for en-
forcing the types of air emissions standards that apply to this
site.
-------
Table 6-24 (continued)
LAWS, REGULATIONS, STANDARDS APPLICABLE TO ALTERNATIVE 3
Law or Regulation
Seattle King County Department of Public Health
Analysis
LOCAL
Land Use Approvals
Sewer Use Permit (City of Kent)
Construction Permits
Stormwater Ordinance No. 2130
This agency regulates the construction of landfills for solid
waste not classified under the WDOE Dangerous Waste Regulations.
The regulations of this agency would apply to this alternative if
the facility is considered a landfill and if the material depos-
ited into the landfill is not considered DW or EHW. However, the
material is expected to be classified as DW or EHW.
This example alternative may require a special use permit for the
construction of a landfill and groundwater treatment facility.
The discharge of treated groundwater into the Kent city sewer
system (which then enters the Metro system) may require a Kent
sewer use permit. This permit is based on the system's capacity
to handle the discharge. Under the existing Metro discharge per-
mit, the allowable discharge into the system is 140,000 gpd.
Building construction may require the following permits:
o Building
o Grade and fill
o Street use and street cut
o Plumbing
o Mechanical
This ordinance requires that stormwater detention facilities be
provided to handle stormwater volumes generated during a 25-year
storm, and discharge from the site is to be limited to the pre-
development release rate during a 10-year storm. The stormwater
control system would be designed to meet this standard.
-------
classified as "dangerous waste," it may be possible to dis-
pose of it in an onsite landfill.
6.4.3.4 Example Alternative 4—PRP Remedial Action
Table 6-25 shows how laws, regulations, and policies apply
to Example Alternative 4. in general, the table shows that
this alternative may be consistent with RCRA and WDOE Dan-
gerous Waste Regulations, which allow contaminant removal by
soil excavation and groundwater extraction.
This example alternative would involve removing large quan-
tities of contaminated soil from the property. Transport of
the contaminated soil would be subject to the Department of
Transportation regulations (interstate transport), WDOE reg-
ulations (intrastate transport), and the generator and
transporter standards under RCRA.
Example Alternative 5—Excavation with Offsite Dis-
Table 6-26 shows the relationship between this example
alternative and governmental laws, regulations, and poli-
cies. In general, the table shows that this alternative may
be consistent with RCRA, which allows removal of wastes,
contaminated soils, and groundwater to background or de
minimus levels. The WDOE Dangerous Waste Regulations would
also allow contaminant removal for offsite disposal.
This example alternative also involves removing large quan-
tities of contaminated soil from the site. Transport of the
contaminated soil may be subject to the Department of Trans-
portation regulations (interstate transport), WDOE regula-
tions (intrastate transport), and the generator and trans-
porter standards under RCRA.
6.4.3.6 Example Alternative 6—Mill Creek No Action
Table 6-27 shows the laws, regulations, and policies that
apply to Example Alternative 6.
The dangerous waste regulations (WAC 173-303-050) provide
authority to the WDOE to conduct cleanups of dangerous waste
where there is a potential for discharge or release. Based
on this authority and the guidance provided on cleanup lev-
els in the WDOE cleanup policy, the WDOE would determine
whether the no action alternative is acceptable.
The City of Kent has been evaluating stormwater drainage
control measures that can be taken to reduce flooding in the
Section provided by PRP's.
6-128
-------
Table 6-25
LAWS, REGULATIONS, STANDARDS APPLICABLE TO ALTERNATIVE 4
THE PRP ALTERNATIVE: EXCAVATION WITH OFFSITE DISPOSAL, DIVERSION WALL,
GROUNDWATER PUMP AND TREAT, AND SURFACE CAP
Law or Regulation
FEDERAL
Resource Conservation and Recovery Act (RCRA)
USEPA Groundwater Protection Strategy
Department of Transportation (DOT)
Clean Air Act (CAA)
Floodplains and Wetlands
Relocation Assistance and Property Aquisition
Protection of Threatened and Endangered Species
Analysis
RCRA standards related to corrective action under the groundwater
protection standards, hazardous waste generation and transportation
standards, and closure standards may apply to this example alterna-
tive. The excavation, groundwater extraction and treatment, surface
cover, and groundwater monitoring components of this alternative
may be consistent with these standards.
This site is located over a Class II aquifer according to USEPA
Groundwater Protection Strategy. The GWPS states: "As a general
rule. Class II aquifers will receive levels of protection consis-
tent with those now provided for groundwater under EPA'6 existing
statutes.... Cleanup of contamination will usually be to background
levels or drinking water standards but alternative procedures may
be applied for potential sources of drinking water.... In these
cases the contamination may be managed in order to avoid migration
into a current source of drinking water or to avoid widespread
damage."
DOT regulations under 49 CFR 172 regulate all interstate shipments
of hazardous materials. This example alternative would require
shipment of contaminated soils to an offsite disposal site. These
materials must be transported according to DOT regulations.
Air stripping equipment used for groundwater treatment would be
considered a source of air emissions and would therefore be
regulated under the CAA.
