Formosa Mine Superfund Site Operable Unit 1 Proposed Plan for Public Comment


** CDA Formosa Mine Superfund Site,
wEnH	Operable Unit 1

U.S. EPA, Region 10 - Seattle, Washington

Proposed Plan for
Public Comment

Introduction

You are invited to comment on the U.S. Environmental
Protection Agency (EPA) Formosa Mine Superfund Site
OU1 Proposed Plan (OU1 Proposed Plan) to clean up
surface and subsurface mine materials at the Formosa
Mine Superfund Site (Site) located near Riddle,

Oregon. Please send us your comments by February 5.
2015.

This OU 1 Proposed Plan summarizes cleanup
alternatives that were evaluated for surface and
subsurface mine materials outside of the underground
mine workings at the Site and identifies EPA's
preferred alternative for managing those materials.
Exhibit 1 provides a list of primary topics and sections
that are in the proposed plan.

OU 1 stands for Operable Unit 1 of the Site, which
includes surface and subsurface mine materials, basically
crushed rock. In a separate evaluation, EPA will develop
a Proposed Plan for Operable Unit 2 (OU2), which
includes groundwater, surface water, and mine materials
within the underground mine workings.

It is more effective for EPA to manage the site cleanup
in two pieces for two main reasons. First, it is important
to evaluate how the cleanup of OU 1 affects the Site,
including OU 2. Second, the U.S. Bureau of Land
Management (BLM) will soon be conducting a Non-
Time Critical Removal Action (NTCRA) on the
Formosa 1 Adit, which discharges contaminated water
from the mine into soil and groundwater at the
headwaters of Upper Middle Creek. The removal action
is intended to seal the adit and prevent the unrestricted
flow of contaminated water to Middle Creek. After the
groundwater level has stabilized, the effectiveness of the
NTCRA will be evaluated in the OU2 remedial
investigation.

January 2015
The OU 1 Proposed Plan describes the preferred
alternative - a modified version of Alternative 3
presented and evaluated in the feasibility study. After
considering public input and any new information
presented, EPA may select the preferred cleanup
alternative, modify it, select another, or develop other
alternatives. EPA will document the selected action in a
Record of Decision (ROD).

The BLM, U.S. Geological Survey, and the Oregon
Department of Environmental Quality (ODEQ) are
supporting EPA in the investigation and cleanup, and
will be involved in the selection of the final remedy.

The Superfund Process

Remedial Action Objectives and
Preliminary Remediation Goals

Site Background

Summary of Remedial
Alternatives

Site Characteristics

Comparative Evaluation of
Alternatives

Conceptual Site Model

Description of the Preferred
Alternative

Scope and Role of the Proposed
Plan

Opportunities for Public
Involvement

Summary of OU1 Investigation

Glossary/Useful Terms

Summary of Site Risks

Comments Sheet

To help you better understand this proposed plan,
commonly used terms that appear in BOLD are defined
in the Useful Terms section at the end of the document.

The Superfund Process

The remedial investigation (RI) for OU1, which
characterizes the site conditions, determines the nature
and extent of the surface and subsurface mine material at
the site, and assesses risk to human health and the
environment, was completed in January 2012. The
feasibility study (FS) for OU1, which identifies,
develops, screens, and evaluates remedial alternatives to
address risks to human health and the environment from
mine materials, was completed in January 2013. The
OU2 baseline ecological risk assessment (BERA),
completed in July 2014, documents the surface water
conditions and the effects of mining-influenced water

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on the aquatic environment downstream of the Formosa
Mine.

After finalizing the RI/FS, a preferred alternative is
presented to the public in a proposed plan (this
document). The proposed plan briefly summarizes the
alternatives studied in the detailed analysis phase of the
FS and highlights the key factors that led to identifying
the preferred alternative. The purpose of the proposed
plan is to summarize the RI/FS information and provide
the public with an opportunity to comment on the
preferred alternative, as well as other alternatives that
were considered. The proposed plan provides the public
the opportunity to provide comments to EPA on the
preferred alternative. Following receipt and evaluation of
public comments, including final comment from the
support agencies, EPA will select and document the
remedial action in the ROD. Exhibit 2 outlines the
Superfund process.

Exhibit 2: CERCLA or Superfund Process

COMPREHENSIVE ENVIRONMENTAL
RESPONSE, COMPENSATION AND
LIABILITY ACT (CERCLA) PROCESS

Site Background

c

c
c

Preliminary Assessment/
Site Inspection
(PA/SI)

Remedial Investigation/
Feasibility Study

(RI/FS)	J

V

Proposed Plan/
Remedy Selection

c
c
c

Record of
Decision
(ROD)

V

Remedial Design/
Remedial Action

(RD/RA)	J

Site
Closure

\

J

Current
Phase

The Formosa Mine Superfund Site is an abandoned mine
located in southwest Oregon in Douglas County,
approximately 25 miles south of Roseburg, Oregon, and
7 miles south of Riddle, Oregon.

The Site has been mined by several operators at various
times during the past 80 years. Early exploration began
in 1910, and historic underground mining occurred
during the 1920s and 1930s. After decades with little
activity, new exploration occurred in the 1980s. Modern
mining was conducted by Formosa Exploration Inc.
(FEI) from 1990 to 1993. Production of copper and zinc
were the primary metals, with some gold and silver as a
byproduct.

In 1993, onsite inspections by the Oregon Department of
Geology and Mineral Industries (DOGAMI) revealed
several violations of state permit requirements, and a
subsequent notice of violation was issued to FEI. By
August 1993, DOGAMI had issued a closure notice for
failing to correct the problems identified in the notice of
violation. After mine closure, FEI conducted reclamation
from 1993 to 1994. Despite these reclamation efforts,
preventing a release of chemicals from the surface mine
materials was not successful.

In the late 1990s and early 2000s, ODEQ evaluated
contamination remaining at the Site and replaced the
aged adit water diversion system for the Formosa 1
and Silver Butte 1 adits built by FEI to prevent mining-
influenced water discharge from directly flowing into
surface water. In 2005, citizens petitioned EPA to
consider adding the site to the National Priorities List
(NPL). In 2006, ODEQ completed emergency repairs on
the adit water diversion system after a pipeline joint had
become separated, which resulted in discharges of up to
48 gallons per minute of adit water to the ground surface
near Upper Middle Creek. EPA added the Site to the
NPL in 2007.

EPA conducted two separate emergency response
actions in 2008 and 2009 to maintain and repair the adit
water diversion system. BLM has maintained the adit
water diversion system since 2009. EPA initiated the RI
sampling in October 2009 and presented results in a final
RI report in January 2012. EPA completed the FS the
following year in January 2013.

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Site Characteristics

The Site is located in Douglas County, Oregon on Silver
Butte in the Coast Range of the Klamath Mountains at
an approximate elevation of 3,700 feet. The 24-acre
primary mine disturbance area (PMDA) is at the
headwaters of several watershed drainages and
surrounded by steep mountainous terrain. Two of these
watershed drainages, Upper Middle Creek and South
Fork Middle Creek, have been impacted by the release
of mine materials and mine-related water from the Site.
See Exhibit 3, a foldout map, at the end of this plan.

During mine reclamation by FEI, some of the surface
mine materials were placed within an existing water
storage lagoon, now called the encapsulation mound,
which contains tailings and low-grade ore. Mounded
low-grade ore and a manufactured clay layer with a soil
cap cover the encapsulation mound. The material within
the encapsulation mound is fully saturated. The
encapsulation mound shows signs of overflow and
erosional damage along with a poorly established
vegetative cover, especially on the steep side slopes. The
steep side slopes contain acid generating rocks, which
are impacting groundwater and surface water, and
prevent vegetation from growing on them.

The underground mine and associated underground mine
entrances were constructed over various periods of
operation and are inaccessible because the portals were
sealed (backfilled) as part of reclamation in the 1990s.
Mining-influenced water discharges from one
underground mine entrance, the Formosa 1 Adit.

At locations where the adit water diversion system has
discharged or leaked, soil and groundwater have been
affected by mining-influenced water. The impacted soils
and the encapsulation mound are included as part of
OU1. The adit water discharge is being addressed by
BLM through a NTCRA and is not part of the OU 1
cleanup plan.

Approximately 234,000 cubic yards (CY) of OU1 mine
materials are found within the PMDA. These materials
are predominantly mixed piles of waste rock and
construction rock although some tailings do exist in the
encapsulation mound. Significant quantities of these
wastes are found at all adits, on and beneath road
surfaces, and in other areas disturbed by mining
activities within the PMDA. Most of these materials are
sources of contamination that pose a potential or actual
release of hazardous substances and impact the ground
and surface water quality at the site.

Conceptual Site Model

A conceptual site model was developed for the Site to
show how contaminants enter the environment, how they
are transported, and how humans and animals may be
exposed. See Exhibit 4, a foldout figure, at the end of
this plan. The model provides a framework to assess
risks from contaminants, develop cleanup strategies, and
determine contaminant source control requirements and
methods to address unacceptable risks. The following
information describes elements of the conceptual site
model.

