United States Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R08-92/059
June 1992
v°/EPA Superfund
Record of Decision:
Silver Bow Creek/Butte Area,
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50272.101
REPORT DOCUMENTATION 1'. REPORTNo.
PAGE EPA/ROD/R08-92/059
I ~
3. Recipient's AcceMion No.
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4. Title and SubtltJa
SUPERFUND RECORD OF' DECISION
Silver Bow Creek/Butte Area, MT
Second Remedial Action - Interim
7. Author(a)
5. Report Date
06/30/92
6.
8. Performing Organization Rept. No.
II. Performing Orgainization Name and Addre..
10. ProjedlTukIWork Unit No.
,
11. Contract(C) or Grant(G) No.
(C)
(G)
12. Sponao,ing Organization Name and Add 18..
U.S. Environmental Protection
401 M Street, S.W.
Washington, D.C. 20460
13. Type of Report & Period Covered
Agency
800/000
14.
15. Supplementary Notea
PB93-964412
16. Abetrad (UmiI: 200 worda)
The Silver Bow Creek/Butte Area site is a mining and processing area located 7 miles
east of Anaconda in the Upper Clark Fork River Basin, Deer Lodge County, Montana. One
part of the site is the Warm Springs Pond inactive area, which covers approximately
2,500 acres of open pond water and interspersed wetlands just above the beginning of
the Clark Fork River. Several onsite creeks (Warm Springs, Silver Bow, Mill, Willow)
and a stream by-pass (Mill-WillOw By-pass) serve as principal headwaters to Clark Fork
River. Three settling ponds, an area between the northern-most pond (Pond 1) and the
Clark Fork River's beginning point, and a series of wildlife ponds are located in
proximity to the creeks. Site contamination is the result of over 100 years of mining
and process operations in the area. Until the early 1970's, mining, milling, and
smelting wastes were dumped directly into Silver Bow Creek and transported downstream.
Three settling ponds were constructed in the early 1900's by Anaconda Copper Mining
Company to allow wastes that were deposited in Silver Bow Creek to settle out before
discharging to the Clark Fork River. Approximately 19 million cubic yards of tailings
and metal-contaminated sediment and sludge have collected in the ponds and 3 million
(See Attached page)
17. Document Analyaia L Descriplora
Record of Decision - Silver Bow Creek/Butte
Second Remedial Action - Interim
Contaminated Media: soil, sediment, gw, sw
Key Contaminants: metals (arsenic, chromium,
Area, MT
lead), inorganics
b. IcIentifieralOpen.Ended Terms
Co COSATI FlllldIGroup
18. Availability Statement
19. Security Clan (Thia Report)
None
21. No. of Pages
126
20. Security Clan (This Page)
None
22. Price
(See ANSI-Z3i.18)
See Ins/fuc!/ons on RevelS8
272 (4.77)
(Formerly NnS-35)
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EPA/ROD/R08-92/059
Silver Bow Creek/Butte Area, MT
Second Remedial Action - Interim
~stract (Continued)
cubic yards of contaminated tailings remain upstream of the ponds along the banks of
Silver Bow Creek. Principal threats from the site include the possibility of pond berm
failure attributed to flood and ~arthquake damage that could release millions of cubic
yards of tailings and sediment into the river. Several removal actions that occurred
during 1967 and 1989 have been 'or will be implemented at the site, including the
Mill-Willow By-pass removal, Travona Mine Shaft Control, and residential soil cleanups.
A 1990 ROD addressed an interim action for the Warm Springs Ponds area, which included
Ponds 1, 2, and 3, but deferred the decision on the area below Pond 1 for a year. When
it was recognized that a decision on Pond 1 and the area below it might delay the remedy
for Ponds 2 and 3, in 1991 EPA wrote an ESD that divided the Warm Springs Pond area into
two operable units: the Active area, composed of Ponds 2 and 3, as OU4: and the Inactive
area, composed of Pond 1 and the area below it, as OUl2. This ROD addresses an interim
remedy for all media at OU12. The primary contaminants of concern affecting the soil,
sediment, ground water, and surface water in the Inactive area are metals, including
arsenic, chromium, and lead; and inorganics.
The selected remedial action for this site includes excavating all tailings and
contaminated soil from the by-pass channel and the area below Pond 1 not planned for
wet-closure, and consolidating the wastes over existing dry tailings within the western
portion of Pond 1: placing a cover of lime, fill, and soil over the dry tailings and
revegetating: modifying the by-pass channel to safely route potential flood flows: using
soil and gravel that meet geotechnical requirements and have copper levels of less than
500 mg/kg to raise and strengthen existing berms: constructing new berms; raising and
strengthening the north-south aspect of the Pond 1 berm, and stabilizing the east-west
aspect of the Pond 1 berm to withstand a maximum credible earthquake for this area;
extending and armoring the north-south aspect of the Pond 1 berm: relocating the
lowermost portion of the by-pass channel, converting the present channel into a ground
water interception trench: installing pumps to allow for a pump-back system to transport
ground water and surface water to the active area for treatment, if levels exceed
specified standards: constructing wet-closure berms to enclose the submerged tailings and
contaminated sediment: chemically fixing tailings and sediment with lime, and flooding
the wet-closure cells with water with a pH of greater than 8.5: constructing a run-off
interception system along the east side of the Inactive area and toe drains, and
installing a collection manifold for both the Active and Inactive areas: and implementing
ecological monitoring and institutional controls, including deed, ground water, and land
use restrictions. The total present worth cost for this remedial action is $18,100,000,
which includes an annual O&M cost of $67,200 for 30 years.
PERFORMANCE STANDARDS OR GOALS:
Soil at final excavation grade for this interim action will exhibit concentrations of
metals within the range of the following concentrations: arsenic 8.4-42.1 mg/kg: cadmium
0.8-4 mg/kg; lead 8.4-45.5 mg/kg: copper 0.6-287 mg/kg; and zinc 0.4-573.
Chemical-specific interim ground water clean-up goals, which are based on state drinking
water criteria, include arsenic SO ug/l: cadmium 10 ug/l; copper 1,000 ug/l: lead
SO ug/l: manganese SO ug/l: zinc 5,000 ug/l: and iron 300 ug/l. Final soil, sediment,
ground water, and surface water action levels for the various contaminants are not
identified in this ROD and will be determined based on ongoing risk assessment work at
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RECORD OF DECISION
Warm Springs Ponds Inactive Area Operable Unit (OU 12)
Silver Bow Creek/Butte Area NPL Site (original portion)
Clark Fork River Basin, Montana
United States Environmental Protection Agency
Region vm
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7.0
8.0
9.0
TABLE OF CONTENTS (continued)
Page
DESCRIPTION OF ALTERNATIVES. . . . . . . . . . . . . . . . . . . . . . . . . .. 11-38
7.1 Alternative 1 (Dry Close Pond.l,
Removal Below Pond 1) ............................ 11-39
7.2 Alternative 2 (Dry Close Pond 1,
Wet Close Below Pond 1) . . . . . . . . . . . . . . . . . . . . . . . . . .. II -40
7.3 Alternative 3 (Dry Close Pond 1,
Dry Close Below Pond 1) ........................... II -41
7.4 Alternative 4 (Wet/Dry Close Pond 1,
Remove Tailings Below Pond 1) ...................... 11-42
7.5 Alternative 5 (Wet/Dry Close Pond 1,
Wet Close Below Pond 1) . . . . . . . . . . . . . . . . . . . . . . . . . .. II-43
7.6 Alternative 6 (Wet/Dry Close Pond 1,
Dry Close Below Pond 1) ........................... 11-44
7.7 Alternative 7 (No-Action) ................................ 11-44
7.8 Alternative 8 (Removal of Pond 1 And Area
Below Pond 1; East Hills Repository) .................. II-45
7.9 Alternative 9 (Removal of Pond 1 and Area Below
Pond 1; Pond 3 Repository) ......................... II-46
7.10 Alternative 10 (Removal of Pond 1 and Area Below
Pond 1; Opportunity Ponds Repository) . . . . . . . . . . . . . . . .. II-47
7.11 Alternative 11 (Removal of Pond 1 and Area Below
Pond 1; Anaconda Ponds Repository) .................. 11-48
COMPARATIVE ANALYSIS OF ALTERNATIVES................ ll-49
8.1 Overall Protection of Human Health.
and the Environment. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. II-54
Compliance With ARARs ................................ II-55
Long-Term Effectiveness and Performance: . . . . . . . . . . . . . . . . . " II-56
Reduction of Toxicity, Mobility, and Volume. . . . . . . . . . . . . . . . .. II-57
Short-Term Effectiveness. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. II-59
Implementability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. II -61
Costs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. II -62
State Acceptance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11-63
Community Acceptance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. II -63
8.2
8.3
8.4
8.5
8.6
8.7
8.8
8.9
TIlE SELECTED REMEDY.................................. 11-65
9.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. II -65
9.2 Remediation and Performance Standards. . . . . . . . . . . . . . . . . . . .. II-67
. 9.2.1 Pond Bottom Sediments. . . . . . . . . . . . . . . . . . . . . . . . . . .. II -68
9.2.2 Surface Water. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ll-68
9.2.3 Tailings Deposits and Contaminated Soils. . . . . . . . . . . . . .. 11-69
9.2.4 Ground Water. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11-69
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10.0
Figure 1
Figure 2A
Figure 2B
Figure 3
Figure 4
Figure 5
Figure 6
Table 1
Table 2
Table 3
Table 4
Table ~
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TABLE OF CONTENTS (continued)
Page
STATUTORY DETERMINATIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . .. II-74
10.1 Protection of Human Health and the Environment. . . . . . . . . . . .. II-74
10.2 Compliance with Applicable or Relevant
and Appropriate Requirements. . . . . . . . . . . . . . . . . . . . . .. II-75
10.3 Cost-Effectiveness...................................... II-75
10.4 Utilization of Permanent Solutions and
Alternative Treatment Technologies or
Resource Recovery Technologies to the
Maximum Extent Practicable. . . . . . . . . . . . . . . . . . . . . . . . . . . . ., II-76
10.5 Preference for Treatment as a Principal Element. . . . . . . . . . . . . .. II-77
LIST OF FIGURES
Warm Springs Ponds System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8
Inactive Area, Present Condition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9
Inactive Area, Showing Components of Remedy. . . . . . . . . . . . . . . . . . 1-9
Pond Bottom Sediments, Tailings, and
Contaminated Soils. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. II-18
Monitored Well Locations and Extent of Ground
Water Exceeding Primary MCL for Cadmium
and Arsenic. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11-21
Pathways of Exposure. . . . . . . . . . . . ~ . . . . . . . . . . . . . . . . . . . . .. 11-29
Location of Source Areas and Receptors. . . . . . . . . . . . . . . . . . . .. 11-30
LIST OF TABLES
Summary of Areas and Volumes of Contaminated
Media. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. II -16
Maximum, Minimum and Average Values Pond 1 Bottom
Sediments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. II -19
Summary of Surface Water Quality Data Pond 1 ............... II-23
Ground Water Quality Data Summary Warm Springs
Ponds Inactive Area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. II-24
Summary of Risks For Current Human
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Table 6
Table 7
Table 8
Table 9
TABLE OF CONTENTS (continued)
Paae
..:.....==
Summary of Comparative Analysis of Alternatives ."............. II-51
Cost Summary Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11-63
Detailed Cost Estimates, Alternative 5 . . . . . . . . . . . . . . . . . . . . . .. 11-70
Operation and Maintenance Costs, Alternative 5 ............... 11-73
ATIACHMENT 1 TO PART II
INSTITUTIONAL CON1ROLS FOR THE WARM SPRINGS PONDS INACTIVE AREA
OPERABLE UNIT (OU 12), SILVER BOW CREEK/BUTTE AREA NPL SITE (original
portion), UPPER CLARK FORK RIVER BASIN, MONTANA
ATIACHMENT 2 TO PART II
APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS,
STANDARDS, CON1ROLS, CRITERIA, OR LIMITATIONS AND OTHER
PERFORMANCE STANDARDS FOR THE WARM SPRINGS PONDS INACTIVE
AREA OPERABLE UNIT, SILVER BOW CREEK/BUTTE AREA NPL SITE (original
portion), UPPER CLARK FORK RIVER BASIN, MONTANA
PART III: THE RESPONSIVENESS SUMMARY
1.0
2.0
3.0
OVERVIEW. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 111-1
BACKGROUND ON COMMUNITY INVOLVEMENT. . . . . . . . . . . . .. 111-3
2.1 Summary of Major Concerns. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 111-5
SUMMARY OF COMMENTS RECEIVED AND AGENCY RESPONSES 111-7
3.1 Preference Regarding Complete or Partial Removal. . . . . . . . . . . .. 111-7
3.2 EPA Site Management Issues. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111-13
3.3 Public Involvement Concerns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111-17
3.4 Adequacy of Proposed Plan and
Alternatives Descriptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III -17
3.5 Water Rights and Reservations on
the Clark Fork River. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111-20
3.6 General Issues of Concern and
Philosophical Differences. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111-22
3.7 Berm Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111-26
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TABLE OF CONTENTS (continued)
Page
3.9 Water Quality Issues. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111-28
3.10 Interception Trench. . . . . . . . . . . . . . . . . . . . . . ~ . . . . . . . . . . . . . . 111-29
3.11 Area Below Pond 1 . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111-30
3.12 Wet Closure Specifics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111-31
4.0
REMAINING CONCERNS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111-33
ATTACHMENT 1 TO PART III
STATE CONCURRENCE wrrn THE SELECTED REMEDY
ATTACHMENT 2 TO PART III
UST OF COMMENTERS ON INACTIVE AREA
ATTACHMENT 3 TO PART III
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RECORD OF DECISION
PART I: THE DECLARATION
Warm Springs Ponds Inactive Area Operable Unit (OU 12)
Silver Bow Creek/Butte Area NFL Site (original portion)
Clark Fork River Basin, Montana
United States Environmental Protection Agency
Region vm
June 1992
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RECORD OF DECISION
PART I
THE DECLARATION
Warm Springs Ponds Inactive Area Operable Unit (OU 12)
Silver Bow Creek/Butte Area NPL Site (original portion)
Upper Clark Fork River Basin, Montana
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected interim remedial action for the Warm Springs
Ponds Inactive Area Operable Unit which is part of the Silver Bow Creek/Butte Area
National Priorities List (NPL) Site. The selected remedial action was developed in
accordance with the Comprehensive Environmental Response, Compensation, and Liability
Act of 1980, as amended (CERCLA), 42 USC Sec. 9601, et. ~. and, to the extent
practicable, the National Oil and Hazardous Substances Pollution Contingency Plan (NCP),
40 CFR Part 300. This decision is based on the administrative record for the Inactive Area
and Active Area operable units of the Warm Springs Ponds, Silver Bow Creek/Butte Area
NPL Site.!
