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EPA/ROD/RIO-90/022
Silver Mountain Mine, WA
Abstract (Continued)
drainage area, and bedrock are metals including arsenic (naturally occurring) and other
inorganics including cyanide. Ground water beneath the site contains relatively high
levels of dissolved anions and cations as well as metals and cyanide associated with the
mine dump material, however, low ground water quality and quantity make it an unlikely
drinking water source and will not be addressed by this remedial action.
The selected remedial action for this site includes consolidating all contaminated soil
and mine dump material with the leach heap, followed by grading and contouring the
consolidated 5,740 cubic yards of contaminated materials; capping the heap and
consolidated materials with a soil/clay cap; plugging the mine entrance and removing a
mine drainage pipe that supplies the animal water supply tank and installing a new well
for an alternate animal water supply; implementing institutional controls including deed
restrictions; and ground water monitoring. The estimated present worth cost for the
remedial action is $635,600, which includes an annual O&M cost of $39,650 for 30 years.
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DECLARATION
for the Silver Mountain Mine
Superfund Site
RECORD OF DECISION
SITE NAME AND LOCATION
Silver Mountain Mine
Okanogan County, Washington
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action
for the Silver Mountain Mine site, developed in accordance with
the Comprehensive Environmental Response, Compensation, and
Liability Act of 1980, as amended by the Superfund Amendments and
Reauthorization Act of 1986, and, to the extent practicable', the
National Contingency Plan. This decision is based on the
Administrative Record for this site. The attached index
identifies the items that comprise the Administrative Record upon
which the selection of remedial action is based.
The State of Washington has verbally concurred on the selected
remedy.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from
this site, if not addressed by implementing the response action
selected in this ROD, may present an imminent and substantial
endangerment to public health, welfare, or the environment.
SELECTED REMEDY DESCRIPTION
This is the first and final Record of Decision, because the
entire site is being handled as a single operable unit. The
Silver Mountain site is an abandoned mine dump where a heap
leaching operation left cyanide and arsenic contamination. The
Washington Department of Ecology stabilized the site in 1985,
treating the immediate threat of cyanide in the leach -heap. The
selected remedy will provide long-term environmental protection
by:
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consolidating and grading approximately 5740 cubic yards
of contaminated materials;
covering the materia-ls with a soil/clay cap";
fencing the site and sealing the entrance to the mine;
disconnecting the mine drainage pipe from the existing
stock tank and installing a new well in the Horse Springs
Coulee aquifer to provide an alternate water supply for
the cattle;
placing a deed restriction to protect the cap; and
monitoring the groundwater to assure that it does not
become contaminated. if groundwater analyses indicate
contamination at a concentration in excess of the U.S.
Environmental Protection Agency health-based levels, a
contingent groundwater treatment program will be
implemented. Notice will be provided to the community of.
the groundwater sampling and results and any potential
contamination.
DECLARATION
The selected remedy is protective of human health and the
environment, complies with federal and state requirements that are
applicable or relevant and appropriate to this remedial action,
and is cost-effective. This remedy utilizes permanent solutions
and alternative treatment (or resource recovery) technologies to
the maximum extent practicable. An early treatment action was
conducted at this site. This final remedy, in conjunction with
the early treatment action, satisfies the statutory preference for
treatment. However, because additional treatment of the wastes at
this site was not found to be practicable, this final remedy alone
does not satisfy the statutory preference for treatment as a
principal element of the remedy. The level of risk remaining at
the site and the existing state of technology rendered treatment
not feasible for this site.
As mining wastes, the wastes at this site are categorically
exempt from classification as hazardous wastes under the Resource
Conservation and Recovery Act (RCRA), pursuant to 40 CFR
261.4(b)(7); therefore, the RCRA Land Disposal Restrictions do not
apply.
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Because this remedy will result in hazardous substances.
remaining onsite above health-based levels, a review will be
conducted within five years after commencement of remedial action
to ensure that the remedy continues to provide adequate protection
of human health and the environment.
-'-7
6-6 t, ~
Date
Thomas P. Dunne
Acting Regional Administrator
U.S. Environmental Protection Agency
Region 10
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DECISION SUMMARY
for the Silver Mountain Mine
Superfund Site
RECORD OF DECISION
Table of Contents
Page
I. Site Description .... 1
II. Site History and Enforcement Actions 3
III. Community Relations History 4
IV. Scope and Role of Response Action 5
V. Site Characteristics 7
VI. Summary of Site Risks 9
VII,.. Description of Alternatives 18
VIII. Summary of Comparative Analysis of Alternatives 21
IX. The Selected Remedy 26
X. Statutory Determinations 31
XI. Responsiveness Summary 37
Administrative Record Index
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I. SITE DESCRIPTION
Name and Location
The Silver Mountain Mine site is located in Okanogan
County, north-central Washington Csouthwest quarter of Section
34, T38N, R26E). The site is six air miles northwest of the
town of Tonasket (population 1055) and lies in a north-south
running valley known as Horse Springs Coulee (see Figure 1).
Description
The Silver Mountain Mine site consists of five acres. The
area surrounding the site is semi-arid with scrub vegetation ,
and is used primarily for cattle grazing. Sagebrush and
bunchgrass characterize the area at and around the site.
Typical wildlife in the area include deer., coyote, field mice,
snakes, and various birds, including raptors. There is
evidence that marmots are also using the site. The Remedial
Investigation (RI) report includes a list of the species of
concern.
From county road 9410, an unpaved access road leads 1.5
miles to the site, part of which is surrounded by a
barbed-wire fence. The nearest residence is a single family
dwelling on a farm three miles south of the site. At this
location a domestic well (sampled during the Remedial
Investigation) serves the residence, and a larger well
supplies water for irrigation. The nearest well to the site
is approximately two miles from the site and is used for
cattle watering and irrigation.
The main features of interest at the site are a heap of
mined material ("leach heap") and a trench remaining from an
abandoned cyanide heap leaching operation ("leachate pond").
Both the heap and the pond are presently covered with a
scrim-reinforced hypalon liner (the "cover"). Directly west
of the leach heap is a larger pile of unprocessed mined
material (the "mine dump").
The foundations of a former mill building are about 250
feet southwest of the heap. A mine entrance is located
approximately 200 feet west of the heap, and water from
saturated mine workings is piped from within the portal to a
cattle watering trough outside the fenced area. Approximately
75 feet south of the heap was a shallow well, now sealed and
abandoned. A small freshwater seep northwest of the heap
creates a small shallow pool of standing water.
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Figure 1. site Location Map
Oroville
1 mile
EXPLANATION
Omak and Okanogan
18 miles
Blisford
SILVER
^MOUNTAIN
? MINE
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II. SITE HISTORY AND ENFORCEMENT ACTIVITIES
History
Historical records for this site are sparse, silver
Mountain Mine was originally opened as the Silver star in 1902
by the Silver Star Mining Corporation, Tonasket, Washington.
Silver, gold, and copper were all extracted from the mine,
which went through several changes in ownership before the
Silver Mountain Mining Company of Tacoma, Washington, acquired
the mineral rights to the property in 1951. By 1956, the mine
workings totalled 2000 feet. A 400-ton-per-day capacity mill
was constructed on the site in 1952 and dismantled by 1977;
observations made in the course of the RI at this site
indicate that little if any ore was ever processed at the
mill.
In 1979, the Silver Mountain Mining Company, Inc., changed
its name to Lead Point Consolidated Mines Company. In
February 1980, Lead Point Consolidated Mines leased the
mineral rights to a limited partnership of J. Wayne Tatman and
G. Patrick Morris, or J.W.T. and G.P.M., Ltd., who operated
the property as Precious Metals Extractions, Ltd. (PME). In
1985, both Lead Point Consolidated Mines and PME were owned in
partnership by J. Wayne Tatman and-G. Patrick Morris.
From 1980 to 1981, PME constructed and operated a cyanide
leach heap of previously mined material in an attempt to
extract silver and gold. • The heap consisted of about 5300
tons of ore in a 100' x 105' x 14' pile on top of a 20 ml
plastic liner. About 4400 pounds of sodium cyanide was mixed
with water and sprayed on the top of the heap. The
cyanide-laden effluent was then collected in a leachate pond
at the base of the heap. The leach heap operation was
abandoned in late 1981 without cleanup of contaminated
material.
In June 1981, the owner of the surface rights to the
property informed Okanogan County Health Department officials
of the heap leaching operation. The Health Department
collected samples from the site, and the Washington Department
of Ecology (Ecology) also investigated the site. In 1982,
Ecology took an early action to treat the cyanide at the site
by using sodium hypochlorite to partially neutralize the
leachate pond and heap. EPA conducted a Preliminary
Assessment and Site Inspection in 1984; the site was added to
the National Priorities List the same year. In 1985, Ecology
conducted a site stabilization effort which included removal
of liquids from the leachate pond and installation of a 33 ml
plastic cover over the heap and pond to reduce infiltration.
Empty cyanide drums were also removed, a fence was installed,
and the site was posted. The U.S. Bureau of Mines, under an
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Interagency Agreement with EPA, performed a Remedial
Investigation/Feasibility Study .(RI/FS) at the site in 1988
and 1989.
Enforcement Activities
No enforcement actions have been taken thus far. Special
notice letters were issued to the identified Potentially
Responsible Parties (PRPs): James E. Brosseau; Norman A.
Lamb; M. Blair Ogden; G. Patrick Morris; J. Wayne Tatman, who
cannot be located and apparently has left the country; and
James McDaniel, the owner of the surface rights to the site.
The Special Notice letters informed the PRPs of the need for
an RI/FS at this site and sought their participation. All of
the recipients of the Special Notice letters declined to
participate in the RI/FS.
III. COMMUNITY RELATIONS HISTORY
The CERCLA requirements (as amended by SARA) for public
participation include releasing the Remedial Investigation and
Feasibility Study Reports and the proposed plan to the public.
EPA did this in January 1990 by placing both of the documents in
the information repositories and mailing copies of the proposed
plan to individuals on the mailing list. EPA published a notice
of the release of the RI/FS and proposed plan in the North
Okanogan County Gazette Tribune on January 25, 1990 and the
Wenatchee World on January 28, 1990. Notice of the public comment
period and the public meeting discussing the proposed plan were
both included in the newspaper notices. The public meeting was
cancelled due to severe weather conditions. Local newspapers were
notified and signs were posted at the meeting hall to notify the
public of the cancelled meeting. Newpaper notices indicating that
comments were still desired from the public were published in the
Wenatchee World on February 11, 1990 and the Gazette Tribune on
(February 15, 1990. EPA received comments, which are summarized in
the Responsiveness Summary portion of this document.
To date, the following community relations activities have
been conducted by EPA at the Silver Mountain Mine site:
b September 1987 - EPA's contractor, Woodward-Clyde
Consultants, interviewed local residents and officials
during preparation of the Community Relations Plan.
o December 1987 - Community Relations Plan was published.
o October 12, 1988 - EPA distributed a fact sheet announcing
the startup of the Remedial Investigation.
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o March 1989 - information repository established at
Okanogan County Courthouse.
o April 28, 1989 - EPA distributed a second fact sheet
explaining the RI work being conducted at the site. The
fact sheet was in response to inquiries from the public to
Bureau of Mines personnel working at the site.
o January 25, 1990 - A public notice in the Gazette Tribune
described the availability of the proposed plan and the
RI/FS, and announced the dates of the public meeting and
public comment period.
o January 26, 1990 - EPA released the proposed plan fact
sheet, which explains the results of the RI/FS and EPA's
preferred plan, to persons on the mailing list for public
comment. The fact sheet announced a public meeting for
February 8, 1990, and gave the dates of the public comment
period.
'*•
o January 28, 1990 - A public notice in the Wenatchee World
described the availability of the proposed plan and the
RI/FS, and announced the dates of the public meeting and
public comment period.
o January 29-February 28, 1990 - Public comment period for
proposed plan and RI/FS.
o February 8, 1990 - Public meeting in Okanogan scheduled,
but cancelled due to snow.
o February 11 and 15, 1990 - Newspapers published notices
indicating that comments were still desired from the
public, and that EPA would reschedule the public meeting
if requested. No requests were received.
o March 1990 - Responsiveness Summary prepared.
IV. SCOPE AND ROLE OF RESPONSE ACTION
Some CERCLA sites are separated into distinct "operable
units," such as the groundwater unit and the soils unit, in order
to most efficiently remediate the contamination and reduce
exposures. The Silver Mountain Mine site is not separated into
operable units; the entire site was addressed in the early
actions at this site or in this Record of Decision.
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Figure 2. Detailed Features of the Silver Mountain Mine site
100 FEET
Silver Mountain Mine
ACCOM Road
Monitor Wall No.
nrtor Wall No.
Abandoned Monitor Wall
Abandoned Min« Wall
1 Monitor Wall No. 3
EXPLANATION
Mine access roads
and dozer cuts
Jeep roads
Adit, dashed
where inferred
Building foundation
Mine tailings
Waterline, buried
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V. SITE CHARACTERISTICS
Leach Heap
The leach heap (see Figure 2) is approximately 180 feet by
140 feet by 14 feet high. It contains about 5300 tons of
soils and rock taken from the mine. The contaminants of
concern in the heap are arsenic and cyanide. The arsenic is
naturally occurring, being an element common to hydrothermal
mineral deposits in the northwestern United States. In order
to determine the mobility of the arsenic, a petrographic
analysis was done. This analysis determined that the arsenic
is predominantly in the forms of arsenopyrite and arsenic-
bearing pyrite, which are stable (relatively immobile)
compounds. However, over time, the sulphur in arsenopyrite
and pyrite can be rxidized, allowing the arsenic to become
more mobile in the environment.
Cyanide in the heap is a result of the leaching operations
conducted in 1980 and 1981. Most of the cyanide used has been
removed during the original operations, through natural
degradation, or during treatment operations carried out by the
Washington Department of Ecology. Concentrations of total
cyanide remaining in the heap range up to 173 mg/kg.
. Approximately 10% of the cyanide in the heap is in the weak
acid dissociable form, meaning it is readily soluble. The
remainder is less mobile, although it could become more mobile
under weathering conditions.
Mine Dump
Approximately 5200 tons of "mine dump" material was placed
in four piles on the site (see Figure 2). This is rock and
soil that was excavated during mining operations but was never
processed. About 40% of the mine dump material was
mineralized by natural hydrothermal solutions and contains
elevated concentrations of arsenic ranging up to 1080 mg/kg.
The remaining 60% is similar to the overburden of a surface
mine. The form and mobility of the arsenic in the mine dump
material is the same as that of the arsenic in the leach heap.
Soil
Soil around the site was sampled to determine the extent
of effects from mining or leaching operations. Soil samples
were analyzed for the same inorganic parameters as heap and
mine dump materials. With the exception of arsenic, the soil
samples beneath the pond liner were found to have
concentrations of major and minor constituents similar to
those found in the heap and mine dump. Concentrations of
arsenic were appreciably lower, with a maximum arsenic
concentration .of 274 mg/kg beneath the pond liner.
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8
Concentrations of several trace elements in soils beneath the
liner were also less than those in the heap and dump,
especially zinc, copper, and lead. One sample, however,
showed very high values, indicating the presence of some
heap-type material, as well as leakage of cyanide (101 mg/kg)
beneath the pond liner.
Nearby soils samples were also similar in major and minor
elemental composition to the leach heap, with the exception of
appreciably lower levels of arsenic, sodium, and several trace
elements. Cyanide was not found in soil samples. The twq
background samples differed in most constituents from both the
heap material and the nearby soil samples; all trace elements
except barium occurred at lower levels.
Soil samples were also analyzed for organic chemicals.
However, none of the field samples had results appreciably
different from the blank samples, indicating that past
operations have not resulted in organic contamination at the
site.
Groundwater
The shallow aquifer under the site ranges from a- few
inches thick to 3.1 feet thick, and groundwater velocity is
estimated to be 1.3 feet per year. Due to its contact with
mineralized bedrock or mine dump material, groundwater
contains relatively high concentrations of dissolved anions
and cations (chloride,- sulfate, calcium, and magnesium) as
well as metals, such as arsenic, antimony, copper, iron,
silver, and zinc. The low quantity and relative quality of
the groundwater make it an unlikely source of drinking water.