See Alternative 2.
No relocation or property purchase is required by this
alternative.
This regulation requires that agencies request information on en-
dangered species in any area affected by a proposed action. This
alternative would require requesting such information, although it
is not expected that endangered species are present in the area.
Notes: See Appendix B for a discussion of some of the laws and regulations cited in this table.
This table was prepared by the PRP's.
-------
Table 6-25 (continued)
LAWS, REGULATIONS, STANDARDS APPLICABLE TO ALTERNATIVE 4
Law or Regulation
STATE
WDOE Final Cleanup Policy
Washington State Dangerous Waste Regulations
(WAC 173-303)
National Pollutant Discharge Elimination System (NPDES)
Permit (State Administered Program)
Washington Industrial Safety and Health Act
Flood Control Zone Permit
Coastal Zone Management Act (CZH)
REGIONAL
Metro Regulations (Industrial Waste Discharge)
Analysis
WDOE'e cleanup policy allows the required level of cleanup to be
defined on a site-specific basis according to established guide-
lines. The excavation and groundwater extraction and treatment
components of this example alternative are consistent with cleanup
measures contemplated by the policy. The WDOE will decide if the
cleanup achieved by this example alternative complies with the
policy guidelines.
The Dangerous Waste Regulations would allow excavation and offsite
disposal of wastes.
The discharge of treated water into the Green River, if this option
is selected, would require compliance with the NPDES water quality
standards. The applicable standards are those printed in the Fed-
eral Register November 28, 1980, for 64 toxic pollutants. Stan-
dards for those pollutants not listed in the Federal Register would
be developed by WDOE. An NPDES permit may also be required for the
discharge of stormwater from capped areas.
This example alternative would require compliance with Chap-
ters 296-62 and 296-24 WAC, which regulate the work environment
and require a site safety plan, hazard evaluation, worker training
programs, use of protective equipment by workers, and emergency
equipment on site.
See Alternative 2.
This regulation applies to construction within shorelines desig-
nated under the CZM as shorelines of statewide significance. Con-
struction of an outfall to the Green River would require a shore-
line substantial development permit to be issued by King County or
the City of Kent, depending on where the outfall was located.
If the option of discharging treated groundwater to the Metro
system were selected, compliance would be required with industrial
waste discharge regulations regarding quantities discharged and
prohibited and restricted substances.
-------
Table 6-25 (continued)
LAWS, REGULATIONS, STANDARDS APPLICABLE TO ALTERNATIVE 4
Law or Regulation
Puget Sound Air Pollution Control Agency (PSAPCA) Regulations
Analysis
PSAPCA will determine whether emissions from the equipment or
from other sources such as dust are occurring in violation of
PSAPCA regulations. PSAPCA regulations incorporate state and
federal regulations and PSAPCA is responsible for enforcing the
state and federal emissions standards that apply to this site.
Air stripping equipment for groundwater treatment is a
regulated source of air emissions and would require a Notice
of Construction to PSAPCA.
I
(-•
U)
LOCAL
Land Use Approval
Sewer Use Permit (City of Kent)
Construction Permits
Stormwater Ordinance No. 2130
This example alternative may require a special use permit for
construction of the surface cap and, if constructed, the
groundwater treatment facility.
If the treated groundwater is discharged into the Kent city sewer
system (which then enters the Metro system) a Kent sewer use per-
mit would be required. This permit is based on the system's
capacity to handle the discharge. Under the existing Metro dis-
charge permit, the maximum allowable discharge into the system
is 140,000 gpd.
Building construction may require the following permits:
o Building
o Grade and fill
o Street use and street cut
o Plumbing
o Mechanical
This ordinance requires that stormwater detention facilities be
provided to handle stormwater volumes generated during a 25-year
storm, and discharge from the site is to be limited to the pre-
development release rate during a 10-year storm. The stormwater
management system included in this example alternative would
comply with the ordinance.
-------
Table 6-26
LAWS, REGULATIONS, STANDARDS APPLICABLE TO ALTERNATIVE 5
15-FOOT-DEEP EXCAVATION
Law or Regulation
FEDERAL
Analysis
Resource Conservation and Recovery Act (RCRA)
EPA Groundwater Protection Strategy
U)
NJ
Department of Transportation (DOT)
Clean Air Act (CAA)
Floodplains and Wetlands
Relocation Assistance and Property Aquisition
Protection of Threatened and Endangered Species
Under RCRA, removal of wastes, contaminated soils, and groundwater
to background or
-------
Table 6-26 (continued)
LAWS, REGULATIONS, AND STANDARDS APPLICABLE TO ALTERNATIVE 5
Law or Regulation
Analysis
U)
OJ
STATE
WDOE Final Cleanup Policy
Washington State Dangerous Waste Regulations
(WAC 173-303)
National Pollutant Discharge Elimination System (NPDES)
Permit (State Administered Program)
Washington Industrial Safety and Health Act
Flood Control Zone Permit
REGIONAL
Metro Regulations (Industrial Waste Discharge)
Puget Sound Air Pollution Control Agency (PSAPCA) Regulations
WDOE's cleanup policy allows the required level of cleanup to be
defined on a site-specific basis according to established guide-
lines. The WDOE will decide if the cleanup achieved by this example
alternative complies with this policy.