All determinations reached in this Record of Decision were made in consultation with the
Montana Department of Health and Environmental Sciences, Solid and Hazardous Waste
Bureau (hereafier referred to as the State or MDHES) , which conducted the remedial
investigation for the Warm Springs Ponds and participated fully in the selection of the
remedy and the development of this decision document. The State of Montana is in
agreement with the EP A concerning the selected remedy. A copy of the State's letter of
concurrence with the selected remedy is attached to Part m.
IThe administrative record index and copies of key site documents are available for public review at the University of Montana
Library, the Montana Tech Library on West Park Street in Butte, and other information repositories in the Oark Fork Basin. The
complete administrative record may be reviewed at the offices of the U.S. EPA, 301 South Park, Federal Building, Helena, MT.
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ASSESSMENT OF THE SITE
Actual and threatened releases of hazardous substances from the Inactive Area Operable
Unit of the Warm Springs Ponds, if not significantly reduced or eliminated by
implementation of the response action selected and described in this Record of Decision,
may present an imminent and substantial endangerment to the public health, welfare, or the
environment.
DESCRIPTION OF THE SELECTED REMEDY
The Warm Springs Ponds are located in Deer Lodge County, approximately seven miles east
of Anaconda, near the historic confluence of Silver Bow, Willow, Mill and Warm Springs
creeks. These streams are principal headwaters of the Clark Fork River, which begins
approximately one-quarter mile north of the Inactive Area Operable Unit boundary.
The Warm Springs Ponds are comprised of three settling ponds, the area below (north of)
Pond 1, a series of wildlife ponds, and the Mill-Willow Bypass (see Figure 1).
In 1991, the Warm Springs Ponds were divided into two operable units:
a)
Active Operable Unit (OU No.4 of the Silver Bow Creek/Butte Area site),
including Ponds 2 and 3, their inlet and outlet channels, their associated water
treatment facilities, the wildlife ponds and the upper bypass channel (Mill-
Willow Bypass); 2 and
b)
Inactive Operable Unit (OU No. 12 of the Silver Bow Creek/Butte Area site),
including Pond 1, the historic Silver' Bow Creek channel and some
uncontaminated grassland and wet meadows below Pond 1, and the lower
bypass channel, which contains not only Mill and Willow creeks, but also
outflows from Pond 2 (see Figures 2A and 2B).
2rhe interim remedy for the Active Area Operable Unit was described in the September 1990 Record of Decision, as modified by
the June 1991 Explanation of Significant Differences including its errata sheet. .
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The selected interim remedy for the Inactive Area Operable Unit includes means for
controlling contamination associated with submerged and exposed tailings, soils, pond
bottom sediments, and ground and surface water. The selected remedy may be summarized
as follows:
1.
2.
Remove all tailings and contaminated soils from the adjacent portion of the pypass
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 cubic feet per second (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.
3.
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 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.
4.
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.
5.
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.
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6.
7.
8.
9.
10.
11.
12.
Relocate the lowermost portion of the bypass channel and convert the present
channel into a ground water 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 ground water 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 2 inches of limestone, 12 inches of fill, and 6 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
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13.
14.
15.
..
engineered solution 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 source discharge standards specified in
Attachment 5 to the Warm Springs Ponds Active Area Unilateral Administrative
Order.
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 institutional controls to prevent residential development, domestic well
construction, disruption of dry-closure caps, and swimming.
The selected remedy is an interim response action; however, not in the usual sense. Interim
actions usually address only portions of site cleanups, or may not intend to utilize permanent
solutions to the maximum extent practicable. Thus, they are usually not intended to be the
final response action for a particular site or set of circumstances.
This interim response action utilizes permanent solutions to the maximum extent
practicable, and the EP A believes that subsequent final evaluations will demonstrate the
effectiveness of the interim remedy. It is an interim remedy for the following reasons:
1.
Hazardous substances will remain on site;
2.
The selected remedy employs innovative methods for reducing or eliminating
threats to human health and the environment, which will require monitoring
over time to evaluate its effectiveness; and
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3.
Contaminated source areas upstream and upgradient have direct implications
on the effectiveness and permanence of any remedy selected for this area.
While every reasonable effort was made to assure that this remedy will be protective of
human health and the environment, the measure of its protectiveness, effectiveness and
permanence requires time and a watchful eye. Clearly, when compared to the 10. other
remedies examined in the feasibility study, the remedy selected affords the most reasonable
balance of objectives and it offers the greatest potential for becoming a final remedy. Thus,
the selected remedy presented in this Record of Decision attempts to permanently
remediate the principal threats posed by contamination within the Inactive Area Operable
Unit.
Additionally, the selected remedy is acceptable to a majority of interested Clark Fork River
Basin residents and local government officials. Several public scoping meetings were held
throughout the basin as the EP A and State examined feasible alternatives. Individuals and
special interest groups requested more studies with respect to totally removing the
contaminated materials from the historic flood plain and consumptive water usage estimates
for the various alternatives. The EP A responded with additional studies and followup
meetings were conducted prior to issuing the proposed plan. While no remedy can be
expected to receive unanimous public support, the remedy selection process in this instance
was carried out with full public participation and the remedy selected is broadly supported.
STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the environment, complies with
Federal and State requirements that are legally applicable or relevant and appropriate to
the remedial action unless a statutory waiver is invoked, and is cost-effective. Although the
remedy is an interim remedy which will be reevaluated in a final remedy decision for the
Warm Springs Ponds active and inactive areas, the remedy utilizes permanent solutions and
alternative treatment technologies to the maximum extent practicable and satisfies the
statutory preference for remedies that employ treatment that reduces toxicity, mobility, or
volume as a principal element.
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Because this remedy will result in hazardous substances remaining on site, above health
based and environmental-based levels, a review will be conducted within five years after
commencement of remedial action to ensure that the remedy continues to provide adequate
protection of human health and the environment. Additionally, the remedy selected by this
Record of Decision will be subject to a separate public review once cleanup work at other
operable units and NPL sites tbat affect this operable unit is completed.
Signed this
30ti
day of June, 1992.
Jack McGraw
Acting Regional Administrator
United States Environmental Protection Agency
Region VIII
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LEGEND
WATER
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FIGURE 2A
INACTIVE AREA
PRESENT CONDITION
WARM SPRINGS PONDS
TAILINGS AND
CONTAMINATED
SOILS
OLD SILVER BOW
CREEK CHANNEL
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WET.
CLOSURE
CELLS
FIGURE 28
INACTIVE AREA
SHOWING COMPONENTS OF REMEDY
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RECORD OF DECISION
PART IT: THE DECISION SUMMARY
Warm Springs Ponds Inactive Area Operable Unit (OU 12)
Silver Bow Creek/Butte Area NPL Site (original portion)
Upper Clark Fork River Basin, Montana
United States Environmental Protection Agency
Region vm
June 1992
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RECORD OF DECISION
PART II
THE DECISION SUMMARY
Warm Springs Ponds Inactive Area Operable Unit (OU 12)
Silver Bow Creek/Butte Area NPL Site (original portion)
Upper Clark Fork River Basin, Montana
1.0 SITE NAME, LOCATION AND DESCRIPTION
The Warm Springs Ponds are located in southwestern Montana, at the lower end of Silver
Bow Creek, approximately 27 miles downstream of Butte. The pond system is a series of
three sediment settling ponds that were constructed over a span of about 60 years. Pond
1 was constructed around 1911; Pond 2 around 1916; and Pond 3 during the late 1950s.
They were constructed by the Anaconda Copper Mining Company in an effort to prevent
tailings and other sediments from entering the Clark Fork River, which begins approximately
. one-half mile below Pond 1 (see Figure 1).
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 the incoming water
decreases. The .addition of lime near the inlet to Pond 3, a practice that began some 20
years ago, also makes it possible to actively treat the dissolved metals, or cause them to
precipitate out of solution and settle to the bottom. Historically, lime has been added only
during the late 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 treatment portion of the
pond system. The relatively small volume of water contained within this inactive area is
present due to seepage from the ponds above.
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Willow and Mill 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. Figure 1 shows the current configuration of these streams, as well
as the three ponds, bypass channel, wildlife ponds, and the old Silver Bow Creek channel
below Pond 1. The entire system is approximately four miles . long and one mile wide,
covering approximately 2,500 acres of open' pond water and interspersed wetlands and
tailings deposits.
The Warm Springs Ponds are divided into two operable units. The Active Area Operable
Unit includes Ponds 2 and 3, their inlet and outlet channels, their treatment facilities, the
adjacent portion of the Mill-Willow Bypass, and the wildlife ponds. The Inactive Area
Operable Unit includes Pond 1, the old Silver Bow Creek channel below Pond 1, an
uncontaminated grassland and wet meadow below Pond 1, and the adjacent lower bypass
channel.
The September 1990 Record of Decision for the Warm Springs Ponds, as modified by the
June 1991 Explanation of Significant Differences and its errata sheet, described the remedy
for the Active Area Operable Unit. A major modification of the Explanation of Significant
Differences was to divide the entire Warm Springs Ponds area into two operable units. As
a result, remedial design and remedial action have proceeded as planned for the ac.tive area,
but at the same time, more time was allowed for the selection of an appropriate remedy for
the inactive area. The final remedial design report for the Active Area Operable Unit,
which was submitted by the potentially responsible party, the Atlantic Richfield Company
(ARCO), has been approved by the EP A and remedial action construction will begin in July
1992.
In July 1990, the EP A and ARCO entered into an Administrative Order on Consent for the
Mill-Willow Bypass Removal Action. This work is completed and is an integral part of the
two remedial actions planned for the Warm Springs Ponds system. Briefly, this action
involved the following work:
o
removal of 436,000 cubic yards of tailings and contaminated soils from the
bypass and disposal in a dry portion of Pond 3,
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o
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); and
o
construction of improved inlet and outlet structures and a divider dike
between Silver Bow Creek and Willow and Mill creeks.
1.1
1HE INACITVE AREA OPERABLE UNIT
The Inactive Area Operable Unit (Pond 1 and the area below Pond 1) contain about 3.4
million cubic yards of contaminated sediments, tailings and soils.
Approximately 475,000 million cubic yards of these materials are contained within the area
below Pond 1. They are overbank deposits that settled out along Silver Bow Creek prior
to the construction of Pond 1. This area is similar to the streamside tailings deposits above
the ponds, and to a limited degree similar to the overbank tailings deposits, or "slickens"
found along the Clark Fork River. The area below Pond 1 is different from these other
areas in respect to the fact that water no longer flows freely through this now-isolated
channel.
Approximately 2.9 million cubic yards of contaminated sediments, tailings and soils are
contained within Pond 1. They settled out of Sil~er Bow Creek over a short period after
Pond 1 was constructed in about 1911. Pond 2 was constructed approximately 5 years later.
The tailings and sediments contain some 20 or more contaminants; however, the
contaminants of primary concern are arsenic, cadmium, copper, lead and zinc. .
Tbe metals-contaminated deposits contained within the inactive area reach depths of 8 to
12 feet. Within the eastern portion of Pond 1 and in the old Silver Bow Creek channel
below Pond 1, the deposits are largely submerged under standing water that has seeped
from the ponds above. Tbe underlying marsh deposits and other naturally deposited silts
and soils, as well as the shallow ground water, have been contaminated by the downward
movement of dissolved metals from the overlying tailings and pond bottom sediments.
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The remaining two-thirds of Pond 1 (middle and western portions) contains tailings that
appear dry on the surface, but are generally in contact with the ground water. That portion
of the area below Pond 1 which lies outside of the old flood plain is uncontaminated
meadow on the surface; however, the underlying shallow ground water has been affected by
seepage from the ponds (see Figures 2A and 2B).
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2.0 SITE HISTORY AND SUMMARY OF ENFORCEMENT ACTMTIES
The discovery of gold along Silver Bow Creek, in 1864, opened the door for mining and its
ancillary activities in the upper Clark Fork River basin. Within a few years the gold was
depleted, but copper and silver ores were found to be plentiful and of a high grade. Within
a span of less than 20 years after the first prospectors found gold in the area's streams and
gulches, more than 300 copper and silver mines, numerous ore processing mills, and at least
eight open air smelters were operating in Butte alone. Many of the mines, mills and
smelters were owned and operated by the Anaconda Copper Mining Company or related
companies. The Atlantic Richfield Company is the successor to ,Anaconda and is the
current owner of some of the upstream facilities and the Warm Springs Ponds area.
These early mining, milling, and smelting activities resulted in extensive damage to the
Silver Bow Creek drainage basin. First, gold mining in the stream channel devastated its
banks and riparian vegetation. The mines, mills and smelters that followed dumped their
wastes directly into Silver Bow Creek. As the city of Butte grew, raw sewage was added to
the wastes entering the stream. These wastes completely choked off flow in Silver Bow
Creek at times, but still had little difficulty finding their way into the Clark Fork River,
which alternately carried them and deposited them along its entire length of over 250 miles.
Lake Pend Oreille (pronounced Ponderay) in Idaho received some of these wastes before
Milltown Dam and the Warm Springs Ponds began to collect them.
Early newspaper accounts and photographs from the turn of the century document the
devastation. About 1911, the Anaconda Copper Mining Company built the first settling
pond on Silver Bow Creek in an attempt to prevent wastes from entering the Clark Fork
River. This is now known as Pond 1 of the Warm Springs Ponds system. Pond 1, and Pond
2 which was built about 5 years later, experienced various breaches and overflows which led
to contamination in the Warm Springs Ponds inactive area and the Clark Fork River below.