Current and Future Land Use

The site and surrounding land are within federal and
private timber lands designated for timber harvest,
mining, and recreational use (hiking, hunting, fishing).
There are mining claims within the area, the closest
being 1,500 feet northwest of the edge of the northern
boundary of the PMDA. There are no residences within
these lands nor would there be anticipated future
residential development. The closest residence is 3.75
miles, as the crow flies, from the Site. Future land use is
anticipated to remain as timber harvesting, mining, and
recreational use. Designated Critical Habitat for
Northern Spotted Owl is present in the vicinity of the
Formosa Mine, but OU 1 (PMDA) does not fall within
the habitat. There are no other special habitat
designations in this area. As part of the remedy selection
process, EPA has completed notifications of Natural
Resource Trustees, and government consultations were
conducted regarding threatened or endangered species. A
habitat survey for the Northern Spotted Owl was
completed in 2014 by BLM for the Formosa Mine area
and follow up, if needed, will continue in 2015.

How Acid Rock Drainage Is Created

The Formosa Mine exploited a natural deposit of rock
that is enriched in metals and sulfide minerals (e.g.,
pyrite). The mining process brought broken rock
containing ore to the surface. The ore was then crushed
and processed to separate payable metals (e.g., copper),
and waste mine materials were deposited on the surface
and back in the mine workings. These waste mine
materials, especially those that contain sulfide minerals
(e.g., pyrite), generate acid rock drainage when
exposed to water, oxygen, and bacteria. Mining-
influenced water is a term used to describe acid rock
drainage once it is generated and transported from the
source. See Exhibit 4, a foldout figure, at the end of this
plan for a diagram of the acid rock drainage and mining-
influenced water process. The materials left on the

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surface are exposed to rain and snowmelt and create
mining-influenced water, which is very acidic and
contains heavy metals.

OU1 mine materials, such as waste rock, tailings, and
mixtures of waste rock with soils, are source materials
for acid rock drainage generation and metals
contamination. Cleanup of the OU1 mine material
sources is the focus of this proposed plan and is intended
to minimize effects to surface and groundwater at the
site from these sources.

A major waste area called the encapsulation mound is a
previous water containment pond that was used to
dispose and contain tailings and mine waste when the
mine closed. Tailings within the encapsulation mound
are currently contained within a lined pond and
submerged in water, which reduces the tailings exposure
to oxygen and prevents the generation of acid rock
drainage. However, the existing cover is not effective at
preventing precipitation from infiltrating the mine
wastes in the encapsulation mound, and the added water
overflows from the pond and impacts groundwater and
surface water.

How People and Wildlife Are Exposed to
Contamination

Contamination can be carried from the Site by surface
water, groundwater, and erosion. Migration of
contaminants in surface water and groundwater will be
addressed in OU2.

People near Formosa Mine, such as hikers or workers,
may be exposed to OU 1 contamination by dermal
contact (touching), inhaling (breathing), or ingesting
(eating) mine materials.

¦	Dermal (skin) contact (touching) can happen when
chemicals from contaminated dust are absorbed
through the skin.

¦	Incidental ingestion (eating) can happen when
people, especially children, swallow soil that sticks
to their hands during outdoor activities.

¦	Inhalation (breathing) of airborne soil particles can
happen when contaminated dust is suspended in air
by wind or mechanical disturbance.

Wildlife can be exposed by direct contact, ingesting and
inhaling mine materials. Vegetation can uptake
contamination through its root system, and growth can
be inhibited by the lack of suitable soil. Fish and other
aquatic life are exposed from leaching and erosion of

mine materials into streams. Because the PMDA does
not support the types or quantity of plants or wildlife
sufficient for humans to eat, the exposure from eating
vegetation or animals at the Site were not evaluated
because the exposure was deemed insignificant. Aquatic
life exposed to the mine materials (both soils and water)
are adversely impacted.

Scope and Role of the Proposed
Plan

Descriptions of OU1 and OU2

OU 1 includes all surface and subsurface mine materials
deposited outside of the underground mine workings.
These materials are considered a major source of
contamination to surface water and groundwater. The
OU 1 RI determined and documents the nature and extent
of the surface and subsurface mine materials. The OU1
RI report also includes an initial evaluation of surface
water and groundwater, which are components of OU2
to be further evaluated in the OU2 remedial
investigation.

OU2 includes surface water, stream sediment,
groundwater, underground workings, and adit water
drainage. Actions for OU2 are being deferred to evaluate
the impacts of addressing OU 1 and the BLM NTCRA
prior to proposing a cleanup approach for the water-
related components of the Site.

Summary of OU1 Investigation

OU 1 mine materials cover an area of approximately 25
acres and were characterized during the OU 1 RI using a
combination of field and laboratory characterization
methods. Over 900 samples were analyzed by a field
geochemical characterization procedure. Field data, such
as rock composition, paste pH and x-ray fluorescence,
provide additional information to evaluate the
geochemistry and extent of OU1 mine materials. A
subset of these samples was submitted for laboratory
analysis for metals concentrations as well as acid base
accounting and modified synthetic precipitation leaching
procedure (used to determine the ability of the rocks to
generate acidity and leach metals).

This information was used to determine the nature and
extent of the OU1 mine materials. More specifically, the
field and laboratory data were used to:

¦ Characterize the mine materials with respect to
acid rock drainage generation potential and
metal content

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¦ Delineate the extent of OU1 mine materials

¦ Evaluate whether there are potentially
recoverable quantities of precious metals in the
mine materials

¦ Identify acid rock drainage generating rock
outcrops

¦ Determine if OU 1 mine materials pose
unacceptable human health and ecological site
risks

Exhibit 5 summarizes laboratory results for metals
identified in the risk assessment as either a potential
cancer risk to human health or adversely affecting
aquatic resources.

Summary of Site Risks

Human health and ecological risk assessments estimate
the health risks to people and the environment from
exposure to mine materials either now or in the future.
For EPA studies, "risk" is the possible harm to people or
wildlife from exposure to chemicals. Two types of
health risks for people are evaluated: the risks that can
cause cancer and the risks that can cause other health
effects. EPA evaluates only non-cancer risks to wildlife.

EPA uses the results of our risk assessment to determine
if the contamination at a site poses an unacceptable risk
to human health or the environment under CERCLA.
The CERCLA regulations give us a range of risk
numbers to use in deciding if federal cleanup is
necessary. EPA established an "acceptable" extra cancer
risk range, from 1 in 10,000 to 1 in 1,000,000 of
developing cancer from exposure to a site contaminant
over a person's lifetime.

For non-cancer health effects, EPA calculates a hazard
quotient (HQ) or hazard index (HI) for both humans and
wildlife. A hazard index is the sum of the hazard
quotient for several chemicals that have the same or
similar effects. The non-cancer hazard index has a
threshold below which EPA does not expect any non-

cancer health effects. If the HQ or HI is 1 or higher, it is
possible that exposure to site contaminants could be a
risk to humans or wildlife's health.

OU 1 was divided into three exposure areas (EA) based
on anticipated contaminant concentration levels.
Potential human health and ecological risks associated
with exposure to these three areas were evaluated during
the OU1 RI:

¦ EA-1: This area covers the entire PMDA. These
materials are a source of metal contamination, via
leaching from precipitation, to groundwater and
surface water. EA-1 does not pose unacceptable
risks to human health but does result in unacceptable
risk to aquatic ecological receptors as identified in
the OU2 BERA. Cadmium, copper, and zinc are the
chemicals of concern impacting aquatic organisms.
Calculated risks to terrestrial receptors are identified
but considered insignificant because of marginal
habitat for exposure.

¦ EA-2: The soils located immediately downslope of
mine materials in EA-1. This area was selected to
determine if material beyond the PMDA posed
unacceptable risks. EA-2 does not pose unacceptable
risks to human health. Calculated risks to terrestrial
receptors are identified but considered insignificant
because of marginal habitat for exposure.

¦ EA-3: Areas that are visibly affected as a result of
discharge from existing and former adit water
diversion system pipeline and drainfields. Exposure
to arsenic within mine materials at this EA results in
cancer risk greater than the other EAs, but the extra
risk is within EPA's acceptable range. Human
exposure to groundwater is being addressed in OU2.

¦ RI report. Ecological exposure to surface water is
evaluated in the OU2 BERA that documents the
adverse effects of mine materials to aquatic wildlife.
Potential effects to terrestrial wildlife are calculated
in the OU 1 RI and determined to be insignificant
because exposure to metal contamination is limited

by marginal habitat at the Formosa Mine Site.