The Dangerous Waste Regulations would allow excavation and offsite
disposal of wastes.
Although not currently proposed, the discharge of treated ground-
water into Mill Creek would require compliance with the NPDES water
quality standards. The applicable standards are those printed in
the Federal Register, November 26, 1980, for 64 toxic pollutants.
Standards for those pollutants not listed in the Federal Register
would be developed by WDOE.
This example alternative would require compliance with Chap-
ters 296-62 and 296-24 WAC, which regulate the work environment and
require a site safety plan, hazard evaluation, worker training pro-
grams, use of protective equipment by workers, and emergency equip-
ment on site.
See Alternative 2.
The discharge of treated groundwater to the Metro system would re-
quire compliance with industrial waste discharge regulations regard-
ing quantities discharged and prohibited and restricted substances.
PSAPCA will determine whether emissions from the equipment or from
other sources such as dust are occurring in violation of PSAPCA re-
gulations. PSAPCA regulations incorporate state and federal
regulations, and PSAPCA is responsible for enforcing the state and
federal emissions standards that apply to this site. Air stripping
equipment for groundwater treatment is a regulated source of air
emissions and would require a Notice of Construction to PSAPCA.
-------
Table 6-26 (continued)
LAWS, REGULATIONS, AND STANDARDS APPLICABLE TO ALTERNATIVE 5
Law or Regulation
Analysis
LOCAL
Land Use Approval
Sewer Use Permit (City of Kent)
Construction Permits
Stormwater Ordinance No. 2130
This example alternative may require a special use permit for the
groundwater treatment facility.
The discharge of treated groundwater into the Kent city sewer
system (which then enters the Metro system) would require a Kent
sewer use permit. This permit is based on the system's capacity to
handle the discharge. Under the existing Metro discharge permit,
the maximum allowable discharge into the system is 140,000 gpd.
Building construction may require the following permits:
o Building
o Grade and fill
o Street use and street cut
o Plumbing
o Mechanical
This ordinance requires that stormwater detention facilities be
provided to handle stormwater volumes generated during a 25-year
storm, and discharge from the site is to be limited to the prede-
velopment release rate during a 10 year storm. The stormwater
control system would be designed to meet this standard.
-------
Table 6-27
LAWS, REGULATIONS, AND STANDARDS APPLICABLE TO ALTERNATIVE 6—MILL CREEK/NO ACTION
Law or Regulation
Analysis
-------
valley. A drainage master plan will be adopted in spring
1985, and at this time it is not known how Example Alterna-
tive 6 would be affected by this plan.
6.4.3.7 Example Alternative 7—Mill Creek Sediment Removal
Table 6-28 shows the relationship between this example al-
ternative and governmental laws, regulations, and policies.
There are three agencies that issue permits or administer
standards for actions such as those proposed for Mill Creek
under this alternative: the U.S. Army Corps of Engineers
(COE), the Washington State Department of Fisheries (WSDOF),
and the Washington State Department of Game (WSDOG). The
COE issues permits for structures in or affecting navigable
waters (Section 10 permit) and for dredging and filling of
water bodies or wetlands (Section 404 permit). Mill Creek
is not considered to be a navigable waterway by the COE and
therefore work in the creek would not require a Section 10
permit. The proposed diversion of Mill Creek and excavation
and filling of the channel may require evaluation under Sec-
tion 404. Whether the proposed action requires an evaluation
will depend on, among other factors, the methods proposed
for diverting Mill Creek and the COE's interpretation of the
regulations. The COE must be provided with a description of
the work proposed in order to make that determination.
Any work within the ordinary high waterline of a creek such
as Mill Creek could require a hydraulics project approval
(hydraulics permit) from WSDOF and WSDOG. WSDOF and WSDOG
also provide a local Indian tribal organization with a list
of all hydraulics permits that have been granted. This is
done at the request of the Indian organization. The
Muckleshoot Indian Tribe has fishing rights in all streams
such as Mill Creek that are tributary to the Duwammish.
The Washington State Dangerous Waste Regulations (WAC 173-
303-050) authorize the WDOE to conduct cleanups of dangerous
waste where there is a potential for discharge or release.
Under this authority, the WDOE will evaluate whether this
alternative accomplishes the required cleanup.
Transport of the dredged sediments may be subject to state
or federal regulations depending on whether transport is
interstate or intrastate and whether the sediments are
classified as hazardous waste.
Another regulation that could apply to this alternative is
the Fish and Wildlife Coordination Act, which requires that
a federal agency consult with the appropriate state and fed-
eral agencies before modifying any body of water.