Cyanide was detected under the heap in concentrations ranging
from 31 to 281 ug/1.
-*
The shallow aquifer under the site is thought to join the
main part of the Horse Springs Coulee aquifer downgradient of
the site. A domestic well and two irrigation wells in the
Horse Springs Coulee aquifer and downgradient of the site were
sampled and no elevated levels of contaminants were found.
Surface Water
Surface water at the site consists of a small seep with
minimal flow and mine drainage which is piped to a stock
watering tank (see Figure 2). Surface water does not travel
from onsite to offsite streams, lakes, or other open water.
Arsenic is the major contaminant found in surface water
onsite. Dissolved arsenic concentration in the stock tank was
91 ug/1, the highest of any water sample taken during the
field investigation.
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Migration Pathways
Contamination is believed to originate from four main
sources: the leach heap, mine dump, mine drainage, and
bedrock. Leaching, weathering, erosion, infiltration and
other processes and mechanisms have intermixed contamination
from man-made and natural sources, and transported it to other
media. The potential exposure pathways are through
groundwater, air, surface water and soil contact.
The potential for airborne migration of arsenic or cyanide
is minimal. The heap is presently covered with a 33-mil
hypalon liner. Should the liner fail, the top layer of the
heap is so course that very little contaminated soil would
blow from the heap, as estimated by worst case modelling.
Likewise, the potential for transport of contaminants from
the site via surface water is minimal. The topography at the
site is relatively flat and there is no connection with
surface water bodies in the area. The closest surface water
is approximately two miles from the site.
The main potential pathway of off-site contaminant
migration identified for this site is the regional groundwater
system (the Horse Springs Coulee aquifer). As stated above,
cyanide and arsenic were detected in the shallow aquifer under
the site during the remedial investigation. The quantity of
water flowing through the shallow aquifer is very low (with an
estimated specific discharge of 0.1 ft/yr), and it currently
is not used as a source of drinking water, rather it connects
with the regional aquifer downgradient of the site.
Groundwater sampling will continue to confirm whether elevated
concentrations of contaminants from the site are affecting the
Horse Springs Coulee aquifer.
Potential exposure pathways for contaminants in soil
include inadvertent ingestion (e.g., while eating or smoking),
direct dermal contact, and inhalation of suspended
particulates. The last of these is not considered
significant, since it is unlikely that contaminated soil
particles will be inhaled unless the heap is disturbed.
VI. SUMMARY OF SITE RISKS
Introduction
A baseline risk assessment was conducted as part of the
Remedial Investigation to estimate the risks to human health
and the environment that are posed by the existing conditions
at the Silver Mountain Mine site. The baseline risk
assessment estimated that there are unacceptable potential
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10
risks to" human health, in particular, to future workers at the
site. Risks to human health and the environment are
summarized below.
Contaminants of Concern
Inorganic contaminants are the most prevalent ones at
Silver Mountain Mine. Soils, sampling conducted in the areas
most likely to be contaminated with organic chemicals (fuels,
solvents, etc.) identified few organics. Low levels of
methylene chloride, benzoic acid, bis (2 ethylhexyl)
phthalate, benzyl alcohol, and acetone were found in some
samples, but are believed to be laboratory contaminants based
on quality assurance of the data.
The contaminants that were considered of potential concern
in the risk assessment are listed in Table 1, along with their
average, highest (upper bound), and "reasonable maximum
exposure" concentrations. To establish the reasonable maximum
exposure concentration, the upper 95% confidence limit on the
average was used, unless it exceeded the maximum value, in
which case the maximum was used. The risk assessment
determined that the media of concern are limited to soil and
groundwater.
Exposure Assessment
a. Population at Risk (Present and Future)
The land immediately surrounding the site is owned by a
Loomis resident who uses the land for cattle grazing. The
nearest residence is three miles away; the nearest towns
(Loomis and Tonasket) are approximately six miles away.
It has been reported that local teenagers frequent the
site. Early reports indicate that warning signs posted around
the site were removed more than once, and Department of
Ecology records document that after the placement of the pond
and heap cover, much of the rope used to hold this down was
removed. Based on this information, only visitors to the site
are thought to be currently exposed.
In the baseline risk assessment (which assumes no cleanup
of the site), it is expected that the site will continue to be
accessible to visitors. Others who could be exposed in the
future include workers at the site, or residents if people
choose to live there. If it becomes profitable to continue
the original mining activity, exposure to mine workers would
be.a distinct possibility. Workers and residents-are expected
to spend far more time at the site than infrequent visitors,
and as a result would be at greater risk.
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11
Table 1. Contaminant Concentrations Used to Estimate Risk
CONTAMINANT
Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromi urn
Copper
Cyanide
Fluoride *
Lead
Manganese
Mercury
Nickel
Nitrate "
Nitrite *
Selenium
Silver
Thallium
Tin
Vanadi urn
Zinc
AVE.
3.0
342.5
53.2
0.3
2.0
10.4
134.7
21.9
o.o
82.4
576.7
0.2
29.6
0.0
0.0
0.8
8.4
0.2
0.0
18. 3
224.3
SOIL
(mg/kg)
U.B.
9.1
631.6
109.5
0.7
4.2
16.0
510.4
96.3
0.0
193.9
938.0
0.6
48.8
0.0
0.0
1.6
33.8
0.9
0.0
30.6
554.1
RME
4.9
420.3
60.9
0.4
2.4
11.8
185.6
35.1
0.0
103.5
630.9
0.3
33.3
0.0
0.0
1-0
11.9
0.3
0.0
21.8
274.9
AVE.
14.7
10.7
61.0
0.9
1.5
11.1
20.2
40.8
0.4
8.7
166.0
0.1
15.6
37.1
0.3
1.7
2.5
0.1
15.4
11.5
. 42.1
WATER
(ug/1)
U.3.
40.4
14.3
136.0
1.5
2.9
31.6
56.7
281.0
0.7
23.2
421.0
0.1
38.4
120.8
1.3
3.9
2.5
0.1
31.5
40.7
129.0
RME
40.4
14.3
136.0
1.5
2.9
31.6
56.7
122.3
0.5
23.2
421.0
0.1
38.4
76.3
1.3
3.9
2.5
0.1
31.5
40.7
129.0
• Water concentrations are in mg/1.
RME • Reasonable maximum exposure
Ave. * Average
U.B. * Upper-bound
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12
As far as could be determined from available records,
there has never been residential occupation at the Silver
Mountain Mine site. Nor does residential growth into the
immediate vicinity appear likely in the near future, due to
the area's sparse population and the low availability of
gro.undwa.ter in the vicinity of the mine as compared with the
central part of the Coulee.
Given the above conditions, a future industrial (i.e.,.
mine worker) exposure was chosen as the reasonable maximum
exposure, in accordance with the National Contingency Plan,
and was used as a basis for the following risk assessment.
b. -Exposure Pathways and Scenarios
The main pathways of concern are:
Ingestion of contaminated groundwater,
Ingestion of soil, and
Dermal contact with soil.
Parameters used to estimate the reasonable maximum
exposure are a combination of average and upper-bound
industrial scenario parameters. Doses were calculated
separately to estimate noncarcinogenic and cancer risks using
two models developed by EPA Region 10. Using the first model,
dose is estimated for noncarcinogenic endpoints by averaging
chemical intake over the critical period of exposure for each
pathway. For chemicals other than copper, nitrate and
nitrite, long-term (chronic) exposure is the most critical,
.and chemical intake was averaged over 7 years. This is the
shortest period to which the chronic oral reference dose may
appropriately be applied. Adverse effects of copper, nitrate
and nitrite result principally from short term (acute)
exposure; therefore, average intakes were calculated
separately for these using a 6-month averaging period.
The second model is used to estimate dose for each pathway
for cancer risk estimation. Current scientific opinion is
that an increase in cancer risk from chemical exposure is a
function of the average lifetime intake, or dose. Dose
received is summed over the exposure period and then averaged
over a person's life.
To determine the overall chemical intake, doses must be
summed across all relevant pathways. In this case, it is
reasonable to assume that a person will be concurrently
exposed to contaminants by three routes: soil ingestion,
dermal contact with soil, and ingestion of drinking water.
Therefore, doses from these pathways have been added to
determine the cumulative dose.
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13
Toxicitv Assessment
Cancer potency factors (CPFs) have been developed by EPA's
Carcinogenic Assessment Group for estimating excess lifetime
cancer risks associated with exposure to potentially
carcinogenic chemicals. CPFs, which are expressed in units of
(mg/kg/day)" , are multiplied by the estimated intake of a
potential carcinogen, in mg/kg/day, to provide an upper-bound
estimate of the excess lifetime cancer risk associated with
exposure at that intake level. The term "upper bound"
reflects a conservative estimate of the risks calculated from
the CPF. Use of this approach makes underestimation of the
actual cancer risk highly unlikely. Cancer potency factors
are derived from the results of human epidemiological studies
or chronic animal bioassays to which animal-to-human
extrapolation and mathematical extrapolation models have been
applied.
Reference doses (RfDs) have been developed by EPA for
evaluating the potential for adverse noncarcinogenic health
effects resulting from chemical exposure. RfDs, which are
expressed in units of mg/kg/day, are estimates of daily
exposure levels for humans, including sensitive individuals,
below which noncarcinogenic effects are not expected to occur.
Estimated intakes of chemicals from environmental media (e.g.,
the amount of a chemical ingested from contaminated drinking
water) can be compared to the RfD. RfDs are derived from
human epidemiological studies or animal studies to which
uncertainty and modifying factors have been applied (e.g., to
account for the use of animal data to predict effects on
humans). These uncertainty factors help ensure that the RfD
will not underestimate the potential for adverse
noncarcinogenic effects to occur.
Table 2 lists cancer potency factors and reference doses
for contaminants of concern identified in the baseline risk
assessment.
Table 2. Cancer Potency Factors & Reference Doses
Contaminant
Arsenic
Cyanide
Antimony
Lead
Nitrate
Nitrite
Oral
CPF
(mg/kg/day)
50
none
none
none
none
none
Chronic Oral
Reference Dose
(mg/kg/day)
1 E-03*
2 E-02
4 E-04
none devel ' d
1 E+00
1 E-01
Level of Confidence
not established
medium
low
not applicable
high
hicrh
* 1 E-03 = 1 x 10"
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14
Risk Characterization
Excess lifetime cancer risks are determined by multiplying
the average daily dose with the cancer potency factor. These
risks are probabilities that are generally expressed in
scientific notation (e.-g^, 1x10"- or 1 E-06). An excess
lifetime cancer risk of 1 E-06 indicates that, as an upper
bound, an individual has a one in one million chance of
developing cancer as a result of site-related exposure to a
carcinogen over a lifetime under the specific exposure
conditions at the site. Because these are upper bound
estimates, it is likely that the actual risk is less than the
estimated excess cancer* risk.
Potential concern for noncarcinogenic effects of a single
contaminant in a single medium is expressed as the hazard
quotient (HQ) (or the ratio of the estimated intake derived
from the contaminant concentration in a given medium to the
contaminant's reference dose). By adding the HQs for all
contaminants within a medium or across all media to which a
given population may reasonably be exposed, the Hazard Index
(HI) can be generated. The HI provides a useful reference
point for gauging the. potential significance of multiple
contaminant exposures within a single medium or across media.
a. Excess Lifetime Cancer Risks
Future lifetime cancer estimates are based entirely on
exposure to arsenic assuming industrial site usage and
reasonable maximum exposure arsenic concentrations« In
addition to arsenic, other contaminants at the Silver Mountain
Mine site that are known or probable human carcinogens are
beryllium, cadmium, chromium, nickel, and lead. However,
beryllium, cadmium, chromium, and nickel have only been found
to be carcinogenic via inhalation. As stated above,
inhalation of particulates and volatiles is not a significant
pathway for this site. The carcinogenicity of lead could not
be evaluated because a cancer potency factor has not been
established at this time. The carcinogenic risk from exposure
to arsenic is shown in Table 3 for each exposure pathway.
b. Noncarcinogenic Effects
Risks of developing noncarcinogenic effects are presented
in terms of a hazard quotient and hazard index. If the
exposure is equal to or less than the RfD—a hazard quotient
of 1.0 or less—then adverse effects are not expected. If the
hazard quotient is greater than 1.0, there is an increasing
chance that adverse effects will occur. The hazard indices,
summed across each exposure pathway, are shown in Table 3.
Table 4 shows the noncarcinogenic and carcinogenic risks
broken down by contaminant and medium.
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15
Table 3. Carcinogenic & Noncarcinogenic Risks
Patl
Soil ingestion 2.3 E-04
Water ingestion 2.4 E-04
Dermal contact 1.9 E-03
Particulate inhalation 0.0 E+00
Vapor inhalation 0.0 E+00
Total Risk 2.3 E-03
renic Ris)
rd Quotient
2.7 E-01
3.1 E+00
2.2 E+00
0.0 E+00
0.0 E+00
5.5
Table 4. Reasonable Maximum Exposure Risks by Medium
A. NONCARCINOGENIC
Rfd
Ratio
Hater
Soil
Antimony
Arsenic
Barium
Beryl 1 1 urn
Cadmium
Chromi urn
Copper
Cyanide
Fluoride
Manganese
Mercury
Nickel
Nitrate
Nitrite
Selenium
Silver
Thallium
Tin
Vanadium
Zinc
1.7E+00
2.5E-01
4.7E-02
5.1E-03
9.8E-02
1.1E-01
2.5E-02
4.2E-01
2.0E-01
3.6E-02
S.7E-03
3.3E-02
O.OEfOO
O.OE+00
2.2E-02
1.4E-02
1.1E-02
9.0E-04
7.8E-02
1.1E-02
6.3E-02
2.2E+00
6.3E-03
4.2E-04
2.SE-02
1.2E-02
1.1 E-04
3.7E-02
O.OE+00
1.6E-02
S.OE-03
8.7E-03
a.OE+00
O.OE+00
1.7E-03
2.1E-02
1.7E-02
O.OE+00
1.3E-02
7.1E-03
Hazard Index:
3.1
2.4
Combined Hazard Index:
5.5
B. CARCINOGENIC (Arsenic only)
Water
2.4E-04
Soil
2.1E-03
Total risk:
2.3E-03
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16
Table 5. Stock Tank Drinking Water Risks
Noncarcinogenic Risks
Compound
Hazard quotient
Antimony
Arsenic
Barium
Beryl 1 ium
Cadmium
Chromium
Cyanide
Fluoride
Manganese
Mercury
Nickel
Selenium
Silver
Thall ium
Tin
Vanadium
Zinc
O.OE*00
1.6E*00
3.4E-03
1.7E-03
1.7E-02
3.4E-03
4.1E-03
7.1E-05
2.0E-04
S.7E-03
1.1E-02
O.OE+00
1.4E-02
1.1E-02
2.9E-04
2.4E-03
S.1E-04
.Carcinogenic Risk
Compound Risk
Arsenic
1.6E-03
Hazard Index
1.7E+00
The total noncarcinogenic hazard quotient for the water in
the stock tank is 1.7. Arsenic, with a hazard quotient of
1.6, accounts for nearly all of this risk. The risks
presented by the stock tank are shown in Table 5 above.
Conclusions - Human Health Risks
At the Silver Mountain Mine site, the most important
exposures routes are ingestion of and dermal contact with
soil, and ingestion of groundwater or surface water.
Using reasonable maximum exposure assumptions, arsenic,
antimony, and cyanide are the most important contaminants in
water. Nitrate/nitrite and lead were each present in a single
groundwater sample at concentrations above extablished
criteria, though these samples may not be representative of
overall site conditions. Exposure to arsenic in water could
result in an increased cancer risk of 2 in ten. thousand.
There is also a risk of noncarcinogenic effects, mainly
neurologic, liver, and skin related, from arsenic, cyanide and
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17
other chemicals. The hazard quotient for these effects is
2.5.
The most important contaminant in soil is arsenic.
Exposure to soil could result in an increased cancer risk of
two in one thousand. The hazard index of 2.4 indicates that
soil exposure could also result in a risk of noncarcinogenic
effects, principally skin and neurologic disorders.