Exhibit 5: Summary of Chemicals of Concern

Media

Number of Samples
Used in Risk Assessment

Chemical Concentration Range (mg/kg)

Arsenic

Cadmium

Copper

Zinc

Min

Mean

Max

Min

Mean

Max

Min

Mean

Max

Min

Mean

Max

EA-1 - Surface Soil

0.41 J

778 J

0.11

29.2

24.6

771

6,860 J

21.4

741

6,190 J

EA-1 - Subsurface Soil

0.56 J

603

0.1 J

51.2

4.1

917

8,400 J

18 J

1066

12,100 J

EA-2 - Surface Soil

1.03

23.47

0.56

1.76

34.23

163

306

99.03

211

408.33

EA-3 - Surface Soil

247

421

576

0.038J

0.19

0.28

268

362

491

63.7

148

211

Klamath Mountains

0.52

110

140

Notes: 1 milligram per kilogram (mg/kg) is equal to 1 part per million (ppm).

Mean is the arithmetic mean of detected values

* Klamath Mountains regional values from ODEQ Fact Sheet Background Levels of Metals in Soils for Cleanups (March 2013)

Cadmium, Copper, and Zinc are aquatic chemicals of concern from the OU2 BERA.

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Human Health Risks

Human health risks from exposure via inhalation,
ingestion, and direct contact (dermal) to mine materials
were evaluated for current and future workers, visitors,
and offsite residents. The study included evaluation of
exposure to offsite residents to dust caused by wind
dispersion. Estimated cancer risks for all populations,
both current and future, are within or below the EPA
acceptable range of 1 in 10,000 to 1 in 1,000,000 over a
person's lifetime. The maximum carcinogenic risk was 6
in 100,000 to an outdoor worker exposed to arsenic at
EA-3, primarily through ingestion of soils. Current and
future non-cancer risks were all less than a HI of 1, with
the exception of a HI of 2 for future onsite construction
worker at EA-1 from ingesting arsenic contaminated
soils. However, the HI of 2 does not represent an actual
risk because, when segregated by target organ,
individual hazard quotients are all below the acceptable
hazard benchmark of 1.0.

Ecological Terrestrial Risks

The ecological risk assessment identified chemicals of
concern in surface and subsurface soils that occur at
concentrations that may cause adverse effects to
terrestrial wildlife (deer, birds, bugs) and vegetation. The
chemicals of concern are presented below:

¦	EA-1: Arsenic (HQ of 6 for plants), cadmium (HQ
of 14 for mammals), copper (HQ of 36 for birds),
lead (HQ of 15 for birds), mercury (HQ of 33 for
soil invertebrates), nickel (HQ of 5 for plants),
selenium (HQ of 5 for plants), and zinc (HQ of 22
for birds)

¦	EA-2: Cadmium (HQ of 5 for mammals), copper
(HQ of 11 for birds), manganese (HQ of 12 for
plants), and zinc (HQ of 9 for birds)

¦	EA-3: Arsenic (HQ 23 for plants), copper (HQ of 13
for birds), and zinc (HQ of 3 for birds)

Because there is no foraging or nesting habitat within the
PMDA, these risks are considered an overestimation of
actual effects for terrestrial wildlife in the area. EPA
determined cleanup solely to address these
overestimated risks is not warranted. EPA is presenting
them to be consistent with information in the OU1 RI.

Ecological Aquatic Risks

EPA completed the OU2 BERA in July 2014 that
demonstrates the current risks to aquatic wildlife by
releases from the mine. Although these risks cannot be
attributed solely to the OU1 materials (soils), there is a

reasonable expectation that soils are contributing to the
adverse impacts identified in the OU2 BERA.

¦	Middle Creek: Cadmium (HQ of 57 for fish),
copper (HQ of 58 for fish), zinc (HQ of 27 for fish);
the cumulative HQ is 141.

¦	South Fork Middle Creek: Cadmium (HQ of 38
for fish), copper (HQ of 41 for fish), zinc (HQ of 23
for fish); the cumulative HQ is 102.

Remedial Action Objectives and
Preliminary Remediation Goals

Remedial action objectives (RAOs) are identified in
the feasibility study. The RAOs for this remedy are
based principally on protection of ecological receptors
and incidentally will provide protection for anticipated
future use by people, primarily for recreational and
commercial (logging) purposes. These objectives focus
on contaminant source control to prevent further
migration of metal contamination into surface water and
groundwater. However, surface water and groundwater
will be addressed under OU2 and not in this action.

The RAOs are:

1.	Manage mine materials to minimize and control
impacts to ecological receptor populations and
communities, including individuals of threatened
and endangered species from chemical
migration. This objective is a source control
objective and was established to protect
terrestrial and aquatic receptors from mine
materials. This objective will be met by
successful revegetation of terrestrial areas,
improvements of benthic macroinvertebrate
communities in surface water, and reduced metal
concentrations in groundwater. OU2 will fully
address surface and groundwater and provide
cleanup levels for those media.

2.	Minimize the generation of acid rock drainage to
reduce impacts to surface water and
groundwater. This objective was established to
improve conditions in surface water to support
aquatic life habitat. This objective will be met by
monitoring benthic macro invertebrate
communities in surface water and monitoring
the alluvial aquifer for reductions in chemicals
of concerns (COCs) and reduced acidity. OU2
will fully address surface and groundwater and
provide cleanup levels for those media.

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RAO 1 and RAO 2 establish that mine materials will be
managed to protect habitat and wildlife by reducing
contaminated mine wastes from contributing metals to
surface and groundwater via leaching or erosion. To
achieve RAOs, mine materials will be distinguished
from surrounding soil and rock during the OU1 cleanup.
The extent of mine materials and area to be remediated
were estimated during the OU1 RI and FS using
information from drilling and trenching investigations.
This area will be redefined during the design. Managing
the mine materials will include processes such as
removal, capping, isolation barriers, containment, and
treatment.

Preliminary remediation goals (PRGs) are

concentrations below which contaminants do not pose an
unacceptable risk. For cancer risk, EPA has established
an acceptable range of extra risk between 1 in 10,000 to
1 in 1,000,000 over a person's lifetime but prefers the
acceptable extra cancer risk to be 1 in 1,000,000 or less.
The goal of 1 in 1,000,000 for acceptable excess cancer
risk is also consistent with Oregon Statute (ORS)
465.315(l)(b)(A).

As stated in the summary of site risks, cancer risk to
humans from exposure to OU 1 mine materials was
determined to be acceptable.

Although risks to terrestrial wildlife were considered
minimal because there are no foraging opportunities or
habitat within the PMDA, there are calculated risks for
terrestrial exposure that show if, or when, the area
became habitat, there would be risk. Risks to aquatic
wildlife in Middle Creek and South Fork Middle Creek
have been evaluated for OU2 and have been determined
to have adverse effects. Hazard quotients exceed 100 in
Middle Creek and South Fork Middle Creek. This is
demonstrated by fish and benthic macroinvertebrate
surveys conducted for OU2 and exceedances of water
quality standards. There are severe impacts on fish and
benthic macroinvertebrates in streams adjacent and
downgradient of the Site. OU1 mine materials are a
significant source of contamination contributing to
aquatic impacts. Reducing the contribution of metals
from OU 1 mine materials to surface waters will reduce
the impacts to aquatic wildlife. EPA will monitor
benthic macroinvertebrate communities and for the
presence of fish in streams to assess the impacts of
remedial actions at OU1. Monitoring levels of COCs in
surface waters will also be conducted to assess
improvement.

Summary of Remedial
Alternatives

EPA identified a range of potential cleanup methods and
technologies that protect human health and the
environment and used them to develop remedial
alternatives. The alternatives initially screened during
the FS consist of varying combinations of those
technologies to create remedy components (Exhibit 6).

The alternatives mainly differ in the use of various
remedy components such as:

¦	Are the mine materials covered in place or
excavated for disposal elsewhere?

¦	Are the tailings within the encapsulation mound
submerged in place either with or without additives
introduced for treatment, or are they excavated and
treated for disposal elsewhere?

¦	Are excavated mine materials disposed of within a
new facility constructed within the PMDA, a new
facility constructed outside the PMDA but still on
site, or at an existing offsite location?

Exhibit 6: Remedy Components Used in Remedial
Alternatives

Remedy Component Used

Remedial Alternative

1

2

3

4

5

6

Five-year site reviews and monitoring

•

•

•

•

•

•

Institutional controls, community
awareness activities, access controls













Partial in-place covering of mine
materials



•

•







Containment of tailings within
encapsulation mound by submerging in
place



•









Treatment of tailings within
encapsulation mound by submerging in
place with the introduction of additives





•







Excavation and treatment of tailings
outside of encapsulation mound







•

•

•

Excavation and consolidation/disposal of
mine materials within PMDA



•

•

•

•



Excavation and consolidation/disposal of
mine materials outside PMDA





•

•

•

•

Excavation and consolidation/disposal of
mine materials at existing permitted
facility









•



Shaded alternative was eliminated from consideration prior to detailed
analysis in FS.

Six alternatives, shown in Exhibit 6, were evaluated in
the FS. Because Alternative 5 resulted in high costs and
low implementability, it was screened out in the FS and
is not discussed further in the OU1 Proposed Plan.

