Standard Mine Remedial Investigation (RI) Report


START 3 Superfund Technical Assessment and Response Team 3
Region 8
STANDARD MINE
Gunnison County, Colorado
TDD No. 0608-07
MAY 14, 2010
United States
Environmental Protection
Agency
Contract No. EP-W-05-050
OPERATING SERVICES, INC
5 RKG0"

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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
REMEDIAL INVESTIGATION REPORT
STANDARD MINE
Gunnison County, Colorado
EPA Contract No. EP-W-05-050
TDD No. 0608-07
Prepared By:
URS Operating Services, Inc.
1099 18th Street, Suite 710
Denver, CO 80202-1908
Approved: 	 Date:
Christina Progess, Remedial Project Manager, EPA, Region 8
Approved: 	 Date:
Charles W. Baker, START 3 Program Manager, UOS
Approved: 	 Date:
Jan Christner, Project Manager, START 3, UOS
This document has been prepared for the U.S. Environmental Protection Agency under Contract
No. EP-W-05-050. The material contained herein is not to be disclosed to, discussed with, or made available
to any person or persons for any reason without prior express approval of a responsible officer of the U.S.
Environmental Protection Agency. In the interest of conserving natural resources, this document is printed on
recycled paper and double-sided as appropriate.

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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
DISTRIBUTION LIST
U.S. ENVIRONMENTAL PROTECTION AGENCY
Christina Progess_(2 copies) Remedial Project Manager, EPA Region 8
U.S. FOREST SERVICE
Mark Hatcher
Linda Lanham
Brian Lloyd
U.S. Forest Service
AML/HazMat/Minerals Manager, U.S. Forest Service
U.S. Forest Service Rocky Mountain Region
COLORADO DEPARTMENT OF PUBLIC HEALTH AND ENVIRONMENT
Jim Lewis (2 copies)	Project Manager, CDPHE
Barbara Nabors	Superfund and Site Assessment Unit Leader, Hazardous
Materials and Waste Management Division, CDPHE
TOWN OF CRESTED BUTTE
John Hess	Town of Crested Butte
URS OPERATING SERVICES, INC.
Jan Christner	Project Manager, START 3, EPA Region 8
File (2 copies)	START 3, EPA Region 8
li

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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
REMEDIAL INVESTIGATION
STANDARD MINE NPL SITE
Gunnison County, Colorado
TABLE OF CONTENTS
Page No.
SIGNATURE PAGE	i
DISTRIBUTION PAGE	ii
TABLE OF CONTENTS	iii
LIST OF ACRONYMS	ix
1.0 INTRODUCTION	1-1
1.1	Purpose of Report	1-1
1.2	Site Background	1-1
1.2.1	Site Description
1.2.2	Site History
1.2.2.1	Mining History
1.2.2.2	Regulatory History and Removal Actions
1.2.3	Previous Investigations
1.2.3.1	Preliminary Assessment
1.2.3.2	Expanded Site Inspection
1.2.3.3	Removal Investigations
1.2.3.4	USFS Investigations
1.2.3.5	Coal Creek Watershed Coalition Investigations
1.2.3.6	Other Investigations
1.3	Report Organization	1-11
2.0 SITE INVESTIGATIONS	2-1
2.1	Surface Features	2-1
2.2	Contaminant Sources	2-1
2.2.1	Waste Rock and Tailings
2.2.2	Mine Workings and Adit Discharges
2.3	Meteorology	2-3
2.4	Surface Water and Sediment	2-4
2.4.1	Surface Water
2.4.2	Sediment
2.4.3	Pore Water
2.5	Geology	2-7
2.6	Hydrogeology	2-8
2.7	Demography and Land Use	2-9
2.8	Ecology	2-9
2.8.1	Wetlands
2.8.2	Threatened and Endangered Species
2.8.3	Fish
2.8.3.1	Fish Habitat Evaluation
2.8.3.2	Fish Inventory
2.8.3.3	Toxicity Testing
2.8.3.4	Fish Tissue Sampling
in

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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE OF CONTENTS (continued)
2.8.4	Macroinvertebrates
2.8.4.1	Macroinvertebrate Assemblage Sampling
2.8.4.2	Macroinvertebrate Tissue Sampling
2.8.5	Vegetation
3.0 PHYSICAL CHARACTERISTICS OF THE STUDY AREA	3-1
3.1	Surface Features and Mine Workings	3-1
3.1.1	Level 1
3.1.2	Level 2
3.1.3	Level 3
3.1.4	Level 4
3.1.5	Level 5
3.1.6	Level 98
3.2	Meteorology	3-7
3.3	Surface Water Hydrology	3-8
3.4	Geology and Soils	3-10
3.5	Hydrogeology	3-12
3.6	Demography and Land Use	3-15
3.7	Ecology	3-16
3.7.1	Wetlands
3.7.1.1	Level 1 Wetlands
3.7.1.2	Level 2 Wetland
3.7.1.3	Level 98 Wetland
3.7.1.4	Level 5 Wetland
3.7.2	Threatened and Endangered Species
3.7.2.1	Birds
3.7.2.2	Mammals
3.7.2.3	Amphibians
3.7.2.4	Plants
3.7.3	Elk Creek Habitat
3.7.4	Mt. Emmons Gossan and Iron Fen
4.0 NATURE AND EXTENT OF CONTAMINATION	4-1
4.1	Sources of Contamination	4-1
4.1.1	Waste Rock and Tailings
4.1.1.1	Level 1 Waste Rock and Tailings
4.1.1.2	Level 2 Waste Rock
4.1.1.3	Level 3 Waste Rock
4.1.1.4	Level 4 Waste Rock
4.1.1.5	Level 5 Waste Rock
4.1.1.6	Level 98 Waste Rock
4.1.2	Mine Adits
4.1.2.1	Level 1 Adit
4.1.2.2	Level 2 Adit
4.1.2.3	Level 3 Adit
4.1.2.4	Level 5 Adit
4.1.2.5	Level 98 Adit Discharge
4.2	Soil	4-10
4.3	Groundwater	4-11
IV

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URS Operating Services, Inc.	Standard Mine - Remedial Investigation
START 3, EPA Region 8	TDD No. 0608-07
Contract No. EP-W-05-050	Date: 05/2010
TABLE OF CONTENTS (continued)
4.4 Surface Water and Sediment	4-13
4.4.1	Elk Creek
4.4.1.1	Elk Creek Surface Water
4.4.1.2	Elk Creek Sediments
4.4.2	Coal Creek
4.4.2.1	Coal Creek Surface Water
4.4.2.2	Coal Creek Sediments
4.4.2.3	Additional Metal Sources along Coal Creek:
4.4.3	On-site Wetlands
4.4.3.1	Level 5 Wetlands
4.4.3.2	Level 98 Wetlands
4.4.4	Metals Loading
4.4.5	Biota
4.4.5.1	Fish Tissue
4.4.5.2	Macroinvertebrate Tissues
5.0 CONTAMINANT FATE AND TRANSPORT	5-1
5.1	Potential Routes of Migration	5-1
5.1.1	Air
5.1.2	Water
5.2	Contaminant Persistence	5-3
5.3	Contaminant Migration	5-4
5.3.1	Contaminant Migration via Air
5.3.2	Contaminant Migration via Surface Water
5.3.3	Contaminant Migration via Groundwater
5.4	Conceptual Site Model	5-7
6.0 BASELINE RISK ASSESSMENT	6-1
6.1	Human Health Evaluation	6-1
6.1.1	Baseline Ecological Risk Assessment
6.1.2	Baseline Human Health Risk Assessment Addendum
6.1.3	Uncertainties
6.2	Ecological Risk Assessment	6-6
6.2.1	Screening Level Ecological Risk Assessment
6.2.2	Baseline Ecological Risk Assessment
6.2.3	BERA Addendum
6.2.3.1	Risks to Aquatic Receptors from Contaminants in Surface Water
6.2.3.2	Risks to Aquatic Receptors from Contaminants in Sediment
6.2.3.3	Risks to Plants and Soil Invertebrates
6.2.3.4	Risks to Birds and Mammals
6.2.3.5	Summary of Risk Addendum
7.0 SUMMARY AND CONCLUSIONS	7-1
7.1 Nature and Extent of Contamination	7-1
7.1.1	Waste Rock Tailings
7.1.2	Adit Discharge
7.1.3	Groundwater
7.1.4	Surface Water and Sediment
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URS Operating Services, Inc.	Standard Mine - Remedial Investigation
START 3, EPA Region 8	TDD No. 0608-07
Contract No. EP-W-05-050	Date: 05/2010
TABLE OF CONTENTS (continued)
7.2	Evaluation of Risk	7-3
7.2.1	Human Health Risk Assessment
7.2.2	Ecological Risk Assessment
7.3	Preliminary Remedial Action Objectives	7-4
8.0 LIST OF REFERENCES	8-1
FIGURES
(Note: Figures show date of preparation)
Figure 1-1	Site Location Map
Figure 1-2	Mine Claim Map
Figure 1-3	Map of Standard Mine
Figure 1-4	Standard Mine Workings Cross Section (Carpenter 1958)
Figure 1-5	Level 1 Pre-Removal Site Map
Figure 1-6	Level 1 Post-Removal Site Map
Figure 2-1	Meteorological and USGS Water Monitoring Stations
Figure 2-2	Monitoring Locations
Figure 2-3	Groundwater Monitoring Wells
Figure 3-1	Level 1 Adit Discharge Data
Figure 3-2	Level 2 Mine Workings (DRMS 2009)
Figure 3-3	Level 3 Mine Workings (DRMS 2007)
Figure 3-4	Level 5 Mine Workings (DRMS 2007)
Figure 3-5	Mean Daily Stream Flow - USGS Gauging Station 09111500
Figure 3-6	Mean Daily Stream Flow - USGS Gauging Station 09112200
Figure 3-7	Peak and Average Stream Flow - USGS Gauging Station 09111500
Figure 3-8	Peak and Average Stream Flow - USGS Gauging Station 09112200
Figure 3-9	Stream Flow Along Coal Creek
Figure 3-10	Stream Flow Along Elk Creek
Figure 3-11	Average Daily Flow Rate for Elk-00
Figure 3-12	Geological Map
Figure 3-13	Topographic Water Flow (USGS 2009b)
Figure 3-14	Water Levels in Groundwater Wells
Figure 3-15	Wetlands Map
Figure 4-1	Level 1 Adit Discharge Water Chemistry
Figure 4-2	Level 1 Adit Discharge Data
Figure 4-3	Soil Metal Concentrations
Figure 4-4	USGS pH
Figure 4-5	USGS Cadmium
Figure 4-6	USGS Copper
Figure 4-7	USGS Lead
Figure 4-8	USGS Manganese
Figure 4-9	USGS Zinc
Figure 4-10	Elk Creek Water Quality
Figure 4-11	Elk Creek Water Quality - Seasonal Variations
Figure 4-12	Elk Creek Sediment Quality
VI

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URS Operating Services, Inc.	Standard Mine - Remedial Investigation
START 3, EPA Region 8	TDD No. 0608-07
Contract No. EP-W-05-050	Date: 05/2010
TABLE OF CONTENTS (continued)
Figure 4-13	Coal Creek Water Quality
Figure 4-14	Coal Creek Water Quality - Seasonal Variations
Figure 4-15	Coal Creek Sediment Quality
Figure 4-16	Metal Loading Along Elk Creek
Figure 4-17	Metal Loading Along Coal Creek
TABLES
Table 2-1
Surface Water Monitoring Locations
Table 2-1A
EPA/USFWS/CDOW Surface Water Monitoring Locations
Table 2-IB
CCWC Surface Water Monitoring Locations
Table 2-2
Sediment Sampling
Table 3-1
Meteorological Data - Crested Butte
Table 3-2
Meteorological Data - Taylor Park
Table 3-3
Meteorological Data - Independence Pass
Table 3-4
Snotel Water Accumulation Data
Table 3-5
Monthly Average Stream Flow - USGS Gauging Station 09111500
Table 3-6
Monthly Average Stream Flow - USGS Gauging Station 09112200
Table 3-7
Monthly Average Stream Flow - USGS Gauging Station 365106106571000
Table 3-8
Annual Average and Peak Stream Flow - USGS Gauging Station 09111500
Table 3-9
Annual Average and Peak Stream Flow - USGS Gauging Station 09112200
Table 3-10
Annual Average and Peak Stream Flow - USGS Gauging Station 365106106571000
Table 3-11
Monitoring Locations
Table 3-12
Wetlands in the Study Area
Table 3-13
Observed Wetland Vegetation
Table 3-14
Observed Wetland Perimeter Vegetation
Table 3-15
Threatened and Endangered Species Occurrence in the Study Area
Table 4-1
Waste Rock and Tailings Chemistry
Table 4-2
Post-Removal Soil Chemistry
Table 4-3
Adit Discharge Water Chemistry
Table 4-4
Water Quality Standards
Table 4-5
Groundwater Chemistry
Table 4-6
Wetland Chemistry
Table 4-7
Fish Tissue Metal Concentrations
Table 4-8
Macroinvertebrate Tissue Metal Concentrations
Table 6-1
Summary of Chemicals of Concern
APPENDICES (Provided on Compact Disk)
Appendix A Colorado Division of Reclamation, Mining, and Safety Reports
A1 Underground Assessment Report - 2007
A2 Underground Assessment Report - 2009
A3 Standard Mine Drilling Report
Appendix B U.S. Geological Survey Reports
B1 Hydrogeochemical Investigation of the Standard Mine Vicinity
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE OF CONTENTS (continued)
Appendix C
Appendix D
Appendix E
Appendix F
Appendix G
Appendix H
B2 Geochemistry of Standard Mine Waters
B3 Characterization of Geologic Structures and Host Rock Properties
B4 Geophysical Characterization of Subsurface Properties
Water and Sediment Monitoring Data
Coal Creek Watershed, Water Quality Report - 2008
Summary Slug Test Report
Elk Creek Fish Habitat Evaluation
Baseline Human Health Risk Assessment
G1 Baseline Human Health Risk Assessment
G2 Baseline Human Health Risk Assessment Addendum
Baseline Ecological Risk Assessment
HI Baseline Ecological Risk Assessment
H2 Baseline Ecological Risk Assessment Addendum
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-050-05
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
LIST OF ACRONYMS
ABA
ARD
ATV
BCR
BERA
bgs
BHHRA
BOD
CCWC
CDOW
CDPHE
CDPS
CDW
CERCLA
cfs
COCs
CRCT
CTE
COPCs
DMG
DRMS
ECB
EE/CA
EPA
FDR
FS
GIS
GMUG
gpm
GPS
HGM
HI
HQs
HRS
IRIS
LIDAR
LOAEL
l-ig/L
m/s
(ig/dL
MCLs
mg/kg
mg/L
MGD
MRB
NCP
NDIS
NO A A
NPL
NRCS
ORP
Acid Base Account
Acid rock drainage
All Terrain Vehicle
Biochemical reactor
Baseline Ecological Risk Assessment
Below ground surface
Baseline Human Health Risk Assessment
Biological oxygen demand
Coal Creek Watershed Coalition
Colorado Division of Wildlife
Colorado Department of Public Health and Environment
Colorado Discharge Permit System
Colorado Division of Wildlife
Comprehensive Environmental Response, Compensation, and Liability Act of 1980
Cubic feet per second
Chemicals of Concern
Colorado River Cutthroat Trout
Central Tendency Exposure
Contaminants of Potential Concern
Colorado Division of Mining and Geology
Colorado Division of Reclamation, Mining, and Safety
Erosion control blanket
Engineering Evaluation/Cost Analysis
U.S. Environmental Protection Agency
Forest Development Road
Feasibility Study
Geographic Information System
Grand Mesa, Uncompahgre, and Gunnison National Forests
Gallons per minute
Global Positioning System
Hydrogeomorphic
Hazard Index
Hazard Quotients or Headquarters
Hazard Ranking System
Integrated Risk Information System
Light Detection and Ranging
Lowest Observed Adverse Effect Level
micrograms per liter
meters per second
micrograms per deciliter
Maximum Contaminant Levels
milligrams per kilogram
milligrams per liter
Million gallons per day
Manganese Removal Bed
National Contingency Plan
National Diversity Information Source
National Oceanic and Atmospheric Administration
National Priorities List
Natural Resource Conservation Service
Oxidation Reduction Potential
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No.
EP-W-050-05
PA
Preliminary Assessment
PEM
Palustrine Emergent (wetlands)
PVC
Polyvinyl chloride
QA/QC
Quality Assurance/Quality Control
RAOs
Remedial Action Objectives
RBCs
Risk-Based Concentrations
RBP
Rapid Bioassessment Protocol
RfC
Reference Concentration
RfD
Reference Dose
RI
Remedial Investigation
RI/FS
Remedial Investigation/Feasibility Study
RME
Reasonable Maximum Exposure
SAP
Sampling and Analysis Plan
SI
Site Inspection
SLERA
Screening Level Ecological Risk Assessment
SPLP
Synthetic Precipitation Leaching Procedure
START
Superfund Technical Assessment and Response Team
T&E
Threatened and Endangered
TCLP
Toxicity Characteristic Leachate Procedure
UOS
URS Operating Services, Inc.
USFS
United States Forest Service
USFWS
United States Fish and Wildlife Service
USGS
US Geological Survey
WQS
Water Quality Standards
WRCC
Western Regional Climate Center
WTP
Water Treatment Plant
XRF
X-Ray Fluorescence Spectrometer
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
1.0 INTRODUCTION
The URS Operating Services, Inc. (UOS) Superfund Technical Assessment and Response Team 3
(START) was tasked by the U.S. Environmental Protection Agency (EPA) to prepare this Remedial
Investigation/Feasibility Study (RI/FS) for the Standard Mine National Priorities List (NPL) site located
in Gunnison County near Crested Butte, Colorado. The Standard Mine was historically mined for silver,
lead, zinc, and copper. The mine is no longer in operation but still discharges metals-laden water. Site
soils contain high levels of arsenic, cadmium, chromium, iron, lead, manganese, and zinc. The Standard
Mine site was added to the NPL in August 2005.
The RI/FS was prepared in accordance with the Guidance for Conducting Remedial Investigations and
Feasibility Studies Under CERCLA, EPA OSWER Directive 9355.3-01 (U.S. Environmental Protection
Agency (EPA) 1988) and with the participation of the United States Forest Service (USFS), United States
Fish and Wildlife Service (USFWS), U.S. Geological Survey (USGS), Colorado Department of Public
Health and Environment (CDPHE), Colorado Division of Wildlife (CDOW), Colorado Division of
Reclamation, Mining, and Safety (DRMS), community groups such as the Standard Mine Advisory group
and the Standard Mine Technical Advisory Group, and stakeholders.
1.1	PURPOSE OF REPORT
The purpose of the Remedial Investigation (RI) is to determine the nature and extent of
contamination present at the site, to assess the risk posed to human health and the environment by
contaminants on site and flowing off-site, and to summarize current water quality conditions at
the site. The purpose of the Feasibility Study (FS), provided under separate cover, is to determine
potential cleanup options and to evaluate these options against the nine criteria specified in the
National Contingency Plan (NCP), 40 CFR 300.430(e)(9)(iii).
The RI/FS includes data collected prior to NPL listing, data collected for Removal Actions
conducted by EPA between 2005 and the present, and data collected solely for the RI/FS. The RI
presents information on site conditions both before and after completion of the Removal Actions
that included general site cleanup; dewatering of the tailings impoundment; removal of tailings
and most of the waste rock from Levels 1, 2, and 3 to an on-site repository; revegetation;
realignment of Elk Creek; and installation of surface water controls. Because the remediation of
the majority of the waste rock and tailings has already been completed, the FS focuses on options
for addressing adit discharges and reducing impact from waste rock piles at the higher mine
levels. The necessity and potential for reducing migration of contaminants from the mine
workings by treatment or by reducing the flow of clean water into the workings via source control
options (bulkheads, reducing contact between water and waste within the mine workings) were
also evaluated.
1.2	SITE BACKGROUND
1.2.1 Site Description
The Standard Mine is located in the Ruby Mining District in the Ruby-Anthracite Range
of west central Colorado at an elevation of approximately 10,900 to 11,600 feet above
mean sea level. It is approximately thirty miles northwest of Gunnison, Colorado, and
five miles west of Crested Butte, Colorado (Figure 1-1). The mine is in Section 35, T. 13
S., R. 87 W. at the 6th Principal Meridian, in Gunnison County, Colorado. The site is
located on the south side of Scarp Ridge, an east-southeast trending ridge on the
southeast flank of the Ruby Ridge (Science Applications International Corporation
(SAIC) 2002).
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
The Standard Mine is within the boundaries of the Gunnison National Forest. The mine
was privately owned and operated and is located on public and private land. The site can
be accessed by traveling west from Crested Butte approximately 1.7 miles on County
Road 12 (Kebler Pass Road), exiting onto private property owned by U.S. Energy
Corporation, traveling two miles to Forest Development Road (FDR) 732, and traveling
2.7 miles to the mine (Figure 1-1). Mine claims are shown on Figure 1-2. The land
surrounding the mine claims is part of the Gunnison National Forest.
The mine area drains into Elk Creek, which flows southeast to Coal Creek. Coal Creek
flows east toward the Town of Crested Butte. The Crested Butte municipal water intake
is located on Coal Creek approximately one mile downstream of the confluence with Elk
Creek. Copley Lake discharges into Elk Creek downstream of the site. The Mount
Emmons Project Water Treatment Plant (WTP) discharges into Coal Creek downstream
of the Elk Creek/Coal Creek confluence.
The Standard Mine has been
inactive since	1966.
Approximately ten acres were
left disturbed by past mining
activities at the site (Figure 1-3).
Disturbances include discharging
adits, a tailings impoundment,
waste rock piles, and mining
structures, including a concrete
pad, a gutted miner's bunkhousc.
a trestle with rails, ore bins, a
corrugated metal shed covering
the rails leading to the waste
rock piles, and inactive power
lines and poles.
The Standard Mine site includes
several discrete areas of mining disturbance: Level 1, Level 2, Level 3, Level 4, Level 5,
and Level 98 (Figure 1-3). The word "level" is not used here to indicate that the areas are
all part of one interconnected mine, but rather indicates different locations of mining
disturbance. The following table, prepared by DRMS, is a cross reference of mine names
(Colorado Division of Reclamation, Mining, and Safety (DRMS) 2007).
Common Name
CGS Numeric
Adit Name by
Adit Name by

Code
Elevation (feet)
Mine Level
Standard Mine
319-4305-2-100
11,000
1
Micawber Mine
319-4305-3-103
11,240
2

319-4305-3-104
11,320
3
Unnamed Mine
319-4305-5-103
11,560
5
Level 98 refers to the Elk Lode Mine. When EPA began work at the site in 2005, the site
consisted of the following primary surface features.
Level 1 Prior to Removal Action - Tailings
Impoundment in the Foreground
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
Level 1 is the most impacted area,
consisting of a tailings impoundment, waste
rock piles, mill site, railroad trestle, and a
discharging adit. Elk Creek flows through
Level 1. The Level 1 adit discharge flows
over waste rock to Elk Creek.
Level 2 consists of an intermittently
discharging adit and waste rock. The adit
discharge flows over waste rock to Elk
Creek. The adit discharges only during the
spring when runoff from snowmelt is high.
Level 3 consists of an open adit that does
not drain, and an associated waste rock pile
located on a steep slope.
Level 4 consists of two twin compartment
shafts and two associated waste rock piles.
Level 5 consists of a discharging adit and a
waste rock pile. The adit discharge flows over the waste rock across a road and into a
flourishing high alpine wetland.
Level 98 consists of a minimally discharging adit and a waste rock pile. The adit
discharge flows over the waste rock and into a wetland. A tributary of Elk Creek flows
past the toe of the waste rock
pile.
Small amounts of waste rock
are located elsewhere at the site.
Some of the mining
disturbances, including a
portion of the tailings
impoundment, waste rock piles,
the mill site, and the railroad
trestle of the Standard Mine,
are/were located on USFS
administered lands.
Due to EPA Removal Actions,
many of the above surface
features have changed since
2005. More information about each portion of the site, including conditions as of the
date of this report, is presented in Section 3.1.
The Standard Mine, located along the Standard fault, consists of a total of 7,250 feet of
drifts on six operating levels (Figure 1-4) (Carpenter 1958). The main portal at Level 1
accesses about 4,500 feet of workings on the main level and two sublevels between Level
1 and Level 2. Level 2 includes about 1,150 feet of workings and connects to Levels 1
and 3 by vertical raises. Level 3 includes about 800 feet of workings that connect to
Level 2 and Level 1 by vertical raises. Level 4 consists of two partially collapsed twin
compartment shafts from Level 3 to the surface. The Level 5 adit accesses about 800 feet
Level 1 Structures
Level 2 Prior to Removal Action
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
of workings and is not connected to the other levels. A fourth adit is located at Level 98
along the Elk Lode fault. The extent of workings associated with the Level 98 adit is
unknown, but does not appear to be extensive.
A former tailings impoundment covered approximately 'A acre of Level 1 below the mill
site and adjacent to Elk Creek. The impoundment had a notched spillway such that
overflow from the tailings pond would flow directly into Elk Creek. Four seeps
discharged water from the toe of the tailings impoundment dam. Water in the
impoundment was recharged by direct precipitation, site runoff, and seeps. The tailings
impoundment was removed by EPA during 2007 as part of the EPA Removal Action.
Figure 1-5 presents an aerial photograph of the tailings impoundment and other Level 1
surface features prior to the Removal Action.
Waste rock piles that were not part of the tailings impoundment are located throughout
the site. Several sulfide minerals including sphalerite, bornite, galena, chalcopyrite,
marcasite, and pyrite have been reported at the mine waste rock piles (SAIC 2002). Most
of the waste rock present at Level 1, Level 2, and Level 3 was taken to a nearby
repository during 2007 and 2008 as part of the EPA Removal Action (URS Operating
Services, Inc. (UOS) 2007).
Several high alpine wetlands are present throughout the site. A gossan and iron fen are
located downstream of the site (Figure 1-1).
1.2.2 Site History
1.2.2.1 Mining History
Mining activity began in the Ruby Mining District in Gunnison County,
Colorado, in 1874. There was a modest amount of activity and production
beginning in the 1880s though the early 1900s. It wasn't until the 1940s and
1950s that significant development and production took place at the Standard
Mine (also known as the Micawber Mine).
Records from the Colorado Bureau of Mines indicate that the Slate River Mining
Company (Slate River) began operating the Standard Mine in 1951. Slate River
was a Colorado corporation and a subsidiary of Standard Uranium Corporation
that was dissolved in 1959. Approximately 100 tons of lead, zinc, copper, silver
ore were produced on a monthly basis in 1951 and 1952 and were trucked to
Leadville, Colorado, and Salt Lake City, Utah. Standard Uranium Corporation
acquired ownership of the mine in 1957 and expanded the facilities, adding a
700-foot drift, an upper tunnel, and a 125-ton flotation mill. Records indicate
that in 1960, the mine produced 6,649 tons of lead zinc ore and the mill
processed 5,254 tons of ore to produce 304,995 pounds of zinc, 193,420 pounds
of lead, and 5,354 ounces of silver. The 1961 Minerals Yearbook (U.S. Bureau
of Mines 1962) reports that the Standard Mine was closed in September 1960.
In 1962 the mill was sold and moved to Breckenridge, Colorado, where it was
used at the Wellington Mine. Documents from the Colorado Bureau of Mines
indicate that in 1963 the Standard Mine was reopened for 31 days by a new
operator, Rocky Mountain Mining Company. Sporadic operations continued in
1964, 1965, and 1966 with Shumway & Dade Mining Company and Elk
Mountain Mining and Milling Corporation (Elk Mountain) being identified as
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operators in documents filed with the state. It appears that no further mining or
milling activities occurred at the Standard Mine after 1974 (EPA 2009).
1.2.2.2 Regulatory History and Removal Actions
The Standard Mine site was added to the NPL in August 2005 based on elevated
concentrations of metals in site soils and in Elk Creek. Since that time, EPA's
Remedial Program has initiated numerous site investigation activities. EPA's
Removal Program has conducted a Removal Assessment, Time-Critical Removal
Actions, and Non-Time-Critical Removal Actions to stabilize site conditions.
An Action Memorandum dated June 9, 2006, documents initial Removal Actions
at the Standard Mine. The Action Memorandum cited elevated levels of
contamination in waste piles and the tailings impoundment, erosion of the
tailings impoundment, and the potential for a failure of the tailings impoundment
that could cause mass loading of metals into Elk Creek and subsequently into
Coal Creek and Crested Butte's water supply as cause for a Time-Critical
Removal Action. Both human health and ecological risks were considered.
Erosion controls and sediment catch basins were installed on Elk Creek to reduce
the impact of site activities on water quality in the creek. Four-foot by two-foot
by two-foot concrete blocks were placed along both sides of Elk Creek from the
upper portion of Level 1 to the upstream boundary of the tailings pond to prevent
erosion of excavated materials into Elk Creek. A dam was placed in Elk Creek in
the upper portion of Level 1 using concrete blocks and a PVC liner to pool water
that could then be pumped around the site to allow construction within or
adjacent to the Elk Creek stream channel. Rolling dips and constructed ditches
were installed to convey water into ditches and prevent erosion along roadways.
Roads were improved throughout the site.
Surface water controls were installed to minimize contamination of Elk Creek
due to erosion and leaching of site wastes. Ditches were installed to convey
surface water around mill tailings and waste rock. The east bank of the upper
Level 1 area has several perennial uncontaminated seeps, so ditches were
installed to convey the clean seep water to Elk Creek to prevent additional
contamination from exposure to waste rock and mill tailings. Ditches were also
installed in lower areas near the tailings pond to prevent runoff from entering the
tailings pond. A sedimentation pond was installed to receive Level 1 adit
discharge water. Piping was installed to convey the adit discharge water from
this sedimentation pond directly to Elk Creek.
Surface water from the tailings impoundment was treated and discharged to Elk
Creek, but subsurface water remained. A liner was placed over the dewatered
tailings during the winter to prevent infiltration during subsequent precipitation
events and snowmelt in the spring.
An investigation conducted by DRMS and EPA found that the Level 1 adit was
blocked approximately 80 feet from the opening; this blockage was not removed.
Numerous mine-related structures, including a concrete service pad, the remains
of a miner's bunkhouse, a trestle with rails, a corrugated metal shed, and inactive
power lines and poles were demolished. The debris was sorted and recycled
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where possible. The remaining debris was removed to a nearby landfill during
2007.
A second Action Memorandum, dated July 10, 2007, documents Non-Time-
Critical Removal Actions, including construction of a waste repository,
excavation of source waste materials and transport to the repository, and site
re storation/re-vegetation.
The actions were based
on an Engineering
Evaluation/	Cost
Analysis (EE/CA) that
was prepared to facilitate
selection of removal
alternatives for the
tailings pond and waste
rock. The EE/CA was
performed in two phases.
The Phase I EE/CA
evaluated	several
potential repository
locations	(URS
Corporation (URS)
2007). The Phase II
EE/CA evaluated several
site specific design alternatives (UQS 2007).
A repository was constructed at a location within 0.4 mile of Level 1. The site
was selected for its favorable topography, easy access on improved roads,
minimal water presence, nearby talus that could be used for cover, availability of
soil borrow, and acceptability to stakeholders. Existing trees were harvested and
waste materials from Level 1, Level 2, and Level 3 were placed in the repository
during 2007 and 2008. After placement of approximately 35,000 cubic yards of
tailings and waste rock, the repository was graded to ensure effective drainage
then covered with at least 12 inches of soil that was then covered by at least one
foot of large rock.
After completion of waste removal, approximately 1,000 linear feet of Elk Creek
in the vicinity of Level 1 was realigned to its original, pre-mining location and
reconfigured to approximate conditions found immediately upstream and
downstream of the Standard Mine site. The new channel is a Rosgen A2/A3
type, which is steep and entrenched with cascading, step/pool flows that are
stabilized by bedrock and boulders. The boulders were placed to form vortex
weirs, which were installed across the new channel every 15 to 25 feet. Some of
the weirs were reinforced with large woody debris and used to create wetlands.
The final layout of Elk Creek is shown on Figure 1-6.
Approximately Zz acre of ecologically functional wetlands were created at the
location of the former tailings impoundment (Figures 1-5 and 1-6). The wetlands
were constructed to the side of Elk Creek with inlet and overflow channels
to/from Elk Creek. Numerous narrow "fringe" wetlands were constructed along
approximately 50 percent of the new channel. The new wetlands consist of both
palustrine emergent and palustrine scmb/shrub types. The wetlands slope gently
upward from the low flow channel of Elk Creek. The portions of the wetlands
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closest to the channel were reinforced with a biodegradable erosion control
blanket (ECB) to protect newly installed wetland plants from high velocity flows.
The area nearest the reconstructed creek was planted with 50,000 herbaceous
wetland plants per acre. The area immediately upgradient of the herbaceous
wetland plantings was planted with 5,600 willow cuttings per acre.
Soils that were impacted by the Removal Action, including native materials left
after excavation of waste rock and waste rock left in place (portions of the area
shown as north slope and northeast slope on Figure 1-6) were revegetated prior to
completion of the Removal Action. Soil conditions varied across the site;
therefore, revegetation included three major types of effort: treatment, cover
with native borrow soil, and no treatment. Native soils that were previously
covered by mine waste were reclaimed by amending the soils with lime, organic
matter, and fertilizer. Soils containing mine waste left in place were reclaimed
by amending the soils with lime and fertilizer and covering the resulting soil with
at least six inches of native borrow soil. The areas were seeded with a
combination of native seeds harvested from a location approved by the USFS and
slender wheatgrass seeds. Exposed bedrock, areas of bedrock covered with a
small amount of residual soil, and areas containing native materials that were not
impacted by the waste rock removal efforts were not revegetated. The
revegetation efforts were monitored in 2009 as part of the Removal Action.
Much of the revegetated areas demonstrated good seed germination and growth.
Bare areas were characterized to determine the cause for lack of vegetation and it
was determined that the bare areas were not adequately seeded or amended.
Actions to fix the deficiencies are planned for 2010.
1.2.3 Previous Investigations
Numerous investigations related to the Standard Mine and downstream water quality
have been performed by EPA and other organizations. EPA performed pre-remedial
investigations including a Preliminary Assessment (PA) and expanded Site Inspection
(SI). EPA's Removal Program conducted several investigations to document site
conditions, evaluate removal options, and plan for removal actions. A local community
watershed group and the USGS have also conducted surface water investigations. The
following sections provide an overview of these studies.
1.2.3.1	Preliminary Assessment
A PA for the Ruby Mining District, which includes the Standard Mine site, was
approved by the EPA on February 1, 1999 (UOS 1999). The PA presents a site
description and history, previous work, potential contaminant sources, and a
preliminary pathway analysis identifying how the contaminants might spread and
impact human health and the environment.
1.2.3.2	Expanded Site Inspection
An expanded SI was conducted during 1999 for the Ruby Mining District -
South, which includes the Standard Mine site (UOS 2000). The objectives of the
expanded SI were to determine source areas and contaminant characteristics of
the source areas within the mining district and evaluate the source areas by
Hazard Ranking System (HRS) criteria; evaluate contaminant migration through
the groundwater and surface water pathways; evaluate the impact on groundwater
and surface water receptor targets; determine if source areas are used
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recreationally or are adjacent to residences; and determine the potential impacts
to public health and the environment from source contaminants. Field sampling
was conducted in two phases: Phase I was conducted from June 21 to June 26,
1999, to coincide with high flow conditions of spring runoff, and Phase II was
conducted from September 20 to 24, 1999, to coincide with low flow conditions
of late summer. During the Phase I sampling, 55 environmental field samples
were collected including 16 surface water samples, 15 sediment samples, 2
groundwater samples, 13 soil and source samples, 4 mine water discharge or
source samples, and 5 quality assurance/quality control (QA/QC) samples.
During the Phase II sampling, 37 environmental field samples were collected and
included 16 surface water samples, 15 sediment samples, 2 groundwater samples,
1 mine water discharge, 1 impoundment water source sample, and 2 QA/QC
samples.
The SI concluded that cadmium, copper, lead, and zinc concentrations were at
elevated levels in Elk Creek immediately below the Standard Mine, and
continued to be present at elevated levels at the Crested Butte municipal intake,
through the town of Crested Butte, and to the last sampling station on Coal Creek
immediately before its confluence with the Slate River, for a total distance of
approximately 7.5 miles. The trail of these contaminants was traced back to the
Standard Mine where mine discharge water was documented to flow directly into
Elk Creek and mine waste rock was documented to be actively eroded by Elk
Creek. Waste rock sample results revealed levels of antimony, arsenic,
cadmium, copper, lead, selenium, silver, and zinc that were above those in
background samples from non-mineralized areas. Of those metals, zinc (600 to
21,000 milligrams per kilogram (mg/kg)) and lead (3,000 to 16,000 mg/kg) had
the highest concentrations. There are other contributing sources in the area, such
as the groundwater under Lake Irwin, the iron gossan and fen, and the Mount
Emmons Project WTP outfall.
1.2.3.3 Removal Investigations
Reports prepared to facilitate EPA's Removal Actions during 2005 through 2008
include a Tailings Dam Inspection Report (UOS 2005), 2006 Sampling Activities
Report (UOS 2006a), Conceptual Project Plan (UOS 2006b), Potential
Repository Site Evaluation (UOS 2006c), Trip Report (UOS 2006d), Phase I
EE/CA (URS 2007), Phase II EE/CA (UOS 2007), and Reclamation Plan (UOS
2008).
The Tailings Dam Inspection Report includes an assessment of the dam for
overall condition. The inspection did not identify items that required immediate
attention but noted poor drainage within the dam that could negatively impact
dam stability and discharge from the overflow spillway. The report
recommended additional study if the tailings dam were to be left in place (UOS
The 2006 Sampling Activities Report includes analytical data from samples
collected in October 2005 including mine waste rock and mill tailings (metals,
Synthetic Precipitation Leaching Procedure (SPLP) metals, and acid base account
(ABA) analysis), soil from two potential repository locations (metals analysis),
and mine adit discharge water from Levels 1, 5, and 98 (dissolved and total
metals, anions, alkalinity, and acidity analysis). A limited amount of historic adit
discharge water and tailings pond water quality data were presented in this
2005).
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report. Global Positioning System (GPS) data were collected for site features
such as waste rock piles and the tailings pond. The report also presents a cross
section of the Standard Mine workings, the abovementioned dam stability report,
waste rock and tailings volume estimate, estimated metal loading calculations,
and boring logs from Geoprobe® borings (UOS 2006a).
The Conceptual Project Plan describes Time-Critical Removal Actions planned
for Summer 2006 (UOS 2006b).
The Potential Repository Site Evaluation Report identifies five potential
repository locations near the Standard Mine site based on Geographic
Information Systems (GIS) analysis, field testing, and visual observations. The
criteria used to identify potential repository sites included topography, size,
aesthetics, bedrock geology, hydrology and hydrogeology, cultural features,
vegetation, and distance from Level 1. The report discusses the logistical,
geologic, biologic, and cost considerations for the location of an on-site
repository (UOS 2006c).
The Trip Report includes flow rates and analytical results of samples collected
from Coal Creek and Elk Creek in April 2006 during spring runoff conditions
(UOS 2006d).
The Phase I EE/CA further evaluated the potential repository locations during a
geologic, ecologic, and engineering site reconnaissance to ground-truth the GIS
evaluation, identify site features that could negatively affect a site's use as a
repository, identify potential construction material borrow sources, and evaluate
the presence or absence of wetlands, other waters of the United States, and
threatened and endangered species at the potential repository and borrow sites.
This information was used to refine the list of potential repository sites. Site
investigations performed for the EE/CA included excavating test pits, collecting
soil and/or rock samples, and geotechnical laboratory testing to further refine the
list of potential repository sites (URS 2007).
The Phase II EE/CA evaluated four potential repository capping alternatives and
two potential repository locations that could accept approximately 80,000 cubic
yards of site wastes from Standard Mine Levels 1, 2, and 3 (UOS 2007).
The Reclamation Plan was prepared to guide removal reclamation activities,
including stream reconstruction, wetlands construction, and upland soil
revegetation (UOS 2008).
1.2.3.4 USFS Investigations
An EE/CA that was prepared in 2002 for the USFS, Rocky Mountain Region,
used data collected during the 1999 EPA expanded SI and evaluated five removal
alternatives: adit and shaft closure; excavation, consolidation, and disposal of
mill tailings in an on-site cell; excavation, consolidation, and disposal into an on-
site cell of the portion of mill tailings and waste rock material that are located in
close proximity to Elk Creek; treatment of acid rock drainage from the Level 1
adit using a bioreactor; and excavation and disposal in a permitted off-site facility
(SAIC 2002). The removal action objectives identified by the USFS were to
minimize safety hazards associated with open mine shafts and adits and to
improve the degraded water quality associated with waste rock piles and acid
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rock drainage discharged from the Level 1 adit. The EE/CA concluded that
further evaluation was needed prior to selecting a removal alternative (SAIC
2002).
The Colorado Geological Survey conducted an investigation of the area under
USFS direction in August 2004. This work included documenting the history of
mining activities and the collection of waste rock and adit discharge water
samples. The report provides a geologic description, history of site mining
activities, identification of the various mining claims, identification of minerals
mined at the site and the fault lines pursued during mining (Colorado Geological
Survey (unpublished)). At this time, only the draft report is available and it
presents limited information about the investigation.
1.2.3.5	Coal Creek Watershed Coalition Investigations
The Coal Creek Watershed Coalition (CCWC) prepared a Watershed Protection
Plan and Sampling and Analysis Plan (SAP) describing efforts to reduce non-
point source pollution and achieve water quality standards in the watershed
(Stantec Consulting, Ltd. (Stantec) 2005a; Stantec 2005b). The Watershed Plan
provided management strategies to achieve the goal of water quality standards in
the watershed. One identified strategy was to reduce most of the metal load from
the Standard Mine site. Other management strategies included identification of
additional mines, reducing erosion from roadways, and erosion control plans for
all construction sites. The goal of the CCWC was to: "Restore the health of
aquatic life and habitat, and protect other water uses in the Coal Creek watershed,
which have been impaired due to metals and other pollutant loading from point
and nonpoint sources." The CCWC identified exceedances of aquatic stream
standards in Segment 11 for cadmium, copper, lead, manganese, and zinc. The
report contained the results of synoptic samples collected on Coal Creek and
tributaries in June 1999 and August 2004.
The SAP describes sampling efforts conducted monthly beginning in June 2006.
The objectives of the ongoing water quality monitoring program were to evaluate
surface water quality in Coal Creek and drainages to Coal Creek; measure stream
flows in Coal Creek and associated drainages; assess the quantity and quality of
drainage from the Standard Mine site; identify the quantity and quality of
drainage from waste rock in areas other than Standard Mine; and to evaluate the
biological health of Coal Creek throughout the watershed. The CCWC sampling
efforts were supplemented during selected times of the year by EPA monitoring
efforts. To avoid duplication, CCWC did not perform water quality sampling
during months when EPA performed sampling. Because the EPA and CCWC
data are interlinked, both data sets are included in the water quality evaluation
presented in Sections 2, 3, and 4 of this document.
1.2.3.6	Other Investigations
A tracer study was performed by a University of Colorado student on Coal Creek
during September 2005 and June 2006. The study was designed to determine
points of metal loading to Coal Creek. The report quantifies surface and
hyporheic flow and provides spatially detailed concentration and metal loading
profiles. The report identifies the water draining from the iron fen and gossan
near Mount Emmons Project Mine as the largest metal contributor in the
watershed. It was a major source of aluminum, cadmium, iron, manganese, and
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zinc to Coal Creek. Elk Creek was identified as a major source of cadmium and
zinc to Coal Creek. An unnamed tributary was identified as a major source of
chromium, iron and nickel to Coal Creek (Shanklin and Ryan 2006).
Based on water quality data for the watershed, Colorado Water Quality Control
Commission Regulation 35, Upper Gunnison River Basin, Segments 11 and 12
are included on Colorado's 303(d) list. Segment 11, Coal Creek from Elk Creek
to the Crested Butte water supply intake, including Elk Creek, is impaired by
cadmium, lead, and zinc; and Segment 12, Coal Creek and tributaries from the
Crested Butte water supply intake to Slate River is impaired by zinc. Both are
listed as high priority segments (Colorado Department of Public Health and
Environment (CDPHE) 2008a).
1.3 REPORT ORGANIZATION
This RI report includes a summary of the investigations used to evaluate site conditions (Section
2), a description of the physical characteristics of the site (Section 3), the results of site
characterization regarding the nature and extent of contamination (Section 4), an evaluation of
contaminant fate and transport (Section 5), and a description and summary of the evaluation of
site risk to human health and the environment (Section 6). A summary of the remedial
investigation and proposed Remedial Action Objectives (RAOs) is presented in Section 7.
The Feasibility Study (FS), provided under separate cover, includes a summary of the RI (Section
1), RAOs, Applicable or Relevant and Appropriate Requirements, and Preliminary Remediation
Goals (PRGs) (Section 2), identification and screening of technologies to meet the remedial
action objectives (Section 3), development and screening of alternatives (Section 4), detailed
analysis of alternatives (Section 5), comparison of alternatives (Section 6), and the preferred
alternative (Section 7). A description of treatability studies is included in FS Section 3.
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Standard Mine
Level 1
JATIONAI
Mt. Emmons
Project WTP
Access Road
FDR732
Crested Butte
Iron Fen
Elk Creeki
Coal Creek
Figure 1-1 Site Location Map
Standard Mine
Gunnison County, CO
Mine Road
Elk Creek 4x4 Road
Intermittent Stream
Perennial Stream
Date: March 8, 2010
Splains Gulch
Map Projection: UTM, Meters,
Zone 13N, NAD 83.
Area Enlarged
Data Sources: Mine & 4x4 Road -
USEPA Region 8 (2005); Supplemental Streams
CDOW (2004); NGS Topographic Base - ESRI (2010).
1 Miles

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.Level 98
Level 5
Level 4
Level 3
Level 2
Level 1
Standard Mine
Gunnison County, CO
Figure 1 -2 - Mine Claim Map
Land Surrounding Claims
Gunnison National Forest
ICS - START 3
TDD Nd. 0608-07
March 2010

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Created: 1/29/2009 12:32:07 PM Drawn By:andrew_longworth
File Location: T:\START3\Standard_Mine\GIS\Projects\RIFS_09\Figure2_MapOfSM.mxd
LEVEL 98
LEVEL 99
LEVEL 4
LEVEL 3
LEVEL 1
FS2 (Repository)
Legend
;^J Levels Boundary
Mine Roads
Repository Boundary
Standard Mine
Gunnison County, CO
Figure 1-3 - Map of Standard Mine
Feet
SOURCE:
SPECTRUM 2006 (AERIAL IMAGE)
UOS - START 3
TDD No. 0608-07
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,000
N 65* 49' W £
TOO 200 30n
Source:
Carpenter 1958
u u mm**
(sss)	^
OPERATHG SERVICES
Standard Mine,
Gunnison County
Figure 1-4: Standard Mine
Workings Cross Section
©
UOS- START 3
TDD No. 0608 -07

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URS
Standard Mine
Gunnison County, CO
Figure 1-5: Level 1 Pre-Removal
Site Map
1 inch equals 100 feet
SOURCE:
SPECTRUM 2006 (AERIAL IMAGE)
UOS - START 3
TDD No. 0608-07
March 2010

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North
Elky
Creek
Northeast
Slope
Legend
Level 1 Adit
Elk Creek - 2006 Alignment
Elk Creek - New Alignment
Wetland
Wetland
Clean Fill over treated native soil/waste rock
Treated Native Soil
Passive Treatment System