Uncertainty is inherent in all risk assessments. The
major sources of uncertainty in the Silver Mountain Mine risk
assessment are toxicity reference values, assumed future land
use, the actual toxicity/risk of the dermal pathway, and the
water data (as mentioned above). Due to the uncertainty in
these and other areas, conservative assumptions were made in
order to be protective of human health.
Actual or threatened releases of hazardous substances from
this site, if not addressed by implementing the response
action selected in this Record of Decision, may present an
imminent and substantial endangerment to public health,
welfare, or the environment.
Environmental Risks
The greatest risk to wildlife and plants appears to be
from the arsenic concentrations in the soils surrounding the
leach heap. These soils are contaminated with levels of
arsenic toxic to vegetation and ruminants, and are likely to
be utilized by sagebrush biota, although the area involved is
small. In the future, once the heap cover deteriorates, there
may be some acute toxicity at times from temporary ponding of
leachate. Soils from the heap and dump may exert their
potential toxicity if they erode, spread out, leach, etc.
There is no current risk to wildlife or plants from
groundwater, and no future risk is anticipated. Surface
waters, however, attract wildlife, enhancing exposure to toxic
levels of pollutants within those waters. The mine drainage
to the trough will probably continue to be a source of
elevated arsenic concentrations. To a lesser extent, the seep
area may continue to be a source of elevated aluminum, copper,
and lead.
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VII. DESCRIPTION OF ALTERNATIVES
The Feasibility Study developed eight alternatives, utilizing
a variety of treatment, containment, and disposal options, to
reduce the risks remaining at the site after early initial
treatment actions. The three alternatives which best met the
evaluation criteria (protectiveness, cost effectiveness,
compliance with regulations) were selected for detailed analysis
and are described below, along with the no action alternative,
which must be considered to comply with the NCP. As discussed
further in Section X of this document, the primary applicable or
relevant and appropriate regulations are action-specific. There
are no location-specific ARARs for this site, and the Safe
Drinking Water Act standards are the only potentially applicable
chemical-specific ARAR. The alternatives are referred to by the
numbers assigned in the Feasibility Study and Proposed Plan.
Alternative 1: No Action
This alternative leaves the site as-is, with no treatment
or containment of contaminated materials and no restrictions
on site access. The leach heap is subjected to all normal
weathering forces and seasonal water runoff. No ARARs are
invoked, and thus none are violated.
Alternative 2: Grading. Clav/Soil Cap. Institutional Controls.
and Groundwater Monitoring
This alternative consists of a series of actions leading
to capping the leach heap. First, all contaminated materials
on site are consolidated onto the leach heap, with sampling
conducted to verify that contaminated materials are adequately
consolidated. These contaminated materials consist of surface
soils surrounding the heap that contain cyanide and elevated
arsenic concentrations and approximately 1600 yd of
mineralized mine dump. The leach heap is then graded and
contoured to a shape that will minimize water erosion of the
surface layer and seasonal runoff contact with the reshaped
heap. A soil/clay mixture is placed and compacted over the
graded heap to reduce infiltration of both air and water into
the contaminated materials.
Because the wastes at Silver Mountain Mine are
specifically exempt from the Resource Conservation & Recovery
Act, the remedy does not involve the disposal of RCRA-
regulated waste, and RCRA land disposal restrictions and
Subtitle C closure standards are not applicable. .The
Washington State Dangerous Waste Act does regulate certain
- wastes containing concentrations of arsenic greater than 100
mg/kg if the waste was generated after 1981. Because the
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19
waste at the site was generated prior to this date, the State
Dangerous Waste rules are not applicable; however, they have
been determined to be relevant and appropriate to the type of
waste being managed.
The cap will be designed and constructed to promote ^
drainage, minimize erosion of the cover, and provide long- *"
term minimization of migration of liquids through the
underlying contaminated materials. Because mean annual
precipitation is only 11.4 inches per year, the cap is
expected to readily meet or exceed these performance criteria.
Long-term operation and maintenance will be conducted to
monitor the groundwater around the site and to ensure the
integrity of the cap.
Groundwater sampling is conducted for five years or more
to verify whether contaminants are migrating. As an added
precaution, a restriction or notice not to disturb the cap
shall be placed on the deed for the site, and a fence with
appropriate warning signs is constructed around the site to
limit access. The community will be provided notice of
groundwater sampling activities, sampling results, and the
potential for contamination of the low-yield aquifer under the
site.
This alternative does not completely eliminate the problem
of the remaining cyanide and toxic metals migrating from the
leach heap, but it does minimize these problems by shielding
the contaminated materials from the conditions that promote
migration of arsenic and cyanide. The cap significantly -
reduces natural oxidation of the metal sulfides and the
remaining cyanide compounds and eliminates casual contact with
the contaminated materials by humans and animals. Future
disturbance of the cap is minimized by the fencing and deed
restrictions placed on the site.
ARARs for this alternative include Occupational Health and
Safety Administration (OSHA) regulations on worker safety.
Clean Air Act (CAA) emission standards during implementation,
Washington State Dangerous Waste regulations on capping,
Maximum Contaminant Levels (MCLs) for groundwater protection,
and the state's Minimum Standards for Construction and
Maintenance of Wells.
Construction of the cap should take 2-3 months. Operation
and maintenance (O&M) requirements include semi-annual
groundwater sampling and yearly inspections of the site to
monitor the condition of the cap. The present value cost,
including construction and O&M, is estimated at $635,600.
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Alternative 6: Removal and Continuous Rinse to Treat for Cyanide
Fine Solids to Resource Conservation and Recovery Act (RCRA)
Disposal to Remove Arsenic
The major feature of this alternative is the additional
treatment of approximately 5740' yd3 of heap ,' mine d'^mp , and
soil to destroy the remaining cyanide and remove the more
mobile arsenic. The material is moved to a trommel where it
is rinsed with water (to remove the cyanide and water-soluble
metals) and sized to remove the finer solids. Oversized
solids are allowed to drain and then are left on the site if
they meet treatment standards of 200 mg/kg arsenic and 95
mg/kg cyanide (see Table 6 below) . The fine solids are
further dewatered and then transported to a landfill that
meets RCRA requirements.
Treatability tests are needed to determine the proper
operating conditions for meeting the arsenic and cyanide
treatment standards. It is doubtful that this alternative can
meet the arsenic standard of 200 mg/kg, because it will not
remove the arsenic that is present in the tightly bound
sulfide mineral form. The arsenic in this form is not mobile
now, but it will slowly oxidize and become available to the
environment over time.
The rinsate is processed to destroy the cyanide and remove
the soluble metal contaminants by precipitation. Treated
rinsate would be released to the ground if it meets State land
application discharge limits. The discharge of treated
rinsate is regulated under the State Water Pollution Control
Act (RCW 90-48) , although no discharge limits specific to this
project have been set by the State. The volume of rinse water
generated is estimated to be 400 gal/hr. The metal-containing
sludge generated by the rinsate treatment is disposed of at a
hazardous waste facility, in accordance with Resource
Conservation and Recovery Act (RCRA) regulations.
ARARs include the OSHA and CAA requirements as under
Alternative 2, and several State of Washington water quality
regulations, including the State Water Pollution Control Act
and the State Waste Discharge Permit Program (although no
permits are required for on-site activities) .
No groundwater monitoring or institutional controls are
included in this alternative. The estimated time required for
implementation is one year. Neither O&M nor monitoring is
anticipated in the cost calculation. However, both
groundwater monitoring and capping may be needed if
treatability study results show that health-based -risk levels
cannot be met through treatment. Estimated present worth
costs are $1.2 million.
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Alternative 7: Offsite RCRA Disposal
The major features of this alternative are the excavation,
transport, and disposal of approximately 5740 yd3 of
contaminated materials (leach heap, mineralized mine dump, and
surrounding soil). The contaminated materials are hauled in
appropriately controlled trucks to an existing RCRA landfill.
After disposal, the site no longer has any contaminated
materials stored on it, and there is no need to restrict site
entry and future use. Because the low-yield aquifer is
affected by naturally occurring arsenic in the bedrock, the
community will be provided notice of the possibility of
groundwater contamination.
ARARs include the State Dangerous Waste Regulations for
transportation and disposal of hazardous wastes; the CAA and
OSHA regulations again apply during implementation.
Implementation time for this alternative is 2-3 months. No
O&M, monitoring, or institutional controls are required.
Disposal costs are estimated at $1.4 million.
VIII. SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
Each of the four alternatives described in the preceding
section was evaluated according to the following nine criteria:
Threshold Criteria
1. Overall protection of human health and the environment:
whether or not the remedy provides adequate protection or
describes the mechanisms for controlling risk for the
different exposure pathways.
2. Compliance with ARARs; whether or not the remedy ensures
compliance with Applicable or Relevant and Appropriate
Requirements of other federal and state environmental
standards or statutes.
Primary Balancing Criteria
3. Long-term effectiveness and permanence; the ability of
the remedy to provide protection and reduce risks to
' health and the environment after cleanup goals have been
met.
4. Reduction of toxicity. mobility, or volume through
treatment; the anticipated effectiveness of treatment
technologies used.
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5. Short-term effectiveness: the speed with which the remedy
achieves protection, as well as any adverse effects which
it may create during construction and implementation.
6. Implementability; the technical and administrative
feasibility of the remedy.
7. Cost: includes capital and O&M costs.
Modifying Criteria
8. State acceptance; whether the state concurs with or
opposes the remedy.
9. Community acceptance; whether or not the remedy is
acceptable to the community, and how it addresses their
continuing concerns about the site.
The following section describes how each alternative meets the
various criteria.
Overall Protection of Human Health and the Environment
The bffsite disposal option affords the strongest measure
of protection at the site, in that the contaminated materials
are completely removed from the site. Once the materials are
removed, there will be no restrictions on activities at the
site. However, disposal at another facility merely moves the
risk from one site to another. Some potential for groundwater
contamination remains at the site due to naturally occurring
arsenic in the bedrock.
The capping alternative prevents direct contact with the
contaminated materials, by means of both the cap itself and
the fence erected around the heap. There still remains a
small potential for arsenic and the remaining cyanide to
mobilize and enter the ground under the capped heap; however,
the cap should minimize that potential by minimizing contact
of air and water with the contaminated materials. Groundwater
monitoring and contingent groundwater treatment included in
this alternative will assure that it remains protective.
The treatment alternative provides a good measure of
protection, because all of the contaminated material will be
washed and the more mobile arsenic in the fine materials will
be removed and disposed offsite. However, the washed coarse
material, which will remain onsite, will still contain
arsenic-bearing sulfide minerals. The arsenic in this form
has a low mobility, but over time the sulfide minerals will
oxidize and the arsenic will become available to the
environment. Depending on treatment results (whether health-
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23
based levels can be achieved), capping and groundwater
monitoring may have to be added to this alternative.
The no action alternative does not protect human health or
the environment. Humans and animals can come in contact with
the contaminated materials, and potentially harmful leachate
could accumulate in the catchment pond downslope from the
leach heap during wet periods of the year, as the existing
cover deteriorates from natural weathering.
Since the no action alternative fails to meet this
threshold criterion, it will not be considered further in this
analysis.
Compliance with ARARs
The capping and offsite disposal alternatives meet all
ARARs. The treatment alternative can be designed to meet
ARARs, but some difficulty may arise due to Washington State
regulations governing wastewater. If rinsate treatment
operations cannot be-designed to meet State standards, the
wastewater might have to be transported a minimum of 30 miles
to a POTW for treatment.
Long-Term Effectiveness and Permanence
Offsite disposal of the contaminated materials eliminates
the long-term risks associated with the site. No
institutional barriers or restrictions are placed on the site
and there is no need for any inspection, repair, or
maintenance activities. Some potential for groundwater
contamination remains at the site due to naturally occurring
arsenic in the bedrock.
The capping alternative is highly reliable and effective.
Due to the dry climate in the area, the need for major repairs
of the cap during its 30-year design life is considered very
low. A notice or restriction in the deed to the property
should restrict future owners from disturbing the cap.
The treatment alternative has, in theory, a high level of
long-term effectiveness. The washed materials left onsite are
free from cyanide and soluble-metal contaminants. While this
technology is not new, its effectiveness in meeting the
arsenic treatment standard is not known. The arsenic
remaining in the cleaned materials is in the form of low
mobility sulfide minerals that undergo slow oxidation. Over
time the arsenic would become more mobile due to natural
weathering conditions. No institutional controls or barriers
are included, but if treatability studies indicated the need,
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capping and groundwater monitoring will be added to this
alternative.
Reduction of Contaminant Mobility. Toxicitv. or Volume
Early treatment actions significantly reduced the
. concentration of cyanide in the leach heap. Further treatment
of the leach heap would reduce the toxicity and somewhat
reduce the volume of the washed materials to be left onsite.
Cyanide and soluble-metal contaminants are washed from the
contaminated material, and the rinsate is subsequently treated
to destroy and precipitate the contaminants. The principal
threat, arsenic, is partially removed (rather than treated)
through sizing operations that separate out the fine
materials. Precipitated sludge and fine solids are disposed
at a hazardous waste site. Arsenic in the form of sulfide
minerals remains in the washed materials, but it has very low
mobility.
Capping the heap greatly reduces the potential for the
contaminants to move into the environment, because it
eliminates wind and water erosion. Capping minimizes water
and air infiltration into thie heap, thus limiting the natural
oxidation rate of the metal sulfides and the cyanide and. metal
complexes; this in turn significantly reduces the potential
for contaminant mobility. Capping slows the natural
degradation of cyanide. This alternative does not reduce the
volume of contaminated materials.
Disposal of the materials at a hazardous waste landfill
does not reduce either the toxicity or the volume of the
contaminants. Placement of the contaminated materials in a
properly constructed RCRA landfill should reduce the mobility
of the contaminants into the environment.
Short—Term Effectiveness
The capping alternative has the highest short-term
effectiveness, as it takes only 2-3 months to implement and
involves the least movement of contaminated materials. Worker
safety is assured through wetting the contaminated materials
to control blowing dust, and taking other routine safety
measures to prevent exposure to contaminated material.
Offsite disposal also takes 2-3 months and requires safety
precautions during the removal of the leach heap materials.
Materials are hauled to the landfill in appropriately sealed
and labeled trucks to minimize the risk of human contact with
the contaminants.
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25
The treatment alternative requires about a year's work.
Safety clothing and equipment are required to assure worker
safety, and precautions are taken when materials are hauled
offsite, as in the above alternative. This alternative has
the lowest short-term effectiveness because the likelihood of
contaminated materials becoming airborne during sizing
operations is very high.
Implementabilitv
Offsite landfilling is easy to implement. Loading,
hauling, and long-term disposal services are readily
available, and landfill capacity does not pose a problem. No
future site remediation or monitoring is required. Some
potential for groundwater contamination remains at the-site
due to naturally occurring arsenic in the bedrock.
Capping is also easily implemented. The technology to
construct the, alternative is well developed and the means to
perform maintenance functions on the cap and monitor the
effectiveness of the remedial action are available.
Treatment is less implementable. The technologies to wash
and size the contaminated materials and to treat the rinsate
are generally proven, and the availability of equipment and
technical personnel should be good. However, treatability
tests are required to determine how effective this alternative
will be in reducing arsenic concentrations. It is doubtful
that treatment/removal of fines could reduce the arsenic
present in the sulfide mineral form to the cleanup standard of
200 mg/kg (see Table 6 below). In addition, the ARARs for
this alternative might necessitate disposal of wastewater off-
site, making implementation more difficult than orginally
planned. Under' this alternative, the site requires no future
monitoring, but if treatability studies indicated the need,
capping and groundwater monitoring will be added to this
alternative.
Cost
The capping alternative has an estimated capital cost of
$370,360 and annual O&M costs of $39,650. The present value,
based on a 30-year period for site activities, is $635,600.
Capital costs for the treatment alternative are estimated
at $855,290, and present worth at $1.2 million. No monitoring
or maintenance costs are included.
Offsite disposal would cost an estimated $1.4 million.
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State Acceptance
The Washington State Department of Ecology has given
verbal approval of Alternate 2, capping.
Community Acceptance
Two commentors suggested using an alternative other than
the selected capping alternative. Community interest in the
site is generally low. A total of three private citizens and
one local official commented on the proposed plan: two
favored a capping option, the official favored taking no
action, and the other citizen gave no opinion. All public
comments are shown in Section XI of this document, the
"Responsiveness Summary."