6-136
-------
Table 6-28
LAWS, REGULATIONS, AND STANDARDS APPLICABLE TO ALTERNATIVE 7—MILL CREEK SEDIMENT REMOVAL
Law or Regulation
analysis
FEDERAL
Resource Conservation and Recovery Act (RCRA)
USEPA Groundwater Protection Strategy (GWPS)
Department of Transportation (DOT)
Floodplains and Wetlands
U>
-J
The November 1984 RCRA reauthorization considers corrective
actions for areas such as Mill Creek that have been affected
by RCRA regulated facilities.
Mill Creek is located over a Class II groundwater according to
the GWPS. Contaminant concentration limits for Class II
groundwater must be met to satisfy the goals of the strategy.
Mill Creek has been contaminated by groundwater discharge.
DOT regulations under 49 CFR 172 regulate all interstate
shipments of hazardous materials. Sediment dredged from Mill
Creek may be subject to these conditions.
These regulations apply to construction in flood plains or
flood hazard areas. The area adjacent to Mill Creek is
designated as s flood hazard area. However, the regulations
do not state whether they would apply to the type of construc-
tion proposed or whether they apply to temporary facilities
such as proposed under this alternative. These regulations
require an analysis of the impacts of construction in these
areas.
Fish and Wildlife Coordination Act (FWCA)
This act requires consultation with the appropriate state and
federal agencies for projects involving the modification of
water bodies. This alternative would require such consulta-
tion.
Protection of Threatened or Endangered Species
Permits for Discharge of Dredged or Fill Materials into
Waters of the U.S. (Section 404 permit).
This regulation requires that agencies request information on
endangered species in any area affected by a proposed action.
This alternative would require requesting such information,
although it is not expected that endangered species are
present in the area.
The Corps of Engineers will determine whether this approval
will be required based on their review of the proposed action.
Note: See Appendix B for a discussion of some of the laws and regulations cited in this table.
-------
Table 6-28 (continued)
LAWS, REGULATIONS, AND STANDARDS APPLICABLE TO ALTERNATIVE 7—MILL CREEK SEDIMENT REMOVAL
Law or Regulation
STATE
Analysis
to
00
WDOE Final Cleanup Policy
Washington State Dangerous Waste Regulations
(WAC 173-303)
Washington Industrial Safety and Health Act
Flood Control Zone Permit
Hydraulics Permit
WDOE's cleanup policy allows the required level of cleanup to
be defined on a site-specific basis according to established
guidelines. The WDOE will decide if the cleanup achieved by
this example alternative complies with the policy.
WAC 173-303-050 provides authority to the WDOE to conduct
cleanups of dangerous waste where there is a potential for
discharge or release. Under this authority the WDOE may
choose to agree or disagree that Mill Creek needs to be
cleaned up and that this alternative accomplishes the required
level of cleanup.
This example alternative would require compliance with Chap-
ters 296-62 and 296-24 WAC which regulate the work place
environment and require a site safety plan, hazard evaluation,
worker training programs, protective equipment for workers and
emergency equipment.
This regulation applies to construction in designated flood
control zones. There is a designated flood hazard area
adjacent to Mill Creek. These regulations may apply to
construction in this area.
A hydraulics permit is required for work within the ordinary
high water line of a creek such as Mill Creek.
REGIONAL
PSAPCA Regulations
Not applicable. This alternative is not expected to generate
air emissions from stationary sources.
LOCAL
Construction Permits
Storm Water Ordinance No. 2130
City of Kent
Drainage Master Plan
Construction of the Mill Creek diversion and transport of
excavated materials may require a grade and fill permit and
street use/street cut permit.
This ordinance requires submission of a stormwater discharge
plan when any grading permit is applied for.
The plan has not been adopted.
would affect this alternative.
It ie not known how this plan
-------
The City of Kent's drainage master plan will be adopted in
spring 1985. At this time, it is not known how Example
Alternative 7 would be affected by this plan.
6.4.5 COST ESTIMATES
The NCP requires that comparative cost estimates be devel-
oped for remedial action alternatives. The estimates pre-
sented in this section encompass the total scope of each
remedial action described in the previous sections of this
chapter. They include all currently identified direct and
indirect costs associated with each component of each example
alternative. Changes in the components, knowledge of site
conditions, work scope, disposal facility siting, and/or
cleanup criteria for an alternative will affect the estimated
costs.
The cost estimates for the example alternatives were develop-
ed using unit costs derived from previous experience on other
hazardous waste management projects, from quotations of
industry sources for specialized items, and from cost infor-
mation contained in the Compendium of Cost of Remedial Tech-
nologies of Hazardous Waste Sites. Tables 6-29 through
6-33 present the cost estimates for Example Alternatives 2,
3, 4, 5, and 7 (all except the two no action alternatives).
The cost estimates presented have an accuracy range of
+50 percent to -30 percent.
6.4.4.1 Cost Estimating Approach
The total cost of a remedial action includes all the capital
and operating costs known to be associated with that example
alternative. Capital costs include costs for equipment,
site development, and buildings, and percent additions to
cover contractor overheads; health, safety, and decontamina-
tion; engineering and legal services; and contingencies.
