Final Record of Decision for the Ballard Mine Caribou County, Idaho.


FINAL

Record of
Decision
for the
Ballard
Mine

Caribou	Coun

August 2019

Prepared by

U.S. Environmental

Protection Agency, Region 10

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RECORD OF DECISION
FOR

THE BALLARD MINE
CARIBOU COUNTY, IDAHO
FINAL

Part 1
Declaration

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Part 1 • Declaration

Site Name and Location

To facilitate site management, the Site has been divided into two operable units: the area of the Ballard
Mine Site (Operable Unit 1 or 0U1), and the Ballard Shop Area (0U2). Only 0U1 is being addressed in
this Record of Decision (ROD).

Statement of Basis and Purpose

This decision document presents EPA's Selected Remedy for 0U1 of the Ballard Mine Site. The remedy
described in this ROD was chosen in accordance with the Comprehensive Environmental Response,
Compensation, and Liability Act of 1980 (CERCLA) and, to the extent practicable, the National Oil and
Hazardous Substance Pollution Contingency Plan (NCP). The decision is based on the Administrative
Record for the Site. This document is issued by EPA Region 10, the lead agency. The Idaho Department
of Environmental Quality (DEQ), as a support agency, provided assistance during development of the
remedial investigation (RI) and feasibility study (FS). The State of Idaho concurs with the Selected
Remedy.

Assessment of Site

The response action selected in this ROD is necessary to protect the public health or welfare or the
environment from actual or threatened releases of hazardous substances, pollutants, or contaminants
into the environment. Such a release or threat of release may present an imminent and substantial
endangerment to public health, welfare, or the environment.

Description of Selected Remedy

This ROD selects a final remedy for the Ballard Mine Site (OU1). The Selected Remedy for the Site is a
combination of engineered source controls, treatment technologies, and other approaches and
components that will work together to achieve remedial action objectives (RAOs). A key element of the
combined remedy is controlling the release of contaminants from waste rock dumps and mine pits by
backfilling pits; consolidating, grading, and shaping waste rock; and constructing an approximately
5- to 6-foot-thick engineered cover system over more than 500 acres. Isolating the waste rock by
constructing the cover system addresses direct contact risks with contaminants and vegetative uptake,
reduces deep infiltration of water, and minimizes release of contaminants to surface water and
groundwater.

Permeable reactive barriers, sediment control best management practices (BMPs), and engineered
wetland treatment cells will be used to treat runoff, residual seepage, and contaminated shallow
groundwater. These other elements will work in conjunction with the cover system to address impacts
to surface water, shallow groundwater and sediment, and may be phased out in the longer term if no
longer needed. It is expected that groundwater cleanup levels will be attained at the completion of the
remedial action (RA). If low levels of groundwater contamination remain, monitored natural
attenuation (MNA) of groundwater will be used as a 'polishing step' or a final stage of treatment,
relying on natural processes of dilution and dispersion to further reduce contaminant concentrations.
Contaminated sediment in intermittent streams on the margins of the site will be addressed by
controlling sources of contamination to the streams and monitored natural recovery (MNR).

The combined remedy includes several other elements to evaluate and optimize the performance of
source controls and treatment technologies and to ensure protectiveness. An adaptive management

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Part 1 • Declaration

approach will be used to guide implementation of source controls and treatment technologies until
RAOs are achieved. The combined remedy also includes institutional controls (ICs), operation and
maintenance (O&M) requirements, and long-term effectiveness monitoring requirements.

The Selected Remedy recognizes that P4 Production LLC (P4) intends to recover phosphate ore
concurrent with implementation of the remedy. Information collected during site characterization
activities confirmed that about 4 million tons of phosphate ore remain at the Site, both exposed at the
surface and in the bottoms and sidewalls of existing mine pits. Although potential ore recovery is not
part of the remedy, EPA is selecting a remedy that allows for and is compatible with remining. EPA
assumes that remining will happen for purposes of designing and implementing the remedy and for
estimating the cost.

The amount of ore P4 intends to recover is an approximation based on currently available information
and may change as more information becomes available or economic considerations change. Specific
plans for possible remining would be accommodated during the remedial design phase of the project.
The key elements of the design (identified in the bullets below) would be implemented even if plans
for remining change (for example, if there is limited or no remining performed) although such
implementation and/or cost of the remedy might change. The potential remining activities are
expected to generate additional waste rock and overburden material for backfill of mine pits and
construction of the evapotranspiration (ET) cover. In addition, the earthworks associated with
potential remining (such as excavation and placement of fill, grading and shaping waste dumps, and
backfilled pits) will also advance remediation efforts, thereby reducing the costs associated with
remediation. No ore processing would occur at the Site. Instead, ore would be transported to a
processing facility about 10 miles away.

For ore to be recovered during implementation of the remedy, P4 would need to acquire a federal
mineral lease and seek approval from the Bureau of Land Management of a plan for ore recovery. If P4
does not obtain legal authority to remine, or if P4 does less (starts and then stops) or more remining
than currently anticipated, then the design, implementation schedule and costs of the remedy would
differ, but the key elements of the remedy (listed below) would remain the same. Such changes arising
from remining are not anticipated to require changes to the Selected Remedy itself.

The Selected Remedy includes the following key components:

• Engineered Cover System. Mine pits will be backfilled regardless of the performed amount of
remining, but the extent of pit backfill and the final shape of remediated surfaces may differ
depending on its scope. At a minimum, mine pits will be backfilled to cover exposed ore beds and
shale units of the Phosphoria Formation. Waste rock dumps and backfilled pits will be graded and
shaped to ensure geotechnical stability and to promote runoff. An ET cover system, approximately
5 to 6 feet thick, will be constructed over the more than 500 acres of the Site where wastes are left
in place.

• Permeable Reactive Barriers (PRBs). A series of PRBs will be constructed downgradient of the
source areas to intercept and treat contaminated shallow alluvial groundwater. The PRBs may be
phased out in the future if no longer needed, as source controls become effective.

• Wetland Treatment Cells. A series of semi-passive bioreactors will be constructed on Site
margins to treat contaminated residual seeps and springs. These treatment units will be designed
and operated to remove selenium and other contaminants. Some of the treatment units may be
phased out in the future as the engineered cover system reduces the infiltration of water and the
flow discharging at seeps and springs is reduced or eliminated.

• Groundwater MNA. The primary strategy to restore groundwater is the implementation of source
controls (cover system) and treatment (PRBs and wetland treatment cells). It is expected that
these technologies will greatly reduce flow and may eliminate many contaminated seeps and
springs. These components are also expected to greatly reduce contaminant concentrations in

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Part 1 • Declaration

groundwater. If necessary, MNA will be used as a polishing step to further reduce contaminant
concentrations to achieve RAOs.

• Stormwater and Sediment Control BMPs. During the construction phase, sediment ponds and
other sediment control BMPs would be constructed to control release of sediment to downstream
waterbodies. BMPs will be specified during remedial design (in a stormwater pollution prevention
plan) and will include a broad suite of techniques to control erosion, such as use of compaction,
construction sequencing, straw mulch and wattles, silt fences, and other techniques.

• Sediment MNR. Intermittent and ephemeral stream sediment and riparian soil will be addressed
through a combination of sediment traps and basins in headwater drainage locations and MNR for
downstream reaches. Over time, natural processes of dilution and dispersion are expected to
result in natural recovery of these impacted areas and attainment of RAOs. Long-term monitoring
(LTM) and a sitewide adaptive management planning approach will be used to evaluate progress
and trigger follow-up actions as needed.

• Adaptive Management. A sitewide adaptive management plan will be developed and
implemented to evaluate critical elements of the remedy and make revisions (such as design
modifications or operational changes) that are within the scope of the Selected Remedy.

• O&M. An O&M plan will be developed and implemented to ensure the integrity, proper functioning
and performance of all engineering controls (for example, ET cover system) and treatment
facilities (for example, PRBs, wetland treatment cells, and BMPs).

• LTM. Monitoring will be conducted to assess the effectiveness of various components of the
remedy and progress toward achieving RAOs.

• ICs and Access Restrictions. ICs will be applied to protect the remedy and prevent human
exposure by limiting land and resource use. In addition, fences, gates and, physical barriers will be
built to prevent damage to engineered and vegetated components of the remedy.

Remedial construction will be implemented in phases, aligning with the anticipated recovery of
phosphate ore from different areas of the Site. The overall timeline for construction is estimated to be
6 to 8 years. The cost of implementing the Selected Remedy, expressed as the present value of future
costs, is approximately $41 million.

A final remedy for the Ballard Shop Area of the Site (0U2) is not being selected in this ROD. P4 intends
to continue the use of the Ballard Shop Area, which covers approximately 10 acres on the
southwestern edge of the Site, to support remedy implementation and nearby mining operations. A
focused FS and Proposed Plan will be developed for this small portion of the Site and a final remedy
selected in a separate ROD. This ROD, however, selects ICs and fencing as interim actions at the Ballard
Shop Area to limit potential exposure to construction and mine workers until a final remedy is selected
and implemented. ICs will include restrictions on the use of this area, including its groundwater.

Statutory Determinations

The Selected Remedy is protective of human health and the environment. It complies with all
federal and state requirements that are applicable or relevant and appropriate to the RA. It is cost-
effective and uses permanent solutions and alternative treatment technologies or resource recovery
technologies to the maximum extent practicable.

The remedy does not satisfy the statutory preference for treatment as a principal element of the
remedy. The NCP establishes an expectation that treatment will be used to address the principal
threats posed by a site whenever practicable. Principal threat waste is defined in EPA guidance as
highly toxic or highly mobile source materials that generally cannot be contained in a reliable manner
or that present a significant risk should exposure occur. No principal threat wastes have been

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Part 1 • Declaration

identified at the Site. Source materials at the Site are waste rock located in the mine dumps and
backfilled pits. The waste rock is present in large volumes, which makes treatment impracticable. The
source materials, however, can be reliably contained by using engineering controls.

Because the Selected Remedy will result in hazardous substance, pollutants, or contaminants
remaining onsite above levels that would allow for unlimited use and unrestricted exposure, a
statutory review of the Site will be conducted within 5 years of initiation of the RA to ensure the
remedy is, or will be, protective of human health and the environment.

ROD Data Certification Checklist

The following information is included in the Decision Summary (Part 2) of this ROD. Additional
information can be found in the Administrative Record for this Site.

•	Chemicals of concern and their concentrations (Section 5 - Summary of Site Characteristics)

•	Baseline risks represented by the chemicals of concern (Section 7 - Summary of Risks)

•	Cleanup levels established for the chemicals of concern and the basis for these levels (Section 8 -
Remedial Action Objectives)

•	How source materials constituting principal threats are addressed (Section 11 - Principal Threat
Wastes)

•	Current and reasonably anticipated future land use assumptions and current and potential future
beneficial uses of groundwater used in the baseline risk assessment and ROD (Section 6 - Current
and Potential Future Land and Resource Use)

•	Potential land and groundwater use that will be available at the Site because of the Selected
Remedy (Section 12 - Selected Remedy)

•	Estimated capital, annual O&M, and total present value (worth) costs, discount rate, and the
number of years over which the remedy cost estimates are projected (Section 12 - Selected
Remedy)

•	Key factors that led to selecting the remedy (Section 12 - Selected Remedy)

4

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Authorizing Signature

r .	g/Ay/w

R, David Allnutt	/	Date /

Acting Division Director

Superfund and Emergency Management Division
EPA Region 10

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Part 1 • Declaration

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RECORD OF DECISION
FOR

THE BALLARD MINE
CARIBOU COUNTY, IDAHO

Part 2
Decision Summary

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Table of Contents

Part 1 Declaration

Site Name and Location	1

Statement of Basis and Purpose	1

Assessment of Site	1

Description of Selected Remedy	1

Statutory Determinations	3

ROD Data Certification Checklist	4

Authorizing Signature	5

Part 2 Decision Summary

Acronyms	v

Section 1 - Site Name, Location, and Description	1-1

1.1	Introduction	1-1

1.2	Site Name and Location	1-1

1.3	General Description of Site	1-1

Section 2 - Site History and Enforcement Activities	2-1

2.1	Site History	2-1

2.2	Enforcement and Investigation Activities	2-1

Section 3 - Community and Tribal Participation	3-1

3.1	Overview	3-1

3.2	Tribal Engagement	3-1

3.3	Community Engagement	3-1

Local Repository	3-1

Email and Postal Updates	3-2

Paid Notices and Media Coverage	3-2

Project Web Site	3-2

Proposed Plan and Public Meeting	3-2

Section 4 - Scope and Role of the Operable Unit	4-1

4.1	Response Action for Ballard Mine Site (0U1)	4-1

4.2	Response Action for the Ballard Shop Area (0U2)	4-1

Section 5 - Summary of Site Characteristics	5-1

5.1	Site Overview	5-1

5.1.1	Surface Features and Size	5-1

5.1.2	Climate	5-3

5.1.3	Geology	5-3

5.1.4	Surface Water	5-7

5.1.5	Groundwater	5-10

5.1.6	Surface Water/Groundwater Interactions	5-14

5.2	Conceptual Site Model	5-14

5.2.1	Sources of Contamination	5-17

5.2.2	Affected Media	5-17

Section 6 - Current and Potential Future Land and Resource Use	6-1

6.1	Land Use	6-1

6.1.1	Current Land Use	6-1

6.1.2	Reasonably Anticipated Future Land Uses	6-1

6.2	Surface Water and Groundwater Use	6-1

Section 7 - Summary of Risks	7-1

7.1 Human Health Risk	7-1

7.1.1 Chemicals of Potential Concern	7-1

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7.1.2	Exposure Assessment	7-1

7.1.3	Toxicity Assessment	7-2

7.1.4	Risk Characterization	7-3

7.1.5	Uncertainty Analysis	7-6

7.1.6	Summary of Human Health Risk Assessment	7-7

7.2	Ecological Risk	7-8

7.2.1	Chemicals of Potential Ecological Concern	7-8

7.2.2	Exposure Assessment	7-8

7.2.3	Effects Assessment	7-11

7.2.4	Risk Characterization	7-11

7.2.5	Summary of Ecological Risk Assessments	7-14

7.3	Livestock Risk	7-15

7.4	Basis of Action	7-16

Section 8 - Remedial Action Objectives and Cleanup Levels	8-1

8.1	Remedial Action Objectives	8-1

8.1.1	Waste Rock and Upland Soils	8-1

8.1.2	Stream Sediments and Riparian Overbank Deposits	8-1

8.1.3	Vegetation	8-1

8.1.4	Surface Water	8-1

8.1.5	Groundwater	8-2

8.2	Cleanup Levels	8-2

Section 9 - Description of Alternatives	9-1

9.1	Development of Alternatives	9-1

9.2	Elements Common to All Alternatives	9-2

9.2.1	Institutional Controls	9-2

9.2.2	Operation and Maintenance	9-3

9.2.3	Long-term Monitoring	9-3

9.2.4	Adaptive Management Planning	9-3

9.2.5	KeyARARs	9-3

9.3	Description of Alternatives for each Medium	9-4

9.3.1	No Action Alternative	9-4

9.3.2	Upland Soil and Waste Rock (USWR) Alternatives	9-5

9.3.3	Surface Water (SW) Alternatives	9-9

9.3.4	Stream Channel Sediment and Riparian Soil (S/RS) Alternatives	9-10

9.3.5	Groundwater (GW) Alternatives	9-12

Section 10 - Comparative Analysis of Alternatives	10-1

10.1	Overall Protection of Human Health and the Environment (Threshold Criterion)	10-2

10.2	ARARs (Threshold Criterion)	10-3

10.3	Long-term Effectiveness and Permanence (Balancing Criterion)	10-4

10.4	Reduction of Toxicity, Mobility or Volume of Contaminants through Treatment (Balancing
Criterion)	10-5

10.5	Short-term Effectiveness (Balancing Criterion)	10-5

10.6	Implementability (Balancing Criterion)	10-6

10.7	Cost (Balancing Criterion)	10-7

10.8	State Acceptance (Modifying Criterion)	10-8

10.9	Community Acceptance (Modifying Criterion)	10-8

Section 11 - Principal Threat Wastes	11-1

Section 12 - Selected Remedy	12-1

12.1	Rationale for the Selected Remedy	12-2

12.2	Description of the Selected Remedy	12-3

12.2.1	Waste Rock Consolidation and Engineered Cover System	12-3

12.2.2	Permeable Reactive Barriers	12-7

12.2.3	Wetland Treatment (Bioreactor) Cells	12-10

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12.2.4	Monitored Natural Attenuation of Groundwater	12-12

12.2.5	Stormwater and Sediment Control Best Management Practices	12-12

12.2.6	Monitored Natural Recovery for Sediment	12-12

12.2.7	Adaptive Management	12-13

12.2.8	Operation and Maintenance	12-13

12.2.9	Long-term Monitoring	12-14

12.2.10	Institutional Controls and Access Restrictions	12-14

12.2.11	Green Remediation	12-15

12.3 Estimated Cost of the Remedy	12-15

Section 13 - Statutory Determinations	13-1

13.1	Protection of Human Health and the Environment	13-1

13.2	Compliance with ARARs	13-2

13.3	Cost Effectiveness	13-3

13.4	Use of Permanent Solutions and Alternative Treatment (or Resource Recovery)
Technologies to the Maximum Extent Practicable	13-3

13.5	Preference of Treatment as a Principal Element	13-4

13.6	Five-Year reviews	13-4

Section 14 - Documentation of Significant Changes	14-1

Section 15 - References	15-1

Part 3 Responsiveness Summary

Overview of Responsiveness Summary	1

Comments and Responses	1

List of Tables

5-1 Data Summary for Contaminants of Concern in Soil, Sediment, and Vegetation	5-19

5-2 Data Summary for Contaminants of Concern in Surface Water and Groundwater	5-20

8-1 Surface Water and Groundwater Cleanup Levels	8-2

8-2	Soil and Sediment Cleanup Levels	8-3

9-1	Alternatives Considered During Initial Screening and During Detailed Evaluation	9-1

9-2 Costs and Construction Timeframe, Alternative 1: No Action	9-5

9-3 USWR4, Estimated Cost and Construction Timeframe	9-7

9-4 USWR6, Estimated Cost and Construction Timeframe	9-8

9-5 USWR7, Estimated Cost and Construction Timeframe	9-9

9-6 SW 2, Estimated Cost and Construction Timeframe	9-10

9-7 SW 3, Estimated Cost and Construction Timeframe	9-10

9-8 S/RS 3, Estimated Cost and Construction Timeframe	9-11

9-9 S/RS 4, Estimated Cost and Construction Timeframe	9-12

9-10 GW 2, Estimated Cost and Construction Timeframe	9-13

9-11 GW 3, Estimated Cost and Construction Timeframe	9-14

9-12 GW 5b, Estimated Cost and Construction Timeframe	9-15

12-1 Cost Summary Estimate for Selected Remedy	12-15

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List of Figures

1-1	Location Map	1-2

1-2	Remnant Partially Vegetated Waste Rock Dump (Eastern Side of Site)	1-3

1-3	Ballard Site - Land Ownership	1-4

1-4	Ballard Site Topography and Mine Features (MWH, 2015)	1-5

4-1	Ballard Mine Operable Units 01 and 02	4-2

5-1	West Ballard Mine Pit	5-2

5-2	Topography and Proximity to other P4 Mines	5-4

5-3	Generalized Stratigraphic Column for the Phosphate Resource Area of Southeastern Idaho	5-5

5-4	Generalized Cross Section through Generic Mine Pit	5-6

5-5	Watershed Features near the Ballard Mine	5-8

5-6	Surface Water Monitoring Locations	5-9

5-7	Selenium Plume in Alluvial Aquifer on Eastern Side of Ballard Mine	5-11

5-8	Selenium Plume in Alluvial Aquifer on Western Side of Ballard Mine	5-12

5-9	Groundwater Monitoring Well Locations	5-13

5-10	Human Health Conceptual Site Model	5-15

5-11	Ecological Conceptual Site Model	5-16

5-12	Livestock Conceptual Site Model	5-16

5-13	Conceptual Site Model Cross Section	5-18

7-1	Human Health RME and CTE Cumulative Site Cancer Risk for all Nonradionuclide Contaminants .7-4

7-2	Human Health RME and CTE Cumulative (all media) Noncancer Hazard Index for all

Nonradionuclide Contaminants	7-5

7-3	Selenium Hazard Quotients for Wildlife	7-15

9-1	Conceptual Monolithic ET Cover	9-6

12-1	Conceptual Cross Section of Key Elements of the Selected Remedy during the Construction

Phase	12-1

12-2	Conceptual Cross Section of Key Elements of the Selected Remedy after the Construction Phase 12-2

12-3	Existing Conditions prior to Remediation	12-5

12-4	Remedial Cover Concept - Extent of ET Cover	12-6

12-5	Approximate Location of PRBs	12-9

12-6	Approximate Location of Wetland Treatment Cells	12-11

Appendixes

A Risk Summary Tables

B	Summary of Federal and State ARARs for the Selected Remedy at the Ballard Mine

C	State Concurrence Letter

D Cost Estimate Breakdown of Remedy

iv

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Acronyms

<

less than

>

greater than

%

percent

°F

degree(s) Fahrenheit

Hg/L

microgram (s) per liter

Hg/m3

microgram (s) per cubic meter

AMSL

above mean sea level

AOC

area of concern

ARAR

applicable or relevant and appropriate requirements

ASTDR

Agency for Toxic Substances and Disease Registry

AWQC

ambient water quality criteria

bgs

below ground surface

BLM

Bureau of Land Management

BMP

best management practice

BTAG

Biological Technical Assistance Group

CCC

Continuous Chronic Criteria

CERCLA

Comprehensive Environmental Response, Compensation, and Liability Act

CFR

Code of Federal Regulations

cfs

cubic feet per second

CIP

Community Involvement Plan

COC

chemical of concern

COEC

chemical of ecological concern

COPC

chemical of potential concern

COPEC

chemical of potential ecological concern

CSF

cancer slope factor

CSM

conceptual site model

CTE

central tendency exposure

CWA

Clean Water Act

DAR

Data Approval Request

DEQ

Idaho Department of Environmental Quality

DQUR

Data Quality and Usability Report

EcoSSL

Ecological Soil Screening Level

EE/CA

engineering evaluation/cost analyses

EPA

U.S. Environmental Protection Agency

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• Acronyms

EPC

exposure point concentration

ERA

ecological risk assessment

ESA

Endangered Species Act

ET

evapotranspiration

FS

feasibility study

FYR

Five-Year Review

GCLL

geosynthetic clay laminate liner

gpm

gallon(s) per minute

GW

groundwater [alternatives]

GYC

Greater Yellowstone Coalition

HASP

health and safety plan

HHRA

human health risk assessment

HI

hazard index

HQ

hazard quotient

HQloael

hazard quotient lowest observed adverse effect level

HQnoael

hazard quotient no observed adverse effects level

IC

institutional control

ID

identification

IDAPA

Idaho Administrative Procedure Act

ILCR

incremental lifetime carcinogenic risk

IRIS

Integrated Risk Information System

LOAEL

lowest observed adverse effect level

LRA

livestock risk assessment

LTM

long-term monitoring

LUC

land use controls

MCL

maximum contaminant level

mg/kg

milligram (s) per kilogram

mg/kg-day

milligram(s) per kilogram per day

mg/L

milligram(s) per liter

mg/m3

milligram(s) per cubic meter

Monsanto

the Monsanto Company

MNA

monitored natural attenuation

MNR

monitored natural recovery

MRL

minimal risk level

MWH

Montgomery Watson Harza

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No.

NCP

NOAA

NOAEL

NPL

NPV

O&M

OR&R

ORNL

OSWER

OU

P4

pCi/g

pCi/m3

PRB

PRG

RA

RAGS

RAO

RAWP

RBCL

RD

RD/RAWP
RfC
RfD
RI

RME
ROD
S/RS
SI

Simplot
Site

SQuiRTs

SW

TBC

• Acronyms

number

National Contingency Plan

National Oceanic and Atmospheric Administration

no observed adverse effects level

National Priority List

net present value

operation and maintenance

(NOAA) Office of Response and Restoration

Oak Ridge National Laboratory

(EPA) Office of Solid Waste and Emergency Response

Operable Unit

P4 Production LLC, a subsidiary of Bayer
picocurie(s) per gram
picocurie(s) per cubic meter
permeable reactive barrier
preliminary remediation goal
remedial action

Risk Assessment Guidance for Superfund
remedial action objective
remedial action work plan
risk-based concentration level
remedial design

remedial design and remedial action work plan

reference concentration

reference dose

remedial investigation

reasonable maximum exposure

Record of Decision

stream channel sediment and riparian soil [alternatives]
site investigation
J.R. Simplot Company
Ballard Mine Site

(NOAA) Screening Quick Reference Tables
surface water [alternatives]
to be considered

vii

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• Acronyms

TRV

toxicity reference value

TRVloael

toxicity reference value lowest observed adverse effect level

TRVnoael

toxicity reference value no observed adverse effect level

UCL

upper confidence limit

UMTRCA

Uranium Mill Tailing Radiation Control Act

URF

unit risk factor

USFS

U.S. Forest Service

USFWS

U.S. Fish and Wildlife Service

USGS

U.S. Geological Survey

USL

upper simultaneous limit

USWR

upland soil and waste rock [alternatives]

UTL

upper tolerance level

yd3

cubic yard

viii

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Section 1-Site Name, Location, and Description

This section summarizes general information about the Ballard Mine Site.

1.1 Introduction

The Ballard Mine Site (U.S. Environmental Protection Agency [EPA] ID No. IDN001002859) is a former
open-pit phosphate mine located in the Phosphate Resource Area of southeastern Idaho (Figure 1-1).
Operation of the mine generated waste rock enriched with various inorganic contaminants, including
selenium, arsenic, uranium, and other elements. Contaminants have been released to soils, surface
water, groundwater, sediment, and vegetation.

The Site is not listed on the National Priority List (NPL). It is a Superfund equivalent site, with EPA
directing and providing oversight of a remedial investigation (RI) and feasibility study (FS) undertaken
and financed by the responsible party (P4 Production LLC, a subsidiary of Bayer [P4]). The RI/FS and
remedy selection followed the structured process established by the Comprehensive Environmental
Response, Compensation, and Liability Act of 1980 (CERCLA) and the National Contingency Plan (NCP)
to guide the cleanup of contaminated sites. As discussed in the Proposed Plan for the Site (EPA, 2018),
the process includes various steps leading from discovery of a site through investigation, remedy
selection, and implementation of a remedy. The NCP includes procedures, expectations, and program
management principles to guide the process.

EPA is the lead regulatory agency. Other agencies providing technical support and assistance
throughout the process included the Idaho Department of Environmental Quality (DEQ), U.S. Fish and
Wildlife Service (USFWS), and Shoshone-Bannock Tribes.

1.2 Site Name and Location

The Ballard Mine Site is located in Caribou County in the southeastern corner of Idaho, approximately
13 miles north-northeast of the city of Soda Springs. The Site is situated about 20 miles west of the
Wyoming border and 50 miles north of the Utah border. The Site is located, specifically, within
Sections 1, 6, 7,12,13,18, Township 7 South, Range 42-43 East.

1.3 General Description of Site

The Ballard Mine Site is a historical open-pit phosphate mine located in southeastern Idaho, an area
where phosphate-rich sedimentary rock formations are present at or near the surface. This area has
been mined for more than 100 years; there are many historical mines within the mining district, as well
as four active and several proposed mines.

The Ballard Mine was operated by the Monsanto Company (Monsanto) from 1951 to 1969 and
includes approximately 534 acres of mining disturbance consisting of six open pits, six external waste
rock dumps, an abandoned haul road, the Ballard Shop Area, and ancillary facilities. Most of the Site
has been revegetated, except for some mine pit areas and steep waste rock dump slopes (Figure 1-2).

The lands at the Site are owned by P4 Production LLC, a wholly-owned subsidiary of Monsanto (which
was acquired by Bayer in 2018), and the state of Idaho. P4 has a surface easement on the state lands.
Adjoining properties are privately owned and used for seasonal ranching and farming.

1-1

-------
Section 1 • Site Name, Location, and Description
Figure 1-1. Location Map

MAP
AREA

'ry <32019 google'" Earth.

MONTANA

IDAHO

ENOCH
VALLEY
MINE

Uilackfnnr]

HENRY
MINE

RASMUSSEN
RIDGE
MINE

WOOLEY
VALLEY
MINE

NORTH
MAYBE
MINE

DRY
VALLEY
MINE

Figure 1-1.

Location Map

Ballard Mine Record of Decision
Caribou County, Idaho

aSoda^'
Springs

Amended from P4 Productions, LLC, Remedial Investigation, MHW, 2014.

1-2

-------
Section 1 • Site Name, Location, and Description

The Site is within the aboriginal territory of the Shoshone and Bannock Tribes. Although the Site is
outside the boundary of the Fort Hall Reservation, the Shoshone-Bannock Tribes have treaty rights on
unoccupied federal lands in the vicinity of the Site for hunting, gathering, and ceremonial uses. The
nearest federal land where treaty rights apply is a 40-acre Bureau of Land Management (BI.M) parcel
located about 1 mile southeast of the Site. A map of the area near the Site, with information on land
ownership, is included as Figure 1-3 and the configuration of the waste rock dumps and pits is
illustrated on Figure 1-4.

The Site is in an arid upland area with the footprint of disturbance on a ridgeline that trends north-
northwest/south-southeast and rises to 7,000 feet above mean sea level (AMSL). The Site is bounded
by three relatively low-gradient drainage basins containing ephemeral and intermittent streams that
originate near the Site.

The primary source of contaminants at the Site is waste rock from historical mining operations;
approximately 19 million cubic yards of waste rock are present at the Ballard Site. The middle waste
shale component of the waste rock dumps is enriched with various naturally occurring contaminants,
including selenium, arsenic, uranium, and uranium-daughter products (for example, radium-226 and
radon-222).

Contaminants from the source material in the waste dumps have been released to various media,
including soil, surface water, groundwater, sediment, and vegetation. Dissolved selenium and other
contaminants have been transported from the source areas by surface water runoff to downstream
waterbodies. Water that infiltrates down through the waste rock dumps may reappear as contaminated
seeps or springs below the dumps or mix with underlying groundwater forming plumes downgradient of
the source material. Vegetation growing on the contaminated surface material is elevated in selenium.
Some plant species (known as hyper-accumulators) can accumulate very high concentrations of selenium.

Figure 1-2. Remnant Partially Vegetated Waste Rock Dump (Eastern Side of Site)

1-3

-------
Section 1 • Site Name, Location, and Description

Figure 1-3. Ballard Site - Land Ownership

P4 PRODUCTION, LLC
HAUL ROAD

EXPLANATION

[STATE"
OF

UdXhq.'

Mine pit location
(approximate)

Waste rock dump location
(approximate)

P4Rroductjon;-llc ' \

STATE OF IDAHO

hlliukjjuitl
fKixayinij

STATE

OF
IDAHO

BALLARD
MINE

[baliSrd

(V4 PRODUCTION

P4 PRODUCTION, LLC

Blackfaot River

Ballard I
Shop |

I PRODUCTION,

LLC

P"4 PRODUCTION, LLC

P4 PRODUCTION. LLC

P4 PRODUCTION. LLC-
HAUL ROAD

P 4 PRODUCTION, LLC

P 4 PRODUCTION. LLC

PRODUCTION.
V v LLC

~
n
n
~

Figure 1-3.

Ballard Mine - Land Ownership

Ballard Mine Record of Decision
Caribou County, Idaho

P4 Production, LLC
US Land
State of Idaho

Private Land

1-4

-------
Section 1 • Site Name, Location, and Description

[MMR039

MWD082

M WD 093

VMMP038

fApproximate mine pit location
as shown in FS Memo No. 1

e	^ Approximate waste rock dump location

as shown in FS Memo No. 1

Amended from P4 Production LLC, FS Technical Memorandum #2, MWH2017

Figure 1-4.

Ballard Mine - Mining Features

Ballard Mine Record of Decision
Caribou County; Idaho

1-5

-------
Section 1 • Site Name, Location, and Description

This page intentionally left blank to allow for double-sided printing.

1-6

-------
Section 2 - Site History and Enforcement Activities

This section summarizes the history of the Site, including previous investigations and removal
activities that predate the start of the RI/FS.

2.1 Site History

Key milestones in the exploration, development, and operation of the Ballard Mine are described
below.

• December 1948 - The area where the Site is located was originally leased to the J. R. Simplot
Company (Simplot) under federal mineral lease BL-055875. Simplot never developed the lease.

• May 23,1951 - Simplot assigned the lease to Monsanto, which started exploration and stripping of
overburden in June 1951. Mining started in 1952 on the southern portion of lease BL-055875 and
expanded to the north.

• July 1955 - Monsanto received a second Ballard Mine BLM lease that included additional
phosphate ore deposits immediately to the west of the initial lease area (1-05723). In 1955,
Monsanto initiated mining operations within this new lease, referred to as Ballard Mine Pit No. 1
or the West Ballard Pit (location number MMP035, Figure 1-4). Ballard Mine Pit No. 1 contained
the largest ore reserves of the five pits at the Ballard Mine and was operated for a longer period
than any of the other pits.

• The Ballard Mine eventually consisted of several side-hill and open-pit excavations. Trucks and
conveyors moved ore to the loading facilities. The loading facilities included tipples, screens,
conveyors, weigh bins, and automatic samplers. Trucks hauled ore from the mine loading facilities
to the elemental phosphorus plant at Soda Springs, Idaho, using public roads until the private haul
road was completed in July 1958. No ore processing was conducted onsite.

• Monsanto operated the Ballard Mine until 1969 and then moved their active mining operations to
the nearby Henry Mine. Monsanto relinquished the Ballard Mine mineral leases to the BLM in April
1984, and BLM accepted relinquishment in July 1984.

• During the 17 years of operations at the Ballard Mine, Monsanto recovered 10.4 million dry net
tons of phosphate rock that were hauled to Monsanto's elemental phosphorus plant at Soda
Springs. During this period, Monsanto excavated approximately 20 million cubic yards of waste
rock; of that amount, two million cubic yards were used to backfill the pits, with the remaining
18 million cubic yards hauled to the waste rock dumps (Lee, 2001).

2.2 Enforcement and Investigation Activities

Investigations to assess the impacts of phosphate mining in southeastern Idaho on human health and
the environment increased after several horses (pastured in another part of the mining district) were
diagnosed with selenosis (i.e., selenium poisoning) in 1996 and were subsequently euthanized. Some
of these early studies were conducted by the U.S. Geological Survey (USGS) and the University of Idaho.
Other investigations in the late 1990s were conducted under direction of the Idaho Mining
Association's Selenium Subcommittee. These studies contributed to EPA's understanding of how
phosphate mining affects the environment.

In 2001, DEQ assumed leadership of an areawide investigation of the contamination caused by
phosphate mining, with participation by other state and federal agencies and the mining companies
with operations in southeastern Idaho. These areawide investigations led the agencies to conclude that

2-1

-------
Section 2 • Site History and Enforcement Activities

site-specific investigations were warranted on the larger historical and active open-pit mines located
in the mining district, including the Ballard Mine.

These conclusions led to negotiations with P4 to conduct site-specific investigations at the historical
mines for which it is responsible: the Ballard Mine, Henry Mine, and Enoch Valley Mine. In
October 2003, DEQ, EPA, the U.S. Forest Service (USFS), the Shoshone-Bannock Tribes, the Bureau of
Indian Affairs, BLM, and P4 (the latter as Respondent) entered into a legal agreement (EPA, 2003)
calling for P4 to conduct investigations and develop site investigation (SI) and engineering
evaluation/cost analyses (EE/CA) reports for the Ballard, Henry, and Enoch Valley mine sites. These
efforts followed a streamlined removal approach. DEQ was designated the lead agency to oversee this
work, which resulted in the collection of a considerable amount of information and a better
understanding of site conditions. Work under the 2003 removal agreement was halted before the SI
reports were prepared, for a variety of reasons, including recognition that using the removal approach
would be inappropriate for sites as large and complex as the Ballard, Henry and Enoch Valley mine
sites. All data collected under the 2003 removal agreement, however, were validated by procedures
prescribed by EPA and included in the RI.

In November 2009, a new legal agreement transitioned work at the P4 sites into a more thorough
remedial approach, and from DEQ-led to EPA-led. The 2009 agreement superseded the 2003
agreement and called for performance of an RI and FS at each of the three P4 mine sites. The 2009
agreement included EPA, DEQ, USFS, the Department of the Interior (for USFWS), BLM, the Shoshone-
Bannock Tribes, and P4 (EPA, 2009a).

Key investigation reports and data submittals relevant to the investigation of the Ballard Mine include
the following:

•	Community Involvement Plan Update for Ballard, Enoch Valley, and Henry (P4) Mines (DEQ, 2017)

•	Final Revision 2 Data Quality and Usability Report (DQUR) and Data Approval Request (DAR)
(MWH, 2010)

•	Ballard, Henry and Enoch Valley Mines, Remedial Investigation and Feasibility Study Work Plan
(MWH, 2011)

•	Background Levels Development Technical Memorandum, Ballard, Henry, and Enoch Valley Mines,
Remedial Investigation and Feasibility Study (MWH, 2013a)

•	Final Ballard Mine Remedial Investigation and Feasibility Study, Remedial Investigation Report,
Baseline Risk Assessment Addendum (MWH, 2014)

•	Final Baseline Risk Assessment Addendum (MWH, 2015c)

•	Final On-Site and Background Areas Radiological and Soil Investigation Summary Report - P4's
Ballard, Henry, and Enoch Valley Mines Remedial Investigation and Feasibility Study (MWH,
2015b)

•	Final Ballard Mine Feasibility Study Report - Memorandum 1 - Site Background and Screening
Technologies (MWH, 2016a)

•	Final Ballard Mine Feasibility Study Report - Memorandum 2 - Screening, Detailed and
Comparative Analysis of Assembled Remedial Alternatives (MWH, 2017a)

•	Ballard Mine Monitored Natural Attenuation Technical Memorandum (MWH, 2017b)

•	Ballard Mine Proposed Plan. Caribou County, ID (EPA, 2018)

2-2

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Section 3 - Community and Tribal Participation

3.1	Overview

A variety of tribal and community involvement activities have occurred during development of the
RI/FS and in conjunction with issuance of the Proposed Plan. These activities are described in a
Community Involvement Plan (CIP), which has been updated periodically since 2008.

In developing the CIP, EPA interviewed the following area stakeholders:

•	Elected officials (such as mayors, city council members, and county commissioners)

•	Staff representatives for Senators Mike Crapo and James Risch and Representative Mike Simpson

•	Local legislative representatives

•	Area landowners and residents

General information was asked about properties, community concerns, and how best to communicate
with the public through the investigative process.

During development of the RI/FS, EPA and support agencies distributed Site-specific and area-wide
fact sheets, established local information repositories, hosted community meetings, developed an
informational display for the local library, and implemented other actions.

The following sections summarize tribal engagement efforts throughout the RI/FS process and
community engagement efforts performed in conjunction with issuance of the Proposed Plan.

3.2	Tribal Engagement

The Ballard Mine Site is within the aboriginal territory of the Shoshone and Bannock Tribes. Although
the Site is outside the boundaries of the Fort Hall Reservation, the Shoshone-Bannock Tribes have
rights under the Fort Bridger Treaty to use unoccupied federal lands in the area for hunting, gathering,
and ceremonial uses. These treaty rights apply to BLM lands approximately 1 mile downstream of the
Site along the Blackfoot River, and to other federally managed lands in the area. The land at the Site is
currently owned by the State of Idaho and P4.

The Shoshone-Bannock Tribes are a signatory to the 2009 legal agreement for performance of an
RI/FS and serve as a Support Agency on investigations at the three P4 sites. Tribal staff in the
Environmental Waste Management Program have actively participated throughout the RI/FS process
and have provided valuable input and assistance in site investigations and in developing cleanup plans.

Because of the history of tribal engagement on the P4 projects and treaty interests on federally
managed lands in the watershed, EPA met with members of the Fort Hall Business Council on
November 8, 2018 and engaged in Government-to-Government Consultation on the proposed cleanup
action for the Site. During the consultation, the Tribes expressed serious and long-standing concerns
about the impacts of phosphate mining and expressed support for making progress on cleaning up
historic phosphate mines in southeastern Idaho. With respect to the Ballard Mine Site, the Tribes
raised many questions and concerns and offered recommendations but did not object to the Preferred
Alternative. The issues that have been raised do not change the analysis supporting the Selected
Remedy.

3.3	Community Engagement

Local Repository

The administrative record, which includes the RI/FS and other documents that form the basis of EPA's
Selected Remedy, is housed at the EPA Superfund Records Center located at 1200 Sixth Avenue,

3-1

-------
Section 3 • Community and Tribal Participation

Suite 155, OMP-161, Seattle, Washington, 98101. The center can be reached by telephone at
206-553-4494 or (toll-free) 800-424-4372.

Additional information repositories have been established at the following locations:

EPA Idaho Operations Office

950 W. Bannock Street
Suite 900

Boise, Idaho 83702
Phone: 208-378-5746
Monday through Friday

DEQ Pocatello Regional Office

444 Hospital Way, #300
Pocatello, ID 83201
208-236-6160

Soda Springs Public Library

149 S Main St

Soda Springs, ID 83276-1496
208-547-2606

Shoshone-Bannock Tribes Library
P.O. Box 306
Fort Hall, ID 83203
208-478-3882

Email and Postal Updates

EPA and DEQ maintained a list of all interested stakeholders that included a base list of residents
derived from Caribou County property ownership information. An email message containing a link to
the Proposed Plan and information on how to submit comments was sent to a distribution list. A
postcard containing the same information was mailed to the regular mailing list. Paper copies of the
Proposed Plan were mailed upon request.

Paid Notices and Media Coverage

Paid notices were placed in the Caribou County Sun, the Idaho State Journal (the Pocatello newspaper),
and the Sho-Ban News in April 2018 to announce issuance of the Proposed Plan and provide
information on public involvement opportunities.

Project Web Site

EPA created the following project website to provide access to documents and information about the
Site: https:/ /cumuli s.epa.gov/supercpad/cursites/csitinfo.cfm?id=1002859

Proposed Plan and Public Meeting

EPA issued a Proposed Plan for the Site on April 2, 2018. An open house and public meeting for the
Proposed Plan were held in the afternoon and evening, respectively, of April 11, 2018. EPA provided a
visual display of the project and a formal presentation. EPA and DEQ representatives were present to
answer questions about the remedial alternatives considered and the preferred remedial option
selected. The public had the opportunity to provide spoken comments during the public meeting or
written comments during the 30-day comment period, which closed on May 2, 2018. EPA received
comments from three individuals and one organization. The comments presented in the written
comments are summarized with EPA's responses in the Responsiveness Summary, Part 3 of this
document.

3-2

-------
Section 4 - Scope and Role of the Operable Unit

In 2009, EPA entered into a settlement agreement with P4 calling for the production of an RI/FS for
each of the three historic phosphate mine sites for which P4 is responsible: the Ballard, Henry and
Enoch Valley mine sites. Planning and data collection activities were implemented concurrently for the
three sites. The Ballard Mine Site is the first of the three sites for which a ROD is being issued; decision
documents for the other two sites will follow.

As with many Superfund sites, the problems at the Ballard Mine Site are complex. As a result, EPA has
organized the Site into two operable units (OUs).

• Operable Unit 1 (0U1): Contamination associated with the area of the Ballard Mine Site that was
mined historically, including impacts to all environmental media. This OU comprises most of the
Site, about 550 acres of historical mining disturbance. Also included are surrounding areas, such as
receiving waters and aquifers, where contaminants have come to be located.

• Operable Unit 2 (0U2): Contamination associated with the Ballard Shop Area. This OU covers a
smaller portion of the Site, approximately 10 acres. This is an area that is currently being used to
support nearby mining operations, and is used for equipment storage, fuel storage, stockpiling of
slag material used as aggregate for active haul roads, and other activities.

A map of the Site showing the location and size of the Ballard Shop Area (0U2) relative to the area of
the Ballard Mine Site (0U1) is shown on Figure 4-1. The following sections describe the overall cleanup
strategy for the Site.

4.1 Response Action for Ballard Mine Site (OU1)

This ROD selects a final remedy for the Ballard Mine Site (0U1). The Selected Remedy for 0U1 is a
combination of engineered source controls, treatment technologies, and other approaches and
components that will work together to achieve the remedial action objectives (RAOs). A key element of
the combined remedy for 0U1 is controlling the release of contaminants from the waste rock dumps
and mine pits. This will be accomplished by backfilling pits; consolidating, grading and shaping waste
rock; and constructing a 5- to 6-foot-thick engineered cover system over the more than 500 acres of
mining disturbance. Isolating the waste rock by constructing the cover system addresses direct contact
risks with contaminants and vegetative uptake, reduces deep infiltration of water, and minimizes
release of contaminants to surface water and groundwater.

4.2 Response Action for the Ballard Shop Area (OU2)

A final remedy for the Ballard Shop Area of the Site (0U2) is not being selected in this ROD and will be
deferred until the OU is no longer in use. P4 intends to continue the use of the Ballard Shop Area,
which covers approximately 10 acres on the southwestern edge of the Site, to support remedy
implementation and nearby mining operations. A focused FS and Proposed Plan will be developed for
this small portion of the Site and a final remedy selected in a separate ROD. This ROD, however, selects
institutional controls (ICs) and fencing as interim actions at the Ballard Shop Area to limit potential
exposure to construction and mine workers until a final remedy is selected and implemented. ICs will
include restrictions on the use of this area, including its groundwater.

4-1

-------
Section 4 • Scope and Role of the Operable Unit

Figure 4-1. Ballard Mine Operable Units 01 and 02

idkHltMl

Legend

OU 01 Approximate boundaries of surface disturbance;includes Groundwater plumes) Ballard M rte Sle
• • • OU 02 Approximate boundaries ot surface disturbance • Bated Stop Area

F»gure 4-1
OPERABLE UNITS 01 AND 02

BALLARD MINE
RECORD OF DECBION
Caribou County, 10

¦AmttOtJ*Ximf>4r*vt*U*UC *5

r«A.-.T» UMKiniA flj WAX xir

4-2

-------
Section 5 - Summary of Site Characteristics

This section contains an overview of the Site and the conceptual site model (CSM). Detailed
information on sampling results and risks are presented in Section 7 and the tables in Appendix A.

5.1 Site Overview

5.1.1 Surface Features and Size

The Site is located about 13 miles north-northeast of Soda Springs, Idaho, in mountainous, semi-arid
Caribou County. P4 owns approximately 865 acres of surface rights and has a surface easement from
the state of Idaho on an additional 360 acres. These properties encompass the entire area disturbed by
mining (Figure 1-4). The adjoining properties are all privately held ranching and farming properties.
The nearest downstream federal land is a 40-acre BLM parcel, approximately 1 mile southeast of the
Site.

The topography of this area is dominated by north-northwest/south-southeast-trending ridgelines of
moderate relief, ranging in elevation from 6,300 to 7,000 feet AMSL. The Site is located on one such
ridgeline and is bounded to the east and west by three low-gradient drainage basins containing
intermittent or ephemeral streams that originate from, or flow past, the Site (including Long Valley
Creek and Wooley Valley Creek).

On the northwestern edge of the Ballard Mine Site, Long Valley Creek drains northward to the Little
Blackfoot River, which empties into the northeastern corner of the Blackfoot Reservoir. Wooley Valley
Creek originates in the basin to the east of the Site and flows about 5 miles to its confluence with the
Blackfoot River. Wooley Valley Creek is intermittent for most of its length, becoming perennial about
1 mile above its confluence with the Blackfoot River. Intermittent stream channels originating near the
eastern side of the Site lead to Wooley Valley Creek. The upper reaches of Wooley Valley Creek flow
during the snowmelt and peak runoff periods in the spring but are often dry in the summer. The
Blackfoot River is located approximately 1 mile to the south of the Site. An intermittent stream channel
(Ballard Creek) leads from the southern portion of the Site to the Blackfoot River.

Significant features at the Site include mine pits (see Figure 5-1), waste rock dumps, a primary haul
road, and a Shop area (approximately 534 acres of mining disturbance). Because of the age of the mine,
much of the area is vegetated, except for some mine pit areas and steep waste-rock dump slopes.

Mine Pits and Waste Rock Dumps

The configuration of the mine pits and waste rock dumps is shown on Figure 1-4. There are six mine
pits at the Ballard Site, with the largest pits (MMP035 [West Ballard Pit] and MMP036 [Central Ballard
Pit]) on the western edge and in the central portion of the Site, respectively. Three other pits
(MMP037, MMP039, and MMP040) are in the eastern portion of the Site. The MMP038 pit is a much
smaller pit located south of the other mine features.

5-1

-------
Section 5 • Summary of Site Characteristics

Figure 5-1. West Ballard Mine Pit

There are six waste rock dumps at the Site: MWD080, MWD081, MWD082, MWD083, MWD084, and
MWD093. The waste rock dumps are located adjacent to the mine pits from which the waste rock was
excavated. These features are generally flat-topped with angle-of-repose outer slopes. Waste rock was
also placed in MMP035 and MMP036, partially backfilling these mine pits. The total volume of waste
rock present is about 19 million cubic yards. The waste rock dumps range in volume from 600,000 to
about 5,000,000 cubic yards of waste rock. Further information on the areas and volumes of the waste
rock dumps and pits is provided in the RI report (MWH, 2014).

Ancillary Facilities

Ancillary facilities remaining at the Ballard Mine include remnants of a partially paved haul road, various
unimproved soft-surface two-track roads, and the Shop area (consisting of a large garage/shop building,
various small storage sheds and buildings, and a stockpile of slag from the P4 Soda Springs plant). The
stockpiled slag is used for maintenance of active haul roads and associated facilities. No ore processing
was conducted at the Site, so except for the slag pile at the Shop area, no process wastes are present.

Surface Materials and Vegetation

Surface material and vegetation at the Site were characterized during the 2009 upland soil and
vegetation investigation (MWH, 2014). Surficial material on mine waste dumps consists of an
approximate 2:1 mixture of weathered brown shale and black shale. The weathered brown shale
represents the weathered rock stripped from the near surface during mining to reach the ore beds of the
Meade Peak Member of the Phosphoria Formation, and the black shale is typically the waste shale that
was located between and immediately above and below the Meade Peak Member ore beds. The surface
materials found in the walls and floors of the mine pits reflect the geology of the sedimentary formations
encountered during mining. Limestone and sandstone are typically found at, or near, the base of Wells
Formation high walls.

The Site is generally well vegetated, consisting of a combination of grasses, forbs (broadleaf plants
such as alfalfa), shrubs, and some trees. Several steep slopes, primarily highwalls and angle-of-repose
slopes in the southern portion of the Site, are unvegetated. The vegetation at the Site was altered in
2012 by a rangeland fire that burned parts of MMP035, MWD080, MWD093, and MMP036 (MWH,

2014).

5-2

-------
Section 5 • Summary of Site Characteristics

5.1.2 Climate

The climate of southeastern Idaho is semi-arid with hot summers and cold winters. The topography
strongly influences wind patterns, temperature, and precipitation. North-trending mountain ranges in
the region create a natural barrier for water-saturated Pacific air masses. Precipitation during the
colder months is snow, while precipitation during the summer is primarily localized thunderstorms.