IX. THE SELECTED REMEDY
The selected remedy is Alternative 2 (grading and capping the
leach heap; institutional controls; and groundwater monitoring).
EPA and the state of Washington agree that this alternative best
meets the selection criteria. A more detailed description of the
components of the remedy follows.
Consolidation and Grading
All contaminated soils and mine dump material will be
consolidated with the leach heap, graded, and contoured to a
shape that will minimize water infiltration. Locations which
might include such materials include the mine dump areas and
surface soils around the leach heap. This work will be
accomplished using conventional earth-moving equipment.
Samples will be collected after contaminated materials have
been consolidated to verify that all material contaminated
with concentrations of arsenic greater than 200 mg/kg or
cyanide greater than 95 mg/kg is made part of the heap. The
rationale for these cleanup standards are shown in Table 6
below.
Table 6. Cleanup Standards for Leach Heap. Mine Dump. and" Soil
Concentration
Constituent at Site Standard Rationale
arsenic 274 mg/kg max 200 mg/kg Hazard Index = 1.0
Cancer Risk = 10"
cyanide 101 mg/kg max 95 mg/kg Hazard Index =0.1
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Capping
Capping is the most important component of this remedy in
terms of preventing contaminant migration. Five .types of caps
were evaluated in the Feasibility Study; the soil/clay type
was selected because it was as protective as any other
evaluated, and it was the most cost effective. The Remedial
Design work will include designing a specific cap to meet the
following criteria: promote drainage, minimize erosion of the
cover, and provide long-term minimization of migration of
liquids through the underlying contaminated materials.
Mine Adit and Stock Tank
The entrance to the mine will be plugged using
conventional techniques in order to protect public safety,
particularly the curious visitor who may enter the mine. The
pipe that now carries mine drainage water to the stock tank
will be removed. A new well will be installed on the land-
owner's property in the Horse Springs Coulee aquifer to
replace the stock tank as an animal water supply.
Institutional Controls
The site will be fenced to prevent people and animals from
disturbing the cap and existing monitoring wells. A
restriction or notice will be placed on the deed to the
property which restricts future disturbance of the cap. The
community will be provided notice of sampling of the low-'
yield aquifer under the site, the sampling results, and the
potential for contamination, including that from naturally
occurring arsenic in the bedrock.
Groundwater Monitoring
A groundwater monitoring program will be implemented to
verify concentrations of potential contaminants, both
spatially and temporally. During the Remedial Investigation,
groundwater concentrations of contaminants exceeded human
health-based standards on a sporadic basis. A groundwater
monitoring program to meet the objective of detecting and
verifying the extent of contamination would be conducted in
two stages:
Stage 1. Existing wells will be sampled on a quarterly basis
for two years for selected parameters to verify any changes in
contaminants of concern at the site, and whether they occur at
concentrations above cleanup standards. All existing wells
will be used in the verification analysis for cyanide,
nitrate, and nitrite, which are the groundwater contaminants
that originate only in the heap. The other contaminants of
concern, arsenic, antimony, and lead, have a probable major
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28
source in bedrock and would therefore be verified primarily in
well 3, which should have the least bedrock influence among
existing wells. If elevated levels of contaminants are not
detected, sampling frequency will be decreased to semi-
annually.
If elevated levels of contaminants are detected and
verified, a more extensive monitoring system will be
established in Stage 2 to monitor contamination at the point
of compliance and to clarify the natural bedrock component of
contamination in relation to contamination coming from on-
site sources. If elevated levels of contaminants are not
verified, Stage 2 will not be needed either for verification
of contamination or for compliance monitoring. The selected
parameters and the standard (acceptable concentration) for
each are shown in Table 7 below.
Stage 2. The more extensive monitoring system will include the
..four existing monitoring wells, three additional downgradient
wells, one additional upgradient well, and a contingency for a
fourth additional downgradient well if required to adequately
span the flow path of groundwater at the point of compliance.
Two of the downgradient wells will be installed at the point
of compliance established in the western margin of the Horse
Springs Coulee aquifer. A third downgradient well and an
upgradient well will be installed to provide an adequate two-
dimensional array of monitoring points to verify the direction
of flow.
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Table 7. Groundwater Parameters & Standards
Rationale
Concentration
Constituent at Site Standard
antimony
arsenic
cyanide
lead
nitrate (N)
40 ug/1
14 ug/1
122 ug/1
23 ug/1
17 mg/1
120 ug/1
6 ug/1
154 ug/1
20 ug/1
10 mg/1 (as N)
Health based level
10 (-4) cancer risk
Health advisory
Proposed MCL
MCL
nitrite (N) 0.4 mg/1
combined 17.4 mg/1
nitrate and
nitrite
(45 mg/1 as NO3)
1 mg/1 (as N)
(3.3 mg/1 as NO2)
10 mg/1 (as N)
Proposed MCL
Proposed MCL
The parameters to be used for ground water monitoring will
include the field parameters (water level, temperature, pH,
electrical conductivity, and Eh) and the parameters of concern
identified in the Remedial Investigation (total cyanide, weak
acid dissociable cyanide, arsenic, antimony, lead, nitrate,
-and nitrite). The need for continued groundwater monitoring
will be evaluated during the five-year review of the site.
A statistical procedure will be used to evaluate
monitoring data for determining the spatial and temporal
trends in contaminant levels. Groundwater treatment design
would begin if the Stage 2 (point of compliance) wells show
contamination coming from the site exceeds the standards in
Table 7 and is not the result of naturally occurring
contamination, based on statistical evaluation of all the
data.
Contingent Groundwater Treatment Program
If groundwater treatment is chosen as a remedial
alternative based on analyses of monitoring results,
groundwater extraction and treatment at the surface will be
employed. Potential treatment for cyanide could be chosen
from methods listed in Section 2.5.4 of the Feasibility Study
Report (EPA, Jan. 17, 1990) for treatment of rinsewater from
leachate. Potential treatment for arsenic will employ arsenic
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30
removal by .use of iron sulfate or other precipitant. In this
method of treatment, .ferric sulfate is added as a floe to the
water to be treated. A high oxidation state is maintained by
aeration during treatment in order to keep iron in the ferric
form .and arsenic in the .arsenate- form. A slightly acidic
operating pH of pH 6-7 is maintained to promote chemical
removal of arsenic., from water, by any of three following
processes:
1. Precipitation of ferric arsenate.
2. Coprecipitation of arsenic with ferric hydroxide.
3. Adsorption of arsenic with ferric hydroxide.
Arsenic removal is then completed by separation of sludge from
water.
As noted above, groundwater treatment would not be
implemented until the level of groundwater contamination is
verified. A design phase would also precede any groundwater
treatment to verify that groundwater extraction is practical
in the shallow aquifer. On the basis of the Remedial
Investigation, groundwater treatment is at present considered
to be an inappropriate alternative because of the low levels
of contaminants and the low hydraulic conductivity of the
shallow aquifer.
Points of Compliance
A point of compliance for groundwater standards will be
established in the western margin of Horse Springs Coulee
aquifer 100-200 feet downgradient from the edge of the leach
heap. This point is chosen on the basis of two findings of
the Remedial Investigation:
1. The shallow aquifer beneath the heap has a very low
hydraulic conductivity on the order of 7 x 10-6 cm/s.
Such low hydraulic conductivity makes the shallow aquifer
unusable as a water supply. Horse Springs Coulee aquifer,
off the other hand, is an important water supply for
irrigation and residential use. The part of Horse Springs
Coulee aquifer adjacent to the mine site irs the most
appropriate point to monitor for effects of contaminants.
2. Some of the contaminants of concern (arsenic, antimony, and
lead) in the shallow aquifer have a potential natural
source in bedrock adjacent to the leach heap and mine
dump. A point of compliance in Horse Springs Coulee
aquifer, rather than the shallow aquifer, is more removed
from the potential bedrock source and will better allow
differentiation of contaminants from the mining activities
versus naturally occurring contaminants.
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X. STATUTORY DETERMINATIONS
The selected remedy meets statutory requirements of Section
121 of CERCLA, as amended by SARA, and to the extent practicable,
the National Contingency Plan. The evaluation criteria ar.e
discussed below.
1. Protectioh of Human Health and the Environment
The selected remedy will protect human health and the
environment by consolidating the contaminated materials onto
the leach heap; capping and covering the heap and implementing
institutional controls to minimize exposure; and monitoring
the groundwater to assure it is not affected by sources at the
site. These are all long-term measures. In the short term,
standard health and safety precautions will be taken to
protect workers; no other populations are currently at risk
from this site.
2. Attainment of ARARs
The selected remedial actions meets all identified ARARs.
These are listed below, by media. Except for the Safe
Drinking Water Act (SDWA) standards, these are all action-
specific ARARs (SDWA standards are chemical-specific). There
are no location-specific ARARs for this site.
Hazardous Waste:
RCRA. Not applicable due to mining waste exclusion (40 CFR
261.4). Not relevant and appropriate because the waste at the
Silver Mountain Mine site does not exhibit a characteristic of
hazardous waste and is not similar to a RCRA waste.
Washington State Dangerous Waste Regulations (WAG 173-303).
Some wastes containing greater than 100 ppm arsenic are
regulated as dangerous wastes. Although the remedial actions
planned do not constitute treatment, storage, or disposal, the
actions are sufficiently similar to make these regulations
relevant and appropriate. Specific sections of the
regulations that are relevant and appropriate include:
Section 610 Closure and Postelosure
Subsection 2a: Closure performance standard. Must close
in a manner that: minimizes the need for further maintenance;
and controls, minimizes or eliminates to the extent nessary to
protect human health and the environment, postclosure escape
of dangerous waste, dangerous constituents, leachate,
contaminated runoff, or dangerous waste decomposition products
to the ground, surface water, groundwater, or the atmosphere;
and returns the land to the appearance and use of surrounding
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land areas to the degree possible given the nature of the
previous dangerous waste-activity.
Subsection 7d: Postclosure care and use of property.
Postclosure use of property on which dangerous wastes remain
after .closure--must-never—be- allowed to disturb the integrity
of the final cover or any other components of any containment
system, or the function of the facility's monitoring systems,
unless the. Department finds that the disturbance is necessary
to the proposed use of the:property, and will not increase the
potential hazard to human health or the environment.
Subsection 10b(i)(A)(B): Notice in deed to property.
Within sixty days of closure the owner or operator must:
record, in accordance with state law, a notation on the deed
to the property, or on some other instrument which is normally
examined during title search, that will in perpetuity notify
any potential purchaser of the property that the land has been
used to manage dangerous wastes; and that its use is
restricted as specified in subsection 7d.
Section 645, subsection 8: Groundvater monitoring
requirements.
Section 665, subsection 6: Closure and postclosure care
for landfills. This subsection contains general requirements
for a final cover, maintenance, and monitoring.
Water:
Safe Drinking Water Act, Maximum Contaminant Levels (MCLs).
An applicable requirement at the point of compliance, these
are the federal standards for drinking water supplies. MCLs
exist for several elements found at the site, including
arsenic, cadmium, lead, silver, and several others.
Minimum Standards for Construction and Maintenance of Wells
(WAG 173.160). An applicable requirement, this state of
Washington regulation addresses how wells must be installed
and abandoned by licenses well contractors. The well to be
drilled to replace the stock tank must comply with both the
administrative and substantive requirements of WAC 173.160 and
WAG 173.162, because the well will be located in the Horse
Springs Coulee aquifer, outside of the site boundaries.
State Water Pollution Control Act (ROW 90.48). This could be
applicable if groundwater treatment were conducted. This act
requires the use of all known available and reasonable methods
to prevent and control pollution of the waters of the state.
Specific substantive requirements are set forth in:
90.48.010 Policy enunciated
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90.48.020 Definitions (pollution & waters of the state)
90.48.080 Discharge of polluting matter in waters
prohibited.
Regulation of Public Ground Waters (ROW 90.44). This could be
applicable if groundwater treatment were conducted. This
chapter establishes that the "first in time, first in right"
doctrine of water appropriation applies to groundwater as well
as surface water. If the groundwater extraction system
adversely impacts either the quantity or quality of a senior
water right holder, the impacts must be mitigated.
Water Resources Act of 1971 (ROW 90.54). This could be
applicable if groundwater treatment were conducted. This act
sets forth fundamentals of water resource policy for the state
to insure that waters of the state are protected and fully
utilized for the greatest benefit to the people of the state
and, in relation thereto, to provide direction to the
Department of Ecology and other state agencies and officials,
in carrying out water and related resources programs.
Specific substantive requirements are set forth in:
90.54.020 General declaration of fundamentals for
utilization and management of waters of the state.
Establishes: beneficial uses; the basis for allocation
which includes the loss of opportunity in the equation for
maximum net benefits; base flow in perennial streams and
rivers shall be retained, and all known available and
reasonable methods of treatment shall be applied to
discharge of wastes into waters of the state.
Protection of Withdrawal Facilities Associated with Ground
Water Rights (WAC 173-150). This could be applicable if
groundwater treatment were conducted. The purpose of this
chapter is to establish and set forth the policies and
procedures of the Department of Ecology in regard to the
protection of the availability of groundwater as it pertains
to the water withdrawal facilities of holders of groundwater
rights. Particularly:
173-150-060 Defines impairment of water rights.
173-150-090 Voluntary agreements. Allows junior and
senior water right holders to reach a mutually satisfying
agreement regarding impairment of water supply by one of
the parties.
173-150-100 Ensures protection of water quality as well
as quantity.
Water Quality Standards for Surface Waters of the State of
Washington (WAC 173-210). This would be applicable if
groundwater treatment-were conducted and resulted - in
discharges to surface water. The purpose of this regulation
is to establish water quality standards for surface water of
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34
the state, and it includes provisions for the protection of
beneficial uses. Particularly:
173-201-035 General considerations. Subsection (3)
states the antidegradation policy of the state as guided
by RCW 90.48 and RCW 90.54.
173-201-045 General water use and criteria classes.
Establishes criteria for the beneficial uses to be
protected.
173-201-047 Toxic substances. The acute surface water
quality criteria for cyanide in freshwatr is 22 ug/L and
the chronic freshwater criteria is 5.2 ug/L.
173-201-070 6 080 General and specific classifications
for all freshwaters of the state.
State Waste Discharge Permit Program (WAG 173-216). Permits
are not required for onsite CERCLA remedial actions, but are
applicable to offsite discharges to ground or surface waters
not already regulated under the NPDES program. This would be
relevant and appropriate to onsite discharges to groundwater.
The pertinent subsections are:
173-216-020 Policy enunciated. Requires the use of all
known available and reasonable methods to prevent and
control the discharge of wastes into the waters of the
.state.
173-216-060 Prohibits discharges.
173-216-110 Permit terms and conditions. Establishes
conditions necessary to prevent and control waste
discharges into waters of the state.
Underground Injection Control Program (WAG 173-218). This
would be applicable if fluids were injected through wells
offsite, and relevant and appropriate if fluids were injected
through wells onsite. This regulation sets forth procedures
and practices to protect groundwaters, including underground
sources of drinking water, from injected fluids. Pertinent
subsections are:
173-218-020 Policy enunciated. Requires the use of all
known available and reasonable methods to prevent and
control the discharge of fluids and waste fluids into the
waters of the state.
173-218-030 Defines beneficial uses and well classes.
173-218-050 Prohibits new Class I injection wells. Class
I wells inject fluids below the lowest aquifer.
173-218-080 Prohibits all Class IV wells, which inject
dangerous or radioactive waste fluids.
173-218-090 Prohibits Class V injection wells that inject
industrial, municipal, or commercial waste fluids into or
above an underground source of drinking water.
173-218-100 Permit terms and conditions. Substantive
requirements for injection.
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35
Submission of Plans and Reports for Construction of Wastewater
Facilities (WAC 173-240). This would be relevant and
appropriate if groundwater treatment were conducted. This
regulation establishes the requirements for engineering
reports, plans and specifications, construction quality
assurance, and the operation and maintenance manual.
Air;
Clean Air Act, PM10 Standard. This applies to any fugitive
emissions from the remedial action work.