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All alternatives utilize the same methods for identifying
materials requiring remediation. Specific qualitative and
quantitative criteria and field methods, such as mineral
composition of the rock, paste pH, and x-ray
fluorescence, were developed and used during the OU1
RI to delineate the extent of mine materials from
surrounding soil and rock. The depth of the
contaminated mine materials across this area were
estimated during the OU1 RI using information gathered
from drilling and trenching investigations. This
information was used in the OU1 FS to determine the
extent of mine materials requiring cleanup to meet
RAOs. The field methods presented in the OU1 RI to
define mine materials can be used as necessary during
cleanup to determine that contaminated mine materials
have been fully identified and adequately addressed to
meet RAOs. Materials adjacent to stream headwaters
and waste rock dumps, which are unstable and at
significant depth, would be prioritized for excavation
and subsequent containment.

Remedial Alternatives Retained for
Detailed Analysis

With the exception of Alternative 1, which is required by
CERCLA, the other alternatives are expected to be
protective of human health and the environment by
meeting the RAOs. The retained alternatives are also
expected to comply with state and federal applicable or
relevant and appropriate requirements (ARARs) as
required by Superfund law. Final ARARs will be
determined in the OU1 ROD.

Description of Alternatives
Alternative 1 - No Further Action
Estimated Capital Costs: $0

Estimated Total Operation and Maintenance (O&M)
Costs (30 years): $0

Estimated Total Periodic Costs (30 years):

$300,000

Estimated Total Present Value Costs: $115,000
Estimated Construction Timeframe: None
Estimated Time to Achieve RAOs: Will never
comply with RAOs

Alternative 1 would leave mine materials at the Site
(approximately 234,000 CY) in their current condition,
and no additional cleanup action would be performed.
Regulations governing the Superfund program require
that the "no action" alternative be evaluated to establish
an environmental baseline for comparison with other
alternatives.

Five-year site reviews would be performed as required
by law to evaluate whether the remedy is protective.
Monitoring would only be performed as necessary to
support the five-year site reviews. This alternative is not
protective of human health or the environment and does
not comply with ARARs and the RAOs.

Alternative 2 - In-Place Containment, Continued
Submergence of Tailings within Encapsulation
Mound, and Limited Excavation/Disposal of Mine
Materials at Proposed Facility within PMDA

Estimated Capital Costs: $5,075,000
Estimated Total O&M Costs (30 years): $750,000
Estimated Total Periodic Costs (30 years): $330,000
Estimated Total Present Value Costs: $5,553,000
Estimated Construction Timeframe: 1 Year
Estimated Time to Achieve RAOs: Upon completion
of remedial action

Alternative 2 includes in-place containment of the
majority of highly acid-generating mine materials
adjacent to creek headwaters and a combination of
various covers to reduce the generation of acid rock
drainage, including the encapsulation mound. The
targeted mine materials for limited excavation would be
from the east waste rock dumps adjacent to the
encapsulation mound, illegal dump area, Formosa 1 Adit
and Formosa 3 Adit waste rock dumps, mine materials
along the upper side slopes of the encapsulation mound,
and adit water diversion affected soils in EA-3. The
specific qualitative and quantitative criteria and field
methods described under the "Remedial Action
Objectives and Remediation Goals" section would be
used to identify contaminated mine materials to be
covered and/or removed within these areas; a total of
234,00 CY are estimated to be addressed under this
alternative. Approximately 72,000 CY would be
excavated and placed at a proposed disposal facility
within the PMDA located at the encapsulation mound,
which would be capped with a manufactured cover layer
and vegetation layer. A combination of manufactured
cover layers, pavement covers, and exposure barriers
would be implemented for remaining mine materials not
targeted for excavation to reduce generation of acid rock
drainage. Pavement covers would be constructed over
mine materials within road alignments. Drainage would
be provided to minimize infiltration and erosion.

Tailings within the encapsulation mound are currently
contained within a lined pond and submerged in water,
which reduces the tailings exposure to oxygen and
prevents the generation of acid rock drainage. However,

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the existing cover is not effective at preventing
precipitation from infiltrating the mine wastes in the
encapsulation mound. The encapsulation mound with the
added mine materials would be capped with a
manufactured cover layer while leaving the
encapsulation mound contents submerged in place.

Excavated areas or areas disturbed during completion of
the remedy would be regraded and seeded or covered in
rocks/gravel. Roads removed during excavation would
be re-constructed using clean native materials and road
gravel.

Additional provisions of this alternative include:

¦	Administrative controls, consisting of institutional
controls, community awareness activities, and access
controls (fences and posted warnings), would protect
covered areas and the disposal facility located at the
encapsulation mound, as well as provide awareness
of risks from potential exposure to mine materials.

¦	Long-term operation and maintenance (O&M)
would preserve the integrity of covers and the
proposed disposal facility within the PMDA. The
State of Oregon will be responsible for long-term
O&M once the remedy is operational and functional.

¦	Monitoring surface water and five-year site reviews
would be performed to determine whether the
remedy remains protective for human health and the
environment.

Alternative 3 - Limited In-Place Containment,
Chemically Reduced Submergence of Tailings within
Encapsulation Mound, and Excavation/Disposal of
Mine Materials at Proposed Facilities within and
outside PMDA

Estimated Capital Costs: $8,878,000
Estimated Total O&M Costs (30 years): $553,000
Estimated Total Periodic Costs (30 years): $330,000
Estimated Total Present Value Costs: $9,275,000
Estimated Construction Timeframe: 2 Years
Estimated Time to Achieve RAOs: Upon completion
of remedial action

Alternative 3 protects human health and the environment
by excavating all OU1 mine materials except the
encapsulation mound. The specific qualitative and
quantitative criteria and field methods described under
the "Remedial Action Objectives and Remediation
Goals" section would be used to identify contaminated
mine materials to be covered and/or removed within
these areas; a total of 234,000 CY are estimated to be

addressed under this alternative. Approximately 194,000
CY of mine materials would be excavated and capped
for this alternative. The remaining 40,000 CY would be
managed in place by either capping or capping and water
diversion.

The removed materials would be placed in two disposal
facilities, one within and one outside the PMDA. The
proposed disposal facility within the PMDA would be
constructed as described for Alternative 2.

The proposed disposal facility outside of the PMDA
would be engineered and constructed to limit migration
of contaminants. This disposal facility would cover the
mine materials and control surface water run-on/runoff
Excavated areas or areas disturbed during completion of
the remedy work would be reclaimed as described in
Alternative 2.

Treatment of tailings within the encapsulation mound
would be completed by leaving the tailings submerged in
place and introducing additives, such as molasses, to
initiate and enhance in-place biological treatment. The
additives would increase the ability of natural bacteria to
transform minerals into a less leachable form, thus,
immobilizing them within the encapsulation mound.

Administrative controls, maintenance, monitoring, and
five-year site reviews are the same as those described for
Alternative 2. Additional access controls, such as
fencing, and monitoring of covers and other facility
features, would be implemented as required at the
proposed disposal facility outside of the PMDA.

Alternative 4 - Excavation,

Stabilization/Solidification of Tailings, and Disposal
of Mine Materials at Proposed Facilities within and
outside PMDA

Estimated Capital Costs: $10,010,000
Estimated Total O&M Costs (30 years): $553,000
Estimated Total Periodic Costs (30 years): $330,000
Estimated Total Present Value Costs: $10,407,000
Estimated Construction Timeframe: 2 Years
Estimated Time to Achieve RAOs: Upon completion
of remedial action

Alternative 4 excavates and places all OU 1 mine
materials, including encapsulation mound tailings, at
disposal facilities within and outside the PMDA. The
proposed disposal facilities within and outside of the
PMDA would be constructed as described for
Alternative 3. The specific qualitative and quantitative
criteria and field methods described under the "Remedial

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Action Objectives and Remediation Goals" section
would be used to identify contaminated mine materials
to be covered and/or removed within these areas; a total
of 234,000 CY are estimated to be addressed under this
alternative. Tailings removed from the encapsulation
mound would be dewatered and treated with an additive,
such as Portland cement, to bind the contaminants and
reduce further release of contamination. Excavated areas
or areas disturbed during completion of the remedy work
would be restored as described in Alternative 2.
Administrative controls, maintenance, monitoring, and
five-year site reviews would be the same as described for
Alternative 3.

Alternative 6 - Excavation,

Stabilization/Solidification of Tailings, and Disposal
of Mine Materials at Proposed Facility outside
PMDA

Estimated Capital Costs: $10,092,000
Estimated Total O&M Costs (30 years): $553,000
Estimated Total Periodic Costs (30 years): $330,000
Estimated Total Present Value Costs: $10,489,000
Estimated Construction Timeframe: 3 Years
Estimated Time to Achieve RAOs: Upon completion
of remedial action

Alternatives 4 and 6 are similar except all excavated
materials in Alternative 6 will be placed in a proposed
disposal facility outside the PMDA. The proposed
disposal facility outside of the PMDA would be
engineered and constructed to limit migration of
contaminants. This disposal facility would cover the
mine materials and control surface water run-on/runoff
Excavated areas or areas disturbed during completion of
the remedy work would be reclaimed as described in
Alternative 2. Administrative controls, maintenance,
monitoring, and five-year site reviews would be
implemented as described for Alternative 3.

