U.S. Environmental Protection
Agency
Second Five-Year Review Report for
Silver Bow Creek/Butte Area Superfund Site
September 2005
Report
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28 North Last Chance Gulch
Helena, Montana 59601
te): 406 495-1414
fax: 406 4g5-1025
September 30, 2005
D. Scott Brown - Remedial Project Manager
Kathy C'hiotti Contracts Specialist
U.S. Environmental Protection Agency
Federal Building
10 West 15th Street, Suite 3200
Helena, MT 5%26
Subject: Final Five-Year Review Report, Silver Bow Creek/ Butte Area Superfund Site
Dear Mr. Brown and Ms. Chiotti;
CDM Federal Programs Corporation (CDM) is pleased to submit two hardcopies of the
attached Final Five-Year Review Report for the Silver Bow Creek/Butte Area Superfund Site
for your approval. If you have any questions or comments regarding this report, please feel
free to call.
Very truly vours,
J * J *
Karen T. Zambrano
Project Manager
CDM Federal Programs Corporation
Cc: D. Nelson. CDM w/out attachment
R.Rennick, CDM - w/out attachment
M. Hills, CDM w/out attachment
PF
Q:\Siiver Bow Creek 5-Yr Review'.Final RrporlVinal five yr revcover letter.din
consulting • engineering • construction • operations
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U.S. Environmental Protection
Agency
Second Five-Year Review Report for
Silver Bow CreetyButte Area Superfund Site
September 2005
Report
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Five-Year Review Report
Second Five-Year Review Report
Silver Bow Creek/Butte Area Superfund Site
Silver Bow and Deer Lodge Counties, Montana
CERCLIS ID: MTD980502777
Prepared by:
CDM
28 North Last Chance Gulch
Helena, Montana 59601
U, S. Environmental Protection Agency
10 West 15th Street, Suite 3200
Helena, Montana 59626
September 2005
for
Fan
Region 8
Approved by:
Date:
Joh
Director, Montana Office
U. S. Environmental Protection Agency, Region 8
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Contents
Section 1 Introduction 1-1
Section 2 Site Chronology 2-1
Section 3 Background 3-1
3.1 Location and Setting 3-1
3.2 Physical Characteristics 3-1
3.3 Land and Resource Use 3-3
3.4 History of Contamination 3-3
3.5 Regulatory History Summary 3-6
3.5.1 Streamside Tailings OU 3-7
3.5.2 Butte Mine Flooding OU 3-8
3.5.3 Warm Springs Ponds OUs 3-9
3.5.4 Rocker OU 3-13
3.5.5 Butte Priority Soils OU 3-14
3.5.6 Active Mining and Milling Area Operable Unit 3-18
3.5.7 West Side Soils OU 3-18
Section 4 Remedial Actions 4-1
4.1 Warm Springs Ponds Active and Inactive OUs 4-1
4.1.1 Remedy Selection 4-1
4.1.2 Remedy Implementation 4-5
4.1.3 Remedy O&M 4-5
4.2 Rocker OU 4-6
4.2.1 Remedy Selection 4-6
4.2.2 Remedy Implementation 4-7
4.2.3 Remedy Operations and Maintenance 4-9
4.3 Butte Mine Flooding OU 4-10
4.3.1 Remedy Selection 4-10
4.3.2 Remedy Implementation 4-11
4.3.3 Remedy O&M Maintenance 4-12
4.4 Streamside Tailings OU 4-13
4.4.1 Remedy Selection 4-13
4.4.2 Remedy O&M 4-15
4.4.3 Remedy Implementation 4-16
Section 5 Progress Since Last Review 5-1
5.1 Evaluation of Warm Springs Ponds OUs 5-1
5.1.1 Previous Statement on Protectiveness 5-1
5.1.2 Significant Events 5-2
5.1.3 Facility Operations and Activities 5-3
5.1.4 March 2003 Overflow Event 5-5
CDM
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Contents
Silver Bow Creek 5-Year Review
5.1.5 Regulatory Standards and System Performance 5-8
5.1.6 Pond 2 Wet Closures 5-13
5.1.7 Mill-Willow Bypass and Lower Silver Bow Creek 5-14
5.1.8 Inactive Area Performance Evaluation 5-17
5.1.9 Dam Safety 5-23
5.1.10 Biomonitoring Investigations 5-24
5.2 Evaluation of Rocker OU 5-30
5.2.1 Previous Statement on Protectiveness 5-30
5.2.2 Follow-Up Actions Since Last Review 5-31
5.2.3 Operations and Maintenance Activities 5-32
Section 6 Five-Year Review Process 6-1
6.1 Administrative Components 6-1
6.2 Community Involvement 6-1
6.2.1 N otif ic ation 6-1
6.2.2 Obtaining Input 6-1
6.2.3 Responses 6-2
6.3 Document Review 6-10
Section 7 Technical Assessment 7-1
7.1 Question A: Is The Remedy Functioning As Intended By The
Decision Documents? 7-1
7.1.1 Warm Springs Ponds Active and Inactive OUs 7-1
7.1.2 Rocker OU 7-3
7.1.3 Butte Mine Flooding OU 7-4
7.1.4 Streamside Tailings OU 7-5
7.2 Question B: Are The Exposure Assumptions, Toxicity Data, Cleanup
Levels, And RAOs Used At The Time Of The Remedy Selection Still
Valid? 7-6
7.2.1 Warm Springs Ponds Active and Inactive OUs 7-6
7.2.2 Rocker OU 7-9
7.2.3 Butte Mine Flooding OU 7-9
7.2.4 Streamside Tailings OU 7-10
7.3 Question C: Has Any Other Information Come to Light that Could
Call Into Question the Protectiveness of the Remedy? 7-10
7.3.1 Warm Springs Ponds Active and Inactive OUs 7-10
7.3.2 Rocker OU 7-10
7.3.3 Butte Mine Flooding OU 7-10
7.3.4 Streamside Tailings OU 7-11
Section 8 Issues 8-1
Section 9 Recommendations and Follow-Up Actions 9-1
Section 10 Protectiveness Statements 10-1
Section 11 References 11-1
CDM
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Contents
Silver Bow Creek 5-Year Review
Appendix A Five-Year Review Notice
Appendix B Summary of Interviews
List of Tables
Table 1-1
Table
2-1
Table
3-1
Table
4-1
Table
4-2
Table
5-1
Table
5-2
Table
5-3
Table
5-4
Table
5-5
Table
5-6
Table
5-7
Table
5-8
Table
5-9
Table
5-10
Table
6-1
Table
6.2
Table
7-1
Table
7-2
Table
8-1
Table
9-1
Remedial Operable Units at the Silver Bow Creek/Butte Area
Superfund Site
Chronology of Site Events (In text - Page 2-1)
Complete List of Remedial and Removal Operable Units at the Silver
Bow Creek/Butte Area Superfund Site as Listed in the CERCLIS
Database
Rocker OU O&M Wells Sampled for Groundwater Quality
Rocker OU Operations and Maintenance Costs
Surface Water Quality Final Discharge Standards for the Warm Springs
Ponds Active Area OU (Station SS-5)
Daily Performance Standards Exceedance Summary for the Warm
Springs Ponds
Monthly Performance Standards Exceedance Summary for the Warm
Springs Ponds
Summary of Approximate Net Arsenic Loads in the Warm Springs
Ponds
Average Concentrations and Statistics for the Unmanifolded Toe
Drains at the Warm Springs Ponds
Maximum, Minimum, and Average Concentrations for Select
Constituents at Inactive Area Sampling Locations Relative to
Performance Standards, March 1998 - December 2004
Average Concentrations for Select Water Quality Constituents
Measured at the Pump-back Pipeline Discharge (IA-1) and the Pond 3
(SS-3E) and Pond 2 (SS-5) Discharge Locations
Warm Springs Ponds Biomonitoring Sampling Locations
Warm Springs Ponds Biomonitoring Sample Types
Five-Year Operation and Maintenance Costs for the Rocker OU
List of Potential Interviewees
List of Questions for Interviewees
Results of Horseshoe Bend WTP Performance Testing, Butte Mine
Flooding OU
Existing Performance Standards at the Warm Springs Ponds OUs and
Current State and Federal Aquatic Life and Human Health Standards
Issues Identified during this Five Year Review
Recommendations and Follow-up Actions for Issues Identified
CDM
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Contents
Silver Bow Creek 5-Year Review
List of Figures
Figure 3-1 Site Location
Figure 3-2 Current Configuration of Warm Springs Ponds Complex
Figure 5-1 Warm Springs Ponds Active Area OU Sampling Locations
Figure 5-2 Warm Springs Ponds Active Area OU General Flow Schematic
Figure 5-3 Influent (SS-1) and Effluent (SS-5) Daily Flow Rates for the Warm
Springs Ponds
Figure 5-4 Influent (SS-1) and Effluent (SS-5) Monthly Flow Rates for the Warm
Springs Ponds
Figure 5-5 Pond 2 Elevations at the Warm Springs Ponds
Figure 5-6 Pond 3 Elevations at the Warm Springs Ponds
Figure 5-7 Comparison of Influent (SS-1) and Effluent (SS-5) pH values with Final
Daily Performance Standard
Figure 5-8 Comparison of Influent (SS-1) and Effluent (SS-5) Total Suspended
Solids Concentration with Final Daily Performance Standard
Figure 5-9 Comparison of Influent (SS-1) and Effluent (SS-5) Total Recoverable
Arsenic Concentrations with final Daily Performance Standard
Figure 5-10 Comparison of Influent and Effluent Arsenic Loading at the Warm
Springs Ponds
Figure 5-11 Comparison of Net Arsenic Loading with Periods of Exceedances
Figure 5-12 Comparison of Arsenic Loads from the Warm Springs Ponds (SS-5)
and Downstream Station MWB-3 against SS 5 Discharge
Concentrations
Figure 5-13 Comparison of Influent (SS-1) and Effluent (SS-5) Total Recoverable
Cadmium Concentrations with final Daily Performance Standard
Figure 5-14 Comparison of Influent (SS-1) and Effluent (SS-5) Total Recoverable
Copper Concentrations with Final Daily Performance Standard
Figure 5-15 Comparison of Influent (SS-1) and Effluent (SS-5) Total Recoverable
Copper concentrations with Final Daily Performance Standard, Scale
Adjusted
Figure 5-16 Comparison of Influent (SS-1) and Effluent (SS-5) Total Recoverable
Iron Concentrations with Final Daily Performance Standard
Figure 5-17 Comparison of Influent (SS-1) and Effluent (SS-5) Total Recoverable
Lead Concentrations with Final Daily Performance Standard
Figure 5-18 Comparison of Influent (SS-1) and Effluent (SS-5) Total Mercury
Concentrations with Final Daily Performance Standard
Figure 5-19 Comparison of Influent (SS-1) and Effluent (SS-5) Total Recoverable
Selenium Concentrations with Final Daily Performance Standard
Figure 5-20 Comparison of Influent (SS-1) and Effluent (SS-5) Total Recoverable
Silver Concentrations with Final Daily Performance Standard
Figure 5-21 Comparison of Influent (SS-1) and Effluent (SS-5) Total Recoverable
Zinc Concentrations with Final Daily Performance Standard
Figure 5-22 Arsenic Concentrations in Pond 3 Effluent Compared to East and West
Wet Closure Ponds
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Silver Bow Creek 5-Year Review
Figure 5-23 Copper concentrations in Pond 3 Effluent Compared to East and West
Wet Closure Ponds
Figure 5-24 Iron Concentrations in Pond 3 Effluent Compared to East and West
Wet Closure Ponds
Figure 5-25 Zinc Concentrations in Pond 3 Effluent Compared to East and West
Wet Closure Ponds
Figure 5-26 Sulfate Concentrations in Pond 3 Effluent Compared to East and West
Wet Closure Ponds
Figure 5-27 Warm Springs Ponds Toe Drains
Figure 5-28 Hardness Concentrations in the Mill-Willow Bypass
Figure 5-29 Arsenic Concentrations in the Mill-Willow Bypass
Figure 5-30 Copper Concentrations in the Mill-Willow Bypass
Figure 5-31 Zinc Concentrations in the Mill-Willow Bypass
Figure 5-32 Dissolved Arsenic in Down-Gradient Piezometers June 1998 -
December 2004
Figure 5-33 Dissolved Cadmium in Down-Gradient Piezometers June 1998 -
December 2004
Figure 5-34 Dissolved Chromium in Down-Gradient Piezometers June 1998 -
December 2004
Figure 5-35 Dissolved Lead in Down-Gradient Piezometers June 1998 - December
2004
Figure 5-36 Dissolved Mercury in Down-Gradient Piezometers June 1998 -
December 2004
Figure 5-37 Nitrate in Down-Gradient Piezometers June 1998 - December 2004
Figure 5-38 Dissolved Arsenic in Up-Gradient Piezometers June 1998 - December
2004
Figure 5-39 Dissolved Cadmium in Up-Gradient Piezometers June 1998 -
December 2004
Figure 5-40 Dissolved Chromium in Up-Gradient Piezometers June 1998 -
December 2004
Figure 5-41 Dissolved Lead in Up-Gradient Piezometers June 1998 - December
2004
Figure 5-42 Dissolved Mercury in Up-Gradient Piezometers June 1998 - December
2004
Figure 5-43 Nitrate in Up-Gradient Piezometers June 1998 - December 2004
Figure 5-44 Dissolved Arsenic in Piezometer P-14 March 1998 - June 2004
Figure 5-45 Dissolved Cadmium in Piezometer P-14 March 1998 - June 2004
Figure 5-46 Dissolved Chromium in Piezometer P-14 March 1998 - June 2004
Figure 5-47 Dissolved Lead in Piezometer P-14 March 1998 - June 2004
Figure 5-48 Dissolved Mercury in Piezometer P-14 March 1998 - June 2004
Figure 5-49 Nitrate in Piezometer P-14 March 1998 - June 2004
Figure 5-50 Total Recoverable Arsenic concentrations in Toe Drain Manifold (IA-3)
Relative to Pond 3 (SS-3E), Pond 2 (SS-5) and the Mill-Willow bypass
(MWB-2)
CDM
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Contents
Silver Bow Creek 5-Year Review
Figure
5-51
Figure
5-52
Figure
5-53
Figure
5-54
Figure
5-55
Figure
5-56
Figure
5-57
Figure
5-58
Total Recoverable Iron Concentrations in Toe Drain Manifold (IA-3)
Relative to Pond 3 (SS-3E), Pond 2 (SS-5), and the Mill-Willow Bypass
(MWB-2)
Total Recoverable Cadmium Concentrations in Inactive Area Wet
Closure Discharge (IA-2) Relative to Pond 3 (SS-3E) and Pond 2 (SS-5)
Total Recoverable Copper Concentrations in Inactive Area Wet Closure
Discharge (IA-2) relative to Pond 2 (SS-3E) and Pond 3 (SS-5)
Total Recoverable Zinc Concentrations in Inactive Area Wet Closure
Discharge (IA-2) Relative to Pond 3 (SS-3E) and Pond 2 (SS-5)
Total Recoverable Arsenic Concentrations in Inactive Area Wet Closure
Discharge (IA-2) Relative to Pond 3 and Pond 2 (SS-5)
Total Recoverable Copper Concentrations in Pump-Back Pipeline (IA-
1) Relative to Pond3 (SS-3e) and Pond 2 (SS-5)
Total Recoverable Zinc Concentrations in Pump-Back Pipeline
Warm Springs Ponds Inactive Area OU Sampling Locations
vi
CDM
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Silver Bow Creek 5-Year Review
Acronyms
AMC Anaconda Mining Company
AOC administrative order on consent
ARAR applicable or relevant and appropriate requirements
ARCO Atlantic Richfield Company
BA&P Butte, Anaconda, and Pacific Railway
BMF Butte Mine Flooding
BMI benthic macroinvertebrate
BPS Butte Priority Soils
BSB Butte-Silver Bow
CDM CDM Federal Programs Corporation
CERCLA Comprehensive Environmental Response, Compensation and Liability
Act
CERCLIS Comprehensive Environmental Response, Compensation, and Liability
Act Information System
CFR Code of Federal Regulations
CFRTac Clark Fork River Technical Assistance Committee
cfs cubic feet per second
CWL critical water level
cy cubic yard
DEQ Montana Department of Environmental Quality
EE/ CA engineering estimate /cost analysis
EqP equilibrium partitioning
EPA U. S. Environmental Protection Agency
ERA expedited response action
ESD explanation of significant differences
GPS Global Positioning System
HDS high density sludge
HRA Historical Research Associates
HSB WTP Horseshoe Bend Water Treatment Plant
IWCTU interstitial water criteria toxic unit
MCE maximum credible earthquake
MCL maximum contaminant level
MCLG maximum contaminant level goal
MDFWP Montana Department of Fish, Wildlife, and Parks
MDHES Montana Department of Health and Environmental Science
mgd million gallons per day
mg/kg milligrams per kilogram
mg/L milligrams per liter
MR Montana Resources
MSL mean sea level
NCP National Contingency Plan
N-TCRA non-time critical removal action
O&M operation and maintenance
CDM vi
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Contents
Silver Bow Creek 5-Year Review
OU operable unit
PMF probable maximum flood
ppb parts per billion
ppm parts per million (equal to mg/L)
PRP potentially responsible party
RAO remedial action objective
RCRA Resource Conservation and Recovery Act
RI remedial investigation
RI/ FS remedial investigation/ feasibility study
Rocker Rocker Timber Framing and Treatment Plant
ROD record of decision
RRU Reclamation Research Unit
SCADA supervisory control and data acquisition system
SEM simultaneously extracted metals
SEM-A VS simultaneously extracted metals and acid volatile sulfide
SST Streamside Tailings
STARS Streambank Tailings and Re vegetation Study
TCLP Toxicity Characteristic Leaching Procedure
TCRA time critical removal action
TOC total organic carbons
UAO Unilateral Administrative Order
USGS U.S. Geological Survey
WSP Warm Springs Ponds
WTP water treatment plant
Hg/L micrograms per liter
viii
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Section 1 Introduction
The U. S. Environmental Protection Agency (EPA) Region 8 has conducted a five-year
review of the remedial actions implemented at the Silver Bow Creek/Butte Area
Superfund Site, Comprehensive Environmental Response, Compensation, and
Liability Act Information System (CERCLIS) ID: MTD980502777 in Silver Bow and
Deer Lodge Counties, Montana. This review was conducted from April 2005 through
June 2005. This report documents the results of the review. CDM Federal Programs
Corporation (CDM), an EPA contractor, supported the EPA in preparation of this
five-year review.
The purpose of the five-year review is to determine whether the remedies or other
response action in place or under construction throughout the Silver Bow
Creek/Butte Area site are protective of human health and the environment. The
methods, findings, and conclusions of such reviews are documented in five-year
review reports. In addition, five-year review reports identify deficiencies found
during the review, if any, and identifies recommendations to address them.
The Silver Bow Creek/Butte Area Superfund Site, part of the Clark Fork River Basin,
is made up of 8 unique remedial operable units (OU), each in various stages of the
Comprehensive Environmental Response, Compensation and Liability Act (CERCLA)
process for implementation of remedial actions at Superfund sites. Table 1-1 presents
a summary of the Silver Bow Creek/Butte Area remedial OUs and dates of completed
record of decision (ROD) documents.
The comprehensive five-year review guidance states that five-year reviews should be
conducted either to meet a statutory mandate or as a matter of EPA policy. EPA must
implement a statutory five-year review to be consistent with CERCLA 121(c), which
states:
If the President selects a remedial action that results in any hazardous substances,
pollutants, or contaminants remaining at the site, the President shall review such
remedial action no less often than each five years after the initiation of such remedial
action to assure that human health and the environment are being protected by the
remedial action being implemented.
EPA interprets this requirement further in the National Contingency Plan (NCP)
Section 300.430(f) (4) (ii) of the Code of Federal Regulations (CFR), which states:
If a remedial action is selected that results in hazardous substances, pollutants or
contaminants remaining at the site above levels that allow for unlimited use and
unrestricted exposure, the lead agency shall review such action no less often than
every five years after the initiation of the selected remedial action.
CDM
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Section One
Introduction
Based on both CERCLA and NCP requirements, statutory five-year reviews are
required in 2005 for the completed remedial actions at the Warm Springs Ponds
(WSP) and Rocker OUs. This will be the second five-year review of the WSP OUs as
their remedial action completion date of 1995 triggered the first five -year review of
the Silver Bow Creek/Butte Area Superfund Site in March 2000. EPA will also
include policy reviews of the Butte Mine Flooding (BMF) and Streamside Tailings
(SST) OUs, since both OUs have signed RODs and ongoing remedial actions. This
second five-year review will also summarize progress within the CERCLA process for
the Active Mining and Milling, West Side Soils, and Butte Priority Soils (BPS) OUs.
1-2
CDM
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Section 2 Site Chronology
Table 2-1 summarizes the important events and relevant dates in the Silver Bow
Creek/Butte Area Superfund Site's chronology.
Table 2-1
c
hronology of Site Events
Event
Operable Unit
Date
Placer gold discovered in Silver Bow Creek
00
1864
Large scale underground mining in Butte
03/08
1875- 1955
Open pit mining at Berkeley Pit
03
1955- 1982
Major smelting period in Butte
03/08
1879- 1900
Discovery of mining-related contamination along Silver Bow Creek between Butte and
Warm Springs, Montana.
01
9/01/1979
Hazard Ranking System Package Completed
00
12/01/1982
Silver Bow Creek Site proposed to the NPL
00
12/30/1982
Silver Bow Creek Site (Original Portion) listed as Final on the NPL
00
09/08/1983
Silver Bow Creek (Original Portion) Phase I Remedial Investigation Final Report
00
01/1987
Butte Area Portion added to Silver Bow Creek Site
02
07/22/1987
Walkerville TCRA completed
08
02/22/1988
Timber Butte TCRA completed
08
1989
Priority Soils TCRA completed
08
1991
ROD for WSP Active Area OU
04
09/28/1990
Explanation of Significant Differences for WSP Active Area OU
04
06/24/1991
Unilateral Administrative Order WSP Active Area OU
04
09/25/1991
Colorado Smelter TCRA completed
08
1992
Anselmo Mine yard and Late Acquisition/Silver Hill TCRA completed
08
1992
Lower Area One Manganese Removal
08
1992
ROD for WSP Inactive Area OU
12
06/30/1992
Unilateral Administrative Order WSP Inactive Area OU
12
06/17/1993
Walkerville II TCRA
08
1994
ROD for Mine Flooding OU
03
09/29/1994
ROD for SST OU
01
11/29/1995
ROD for Rocker OU
07
12/22/1995
Unilateral Administrative Order for Rocker OU ( Remedial Design/Remedial Action)
07
3/29/1996
Unilateral Administrative Order for SST OU ( Remedial Design/Remedial Action)
01
3/29/1996
Explanation of Significant Differences for SST OU
01
08/31/1998
Consent Decree for SST OU
01
11/13/1998
Initial Five Year Review Silver Bow Creek/Butte Area Site Wth Emphasis on WSP OUs
04/12
03/23/2000
Consent Decree for Rocker OU
07
11/07/2000
Walkerville Residential Removal
08
2000
Consent Decree for BMF OU
03
08/14/2002
Stormwater TCRA
08
On-going
Railroad Beds TCRA
08
On-going
Lower Area One N-TCRA
08
On-going
BPS Residential Soils/Source Areas N-TCRA
08
On-going
Proposed Plan for Butte Priority Soils OU
08
12/21/2004
CDM
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Section Two
Site Chronology
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Section 3 Background
3.1 Location and Setting
The Silver Bow Creek/Butte Area Superfund Site centers around the town of Butte,
Montana. The urban center of "Uptown" Butte, Montana is located on the Butte Hill,
which is widely referred to as the "richest hill on earth". The Butte Hill lies just west
of the Continental Divide at the head of Silver Bow Creek and the Clark Fork River
watershed. Historically, metal mines and ore processing facilities on the Butte Hill
produced globally significant quantities of copper, lead, zinc, molybdenum, gold, and
silver. Throughout much of the 20th century, the Butte Mining District was the
largest producer of copper in North America. Large scale mining in Butte as well as
the operation of silver mills and copper and zinc concentrators/ smelters has resulted
in the generation of tremendous volumes of mining-related waste including waste
rock, mill tailings, slag, and aerial smelter emissions. Historically, Silver Bow Creek
was used to impound smelter tailings and to convey wastes out of Butte. Mining
wastes carried from Butte have impacted water quality throughout the entire length
of Silver Bow Creek and the upper Clark Fork River between Butte and Missoula,
Montana. The Silver Bow Creek/Butte Area Superfund Site includes the urban
uptown part of the city of Butte (the Butte Hill), the underground mines beneath the
Butte Hill, the Berkeley Pit, the mining area associated with the historic Berkeley Pit
operation and the active Continental Pit operation, the entire reach of Silver Bow
Creek between Butte and Warm Springs, Montana, and the Warm Springs treatment
ponds. The site encompasses approximately 85 square miles (Figure 3-1).
3.2 Physical Characteristics
The boundary of the Silver Bow Creek/Butte Area site begins above Butte, at the
Continental Divide, and extends northwestward along Silver Bow Creek to and
including the Warm Springs Ponds. Historically, Silver Bow Creek began at the
Continental Divide and flowed through the area that is now the Berkeley Pit and the
Montana Resources (MR) permitted mine area. Mining activity has completely
obliterated this uppermost reach of Silver Bow Creek. The creek now originates at the
confluence of Blacktail Creek and the Metro Storm Drain at the base of the Butte Hill.
The Metro Storm Drain was an open channel that was constructed in the early 1930s
under the Works Progress Administration Program by realigning and filling the
original Silver Bow Creek drainage. The purpose of the storm drain was to provide a
means of transporting mine water, sewage, and storm water out of Butte. There is
now no surface water flow in the Metro Storm Drain except during storm runoff or
snowmelt conditions. Downstream of Butte, Silver Bow Creek flows west about 10
miles, into Durant Canyon. Within the Canyon, the creek swings northward and
enters the Southern Deer Lodge Valley and continues to flow for another 6.5 miles
before entering the Warm Springs Ponds.
The site ranges in elevation from about 6,400 feet above mean sea level (MSL) at the
Continental Divide, to about 4,800 feet above MSL at the toe of the Warm Springs
CDM
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Section Three
Background
Ponds. The site encompasses the urban uptown portion of Butte as well as the entire
length of Silver Bow Creek from its origin in the Summit Valley through Durant
Canyon to its end at the confluence with Warm Springs Creek in the Southern Deer
Lodge Valley. The site includes approximately 26 miles of stream and stream-side
habitat, the urban centers of Butte and Walkerville, the Berkeley Pit and the
underground mine workings of the historic Butte Mining District, the active mining
area associated with the MR operation at the Continental Pit, and the
treatment/ settling lagoons at the Warm Springs Ponds.
The site lies within the Northern Rocky Mountain Physiographic Province and is
characterized by cool, semi-arid climate. Winters are long, cold, and dry, and
summers are short, warm, and dry. Average maximum daily temperatures range
from 14 °F in January to 79 °F in July. Annual precipitation in Butte averages 11.72
inches per year and generally varies from 6 to 20 inches (BPSOU PRP Group 2002).
The wettest months are May and June when the area typically receives approximately
one third of the annual precipitation. The landscape surrounding the site is
characterized by high mountain peaks reaching elevations above 10,000 feet.
Typically, higher elevations are snow-covered from October until May. Surface water
and groundwater resources receive the most recharge in the spring and early summer
due to melting mountain snow pack and spring rains.
The geology of the site is diverse and varies significantly from east to west. In the
east, rocks in the Butte Area are largely Cretaceous intrusive rocks of the Boulder
Batholith. The Boulder Batholith is comprised predominantly of quartz monzonite
and is host to the ore deposit that has been extensively mined in the Butte area.
Batholithic rocks extend north and west from Butte and comprise the mountains on
the southern and eastern margins of the Southern Deer Lodge Valley. The Boulder
Batholith is locally overlain by the Eocene Lowland Creek Volcanics, a suite of
extrusive igneous rocks of quartz-latite composition (ARCO 1995a). Silver Bow Creek
flows onto the Lowland Creek Volcanics as it passes through Durant Canyon between
Miles Crossing and Gregson. The Lowland Creek Volcanics are generally more
resistant to weathering than the Boulder Batholith. This results in the steep-sided
valley walls of Durant Canyon. The Anaconda Pintlar and Flint Creek Mountains
west of the Southern Deer Lodge Valley consist of folded and faulted complexes of
Precambrian metasedimentary rocks (Belt Series) and Paleozoic and Mesozoic
sedimentary rocks that are intruded by granitic plutons. The Silver Bow Creek
floodplain is dominated by Tertiary and Quaternary alluvium overlying bedrock.
The thickness of alluvium ranges from less than 10 feet west of Butte to several
hundred feet in the Summit and Southern Deer Lodge Valleys.
Silver Bow Creek is the primary drainage in the study area. Stream flow is measured
continuously at three monitoring stations within the site by the United States
Geological Survey (USGS). Monthly mean flow in Silver Bow Creek below Butte
(period of record October 1983 to September 2004) ranges from 17.9 cubic feet per
second (cfs) to 29.6 cfs, with highest average flows measured in May and lowest
average flows measured in January. Similarly, monthly mean flow measured in Silver
Bow Creek below the Warm Springs Ponds (period of record March 1972 to
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September 2003) ranges from 61.6 cfs (September) to 273 cfs (June). Over the
respective periods of record for the Butte and Warm Springs stations, peak stream
flow was measured at 447 cfs (June 30,1998) and 1,320 cfs (June 20,1975),
respectively.
Groundwater occurs in both bedrock and alluvial aquifers within the Silver Bow
Creek/Butte Area site. Movement of groundwater within bedrock aquifers is
controlled by open fractures and joints in the rock and, beneath the Butte Hill, by
interconnected mine workings. Groundwater flow in alluvial aquifers is controlled by
the primary porosity of the unconsolidated alluvial sediments and these aquifers
generally report to Silver Bow Creek. Alluvial aquifers at the site are typically
impacted by mining-related contaminants. Bedrock aquifers show less impact, except
within the Mine Flooding OU, where bedrock groundwater is severely degraded from
acid rock drainage occurring within the underground mine workings.
3.3 Land and Resource Use
The Silver Bow Creek/Butte Area Superfund Site covers an area of approximately 85
square miles. It is a very large site with diverse land uses and resources. The site lies
within both Silver Bow and Deer Lodge Counties and encompasses the urban areas of
uptown Butte, Walkerville, Rocker, and Ramsay, Montana. These urban areas include
both urban residential, commercial, and industrial land use. Significantly, the site
also encompasses the entire active mining area east of the Butte Hill. West and north
of Butte, the site includes stream and streamside habitat over the length of Silver Bow
Creek between Butte and the confluence with Warm Springs Creek. Aquatic life in
Silver Bow Creek is severely impaired as a result of water quality and habitat
degradation from mining-related contamination. Land within the Silver Bow Creek
corridor is predominantly privately owned (NRIS 2005) and consists of sparsely
populated open land used primarily for agricultural purposes. The Warm Springs
Ponds are located at the downstream end of the site and cover an area of
approximately 2,500 acres. These ponds consist of three treatment ponds and two
wildlife ponds. Together the treatment ponds and wildlife ponds offer habitat for
migrating waterfowl and breeding areas for dozens of songbird and osprey. The area
is designated a wildlife refuge that is administered by the Montana Department of
Fish Wildlife and Parks.
3.4 History of Contamination
The following history of site contamination was taken from the ROD for the SST
Decision OU of the Silver Bow Creek/Butte Area National Priories List (NPL) Site
(DEQ 1995).
The first recorded disturbance of the Silver Bow Creek channel occurred in 1864 when
placer mining techniques were used to extract gold along the stream and its
tributaries (Freeman, 1900 and Smith 1952). The gold recovered by placer mining was
relatively pure, in the form of dust, flakes, or nuggets. Mercury was sometimes used
to "attract" small pieces of gold. This phase of mining activity was short-lived; most
placer operations in the area had ceased by 1869, although minor activity continued
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on a few local streams (Reclamation Research Unit and Schafer and Associates [RRU
and Schafer), 1993).
Some evidence of early placer mining along upper portions of Silver Bow Creek is still
evident in the form of waterways required to convey water for hydraulic mining and
spoils piles (Historical Research Associates [H RA], 1983). The waterways are in
disrepair and no longer convey water. As Butte's placer deposits played out during
the 1870s, miners turned their attention to the area of hardrock mining. There is no
clear record of the amount of mining wastes produced and disposed of by placer
miner operations.
Concomitant with placer mining along Silver Bow Creek, hard rock mining started on
mineralized vein outcroppings on Butte Hill, north of Silver Bow Creek (Smith, 1952).
Some mining claims on the Butte Hill were re-staked in the 1870s because of favorable
assays of silver ore found in the area (Smith, 1952). Silver mill construction during the
mid-1870s ushered in the era of industrial mining in Butte. This rejuvenated mining
activity in Butte and, by 1878, several small mills were operating in the area. A
combination of factors contributed to a boom in Butte's silver production during the
early 1880s. Completion of railroads to Butte in 1881 along with favorable silver
prices led to a drastic increase in mine production. Most existing mills increased their
production.
Between 1879 and 1885, at least six major mills were built along Silver Bow Creek
from Meaderville to Williamsburg. These mills were operated more or less
continuously until 1910 (Freeman, 1900; Smith, 1952; HRA, 1983). The early mills
were steam-powered stamp mills (50-10 stamps) designed to crush, concentrate, and
amalgamate silver ore. Mills constructed during this time were the: Centennial,
Dexter, Davis, Young and Roudebush, Walker Brothers, Clipper, Silver Bow, Grove
Gulch, and Thornton (HRA 1983). By 1886, five new mills appeared in the vicinity of
Butte's Missoula Gulch and along Silver Bow Creek: the Alice, the Moulton, the
Lexington, the Marget Ann, and the Blue Bird (HRA, 1983). The Blue Bird mill was
located on Silver Bow Creek east of the town of Rocker and contained 90 stamps
which was unusually large at the time. Production capacities from these new mills
were many orders of magnitude greater than previous mills. Butte's silver era ended
with the repeal of the Sherman Silver Act in 1893. These mills produced tailings and
other mining wasters, which were disposed of near the mills. Some of that waste
material was disposed directly into or washed into Silver Bow Creek.
By the late 1880s copper mining had become more important, and Butte became one
of the nation's prominent copper mining centers. Many of the previously described
mills and smelters were used for copper production, and more mills and smelters
were added. Five such facilities located along Silver Bow Creek were especially
significant. They are the Colorado Smelter, the Butte Reduction Works Facility, the
Parrott Smelter, the Montana Ore and Purchasing Company Smelter, and the Butte
and Boston Smelter. All of the described facilities along Silver Bow Creek discharged
wastes alongside or directly into Silver Bow Creek. These facilities operated large
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concentrators and smelters and disposed of very volumes of waste directly into or
near Silver Bow Creek.
A copper smelter (Old Works) was constructed at the lower end of Warm Springs
Creek at the new town of Anaconda, 27 miles west of Butte, in 1884 (Smith, 1952; RRU
and Schafer, 1993). The newer Washoe Smelter was constructed and began operations
on Smelter Hill, directly east of Anaconda, in 1903. The major smelters erected along
Silver Bow Creek in the Butte vicinity continued to operate until approximately 1910
(HRA, 1983). The Amalgamated Copper Company and the Anaconda Copper Mining
Company took possession and control of almost all other companies and facilities in
the Butte area. These companies ultimately combined into the Anaconda Copper
Mining Company. After 1910, most of the ore mined in Butte was then shipped via
the Butte, Anaconda and Pacific Railway (BA&P) to the Anaconda Copper Mining
Company's (AMC) Washoe Smelter for processing (RRU and Schafer, 1993).
By 1917, approximately 150 mines were located in and near Butte and the population
of Butte grew to over 100,000. The mines, which were controlled by AMC or its
predecessors, produced a total of approximately 934 million pounds of copper
(Techlaw, 1985). This corresponds to a maximum of approximately 4.2 million cubic
yards of ore assuming a 5 percent copper content and an ore density of 163 pounds
per cubic foot (Techlaw, 1985). Water pumped from these mines contributed to the
contamination of Silver Bow Creek.
About 1908, AMC began constructing dikes near the mouth of Silver Bow Creek.
These several, often meager construction efforts were intended to trap sediments and
prevent further downstream movement of mining, milling, and smelter wastes.
By about 1917, after several washouts of the original series of dikes, a larger dike was
constructed above, thus creating Pond 2. During the mid 1950s, AMC constructed
still larger dikes to contain the increasing volume of waste that continued to move
down Silver Bow Creek. Thus, Pond 3 was created, and altogether, 19 million cubic
yards of tailings were contained within three settling ponds.
AMC commenced surface mining of low-grade copper ore with the opening of the
Berkeley Pit in 1955 and built the Weed Concentrator in 1963 to process this ore.
These operations contributed contamination to Silver Bow Creek.
In 1977, AMC was purchased by the Atlantic Richfield Company (Atlantic Richfield)
which expressly assumed liability for AMC. Atlantic Richfield closed all
underground mines in 1980 and continued active mining only in the Berkeley Pit.
Atlantic Richfield closed the Berkeley Pit in 1982 and the East Berkeley Pit in 1983.
There was a hiatus of mining in Butte until 1986, when Montana Resources (MR)
initiated open-pit mining operations in the Continental Pit. Aside from a 3-year break
in operations between July 2000 and November 2003 (due to economic
considerations), MR continues to mine copper and molybdenum in the Continental
Pit.
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Although floods and storm events contributed to the transport of waste in Silver Bow
Creek and as far downstream on the Clark Fork River as Lake Pend Oreille in Idaho,
they were not the exclusive cause of contamination downstream. Upstream facilities
in Butte, discharged waste directly into or along Silver Bow Creek, and did not
exercise due care in anticipating flood events or storm events and taking precautions
to avoid waste movement.
Waste was transported from these operations downstream via overland flow and
surface water transport.
In June of 1908, the largest flood in recorded history in the Silver Bow Creek basin
occurred, contributing to the extent of fluvially-deposited tailings found today.
Heavy rains fell in late May and early June, melting the snow pack and causing
extensive flooding (CH2M Hill, 1989a). Flood waters transported tailings from
smelting facilities in Butte and along Silver Bow Creek and deposited them
downstream as flood waters waned. Flood flows and fluvial deposits were physically
constrained by railroad grades constructed parallel to Silver Bow Creek, limiting the
areal extent of flood deposited tailings.
Other recorded significant storm events occurred in 1892,1894,1938,1948,1964,1975
and 1980 (CH2M Hill, 1989a). All of these events occurred during the spring and
early summer when precipitation and melting snow combined to produce large
runoffs. These events also contributed to the movement of mine wastes from their
sources into the Silver Bow Creek floodplain.
3.5 Regulatory History Summary
The Silver Bow Creek/Butte Area NPL Site is located in Silver Bow and Deer Lodge
counties of Montana at the easternmost extent and headwaters of the upper Clark
Fork River drainage. EPA designated the original Silver Bow Creek Site as a
Superfund site in September 1983, under the authority of the CERCLA. Work began
on a remedial investigation and feasibility study (RI/FS) in 1984. During the course
of the RI/FS, the importance of Butte as a source of contamination to Silver Bow
Creek was formally recognized. Preliminary results from the Silver Bow Creek RI/FS
indicated that upstream sources were partly responsible for the contamination
observed in the creek. After a thorough analysis of the relationship between the two
sites (Butte and Silver Bow Creek), EPA concluded that they should be treated as one
site under CERCLA. EPA subsequently modified the existing Silver Bow Creek Site
to include the Butte Area and the formal name was changed to the "Silver Bow
Creek/Butte Area NPL Site" in 1987.