Standard Mine
Gunnison County, CO
1 inch equals 103 feet
Figure 1-6 Level 1 Post-Removal Map
SOURCE:
SPECTRUM 2006 (AERIAL IMAGE)
UOS - START 3
TDD No. 0608-07
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2.0 SITE INVESTIGATIONS
This section describes the investigations performed specifically for the RI. In some cases, the results of
previous studies are presented in later sections of this report and the sources of the data are presented
here.
2.1	SURFACE FEATURES
Site features were mapped using a GIS database. GIS was also used for site interpretation.
Mapping includes base features such as geologic and topographic maps and aerial images plus
contouring and site feature data collected during the site investigation. Light detection and
ranging (LIDAR) technology was used to create a grid of elevations that were used to create
contour maps and to allow more accurate characterization of physical features. Site features were
identified with GPS units.
The following features are available in the GIS database. Many of these features are presented in
maps in this RI/FS.
•	1:24,000 quadrangle map (USGS 1961a; USGS 1961b)
•	Geological map (USGS 1967)
•	Faults
•	Aerial images (Spectrum Mapping 2006)
•	2-foot, 1-foot, 20-foot and 1-meter contours
•	Mining claims (Schaaf and Associates)
•	Access roads
•	Buildings
•	Soil sample locations
•	Surface water sample locations
•	Groundwater well locations
•	Waste rock piles
•	Tailings pond areas
•	Wetland locations
•	Calculated viewshed for potential repository locations
•	Repository contours
•	Seeps
•	Piezometers
•	Elk Creek alignment
•	Reclamation features
•	Vegetation
•	Wetlands
Additional layers specific to the evaluation of repository locations are also available.
2.2	CONTAMINANT SOURCES
Contamination emanates from materials excavated from the mine but left on site and from
leaching of exposed minerals within the mine workings. Additional contamination may have
been present in mine and mill infrastructure and supplies brought to the site during historic
mining operations. This section describes studies performed to investigate sources of
contamination related to mining at the Standard Mine. Natural sources of contamination were
also investigated as described in Section 2.8.
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2.2.1	Waste Rock and Tailings
On-site materials that had been excavated from the mine but left on site were evaluated in
several stages. Aerial photos and site reconnaissance were used to identify source
locations (Figure 1-3). Preliminary samples of the waste materials were collected for the
expanded SI (UOS 2000). Thirteen soil samples were collected from the Standard Mine
and surrounding area and submitted to a laboratory for total metals analysis. Six of the
samples were from the Standard Mine site, and the remaining soil samples were collected
from other parts of the Coal Creek drainage including two samples that were collected to
demonstrate "background" conditions, two samples from the Mount Emmons Project
Mine property, and one sample from the iron fen.
Soil samples were collected from tailings piles during 2005 for a Removal Assessment
(UOS 2006a). Thirteen samples were collected from seven distinct areas (Levels 1
through 5, Level 98, and Level 99, a small area that was not investigated further). The
samples were analyzed for total metals, SPLP metals, and ABA.
The mine site soils were more thoroughly evaluated and delineated in July 2006 to
support the Baseline Human Health Risk Assessment (BHHRA) and the Baseline
Ecological Risk Assessment (BERA) (See Section 6) (TechLaw 2007). An initial
assessment of the extent of soil contamination was made based on visual observations.
The area included Levels 1, 2, 3, 4, and 98. Sampling locations were based on a
triangular grid pattern with nodes spaced approximately 50 feet apart along the perimeter
and within the site boundary. The grid was extended approximately two sampling points
outside of the estimated boundary. Samples were collected from the surface to two
inches below ground surface. Soil samples were screened for total metals using an
X-Ray Fluorescence Spectrometer (XRF) and key samples were also submitted to an
independent laboratory for metals analysis to confirm the XRF results. Additional
samples were extended farther outside the estimated boundary if field analytical results
indicated lead concentrations greater than 400 mg/kg and arsenic concentrations greater
than 100 mg/kg. Subsurface samples were collected at 10 discrete locations along the
perimeter of the site at depths of 2 inches to 6 inches and 6 inches to 18 inches.
Post-removal soil samples were collected during July 2009 to support the evaluation of
risks to human health and the environment under post-removal conditions (Syracuse
Research Corporation, Inc. (SRC) 2009).
2.2.2	Mine Workings and Adit Discharges
The mine workings are the second primary source of contaminants at the site. DRMS
Inactive Mine Site Field Forms provide locations, descriptions, dimensions, and
preliminary closure recommendations for approximately 20 mine adits and shafts in the
vicinity of the Standard Mine (Colorado Division of Mining and Geology (DMG) 2003).
During August 2006, DRMS and USGS performed a mine entry to Levels 3 and 5 to
make hydrologic and geologic observations and collect water samples. The investigation
of the sources was limited by the inability to access all areas of the mine. Collapses at or
near the portals of Levels 1 and 2 prevented entry into these tunnels. The work is
documented in two reports that include mine workings maps for Levels 3 and 5 (DRMS
2007 (Appendix A); USGS 2007 (Appendix B)).
During July 2009, an additional mine entry was undertaken by DRMS and USGS to
characterize the mine workings and the sources of metals in the adit discharges. A
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DRMS report describes the observations from the July 2009 mine entry and provides a
mine workings map for Level 2 (DRMS 2009). A USGS report documents the
geochemistry of waters sampled from within the mine workings relative to adit
discharges, seeps, and Elk Creek (USGS 2010a). The scopes of these studies are
described more fully in Sections 2.5 and 2.6.
A flume was installed during October 2006 to measure flow from the Level 1 adit and
instrumentation was added to allow real-time monitoring of water flow rate, conductivity,
and temperature. Data are sporadic because of difficulties in data collection and
transmission during winter conditions.
Adit discharge samples were collected for the expanded SI, the Removal Assessment,
ongoing site-wide surface water monitoring, and the biochemical reactor (BCR)
treatability study described in FS Section 3. Samples were collected from the Level 1
adit discharge during June 1999 and September 1999 for the expanded SI (UOS 2000).
The samples were analyzed for total and dissolved metals. Adit discharge samples were
collected from Level 1, Level 5, and Level 98 during October 2005 for the Removal
Assessment (UOS 2006a). The samples were analyzed for dissolved metals, pH, and
conductivity. Level 1 adit discharge water samples were collected as part of the long
term site wide surface water monitoring described in Section 2.4. Adit discharge samples
from Levels 5 and 98 were collected during the September 2007, September 2008, and
September 2009 surface water monitoring events. A sample from the Level 5 adit was
also collected during the June 2008 surface water monitoring event. Samples collected
during the site wide surface water monitoring events were analyzed for total and
dissolved metals, pH, and conductivity (TechLaw 2009a). Additional Level 1 adit
discharge samples were collected as part of the BCR pilot scale treatability study. The
samples were analyzed for total and dissolved metals, sulfate, acidity, alkalinity, pH,
sulfide, biological oxygen demand (BOD), nitrate/nitrite, oxidation reduction potential
(ORP), dissolved oxygen, conductivity, and temperature (Golder Associates, Inc. 2009).
2.3 METEOROLOGY
Meteorological data for Crested Butte is available from the National Oceanic and Atmospheric
Administration (NOAA) and the Western Regional Climate Center with a period of record from
1909 to 2007 (Western Regional Climate Center (WRCC) 2009). Additional monitoring stations
are located near Taylor Park with a period of record from 1940 to 2007 and Independence Pass
with a period of record from 1947 to 2007. The Taylor Reservoir and Independence Pass data
were included to show variations that may be expected due to altitude.
Additional information is available from Snotel stations that are generally located at elevations
greater than 9,500 feet. The Snotel data are included in this report because they contain daily
readings for each water year, allowing a comparison of data between years. The Snotel stations
record daily minimum and maximum temperatures (period of record since 1986), snow water
equivalent (period of record since 1986), and accumulated precipitation (period of record since
1980). The nearest Snotel stations are the Butte (Site #380, Station ID 06111s, elevation 10,160),
Park Cone (Site #680, Station ID 06102s, elevation 9,600), Independence Pass (Site #542, Station
ID 06k04s, elevation 10,600), and Schofield Pass stations (Site #737, Station ID 07klls,
elevation 10,700) (Figure 2-1). The period of record for most of the Snotel data is from 1969 to
the present; however, the accumulated precipitation data typically available for these stations are
from 1980 or 1981.
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The Crested Butte Mountain Resort reports their average snowfall on their website:
http: //www. skicb.com/cbmr/mountain/mountain-stats. aspx (Crested Butte Mountain Resort
2009).
2.4 SURFACE WATER AND SEDIMENT
Surface water flow rate and water quality monitoring has been performed by the CCWC and EPA
since 2005. Surface water field parameter measurements and water quality samples were
collected by EPA-led monitoring events and CCWC-led events. Sediment and pore water were
also collected during some EPA-led monitoring events. The following sections describe the data,
including water flow, surface water quality, pore water quality, and sediment quality, that was
collected during each sampling event.
2.4.1 Surface Water
Surface water flow measurements are available for three USGS Monitoring Stations near
Crested Butte (Figure 2-1).
USGS 385106106571000
SLATE R AB BAXTER GL @ HWY 135 NR CRESTED BUTTE CO
Gunnison County, Colorado
Hydrologic Unit Code 14020001
Latitude 38o51'06", Longitude 106°57'10" NAD27
Drainage area 73.4 square miles
Gage datum 8,810 feet above sea level NGVD29
Station 385106106571000 has data for 2006 through the present.
USGS 09112200
EAST RIVER BL CEMENT CREEK NR CRESTED BUTTE, CO.
Gunnison County, Colorado
Hydrologic Unit Code 14020001
Latitude 38°47'03", Longitude 106°52'13" NAD27
Drainage area 238 square miles
Contributing drainage area 238 square miles
Gage datum 8,440.00 feet above sea level NGVD29
Station 09112200 has data over a period of record from October 1, 1963, to the present.
USGS 09111500
SLATE RIVER NEAR CRESTED BUTTE, CO
Gunnison County, Colorado
Hydrologic Unit Code 14020001
Latitude 38°52'11", Longitude 106°58'08" NAD27
Drainage area 68.9 square miles
Gage datum 8,820 feet above sea level NGVD29
Station 09111500 has data over a period of record of 1940 to 1951 and 1993 to 2006.
Data from all three USGS stations were used because the period of record for station
09111500 ends in 2006, and station 09112200 is located farthest from the site (National
Water Information System (NWIS) 2009). Data from station 385106106571000 is not
presented here because of the limited period of record.
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Surface water monitoring was conducted by representatives of EPA, USFWS, and
CDOW on Elk Creek and Coal Creek on the following dates:
June 13, 2005
September 26, 2005
June 19 through 23, 2006
July 17 through 21, 2006
September 11 through 15, 2006
June 11 through 13, 2007
September 17 through 20, 2007
June 23 through 25, 2008
September 15 through 17, 2008
June 22, 2009
September 14 and 15, 2009
Samples were collected on Elk Creek from the headwaters at the Standard Mine site to
the confluence with Coal Creek and on Coal Creek upstream of Elk Creek to the
confluence with the Slate River. Sampling locations are shown on Figure 2-2. Flow
rates associated with each surface water sample location were measured and field
parameters including pH, temperature, conductivity, and dissolved oxygen were
measured and recorded. Flow measurements were collected using a Marsh-McBirney
flow meter at all stations along Coal Creek and Elk Creek with the exception of Elk-00
where a flume and data logger were installed to collect more frequent and accurate flow
measurements. Water samples were analyzed for total and dissolved metals, anions,
alkalinity, dissolved organic carbon, and hardness. The locations sampled during each
sampling event are shown on Table 2-1 A. The sampling and analysis methods and
analytical results are presented in the 2006, 2007, and 2008 Sampling Activities Reports
(TechLaw 2007; TechLaw 2008; Tech Law 2009b). The 2009 results are not yet
published but are available in EPA's Scribe database for the Standard Mine site
(Appendix C).
The CCWC has monitored streams in the watershed between EPA sampling events.
Sampling was performed in accordance with a Sampling and Analysis Plan (Stantec
2005b). Additional surface water field parameter measurement, stream flow
measurement, and water quality sampling was conducted by CCWC on the following
dates.
June 2006
August 2006
October 2006
March/April 2007
May 2007
August 2007
September 2007
October 2007
February 2008
March 2008 (Runoff samples)
April 2008
May 2008
June 2008 (Standard Mine Level 1 Adit Samples)
August 2008
September 2008
October 2008
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February 2009
April 2009
August 2009
October 2009
The locations sampled during each event are shown on Table 2-1B. The samples were
analyzed for total recoverable and dissolved metals. The analytical results are available
in EPA's Scribe database for the Standard Mine site (TechLaw 2009a). During one
CCWC sampling event that began in March 2008, samples were collected at one location
over a period of time to quantify conditions during spring runoff. Water quality data is
summarized in the 2008 Coal Creek Watershed Water Quality Report (Coal Creek
Watershed Coalition (CCWC) 2009) (Appendix D).
Fifteen water samples were collected during June 1999 and sixteen samples were
collected during September 1999 from Coal Creek and tributaries for the expanded SI.
The samples were analyzed for total and dissolved metals (UOS 2000).
Sixty water samples were collected as part of a low-flow tracer study conducted during
fall 2005. The samples were analyzed for pH, total organic carbon, calcium, magnesium,
hardness, and metal concentrations. Individual data points are not available; however,
there is a comparison of metal loading rates to Coal Creek from various sources in the
watershed (Shanklin and Ryan 2006).
Data regarding the Mount Emmons Project WTP effluent was obtained from the
Colorado Discharge Permit System (CDPS) (Colorado Department of Public Health and
Environment (CDPHE) 2007).
Current uses of the surface waters within the Coal Creek watershed are presented in the
Coal Creek Watershed Protection Plan (Stantec 2005a).
2.4.2 Sediment
Sediment samples were collected to determine contaminant loading in streambed
sediments (TechLaw 2007; TechLaw 2008; TechLaw 2009).
September 28, 2005
July 17 through 21, 2006
September 11 throughl5, 2006
September 17, 2007
September 15, 2008
September 14, 2009
The locations sampled during each event are shown on Table 2-2. The sampling and
analysis methods and analytical results are presented in the 2006, 2007, and 2008
Sampling Activities Reports (TechLaw 2007; TechLaw 2008; TechLaw 2009b). The
analytical results are also available in EPA's Scribe database (TechLaw 2009a).
Fourteen sediment samples were collected during June 1999 and fifteen samples were
collected during September 1999 from Coal Creek and tributaries for the expanded SI.
The samples were analyzed for total metals (UOS 2000).
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2.4.3 Pore Water
Pore water was sampled to evaluate potential ecological impacts to the existing biological
agents in the streambed (TechLaw 2007; TechLaw 2008). Pore water samples were
analyzed for anions, alkalinity, dissolved organic carbon, and dissolved metals.
July 17 through 21, 2006
September 15, 2008
September 14, 2009
The sampling and analysis methods and analytical results are presented in Sampling
Activities Reports (TechLaw 2007; TechLaw 2009b). The analytical results are also
available on EPA's Scribe database (TechLaw 2009a).
2.5 GEOLOGY
Information regarding the site geology was summarized in the hydrologic investigation of the
Standard Mine vicinity (USGS 2007) that is described in Section 2.6. Additional information on
the site geology was obtained from the Colorado Geological Survey report described in Section
1.2.3.4 (Colorado Geological Survey (unpublished) and USGS geological maps (USGS 1967;
USGS 1987).
During 2007, the USGS and DRMS performed an underground assessment of the Standard Mine.
The accessible portions of the mine were mapped, noting subsurface geology and important
mining-related features and conditions likely to impact remediation actions (DRMS 2007).
Further underground assessment was performed during 2009 to acquire additional information
regarding the structure of the Level 2 mine workings (DRMS 2009).
During 2009 the USGS performed a study to locate and characterize geologic structures and
associated mineralogy within Elk Basin. The purpose of this study was to evaluate the geology
and geologic structures at the site and determine what influence they might have on the
groundwater flow system. In particular, the purpose of the study was to evaluate the likelihood
that the Standard fault-vein might act as a conduit for the flow of near-surface groundwater
downward to the mine workings. Two main fault traces were identified for further examination:
the Elk Lode fault and the Standard fault. Both of these faults were observed cutting through the
two main sedimentary rock units exposed in the basin, the Ohio Creek formation and a younger-
aged Wasatch Formation. The two faults were previously believed to be major conduits for
surface water interacting with groundwater, and in turn, contributing to the large amounts of
water infiltrating the Standard mine workings (USGS 2010b).
The study focused on characteristics and properties that may affect subsurface water flow and
contaminant transport. Reconnaissance mapping of faults and other geologic features was
performed using real time kinematic GPS equipment. The results were used to update the
existing USGS geological maps. The fault zone was identified and the core and damage zones
were sampled and characterized. A borehole that was installed at the same time as groundwater
wells (see Section 2.6) and used to supplement the hydrogeological investigation was logged,
including the measurement of the orientation and intensity of joints, faults, veins, bedding, and
other features. The core from the well was logged for detailed lithology, mineralogy,
hydrothermal alteration, and structural characterization and was sampled. Intergranular porosity
and permeability were measured in a limited number of samples from the Ohio Creek bedrock,
Wasatch bedrock, and the clay-rich gouge from the Standard fault-vein. Minerals were identified
in the field and some were collected and analyzed to characterize hydrothermal alteration,
mineralization, and leaching of metals from the rocks. Surface and subsurface observations,
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fault-vein and fracture network characterization, borehole geophysical logging, and mercury
injection capillary entry pressure data were used to document potential controls on the hydrologic
system.
A geophysical study was conducted by the USGS to increase understanding of the hydrogeologic
controls in the basin and how they influence surface and groundwater interactions with the mine
workings (USGS 2010c). Surface geophysical data collection included (1) electrical resistivity
profiles aimed at imaging variability in subsurface structures and fluid content; (2) self-potentials,
which are sensitive to mineralized zones at this site and, to a lesser extent, shallow flow patterns;
and (3) magnetic measurements, which provide information on lateral variability in near-surface
geologic features. Data acquired from the geophysical study were used in conjunction with
geological data to enhance the understanding of subsurface conditions.
The DRMS and USGS studies are provided in Appendix A and Appendix B, respectively.
2.6 HYDROGEOLOGY
In addition to the tasks described in Section 2.5, the 2006 and 2009 USGS and DRMS
underground assessments of the Standard Mine investigated site hydrogeology, including
subsurface sampling, observations of mining related features and conditions likely to impact
remediation actions, and mapping of water inflow points and water impoundments within the
mine workings (DRMS 2007; DRMS 2009; USGS 2007; USGS 2010a; USGS 2010b).
Groundwater in the immediate vicinity of the Standard Mine was investigated by the USGS in
2006 (USGS 2007). Groundwater and surface water samples were collected to characterize the
local groundwater flow system, determine metals concentrations in groundwater, and better
understand factors controlling the discharge of metal-rich waters from the mine. The
investigation included one-time sampling of springs, adits, and exploration pits in Elk Basin and
Redwell Basin to the north, repeated sampling of the Level 1 discharge and Elk Creek near the
Coal Creek confluence, and one-time sampling of underground sites in Standard Mine Levels 3
and 5. Samples were analyzed for major ions and trace elements, deuterium and oxygen-18
isotopes, strontium isotopes, tritium, and dissolved noble gases (including helium isotopes) for
tritium/helium-3 age dating. Additional information regarding this study, including sampling and
analytical methods, data, and data analyses are provided in the USGS Scientific Investigations
Report (USGS 2007).
A follow-on study was performed by USGS during 2009 (USGS 2010a). The purpose of the
2009 geochemistry study was to further the evaluation of the source of elevated metal
concentrations in the Level 1 adit discharge. The 2006 study had shown a significant increase in
metal concentrations in the Level 1 adit discharge compared to concentrations in the Level 3
tunnel. The mine workings between Level 3 and Level 1 were identified as a likely source of the
contamination, but the Level 2 workings were not accessible during the 2006 mine entry, limiting
the evaluation of the source of the elevated metals concentrations. The 2009 study included
evaluation of water chemistry in samples collected from the Level 1 and Level 5 adit discharge,
underground sample points in Levels 2 and 3, two springs, and Elk Creek. The adit discharge
samples, spring samples, Elk Creek sample, and Level 3 tunnel samples were collected at the
same locations as were sampled in 2006. Samples were analyzed for field parameters (pH,
specific conductance, dissolved oxygen, redox potential, and water temperature), major
constituents, trace elements, and hydrogen and oxygen isotopes.
The USGS geological structures and geophysics studies described in Section 2.5 provided
additional insight regarding site hydrogeology (USGS 2010b; USGS 2010c).
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Seven wells were installed in the vicinity of and uphill from the Level 3 adit during September
2008 to evaluate the shallow groundwater system near the Standard Fault and assist in evaluation
of potential Remedial Actions. Both shallow wells (B-2, B-3, B-4, B-6, and B-7) and deep wells
(B-l and B-5) were installed. An additional boring (B-8) was installed by core drilling in an
attempt to intersect the mine workings at depth. The core was logged in the field and
subsequently analyzed by USGS (USGS 2010b). The B-8 boring was not finished as a
monitoring well but was left open for subsequent analysis by USGS (USGS 2010b). Well
locations are shown on Figure 2-3. A well drilling report was prepared by the driller, Shannon
and Wilson, for DRMS (Shannon and Wilson 2008 (Appendix A)). Transducers with dataloggers
were installed in the seven monitoring wells during October 2008 to allow evaluation of the depth
of groundwater in each well on an hourly basis. The wells were sampled during October 2008,
April 2009, June 2009, August 2009, and September 2009. Field data collected during sampling
include pH, conductivity, and temperature. The samples were submitted to the EPA laboratory
for analysis of dissolved metals concentrations and total metals concentrations.
Slug tests were performed in two of the groundwater wells (B1 and B5) to estimate the hydraulic
conductivity of the bedrock. The untested wells did not contain enough water during July 2009 to
conduct the tests. Well B-l was constructed in sandstone, siltstone, and mudstone of the Wasatch
Formation. Well B-5 was constructed in sandstone and claystone of the Wasatch Formation.
General limitations of slug test data include measurements that are only of the immediate area
around the borehole and may be more representative of well construction, well development and
alteration of strata (e.g., borehole smearing) than formation conductivity. In addition, assumptions
made during data processing significantly affect the reported hydraulic conductivity (UOS 2009
(Appendix E).
2.7	DEMOGRAPHY AND LAND USE
Demographic information was obtained from the Coal Creek Watershed Protection Plan (Stantec
2005a).
2.8	ECOLOGY
EPA, USFWS, and CDOW performed ecological investigations in addition to surface water
monitoring during specific surface water sampling events from 2005 through 2009. Additional
ecological investigations were performed as part of the Removal Actions. The following sections
describe the ecological investigations performed at the Standard Mine site.
2.8.1 Wetlands
Wetlands near the Standard Mine site were investigated in 2006 to support the Removal
Actions, specifically to describe the biological resources in and around the Standard Mine
site that may be impacted by site activities (URS 2007). Wetland areas were delineated
within the 26-acre study area that included Standard Mine Levels 1, 2, 3, 4, 98, and 5.
The areas were field surveyed on July 10, 11, and 12, 2006, and all wetland areas
identified were delineated using the protocol outlined in the Corps of Engineers Wetlands
Delineation Manual (Environmental Laboratory 1987). Information collected from each
wetland area included:
Dominant wetland vegetation (if greater than 4 percent of the vegetative
community)
Other vegetation (less than 5 percent of the vegetative community,
Perimeter vegetation
Noxious weeds
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Wetland community classification, based on Cowardin el al. (1979)
Hydrological indicators
Soil characteristics (upland and wetland)
Physical and biological characteristics of other water features
Wildlife observed
Photographs
During field surveys, wetlands were classified using the Cowardin et al. (1979) and the
hydrogeomorphic (HGM) wetland systems (Smith et al. 1995).
To assist in evaluating the functions of wetlands within the study area, a modified version
of the Montana Department of Transportation Wetland Functional Assessment Method
(Berglund 1999) was used to determine the high-rated functions of the wetlands. This
method was used because it is efficient and concise, and is generally relevant to the
region. The Montana Method evaluates wetlands based on 10 ecological functions,
including:
Federal Threatened and Endangered (T&E) species habitat
State T&E species habitat
General wildlife habitat
General fish habitat
Flood attenuation
Short- and long-term surface water storage
Sediment/nutrient/toxicant removal and retention
Sediment/shoreline stabilization
Production export/food chain support
Groundwater discharge/recharge
Water from wetlands at Levels 5 and 98 was sampled during the September 2007,
September 2008, and September 2009 surface water monitoring events. The sampling
and analysis methods and 2007 analytical results are presented in the 2007 Sampling
Activities Report (TechLaw 2008). The 2008 and 2009 results are available in EPA's
Scribe database for the Standard Mine site (Appendix C).
Samples were collected from the gossan and iron fen during the 2005 low-flow tracer
study (Shanklin and Ryan 2006) and the 2006 high-flow tracer study (unpublished and
unavailable at the time of this draft RI). The samples were analyzed for pH, total organic
carbon, calcium, magnesium, hardness, and metal concentrations. Individual data points
are not available; however, there is a comparison of metal loading rates to Coal Creek
from various sources in the watershed, including the gossan and fen.
One water sample was collected from the fen and one water sample was collected from
the wetland downgradient of the fen during June 1999 for the expanded SI (UOS 2000).
The samples were analyzed for total and dissolved metals and the fen sample was also
analyzed for iron speciation.
2.8.2 Threatened and Endangered Species
T&E species that potentially inhabit the vicinity of the Standard Mine site were
investigated in 2006 to support the Removal Actions, specifically to describe the
biological resources in and around the Standard Mine site that may be impacted by site
activities (URS 2006). Information on the biology, distributions, and listing history of
each T&E species was obtained from USFWS Federal Register documents; the USFWS,
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USFS, CDOW, and National Diversity Information Source (NDIS) web pages (U.S. Fish
and Wildlife Service (USFWS) 2006, U.S. Forest Service (USFS) 2006a, Colorado
Division of Wildlife (CDOW) 2006a, National Diversity Information System (NDIS)
2006); the Colorado Natural Heritage Program (CNHP) database (CNHP 2006); various
field guides; and communication with field experts at USFS (USFS 2006b).
In addition to the general T&E species evaluation, the area immediately surrounding the
Standard Mine was reviewed using aerial photographs and topography maps and a field
survey was conducted to identify potential T&E species habitat. The field survey was
conducted by walking and/or driving to the sites identified on the aerial photographs
including the potential repository locations and mine waste locations on June 23 and July
10, 11, 12, and 31, 2006. Information was recorded regarding dominant vegetation
(including the general mapping of vegetation communities), the presence and condition
of aquatic habitats, and the presence of wildlife species.
2.8.3 Fish
2.8.3.1 Fish Habitat Evaluation
Fish habitat was evaluated using Rapid Bioassessment Protocol (RBP) (EPA
1999) at locations along Coal Creek, Elk Creek, and reference sites in Splain's
Gulch. The evaluation included the following characteristics applicable to high
gradient streams: epifaunal substrate, embeddedness, velocity/depth regime,
sediment deposition, channel flow status, channel alteration, frequency of riffles,
bank stability, vegetation protection, and riparian vegetative zone width. Habitat
assessment results include a basic narrative describing each site, individual field
data sheets, habitat score summaries, and site photographs. These data were used
to develop a Biological Condition Score for each evaluated location and is
expressed as a percentage of the reference station score.
RBP assessments were conducted on the following dates:
July 17 through 21, 2006
September 11 through 15, 2006
September 17 through 20, 2007
September 15 through 17, 2008
September 14, 2009
The results of the evaluations are presented in Sampling Activities Reports
(TechLaw 2007; TechLaw 2008; TechLaw 2009b) and interpreted as part of the
BERA and BERA Addendum that are summarized in Section 6 of this RI report.
Additional fish habitat assessment was performed by USFS to identify reaches of
Elk Creek that could support a trout population (USFS 2009) (Appendix F).
Field surveys of Elk Creek were conducted on August 5 through 7, 2009 by
biologists from the Grand Mesa, Uncompahgre, and Gunnison (GMUG) National
Forests. Surveys included stream gradient, water temperature, spawning
substrate, pool density, residual pool depth, large wood pieces, boulders, bank
stability, undercut banks, and base flow discharge and velocity. The habitat data
collected from Elk Creek were compared to a core set of habitat variables
representative of habitat conditions that support trout populations (brook and
cutthroat trout) in the GMUG National Forest. Thermographs were deployed
within Reach 1 by CDOW personnel and recorded continuous temperatures for
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the months of July and August 2009. Approximately 1.13 miles of Elk Creek
were inventoried in 4 discrete stream reaches. The results were included in the
BERA Addendum that is summarized in Section 6 of this RI report.
2.8.3.2	Fish Inventory
Fish population surveys were conducted by CDOW on the following dates:
July 17 through 18, 2006
September 17 through 20, 2007
September 15 through 17, 2008
September 14, 2009
The population surveys were conducted at locations Coal-15 (Coal Creek below
Elk Creek), Coal 25-E (0.3 miles above confluence with Splains Gulch), Elk-00
(Elk Creek just above Kebler Pass Road), and Elk-01 (Elk Creek 0.2 miles above
Kebler Pass Road), SP-00 (Splains Gulch above confluence with Coal Creek),
and SP-01(Splains Gulch below Forest Road Crossing). Fish were not observed
at upstream locations on Elk Creek so the inventory was not conducted upstream
of location Elk-01 on Elk Creek (CDOW 2006b; CDOW 2008; CDOW 2009).
2.8.3.3	Toxicity Testing
Surface water and sediments were collected by EPA and USFWS during the
following water monitoring events for use in toxicity tests:
July 17 through 21, 2006
September 17 through 20, 2007
September 15, 2008
September 14, 2009
The 96-hour static renewal toxicity tests were performed to determine the acute
toxicity of site water. Simultaneous reference toxicity tests were performed
using Moderately Hard Reconstituted Water spiked with zinc sulfate. All tests
were performed using rainbow trout (Oncorynchus mykiss), with an evaluation
endpoint of mortality.
The 10-day flow-through sediment toxicity tests were performed to determine the
acute toxicity of sediments. Simultaneous reference toxicity tests were
performed using control sediments. All tests were conducted on the amphipod
Hyalella azteca (H. azteca), with evaluation endpoints of growth and mortality.
Test methods, analytical methods, and analytical results for both the surface
water and sediment toxicity tests are presented in the 2006, 2007, and 2008
Sampling Activities Reports (TechLaw 2007; TechLaw 2008; TechLaw 2009b).
Additional toxicity tests were performed by EPA on a series of dilutions of Level
1 adit discharge water. The results are included in the BERA Addendum that is
summarized in Section 6 of this RI report.
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2.8.3.4 Fish Tissue Sampling
Fish tissues (filet, carcass, and forage fish composite) were sampled by EPA,
CDOW, and USFWS in order to evaluate exposure point concentrations for use
in the BERA. Fish tissues were collected from sampling locations Coal-02,
Coal-10, Coal-15, Coal 25, Elk-00, SP-00, and SP-01 on July 17-20, 2006. The
tissues were analyzed for total metals. The sampling and analysis methods and
analytical results for the biological tissue samples are presented in the 2006
Sampling Activities Report (TechLaw 2007).
2.8.4	Macroinvertebrates
2.8.4.1	Macroinvertebrate Assemblage Sampling
Semi-quantitative benthic macroinvertebrate assemblage sampling was
performed by EPA, CDOW, and USFWS at locations along Coal Creek, Elk
Creek, Splain's Gulch, and the Copley Lake outfall during 2006, 2007, and 2008.
Samples were evaluated for macroinvertebrate density and identification to the
species level where possible. Organisms are sorted by family and numbers of
each taxa are reported. Samples were collected on the following dates:
July 17 through 21, 2006
September 11 through 15, 2006
September 17 through 20, 2007
September 15, 2008
September 14, 2009
The results for the macroinvertebrate assemblage samples are presented in the
2006, 2007, and 2008 Sampling Activities Reports (TechLaw 2007; TechLaw
2008; TechLaw 2009b). The 2009 results are not yet published but are available
in EPA's Scribe database for the Standard Mine site (TechLaw 2009a).
2.8.4.2	Macroinvertebrate Tissue Sampling
Macroinvertebrate tissues were sampled by EPA, CDOW, and USFWS during
July 17-20, 2006, in order to evaluate exposure point concentrations for use in
the BERA. The tissues were analyzed for total metals. Macroinvertebrate tissues
were collected from sampling locations Coal-05, Coal-10, Coal-15, Coal-20,
Coal-25, Coal-Opp2, Cop-01, Elk-00, Elk-05, SP-00, and SP-01. The sampling
and analysis methods and analytical results for the biological tissue samples are
presented in the 2006 Sampling Activities Report (TechLaw 2007).
2.8.5	Vegetation
Vegetation samples were collected in the vicinity of four water quality sampling locations
during the 2006 sampling event to support preparation of the BERA. The analytical
results are presented in the 2006 Sampling Activities Report (TechLaw 2007).
2-13

-------
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Legend
Snotel Station
Meterological Station
Gauging Station
I Miles
URS
OPERATING SERVICES
Standard Mine
Gunnison County, CO
Figure 2-1 - Meterological and
USGS Water Monitoring Stations
March 2010
UOS - START 3
TDD No. 0608-07

-------
Standard Mine
Level 1
JU2H&S*i
Mt. Emmons
Project WTP
Access Road
FDR732
COAL-05
COAL-02
COAL-10
Figure 2-2
Surface Water Monitoring Locations
Standard Mine
Gunnison County, CO
COAL-OPP2
COAL-OPP1
COAL-25
Surface Water
Monitoring Location
Mine Road
Intermittent Stream
COAL-15
COAL-20
Perennial Stream
Date: March 8. 2010
Map Projection: UTM, Meters,
Zone 13N, NAD 83.
Data Sources: Mine Road - USEPA
Region 8 (2005): Supplemental Streams -
CDOW (2004): NGS Topographic Base - ESRI
(2010): Monitoring Locations - USEPA Region 8 (2010)

-------
-a
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Legend
© Groundwater Monitoring Weils
v' Adit Location
Base Map: Gaskill et al., 1967
URS
0PERA1UK SERVICES
Standard Mine
Gunnison County, CO
Figure 2-3 - Groundwater
Monitoring Wells
UOS - START 3
TDD No. 0608-07

-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 2-1
Surface Water Monitoring Locations
TABLE 2-1A
EPA/USFWS/CDOW Surface Water Monitoring Locations

6/05
9/05
6/06
7/06
9/06
6/07
9/07
6/08
9/08
6/09
9/09
Bog-00
•
•
o
o
o
o
o
o
o
o
o
Bog-01
o
o
•
o
o
o
o
o
o
o
o
Coal-00
•
•
•
•
•
o
o
o
o
o
o
Coal-02
•
•
•
•
•
o
o
o
o
o
o
Coal-05
•
•
•
•
•
o
o
o
o
o
o
Coal-10
•
•
•
•
•
•
•
•
•
•
•
Coal-15
•
•
•
•
•
•
•
•
•
•
•
Coal-20
•
•
•
•
•
•
•
•
•
•
•
Coal-25
•
•
•
•
•
•
•
•
•
•
•
Coal-Oppl
o

•
•
•
•
•
•
•
•
•
Coal-Opp2
o

•
•
•






Elk-00
•
•
•
•
•
•
•
•
•
•
•
Elk-05
•
•
•
•
•
•
•
•
•
•
•
Elk-06
o
•
•
•
•
•
•
•
•
•
•
Elk-08
o
•
•
•
•
•
•
•
•
•
•
Elk-10
•
•
•
•
•
•
•
•
•
•
•
Elk-12
o




•





Elk-29
•
•
•
•
•
•
•
•
•
•
•
SM-00
•
•
•
•
•
•
•
•
•
•
•
SM-02
•
•
•
o

o
o
o
o
o
o
Key-00
•
•
o
•
•
o
o
o
o
o
o
Key-Opp 1
o
o
o
o
•
o
o
o
o
o
o
Key-01
o
o
•
o

o
o
o
o
o
o
Key-02
o
o
•
o

o
o
o
o
o
o
Slate-01
o
•
•
•
•
o
o
o
o
o
o
Slate-02
o
•
•
•
•
o
o
o
o
o
o
Wild-00
•
•
•
•
•
o
o
o
o
o
o
SP-00
•
•
•
•
•
•
•
•
•
•
•
SP-01
o
o
•
•
•
•
•
•
•
•
•
Cop-01
o
o
•
•
•
•
•
•
o
o
o
Cop-00
o
•
o
o
o
o
o
o
o
o
o
IR-00
•
•
o
o
o
o
o
o
o
o
o
IR-02
o
•
o
o
o
o
o
o
o
o
o
EPA	Environmental Protection Agency
USFWS	U. S. Fish and Wildlife Service
CDOW	Colorado Division of Wildlife
CCWC	Coal Creek Watershed Coalition
o	No data collected
•	Data collected
2-17

-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 2-1B
CCWC Surface Water Monitoring Locations

<»/0(»
X/0(.
10/06
3/07
5/07
8/07
9/07
I0/0"7
2/OX
4/OX
5/OX
X/OX
9/OX
I0/0X
2/09
4/09
X/09
10/09
1 lOiHHl

•
•

•
•
•
•
•
•
•
•

•

•
•

('o;||-( M)

•
•
•
•
o
o
•
•
•
•
•
•
•
•
•
•
•
Coal-01
o
o

o

•
o
•
o
o
•
•
o
•
o
•
•
•
Coal-02
o
•
•
o

•
o
•
o
o
•
•
o
•
o
•
•
•
Coal-05
•
•
•
o
•
•
o
•
•
•
•
•
o
•
o


o
Coal-06
o
o

o

o
o

o
o
•
•
•
•
•
•
•
•
Coal-10
•
•
•
o
•
•
•
•
•
•
•
•
•
•
•
•
•
o
Coal-10.5
o
o

o

o
o

o
o
•
•
o
•

•

o
Coal 11
o
o

o

o
•
•
•
•
•
•
o
•
•
•
•
o
Coal-12
o
•
•
o
•
•
o
•
•
•
•
•
o
•
•
•
•
•
Coal-15
•
•
•
o
•
•
•
•
•
•
•
•
•
•
•
•
•
o
Coal-20
•
•
•
o
•
•
o
•
•
•
•
•
•
•
•
•
•
•
Coal-25
o
•

o

•
o
•
o
o
o
•
o
•


•
o
Coal-30
o
o

o

•
o
•
o
o
o
•
o
•
•
•
•
•
Elk-00
•
•
•
o
•
•
•
•
•
•
•
•
o
•
•
•
•
o
Key-00
•
•

o

o
•
•
o
•
•
•
o
•
•
•
•
o
Key-01
o
o
•
•
•
•
•
•
o
o
•
•
o
•
o
•
•
o
Key-02
o
o
•
•
•
•
•
•
o
o
•
•
o
o
o
•
•
o
Key-Opp
o
o





•
o
o
•
•
o
o
o
•

o
Key-Ditch
o
o
•
o
•
•
•
•
o
o
•
•
o
•
o
•

o
IR-00
o
•
•
o
•
o
o

o
o
o
•
•
o
•
o
•
•
IR-02
o
•
•
o
o
o
o
•
o
o
o
•
o
o
•
o

•
SP-00
o
•

o
o
o
o
•
o
o
o
•
o
o
o
o
•
o
Wild-00
o
•

o
o
o
o
o
o
o
o
•
o
o
o
o
o
o
Town Res
o
o
•
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
PM
Culvert
o
o
•
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
CCWC Coal Creek Watershed Coalition
o	No data collected
•	Data collected
2-18

-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 2-2
Sediment Sampling

4)/26-2S/2005
<)/11-13/2006
')/17-19/2007
*>/15-17/2008
9/14/2009
1 )(1
•
o
o
o
o
Bog-Opp
•
o
o
o
o
Coal-00
•
•
o
o
o
Coal-02
•
•
o
o
o
Coal-05
•
•
o
o
o
Coal-10
•
•
•
•
•
Coal-15
•
•
•
•
•
Coal-20
•
•
•
•
•
Coal-25
•
•
o
o
o
Coal-30
•

o
o
o
Coal-Oppl
o
•
•
•
•
Coal-Opp2
o
•
o
o
o
Elk-00
•
•
•
•
•
Elk-05
•
•
•
•
•
Elk-06
•
•
•
•
•
Elk-08
•
•
•
•
•
Elk-10
•
•
•
•
•
Elk-29
•
•
•
•
•
Elk-30
•
o
o
o
o
IR-00
•
o
o
o
o
IR-02
•
o
o
o
o
IR-Opp
•
o
o
o
o
Key-00
•
o
o
o
o
Slate-01
•
•
o
o
o
Slate-02
•
•
o
o
o
SM-00
•
o
o
o
o
SM-02
•
o
o
o
o
SP-00
•
•
•
o
o
SP-01

•
•
o
o
Cop-00
•
o
o
o
o
Cop-01

•
o
o
o
FQ-01
•
o
o
o
o
FQ-02
•
o
o
o
o
Wild-00
•
o
o
o
o
CD-01
o
•
o
o
o
CD-02
o
•
o
o
o
Additional samples from Level 1, 5, and 98 were collected during September 2008
o	No data collected
•	Data collected
2-19

-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
3.0 PHYSICAL CHARACTERISTICS OF THE STUDY AREA
This section describes the physical characteristics of the Standard Mine vicinity. Emphasis is given to
those characteristics that contribute to understanding the nature and extent of contamination, the fate and
transport of contaminants, and the ability to effectively implement technologies to eliminate or reduce the
impacts of contamination.
3.1 SURFACE FEATURES AND MINE WORKINGS
The Standard Mine is located between 10,900 and 11,600 feet above mean sea level in Elk Basin
near Scarp Ridge between Mt. Emmons and the Ruby Range. The terrain is mountainous with an
incised stream valley with steep slopes.
The surface features at Levels 1, 2, and 3 of the Standard Mine site have changed dramatically
since the completion of the EPA Removal Actions. Features in other areas of the site remain as
they were in 2005 except that portions of Level 98 were used by E PA' s Environmental Response
Team for revegetation test plots. The following sections describe the current condition of the site,
including features installed after the removal of the tailings impoundment, waste rock, and the
remains of mining structures.
Additional surface features located near and downstream of the site, including wetlands, an iron
fen, a naturally-occurring iron-rich surface deposit (gossan), and the Mt. Emmons Project Mine
and WTP are described m later sections of this report.
3.1.1 Level 1
Level 1 currently consists of a draining adit, revegetated upland soils, Elk Creek,
wetlands associated with Elk Creek and upgradient seeps, surface water control features,
and a pilot scale BCR. Features are shown on Figure 1-6.
The Level 1 adit is approximately 3,000 feet long and is connected to Levels 2 and 3 by
intervening raises. There are two intermediate levels, approximately 1,500 feet in total
length, between Levels 1 and 2
(Carpenter 1958). While the adits
to Levels 2 and 3 appear to have
been developed along the strike of
the fault trace, the portal to Level
1 appears to have been developed
so that the direction of the mine is
driven at an angle to the strike of
the fault trace.
The Level 1 adit is blocked by
what appears to be a substantial
roof fall approximately 80 feet in
from the portal. The fall blocks
the mine from rib to rib and from
Level 1 Adit	floor to back. The volume of fall
material appears to be substantial,
given the nature of the material and dimensions of the plug. The ribs and back are
timbered from the portal to the collapse and rail is present on the floor. Water drains
from the caved material and can be heard to cascade in from the blockage. Water enters
the tunnel from raises that connect Level 1 to Level 2 and intermediate levels. It is
3-1

-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
possible that water enters the tunnel from other sources behind the blockage as well, but
it is impossible to verify the location of additional sources of water into the Level 1
workings due to the collapse near the portal (DRMS 2007). Water flows across the floor
of the Level 1 tunnel and discharges from the portal at documented flow rates ranging
from approximately 3 to 70 gallons per minute depending on the season. Higher flows
may occur but have not been documented due to limitations in the adit flume sizing and
layout, power loss and transmission problems due to severe winter weather and heavy
snow, ponding of water inside the adit due to ice dams, and sedimentation of overflow
pipes outby the flume. Flows are significantly higher during the peak snowmelt months
of May and June than at other times of year. Figure 3-1 presents the flow data that have
been collected from the adit flume. Currently the Level 1 adit discharge is conveyed to
Elk Creek through two polyvinyl chloride (PVC) pipes with a fraction of the flow
diverted and conveyed through additional piping to the BCR.
The soils at Level 1 were altered significantly during the Removal Action. The surface
currently has areas with native soil, residual waste rock, clean fill from a nearby borrow
location, and bedrock. The areas are shown on Figure 1-6. The areas designated as
"wetland," "west slope," and "south slope" and the area surrounding the new creek
alignment contain native soil or bedrock at the surface. Areas designated as "north
slope" and "northeast slope" contain native soil with residual waste rock covered with
clean fill. The area immediately in front of the Level 1 adit and surrounding the BCR
was not excavated as part of the removal action and still contains bedrock or waste rock.
All areas but the bedrock and the area immediately m front of the Level 1 adit and
surrounding the BCR were
treated and seeded in 2008 in
accordance with the Reclamation
Plan (UOS 2008). Site soils
were sampled and analyzed for
metal concentrations in July
2009 to assist in revising the
BERA and BHHRA to account
for post-removal site conditions.
In order to minimize the impact
of site contaminants and site
activities on water quality in Elk
Creek, a portion of Elk Creek at
Level 1 was realigned and
isolated during the Removal
Action. After the removal
action, approximately 1,000
linear feet of Elk Creek were reconfigured to approximate conditions found immediately
upstream and downstream of the Standard Mine site. The new channel is a Rosgen
A2/A3 type, which is steep and entrenched with cascading, step/pool flows that are
stabilized by bedrock and boulders. The boulders used to stabilize the channel are in the
form of vortex weirs, which were installed across the new channel every 15 to 25 feet.
Three wetlands were identified near Level 1. Information regarding the wetlands is
provided in Section 3.7.1.1. After the Removal Action, approximately 0.5 additional
acres of ecologically functional wetlands were created along the 1,000 feet of the
reconfigured Elk Creek channel. Three wetlands were constructed immediately upstream
of the reinforced vortex weirs, and numerous narrow "fringe" wetlands were constructed
along approximately 50 percent of the new channel. The wetlands slope gently upward
Level 1 after Removal Action showing Treated
Soils and Elk Creek Realignment
3-2