Comparative Evaluation of
Alternatives

The federal Superfund law requires that alternatives be
evaluated using the nine criteria described in Exhibit 7.
These criteria are grouped into three categories:
threshold, balancing, and modifying.

The preferred alternative (except No Further Action)
must meet the two threshold criteria. The five balancing
criteria weigh tradeoffs and are used to compare the
alternatives; a low rating on one balancing criterion can
be compensated by a high rating on another. The two

modifying criteria consider public and state concerns and
are not completed until after the public comment period.

Exhibit 7: Evaluation Criteria for Remedial Alternatives

Evaluation Criteria

THRESHOLD CRITERIA

Overall protection
of human health
and the
environment

Determines whether an alternative
eliminates, reduces, or controls threats to
public health and the environment through
institutional controls, access controls,
containment, treatment, or other remedial
actions.

Compliance with
ARARs

Evaluates whether the alternative meets
federal and state environmental statutes,
regulations, and other requirements that
are ARARs or whether a waiver is justified.

BALANCING CRITERIA

Long-term
effectiveness and
permanence

Considers the ability of an alternative to
maintain protection of human health and
the environment over time.

Reduction of
toxicity, mobility,
or volume through
treatment

Evaluates an alternative's use of treatment
to reduce (a) the harmful effects of principal
contaminants, (b) the contaminant's ability
to move in the environment, and (c) the
amount of contamination remaining after
remedy implementation.

Short-term
effectiveness

Considers the length of time needed to
implement an alternative and the risk the
alternative poses to workers, residents, and
the environment during implementation.

Implementability

Considers the technical and administrative
feasibility of implementing the alternative,
including factors such as the availability of
materials and services.

Cost

Includes estimated capital and annual
operations and maintenance costs as well as
present value cost. Present value cost is the
total cost of an alternative over time in
terms of today's dollar value. Cost estimates
are expected to be accurate within a range
of +50 to -30 percent of actual cost.

MODIFYING
CRITERIA

State/Support
agency acceptance

Considers whether the state agrees with
EPA's analyses and recommendations as
described in the RI/FS and proposed plan.

Community
acceptance

Considers whether the local community
agrees with EPA's analyses and preferred
alternative. Comments received on the
proposed plan are an important indicator of
community acceptance.

The FS provides a detailed description of how the
comparison of alternatives was made, but a general
summary is included in this proposed plan.

Overall Protection of Human Health and
the Environment

All of the alternatives, except Alternative 1, protect
human health and the environment. Since Alternative 1
is not protective, it will not be discussed further.

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Alternative 2 protects the environment by installing in-
place covers for the majority of mine materials to reduce
generation or acid rock drainage, with excavation and
disposal of targeted mine materials at a proposed facility
within the PMDA. Tailings would continue to be
submerged within the covered encapsulation mound to
limit acid rock drainage generation. Covering provides
an exposure barrier to the mine materials and reduces the
generation of acid rock drainage. However, mine
materials still remain beneath covers across a large
extent of OU1 and could pose risks if the covers are
compromised.

Alternatives 3, 4, and 6 protect human health and the
environment by excavating and disposing of mine
materials at proposed disposal facilities. Long-term
protection of human health and the environment is more
certain than leaving mine materials in place. Alternatives
3, 4, and 6 would provide better protection than
Alternative 2 because the disposal facility outside the
PMDA could be sited, engineered, and constructed to
limit the migration of contaminants. Alternative 3 treats
submerged tailings using additives, such as molasses, to
initiate in-place biological treatment, and Alternatives 4
and 6 treat tailings using solidification/stabilization prior
to disposal to reduce further acid rock generation.
However, the volume of tailings is small relative to the
overall volume of mine materials.

Compliance with ARARs

Three key ARARs significantly affected EPA's
evaluation of the remedial alternatives listed above:

1.	The Oregon Hazardous Substance Remedial
Action Rules (OAR 340-122-0115(2)(a)) define
"acceptable risk level for human exposure to
individual carcinogens" as a lifetime excess
cancer risk of less than or equal to 1 per
1,000,000 (1 E-06) for an individual at an upper-
bound exposure.

2.	The Oregon Hazardous Substance Remedial
Action Rules (OAR 340-122-0040(2)(c)) affect
the development of the PRG for arsenic.

Because of this rule, the determination of a PRG
for arsenic is not solely based on the
determination of risk but also whether that risk
represents concentrations above background
concentrations for the site.

3. The Oregon Revised Statute (ORS 459) governs
the management of solid wastes at land disposal
sites other than municipal solid waste landfills.
Substantive requirements would be applicable
for any management and disposal of mine
materials in proposed facilities within or outside
of the PMDA.

In general, Alternatives 2, 3, 4, and 6 are expected to
comply with the chemical-, location-, and action-specific
ARARs identified in the FS. No key ARARs
significantly differ between these alternatives.

Long-term Effectiveness and Permanence

Alternative 2 provides long-term effectiveness and
permanence primarily through in-place covering of mine
materials with limited removal and disposal of targeted
materials at a proposed disposal facility within the
PMDA. Tailings would continue to be submerged within
the covered encapsulation mound to limit acid rock
drainage generation. Proper construction of the covers
would limit direct exposure to mine materials by people,
reduce infiltration of water, and prevent acid rock
drainage generation and mining-influenced water
migration, but the materials covered and left in place
could pose risks if the covers ever deteriorate. Because
mine materials would remain in place on steep slopes,
long-term effectiveness and permanence is not as certain
for alternatives that excavate contaminated mine
materials and dispose of them in proposed facilities
constructed with shallower slopes. The use of stability
measures, such as retaining walls, may be needed to
maintain slope stability.

Alternative 3 provides long-term effectiveness and
permanence primarily through removal and disposal at
proposed disposal facilities within and outside the
PMDA. Disposal of mine materials at a location outside
the PMDA increases effectiveness because it would be
constructed with shallower slopes than are currently
present at the site and would be engineered and
constructed to limit the migration of contaminants.
Alternative 3 also treats submerged tailings using
additives to initiate in-place biological treatment and
further reduce acid rock drainage generation. Alternative
4 is similar to Alternative 3 but includes removal and
treatment (stabilization/solidification) of tailings outside
of the encapsulation mound, which increases the long-
term effectiveness and permanence of the remedy
compared to alternatives without additional treatment.

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Alternative 6 is similar to Alternative 4 with the
exception that all mine materials would be disposed of at
a proposed disposal facility outside the PMDA. The
proposed disposal outside the PMDA could be designed
to be fully contained and capable of collecting leachate
for treatment and sited at a more environmentally
favorable location than the PMDA to enhance
permanence. The use of one disposal facility outside of
the PMDA, coupled with the removal of all mine
materials from the PMDA, would also increase long-
term effectiveness by decreasing the environmental
footprint (measured by surface area) of mine materials as
compared to Alternative 4, making Alternative 6 the best
alternative for long-term effectiveness and permanence.

All alternatives, with the exception of Alternative 6,
include disposing of mine materials at a proposed
disposal facility within the PMDA located at the
encapsulation mound. Long-term stability of this
location is not as certain as proposed facilities
constructed with shallower slopes at other locations.

Reduction of Toxicity, Mobility, or Volume
of Contaminants through Treatment

Alternatives 2, 3, 4, and 6 reduce toxicity, mobility, and
volume through treatment of the tailings within the
encapsulation mound. The tailings are a relatively small
percentage of the volume of mine materials within OU1.
In Alternative 2, tailings would continue to be
submerged within the encapsulation mound under the
new cover of the disposal facility within the PMDA,
which reduces acid rock drainage generation. Alternative
3 would increase treatment of tailings through the
introduction of additives to the tailings within the
encapsulation mound to initiate in place biological
treatment and further reduce acid rock drainage
generation. These tailings would again be covered by the
new cover of the disposal facility within the PMDA.

Under Alternatives 4 and 6, tailings would be treated by
stabilization/solidification prior to disposal. Treatment
would provide additional protection to groundwater from
generation of acid rock drainage and migration of
mining-influenced water from the tailings after disposal
within a proposed facility outside of the PMDA. Water
removed from the tailings would also be treated.

Short-term Effectiveness

Alternative 2 addresses short-term risks to workers, the
community, and the environment primarily through in-
place containment of mine materials. Limited excavation
of mine materials and disposal at the proposed facility

within the PMDA would require some disturbance of
mine materials. While limited excavation of mine
materials and construction of covers would involve
surface disturbance of mine materials, short-term risks to
workers would be prevented through the use of safety
measures, such as personal protective equipment, dust
suppression, and other best management practices. This
alternative has the shortest construction duration
compared to the other alternatives. However, trucks used
to haul offsite materials, such as cover materials, as well
as reclamation within the PMDA, increase short-term
risks to the community. Transport and placement of
borrow materials have potential environmental impacts
from equipment emissions and disturbance of borrow
locations. These factors affect overall short-term
effectiveness.