Early on, Montana Department of Health and Environmental Sciences (MDHES) (now
Montana Department of Environmental Quality - DEQ) was the lead agency for the
Butte Metro Storm Drain, Butte Reduction Works and Colorado Tailings, Rocker, all
of Silver Bow Creek including the Warm Springs Ponds, and the Clark Fork River to
Milltown. EPA was lead agency for the Berkeley Pit and remaining OUs of the Butte
Area portion of the site. In 1989, EPA became the lead agency for all OUs except for
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Silver Bow Creek proper, which by then had become known as the Streamside
Tailings OU. Within 18 months, EPA shifted the Clark Fork River OU from the Silver
Bow Creek/Butte Area Superfund Site to the Milltown Reservoir Sediments
Superfund Site, a site for which EPA had been the lead agency since its listing in 1983.
That situation remains true today.
CERCLIS officially identifies 13 OUs within the Silver Bow Creek/Butte Area Site
(Table 3-1) (USEPA 2005). Four of the thirteen OUs are removal OUs and, therefore,
are addressed under the ROD for one or more of the remedial OUs and do not require
a five year review. For example, the Lower Area One OU was incorporated into the
Priority Soils OU and will be addressed accordingly under the ROD for the Priority
Soils OU. As described previously in Section 1, this report presents statutory 5-year
reviews for the Warm Springs Ponds Active Area OU (OU4), Rocker Timber Framing
and Treatment Plant OU (OU7), the Warm Springs Ponds Inactive Area OU (OU12),
the Streamside Tailings OU (OU1), and the Mine Flooding OU (OU3). A brief review
of site activities is all that is done for the five-year review for the Priority Soils OU,
Active Mining and Milling OU, and the West Side Soils OU because RODs for these
OUs have not had remedial action selected or undertaken.
A summary of the contamination and regulatory history for the 8 OUs covered in this
5-year review is presented in the following sections.
3.5.1 Streamside Tailings OU
The SST OU is the portion of the Silver Bow Creek/Butte Area site located between
the city of Butte and the community of Warm Springs, Montana. DEQ is the lead
agency for the OU, which includes Silver Bow Creek from Butte, 26 miles downstream
to the inlet of the Warm Springs Ponds. The SST OU includes not only Silver Bow
Creek, but also the mining wastes along the stream and in the adjacent floodplain and
railroad beds.
Wastes from mining, milling and smelting facilities once located in Butte and along
Silver Bow Creek have been washed down the creek for more than 100 years. These
wastes, primarily tailings, contain high levels of arsenic, and metals such as cadmium,
copper, lead, mercury, and zinc. At the time the ROD was signed in 1995, it was
estimated that 2,500,000 to 2,800,000 cubic yards of tailings and contaminated soils
cover about 1,300 acres. In some areas, the tailings are several feet thick. The largest
single tailings deposit, 160 acres, lies near the town of Ramsay and is known as
Ramsay Flats. The tailings are largely unvegetated. Silver Bow Creek also contains
tailings and is devoid of most aquatic life (DEQ 1995a).
Environmental investigations in the vicinity of the SST OU were initiated by the EPA
in 1982 to address mining impacts along Silver Bow Creek. The Silver Bow
Creek/Butte Area Site (original portion) was listed on the NPL in 1983 by EPA under
the CERCLA and site investigations began in 1984 with the Phase I Remedial
Investigation (RI) prepared by MultiTech Services under contract to the DEQ
(MutiTech 1987). The Phase II RI described in the draft RI report (ARCO 1995a) was
conducted by the potentially responsible party (PRP), Atlantic Richfield, and
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describes investigation activities, characterizations and interpretations performed
since 1991. All pre-1991 studies or data that were determined by Atlantic Richfield
and DEQ to be applicable or pertinent to current OU conditions were incorporated in
the OU characterization in the draft RI report (Phase II). The draft RI report complied
with Superfund law, defined the nature and extent of the contamination to the extent
necessary to determine remedial action and provided information to complete the
baseline human health and ecological risk assessments (ARCO 1995a). The baseline
risk assessment was released by DEQ in December of 1994 (DEQ 1994). The feasibility
study, released by Atlantic Richfield in June 1995, included the development,
screening and evaluation of potential OU remedies (ARCO 1995b).
The proposed plan was released in June 1995 and delineated the preferred alternative
(DEQ, 1995b). In November 1995, EPA and DEQ, as lead agency, issued the ROD.
The ROD was modified by a 1998 Explanation of Significant Differences (ESD) (DEQ
1998).
In April 1998, a settlement between Atlantic Richfield, EPA, and DEQ was finalized
which provided $80 million for the remediation of the SST OU.
3.5.2 Butte Mine Flooding OU
The BMF OU is located within the city of Butte. EPA is the lead agency on the OU
and DEQ is the support agency. The BMF OU consists of waters within the Berkeley
Pit, the underground mine workings hydraulically connected to the Pit, the associated
alluvial and bedrock aquifers, and other contributing sources of inflow to the Berkeley
Pit/East Camp System. BMF OU is within the historic Butte Mining District in the
upper Silver Bow Creek drainage and covers about 23 square miles (USEPA 1994).
The BMF OU is part of the Butte Area portion of the Silver Bow Creek/Butte Area
Site.
The Berkeley Pit/East Camp System is located in the northern and eastern portions of
the OU. The Berkeley Pit is the major feature of the OU, encompassing an area of 675
acres, a depth of 1,780 feet, and a volume of 35 billion gallons of contaminated water.
The water is an acidic sulfate solution containing high levels of copper, zinc, iron,
lead, arsenic, aluminum, cadmium, and sulfate. Approximately 3,000 miles of
underground mine workings are hydraulically connected to the Pit. The West Camp
System, located in the southwest corner of the OU, and includes the Travona, Emma,
and Ophir mines and their associated underground workings. The East Camp and
West Camp systems are separated by bulkheads installed in the late 1950s and are
considered to be separate hydraulic systems. Water levels in the West camp system
are notably higher than water levels in the East Camp system (USEPA 1994).
A major seepage area of acidic mine water originates in the Horseshoe Bend Area,
located north of the Berkeley Pit. Discharge from the Horseshoe Bend Area varies
from 1.7 to 5.9 million gallons per day depending upon current climatic conditions
and the MR mining operation. This water was partially used in the active mining
operation and the remainder flowed into the Berkeley Pit.
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A removal action was implemented in the West Camp Area to control potential
impacts of rising mine waters. The purpose of the removal action was to prevent
flooding of basements and discharge of contaminated groundwater to Silver Bow
Creek. An engineering evaluation/cost analysis (EE/CA) of potential alternatives
was conducted by EPA in support of the West Camp Removal action. On March 31,
1989, EPA entered into an administrative order of consent (AOC) with Atlantic
Richfield and Dennis Washington (the consenting PRPs) in connection with the West
Camp removal action. The West Camp order required the consenting PRPs to convey
water pumped from the Travona shaft to the Butte Metro Sewage Treatment Plant for
treatment and discharge to Silver Bow Creek. This AOC established a preliminary
critical water level for the West Camp and required the consenting PRPs to maintain
the water level elevation within the West Camp System below 5,435 feet (USGS
datum) (USEPA 1994).
A unilateral order was issued to the non-consenting PRPs to install the pipeline which
carried Travona shaft water to the Butte Metro Sewage Treatment Plant. The non-
consenting PRPs complied with this order.
EPA completed the RI/FS work plan for the BMF OU in April 1990 (CDM 1990). This
document outlined the work to be conducted during the RI/FS, the schedule for the
work, and the parties responsible for each portion of the work. EPA and DEQ then
entered into an AOC with the consenting PRPs to implement the major portion of the
work plan. This AOC established a critical water level of 5,420 feet (USGS datum) for
the East Camp/Berkeley Pit System and required the PRPs to maintain the water level
in the East Camp/Berkeley Pit System below this level. A unilateral order was also
issued to the non-consenting PRPs to implement a small portion of the RI/FS work
plan. The RI/FS was conducted from July 1990 through January 1994. Site
investigations, results, and remedial alternative development and evaluation are
presented in the draft RI report (ARCO 1994a) and the draft FS report (ARCO 1994b).
The ROD was issued in September 1994 (USEPA 1994).
A unilateral administrative order (UAO) was issued to Atlantic Richfield, Montana
Resources Inc., ASAR, and Dennis Washington on June 11,1996 to implement the
remedial design/ remedial action activities associated with the ROD. The
requirements of the ROD were modified in a March 2002 ESD (USEPA 2002).
A consent decree (CD) was signed between Atlantic Richfield, the MR related entities,
the United States, and the State of Montana in June 2002 and entered by the Federal
district court in August 2002. This CD superseded all previous AOCs and UAOs
issued for this OU.
3.5.3 Warm Springs Ponds OUs
3.5.3.1 Active Area OU
The WSP are located in the Southern Deer Lodge Valley at the downstream end of
Silver Bow Creek, approximately 26 river miles downstream of Butte, Montana. The
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WSP are a series of three large settling and treatment basins, known as Pond 1, Pond
2, and Pond 3, located near Warm Springs, Montana. The complex covers an area of
approximately 2,600 acres, and is bordered by the Mill-Willow Bypass (stream
diversion around the WSP) to the west, the Clark Fork River to the north, hills to the
east, and marsh lands and incoming streams to the south (USEPA 1992). The stream
reach below the confluence of Mill-Willow Bypass and the discharge from the WSP is
designated as lower Silver Bow Creek. Just north of the WSP, the confluence of lower
Silver Bow Creek and Warm Springs Creek is the defined beginning point of the Clark
Fork River. Figure 3-2 shows the current configuration of the Warm springs Ponds
complex, including Ponds 1, 2, and 3, the Mill-Willow Bypass, and the wildlife ponds.
During initial remedial design/remedial action (RD/RA) activities for the entire the
Warm Springs Ponds OU, the site was divided into two separate interim OUs: 1) the
Active Area OU; and 2) the Inactive Area OU. The Active Area OU represents the
portion of the WSP complex where active water treatment occurs and encompasses
Pond 3, the inlet area above Pond 3, Pond 2, and the portion of the Mill-Willow
Bypass adjacent to Ponds 2 and 3. The Inactive Area OU includes Pond 1, the area
downstream of Pond 1, and the lower portion of the Mill-Willow Bypass.
From the beginning of ore processing (concentrating/smelting) activities in 1880 until
about 1911, mine and mill tailings from the Butte and Anaconda areas were carried
down Silver Bow Creek to the Clark Fork River, at least as far as the Milltown
Reservoir (built in 1907), approximately 145 river miles, and probably farther. AMC
made the first attempt to control the amount of sediment carried into the Clark Fork
River from Silver Bow Creek in 1911 by building a 20-foot-high tailings dam on Silver
Bow Creek near the town of Warm Springs; this created WSP 1 (CH2MHill and Chen
Northern 1989).
In 1916, another 18-foot high dam was built at Warm Springs by AMC upstream from
the first dam, creating WSP 2. This dam subsequently was raised five feet to a total
height of 23 feet during 1967-1969. WSP 1 and 2 trapped and settled out sediment
from Silver Bow Creek. The primary sources of this sediment were tailings eroded
from deposits, in and along the Silver Bow Creek channel as well as increased natural
sedimentation resulting from vegetation disturbance. Additional sediment also may
have been contributed by overflow discharge from the adjacent Anaconda and
Opportunity Ponds at the Anaconda Smelter. This water was routed into Silver Bow
Creek above the WSP (CH2MHill and Chen Northern 1989).
A third, and much larger, 28-foot high dam was built upstream of WSP 2 by AMC
between 1954 and 1959, primarily for sediment control. This structure created WSP 3.
The height of this dam was increased by five feet during 1967-1969 to a maximum
height of 33 feet (CH2MHill and Chen Northern 1989).
As a result of the activities described above, over 19 million cubic yards of
contaminated sediments accumulated in the WSP, and a substantial volume of
contaminated soils and tailings were present in areas surrounding the WSP, including
the Mill-Willow Bypass and the area downstream (north) of Pond 1 (USEPA 1992).
3-10
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Concerns about the stability of the dams at the VVSP, not water quality concerns alone,
initiated rapid action under Superfund authority on the WSP in the early 1990s.
These actions have proven successful and have eliminated the threat of dam failure
due to a flood or earthquake.
Ponds 2 and 3 have been retained as settling ponds. Tailings and other sediments
from Silver Bow Creek physically settle to the bottom as the velocity of incoming
water decreases. The addition of lime near the inlet of Pond 3 enhances the removal
of metals from the influent water. Historically, lime has been added only during fall,
winter, and early spring.
Pond 1 was never involved in the active treatment of water from Silver Bow Creek by
the addition of lime, and it no longer plays a role in settling sediments. This inactive
area, and the area below Pond 1, are essentially isolated from the active portion of the
WSP system. The relatively small volume of water contained within the inactive area
OU is present due to seepage and minimal flow from the ponds above (USEPA 1993).
Mill and Willow creeks, which historically joined with Silver Bow Creek in the area
above the present pond system, were diverted away from Silver Bow Creek and
around the pond system in the late 1960s. This diversion became known as the Mill-
Willow Bypass.
In 1967, WSP 3 was converted into a treatment facility to treat mill losses,
precipitation plant spent solution from Butte Operations, and overflow from the
Opportunity Ponds. Treatment consisted of introducing a lime/ water suspension
from the Anaconda Smelter into Silver Bow Creek above WSP 3. The addition of the
lime suspension raised the pH of the creek water to facilitate precipitation of heavy
metals in the WSP (CH2MHill and Chen Northern 1989).
Wildlife ponds were constructed about 1967 by the Montana Department of Fish,
Wildlife, and Parks in association with AMC. The purpose of the ponds was to
enhance waterfowl habitat in the Southern Deer Lodge valley. Two large cells and
several smaller sub-cells and islands were constructed for this purpose. Water within
the Wildlife Ponds is obtained from siphon structures in Pond 3 (CH2MHill and Chen
Northern 1989).
Currently, the WSP treatment system is operated by Atlantic Richfield. Pond 1 is not
used in the treatment process at the site because the pond is largely filled with
sediment. Lime is added to Silver Bow Creek above Pond 3, primarily during the
winter months, to raise the pH of the influent to facilitate metals precipitation.
Prior to 1989, MDHES (now DEQ) was the lead agency for the WSP OU. The DEQ in
consultation with EPA, completed site characterization studies, some feasibility
studies, and the proposed plan for the WSP OU. Following the release of the
proposed plan, EPA became the lead agency.
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In July 1990, EPA and Atlantic Richfield entered into an AOC for the Mill-Willow
Bypass Removal Action. This work was completed and is an integral part of the two
remedial actions (Active Area and Inactive Area) for the WSP. Briefly, the Mill-
Willow Bypass Removal Action involved the following work (USEPA 1992):
¦ Removal of 436,000 cubic yards of tailings and contaminated soils from the bypass and
disposal in a dry portion of Pond 3.
¦ Reinforcing and armoring the Pond 2 and 3 berms (an additional 1 million cubic yards
of uncontaminated fill dirt was excavated from the bypass for this purpose).
¦ Construction of improved inlet and outlet structures and a divider dike between Silver
Bow Creek and Willow and Mill creeks.
The initial ROD for the WSP OU was released by EPA on September 28,1990. In June
of 1991, EPA released an ESD that modified certain elements of the initial Warm
Springs Ponds ROD. Most significantly, the ESD identified the inactive area of Pond 1
and the area beneath Pond 1 as a separate action that would addressed under a
separate ROD. The ESD divided the WSP into two separate OUs: 1) the WSP Active
Area OU; and 2) the WSP Inactive Area OU. The Active Area OU would address
Ponds 2 and 3, as well as the Mill-Willow Bypass and berms, inlet and outlet
structures, treatment improvement features, and monitoring systems. The Inactive
Area would address the inactive areas (Pond 1 and the area downstream of Pond 1).
In September, 1991, EPA issued a Unilateral Administrative Order directing
implementation of the Active Area ROD.
In 1997, Atlantic Richfield issued the initial Five Year Review Report (ARCO 1997) for
the WSP OUs. The Atlantic Richfield report presented data collected during
construction of the remedial action improvements and an evaluation of the system's
performance since completion of the improvements in 1995. An addendum to
Atlantic Richfield's report was issued in 1998 (ARCO 1998). The addendum
presented additional operational data gathered in the interim and the results of
additional investigations completed to understand the system's dynamics. In 2000,
after the system had been operating for approximately five years, EPA issued its
initial five-year review report for the Silver Bow Creek/Butte Area NPL site, which
emphasized the performance of the Warm Springs Ponds (ARCO 2005).
3.5.3.2 Inactive Area OU
As described previously, the WSP are divided into two separate OUs to address
environmental contamination at the WSP: 1) the Active Area OU and 2) the Inactive
Area OU. The WSP Inactive Area OU includes Pond 1, the area downstream of Pond
1, and the lower portion of the Mill-Willow Bypass.
Prior to implementing remedial action, the Inactive Area OU contained an estimated
3.4 million cubic yards of contaminated sediments, tailings, and soils. Approximately
475.000 cubic yards of these materials were contained within the area downstream of
Pond 1. These source materials consisted of over-bank deposits that settled out along
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Section Three
Background
Silver Bow Creek prior to the construction of Pond 1. Approximately 2.9 million cubic
yards of contaminated sediments, tailings, and soils were contained within Pond 1.
These materials settled out of Silver Bow Creek over a short period of time after Pond
1 was constructed in 1911. Pond 2 was constructed in 1916.
The original ROD for the WSP OUs (USEPA 1990) described a remedy selected by
EPA for controlling the contaminated tailings, sediment, and water contained within
the WSP and for preventing these contaminated materials and water from entering
the Clark Fork River (USEPA 1991). In June of 1991, EPA released an ESD that
modified certain elements of the initial WSP ROD. Most significantly, the ESD
identified the inactive area of Pond 1 and the area beneath Pond 1 as a separate action
that would addressed under a separate ROD. The ESD divided the WSP into two
separate OUs: 1) the WSP Active Area OU; and 2) the WSP Inactive Area OU. The
WSP Active Area OU would address Ponds 2 and 3, as well as the Mill-Willow
Bypass and berms, inlet and outlet structures, treatment improvement features, and
monitoring systems. The Inactive Area would address the inactive areas (Pond 1 and
the area downstream of Pond 1).
In March, 1992, EPA released the proposed plan for the Inactive Area OU followed by
the ROD in June 1992. In July 1993, EPA issued a UAO to Atlantic Richfield, the
respondent, to conduct the remedial action. Remedial action was implemented from
1993 to 1995.
In 1997, Atlantic Richfield issued the initial five-year review report (ARCO 1997) for
the WSP OUs. The Atlantic Richfield report presented data collected during
construction of the remedial action improvements and an evaluation of the system's
performance since completion of the improvements in 1995. An addendum to
Atlantic Richfield's report was issued in 1998 (ARCO 1998). The addendum
presented additional operational data gathered in the interim and the results of
additional investigations completed to understand the system's dynamics. In 2000,
after the system had been operating for approximately five years, EPA issued its
initial five-year review report for the Silver Bow Creek/Butte Area NPL site, which
emphasized the performance of the WSP (ARCO 2005).
3.5.4 Rocker OU
The Rocker OU covers approximately 16 surface acres, and is located approximately 3
miles west of the community of Butte and adjacent to the community of Rocker,
Montana. EPA is the lead agency on the Rocker OU and DEQ is the support agency.
The Rocker Timber Framing and Treating Plant was constructed in 1909 and operated
until the plant was closed in approximately 1957. The Anaconda Company,
predecessor in interest to Atlantic Richfield, owned and operated the site. Initially,
the facility treated mining timbers with a creosote solution. Subsequently, the facility
began using arsenic trioxide solutions for treatment, and this formulation became the
primary treatment process up to the final days of plant operation.
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Section Three
Background
During the approximate 48 year history of plant operation, spilled process materials
(arsenic trioxide powder), treated wood chip residues, and dripped or leaked process
solutions (creosote and caustic heated arsenic brines) have resulted in contaminated
soils throughout the plant site and significant groundwater contamination. Rocker
wood treating wastes were also mixed with contaminated tailings and other mining
waste washed downstream to Rocker from mining/ smelting facilities in Butte.
The Rocker OU is part of the original Silver Bow Creek superfund site that was listed
on the NPL in 1983. In 1989, the State of Montana directed Atlantic Richfield to
remove contaminated soils and debris with concentrations exceeding 10,000
milligrams per kilogram (mg/kg) arsenic. Approximately 1,000 cubic yards (cy) of
contaminated material were removed to a licensed disposal facility. Areas involved
in the removal action were subsequently covered with approximately one foot of
"clean" fill material from a nearby off-site area. Nevertheless, materials exceeding the
10,000 parts per million (ppm) concentration were identified at three locations
remaining on the site. Between 1989 and 1995, numerous technical investigations
were conducted at the site to characterize the nature and extent of soil and
groundwater contamination. These investigations culminated with the final remedial
investigation report in March 1995 (ARCO 1995c) and the final feasibility study in July
1995 (ARCO 1995d).
A ROD for the Rocker OU was signed in December 1995 (USEPA 1995). EPA initially
ordered the implementation of the ROD. In November 2000, EPA and Atlantic
Richfield entered into a consent decree for implementation of the Rocker OU ROD.
3.5.5 Butte Priority Soils OU
The BPS OU consists of a five square mile area encompassing the town of Walkerville
and a large portion of the city of Butte. The OU is centered on "Butte Hill", which is
the location of the historic Butte Mining District. Silver Bow Creek flows along the
base of the Butte Hill. The OU is situated in a predominantly urban setting, and
includes residential neighborhoods, schools and parks, as well as commercial and
industrial areas.
Mining and ore-processing wastes in Butte represent the primary source of
contamination. These wastes come in several different forms, including mill tailings,
waste rock, slag, smelter fallout, and mixed combinations of each. Arsenic and metals
contained in, or released from these wastes to soil, surface water, and groundwater
pose significant risks to human and ecological receptors.
EPA is the lead agency and Montana DEQ is the support agency for this OU.
The RI/FS for this OU was conducted by the BPS OU PRP Group. The final remedial
investigation report was issued in April 2002 and the final feasibility study was issued
in April 2004. EPA released the proposed plan in December 2004 and completion of
the ROD is scheduled for 2006.
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Section Three
Background
During the course of the RI/FS, EPA implemented several response actions to address
high priority human health risks and reduce the severity of contaminant loading to
Silver Bow Creek and to protect downstream remedies at other OUs (e.g., SST OU and
the WSP OUs). Response actions have addressed over 8 million cy of waste within
the OU using removal, capping, and/ or land reclamation. Over 400 acres of mine-
impacted land on the Butte Hill has been reclaimed. Also, approximately 1.2 million
cy of tailings that were previously in contact with ground and surface water have
been removed from the Silver Bow Creek floodplain, and storm water controls,
including conveyance channels, diversions, and detention basins, have been
constructed to reduce contaminant loading carried from the Butte Hill via storm
water runoff.
Despite the past response actions completed at the BPS OU, remedial goals have yet
to be achieved and significant risks still threaten human and environmental receptors.
The potential exposure to lead and arsenic in residential soil and interior dust
continue to pose a significant human health risk. Arsenic and metal contaminants in
surface water and alluvial groundwater exceed applicable water quality standards
and continue to affect aquatic life in Silver Bow Creek.
Summary of Butte Priority Soils OU Response Actions
Prior to the final FS and remedial decision process, extensive areas within the OU
have been addressed by response actions (Time Critical Removal Actions [TCRAs]
and Non-Time Critical Removal Actions [N-TCRAs]). Most of this work was
completed in the late 1980s through late 1990s. Two remaining TCRAs (railroad beds
and storm water) will be completed in 2005 and final actions for the two remaining
expedited response actions (ERAs) (Lower Area One and one for residential
soils/ source areas) will be determined in the ROD. These response actions were done
as efforts to address the more pressing problems at BPSOU using the faster Superfund
removal process. Although an accelerated process was used to conduct these response
actions, Superfund law requires that they be implemented in ways that contribute to
the efficient performance of a final long-term remedial action, to the extent
practicable. Therefore, EPA Region 8 required that the response actions be designed
and constructed in a manner intended to be permanent.
If the remedy selection process chooses a remedy which leaves some or all of these
actions as-is, the remedy will address long-term monitoring and operation and
maintenance for these actions and for the site as whole.
Response actions were selected using removal criteria that give EPA broad discretion
in determining what cleanup actions are appropriate. EPA used its authority at the
BPSOU in the selection of the type of actions implemented and the oversight of the
construction of response actions. Where capping of wastes was selected as part of the
early response actions, sound engineering designs were implemented to ensure the
stability and performance of the caps. Intensive monitoring and inspections of the
caps has been, and will continue to be, performed.
The following is a brief summary of the response actions performed at the BPSOU:
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Section Three
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¦ Walkerville TCRA (1988). Addressed mine waste dumps (e.g., Lexington Mine Yard)
and residential soil areas contaminated with lead above 2,000 milligrams per kilogram
(mg/kg) or mercury above 10 mg/kg in Walkerville (Exhibit 2-2). Nearly 300,000 cy of
material were removed from 10 sites. One mile of rock-lined ditch was also constructed
to control surface water runoff from the recontoured waste piles. EPA Region 8 also
removed contaminated soil from six earthen basements and 33 residential yards.
¦ Timber Butte TCRA (1989). Approximately 40,000 cy of contaminated soil were
removed and consolidated in an on-site repository that was recontoured, covered with
fill soil, and revegetated. Drainage was improved with recontouring and the
installation of drainage ditches. Contaminated soil was removed from two residential
yards and the yards were recontoured, covered with soil, and revegetated.
¦ Butte Priority Soils TCRA (1990 and 1991). Mitigated risks from a number of mine
waste dumps, a concentrate spill, and seven residential yards located in Butte and
Walkerville (Exhibit 2-3). Response actions were taken at 30 waste dumps (100,000 cy)
that were either capped or removed. In addition, a railroad bed and seven residential
yards were reclaimed. These actions included removing waste, adding lime rock,
capping with soil, application of fertilizer, and seeding each site.
¦ Colorado Smelter TCRA (1992). Addressed wastes associated with the Colorado
Smelter. Approximately 40,000 cy of mine waste were removed and consolidated in an
on-site repository. The site was reclaimed and drainage channels were installed.
¦ Anselmo Mine Yard and Late Acquisition/Silver Hill TCRA (1992). Addressed a
mine yard and several mine dumps in Butte. The work involved excavation of mine
waste, recontouring, capping, and revegetation. Terracing, rock-lined ditches, and
other drainage control measures were used for storm water management purposes.
¦ Walkerville II TCRA (1994). EPA conducted further removal activities in Walkerville
to address four additional dump areas with elevated soil lead levels. In 1994 and 1995,
12 more waste dumps were either removed or capped in place.
EPA is currently conducting the following response actions:
¦ Railroad Beds TCRA. Addresses railroad beds and adjacent residential yards at the
OU that contain elevated concentrations of metals and arsenic. The railroad beds were
constructed using mining-related waste or contaminated by spillage during transport
of ore or ore concentrates. The TCRA includes significant storm water drainage
improvements. EPA expects to complete the TCRA in 2005.
¦ Storm Water TCRA. Begun in 1997 to address storm water problems in Butte. To
control storm water flow and minimize soil erosion and transport of contaminated
sediment to Silver Bow Creek, storm water conveyance structures were built and large
areas of barren land and contaminated soil were reclaimed with cover soil and
revegetation. Storm water channels and detention ponds were placed in critical areas to
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Section Three
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minimize erosion and reduce the release and transport of contaminants from historic
mining areas.
This response action also included reclamation of the Alice Dump and the removal of
about 50 cy of soils contaminated with elemental mercury in the Dexter Street area. The
Alice Dump is a large waste rock dump located in upper Missoula Gulch that contained
about 2 million cy of contaminated soil and waste rock. At Dexter Street, a limited
quantity of the mercury-contaminated soils failed Toxicity Characteristic Leaching
Procedure (TCLP) and required disposal at an EPA-approved Resource Conservation
and Recovery Act (RCRA) hazardous waste disposal facility. The remaining soils were
disposed at an on-site waste repository.
¦ Lower Area One ERA. Focused on the removal of accessible mine tailings impounded
in the Silver Bow Creek floodplain from the historic Colorado Smelter and Butte
Reduction Works facilities and the interception and treatment of groundwater. In 1997,
the PRP excavated and removed approximately 1.2 million cy of tailings from the
floodplain. The area was then backfilled with imported material, and the stream
channel was reconstructed. Waste removal during the Lower Area One ERA was
completed to a predetermined depth-of-excavation contour. Tailings remain beneath
the limits of the excavation and beneath the Metro Sewage Treatment Plant facility,
historic slag walls, and other immovable structures. As a result, a groundwater
collection system was constructed in 1998 and the Lower Area One revegetation plan
was completed, including stream bank reclamation. Phase II of the Lower Area One
ERA was an interim hydrologic equilibration and monitoring period that included
ground and surface water sampling, water level monitoring, and water treatability
studies. Phase III, which includes final reclamation and land use planning, will be
decided and implemented as a component of the ROD. The groundwater treatment
system will be part of the complete site-wide collection and treatment needs.
¦ BPS OU ERA (residential soils/source areas). Addresses residential areas with soil-
lead concentrations above the residential lead action level (1,200 mg/kg) via the work
plan for residential areas and the Butte-Silver Bow County Lead Prevention and
Abatement Program. This action also reclaimed, or repaired to EPA standards, more
than 50 sites above the lead action level for non-residential source areas (2,300 mg/kg).
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Section Three
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Other Actions
¦ Lower Area One Manganese Removal (1992). The objective of this removal action was
to remove manganese ore stockpiles in Lower Area One within the floodplain of Silver
Bow Creek. The piles were located east of the Metro Sewage Plant and west of
Montana Street in Lower Area One. The action was done by the U.S. Bureau of
Reclamation in cooperation with the Defense Logistics Agency and EPA. The
stockpiles included ore and process tailings remaining after efforts by the Department
of Defense to process manganese ore at the Butte Reductions Works Plant in World
War II.
A total of 261,000 cy were moved to a private repository in Whiskey Gulch, west of the
BPS OU (Bureau of Reclamation 1992). The action was a critical ancillary action to the
Lower Area One ERA.
¦ Old Butte Landfill/ Clark Mill Tailings (1998). A RCRA corrective action was
completed at this site southwest of Butte. The site consisted of a 60-acre impoundment
with approximately 1 million cy of mill tailings immediately adjacent to, and partially
mixed with, the old Butte Municipal Landfill. The mixed nature of the wastes
necessitated a combined remedy be performed under RCRA jurisdiction. At the Clark
Mill Tailings, approximately 800,000 cy of the Colorado Tailings removed from Lower
Area One were placed were in the repository constructed at this site. The final RCRA
repository cover was designed in 1997 and constructed in 1997 and 1998. The overall
design included the subsequent construction of a recreational complex on top of the
repository that included several irrigated ball fields, play areas, and park buildings.
The recreational complex was opened in 2001.
¦ Walkerville (2000). All unsampled residential properties in Walkerville were tested by
EPA and cleanups implemented at those residences with elevated arsenic, lead, and/or
mercury above action levels. In all, approximately 40 properties were addressed.
3.5.6 Active Mining and Milling Area Operable Unit
This area is located west and northwest of the BPS OU and consists of the permitted
mine area currently operated by MR. In 2002, EPA deferred Superfund action at the
site to state authority under the operating permit.
3.5.7 West Side Soils OU
This OU encompasses areas of Silver Bow County that have experienced mining
activity but lie outside of other OU boundaries. This is generally north and west of
Butte Hill. EPA is currently conducting preliminary RI/FS forward planning for this
OU, but the site has not been funded over the past several years.
3-M
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Section 4 Remedial Actions
Summaries of the remedial actions selected, their implementation, and operations and
maintenance (O&M) activities for the WSP Active and Inactive OUs, the Rocker OU,
the BMF OU, and the SST OU are presented below.
4.1 Warm Springs Ponds Active and Inactive OUs
4.1.1 Remedy Selection
4.1.1.1 WSP Active Area OU
The overall remedial action objectives established for the WSP Active OU are:
¦ Prevent releases of pond bottom sediments due to earthquakes or floods. The Montana
Department of Natural Resources and Conservation dam safety requirements have
been identified as the applicable standard. The standard requires protecting the ponds
to fractions of a probable maximum flood and to the maximum credible earthquake.
¦ Meet Montana Water Quality Act ambient water quality standards for arsenic,
cadmium, lead, mercury, copper, iron and zinc at a compliance point just above the
defined starting point of the Clark Fork River, and to comply with discharge standards
for the Pond 2 discharge after implementation of the Warm Springs Ponds response
actions and the upstream cleanup actions.
¦ Prevent ingestion of water above concentrations deemed safe by the Montana Public
Water Supply Act for arsenic, cadmium, lead, mercury, and silver and above
established reference doses for copper, iron, lead, zinc, and cadmium. Also, prevent
ingestion of water containing arsenic concentrations that would cause risk greater than
one chance in 10,000.
¦ Inhibit the migration of tailings from the Mill-Willow Bypass to the Clark Fork River in
order to reduce the potential for future exceedances of ambient water quality standards
in the Clark Fork River.
¦ Inhibit the migration of tailings from the upper reaches of Silver Bow, Mill and Willow
creeks to the Clark Fork River in order to reduce the potential for re-contamination of
the Mill-Willow Bypass and future exceedances of ambient water quality standards in
the Clark Fork River.
¦ Reduce the potential for direct human contact, inhalation, and ingestion of exposed
tailings and contaminated soils and tailings posing excess cancer risks above one
chance in 10,000.
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Remedial Actions
¦ Reduce the levels of arsenic, cadmium, and other contaminant concentrations in the
groundwater of the Pond 1 area to achieve compliance with ground water performance
standards.
Major components of the selected remedy for the WSP Active OU are:
¦ Allow the ponds to remain in place; Ponds 3 and 2 will continue to function as
treatment ponds until upstream sources of contamination are cleaned up and standards
can be met without treatment.
¦ Raise and strengthen all pond berms according to specified criteria, which will protect
against dam failure in the event of major earthquakes or floods, and increase the
storage capacity of Pond 3 to receive and treat flows up to the 100- year flood.
¦ Construct new inlet and hydraulic structures to prevent debris from plugging the Pond
3 inlet and to safely route flows in excess of the 100-year flood around the ponds.
¦ Comprehensively upgrade the treatment capability of Ponds 2 and 3 to fully treat all
flows up to 3,300 cfs (100-year peak discharge) and construct spillways for routing
excess flood water into the bypass channel.
¦ Remove remaining tailings and contaminated soils from the Mill-Willow Bypass,
consolidate them over existing dry tailings and contaminated soils within the Pond 1
and Pond 3 berms and provide adequate cover material which will be revegetated.
¦ Reconstruct the Mill-Willow Bypass channel and armor the north-south berms of all
ponds to safely route flows up to 70,000 cfs (one half of the estimated probable
maximum flood).
¦ Flood (wet-close) all dry portions of Pond 2.
¦ Establish surface and ground water quality monitoring systems and perform all other
activities necessary to ensure compliance with all applicable or relevant and
appropriate requirements.
¦ Implement institutional controls to prevent future residential development, to prevent
swimming, and to prevent consumption of fish by humans.
¦ Defer, for not more than one year after the effective date of the ROD, decisions
concerning the remediation of contaminated soils, tailings, and groundwater in the area
below Pond 1, pending evaluation of various wet- and dry-closure alternatives and
public review.
The ESD (USEPA 1991) modified the initial ROD (USEPA 1990) for the Warm Springs
Ponds by dividing the original OU into two separate OUs. Components of the
remedy associated with Pond 1 and the area downstream of Pond 1 (the inactive
area), including the Pond 1 berms, the old Silver Bow Creek channel, and the
lowermost portion of the Mill-Willow bypass, were removed from the 1990 ROD for
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the Warm Springs Ponds. The ESD called for a separate and thorough evaluation of
remedial alternatives for the inactive area and a separate proposed plan and ROD for
the Warm Springs Ponds Inactive Area OU.
4.1.1.2 WSP Inactive Area OU
The overarching remedial action objectives for the Inactive Area OU were to
substantially reduce or eliminate risks to human health and the environment and
meet federal, state, and local laws. Media specific remedial action objectives were as
follows (USEPA 1992b):
¦ Prevent releases of pond bottom sediments during floods or earthquakes.
¦ Meet ambient water quality standards established pursuant to the Montana Water
Quality Act for arsenic, cadmium, lead, mercury, copper, iron, and zinc at a compliance
point just above the starting point of the Clark Fork River.
¦ Prevent ingestion of water above the Montana Public Water Supply Act's MCLs for
arsenic, cadmium, lead, mercury, and silver, and established reference doses for
copper, iron, lead, zinc, and cadmium.
¦ Prevent ingestion of water containing arsenic in concentrations that would cause
increased cancer risks greater than 1 in 10,000.
¦ Substantially reduce the potential for direct contact, inhalation, and ingestion of
exposed tailings and contaminated soils. This objective applied to both humans and
fish and wildlife.
¦ Reduce the levels of arsenic, cadmium, and other contaminant concentrations in the
groundwater within the Inactive Area to preclude off-site migration of water in excess
of Montana groundwater MCLs.
The WSP Inactive Area remedy may be summarized as follows:
¦ Remove all tailings and contaminated soils from the adjacent portion of the bypass
channel and from the area below Pond 1 not planned for wet-closure. Consolidate the
wastes over existing dry tailings within the western portion of Pond 1.
¦ Modify, or enlarge if necessary, the adjacent portion of the bypass channel to safely
route flood flows up to 70,000 cfs, which is one-half the estimated probable maximum
flood (PMF) for the combined flows of Silver Bow, Willow, and Mill creeks. Soils and
gravels that have copper concentrations below 500 mg/kg and meet geotechnical
requirements will be used for raising and strengthening the existing berms and
constructing new berms.
¦ Raise, strengthen, and armor with soil cement the north-south aspect of the Pond 1
berm. In accordance with specified state safety standards for high hazard dams and for
the protection of human health and the environment, the reconstructed berm must
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withstand the estimated maximum credible earthquake (MCE) for this area. In
addition, the reinforced berm must be constructed to withstand flood flows up to
70,000 cfs (0.5 PMF) in the enlarged bypass channel.
¦ Stabilize the east-west aspect of the Pond 1 berm. The reconstructed berm must
withstand a maximum credible earthquake for this area, thus protecting against the
movement of contained pond bottom sediments or tailings into the uncontaminated or
wet-closed areas below Pond 1 in accordance with specified state dam safety standards,
and for the protection of human health and the environment.
¦ Extend and armor the north-south aspect of the Pond 1 berm approximately 2,400 feet
in a north-northeasterly direction. This extended berm will be constructed to provide
maximum credible earthquake protection and the ability to withstand one-half the
estimated probable maximum flood (70,000 cfs) in the adjacent bypass channel.
¦ Relocate the lowermost portion of the bypass channel and convert the present channel
into a groundwater interception trench. The relatively straight reach of the bypass
channel, from the apex of the existing Pond 1 berm to the historic Silver Bow Creek
channel, will be relocated north of the extended berm. The entire reach of the bypass
channel that is adjacent to the inactive area will be reconstructed, reclaimed, and
restored to a more natural, meandering condition. Other excavated areas will be
reclaimed and restored to their natural condition.
¦ The converted groundwater interception trench will be deepened and pumps will be
installed to allow for a pump-back system. Intercepted water that fails to meet
specified standards will be pumped back to the active area for treatment. Monitoring
wells and surface water quality monitoring stations will be placed at strategic locations.