-------
Standard Mine — Remedial Investigation
TDD No. 0608-07
Date: 05/2010
from the low flow channel of
Elk Creek. The portion of the
wetlands closest to the channel
were reinforced with a
biodegradable erosion control
blanket (ECB) to protect newly
installed wetland plants from
high velocity flows. The new
wetlands are both palustrine
emergent and palustrine
scrub/shrub types. There are
three wetland planting zones
including the ECB/Plugs Zone,
Plugs Zone, and Willow Zone.
An ECB/Plugs Zone was
created immediately adjacent to
the newly created channel with
50,000 herbaceous wetland plants per acre. The Willow Zone, immediately upgradient of
the Plugs Zone, has 5,600 willow cuttings per acre.
Ditches were installed to provide surface water run-on/runoff control and reduce the
amount of water flowing across site soils.
A pilot-scale BCR is located near the discharging adit. The BCR consists of a buried 40-
foot by 40-foot lined reactor containing chipped wood, limestone,. sand, bacterial
inoculum, hay, and a small quantity of manure buried underneath a layer of wood chips.
The treatment system also contains an aerobic polishing cell, a buried Chitorem reactor,
and associated plumbing. The BCR system is described more fully in the Standard Mine
Feasibility Study.
3.1.2 Level 2
Level 2 consists of an ephemerally discharging adit and waste rock (Figure 1-3). Level 2
is located adjacent to a substantial bedrock outcrop and scree slope that is located a few
hundred feet east of Elk Creek. The area contains a number of bedrock outcrops.
The Level 2 adit, known as the Micawber Mine, was the primary mine developed in the
area. The Level 2 adit is collapsed at the portal but was accessible to DRMS personnel
from Level 3 through the second inby raise (Figure 1-4). The accessed raise is located
immediately outbv of two winzes that both intersect Level 1 and two intermediate sub-
levels. Over 825 feet of the Level 2 workings were investigated. The drifts average six
feet wide and eight feet high. Where drifts run parallel, stoping appears to take place
along the northern drift as indicated by numerous ore chutes and timbering. Timbering is
confined to ore chutes and areas of stoping and did not appear to be required for general
ground support. Minor and sporadic amounts of roof fall are present along the floor, with
the most muck directly correlated to ore chutes or zones of collapsed lagging. The ore
chutes still contain sulfide ore. Vein mineralization is not as discemable as on Level 3
due to the extensive mine timbering and thick flowstone deposits covering the ribs and
back. Near the back of the tunnel, a raise down to a sublevel drift is present that is not
shown on the cross section. The sublevel descends at least 30 feet. Further investigation
of the sublevel was limited by restricted access. Both rail lines and rigid air lines are
present in most of the accessible workings. No oxygen deficient environments were
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Wetland Areas Adjacent to Elk Creek Realignment
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START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
encountered during the mine entry. The features of the Level 2 adit are mapped on Figure
3-2 provided by DRMS (DRMS 2009).
During the 2009 entry, approximately 300 feet of the visible portion of the tunnel
contained pooled water in excess of one foot. As much as three feet of water was backed
up behind a muck pile on the floor of the Level 2 adit outby the first winze to Level 1.
The pooled water flows to Level 1 via the first winze. The pooled water in Level 2 is not
water backed up from Level 1 as evidenced by the absence of significant amounts of
pooled water deeper in the tunnel (DRMS 2009).
Water enters Level 2 from Level 3 via raises, stopes, and surrounding rock.
Approximately 80 percent of the inflow to Level 2 that was observed during the July
2009 underground assessment was from Level 3 and open stopes and timbered areas
between Levels 2 and 3. The remaining 20 percent of inflow appeared to be from
surrounding rock joints and fractures. The areas with the most intense groundwater
inflows were in drifts driven toward the footwall Ohio Creek formation, but some diffuse
inflows were observed in the hanging wall Wasatch formation. The inflows from both
formations form iron flowstone. Water exits Level 2 from at least three locations. At the
farthest inby raise on Level 2, water just passes through Level 2 as it pours from the
Level 3 raise and into the Level 1 winze. Water flowing down the center winze comes
from rock formations and ore chutes to the east. Most of the water flowing down the first
raise is backflow from the water ponded behind muck piles (DRMS 2009).
Waste rock that had been located outside the Level 2 entrance was removed down to
bedrock during 2008 and the disturbed soils were reclaimed in the same manner as Level
1.	The small amount of remaining waste rock and impacted native soils were amended
with lime (where necessary to provide a plant-friendly pH), organic matter, and fertilizer,
and seeded.
A small amount of non-discrete
adit discharge flows over the
reclamation area, but the
discharge is not channelized or
controlled in any manner. Logs
and felled trees were placed
perpendicular to the flow of the
discharge in the area between
Levels 1 and 2 in an effort to
control erosion during the spring
runoff when scouring by the adit
discharge is evident.
A wetland is present near Level
2.	The wetland is described in
Section 3.7.1.2.
3.1.3 Level 3
Level 3 consists of an adit that does not discharge and a waste rock pile (Figure 1-3).
The Level 3 portal is open and readily accessible. The historic mine entrance is collapsed
immediately inside the entrance but has been reopened at a timber set near the original
mine entrance. The portal at Level 3 accesses about 800 feet of workings that connect to
Level 2 after Waste Rock Removal
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
Level 2 and ultimately Level 1 by vertical winzes. Level 3 was accessed during the 2006
and 2009 mine entries (DRMS 2007; DRMS 2009). The features of the Level 3 adit are
mapped on Figure 3-3 provided by DRMS (DRMS 2007). Level 3 follows the Standard
Fault along nearly the entire tunnel. The fault zone is typically 3 to 5 feet wide, contains
mineralization, strikes North 70° to 80° East, and dips 50° to 70° East. Minerals and
waste within Level 3 are potential sources of water contamination. The ore minerals
occur within unmined portions of the fault, within plugged ore chutes, and in muck piles
in the mine workings. An ore chute with a pile of mine material beneath was observed
during the mine entry. The material was coated with iron oxyhydroxides such as goethite
and plumbojarosite that form by the oxidation of sulfides. The interior of the pile was
unoxidized and shown to contain galena and quartz with minor pyrite. The most
extensive area of sulfide mineralization was observed surrounding the center raise
connecting Levels 2 and 3. Muck piles were composed of substantial unoxidized vein
material consisting of pyrite, sphalerite, and galena (DRMS 2009; USGS 2010a; USGS
No substantial discrete inflows were observed in Level 3. Instead, water enters the tunnel
as diffuse drips from the ceiling and walls. Discrete and asymmetric groundwater flow
was observed throughout Level 3 in the form of point emanations and sheets. It
emanated primarily from the Ohio Creek footwall side of the Standard fault-vein and on
the footwall side of the nearly continuous seam of clay rich fault gouge marking the
contact between the footwall damage zone and fault core. Adjacent to many of these
flow zones, the Wasatch hanging wall was dry. This suggests that the Standard fault vein
is a partial barrier to flow across the fault but may locally or seasonally behave as an
asymmetric, discrete conduit along the fault at depth in spite of what appears to be a
poorly developed damage zone. Possible seasonal variations of this flow asymmetry are
unknown. Water is on the floor throughout the tunnel, but flow is either non-existent or
extremely slow. Water flows down the two raises to Level 2 on both the outby (portal)
side and the inby (tunnel end) side of each raise, indicating at least some inward and
outward flow on the tunnel floor toward the raises (DRMS 2007; USGS 2007).
The bulk of the waste rock located outside the Level 3 portal was excavated and taken to
the on-site repository during the Removal Action, but steep slopes prevented removal of
the remaining waste rock. Approximately 0.1 acre of waste rock remains. Disturbed
soils and the remaining waste rock were revegetated during 2008 using methods similar
to those implemented at Level 1.
3.1.4	Level 4
Level 4 consists of two partially collapsed twin compartment shafts that communicate
with Level 3. Small waste rock piles are associated with these shafts. These shafts are
located just south of the road that accesses Level 98.
3.1.5	Level 5
Level 5 consists of a discharging adit and waste rock (Figure 1-3). The adit discharge
flows over the waste rock across a road and into a flourishing high alpine wetland. The
wetland is described in Section 3.7.1.4.
2010b).
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
The Level 5 tunnel is readily accessible and discharges acid rock drainage continuously
throughout the year. The Level 5 adit
includes about 800 feet of workings and is
not connected to the other levels. Level 5
follows the Standard Fault, or segments of the
fault, along most of the length of the tunnel.
Exposed fault zones are typically one to four
feet wide, contain mineralization, strike North
65° to 85° East and dip 60° to 80° East. Two
cross faults striking approximately
perpendicular to the Standard Fault segments
were observed, both one to two feet wide and
dipping 80° to 85°. The tunnel runs fairly
straight for approximately 250 feet where it
splits. The left drift follows the strike of the
fault, which is not as well defined as in Level
3. The left drift is blocked by a substantial
collapse 300 feet in from the split in the
workings. The collapse apparently acts as a
dam because a small quantity of water flows
into Level 5 from the upper portions of the
collapse material. The right drift generally
follows the strike of the main drift and ends
approximately 200 feet in from the tunnel split. A discontinuous fault trace is observed
through this drift, with evidence of faulting apparent only on an intermittent basis
(DRMS 2007; USGS 2007). The features of the Level 5 adit are mapped on Figure 3-4
provided by DRMS (DRMS 2007).
As with Level 3, water enters the tunnel pervasively as diffuse drips. Discrete and
asymmetric groundwater flow in the form of point emanations and sheets was observed
throughout Level 5. No increases in tunnel inflows were noted near the cross-faults.
Flow emanates primarily from the Ohio Creek footwall side of the Standard fault-vein
and on the footwall side of the nearly continuous seam of clay rich fault gouge marking
the contact between the footwall damage zone and fault core. Adjacent to many of these
flow zones, the Wasatch hanging wall was dry. This suggests that the Standard fault vein
is a partial barrier to flow across the fault but may locally or seasonally behave as an
asymmetric, discrete conduit along the fault at depth in spite of what appears to be a
poorly developed damage zone. Possible seasonal variations of this flow asymmetry are
unknown. Few notable inflows were observed during the August 2007 mine entry, so it
is assumed that water within the mine can be attributed to seasonal inflows from the
surface. Water is accumulated on the floor throughout the tunnel and flows slowly
toward the portal (no raises are present). A small sill of colluvial material acts as a dam
for water accumulated within the drift. High water marks were noted at approximately
three feet above the floor (DRMS 2007; USGS 2007).
The waste rock pile is steep and consists of two characteristically different waste rock
types, one dominated by orange and tan materials that exhibit low paste pFI values and
the other dominated by gray materials with higher paste pH. Chemical characteristics of
the waste rock are discussed in Section 4.
Level 5 Portal
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3.1.6 Level 98
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Level 98 consists of a lightly discharging adit and waste rock (Figure 1-3). Level 98 was
mined as the Elk Lode Mine.
The adit discharges small flows over the waste rock and into a flourishing high alpine
wetland. The wetland is described in Section 3.7.1.3.
Level 98 Waste Rock. Adit is at left end of log.
Unlike Levels 1 through
5, the Level 98 adit is
part of the Elk Mine
located on a
discontinuous northwest
Elk vein, northwest of
the Elk fault-vein, rather
than part of the
Standard/Micawber mine
that is located on the
Standard fault Level 98
was included in the
Standard Mine site
because of its proximity
to the site and potential
impacts on water quality
in Elk Creek.
The tributary to Elk Creek at
Level 98 is one of at least three
branches of Elk Creek that are
present above the main mine site.
This tributary consists of a
relatively high-gradient channel
approximately three feet wide.
The channel bottom is mostly
cobble with some boulders, and
water flows less than 10 inches
deep during summer months. The
channel also includes two small
ponds that appear to have been
created by mining activities
(URS 2006). Elk Creek flows
past the toe of the waste rock pile. South Portion of Level 98 with Pond Along Elk
The waste rock pile at Level 98	Creek Tributary
consists of boulder-sized
materials interspersed with fines. Revegetation test plots were installed on the Level 98
waste rock pile during 2007.
3.2 METEOROLOGY
The NOAA and the WRCC data for Crested Butte, Taylor Reservoir, and Independence Pass are
presented on Tables 3-1 through 3-3.
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START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
The annual precipitation for Crested Butte is 23.6 inches. Annual snowfall averages 198 inches.
The greatest snowfall typically occurs during January with 40.1 inches. Snow depth is typically
greatest in February with 35 inches. The highest temperatures are seen in July with an average
daily high of 75.5°F and average daily low of 38.4°F. The lowest temperatures are seen in
January with an average daily high of 35.9°F and average daily low of -4.3°F (WRCC 2009).
Annual precipitation for the Taylor Reservoir station is 16.6 inches. Annual snowfall averages
106.3 inches. The greatest monthly snowfall typically occurs during January with an average of
22.5 inches. Snow depth is typically greatest in February and March with an average of 25
inches. The highest temperatures are seen in July with an average daily high of 75.5°F and
average daily low of 38.4°F. The lowest temperatures are seen in January with an average daily
high of 35.9°F and average daily low of -4.3°F (WRCC 2009).
Annual precipitation for the Independence Pass station is 29.8 inches. Annual snowfall averages
335.9 inches. The highest snowfall typically occurs during March with 58.8 inches. Snow depth
is typically highest in March with 56 inches. The highest temperatures are seen in July with an
average daily high of 35.9°F and average daily low of 67.8°F. The lowest temperatures are seen
in January with an average daily high of 35.9°F and average daily low of-1.8°F (WRCC 2009).
Snotel data available for the Independence Pass site indicate the relative amount of precipitation
in each water year that runs from October 1 to September 30. The Snotel Water Accumulation
data are presented on Table 3-4. The data indicate that 2002 was the lowest water year for all
stations, 1995 was the highest water year for the Independence Pass and Park Cone stations, 1984
was the highest water year for the Butte station, and 1986 was the highest water year for the
Schofield Pass station. Temperatures were not compared for the Snotel stations because of
irregularities in the data (WRCC 2009).
The Crested Butte Mountain Resort reports an annual average snowfall of 300 inches (Crested
Butte Mountain Resort 2009).
3.3 SURFACE WATER HYDROLOGY
Elk Creek is a tributary to Coal Creek and drains an area of approximately one square mile. The
creek begins at elevations near 11,300 feet above sea level and travels approximately two miles
before it enters Coal Creek at an elevation of approximately 9,500 feet, four miles west of Crested
Butte. At least three branches of Elk Creek are present above Level 1 of the Standard Mine site.
Outfall from Copley Lake, located at an elevation of 10,600 feet, enters Elk Creek less than one
mile downstream of Standard Mine Level 1. Elk Creek is a perennial creek that gets most of its
water from snowpack and groundwater discharge from a relatively small watershed. The channel
is relatively high-gradient and is comprised of mostly cobble and boulders.
Coal Creek drains a watershed of 24.4 square miles. It flows east from headwaters near Lake
Irwin and receives water from the Forest Queen Mine drainage, Splain's Gulch, Elk Creek, an
iron fen (described more fully in Section 3.7.4), the Mt. Emmons Project WTP outfall, and
Wildcat Creek then flows through Crested Butte and enters the Slate River. Slate River is a
tributary of the East River.
Coal Creek is the primary municipal water source for the town of Crested Butte. The diversion in
Coal Creek is approximately 4.25 miles downstream of Lake Irwin, 2.5 miles downstream of the
Standard Mine, 1 mile downstream of the Elk Creek confluence with Coal Creek, downstream of
the drainage from the Mt. Emmons iron fen, and 50 feet upstream of the Mt. Emmons Project
WTP outfall. A secondary intake diverts water at Wildcat Creek as an emergency water source.
Crested Butte holds storage rights in Lake Irwin of 367.3 acre-feet with a junior right of 6 cubic
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START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
feet per second (cfs). The water rights are intended to provide a water supply in the event that the
natural flow in Coal Creek is insufficient or that a call by a senior right downstream affects the
town's diversion. The water diverted from Lake Irwin by the town of Crested Butte averages
slightly less than one acre-foot per day over a one-year period, or an average of 0.5 cfs (Stantec
2005a).
The Mt. Emmons Project WTP treats mine drainage, surface water, and a small amount of
sanitary wastewater using lime neutralization, flocculation, floatation, and filtration. The facility
discharges the effluent to Coal Creek according to CDPS permit number CO-0034394. The
facility capacity is 2.2 million gallons per day (MGD); however, the facility is only permitted to
discharge 0.675 MGD from October through June and 0.75 MGD from July through September.
Actual annual average flows reported to CDPHE in the period from 2002 through 2007 averaged
0.32 MGD with a range of 0.238 MGD to 0.393 MGD during the months of October through
June. During the months of July through September, the annual average flows were 0.36 MGD
with a range of 0.292 to 0.667. Annual peak flows reported to CDPHE in the period from 2002 to
2007 were 0.4 MGD with a range of 0.292 MGD to 0.667 MGD during the period of October
through June. During July through September, annual peak flows reported to CDPHE in the
period from 2002 to 2007 were 0.42 MGD with a range of 0.372 MGD to 0.466 MGD (CDPHE
2007).
Surface water flow patterns were evaluated using both site-specific data and USGS gauging
station data. The EPA/CCWC data were used to evaluate relative flow contributions of sources in
the Coal Creek basin. Because these data do not provide enough information to identify long-
term seasonal trends and yearly variations, data were used from USGS gauging stations 09112200
located on the East River below Cement Creek, 09111500 located on the Slate River near Crested
Butte, and 365106106571000 located on the Slate River above Baxter Gulch (Figure 2-1)
(National Water Information System (NWIS) 2009).
The period of record hydrographs for the three USGS gauging stations were used to evaluate
seasonal trends (Figures 3-5 and 3-6) (NWIS 2009). The daily mean stream flow data from all
three stations is typical of streams and rivers in Colorado, where most of the flow is derived from
snow melt. The peak of snow melt in May and June of each year coincides with the highest
stream flow rates. The average May and June stream flow is 540 cfs, 1120 cfs, and 531 cfs for
USGS gauging stations 09111500, 09112200, and 365106106571000, respectively (Tables 3-5
through 3-7). The average peak stream flow for USGS gauging station 09111500 is 1070 cfs,
with a range of 476 cfs to 1420 cfs (Table 3-8). The average peak stream flow for USGS gauging
station 09112200 is 2084 cfs, with a range of 847 cfs to 4350 cfs (Table 3-9). The average peak
stream flow for USGS gauging station 365106106571000 is 1000 cfs, with a range of 678 cfs to
1320 cfs (Table 3-10). Over the period of record, peak stream flow has occurred between May 8
and June 18. Base stream flow, measured between September and March, averages 21 cfs, 85
cfs, and 37 cfs for USGS gauging stations 09111500, 09112200, and 365106106571000,
respectively. Peak flow is typically 7 to 10 times greater than average stream flow and averages
50 times greater than base stream flow. Average May and June stream flow is generally 10 to 15
times base stream flow. Although these hydrographs are for the Slate and East Rivers, the same
seasonal pattern would be expected for Coal Creek and Elk Creek.
Data from USGS gauging stations 09111500 and 09112200 were used to compare annual
hydrologic conditions (Figures 3-7 and 3-8) (NWIS 2009). At station 09111500, the wettest year
during the period of record was 1995 when a peak flow of 1,550 cfs and an average flow of 213.6
cfs were recorded. The peak flow during 1995 was more than double the average peak stream
flow at this station. The driest year was 2002 with a peak flow of 476 cfs and average flow of
61.6 cfs. The average peak flow is more than 2.5 times the peak flow during 2002. At station
09112200, the wettest year during the period of record was 1995 when a peak flow of 4,350 cfs
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START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
and an average flow of 530 cfs were recorded. The driest year was 2002 with a peak flow of 847
cfs and average flow of 140 cfs. It is expected that 1995 and 2002 were also the wettest and
driest years in the Coal Creek and Elk Creek basins.
Site-specific water data that were collected in support of the RI/FS were used to evaluate
conditions near the site. Figure 2-2 shows the monitoring locations and Table 3-11 provides
location descriptions. Coal-25 is the most upstream measuring point in Coal Creek that was
sampled by EPA on a regular basis. Coal-20 is located downstream of the Spain's Gulch
confluence and just upstream of the confluence with Elk Creek. Coal-15 is downstream of the
Elk Creek confluence. Coal-10 and Coal-05 are located upstream and downstream, respectively,
of where the Mt. Emmons Project WTP outfall enters Coal Creek. Coal-02 is located as Coal
Creek enters Crested Butte, and Coal-00 is located just above the confluence with the Slate River.
The intake for the municipal water supply is located at Coal-10, upstream of the Mt. Emmons
Project WTP outfall. Stream flow data collected at the various sampling locations along Coal
Creek are presented on Figure 3-9.
Along Elk Creek, Elk-29 and Elk-10 are located immediately upstream and downstream,
respectively, of Standard Mine Level 1. Elk-08 is located downstream of the Copley Lake
outfall. Elk-06 and Elk-05 are located upstream and downstream, respectively, of a large
perennial spring that feeds Elk Creek. Elk-00 is located immediately upstream of the Kebler Pass
Road crossing, near the confluence with Coal Creek. Elk Creek stream flow is presented on
Figures 3-10 and 3-11. The patterns of Elk Creek follow those observed at the USGS gauging
stations described above, with a significant increase in flow during May and June followed by
lower flows that trail into a base flow between September and March. Flow generally decreases
between Elk-08 and Elk-06. It is unknown whether that is due to difficulty in making accurate
measurements at one of the locations or whether some of the water is recharging localized
groundwater or feeding a wetland in that vicinity. Flow then increases downstream of Elk-06,
probably due to water returning from subsurface to the creek, surface drainage, and inflow from
the nearby spring. Flow increases downstream to Elk-00.
The Standard Mine Level 1 adit discharge (Figure 3-1) follows a similar pattern to surface water
flow. The Level 1 discharge is typically about one to two percent of the flow at Elk-00 and
possibly higher during high flow periods.
During three EPA sampling events performed during high flow conditions, Elk Creek contributed
approximately 20 percent of the flow at Coal-15 and 16 percent of the flow at Coal-10. During
three EPA sampling events performed during low flow conditions, Elk Creek contributed
approximately 30 percent of the flow at Coal-15 and 18 percent of the flow at Coal-10. These
values are only estimates because of the limited nature of the data. The contribution of Elk Creek
to downstream locations on Coal Creek was not calculated because additional uncertainty is
introduced due to the intermittent nature of discharges from the Mt. Emmons Project WTP and
the intake for the Crested Butte municipal water system.
3.4 GEOLOGY AND SOILS
The area is characterized by rugged mountains separated by glaciated valleys that are drained by
small creeks. Glaciation in the region created numerous U-shaped valleys, lakes, and cirques.
Elk Basin is a horseshoe shaped cirque located on the south side of Scarp Ridge. Soils and
surficial deposits are thin yet rich in organic matter underlain by Tertiary sedimentary bedrock at
or near the surface in the upper watershed. Numerous springs exist along the valley bottom and
near the break in slope of the upper cirque.
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START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
The bedrock in upper Elk Basin is the Wasatch Formation that is composed mainly of
ferromagnesian-rich sandstone, siltstone, and mudstone with massive pebbly sandstones and
conglomerates near its base, siltstone, and mudstone with conglomerate lenses, and the
underlying Tertiary-age Ohio Creek Formation that is composed mainly of aluminosilicate-rich
sandstone. The Wasatch and Ohio Creek Formations are underlain by the Cretaceous Mesaverde
Formation that is composed of interbedded sandstone, shale, coal, and carbonaceous shale. These
rocks were later intruded by Tertiary-age quartz monzonite porphyry dikes and sills. Quaternary-
age glacial, landslide, and talus deposits partly cover the Tertiary-age rocks (USGS 2010b).
The Ohio Creek Formation is leached of pyrite in at least the upper meter of outcrop within much
of the upper Elk Basin. The only place leaching was not observed was adjacent to polymetallic
quartz veins that are present primarily in the northeastern portion of the upper basin. Where
pyrite occurs in the Wasatch Formation it is fresh on freshly broken surfaces and slightly
weathered on exposed surfaces (USGS 2010b).
Geological structures in the basin include joints, faults, veins, fault-veins, dikes, sedimentary
structures, and tilted sedimentary strata. The bedrock in Elk Basin is jointed except in the clay-
rich fault gouge. The bedrock contains three main sets of joints, two of these joint sets are nearly
vertical, and are approximately orthogonal to each other, and one set is sub-parallel to bedding
within the Ohio Creek and Wasatch formations. The Wasatch Formation appears to have fewer
subhorizontal joints than the Ohio Creek Formation (USGS 2010b; URS 2007).
The Standard Mine site consists mainly of the Standard Mine (initially worked as the Micawber
Mine) that was worked on the Standard Fault and to a lesser extent the Elk Lode Mine (Level 98)
that was worked on the Elk Lode Fault. The Micawber/Standard Mine developed the Standard
fault-vein, which is a normal, dip slip fault zone that dips steeply southeast. The Standard fault-
vein is part of a set of structures, including the Daisy and Keystone veins, that have radial
symmetry about the rhyolite plug at Mt. Emmons (Thomas and Galey 1982). Lead-zinc-silver
deposits are associated with the northeast-trending system of faults. The Standard fault has a
clay-rich core that cuts the alteration halo of the polymetallic sulfide-rich quartz vein in the
footwall of the fault zone. The fault juxtaposes the Ohio Creek formation on its northwest,
footwall side against the younger Wasatch formation on its southeast, hanging wall side.
Formation of the primary quartz vein, associated alteration halo and fault core also appear to have
been primarily formed in the Ohio Creek formation. About 600 feet of the one- to five-foot-wide
vein is well defined and contains lenses of ore composed of pyrite, sphalerite, and galena with
some chalcopyrite and quartz. The fault-vein has a poorly developed but complex damage zone
composed of polymetallic quartz veins, some open fractures, vugs, breccia zones, small faults,
and some minor slip surfaces (USGS 2010b).
The Elk Mine was driven on a northeast-trending fault-vein, about 300 feet to the west and
parallel to the Standard fault-vein developed in the Micawber Mine. In the vicinity of the Elk
Mine, the Ohio Creek formation is found on both sides of the structure with a small amount of
hangingwall-down-to-the-southeast normal displacement. The fault-vein is nearly vertical. There
is little fault-related damage on either side of the fault, but the fault-vein is jointed. The core of
this fault-vein is composed of massive to vuggy, coarse-grained, and largely unweathered pyrite.
Galena was observed on the hanging wall side of the Elk Lode fault-vein core (USGS 2010b).
The USGS geologic map of the site vicinity is presented as Figure 3-12. This map includes
features delineated during the 2009 USGS characterization of geologic structures in upper Elk
Basin (USGS 2010b).
The geophysics study conducted by USGS during 2009 included resistivity, self-potential, and
magnetic imaging data. The resistivity data are explained to a first order approximation as a two-
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START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
layer model with a resistive near surface and less resistive subsurface. The resistive near surface
layer is an indication of unsaturated conditions and the less resistive lower layer indicates
saturated conditions. Superimposed on this is site heterogeneity. Significant lateral heterogeneity
in the resistivity data indicates the presence of major features such as the Standard and Elk fault-
veins and likely heterogeneous joint intensity consistent with observations from outcrops and
bore hole geophysical logging data. Very high resistivities were observed in locations
corresponding to inferred quartz veins, possibly with lower porosity (relative degrees of
silicification were not quantified). The self-potential data analysis highlights the Standard fault-
vein, the northwest Elk vein near the Elk portal, and several polymetallic quartz veins that are all
expected to contain sulfide minerals. Magnetic data showed little variation, consistent with the
mostly non-magnetic host rocks and mineralization at the site, which was verified by magnetic
susceptibility measurements and x-ray diffraction mineralogy data on local rock samples. The
contact between the Ohio Creek and Wasatch Formations coincides with a change in character of
the magnetic signature, though there was some ambiguity that is possibly due to variations in
shallow surficial deposits composed of Wasatch over portions of the Ohio Creek Formation.
Magnetic anomalies are associated with several, though certainly not all, mapped polymetallic
veins, which may be related to the heterogeneous distribution of magnetic minerals at the site
(USGS 2010c).
3.5 HYDROGEOLOGY
Simple topography, rather than large-scale geologic features, appears to be the primarily control
on the occurrence and flow of shallow groundwater. A vector diagram overlain on the geologic
and topographic map of Elk Basin shows the relative magnitude and direction of surface elevation
gradients (Figure 3-13, provided by USGS). The diagram shows the expected general direction
of surface water flow and likely the shallow groundwater flow in the basin. Localized variations
are expected due to physical features and variations in the hydraulic conductivity of soils and
shallow bedrock. The diagram indicates that surface water and shallow groundwater probably
flow toward the Standard fault-vein from both sides. This diagram does not represent deeper
groundwater flow. Observations of rock outcrops indicate that quartz veins may act as localized
baffles to groundwater flow (USGS 2007; USGS 2010b).
Groundwater levels were measured in wells installed near the Standard fault and are presented on
Figure 3-14. Stream flow from USGS Gauging Station 09112200 is also plotted on Figure 3-14
for comparison with the well data. Two scales of fluctuations were apparent in the wells:
seasonal fluctuations that appear to be related to spring snowmelt and short-term (week- to day-
time periods) fluctuations that are more reflective of local aquifer conditions. Wells B1 (60.5 feet
deep), B3 (8 feet deep), B4 (15 feet deep), B5 (60.5 feet deep), and B7 (7 feet deep) contain some
water year-round, while wells B2 (8 feet deep) and B6 (5 feet deep), collocated with wells B1 and
B5, respectively, are primarily dry.
Water levels remain nearly constant from August to April. This period of time includes fall and
winter, when most precipitation is unavailable to infiltration and runoff due to seasonal freezing
and snowfall precipitation. Beginning in April, the water levels rise quickly, stay elevated
through the beginning of June, and begin to trail off until their respective low points in August
through November. Short-term fluctuations in water levels are dramatic during spring snowmelt.
Well B1 shows increases and decreases of water level of as much as 10 feet within a single day;
water levels in other wells increase at the same magnitude on the order of a few days to a week.
The dramatic increase in water level in the wells is coincident with the beginning of seasonal
snowmelt, suggesting that residence times within the unsaturated zone are short and groundwater
is well connected to the surface. The seasonal response closely parallels stream flow fluctuations
during the same period. The spring increase in water levels in the wells lags behind the increase
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in stream flow, as might be expected since USGS Gauging Station 09112200 is located on a
stream that receives snowmelt from lower altitudes before melting begins near the Standard Mine.
In addition to the seasonal variations, the shallow wells also show short-term fluctuations such as
those seen in November 2008. The increase in water levels in wells B3 and B7 are concurrent
with stream flow increases, indicating that the increases are likely tied to rain events or snow that
melts rapidly. The high water levels during spring snowmelt relative to lower levels observed
during other seasons suggests that snowmelt is the primary source of recharge whereas seasonal
rain events are only a minor source.
Despite being screened at a deeper depth than the other wells, wells B1 and B5, both located on
the Ohio Creek Formation side of the Standard fault-vein, share the same seasonal variations as
the shallow wells. The observation that the deep wells respond in much the same time-scale and
during the same time periods as the shallow wells is consistent with vertical transmissivities being
similar among the wells and indicates that shallow rock units are in direct hydraulic
communication via interconnected fracture networks with deeper rock units.
Inter-granular permeability is low in the Ohio Creek and Wasatch Formations, but relatively
higher in the Ohio Creek Formation versus the clay-rich gouge found in the Standard fault-vein
and the Wasatch Formation. Porosity and permeability measurements performed on small hand
samples of bedrock indicate that the Ohio Creek surface outcrop sample had a porosity of 9.2
percent and an estimated hydraulic conductivity of 8.4 x 10"10 meters per second (m/s), fault
gouge from the Standard fault-vein had a porosity of 21.3 percent and an estimated hydraulic
conductivity of 3.5 x 10"11 m/s and the Wasatch surface outcrop sample had a porosity of 0.7
percent and an estimated hydraulic conductivity of 1.6 x 10"15 m/s (USGS 2010b).
Given the relatively low inter-granular permeability of the host rocks, the heterogeneously
distributed but relatively high-permeability iron-oxide stained joint networks are likely the major
control on infiltration and groundwater flow in the subsurface. Because the Ohio Creek and
Wasatch formations are highly fractured, water is expected to flow through the fractures and the
bulk permeability is expected to be much higher than the intergranular permeability. The average
hydraulic conductivities measured during slug tests in two groundwater wells in the Wasatch
formation was 1.38 x 10"6 m/s and 1.87 x 10"6 m/s. As expected, these values are significantly
higher than the intergranular permeability but the values should be considered an estimate at best.
The hydraulic conductivity values derived from slug tests are estimates based on aquifer and well
geometry assumptions and are only representative of the limited area around each tested well.
Estimates of hydraulic conductivity were similar in both wells B1 and B5 indicating that the
range of conductivities may also be representative of a larger radius beyond the wells. The
relatively low hydraulic conductivities were consistent with the low recharge rates observed
during sample collection. The slug-test-derived conductivities are typical for fractured
sedimentary rocks; however, they are low in comparison to those for unconsolidated materials,
and are thus consistent with relatively slow well recharge rates observed during well sampling
(UOS 2009).
The juxtaposition of possibly lower porosity and permeability Tertiary Wasatch formation against
the Tertiary Ohio Creek formation along the Standard fault-vein in combination with relatively
low-permeability clay-rich fault gouge in the core of the fault likely controls the occurrence and
flow of groundwater in the vicinity of the fault-vein and in the mine workings. Joints of a
regional joint set and joints related to faulting in Elk Creek Basin are the main pathways of
groundwater flow from the shallow subsurface to the mine workings. The fault-vein itself is
interpreted as a partial barrier to flow. The damage zone on either side of the fault core appears
to be poorly developed, suggesting that the damage zone does not consistently act as a direct
conduit to the mine workings. However, localized and high intensity fracture networks and
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breccia zones within the fault-vein may be discrete pathways of water infiltration, reaction of
oxygenated waters with sulfides, and shallow groundwater flow around and into the mine.
Groundwater that intersects the Standard fault-vein is likely impeded from crossing the fault but
may flow along the fault before discharging into the mine. Another source of water entering the
mine is deeper groundwater flow potentially rapidly transported through joint networks from the
sedimentary bedrock in the Upper Elk Basin (USGS 2010b). The fault-vein appears to act as an
asymmetric, combined conduit-barrier to groundwater flow, and groundwater likely flows from
the surface to the mine workings within joint networks distributed throughout the greater volume
of the sedimentary bedrock in the Upper Elk Basin. Once within the workings, water freely flows
from higher to lower levels via raises and stopes to ultimately discharge at the various mine
portals (USGS 2010b).
Based on observations from within the Level 3 and Level 5 tunnels, groundwater flows into these
levels primarily on the footwall (Ohio Creek Formation) side of the Standard fault-vein and on
the footwall side of the contact between the footwall damage zone and fault core. The geology in
the Level 2 tunnel is less visible due to the presence of timbers and flowstone. The fault-vein
itself appears to be a barrier to flow, and the hanging wall (Wasatch Formation) side conducts
minimal flow. The flow is primarily from fractures in the fault damage zone on the footwall side
of the fault, which was coated with a variety of precipitates. Flowstone deposits, meters long and
ranging from a few centimeters to several meters wide, are located at the present inflow locations
(DRMS 2007; DRMS 2009; USGS 2007; USGS 2010a; USGS2010b).
Flow into, within, and out of the mine workings was investigated during the 2006 and 2009
underground assessments (DRMS 2007; DRMS 2009). The findings of the USGS and DRMS
2006 and 2009 underground assessments related to the flow of water in the workings include the
following. The assessments were performed during July and August and relative flow patterns
during other times of the year may be different from those described below. Refer to Figure 1-4
for the mine workings cross section.
•	Water enters the accessible portion of Level 1 from behind the blockage. Water drains
from the caved material and can be heard to cascade inby the blockage.
•	Water enters Level 2 from Level 3 via raises, stopes, and surrounding rock.
Approximately 80 percent of the inflow observed during the July 2009 underground
assessment was via raises to Level 3 and open stopes and timbered areas between Levels
2 and 3. The remaining 20 percent of inflow appeared to be from surrounding rock joints
and fractures. The areas with the most intense groundwater inflows were in drifts driven
toward the footwall Ohio Creek formation, but some diffuse inflows were observed in the
hanging wall Wasatch formation. The inflows from both formations form iron flowstone.
Water exits Level 2 from at least three locations. At the farthest back raise on Level 2,
water just passes through Level 2 as it pours from the Level 3 raise and into the Level 1
winze. Water flowing down the center winze comes from rock formations and ore chutes
to the east. Most of the water flowing down the first raise is backflow from the mine
pool that was formed behind muck piles. The mine pool at Level 2 is water backed up
between a muck pile (outby) and the first winze to Level 1 (inby) and is not water backed
up from Level 1.
•	Water enters Level 3 via discrete and asymmetric groundwater flow from fractures in the
bedrock (primarily from the Ohio Creek Formation) and potentially a small amount of
flow from irregularities associated with the mineralized fault zone. Water exits from
Level 3 to Level 2 via a twin compartment raise/winze complex and at least one other
winze. Water has not been observed exiting the Level 3 portal.
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• Water enters Level 5 in a manner similar to Level 3, with the addition of water that enters
Level 5 from behind a collapse in the inby left drift. Water was accumulated on the floor
of the tunnel and high water marks were observed approximately three feet above the
floor. Water exits the Level 5 adit via the portal.
Much of the groundwater in the vicinity of the Standard mine is very young, being weeks to
months old rather than years old as determined by the tritium/helium-3 method. Short residence
times for much of the water in Standard Mine are consistent with the pronounced seasonal
variations in the geochemistry of groundwater discharging from the Level 1 tunnel. The short
residence times are not consistent with a large mine pool extending above the Level 1 tunnel
(USGS 2007). The oxygen and hydrogen isotope data in the 2009 water samples are consistent
with precipitation being the dominant control of the isotopic composition (USGS 2010a).
3.6 DEMOGRAPHY AND LAND USE
The Coal Creek watershed includes a total area of 24.4 square miles or 15, 600 acres. Much of
the watershed is made up of USFS land. The Coal Creek Watershed has a long history of mining.
Successive periods of mining activity have occurred in the area inducing precious metals
extraction, coal mining, and the mining of heavy metals. Mining first began in the Irwin silver
district in 1874 when the land was still a part of the Ute Indian Reservation with silver mining
activity ceasing by 1890 in this area except for the Forest Queen Mine. Sporadic mining activity
occurred between 1901 and 1974 with the tree largest producing mines the Standard Mine, the
Forest Queen Mine, and the Mt. Emmons Project mine. Two major molybdenum deposits were
discovered in the 1970s in the Mt. Emmons-Redwell Basin areas. Neither has been developed.
Active mining in the Coal Creek watershed has ceased although there are several abandoned mine
shafts and adits discharging water from underground workings into the surface water streams
(Stantec 2005a).
Other land uses include residential and vacation housing at the town of Irwin and the town of
Crested Butte. With most of the watershed comprised of USFS land, recreation is the
predominant land use in the area. Multiple-use trails for horseback riding, hiking, and mountain
biking exist for summer recreation and forest roads are used for cross-country skiing,
snowshoeing, and snowmobiling in the winter. Motorized vehicle traffic during summer months
is high. Off-road traffic on forest service roads also occurs during summer months (Stantec
2005a).
The town of Crested Butte uses water diverted from Coal Creek for domestic water supply. The
intake is located upgradient of the Mt. Emmons Project WTP outfall (Figure 2-2).
The town of Crested Butte does not have any municipal groundwater wells although several
private wells are used for domestic water supply (UOS 1999). UOS collected two groundwater
samples during the expanded SI, a background water sample from an artesian well 0.5 miles east
of Kebler Pass, and one domestic well for the residence located at 1060 County Road 12. This
well was believed to be the domestic use well closest to the potential sources of mining
contamination. The analytical results determined that the groundwater well downgradient of the
mining district was more mineralized than the background well, but the elevated concentrations
could not be attributed to a specific source and may be the result of groundwater exposed to
naturally occurring regional mineralization. Contaminant levels in the domestic use well were
not above primary or secondary drinking water maximum contaminant levels (MCLs).
Pesticides and fertilizers are not currently used within the watershed although they could be used
in the future by individual homeowners.
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3.7 ECOLOGY
The Standard Mine is located in the Rocky Mountain Physiographic Province, and the Southern
Rocky Mountain Sedimentary Subalpine Forest Ecoregion. The area is dominated by subalpine
forest with openings containing wetlands, waterways, rock outcrops, and areas disturbed by
mining activities. The upper reaches of the site are in the Alpine Ecoregion and are dominated by
relatively low growing herbaceous and woody plants (URS 2007).
Wetlands adjacent to site features, threatened and endangered species present at or near the site,
the nearby gossen and iron fen were investigated and the results are presented in the following
section. The results of investigations of other ecological resources including fish, fish habitat,
and aquatic macroinvertebrates are included in the BERA that is summarized in Section 6.
3.7.1 Wetlands
The wetlands were classified according to the Cowardin system as palustrine emergent
(PEM). PEM wetlands are defined as those wetlands that are 100 percent dominated by
erect, rooted, herbaceous plants. At the elevation of the study area, PEM wetlands are
commonly dominated by sedges (Carex spp.), rushes (Juncus spp.) and various forbs.
The HGM system classifies the wetlands in the study area as either slope or riverine.
Slope wetlands are located on a topographic slope and receive most of their water from
groundwater discharge. Riverine wetlands are associated with a stream channel,
floodplain, or terrace and get most of their water from an intermittent, ephemeral, or
perennial waterway.
Wetlands covering 1.04 acres were identified at Levels 1, 2, 98, and 5. Additional
wetlands are located near the site but away from mining impacts. The following sections
provide a description of each of the wetlands. More details on each site can be found in
Tables 3-12 through 3-14 and in the Standard Mine Wetland, Other Water Features, and
Threatened and Endangered Species Assessment, Gunnison County, Colorado (URS
2007). The wetlands are listed on Table 3-14 and mapped on Figure 3-15.
3.7.1.1 Level 1 Wetlands
Wetland 1-1
Size: 0.45 acre
Classification: PEM, Slope
Primary Functions: Wildlife habitat, production export/food chain support,
short- and long-term surface water storage, groundwater discharge
General Description: Hillside seep/spring adjacent to Level 1
Wetland 1-1 is the largest wetland in the study area and encompasses 0.45 acre.
It is located between the main mine facility and a mining road at Level 1. It is
classified as a PEM slope wetland and is dominated by marsh marigold (Caltha
leptosepala), brook saxifrage (Saxifraga odontoloma), Sierra fumewort
(Corydalis caseana), arrow leaf ragwort (Senecio triangularis), Fendler's
eowfaane (Oxypolis fendleri), and heartleaf bittercress (Cardamine cordifolia),
with numerous small pockets of diamondleaf willow (Salixplanifolia).
The wetland hydrology is provided primarily by groundwater discharge. The
wetland contains several small springs that converge into two small channels.
These channels discharge along the western edge of the wetland. Most of the site
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was saturated to the surface, with some areas inundated with as much as four
inches of water.
The soil is hydric and consists of a silty loam down to 14 inches. The soil has a
chroma of 1 (very dark color) (Kollmorgen Instruments, Inc. 1994), indicating
reducing conditions.
The primary ecological functions provided by Wetland 1-1 include wildlife
habitat, production export/food chain support, short- and long-term surface water
storage, and groundwater discharge. These functions are a result of the overall
size of the wetland combined with the presence of a perennial water source
(seeps and springs). The site discharges a substantial amount of groundwater
directly to Elk Creek (via two somewhat restricted outlets), moving nutrients
from the terrestrial environment to the aquatic system. The size of the wetland
and the restricted outlets result in both short- and long-term storage of
groundwater.
Wetland 1-2
Size: 0.01 acre
Classification: PEM, Riverine
Primary Functions: Sediment/nutrient/toxicant removal and retention
General Description: Numerous small fringe wetlands along Elk Creek, above
the tailings pond at Level 1
Wetland 1-2 consists of numerous very small pockets of wetlands immediately
adjacent to Elk Creek at Level 1. The sum of all the wetland parts encompasses
approximately 0.01 acre. The wetland is classified as a PEM riverine and is
dominated by water sedge, tufted hairgrass, heartleaf bittercress, Drummond's
rush, beaked sedge, and Fendler's cowbane.
The wetland hydrology is provided primarily through capillary action and
overbank flooding associated with Elk Creek. Some sheet flow from snowmelt
and other precipitation runoff may supplement the hydrology. Most of the site
was saturated to the surface, with some areas inundated with as much as four
inches of water.
The soil was assumed to be hydric due to the distinct wetland boundary, presence
of hydrophytic vegetation, and wetland hydrology indicators.
The primary ecological function provided by Wetland 1-2 is
sediment/nutrient/toxicant removal and retention. Since this wetland is overall
very small and divided into numerous parts, it is not as functional as some of the
other wetlands in the study area. As a result of its proximity to Elk Creek and the
presence of relatively dense vegetation, it does provide limited water quality
improvement by capturing and retaining sediments and toxicants.
Wetland 1-3
Size: 0.04 acre
Classification: PEM, Slope
Primary Functions: Wildlife habitat, groundwater discharge
General description: Hillside seep/spring immediately adjacent to Elk Creek at
Level 1
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Wetland 1-3 is a hillside seep/spring situated at the confluence of Elk Creek and
a small tributary immediately west of the tailings pond at Level 1. The wetland
encompasses approximately 0.04 acre and is classified as a PEM slope wetland.
The site is dominated by marsh marigold, Fendler's cowbane, brook saxifrage,
tufted hairgrass, and beaked sedge.
The wetland hydrology is provided by groundwater discharge and is likely
supplemented by sheetflow during snowmelt and overbank flooding from Elk
Creek. Most of the site was saturated to the surface, with some areas inundated
with as much as two inches of water.
The soil was assumed to be hydric due to the distinct wetland boundary, presence
of hydrophytic vegetation, and wetland hydrology indicators.
The primary ecological functions provided by Wetland 1-3 include general
wildlife habitat and groundwater discharge. These functions are a result of the
combination of the presence of a perennial water source (Elk Creek and seep)
and the discharge of groundwater. The wetland is also providing some limited
production export/food chain support and surface water storage.
3.7.1.2	Level 2 Wetland
Wetland 2-1
Size: 0.02 acre
Classification: PEM, Slope
Primary Function: Groundwater discharge
General Description: Hillside seep immediately downgradient from a mining
road near Level 2
Wetland 2-1 is a small hillside seep situated just below an existing mining road at
Level 2. The wetland encompasses approximately 0.02 acre and is classified as a
PEM slope wetland. The site is dominated by arrowleaf ragwort and heartleaf
bittercress, and is closely surrounded by Douglas fir and Englemann spruce.
The wetland hydrology is provided by groundwater discharge and snowmelt.
Most of the site was saturated to the surface, with some areas inundated with as
much as two inches of water.
The soil is hydric and consists of sandy clay down to 14 inches. The soil has a
chroma of 1 (very dark color) (Kollmorgen Instruments 1994), indicating
reducing conditions.
The primary ecological function provided by Wetland 2-1 is groundwater
discharge. The wetland is very small and somewhat isolated. Based on its
proximity to the mining road, it may provide a very limited amount of sediment
removal during major storm events.
3.7.1.3	Level 98 Wetland
Wetland 98-1
Size: 0.19 acre
Classification: PEM, Slope, Riverine, Depression
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Primary Functions: Wildlife habitat, sediment/nutrient/toxicant removal and
retention, sediment/shoreline stabilization, short-term water storage, groundwater
discharge
General description: Hillside seeps, small depression on waste rock, and Elk
Creek tributary fringe wetlands at Level 98
Wetland 98-1 encompasses approximately 0.19 acre. It includes three main
seeps (PEM, slope wetlands), several fringe wetlands along a tributary to Elk
Creek (PEM, riverine wetlands), and one small PEM depression wetland that is
the result of surface water collection on a waste rock pile. The dominant plant
species include water sedge, marsh marigold, arrowleaf ragwort, blue-joint grass,
and diamondleaf willow.
The wetland hydrology for is provided by groundwater discharge, snowmelt,
capillary action, and overbank flooding from the tributary to Elk Creek. Most of
the site was saturated to the surface, with some areas inundated with as much as
six inches of water.
The soil is hydric and consists of a sandy clay loam down to 14 inches. The soil
has a chroma of 1 (very dark color) (Kollmorgen Instruments 1994), indicating
reducing conditions.
The most important ecological functions provided by Wetland 98-1 include
wildlife habitat, sediment/nutrient/toxicant removal and retention,
sediment/shoreline stabilization, short-term surface water storage, and
groundwater discharge. These functions are the result of the presence of a
perennial water source (seeps and tributary to Elk Creek, including two small
ponds) and dense vegetation along the banks of a waterway (tributary to Elk
Creek).
3.7.1.4 Level 5 Wetland
Wetland 5-1
Size: 0.33 acre
Classification: PEM, Slope
Primary Functions: Wildlife habitat, short- and long-term surface water
storage, sediment/nutrient/toxicant removal and retention, groundwater discharge
General Description: Hillside seeps at Level 5
Wetland 5-1 encompasses approximately 0.33 acre and is classified as a PEM
slope wetland. The site includes three hillside seeps on both sides of the existing
mining road at Level 5. The dominant plant species include water sedge, tufted
hairgrass, and beaked sedge.
The wetland hydrology is provided by groundwater discharge and snowmelt.
The lower two seeps are connected via flow under the mining road. Most of the
site was saturated to the surface, with small areas inundated with as much as
inches of water.
The soil is hydric and consists of sandy clay loam down to 12 inches. The soil
has a chroma of 1 (very dark color) (Kollmorgen Instruments 1994), indicating
reducing conditions.
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The primary ecological functions provided by Wetland 5-1 include wildlife
habitat, short- and long-term surface water storage, sediment/nutrient/toxicant
removal and retention, and groundwater discharge. These functions are the result
of the overall size of the wetland, the presence of a perennial water source
(groundwater discharge), and the presence of dense vegetation combined with the
input of potentially contaminated water from the Level 5 adit.
3.7.2 Threatened and Endangered Species
Based on field evaluations, 51 of the nearly 100 T&E species listed as possibly occurring
in Gunnison County and the greater Gunnison National Forest have potential habitat in or
near the study area. These include 12 bird, 7 mammal, 2 amphibian, 2 invertebrate, and
28 plant species. Table 3-15 lists these species, their status, basic habitat requirements,
and possibility of occurrence. Those species that have a high likelihood of occurrence
(listed as "likely" or "possibly" occurring in Table 17) are discussed below by group.
The species listed in Table 3-15 as "unlikely" to occur in the study area are not discussed
further.
3.7.2.1	Birds
Based on field evaluations, six of the twelve bird species listed in Table 17 have
suitable habitat in the study area. These six species include the northern
goshawk, boreal owl, olive-sided flycatcher, peregrine falcon, white-tailed
ptarmigan, and the three-toed woodpecker.
The northern goshawk, boreal owl, three-toed woodpecker, and olive-side
flycatcher nest mostly in forested sites, while the other two species are most
likely to nest in more open areas, cliffs, or on rock outcrops. Although none of
these species were observed during the field surveys, they could be present
within the study area during nesting and/or foraging. Additionally, the northern
goshawk has been observed migrating elevationally and staying in or near
nesting locations year-round (USFS 2007).
The boreal owl, white-tailed ptarmigan, and three-toed woodpecker are year-
round residents (staying in the general location of their nests all year), whereas
the other three species are at least somewhat migratory and travel farther south
for the winter (Kingery 1998; Andrews and Righter 1992).
3.7.2.2	Mammals
Based on field evaluations, six of the seven mammal species listed in Table 3-15
have suitable habitat in the study area. These six species include Townsend's
big-eared bat, wolverine, Canada lynx, American marten, pygmy shrew, and
dwarf shrew.
The wolverine, lynx, and marten are very mobile species that use relatively large
areas and diverse habitats for foraging and denning, whereas the shrews are
likely to be found in deeply forested areas. The Townsend's big-eared bat is a
generalist in terms of foraging (forest, riparian, open areas), but only hibernates
or roosts in old mine shafts, adits, or buildings (Fitzgerald et al. 1994).
All six of these mammals are year-round residents of their Colorado habitats and
could potentially be found nesting, denning, and/or roosting in the study area.
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3.7.2.3	Amphibians
Only two amphibians have suitable habitat in the study area (Table 3-15),
including the boreal toad and northern leopard frog. Both species would only be
found in wetland or streamside habitats with slow-moving water and deeper
pools. The northern leopard frog over-winters at the bottom of bodies of water,
whereas the boreal toad spends the winter in a crevice or rock-lined chamber and
does not burrow deeply into the soil (Hammerson 1999).
Both the boreal toad and northern leopard frog could potentially be found year-
round along Elk Creek, its tributaries, and nearby wetlands in the study area.
3.7.2.4	Plants
Ten plant species listed in Table 3-15 have suitable habitat in the study area.
Four of the ten species are associated with wetlands and moist mountain
meadows, including Park milkvetch, marsh cinquefoil, autumn willow, and lesser
bladderwort. Five of the plants are found in areas with gravelly soil or on rocky
slopes, including Leadville milkvetch, reflected moonwort, Colorado wild
buckwheat, Colorado tansy aster, and Kotzebue's grass of Parnassus. The other
species, northern twayblade, is usually found in moist forested sites.
All, some, or none of these plants may occur in their appropriate habitats in the
study area. Generally, these plants will not be found in areas that have been
previously disturbed by human activity. Thus, the tailings area and waste rock
piles are not likely to contain any populations. However, populations could
potentially be found in or around the repository locations and/or in other
undisturbed areas in the study area.
3.7.3 Elk Creek Habitat
The first 200 to 300 feet of Elk Creek above the Coal Creek confluence currently
supports a brook trout fishery. Upstream movement of these fish is limited because of
the presence of two four-foot high waterfalls approximately 600 feet upstream from the
confluence of Elk and Coal Creeks. Elk Creek up to Elk-05 has similar habitat
characteristics as reference streams of similar size documented to support trout
populations on the GMUG National Forests; however, water temperatures in Elk Creek
are generally colder than reference streams and therefore may limit reproduction and
growth of trout. If brook trout were stocked into Elk Creek in the reach between 0.15
miles to 1.05 miles upstream of the confluence, they would most likely persist at low
numbers. Upstream of Elk-05, the amount of flow and usable habitat is greatly
diminished and therefore not suitable to support a trout fishery.
Habitat and water temperatures in the Elk Creek reach between 0.15 miles to 1.05 miles
upstream of the confluence were also examined to determine suitability to support a
Colorado River cutthroat trout (CRCT) fishery using a logistic regression model. The
model predicted a 5 percent probability of Elk Creek supporting a high number of CRCT,
a 37 percent probability of supporting a low population of CRCT, and a 58 percent
probability of not supporting a CRCT population. Cold water temperatures and small
stream size appear to be primary factors limiting establishment of a CRCT fishery.
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If a brook trout or a CRCT population were established in Elk Creek they would be
reproductively isolated because of the presence of two four-foot high waterfalls
approximately 400 to 600 feet upstream from the confluence with Coal Creek. Genetic
exchange would be limited so long-term persistence of a reproductively healthy
population is doubtful (USFS 2009, provided as Appendix F).
3.7.4 Mt. Emmons Gossan and Iron Fen
An iron gossan is located just west of the Mt. Emmons Project Mine at an elevation of
9,550 feet and covers approximately three acres (Figure 1-1). A gossan is formed when a
series of springs flow over highly mineralized and fractured bedrock rich in pyrite. This
process forms peat terraces composed of limonite, or natural aggregate of hydrous ferric
oxides lacking crystallization. Pyrite oxidation produces acidic byproducts that lower
pH. Pyritic gossans are characterized by a very dusky red to dark reddish brown or
moderate brown color. This gossan is one of eight in Colorado.
An iron bog, or fen, is present downgradient of the gossan. The fen is a peat wetland
with high nutrient content fed from upslope mineral-rich soil and groundwater
movement. Fens are defined by the USFWS as wetlands that are groundwater driven and
that have accumulated organic material (USFWS 1998). Fens are generally rare in the
region and often contain unique biotic assemblages. The soil in most fens meets the
Natural Resource Conservation Service (NRCS) definition of a histosol with at least 20 to
30 percent organic matter in at least 16 of the upper 32 inches. As a result of their
uniqueness, protection of fens is a priority for the USFWS and other regulatory agencies.
According to Cooper (2003), groundwater discharged from the base of Mt. Emmons
produces sheet flow and subsurface flow that perennially saturates the Mt. Emmons iron
fen. Unlike most fens, it contains water with very high concentrations of iron due to the
presence of iron pyrite rich bedrock that has been oxidized to create iron-leaching
sulfuric acid (Cooper 2003). As a result, the fen has very low pH and supports one of
only two known populations of the USFS sensitive roundleaf sundew (Drosera
rotundifolia). This small carnivorous plant has not been found anywhere else in the
Central or Southern Rocky Mountains in spite of extensive searches in similar acidic
fens. The USFS is concerned that molybdenum mining on Mt. Emmons may alter or
exterminate the sundew population. Another concern is the alteration of groundwater
flow by mining operations, which may remove water from springs that feed the fen.
Surface drainage from the iron fen sampled in 2005 indicated elevated aluminum, iron,
manganese, and zinc concentrations. The fen drainage had a pH of 3.4. Drainage from
the fen enters Coal Creek upstream of Crested Butte's drinking water intake from two
point sources. Observations also indicate that a large percentage of the drainage from the
iron fen and the gossan returns to the groundwater system and enters Coal Creek as
dispersed subsurface flow (Shanklin and Ryan 2006).
In order to ensure that site activities would not adversely affect the fen during Removal
Actions, potential impacts to the fen from site activities were investigated prior to
initiation of work. Although the Mt. Emmons Iron Fen is downgradient and within
approximately 0.3 mile of the Standard Mine main access road, work that is being done at
the Standard Mine and along the access road were not considered likely to adversely
affect the fen. The fen reportedly receives most of its water via groundwater discharge
(Cooper 2003), the mine is in a different subwatershed, and the access road
improvements (including culvert installation and increased construction traffic) are too
minor to have an effect on any surface flows or precipitation infiltration. The 0.3-mile
3-22

-------
URS Operating Services, Inc.
START 3, EPA Region 8
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Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
distance between the access road and the fen was considered adequate to intercept any
reasonably foreseeable increase in sediments or other toxicants that may make it through
the best management practices that were installed at key runoff locations along the
improved access road. In addition, none of the access road improvements should change
the quantity or direction of any surface flows in the area (URS 2007).
3-23

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Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 3-1
Level 1 Adit Discharge Data
SM-00 Flow Rate
(excluding flows over 200 gpm)
200
180
160
51 140
3
C
t 120
Q.
to
o 100
51 80	
I
5	~ ~
° 60	
40
20
0
«
~ ~
•V
~
10-Apr-08	19-Jul-08	27-Oct-08	4-Feb-09	15-May-09	23-Aug-09	l-Dec-09
3-24

-------
Standard Mine Level 2
Sample #6,
USGS EC-MSTDL26
Twin compartment
raise to Level #1
Entered drift
through orechute
from Level 3
-Water too deep to
continue; Open and
flooded to extent visible
Raise to Level #1?; Visible
sublevel at 30ft with drifts
Sample #3
USGS EC-MSTDL23
Large raise/ore pass to
Level #1 with grizzly
Raise to Level #3
Diffuse inflows
Sample #2
USGS EC-MSTDL22
Poo ed water
Sample #4,
USGS EC-MSTDL24
Poo ed water
Sample #1, USGS EC-MSTDL21
Center pillar
extensively silicified
Extensive f owstone
Stoped up 15ft
Sample #5, USGS EC-MSTDL25
- Extensively timbered
back: Diffuse inflows
Unsafe to continue due
to collapsed timber; Drift
continues out of site;
Drier down drift
COLORADO
C I Ore Chute
Foot of Raise
\/\ Head of Raise
I I I I I I I I M I
0'	25'	50'
Mapped by Jeff Graves and Al Amundson
N
f £5 %
w
aorrtv'
URS
OPERATING SERVICES
Standard Mine,
Gunnison County
Figure 3-2: Level 2 Mine Workings
©
UOS- START 3
TDD No. 0608 -07

-------
LEVEL 3 STANDARD MINE
1"oc shaft connects
to lower levels
laise and chute
extends >40' up\^
sloped up 15' x.
fault zone 5' . . t,
-rrirt^ h water inflows Sjy*^
fault zone 2.5-3' min' zone 1-2
fault zone 4.5' wk. min. zone timbered back^
min. 7one 1 5'
Toe / I
double compartment shaft extends 	| W I
dov/nv/ard and to surface \ 		 ' t qmp j USGS sample
lw j MSTDL3-3
USGS sample
MSTDL3 2
Tov fault zone 5'
n. min. zone 1.5-2' diffuse water Inflows 	-
stoped up 15* \ r-1—	
			