Operation and maintenance costs include costs for labor,
laboratory analyses, energy, chemicals for groundwater treat-
ment, and sludge transportation and disposal. Direct costs
such as soil removal, personnel protection, onsite construc-
tion, transport, storage, and treatment and disposal costs
are included. Indirect costs are also a major part of a
remedial action cost and include items such as decontami-
nation stations, perimeter fencing, traffic control, addi-
tional soil testing, rebuilding local roads, public relations,
groundwater monitoring, and pilot testing costs.
Because this feasibility study is conceptual, a contingency
allowance has also been included. This allowance includes a
limited amount for normal process refinement, unknown site
conditions, engineering, administrative costs, and other
contingencies. Allowances for inflation, additional material
6-139
-------
Table 6-29
COST ESTIMATE FOR EXAMPLE ALTERNATIVE 2
(in thousands of dollars)
CAPITAL COSTS:
Elements Costs
Groundwater Pumping System $330
Surface Cap 3,628
Groundwater Treatment Facility 1,832
Decontamination Facility 24
Buffer Zone 89
Monitoring Wells 66
Subtotal $5,969
Contractor Mobilization(5%) 298
Contractor Bond and Insurance(3%) 188
Health, Safety, and Decontamination(15%) 895
Subtotal $7,351
Contingency(30%) 2,205
Subtotal $9,556
Engineering and Legal(20%) 1,911
Sales Tax(8.1%) 774
TOTAL CAPITAL COST $12,200
OPERATION AND MAINTENANCE COSTS(Year One): $ per year
Monitoring $540
Labor 350
Power 31
Chemicals 687
Sludge disposal 118
Maintenance 24
Sewer service charge 150
TOTAL O&M COST $1,900
6-140
-------
Table 6-29
(continued)
Example Alternative 2
PRESENT WORTH ANALYSIS:
Year Plant Cost Annual
1985 $12,
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
rOTALS
241
$1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1
•*- f
1,
1.
1,
O&M Replacements Total
900
872
870
869
869
869
869
869
869
869
869
869
869
869
869
869
869
869
869
869
869
869
869
869
869
869
869
869
869
869
$12,
1,
1.
1,
1,
1,
1.
1,
1,
1.
1,
1,
1,
1,
1,
1,153 3,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
$69.
241
900
872
870
869
869
869
869
869
869
869
869
869
869
869
022
869
869
869
869
869
869
869
869
869
869
869
869
869
869
869
500
Present
Worth
$12.241
1,727
1,547
1,405
1,277
1,161
1,055
959
872
793
721
655
596
541
492
723
407
370
336
306
278
253
230
209
190
173
157
143
130
lib
107
$30,200
6-141
-------
Table 6-30
COST ESTIMATE FOR EXAMPLE ALTERNATIVE 3
(in thousands of dollars)
CAPITAL COSTS:
Elements Costs
Groundwater Pumping System $204
Surface Cap 3,628
Groundwater Treatment 1,664
Excavation 1,108
Landfill 1,851
Decontamination Facility 302
Buffer Zone 89
Monitoring Wells 66
Subtotal $8,912
Contractor Mobilization(5%) 446
Contractor Bond and Insurance(3%) 281
Health, Safety, and Decontamination(15%) 1,337
Subtotal $10,975
Contingency(30%) 3,293
Subtotal $14,268
Engineering and Legal(20%) 2,854
Sales Tax(8.1%) 1,156
TOTAL CAPITAL COST $18,300
ANNUAL OPERATION AND MAINTENANCE COSTS:
Elements Costs
Monitoring $540
Labor 320
Power 26
Chemicals 585
Sludge disposal 101
Maintenance 22
Sewer service charge 128
TOTAL O&M COST(First Year) $1,722
Note that O&M costs decrease during the initial years
of operation.
6-142
-------
Example Alternative 3
PRESENT WORTH ANALYSIS:
Table 6-30
(continued)
Year
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2005
2007
2008
2009
2010
2011
2012
2013
2014
2015
Plant Cost Annual O&M Replacements
$5,006
5,424
5,846
6,269
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694 1,038
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
Total
$5,424
5,424
5,846
6,269
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
2,732
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
1,694
Present
Worth
$5,424
4,931
4,831
4, 710
1, 157
1,052
956
869
790
718
653
594
540
491
446
654
369
335
305
277
252
229
208
189
172
156
142
129
117
107
97
TOTALS
$69.700
$31,900
6-143
-------
Table 6-31
COST ESTIMATE FOR EXAMPLE ALTERNATIVE 4
(in thousands of dollars)
CAPITAL COSTS:
Elements
Diversion barrier
Ground-.vater pumping system
Treatment facility
Excavation with offsite disposal
Infiltration System
Fill
Asphaltic concrete pavement(cap)
Decontamination Facility
Buffer Zone
Monitoring wells
Subtotal
Contractor Mobilization(5%)
Contractor Bond and Insurance(3%)
Healt^, Safety, and Decontamination(15'
Subtotal
Contingency(30%)
Subtotal
Engineering and Legal(20%)
Sales Tax(8.1%)
TOTAL CAPITAL COST
Costs
$986
202
1,832
17,558
50
490
582
302
89
66
$22,157
1,108
698
3,324
$27,286
8,186
$35,472
7,094
2,873
$45,400
ANNUAL OPERATION AND MAINTENANCE COSTS:
Elements
Monitoring
Labor
Power
Chemicals
Sludge disposal
Maintenance
Sewer service charge
TOTAL O&M CGGT
Costs
$540
350
31
663
142
24
150
$1,900
Note: These estimates were prepared using EPA cost bases
and do not reflect the PRP cost assumptions.