¦ Construct wet-closure berms to enclose the submerged and partially submerged
tailings and contaminated soils. Within the eastern portion of Pond 1 and along the
historic Silver Bow Creek channel below Pond 1, these smaller berms will create a
series of cells, which when flooded will vary in depth from a minimum of one foot to a
maximum of six feet.
¦ Chemically fix (immobilize) the tailings and contaminated soils, now enclosed by
smaller berms, by incorporating lime and lime slurry onto or into them.
¦ Flood the wet-closure cells with water adjusted to a pH greater than 8.5 and maintain
proper water surface elevations in the wet-closure cells.
¦ Cover the dry tailings and contaminated soils within the western portion of Pond 1
with two inches of limestone, 12 inches of fill, and six inches of a suitable soil cap. This
dry-closed area will be contoured to control runoff and seeded with native vegetation.
¦ Construct a runoff interception system along the east side of the inactive area. This
system will prevent floods originating in the eastern hills from entering the wet-closure
cells. It will be designed to intercept one-half the probable maximum flood, which is
estimated to be 8,500 cfs at its peak. A collection system or other engineered solution
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will be constructed to prevent excessive sediments from entering the Clark Fork River
immediately below.
¦ Install toe drains along the armored berms and construct a collection manifold for both
the active and inactive areas. The water collected will be pumped to the active area for
treatment if it exceeds final point discharge standards specified in Attachment 5 to the
WSP Active Area UAO.
¦ Implement long-term ecological monitoring. By means of an unbiased set of
measurements, this monitoring effort will concentrate on the effects of biological
systems living in contact with metals in the water and substrate of ponds and wetlands
environments. The results will validate or invalidate the decision to chemically fix,
wet-close and contain in place the exposed and submerged tailings and contaminated
soils.
¦ Implement ICs to prevent residential development, swimming, domestic well
construction, and disruption of dry-closure caps.
4.1.2 Remedy Implementation
Response actions were conducted by Atlantic Richfield under extensive EPA
enforcement from July 1990 through September 1995. Beginning with the Mill-Willow
Bypass ERA in 1990 and 1991, and continuing through remedial action construction
for both the active and inactive areas in 1992 through 1995, EPA has determined that
Atlantic Richfield has met all remedial action construction requirements that were set
forth in the two RODs (1990 and 1992) and three administrative orders ((Mill-Willow
Bypass Removal Action -1990, Active Area Remedial Action - 1991, and Inactive Area
Remedial Action -1993).
4.1.3 Remedy O&M
The WSP OU is a series of ponds and wet closures that serve as settling and treatment
facilities, removing suspended particles from the influent water prior to discharge
back to the natural stream system. Influent flows from Silver Bow Creek enter the
WSP OU at the inlet structure where pH is adjusted by lime addition as required to
maintain a target pH of 9.2 to 9.5 at monitoring point SS2. Flow passes from the inlet
structure through Pond 3 and into Pond 2 with a portion being diverted through the
Wildlife Ponds and Pond 2 wet closures, which both discharge back into Pond 2.
These discharges are combined with all flows prior to discharge from the outlet
structure of the treatment ponds. The Mill-Willow bypass routes the flows of both
Mill and Willow Creeks and any seasonal flows in excess of the Silver Bow Creek inlet
channel capacity around the WSP system in a reconfigured meandering channel.
The WSP OU has a noxious weed control program to control noxious weed through
the site and through the Mill-Willow bypass. Routine clearing of debris on the trash
rack prevents overflow events of untreated water into the Mill-Willow bypass.
Mixing of the lime with the influent flow is facilitated by the installed baffles at the
inlet channel and the meandering stream channel that flows from the inlet into Pond
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3. Hydraulic controls are used to control the retention time required for maximum
settling and treatment in both Ponds 2 and 3.
4.2 Rocker OU
4.2.1 Remedy Selection
The primary objective of the groundwater portion of the remedy for the Rocker OU
was to prevent further contamination of high quality groundwater resources in
contact with the plume of arsenic-contaminated water. Included in this objective was
the goal of returning the groundwater resource to the community at the earliest
opportunity to allow further development. A second long-term objective is to reduce
arsenic concentrations within the area of the arsenic plume to levels suitable for
drinking water.
The primary objective of the soil treatment portion of the Rocker OU remedy was to
prevent further releases of arsenic into the groundwater or into Silver Bow Creek. The
soil remedy is also designed to prevent human health risks for occupational use and
to remove contaminated materials from contact with the groundwater or the stream
and store them long-term in a repository.
The remedy for the Rocker OU is summarized as follows:
¦ Excavate and treat contaminated soils above 1,000 ppm arsenic.
¦ Dispose of treated soils in an on-site repository.
¦ Cover arsenic-contaminated soils ranging from 380 ppm to 1,000 ppm remaining on site
with 18 inches of clean soil and revegetate.
¦ Treat contaminated groundwater and rely on natural attenuation to achieve cleanup
standards.
¦ Construct an expanded capacity water supply system for the community.
¦ Monitor and demonstrate that the requirements of the ROD have been met. Return the
groundwater resource to the community, and provide operation and maintenance of
the repository and soil covers.
¦ Implement institutional controls to ensure non-residential use of the OU, and prevent
domestic groundwater use until cleanup is achieved.
The ROD for the Rocker OU recognized that achieving the arsenic concentrations
acceptable for drinking water within the area of the arsenic plume was a goal that
could take several years to achieve. Further development of groundwater resources
was restricted (via a well ban) to prevent migration of the contaminated groundwater
into the deeper, high quality groundwater systems in the area. The ROD stated that
when it can be verified that the arsenic plume has been controlled sufficiently to
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prevent the threat of further migration, the restrictions on groundwater development
will be lifted for some of the aquifers.
4.2.2 Remedy Implementation
Final remedial design for Rocker began in spring 1996 under EPA order. The project
team developed the ferrous iron and lime/pH adjustment groundwater treatment
process called for in the ROD through bench-scale tests, and produced greater
removal of arsenic from the groundwater than expected. The ROD prescribed a
process predicted to reduce arsenic concentrations to approximately 2,000 (ig/L.
With the developed process, groundwater arsenic concentrations could be reduced to
about 30 (ig/L.
In fall 1996, pilot-scale groundwater and soil treatments were tested. In the field,
1,230 cy of contaminated soil were excavated from the "hot-zone" of the site and were
treated in a pug mill (an industrial mixer) with iron sulfate and lime amendments.
Groundwater exposed in the open excavation trench was treated with iron sulfate,
lime, and potassium permanganate. The reduction in arsenic concentration following
field-scale groundwater treatment was the same as achieved during bench-scale
experiments. Soil treatment had similar success, resulting in arsenic concentrations
that were at least ten times lower than necessary to meet regulatory requirements for
disposal. This work set the stage for completing the design for the full-scale remedy.
After completing the design of the remedy in March 1997, groundwater and soil
treatment was initiated and completed in the period from April through October
1997. To facilitate the cleanup at the site, the contaminated materials were divided
into two separate treatment actions: 1) soil and debris excavation and treatment in an
aboveground treatment plant; and 2) in-place treatment of contaminated groundwater
in open trenches. Final disposition of the treated soil materials is in an on-site
repository.
Soils contaminated with arsenic above 1,000 ppm were excavated to a depth of five
feet below the seasonally low groundwater level and treated in a pug mill with iron
sulfate and lime amendments. The iron and lime chemically fix (immobilize) the
arsenic to levels below that necessary to allow disposal on-site, as defined by a testing
procedure called Toxicity Characteristic Leaching Procedure (TCLP).
Groundwater contaminated with arsenic above 1,000 (ig/1 was treated in open
excavation trenches using iron sulfate, lime, and potassium permanganate
amendments. These amendments were added to precipitate arsenic from the water
and reduce the amount of arsenic in water to levels approaching the state water
quality standard of 18 (ig/L.
Based on the final design, the remedy was implemented over a little more than two
acres. The total amount of contaminated soils (both above and below the
groundwater table) was estimated at 48,000 cy. The excavation of the contaminated
soils started at the west end of the site and a series of north-south running trenches
were excavated to a depth of five feet below the seasonally low groundwater level.
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The soil removed from each strip was stockpiled above ground, sampled for arsenic
content, and subsequently treated in the pug mill with iron sulfate and lime
amendments in amounts proportional to the arsenic concentration in the soil. Soil
samples were collected at 10,000 ton intervals and analyzed using TCLP methods to
verify the effectiveness of the treatment process.
The groundwater exposed in the open excavation was treated in a two-step process.
The first step involved adding pre-determined amounts of iron sulfate and lime
directly to the water surface and mixing the water in the excavated strip (using an
excavator bucket) to ensure uniform concentrations of the amendments in the water.
The second step involved adding a pre-determined amount of potassium
permanganate to the water and mixing. Water samples were collected before and
after treatment to verify the success of the operation.
4.2.2.1 Implementation Problems and Subsequent changes to Remedy
During remedy implementation, two areas of contamination were identified that had
not been included in the remedy design. Groundwater contamination on the south
side of the site within the Rocker rail siding was treated with ferrous iron though a
groundwater injection trench. An infiltration gallery was left in place in the event that
groundwater needs to be re-dosed in this area. A second area of soil contamination
was identified in the floodplain of Silver Bow Creek. These materials were excavated,
treated, and stored in the on-site repository.
Based on TCLP analysis, soils exhibiting 5 milligrams per liter (mg/L) or greater
leachable arsenic are characterized as hazardous wastes. According to the ROD for
the Rocker site, soils exhibiting total arsenic concentrations above 1,000 ppm were to
be treated with iron sulfate and lime amendments. The actual total arsenic
concentrations were found to vary between several hundred to several thousand ppm
at the Rocker OU. After treatment, the average value of TCLP results for the entire
project was below 0.30 mg/L leachable arsenic (well below the 5 mg/L requirement
for a hazardous waste). Only one TCLP result was greater that 1.0 mg/L leachable
arsenic. The next highest TCLP value was 0.27 mg/L leachable arsenic.
From data gathered for the risk assessment, EPA determined that the Rocker site
overlies three aquifers that are hydraulic ally connected to each other. Of the three,
only the shallow alluvial aquifer was determined to be contaminated with arsenic.
Neither the deep alluvial aquifer nor the underlying Tertiary aquifer were found to be
impacted by the arsenic contamination at the site. However, because of the hydraulic
connections between the contaminated shallow alluvial aquifer and the underlying
aquifers, concerns were raised by EPA and citizens of Rocker about potential
migration of the contamination into the deeper aquifer systems.
The Montana DEQ instituted a groundwater control area (well ban) to protect the
aquifers from potential contamination. The ban restricted the development of new
wells within a Vi -mile radius of the Rocker site. The ROD called for an alternate
water supply for the Rocker community to ensure that further groundwater use did
not occur. Concurrent with the cleanup at the Rocker site, approximately 2 V2 miles of
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new water main was constructed from the existing Butte-Silver Bow County water
supply line to the community of Rocker. A 300,000-gallon water supply reservoir was
also constructed to provide constant flows during periods of peak water usage.
4.2.3 Remedy Operations and Maintenance
Quarterly O&M activities began in 1998. The specific objectives of the Rocker OU
quarterly groundwater monitoring program are as follows:
¦ Confirm treatment results and track groundwater quality trends
¦ Document the long-term efficacy of the iron/lime/oxidant groundwater treatment
process carried out in 1997
¦ Document potential migration of the arsenic plume
¦ To document that nearby public and domestic water supplies remain unaffected by the
Rocker arsenic plume
¦ Document changes in water table elevation and flow patterns following excavation and
treatment of the shallow alluvial hydrostratigraphic unit
¦ Monitor compliance with groundwater performance standards
During remedy implementation, a total of seven wells were constructed within the
remediation footprint as treated source materials were backfilled into excavated areas;
thus, those wells (RH-60 through RH-66) were designated as interior "gravel wells"
because their screened intervals were within the treated groundwater that was
backfilled with clean gravel. The groundwater monitoring network also includes
exterior and contingency (i.e., point-of-compliance) wells screened in each of the three
aquifer zones. A summary of the O&M wells sampled for groundwater quality is
provided in Table 4-1.
In general, the same tasks are performed during each quarterly sampling event. On
the first day of an event, the water level in all site monitoring wells and staff gages in
Silver Bow Creek are measured. Subsequently, the three private wells and 31
monitoring wells are sampled. Analytical parameters include 12 dissolved metals, 3
anions, and total dissolved solids. Field parameters measured include temperature,
pH, conductivity, redox potential, and dissolved oxygen. Field parameters are also
measured in Silver Bow Creek once during each event. Contingency wells located
outside the arsenic plume are used to monitor compliance and to determine if and
when it may be appropriate, using statistical methodologies, to initiate contingency
remedy actions. Provisions within statistical evaluation and implementation plan are
designed to objectively identify any expansion of the spatial distribution of the arsenic
groundwater plume.
An annual qualitative inspection of general site conditions is also performed,
including uniformity of vegetation cover, presence of bare areas, identification of
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noxious weed infestations, location of erosive areas, condition of ditches, damage due
to trespassing, etc. Qualitative recommendations are made based on the overall
condition of individual components (e.g., vegetation, erosion, security, channels, etc.)
of the reclaimed area.
4.3 Butte Mine Flooding OU
4.3.1 Remedy Selection
The overall remedial action objectives established for the BMF OU in the September
1994 ROD is:
¦ To prevent human and aquatic exposure to contaminated groundwater and surface
water.
This overall objective will be met by accomplishing the following remedial action
objectives:
¦ Ensuring that the critical water levels (CWLs)in the Berkeley Pit System (5,410 feet)
and the West Camp System (5,435 feet) are not exceeded so that contaminated mine
water is contained and does not discharge to the alluvial aquifer or into Silver Bow
Creek.
¦ Ensuring that treated water discharged to the Silver Bow Creek drainage meets State of
Montana and other pertinent water quality standards.
¦ Implementing institutional controls on the public's access to contaminated bedrock
aquifer water to ensure the protection of public health.
¦ Implementing a comprehensive monitoring program to verify the protectiveness of the
critical water levels and to ensure that the contaminated water is being contained.
The selected remedy for the Butte Mine Flooding OU is summarized below:
¦ All surface water from the Horseshoe Bend area is intercepted and treated using a high
density lime precipitation treatment system. This treated water is either recycled back
into the Montana Resources mining operations or discharged into Silver Bow Creek
¦ The water level in the Berkeley Pit system is kept below the CWL (5,410 feet) through
pumping, treatment, and discharge to Silver Bow Creek (or used for some other
beneficial uses).
¦ The Butte Mine Flooding OU monitoring plan tracks the elevations and quality of
water inflows into the Berkeley Pit and West Camp Systems against the CWL for both
the Pit and the West Camp. This information is updated annually and used in models
of the Berkeley Pit and West Camp to provide EPA and DEQ with a projected date at
which the CWLs will be met. The effectiveness of this monitoring plan is reviewed
every 3 years by both EPA and MDEQ.
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¦ Produce a focused feasibility study 24 months prior to mine closure or before the
Berkeley Pit reaches the CWL. At that time, EPA will evaluate all existing and
emerging technologies to provide EPA with information to select a final treatment
technology for the Berkeley Pit water prior to discharge of this water into Silver Bow
Creek. This treatment technology will treat the Berkeley Pit water to the State of
Montana and other pertinent water quality standards.
¦ Institute a long-term, comprehensive monitoring program.
¦ Implement an institutional control program to restrict use of contaminated
groundwater. Create and implement a public education program to inform the public
on the progress of the Mine Flooding project.
An ESD (USEPA 2002) modifies the selected remedy ROD in the following ways:
¦ It adds more stringent contaminant requirements for the water discharge from the
treatment plant. The cadmium (Cd) standard was the most important standard made
more stringent by the ESD because of a post-ROD change in water quality standards by
the State of Montana.
¦ It acknowledges DEQ's primary responsibility for the active mine area and the Yankee
Doodle Tailings Pond and EPA's responsibility for the sludge repository.
¦ It acknowledges EPA's prior decision to send West Camp contaminated water into the
BPS OU as long as it can be handled effectively there.
¦ It notes that a full feasibility study level examination of different treatment options for
the mine flooding water is no longer required.
¦ It allows storm water from uptown Butte to be diverted to the Berkeley Pit and sludge
from the Horseshoe Bend treatment plant to go to Berkeley Pit.
4.3.2 Remedy Implementation
On April 15,1996, the PRPs instituted the inflow control program by capturing and
integrating the Horseshoe Bend discharge into the mining process at the MR Mine.
However, a hiatus in MR mining operation from July 2000 to September 2003
triggered construction of a water treatment facility for the Horseshoe Bend discharge.
At the time of this 5 year review, the Horseshoe Bend water treatment plant (HSB
WTP) is completed, but it is discharging to the resumed MR Mine operations and will
not discharge into Silver Bow Creek in the near future.
Treatment of West Camp waters at Butte Metro Sewage Treatment Plant terminated
in 2002 in favor of treatment at LAO treatment lagoons. In the 2002 ESD, the
requirement to conduct a focused feasibility study to determine the best treatment
technology was changed instead to evaluate if the existing HSB WTP can treat the
combined HSB and Berkeley Pit flows. This evaluation must be completed four years
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prior to reaching the CWL. Any necessary upgrades to the WTP must be competed
two years prior to the CWL.
4.3.3 Remedy O&M Maintenance
The HSB WTP is the only completed component of the remedy for the BMF OU at this
time. Therefore, the O&M for the Mine Flooding OU remedy presented in this five
year review will only discuss the HSB WTP at this time. In subsequent five year
reviews, O&M of other portions of the remedy for the Mine flooding OU will be
discussed as they are completed.
The HSB WTP uses lime precipitation for metals removal. It is a fully automated
facility with remote alarm indication. The HSB WTP utilizes a high density sludge
(HDS) process, recycling a slip stream of sludge to the front end of the treatment
process. This HDS recycle helps improve the efficiency of the lime precipitation step
while minimizing sludge blowdown.
The HSB WTP has both an influent equalization basin minimizing influent variations
and an effluent lagoon controlling effluent discharge and providing a final polishing
step. The major treatment components of the WTP such as lime feed, influent pumps,
effluent pumps, aeration blowers, polymer feed pumps and clarification stages have
completely redundant systems to eliminate downtime due to equipment failure.
Major tanks in the WTP process were constructed of concrete to provide longevity.
The WTP is also equipped with an automated effluent control loop. If effluent
exceeds the acceptable pH range, this system will automatically send water to
Berkeley Pit rather than discharge into the Silver Bow Creek.
The HSB WTP uses aeration to enhance sludge stability, as ferric sludge is more stable
than ferrous. The WTP was designed with operational flexibility provided by variable
frequency drives on influent, effluent, and sludge pumps that can vary influent rates
to the plant. This "turn-down" capacity also reduces power consumption at lower
flows to the WTP.
The annual system O&M costs are presented in Table 4-2.
4.3.3.1 Implementation Problems and Subsequent changes to Remedy
The HSB WTP experienced problems with the lime slaking system during start-up.
While the system has a slaking capacity of 8,000 lbs/ hour, the start up slaking needs
were only 8% to 12% of capacity, making slaker operations difficult. Modifications to
the spray nozzles, lime addition valves and the PID logic control loop solved this
problem. However, no changes in the remedy as defined in the ROD for the BMF OU
were required.
Ongoing problems with several WTP systems are described below.
Blowers
The blowers providing low pressure air to the reactors were recalled by the factory for
a bearing modification. The air flow meters for these blowers were sent back for
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recalibration to the correct pipe diameter then relocated to a more ideal flow
measurement location. The No. 2 blower failed in October 2004. This failure was
believed to be a result of operating the blowers at the lower end of the performance
curve resulting in a surging problem. This is a result of the air capacity of the reactors
being significantly lower than the maxim operating capacity of the blowers. An
engineered solution to this problem is being investigated.
Lime Unloading
The lime unloading system is not operating at the design specified capacity of 1,000
pounds/minute. Currently the actual unloading rates are 30% to 40% of the design
rate. The lime unloading equipment supplier is currently looking at design options
and system modifications to reach the desired unloading rate.
Clarifier Rake
The number two clarifier stalled out on high torque in December 2003. Numerous
factors contributed to this incident, which were resolved by re-labeling the polymer
lines, redesigning the feed well inlet, repairing a rubbing problem on the feed well, re-
leveling the rake mechanism, and replacing the bearings in the rake lift assembly.
However, some rake torque issues in both the No. 1 and No. 2 clarifiers still exist.
Solutions for these problems are being investigated at this time.
In December 2004 the sludge pump in the No. 1 clarifier failed electrically. The spare
pump was installed and a similar replacement pump ordered. Upon examination of
the pump, the root cause of the failure was corrosion of the materials of construction
eventually resulting in a motor seal failure. Currently the materials of construction are
being reviewed by the plant designer to determine the correct materials of
construction.
4.4 Streamside Tailings OU
4.4.1 Remedy Selection
As stated in the ROD (DEQ 1995a), the final remedial action objectives and final
remediation standards for surface water, tailings and impacted soils, railroad
materials, groundwater, and air resources in the SST OU are listed below.
¦ Meet the more restrictive of the aquatic life or human health standards for surface
water identified in DEQ Circular WQB-7, through application of I-classification
requirements.
¦ Prevent exposure of humans and aquatic species to in-stream sediments having
concentrations of inorganic contamination in excess of risk-based standards. A
physical criterion is used to define those sediments posing the greatest risk to receptor
species. A contingency is established to develop metal-specific concentrations which
would be risk-based, and allow sediment cleanup standards if the physical criterion
standard cannot be employed appropriately.
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¦ Provided that upstream sources of Silver Bow Creek contaminants are eliminated,
meeting the two remediation standards identified above should attain the remedial
action objective to improve the quality of Silver Bow Creek's surface water and in-
stream sediments to the point that Silver Bow Creek could support the growth and
propagation of fishes and associated aquatic life, one of the designated goals for an I-
class stream, including a self sustaining population of trout species.
¦ Prevent human exposure to tailings/impacted soils from residential or occupational
activity within the SST OU. This will be accomplished, in part, through ICs that will
require the entire OU to be developed into a recreational corridor.
¦ Prevent erosion or migration of inorganic contaminants of concern in tailings/ impacted
soils into Silver Bow Creek or into groundwater that would prevent attainment of
groundwater, surface water, and sediment remediation levels.
¦ Protect all solid waste within the SST OU from flood displacement, washout or erosion
in accordance with applicable or relevant and appropriate requirements (ARARs).
¦ Prevent the situation of tailings/ impacted soils by groundwater during any period of
the hydrologic year or by bank storage of high-flow stream discharge.
¦ Prevent exposure by recreational users of the railroad beds in excess if acceptable
cancer and non-cancer risks from arsenic. Risks will be adequately reduced by removal
of ore concentrate spills and other impacted railroad materials exhibiting arsenic
concentrations in excess of 2,000 milligrams per kilogram (mg/kg).
¦ Prevent erosion of contaminated railroad bed materials into Silver Bow Creek to the
degree that surface water standards would be exceeded, or in-stream sediments would
be contaminated, or vegetation on adjacent relocation or Streambank Tailings and
Revegetation Study (STARS) treated areas would be adversely impacted.
¦ Attain compliance with applicable DEQ Circular WQB-7 standards, federal MCLs and
federal non-zero maximum contaminant level goals (MCLGs) for all OU groundwater.
¦ Prevent discharge of groundwater that would prevent attainment of Silver Bow Creek
ambient Circular WQB-7 standards or in-stream sediment remediation goals.
¦ Compliance with air ARARs within or adjacent to the SST OU during implementation
of the remedial action.
The major components of the remedy selected for the SST OU are (USEPA 2000):
¦ Removal of tailings/impacted soils from the floodplain where (a) they are saturated by
groundwater; (b) in-place treatment would not be effective due to thickness of tailings
or lack of buffer material between the tailings and groundwater, or (3) treated
tailings/impacted soils could be eroded into Silver Bow Creek. Excavated
tailings/impacted soils will be placed in mine waste relocation repositories outside of
the floodplain, or transported to the Opportunity Ponds disposal area.
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¦ Fine-grained in-stream sediments located in depositional areas are to be removed and
placed in repositories with the excavated tailings/impacted soils. After removal of
contaminated in-stream sediments, the channel bed and streambank will be
reconstructed.
¦ All contaminated railroad materials that pose a risk to human health or the
environment will be excavated, treated, and/ or capped. Excavated railroad materials
will be placed in the repositories.
¦ No separate remedial action is planned for groundwater or surface water. Remedial
activities for SST OU tailings/impacted soils and for sources of contaminants upstream
or offsite under other cleanup actions are expected to reduce contaminant releases to
groundwater and surface water with the goal of ultimately attaining State water quality
standards.
¦ The ROD called for an institutional controls program which will be coordinated
through a joint effort of the Butte-Silver Bow and Anaconda-Deer Lodge local
governments.
The ESD presented the following nine changes from the remedy described in the ROD
(DEQ 1998):
¦ An increase in the volume of tailings/ impacted soil in the SST OU.
¦ Modifications to the alignment of Silver Bow Creek and the channel profile (i.e.
elevation profile).
¦ Use of a temporary stream diversion during and after construction to facilitate
dewatering and excavation of near-stream tailings and to enhance floodplain and
streambank revegetation efforts.
¦ Changes in the criteria for in-stream sediment removal as a result of other design
changes.
¦ Modifications to the mine waste relocation repository design.
¦ The inclusion of sediment basins to contain contaminated overland flow run-on from
off-site mine waste sources.
¦ Elimination of treatment wetlands as the end land use in Subarea 1.
¦ Changes in the estimated schedule to implement the SST OU remedy.
¦ An increase in the estimated cost of the SST OU remedy.
4.4.2 Remedy O&M
The only O&M activities established under the ROD for the SST OU was a permanent
monitoring, management, and maintenance of reclaimed areas and onsite
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repositories. This monitoring, management and maintenance will address vegetative
performance on both STARS treatment areas, onsite repositories, remediated
stream banks, streambank stability, and channel meander. It will also address
instream sediment sampling for both contaminant concentrations and
macroinvertebrate abundance and diversity. Repairs to areas damaged or eroded over
time will be completed on an as needed basis. Vadose zone, saturated zone, and
overland flow monitoring will ensure that the metals are immobilized in all in situ
remediated areas in the SST OU.
4.4.3 Remedy Implementation
Construction to implement the remedy was initiated in 1999 involving removal of
streamside tailings and stream channel reconstruction. At the time of this five-year
review, construction and revegetation has been completed for Subarea 1 (Reaches A-
E) and Subarea 4 (Reach R, parcel 152). Construction is completed for Reach F of
Subarea 2 and is beginning for Reach G. Of the 1,400 acres of contaminated tailings
and soils alongside Silver Bow Creek, approximately 200 acres of tailings impacted
area have been remediated. Over 874,000 cubic yards of tailings have been removed
from the floodplain. Cleanup is scheduled to be completed sometime between 2011
and 2013.
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Section 5 Progress Since Last Review
This section discusses the performance of the remedies at the Warm Springs Ponds
OUs and the Rocker OU since they are complete and functioning.
5.1 Evaluation of Warm Springs Ponds OUs
To simplify the discussion of the WSP OUs, the performance of the WSP Active and
Inactive OUs will be discussed concurrently. No major new actions have been
conducted at the WSP OUs during the 2000 to 2004 time period, hence, the "progress"
consists of operation and maintenance of the WSP treatment system. This section will
present the performance of the WSP OUs with respect to performance standards
during this last review period.
5.1.1 Previous Statement on Protectiveness
From the first five-year review in 2000, the following statements were made regarding
the protectiveness of the WSP Inactive and Active OUs:
The WSP effectively remove or reduce acutely toxic concentrations of metals that enter
the treatment system from Silver Bow Creek. Whereas Silver Bow Creek above the
ponds supports absolutely no fish population and is severely impaired in respect to
invertebrate and periphyton (algal) community structure, the aquatic environment
immediately below the WSP supports healthy populations of trout, good biological
integrity for periphyton, and biological integrity for invertebrates that has progressed
from severely impaired to slightly impaired just within the past few years since
cleanup efforts were initiated. The pond system has become a safety net for the Clark
Fork River.
Fish kills within and below the Mill-Willow bypass, which occurred frequently during
the 1970s and 1980s, are today a thing of the past because of implementation of the
WSP response actions. Several acute toxicity tests conducted within the past few
years, involving sensitive trout fry, yielded "no effects" concentrations or LC 10
concentrations of dissolved copper that are significantly higher than concentrations of
copper to which aquatic receptors living below the ponds are subjected. EPA deems
the remedy to be protective in terms of substantially reducing—quite possibly
eliminating—the threat of acute lethality to fish.
With regard to chronic effects, the weight of evidence for fish indicates that an
intermittent low-level of stress may be occurring below the Ponds, and the most
plausible manifestation of this stress is slightly reduced body mass. It is unlikely that
such chronic stress results in mortality. The weight of evidence for invertebrate and
possibly periphyton community structure measures indicate to EPA that impacts
persist. These impacts, though subtle and apparently steadily being reduced, originate
from Silver Bow Creek above the pond system: Despite the effective manner that
dissolved and particulate-bound metals are removed within this treatment system, a
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low level of chronic, less-than-lethal stress persists. The presence of this continued risk
emphasizes the need to fully meet performance standards in order to ensure full
protectiveness. EPA will continue to monitor the Ponds and progress on upstream
cleanups to ensure that this happens. EPA also notes that DEQ rejected ARCO's
petition to change these standards, and that ARCO's challenge to these standards has
been stayed. EPA fully supports the State's position on these matters.
In light of the current and long-standing status of severe contamination in Silver Bow
Creek above the ponds, and in light of the rapid degradation of water quality that
occurs in the upper Clark Fork River, beginning within a few miles downstream of the
WSP and continuing for about 40 miles, any attempt to eliminate chronic threats that
persist immediately below the ponds through modification of the WSP system would
produce virtually no change in protectiveness for the river in the Deer Lodge valley.
The WSP response actions were designed to provide the maximum reasonable degree of
compliance and protectiveness. But, they were also designed and constructed with the
expectation that a cleanup of Silver Bow Creek would follow close behind. Then, in
turn, the upper Clark Fork River cleanup was expected to follow closely on the heels of
the Silver Bow Creek cleanup. EPA believes there are limits on the degree of
protectiveness which each operable unit cleanup can, by itself, provide for the aquatic
life of the upper basin. The level of protectiveness provided by the three response
actions for the WSP reviewed here has been shown to be both effective and reasonable.
While a high degree of protectiveness has been achieved, an even higher degree of
protectiveness is achievable. But, such a higher degree of protectiveness for the river
can be attained only after all remaining operable units along this continuum of stream
environments have been cleaned up and are functioning as a whole.
EPA has determined that the WSP response actions have been constructed and are
being operated and maintained in a manner that is as protective as is reasonably
possible in the context of a Superfund complex with multiple operable units and
critical, unfinished work both upstream and downstream. Continued long-term
operations and maintenance, coupled with annual dam safety inspections, required
water quality monitoring and biological monitoring, will assure that maximum
reasonable protectiveness and effectiveness are maintained until the response actions
for Silver Bow Creek and the upper Clark Fork River are completed and have
undergone post-construction healing. At that point, full protectiveness and
performance standard compliance will be achieved.
5.1.2 Significant Events
The following provides a brief summary of some of the more significant events that
have taken place during the report period from January 1, 2000 through December 31,
2004. The events listed involve the Active Area of the WSP system and may have
directly or indirectly affected pond water quality. Figure 5-1 presents an overview of
the WSP site and indicates Active Area OU sampling locations.
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¦ Entire review period: Montana, including the Upper Clark Fork River drainage basin,
is experiencing a significant and prolonged drought, causing decreased influent and
effluent flows to and from the WSP system.
¦ Biomonitoring investigations completed to evaluate ecological performance of the WSP
System and the MWB. Investigations were conducted in the WSP in 1998-2000 and in
2003. Spawning surveys conducted in MWB in and 2001, and detailed biomonitoring
was conducted in 2000.
¦ 2002: The Cook Creek sedimentation basin (upgradient of Pond 1) was cleaned and
deepened to reduce storm water inputs into Pond 1.
¦ 2002: A geotextile and soil cap was added to portions of the west Pond 3 dike to create
a better habitat for vegetation and improve the appearance of the dike.
¦ March 14, 2003: The overflow spillway upstream of the inlet structure leading into the
WSP was overtopped for a short period of time due to rapid debris accumulation on
the trash rack at the WSP inlet (associated with the high-flow runoff event).
Subsequent environmental investigations indicated no environmental damage
associated with this overflow. However, because EPA and DEQ were not notified
within 24 hours of the overflow event, a Notice of Violation (of the reporting
requirements) was issued. This event will be discussed in more detail in Section 5.4
5.1.3 Facility Operations and Activities
The primary processes involved in the WSP system are two-fold:
¦ Hydrated lime is added to the influent stream (Silver Bow Creek) to raise the pH to the
target level of 9.2 to 9.5 at Station SS-2. This is the first step toward maximizing the
chemical and physical changes that cause dissolved metals to become solids and begin
settling out (precipitation).
¦ The WSP are both a treatment and settling facility. The addition of large volumes of
lime at the inlet initiates the alkaline precipitation processes. But, adequate retention
time (approximately 21 days) and a final "polishing action" (principally in Pond 2 by
algae) are also needed to reduce metal concentrations to acceptable levels prior to
discharge back into the natural stream system below.
Reducing dissolved copper and zinc is the system's greatest challenge for protection
of aquatic life. The dissolved copper and zinc entering the pond system from Silver
Bow Creek are almost always acutely toxic. Solubilities of these metals are minimized
in the targeted pH range of 9.2 to 9.5. Settling of the metal oxide/hydroxide
precipitates is facilitated by the large volume of water in the WSP system.
The opportunities for controlling these processes generally involve two operations or
activities. First, the quantity of lime added to the influent stream can be adjusted.
When lime is added to Silver Bow Creek, mixing is facilitated by installed baffles at
the inlet channel and by the meandering stream channel that flows into Pond 3.
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Second, hydraulic controls can be altered so that the water surface elevations (and
subsequent volumes) of Ponds 3 and 2 are raised or lowered. Water flows can also be
routed differently between or around the ponds and wet closures. The hydraulic
controls are applied to create an environment that promotes maximum sedimentation
of suspended particles in Pond 3. The wet closures and Pond 2 provide additional
sedimentation and treatment polishing. During periods of increased suspended
particle loads, the sedimentation process can be prolonged by using the hydraulic
controls to increase pond volumes and retention times.
5.1.3.1 Lime Addition
As previously discussed, hydrated lime is added to the influent stream (SS-1) to a
target level between 9.2 and 9.5 as measured at SS-2. During the report period, the
typical lime dosage rate was 35 mg/L during the time when lime was being added.
During high flow/high turbidity influent conditions, the lime dosage rate is increased
to ensure sufficient lime addition to maximize treatment of metals, and subsequent
settling of metal oxides and hydroxides.
5.1.3.2 Hydraulic Controls
Flows from Silver Bow Creek enter the WSP system at the inlet structure where the
pH is adjusted by lime addition. Flow passes through Pond 3 and Pond 2 with a
portion being diverted through the Wildlife Ponds and Pond 2 wet closures. The
Wildlife Ponds and wet closures discharge back into Pond 2 where all flows are
combined prior to discharge from the outlet structure. Flows from Mill and Willow
Creeks are diverted into the MWB above the inlet structure. Other system flows
include the effluent from the Inactive Area Pumpback Station which pumps water
from the Ground Water Interception Trench back to Pond 2. In addition, a small flow
is maintained from Pond 2 into Pond 1 of the Inactive Area, which is subsequently
returned to Pond 2 as part of the pumpback discharge. A general flow schematic for
the Active Area is provided in Figure 5-2.
Flows entering the system vary greatly. Figure 5-3 illustrates the daily flow rates
measured at SS-1 and SS-5. Monthly average flow measurements are presented in
Figure 5-4. Increased flow periods each spring/early summer correspond to seasonal
runoff. Increased flows are also observed after isolated precipitation events.
Low discharge rates at SS-5 occur primarily during summer and fall months when
influent flows are lower in order to increase the residence time (and sedimentation
time) in the ponds.
Although flow patterns can be changed within the pond system, the main control on
flow detention is the fluctuation of Pond 3 elevation. Pond 2 elevations have
remained relatively constant since being filled in 1993 (Figure 5-5), ranging from
about 4,835 to 4,836 feet. Pond 3 elevations vary depending on seasonal flows, and
ranged from about 4,868 feet to 4,871 feet (target elevation is 4,870 feet, which
minimizes sediment resuspension from previously flooded areas). High or low spikes
in data are considered to be instrumentation error.
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Pond 3 levels vary based on climatic conditions (Figure 5-6). In years when there is
high snowpack, Pond 3 levels are kept low through the winter and spring so as to be
able to accommodate high inflow runoff events. During drier years, levels in Pond 3
are maintained at somewhat higher levels in order to maintain flow through the
system and maintain habitat for aquatic life.
5.1.4 March 2003 Overflow Event
The following information is summarized from information provided by EPA from
the Administrative Record project files and from Atlantic Richfield's summary of the
event.
A high flow event occurred in Silver Bow Creek from March 12 through 13, 2003.
This high flow event occurred over the course of approximately 72 hours on Silver
Bow Creek beginning around 6:00 PM on March 12, 2003 and then subsiding during
the afternoon of March 15, 2003. The overall event was characterized by three
separate diurnal peak flow events caused by surface runoff of melting snow in the
upgradient Silver Bow Creek drainage basin.
These high flows resulted in a large amount of debris being washed down Silver Bow
Creek and collecting on the trash rack inlet at SS-1. EPA and USGS also found
evidence that debris jams upstream of the ponds (three upstream bridges) broke loose
all at once leading to a sudden blocking of the trash rack or a sudden pulse of high
water. During the late evening and early morning of March 13-14, 2003, either or both
of these events (backed up water due to a clogged trash rack or a sudden pulse of
high water when the debris jams broke apart) led to overflow of Silver Bow Creek
water over the Approach Channel Overflow Spillway (the Overflow Spillway)
upstream of the WSP inlet.
The overflow occurred at a flow rate less than the expected high flow rate due to the
way water was blocked and backed up by the debris. Atlantic Richfield noted that the
"high level alarm" notified the operator who cleared debris from the trash rack
several times on March 12 and 13. However, this same "high level alarm" did not
sound during the night of March 13-14 when the overflow occurred. The operator
discovered substantial blockage of the trash rack the morning of March 14 and
evidence that water had recently passed over the overflow spillway. However, the
high water level had since subsided. The trash rack was cleaned several times during
the next few days.
Several meetings were held over the next month or so among Agency and Atlantic
Richfield representatives to determine the cause and magnitude of the overflow event
and to ascertain the potential ecological damage that may have occurred as a result of
the overflow. Silver Bow Creek carries high concentrations of metals such as copper
and zinc, to which aquatic life are sensitive. Concentrations in the overflow were
estimated based on concentrations in Silver Bow Creek water. However, the actual
flow rates in Mill and Willow Creeks, along with an unknown amount of water that
flowed over the spillway made it difficult to estimate the resulting concentrations in
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the Mill-Willow Bypass. A rapid bioassessment of macroinvertebrate populations
above and below the overflow was conducted by McGuire on April 1, 2003. This
assessment concluded that:
¦ Macroinvertebrates were equally abundant at the upstream reference and downstream
(impact) site.
¦ Taxa richness was not significantly different between sites.
¦ Macroinvertebrate community composition was similar between sites. Percent
community similarity between sites was 72%.
McGuire also noted that "an acutely toxic event would have resulted in significant
decreases in the occurrence and abundance of sensitive species and been evident as
numerous distinct differences in the communities at each site. Data suggesting acute
impacts from the spill were weak".