T™
•^sloped below \
\ timbered over \
faultzone 6-7' ^ sample
MSTDL3-4
Mapped by Jeff Graves and Steve Renner
Colorado Division of Reclamation, Mining
and Safety
August, 2006
1 1 1 1 1 1 I 1 1 1 1
0' 50' 101)'
USGS samp'e
MSTDL3-5 \
fault zone 4-fi' \
min. zone 
-------
exploration blocked by c
water flowing over top
fault splits
Fault near vertical
no mm
fault splits and rolls
USGS sample

minor stopmg in back
fault zone 3.5-4
min. zone 0.5
fault zone 1
no min
USGS sample
MSTDL5-1
Mapped by Jim Herron and Steven Renner
Colorado Division of Reclamation, Mining
and Safety
August, 2006
J	L

J	L
~fso' Fault- dip direction and magnitude indicated
Tw Wasatch Formation
W
aorrtv'
URS
OPERATING SERVICES
Standard Mine,
Gunnison County
Figure 3-4: Level 5 Mine Workings
©
UOS- START 3
TDD No. 0608 -07
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 3-5
Mean Daily Stream Flow
USGS Gauging Station 09111500, Slate River near Crested Butte
Period of Record October 1,1940, through September 30, 2006
800
700
600
500
400
300
200
100
0
o
Month
3-28
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URS Operating Services, Inc.
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TDD No. 0608-07
Date: 05/2010
FIGURE 3-6
Mean Daily Stream Flow
USGS Gauging Station 09112200, East River below Cement Creek
Period of Record October 1,1963, through January 16, 2009
1600
1400
1200
1000





Month

O
*
9
3-29
-------
URS Operating Services, Inc.
START 3. EPA Region 8
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Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 3-7
Peak and Average Stream Flow
USGS Gauging Station 0911500, Slate River near Crested Butte
Period of Record October 1,1963, through September 30, 2006
1600.0
1400.0
o 1200.0
1000.0
800.0
600.0
400.0
200.0
0.0
1930
1940
1950
1960
1970
1980
1990
2000
2010
Year
—¦— Peak Flow	—•— Average Flow
3-30
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URS Operating Services, Inc.
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Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 3-8
Peak and Average Stream Flow
USGS Gauging Station 09112200, East River below Cement Creek
Period of Record October 1,1963 through January 16, 2009
5,000
4,500
4,000
3 3,500
,000
=2 2,500
2,000
1,500
1,000
500
0
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Year
—¦— Peak Flow	—•— Average Flow
3-31
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URS Operating Services, Inc.
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Date: 05/2010
FIGURE 3-9
Stream Flow Along Coal Creek
Flow Rate Along Coal Creek - June
Ol
4—1
3
90
80
70
60
50
TO
M 40
2 30
20
10
0
]


hi




 6>
5?
¦Vr	^
^	fC?
£
$
§
i
i
i
3-32
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 3-10
Stream Flow Along Elk Creek

70

60
CD




50
c


ui
ci
40
_o

"ro

tuO
30

CD

ro

cc

5
20
_o

Ll_


10

0
Flow Rate Along Elk Creek - June























I	L 1	L


3 1 b 1
B .1
hi
\\m
ELK-29 ELK-10 COP-01 ELK-08
ELK-06 ELK-05
ELK-00
¦	Jun-05
¦	Jun-06
~	Jun-07
¦	Jun-08
~	Jun-09
01
4—"
£
d
_o
"ro
tuO
cc
Flow Rate Along Elk Creek - September
2.5
1.5
0.5
_~
ELK-29
J]
	
ELK-10 COP-01

ELK-08 ELK-06 ELK-05
I
¦	Sep-05
¦	Sep-06
~	Sep-07
~	Sep-08
~	Sep-09
ELK-00
3-33
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URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 3-11
Average Daily Flow Rate for Elk-00
ELKOO Flow Rate
(excluding flow over 11040 GPM)
10000.00
8000.00
2
Q.
^ 6000.00
(U
~ ~~
4000.00
2000.00
0.00
7-Jul-07 15-Oct-07 23-Jan-08 2-May-08 10-Aug-08 18-Nov-08 26-Feb-09 6-Jun-09 14-Sep-09 23-Dec-09
3-34
-------
(1)
3
D)
Li.
6)
o
_s- W1
t Lb
I XL
0)|
0	CD
J 21
1	9=
1S:
I -S
Q -g
s §
< In
p
ss
Ste
0	i-'
C! e
CD o
™ 1
1	j
LEVEL 981
LEVEL 1
\ qrnp
Kmvo
Legend
Mine Roads
Feet
Map Base: Gaskill, et al., 1967
Levels Boundary
Quaternary talus
deposits
Quaternary landslide
deposits
Quaternary glacial
deposits
Tertiary fetsite
Tertiary quartz
monzonite porphyry
Tertiary Wasatch
Formation
Upper Cretaceous
Ohio Creek member
ot Mesaverde Formation
Upper Cretaceous Mesaverde
Formation undivided
UBS
QPERAIIRill SERVICES
Standard Mine
Gunnison County, CO
Figure 3-12 - Geological Map
March 2010
UOS - START 3
TDD No. 0608-07
-------
EXPLANATION
Faults
Certain
Inferred
Concealed
Rock Units
I IQI
~ Qm
I lot
¦ it
I I Toe
	I	I Tqmp
II	I Tw
I I Kmv
Quartz Veins
Portal RTKGPS
Borehole RTKGPS
¦	Elk Creek
¦	Watershed Divide
¦	Topo Gradient Vectors
Contours
o
' /c
, °
Approximate Mean
Declination. 2009
SCALE
1:11,567
0	0.1 0.2
1	i I i I
Kilometers
RECONNAISSANCE GEOLOGIC MAP OF THE UPPER ELK BASIN, OH-BE-JOYFUL QUADRANGLE, GUNNISON COUNTY, COLORADO
Modified
ul Caine. 2009
J.S. Caine and others. USGS Open File Report 2010-1008
* A \
URS
OPERAUNC SERVICES
Standard Mine,
Gunnison County
Figure 3-13: Geologic Map and
Water Flow
©
UOS- START 3
TDD No. 0608 -07
-38e53'0"N
107e4'30"'W
I
107a4'0"W
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URS Operating Services, Inc.
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Date: 05/2010
FIGURE 3-14
Water Levels in Groundwater Wells
Water Levels in Groundwater Wells and Stream Flow
10
20
a 30
40
50






tod

1
m
iCv
M


—	



60
& & _<§>	_<$ jS1 .5?
3000
2500
2000
1500
1000
500
Strea m


Streamflow data from USGS Gauging Station 09112200, East River below Cement Creek near Crested Butte, Colorado
3-37
-------
N Level 98 Adit
EtlarM9s!
Level 98 WL-5,
Level 5 WL-2 v 11 'il11'PWl
. \_JI^llleve l[5/Adltj
¦f ' Il WL-'4<
I ¦ 11
Level sMlm
Level 98 WL-3
I 8,9
Leyel;§8,WL-2
"* -Level 5 WL-1
Levei 98 VVL
V\fetlandr2al

lWetlandl1g2-
Wetiand 1-1
Wetlanq, 1 -3
Legend
2007 Wetland Sample Locations
Study Area
El Wetland Area
no Other Water Feature
Soil Pit
Photo Point
0 75 150
I Feet
1 inch equals 300 feet
URS
OPERMIIG SE81SES
Standard Mine
Gunnison County, CO
Figure 3-15 Wetlands Map
March 2010
UOS - START 3
TDD No. 0509-08
<-o
r: to
CO %
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 3-1
Meteorological Data - Crested Butte (Station 051959)
Period of Record: 6/1/1909 to 12/31/2007


lel>
Miir
Apr
M;i\
.lllll
Jul
Auii
Sop
Oc(
No\
Dec
Auniiiil
Average Max.
Temperature (F)
27.9
31.6
38.2
47.3
59.2
70.2
75.9
73.9
66.6
56.3
40.9
30.2
51.5
Average Min.
Temperature (F)
-4.3
-1.1
7.2
18.3
27.8
33.2
38.4
37.6
30.2
20.8
8.6
-2.1
17.9
Average Total
Precipitation (in.)
2.70
2.35
2.33
1.78
1.43
1.32
2.01
2.14
2.04
1.52
1.73
2.26
23.61
Average Total
Snowfall (in.)
40.1
34.6
31.8
17.3
6.4
0.7
0.0
0.0
1.3
7.7
24.1
33.8
197.9
Average Snow
Depth (in.)
26
35
33
13
0
0
0
0
0
0
4
14
10
Western Regional Climate Center, wrcc(a),dri.edu
TABLE 3-2
Meteorological Data - Taylor Park (Station 058184)
Period of Record: 10/19/1940 to 7/31/2007

.I:iii
Ich
Miir
Apr
M;i\
Jim
Jul
Aim
Sop
(Hi
\»\
Doc
Auniiiil
Average Max.
Temperature (F)
26.7
31.9
37.8
45.7
56.2
67.2
71.7
69.2
63.4
53.4
38.4
27.9
49.1
Average Min.
Temperature (F)
-10.6
-8.7
-0.1
14.4
26.6
34.0
40.7
39.7
32.2
23.6
10.0
-5.8
16.3
Average Total
Precipitation (in.)
1.33
1.26
1.46
1.38
1.30
1.00
1.83
1.82
1.41
1.27
1.28
1.30
16.64
Average Total
SnowFall (in.)
22.5
16.3
18.2
11.2
2.5
0.2
0.0
0.0
0.2
3.1
12.8
19.3
106.3
Average Snow
Depth (in.)
21
25
25
13
1
0
0
0
0
0
3
10
8
Western Regional Climate Center, wrcc(a),dri.edu
TABLE 3-3
Meteorological Data - Independence Pass 5SW (Station 054270)
Period of Record: 7/ 1/1947 to 1/31/1980

Jim
lcl>
Miir
Apr
M;i\
Jim
Jul
Auii
Sop
Oc(
No\
Dec
Auniiiil
Average Max.
Temperature (F)
27.2
30.1
36.2
41.6
50.8
63.3
67.8
66.3
57.4
47.2
34.3
27.2
45.8
Average Min.
Temperature (F)
-1.8
-0.8
6.8
11.7
22.1
30.4
35.9
34.3
28.7
19.9
6.9
-0.2
16.2
Average Total
Precipitation (in.)
3.51
2.46
3.97
3.48
1.96
1.11
2.23
1.91
1.70
1.76
2.72
3.02
29.82
Average Total
SnowFall (in.)
50.1
38.6
58.8
45.1
20.6
3.8
0.0
0.0
4.9
20.3
43.0
50.8
335.9
Average Snow
Depth (in.)
39
48
56
55
23
1
0
0
0
2
12
26
22
Western Regional Climate Center, wrcc(a),dri.edu
3-39
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 3-4
Snotel Water Accumulation Data (For period ending in October of the year shown, in inches)
Year
lillllO
1 ii(k'|K'M(k'iici' P;iss
Park Com.'
Schollcld Pass
1980
--
—
26.0
--
1981
--
27.2
18.2
--
1982
29.3
34.2
20.5
--
1983
24.8
35.0
20.1
--
1984
38.5
42.2
29.0
--
1985
30.1
34.4
25.1
--
1986
34.4
35.7
28.5
69.8
1987
23.6
26.8
21.6
39.8
1988
23.1
25.3
17.6
39.7
1989
24.3
29.1
20.0
44.7
1990
21.8
29.5
19.6
39.0
1991
25.3
27.7
21.0
47.5
1992
24.9
28.0
21.6
41.1
1993
33.1
35.2
22.7
60.0
1994
20.9
25.6
19.0
41.1
1995
37.3
43.8
31.8
68.7
1996
27.8
33.9
23.2
54.6
1997
33.3
34.8
27.0
62.1
1998
22.1
28.2
16.5
43.5
1999
30.8
33.8
25.2
52.6
2000
22.8
27.4
18.1
43.7
2001
24.1
30.0
15.5
46.4
2002
19.2
21.2
14.3
34.6
2003
25.0
27.9
18.6
46.4
2004
21.7
25.9
18.1
44.8
2005
28.8
28.4
20.0
54.7
2006
28.4
33.7
22.4
49.6
2007
22.0
33.4
17.1
42.3
2008
31.4
35.4
24.5
58.8
http://www.wrcc.dri.edu/snotel.html
3-40
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TABLE 3-5
Monthly Average Stream Flow (Cubic Feet per Second)
USGS Gauging Station 09111500, Slate River near Crested Butte

Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
1940
--
--
--
133.7
488.5
280.1
50.7
15.2
28.1
29.6
19.2
13.0
1941
10.0
10.0
11.0
67.3
778.0
579.1
196.7
43.8
32.6
63.9
37.9
20.1
1942
13.5
13.4
13.0
143.0
487.6
628.2
155.2
30.9
13.8
10.2
8.63
8.03
1943
9.09
9.45
15.0
303.0
500.6
560.4
175.8
57.5
32.9
21.4
24.6
14.5
1944
10.1
8.74
10.3
36.4
497.0
711.9
242.1
50.0
16.1
18.6
22.3
14.0
1945
8.80
6.20
12.0
38.0
505.8
586.5
281.3
89.1
21.2
22.1
27.8
19.8
1946
12.1
9.36
17.0
243.2
394.3
595.8
113.8
30.6
16.4
23.8
18.8
13.1
1947
8.35
8.96
15.0
77.3
606.3
594.6
292.9
67.1
37.6
47.6
30.7
20.5
1948
13.1
11.1
11.8
104.1
772.3
633.1
174.6
41.3
15.5
19.8
13.0
10.5
1949
10.9
9.45
12.3
131.8
440.5
726.4
229.7
39.2
19.3
24.9
17.0
12.3
1950
10.9
9.28
8.52
142.1
440.2
598.0
159.5
23.2
23.2
14.5
11.0
11.2
1951
10.1
8.41
13.7
58.0
471.7
618.6
224.1
46.1
17.1
--
--
--
1993
--
--
--
--
--
--
--
--
--
51.6
37.1
25.1
1994
16.7
11.9
27.8
130.8
541.1
484.7
71.4
21.5
18.2
32.6
24.5
16.1
1995
14.1
16.7
27.8
66.0
280.7
971.3
804.3
236.5
62.7
42.5
28.8
23.8
1996
23.5
20.0
21.3
164.3
775.2
682.5
167.4
37.7
26.3
29.3
28.5
21.1
1997
18.5
17.9
40.2
166.8
765.7
795.2
224.8
87.3
56.1
68.4
38.4
21.9
1998
20.6
15.2
34.3
90.0
455.1
547.6
280.0
46.8
17.0
22.0
21.8
16.3
1999
14.9
14.8
44.3
102.5
382.7
592.0
163.5
53.1
49.6
32.5
16.6
15.7
2000
16.5
13.9
19.6
148.0
527.9
332.9
63.5
18.9
19.0
20.2
16.7
12.7
2001
11.7
12.4
19.4
102.6
641.0
365.9
91.1
56.6
23.4
22.0
25.4
19.3
2002
20.3
21.6
25.0
180.4
247.7
133.7
17.9
7.74
17.6
30.6
21.5
17.6
2003
14.7
14.3
20.4
96.2
548.0
428.8
65.7
23.0
27.5
15.5
15.0
12.1
2004
11.0
10.3
52.8
129.6
423.5
319.4
90.0
12.8
18.4
23.4
20.4
18.8
2005
17.3
15.4
20.6
130.7
536.2
579.3
241.0
54.5
30.4
36.6
29.9
21.4
2006
20.0
19.0
25.3
195.6
696.6
450.2
115.5
41.8
37.2
--
--
--
Mean
14
13
22
127
528
552
188
49
27
30
23
17
http://waterdata.usgs.gov/nwis/sw
3-41
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 3-6
Monthly Average Stream Flow (Cubic Feet per Second)
USGS Gauging Station 09112200, East River below Cement Creek

Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
1963
--
--
--
--
--
--
--
--
--
58.5
62.4
51.7
1964
46.6
42.7
43.5
77.0
883.4
1,010
431.4
181.0
103.1
74.5
72.8
60.5
1965
59.5
52.1
46.1
155.9
1,115
1,914
1,345
395.7
270.9
187.5
112.6
96.2
1966
76.0
59.8
76.5
363.9
916.0
662.4
224.6
118.8
70.0
71.9
67.4
67.8
1967
56.5
55.9
75.6
269.5
895.9
1,191
476.4
180.6
150.9
103.2
75.4
71.4
1968
56.9
63.6
54.2
113.8
884.5
1,690
487.1
311.0
137.5
114.5
92.0
72.1
1969
63.4
56.7
53.7
373.8
1,328
966.0
587.6
210.0
154.6
150.5
106.5
82.1
1970
67.9
67.1
64.6
102.5
1,432
1,402
540.5
199.3
261.0
143.9
114.8
93.8
1971
83.2
76.0
84.9
404.0
765.6
1,460
623.0
213.5
133.8
118.6
93.1
75.4
1972
66.7
63.0
111.1
271.5
814.8
1,049
242.7
102.1
118.8
--
--
--
1979
--
--
--
--
--
--
--
--
--
97.2
84.2
72.6
1980
63.9
60.3
56.3
183.6
1,145
1,978
745.5
206.5
120.6
93.2
74.8
61.2
1981
50.1
47.7
47.9
181.0
406.1
632.6
181.3
91.7
77.6
--
--
--
1993
--
--
--
--
--
--
--
--
--
160.4
76.1
59.0
1994
56.4
50.4
64.6
270.9
1,071
1,064
237.0
104.8
64.3
87.1
79.6
52.8
1995
43.8
53.9
80.0
140.6
774.0
2,450
1,796
608.6
179.8
142.6
121.0
66.5
1996
66.8
68.4
59.9
275.5
1,606
1,524
495.5
163.9
109.4
116.4
90.0
67.6
1997
66.5
53.2
94.0
352.4
1,588
2,125
705.4
261.4
179.0
182.0
124.8
88.4
1998
76.9
69.4
86.6
170.1
833.4
980.0
552.1
151.4
99.2
95.0
89.0
64.8
1999
63.2
61.5
113.3
262.6
954.5
1,523
576.4
257.9
187.9
130.2
89.3
67.3
2000
61.8
54.0
54.2
338.5
1,101
744.3
182.1
94.8
95.3
86.3
73.3
57.9
2001
53.6
49.6
56.2
219.8
1,055
789.9
222.1
179.2
107.4
83.1
79.1
58.1
2002
48.5
47.0
59.4
309.2
450.2
308.5
101.5
63.5
72.2
84.7
69.2
48.6
2003
44.3
44.5
55.4
227.3
1,066
1,050
248.8
136.9
122.8
75.3
69.6
59.6
2004
61.0
54.8
126.7
322.0
805.3
710.0
238.7
95.0
82.1
91.9
86.2
58.5
2005
53.4
55.3
58.4
251.3
1,047
1,279
605.8
180.1
110.3
130.8
98.0
73.9
2006
75.0
64.8
68.9
427.2
1,211
958.5
344.0
161.3
148.4
256.3
147.7
100.8
2007
69.8
60.5
137.4
337.4
802.5
644.5
199.7
107.1
120.6
111.4
76.8
70.5
2008
60.6
61.2
66.8
200.1
1,268
1,890
846.3
241.4
138.4
--
--
--
Mean
61
57
73
254
1,010
1,230
509
193
131
117
89
69
http://waterdata.usgs.gov/nwis/sw
3-42
-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 3-7
Monthly Average Stream Flow (Cubic Feet per Second)
USGS Gauging Station 365106106571000, Slate River above Baxter Gulch

Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
2006
--
--
--
--
--
--
--
--
--
89.3
48.4
27.7
2007
26.4
31.4
71.8
185.2
419.6
276.0
60.6
26.6
40.6
46.5
25.7
20.1
2008
21.4
20.6
22.3
89.0
577.4
854.9
294.5
54.8
22.6
--
--
-
Mean
24
26
47
137
498
565
178
41
32
68
37
24
http://waterdata.usgs.gov/nwis/sw
3-43
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 3-8
Annual Average and Peak Stream Flow
USGS Gauging Station 09111500, Slate River near Crested Butte
00060, Average
Discharge, cubic feet per
second
Annual Average Stream
Flow
Annual Peak Stream
Flow
Date of Peak Stream
Flow
1940
--
696
May 11, 1940
1941
150.1
1,240
May 13, 1941
1942
135.3
1,180
May 27, 1942
1943
141.0
1,200
Jun. 02, 1943
1944
137.0
1,070
May 16, 1944
1945
134.3
930
Jun. 15, 1945
1946
125.1
1,040
Jun. 09, 1946
1947
147.7
1,040
Jun.09, 1947
1948
156.7
1,130
May 22, 1948
1949
138.7
1,090
Jun. 18, 1949
1950
122.6
882
Jun.02, 1950
1951
125.8
1,020
May 29, 1951
1994
120.2
981
Jun. 01, 1994
1995
213.6
1,550
Jun.17, 1995
1996
168.0
1,330
May 17, 1996
1997
188.2
1,400
Jun. 01, 1997
1998
136.9
915
Jun. 02, 1998
1999
123.3
878
May 24, 1999
2000
102.3
958
May 25, 2000
2001
115.2
1,170
May 15,2001
2002
61.6
476
Jun. 01,2002
2003
109.4
1,420
May 30, 2003
2004
92.7
667
Jun.08,2004
2005
141.1
1,210
May 23, 2005
2006
141.3
1,240
May 23, 2006
Mean
134.5
1,068.52

http://waterdata.usgs.gov/nwis/sw
3-44
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 3-9
Annual Average and Peak Stream Flow
USGS Gauging Station 09112200, East River below Cement Creek
00060, Average
Discharge, cubic feet per
second
Annual Average Stream
Flow
Annual Peak Stream
Flow
Date of Peak Stream
Flow
1964
249.8
2,020
May 21, 1964
1965
465.4
2,650
June 21, 1965
1966
248.0
1,530
May 8, 1966
1967
297.2
2,160
May 24, 1967
1968
337.0
2,640
June 06, 1968
1969
341.1
1,820
May 30, 1969
1970
374.5
2,300
May 27, 1970
1971
350.0
2,070
June 18, 1971
1972
260.3
1,830
June 02, 1972
1980
400.9
3,360
June 12, 1980
1981
162.2
1,250
June 08, 1981
1994
274.0
2,000
June 01, 1994
1995
530.8
4,350
June 18, 1995
1996
392.2
2,860
May 20, 1996
1997
476.0
3,190
June 04, 1997
1998
285.7
1,560
June 04, 1998
1999
354.7
2,010
May 29, 1999
2000
251.4
1,980
May 25, 2000
2001
246.9
1,660
May 16, 2001
2002
140.2
847
June 1, 2002
2003
267.3
2,870
May 30, -2003
2004
225.2
1,340
Jun.07, 2004
2005
324.1
2,320
May 25, 2005
2006
314.5
2,250
May 23, 2006
2007
249.5
1,310
May 20, 2007
2008
419.5
2,820
May 21, 2008
Mean
316.86
2,083.73
--
http://waterdata.usgs.gov/nwis/sw
3-45
-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 3-10
Annual Average and Peak Stream Flow
USGS Gauging Station 365106106571000, Slate River above Baxter Gulch
00060, Average
Discharge, cubic feet per
second
Annual Average Stream
Flow
Annual Peak Stream
Flow
Date of Peak Stream
Flow
2007
109.0
678
May 20, 2007
2008
170.8
1,320
May 21, 2008
--
139.9
999
--
http://waterdata.usgs.gov/nwis/sw
3-46
-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 3-11
Monitoring Locations
Monitoring
Location
Latitude
Longitude
Location Description
Bog-00
38.86289128
-107.04484622
Iron fen outfall at Kebler Pass Road. 800 feet downstream of mile marker
20.
Coal-00
38.87694909
-106.978413386
Coal Creek upstream of pedestrian bridge on Butte Ave. just upstream of
Slate River confluence.
Coal-01
38.866738
-106.983376
Totem Pole Park near intersection of 3rd Ave. and Maroon Ave. Sampled
downstream of bridge to allow for mixing of stormwater discharge at the
bridge.
Coal-02
38.867593416
-106.991144117
Coal Creek upstream of town of Crested Butte on Kebler Pass Road.
Coal-05
38.86724553
-107.02320837
Coal Creek approximately 10 meters downstream of Wildcat Trail bridge.
Coal-06
38.866864
-107.016744
Upstream of Coal-05. Approximately 300 meters downstream of confluence
of Coal Creek and the Keystone tributary.
Coal-10
38.86687606
-107.02365541
Coal Creek approximately 100 meters upstream of Mt. Emmons Project
WTP outfall.
Coal-10.5
38.864889
-107.03
Upstream of Coal-10 and downstream of Coal-11. Sampled downstream of
1st culvert upstream of Key-00
Coal-11
a.k.a. Bog-01
38.86357807
-107.04232123
50 meters upstream of 4x4 road down to creek. This site is downstream of
3rd outfall possibly receiving inputs from the fen.
Coal-15
38.85608812
-107.05862559
Coal Creek 100 meters downstream of Elk Creek confluence.
Coal-20
38.8558865
-107.06012541
Coal Creek approximately 50 yards upstream of Elk Creek confluence.
Coal-25
38.8548922
-107.09041652
Coal Creek downstream from Independence and Anthracite/Ruby
confluence.
Coal-30
38.866768
-107.09363
Coal Creek downstream of Irwin and the Forest Queen mine workings.
Coal-Oppl
38.86203669
-107.04403718
Coal Creek upstream of iron fen outfall.
Coal-Opp2
38.8625742966
-107.03874037
Coal Creek downstream of iron fen outfall.
Cop-00
38.871335376
-107.078837486
Copley Lake outfall
Cop-01
38.87133538
-107.07883749
Copley Lake outfall approximately 30 yards upstream of Elk Creek
confluence and downstream of Cop-00.
Elk-00
38.85690185
-107.0598188
Elk Creek at County Road 12 crossing approximately 100 yards upstream of
confluence with Coal Creek.
Elk-01

Elk Creek 0.1 mile above County Road 12 and upstream from Elk-00.
Elk-05
38.86529353
-107.07395799
Elk Creek approximately 130 feet downstream of confluence of several
seeps that feed Elk Creek from the eastern bank.
Elk-06
38.86629066
-107.07497838
Elk Creek upstream of several seeps that feed Elk Creek.
Elk-08
38.87065355
-107.07870823
Elk Creek downstream of Copley Lake outfall.
Elk-10
38.87810409
-107.07521878
Elk Creek approximately 30 meters below historic tailings impoundment.
Elk-12

Elk Creek upstream from Elk-10 located within engineered channel and
formerly underneath the support beams for the RR trestle, which have since
been removed.
Elk-15
38.88010685
-107.07413446
Small tributary to Elk Creek upstream of Elk-10.
3-47
-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 3-11
Monitoring Locations
Monitoring
Location
Latitude
Longitude
Location Description
Elk-20, -21,
-22, -23, -24,
-25, -26,
and -27

Prospect pits in the upper Elk Creek basin in the vicinity of the Standard
Mine.
Elk-29
38.88203818
-107.07298851
Elk Creek upstream of the primary mine site and downstream of confluence
of individual Elk Creek flows (tributaries near headwaters).
Elk-30
38.883793039
-107.070287034
Upstream of Elk-29 in middle Elk Creek tributary. Downstream of a small
prospect pit and waste rock pile.
IR-00
38.87524824
-107.10065081
Lake Irwin outfall approximately 75 meters downstream of pump house.
IR-02
38.887959
-107.11204
Inflow to Irwin Lake upstream of all mining activity and the lake.
Key-00
38.86725026
-107.02378392
Approximately 3 meters upstream of Kebler Pass Road below the
confluence of Key-01 and Key-02.
Key-Oppl
38.86763959323
-107.02421190013
Tributary upstream of Coal-05 and Wildcat Trail bridge. Enters Coal Creek
from the north but is downstream of the wither trailhead and all "Key"
tributaries.
Key-01
38.86763959323
-107.02421190013
15 meters up the hillside from Kebler Pass Road. Key-01 is the western
contributor to Key-00. Contains discharge from the WTP.
Key-02
38.8676640777
-107.02416275667
15 meters up the hillside from Kebler Pass Road. Key-02 is the east
contributor to Key-00.
Key-Ditch
38.866675
-107.024083
Metal culvert a few feet to the west of Key-00. Water enters from the west
via a bar ditch and flows into Key-00.
Level 5 Adit
38.88403595
-107.06760827
Sampled directly in pool at the mouth of the Level 5 adit.
Level 5 WL-1
38.88381088
-107.06868695
Flowing seep approximately 75 m downstream of waste rock piles at Level
5.
Level 5 WL-2
38.88397029
-107.06820383
Sampled immediately below road between waste rock and wetlands
Level 5 WL-3
38.88389956
-107.06810059
Sampled at the toe of waste rock pile on the right.
Level 98 Adit
38.884051
-107.07062599
Sampled approximately 15 m downstream of the adit opening above the
seep flowing down the hillside.
Level 98 WL-1
38.88313752
-107.07116301
Sampled in Elk Creek channel below wetland seep influences flowing
through waste rock at Level 98.
Level 98 WL-2
38.88340983
-107.07107982
Facing downstream, farthest left seep from wetland below Level 98 adit.
Sampled in trees 20 m upstream of Elk Creek confluence.
Level 98 WL-3
38.8835015
-107.07149772
Facing downstream, farthest right seep from wetland below Level 98 adit.
Samples 25 meters downstream of berm near Level 98 WL-4.
Level 98 WL-4
38.88377314
-107.07112975
Downstream of vegetation test plots and approximately 50 meters
downstream of Level 98 adit flowing down the hillside.
Level 98 WL-5
38.88404833
-107.06997594
Above adit indraw coming down the slope; runs into wetland system east of
adit drainage.
Slate-01
38.878482039
-106.977844317
Slate River upstream of confluence with Coal Creek, approximately 100
meters upstream of bridge.
Slate-02
38.87669401
-106.976659136
Slate River downstream of confluence with Coal Creek, approximately 100
meters downstream of bridge.
SM-00
38.88011481
-107.07374625
Standard Mine adit as it passes through the flume.
SM-02
38.878582114
-107.075186562
Northwest corner of tailings pond.
3-48
-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 3-11
Monitoring Locations
Monitoring
Location
Latitude
Longitude
Location Description
SP-00
38.85542577
-107.06407113
Splain's Gulch immediately above confluence with Coal Creek: reference
location for Elk Creek
SP-01
38.84196435
-107.06257191
Upper Splain's Gulch above road crossing: reference location for Elk Creek.
Wild-00
38.86909399
-107.00889489
Wildcat Creek 50 meters upstream of confluence with Coal Creek.
3-49
-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 3-12
Wetlands in the Study Area
Well a nd
Si/e
(acres)
Classification1
Notes
Level 1



1-1
0.45
PEM, Slope
Hillside seep/spring; contains multiple
parts
1-2
0.01
PEM, Riverine
Elk Creek fringe; contains multiple parts
1-3
0.04
PEM, Slope
Hillside seep/spring; contains multiple
parts
Level 2



2-1
0.02
PEM, Slope
Hillside seep
Level 98



98-1
0.19
PEM, Slope,
Depression, and
Riverine
Hillside seeps and Elk Creek tributary
fringe wetlands; contains multiple parts
Level 5



5-1
0.33
PEM, Slope
Hillside seeps; contains multiple parts
Total
1.04


'Classification from Cowardin el al. 1979 and Smith et al. 1995
PEM Palustrine Emergent
3-50
-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 3-13
Observed Wetland Vegetation


Imliciilor
Siiiius"

\\cll;nul l ocution iind II)
( (MllilKiil \;mu'
Scientific \;imc'

c\cl 1
l.c\cl 2
l.c\cl ')S
l.c\cl 5


l-l
1-2
1-3
2-1
<)S-I
5-1
Narcissusanemone
Anemone narcissiflora
NL
X



X

Blue-joint grass
Calamagrostis canadensis
OBL




X
X
White marsh marigold
Caltha leptosepala
OBL
X
X
X
X
X
X
Heartleaf bittercress
Cardamine cordifolia
FACW+
X
X

X
X

Water sedge
Carex aquatilis
OBL
X
X


X
X
Northern bog sedge
Carex gynocrates (C. dioica)
OBL




X
X
Beaked sedge
Carex rostrata (C. utriculata)
OBL

X
X


X
Splitleaf Indian paintbrush
(Rosy paintbrush)
Castilleja rhexiifolia
FACU
X

X



Sierra fumewort
Corydalis caseana
FACW
X





Subalpine larkspur
Delphinium barbeyi
FAC
X





Tufted hairgrass
Deschampsia caespitosa
FACW
X
X
X
X
X
X
Spikerush
Eleocharis sp.
NA




X

Pimpernel willowherb
Epilobium anagallidifolium
FACW
X


X
X

Rocky Mountain fringed
gentian
Gentianopsis thermalis
OBL




X

Drummond's rush
Juncus drummondii
FACW*
X
X


X
X
Porter's licorice root
Ligusticum porteri
FACU-
X





Northern green orchid
Limnorchis aquilonis (L.
hyperborean)
NL


X



Small-flowered woodrush
Luzula parviflora
FAC
X





Tall fringed bluebells
Mertensia ciliata
OBL
X

X
X


Seep monkeyflower
Mimulus guttatus.
OBL
X

X



Fe ndle r's cowfaa ne
Oxypolis fendleri
OBL
X
X
X
X
X

Elephanthead lousewort
Pedicularis groenlandica
OBL
X
X
X

X
X
Penstemon
Penstemon sp.
NA




X

Buttercup
Ranunculus sp.
NA




X

Redpod stonecrop
Rhodiola rhodantha
FACW+
X





Park willow
Salix monticola
OBL




X
X
Diamondleaf willow
Salix planifolia
OBL
X

X

X

Brook saxifrage
Saxifraga odontoloma
FACW+
X

X
X


Oregon saxifrage
Saxifraga oregana
OBL




X

Arrowleaf ragwort
Senecio triangularis
OBL
X
X
X
X
X
X
Felwort (Star gentian)
Swertia perennis
FACW-




X

Mountain death camas
Zigadenus elegans
FACU

X


X

Plant nomenclature follows NRCS 2006
indicator status is based on national indicators for Region 8 developed by Reed (1988). OBL = obligate wetland species, >99% probability of
occurring in a wetland; FACW = facultative wetland species, 67-99% probability of occurring in a wetland; FAC = facultative species, 34-66%
probability of occurring in a wetland; FACU = facultative upland species, <33% probability of occurring in a wetland. If the species is not
included in Reed (1988), then the designation NL, Not Listed, is shown. If insufficient data were available to determine the indicator status of a
species, then NI, No Indicator, is shown. If the plant is listed as not occurring in the region, NO, no occurrence is shown. A positive (+)
indicates a frequency of occurrence toward the higher end of the category (more frequently found in wetlands) and a negative (-) indicates a
frequency of occurrence toward the lower end of the category (less frequently found in wetlands). If an asterisk (*) follows the indicator, it
identifies a tentative assignment, based on limited information. NA, not available, is shown for those plants not identified to the species level.
3-51
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 3-14
Observed Wetland Perimeter Vegetation
( (iiniiKiii Niimo
Scienlific Viiih*1
Inriiciilor
Sliilus"
\\ Cl hi 11(1 II)
l.oel 1
l.e\el
2
l .o\d ')X
l.oel
5
1-1
1-2
1-3
2-1
98-1
5-1
Alpine avens
Acomastylis rossii
NO
X
X


X
X
Wild chives
Allium schoenoprasum
FACW



X


Pygmyflower rockjasmine
Androsace septentrionalis
NO
X



X

Pussytoes
Antenneria sp.
NA




X

Colorado blue columbine
Aquilegia coerulea
NO


X

X

Western red columbine
Aquilegia elegantula
NL


X



Heartleaf arnica
Arnica cordifolia
NL
X





Rockcress
Boechera drummondii
FACU
X





Blue-joint grass
Calamogrostis canadensis
OBL


X
X


Dunhead sedge
Carex phaeocephala
NO
X



X
X
Sulphur paintbrush
Castilleja occidentalis
NO
X



X

Splitleaf Indian paintbrush
(Rosy paintbrush)
CastiUeja rhexiifolia
FACU




X

Dwarf fireweed
Chamerion subdentatum
NO


X
X


Sierra fumewort
Corydalis caseana
FACW
X





Larkspur
Delphinium sp.
NA
X





Tufted hairgrass
Deschampsia cespitosa
FACW
X

X
X

X
Yellow avalanche-lily
Erythronium grandiflorum
FACU
X
X
X
X
X
X
Virginia strawberry
Fragaria virginiana
FACU
X



X
X
Richardson's geranium
Geranium richardsonii
NO
X

X



Drummond's rush
Juncus drummondii
FACW*
X




X
Porter's licorice root
Ligusticum porteri
FACU-
X





Wild honeysuckle
Lonicera involucrata
NO
X

X



Small-flowered woodrush
Luzula parviflora
FAC
X

X

X

Spiked woodrush
Luzula spicata
FACU




X
X
Tall fringed bluebells
Mertensia ciliata
OBL
X



X
X
Five-stamened mitrewort
Mitella pentandra
NO
X





Sickletop lousewort
Pedicularis racemosa
NL
X

X
X

X
Whipple's penstemon
Penstemon whippleanus
NO




X

Alpine timothy
Phleum alpinum
NO
X



X
X
Engelmann spruce
Picea engelmannii
NO
X
X
X
X
X
X
Muttongrass
Poafendleriana
UPL




X
X
Jacob's ladder
Polemonium pulcherrimum
NL
X

X
X
X
X
3-52
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 3-14
Observed Wetland Perimeter Vegetation
( (iiniiKiii Niimo
Scienlific Vnm*1
Inriiciilor
Sliilus"
\\ Cl hi 11(1 II)
l.oel 1
l.e\el
2
l .o\d ')X
l.oel
5
1-1
1-2
1-3
2-1
98-1
5-1
American bistort
Polygonum bistortoides
FAC*


X

X
X
Douglas fir
Pseudotsuga menziesii
NO
X
X
X
X


Ledge stonecrop
(King's crown)
Rhodiola integrifolia
NL
X



X
X
Redpod stonecrop
(Queen's crown)
Rhodiola rhodantha
FACW+


X

X

Gooseberry currant
Ribes montigenum
NL
X

X
X
X
X
Red elderberry
Sambucus microbotrys
NO
X





Ragwort
Senecio sp.
NA
X
X


X

Dandelion
Taraxacum officinale
FACU
X



X

Whortleberry
Vaccinium myrtillus
NO


X

X
X
False hellebore
Veratrum tenuipetalum
NL




X

Hookedspur violet
Viola adunca
FAC
X
X


X
X
Plant nomenclature follows NRCS 2006
indicator status is based on national indicators for Region 8 developed by Reed (1988). OBL = obligate wetland species, >99% probability of
occurring in a wetland; FACW = facultative wetland species, 67-99% probability of occurring in a wetland; FAC = facultative species, 34-66%
probability of occurring in a wetland; FACU = facultative upland species, <33% probability of occurring in a wetland. If the species is not
included in Reed (1988), then the designation NL, Not Listed, is shown. If insufficient data were available to determine the indicator status of a
species, then NI, No Indicator, is shown. If the plant is listed as not occurring in the region, NO, no occurrence is shown. A positive (+) indicates
a frequency of occurrence toward the higher end of the category (more frequently found in wetlands) and a negative (-) indicates a frequency of
occurrence toward the lower end of the category (less frequently found in wetlands). If an asterisk (*) follows the indicator, it identifies a
tentative assignment, based on limited information. NA, not available, is shown for those plants not identified to the species level.
3-53
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 3-15
Threatened and Endangered Species Occurrence in the Study Area
( (imiiKiii Name
Scientific Name
Sliilus1
llahilal
Occurrence in Siiulj
Area
SWIS 1
(DOW
SIS 1
('Mil'
Birds
Northern goshawk
Accipiter gentilis


s

Mostly coniferous forest
areas above 7,500 feet
Likely; suitable nesting and
foraging habitat
Boreal owl
Aegolius funereus


s
S2
Mature spruce-fir or spruce-
fir-lodgepole forest above
9,000 feet
Likely; suitable nesting and
foraging habitat; known
occurrences nearby
Northern harrier
Circus cyaneus


s

Grasslands, agricultural
areas, and marshes
Unlikely; marginal nesting
habitat; have been
observed in nearby alpine
areas foraging during
migration
Olive-sided flycatcher
Contopus borealis


s

Mature spruce-fir on steep
slopes or near cliffs from
7,000 to 11,000 feet
Possibly; suitable habitat
Black swift
Cypseloides niger


s
S3
Montane and lowland
habitats with cliffs and
waterfalls
Unlikely; no suitable
habitat
Peregrine falcon
Falco peregrinus

sc
s
S2
Nests on cliffs and forages
over coniferous and riparian
forests
Possibly; no suitable
nesting locations, but
suitable foraging habitat
Bald eagle
Haliaeetus leucocephalus
T
E
T

Near large lakes, reservoirs,
and major rivers in which
there are adequate prey,
perching areas, and nesting
sites
Unlikely; very little
suitable nesting or foraging
habitat; none observed
during field visit
White-tailed ptarmigan
Lagopus leucurus


S

Alpine tundra
Likely; suitable nesting and
foraging habitat
Lewis' woodpecker
Melanerpes lewis


S
S4
Lowland and foothill
riparian forests, agricultural
areas, and urban areas
Unlikely; no suitable
habitat
Flammulated owl
Otus flammeolus


S

Ponderosa pine/aspen
habitats from 6,000 to
10,000 feet
Unlikely; marginal habitat;
no ponderosa pine and very
little aspen
Three-toed woodpecker
Picoides tridactylus


S

Primarily spruce-fir forests
above 9,000 feet
Possibly; suitable habitat
Purple martin
Progne subis


s

Ponderosa pine/aspen
habitats 8,000 to 9,000 feet
Unlikely; no suitable
habitat
Mammals
Townsend's big-eared bat
Corynorhinus townsendii

SC
s
S2
Variety of habitats, including
montane and mixed forest to
9,500 feet. Inhabits caves,
mines, and buildings.
Possibly; above elevational
range, but suitable roosting
sites (mine adits)
Wolverine
Gulo gulo

E
s
SI
Forests, marshy areas, and
tundra
Possibly; suitable habitat
present
Northern river otter
Lutra canadensis

E
s

Riparian areas desert to
alpine
Unlikely; require ice-free
reaches of streams in
winter
Canada lynx
Lynx canadensis
T
E
T
SI
Coniferous forest with open
areas; usually occur in areas
with healthy snowshoe hare
populations
Likely; suitable habitat
present; documented
occurrences nearby
3-54
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 3-15
Threatened and Endangered Species Occurrence in the Study Area
( (imiiKiii Name
Scientific Name
Slums'
lliihiliil
Occurrence in Siuclj
Area
SWIS 1
(DOW
I SI S
(Mil*
American marten
Martes americana


s

Subalpine spruce/fir,
lodgepole pine, and montane
forests
Likely; suitable habitat
present
Pygmy shrew
Sorex hoyi montanus


s
S2
Moist habitats in montane
and subalpine forests
Likely; suitable habitat
present
Dwarf shrew
Sorex nanus



S2
Moist habitats in montane
and subalpine forests
Likely; suitable habitat
present
Amphibians
Boreal toad
Bufo boreas

E
s
SI
Subalpine wetlands, streams,
and lakes
Likely; suitable habitat
present
Northern leopard frog
Rana pipiens

SC
s

Wetlands and shallow ponds
from 3,500 to 11,000 feet
Likely; suitable habitat
present
Invertebrates
Northern blue butterfly
Lycaeides idas sublivens



S2S3
Diverse habitats; known in
Colorado only from San
Juan Mountains
Unlikely; no known
occurrences nearby
Hudsonian emerald dragonfly
Somatochlora hudsonica


s

Bogs, fens and ponds with
boggy edges
Unlikely; no suitable
habitat and no known
occurrences nearby
Plants
Dwarf hawksbeard
Askillia nana



S2
Steep alpine scree and talus
Unlikely; no suitable
habitat
Park milkvetch
Astragalus leptaleus


s
S2
Wet meadows and among
streamside willows
Possibly; suitable habitat
present
Leadville milkvetch
Astragalus molybdenus


s
S2
Rocky slopes and hillsides
above timberline
Possibly; suitable habitat
present in upper portions ol
study area
Reflected moonwort
Botrychium echo



S3
Gravelly soil, rocky
hillsides, grassy slopes, and
meadows from 9,500 to
11,000 feet
Possibly; suitable habitat
present
Leathery grape fern
Botrychium multifidum


s
SI
Moist, open, disturbed sites
Unlikely; limited suitable
habitat, but no known
occurrences in the area
Smooth northern rockcress
Braya glabella


s

Alpine, on dolomite or other
calcareous substrates
Unlikely; no suitable
habitat
Lesser panicled sedge
Car ex diandra


s

Fens and wet meadows with
peaty soil
Unlikely; no suitable
habitat
Marsh cinquefoil
Comarum palustre



S1S2
Bogs and wet meadows up to
subalpine; known only from
two Colorado locations (one
in Gunnison County)
Possibly; suitable habitat
present
Slender rockbrake
Cryptogramma stelleri



S2
Sheltered calcareous cliffs
Unlikely; no suitable
habitat
Thickleaf whitlow grass
Draba crassa



S3
Talus and boulder fields on
the highest mountains
Unlikely; no suitable
habitat
Roundleaf sundew
Drosera rotundifolia


s
S2
Sphagnum mats in open acid
fens and bogs
Unlikely; no suitable
habitat
Colorado wild buckwheat
Eriogonum coloradense



S2
Gravelly and sandy soil from
8,500 to 12,500 feet
Possibly; suitable habitat
present
Altai cottongrass
Eriophorum altaicum var. neogaeum


s
S3
Margins of pools and fens
with slow moving water
from 10,500 to 12,600 feet
Unlikely; no suitable
habitat
3-55
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 3-15
Threatened and Endangered Species Occurrence in the Study Area
( (imiiKiii Name
Scientific N:1111c
Sl:ilus'
11 :i l> it :i 1
Occurrence in Siiulj
Area
SWIS 1
(DOW
I SI S
(Mil*
Chamisso's cottongrass
Eriophorum chamissonis


s
SI
Margins of pools and fens
with slow moving water
from 10,500 to 12,600 feet
Unlikely; no suitable
habitat
Slender cottongrass
Eriophorum gracile


s
S2
Fens and margins of lakes
and ponds from 8,100 to
12,000 feet
Unlikely; no suitable
habitat
Stonecrop gilia
Gilia sedifolia


s
SI
Rocky open alpine slopes on
volcanic ash
Unlikely; no suitable
habitat
Variegated scouringrush
Hippochaete variegata



SI
Sandy bars of streams
Unlikely; very little
suitable habitat
Simple bog sedge
Kobresia simpliciuscula


s

Moist tundra and wetlands
with peaty soil from 11,000
to 12,800 feet
Unlikely; no suitable
habitat
Northern twayblade
Listera borealis



S2
Moist spruce-fir forest from
8,700 to 10,800 feet
Possibly; suitable habitat
present
Colorado tansy aster
Machaeranthera coloradoensis


s
S2
Gravelly places in higher
mountain parks and dry
tundra
Possibly; suitable habitat in
upper, open areas
Tundra saxifrage
Muscaria monticola



SI
Stony tundra
Unlikely; very little
suitable habitat
Kot/ebue's grass of Parnassus
Parnassia kotzebuei


s

Rocky ledges and rills;
subalpine and alpine
Possibly; suitable habitat,
but no known occurrences
nearby
Grand Mesa penstemon
Penstemon mensarum



S3
Mountain slopes; only
known from Grand Mesa
Unlikely; very little
suitable habitat; no known
occurrences nearby
Silver willow
Salix Candida


s
S2
Wet meadows and cold fens;
typically on calcareous soils
Unlikely; no suitable
habitat
Blueberry willow
Salix myrtillifolia


s
SI
Riparian willows and willow
carrs
Unlikely; very little
suitable habitat
Autumn willow
Salix serissima


s

Very rare in mountain
meadows; one record from
Routt County
Possibly; suitable habitat
present
Altai chickweed
Stellaria irrigua