The direct discharge of mining, milling and smelting wastes into Silver Bow Creek continued
until the early 1970s. Altogether, over 19 million cubic yards of tailings and sediments have,
settled in the Warm Springs Ponds and an additional 3 million cubic yards reside along the
banks of Silver Bow Creek above the ponds. Leaching and run off from upstream sources
continue to degrade Silver Bow Creek and add contamination to the ponds.
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The volume of waste in the three ponds, if removed and transferred to another location,
would cover an area equal to 100 football fields, 90 feet deep. In addition to the
extraordinary volume of waste present, their moisture content and their ability to retain
moisture for many decade, after being removed from a wet environment present difficulties
with respect to moving and containing them..
The sources of hazardous substances, pollutants, and contaminants at the Warm Springs
Ponds inactive area are varied. The several smelters and mills that were established and
operated in Butte, from approximately 1880 until 1940, disposed their mining wastes in
Silver Bow Creek. Tailings and other mine wastes are still located at these former facilities,
and they continue to leach contaminants 'into Silver Bow Creek. Additionally, mine water
and discharges from the Weed Concentrator were discharged into Silver Bow Creek for
several years. The Anaconda Smelter operations also contributed waste to the Warm
Springs Ponds area, through various ditches and conveyances. All of these sources led to
the migration of substantial quantities of mine wastes downstream to, among other places,
the Warm Springs Ponds inactive area.
The land uses in this area are principally agriculture and tourism. The adjacent community
of Warm Springs grew up around a major state facility for mental rehabilitation. The small
community of Opportunity and a few rural homes are located within a few miles of the
ponds. The nearest city is Anaconda, about 7 miles to the west.
The Opportunity tailings ponds are located less than one mile west of the Warm Springs
Ponds. The Opportunity tailings ponds cover over 4,600 acres and are mostly dry, exposed
tailings deposits. This area is part of the Anaconda Smelter Superfund Site.
The Silver Bow Creek site was listed on the NFL in 1983. The site was expanded to include
large areas in and around Butte, in 1987. EPA, through a cooperative agreement with
MDHES, conducted a site wide remedial investigation-the Phase I investigation-which was
released in 1987. MDHES also conducted a Phase n investigation, which focused on the
Warm Springs Ponds area specifically, was released in 1989. A feasibility study, which
included a risk assessment for the Warm Springs Ponds area, was released in 1989.
Following public comment on a proposed plan for the entire Warm Springs Ponds area,
EP A issued a Record of Decision in 1990. The Record of Decision was changed in an
Explanation of Significant Differences and its errata sheet, which limited EP A's cleanup
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decision to the active area only, and reserved further decisions for the inactive area for a
future Record of Decision. Under EP A oversight, ARca conducted an analysis of
remediation alternatives for the inactive area. The alternatives analysis was released in
1991. EPA issued a proposed plan for the inactive area in March 1992.
ARca, the successor-in-interest to the Anaconda Minerals Company and other smelter and
mill operators in Butte, is the current owner of the Warm Springs Ponds inactive area.
MDHES, through its Water Quality Bureau, issued an order in 1967 which required the
Anaconda Minerals Company to prevent the introduction of heavy metal salts from the
. Warm Springs Ponds into the Clark Fork River by, among other things, pumping back
contaminated water from below Pond 1 to the treatment system above. In 1989, MDHES,
again through its Water Quality Bureau, issued an order to ARCa requiring berrning below
the Warm Springs Ponds to prevent migration of tailings and other contaminated material
which were causing fish kills in the Clark Fork River.
In 1990, pursuant to CERCLA Section 106, EP A ordered ARCa to remove all tailings and
soils contaminated with heavy metals from the Mill-Willow Bypass. This work is essentially
completed and to some extent is incorporated into this Record of Decision and the
September 1990 Record of Decision for the active area. In 1991, EP A ordered ARCa to
implement the Warm Springs Ponds active area remedy, again pursuant to CERCLA Section
106. ARca will begin remediation of the active area in July 1992.
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3.0 HIGHLIGHTS OF PUBLIC PARTICIPATION
In 1983, the initial community relations plan for the Silver Bow Creek site (the site name
has since been changed to include the Butte area) designated the Butte-Silver Bow County
Health Department as the focal point for community involvement and included the
formation of a local citizens' advisory committee. The committee assisted the State in the
selection of a contractor for the Phase I remedial investigations of the site. A significant
portion of the Phase I study characterized the contamination present at the Warm Springs
Ponds.
In 1985, a review of the community relations plan by the EP A brought about several
improvements, including a toll-free telephone number, fact sheets and updates, and an
increase in the number of informal meetings with the public. These improvements were put
in place by the State over a period of about two years.
The Phase n remedial investigation, followed by a feasibility study, began in 1986 at what
was then a single Warm Springs Ponds operable unit. The RIfFS continued through 1989
as a State-lead effort. During that time, MDHES and EP A staff provided information about
the Warm Springs Ponds activities at public meetings and through fact sheets and progress
reports. These reports were distributed to people on a mailing list in November 1986,
November 1987, May 1988, July 1988, August 1988, October 1988, June 1989, September
1989, and May 1990. The mailing list grew from 271 individuals in 1987 to about 800
individuals in 1990. Special interest groups that indicated concern about the site included
the Clark Fork Coalition, Butte Chapter of Trout Unlimited, Skyline Sportsmen of
Anaconda, the Deer Lodge Chapter of Trout Unlimited, George Grant Chapter of Trout
Unlimited, Anaconda Sportsmen's Club, Pintlar Audubon, and Upper Clark Fork Chapter
of Trout Unlimited.
The Warm Springs Ponds Feasibility Study and proposed plan were released for public
review in October 1989. The MDHES held public informational meetings in Butte,
Anaconda, and Missoula during October 1989 and formal public hearings in the same cities
in December. The public comment period for the feasibility study and proposed plan was
open from October 1989 until the end of January 1990.
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Toward the close of the public comment period in January 1990, the EP A became the lead
agency for the Silver Bow Creek site. Overwhelming opposition to an impoundment
proposed for the Opportunity area caused the EP A to reject much of the proposed plan for
the Warm Springs Ponds remedy and combine the elements of other alternatives examined
in the feasibility study in order to devise a remedy that was both acceptable to the majority
of the public and adequately protective of human health and the environment.
Although the record shows there was considerable effort put forth by the agencies to involve
the public, many commenters expressed dissatisfaction with the level of public involvement
in the process of selecting a remedy for the Warm Springs Ponds. That perception, more
than any other consideration, influenced the EP A to defer a decision with respect to Pond
1 and the area below Pond 1, examine feasible alternatives more carefully, and involve the
public fully in the selection of a remedy. Thus, EPA divided the Warm Springs Ponds into
two operable units.
The Record of Decision (ROD) for the Warm Springs Ponds was signed in September 1990.
The ROD included Pond 1, but deferred the decision on the area below Pond 1 for a year.
By May 1991, EPA and the State realized that a decision for Pond 1 (and the area below)
would involve more time and effort, and would delay the remedy for Ponds 2 and 3. EPA
wrote an Explanation of Significant Differences (ESD) which laid out the rationale for
splitting Warm Springs Ponds into two operable units: the Active Area (Ponds 2 and 3) and
the Inactive Area (Pond 1 and the area below), as well as documenting some changes to the
active area remedy. Using this division, EP A could proceed with the active area remedy
and yet give sufficient time and effort to deciding on an appropriate remedy for the inactive
area.
The EP A endeavored for over a year to involve all affected parties before arriving at a
recommended remedial action plan for the inactive area. Five public scoping meetings were
held throughout the basin and numerous briefings and individual contacts were conducted
during 1991 and early part of 1992. In response to concerns expressed at these meetings,
particularly by Deer Lodge and Missoula residents, the EP A ordered or conducted
supplemental feasibility studies. A fact sheet outlining the EP A's plans for both the inactive
and active areas was issued in July 1991 to residents of the basin.
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The proposed plan for the Inactive Area Operable Unit was issued in March 1992 and two
final public hearings were held in Anaconda and Missoula before the close of the public
comment period. While no single remedy preferred by the EP A ever seems to be
unanimously favored by all parties concerned, this remedy selection process was carried out
under intense public scrutiny and the selected remedy is favored by a clear majority of the
affected public.
Information repositories, containing key site studies, indexes and reports, are presently
maintained at the following locations: University of Montana Library in Missoula, National
Park Service Main Office in Deer Lodge, Hearst Free Library in Anaconda, Montana Tech
. Library in Butte, and the Butte EP A office. The complete administrative record is
maintained in microfilm at the University of Montana and Montana Tech, and in hard copy
at the EPA's offices in the Helena Federal Building, 301 South Park.
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4.0 SCOPE AND ROLE OF OPERABLE UNIT WITHIN SITE STRATEGY
The Silver Bow Creek/Butte Area Superfund Site, because of its complexity and size, has
been separated into several remedial operable units. They are:
OUI Streamside Tailings (Silver Bow Creek from the Colorado Tailings to the
Warm Springs Ponds; RI/FS underway)
OU3 Mine Flooding/Berkeley Pit (RI/FS underway; ROD expected in 1994)
OU4 Warm Springs Ponds Active Area (Remedial Action begins in 1992; Mill-
Willow Bypass Removal Action completed)
OU7 Rocker (Removal of 1,000 cu yds completed in 1989; RI/FS underway)
OU8 Butte Priority Soils (RI/FS began in 1992)
OU12 Warm Springs Ponds Inactive Area (Record of Decision in 1992; Remedial
Action begins in 1993; Remedial Action completion expected in 1994).
OU13 Butte Non Priority Soils Operable Unit (RI/FS and ROD pending)
OU14 Butte Active Area (RI/FS and ROD pending)
OU15 Final Evaluation of the Warm Springs Ponds (following upstream cleanup)
In addition, several removal actions have been or will be implemented at the site, including
the Mill-Willow Bypass removal, Travona Mine Shaft Control, residential soils cleanups, and
the Lower Area One cleanup.
The site and its operable units are part of the larger and more encompassing Clark Fork
River Basin Superfund Complex, which consists of three additional NPL sites and their
approximately 17 operable units. They are the Montana Pole, Anaconda Smelter, and
Milltown Reservoir NPL sites. .
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The studies and actual cleanup activities being conducted at each site vary greatly. The
Clark Fork River Basin Master Plan established priorities among the sites and operable
units, based upon their relative importance in terms of risks to human health and the
environment. The Warm Springs Ponds ranked very high in terms of environmental risks.
The remedial investigations (Phase I and II),. public health and environmental assessment,
and initial feasibility study for the Warm Springs Ponds were conducted with a single,
comprehensive remedy intended. The decision to divide the pond system into two operable
units was made late in the process. The rationale for that decision is adequately discussed
in previous sections~ It is emphasized here in order to point out that for the inactive area,
the characterization of the nature and extent of contamination, the identification of risks,
the definition of problems, and the development of possible remedies were largely the
product of a single, comprehensive study that made no distinction between the active and
inactive areas. That fact has not necessarily complicated the remedy selection process for
the inactive area; it has simply made it necessary to discuss the active area throughout much
of this decision document.
The selected remedial action for the inactive area is the third, and possibly the last,
response action planned for the Warm Springs Ponds. It follows the Mill-Willow Bypass
Removal Action and it will dove-tail with the remedial action for the active area. In fact,
a few components of the active area remedy must await initiation of remedial action
construction for the inactive area. For example, the final excavation of a flood channel in
the portion of the bypass .adjacent to Ponds 2 and 3 cannot be carried out until work begins .
on Pond 1. The excavated fill material will be used to raise and strengthen the Pond 1
berms and the newly proposed extended berm.
Once completed, the inactive area will be an important buffer area between the Clark Fork
River and the active portion of the ponds. The inactive area will also, when completed,
provide much improved fish and waterfowl habitat. Wetlands areas will be greatly
enhanced.
The Warm Springs Ponds, as a whole, are an initial safety net for the Clark Fork River.
Until contaminated areas upstream are remediated, the ponds are necessary for water
treatment and protection in the event of floods or earthquakes.
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The interim nature of the remedy selected for the inactive area, as is the case for the active
area, is an expression of the fact that no remedy here can be considered final until the
upstream sources of contamination have been eliminated and the decisions to leave wastes
in place at the ponds have been monitored and fully evaluated.
Although tailings and contaminated sediments will be left in place by the selected remedy,
they will be confined behind berms that will meet stringent flood and earthquake protection
requirements and they will be rendered less mobile and less toxic by chemical fixation and
wet-closure. Therefore, the selected remedy will conform with the statutory preference for
reducing toxicity and mobility as a principal element of the remedy. It will not reduce the
volume; however, it will immobilize the waste in a permanent manner, as opposed to
transferring this extraordinary volume of waste. to another area in the basin, which would
raise difficult implementability and safety issues.
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5.0 SUMMARY OF SITE CHARACTERISTICS
5.1. SURFACE HYDROLOGY
The Warm Springs Ponds Inactive Area Operable Unit consists of Pond 1, the area below
Pond 1 north to approximately one-quarter mile above the Clark Fork River, and the
downstream portion of the Mil1~ Willow bypass (lower bypass). The bypass channel in this
area carries the combined flows of Mill, Willow, and Silver Bow creeks, the last of which
flows through Ponds 3 and 2 before joining the bypass (Figure 1). The lower bypass
combines with Warm Springs Creek north of the inactive area to form the Clark Fork
River. The bypass was constructed during the late 1960s to route the relatively
uncontaminated Mill and Willow creeks around the pond system. The average flow of Silver
Bow Creek is 73 cfs, and the combined flows of Mill and Willow creeks average 27 cfs.
The total average flow of 100 cfs in the lower bypass is augmented by the average flow of
47 cfs in Warm Springs Creek north of the inactive area to form the Clark Fork River.
Warm Springs Creek occasionally exhibits elevated levels of metals, due to past milling and
smelting activities in the Anaconda area, west of the Warm Springs Ponds. It is being
addressed as part of the Anaconda Smelter Superfund site cleanup.
5.2 GROUND WATER HYDROLOGY
The shallow ground water system in the inactive area is complex, due to the heterogeneity
of the surface geology in the area. The site is in a ground water discharge area for the
upper Deer Lodge Valley, typified by shallow ground water tables and swamps. The
presence of the Warm Springs Ponds affects shallow ground water elevations and ground
water movement within the area.