It does appear, however, that the increased loading from this high flow event did
make its way through the pond system, leading to some water quality exceedances
(see water quality discussion in subsequent sections).
Regardless of the actual cause, magnitude, or duration of the spill, the ecological
significance of this event appears to be minor. While EPA concluded that it was not
necessarily reasonable to expect the operators to have anticipated the magnitude of
the trash rack clogging and the debris jams forming upstream and suddenly breaking
loose, the issue was that the Agencies were not notified of the incident within 24
hours as mandated by the UAO. The event occurred during the overnight hours of
March 13-14, 2003, but EPA was not notified until Friday March 21, 2003, and the
incident was not formally reported until April 4, 2003. This resulted in Atlantic
Richfield receiving a Notice of Violation.
As a result of this Notice of Violation, EPA required that additional work would be
necessary to prevent a similar incident from occurring in the future, and to otherwise
improve the performance of the Active Ponds treatment (EPA 2003). Additional work
that was required by Atlantic Richfield included:
¦ Replace the existing stage sensor with a continuous measuring device that is capable of
monitoring water levels entering the inlet, at all times. The new device must be capable
of producing data that are retrievable at all times by telecommunication with the
computer. This device should be in place and functioning prior to the early runoff of
2004.
¦ Develop an awareness and revised safety plan for spring runoff and summer
thunderstorms. The plan should account for events such as the event that occurred in
early and mid-March of 2003, including upstream inspections whenever a potential for
debris build-up at county highway and Interstate highway bridges.
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¦ Conduct sediment sampling and analysis of the uppermost bypass pond, into which
the initial flows of the spillover occurred. The analytical results will determine whether
or not, and to what extent, additional sampling or other corrective actions may be
necessary.
¦ Eradicate Russian olive shrubs and trees introduced into the Mill-Willow Bypass. As
part of Atlantic Richfield Company's ongoing efforts to ensure dam safety and flood
passage requirements are met, by periodically trimming willows and other shrubs and
trees adjacent to the berms, EPA urgently requests the eradication of Russian olive from
the bypass and entire pond system.
(Additional Work items in the Notice of Violation that were not listed here consisted
of specific data reporting requirements and requests concerning concentrations, flows,
hydrographs, and exceedances that did not require installation of new equipment or
changes to O&M procedures.)
To implement these Additional Work items, the following improvements/
modifications were implemented:
1. Improvements to the supervisory control and data acquisition system
(SCADA) were implemented. These improvements include a real-time
continuous stage recorder upgradient of the trash rack that, in addition to
providing an emergency call-out for high stage conditions, can be accessed
remotely so that the operator can determine the exact stage.
2. A safety and awareness plan was developed for spring runoff and summer
thunderstorm events and incorporated into the Operations and Maintenance
Plan. The plan includes inspections of the inlet channel and upstream bridges
and channels for debris, and plans for action to address conditions that could
lead to a similar overflow event as that which occurred in March 2003.
3. Section 9.0 of the Operations and Maintenance Plan, Routine Inspection and
Maintenance Guidelines, was modified to address Russian olive at the site.
Since these modifications were adopted, Atlantic Richfield has worked to
eradicate Russian olive from the MWB and they anticipate it will be an annual
O&M activity.
The additional sediment sampling results in MWB from the uppermost bypass pond
were reported in the 2003 WSP Biomonitoring Report (ENSR 2004). The report stated:
Metal concentrations measured at the four MWB sites were on the low end of
concentrations measured in the ponds, except for copper and lead. For copper,
concentrations were at least two times lower than in the ponds and concentrations for
lead overlapped those measured in the ponds.
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5.1.5 Regulatory Standards and System Performance
Compliance with the performance standards for the WSP Active Area is described in
the Active Area UAO. Most of the regulatory standards at the WSP are applied to
effluent composite samples taken at SS-5. Additional standards have been established
for SS-3B for special instances when circumstances dictate discharge directly from
Pond 3, via SS-3B. The SS-3B discharge was not used during this report period. Final
standards are in effect for the entire report period of January 1,1998 through
December 31, 2004. The standards contain daily maximum and monthly average
limitations for the total recoverable concentrations of nine trace elements (arsenic,
cadmium, copper, iron, lead, mercury, selenium, silver, and zinc), TSS, and pH, as
stated in the Active Area UAO (EPA 1991).
As required in the UAO, several of the constituents (cadmium, copper, lead, silver,
and zinc) have standards that are hardness-based. This means that the maximum
allowable concentration varies with each sample depending on the amount of
hardness measured in the sample. Therefore, the standards for these metals, as
shown on the figures, have been adjusted for each measurement based on the
hardness in that sample (or set of samples, for the monthly average standards).
Values for final standards that apply to SS-5 are presented in Table 5-1. Hardness-
based standards are presented at 150 mg/L hardness.
During the report period, influent quality at the WSP has been impacted by upstream
remedial construction on the SST OU. The SST OU work, conducted by the State of
Montana, has been ongoing. According to the SST OU Consent Decree, the WSP are
not responsible for the unintentional and temporary exceedances associated with
upset influent conditions caused by SST OU construction.
Prior to 1998, both total recoverable and dissolved samples were analyzed to better
understand removal mechanisms in the system. After the first quarter of 1998,
dissolved metals analyses were discontinued because the Active Area performance
standards (outlined in the UAO) for surface water discharge are based on total
recoverable concentrations.
The number of exceedances observed during the report period using final daily
maximum standards and monthly average standards are presented in Table 5-2 and
Table 5-3.
pH. The final daily standard for pH requires SS-5 values to be between 6.5 and 9.5
standard units (s.u.). Figure 5-7 depicts the pH measurement for SS-1 and SS-5 for the
report period. The pH standard was exceeded approximately 12 percent of the time
(Table 5-2). The exceedances occur consistently in the summer months, and are due to
increased biological activity in the system. During this time of year, lime is not being
added to the system because natural biological activity raises the pH to the target
level (and sometimes above). The high pH is not due to "overliming". This is a
naturally occurring phenomenon and is not attributable to the operation of the WSP.
EPA's previous Five-Year Review report on the WSP (EPA 2000) stated that
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"exceedances occur invariably during the late summer months as a consequence of
warmer temperatures and natural biological activity."
Total Suspended Solids. Concentrations of TSS observed in SS-5 samples have always
been less than the final daily standard (Figure 5-8), and the majority of the samples
are at or below the detection limit. The figure illustrates that even though TSS
concentrations at the effluent vary, high concentrations observed at SS-1 (influent) are
decreased significantly through the system.
Arsenic. Comparison of influent and effluent total recoverable arsenic concentrations
are presented for the report period in Figure 5-9. The daily maximum discharge
standard was exceeded 44 percent of the time, and the monthly average discharge
standard was exceeded 46 percent of the time (Table 5-2). The maximum effluent
concentration measured was 0.068 mg/L. Exceedances of the arsenic discharge
standard of 0.020 mg/L occur seasonally. Figure 5-9 shows that the seasonal period
of arsenic exceedances was of longer duration in 2003 than in 2004.
These arsenic exceedances do not necessarily mean that the discharge is not protective
of human health and the environment. Arsenic at these concentrations does not
exceed aquatic life criteria (the aquatic life standards for arsenic are 340 ng/L acute
and 150 ng/L chronic). There are no domestic or municipal water users that
withdraw water immediately downstream of the WSP or from the shallow alluvium.
There is also a ban on construction of shallow wells in the vicinity of the WSP.
The persistent, seasonal arsenic exceedances at the WSP have received a great deal of
attention and concern from regulatory agencies, technical committees, Atlantic
Richfield, and citizens. Meetings among technical experts have been conducted to
explain the reasons behind the arsenic exceedances. The current theory under
evaluation by technical experts is that natural biological activity, which changes the
geochemical conditions of the pore water in the pond sediments, is responsible for the
seasonal releases of arsenic. The process for arsenic release that has been discussed is
summarized below.
As Silver Bow Creek enters the WSP system, arsenic, along with other trace elements
of concern, are settled from the water column and sequestered in the pond sediments
via precipitation/coprecipitation or adsorption. Arsenic is typically sequestered via
adsorption to ferric oxides. During warmer weather and warmer temperatures,
biological activity increases, resulting in the production of additional organic material
that settles to the bottom. The extra organic material, coupled with warmer
temperatures, leads to increased biological decay and the consumption of oxygen in
the sediment pore waters. Under these conditions, the iron oxides become soluble as
the iron is reduced from ferric to ferrous iron. The solubilization of the iron releases
the adsorbed arsenic to the water column.
Since arsenic solubility can be higher at higher pH values, it was suggested that
"over-liming" may be causing or exacerbating the arsenic exceedances. However,
lime is added to the influent to maintain a pH between 9.2 and 9.5, until biological
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activity raises the pH to these levels without lime addition. When this occurs, lime
addition is discontinued, typically in early summer. The arsenic exceedances in the
summer do not correlate to the addition of lime and it cannot be concluded that
"over-liming" is the cause of the arsenic exceedances. A more plausible explanation is
that arsenic is released due to reducing conditions in sediment pore waters (as
explained above).
To put the arsenic exceedances in perspective, arsenic loads were examined in several
different ways. First, annual influent and effluent arsenic loads were estimated to
quantify the amount of arsenic removed each year. Second, net loads were compared
with the timing of arsenic exceedances. Third, arsenic loads were compared with
arsenic loads in the Mill-Willow Bypass.
The total influent and effluent arsenic loads were calculated for each year of the report
period and are shown in Table 5-4. The annual loads were calculated using the
available daily concentrations and flow data to calculate a loading rate. This loading
rate was then applied to the number of days between sampling events (typically three
or four days) to obtain a mass load for the three or four day time period. These loads
were then totaled for each calendar year (the calculations were checked to make sure
the number of days in each year was correct). For the years 1998-2003, approximately
40 to 50 percent of the influent arsenic was removed. However, in 2004, removal
dropped to only 1.8 percent, essentially indicating no net arsenic removal. In 2003,
the largest influent load of arsenic was measured, at about 3-4 times what had been
measured in recent years. Most of this was associated with the large influent event of
March 2003. During late 2003 through 2004, the arsenic exceedances persisted
throughout the winter, rather than ceasing in mid to late fall as in previous years.
This partially accounts for the larger release of arsenic from the WSP; however, if the
period of arsenic exceedances in early 2004 is removed from the loading analysis (i.e.,
only March through December loads are summed), percent removal only improves to
about 12 percent.
Arsenic loads were also examined using a two-year averaging period; these results
are also show in Table 5-4. This analysis shows the percent removal for arsenic is
consistently about 45 to 50 percent.
Secondly, the net arsenic loads were compared with the timing of the seasonal periods
of arsenic exceedances to determine if arsenic exceedances were a sign that the WSP
were acting as a source of arsenic. This comparison is illustrated in Figures 5-10 and
5-11. Figure 5-10 shows a comparison of arsenic mass loads calculated for the influent
and the effluent. The thick, horizontal lines indicate periods of time when arsenic
exceedances occurred. For much of the year, influent and effluent loads are similar
and do not show drastic differences. The exception to this is appears to be during
spring runoff periods when influent arsenic loads increase.
The comparison of influent and effluent loads was difficult to clearly illustrate on
Figure 5-10. Therefore, Figure 5-11 was generated showing net arsenic loads on an
"instantaneous" basis (calculated from the daily monitoring data) and on a quarterly
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average basis. A net retention of arsenic is indicated by a negative load, a net release
of arsenic is shown by a positive load. Similar to Figure 5-10, the thick horizontal
lines indicate the time periods when arsenic exceedances occurred. In general, for the
first 5 years of the report period (through the end of 2002), the graph shows that the
arsenic exceedances were not necessarily indicative of a net release of arsenic from the
ponds (all quarterly net arsenic loads were negative). However, during each seasonal
time period of arsenic exceedances, the average net load trended upward (less
negative or closer to zero), indicating less removal effectiveness and/ or release of
arsenic from the pond sediments. Interestingly, the quarterly net arsenic loads often
showed a seasonal maximum (without crossing zero) in the winter months, when
arsenic exceedances were not occurring.
Figure 5-11 shows that the first positive quarterly net load average (net arsenic
release) occurred during the fourth quarter of 2002. The large runoff event of March
2003 is shown with a large influent load retained. However, after this event, the WSP
were acting as a source of arsenic more frequently than during the previous years.
The positive net arsenic loads appeared to occur during the later periods of the
seasonal arsenic exceedance timeframes. Positive net loads were not observed
immediately once arsenic exceedances began.
Third, the arsenic load contributed by the WSP via SS-5 was compared with the
arsenic load present in the Mill-Willow Bypass at MWB-3 (downstream of SS-5).
Water quality data are collected at MWB-3 by Atlantic Richfield, however, they do not
measure discharge. In order to estimate loads in the MWB, average monthly flow
data was obtained from the USGS for the station 12323750 (Silver Bow Creek at Warm
Springs), which is located in the same stream reach as MWB-3. The flow data were
only available through September 2003; however, this time period is long enough to
show the significance of the arsenic discharge from the WSP relative to the MWB. A
comparison of the arsenic loads in SS-5 and the MWB are shown on Figure 5-12.
Arsenic concentrations are shown in the background for reference. For both the MWB
and WSP, high loads occur during spring runoff, as is expected. However, when
exceedances of arsenic are occurring in the WSP, arsenic loads at SS-5 are minimal,
and loads from the MWB are comparatively higher and more significant than the
loads from the WSP.
The intent of these loading analyses was to determine the significance of the arsenic
exceedances in the WSP. The arsenic exceedances are consistently a seasonal problem
at the WSP. However, the loading analyses show that the ponds have been acting as a
significant sink for influent arsenic, until 2004. Yet, another important conclusion can
be made from the loading analyses. The arsenic exceedances from the WSP do not
necessarily correspond to a release of a large mass of arsenic to the upper Clark Fork
River. The net loads show that even if arsenic concentrations are exceeded, for most
of this time, the WSP are still acting as a sink for arsenic. Additionally, the arsenic
loads from the WSP are often less than the loads contributed by the MWB. In other
words, if arsenic concentrations could be brought into compliance at SS-5, the arsenic
load to the Upper Clark Fork River would not decrease drastically because loads are
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already small, and the reduction would be relatively insignificant (and maybe
unmeasurable) compared to loads transported by the MWB.
Cadmium. Comparison of influent and effluent total recoverable cadmium
concentrations are presented for the report period in Figure 5-13. Concentrations are
in compliance with the final standards; there were no exceedances of the daily
maximum or monthly average cadmium standards during the reporting period.
Copper. Comparison of influent and effluent total recoverable copper concentrations
are presented for the report period in Figure 5-14. Exceedances of the daily maximum
standard occur principally during the spring runoff. It is unclear whether this is due
to high flow rates/lower residence times, higher influent loads, or some other issue.
Figure 5-15 presents influent and effluent copper concentrations but with the scale
adjusted to show the magnitude of the influent concentrations. The exceedances
during spring 2002 did not appear to be preceded by excessively large influent
concentrations or flows, unlike the March 2003 event. Importantly, the final daily
maximum discharge standard was met 98 percent of the time (two percent of the
samples exceeded the standard). The average monthly standard was exceeded
approximately ten percent of the time (eight times out of 84 months). However, six of
these eight monthly exceedances were in 1998 and 1999; therefore, compliance with
the monthly standard has improved in recent years. The remaining two monthly
exceedances occurred during spring runoff conditions, including the March 2003 high
flow event.
Monitoring of the dissolved fractions of the constituents was discontinued in 1998. In
the past, paired dissolved and total recoverable data indicated that the majority of the
copper after treatment is in the solid fraction. Because dissolved copper
concentrations after treatment are significantly less than total recoverable
concentrations, it can be concluded that dissolved copper concentrations leaving the
pond system have been significantly below the 96-hour TRV for over ten years. The
96-hour TRV for trout fry, the most sensitive life stage for trout, is 0.037 mg/L
(Erickson, et al. 1999).
Iron. Comparison of influent and effluent total recoverable iron concentrations are
presented for the report period in Figure 5-16. There was only one exceedance of the
final daily maximum iron discharge standard during the report period, associated
with the very high load during the March 2003 runoff event. Other than high loading
events such as these, historical data suggest that iron concentrations should remain
below final standards. There were no exceedances of the final monthly discharge
standard.
Lead. Comparison of influent and effluent total recoverable lead concentrations are
presented for the report period in Figure 5-17. There were no lead exceedances of the
final daily maximum lead standard during the report period; however, one
exceedance of the monthly average standard was measured. This was also due to the
high influent load during the March 2003 runoff event.
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Mercury. Comparison of influent and effluent total mercury concentrations are
presented for the report period in Figure 5-18. The concentration of mercury in SS-5
samples has generally been below the final daily maximum discharge standard of
0.0002 mg/ L, although one percent of the sampled did exceed the daily maximum
standard during the report period. There has only been one exceedance since 2001,
and that was during the March 2003 runoff event.
Selenium. Comparison of influent and effluent total recoverable selenium
concentrations are presented for the report period in Figure 5-19. Concentrations are
in compliance with the final standards; there were no exceedances of the daily
maximum or monthly average cadmium standards during the reporting period.
Selenium is rarely detected in either influent or effluent from the WSP.
Silver. Comparison of influent and effluent total recoverable silver concentrations are
presented for the report period in Figure 5-20. Concentrations of silver are typically
low and are seldom detected in the influent or effluent. There were no exceedances of
the daily maximum standard during the report period. The monthly average
standard of 0.00012 mg/L is less than the analytical detection limit for silver.
Zinc. Comparison of influent and effluent total recoverable zinc concentrations are
presented for the report period in Figure 5-21. There were three exceedances of the
daily maximum standard for zinc during the report period. The exceedances
occurred during runoff events in spring 2002 and after the March 2003 event.
However, concentrations and flows during spring 2002 were not as high as
concentrations or flows measured at other times during the report period, where
exceedances did not occur. The exceedances were minor, and interestingly were
consistently about 20 micrograms per liter above the standard. There were no
exceedances of the monthly average zinc standard during the report period. Overall,
the WSP system is effective at removing zinc from influent waters.
5.1.6 Pond 2 Wet Closures
A fraction of the discharge from Pond 3 is diverted from the Pond 3 discharge channel
into the Pond 2 wet closures. Water flows through the wet closures (East Wet Closure
and West Wet Closure) and subsequently discharges into Pond 2.
The base flow from the East and West Outlets of Pond 3 is routed into the Pond 2 Wet
Closures to maintain inundation of the tailings deposits. A weir structure in the Pond
2 inlet channel allows adjustment of the quantity of flow entering each wet closure
with excess flow bypassing the cells directly into Pond 2. The pool level for each wet
closure is held at a constant level to ensure that the tailings within the cells remain
covered.
The wet closures also provide wetland and wildlife habitat. Construction of islands
and nest boxes within certain ponds has increased suitable habitat for waterfowl
nesting.
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Throughout the report period, the wet closures have remained inundated, thereby
achieving the RAOs and this performance standard for the wet closure cells. The wet
closure outlets were sampled quarterly during the report period. The performance of
each cell was evaluated based on the water quality in the Pond 3 discharge water
quality (SS-3E) and the wet closure outlet water quality. Note that SS-3E represents
only a fraction of the discharge from Pond 3 to the wet closures because the other
portion comes from SS-3VV, which is not sampled.
Data showing the quarterly concentrations from SS-3E, the East Wet Closure (EWC)
and West Wet Closure (WWC) are shown in Figures 5-22 through 5-26 (5graphs). The
wet closures provided additional copper and zinc removal. Iron concentrations were
more inconsistent, with some increases in iron concentrations measured at the wet
closure outlets. Sulfate concentrations showed a consistent increase through the wet
closures. Seasonal increases in arsenic concentrations were measured in the wet
closure ponds. During summer and fall, effluent arsenic concentrations from the wet
closures were generally greater than influent concentrations, with higher
concentrations consistently measured from the West Wet Closure.
In general, it appears that the Wet Closures are functioning as intended, and are
providing some additional contaminant removal and polishing, with the exception of
arsenic and sulfate. The arsenic data show that the wet closure ponds are subject to
the same arsenic mobilization geochemistry as the main ponds.
5.1.7 Mill-Willow Bypass and Lower Silver Bow Creek
5.1.7.1 Channel stability
The MWB is the primary floodway for the WSP. In addition to flows from Mill and
Willow Creeks, it was designed and constructed to divert excessive flows from Silver
Bow Creek around the WSP System.
Overall, the vegetative development along the MWB has been excellent. A 1998
investigation (R2 Resource Consultants) concluded that the riparian plan
communities were developing well and should be allowed to continue to develop
naturally, although additional willow plantings would be helpful (R2 Resource
Consultants, February 2000). Limited overbank scour and bank erosion were
occurring as part of the natural maturation of the channel; the overbank scour was
creating habitat for willow species that were developing communities in these areas.
In accordance with R2 Resources recommendations, 5,880 containerized (10 cubic
inch) sandbar willows (Salix exigua) and 12 mature willow transplants were installed
to assist the development of the riparian community and stabilize approximately 200
feet of streambank in the upper reach of the MWB.
5.1.7.2 Soil-Cement Toe Drains
Dike side slopes adjacent to the MWB were faced with soil-cement to protect them
from erosion. Perforated pipe drains were installed behind the soil-cement to relieve
seepage pressures that could build behind the relatively impervious soil-cement.
Outfall pipes convey the seepage flow through the soil-cement to the MWB side of the
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dikes. These outfalls, or toe drains, are illustrated on Figure 5-27. Toe drains along
the Pond 2 dike, (165 through 193) discharge into a collection pipeline called the soil-
cement toe drain manifold. The toe drain manifold collects the seepage and conveys
the water to the interception trench.
Minor seepage from around the toe drain laterals has been observed during routine
inspections. This seepage has always been clear and there is no evidence of piping or
related dam instability. The seeps are checked periodically to ensure that there is no
increase in flow rate or evidence of piping. There have been no observations of a
direct discharge to surface water; the seepage rates are so low that water typically
collects in low spots at or near the toe of the Pond 2 dike where it presumably
infiltrates or evaporates.
Some toe drains are not manifolded, as it was determined during RD that such a
manifold may not be implementable. Several of the un-manifolded toe drains were
selected for water quality sampling on an annual basis. During the evaluation period,
samples were collected in October of each year. The toe drains selected as being
representative of the overall outfall water quality are numbers 67, 84, 87, 90, 91, 99,
104,152,157,160, and 161. Most of these toe drains are located along Pond 3. Annual
and overall average concentrations of selected constituents are presented in Table5-5.
In addition, the toe drain where the maximum concentration was measured is noted,
along with the sample year. This is then followed by the concentration in this toe
drain in 2004 so that current conditions are known. Of the trace elements analyzed,
concentrations of cadmium, copper, and zinc are all low or non-detectable. Arsenic
concentrations in toe drain samples averaged 0.066 mg/L during the evaluation
period. The maximum arsenic concentration was 0.145 mg/L in TD-84 in 1999.
The soil-cement toe drains are successfully draining water from the soil-cement dikes,
maintaining the piezometric surface at levels that are safe and ensure dam stability, as
designed. The manifolds are collecting and routing water to the Ground Water
Interception Trench where intended. Overall the toe drains are functioning as
designed and protecting human health and the environment.
5.1.7.3 Water Quality Trends
Monthly water quality samples are collected in the MWB at three stations, MWB-1
(farthest upstream station), MWB-2 (just above the SS-5 discharge point), and MWB-3
(immediately below the SS-5 discharge). Flow data are not collected at these stations
(although USGS station 12323750 Silver Bow Creek at Warm Springs is located in the
vicinity of MWB-3), therefore, it was not possible to do a loading analysis on the
MWB.
The water quality data were examined to determine the possible effects that the
Warm Springs Ponds system may be having on the MWB, either through direct
discharge or through groundwater inflow. Some comparisons are made to
performance standards to aid with the data analysis and discussion; however, the
UAO does not mandate that the MWB be in compliance with these performance
standards. Specifically, arsenic, copper, zinc, and hardness data were examined.
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Hardness data for the three stations is presented in Figure 5-28. The hardness data
are interesting because the hardness in MWB approximately doubles from upstream
to downstream (MWB-1 to MWB-2). Within this stream reach, there are no point
source discharges, indicating inflow of groundwater with a high hardness. Surface
water at the base of the nearby Opportunity Ponds typically has hardness levels well
in excess of 1,000 mg/L; therefore, even a small inflow of this groundwater could
impact the hardness in the MWB. The seasonal decrease in hardness is clearly seen
during spring runoff. Downstream of the SS-5 discharge from the WSP, hardness
levels decrease, indicating that the WSP effluent is diluting the hardness of the water
in the MWB.
Arsenic concentrations within the MWB are graphed in Figure 5-29. Arsenic shows
the same seasonal oscillation as observed in the WSP monitoring data. The peak
concentrations are similar to those observed in the WSP (often near 0.040 to 0.050
mg/L). Arsenic concentrations exceed the 0.020 mg/L performance standard about
45 to 50 percent of the time, similar to the Warm Springs Ponds. This adds weight to
the explanation for the arsenic exceedances presented previously, that the
exceedances are caused by natural biological processes during warm periods.
Additionally, a comparison of MWB-2 and MWB-3 concentrations shows that the
effluent from SS-5 typically has a dilution effect on arsenic concentrations in the
MWB, except towards the end of the seasonal arsenic exceedances. It appears that the
arsenic exceedance oscillation lasts slightly longer in the WSP than in the MWB and
that this can lead to a short period of time where arsenic concentrations increase in the
MWB as a result of effluent from the WSP.
Copper and zinc concentration data are shown in Figures 5-30 and 5-31. After about
2000, it appears that effluent copper and zinc from the WSP did not typically have a
large impact on concentrations in the MWB, and sometimes had a dilution effect in
the MWB. Notably, copper concentrations in the MWB showed frequent exceedances
of chronic water quality criteria upstream of the WSP effluent. The only zinc
exceedances in the MWB were measured upstream at MWB-1 (the large concentration
peak of 0.143 mg/L at MWB-3 in August 2001 was not an exceedance).
A comparison of MWB-1 and MWB-2 concentrations was conducted to determine
whether or not the unmanifolded toe drains paralleling the MWB were having a
measurable impact on water quality in the MWB. Because discharge is not measured
at these two stations, a comparison between upstream and downstream loads could
not be performed. There does not appear to be a significant change in contaminant
water quality from upstream to downstream; however, resolution is limiting in the
available data to quantify the extent of any water quality impacts from the
unmanifolded toe drains. Because there is little change in contaminant concentrations
from upstream to downstream, and because contaminant concentrations in the toe
drains are typically low, it is likely any loading contribution from the toe drains is
insignificant.
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5.1.8 Inactive Area Performance Evaluation
The Inactive Area is not directly involved in the treatment of flows entering the Warm
Springs Ponds from Silver Bow Creek, as are Ponds 2 and 3. Although some
additional treatment of surface water occurs in the wet-closures of the Inactive Area,
it is a relatively small volume and the additional treatment benefits only the wet-
closure cells. The principal functions of constructed features within the Inactive Area
are to prevent migration of contaminated groundwater. Briefly, the constructed
features include raised, reinforced and armored berms; toe ditches; manifolded toe
drains; the interception trench and pump-back system; and wet- and dry-closure cells
(Figure 5-58).
The 1993 unilateral administrative order (UAO) specifies that the performance
standards for groundwater are defined as the maximum contaminant levels (MCL)
and non-zero MCL goals for contaminants of concern, as promulgated by the Federal
Safe Drinking Water Act and the Montana Public Water Supplies Act. The
performance standards for the contaminants of concern in groundwater at the Warm
Springs Ponds are as follows:
Arsenic
0.050 mg/1
Cadmium
0.010 mg/1
Chromium
0.050 mg/1
Lead
0.050 mg/1
Mercury
0.002 mg/1
Nitrate (N)
10.0 mg/1
Both the time and point of compliance for these performance standards are influenced
by the temporary groundwater interception and pump-back system. During the time
that the pump-back system is operational, intercepted water is pumped from the
interception trench to the east side of Pond 2 via a 32-inch pipe that is 7,600 feet long.
When the pump-back system is operational, the point of compliance for groundwater
is the north, or down-gradient side of the interception trench. Piezometers P-02, P-04,
P-06 and P-08 are the measurement points of compliance when the pump-back system
is operational (Figure 5-58).
When it is demonstrated that all groundwater performance standards have been
consistently met at all monitoring wells, both up-gradient and down-gradient of the
interception trench, for a period of at least 24 consecutive months, EPA may
determine that the pump-back system is no longer needed. If such an action is carried
out and it is determined following analysis of the data that migration of groundwater
is adversely affecting the lower MWB or the Clark Fork River, then EPA will require
that operation of the pump-back system be resumed.
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At such time as the pump-back system is deemed by EPA to be no longer needed, the
points of compliance for groundwater will shift to the south, or up-gradient side of
the interception trench. Piezometers P-01, P-03, P-05, P-07 and P-09 are the
measurement points of compliance when the pump-back system is not operational
(Figure 5-58).
5.1.8.1 Interception Trench
The interception trench receives groundwater flow from the upper sand and gravel
aquifer beneath Pond 1 and surface water flow from Pond 1 and the lower wet
closures, the manifolded toe drains, and the Pond 1 and the Pond 2 toe ditches. The
eastern-most part of the interception trench is excavated deeper to form a sump for
the pump-back system inlet. The interception trench together with the Pond 1 and
Pond 2 toe ditches were designed to prevent off-site migration of groundwater that
may have constituent concentrations exceeding performance standards.
Groundwater Quality
The UAO specifically identifies the groundwater standards that must be met by
groundwater that flows off-site toward the MWB, and eventually enters the Clark
Fork River. While the interception trench and pump-back system are operating, the
standards must be met immediately north (down-gradient) of the interception trench.
For a 24-month period prior to shutting down the interception trench and pump-back
system, and thereafter, these standards must be met immediately south (up-gradient)
of the interception trench. A series of piezometers were installed up-gradient and
down-gradient of the Interception trench to evaluate compliance with these
standards. These piezometers are shown on Figure 5-58. Groundwater samples were
collected semi-annually over the evaluation period (1998 - 2004) to obtain
groundwater quality data for measuring compliance at the interception trench.
The UAO also requires that hydraulic gradients be maintained toward the
interception trench to ensure all affected groundwater that potentially exceeds
performance standards is collected and routed via the pump-back system to Pond 2
for treatment. Groundwater elevation data were not available to CDM at the time this
Draft report was prepared and, therefore, hydraulic gradients near the interception
trench were not assessed. Piezometer P-14 is located in the south west corner of the
Pond 1 dry closure area. Historically, groundwater flow in this area does not report
to the interception trench. To insure that groundwater exceeding performance
standards was not escaping the Warm Springs Ponds system, groundwater quality in
P-14 was also measured semi-annually over the evaluation period and is reported
herein.
The pump-back system was operated nearly continuously throughout the evaluation
period (the system was shut down for 29 consecutive days in December 2001 - see
Section 5.8.4). Therefore, piezometers on the down-gradient (north) side of the
interception trench (P-02, P-04, P-06, and P-08) and Piezometer P-14 [since there is not
a documented gradient from this piezometer to the interception trench]), represent
the points of compliance for the entire evaluation period. All individual
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measurements from all down-gradient piezometers, and for Piezometer P-14, during
this period were below the groundwater performance standards with the exception of
one cadmium measurement in Piezometer P-02 in December 2001, with a
concentration of 0.0136 mg/L. Not coincidentally, the cadmium exceedance
coincided with the shut-down of the pump-back system. Individual sample results
from the down-gradient piezometers and for Piezometer P-14 over the evaluation
period are shown on Figures 5-32 through 5-43.
All measurements for all constituents in the up-gradient piezometers (P-01, P-03, P-05,
P-07, and P-09), located south of interception trench, complied with the performance
standards during the period with the exception of arsenic in P-03. The arsenic
concentration in Piezometer P-03 exceeded the performance standard for arsenic
(0.050 mg/L) in June 2003 and June 2004, with concentrations of 0.062 and 0.065
mg/L, respectively. Individual sample results from the up-gradient piezometers over
the evaluation period are shown on Figures 5-44 through 5-49.
5.1.8.2 Manifold Toe Drains and Toe Ditches
For the approximate length of the north-south Pond 2 dike, flows from the toe drains
between Stations 165 and 193 are collected in the toe drain manifold (Figure 5-27). The
Pond 2 toe ditch is located at the toe of the western portion of the dam separating
Pond 2 and Pond 1 (Figure 5-32). The purpose of this ditch is to intercept seepage
originating in Pond 2, thereby controlling the groundwater table throughout the
western dry-closure area of Pond 1 dry closure. The toe drain manifold collects the
drainage from toe drains along Pond 2 and from the Pond 2 toe ditch and the
combined system discharges to the upper end of the interception trench (Figure 5-32).
Water quality samples were collected quarterly at the manifold outlet to the
interception trench (Station IA-3) over the evaluation period. In general, total
recoverable concentrations of cadmium, copper, lead, mercury, and zinc were all low
or undetectable throughout the period (Table 5-6). Arsenic concentrations in the
manifold samples have averaged 0.029 mg/L, which is generally comparable to
seasonal concentrations observed at the Pond 3 (SS-3E) and Pond 2 (SS-5) discharge
points and in the MWB (Figure 5-50).
Total recoverable iron concentrations in the manifold samples averaged 4.36 mg/L
over the evaluation period and spiked at 21.0 mg/L in June of 2000 (Figure 5-51).
Concentrations of iron were notably higher in the toe drain manifold samples than
were observed in the MWB and at the Pond 3 (SS-3E) and Pond 2 (SS-5) discharge
locations. Also, iron concentrations in the manifolded toe-drains were significantly
higher than from the individual, non-manifolded toe drain samples. (It should be
noted that total recoverable iron was measured in the manifolded toe drain samples
while dissolved iron was measured in the individual, non-manifolded samples.)
Dissolved iron concentrations in non-manifolded toe drains average 0.091 mg/L
while total recoverable concentrations measured at the manifold discharge average
4.36 mg/L. From this comparison and visual observation of the Pond 2 toe ditch
(orange precipitation layer in the bottom of the ditch), it is evident that the toe ditch is
collecting iron rich seepage and groundwater flows (Atlantic Richfield 2005).
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5.1.8.3 Pond 1 Wet Closures
At the time of remediation, Pond 1, the original settling pond in the WSP System, was
no longer functional as a settling pond. The relatively small volume of water
contained within and flowing through the Inactive Area was due to seepage from the
up-gradient ponds, precipitation, and from local runoff. Flows are now managed by
means of the pump-back system which intercepts and returns all Pond 1 outflows to
Pond 2 for treatment prior to discharge to the MWB.
System Description
The Pond 1 Wet Closure inundates approximately 141 acres. A small diversion of flow
from Pond 2 into Pond 1 maintains the wet closure. The wet closures below Pond 1
consist of three cells that inundate previously exposed tailings.
A structure between the Pond 2 outlet and the Pond 1 inlet transfers flows, typically
less than 4 million gallons per day (mgd), from Pond 2 into the wet-closure area of
Pond 1. In addition, inlet and outlet facilities provide flow from the Pond 1 Wet
Closure to the lower wet closures. These lower wet closures are referred to as the
north, middle, and south cells (Figure 5-32). The lower wet closures were initially
filled by flows from Pond 1 from October through November 1995. Flow from the
Pond 1 Wet Closure moves consecutively through the south cell, middle cell, and then
to the north cell, before discharging to the interception trench and is returned to Pond
2 via the pump-back system.
Pond 1 and the lower wet closures also provide a significant enhancement to
wetland/ wildlife habitat with minimal risk to the wildlife. Willow stands within and
around certain ponds also provide refuge for deer, waterfowl, and songbirds. Nest
boxes and islands within certain ponds also continue to provide habitat suitable for
waterfowl nesting.
Cell Performance
The Pond 1 Wet Closure has remained inundated during the evaluation period,
achieving the RAOs for the wet closure areas. Water quality samples are collected
quarterly at the north cell outlet (IA-2, Figure 5-58). Concentrations of hardness,
sulfate and total recoverable iron in samples from IA-1 suggest a groundwater
influence on the wet-closure flows (Table 5-7). Higher concentrations of these
constituents are generally observed to be associated with groundwaters as opposed to
surface waters.
As reported previously (ARCO, 1997a), several trace metals appeared to have
undergone an initial period of elevated concentration immediately following filling of
the wet closures. These elevated total recoverable and dissolved concentrations were
very short lived. From 1998 through 2004, trace metals measured at IA-2 are relatively
low when compared to Active Area concentrations. Figures 5-52, 5-53, and 5-54 show
relative concentrations of cadmium, copper, and zinc in the Inactive Area wet closure
cells, respectively, compared to concentrations at the Pond 3 (SS-3E) and Pond 2 (SS-5)
discharges.
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Arsenic and concentrations through Pond 1 and the lower wet closures do not display
the same trends as the trace metals. Total recoverable concentrations of arsenic
appear to be following the same pattern of seasonal fluctuation that is observed in
Pond 3 and Pond 2 of the Active Area (Figure 5-55).
Figures 5-52 to 5-55 illustrate relative concentrations of total recoverable arsenic,
cadmium, copper and zinc measured at the north cell discharge (IA-2). The total
recoverable concentrations of other trace elements currently measured at IA-2 are
generally near or less than corresponding total recoverable concentrations measured
at SS-5 and SS-3E.
5.1.8.4 Pump-back System
The pump-back system for the Inactive Area is designed to: 1) maintain the necessary
water level elevation in the interception trench to achieve hydraulic capture of
groundwater; and 2) to return flows collected from the interception trench, Pond 1 toe
ditch, Pond 2 toe ditch, the soil-cement toe drain manifold, and the Inactive Area wet
closures (Pond 1, south, middle and north cells to Pond 2 for treatment prior to
release to the MWB. The pump-back system consists of two major elements, the pump
station facilities and the pump-back pipeline (Figure 5-58).
The pump-back pipeline that discharges to Pond 2 (IA-1) was sampled quarterly over
the evaluation period for water quality in accordance with the Operations and
Maintenance Plan (ARCO, 1995a). The water quality measured at IA-1 typically
reflects the combination of flows that enter the interception trench. The quality of
these flows entering the interception trench (IA-2 and IA-3) was previously discussed
in Sections 5.7.2 and 5.7.3, and in summary, these constituents are generally at levels
similar to Pond 2 concentrations. In addition, concentrations of hardness, sulfate, and
iron are typically higher than those observed in Active Area surface waters,
illustrating continued groundwater influence on the Inactive Area flows.
Pump-back flows have not been measured frequently during the 1998-2004 period.
They were measured daily in 1996, when the average flow was 6.4 cfs. Current
operations are not significantly different than in 1996 (the system is pumped as
needed to maintain the hydraulic gradient to the trench), so current average pumping
rates are most likely similar to those in 1996. Typically, pump-back flows are
significantly lower than flows through the Active Area system (average flow during
the evaluation period was 39 and 36 cfs, respectively, at SS-1 and SS-5). However,
during low flow times of the year, the pump-back flows can account for a significant
fraction of the discharge from Pond 2 to MWB (flows from SS-5 have averaged less
than 6 cfs during August each year since 2001). Note that if the water was not
returned to Pond 2 via the pump-back system, the water would discharge as
groundwater to MWB or lower Silver Bow Creek, and therefore, in-stream flows
should not be affected if the pump-back system is shut down. It does not appear that
the pump-back flows have any effect on the water quality in Pond 2 (as observed at
the Pond 2 discharge, SS-5). Total recoverable trace metal concentrations do not have
an obvious effect on SS-5 concentrations when compared to SS-3E concentrations.
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This is illustrated on Figures 5-56 and 5-57 with total recoverable copper and zinc
concentrations, respectively.