S2
Mountain rills and scree
from 8,100 to 13,000 feet
Unlikely; no suitable
habitat
Lesser bladderwort
Utricularia minor


s
S2
Shallow ponds, lakes, slow-
moving streams, fens, and
fresh-water wetlands
Possibly; suitable habitat
present
'Status: E—endangered, T—threatened, S—sensitive, SC—special concern, SI—critically imperiled, S2—imperiled, S3—vulnerable,, S4—rare
in parts of its range, S1S2 or S2S3—rank falls between the two numbers
Sources: USFS 2003, CNHP 2006, NDIS 2006, USFS 2006b, USFS 2006c, USFS 2007, Fitzgerald et al. 1994, Andrews and Righter 1992,
Kingery 1998, Hammerson 1999, Spackman et al. 1997, Weber and Wittmann 1996, NRCS 2006, Packauskas 2005
3-56
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
4.0 NATURE AND EXTENT OF CONTAMINATION
This section describes the nature and extent of contamination at the Standard Mine. It focuses on the
main contaminants of concern: cadmium, copper, lead, manganese, and zinc. Waste rock and tailings
and acid rock drainage (ARD) discharging from the mine workings are the main sources of contamination
at the Standard Mine site. These sources of contamination are impacting, or have the potential to impact,
nearby soils, wetlands, groundwater, downstream surface water and sediments, and biota.
The sources of contamination are discussed in Section 4.1. The extent of soil contamination within and
adjacent to visually impacted areas is discussed in Section 4.2. The extent of groundwater contamination
is discussed in Section 4.3. The extent of contamination in surface water and sediments is presented in
Section 4.4. Additional sources of metals to Coal Creek (an iron gossan and fen located near Coal Creek
downstream of the Elk Creek confluence and the Mount Emmons Project WTP) are also discussed in
Section 4.4.
Air contamination is not a part of this investigation because the only exposure pathway of a human health
concern was from inhalation of manganese dust by child all terrain vehicle (ATV) riders. The air
exposure pathway is difficult to monitor due to the infrequency or complete lack of ATV activity at the
site and a lack of other activity that would produce measurable dust levels for a long enough duration to
mimic the exposure frequency and duration that was analyzed during the risk assessment. This limited
risk was likely to be further diminished by the Removal Action; therefore an evaluation of air quality was
not performed.
4.1 SOURCES OF CONTAMINATION
The two primary sources of contamination at the Standard Mine site are waste rock/tailings and
ARD discharging from the mine workings.
4.1.1 Waste Rock and Tailings
The nature and extent of the waste rock and tailings piles present at the Standard Mine
site were evaluated for the Removal Assessment (UOS 2006a). The volume and
chemical characteristics of the tailings and waste rock located at the site prior to the
Removal Actions are presented in the following sections along with a qualitative
description of the post-removal conditions. Data collected specifically for the waste rock
and tailings characterization are presented in Table 4-1. Soil samples collected from
within waste rock and tailings during the 2006 Risk Assessment sampling were also
considered in this evaluation. Those results are discussed further in Section 4.2.
Waste rock and tailings were analyzed for total recoverable metals, ABA, and SPLP
metals. To provide perspective, the metal concentrations in waste rock and tailings were
compared to concentrations in a background sample and the EPA Region 3 Risk-Based
Concentrations (RBCs) for industrial soils (EPA 2005). The background soil sample was
collected from the Elk Creek basin uphill from the Standard Mine site during the 1999
expanded SI to indicate possible pre-mining soil characteristics. The background sample
contained cadmium at 0.23 mg/kg, copper at 4.8 mg/kg, lead at 31.6 mg/kg, manganese
at 598 mg/kg, and zinc at 40 mg/kg. In the absence of standards for SPLP metals, the
SPLP metals results were compared with Toxicity Characteristic Leachate Procedure
(TCLP) standards that are used to characterize hazardous waste (40 CFR 261). SPLP is a
less rigorous leaching procedure than TCLP; therefore, exceeding TCLP limits indicates
that a metal would be highly leachable from the waste rock or tailings. Detectable
concentrations of metals in the SPLP extract were also noted and indicate the potential
for leaching from the waste rock. ABA is a measure of the potential acidity of a soil and
4-1
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
indicates whether a source of alkalinity, such as lime, must be added to the soil to prevent
low pH conditions from developing. The ABA results from the background sample were
compared with neutral soils and with ABA results from other waste rock piles at the site.
Additional soil samples were collected from Levels 1, 2, and 3 during 2008 to
characterize post-removal and treatment site conditions.
4.1.1.1 Level 1 Waste Rock and Tailings
Prior to the Removal Action, Level 1 contained an estimated 30,000 cubic yards
of waste rock and tailings. The tailings were contained in an impoundment that
held water that regularly overflowed or seeped into Elk Creek. Elk Creek and
several seeps and springs ran over and through the Level 1 waste rock. The
Level 1 waste rock was divided into four different locations for Removal
Program characterization and removal/treatment: the mill site, northeast, north,
and west (Figure 1-6). Analytical results for the waste rock are presented on
The waste rock and tailings contained copper concentrations up to 1,100 mg/kg;
lead concentrations up to 19,000 mg/kg; manganese concentrations up to 9,300
mg/kg; and zinc concentrations up to 11,000 mg/kg. Concentrations of
cadmium, copper, lead, manganese, and zinc were higher in all Level 1 waste
rock samples than in the background sample. The lead concentrations were
higher than the RBC.
Some of the Level 1 waste rock contained significant quantities of leachable lead
as evidenced by SPLP lead concentrations greater than the TCLP lead limit.
Detectable concentrations of SPLP copper and zinc show the potential for copper
and zinc to leach from the piles.
The ABA results indicate that the north and northeast waste rock had more acid
generation potential than waste rock or tailings in other segments of Level 1. All
the piles had acid generating potential higher than the acid neutralizing potential,
indicating that the soils may become more acidic over time.
During the Removal Action, the tailings and much of the waste rock were
excavated down to native soil or bedrock and placed in the nearby repository.
Waste rock was left in place near the Level 1 adit and the pilot scale passive
water treatment system to avoid disrupting the system. After the material was
removed, the underlying native soils were treated to reduce potential effects from
residual contamination and enhance the potential for successful revegetation.
The west slope was treated to a depth of six inches with lime, compost, and
nitrogen-phosphate fertilizer. The south slope, including the former mill site and
tailings impoundment, was treated with lime, compost and fertilizer to a depth of
12 inches. The north slope was treated with lime and fertilizer then capped with
native borrow soil and fertilized. The northeast slope was treated with lime and
fertilizer then capped with native borrow soil and fertilized. The areas were
seeded with a combination of native seed and chaff gathered near Taylor
Reservoir and slender wheatgrass seeds provided by the NRCS. Elk Creek was
reconfigured to a stable alignment that does not contact remaining waste rock.
Drainage controls were installed to minimize surface water contact with
remaining waste rock and erosion of site soils.
Table 4-1.
4-2
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
Analytical results from samples collected to characterize post-removal site
conditions show neutral pH, excess lime neutralization potential, and organic
carbon content greater than 2.5 percent (Table 4-2). This indicates that adequate
lime was used to neutralize the soils and that the organic carbon content is
adequate to permit vegetation growth.
4.1.1.2 Level 2 Waste Rock
Prior to the Removal Action, an estimated 5,000 cubic yards of waste rock were
present at Level 2. The waste rock was located such that seeps from the Level 2
adit as well as surface runoff passed through the waste rock prior to entering Elk
Creek near Level 1. Data regarding the Level 2 waste rock are presented on
The Level 2 sample collected for the 2005 Removal Assessment contained
copper at 580 mg/kg, lead at 7,700 mg/kg, manganese at 6,700 mg/kg, and zinc
at 3,200 mg/kg. Concentrations of all of these metals are above the background
soil concentrations and the lead concentration is higher than the RBC.
The waste rock contained leachable cadmium, lead, and zinc as evidenced by
detectable SPLP concentrations.
The acid generating potential of the Level 2 waste rock was moderate.
During the Removal Action, the waste rock at Level 2 was removed down to
bedrock. A small amount of residual soil that could not be excavated remains at
Level 2. Logs and riprap from the site were constructed into small check dams to
direct and slow the velocity of surface water flows to help prevent soil erosion
and help establish vegetation between Level 2 and Level 1.
Analytical results from samples collected to characterize post-removal site
conditions show neutral pH, excess lime neutralization potential, and organic
carbon content greater than 2.5 percent. This indicates that adequate lime was
used to neutralize the soils and that the organic carbon content is adequate to
permit vegetation growth (Table 4-2).
4.1.1.3 Level 3 Waste Rock
Prior to the Removal Action, an estimate of 7,500 cubic yards of waste rock was
located at Level 3. The waste rock at Level 3 was located on a hillside above
Level 2 that is steeper at the bottom than at the top of the pile. Data regarding
the Level 3 waste rock are presented on Table 4-1.
The Level 3 sample collected for the 2005 Removal Assessment contained
copper at 1,900 mg/kg, lead at 38,000 mg/kg, manganese at 390 mg/kg, and zinc
at 810 mg/kg. All of these metal concentrations are higher than those contained
in the background sample. The lead concentration is higher than the RBC.
The waste rock contained significant quantities of leachable lead as evidenced by
an SPLP lead concentration greater than the TCLP lead limit. The waste rock
also contained leachable cadmium and zinc as evidenced by detectable SPLP
concentrations.
Table 4-1.
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The acid generating potential of the Level 3 waste rock was higher than the acid
neutralizing potential, meaning that the soils may become more acidic over time.
The acid generating potential of the Level 3 waste rock was high relative to the
other Standard Mine waste rock piles.
During the Removal Action, waste rock was removed from the upper portion of
the slope; however, waste rock was not removed from the steeper lower portion
of the slope.
Analytical results from samples collected to characterize post-removal site
conditions show neutral pH, excess lime neutralization potential, and organic
carbon content greater than 2.5 percent (Table 4-2). This indicates that adequate
lime was used to neutralize the soils and that the organic carbon content is
adequate to permit vegetation growth.
4.1.1.4	Level 4 Waste Rock
An estimated 1,000 cubic yards of waste rock are located at Level 4 adjacent to
two shafts that connect the surface to the Level 3 tunnel. There are no obvious
signs such as surface water, erosional features, or seeps that would indicate that a
significant amount of water passes through the Level 4 waste rock. Data
regarding the Level 4 waste rock are presented on Table 4-1
The Level 4 waste rock samples contained copper at 6,700 mg/kg, lead at 61,000
mg/kg, manganese at 1,000 mg/kg, and zinc at 2,400 mg/kg. All of these
concentrations are above the concentrations in the background sample and the
lead concentration is higher than the RBC.
The waste rock contained significant quantities of leachable lead as evidenced by
a SPLP lead concentration greater than the TCLP lead limit. The waste rock also
had evidence of leachable zinc.
The acid generating potential of the Level 4 waste rock was higher than the acid
neutralizing potential, meaning the soils may become more acidic overtime. The
acid generating potential of the Level 4 waste rock is high relative to other waste
rock piles at the site.
No waste rock was removed from Level 4 during the EPA Removal Action.
4.1.1.5	Level 5 Waste Rock
An estimated 1,000 cubic yards of waste rock are located at Level 5. The Level
5 waste rock is located such that the Level 5 adit discharge passes over the waste
rock prior to crossing a road and entering a wetland at the base of the pile. Data
regarding the Level 5 waste rock are presented on Table 4-1. The waste rock
appears to be segmented into a "gray" (higher pH) and an "orange" (lower pH)
side.
The two Level 5 samples collected for the 2005 Removal Assessment contained
copper at 570 mg/kg and 280 mg/kg, lead at 7,600 mg/kg and 1,500 mg/kg,
manganese at 4,800 mg/kg and 10,000 mg/kg, and zinc at 1,300 mg/kg and 1,800
mg/kg, respectively. The variable metal concentrations may be due to the
different chemical characteristics of the two segments of the pile. The lead
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concentrations are higher than the RBCs for industrial soil. All of these metal
concentrations are higher than those contained in the background sample.
The waste rock contained significant quantities of leachable lead as evidenced by
SPLP lead concentration greater than the TCLP lead limit that is used to
characterize hazardous waste. The waste rock also had evidence of leachable
zinc.
The acid generating potential of the Level 5 waste rock was higher than the acid
neutralizing potential, meaning that the soils may become more acidic over time.
The acid generating potential of the Level 5 waste rock was moderate relative to
the other waste rock piles at the site.
No waste rock was removed from Level 5 during the EPA Removal Action
because of potentially severe environmental damage that could result from
improving the road to accommodate haul trucks. In addition, the damage to the
downgradient wetland as a result of these road improvements could have been
extensive. Runoff from this level does not directly impact Elk Creek.
4.1.1.6 Level 98 Waste Rock
An estimated 2,500 cubic yards of waste rock is located at Level 98. The Level
98 waste rock is located such that the small discharge from the Level 98 adit
passes over the southern portion of the pile to a wetland located at the base of the
pile. A tributary to Elk Creek flows past the waste rock to the east but does not
appear to be eroding the waste rock. The waste rock is primarily large rock
interspersed with finer grained material. The proportion of finer grained material
increases toward the lower, southern portion of the pile. Data regarding the
Level 98 waste rock are presented on Table 4-1.
The Level 98 sample collected for the 2005 Removal Assessment contained
copper at 630 mg/kg, lead at 8,000 mg/kg, manganese at 4,400 mg/kg, and zinc
at 1,200 mg/kg. All of these metal concentrations are higher than those
contained in the background sample. The lead concentration is higher than the
RBC for industrial soil.
Level 5 waste rock contains significant quantities of leachable lead as evidenced
by SPLP lead concentration greater than the TCLP lead limit. The waste rock
also had evidence of leachable zinc.
The acid generating potential of the Level 98 waste rock is moderate.
No waste rock was removed from Level 98 during the EPA Removal Action
because excavation of the waste rock would have caused extensive damage to the
wetland immediately downstream. EPA determined that the potential damage to
the wetlands would be more severe than the benefit gained by removing the
waste rock, therefore the waste rock was left in place.
4.1.2 Mine Adits
Acid rock drainage from the mine workings is also a source of metals contamination at
the Standard Mine site. Water flowing through the tunnels contacts highly mineralized
materials that add metals to the water and seasonally lower the water's pH. This section
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presents adit discharge water quality. In addition, a description of source materials
within the mine workings and data from water collected within the workings are
presented, when available, to enhance understanding of flow paths and locations within
the workings that potentially contribute the most metals to water flowing through the
workings.
The evaluation of adit discharges is focused on the EPA data collected during June and
September of 2005 through 2009. The EPA data are supplemented by data from the
2006-2007 USGS study (USGS 2007) and a 2009 USGS study (USGS 2010a). The
results of the adit discharge sampling for select analytes are presented in Table 4-3.
Characteristics of the mine workings were obtained from the Standard Mine
Underground Assessments (DRMS 2007; DRMS 2009). The DRMS reports are
provided in Appendix A. The USGS reports are provided in Appendix B. A complete
set of EPA adit discharge monitoring data are provided in Appendix C.
This section presents and compares the data in several ways. First, the EPA and USGS
values are presented in tables and compared against Colorado surface water quality
standards (WQS) (Table 4-4). The Level 1 EPA data were also graphed to show
temporal variations in metal concentrations, alkalinity, and pH.
The relevant WQS are the CDPHE Water Quality Control Commission Regulation 35 (5
CCR 1002-35) and Classifications and Numeric Standards for the Gunnison and Lower
Dolores River Basins, Upper Gunnison River Basin Segment 11. These standards are
based on the hardness of the water. The hardness that should be used in the equations is
calculated as the lower 95th confidence limit of the mean hardness in the water body
during low flow conditions. While the lower 95th confidence limit of the mean hardness
for the Level 1 adit discharge is 137 milligrams per liter (mg/L), a hardness of 65 mg/L
was used to calculate the WQS used to compare to the adit discharge results. The lower
hardness, 65 mg/L, was selected because that is the hardness in the receiving water, Elk
Creek (see Section 4.4.4).
4.1.2.1 Level 1 Adit
Water discharges from the Level 1 portal at flow rates ranging from
approximately 3 to 70 gallons per minute (gpm). Higher flows may occur but
have not been documented due to limitations in the adit flume sizing and layout,
power loss and transmission problems due to severe winter weather and heavy
snow, ponding of water inside the adit due to ice dams, and sedimentation of
overflow pipes outby the flume. Discharge is significantly higher during spring
runoff than at other times of year (Figure 3-1).
The Level 1 adit discharge was sampled by EPA in June and September each
year from 2005 to 2009. The full analytical results are presented in Appendix C.
Graphs of dissolved cadmium, copper, lead, manganese, and zinc concentrations
are shown on Figure 4-1. Separate graphs are shown for the June and September
results.
The cadmium, copper, lead, manganese, and zinc concentrations in all of the
Level 1 adit discharge samples exceeded acute and chronic WQS as calculated at
a hardness of 65 mg/L. For all metals except manganese, the standards were
exceeded by one to two orders of magnitude. The pH of the adit discharge lay
below the water quality standard range of 6.5 to 9.0. The greatest variation from
the pH standard occurred during spring runoff and into mid-summer.
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The data indicate that adit discharge water quality varies throughout the year.
Cadmium concentrations remained relatively constant seasonally and between
years. The copper concentration varies seasonally with the higher concentrations
observed during spring and lower concentrations during fall and winter. The lead
concentration varies seasonally with the higher concentrations observed during
spring and the lower concentrations during fall/winter. The manganese
concentration varies seasonally with the lower concentrations observed during
spring and the higher concentrations during fall/winter. The zinc concentration
has a moderate seasonal variation with the lower concentrations observed during
spring and the higher concentrations during fall/winter. The pH of the Level 1
adit discharge varies widely. The June and September EPA data show Level 1
adit discharge pH ranging from 3.3 to 6.2.
Detailed evaluation of seasonal trends using the EPA data is limited because the
samples were collected only during June and September. More detail on
seasonal trends was provided by a USGS study (USGS 2007) in which the Level
1 adit discharge was sampled on nine occasions between July 2006 and June
2007 (Table 4-2). The results showed that metal concentrations change
seasonally with copper and lead concentrations peaking in the spring while other
metal concentrations (cadmium, manganese, and zinc) peak in the spring but are
also elevated at other times of year. The USGS study also showed a flushing
effect during early May when there is a spike in metal concentrations in the
Level 1 discharge, followed by lower concentrations beginning in mid- to late-
May. Estimated metal fluxes along with similar seasonal fluctuations in
chemistry (field parameters, chemical constituents, and stable isotopes) observed
in Level 1 discharge and Elk Creek are consistent with Level 1 discharge being
the primary source of metals in Elk Creek.
Additional pH data were collected as part of the pilot scale bioreactor system
(Figure 4-2) (Golder Associates, Inc. Unpublished). The Golder data, similar to
the USGS data, show a marked decrease in pH during spring runoff followed by
gradual recovery to near neutral pH by late summer.
Prior to the removal action, the adit discharge flowed across waste rock before
entering Elk Creek, potentially increasing the metal concentrations in the water
and reducing pH. During the Removal Action, a pond was installed outside of
the portal to contain and redirect adit discharge and to allow metals to precipitate
out of solution before the water entered Elk Creek. The pond was constructed
using clean materials, but the pond soon filled with sediment and became non-
functional. When the pilot scale passive treatment system was installed, the adit
discharge was directed into an infiltration gallery constructed inside the adit,
from which one gpm flowed into a holding tank and the remaining discharge
flowed to Elk Creek via a pipe. The overflow pipe clogged over the winter of
2008-09, so the pipe was replaced with an overflow trench during 2009 to
convey excess water to Elk Creek.
4.1.2.2 Level 2 Adit
Six samples were collected from within the Level 2 adit during the 2009
underground assessment and analyzed by USGS. Sample ECMSTDL21 was
collected from water dripping from a drill hole near the center pillar. Sample
ECMSTDL22 was collected from water dripping from a fracture onto a
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flowstone deposit. Sample ECMSTDL23 was collected from water dripping
from the farthest inby raise on Level 2. Sample ECMSTDL24 was collected
from water dripping from an ore chute. Samples ECMSTDL25 and
ECMSTDL26 were collected from water dripping from the tunnel back.
Selected analytical results are presented in Table 4-3. Sample locations are
shown on Figure 3-2, provided by DRMS.
The samples had circumneutral pH values with the exception of the sample
collected as water dripped from an ore chute (ECMSTDL24) that had a pH of
3.2. Redox potential measurements in water samples in Level 2 indicate the
waters are well oxygenated (USGS 2009).
Metal concentrations in the tunnel samples varied by location. The highest metal
concentrations occurred in samples collected from fracture inflows and drips
from ore chutes. The most extensive area of sulfide mineralization was observed
surrounding the center raise connecting Levels 2 and 3, a likely explanation for
the high metal concentrations in Sample ECSMTDL24. Lesser metal
concentrations were observed in samples collected as water dripped from a raise,
a drill hole, or the tunnel back. Samples collected in the Level 2 tunnel contained
substantially higher metal concentrations than samples collected from Level 3.
Concentrations of dissolved metals in samples collected within Level 2 approach
or exceed concentrations in the Level 1 adit discharge, suggesting that water-rock
interactions between Level 3 and Level 1 can account for the elevated
concentrations of metals in the Level 1 adit discharge (USGS 2010a).
During the 2009 underground assessment, numerous ore chutes and muck piles
containing with sulfide ore were observed (DRMS 2009). These features are
likely sources of water contamination. The considerable amount of standing
water observed on the floor of the Level 2 tunnel is an indication that water has
an appreciable residence time in Level 2 during which sulfide minerals may react
with the oxidized water, thus increasing dissolved metal concentrations.
The Level 2 adit discharge has not been sampled frequently because it discharges
only sporadically and at a very low flow rate from the base of a waste rock pile.
A sample was collected from the Level 2 seep by the USGS during 2006 and the
results are shown on Table 4-3. The water chemistry shows very high metal
concentrations and low pH. The metal concentrations in the seep sample were
similar to the highest values measured within the Level 2 tunnel. It is unclear
whether the high concentrations and low pH are the result of contact between the
water and the mine workings or the result of contact with the waste rock located
outside of the adit through which the water flowed prior to collection of the
sample. The seep has not been sampled since the Level 2 waste rock was
removed.
4.1.2.3 Level 3 Adit
Level 3 does not discharge water, but adit water from within Level 3 was
sampled by the USGS during August 2006 and July 2009 (USGS 2007; USGS
2010a). Five samples were collected and analyzed for total and dissolved metals.
Samples ECMSTDL31 and ECMSTDL32 were collected from water flowing
toward and down the first raise. Sample ECMSTDL33 was collected as the
water dripped from the ceiling. Sample ECMSTDL34 was collected as water
flowed toward and down the second raise, and sample ECMSTDL35 was
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collected from inflow from the end of the tunnel. Sample locations are shown on
Figure 3-3, provided by DRMS.
Metal concentrations in the tunnel samples varied by location. The results
showed the lowest concentrations in the samples collected directly from ceiling
inflows and the highest concentrations on the floors near the raises. Metal
concentrations in the Level 3 samples were lower than observed in the Level 1
adit discharge samples collected during the same trips, indicating that there is a
source of additional metal loading between Level 3 and where the water exits the
mine at Level 1. Redox potential measurements in water samples collected
within Level 3 indicate the waters are well oxygenated. Concentrations
measured in 2009 were similar to those measured in 2006 at the same sample
locations.
Waste piles located within the Level 3 adit are potential sources of water
contamination. The ore minerals occur within unmined portions of the fault,
within plugged ore chutes, and in muck piles in the mine working. An ore chute
with a pile of mine material beneath was observed during the mine entry. The
material is coated with iron oxyhydroxides such as goethite and plumbojarosite
that form by the oxidation of sulfides. The interior of the pile was unoxidized
and shown to contain galena and quartz with minor pyrite. The most extensive
area of sulfide mineralization was observed surrounding the center raise
connecting Levels 2 and 3. Muck piles were composed of substantial unoxidized
vein material consisting of pyrite, sphalerite, and galena (USGS 2007).
Water flows from Level 3 to Level 2 via winzes. Water has not been observed
exiting the Level 3 portal.
4.1.2.4 Level 5 Adit
During August 2006, the USGS collected water samples from within Level 5 and
from the Level 5 adit (USGS 2007). The concentrations of metals are shown on
Table 4-3. Sample ECSMTDL51 was collected from the outside of the blockage
in the left drift and sample ECMSTDL52 was collected from a stream of water
flowing from the tunnel ceiling. Sample locations are shown on Figure 3-4,
provided by DRMS.
The Level 5 adit discharge was sampled for total and dissolved metals by UOS in
October of 2005, by EPA in June and October of 2007 and 2008, and by the
USGS in August 2006. The results for select metals are shown on Table 4-3.
The dissolved cadmium, lead, and zinc concentrations exceeded water quality
standards but were lower than the concentrations measured in the Level 1 adit
discharge. The manganese concentrations exceeded the chronic water quality
standard and sometimes exceeded the acute standard. The copper concentrations
did not exceed the acute or chronic water quality standards. A comparison of
total and dissolved metal concentrations shows similar concentrations except for
lead, indicating the presence of suspended lead in the adit discharge.
The relative water quality of the two tunnel locations and the adit discharge
varied by metal. The cadmium concentration was higher in the adit discharge
than the sample collected from the ceiling which was surprisingly higher than the
cadmium concentration in the sample collected from outside the blockage. This
did not hold true for manganese and zinc. The manganese concentration was
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highest in the sample collected outside the blockage, lower in the adit discharge,
and lowest in the sample collected from the ceiling. The zinc concentrations
were similar in the adit discharge and blockage sample and lower in the sample
collected from the ceiling. Copper and dissolved lead were not detected in the
samples collected by USGS. Cadmium concentrations were greater than both
acute and chronic water quality standards in the adit and ceiling samples but not
the sample collected outside the blockage. Manganese concentrations exceeded
the chronic water quality standard in all three samples and exceeded the acute
standard in the sample collected outside the blockage. Zinc concentrations
exceeded the acute and chronic water quality standards in all three samples. The
metal concentrations in the Level 5 tunnel samples were much lower than those
found in the Level 1 adit discharge.
A sample was collected by USGS during 2006 from a seep in the waste rock
outside of the Level 5 tunnel. The sample contained significantly higher metal
concentrations than the sample collected from the adit during the same sampling
event or any other event, likely the result of sulfide oxidation in the waste rock.
4.1.2.5 Level 98 Adit Discharge
Adit discharge from Level 98 was sampled and analyzed for total and dissolved
metals by UOS in October of 2005 and by EPA in September of 2007 and 2008.
The results are shown on Table 4-3.
The concentrations of all metals were significantly higher during September
2007 than during the other sampling events. The reason for this variation is
unknown but a possible cause is the introduction of additional metals during
installation of demonstration revegetation test plots during 2007. A comparison
of total and dissolved metal concentrations shows similar concentrations.
Cadmium, lead, and zinc concentrations exceeded water quality standards during
all sampling events. Copper concentrations exceeded the standard during 2005
and 2007 but copper was not detected in the sample collected during 2008.
Manganese concentrations at Level 98 did not exceed either the acute or chronic
water quality standard.
A sample was collected by USGS during 2006 from a seep in the waste rock
outside of the Level 98 tunnel. Unlike the seep samples collected from Levels 2
and 5, the sample contained lower metal concentrations than the sample collected
from the adit during the same sampling event.
4.2 SOIL
The 2006 EPA Risk Assessment sampling event, which involved sampling on-site soils within
Levels 1, 2, 3, and 98 including both the waste rock and tailings and the soils outside of the
visually impacted area, provides an indication of the areal distribution of metals in site soils
(TechLaw 2007). The results provide an indication of the effect of mining activities on the soils
at the site. The soils in some locations, primarily Levels 1, 2, and 3, were re-sampled during
2009 to assess post-removal conditions.
Figure 4-3 shows the areal extent of contamination. The sample locations are shape-coded to
indicate whether the value indicates pre-removal or post-removal site conditions. The sample
locations are also color-coded to enhance understanding of the distribution of metals within and
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adjacent to visually impacted areas. The color coding is provided only to indicate relative
concentrations and is not an indication of risk. The highest metal concentrations were observed
in waste rock located at Level 1 during 2006, prior to the Removal Action. Concentrations at
Levels 2, 3, 4, and 98 were lower than at Level 1. The Standard Mine site is located in a highly
mineralized area, so the presence of elevated metal concentrations in soils located away from the
visibly impacted areas may occur from the native mineralization or from a combination of native
mineralization and mining activities.
4.3 GROUNDWATER
This section presents several lines of evidence to identify the presence and movement of
contaminants within the groundwater system. The overall patterns in groundwater quality in the
basin and the relationship between groundwater and surface water quality were studied by USGS
in 2006, 2007, and 2009. The results of the USGS groundwater sampling are shown in their
documents (USGS 2007; USGS 2010a). Groundwater wells located near Level 3 were sampled
in October 2008 and throughout 2009. Data from samples collected during the 1999 expanded SI
are also discussed here because they provide the only available information about the nearest
residential well. The results of sampling from the Level 3 groundwater wells and residential
wells are presented in Table 4-5. Refer to Section 3.5 for more information regarding
groundwater flow and to Section 4.1.2 for more information regarding groundwater flowing
through the mine workings.
The USGS previously studied contaminant transport in Redwell Basin, on the other side of Scarp
Ridge to the north of the site. Because the systems are similar, it could be expected that
groundwater contaminant patterns would be similar. Studies in Redwell basin showed that
springs and streams located in unmineralized sedimentary rocks were dilute in metals and had
circumneutral pH. Water from mine drainages and immediately downgradient of mines or
mineralized rock had high metals and lower pH. Map-scale faults apparently controlled the flow
of hydrothermal fluids in the Mount Emmons area in the geological past and are still areas of
enhanced permeability and groundwater flow. There is little reason to say this is not also true for
the Elk Creek basin (USGS 2007).
The 2007 USGS investigation included sampling of springs, mine adits, and exploration pits to
determine where metal-laden water is discharged, the primary source of elevated metal
concentrations, temporal and spatial variations in water flow and chemistry, where groundwater
discharges into the mine workings, and the chemical composition of different waters that
contribute to mine outflow. The Level 1 discharge and Elk Creek (Elk-00) were sampled
repeatedly during 2006-2007, and Levels 3 and 5 were sampled within the tunnels. Elevated
concentrations of cadmium, copper, lead, manganese, and zinc and low pH were measured within
or immediately downgradient of areas where sulfides are abundant, including the Standard fault
and the Elk Lode Mine (Level 98) portal. Concentrations of these metals are lower and pH
values are circumneutral at surrounding locations. Figures 4-4 through 4-9, provided by the
USGS, show the areal extent of contamination in groundwater, adit water, and seeps in the basin.
Metal concentrations in samples collected from within the mine workings at Levels 3 and 5 were
generally higher than in samples collected at aboveground sites located outside of sulfide-rich
areas. Metal concentrations in discharge from the Level 1 adit were among the highest measured
in Elk Basin. All of these observations suggest that sulfide-rich mineralized rock is the primary
control on dissolved metal concentrations and pH in groundwater in the Standard Mine vicinity.
Waste rock piles apparently exert another major control on metal concentrations and pH; the
lowest pH and highest metal concentrations were found in discharge from waste rock piles
(USGS 2007).
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Concentrations of several chemical constituents, along with strontium isotope data, indicated that
none of the waters sampled during 2007 could have been the primary source of metals from Level
1. Therefore, a follow-up study was performed during 2009. The mine adits and selected springs
sampled during 2006 were re-sampled during 2009. Samples from the Level 2 adit and Elk Creek
were also collected. The data from re-sampled locations were similar to the 2006 data with the
exception of water that discharges to the wetland located at the base of the Level 5 waste rock
pile where the 2009 data showed lower metal concentrations. Samples collected from the Level 2
adit contained highly elevated metal concentrations relative to the Level 3 adit concentrations and
similar concentrations to the Level 1 adit discharge, suggesting that water-rock interaction
between Level 3 and Level 1 can account for the elevated concentrations of metals in the Level 1
adit discharge. Ore minerals such as sphalerite, argentiferous galena, and chalcopyrite are the
likely sources of cadmium, copper, lead, and zinc, and are present within the mine in unmined
portions of the vein system, within plugged ore chutes, and in muck piles (USGS 2010a).
Oxidation-reduction measurements and dissolved oxygen concentrations indicate that the water in
Levels 2 and 3 are well oxygenated.
Seasonal groundwater variations may impact the transport of metals within the groundwater
system. In years when water chemistry data were collected, a spring flush was observed in which
pH dropped and some metal concentrations rose at the onset of spring runoff. The source of the
high metal concentrations was probably within a shallow portion of the groundwater flow system
or within the mine workings themselves. Reasonable candidate locations include pockets of high
capillarity material (fine-grained fault gauge or intensely microfractured rock) within the
seasonally saturated zone (unsaturated in the winter, saturated in spring) near the ground surface
or within portions of the mine workings that only become saturated during spring high flows
Groundwater was sampled from wells installed near Level 3 and the data provide additional
information regarding site groundwater. The wells are located near and upgradient of Level 3 on
either side of the Standard Fault. The well locations are shown on Figure 2-3; data for select
analytes are shown on Table 4-5 and a complete set of the data is presented in Appendix C.
Wells B1 (60.5 feet deep), B3 (8 feet deep), B5 (60.5 feet deep), and B7 (7 feet deep) contained
adequate water to be sampled on at least one occasion, well B4 (15 feet deep) did not contain
enough water to sample, and wells B2 (8 feet deep) and B6 (5 feet deep) were dry. Wells B1 and
B5, both deep wells in the Wasatch Formation, generally showed low levels of metals, though
high total metal concentrations were measured for the initial sampling events, probably due to
inadequate well development. Wells B3 and B7, located in shallow groundwater on the Ohio
Creek Formation side of the Standard fault, showed the highest metal concentrations. It is
unknown whether the high concentrations are indicative of overall groundwater quality in the
shallow groundwater or are the result of a localized effect such as the presence of nearby waste
rock piles or native sulfide-rich rock. Cadmium, copper, and lead concentrations in wells B3 and
B7 are less than those observed in the Levels 2, 3, and 5 tunnels, manganese concentrations are
higher in the two wells than in the tunnels, and zinc concentrations are similar to (B3) or lower
than (B7) in the tunnels. The same pattern holds when comparing concentrations in wells B3 and
B7 with the Level 98 adit discharge with the exception of cadmium, which is similar in the wells
and the Level 98 discharge.
Groundwater concentrations were compared to the domestic water supply (Tables 1 and 2) and
agricultural use (Table 3) groundwater standards found in Colorado Code of Regulations (CCR)
1002 - Regulation 41. Cadmium concentrations exceeded the domestic water supply and
agricultural use standards once in well B1 and for all measurements in well B3. The lead
concentration exceeded the domestic water supply standard in well B3 on one occasion. The
manganese concentrations in all of the wells exceeded either the domestic water supply or
agricultural use standard or both on at least one occasion, and both manganese standards were
(USGS 2007).
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exceeded in wells B3 and B7 during all sampling events. The zinc concentrations in well B3
exceeded the agricultural use standard during most of the sampling events.
Two groundwater samples were collected during the expanded SI. A background sample was
collected from an artesian well at Dale's Cabin, approximately 'A mile east of Kebler Pass. The
well is 82.3 feet deep and is not used for domestic water supply. The domestic well considered
closest to the sources of contamination is located at the residence at 1060 County Road 12, which
is located greater than three miles from the Standard Mine site. The domestic well contained
concentrations of copper and lead significantly higher than the background sample from Dale's
Cabin. None of the concentrations exceeded the Maximum Contaminant Levels (MCLs)
established under Colorado State Drinking Water Standards (CDPHE 2009).
4.4 SURFACE WATER AND SEDIMENT
This section describes surface water and sediment quality and general spatial, seasonal, and
temporal trends. Surface water and sediment toxicity data and the implications of water and
sediment quality are presented in the Ecological Risk Assessment and are discussed in Section 6.
The evaluation of spatial trends focuses on the data collected by EPA during 2005 through 2008
sampling events. Seasonal trends for surface water were also evaluated using USGS data for Elk
Creek and CCWC data for Coal Creek.
To put the water chemistry data into context, the data were compared to the Colorado WQS for
Segment 11 of the Upper Gunnison River Basin (CDPHE 2007) (Table 4-4). The standards were
calculated at a hardness of 65 mg/L which was the lower 95th confidence limit of the mean
hardness in Elk Creek during low flow conditions between 2005 and 2008.
Evaluation of water chemistry focuses on dissolved metals because the WQS for the
contaminants of concern are for dissolved metals. In general, total and dissolved metal
concentrations were similar; however, total lead concentrations were typically higher than
dissolved lead with the greatest variations between total and dissolved metals occurring during a
few spring sampling events.
Due to the large amount of water data, graphs are used to describe water quality in Elk Creek.
Water quality chemistry for all analytes and sampling dates are presented in Appendix C (Tables
CI and C2). Sediment chemistry for all analytes is presented in Appendix C (Table C3). It
should be noted that the September 2007 samples were collected during and after a storm and
may not be indicative of non-storm conditions.
Elk Creek and Coal Creek are discussed in Sections 4.4.1 and 4.4.2, on-site wetlands are
discussed on Section 4.4.3, contaminant loading is discussed in Section 4.4.4, and metals found in
surface water-related biota is discussed in Section 4.4.5.
4.4.1 Elk Creek
Several small tributaries upstream of and within the Standard Mine site form Elk Creek
within Elk Basin. One of the tributaries passes by the Level 98 waste rock. Elk Creek
flows through non-mine-impacted land down to Level 1, through Level 1, then down to
Coal Creek. Prior to the Removal Action, Elk Creek passed through the mine waste and
tailings at Level 1. In 2008, after the removal of the waste rock and tailings, the channel
was reconstructed through Level 1. The channel does not contact the small amount of
remaining waste rock.
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Elk Creek was sampled at several locations (Figure 2-2) during June and September
beginning in 2005. The consistent sampling locations include, from upstream to
downstream, Elk-29, Elk-10, Elk-08, Elk-06, Elk-05, and Elk-00. Elk-29 is located
upstream of Level 1 but is downstream of the other levels. Elk-29, while upstream of the
most contaminated portion of the site, may be impacted both by naturally occurring
highly mineralized zones and by mining-related contaminant sources. Elk Creek forms
below mining-impacted areas, thus a "background" sampling location was not available.
Elk-10 is located near Level 1 just downstream of where the old tailings impoundment
overtopped into Elk Creek. The effluent from Copley Lake (COP-01) enters Elk Creek
between Elk-10 and Elk-08. Seeps are located between Elk-10 and Elk-08, and between
Elk-06 and Elk-05. The source of the seep water is unknown. Elk-00 is located just
upstream of the confluence with Coal Creek.
4.4.1.1 Elk Creek Surface Water
The June and September water quality data for Elk Creek are presented from
upstream to downstream on Figure 4-10. The graphs show dissolved cadmium,
copper, lead, manganese, zinc, hardness, pH, and alkalinity data collected by
EPA from 2005 through 2009 EPA data. The detection limit is shown on the
graphs when the contaminant was not detected in a sample. WQS are provided
for comparison.
Metal concentrations are low at Elk-29, increase at Elk-10, and generally
decrease slowly down to Elk-00. Metal concentrations in Elk Creek are
generally an order of magnitude or more below those of the Level 1 portal
discharge (SM-00). There is a decrease in pH along Elk Creek at Elk-10, but the
pH quickly recovers at downstream locations. Alkalinity generally increases
downstream. There is no obvious impact on alkalinity from the Level 1 adit
discharge. Hardness in Elk Creek increased during 2009. Two potential causes
for the increase are the pilot-scale BCR and the lime that was added to Level 1,
2, and 3 soils after the Removal Action. Elk Creek metal concentrations were
generally lower during 2008 and 2009 than in previous years.
The Elk Creek data collected by EPA and CCWC (Appendix C) were compared
to WQS. The acute cadmium WQS was exceeded at all sampling locations in
Elk Creek downstream of the Standard Mine until 2008 when the concentrations
at Elk-05 and Elk-00 occasionally met the standard. The cadmium
concentrations in Elk Creek almost always exceeded the chronic WQS, even at
Elk-29. Copper concentrations met both the acute and chronic WQS at Elk-29
during all years but exceeded the standards at Elk-10. The chronic and often the
acute standard was exceeded at Elk-08 and downstream locations until 2008.
Since 2008 the copper concentrations have met the acute standard at Elk-08 and
downstream locations and the chronic standard is met during the fall and either
met or slightly exceeded in the spring. Lead concentrations exceeded the chronic
WQS during the spring sampling events, even at Elk-29, but rarely exceeded the
acute WQS. Lead concentrations generally met both acute and chronic standards
at Elk-08 and downstream locations during the fall since 2008. The acute WQS
for manganese was exceeded only once in Elk Creek (at Elk-10) and the chronic
WQS was only exceeded at Elk-10 during fall sampling events. The zinc chronic
and acute WQS were exceeded for all measurements in Elk Creek with the
exception of one measurement at Elk-29, located upstream of Level 1.
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Seasonal effects calculated using 2005 through 2009 data are shown on Figure 4-
11. Cadmium, manganese, and zinc concentrations are generally higher in
September than in June at all Elk Creek sampling locations. The reverse is true
for copper and lead. The pH of the Level 1 adit discharge is much lower during
June than during September but the pH in Elk Creek stays relatively constant
throughout the year. Alkalinity was higher in September than in June at all Elk
Creek locations and in the Level 1 adit discharge.
The USGS sampled water from the Level 1 adit discharge and Elk-00 during
2006 and 2007 to identify seasonal patterns in water quality. The USGS study
determined that the seasonal variations in field parameters and chemical
constituents in Level 1 adit discharge and Elk Creek are very similar. The study
showed a spring flush during which pH dropped and metal concentrations rose in
the early stages of spring runoff. Concentrations increase through summer, fall,
and winter, peaking in late winter at base flow, then decrease during the spring
snowmelt runoff. The pattern is more muted for Elk Creek than for the Level 1
adit discharge. Copper and lead concentrations displayed a pronounced increase
during spring snowmelt runoff, mirroring the pronounced decrease in pH, and
they reached their highest concentrations of the year in May or early June.
Cadmium, manganese, and zinc concentrations also increased sharply during
spring runoff although high concentrations were also observed in the fall.
4.4.1.2 Elk Creek Sediments
Sediments were collected at the same locations as the water quality samples in
Elk Creek. The creek is lined with bedrock, cobble, and gravel with little fine-
grained sediment. It is expected that most of the fine-grained sediment in upper
portions of Elk Creek is waste rock and tailings that have been flushed from the
Standard Mine site. In some locations it was difficult to find enough sediment
for a sample. Because of this, the samples do not indicate the amount of
contaminants present within a certain area or volume of streambed, but rather the
concentration of contaminants within the limited amount of fine material that is
present.
Sediment chemistry is presented in Appendix C and is graphed for select analytes
on Figure 4-12. The sediment metal concentrations at Elk-29 are higher than at
the Copley Lake sampling location. Sediment metal concentrations increase
between Elk-29 and Elk-10. Cadmium, manganese, and zinc concentrations
increase between Elk-10 and Elk-08 and increase further at Elk-06, but the
concentrations decrease to a value less than the Elk-10 concentration at Elk-00.
Average copper and lead concentrations decrease gradually from Elk-10 down to
Elk-00.
In general, the metal concentrations in Elk Creek sediments were lowest during
July 2006 and 2008.
4.4.2 Coal Creek
Coal Creek begins near Lake Irwin and flows south then east where water from Splains
Gulch, Elk Creek, and Wildcat Creek enter Coal Creek before it enters Crested Butte.
The iron fen and gossan and the Mount Emmons Project WTP effluent are located
between the Elk Creek and Wildcat Creek inflows.
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Sample location Coal-25 is located on Coal Creek upstream of the Splains Creek and Elk
Creek inflows. Coal-20 and Coal-15 are located immediately upstream and downstream,
respectively, of the Elk Creek confluence. Coal-Opp2 is located immediately upstream
of the iron fen discharge and Coal-Oppl is located downstream of the iron fen and
gossan. Coal-10 and Coal-05 are located immediately upstream and downstream,
respectively, of the Mount Emmons Project WTP discharge. Coal-02 is located upstream
of the town of Crested Butte and Coal-00 is just upstream of the Slate River confluence.
4.4.2.1 Coal Creek Surface Water
Water quality data for Coal Creek are presented on Figure 4-13. The graphs
show select dissolved metal concentrations, hardness, pH, and alkalinity. Copper
(June and September) and lead (September) were infrequently detected above the
method detection limit, so the graphs are of limited usefulness in understanding
conditions in Coal Creek. The graphs show the 2005 through 2009 EPA data
from upstream to downstream. Data are available from 2005 and 2006 only for
Coal-05 and Coal-00, so the absence of a bar at those locations is not an
indication of a low value. The detection limit was graphed when the contaminant
was not detected in a sample.
Spatial and temporal trends in metal concentrations are not as clear-cut in Coal
Creek as in Elk Creek. Metal concentrations are low at Coal-25 and Coal-20 and
generally increase at Coal-15, downstream of the Elk Creek confluence. The
increase in metal concentrations at Coal-15 compared to upstream locations
(Coal-20 and Coal-25) appears to have lessened during 2008 and 2009 compared
to previous years. Metal concentrations do not necessarily decrease and often
increase between Coal-15 and Coal-10, particularly since 2008. The reason for
the increase is unclear but may be related to another source such as the iron fen
and gossan. More information about the iron fen is presented in Section 4.4.2.3.
pH and alkalinity remain relatively constant along Coal Creek, with a possible
increase downstream of Coal-10. There is no obvious impact on pH and
alkalinity in Coal Creek from the Elk Creek water. The pH decreased between
Coal-15 and Coal-10, perhaps due to the iron fen and gossan, then increased
between Coal-10 and Coal-05, probably due to inflows from the Mount Emmons
Project WTP. EPA did not sample Coal-05 and Coal-00 during 2007 through
2009 so trends since 2006 cannot be evaluated for those locations.
The Coal Creek data collected by EPA and CCWC were compared to WQS as
calculated at hardness of 65 mg/L. Metal concentrations in Coal Creek upstream
of the Elk Creek confluence were consistently lower than the acute and chronic
WQS. Cadmium did not exceed the acute standard in Coal Creek downstream of
the Elk Creek confluence except during 2007 when metal concentrations were
high throughout the watershed. In general, cadmium concentrations have met the
chronic standard at Coal-15 since 2007 but concentrations often increase
downstream at Coal-10 where the chronic standard is met only intermittently.
Lead concentrations rarely exceeded either the acute or chronic WQS in Coal
Creek with the exception of the Coal-15 station where both standards were
exceeded twice (June 2005 and June 2007). Manganese concentrations were
below WQS in all Coal Creek samples. Zinc concentrations exceeded WQS at
Coal-15 during 2006 and 2007 but decreased to meet the acute standard and
usually the chronic standard in 2008 and 2009. The same is not true at Coal-10,
where both standards were met only once and the acute standard was met two
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other times out of 21 measurements. The zinc WQS were rarely met at Coal-05
and Coal-00.
Seasonal effects are shown on Figure 4-14. The seasonal trends in metal
concentrations in Coal Creek are similar to the trends described above for Elk
Creek with the exception of cadmium and zinc concentrations between Coal-15
and Coal-00.
4.4.2.2	Coal Creek Sediments
Sediments were collected at the same locations as the water quality samples in
Coal Creek. Sediment chemistry is presented in Appendix C and graphed for
select analytes on Figure 4-15.
Sediment metal concentrations are similar at Coal-25 and Coal-20.
Concentrations increase at Coal-15, then increase further at Coal-10 and Coal-05.
Cadmium, manganese and zinc concentrations increase but copper and lead
concentrations decrease between Coal-05 and Coal-00.
4.4.2.3	Additional Metal Sources Along Coal Creek
Water discharging from the iron fen and gossan and the Mount Emmons Project
WTP were sampled by EPA to provide a better understanding of metal
contamination in Coal Creek. The fen and gossan samples were labeled "Bog-"
and the Mount Emmons Project WTP samples were labeled "KEY-" because the
WTP was once known as the Keystone WTP.
A low-flow tracer study conducted by University of Colorado (CU) researchers
provides additional insight into the relative impacts of Elk Creek and other metal
sources on Coal Creek water quality.
The CCWC 2008 Water Quality Report identifies additional inputs of metals
from mining sources upstream of the Elk Creek confluence and undetermined
sources in the reach between Coal-15 and Coal-10 (Coal Creek Watershed
Coalition (CCWC) 2009).
Iron Fen and Gossan
Cadmium and zinc concentrations in water samples collected in the fen and
gossan were above WQS; copper, lead, and manganese concentrations were not.
In general, the iron concentrations in samples collected from the fen and samples
collected in Coal Creek below the fend discharge points were not above the
chronic WQS. Metal concentrations in the fen and gossan were typically higher
than in Coal Creek.
Fen and gossan water metal concentrations appear to be seasonal. The seasonal
effects depend on the metal. Cadmium concentrations from Bog-01 are highest
in the spring. The trend is not obvious at Bog-00. The fen and gossan had low
copper concentrations. Lead concentrations show little seasonal variation.
Manganese concentrations appear lower in the spring than in the fall at Bog-00
but higher at Bog-01. Zinc concentrations were lower during snowmelt than at
other times of the year.
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Only two sediment samples were collected in the fen and gossan. Sediment
concentrations in the fen and gossan were similar to values at Coal-10 and
The low-flow tracer study indicated that the fen and gossan were the largest
metal contributors in the watershed. It was a major source of aluminum,
cadmium, iron, manganese, and zinc to Coal Creek. Two point sources of water
discharging from the fen to Coal Creek and another discharge from the gossan
were sampled. The study determined that a large percentage of drainage from
the fen and gossan returns to the groundwater and enters Coal Creek as dispersed
subsurface flow. The study showed an increase in manganese concentration
downstream of the fen. Of the manganese loading in Coal Creek, 67 percent was
attributed to the fen and gossan. The low flow study indicated a spike in the Coal
Creek zinc concentration at the Elk Creek confluence. Zinc loading from Elk
Creek accounted for 16 percent of the zinc load in Coal Creek and the gossan
accounted for 49 percent of zinc in Coal Creek. The highest copper contribution
to Coal Creek was from the gossan. The iron fen and gossan contributed the
highest load of cadmium to Coal Creek (39 percent of the load) followed closely
by Elk Creek, which contributed 32 percent of the load. The drinking water
return contained the largest tributary lead loading (50 percent of total loading).
Splains Gulch added 22 percent of the loading and the fen/gossan added 10
percent (Shanklin and Ryan 2006).
Mount Emmons Project Water Treatment Plant
Metal concentrations in samples collected from Mount Emmons Project WTP
locations are highly variable. The variability could be due to many factors
including discharge timing and changes in process efficiency. Water quality in
downstream Coal Creek locations may vary significantly depending on the status
of the Mount Emmons Project WTP discharge. Under their Colorado Discharge
Permit System (CDPS) permit, the facility is allowed to discharge 0.675 million
gallons per day during October through June and 0.75 million gallons per day
from July through September (CDPHE 2008b). The permit allows discharges
with a daily maximum concentration of 1.9 micrograms per liter ((.ig/L) cadmium
and 390 (ig/L zinc. Other contaminants must be reported to the permitting
authority.
WQS increase in Coal Creek downstream of the Mount Emmons Project WTP
due to the significant increase in hardness introduced by residual lime in the
WTP effluent. For evaluation of the Mount Emmons Project WTP discharge
samples, the WQS were calculated at a hardness of 160 mg/L, the lower 95th
confidence limit of the mean hardness in Coal-05 during low flow conditions
(Table 4-4). The comparison with WQS indicates that standards were generally
met for copper, lead, and manganese with the exception of a few events where
metal concentrations were extremely high. Cadmium and zinc WQS were not
met in WTP discharge on several occasions.
The low-flow tracer study was performed during a period when the WTP was not
discharging effluent, so a direct comparison of the impacts from Elk Creek
versus the Mount Emmons Project WTP is not available. The contributions from
the WTP may be significantly higher than shown in the tracer study. Even when
the plant was not discharging, a large increase in hardness was observed
downstream of the Mount Emmons Project WTP. The WTP effluent and impacts
Coal-15.
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to Coal Creek were evaluated the day after the primary tracer study. Fluctuations
in the discharge from the WTP caused fluctuations in water quality in Coal
Creek, and the discharge from the WTP caused increased aluminum, cadmium,
copper, and zinc loads at downstream locations.
When considering the ability to meet WQS in Coal Creek, the increased metal
load at the Mount Emmons Project WTP is offset by the increase in hardness.
4.4.3 On-site Wetlands
Wetlands located at Levels 5 and 98 were sampled during EPA's 2007 and 2008
sampling events. The data for select analytes are presented on Table 4-6. The full
analytical results are presented in Appendix C.
4.4.3.1 Level 5 Wetlands
Three locations were sampled near the wetland just downgradient of the Level 5
adit discharge (Figure 3-15). WL-1 is a flowing seep discharging at the
downstream end of the wetland below the Level 5 waste rock piles. Both WL-2
and WL-3 are located at the upstream end of the wetland. WL-2 is located
immediately below the road at the base of the Level 5 waste rock piles, and
WL-3 is located at the base of the southern portion of the waste rock pile at
Level 5.
The wetlands at Level 5 have concentrations that are consistently higher than are
seen in the Level 5 adit discharge except for the WL-2 sample collected during
September 2008. The presence of higher metal concentrations at the base of the
waste rock piles (WL-2 and WL-3) during 2007 indicates that the water is
picking up metals as it passes over and through the waste rock piles prior to
entering the wetlands. The reason for low concentrations at WL-2 in 2008 is
unclear. The adit discharge had higher pH in September 2008, possibly allowing
some metals to precipitate out of solution upgradient of the sample location.
Alternatively, a storm could have left standing water at the sample location. Data
from 2009 will be used to determine if the low metal concentrations continue.
A comparison of dissolved and total metal concentrations shows that the results
are similar in WL-1 and WL-3, but there was a large amount of suspended metals
in WL-2. WL-2 is located at the base of a waste rock pile, so the suspended
metals are not unexpected.
Cadmium, copper, lead, and zinc concentrations were lower at the downstream
portion of the wetland (WL-1) than the upstream locations (WL-2 and WL-3),
indicating potential attenuation of metals in the wetland. The manganese
concentrations were higher at the downstream portion of the wetland, indicating
possible mobilization of manganese in this segment. Evaluation of trends is
difficult because only two years data are available and the data are not consistent
from year to year.
The Level 5 wetland samples all exceeded the WQS calculated at a hardness of
65 mg/L for cadmium, copper, lead, manganese, and zinc. The pH was lower
than the WQS pH range in all Level 5 wetland samples with the exception of
WL-2 during 2008.
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4.4.3.2 Level 98 Wetlands
Five wetland locations were sampled at Level 98 (Figure 3-15). WL-1 was
collected from a seep in the Elk Creek tributary channel where water enters the
channel after flowing through waste rock. WL-2 and WL-3 are located below
Level 98. WL-4 is located within the Level 98 waste rock downstream of the
Level 98 adit discharge. WL-5 is located upstream of the Level 98 waste rock.
The Level 98 wetlands generally had lower lead and manganese concentrations
than the Level 98 adit discharge. This may indicate either that the adit discharge
entering the wetlands is being diluted by other water sources in the wetland or
that metals are being attenuated in the wetland. The comparison is not direct for
the other metals. Level 98 WL-4 had the highest metal concentrations, as would
be expected since it is located within the waste rock and receives water from the
Level 98 adit. WL-5 had the lowest metal concentrations, followed by WL-1.
WL-5 would be expected to have low metals because it is located upstream of the
waste rock and adit discharge.
A comparison of dissolved and total metal concentrations shows that the results
were similar in all samples except WL-4 where the total metals were
significantly higher than dissolved metal concentrations. WL-4 is located within
the waste rock pile, so the presence of suspended metals was not unexpected.
The cadmium concentrations exceeded the chronic WQS in all locations except
WL-5, and exceeded the acute standard for WL-2, WL-3, and WL-4. The copper
concentrations exceeded acute and chronic water quality standards at WL-2,
WL-3, and WL-4 but not at WL-1 or WL-5. The lead concentrations exceeded
the chronic WQS except WL5 in 2008, and exceeded the acute WQS at WL-4.
The manganese concentrations in wetlands near Level 98 did not exceed water
quality standards. The zinc concentrations exceeded the water quality standards
in samples collected from WL-1, WL-2, WL-3, and WL-4. The pH was lower
than the WQS pH range in the wetland upstream of the site (WL-5) and in WL-4
(2008 only).
4.4.4 Metals Loading
Metals loading analysis can provide insight into the fate and transport of contaminants in
the watershed. Loading (concentration multiplied by flow) shows how much of a
contaminant, by weight, is being transported downstream per day. Loading analysis
focuses on variations in load between sample locations because that indicates where
metals are introduced or removed from the water column. Distinct variations in metal
load between sampling locations can indicate a source or sink of contaminants. The
analysis is limited by the quality and consistency of the flow and concentration data.
Loading calculations depend on the metal concentration and flow measured at the
sampling location. Uncertainties in the flow rate measurements can strongly influence
the loading calculations, particularly if the measurement may be different at the different
measurement locations during the same sampling event or at an individual location
during different events. The Standard Mine flow measurements contain some uncertainty
introduced by the inherent limitations in using the Marsh McBirney to gather accurate
flow measurements in the extremely rocky stream bed and turbulent water in Elk Creek,
variations in flow measurement personnel, difficulties in measuring higher flows due to
dangerously high water levels, and technical problems with flume instrumentation. Flow
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measurements may also have been influenced by irregularities in channel geometry and
difficulty in measuring very high and very low flows. Since 2007, field personnel did not
measure the flow at sample locations SM-00 and Elk-00, relying instead on the flow
measurements taken by dedicated flumes at these locations. By using the flume
measurements instead of field techniques for just two locations introduces variations
between these locations and those measured by samplers. For example, during June
2007, the flow at Elk-00 was measured by field personnel and flume data are also
available. Comparison of the values shows the flume-measured flow was 28% less than
that measured by sampling personnel. To determine which value was more valid, the
loading graphs were prepared both by using the flume values and by using the measured
value for 2007 and adjusted flow rates for subsequent sampling events. When the Elk-00
load was calculated using the flow rate measured in the field, a large increase in load
occurred between Elk-08 and Elk-00. This effect in load at Elk-00 was moderated, but
not eliminated, by using the flume data. The increase did not occur during the other
sampling events. Due to reports from samplers that flow measurements at Elk-00 were
difficult to accurately attain due to extremely rocky substrate conditions at the Elk-00
location, it was assumed that the flume data more accurately reflected site conditions.
Flume measurements at SM-00 were limited by instrumentation and flow problems.
Flow measurements appeared random and exceeded the maximum flow rates for which
the flume was designed during some high-flow periods. For example, flows above 500
gpm were observed during spring 2009. While it is possible, though not likely, that such
high flows occurred, the flume is not sized to measure such flows accurately. Personnel
visiting the site observed ponded water at the flume due to a clog in the BCR and
overflow piping. Since water was not freely flowing, the flume measurements cannot be
considered valid. For purposes of the loading analysis, the SM-00 flow for June 2009
was assumed to be 80 gpm, a "maximum" value measured directly at the SM-00 flume
during previous years. The Standard Mine flume instruments were not operating during
the September 15, 2008, sampling event, so the flow rate was interpolated from the
available data (July 30, 2008, and October 16, 2008).
For the concentration graphs presented in Section 4.4, non-detects were graphed at the
detection limit. This was done to indicate that while the contaminant was not detected
above the detection limit, there was no guarantee that the contaminant wasn't present in
quantities just under the detection limit. In some cases, the detection limits were near or
above the WQS, so showing the concentration as a specific value (such as zero or the
detection limit) might falsely imply that the WQS was met. Because of the strong
influence of flow on loading, using the detection limit for non-detects resulted in
apparently high loading during sampling events when the flow rate and/or detection limit
were high. Since it is not reasonable to assume such high loading just because the flow
rate or detection limit were high, non-detects are shown on the loading graphs as zero
load.
The loading data were evaluated with the above mentioned limitations in mind. Loading
graphs for Elk Creek and Coal Creek are presented on Figures 4-16 and 4-17,
respectively. The metal load consistently increased between Elk-29 and Elk-10 for all
metals, indicating the Standard Mine site is the source of the increase in load between
these locations. The Elk-10 load was often greater than the load from the adit discharge.
This is likely due to the increase in contaminants leaching from the Level 1 waste rock
and tailings. This did not occur during the June 2009 sampling event, a possible
indication of the positive effects of removing the waste rock and tailings from Level 1 to
the repository. Generally, the metal load decreased or remained constant going
downstream. In a few cases, the June metal load increased between Elk-06 and Elk-05,
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possibly the result of streamflow measurement inaccuracies or increased load due to the
seep between the sample locations.
The load varied significantly between years. In many cases, the concentrations were
similar, but the load increased due to high flow rates. The June 2008 metals loads were
significantly higher than those seen in other years, a reflection of very high flow rates
relative to other years. The lead load at Elk-29 was atypically high during June 2008,
reflecting the very high lead concentration in the sample. It might be considered that the
measurement was an error, but the load at Elk-10 was higher than the load at SM-00, so it
is reasonable that the increased lead load came from upstream. A similar trend was seen
during September 2007. Loading patterns during September 2007 appear different than
for the other September sampling events, particularly an increase in load at Elk-00.
There is an apparent increase in load at Elk-00 during 2007. While this could be caused
by the Removal Action that took place at the Standard Mine during that time, it could
also be an artifact of flow rate inconsistencies. The increase was less apparent during
September.
In Coal Creek, copper and lead loading is minimal. Since 2008, cadmium, manganese
and zinc loading increased downstream of Coal-15 during September and manganese and
zinc loading increased downstream of Coal-15 during June. This is likely an indication
of contributions of other sources of metals, such as the gossan and fen and/or the Mount
Emmons Project WTP. For a point of reference, the Mount Emmons Project WTP is
permitted to contribute a load of up to 0.012 pounds of cadmium per day and 2.5 pounds
of zinc per day based on the maximum effluent flow and maximum daily concentrations
cited in their discharge permit.
4.4.5 Biota
Site contaminants are present in fish and macroinvertebrates located near the site. The
data are presented here and the significance of the data related to risks to human health
and the environment are presented in the baseline human health and ecological risk
assessments and summarized in Section 6. Fish and macroinvertebrate habitat,
abundance, and toxicity data that were collected for the Remedial Investigation (RI) are
presented in the BERA and discussed in Section 6.
4.4.5.1	Fish Tissue
Fish tissues sampled during 2006 showed detectable concentrations of cadmium,
chromium, copper, iron, lead, manganese, and zinc (Table 4-7).
4.4.5.2	Macroinvertebrate Tissues
Macroinvertebrate tissues showed detectable concentrations of cadmium,
chromium, copper, iron, lead, manganese, and zinc (Table 4-8).
4-22
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-1
Level 1 Adit Discharge Water Chemistry
180
Cadmium Concentration in Level 1 Adit Discharge
160
140
M 120
.1 100
'+¦»
ra
£ 80
aj
u
i 60
u
40
20
0
2005
n
2006
2007
2008
2009
¦ June
¦ September
Copper Concentration in Level 1 Adit Discharge
1000
900
800
< 700
a
600
o
ro 500
i_
S 400
u
C
5 300
200
100
0