Shallow aquifers occur along present-day stream channels, but do not extend laterally
throughout the area. Deeper aquifers are associated with Tertiary-age valley fill and thick
deposits of glaciofluvial material. These aquifers generally exhibit moderate to low
permeabilities and are probably connected on a regional scale, although fine-grained
interbeds tend to confine the deeper aquifers locally.
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The uppermost aquifer at the site is a 10- to 15-feet-thick sand and gravel unit, which is
typically present approximately 10 feet below ground surface. This sand and gravel aquifer
appears to be present throughout most of the area. Ground water movement through the
area is generally from south to north.
No domestic wells are located within the inactive area. Several wells are located within a
mile to the east of the inactive area, but these wells are completed in bedrock aquifers that
do not appear to be affected by the pond system. The town of Warm Springs, to the west
of the inactive area, derives its water from supply wells constructed in unconsolidated
Tertiary deposits, from depths of approximately 200 feet. These wells appear to be supplied
with water derived from ground water resources west of and hydraulically isolated from the
inactive area.
5.3
NATURE AND EXTENT OF CONTAMINATION
Sediments, surface water, soils, and ground water are all affected by contaminants in the
inactive area. Four contaminated media have been identified for the operable unit: pond
bottom sediments, surface water, ground water, and tailings deposits and contaminated
soils. The patterns of contamination of each of these environmental media are the result
of migration of the contaminants within and between them. The media are discussed in the
following sections. Table 1 presents a breakdown of the areas and volumes for ground
water, pond bottom sediments, exposed tailings and contaminated soils.
5.;3.1 Sediments. Tailings. and Contaminated Soils
Two of the media-the pond bottom sediments, and the tailings deposits and contaminated
soils-contain the majority of the contaminants in the inactive area. These materials are
typically fine to coarse sand ~d generally contain metals associated with the sulfide ore
body present near Butte. Pond bottom sediments are also comprised of precipitated
hydroxides and oxyhydroxides resulting principally from the addition of lime to treat the
water entering the pond system and from biologically mediated precipitation.
The exposed (unsubmerged) sediments, tailings deposits and contaminated soils in the
inactive area cover approximately 135 acres. Thicknesses of these deposits range from about
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Table 1
Summary of Areas and Volumes
of Contaminated Media
Area Volume Volume
(acres) (acre-feet) (cubic yards)
Pond Bottom Sediments
Pond 1
Exposed Sediments 59 455 734,000
Vegetated/Submerged Sediments 225 1,340 2,156,000
Total Pond Bottom Sediments 284 1,795 2,890,000
Tailings Deposits and Contaminated Soil
Area Below Pond 1
Exposed Tailings 17 48 77,400
Vegetated Tailings & Contaminated Soil 59 246 397,000
Total Tailings Deposits and Contaminated Soil 76 294 474,400
Ground water*
Area of contaminated aquifer beneath and
downgradient of Pond 1 180
*Exceedences of primary maximum contaminant levels for arsenic and cadmium.
Source: CH2M HILL, 1989
an inch to several feet. The submerged sediments "in Pond 1 cover an area of approximately
225 acres and range in thickness from less than one foot to approximately 13 feet. (See
Table 1.)
The tailings and associated soils below Pond 1 occur primarily within and adjacent to the
old channel of Silver Bow Creek and were likely deposited before the ponds were
constructed. The estimated area and volume of tailings and associated soils between the
Pond 1 berm and the existing lower bypass ranges from 63 acres and 390,600 cubic yards 1
1 CH2M HILL, 1989
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to 70 acres and 283,000 cubic yards2. The average depth of tailings and associated soils is
about 2.5 feet. Natural fine-grained soils are present beneath the tailings and associated
soils to an average depth of five feet, where the sand and gravel aquifer unit is encountered.
An additional 10,000 cubic yards of metals-bearing bottom sediments are estimated to be
present within man-made channels below Pond 1.
Figure 3 shows the extent of tailings and pond bottom sediments within the inactive area.
The differentiation between tailings and pond bottom sediments is not distinct because the
material types associated with each are similar. Figure 3 shows pond bottom sediments that
are or were historically submerged. Tailings are those metals-enriched materials that are
. generally located adjacent to the old Silver Bow Creek channel. These materials are often
mixed with native soils and are present both in exposed areas and in areas that are partially
to well vegetated. Calculations indicate that 2.9 million in-place cubic yards of pond bottom
material has accumulated in Pond 1.
Tailings along the lower bypass are visible within the active channel and along the first
terrace adjacent to the channel. Contaminated soils are present between visible tailings
deposits and mixed with tailings.
Metallic salts are commonly present during summer months along the bypass at the surface
of the tailings deposits. These salt deposits are derived from slow oxidation of the metal
sulfides in the tailings deposits, which then wick to the surface during dry periods as soluble
salts. These salts form crystalline deposits that dissoive during rainstorms and wash into
the bypass. This phenomenon is probably responsible for the fishkills that occurred in the
past along the bypass and in the upper Clark Fork River. The majority of these tailings
deposits were located along the upper bypass channel, which was cleaned up in 1990 and
1991 under an Administrative Order on Consent.
Pond bottom sediments were sampled at six sites throughout Pond 1. At each site, multiple
samples were taken with depth in the sediment profile. The samples were analyzed for total
metals, common ions, cyanide, and percent solids. Average concentrations of arsenic,
cadmium, copper, lead, manganese, and zinc in Pond 1 sediments are present above
reported background levels (Table 2).
%ESA, 1991
-------
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FIGURE 3
POND BOTTOM SEDIMENTS, TAILINGS, AND
CONTAMINATED SOILS
WARM SPRINGS PONDS INACTIVE AREA
eo 16BC59.E5.RD
18- Jun- 1S!32 13:34:26
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..
.
Table 2
Maximum, MiDimum and Average Values
Pond 1 Bottom Sediments
Parameters No. of Samples Minimum" Maximum" Average" Backgroundb
Aluminum 28 3,190 20,300 9,174 -
Antimony 28 7 17 10 -
Arsenic 28 6 1,850 408 10
Barium 28 47 287 199 -
Beryllium 28 0 2 1 -
Cadmium 28 1 66 10 0.4
Calcium 28 1,690 198,000 37,318 -
Chromium 28 5 76 29 -
Cobalt 28 2 19 5 -
Copper 28 19 9,390 2,886 35
Iron 28 4,880 119,000 51,012 -
Lead 28 8 1,920 670 25
Magnesium 28 1,230 27,700 5,864 -
Man23nese 28 120 9,320 2,717 250
MercuIY 28 0 6 2 -
Nickel 28 3 50 10 -
Potassium 28 928 3.210 2,040 -
Selenium 28 0 11 3 -
Silver 28 1 26 11 -
Sodium 28 326 1,120 512 -
Thallium 28 0 1 1 -
Vanadium 28 6 63 33 -
Zinc 28 70 7,900 2,212 60
Cyanide 28 1 1 1 -
% Solids (wt. %) 28 37.4 92.1 64.8 -
Specific Conductance (umbo/em) 28 555.0 4180.0 1522.8 -
pE (mY) 28 -160.0 510.0 40.2 -
pH (pH units) 28 2.3 8.3 5.6 -
"All units are mg/kg unless otherwise Doted.
bFrom Moore, 1985.
NOTES: Undetected parameters are assumed to be at the detection limit. Statistics are computed from the results from natural
samples.
SOURCE: CH2M HILL, 1989.
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It
.
5.3.2 Surface Water
Surface water in the inactive area includes Pond 1, standing water below Pond 1, and the
lower bypass channel. Pond 1 currently collects seepage from Pond 2. This water is
pumped back into Pond 2 periodically (see Table 3). Water seeping from below the Pond 1
berm is also pumped back into Pond 1 periodically. Seepage water pumped back into Pond
1 has historically been treated with lime slurry, although no observations of this practice
were made during the remedial investigation.
The data obtained during the remedial investigation characterize the surface water for near-
average bypass flow rates. Few data are available to characterize the surface water quality
during higher flows because of drier-than-normal conditions in the area experienced during
the remedial investigation. No opportunity was available during the sampling period to
collect flow and contamination data during. one of the high runoff events that caused Silver
Bow Creek to flow around the pond system, through the bypass.
Surface water samples were collected at seven sampling points in and adjacent to the
inactive area during the Phase I remedial investigation. Although metals concentrations are
reduced in the pond system upstream of the inactive area, Montana's chronic ambient water
quality standards for copper, lead, and zinc were occasionally exceeded in the lower bypass,
particularly in winter months.
Surface water quality data also indicate that Montana primary drinking water standards for
arsenic (0.05 mg/l) were exceeded in the lower bypass during the two highest measured flow
events, and the arsenic standard was regularly exceeded in surface water pumped from
below Pond 1.
5.3.3 Ground Water
Ground water quality data were generated through sampling of 14 monitoring wells on two
occasions (January and May, 1988). Figure 4 shows the locations of the monitoring wells
within the area. Table 4 summarizes ground water quality data for these monitoring wells.
With one exception, all detected exceedences of the primary maximum contaminant levels
for metals (arsenic and cadmium) were north of the Pond 1 berm. Ground water quality
downgradient of Pond 1 is generally of poorest quality immediately north of the berm; most
-------
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WELL NUMBER
APPROXIMATE EXTENT
OF CONTAMINATION
(DASHED WHERE INFERRED)
FIGURE 4
MONITORED WELL LOCATIONS AND
EXTENT OF GROUNDWATER EXCEEDING
PRIMARY MCL FOR CADMIUM AND ARSENIC
WARM SPRINGS PONDS INACTIVE AREA
BOI68059.E5.RD
18- Jun-1992
13:34:26
-------
,
.
metal contaminants decrease to the north, or downgradient of the pond system (see Table
4). Concentrations of most metals also decrease with depth. Only one sample obtained
from monitoring wells located adjacent to the bypass exceeded maximum contaminant levels
(MCLs) for primary drinking water standards. The sample was obtained from the area just
north of the northwest comer of Pond 1. This sample contained a cadmium concentration
of 11.7 p.g/l which is slightly in excess of the standard for cadmium of 10.0 p.g/l.
Highest concentrations of metals are generally associated with the shallow sand and gravel
aquifer in the area immediately below the Pond 1 berm. Calculations of ground water
discharge from the area below Pond 1 into the Clark Fork River indicate that the ground
water system contributes very little flow to the river because of the relatively low
permeability and low gradient of the shallow aquifer. Under average conditions, the flow
in the Clark Fork River is approximately 137 cfs, while the ground water discharge to the
river is approximately 1.0 cfs. Nevertheless, the exceedences of the maximum contaminant
levels for arsenic and cadmium in the ground water constitute a violation of the drinking
water standards.
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.
Table 3
Summary of Surface Water Quality Data
Pond 1
Parameter Average Maximum Minimum
Flow (cfs) 12.1 2.2 0.40
Temperature (OC) 10.9 25 1.0
pH (s.u.) 7.4 8.1 6.5
SC (}'mhos/cm @ 25°C) 1489 1740 1130
TSS 12 19 2
.S04 741 998 425
Nitrate 2.00 4.20 0.48
Alkalinity 132 192 95
Hardness 779 988 499
As(T) 0.004 0.012 b
Cd (T) b b b
Cu(T) 0.014 0.055 b
Cu (D) b b b
Pb (T) 0.001 0.0086 b
Fe (T) 2.32 7.99 0.047
Fe (D) 1.16 5.34 b
Zn (T) 0.056 0.135 0.016 .
Zn (D) 0.105 0.127 b
IValues in mg/l unless otherwise noted; (T) is total; (D) is dissolved.
bParameter not analyzed.
Source: CHZM HILL, 1989
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f1
..
Table 4
Ground water Quality Data Summary
Warm Springs Ponds Inactive Area
Maximum Contaminant
Level" (Montana
Maximum Minimum Average Number of Ground water
Parameter Concentration" Concentration" Concentration" Samples Regulations)
.:,::__BliI~:::~::~I@~::m~i.~i[[['::::::::::'[[['[[[':::::!:::::::::!!:'[[['::::::::::::::::::::::
Arsenic 197.0 <2.0 28.0 14 SOb
Cadmium 12.7 <5 .0 3 .6 14 lOb
Copper 15.9 < 6.0 5.8 14 1 , ()()()"
Lead <2.0 < 1 .0 2.0 14 SOb
Manganese 3 1 ,600 309 10,297 14 50"
Zinc 253 16.3 89.0 14 5 ,()()()"
Iron 80,900 45 16,220 14 300'
Sulfate (mglL) 1 ,620 250 950 14 2SO'
:':!:___:~:iii::!:::.:I_[[[i[[[
Arsenic < 3.0 <2.0 1 .0 13 SOb
Cadmium 8.4 < 5.0 4.3 13 lOb
Copper < 8.0 < 6.0 3 .5 13 1 , ()()()"
Lead <2.0 < 1 .0 0.8 13 SOb
Manganese 4,460 3.0 577 13 50"
Zinc 43 6.2 19.8 13 5,000'
Iron 409 < 15 52 13 300'
Sulfate (mglL) 1,ISO < 55 53 1 13 250'
"All values in ugll unless otherwise noted.
bPrimary standard (based on health criteria).
'Secondary standard (based on suitability criteria).
NOTES
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"
-
5.3.4 Exposure
The types and characteristics of contaminants with respect to toxicity, carcinogenicity, and
mobility are covered in Section 6.0 (Summary of Public Health and Environmental
Assessment). Discussion of contaminant -migration pathways arid potential effects on
humans and environmentally sensitive areas is also presented in this section.
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.,
...
6.0 SUMMARY OF HUMAN HEALTH AND ENVIRONMENTAL RISKS
A public health and environmental assessment (PHEA) was conducted by the Montana
Department of Health and Environmental Sciences in support of the Warm Springs Ponds
Feasibility Study. As noted earlier, the feasibility study, and likewise the public health and
environmental assessment, were prepared with the intent of a single, comprehensive remedy
for the Warm Springs Ponds. Although the ponds were later divided into two separate
operable units, the EP A believes that the human health and environmental risks
characterized by the comprehensive risk assessment clearly establish endangerment not only
for the pond system as a whole, but for" each operable unit by itself.