The only constituents that appear to have an effect on Pond 2 water quality are
hardness and sulfate. The effect is not extreme, but slight increases on average (8.4%
and 24%, respectively, during the evaluation period) in these two constituents are
observed from SS-3E to SS-5 (Table 5-7). These increases may not be due solely to the
pump-back system since increased concentrations of hardness and sulfate are also
observed in the Pond 2 wet closure discharges, as compared to concentrations at SS-
3E.
As previously mentioned, the UAO requires that hydraulic gradients be maintained
toward the interception trench to ensure all affected groundwater that potentially
exceeds performance standards is collected and routed via the pump-back system to
Pond 2 for treatment. Groundwater elevation data were not available to CDM at the
time this Draft report was prepared and, therefore, hydraulic gradients near the
interception trench were not assessed.
The pump-back system was shut down from December 3 through December 31, 2001
to evaluate the level to which the interception trench would recover. During this
period, groundwater elevation and groundwater quality data were collected. These
data were reportedly analyzed in the Draft Technical Memorandum: Groundwater
Interception Trench Demonstration of Compliance (Atlantic Richfield Company,
2002), which was not available to CDM at the time this report was prepared. Atlantic
Richfield (2005) reported that during the period when the pump-back system was
shut down, the water quality in the interception trench, which would likely represent
water quality that would be discharged to lower Silver Bow Creek, would not have a
detrimental impact on surface water quality. Atlantic Richfield further reported that
shutting down the pump-back system would not compromise the interception trench
dike stability, although further analysis was recommended. This cannot be verified
without further review of groundwater elevation and groundwater quality data
collected at the time the pump-back system was shut down.
As mentioned previously, cadmium was detected in down-gradient piezometer P-02
during the period when the pump-back system was shut down (December 2001) at a
concentration of 0.136 mg/L, an exceedance of the performance standard (0.010
mg/L). Cadmium levels also were elevated to 0.0041 in December 1999 and 0.0068 in
June 2003 when the pump-back system was operating, but in these instances, the
elevated concentrations did not exceed the standard. The source of cadmium to P-02
groundwater is uncertain, but it is surely notable that the concentration was at its
highest level when the pump-back system was shut down.
5.1.8.5 Dry Closures
All of the dry closure cells occur on sites that are essentially flat with little or no
topographic diversity. Cell 1 is a small area (7 acres) located in the southern part of
the WSP; Cell 2 is somewhat larger (19 acres) and located approximately 0.5 miles
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north of Cell 1; and Cell 3 is located at the north end of the WSP area and covers
approximately 140 acres (Figure 5-58).
In general, the vegetation on the dry closure areas is well established; in spite of dry
conditions that have been prevalent since the last detailed vegetation surveys (ARCO,
1997b). Dominance by the major perennial grass species has continued. The dry
closure areas are monitored as part of the annual voluntary dam safety inspections, in
accordance with Earthwork Inspection and Maintenance Procedure IMP-3
(Operations and Maintenance Plan [ARCO, 1995a]). During the 1998 through 2002
annual inspections, no reportable items (i.e., items in need of repair or items observed
to be potential areas of concern) were documented. During the 2003 and 2004
inspections, some weeds were noted. Weed controls (chemical spraying) were
implemented in response to these observations, and will be continued until weeds are
controlled. Several weedy species were noted in this area but were present at amounts
of less than 1 % of the vegetative cover.
Overall, dry closure covers are intact and vegetation success ensures stability of the
covers. The dry closures are meeting the RAOs for dry closures of reducing the
potential for human exposure to exposed tailings and other surface contamination.
5.1.9 Dam Safety
Prior to remedial actions, the dams at the WSP were determined to be unsafe. Dam
safety concerns, not water quality concerns alone, initiated rapid response actions on
the WSP. Dam safety aspects of the response actions required the most significant
amount of construction activity and the greatest cost. These results have proven
successful because the threats of failure in a flood or earthquake have been
eliminated.
In addition to the routine inspection and maintenance activities identified in the
Operations and Maintenance Plan (ARCO, 1995a), voluntary annual Dam Safety
Inspections were conducted by the PRP (Atlantic Richfield Company) to evaluate the
condition of earthwork and hydraulic facilities. The results of these inspections were
documented in an annual inspection report, and any findings were brought to the
attention of the site manager and operator to be addressed.
In addition to the annual inspection, once every five-years an inspection by a qualified
third-party engineer is completed in accordance with the Operations and
Maintenance Plan (Section 9.2.3) (ARCO, 1995a) and Montana Dam Safety
Regulations. One five-year third party inspection was conducted during the period
covered by this report. This inspection was conducted in 2001 by Todd Lorenzen, P.E.,
of Pioneer Technical Services, Inc. (AERL, December 2001). This inspection found no
critical conditions or maintenance items requiring immediate attention. The
inspection did document a number of erosional and other miscellaneous features that
required attention; these items were subsequently addressed.
Also, the Emergency Action Plan for the Warm Springs Ponds is updated annually.
This plan was updated in accordance with the requirements of the Montana Dam
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Safety Regulations to reflect changes in the system and responsible personnel in the
event of an emergency. Copies of the updated plan were provided to the EP A, the
Montana Department of Natural Resources and Conservation, and Montana DEQ, as
well as local emergency response personnel.
The dam safety inspections confirmed that the WSP facilities comply with the State of
Montana Dam Safety regulations, and therefore, are protecting human health and the
environment. The next third-party dam safety inspection is scheduled for 2006.
5.1.10 Biomonitoring Investigations
This section summarizes the results of biomonitoring investigations conducted at the
WSP during the 1998 through 2004 period. Two types of biomonitoring investigations
of the WSP were completed: one type within the ponds themselves and the other type
for the MWB channel. The majority of the following text was taken directly from
Atlantic Richfield's Five Year Review report (Atlantic Richfield 2005).
5.1.10.1 Warm Springs Ponds Biomonitoring Investigations
This section summarizes the results from 7 years (1995-2000, and 2003) of
biomonitoring at the WSP. The scope and methods used during this extensive
sampling and analysis effort over this period of time were based upon the final 1995
Biomonitoring Work Plan for the Warm Springs Ponds (Work Plan) (ARCO, 1995b),
1996 Work Plan Addendum-Biomonitoring Work Plan for the Warm Springs Ponds
(1996 Work Plan Addendum) (ARCO, 1996a), the Warm Springs Ponds/Mill-Willow
Bypass 1997 Biomonitoring Work Plan Addendum (1997 Work Plan Addendum)
(ARCO, 1997c), the Warm Springs Ponds 1998 Biomonitoring Work Plan Addendum
(1998 Work Plan Addendum, AERL, 1998a), and the WSP Biomonitoring 1999, 2000a,
and 2003 Scopes of Work (1999 SOW; AERL, 1999, AERL, 2000a; Atlantic Richfield
Company, 2003) developed in cooperation among the EPA, the U.S. Fish and Wildlife
Service (USFWS), and Atlantic Richfield, as a direct result of the RODs for the Active
and Inactive OUs of WSP. Since certain aspects of the selected RAs are interim actions,
in that metals-contaminated mine wastes will be isolated (in some cases treated) and
left on-site, the EP A has determined that long-term monitoring of biological
communities was necessary.
The objectives of the long-term biomonitoring program, as provided by the EP A in
the Final Draft Biomonitoring Plan, Warm Springs Ponds Operable Unit (EPA,
December 1994) included:
¦ Monitor diversity and abundance in selected biological communities.
¦ Directly measure the potential toxicity of the submerged sediments using standard
toxicity tests.
¦ Directly measure metals concentrations in water and sediments.
¦ Directly measure metals concentrations in selected plant and animal tissues to evaluate
exposure and metals bioavailability.
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¦ A multi-year sampling program was originally established because potential effects
may manifest themselves over an extended period of time, and to discriminate between
normal year-to-year variations in assessing meaningful long-term trends. The WSP
biomonitoring results can be used to provide an extensive database to support future
decisions regarding the effectiveness of the WSP remedy. The number of sampling sites
and types of samples that took place since 1998 decreased slightly, while still providing
the necessary data for continued monitoring of metals bioavailability within the WSP
system. The specific sampling that took place each sampling year is discussed in brief
below or can be found in the respective reports (ARCO, 1996b, 1997b, AERL, 1999;
AERL, 2000b, 2000c, 2001; and Atlantic Richfield Company, 2004).
The compilation and comparisons (both within a given year and among all years) of
these annual data sets will characterize and evaluate the status of the WSP System
biological communities. In certain areas, where expected equilibrium (mature)
conditions have been achieved, few, if any, changes among the measured parameters
are expected over the long term, other than those associated with natural biological
variability.
The original biomonitoring study measurement endpoints selected at the WSP
included:
¦ Metal concentrations in water and sediments
¦ Toxicity of sediments
¦ Tissue metal concentrations of key receptors (benthic macroinvertebrates, pelagic
macroinvertebrates, aquatic macrophytes, bottom fish, forage fish, and waterfowl)
¦ Benthic macroinvertebrate and zooplankton abundance and diversity
¦ Macrophyte abundance and diversity
¦ Waterfowl abundance and diversity
With the exception of fish tissue, waterfowl liver samples, and vegetation surveys, all
field collections required within a given area were collected from common sampling
locations as specified in the 1995 Work Plan (ARCO, 1995b). Sampling locations were
marked in 1995 with floating buoys or permanent stakes so that these locations could
be resampled in subsequent years. In addition, Global Positioning System (GPS)
readings were taken at each marker and at the ends of each vegetative survey transect
to ensure location consistency with future sampling events. Sites were re-marked as
needed depending on the condition of the buoy, which was evaluated during each
sampling event.
Methods. Measurements from 1995 -1998 were made at a total of nine sampling sites
representing different types of wetland treatment areas (i.e., active areas versus wet
closure cells) and a range of wetland maturity levels. The five original main sampling
sites, in which all sample types were collected, consisted of P3WH, P2-WWC, P2-NW,
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and PI-MWC. The four remaining ancillary sites, P3-N, P2-S, PI-VV A, and P 1- WAN,
had varying levels of samples collected at each for comparisons. Sampling at all nine
sites was consistent through the 1998 sampling event. In 1999 and 2000, the number of
sampling sites was reduced to four sites: P3-VVH, P2-VVVVC, P2-NVV, and Pl-MWC. In
2003, only three sites (P3-WH, P2-WWC and PI-MWC) were sampled. Sampling
locations are summarized in Table 5-8.
Original sample types collected at each site are presented in Table 5-9. The type of
samples collected from each site was consistent through 1998 after some slight
method changes from 1995 to 1996. The types of samples were altered after 1998 to
focus on key receptors. The metals of interest at the WSP include arsenic, cadmium,
copper, lead, and zinc. Mercury analysis was included in 1995 but was subsequently
excluded in 1996 because of extremely low levels measured in different media the first
year of sampling.
In 1999 and 2000, sampling changes consisted of no aqueous metals concentrations,
tissue metals concentrations for only benthic macroinvertebrates, and abundance and
diversity measures for benthic macroinvertebrates and waterfowl. The 2003 SOW
(Atlantic Richfield Company, 2003) was similar to the 2000 Work Plan (AERL, 2000a),
except the analysis of in-situ pore water metals concentrations and one site (P2-NW)
were excluded.
Results and Discussion. Results of individual sampling events are reported in the
respective biomonitoring reports. The information presented below attempts to
briefly summarize the overall trends and comparisons of seven years worth of data
collected in the Warm Springs Ponds system.
Surface Water. In general, water quality measured as grab samples during each
sampling event (e.g., hardness, alkalinity, pH, conductivity and dissolved oxygen
levels) indicates characteristics of productive waters. Total recoverable and dissolved
metals concentrations were measured at each of the 5 main sites through 1998. For
some metals (e.g., copper and zinc) the dissolved surface water metals concentrations
were less than the total recoverable concentrations by a factor of approximately 2.
However, total recoverable and dissolved arsenic values were similar. Aqueous
metals analysis was discontinued after the 1998 sampling event.
Sediments. While there were some differences in sediment metals concentrations
among sampling years (1995 - 2000, 2003), bulk sediment metals concentrations
showed no strong temporal trends. Concentrations varied for each site and each
metal. It is more probable that differences in sediment metal concentrations among
sampling years represent spatial variability within the individual ponds, as these
were single composited samples. While there were no real trends in sediment metals
concentrations over time, there has been a noticeable decrease in sediment toxicity
from 1995 to 1998, after which toxicity increased slightly in 1999. Sediment toxicity
has generally decreased in 2000 and 2003 from values observed in 1999.
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While there were some significant correlations from time to time, bulk sediment
metals concentrations did not consistently explain amphipod survival in laboratory
sediment tests when data from all years were combined. If bulk metal concentrations
were the primary factor for determining toxicity, then a dose:response relationship
should be observed with amphipod mortality. Overall, amphipod toxicity was
independent of bulk sediment levels. The role of other factors, such as the difference
in simultaneously extracted metals (SEM) and acid volatile sulfide (SEM-AVS) values,
pore water metals and ammonia (since 1999) concentrations were evaluated to
determine if they were more important in explaining amphipod toxicity.
Using the equilibrium partitioning (EqP) theory (Ankley et al., 1996; or see one of the
WSP reports), SEM-AVS values were compared with sediment toxicity. While this
approach is used to predict the lack of toxicity, mortality (i.e., less than or equal to 24
percent) was still observed at 2 sites sampled in 1995,4 sites sampled in 1996, and 1
sampled in 2003 when toxicity would not be expected due to metals (i.e., SEM-AVS <
0). According to the EqP theory, metals could not have caused the resulting toxicity
because they would be bound to excess sulfides. Therefore, factors other than divalent
metals (e.g., ammonia) were likely responsible for the observed amphipod mortality.
While excess SEM concentrations do not necessarily predict sediment toxicity (i.e.,
sulfides are not binding metals but other phases could be complexing metals), the
majority of WSP sites with SEM > 0 were toxic.
Amphipod response was then compared to sediment pore water metal concentrations
normalized as interstitial water criteria toxic units (IWCTUs). The IWCTUs take into
account the hardness-adjusted A WQC for each individual metal. No toxicity should
be expected below a value of 1.0 IWCTU (at 1.0 IWCTU all metals would be at their
respective chronic A WQC). Alternatively, IWCTU values> 1.0 mayor may not cause
toxicity (i.e., IWCTU is a better predictor of non-toxicity than actual toxicity levels), as
other factors could mitigate toxicity (e.g., dissolved organic carbon). Compared to
bulk metal concentrations and SEM-A VS values, IWCTU was a better model for
explaining the observed amphipod response to WSP sediments. Individual IWCTU
values were not comprised of a single dominant metal, although copper and arsenic
were typically the highest.
As the EqP approach identified toxic sediments that were not explained by metals
concentrations, ammonia was evaluated as a potential source of sediment toxicity.
Combining data collected since 1999, there is a significant relationship between
sediment toxicity and total pore water ammonia concentrations compared with either
bulk sediment metals concentrations or pore water metals concentrations. While it
cannot be definitively stated that ammonia was the toxicant in these sediments
because the toxicity is dependent on temperature and pH and there are no directly
comparable studies, it appears to be a strong candidate.
Benthic Macroinvertebrate Tissue Residues. There were no significant temporal
relationships in all BMI tissue metals residues at any of the three sites. However, there
appeared to be some slight increases from 1999 to 2003 for arsenic, copper, and lead at
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P3- WH. The lowest historical tissue residues (arsenic milligrams per kilogram
[mg/kg] wet weight) measured since the initiation of biomonitoring was taken in
2003 for three metals at Pl-MWC (arsenic, cadmium, and zinc) and P2-WWC
(cadmium, copper, and zinc). However, there were two metals at P3-WH (arsenic and
copper) that were the maximum concentrations measured historically at this site,
although these values are only slightly above the previous highest values observed at
this site.
Potential factors that can confound the results in tissue residue concentrations are
differences in species composition that can change spatially and temporally.
Benthic Macroinvertebrate (BMI) Community Analysis. In general, benthic
macroinvertebrate abundance has been similar among sampling years or has
increased since 1995. For example, in 2003 densities at P3-WH and Pl-MWC were
among the highest values measured historically, 12,657 and 1,509 per square meter,
respectively. (Densities were among the highest observed at these sites even though
tissue metal residues were also among the highest observed at these locations.) BMI
density at P2-WWC has appeared to decrease since 1997 to levels observed in 1996
(2,444 per square meter). Hyalella azteca densities in 2003 at all 3 sites were typically
on the low end of numbers observed in past sampling efforts. Species richness
measured in 2003 was similar to values measured previously, although there was a
significant increase at Pl-MWC (r2= 0.659). Density and diversity measurements did
not appear to be strongly affected by the chemistry of the sediment samples analyzed
or tissue metal residues. In some cases, low invertebrate densities corresponded with
areas of high metals bioavailability and the observance of high laboratory toxicity; in
others, such relationships were not apparent. Numerous chemical, physical, and
ecological factors are controlling the benthic invertebrate community within the WSP
System, and may be masking correlations to sediment metals concentrations.
Avian Population Estimates. Bird population densities assessed as part of the
biomonitoring program (i.e., all huntable species excluding coots, grebes or
shorebirds) suggest that the ponds support a highly abundant and diverse
community, especially evident by the sheer number of waterfowl observed.
Populations have been fairly consistent over time, with 2003 numbers comparable to
those measured in previous years. In addition to the huntable species, the ponds are
widely used for nesting by raptors. For example, MDFWP personnel observed in 2003
that four Osprey chicks fledged from the Osprey nests within the WSP System. The
Bald Eagle nest at the Great Blue Heron Rookery fledged two eaglets.
Habitat within the WSP appears to be highly suitable for a diverse assemblage of
wildlife species. The WSP provide highly abundant invertebrate populations for food,
a diverse macrophyte community for food, cover, and nesting, and a number of other
man-made amenities that should increase wildlife utilization and success.
Correlation of Measured Endpoints and Pond Maturity Status. In general, older
ponds have been associated with lower tissue metals concentrations in benthos,
higher sediment AVS concentrations, and lower SEM-A VS values. While there were
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similar trends among sampling years, most matrices indicated that metals
bioavailability was reduced among the more mature sampling locations compared to
more recently flooded wetlands. These findings suggest that, as recently flooded
locations within the WSP System age and mature, and as sediment AVS and Total
Organic Carbon (TOC) concentrations increase, metals should become less
bioavailable and metals residues should decrease. A good indication of this is the
decreasing trend in sediment toxicity (i.e., amphipod survival overall has increased)
since 1995.
Fluctuations among the various parameters are also likely dependent on non-metals
related factors. For example, pond depth, sediment particle size distributions, water
temperature, and the presence/ absence of insectivorous fish are likely contributing to
the regulation of invertebrate populations.
Summary. The results of chemical and biological sampling at the WSP demonstrate
that complex interactions are operating to control metals concentrations and organism
distributions within the OU. Locations bearing maximum sediment metals were not
necessarily areas indicating elevated tissue metals concentrations or decreased
invertebrate abundance, although analyses indicate metals exposure within the WSP
System.
5.1.10.2 Mill-Willow Bypass Biomonitoring Investigations
During the report period (1998 through 2004), a number of biomonitoring
investigations were conducted of the MWB. These include the 1997-1998 Mill Willow
Bypass Biomonitoring Report Addendum (R2 Resource Consultants, February 2000);
the Fall Spawning Survey, Upper Clark Fork River, 1999 Data Report (R2 Resource
Consultants, December 1999); the Assessment of Trout Population Dynamics and
Spawning Use of the Mill-Willow Bypass, Year 2000 Biomonitoring Report (R2
Resource Consultants, June 2001); the Fall Spawning Survey, Upper Clark Fork River,
2001 Data Report (R2 Resource Consultants, January 2002); and the Macroinverebrate-
Based Rapid Bioassessment: Mill-Willow Bypass (McGuire, D., April 1, 2003).
The 1998 Addendum (R2 Resource Consultants, February 2000) concluded that
riparian vegetation was generally high. In the middle and upper reaches, bank top
total vegetation cover was 75% to 100%, with most cover herbaceous vegetation. The
lower reaches had somewhat less cover, which may be due to trampling impacts from
fisherman, as this reach received a lot of fishing pressure. Shrubs were present in the
bank top areas, and almost all shrubs were willows. Shrubs were heavily browsed.
Along the bank slopes, plant cover was moderate in 1998. Some subreaches had high
(75% to 100%) cover, but most were in the moderate (26% to 75% category). Some
invasive weed species were present (primarily Canada thistle) in 1998, but an on-
going weed control program was (and still is) in-place to control the spread of weeds
at the WSP.
The 1998 Addendum also included invertebrate surveys, which indicated the
"presence of a diverse and abundant invertebrate community throughout the Mill-
Willow Bypass project site" (R2 Resource Consultants, February 2000, p. 21). The
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results indicated a continuing improvement in conditions throughout the channel.
The results indicated no impairment from metals in the upper three (of four) sites and
slight impairment due to metals at the lower site.
Spawning surveys were conducted annually in the MWB through 2001, with the
summary of results reported in the 2001 fall spawning survey report (R2 Resource
Consultants, January 2002). The surveys showed a continuous improving trend in
redd densities in the MWB, from less than 3 redds per 1,000 feet of stream prior to
1999 to 12.9 per 1,000 feet of stream in 2001.
The redd densities from 1998 through 2001 compared very favorably with other
tributaries in the basin. It is likely that the fish observed in MWB in 2001 were the
second generation of adult fish that spawned in the MWB during 1995, its first year
after reconstruction (R2 Resource Consultants, January 2002).
During 2000, in addition to the spawning surveys summarized above, fish population
and water quality studies were completed in the MWB (R2 Resource Consultants,
June 2001). The 2000 investigation was the first quantitative fish study since the
channel reconstruction was completed in 1995. R2 concluded that the 2000 study
showed that the MWB was continuing to mature and develop as a functioning
ecosystem, and "that healthy and self-sustaining salmonid populations of brown trout
and mountain whitefish have developed in the MWB" (R2 Resource Consultants, May
2001, p. 5-1). All age and size classes of trout were captured, indicating that successful
reproduction is occurring, an observation that was substantiated by the even-greater
redd density documented in the 2001 fall spawning survey.
Basin-wide studies of macroinvertebrates have been conducted basin-wide since 1986
for the DEQ. This study has a station on the MWB, which was sampled 3 times during
the report period (1999, 2000, and 2001). Each year, it was concluded that the MWB
station was unimpaired based on biointegrity scores greater than 90% (McGuire, 2002
[Clark Fork River Macroinvertebrate Community Biointegrity: 2001 Assessments,
Draft]). These studies corroborate R2's findings.
5.2 Evaluation of Rocker OU
5.2.1 Previous Statement on Protectiveness
From the first five-year review in 2000, the following statement was made regarding
the protectiveness of the Rocker remedy:
The Rocker OU cleanup is nearly complete. Some operation and maintenance
activities, including monitoring, began in November 1997, and EPA is discussing a
more complete operation and maintenance plan with the responsible party. Most
remedial objectives have been attained, such as reduction in plume concentrations and
protection of uncontaminated aquifers. EPA will continue to monitor the site, and
may invoke additional work or contingency measures to meet cleanup standards in
groundwater and insure that the plume does not migrate. EPA certifies that the
remedy for this operable unit remains protective of human health and the environment
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because of the presence of the alternative water supply and the institutional controls
which prevent contaminated groundwater use. However, continued monitoring,
further institutional control implementation, and aggressive operation and
maintenance activities are required.
5.2.2 Follow-Up Actions Since Last Review
Soils and groundwater at the Rocker OU were remediated in 1997, yet arsenic
concentrations in groundwater rebounded to above 10,000 (ig/1 in certain wells, such
as RH 62 and RH 65 below the repository. At the time the Consent Decree was
prepared in fall of 2000, it was known that construction activities in the adjacent
Streamside Tailings OU could impact groundwater conditions at the Rocker OU and
would change the location, elevation, and gradient of Silver Bow Creek in the area of
the Rocker OU. These construction activities and the rebound in arsenic
concentrations at the Rocker site prompted the development of a supplemental
treatment plan to be implemented prior to and contemporaneous with SST OU
construction activities adjacent to the Rocker OU. The July 2000 Streamside Tailings
Operable Unit Construction - Treatment Sampling and Analysis Plan contained in
Appendix G of the Consent Decree described a two-phase strategy to determine
groundwater hydraulic parameters and develop an in situ zone to reduce arsenic
concentrations. The objectives of the supplemental treatment were to
¦ Implement supplemental treatment in coordination with SST OU construction activities
¦ Reduce dissolved arsenic concentrations at interior well locations, primarily wells RH-
62 and RH-65
¦ By means of a tracer test, determine groundwater flow velocity, flow direction, reagent
mixing, and oxidant consumption
¦ Analyze the results of monitoring to determine the effects of reagent delivery
Nine delivery ports in two arrays were installed in September 2001 for the
introduction of reagents into the gravel zone. Each delivery port was constructed
using 2-inch diameter PVC casing with 5-foot perforated well screen. Injection of
reagents was made by V2 -inch PVC pipe, with the bottom four feet slotted, inserted
into each delivery port to distribute reagent amendments throughout the water
column. In late September through early November 2001, alternating deliveries of
potassium permanganate and ferrous sulfate, at approximately seven day intervals,
until four deliveries of each reagent had been performed. Weekly sampling to assess
the results of reagent delivery was conducted until February 2002.
Arsenic levels in well RH-62 temporarily declined from 17,800 (ig/1 before treatments
to as low 3,060 (ig/1. The arsenic concentration in RH-65 dropped to 3,090 (ig/l (from
a pretreatment concentration of 7,490 (ig/1). There were broad fluctuations in the
arsenic concentrations in wells RH-62 and RH-65, but overall, concentrations
appeared to decline during the course of the supplemental treatment. However,
drawing firm conclusions regarding the efficacy of the treatments was made more
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difficult by the temporary alteration of groundwater flow patterns and elevation
changes at the Rocker site induced by dewatering actions during SST OU construction
activities. Because of this uncertainty, Atlantic Richfield, EPA, and DEQ jointly
agreed to re-implement the treatment plan in 2002. The 2002 treatment work was
completed in three parts beginning in August and ending in December 2002. Re-
treatment data indicated that arsenic concentrations were temporarily reduced by
more than 50 percent in both wells RH-62 and RH-65 as a consequence of the
delivered reagents.
5.2.3 Operations and Maintenance Activities
Quarterly groundwater sampling has been conducted since 1998 to monitor trends in
water quality. Four quarterly groundwater sampling events are conducted each year
in February, May, August, and November. The specific details of each sampling
event are provided in quarterly reports submitted after each event. Each report
presents all the data collected during that event, including field notes and field data
sheets. In addition, an annual qualitative monitoring inspection and evaluation of
general site conditions is conducted at the site. The result of O&M activities are
summarized in Annual Operations and Maintenance Reports. A summary of the
O&M costs at the Rocker OU for the last five years is provided in Table 5-10.
Since the last five-year review, the water quality in the treatment zone appears to
have reached equilibrium with the hydrology and geochemistry of the site, and the
effect of the supplemental dosing operations was short-lived. This equilibration has
resulted in a rebound in arsenic concentrations above 10,000 (ig/1 in the gravel zone
below the repository. The source of the arsenic appears to be arsenic-containing
groundwater immediately underlying the gravel. There is no evidence to suggest that
source of arsenic is the gravel zone itself or the stabilized soil mass overlying the
gravel zone. Groundwater data from the gravel zone and other surrounding monitor
wells indicates minimal expansion of the arsenic plume since completion of the
remedial action.
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6.1 Administrative Components
The Silver Bow Creek/Butte Area five year review team was lead by Scott Brown, an
EPA project manager, and included EPA and state of Montana project managers of
the OUs covered in this review, and technical staff from EPA's contractor CDM with
expertise in areas of geology, civil and environmental engineering, and community
involvement.
The review was initiated in May 2005 and included the following components:
¦ Community involvement
¦ Local interviews
¦ Document review
¦ Data review
¦ Site Inspection
¦ Five year review report development and review
The schedule for the review extended through August 2005.
6.2 Community Involvement
Activities to involve the community in the five year review process were initiated
with a kick-off meeting on April 12, 2005. The project team discussed the best ways of
notifying the affected communities and of obtaining input from members of the
public, regulatory agencies, and other entities.
6.2.1 Notification
As specified in the guidance, it was agreed that CDM would place display ads in the
local papers (the Montana Standard and the Anaconda Leader) (Appendix A). The
content of both ads followed the guidance and was approved by EPA prior to
placement. The first ad announced the start of the five-year review process and ran in
the Montana Standard on May 7, 2005 and in the Anaconda Leader on May 11, 2005.
The second ad will announce the completion of the five-year review process and ran
in both papers in August 2005.
6.2.2 Obtaining Input
A number of brief interviews were planned with persons identified by the project
team. As suggested in the guidance, potential interviewees included members of the
general public, site neighbors, members of special interest groups, representatives of
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local government and oversight personnel. CDM prepared an initial list of
interviewees and questions to EPA and DEQ team members, who made revisions to
the proposed list. This final list of potential interviewees included 12 individuals
(Table 6-1).
The site includes a number of communities spread out over a very large area. The
intent of the interviews was to gain additional perspective on the remedies under
review. Due to the very small sample size, the input cannot be considered to be
representative of one or more of the communities within the site. In some instances,
the input identified areas issues that were potential concerns and the reviewers were
made aware of the input as part of the review process. However, community input
itself was not used to determine the protectiveness of the remedy.
Individuals listed in Table 6-1 were called and asked to participate in the interviews.
They were sent a list of six questions via mail or email. Those questions were based on
examples provided in the guidance. They were modified slightly to relate to the
specific OU or OUs being discussed.
Most interviewees were asked the same basic questions. The exception was the
individual providing Bureau of Land Management construction oversight for SST OU
and the individual providing regulatory input from the Fish Wildlife and Parks
Department (Table 6-2).
Most people elected to provide their answers to the interviewer over the telephone.
The answers were then written up by the interviewer and sent to them via email for
review. Several people provided their answers in writing, either via email or direct
mail. Responses were obtained from 11 individuals (Table 6-2). In addition to the
input received from these individuals, a letter was received from Mr. Jim Kuipers of
CFRTac.
6.2.3 Responses
The complete, unabridged written responses from the 12 individuals that were
interviewed and from Mr. Kuipers, are provided in Appendix B. Annotated responses
to the most frequently answered questions are presented below:
What is your overall impression of the project?
¦ The project was not a success. There are still rebound effects, and EPA did not clean up
the aquifer as planned. They are still doing work, so maybe it will be cleaned up
eventually - by EPA or Mother Nature (Molignoni).
¦ The SST OU seems to be going along as planned. The WSP OU has a few issues that
concern the county. The primary concern is with long-term preservation and
maintenance of Rainbow Bridge. ARCO was supposed to ensure that this historic
bridge would be preserved. However, that is not occurring. It has been flooded and
pieces of the concrete base are broken (Bouck).
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¦ My overall impression is that work that has been completed has vastly improved the
condition of Silver Bow Creek. Definitely the looks of the area have changed
dramatically in a positive direction (Dziak).
¦ Reasonable progress is being made (Peoples).
¦ The SST OU is coming along fabulously. The new contractor is very fast, and it looks
nice when they move on. EPA is also doing a good job in Rocker, and we are hoping
that the ROD for the Butte Hill will also be successful (Kerns).
¦ The work done to date is wonderful. Total removal of the mine wastes from the
streamside was more than what was needed, but is very positive. The streamside looks
better than the natural environment nearby. The WSP are doing their job, and the Mill
Willow Bypass is great - especially the meanders. I am generally very happy with the
cleanup (Ueland).
¦ The Greenway Service District has been closely involved with remedial activities along
Silver Bow Creek as efforts to coordinate remediation with habitat restoration along the
Silver Bow Creek Corridor. We believe remediation goals and objectives are being met.
DEQ has demonstrated the ability to respond to our restoration objectives to improve
the character and the quality of the corridor. Their remediation strategies have adapted
to varying conditions within the corridor to achieve remediation and restoration goals,
including the removal of additional tailings in areas where tailings were slated to have
remained for "in situ" treatment (Skrukrud).
¦ Superfund projects take way too long to complete, and EPA does not put enough
emphasis on public involvement. At SSTOU, remediation seems to be proceeding as
planned although there are unresolved issues with long-term O&M and stewardship of
the reclamation. DEQ appears to think it is premature to commit to a level of O&M&M,
especially in relation to the Greenway, but that is a vital part of remediation success. At
the MFOU, the public felt their concerns and input were not attended to during the
ROD process. It was a disappointment that innovative treatment technologies were not
fast tracked as part of the process selected (Sesso).
¦ The project is going well and has been a success. The design is done in stages from
upstream to downstream and is evolving as new information is obtained during
construction. The vegetation along the streambank is excellent. The vegetation on the
floodplain is very good with the exception of several small areas where I believe the
soil has conductivity levels that prevent vegetation from growing (Brockman).
¦ The parts of the project I have seen (SST OU and WSP OU) seem to be well-planned
and, given all the glitches that are inevitable on big undertakings, seem to be
progressing pretty well. Visually, portions of the SST OU and the bypass at WSP OU
give the impression that things are on the mend (Benson).
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What effect have site activities had on the surrounding community or local
government?
¦ There were not too many effects. EPA was in and out pretty quickly. The most visible
and lasting effect is the grassy mound where the contaminated soils are stored. It
doesn't look natural and sticks out. It just looks like a Superfund site (Molignoni).
¦ There are occasional problems with chain of command. For instance, DEQ located a
haul road that splits a county road (Stewart Street crossing) without going through
channels. (A letter from DEQ responding to this concern is included in Appendix B.)
Also, with the recent concerns about the spread of West Nile Virus across the state, the
county is worried about having breeding areas for mosquitoes and the borrow pits
have large areas of standing, stagnant water in them (Bouck).
¦ There have been many aesthetic improvements. Recreational opportunities have been
increased by the addition of numerous walking trails. With the cooperation of the
agencies and Atlantic Richfield, MERDI has been instrumental in the redevelopment of
over 30 acres of Brownfield area (BPSOU). This includes a sports complex and has had
many aesthetic and economic benefits for the community (Peoples).
¦ The effects have been positive. Many mine waste areas have been turned into green
spaces, and it has greatly improved the aesthetics in the area. Additionally, the health
risks have been greatly decreased to EPA's work (Kerns).
¦ The major impact has been a temporary influx of money into the community from jobs
and expenses associated with the construction work. Not aware of any negative
impacts (Ueland).
¦ I believe site operations have had a positive effect. The ongoing activities are tangible
and the outcome, the new stream corridor and healthy vegetative cover, represent a
new beginning for the stream corridor that is apparent to anyone who visits or sees the
corridor. I am unaware of any adverse effects on the community - every effort is made
to work with property owners and adjoining landowners to cause as little disruption in
day-to-day activity for the community (Skrukrud).
¦ Involvement in Superfund has been a burden for BSB. Existing resources were not
sufficient to take on the tasks of reviewing documents and active participation in
Superfund activities. We were fortunate to maintain staff continuity, and the burden
has been made manageable by grants from the State and ARCO to hire additional
personnel. BSB is doing a good job keeping up with the process. The activities at SST
OU have not had an immediate impact on citizens of BSB. When remediation is
complete and the Greenway is finished, the community will benefit from the added
recreational benefits, but most people are not affected at this time. For the MFOU, site
operations have not had a significant impact on the community. However, unresolved
concerns associated with the OU have had a negative impact (Sesso).
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Five-Year Review Process
¦ At WSP OU, I had heard there was some concern over traffic and dust when the ponds
were being reconstructed. This is only hearsay however, as our TAG was limited to
Milltown at the time (Benson).
Are you aware of any community concerns?
¦ The biggest concern is that people in Rocker cannot drill wells anymore because of the
Institutional Controls. Because the cost of water is rising, people have to cut back on
watering to stay within their household budgets. This has a negative impact on the
aesthetics of the community (Molignoni).
¦ The primary community concerns are those with citizens of Opportunity. A number of
people had used pasture owned by ARCO but leased long-term to the community.
When the SST OU remediation began, they were no longer allowed to graze livestock
on the land. This has been a hardship for them. A citizens group has recently been
formed to deal with Superfund issues (Bouck).
¦ The recent controversy over attic dust (BPSOU) has somewhat polarized the
community. People are also concerned that the cleanup is both protective and
supportive of future redevelopment (Peoples).
¦ Attic dust at the Butte Hill (BPSOU) is a new concern that resulted from Imagine
Butte's survey of the low-income community in that area. Interest in the MF OU seems
to have died down. There is also some debate as to whether EPA should make ARCO
remove the Parrott Tailings or leave them in place. I am not aware of any concerns for
Rocker or SST OU (Kerns).
¦ Most people were not terribly concerned with contamination prior to cleanup. The area
had been contaminated for over 100 years, and we just lived with it. There were no
obvious health effects that people were aware of, and environmental effects seemed to
be limited. Most people are aware that a cleanup has taken place, although many do
not know the details. They can tell that the area looks better. Not aware of any specific
community concerns - other than a desire for the economic boost to continue (Ueland).
¦ One concern is the uncertainty of funding and plans for long-term operations,
maintenance and management of the remedy (SST OU). Sufficient funds and plans
must be in place to protect and preserve the remedy in perpetuity. Community
members have discussed these concerns with the agencies. The reality is that
operations, maintenance and management are a reality for this site and must be readily
acknowledged and planned for to ensure the health of the corridor (Skrukrud).
¦ For SST, there have not been a lot of community concerns. There is a feeling that public
health-related concerns at other OUs have not received as much attention as did the
impacts to fish in the SST OU. There is also a concern that long-term stewardship of
remediation and restoration activities will not get the attention needed. For MFOU,
there has been some concern about future catastrophic events, such as a large
earthquake, or that the critical water level was not the most appropriate decision point.
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What would happen if PRPs and EPA are gone? There are concerns about health
impacts from the fog off the pit in winter and whether contaminated water in the
bedrock aquifer will affect wells in the alluvial aquifer. There is disappointment that
the water treatment selected did not include a resource recovery stage. There is residual
anger at ARCO for shutting off the pumps in the first place. There are issues related to
confusion over the reclamation obligations of the current mine operations by MR and
remedial obligations by MR and Arco under Superfund (Sesso).
¦ Citizen's groups have asked EPA to consider possible effects of the Warm Springs
Ponds operation due to likely changes in the influent water quality from improvements
(nitrate reductions) in the Butte Silver Bow municipal wastewater treatment facility and
due to future discharges of high hardness water from the HSB WTP.
Do you feel the remedy is protective?
¦ Yes, as long as they keep the Institutional Controls in place (Molignoni).
¦ We can't say at this time whether the remediation is protective. It needs time to age, to
see how things will work out. We had no significant concerns with the proposed
remedy. However, there have been some issues that lead us to question if work is being
done as planned. For instance, if the Rainbow Bridge preservation is not being handled
successfully, there may be other less visible issues that are also going wrong. This
concern was reinforced by recent problems with cleanup at the Anaconda Smelter Site
where an area that had been remediated ended up having beryllium contamination at
depth that needed to be cleaned up (Bouck).
¦ I believe the remedy is somewhat protective, as it has removed some degree of tailings
from the immediate stream banks. My concern is that much of the railroad grades that
parallel the stream still contain high concentrations of heavy metals and the possible
leaching of these metals back into the system. My other concern is for water quality as
it comes into the system from the Butte area. This relies greatly on Butte mine flooding
and the Treatment plant system when it comes on line (Dziak).
¦ Yes, providing they continue to monitor the wastes left in place. The underlying
groundwater is contaminated - that is a given. We need to be sure that the
contamination does not migrate to any other aquifers (Peoples).