6-144
-------
Example Alternative 4 Table 6-31
(continued)
PRESENT WORTH ANALYSIS:
Year Plant Cost Annual O&M Replacements
1985 $22,135 $0
1986 22,130 0
1987 1,900
1988 1,900
1989 1,900
1990 1,135 1,900
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
Total
$22, 130
22, 130
1,900
1,900
1,900
3,035
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Present
Worth
$22,130
20, 118
1,570
1,427
1,298
1,884
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
TOTALS $53,000 $48,400
6-145
-------
Table 6-32
COST ESTIMATE FOR EXAMPLE ALTERNATIVE 5
(in thousands of dollars)
CAPITAL COSTS:
Elements
Dewatering system
Groundwater treatment facility
Excavation with offsite disposal
Fill
Decontamination facility
Buffer zone
Monitoring wells
Subtotal
Contractor Mobilization(5%)
Contractor Bond and Insurance(3%)
Health, Safety, and Decontamination(15%)
Subtotal
Contingency(30%)
Subtotal
Engineering and Legal(20%)
Sales Tax(8.1%)
TOTAL CAPITAL COST
Costs
$204
1,832
83,164
2,272
302
89
66
$87,929
4,396
2, 770
13,189
$108,285
32,485
$140,770
28,154
11,402
$180,300
ANNUAL OPERATION AND MAINTENANCE COSTS;
Elements
Monitoring
Labor
Power
Chemicals
Sludge disposal
Maintenance
Sewer service charge
TOTAL O&M COST(First Year)
Costs
$540
350
31
663
142
24
150
$1,900
Note that 0 & K costs decrease during the years of operation.
6-146
-------
Example Alternative 5
PRESENT WORTH ANALYSIS:
Table 6-32
(continued)
Year Plant Cost Annual O&M Replace
1985 $46,975
1986 46,975
1987 46,975
1988 46,975
1989 100
1990 100
1991 100
1992 100
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
jments Total
$46,975
46,975
46,975
46,975
100
100
100
100
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Present
Worth
$46,975
42,705
38,822
35,293
68
62
56
51
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
TOTALS
$188,300
$164,000
6-147
-------
Table 6-33
COST ESTIMATE FOR EXAMPLE ALTERNATIVE 7
(in thousands of dollars)
CAPITAL COSTS:
Elements Costs
Temporary Diversion $108
Excavate and Dispose of Sediments 480
Bank and Bed Restoration 50
Subtotal $638
Contractor Mobilization(5%) 32
Contractor Bond and Insurance(3%) 19
Health, Safety, and Decontamination(15%) 96
Subtotal $785
Contingency(30%) 235
Subtotal $1,020
Engineering and Legal(20%) 204
Sales Tax(8.1%) 83
TOTAL CAPITAL COST $1,300
ANNUAL OPERATION AND MAINTENANCE COSTS:
This example alternative does not require operation and
maintenance.
PRESENT WORTH ANALYSIS:
This example alternative has costs for only one month thus
present worth analysis is not applicable.
6-148
-------
volume, and abnormal technical difficulties are not accounted
for in the contingency.
6.4.4.2 General Assumptions
General assumptions made in estimating costs were as follows:
1. Costs are for the Seattle area, first quarter 1985.
2. A minimum of Level C personnel protection would be re-
quired for all onsite activities associated with con-
taminated soil handling or processing, with the exception
of vehicle operators working entirely in enclosed vehicle
cabs. These workers would be required to use a minimum
of Level D protection gear. The use of Levels C and D
personnel protective gear can reduce worker efficiency,
shorten summer work periods, and have other health and
safety requirements. For Level C, these effects have
been reported to increase labor costs by at least three
times over standard conditions. Decontamination trail-
ers, truck wash stations, and site safety officers would
also have to be present for all onsite activities.
3. Stringent dust control would be required for any alter-
native that involves significant soil disruption.
4. A program for monitoring airborne particulates and or-
ganics would be operated through all phases of exca-
vation. The program is anticipated to include the use
of perimeter air samplers, onsite air samplers, and one
onsite meterological station.
5. Onsite security would be provided during all construc-
tion, excavation, stabilization, and treatment activi-
ties .
6. Yearly maintenance of a RCRA cap would consist pri-
marily of inspections and mowing and other maintenance
of the seeded cover. In addition, portions of the RCRA
cover would be regraded at 3- to 5-year intervals to
account for subsidence of the cover. Significant re-
grading may be required the year after capping is
completed. Imported soils would be used for regrading.