The subsections that follow will:
o Identify the contaminants present in the inactive area;
o Briefly review concentrations of the contaminants of primary concern for human health;
o Summarize the human exposure assessment and human toxicity assessment;
o Characterize the migration pathways and associated human health risks (both
carcinogenic and noncarcinogenic risks);
o Summarize the effects of the contaminants on plants, fish and wildlife, including
endangered species; and
o Summarize the potential catastrophic risks associated with dam failure.
6.1
IDENTIFICATION OF CONTAMINANTS
Section 5.0, Summary of Site Characteristics, identifies the contaminants present in the
inactive area, describes their nature and extent, and discusses pathways of migration. The
media affected are surface water, ground water, pond bottom sediments, exposed and
submerged tailings deposits, and soils. These media are affected by elevated concentrations
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It
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of some 20 or more elements, each of which is defined as a hazardous substance when
present at the concentrations found in the inactive area. Table 2 (see Sec.5.0, Summary of
Site Characteristics) lists these elements and their maximum and average concentrations as
measured in the pond bottom sediments of Pond 1. Other tables show contaminants present
in the other media. (See Tables 3 and 4). .
The elements of primary concern, or indicator chemicals, were selected from the entire list
of elements in order to focus on those which pose the greatest risks to human health and
the environment. Based on their potential to promote or cause adverse effects in humans,
arsenic, cadmium, and lead were selected as indicator chemicals. These three elements,
together with copper and zinc, were also selected as indicator chemicals based on their
potential to promote or cause adverse environmental effects. Copper and zinc are
particularly harmful to many aquatic organisms.
The average concentration of arsenic in Pond 1 bottom sediments is 408 mg/kg, and in
tailings and soils below Pond 1 arsenic averages 593 mg/kg. These average concentrations
are more than one order of magnitude greater than background. The maximum
concentration of arsenic measured in Pond 1 bottom sediments was 1,850 mg/kg, or roughly
two orders of magnitude greater than background.
The shallow ground water in the area below Pond 1 averages 0.028 mg/l arsenic, with a
maximum concentration measured as 0.197 mg/I. The maximum contaminant level (MCL)
for arsenic is 0.05 mg/I.
The average concentration of copper in Pond 1 bottom sediments is 2,886 mg/kg, and in
tailings below Pond 1 averages 18,147 mg/kg. The maximum copper concentration
measured in Pond 1 bottom sediments is 9,390 mg/kg, and the maximum copper
concentration measured in tailings below Pond 1 was over 66,000 mg/kg. The background
concentration of copper for this area is about 35 mg/kg.
The concentrations of the remaining contaminants of concem--cadmium, lead and zinc--in
tailings and pond bottom sediments of the inactive area show significant enrichment over
background levels as well, as shown in the tables of Section 5.0, Summary of Site
Characteristics.
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..
Briefly, other parameters indicative of the presence of metals, such as pH and specific
conductance, are noteworthy. Porewater from Pond 1 bottom sediments, for example, was
found to be very acidic (pH as low as 2.3) and very high in terms of specific conductance
(as high as 4,180 umbo/em). These extreme conditions do not depict the average; however,
aquatic organisms are very susceptible to low pH levels.
6.2
SUMMARY OF HUMAN EXPOSURE ASSESSMENT
A thorough human exposure assessment is presented in the 1989 Warm Springs Ponds
Feasibility Study Report (Section 3.0 and Appendix A). The humaJ? exposure assessment
combines contaminant concentrations of the various media with known or suspected
mechanisms by which humans may be exposed to these media. Figure 5, Pathways of
Exposure, depicts the mechanisms by which people who recreate or work at the Warm
Springs Ponds and people who reside nearby may be exposed.
The ponds are a favorite fishing and hunting spot for many residents of Anaconda, Deer
Lodge, Butte, and surrounding areas. These recreational users and year around workers,
such as fish and wildlife biologists or employees of ARCO, frequently come into contact
with the surface water, exposed tailings, and pond sediments. Their direct contact with these
contaminated media (incidental ingestion and dermal absorption), and their indirect contact
by inhalation of wind-entrained tailings and soils, constitute exposure.
Residents of the small community of Warm Springs are exposed by means of inhalation of
wind-entrained tailings and soils. (See Figure 6, Source Areas and Receptors of Wind-
Entrained Contaminants.) .
No direct human exposure to contaminated ground water has been identified, therefore no
current pathway exists for the contaminants dissolved in ground water. However, potential
pathways are possible if the ground water contamination is not contained and the ground
water is used. The ground water also flows into nearby surface water, which has
recreational, wildlife, and public uses.
The exposure assessment calculated the quantity of contaminated media that a human
receptor ingests, inhales, or absorbs (dermal contact). The incidental ingestion of
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FIGURE 6
LOCATION OF
SOURCE AREAS AND RECEPTORS
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.
.
contaminated sediments by a year around worker, for example, was based on a daily intake
estimate of 10-50 mg/day. After factoring the receptor's age and weight, the lifetime daily
intake estimate was calculated to be 0.04 to 0.21 mg/kg/day.
One additional mechanism for exposure is noteworthy. Failure of the Pond 1 berms due
to a flood or earthquake is not an unlikely scenario. The berms do not meet current dam
safety standards. Should either a flood or earthquake occur, of sufficient magnitude to
cause dam failure, contaminated surface water, bottom sediments and tailings would move
down the Clark Fork River, creating not only a brief catastrophic risk of loss of life, but also
a broader area of contamination than exists within Pond 1 at present.
Finally, future residential exposure and the risks posed by this scenario were examined in
the feasibility study; however, the likelihood of residences being constructed in this area is
so remote that future residential risks do not deserve further discussion. Institutional
controls will assure this does not occur.
6.3
SUMMARY OF HUMAN TOXICITY ASSESSMENT
The toxicity assessment describes the potential human health effects that have been shown,
through toxicological studies, to be identified with the contaminants of concern. As noted
earlier, more than 20 individual hazardous substances (metals and arsenic) have been
characterized in the various media. The following ~iscussion summarizes the major toxic
effects of the contaminants of primary concern.
Arsenic is a known human carcinogen which causes lung cancer when inhaled and skin
cancer when ingested in sufficient quantities over time. Incidental ingestion may cause other
internal tumors. Acute oral exposure can cause muscle -reactions, gastrointestinal damage,
liver or kidney damage, and vascular collapse that may lead to death. Inhalation of arsenic
can also cause severe irritation of the nasal lining and respiratory tract.
Cadmium is a known human carcinogen when inhaled. Lung cancer and increased incidents
of prostate cancer have been documented in workers exposed to cadmium by the inhalation
pathway. There is no evidence of carcinogenicity as a result of chronic oral exposure.
Acute exposure to cadmium by means of oral exposure, however, produces nausea,
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.,
.
salivation, spasms, drops in blood pressure, loss of consciousness and collapse. Acute
exposure by inhalation can cause coughing, acute chemical pneumonitis and pulmonary
edema. Respiratory and renal toxicity are major effects in workers.
Copper is beneficial to humans at very low doses. Excessive doses can cause gastrointestinal
irritation, hemolysis, liver necrosis, kidney failure, tachycardia, and convulsions. Copper is
believed to be strictly noncarcinogenic.
Lead is a suspected human carcinogen; however, the noncarcinogenic effects of lead
exposure are of great concern to toxicologists and physicians. Low levels of exposure to
lead, over relatively brief periods, can irreversibly injure the nervous system. Young
children, infants and fetuses are particularly susceptible. Epidemiological studies indicate
that chronic lead exposure is associated with hypertension in adults.
Zinc is beneficial to humans at very low doses. The recommended dietary allowance (RDA)
for zinc is about 12-15 mg/day. Excessive amounts of zinc (10-15 times the RDA, or more),
taken by means of ingestion or inhalation of zinc-laden soils or dust, can cause stomach
cramps and digestive system disorders. Excessive zinc may interfere with the body's immune
system and with the body's ability to absorb and metabolize other essential trace elements.
6.4
SUMMARY OF HUMAN RISK CHARACTERIZATION
The risk assessment calculated and evaluated human health risks associated with exposure
to both carcinogenic and noncarcinogenic contaminants.
Contaminants known to cause cancer in humans were assigned a cancer potency factor. The
cancer potency factor was derived by applying the upper 95-percent confidence limit on the
slope of a dose-response curve obtained from human epidemiological studies. Potency
factors use conservative assumptions, thus they are less likely to underestimate actual
carcinogenic risk.
The excess lifetime cancer risk was calculated using the cancer potency factor, lifetime daily
intake, and exposure point concentration (the concentration of each contaminant in a
specific medium where there is contact by a human receptor)~ Carcinogenic risks were
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presented for each exposure scenario (recreational, occupational and residential) and for
each pathway that was possible to quantify (ingestion, inhalation, dermal absorption). Risks
resulting from exposure to multiple media were added together.
For contaminants known to produce noncarcinogenic health effects, the dose estimated for
each exposure scenario and pathway was compared to a dose level believed to be safe which
is termed the reference dose (RID).
Table 5 summarizes the carcinogenic and noncarcinogenic health effects for the curtent
human exposure scenarios at the Warm Springs Ponds.
Due to day-to-day contact with contaminated tailings, sediments, and water, people who
work year around at the ponds (occupational scenario) face greater increased cancer risks
than people who live nearby or who use the area for recreation. Workers are faced with
cancer risks being increased over normal cancer risks by 2 chances in 10,000. People who
use the ponds for recreation face an estimated increase of eight chances in 100,000.
Residents of the nearby community of Warm Springs and rural areas east and north of the
ponds face some estimated increase in cancer risk due to inhalation and ingestion of wind-
entrained contaminants, which originate from the exposed tailings and contaminated soils.
The increase is estimated to be about one chance in 100,000.
With respect to noncarcinogenic risks, none of the estimated doses was greater than the
reference doses. Therefore, except for lead, these risks are considered acceptable.
There is no agreed upon reference dose for lead. The EPA believes there is no safe level
of lead.
6.5
ENVIRONMENTAL RISKS
Our understanding of the environmental risks present at the Warm Springs Ponds is limited
and strictly qualitative. Early site studies of algae, fish, aquatic insects, and waterfowl, taken
from the ponds and the Clark Fork River immediately downstream, were conducted
primarily to determine whether edible fish and waterfowl are accumulating metals to the
extent that humans who consume them might be at risk. While the risks to humans were
found to be negligible, the studies showed that metals and arsenic accumulate in the plants
-------
IIfF.OIA
(;ROIINnWATF.R
SURFACF. WATER
Incidenlal
Inge"inn
Dermal
Contact
SF.OIIIfF.NT
Incidenlal
Ingestion
Dennal
Conlacl
AIR
Inhalalion
IngC:~lion
TOTAl. IlfULTI IIIF.DI A
RISK
TARLE 5
SUMMARY OF RISKS FOR CURRENT HUMAN EXPOSURE SCENARIOSm
RF.CREATIONAL
None
Maximum excess lirelime cancer risk.or 6 x 10-' and average risk"' or 5 x 10".
No risk idc:nliric:d (rom exposure 10 "on..carcinogenic compounds.
No dala wilh which 10 evaluate carcinogenic risk.'"
No risk hom exposure 10 dissolved concenlralion 01 non-can:inogenic compounds
was idenlilied. lIalard index ~ 0.00000OO9 (9E").'"
Maximum excess lireHme cancer risk or 4 x 10" and average risk or 3 x 10..
Mosl prohable CD' or maximum plausible CD! 01 non-carcinogenic compounds
did nol indicate a risk.
1'101 quanlified. Anlicipaled Ihal addilional risk rrom Ihis palhway would be
minimal, see dermal contact with surface: water.
Maximum excess lirelime roncer risk or I x 10" and average risk or 5 x 10" driven
by arsenic and cadmium. Maximum plausible and moSi prohahle COIs did nol
exceed acceptahle inlake values.
Ingeslion as a resull or inhalation or wind-blown sedimenl may lead 10 an excess
lilelime cancer risk or 2 x 10' ror maximum inhalalion rales and 7 x 10" ror mosl
prohahle inhalalion rales. No risk was idenlilied rrom exposure 10 non-
carcinogenic compounds.
I X 10. exces.s lirelim~ ranfer risk ~ssorialed wilh assumed .maximum plausihle
chronIc dally onlake (CDI)' '. rOlenhallhreal rrom non-camnngenic compounds
was nol idcnlilied.
OCCIJPATIONAI.
None
Maximum excess lirelime cancer risk or 2 x 10" and average
risk or 2 x 10". lIighesl conlribulion rrom pond oulnow.
No risk idenlilied from exposure 10 non-carcinogenic
compounds.
Dala available 10 evaluale cancer risk during high now evenls
only. Maximum excess lirelime cancer risk or 4 x 10" rrom
arsenic.
No risk rrom exposure to dissolved concentralion on non-
carcinogenic compounds was idenlilied. lIazard index ~
0.00058 (5.8E.).
Maximum excess lirelime cancer risk or 2 x 10. and average
risk or 2 x 10".
Maximum plausible CD! and mosl probable CD! or non-
carcinogemc compounds did nol indicale a risk.
1'101 quanlified. AnHcipaled Ihal additional risk from Ihis
palhway would be mimmal, see dennal conlaCI wilh surface
waler.
o Maximum excess liretime cancer risk or 2 x 10. and average
risk of 9 10" driven by arsenic and cadmium. Maximum
plausible and most probable CDls did nol exceed
acceplable intake values.
o Ingeslion as a resull or inhalation of wind-blown sedimenl
may lead 10 an exc«s liretime cancer risk of 4 x 10" ror
maximum inhalalion rales and 2 x 10" ror m~1 prohable
inhalalion rales: No risk was idenlified rrom bposure 10
non.carclnogcmc compounds.
2 x 10" excess lirelime cancer risk associaled wilh assumed
maximum plausible chronic daily inlake (CDI) driven by
ingeslion.
RESlnENTIAI.
None
None
No dala wilh which to evaluale downstream residential COnlarl.