¦ Yes. Anyone who has been to the SST OU can see that it is working. For the BPSOU, I
would prefer to see the water treatment plant become part of the final remedy, rather
than the lagoons that are now in place. BSB have been working hard to make sure that
the community will benefit in the long run (Kerns).
¦ Yes. It is certainly better than it was before. Although we won't know for sure for many
years, it seems to be working well. I trust that Atlantic Richfield and the regulators will
keep up the monitoring and will do what is right to ensure protectiveness (Ueland).
¦ Remedial actions (including tailings removal, stream reconstruction and riparian,
floodplain and uplands revegetation strategies) coupled with restoration enhancements
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and the long-term land use strategy for the corridor to remain as open space for public
benefit will be protective of the remedy. It is imperative that costs of operations,
maintenance and management be acknowledged and funded (Skrukrud).
¦ For SST, the remedy appears to be protective. It is based primarily on threats to fish and
other organisms in the water - not on a threat to human health. DEQ is making good
decisions on over excavating where needed, such as at Ramsey Flats. The area is
definitely in much better shape than it was before. They are also making good decisions
on scheduling, by accelerating cleanup of some areas, such as the rest stop on the way
to Anaconda, without compromising the quality of the cleanup. Long term O&M of the
remediation and restoration will be the key to overall protectiveness of the remedy. For
MFOU, BSB hopes that the remedy is protective and that the scientists who defined the
hydrogeologic system are correct. There is less confidence that anyone really knows for
sure if the critical water level of 5410 feet is accurate. If it is, then the remedy appears to
be protective (Sesso).
¦ I think the jury is still out on this. For SST OU, we won't know until the work is
complete, stabilization measures are in place, and vegetation has been established and
grown. The real proof will be a 50-year flood event! At WSP OU, the last meeting I was
at in Opportunity indicated there was still a concern over arsenic. Our technical
advisor, Jim Kuipers, wrote a white paper on arsenic. If the fish biologists are correct,
the liming operations at the pond are probably a contributor to the algae blooms we see
all along the river in summer. But this is of course compounded by ag operations,
sewers and septics, and other runoff sources of nutrients (Benson).
Do you feel informed about site progress and activities?
¦ Not really. It would be nice if EPA and DEQ could send out more fact sheets or get
stories in the newspaper to keep people up to date. It is a complicated site and people
get confused just trying to keep all the pieces separate. The fact sheet inserts in the
Anaconda Leader that EPA does for the Anaconda site are helpful (Ueland).
¦ Yes, but BSB is directly involved in the activities, and is therefore better informed than
most people in Butte. The public sees BSB staff members as an advocate for them. There
is a reasonable level of trust that the people in local government are looking out for all
citizens of Butte. In general, EPA does not spend the effort needed in Butte to inform
and engage the citizens (Sesso).
¦ The DEQ has been responsive to requests for updates on the status of the project and
available to the public in many forums (Skrukrud).
¦ Yes. EPA does a good job of keeping people aware of what is going on. It is hard to
keep people's interest alive about a complicated subject over so many years. It was
easier in Missoula, where they only had one issue to deal with and it was over a
relatively short time frame (Kearns).
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¦ Most of the information I receive comes from local newspaper articles or sections of the
newspaper that devote a section for the work that has been done. I have attended a few
meetings both public and state sanctioned. I also receive an update once in a while on
the work being performed as a signed attendee of a local meeting (Dziak).
¦ Yes, but there needs to be more effort informing County Commissioners. DEQ should
hold annual pre- and post-construction meetings with the commissioners that will
bring them up to speed so that they can answer questions from the community. DEQ
should also consider speaking to the community group from Opportunity (Bouck).
¦ I used to, but EPA has cut back on the communication over the last year or so. Even
though the site is pretty quiet, people still need to be updated fairly regularly. A public
meeting where we can ask questions would be a good thing at least once a year, if not
more often (Molignoni).
¦ Yes. Because our company works in redevelopment of this area, I am better informed
than the average person in Butte about the cleanup (Peoples).
¦ Fairly well informed. I could do more on my own to get more info. However, I have
noticed that the media have not given much coverage unless there is some unusual
event like the dead birds at the pit. That is where most people get their info (Benson).
Do you have an additional comments or suggestions?
¦ EPA should put some additional vegetation, like trees or bushes, out on the grassy
mound at Rocker to make it look more natural (Molignoni).
¦ We need to ensure that the long-term O&M is adequately planned, implemented, and
funded. There appears to be a belief among regulators that once the remediation is
complete, all land uses can be allowed. However, the area has been damaged and
wastes are left in place in many areas. Community standards for how we maintain
things may be higher than what would otherwise be done. We need to get on the same
page in this regard. For example, we believe restoration projects are a part of the overall
O&M strategy and a good way to help achieve that end. Since most remedies selected
involve wastes-left-in-place, these sites will require more money at the back end of the
project than typical Superfund sites. The track record for stewardship, ICs, and O&M at
Superfund sites is not so good. Leaving wastes in place is likely the most practical
option and can/will be protective, but we must face concerns related to maintaining
these sites for future generations. Vigilance has to be maintained to weather losses that
will occur when the people working on the projects turn over. EPA's review and other
monitoring processes must be substantial and have the teeth needed to ensure that
remediation is being maintained as promised (Sesso).
¦ I have concerns with the Greenway project and the expected increase use of the area by
the public. Items that need to be addressed will be trail maintenance, ORV travel,
trespass and injured wildlife (Dziak).
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¦ MERDI is concerned with two issues: there needs to be a redevelopment fund that is of
sufficient size to make an impact of the community, and the O&M funding must be
sufficient so that the county is not stuck with the costs for O&M in the future. Finally,
the remedy must obviously be protective of human health, but it should also allow for
(and support) future redevelopment of the area (Peoples).
¦ We need to discuss the need for a solid operations, maintenance and management
plans for the corridor and receive assurances that funds will be available to implement
these strategies (Skrukrud).
¦ The Greenway trails that were constructed as part of the floodplain were never finished
by the Greenway organization. These trails are deteriorating due to vegetation
encroaching on the trail. Also, the bridges planned for the trail to cross the creek were
never installed. Future work on the trail and bridges could damage the good vegetation
on the floodplain and creek banks. Work on the Greenway Trail should be coordinated
better with work on the remedy. This would also allow for the area to be re-opened for
public use (Brockman).
¦ Maybe getting more media coverage on how things are going at these sites, such as a
field trip in connection with the 5-year review. I think also that what would be of
interest to landowners along the river in the Deerlodge valley would be some
information on the type, duration, and other experience of landowners along Silver
Bow Creek (Benson).
What is the current state of construction?
¦ Reach A was essentially completed in 2000. However, the creek flow control dike and
bypass channel that protected the new channel and floodplain during the grow-in
period were removed in late 2004/early 2005. The regraded areas were seeded in
Spring of 2005 (Brockman).
Have you encountered any problems that changed or will change the remedy?
¦ There were no major problems encountered. There were several minor problems that
resulted in minor adjustments to the design as it progressed downstream, but these
were mostly reactions to what was learned during construction (Brockman).
Have any problems impacted construction or implementability?
¦ No problems that impacted construction or implementability come to mind
(Brockman).
Have you done any site visits, inspections, reporting, etc at the site?
¦ I have on a very limited basis toured sub-area 2 as construction was taking place (WSP
OU). I do make a point of looking at the area as I drive by/or near while working or
otherwise (Dziak).
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Have there been any complaints, violations, or other incidents?
¦ I have received a couple of calls on "problem" beaver that inhabit some of the
completed areas on Silver Bow creek. These calls have been from state personnel
concerned about possible destruction of re-vegetated areas. I have also received calls
regarding bridges and structures built over the stream without permits (Dziak).
6.3 Document Review
In preparing this five year review, the following documents were reviewed:
¦ Atlantic Richfield Company, WSP, Five-Year Review Report, 2005
¦ Atlantic Richfield Company, WSP, Quarterly Operations and Maintenance Report,
Fourth Quarter 2004
¦ Bighorn Environmental, Monitoring Report 2004, SST OU, 2005
¦ EPA ROD for BMF OU, 1994
¦ EPA ROD for SST OU, 1995
¦ EPA Comprehensive Five-Year Review Guidance, 2001
Full reference citations are included in Attachment 2 for each document reviewed.
Applicable or relevant and appropriate requirements (ARARs) were reviewed to
determine whether any changes to the ARARs has occurred since the sign of RODS or
ESDs at any of the eight OUs included in this review that could impact the
protectiveness of the remedy of the site. The results of this review are discussed in
Section 7.0, under Question B: Are the Exposure Assumptions, Toxicity Data,
Cleanup Levels, and Remedial Action objective (RAOs) Used at the Time of the
Remedy Selection Still Valid?
6-10
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Section 7 Technical Assessment
A technical assessment of the remedies for the five Silver Bow Creek/Butte Area OUs
undergoing a full statutory review is performed as part of the five-year review
process. This technical assessment, focusing on answers to three unique questions, is
presented in this section of the five-year review.
7.1 Question A: Is The Remedy Functioning As
Intended By The Decision Documents?
7.1.1 Warm Springs Ponds Active and Inactive OUs
Remedial Action Performance
In general, the remedial action at the WSP OUs is protective of human health and the
environment. The WSP OUs are functioning as designed and effectively remove
influent contaminants from Silver Bow Creek, protecting the Clark Fork River
downstream. Wet and dry closures over tailings are protective of human health and
the environment by preventing human exposure to surface wastes and by minimizing
further oxidation and mobilization of heavy metals in the waste materials. The dams
are routinely inspected for stability and have met all dam safety requirements.
The remedy is supporting a healthy, diverse, and abundant aquatic, terrestrial, and
avian wildlife population, as documented by the WSP and MWB biomonitoring
studies. These studies are corroborated by the benthic macroinvertebrate surveys
conducted by McGuire on Lower Silver Bow Creek and the Upper Clark Fork River,
which indicate continued improvement of benthic macroinvertebrates and no
indications of metals impacts on the diversity or abundance of benthic
macroinvertebrates.
Groundwater is being prevented from migrating offsite through use of the
groundwater interception trench and the pumpback system. Exceedances in
downgradient piezometers resulted from a shutdown of the pumpback system;
therefore, the pumpback system will need to continue operation into the foreseeable
future.
Performance standards were largely met for cadmium, iron, lead, mercury, silver, and
selenium, and total suspended solids in the WSP effluent. The only exceedances of
these constituents were generally attributed to the large runoff event of March 2003.
Copper and, to a lesser extent, zinc exceedances have occurred primarily during
spring runoff. The final daily maximum discharge standard for copper has been met
98 percent of the time during this performance evaluation period. It is also
noteworthy that the 96-hour TRV for dissolved copper has not been approached
during the past ten years. The number of monthly exceedances for copper has
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Section Seven
Technical Assessment
decreased in recent years. This is likely due to better operation, performance,
optimization, and maturation of the WSP system. Or, it could be because the WSP
have been treating lower than normal flows and contaminant loads due to the
prolonged drought. For example, exceedances occurred in spring of 2002 but the
influent loads and concentrations were not exceptionally high. Special consideration
should be given to operational procedures at the WSP during the spring runoff period
so that treatment needs can be better anticipated during high flows. Or, other reasons
for the spring exceedances need to be determined. For instance, seasonal turnover of
the ponds or ice scour may be impacting the WSP performance. However, it is
possible that the WSP are operating at their maximum potential given the inherent
limitations of alkaline precipitation and settling technology and the physical
limitation on the size of the ponds. The best method to achieve compliance will be to
complete the upstream SST OU cleanup, and further control releases from the BPS OU
into Silver Bow Creek.
The seasonal exceedances/concentration oscillation for arsenic is a problematic
performance issue. Other waters at the site such as the Mill-Willow Bypass show
similar concentration oscillations and are likely affected by similar geochemical
processes for arsenic. Therefore, despite the fact that the ponds are exceeding the
performance standard based on protecting human health, human health risks from
arsenic should be minimal because there is no human consumption of surface water
or ground water from the WSP, and there is no indication that this water is impacting
downstream domestic wells. Arsenic concentrations do not exceed aquatic life
criteria, and based on these levels, the discharge should be protective of aquatic
receptors.
The loading analysis presented in Section 5 shows that the loads from the WSP during
the period of exceedances is generally low compared to the loads from the MWB.
Thus, from a basin-wide perspective, bringing arsenic concentrations into compliance
will not result in a large decrease in arsenic loading to the upper Clark Fork River.
The loading analysis presented in Section 5 was a cursory analysis performed on a
less than ideal dataset. The water quality at MWB-3 had to be coupled with flow data
from the USGS to approximate loads. Additionally, there was not enough resolution
in the data to determine whether or not seepage from the toe drains was having an
impact on the MWB. In order to resolve these questions, first, it is recommended that
concurrent flow measurements be made at the time of water quality sampling in the
MWB. Secondly, these issues could be resolved with a supplemental loading analysis
performed to determine loads along the MWB, in Silver Bow Creek below the WSP,
and at the headwaters of the Clark Fork River. Understanding the relative
significance of the arsenic loading from the WSP would aid decision-makers in
determining whether or not additional arsenic treatment in the WSP would result in a
significant benefit when other arsenic sources in the upper CFR basin are considered.
If EPA ultimately decides that arsenic issues in the WSP effluent must be addressed,
this will require a separate treatment step in addition to the current treatment of lime
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Section Seven
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addition and settling. The feasibility of adding an arsenic polishing treatment step to
facilitate arsenic removal would need to be studied.
System Operations/O&M
In general, system operations and O&M activities appear to be protective of the
remedy. System operations and O&M activities appear to be protective. The
exception to this was the March 2003 overflow event, where upstream debris jams
broke loose, resulting in clogging of the inflow trash rack and large pulse of water
that overwhelmed the treatment system. In order to prevent system upsets resulting
from similar situations in the future, a safety and awareness plan was developed for
spring runoff and summer thunderstorm events and incorporated into the Operations
and Maintenance Plan. The plan includes inspections of the inlet channel and
upstream bridges and channels for debris, and plans for action to address conditions
that could lead to a similar overflow event as that which occurred in March 2003.
Improvements to the supervisory control and data acquisition system (SCADA) were
implemented that include a real-time continuous stage recorder upgradient of the
trash rack that, in addition to providing an emergency call-out for high stage
conditions, can be accessed remotely so that the operator can determine the exact
stage.
Opportunities for Optimization
As was shown in the performance evaluation in Section 5, concentrations of silver and
selenium were constantly well below performance standards. It appears these
parameters could be dropped from the analytical list.
Early Indicators of Potential Issues
There are no early indicators of additional potential issues (the major performance
issues have been discussed in this report).
Implementation of Institutional Controls and Other Measures
There are no domestic or municipal water users that withdraw water immediately
downstream of the WSP or from the shallow alluvium. There is also a ban on
construction of shallow wells in the vicinity of the WSP. Therefore, these institutional
controls are protective of human receptors.
7.1.2 Rocker OU
Remedial Action Performance
The remedy is functioning within the scope outlined in the ROD, as modified in the
documentation of significant changes. Because EPA projected moderate difficulty in
meeting the ARARs in a limited part of the groundwater system (i.e., the shallow
alluvium), the RAOs were prioritized according to the actual or potential use of these
groundwater zones. The prime objective is to prevent pollution from reaching the
high quality lower aquifers which are currently used (Tertiary groundwater system)
and that have the potential to be used (deep alluvium). Monitoring to date has
documented the effectiveness of the remedy in meeting this prime objective. The soils
component of the remedy continues to perform as designed.
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Section Seven
Technical Assessment
Remedy O&M
Systems operation and O&M activities for the Rocker OU are consistent with site
requirements and objectives. Monitoring of the plume continues on a quarterly basis,
and repository cap and other site maintenance actions are implemented, as necessary,
on an annual basis. Costs for system operation and O&M have been within an
acceptable range.
Early Indicators of Potential Issues
As stated in Section 4.2.2.1 of this five-year review, two areas of arsenic contaminated
soils were identified during implementation of the remedy. These materials were
evacuated, treated, and stored in the on-site repository. EPA will continue to examine
whether additional work is needed to address non-compliance with performance
standards in the shallow, deep, or tertiary aquifers. EPA may also look at the
appropriateness of a waiver of standards for the affected aquifers. Finally, EPA will
examine the existing institutional controls relevant to these aquifers.
Implementation of Institutional Controls
The MDEQ instituted institutional controls on groundwater wells, eliminating a
potential pathway for arsenic contaminated water in the shallow alluvial aquifer to
enter both the deep alluvial and tertiary aquifers through well installation. This ban
also controls the exposure pathway for humans from the contaminated groundwater
in the shallow alluvial aquifer.
7.1.3 Butte Mine Flooding OU
Remedial Action Performance
The overall remedy as defined by the decision documents on the BMF OU is ongoing.
The HSB WTP, the only portion of the remedy that is complete, is sending effluent to
the MR mining operations and not discharging into Silver Bow Creek at this time.
Long term monitoring of the Berkeley Pit and all ancillary mine shafts and monitoring
wells is ongoing. As stated in Section 4.3.2, modeling predicts the CWL in the
Berkeley Pit will not be reached until 2020. The water levels in several monitoring
wells measured in 2004 increased only 60% of the increases seen in 2003. This is a
direct result of the diversion of Horseshoe Bend drainage water from the Berkeley Pit
and into the HSB WTP. Berkeley Pit water quality samples were collected twice in
2004 during depth profiling of the pit. The analytical results for these samples and
other water quality samples collected from monitoring wells and selected mine shafts
were for the most part unchanged.
Remedy O&M
A performance test run on the HSB WTP in December 2003 demonstrated the ability
to meet all the established interim effluent metals criteria. The final standard for
cadmium was not met during the 2003 performance testing. The results of this
performance test are presented below and summarized in Table 7-1. Additional
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Section Seven
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performance testing is scheduled for Fall 2005 to evaluate whether the HSB WTP can
meet the final cadmium standard without further modifications.
Opportunities for Optimization
The HSB WTP has three systems, the lime unloading, blowers and the clarifier rake
systems that are presently operating at lower than specified design rates. Each of
these systems is undergoing an engineering evaluation to determine the cause of this
operational bottle neck. Recommended upgrades to these systems are schedule to be
performed after completion of this evaluation.
Early Indicators of Potential Issues
There are no indications of potential equipment problems or operational problems
that would put the protectiveness of the HSB WTP at risk.
Implementation of Institutional Controls
Institutional controls are in place restricting the use of contaminated groundwater
from the BMF OU. Publications such as the PIT Watch, inform the public as to
progress on the Mine Flooding OU.
7.1.4 Streamside Tailings OU
Remedial Action Performance
The removal of contaminated materials from Silver Bow Creek has resulted in major
improvements in physical and ecological systems as measured in a variety of media.
Vegetation has been successfully reestablished in most remediated areas where
vegetation was originally sparse to non-existent. The decreases in instream sediment
metals concentrations and surface water metals concentrations have created an
environment in which healthier populations of macroinvertebrates and fish have
established. Further improvements in aquatic biota in remediated reaches appear to
be limited primarily by nutrient loading originating at the Butte POTW.
Opportunities for Optimization
Because the remediation and restoration implemented thus far for Silver Bow Creek
has been successful as measured by most parameters, only limited recommendations
are made for changes. DEQ and their consultants have made the following
recommendations.
¦ The most important recommendation for revegetation is to plant willows in the spring
to minimize mortality.
¦ Data collection for solid and water media should continue to follow the Comprehensive
Long-Term Monitoring Plan.
¦ Aquatic biotic resources should continue to be monitored according to the plan. In
addition to the existing battery of periphyton metrics, additional metrics may prove
useful for evaluating recovery in Silver Bow Creek and will be developed in the future.
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Section Seven
Technical Assessment
¦ Finally, multiple pass fish population estimates should be conducted to improve the
understanding of fishery trends in Silver Bow Creek after populations have increased
or multiple age groups appear.
Early Indicators of Potential Issues
There are no indications of potential equipment problems or operational problems
that would put the protectiveness of the SST OU remedy at risk.
Implementation of Institutional Controls
Institutional controls developed by Deer Lodge and Anaconda governments are in
place protecting the reclaimed corridor along the Silver Bow Creek Reaches (A
through R), comprising the SST OU.
7.2 Question B: Are The Exposure Assumptions,
Toxicity Data, Cleanup Levels, And RAOs Used At The
Time Of The Remedy Selection Still Valid?
7.2.1 Warm Springs Ponds Active and Inactive OUs
Changes in standards, newly promulgated standards, standards to be considered
(TBC).
Since EPA issued the RODs for the Warm Springs Ponds Active Area and Inactive
Area OUs, both the State and Federal aquatic and human health standards have
changed for several constituents of concern (Table 7-2). In accordance with the
preamble to the National Contingency Plan, ARARs are frozen at the time of the ROD
unless "a new or modified requirement calls into question the protectiveness of the
selected remedy" (55 FR 8757 [March 8,1990]). A discussion is provided below with
respect to surface water and groundwater performance standards, and each of the
State and Federal standards that have been modified since the time of the ROD.
Surface Water
Arsenic
The current daily maximum and monthly average performance standard for arsenic
in surface water discharge from the Warm Springs Ponds is 0.020 mg/L. This
performance standard is lower than the State and Federal acute and chronic aquatic
life standards, but exceeds the State human health standard for surface water (0.018
mg/L) and the federal MCL of 10 (ig/L. Water quality in the discharge from the
Warm Springs Ponds does not exceed current Federal and State aquatic life standards
and, therefore, must be considered protective of aquatic life to downstream ecological
receptors. Arsenic in discharged surface water from the ponds does exceed the
current federal and state human health standards. However, the water in the upper
Clark Fork River is not used directly as a drinking water source. Additionally,
existing institutional controls prohibit swimming in the Warm Springs Ponds the
upper Clark Fork River. Thus, there is not a pathway for human exposure to arsenic
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Section Seven
Technical Assessment
at levels that would reasonably present a health risk and the current performance
standard for arsenic in surface water continues to be protective of human health.
Biological monitoring conducted between 1995 and 2003 shows no clear trends with
respect to arsenic bioaccumulation in vertebrate and invertebrate species that inhabit
the Warm Springs Ponds. There appears to be an upward trend in tissue arsenic
residue in benthic macroinvertebrates at one of three monitoring stations within the
Ponds, but other biological data indicate that complex interactions are operating to
control metals concentrations and organism distributions within the Warm Springs
Ponds. Locations bearing maximum sediment metals were not necessarily areas
indicating elevated tissue arsenic concentrations or decreased invertebrate
abundance, although analyses indicate metals exposure within the WSP System.
Collection and analysis of biological data should continue at the Warm Springs Ponds
to clarify the presence and significance of increasing tissue arsenic trends to benthic
macroinvertebrates within the Pond system. However, the current performance
standard for arsenic in surface water does not affect the performance of the remedy.
Cadmium
The Federal and State aquatic life acute and chronic standards for cadmium have been
lowered (Table 7-2). The new acute standard is lower than the current daily maximum
performance standard by a factor of approximately 2 and the chronic standard is
approximately 4 times lower than the monthly average concentration. From 1998
through 2004, there were no exceedances of the existing daily maximum or monthly
average performance standards for cadmium. However, the Pond 2 discharge (SS-5)
exceeded the Federal chronic criterion continuous concentration (CCC - analogous to
State chronic standard) in approximately 8 percent of the samples analyzed (assuming
a hardness of 150 mg/L) over the evaluation period. It is believed that operation of
the WSP cannot be improved to consistently meet the lower cadmium standard
because the WSP are performing at their maximum ability given the inherent
limitations of size (i.e., they cannot be made larger) and alkaline precipitation
technology.
Copper
The Federal and State aquatic life acute and chronic standards for copper have been
lowered (Table 7-2). From 1998 through 2004, the existing daily maximum (0.026
mg/L) and monthly average (0.017 mg/L) performance standards for copper, were
exceeded in 2 percent and 10 percent of the samples analyzed for Pond 2 discharge
(SS-5), respectively. Lowering of the standard would increase the number of
exceedances, but would provide a higher level of protection to downstream aquatic
receptors. Similar to cadmium above, it is believed that operation of the WSP cannot
be measurably improved because the WSP are performing at their maximum ability.
Lead
The federal criteria maximum concentration (CMC) and criterion continuous
concentration (CCC) for lead have been lowered (Table 7-2). State of Montana
Aquatic life standards for lead have not changed. From 1998 through 2004, the
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Section Seven
Technical Assessment
existing daily maximum performance standard for lead (0.137 mg/L) was not
exceeded in any samples analyzed for Pond 2 discharge (SS-5). The monthly average
performance standard (0.017 mg/L) was exceeded in 3.5 percent of the samples
analyzed. Lowering of the standard would increase the number of exceedances, but
would provide a higher level of protection to downstream aquatic receptors.
Groundwater
Since implementation of the remedy at the Warm Springs Ponds OUs, the federal Safe
Drinking Water Act MCLs and the State of Montana human health standards for
groundwater for arsenic, cadmium, chromium, and lead have been lowered, relative
to the groundwater performance standards established for the Warm Springs Ponds
(Table 7-2). (Currently, groundwater in the area of the Warm Springs Ponds is not
used as a drinking water source and, therefore, lowering of the groundwater
performance standards to be consistent with State and/or Federal drinking water
standards would not affect the protectiveness of the remedy with regard to human
health). EPA will consider revising or keeping existing standards after further
examination of institutional controls and groundwater usage at the two WSP OUs.
Expected progress towards meeting RAOs
In large part, RAOs at the WSP OUs have been met and conditions have improved
dramatically over pre-remedial conditions. In large part, performance standards are
being met, and the WSP are supporting a healthy, diverse, and abundant aquatic,
terrestrial, and avian wildlife population. There is uncertainty as to whether the
arsenic performance standard can be met and whether or not meeting this
performance standard is a requisite for protectiveness in the upper Clark Fork River
basin.
Changes in Exposure Pathways
No changes in site conditions that affect exposure pathways were identified as part of
this five-year review.
Changes in Land Use
No changes in land use at the WSP OUs have been made since completion of the
remedy.
New Contaminants and/or Contaminant Sources
No new contaminants or contaminant sources have been identified at the site since
completion of the remedy.
Changes in Toxicity and Other Contaminant Characteristics
Toxicity and other contaminant characteristics have not significantly changed.
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7.2.2 Rocker OU
Changes in Standards and To Be Considereds
Since implementation of the remedy at the Rocker OU, a revised drinking water
standard for arsenic has been promulgated. The Arsenic Rule was published in the
Federal Register on January 22, 2001 (66 FR 6976). This Rule updates the current MCL
for arsenic to 10 (ig/L (from the previous arsenic MCL of 50 (ig/L). The effective date
of the Arsenic Rule was February 22, 2002. The revised Arsenic MCL is being applied
prospectively at all Superfund sites. Currently, the shallow groundwater system in
the area of the Rocker OU is not used as a drinking water source, but may be in the
future. The lower arsenic MCL may be applied as the cleanup standard for the
Rocker OU (replacing the prior standard of 18 (ig/L) through an appropriate ROD
modification or Explanation of Significant Differences. The application of the new
standard does not change the findings of this five-year review for the Rocker OU
because institutional controls are in place at the OU.
Although the arsenic concentrations in the shallow aquifer and gravel zone beneath
the repository have rebounded to a greater extent than originally anticipated, the
concentrations are, on the whole, significantly reduced compared to pre-remediation
results. The highest levels of arsenic in groundwater generally coincide with the
location of past operations at the site and the arsenic plume has not expanded beyond
the site's contingency wells. Any expansion of the arsenic plume will be detected
under the current monitoring program. However, the remedy is still considered to
have a moderate uncertainty when considering the potential time-frame to achieve
the cleanup standard of 10 (ig/L.
Changes in Exposure Pathways
No changes in site conditions that affect exposure pathways were identified as part of
this five-year review. Also, no changes in land use at the Rocker OU have been made
since completion of the remedy.
7.2.3 Butte Mine Flooding OU
There have been no changes in the physical condition of the Butte Mine Flooding OU
that would affect the protectiveness of the remedy.
Changes in Standards and To Be Considereds
The ARARs cited in the ROD for groundwater and surface water contamination have
been met by the HSB WTP. Since the signing of the ROD in September 1994, the Safe
Drinking Water Act (SDWA) (40 CFR141 /11-141.16) from which the discharge limits
of the WTP were based has modified the maximum contaminant level (MCL) for
arsenic. However, the effluent level for arsenic was set at the anticipated new
standard as illustrated in Table 7-2. The State of Montana also modified the cadmium
standard. This change was reflected in the 2002 ESD and incorporated into a final
discharge standard.
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Section Seven
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Changes in Exposure Pathways
The exposure assessments used to determine clean up levels included both current
and future exposures. There have been no changes in the toxicity factors for the COC
or the assumptions used to establish clean up levels for the Mine Flooding OU. The
remedy is progressing as expected and will be completed in 2020.
7.2.4 Streamside Tailings OU
There have been no changes in the physical condition of the Streamside Tailings OU
that would affect the protectiveness of the remedy.
Changes in Standards and To Be Considereds
Revised standards similar to those presented for the Warm Springs Ponds OUs, for
groundwater and surface water, have been promulgated and may be relevant to the
SST OU. EPA will work with the State (the State is the lead agency) regarding
whether these new standards are necessary or appropriate for the OU.
Changes in Exposure Pathways
The exposure assessments for used to determine clean up levels included both current
and future exposures. There have been no changes in the toxicity factors for the COC
or the assumptions used to establish clean up levels for the SST OU. The remedy is
progressing as expected and will be completed by 2011.
7.3 Question C: Has Any Other Information Come to
Light that Could Call Into Question the Protectiveness of
the Remedy?
7.3.1 Warm Springs Ponds Active and Inactive OUs
There is no other information that has come to light that would call into question the
protectiveness of the remedy. The remedy is functioning as intended and is
effectively removing contaminants from Silver Bow Creek that would have otherwise
discharged directly into the Upper Clark Fork River. Issues with respect to arsenic
and copper exceedances have been discussed. The site will continue to be monitored
for any changes in this regard.
7-10
7.3.2 Rocker OU
No additional information has been identified that would call into question the
protectiveness of the remedy. The site will continue to be monitored for any changes
in this regard. However, data and information obtained from the supplemental
treatment plan prepared in conjunction with the SST OU and implemented in 2001
and 2002 may be useful if any further action at the site is proved necessary.
7.3.3 Butte Mine Flooding OU
There has been no information gathered during this five year review that calls into
question the protectiveness of the remedy for the Mine Flooding OU.
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Section Seven
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7.3.4 Streamside Tailings OU
There has been no information gathered during this five year review that calls into
question the protectiveness of the remedy for the Streamside Tailings OU.
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Section 8 Issues
Based on information collected during preparation of this five year review report, the
following issues were identified (Table 8 -1).
Table 8-1
Issues Identified during this Five Year Review
Applicable
OU
Issue
No.
Issue
Affects Current
Protectiveness? (Y/N)
Affects Future
Protectiveness? (Y/N)
WSP Active and
Inactive OUs
1
Continual seasonal exceedances of
arsenic concentrations in effluent.
No - Arsenic concentrations are well
below aquatic life standards and the
water in the upper Clark Fork River
is not used directly as a drinking
water source. Additionally, existing
ICs prohibit swimming in the ponds
and the Clark Fork River.
Uncertain - If current ICs are
continued, human exposure to
arsenic in water will be prevented.
Nevertheless, new standards for
groundwater may be necessary in the
future.
WSP Active and
Inactive OUs
2
Meeting arsenic standards for surface
water will require an additional
treatment step (beyond lime addition
and settling) because the ponds are
operating at their maximum efficiency
and capacity. The cost-benefit of
additional treatment to meet lower
arsenic standards could be examined,
keeping in mind that the upstream SST
and BPS OU remedial actions will
decrease influent loading, improving
treatment performance, and that
significant additional arsenic loads are
discharged by the Mill-Willow Bypass
No - arsenic performance standards
are not consistently met throughout
the year. However, arsenic in WSP
discharge does not exceed aquatic
life standards and pathways for
human exposure are prevented by
ICs.
Uncertain - Additional arsenic
removal could enable consistent
achievement of the arsenic
performance standard. However, this
may not be necessary depending on
the effectiveness of upstream
remedial actions, and may not be
warranted if arsenic loads from the
WSP are low compared to loads
contributed by the Mill-Willow
Bypass..
WSP Active and
Inactive OUs
3
Increasing trend in benthic
macro invertebrate tissue metal
concentrations
Uncertain - Increasing tissue-metal
trends observed at only 1 of 3
monitoring stations. Data do not
correlate to metal sediment data and
significance is confounded by
increasing benthic invertebrate
abundance and diversity.
Uncertain - Continued monitoring of
trends in tissue metal concentrations
should be performed to determine if
risks are significant to fish or wildlife
inhabiting the WSP.
Rocker OU
4
Rebound of arsenic concentrations
below repository is greater than
expected
No - the well ban (1/4 mile radius) is
in place protecting human health.
Any significant changes in site
conditions will be detected with the
current monitoring program.
Possibly - the existing well ban
assures protectiveness. However,
the well ban in the area may be
changed. Implementation of additional
work or contingent remedies may be
required in the future.
Butte Mine
Flooding OU
5
The HSB WTP did not meet the final
cadmium performance criterion.
No - Effluent from the WTP is
currently recycled to MR mining
operations
Yes - should MR suspend their mining
operations, cadmium must meet the
final discharge standard or it must be
shown that an alternate standard is
protective before discharge to Silver
Bow Creek. Additional performance
testing is planned for Fall 2005 to
evaluate whether the HSB WTP can
meet the final cadmium standard
without further modifications.
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Section Eight
Issues
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Section 9 Recommendations and Follow-Up Actions
The recommendations and follow-up actions for the issues identified within the Silver Bow Creek/Butte Area site are summarized in
Table 9-1.
Table 9-1
Recommendations and Follow-up Actions for Issues Identified
Applicable OU
Issue
Recommendations and Follow-up Actions
Party
Responsible
Oversight
Agency
Milestone Date
Affects Protectiveness (Y/N)
Current
Future
WSP Active and
Inactive OU
1,2
EPA may conduct arsenic mass loading studies
(seasonal) to determine the significance of the
arsenic load from the WSP as compared to other
sources of arsenic loading in the basin. This may
provide a better understanding of arsenic loading
from numerous sources in the upper reaches of the
system.
EPA may initiate additional wildlife studies to
determine whether bioaccumulation of arsenic in
birds requires mitigation.
EPA
EPA/DEQ
January 2007
No
Uncertain
WSP Active and
Inactive OU
3
Continued periodic monitoring of trends in tissue
metal concentrations should be performed to
determine if risks are significant to fish or wildlife
inhabiting the WSP.
Atlantic Richfield
EPA/DEQ
Ongoing
Uncertain
Uncertain
Rocker OU
4
Atlantic Richfield will continue quarterly
groundwater sampling and O&M activities so that
any changes in site conditions will be detected.
Atlantic Richfield
EPA/DEQ
Ongoing
No
No - unless site
changes such as
changes to ICs
occurs
Rocker OU
4
EPA to evaluate the protectiveness and
continuation of the 1/4-mile radius well ban
EPA
EPA
Ongoing
No
No
Butte Mine Flooding OU
5
Atlantic Richfield and MR to conduct additional
performance testing. If the testing shows that the
final Cd standard cannot be met at the HSB WTP
without further modification, Atlantic Richfield and
MR will explore potential additional treatment
solutions or perform a protectiveness analysis to
determine if the discharge is protective of Silver
Bow Creek.
Atlantic Richfield
EPA/DEQ
Ongoing
No
Yes - this issue
must be
addressed once
discharge to Silver
Bow Creek begins
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Section Nine
Recommendations and Foiiow-Up Actions
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Section 10 Protectiveness Statements
With only the WSP and Rocker OUs having completed Remedies, it is difficult to
quantify the protectiveness of the entire Silver Bow Creek/Butte Area Superfund site
at this time. Statements are made below with respect to the remedies specific to the
Rocker and WSP OUs, respectively, and it can be stated that with the future
completion of remedies at other OUs, protection of human health and the
environment at the Silver Bow Creek/Butte Area site as a whole will improve.
Rocker OU. The original remedy is presently protective of human health and the
environment. Most remedial objectives have been attained, such as reduction in
plume concentrations and protection of uncontaminated aquifers. EPA will continue
to monitor the site and, if warranted, may invoke additional work or contingency
measures to meet cleanup standards in groundwater and insure that the arsenic
plume does not migrate. EPA certifies that the remedy for this operable unit remains
protective of human health and the environment because of the presence of the
alternative water supply and the institutional controls which prevent contaminated
groundwater use. However, ongoing monitoring, continued implementation of
institutional controls, and O&M activities are required to maintain protectiveness.
Warm Springs Ponds OUs. The remedy for the WSP Active Area and Inactive Area
OUs is currently functioning as designed. The Ponds serve to capture, treat, and
retain contaminants from upstream sources in other OUs, and greatly reduce
contaminant loading to the Clark Fork River. Discharge from the Active Area
treatment system is generally in compliance for most constituents. Arsenic
exceedances occur seasonally as a result of changing geochemical conditions in the
pond bottom sediments within the treatment ponds (Ponds 2 and 3) and copper and
zinc exceedances occur infrequently as a result of seasonal high flows into the Pond
system. Surface water discharge from the WSP treatment system typically exceeds
human health standards for arsenic during the late summer and fall of the year.
However, aquatic life standards for arsenic are never exceeded and institutional
controls are in place to protect against human exposure. During this evaluation
period, the frequency of exceedances of copper and zinc were reduced from the initial
five-year review period. Continued long-term operations and maintenance, coupled
with annual dam safety inspections, required water quality and biological
monitoring, will ensure that maximum protectiveness and effectiveness are
maintained within the recognized limitations of alkaline precipitation technology and
the physical size of the WSP system.
The WSP effectively remove or reduce acutely toxic concentrations of metals that
enter the treatment system from Silver Bow Creek. Whereas Silver Bow Creek above
the ponds supports absolutely no fish population and is severely impaired in respect
to invertebrate and periphyton (algal) community structure, the aquatic environment
immediately below the WSP supports healthy populations of trout, good biological
integrity for periphyton, and biological integrity for invertebrates. The pond system
CDM 10-1
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Section Ten
Protectiveness Statements
has become a safety net for the Clark Fork River. EPA deems the remedy to be
protective in terms of substantially reducing - quite possibly eliminating - the threat
of acute lethality to fish.
In light of the current and long-standing status of severe contamination in Silver Bow
Creek above the ponds, and in light of the gradual degradation of water quality that
occurs in the upper Clark Fork River, beginning within a few miles downstream of
the WSP and continuing for about 40 miles, any attempt to eliminate occasional
chronic threats that persist immediately below the ponds through modification of the
WSP system would produce virtually no change in protectiveness for the river in the
Deer Lodge valley. However, as the Clark Fork River water quality is improved, this
issue will need to be re-examined, as will standards.
While a high degree of protectiveness has been achieved, an even higher degree of
protectiveness is achievable. But, such a higher degree of protectiveness for the river
can be attained only after all remaining operable units along this continuum of stream
environments have been cleaned up and are functioning as a whole.
10-2
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Section 11 References
AERL 2001. Warm Springs Ponds 2000 Biomonitoring and Analysis Results, Draft
Report. Silver Bow Creek/Butte Area NPL Site, Warm Springs Ponds Operable Units.
Report prepared by ENSR Environmental Toxicology Services. May 2001.
Ankley, C.T., D.M. Di Toro, D.J. Hansen, W.J. Berry. 1996. Technical Basis and
Proposal for Deriving Sediment Quality Criteria for Metals. Environmental
Toxicology and Chemistry. 15:2056-2066.