¦
¦ June
¦ September
2005
2006
2007
2008
2009
4-23
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine
Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-1
Level 1 Adit Discharge Water Chemistry
(Continued)
1800
1600
1400
Lead Concentration in Level 1 Adit Discharge
m 1200
c
o
1000
£ 800
01
§ 600
u
400
200
0
¦ June
¦ September
2005
2006
2007
2008
2009
Manganese Concentration in Level 1 Adit Discharge
14000
12000
^ 10000
J
= 8000
ra
s—
c 6000
0)
u
c
U 4000
2000
0
2005	2006	2007	2008	2009
¦ June
¦ September
4-24
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-1
Level 1 Adit Discharge Water Chemistry
(Continued)
30000
Zinc Concentration in Level 1 Adit Discharge
25000
m 20000
c
o
ro 15000
c
u
= 10000
u
5000
I
¦ June
¦ September
2005
2006
2007
2008
2009
5
pH in Level 1 Adit Discharge
¦ June
¦ September
2005
2006
2007
2008
2009
4-25
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-2
Level 1 Adit Discharge Data
Golder and Associates, Inc.
Level 1 Adit Discharge pH
. r
•— i t~ . •
~ ~
« «~
~~
~
~
~
«
*
~ ~
~i m
~~
~~~ /
If
~
$
~
~~
~ ~
~

8/6/2007 11/14/2007 2/22/2008 6/1/2008 9/9/2008 12/18/2008 3/28/2009 7/6/2009 10/14/2009 1/22/2010
4-26
-------
Created: 12/14/2009 5:48:07 PM Drawn By:andrew_longworth
File Locatio n: T: \ST ART 3\Sta nd a rd_M i n e\G I S\P rojects\Assess me nt\E SAT MA PS\ES AT_C D_Res u Its 11 x 17_l ev e 11 _2009. mxd
Legend
2009 Sample Results (mg/kg) Cadmium Result - 2006 (mg/kg)
Cadmium	[g Not-Detected
(•) Not Detected	—
10-50
Level 1
URS
Standard Mine
Gunnison County, CO
Figure 4-3 Soil Cadmium Concentrations
2006 and 2009 Level 1
UOS - START 3
TDD No. 0608-07
March 2010
Orthoimagery: July 2006
-------
Created: 12/15/2009 7:55:18 AM Drawn By:andrew_longworth
File Location: T:\START3\Standard_Mine\GIS\Projects\Assessment\ESATMAPS\ESAT_CD_ResuIts 11 x17_level 2etal_2009.mxd
Legend
Cadmium Result - 2006 (mg/kg)
Cadmium
Not-Detected
2009 Sample Results (mg/kg)
Cadmium
Not Detected
URS
Standard Mine
Gunnison County, CO
Figure 4-3 Soil Cadmium Concentrations
2006 and 2009 Level 2-5
UOS - START 3
TDD No. 0608-07
March 2010
Orthoimagery: July 2006
-------
Created: 12/15/2009 8:02:56 AM Drawn By:andrew_longworth
File Location: T:\START3\Standard_Mine\GIS\Projects\Assessment\ESATMAPS\ESAT_Cu_Results11x17_level 1_2009.mxd
Legend
2006 Sample Results (mg/kg) 2009 Sample Results (mg/kg)
Copper	Copper
Level 1
URS
Standard Mine
Gunnison County, CO
Figure 4-3 Soil Copper Concentrations
2006 and 2009 Level 1
UOS - START 3
TDD No. 0608-07
March 2010
Orthoimagery: July 2006
-------
Created: 12/15/2009 7:57:38 AM Drawn By:andrew_longworth
File Location: T:\START3\Standard_Mine\GIS\Projects\Assessment\ESATMAPS\ESAT_Cu_Results11x17_level 2etal_2009.mxd
Legend
2006 Sample Results (mg/kg)
Copper
Level 5
2009 Sample Results (mg/kg)
Copper
Level 98
Level 4
Level 3
	!
Level 2
URS
Standard Mine
Gunnison County, CO
Figure 4-3 Soil Copper Concentrations
2006 and 2009 Level 2-5
UOS - START 3
TDD No. 0608-07
March 2010
Orthoimagery: July 2006
-------
Created: 12/15/2009 8:19:00 AM Drawn By:andrew_longworth
File Location: T:\START3\Standard_Mine\GIS\Projects\Assessment\ESATMAPS\ESAT_Pb_Results11x17_level 1_2009.mxd
Legend
2006 Sample Results (mg/kg)
Lead
3000 -10000
>10000
2009 Sample Results (mg/kg)
Lead
3000 -10000
>10000
Level 1
URS
Standard Mine
Gunnison County, CO
Figure 4-3 Soil Lead Concentrations
2006 and 2009 Level 1
UOS - START 3
TDD No. 0608-07
March 2010
Orthoimagery: July 2006
-------
Created: 12/15/2009 8:30:55 AM Drawn By:andrew_longworth
File Location: T:\START3\Standard_Mine\GIS\Projects\Assessment\ESATMAPS\ESAT_Pb_Results11x17_level 2etal_2009.mxd
Legend
2006 Sample Results (mg/kg)
Lead
Level 5
3000 - 10000
>10000
2009 Sample Results (mg/kg)
Lead
3000 - 10000
>10000
Level 98
Level 4
Level 3
	:
Level 2
URS
Standard Mine
Gunnison County, CO
Figure 4-3 Soil Lead Concentrations
2006 and 2009 Level 2-5
Level 1
UOS - START 3
TDD No. 0608-07
March 2010
Orthoimagery: July 2006
-------
Created: 12/15/2009 8:10:02 AM Drawn By:andrew_longworth
File Location: T:\START3\Standard_Mine\GIS\Projects\Assessment\ESATMAPS\ESAT_Mn_Results11x17_level 1_2009.mxd
Legend
2006 Sample Results (mg/kg)
Manganese
5000 -10000
>10000
2009 Sample Results (mg/kg)
Manganese
5000 -10000
>10000
Level 1
URS
Standard Mine
Gunnison County, CO
Figure 4-3 Soil Manganese Concentrations
2006 and 2009 Level 1
UOS - START 3
TDD No. 0608-07
March 2010
Orthoimagery: July 2006
-------
Created: 12/15/2009 8:13:46 AM Drawn By:andrew_longworth
File Location: T:\START3\Standard_Mine\GIS\Projects\Assessment\ESATMAPS\ESAT_Mn_Results11x17_level 2etal_2009.mxd
Legend
2006 Sample Results (mg/kg)
Manganese
Level 5
5000 -10000
>10000
2009 Sample Results (mg/kg)
Manganese
5000 -10000
>10000
Level 98
Level 4
Level 3
Level 2
URS
Standard Mine
Gunnison County, CO
4-3 Soil Manganese Concentrations
2006 and 2009 Level 2-5
* Level 1
UOS - START 3
TDD No. 0608-07
March 2010
Orthoimagery: July 2006
-------
Created: 12/15/2009 8:36:38 AM Drawn By:andrew_longworth
File Location: T:\START3\Standard_Mine\GIS\Projects\Assessment\ESATMAPS\ESAT_Zn_Results11x17_level 1_2009.mxd
Legend
2006 Sample Results (mg/kg)
5000 -10000
>10000
2009 Sample Results (mg/kg)
5000 -10000
>10000
Level 1
URS
Standard Mine
Gunnison County, CO
Figure 4-3 Soil Zinc Concentrations
2006 and 2009 Level 1
UOS - START 3
TDD No. 0608-07
March 2010
Orthoimagery: July 2006
-------
Created: 12/15/2009 8:42:43 AM Drawn By:andrew_longworth
File Location: T:\START3\Sta ndard_Mine\G IS\Projects\Assessment\ESATMAPS\ESAT_Zn_ResuIts11x17_leveI 2etal_2009. mxd
Legend
2006 Sample Results (mg/kg)
Level 5
5000 - 10000
>10000
2009 Sample Results (mg/kg)
5000 - 10000
>10000
Level 98
Level 4
Level 3
	:
Level 2
URS
Standard Mine
Gunnison County, CO
Figure 4-3 Soil Zinc Concentrations
2006 and 2009 Level 2-5
Level 1
UOS - START 3
TDD No. 0608-07
March 2010
Orthoimagery: July 2006
-------
Lower Elk Creek
Explanation
Field phi
METERS
Source:
A.H. Manning and Others, USGS Open File Report 2007-5265
cm urs
OPERATING services
Standard Mine,
Gunnison County
Figure 4-4: USGS pH
©
UOS- START 3
TDD No. 0608 -07
-------
Elk Basin
0.0540

k;:>. .VJ?"
HI'A
<0.0t)002
' M 'MA
¦;1;! '¦ IS
	
<0.00002
0.00006
'•'r ,'2»'
gBP *
•:.W
0.0171 0.00006

1
• f*
0.00002
7 -S.I
ft
0.00220
*T
o	100
METERS
Explanation
Cd Concentration (mg/L)
O <0.00002	O 0.00024-0.02
O 0.00002-0.00024 Q >0.02
Orange symbols exceed water quality standard
t St..i
\m)
URS
DPERATING SERVICES
Standard Mine,
Gunnison County
Figure 4-5: USGS Cadmium
Source:
A.H. Manning and Others, USGS Open File Report 2007-5265
©
UOS- START 3
TDD No. 0608 -07
-------
Elk Basin
• &*¦¦,'-:
- .	0.625
s9sl j&fmLo
ISi
<0.0005«
0.225
<0.0005
'
rm
t>m
•	<0.0005.
.-'\: *<0.0005
HP, illl -M, -¦
2*..	• mR' i J -.s *?,<.•! ]?« 'tii.fr*', 'V ."-k
> '^r y&t5s', f viS-'*. >?s® ix-i'A-
•	<0.0005
FEET
0	300
600 900 1200 1500
0	100
METERS
i—
200
—I—
300
400
500
Lower Elk Creek
Explanation
Cu Concentration (mg/L)
O <0.0005	O 0 0047-0.05
O 0.0005-0.0047 Q >0.05
Orange symbols exceed water quality standard
Source:
A.H. Manning and Others, USGS Open File Report 2007-5265
URS
OPERATING services
Standard Mine,
Gunnison County
Figure 4-6: USGS Copper
©
UOS- START 3
TDD No. 0608 -07
-------
.480 fr.00087
0.00009
* <0.00005
Lower Elk Creek
Explanation
Pb Concentration (mg/L)
METERS
Q 0.0011-0.1
O 0 0001-0 0011 Q>o.i
Orange symbols exceed water quality standard
Source:
A.H. Manning and Others, USGS Open File Report 2007-5265
cm urs
OPERATING services
Standard Mine,
Gunnison County
Figure 4-7: USGS Lead
©
UOS- START 3
TDD No. 0608 -07
-------

Elk Basin
**
•Vkfej)
<0.0002
0.0271
FEET
0	300
600 900 1200 1500
0	100
METERS
200 30Q 400 500
Explanation
Mn Concentration (mg/L)
o <0.005	O °-05-°-5
O 0.005-0.05 (j >0.5
Orange symbols exceed water quality standard
t
iSEZJ
URS
OPERATING SERVICES
Standard Mine,
Gunnison County
Figure 4-8: USGS Manganese
Source:
A.H. Manning and Others, USGS Open File Report 2007-5265
©
UOS- START 3
TDD No. 0608 -07
-------
Elk Basin


«
#
•¦.«F	;
v" /•' *Vj. J «ri«u3Pf* '':
0.0012
:- . Vo,W'
I
€l3.06
-
0	100
METERS
200	300	400	500
Explanation
Zn Concentration (mg/L)
O <0.005 O 0.066-1.0
O 0.005-0.066 Q>1.0
Orange symbols exceed water quality standard
Source:
A.H. Manning and Others, USGS Open File Report 2007-5265
cm urs
OPERATING services
Standard Mine,
Gunnison County
Figure 4-9: USGS Zinc
©
UOS- START 3
TDD No. 0608 -07
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-10
Elk Creek Water Quality
Dissolved Cadmium Concentration Along Elk Creek - June
tuO
O
4—1
TO
01
<_)
o
u
18
16
14
12
10
8
6
4
2
0
aj
00
"a
<
1
	,




~
J1
n
ELK-29
I Jun-05
I Jun-06
I Jun-07
I Jun-08
I Jun-09
Chronic
WQS
Acute
WQS
ELK-10 ELK-08 ELK-06 ELK-05 ELK-00
Dissolved Cadmium Concentration Along Elk Creek - September
45
40
35
cr
~5s 30
o
4—1
to
01
u
O
U
25
20
15
10
5
0
aj
00
"a
<
ELK-29
JLdjUJL
I Sep-05
I Sep-06
I Sep-07
I Sep-08
I Sep-09
Ch ronic
WQS
Acute WQS
ELK-10 ELK-08 ELK-06 ELK-05 ELK-00
4-43
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-10
Elk Creek Water Quality
(Continued)
tuO
o
4—1
50
45
40
35
30
25
20
01
u
o 15
10
5
0
Dissolved Copper Concentration Along Elk Creek - June
"a
<
¦ Jun-05
¦ Jun-06
n (1 fc l_i_i
~ Jun-07
liiiii iiffl IJiDiiimlnhi
I Jun-08
I Jun-09
Chronic WQS
Acute WQS
ELK-29
ELK-10
ELK-08 ELK-06 ELK-05 ELK-00
tuO
o
"¦4—'
ai
u
O
U
Dissolved Copper Concentration Along Elk Creek - September
n
T T "T
lL
I Sep-05
I Sep-06
I Sep-07
I Sep-08
I Sep-09
Chronic WQS
Acute WQS
ELK-29
ELK-10 ELK-08 ELK-06 ELK-05 ELK-00
4-44
-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine -
FIGURE 4-10
Elk Creek Water Quality
(Continued)
Remedial Investigation
TDD No. 0608-07
Date: 05/2010
tuO
o
4—1
TO
01
<_)
70
60
50
40
30
U 20
10
0
Dissolved Lead Concentration Along Elk Creek - June
"O
<
GS
ELK-29
ILl.IL
ELK-10 ELK-08 ELK-06 ELK-05
¦a.
ELK-00
Jun-05
Jun-06
Jun-07
Jun-08
Jun-09
Chronic WQS
Acute WQS
Dissolved Lead Concentration Along Elk Creek - September
tuO
o
4—1
50
45
40
35
30
25
8	20
c
°	1 c
U	15
10
5
0


CD
&0



_C
u



+->
~D
<



1
ID



3
















	

II1
1 1 _
in ¦ m
11P-I—l j-i i„ ^-i i n
I Sep-05
I Sep-06
I Sep-07
I Sep-08
I Sep-09
Chronic WQS
Acute WQS
ELK-29
ELK-10 ELK-08 ELK-06 ELK-05 ELK-00
4-45
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine
Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-10
Elk Creek Water Quality
(Continued)
Dissolved Manganese Concentration Along Elk Creek - June
o
'+-»
tc
a)
u
o
u
900
800
700
600
500
400
300
200
100
0
aj
00
"a
<
ELK-29
¦
1
U I
LL
ELK-10
ELK-08
ELK-06
ELK-05
ELK-00
Jun-
05
Jun-
06
Jun-
07
Jun-
08
Jun-
09
WS
Dissolved Manganese Concentration Along Elk Creek - September
3500
3000
tuo
o
4—1
to
01
u
O
U
2500
2000
I Sep-05
I Sep-06
I Sep-07
I Sep-08
I Sep-09
Chroni
c WQS
Acute
WQS
WS
ELK-29
ELK-10 ELK-08 ELK-06 ELK-05 ELK-00
4-46
-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine -
FIGURE 4-10
Elk Creek Water Quality
(Continued)
Remedial Investigation
TDD No. 0608-07
Date: 05/2010
tuO
O
"¦4—'
03
CD
U
Dissolved Zinc Concentration Along Elk Creek - June
3500
3000
2500
2000
1500
U 1000
500
0
CD
CUD
"O
<
d\r.
fl
it] .Do too
I Jun-05
I Jun-06
I Jun-07
I Jun-08
I Jun-09
Chronic WQS
-Acute WQS
ELK-29
ELK-10 ELK-08 ELK-06 ELK-05 ELK-00
Dissolved Zinc Concentration Along Elk Creek - September
9000
8000
7000
cr
~5o 6000
Zl
I 5000
"¦4—'
ro
£ 4000
01
u
O 3000
U
2000
1000
0
CD
CUD
"O
<

ILiL

I Sep-05
I Sep-06
I Sep-07
I Sep-08
I Sep-09
Chronic WQS
Acute WQS
ELK-29
ELK-10 ELK-08 ELK-06 ELK-05 ELK-00
4-47
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-10
Elk Creek Water Quality
(Continued)
9
8
7
6
5
4
3
2
1
0
1
ELK-29
pH Along Elk Creek - June
CD
Q0
"O
<
CD
>
CD
l~k

¦	Jun-05
¦	Jun-06
~	Jun-07
¦	Jun-08
~	Jun-09
ELK-10 ELK-08 ELK-06 ELK-05 ELK-00
9
8
7
6
5
4
3
2
1
0
pH Along Elk Creek - September



fl
L
CD
GO
ro
	c	



u
to
h




-TD
<




"aj
>
CD
_l









t




t



W
t

¦	Sep-05
¦	Sep-06
~	Sep-07
¦	Sep-08
~	Sep-09
ELK-29
ELK-10 ELK-08 ELK-06 ELK-05 ELK-00
4-48
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-10
Elk Creek Water Quality
(Continued)
Total Alkalinity Along Elk Creek - June
35
tuO
30
25
20
15
o 10
U
L
¦	Jun-05
¦	Jun-06
~	Jun-07
¦	Jun-08
~	Jun-09
ELK-29
ELK-10 ELK-08 ELK-06 ELK-05 ELK-00
Total Alkalinity Along Elk Creek - September
45
40
35
tuO 30
E
o
4—1
to
01
u
O
U
25
20
15
10
5
0
aj
00
"a
<

1


1
¦ Sep-05
~	Sep-06
~	Sep-07
~	Sep-08
~	Sep-09
ELK-29
ELK-10
ELK-08
ELK-06
ELK-05
ELK-00
4-49
-------
URS Operating Services, Inc
START 3. EPA Region 8
Contract No. EP-W-05-050
FIGURE 4-11
Elk Creek Water Quality - Seasonal Variations
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
Dissolved Cadmium Concentration Along Elk Creek
tuO
O
4—1
TO
01
<_)
35.00
30.00
25.00
20.00
15.00
U 10.00
5.00
0.00


rc
_c
u
to

¦¦

Q
4->
~o
<


"aj
>






i







¦¦



|
¦
rf! rn
¦	Average
June
¦	Average
Sep
Chronic
WQS
— Acute WQS
ELK-29
ELK-10 ELK-08 ELK-06 ELK-05 ELK-00
Dissolved Copper Concentration Along Elk Creek
tuO
O
4—1
to
01
u
O
U
35.00
30.00
25.00
20.00
15.00
10.00
5.00
0.00
aj
00
"a
<
HI Lti Lb Lh
I Average
June
I Average
Sep
Chronic
WQS
-Acute WQS
ELK-29
ELK-10 ELK-08 ELK-06 ELK-05 ELK-00
4-50
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-
Date:
FIGURE 4-11
Elk Creek Water Quality - Seasonal Variations
(Continued)
Dissolved Lead Concentration Along Elk Creek
tuO
O
4—1
TO
01
<_)
o
u
50.00
45.00
40.00
35.00
30.00
25.00
20.00
15.00
10.00
5.00
0.00
aj
00
"a
<
ELK-29
I ¦
ELK-10 ELK-08 ELK-06 ELK-05 ELK-00
¦	Average
June
¦	Average
Sep
Chronic
WQS
— Acute WQS
S-
Dissolved Manganese Concentration Along Elk Creek
2£
C
O
c
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-11
Elk Creek Water Quality - Seasonal Variations
(Continued)
Dissolved Zinc Concentration Along Elk Creek
tuO
O
4—1
TO
01
<_)
o
u
7000.00
6000.00
5000.00
4000.00
3000.00
2000.00
1000.00
0.00
CD



CUD
rc
_c
u
in


O
~D
<


CIJ
>
O)
_l

















I
rfl rn
I Average
June
I Average
Sep
Chronic
WQS
¦Acute WQS
ELK-29
ELK-10 ELK-08 ELK-06 ELK-05 ELK-00
pH Along Elk Creek
7.60
7.40
7.20
7.00
6.80
6.60
6.40
6.20
aj
00
"a
<
~ Average
June
I Average
Sep
ELK-29
ELK-10 ELK-08 ELK-06 ELK-05 ELK-00
4-52
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-11
Elk Creek Water Quality - Seasonal Variations
(Continued)
Total Alkalinity Along Elk Creek
40.00
35.00
_ 30.00
	I
CuO
E 25.00
c
o
20.00
g 15.00
c
o
u
10.00
5.00
0.00
0)
ao
T3
<
¦ Average June
~ Average Sep
ELK-29
ELK-10
ELK-08
ELK-06
ELK-05
ELK-00
4-53
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-12
Elk Creek Sediment Quality
80
Sediment Cadmium Concentration Along Elk Creek
60
C
QJ
U
c
o
u
70
60
50
40
30
20
10
Lig
ELK-29
CuO
CuO
c
o
c
CD
U
c
o
u
L
L
ELK-10
ELK-08	ELK-06
ELK-05
ELK-00
i Id m OfflD Dmo
¦	Sep-05
¦	Jul -06
~	Sep-06
¦	Sep-07
¦	Sep-08
~	Sep-09
Sediment Copper Concentration Along Elk Creek
2000
1800
1600
1400
1200
1000
800
600
400
200
0
¦	Sep-05
¦	Jul -06
~	Sep-06
¦	Sep-07
¦	Sep-08
~	Sep-09
ELK-29	ELK-10	ELK-08	ELK-06	ELK-05	ELK-00
4-54
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-12
Elk Creek Sediment Quality
(Continued)
Sediment Lead Concentration Along Elk Creek
60
60
C
o
c
QJ
U
c
o
u
6000
5000
4000
3000
2000
1000

-









¦
rtJi

] Htl DlttD Kb iJL
¦	Sep-05
¦	Jul -06
~	Sep-06
¦	Sep-07
¦	Sep-08
~	Sep-09
ELK-29
ELK-10	ELK-08	ELK-06	ELK-05	ELK-00
Sediment Manganese Concentration Along Elk Creek
CuO
c
o
c
QJ
U
c
o
u
10000
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
I
[L
I
I
¦	Sep-05
¦	Jul -06
~	Sep-06
¦	Sep-07
¦	Sep-08
~	Sep-09
ELK-29
ELK-10
ELK-08	ELK-06
ELK-05
ELK-00
4-55
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-12
Elk Creek Sediment Quality
(Continued)
Sediment Zinc Concentration Along Elk Creek
60
C
o
c
QJ
U
c
o
u
8000
7000
6000
5000
4000
3000
2000
1000
Lfln
i
L
n.
L
¦	Sep-05
¦	Jul -06
~	Sep-06
¦	Sep-07
¦	Sep-08
~	Sep-09
ELK-29
ELK-10
ELK-08
ELK-06
ELK-05
ELK-00
4-56
-------
URS Operating Services, Inc.	Standard Mine - Remedial Investigation
START 3. EPA Region 8	TDD No. 0608-07
Contract No. EP-W-05-050	Date: 05/2010
FIGURE 4-13
Coal Creek Water Quality
Dissolved Cadmium Concentration Along Coal Creek - June
1.2
tuO
zi.
C
O
4—1
ro
4—"
d
CD
£ 0.4
o
u
0.2
0.6

j
c
	qj
	Q-—
H
5
to
	C	

QJ
U
LU
1 1

LL
C
o
n
1
o
E
E
LU
1
1
i
iJmi
I.'iIj
U
1
ii
y •y
(9 <9
* 
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine
Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-13
Coal Creek Water Quality
(Continued)
tuO
o
4—1
TO
01
<_)
o
u
10
9
8
7
6
5
4
3
2
1
0


I

o
E
£
&
$




¦ Sep-05
¦ Sep-06
~ Sep-07
¦ Sep-08
I =
1 Sep-09
Chronic WQS
Acute WQS
4-58
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-13
Coal Creek Water Quality
(Continued)
Dissolved Lead Concentration Along Coal Creek - June

2

1.8

1.6
cr

~5o
1.4
Zl

c
1.2
O

4—1
TO
1
L_

C
0.8
01
u

c
o
0.6
u


0.4

0.2

0
CD
CD
U
MID

c
o
E
kl -
Jun-05
Jun-06
Jun-07
Jun-08
Jun-09
Chronic WQS

-------
URS Operating Services, Inc.	Standard Mine - Remedial Investigation
START 3. EPA Region 8	TDD No. 0608-07
Contract No. EP-W-05-050	Date: 05/2010
FIGURE 4-13
Coal Creek Water Quality
(Continued)
Dissolved Manganese Concentration Along Coal Creek - June

40

35

30


ZL

—
25
d

o

4—1
ro
20
4—"

d

CD
15
u
a

O
10
u

5

0








Q_
1-



QJ
CD

C
CD
U_
c

to
C
o
	£	



U
UJ

o
1_

E
LU


¦
__

L






L

k






i ifi

1
y





¦	Jun-05
¦	Jun-06
~	Jun-07
¦	Jun-08
~	Jun-09


<$>

Dissolved Manganese Concentration Along Coal Creek - September
tuO
O
4—1
to
01
u
O
U
250
200
150
100
50



Q_
H
	>	

QJ
dJ
u

)
'on Fen
to
C
o
E
	lik	P


UJ




LU
-t-j










r_.
flJL


Q

ll



£
6> 6>



£


&

<§>

I Sep-05
I Sep-06
I Sep-07
I Sep-08
I Sep-09
WS
4-60
-------
URS Operating Services, Inc.	Standard Mine - Remedial Investigation
START 3. EPA Region 8	TDD No. 0608-07
Contract No. EP-W-05-050	Date: 05/2010
FIGURE 4-13
Coal Creek Water Quality
(Continued)
250
Dissolved Zinc Concentration Along Coal Creek - June
tuO
O
4—1
CD
u
O
U
200
150
100
50
aj
aj
u
- ¦ ¦
li
c
o
E
E
I Jun-05
I Jun-06
I Jun-07
I Jun-08
I Jun-09
Chronic WQS
¦Acute WQS

£


-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-13
Coal Creek Water Quality
(Continued)
pH Along Coal Creek - June





¦	Jun-05
¦	Jun-06
~ Jun-07
¦	Jun-08
UJun-09
pH Along Coal Creek - September
9
8
7
6
5
4
3
2
1
0





&
$

<9*

¦	Sep-05
¦	Sep-06
~	Sep-07
~	Sep-08
~	Sep-09
4-62
-------
URS Operating Services, Inc.	Standard Mine - Remedial Investigation
START 3. EPA Region 8	TDD No. 0608-07
Contract No. EP-W-05-050	Date: 05/2010
FIGURE 4-13
Coal Creek Water Quality
(Continued)
Total Alkalinity Along Coal Creek - June
o
4—1
TO
01
<_)
o
u
30
25
^ 20
15
10
u
11
 6>
£

9?



¦	Jun-05
¦	Jun-06
~	Jun-07
¦	Jun-08
~	Jun-09
Total Alkalinity Along Coal Creek - September
tuO
c
o
4—1
TO
01
<_)
o
u
60
50
40
30
20
10

CD
CD
u
I
IL
lb
¦	Sep-05
¦	Sep-06
~	Sep-07
~	Sep-08
~	Sep-09


£

/ /
£





4-63
-------
URS Operating Services, Inc
START 3. EPA Region 8
Contract No. EP-W-05-050
FIGURE 4-14
Coal Creek Water Quality - Seasonal Variations
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
Dissolved Cadmium Concentration Along Coal Creek
tuO
O
"¦4—'
CD
u
O
U
1.20
1.00
0.80
0.60
0.40
0.20
0.00
CD
CD
U
bb
fy $
6> 6>
c
o
-------
URS Operating Services, Inc
START 3. EPA Region 8
Contract No. EP-W-05-050
FIGURE 4-14
Coal Creek Water Quality - Seasonal Variations
(Continued)
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
Dissolved Lead Concentration Along Coal Creek
tuO
O
4—1
TO
01
<_)
o
u
1.80
1.60
1.40
1.20
1.00
0.80
0.60
0.40
0.20
0.00
u
¦ ft


£

C
QJ
C
o
c
o
E
]
-------
URS Operating Services, Inc
START 3. EPA Region 8
Contract No. EP-W-05-050
FIGURE 4-14
Coal Creek Water Quality - Seasonal Variations
(Continued)
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
Dissolved Zinc Concentration Along Coal Creek
60
ZJ.
c
o
c
QJ
U
c
o
u
180.00
160.00
140.00
120.00
100.00
80.00
60.00
40.00
20.00
0.00

£




Q_




C
1—
5
to

Oi
u



LL
C


c
o
E

LU






b
LU
¦4—3
















































m m












<0
>



I Average June
I Average Sep
Chronic WQS
¦Acute WQS
pH Along Coal Creek
.40
.20
.00
.80
.60
.40
.20
.00
.80
.60
.40
.20
o
E
~ Average June
¦ Average Sep


o
9
&
o
y
&
&
&
9

sS>

S

4-66
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-14
Coal Creek Water Quality - Seasonal Variations
(Continued)
50.00
45.00
_ 40.00
	i
"So 35.00
E
~ 30.00
'¦§ 25.00
ru
c 20.00
QJ
§ 15.00
U
10.00
5.00
Total Alkalinity Along Coal Creek
1 1 1
1 1 1

¦	Average June
¦	Average Sep
1 1 1
1 I Q_ I
1 i I
01 , , > .
CD 1 C 1 ^ 1
u 1 £ 1 g i
^ 1 c 1 p 1
— 1
1

£ 1 El
- 1 w ,


1
1



1
1
—
5 [

—





1
1




1
1


I
i




1
1

1
1
i
i


1
1

1
1
i
i


1
1

1
1
i
i

V
X
X
X
4-67
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-15
Coal Creek Sediment Quality
Sediment Cadmium Concentration Along Coal Creek
35
tuO
~5o
E
u
30
25
20
15
10
¦	Sep-05
¦	Jul -06
¦	Sep-06
¦	Sep-07
~	Sep-08
~	Sep-09
j? ft # 0
o
oY
o
ox
o° o° o°
4-68
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-15
Coal Creek Sediment Quality
(Continued)
Sediment Lead Concentration Along Coal Creek
450
400
"m 350
I 250
£ 200
S 150
c
o
U 100
50
0










d Glim Dill lU A It

3
s
"P $ & 0^v
o v° O'
o	rP	ro	^	^	ro
Cr O
O
&
cy
,N
oV
<3?	sS*
c/ ^ cP* cP* cP*
¦	Sep-05
¦	Jul -06
¦	Sep-06
¦	Sep-07
~	Sep-08
~	Sep-09
Sediment Manganese Concentration Along Coal Creek
tuO
"S3
E
8000
7000
6000
5000
¦4= 4000
3000
O 2000
1000
¦	Sep-05
¦	Jul -06
¦	Sep-06
¦	Sep-07
~	Sep-08
~	Sep-09
'P $	^ ^	^ & & <9
ou' cy
^
^	r^' r^'
cPx C?x cPx 0vv° 0^°	^ cPx C?x cP'
4-69
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-15
Coal Creek Sediment Quality
(Continued)
6000
Sediment Zinc Concentration Along Coal Creek
5000
4000

 ^	cr
^
o° o° o° ^
¦	Sep-05
¦	Jul-06
¦	Sep-06
¦	Sep-07
~ Sep-08
I Sep-09
4-70
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-16
Metal Loading Along Elk Creek
Cadmium Load Along Elk Creek - June
0.8
0.7
0.6
>• n s
"O
S °-4
T3
to
O 0.3
0.2
0.1
0
_ I
afl]
]
i
o
w
ELK-29
SM-00
ELK-10
ELK-08
ELK-06
ELK-05
ELK-00
¦	Jun-05
¦	Jun-06
~ Jun-07
¦	Jun-08
UJun-09
T3
n:
O
Cadmium Load Along Elk Creek - September
0.25
0.2
M 0.15
0.1
0.05
ELK-29
I
th
lln nib.
J
i
SM-00
ELK-10
ELK-08
ELK-06
ELK-05
ELK-00
¦	Sep-05
¦	Sep-06
~	Sep-07
~	Sep-08
~	Sep-09
4-71
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-16
Metal Loading Along Elk Creek
(Continued)
3.5
3
2.5
>
TO
T3
"S 1-5
(T3
0.5
ELK-29
Copper Load Along Elk Creek - June


¦




—

¦
Ih
I-* n n
fll {
J & J Ufl
SM-00
ELK-10
ELK-08
ELK-06
ELK-05
ELK-00
¦	Jun-05
¦	Jun-06
~	Jun-07
¦	Jun-08
~	Jun-09
0.4
0.35
0.3
>- 0.25
T3
to
0.2
T3
to
9 0.15
0.1
0.05
0
Copper Load Along Elk Creek - September













r-
1 n
r
"K
j]= J]Q iL
¦ Sep-05
~	Sep-06
~	Sep-07
~	Sep-08
~	Sep-09
ELK-29 SM-00 ELK-10 ELK-08 ELK-06 ELK-05 ELK-00
4-72
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine
Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-16
Metal Loading Along Elk Creek
(Continued)
Lead Load Along Elk Creek - June
>
"O
"O
ro
O
2
0.12
0.1
0.08
>
"O
=9 0.06
"O
ro
O
0.04
0.02
J. u
L
3 1 1
rXrh-h
ELK-29 SM-00 ELK-10 ELK-08 ELK-06 ELK-05 ELK-00
.ead Load Along Elk Creek - September












1
u
fin ji Ji .
¦	Jun-05
¦	Jun-06
~	Jun-07
¦	Jun-08
~	Jun-09
¦ Sep-05
~	Sep-06
~	Sep-07
~	Sep-08
~	Sep-09
ELK-29 SM-00 ELK-10 ELK-08 ELK-06 ELK-05 ELK-00
4-73
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-16
Metal Loading Along Elk Creek
(Continued)
Manganese Load Along Elk Creek - June
>
TO
T3
T3
TO
O
35
30
25
20
15
10






1








m r

—
r—
¦
r 1
Ij i
11
n i
l HDi
¦	Jun-05
¦	Jun-06
~	Jun-07
¦	Jun-08
~	Jun-09
ELK-29
SM-00
ELK-10 ELK-08 ELK-06 ELK-05
ELK-00
>
TO
T3
T3
to
o
18
16
14
12
10
8
6
4
2
0
Manganese Load Along Elk Creek - September


















nr>i

n \
~

r
u 11LL
1
11 J
trl

¦ Sep-05
~	Sep-06
~	Sep-07
~	Sep-08
~	Sep-09
ELK-29
SM-00
ELK-10 ELK-08
ELK-06
ELK-05 ELK-00
4-74
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-16
Metal Loading Along Elk Creek
(Continued)
>
TO
T3
T3
TO
O
120
100
80
=5 60
40
20
Zinc Load Along Elk Creek - June

I
I
J J
]
tl
ELK-29
SM-00
ELK-10
ELK-08
ELK-06
ELK-05
ELK-00
~	Jun-05
¦	Jun-06
~	Jun-07
¦	Jun-08
~	Jun-09
>
TO
T3
45
40
35
30
25
T3 20
to
O
	i
15
10
5
0
Zinc Load Along Elk Creek - September













¦






1
1 ~
n



r
"h r

I
Li\
¦
Lj
"K S

ELK-29
SM-00
ELK-10
ELK-08
ELK-06
ELK-05
ELK-00
¦	Sep-05
¦	Sep-06
~	Sep-07
~	Sep-08
~	Sep-09
4-75
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine
Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-17
Metal Loading Along Coal Creek
0.4
0.35
0.3
Jr 0.25
to
-Q
T3
TO
O
0.2
0.15
0.1
0.05
0

G

£

Cadmium Load Along Coal Creek - June
J



to
T3
T3
TO
o
0.16
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0


Cadmium Load Along Coal Creek - September
£

1
1

1
1


Fen


Iron



1 |-
1




1
1




1
1

.1
. 1
I I.
!
.i ¦
<§>





&





¦	Sep-05
¦	Sep-06
~	Sep-07
~	Sep-08
~	Sep-09
4-76
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-17
Metal Loading Along Coal Creek
(Continued)
Copper Load Along Coal Creek - June
tc
T3
i/)
-Q
1.4
1.2
1
0.8
T3 0.6
to
o
"" 0.4
0.2
0
: 0.06
TO
T3
1/1
_Q
T3
to
O
0.05
0.04
0.03
0.02
0.01
0
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine
Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-17
Metal Loading Along Coal Creek
(Continued)
>
tc
T3
i/)
-Q
0.7
0.6
0.5
0.4
T3 0.3
to
o
	I
0.2
0.1
0
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-17
Metal Loading Along Coal Creek
(Continued)
Manganese Load Along Coal Creek - June
£
¦	Jun-05
¦	Jun-06
~	Jun-07
~	Jun-08
~	Jun-09
Manganese Load Along Coal Creek - September
>
TO
T3
T3
TO
O
20
18
16
14
12
10
8
6
4
2
0
-------
URS Operating Services, Inc.
START 3. EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
FIGURE 4-17
Metal Loading Along Coal Creek
(Continued)
Zinc Load Along Coal Creek - June

90

80

70
>
60
TO

T3

to
50
_Q

T3
40
TO

O
	I
30

20

10

0

y

$


I
] qJd
£ # ^
* / /
° $
$ £
&
^ ^ ^
6> 6> 6>
¦	Jun-05
¦	Jun-06
~	Jun-07
¦	Jun-08
~	Jun-09
Zinc Load Along Coal Creek - September
>
TO
T3
T3
to
o
30
25
20
15
10




C




u_
C
o












r-

¦ 1
. J
L i

1
nd ¦
¦	Sep-05
¦	Sep-06
~	Sep-07
¦	Sep-08
~	Sep-09
¦y

£

<2?







&

&

4-80
-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 4-1
Waste Rock and Tailings Chemistry
Siimplc Locution
Screening
( rileriii/
K I P l imits
liiickgruiinri
1 .e\ el 1
Wesl
1 .e\ el 1
North
1 .e\ el 1
Noriheiisl
l.e\el 1
Mill Site
1 .e\ el 1
T;iiliii;i Pond
1 .e\ el 2
1 .e\ el 3
1 .e\ el 4
l.e\el 5 \
l.e\el 515
l.e\el ')X
l.e\el «>«).\
l .e\el
Arsenic
1.9 C
8.7 J
460 U
1,500 U
1,900 U
580 U
460
770 U
3,800 U
6,100 U
760 U
160 U
800 U
2,300 U
880 U
Chromium
1,500,000 N
2.8
200 U
200 U
200 U
200 U
200 U
200 U
200 U
200 U
200 U
260 J
400 J
200 U
200 U
Cobalt
20,000 N
2.83
300 U
300 U
300 U
300 U
300 U
300 U
300 U
300 U
300 U
300 U
300 U
300 U
300 U
Copper
41,000 N
4.8 J
280
690
1,100
310
63 U
580
1,900
6,700
570
280
630
1,500
200 J
Iron
310,000 N
9130
82,000
130,000
160,000
65,000
80,000
73,000
86,000
230,000
180,000
100,000
190,000
180,000
70,000
Lead
750 1
31.6
4,600
15,000
19,000
5,800
470
7,700
38,000
61,000
7,600
1,500
8,000
23,000
8,700
Manganese
20,000 N
598
7,000
9,300
4,000
630
820
6,700
390 J
1,000
4,800
10,000
4,400
2,400
3,300
Mercury
NL
0.02 J
5 U
5 U
12 J
5 U
5 U
5 U
5 U
5 U
5 U
6.9 J
5 U
5 U
5.3 J
Molybdenum
NL
0.32
5.7 U
5.7 U
5.7 U
5.7 U
5.7 U
5.7 U
5.7 U
5.7 U
5.7 U
5.7 U
5.7 U
5.7 U
5.7 U
Nickel
20,000 N
3.2
81 U
180 J
81 U
81 U
81 U
81 U
81 U
96 J
100 J
81 U
99 J
81 U
81 U
Rubidium
NL
--
170
190
210
150
76
160
250
200
210
260
220
210
290
Selenium
5,100 N
1 UJ
12 J
39
51
8.4 U
13 J
21 J
69
190
57
13 J
47
55
8.4 U
Strontium
NL
--
46 J
61
65
130
17 U
44 J
140
48 J
79
42 J
86
93
230
Zinc
310,000 N
40
4,800
11,000
4,700
660
820
3,200
810
2,400
1,300
1,800
1,200
650
410
Zirconium
NL
--
300
240
270
400
130
180
460
340
240
320
300
410
640
SPLP Arsenic
5.0*
--
0.1 U
0.1 U
0.1 U
0.1 U
0.1 U
0.1 U
0.1 U
0.1 U
0.1 U
0.1 U
0.1 U
0.1 U
0.1 U
SPLP Barium
100*
--
0.05 U
0.05 U
0.05 U
0.11
0.05 U
0.098
0.05 U
0.05 U
0.05 U
0.05 U
0.14
0.16
0.05 U
SPLP Cadmium
1.0*
--
0.05 U
0.33
0.14
0.05 U
0.05 U
0.078
0.05 U
0.05 U
0.05 U
0.05 U
0.05 U
0.05 U
0.05 U
SPLP Chromium
5.0*
--
0.05 U
0.05 U
0.05 U
0.05 U
0.05 U
0.05 U
0.05 U
0.05 U
0.05 U
0.05 U
0.05 U
0.05 U
0.05 U
SPLP Copper*
--
--
0.05 U
0.05 U
1.1
0.068
0.05 U
0.05 U
0.05 U
0.13
0.05 U
0.05 U
0.05 U
0.05 U
0.05 U
SPLP Lead
5.0*
--
0.1 U
1.8
7.3
11
0.15
0.29
12
17
8.7
0.1 U
11
14
0.1 U
SPLP Selenium
1.0*
--
0.1 U
0.1 U
0.1 U
0.1 U
0.1 U
0.1 U
0.1 U
0.1 U
0.1 U
0.1 U
0.1 U
0.1 U
0.1 U
SPLP Silver
5.0*
--
0.1 U
0.1 U
0.1 u
0.1 U
0.1 U
0.1 U
0.1 U
0.1U
0.1 U
0.1U
0.1 U
0.1 U
0.1 U
SPLP Zinc*
--
--
1.9
53
22
1.4
0.3
7.1
0.99
1.7
3.1
0.091
1.1
0.21
0.064
Acid Potential
--
--
37.5
93.8
71.9
11.1
5.2
19.1
103.1
74.2
28.4
43.8
12.3
36.1
12.3
Acid/Base Potential
--
--
-26.7
-91.6
-71.9
-11.1
-5.2
-19.1
-103.1
-74.2
-28.4
-34.4
-12.3
-36.1
-10.9
Neutralization
Potential
--
--
10.8
2.2
0.5
0.5
0.5
0.5
0.5
0.5
0.5
9.4
0.5
0.5
1.4
Lime Requirement
--
--
49.1
127.4
107.4
25
11.4
25
142.8
108.4
54.9
57.8
29.2
64.5
20.2
pH
--
--
6.7
5.8
5
5.7
6.4
5.7
5.4
5.2
4.5
6.6
5.4
4.8
6.4
SMP Buffer Lime
Requirement
--
--
1.8
8.1
14
8.9
3.9
8.9
11.1
12.5
15.5
2.4
11.1
15.5
3.9
J	Estimated value due to analyte detection between the Method Reporting Limit and Detection Limit.	U	Analyte was not detected. Reported value is less than the detection limit shown.	D	Sample was diluted prior to analysis.
C	Carcinogen	N	Noncarcinogenic effects	NL	Not Listed
*	RBCs are shown for comparison with metal concentrations, TCLP limits are shown for comparison with the SPLP metal concentrations in the same column as the Region 3 RBCs.	EPA Region 3 Risk Based Concentrations (RBCs) for Industrial Soils from http://www.epa.gov/reg3hwmd/risk/human/rbc/rbc 1005.pdf
Units of Measure: Metal Concentrations in milligrams per kilogram
SPLP metals in milligrams per liter
Acid Potential in tons CaC03/1000 tons
SMP Buffer Lime Requirement and the Acid/Base potential combine to determine the amount of lime required to neutralize the active acidity in the waste rock plus the potential acidity that results from the presence of sulfide minerals in the waste rock.
4-81
-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 4-2
Post-Treatment Soil Chemistry
(Concentrations in tons/1000 tons soil unless noted)
Sample Location
Level 1
South
Slope
Level 1
West
Slope
Level 1
North
Slope
Level 1
Northeast
Slope
Level 2
Level 3
Acid Potential
2
6
1
2
6
17
Acid-Base Potential
36
146
37
171
247
290
Neutralization Potential
38
152
38
173
253
307
SMP Lime Requirement
U
U
2
U
U
U
pH, Saturated Paste
7.1
7.3
7
7.2
7.1
7.1
Organic Matter, %
3.4
2.6
4.6
1.6
2.3
6.6
Organic Matter (Ignition @
400), %
4.5
4
5.4
4.1
4.2
4.9
U	Analyte was not detected. Reported value is less than the detection limit shown.
4-82
-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 4-3
Adit Water Quality (Concentrations in micrograms per liter except as noted)

Diilo1
pll
lliird
( ;i«l in in ill
Copper
lc
;i(l
MSIIIKSIIK'SC
Zinc

IIOSS"
Inliil
Diss
llllill
Diss
Toliil
Diss
1 olid
Diss
llllill
Diss
wns
(limine
0.5-9
lou
--
0.4
--
9.0
--
:,5
--
Icon
--
124

Acute

100
--
1.7
--
13.4
--
65
--
2990
--
143
Level 1
6/1/1999
--
--
85.7
94.1
751
780
1,270
1,290
4,690
4,830
17,800
18,000

9/1/1999
--
--
5
5
470
140
4.7
34
8,000
3,600
4,400
32,000

6/15/2005
3.34
116
139
133
821
867
1,630
1,530
6,000
6,760
20,900
22,800

9/28/2005
6.2
221
150
126
249
138
924
207
10,400
11,200
21,800
23,800

10/1/2005
--
--
170
150
320
220
1,220
500
11,800
8,510
26,600
19,100

6/22/2006
3.95
159
142
142
730
733
1,320
1,290
8,550
8,450
26,100
25,100

7/18/2006
5.62
--
154
154
414
419
1,010
859
8,590
9,000
23,500
24,000

7/19/2006
5.72
255
157
161
488
454
1,270
913
9,350
10,000
26,700
25,000

8/16/2006
6.20
--
148
156
258
226
917
661
9,740
10,000
13,500
24,000

9/13/2006
6.17
228
147
154
251
212
846
546
11,200
11,100
25,700
26,500

10/9/2006
5.58
--
150
155
389
375
1,450
1,090
9,180
9,790
24,600
25,000

1/25/2007
7.22
256
142
142
561
561
1,350
1,350
11,100
11,100
26,300
26,300

2/25/2007
6.6
266
132
132
131
80
321
67
10,700
11,000
26,000
25,000

4/14/2007
6.68
252
134
138
203
113
678
205
11,000
10,000
26,000
25,000

5/5/2007
4.03
177
133
141
560
590
1,670
1,780
7,960
7,960
22,000
23,000

5/15/2007
3.56
174
139
145
459
439
1,320
1,230
9,190
8,920
25,000
24,000

6/3/2007
3.42
128
128
132
842
869
1,360
1,430
6,200
6,310
21,000
21,000

6/13/2007
4.19
120
114
113
611
624
1,170
990
5,780
5,720
18,500
19,900

6/17/2007
3.84
125
115
121
624
630
1,390
1,400
5,770
5,820
18,000
18,000

9/19/2007
5.76
215
139
147
287
228
1,060
716
10,700
10,500
24,800
25,400

6/16/2008
--
96
124
131
841
822
1,270
1,090
5,100
5,090
17,400
18,600

6/19/2008
--
66
96.4
93.6
729
698
1,120
1,060
4,090
4,040
13,100
13,500

6/24/2008
3.59
80
77.9
80.1
525
495
1,180
994
3,970
3,990
12,300
12,900

9/17/2008
5.94
236
147
154
426
159
1,470
239
11,200
11,400
25,000
26,500

6/23/2009
--
113
134
131
603
594
1,210
1,250
6,540
6,480
18,900
19,400

7//202009
5.99
--
170
171
518
600
633
475
11,300
11,000
27,100
26,700

9/16/2009
--
269
149
153
143
105
285
134
11,700
11,800
26,100
27,200
4-83
-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 4-3
Adit Water Quality (Concentrations in micrograms per liter except as noted)
(Continued)

Diilo1
pll
Mil rd
( ;i«l in in ill
Copper
l.o
iiri
Mil n ^ii nose
Zinc

IIOSS"
Ttllill
Diss
llllill
Diss
loliil
Diss
Toliil
Diss
loliil
Diss
Level 24
7/18/2006
2.97
—
181
185
1,190
1,080
644
622
6,180
5,420
27,000
24,000
Level 2
1-7/22/2009
7.28
—
76
13
1,560
5 U
8,960
1.5
4,850
3,690
6,530
1,830
Inside
2-7/22/2009
6.25
—
328
244
132
8
10,300
51.9
10,900
11,000
27,500
22,300
Tunnel
(ECMS
TDL2
....)
3-7/22/2009
7.00
--
58
55
256
100
245
10.2
2,270
2,210
7,440
7,390
4-7/22/2009
3.24
—
190
189
1,500
1,420
2,250
970
5,080
5,070
24,600
24,800
5-7/22/2009
7.39
—
21
19
83
5 U
43.6
1.3
136
137
2,210
2,050
6-7/22/2009
7.53
--
6
6
5
6
6.3
4.7
553
565
370
676
Level 3
1-8/17/2006
4.29
41.8
36.2
34.8
385
365
2,030
1,980
1,830
1,700
5,880
5,580
- Inside
1-7/21/2009
4.48
—
28
28
380
308
3,030
2,120
1,800
1,600
4,180
4,280
Tunnel
(ECMS
TDL3
....)
2-8/17/2006
3.26
59.2
106
112
1,880
1730
2,520
2,350
1,150
1,020
8,440
7,550
2-7/21/2009
3.39
—
93
79
1,090
955
2,790
2,450
1,270
1,070
9,850
8,950
3-8/17/2006
6.95
55.5
7.8
7.4
162
110
303
103
20
13
1,240
1,060
3-7/21/2009
6.59
--
20
20
388
298
656
279
89.3
92.2
2,980
2,960

4-8/17/2006
6.95
77.8
23.1
23
201
54
393
50 U
280
243
2,290
2,020

4-7/21/2009
7.02
—
21
20
108
89
168
108
276
272
2,410
2,400

5-8/17/2006
6.77
110
20.9
22
491
435
159
152
237
207
3,140
2,800

5-7/21/2009
6.89
--
26
26
532
534
223
221
404
415
3,460
3,500
Level 5
10/1/2005
5.11
--
26
28
9 U
1U
430
3U
2,330
2,640
2,680
2,650

8/15/2006
6.66
83.4
24.1
25
10 U
10 U
227
50 U
2,570
2,310
3,310
2,950

9/19/2007
5.72
84
26
26.9
11.3
2 U
429
17.6
2,850
2,810
3,430
3,510

6/24/2008
6.46
54
27.1
22.9
20.8
2 U
607
42.9
1,770
1,660
2,700
2,410

9/18/2008
7.21
83
27.7
28.3
2 U
2 U
395
12.9
2,690
2,660
3,160
3,280

7/21/2009
6.35
--
35
36
14
5
722
20.4
2,680
2,750
3,200
3,240
Level 5
1-8/17/2006
6.7
131
0.11
0.08
10 U
10 u
50 U
50 U
5,010
4,400
2,500
2,260
- Inside
Tunnel
2-8/17/2006
7.2
103
3.5
3.46
10 u
10 u
50 U
50 U
1,620
1,410
626
536
4-84
-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 4-3
Adit Water Quality (Concentrations in micrograms per liter except as noted)
(Continued)

Diilo1
pll
Mil rd
( ;i«l in in ill
Copper
l.o
iiri
Mil n ^ii nose
Zinc

IIOSS"
Ttllill
Diss
llllill
Diss
loliil
Diss
Toliil
Diss
loliil
Diss
Seep In
Waste
Rock
Outside
Level 5
8/15/2006
3.18
172
186
197
681
617
1,230
1,180
26,000
23,000
28,000
25,000
Level
10/1/2005
6.22
—
6.2
6.1
24
20
160
84
130
140
1,060
1150
98
8/15/2006
6.28
30.4
16.7
17.1
126
87
1,240
525
432
359
3,300
3,030

9/19/2007
4.44
44
32.3
34
205
210
1,340
1,340
1,600
1,660
6,250
6,860

9/18/2008
5.86
26
4.43
4.39
18.2
2 U
146
96
357
381
734
803
Seep In
Waste
Rock
Outside
Level 98
8/15/2006
6.2
20.3
5.30
5.53
10 U
10 u
110
102
10 U
10 U
944
882
1	Date column shows sample number prior to the date for samples collected within the Level 3 and Level 5 tunnels.
2	Hardness in milligrams per liter (mg/L)
3	Water quality standard calculated at hardness of 100 mg/L
4	The Level 2 sample was collected from a seep outside the Level 2 portal.
U	Analyte was not detected. Reported value is less than the detection limit shown.
Samples collected on 7/18/2006, 8/15-17/2006, 10/9/2006, 10/9/2006, 2/25/2007, 4/14/2007, 5/5/2007, 5/15/2007, 6/3/2007, 6/17/2007, and 7/2009 were collected by USGS.
4-85
-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 4-4
Water Quality Standards1
(Concentrations are dissolved concentrations in micrograms per liter unless noted)
Hardness
Acute
Chronic
Acute
Chronic
Acute
Chronic
65 mg/L
100 mg/L
160 mg/L
Arsenic (total recoverable)
340
0.2
340
0.2
340
0.2
Cadmium
1.2
0.31
1.7
0.4
2.5
0.6
Chromium III (total
recoverable)
50
NL
50
NL
50
NL
Chromium VI
16
11
16
11
16
11
Copper
9.0
6.2
13.4
9
20.9
13.4
Iron (water supply)
NL
300
NL
300
NL
300
Iron (total recoverable)
NL
1000
NL
1000
NL
1000
Lead
40
1.6
65
2.5
107
4.2
Manganese (water supply)
NL
50
NL
50
NL
50
Manganese
2590
1430
2990
1650
3490
1930
Mercury (total)
NL
0.01
NL
0.01
NL
0.01
Nickel
325
36
468
52
697
77
Selenium
18.4
4.6
18.4
4.6
18.4
4.6
Silver
0.97
0.036
2.03
0.075
4.55
0.169
Zinc
99
86
143
124
214
186
NH3, mg/L
*
*
*
*
*
*
Cl2, mg/L
0.011
0.019
0.011
0.019
0.011
0.019
D O., mg/L
6
6
6
D O. (sp), mg/L
7
7
7
PH
6.5-9.0
6.5-9.0
6.5-9.0
F. Coli, per 100 ml
NL
NL
NL
E. Coli, per 100 ml
126
126
126
CN, mg/L
0.005
0.005
0.005
Sulfur, mg/L
0.002
0.002
0.002
Boron, mg/L
0.75
0.75
0.75
N02, mg/L
0.05
0.05
0.05
N03, mg/L
10
10
10
Chloride, mg/L
250
250
250
S04, mg/L (water supply)
250
250
250
NL Not Listed
Sp Spawning
*	Ammonia standards are based on whether early life stages are present or absent and are based on pH.
1	WQS are provided in 5 CCR 1002-35, Stream Segment 11, Upper Gunnison River Basin. Where applicable, the
standards were calculated at the given hardness using the equations from the Table Value Standards found in 5 CCR
1002-31.
4-86
-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 4-5
Groundwater Monitoring Results
(Concentrations in micrograms per liter unless noted)
Siiindiird/
Locution

P""
Comliicl-
i\ i(\1
1 hi rri-
< ;i«l in in ill
Copper
l.oiid
M;iii}i;iiK'se
/.inc

ness
Diss
TolSlI
Diss
1 Olill
Diss
1 Olill
Diss
1 Olill
Diss
1 Olill
Table 1 Water Supply
—
--
--
5
--
--
--
50
—
--
—
--
—
Table 2 - Water Supply*
6.5-8.5
--
--
--
--
1,000
--
--
—
50
—
5,000
—
Table 3 - Agriculture*
6.5-8.5
--
--
10
--
200
--
100
--
200
--
2,000
--
B1
10/29/2008
--
189.57
89
0.2 U
2.84
2 U
88.7
1.32
33.3
111
8,950
39.4
1,840

4/29/2009
8.12
228
92
0.2 U
1U
2 U
14.1
0.2 U
5.61
23
690
32.8
188

6/17/2009
7.06
101.7
38
0.547
1U
1.20
2.15
0.2 U
1.79
5 U
20.4
103
112

8/5/2009
7.78
138.8
83
11.1
1U
17.22
6.40
11.8
5.47
766
344
1,870
114

9/1/2009
8.3
264
81
0.642
2.71
1.35
33.1
0.2 U
58.5
74.6
1,640
71.6
567
B3
10/29/2008
--
284
113
24.1
25.1
2 U
52.8
11.2
1,120
4,570
8,100
3.480
3,150

6/18/2009
5.53
94.4
34
14.8
15.7
2.32
14.3
34
174
1,940
2,200
1.790
1,910

8/5/2009
6.14
175.3
74
26.7
26.3
16.4
14.6
50.9
66.3
2,450
2,480
3.630
3,500

9/1/2009
8.3
264
84
29.1
29.1
10.9
16.1
42
77.1
3,560
3,600
3.980
3,870
B5
10/29/2008
--
149.6
68
0.2 U
1U
2 U
2 U
0.2 U
5.59
39.5
136
20.5
54.4

4/29/2009
8.1
104.3
43
0.508
1.7
2 U
31.4
0.2 U
79
54.4
629
72.4
291

6/17/2009
6.37
82.2
25
0.293
1.13
1.70
26.8
0.2 U
60.8
25.7
671
72.9
307

8/5/2009
7.93
105.5
50
0.338
1U
1.16
4.75
0.479
5.28
25.7
93.8
64
73.7

9/1/2009
9.76
457
61
0.2 U
2.91
1.20
36.8
0.355
72
181
1,370
20 U
459
B7
4/29/2009
--
356
--
--
--
--
--
--
--
--
--
--
--

6/17/2009
6.91
196.9
55
1.22
11.5
2.49
118
13.2
2,390
3,250
5,010
423
1,940

8/5/2009
7.8
2.62
81
1.41
5.79
1.08
49.3
16.8
1,040
5,000
5,660
726
1,220
Dale's
6/1999
—
—
—
0.03 UJ
0.004 U
0.65
0.46
0.051
0.051
2.01
1.73
19.6
0.2 U
Cabin
9/1999
--
--
--
5 U
6.2
25 U
25 U
3 U
3.8
15 U
15 U
20 U
90
Domestic
6/1999
--
--
--
0.1 UJ
0.004 U
42.6
50.7
0.298
0.622
3.62
4.93
26.2
4.6
Well
9/1999
--
--
--
5 U
5 U
29
36
3 U
3.2
15 U
15 U
52
87
1	Conductivity units are mmhos per centimeter
2	Hardness units are milligrams per liter
U	Analyte was not detected. Reported value is less than the detection limit shown.
Diss Dissolved
*	Water quality standard as listed in Colorado Code of Regulations 1002 Regulation 41, Tables 1, 2, and 3. Bold and shaded cells show values greater than the domestic
water supply (Tables 1 and 2) and agricultural groundwater quality standards (Table 3). Shaded cells show values greater than the agricultural groundwater quality standards
(Table 3).
4-87
-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 4-6
Wetland Water Quality
l.ociilion
l);iU*
pll
Mil rd noss1
C in in
Copper
l.i'iiri
Miini
.illK'SO
Zinc
1 (Hill
Diss
Tuliil
Diss
Toliil
Diss
lot ill
Diss
Idlill
Diss
Level 5 Adit
9/19/2007
5.72
84
26 D
26.9
11.3
2 U
429 D
17.6
2,850
2,810
3,430
3,510

6/24/2008
6.46
54
27.1 D
22.9
20.8
2 U
607 D
42.9
1,770
1,660
2,700
2,410

9/18/2008
7.21
83
27.7 D
28.3
2 U
2 U
395 D
12.9
2,690
2,660
3,160
3,280
Level 5 WL-1
9/19/2007
3.43
104
64.9 D
68.9
70.4
68.3
223 D
226
12,400
12,300
9,370
9,620

9/18/2008
3.65
88
60.6 D
59.5 D
151
148
444 D
474 D
6,430
6,450
6,990
7,320
Level 5 WL-2
9/19/2007
3.09
131
186 D
88.2
606
217
1060 D
675
24,900
10,900
27,500
12,800

9/18/2008
6.87
95
20.2 D
8.74
59.9
2 U
267 D
7.67
5,110
3,390
2,520
1,820
Level 5 WL-3
9/19/2007
4.11
126
54.3 D
56.2
77.8
74.9
66.8 D
50.9
5,370
5,330
8,050
8,330
Level 98 Adit
9/18/2008
5.86
26
4.43 D
4.39
18.2
2 U
146 D
96
357
381
734
803

9/19/2007
4.44
44
32.3 D
34
205
210
1340 D
1340
1,600
1,660
6,250
6,860
Level 98 WL-1
9/19/2007
6.57
25
0.1 UD
0.925
2 U
2 U
16.4 D
7.14
45.1
38.8
191
202

9/18/2008
7.12
28
1UD
0.657
2 U
2 U
9.39 D
3.63
5.55
5 U
134
146
Level 98 WL-2
9/19/2007
6.57
29
5.47 D
5.65
14.1
10.3
49.6 D
23.9
78.7
78.4
905
1,000
Level 98 WL-3
9/19/2007
6.64
31
6.04 D
6.21
18
15.8
13.3 D
11.5
5.39
8.3
982
1,040

9/18/2008
5.93
30
7.15 D
7.2
22.2
18.2
42 D
11.6
18.7
5 U
1,130
1,200
Level 98 WL-4
9/19/2007
6.59
29
6.48 D
5.18
68.7
17.2
664 D
60.3
309
278
1,150
945

9/18/2008
5.27
19
13.8 D
12.8
49.8
27.4
284 D
26.8
650
295
2,450
2,550
Level 98 WL-5
9/19/2007
5.91
19
0.1 UD
0.02 U
2 U
2 U
2.7 D
0.724
159
153
31.2
31.5

9/18/2008
5.24
34
1UD
0.2 U
2 U
2 U
1 UD
0.2 U
77.8
75.2
36.5
36.6
1	Hardness units are milligrams per liter.
J	Estimated value due to analyte detection between the Method Reporting Limit and Detection Limit.
U	Analyte was not detected. Reported value is less than the detection limit shown.
D	Sample was diluted prior to analysis.
4-88
-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 4-7
Fish Tissue Metal Concentrations (Concentrations in milligrams per kilogram dry weight)
l.oc;ilion
Sill)
l.oc;ilion
Aluminum
Arsenic
( ;i«l in in ill
( iilciiim
( h mm in in
Copper
Iron
l.ciid
COAL-02
Comp-7
21.9D
0.4 D
2.2 D
19000 D
2.6 D
6.7 D
73.7 D
0.1 D
COAL-02
Fil-1
3.6 JD
1.1D
0.1 D
2580 D
3.2 D
3.5 D
17.9 JD
0.02 UD
COAL-02
Fil-2
5.7 JD
2.3 D
0.2 D
9540 D
2.9 D
3.ID
23.9 JD
0.08 JD
COAL-02
Fil-3
6.1 JD
0.9 D
0.1 D
2010 D
3.ID
2.7 D
15.6 JD
0.02 UD
COAL-02
Fil-4
2.4 JD
0.7 D
0.3 D
5830 D
2.8 D
3 D
11.8 UD
0.02 UD
COAL-02
Fil-5
3.6 JD
0.7 D
0.2 D
6390 D
2.8 D
3.9 D
16.8 D
0.02 UD
COAL-02
Fil-6
6.3 JD
0.7 D
0.2 D
7720 D
3 D
4.7 JD
25.2 D
0.3 D
COAL-10
Comp-4
17.3 D
1.9 D
2.6 D
19200 D
2.8 D
6.2 D
74.1 D
0.2 D
COAL-10
Fil-1
4.8 JD
4.3 D
0.2 D
2220 D
3.ID
8.3 D
25.1 JD
0.02 JD
COAL-10
Fil-2
4.7 JD
1.6 D
0.3 D
2770 D
2.9 D
3.7 D
30.8 JD
0.07 JD
COAL-10
Fil-3
4.5 JD
1.5 D
0.3 D
3720 D
3D
7.2 D
18.3 JD
0.02 UD
COAL-10
Fil-5
7.1 JD
0.9 D
0.3 D
5700 D
3D
4.8 D
25.3 D
0.02 UD
COAL-15
Comp-4
31.7 D
2.1 D
2.2 D
17200 D
3.5 D
10.4 JD
129 D
0.6 D
COAL-15
Fil-1
7.6 JD
13.5 D
0.2 D
2300 D
3.2 D
3.9 JD
27.1 JD
0.02 UD
COAL-15
Fil-2
7.5 JD
9.4 D
0.2 D
5890 D
3.ID
4.9 JD
20.5 JD
0.02 UD
COAL-15
Fil-3
6.7 JD
12.3 D
0.4 D
4180 D
3.3 D
5.8 JD
35.8 JD
0.09 JD
C0AL-25
Carc-1
109 D
12.7 D
0.4 D
20000 D
9.5 D
7.1 JD
406 D
0.4 D
C0AL-25
Care-2
233 D
16 D
0.3 D
19800 D
6.5 D
7.9 JD
530 D
0.9 D
C0AL-25
Carc-3
11.9 JD
9.8 D
1.4 D
17600 D
3.2 D
6.8 JD
85.5 D
0.1 D
C0AL-25
Fil-1
4 JD
17.6 D
0.03 JD
1880 D
3.2 D
4.8 JD
11.6 UD
0.02 UD
C0AL-25
Fil-2
3.6 JD
18.6 D
0.03 JD
4310 D
3.ID
3.8 D
15.9 JD
0.02 UD
C0AL-25
Fil-3
3.7 JD
14.2 D
0.08 JD
4020 D
3.3 D
13.7 JD
13.5 JD
0.02 UD
ELK-00
Carc-1
16.4 D
1.7 D
3.ID
14800 D
3.8 D
11.5D
91.9 JD
1.8 D
ELK-00
Care-2
15.6 D
3.6 D
1.6 D
18300 D
2.8 D
4.7 D
99.3 D
0.6 D