Because meteorological data are not directly available for the Site, data were obtained from nearby
stations, including the meteorological station at the Blackfoot Bridge Mine. Precipitation is distributed
through the year, with spring and summer having some of the wetter months. The data collected at the
Blackfoot Bridge Mine suggest that the average annual precipitation near the Site is on the order of
13 inches per year. July and August are the warmest months of the year, while December and January
are the coldest. Average temperatures range from a minimum of 7.9 degrees Fahrenheit (°F) in
December to a maximum of 80.9°F in July.

5.1.3 Geology

The geology in the Ballard Mine area is transitional between the Basin and Range and Rocky Mountain
Physiographic Provinces. Figure 5-2 depicts the topography of the area and the locations of the three
P4 mine sites (Ballard, Henry, and Enoch Valley). The geology of the area is complex, characterized by
linear, north-south-trending, fault-bounded ranges and basins.

Ranges in southeastern Idaho are generally composed of deformed sedimentary rock of the Paleozoic
and Mesozoic age, and include thick marine clastic units, cherts, and limestones. The valleys are largely
filled with Quaternary alluvium and colluvium. In some areas, the Quaternary alluvial deposits overlie
Pleistocene basalt flows. Thick basaltic flows of the Snake River Plain and rhyolite domes south of the
Blackfoot Reservoir are also present in other parts of the region.

The Paleozoic and Mesozoic sedimentary rocks cover a large area of eastern Idaho, southwestern
Montana, and northern Utah. During the Permian geologic period, the Phosphoria Formation was
deposited, creating the western phosphate field that includes the southeast Idaho Phosphate Resource
Area. The Phosphoria Formation has four members (from oldest to youngest): the Meade Peak
Phosphatic Shale, Rex Chert, Cherty Shale, and Retort Phosphatic Shale. The Meade Peak Member,
which ranges in thickness from about 55 to 200 feet, is the source of most of the extracted phosphate
ore. This is the oldest member of the Phosphoria Formation and is typically overlain by either the Rex
Chert or the Cherty Shale and underlain by the upper unit of the Wells Formation, which consists of
sandstone interbedded with limestone and dolomite. Figure 5-3 presents a generalized stratigraphic
column, while Figure 5-4 shows a generalized cross section through a generic mine pit.

5-3

-------
Section 5 • Summary of Site Characteristics

Figure 5-2. Topography and Proximity to other P4 Mines

5-4

-------
Section 5 • Summary of Site Characteristics

Figure 5-3. Generalized Stratigraphic Column for the Phosphate Resource Area of Southeastern
Idaho.





Quaternary

Alluvium

Qal

Alluvium and Colluvium: 0-50 feet

(Unconsolidated Silt, Sand, and Gravel)





Triassic

Dinwoody
Formation

TM1

Lower Dinwoody

fS//f stone. Limestone, ondSbole)

*

i







Frandson Limestone







Rex Chert
Member

CljJ?

Rex Chert: 150*160 feet

(Cherty Mudstone and Limestone)

o
c







Hanging Wall Mudstone: 15-30 feet

e

Q

Permian





Ore: 2-5 feet

u.

fO





Lower Rich Bed: 2-5 feet

O







Hanging Wall Shale: 2-6 feet

JZ
Q.
v>
n



Meade





j:

Q

_



Peak
Member



Center Waste Shale: 75-120 feet











Ore: 5-10 feet











Upper Footwall Shale: 2-5 feet











Lower Footwall Shale: 5-10 feet











Ore: 4-5 feet



f







Footwall Mudstone: 5-10 feet











Grandeur Limestone: 100 feet





Pennsylvanian

Wells
Formation

CRjctdq

Wells Sandstone and Limestone:
500-1500 feet

5-5

-------
Section 5 • Summary of Site Characteristics

Figure 5-4. Generalized Cross Section through Generic Mine Pit

I -¦ I: :*.v vi: -1: iw

GEOCHEM ICALi'B IQLOG CAL PROCESSES

WELL LOCA'CNS

WELLS FORMATION

% \
xV



V





5-6

WASTE ROCK

(B) \

-------
Section 5 • Summary of Site Characteristics

Another significant sedimentary unit in the area is the Triassic Dinwoody Formation, which is made up
of upper and lower units consisting of limestone, siltstone, and shale layers. The lower Dinwoody
Formation directly overlies the Phosphoria units in the stratigraphic section.

5.1.4 Surface Water

The Site is in a watershed catchment ranging in elevation from 6,000 to 7,000 feet AMSL and is
bounded by three relatively low-gradient drainage basins (Figure 5-5). The Site is a headwater area for
ephemeral and intermittent streams flowing towards larger drainages off the Site. Most of the streams
in the area flow only during snowmelt runoff and intense precipitation events; however, a few
intermittent streams are fed by perennial springs. There is no reliable flow in these stream channels
for approximately 9 months of the year. Drainages fed by perennial seeps and springs dry up through
evaporation and infiltration within about 100 feet of the source during baseflow months. On the
eastern side of the Site, the surface tributary system drains to Wooley Valley Creek, which becomes
perennial approximately 3 to 4 miles downgradient of the Site. There are some ponds along Wooley
Valley Creek below the Site that retain water throughout the year.

The following sources of water at the Site discharge to surface water or groundwater:

• Intermittent stormwater and snowmelt surface runoff. Runoff is generally diffuse with very few
defined overland runoff channels. Much of the runoff reaches the offsite channels as interflow in
the waste rock and adjacent soils.

• Mine dump seeps and associated springs. These features discharge during snowmelt and runoff
events. The springs are primarily mine dump seepage, but do not always discharge directly from
the toe of a mine waste rock dump. Flow from these discharges range from a peak of
approximately 90 gallons per minute (gpm) to 4.5 gpm during snowmelt and from 4.5 gpm to dry
during the baseflow period. Most of the contaminant loading to the drainages originates from the
mine dump seeps and associated springs (Figure 5-6).

• Five small seasonal ponds are located within the mining disturbed area. These ponds form
naturally in depressions in the mine pit floors. These onsite ponds are all less than 0.25 acre in size
and are dry during parts of the year.

Runoff and stormwater contribution from the Site to the Blackfoot River is seasonal and a very minor
contributor to flow in the Blackfoot River. The Site contributes very little flow to Long Valley Creek
(north of the Site). Additional information on runoff and baseflow discharges can be found in the RI
report (MWH, 2014).

5-7

-------
Section 5 • Summary of Site Characteristics

Figure 5-5. Watershed Features near the Ballard Mine

.Angus
Creek

Mallard Creek

Mine pit location (approx )

Waste rock pile locatxxi (approx)

j- Surface water arid riparian
sampte legation

lilack/oof
Reservoir

K4

M8T773 C, t

Figure 6-S
BALLARD MINE -
SURFACE WATER FEATURES

BALLARD MINE
RECORD OF DECISION
Caribou County, ID

5-8

-------
Section 5 • Summary of Site Characteristics

Figure 5-6. Surface Water Monitoring Locations

5-9

-------
Section 5 • Summary of Site Characteristics

5.1.5 Groundwater

Groundwater at the Site can be divided into the following three types of aquifers:

•	Local shallow groundwater systems within basin-fill alluvium

•	Shallow to deep intermediate systems within sedimentary bedrock units (Dinwoody Formation)

•	Regional groundwater flow systems within deeper sedimentary bedrock units (Wells Formation)

The Ballard Mine RI report (MWH, 2014) identified two of the groundwater systems with contaminant
concentrations above cleanup levels: the alluvial aquifer on the eastern, southern, and western sides of
the Site (Figures 5-7 and 5-8) and portions of the regional aquifer (Wells Formation) beneath, and
adjacent to, the West Ballard Mine Pit (MMP035).

The depth to first groundwater in the alluvial system ranges from 1 foot below ground surface (bgs) to
15 feet bgs, but rarely as deep as 20 feet bgs. The groundwater in the alluvial system is contained in
alternating sand, clay, and silt beds with rare gravel beds of colluvial and alluvial origin. Beds are
typically thin, being 1 foot thick or less, but they can be highly variable. Alluvial groundwater is best
characterized as being unconfined to semiconfined between clay beds. Hydraulic testing of alluvial
wells indicates that the average hydraulic conductivity of the water-bearing portions of the unit is on
the order of 10 4 centimeters per second, and groundwater flow velocities were estimated as ranging
from 17 to 109 feet per year at the Site.

The hydrogeologic setting of the Wells Formation system is markedly different than the alluvial
system. Groundwater contained in the Pennsylvanian Wells Formation is dominated by sand and
limestone beds tens of feet thick. Water-bearing beds have hydraulic conductivities on the order of
10"3 to 10"2 centimeters per second and can produce significant groundwater. Within the Site, the
bedrock units are folded and faulted, resulting in compartmentalization and complex groundwater
flow systems through fractures and geologic formation boundaries. The depth to groundwater in the
Wells Formation at the Site ranges between 200 and 400 feet bgs in the West Ballard Mine Pit
(MMP035) and between 100 to 200 feet bgs in the other perimeter areas. The regional groundwater
flow in the Wells Formation is to the northwest, but because of the complex hydrogeologic conditions
of the Site, a specific flow field has not been defined.

5-10

-------
Section 5 • Summary of Site Characteristics

Figure 5-7. Selenium Plume in Alluvial Aquifer on Eastern Side of Ballard Mine

Figure 5-7

ALLUVIAL AQUIFER SELENIUM PLUMES -
EAST SIDE OF BALLARD MINE

BALLARD MINE
RECORD OF DECISION
Caribou County, ID

'Amended from P4 Product/on LLC. Rt.
Drawing 4-27. MMl 201f

STATION TYPE:

use	-	STATU*

•	l»ST	- SPEM1 STKKH

~	Win. . CTOJMJ *AJT* uCNroBKS "IU

V KB"	- 3«CT MW MOHTOWtC WU	m TOCt

~	wtw	- >R£r push ttwrcitwa wu njtmiid m act

» W	- Ktm PVT HSH towxs

•	(h	- jooo ti*e? cvSH #ewn«

5-11

-------
Section 5 • Summary of Site Characteristics

Figure 5-8. Selenium Plume in Alluvial Aquifer on Western Side of Ballard Mine

5-12

-------
Section 5 • Summary of Site Characteristics

Figure 5-9. Groundwater Monitoring Well Locations



Mine pit location
(approximate)



waste roctc pile locabon
(approximate)



Direct posh alluvial
aquifer well

*
~

Agricultural, domestic
or production well

Local aquifer monitoring well
(generally alluvial system)

+

Intermediate aourfer monitoring
well (generaly Dinwoody Fm.)

•*

Regional aquifer monitoring well
(VtellsFm)

totoo

Red concentration numbers
indicate concentrations above
screening and background levels

ND
RL

Not detected
Reporting limit

LAND OWNERSHIP

L~] P4 Property Boumfcry
I 1 Other Prvit* land

Bureau of Lino Min»gement
a U S Forefl StMt*
I 1 Stale

/. Average Concentration (Avgf - Avenge
of detected concentration*. //alt results
are XD, the maximum RI. if shown.

Selenium concentrations reported in
milligrams per titer (mg IJ

Background
Screening level

Figure 5-9
GROUNDWATER MONITORING
LOCATIONS AND SELENIUM RESULTS

BALLARD MINE
RECORD OF DECISION
Caribou County, ID

'Amended from P4 Production LLC.
Rt, Drawing 4-23, MWH 2014'

5-13

-------
Section 5 • Summary of Site Characteristics

Three Wells Formation monitoring wells detected concentrations of chemicals of concern (COCs) at
greater than the groundwater cleanup levels (see Figure 5-9 for locations). One monitoring well on the
western side of the pit has elevated COC concentrations but does not exceed the groundwater cleanup
levels. Other Wells Formation wells at the perimeter of the Site were found to contain background
concentrations of COCs.

The extent of the affected alluvial groundwater is illustrated by groundwater plumes delineated during
the RI. The locations of the six identified plumes are shown on Figures 5-7 and 5-8. These plumes are
associated with waste rock dumps that act as sources of contamination and are labeled accordingly
(MWD084, MWD082 North, MWD082 South, MWD080 North, MWD081 South, and MWD080/081
Central). The plumes originating from MWD081 South and MWD080/081 Central flow toward the
Blackfoot River (Figure 5-8).

Monitoring results from the Blackfoot River upgradient and downgradient of the plume in this area do
not show a measurable change in selenium concentration. No other plumes have reached a potential
discharge location along the Blackfoot River.

5.1.6 Surface Water/Groundwater Interactions

Runoff at the Site is generally diffuse with very few defined overland runoff channels. Precipitation and
snowmelt that infiltrate waste rock dumps reach the offsite channels as interflow in the waste rock
and adjacent soils or enters the shallow alluvial aquifer.

Groundwater flow in the shallow alluvial aquifers typically follows the local topography. If the
alluvium intercepts an abrupt change in topography, bedrock elevation, an erosion/mining feature, or
stream channel, the shallow groundwater will daylight as a discrete spring or seep, or contribute to
stream flow (Figure 5-13).

Seeps and springs (MDS030 to MDS033, and MSG003) that do not discharge offsite are located on the
hill above the West Ballard Mine Pit (MMP035). These seeps and springs discharge to the mine pit
where the impacted seepage-derived surface water infiltrates to the regional groundwater system.
Groundwater in the Wells Formation was found to contain elevated concentrations of COCs around the
West Ballard Mine Pit.

The flow direction within the regional aquifer, composed primarily of the Wells Formation at the Site,
is to the northwest toward a series of prolific springs near the village of Henry. These springs
represent a recognized discharge area for the regional groundwater system for this part of southeast
Idaho (MWH, 2008). Sampling of three large springs in the area occurred in fall 2017 and showed no
water quality impacts from mining activity (Stantec, 2018).

5.2 Conceptual Site Model

A CSM was developed to show the relationship between the sources of contaminants at the Site,
mechanisms for release of contaminants, and transport pathways to various environmental media
(Figures 5-10 through 5-12). The model provides a framework to assess risks from contaminants and
develop cleanup strategies.

5-14

-------
Section 5 • Summary of Site Characteristics

Figure 5-10. Human Health Conceptual Site Model

Primary	Primary Release Secondary

Sources	Mechanisms	Sources

Secondary
Mechanisms

Tertiary
Sources

Wind Erosion of
Particulates

Exposure Routes

Fugitive Dust Inhalation

5 c
® 3
O I

Potential Receptors3

0	U.

01

ce

i ° i • i • i ' i • i

Soils0

Inorganics
in Mining
Waste Rock

Weathering and
Leaching

Surface and
Subsurface
Soil

Surface Water
Runoff

Incidental Ingestion

Dermal Contact

Uptake by Plants

Uptake by Moose, Elk, and other Wild Game

Uptake by Beef Cattle and Livestock

Incidental Ingestion

Dermal Contact

Uptake by Plants

Uptake by Fish6

Surface Water

Incidental Ingestion

Dermal Contact1

Inhalation

Uptake by Plants

Uptake by Fishe

Uptake by Moose, Elk, and other Wild Game

Uptake by Beef Cattle and Livestock

Potentially Complete Exposure Pathway
Potentially Complete but Insignificant Pathway
Incomplete Pathway
Complete Exposure Pathway
Potentially Complete but Insignificant Pathway
Incomplete Exposure Pathway

Infiltration/
Percolation

Ingestion

Washing/Bathing

Irrigation of Plants

Water for Livestock

Notes:

J All potential receptors are toth current and future receptors except for hypothetical future residential receptor

5 It is also possible that some bota consumption pathways caW be applicable to multiple receptors. For example, a recreational camper-'hiker could hunt Such alternate exposure pathways are evaluated qualitatively h the Uncertainty Analysis section of the HHERA
0 All exposure pathways are inccmpete fcr the cutrenWuture recreational fsher because the surfaoe water bodies in the Ballard Mine do not support fish, as described in the Remedial Investigation and Feasibility Study Work Plan (MWH. 2011).

' Exposure to constituents in soil to the currentfuture recreational hunter, currently re camper-'hiker, hypothetical future resident, and currenbtoire seasonal rancher will only be evaluated qiantitatvely for upland soil because these receptors are not expecsed to spend a significant amount of time neat surface water because no fish are
present in Ballard Mire surface todies and swimming is an msgnificant pathway due to low surface water temperatures.

' The consumption of fish pathway is incomplete fcr all receptors because the surface water bodies in the Ballard Mine do not support fish, as described in the Remedial Investigation and Feasibility Sudy Work Plan (MWH 2011).

' Direct sjrface water pathways are only complete for the currenvluture Native American because the other receptors are un'ikeiy to spend a significant amount of time near surface water because no fish are present n Ballard Mine surface bodies and swimming is an insignificant pathway due to low surface water temperatures.

5-15

-------
Section 5 • Summary of Site Characteristics

Figure 5-11. Ecological Conceptual Site Model

1" Release
Mechanisms

2" Release
Mechanisms

Potential Ecological Receptors

, i. » a Reptiles
Invertebrates .
and

Aquatic Terrestrial Fishb Amphibians3

Long-tailed
Vole,
Elk, and
American
Goldfinch

Mouse
and
American
Robin

Great

Blue Northern

Raccoon Mallard Mink Coyote Heron Harrier

Inorganics
in Mining
Waste
Rock

Weathering
and
Leaching

Surface and
Subsurface
Soil

Surface
Runoff/
Leaching

Infiltration/
Percolation

Upland and/
or Riparian
Soila

I Sediment I

Surface
Water

Fugitive
Dust
Inhalation1

•

Ingestion

•

Plants

•

Animals

•

Plants

„

•

Animals

•

Plants 0

•

Animalsc

•

Inqestion

¦'

Animals

Potentially Complete Exposure Pathway
Potentially Complete but Insignificant Pathway
Incomplete Pathway
Complete Exposure Pathway
Potentially Complete but Insignificant Pathway
Incomplete Exposure Pathway

3 Potential effects to invertebrates and reptiles will be evaluated qualitatively.

°The surface water bodies in the Ballard Mine do not support fish, as described in the Remedial Investigation and Feasibility Study Work Plan (MWH, 2011).

" The inhalation pathway is minor relative to the incidental ingestion pathway and there is a lack of relevant toxicological information; therefore this pathway was not evaluated quantitatively for ecological receptors.

" For the purpose of the risk assessment, American goldfinch, American robin, coyote, deer mouse, elk, long-tailed vole, and Northern harrier will only be exposed to upland soil; and mink, great blue heron and raccoon will only be exposed to
riparian soil.

9 Exposure to chemicals of potential ecological concern in surface water through the ingestion of aquatic plants and/or animal pathways were quantitatively evaluated using sediment data when sediment data were available.

Figure 5-12. Livestock Conceptual Site Model

1 Sources

1" Release
Mechanisms

Sources

2' Release
Mechanisms

Sources

Exposure
Routes

Beef Cattle

Inorganics
in Mining Waste
Rock

Weathering and
Leaching

Surface and
Subsurface Soil

Wind Erosion
of Particulates

Surface
Runoff/
Leaching

Infiltration/
Percolation

Ambient Air

Fugitive
Dust Inhalation3

Upland and/ or
Riparian Soil b

Sediment

Surface Water

Groundwater

Ingestion

Plants

Animals

Inqestion

Plants

Animals

Inqestion

•

Plants

Animals

T—"

Inqestion

l—-~

Plants

Animals

Notes:

The inhalation pathway is minor relative to the ingestion pathway and there is a lack of relevant methods and information for evaluating the
inhalation pathway in cattle. Therefore this pathway was not evaluated quantitatively for beef cattle.

b For the purpose of the livestock risk assessment (LRA), beef cattle are assumed to only be exposed to upland soil.

5-16

-------
Section 5 • Summary of Site Characteristics

The following sections present additional information describing sources of contamination and
affected media. Additional information on exposure pathways and potential receptors is presented in
Section 7—Summary of Risks.

5.2.1 Sources of Contamination

The nature and extent of contamination associated with the Ballard Mine was investigated through
review of background information and extensive sampling of the various media within and near the
Site. The primary source of contaminants at the Site is waste rock located in partially backfilled mine
pits and waste rock dumps. The shale material represents a significant portion of the waste rock
stockpiled in waste rock dumps.

The concentrations of contaminants in waste rock are spatially variable and reflect the chemical
composition of the types of waste rock located on the surface of the dumps. Waste rock produced
during mining included shale, chert, and limestone, with the Center Waste Shale of the Phosphoria
Formation containing the highest concentration of selenium and other contaminants.

This shale material is enriched with selenium (a nonmetal) as well as metals, metalloids and uranium
daughter products (for example, radium and radon). Mine pit walls and roads associated with the Site
represent minor source areas.

Another potential source area within the Site is the Shop (Figure 1-3). As stated in Section 1.3.2, the
Shop will continue to be used for equipment storage, fuel storage, stockpiling of slag material used for
active haul roads, and other activities as needed. Previous investigations identified the presence of
organic contaminants, primarily fuel and solvent-related organic compounds, in soil and groundwater
at the Shop. Selection of a final remedy for the Shop area will be deferred until this area is no longer in
use.

5.2.2 Affected Media

One objective of the RI was to better understand the release of contaminants from source areas and
their subsequent transport to other media. Media affected by mine waste and associated contaminants
include the following:

• Upland soil, surface material/waste rock (18 million cubic yards [yd3])

• Riparian soil and sediment (approximately 5 acres of impacted stream channel sediments and
riparian soil in the Ballard Creek and Wooley Valley Creek drainages)

• Surface water (ephemeral and intermittent streams, ponds, seeps)

• Groundwater (alluvial, and regional bedrock aquifers)

• Upland and riparian vegetation (secondary medium)

Mine-related constituents are released as the result of dissolution or leaching (from contact with rain
or snowmelt) of contaminants from center waste shales present in source areas, and the subsequent
migration (movement) of dissolved constituents into surface water (runoff and seeps) and
groundwater. There has also been erosion of contaminated particles from waste rock dumps, transport
off the dumps, and subsequent deposition in ephemeral and intermittent streams, resulting in impacts
to both stream sediment and riparian soil downgradient of source areas.

5-17

-------
Section 5 • Summary of Site Characteristics

Figure 5-13. Conceptual Site Model Cross Section

^ Evaporation

Runoff

Waste Rock

Former Ground
^ Surface

< i i
^**Mtoto to.

f Waste Rock «
i Dump *

£«pa«Km

Mine Pit

Weathering
Zone

Wells
Formation

Dlrmoody
Formation

Perflation to
Groundwater'

Plants may

• Rain ar>d snowmelt
infiltrate waste rocK

• Water transports
contaminants info
runoff, seeps, and
groundwater

• Runoff lows into
intermittant or
ephemeral streams

accumulate selenium

Riparian plants and
deposited sol and sediment

lEGEW0 No! to Scale

—~ Wderltow
Z Wdcr level

i s«r>

f Plan! irartpftfjon

J Man»!cong»«!

Figure 5-13
CONCEPTUAL SITE MODEL

BALLARD MINE
RECORD OF DECISION
Caribou County, ID

W3!631lrt722&AC

In addition, vegetation growing on mine waste and in contaminated riparian areas near the Site
contain elevated levels of selenium. This occurs through uptake of selenium through the root system
and into plant tissue. Certain types of plants, such as milk-vetch or asters, concentrate (hyper-
accumulate) selenium. Animals that graze on such hyper-accumulating plants growing on mine
materials may be fatally poisoned. Insects and amphibians may be exposed to contaminated water and
sediment in intermittent streams.

Evidence suggests that wind erosion and dispersion does not play a significant role in transporting
contaminants. Figure 5-13 illustrates the relationships between source areas, release and transport
mechanisms, and affected media.

During the RI, a list of COCs was developed for each affected media. COCs are those chemicals that pose
unacceptable risks to human health or the environment. The range of concentrations of COCs in
affected media at the Site are presented in Tables 5-1 and 5-2. Background concentrations for the same
contaminants are presented for comparison. Although there are several COCs associated with the Site,
there has been a focus on selenium because it is widespread and is found to highly exceed risk-based
concentration levels (RBCLs).

5-18

-------
Section 5 • Summary of Site Characteristics

Table 5-1. Data Summary for Contaminants of Concern in Soil, Sediment, and Vegetation
Ballard Mine Site, Caribou County, Idaho

Contaminant

Number of
Samples

Maximum
Concentration
(mg/kg)

Minimum
Concentration
(mg/kg)

Mean
Concentration
(mg/kg)

Exposure Point
Concentration9
(mg/kg)

Background11
(mg/kg)

Upland Soil

Antimony

94

10.9

0.621

4.61

4.89

3.60

Arsenic

94

45.5

3.51

20.0

21.8

15.6

Cadmium

104

167

1.44

32.7

37.6

41.0

Chromium

104

594

0.600

230

327

410

Copper

104

174

6.80

69.8

87.2

51.9

Molybdenum

104

48.7

2.36

20.5

20.0

29.0

Nickel

104

635

4.80

186.5

205

220

Radium-226c

> 300,000d

82.4

0.4

12.7

29.2

15.1

Selenium

130

209

0.120

38.0

53.5

29.0

Thallium

94

3.68

0.176

1.08

1.2

1.10

Uranium

94

87.1

1.10

29.8

38.3

36.0

Vanadium

104

808

1.06

200

239

300

Zinc

104

1,810

38.5

764

835

1,200

Riparian Soil

Arsenic

14

8.91

1.83

4.47

5.83

5.93

Cadmium

44

131

0.440

16.7

25.4

7.24

Chromium

44

2,780

13.9

200

503

43.3

Copper

44

272

7.00

40.3

71.1

24.3

Molybdenum

44

48.6

0.33

9.34

16.4

0.653

Nickel

44

1,620

10.7

108

281

29.6

Selenium

44

570

0.70

34.5

89.5

2.03

Thallium

14

0.681

0.164

0.292

0.376

2.03

Vanadium

44

773

22.2

123

233

0.483

Sediment

Antimony

7

6.60

4.60

5.88

6.05

5.00

Arsenic

7

13.4

3.33

6.06

13.0

4.55

Cadmium

32

138

0.550

19.6

42.1

4.17

Copper

7

70.6

13.2

29.0

51.1

25.5

Molybdenum

7

12.8

8.80

10.8

12.8

0.541

Selenium

32

1,300

0.60

120

208

1.48

Thallium

7

1.63

0.122

0.536

1.30

0.378

Vanadium

32

920

25.0

152

321

113

Upland Vegetation (All Plants)

Arsenic

128

14.2

0.075

0.806

1.42

-

Cadmium

129

4.54

0.0257

1.17

1.55

-

Selenium

160

366

0.304

26.2

39.7

-

a An upper estimate (95 percent) of the mean used for calculation of Site risk exposure point concentration is the level of a chemical to
which a receptor is potentially exposed with the exception of radium-226 that provides the estimated maximum value as predicted using a
uranium sequential decay model.
bThe 95 to 95 upper threshold limit was selected as the proposed background level for upland soils collected in 2009 and 2014.
The 95 percent upper simultaneous limit (USL) was selected as the proposed background level for sediment and riparian soil data sets
collected in 2004 and 2010 (MWH 2013a, 2013b).
c Radium-226 are in pCi/g (MWH, 2015b) and the values provided are the maximum, minimum and mean detected values as predicted from
Site gamma counts.

d Greater than 300,000 discrete gamma count measurements were collected to predict radium-226 concentrations in upland soil.

Notes:

> = greater than

mg/kg = milligram(s) per kilogram
pCi/g = picocuries per gram

5-19

-------
Section 5 • Summary of Site Characteristics

Table 5-2. Data Summary for Contaminants of Concern in Surface Water and Groundwater
Ballard Mine Site, Caribou County, Idaho

Contaminant

Number of
Samples

Maximum
Concentration
(mg/L)

Minimum
Concentration
(mg/L)

Mean
Concentration
(mg/L)

Background3
(mg/kg)

Surface Water (Dissolved, all locations)

Arsenic

63

0.0556

0.0005

0.01

0.00109

Cadmium

184

0.0044

0.0000350

0.000837

0.0001

Selenium (Total)

187

2.84

0.000758

0.334

0.000772

Groundwater (Total)

Arsenic

16

0.0267

0.000456

0.00491

0.00103

Cadmium

84

0.0215

0.00017

0.00333

0.000401

Selenium

148

3.2

0.000534

0.273

0.00278

a Background concentration is equal to the 95% USL of background data set (MWH, 2013a).

Notes:

All concentrations are mg/L.

% = percent

mg/L = milligram(s) per liter

In surface water, sampling shows that the highest concentrations of selenium and other contaminants
are typically found in seeps and intermittent streams close to the waste rock dumps on the margins of
the Site. Concentrations decrease moving away from the source areas because of dilution and
attenuation.

In groundwater, sampling shows that the highest concentrations of selenium are found in three places:
close to the waste rock dumps, in the alluvial aquifers on the margins of the Site, and in the bedrock
aquifer in the southwest portion of the Site. Contaminant plumes in groundwater dissipate moving
away from the source areas.

With respect to sediment and riparian soil, sampling shows a similar pattern, with the most impacted
areas close to the waste rock source areas, with contaminants found in and along intermittent stream
corridors and dissipating downstream.

5-20

-------
Section 6 - Current and Potential Future Land and
Resource Use

6.1 Land Use

6.1.1 Current Land Use

The Site is in a rural and sparsely populated area; the nearest town is Soda Springs, approximately
13 miles away. Farming and seasonal ranching are the dominant land uses in vicinity of the Site. There
are many active and inactive phosphate mines in the area. The surrounding area is also used for
recreation, including hunting on private and public lands, and fishing on the Blackfoot Reservoir and
Upper Blackfoot River.

The Site includes the former mine area and contaminated portions of adjacent properties. The former
mine area is fenced, and access is restricted. The mining haul road on the western edge of the Site is
still used. Current land uses of the adjoining properties include dry-land farming and seasonal
ranching (grazing of cattle). There is likely some limited recreational and tribal use of the state lands at
the Site as well. There are no residences at, or near, the Site. The Site provides suitable habitat to
support wildlife (birds and mammals). Specific habitats and species, including the potential presence
of threatened and endangered species, are described in Section 7.

6.1.2 Reasonably Anticipated Future Land Uses

Reasonably anticipated future uses of the land at the Site include agriculture, seasonal grazing of cattle
and sheep, recreation, and tribal hunting, gathering, and ceremonial use. Residential use of the Site is
unlikely because of the remote location and limited accessibility to existing infrastructure. In addition,
the Selected Remedy assumes that remining will occur during implementation of the remedial action
(RA) (contingent on BLM issuing a phosphate mineral lease and approving a mine plan for extraction
of ore). It is expected that potential remining would end with completion of the remedy.

6.2 Surface Water and Groundwater Use

Surface water resources at and near the Site currently support stock watering, irrigation, and wildlife
uses. These uses are expected to continue. Because of the intermittent nature of the streams in the Site
vicinity, there is limited potential for use of surface water resources for other uses, such as industrial
and recreational use. The streams in the vicinity of the Ballard Mine are intermittent and support the
following organisms: aquatic invertebrates, amphibians, and aquatic dependent wildlife when water is
present. As previously stated, runoff and baseflow from the area near the Site seasonally contribute to
flows in Wooley Valley Creek (on the east) and Ballard Creek (on the south and west) as tributaries to
the Blackfoot River, with very little flow draining to Long Valley Creek to the north. The surface water
bodies in the Ballard Mine area do not sustain fish.

Groundwater use in the Site vicinity is dependent on population, land use, and availability and quality
of surface water and groundwater. Groundwater use near the Site is limited; it is used for livestock
watering and as a water supply for P4's operations. Farming is primarily not irrigated. It is not
anticipated that the shallow alluvial aquifer near the Site will be used for domestic use in the future. It
is possible that water from the Regional Wells Formation aquifer near the Site may be used for
domestic purposes if land uses change in coming decades.

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Section 6 • Current and Potential Future Land and Resource Use

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Section 7 - Summary of Risks

Baseline human health risk assessments (HHRAs) and ecological risk assessments (ERAs) for the Site
are presented in Appendix A of the RI and in the Ballard Mine RI Report Baseline Risk Assessment
Addendum (MWH, 2014). This section summarizes the risk assessments and provides the basis for
taking remedial actions. Methods used to evaluate human health and ecological risks were in
accordance with EPA guidelines for evaluating risks at Superfund sites (EPA, 1989; 1997a). Detailed
explanations of the steps used to conduct the risk assessment are provided in the RI report, including
background information, the exposure model and quantification of exposure, a toxicity assessment,
risk characterization, and an evaluation of uncertainties. Tables associated with Section 7 are
presented in Appendix A.

7.1 Human Health Risk

A baseline HHRA was completed in November 2014 to assess potential risks to humans (both current
and future) from Site-related contaminants. The following sections summarize key elements and
findings of the HHRA.

7.1.1	Chemicals of Potential Concern

Chemicals of potential concern (COPCs) identified in the RI from historical mining operations were
based on inorganic constituents detected in media samples, including soil (collected from 0 to 2 feet
bgs), surface water, sediment, groundwater, and vegetation. The data used in the risk assessment were
collected during the RI, validated and evaluated per EPA's guidance for data usability, and determined
to be usable in the HHRA.

7.1.2	Exposure Assessment

The exposure assessment identified human health exposure scenarios through which a receptor could
contact COPCs in Site media and provide quantitative estimates of the extent of exposure.

7.1.2.1 Exposure Model

Figure 5-10 presents a CSM depicting contaminant sources, release mechanisms, impacted media,
exposure routes, and potential exposed human receptors that were evaluated in the HHRA. Human
health risks were estimated for each exposure scenario, based on current and reasonably anticipated
future land uses (as presented in Section 6), including current and future Native American (e.g., elk
hunting and harvesting vegetation by the Shoshone-Bannock Tribe), current and future seasonal
rancher, current and future recreational hunter, and current and future recreational camper/hiker.
Although future residential use is unlikely, a residential use scenario was used in the HHRA to
determine if land use controls restricting residential use would be warranted. These scenarios
evaluated the exposure to historical mining-related contaminants in environmental media (soil,
sediment, surface water, and groundwater) at the Site.

The routes of exposures evaluated included ingestion, inhalation, dermal contact, and direct radiation.
More specifically, the following exposure routes were evaluated:

•	Current/future recreational hunters - Direct soil contact (incidental soil ingestion, dermal contact
with soil, and inhalation of fugitive dust) and consumption of wild game

•	Current/future recreational campers/hikers - Direct soil contact

•	Current/future Native American hunters and gatherers - Direct soil contact, direct surface water
contact, and consumption of elk and vegetation

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Section 7 • Summary of Risks

• Current/future seasonal ranchers - Direct soil contact, direct contact with groundwater used as a
potable water supply (ingestion and dermal contact with groundwater), and consumption of beef
cattle that ingest contaminants while grazing at the Site

• Hypothetical future residents - Direct soil contact, direct contact with groundwater used as a
potable water supply, and consumption of homegrown fruits and vegetables

In addition, radiological risk from exposure to uranium decay products (such as radium-226 or radon
gas) that emit high-energy electromagnetic radiation was evaluated.

7.1.2.2 Exposure Estimation

The HHRA calculated risks using central tendency exposure (CTE) and reasonable maximum exposure
(RME) assumptions and used the lower of the maximum detected concentration or an upper-bound
average concentration for the exposure point concentration (EPC). The RME is defined as the highest
exposure that is reasonably expected to occur at a site, which in practice combines the 90th to 95th
percentile exposure assumptions for some but not all exposure assumptions. The intent of the RME
scenario is to estimate a conservative exposure case that is still within the range of possibilities. The
CTE uses 50th percentile or median exposure assumptions to approximate an average exposure
scenario. Risks were also calculated for background concentrations. Tables 5-1 and 5-2 show the range
of detected concentrations, the EPC, and background concentrations for the COCs identified at the Site.
Exposure assumptions used for each receptor are presented in Table A-l. Detailed information on the
methods and equations used for calculating the exposure estimates were provided in Appendix A,
Section 3.3.2.2, of the RI report (MWH, 2014).

In addition to exposure to non-radionuclide COPCs, human receptors can be exposed to direct
radiation from uranium-238 and its decay products found in upland soil and from radon-222, a decay
product from uranium-238, in indoor air. Therefore, risk estimates for exposures to uranium-238 and
its decay products in upland soil (for all receptors) and radon-222 in indoor air (for hypothetical
future residents) were also evaluated in the HHRA.

7.1.3 Toxicity Assessment

The toxicity assessment involved a critical review and interpretation of toxicology data from
epidemiological, clinical, animal, and in vitro studies. A review of toxicology data ideally determines
both the nature of health effects associated with a COPC and the probability that a given dose of a COPC
could result in an adverse health effect. The toxicity assessment considered the adverse health effects
associated with exposure to individual and multiple COPCs for long-term health effects. The potential
for adverse health effects was evaluated separately for the following two categories:

• Potential for carcinogenic health effects

• Potential for chronic noncarcinogenic, adverse health effects

Risks of getting cancer because of site exposures were evaluated using cancer slope factors [CSF] and
inhalation unit risk values developed by EPA. Quantification of noncancer hazards relied on published
reference doses (RfD) or reference concentrations (RfC). CSFs are used to estimate the probability of a
receptor getting cancer during their lifetime given exposure to Site-specific contamination; this Site-
specific risk is in addition to the risk of developing cancer because of other causes. RfDs are threshold
values that represent a daily contaminant intake below which no adverse human health effects are
expected even for sensitive receptors (e.g., children or the elderly) exposed over long periods of time.
To evaluate noncarcinogenic health effects, a hazard quotient (HQ) is calculated. The HQ is the ratio of
the Site-specific exposure dose with the chemical-specific RfD. Table A-2 provides the toxicity values
used in the HHRA.

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Section 7 • Summary of Risks

7.1.4 Risk Characterization

The baseline human health risk characterization for the Site integrated results of the exposure and
toxicity assessments to derive a quantitative and qualitative evaluation of potential risks to current
and potential future human receptors. Calculated exposure doses for each COPC identified for a
medium were used to estimate chemical-specific and cumulative carcinogenic risks, and
noncarcinogenic HQs and hazard indices (HI). Methods that were used in the characterization of
human health risks are summarized below.

7.1.4.1 Carcinogenic Risk Characterization

The pathway-specific risk of developing carcinogenic exposure to a carcinogenic chemical was
estimated by multiplying the CSF by the exposure dose, or the unit risk factor (URF) by the
concentration as presented in the following equation:

ILCR(unitless) = CSF (or URF) x Dose (or Concentration)

Where:

ILCR	= Incremental lifetime carcinogenic risk (unitless)

CSF	= Carcinogenic slope factor (milligrams per kilogram per day [mg/kg-day)-1

URF	= Unit risk factor (micrograms per cubic meter [[ig/m3])1

Concentration	= Exposure concentration ([ig/m3)

Dose	= Exposure dose (mg/kg-day)

Carcinogenic risks from multiple COPCs identified for a Site medium are assumed to be additive and
were summed to estimate a cumulative ILCR for all carcinogenic Site COPCs for a given medium. In
addition, carcinogenic risks calculated for various Site media were summed, as appropriate, to
estimate cumulative ILCRs for each receptor.

7.1.4.2 Noncarcinogenic Risk Characterization

The HQ describes the potential for Site COPCs to produce noncarcinogenic effects. The pathway-
specific HQ is defined as the ratio of the exposure dose to the RfD, or the concentration to the RfC (EPA,
1989), as presented in the following equation:

Dose (or Concentration)

HQ (unitless) =

RfD (or RfC)

Where:

HQ	= Hazard quotient (unitless)

Concentration = Exposure concentration (milligrams per cubic meter [mg/m3])

Dose	= Exposure dose (mg/kg-day)

RfC	= Reference concentration (mg/m3)

RfD	= Reference dose (mg/kg-day)

A chemical-specific HQ was derived by summing the pathway specific hazards. An HQ greater than 1
indicates that exposure to that COPC may not be protective of noncarcinogenic adverse health effects.
An HQ of less than 1 means that adverse health effects are unlikely to occur. Individual HQs for Site
COPCs were summed to produce a cumulative HI. In cases where the cumulative HI exceeds 1, the HI
was re-evaluated based on target organ effects, and a maximum target organ-specific HI was reported.
This procedure is consistent with EPA risk assessment guidance (EPA, 1989).

In addition to the estimation of Site risk, Site-specific background data for metals were used to
estimate the risk attributable to naturally occurring concentrations of COPCs. Methods and procedures
that were used in the derivation of background statistics for background data sets are presented in the
final background-levels technical memorandum fMWH, 2013a). Background data were used to

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Section 7 • Summary of Risks

calculate background risks for metals that were retained as refined COPCs using the same process as
described above. In addition, incremental risk estimates were calculated for each Site by subtracting
ambient carcinogenic risk and noncarcinogenic estimates from total carcinogenic risk and
noncarcinogenic hazards for each receptor and COPC combination. The rationale for calculating
incremental risk estimates for metals in environmental media is that some fraction of the
concentration of a metal is naturally occurring. Therefore, an incremental risk estimate represents that
portion of the total risk (Site-related and ambient risk) that is above natural, baseline conditions.

7.1.4.3 Summary of Carcinogenic and Non-Carcinogenic Risk Characterization

Human health RME risk estimates are described here and summarized in Table A-3. Total site risk and
incremental risk estimates are provided for each human health exposure scenario. The HHRA used
acceptable risk and hazard values defined by CERCLA to determine if the contamination at the Site
poses an unacceptable risk to human health. EPA established an acceptable excess cancer risk range
under CERCLA, from 1 in 1,000,000 [1 x 10 6] to 1 in 10,000 [1 x 10 4], of developing cancer from
cumulative exposure to nonradiological Site contaminants over a person's lifetime. The established
threshold below which noncancer health effects are not expected is a hazard index of 1 (EPA, 1997a).
Risk characterization findings are presented separately for radiological and nonradiological exposures.
Cumulative Site cancer risk and noncancer hazard estimates for nonradionuclide contaminants are
shown relative to the regulatory limits on Figures 7-1 and 7-2, respectively. For the recreational
hunter and camper/hiker exposure scenario, cancer risk and noncancer hazard estimates for
nonradiological contaminants were less than EPA-acceptable levels, indicating that these current and
anticipated future land uses are not adversely affected at the Site. For other exposure scenarios
evaluated (Native American, seasonal rancher, and future resident), cancer risk and noncancer hazard
estimates for nonradiological contaminants were greater than EPA-acceptable levels.

Figure 7-1. Human Health RME and CTE Cumulative Site Cancer Risk for all Nonradionuclide
Contaminants

I RME

CTE

l.OE-01

— 1.0E-02

« 1.0E-03
oc

Q>
u

3 1.0E-04

s= 1.0E-05

i.0E-06

1.0E-07

Upper

Acceptable Risk
Level

DEQ Risk Target

Lower Acceptable
Risk Level

Native American

Future Resident

Seasonal Rancher

Recreational User

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Section 7 • Summary of Risks

Figure 7-2. Human Health RME and CTE Cumulative (all media) Noncancer Hazard Index for all
Nonradionuclide Contaminants

RME

¦ CTE

Native American

Future Resident

Seasonal Rancher

Recreational User

Acceptable Risk
Level

The following identifies contaminants and media contributing the greatest to cancer risk and
noncancer hazard indices for exposure scenarios that exceeded regulatory limits:

•	Native American Hunting and Gathering - The primary contributor to risk is incidentally ingested
arsenic in upland soil, incidentally ingested Site surface water, and culturally significant plants
harvested from riparian soil. Primary contributors to the hazard estimate, in order of decreasing
contribution to the HI, are vanadium, nickel, and arsenic in culturally significant plants harvested
from riparian soil.

•	Future Resident - The primary contributor to risk is arsenic in upland soil and ingestion of
groundwater. Primary contributors to the hazard estimate, in order of decreasing contribution to
the HI, are thallium, selenium, and molybdenum in fruits and vegetables grown in upland soil and
irrigated with Ballard Mine groundwater and selenium and arsenic in Site groundwater used as a
drinking water source.

•	Seasonal Rancher - The primary contributor to risk is arsenic in cattle tissue that have grazed on
upland soil and have ingested Site groundwater or surface water. Primary contributors to the
hazard estimate, in order of decreasing contribution to the HI, are thallium and selenium in cattle
that have grazed on upland soil and have ingested Site groundwater or surface water.

Summary of Radiological Risk

Radiological risk was evaluated during the HHRA using sequential decay modeling from total uranium
concentrations and EPA's radiological risk calculator tool (EPA, 2014). All human exposure scenarios
were above EPA's cancer risk threshold except for the recreational camper/hiker. Radium-226 and
radon-222 (hypothetical future resident only) were identified as COCs. A supplemental radiological
Site and background investigation was conducted in 2014 with the results reported in the background
and radiological soil report (MWH, 2015b). There are four distinct lithologies onsite and at
background areas that underlie the surface soils: Dinwoody shales, Meade Peak shales and phosphate
ore beds, Rex Chert, and Wells Formation limestone. Sampling showed that uranium, Radium-226 and

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Section 7 • Summary of Risks

other COCs (e.g., selenium) are highly variable and are particularly elevated in soils overlying the
Meade Peak. The pooled (combined) background data set results in a mean of 4.72 pCi/g and a 95-95
upper tolerance limit of 15.1 pCi/g. The supplemental radiological investigation found that radiological
cancer risk estimates predicted from maximum gamma count results in upland soils and radon flux
measurements confirmed risks were above EPA's cancer risk threshold. The maximum predicted
onsite concentrations of radium-226 and radon-222 are 82.4 pCi/g and 15,600 picocuries per cubic
meter (pCi/m3), respectively. The maximum radium-226 concentration in Site soils (82.4 pCi/g) was
found to be about threefold higher than the maximum radium-226 concentration in background areas
(27.2 pCi/g); maximum radon-222 concentrations measured onsite and in background areas were
roughly equivalent. Considering this, the total cumulative radiological cancer risk estimates for
exposures to radionuclides in Site areas were higher than, but similar to, risk in background areas.

7.1.5 Uncertainty Analysis

Risk assessment methods used, and exposure assumptions made in assessing potential human health
risks, are subject to uncertainty. To compensate for these uncertainties, inherent and intentional
conservatism is generally used to result in protective estimates of risk. However, cancer risk estimates
for radionuclides are generally more accurate than cancer risk estimates for other chemicals. Arsenic
is a notable exception because its cancer risk is likely underestimated based on ongoing EPA studies to
assess its carcinogenicity. In cases where information is limited, assumptions may be based on
professional judgment or subjective estimates that may under or overestimate risks. To assist with
interpretation of the HHRA results, the primary sources of conservatism and uncertainty were
described in the Appendix A, Section 6, of the 2014 RI report (MWH, 2014). Key uncertainties are
described in the following section.

7.1.5.1 Uncertainties in Exposure

Medium-specific EPCs used to quantify exposures are intended to reflect RMEs and there is
uncertainty in what the actual exposure to humans would be. To address this potential uncertainty,
maximum or 95 percent upper confidence limit (UCL) of the mean concentrations are used to estimate
exposure doses for current and hypothetical future receptors exposed to Site-related media. Where the
number of samples are insufficient to calculate 95 percent UCL of the mean concentrations, maximum
concentrations of Site COPCs were used to quantify exposure doses and risk estimates. Based on these
considerations, the exposure doses that are used in the HHRA are believed to represent protective
estimates of exposure.

The risk from an ingested chemical depends on how much is absorbed from the gastrointestinal tract.
This is important for metals in soil at mining sites because some metals exist in poorly absorbable
forms. Failure to account for this may result in a substantial overestimation of exposure and risk. EPCs
for all metals/metalloids, used to evaluate both cancer and noncancer health effects associated with
exposure, assume a bioavailability of 100 percent, except for arsenic, which used EPA's default
bioavailability of 60 percent. The bioavailability assumptions are protective and likely overestimate
the actual risk associated with exposure.

Exposure assumptions (e.g., incidental soil ingestion rates, exposure duration and frequency, and
ingestion of wild game and water) for each exposure scenario were selected, with the intention of
reflecting RMEs. It is unlikely any actual exposure would exceed the levels assumed based on these
assumptions. The exposure pathways evaluated in the HHRA were identified based on current and
anticipated future land use. If Site use changes significantly in the future, exposure pathways and
assumptions may require further evaluation.

7.1.5.2 Uncertainties in Toxicity Assessment

Toxicity information for many chemicals is often limited. Consequently, there are varying degrees of
uncertainty associated with toxicity values (cancer slope factors, reference doses). For example,

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Section 7 • Summary of Risks

(1) uncertainties can arise from extrapolation from animal studies to humans, from high dose to low
dose, and from continuous exposure to intermittent exposure and (2) EPA uses the linearized
multistage mathematical model to extrapolate animal toxicological data for carcinogens, which
assumes that there is no threshold for carcinogenic substances. In addition, some uncertainties exist
not only in the dose response curve but also in the nature and severity of the adverse effects the
chemical may cause. EPA typically deals with this uncertainty by applying an uncertainty factor of 10
to 100 to account for limitations in the database. As a result, in cases where available data do identify
the most sensitive endpoint of toxicity, risk estimates will substantially overestimate true hazard. In
general, uncertainty in toxicity factors is one of the largest sources of uncertainty in risk estimates at a
site; however, is mitigated here because cancer risks are driven by radionuclides and arsenic. Cancer
risk estimates for radionuclides are generally more accurate than cancer risk estimates for other
chemicals. Arsenic is a notable exception because its cancer risk is likely underestimated based on
ongoing EPA studies to assess its carcinogenicity (National Research Council, 2013).

Dermal toxicity criteria are generally not available from EPA. Typically, a simple route-to-route (oral-
to-dermal) extrapolation is assumed such that the available oral toxicity criteria (RfD and CSF) are
used to quantify potential effects associated with dermal exposure. However, as noted in the EPA Risk
Assessment Guidance for Superfund, Part E Supplemental Guidance for Dermal Risk Assessment (2004),
depending upon the COPC being evaluated, there is uncertainty and underestimation of risk and
hazard to human health associated with this approach because the oral toxicity criteria are based on
an administered dose and not an absorbed dose. In general, EPA guidance recommends an adjustment
to the oral toxicity criteria to convert an administered dose into an absorbed dose (EPA, 2004). The
adjustment accounts for the absorption efficiency of the constituent in the "critical study" that is the
basis of the oral toxicity criterion. If the gastrointestinal absorption in the critical study is a high
percent, then the absorbed dose is assumed to be equivalent to the administered dose and no
adjustment is necessary. If the gastrointestinal absorption of a constituent in the critical study is poor
(less than 50 percent), an adjustment to the oral toxicity criteria is recommended to reduce
uncertainty.

7.1.5.3 Uncertainties in Risk Characterization

In general, uncertainty is inherent in the risk characterization step by adding His and cancer risks
across chemicals and media for each receptor. This assumption of additive risk from multiple chemical
exposures may overestimate or underestimate risk because actual interactions among chemicals may
be synergistic or antagonistic rather than additive.

7.1.6 Summary of Human Health Risk Assessment

The conclusions from the HHRA are as follows:

• For the future residential exposure scenario, risk and hazard estimates were much greater than
the acceptable regulatory limits. Risks are driven by arsenic in soil (incidental ingestion and
uptake into homegrown produce), uranium decay products in soil (direct radiation from radium-
226 and inhalation of radon gas in indoor air), and arsenic in groundwater used by a resident as
drinking water and to water garden vegetables. Noncancer hazards are driven by uptake into
homegrown produce from arsenic, cadmium, molybdenum, tin, selenium, and thallium in soil or
groundwater used for drinking.

• For the seasonal rancher exposure scenario, risk and hazard estimates were greater than the
acceptable regulatory limits. Risks are driven by arsenic in soil (incidental ingestion and uptake
into beef consumed by the rancher), uranium decay products in soil (direct radiation), and
ingestion of arsenic in groundwater. Noncancer hazards are driven by consumption of beef that
uptakes arsenic, cobalt, selenium, and thallium from soil, surface water, and groundwater into beef.