Alternatives 3, 4, and 6 involve excavation of mine
materials, which creates a greater short-term disturbance,
and the construction of the proposed facility outside of
the PMDA will increase the duration of construction.
Hauling of mine materials to the proposed facility
outside of the PMDA and additional construction
materials to build the facility outside the PMDA increase
truck traffic and related risks to workers and the
community compared to Alternative 2. Potential
environmental impacts include increased equipment
emissions and disturbance of borrow location outside of
PMDA. However the lower volume of borrow developed
for covers and transported to the proposed disposal
facilities for these alternatives as compared to
Alternative 2 somewhat offsets the additional short-term
risks from the transport and disposal of mine materials
outside of the PMDA.

Alternatives 4 and 6 also increase short-term risks to
workers and the community through the additional step
of contact with the removed tailings within the
encapsulation mound (a relatively small amount of OU 1
mine materials) and truck traffic to bring in the
stabilization agent for the solidification/stabilization
treatment of the tailings.

Alternative 6 requires the most movement of and
exposure to mine materials because this alternative
involves transport of 234,000 cubic yards of material
from the mine site to a disposal facility yet to be
constructed outside of the PMDA. This would require
nearly 11,000 trucks to travel on local roads. This
significant increase of short-term risks to workers and
the community results in lower short-term effectiveness
than the other alternatives.

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Implementability

Alternative 2 includes limited removal and disposal of
targeted mine materials at a proposed facility within the
PMDA. Construction of covers over the majority of in-
place mine materials is a common practice and results in
the shortest construction duration. Excavation of mine
materials and placement of covers on steep slopes may
require use of specialty equipment and practices to
ensure worker safety. Alternatives 3 and 4 include the
removal, transport, and disposal of larger volumes of
mine materials, which is a common practice, but results
in a longer construction period with more complicated
coordination and uses more equipment to complete than
Alternative 2. Alternative 6 includes transport of the
largest quantities of mine materials for disposal at a
proposed facility outside of the PMDA and has the
longest construction period.

Alternative 2 uses disposal at a proposed facility entirely
within the PMDA, which limits the need for
administrative coordination with other agencies or
selecting a suitable disposal facility location.

Alternatives 3, 4, and 6 use disposal at a proposed
facility outside the PMDA, which increases
administrative coordination and difficulty in selecting a
suitable disposal facility location. Alternatives 3 and 4
also require the use of disposal at two separate proposed
disposal facility locations.

Alternatives 2, 3, 4, and 6 require importing outside
construction resources such as asphalt (Alternative 2),
Portland cement for solidification/stabilization
(Alternatives 4 and 6), soil amendments, and cover
materials. Uncontaminated borrow sources within or
outside the PMDA would need to be identified.
Excavation and covering of materials on steep slopes
may require special equipment and worker safety
practices as well as engineering measures to ensure
stability. Maintaining institutional and access controls
are not anticipated to be difficult. It is routine activity to
maintain signage and fencing.

The introduction of additives, such as molasses to
initiate in-place biological treatment in Alternative 3,
would require the use of specialized operators,
equipment, and material. Additional testing would be
required to assess performance of
stabilization/solidification practices in Alternatives 4 and
6 before full-scale application to maximize treatment.
The amount of space needed to apply the
stabilization/solidification material (Portland cement)
and application of stabilization/solidification material

would make this treatment approach more difficult to
implement.

Alternative 2 would be the easiest to implement, and
Alternatives 3, 4, and 6 have relatively similar
implementability concerns due to increasing
construction complexity and difficulties in selecting a
disposal facility location outside of the PMDA.

Cost

The cost from lowest to highest is Alternative 2, 3, 4,
and 6, respectively. The estimated present value cost of
Alternative 2 (primarily in-place covers) is
approximately half that of the most expensive
alternative, Alternative 6 (full excavation and disposal).
Differences in present value costs between alternatives
are primarily due to the capital costs for each alternative.

Alternatives 3 and 4 differ in cost primarily because of
the increase of mine materials volume excavated,
transported, and disposed of outside of the PMDA in
Alternative 4. The method of treatment for the tailings
was also a factor in the difference between costs.
Alternative 3 uses submergence of tailings with the
addition of additives, such as molasses, to initiate in-
place biological treatment, and Alternative 4 removes
the tailings and treats via stabilization/solidification.
Stabilization/solidification is a more costly approach to
treatment than in-place biological treatment

Alternatives 4 and 6 are very close in cost. The increase
in excavation and transportation costs for the additional
mine material volume in Alternative 6 is offset by the
lack of cost to build a second disposal facility (within the
PMDA) as in Alternative 4.

State Acceptance

The State of Oregon (through ODEQ) has been
consulted frequently throughout the remedial
investigation, feasibility study process, and development
of the preferred alternative. State acceptance will be
evaluated after public comment period ends and will be
described in the ROD for the site.

Community Acceptance

Community acceptance of the preferred alternative will
be evaluated after the public comment period ends and
will be described in the ROD.

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Description of the Preferred
Alternative

The preferred alternative selected was Alternative 3, as
presented in the feasibility study, with minor
modifications as described here. The preferred
alternative described in this plan may be modified based
on new information or public comments. Consistent with
the National Oil and Hazardous Substances Pollution
Contingency Plan (NCP). the remedial alternatives are
developed sufficiently for evaluation against the
threshold and balancing criteria and presented to the
public. Additional design work and data collection will
be required after selection of an alternative to refine the
approach to implement the cleanup action.

The title of the preferred alternative (modified
Alternative 3) is Capping of Mine Materials,
Continued Submergence of Tailings within
Encapsulation Mound, and Excavation/Disposal of
Targeted Mine Materials at Proposed Facilities inside
PMDA and outside PMDA on FEI Property. The
preferred alternative would protect human health and the
environment through the combination of targeted
removals and in-place covering of OU1 mine materials.

Modifications from Alternative 3 for the preferred
alternative include:

¦	The proposed disposal facility outside of the PMDA
will be constructed on former FEI property close to
the PMDA, possibly combining with the proposed
disposal facility within the PMDA, to reduce
impacts to the public and simplify the disposal
facility location selection process.

¦	Continued submergence of tailings within
encapsulation mound without additional treatment as
described in Alternative 2.

¦	Excavation and consolidation of mine materials that
directly affect the headwaters near the site or that are
unstable on their current slope.

¦	Capping of mine materials not in close proximity to
headwaters near the site and are stable on their
current slopes.

Mine materials that are not in close proximity to
impacted surface water, which have a relatively higher
potential for long-term slope stability and a lower risk of
contaminant release, will be capped in place. A
combination of manufactured cover layers, pavement
covers, and rock or vegetative covers would be used as

the cover materials depending upon specific waste area
characteristics. For example, roadbeds would receive a
paved cover system and drainage controls to divert water
from the underlying mine wastes.

Mine materials, which are stable on slopes but cannot be
successfully capped with vegetative covers or
manufactured covers, would receive a cover of inert rock
to maintain slope stability and prevent erosion.

Similarly, waste areas on slopes that have been
excavated would receive a cover of inert rock.

The encapsulation mound and new repository would be
capped with a manufactured cover to prevent infiltration
of precipitation. Manufactured cover layers would be
constructed on a limited basis in areas of mine materials
outside proposed disposal facilities where conditions
warrant (i.e., level areas and shallow slopes). Pavement
covers would be constructed over mine materials within
existing road alignments. Both pavement and
manufactured cover layers are capable of preventing acid
rock drainage generation.

Mine materials targeted for excavation and disposal
directly impact the headwaters of the South Fork Middle
Creek and Upper Middle Creek and/or affect the stability
of the encapsulation mound. Identification of mine
materials would be completed as described for
Alternative 2. Approximately 139,000 CY of mine
materials would be excavated for this alternative. This is
55,000 CY less than the targeted removal volume in the
original Alternative 3 described in the FS. The non-
excavated materials will be graded and or capped to limit
infiltration and generation of acid rock drainage. The
tailings would continue to be submerged within the
encapsulation mound without additives as described in
Alternative 2 since this approach has continued to be
effective at limiting acid rock drainage generation.

The proposed disposal facilities within and outside the
PMDA would largely be constructed as described in
Alternative 3, with a few modifications. The overall
profile of the disposal facility within the PMDA would
be lowered to enhance stability and resistance to erosion
from storm events, and the encapsulation mound area
would be targeted for excavations to increase stability of
the remaining mine materials on slopes.

The proposed disposal facility outside of the PMDA
would be constructed on former FEI land in close
proximity or adjacent to the PMDA. Construction of
collection and storage facilities for leachate generated

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from the proposed disposal facility outside of the PMDA
(assumed to be leachate collection piping and an acid
rock drainage storage tank), if needed, would be
considered during design depending on the location-
specific conditions. Treatment facilities would be
addressed as part of acid rock drainage management and
treatment conducted as part of OU2.

The location and extent of the proposed disposal
facilities within and outside of the PMDA shown on
Exhibit 3 are conceptual. Evaluation during remedial
design would determine if the facilities would be
developed separately or combined for containment of
excavated mine materials. Combining the facilities may
result in a smaller environmental footprint and may have
related benefits of reducing overall construction costs
and O&M costs for a smaller footprint.