7. Present worth calculations were performed using a 10
percent interest rate.
8. Operating costs were calculated based on the provisions
of each example alternative.
9. Where imported fill materials are needed, they are
assumed to be available locally in sufficient
quantities.
6-149
-------
10. Process, mechanical, and electrical equipment has been
assigned a 15-year life. Salvage values were calcula-
ted using straight-line depreciation.
11. No land costs were included in the calculations.
6.4.4.3 Specific Assumptions for Example Alternatives
EXAMPLE ALTERNATIVE 1
No cost estimate was prepared for the no action alternative.
EXAMPLE ALTERNATIVE 2
1. Construction duration would be 8 months to one year.
2. The operating period would be 30 years.
3. For costing purposes, the groundwater monitoring system
was assumed to consist of 10 wells with a total of
500 feet of drilling, sampled quarterly for 30 years.
EXAMPLE ALTERNATIVE 3
1. Construction duration would be 4 years.
2. Treatment plant operations and maintenance costs during
the construction period are considered to be construc-
tion costs.
3. The operating period would be 30 years.
4. Contaminated material excavated from the site would be
eligible for inclusion in the landfill under Washington
State regulations.
5. For costing purposes, the groundwater monitoring system
was assumed to consist of 10 wells with a total of
500 feet of drilling, sampled quarterly for 30 years.
EXAMPLE ALTERNATIVE 4
1. Construction duration would be 2 years.
2. The operating period would be 5 years. Dismantling
and capping activities would occur in the sixth year
following construction.
3. For costing purposes, the groundwater monitoring system
was assumed to consist of 10 wells with a total of
500 feet of drilling, sampled quarterly for 5 years.
6-150
-------
EXAMPLE ALTERNATIVE 5
1. Construction duration is assumed to be 4 years.
2. The dewatering system and plant operations and mainte-
nance costs during the construction period are con-
sidered to be construction costs.
3. A 5-month-per-year, 5-day work week construction season
is assumed for excavation activities.
4. For costing purposes, the groundwater monitoring system
was assumed to consist of 10 wells with a total of
500 feet of drilling, sampled quarterly for 5 years.
EXAMPLE ALTERNATIVE 6
No cost estimate was prepared for the Mill Creek no action
alternative.
EXAMPLE ALTERNATIVE 7
1. Construction duration would be one month.
2. No costs have been included for a temporary easement
for the diversion line.
3. Sediments would be shippable and disposed in a hazard-
ous waste landfill as removed from the creek.
4. No monitoring costs were included.
6.5 SUMMARY
A summary of the conclusions of the technical, environmental/
public health, and cost evaluations of the seven example
alternatives is provided in Table 6-34. Included in this
table, as appropriate, are summary statements related to
other considerations such as the institutional evaluation.
The summary focuses primarily on evaluation results related
to the following factors:
o Prevention of direct human and animal contact with
contaminated materials
o Prevention of contaminated stormwater runoff from
the Western Processing site
o Prevention or minimization of infiltration and
leaching of contaminants from unsaturated zone
soils
6-151
-------
Improvement of groundwater quality in the shallow
aquifer beneath the site
Reduction in contaminant discharge from the site
to Mill Creek via groundwater to a level that
would allow contaminant levels in the creek to
meet ambient quality criteria or background
levels, whichever are higher.
6-152
-------
Example
Alternative
Cost (Millions)
Present
Horth
01
U)
Table 6-34
SUMMARY OP PUBLIC HEALTH, ENVIRONMENTAL,
AND TECHNICAL EVALUATIONS
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" .
Groundwater contamination from
Western Processing would pose
no threat to City of Kent or
any other public water supply
wellfields.
The concentrations of organic
and inorganic (metal) contam-
inants in the groundwater
immediately below Western Pro-
cessing exceed drinking water
standards and Acceptable Daily
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-
stream of Western Processing
exceed chronic and acute am-
bient water quality criteria
for aquatic organisms. These
metal concentrations probably
are and would continue to be
toxic to a wide variety of aqua-
tic organisms 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 them
into the groundwater beneath
the site.
Contaminated groundwater from
Western Processing would con-
tinue to discharge into Mill
Creek at 50 to 70 gpm. 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
Since 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 may be
restricted by local
authorities.
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,
$12.2 $30.2 Would eliminate direct human
and anijnal contact with contam-
inated surface soils in capped
Average areas; however, all soils
annual would remain in place.
opera-
tion & Drinking water standards and
mainten- ADI's for organics in the
ance groundwater under the site
cost/ would be met in less than
$1.87 15 years of pumping; SNARL's*
for longer term use would not
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
Mill Creek waters may delay
achieving ambient water qual-
ity criteria or background.
The pumping system would elim-
inate d-lscharge 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
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.
*Suggested No Adverse Response Level(s).
-------
Example
Alternative
Cost [Millions)
Present
apital Worth
Continued
Public Health
Aspects
Table 6-34
(continued)
Environmental
Aspects
Technical
Aspects
I
h-1
l/l
onsite treatment and
discharge into Metro
system (100 gpn)
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 ll-acref
double-lined, RCRA on-
site landfill.