• For the Native American exposure scenario, risk and hazard estimates were much greater than the
acceptable regulatory limits. Cancer risks are driven by arsenic in soil (incidental ingestion and

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Section 7 • Summary of Risks

uptake into vegetation) and sediment (uptake into vegetation) and uranium decay products in soil
(uptake into vegetation). Noncancer hazards are driven by uptake into vegetation from arsenic,
cadmium, cobalt, manganese, molybdenum, nickel, tin, selenium, thallium and vanadium in soil,
sediment, or surface water.

•	For the recreational hunter and camper/hiker exposure scenario, cancer risk and noncancer
hazard estimates for nonradiological contaminants were less than EPA-acceptable levels,
indicating that these current and anticipated future land uses are not adversely affected at the Site.

Arsenic (in soil and groundwater) and uranium decay products (in soil; radium-226 and radon-222)
were identified as the contaminants that pose the greatest risk to humans. Risks associated with
Site-related activities are higher than, but similar to, risks in background areas.

7.2 Ecological Risk

ERAs evaluate the likelihood that adverse ecological effects may occur or are occurring at a Site
because of exposure to single or multiple chemical stressors. Risk of such effects results from contact
between ecological receptors (wildlife and aquatic organisms) and stressors (mining-related
contaminants) that are of sufficient exposure to elicit adverse effects. The primary purpose of an ERA
is to identify, evaluate, and describe actual or potential conditions stemming from releases of Site-
related contaminants that can result in adverse effects to existing or future ecological receptors. The
following sections summarize key elements of the ERA.

7.2.1	Chemicals of Potential Ecological Concern

Chemicals of potential ecological concern (COPECs) identified in the RI from mining operations were
based on inorganic constituents detected in media samples, including soil (collected from 0 to 2 feet
bgs), surface water, sediment, and vegetation. Concentrations of COPECs were initially screened
against published screening benchmarks and promulgated standards to refine the list of COPECs
evaluated further in the ERA.

7.2.2	Exposure Assessment

The exposure assessment identified scenarios through which a receptor could contact COPECs in Site
media and provide quantitative estimates of the extent of exposure. Figure 5-11 presents a CSM
depicting contaminant sources, release mechanisms, impacted media, exposure routes, and potential
exposed ecological receptors that were evaluated in the ERA. Ecological receptors are exposed to
COPECs through direct contact with contaminated media and through food web transfer. More
specifically, the following exposure routes were evaluated:

Terrestrial (Upland) Wildlife

•	Incidental ingestion of contaminants in source materials, soil, and surface water through feeding,
foraging, or grooming

•	Plant uptake of contaminants in source materials and soil

•	Dietary uptake of contaminants in prey (food web transfer)

Terrestrial fRiparian") Wildlife

•	Incidental ingestion of contaminants in soil, sediment, and surface water through feeding, foraging,
or grooming

•	Plant uptake of contaminants in soil, sediment, and surface water

•	Dietary uptake of contaminants in prey (food web transfer)

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Section 7 • Summary of Risks

Aquatic and Benthic Receptors

• Direct contact with surface water and sediment

• Dietary uptake (food web transfer)

7.2.2.1 Ecological Resources at Risk

Disregarding the influence of environmental contaminants, the abundance and diversity of wildlife in
an area is dependent on habitat characteristics such as type, quality, and quantity. The Site exists in a
transitional ecosystem between the Great Basin vegetation to the south and the Rocky Mountain
vegetation to the north and east. Land within the area is managed by the state of Idaho, USFS, and BLM.
There is also private land ownership, and parts of the area are developed and used for agriculture or
grazing.

Habitats

There are several terrestrial plant communities present because of variations in elevation, moisture,
temperature, soil type, slope, and aspect. Plant communities include mixed conifer/aspen forest,
sagebrush/grassland, aspen forest, and riparian/wetlands. The mixed aspen and conifer forests are
characterized by occasional dense stands of aspen surrounded by open stands of aspens or conifers.
Dominant conifer species within the vicinity of the Site include lodgepole pine, Douglas fir, and
subalpine fir with understory plants including snowberry, serviceberry, chokecherry, and various
grasses and forbs. The sagebrush communities occur mainly on dry soils or rocky outcrops. Dominant
species include big sagebrush, mountain snowberry, yellow rabbitbrush and antelope bitterbrush, and
various forbs (alfalfa, lupine, scorpion weed, white sage, sticky geranium and mule's ears), as well as
various grass species. Riparian and wetland vegetation is similar in composition to other vegetation
communities, with willow, cattail, rush, and sedge species often present. Surface water features
provide riparian and wetland habitats that support periphyton, plankton, macrophytes, and benthic
invertebrates.

These habitats support a variety of mammalian and avian species. Conifer-aspen communities support
black bear, snowshoe hare, yellow pine chipmunk, great horned owl, downy woodpecker, and western
bluebird. Animals that the sagebrush-grass communities support include but are not limited to coyote,
deer mouse, prairie falcon, sage grouse, and mourning dove. Animals that the riparian and marsh
communities support include but are not limited to moose, beaver, muskrat, belted kingfisher, mallard
duck, great blue heron, sandhill crane, and common snipe.

An aquatic functional use survey of ponds (nonregulated surface water features) was conducted in
June 2004 (DEQ, 2004a). None of the ponds at the Site were characterized as adequate open water,
emergent vegetation, protective cover, and food sources to support a local resident migratory bird
population during typical nesting/breeding seasons. In addition, none of the streams at the Site had, or
were likely to have, supported fish.

Ecological Receptors

This section details specific invertebrates, reptiles and amphibians, birds, mammals, and threatened
and endangered species that have been identified at, or near, the Site.

Invertebrates - Invertebrates such as worms, insects, crustaceans, and spiders are present at the Site.
These organisms are important prey for birds, reptiles, amphibians, and small mammals.

Reptiles and Amphibians - Amphibians include the tiger salamander, the western toad, the leopard
frog, and the western chorus frog. Reptiles include the sagebrush lizard, the gopher snake, the western
and common garter snake, the racer, and the western skink. These organisms are secondary
consumers and may be prey for higher trophic level species.

Birds - Birds near the Site exist in all trophic levels. Species like the house finch, the mourning dove,
and the trumpeter swan are all herbivores. Most species such as the robin, the crow, and nuthatch,

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Section 7 • Summary of Risks

sparrow, and warbler species consume both invertebrates and plant materials. There are also several
species that are primarily carnivorous, including the great blue heron, which consume a diet
dominantly composed of fish (piscivorous), and hawks such as the red-tailed hawk, the northern
harrier and the Cooper's hawk, and several owl species all of which eat mostly small mammals
including mice and voles.

Mammals - Mammal species include species at many trophic levels. These species include primary
consumers and omnivores such as the deer mouse, the long-tailed vole, the least chipmunk, and the
Uinta ground squirrel. These species are often prey for upper trophic level consumers like coyotes. The
mink, which dominantly feeds on area fish, is also a high-trophic-level species potentially occurring in
the Site vicinity. Elk are also present near the Site as primary consumers. Other mammals may include
bats, gophers, beavers, chipmunks, deer, raccoons, porcupines, and hares.

Threatened and Endangered Species - The only threatened or endangered species to potentially use
the Site is the Canada lynx (Lynx canadensis). The greater sage-grouse (Centrocercus urophasianus),
listed as a candidate species, and the North American wolverine (Gulo gulo luscus), listed as a proposed
threatened or endangered species, may use the Site. None of these species have been observed at the
Site to date.

Endpoint Receptor Selection

Endpoints define the focus of the ERA and include both assessment and measurement endpoints.
Assessment endpoints are explicit statements about what aspects of the ecological system are valued
for protection. Each assessment endpoint is evaluated for risk, which may not be directly quantifiable.
In general, assessment endpoints are populations or communities of ecological receptors (EPA,
1997a). Measurement endpoints are the various means by which the assessment endpoints are
evaluated. Measurement endpoints are quantifiable indicators of the state of the valued conditions or
processes through laboratory or field experimentation that are related to the characteristic chosen as
the assessment endpoint. The assessment and measurement endpoints for this ERA are shown in
Table A-4.

Measurement endpoints for upper-trophic-level wildlife are evaluated based on an evaluation of risk
to specific target receptors, because it is neither possible nor practical to evaluate the risk posed to
every potentially exposed species. Therefore, representative species from each feeding guild
potentially using the Site habitats were identified. A feeding guild represents a group of species that
exploit the same ecosystem resources in the same way, and therefore could be expected to have the
same exposure to environmental contaminants. Representative wildlife receptors selected for the ERA
are American goldfinch, American robin, coyote, deer mouse, elk, great blue heron, long-tailed vole,
mallard, mink, raccoon, and northern harrier. In addition, aquatic organisms as a group were
evaluated.

Exposure Estimation for Wildlife

The ERA calculated risks using the lower of the maximum detected concentration or an upper-bound
average concentration for the EPC. Risks were also calculated for background concentrations.

Tables 5-1 and 5-2 show the range of detected concentrations, the EPC, and background
concentrations for the chemicals of ecological concern (COECs) identified at the Site. Exposure
assumptions used for each receptor are presented in Table A-5. Detailed information on the methods
and equations used for calculating the exposure estimates were provided in the RI (MWH, 2014).

The exposure model used for wildlife was focused on ingestion exposure pathways that may include
the ingestion of food, water, or soils and sediments. Food ingestion is the pathway by which most of
the exposure occurs, particularly for bioaccumulative chemicals.

7-10

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Section 7 • Summary of Risks

7.2.3 Effects Assessment

7.2.3.1 Wildlife

Ecological effects associated with exposure to COPECs in the environment were evaluated by
comparing dose estimates to toxicity reference values (TRV). Avian and mammalian TRVs are reported
in terms of mg/kg-day to correspond to the daily dose exposure units for wildlife. Two TRVs were
determined for each avian and mammalian receptor evaluated: (1) the TRVnoael is defined as the
highest dose at which adverse effects are unlikely to occur and (2) the TRVloael is defined at the lowest
dose where a specific biological effect is expected to occur. Toxicity reference values used in the ERA
for mammalian and avian receptors are presented in Tables A-6 and A-7, respectively.

7.2.3.2 Ecological Screening Levels for Aquatic Receptors

Table A-8 presents surface water screening levels used to evaluate effects to aquatic receptors.

7.2.4 Risk Characterization

Risk characterization is the final phase of risk assessment, in which the likelihood of adverse effects is
evaluated by combining the exposure analysis and effects analysis. Risk characterization consists of
estimating and describing risk, including the assumptions and associated level of confidence. The
assessment endpoints are evaluated, and each evaluation method is a line of evidence. In this ERA, the
analyses and risk characterization phases are reported for each assessment endpoint.

The risk characterization for aquatic receptors (amphibians) compared measured COEC
concentrations in surface water to the appropriate water quality criteria to calculate a HQ as described
by the following:

_c*w_
v AWQC

Where:

HQ = Hazard quotient

Csw = Measured surface water concentration (mg/L)

AWQC = Ambient water quality criteria (mg/L)

The risk characterization for wildlife integrates the modeled dietary receptor exposures and chemical
toxicity information. Wildlife exposure and toxicity data were used to calculate the HQ, as follows:

Dose
HQ= TRV

Where:

HQ = Hazard quotient

Dose = Total ingested daily dose of a chemical (mg/kg-d)

TRV = Toxicity reference value (mg/kg-d)

The ERA used the following to interpret HQs:

• An HQnoael less than (<) 1.0 indicates that toxicological effects and potential risk are likely not
occurring.

• An HQnoael > 1-0 and an HQloael < 1-0 generally indicate that toxicological effects and potential risk
may occur. Whether or not risks occur is dependent on the confidence in the toxicity values used
and the LOAEL's magnitude relative to the NOAEL.

• An HQloael >1.0 indicates that toxicological effects and potential risk may occur.

7-11

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Section 7 • Summary of Risks

7.2.4.1 Risks to Aquatic Life

The streams at or near the Site do not support fisheries because of their intermittent or ephemeral
nature; however, these tributaries do flow seasonally into Wooley Valley Creek and the Blackfoot
River. HQs for aquatic organisms (e.g., amphibians) exposed to contaminants in surface water at the
Site are greater than EPA's acceptable hazard criterion of 1 for dissolved barium (HQ=10), boron
(HQ=19), dissolved cadmium (HQ=2), dissolved manganese (HQ=3), total selenium (HQ=101), and
dissolved uranium (HQ=4).

7.2.4.2 Risks to Wildlife

NOAEL- and LOAEL-based ecological hazard estimates for representative wildlife receptors exposed to
environmental media at the Site and background are summarized in Table A-9. The following discusses
LOAEL-based HQs for the Site and background areas.

Long-tailed Vole

HQ estimates for the long-tailed vole exposed to upland surface soil, surface water, and vegetation
range from less than 1 to 90. Selenium was the only COEC with a HQ exceeding 10. Other COECs
exceeding an HQ of 1, in order of decreasing magnitude, are molybdenum, thallium, nickel, and total
chromium. The background HQ for selenium was 1.5, which is well less than the HQ for the Site.

American Goldfinch

HQ estimates for the American goldfinch exposed to upland surface soil, surface water, and vegetation
range from less than 1 to 34. COECs with hazard estimates greater than an HQ of 10, in order of
decreasing magnitude, are selenium and vanadium. One additional COEC, total chromium, has a hazard
estimate exceeding an HQ of 1. The background HQ for selenium was 1.6, which is well less than the
HQ for the Site.

Deer Mouse

HQ estimates for the deer mouse exposed to upland surface soil, surface water and vegetation, and
modeled invertebrates range from less than 1 to 46. COECs with hazard estimates exceeding an HQ of
10, in order of decreasing magnitude, are selenium and cadmium. Additional COECs exceeding an HQ
of 1, in order of decreasing magnitude, are nickel, total chromium, thallium, and molybdenum. The
only COEC with a background hazard estimate exceeding the ecological hazard criterion of 1 is
cadmium.

Raccoon

HQ estimates for the raccoon exposed to riparian surface soil, surface water, sediment, and vegetation
and modeled terrestrial small vertebrates and invertebrates and aquatic invertebrates range from less
than 1 to 1.2. The only COEC with an HQ that exceeds the ecological hazard criterion of 1 is selenium.
Background HQs for were all less than 1.

American Robin

HQ estimates for the American robin exposed to upland surface soil, surface water, and vegetation, and
modeled invertebrates range from less than 1 to 13. The only hazard estimate exceeding an HQ of 10 is
for selenium. Additional COECs exceeding an HQ of 1 are, in order of decreasing magnitude, vanadium,
cadmium, total chromium, nickel, and zinc. Background HQs were all less than 1.

Mallard Duck

HQ estimates for the mallard duck exposed to surface water, sediment, and vegetation, and modeled
aquatic plants and invertebrates, range from less than 1 to 7. The only HQ exceeding 1 is for selenium.
Background HQs were all less than 1.

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Section 7 • Summary of Risks

Coyote

HQ estimates for a coyote exposed to Site upland surface soil, surface water, and vegetation, and
modeled small mammals and invertebrates, are less than 1. Background HQs were all less than 1.

Northern Harrier

HQ estimates for a northern harrier exposed to upland surface soil and surface water and modeled
terrestrial small vertebrates, range from less than 1 to 1.1. The only COEC with HQ that exceeds 1 is
selenium. Background HQs were all less than 1.

Great Blue Heron

HQ estimates for a great blue heron exposed to riparian surface soil, surface water, and sediment, and
modeled terrestrial small vertebrates and aquatic invertebrates range from less than 1 to 7. COECs
with HQs that exceed 1, in order of decreasing magnitude, are selenium and vanadium. Background
HQs were all less than 1.

Mink

HQ estimates for a mink exposed to riparian surface soil, surface water, and sediment, and modeled
terrestrial small vertebrates and aquatic invertebrates, range from less than 1 to 94. COECs with HQs
exceeding 10 for the mink are, in order of decreasing magnitude, selenium, and total chromium. COECs
with HQs that exceed 1 are, in order of decreasing magnitude, thallium, nickel, cadmium, molybdenum,
vanadium, antimony, copper, and zinc. The background HQ for selenium is 2.9, which is well less than
the Site HQ.

7.2.4.3 Uncertainty Analysis

Risk assessment methods used, and assumptions made in assessing potential risks to ecological
receptors, are subject to a certain degree of uncertainty. To compensate for these uncertainties,
inherent and intentional conservatism is generally used to result in protective estimates of risk. In
cases where information is limited, assumptions may be based on professional judgment that may
under or overestimate risks. To assist interpretation of the ERA results, the primary sources of
conservatism and uncertainty were described in Appendix A, Section 6, of the RI report (MWH, 2014).
The following describes key uncertainties related to exposure, effects, and risk characterization.

Uncertainties in Exposure

Major sources of uncertainty in the exposure assessment include the values used to represent the
magnitude and distribution of medium-specific contamination. Because all media cannot be sampled at
all locations, modeling and data extrapolation is necessary. The most likely causes of uncertainty in the
exposure portion of this assessment are the COEC concentrations selected as EPCs for risk estimation.
Contaminants in soils are most often unevenly distributed, and there are uncertainties in the mean,
maximum, and 95 percent UCL values. It is believed, however, that sufficient samples have been
collected and appropriately analyzed to adequately describe the nature and extent of chemical
contamination at the Site.

The risk from an ingested chemical depends on how much is absorbed from the gastrointestinal tract.
This is important for metals in soil at mining sites because some metals are likely not very bioavailable.
Failure to account for this may result in a substantial overestimation of exposure and risk. EPCs for all
metals/metalloids, used to evaluate both cancer and noncancer health effects associated with
exposure, assume a bioavailability of 100 percent. The bioavailability assumptions are protective and
likely overestimate the actual risk associated with exposure.

The selection of representative ecological receptors to evaluate ecological risks in the ERA can be a
source of uncertainty in the risks to receptors. For example, although representative ecological
receptors were chosen for feeding guilds, exposure for risk to piscivorous receptors, including mink
and great blue heron, is likely overestimated because the Site does not support fish.

7-13

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Section 7 • Summary of Risks

Concentrations of COECs in biotic media were estimated using literature-derived bioaccumulation
factors when Site-specific biota concentrations were not available. Uncertainty is associated with using
literature values because the data used to derive those may have been obtained from sites with
different environmental conditions than the Site.

Area-averaging of data over the entire Site potentially underestimates exposures to receptors with
small foraging areas.

Uncertainties in Toxicity Assessment

Toxicity data and other information providing the basis for most of screening benchmarks and TRVs
are commonly based on effects experienced by individual organisms under controlled laboratory
conditions. There is, therefore, considerable concern regarding the ability of these data to reflect or
predict population-level or community-level effects in the field. Adequate field data are lacking for
most chemical stressors and receptor species, and laboratory-based data are therefore used and
accepted in most cases to estimate effects in the field. Effects to individuals in the laboratory may or
may not be representative of effects that may be seen in populations and communities in the field.

Screening benchmarks are generally protective values that likely overestimate risk when used as
thresholds for adverse effects. TRVs derived from lab animals may under or overestimate the actual
toxicity to wildlife. However, because the ERA relied on screening benchmarks and TRVs from a large
variety of appropriate and relevant data sources, the overall uncertainty should decrease compared to
assessments based on only one or a few data sources.

Uncertainties in Risk Characterization

The risk characterization method itself can contribute to uncertainties in the ERA. These uncertainties
are reduced by not relying only on a line of evidence.

7.2.5 Summary of Ecological Risk Assessments
7.2.5.1 Risks to Wildlife Receptors

Effect-based (LOAEL-based) ecological HQs were calculated for terrestrial and riparian upper trophic
level wildlife exposed to contaminants in combined media (soil, sediment, and surface water) at the
Site. Eleven representative upland/riparian receptors were evaluated in the baseline ERA: American
goldfinch, American robin, coyote, deer mouse, elk, great blue heron, long-tailed vole, mallard, mink,
raccoon, and northern harrier. Table A-9 shows the range of sitewide HQs for ecological receptors and
COECs that exceed a HQ of 1. Wildlife risks from exposure to COECs at the Site are summarized as
follows:

•	Four types of COECs resulted in HQ estimates above acceptable thresholds (listed by medium):

Upland Soil - antimony, cadmium, chromium, copper, molybdenum, nickel, selenium, thallium,
vanadium, and zinc

Riparian Soil - antimony, cadmium, chromium, copper, molybdenum, nickel, selenium,
thallium, and vanadium

Surface Water - selenium

Sediment - antimony, cadmium, copper, molybdenum, selenium, and thallium

•	HQ estimates greater than 1 were calculated for the following receptors: long-tailed vole, American
goldfinch, deer mouse, raccoon, American robin, mallard, mink, great blue heron, and northern
harrier.

7-14

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Section 7 • Summary of Risks

• The greatest risk to wildlife was identified from exposure to selenium (Figure 7-3). Comparisons of
Site and background HQ indicate that risk from exposure to selenium is largely attributable to
historic mining activities.

• Risk estimates for the mink and great blue heron are likely significantly overstated because
current conditions in Site waters do not support fish (their preferred prey) to forage upon.

7.2.5.2 Risks to Aquatic Receptors

Figure 7-3. Selenium Hazard Quotients for Wildlife

120

100

Selenium NOAEL

Selenium LOAEL

I Long-tailed vole

I American
goldfinch
i Deer mouse

i American robin

i Mallard

i Mink

Great blue heron

Acceptable Risk
Level

7.3 Livestock Risk

A livestock risk assessment (LRA) is not typically performed for a CERCLA site; however, an LRA was
performed at the Site to evaluate potential impacts of selenium to livestock and to provide land
managers with information that can be used for developing grazing plans and BMPs. Beef cattle, sheep,
and horses currently graze on reclaimed mine sites in the southeastern Idaho Phosphate Resource
Area. These animals graze near the Site, but not currently on the mine itself. Sheep prefer forbs that
may include selenium hyper-accumulator plant species, while beef cattle prefer grasses. As described
in the RI report (MWH, 2014), sheep-grazing on the Site is not allowed under current Site BMPs.
However, the use of the land for the grazing of beef cattle may be a desired beneficial use of reclaimed
mine sites. Based on this information, beef cattle were selected as the livestock indicator receptor for
evaluation in the LRA. Figure 5-12 depicts the livestock exposures pathways evaluated for the Site.

Potential risks to beef cattle were evaluated following the methods and assumptions used to model
exposures for large herbivorous ecological receptors. Beef cattle exposures were modeled for all

7-15

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Section 7 • Summary of Risks

COPECs identified in surficial media at the Site. HQ estimates for beef cattle ranged from 0.32 to 2.5.
The only COEC identified with a HQ greater than 1 for beef cattle was selenium in upland soil.

Note that there are several documented cases of livestock mortality occurring at or near phosphate
mine sites in southeastern Idaho, including the Site. These incidents are believed to have occurred
during acute short-term exposures when grazing animals ingest vegetation with high concentrations of
selenium. Some species of plants (such as milk-vetch and asters) are known to hyper-accumulate
selenium when rooting in surface materials with selenium, such as the waste rock from the Phosphoria
Formation.

7.4 Basis of Action

The response action selected for the Site in this ROD is necessary to protect the public health or
welfare or the environment from actual or threatened releases of hazardous substances, pollutants, or
contaminants into the environment. Such a release or threat of release may present an imminent and
substantial endangerment to public health, welfare, or the environment. A response action is necessary
for the Site because of the following:

Ecological Risk: Individual receptor-specific HQ estimates greater than 50 were associated with
selenium (long-tailed vole and mink) and thallium (mink); individual receptor-specific HQ estimates
between 20 and 50 were associated with antimony (mink), molybdenum (long-tailed vole and mink),
selenium (American goldfinch and deer mouse), and thallium (deer mouse); and individual
receptor-specific HQ estimates between 10 and 20 were associated with cadmium (deer mouse), total
chromium (mink), molybdenum (deer mouse), selenium (American robin), thallium (long-tailed vole),
and vanadium (American goldfinch and American robin).

In addition, the chemical-specific HQs for amphibians exposed to surface water selenium (HQ greater
than 100) is well greater than EPA's acceptable hazard criterion of 1.

Human Health Risk: The cumulative excess cancer risks for an individual under Native American and
seasonal rancher exposure scenario exceed 1 x 10 4 (using reasonable maximum exposure
assumptions). This risk is a result of, in large part, exposure to arsenic in soil, groundwater, surface
water and vegetation, as well as exposure to radium-226 from site soils.

Th noncancer hazard index is greater than 1 for Native American and seasonal rancher exposure
scenarios. These risks are associated with exposure to several noncarcinogenic metals in Site soils,
surface water, and groundwater.

In addition, in some portions of the Site, drinking water standards are exceeded in groundwater.

7-16

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Section 8 - Remedial Action Objectives and
Cleanup Levels

This section presents the RAOs and cleanup levels for the Ballard Mine Site (0U1). The RAOs and
cleanup levels pertain to all portions of the Site except the Ballard Shop Area (0U2). The RAOs provide
a general narrative description of what the Selected Remedy is expected to accomplish. The cleanup
levels are medium-specific standards that will be used to provide a design basis for the Selected
Remedy and evaluate the attainment of RAOs. The RAOs and cleanup levels are based on identified
current and potential future land uses (described in Section 6), results of the human health and
ecological risk assessments (described in Section 7) and identified applicable or relevant and
appropriate requirements (ARARs) (Appendix B).

8.1 Remedial Action Objectives

The following sections describe the RAOs by medium.

8.1.1	Waste Rock and Upland Soils

•	For Human Health - Prevent or reduce risks to seasonal ranchers or tribal users through direct
contact (incidental ingestion) of waste rock and upland soils contaminated with COCs, including
arsenic or uranium (radionuclides of concern: radium-226, radon-222) and others.

•	For the Environment - Prevent or reduce risks to birds and mammals from incidental ingestion of
waste rock and upland soil particles and ingestion of prey contaminated with COCs (antimony,
cadmium, chromium, copper, molybdenum, nickel, selenium, thallium, vanadium, and zinc).

•	Prevent or reduce migration of selenium, arsenic and cadmium from waste rock and upland soils
to groundwater and surface water to protect human and ecological receptors.

8.1.2	Stream Sediments and Riparian Overbank Deposits

•	For Human Health - Prevent or reduce risks to seasonal ranchers or tribal users from direct
contact (dermal contact or incidental ingestion) of stream sediment and riparian overbank
material containing arsenic or radionuclides of concern.

•	For the Environment - Prevent or reduce risks to amphibians and macroinvertebrates and birds
and mammals by incidental ingestion of sediments and riparian overbank deposits and ingestion
of prey contaminated with COCs (antimony, cadmium, chromium, copper, molybdenum, nickel,
selenium, thallium, vanadium, and zinc).

8.1.3	Vegetation

•	For Human Health - Prevent or reduce risks to tribal users or seasonal ranchers from ingestion of
vegetation contaminated with arsenic, selenium, or uranium.

•	For the Environment - Prevent or reduce risks to aquatic (amphibians and macroinvertebrates)
and terrestrial receptors (mammals) from ingestion of vegetation contaminated with selenium.

8.1.4	Surface Water

•	For Human Health - Prevent or reduce risks to seasonal ranchers or tribal users from direct
contact (dermal contact or incidental ingestion) of surface water, and the uptake of surface water
containing arsenic, cadmium, and consumption of selenium in food (for example, livestock and
vegetation); comply with ARARs.

8-1

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Section 8 • Remedial Action Objectives and Cleanup Levels

• For the Environment - Prevent or reduce risk to amphibians and macroinvertebrates from direct
contact with surface water contaminated with cadmium and selenium; comply with ARARs.

8.1.5 Groundwater

• For Human Health - Prevent or reduce risks to seasonal ranchers from ingestion of groundwater
containing arsenic, cadmium, or selenium; comply with ARARs; return useable groundwater to
beneficial uses within a reasonable timeframe.

8.2 Cleanup Levels

The cleanup levels presented here establish acceptable exposure levels for each medium that are
protective of human health and the environment. The cleanup levels specify concentration thresholds
for each contaminant of concern for each medium of concern. The cleanup levels were determined by
considering several factors, including the (1) ARARs, (2) acceptable exposure levels or RBCLs for
human and ecological receptors, and (3) background concentrations of contaminants in soil and
sediment. The cleanup levels will be used as a design basis for and to evaluate the protectiveness of the
remedy.

Table 8-1 presents the cleanup levels for surface water and groundwater; these are based primarily on
the ARARs. The exception is the cleanup level for arsenic in surface water, the basis for which is
described in the notes to Table 8-1.

Table 8-1. Surface Water and Groundwater Cleanup Levels
Ballard Mine Site, Caribou County, Idaho

Medium
COC

Background Concentration3
(Hg/L)

Cleanup Level (|Jg/L)

Basis

Surface Water

Arsenic

1.09

6.2

Cadmium

0.10

0.6

IDAPA 58.01.02c

Selenium

0.772

3.1

FWQCd (EPA, 2016)

Groundwater8

Arsenic

1.03

MCL

Cadmium

0.401

MCL

Selenium

2.78

MCL

a Background concentration is equal to the upper threshold value (95% USL) of the background data set.

b Letter to Barry Burnell, DEQfrom Daniel Opalski, EPA Region 10, dated September 15, 2016, Re: EPA Disapproval of Idaho's Arsenic
Human Health Water Quality Criteria, and Letter to Barry Burnell, DEQfrom Daniel Opalski, EPA Region 10, dated September 27, 2016,
Re: Arsenic Human Health Water Quality Standards for Surface Waters in Idaho.
cState of Idaho Surface Water Quality for Aquatic Life (IDAPA 58.01.02); Criterion Continuous Concentration for Water and Organisms.

Note that criterion is hardness-dependent and that progress toward attaining PRGs needs to consider Site-specific hardness.
d Federal Water Quality Criterion. Aquatic Life Ambient Water Quality Criterion for Selenium - Freshwater 2016 (EPA 822-R-16-006,

June 2016). Note that the criterion includes elements for concentration in both fish tissue and water. If fish-tissue data become available
at any monitoring stations, they will be compared with fish-tissue element(s) of the criterion to evaluate progress toward attaining PRGs.
Fish-tissue elements, in order of hierarchy are: (1) Egg-Ovary = 15.1 mg/kg dry weight; (2) Whole Body = 8.5 mg/kg dry weight; and
(3) Muscle = 11.3 mg/kg dry weight.

8 EPA National Primary Drinking Water Regulations
Notes:

|ig/L = microgram(s) per liter

IDAPA = Idaho Administrative Procedure Act

MCL = maximum contaminant level

PRG = preliminary remediation goal

8-2

-------
Section 8 • Remedial Action Objectives and Cleanup Levels

Table 8-2 presents cleanup levels for COCs in solid media. The cleanup level for each COC in soil or
sediment is equal to the lowest RBCL developed for a human that may be exposed under the current
and reasonably anticipated land uses (seasonal ranching, recreation, and tribal use) and ecological
receptors, unless the background concentration is greater. In cases where the background level is
greater than the RBCL, the cleanup level is set at background. For most contaminants in soil and
sediment, cleanup levels are based on background levels. By setting cleanup levels at background, this
remedy will reduce Site-related risks to levels associated with natural conditions. For contaminants
with a cleanup level based on RBCLs, the cleanup level used an HQ of 1.

Additional information on the derivation of background levels can be found in the Baseline Risk
Assessment, Appendix A of the Ballard Mine RI Report (MWH, 2014), and the On-Site and Background
Areas Radiological and Soil Investigation Summary Report - P4's Ballard, Henry, and Enoch Valley Mines
Remedial Investigation and Feasibility Study (MWH, 2015b). Background samples were collected from
locations near the P4 mine sites that were unimpacted by historical mining activities. In addition, for
upland soil, the background data set was supplemented by samples collected at two reference areas in
the watershed. These reference areas are locations unimpacted by mining and where the range of
lithologies (sedimentary rock formations) are present.

Table 8-2. Soil and Sediment Cleanup Levels
Ballard Mine Site, Caribou County, Idaho

Primary Media
COC

Background Value3
(mg/kg)

Cleanup Levelsb,e
(mg/kg)

Basis'

Upland Soil



Antimony

3.60

3.60

Background

Arsenic

15.6

15.6

Background

Cadmium

41.0

41.0

Background

Chromium

410

410

Background

Copper

51.9

74.5

Risk-based

Molybdenum

29.0

29.0

Background

Nickel

220

220

Background

Radium-226c

15.1

15.1

Background

Radon-222d





d

Selenium

29.0

29.0

Background

Thallium

1.10

1.10

Background

Uranium

36.0

36.0

Background

Vanadium

300

300

Background

Zinc

1,200

1,200

Background

Riparian Soil



Arsenic

5.93

5.93

Background

Cadmium

5.02

7.24

Risk-based

Chromium

43.3

43.3

Background

Copper

24.3

24.3

Background

Molybdenum

0.653

0.653

Background

8-3

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Section 8 • Remedial Action Objectives and Cleanup Levels

Table 8-2. Soil and Sediment Cleanup Levels
Ballard Mine Site, Caribou County, Idaho

Primary Media
COC

Background Value3
(mg/kg)

Cleanup Levelsb'8
(mg/kg)

Basis'

Nickel

29.6

29.6

Background

Selenium

2.03

2.03

Background

Thallium

0.483

0.483

Background

Vanadium

57.9

57.9

Background

Sediment



Antimony

5.00

5.00

Background

Arsenic

4.55

4.55

Background

Cadmium

4.17

4.17

Background

Copper

25.5

25.5

Background

Molybdenum

<0.5

0.541

Risk-based

Selenium

1.48

1.48

Background

Thallium

0.378

0.378

Background

Vanadium

49.1

113

Risk-based

aThe 95 to 95% upper threshold limit was selected as the background level for upland soils collected in 2009 and 2014. The 95% USL was
selected as the background level for sediment and riparian soil data sets collected in 2004 and 2010.(MWH 2013a; 2015b)

bThe cleanup level is equal to the greater of the background concentration or the lowest human health and ecological RBCL.

c Radium-226 are in pCi/g.

d Radon is an inhalation risk, typically associated with residential indoor air scenario, which is not a foreseeable future use.

8 All cleanup levels for soil and sediment are based on background levels, except those noted by footnote f, unless otherwise noted

f Risk level for copper (based on HQ = 1 for birds [American robin]; cadmium (based on a HQ = 1 for protection of Native Americans
consuming culturally significant vegetation in riparian areas); molybdenum (based on HQ = 1 for mammals [mink]); vanadium (based on
a HQ = 1 for birds [great blue heron])

Performance targets will be used to monitor the uptake of selenium in vegetation. It is expected that
meeting the soil cleanup levels (by constructing the ET cover system over source materials in upland
areas and by monitored natural recovery [MNR] in riparian areas) will result in meeting RAOs for
vegetation. The performance targets for the acceptable concentration of selenium in vegetation will be
based on published research related to toxic substances in the diets of animals.

8-4

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Section 9 - Description of Alternatives

This section summarizes and presents the remedial alternatives evaluated in detail in the FS.

It is organized into three subsections: Section 9.1 describes the alternative development process,
Section 9.2 describes the elements that are common to all action of alternatives, and Section 9.3
describes for each medium the alternatives evaluated in detail and provides a summary of remedy
components, distinguishing features, and expected outcomes.

9.1 Development of Alternatives

Initially, a broad range of alternatives were identified and screened, in accordance with the NCP. These
alternatives included a variety of remedial technologies and process options that were potentially
useful to address the RAOs for contaminated media. Cleanup methods and technologies were
evaluated for each of the following media: upland soils and waste rock, stream channel sediment and
riparian soil, surface water, and groundwater.

A list of the alternatives considered for each medium during detailed evaluation is shown in Table 9-1.
The numbering of alternatives in the table is not sequential because some alternatives were screened
out during an initial screening step and the remaining alternatives were not renumbered. For each
medium-specific alternative retained for detailed evaluation, basic information about the components,
distinguishing features, expected outcomes, cost, and other information is summarized.

The Selected Remedy for the Site, presented in Section 12 of this ROD, is the combination of medium-
specific alternatives. Table 9-1 identifies the alternative included in the Selected Remedy for each
medium.

Table 9-1. Alternatives Considered During Initial Screening and During Detailed Evaluation
Ballard Mine Site, Caribou County, Idaho

No.

Remedial Alternative

Cover Notes

Selected
Remedy

ICs

LUCs

O&M

LTM

Upland Soil/Waste Rock Alternatives (USWR)

1

No Action

No cover











4

Grading and Consolidation with ET Cover

5 feet alluvial soil,
1 foot capillary break



Y

Y

Y

Y

6

Grading and Consolidation, with Potential
Incidental Ore Recovery, ET Cover

5 feet alluvial soil,
1 foot capillary break

Y

Y

Y

Y

Y

7

Consolidation of Upland Soil/Waste Rock into
Pits, ET Cover

5 feet alluvial soil,
1 foot capillary break



Y

Y

Y

Y

Surface Water Alternatives" (SW)

1

No Action













2

Sediment traps





Y

Y

Y



3

In Situ Biological Treatment (Wetlands) of Seeps



Y

Y

Y

Y

Y

Sediment/Riparian Soil° (S/RS)

1

No Action













3

Sediment Traps/Basins and MNR



Y

Y

Y

Y

Y

4

Removal with Onsite Disposal and MNR





Y

Y



Y

9-1

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Section 9 • Description of Alternatives

Table 9-1. Alternatives Considered During Initial Screening and During Detailed Evaluation
Ballard Mine Site, Caribou County, Idaho

No.

Remedial Alternative

Cover Notes

Selected
Remedy

ICs

LUCs

O&M

LTM

Groundwater ° (GW)

No Action

MNA

Limited PRB Treatment (Alluvial Groundwater)
and MNA

Extraction and Treatment of Alluvial and Wells
Formation Groundwater

a Except for the No Action alternatives, all SW, S/RS, and GW alternatives rely on upland soil/waste rock source control measures to
mitigate future generation of contaminated surface water, sediment and groundwater, respectively.

Notes:

ET = evapotranspiration

LTM = long-term monitoring

LUC = land use control

MNA = monitored natural attenuation

MNR = monitored natural recovery

O&M = operation and maintenance

PRB = permeable reactive barrier

9.2 Elements Common to All Alternatives

All alternatives (except the No Action Alternative) include ICs, O&M requirements, LTM, and adaptive
management planning. All these elements supplement the engineering controls and treatment
technologies included in the medium-specific alternatives. Costs for these common elements are
included in the medium-specific alternatives described in Section 9.3.

9.2.1 Institutional Controls

ICs are administrative and/or legal mechanisms intended to control land use and site access and to
maintain the integrity of the remedy. There are four categories of IC included in the alternatives:

• Governmental Controls - Imposed land or resource restrictions under the authority of an
existing unit of government. Such controls may include use or changes in local zoning, permits,
codes, or regulations. The alternatives include restrictions on drilling of water supply wells where
contaminated groundwater is present. These restrictions would remain in place until cleanup
levels are achieved.

• Legal Controls - Various legal instruments based on state law, such as easements or covenants,
which prohibit activities that could pose an unacceptable risk from exposure to contamination or
compromise the effectiveness of the remedy components. The alternatives include deed
restrictions, such as easements and covenants, to prevent future land and resource uses that are
incompatible with the remedy. For example, restrictions that are legally enforceable against
current and future land owners would be placed on the lands comprising the Site, to prevent any
future residential use. These deed restrictions would also be structured to prevent or limit future
land uses that may adversely impact the cover system or treatment components of the remedy.

• Communication - Includes community outreach. Risk communications also may be used to
provide notice of contamination on the property and discourage uses that could lead to
unacceptable exposures to such contamination. The alternatives include use of communication

9-2

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Section 9 • Description of Alternatives

tools such as information notices, fact sheets, model grazing plans, and other communication
methods to educate neighboring land owners and potential user groups (such as hunters, hikers
and tribal members) on issues, concerns, and best practices related to Site use.

• Enforcement Tools - States often play a major role in implementing and enforcing ICs. The NCP
requires the state to ensure that any ICs implemented as part of the Selected Remedy are in place,
are reliable, and will remain in place after the RA is complete and the post-RA monitoring occurs.
CERCLA and the NCP do not specify a role for local governments in implementing the IC
instruments identified for the Selected Remedy. However, a local government is often the only
entity that has the legal authority to implement, monitor, and enforce certain types of ICs,
particularly governmental controls such as zoning changes. In addition, difficulties implementing
ICs may be encountered because the property is privately owned, requiring coordination for
access, implementation, and operations of the Selected Remedy.

Because the Site is large and includes several owners (the state, P4, and landowners adjacent to the
mining disturbance), ICs may be selected and implemented on a parcel basis or implemented for
specific components of the Selected Remedy. LUCs such as fences, gates, signs, and similar measures
are also included in the alternatives.

9.2.2 Operation and Maintenance

O&M is an integral component of all alternatives to ensure the integrity of engineering controls such as
the cover system and the proper functioning of treatment facilities, sediment control BMPs, and others.
Each medium-specific alternative includes a variety of O&M requirements. The specific O&M
requirements vary depending on the cleanup method or technology and will be refined during
remedial design.

9.2.3 Long-term Monitoring

Monitoring is also an integral component of all alternatives to assess the performance of different
components of the remedy and the effectiveness of the remedy at attaining cleanup levels.
The monitoring program will include periodic inspections of engineered facilities, and sampling and
analysis of groundwater, surface water, sediment, riparian soil, vegetation, and upland soil.

The information collected through the LTM program would support the Five-Year Review (FYR) process.
FYRs will be performed because site conditions and facilities would not allow for unlimited use and
unrestricted exposure under the current and potential future land uses. These reviews will be used to
evaluate where the remedy is functioning as intended and whether RAOs are being attained.

9.2.4 Adaptive Management Planning

Adaptive management is a structured, iterative process for making decisions on complex projects
where there is uncertainty about the effectiveness of cleanup methods or technologies. Adaptive
management for the Site will create a structured process for measuring and/or monitoring elements of
the remedy, and determine if additional designs, design modifications, or operational changes are
necessary to achieve RAOs. An adaptive management plan will be developed for the selected combined
remedy during remedial design. None of these modifications are anticipated to constitute a significant
or fundamental change to the remedy selected in the ROD.

9.2.5 KeyARARs

This section identifies ARARs that drive the RAOs and response options. These key ARARs are those
that provide a basis for developing an alternative or that help distinguish between alternatives.
Additional information on all ARARs is presented in Appendix B, including information on type (i.e.,
chemical-, location-, and action-specific) and status (i.e., applicable or relevant and appropriate), a
synopsis of the requirement, and a summary of the action to be taken to attain requirements.

9-3

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Section 9 • Description of Alternatives

Key ARARs include the following:

• Idaho Water Quality Standards, including water quality criteria

• National Recommended Water Quality Criteria established under the Clean Water Act (CWA)

• National Primary Drinking Water Regulations, including MCLs, established under the Safe Drinking
Water Act

• Idaho Ground Water Quality Rule

• Portions of the regulations established under the Uranium Mill Tailing Radiation Control Act
(UMTRCA)

• Regulations established under the Mineral Leasing Act that control the development and
reclamation of phosphate mines

• Regulations under the Idaho Surface Mine Reclamation Act pertaining to reclamation of surface
mining operations

Cleanup levels for surface water are based on federal and state water quality criteria for surface
waters, while cleanup levels for groundwater are based on MCLs. These chemical-specific ARARs
influenced development and evaluation of surface water and groundwater alternatives and the
treatment elements included in those alternatives. These chemical-specific ARARs also drove
development of the USWR alternatives. Action-specific ARARs, including state and federal mining and
reclamation requirements, also influenced development of USWR alternatives. These action-specific
ARARs also establish performance requirements for the remediated areas, including the source areas
and intermittent and ephemeral drainages, to ensure the effectiveness and integrity of the cleanup
actions. A key ARAR for developing and distinguishing between sediment and riparian soil alternatives
is Section 404 of the CWA, which requires avoiding disturbances to riparian areas (wetlands) and
minimizing disturbances where they cannot be avoided.

9.3 Description of Alternatives for each Medium

The following subsections provide general descriptions and expected outcomes of the alternatives
considered during the detailed evaluation in the FS. Complete descriptions of the alternatives are provided
in the FS report (MWH, 2017a).

9.3.1 No Action Alternative

Superfund regulations require a No Action Alternative be evaluated for comparison with other
alternatives. For each medium, a No Action Alternative was developed. Under the No Action
Alternative, mine materials would be left in their current condition and no additional cleanup action
would be performed. FYRs would be performed as required by law where the remedy leaves
contamination in place. Monitoring would only be performed as necessary to support FYRs.

Costs associated with the No Action Alternative (for all media) are summarized in Table 9-2. The
expected outcomes for the No Action Alternative are as follows:

• RAOs for upland soil and waste rock would not be attained. Direct exposure risks would persist.
Release and transport of contaminants to other media would continue unabated.

• RAOs for vegetation would not be attained. Uptake of contaminants into plant tissue would
continue, posing risks to humans and ecological receptors.

• RAOs for groundwater and surface water would not be attained. Risks to humans and ecological
receptors would continue unabated.

• RAOs for sediment and riparian soil would not be attained. Risks to humans and ecological
receptors would continue unabated.

9-4

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Section 9 • Description of Alternatives

Table 9-2. Costs and Construction Timeframe, Alternative 1: No Action
Ballard Mine Site, Caribou County, Idaho

Estimated Cost/Time

Capital Costs

$0

Total O&M Costs (30 years)

$0

Total Periodic Costs (30 years)

$107,885

Total Present Value Costs

$108,000

Construction Timeframe

None

Time to Achieve RAOs

Will never comply with RAOs

9.3.2 Upland Soil and Waste Rock (USWR) Alternatives

Three alternatives were evaluated to address risks associated with upland soil and waste rock. Each of
these alternatives share some common elements. All would grade and shape waste rock dumps to
promote runoff, but with varying degrees of pit backfill and earthworks. All alternatives would include
construction of a cover system over the mine wastes that are left at the Site, an area of more than 500
acres. One alternative (USWR 6, developed at the request of P4) allows for the possibility of ore recovery
during implementation of the remedy and two others (USWR 4 and USWR 7) assume no ore recovery
during the RA. All the retained USWR alternatives will achieve RAOs for soil and waste rock in a
reasonable timeframe through construction of an ET cover system. All USWR remedial alternatives will
comply with federal and state mine reclamation requirements. The cover system will also meet
requirements under UMTRCA that engineering controls be designed to be effective for at least
200 years.

The Selected Remedy includes USWR 6.

USWR 4—Grading and Consolidation with an Evapotranspiration Cover System, Institutional
Controls, and Operations and Maintenance/Long-term Monitoring

Under USWR 4, portions of the upland soil/waste rock dumps throughout the Site would be excavated
and consolidated in the onsite pits to cover any exposed beds of the Phosphoria Formation or
graded/contoured in-place to create slopes that effectively shed stormwater and snowmelt (maximum
of 3:1 slopes). The new USWR surfaces inside and outside of the pits would be capped with an ET cover
system. The ET cover would be constructed of materials from designated borrow sources onsite and
adjacent to the Site. The ET cover system would be designed to store water that would evaporate or be
transpired by the vegetation planted on the surface of the cover system, thus minimizing infiltration
into the underlying waste rock. Based on current information regarding nearby borrow material and a
preliminary cover analysis (modeling), the selected ET cover would require 3.7 million yd3 of material
and would consist of (starting from the top of the cover) the following layers (Figure 9-1):

•	Approximate 5-foot thickness of medium-grained, unimpacted alluvial material

•	At least 1-foot thickness of high-permeability (coarse grained), unimpacted fill material as a
capillary break

An ET cover would also extend over areas where the original waste rock was excavated for placement
into the pits, thereby exposing the underlying native surface soils (assumed to have elevated residual
contaminant concentrations).

9-5

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Section 9 • Description of Alternatives

Figure 9-1. Conceptual Monolithic ET Cover

Figure 9-1.

Monolithic ET Cover

Ballard Mine, Caribou County, ID-Record of Decision
Amended from P4 Productions, LLC, FS Technical Memorandum #2; ET Cover Conceptual Design, 2017.	Caribou County, Idaho

	cti2m-

AXOBU1S14S2BOI

Reclamation vegetation types would be selected to form an extensive root system to effectively
mi tigate stormwater and snowmelt sheet flow and rill erosion of the cover surface and to transpire
water that infiltrates the upper layer of the cover system. LTM and O&M would be necessary to ensure
that revegetation is successful and is not incompatible with the selected cover system (such as
vegetation with roots that could penetrate the ET cover system) and to repair any stormwater erosion
that might occur to the cover system. ICs, fencing, and signage would be implemented to preserve the
integrity of the waste rock cover by preventing activities that could compromise the cover.

USWR 4 effectively reduces infiltration of water through the waste rock, which prevents or reduces
migration of contaminants and, therefore, is protective of human health and the environment.

This cover is made of earthen materials that are available onsite or adjacent to the Site.

The schedule and costs associated with USWR 4 are summarized in Table 9-3. The expected outcomes
for USWR 4 are as follows:

•	RAOs for USWR will be attained by construction of an ET cover system, which will isolate the
waste rock (source materials) from direct contact by receptors.

•	The cover system will also contribute to achieving RAOs for all other media, by isolating source
materials from surface runoff, minimizing deep infiltration of precipitation and snowmelt into
waste rock and subsequent release of contaminants to groundwater, providing clean growth
media to minimize uptake of selenium into vegetation, and minimizing release of contaminants
from source areas into the ephemeral and intermittent channels on the margins of the Site.

9-6

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Section 9 • Description of Alternatives

Table 9-3. USWR 4, Estimated Cost and Construction Timeframe
Ballard Mine Site, Caribou County, Idaho

Estimated Cost/Time

Capital Costs

$50,099,136

Institutional Control Costs

$25,000

Total O&M Costs (30 years)

$388,294

Total Periodic Costs (30 years)

$215,770

Total Present Value Costs

$50,679,000

Construction Timeframe

3 to 5 years

Time to Achieve RAOs

3 to 5 years

USWR 6—Grading and Consolidation, Possibility of Incidental Ore Recovery,
Evapotranspiration Cover System, Institutional Controls, and Operations and
Maintenance/Long-term Monitoring

USWR 6 is similar to USWR 4 in most respects. The primary differences arise because USWR 6 allows
for the possibility that phosphate ore would be recovered during remedy implementation. Information
collected during site characterization activities confirmed that approximately 4 million tons of
phosphate ore remain at the Site, both exposed at the surface and in the bottoms and sidewalls of
existing mine pits. Although ore recovery is not part of USWR 6, the alternative was developed to be
compatible with ore recovery.

In addition, the CERCLA 121(e) permit exemption does not apply to BLM mineral leasing and mine
permitting requirements. For ore to be recovered during implementation of the remedy, P4 would
need to acquire a federal mineral lease and seek BLM approval of a plan for ore recovery. The CERCLA
process cannot authorize ore recovery activities. EPA would coordinate remedial design/remedial
action (RD/RA) activities with concurrent remining through coordination with P4 and BLM.