Washington State General Regulations for Air Pollution sources
(WAC 173-400), Section 40: General Standards for Maximum
Emissions. This section is applicable and addresses fugitive
dust and other emissions during excavation and cleanup related
activities.
Ambient Air Quality Standards for Particulate Matter (WAC 173-
470). Applicable state requirement.
Safety;
Occupational Safety and Health Act, 29 CFR 1910. This
applicable federal act governs worker safety at hazardous
waste sites.
Occupational Health standards—Safety standards for
Carcinogens, Part P, Hazardous Waste operations and Emergency
Response (WAC 296-62-300). This applicable regulation
includes training requirements for workers potentially exposed
to hazardous substances. Effective June 1, 1990 the training
requirement for general site workers (e.g., equipment
operators, transport vehicle operators, general laborers, and
supervisory personnel) engaged in hazardous substance work
must receive 40 hours of health and safety training, and a
minimum of three days actual field experience under the direct
supervision of a trained, experienced supervisor. Workers
engaged in hazardous waste operation within the exclusion zone
and the contamination reduction zone must have 80 hours of
instruction in addition to the field experience.
3. Cost Effectiveness
The selected action was the most cost-effective of the
alternatives that passed screening, being significantly less
expensive than Alternatives 6 and 7 (Alternative 1, No Action,
failed the protectiveness criterion).
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4. Utilization of Permanent Solutions and Alternative Treatment
Technologies
An early treatment action was taken to reduce the
concentration of cyanide in the leach heap at this site. For
this Record of Decision,"several treatment technologies were
considered, but were not selected because their higher cost
(compared to capping) was not justified by any increase in
protectiveness. There are no known technologies for treating
the arsenic in the waste; all of the technologies evaluated
treat only the cyanide, which is no longer the principal
threat at the site. The technology that passed screening—
cyanide rinsing with removal of fine solids containing mobile
arsenic, followed by rinsate treatment—may not be a permanent
solution because its effectiveness in removing the relatively
stable arsenic compounds, which are currently the principal
threat, is somewhat in doubt. Arsenic remaining in the rock
after treatment/removal would oxidize over time and become
available to the environment. In addition, the treatment
alternative would be difficult to implement if'rinsate
treatment pilot tests revealed that state ARARs concerning
disposal of treated rinsate could not be met.
5. Land Disposal Restrictions
Wastes resulting from the beneficiation of mining
materials are categorically excluded from regulation as
hazardous wastes under RCRA (40 CFR 261.4[b][7]). Heap
leaching operations are included undsr the definition of
"beneficiation." . Therefore, the Land Disposal Restrictions
are not applicable. Land Disposal Restrictions are also not
relevant and appropriate for two reasons: (1) waste is not
being disposed of in a new unit, an expansion of an existing
unit, or a replacement unit, and (2) the waste does not
exhibit a RCRA characteristic and is not sufficiently similar
to a RCRA waste to invoke the RCRA regulations.
6. Preference for Treatment as a Principal Element
An early treatment action was taken to reduce the
concentration of cyanide in the leach heap at this site. For
this Record of Decision, several treatment technologies were
considered, but were not selected because their higher cost
was not justified by any increase in protectiveness. There
are no known technologies for treating the arsenic, which is
now the principal threat. Technologies for treating cyanide,
which is no longer the principal threat at the site, were
evaluated. The technology that passed screening—cyanide
rinsing with removal of fine solids containing mobile arsenic,
followed by rinsate treatment—may not be effective for
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37
removing stable arsenic compounds. The capping alternative
was believed to better meet the selection criteria overall.
XI. Responsiveness Summary
Overview
This section contains a summary of comments and concerns
raised during the comment period held from January 29 to
February 28, 1990, as well as comments received on the draft
Remedial Investigation and Feasibility Study Reports. A brief
description of community background and involvement is also
included.
Background of Community Involvement
EPA conducted community interviews in September 1987, and
found community interest in the site to be low. The owner of
the" site was the most concerned citizen at that time, other
citizens and local officials interviewed expressed concern
over other environmental issues in the area, such as a local
landfill contaminated with pesticides and a large sawdust pile
at an inoperative mill which periodically catches fire. Mines
are relatively common in this area.
The concerns expressed to EPA during community interviews
were:
1) Citizens wanted timely and accurate information on the
site.
2) Some citizens expressed concern over the implications this
cleanup would have for other mining operations of similar
types in the area.
3) Citizens were surprised at EPA's involvement at the site.
They appeared to consider it a non-threatening, low
priority site.
Summary of Comments Received
EPA held a public comment period from January 29 to
February 28, 1990. The public sent. 3 letters and placed four
telephone calls to the Environmental Protection Agency's site
manager during this time. In addition, two agencies commented
on the draft Remedial Investigation and Feasibility Study
(RI/FS) Reports prior to the public comment period. All
comments received are summarized below and grouped by
category, e.g. EPA's preferred alternative, cost, groundwater,
etc.
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1. EPA's Preferred Alternative
Comment: One citizen supported the proposed cap remedy,
particularly for control of any contaminants that could become
airborne. •
Response: EPA agrees that the cap will prevent the spread of
contamination through air releases, and believes that in
addition the cap will minimize the spread of contamination
through all media.
Comment: The same citizen commented that local soils are
sandy/ therefore EPA may have to import the clay.
Response: If this alternative is the final remedy selected,
the .specifics will be determined during the remedial design
phase. EPA agrees that it is likely that clay will have to be
imported and mixed with local soil for the cap.
Comment: The property owner asked if the preferred alternative
would include a new well to replace the stock tank and if
there would be a pump in it.
Response: The preferred plan does include a new well to be
drilled into the Horse Springs Coulee aquifer to provide an
alternative water supply for livestock. It is likely to be
placed east of the original stock tank in the Horse Springs
Coulee aquifer. The actual location and configuration of the
well will be part of the remedial design and can not be
determined at this point. EPA will work with the land owner
to ensure water is provided to his livestock.
Comment: The property owner asked if a chain-link fence will
be put up. The owner had noticed the top of one of the wells
had been broken off, and a fence would help reduce further
vandalism.
Response: The preferred alternative includes fencing the site
to prevent humans and livestock from entering and disturbing
the cap or monitoring wells once the cap is in place. This
should minimize further damage to existing or .new wells.
Comment: One commentor asked whether a liner would be placed
under the leach heap prior to capping.
Response: EPA considered moving the heap onto a newly
constructed liner, but determined this would not provide
additional protection of human health and the environment to
offset the risks of moving contaminated materials. This is
primarily because the contaminated materials are dry and
relatively stable, and the cap will minimize the water and air
that can come into contact with them. Constructing a bottom
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39
liner could be more protective if the wastes were wet and/or
leachate was likely to be generated from the heap. However,
EPA believes the conditions at the Silver Mountain Mine site
do not warrant this extra step.
Comment: In commenting on the RI/FS Reports/ one federal
official felt that the capping alternative should only be
considered a temporary solution/ which displaces the problem
until sometime in the future. If the material is left in
place/ an irreversible contamination of groundwater in the
area could occur.
Response: EPA does not believe that the preferred alternative
will fail as the commentor suggests. Once the cover is in
place, the threat to the groundwater from the materials on
site is greatly reduced, because oxidation of the tightly
bound arsenic will be minimized. EPA determined during the
feasibility study that treatment of the material on site to
remove arsenic to health-based concentrations is not possible,
and that the capping alternative is the most protective of the
environment overall. Groundwater sampling indicates little or
no contamination has occurred to date, and groundwater
monitoring will continue under the chosen alternative.
2. Remedial Investigation Report
Comment: A federal Public Health official wrote that since-
arsenic concentration was so high In mine tailings/ more soil
sampling should be done on rest of the property.
Response: During the remedial investigation, soil near the
leach heap and at several locations around the site was
sampled. The results showed that high concentrations of
arsenic were limited to the soils immediately surrounding the
heap. When this contaminated soil is consolidated with the
heap prior to capping, sampling will be done to verify that
the remaining soil does not contain arsenic above health-
based concentrations.
Comment: The commentor above suggested that the tailings piles
be included in any remedial action at the site.
Response: The contaminated mine tailings are included in the
remedial action chosen for the site; they will be
consolidated with the leach heap prior to capping.
Comment: The commentor above believes that the
airborne/inhalation exposure route should be considered.
Response: The cap will eliminate this route of exposure.
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40
Comment: The commentor above questioned whether the addition
of the amount of arsenic ingested daily (about 50 ug/day) to
the reasonable maximum exposure would change the estimated
cancer risk.
Response: Including the arsenic ingested from other sources
would result in a higher overall risk estimate, however, this
is not the usual method for assessing risks at Superfund
sites. EPA attempts to predict the excess risk resulting from
the reasonable maximum exposure at the site; this represents
risks above those from other sources, such as average daily
ingestion from food sources.
Comment: A citizen pointed out that in Appendix P of the
Remedial Investigation Report/ the concentrations of
contaminants in groundwater at the site were lower than those
in background samples.
Response: The commentor has misinterpreted this particular
table. The "gdw/ref" column does not represent on-site
groundwater, rather it shows the concentration of on-site
groundwater as it enters (and is diluted by) the Horse Springs
Coulee aquifer. The purpose of this table is to indicate
incremental contamination to the regional aquifer for the
ecological risk assessment. Actual concentrations of
contaminants in the on-site groundwater are given in several
other places in the RI/FS Reports, including Appendix D.
3. Groundwater
Comment: A citizen questioned whether the actual water flow is
being tapped into when the groundwater is monitored. He would
like to be allowed to confirm this by using the "dousing"
method.
Response: EPA uses scientific methods when conducting
remedial investigations, and therefore has not used the
dousing method at this site. EPA believes that it has
accurately characterized the aquifer at the site; detailed
information is given in the Remedial Investigation Report.
Comment: One citizen asked what the location and frequency of
groundwater sampling will be.
Response: The sampling will be conducted in two phases.
During the first phase each existing well will be sampled on a
quarterly basis for two years. If elevated levels of
contaminants are not detected, sampling frequency-will be
decreased to semi-annually and no new wells will be
constructed. Groundwater monitoring will continue for five
years, and then results will be analyzed to determine whether
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41
the monitoring should continue. If elevated concentrations
are found and verified, a more extensive monitoring system
will be established in the second phase.
In the second phase, if necessary, EPA will be installing
three or four new wells at locations to be determined during
the design of the remedy. Three wells will be downgradient of
the site, one will be upgradient, and possibly another will be
installed downgradient if more information is needed. These
are in addition to the four existing wells.
If the contamination becomes high enough to exceed EPA
health-based levels, design of a groundwater treatment system
will be implemented during the second phase.
Comment: One citizen expressed that "slugs" of contaminants
could be released to the groundwater. His concern was that
future landowners should be notified of this potential for
groundwater contamination.
Response: The selected remedy includes a notice or
restriction to be placed on the property deed to prevent
owners from disturbing the cap. In response to this comment,
the chosen remedial alternative also states that if the
shallow aquifer becomes contaminated, the deed notice will be
modified to prevent owners from using the aquifer.
4. other Alternatives Under Consideration
Comment: One citizen asked why EPA did not choose alternative
#3, the multimedia cap.
Response: EPA considers the multimedia cap to be non-cost-
effective for several reasons, including the low net
precipitation (making the low-permeability soil cap virtually
as effective as the multimedia cap) and the temperature
extremes (which can reduce the expected life of a synthetic
membrane). The solid, stable physical structure of the waste
and the goal to reduce future exposures to arsenic made the
clay/soil cap a comparable alternative, at a lower cost than
the multimedia cap.
Comment: A county official wrote a recommendation for
alternative fi (No Action). The official felt that the site
had been stabilized for several years and is now fenced, so
the threat is gone.
Response: EPA believes that alternative #1 does not
effectively reduce the potential health risks from the site.
Although the immediate threat from cyanide leaching into the
pond was reduced by "stabilization" actions in 1981, 1982, and
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42
1985, there remains a significant risk from the arsenic at the
site. In addition, the cyanide remaining in the leach heap
could migrate to the groundwater. These are the primary risks
that caused the "no action" alternative to be judged
unprotective of human hea-lth and the environment.
•»
Comment: A federal official recommended alternative #6
(removal and continuous rinse for cyanide). He suggested the
cost could be partially covered by recovering ore, while
eliminating an environmental problem.
Response: While EPA seriously considered additional
treatment, it found that treatment could not remove or destroy
the arsenic, which is currently the principal threat, to
health-based concentrations. The arsenic remaining on site
could slowly oxidize and become available to the environment.
In addition, the estimated costs of treatment are considerably
higher than those of the selected remedy, and the ultimate
fate of the treatment rinse water cannot be determined without
treatability tests. For these reasons, EPA did not select a
treatment alternative.
5'. Technical Assistance Grants
Comment: One citizen wanted to know* if Technical Assistance
Grant (TAG) recipients could sample veils after EPA has
finished monitoring the wells.
Response: Technical Assistance Grant funds may not be used for
any monitoring or other technical field or laboratory use.
Comment: A citizen asked if a TAG for Silver Mountain Mine
could be used to cover other mining sites in the area as well.
Response: Technical Assistance Grant funds are to be used only
at the Superfund site they are granted for.
6. Other
Comment: A hazardous waste treatment firm representative
wrote requesting to be put on the mailing list.
Response: EPA added the firm to the mailing list when the
letter arrived and sent it a copy of the proposed plan, as
requested.
Comment: A county official commented on the Oroville Dump
site and felt that the "Bureaucratic Blunder** should not occur
again with this site.
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43
Response: EPA believes its activity at the Silver Mountain
Mine site reflects consideration of community concerns about
"bureaucratic waste" while still striving to protect the
environment.
Comment: One commentor had difficulty in getting copies of
the RI/FS Reports.
Response: EPA appreciates being notified of the problems
associated with locating the reports. The commentor was
mailed copies of the reports during the comment period. EPA
is verifying that the administrative record will be accessible
to the public.
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U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION 10
1200 Sixth Avenue
Seattle, Washington 98101
ADMINISTRATIVE RECORD INDEX
for
SILVER MOUNTAIN MINE
March 27, 1990
-------
03/27/90
U. S. Environmental Protection Agency, Region 10
Page
SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
HEADING:
SUB-HEAD:
•»
1. 1.
AUTHOR:
ADDRESSEE:
DESCRIPTION:
1. 0.
1. 1.
SITE IDENTIFICATION
Correspondence
- 0001 DATE: 07/30/81 PAGES: 1
CLAR PRATT/WASHINGTON STATE DEPARTMENT OF ECOLOGY
FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
MEMORANDUM: SILVER MOUNTAIN MINE CYANIDE LEACH OPERATION
1. 1.
AUTHOR:
ADDRESSEE:
DESCRIPTION:
- 0002 DATE: 08/20/81 PAGES: 2
JOHN HODGSON/WASHINGTON STATE DEPARTMENT OF ECOLOGY
FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
MEMORANDUM: LEADPOINT CONSOLIDATED MINES, INC. TOATS COULEE,
OKANOGAN COUNTY AND THE USE OF SODIUM CYANIDE IN HEAP LEACHING
OPERATIONS
1. 1.
AUTHOR:
ADDRESSEE:
DMfcRIPTION:
• 0003 DATE: 09/11/81 PAGES: 1
KAREN K. ALBRECHT/OKANOGAN COUNTY HEALTH DEPARTMENT
JOHN HODGSON/WASHINGTON STATE DEPARTMENT OF ECOLOGY
LETTER: INFORMATION REGARDING VISIT TO THE SILVER MOUNTAIN MINE
SITE
1. 1.
AUTHOR:
ADDRESSEE:
DESCRIPTION:
- 0004 DATE: 09/25/81 PAGES: 1
DENNIS BOWHEY/WASHINGTON STATE DEPARTMENT OF ECOLOGY
FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
MEMORANDUM: TELEPHONE CONVERSATION WITH KEN RUSSELL OF THE MINE
SAFETY AND HEALTH ADMINISTRATION CONCERNING UNSAFE OPERATION OF
THE SILVER MOUNTAIN MINE
1. 1.