None
None
o Allhe lown or War:m ~prings, mod.eled dusl em)ssions from Ih~ pond syslem
resull in an excess hrellme cancer nsk or 6 x 10. No nsk was Idenlll,ed rrorn
exposure 10 noncarcinogenic compounds for any age group.
o Allhe lown or Warm Springs, AMC rMIO dala on air ronlaminants (I?Rl
dala) resulls in an excess liICllme cancer risk or 10..
o AI residences easl "r Ihe ponds, excess lirelime cancer risks ranges rrom 0 10 7
x 10., Wind direclion/duntlion were roughly included in Ihe conversion or
modeled dusl concentration rrom I-hr maximums 10 24 hr values and annual
values. Howeverl resulls may overeslimale aClua' risks due 10 topographic
chances and ils elrerl or dust dispersion.
o No risk was idenlified rrom exposure 10 non-carcinogenic compounds ror any
age group.
o Allhe lown of Warm Sprinp, modeled emissions resulls in an excess lire lime
cancer risk of I x 10.lhrough ingeslion rrom inhalalion. Using ingeslion rrom
inhalalion. Using AMC air dala Ihe resulting risk is 2 x 10.. No nsk was
idenlified rrom exposure 10 non-can:inogenic compounds ror any age group.
o For Ihose residences easl or the .P."nds, Ihe excess lirelime cancer risk ranger is
I x 10.108 x 10". No risk was .denliried from uposure 10 non-carcinogenic
compounds ror any age group.
Multimedia exposures nol considered ror Ihis scenario. Exposures could includes
Ihose rrom either recrealional use or Ihe area or rrom working al Ihe ponds or
bolh. .
1 See Appendix A or I'S ror a complele discussion or polentia' risk. .
. The lerms 'n,aximum' and 'average' in relalion 10 risk are modifiers meanl 10 indicale Ihe use or maximum and average inlakes and concenlralions and is nol meanl 10 imply Ihal risk is anything olher than upper bound eSlimales.
. No dissolved conrenlralions or consliluents assumed 10 be cardnogenic through dermal exposure. Compounds exhiblling can:inogenicily through dermal eryesure assumed 10 be Ihose Ihal arc carcinogenic lfirough ingeslion.
IIA7.ard index is a metbod or delennining p'olenlial heallh risk rrom Iota' exposure 10 non-carcinngenic compound Ihrougn a single exposure roule and medIa.
t CDI is a term thai comhlncs the Assumed Intake rate and the concentration of the contaminanl in a spedrie rntdia.
..
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and animals examined. In addition, there are clear indications that certain life stages of
aquatic vertebrates and invertebrates, such as the eggs and developing young of sensitive fish
species, are affected by the contaminants.
On the other hand, there are clear indications of productive wetlands and healthy
populations of waterfowl, invertebrates and terrestrial and aquatic wildlife, in the inactive
and active areas alike. Fish are found in Ponds 2 and 3, the wildlife ponds, and the entire
length of the bypass; however, there are no fish in Pond 1 or the old Silver Bow Creek
channel immediately below Pond 1. The surface water of Pond 1 and the area below Pond
1 is significantly more degraded than the surface water of Ponds 2 and 3 or the wildlife
ponds.
Copper is particularly toxic to aquatic organisms, even at moderately elevated
concentrations. Zinc is also toxic to aquatic organisms. The state's standards for the
protection of aquatic life are .012 mgfl (chronic) and 0.018 mgfl (acute) for copper, and
0.11 mgfl (chronic) and 0.12mgfl (acute) for zinc. Surface water samples (grab samples)
from Pond 1, which receives pumped-back water from the area below Pond 1, show total
copper concentrations in the range of 0.014-0.055 mgfl and total zinc concentrations in the
range of 0.016-0.135 mgfl.
As in the case of human health risks, the catastrophic risks associated with dam failure, due
to floods or earthquakes, are important to note as environmental risks as well. In the event
of dam failure, as much as 3.4 million cubic yards of tailings and contaminated sediments
could be moveciinto the Oark Fork River. This could devastate a valuable river resource
which is improving over time, but remains stressed due to metals loading, overbank tailings,
and severe agricultural dewatering.
As noted, the public health and environmental assessment was completed for the entire
pond system. Characterizing risks for the inactive area alone would be possible, but hardly
necessary. It is likely that such an exercise would demonstrate that there are less severe
human health risks and more severe environmental risks in the inactive area than in the
active area or the pond system ~ a whole. Workers and recreational users spend far more
of. their time in the active area than the inactive area. Additionally, the overall quality of
the water is poorer, and the accessibility to exposed tailings deposits is greater in the
inactive area than in the active area.
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6.6
THREATENED AND ENDANGERED SPECIES
Two species of birds protected under the Endangered Species Act ( 16 USC ~ 1651 et seq.),
the bald eagle and peregrine falcon, are occasionally observed at the ponds. No quantitative
data are available; however, fish and waterfowl tissue analysis show that elevated metals
levels are present in their kidneys and livers. It is reasonable to conclude that raptors could
bioaccumulate metals if their diet includes significant amounts of fish and waterfowl from
the ponds. The effects over time are unknown. There is no evidence of acute exposure
effects.
6.7
ACI10NS REQUIRED
The actions required by this Record of Decision are necessary and appropriate to
significantly reduce or eliminate the principal risks identified in this section. Clearly
endangerment has been established with respect to both human health and the environment.
In order to effectively carry out the reduction or elimination of principal risks, however,
criteria are necessary for the identification of contaminated tailings and soils. The criteria
to be applied for soils were developed and successfully implemented during the Mill-Willow
Bypass Tailings Removal Action. The performance standards are specified in Attachment
2 to Part ll.
2)
1)
Tailings and associated contaminated. soils will be identified by color. These
materials are readily identified by their discoloration, as compared to the
natural color of uncontaminated soils.
Borrow, or fill materials are suitable, if after excavation of the discolored
materials, the concentration of copper is less than 500 mg/kg as measured by
a properly calibrated X-ray fluorescence (XRF) analyzer. These materials will
be used to construct or strengthen the berms specified as elements of the
remedial action.
3)
Soils at final excavation grade, following removal of tailings and associated
soils, and borrow materials, will exhibit concentrations of metals within the
range of concentrations shown in Column 4 of Table E-1 of the Soils Removal
Report, Mill-Willow Bypass Removal Action, March 1991.
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4)
In contaminated areas where excavation is not conducted, a combination of
color identification and confirmation sampling will be used to establish the
boundaries for wet-closure or dry-closure of contaminated areas. Soils
remaining outside of the boundaries of wet-closure or dry-closure cells will
exhibit concentrations of metals within the range of concentrations shown in
Column 4 of Table £-1 of the Soils Removal Report, Mill-willow Bypass
Removal Action, March 1991.
A complete removal and closure protocol for tailings and associated contaminated soils in
. the inactive area of the Warm Springs Ponds will be developed in the remedial design
. phase, and will closely follow the protocol presented in appendix B of the Mill. Willow
Bypass Tailings Removal Work Plan.
The expected remaining concentration of contaminants, after excavation or wet -or dry-
closure, will be within the following ranges for the following indicator elements:
Concentration (mg/kg)
Indicator Element Minimum Maximum Mean
Arsenic 8.4 42.1 14.8
Cadmium 0.8 4 1.1
Lead 8.4 45.5 16.3
Copper 0.6 287 64.7
Zinc 0.4 573 124.4
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7.0 DESCRIPTION OF ALTERNATIVES
Objectives for remediation of the Warm Springs Ponds Operable Unit Inactive Area were
identified in the feasibility study and in the Draft Evaluation of Alternatives-Pond 1 Area
and Below (ARCO, 1991). These objectives were developed from the identification of the
environmental and human health problems, utilizing ARARs and site-specific human health
and environmental protectiveness standards identified through the public health and
environmental assessment.
Following the identification of the remediation objectives, potential remedial technologies
and process options were identified' and evaluated for use at the site. All of the
technologies and process options were screened based on effectiveness, implementability,
and cost to reduce the list of potential technologies.
The technologies remaining following the second screening were combined to form media-
specific actions addressing the remedial objectives identified for each of the media. The
media-specific actions were developed to the conceptual design level in the Draft Evaluation
of Alternatives-Pond 1 Area and Below.
Six comprehensive remedial action alternatives were assembled in the Draft Evaluation of
Alternatives by combining one or more media-specific actions for each of the affected media
into an overall remediation package. The actio~ alternatives were assembled from 14
media-specific actions. . In addition, a "no-action" alternative was added to the range of
alternatives and evaluated with the action alternatives as required by the National
Contingency Plan. The seven alternatives developed in the Draft Evaluation of Alternatives
cover a range of possible combinations for onsite remediation of the pond bottom sediments
and tailings.
Following public comments received at public workshops and meetings in October 1991, the
EP A decided to evaluate options for removal of all of the contaminated soils and tailings
within Pond 1 and in the area below Pond 1. A technical memorandum (CH2M HILL,
1992) was prepared to investigate removal alternatives. The technical memorandum went
through the steps of screening of technologies, combining technologies to form media-
specific actions, then assembling of media-specific actions to form alternatives. Based upon
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this technical memorandum, four additional alternatives were added to the seven
alternatives identified by ARCO in the Draft Evaluation of Alternatives. These removal
alternatives are numbered 8 through 11. All of the alternatives are described below.
7.1
ALTERNATIVE 1 (DRY CLOSE POND 1, REMOVAL BELOW POND 1)
Alternative 1 would consist of the following:
o
Drain the wet areas in the eastern portions of Pond 1, regrade the dry areas
in the western portions of Pond 1, then cap/cover (dry-close) with 2 inches of
crushed limestone, 12 inches of fill, 6 inches of topsoil, then revegetate with
native species.
o
Construct a ground water dewatering/interception trench system within
Pond 1 and below Pond 1 to intercept contaminated ground water and pump
it back to Pond 3 for treatment.
o
Upgrade and armor the north-south berm of Pond 1 for protection against the
maximum credible earthquake (MCE) and one-half the probable maximum
flood (0.5 PMF).
o
Construct a flood interception channel to the east of Pond 1 to protect against
floods up to the 0.5 PMF in the East Hills.
o
Modify the east-west portion of the Pond 1 dike to protect against a maximum
credible earthquake (MCE).
o
Remove all tailings and contaminated soils in the area below Pond 1 and
transport them to Pond 1 pnor to dry closure of Pond 1.
The estimated present worth cost for Alternative 1 is $29,100,000.
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7.2
ALTERNATIVE 2 (DRY CLOSE POND 1, WET CLOSE BELOW POND 1)
This alternative would include the following actions:
o
Dry close the wet and dry areas of Pond 1 similar to Alternative 1.
o
Modify the east-west portion on the Pond 1 dike to stabilize the dike up to
a full MC£.
o
Construct low dikes in the area below Pond 1 to provide for flooding of all
contaminated soils and tailings. The soils and tailings would be treated with
lime prior to flooding and the water in the wet-closed areas would be kept at
an elevated pH (above 8.5) to immobilize the metals within the soil matrix by
maintaining a reducing environment.
o
Construct an interceptor channel to the east of Pond 1 and the area below
Pond 1 to protect against floods in the east hills up to a 0.5 PMF.
o
Upgrade and armor the north-south berm of Pond 1 for protection against the
maximum credible earthquake (MCE) and one-half the probable maximum
flood (0.5 PMF). .
o
Construct an extension of the Mill-Willow Bypass flood protection dike north
of Pond 1 to protect the wet-closed area below Pond 1. The dike would be
designed for the 0.5 PMF in the combined Mill- Willow-Warm Springs Creeks
and would include soil-cement armoring to protect against scour.
o
Construct a ground water interception system that would include a trench on
the upgradient side of the flood protection dike. This trench would intercept
any contaminated ground water remaining following remediation. The ground
water would be pumped through a pipeline back to Pond 3 for treatment.
o
Construct a new channel to replace the portion of the existing Mill-Willow
channel utilized during construction of the ground water interceptor trench.
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The estimated present worth cost for Alternative 2 is $27,500,000.
.
7.3
ALTERNATIVE 3 (DRY CLOSE POND 1,DRY CLOSE BELOW POND 1)
This alternative would dry close all of Pond. 1 similar to Alternative 1, but would dry close
the area below Pond 1.
All of the elements to dry close Pond 1 would be included, plus the following elements
would be added for the dry closure below Pond 1:
o
Drain the wet areas below Pond 1, regrade the dry areas, then cover the area
with 2 inches of limestone, 12 inches of fill, 6 inches of topsoil, and revegetate
with native species.
o
Upgrade and annor the north-south berm of Pond 1 for protection against the
maximum credible earthquake (MCE) and one-half the probable maximum
flood (0.5 PMF).
o
Construct a northern extension of the Mill-Willow Bypass flood protection
dike to protect the dry-closed area below Pond 1. The dike would be
armored and designed to protect against the 0.5 PMF.
o
Construct .a ground water interception system on the upgradient side of the
flood protection dike. The system would include a trench along the toe of the
dike plus pumping and piping to transport the contaminated ground. water to
Pond 3 for treatment.
o
Extend the East Hills flood interception channel to protect the dry-closed area
below Pond 1. The channel would be sized for the 0.5 PMF in the East Hills.
o
Replace those portions of the existing lower by-pass channel used to construct
the ground water interceptor trench.
The total present worth cost for Alternative 3 is estimated to be $28,000,000.
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7.4
ALTERNATIVE 4 (WET/DRY CLOSE POND 1, REMOVE TAILINGS BELOW
POND 1)
This alternative would dry close the western portions of Pond 1 and would wet close the
eastern portions. The tailings below Pond 1- would be removed and deposited in the dry-
closure area of Pond 1 prior to capping, similar to Alternative 1. The specific elements
included in Alternative 4 are:
o
Regrade the dry areas of Pond 1, then cap/cover with. 2 inches of limestone,
12 inches of fill, 6 inches of topsoil, and then revegetate with native species.
o
Construct low dikes in the wet areas of Pond 1 to provide for flooding of all
contaminated soils and tailings. The soils and tailings would be treated with
lime prior to flooding and tQe water in the wet-closed areas kept at an
elevated pH (above 8.5) to immobilize the metals within the soil matrix by
maintaining a reducing environment.
o
Upgrade and armor the north-south berm of Pond 1 for protection against the
maximum credible earthquake (MCE) and one-half the probable maximum
flood (0.5 PMF).
o
Stabilize the east-west dike of Pond 1 to withstand the MCE.
o
Construct a flood interception channel to the east of Pond 1 to protect against
floods up to the 0.5 PMF in the East Hills.
o
Construct a ground water interceptor system along the lower bypass to prevent
contaminated ground water from reaching the Clark Fork River. The system
would include a trench to intercept the ground water and a pump and piping
system to transport the ground water to Pond 3 for treatment. The system
would also include a berm between the lower bypass and the interceptor
trench to keep smaller flood flows (up to the lOG-year event) out of the
interceptor trench.