USWR 6 has the following features that distinguish it from USWR 4 and USWR 7:

• Potential remining activities are expected to generate additional waste rock and overburden
material for backfill of mine pits and for construction of portions of the ET cover system (such as
the capillary break layer). As a result, under USWR 6, mine pits would be backfilled to a greater
extent than USWR 4, creating landforms that are more prominent in appearance. Because plans for
remining may change, and because of uncertainty associated with acquiring a mineral lease and
BLM approval of a mine plan, USWR 6 includes backfilling of mine pits regardless of the amount of
remining. However, the extent of pit backfilling and the final shape of remediated surfaces may
differ depending on the scope of remining. At a minimum, mine pits will be backfilled to cover
exposed ore beds and shale units of the Phosphoria Formation. Waste rock dumps and backfilled
pits will be graded and shaped to ensure geotechnical stability and promote runoff. The conceptual
cover design is the same for all alternatives and will cover all mining wastes. The exterior
boundaries of the cover system under USWR 6 would be similar to USWR 4 and USWR 7, but there
will be some differences in the placement of cover within the footprint of the mining disturbance.

9-7

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Section 9 • Description of Alternatives

Under USWR 6, the cover system is expected to be more contiguous within the exterior
boundaries. The expected performance of the cover system is similar for all alternatives. The
sequence and timing of remedial actions, as well as the plans and specifications for the USWR
component of the remedy, will be developed during remedial design.

• The cost associated with earthworks also distinguishes USWR 6 from USWR 4 and USWR 7.

Earthworks associated with potential remining (such as excavation and placement of waste rock,
grading and shaping waste dumps and backfilled pits) will also advance remediation efforts,
thereby reducing costs associated with remediation. Of the total capital cost of all earthworks,
approximately 75 percent are associated with potential remining and 25 percent are associated
with remediation. The estimated cost for USWR 6 is $36.9 million, which is significantly less than
for USWR 4 and USWR 7. Costs associated with USWR 6 are summarized in Table 9-4. Additional
documentation of cost estimates is presented in the FS.

The expected outcomes for USWR 6, with respect to RAOs, are the same as for USWR 4 and USWR 7.

Table 9-4. USWR 6, Estimated Cost and Construction Timeframe
Ballard Mine Site, Caribou County, Idaho

Estimated Cost/Time

Capital Costs

$36,974,250

Institutional Control Costs

$50,000

Total O&M Costs (30 years)

$388,294

Total Periodic Costs (30 years)

$215,770

Total Present Value Costs*

$36,974,250

Construction Timeframe

6 to 8 years

Time to Achieve RAOs

6 to 8 years

USWR 7—Complete Consolidation of Existing Upland Soil/Waste Rock into the Pits,
Evapotranspiration Cover System, Institutional Controls, and Operations and
Maintenance/Long-term Monitoring

USWR 7 would excavate and consolidate all waste rock from external waste rock dumps and fill the
existing pits. The volume of existing waste rock is sufficient to fill existing pits from crest to crest,
cover the exposed ore beds, and create 3:1 maximum slopes and a topographic surface that directs
stormwater out of the pits and away from the source area. The graded upland soil and waste rock
surfaces (including external waste rock dump areas where contamination remains) would be capped
with the ET cover system, as described in USWR 4. As with USWR 4 and USWR 6, this alternative
includes ICs to restrict activities that could disturb the cover systems and O&M and LTM to maintain
the integrity of the cover system and limit growth of plants that are incompatible with the selected
cover system.

Under this alternative, the final landforms following remediation would be different than USWR 4 or
USWR 6. Much of the waste rock in the external dumps would be removed and mine pits would be
backfilled to a greater extent than USWR 4 or USWR 6. Implementation of this alternative would cost
significantly more than USWR 4 or USWR 6.

The schedule and costs associated with USWR 7 are summarized in Table 9-5. The expected outcomes
for USWR 7, with respect to RAOs, are the same as for USWR 4 and USWR 6.

9-8

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Section 9 • Description of Alternatives

Table 9-5. USWR 7, Estimated Cost and Construction Timeframe
Ballard Mine Site, Caribou County, Idaho

Estimated Cost/Time

Capital Costs

$112,540,985

Institutional Control Costs

$25,000

Total O&M Costs (30 years)

$388,294

Total Periodic Costs (30 years)

$215,770

Total Present Value Costs

$113,121,000

Construction Timeframe

5 to 7 years

Time to Achieve RAOs

5 to 7 years

9.3.3 Surface Water (SW) Alternatives

Two alternatives were evaluated to address impacts to surface water: SW 2 focuses on ICs, while SW 3
focuses on treatment of contaminated seeps and springs. This section presents a general description of
each alternative.

Both SW alternatives would work in concert with other components of the remedy described in the
USWR alternatives, GW alternatives, and S/RS alternatives. The ET cover system, included in the USWR
alternatives, will substantially contribute to meeting surface water RAOs because releases of
contaminants to surface water will be greatly reduced over time. These load reductions will occur
because stormwater runoff from the cover system will not contact source materials, and because the
cover system will reduce recharge to the seeps over time. The seeps and springs located below waste
rock dumps are expected to dry up or significantly decrease in flow over time; however, residual seeps
and springs would remain in some locations for an indefinite period. PRBs, described in the
groundwater component of the Selected Remedy, will also reduce the concentrations of contaminants
that discharge to ephemeral and intermittent headwater reaches of area streams, contributing to
achievement of surface water RAOs. Sediment traps/basins, described in the S/RS alternatives, will
also address releases of contaminants to headwater reaches during construction of the cover system.

The other components of the remedy (i.e., cover system, PRBs, and sediment basins) summarized in
this section and described in greater detail under the USWR, GW, and S/RS alternatives are expected to
substantially contribute to attainment of surface water RAOs over the long term. The two alternatives
that were evaluated address remaining impacts to surface water by focusing on the residual seeps and
springs, and these elements may be phased out over time depending on the effectiveness of the cover
system (under the USWR alternatives).

The Selected Remedy includes SW 3.

SW 2—Institutional Controls

Under this alternative, ICs and fencing would restrict access to surface water until source controls
(cover system) and treatment (PRBs) described under the alternatives for other media have
substantially reduced mine-affected seep/spring discharge or until cleanup levels are achieved.

The schedule and costs associated with SW 2 are summarized in Table 9-6. The expected outcomes for
SW 2 are as follows:

• RAOs will be attained in the long term by relying on components of the remedy described in other
media alternatives, including the cover system, PRBs, and sediment basins.

• In the short term, RAOs will not be fully attained. Discharges of contaminated water at springs and
seeps would persist until the cover system is constructed and effective.

9-9

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Section 9 • Description of Alternatives

Table 9-6. SW 2, Estimated Cost and Construction Timeframe
Ballard Mine Site, Caribou County, Idaho

Estimated Cost/Time

Capital Costs

$86,112

Institutional Control Costs

$50,000

Total O&M Costs (30 years)

$497,924

Total Periodic Costs (30 years)

$215,770

Total Present Value Costs

$850,000

Construction Timeframe

5 to 10 years (constructed with cover)

Time to Achieve RAOs

5 to 10 years (after construction)

SW 3—In Situ Biological (Wetlands) Treatment of Source Area Seepage

Under alternative SW 3, in situ biological treatment cells (or constructed wetlands), would be
constructed at mine-affected seep/spring locations. The residual mine-affected water at the
seeps/springs would be treated via biologically mediated reactions, including reduction using
anaerobic bacteria, resulting in the removal of contaminants through precipitation or sorption.
The treated water would flow out of the treatment cells to the downstream drainages or
evapotranspire within the treatment cells. ICs and fencing would be used to control human exposure at
the treatment cells. Treatment cells may be phased out over the long term as source controls (i.e.,
cover system) and treatment technologies (e.g., PRBs) described in other media alternatives become
effective and reduce mine-affected seep/spring discharge or as cleanup levels are achieved.

The schedule and costs associated with SW 3 are summarized in Table 9-7. The expected outcomes for
SW 3 are as follows:

•	RAOs will be attained at the conclusion of RA, more quickly than SW 2. The quality of surface water
in drainages near the site would improve soon after the treatment units are constructed and
operational.

•	Treatment of seeps and springs will also contribute to water quality improvement in shallow
alluvial aquifer, as some treated water will infiltrate and recharge the alluvial aquifer.

• ICs and fencing will be used to control human exposure.

Table 9-7. SW 3, Estimated Cost and Construction Timeframe
Ballard Mine Site, Caribou County, Idaho

Estimated Cost/Time

Capital Costs

$576,835

Institutional Control Costs

$50,000

Total O&M Costs (30 years)

$589,254

Total Periodic Costs (30 years)

$215,770

Total Present Value Costs

$1,432,000

Construction Timeframe

5 to 10 years (concurrent with cover construction)

Time to Achieve RAOs

5 to 10 years (after construction)

9.3.4 Stream Channel Sediment and Riparian Soil (S/RS) Alternatives

Two alternatives were evaluated to address sediment and riparian soil in the ephemeral and
intermittent drainages near the Site. S/RS 3 relies on MNR, over time, as a primary element of the

9-10

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Section 9 • Description of Alternatives

alternative to achieve RAOs. S/RS 3 also includes use of sediment traps and basins near the source
areas to capture sediment that may be mobilized during RA. S/RS 4 focuses on excavation of all
contaminated material in stream corridors followed by reconstruction and revegetation of the stream
corridor to a naturally functioning condition. A general description of each alternative for stream
channel sediment/riparian soil is presented in the following paragraphs. RAOs for sediment and
riparian soil are expected to be achieved by both alternatives.

Both S/RS alternatives rely on construction of the cover system (described in the USWR alternatives).
The cover system will contribute to attaining RAOs by isolating source materials from surface runoff
and eliminating or minimizing the erosion and transport of contaminated particles into the ephemeral
and intermittent stream channels on the margins of the Site. The cover system will also reduce
contaminant loading from seeps and springs.

The Selected Remedy includes S/RS 3.

S/RS 3—Sediment Traps/Basins, Monitored Natural Recovery, and Institutional Controls

Under S/RS 3, MNR will reduce concentrations of contaminants through natural processes. Over time,
clean runoff, and associated sediment transport and erosion will disperse and dilute or cover
contaminated stream channel/overbank deposits and thus reduce risks to receptors. Implementation
of MNR during the RA includes routine sediment/riparian soil sampling in impacted stream corridors
down to the confluence with the Blackfoot River, and periodic data evaluations to monitor the progress
of natural recovery and to support CERCLA FYRs. S/RS 3 also includes sediment traps and basins that
would be installed below source areas in the upper reaches of the mine-affected drainages to capture
contaminated sediment entrained in the stormwater runoff during construction of the remedial cover.
Sediment in these traps would be cleaned out and disposed of in a designated area under the USWR
cover system. This alternative also includes fencing and implementation and enforcement of ICs to
prevent human exposure to contaminated sediment and riparian soil until RAOs are achieved.

The schedule and costs associated with S/RS 3 are summarized in Table 9-8. The expected outcomes
for S/RS 3 are as follows:

• Sediment mobilized by construction activities would be captured in sediment traps, preventing
transport during runoff events.

• Intrusive physical damage to existing riparian environment will be minimal, as construction
activities will avoid or minimize impacts to intermittent stream channels.

• RAOs will be attained by controlling sources of contamination to the intermittent streams, MNR,
and ICs.

• Time to achieve RAOs is uncertain, but conditions are expected to improve slowly over time, taking
more than 10 years beyond remedy completion.

Table 9-8. S/RS 3, Estimated Cost and Construction Timeframe
Ballard Mine Site, Caribou County, Idaho

Estimated Cost/Time

Capital Costs

$240,433

Institutional Control Costs

$75,000

Total O&M Costs (30 years)

$204,216

Total Periodic Costs (30 years)

$215,770

Total Present Value Costs

$736,000

Construction Timeframe

5 to 10 years (concurrent with cover construction)

Time to Achieve RAOs

10+ years after construction

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Section 9 • Description of Alternatives

S/RS 4—Removal and Onsite Disposal, Monitored Natural Recovery, and
Institutional Controls

Sediment and riparian soil and associated vegetation in the upper reaches of the mine-affected
drainages, where the highest contaminant concentrations are detected, would be excavated,
transported, and consolidated under the ET cover system. Impacted drainages would then be
reconstructed and revegetated to a naturally functioning condition. MNR, ICs, and fencing would be
implemented, in a similar fashion as described in S/RS 3, for sediment and riparian soil in the distal
reaches of the mine-affected drainages where contaminant concentrations are lower.

The schedule and costs associated with S/RS 4 are summarized in Table 9-9. The expected outcomes
for S/RS 4 are as follows:

• In reaches where excavation of contaminated sediment occurs, cleanup levels will be achieved
quickly. In the more distal reaches where MNR is implemented, conditions will improve slowly
over time, likely taking more than 10 years after construction to achieve RAOs.

• Excavation of contaminated sediment from stream channels and adjacent riparian zones will
temporarily destroy stream channels. There is significant uncertainty about the recovery of
ecological functions and values in these sensitive areas.

Table 9-9. S/RS 4, Estimated Cost and Construction Timeframe
Ballard Mine Site, Caribou County, Idaho

Estimated Cost/Time

Capital Costs

$1,219,988

Institutional Control Costs

$75,000

Total O&M Costs (30 years)

$80,126

Total Periodic Costs (30 years)

$215,770

Total Present Value Costs

$1,591,000

Construction Timeframe

5 to 10 years (concurrent with cover construction)

Time to Achieve RAOs

10 years after construction

9.3.5 Groundwater (GW) Alternatives

Three alternatives were evaluated to address impacts to groundwater. The alternatives ranged from a
passive approach using MNA (GW 2) to a semipassive approach using PRBs (GW 3) and an active
approach including pumping and treatment of groundwater (GW 5b). This section presents a general
description of each alternative.

All three alternatives would rely primarily on other components of the remedy to attain RAOs. The ET
cover system (included in the USWR alternatives) is a key element that will substantially contribute to
meeting groundwater RAOs. The cover system will greatly reduce deep infiltration of precipitation and
snowmelt, recharge to groundwater, and contaminant release to groundwater. In addition, collection and
treatment of contaminated seeps and springs (under SW 3) will also contribute to meeting groundwater
RAOs because the seeps and springs recharge shallow alluvial groundwater. In the longer term,
groundwater RAOs are expected to be attained through implementation of the USWR and SW alternatives.

The GW alternatives described here will provide a higher level of confidence that RAOs will be achieved.
Alternatives GW 3 and GW 5b, which include treatment components, will accelerate progress toward
achieving RAOs. All alternatives include implementation and enforcement of ICs to prevent well drilling
and domestic use of groundwater in areas where contaminant plumes are located until RAOs are attained.

The Selected Remedy includes GW 3.

9-12

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Section 9 • Description of Alternatives

GW 2—Monitored Natural Attenuation and Institutional Controls

All GW alternatives rely primarily on the strategy of constructing a cover system (under the USWR
alternatives) and treating seeps and springs (under the SW 3) to reduce the concentration of contaminants
in groundwater.

GW 2 includes MNA, which relies on physical, chemical, and biological processes to further reduce
contaminant concentrations in groundwater over time. It may be used as a polishing step depending
on the effectiveness of source controls and treatment. It is anticipated that GW 2 would require more
time to achieve RAOs than GW 3 and GW 5b, which include treatment. Use of MNA during the RA
would require routine groundwater monitoring, periodic data evaluations to track the progress of
natural attenuation, and implementation of an adaptive management strategy. The schedule and costs
associated with GW 2 are summarized in Table 9-10. The expected outcomes for GW 2 are as follows:

• In the short term, RAOs will not be fully attained. Implementation and enforcement of ICs
regarding well drilling and use of groundwater will prevent direct human exposure until cleanup
levels are achieved.

• RAOs will be attained in the long term by relying on components of the remedy described in other
media alternatives, including the cover system and treatment of seeps and springs.

• MNA would be used as a polishing step to dilute and disperse contaminants in the existing plumes
over time. The length of time needed to achieve RAOs is uncertain, but conditions are expected to
improve slowly over time, taking more than 10 years beyond remedy completion.

Table 9-10. GW 2, Estimated Cost and Construction Timeframe
Ballard Mine Site, Caribou County, Idaho

Estimated Cost/Time

Capital Costs

$166,222

Institutional Control Costs

$125,000

Total O&M Costs (30 years)

$881,076

Total Periodic Costs (30 years)

$215,770

Total Present Value Costs

$1,389,000

Construction Timeframe

5 to 10 years (constructed concurrent with cover)

Time to Achieve RAOs

10+ years after cover construction

GW 3—Limited Permeable Reactive Barrier Treatment of Alluvial Groundwater, Monitored
Natural Attenuation, and Institutional Controls

Similar to GW 2 and GW 5b, this alternative also relies on the strategy of constructing a cover system
(under the USWR alternatives) and treating seeps and springs (under SW 3) to reduce the
concentration of contaminants in groundwater.

Under this alternative, PRBs (trenches filled with reactive media to treat groundwater via
precipitation) would be constructed near the margins of waste rock dumps to intercept and treat
shallow alluvial groundwater. The PRBs would be sited upgradient of perennial seeps/springs. In some
cases where the affected alluvial groundwater is excessively deep, extraction wells may supplement
the system and discharge to the PRBs. PRBs will also reduce the concentrations of contaminants that
discharge to ephemeral and intermittent headwater reaches of area streams. If contaminant
concentrations are not reduced to cleanup levels through the use of PRBs, MNA would be used as a
polishing step to further reduce concentrations of contaminants in groundwater plumes.
Implementation and enforcement of ICs will prevent human exposure to contaminated groundwater
until RAOs are achieved.

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Section 9 • Description of Alternatives

The schedule and costs associated with GW 3 are summarized in Table 9-11. The expected outcomes

for GW 3 are as follows:

• It is expected that RAOs would be attained at RA completion (10+ years following construction of
the cover system). If low levels of groundwater contamination remain, MNA would be used as a
polishing step to further reduce the concentration of contaminants in groundwater plumes.

• Use of PRBs will accelerate progress toward meeting RAOs compared to GW 2.

• If contaminant concentrations are not reduced to cleanup levels through the use of PRBs (and
construction of the cover system), MNA would be used as a polishing step.

• Implementation and enforcement of ICs will prevent human exposure to contaminated
groundwater until RAOs are achieved.

Table 9-11. GW 3, Estimated Cost and Construction Timeframe
Ballard Mine Site, Caribou County, Idaho

Estimated Cost/Time

Capital Costs

$727,004

Institutional Control Costs

$125,000

Total O&M Costs (30 years)

$1,004,968

Total Periodic Costs (30 years)

$215,770

Total Present Value Costs

$2,073,000

Construction Timeframe

5 to 10 years (constructed concurrent with cover)

Time to Achieve RAOs

10+ years after cover construction

GW 5b—Groundwater Recovery and Treatment and Institutional Controls

Similar to GW 2 and GW 3, this alternative relies on the strategy of constructing a cover system (under
the USWR alternatives) and treating seeps and springs (under SW 3) to reduce the concentration of
contaminants in groundwater.

This alternative includes extraction and treatment of mine-influenced groundwater, including the
alluvial and Wells Formation groundwater (deep regional water). Extraction trenches, or a limited
number of extraction wells in areas of deep alluvium, would be used to remove mine-affected alluvial
groundwater upgradient of the perennial seeps and springs and in downgradient locations on the
eastern and western sides of the Site. Extraction wells would be used to remove groundwater from the
Wells Formation. The extracted groundwater would be treated to remove selenium and other
contaminants using a physical, chemical, or biological treatment system (for the Wells Formation
either alone or in combination with alluvial water). Water from the Wells Formation would be
returned to the Wells Formation through engineered infiltration wells following treatment. Water
from the alluvial aquifer would be discharged to a constructed basin and allowed to infiltrate back into
the alluvial aquifer following treatment. Implementation and enforcement of ICs will prevent human
exposure to contaminated groundwater until RAOs are achieved.

The schedule and costs associated with GW 5b are summarized in Table 9-12. The expected outcomes
for GW 5b are as follows:

• It is expected that RAOs would be attained at RA completion (10+ years after construction of the
cover system).

• Extracting and treating contaminated groundwater will accelerate progress toward meeting RAOs,
compared to GW 2.

• Implementation and enforcement of ICs will prevent human exposure to contaminated
groundwater until RAOs are achieved.

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Section 9 • Description of Alternatives

Table 9-12. GW 5b, Estimated Cost and Construction Timeframe
Ballard Mine Site, Caribou County, Idaho

Estimated Cost/Time

Capital Costs

$15,271,969

Institutional Control Costs

$100,000

Total O&M Costs (30 years)

$8,631,241

Total Periodic Costs (30 years)

$215,770

Total Present Value Costs

$24,219,000

Construction Timeframe

5 to 10 years (constructed concurrent with cover)

Time to Achieve RAOs

10+ years after cover construction

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Section 9 • Description of Alternatives

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Section 10 - Comparative Analysis of Alternatives

This section summarizes the comparative analysis of alternatives that was presented in the FS. The
Superfund regulations require that alternatives be evaluated using the nine criteria presented here,
which are organized into three groups: Threshold Criteria, Primary Balancing Criteria, and Modifying
Criteria.

• Threshold Criteria (2) - The two threshold criteria must be satisfied by any alternative to be

eligible for selection:

1. Overall Protection of Human Health and the Environment evaluates whether an
alternative eliminates, reduces, or controls threats to public health and the environment
through ICs, engineering controls, or treatment.

2. Compliance with ARARs evaluates whether the alternative meets federal and state
environmental statutes, regulations, and other requirements that pertain to the Site, or
whether a waiver is justified.

• Primary Balancing Criteria (5) - The five balancing criteria are used to make comparisons and to

identify tradeoffs among alternatives:

1. Long-term Effectiveness and Permanence considers the ability of an alternative to maintain
protection of human health and the environment over time.

2. Reduction of Toxicity, Mobility, or Volume of Contaminants through Treatment evaluates
an alternative's use of treatment to reduce the harmful effects of principal contaminants, their
ability to move in the environment, and the amount of contamination present.

3. Short-term Effectiveness considers the length of time needed to implement an alternative
and the risks the alternative poses to workers, the community, and the environment during
implementation.

4. Implementability considers the technical and administrative feasibility of implementing the
alternative, including factors such as the relative availability of goods and services.

5. Cost includes estimated capital and annual O&M 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.

• Modifying Criteria (2) -Assessment of modifying criteria is based on public comments on the

Proposed Plan, discussions with the state, and consultation with affected Tribes.

1. State/Tribal Acceptance considers whether the state and affected Tribes agree with EPA's
analyses and recommendations.

2. Community Acceptance considers whether the local community agrees with EPA's analyses
and Preferred Alternative.

Using these criteria, the alternatives that were carried forward following screening were evaluated in
detail independently and then compared to identify the relative advantages and disadvantages.

This section summarizes the results of this evaluation for each media. A more thorough evaluation of
the alternatives in relation to each criterion is provided in the FS report (MWH, 2017a).

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Section 10 • Comparative Analysis of Alternatives

10.1 Overall Protection of Human Health and the
Environment (Threshold Criterion)

All action alternatives for each medium are expected to be protective of human health and the
environment. An alternative is protective if it achieves RAOs though some combination of engineering
controls, treatment, and ICs.

As required by the NCP, a No Action Alternative was developed to provide a baseline for comparing
other alternatives. The No Action Alternative (Alternative 1 for each medium) would not be protective
of human health and the environment. Contaminants in source materials would continue to be
released and transported to nearby surface water, groundwater, and sediment and riparian soils.

Risks associated with exposure to waste rock and vegetation would remain. RAOs and cleanup levels
for various contaminants would not be achieved and the alternative is not discussed further.

This section summarizes the comparative evaluations for medium-specific alternatives.

Upland soil and waste rock alternatives USWR 4, USWR 6, and USWR 7 would be protective of
human health and the environment. These alternatives all include a similar remedial strategy
consisting of a combination of grading and consolidation of waste materials, construction of an ET
cover system over areas where waste rock is left in place, ICs, O&M, and LTM. The primary difference
between the alternatives is the amount of grading and consolidation of waste materials and the extent
to which open pits are backfilled. In addition, USWR 6 would allow for the possibility of remining
phosphate ore during implementation of the remedy.

For each USWR alternative, RAOs would be achieved by isolating the source materials (upland soil, waste
rock, and exposed ore beds) under an ET cover system that would prevent direct exposure of people and
wildlife to COCs. The cover system would provide clean growth material for vegetation that would
address risks associated with ingestion of vegetation that contains elevated levels of selenium.
All alternatives would stabilize waste material and reduce the release of COCs from source materials to
downgradient groundwater, surface water, and sediment and riparian soil. ICs would be applied to limit
future uses of the Site that are incompatible with the remedy and to protect the integrity of the remedy.

Surface water alternatives SW 2 and SW 3 would be protective of human health and the environment.
Both alternatives rely on source controls described in the USWR alternatives. Implementation of the
USWR alternatives would result in two important effects. First, snowmelt and runoff from the
historical mining disturbance would no longer contact source materials. Any surface runoff to nearby
intermittent streams will meet RAOs. Second, the cover system would greatly reduce the infiltration of
precipitation through waste rock, which over time will reduce or eliminate the flow of springs and
seeps near the waste rock dumps and the concentration of COCs in remaining seeps and springs. Both
alternatives include ICs and fencing to limit access until the cover system becomes fully effective and
RAOs are achieved. The key difference between the two SW alternatives is that SW 3 also includes the
capture and treatment of residual seepage prior to discharge into downstream intermittent drainages
using constructed in situ biological treatment cells. Therefore, SW 3 is more effective in the short term
than SW 2, which relies on ICs and source controls to achieve RAOs.

Stream channel sediment and riparian soil alternatives S/RS 3 and S/RS 4 would be protective of
human health and the environment. Both alternatives rely on source control measures described in the
USWR alternatives to minimize the delivery of contaminated particles to downgradient intermittent
streams and riparian areas.

S/RS 3 includes sediment traps and basins, MNR, and ICs. Sediment traps and settling basins would be
constructed to capture sediment leaving the Site during construction of the soil cover. Once the source
of contamination is controlled, MNR is the mechanism for further reducing contamination to protective
levels. A monitoring program will be established to track progress. ICs will be applied to limit access to

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Section 10 • Comparative Analysis of Alternatives

impacted areas until cleanup levels are achieved. An adaptive management plan will provide a
structured process for making management decisions to improve remedy performance.

S/RS 4 includes excavations and removal of contaminated sediment and riparian soil from most
contaminated reaches of the intermittent and ephemeral drainages. The contaminated material would
be disposed of under a designated portion of the cover system. While both alternatives are expected to
achieve RAOs, S/RS 4 would destroy ecological functions and values during construction, and there is
uncertainty regarding the recovery of ecological values in excavated areas.

Groundwater alternatives GW 2, GW 3, and GW 5b would be protective of human health and the
environment over time. All three rely on the cover system described in the USWR alternatives to
reduce the concentration of contaminants in groundwater.

GW 2 includes MNA and ICs. Once the release and transport of COCs from the source areas are
controlled by the cover system, MNA will further reduce concentration of contaminants over time.

GW 3 includes the elements of GW 2 and also includes use of PRBs to treat shallow alluvial
groundwater along selected flow paths. If low levels of contamination remain following treatment by
PRBs, MNA would be used as a polishing step to further reduce the concentration of contaminants.

Under this approach, RAOs in shallow groundwater would be achieved sooner than GW 2.

GW 5b includes extraction and treatment of groundwater from the alluvial and Wells Formation aquifers.
This approach is expected to meet RAOs by removing contaminants from areas of impacted groundwater.
A number of technical factors (such as the influence of geologic structures on groundwater flow
direction) introduce some uncertainty into the effectiveness of this approach. Both GW 3 and GW 5b
include treatment of contaminated groundwater and would meet RAOs more quickly than GW 2.

ICs would be applied to restrict well drilling and use of groundwater in impacted areas until cleanup
levels are achieved. An adaptive management plan would be developed to provide a structured process
for evaluating progress and making defensible management decisions to improve overall remedy
performance.

10.2 ARARs (Threshold Criterion)

All action alternatives for each medium will attain ARARs under federal environmental laws and state
environmental or facility-siting laws. Key ARARs that drove development of alternatives are
summarized in this section. A complete list of ARARs and a discussion of how the alternatives would
comply is presented in Appendix B.

Key ARARs at the Ballard Mine include the following:

• Idaho Water Quality Standards, including surface water quality criteria

• National Recommended Water Quality Criteria, established under the CWA

• National Primary Drinking Water Regulations, including MCLs, established under the Safe Drinking
Water Act

• Idaho Ground Water Quality Rule, which provides minimum requirements for the protection of
groundwater quality

• Regulations established under the Mineral Leasing Act that control the development and
reclamation of phosphate mines

• Regulations under the Idaho Surface Mine Reclamation Act pertaining to reclamation of surface
mining operations

• CWA Section 404 and implementing regulations, which regulate actions that discharge fill material
into waters of the United States, including wetlands

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Section 10 • Comparative Analysis of Alternatives

Chemical-specific ARARs that strongly influenced the development of alternatives included the state
and federal water quality criteria for surface waters and MCLs for groundwater. Cleanup levels for
these media are based on these ARARs. All SW and GW alternatives are expected to comply with key
ARARs. Achieving ARARs for groundwater and surface water are the action-driving requirements of
the remedy and led to development of the source controls described in the USWR alternatives, as well
as the SW and GW alternatives.

Action-specific ARARs that influenced the development of alternatives included state and federal
mining and reclamation requirements. These ARARs establish performance requirements for the
remediated areas, including the source areas to ensure the effectiveness and integrity of the cleanup
actions. In general, all USWR and S/RS alternatives are expected to comply with key ARARs. For S/RS
alternatives, ARARs will more readily be achieved by S/RS 3, which relies on MNR to remedy impacted
reaches (rather than S/RS 4, which includes excavation and reconstruction of impacted reaches).
S/RS 3 also complies with Section 404 of the CWA, which requires consideration of impacts to
wetlands and waters of the United States and evaluation of opportunities to avoid and minimize
impacts.

10.3 Long-term Effectiveness and Permanence (Balancing
Criterion)

Upland soil and waste rock alternatives USWR 4, USWR 6, and USWR 7 are similar with respect to
long-term effectiveness and permanence. They all include excavation, consolidation, or grading,
followed by construction of a cover system to meet RAOs. All use ET covers constructed with locally
sourced natural materials and are expected to be durable over the long term. There are differences in
the amount of earthworks between the alternatives but these differences do not affect the expected
long-term effectiveness and permanence. These differences include the extent to which waste rock is
consolidated and mine pits backfilled. The exterior boundaries of the cover system are similar under
all alternatives, but the cover system under USWR 6 would be more contiguous within the boundaries
of the mining disturbance. In addition, there are differences between the alternatives in the final
landforms created through excavation and backfilling. USWR 6 and USWR 7 would be more mounded
and prominent than USWR 4. All alternatives are expected to function effectively and be resilient
under various climate change scenarios.

USWR 6 anticipates the possibility of remining of phosphate ore during RA, while USWR 4 and USWR 7
do not. Removal of some near-surface ore removes source material containing contaminants and
would generate additional waste rock that may be used for backfilling of mine pits or construction of
portions of the cover system. With respect to long-term effectiveness and permanence, these are minor
considerations. All candidate alternatives rank similarly highly with respect to long-term effectiveness
and permanence.

Surface water alternatives SW 2 and SW 3 rank similarly highly with respect to long-term
effectiveness and permanence. They both rely on source controls described in the USWR alternatives
to reduce the release and transport of contaminants in runoff and seepage to surface water. SW 3
would be effective as soon as the cover system (under USWR alternatives) and wetland treatment cells
are constructed and operational and would continue to be effective in the long term. The wetland
treatment cells may be phased out once the cover system is effective. Alternative 2 is effective in the
long term but relies on the cover system to control release of contaminants to surface water (in runoff
and seepage) and ICs in the short term to prevent human exposure.

Sediment and riparian soil alternatives S/RS 3 and S/RS 4 offer different remedial strategies that
carry advantages and disadvantages with respect to this criterion. S/RS 3 would rely on MNR
combined with sediment basins constructed in the upper reaches of the mine-affected drainages to
capture sediment entrained in runoff. S/RS 4 relies on excavation of contaminated sediment and

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Section 10 • Comparative Analysis of Alternatives

riparian soils from the areas close to the mine dumps and MNR for reaches further from the Site. Both
include implementation of ICs. Both alternatives also rely on source controls described in the USWR
alternatives to reduce the release and transport of contaminants that may accumulate in sediment in
downstream waterbodies. Over the long term, these alternatives both rank highly for this criterion,
although excavation under S/RS 4 introduces uncertainty over recovery of ecological functions and
values in the area that would be excavated.

Groundwater alternatives GW 2, GW 3, and GW 5b rely heavily on the cover system previously
described under the USWR alternatives. With source controls in place, and once RAOs are achieved, all
alternatives should be effective in maintaining protection over time. The GW alternatives include
elements to more quickly achieve and maintain RAOs. GW 2 includes ICs and MNA to maintain
protectiveness over time. GW 3 and GW 5b include treatment to reduce the concentration of
contaminants in a relatively short timeframe, and these treatment elements would remain in place as
long as necessary to maintain protectiveness. GW 3 also includes MNA which may be used as a
polishing step, if necessary, to achieve and maintain protectiveness. Overall, GW 3 and GW 5b rank
more highly than GW 2 with respect to this criterion.

10.4 Reduction of Toxicity, Mobility or Volume of
Contaminants through Treatment (Balancing Criterion)

Upland soil and waste rock alternatives USWR 4, USWR 6, and USWR 7 reduce contaminant mobility
in a similar way by isolating source material under a cover system to prevent direct contact and reduce
potential for migration of contaminants from source areas. None of the USWR alternatives, however,
reduce toxicity or volume of contamination through treatment. Therefore, all rank similarly with
respect to this criterion.

Surface water alternative SW 3 ranks higher than SW 2 with respect to this criterion. Under SW 3,
discharges from seeps and springs would be collected and treated using constructed wetlands.
Treatment would be implemented at various locations until seeps or springs diminish in flow and
cleanup levels are met. Treatment media would be replaced as needed and disposed of onsite under
the USWR cover system. SW 2 ranks low because it does not actively reduce toxicity, mobility, or
volume of contaminants through treatment.

For sediment and riparian soil, neither of the alternatives include treatment. S/RS 4 would, however,
result in the greatest reduction in volume and mobility of contamination because some contaminated
sediment is removed through excavation, reducing the contaminants available for remobilization.

Groundwater alternative GW 5b includes extraction and treatment of mine-affected groundwater in
the shallow alluvial aquifer and the deeper regional aquifer. GW 3 treats shallow alluvial groundwater
by installing PRBs along selected flow paths near the source areas. GW 2 doesn't actively treat
groundwater. Overall, GW 5b ranks most highly with respect to this criterion.

10.5 Short-term Effectiveness (Balancing Criterion)

Upland soil and waste rock alternatives USWR 4, USWR 6, and USWR 7 all involve extensive
earthworks to implement. The differences in the extent of earthworks are reflected in the amount of
time needed to complete construction of the alternative and achieve RAOs. USWR 4 would achieve
RAOs in 3 to 5 years, USWR 6 in 6 to 8 years, and USWR 7 in 5 to 7 years.

All alternatives would use similar construction and worker protection practices and protocols to
protect the community and workers during implementation of the remedy. Earthworks associated
with all alternatives, including excavation, hauling, and grading of mine materials, introduce short-
term risks for construction workers, which would be mitigated with safety measures, including
personal protective gear and appropriate training. These short-term risks will be mitigated through

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Section 10 • Comparative Analysis of Alternatives

measures including dust suppression, use of green-remediation practices, and carefully controlled
access to haul routes near the Site.

In addition, transport of ore under USWR 6, which assumes potential remining concurrent with
remedy implementation, from the Site to P4's processing facility near Soda Springs creates short-term
risks for workers, the community, and the environment. These risks are not specific to the cleanup of
the Site, mitigation measures are already in place for the haul road, with oversight from other agencies.

In summary, short-term effectiveness is similar among the alternatives, although USWR 6 would take
slightly longer to implement and additional care would be necessary when transporting ore to the
processing facility.

Surface Water alternative SW 2 is not as effective in the short-term as SW 3, because it relies on ICs
(and the cover system in the USWR alternatives) and does not include treatment of seepage. SW 3
includes treatment of seepage to remove contaminants and is expected to be effective in the short
term. Under SW 3, significant improvement in surface water quality is expected within a year of
constructing the wetland treatment cells. The time needed to fully attain RAOs is uncertain and
depends on cover system effectiveness, taking 5 to 10 years following construction for both
alternatives.

Risks to the community and workers during implementation of the remedy are limited and would be
mitigated by implementation of a health and safety plan and restrictions on access.

Sediment and riparian soil alternative S/RS 3 (which relies on sediment traps and MNR) has a
shorter construction time than S/RS 4 (which involves excavation of some sediment and riparian soil).
In the short term, risks to workers and the community are greater for S/RS 4. These risks, however,
would be mitigated by implementation of a worker health and safety plan and access controls. In the
short term, risks to the environment are lower for S/RS 4 because contaminants are removed from
impacted stream reaches rather than relying on MNR. Implementation of S/RS 4, however, would
harm ecological functions and values in the short term in the reaches of intermittent streams that are
excavated. These corridors would need to be reconstructed, introducing uncertainty about the length
of time needed to recover ecological functions and values. The time needed to achieve RAOs under
S/RS 4 is estimated to be 10 years following construction. For S/RS 3, there is considerable
uncertainty, but it is anticipated to take 10 or more years to achieve RAOs. Overall, S/RS 3 ranks more
highly than S/RS 4 with respect to this criterion.

For groundwater, all the alternatives depend on source controls described in the USWR alternatives
and would require many years to achieve cleanup levels. GW 5b and GW 3 include removal of
contaminants through treatment in the short term, and thus are likely to reduce the concentration of
contaminants in groundwater plumes and achieve RAOs more quickly than GW 2. The timeframe
necessary to achieve RAOs is uncertain and depends on implementation and performance of source
controls and treatment. All are expected to take 10 years or more to achieve RAOs following
construction of the cover system. The construction of treatment elements of GW 3 and GW 5b would
involve use of heavy equipment and would introduce short-term risks to workers. GW 5b also has the
largest environmental footprint because of the scope of construction activities. Transport of
construction equipment and materials on county roads also introduces a minor risk to the community.
Overall, GW 3 ranks most highly with respect to this criterion.

10.6 Implementability (Balancing Criterion)

All upland soil and waste rock alternatives include extensive but varying degrees of earthworks.
USWR 4 is easier to construct than USWR 6 and USWR 7 because of less extensive earthworks. All
alternatives use technologies that are demonstrated to be reliable and would use equipment and
expertise that are locally available. USWR 6 has greater administrative complexity than USWR 4 and

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Section 10 • Comparative Analysis of Alternatives

USWR 7 because of the approvals and coordination associated with potential remining. Overall, USWR
4 ranks more highly than USWR 6 and USWR 7 with respect to this criterion.

Surface water alternative SW 2 is easier to implement than SW 3 because it relies on ICs and does not
include any construction. SW 3 involves the strategic placement and construction of wetland treatment
cells in addition to ICs. SW 3 also requires substantive compliance with ARARs, including CWA Section
404, as construction work may occur in or near wetlands. In addition, SW 3 requires specialized
expertise to design the wetland treatment cells. Overall, SW 2 ranks more highly than SW 3 with
respect to this criterion.

Sediment and riparian soil alternative S/RS 3 would be easier to implement than S/RS 4, as it only
includes construction of sediment basins and implementation of ICs and MNR. S/RS 4 would be more
difficult to implement because, in addition to ICs and MNR (in the lower, less-contaminated reaches), it
includes excavation of contaminated material, confirmation sampling, onsite disposal under the USWR
cover system, and restoration of the stream reaches where excavation occurred. The services,
materials, and equipment necessary for implementation of S/RS 3 and S/RS 4 are available regionally
and are not a distinguishing factor. Overall, S/RS 3 ranks more highly than S/RS 4 with respect to this
criterion.

Groundwater alternative GW 2 (MNA and ICs) ranks most highly with respect to technical feasibility
because no construction or O&M are required. GW 3 (PRBs, MNA, and ICs) and GW 5b (pump and
treat) follow, respectively, with construction, O&M, and additional infrastructure needs.

Technical feasibility challenges associated with GW 3 and GW 5b are installing the treatment cells,
extraction wells, and treatment equipment specific to each reclamation alternative. These alternatives
are considered equivalent with respect to technical implementability and rank below GW 2.

Spent reactive barrier media generated by groundwater movement through the PRB may need to be
stabilized or treated prior to placement in an onsite repository. Wastes associated with treatment by
membrane technology would also require disposal in an approved manner. GW 2, with no sludge or
waste disposal, would rank higher than GW 3 and GW 5b.

Most of the services and materials associated with the implementation of each of the GW alternatives
would be available regionally. However, specialized drilling services and treatment equipment and
dedicated facility required by GW 5b would be more difficult to obtain than the other equipment
associated with implementation of GW 3; therefore, GW 5b is ranked below GW 3 in availability of
services and materials.

10.7 Cost (Balancing Criterion)

Cost represents the balancing criteria that most clearly differentiates the alternatives. The present
value costs for all alternatives were evaluated over a 30-year period (0 to 29 years).

Upland soil and waste rock alternative USWR 4 is estimated to cost $51 million, USWR 6 is estimated
to cost $36.9 million, and USWR 7 is estimated to cost $113 million. These costs reflect the relative
amount and cost of earthworks associated with each alternative. The cost of USWR 6 is lower because
earthworks associated with possible remining would involve waste consolidation and pit backfilling
and reduce cost associated with remediation. Therefore, USWR 6 ranks most highly with respect to
this criterion.

Surface water alternative SW 2 is estimated to cost $850,000 and SW 3 is estimated to cost
$1.4 million. Both include similar costs for implementation of ICs, but SW 3 also includes design,
construction and operation of wetland treatment cells. Therefore, SW 2 ranks slightly more highly than
SW 3 with respect to this criterion.

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Section 10 • Comparative Analysis of Alternatives

Sediment and riparian soil alternative S/RS 3 (MNR focused) is estimated to cost $736,000 and
S/RS 4 (excavation and MNR) is estimated to cost $1.59 million. Therefore, S/RS 3 ranks slightly more
highly with respect to this criterion.

Groundwater alternative 2 (MNA and ICs) is estimated to cost $1.4 million, GW 3 (treatment of
shallow groundwater using PRBs) is estimated to cost $2.1 million, and GW 5b (groundwater
extraction and treatment) is estimated to cost $24 million. GW 3 requires more construction than
GW 2, but is in the same general range. GW 5b would likely achieve RAOs more quickly, but at a much
higher cost. GW 2 and GW 3 rank more highly than GW 5b with respect to this criterion.

10.8 State Acceptance (Modifying Criterion)

The Idaho DEQ has been an active participant and has been fully engaged throughout the RI and FS
process and development of the Proposed Plan. Idaho, through DEQ, concurs with the Selected Remedy
in this ROD. A copy of the concurrence letter is included as Appendix C.

In addition to state acceptance through DEQ, information on tribal engagement is presented in
Section 3.2.

10.9 Community Acceptance (Modifying Criterion)

EPA issued a Proposed Plan for the Ballard Mine Site on April 2, 2018, and accepted comments during
a public comment period that ran from April 2 to May 1, 2018. During the formal comment period,
comments were received from three individuals and one organization.

The comments received covered a range of topics. Some commenters expressed preferences among
the alternatives and provided opinions about the importance of recovering the remaining phosphate
resources during implementation. Commenters also expressed concerns about the Superfund cleanup
process, adequacy of outreach to stakeholders during the process, and risks posed by current
conditions. One organization stated concerns about various elements of the Preferred Alternative and
provided recommendations to address concerns. No significant changes were made to the Preferred
Alternative in response to the comments.

Part 3 of this ROD, the Responsiveness Summary, presents the comments submitted and EPA's
responses. In addition, the original comments and a transcript of the public meeting are available in
the Administrative Record for the Site.

10-8

-------
Section 11 - Principal Threat Wastes

The NCP establishes an expectation that EPA will use treatment to address principal threats posed by a
site wherever practicable (NCP at 40 Code of Federal Regulations [CFR] § 300.430(a)(l)(iii)(A)). Principal
threat waste is defined in EPA guidance as source materials that are highly toxic or highly mobile that
generally cannot be contained in a reliable manner or would present a significant risk to human health
or the environment should exposure occur. Conversely, non-principal threat wastes are those source
materials that generally can be reliably contained and that would present only a low risk in the event of
exposure.

A source material is one that includes or contains hazardous substances, pollutants, or contaminants
that act as a reservoir for migration of contamination to groundwater, surface water, or air, or acts as a
source for direct exposure. At the Ballard Mine Site, source materials consist primarily of waste rock of
various lithologies located in mine dumps and backfilled pits. These source materials contain
contaminants that can be released to groundwater and surface water and are a source for direct
exposure.

Source materials present at the Ballard Mine Site are not principal threat wastes, as follows:

• Source materials are not highly toxic, considering current and reasonably anticipated future land
uses.

For non-radiological contaminants, cumulative ILCR and noncancer HI estimates for the Native
American exposure scenario are 1 x 10 3 and 150, respectively. Cumulative ILCR and
noncancer HI estimates for a seasonal rancher are 2 x 10 4 and 36, respectively, and risks for a
recreational hunter and camper/hiker are less than the EPA risk range. Cancer risks are driven
by arsenic in soil (incidental chronic ingestion, uptake into vegetation and uptake into beef
[consumed by rancher]) and sediment (uptake into vegetation). Background concentrations
account for much of the cumulative ILCR. For example, concentrations of arsenic in upland soil
used for Site and background risk estimates were 21.8 and 15.6 mg/kg, respectively.

For radiological contaminants, Native American, seasonal rancher, recreational hunter, and
recreational camper/hiker had risk estimates greater than the EPA acceptable risk range at 1 x
lO 2, 5 x lO 4, 2 x lO 4 and 1 x 10 4 respectively. The primary radiological risk driver was
radium-226. However, because of naturally elevated levels of uranium in soil in background
reference areas, the estimated Site risk was found to be only marginally different from
background risk.

• Source materials present at the Site are not highly mobile.

Contaminants present at the Site are inorganics that are generally bound as part of mineral
assemblages in waste rock and are only mobile when exposed to air and water.

• Source materials present at the Site can be reliably contained.

Waste rock can be reliably contained by using engineering controls (grading, shaping, and
construction of a cover system) to prevent direct exposure and minimize release of
contaminants to other media.

n-i

-------
Section 11 • Principal Threat Wastes

This page intentionally left blank to allow for double-sided printing.

11-2

-------
Section 12-Selected Remedy

This section describes the Selected Remedy for 0U1 of the Ballard Site. Included is a summary of the
rationale for the Selected Remedy, a description of the key components and outcomes expected to be
achieved, and a summary of the estimated remedy costs.

The Selected Remedy for the Site is a combination of medium-specific components and the elements
common to all alternatives. The selected medium-specific components are USWR 6 (Grading and
Consolidation, Possibility of Incidental Ore Recovery, Evapotranspiration Cover System, Institutional
Controls, and Operations and Maintenance/Long-term Monitoring), SW 3 (In Situ Biological
[Wetlands] Treatment of Source Area Seepage), S/RS 3 (Sediment Traps/Basins, Monitored Natural
Recovery, and Institutional Controls), and GW 3 (Limited Permeable Reactive Barrier Treatment of
Alluvial Groundwater, Monitored Natural Attenuation, and Institutional Controls). The other selected
elements are ICs, O&M, LTM, and adaptive management planning. The relationship between the
elements of the combined remedy are illustrated in conceptual cross sections shown on Figures 12-1
and 12-2.

Figure 12-1. Conceptual Cross Section of Key Elements of the Selected Remedy during the
Construction Phase

Remedial Action ¦ Installation of All Remedy Elements

Surface Water
Remedy

Outfall

NOT TO SCALE

Note: Water quality concentrations are projected values to convey the cleanup concept.

12-1

-------
Section 12 • Selected Remedy

The medium-specific alternatives of the Selected Remedy are described in more detail in the FS report
(MWH, 2017). The Selected Remedy mirrors the Preferred Alternative, with minor modification and
clarifications, and did not change in response to public comment or new information.

Implementation of the Selected Remedy will achieve the RAOs and cleanup levels listed in Section 8,
return useable groundwater to beneficial uses within a reasonable timeframe, and restore the
environmental media in the area to levels that are compatible with reasonably anticipated future land
uses: recreation, seasonal ranching, and tribal hunting and gathering. It will also address ecological
risks. Sections 7, 8 and 9 of this ROD contain additional information about the Selected Remedy,
including RAOs for each media for current and potential future land uses, methods and approaches and
timeframe to achieve RAOs, expected outcomes, and risk associated with the cleanup levels.

Figure 12-2. Conceptual Cross Section of Key Elements of the Selected Remedy after the
Construction Phase

The Selected Remedy achieves the threshold criteria and provides the best balance of tradeoffs with
respect to the balancing and modifying criteria. The Selected Remedy is a comprehensive cleanup of
the Site that will protect human health and the environment and that complies with ARARs (described
more fully in Section 13.2). It has long-term effectiveness and permanence because it reliably
consolidates and contains source materials (primarily waste rock) under a robust ET cover. The cover
will be designed to eliminate direct exposure to source materials and minimize contact between waste
rock and infiltrating surface water. The Selected Remedy is feasible and implementable, does not
require offsite transport and disposal of waste rock, and has long-term cost effectiveness.
Consolidation and covering of waste rock are remedial actions selected and applied at other area
phosphate mines similar to the Site. The Selected Remedy includes requirements for ICs, monitoring
(visual inspections), access controls, and maintenance of the cover to prevent exposure of source
materials and maintain protectiveness. EPA will formally review the protectiveness of the remedy at
least every 5 years after the remedy has been initiated.

*¦— i

MNA

f<0.05 mg/L SeJ /
~

NOT TO SCALE

Note: Water quality concentrations are projected values to convey the cleanup concept.

12.1 Rationale for the Selected Remedy

12-2

-------
Section 12 • Selected Remedy

The following key factors led to selection of this remedy:

• The selected upland soil and waste rock cover alternative (USWR 6) provides a similar level of
protectiveness compared to the other two alternatives (USWR 4 and USWR 7), but costs
significantly less. A significant portion of the cost of all earthworks (excavation, consolidation,
backfilling, grading tasks) is attributed to the potential ore recovery, which reduces the scope and
cost of remaining earthworks associated with implementation of the remedy.

• The selected surface water alternative collects and treats contaminated seepage near the dumps
during remedial construction and in the post-construction period. In the longer term, seeps and
springs are expected to dry up or reduce in flow in response to source controls. In the short-term,
the concentration of contaminants is reduced quickly and the timeframe needed to achieve
cleanup levels is shortened relative to alternatives without treatment.

• The selected surface water alternative uses wetland cells to treat contaminated seeps and springs,
increasing the reliability of the remedy in meeting RAOs compared to use of MNA (in conjunction
with source controls).

• The selected sediment and riparian soil alternative focuses on sediment-control BMPs (sediment
traps and basins adjacent to the source areas) and MNR and avoids extensive excavation in the
corridors around the intermittent streams near the Site. It is uncertain whether ecological function
and values could be fully restored in excavated reaches.

• The selected groundwater alternative treats contaminated groundwater using PRBs along alluvial
flowpaths near the margins of the Site. Short-term human health exposures during construction
are reduced compared to the groundwater pump and treat alternative, and the timeframe to meet
PRGs in shallow groundwater is shortened compared to the alternative that relies on MNA and ICs.

• The PRB treatment process will be more adaptable than MNA and pump and treat alternatives to
expected changes in flow and contaminant concentrations over time, as the shallow groundwater
system responds to upland soil and waste rock source controls. PRBs can be maintained as needed,
providing more certainty than the MNA alternative that RAOs will be achieved.