AUTHOR:
ADDRESSEE:
DESCRIPTION:
- 0005 DATE: 09/29/81 PAGES: 1
DENNIS BOWHEY/WASHINGTON STATE DEPARTMENT OF ECOLOGY
FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
MEMORANDUM: TELEPHONE CONVERSATION WITH J. WAYNE TATMAN
CONCERNING SILVER MOUNTAIN MINE
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Q'3/27/90 U. S. Environmental Protection Agency, Region 10 Page
SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
1.1. . - 0006 DATE: 08/20/82 PAGES: 3
AUTHOR: PATRICIA D. EWING/-
ADDRESSEE: DENNIS BOWHEY/WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: LETTER: PROVIDING INFORMATION ABOUT OWNERSHIP AND PHYSICAL
CONDITIONS OF THE SILVER MOUNTAIN MINE SITE
1. 1. . - 0007 DATE: 11/17/82 PAGES: 5
AUTHOR: J. MEYER/
ADDRESSEE: /
DESCRIPTION: SITE DESCRIPTION OF SILVER MOUNTAIN MINE
1.1. . - 0008 DATE: 04/13/84 PAGES: 1
AUTHOR: DONALD WESTON/J.R.B. ASSOCIATES
ADDRESSEE: FILE/J.R.B. ASSOCIATES
DESCRIPTION: REPORT OF CONTACT WITH BARRY NELSON OF THE OKANOGAN COUNTY
HEALTH DEPARTMENT CONCERNING SILVER MOUNTAIN MINE
1.1. . - 0009 DATE: 11/15/84 PAGES: 1
AUTHOR: LORI COHEN/EPA
ADDRESSEE: FILE/EPA
DESCRIPTION: RECORD OF TELEPHONE CONVERSATION WITH DENNIS BOWHEY OF THE
WASHINGTON STATE DEPARTMENT OF ECOLOGY CONCERNING THE STATUS OF
SILVER MOUNTAIN MINE
1.1. . - 0010 DATE: 02/22/85 PAGES: 10
AUTHOR: /
ADDRESSEE: /
DESCRIPTION: REPORT ON SILVER MOUNTAIN MINE. GEOLOGICAL DESCRIPTION AND MAPS
INCLUDED
1.1. . - 0011 DATE: / / PAGES: 1
AUTHOR: DENNIS BOWHEY/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: MEMORANDUM: TELEPHONE CONTACT WITH DOUG OSTRUM CONCERNING
SILVER MOUNTAIN MINE
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1.1. . - 0012 DATE: / /' PAGES: 1
AUTHOR: /
. ADDRESSEE: /
DESCRIPTION: BRIEF DESCRIPTION OF OPERATION AND STATUS OF SILVER MOUNTAIN
MINE SITE
1.1. . - 0013 DATE: / / PAGES: 5
AUTHOR: /.
ADDRESSEE: PETE KMET, ET AL./
DESCRIPT!ON: HANDWRITTEN NOTES CONCERNING DATA ON SILVER MOUNTAIN MINE.
INCLUDES A ONE-PAGE TYPED STATUS REPORT
SUB-HEAD: 1. 2. . Site Inspection/Preliminary Assessment Reports
1. 2. . - 0001 DATE: 11/01/80 PAGES: 1
AUTHOR: /WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: KEN J. ECKSTEIN/WELL OWNER
DESCRIPTION: WELL WATER REPORT
. . - 0002 DATE: 06/01/81 PAGES: 1
AUTHOR: /WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: DAVE GILLESPIE/WELL OWNER
DESCRIPTION: WELL WATER REPORT "
1. 2. . - 0003 DATE: 06/04/81 PAGES: 17
AUTHOR: JIM HUDGINS, DICK SIRGINSON, DEAN HARNING/MINE SAFETY AND HEALTH
ADMINISTRATION
ADDRESSEE: FILE/MINE SAFETY AND HEALTH ADMINISTRATION
DESCRIPTION: REPORT: FEDERAL INSPECTION OF THE SILVER STAR MOUNTAIN MINE.
SEE ALSO: 1.2. -0009
1. 2. . - 0004 DATE: 08/22/81 PAGES: 5
AUTHOR: DONALD WESTON/J.R.B. ASSOCIATES
ADDRESSEE: FILE/EPA
DESCRIPTION: POTENTIAL HAZARDOUS WASTE SITE PRELIMINARY ASSESSMENT
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SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
1. 2. . - 0005 DATE: 04/13/82 PAGES: 1
AUTHOR: /WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: DAVE GILLESPIE/WELL OWNER
DESCRIPTION: WELL WATER REPORT
1. 2. . - 0006 DATE: 09/17/84 PAGES: 2
AUTHOR: MICHAEL J. GALLAGHER/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: MEMORANDUM: ON-SITE INSPECTION OF SILVER MOUNTAIN MINE BY
ECOLOGY & ENVIRONMENT, INC., 09/04/84
1. 2. . - 0007 DATE: 01/25/85 PAGES: 102
AUTHOR: WILLIAM CARBERRY/ECOLOGY AND ENVIRONMENT, INC.
ADDRESSEE: J. E. OSBURN/EPA
DESCRIPTION: PRELIMINARY SITE INSPECTION REPORT OF SILVER MOUNTAIN MINE
1. 2. . - 0008 DATE: 05/13/85 PAGES: 1
AUTHOR: DAVE MURDOCK,.MIKE GALLAGHER, DENNIS BOWHEY/WASHINGTON STATE
DEPARTMENT OF ECOLOGY
ADDRESSEE: FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: WASHINGTON STATE DEPARTMENT OF ECOLOGY INSPECTION REPORT ON
SILVER MOUNTAIN MINE SITE
1. 2. . - 0009 DATE: 08/12/86 PAGES: 1
AUTHOR: MIKE GALLAGHER AND DOUG DUNSTER/WASHINGTON STATE DEPARTMENT OF
ECOLOGY
ADDRESSEE: GLYNIS STUMPF/WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: INSPECTION REPORT ON SILVER MOUNTAIN MINE
1. 2. . - 0010 DATE: 10/15/86 PAGES: 1
AUTHOR: MIKE GALLAGHER, DOUG DUNSTER, BRAD EWY/WASHINGTON STATE
DEPARTMENT OF ECOLOGY
ADDRESSEE: FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ASCRIPTION: WASHINGTON STATE DEPARTMENT OF ECOLOGY INSPECTION REPORT ON
SILVEF. MOUNTAIN MINE
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1. 2. . - 0011 DATE: 12/12/88 PAGES: 16
AUTHOR: LYNN WILLIAMS/EPA
ADDRESSEE: WALTER TURNER/MINE SAFETY AND HEALTH ADMINISTRATION '
DESCRIPTION: LETTER: REQUEST FOR COPY OF SILVER STAR MOUNTAIN MINE
VIOLATION. COPY OF VIOLATION INCLUDED. SEE ALSO: 1.2. -0003
1. 2. . - 0012 DATE: / / PAGES: 1
AUTHOR: /EPA
ADDRESSEE: /
DESCRIPTION: REPORT: CONDITIONS AND STATUS OF SILVER MOUNTAIN MINE SITE 1984
AND 1986
1. 2. . - 0013 DATE: / / PAGES: 5
AUTHOR: DENNIS BOWHEY/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: FILE/EPA
DESCRIPTION: SITE INSPECTION REPORT
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Page
SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
HEADING: 2. 0.
SUB-HEAD: 2. 1.
2.
SITE STABILIZATION (WDOE) - BACKGROUND
Correspondence
1. - 0001 DATE: 11/18/82 PAGES: 2
AUTHOR: ED DENIKE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: DENNIS BOWHEY/WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: MEMORANDUM: SILVER MOUNTAIN MINE CYANIDE NEUTRALIZATION
2. 1.
AUTHOR:
ADDRESSEE:
DESCRIPTION:
- 0002 DATE: 03/13/85 PAGES: 1
MIKE BLUM/WASHINGTON STATE DEPARTMENT OF ECOLOGY
FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
RECORD OF TELEPHONE CONVERSATION WITH DENNIS BOWHEY CONCERNING
SILVER MOUNTAIN MINE SITE
2. 1.
AUTHOR:
ADDRESSEE:
DESCRIPTION:
- 0003 DATE: 04/10/85 PAGES: 1
MIKE BLUM/WASHINGTON STATE DEPARTMENT OF ECOLOGY
FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
RECORD OF TELEPHONE CONVERSATION WITH DENNIS BOWHEY CONCERNING
SILVER MOUNTAIN MINE SITE
2. 1.
AUTHOR:
ADDRESSEE:
DESCRIPTION:
- 0004 DATE: 05/10/85 PAGES: 5
DENNIS BOWHEY/WASHINGTON STATE DEPARTMENT OF ECOLOGY
MIKE BLUM/WASHINGTON STATE DEPARTMENT OF ECOLOGY
MEMORANDUM: SILVER MOUNTAIN MINE CLEAN UP PROPOSAL FOR IN-HOUSE
REVIEW
2. 1.
AUTHOR:
ADDRESSEE:
DESCRIPTION:
• 0005 DATE: 06/01/85 PAGES: 3
GLYNIS STUMPF/WASHINGTON STATE DEPARTMENT OF ECOLOGY
FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
HANDWRITTEN MEMORANDUM: NOTES CONCERNING ACTIVITIES AT
MOUNTAIN MINE SITE
SILVER
2. 1.
AUTHOR:
ADDRESSEE:
DESCRIPTION:
• 0006 DATE: 06/28/85 PAGES:
LORI COHEN/EPA
FILE/EPA
SILVER MOUNTAIN MINE SITE UPDATE
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SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
2. 1. . - 0007 DATE: 07/08/85 PAGES: 3
AUTHOR: DAVE MURDOCK/WASHINGTON STATE DEPARTMENT OF ECOLOGY
.ADDRESSEE: FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: MEMORANDUM: SITE STABILIZATION OPERATION AT SILVER MOUNTAIN
MINE SITE, 06/15/85 TO 06/28/85
2. 1. . - 0008 DATE: 10/18/85 PAGES: 1
AUTHOR: DAVE MURDOCK/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: MEMORANDUM: FOLLOW-UP STABILIZATION AT SILVER MOUNTAIN MINE
SITE
2. 1. . - 0009 DATE: 05/27/86 PAGES: 1
AUTHOR: DAVE MURDOCK/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: REPORT: TELEPHONE CONVERSATION WITH JIM MCDANIEL CONCERNING
SILVER MOUNTAIN MINE SITE
- 0010 DATE: 05/29/86 PAGES: 2
I: GLYNIS STUMPF/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: KERRY JEWETT/
DESCRIPTION: HANDWRITTEN MEMORANDUM: ROPES SECURING THE COVER, WHICH IS
STABILIZING THE HEAP AT SILVER MOUNTAIN MINE SITE, ARE BEING
STOLEN
2. 1. . - 0011 DATE: 12/19/88 PAGES: 3
AUTHOR: JOHN R. BENHAM/U.S. DEPARTMENT OF THE INTERIOR, BUREAU OF MINES
ADDRESSEE: KEITH ROSE/EPA
DESCRIPTION: LETTER: CONCERNING A DETAILED SURVEY OF THREE MONITOR WELLS AND
CONSIDERATION OF A FOURTH WELL AT THE SILVER MOUNTAIN MINE SITE.
INCLUDES 2 GRAPHS
2. 1. . - 0012 DATE: 01/06/89 PAGES: 6
AUTHOR: DAVID A. DENTON, JR./U.S. DEPARTMENT OF THE INTERIOR, BUREAU OF
MINES
ADDRESSEE: KEITH ROSE/EPA
DESCRIPTION: MEMORANDUM: CONCERNING A SCHEDULE FOR WORK COMPLETION AT THE
SILVER MOUNTAIN MINE SITE. INCLUDES 4 PAGES OF "INITIAL WET LAB
ANALYSIS"
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SUB-HEAD: 2. 2. . Sampling Data
2. 2. . - 0001 DATE: 06/18/81 PAGES: 2
AUTHOR: /OKANOGAN COUNTY HEALTH DEPARTMENT
ADDRESSEE: FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: DATA SUMMARY, METAL: SILVER MOUNTAIN MINE SITE
!"-•»
2. 2. . - 0002 DATE: 06/11/81 PAGES: 1
AUTHOR: KAREN ALBRECHT/OKANOGAN COUNTY HEALTH DEPARTMENT
ADDRESSEE: FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: DATA SUMMARY: SILVER MOUNTAIN MINE SITE -
2. 2. . - 0003 DATE: 10/26/81 PAGES: 2
AUTHOR: J. HODGSON, H. PORATH/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
JESCRIPTION: DATA SUMMARY: SILVER MOUNTAIN MINE SITE
2. 2. . - 0004 DATE: 11/19/81 PAGES: 1
AUTHOR: H. PORATH/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
JESCRIPTION: DATA SUMMARY: SILVER MOUNTAIN MINE SITE
2. 2. . ' - 0005 DATE: 11/19/81 PAGES: 1
AUTHOR: H. PORATH/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
JESCRIPTION: DATA SUMMARY, METALS: SILVER MOUNTAIN MINE SITE
2. 2. .- - 0006 DATE: 04/05/82 PAGES: 1
AUTHOR: /
ADDRESSEE: FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
JESCRIPTION: DATA SUMMARY: SILVER MOUNTAIN MINE SITE
2. 2. . - 0007 DATE: 12/03/82 PAGES: 1
AUTHOR: DENNIS BOWHEY/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
JESCRIPTION: DATA SUMMARY: SILVER MOUNTAIN MINE SITE
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SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
2. 2. . - 0008 DATE: 06/04/83 PAGES: 1
AUTHOR: DENNIS BOWHEY/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: DATA SUMMARY: SILVER MOUNTAIN MINE SITE
2. 2. . - 0009 DATE: 11/29/83 PAGES: 1
AUTHOR: DENNIS BOWHEY/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: DATA SUMMARY: SILVER MOUNTAIAN MINE SITE
2. 2. . - 0010 DATE: 09/04/84 PAGES: 1
AUTHOR: /E AND E, INC.
ADDRESSEE: FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: DATA SUMMARY: SILVER MOUNTAIN MINE SITE
2. 2. . - 0011 DATE: 11/07/84 PAGES: 1
AUTHOR: DENNIS BOWHEY/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: FILE/WASHINGTQN STATE DEPARTMENT OF ECOLOGY
DEJJRIPTION: DATA SUMMARY: SILVER MOUNTAIN MINE SITE
SUB-HEAD: 2. 3. . Orders
2. 3. . - 0001 DATE: 11/13/81 PAGES: 4
AUTHOR: /WASHINGTON STATE SUPERIOR COURT
ADDRESSEE: BARRY NELSON, BLACKBURN S. JOSLIN/OKANOGAN COUNTY HEALTH
DEPARTMENT
DESCRIPTION: ORDER: PERMITTING COUNTY HEALTH OFFICIALS TO ENTER THE SILVER
MOUNTAIN MINE SITE TO ABATE HEALTH HAZARDS
SUB-HEAD: 2.4. . Pilot Site Mitigation Plan
2. 4. - 0001 DATE: 06/17/85 PAGES: 22
AUTHOR: /RIEDEL ENVIRONMENTAL SERVICES, INC.
ADDRESSEE: /WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: PILOT SITE MITIGATION PLAN FOR SILVER MOUNTAIN MINE SITE
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SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
2. 4. . - 0002 DATE: 05/22/85 PAGES: 18
AUTHOR: JOHN H. RUDDICK/RIEDEL ENVIRONMENTAL SERVICES, INC.