Excavated areas or areas disturbed during completion of
the remedy work would be restored as described in
Alternative 3. Administrative controls, maintenance,
monitoring, and five-year site reviews would be
implemented as described for Alternative 3.

A summary of how the alternative compares against the nine
criteria is presented in Exhibit 8.

A summary of alternative costs is presented in Exhibit 9.

The preferred alternative was selected over other

alternatives because:

1.	It protects human health and the environment and
complies with ARARs.

2.	There are less significant impacts to the community
and environment from truck traffic since disposal of
mine materials is limited to the boundaries of former
FEI property. This would reduce fuel costs and
related engine emissions for transportation and
minimize transportation-related safety issues.

3.	The long-term effectiveness is greater because the
disposal facility constructed within the PMDA is
more stable as a result of improving the slopes and
lowering the profile exposed to adverse weather.

4.	The use of former FEI property lessens
administrative activities such as acquiring property
and meeting substantive permit requirements during
selection and design of a disposal facility outside of
the PMDA.

5.	It simplifies development of borrow sources for
proposed facility construction, cover, and
reclamation materials due to use of former FEI
property.

6.	Location of the disposal facility within or close
proximity to the PMDA would simplify future O&M
activities because the facility would be adjacent to
mine workings (addressed with OU2) that may also
require O&M.

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Opportunities for Public Involvement

Public Meeting

EPA will hold a public meeting to explain the OU1 Proposed Plan,
the preferred cleanup alternative for the Formosa Mine Superfund
Site, and all the alternatives presented in the feasibility study. We
encourage you to attend. It's a great opportunity to learn more
about the details.

Formosa Mine Superfund Site
Public Comment Meeting

January 20,2015
6:30 to 9:00 pm
Riddle City Council Chambers
647 East First St.

Riddle, OR. 97469

If you like, you can provide your
comment orally at the public meeting,
and the meeting stenographer will record
it.

Contacts

If you have questions or need additional
information, please contact the following
representatives:

Christopher Cora, Project Manager
US EPA Region 10
1200 Sixth Ave., Suite 900,
Mailstop ECL -115
Seattle, WA 98101
(206)553-1478
cora.christopher@epa. gov

Judy Smith, Community Outreach
US EPA, Region 10, Oregon Operations
805 SW Broadway, Suite 500
Portland, OR 97205

(503) 326-6994
smith, judyf/cpa. gov

Greg Aitken, Project Manager
Oregon DEQ
165 East 7th Street #100
Eugene, OR 97401
(541)687-7361
aitken. greg@dea. state, or.us

Written Comments and Extensions

The public comment period runs from January 6 to February 5,
2015. During that time, you may submit a comment in writing by
mail, email, or at the public meeting. The mailing address for
written comments is:

Christopher Cora
US EPA Region 10
1200 Sixth Ave., Suite 900,

Mailstop ECL-115
Seattle, WA 98101
E-mail: cora.christopher@epa. gov

EPA will respond in writing to all significant public comments
in a responsiveness summary. The responsiveness summary will
be included as part of the record of decision for OU1.

Documents

Documents that provide the basis for
selecting the final cleanup alternative will
be available for viewing at:

Riddle Public Library

637 First St.

Riddle, OR 97469-0033
and

US EPA Region 10 Superfund Records
Center

1200 6th Ave., 7th Floor
Seattle, WA 98101
(206) 553-4494*

* Please call for the most current
information on office hours.

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Glossary/Useful Terms

The following terms used in the Formosa Mine Superfund Site OU1 Proposed Plan are defined here to aid your
understanding of this document:

• Access controls - Physical methods to discourage
people from entering the site, including fencing
and posting warning and informational signs.

• Acid rock drainage - A chemical process by
which contaminants are released from rocks due to
exposure to water and air. Outflow of acidic (low
pH) water from abandoned metal mines caused by
oxidation of rock sources.

• Adit - Underground mine entrances.

• Adit water diversion system - A system at the
Formosa Mine Site that collects mining-
influenced water discharging from the Formosa 1
and Silver Butte 1 adits and diverts it from entering
surface water.

• Administrative controls - A combination of
institutional controls, community awareness
activities, and access controls. Land use controls
are generally used to protect remedy components,
restrict access and use of contaminated areas, and
provide awareness of risks from potential exposure
to mine materials.

• Applicable or relevant and appropriate
requirements (ARARs) - Any state or federal
statutes or regulations that pertain to the protection
of human health and the environment in addressing
specific conditions (chemical, action, and location)
or use of a particular cleanup technology at a
Superfund site.

• Capital cost - The initial expenditure required to
build or install the remedial action.

• Comprehensive Environmental Response,
Compensation, and Liability Act of 1980
(CERCLA) - A federal law enacted to clean up
abandoned sites where there is a release or threat
of release of a hazardous substance into the
environment.

• Community awareness activities - Includes
community education and outreach programs used
to inform the community of potential risks
associated with exposure to mine materials and
how to prevent future risks.

• Chemical of concern (COCs) - Chemicals that
pose unacceptable risk to humans, wildlife, or
plants. For OU1, arsenic, cadmium, copper and
zinc pose unacceptable risk to aquatic wildlife.

• Cap - An engineered cover that acts a barrier to
prevent downward migration of water to mine
materials or prevents exposure of humans and
wildlife to mine materials. A cover is generally
constructed in layers, such as pavement,
manufactured materials, rock or soil, and may be
covered with vegetation after it is completed.

• Encapsulation mound - An area at the Formosa
Mine Site where acid-generating tailings and ore
were enclosed in a lined and covered repository.

• Exposure - The path from sources of pollutants to
people and animals.

• Feasibility study (FS) - A required process at a
Superfund site to develop, screen, and evaluate
various alternatives being considered for selection
of a remedial action.

• Five-year site review - A periodic review required
by CERCLA to make sure that the site cleanup
continues to protect human health and the
environment when contaminants remain on site.

• Institutional controls - Non engineered legal
methods that help to discourage human contact
with mine materials and encourage safe land uses
and/or the integrity of a remedy. Institutional
controls may be governmental controls (like
zoning or permits), proprietary controls (like
covenants, conditions, and restrictions), and
informational devices (like deed notices).

• Mine materials - Media (such as waste rock,
tailings, and soil) remaining after mining that
contain contaminants that pose risks to humans and
the environment.

• Mine workings - Tunnels or shafts related to the
extraction of ore.

• Mining - Activities related to the extraction of ore
from the earth that contains valuable minerals such
as metals.

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•	Mining-influenced water - Water affected by
mining activities that is potentially toxic to the
environment, regardless of water pH.

•	Monitoring - Information collected to help gauge
the effectiveness of a cleanup action. Monitoring
can be either by data collection or visual
inspection.

•	National Oil and Hazardous Substances
Pollution Contingency Plan (NCP) -Federal
regulations for responding to oil spills and
hazardous substance releases.

•	National Priorities List (NPL) - EPA's list of the
most serious uncontrolled or abandoned hazardous
waste sites identified for possible long-term
remedial action under Superfund. A site must be
on the NPL to receive money for remedial action.

•	Operable unit (OU) - Term for each of a number
of separate activities undertaken as part of a
Superfund site cleanup. An OU can be based on
geography, media, or other characteristics that are
used to manage the Superfund process.

•	Operation and maintenance (O&M) - Activities
conducted after a Superfund cleanup action is
completed to ensure that the action is effective for
the long term.

•	O&M cost - The post-construction cost required to
ensure the effectiveness of the remedial action.

•	Periodic cost - Cost that occurs only once every
few years, such as 5-year site reviews.

•	Preliminary Remediation Goals (PRGs) - The
average concentration below which a contaminant
does not pose an unacceptable risk.

•	Present value - The present value cost represents
the amount of money that, if invested in the initial
year of the remedial action at a given rate, would
provide the funds required to make future
payments to cover all costs associated with the
remedial action over its planned life. The present
value analysis was performed on remedial
alternatives using a 7 percent discount (interest)
rate over the period of evaluation for each
alternative.

•	Primary Mine Disturbance Area (PMDA) -
Portion of OU 1 that has been impacted by surface
deposition of mine materials because of mining-
related activities.

•	Record of Decision (ROD) - A formal decision
document that describes the selected remedy for
CERCLA sites. Remedial action objectives
(RAOs) - Specific goals for protecting human
health and the environment developed by
evaluating ARARs and the results of the remedial
investigation, including the risk assessment.

•	Remedial investigation (RI) - A required study at
Superfund sites that determines the nature and
extent of contamination and assesses the risk to
human health and the environment.

•	Superfund - The common name for the
Comprehensive Environmental Response,
Compensation and Liability Act of 1980
(CERCLA), a federal law designed to clean up
sites contaminated with hazardous materials.

•	Tailings - Ground up mine materials left over after
the valuable metals have been extracted out of the
ore.