• The Selected Remedy, which relies on a combination of source controls (ET cover), treatment
(PRBs and wetlands), MNA, and ICs is expected to restore mining-influenced groundwater to
beneficial uses within a reasonable timeframe. Although it is anticipated that RAOs will be
achieved more than 10 years after remedial construction, this timeframe is considered reasonable
because there are no current users of mine-affected groundwater, and ICs will restrict use of
groundwater until cleanup levels are met.

12.2 Description of the Selected Remedy

The following sections describe the Selected Remedy and how the medium-specific elements work
together to achieve RAOs. Minor changes to the remedy may occur during RD/RA to adapt the
elements of the Selected Remedy to its location and optimize effectiveness. Changes to the RD and RA
will remain protective and comply with ARARs.

12.2.1 Waste Rock Consolidation and Engineered Cover System

The RAOs for upland soil and waste rock will be met by consolidation of waste rock into mine pits,
regrading of waste rock in the backfilled mine pits and external waste rock dumps, and construction of
an ET cover to isolate contaminated source materials. The ET cover system is a key element that will
substantially contribute to the success of the other remedial components and to meeting RAOs.

The Selected Remedy recognizes that P4 intends to recover phosphate ore concurrent with
implementation of the remedy. Information collected during site characterization activities confirmed

12-3

-------
Section 12 • Selected Remedy

that about 4 million tons of phosphate ore remain at the Site, both exposed at the surface and in the
bottoms and sidewalls of existing mine pits. The amount of ore P4 intends to recover is an
approximation based on currently available information and may change as more information
becomes available or economic considerations change. Specific plans for possible remining would be
accommodated during the remedial design phase of the project.

Although potential ore recovery is not required as part of the remedy, the Selected Remedy allows for
and is compatible with remining concurrent with remedy implementation. The key elements of the
design (including the engineered cover system, permeable reactive barriers, wetland treatment cells,
and other elements identified in Section 12.2) would be implemented even if plans for remining
change - for example, if there is more or less remining performed - although the specifics of the
design, implementation schedule or cost may change.

The potential remining activities are expected to generate additional waste rock and overburden
material for backfill of mine pits and construction of the evapotranspiration (ET) cover. In addition, the
earthworks associated with potential remining (such as excavation and placement of fill, grading and
shaping waste dumps, and backfilled pits) will also advance remediation efforts, thereby reducing the
costs associated with remediation. No ore processing would occur at the Site. Instead, ore would be
transported to P4's existing processing facility about 10 miles away.

In addition, the CERCLA 121(e) permit exemption does not apply to BLM mineral leasing and mine
permitting requirements. The CERCLA process cannot authorize ore recovery activities. Thus, for ore
to be recovered during implementation of the remedy, P4 would need to acquire a federal mineral
lease and seek approval from BLM of a plan for ore recovery. If P4 does not obtain legal authority to
remine or if P4 does less (starts and then stops) or more remining than currently anticipated, then the
design, implementation schedule and costs of the remedy would change, but the key elements would
remain the same. Such changes related to the amount of remining are not anticipated to require
changes to the Selected Remedy itself. EPA would integrate RD/RA activities with concurrent remining
through coordination with P4 and BLM.

Key features of this element of the Selected Remedy include:

• During remedial construction, waste rock dumps will be partially excavated, transported, and
placed into mine pits to cover exposed ore beds and shale units of the Phosphoria Formation.
Waste rock dumps and backfilled pits will be graded and shaped to ensure geotechnical stability,
typically to a 3:1 slope or less, and to promote runoff away from potential source areas. Grading
plans developed during remedial design will minimize expansion of the exterior boundaries of
existing disturbance. Remedial construction activities will be sequenced so that excavated and
regraded waste rock will be covered soon after grading to limit environmental exposures of fresh
waste rock surfaces. Figure 12-3 presents the existing mine features prior to remediation.

• An ET cover system, approximately 5 to 6 feet thick, will be constructed over all areas of the Site
where waste rock is present. This cover system is expected to cover more than 500 acres of the
Site. In concert with the grading plan, the ET cover will be designed and constructed to cover and
isolate all waste rock, establish drainage and minimize infiltration into waste rock, and promote
clean runoff without causing erosion.

• To the degree possible, the ET cover will be constructed concurrently as the waste rock is placed
and final grading is completed. The anticipated footprint of the cover is presented on Figure 12-4.
In addition to covering all source materials in the backfilled mine pits and the external dumps, the
cover will also extend over areas where original waste rock dumps were excavated for placement
into pits, to prevent exposure of contaminated soils.

12-4

-------
Section 12 • Selected Remedy

Figure 12-3. Existing Conditions prior to Remediation

Approximate mine pit location
as shown in FS Memo No. 1

^—9 Approximate waste rock dump location
as shown in FS Memo No. 1

Figure 12-3
EXISTING CONDITIONS
PRIOR TO REMEDIATION

BALLARD MINE
RECORD OF DECISION
Caribou County, ID

"Amended from P4 Production LLC, FS
Technical Memorandum #2, MWH 2017".

12-5

-------
Section 12 • Selected Remedy

Figure 12-4. Remedial Cover Concept - Extent of ET Cover

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Surface shading of completed reclamation areas is an

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arust rendering and does not represent final engineered
surfaces to be developed during' tfie remedial design

Estimated completed reclamation
areas in upland soil/waste rock

Mine-affected seep/spring

Proposed Permeable Reactive
Barrier (PRB)

/

Performance monitoring well
(approximately 25 feet from PRB)

Approximate direction of
groundwater flow

Figure depicts conceptual locations of permeable reactive barriers and associated performance
monitoring wells. Actual locations and associated design details will be determined during remedial
design and is dependant on fooprint of remedial activities in the mine pits and waste rock dumps
(i.e., upland soiVwaste rock source controls). Insitutional Controls (tCs), Land Use Contois (LUCs),
and other long-term surface water monitoring locations will be as shown on Figure 3-d.

Figure 12-4
REMEDIAL COVER CONCEPT -
EXTENT OF ET COVER

BALLARD MINE
RECORD OF DECISION
Caribou County, ID

" Amended torn P4 Production LLC, FS
Technical Memorandum #2, MWH 2017".

12-6

-------
Section 12 • Selected Remedy

• The ET cover system will be comprised of two layers. A layer of coarse unimpacted material (such
as chert) will be placed above the regraded waste rock surface to serve as a capillary break
(approximately 1 foot thick). Above the capillary break layer, an approximately 5-foot-thick layer
of medium-textured alluvium will be placed. The cover material will be designed to store water
during wet periods and release water back to the atmosphere via evapotranspiration during dry
periods. The cover will be constructed of material of suitable quality to sustain and perpetuate
healthy vegetation, to accommodate the rooting depth of native plants without intercepting waste
rock. The final configuration and dimensions of the cover as well as material properties and
thicknesses will be refined during remedial design.

• The cover system will be designed to achieve RAOs by eliminating direct contact with waste rock
by human and ecological receptors and minimizing the migration of selenium, arsenic, and
cadmium from waste rock and upland soils to groundwater and surface water. During remedial
design, cover system details will be refined and infiltration models will be validated using data on
performance of engineered cover systems from nearby sites. The design of the cover system (and
other elements of the remedy) will be optimized to the extent practicable. Performance of the
cover system will be evaluated by inspections, spring and seep surveys, instrumentation, and by
comparing concentration of contaminants in downgradient surface water and groundwater
monitoring stations with cleanup levels. Fill material for the various construction phases will be
imported from the borrow areas used to construct the cover or from borrow sources exposed or
waste rock produced during potential ore recovery. This work could be accomplished at any point
during the remediation process. Final ET cover design and geometry will be optimized during
remedial design to shed runoff and blend into the surrounding natural topography. O&M
requirements will be defined and applied and ICs and LUCs will be implemented to restrict access
and protect human health and the environment.

• Native seed mixes and vegetation types will be selected to form an extensive root system to
penetrate the majority of the vertical cover profile (without intercepting waste rock), slow the
flow of stormwater and snowmelt runoff, limit erosion, and transpire water that infiltrates the
cover. Frequent and consistent LTM will be performed to inspect the cover for plants incompatible
with the cover system (i.e., deep rooted species and selenium accumulators such as Asters).

• Remedial action will be implemented using a phased construction approach, with the actual
number and sequence of construction phases refined during remedial design to optimize
implementation. However, any modifications would not fundamentally change the remedy
components or ability to achieve remedial objectives. For this ROD, remedial construction is
assumed to occur in three phases, consistent with the concept presented in the Proposed Plan. The
conceptual RA presented is based on current information regarding the location and volume of
cover materials (and potential ore deposits) (MWH, 2017a). Existing mine features (dumps and
pits) are indicated on Figure 12-3. As explained in Section 9.3.2, remining is not a required part of
the Selected Remedy. Rather, the remedy assumes that P4 will recover phosphate ore concurrent
with implementation of the remedy. Plans for remining will be accommodated during the remedial
design stage. As with remedial construction, remining will be sequenced and completed in phases.

12.2.2 Permeable Reactive Barriers

Use of PRBs is one element of an overall approach for meeting groundwater RAOs. PRBs will be
installed downgradient of the source areas, near the margins of the waste rock dumps, to intercept and
treat contaminated, shallow alluvial groundwater to reduce selenium and COC concentrations to less
than cleanup levels. The PRBs will be sited upgradient of select perennial seeps and springs. PRBs are
trenches filled with reactive media selected to treat specific target contaminants in groundwater, in
this case via reduction and precipitation. The approximate number and locations of PRBs are
illustrated on Figure 12-5.

12-7

-------
Section 12 • Selected Remedy

The actual geometry and composition of each PRB will be determined by the results of RD treatability
studies along with other directly applicable research involving similar COCs from local phosphate
mines, to optimize treatment effectiveness. Each PRB will be designed for its unique location. In some
cases, where the affected alluvial groundwater is excessively deep, extraction wells may supplement
the system and discharge to the PRB.

Each PRB will comprise a trench filled with reactive media that is designed to intercept and treat
shallow alluvial groundwater. Treatability testing will determine an appropriate reactive media mix
for Site COCs (e.g., organic materials, sand and limestone, iron filings, or other media combinations).
The selected medium will have permeabilities appropriate for the hydraulic conductivities of
surrounding materials and adequate retention times to treat the target contaminants to cleanup levels.

Performance of the PRBs will be assessed using monitoring wells located up- and downgradient of the
PRBs and at downgradient springs and seeps where groundwater discharges. If contaminant
concentrations in groundwater are not reduced to cleanup levels by the PRBs, an adaptive
management strategy will guide decisions on follow-up actions, which may include revisions to the
PRBs. MNA will be used as a polishing step to further reduce concentrations of contaminants in distal
portions of alluvial aquifers (see Section 12.2.4).

Decision rules for determining media testing, replacement, disposal procedures, and whether PRBs
may be decommissioned in place (after groundwater treatment is complete and meets cleanup levels)
will be developed during remedial design. ICs will be implemented to protect the integrity of these
remedial elements.

12-8

-------
Section 12 • Selected Remedy

Figure 12-5. Approximate Location of PRBs

Estimated completed reclamation
areas in upland soil/v^ste rock

Mine-affected seep/spring

Proposed Permeable Reactive
Barrier (PRB)

/

Performance monitoring v\ell
(approximately 25 feet from PRB)

Approximate direction of
groundv^ater flow

Figure depicts conceptual locations of permeabfe reactf/e barriers and associated performance
won Coring wells. Actual locations and associated design details will be determined during feme dial
design and is dependant on fooprint of remedial actf/ities in the mine pits and waste rock dumps
(i.e., upland soifwaste rock source controls), fns&utionai Controls (iCs), Land Use Contois (LO'Cs),
and other long-term surface water momioring loc ations will be as shown on Figure -3-8.

Figure 12-5
REMEDIAL
PRB LOCATIONS

BALLARD MINE
RECORD OF DECISION
Caribou County, ID

"Amended from P4 Production LLC, FS
Tec fin icai Me moran dum #2, MWH 2017".

12-9

-------
Section 12 • Selected Remedy

12.2.3 Wetland Treatment (Bioreactor) Cells

Wetland treatment cells are one element of an overall approach to attaining RAOs for surface water.
The approach includes collection and treatment of contaminated seeps and springs, along with
installation of the ET cover. A series of wetland treatment cells will be constructed and operated, on
Site margins, to treat contaminated, perennial mine-affected seeps and springs. The approximate
number and location of the wetland treatment cells are identified on Figure 12-6. As illustrated on
Figure 12-6, flow from other nearby springs and seeps will be captured and conveyed to one of the
wetland treatment cells. Likewise, flow from seeps and springs within the footprint of waste rock and
upland soil will be captured and conveyed downstream to a wetland treatment cell.

A cross section of a conceptual treatment wetlands is presented on Figure 12-2. Actual dimensions and
construction details, flow rates, and water retention times will be determined during remedial design.
In general, the bioreactors will consist of plant growth media placed on a bed of organic matter and
limestone underlain by a gravel base, constructed either atop or just downgradient of the seep
locations so water flows up through the system. The treatment cells will be designed and operated to
remove selenium and other contaminants. The residual mine-affected water at the seeps and springs
will be captured and treated via biologically mediated reactions, including reduction by anaerobic
bacteria, resulting in the removal of contaminants through precipitation or sorption. The treated water
would flow out of the treatment cells to the downstream drainages or evapotranspire within the
treatment cells. Cleanup levels will be met where treated water is discharged to waters of the United
States. A monitoring program will be implemented to assess effectiveness of the wetland treatment
cells and will include periodic testing of influent and effluent.

The treatment effectiveness of the biochemical reactors in some areas will be enhanced by the PRBs
that are installed upgradient to treat the shallow groundwater before it discharges at the seep
locations (see Figure 12-5 and the groundwater discussion in Section 12.2.2). These PRBs will have the
effect of reducing the concentration of contaminants in the influent to the wetland treatment cells.

During RD, the number, location and size of the wetland treatment cells will be refined. In siting the
location of wetland treatment cells, potential impacts to delineated wetlands and other waters of the
United States (Newfields, 2017) will be considered as part of substantive compliance with Section 404
of the CWA.

Treatment cells may be phased out over the long-term as source controls (cover system) and
treatment technologies (PRBs) described in other media alternatives become effective and reduce
mine-affected seep and spring discharge or as cleanup levels are achieved. Decision rules for
determining media testing, replacement, disposal procedures, and whether wetlands may be
decommissioned in place will be developed during remedial design. ICs will be implemented to
prevent human exposure to contaminants at the treatment facilities and to protect the integrity of
these features.

12-10

-------
Section 12 • Selected Remedy

Figure 12-6. Approximate Location of Wetland Treatment Cells



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NO TE: Surf a ce shading is sr.' artist ren tiering o f corn pie ted re ciarn atio n a re as and doe s not
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Approximate extent of reclamation areas in upland soil/waste rock
Potential location of water conveyance line or trench
Potential location ofin-situ constructed wetland
Mine-affected seep/spring

Assumed future long-term surface water monitoring location. Samples wll be
collected from both influent and effluent at each constructed wetland.

figure depicts conceptual locations of constructed in-situwetiands and associated water conveyance lines. Adual

locations will be dete m ine d during re medial cfesg nfam edial action and is dependant or? fooprint of rem edial
activities in the mine pits and Haste rock dumps {i.e., upland soil/waste rock source controls). InsHutional Contiols
(ICs), Land Use Contois (LUCs), andotherlong-term surface water monitoring locations will be as shown on F^ure 3-4.

Figure 12-6
REMEDIAL TREATMENT
WETLANDS LOCATIONS

BALLARD MINE
RECORD OF DECISION
Caribou County, ID

"Amended ftom P4 Production LLC, FS
Technical Memorandum #2, MWH 201T.

12-11

-------
Section 12 • Selected Remedy

12.2.4 Monitored Natural Attenuation of Groundwater

The primary strategy for remediating groundwater is the implementation of source controls (cover
system) and treatment (PRBs and wetland treatment cells). These technologies are expected to reduce
contaminant concentrations in groundwater to the cleanup levels over time.

If levels of contaminants in groundwater remain elevated above cleanup levels following
implementation of other elements of the remedy, MNA will be used as a polishing step to achieve
cleanup levels. MNA relies on physical, chemical, and biological processes to further reduce
contaminant concentrations in groundwater, primarily through dilution and dispersion. Additional
data (evaluation of the minerology of aquifer solids, dissolved organic carbon, redox conditions, and
other relevant information) will be obtained during remedial design to refine estimates of contaminant
sorption and attenuation rates. MNA will help reduce contaminant concentrations over the long term,
approximately 10 to 20 years after remedy implementation. Use of MNA during the RA will require
routine groundwater monitoring, periodic data analysis to evaluate removal mechanisms and track the
progress of natural attenuation, and implementation of an adaptive management strategy (see
Section 12.2.7).

12.2.5 Stormwater and Sediment Control Best Management Practices

Sediment control is predicated on successful implementation of source controls (i.e., waste rock
consolidation, surface grading, and cover installation) to prevent contaminant transport from the mine
area into downstream sediment and riparian soil. In the long-term, source controls will minimize or
eliminate erosion of source materials, and downstream transport of contaminants as stormwater and
snowmelt will no longer contact waste rock before flowing off the mine site.

During the construction phase, sediment traps or basins will be constructed in the upper reaches of
mine-affected drainages. These features will be sited in the upper drainage reaches to capture or
control mine-affected sediment entrained by stormwater, allowing sediment to settle out and less
turbid water to continue downstream. The basins will provide control points for sediment laden runoff
from the Site during construction and through maturation of the remedy and establishment of
vegetation on the cover. During RD, the number, location and size of the sediment basins will be
refined. In siting the location of these BMPs, potential impacts to delineated wetlands and other waters
of the United States (Newfields, 2017) will be considered as part of substantive compliance with
Section 404 of the CWA. In addition, other BMPs will be specified during remedial design and will
include a broad suite of techniques to control erosion, such as use of compaction, construction
sequencing, straw mulch and wattles, silt fences, and other methods.

Downstream in mine-affected drainages, natural recovery will be monitored over time (see
Section 12.2.6). Disposal of contaminated sediment from these structures over the long term will
consist of placement under the ET cover during the RA, and disposal in a designated, properly
designed, onsite landfill after RA completion, as needed.

Sediment traps and basins will require appropriate planning during RD to confirm geotechnical
stability and protection of human health and the environment, and to track progress toward meeting
RAOs. Siting and construction of sediment traps and basins are predicated on an approved RD/RAWP.
The RD/RAWP would include sediment trap and basin design information, design of temporary roads,
engineered access restrictions, a site restoration plan, an HASP, and a stormwater management plan.
ICs will be implemented to protect the integrity of these features and to prevent human exposure to
contaminated sediment until RAOs are achieved. Effectiveness will be evaluated through monitoring.

12.2.6 Monitored Natural Recovery for Sediment

Contaminants in intermittent and ephemeral stream sediment and riparian soil will be addressed
through a combination of sediment traps and basins in headwater drainage locations (see
Section 12.2.5) and MNR for downstream reaches.

12-12

-------
Section 12 • Selected Remedy

MNR will reduce concentrations of contaminants through natural processes. Over time, clean runoff
and associated sediment transport, decaying organic debris, and erosion will disperse and dilute or
cover contaminated stream channel and overbank deposits and therefore reduce risks to receptors.
Implementation of MNR during the RA includes routine sediment and riparian soil sampling in
impacted stream corridors down to the confluence with the Blackfoot River, and periodic data
evaluations to monitor the progress of natural recovery and to support CERCLA FYRs. This remedial
element requires implementation and enforcement of ICs to prevent human exposure to contaminated
sediment and riparian soil until RAOs are achieved (more than 10 years beyond remedy completion).

MNR requires no construction or O&M. Implementation of MNR will require a preliminary study to
predict the effectiveness of the MNR process, identify and designate downstream sampling stations,
and collect baseline samples. Initiation of MNR during RA will require an approved long-term sampling
and analysis plan, designated riparian soil and vegetation sampling frequencies over a specified
timeframe, and periodic data evaluations to track progress and support CERCLA FYRs.

12.2.7 Adaptive Management

A sitewide adaptive management plan will be developed during RD and implemented during RA. The
adaptive management plan will describe a structured iterative process for making management
decisions for elements of the remedy with significant uncertainty or vulnerability regarding
performance. The plan will provide a linkage and feedback loop between various stages of remedy
implementation, including design, construction, monitoring and comparison to cleanup levels and
performance specifications, and potential management actions and responses.

The adaptive management plan will include the following elements:

• Problem statement, including a description of vulnerabilities, uncertainties, and potential
consequences associated with key components of the remedy.

• Monitoring strategy that includes specific indicators and describes the type, amount, and quality of
information needed to make management decisions.

• Performance thresholds for initiating follow-up actions, including cleanup levels, and performance
goals and specifications.

• Potential management actions and responses to address unanticipated monitoring results or
conditions. These may include additional designs, design modifications, or operational changes to
optimize the performance of remedy components, correct design oversights or construction
defects, or other actions necessary to achieve intended remedial outcomes.

Follow-up actions and modifications made through the adaptive management process would be
consistent with and within the scope of the Selected Remedy and would not constitute a significant or
fundamental change to the Selected Remedy.

12.2.8 Operation and Maintenance

O&M is an integral part of every component of the Selected Remedy and is necessary to ensure the
success of engineering controls. An O&M plan will be developed and implemented to ensure the proper
functioning and performance of all engineering controls. The specific O&M requirements will vary
depending on the cleanup method or technology and will be developed during remedial design.

The plan will address maintenance and repairs of the permanent and secondary access roads,
associated stormwater control and drainage features, and the ET cover (e.g., erosion of cover material,
drainage issues, enhancing vegetative growth on the cover, and other issues to ensure sustainability).
The plan will address all aspects of operation, maintenance, and repair of the PRBs, engineered
wetland cells, sediment traps and basins, groundwater monitoring well networks, and general BMPs
for treatment facilities (e.g., dike or berm repairs, spent media replacement, proper disposal of

12-13

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Section 12 • Selected Remedy

excavated sediment trap and basin material, rodent control, maintaining engineered ICs to restrict
access, and other issues as needed). The plan will include best practices for operating and maintaining
treatment features, schedules (short- and long-term) for implementing maintenance of all remedial
site features, and records for documenting conditions encountered and remedial action applied. The
plan will be updated annually.

12.2.9 Long-term Monitoring

Monitoring is also an integral part of every component of the Selected Remedy. LTM will be designed
and implemented to assess the performance of different components of the remedy and the
effectiveness of the remedy at attaining cleanup levels. To track and measure progress toward
achieving RAOs and cleanup goals at the Site, an LTM program that includes physical, chemical, and
biological components will be prepared and implemented. The monitoring program will include
sampling and analysis of groundwater, surface water, sediment, riparian soil, vegetation, and upland
soil. Frequency of monitoring, specific data quality objectives, and requirements for appropriate
monitoring will be developed during remedial design and initial operations.

The information collected through the LTM program will support the FYR process. FYRs are required
under the CERCLA process because Site conditions do not allow for unlimited use and unrestricted
exposure under the current and potential future land uses. These reviews will be used to evaluate
where the remedy is functioning as intended and whether RAOs are being attained.

12.2.10 Institutional Controls and Access Restrictions

ICs are administrative or legal mechanisms, or a combination of both, intended to control land use and
Site access and to maintain the integrity of the remedy. The ICs will be tailored to the property to
provide protection of human health and to maintain protectiveness until cleanup objectives are met.
The general categories of ICs (i.e., Government Controls, Legal Controls, and Communication and
Enforcement Tools) are explained in detail in Section 9.2.1. Because the Site is large and includes
multiple private and government owners, ICs may be selected and implemented on a parcel basis or
implemented for specific components of the Selected Remedy. Site-specific ICs will be determined
during RD/RA and will include the following:

• Restrictions on drilling of water supply wells where contaminated groundwater is present. These
restrictions would remain in place until cleanup levels are achieved.

• Legally enforceable deed restrictions applied to current and future owners of lands that comprise
the Site to prevent any future residential use. These deed restrictions would also be structured to
prevent or limit future land uses to preserve and safeguard the cover system or treatment
components of the remedy.

• Community outreach distributed through public notices, fact sheets, or onsite signage to provide
notice of contamination on the property and to discourage uses that could lead to unacceptable
exposures. Communication methods will target and educate neighboring land owners and
potential user groups (such as seasonal ranchers, hunters, hikers, and tribal members) on issues,
concerns, and best practices related to Site use.

• LUCs such as fencing (an engineering control), locked gates, and signage to discourage public
access (offroad vehicles) to the cover, PRBs, wetland treatment cells, and areas where MNR is
being implemented, to protect the integrity of the remedy.

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Section 12 • Selected Remedy

12.2.11 Green Remediation

To the extent practicable, the RA will be carried out consistent with EPA's Region 10 Clean and Green
Policy (EPA, 2009b), including the following practices:

• Use renewable energy and energy conservation and efficiency approaches, including Energy Star
equipment.

• Use cleaner fuels such as low sulfur fuel or biodiesel, diesel emissions controls and retrofits, and
emission reduction strategies.

• Use water conservation and efficiency approaches including WaterSense products.

• Use locally sourced materials when available and financially competitive.

• Use reused or recycled materials within regulatory requirements.

• Minimize transportation materials and use rail rather than truck transport to the extent practicable.

12.3 Estimated Cost of the Remedy

The costs for the Selected Remedy presented in this section are estimates, with an accuracy
expectation of +50 percent to -30 percent. The estimates will be refined as the remedy is designed and
implemented. Even after the remedial action is constructed, the total project costs will be reported as
an estimate because of the uncertainty associated with the O&M and LTM expenditures. Periodic costs
are those costs that occur only once every few years or expenditures that occur only once during the
entire O&M and LTM period or remedial timeframe (e.g., Site closeout or remedial feature replacement
resulting from chemical or physical degradation). These costs may be either capital or O&M and LTM
costs. Because of the duration of the cost evaluation for this ROD (30 years), periodic costs were
primarily associated with O&M and LTM and the FYRs. It is believed that a 30-year cost evaluation is
justified for this project, because implementation of the ROD is expected to take up to 10 years.

Table 12-1 presents a breakdown of the cost estimate for the Selected Remedy, including net present
value (NPV) analysis on a year-by-year basis (discounted by 7 percent per year). A detailed cost
breakdown of each remedial component is provided in Appendix D.

Costs for the selected remedy are summarized in the following points:

1) The NPV cost for the remedy is approximately $41,214,250. The individual components of this cost are
as follows:

a) Estimated total capital costs: $148,837,186

b) Estimated total O&M costs (first 30 years): $2,136,732

c) Estimated construction time: 10 Years (3-phased Construction Approach)

Table 12-1. Cost Summary Estimate for Selected Remedy

Ballard Mine Site, Caribou County, Idaho

Item No.

Item

Description

Quantity

Unit

Unit Cost ($)

Item Cost ($)

1 Direct Capital Costs

Mobilization/Demobilization (Combined Remedy Totals)

Mobilization/Demobilization of Equipment

$91,824

Construction Field Offices, Facilities, and Utilities

$325,035

Preparation of Institutional Control Implementation and
Assurance Plan and Plans

$363,895

12-15

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Section 12 • Selected Remedy

Table 12-1. Cost Summary Estimate for Selected Remedy
Ballard Mine Site, Caribou County, Idaho

Item No.

Item

Description

Quantity

Unit

Unit Cost ($)

Item Cost ($)



Upland Soil and Waste Rock











Site Consolidation, Grading, and ET Cover

538

ac

$214,868

$115,599,206



Surface Water











Constructed Wetlands at six seep/springs areas

6

ea

$57,082

$342,492



Sediment











Sediment Traps

6

ea

$3,500

$21,000



Groundwater











Installation of nine PRBs and associated monitor wells

9

ea

$37,322

$335,894







Subtotal Capital Costs

$117,079,346



Project Management



Capital Costs

$5,878,505



Remedial Design



Capital Costs

$7,111,097



Construction Management and Oversight



Capital Costs

$7,060,305



Contingency Costs3



Capital Costs

$11,707,935







Other Direct Costs

$31,757,841



Total Capital Costs (including ore recovery and remedial
action)







$148,837,186

la

Total Capital Costs adjusted for Remediation Costs only
(Item 1 * 25.47%)







$37,914,438













2 Annual Costs (O&M)



Long-term Inspections (on 1-year and 5-year schedules)

1

LS



$202,870



30-year Present Worth







$2,136,732

3

Summary Report (Every 5 years for each medium)

4

5 years

$100,000

$400,000



30-year Present Worth Summary (i=7%; P/F =
0.7130+0.5083+0.3624+0.2584+0.1842+0.1314=2.1577)







$863,080

4

Institutional Controls b



EA

$25,000

$300,000



Subtotal: 30-year Present Worth Cost (Items 1+2+3+4)







$152,137,000

5

Site Remedy Totalc: 30-year Present Worth Cost (Items
la+2+3+4)







$41,214,250

a For an FS that represents 0% to 10% design completion, scope contingency typically ranges from 10% to 25%. The July 2000 EPA
guidance, A Guide to Developing and Documenting Cost Estimates During the Feasibility Study (EPA 540-R-00-002) shows a rule-of-
thumb scope contingency of 10% to 30%.

b ICs are non-engineering or legal/administrative measures to reduce or minimize the potential for exposure to site contamination

or hazards by limiting or restricting site access. These controls could include IC plans, restrictive covenants, property easements,

zoning, deed notices, advisories, groundwater use restrictions, and site information database, as referenced in EPA 540-R-00-002.

Costs are determined by number of landowners affected by each medium where ICs will be necessary.

c Earthworks associated with potential remining will also advance remediation efforts, thereby reducing costs associated with

remediation. Of the total capital cost of all earthworks, approximately 75 percent are associated with assumed ore recovery and

approximately 25 percent are associated with remediation. The basis for this apportionment is provided in the FS.

Notes:

ac = acre

ea = each

LS = lump sum

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Section 13-Statutory Determinations

Under CERCLA Section 121 and the NCP, EPA must select a remedy that is protective of human health
and the environment, complies with ARARs (unless a statutory waiver is justified), is cost-effective,
and uses permanent solutions and alternative treatment technologies or resource recovery
technologies to the maximum extent practicable. Furthermore, CERCLA includes a preference for
remedies that include treatment that permanently and significantly reduces the volume, toxicity, or
mobility of hazardous wastes as a principal element. The following sections discuss how the Selected
Remedy meets these statutory requirements.

13.1 Protection of Human Health and the Environment

The Selected Remedy will protect human health and the environment. The Selected Remedy is a
combination of source controls, treatment technologies, and other elements that will work together to
achieve RAOs.

For upland soil and waste rock, RAOs will be attained by construction of an ET cover system that will
isolate the waste rock (source materials) from direct contact by receptors. The cover system will be
constructed by backfilling mine pits; consolidating, grading and shaping waste rock; and constructing a
5- to 6-foot-thick engineered cover system over all source materials present at the Site. The cover
system will cover more than 500 acres. The cover system will be constructed of clean materials that
meet cleanup levels and will therefore address direct contact risks. The cover system will also
contribute to achieving RAOs for other media by isolating source materials from surface runoff,
minimizing deep infiltration of precipitation and snowmelt into waste rock and subsequent release of
contaminants to groundwater, providing clean growth media to minimize uptake of selenium into
vegetation, and minimizing release of contaminants from source areas into the ephemeral and
intermittent channels on the margins of the Site.

For surface water, RAOs will be attained by capturing and treating contaminated seepage using
constructed wetland treatment cells prior to discharge. ICs and fencing will be used to control human
exposure. The cover system, described in detail in Section 12.2.1, will substantially contribute to
meeting surface water RAOs because releases of contaminants to surface water will be greatly reduced
over time. These load reductions will occur because stormwater runoff from the cover system will not
contact source materials and the cover system will reduce recharge to the seeps over time. PRBs,
described in Section 12.2.4, will also reduce the concentrations of contaminants that discharge to
ephemeral and intermittent headwater reaches of area streams, contributing to achievement of
surface water RAOs.

For groundwater, RAOs will be attained by constructing PRBs near the margins of the waste rock
dumps to intercept and treat shallow contaminated groundwater. Extraction wells may be used to
supplement the system in areas where groundwater is deeper and cannot be intercepted by PRBs. The
cover system described in Section 12.2.1 will substantially contribute to meeting groundwater RAOs
for shallow and deep aquifers because recharge to and releases of contaminants to groundwater will
be greatly reduced over time. These actions are expected to result in groundwater meeting cleanup
levels over time. If contaminant concentrations are not reduced to cleanup levels through the use of
PRBs (and construction of the cover system), MNA would be used as a polishing step to further reduce
concentration of contaminants in groundwater plumes. Implementation and enforcement of ICs will
prevent human exposure to contaminated groundwater until RAOs are achieved.

For sediment and riparian soil, RAOs will be attained by controlling sources of contamination to the
intermittent streams, MNR, and ICs. Engineering controls will include construction of the cover system
described in Section 12.2.1 in combination sediment traps and basins near the margins of waste rock
dumps. The engineering controls will minimize the erosion and transport of contaminated particles of
source material into local ephemeral drainages during intermittent periods of storm and snowmelt

13-1

-------
Section 13 • Statutory Determinations

runoff. MNR will further reduce concentrations of contaminants through natural processes. Over time,
clean runoff, and associated sediment transport and erosion will disperse and dilute or cover
contaminated stream channel/overbank deposits and therefore reduce risks to receptors.
Implementation and enforcement of ICs will prevent human exposure to contaminated sediment and
riparian soil until RAOs are achieved.

For Vegetation, RAOs will be achieved through construction of the ET cover system described in
Section 12.2.1. The cover system will provide clean growth media for vegetation and prevent root
uptake of selenium into plant tissue. In addition, vegetation will be surveyed and monitored
periodically for the presence of plant species (such as asters or milk-vetch) known to biologically
accumulate selenium from soil. These target species will be eradicated by use of herbicides. These
actions will reduce selenium exposure to grazing deer, elk, domestic livestock, and other animals that
will potentially feed on post-reclamation vegetation. Implementation and enforcement of ICs will
prevent human exposure to contaminated vegetation until RAOs are achieved.

The Selected Remedy includes several other elements to evaluate and optimize the performance of
source controls and treatment technologies, and to ensure protectiveness. An adaptive management
approach will be used to guide implementation of source controls and treatment technologies until
RAOs are achieved. The combined remedy also includes O&M and LTM requirements.

There are no short-term threats associated with the Selected Remedy that cannot be readily controlled
through applicable health and safety requirements, monitoring, and standard construction practices.
In addition, the Selected Remedy will not result in any adverse cross-media effects

13.2 Compliance with ARARs

The Selected Remedy will comply with all ARARs. The ARARs are presented in Appendix B and include
information on type (i.e., chemical-, location-, and action-specific) and status (i.e., applicable or
relevant and appropriate), a synopsis of the requirement, and a summary of the action to be taken to
attain requirements.

Key ARARs for the Ballard Mine Site include the following:

• Idaho Water Quality Standards, including water quality criteria

• National Recommended Water Quality Criteria established under the CWA

• National Primary Drinking Water Regulations, including MCLs, established under the Safe Drinking
Water Act

• Idaho Ground Water Quality Rule

• Portions of the regulations established under UMTRCA

• Regulations established under the Mineral Leasing Act that control the development and
reclamation of phosphate mines

• Regulations under the Idaho Surface Mine Reclamation Act pertaining to reclamation of surface
mining operations

Cleanup levels are based on federal water quality criteria for surface waters and MCLs for
groundwater. During remedy implementation, the Selected Remedy will comply with action-specific
ARARs, including state and federal mining and reclamation requirements. These ARARs establish
performance requirements for the remediated areas, including the source areas and intermittent and
ephemeral drainages, to ensure the effectiveness and integrity of the cleanup actions. The Selected
Remedy will also comply with Section 404 of the CWA, which requires avoiding disturbances to
riparian areas (wetlands) and minimizing disturbances where they cannot be avoided.

13-2

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Section 13 • Statutory Determinations

13.3 Cost Effectiveness

In EPA's judgement, the Selected Remedy is cost-effective and represents a reasonable value for the
money to be spent. In making this determination, the following definition was used: "A remedy shall be
cost effective if its costs are proportional to its overall effectiveness." (NCP §300.430(f)(l)(ii)(D)). This
was accomplished by evaluating the "overall effectiveness" of those alternatives that satisfied the
threshold criteria (i.e., were both protective of human health and the environment and were ARAR-
compliant). Overall effectiveness was evaluated by assessing three of the five balancing criteria in
combination (long-term effectiveness and permanence; reduction in toxicity, mobility, and volume
through treatment; and short-term effectiveness). Overall effectiveness was then compared to costs to
determine cost-effectiveness. The relationship of the overall effectiveness of the combined remedial
alternative (being selected in this ROD) was determined to be proportional to its costs and this
alternative therefore represents a reasonable value for the money to be spent.

The estimated present value cost of the Selected Remedy is approximately $41,323,000. The most-
costly component of the Selected Remedy is the upland soil and waste rock component. The USWR
alternative selected (USWR 6) provides a similar level of protectiveness compared to the other two
alternatives (USWR 4 and USWR 7) evaluated, but costs significantly less ($37 million for USWR 6
compared to $51 million for USWR 4 and $113 million for USWR 7). The cost of the USWR component
in the Selected Remedy (USWR 6) is considerably less than the other two alternatives because
earthworks associated with potential ore recovery reduce the scope and cost of remaining earthworks
associated with implementation of the remedy.

The Selected Remedy includes treatment of contaminated seeps discharging to surface water using
constructed wetlands. Although this component of the Selected Remedy (SW 3) costs more than SW 2,
which focuses on ICs ($1,430,000 versus $850,000), its overall effectiveness is greater because it
reduces toxicity through treatment and has better short-term effectiveness.

For groundwater, the Selected Remedy includes treatment of shallow alluvial groundwater using PRBs.
This component of the Selected Remedy (GW 3) costs significantly less than the groundwater
extraction and treatment alternative (GW 5b) and more than the alternative focused on ICs and MNR
(GW 2). The overall effectiveness of GW 3 is greater than GW 2 because it includes treatment to reduce
toxicity and is more effective in the short term. Compared to GW 5, GW 3 provides an overall level of
protection that is comparable at a significantly lower cost ($2.1 million versus $24.2 million).

For sediment and riparian soil, the selected alternative (S/RS 3) provides a similar level of
protectiveness compared to S/RS 4 at a lower cost ($736,000 for S/RS 3 versus $1,591,000 for S/RS 4).

13.4 Use of Permanent Solutions and Alternative Treatment
(or Resource Recovery) Technologies to the Maximum
Extent Practicable

The Selected Remedy represents the maximum extent to which permanence and treatment can be
practically used at the Site. NCP §300.430(f)(l)(ii)(E) provides that the balancing shall emphasize the
factors of long-term effectiveness and reduction of toxicity, mobility or volume through treatment, and
shall consider the preference for treatment and bias against offsite disposal. The modifying criteria
were also considered in making this determination.

EPA has determined that the Selected Remedy represents the maximum extent to which permanent
solutions and treatment technologies can be used in a cost-effective manner at the Site. Of the
assortment of media alternatives evaluated that are protective of human health and the environment
and comply with ARARs, EPA has determined that the Selected Remedy provides the best balance of

13-3

-------
Section 13 • Statutory Determinations

tradeoffs in terms of the five balancing criteria, while also considering the statutory preference for
treatment and bias against offsite disposal and considering state and community acceptance.

13.5	Preference of Treatment as a Principal Element

The Selected Remedy does not satisfy the statutory preference for treatment as a principal element.
The NCP establishes the expectation that treatment will be used to address principal threat wastes
whenever practicable (40 CFR 300.430[a] [1] [iii] [A]). Principal threat wastes are those source
materials considered to be highly toxic or highly mobile that generally cannot be contained in a
reliable manner or will present a significant exposure risk to human health and the environment.
The Ballard Mine waste rock (mine materials) are of large volume and generally low toxicity, which
are difficult to treat effectively; however, they may be contained effectively. As discussed in Section 11,
EPA has determined that the waste rock source material is not acutely toxic, direct exposure risk can
be mitigated by ICs and LUCs, and it can be reliably contained; therefore, the waste rock source
material does not constitute a principal threat waste.

13.6	Five-Year reviews

Because the Selected Remedy results in hazardous substances, pollutants, or contaminants remaining
onsite (although contained within a robust ET cover) at greater than levels that allow for unlimited use
and unrestricted exposure, FYRs will be performed pursuant to CERCLA §121(c) and
NCP §300.430(f)(5)(iii)(C). EPA will perform a review of the RAs no less than 5 years after initiation of
such RA to ensure the remedy is or will be protective of human health and the environment.

13-4

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Section 14 - Documentation of Significant Changes

The Preferred Alternative described in the Proposed Plan remains unchanged as the Selected Remedy
for the Site. During the public comment period, EPA received four comments from individuals, citizen
groups, and the state. EPA reviewed all comments submitted during the public comment period and
determined that no significant changes to the remedy, as originally identified in the Proposed Plan,
were necessary or appropriate.

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Section 14 • Documentation of Significant Changes

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14-2

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Section 15 • References

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Section 15 • References

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U.S. Environmental Protection Agency (EPA). 1997b. Rules of Thumb for Superfund Remedy Selection
(pp. 23). (EPA 540-R-97-013; OSWER 9355.0-69; PB97-963301). Washington D.C.: Office of Solid
Waste and Emergency Response, http: //www.epa.gov/superfund/policv/remedy/rules/rulesthm.pdf

U.S. Environmental Protection Agency (EPA). 1997c. Exposure Factors Handbook. Office of Emergency
and Remedial Response. USEPA/600/P-95/002. August.

U.S. Environmental Protection Agency (EPA). 2000. A Guide to Developing and Documenting Cost
Estimates During the Feasibility Study. EPA/540-R-00-002. July.

U.S. Environmental Protection Agency (EPA). 2003. Consent Order/Administrative Order on Consent
for the Performance of Site Investigations (Sis) and Engineering Evaluations/Cost Analyses (EE/CAs)
at P4 Production, L.L.C. Phosphate Mine Sites in Southeastern Idaho. United States Environmental
Protection Agency, United States Forest Service, Idaho Department of Environmental Quality, in the
Matter of Enoch Valley Mine, Henry Mine, Ballard Mine, P4 Production, L.L.C., respondent, August 20.

U.S. Environmental Protection Agency (EPA). 2004. Risk Assessment Guidance for Superfund (RAGS)
Volume I: Human Health Evaluation Manual (PartE, Supplemental Guidance for Dermal Risk
Assessment). EPA/540/R/99/005.

U.S. Environmental Protection Agency (EPA). 2005a. Ecological Soil Screening Levels for Antimony.
Interim Final. OSWER Directive 9285.7-61, Revised. Office of Solid Waste and Emergency Response.
February.

U.S. Environmental Protection Agency (EPA). 2005b. Ecological Soil Screening Levels for Cadmium.
Interim Final. OSWER Directive 92857-65, Revised. Office of Solid Waste and Emergency Response.
March.

U.S. Environmental Protection Agency (EPA). 2005c. Ecological Soil Screening Levels for Vanadium.
Interim Final. OSWER Directive 92857-70, Revised. Office of Solid Waste and Emergency Response.
April.

U.S. Environmental Protection Agency (EPA). 2007a. Ecological Soil Screening Levels for Copper.
OSWER Directive 92857-68, Revised. Office of Solid Waste and Emergency Response. February.

U.S. Environmental Protection Agency (EPA). 2007b. Ecological Soil Screening Levels for Nickel.
Interim Final. OSWER Directive 92857-76, Revised. Office of Solid Waste and Emergency Response.
March.

15-3

-------
Section 15 • References

U.S. Environmental Protection Agency (EPA). 2007c. Ecological Soil Screening Levels for Selenium.
Interim Final. OSWER Directive 92857-72, Revised. Office of Solid Waste and Emergency Response.
July.

U.S. Environmental Protection Agency (EPA). 2007d. Ecological Soil Screening Levels for Zinc. Interim
Final. OSWER Directive 92857-73, Revised. Office of Solid Waste and Emergency Response. June.

U.S. Environmental Protection Agency (EPA). 2008a. Ecological Soil Screening Levels for Chromium.
Interim Final. OSWER Directive 9285.7-66, Revised. Office of Solid Waste and Emergency Response.
April.

U.S. Environmental Protection Agency (EPA). 2008b. Recommended Toxicity Value for Uranium,
Noncancer Endpoint for the Eastern Michaud Flats Site. Technical memorandum from Marc
Stifelman/EPA Region 10 to Office of Environmental Assessment.

U.S. Environmental Protection Agency (EPA). 2009a. Administrative Settlement Agreement and Order
on Consent/Consent Order for Performance of Remedial Investigation and Feasibility Study at the
Enoch, Henry, and Ballard Mine Sites in Southeastern Idaho. EPA Region 10, Idaho Department of
Environmental Quality, United States Department of Agriculture, Forest Service Region 4, United States
Department of the Interior, Bureau of Land Management, Shoshone-Bannock Tribes, in the Matter of
Enoch Valley Mine, Henry Mine, Ballard Mine, P4 Production, L.L.C., Respondent. Effective Date of
November 30, 2009.24.

U.S. Environmental Protection Agency (EPA). 2009b. Region 10 Superfund, RCRA, LUST, and Brownflelds
Clean and Green Policy. August 13.

U.S. Environmental Protection Agency (EPA). 2011. Exposure Factors Handbook. Exposure Factors
Handbook2011 Edition (Final). EPA/600/R-09/052F.

U.S. Environmental Protection Agency (EPA). 2013a. National Recommended Water Quality Criteria.
Accessed August 2013. https: //www.epa.gov/wa_c/national-recommended-water-aualitv-criteria.

U.S. Environmental Protection Agency (EPA). 2013b. Integrated Risk Information System (IRIS)
Database, http: / / cfpub.epa.gov/ ncea / iris / index.cfm.

U.S. Environmental Protection Agency (EPA). 2013c. Region 3 BTAG Freshwater Sediment Screening
Benchmarks, http://www.epa.gov/reg3hwmd/risk/eco/btag/sbv/fwsed/screenbench.htm.

U.S. Environmental Protection Agency (EPA). 2013d. Regional Screening Levels for Chemical
Contaminants at Superfund Sites. May 2013. http: //www.epa.gov/region9 /superfund/prg/.

U.S. Environmental Protection Agency (EPA). 2014. Preliminary Remediation Goals for Radionuclides.
November 11, 2014. https://epa-prgs.ornl.gov/cgi-bin/radionuclides/rprg search.

U.S. Environmental Protection Agency (EPA). 2018. Ballard Mine Proposed Plan, Caribou County, ID.
Final. April 2.

U.S. Fish and Wildlife Service (USFWS). 2018. Threatened and Endangered Species Status for Caribou
County, ID. E-mail from J. Moore/USFWS to D. Tomten/EPA. December 6.

Woodruff, R.A. and B.L. Keller. 1982. "Dispersal, daily activity, and home range of coyotes in
southeastern Idaho." Northwest Science 56:199-207.

15-4

-------
Appendix A
Risk Summary Tables

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This page intentionally left blank to allow for double-sided printing.