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Remove all tailings and contaminated soils in the area below Pond 1 and
transport them to the dry areas of Pond 1 prior to dry closure of Pond 1.
The estimated present worth cost for Alternative 4 is $21,200,000.
7.5
ALTERNATIVE 5 (WET/DRY CLOSE POND 1, WET CLOSE BELOW
POND 1)
This alternative would involve wet closure of the eastern portions of Pond 1 and dry closure
of the western portions of Pond 1. The elements required to reme4.iate Pond 1 are similar
to those listed for Alternative 4. The area below Pond 1 would be wet closed and would
include the same elements listed under Alternative 2. The required elements include:
o
Regrade the dry areas of Pond 1, then cap/cover with 2 inches of limestone,
12 inches of fill, 6 inches of topsoil, then revegetate with native species.
o
Construct low dikes in the wet areas of Pond 1 to provide for flooding of all
contaminated soils and tailings. The soils and tailings would be treated with
lime prior to flooding and the water in the wet-closed areas kept at an
elevated pH (above 8.5) to immobilize the metals.
o
Upgrade and armor the north-south berm of Pond 1 for protection against the
maximum credible earthquake (MCE) and one-half the probable maximum
flood (0.5 PMF).
o
Stabilize the east-west dike of Pond 1 to withstand the MCE.
o
Construct low dikes in the area below Pond 1 to provide for flooding of all
contaminated soils and tailings. The soils and tailings would be treated with
lime prior to flooding and the water in the wet-closed areas kept at an
elevated pH (above 8.5) to immobilize the metals within the soil matrix by
maintaining a reducing environment.
o
Construct an interceptor channel to the east of Pond 1 and the area below
Pond 1 to protect against floods in the east hills up to a 0.5 PMF.
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11
o
Construct an extension of the flood protection dike north of Pond 1 to protect
the wet-closed area below Pond 1. The dike would be designed for the
0.5 PMF and would include soil-cement armoring to protect against scour.
o
Construct a ground water interception system. This would include a trench
on the upgradient side of the flood protection dike. This trench would
intercept any contaminated ground water remaining following remediation.
The ground water would be pumped through a pipeline back to Pond 3 for
treatment.
o
Construct a new channel to replace the portion of the existing bypass channel
utilized during construction of the ground water interceptor trench. .
The estimated present worth cost for Alternative 5 is $18,100,000.
7.6
ALTERNATIVE 6 (WET/DRY CLOSE POND 1, DRY CLOSE BELOW
POND 1)
Alternative 6 would be essentially a combination of the various elements of Alternatives 4
and 3. The Pond 1 area would be wet and dry closed similar to Alternative 4. The area
below Pond 1 would be dry closed and would include the elements of Alternative 3 specified
for below Pond 1.
The estimated present worth cost for Alternative 6 is $18,800,000.
7.7
ALTERNATIVE 7 (NO-ACTION)
Alternative 7 is the no-action alternative required by the National Contingency Plan (NCP)
. and is used as a baseline against which the action alternatives can be evaluated.
Since there would be no remediation associated with Alternative 7, the present worth cost
is $0.00.
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7.8 ALTERNATIVE 8 (REMOVAL OF POND 1 AND AREA BELOW POND 1; EAST
HILLS REPOSITORY)
.
This alternative would include excavating wet and dry areas of Pond 1, excavating wet and
dry areas below Pond 1, and truck transport of excavated materials to the repository site in
the east hills. The dry areas of Pond 1 and below Pond 1 would be excavated using a
combination of conventional excavation equipment including bulldozers, backhoes, front-end
loaders, anc;i scrapers. Excavated dry material would be loaded onto trucks for transport.
The wet areas of Pond 1 and below would be excavated using either mechanical dredging
(clamshells or draglines) or hydraulic dredging (cutter-head suction dredge) depending upon
. conditions. Excavated material from the mechanical dredging would be loaded onto trucks
for transport. The excavated material from the hydraulic dredging would be pumped to a
centrally located gravity thickener. Underflow from the gravity thickener would be pumped'
directly into trucks for transport. Tbe trucks would have to be modified utilizing liners or
other methods to handle the wet materials without spillage or leakage. For the east hills
repository, it was assumed that off-road haulers with capacities up to 60 cubic yards would
be utilized over specially constructed haul roads.
Two sites were required for the east hills repository to contain all of the wastes-Cook Creek
and Whitcraft Gulch. Each. is capable of storing approximately one-half of the wastes.
Dams near the mouths of the existing drainages would be constructed approximately
120 feet high. Grout curtains would be constructed beneath the dams to reduce seepage.
Construction of these repositories in existing drainages 'would require that surface runoff be
diverted, either through a piped system or diversion channels to avoid erosion of the tailings
and pond bottom sediments. This diversion system would be designed to handle up to a
100-year event, with the dams designed to be able to contain and hold surface runoff flows
exceeding the lOO-year event (up to the 0.5 PMF). A ground water collection system would
also be required downgradient of the dams. The ground water collection system would
include trench drains to intercept any ground water contaminated by seepage from the
tailings and pond bottom sediments. The collected ground water would be pumped back
to Pond 3 for treatment. Following deposition and drying of all materials, the repository
would be capped with 2 inches of limestone, 12 inches of fill, 6 inches of topsoil, and
revegetated with native species.
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A ground water interception system would still be required to prevent the existing
contaminated ground water from reaching the Clark Fork River. The system would include
a trench to intercept the ground water and a pump and piping system to transport the
ground water to Pond 3 for treatment. The system would also include a berm betWeen the
Mill- Willow Bypass and the interceptor trench to keep smaller flood flows (up to the 100-
year event) out of the interceptor trench. The ground water interceptor system could be
taken out of service once the ground water no longer exceeded MCLs.
The estimated present worth cost of Alternative 8 is $50,500,000.
7.9
ALTERNATIVE 9 (REMOVAL OF POND 1 AND AREA BELOW POND 1;
POND 3 REPOSITORY)
This alternative would include removal of all materials in Pond 1 and the contaminated
materials below Pond 1 using the same combination of excavation techniques as listed for
Alternative 8. The materials would be transported by off-road haulers to the repository at
the south end of Pond 3.
The area at the south end of Pond 3 above the high waterline was selected as a repository
option. Use of this location would represent a consolidation of the wastes within the pond
system and would minimize construction period risks and impacts since the wastes would be
handled and transported mainly within the pond system. To provide sufficient area for
disposal of all wastes, it was assumed that the repository would extend to the south of the
existing Pond 3 berm. The western berm of the repository in this area would be constructed
similar to the Pond 3 berms with soil-cement armoring on the west side to protect against
erosion of up to the 0.5 PMF in Silver Bow Creek. The remainder of the berms would be
constructed similar to the east-west Pond 3 berm with protection against the Maximum
Credible Earthquake. The berms would have to be approximately 30 feet high to contain
all of the wastes. The berms would be constructed either from onsite materials or from
selected materials excavated from the west half of Pond 1. Following deposition and drying
of all materials, the repository would be capped using 2 inches of limestone, 12 inches of
fill, 6 inches of topsoil, then revegetated with native species.
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A ground water interceptor system below Pond 1 similar to that specified for Alternative 8
would be required until the ground water was cleaned up.
The estimated present worth cost for Alternative 9 is $50,000,000.
7.10
ALTERNATIVE 10 (REMOVAL OF POND 1 AND AREA BELOW POND 1;
OPPORTUNITY PONDS REPOSITORY)
This alternative is identical to Alternatives 8 and 9, except for the transport of excavated
. materials. All excavated materials (both wet and dry) would be trucked or pumped, as
. appropriate, to a centrally located materials processing/conditioning facility. This facility
would include a gravity thickener (for hydraulically dredged materials), a mixing facility, and
a pug mill to mix the wet and dry materials in the proper proportions to allow efficient
transportation by conveyor. It was assumed that a 48-inch belt conveyor with a capacity of
approximately 1,000 tons/hour would be required to transport the materials to the
Opportunity Ponds repository.
The Opportunity Ponds site was considered for a waste repository because it is relatively
close to the WSP inactive site (approximately 4 miles average distance), and already
contains similar waste materials. It was assumed for cost estimating purposes that berms
would be constructed within the Opportunity Ponds on top of the existing tailings. The
berms would be constructed from selected materials excavated from the west half of
Pond 1. The berms would be necessary to differentiate materials, limit capping
requirements, and control the free water remaining after disposal. These berms would be
approximately 20 feet high. Following deposition and drying of all materi~, the repository
would be capped using 2 inches of limestone, 12 inches of fill, 6 inches of topsoil, then
revegetated with native species.
As with Alternatives 8 and 9, the ground water interceptor system below Pond 1 would be
required until the ground water was able to meet MCLs.
The estimated present worth cost of Alternative 10 is $49,500,000.
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7.11
ALTERNATIVE 11 (REMOVAL OF POND 1 AND AREA BELOW POND 1;
ANACONDA PONDS REPOSITORY)
This alternative is similar to Alternative 10, except that transport of excavated materials
would be by slurry pipeline. All excavated materials would be trucked or pumped, as
appropriate, to a centrally located materials handling facility. This facility would include a
pug mill, a sizing facility, and a mixing facility to size and mix the wet and dry materials and
add water in the proper proportions to allow transportation in a slurry pipeline. It was
assumed that the materials would be pumped at approximately 30 perceni solids (by
weight). This would require pumping at approximately 2,200 gpm (two shifts) to move all
the materials within a 3-year time frame: The slurry pipeline would transport the materials
to the repository site within the Anaconda Ponds.
It was -assumed for cost estimating purposes that berms would be constructed within the
Anaconda Ponds on top of the existing tailings. The berms would likely be constructed from
onsite materials. The berms would be necessary to differentiate materials, limit capping
requirements, and control the free water remaining after disposal. These berms would be
approximately 20 feet high.
The Anaconda Ponds repository would have a different configuration from the other total
removal alternatives. It would likely be composed of multiple cells (four to eight cells) to
allow for efficient deposition and handling of slurry. materials. After all tailings have been
transported to the repository, the materials would be allowed to dry out through
evaporation. If allowed by regulatory agencies, the drying process could be speeded up by
decanting free water to the surface of the Anaconda Ponds outside the repository. Even
with decanting, it would likely require several years until the surface would be stable enough
to support equipment. The repository would then -be capped using a geomembrane,
followed by limestone, soils, and native vegetation. The geomembrane would be required
to allow capping within a reasonable period of time.
As with the other total removal alternatives (Alternatives 8, 9, and 10), the ground water
interceptor system would be required below Pond 1 until the shallow ground water achieved
MCLs.
The estimated present worth cost of Alternative 11 is $50,700,000.
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t
8.0 COMPARATIVE ANALYSIS OF ALTERNATIVES
..
The alternatives presented in the previous section were evaluated against each other
according to nine criteria established by CERCLA [40 CPR ~300.515(e)(9)(iii):
~300.515(t)(I)(i)J. The criteria are:
1.
Overall Protection of Human Health and the Environment addresses how the
alternative, as a whole, will protect human health and the environment. This
includes an assessment of how public health and environmental risks are properly
eliminated, reduced, or controlled through treatment, engineering controls, or
institutional controls.
2.
Compliance with Applicable or Relevant and Appropriate Requirements (ARARs)'
addresses whether or not a remedy complies with all state and federal environmental
and public health laws and requirements that apply or are relevant and appropriate
to the conditions and remediation options at a specific site. IT an ARAR cannot be
met, the analysis of the alternative must provide the grounds for invoking a statutory
waiver.
3.
Long-tenn effectiveness and Pennanence refers to the ability of an alternative to
maintain reliable protection of human health and the environment over time once
the remediation goals have been met.
Reduction of Toricity, Mobility, or Volume are three principal measures of the overall
performance of an alternative. The 1986 amendments to the Superfund statute
emphasize that, whenever possible, EP A should select a remedy that uses a treatment
process to permanently reduce (1) the level of toxicity; (2) the spread of
contaminants away from the source of contamination; and (3) the volume, or
amount of contamination at the site.
ShoTt-tenn Effectiveness refers to the likelihood of adverse impacts on human health
or the environment that may be posed during the construction and implementation
. of an alternative until remediation goals are achieved.
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9.
6.
lmplementllbility refers to the technical and administrative feasibility of an
alternative, including the availability of materials and services needed to implement
the alternative.
7.
Cost includes the capital (upfront) cost of the implementing an alternative, the cost
of operating and maintaining the alternative over the long term, and the net present
worth of capital and operation and maintenance costs.
8.
Stale Acceptance addresses whether, based on its review of the Remedial
Investigation/Feasibility Study (RI/FS), the FS supplement, and proposed plan, the
State concurs with, opposes, or has no comment on the alternative EP A is proposing
as the remedy for the site. . .
Community Acceptance addresses whether the public concurs with EP A's Proposed
Plan. Community acceptance of this proposed plan will be evaluated based on
comments received at the upcoming public meeting and during the public comment
period.
Two of the criteria are threshold criteria-the remedy must be protective of human health
and the environment and must comply or result in compliance with applicable, or relevant
and appropriate requirements (ARARs), unless a specific ARAR is waived.
Five of the criteria are primary balancing criteria-long-term effectiveness and permanence;
. reduction of toxicity, mobility, or volume through treatment; short-term effectiveness;
imPlementability; and cost.
The two remaining criteria are modifying criteria-state and community acceptance.
This section of the Record of Decision (ROD) analyzes the various alternatives against each
of these criteria and weighs the advantages and disadvantages of each alternative relative
to the other alternatives. Table 6 is a Summary of Comparative Analysis of Alternatives.
The evaluation is presented using the nine evaluation criteria as headings. Under each
heading, the alternatives are discussed according to the various factors that constitute that
criterion. The comparative evaluation is summarized in Table 6.