ARCO 1995a. Draft Remedial Investigation. Streamside Tailings Operable Unit Silver
Bow Creek/Butte Area National Priorities List site. Prepared by the Atlantic Richfield
Company. 1995
ARCO 1995b. Feasibility Study. Streamside Tailings Operable Unit Silver Bow
Creek/Butte Area National Priorities List Site. Prepared by the Atlantic Richfield
Company. 1995.
ARCO 1995c. Final Remedial Investigation Report. Rocker Timber Framing and
Treatment Plant Operable Unit Silver Bow Creek/Butte Area National Priorities List
Site. Prepared by the Atlantic Richfield Company. March 1995.
ARCO 1995d. Final Feasibility Study Report. Rocker Timber Framing and Treatment
Plant Operable Unit Silver Bow Creek/Butte Area National Priorities List Site.
Prepared by the Atlantic Richfield Company. July 1995.
ARCO 1997. Initial 5-Year Review. Warm Springs Ponds Operable Unit Silver Bow
Creek/Butte Area National Priorities List Site.
ARCO 1998. Initial 5-Year Review Addendum. Warm Springs Ponds Operable Unit
Silver bow Creek/Butte Area National Priorities List Site.
Atlantic Richfield. 2004. Warm Springs Ponds Operable Units of the Silver Bow
Creek Area NPL Site, Docket No. CERCLA-VIII-91-25; Response to EPA's Letter of
December 5, 2003: Notice of Violation and Request for Additional Work - Warm
Springs Ponds spill incident; and submittal of Work Plan for Additional Work.
January 6, 2004.
Atlantic Richfield 2004. Warm Springs Ponds 2003 Biomonitoring and Analysis
Results Draft Report. Silver Bow Creek/Butte Area NPL Site, Warm Springs Ponds
Operable Units, Upper Clark Fork River Basin, Montana. Prepared for Atlantic
Richfield Company by ENSR International. June 2004.
Atlantic Richfield 2005. Warm Springs Ponds Five-Year Review Report. Silver Bow
Creek/Butte Area NPL Site, Warm Springs Ponds Operable Units, Upper Clark Fork
River Basin, Montana. April 27, 2005.
CDM
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Section Eleven
References
BPSOU PRP Group 2002. Butte Priority Soils Operable Unit Silver Bow Creek/Butte
Area Superfund Site. Phase II Remedial Investigation Report. Prepared by MFG Inc.
for the PRP Group. April 2002.
CDM 1990. Final Work Plan for Remedial Investigation Feasibility Study, Butte Mine
Flooding Operable Unit, Butte Addition to the Silver Bow Creek/Butte Area NPL Site,
Butte, Montana. Prepared for the U.S. Environmental Protection Agency by CDM
Federal Programs Corporation. April 27,1990.CH2MHill & Chen Northern 1989.
CH2MHill and Chen Northern 1989. Final Silver Bow Creek CERCLA Phase II
Remedial Investigation Data Summary, Warm Springs Ponds Operable Unit, volumes
I, II, and III. Prepared by CH2MHill, Inc. and Chen-Northern, Inc. May 5,1989.
CH2MHill & Chen Northern 1990. Draft Final Silver Bow Creek CERCLA Phase II
Remedial Investigation Summary, Area 1 Operable Unit, Volumes I and II. Prepared
by CH2MHill, Inc. and Chen-Northern, Inc. August 1990.
DEQ 1994. Draft Baseline Risk Assessment, Streamside Tailings Operable Unit Silver
Bow Creek/ Butte Area Site. Prepared by Camp, Dresser, and McKee, Inc. December.
DEQ 1995b. Streamside Tailings Operable Unit - Proposed Plan. June.
DEQ 1995a. Record of Decision. Streamside Tailings Operable Unit Silver Bow Creek
Butte Area (Original Portion) National Priorities List Site. Prepared by the Montana
Department of Environmental Quality. November 29,1995.
DEQ 1998. Explanation of Significant Differences. Streamside Tailings Operable Unit
Silver Bow Creek/Butte Area (Original Portion) National Priorities List Site. Prepared
by the Montana Department of Environmental Quality. August 31,1998.
Erickson, R., D. Mount, and C. Stephan. 1999. Derivation of Recommended Chronic
Copper TRVs for Salmonids. Report prepared by USEPA, Duluth, MN, November,
1999.
McGuire, Daniel. 2003. Macroinvertebrate-Based Rapid Bioassessment: Mill-Willow
Bypass. Deerlodge County, MT. April 1, 2003.
NRIS 2005. Montana Natural Resource Information System Web Page
http:/ / maps2.nris.state.mt.us/mapper/ThemeList.asp?Profile=1546514&qLayerl=F
WPSTREAMROUTE&qFieldl=LLID&qValuel=1127708461870&Qperl=&Bufferl=805
.5&T abName=Land% 20Information
Online Highways 2005. Web Page http: / /www.ohwy.com/mt/b/butte.htm
U.S. Census Bureau 2005. 2000 Census Data for Montana (Web Page).
http://factfinder.census.gov/servlet/GCTTable? bm=v&-geo id=04000US30&-
box head nbr=GCT-PHl&-ds name=DEC 2000 SF1 U&-format=ST-2
CDM
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Section Eleven
References
USEPA 1990. Record of Decision, Warm Springs Ponds Operable Unit, Silver Bow
Creek Butte Area NPL Site, Butte, Montana. U.S. Environmental Protection Agency,
Montana Office. September 28,1990.
USEPA 1991. Explanation of Significant Differences for the Warm springs Ponds
Operable Unit, Silver Bow Creek/Butte Area NPL Site, Butte, Montana. U.S.
Environmental Protection Agency, Montana Office. June 24,1991.
EPA 1991. Unilateral Administrative Order for Remedial Design/Remedial Action
EPA Docket Number CERCLA-VIII-91-25. Silver Bow Creek/Butte Area (Original
Portion) Warm Springs Ponds Operable Unit. September 25,1991.
USEPA 1992b. Silver bow Creek/Butte Area Superfund site, Warm Springs Ponds
Inactive Area Proposed Plan. Prepared by the U.S. Environmental Protection Agency,
Montana Office and the Montana Department of Health and Environmental Sciences.
March 1992.
EPA 1993. Unilateral Administrative Order for Remedial Design/Remedial Action
EPA Docket Number CERCLA-VIII-93-23. Silver Bow Creek/Butte Area (Original
Portion) Warm Springs Ponds Operable Unit (Inactive Area). June 19,1993.
USEPA 1994. Record of Decision, Butte Mine Flooding Operable Unit, Silver Bow
Creek Butte Area NPL Site, Butte, Montana. U.S. Environmental Protection Agency,
Montana Office. September 29,1994.
USEPA 1995. Record of Decision, Rocker Timber Framing and Treatment Plant
Operable Unit, Silver Bow Creek Butte Area NPL Site, Butte, Montana. U.S.
Environmental Protection Agency, Montana Office. December 22,1995.
USEPA 2000. Statutory Five Year Review Report. Silver Bow Creek/Butte Area
Superfund Site. Clark Fork Basin, Montana with Emphasis on the Warm Springs
Ponds Operable Units. U.S. Environmental Protection Agency, Montana Office.
March 23, 2000.
USEPA 2002. Explanation of Significant Differences for the Butte Mine flooding
Operable Unit, Silver Bow Creek/Butte Area NPL Site, Butte, Montana. U.S.
Environmental Protection Agency, Montana Office. March 2002
USEPA 2002. Superfund Cleanup Proposal (Proposed Plan) for the Clark Fork River
Operable Unit of the Milltown Reservoir/Clark fork River Superfund Site. Prepared
by the US Environmental Protection Agency, Montana Operations Office. Helena,
Montana. August 2002.
EPA. 2003. Notice of Violation and Request for Additional Work - Warm Springs
Ponds spill incident. Letter from D. Scott Brown (EPA) to David McCarthy (Atlantic
Richfield Company). December 5, 2003.
CDM
Q:\Silver Bow Creek 5-Yr Revie\MFinal Report\SBC 5-Year Review FINAL.doc
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Section Eleven
References
USEPA 2005. USEPA Comprehensive Environmental Response Compensation and
Liability Act Information System (CERCLIS) Web Page.
http:/ / cfpub.epa.eov/supercpad/cursites/copinfo.cfm?id=0800416
11-4
CDM
Q:\Silver BowCreek5-Yr Reviev\AFinal Report\SBC 5-Year Review FINAL.doc
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Appendix A
5-Year Review Notification for Local Newspapers
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EPA Conducting Mandatory 5-Year • a *
Review of Silver Bow Creek/
Butte Area Site
The U.S. Environmental Protection Agency (EPA) will be conducting
a required 5-year review of the response actions (cleanup work) done
to date for the Silver Bow Creek/Butte Area Superfund Site. This site
extends from Butte to the Warm Springs ponds, near Anaconda. The
site has eight operable units (OUs).
The emphasis of the review is on the site's five most active OUs:
¦ Butte Mine Flooding
¦ Rocker Timber Framing and Treatment Plant
¦ Streamside Tailings
¦ Warm Springs Ponds - Active Area
¦ Warm Springs Ponds - Inactive Area
Site contamination is the result of over 100 years of historic mining
activities. Contaminants of concern are heavy metals and arsenic.
Cleanup has included source removals, wet closures and capping,
groundwater and surface water controls, stream rehabilitation, land
reclamation, water treatment systems, and flood controls.
The review assesses the protectiveness of the various response
actions done to date. The results of the 5-year review will be made
available to the public this summer.
EPA welcomes public comments regarding work done at any of the
OUs. Public comments received by EPA will be appended to the
final 5-year review document when it is sent to EPA headquarters. If
you have comments about the response actions, please send them
in writing to:
Scott Brown
EPA Review Coordinator
10 West 15th Street, Suite 3200
Helena, MT 59626
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Appendix B
Summaries of Telephone Interviews (Molignoni, Bouck, Peoples, Kerns,
Sesso, and Ueland), Written Responses to Interview Questions (Skrukrud,
Dziak, Brockman, Benson, and CTEC), a letter from MDEQ (Chavez), and an
unsolicited letter (Kuipers)
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Telephone interview with A1 Molignoni (6/9/05)
Mr. Molignoni is a resident who lives near the Rocker OU.
1. What is your overall impression of the project?
The project was not a success. There are still rebound effects and EPA did not clean up the
aquifer as planned. They are still doing work, so maybe it will be cleaned up eventually - by
EPA or Mother Nature.
2. What effects have site activities/operations had on the surrounding community?
There were not too many effects. EPA was in and out pretty quickly. The most visible and
lasting effect is the grassy mound where the contaminated soils are stored. It doesn't look
natural and sticks out. It just looks like a Superfund site.
3. Are you aware of any community concerns regarding the Rocker OU?
The biggest concern is that people cannot drill wells anymore because of the Institutional
Controls. Because the cost of water is rising, people have to cut back on watering to stay
within their household budgets. This has a negative impact on the aesthetics of the
community.
4. Do you feel the remedy in Rocker is effective?
Yes, as long as they keep the Institutional Controls in place.
5. Do you feel well informed about the site progress and activities?
I used to, but EPA has cut back on the communication over the last year or so. Even though
the site is pretty quiet, people still need to be updated fairly regularly. A public meeting
where we can ask questions would be a good thing at least once a year, if not more often.
6. Do you have any other comments or suggestions?
Put some additional vegetation, like trees or bushes, out on the grassy mound to make it
look more natural.
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Telephone interview with Linda Bouck, Anaconda-Deer Lodge County, Planning
Department (7/5/05)
Ms. Bouck is the head of the Planning Department for Anaconda-Deer Lodge County. The
Planning Department has significant input with the adjacent Anaconda Smelter NPL Site
and more limited involvement with the Silver Bow Creek/Butte Area Superfund Site. Her
comments primarily address the SST OU and Warm Springs Ponds OU.
1. What is your overall impression of the project?
The SST OU seems to be going along fairly well - everything is going as planned. The Warm
Springs Ponds OU has a few issues that concern the county. The primary issue is a concern
with the long-term preservation and maintenance of the Rainbow Bridge. ARCO was
supposed to ensure that this historic bridge would be preserved. However, that is not
occurring. Since remediation of Warm Springs Ponds OU began, the bridge has been flooded
and pieces of the concrete base are broken.
2.What effects have site activities/operations had the Anaconda/Deer Lodge County?
There are occasional problems with chain of command. For instance, the DEQ located a haul
road that splits a county road (Stewart Street crossing), they did not clear it first with the
transportation director. Another issue that has arisen is that of standing, stagnant water in
the borrow pits. With the recent concerns about the spread of West Nile Virus across the
state, the county is worried about having breeding areas for mosquitoes.
3.Are you aware of any community concerns regarding the site?
The main community concerns are those with citizens of Opportunity. For many years, a
significant number of people had used pasture owned by ARCO but leased long-term to the
community. When the SST OU remediation began, these people were no longer allowed to
graze livestock on the land, which has been a hardship for them. Several citizens in
Opportunity have recently formed a citizen's group to deal with Superfund issues.
4.Do you feel the remedy is protective?
We can't say at this time whether or not the remediation is protective. The remedy needs
time to cure, or age, to see how things will work out. There were no significant concerns
with the proposed remedy when it was proposed or implementation began. However, there
have been some issues that lead the county to question if the work is being done as planned.
For instance, if such a visible component of the remediation as the Rainbow Bridge
preservation is not being handled successfully, there may be other issues that are not so
visible that are also going wrong. This concern was reinforced by problems with cleanup at
the Anaconda Site where beryllium contamination at depth was found in a remediated area.
5.Do you feel well informed about the site progress and activities?
Yes, but there needs to be more effort informing the County Commissioners. The DEQ
should hold a pre- and post-construction meeting each year with the commissioners that will
bring them up to speed so that they can answer questions from the community. DEQ should
also consider speaking to the community group from Opportunity. Connie Daniels would
be a good county commissioner to interface with on this issue.
6.D0 you have any other comments or suggestions?
No.
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Telephone interview with Don Peoples, Montana Economic Revitalization and
Development Institute (MERDI) (6/3/05)
1. What is your overall impression of the project?
Reasonable progress is being made.
2.What effects have site activities/operations had on the surrounding community?
There have been many aesthetic improvements resulting from site operations. Recreational
opportunities have been increased by the addition of numerous walking trails. Also, with
the cooperation of the agencies and Atlantic Richfield, MERDI has been instrumental in the
redevelopment of over 30 acres of Brownfield area east of Arizona Street in the BPSOU. This
redevelopment includes a sports complex. This has had many aesthetic and economic
benefits for the community.
3.Are you aware of any community concerns regarding the BPSOU?
The recent controversy over attic dust has somewhat polarized the community. People are
also concerned that the cleanup is both protective and supportive of future redevelopment.
4.Do you feel the proposed remedy at the BPSOU is effective?
Yes, providing they continue to monitor the Parrott Tailings that are left in place. The
underlying groundwater is contaminated - that is a given. We need to be sure that the
contamination does not migrate to any other aquifers.
5.Do you feel well informed about the site progress and activities?
Yes. Because our company works in redevelopment of this area, I am better informed than
the average person in Butte about the cleanup. We have done pro bono reviews of the
remedy, at the request of Atlantic Richfield, to provide our opinion on the protectiveness
and overall merits of the proposed remedy. For the most part, we agree with the proposed
remedy. But we have expressed concerns over some issues such as funding for long-term
O&M and redevelopment.
6.Do you have any other comments or suggestions?
MERDI is concerned with two issues: there needs to be a redevelopment fund that is of
sufficient size to make an impact of the community, and the O&M funding must be sufficient
so that the county is not stuck with the costs for O&M in the future. Finally, the remedy
must obviously be protective of human health, but it should also allow for (and support)
future redevelopment of the area.
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Telephone interview with Mike Kerns, Butte-Silver Bow County Commissioner (6/11/05)
Mr. Kerns has been a commissioner for 19 years and has been involved with the project since
the early years. He also works at the Port of Montana, which is very near Ramsey Flats (SST
OU) and the Rocker OU. His comments primarily address the SST OU, Rocker OU, and
BPSOU.
1. What is your overall impression of the project?
The SST OU is coming along fabulously. The new contractor (an Irish company who also
owns Helena Sand and Gravel) is fabulous. They are very fast, and it looks nice when they
move on. They are really impressive. EPA is also doing a good job in Rocker, and we are
hoping that the ROD for the Butte Hill (BPSOU) will also be successful.
2.What effects have site activities/operations had on the surrounding community?
The effects have been positive. Many mine waste areas have been turned into green spaces,
and it has greatly improved the aesthetics in the area. Additionally, the health risks have
been greatly decreased to EPA's work.
3.Are you aware of any community concerns regarding the site?
Attic dust at the Butte Hill (BPSOU) is a new concern that resulted from Imagine Butte's
survey of the low-income community in that area. Interest in the Mine Flooding OU seems to
have died down. There is also some debate as to whether EPA should make ARCO remove
the Parrott Tailings or leave them in place. I am not aware of any concerns for Rocker or SST
OU.
4.Do you feel the remedy is protective?
Yes. Anyone who has been to the SST OU can see that it is working. For the BPSOU, I would
prefer to see the water treatment plant become part of the final remedy, rather than the
lagoons that are now in place. Jon Sesso, Jimmy Johnson, and others in BSB have been
working hard to make sure that the community will benefit in the long run.
5.Do you feel well informed about the site progress and activities?
Yes. EPA does a good job of keeping people aware of what is going on. It is hard to keep
people's interest alive about a complicated subject over so many years. It was easier in
Missoula, where they only had one issue to deal with and it was over a relatively short time
frame.
6.Do you have any other comments or suggestions?
No.
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Telephone interview with Jon Sesso, Butte Silver Bow Planning Department (6/20/05)
Summarized by EPA and edited and approved by Mr. Sesso.
1. What is your overall impression of the SST OU and MFOU?
The Superfund projects take way too long to complete. Also, EPA does not put enough
emphasis on public involvement.
At the SSTOU, the remediation seems to be proceeding as planned although there are still
some unresolved issues regarding long-term operation and maintenance (O&M) of the
remediation and stewardship of the subsequent reclamation. The state appears to think it is
premature about committing to a level of O&M&M (operation, maintenance, monitoring),
especially in relation to the greenway (as the final end use) but that is a vital part of the
success of the remediation.
At the MFOU, the public generally felt that their concerns and input were not attended to
during the whole ROD/Consent Decree process. Also, it was a disappointment that
innovative treatment technologies (i.e., resource recovery stages) were not fast tracked as
part of the process selected.
2.What effects have site activities/operations had on BSB and the surrounding
community?
Involvement in the Superfund process has been a burden for the BSB government. The
existing personnel resources were not sufficient to take on the extra tasks of reviewing
documents and active participation in other Superfund activities. We were fortunate to
maintain in-house staff continuity, and this burden has been made more manageable by
grants from the State and ARCO to hire additional personnel. BSB is doing a good job
keeping up with the process with these additional resources.
The activities at SST have not had an immediate impact on the citizen's of BSB. Once the
remediation is complete and the Greenway is finished, the community will benefit from the
added recreational benefits, but most people are not affected at this time. For the MFOU, the
site operations themselves have not had a significant impact on the community. However,
the unresolved concerns associated with the OU (see below) have had a negative impact on
the community.
3.Are you aware of any community concerns regarding the SSTOU or MFOU?
For SST, there have not been a lot of community concerns. There is a general feeling that
perhaps the public health-related concerns at other OUs have not yet received as much
attention as did the impacts to fish in the SST OU. There is also a concern that the long-term
stewardship of both the remediation and restoration activities planned for the site will not
get as much attention as needed
For MFOU, there has been some community concern related to the potential for future
catastrophic events, such as a large earthquake, or that the critical water level was not the
most appropriate decision point. What would happen and how would the contamination be
remediated if Montana Resources (MR), ARCO and EPA are gone? Also, people who reside
near the MFOU have current concerns about the potential health impacts from the fog that
rises off the pit in winter and whether contaminated water in the bedrock aquifer will affect
their wells in the alluvial aquifer. EPA says there is no health threat with the fog, but the
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entire community is not convinced. Some people also have a general disappointment that
the water treatment technology selected did not include a resource recovery stage. There is
also residual anger at the Atlantic Richfield Co for shutting off the pumps in the first place.
There are also issues related to confusion over the reclamation obligations of the current
mine operations by MR and remedial obligations by MR and Arco under Superfund.
4.Do you feel the remedies at the SST OU and MFOU are protective?
For SST, the remedy appears to be protective. It is based primarily on threats to fish and
other organisms in the water - not on a threat to human health. DEQ is making good
decisions on over excavating where needed, such as at Ramsey Flats. The area is definitely
in much better shape than it was before. They are also making good decisions on scheduling,
by accelerating cleanup of some areas, such as the rest stop on the way to Anaconda, without
compromising the quality of the cleanup. Long term O&M of the remediation and
restoration will be the key to overall protectiveness of the remedy.
For MFOU, BSB hopes that the remedy is protective and that the scientists who defined the
hydrogeologic system are correct. There is less confidence that anyone really knows for sure
if the critical water level of 5410 feet is accurate. If it is, then the remedy appears to be
protective.
5.Do you feel well informed about the site progress and activities?
Yes, but BSB is directly involved in the activities, and is therefore better informed than most
people in Butte. The public sees BSB staff members as an advocate for them. There is a
reasonable level of trust that the people in local government are looking out for all citizens of
Butte. In general, EPA does not spend the effort needed in Butte to inform and engage the
citizens.
6.D0 you have any other comments or suggestions?
EPA, DEQ, and ARCO need to ensure that the long-term O&M&M is adequately planned,
implemented, and funded. There appears to be a belief among regulators that once the
remediation is complete, all land uses can be allowed, i.e., like the way they were before the
contamination occurred. However, the area has been damaged and wastes are left in place
in many areas. The local community's standards for how we maintain things may be higher
than what the regulators or PRP's would otherwise do. We need to get on the same page in
this regard. For example, we believe restoration projects are a part of the overall O&M
strategy and a good way to help achieve that end, i.e., if people perceive a benefit from
something like the Greenway project, they are much more likely to treat it gently and not
tear it up.
Also, everyone has to recognize that, given the fact that most remedies selected for this Site
involve wastes-left-in-place, these sites will require a lot more money at the backend of the
project, relative to typical Superfund sites where a small amount of very toxic material is
removed. The track record for stewardship, ICs, and O&M at Superfund sites in general is
not so good. Leaving the wastes in place is likely the most practical option and can/will be
protective, but we must face the concerns related to maintaining these sites for generations
to come. The vigilance has to be maintained at a level sufficient to weather the losses of
institutional knowledge that will occur when the people currently working on the projects
turn over. EPA's 5-year review process and other monitoring processes have to be
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substantial and have the teeth needed to ensure that remediation is being maintained as
promised.
Note: Mr. Sesso also had concerns relating to the Butte Priority Soils OU (BPSOU).
Although a ROD has not yet been signed and remediation has not technically started, there
has been a lot of remediation done under the TCRA and ERA process. The community was
told that these early actions would be consistent with the ROD and would be thoroughly
reviewed for completeness and effectiveness prior to the ROD. Anything that was not
successful would be upgraded as part of the ROD. Now, the EPA and to a certain extent the
DEQ have concluded that all past actions are good enough. Yet, it appears to some members
of the community that no cognitive review was done (i.e., no field analysis, etc.), because
some of the past actions clearly have room for upgrading and improvement. BSB expects
that EPA intends to require these improvements to be made as part of long-term monitoring
and maintenance, but EPA has not yet expressed that in any official way (i.e., until the ROD
is released), and thus, during the process to release the Proposed Plan for BPSOU, the
Agency has not done an adequate job of relaying information about the status of these
previous actions to the public.
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Telephone interview with Don Ueland, Rancher (6/13/05)
Don Ueland is a local rancher who has sold property along Silver Bow Creek to Atlantic
Richfield. He and his family also have the first water right coming out of Warm Springs
Ponds and have dealing with AR over water rights issues. Also, he lives near the Rocket OU
and is familiar with what is going on at most of the OUs.
1. What is your overall impression of the project?
The work done to date is wonderful. Total removal of the mine wastes from the streamside
was more than what was needed, but is very positive. The streamside looks better than the
natural environment nearby. The Warm Springs Ponds are doing their job, and the Mill
Willow Bypass is great - especially the meanders. I am generally very happy with the
cleanup.
2.What effects have site activities/operations had on the surrounding community?
The major impact has been a temporary influx of money into the community from jobs and
expenses associated with the construction work. Not aware of any negative impacts.
3. Are you aware of any community concerns regarding the site?
Most people were not terribly concerned with the contamination prior to the cleanup. The
area had been contaminated for over 100 years, and people just lived with it - it was the way
things were. There were no obvious health effects that people were aware of, and the
environmental effects seemed to be limited to poor plant growth and the occasional fish kill.
Most people are aware that a cleanup has taken place, although many do not know the
details. They can tell that the area looks better. Not aware of any specific community
concerns - other than a desire for the economic boost to continue.
4.Do you feel the remedy is protective?
Yes. It is certainly better than it was before. Although we won't know for sure for many
years, it seems to be working well. I trust that AR and the regulators will keep up the
monitoring and will do what is right to ensure protectiveness.
5.Do you feel well informed about the site progress and activities?
Not really. It would be nice if EPA and DEQ could send out more fact sheets or get stories in
the newspaper to keep people up to date. It is a complicated site and people get confused
just trying to keep all the pieces separate. The fact sheet inserts in the Anaconda paper are
helpful.
6.Do you have any other comments or suggestions?
No.
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Written submission from Dori Skrukrud
June 29, 2005
Karen L. Ekstrom
CDM
28 N. Last Chance Gulch
Helena, MT 59601
(406) 495-1414 x311
RE: Response to questions regarding the protectiveness of the clean up actions taken to
date at the Silver Bow Creek/Butte Area Superfund Site for EPA for the 5-year
review
Dear Karen:
I have responded to your questions regarding the protectiveness of the cleanup action taken
to date on Silver Bow Creek, as that is the area that I am most involved with in my activities
related to the development of the Silver Bow Creek Greenway project.
1. What is your overall impression of the project?
The Greenway Service District has been closely involved with the remedial activities
along Silver Bow Creek as efforts to coordinate remediation with habitat restoration
along the Silver Bow Creek Corridor. Overall, we believe that the project
remediation goals and objectives are being met by the actions taken by the MT
Department of Environmental Quality (DEQ). DEQ has demonstrated the ability to
respond to our restoration objectives to improve the character and the quality of the
corridor and their remediation strategies have adapted to varying conditions within
the corridor to achieve remediation and restoration goals, including the removal of
additional tailings in areas where tailings were slated to have remained for "in situ"
treatment.
2. What effects have site operations had on the community?
I believe that the site operations have had a positive effect on the community.
The ongoing activities of the remedial efforts are tangible and the outcome, the new
stream corridor and healthy vegetative cover, represent a new beginning for the
stream corridor that is apparent to anyone who visits or sees the corridor.
I am unaware of any adverse effects on the community - every effort is made to
work with property owners and adjoining landowners to cause as little disruption in
day-to-day activity for the community.
3. Are you aware of any community concerns regarding the site or its operation?
The one concern is the uncertainty of funding and plans for long-term operations,
maintenance and management of the remedy. Sufficient funds and plans must be in
place to protect and preserve the remedy in perpetuity. Community members have
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discussed these concerns with those agencies associated with the project; the reality
is that operations, maintenance and management are a reality for this site and must
be readily acknowledged and planned for to ensure the health of the corridor.
4. Do you feel the remedy is protective?
The remedial actions including tailings removal, stream reconstruction and riparian,
floodplain and uplands revegetation strategies, coupled with restoration
enhancements and the long-term land use strategy for the corridor to remain as open
space for the public benefit will be protective of the remedy. It is imperative,
however, that the costs of operations, maintenance and management be
acknowledged and funded.
5. Do you feel well informed about site progress and activities?
The DEQ has been responsive to requests for updates on the status of the project and
available to the public in many forums.
6. Do you have any comments or suggestions?
We need to discuss the need for a solid operations, maintenance and management
plans for the corridor and receive assurances that funds will be available to
implement these strategies.
Thank you for requesting input.
Sincerely,
Dori Skrukrud, Project Manager
Silver Bow Creek Greenway
A Greenway Service District Project
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Written submission from Dave Dziak, MT Fish Wildlife and Parks
Streamside Tailings and Warm Springs Ponds question Review.
Streamside tailings -
Question 1.
My overall impression is that work that has been completed has vastly improved the
condition of Silver Bow Creek. Definitely the looks of the area have changed dramatically in
a positive direction.
Question 2.
I have on a very limited basis toured sub-area 2 as construction was taking place. I do make
a point of looking at the area as I drive by/or near while working or otherwise.
Question 3.
I have received a couple of calls on "problem" beaver that inhabit some of the completed
areas on Silver Bow creek. These calls have been from state personnel concerned about
possible destruction of re-vegetated areas. I have also received calls regarding bridges and
structures built over the stream without permits.
Question 4.
I believe the remedy is somewhat protective, as it has removed to some degree of tailings
from the immediate stream banks. My concern is that much of the railroad grades that
parallel the stream still contain high concentrations of heavy metals and the possible
leaching of these metals back into the system. My other concern is for water quality as it
comes into the system from the Butte area. This of course relies greatly on Butte mine
flooding and the Treatment plant system when it comes on line.
Question 5.
Most of the information I receive comes from local newspaper articles or sections of the
newspaper that devote a section for the work that has been done. I have attended a few
meetings both public and state sanctioned. I also receive an update once in a while on the
work being performed as a signed attendee of a local meeting.
Question 6.
Comments: I have concerns with the Greenway project and the expected increase use of the
area by the public. Items that need to be addressed will be trail maintenance, ORV travel,
trespass and injured wildlife.
Warm Springs Ponds (WSP) -
Question 1.
My overall impression of WSP is that it is a "water treatment faculty" first and foremost.
Water quality remains an issue as the ponds continue to exceed water quality standards in
Arsenic and high PH values. Also though the system was not designed as a Municipal
Public treatment system it contains nutrient loads that exceed effluent reporting values.
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Waterfowl habitat has changed from a shallow water system with dense vegetative shoreline
cover to deep water, non-vegetative, steep armored rock shoreline. On a positive side the
clean up of the Mill-Willow Bypass has been a good step.
Question 2.
I have been on WSP both as an employee of ARCO and an employee of state government
since 1975. I have witnessed first hand the changes that have been made both positive and
negative at the site. I continue to monitor waterfowl use of the area through waterfowl
counts, nest searches and hunter information.
Question 3.
There have been both complaints and violations that agencies and ARCO have been made
aware of.
Question 4.
I feel the remedy to some degree has been effective. No doubt there are still issues with
water quality both as water comes into the system and as it flows out of the system.
Question 5.
I am well informed about site progress and activities.
Question 6.
A solution to water quality problems needs to found.
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Written submission from Ken Brockman, U.S. Bureau of Reclamation
From: KBrockmanPE@aol.com
Sent: Monday, July 04, 2005 11:20 AM
To: Ekstrom, Karen
Subject: Silver Bow Creek 5 year review
Karen,
I wanted to take a closer look at the completed portions of the project before I replied so it
took a couple of days longer than I expected. As you probably know, this is about an 11 year
project that started in September, 1999. Construction has occurred under several contracts
over the last several years. The first mile (Reach A) was completed in late 2000, so I suppose
this is the subject of the 5 year review. Since then the State has also completed Reaches B
and C (about 2 miles), Reaches D&E (another two miles) and are currently constructing
Reaches F,G and H, a 3 mile stretch that will get them to the head of Durant Canyon. This
contract is scheduled for completion in 2006. The State has also been working on a mile or so
of tailings removal near the downstream end at Highway 1.
You should also note that some of the questions you ask are more appropriate for a final
construction report than for a project that has supposedly been complete for 5 years. It
seems to me that questions for a 5 year review would focus on whether the remedy is still
performing as designed, whether there are any unforeseen maintenance issues, any
modifications that have been necessary, etc.
My comments relate to only Reach A.
What is your overall impression of the project?
The project is going well and has been a success. The design is done in stages from upstream
to downstream and is evolving as new information is obtained during construction. The
vegetation along the streambank is excellent. The vegetation on the floodplain is very good
with the exception of several small areas where I believe the soil has conductivity levels that
prevent vegetation from growing.
What is the current state of construction?
Reach A was essentially completed in 2000. However, the creek flow control dike and
bypass channel that protected the new channel and floodplain during the grow-in period
were removed in late 2004/early 2005. The regraded areas were seeded in the Spring of
2005.
Have you encountered any problems that changed or will change the remedy?
There were no major problems encountered. There were several minor problems that
resulted in minor adjustments to the design as it progressed downstream, but these were
mostly reactions to what was learned during construction.
Have any problems impacted construction or implementability?
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No problems that impacted construction or implementability come to mind.
Do you have any comments, suggestions, or recommendations?
The Greenway trails that were constructed as part of the floodplain were never finished by
the Greenway organization. These trails are deteriorating due to vegetation encroaching on
the trail. Also, the bridges planned for the trail to cross the creek were never installed.
Future work on the trail and bridges could damage the good vegetation on the floodplain
and creek banks. Work on the Greenway Trail should be coordinated better with work on
the remedy. This would also allow for the area to be re-opened for public use.
-------
Written submission from CTEC
CTEC responses to CDM questions regarding the 2005 Statutory Five-Year Review Report
Silver Bow Creek/Butte Area Superfund Site. July 8,2005
1. What is your overall impression of the project?
CTEC believes that cleanup at the Silver Bow Creek/ Butte Area Site has done a lot for
beginning the restoration of economic and environmental health to the Upper Clark Fork
Basin. Many of the cleanup actions performed in Butte and in the watershed below
Butte have shown to be appropriate ways of removing hazardous waste and/or
managing waste in place. However, CTEC contends that some of the remedy solutions
could go further in protecting human health and the environment while still being cost
effective—for instance mandating cleanup of contaminated attic dust and more
aggressive, less time consuming approaches of removing or containing waste.
2. What effect have site activities had on the surrounding area?
Site activities have had many positive affects including lessening people's exposure to
toxic substances, beginning the process of restoring ecological health, and increasing
people's awareness of hazardous waste in their community. Some negative affects may
include the "Superfund stigma" and depressed property values owing to the perception
that dangerous exposure to wastes still exists.
3. Are you aware of any concerns regarding the site or its operation?
There are many concerns owing to site complexity. The Silver Bow Creek/Butte Area
Site covers an incredibly large area; soil, water, and air are contaminated, and a large
population lives within and on the contaminated media. Major concerns include a lack
of an adequate site-wide exposure and toxicological assessment for contaminated attic
dust. Concerns also exist that site remedies are not aggressively implemented and
pathways of exposure contaminated waste exist to humans and the environment that
have been know about for decades; an example of this has been the slow response to
treating contaminated runoff on the Butte Hill and the slow response to remediation of
lead and arsenic sources in Butte residences.
4. Do you feel the proposed remedy is protective?
This question is too complicated and there are too many remedies within the Silver Bow
Creek/Butte Area Site to adequately describe here. The answer is yes and no.
5. Do you feel well informed about site progress and activities?
Yes, CTEC believes that EPA and ARCO do a good job of documenting site activities and
monitoring. CTEC found that the Year 2000 Statutory Five-Year Review Report Silver
Bow Creek/Butte Area Superfund Site appeared to be biased towards promoting site
successes and was not always objective in describing site failures. CTEC hopes that the
forthcoming Five Year Review Report will provide objective analysis of site short-
comings such as recontamination of remediated portions of the Silver Bow Creek
Stream-side Tailings OU and exceedences of performance standards at Warm Springs
Ponds OU.
6. Do you have any comments or suggestions?
-------
Please see the attached review and comments of the Year 2000 Statutory Five-Year
Review Report Silver Bow Creek/ Butte Area Superfund Site.
-------
Written submission from Bob Benson, Clark Fork River Technical Assistance
Committee (CFRTac)
-------
* RECFM":r) MAY 3120(15
Karen Ekstrom
Community Involvement Specialist, CDM
Dear Karen,
As I mentionrd on the phone the other day, I have not been as deeply involved
in the upstream Superfund sites, but have tried to keep up with what is going
on, particularly at WSP. So some of these answers will beshort.
1. The parts of the project I have seen (SBC & WSP) seem to be well planned
and given the glitches that are inevitable on big undertakings, seem to be
progressing pretty well. Visually portions of SBC and the bypass at WSP give
the impression at least that things are on the mend.
2.Don't know about SBC. At WSP I had heard there was scxne concerns over
traffic and dust when the ponds were being reconstructed. This is only heresay
however, as our TAG was limited to Milltown at that time.
3. Pretty much covered in 2 above.
4.Think the jury is still out on this. For SBC we wont really know until the
work is complete, stabiliztion measures are all in place, and vegetation has
been established and grown. The real proof will be a 50 yr. flood event! At VISp
the last meeting I was at in Opportunity indicated there is still some concern
over Arsenic. Our technical advisor. Jim Kuipers wrote a white paper on arsenic
and I have looked at discharge data from time to time but to be honest about
it, I don't understand very well arsenic transport and fate, and what it may
mean to water downstream and at Milltown pond. If the fish biologists are
correct, the liming operations at the pond are probably a contributor to the
algea blooms we see all along the river in summer. But this is of course
confounded by ag operations, sewers and septics, and other runoff sources of
nutrients.
5. Fairly well informed. I could do more on my own to get more info. However,
I have noticed that the media have not given much coverage unless there is
some unusual event like the dead birds at the pit. And that is where most
people get their info.
6. Maybe getting more media coverage on how things are going at these sites
such a field trip in connection with the 5-yr review, (realize that there is
probably much better coverage in Butte area than we get here in Missoula).
I think also that what would be of interest to la^owners along the river in
the Deerlodge valley would be some information on type, duration, and other
experiences of land owners along SBC.
Please excuse the sloppy typing - my secretary retired when I did!
Bob Benson
-------
y
.6s3E3s3
Montann Dcptinmcnt of
Kf ^nurtjvmTi «r>M»p tt r 11 BTT » ¥ TPl^lT
riNViHONMENTAL ^uAJLiiY
July 28, 2005
Environmental Protection Agency
Scott Brown, Regional Project Manager
10 West 15th Street
Helena, MT 59601
Dear Mr. Brown;
The Department of Environmental Quality (DEQ) would like to take this opportunity to
respond to comments received on the Silver Bow Creek Five-Year Review.
In a telephone interview with Linda Bouck of Anaconda-Deerlodge County's Planning
Department, Ms. Bouck states that DEQ did not clear our proposed haul road crossing
on a county road with the transportation director. In fact, the DEQ on-site project
manager and the design engineer took the plans to the Anaconda-Deerlodge Roads
Department, spoke with Larry Sturm, the county's Road Shop Supervisor, and asked for
any comments he had on the project. The county does not have a Transportation
Department, or a Transportation Director according to the Chief Executive's office.
At the time, this was the procedure for such activities. As construction neared, the
department was informed that issues regarding the roads should be brought before the
county commissioners. This was a change in policy since the time we approached the
Roads Department. DEQ then contacted the Chief Executive's office to be placed on
the schedule. Both the on-site project manager and I went to two consecutive meetings
to present the proposed crossing and for the commissioners" vote. Very limited input
was received at these meetings regarding the crossing. I feel that DEQ adequately
followed the chain of command, even as it changed.
In the written comments for Dave Dziak of the Montana Fish, Wildlife and Parks (FWP),
he states he 'received calls regarding bridges and structures built over the stream
without permits.' The department feels it is important to clarify that in a superfund
cleanup, permits are not required per 42 USC § 9621(e)(1), although substantive
compliance with the law and rules associated with those permits is required as stated in
the CERCLA Compliance with Other Laws Manual, August 8, 1988. Unfortunately,
while the majority of the construction of these structures fulfilled the substantive
-------
compliance requirements, there were errors on the part of the contractor that led to
sediment discharge on Silver Bow Creek. DEQ worked with the contractor and FWP to
resolve these issues and agreed to inform FWP of our activities on or near Silver Bow
and Willow Creeks.