ADDRESSEE: DAVID .MURDOCH/WASHINGTON STATE- DEPARTMENT- OF ECOLOGY
DESCRIPTION: LETTER: TRANSMITTAL OF 17-PAGE SITE MITIGATION PLAN SUMMAR^,
DATED 05/21/85, FOR SILVER MOUNTAIN MINE SITE
SUB-HEAD: 2.5. . Consent for Access Agreement
2. 5. . - 0001 DATE: 06/03/85 PAGES: 1
AUTHOR: JIM MC DANIEL/SILVER MOUNTAIN MINE
ADDRESSEE: /WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: AGREEMENT TO ALLOW WDOE PERSONNEL ON THE SILVER MOUNTAIN MINE
SITE TO NEUTRALIZE AND DISMANTLE HEAP LEACHING OPERATIONS
SUB-HEAD: 2. 6. . Notification of Hazardous Waste Activities
2. 6. . - 0001 DATE: 06/24/85 PAGES: 1
AUTHOR: GLYNIS A. STUMPF/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: FILE/EPA
DESCRIPTION: UNIFORM HAZARDOUS WASTE MANIFEST NO. 13494
2.6. . - 0002 DATE;. 06/28/85 PAGES: 1
AUTHOR: DAVID O. MURDOCH/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: FILE/EPA
DESCRIPTION: UNIFORM HAZARDOUS WASTE MANIFEST NO. 13495
2.6. . - 0003 DATE: 09/03/85 PAGES: 3
AUTHOR: DAVID 0. MURDOCH/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: FILE/
DESCRIPTION: NOTIFICATION OF DANGEROUS WASTE ACTIVITIES. INCLUDES NOTE BY
LAWRENCE ASHLEY CONFIRMING TELEPHONE CONVERSATION WITH ROSS
POTTER 06/25/85
2. 6. . - 0004 DATE: 04/03/86 PAGES: 2
AUTHOR: DAVID O. MURDOCH/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: FILE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: GENERATOR ANNUAL DANGEROUS WASTE REPORT FOR SILVER MOUNTAIN MINE
SITE
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'SUB-HEAD: 2. 7. . Photos
2. ' 7. . - 0001 DATE: 06/26/85 PAGES: 9
AUTHOR: GLYNIS STUMPF/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: /WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: XEROGRAPHIC COPIES OF PHOTOGRAPHS TAKEN AT SILVER MOUNTAIN MINE
SITE. 3 TO 5 PHOTOGRAPHS PER PAGE, EACH LABELED
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HEADING: 3.0. . REMEDIAL INVESTIGATION (RI) - FEDERAL LEAD
SUB-HEAD: 3.1. . Correspondence
3. 1. . - 0001 DATE: 11/11/88 PAGES: 1
AUTHOR: DEDE MONTGOMERY/EPA
ADDRESSEE: KEITH ROSE/EPA
DESCRIPTION: LETTER: REVIEW OF SITE SAFETY PLAN PREPARED BY BUREAU OF MINES
FOR THE SILVER MOUNTAIN MINE SITE. SEE ALSO 3.4. -0005
SUB-HEAD: 3.2. . Memo of Understanding
3. 2. . - 0001 DATE: 09/01/87 PAGES: 15
AUTHOR: HENRY L. LONGEST, II/EPA
ADDRESSEE: REGIONAL DIRECTORS/EPA
DESCRIPTION: MEMORANDUM: AGREEMENT BETWEEN EPA AND BUREAU OF MINES TO OBTAIN
BUREAU ASSISTANCE IN TREATMENT OF INORGANIC HAZARDOUS WASTE
SUB-HEAD: 3. 3. . Meetings
3. 3. . - 0001 DATE: 12/07/87 PAGES: 2
AUTHOR: KEITH ROSE/EPA
ADDRESSEE: /
DESCRIPTION: AGENDA: SILVER MOUNTAIN MINE SITE RI/FS SCOPING MEETING
3. 3. . - 0002 DATE: 12/22/87 PAGES: 3
AUTHOR: KEITH ROSE/EPA
ADDRESSEE: /
DESCRIPTION: NOTES: SILVER MOUNTAIN MINE MEETING. INCLUDES LIST OF
ATTENDEES
SUB-HEAD: 3. 4. . Work Plans
3. 4. . ' 0001 DATE: 06/01/88 PAGES: 71
AUTHOR: /CH2M HJLL
ADDRESSEE: /EPA
ASCRIPTION: WORK PLAN FOR REMEDIAL INVESTIGATION OF THE SILVER MOUNTAIN MINE
SITE
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'3.4. . - 0002 DATE: 06/01/88 PAGES: 183
AUTHOR: /CH2M HILL
-ADDRESSEE: /EPA
'DESCRIPTION: PLANS: QUALITY ASSURANCE, FIELD SAMPLING, AND SITE SAFETY FOR
SILVER MOUNTAIN MINE SITE
3. 4. . - 0003 DATE: 07/28/88 PAGES: 10
AUTHOR: WILLIAM B. SCHMIDT/U.S. DEPARTMENT OF THE INTERIOR
ADDRESSEE: KEITH ROSE/EPA
DESCRIPTION: LETTER: DISCUSSION OF QUALITY ASSURANCE AND SAFETY PROCEDURES.
INCLUDES STATEMENT OF SERVICES AND ESTIMATED COSTS FOR SILVER
MOUNTAIN MINE SITE
3.4. . - 0004 DATE: 09/15/88 PAGES: 5
AUTHOR: WILLIAM B. SCHMIDT/U.S. DEPARTMENT OF THE INTERIOR
ADDRESSEE: KEITH ROSE/EPA
DESCRIPTION: RESPONSE TO TECHNICAL QUESTIONS RAISED BY EPA-AND WASHINGTON
STATE DEPARTMENT OF ECOLOGY
4. - 0005 DATE: 10/31/88 PAGES: 41
AUTHOR: /BUREAU OF MINES
ADDRESSEE: /EPA
DESCRIPTION: SITE SAFETY PLAN FOR THE SILVER MOUNTAIN MINE SITE. FOR
AMENDMENTS AND REVISIONS, SEE 3.4. -0006. SEE ALSO 3.1. -0001
3. 4. . - 0006 DATE: / / PAGES: 3
AUTHOR: DAVID K. DENTON, JR./BUREAU OF MINES
ADDRESSEE: BURTON GOSLING/BUREAU OF MINES
DESCRIPTION: MEMORANDUM: REVISION TO SILVER MOUNTAIN MINE SITE SAFETY PLAN.
SEE ALSO: 3.4. -0004
SUB-HEAD: 3.5. . Comments on Work Plan
3. 5. . - 0001 DATE: 08/01/88 PAGES: 5
AUTHOR: KEITH ROSE/EPA
ADDRESSEE: WILLIAM B. SCHMIDT/U.S. DEPARTMENT OF THE INTERIOR
DESCRIPTION: LETTER: COMMENTS BY EPA AND WASHINGTON STATE DEPARTMENT OF
ECOLOGY ON THE WORK PLAN FOR THE SILVER MOUNTAIN MINE SITE
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SUB-HEAD: 3.6. . Sampling and Analysis Data
3. 6. . — 0000 DATE: / / PAGES: 0
AUTHOR: /
ADDRESSEE: /
DESCRIPTION: SEE 3.7 0002 AND 3.7 0003 FOR SAMPLING AND ANALYSIS DATA
SUMMARIES
SUB-HEAD: 3.7. . Remedial Investigation Reports
3. 7. . - 0001 DATE: 01/19/90 PAGES: 218
AUTHOR: /EPA
ADDRESSEE: /
DESCRIPTION: REMEDIAL INVESTIGATION REPORT, SILVER MOUNTAIN MINE, OKANOGAN
COUNTY, WASHINGTON
3. 7. . - 0002 DATE: 12/15/89 PAGES: 401
AUTHOR: /EPA
ADDRESSEE: /
DESCRIPTION: REMEDIAL INVESTIGATION REPORT VOLUME 2 - APPENDICES SILVER
MONTAIN MINE, OKANOGAN COUNTY, WASHINGTON
3. 7. . - 0003 DATE: 12/15/89 PAGES: 582
AUTHOR: /EPA
ADDRESSEE: /
DESCRIPTION: APPENDIX .D CHEMICAL ANALYSES AND DATA QUALITY VALIDATION
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HEADING: 4. 0. . FEASIBILITY STUDY (FS)
SUB-HEAD: 4.1. . Feasibility Study Report
4. 1. . - 0001 DATE: 01/17/90 PAGES: 300
AUTHOR: /EPA
ADDRESSEE: /
DESCRIPTION: FEASIBILITY STUDY REPORT SILVER MOUNTAIN MINE, OKANOGAN COUNTY,
WASHINGTON
SUB-HEAD: 4.2. . Proposed Plan
4. 2. . - 0001 DATE: 01/26/90 PAGES: 6
AUTHOR: /EPA
ADDRESSEE: /
DESCRIPTION: SILVER MOUNTAIN MINE SUPERFUND SITE FACT SHEET HORSE SPRINGS
COULEE, WASHINGTON THE PROPOSED PLAN
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HEADING: 5. 0. . RECORD OF DECISION (ROD)
SUB-^HEAD: 5.1.. -
5. 1. . - 0001 DATE: / / PAGES: 0
AUTHOR: /
ADDRESSEE: /
DESCRIPTION: RESERVED
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SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
HEADING: 6. 0. . STATE COORDINATION
SUB-HEAD: 6. 1. . Correspondence
6. 1. . - 0001 DATE: 11/30/82 PAGES: 1
AUTHOR: JOHN MEYER/EPA
ADDRESSEE: FILE/EPA
DESCRIPTION: RECORD OF TELEPHONE CONVERSATION WITH DENNIS BOWHEY CONCERNING
SILVER MOUNTAIN MINE SITE. CLEAN-UP WOULD HAVE TO BE A STATE
RESPONSIBILITY
6. 1. . - 0002 DATE: 10/18/84 PAGES: 1
AUTHOR: ROBERT E. LANDRETH/EPA
ADDRESSEE: DENNIS BOWHEY/WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: LETTER: THANKING WDOE FOR THE OPPORTUNITY TO BE INVOLVED AND
GAINING EXPERIENCE FROM THE FIELD WORK AT SILVER MOUNTAIN MINE
SITE
6. 1. . - 0003 DATE: 06/02/85 PAGES: 2
^^ AUTHOR: KATHRYN DAVIDSON/EPA
^•DRESSEE: KEN BACK/WASHINGTON PLANNING AND COMMUNITY AFFAIRS AGENCY
DESCRIPTION: LETTER: NOTIFICATION OF SILVER MOUNTAIN MINE SITE BECOMING AN
EPA FUNDED PROJECT
6. 1. . - 0004 DATE: 07/01/85 PAGES: 1
AUTHOR: LORI COHEN/EPA
ADDRESSEE: CAROL KRAEGE/WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: LETTER: MATERIALS ON SILVER MOUNTAIN MINE SITE PRP SEARCH. IS
SILVER STAR AND SILVER MOUNTAIN THE SAME MINE?
6. 1. . - 0005 DATE: 08/28/85 PAGES: 1
AUTHOR: DORI GOODRICH/WASHINGTON STATE DEPARTMENT OF COMMUNITY
DEVELOPMENT
ADDRESSEE: LORI COHEN/EPA
DESCRIPTION: LETTER: NOTIFICATION THAT THE INTERGOVERNMENTAL REVIEW PROCESS
IS COMPLETE, CONCERNING SILVER MOUNTAIN MINE SITE AND THE
U.S.D.A. PESTICIDE LABORATORY
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SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
6. 1. . - 0006 DATE: 03/24/88 PAGES: 7
AUTHOR: BRAD J. EWY/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: KEITH ROSE/EPA
DESCRIPTION: LETTER: REVIEW OF REMEDIAL INVESTIGATION WORK, QUALITY
ASSURANCE, FIELD SAMPLING, AND SITE SAFETY PLANS FOR THE SILVER
MOUNTAIN MINE SITE
6.1. . - 0007 DATE: 07/19/88 PAGES: 1
AUTHOR: BRAD J. EWY/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: KEITH ROSE/EPA
DESCRIPTION: LETTER: REVIEW OF 06/88 REMEDIAL INVESTIGATION WORK, QUALITY
ASSURANCE, FIELD SAMPLING, AND SITE SAFETY PLANS FOR THE SILVER
MOUNTAIN MINE SITE
6. 1. . - 0008 DATE: 09/20/88 PAGES: 2
AUTHOR: LYNN WILLIAMS/EPA
ADDRESSEE: DOROTHY MILHOLLIN/WASHINGTON STATE DEPARTMENT OF ECOLOGY
DESCRIPTION: LETTER: REQUEST FOR ECOLOGY RECORDS SEARCH CONCERNING THE
SILVER MOUNTAIN MINE. SITE
6. 1. . - 0009 DATE: 02/14/90 PAGES: 7
AUTHOR: BRAD EWY/DOE
ADDRESSEE: JANET O'HARA/EPA
DESCRIPTION: LETTER LISTING WASHINGTON STATE ARAR'S
6. 1. - 0010 DATE: 03/21/90 PAGES: 3
AUTHOR: Carol Kraege/Washington Dept. of Ecology
ADDRESSEE: Janet O'Hara/EPA
DESCRIPTION: Letter listing applicable ARAR's to pump and treat scenario
outlined in the draft ROD.
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SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
HEADING: 7.0, . ENFORCEMENT
SUB-HEAD: 7. 1. . Correspondence
7. 1. . - 0001 DATE: 05/29/85 PAGES: 1
AUTHOR: BONNIE B. BUNNING/WASHINGTON STATE DEPARTMENT OF NATURAL
RESOURCES
ADDRESSEE: WALTER STEINWEG/PRC ENGINEERING
DESCRIPTION: LETTER: INFORMATION ABOUT POSSIBLE LOCATION OF WAYNE TATMAN,
PRP FOR SILVER MOUNTAIN MINE
SUB-HEAD: 7. 2. . Notice Letters and Requests for Information
7. 2. . - 0001 DATE: 06/26/85 PAGES: 1
AUTHOR: DAVE MURDOCK/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: WAYNE TATMAN/SILVER MOUNTAIN MINE
DESCRIPTION: NOTICE LETTER
7. 2. . - 0002 DATE: 01/29/88 PAGES: 6
•AUTHOR: CHARLES E. .FINDLEY/EPA
DRESSEE: JAMES E. BROUSSEAU/LEADPOINT CONSOLIDATED MINES COMPANY
DESCRIPTION: NOTICE LETTER
7.2. .' - 0003 DATE: 01/29/88 PAGES: 6
AUTHOR: CHARLES E. FINDLEY/EPA
ADDRESSEE: NORMAN A. LAMB/LEADPOINT CONSOLIDATED MINES COMPANY
DESCRIPTION: NOTICE LETTER
7. 2. . - 0004 DATE: 01/29/88 PAGES: 7
AUTHOR: CHARLES E. FINDLEY/EPA
ADDRESSEE: JIM MC DANIEL/LEADPOINT CONSOLIDATED MINES COMPANY
DESCRIPTION: NOTICE LETTER
7. 2. . - 0005 DATE: 01/29/88 PAGES: 6
AUTHOR: CHARLES E. FINDLEY/EPA
ADDRESSEE: G. PATRICK MORRIS/SILVER MOUNTAIN MINE
DESCRIPTION: NOTICE LETTER
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SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
7.2. . - 0006 DATE: 01/29/88 PAGES: 6
AUTHOR: CHARLES E. FINDLEY/EPA
ADDRESSEE: M. BLAIR OGDEN/SILVER MOUNTAIN MINE
DESCRIPTION: NOTICE LETTER -
7.2. . - 0007 DATE: 01/29/88 PAGES: 6
AUTHOR: CHARLES E. FINDLEY/EPA
ADDRESSEE: J. WAYNE TATMAN/LEADPOINT CONSOLIDATED MINES COMPANY
DESCRIPTION: NOTICE LETTER
SUB-HEAD: 7. 3. . Responses to Requests for Information
7. 3. . - 0001 DATE: 02/12/88 PAGES: 3
AUTHOR: WILLIAM V. COTTRELL/ATTORNEY AT LAW
ADDRESSEE: KEITH ROSE/EPA
DESCRIPTION: RESPONSE LETTER: WRITTEN FOR JAMES MC DANIEL AND HIS WIFE,
CLAIMING NON-RESPONSIBILITY FOR THE SILVER MOUNTAIN MINE SITE.
INCLUDES COPY OF THE DEED
7. 3. . - 0002 DATE: 03/11/88 PAGES: 25
AUTHOR: NORMAN A. LAMB/LEADPOINT CONSOLIDATED MINES COMPANY
ADDRESSEE: KEITH ROSE/EPA
DESCRIPTION: RESPONSE LETTER: INFORMATION ABOUT SILVER MOUNTAIN MINE SITE,
INCLUDING COPIES OF DEED, ARTICLES OF INCORPORATION, TITLE
INSURANCE, ETC.