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Exhibit 8. Key Considerations from Analysis of Preferred Alternative (Modified Alternative 3)

Evaluation Criteria

Overall protection of human health and
the environment

Acid generating mine materials at headwaters of creek areas, on steep
or unstable slopes, and other targeted areas would be excavated and
disposed of at proposed facilities within and outside the PMDA on FEI
property. This would eliminate exposure of mine materials to the
environment and significantly reduce migration of contamination for
mine materials.

Overburden currently on top of the encapsulation mound would be
removed and regraded to stabilize the proposed facility within the
PMDA.

Tailings stored within the former water and tailings storage pond would
continue to remain submerged under the new cover system at the
encapsulation mound. Submergence would continue to mitigate acid
rock drainage generation.

Compliance with ARARs

The preferred alternative would be compliant with location-, action-,
and chemical-specific ARARs.

Long-term effectiveness and permanence

Location of the proposed disposal facility or facilities on FEI property is
on and/or adjacent to the PMDA, which simplifies future O&M activities.
Excavation and disposal of mine materials at proposed facilities within
and outside PMDA would provide significant reduction of acid rock
drainage generation and migration.

The tailings would continue to be submerged within the encapsulation
mound under the new cover of the disposal facility within the PMDA.
The use of stability measures, such as geocells, retaining walls, or
buttressing, will be used as needed to maintain stability due to
excavation, disposal, and in-place covering of mine materials on steep
slopes. Geotechnical monitoring will be used as needed to be conducted
after construction.

Reduction of toxicity, mobility, or volume
through treatment

There is no reduction of toxicity, mobility, or volume through treatment
for mine materials.

Short-term effectiveness

Location on FEI property would keep disposal activities within a localized
area near the PMDA rather than over a larger area, thus, reducing
traffic.

There would be minor impacts to the community under this alternative
as truck traffic required for disposal of mine materials at the proposed
facility outside of the PMDA on former FEI property would be contained
within the boundaries of former FEI property. There could also be minor
impacts to the environment during the implementation of the remedial
action due to the use of heavy construction and hauling equipment and
import of borrow, cover, and reclamation materials from within and
outside the PMDA.

Use of fuel efficient and low emission equipment, careful selection and
reclamation of borrow areas, and relatively short haul distance of
excavated mine materials to disposal facility outside PMDA will be used,
to the extent practicable, during design and remedial action to reduce
environmental impacts.

The duration of remedial construction and implementation would be
similar or less than Alternative 3 given the shorter distance to the
disposal facility outside of the PMDA and smaller volume of material
removed.

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Exhi

}it 8. Key Considerations from Analysis of Preferred Alternative (Modified Alternative 3) (continued)

Implementability

Cost

Location on FEI property lessens administrative impacts during selection
and design of a disposal facility outside of the PMDA.

Construction of the proposed disposal facility or facilities will consider
the stability of steep slopes.

Transportation of excavated mine and borrow materials would be a

relatively short distance and would reduce fuel usage.

Suitable rock and soil materials for proposed facility construction, cover

construction, and reclamation would be required from within and

outside the PMDA. The use of materials available within the former FEI

property would simplify the development of suitable material at other

locations.

The estimated present value cost of the preferred alternative is assumed
to be similar in magnitude to Alternative 3 ($9,275,000).

<
0£

0£
U
UJ

O
O

State/Support agency acceptance

The State of Oregon (through ODEQ) has been consulted frequently
throughout the remedial investigation, feasibility study process, and
development of the preferred alternative. State acceptance will be
evaluated after public comment period ends and will be described in the
ROD for the site.

Community acceptance

Community acceptance of the preferred alternative will be evaluated
after the public comment period ends and will be described in the ROD.

Exhibit 9. Summary of Alternative Costs

Alternative

Est. Total Capital
Costs

Est. Total
O&M Costs
(first 30 years)

Est. Total
Periodic Costs
(first 30 years)

Est. Construction
Timeframe

Est. Total
Alternative Cost
(Present Value)

o
-co-

$300,000

None

$115,000

$5,075,000

$750,000

$330,000

1 Year

$5,553,000

$8,878,000

$553,000

$330,000

2 Years

$9,275,000

$10,010,000

$553,000

$330,000

2 Years

$10,407,000

$10,092,000

$553,000

$330,000

3 Years

$10,489,000

Note: The preferred alternative is a modification of Alternative 3 and is expected to have a similar magnitude of cost.
Definitions of cost terms can be found in the Glossary/Useful Terms list.

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Silver Butte Adit
Waste Rojck Dump

Formosa 1 Adit

Silver Butte.VAdit

Encapsulation
Mound

Legend

# Adit
)( Culverts

	 Adit Water Diversion System

	 Roads

~	Primary Mine Disturbance Area (EA-1)

~	Downslope Soils (EA-2)

Adit Drainage Affected Soil (EA-3)

,	Approximate Extent of

L«_ j Proposed Facility within PMDA

Approximate Extent
i	i of Proposed Facility Outside PMDA

Former Water and Tailings Storage Pond

~	Sections 26 Section Number

Note(s):

1. The location and extent of the proposed
disposal facilities within and outside of the
PMDA are conceptual Evaluation during
remedial design would determine if the facilities
would be developed separately or combined for
containment of excavated mine materials.
2 "jr^" = "Exposure Area"

250

500

1,000
I Feet

Geographic Data Standards:

Projected Coordinate System:	N

NAD 1983 State Plane Oregon FIPS Zone 3602

Data Sources:

Bureau of Land Management:
2001 Hydrography

2005 Township, Range, and Topography
2010 ESRI World Imagery Service Layer

A

*rAi

%



Exhibit 3

Site Map

Formosa Mine Superfund Site
Douglas County, Oregon

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Surface Discharge
Conveyed Into Adit
Water Diversion System

ARD Generating
Mine Materials

10 Inch Opening into Adit

V

Water
Infiltration

Oxygen
Ingress

& Inch Concrete Cap

Subsurface MIW Discharge
-7A	to Perched Alluvial Aquifer

Max Groundwater
Elevation 3263 ft.

Natural Colluvium /

Alluvium in MB Tributary

Perennial Discharge
of MIW from
Formosa 1 Adit

V

¦ Perennial MIW Transport
in Perched Alluvial Aquifer

Detail of Formosa 1 Adit Area

Active ARD Generation
and Accumulation of
Secondary Acidity -
Periodic Flushing

Partial Diversion of
MIW to Adit Water -4
Diversion System

MIW Transport
Via Overland Flow

MIW Transport Via
Perched Aliuvial Aquifer

MIW Discharge
to Surface-Active
Precipitation of
Metals in Sediments
Elevation Range
3064 ft. - 2502 ft.

Resistant Bedrock Outcrop
at Raymond Bear Falls
Truncates Upper Middle
Creek Alluvial Aquifer
Elevation 2776 ft.

Downstream Migration —
of MIW and Contamination
of Sediments, Surface
Water, and Groundwater

Middle Creek
Watershed

Exhibit 4a

Schematic Diagram of Contaminant

Generation, Transport, and Fate

Formosa 1 Adit Area and Upper Middle Creek
Formosa Mine Superfund Site, Douglas County, Oregon

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V

Water
Infiltration

I

Oxygen
Ingress

v

V

Former Water Pond
Backfilled with ARD
Generating Mine Materials

West Encapsulation
Mound Waste
Rock Dump

Encapsulation
Mound

Active ARD Generation and
Accumulation of Secondary
Acidity - Periodic Flushing

East Encapsulation Mound Waste Rock Dump

MIW Infiltration to Groundwater

MIW Transport Via Overland Flow

Middle Creek Watershed
(Area of MF-Subdrainage)

South Fork
Middle Creek
Watershed

ARD Generating Mine Materials

MIW Transport Via
Perched Alluvial Aquifer

Potential Discharge of Bedrock
Groundwater to Surface Water

Seep of MIW
at Road Cut
(SFA5 @ 3026 ft.)

Exhibit 4b

Schematic Diagram of Contaminant

Generation, Transport, and Fate

Encapsulation Mound and South Fork Middle Creek
Formosa Mine Superfund Site, Douglas County, Oregon

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COMMENT SHEET

Use this space to write your comments.

The EPA encourages you to submit written comments on the Formosa Mine Superfund Site OU1 Proposed Plan. You
can use the form below to send written comments, or bring your comments to the public meeting. If you have
questions about how to comment, please contact the EPA's Project Manager, Mr. Christopher Cora.

This form is provided for your convenience. Please mail this form or bring your comments to the public meeting. You
may use additional sheets as needed. Comments by email can be sent to Cora.Christopher@epa.gov. Comments by
mail must be postmarked no later than Thursday, February 5, 2015, to the address shown below:

Christopher Cora, Project Manager
US EPA Region 10
1200 Sixth Ave., Suite 900,

Mailstop ECL - 115
Seattle, WA 98101

Comment Submitted by:
Address:

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Return Address

affix postage here

Mr. Christopher Cora
US EPA Region 10
1200 Sixth Ave., Suite 900,
Mailstop ECL - 115
Seattle, WA 98101

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