Multimedia cap over
landfill (Area I),
Area II, and a portion
of Area V (see Example
Alternative 2).
$18.3
Average
annual
O&M
cost:
SI.69
be met until after approxi-
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 cadmium
standard, while the standard
for lead may never be
achieved.
$31.9 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.
Nould eliminate contaminated
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
groundwater to levels that
would not cause continued de-
gradation of Mill Creek after
the pumping system Is turned
off.
Hater 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.
Would be Identical to Example
Alternative 2.
background levels could be met
In Mill Creek after the pumping
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
extremely 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.
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 HDOE Dangerous Haste Regu-
lations. No "Extremely Hazard-
ous Waste" may be landfllled
within Washington State.
Certain excavated materials
such as PCB's, buried drums,
and concentrated wastes would
-------
Table 6-34
(continued)
Example
Alternative
Cost (Millions)
Present
apltal Worth
Public Health
Aspects
Environmental
Aspects
Technical
Aspects
Other
Ul
Ul
Continued
Controlled stormwater
discharged from capped
areas into Mill Creek
Groundwater pumping
around landfill and in
portions of Areas II
and V, onslte treat-
ment, and discharge
into Metro system
(85 gpm)
Monitoring
Health and safety plans
and training prior to
construction.
Would require the same type of
access as In Example
Alternative 2.
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.
require special handing and
possibly disposal procedures.
Future use of the landfill and
capped areas would be
prohibited.
Construction impacts could be
mitigated by good construction
practices, dust and run-off
controls, and scheduling.
-------
Table 6-34
(continued)
Example
Alternative
The PRP Proposal*
Excavate to variable
depths (I1 to 8') in
Area 1
Offsite disposal of all
excavated material
(75,000 cubic yards) in
a double-lined RCRA
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, onsite 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
construction
Cost (Millions)
Present
Worth
$48.9
Public Health
Would eliminate direct human
and animal contact with all
surface soils in Area I.
ADI's, drinking water stan-
dards, and SNARL's for all
except one Indicator organic
would be 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.
Environmental
Aspects
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. Hater quality
problems In the creek not
related to Western Processing
would continue.
Technical
Aspects
Once the diversion barrier is
Installed, the discharge of
contaminated groundwater to
Mill Creek from Area I would
be reduced by approximately
50 percent.
Once pumping starts, the dis-
charge of all contaminated
groundwater from Area I would
be prevented.
The potential for discharge of
contaminated stormwater 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 88 percent of
the zinc contamination in
Area I.
Other
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
described In the other example
alternatives would be one of
the subjects of negotiations.
The groundwater extraction
rate for this alternative is
primarily United 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 ald-1985. The
disposal costs were estimated
to be $100 per ton, but could
vary substantially.
Property would be suitable for
future use.
*Sumraary prepared by PRPs.
-------
Table 6-34
(continued)
en
-o
Example
Alternative
Excavate 15 feet in
Areas I and II, 3 feet
in a portion of Area V
(including the old dis-
charge line), 3 feet in
Area IX, and 1 foot in a
portion of Area VIII.
Offslte disposal of all
excavated material
(300,000 cubic yards)
in a double-lined RCRA
landfill
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.
Cost (Millions)
Present
'an Hal Worth
S180.3
Average
annual
O&H Cost:
SO.l
$164.0
Public Health
Aspects
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
sufficiently to meet the drink-
ing water standard; however,
cadmium will not.
Environmental
Aspects
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
stormwater discharge to ground-
water and Mill Creek.
Water quality problems in Mill
Creek not related to Western
Processing would continue to
limit habitat quality.
Technical
Aspects
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.
20 months of excavation over a
4-year construction period.
Dewatering 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.
Other
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.
No permanent access would be
required.
Construction impacts could be
mitigated by good construction
practices, dust and run-off con-
trols, transportation plans,
and scheduling.
6. Mill Creek No Action
(After implementation of
Example Alternative 2,
3, 4, or 5)
None. Hill Creek sediments do
not pose a threat to human
health.
The Hill 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.
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
uncontaminated.
Modification of Mill Creek
above Western Processing as
part of Kent's drainage master
plan could change the effec-
tiveness of this example al-
ternative, as could the intro-
duction of upstream sources of
contaminants.
-------
Example
Alternative
Cost (Millions)
Present
aoltal Horth
Public Health
Aspects
Table 6-34
(continued)
Environmental
Aspects
Avoids the adverse Impacts of
diversion and excavation.
Technical
Aspects
in
oo
Mill Creek Sediment
Removal (after implemen-
tation of Example Alter-
native 2, 3, 4, or 5)
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-pipe system during
excavation (approxi-
mately one month during
low flow season)
Rehabilitate stream bed
with gravel riffles and
natural vegetation
Monitoring
SI.3
None. Hill 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.
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.
Monitoring of groundwater
quality and flow near the
creek would be necessary to
determine the optimal time to
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.
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.
-------
Chapter 7
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