-------










Table A-1



























Exposure Parameters for Use in the Human Health Risk Assessment



























Hypothetical Future



Seasonal



Recreational





Recreational









lidllvc HlflcllUdll



Resident



Rancher



Hunter





Camper / Hiker



Exposure Parameter



Units

Child

Adult



Child

Adult



Adult



Adult



Child

Youth

Adult



General

































BW = body weight



kg

15

70

a

15

70

a

70

a

70

a

15

55

70

a

ATc = averaging time for carcinogens



days

25,550



a

25,550



a

25,550

a

25,550

a



25,550



a

ATn = averaging time for non-carcinogens



































CTE

days

584

2336

D

584

2336

D

2336

D

2336

D

584

876

1460

D



RME

days

2,190

8,760

a

2,190

8,760

a

8,760

D

8,760

D

2,190

3,285

5,475

D

ED = exposure duration



































CTE

years

1.6

6.4

D

1.6

6.4

D

6.4

D

6.4

D

1.6

2.4

4

D



RME

years

6

24

a

6

24

a

24

D

24

D

6

9

15

D

Soil Direct Exposure Pathways - Oral, Dermal, and Inhalation































EF = exposure frequency for soil exposures



































CTE

days/year

183

183

e

183

183

e

90

T

8

c

3

3

3

a



RME

days/year

270

270

e

270

270

e

120

T

14

c

7

7

7

a

IRsoii = soil intake rate



































CTE

mg/day

100

50

g

100

50

g

50

g

50

g

100

50

50

g



RME

mg/day

200

100

g

200

100

g

100

g

100

g

200

100

100

g

SA = surface area for soil dermal contact



































CTE

cm2

1,562

5,092

h

1,562

5,092

h

5,092

h

5,092

h

1,562

3,285

5,092

h



RME

cm2

2,434

5,657

h

2,434

5,657

h

5,657

h

5,657

h

2,434

2,434

5,657

h

AF = soil-to-dermal adherence factor



































CTE

mg/cm"'

0.04

0.07

K

0.04

0.07

K

0.1

i

0.1

i

0.04

0.04

0.01

J



RME

mg/cm2

1

0.3

a

1

0.3

a

0.4

i

0.3

a

1

0.3

0.3

a

ABS = absorption fraction through skin



unitless

CS

CS

a

CS

CS

a

CS

a

CS

a

CS

CS

CS

a

ET = exposure time for dust inhalation



































CTE

fraction of a day

1/24

1/24

m

1/24

1/24

m

4/24

n

12/24

I

12/24

12/24

12/24

i



RME

fraction of a day

2/24

2/24

a

2/24

2/24

a

12/24

n

1

I

1

1

1

I

PEF = particulate emission factor



































RME

m3/kg

6.45E+09

a

6.45E+09

a

6.45E+09

a

6.45E+09

a



6.45E+09



a

Ingestion of Plants

































EF = exposure frequency for plant ingestion



days/year

350



0

350



0

NA



NA





NA





IRpiant = Plant intake rate



































CTE

g/day

30

57

P

30

57

P

NA



NA





NA







RME

g/day

156

293

P

156

293

P

NA



NA





NA





MLF = mass loading factor



unitless

0.26



r

0.26



r

NA



NA





NA





Ingestion of Game

































EF = exposure frequency for game ingestion



days/year

350



0

NA





NA



350

0



NA





IRgame = game intake rate



































CTE

g/day

0.032

0.070

q

NA





NA



30.2

q



NA







RME

g/day

8.0

17.9

q

NA





NA



93.9

q



NA





MLF = mass loading factor



unitless

0.25



r

NA





NA



0.25

r



NA





Qp_e = elk fodder intake



kg/day

2.29



s

NA





NA



2.29

s



NA





Fp_e = fraction of year animal on site



unitless

0.025



r

NA





NA



0.025

r



NA





1 of 4

-------












Table A-1



















Exposure Parameters for Use in the Human Health Risk Assessment



















Hypothetical Future

Seasonal



Recreational

Recreational







IN9HV6 HmsNcan



Resident

Rancher



Hunter

Camper / Hiker

Exposure Parameter



Units

Child



Adult



Child



Adult

Adult



Adult

Child Youth Adult

Fs_e = fraction of animal's food on site



unitless



1



t



NA



NA



1 1

NA

Qs_e = elk soil intake rate



kg/day

0.0459



u



NA



NA



0.0459

NA

Qw_e = elk water intake rate



L/day



16.1



V



NA



NA



16.1

NA

BWe = elk body weight



g

286,000

w



NA



NA



286,000

NA

Ingestion of Beef



























EF = exposure frequency for beef ingestion



days/year



NA







NA



350

O

NA

NA

IRbeef = beef intake rate





























CTE

g/day



NA







NA



124

X

NA

NA



RME

g/day



NA







NA



476

X

NA

NA

MLF = mass loading factor



unitless



NA







NA



0.25

r

NA

NA

Qp_c = cattle fodder intake



kg/day



NA







NA



11.77

r

NA

NA

Fp_c = fraction of year animal on site



unitless



NA







NA



0.33

y

NA

NA

Fs_c = fraction of animal's food on site



unitless



NA







NA



1

r

NA

NA

Qs_c = cattle soil intake rate



kg/day



NA







NA



0.39

r

NA

NA

Qw_c = cattle water intake rate



L/day



NA







NA



53

r

NA

NA

Surface Water Direct Exposure Pathways - Incidental Ingestion and

Dermal Contact























EF = exposure frequency for surface water





























CTE

days/year

70



70

z



NA



NA



NA

NA



RME

days/year

122



122

z



NA



NA



NA

NA

IRsurface water= surface water incidental intake rate





























CTE

m L/day

7.2



7.2

aa



NA



NA



NA

NA



RME

m L/day

21.6



21.6

aa



NA



NA



NA

NA

SA = surface area for surface water dermal contact





























CTE

cm2

933



2,587

aD



NA



NA



NA

NA



RME

cm"

1,968



6,362

aD



NA



NA



NA

NA

DA = absorbed dose per dermal contact event



mg/cm2-event

CS



CS





NA



CS



NA

NA

ET = exposure time for dermal contact





























CTE

hours / day

1



1

ac



NA



NA



NA

NA



RME

hours / day

2



2

ac



NA



NA



NA

NA

Groundwater Direct Exposure Pathways - Ingestion and Dermal Contact























EF = exposure frequency for groundwater





























CTE

days/year



NA





350



350 a

90

r

NA

NA



RME

days/year



NA





350



350 a

120

T

NA

NA

1 ^groundwater= groundwater intake rate





























CTE

L/day



NA





0.315



0.922 aa

0.922

aa

NA

NA



RME

L/day



NA





1.5



2

2

a

NA

NA

SA = surface area for groundwater dermal contact while showering



























CTE

cm2



NA





6,365



18,979 ae

18,979

ae

NA

NA



RME

cm"



NA





7,694



23,654 ae

23,654

ae

NA

NA

DA = absorbed dose per dermal contact event



mg/cm2-event



NA





CS



CS

CS



NA

NA

ET = exposure time for dermal contact





























CTE

hours / day



NA





0.33



0.25 af

0.25

at

NA

NA



RME

hours / day



NA





1



0.58 ai

0.58

dl

NA

NA

2 of 4

-------
Table A-1

Exposure Parameters for Use in the Human Health Risk Assessment

Exposure Parameter

Units

Native American
Child	Adult

Hypothetical Future
Resident

Child

Adult

Seasonal
Rancher

Adult

Recreational
Hunter

Adult

Recreational
Camper I Hiker

Child Youth	Adult

J&E SOIL PARAMETERS

Soil type

pb = dry soil bulk density	g/cmJ

n = total soil porosity	unitless

0W = water-filled soil porosity	cmJ/cmJ

0a = air-filled soil porosity	cmJ/cmJ

J&E MODEL PARAMETERS

Ts = Average soil or groundwater temperature (Groundwater model)	°C

Ts = Average soil temperature (Soil model)	°C

l_F = Depth below grade to bottom of enclosed space floor	cm

Lwt = Depth below grade to water table	cm

Qsoil - Average vapor flow rate into building	L/m

Ls - Depth below grade to soil sample	cm

NA
NA
NA
NA
NA

NA
NA
NA
NA
NA
NA

SI

1.35
0.489
0.167
0.322

8
8

15
1,136
calculated in model
152

ah
ah

ak

NA
NA
NA
NA
NA

NA
NA
NA
NA
NA
NA

NA
NA
NA
NA
NA

NA
NA
NA
NA
NA
NA

NA
NA
NA
NA
NA

NA
NA
NA
NA
NA
NA

Notes:

UC = degree(s) Celsius

cm = centimeter(s)

cm^ = square centimeter(s)

cm"3 = cubic centimeter(s)

CTE = central tendency estimate

CS = chemical specific
g = gram(s)
kg = kilogram(s)
L = liter(s)
m = meter(s)

mJ = cubic meter(s)

mg = milligram(s)

ml_ = milliliter(s)

NA = not applicable

RME = reasonable maximum estimate

a Idaho Department of Environmental Quality (DEQ). 2004a. Idaho Risk Evaluation Manual.

b For the RME scenario, an adult recreational hunter who resides in the area was assumed to hunt every season for 24 years, an recreational camper/hiker was assumed to camp in the area as a child, youth, and adult for 30 years, and an adult
seasonal rancher was assumed to graze cattle in the area for 24 years. These RME assumptions are consistent with an exposure duration of 30 years suggested in the Idaho Risk Evaluation Manual (DEQ, 2004a). For the CTE scenario, the
exposure duration for all receptors were based on a 50th percentile residential occupancy period of 8 years (EPA, 2011). The CTE exposure durations were calculated by multiplying each RME exposure duration by a factor of 8/30.
c Archery season for elk is a month (September), any weapon season for elk is October 25 to November 15 and muzzle loader season is November 16 to 30. The exposure frequency is based on the assumption that a hunter goes out every

weekend during the archery season (CTE) or a total of 14 days over the entire season (RME).
d Based on one 3-day weekend (CTE) or week-long (RME) camping trip per year.

e The RME exposure frequency for direct soil contact is from DEQ (2004a); the CTE exposure frequency assumes that the ground is covered in snow for half of the year.
f Cattle are assumed to graze at the Site for 90 (CTE) to 120 (RME) days per year; seasonal ranchers are conservatively assumed to reside at the site while cattle are grazing,
s The RME soil ingestion rates are from DEQ (2004a); CTE soil ingestion rates are central tendency values from Table 5-1 of EPA's Exposure Factors Handbook (2011).

h The RME dermal surface area for soil exposures is from DEQ (2004a). The CTE is from Table 7-2 of EPA's Exposure Factors Handbook (2011), and assumes that the face, forearms, hands, and lower legs are exposed to soil.

' Equal to the geometric mean (CTE) and 95th percentile (RME) for a farmer presented in EPA (2004) Exhibit 3-3.

i Equal to the geometric mean for a child playing in dry soil (child) and adult playing outdoor sports - soccer (adult) presented in EPA (2004) Exhibit 3-3.
k Equal to the geometric mean for a child playing indoors and outdoors (child) and an adult residential gardener presented in EPA (2004) Exhibit 3-3.

1 Time outdoors for tent camping (RME) and RV camping (CTE).
m Based on 50% of the RME assumption (Refer to footnote "a").

n The exposure time for a seasonal rancher is assumed to be similar to the time spent outdoor for someone on a farm. The 95th and 50th percentile time spent outdoor for someone on a farm in the summer is 12 hours and 4 hours, respectively
(EPA, 2011).

0 Ingestion frequency (days per year) for homegrown, hunted, and foraged food was assumed to match the number of days at home in DEQ (2004). Although it is conservatively assumed that homegrown, hunted, and foraged foods are eaten

daily, the daily food ingestion rates derived from EPA (2011) do not assume that these foods comprise an individual's entire daily food intake.
p Consumption of home grown produce from Table 13-1 of EPA (2011): per capita for populations that garden or farm, adjusted for cooking. Body weight specific ingestion rates in Table 13-1 were adjusted to total grams consumed using body
weights in Table 8-1 of EPA (2011). The CTE and RME ingestion rates are equal to the mean and 95th percentile estimates of consumption rates, respectively.

3 of 4

-------
Table A-1

Exposure Parameters for Use in the Human Health Risk Assessment

.. .. Hypothetical Future Seasonal Recreational Recreational
Native American

Resident Rancher Hunter Camper/Hiker

Exposure Parameter Units Child Adult child Adult Adult Adult child Youth Adult

q The ingestion of game rates for a seasonal hunter were time-weighted ingestion rate for ages 16-46 from Table 13-41 of EPA's Exposure Factors Handbook (2011) and adjusted for 29.7% meat preparation and cooking loss and 29.7% post-
cooking loss (Table 13-69 from EPA, 2011), consistent with the human health risk assessment technical memorandum for the Smoky Canyon Mine Site (Formation Environmental LLC, 2013). The CTE (mean) and RME (99th percentile) adult
Native American ingestion of game rates were obtained from Table 11-6 of the 1997 Exposure Factors Handbook (EPA, 1997c). The child Native American ingestion rates were estimated from the adult ingestion rates assuming a child eats
45% of the meat consumed by an adult (based on values in Table 13-1 of EPA, 2011). All grams per kilogram per day adult ingestion rates were converted to grams per kilogram assuming a body weight of 70 kilograms.

r Mass loading factor obtained from ORNL (2013). The fraction of an animal's food on site was assumed to be 100% during the time the animal is onsite.
s The game animal fodder intake was estimated using Equation 29 in Nagy (2001).

' The fraction of year an animal is on site was estimated using the Ballard Mine site area and a home range of 16,640 acre (Kuck, 2003).
u Soil ingestion rates as percent of diet from Beyer et al. (1994).
v Calculated using Equation 3-17 for ingestion rates for mammal from EPA, 1993.

w Senseman, R. 2002. "Cervus elaphus." Animal Diversity Web. Accessed February 22, 2011. http://animaldiversity.ummz.umich.edu/site/accounts/information/Cervus_elaphus.html.

x The CTE (50th percentile) and RME (95th percentile) consumer-only intake rates for home grown beef (g/kg-day) from Table 13-33 of EPA (2011); adjusted using adult body weight from Table 8-1 of EPA (2011).
v The beef cattle was assumed to graze the Ballard Mine 120 days/year because snowpack and ice are present approximately 6 months of the year.
z Native Americans are assumed to spend 2 hours per day gathering food or medical plants near streams, for 4 days per week during June, July, August, and September.

aa RME (upper confidence limit) and CTE (mean) incidental surface water ingestion rates for Native Americans while collecting culturally significant riparian vegetation were assumed to be similar to ingestion rates for fishing from Table 3-93 of

EPA's Exposure Factors Handbook (2011). Native Americans are assumed to spend 2 hours per day gathering culturally significant riparian vegetation.
ab Native Americans are potentially dermally exposed to surface water while collecting culturally significant riparian vegetation; CTE assumes hands, forearms, and face are exposed, and RME assumes that feet and lower legs are also exposed.
Surface areas were calculated according to Table 7-2 of EPA (2011). For the purposes of this calculation, the surface area of the face was assumed to be 1/3 that of the head, forearms were assumed to represent 45% of the arms, and lower
legs were assumed to represent 40% of the legs (EPA, 2011)
ac Native Americans are assumed to spend 2 hours per day (RME) gathering food or medical plants near streams. The CTE is based on 50% of the RME assumption.
ad Intake rate is the mean from Table 3-1 of EPA (2011).
ae Mean (CTE) and 95th percentile (RME) From Table 7-1 of EPA (2011).
af EPA (2004) Exhibit 3-2.

as A review of soil boring data for the Ballard Shop indicated the soil types of silt loam, silt, silty clay and clay were present. To be conservative, silt was selected as the soil type for the Ballard Shop. The soil parameters listed are default values from

the Johnson and Ettinger model for the soil type selected.
ah Average groundwater temperature from the Spring/Fall 2010, Spring/Fall 2012, and Spring 2013 monitoring events.

ai The slab-on-grade mode was used because the maximum detected concentrations of volatile chemicals of potential ecological concern and chemicals of potential concern were found in soils shallower than 200 centimeters.
ai Average depth to groundwater for monitoring wells SB-01, SB-03 and SB-07 measured in July and November 2011.

ak Depth to the soil sample containing maximum detected concentration of each chemicals of potential concern and chemicals of potential ecological concern.

4 of 4

-------
Table A-2

Toxicity Values used in the Human Health Risk Assessment

Chemical of Potential

CAS

Cancer Slope Factor
(mg/kg-d)"1

URF Chronic Reference Dose - RfD
(|jg/m3)-1 (mg/kg-d)

RfC
(mg/m3)



ABSGla

Critical

Concern

Number

Oral

Dermalb

Inhalation

Oral



Dermalb



Inhalation



(%)

Effect

Metals

Antimony

7440-36-0

NA

NA

NA

4.0E-04

I

6.0E-05

R

NA



15%

Longevity, blood glucose,
and cholesterol

Arsenic

7440-38-2

1.5E+00 I 1.5E+00 R

4.3E-03 I

3.0E-04

I

3.0E-04

R

1.5E-05

C

95%

Dermal effects:
Hyperpigmentation and
keratosis

Cadmium, soil

7440-43-9

NA

NA

1.8E-03 I

1.0E-03

I

2.5E-05

R

1.0E-05

A

2.5%

Hematologic: proteinuria

Cadmium, water

7440-43-9

NA

NA

1.8E-03 I

5.0E-04

I

2.5E-05

R

1.0E-05

A

5%

Hematologic: proteinuria

Chromium, total

16065-83-1

NA

NA

NA

1.5E+00

I

2.0E-02

R

NA



1.3%

NA

Manganese

7439-96-5

NA

NA

NA

1.4E-01

I

5.6E-03

R

5.0E-05

I

4%

Neurological and neuro-
behavioral effects

Molybdenum

7439-98-7

NA

NA

NA

5.0E-03

I

5.0E-03

I

NA



100%

Increased uric acid levels

Nickel

7440-02-0

NA

NA

2.6E-04 C

2.0E-02

I

8.0E-04

R

9.0E-05

A

4%

Decreased body and organ
weights

Selenium

7782-49-2

NA

NA

NA

5.0E-03

I

1.5E-03

R

2.0E-02

C

30%

Clinical selenosis

Thallium

7440-28-0

NA

NA

NA

1.0E-05

P

1.0E-05

R

NA



100%

Increased levels of SGOT
and LDH

Uranium

NA

NA

NA

NA

6.0E-04

E

6.0E-04

R

4.0E-05

A

100%

Body weight loss and
moderate nephrotoxicity

Vanadium

NA

NA

NA

NA

5.0E-03

U

1.3E-04

R

1.0E-04

A

2.6%

Decreased hair cystine

Zinc

7440-66-6

NA

NA

NA

3.0E-01

I

3.0E-01

R

NA



NA

Decrease in ESOD activity

Sources:

A Agency for Toxic Substances and Disease Registry (ATSDR) minimal risk levels (ATSDR, 2013)
E Office of Environmental Assessment (EPA, 2008b)

I Integrated Risk Information System (IRIS) Database (EPA, 2013c).

P Provisional Peer Reviewed Toxicity Values (PPRTVs) as cited in EPA's RSL Table (EPA, 2013a)
U United States Regional Screening Levels (RSLs) (EPA, 2013a)

C CalEPA Toxicity Values as cited in EPA's RSL Table (EPA, 2013a)

R Route Extrapolation















Notes:

% = percent

ng/m3 = microgram(s) per cubic meter

ABSGI = oral absorption efficiencies
CSF = cancer slope factor

EPA = U. S. Environmental Protection Agency
ESOD = erythrocyte superoxide dismutase

IRIS = Integrated Risk Information System
LDH = lactate dehydrogenase



mg/kg-d = milligram(s) per kilogram per day
mg/m3 = milligram(s) per cubic meter

NA = not available

RfC = reference concentration

RfD = reference dose

SGOT = serum glutamic-
oxaloacetic transaminase
URF = unit risk factor

a Values are from EPA RAGS Part E. Where no specific ABSGI is available, the ABSGI is assumed to be 100%. (EPA 2004)

b The following equations are used as recommended by EPA (2004) to estimate dermal CSF and RFDs from the ingestion toxicity values when ABSGI is less than 50 percent:
Dermal RFD = Oral RfD x ABSGI and Dermal CSF = Oral SF/ABSGI. When ABSGI is greater than 50 percent, the dermal CSF and/or RfD is assumed to be equal to the oral CSF
and/or RfD (EPA, 2004).

1 of 1

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-------
Table A-3

Summary of RME Cumulative Risk Estimates for Human Receptors



Current/Future Native American

Hypothetical Future Resident

Current/Future Seasonal Rancher

Current/Future Recreational Hunter &
Current/Future Recreational Camper/Hiker

ILCR a

COCs b

HI a

COCs b

ILCR a

COCs b

HI a

COCs b

ILCR a

COCs b

HI a

COCs b

ILCR a

COCs b

HI a

COCs b

Upland Soil

Site-Related

4E-05

As

1

—

4E-05

As

1

—

1E-05

As

0.6

—

<1E-06

--

< 1

—

Background

1E-05

As

0.2

—

1E-05

As

0.2

—

3E-06

As

0.08

—

<1E-06

--

< 1

--

Incremental

3E-05

As

1

—

3E-05

As

1

—

8E-06

As

0.5

—

<1 E-06

--

< 1

—

Riparian Soil

Site-Related

1E-05

As

0.9

—

























Background

8E-06

As

0.2

—

























Incremental

3E-06

As

0.7

—

























Culturally Significant Plant - Upland Soil0

Site-Related

2E-03

As

169

As, Cd, Co,
Mn, Sb, Se,
Tl, U

























Background

6E-03

As

135

As, Cd, Co,
Mn, Sb, Tl, U

























Incremental

—

—

149

Cd, Sb, Se, U

























Culturally Significant Plant - Riparian Soil0

Site-Related

5E-03

As

221

As, Cd, Co,
Mn, Mo, Ni,
Sb, Se, Tl, V

























Background

4E-03

As

142

As, Co, Mn,
Ni, Sb, Tl, V

























Incremental

1E-03

As

93

As, Cd, Mo,
Ni, Se, Tl, V

























Aquatic Plant - Sediment0

Site-Related

6E-04

As

82

As, Cd, Mn,
Mo, Se, Zn

























Background

2E-04

As

4

Cd

























Incremental

4E-04

As

77

As, Cd, Se

























Fruits and Vegetables - Upland Soil and Groundwater0'6''

Site-Related









2E-03

As

94

As, Cd, Mo,
Sb, Se, Tl

















Background









6E-03

As

152

As, Cd, Co,
Mn, Mo, Ni,
Sb, Se, Tl, V

















Incremental









—

—

46

Mo, Se, Tl

















Surface Waterd

Site-Related

2E-06

As

0.01

--

























Background

1E-07

--

0.0006

--

























Incremental

2E-06

As

0.009

--

























Groundwater®

Site-Related









3E-04

As

7

As, Se, Tl

6E-05

As

2

--









Background









2E-05

As

1

--

4E-06

As

0.01

--









Incremental









3E-04

As

6

As, Se

5E-05

As

2

--









Cattle - Upland Soil and Surface Waterd'g

Site-Related

















2E-04

As

44

As, Co, Se, Tl









Background

















5E-05

As

11

Co, Tl









1 of 2

-------














Table A-3

























Summary of RME Cumulative Risk Estimates for Human Receptors















Current/Future Native American

Hypothetical Future Resident

Current/Future Seasonal Rancher

Current/Future Recreational Hunter &
Current/Future Recreational Camper/Hiker



ILCR a

COCs b

HI a

COCs b

ILCR a

COCs b

HI a

COCs b

ILCR a

COCs b

HI a

COCs b

ILCR a

COCs b

HI a

COCs b

Incremental

















1E-04

As

34

Se, Tl









Cattle - Upland Soil and Groundwater6'9

Site-Related

















2E-04

As

44

As, Co, Se, Tl









Background

















5E-05

As

11

Co, Tl









Incremental

















1E-04

As

34

Se, Tl











Site-Related Cumulative Ri





























Background Cumulative Ri

























JC-I»C-I

™ " nf j

Notes:

































a Media-specific cumulative ILCR and HI for all COPCs





























b Analytes with a chemical-specific Incremental RME ILCR or HQ greater than the EPA's risk management range and/or DEQ's acceptable risk criteria are listed as











media-specific COCs.

































c All media-specific COPCs were evaluated for the indirect pathways in addition to direct exposure pathways (i.e., ingestion, inhalation, and dermal contact)













except sediment COPCs, which were evaluated through the indirect uptake to aquatic culturally significant plant pathway only. The indirect exposure route -













ingestion of elk tissue - was not evaluated in the Tier II risk assessment due to the absence of excess Tier 1 risk or hazard.

















d Dissolved concentration of metals in surface water was used in human health risk and hazard calculations for all analytes except for selenium, where the













total surface water concentration was used































8 Total concentration of metals in groundwater was used in human health risk and hazard calculations for all analytes.



















f The indirect exposure route - ingestion of fruits and vegetables grown in upland soil and irrigated with groundwater -

was evaluated for all soil and













groundwater COPCs. For an analyte that was a COPC in soil only, the measured non-culturally significant plant concentration, when available, was used to













represent the fruits and vegetables concentration. If an analyte was a COPCs in groundwater, the fruits and vegetables exposure concentration was equal













to the modeled concentration from groundwater plus either the measured non-culturally significant plant concentration when available, or the modeled













concentration from soil. Fruit and vegetable COPCs from resulting from elevated measured metals concentrations plant tissue are indicated as COPCs in













upland soil as well as in measured plants.































9The indirect exposure route - ingestion of cattle grazed on upland pasture - was evaluated with either surface or groundwater ingestion. Excess human













health risk due to arsenic in cattle tissue resulted from both pasture and livestock drinking water.





















Bold indicates exceedance of EPA's risk management range and/or DEQ's acceptable risk criteria.













Key:







COC = chemical of concern

































COPC = chemical of potential concern























As = arsenic

Se = selenium

EPA = U.S. Environmental Protection Agency





















Cd = cadmium

Tl = thallium

HI = hazard index

























Co = cobalt

U = uranium

HQ = hazard quotient

























Mn = manganese

V = vanadium

DEQ = Idaho Department of Environmental Quality





















Ni = nickel



Zn = zinc



ILCR = Incremental lifetime cancer risk























Rn = radon





RME = reasonable maximum exposure































2 of 2

-------
Table A-4

Assessment Endpoints and Indicator Receptors

Measures of

Feeding Guild

Assessment Endpoint

Receptor

Exposure

Effect

2 " Consumers Protect amphibians from acute and chronic
Amphipians adverse effects from direct and/or

secondary exposure to metals resulting
from phosphate mining activities.

Frog

Measured surface water COPEC
concentrations

Compare measured
surface water
concentration with
acceptable levels

1 ° Consumers Protect herbivorous mammals (avian and
Terrestrial terrestrial predator prey items) by limiting
Herbivore acute and chronic adverse effects from
exposure to metals resulting from
phosphate mining activities.

Long-tailed Vole

Calculated daily dosage using
exposure models, measured
chemical concentrations in abiotic
and biotic media, and food web
interactions.

Compare calculated dose
to NOAEL and LOAEL
dosages for similar prey
species.

Protect large herbivorous mammals (game
species) by limiting acute and chronic
adverse effects from exposure to metals
resulting from phosphate mining activities.

Elk

Calculated daily dosage using
exposure models, measured
chemical concentrations in abiotic
and biotic media, and food web
interactions.

Compare calculated dose
to NOAEL and LOAEL
dosages for similar
species.

1 ° Consumers
Avian Herbivore

Protect herbivorous bird species from acute
and chronic adverse effects from direct
and/or secondary exposure to metals
resulting from phosphate mining activities.

American Goldfinch

Calculate daily dosage using
exposure models, measured
chemical concentrations in abiotic
and biotic media, and food web
interactions.

Compare calculated dose
to NOAEL and LOAEL
dosages for similar
species.

2 ° Consumers
Terrestrial
Omnivore

Protect small omnivorous mammals (avian
and terrestrial predator prey items) by
limiting acute and chronic adverse effects
from exposure to metals resulting from
phosphate mining activities.

Deer Mouse	Calculated daily dosage using Compare calculated dose

exposure models, measured to NOAEL and LOAEL
chemical concentrations in abiotic dosages for similar
and biotic media, and food web species,
interactions.

Protect omnivorous mammals by limiting
acute and chronic adverse effects from
exposure to metals resulting from
phosphate mining activities.

Raccoon

Calculated daily dosage using Compare calculated dose
exposure models, measured to NOAEL and LOAEL
chemical concentrations in abiotic dosages for similar prey
and biotic media, and food web species,
interactions.

1 of 2

-------
Table A-4

Assessment Endpoints and Indicator Receptors

Measures of

Feeding Guild

Assessment Endpoint

Receptor

Exposure

Effect

2 ° Consumers
Avian Omnivore

Protect omnivorous bird species from acute
and chronic adverse effects from direct
and/or secondary exposure to metals
resulting from phosphate mining activities.

American Robin

Calculate daily dosage using
exposure models, measured
chemical concentrations in abiotic
and biotic media, and food web
interactions.

Compare calculated dose
to NOAEL and LOAEL
dosages for similar
species.

Protect omnivorous water bird species from
acute and chronic adverse effects from
direct and/or secondary exposure to metals
resulting from phosphate mining activities.

Mallard

Calculate daily dosage using
exposure models, measured
chemical concentrations in abiotic
and biotic media, and food web
interactions.

Compare calculated dose
to NOAEL and LOAEL
dosages for similar
species.

3 ° Consumers Protect upper trophic level aquatic feeding
Terrestrial terrestrial species from acute and chronic
Predator adverse effects from direct and/or

secondary exposure to metals resulting
	from phosphate mining activities.	

Mink

Calculated daily dosage using
exposure models, measured
chemical concentrations in abiotic
and biotic media, and food web
interactions.

Compare calculated dose
to NOAEL and LOAEL
dosages for similar prey
species.

Protect upper trophic level terrestrial
species from acute and chronic adverse
effects from direct and/or secondary
exposure to metals resulting from
phosphate mining activities.	

Coyote

Calculated daily dosage using
exposure models, measured
chemical concentrations in abiotic
and biotic media, and food web
interactions.

Compare calculated dose
to NOAEL and LOAEL
dosages for similar prey
species.

3 ° Consumers
Avian Predator

Protect upper trophic level aquatic feeding
avian species from acute and chronic
adverse effects from direct and/or
secondary exposure to metals resulting
from phosphate mining activities.

Great Blue Heron

Calculated daily dosage using
exposure models, measured
chemical concentrations in abiotic
and biotic media, and food web
interactions.

Compare calculated dose
to NOAEL and LOAEL
dosages for similar prey
species.

Protect upper trophic level avian species
from acute and chronic adverse effects
from direct and/or secondary exposure to
metals resulting from phosphate mining
activities.

Northern Harrier

Calculated daily dosage using Compare calculated dose
exposure models, measured to NOAEL and LOAEL
chemical concentrations in abiotic dosages for similar prey
and biotic media, and food web species,
interactions.

Notes:

COPEC = chemical of potential ecological concern
LOAEL = lowest observed adverse effects level
NOAEL = no observed adverse effects level

2 of 2

-------










Table A-5



















Exposure Parameters for Ecological Receptors













Exposure Value



Long-Tailed
Vole

Elk

American
Goldfinch

Deer Mouse

Raccoon

American Robin

Mallard

Mink

Coyote

Great Blue Heron

Northern
Harrier



Microtus

Cervus



Peromyscus

Procyon

Turdus

Anas









Exposure Parameter

longicaudus

elaphus

Spinus tristis

maniculatus

lotor

migratorius

platyrhynchos

Mustela vison

Canis latrans

Ardea herodias

Circus cyaneus

Body Weight (g)a

37 h<'

2.9E+05 k

16

19.5 h

5,800 h

82.0 h

1,178 h

1,075 h

13,600 p

2,336 h

449 '

Fraction of Prey Items in Diet (%)

Terrestrial

Plant

100

100 k

100

61.5 h

64 h

44.7 h

0

0

2 q

0

0

Invertebrates

0

0

0

38.5 h

19 h

55.3 h

0

0

2 q

12.5

2 '

Mammals/Birds

0

0

0

0

9 h

0

0

63 h

96 q

12.5

98 '

Aquatic

Plant

0

0

0

0

0

0

25.3 h

0

0

0

0

Invertebrates

0

0

0

0

7 h

0

74.7 h

6 h

0

0

0

Fish

0

0

0

0

1 h

0

0

31 h

0

75

0

Ingestion Rate of Prey (g dw/d)b

11.5

2,294

4.10

3.8

154

11

56

516

4,286

145

49

Soil/Sediment Ingestion Rate (g dw/d)c

0.276

45.9

0.426

0.076

14.5

1.10

1.86

48.51

120.01

1.0

0.34

Fraction of Upland Soil in the Diet (%)

2.40 u

2 j

10.4 jn

2 J."

0

10.4 jn

0

0

2.8 jn

0

0.7

Fraction of Riparian Soil in the Diet (%)

0

0

0

0

9.40 j

0

0

9.4 jn

0

0

0

Fraction of/Sediment in the Diet (%)

0

0

0

0

0

0

3.3 j

0

0

0.7

0

Water Ingestion Rate (L/d)d

0.00512

16.1

0.00362

0.00286

0.482

0.011

0.066

0.106

1.037

0.10

0.034

Home Range (acres)

0.0659 hJ

16,640 1

0.119

0.270 h

2,272 h

0.7 h

1,074 h

50 h

7,240

11 h

642 '

Area being Evaluated (acres)e

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

Site Utilization Factor (unitless)f

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

Exposure Duration (percent of year)9

1

1

m

1

1

1

1

1

1

1

1

Notes:























a Average body weight for males and females combined.









m From Cornell Lab of Ornithology web site (www.birds.cornell.edu).





b Calculated using Equations 25 (mink and coyote), 29 (elk), 33 (raccoon), 37 (passerines), 61 (American robin and
mallard), and 63 (great blue heron and northern harrier) from Nagy (2001). The food ingestion rate for the long-tailed vole
and deer mouse were based on values in Table 1 (Nagy, 2001) for meadow vole and deer mouse, respectively. The cattle
food ingestion rate is based on beef cattle fodder intake rates from Risk Assessment Information System (ORNL) (2013).

"The American woodcock was used as a surrogates for the American goldfinch and American Robin. The
white footed mouse was used as a surrogate for the deer mouse. The raccoon was used as a surrogate for
the mink. The red fox was used as a surrogate for the coyote.

0 Life history account from Zeiner, D.C. et al. (1988-1990). Maintained by California Wildlife Habitat
Relationship Program of the California Department of Fish and Wildlife. Accessed at

0 Calculated as percent soil ingestion rate multiplied by the food ingestion rate (g/d).





https://www.wildlife.ca.gov/Data/CWHR/Life-History-and-Range.





d Calculated using Equation 3-15 (all birds) and Equation 3-17 (all mammals) from EPA, 1993.





p Idaho digital atlas: http://imnh.isu.edu/digitalatlas/bio/mammal/mamfram.htm



e Exposure area based on the total area of

f Site utilization factors are calculated as the exposure area divided by the home range. Instances where the home range >

q MacCracken and Hansen. 1982. Seasonal Foods of Coyotes in Southeastern Idaho: A Multivariate Analysis.

exposure area are reported as 1.











rMean coyote homerange for southeastern Idaho from Woodruff and Keller (1982).



9 Exposure duration (percent of year exposed) is assumed to be 1 for most species based on species range maps.

s Sediment ingestion percent for bald eagle from Pascoe et al. (1996) as cited in the Area Wide Risk

h Wildlife Exposure Factors Handbook (EPA, 1993).









Management Plan for the Southeast Idaho Phosphate Mining Resource Area (DEQ, 2004a) were used to
calculate the sediment ingestion rate for the great blue heron and northern harrier.

' Meadow vole used as a surrogate species.























'Soil ingestion rates as percent of diet from Beyer (1994).









' Northern harrier average body weight reported in Slater and Rock (2005).



kSenseman, R. 2002. "Cervus elaphus." Animal Diversity Web. Accessed February 22, 2011.

















http://animaldiversity.ummz.umich.edu/site/accounts/information/Cervus_elaphus.html.

















'An Evaluation of the Effects of Selenium on Elk, Mule Deer, and Moose in SE Idaho (Kuck, 2003).















% = percent



dw = dry weight



L = liter













d = day



g = gram





SS = site-specific











1 of 1

-------
Table A-6

Toxicity Reference Values for Mammalian Receptors

TRV,

NOAEL

TRV,

LOAEL

Analyte

Toxicity
Value

(mg/kg- Test Study
dry) Species Endpoint

UF

0.059

Rat

NOAEL

0.770

Rat

NOAEL



Cattle,



2.40

Mouse,

NOAEL



Pig, Rat,



5.60

Pig

NOAEL

0.260

Mouse

NOAEL

1.70

Mouse

NOAEL

Type

Effects

Source

LOAEL Subchronic TRVN0AEL
to	to	(mg/kg-

NOAEL Chronic dry)

Toxicity
Value
(mg/kg-
dry)

UF

Test Study
Species Endpoint Type

Effects

Source

Subchronic TRVL0AEL
to	(mg/kg-

Chronic dry)

Metals

Antimony

Cadmium

Chromium

Copper

Molybdenum

Nickel

Selenium

Thallium

Vanadium

Zinc

Chronic

Chronic

Growth
Growth b

Growth
Reproduction

EcoSSLs
(Antimony)
EcoSSLs
(Cadmium)

EcoSSLs
(Chromium)

EcoSSLs
(Copper)
ORNL 1996

NOAEL Subchronic Reproduction EcoSSLs (Nickel)

0.143
0.00740
4.16

75.4

Pig
Rat
Mouse

NOAEL
NOAEL
NOAEL

Various NOAEL

Subchronic
Subchronic
Chronic

Chronic

Growth

Growth

Growth

Growth and
Reproduction :

EcoSSLs
(Selenium)
ORNL 1996
EcoSSLs
(Vanadium)

EcoSSLs (Zinc)

0.0590
0.770

2.40

5.60
0.260
1.70

0.143
0.00370
4.16

75.4

Notes:

a Geometric mean of NOAEL and LOAEL values for growth and reproduction were calculated as the TRVNOael ar|d TRVLOael values, respectively.
u Geometric mean of NOAEL values for growth were calculated as the TRVNOael-

Sources

EcoSSLs (Antimony) = Ecological Soil Screening Levels for Antimony (EPA, 2005a).

EcoSSLs (Cadmium) = Ecological Soil Screening Levels for Cadmium (EPA, 2005b).

EcoSSLs (Chromium) = Ecological Soil Screening Levels for Chromium (EPA, 2008a).

EcoSSLs (Copper) = Ecological Soil Screening Levels for Copper (EPA, 2007a).

EcoSSLs (Nickel) = Ecological Soil Screening Levels for Nickel (EPA, 2007b).

EcoSSLs (Selenium) = Ecological Soil Screening Levels for Selenium (EPA, 2007c).

EcoSSLs (Vanadium) = Ecological Soil Screening Levels for Vanadium (EPA, 2005c).

EcoSSLs (Zinc) = Ecological Soil Screening Levels for Zinc (EPA, 2007d).

ORNL 1996 = Toxicological Benchmarks for Wildlife: 1996 Revision (ORNL, 1996a).

0.590
0.909

2.82

EcoSSLs = Ecological Soil Screening Levels
LOAEL = lowest observed adverse effect level
UF = uncertainty factor

mg/kg-dry = milligram(s) per kilogram dry weight
NOAEL = no observed adverse effect level
TRV = toxicity reference value

Rat

LOAEL Chronic

Sheep LOAEL Subchronic
Rat LOAEL Subchronic

Subchronic

Chronic
Subchronic

Subchronic
Subchronic
Subchronic

6.79

Mink

LOAEL

2.60

Mouse

LOAEL

2.71

Mouse

LOAEL

0.145

Mouse

LOAEL

0.074

Rat

LOAEL

5.11

Rat

LOAEL

75.9

Cattle

LOAEL

Reproduction
Growth

Survival

Reproduction
Reproduction
Reproduction

Reproduction
Growth
Growth

EcoSSLs
(Antimony)
EcoSSLs
(Cadmium)

EcoSSLs
(Chromium)

EcoSSLs
(Copper)
ORNL 1996

EcoSSLs (Nickel)

EcoSSLs
(Selenium)
ORNL 1996
EcoSSLs
(Vanadium)

Subchronic Reproduction EcoSSLs (Zinc)

0.590
0.909

2.82

6.79
2.60
2.71

0.145
0.0370
5.11

75.9

1 of 1

-------
Analyte

Table A-7

Toxicity Reference Values for Avian Receptors

TRVn

TRV,

Toxicity
Value

(mg/kg- Test Study
dry) Species Endpoint

Type

Effects

Source

UF

Acute

LD50 to LOAEL
chronic to
NOAEL NOAEL

UF

Subchronic

to TRVNOael3
Chronic (mg/kg-dry)

Toxicity
Value

(mg/kg- Test Study
dry) Species Endpoint

Type

Effects

Source

Acute
LD50 to
chronic
LOAEL

Subchronic
to

Chronic

TRVLOael
(mg/kg-
dry)

Metals

Antimony

Cadmium

1.47

Chicken,
Mallard duck

NOAEL

Chronic

Growth and
Reproduction a

EcoSSLs
(Cadmium)

1

1

1

1.47

2.37

Chicken

LOAEL

Subchronic

Reproduction

EcoSSLs
(Cadmium)

1

1

2.37

Chromium

2.66

Chicken,
Duck,
Turkey

NOAEL

Chronic

Growth and
Reproduction a

EcoSSLs
(Chromium)

1

1

1

2.66

2.78

Duck

LOAEL

Subchronic

Reproduction

EcoSSLs
(Chromium)

1

1

2.78

Copper

4.05

Chicken

NOAEL

Chronic

Reproduction

EcoSSLs
(Copper)

1

1

1

4.05

4.68

T urkey

LOAEL

Subchronic

Growth

EcoSSLs
(Copper)

1

1

4.68

Molybdenum

3.50

Chicken

NOAEL

Chronic

Reproduction

ORNL 1996

1

1

1

3.50

35.3

Chicken

LOAEL

Chronic

Reproduction

ORNL 1996

1

1

35.3

Nickel

6.71

Chicken,
Duck

NOAEL

Chronic

Growth and
Reproduction a

EcoSSLs
(Nickel)

1

1

1

6.71

11.5

Chicken

LOAEL

Subchronic

Growth

EcoSSLs
(Nickel)

1

1

11.5

Selenium

0.290

Chicken

NOAEL

Subchronic

Survival

EcoSSLs
(Selenium)

1

1

1

0.290

0.368

Chicken

LOAEL

Subchronic

Reproduction

EcoSSLs
(Selenium)

1

1

0.368

Thallium

34.6

Starling

LD50

Acute

Mortality

Schafer 1983

100

1

1

0.346

34.6

Starling

LD50

Acute

Mortality

Schafer 1983

10

1

3.46

Vanadium

0.344

Chicken

Chicken,
Mallard

NOAEL

Subchronic

Growth

EcoSSLs
(Vanadium)

1

1

1

0.344

0.413

Chicken

LOAEL

Subchronic

Reproduction

EcoSSLs
(Vanadium)

1

1

0.413

Zinc

66.1

duck,
Japanese
Quail,
Turkey

NOAEL

Chronic

Growth and
Reproduction a

EcoSSLs
(Zinc)

1

1

1

66.1

66.5

Chicken

LOAEL

Subchronic

Reproduction

EcoSSLs
(Zinc)

1

1

66.5

Notes:

1 Geometric mean of NOAEL and LOAEL values for growth and reproduction were calculated as the TRVNOael
1 Geometric mean of NOAEL values for growth were calculated as the TRVNOael-

Sources

EcoSSLs (Cadmium) = Ecological Soil Screening Levels for Cadmium (EPA, 2005b).

EcoSSLs (Chromium) = Ecological Soil Screening Levels for Chromium (EPA, 2008a).

EcoSSLs (Copper) = Ecological Soil Screening Levels for Copper (EPA, 2007a).

EcoSSLs (Nickel) = Ecological Soil Screening Levels for Nickel (EPA, 2007b).

EcoSSLs (Selenium) = Ecological Soil Screening Levels for Selenium (EPA, 2007c).

EcoSSLs (Vanadium) = Ecological Soil Screening Levels for Vanadium (EPA, 2005c).

EcoSSLs (Zinc) = Ecological Soil Screening Levels for Zinc (EPA, 2007d).

ORNL 1996 = Toxicological Benchmarks for Wildlife: 1996 Revision (ORNL, 1996a).

EcoSSLs = Ecological Soil Screening Levels
LC50 = lethal concentration to 50% of test population
LOAEL = lowest observed adverse effect level

and TRVLoael values, respectively.

mg/kg-dry = milligram(s) per kilogram dry weight
NOAEL = no observed adverse effect level
TRV = toxicity reference value
UF = uncertainty factor

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Table A-8

Ecological Hazard Calculations for Amphibians

Water Quality Criteria



Surface Water

National









Exposure Point

Standards

Tier II

Final Water





Concentration a

Aquatic Life b

SCVc

Quality



COPEC

(mg/L)

(mg/L)

(mg/L)

Criteria d

HQ

Barium, dissolved

0.0416



0.0040

0.0040

10

Boron, dissolved

0.0299

-

0.0016

0.0016

19

Cadmium, dissolved

0.000406

0.00025 e

--

0.00025

1.6

Manganese, dissolved

0.307

-

0.12

0.12

2.6

Selenium, total

0.506

0.0050 f

--

0.0050

101

Uranium, dissolved

0.0100

--

0.0026

0.0026

3.8

Notes:

a The surface water exposure point concentrations are equal to the lower of the maximum detected
b National Recommended Water Quality Criteria (EPA, 2013a); Freshwater CCC listed for all
c Tier II Secondary Chronic Value. Source: ORNL, 1996a.

d The final water quality criteria were obtained from the following hierarchy: (1) National
Recommended Water Quality Criteria (EPA, 2013a) and (2) Tier II Secondary Chronic Value (ORNL,
1996a).

8 The freshwater criterion for this metal is expressed as a function of hardness in the water column.
' The CMC = 1/[(f1/CMC1)+(f2/CMC2)] where f1 and f2 are the fractions of total selenium that are
treated as selenite and selenate, respectively, and CMC1 and CMC2 are 0.1859 mg/L and 0.01282
mg/L, respectively.

= not available
CCC = Criterion Continuous Concentration
CMC = Criteria Maximum Concentration
COPEC = chemical of potential ecological concern
HQ = hazard quotient
mg/L = milligram(s) per liter

SCV = secondary chronic value	

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Table A-9



















Contaminants of Ecological Concern











Long-
Tailed Vole

Elk

American
Goldfinch

Deer
Mouse

Raccoon

American
Robin

Mallard

Mink

Coyote

Great
Blue
Heron

Northern
Harrier

NOAEL-Based Ecological Hazard Estimates

Site - Related:

Hazard

<0.1 - 91



<0.1 - 44

<0.1 -

<0.1 -

<0.1 -

<0.1 -

<0.1 -

<0.1 -

<0.1 -

<0.1 - 1.3

Range



47

1.2

16

8.5

96

1.4

9.0

COECs a

Cr Mo Ni
Sb Se Tl

-

Cr Mo Se
V

Cd Cr
Mo Ni Sb
Se Tl

Se

Cd Cr Cu
Ni Se V
Zn

Se V

Cd Cr Cu
Mo Ni Sb
Se Tl V
Zn

Mo

Cd Se V

Se

Background:

Hazard

< 0.1 - 2.6



<0.1 - 2.0

<0.1 -

<0.1 -

<0.1 -

<0.1 -

<0.1 -

<0.1 -

<0.1 -

<0.1 -

Range



4.3

0.17

1.3

0.12

25

0.24

0.39

0.21

COECs a

Mn Mo Se
Tl

-

V

Cd Mo Ni
Tl

--

Cd V

-

Cr Cu Ni
Sb Se Tl

--

--

--

LOAEL-Based Ecological Hazard Estimates

Site - Related:

Hazard

<0.1 - 90



< 0.1 - 34

<0.1 -

<0.1 -

<0.1 -

<0.1 -

<0.1 -

<0.1 -

<0.1 -

<0.1 - 1.1

Range



46

1.2

13

6.7

94

0.76

7.1









Cd Cr
Mo Ni Se
Tl







Cd Cr Cu







COECs a

Cr Mo Ni
Se Tl

-

Cr Se V

Se

Cd Cr Ni
Se V Zn

Se

Mo Ni Sb
Se Tl V
Zn

--

Se V

Se

Background:

Hazard

<0.1 - 1.5



<0.1 - 1.6

<0.1 -

<0.1 -

<0.1 -

<0.1 -

<0.1 -

<0.1 -

<0.1 -

<0.1 -

Range



2.2

0.031

0.96

0.096

2.9

0.080

0.34

0.18

COCs a

Mn Se

-

-

Cd

--

--

--

Cr Cu Ni
Sb Se Tl

--

--

--

Notes:























a Contaminants of ecological concern (COECs) are analytes for which an analyte-specific greater than EPA's and



DEQ's acceptable criterion of 1 was calculated.















< = less than









Cd = cadmium



Sb = antimony



- = not applicable









Cr = chromium



Se = selenium



DEQ = Idaho Department of Environmental Quality



Cu = copper



Tl = thallium



LOAEL =

owest observed adverse effects level



Mo = molybdenum



V = vanadium



NOAEL =

no observed adverse effects level



Ni = nickel





Zn = zinc





EPA = United States Environmental Protection Agency













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Appendix B

Summary of Federal and State ARARs
for the Selected Remedy at the

Ballard Mine

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Appendix B. Summary of Federal and State ARARs and TBCs for the Selected Remedy at the Ballard Mine, Caribou County, Idaho

Medium

Type of
ARARC

Requirement3

Status

Synopsis of Requirement

Action to be Taken to Attain Requirement

Surface Water

Chemical-
specific

National Recommended
Water Quality Criteriad
(33 U.S.C. § 1314(a)
and 40 CFR Part 131)

Relevant and
Appropriate

Under Section 304(a) of the Clean Water Act,
EPA establishes National Recommended Water
Quality Criteria that are protective of aquatic life
and human health. Under CERCLA, water
quality criteria for the protection of aquatic life
are considered relevant and appropriate for
actions that involve releases to surface waters or
groundwater discharges to surface waters.
The National Recommended Water Quality
Criterion for selenium, published in 2016,
provides the basis for the surface water cleanup
level for selenium.

The Selected Remedy includes actions to be taken to
achieve surface water cleanup levels. The Selected
Remedy includes a combination of components that will
work together to meet cleanup levels, including source
controls (cover system), water treatment (engineered
wetland treatment cells), implementation of BMPs, and
other actions.

Surface Water

Action-specific

CWA (Sect. 402
NPDES)(33 U.S.C. §
1342) and implementing
regulations (40 CFR
Parts 122-125)

Relevant and
Appropriate

The NPDES (also known as Section 402 of the
CWA) program establishes a comprehensive
framework for addressing waste water and storm
water discharges under the program. Requires that
point-source discharges not cause the exceedance
of surface water quality standards outside the
mixing zone. Specifies requirements under
40 CFR § 122.26 for point-source discharge of
storm water from construction sites to surface
water and provides for BMPs such as erosion
control for removal and management of sediment
to prevent run-on and run-off

The Selected Remedy will comply with these
regulations through implementation of actions to control
discharges of pollutants from point sources to waters of
the United States.

Contaminated water discharging at springs and seeps
will be collected and treated using engineered wetland
treatment cells. Other elements of the remedy will also
control releases, including construction of the cover
system and implementation of stormwater BMPs.
Discharges of treated effluent and runoff are expected to
meet surface water cleanup levels where discharges
enter waters of the United States.

PAGE 1 OF 13

-------
Medium

Type of
ARARC

Requirement3

Status

Synopsis of Requirement

Action to be Taken to Attain Requirement

Surface Water

Chemical-
specific

Idaho Water Quality
Standards
(IDAPA 58.01.02)

Applicable

The State of Idaho has established surface water
quality standards that designate uses of the waters
of the state and establish standards of water
quality protective of those uses. These rules also
restrict the discharge of wastewaters that may
adversely affect water quality.

The rules include many components: water
quality criteria for aquatic life use designations
(.250), designations of surface waters found
within Blackfoot Basin (.150), general surface
water quality criteria (.200), numeric criteria for
toxic substances (.210), antidegredation policy
(.051), and mixing zone policy (.060).
The cleanup level for cadmium in surface water
is based on these requirements.

Other components of the rules that are ARARs
for other components of the remedy are listed
below.

The Selected Remedy will comply with these
regulations through implementation of actions that will
control releases of contaminants to surface water above
cleanup levels.

Specific actions to control releases include: construction
of the cover system, BMPs, treatment of springs and
seeps using engineered wetland treatment cells, and
other measures.

The Selected Remedy will achieve the surface water
cleanup levels at the point where discharges of treated
effluent enter waters of the United States and in
downstream waters.

Surface Water

Chemical-
specific

Letter to Barry Burnell,
DEQ, from Daniel
Opalski, EPA Region
10, dated September 15,
2016, Re: EPA
Disapproval of Idaho's
Arsenic Human Health
Water Quality Criteria,
and follow-up letter to
Barry Burnell, DEQ,
from Daniel Opalski,
EPA Region 10, dated
September 27, 2016, Re:
Arsenic Human Health
Water Quality Standards
for Surface Waters in
Idaho.

TBC

In 2016, EPA disapproved the State of Idaho's
existing water quality criterion for arsenic. This
letter provides guidance on protective levels of
arsenic in surface water that EPA recommends
using until the State of Idaho promulgates and
EPA approves a revised criterion.

The cleanup level for arsenic in surface water is
based on this guidance.

The Selected Remedy includes actions to be taken to
achieve surface water cleanup levels. The Selected
Remedy includes a combination of components that will
work together to meet cleanup levels, including source
controls (cover system), water treatment (engineering
wetland treatment cells), implementation of BMPs, and
other actions.

The Selected Remedy will achieve the surface water
cleanup levels at the point where discharges of treated
effluent enter waters of the U.S. and in downstream
waters.

PAGE 2 OF 13

-------
Medium

Type of
ARARC

Requirement3

Status

Synopsis of Requirement

Action to be Taken to Attain Requirement

Surface Water

Action-specific

Idaho Water Quality
Standards, Rules
Governing Point Source
Discharges

(IDAPA 58.01.02.400)
and

Idaho Water Quality
Standards, Point Source
Wastewater Treatment
Requirements
(IDAPA 58.01.02.401)

Applicable

This portion of the Idaho Water Quality
Standards provides limits and restrictions on
point source discharges, including limits on
turbidity and temperature for wastewaters
discharged into surface waters of the state.

The Selected Remedy will comply with these
regulations by implementing remedial actions that
control discharges of contaminants from point sources to
the intermittent streams near the Site.

Point source discharges may be associated with remedial
features such as sediment control ponds and engineered
wetland treatment cells.

Points of compliance will be determined during remedial
design and monitored for compliance with surface water
quality standards once the remedial features are
constructed and operating.

Surface Water

Action-specific

Idaho Water Quality
Standards, Rules
Governing Nonpoint
Source Activities
(IDAPA 58.01.02.350)

Applicable

This portion of the Idaho Water Quality Standards
provides the policy and procedures for regulating
nonpoint source activities. It also designates
approved BMPs by reference, including for
example the "Rules Governing Exploration,
Surface Mining, and Closure of Cyanidation
Facilities," (IDAPA 20.03.02) and other rules.

The Selected Remedy will comply with these
regulations by implementing remedial actions that
control nonpoint source activities and associated
nonpoint source discharges of contaminants to the
intermittent streams near the Site.