ELK-00
Carc-3
38.6 D
1.3 D
2.3 D
10700 D
3.ID
11.5 JD
118 D
1.4 D
ELK-00
Fil-1
5.9 JD
1.8 D
0.5 D
4320 D
2.8 D
2.8 JD
16 JD
0.03 JD
ELK-00
Fil-2
2 UD
4.2 D
0.2 D
4020 D
2.8 D
2.5 D
32.7 JD
0.05 JD
ELK-00
Fil-3
5 JD
1.3 D
0.1 D
2850 D
3.ID
3.1 JD
16.3 JD
0.03 JD
SP-00
Fil-1
7.8 JD
5.2 D
0.03 JD
3100 D
3.3 D
5.2 JD
61.3 D
0.02 UD
SP-01
Carc-1
34.4 JD
0.3 D
0.1 D
18800 D
5.2 D
6.1 JD
120 D
0.3 UD
SP-01
Care-2
30.6 JD
0.4 D
0.1 D
14800 D
2.8 D
10.2 JD
104 D
0.02 UD
SP-01
Carc-3
32.3 JD
0.2 D
3.ID
21300D
3.4 D
10.2 JD
110D
0.02 UD
SP-01
Fil-1
7.3 JD
0.6 D
0.06 JD
5640 D
4 D
3.3 JD
30 JD
0.02 UD
SP-01
Fil-2
5.8 JD
0.4 D
0.05 JD
2470 D
3.2 D
6 JD
17.3 JD
0.02 UD
SP-01
Fil-3
6.2 JD
0.2 D
0.06 JD
2610 D
3.5 D
3.5 JD
19.9 JD
0.02 UD
J	Estimated value due to analyte detection between the Method Reporting Limit and Detection Limit.
U	Analyte was not detected. Reported value is less than the detection limit shown.
D	Sample was diluted prior to analysis.
4-89
-------
URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 4-7
Fish Tissue Metal Concentrations (Concentrations in milligrams per kilogram dry weight)
(Continued)

Sill)
Mii^ncsiiiiii
M;ui}i;incsc
Mercun
Nickel
Selenium
Sil\cr
Si ron tin in
Zinc
l.ociilion
l.oc;ilion








COAL-02
Comp-7
1,310 D
15 D
0.06 D
ID
4.4 D
0.02 UD
37.4 D
291 JD
COAL-02
Fil-1
1,380 D
2.8 D
0.11 D
0.4 D
2.6 D
0.02 UD
5.9 D
124 JD
COAL-02
Fil-2
1,430 D
4.7 D
0.16 D
0.7 D
3D
0.02 UD
16.9 D
119 JD
COAL-02
Fil-3
1,410 D
2.1 D
0.12 D
0.3 D
2.5 D
0.02 UD
3.92 D
132 JD
COAL-02
Fil-4
1,440 D
3.3 D
0.08 D
0.4 D
2.8 D
0.02 UD
10.6 D
110 JD
COAL-02
Fil-5
1,420 D
4.4 D
0.09 D
0.5 D
2.6 D
0.02 UD
10.7 D
97.9 JD
COAL-02
Fil-6
1,590 D
10.9 D
0.1 D
0.4 D
2.5 D
0.02 UD
13.3 D
146 D
COAL-10
Comp-4
1,360 D
27.1 D
0.08 D
1.3 D
4.5 D
0.02 UD
48 D
343 JD
COAL-10
Fil-1
1,490 D
2.4 D
0.2 D
0.4 D
3.2 D
0.02 UD
6.54 D
145 JD
COAL-10
Fil-2
1,410 D
3.ID
0.1 D
0.3 D
2.1 D
0.02 UD
6.15 D
115 JD
COAL-10
Fil-3
1,400 D
3D
0.18 D
0.3 D
3.2 D
0.02 UD
10.1 D
184 JD
COAL-10
Fil-5
1,460 D
4.3 D
0.11 D
0.4 D
3.3 D
0.02 UD
12.4 D
157 JD
COAL-15
Comp-4
1,350 D
19.9 D
0.13 D
1.5 D
3.3 D
0.02
53.4 JD
284 D
COAL-15
Fil-1
1,450 D
2.4 D
0.32 D
0.3 D
2.8 D
0.02 UD
7.16 JD
152 D
COAL-15
Fil-2
1,300 D
2.2 D
0.24 D
0.6 D
2.9 D
0.02 UD
18.8 JD
131 D
COAL-15
Fil-3
1,400 D
2.5 D
0.34 D
0.5 D
2.8 D
0.02 UD
11.9 JD
124 D
C0AL-25
Carc-1
1,330 D
24.9 D
0.24 D
5.9 D
4.5 D
0.4
58.9 JD
123 D
C0AL-25
Care-2
1,360 D
37.7 D
0.21 D
3.7 D
4 D
0.4
62.8 JD
148 D
C0AL-25
Carc-3
1,170 D
9.2 D
0.2 D
1.3 D
3.2 D
0.1
55 JD
109 D
C0AL-25
Fil-1
1,430 D
1.4 D
0.34 D
0.2 D
2.8 D
0.02 UD
5.99 JD
43.5 D
C0AL-25
Fil-2
1,380 D
2.3 D
0.28 D
0.5 D
2.9 D
0.02 UD
11 D
63.8 JD
C0AL-25
Fil-3
1,310 D
2.4 D
0.25 D
0.4 D
2.9 D
0.02 UD
13.4 JD
92.5 D
ELK-00
Carc-1
1,230 D
13.6 D
0.09 D
1.7 D
3.9 D
0.03
40 D
267 JD
ELK-00
Care-2
1,400 D
8.4 D
0.12 D
1.1 D
3.5 D
0.02
48.7 D
195 JD
ELK-00
Carc-3
1,180 D
12.4 D
0.08 D
ID
3.6 D
0.02 UD
31.7 JD
230 D
ELK-00
Fil-1
1,380 D
2.7 D
0.1 D
0.4 D
3.2 D
0.02 UD
14.6 JD
132 D
ELK-00
Fil-2
1,550 D
2.2 D
0.16 D
0.3 D
3.3 D
0.02 UD
11.2 D
129 JD
ELK-00
Fil-3
1,430 D
1.7 D
0.13 D
0.2 D
3D
0.02 UD
9.11 JD
129 D
SP-00
Fil-1
1,400 D
1.9 D
0.29 D
0.5 D
3.ID
0.02 UD
10.8 JD
72 D
SP-01
Carc-1
1,200 D
11.8 D
0.16 D
2.7 D
1.8 D
0.03 UD
61.8 JD
97.1 D
SP-01
Care-2
1,260 D
14.9 D
0.15 D
ID
1.8 D
0.02 UD
48.5 JD
90.7 D
SP-01
Carc-3
1,360 D
10.5 D
0.16 D
1.5 D
2.4 D
0.02 UD
65.5 JD
132 D
SP-01
Fil-1
1,290 D
3.1 D
0.17 D
1.3 D
1.6 D
0.02 UD
19.8 JD
71 D
SP-01
Fil-2
1,380 D
1.8 D
0.18 D
0.3 D
1.7 D
0.02 UD
8.32 JD
67.5 D
SP-01
Fil-3
1,390 D
1.8 D
0.2 D
0.4 D
1.6 D
0.02 UD
8.72 JD
88.4 D
J	Estimated value due to analyte detection between the Method Reporting Limit and Detection Limit.
U	Analyte was not detected. Reported value is less than the detection limit shown.
D	Sample was diluted prior to analysis.
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START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
TABLE 4-8
Macroinvertebrate Tissue Metal Concentrations
(Concentrations in milligrams per kilogram dry weight)
l.oi'iiliun
( ;i«l in in in
Copper
l.oiid
M.ing.ini'si'
/.inc
COAL-05
lo.o D
52.5 D
8.59 JD
355 D
2,230 D
COAL-10
22.3 D
34.4 D
10.0 JD
609 D
3,290 D
COAL-15
19.0 D
44.3 D
8.23 D
257 D
1,980 D
COAL-20
2.52 JD
25.7 D
0.702 JD
318 D
514 D
COAL-25
2.11 JD
20.4 D
7.37 JD
769 D
439 D
COAL-OPP2
9.90 D
25.7 D
8.23 JD
267 D
1,460 D
COP-01
3.95 JD
19.3 D
5.80 JD
1,540 D
435 D
ELK-00
32.9 D
149 D
60.6 D
370 D
3,530 D
ELK-05
21.4 D
124 D
157 D
1,300 D
2,740 D
SP-00
2.29 JD
19.1 D
5.36 JD
143 D
398 D
SP-01
1.28 JD
20.4 D
0.272 UD
75.3 D
341 D
J	Estimated value due to analyte detection between the Method Reporting Limit and Detection Limit.
U	Analyte was not detected. Reported value is less than the detection limit shown.
D	Sample was diluted prior to analysis.
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START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
5.0 CONTAMINANT FATE AND TRANSPORT
The Standard Mine site is located in a highly mineralized zone that contains pyrite and other sulfide
minerals. Some of the metals in the rock are released during natural erosion processes. Mining hastened
the release of metals by bringing the highly mineralized rock to the surface and by exposing new rock
surfaces within the mine. Sulfide minerals on the exposed surfaces oxidize, resulting in the release of
contaminants to water that carries the contaminants away from the source materials, potentially causing
adverse effects on human health and the environment.
This section describes the mobilization and fate of the major site contaminants: cadmium, copper, lead,
manganese, and zinc. Potential routes for contaminants to migrate from source locations are presented in
Section 5.1. Characteristics that may affect the behavior of the contaminants in the environment are
briefly described in Section 5.2. Contaminant migration processes and evidence that migration is
occurring are presented in Section 5.3. A conceptual site model is presented in Section 5.4
5.1 POTENTIAL ROUTES OF MIGRATION
5.1.1	Air
Fine-grained waste rock and tailings can become airborne by wind or mechanical means
such as vehicular traffic. The primary factors affecting air migration of metals are the
particle size and the wind speed or other shear forces that distribute the particles from the
ground to the air. Smaller particles become airborne with less force so are more mobile.
Higher wind speeds or shear forces from vehicles driving over the particles add to the
amount of particles transported via air. The concentration of metals in the particles
affects how much of the metal is transported.
5.1.2	Water
Water plays a large role in the distribution of metals from the Standard Mine. Water acts
as a chemical agent in the oxidation of sulfide minerals and also physically transports
metals (both dissolved and particulates) and acidity to downstream surface water,
groundwater, and soils.
Surface water and groundwater become contaminated with metals when sulfide-bearing
minerals such as iron pyrite are exposed to water and oxidizing conditions. Oxidation of
sulfide mineral occurs slowly as a natural weathering process, but oxidation is
accelerated when mining activities increase the surface area of rock exposed to oxygen
and water. Rock brought to the surface is exposed to oxygen and water on a regular
basis, and water and oxygen can easily enter mine workings.
The chemical reaction that occurs when pyrite is exposed to water and air is:
Iron II ions (Fe2+) and acidic hydrogen ions (H ) are released into water that flows from
mine drainage tunnels or tailings piles. The pH represents the hydrogen ion
concentration. Because the scale is negative logarithmic, a high pH indicates a low
hydrogen ion concentration and a low pH represents a high hydrogen ion concentration.
The above reaction increases the hydrogen ion concentration and therefore decreases pH.
Iron II ions are oxidized to form iron III ions as shown in the following reaction:
4FeS2(s) + 1402(g) + 4H20(1) -> 4Fe2+(aq) + 8S042"(aq) + 8lT(aq)
4Fe2+(aq) + 02(g) + 4lT(aq) -> 4Fe3+(aq) + 2H20(1)
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START 3, EPA Region 8
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Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
The iron III ions then hydrolyze in water to form iron III hydroxide.
4Fe3+(aq) + 12 H20(1) -> 4Fe(OH)3(s) + 12H+(aq)
This process releases even more hydrogen ions into the aquatic environment and
continues to reduce the pH. The iron III hydroxide formed in this reaction is called
"yellow boy," a yellowish-orange precipitate that turns the acidic runoff in the stream to
an orange or red color and covers the stream bed with a slimy coating. Aquatic life that
dwells on the bottom channel of the stream is soon killed off by the presence of yellow
boy.
The sum of these reactions is shown in the following equation:
4FeS2(s) + 1502(g) + 14H20(1) -> 4Fe(OH)3(s) + 8S042"(aq) + 16lT(aq)
This is not the only process occurring in the mine workings and waste piles. Sulfides of
cadmium, copper, lead, manganese, and zinc undergo similar geochemical reactions
resulting in the contribution of toxic metal ions into mine waste water. Factors such as
the presence of acid tolerant bacteria (Thiobacillus ferroxidans) can speed up the process
of sulfide oxidation.
In addition to its influence on the production and mobilization of contaminants by sulfide
oxidation, water also acts as an erosive agent, physically picking up particles containing
metals and carrying them to downstream/downgradient locations. Surface water and
groundwater can transport dissolved metal contaminants to locations where a change in
chemical conditions (e.g., higher pH or different oxidation-reduction state) may cause the
metals to drop out of solution, precipitating onto soil, rocks, sediments, or other
environmental media. It is often the case that metal concentrations in groundwater
decrease (attenuate) as the groundwater flows through "clean" soils.
Many factors influence the concentration of metals in water exposed to mine tunnels or
waste rock, including the composition and physical characteristics (e.g., particle size) of
the minerals and exposure time.
•	The composition of the mineral determines if sulfide oxidation will occur and
what metals are present that may become mobile in the water.
•	Particle size is important because it affects the amount of mineral that is exposed
to water and oxygen. Fine particles have more surface area than larger rock, so
larger quantities of metals will be generated in the fine rock in a given period of
time.
•	Exposure time becomes a factor in the unsaturated zone of soil or waste rock and
in mine workings. For example, when the chemical reactions occur in the vadose
zone (the seasonally saturated zone above the water table), the water may be
exposed to the reactive rock for a long period of time before being washed away
into surface water or groundwater. The long contact time can cause metal
concentrations that are higher than they would be if the water flowed quickly past
the rock (short contact time). A similar effect can occur within a mine tunnel,
where long exposure to mineralized rock and oxygen can cause water to become
more acidic and saturated with metals. This can cause a "spring flush" as water
that has been in contact with reactive minerals over the fall and winter are
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Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
washed through the system when the spring runoff causes water to flow over the
surface and through the subsurface.
5.2 CONTAMINANT PERSISTENCE
The metals of concern at the site are persistent in water and soil. The form of the metal can affect
its mobility and fate. Solid particles in the water will behave differently than dissolved metal
ions. Metal ions generated during sulfide oxidation can remain as metal ions in the water,
precipitate, adsorb onto solid surfaces, or form complexes with other ions or organic material
when the water chemistry changes, for example when the oxidation-reduction state of the water
changes or when the acidity is changed. Sulfide oxidation is inhibited in a reducing environment,
and cadmium, copper, lead, and zinc already in solution will form sulfide precipitates, causing a
decrease in the concentration of dissolved metals in the water. The presence of limestone-bearing
minerals or other forms of alkalinity can neutralize pH, allowing precipitation of metal
hydroxides. Hydroxide-coated surfaces and organic materials provide sites onto which the metals
may adsorb, providing another means of attenuating metal ion concentrations in water.
The following list provides a brief overview of information regarding the five metal
contaminants.
•	Cadmium occurs as an impurity in ore minerals such as sphalerite. Cadmium is present
as a divalent ion (Cd2+) or CdS04 at pH values less than 8. Cadmium precipitates as pH
rises above 8 and it adsorbs to hydrous, aluminum, and manganese oxides and clays.
Sulfate may inhibit cadmium adsorption.
•	Copper occurs in chalcopyrite, covellite, tennanite, and pyrite. Copper is present as Cu+,
Cu2+, or CuS04 at pH values of less than 7. At pH of 7 or greater, Cu(OH)2 is present in
aqueous forms. Aqueous copper complexes with dissolved organic matter, which can
enhance copper mobility. Copper is also strongly adsorbed by hydrous ion, aluminum,
and manganese oxides. The adsorption of copper on hydrous metal oxides is strongly pH
dependent. Copper adsorption is dependent on the ratio of iron to copper and
complexation of copper by anions such as sulfate. The presence of organic copper
complexes may increase copper adsorption to hydrous metal oxides at pH less than 6 but
enhances copper mobility at higher pH values. Aquatic organisms are sensitive to
copper. The presence of dissolved organic carbon can decrease the toxicity of copper.
•	Lead occurs as a sulfide in galena (PbS, which contains 86.6% lead), cerussite (PbC03)
and anglesite (PbS04). Lead solubility is a function of pH, hardness, salinity, and the
presence of humic material. Lead is strongly adsorbed to soil.
•	Manganese occurs as a substitute for iron, magnesium, and calcium in silicate minerals
and in oxidized forms such as pyrolusite (Mn02) in oxidizing environments. Manganese
is generally present as Mn2+ in aqueous solutions but also occurs as Mn3+ and Mn4+.
Dissolved manganese does not precipitate readily in oxidizing or reducing conditions. It
is mobile in acidic, neutral, and moderately alkaline solutions. At pH values of about
10.5, manganese precipitates as a hydroxide. Manganese forms complexes with organic
matter and may sorb to clays and hydrous iron oxides suspended in water or on stream
bottoms.
•	Zinc is found in sphalerite (ZnS) and as a substitute for iron and manganese in silicate
minerals. Zinc is a mobile metal and takes the form of a divalent ion (Zn2+) and zinc
sulfate complexes (ZnS04) in acidic to neutral solutions. Zinc precipitates out of solution
as the pH of the solution is increased to greater than 9. Sulfate may enhance zinc
adsorption. Zinc precipitates as a sulfide under reducing conditions.
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START 3, EPA Region 8
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Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
5.3 CONTAMINANT MIGRATION
The following sections provide a qualitative evaluation of contaminant migration at and from the
Standard Mine site. Quantitative contaminant transport modeling has not been performed. The
evidence of migration of contaminants from the Standard Mine site is discussed below. Transport
of metal contaminants to human and environmental receptors was evaluated in the BHHRA and
BERA and is summarized in Section 6.
5.3.1	Contaminant Migration via Air
The potential for air migration of contaminants at Levels 1, 2, and 3 was reduced as a
result of the Removal Action. The most highly contaminated materials were taken to a
repository and covered with soil and riprap, making them unavailable for air transport.
The residual soils at the site contain lower levels of metals, so particles that become
airborne would be less toxic to receptors. The potential for air migration was reduced
further by establishing a vegetative cap over the residual soils and waste rock that was
left in place. Areas where waste rock was excavated down to native soils or bedrock
were treated with lime, fertilizer, and compost and seeded to allow successful
revegetation. Where waste rock was left in place, the area was treated with lime and
fertilizer to reduce contaminant mobility, covered with native soil, and revegetated.
Air transport from the waste rock piles is now limited to Levels 5 and 98. Neither area is
suitable for vehicle traffic due to the steep slope of the Level 5 waste rock piles and large
rocks at Level 98. The remaining mechanism to mobilize the particles into the air from
Levels 5 and 98 is wind. The quantity of airborne particulates has not been measured or
modeled because visible particulates were rarely observed except during construction
activities.
5.3.2	Contaminant Migration via Surface Water
Because the source of water recharge to the Elk Creek basin is precipitation, the primary
source of solutes in site waters must be water-rock interactions. The basin is a naturally
mineralized zone so some metal dissolution is expected, but natural weathering processes
cannot account for the high concentrations of cadmium, copper, lead, manganese, and
zinc in waters emanating from the waste rock piles (Section 4.1.1) and mine workings
(Section 4.1.2). Therefore, it was determined that mining activities at the site are the
primary cause of metal contamination in surface water and sediments immediately
downstream of the site (USGS 2007). The exposed sulfide minerals within the mine
workings and in waste rock outside of the workings are the primary source materials.
Contaminants mobilized from within the mine workings migrate from the tunnel via adit
discharges. This release of contaminants occurs at Levels 1, 2, 5, and 98. The greatest
release of contaminants from the mine workings is at Level 1 because both the flow rate
and metal concentrations in the Level 1 adit discharge is significantly greater than in the
discharge from Level 2, 5, or 98. The adit discharges all have elevated contaminant
concentrations relative to Elk Creek.
Flow of groundwater, adit discharge water, or surface water across and through waste
rock and tailings enhances contaminant mobilization as the water reacts with minerals
and carries dissolved and particulate metals to downstream locations. At one time this
occurred at all of the Standard Mine levels. The Removal Action has limited the flow of
water over waste rock at Levels 1, 2, and 3 by isolating much of the waste rock in a
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TDD No. 0608-07
Date: 05/2010
covered repository that is located above the groundwater table. Elevated metals
concentrations are still present in the soil within limited areas of Levels 1 and 3, but
water flow across and through the waste rock has been minimized by the installation of
surface water controls, the realignment of Elk Creek, and treatment of the remaining
waste rock and residual soils. These actions have reduced the contact between the
reactive minerals and water and reduced the mobility of the metals in soils that do contact
water. The Level 5 and Level 98 adit discharges still flow over waste rock prior to
flowing into downgradient streams and wetlands, providing an ongoing source of
contaminant loading to Elk Creek.
Dissolved and particulate metals are carried via surface water from where they are
generated in the mine workings and waste rock piles to downstream locations such as
wetlands and Elk Creek. The significant increase in surface water and sediment
contaminant concentrations between Elk-29 and Elk-10 is evidence that contaminants are
migrating from the Level 1 site into Elk Creek. At Level 98, the increase in metal
concentrations in the water from the upgradient (WL-5) to the downgradient locations
(WL-1, WL-2, and WL-3) plus the high metal concentrations in water within the wetland
located on the waste rock pile (WL-4) are indications that contaminants are being
generated at Level 98 and transported to downgradient wetlands and Elk Creek. Elevated
metal concentrations in adit discharge from Level 5 and sample locations at the base of
the Level 5 waste rock piles are evidence that contaminants are being generated at Level
5 and discharged to, at a minimum, the receiving wetland. A comparison of metals
content upstream and downstream of Level 5 and Level 98 wetlands shows attenuation of
dissolved metals within the wetlands via complexation, adsorption, and/or precipitation.
The highly elevated concentrations of seep water emanating from the Level 2 waste rock
and flowing toward Elk Creek is evidence that Level 2 also contributed metals to Elk
Creek prior to the Removal Action. (Additional sampling is required to determine if
seeps from the Level 2 mine workings continue to flow after the Removal Action and, if
so, whether the metal concentrations in the seep water remain high.)
The spatial pattern of metal concentrations in Elk Creek water (low at Elk-29, higher at
Elk-10, with a general decrease down to Elk-00) suggests that contaminants are
transported down Elk Creek where they are diluted and attenuated by precipitation,
adsorption, and complexation. Elevated metal concentrations persist, despite the
attenuation, but the pH quickly recovers at downstream locations. It was expected that
since metal loading from the Standard Mine site has decreased due to the Removal
Action, metal concentrations in downstream surface water, sediments, and biota will
slowly decrease. This has proven true in 2008 and 2009 when metal concentrations have
decreased at Elk-08 and downstream locations.
The spread of metal contaminants from the Standard Mine into Coal Creek can be seen
by comparing metal concentrations in Coal Creek both upstream and downstream of the
Elk Creek confluence. Metal concentrations are low at Coal-25 and Coal-20 and increase
at Coal-15, downstream of the Elk Creek confluence, consistent with the Standard Mine
being the primary source of contaminants. The increase in metals concentrations at Coal-
15 appears to have lessened during 2008 and 2009, consistent with a reduction in loading
from the site due to waste rock removal. Increases in metal concentrations and loading at
Coal Creek monitoring locations downstream of Coal-15 are an indication that there are
other significant sources of metal loading to Coal Creek. CCWC has identified the fen
and gossan and the Mt. Emmons Project WTP as likely sources.
Surface water also transports sediment to downstream locations where it can remain for
periods of time, then be remobilized and transported farther downstream. If the sediment
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Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
contains reactive minerals and is deposited such that it contacts both air and water, an
additional source of metal contamination to the water column is created. There is no
obvious evidence that reactive mineral deposits are located adjacent to Elk Creek or Coal
Creek at downstream locations.
Sediment metal concentrations increase in Elk Creek downstream of Level 1 relative to
the upstream location (Elk-29). Potential causes for the increase in sediment metals
concentrations include erosion and subsequent settling of contaminated soils, settling of
particulates from the Level 1 adit discharge, precipitation and settling of metals from the
adit discharge, and sorption of metals from the Level 1 adit discharge water onto the
sediments. The cadmium, manganese, and zinc concentrations increase between Elk-10
and Elk-08 and increase further at Elk-06. It might be expected that the concentrations
would decrease downstream of Elk-10 as sediments released from the mine were
"diluted" with sediments released from non-contaminated portions of the watershed. It is
possible, however, that the precipitation and sorption of the more mobile metal ions, such
as manganese and zinc, is enhanced by the downstream water chemistry, leaving
additional metals in the sediments. Sediment metals concentrations decrease to a value
less than the Elk-10 concentrations at Elk-00, perhaps indicating that the precipitation
and sorption reactions have slowed or ceased by the time the water reaches Elk-00.
Copper and lead concentrations in sediment decrease gradually from Elk-10 down to
Elk-00.
The increase in sediment metal concentrations between Coal-20 and Coal-15 is likely due
to the elevated metals in sediments from Elk Creek drainage. The increases in metal
concentrations downstream of Coal-15 may be due to other sources. Possible interactions
causing the increase include the following.
•	Contaminated sediments are being flushed through the system and the sediments
with high metal content are not being replenished by upstream sampling
locations because the waste rock at Level 1 has been stabilized and/or removed.
This leaves upstream concentrations lower than downstream locations.
•	Metals are precipitating from high metal content water onto stream sediments as
water chemistry changes to conditions that favor precipitation and adsorption.
The change in water chemistry could be from dilution of acidity due to inflow of
other drainages or from the increase in specific water chemistry elements (iron,
organic carbon, alkalinity) from the other drainages, the fen and gossan, and/or
the Mt. Emmons Project WTP.
•	High metal content sediment is being supplied directly from other sources such
as the iron fen and gossan or the Mt. Emmons Project WTP. Based on the
relative metal concentrations in the sediments in the fen and gossan and at SW-
10, it does not appear that the increase in sediment metals concentrations
between Coal-15 and Coal-10 are due entirely to sediments from the iron fen and
gossan.
•	Metals are precipitating from high metal content water from the iron fen and
gossan and the Mt. Emmons Project WTP onto stream sediments.
It is expected that sediment loading to Elk Creek and Coal Creek from the Standard Mine
site will decrease since the completion of the Removal Action that isolated much of the
site waste rock and tailings from surface water.
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START 3, EPA Region 8
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TDD No. 0608-07
Date: 05/2010
5.3.3 Contaminant Migration via Groundwater
EPA performed limited investigation of contaminant migration in groundwater at the
Standard Mine site. Groundwater wells were installed for evaluation of remedial
alternatives but well locations were not selected for the purpose of characterizing site-
wide or downgradient groundwater quality. Evaluation of specific groundwater pathways
taken by site contaminants is limited by the absence of spatially diverse groundwater
data.
Available groundwater data indicate that shallow groundwater in the Ohio Creek
Formation near the Standard fault contains elevated concentrations of metals. Deep
groundwater in the Wasatch formation contained significantly lower concentrations of
metals than the shallow Ohio Creek Formation wells. Deep wells were not installed in
the Ohio Creek Formation and water was not present in the shallow Wasatch Formation
wells, so a correlation between shallow and deep groundwater quality in either formation
could not be established.
The primary indicators of site-wide groundwater quality in the basin are adit discharge
water quality, water quality within the mine workings, and water quality of seeps
investigated by the USGS. The USGS study indicates that contamination primarily
follows the Standard Fault. Surface water enters the subsurface via percolation of
precipitation into the alluvial and fractured bedrock aquifers. Groundwater enters the
mine workings, primarily via fractures in the bedrock and partially via irregularities in
the Standard fault-vein. Water that reaches the mine workings becomes contaminated
within the workings, as evidenced by elevated metals concentrations found in adit
discharges and samples collected from within the tunnels, then is discharged from the
adits to Elk Creek. A portion of the water in the adits may seep into the groundwater.
Groundwater transports metals in a manner similar to surface water: Dissolved and
particulate metals are transported to downgradient locations where they are diluted or
attenuated by precipitation or sorption. Particulates are unlikely to travel far from the
point of entry into the groundwater system. Dissolved metals are often attenuated in the
alluvium and bedrock. An abundance of sorption sites on the soils and bedrock are likely
to adsorb metals, and the presence of carbonate rock is likely to cause precipitation of
metals. There is no indication that a large source of dissolved metals is reaching Elk
Creek downgradient of the site via groundwater flowing from the site. There was a small
increase in metals concentrations between Elk-06 and Elk-05 during one or two sampling
events that could indicate that a small amount of contaminated groundwater feeds the
surface water at that location. The increase only occurred during certain sampling events
and samples of the seeps contain very low metals concentrations, indicating that the
groundwater at that location is not contaminated and therefore not contributing to
contamination in Elk Creek.
5.4 CONCEPTUAL SITE MODEL
The primary source of contamination from the Standard Mine is sulfide minerals in the mine
workings and waste rock that release metal contaminants during sulfide oxidation.
Snowmelt and rain infiltrate the ground surface and enter the shallow and deep groundwater
system. Groundwater enters the mine workings primarily from fractures in the Ohio Creek
formation and to a lesser degree from localized fractures and breccia zones within the fault-vein.
Little water has been observed to enter the mine workings from the Wasatch Formation.
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TDD No. 0608-07
Date: 05/2010
The bulk of the site mining occurred at the Standard and Micawber Mines associated with Levels
1, 2, and 3. Water enters this system as described above and can also enter the mine from the
Level 4 shaft. Once in the mine, water accumulates metals as it flows over sulfide minerals
present on the floors, ribs and backs of the tunnels. Water in Level 3 flows to Level 2 through
open stopes, raizes, and filled ore chutes where it is believed that the most significant
mobilization of metals occurs. Additional water enters Level 2 from the Ohio Creek Formation
and the fault-vein system. Water flows through muck on the floor of Level 2. The water pooled
up behind debris in Level 2 compounds loading by providing additional residence time for
leaching of metals before the water is discharged via winzes to Level 1. Water is discharged at
the Level 1 portal and flows into Elk Creek where it transports contaminants downstream in
particulate or dissolved form. A portion of the water in the mine workings may enter the local
groundwater system.
The Level 5 and Level 98 mine workings are not connected with Levels 1, 2, 3, or 4 or with each
other. Water enters these tunnels from the surrounding rock and accumulates metals as it flows
over sulfide minerals in the tunnels. A blockage within Level 5 may contribute to loading by
pooling water and providing additional residence time for leaching of metals into the water.
Water is discharged from the respective portals and flows over the waste rock prior to entering
wetlands immediately downhill from the waste rock. Contaminants in the water may contribute
to elevated metal concentrations at the Elk-29 sampling station.
Surface water, groundwater, and adit discharge water that flows over and through waste rock
mobilizes contaminants as the water reacts with minerals. Dissolved and particulate metals are
transported to downgradient surface water and groundwater locations. Some attenuation of metal
contaminants occurs in the groundwater system and in Elk Creek and downstream waters. The
mobilization of contaminants from Standard Mine site waste rock piles and tailings was reduced
after the Removal Actions that isolated most of the Level 1, 2, and 3 waste rock and directed Elk
Creek, Level 1 adit discharge water, and runoff from uphill areas away from the remaining waste
rock and residual soils. Soil treatment of the remaining waste rock and residual soils further
reduced the potential for contaminant mobilization. Level 5 and Level 98 waste rock piles are
uncontrolled and adit discharges still flow over waste rock prior to flowing into downgradient
streams and wetlands, providing an ongoing source of contaminant loading to Elk Creek.
Site contaminants are released to the environment where they can affect human and ecological
receptors.
•	Metals in waste rock particulates that become airborne can affect human and ecological
receptors via inhalation or direct contact. Metals in the waste rock piles can affect birds,
mammals, and invertebrates via direct contact or ingestion of the soil or affected food
items. Plants are exposed to elevated metals concentrations in the waste rock via direct
contact.
•	Metals suspended in the water column may impact aquatic organisms, such as fish and
benthic invertebrates, via direct contact or ingestion. Birds and mammals, including
humans, may ingest the surface water or food items with elevated metals concentrations.
Risks to human and ecological receptors are discussed in Section 6.
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START 3, EPA Region 8
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Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
6.0 BASELINE RISK ASSESSMENT
The Baseline Human Health Risk Assessment (BHHRA) (Syracuse Research Corporation (SRC) 2008a)
and the Baseline Ecological Risk Assessment (BERA) (SRC 2008b) were prepared by Syracuse Research
Corporation to evaluate human health and ecological impacts associated with mining-related metals
contamination at the Standard Mine site. The risk assessments were performed with sediment and surface
water data collected during 1999, 2005, and 2006, and soil and fish tissue data collected in 2006. Both
assessments were based on site conditions prior to EPA's Removal Actions that included dewatering the
tailings impoundment, removal of tailings and waste rock from Levels 1, 2, and 3 to an on-site repository,
installation of run-on/runoff controls at Level 1, reclamation of site soils at Levels 1, 2, and 3,
realignment of Elk Creek through Level 1, and creation of 'A acre of wetlands at Level 1. The BHHRA
and BERA were updated during 2009 to reflect post removal conditions (SRC 2009; SRC 2010). The
assessment methods were the same as for the initial documents but use soil data collected during 2009
and water, sediment, toxicity, macroinvertebrate, and fish data collected in 2008 and 2009. The BHHRA
and BHHRA Addendum are provided in Appendix G. The BERA and BERA Addendum are provided in
Appendix H.
To address community concerns, EPA provided an assessment of increased risks from cadmium exposure
to community members that both visit the site and regularly ingest Crested Butte drinking water (EPA
2010). This evaluation is outside of the scope of the Baseline Human Health Risk Assessment and is
therefore not summarized below but is referenced here for the convenience of interested parties.
6.1 HUMAN HEALTH RISK ASSESSMENT
The following information is condensed from the Executive Summary of the BHHRA (SRC
2008a) and BHHRA Addendum (SRC 2009).
6.1.1 Baseline Human Health Risk Assessment
The Standard Mine site was divided into two main areas for the risk assessment, the Mine
Facility Area and the Drainage Area. For the Mine Facility Area, the population of
concern is the older child (ages 6 to 12), adolescent, and adult recreational visitor who
may visit the site for hiking, ATV riding, horseback riding, snowmobile riding, or other
outdoor activities. Two representative activities for recreational users were selected for
evaluation, the hiker and the ATV rider.
Hiker: The hiker population is assumed to include older children, adolescents, or
adults who pass across the site while hiking in the area.
ATV Rider: ATV riders were selected to represent higher than average
exposures to on-site soils.
For the Drainage Area, the receptors most likely to be exposed are residents from nearby
communities who may visit the surface streams for recreational uses such as fishing and
wading. Three representative populations were selected for evaluation of risk:
Recreational Fisherman: This population represents individuals who may fish
along streams flowing from the site.
Recreational Child Visitor: Children living in the general area of the site may
visit the surface streams flowing from the site for play. This population is
assumed to consist of older children/adolescents (6 to 12 years old).
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Camper: This population consists of individuals (adults and older children) who
may camp along Elk Creek.
Not all of the potential exposure routes to these populations of receptors are likely to be
of equal concern. Exposure scenarios that are the most likely to result in the highest level
of exposure were used in the evaluation of risk.
Incidental Ingestion of Surface Soil: Even though few people intentionally ingest
soil, recreational visitors who have direct contact with soil might ingest small
amounts that adhere to their hands during outdoor activities. This pathway was
evaluated for all receptors at the mine site. It is expected that any soil or mine
waste contamination that has eroded from the site will be confined primarily to
the sediments in Elk Creek and that bank soils will be largely unimpacted.
Therefore, ingestion of bank soils by a camper in the drainage is considered to be
a minor pathway and is not evaluated quantitatively.
Inhalation of Airborne Soil Particulates: Whenever contaminated soil is exposed
at the surface, particles of contaminated surface soil may become suspended in
air by wind or mechanical disturbance, and humans in the area could inhale those
particles. Screening calculations indicate that inhalation of wind-eroded particles
is likely to be minor compared to presumptive oral exposure. Therefore this
pathway was not evaluated quantitatively. Mechanical disturbances, such as
ATV riding might release much higher levels of particulates into air that may be
inhaled by the ATV riders, so this pathway was evaluated quantitatively for ATV
riders.
Ingestion of Surface Water and Sediment: With the possible exception of
campers along site drainages, it is not expected that most visitors to the site and
the drainage area will intentionally ingest surface water. However, campers may
ingest water from the creek as drinking water, and incidental ingestion of water
and/or sediment might occur during other types of recreational activities (e.g.,
wading, playing along the creek). Based on this, oral exposure to these media
were evaluated for all receptors except the ATV rider.
Dermal Contact with Soil and Sediment: All receptors may have dermal
exposure to metals-contaminated soil and/or sediment. Dermal contact with soil
was not evaluated quantitatively due to agreement among scientists that dermal
exposure to inorganic chemicals is likely to be minor in comparison to exposure
from ingestion and because the means to quantify dermal absorption of chemicals
from soil is limited.
Dermal Contact with Surface Water: Recreational visitors along Elk Creek or
Coal Creek may have occasional dermal contact with surface water while fishing
or playing along the streams. For the reasons discussed above for contact with
soil and sediment, this pathway was not evaluated quantitatively.
Ingestion of Fish: Fish that live in contaminated streams may take up the
contaminants from surface water, sediment or their diet, leading to exposure of
humans who eat fish caught from the contaminated waters. Thus, this pathway is
evaluated quantitatively for the adult fisherman and for a child who is part of the
family of the fisherman.
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For the Mine Facility Area, the exposure pathways evaluated in the assessment are as
follows.
Hiker: The exposure pathways of primary concern for the hiker are incidental
ingestion of surface soil, surface water, and sediment.
ATV Rider: ATV riders were selected to represent higher than average
exposures to on-site soils, both by incidental ingestion of surface soil and by
inhalation of dust particles released from soil into air during riding.
For the Drainage Area, the exposure pathways considered are as follows.
Recreational Fisherman: The primary exposure pathways for the fisherman are
incidental ingestion of surface water and sediment while fishing and ingestion of
fish caught from streams draining from the site.
Recreational Child Visitor: The primary exposure pathways for the child visitor
are incidental ingestion of surface water and sediment while playing along the
streams draining the site and ingestion of fish caught from the streams draining
from the site.
Camper: The primary exposure pathway is ingestion of surface water from Elk
Creek used for drinking or cooking and incidental ingestion of sediments from
the Creek.
Chemicals of Potential Concern
The following chemicals of potential concern (COPCs) were identified by comparing the
maximum detected concentration for each analyte in each medium to a Risk-Based
Concentration (RBC). If the maximum detected concentration was below the RBC, it
was concluded that the chemical does not pose a significant risk to humans.
Aiv:i
Medium
Choiniciils of Polenliiil C oncern
Mine Facility Area
Soil
Aluminum, Arsenic, Cadmium,
Chromium, Iron, Lead, Manganese
Surface Water
None
Sediment
None
Site Drainages
Surface Water
Arsenic, Cadmium
Sediment
Arsenic
Fish
Arsenic
Non-Lead Risk Assessment
Exposure to non-lead COPCs was evaluated using the standard equations recommended
by EPA for use at Superfund sites. Data from a site-specific community interview were
used to estimate frequency and duration of site visits. Other exposure parameters were
based on EPA default guidelines or on professional judgment. Exposure point
concentrations in soil, sediment, water, and fish tissue were derived using EPA's ProUCL
software system. Concentrations of COPCs in air during ATV riding were estimated
using a screening-level soil-to-air transfer model. Toxicity values were derived from
EPA recommended sources including an on-line database referred to as IRIS (Integrated
Risk Information System) and EPA's Superfund Technical Assistance Center.
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Non-cancer risks were evaluated by computing the Hazard Index. If the Hazard Index
(HI) is less than or equal to 1, then risks of non-cancer effects are not of concern. If the
HI exceeds 1, then there may be a risk of non-cancer effects, with the probability and/or
severity tending to increase as the HI increases. Cancer risks are expressed in terms of
the probability that site-related exposures will result in the occurrence of cancer. The
EPA generally considers a risk level of lxlO"4 or less to be sufficiently low that no
response action is needed, although this judgment may vary from site to site.
There are differences between individual exposure based on intake rates, body weights,
exposure frequencies, and exposure durations. Exposures were estimated based on
intakes of site contaminants near the central portion of the range (central tendency
exposure, or CTE) and near the upper end of the range (reasonable maximum exposure,
or RME). Based on this approach, the calculated risks to on-site recreational visitors and
to recreational visitors along site drainages as calculated for CTE and RME values are as
follows.
Estimated Risks to On-Site Recreational Visitors and Recreational Visitors Along
	Site Drainages	
Receptor
Exposure
Pathways
Non-Cancer 1 lazaril
Index
Excess C ancer Risk
C 1 i:
RME
CTE
rmi:
Oil-Site Recreational Visitors