I appreciate the opportunity to respond to these comments and will continue to work
towards the successful remediation of Silver Bow Creek.
Sincerely,
Joel Chavez
Construction Services Section Supervisor
Mine Waste Cleanup Bureau
Remediation Division
-------
April 19, 2004
Scott Brown
U.S. EPA Region 8 (8MO)
10W. 15 th St.; Suite 3200
Helena, MT 59626
Dear Scott:
We appreciated the opportunity to meet with you and others on April 1st, 2004 to discuss
the Warm Springs Ponds (WSP). We feel the meeting was very constructive and we
would like to express our interest in working with you to address the concerns raised by
CFRTAC and others at the meeting. We agree that the upcoming Five-Year Review
Report and underlying review process would be a timely and appropriate opportunity to
work to address any issues concerning the WSPs. Specifically, we would recommend the
five-year review address the following items:
1. Human and ecological risk analysis of exceedances of arsenic performance
standards.
2. Optimization of WSPs operation for removal of arsenic (to address seasonal
arsenic desorption).
3. Ground and surface water and contaminant mass balance to allow for better
understanding of WSPs overall performance and monitoring.
4. Short-term future potential impacts on WSPs from increases in Silver Bow Creek
flow due to discharges from Butte Mine Flooding OU water treatment; nitrogen
treatment by Butte Silver Bow potentially affecting biology of ponds; and
ongoing upstream cleanup and other activities.
5. Long-term future of ponds once Silver Bow Creek cleanup and other activities
have been completed (dry versus wet closure; managing agency; financial
assurance for operation and maintenance).
We appreciate your efforts to provide access to the WSPS database maintained by ARCO
and look forward to having done so in the near future (Pioneer Technical Services has
contacted our technical advisor and has indicated the database will be forthcoming). We
also look forward to being invited to future additional technical meetings. We believe
that sufficient interest exists for EPA to consider a formal technical review process over
the coming year in which we and others could participate.
-------
If you have any questions or comments please contact me at XXX-XXXX or Jim
Kuipers, our technical advisor, at 782-3441.
Sincerely,
CFRTAC
Cc: Bob Fox, EPA
John Wordell, EPA
Darrel Reed, MDEQ
Doug Martin, MNRDP
Tom Malloy, BSB County
Scott Payne, CTEC
Bill Olsen, USFWS
David Nimick, USGS
Don Skaar, MFWP
-------
Table 1-1
Remedial Operable Units at the
Silver Bow Creek/Butte Area Superfund Site
Operable Unit
ROD Date
Remedial
Action Status
Date of
Previous
Five-Year
Review
2005 Five-
Year Review
Requirement
Active Mining and Milling OU
None
None
3/23/2000
Statutory
Butte Priority Soils(BPS) OU
None
None
3/23/2000
Statutory
Butte Mine Flooding (BMF) OU
9/29/1994
On-going
3/23/2000
Statutory
Rocker Timber Framing and
Treatment Plant (Rocker) OU
12/22/1995
Complete
3/23/2000
Statutory
Streamside Tailings (SST) OU
11/29/1995
On-going
3/23/2000
Statutory
Warm Springs Ponds (WSP) -
Active Area OU
9/28/1990
Complete
3/23/2000
Statutory
WSP OU - Inactive Area OU
6/30/1992
Complete
3/23/2000
Statutory
West Side Soils OU
None
None
3/23/2000
Statutory
CDM
Q:\Silver Bow Creek 5-Yr Reviev\AFinal ReportYTables and FiguresYTable 1-1 .doc
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Table 2-1
Chronology of Site Events
Event
Operable Unit *
Date
Placer gold discovered in Silver Bow Creek
00
1864
Large scale underground mining in Butte
03/08
1875-1955
Open pit mining at Berkeley Pit
03
1955-1982
Major smelting period in Butte
03/08
1879-1900
Discovery of mining-related contamination along Silver Bow Creek
between Butte and Warm Springs, Montana.
01
9/01/1979
Hazard Ranking System Package Completed
00
12/01/1982
Silver Bow Creek Site proposed to the NPL
00
12/30/1982
Silver Bow Creek Site (Original Portion) listed as Final on the NPL
00
09/08/1983
Silver Bow Creek (Original Portion) Remedial Investigation Final Report
00
01/1987
Butte Area Portion added to Silver Bow Creek Site
02
07/22/1987
Walkerville TCRA completed
08
02/22/1988
Timber Butte TCRA completed
08
1989
Priority Soils TCRA completed
08
1991
ROD for WSPs Active Area OU
04
09/28/1990
Explanation of Significant Differences for WSPs Active Area OU
04
06/24/1991
Unilateral Administrative Order WSPs Active Area OU
04
09/25/1991
Colorado Smelter TCRA completed
08
1992
Anselmo Mine yard and Late Acquisition/Silver Hill TCRA completed
08
1992
Lower Area One Manganese Removal
08
1992
ROD for WSPs Inactive Area OU
12
06/30/1992
Unilateral Administrative Order WSPs Inactive Area OU
12
06/17/1993
Walkerville II TCRA
08
1994
ROD for Mine Flooding OU
03
09/29/1994
ROD for SST OU
01
11/29/1995
ROD for Rocker OU
07
12/22/1995
Explanation of Significant Differences for SST OU
01
08/31/1998
Consent Decree for SST OU
01
04/19/1999
Explanation of Significant Differences for SST OU
08
08/31/1998
Initial Five Year Review Silver Bow Creek/Butte Area Site With Emphasis
on WSPs OUs
04/12
03/23/2000
Consent Decree for Rocker OU
07
11/07/2000
Walkerville Residential Removal
08
2000
Consent Decree for BMF OU
03
08/14/2002
Stormwater TCRA
08
On-going
Railroad Beds TCRA
08
On-going
Lower Area One N-TCRA
08
On-going
BPS Residential Soils/Source Areas N-TCRA
08
On-going
Proposed Plan for Butte Priority Soils OU
08
12/21/2004
Notes:* Operable Units (OUs) are numbered as follows: (00) Sitewide; (01) SST; (02) Area 1; (03) Mine
Flooding; (04) WSPs Active Area; (05) Reduction Works Tailings; (06)Travona Mine; (07) Rocker Timber
Framing and Treatment Plant; (08) Priority Soils; (10) Butte Residential Soils; (11) Lower Area One; (12);
WSPs Inactive Area (13); West Side Soils.
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and FiguresYTable 2-1.doc
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Table 3-1
Complete List of Remedial and Removal Operable Units at the Silver Bow
Creek/Butte Area Superfund Site as Listed in the CERCLIS Database
Operable Unit ID
Operable Unit Name
Function
Site Portion
01
SST
Remedial
Original
02
Area One
Butte Area
03
BMF
Remedial
Butte Area
04
WSP (Active Area)
Remedial
Original
05
Reduction Works Tailings
Removal
Original
06
Travona Mine
Removal
Butte Area
07
Rocker
Remedial
Original
08
BPS
Remedial
Butte Area
09*
Active Mining and Milling
Remedial
Butte Area
10
Residential Soils
Removal
Butte Area
11
Lower Area One
Removal
Original
12
WSP Inactive Area
Remedial
Original
13
West Side Soils
Remedial
Butte Area
*The Active Mining and Milling OU is not included in the list of OUs in the on-line CERLIS Database listing.
CDM
Q:\Silver Bow Creek 5-Yr RevievMDraft Report\Section 5 Tables and FiguresYTable 3-1.doc
-------
Table 4-1
Rocker OU O&M Wells Sampled for Groundwater Quality
SHALLOW ALLUVIAL WELLS
(17 total)
INTERIOR
RH-60, RH-61, RH-62, RH-63, RH-64,
RH-65, RH-66
EXTERIOR
RH-5, RH-7, RH-15, RH-17, RH-19, RH-41,
RH-44, RH-47
CONTINGENCY
RH-52R, RH-75
DEEP ALLUVIAL WELLS
(7 total)
EXTERIOR
RH-14R, RH-16, RH-18, RH-20
CONTINGENCY
RH-12R, RH-51, RH-55
TERTIARY SEDIMENT WELLS
(10 total)
EXTERIOR
RH-6, RH-43, RH-48
CONTINGENCY
RH-36R, RH-46, RH-53, RH-76, Town
Pump 1, Ayers, Palmer
Table 4-2
Rocker OU Operations and Maintenance Costs
Dates
Total Cost Rounded to Nearest $1,000
From
To
January 2004
December 2004
$1,068,000
CDM
Q:\Silver Bow Creek 5-Yr Reviev\AFinal ReportYTables and FiguresYTable 4-1 and 4-2.doc
-------
Table 5-1
Surface Water Quality Final Discharge Standards for the
Warm Springs Ponds Active Area OU (Station SS-5)
Constituent
Daily Maximum (mg/L)
Monthly Average (mg/L)
Arsenic
0.02
0.02
Cadmium
0.0062**
0.0016**
Copper
0.026**
0.017**
Iron
1.5
1.0
Lead
0.137**
0.0053**
Mercury
0.0002
0.0002
Selenium
0.26
0.035
Silver
0.0082**
0.00012
Zinc
0.16**
0.15**
TSS
45.0
30.0
PH
6.5-9.5 units
—
Notes:
Metals are total recoverable analyses
"These standards are hardness-dependent and are shown at a hardness of 150 mg/L as CaC03
CDM
Q:\Silver Bow Creek 5-Yr Reviev\AFinal ReportYTables and FiguresYTable 5-1 .doc
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Table 5-2
Daily Performance Standards Exceedance Summary
for the Warm Springs Ponds
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
Constituent
Final Daily Maximum Standards
January 1,1998 - December 31, 2004
No. of Measurements
No. of Exceedences
% of Exceedences
TSS
730
0
0
PH (1)
731
86
12
Arsenic
730
321
44
Cadmium
730
0
0
Copper
730
14
1.9
Iron
730
1
<1
Lead
730
0
0
Mercury (2)
730
10
1.4
Selenium
168
0
0
Silver
168
0
0
Zinc
730
3
<1
Notes:
(1) pH measurements at SS-5 greater than 9.0 result from natural biological activity.
(2) Mercury as total analysis, all other metals as total recoverable analysis.
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\2005 WSP monitoring data graphs.xls Daily exceed table
-------
Table 5-3
Monthly Performance Standards Exceedance Summary
for the Warm Springs Ponds
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
Constituent
Monthly Average Standards
January 1,1998 - December 31, 2004
No. of Measurements
No. of Exceedences
% of Exceedences
TSS
84
0
0
Arsenic
84
39
46
Cadmium
84
0
0
Copper
84
8
10
Iron
84
0
0
Lead
84
1
1
Mercury
84
1
1
Selenium
84
0
0
Silver
84
See Note 2.
Zinc
84
0
0
Notes:
(1) Mercury as total analysis, all other metals as total recoverable analysis.
(2) The detection limit for silver is greater than the monthly average standard of 0.00012 mg/l.
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\2005 WSP monitoring data graphs.xls Monthly Exceed table
-------
Table 5-4
Summary of Approximate Net Arsenic Loads in the Warm Springs Ponds
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
Annual Averages
Two-Year Averages
Year
SS-1
(kg)
SS-5
(kg)
Net Load
Removed
(kg)
Percent
Removed
Two-Year
Period
Net Load
Removed
(kg)
Percent
Removed
1998
1,530
929
602
39.3
1999
1,301
637
664
51.0
1998-1999
1,266
44.7
2000
587
329
258
43.9
1999-2000
921
48.8
2001
553
301
252
45.5
2000-2001
509
44.7
2002
597
301
296
49.5
2001-2002
547
47.6
2003
2,161
1,042
1,119
51.8
2002-2003
1,414
51.3
2004
625
614
11
1.8
2003-2004
1,130
40.6
Notes:
The arsenic loads were calculated using daily concentration and flow data to obtain a daily loading rate (kg/day).
The number of days between daily samples was calculated (ususally 3 or 4 days) and multiplied by the daily loading rate
This gave an approximate load for the period between samples. These loads were then totaled for each year.
The total number of days in the calculation was checked to make sure it was 365 days (or 366 for leap year).
If concentration data were absent, the concentration from the previous sample date was used.
If flow data were absent, the average of the two measurements immediately before and after the missing date was used.
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\As Loading.xls Table NetAsLoads
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Table 5-5
Average Concentrations and Statistics for the Unmanifolded Toe Drains at the Warm Springs Ponds
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
Toe Drain Average Concentration
Statistics for Entire Report Period
Toe Drain and
Concentration
1998
1999
2000
2001
2002
2003
2004
Average
Minimum
Maximum
Date of Maximum
in 2004
Arsenic
0.071
0.076
0.068
0.058
0.051
0.070
0.067
0.066
0.016
0.145
TD-84 in 1999
0.110
Cadmium
0.0001
0.0001
0.0001
0.0001
0.00015
0.0002
0.0001
0.00012
0.00005
0.0005
TD-161 in 2002
0.0001
Copper
0.0027
0.0013
0.0020
0.0028
0.0031
0.0024
0.0021
0.0023
0.0010
0.0100
TD-67 in 2001
0.0080
Iron
0.059
0.017
0.074
0.092
0.113
0.132
0.152
0.091
0.008
0.51
TD-152 in 2004
0.51
Zinc
0.007
0.010
0.011
0.004
0.038
0.008
0.010
0.013
0.004
0.190
TD-104 in 2002
0.010
Hardness
281
232
273
257
225
229
261
251
192
687
TD-67 in 1998
484
Notes:
Toe drains 67, 84, 87, 90, 91, 99, 104, 152, 157, 160, and 161 were sampled annually; these concentrations were averaged.
The statistics for the entire report period include all of the data from 1998 through 2004.
"Toe Drain and Date of Maximum" indicates the specific toe drain and year where the maximum concentration was measured.
"Concentration in 2004" shows the 2004 concentration of the toe drain where the maximum concentration was measured.
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\Active areas toe drains.xls Toe Drains Table
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Table 5-6
Maximum, Minimum, and Average Concentrations for Select Constituents at Inactive Area Sampling Locations
Relative to Performance Standards, March 1998 - December 2004
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
Constituent
Station IA-1
Station IA-2
Station IA-3
Monthly
Average
Surface Water
Performance
Std
Maximum
Minimum
Average
Maximum
Minimum
Average
Maximum
Minimum
Average
Arsenic
0.130
0.008
0.030
0.092
0.040
0.031
0.100
0.002
0.029
0.020
Cadmium
0.0007
0.00001
0.00032
0.0006
0.0001
0.0001
0.0010
0.0001
0.0003
0.0016
Copper
0.022
0.004
0.012
0.018
0.001
0.008
0.011
0.001
0.004
0.017
Iron
16.4
0.28
2.25
6.2
0.034
0.870
21.00
0.85
4.36
1.0
Lead
0.0020
0.0007
0.0011
0.003
0.0005
0.0009
0.0040
0.0005
0.0008
0.0053
Mercury
0.0002
0.0001
0.0001
0.00040
0.00005
0.00008
0.00040
0.00005
0.00008
0.0002
Selenium
0.004
0.001
0.001
0.0030
0.0005
0.0010
0.0030
0.0005
0.0007
0.035
Silver
0.0006
0.0005
0.0005
0.00070
0.00050
0.00051
UNDETECTED (<0.001)
0.00012
Zinc
0.310
0.052
0.111
0.502
0.005
0.056
0.850
0.047
0.137
0.015
TSS
41
2
8
15
2
5
51
2
11
30
Hardness
516
241
397
560
212
363
792
193
301
...
Notes:
1. Station IA-1: Discharge of Inactive Area pump-back system pipeline to Pond 2.
2. Station IA-2: Pond 1 Wet closure North Cell Discharge.
3. Station IA-3 Soil-cement toe drain manifold discharge into interception trench.
4. For undetected values, one half the detection limit was used to calculate statistics.
5. Performance standards shown for reference only. IA monitoring stations are not points of compliance.
6. Performance standards presented in bold type are hardness-dependent. Values shown are for a hardness of 150 mg/L and are calculated in
accordance with the standards in the 1991 UAO.
-------
Table 5-7
Average Concentrations for Select Water Quality Constituents Measured at
the Pump-back Pipeline Discharge (IA-1) and the
Pond 3 (SS-3E) and Pond 2 (SS-5) Discharge Locations
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
Constituent
Units
Pump-back
Discharge,
IA-1
Pond 3
Discharge,
SS-3E
Pond 2
Discharge,
SS-5
% Increase in
Concentration
from Pond 3
to Pond 2
Hardness
mg/L
397
194
211
CO
CO
Sulfate
mg/L
323
116
144
24.1
Total Recoverable Arsenic
mg/L
0.030
0.0255
0.0233
-8.6
Total Recoverable Iron
mg/L
2.25
0.2493
0.226
-9.3
Total Recoverable Cadmium
mg/L
0.00032
0.00072
0.00018
-75.0
Total Recoverable Copper
mg/L
0.012
0.0366
0.0126
-65.6
Total Recoverable Zinc
mg/L
0.111
0.1066
0.0354
-66.8
-------
Table 5-8
Warm Springs Ponds Biomonitoring Sampling Locations
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
Site Designation
Location
Site Description
Events
Sampled
P3-WH
Wetlands at head of
Pond 3
Upstream portion of active treatment
area; receives direct input from Silver
bow Creek (post liming); this area
was flooded in 1993.
1995- 1998,
1999, 2000,
2003
P3-N
North end of Pond 3
Near outlet in northwest corner of
Pond 3; water discharges from here
into Pond 2; Pond 3 was initially
flooded during the late 1950s (circa
1956-1959)
1995-1998
P2-VWVC
West wet closure
area, Pond 2
Wet closure cell to the south of and
separated from the active area of
Pond 2; this are was flooded in 1995.
1995- 1998,
1999, 2000,
2003
P2EWC
East wet closure area,
Pond 2
Wet closure cell to the south(east) of
and separated from the active area of
pond 2; this area was flooded in
1995.
1995-1998
P2-S
Southern end of Pond
2
Inlet portion of active treatment areas
(receives water from Pond 3); this
area was flooded in 1993.
1995-1998
P2-NW
Northwestern part of
Pond 2
Near outlet of Pond 2 (and, therefore,
of the active WSP treatment area as
a whole); Pond 2 was initially flooded
in 1916.
1995- 1998,
1999, 2000
P1-WA
Wetlands adjacent to
Pond 1
Flooded areas adjacent to the Pond 1
- Center; this area has been flooded
for many years. No longer part of the
active treatment system.
1995-1998
P1-C
Central part of Pond 1
Pond 1 has been flooded since
approximately 1911 and is no longer
part of the active treatment system.
1995-1998
P1-MWC
Middle wet closure
area, north of Pond 1
Wet closure cell north of Pond 1 -
wet closure area; flooded with water
in late 1995. not part of the active
treatment system.
1995- 1998,
1999, 2000,
2003
P1-WAN
Wetlands adjacent to
middle Pond 1 wet
closure area
Wetland area adjacent to the wet
closure cell north of Pond 1; flooded
with water in late 1995. Not part of
the active treatment system.
1995-1998
-------
Table 5-9
Warm Springs Ponds Biomonitoring Sample Types
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
Site Designation
Benthic
Invertebrate
Pelagic
Invertebrate
Fish/Waterfowl
Tissue*
Vegetation
Chemistry
P3-WH
C, T, Tox
C, T
(Collected in '95)
MT
W, S, PW
P3-N
C
P3-General Area
BFT
C
P2-WWC
C, T, Tox
C, T
BFT, L
C, MT
W, S, PW
P2EWC
T, Tox
S, PW
P2-S
C
C, T
MT
P2-NW
C, T, Tox
C, T
MT
W, S, PW
P2 General Area
BFT, L
P1-WA
C
P1-C
C, T, Tox
C, T
MT
W, S, PW
P1 General Area
BFT, L
C
P1-MWC
C, T, Tox
C, T
BFT, L
C, MT
W, S, PW
P1-WAN
C
Where: C Community Data
T Whole body tissue metal concentrations (all collected organisms for benthic
macroinvertebrates, and specifically Corixidae for pelagic invertebrates)
Tox Laboratory sediment toxicity tests using H. azteca (10-d)
L Coot liver tissue metal concentration (Sampled from the vicinity of fixed locations
listed, P1-MWC was included in 1996)
MT Aquatic macrophyte tissue metal concentration (initiated in 1996 biomonitoring)
BFT Bottom fish tissue metal concentration (fish were collected in P1-GA and P1-
MWC in 1997)
W Water Chemistry
S Sediment Chemistry
PW Sediment pore water chemistry (in addition to laboratory pore water
measurements, in situ pore water samplers were included in 1997, 1998, and
1999)
* Forage fish (Redside shiners) were originally included in the 1995 biomonitoring
effort, but were subsequently excluded as tissue residues were similar to those in
bottom fish
Note: Changes made after the 1995 sampling seasons included modifications in the
collection methods for sediments/benthic macroinvertebrates and pelagic invertebrates.
Table modified from Warm Springs Ponds 2003 Biomonitoring and Analysis Results,
ENSR International, June 2004.
-------
Table 5-10
Five-Year Operation and Maintenance Costs for the Rocker OU
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
Year
2000
2001
2002
2003
2004
5-Year
Total
Average Annual
O&M Cost
O&M
Cost
$59,776
$87,527
$137,248
$63,325
$61,829
$409,705
$81,941
-------
Table 6-1
List of Potential Interviewees
Name
Affiliation
Response
Received?
Background Information
Don Ueland
Landowner (SST OU)
Yes
Albert Molignoni
Neighbor (Rocker OU)
Yes
Scott Payne
CTEC(BPSOU)
Yes
Bob Benson
CFRTac (WSP OUs and SST OU)
Yes
Don Peoples
MERDI (Redevelopment Group) (BPS OU)
Yes
State and Local Considerations
Linda Bouck
Anaconda-Deer Lodge Co. Planning Department
Yes
Jon Sesso
Butte-Silver Bow (BSB) Planning Department
Yes
Dori Skrukrud
BSB (Greenway Issues - SST OU)
Yes
Mike Kerns
BSB Commissioner (SST OU, Rocker OU)
Yes
Dave Dziak*
MT Dept. of Fish, Wildlife, and Parks (WSP OU)
Yes
Construction Considerations
Ken Brockman
Bureau of Land Management (oversight - SST OU)
Yes
* Regulatory perspective
CDM
Q:\Silver Bow Creek 5-Yr Reviev\AFinal ReportYTables and Figures\Table 6-1.doc
-------
Table 6-2
List of Questions for Interviewees
Question
Area of Concern
Back-
ground
State or
Local
Construc-
tion
What is your overall impression of the project?
X
X
X
What effects have site activities or operations had on the
surrounding community?
X
X
Are you aware of any community concerns regarding the site or its
operation?
X
X
Do you feel the remedy (or proposed remedy) is protective?
X
X
Do you feel well informed about site progress and activities?
X
X
Do you have any comments or suggestions?
X
X
X
Have you done any site visits, inspections, reporting, etc at the
site?*
X
Have there been any complaints, violations, or other incidents?*
X
What is the current state of construction?
X
Have you encountered any problems that changed, or will change,
the remedy?
X
Have any problems impacted construction or implementability?
X
* Asked ofFWP only
CDM
Q:\Silver Bow Creek 5-Yr RevievMDraft Report\Section 5 Tables and FiguresYTable 6-2.doc
-------
Table 7-1
Results of Horseshoe Bend WTP Performance Testing
Butte M
ine Flooding OU
Metals
Performance
Test Results
(ug/L)
Interim Limits
Monthly Average
(ug/L)
Final Limits Daily
Maximum (ug/L)
Final Limits Monthly
Average (ug/L)
Arsenic
<0.8
10
10
10
Cadmium
1.5
11
5
0.8
Copper
8.9
30.5
51.6
30.5
Iron
57
1000
1500
1000
Lead
Non detect
15
15
15
Mercury
Non detect
0.91
1.7
0.91
Uranium
Non detect
30
30
30
Zinc
123
388
388
388
CDM
Q:\Silver Bow Creek 5-Yr Reviev\AFinal ReportYTables and FiguresYTable 7-1 .doc
-------
Table 7-2
Existing Performance Standards at the Warm Springs Ponds Oils
and Current State and Federal Aquatic Life and Human Health Standards
Constituent
Surface Water
Groundwater
Existing
Performance Std.
State(1)
Federal(2)
Existing
Performance Std.
(mg/L)
State(1)
Federal(3)
Current Aquatic Life
Standards
Current
Human
Health
Std.
(mg/L)
Ambient Water Quality
Criteria
Current
Human
Health Std.
(mg/L)
Current
MCL
(mg/L)
Daily
Maximum
(mg/L)
Monthly
Average
(mg/L)
Acute
(mg/L)
Chronic
(mg/L)
cmc(4)
(mg/L)
CCC (5)
(mg/L)
Arsenic
0.020
0.020
0.340
0.150
0.018
0.340
0.150
0.050
0.020
0.010
Cadmium
0.0062lb)
0.0016lb)
0.0032
(6)
0.00037 lb)
0.005
0.0030 lb)
0.00033 lb)
0.010
0.005
0.005
Chromium
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0.050
0.1
0.1
Copper
0.026lb)
0.017lb)
0.0205
(6)
0.0132lb)
1.3
0.0197 lb)
0.0127lb)
N/A
1.3
1.3
Lead
0.137lb)
0.0053lb)
0.137(b)
0.0053lb)
0.015
0.1001 lb)
0.0039lb)
0.050
0.015
0.015
Notes:
1. Montana Numeric water Quality Standards - Circular WQB-7. January 2004
2. Current National Recommended Water Quality Criteria; U.S. Environmental Protection Agency Web Page:
http://www.epa. aov/waterscience/criteria/wacriteria.html#notes
3. Safe Drinking Water Contaminants and Federal Maximum Contaminant Levels(MCLs); U.S. Environmental Protection Agency Web Page:
http://www.epa.goV/safewater/mcl.html#mcls
4. CMC - Criteria Maximum Concentration is an estimate of the highest concentration of a material in surface water to which an aquatic community can be
exposed briefly without resulting in an unacceptable effect.
5. CCC - Criterion Continuous Concentration (CCC) is an estimate of the highest concentration of a material in surface water to which an aquatic community
can be exposed indefinitely without resulting in an unacceptable effect.
6. Hardness-dependent aquatic life standards(Cd, Cu, Pb) are presented based on a hardness of 150 mg/L as CaC03.
-------
Figure 3-1
Site Location
BERKELEY
PIT
Legend
Butte Priority Soils Operable Unit
KWN Mine Flooding Operable Unit (approx.)
Active Mining Area (approx.)
Warm Springs Ponds Operable Unit
Streamside Tailings Operable Unit
West Side Soils Operable Unit
Rocker Timber Framing and Treatment Plant Operable Unit
WARM
FORK RIVER
CDM
Q:\Silver Bow Creek 5-Yr RevievMDraft Report\Section 5 Tables and Figures\Figure 3-1.doc
-------
^ ACTIVE \REA OPERABLE UNIT
\ \
INACTIVE AREA
OPERABLE UNIT
ACTIVE AREA
OPERABLE UNIT
Figure 5-1
ACTIVE AREA
SAMPLING LOCATIONS
SCALE: 1"=3000'
DATE: 4/25/05
-------
\
\
I
\
FEED UVF
TJfEA TUDtf/CHEWCAL FEW FACILITIES
LEGEND
—ACTIVE AREA
INACTIVE AREA
p/OAfFJ?/?
_l OTOTi SfAWCffS,
/JVC.
Figure 5-2
ACTIVE AREA
SCHEMATIC
GENERAL FLOW
SCALE: NXS.
DATE: 4/25/05
-------
Figure 5-3
Influent (SS-1) and Effluent (SS-5) Daily Flow Rates for the Warm Springs Ponds
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
Date
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\SS-1 SS-5 flow rates.xls SS-1 SS-5 flow rates.xls daily flow
-------
Figure 5-4
Influent (SS-1) and Effluent (SS-5) Monthly Flow Rates for the Warm Springs Ponds
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
Date
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\SS-1 SS-5 flow rates.xls SS-1 SS-5 flow rates.xls monthly flow
-------
Figure 5-5
Pond 2 Elevations at the Warm Springs Ponds
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
Date
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\water levels.xls water levels.xls Pond 2 graph
-------
Figure 5-6
Pond 3 Elevations at the Warm Springs Ponds
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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4,871
4,870
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ra
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CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\water levels.xls water levels.xls Pond 3 graph
-------
9.5
9.0
ra
¦o
c
ra
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X
Q.
8.5
8.0
7.5
Figure 5-7
Comparison of Influent (SS-1) and Effluent (SS-5) pH values with Final Daily Performance Standard
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
10.0
Month-Year
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\2005 WSP monitoring data graphs.xls pH 98-04Chart
-------
Figure 5-8
Comparison of Influent (SS-1) and Effluent (SS-5) Total Suspended Solids Concentration with Final
Daily Performance Standard
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
(—)
(—)
(—)
(—)
(—)
(—)
(—\
CD
5
CD
^—'
CD
5
CD
^—'
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o
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o
CO
o
Month-Year
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\2005 WSP monitoring data graphs.xls TSS 98-04Chart
-------
Figure 5-9
Comparison of Influent (SS-1) and Effluent (SS-5) Total Recoverable Arsenic Concentrations with Final
Daily Performance Standard
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
Month-Year
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\2005 WSP monitoring data graphs.xls As 98-04Chart
-------
Figure 5-10
Comparison of Influent and Effluent Arsenic Loading at the Warm Springs Ponds
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
Date
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\As Loading.xls As Load Graph
-------
30
20
10
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re
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0
*'
u
re
o
-10
_i
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0)
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-20
<
0)
-30
-40
-50
The thick horizontal bars indicate
periods when arsenic
exceedances occurred.
Net Load
• Net Load Quarterly Average
Figure 5-11
Comparison of Net Arsenic Loading with Periods of Exceedances
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
Date
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\As Loading.xls Net As Loads Graph
-------
Figure 5-12
Comparison of Arsenic Loads from the Warm Springs Ponds (SS-5) and Downstream Station MWB-3
against SS-5 Discharge Concentrations
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
o
o
o
o
o
o
o
o
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c
Date
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\As Loading.xls As & MWB Compare
-------
Figure 5-13
Comparison of Influent (SS-1) and Effluent (SS-5) Total Recoverable Cadmium Concentrations with
Final Daily Performance Standard
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
0.012 n
0.010
O)
E
E
3
E
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re
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aj
5
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0.006
re 0.004
O
0.002
0.000
Month-Year
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\2005 WSP monitoring data graphs.xls Cd 98-04Chart
-------
Figure 5-14
Comparison of Influent (SS-1) and Effluent (SS-5) Total Recoverable Copper Concentrations with
Final Daily Performance Standard
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
0.20
0.15
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Month-Year
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\2005 WSP monitoring data graphs.xls Cu 98-04Chart
-------
Figure 5-15
Comparison of Influent (SS-1) and Effluent (SS-5) Total Recoverable Copper Concentrations with
Final Daily Performance Standard, Scale Adjusted
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
CD
00
CD
00
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00
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00
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ro
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CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\2005 WSP monitoring data graphs.xls Cu 98-04Chart #2
-------
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a;
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1.0
0.5
Figure 5-16
Comparison of Influent (SS-1) and Effluent (SS-5) Total Recoverable Iron Concentrations with Final
Daily Performance Standard
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
Daily Maximum Discharge Standard =1.5 mg/L
• ¦¦ >
I... .if'.
¦¦
Month-Year
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\2005 WSP monitoring data graphs.xls Fe 98-04Chart
-------
0.35
Figure 5-17
Comparison of Influent (SS-1) and Effluent (SS-5) Total Recoverable Lead Concentrations with Final
Daily Performance Standard
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
0.25
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CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\2005 WSP monitoring data graphs.xls Pb 98-04Chart
-------
Figure 5-18
Comparison of Influent (SS-1) and Effluent (SS-5) Total Mercury Concentrations with Final Daily
Performance Standard
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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Month-Year
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\2005 WSP monitoring data graphs.xls Hg 98-04Chart
-------
Figure 5-19
Comparison of Influent (SS-1) and Effluent (SS-5) Total Recoverable Selenium Concentrations with
Final Daily Performance Standard
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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-------
Figure 5-20
Comparison of Influent (SS-1) and Effluent (SS-5) Total Recoverable Silver Concentrations with Final
Daily Performance Standard
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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Hardness Adjusted Final Daily Maximum Discharge Standard
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\2005 WSP monitoring data graphs.xls Ag 98-04Chart
-------
Figure 5-21
Comparison of Influent (SS-1) and Effluent (SS-5) Total Recoverable Zinc Concentrations with Final
Daily Performance Standard
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
;
r
"¦5
Si
Hardness Adjusted Final Daily Maximum Discharge Standard
Month-Year
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\2005 WSP monitoring data graphs.xls Zn 98-04Chart
-------
Figure 5-22
Arsenic Concentrations in Pond 3 Effluent Compared to East and West Wet Closure Ponds
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
0.08 n
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Date
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\Active areas wet closure.xls As
-------
Figure 5-23
Copper Concentrations in Pond 3 Effluent Compared to East and West Wet Closure Ponds
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
00
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CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\Active areas wet closure.xls Cu
-------
Figure 5-24
Iron Concentrations in Pond 3 Effluent Compared to East and West Wet Closure Ponds
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\Active areas wet closure.xls Fe
-------
Figure 5-25
Zinc Concentrations in Pond 3 Effluent Compared to East and West Wet Closure Ponds
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\Active areas wet closure.xls Zn
-------
Figure 5-26
Sulfate Concentrations in Pond 3 Effluent Compared to East and West Wet Closure Ponds
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CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\Active areas wet closure.xls S04
-------
DRY-CLOSURES
LEGEND
I 5 | TOE DRAIN
Figure 5-27
SOIL CEMENT
TOE DRAINS
SCALE: 1 "=2500'
DATE: 4/26/05
-------
Figure 5-28
Hardness Concentrations in the Mill-Willow Bypass
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\MWB graphs.xls Hardness
-------
Figure 5-29
Arsenic Concentrations in the Mill-Willow Bypass
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\MWB graphs.xls As MWB
-------
Figure 5-30
Copper Concentrations in the Mill-Willow Bypass
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CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\MWB graphs.xls Cu MWB
-------
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CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\MWB graphs.xls Zn MWB
The extra large symbols indicate the sample
concentration exceeded the hardness-based
chronic water quality standard on that date.
Figure 5-31
Zinc Concentrations in the Mill-Willow Bypass
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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Figure 5-32. Dissolved Arsenic in Down-gradient Piezometers
June 1998 - December 2004
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\2005 04 15 TRENCHPIEZO-mwh.xls Fig 5-32. North Side Arsenic
-------
0.016 n
0.014
0.012
Figure 5-33. Dissolved Cadmium in Down-gradient Piezometers
June 1998 - December 2004
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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Figure 5-34. Dissolved Chromium in Down-gradient Piezometers
June 1998 - December 2004
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\2005 04 15 TRENCHPIEZO-mwh.xls Fig 5-34 North Side Chromium
-------
Figure 5-35. Dissolved Lead in Down-gradient Piezometers
June 1998 - December 2004
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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June 1998 - December 2004
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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c
-------
Figure 5-37. Nitrate in Down-gradient Piezometers
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
10
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-------
Figure 5-38. Dissolved Arsenic in Up-gradient Piezometers
June 1998 - December 2004
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\2005 04 15 TRENCHPIEZO-mwh.xls Fig 5-38 South Side Arsenic
-------
Figure 5-39. Dissolved Cadmium in Up-gradient Piezometers
June 1998 - December 2004
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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June 1998 - December 2004
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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Figure 5-41. Dissolved Lead in Up-gradient Piezometers
June 1998 - December 2004
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
~ P-01
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&
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Date
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\2005 04 15 TRENCHPIEZO-mwh.xls Fig 5-41 South Side Lead
-------
Figure 5.-42. Dissolved Mercury in Up-gradient Piezometers
June 1998 - December 2004
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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Date
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\2005 04 15 TRENCHPIEZO-mwh.xls Fig 5-42 South Side Mercury
-------
Figure 5-43. Nitrate in Up-gradient Piezometers
June 1998 - December 2004
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
10
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March 1998 - June 2004
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\2005 04 15 TRENCHPIEZO-mwh.xls Fig 5-44 P-14 Arsenic
-------
Figure 5-45. Dissolved Cadmium in Piezometer P-14
March 1998 - June 2004
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
0.014
0.012
0.01
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0.004
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Figure 5-46. Dissolved Chromium in Piezometer P-14
March 1998 - June 2004
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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Figure 5-47. Dissolved Lead in Piezometer P-14
March 1998 - June 2004
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
O Lead
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Figure 5-48. Dissolved Mercury in Piezometer P-14
March 1998 - June 2004
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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Date
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-------
Figure 5-49. Nitrate in Piezometer P-14
March 1998 - June 2004
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
10
~ Nitrate
GW Limit
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-------
Figure 5-50. Total Recoverable Arsenic Concentrations in Toe Drain Manifold (IA-3)
Relative to Pond 3 (SS-3E), Pond 2 (SS-5) and the Mill-Willow Bypass (MWB-2)
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
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Figure 5-51. Total Recoverable Iron Concentrations in Toe Drain Manifold (IA-3) Relative to
Pond 3 (SS-3E), Pond 2 (SS-5), and the Mill-Willow Bypass (MWB-2)
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
COM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\SS-5 SS-3E IA-1 IA-2 IA-3 Data.xls Figure 5-51. IA-3 Fe
-------
Figure 5-52. Total Recoverable Cadmium Concentrations in Inactive Area Wet Closure
Discharge (IA-2) Relative to Pond 3 (SS-3E) and Pond 2 (SS-5)
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
0.003 n
<£> <£>
>*' rjt
tf'
-------
Figure 5-53. Total Recoverable Copper Concentrations in Inactive Area Wet Closure
Discharge (IA-2) Relative to Pond 2 (SS-3E) and Pond 3 (SS-5)
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
COM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\SS-5 SS-3E IA-1 IA-2 IA-3 Data.xls Figure 5-53 IA2 Cu
-------
Figure 5-54. Total Recoverable Zinc Concentrations in Inactive Area Wet closure Discharge
(IA-2) Relative to Pond 3 (SS-3E) and Pond 2 (SS-5)
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
COM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\SS-5 SS-3E IA-1 IA-2 IA-3 Data.xls Figure 5-54 IA-2 Zn
-------
Figure 5-55. Total Recoverable Arsenic Concentrations in Inactive Area Wet Closure
Discharge (IA-2) Relative to Pond 3 and Pond 2 (SS-5)
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
0.100 1
0.090
0.080
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-------
Figure 5-56. Total Recoverable Copper Concentrations in Pump-back Pipeline (IA-1) Relative
to Pond 3 (SS-3E) and Pond 2 (SS-5)
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
Date
CDM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\SS-5 SS-3E IA-1 IA-2 IA-3 Data.xls Figure 5-56. IA-1 Cu
-------
Figure 5-57. Total Recoverable Zinc concentrations in Pump-back Pipeline (IA-1) Relative to
Pond 3 (SS-3E) and Pond 2 (SS-5)
Silver Bow Creek/Butte Area Superfund Site, Five-Year Review, July 2005
COM
Q:\Silver Bow Creek 5-Yr Review\Draft Report\Section 5 Tables and Figures\SS-5 SS-3E IA-1 IA-2 IA-3 Data.xls Figure 5-57. IA-1 Zn
-------
------- |