Nonpoint source discharges would typically occur
during remedy implementation, including construction
of access roads and the cover system (before the
vegetation is established).

The selected remedy will comply with these
requirements by implementing BMPs and actions to
stabilize construction areas and control runoff. Specific
BMPs will be specified during remedial design and
refined as necessary during remedy implementation.
Water quality monitoring and surveillance will be
implemented

PAGE 3 OF 13

-------
Medium

Type of
ARARC

Requirement3

Status

Synopsis of Requirement

Action to be Taken to Attain Requirement

Surface Water
and
Aquatic
Resources

Location-
specific
and

Action-specific

Clean Water Act
Section 404
(33 U.S.C. § 1344) and
implementing
regulations (40 CFR
Part 230)

Relevant and
Appropriate

Section 404 of the CWA establishes a program to
regulate the discharge of dredge to fill materials in
the waters of the United States, including
wetlands. The substantive provisions of this
requirement are relevant and appropriate to
remedial actions involving dredging, filling,
diversion, and/or any construction activity in
stream or wetlands at the Site.

These provisions are relevant to any work effecting
wetlands, intermittent streams and other waters of the
U.S. at the site. Impacts to wetlands were considered
during the remedy selection process, particularly with
respect to selection of remedy components for sediment
and riparian soil.

In addition, during remedial design and remedial action,
potential impacts to wetlands will be further considered
for discrete elements of the design. As various
components of the remedy are sited, such as access
roads, culverts, engineered wetland treatment cells, and
other facilities during design, the project team will
evaluate opportunities to avoid and minimize impacts to
wetlands. If impacts cannot be avoided, wetland impacts
will be mitigated.

Surface Water
and
Aquatic
Resources

Location-
specific
and

Action-specific

Considering Wetlands at
CERCLA Sites (EPA
Publication 9280.0-03,
May 1994)

TBC

EPA guidance regarding the potential impacts of
response actions on wetlands at Superfund sites.

Impacts to wetlands were considered during the remedy
selection process, particularly with respect to selection
of remedy components for sediment and riparian soil.
In addition, this guidance may be useful during remedial
design and remedial action. As various components of
the remedy are sited, such as access roads, engineered
wetland treatment cells, and other facilities during
design, the project team will evaluate opportunities to
avoid and minimize impacts to wetlands. If impacts
cannot be avoided, wetland impacts will be mitigated.

Groundwater

Chemical-
specific

National Primary
Drinking Water
Regulations
(40 CFR Part 141)

Relevant and
Appropriate

Groundwater at the Site is a potential source of
drinking water. Under the Safe Drinking Water
Act, EPA establishes health-based standards
(MCLs and MCLGs) for public water systems.
MCLs provide the basis for groundwater cleanup
levels for selenium, arsenic, and cadmium.
Secondary MCLs, which are not health-based but
rather are based on aesthetic criteria, are not
ARARs at the Site.

The Selected Remedy includes actions to be taken to
achieve groundwater cleanup levels. Groundwater
cleanup levels will be met in all areas of the Site where
groundwater is a potential source of drinking water. The
Selected Remedy includes a combination of components
to meet cleanup levels, including construction of a cover
system over source materials, treatment of groundwater
using permeable reactive barriers, and use of monitoring
natural attenuation, as needed, as a polishing step.

In the short-term, until source controls and treatment are
operational and effective, institutional controls will be
used to restrict use of groundwater.

PAGE 4 OF 13

-------
Medium

Type of
ARARC

Requirement3

Status

Synopsis of Requirement

Action to be Taken to Attain Requirement

Groundwater

Chemical-
specific

Idaho Ground Water
Quality Rule
(IDAPA 58.01.11.200)

Applicable

The State of Idaho has established the Ground
Water Quality Rule which identifies minimum
requirements for protection of ground water
quality through standards and an aquifer
categorization process.

The rules include standards for the protection of
human health. The cleanup levels for selenium,
arsenic and cadmium in groundwater are based
on these requirements.

The Selected Remedy includes actions to be taken to
achieve groundwater cleanup levels. These actions
include construction of an ET cover system over source
materials, treatment of groundwater using permeable
reactive barriers, and use of monitoring natural
attenuation, as needed, as a polishing step.

It is expected to take 10+ years after the ET cover
system is constructed to achieve groundwater cleanup
levels. In the shorter-term, until source controls and
treatment are operational and effective, institutional
controls would be used to restrict use of groundwater.

Surface Water

And
Ground Water

Chemical-
specific

Idaho Rules for Public
Drinking Water Systems
(IDAPA 58.01.08)

Applicable
and/or Relevant
and Appropriate

The State of Idaho has established rules to
control and regulate the design, construction,
operation, and quality control of public drinking
water systems.

These rules include health-based standards, or
MCLs, to protect consumers using public
drinking water systems. The MCLs are relevant
and appropriate for surface water and
groundwater at the Site and provide a basis for
the groundwater cleanup levels for selenium,
arsenic, and cadmium.

The Selected Remedy includes actions to be taken to
achieve groundwater cleanup levels. These actions
include construction of an ET cover system over source
materials, treatment of groundwater using permeable
reactive barriers, and use of monitoring natural
attenuation, as needed, as a polishing step.

It is expected to take 10+ years after the ET cover
system is constructed to achieve groundwater cleanup
levels. There are currently no public water systems at
the Site that use impacted groundwater. Institutional
controls will be used to restrict use of water as a potable
water supply source until cleanup levels are achieved.

Ground Water

Action-specific

Idaho Well Construction
Standards Rules
(IDAPA 37.03.09)

Applicable

The State of Idaho has established rules
providing minimum standards for the
construction of all new wells and the
modification and decommissioning
(abandonment) of existing wells.

The Selected Remedy will comply with the substantive
requirements of this regulation. The particular portions of
the selected remedy to which this ARAR is applicable
will be identified through the remedial design process,
including any identified future site investigation activity.

Cultural
Resources

Location-
specific

National Historic
Preservation Act
(NHPA) [16 U.S.C.
470], and implementing
regulations [36 CFR
Part 800, 40 CFR
6.301(b)]

Applicable

Statute and implementing regulations require
federal agencies to take into account the effect of
a response action upon any district, site, building,
structure, or object included in or eligible for the
National Register of Historic Places (generally,
50 or more years old). NHPA requires federally
funded projects to assess if cultural resources on
or eligible for the National Register are present,
determine if there will be an adverse effect and, if
so, how the effect may be minimized/mitigated,
in consultation with the appropriate State Historic
Preservation Office.

Should NHPA issues arise during remedial design and
action, they will be handled in compliance with this
regulation. It is possible the mine itself or remnants of
the first mining activities are of historic interest;
however, no property/resources at the Site are currently
included in the National Register and no building in the
project area was constructed prior to 1950, a date
typically used as an initial screen for determining
eligibility for the Register.

PAGE 5 OF 13

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Medium

Type of
ARARC

Requirement3

Status

Synopsis of Requirement

Action to be Taken to Attain Requirement

Cultural
Resources

Location-
specific

Archeological and
Historic Preservation
Act (52 USC 312501 et
seq.) and implementing
regulations

Applicable

For areas designated as historic sites, the RA
should avoid undesirable impacts on landmarks
and encourage the long-term preservation of
nationally significant properties that illustrate or
commemorate the history/prehistory of the US. In
conducting an environmental review of a
proposed action, the responsible official shall
consider the existence and location of natural
landmarks using information provided by the
National Park Service pursuant to 36 CFR §
62.6(d) to avoid undesirable impacts on such
landmarks.

The particular portions of the selected remedy to which
this ARAR is applicable would be identified and
complied with during the remedial design process.
Previous archeological surveys of the property have not
demonstrated any significant historic or cultural
landmarks.

A cultural resource survey will be completed for any
portions of the Site not already surveyed.

Cultural
Resources

Location-
specific

Executive Order 11593
Protection and
Enhancement of the
Cultural Environment
[36 CFR8921]

Applicable

Requires federal agencies to consider the
existence and location of potential and existing
cultural landmarks to avoid undesirable impacts
on them.

Applicability will be determined in conjunction with
NHPA and other cultural resource statutes and
regulations.

Cultural
Resources

Location-
specific

Archaeological and
Historic Preservation
Act (AHPA) [16 U.S.C.
469], and implementing
regulations [40 CFR
6.301(c)]

Archaeological
Resources Protection
Act of 1979, as amended
1988 [16 U.S.C. 470aa-
470mm]

Applicable

The statutes and implementing regulations
require federally approved projects to evaluate
and preserve significant scientific, prehistoric,
historic, and archaeological data which may be
irreparably lost or destroyed through alteration of
terrain as a result of a federal construction project
or a federally licensed activity or program. The
data must be preserved by the agency
undertaking the project, or the Department of the
Interior if requested by the agency.

The particular portions of the Selected Remedy to which
this ARAR is applicable would be identified and
complied with during the remedial design process.

Cultural
Resources

Location-
specific

Native American Graves
Protection and
Repatriation Act
(NAGPRA) [25 U.S.C.
§§ 3001 et seq.]

Relevant and
Appropriate

Requires federal agencies and institutions that
receive federal funding to return Native
American cultural items to lineal descendants and
culturally affiliated Indian tribes. NAGPRA also
establishes procedures for the inadvertent
discovery or planned excavation of Native
American cultural items on federal or tribal
lands.

The particular portions of the Selected Remedy to which
this ARAR is applicable would be identified and
complied with during the remedial design process.

PAGE 6 OF 13

-------
Medium

Type of
ARARC

Requirement3

Status

Synopsis of Requirement

Action to be Taken to Attain Requirement

Cultural
Resources

Location-
specific

Idaho Preservation of
Historical Sites
(Idaho Code §§67-4111
to-4131 and 67-4601 to
-4619)

Applicable

Requirements for protection of public lands and
preservation of historical or archaeological sites
in consideration of waste disposal.

If historical or archeological sites are detected during
remedial construction, the particular portions of the
selected remedy to which this ARAR is applicable
would be identified and complied with during the
remedial design process. However, site activities are not
anticipated to trigger compliance during the selected
remedial action.

Waste

Chemical-
specific
and

Action-specific

Uranium Mill Tailings
Radiation Control Act
(UMTRCA)— (42
U.S.C. §§ 7901 etseq.)
and implementing
regulations:

Health and
Environmental
Protection Standards for
Uranium and Thorium
Mill Tailings, Subpart A
- Standards for the
Control of Residual
Radioactive Materials
from Inactive Uranium
Processing Sites (40
CFR Part 192.02 (a))

Relevant and
Appropriate

The Subpart A standards include design
requirements for remedial actions at inactive
uranium processing sites. The portion of the
standards that is relevant and appropriate is the
design standard requiring that control of residual
radioactive materials and their listed constituents
be designed to be effective for at least 200 years.

The selected remedy will comply with this requirement
during remedial design by including design criteria for
source controls, in particular for the ET cover system.
The ET cover system will be designed to contain and
prevent direct exposure to waste rock, which contain
naturally occurring uranium and daughter products.

Waste

Action-specific

Resource Conservation
and Recovery Act -
Subtitle D [42 U.S.C.
6901 et seq.]
and implementing
regulations,

Solid Waste, Criteria for
Classification of Solid
Waste Disposal
Facilities and Practices
[40 CFR 257]

Relevant and
Appropriate

These regulations establish a framework for
management of nonhazardous solid waste. The
regulations include criteria for determining which
solid waste disposal practices pose threats to
human health and the environment, and control
impacts to floodplains, endangered species,
surface water, and groundwater.

Relevant criteria may be useful for siting and
design of a disposal facility.

Substantive provisions of the solid waste requirements
will be identified and complied with during the remedial
design process.

PAGE 7 OF 13

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Medium

Type of
ARARC

Requirement3

Status

Synopsis of Requirement

Action to be Taken to Attain Requirement

Waste

Action-specific

RCRA: Subtitle D -
Disposal of
Nonhazardous Solid
Waste [42 U.S.C. 6901
et seq., 40 CFR Part
258]

Relevant and
Appropriate

Provides criteria for cover material, run-on/runoff
control systems, access control, restrictions on
disposal of liquid wastes.

Remedial cover design for the selected remedy will
incorporate substantive features to control run on/off,
site access, and disposal of liquid wastes in accordance
with this regulation. Attainment will require careful
implementation of these features during remedial
construction.

Waste

Action-specific

Idaho Best Management
Practices and
Reclamation for Surface
Mining Operations
(IDAPA 20.03.02.140)

Applicable
and/or Relevant
and Appropriate

Provides requirements for design, construction
and maintenance of BMPs and standards for
reclamation of surface mining operations,
including standards pertaining to nonpoint source
controls, sediment controls, clearing and
grubbing, overburden/topsoil management, roads,
backfilling and grading, waste disposal, settling
ponds, and revegetation.

The Selected Remedy will comply with these
requirements during design and implementation of the
remedy. During remedial design, appropriate design
criteria will be developed to comply with the substantive
portions of the regulations. During implementation of
the remedial action, tasks will be implemented to
comply with BMP requirements and reclamation
standards for the various components of the remedy.

Waste

Action-specific

Idaho Solid Waste
Management Rules
(IDAPA 58.01.06)

Relevant and
Appropriate

Provides substantive requirements for operation
and closure of solid waste management facilities.

Only material uniquely associated with phosphate
mining is being addressed in remediation, so these
requirements are not applicable because the Site is not a
solid waste management facility. See IDAPA
58.01.06.001.03(b)(iv). Some requirements may be
relevant and appropriate with regard to regulated solid
waste generated during the remedial action.

Hazardous
Waste

Action-specific

Resource Conservation
and Recovery Act
(RCRA): Subtitle C -
Exemption for
Extraction,
Beneficiation, and
Processing Mining
Waste [40 CFR
261.4(b)(7)]

Applicable

These provisions exempt mining wastes from the
extraction, beneficiation, and some processing of
ores and minerals from the RCRA Subtitle C
requirements, in accordance with the Bevill
amendment to RCRA.

No action needed. The waste rock at the Ballard Site is
exempt from the Subtitle C requirements.
If non-exempt wastes are encountered during
remediation, then management of such wastes would
comply with other ARARs.

Hazardous
Waste

Action-specific

RCRA- Requirements
for Hazardous Waste
Transport

42 U.S.C §§ 6901 et
seq.

40 CFR Parts 261-262

Relevant and
Appropriate

Requirements for handling and transporting
hazardous waste.

The Selected Remedy will comply with the requirements
for transport of hazardous waste during implementation
of the selected remedy. Although no hazardous wastes
have been identified or anticipated, if hazardous wastes
are encountered (e.g. removal and disposal of spent
media from the PRBs) they would be handled and
transported appropriately.

PAGE 8 OF 13

-------
Medium

Type of
ARARC

Requirement3

Status

Synopsis of Requirement

Action to be Taken to Attain Requirement

Hazardous
Waste

Action-
specific

Resource Conservation
and Recovery Act
(RCRA):

(40 CFR§ 261.20)

Applicable

Generators of solid waste must determine
whether the waste is hazardous. A solid waste is
hazardous if it exhibits the toxicity characteristic
(based on extraction procedure Method 1311).

The selected remedy addresses the source material as
mining wastes that fall under the Bevill Amendment.
For these mining wastes, no action is necessary.

If other wastes are identified or generated during remedy
implementation (such as spent reactive media from
wetland treatment cells or PRBs), processes for
characterization will be developed. Results of
characterization will guide decisions on appropriate
disposal methods.

Hazardous
Waste

Action-specific

Hazardous Waste
Operations and
Emergency Response
[29 CFR 1910.120,40
CFR311]

Applicable

Worker protection during hazardous waste
cleanup and CERCLA removal actions

The selected remedy will incorporate work protection
criteria to be in compliance with this regulation.
Provisions will be identified during pre-design and
construction planning activity.

Hazardous
Waste

Chemical-
specific

Idaho Rules and
Standards for Hazardous
Waste

(IDAPA 58.01.05)

Relevant and
Appropriate

Rules and standards for hazardous waste.
Identifies characteristic and listed hazardous
wastes and provides rules for hazardous waste
permits

If hazardous waste is identified or generated during
implementation of the selected remedy, (for example,
removal and replacement of PRB media if such waste
material meets the definition of hazardous waste)
remedial design will identify the appropriate process for
handling it in compliance with this regulation.

Hazardous
Waste

Action-specific

Idaho Hazardous Waste
and Hazardous Waste
Management Act of
1983

(IDAPA 58.01.05
1993 Session Law, Ch.
291, Sections 1-8)

Applicable

Adopts federal RCRA regulations concerning the
identification of hazardous waste and standards
applicable to generators and transporters of
hazardous waste as well as standards for owners
and operators of hazardous waste treatment,
storage and disposal facilities.

The selected remedy will comply with hazardous waste
regulations. The particular portions of the selected
remedy to which this ARAR is applicable will be
identified and complied with through the remedial
design process and implemented during construction
activities at the Site.

Hazardous
Waste

Action-specific

Idaho Storage of
Hazardous and
Deleterious Materials
(IDAPA 58.01.02.800)

Applicable

Prohibits the storage, disposal or accumulation of
hazardous and deleterious materials "adjacent to
or in the immediate vicinity of state waters"
without adequate measures and controls to insure
the materials will not enter state waters.

Applicable if the remedial action results in the storage of
hazardous and deleterious materials near state waters.
Attainment of this regulation will be addressed during
remedial design which will avoid the storage or disposal
of hazardous and deleterious materials "adjacent to or in
the immediate vicinity of state waters". An inventory of
"state waters" has been completed to help guide the
remedial design.

PAGE 9 OF 13

-------
Medium

Type of
ARARC

Requirement3

Status

Synopsis of Requirement

Action to be Taken to Attain Requirement

Habitat

Location-
specific

Endangered Species Act
(ESA) [16 U.S.C. 1531]
Responsible official
requirements [40 CFR
6.302(h)]

Endangered and
threatened wildlife and
plants [50 CFR 17]
Interagency cooperation
-ESA of 1973, as
amended [50 CFR 402]

Applicable

Statute and implementing regulations require that
federal activities not jeopardize the continued
existence of any threatened or endangered
species. Section 7 of the ESA requires
consultation with the USFWS to identify the
possible presence of protected species and
mitigate potential impacts on such species.

None - to date, no threatened or endangered species
have been identified within the Site.

Habitat

Location-
specific

Migratory Bird Treaty
Act [16 U.S.C. 703, et
seq.]

List of Migratory Birds
[50 CFR 10.13]

Relevant and
Appropriate

The Act makes it unlawful to "hunt, take,
capture, kill," or take other various actions
adversely affecting a broad range of migratory
birds, without the prior approval of the
Department of the Interior.

The Selected Remedy, through careful remedial design,
will be implemented in a manner to avoid taking or
killing of protected migratory bird species, including
individual birds, their nests, or eggs.

Habitat

Location-
specific
and

Action-specific

Fish and Wildlife
Coordination Act [16
U.S.C. §661 etseq.]

Relevant and
Appropriate

Requires that federal agencies involved in actions
that will result in control or modification of any
natural stream or water body must protect fish
and wildlife resources that may be affected by the
actions.

The substantive requirements of the Fish and Wildlife
Coordination Act that are applicable to the selected
remedy would be identified and complied with through
the remedial design process. Consultation with the
USFWS would be conducted during the design phase.
Impacts to water or the stream channel would be
monitored during implementation.

Habitat

Location-
specific
and

Action-specific

Bald and Golden Eagle
Protection Act [16
U.S.C. §§ 668 etseq.
50 CFR Part 22]

Relevant and
Appropriate

Prohibits any person from knowingly, or with
wanton disregard, selling, offering to sell, taking,
purchasing, transferring, bartering, exporting,
importing, or possessing or harming a bald or
golden eagle, or any part, nest, or egg thereof
without obtaining a permit.

Remedial action at the Site must be designed and
implemented to avoid harm to bald or golden eagles,
their nests, or eggs. The occurrence of these birds and
nesting features within the Site
will be determined during remedial design to comply
with these requirements.

Habitat

Action-specific

Protection of Birds
[Idaho Code Ann. §
36-1102]

Applicable

Prohibits the "take" or intentional disturbance or
destruction of eggs or nests of any "game, song,
rodent killing, insectivorous or other innocent
bird." The prohibition does not apply to English
Sparrows or starlings.

The substantive requirements of the Idaho Protection of
Birds regulation that are applicable to the selected
remedy would be identified and complied with through
the remedial design process. Critical periods include
nesting and young rearing months of the year, which
will be noted during remedial design to guide remedial
construction.

PAGE 10 OF 13

-------
Medium

Type of
ARARC

Requirement3

Status

Synopsis of Requirement

Action to be Taken to Attain Requirement

Habitat

Action-specific

Idaho Classification
and Protection of
Wildlife Rule
[IDAPA 13.01.06.300]

TBC

Classifies fish and wildlife species; identifies
threatened or endangered species; and specifies
wildlife species that are protected from taking
and possessing.

To be considered during mitigation of ecological risk.

Land

Location-
specific
and

Action-specific

Mineral Leasing Act
[30 U.S.C. §§ 181 et
seq.\ and
implementing
regulations
43 CFR Parts 3500 and
3590]

TBC
and
Relevant and
Appropriate

Part 3500 establishes regulations pertaining to the
leasing of federally-owned solid minerals,
including phosphate.

Part 3590 establishes regulations pertaining to
mineral mining and reclamation operations.

The Selected Remedy was designed to be compatible
with the possibility of ore recovery. Ore recovery is
assumed, but is not part of the Selected Remedy. If ore
recovery is implemented, provisions regarding mineral
leasing must be considered because phosphate ore at
the Site is a federally-owned mineral. For ore to be
recovered during implementation of the remedial
action, P4 must acquire a mineral lease prior to
recovery of ore.

In addition, provisions regarding mineral mining and
reclamation are relevant and appropriate because
assumed ore extraction would occur concurrent with
implementation of the selected remedy, pursuant to a
BLM-approved operating plan.

The Selected Remedy will comply with the substantive
requirements of the Part 3590 regulations, by
incorporating relevant provisions of the BLM-
approved mine plan in the remedial design

Land

Location-
specific
and

Action-specific

Federal Land Policy and
Management Act [43
U.S.C. §§ 1732 etseq.]

Applicable

Prevents unnecessary or undue degradation of
public lands by operations authorized by the
mining laws. Establishes public land policy and
guidelines for the administration of public lands;
provides for the management, use, occupancy,
and development of public lands.

Provisions regarding multiple use and unnecessary or
undue degradation are applicable to the extraction of
minerals. If ore recovery is implemented, P4 will need
to incorporate appropriate mining and reclamation
practices into its BLM-approved mine plan, and
remedial design documents.

PAGE 11 OF 13

-------
Medium

Type of
ARARC

Requirement3

Status

Synopsis of Requirement

Action to be Taken to Attain Requirement

Land

Location-
specific
and

Action-specific

U.S. Bureau of Land
Management (BLM)
Record of Decision and
Pocatello Resource
Management Plan (April
2012), as amended Sept.
21,2015

Available online at

httDs://eDlannina.blm.ao

v/eDl-front-

office/Droiects/neDa/328
03/38812/40712/RODan
dSIR 508.pdf

TBC

Resource Management Plan established to sustain
the health, diversity, and productivity of the public
lands. The plan provides objectives, land use
allocations, and management direction to maintain,
improve or restore resource conditions, and
provide for the economic needs of local
communities over the long term. The plan applies
to BLM-managed public lands and split estate
lands where minerals are federally owned in
southeast Idaho.

Should be considered due to BLM's ownership of the
mineral rights and authorized stewardship of this
resource.

Land

Action-specific

Stream Channel
Alteration Rules
[IDAPA 37.03.07.055]

Applicable

Provides substantive construction standards for
working in stream channels.

Applicable as a result of remedial action on stream
channels and sediment basins; however, procedural
requirements are not ARAR.

Land

Action-specific

Idaho Fences in General
(LEAs) [Idaho Code §§
35-101 to-112]

Applicable

Establishes construction requirements, such as
height and distance between posts, for all types of
fences. Defines who is responsible for
construction and maintenance of enclosure and
partition fences.

Requirement must be implemented when fencing is
required to protect components of the selected remedy
(e.g., a cover system; as institutional controls, etc.).

Air

Action-specific

Clean Air Act [42
U.S.C. §§ 7409 et seq.
40 CFR Part 50]

Potentially
Applicable

Requirements for maintaining air quality.

The particular portions of the selected remedy to which
this ARAR is applicable will be identified and complied
with through the remedial design process and
implemented prior to construction activities at the Site.

Air

Action-specific

Idaho Rules for Control
of Fugitive Dust
[IDAPA 58.01.01.650-
651]

Applicable

Provides guideline and practices for controlling
fugitive dust emissions, including use of water or
chemicals, application of dust suppressant, and
covering trucks.

The particular portions of the selected remedy to which
this ARAR is applicable will be identified and complied
with through the remedial design process and
implemented during construction activities at the Site.
BMPs that utilize a form of dust suppressant and
institutional controls to restrict access to the public will
help promote compliance.

Air

Action-specific

Idaho Toxic Air
Pollutants

[IDAPA 58.01.01.585-
586]

Applicable

Requirements for maintaining air quality (none
currently nor will they be likely associated with
any remedial action).

The particular portions of the selected remedy to which
this ARAR is applicable will be identified and complied
with through the remedial design process and
implemented during construction activities at the Site.

PAGE 12 OF 13

-------
Medium

Type of
ARAR'

Requirement3

Status

Synopsis of Requirement

Action to be Taken to Attain Requirement

Assessment

Action-specific

Idaho Uniform
Environmental
Covenants Act
[Idaho Code §§55-3001
to-3015]

Applicable

Allows recordation of an environmental
covenant, which is a written agreement where the
parties bind themselves, and their successors in
interest to the land, to comply with activity and
use limitations.

This regulation endorses the use of some form of formal
administrative land use or deed restriction (Land use
controls) to sustain conditions achieved by remedial
cleanup. The selected remedy will include institutional
controls that limit access to the site until the Site is
deemed functional and operational.

Assessment

Action-specific

DEQ Area Wide Risk
Management Plan
[DEQ, 2004a]

TBC

This plan offers guidance to agencies responsible
for risk management decision-making at historic
phosphate mines in Southeast Idaho. The plan
includes goals and objectives for monitoring and
for addressing releases and impacts from
historical phosphate mining operations in
southeast Idaho.

Portions of this guidance may be useful in developing
the remedial design for the Site, including effectiveness
monitoring.

Assessment

Action-specific

Idaho Risk Evaluation
Manual
[DEQ, 2004b]

Available online at
httDS://www. dea. idaho. a
ov/media/967298-
risk evaluation manual
_2004.pdf]

TBC

Provides guidelines and criteria to apply in risk-
based decision making.

Framework for decision making should be considered in
developing human and environmental risk-based
cleanup levels

a Statute/Regulation/Standard/Policy (and appropriate citations) used to identify general category of ARAR/TBC. This listing does not indicate acceptance of the entire
statute/regulation/standard/policy as an ARAR/TBC; specific ARARs/TBCs are addressed in the table for each general heading. Only substantive provisions of the specific requirement are
considered potential ARARs/TBCs.

b The preamble to the NCP indicates that state regulations that are components of a federally authorized or delegated state program are generally considered federal requirements and
potential federal ARARs for the purposes of ARARs analysis (55 Fed. Reg. 8666, 8742 [1990]). DEQ received final authorization for the regulation of hazardous wastes on September 21,
2015. Substantive RCRA requirements are applicable to response actions on CERCLA sites if the waste is a RCRA hazardous waste, and either: the waste was initially treated, stored, or
disposed after the effective date of the particular RCRA requirement (1976 for RCRA, and 1984 for the amendments including land disposal restrictions); or the activity at the CERCLA site
constitutes treatment, storage, or disposal as defined by RCRA EPA 1988a CERCLA Compliance With Other Laws Manual, Draft Guidance (Part I). Interim Final EPA/540/G 89/006,
Office of Emergency and Remedial Response, Washington, D.C. August.
c Type of ARAR: C = Chemical-Specific; L= Location Specific; A = Action- Specific
d National Recommended Water Quality Criteria are available at fattp: //www, epa. gov/ost/cri teria/wqctable/

ARAR = Applicable or Relevant and Appropriate Requirements ET = evapotranspiration

BLM = Bureau of Land Management MCL = maximum contaminant level

BMPs = best management practices MCLG = maximum contaminant level goal

CFR = Code of Federal Regulations NCP = National Contingency Plan

CWA = Clean Water Act NPDES = National Pollutant Discharge Elimination System

DEQ = Idaho Department of Environmental Quality PRB = permeable reactive barrier

EPA = U.S. Environmental Protection Agency RCRA = Resource Conservation and Recovery Act of 1976

TBC = To be considered

PAGE 13 OF 13

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Appendix C
State Concurrence Letter

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STATE OF IDAHO

DEPARTMENT OF
ENVIRONMENTAL QUALITY

1410 North Hilton • Boise, ID 83706 • (208) 373-0502
www deq idaho gov

Brad Little, Governor
John H Tippets, Director

August 22, 2019

R. David Allnutt, Acting Director

Superfund and Emergency Management Division

U.S. EPA Region 10

1200 6th Avenue 12-D12-1

Seattle, WA98101

Subject: State of Idaho Concurrence on the Selected Remedy for the Record of Decision for Ballard
Mine

Dear Mr. Allnutt:

This letter notifies the Environmental Protection Agency (EPA) that the State of Idaho, Department of
Environmental Quality (IDEQ) concurs with the selected remedy outlined in the Record of Decision
(ROD) for Ballard Mine. As summarized in the ROD it appears the selected remedy will address
contaminants of concern identified in upland and riparian soils, sediment, surface water, and
groundwater. IDEQ agrees the chosen remedy can meet all applicable or relevant and appropriate
requirements (ARARs).

However, IDEQ does not fully agree that all requirements have been properly listed in the ROD. IDEQ
believes that the state's surface water standard for arsenic of 0.010 mg/L should be the goal unless and
until EPA approves a revised state criterion or promulgates a federal criterion.

IDEQ eagerly awaits implementation of this ROD as the project moves to the design phase. We look
forward to working cooperatively with the EPA and the Tribes in implementing a remedy that best
meets our mutual goal of protecting human health and the environment at Ballard Mine.

Director

c: Bruce Olenick, DEQ-Pocatello
Doug Tanner, DEQ-Pocatello
Lisa O'Hara, DAG-Boise
Mark Cecchini-Beaver, DAG-Boise
Davis Zhen, EPA-Seattle

Sincerely,

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Appendix D

Cost Estimate Breakdown of Remedy

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UPLAND SOIL ALTERNATIVE 6: ORE RECOVERY AND RECLAMATION
FEASIBILITY STUDY TECHNICAL MEMORANDUM #2
P4 Production LLC, Ballard Mine

Description : Alternative 6 - Ore Recoverv/Waste Rock Grading and Consolidation with ETCover. ICs. LUCs. and O&M/LTM. This alternative is similar to Alternative 4 except that incidental ore deposits would be recovered in a phased approach during the upland soil/waste rock removal,
consolidation, grading and capping efforts. The cover system included in Alternative 6 would be the ET cover as described in Alternative 4. See Figures 3-3a through 3-3c for a depiction of this alternative. Additional details regarding Alternative 6 can be found in Section 3.

Item Unit Cost

No. Item Description Quantity Unit Activity ($) Item Cost ($) Comments/Assumptions

1 DIRECT CAPITAL COSTS

Mobilization/Demobilization

Mobilization/Demobilization of Equipment (phase 1)

Site mobilization, over 75 ton, + 10% per addn'l 5 mi mob

$530.00

$10,176

Assumed fewer pieces of equipment (3 dozers and 3 loaders) due to phased nature of the ore recovery.

dist. 01 54 36.50 0100/2500

Quantity accounts for both mob and demob of equipment. Unit cost escalated 60% to account for haul

distance to site from Pocatello, ID. 2016 Means 01 54 36.50 0100/2500

Mobilization/Demobilization of Equipment (phase 2)

Site mobilization, over 75 ton, + 10% per addn'l 5 mi mob

$530.00

$5,936

dist. 01 54 36.50 0100/2500

Construction Field Offices

Field office, 32'x8', rent per month 01 52 13 13.20 0350

$270.00

$22,950

Assumed 3 - 32'x8' office trailers rented for monthly term.

2016 Means 01 52 13 13.20 0350

Portable Toilets

11,420

Blue rooms, /day 01 54 33 6410

$21.50

$245,530

Assumed 4 rental units. 2016 Means 01 54 33 6410

Temporary Utilities

Power

246

Power/HVAC combined, /month 01 51 13.80 0430

$176.00

$43,296

2016 Means 01 51 13.80 0430

Heat

$68.50

$1,578

Assumed 768 sf of trailer. 2016 Means 01 51 13.8 0200

Preparation of ICIAP

$50,000.00

$50,000

Engineering Judgement - Cost is rough order of magnitude based on plan preparation from other similar projec

Phase 1: Mine dumps MWD084. MWD082. and MWP035: Little Pit

Site Preparation

Clearing and Grubbing

223

Selective clearing, with dozer and brush rake, light 31 11

$262.00

$58,387

Assume dozer and brush rake, average brush diameter less than 4-inches. 2016 Means 31 11 13.10 0500.

13.10 0500

Crew = 1 operator and 1 laborer.

Excavate Waste Rock for On-Site Consolidation

Mine dump MWD084

250,000

bey

P4 Unit Rate for ROM LHD, Graded 3:1

$3.71

$927,500

Waste rock dump to be regraded to 3:1 slopes or less, material to be consolidated into open mine pits.

Regrade volume provided by P4 in support of ore recovery operations.Material volumes based on output from

mine planning software. Unit rates based on $3.71 to load, dump, and push at BFB in 2014. NAD trucks

(777) are 40-48 bey. Unit costs would be less for larger equipment. 777s are largest trucks that can mob with

limited assembly

Mine dump MWD082

1,311,111

bey

P4 Unit Rate for ROM LHD, Graded 3:1

$3.71

$4,864,222

As above

Mine dump within open pit MWP035

27,778

bey

P4 Unit Rate for ROM LHD, Graded 3:1

$3.71

$103,056

As above

Ore Recovery

Excavation of ore reserve

938,274

bey

P4 Unit Rate for Haulage to Process Area

$3.88

$3,640,503

Material volumes based on output from mine planning software. Unit rates based on $3.88 for excavation and

transport to plant.

Load overburden from mined are to haul vehicles, haul to MM P040 and

4,276,978

bey

P4 Unit Rate for ROM LHD, Graded 3:1

$3.71

$15,867,588

Material volumes based on output from mine planning software. Unit rates based on $3.71 to load, dump,

MMP035, and spread material with dozer (track compaction)

and push at BFB in 2014. NAD trucks (777) are 40-48 bey. Unit costs would be less for larger equipment.

777s are largest trucks that can mob with limited assembly.

Phase 2: Mine dump MWD093 (partial): Island Pit

Site Preparation

Clearing and Grubbing

Selective clearing, with dozer and brush rake, light 31 11

$262.00

$20,174

Assume dozer and brush rake, average brush diameter less than 4-inches. 2016 Means 31 11 13.10 0500.

13.10 0500

Crew = 1 operator and 1 laborer.

Waste Rock Consolidation

Mine dump MWD093 (partial)

118,519

bey

P4 Unit Rate for ROM LHD, Graded 3:1

$3.71

$439,705

Waste rock dump to be regraded to 3:1 slopes or less, material to be consolidated into open mine pits.

Regrade volume provided by P4 in support of ore recovery operations.Material volumes based on output from

mine planning software. Unit rates based on $3.71 to load, dump, and push at BFB in 2014. NAD trucks

(777) are 40-48 bey. Unit costs would be less for larger equipment. 777s are largest trucks that can mob with

limited assembly

Ore Recovery

Excavation of ore reserve

2,221,570

bey

P4 Unit Rate for Haulage to Process Area

$3.88

$8,619,692

Material volumes based on output from mine planning software. Unit rates based on $3.88 for excavation and

transport to plant.

Load overburden from mined area into haul vehicles, haul to MMP040

7,648,656

bey

P4 Unit Rate for ROM LHD, Graded 3:1

$3.71

$28,376,514

Material volumes based on output from mine planning software. Unit rates based on $3.71 to load, dump,

and MMP035, and spread material with a dozer (track compaction)

and push at BFB in 2014. NAD trucks (777) are 40-48 bey. Unit costs would be less for larger equipment.

777s are largest trucks that can mob with limited assembly.

Phase 3: Mine dump MWD093 (parital). MWD080 (partial), and MWD081 (partial): Long Pit

Site Preparation

208

Selective clearing, with dozer and brush rake, light 3111

$262.00

$54,496

Assume dozer and brush rake, average brush diameter less than 4-inches. 2016 Means 31 11 13.10 0500.

Clearing and Grubbing

13.10 0500

Crew = 1 operator and 1 laborer.

Waste Rock Consolidation

Mine dump MWD093 (partial)

790,741

bey

P4 Unit Rate for ROM LHD, Graded 3:1

$3.71

$2,933,649

Waste rock dump to be regraded to 3:1 slopes or less, material to be consolidated into open mine pits.

Regrade volume provided by P4 in support of ore recovery operations. Assumed 700hp dozer, 300 ft haul.

2016 Means 31 23 16.46 6060. Crew = 1 operator and one laborer.

Mind dumps MWD080 and MWD081 (partial)

1,857,407

bey

P4 Unit Rate for ROM LHD, Graded 3:1

$3.71

$6,890,980

Waste rock dump to be regraded to 3:1 slopes or less, material to be consolidated into open mine pits.

Regrade volume provided by P4 in support of ore recovery operations. Assumed 700hp dozer, 300 ft haul.

2016 Means 31 23 16.46 6060. Crew = 1 operator and one laborer.

Ore Recovery

Excavation of ore reserve

784,779

bey

P4 Unit Rate for Haulage to Process Area

$3.88

$3,044,943

Material volumes based on output from mine planning software. Unit rates based on $3.88 for excavation and

transport to plant.

Load overburden from mined area into haul vehicles, haul to Island Pit,

5,771,484

bey

P4 Unit Rate for ROM LHD, Graded 3:1

$3.71

$21,412,206

Material volumes based on output from mine planning software. Unit rates based on $3.71 to load, dump,

Long Pit, MMP035 and MMP036, and spread material with dozer (track

and push at BFB in 2014. NAD trucks (777) are 40-48 bey. Unit costs would be less for larger equipment.

compaction)

777s are largest trucks that can mob with limited assembly.

Confirmation Sampling

Sample Collection

It is assumed that waste rock will be graded and placed in existing mine pits without exposing the pre-mine

ground surface. Therefore, this type of sampling is not included.

ET Cover Construction (for entire area)

Cover construction will be done in phases but the costs herein are determined for the total acreage.

, , r, a

. . , ,

r_. r._ a ri

(assume 5 ft of alluvium amended to support plant growth over entire

alternative. Equipment and task costs based on recent (2014) P4 competitive bid for similar work at active

area underlain by material derrived from the ore recovery operation)

mine site. Assume that the coarse capillary break material underlying the 5 feet of alluvium will be produced

as part of the ore recovery operation.

Revegetation of all graded surfaces underlain by waste rock

23,435

msf

Revegetation, hydro or air seeding, with mulch and

$44.50

$1,042,870

A total of 538 acres. Cover surface area determined from mine planning and ArcMap software. Unit rate

fertilizer 32 92 19.14 5400

based on internal vegetation cost estimate of $1,550 per acre (or $35.60 per MSF) plus 25% increase to cover

additional erosional controls .

Landfill Cell for Miscellaneous Disposal

Load contaminated wastes from various locations throughout the

15,831

Using One Conservative Unit Rate for all materials

$10.00

$158,310

Assume 10,000 cy of contaminated material will need to be disposed on-Site during the implementation of the

project area for containment in this landfill at various times during the

associated with the Landfill

Site remedy. Assume average thickness of placed waste is 15 feet thick and as a result, would cover an area

life of the landfill. Load clean material from Borrow Area, Haul, Dump,

of approximately 18,000 square feet or a repository of 150' by 150' feet (allows for cover to extend beyond the

and grade cover material (assume 5 ft of alluvium amended to support

limits of the backfill). Assume base beneath landfill is compacted and 1 foot thick, cover is standard ET cover

plant growth over entire area underlain by 1 foot of coarse material for

(1 foot coarse material, 5 feet of alluvium, with revegetation). Increased per yard cost is the result of

capillary break)

numerous disposal events over life of landfill.

Revegetation of landfill surface

msf

Revegetation, hydro or air seeding, with mulch and

$44.50

$1,938

Conservatively assume a total of 1 acre of disturbance. Unit rate based on internal vegetation cost estimate

fertilizer 32 92 19.14 5400

of $1,550 per acre (or $35.60 per MSF) plus 25% increase to cover additional erosional controls.

Subtotal Capital Costs

$115,978,672

Project Management

Capital Costs

$115,978,672

$5,798,934

Project management cost when the capital costs are greater than $10M is esitmated at 5 percent (Table 5-8,

EPA 540-R-00-002).

Remedial Design

Capital Costs

$115,978,672

$6,958,720

Remedial Design costs when the capital costs are greater than $10M are estimated at 6 percent (Table 5-8,

EPA 540-R-00-002).

Construction Management and Oversight

Capital Costs

$115,978,672

$6,958,720

Construction management costs, including construction QA/QC, when the capital costs are greater than

$10M are estimated at 6 percent (Table 5-8, EPA 540-R-00-002).

Contingency Costs

10%

Capital Costs

$115,978,672

$11,597,867

See Note 1

Other Direct Costs

$31,314,242

TOTAL DIRECT COSTS

$147 292 914 Does not include subcontractor mark-up or profit

-------
UPLAND SOIL ALTERNATIVE 6: ORE RECOVERY AND RECLAMATION
FEASIBILITY STUDY TECHNICAL MEMORANDUM #2
P4 Production LLC, Ballard Mine

Description : Alternative 6 - Ore Recovery/Waste Rock Grading and Consolidation with ET Cover. ICs. LUCs. and O&M/LTM. This alternative is similar to Alternative 4 except that incidental ore deposits would be recovered in a phased approach during the upland soil/waste rock removal,
consolidation, grading and capping efforts. The cover system included in Alternative 6 would be the ET cover as described in Alternative 4. See Figures 3-3a through 3-3c for a depiction of this alternative. Additional details regarding Alternative 6 can be found in Section 3.

Item

Item Description Quantity

Unit

Activity

Unit Cost

Item Cost ($)

Comments/ Assumptions

No.

($)

ANNUAL COSTS

Long-term Cover Inspections (Semi-annual basis) 1

$27,262

Assumes semiannual inspections performed by 2-man crew consisting of senior and prof level staff 56 hours
per inspection; 6 days of per diem at $101 per day (lodging and food); Avis SUV rental 6 days at $99/day.
Site inspection to be conducted on foot to mitigate disturbance of covers by motorized vehicles.

30-YEAR PRESENT WORTH (i=7%;n=30,P/A=12.4090)

$338,294

SUMMARY REPORT (Every 5 Years) 1 5Yrs

30-YEAR PRESENT WORTH (i=7%; P/F=0.7130+0.5083+0.3624+0.2584+0.1842+0.1314=2.1577)

$100,000

$215,770

Engineering Judgement based on similar projects. Assumed LOE for summarizing inspection findings,
summarizing operation and maintenance activities completed, preparing presentation graphics for EPA lead 5-
year review meetings.

INSTITUTIONAL CONTROLS 2

$25,000

$50,000

See Note 2. Assumed property easement and deed restriction will need to be exeed with 2 property owner
CP4 and State nf Iriahnnrnnertiesl

ALTERNATIVE 6: 30 Year Present Worth Cost (items i+2+an)

$147,897,000

Notes:

1. For an FS which represents 0%-10% design completion, scope contingency typically ranges from 10 to 25 percent. The EPA guidance, "A Guide to Developing and Documenting Cost Estimates During the Feasibility Study,"July 2000, (EPA 540-R-00-002) shows a rule-of-thumb scope contingency of 10%-30%.

2. Institutional controls are non-engineering or legal/administrative measures to reduce or minimize the potential for exposure to site contamination or hazards by limiting or restricting site access. These controls could include institutional control plans, restrictive covenants, property easements, zoning, deed notices,
advisories, groundwater use restrictions, and site information database, as referenced in EPA 540-R-00-002.

ac acre

bey bank cubic yard

CSF Fir 100 square feet of floor

cy cubic yard

EA each

LOE Level of Effort

Icy loose cubic yard

LF linear feet

Is lump sum

MSF thousand square feet

QA/QC quality assurance / quality control

Yrs years

-------
SEDIMENT AND RIPARIAN SOILS ALTERNATIVE 3: SEDIMENT TRAPS/BASINS,

MNR, ICs, AND LUCs FEASIBILITY STUDY TECHNICAL MEMORANDUM #2
P4 Production LLC,

Ballard Mine

Description: Alternative 3 - Sediment Traps/Basins. MNR. ICs. and LUCs. This alternative uses sediment traps in the upper reaches of the mine-affected drainages to capture/control any mine-affected sediment
entrained in the intermittent storm water/stream flow. MNR would be implemented in lower reaches, and relies on natural processes to disperse and ultimately reduce COC/COEC concentrations in the affected media over
time. In order for MNR to be successful, source controls need to be implemented in the upland soil/waste rock to prevent migration of COCs/COECs to the downstream drainages. MNR also requires ICs and LUCs to
restrict Site activities until the cleanup levels are achieved. See Figure 3-7 for general depiction of alternative. Additional details regarding Alternative 3 can be found in Section 3.

Item

Item Description Quantity

Unit

Item Cost

Comment

No.

Cost

($)

(S)

DIRECT CAPITAL

COSTS

Sediment and Riparian Soil Remedial Components

Install Sediment Traps in upstream locations

Excavate, place, compact as necessary 6

per

$3,500.00

$21,000

location

Assumed the sediment traps average 90 feet long, are 6 feet high, with a 12 foot base. Assume it will require

one excavator or dozer and one laborer (with a hand operated compactor) 1 day to construct each of these

sediment traps. Spillways will be cut into the adjacent native material around the edge and if necessary, lined

with coarser materials or fabric. Assume mobilization of the equipment is included in this per day cost.

MNR

Plans/Implementation

Prepare Sampling and Analysis Plan 1

$60,000

Assumed preparation of sampling plan will require three iterations prior to approval by EPA. Engineering

judgement based on other similar projects.

MNR Baseline Sampling 1

$37,135

Assumed all drainages where PCLs are exceeded. Three discrete samples of soil, sediment, and vegetation will

Program

be collected from 25 locations resulting in a total of 75 samples. Assumed 15% for QA/QC resulting in 87

laboratory samples. Each sample will be analyzed for nine COC metals by SW6010C. Assumed one-person

field crew and 1 hour per sample (layout to shipping). Includes preparation of summary report.

Preparation of ICIAP 1

$50,000

Engineering Judgement - Cost is rough order of magnitude based on plan preparation from other similar projects.

Subtotal Capital

$168,135

Costs

Project Management 8%

Capital

$168,135

$13,451

Project Management costs, when the capital costs are between $100 to 500K, are estimated at 8 percent (Table

Costs

5-8, EPA 540-R-00-002).

Remedial Design 15%

Capital

$168,135

$25,220

Remedial Design costs, when the capital costs are between $100 to 500K, are estimated at 15 percent (Table 5-

Costs

8, EPA 540-R-00-002).

Construction Management and Oversight 10%

Capital

$168,135

$16,814

Construction management costs, including construction QA/QC, when capital costs are between $100 to 500K,

Costs

are estimated at 10 percent (Table 5-8, EPA 540-R-00-002).

Contingency Costs 10%

Capital

$168,135

$16,814

See Note 1

Costs

Other Direct

$72,298

Costs

TOTAL DIRECT COSTS

$240,433

Does not include subcontractor mark-up or profit

ANNUAL COSTS

LTM and OM&M of sediment 1

annual

$10,000

Assumes semiannual inspections performed by 1-man crew and that minor repairs will be necessary each year

traps

to the 6 sediment traps. See Note 2.

30-YEAR PRESENT WORTH

$124,090

(i=7%; n=30, P/A=12.4090)

Long-term MNR sampling 1

15 Yrs

$37,135

Assumed that sampling at the baseline monitoring locations will be repeated every 5 years for a period of 30

years.

30-YEAR PRESENT WORTH (i=7%;

$80,126

P/F=0.7130+0.5083+0.3624+0.2584+0.1842+0.1314=2.1577)

Subtotal Annual

$204,216

Costs

SUMMARY REPORT (Every 5 Years) 1

/5 Yrs

$100,000

Engineering Judgement based on similar projects. Assumed LOE for summarizing inspection findings,

summarizing operation and maintenance activities completed, preparing presentation graphics for EPA lead 5-

year review meetings.

30-YEAR PRESENT WORTH (i=7%;

$215,770

P/F=0.7130+0.5083+0.3624+0.2584+0.1842+0.1314=2.1577)

INSTITUTIONAL CONTROLS 3

$25,000

$75,000

See Note 3. Assumed property easement and deed restriction will need to be executed with one property owner

("Tucker Toraeson Farms. P4 Production LLC. Clair Holmaren")

ALTERNATIVE 3: 30 Year Present Worth Cost (items

$736,000

1+2+3+4)

Notes:

1. For an FS which represents 0%-10% design completion, scope contingency typically ranges from 10 to 25 percent. The EPA guidance, "A Guide to Developing and Documenting Cost Estimates During the Feasibility Study,"July 2000, (EPA 540-R-
00-002) shows a rule- of-thumb scope contingency of 10%-30%.

2. Costs for installation of a on-Site landfill for disposal of sediments from these sediment traps are included in the upland soils/waste rock alternatives.

3. Institutional controls are non-engineering or legal/administrative measures to reduce or minimize the potential for exposure to site contamination or hazards by limiting or restricting site access. These controls could include institutional control plans,
restrictive covenants, property easements, zoning, deed notices, advisories, groundwater use restrictions, and site information database, as referenced in EPA 540-R-00-002.

COC constituent of concern
EA each
Is lumpsum
MNR monitored natural recovery
PCL preliminary cleanup level
QA/QC quality assurance / quality

control
Yrs years

-------
SURFACE WATER ALTERNATIVE 3: IN-SITU TREATMENT,
ICs, and LUCs FEASIBILITY STUDY TECHNICAL
MEMORANDUM #2
P4 Production LLC, - Ballard Mine

Description: Alternative 3 - ICs and LUCs would be implemented as in Alternative 2, and in-situ wetlands treatment would be constructed at mine-affected seep locations. Upon competition of source controls in the upland soil/waste
rock, all surface water runoff would be un impacted and only residual flows from seeps are expected to exceed cleanup levels for a period of time (i.e., until the regrading and cover systems mitigate the source of water that recharges
through the upland soil/waste rock and ultimately discharges to the seeps). The wetlands would treat the residual mine-affected surface water at the perennial seeps via biologically mediated reactions including reduction using
anaerobic bacteria resulting in precipitation and/or sorption of the COC/COECs. The treated water would discharge from the wetlands to the downstream drainages or evapotranspire within the wetlands. See Figure 3-6 for general
depiction of alternative. Additional details regarding Alternative 3 can be found in Section 3.

Item Description

Quantity

Unit



Item Cost ($)

Comments/Assumptions

Item





Unit Cost





No.