Adult Hiker
Ingestion
0.003
0.02
7 x 10"8
2 x 10"6
Adult ATV Rider
Ingestion
+
Inhalation
0.2
1
4 x 10"7
9x 10"6
Child ATV Rider
Ingestion
+
Inhalation
0.3
2
2 x 10"7
4x 10"6
Recrcationa
Visitors Along Site Drainages
Adult Fisherman
Ingestion
0.008
0.08
4 x 10"6
1 x 10"5
Child Visitor
Ingestion
0.01
0.09
1 x 10"7
3 x 10"6
Adult Camper
Ingestion
0.004
0.02
9 x 10 s
2 x 10"6
Child Camper
Ingestion
0.005
0.03
3 x 10"8
6x 10-7
The table shows risks below a level of concern for all adult users, both on-site
recreational visitors and recreational visitors along site drainages, using the CTE and
RME values. The table shows a non-cancer HI of 2 (greater than the acceptable limit of
1) for child ATV rider using the RME values, but a non-cancer HI of 0.3 using CTE
values. Excess cancer risks were below a level of concern for the child ATV rider using
both the CTE and RME values. The table shows risks below a level of concern for child
recreational visitors along site drainages.
Regarding ingestion of arsenic in fish, it should be noted that the concentration of arsenic
in fish from the site is similar to what would be expected in seafood purchased from a
store. In addition, the concentrations of arsenic in fish are lower in Elk Creek than in
Coal Creek, especially in Coal Creek above the confluence with Elk Creek. This
indicates that Standard Mine is not the source of most of the arsenic in fish.
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Lead Risk Assessment
Screening-level calculations indicated that lead is not of concern to off-site visitors, but
might be of concern to on-site visitors who are exposed to on-site soils. The population
of particular concern for lead exposure is young children and pregnant women. At this
site, the populations that are exposed to on-site soils include adult hikers and ATV riders
and older children (age 6 to 12) riding ATVs. Because children in this age range are not
expected to become pregnant, this assessment focuses on risks to the fetus of adult
women hikers or ATV riders exposed by incidental ingestion of on-site soils and/or
inhalation of on-site airborne dusts.
Risks to the fetus of adult women hikers or ATV riders exposed by incidental ingestion
of on-site soils and/or inhalation of on-site airborne dusts were evaluated using the adult
lead model recommended by EPA and the default values recommended by EPA Region
8. This model predicts the average blood lead level in a person with a site-related lead
exposure by summing the baseline blood lead level with the increment in blood lead that
is expected as a result of increased exposure due to contact with the lead-contaminated
site medium. Once the average blood lead value is calculated, the full distribution of
likely blood lead values in the population of exposed people is estimated by assuming the
distribution is lognormal with a specified individual geometric standard deviation. The
measure of chief concern is the probability that an individual will have a blood lead level
that exceeds 10 micrograms per deciliter (j^ig/dL). This probability is referred to as PI0.
Based on the exposure assumptions for recreational visitors along with the default
biokinetic parameters recommended by EPA, the adult lead model predicts that the
probability of a woman visitor to the site having a blood lead level above the level of
concern is very low (< 0.001%) for both hikers and ATV riders, and does not approach
the risk based goal (P10 < 5%). These results indicate that levels of lead in on-site soils
will not likely pose a risk to on-site recreational visitors.
6.1.2 Baseline Human Health Risk Assessment Addendum
The only risk to humans identified in the BHHRA was for exposure of child ATV riders
at the mine site; therefore, this scenario was re-evaluated in the BHHRA Addendum
using new soil data that were collected after EPA had completed its removal actions. The
basic approach for estimating oral and inhalation exposure and risk was the same as that
used in the BHHRA, except inhalation exposures were evaluated in accordance with new
guidance from EPA that employs a reference concentration (RfC) approach rather than a
reference dose (RfD) approach.
Based on this approach, the updated cancer and non-cancer risk estimates for child ATV
riders at this site for CTE and RME are as follows:
Estimated Risks to On-Site Recreational Visitors - 2009 BHHRA Addendum
Receptor
Exposure
Pathways
Non-Cancer Hazard
Index
Excess Cancer Risk
CTE
RME
CTE
RME
Child
ATV
rider
Ingestion +
Inhalation
0.08
0.5
9xlO"08
2xlO"06
As shown, for child ATV riders exposed by ingestion and inhalation of on-site soils, non-
cancer risks are below a level of concern (HI < 1), and excess cancer risks are at the low
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end or below EPA's usual risk range of concern (1 x 10"4 to 1 x 10"6). Because the child
ATV rider is the maximally exposed receptor at the site, this indicates that risks to
humans who visit the site for recreational purposes are not a significant health concern.
6.1.3 Uncertainties
Quantitative evaluation of the risks to humans from environmental contamination is
frequently limited by uncertainty regarding a number of key data items including
contaminant concentrations in the environment, the true level of human contact with
contaminated media, and the true dose-response curves for non-cancer and cancer effects
in humans. This uncertainty is usually addressed by making assumptions or estimates for
uncertain parameters based on whatever limited data are available. Because of these
assumptions and estimates, the results of risk calculations are themselves uncertain, and it
is important for risk managers and the public to keep this in mind when interpreting the
results of a risk assessment.
For non-lead COPCs, the only exposure scenario of potential concern identified in the
original BHHRA was from inhalation of manganese in airborne dusts generated during
ATV riding. The BHHRA addendum indicates that inhalation of manganese in airborne
dusts generated during ATV riding is no longer a scenario of potential concern after the
EPA removal action. These risk estimates are uncertain because the concentration of
manganese in air was not measured directly but was estimated using a screening-level
soil-to-air transfer model. In addition, the inhalation reference dose is uncertain, as
reflected by application of an uncertainty factor of 1000 in the derivation of the
inhalation reference dose. Thus, risk estimates for inhalation of manganese should be
considered uncertain, and true risks are more likely to be smaller than the calculated
risks.
For lead, there are many uncertainties that influence the calculation of the P10 value,
including uncertainty in the amount of soil ingested, the amount of lead absorbed, and the
true values from the baseline blood lead and the geometric standard deviation of the
assumed lognormal distribution of blood lead values in exposed women. Because the
calculated P10 values are well below a level of concern, there is very little uncertainty in
the conclusion that lead is not a significant source of concern at this site.
6.2 ECOLOGICAL RISK ASSESSMENT
The following information is condensed from the executive summaries of the BERA (Syracuse
2008b) and the BERA Addendum (Syracuse 2010).
6.2.1 Screening Level Ecological Risk Assessment
Characterization of ecological risks at the site began with the preparation of a screening
level ecological risk assessment (SLERA) (EPA 2006). The purpose of the SLERA was
to formulate an initial conceptual model that characterized ecological exposure scenarios
of potential concern, to determine which, if any, exposure scenarios may be excluded
from further assessment, and to identify data gaps that limit confidence in the initial risk
characterization. The SLERA identified the following exposure pathways as the primary
means by which ecological receptors might be impacted by contaminants released from
the site into the environment:
•	Direct contact of fish and benthic invertebrates with surface water;
•	Direct contact of benthic invertebrates with sediment;
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•	Direct contact of terrestrial plants and soil invertebrates with on-site soil; and
•	Ingestion of on-site soil, surface water, and food items by birds and mammals.
Each of these exposure pathways was evaluated in the SLERA using the data that were
available at that time, and using simplified and conservative approaches. The SLERA
found that none of the exposure scenarios listed above could be excluded from further
evaluation, so all were carried forward to the BERA for further analysis.
6.2.2 Baseline Ecological Risk Assessment
Based on the results of the SLERA, the BERA performed a more detailed assessment of
each of the exposures scenarios above, using 1999 and 2005 data plus new data that were
collected by EPA in 2006 to support the assessment. Whenever possible, the assessment
considered the findings from three alternate approaches for risk characterization:
•	Hazard Quotients (HQs);
•	Site-specific toxicity tests; and
•	Observations of population and community demographics.
Because each of these approaches has advantages and limitations, final conclusions were
based on a weight of evidence consideration of all of the available data. The findings of
the BERA are as follows.
Risks to Aquatic Receptors from Surface Water
Three lines of evidence (HQ calculations, fish toxicity tests, and fish population studies)
were evaluated to assess the potential effects of contaminated surface water on aquatic
receptors. Based on these three lines of evidence, the BERA concluded the following.
•	Mining-related releases from Standard Mine into surface water are substantially
toxic to fish in Elk Creek.
•	Water discharged from Elk Creek into Coal Creek elevates concentrations of
metals in Coal Creek but this appears to have only minimal to moderate toxicity
on fish.
Risks to Aquatic Receptors from Sediment
Four lines of evidence (HQ calculations for sediment, HQ calculations for sediment
porewater, benthic toxicity tests, and benthic population surveys) were evaluated to
assess the potential effects of contaminated sediments on benthic macroinvertebrates.
Based on these multiple lines of evidence, the BERA concluded the following.
•	Sediments in Elk Creek are likely to have significant adverse effects on benthic
organisms residing in the sediment, especially in the upper reaches of Elk Creek.
•	Hazards are lower and of lesser concern in Coal Creek.
Risks to Plants and Soil Invertebrates from Soil
One line of evidence (the HQ approach) was available for evaluation of risks to plants
and soil invertebrates from contaminated soil. Based on this approach, it was concluded
that most metals in soil were likely to be above a level of concern to plants and/or soil
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invertebrates. However, the BERA noted that this conclusion is uncertain because of
uncertainty in the toxicity values. In addition, data on background concentrations were
too limited to draw firm conclusions as to whether some metals might be at background
levels or not.
Risks to Wildlife Receptors
The BERA evaluated risks to a range of birds and mammals based on exposure from
three pathways: 1) ingestion of contaminated food items, 2) incidental ingestion of soil
or sediment while feeding, and 3) ingestion of on-site surface waters. Only one line of
evidence (the HQ approach) was available for assessment of risks to birds and mammals
from these pathways. Many receptors had no significant HQ exceedences, indicating that
risk to these receptors from site-related contaminants was likely to be minimal.
However, some receptors (mainly those with an assumed high soil intake) were found to
have HQ values in a range of potential concern. The BERA noted that these conclusions
regarding risks to birds and mammals should interpreted with caution, since calculations
of exposure require a number of assumptions and approximations, and toxicity data were
limited for many of the receptor types included in the assessment.
6.2.3 BERA Addendum
EPA continued to collect data to help evaluate whether the response actions have been
effective in reducing environmental impacts of the site and to provide an improved basis
for evaluating ecological risks under current site conditions. The BERA Addendum
provides an updated evaluation of the potential risks to ecological receptors posed by
residual site-related environmental contamination. The new data span three additional
years (2007, 2008 and 2009), and include new data of three main types:
•	Concentrations of site-related contaminants in abiotic media (on-site soil,
background soil, surface water, sediment, and sediment porewater);
•	Fish and benthic organism population surveys; and
•	Surface water and sediment toxicity tests.
The new data have been used to help evaluate if environmental conditions for ecological
receptors at the site are improving, and to derive updated risk estimates for ecological
receptors, as described below.
6.2.3.1 Risks to Aquatic Receptors from Contaminants in Surface Water
HQ Approach
HQ values in Elk Creek have been tending to decrease somewhat over time at
most stations. No consistent time pattern for Coal Creek was detected.
However, all HQ values for Elk Creek remain well above 1.0, and many values
remain above 1.0 in Coal Creek. Panels A and B of Table 6-1 contains a
summary of the primary chemicals of concern (COCs) based on the HQ
evaluation. COCs are contaminants that have a high frequency and/or magnitude
of HQ values above 1.0
Site-Specific Surface Water Toxicity Testing
Toxicity tests using rainbow trout fry as the test organisms indicate that risk of
mortality is decreasing at most Elk Creek stations. In downstream stations in Elk
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Creek (Elk-05 and Elk-00), water from 2006 and 2007 was highly toxic to fish,
while water from 2008 and 2009 showed a consistent pattern toward decreased
toxicity. In 2009 stations as high upstream as Elk-08 had statistically similar
mortality to the reference location. These findings support the conclusion that
surface water in Elk Creek was highly toxic to fish in previous years, but current
surface water conditions at Elk-08 and below are supportive of life.
Toxicity test results for fish exposed to water from Coal Creek immediately
downstream of the confluence with Elk Creek (Coal-15) show low mortality, and
this level of mortality is not different from that observed in Coal Creek just
upstream of Elk Creek (Coal-20). This suggests that waters from Elk Creek do
not pose a risk to surface water receptors in Coal Creek.
Site-Specific Surveys of Fish Populations
Fish population surveys conducted each fall in 2006 through 2009 indicate the
following:
•	At any one station where data are available for more than one year,
values vary substantially. Thus, the data are not considered to be
sufficient to draw conclusions with regard to time trends in fish
population statistics.
•	For Elk Creek, some fish are present at the mouth of the creek (Elk-00),
but none are present at stations farther upstream (Elk-01 and Elk-08).
The fish sampled at Elk-00 are probably immigrants from Coal Creek.
Fish have not been detected at upstream stations on Elk Creek, but this
may be due to two four-foot high waterfalls that may limit upstream
movement of fish, limited stream flow in upper reaches during low flow
periods, and cold water temperature.
•	Fish density and biomass in Coal Creek appear to be slightly greater
below the confluence with Elk Creek as compared to upstream of Elk
Creek. This suggests that fish in Coal Creek are not impacted by
releases from Elk Creek.
Habitat
In the fall of 2009, an extensive evaluation of Elk Creek habitat was performed to
assess the quantity and quality of aquatic habitat on Elk Creek in order to
determine how suitable the stream is to support a trout population (USFS 2009).
The main findings of this evaluation include the following.
•	The first 200 to 300 feet of Elk Creek currently supports a brook trout
fishery.
•	The lower reaches of Elk Creek (downstream of Elk-06) have similar
characteristics to reference streams, but colder water temperatures and
small stream size will likely limit growth and reproduction of brook trout
but they would likely persist at low numbers.
•	Reaches upstream of Elk-01 do not have suitable habitat to support a
Colorado River cutthroat trout (CRCT) fishery. Using a logistic
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regression model, there is only a 5% probability of reaches above Elk-01
supporting a high number of brook trout, a 37% probability of supporting
a low number of brook trout, and a 58% probability of not supporting
brook trout at all.
• Upstream movement of fish above Elk-00 is limited because of the
presence of two four-foot high waterfalls approximately 600 feet
upstream from the confluence of Elk and Coal Creeks. This results in
limited genetic exchange and therefore long-term persistence of a CRCT
or brook trout population is unlikely.
Overall Weight of Evidence Evaluation for Surface Water
Taken together, the weight of evidence supports the conclusion that mining-
related releases from Standard Mine are less toxic to fish in Elk Creek than in the
past, especially in the lower reaches. Given the proper habitat, fish could survive
in the lower reaches of Elk Creek.
For fish in Coal Creek below the confluence with Elk Creek, the weight of
evidence indicates that water discharged from Elk Creek into Coal Creek elevates
concentrations of metals in Coal Creek but is not likely to be toxic to fish.
6.2.3.2 Risks to Aquatic Receptors from Contaminants in Sediment
HQ Approach Based on Bulk Sediment
HQ values for sediment have not demonstrated a significant downward trend at
most Elk Creek stations, although some improvement was detected at the station
nearest the mine (Elk-10). This indicates that sediment concentrations are slower
to improve in comparison to surface water. HQ values based on bulk sediment
remain above a level of concern at all locations in Elk Creek. No significant
changes in Coal Creek have been detected. Panels A and B of Table 6-1 contain
a summary of the primary COCs based on the HQ evaluation.
HQ Approach Based on Sediment Porewater
Sediment porewater samples are available from 2006, 2008, and 2009.
Although three data points are not sufficient to draw firm conclusions, it appears
that there is a general tendency toward slightly decreasing porewater
concentrations for both cadmium and zinc at all Elk Creek stations located below
the mine. However, HQ values remain above 1.0 for both chemicals, indicating
that risks to benthic organisms may still be of concern. Panel A of Table 6-1
contains a summary of the primary COCs based on the HQ evaluation.
For sediment porewater from Coal Creek, the data do not show any consistent
time trend patterns. Panel B of Table 6-1 contains a summary of the primary
COCs based on the HQ evaluation.
Site-Specific Sediment Toxicity Tests
Benthic toxicity tests using sediments from Elk Creek have not revealed any
clear time trends toward decreased risk. Statistically significant increases in
mortality were seen for all locations tested in all years, with mortality rates
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ranging from 61% to 100%. These findings support the conclusion that
sediments in Elk Creek are toxic to benthic organisms and that improvement is
slow.
Similarly, toxicity test results for sediments from Coal Creek do not show any
clear time trends. Values are similar to background locations and do not reveal
any statistically significant differences in toxicity.
Site-Specific Benthic Community Surveys
Benthic population data are available for 2006, 2007, 2008, and 2009. The data
at any one station are quite variable over time, making detection of time trends
difficult. Spatial patterns indicate that benthic communities at stations in Elk
Creek closest to the mine are most impacted, and the status of the benthic
community tends to improve at stations farther from the mine. The available
data suggest there has been a time trend toward improved sediment conditions,
which is most apparent in the middle reaches of Elk Creek (Elk-06 and Elk-08).
For Coal Creek, spatial patterns are not as clear as in Elk Creek. In general, no
clear differences are detected between Coal Creek just below the confluence with
Elk Creek and a reference station on Coal Creek above Elk Creek, suggesting
that discharge from Elk Creek is having no substantial effect on benthic
organisms in Coal Creek. Changes in benthic community farther downstream
may be related to changes in habitat and/or to sources other than Standard Mine.
Biological Condition Score and Habitat Quality
When comparing benthic community metrices between stations, it is important to
recognize that differences may result from differences in habitat as well as
differences in chemical contamination level. The EPA has developed a
standardized approach for performing this habitat adjustment. In this approach, a
number of alternative metrices of benthic community status are combined to
yield the Biological Condition Score, and a number of metrices of community
status are combined to derive the Habitat Quality Score. Both the Biological
Condition Score and the Habitat Quality Score are then expressed as a percentage
of corresponding scores from a suitable reference station.
Habitat Quality Scores and Biological Condition Scores are available for
multiple stations on Elk Creek and Coal Creek for 2006, 2007, 2008, and 2009.
The data are variable, but biological condition scores appear to be improving at
some Elk Creek stations. In general, both Biological Condition and Habitat
Quality scores are lower for the upper reaches of Elk Creek than for the lower
reaches, or for Coal Creek.
Overall Weight of Evidence Evaluation for Sediment
Four different lines of evidence are available to support an evaluation of risks to
benthic organisms in Elk Creek and Coal Creek:
1.	HQ values based on bulk sediment
2.	HQ values based on pore water measurements
3.	Sediment toxicity tests
4.	Benthic community surveys
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Taken together, the weight of evidence supports the conclusion that sediments in
Elk Creek are slowly improving, but are likely to remain toxic to benthic
organisms residing in the sediment. For Coal Creek, hazards from sediment are
lower and not likely to be of significant concern.
6.2.3.3	Risks to Plants and Soil Invertebrates
The Removal Actions have reduced concentrations of mining-related
contaminants in the soils of the remediated areas, especially in the main area of
the mine (Level 1). However, the soil concentrations of a number of chemicals
over the entire site (not just the waste rock piles) remain higher than are observed
in a nearby area selected to represent background, and HQ values remain above
1.0 in many locations. For other chemicals, the HQ exceedences in site soil were
very similar to that for background soil, suggesting that these chemicals may not
be attributable to mining-related releases. Panel C of Table 6-1 contains a
summary of the primary COCs based on the HQ evaluation. As discussed in the
BERA, these HQ results indicate that risks to plants and soil organisms may be
of concern, but additional studies would be needed to determine if significant
effects are actually occurring.
6.2.3.4	Risks to Birds and Mammals
Birds and mammals that reside on or near the Standard Mine site may be exposed
by three pathways: 1) ingestion of contaminated food items, 2) incidental
ingestion of soil or sediment while feeding, and 3) ingestion of on-site surface
waters.
Based on the findings of the BERA, in most cases, the majority of exposure and
risk is derived from ingestion of soil or from ingestion of food items that have
taken up contaminants from soil, and exposure from water is generally minor.
Because the site-wide distributions of soil concentrations have changed little
since the time of the BERA, HQ-based estimates of exposure and risk to birds
and mammals have also changed little. As noted earlier, the BERA found that
risks to many receptors were low, although there may be risks to receptors with a
high intake of soil (American robin, northern flicker, meadow vole, masked
shrew, and deer mouse). These findings are still valid; however, some risk may
be attributable to background conditions because LOAEL-based HQ (Lowest
Observed Adverse Effect Level) values for background are at or above on-site
levels. Panel C of Table 6-1 contains a summary of the primary COCs based on
the HQ evaluation.
6.2.3.5	Summary of Risk Addendum
Based on the findings summarized above, the main conclusions of the BERA
Addendum are as follows.
• Actions taken by EPA at the Standard Mine Superfund Site have been
effective in decreasing risks to fish in Elk Creek. The lower reaches of
the stream are presently occupied by fish, but the upper reaches are not.
This may be the result of waterfalls that block upstream migration, flow
of the stream, and water temperature.
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Sediment quality in Elk Creek appears to be improving only slowly, and
risks to benthic macroinvertebrates in Elk Creek remain above a level of
concern, especially at upstream stations closest to the site.
Removal actions taken by EPA have decreased the level of mine waste
contamination in localized areas, and this has decreased predicted risk to
plants and soil invertebrates in these areas. However, the distribution of
soil concentrations of a number of chemicals remain higher than
background, and HQ values remain above 1.0 in many locations. These
HQ results indicate that risks to plants and soil organisms may be of
concern, but additional studies would be needed to determine if
significant effects are actually occurring.
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TABLE 6-1
Summary of Chemicals of Concern
Panel A: Aquatic Receptors in Elk Creek
Receptor
Medium
Pathway
Contaminants of Concern
Fish
Surface Water
Direct Contact
Cadmium, Lead, Zinc
Benthic Macro-
invertebrates
Surface Water
Direct Contact
Cadmium, Lead, Zinc
Pore Water
Direct Contact
Cadmium, Lead, Zinc
Bulk Sediment
Direct Contact
Arsenic, Cadmium, Copper, Lead,
Manganese, Zinc
Panel B: Aquatic
(Downstream of E
Receptors in Coal Creek
k Creek but Above Mt. Emmons Project)
Receptor
Medium
Pathway
Contaminants of Concern
Fish
Surface Water
Direct Contact
Cadmium, Zinc
Benthic Macro-
invertebrates
Surface Water
Direct Contact
Cadmium, Zinc
Pore Water
Direct Contact
Cadmium, Zinc
Bulk Sediment
Direct Contact
Arsenic, Cadmium, Manganese, Zinc
Panel C: Terrestrial Receptors at the Mine Site
Receptor
Medium
Pathway
Contaminants of Concern
Plants
Soil
Direct Contact
Arsenic, Chromium, Copper, Lead,
Manganese, Selenium, Thorium, Zinc
Invertebrates
Soil
Direct Contact
Arsenic, Chromium, Copper, Lead,
Manganese, Mercury, Selenium, Zinc
Birds
Soil/Diet
Ingestion
Lead
Water
Ingestion
No COCs
Mammals
Soil/Diet
Ingestion
Aluminum, Antimony, Cadmium, Lead,
Zinc
Water
Ingestion
No COCs
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7.0 SUMMARY AND CONCLUSIONS
The purpose of the RI was to determine the nature and extent of contamination present at the site and to
assess the risk posed to human health and the environment by contaminants on site and flowing off-site.
The RI investigated both pre- and post-Removal Action site conditions. Removal actions performed at
the Standard Mine site have reduced the human health risk and downstream water quality degradation that
previously resulted from the presence of waste rock and tailings. Adit discharges and the Level 4, Level
5, and Level 98 waste rock piles remain unremediated.
7.1 NATURE AND EXTENT OF CONTAMINATION
The RI identified contamination in waste rock and tailings, adit discharges, groundwater, surface
water, and sediment.
7.1.1	Waste Rock and Tailings
Waste rock and tailings have been removed from Levels 1, 2, and 3. Isolated areas of
waste rock remain in place, but were treated with lime and fertilizer to reduce metals
mobility and then covered with native soil and seeded. Native soils that were uncovered
during the Removal Action were treated with lime and fertilizer to reduce the mobility of
any remaining metal contaminants and seeded to provide a vegetative cover that reduces
the potential for airborne dust and provides erosion control. Erosion control structures
minimize the flow of water through remaining waste rock and stabilize the reclaimed
soils. Apart from monitoring to ensure that the erosion controls and vegetation are
functional, it is not expected that any additional actions will be required to address waste
rock and tailings at Levels 1, 2, and 3.
Waste rock remains at Level 4 but is isolated from significant runoff from nearby slopes.
Waste rock remains at Level 5. Adit discharge water flows over the waste rock prior to
entering a wetland at the base of the waste rock pile. Water quality in the wetland located
immediately downgradient of Level 5 is degraded as indicated by metals concentrations
greater than WQS.
Waste rock at Level 98 was the subject of a revegetation study by EPA's Environmental
Response Team, but the waste rock and tailings are primarily uncontrolled. Adit
discharge water flows over the waste rock prior to entering a wetland at the base of the
waste rock pile. The Level 98 waste rock has the potential to impact downstream waters
as indicated by elevated metals concentrations in surface water samples collected in a
wetland located on the waste rock pile and downstream wetlands.
7.1.2	Adit Discharges
Adit discharges from Level 1, Level 2 (small seep), Level 5, and Level 98 remain
uncontrolled.
The Level 1 adit discharge contributes the greatest loading of metals to Elk Creek
because it has the highest flow rate and the highest metal concentrations of the
discharging adits. The average annual loading from the Level 1 adit includes 0.015
tons/year cadmium, 0.038 tons/year copper, 0.074 tons/year lead, 0.97 tons/year
manganese, and 2.5 tons per year zinc.
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The Level 5 and Level 98 adit discharges flow over waste rock prior to entering
downstream wetlands and Elk Creek. The flow from these sources is minimal, less than
one gpm, and the concentrations are significantly lower than the discharge from Level 1.
7.1.3	Groundwater
There are indications that localized shallow groundwater in the Ohio Creek Formation
near the Standard fault has elevated metal concentrations. It is unknown whether the
high concentrations are indicative of overall groundwater quality in the shallow
groundwater or are the result of a localized effect such as the presence of nearby waste
rock piles or native sulfide-rich rock. Low metal concentrations were observed in deeper
groundwater.
Groundwater downgradient of the site has not been sampled, but there is no indication
that contaminated groundwater is present to the degree that would impact downstream
surface water.
7.1.4	Surface Water and Sediment
Surface water and sediment contain elevated concentrations of site contaminants, even
after the Removal Action. Elk Creek metal concentrations were lower during 2008 and
2009 than years before and during the Removal Action.
Water quality is impaired at the most upstream sample location in Elk Creek, located
immediately upstream of Level 1. Even though this location is upstream of the most
contaminated portion of the site, the cadmium, lead (spring only), and zinc concentrations
are greater than the chronic WQS. Cadmium concentrations approach or exceed the
acute WQS during the fall, and zinc concentrations exceed the acute WQS at all times of
the year. There is no pure "background" sample location for Elk Creek because Elk
Creek forms below Levels 5 and 98.
Metal concentrations increase significantly where Level 1 adit discharge enters Elk Creek
and generally decrease slowly down to the confluence with Coal Creek. The pH
decreases in Elk Creek where the adit discharge enters Elk Creek but quickly recovers to
neutral at downstream locations. At Elk-08, located approximately 0.8 miles downstream
of Level 1, cadmium, copper, lead (spring only), and zinc concentrations exceed the
chronic WQS. Cadmium and zinc concentrations also exceed the acute WQS.
Immediately above the confluence of Elk Creek and Coal Creek, the cadmium and zinc
concentrations exceed the acute and chronic WQS, but the concentrations are much lower
than those observed at Elk-08.
Cadmium, manganese, and zinc concentrations are typically higher in Elk Creek during
September than during June. The reverse is true for copper and lead. The pH of the
Level 1 adit discharge is much lower during June than during September but the pH in
Elk Creek stays relatively constant throughout the year.
Metal concentrations are generally low in Coal Creek upstream of the Elk Creek
confluence and increase immediately downstream of the confluence. Since the Removal
Action, none of metal concentrations measured in Coal Creek immediately downstream
of the Elk Creek confluence exceeded the Coal Creek WQS with the exception of
cadmium where concentrations approach or slightly exceed the chronic standard. Other
sources of metal contaminants located downstream of the Elk Creek confluence,
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including an iron gossan and fen and the Mt. Emmons Project WTP, cause increases in
Coal Creek metal concentrations downstream of the Elk Creek confluence.
Sediment metal concentrations are elevated and have not decreased significantly since the
Removal Action.
7.2 EVALUATION OF RISK
7.2.1	Human Health Risk Assessment
A Baseline Human Health Risk Assessment (BHHRA) was performed to evaluate risks to
human receptors that visit the Standard Mine and the Elk Creek drainage area. The
evaluation concluded that risks for all adult users, both on-site recreational visitors and
recreational visitors along site drainages, were below a level of concern. Non-cancer
risks for the child ATV rider were above a level of concern for exposure to manganese,
but excess cancer risks were below a level of concern for the child ATV rider. The risks
for child recreational visitors along site drainages were also below a level of concern.
Because the only risk to humans identified in the BHHRA was for exposure of child
ATV riders at the mine site, this scenario was reevaluated in the BHHRA Addendum
using new soil data that were collected after the Removal Action was completed. Given
post-Removal Action site conditions, the non-cancer risks for child ATV riders exposed
by ingestion and inhalation of on-site soils are below a level of concern, and excess
cancer risks are below EPA's acceptable risk limits. Because the child ATV rider is the
maximally exposed receptor at the site, this indicates that risks to humans who visit the
site for recreational purposes are not significant.
7.2.2	Ecological Risk Assessment
An Ecological Risk Assessment was performed to evaluate risks to ecological receptors
that may be impacted by site contaminants. The evaluation concluded the following.
•	Mining-related releases from Standard Mine into surface water are substantially
toxic to fish in Elk Creek, primarily due to elevated concentrations of cadmium,
lead, and zinc. Actions taken by EPA at the Standard Mine Superfund Site have
been effective in decreasing risks to fish in Elk Creek, but the risk has not be
eliminated. The lower reaches of the stream are presently occupied by fish, but
the upper reaches are not. This may be the result of waterfalls that block
upstream migration, low flow of the stream in the upper reaches, and cold water
temperature.
•	Water discharged from Elk Creek into Coal Creek elevates concentrations of
metals in Coal Creek but this appears to have only minimal to moderate toxicity
on fish.
•	Sediments in Elk Creek are likely to have significant adverse effects on benthic
organisms residing in the sediment, especially in the upper reaches of Elk Creek.
Sediment quality in Elk Creek appears to be improving only slowly, and risks to
benthic macroinvertebrates in Elk Creek remain above a level of concern,
especially at upstream stations closest to the site.
•	Hazards to benthic organisms from site sediments are lower and of lesser concern
in Coal Creek.
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•	Plants and soil invertebrates may be impacted by metals levels in soil, but this
conclusion is uncertain because of uncertainty in the toxicity values. In addition,
data on background concentrations were too limited to draw firm conclusions as
to whether some metals might be at background levels or not. Removal actions
taken by EPA have decreased the level of mine waste contamination in localized
areas, and this has decreased predicted risk to plants and soil invertebrates in
these areas; however, soil concentrations in the area remain higher than
background. Additional studies would be needed to determine if significant
effects are actually occurring.
•	Risk to many wildlife receptors from site-related contaminants was likely to be
minimal. Wildlife receptors with an assumed high soil intake may be at risk due
to high soil intake; however, calculations of exposure require a number of
assumptions and approximations, so risks to birds and mammals should be
interpreted with caution.
7.3 PRELIMINARY REMEDIAL ACTION OBJECTIVES
Based on the evaluation of site conditions and the evaluation of risk to human and ecological
receptors, Remedial Action Objectives (RAOs) were developed to focus efforts in developing
remedial action alternatives for the Feasibility Study. The RAOs presented here are focused on
objectives for Remedial Actions that may be performed to address site conditions present after
completion of the Removal Action. The RAOs were developed by EPA, USFS, and CDPHE to
address surface water, soils, and groundwater.
Surface Water
1.	Reduce in-stream metals concentrations and sediment loading to the extent practicable in
Elk Creek to lessen water quality impacts and to maximize reasonably attainable water
uses in Elk Creek.
2.	Reduce in-stream metals concentrations and sediment loading to the extent practicable in
Coal Creek to lessen water quality impacts and maximize reasonably attainable water
uses.
3.	Ensure that in-stream metals concentrations attributable to contamination from Elk Creek
do not exceed drinking water standards at Crested Butte's drinking water intake on Coal
Creek.
Soil
1.	Control and/or reduce run-on and runoff from tailings/waste rock piles to minimize
generation of contaminated runoff and/or groundwater, and to reduce sediment loading of
streams.
2.	Reduce human exposure (i.e., child ATV riders) to manganese from incidental ingestion
and inhalation of on-site soils to minimize the potential threat to human health.
Groundwater
1. Reduce water flow through mine workings and contaminated soils to reduce metal
loading to Elk Creek.
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Gay Austin (USFS) regarding bird occurrences. January 11 and 16, 2007.
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U.S. Geological Survey (USGS). 1961b. 7.5 Minute Topographic Map Quadrangle, Marcellina
Mountain, Colorado.
U.S. Geological Survey (USGS). 1967. Geologic Map of the Oh-Be-Joyful Quadrangle, Gunnison
County, Colorado: U.S. Geological Survey Geologic Quadrangle Map GQ-578, Scale 1:24,000. By D.
L. Gaskill, L. H, Godwin, and F. E. Mutschler.
U.S. Geological Survey (USGS). 2007. Hydrogeochemical Investigation of the Standard Mine Vicinity,
Upper Elk Creek Basin, Colorado. U.S. Geological Survey Scientific Investigations Report 2007-5265 by
A. H. Manning, P. L. Verplanck, M. A Mast, and R. B Wanty.
U.S. Geological Survey (USGS). 2010a. Geochemistry of Standard Mine Waters, Gunnison County,
Colorado, July 2009. U.S. Geological Survey Open File Report 2009-1292. By P. L. Verplanck, A. H.
Manning, J. T. Graves, R. B. McCleskey, T. Todorov, and P. J. Lamothe.
U.S. Geological Survey (USGS). 2010b. Characterization of Geologic Structures and Host Rock
Properties Relevant to the Hydrogeology of the Standard Mine in Elk Creek Basin, Colorado. U.S.
Geological Survey Open File Report 2010-1008. By J.S. Caine, A.H. Manning, B.R. Berger, Y. Kremer,
M.A. Guzman, D.D. Eberl, and K.Schuller.
U.S. Geological Survey (USGS). 2010c. Geophysical Characterization of Subsurface Properties
Relevant to the Hydrology of the Standard Mine in Elk Creek Basin, Colorado. U.S. Geological Survey
Open File Report 2009-1284. By B. J. Minsley, L. B. Ball, B. L. Burton, J. S. Caine, E. Curry-Elrod, and
A. H. Manning.
URS Corporation (URS). 2007. Phase I Engineering Evaluation/Cost Analysis (EE/CA), Standard Mine
Site. November 9, 2006. April 2007.
URS Operating Services, Inc. (UOS). 1999. Preliminary Assessment for Combined Assessment, Ruby
Mining District - South and Ruby Mining District - West, Gunnison County Colorado. January 22,
1999.
URS Operating Services, Inc. (UOS). 2000. Analytical Results Report for Expanded Site Inspection,
Ruby Mining District - South, Gunnison County, Colorado. September 2000.
URS Operating Services, Inc. (UOS). 2005. Tailings Dam Inspection Report, Standard Mine Site,
Gunnison County, Colorado. November 11, 2005.
URS Operating Services, Inc. (UOS). 2006a. Sampling Activities Report, Standard Mine Site, Gunnison
County, Colorado. March 20, 2006.
URS Operating Services, Inc. (UOS). 2006b. Conceptual Project Plan - Revision 2, Standard Mine Site,
Crested Butte, Gunnison County, Colorado. April 25, 2006.
URS Operating Services, Inc. (UOS). 2006c. Potential Repository Site Evaluation, Standard Mine Site,
Gunnison County, Colorado. May 19, 2006.
8-5
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URS Operating Services, Inc.
START 3, EPA Region 8
Contract No. EP-W-05-050
Standard Mine - Remedial Investigation
TDD No. 0608-07
Date: 05/2010
URS Operating Services, Inc. (UOS). 2006d. Trip Report, Standard Mine, Gunnison County, Colorado.
June 9, 2006.
URS Operating Services, Inc. (UOS). 2007. Phase II Engineering Evaluation/Cost Analysis, Standard
Mine Site, Crested Butte, Gunnison County, Colorado. July 2, 2007.
URS Operating Services, Inc. (UOS). 2008. Reclamation Plan, Standard Mine Removal Project,
Gunnison County, Colorado. May 23, 2008.
URS Operating Services, Inc. (UOS). 2009. Standard Mine Slug Tests Summary Report, Gunnison
County, Colorado. October 14, 2009.
Western Regional Climate Center (WRCC). 2009. Website: http://www.wrcc.dri.edu/.
Weber, W. and Wittmann, R. 2001. Colorado Flora Western Slope. Third edition. University Press,
Niwot, Colorado.
8-6
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APPENDICES
Appendices are provided on compact disk.
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APPENDIX A
Colorado Division of Reclamation, Mining, and Safety
Reports
A1 Underground Assessment Report - 2007
A2 Underground Assessment Report - 2009
A3 Standard Mine Drilling Report
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APPENDIX B
U.S. Geological Survey Reports
B1 Hydrogeochemical Investigation of the Standard Mine Vicinity
B2 Geochemistry of Standard Mine Waters
B3 Characterization of Geologic Structures and Host Rock
Properties
B4 Geophysical Characterization of Subsurface Properties
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APPENDIX C
Water and Sediment Monitoring Data
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APPENDIX D
Coal Creek Watershed Water Quality Report - 2008
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APPENDIX E
Summary Slug Test Report
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APPENDIX F
Elk Creek Fish Habitat Evaluation
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APPENDIX G
Baseline Human Health Risk Assessment
G1 Baseline Human Health Risk Assessment
G2 Baseline Human Health Risk Assessment Addendum
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APPENDIX H
Baseline Ecological Risk Assessment
HI Baseline Ecological Risk Assessment
H2 Baseline Ecological Risk Assessment Addendum
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