SUB-HEAD: 7. 4. . Consent for Access Agreements
7. 4. . - 0001 DATES 08/05/88 PAGES: 1
AUTHOR: KEITH A. ROSE/EPA
ADDRESSEE: NORMAN A. LAMB/LEADPOINT CONSOLIDATED MINES COMPANY
DESCRIPTION: LETTER: REQUEST FOR ACCESS TO THE SILVER MOUNTAIN MINE SITE
7. 4. . - 0002 DATE: 08/05/88 PAGES: 1
AUTHOR: KEITH A. ROSE/EPA
ADDRESSEE: JAMES MC DANIEL/LOOMIS, WA 98827
DESCRIPTION: LETTER: REQUEST FOR ACCESS TO THE SILVER MOUNTAIN MINE SITE
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0.-3/27/90 U. S. Environmental Protection Agency, Region 10 Page 21
SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
.7. 4. . - 0003 DATE: 08/10/88 PAGES: 3
AUTHOR: KEITH A. ROSE/EPA
ADDRESSEE: JAMES MC DANIEL/LOOMIS, WA 98827
DESCRIPTION: LETTER: REQUEST FOR ACCESS TO THE SILVER MOUNTAIN MINE SITE.
INCLUDES BLANK, REVISED CONSENT AGREEMENT
7. 4. . - 0004 DATE: 10/17/88 PAGES: 2
AUTHOR: NORMAN LAMB/LEADPOINT CONSOLIDATED MINE COMPANY
ADDRESSEE: FILE/EPA
DESCRIPTION: SIGNED CONSENT FORM FOR ACCESS TO THE SILVER MOUNTAIN MINE SITE
7. 4. . - 0005 DATE: 12/21/88 PAGES: 5
AUTHOR: KEITH A. ROSE/EPA
ADDRESSEE: JAMES W. MC DANIEL/LOOMIS, WA 98837
DESCRIPTION: LETTER: FOLLOW-UP OF TELEPHONE CONVERSATION SEEKING CONSENT FOR
ACCESS TO THE SILVER MOUNTAIN MINE SITE. INCLUDES A 2-PAGE
UNSIGNED CONSENT FORM AND A 2-PAGE SIGNED CONSENT FORM
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(33/27/90 u. S. Environmental Protection Agency, Region 10 Page 22
SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
HEADING: 8.0. . HEALTH ASSESSMENTS
SUB-HEAD: 8. 1. . Correspondence
8. 1. . - 0001 . DATE: 07/28/88 PAGES: 1
AUTHOR: STEPHEN D. VON ALLMEN/U.S. DEPARTMENT OF HEALTH & HUMAN SERVICES
ADDRESSEE: JOEL MULDER/EPA
DESCRIPTION: MEMORANDUM: TRANSMITTAL OF PRELIMINARY HEALTH ASSESSMENT FOR
THE SILVER MOUNTAIN MINE SITE
8. 1. . - 0002 DATE: 01/09/90 PAGES: 2
AUTHOR: Gregory D. Thomas/Agency for Toxic Substances and Disease
Registry
ADDRESSEE: Janet O'Hara/EPA
DESCRIPTION: Letter commenting on draft RI/FS Report
SUB-HEAD: 8. 2. . ATSDR Health Assessments
8. 2. . - 0001 DATE: 07/28/88 PAGES: 4
AUTHOR: STEPHEN D. VON ALLMEN/U.S. DEPARTMENT OF HEALTH AND HUMAN
SERVICES
ADDRESSEE: JOEL MULDER/EPA
DESCRIPTION: LETTER: TRANSMITTAL FOR PRELIMINARY HEALTH ASSESSMENT FOR
SILVER MOUNTAIN MINE SITE. INCLUDES A 3-PAGE PRELIMINARY HEALTH
ASSESSMENT DATED 07/27/88
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SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
HEADING: 9.0. . NATURAL RESOURCE TRUSTEES
SUB-HEAD: 9.1. . Correspondence
9. f. . - 0001 DATE: 08/15/85 PAGES: 1
AUTHOR: Allen D. Klein/U.S. Dept. of the Interior
ADDRESSEE: Robert Kievit/EPA
DESCRIPTION: Letter stating that DOI has no present plans for work at Silver
Mt. Mine and does not anticipate any work in future
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03/27/90 U. S. Environmental Protection Agency, Region 10 Page 24
SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
HEADING: 10. 0. . PUBLIC PARTICIPATION
SUB-HEAD: 10. 1. . Correspondence
10. 1. . - 0001 DATE: 03/29/85 PAGES: 1
AUTHOR: DEBORAH FLOOD/EPA
ADDRESSEE: JAMES MC DANIEL/LOOMIS, WA 98827
DESCRIPTION: LETTER: COMPLETION OF 09/04/84 INVESTIGATION OF THE SILVER
MOUNTAIN MINE SITE
10. 1. . - 0002 DATE: 11/10/87 PAGES: 1
AUTHOR: BERT SANGER/OROVILLE REGIONAL PLANNING ADVISORY COMMISSION
ADDRESSEE: DEBORAH J. YAMAMOTO/EPA
DESCRIPTION: LETTER: TRANSMITTAL OF DRAFT COMPREHENSIVE PLAN FOR THE
OROVILLE REGION. LETTER ALSO ADDRESSED TO JENNIFER RUFFOLOS OF
ICF TECHNOLOGY
10. 1. . - 0003 DATE: 12/18/87 PAGES: 1
AUTHOR: JENNIFER RUFFOLO/ICF TECHNOLOGY INCORPORATED
ADDRESSEE: ELLEN WEAVER/OKANOGAN PUBLIC LIBRAY
DESCRIPTION: LETTER: TRANSMITTAL OF EPA'S -COMMUNITY RELATIONS PLAN FOR THE
SILVER MOUNTAIN MINE SITE
10. 1. . - 0004 DATE: 02/15/90 PAGES: 1
AUTHOR: Jackie Scott/Hazardous Waste Treatment Control
ADDRESSEE: Jeff Webb/EPA
DESCRIPTION: Letter requesting that they be put on the Silver Mt. Mine
mailing list
SUB-HEAD: 10. 2. . Community Relations Plan
10. 2. . - 0001 DATE: 12/01/87 PAGES: 25
AUTHOR: HANS EWOLDSEN/WOODWARD-CLYDE CONSULTANTS
ADDRESSEE: DEBBIE YAMAMOTO AND TIMOTHY BRINCEFIELD/EPA
DESCRIPTION: COMMUNITY RELATIONS PLAN FOR THE SILVER MOUNTAIN MINi; SITE
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03/27/90 U. S. Environmental Protection Agency, Region 10 Page 25
SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
SUB-HEAD: 10. 3. . Fact Sheets and Press Releases
10. 3. . - 0001 DATE: 07/30/85 PAGES: 2
AUTHOR: DAVE MURDOCK, ED IVES/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: /
DESCRIPTION: INFORMATION REGARDING PROGRESS OF NEUTRALIZING HEAP LEACHING
OPERATIONS AT THE SILVER MOUNTAIN MINE SITE
10. 3. . - 0002 DATE: 07/01/87 PAGES: 1
AUTHOR: TIM BRINCEFIELD/EPA
ADDRESSEE: /
DESCRIPTION: NEWS RELEASE CONCERNING PUBLIC ASSISTANCE GRANTS
10. 3. . - 0003 DATE: 09/14/87 ' PAGES: 2
AUTHOR: DEBORAH J. YAMAMOTO/EPA
ADDRESSEE: /
DESCRIPTION: ANNOUNCEMENT OF EPA'S PREPARATION FOR AN IN-DEPTH INVESTIGATION
OF CONTAMINATION AT THE SILVER MOUNTAIN MINE SITE
- 0004 DATE: 10/12/88 PAGES: 3
: KEITH ROSE/EPA
ADDRESSEE: /
DESCRIPTION: ANNOUNCEMENT OF THE BEGINNING OF EPA'S REMEDIAL INVESTIGATION AT
THE SILVER MOUNTAIN MINE SITE
10. 3. . - 0005 DATE: 09/21/89 PAGES: 1
AUTHOR: /
ADDRESSEE: /
DESCRIPTION: BACKGROUND AND STATUS INFORMATION CONCERNING SILVER MOUNTAIN
MINE SITE (DOCUMENT DATE IS APPROXIMATE)
10. 3. . - 0006 DATE: 01/26/90 PAGES: 6
AUTHOR: /EPA
ADDRESSEE: /
DESCRIPTION: SEE 4.2 0001 FOR FACT SHEET INFORMATION ON THE PROPOSED PLAN
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03/27/90 U. S. Environmental Protection Agency, Region 10 Page 26
SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
SUB-HEAD: 10. 4. . Comments and Responses
10. 4. . - 0001 DATE: 01/10/90 PAGES: 1
AUTHOR: Ron Eggers/Bureau of Indian Affairs, Portland Area Office
ADDRESSEE: Janet O'Hara/EPA
DESCRIPTION: Letter commenting on draft RI/FS (See also Section 9.0)
10. 4. . - 0002 DATE: 02/01/90 PAGES: 1
AUTHOR: Melvin E. Kuhlmann/Board of County Commissioners, Okanagan
County
ADDRESSEE: Janet B. O'Hara/EPA
DESCRIPTION: Letter recommending alternative #1, commenting on expense of
remediation
10. 4. . - 0003 DATE: 02/20/90 PAGES: 1
AUTHOR: Janet B. O'Hara/EPA
ADDRESSEE: Administrative Record/EPA
DESCRIPTION: Record of Communication.- phone call received from Michael
Mazetti by Janet O'Hara regarding proposed plan for Silver Mt.
Mine " .
10. 4. . - 0004 DATE: 02/22/90 PAGES: 1
AUTHOR: Janet O'Hara/EPA
ADDRESSEE: Administrative Record/EPA
DESCRIPTION: Record of Communication - phone call from Richard Bayless to
Janet O'Hara regarding proposed plan for Silver Mt. Mine
10. 4. ". - 0005 DATE: 02/22/90 PAGES: 1
AUTHOR: Janet B. O'Hara/EPA
ADDRESSEE: Richard Bayless/
DESCRIPTION: Letter accompanying copies of the RI/FS Study Reports
LO. 4. . - 0006 DATE: 02/26/90 PAGES: 1
AUTHOR: Janet O'Hara/EPA
ADDRESSEE: File/
DESCRIPTION: Handwritten comments on RI/FS Reports received by Janet O'Hara
in a phone communication from Richard Bayless
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03/27/90 U. S. Environmental Protection Agency, Region 10 Page 27
SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
1-0. 4. . - 0007 DATE: 02/26/90 PAGES: 1
AUTHOR: Richard Bayless/
ADDRESSEE: Janet O'Hara/EPA
DESCRIPTION: Letter commenting on RI/FS Reports
10. 4. . - 0008 DATE: 02/28/90 PAGES: 1
AUTHOR: Janet O'Hara/EPA
ADDRESSEE: Mr. McDaniel/
DESCRIPTION: Record of Communication - phone call received by Janet O'Hara
from Mr. McDaniel regarding new well to replace his stock tank
10. 4. . - 0009 DATE: 03/19/90 PAGES: 1
AUTHOR: Gretchen Schmidt/EPA
ADDRESSEE: Michael Mazetti/
DESCRIPTION: Handwritten notes from phone conversation of 3/19/90 -
confirmation of comments and comments on groundwater
10, 4. . - 0010 DATE: 03/19/90 PAGES: 1
AUTHOR: Gretchen Schmidt/EPA •*>
5RESSEE: Richard Bayless/
DESCRIPTION: Handwritten notes from phone conversation of 3/19/90
SUB-HEAD: 10. 5. . Public Notice of Availability of Information,
Notice of Meetings
10. 5. . - 0001 DATE: 01/29/90 PAGES: 1
AUTHOR: /The Wenatchee World
ADDRESSEE: /
DESCRIPTION: Newspaper ad announcing public meeting and public comment period
10. 5. . - 0002 DATE: 02/13/90 PAGES: 1
AUTHOR: /The Wenatchee World
ADDRESSEE: /
DESCRIPTION: Newspaper ad announcing 3 week remainder of public comment
period
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03/27/90 U. S. Env-ironmental Protection Agency, Region 10 Page 28
SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
10. 5. . - 0003 DATE: 02/15/90 PAGES: 1
AUTHOR: /Gazette Tribune
ADDRESSEE: /
DESCRIPTION: Newspaper ad announcing 3 week remainder of public comment
period
10. 5, . - 0004 DATE: 01/25/90 PAGES: 1
AUTHOR: /Gazette Tribune
ADDRESSEE: /
DESCRIPTION: Newspaper ad announcing investigation results and public meeting
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03/27/90 U. S. Environmental Protection Agency, Region 10 Page 29
SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
HEADING: 11. 0. . TECHNICAL SOURCES AND GUIDANCE DOCUMENTS
SUB-HEAD: 11. 1. . Guidances
11. 1. . - 0001 DATE: 03/07/89 PAGES: 3
AUTHOR: /EPA
ADDRESSEE: FILE/EPA
DESCRIPTION: LIST OF EPA GUIDANCES USED IN THE INVESTIGATION AND
DECISION-MAKING PROCESSES FOR THE SILVER MOUNTAIN MINE SITE
SUB-HEAD: 11. 2. . Maps and Photos
11. 2. . - 0001 DATE: 04/01/70 PAGES: 1
AUTHOR: /U.S. GEOLOGICAL SURVEY
ADDRESSEE: /
DESCRIPTION: COPY OF MAP OF OKANOGAN COUNTY. NOTE: ORGINAL IS ONE LARGE
SHEET AND HAD TO BE COPIED ONTO TWO SMALLER SHEETS
11. 2. . - 0002 DATE: 07/24/81 • PAGES: 1
•AUTHOR: /
RESSEE: /
DESCRIPTION: COPY OF PHOTOS OF THE SILVER MOUNTAIN MINE SITE. ACTUAL PHOTOS
LOCATED AT EPA REGION X HEADQUARTERS
11. 2. . - 0003 DATE: 07/01/82 PAGES: 1
AUTHOR: /
ADDRESSEE: /
DESCRIPTION: COPY OF PHOTOS OF THE SILVER MOUNTAIN MINE SITE. ACTUAL PHOTOS
LOCATED AT EPA REGION X HEADQUARTERS
11. 2. . - 0004 DATE: 08/12/86 PAGES: 1
AUTHOR: MIKE GALLAGHER/WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: /
DESCRIPTION: COPY OP PHOTOGRAPHS, PROBABLY OF THE SILVER MOUNTAIN MINE SITE.
ACTUAL PHOTOS LOCATED AT EPA REGION X HEADQUARTERS
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d'3/27/90 U. S. Environmental Protection Agency, Regi-n 10 Page 30
SILVER MOUNTAIN MINE - ADMINISTRATIVE RECORD INDEX
SUB-HEAD: 11. 3. . Technical Sources
11. 3. . - 0001 DATE: 01/01/72 PAGES: 31
AUTHOR: /WASHINGTON STATE DEPARTMENT OF ECOLOGY
ADDRESSEE: /
DESCRIPTION: INVESTIGATIONS; GEOHYDROLOGIC EVALUATION OF ANEAS LAKErHORSE
SPRINGS COULEE, OKANOGAN COUNTY, WASHINGTON
11. 3. . - 0002 DATE: 12/26/86 PAGES: 8
AUTHOR: F. W. DE VRIES/E. J. DU PONT DE NEMOURS & COMPANY
ADDRESSEE: LORI COHEN/EPA
DESCRIPTION: LETTER: TRANSMITTAL OF BULLETIN ON CHLORINATION OF CYANIDE
RESIDUES FROM MINING INDUSTRY OPERATIONS
11. 3. . - 0003 DATES / / PAGES: 3
AUTHOR: /E. J. DU PONT DE NEMOURS & COMPANY
ADDRESSEE: /
DESCRIPTION: TECHNICAL INFORMATION BULLETIN ON- "CHLORINATION OF CYANIDE
RESIDUES FROM MINING INDUSTRY OPERATIONS"
11. 3. . - 0004 DATE: 03/01/84 PAGES: 4
AUTHOR: /DU PONT
ADDRESSEE: /
DESCRIPTION: DATA SHEET ON "KOSTONE B PEROXYGEN COMPOUND" FOR TREATMENT OF
MINING WASTE CONTAINING CYANIDE
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