($)





1 DIRECT CAPITAL











COSTS











Mobilization/Demobilization











Mobilization/Demobilization of Equipment

7

EA

$816

$5,712

Assumed 2 trackhoes, 1 dozer, and 3 off-road haul vehicles. Quantity accounts for both mob and demob of











equipment. Unit cost escalated 60% to account for haul distance to site from Pocatello, ID. 2014 Means 01 54











36.50 0100/2500

Construction Field Offices

2

month

$223

$446

Assumed 1 - 32'x8' office trailers rented for monthly











term. 2014 Means 01 52 13 13.20 0350

Portable Toilets

240

day

$13

$3,204

Assumed 4 rental units for 60 days each. 2014 Means 01 54 33 6410

Temporary Utilities











Power

2

month

$2

$4

2014 Means 01 51 13.80 0430

Heat

8

CSF Fir

$69

$526

Assumed 768 sf of trailer. 2014 Means 01 51 13.8 0200

Preparation of ICIAP

1

Is

$50,000

$50,000

Engineering Judgement-Cost is rough order of magnitude based on plan preparation from other similar projects.

Update to Surface Water Monitoring Plan

1

Is

$21,760

$21,760

Existing surface water monitoring plan will be updated to conform with post RA monitoring program.

Surface Water Remedial Components











1A) Seep MST069/MSG008 - Constructed Wetlands (Refer to Figure 3-6)









Construction of collection basin at seep location MST069

1

LS

$4,749.00

$4,749

Assumed a 5ftx5ftx3ft excavation, lined with 60-mil HDPE. Collected water conveyed via 2-inch PVC pipeline to











seep location MSG005. Component costs:











Basin excavation-2014 Means 31 23 16.13 0050. Crew = I operator and I laborer.











60-mil HDPE (includes 20% increase to account for sag and anchortrenching)-2014 Means Site Work &











Landscaping 33 47 13.53 120. Crew = 3 skilled workers.











Pipeline trenching (900 feet, avg depth 4 ft)-2014 Means 31 23 16.13 0050. Crew= I operator and I laborer.











2-inch PVC piping-2014 Means Site Work & Landscaping 33 47 13.53 120. Crew= 1 foreman, 1 plumber.











Pipeline backfill (Assumed 30% fluffing of excavated material)-2014 Means 31 23 16.13 3020. Crew= 1











operator and 1 laborer

Excavation of wetland basin at seep location MSG008

1,966

bey

$1.80

$3,538

Basin size based on 400 sf/gpm (engineers judgement) and 4 ft depth. Anticipated inflow to wetland of 33.1











gpm based on average Spring flow rate from seeps MST069, MSG008, MDS030- MDS033, and MSG003.











Assumed trackhoe with 3 CY bucket, 2014 Means 31 23 16.42 0300. Crew= 1 operator and 1 laborer.

Placement of gravel bedding

491

cy

$133.00

$65,357

Assumed 13,268 sf of basin and pea gravel placed to a thickness of 1 ft. 2014 Means 32 91 13.16 1600. Crew =











1 foreman and 2 laborers.

Load organic soil from on-site source into haul vehicles

1,597

bey

$1

$958

Assumed a source of organic soil is available on-site and 30% increase in volume due to fluffing of excavated











material. Assumed front loader with 10 cy bucket, 100% fill factor. 2014 Means 31 23 16.43 0450. Crew= 1











operator and 1 laborer.

Haul to constructed wetland location

1,597

bey

$3

$4,871

Assumed 42cy off-road vehicle, 1 mile cycle distance, 10 MPH speed limit. 2014 Means 31 23 23.20 7100.











Crew = 1 driver.

Spread material with dozer, no compaction

1,597

pcy

$4.70

$7,506

Assumed 300 hp dozer, max 300 ft push. 2014 Means 31 23 23.17 0190. Crew = 1 operator and 1 laborer.

Installation of wetland plants

0.5

ac

$800.00

$400

Unit cost from a constructed wetland study by NC State University

1B) Seeps MDS030-033/MSG003to MSG008- Conveyance System (refer to Figure









Construction of collection basin at each seep location

1

LS

$25,000.00

$25,000

Assumed a 5ftx5ftx3ft excavation, lined with 60-mil HDPE at each seep location. Collected water conveyed via











2-inch PVC pipeline to central location (MSG008). Component costs:











Basin excavation-2014 Means 31 23 16.13 0050. Crew = I operator and I laborer.











60-mil HDPE (includes 20% increase to account for sag and anchortrenching)-2014 Means Site Work &











Landscaping 33 47 13.53 120. Crew = 3 skilled workers.











Pipeline trenching (7300 feet, avg depth 4ft)-2014 Means 31 23 16.13 0050. Crew= I operator and I laborer.











2-inch PVC piping-2014 Means Site Work & Landscaping 33 47 13.53 120. Crew= 1 foreman, 1 plumber.











Pipeline backfill (Assumed 30% fluffing of excavated material)-2014 Means 31 23 16.13 3020. Crew= 1











operator and 1 laborer

2j Seep MST067 -Constructed Wetlands (refer to Figure 3-











Excavation of wetland basin at seep location MST067

1,067

bey

$1.80

$1,920

Basin size based on 400 sf/gpm (engineers judgement) and 4 ft depth. Anticipated inflow to wetland of 18 gpm











based on average Spring flow rate from seep MST067. Assumed trackhoe with 3 CY bucket, 2014 Means 31











23 16.42 0300. Crew = 1 operator and 1 laborer.

Placement of gravel bedding

267

cy

$133.00

$35,467

Assumed 7200 sf of basin and pea gravel placed to a thickness of 1 ft. 2014 Means 32 91 13.16 1600. Crew= 1







forman and 2 laborers.

Load organic soil from on-site source into haul vehicles

867

bey

$1

$520

Assumed a source of organic soil is available on-site and 30% increase in volume due to fluffing of excavated











material. Assumed front loader with 10 cy bucket, 100% fill factor. 2014 Means 31 23 16.43 0450

Haul to constructed wetland location

867

bey

$3

$2,643

Assumed 42cy off-road vehicle, 1 mile cycle distance, 10 MPH speed limit. 2014 Means 31 23 23.20 7100

Spread material with dozer, no compaction

867

bey

$4.70

$4,073

Assumed 300 hp dozer, max 300 ft push. 2014 Means 31 23 23.17 0190

Installation of wetland plants

0.2

ac

$800.00

$160

Unit cost from a constructed wetland study by NC State University

3) Seep MSG004/MSG005 - Constructed Wetlands (refer to Figure 3-6)









Construction of collection basin atseep location MSG004 and

1

LS

$4,749.00

$4,749

Assumed a 5ftx5ftx3ft excavation, lined with 60-mil HDPE. Collected water conveyed via 2-inch PVC pipeline to

conveyance pipeline to MSG005









seep location MSG005. Component costs:











Basin excavation-2014 Means 31 23 16.13 0050. Crew = I operator and I laborer.











60-mil HDPE (includes 20% increase to account for sag and anchortrenching)-2014 Means Site Work &











Landscaping 33 47 13.53 120. Crew = 3 skilled workers.











Pipeline trenching (900 feet, avg depth 4 ft)-2014 Means 31 23 16.13 0050. Crew= I operator and I laborer.











2-inch PVC piping-2014 Means Site Work & Landscaping 33 47 13.53 120. Crew= 1 foreman, 1 plumber.











Pipeline backfill (Assumed 30% fluffing of excavated material)-2014 Means 31 23 16.13 3020. Crew= 1











operator and 1 laborer

Excavation of wetland basin atseep location MSG005

516

bey

$1.80

$928

Basin size based on 400 sf/gpm (engineers judgement) and 4 ft depth. Anticipated inflow to wetland of 8.7 gpm











based on average Spring flow rate from seeps MSG004 and MSG005. Assumed trackhoe with 3 CY











bucket, 2014 Means 31 23 16.42 0300. Crew = 1 operator and 1 laborer.

Placement of gravel bedding

129

cy

$133.00

$17,142

Assumed 3480 sf of basin and pea gravel placed to a thickness of 1 ft. 2014 Means 32 91 13.16 1600. Crew= 1











foreman and 2 laborers.

Load organic soil from on-site source into haul vehicles

419

bey

$1

$251

Assumed a source of organic soil is available on-site and 30% increase in volume due to fluffing of excavated











material. Assumed front loader with 10 cy bucket, 100% fill factor. 2014 Means 31 23 16.43 0450. Crew= 1











operator and 1 laborer.

Haul to constructed wetland location

419

bey

$3

$1,278

Assumed 42cy off-road vehicle, 1 mile cycle distance, 10 MPH speed limit. 2014 Means 31 23 23.20 7100.











Crew = 1 driver.

Spread material with dozer, no compaction

419

pcy

$4.70

$1,969

Assumed 300 hp dozer, max 300 ft push. 2014 Means 31 23 23.17 0190. Crew = 1 operator and 1 laborer.

Installation of wetland plants

0.1

ac

$800.00

$80

Unit cost from a constructed wetland study by NC State University

4) Seep MSG006/MSG007 - Constructed Wetlands (refer to Figure 3-6)









Construction of collection basin atseep location MSG006 and

1

LS

$4,749.00

$4,749

Assumed a 5ftx5ftx3ft excavation, lined with 60-mil HDPE. Collected water conveyed via 2-inch PVC pipeline to

conveyance pipeline to MSG007









seep location MSG007. Component costs:











Basin excavation-2014 Means 31 23 16.13 0050. Crew = I operator and I laborer.











60-mil HDPE (includes 20% increase to account for sag and anchortrenching)-2014 Means Site Work &











Landscaping 33 47 13.53 120. Crew = 3 skilled workers.











Pipeline trenching (900 feet, avg depth 4 ft)-2014 Means 31 23 16.13 0050. Crew= I operator and I laborer.











2-inch PVC piping-2014 Means Site Work & Landscaping 33 47 13.53 120. Crew= 1 foreman, 1 plumber.











Pipeline backfill (Assumed 30% fluffing of excavated material)-2014 Means 31 23 16.13 3020. Crew= 1











operator and 1 laborer

Excavation of wetland basin atseep location MSG007

1,304

bey

$1.80

$2,347

Basin size based on 400 sf/gpm (engineers judgement) and 4 ft depth. Anticipated inflow to wetland of 22 gpm











based on average Spring flow rate from seeps MSG006 and MSG007. Assumed trackhoe with 3 CY bucket,











2014 Means 31 23 16.42 0300. Crew = 1 operator and 1 laborer.

Placement of gravel bedding

326

cy

$133.00

$43,348

Assumed 8800 sf of basin and pea gravel placed to a thickness of 1 ft. 2014 Means 32 91 13.16 1600. Crew= 1











forman and 2 laborers.

Load organic soil from on-site source into haul vehicles

1,059

bey

$1

$636

Assumed a source of organic soil is available on-site and 30% increase in volume due to fluffing of excavated











material. Assumed front loader with 10 cy bucket, 100% fill factor. 2014 Means 31 23 16.43 0450

Haul to constructed wetland location

1,059

bey

$3

$3,231

Assumed 42cy off-road vehicle, 1 mile cycle distance, 10 MPH speed limit. 2014 Means 31 23 23.20 7100

Spread material with Dozer, no compaction

1,059

pcy

$4.70

$4,979

Assumed 300 hp dozer, max 300 ft push. 2014 Means 31 23 23.17 0190

Installation of wetland plants

0.2

ac

$800.00

$160

Unit cost from constructed wetland study by NC State University

-------
SURFACE WATER ALTERNATIVE 3: IN-SITU TREATMENT, ICs, and LUCs
FEASIBILITY STUDY TECHNICAL MEMORANDUM #2
P4 Production LLC, Ballard Mine

Description: Alternative 3 - ICs and LUCs would be implemented as in Alternative 2, and in-situ wetlands treatment would be constructed at mine-affected seep locations. Upon competition of source controls in the upland soil/waste rock, all
surface water runoff would be un impacted and only residual flows from seeps are expected to exceed cleanup levels for a period of time (i.e., until the regrading and cover systems mitigate the source of water that recharges through the
upland soil/waste rock and ultimately discharges to the seeps). The wetlands would treat the residual mine-affected surface water at the perennial seeps via biologically mediated reactions including reduction using anaerobic bacteria resulting
in precipitation and/or sorption of the COC/COECs. The treated water would discharge from the wetlands to the downstream drainages or evapotranspire within the wetlands. See Figure 3-6 for general depiction of alternative. Additional details
regarding Alternative 3 can be found in Section 3.

Item
No.

Item Description

Quantity

Unit

Unit Cost
($)

Item Cost ($)

Comments/Assumptions

5) Seep MST095 - Constructed Wetland (refer to Figure 3-6)

Excavation of wetland basin at seep location MST095

Placement of gravel bedding

Load organic soil from on-site source into haul vehicles

1,659

415
1,348

bey

cy
Icy

$1.80

$133.00
$1

$2,987

$55,170
$809

Basin size based on 400 sf/gpm (engineers judgement) and 4 ft depth. Anticipated inflow to wetland of 28 gpm
based on average Spring flow rate from seep MST095. Assumed trackhoe with 3 CY bucket, 2014 Means 31
23 16.42 0300. Crew = 1 operator and 1 laborer.

Assumed 11200 sf of basin and pea gravel placed to a thickness of 1 ft. 2014 Means 32 91 13.16 1600. Crew =
1 forman and 2 laborers.

Assumed a source of organic soil is available on-site and 30% increase in volume due to fluffing of excavated
material. Assumed front loader with 10 cy bucket, 100% fill factor. 2014 Means 31 23 16.43 0450

Haul to constructed wetland location

1,348

Icy

$4,112

Assumed 42cy off-road vehicle, 1 mile cycle distance, 10 MPH speed limit. 2014 Means 31 23 23.20 7100

Spread material with dozer, no compaction
Installation of wetland plants
6) Seep MST094 - Constructed Wetland (refer to Figure 3-6)

Excavation of wetland basin at seep location MST094

Placement of gravel bedding

Load organic soil from on-site source into haul vehicles

1,348
0.3

711

178
578

Icy
ac

bey

cy
bey

$4.70
$800.00

$1.80

$133.00
$1

$6,336
$240

$1,280

$23,644
$347

Assumed 300 hp dozer, max 300 ft push. 2014 Means 31 23 23.17 0190
Unit cost from constructed wetland study by NC State University

Basin size based on 400 sf/gpm (engineers judgement) and 4 ft depth. Anticipated inflow to wetland of 12 gpm
based on average Spring flow rate from seep MST094. Assumed trackhoe with 3 CY bucket, 2014 Means 31
23 16.42 0300. Crew = 1 operator and 1 laborer.

Assumed 4800 sf of basin and pea gravel placed to a thickness of 1 ft. 2014 Means 32 91 13.16 1600. Crew= 1
forman and 2 laborers.

Haul to constructed wetland location

578

bey

$1,762

Assumed 42cy off-road vehicle, 1 mile cycle distance, 10 MPH speed limit. 2014 Means 31 23 23.20 7100

Spread material with dozer, no compaction
Installation of wetland plants

578
0.1

pcy $4.70
ac $800.00
Subtotal Capital Costs

$2,716
$80
$424,143

Assumed 300 hp dozer, max 300 ft push. 2014 Means 31 23 23.17 0190
Unit cost from constructed wetland study by NC State University

Project Management

Capital Costs

$424,143

$25,449

Project management costs when the capital costs are greater than $500K are estimated at 6 percent (Table 5-8,
EPA540-R-00-002). Because our capital cost are close to $500K, we selected the $500Kto $2M cost spread.

Remedial Design

12%

Capital Costs

$424,143

$50,897

Remedial Design costs when the capital costs are greaterthan$500Kare estimated at 12 percent (Table 5-8,
EPA 540-R-00-002). Because our capital cost are close to $500K, we selected the $500Kto $2M cost spread.

Construction Management and Oversight
Contingency Costs

8%
10%

Capital Costs $424,143

Capital Costs $424,143
Other Direct Costs

$33,931

$42,414
$152,692

Construction management costs, including construction QA/QC, when the capital costs are greater than $500K
are estimated at 8 percent (Table 5-8, EPA 540-R-00-002). Because our capital cost are close to $500K, we
selected the $500K to $2M costspread.

See Note 1

TOTAL DIRECT COSTS

$576,835

Does not include subcontractor mark-up or profit

ANNUAL COSTS

Long-term surfacewater monitoring (seeps/springs/wetlands) and
maintenance of 6 wetlands

$38,486

$47,486

Sampling will be conducted by a 2-person field crew over a 5-day period. Assumed 15 surface water locations to
be monitored on a semi-annual basis. Includes field sampling activities, laboratory costs (including QA/QC
samples), data validation, data summary report preparation, and field sampling activities. Assume maintenance
of the each wetland will be $1,500/year.

30-YEAR PRESENT WORTH (i=7%;n=30,P/A=l2.4090)

$589,254

SUMMARY REPORT (Every 5 Years) 1 /5Y[S

30-YEAR PRESENT WORTH (i=7%; P/F=0.7130+0.5083+0.3624+0.2584+0.1842+0.1314=2.1577)

$100,000

$215,770

INSTITUTIONAL CONTROLS

$25,000

$50,000

See Note 2. Assumed property easement and deed restriction will need to be executed with two property owner
CP4 oroduction. LLC and Clair Holmaren")

ALTERNATIVE 3: 30 Year Present Worth Cost

(Items 1+2+3+4)

$1,432,000

Notes:

1. For an FS which represents 0%-10% design completion, scope contingency typically ranges from 10 to 25 percent. The EPA guidance, "A Guide to Developing and Documenting Cost Estimates During the Feasibility Study,"July 2000, (EPA540-R-00-002)showsa rule-
of-thumb scope contingency of 10%-30%.

2. Institutional controls are non-engineering or legal/administrative measures to reduce or minimize the potential for exposure to site contamination or hazards by limiting or restricting site access. These controls could include institutional control plans, restrictive covenants,
property easements, zoning, deed notices, advisories, groundwater use restrictions, and site information database, as referenced in EPA 540-R-00-002.

ac acre

bey bank cubic yard

CSF Fir 100 square feet of floor

EA each

pcy placed cubic yard

Is lumpsum

ICs Institutional Controls

LUCs Land Use Controls

ICIAP Institutional Controls Implementation and Assurance Plan
QA/QC quality assurance/quality control
Yrs years

-------
GROUNDWATER ALTERNATIVE 3: LIMITED PRB TREATMENT,
MNA, AND ICs FEASIBILITY STUDY TECHNICAL MEMORANDUM #2
P4 Production LLC, - Ballard Mine

Description: Alternative 3 - Limited Permeable Reactive Barrier (PRB) Treatment of Alluvial Groundwater. MNA and ICs. MNA and ICs would be implemented as in Alternative 2, and PRBs would be installed up gradient of
select perennial seeps near the margins of the waste rock piles at the Site to treat shallow alluvial groundwater before it discharges at the seeps/springs. See Figure 3-10 for general depiction of alternative. Additional details
regarding Alternative 2 can be found in Section 3.

Item
No.

Item

Description

Quantity

Unit

Unit Cost

	($L_

Item Cost ($)

Comment

1 DIRECT CAPITAL COSTS

Mobilization/Demobilization

Mobilization/Demobilization of Drilling Equipment	1

Mobilization of Single-Pass Trencher for PRB Installation	1

Construction Field Offices	3

Portable Toilets	360
Temporary Utilities

Power	246

Heat	23

Preparation of ICIAP	1

Update to Groundwater Monitoring Plan to accommodate MNA	1
work

Groundwater Remedial Components

1)	PRB Construction near (upslope of) seep location MSG008

Iron Filings (PMP Cast Iron Aggregate ETI 8/50) for the PRB	17

Crushed Limestone (Iron:limestone is 0.6 feet:0.9 feet) for the	18
PRB

ZVI PRB Installation	50

Installation of four monitoring wells	40

Surface completion for monitoring well	4

2)	PRB Construction upslope from Seep location MST067

Iron Filings (PMP Cast Iron Aggregate ETI 8/50) for the PRB	17

Crushed Limestone (Iron:limestone is 0.6 feet:0.9 feet) for the	18
PRB

ZVI PRB Installation	50

Installation of four monitoring wells	40

Surface completion for monitoring well	4

3)	PRB Construction near seep location MST069

Iron Filings (PMP Cast Iron Aggregate ETI 8/50) for the PRB	17

Crushed Limestone (Iron:limestone is 0.6 feet:0.9 feet) for the	18
PRB

ZVI PRB Installation	50

Installation of four monitoring wells	40

Surface completion for monitoring well	4

4)	PRB Construction near seep location MSG004

Iron Filings (PMP Cast Iron Aggregate ETI 8/50) for the PRB	17

Crushed Limestone (Iron:limestone is 0.6 feet:0.9 feet) for the	18
PRB

ZVI PRB Installation	50

Installation of four monitoring wells	40

Surface completion for monitoring well	4

5)	PRB Construction near seep location MSG005

Iron Filings (PMP Cast Iron Aggregate ETI 8/50) for the PRB	17

Crushed Limestone (Iron:limestone is 0.6 feet:0.9 feet) for the	18
PRB

ZVI PRB Installation	50

Installation of four monitoring wells	40

Surface completion for monitoring well	4

6)	PRB Construction near seep location MSG007

Iron Filings (PMP Cast Iron Aggregate ETI 8/50) for the PRB	17

Crushed Limestone (Iron:limestone is 0.6 feet:0.9 feet) for the	18
PRB

ZVI PRB Installation	50

Installation of four monitoring wells	40

Surface completion for monitoring well	4

7)	PRB Construction near seep location MSG006

Iron Filings (PMP Cast Iron Aggregate ETI 8/50) for the PRB	17

Crushed Limestone (Iron:limestone is 0.6 feet:0.9 feet) for the	18
PRB

ZVI PRB Installation	50

Installation of four monitoring wells	40

Surface completion for monitoring well	4

8)	PRB Construction near seep location MST095

Iron Filings (PMP Cast Iron Aggregate ETI 8/50) for the PRB	17

Crushed Limestone (Iron:limestone is 0.6 feet:0.9 feet) for the	18
PRB

ZVI PRB Installation	50

Installation of four monitoring wells	40

Surface completion for monitoring well	4

Is
Is

month
each

month
CSF
Fir
Is
Is

tons
tons

LF
LF

tons

tons

LF
LF

ea

tons

tons

LF
LF

ea

tons

tons

LF
LF

ea

tons

tons

LF
LF

ea

tons

tons

LF
LF

ea

tons

tons

LF
LF

ea

tons

tons

LF
LF

$10,000
$60,000
$223

$13
$2

$50,000
$45,000

$1,070
$67

$250
$77

$500

$1,070
$67

$250
$77

$500

$1,070
$67

$250
$77

$500

$1,070
$67

$250
$77

$500

$1,070
$67

$250
$77

$500

$1,070
$67

$250
$77

$500

$1,070
$67

$250
$77

$500

$1,070
$67

$250
$77

$500

$10,000 Driller mobilization based on driller quote for similar work in SE Idaho
$60,000 Mobilization of single-pass trencher from Michigan
$669 Assumed 3 - 32'x8' office trailers rented for monthly
term. 2014 Means 01 52 13 13.20 0350
$4,806 Assumed 4 rental units for 90 days each. 2014 Means 01 54 33 6410

$448 2014 Means 01 51 13.80 0430
$1,578 Assumed 768 sf of trailer. 2014 Means 01 51 13.8 0200

$50,000 Engineering Judgement-Cost is rough order of magnitude based on plan preparation from other similar projects.
$45,000 Existing groundwater monitoring plan will be updated to conform with post RA monitoring program.

$18,538 50ftx10ftx0.6ftx1.1 at 150lb/cf; Includes shipping by flatbed trucks in 3,000 Ibsupersacksfrom Michigan to site;
Includes material for construction of trench from 3 ft to 10 ft depth
$1,204 50ftx10ftx0.9ftx1.1 at 1.4ton/cy; Includes labor for mixing and delivering the limestone/iron mix to the trencher;
Includes material for construction of trench from 3 ft to 10 ft depth
$12,500 The trencher will lay the PRB 10 feet bgs with automatic backfill with Iron/limestone mix
$3,080 Assumed four piezometers per PRB to provide additional GW sampling locations. Assumes 2-inch SCH 40 PVC

casing and well screen. Based on driller estimate from a similar site in SE Idaho
$2,000 4-inch steel protective casing, four steel concrete filled bollards, and concrete pad. Based on driller estimate
from a similar site in SE Idaho

$18,538 50ftx10ftx0.6ftx1.1 at 150lb/cf; Includes shipping by flatbed trucks in 3,000 Ibsupersacksfrom Michigan to site;
Includes material for construction of trench from 3 ft to 10 ft depth
$1,204 50ftx10ftx0.9ftx1.1 at 1.4ton/cy; Includes labor for mixing and delivering the limestone/iron mix to the trencher;
Includes material for construction of trench from 3 ft to 10 ft depth
$12,500 The trencher will lay the PRB 10 feet bgs with automatic backfill with Iron/limestone mix
$3,080 Assumed four piezometers per PRB to provide additional GW sampling locations. Assumes 2-inch SCH 40 PVC

casing and well screen. Based on driller estimate from a similar site in SE Idaho
$2,000 4-inch steel protective casing, four steel concrete filled bollards, and concrete pad. Based on driller estimate
from a similar site in SE Idaho

$18,538 50ftx10ftx0.6ftx1.1 at 150lb/cf; Includes shipping by flatbed trucks in 3,000 Ibsupersacksfrom Michigan to site;
Includes material for construction of trench from 3 ft to 10 ft depth
$1,204 50ftx10ftx0.9ftx1.1 at 1.4ton/cy; Includes labor for mixing and delivering the limestone/iron mix to the trencher;
Includes material for construction of trench from 3 ft to 10 ft depth
$12,500 The trencher will lay the PRB 10 feet bgs with automatic backfill with Iron/limestone mix
$3,080 Assumed four piezometers per PRB to provide additional GW sampling locations. Assumes 2-inch SCH 40 PVC

casing and well screen. Based on driller estimate from a similar site in SE Idaho
$2,000 4-inch steel protective casing, four steel concrete filled bollards, and concrete pad. Based on driller estimate
from a similar site in SE Idaho

$18,538 50ftx10ftx0.6ftx1.1 at 150lb/cf; Includes shipping by flatbed trucks in 3,000 Ibsupersacksfrom Michigan to site;
Includes material for construction of trench from 3 ft to 10 ft depth
$1,204 50ftx10ftx0.9ftx1.1 at 1.4ton/cy; Includes labor for mixing and delivering the limestone/iron mix to the trencher;
Includes material for construction of trench from 3 ft to 10 ft depth
$12,500 The trencher will lay the PRB 10 feet bgs with automatic backfill with Iron/limestone mix
$3,080 Assumed four piezometers per PRB to provide additional GW sampling locations. Assumes 2-inch SCH 40 PVC

casing and well screen. Based on driller estimate from a similar site in SE Idaho
$2,000 4-inch steel protective casing, four steel concrete filled bollards, and concrete pad. Based on driller estimate
from a similar site in SE Idaho

$18,538 50ftx10ftx0.6ftx1.1 at 150lb/cf; Includes shipping by flatbed trucks in 3,000 Ibsupersacksfrom Michigan to site;
Includes material for construction of trench from 3 ft to 10 ft depth
$1,204 50ftx10ftx0.9ftx1.1 at 1.4ton/cy; Includes labor for mixing and delivering the limestone/iron mix to the trencher;
Includes material for construction of trench from 3 ft to 10 ft depth
$12,500 The trencher will lay the PRB 10 feet bgs with automatic backfill with Iron/limestone mix
$3,080 Assumed four piezometers per PRB to provide additional GW sampling locations. Assumes 2-inch SCH 40 PVC

casing and well screen. Based on driller estimate from a similar site in SE Idaho
$2,000 4-inch steel protective casing, four steel concrete filled bollards, and concrete pad. Based on driller estimate
from a similar site in SE Idaho

$18,538 50ftx10ftx0.6ftx1.1 at 150lb/cf; Includes shipping by flatbed trucks in 3,000 Ibsupersacksfrom Michigan to site;
Includes material for construction of trench from 3 ft to 10 ft depth
$1,204 50ftx10ftx0.9ftx1.1 at 1.4ton/cy; Includes labor for mixing and delivering the limestone/iron mix to the trencher;
Includes material for construction of trench from 3 ft to 10 ft depth
$12,500 The trencher will lay the PRB 10 feet bgs with automatic backfill with Iron/limestone mix
$3,080 Assumed four piezometers per PRB to provide additional GW sampling locations. Assumes 2-inch SCH 40 PVC

casing and well screen. Based on driller estimate from a similar site in SE Idaho
$2,000 4-inch steel protective casing, four steel concrete filled bollards, and concrete pad. Based on driller estimate
from a similar site in SE Idaho

$18,538 50ftx10ftx0.6ftx1.1 at 150lb/cf; Includes shipping by flatbed trucks in 3,000 Ibsupersacksfrom Michigan to site;
Includes material for construction of trench from 3 ft to 10 ft depth
$1,204 50ftx10ftx0.9ftx1.1 at 1.4ton/cy; Includes labor for mixing and delivering the limestone/iron mix to the trencher;
Includes material for construction of trench from 3 ft to 10 ft depth
$12,500 The trencher will lay the PRB 10 feet bgs with automatic backfill with Iron/limestone mix
$3,080 Assumed four piezometers per PRB to provide additional GW sampling locations. Assumes 2-inch SCH 40 PVC

casing and well screen. Based on driller estimate from a similar site in SE Idaho
$2,000 4-inch steel protective casing, four steel concrete filled bollards, and concrete pad. Based on driller estimate
from a similar site in SE Idaho

$18,538 50ftx10ftx0.6ftx1.1 at 150lb/cf; Includes shipping by flatbed trucks in 3,000 Ibsupersacksfrom Michigan to site;
Includes material for construction of trench from 3 ft to 10 ft depth
$1,204 50ftx10ftx0.9ftx1.1 at 1.4ton/cy; Includes labor for mixing and delivering the limestone/iron mix to the trencher;
Includes material for construction of trench from 3 ft to 10 ft depth
$12,500 The trencher will lay the PRB 10 feet bgs with automatic backfill with Iron/limestone mix
$3,080 Assumed four piezometers per PRB to provide additional GW sampling locations. Assumes 2-inch SCH 40 PVC

casing and well screen. Based on driller estimate from a similar site in SE Idaho
$2,000 4-inch steel protective casing, four steel concrete filled bollards, and concrete pad. Based on driller estimate
from a similar site in SE Idaho

-------
GROUNDWATER ALTERNATIVE 3: LIMITED PRB TREATMENT, MNA, AND ICs
FEASIBILITY STUDY TECHNICAL MEMORANDUM #2
P4 Production LLC, Ballard Mine

Description: Alternative 3 - Limited Permeable Reactive Barrier (PRB) Treatment of Alluvial Groundwater. MNA and ICs. MNA and ICs would be implemented as in Alternative 2, and PRBs would be installed up gradient of select
perennial seeps near the margins of the waste rock piles at the Site to treat shallow alluvial groundwater before it discharges at the seeps/springs. See Figure 3-10 for general depiction of alternative. Additional details regarding Alternative 2
can be found in Section 3.



Item Description

Quantity

Unit



Item Cost ($)

Comment

Item







Unit Cost





No.







($)







9) PRB Construction near seep location MST094













Iron Filings (PMP Cast Iron Aggregate ETI 8/50) for the PRB

17

tons

$1,070

$18,538

50ftx10ftx0.6ftx1.1 at 150lb/cf; Includes shipping by flatbed trucks in 3,000 Ibsupersacksfrom Michigan to site;
Includes material for construction of trench from 3 ft to 10 ft depth



Crushed Limestone (lron:limestone is 0.6 feet:0.9 feet) for the PRB

18

tons

$67

$1,204

50ftx10ftx0.9ftx1.1 at 1.4ton/cy; Includes labor for mixing and delivering the limestone/iron mix to the trencher;
Includes material for construction of trench from 3 ft to 10 ft depth



ZVI PRB Installation

50

LF

$250

$12,500

The trencher will lay the PRB 10 feet bgs with automatic backfill with Iron/limestone mix



Installation of four monitoring wells

40

LF

$77

$3,080

Assumed four piezometers per PRB to provide additional GW sampling locations. Assumes 2-inch SCH 40 PVC
casing and well screen. Based on driller estimate from a similar site in SE Idaho



Surface completion for monitoring well

4

ea

$500

$2,000

4-inch steel protective casing, four steel concrete filled bollards, and concrete pad. Based on driller estimate
from a similar site in SE Idaho







Subtotal Capital Costs

$508,395





Project Management

8%

Capital Costs

$508,395

$40,672

Project Management costs, when the capital costs are between $100 to 500K, are estimated at 8 percent (Table
5-8, EPA 540-R-00-002).



Remedial Design

15%

Capital Costs

$508,395

$76,259

Remedial Design costs, when the capital costs are between $100 to 500K, are estimated at 15 percent (Table 5-











8, EPA 540-R-00-002).



Construction Management and Oversight
Contingency Costs

10%
10%

Capital Costs
Capital Costs

$508,395
$508,395

$50,839
$50,839

Construction management costs, including construction QA/QC, when capital costs are between $100 to 500K,
are estimated at 10 percent (Table 5-8, EPA540-R-00-002).

See Note 1







Other Direct Costs

$218,610





TOTAL DIRECT COSTS







$727,004

Does not include subcontractor mark-up or profit

2

ANNUAL COSTS













Long-term MNA Groundwater Monitoring and Reporting

1

Is

$80,987

$80,987

Sampling will be conducted by a 2-person field crew over a 15-day period. Assumed 78 groundwater locations
to be monitored on an annual basis. Samples to be analyzed for site COCs using SW 6020 at $92.60 per



30-YEAR PRESENT WORTH (i=7%;n=30,P/A=l2.4090)







$1,004,968

sample. Includes field sampling activities, laboratory costs (including QA/QC samples), data validation, data
summary report preparation, and field sampling activities.

3

SUMMARY REPORT (Every 5 Years)

1

15 Yrs

$100,000

$100,000

Engineering Judgement based on similar projects. Assumed LOE for summarizing inspection findings,
summarizing operation and maintenance activities completed, preparing presentation graphics for EPA lead 5-



30-YEAR PRESENT WORTH (i=7%; P/F=0.7130+0.5083+0.3624+0.2584+0.1842+0.1314=2.1577)



$215,770

year review meetings.

4

INSTITUTIONAL CONTROLS

5

EA

$25,000

$125,000

See Note 2. Assumed property easement and deed restriction will need to be executed with one property owner
(Tucker Torgeson Farms, Hunsaker Ranching, Nu West Industries, Mark & Beth Carter Trust, Clair Holmgren)

5

ALTERNATIVE 3: 30 Year Present Worth Cost

(Items 1+2+3+4)





$2,073,000



Notes:

1.	For an FS which represents 0%-10% design completion, scope contingency typically ranges from 10 to 25 percent. The EPA guidance, "A Guide to Developing and Documenting Cost Estimates During the Feasibility Study,"July 2000, (EPA540-R-00-002)showsa rule-
of-thumb scope contingency of 10%-30%.

2.	Institutional controls are non-engineering or legal/administrative measures to reduce or minimize the potential for exposure to site contamination or hazards by limiting or restricting site access. These controls could include institutional control plans, restrictive covenants,
property easements, zoning, deed notices, advisories, groundwater use restrictions, and site information database, as referenced in EPA 540-R-00-002.

ac	acre

bey	bank cubic yard

CSF Fir 100 square feet of floor

EA	each

Icy	loose cubic yard

LF	linear feet

MSF	thousand square feet

Yrs	years

-------
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-------
RECORD OF DECISION
FOR
BALLARD MINE
CARIBOU COUNTY, IDAHO

Part 3

Responsiveness Summary

-------
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-------
Part 3 • Responsiveness Summary

Overview of Responsiveness Summary

This part of the Record of Decision (ROD), the Responsiveness Summary, presents the comments
submitted during the public comment period on the Proposed Plan for the Ballard Mine Site (Site) and
the U.S. Environmental Protection Agency (EPA) responses. EPA issued the Proposed Plan for the
Ballard Mine Site on April 2, 2018, and accepted comments during a public comment period that ran
from April 2 through May 1, 2018.

No one requested an extension to the public comment period. A public meeting was held in Soda
Springs, Idaho, on April 11, 2018, to present information on the Proposed Plan, answer questions, and
provide the public with an opportunity to give written and spoken comments. No spoken comments
were made during the formal portion of the public meeting. Written comments were received from
three individuals and one organization during the comments period. The original comments and a
transcript of the public meeting is available in the Administrative Record.

The comments received covered a range of topics. Some commenters expressed preferences regarding
the alternatives and potential ore recovery during implementation and stated concerns about the
Superfund cleanup process, adequacy of outreach to stakeholders during the process, and risks posed
by current conditions. One organization stated concerns and provided recommendations about various
elements of the Preferred Alternative.

Comments and Responses

This section of the Responsiveness Summary presents each substantive comment received during the
public comment period. Following each comment is a response that explains how the commenter's
concerns were addressed and their preferences considered during the remedy selection process.

Comment 1: Support for preferred alternative and ore recovery

I am in favor of the EPA's Preferred Alternative as it meets the Remedial Action Objectives while also
providing the money needed for the cleanup through ore recovery. As a former employee, I am personally
aware of the effort, thought, and hours over many years that have been put into this cleanup plan by
Monsanto, consultants, and government agencies and am satisfied that is the best step forward to make
right now for the Ballard site. I am also a member of the local community and am supportive of this
action for how it will improve the land on the Ballard site and for the revenue it will bring to the area.

EPA Response:

Comment noted. The Selected Remedy is consistent with the Preferred Alternative identified in the
Proposed Plan.

Comment 2: Support for ore recovery and concern about whether risks justify cleanup

When mining was done these pits were left open specifically so that they could be reopened in the future.
There should be no reshaping unless it goes hand-in-hand with total mining of all the remaining ore (I
would guess that there is much more than 4M ton). This is a valuable resource in Caribou County that
shouldn't be left up to the whims of some foreign owned multinational corporation whether or not to
mine. This ore might be more desirable to another company. I do not believe that the environmental
hazards warrant action that would destroy our natural resource. I do think that hand spraying the aster
could be tried to control selenium problem until such time that the pits are re-mined.

EPA Response:

The Selected Remedy assumes that P4 will recover phosphate ore during the implementation of the
remedy. EPA notes, however, that ore recovery is a business decision; cleanup of the Site does not
depend on potential ore recovery.

l

-------
Parts • Responsiveness Summary

During the Feasibility Study process, the project team developed and evaluated a range of alternatives
for cleanup. EPA concluded that the Preferred Alternative (with potential ore recovery) meets the
threshold criteria (of protectiveness and achieving Applicable or Relevant and Appropriate
Requirements [ARARs]) and provides the best balance of tradeoffs among the other alternatives with
respect to the modifying criteria. The Selected Remedy mirrors the Preferred Alternative identified in
the Proposed Plan. However, potential ore recovery is a business decision that depends on many
factors. Any decision on whether to recover ore during implementation of the cleanup would be up the
owner of the mineral lease.

EPA's Selected Remedy assumes that remining will occur during implementation of the remedial
action. For potential ore recovery to proceed, Bureau of Land Management (BLM) will need to issue a
phosphate mineral lease and approve a mine plan for ore recovery. The Selected Remedy will be
designed to accommodate, but not require, the recovery of ore during remedy implementation. EPA
will work closely with P4 Production and BLM to coordinate the cleanup with ore recovery.

EPA disagrees with the comment expressing belief that risks do not warrant cleanup action. The
remedial investigation of the Site documented the presence of many millions of tons of waste rock and
ongoing releases of contaminants from the waste rock to upland soil, vegetation, groundwater, surface
water, and sediment. In addition, the concentrations of contaminants in affected media exceed risk-
based thresholds and present unacceptable risks to people and ecological receptors. Cleanup action is
necessary to address the risks identified.

The commenter also notes that asters (a type of plant that may contain high levels of contaminants)
may be controlled by hand spraying until the cleanup plan is implemented. EPA agrees with this
suggestion. The land owner, P4, has implemented this method of controlling plants for several years as
a best management practice (BMP). EPA anticipates continuing this BMP during remedial design and
implementation. Following implementation, a monitoring and maintenance program will be prepared
for the Site. EPA anticipates that preventing the occurrence and growth of known selenium
bioaccumulating plants will be an important part of any long-term maintenance plan for the
remediated mine site. The evapotranspiration (ET) cover will be planted with a mix of native plant
species. Bioaccumulating species, such as asters, will not be included.

Comment 3: Concern about the length of time it has taken to study the site and develop a
cleanup plan, and adequacy of outreach of stakeholders.

First I'd like to say that the presentation you put on was very informative and helpful. Second.....why has it
taken this long to come to some sort of a plan to take care of a problem that the mining community and
EPA have known about for some 20 years, if not more? Third, one ofthefamilys' most effected by the
Ballard Mine pollution expected more frequent and timely updates than were provided by agencies on the
progress of the project.

EPA Response:

EPA acknowledges that it has taken many years to characterize site conditions and develop a cleanup
plan. There are many factors that have contributed to the schedule for this project, some of which are
described in the Introduction and Site Background sections of the Proposed Plan. EPA remains
committed to advancing this project in a timely fashion. EPA acknowledges that more effort could have
been focused on community outreach and engagement, particularly for landowners with property near
the site. A summary of efforts on community involvement are included in the Site Background section
of the Proposed Plan and Section 3 - Community Participation of this document. In addition, EPA has
developed a Community Involvement Plan (CIP) for the project that is updated from time to time. EPA
will review and update the CIP in the coming months and will strengthen components related to
outreach to local landowners.

-------
Part 3 • Responsiveness Summary

Comment 4: Greater Yellowstone Coalition (GYC) provided comments and recommendations on
each of the four media-specific components of the combined preferred alternative.

GYC Comments on Upland Soil/Waste Rock Alternative 6:

GYC encourages the agencies to evaluate and confirm the effectiveness of the final cover In 2011, EPA

reported that the ability to abate percolation is performance criteria for final cover systems, and only
"limited data are available about percolation performance and alternative designs". Given this statement
regarding limited data for cover design effectiveness, EPA should incorporate a significant factor of safety
with regard to both cover infiltration and evapotranspiration for final designs. Alternatively providing for
a robust cover infiltration monitoring system to provide options for adaptive management, should cover
performance not meet the infiltration criteria.

GYC suggests that EPA and [I]DEQ monitor the following factors identified by EPA to maintain
effectiveness of the cover system for an extended period of time: settlement effects, gas emissions, erosion,
slope failure, and vegetative cover maintenance.

GYC further recommends that the agencies ensure that the ET cover in fact prevents or greatly reduces
the release of contaminants to surface water and groundwater.

GYC additionally requests that the cover eliminates direct contact exposures, prevents vegetative uptake,
and eliminates the releases of contaminants to riparian soil and sediment.

Given the last 20 years of experimentation on effectiveness of covers in southeast Idaho, GYC encourages
EPA to fully understand what covers work in specific situations, and to employ a rigorous monitoring plan
and adaptive management plan.

EPA Response:

EPA generally agrees with the comments and recommendations regarding the need for care in
developing the design and performance monitoring strategy for the ET cover system. A detailed
design, performance monitoring plan, and adaptive management plan will be developed during the
remedial design phase of the project.

Effectiveness, both short- and long-term, are criteria by which EPA evaluates each of the proposed
remedial alternatives. The ET cover was selected from a variety of proposed cover
designs/configurations modeled for water infiltration effectiveness based on soil characteristics and
design attributes (see the 2016 Ballard Mine Feasibility Study Report). Modeling results were
compared with data from actual covers that had been constructed and monitored by other local mines
to take advantage of lessons learned by others. The information obtained from these studies will be
incorporated into the design of a remedial cover. Once constructed, the effectiveness of the cover to
mitigate infiltration will be monitored by inspections, spring and seep surveys, instrumentation, and
by comparing concentration of contaminants in downgradient surface water and groundwater
monitoring stations with cleanup levels.

During the remedial design phase, a detailed design of the ET cover system will be developed. This will
include specifications related to hydraulic conductivity and ability to retain water. The characteristics
of the soil used for cover will dictate these attributes, and the thickness of the cover will be adjusted
accordingly to be most effective. Factors of safety, with respect to cover infiltration and ET, will be
addressed during remedial design.

A monitoring plan, describing specific methods, will also be developed during remedial design. The
plan will include elements necessary to evaluate infiltration and soil moisture. It is anticipated that soil
moisture monitoring will include installation of monitoring stations at strategic locations on the cover
and at various depths within the cover profile.

An adaptive management plan will be prepared concurrently with the remedial design. The plan shall
set performance criteria or targets for key performance measure (if other than state or federal

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Parts • Responsiveness Summary

standards) and identify potential follow-up actions to correct identified problems or optimize cover
performance. Application of adaptive management actions will be guided by monitoring results.

Because contamination is left in place as part of the remedy, EPA will perform a Five-Year Review
(FYR). The objective of the FYR is to evaluate whether the remedy is functioning as originally intended.
If the integrity of the remedy has been compromised, specific actions are undertaken to mitigate the
situation and restore the remedy. This includes inspection of the remedial cover for settlement effects,
accelerated erosion, slope failure, and vegetative cover maintenance issues.

GYC Comments on Surface Water Alternative 3:

GYC encourages the agencies to identify and implement a rigorous monitoring plan to ensure that the
wetland treatment cells do not themselves become sources of contamination.

GYC suggests EPA and [I]DEQ follow EPA's guidelines for a successful constructed treatment wetland,
including site-specific examinations of soil suitability, hydrology, vegetation, the presence of endangered
species, the presence of species of concern, critical wildlife corridors, and/or critical wildlife habitat.

GYC encourages the agencies to not only examine these qualities but identify a plan to protect
conservation resources while avoiding further natural resource damage such as the introduction of
invasive species.

Furthermore, EPA and [I]DEQ should consider potential water quality impacts as well as impacts to the
surrounding future uses.

The adaptive management plan to be prepared during remedial design phase should set clear standards
for monitoring contaminants in the wetland treatment cells, create well-defined decision rules for
determining whether the wetland treatment cell may remain in place, and create a precise process for the
disposal of spent treatment media.

Additionally, a rapid and reasonable time limit should be specified for the implementation of adaptive
management actions.

EPA Response:

EPA generally agrees with the comments and recommendations regarding the need for care in
developing the design and performance monitoring strategy for the wetland treatment cells. A detailed
design, operation and maintenance (O&M) plan, performance monitoring plan, and adaptive
management plan will be developed during the remedial design phase of the project.

Engineered wetlands were identified as a viable alternative at this site because they have proven to be
effective at selenium removal, are simple to construct, and are relatively low cost. When these
treatment cells are combined with the cover system and upgradient permeable reactive barriers
(PRB), cleanup levels are expected to be attained where treated water enters waters of the United
States.

The conceptual design for the engineered wetland treatment cells include an upflow
anaerobic/aerobic wetlands system that includes seepage interception and collection, a gravel
distribution bed, an anaerobic organic bed, and a growth bed for wetlands plants along with open
water surface (aerobic portion of the system). Site-specific design variables (for example, residence
time, peak and low flow requirements, and material needs) will be evaluated and considered in
developing the design. Designs may later be modified to optimize performance and efficiency, and cells
may be phased out once other elements of the remedy become effective.

EPA agrees with comments on the need to monitor the initial and sustained effectiveness of the
wetland treatment cell, the need to site and construct the treatment cells to maximize their treatment
effectiveness without compromising other natural resources, to avoid introduction of invasive species,
evaluate residual effects of water quality impacts on future use, and be proactive in implementing
adaptive management strategies.

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Part 3 • Responsiveness Summary

During remedial design, a monitoring plan will be developed to assess the effectiveness of the wetland
treatment cells. Monitoring will be conducted to evaluate contaminant removal rates and loading in
the wetland media. Loading thresholds will be determined to prevent the wetlands from becoming a
source of contamination. In addition, an O&M plan will be developed that will include decision rule and
procedures for removal, replacement and disposal of the wetlands media, and decision rules for
decommissioning treatment cells.

An adaptive management plan will be prepared concurrently with the remedial design. The plan shall
set performance criteria or targets for key performance measures and identify potential follow-up
actions to correct identified problems or optimize treatment performance. Application of adaptive
management actions will be guided by monitoring results.

GYC Comments on Stream Channel Sediment and Riparian Soil Alternative 3:

GYC encourages the agencies to identify a rigorous monitoring plan to ensure that the sediment
traps/basins do not themselves become sources of contamination.

GYC recommends the adaptive management plan to be prepared during the remedial design phase should
set clear standards for monitoring contaminants in sediment traps/basins, create well-defined decision
rules for determining whether the sediment traps/basins may remain in place, and create a precise
process for disposal of contaminated sediment. Additionally, long term risks and effects of abandoned or
buried in-place sediment traps becoming exposed and/or eroded should be evaluated on a site or
individual basis.

EPA Response:

EPA agrees with the comments and recommendations regarding the need for care in developing the
design and performance monitoring strategy for the sediment control features included in the selected
alternative. A detailed design, O&M plan, performance monitoring plan, and adaptive management
plan will be developed during the remedial design phase of the project.

EPA agrees with comments regarding the importance of monitoring the effectiveness of the sediment
traps/basins to capture and retain sediment during and following construction of the ET cover system.
A monitoring plan and O&M plan will be developed to evaluate these features and will address
accumulation of sediment, and procedures for removal and disposal. The O&M plan will also include
decision rules for decommissioning sediment traps/basins.

An adaptive management plan will be prepared concurrently with the remedial design. The plan shall
set performance criteria for evaluating the effectiveness of the sediment control features and identify
potential follow-up actions to correct identified problems or optimize performance. Application of
adaptive management actions will be guided by monitoring results.

GYC Comments on Groundwater Alternative 3:

GYC encourages the agencies to identify a rigorous monitoring plan to ensure that the permeable reactive

barriers (PRBs) do not themselves become sources of contamination Should the PRBs themselves

become sources of contamination, the agencies should follow their guidelines for appropriate disposal of
spent treatment materials and impacted area clean up. The adaptive management plan to be prepared
during the remedial design phase should set clear standards for monitoring contaminants in the PRBs,
create well-defined decision rules for determining whether the PRBs may remain in place, and create a
precise process for the disposal of spent treatment media.

EPA Response:

EPA generally agrees with the comments and recommendations regarding the need for care in
developing the design and performance monitoring strategy for the permeable reactive barriers
included in the selected alternative. A detailed design, O&M plan, performance monitoring plan, and
adaptive management plan will be developed during the remedial design phase of the project.

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Parts • Responsiveness Summary

A monitoring plan will be developed to track variables that have a bearing on performance. In addition,
bracketing monitoring wells will be used to measure the chemistry of influent and effluent
groundwater and surface water. The plan will describe monitoring of the hydraulic conductivity,
reactive condition of the PRB treatment media, and other measures.

A plan will also be developed to guide O&M of the PRBs, and will include procedures and decision rules
for removal, replacement, and disposal of the wetlands media. The contaminant concentration
thresholds linked to breakthrough that trigger removal and disposal of the treatment media will be
described in the O&M plan. The plan will also describe abandonment of PRBs and decision rules for
removal or abandonment in place.

An adaptive management plan will be prepared concurrently with the remedial design. The plan shall
set performance criteria for evaluating the effectiveness of the PRBs and identify potential follow-up
actions to correct identified problems or optimize performance. Application of adaptive management
actions will be guided by monitoring results.

Together, implementation of monitoring, O&M, and adaptive management will ensure that the PRBs
are working as designed and do not themselves become a source of contamination.

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