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Table 6
Summal')' 01 Comperalin AoaIyds 01 Allemalhes
Paae 1 01 ]
O.eraU Comp\iaDce Lolli-Term Reduc:lioD 01 Tomity Short-Term Stale Communily
Proledi.euess willi ARARI Effecli,euess Mobility ud Volume Effeclheuess Implemeulabilil)' Cnsl Attepl8DCe Accepl8DCe
All IClion .lIematiYeJ protect All aclion Iltoma- Completo remo.al below Toxicily will bo reduced by Allemali... I, 4, 8, 9, 10, Tho majorily of componenl. The prclcnt worth co... for Tho 51810 of Thero i.
humin health Ind the environ- Ii... comply with Pond 1 (Altemali.o. I and implemenl8lion 01 Alloma- and 11 which includo tho propo.ed lor tho allemali.e. are the eleven Iction .llemltivCl MontlnA, acnera'
menl. Dry Ind wet clolUrel fedo",1 Ind I18la 4) dOO8 nol reduco tho li.OI 2, 4, 5, and 6, by completo remo.a' of l8il- well de.eloped I..hnologie. and are II follows: Departmonl community
under Allemali.e. I through 6 ARARI for tho lilo 0'1",11 relidull ri.k. chemicilly fixing dil8Ol.ed ing. and lllOCilled lOill are expecled 10 be ellily uf H..lth and acceptlnco uf
will pre.enl human and or hl.e approprille compared to either dry or IOluble motall in e Ie.. below Pond I, pOlO rilk 10 implemenled althe Warm Springl A!temltive I $29,100,000 Environmenta Ahomali.. 5.
environmental contlet, Ind bali. for ARAKI cll>lll'" (Altemali...3endlOlublell8lothrou.hlimolholUrroundingcommuniIyPondllilo.Thil includel Allemlli.e 2 $21,500,000 I Science., tho proforred
decrulo migrltion of the waiven. 6) or wet clolUre treatment and mlintoRlocO and en.ironmonlthrough exclvation IClivitiel involving Allemlli.e 3 $28,000,000 8sreel with Illem.livo. ..
contaminated O\Ilori.IIO (Altomali.ea 2 and 5). 0" high pH en.ironmenl. potential contlminalion of drlgline., bulldo..rl, fronl-end Allemali.e 4 $21,200,000 1110 EPA an interim
groundwater. With either we. or dry .hallow Iquife.. during the loadera, Icuperl, and olher Allemllive S $18,100,000 .olecled remedy.
CIOIUI"8, no lignificanl ri.b The pOlenlil1 for mobilizing removal proc.... Ahoml- conventional excavation Allomali.o 6 $18,800,000 remedy.
Comple'o remo.al below remoin relali.e 10 tho the l8ilingl and lllOCilled Ii... 2, 3, 5, and 6 do nol equipmenl. Allemlli.o 1 $0
Pond I (Allemali... I and 4) potenlial lor mig"'lion of lOil. and pond bottom include remo.al Ind would Ahemali.e 8 $50,500,000
would reduce the or.. of 1110 contami...nl8. Offlile aedimentl due to wind, thorefore po.e I... Ihort. For Ahemllivel I, 4, Ind 8 Ahemali.e 9 $50,000,000
potential human or mig""ion of groundwI'er nood. or ..rthqulk81 il lerm ri.k. through II, dredging oxcl.alion Allemali.e 10 $49,500,000
environmental conlacl. Aller- excoedina MC'" will be reduced 10 iOlignificlnt and conveyor Irlnlport may Allemlli.o II $50,100,000
nil i... 2,3, 5, and 6 (wet Ind pre.ented. le..l. for Ahemali... I involve potenlial jmplemenl1lion
dry clo.urel of Pond 1 and through 6. difficullie.. Dredging may be
helow would involve leaving Ahemali.el 8 through II hindered by .ubmerged debri.
conlaminated malerial below h..e long-Ierm eff..- including log. and brulh.
Pond I Ind would thoro fore be livene.., II . reaull of the Dredged mllerill. would require
Ie.. prolecli.elo wildlife. remo.al of the l8iling.. mixing in proper proportion with
Thil remo.al reduce. 1110 dry mllerill. prior 10 beh-
Allem8li... 8 IIIrough 11 ere pOIenlial for direc' conl8cl conveyor trllnaport. Dredging
protective in tenna of human end futuro expolurelo would require expertilo and
health Ind permanenco of the conl8mi...led malerilll left I",ined perlonnel nol locally
remediallclion. Remo.alof in placo. availlble.
'"iling. from Pond I and below
reduce I .ite rilt of direct Allomali.o 9 may be Ahemlli.e. 10 and II may bo
expo.urelo l8iling. and oilier implcled by future rellli.ely difficuh 10 implemenl
contaminated mlleria", .nd remediltion offort. requiring poliliclily. Re.idenl8 near lIIe
remo.e. Ihe IOUrce of ground- Ihll all conl8mi...led A...condl and Opportunicy
water conllmination. maleri.l. be removed from rcpo.itory lilel are concerned Ihat
Pond 3. Ilrgo .01ul1lO8 of potenlilily
h..ardoul wille would be loclled
near Iheir homea.
...
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Table 6
Summary of Comparalite Analysis of Allemati,es
Paae 1 of 3
(heraU Compliance Loaa-Term Reduction of Toddly Sbort- Term Slale Community
Protectiteness wilb ARARI Klfecti,eness Mobility and Volume Elfecti,eness Implementahility C051 Acceptance Arreptance
Remov.1 he low Pond I A d.,ree of monitoring Allemotive. 8 through II Allemotivo. I throuah 6
(AUem.livo. I .nd 4) would would be required with ell ,educe the potentie' mobili!)' un be fully implemenled
lubltlnlially reduco Illemotivel II the 'epolhory of cOJl1Jlminlntl by over I 2-year con'IRIction
mobiliution of contaminated lite.. removin, them from the poriod. However. Ahoma.
marerial. to sroundwlter for tho flood pllin. Allomolivo. 8 livo. I .nd 4 would 'equire
area below Pond It wherul Ind 9 Ire .u.ceptibl. 10 . .ignificlnlly highor I.vol
wel 0' dry clo.u,e would potentia' con~miR8nt of .clivi!)' during tho
reduce the rilt 10 minimal mobili!)' ...ulling from c:ooltruc:lion period 10
level.. flood. g,..t.. then one-heir accomplish the complete
PMF. removal of .ailing. .nd
..lOCialed loil, from below
AUemltivo. 10 end II mey Pond I.
be ,uICopliblo 10 contlmi-
nont mobilily ...ulling rrom AlIem.livu 8 th,ough II
flood. 10.. thin In PMF would ,oqui,. 3 to 4 y....
Ind ..rthqulko. 10.. thin 10 complol. boc.u.. of th.
th. MCE. I..g. volum. of matorilllO
bo removed. Somo timo
ExcaYllion and removal mlY b. 'equired 10 ob..in
(Allemltive. I, 4, 8, 9, 10, th. n..e...ry permit. end
end II) would in...... fulfill the politic.1 'equire-
wul. volum.through menla ..IOCi.led with
"bulking" or lOil during remediation.
excavltion.
All IlIemltive. .ffoctth.
None of ehe allemafivea communifie. of Wlfm
would chlnge the loxicity or Spring. Ind Opportunily
penillence of conlaminanll during implemenillion. II
I..ocialeel wilh lolid i. likely thlt conllnlclion
materiall. Mo..1 con..mi- and eXCIvalion aCliviliea
OInl. .re nol amendablo 10 would re.ult in aome local
being deol,oyed 0' chlnged lirborne rei..... of th.
inlo ,elelively inert .ub- molerill. Th. ,emovil
.110COI. Illemotivu moy imp.cl
water quality II I relull of
remedillion work in or
IdjlconllO th. bypu. .nd
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Table 6 :
Summary 0' Compar.lhe Analysis 0' AIlel'll8lites
Paae 3 on
Onrall CompliaDCe Loq-Term Reduclioll 01 Toddly Short-Term Stale Communily
Prolecti,eoess wilh ARARa Etfecd,- MoIIWly aud Volume [lrectin.eo Implemeolabilily Cosl AttepCaDCe Acceptance
Allenulive. I, 4, 8, 9 10, Ind Allenutive 8 would require
II will develop pond I Ind purchue of property in the
eventually crute wed.Rd.. EUI Hilil Ind nay be
Allemllivel I, 2, Ind 3 would lubjecllo Iind UI8
relllil in the lOll of exi.ting requirement..
wellindl by drlining the lreo
Ind pllcemenl of In ..rlllen Exc""lion Allemolivel I,
Clp. Aheml.ivel I and 3, 4, 8, 9, 10, Ind II would
which p.opole dry clolure of include remoVlI of Ihe wet-
III of Pond 1 coupled with Iindl below Pond I.
removal or dry cloluro below However f wed.nd. around
Pond 1, rCluh in the srutell Ibe elcavltion perimeter
Iou of Wellindi. Allemolive 5 would develop over lime.
maximize. lhe .rel of enhanced
wellindl both within Ind below Remediation conlrlcton
Pond I. Allemotivel 4 Ind 6 would hive 10 be prolecled
explnd Ind enhlnce wllerfowl Iglillll dennol Ind
hlbi..1 Ind improve the Vllue inhllilion threotl while
of exilting wetland. in the warkin. in area. containing
e..lem third of Pond I, while tlm"," Ind COnllminoled
Allemllive 6 doel Ihe ume lOill. ThIl8 threetl could
below Pond I. be controlled uling molb
Ind prolettive clothing.
All of the Iction Illemllivel Thil Ippli.. 10 In
would create 8 p01itive environ- Illemotiv...
ment implct by e""bli"hing
gr,,"llnd hlhitlt in the
pre.colly unvegetlted area. of
expoled loilingl or pond bonom
swimenll in the wettem
portion of Pond I.
I!OrrK781OH 5I1j.;
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8.1 OVERALL PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT
All of the action alternatives are protective of human health and the environment. There
are minor differences among the alternatives, especially in terms of ancillary effects on the
environment, including risks of exposure to .aquatic organisms and creation/destruction of
wetlands.
Dry and wet closures of tailings and contaminated soils discussed in Alternatives 1 through
6 will prevent human contact, either through a cap or through flooding. The dry-
closed/ capped portions of these alternatives will reduce the migration of contaminants into
the ground water by reducing the source for the ground water. The wet-closed portions will
also reduce the migration of contaminants to the ground water by creating and maintaining
a reducing environment in the contaminated materials. The wet-closed portions do not
alleviate the slight risk of continued exposure of contaminants to the environment, either
through the uptake of metals by plants or direct ingestion by aquatic organisms. The
existing contaminated shallow ground water would be precluded from reaching the Clark
Fork River under all alternatives. The interceptor trench and ground water pumping system
to be constructed between the reconstructed lower bypass channel and the area below
Pond 1 would effectively eliminate migration of the shallow ground water out of the inactive
area. The interceptor trench would also serve to intercept any sediments generated during
construction, thereby minimizing sediment contamination of the Clark Fork River.
Removal below Pond 1 (Alternatives 1 and 4) and total removal (Alternatives 8 through 11)
are protective in terms of human health and permanence of the remedial action. Removal
of tailings from the operable unit reduces onsite risks of direct exposure to tailings and
other contaminated materials and removes the source of ground water contamination. It
also removes chances of catastrophic failure due to. flooding. However, risk of direct
exposure and risk to ground water would occur at the waste repository site. These risks
. would be minimi7'ed through proper design at the repository site. The repository would
include a cap to reduce direct exposure to humans and the environment, plus ground water
controls (drainage systems or cutoff'systems) if these were deemed necessary.
Alternatives 1, 4, 8, 9, 10, and 11 would result in excavation below existing ground water.
For Alternatives 1 and 4, Pond 1 seepage would require a second interception trench along
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.4
the toe of the Pond 1 berm. Pumping from this trench would dewater the excavated area
below Pond 1 and would result in reduced wetlands. Such an interception trench would not
likely be necessary in the case of total removal alternatives because seepage from Pond 2
is not as contaminated as seepage from Pond 1. Therefore, more extensive wetlands would
likely be created by Alternatives 8-11.
Dry closure by draining the area and covering it with an earthen cap would result in the 1055
of existing wetlands. Implementation of Alternatives 1 and 3, which propose dry closure of
Pond 1 coupled with removal or dry closure below Pond 1, would result in the greatest 1055
of wetlands.
The wet closures associated with Alternatives 4, 5 and 6 in the eastern third of Pond 1 and
in the area below Pond 1 would result in an expansion of waterfowl habitat. The wet-closed'
areas would be shallow ponds resembling the existing Wildlife Ponds. The wet-closed areas
would change the nature of the existing wetlands in these areas by increasing water depths
and expanding the potential for development of shallow marshy areas.
The no-action alternative (Alternative 7) would not alter the site and, therefore, would not
provide for protection of human health and the environment.
8.2
COMPLIANCE WITII ARARs
All of the action alternatives would comply with ARARs. Alternatives 2 and 3 entail dry
closure within Pond 1 and either dry closure or removal below Pond 1, so mitigation would
be required under those alternatives to offset wetland losses in order to meet the wetlands
ARAR.
Alternative 7, the no-action alternative, would not achieve compliance with many of the
identified ARARs.
EP A believes that all inplace alternatives comply with solid waste disposal requirements,
because the reinforced and added berms change the floodplain and remove the materials
from the floodplain. H the area within the berms is found to be within the floodplain, EP A
believes an ARAR waiver is justified as described in the ARARs attachment. EP A also has
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waived surface water standards for all options for mercury and arsenic and pH but has
established conservative replacement standards.
8.4
LONG-TERM EFFECTIVENESS AND PERFORMANCE
All of the alternatives incorporate a ground water interception trench adjacent to the lower
bypass and, thus, prevent offsite migration of ground water that exceeds the maximum
contaminant levels. The removal alternatives (Alternatives 1, 4, and 8 through 11) have
slightly greater long-term effectiveness because they remove the tailings that are the source
of the contaminated ground water. The wet-closure alternatives (Alternatives 2 and 5) will
also substantially eliminate the tailings as a source of contamination by providing a reducing
environment to immobilize the metals. Thus, for the removal and wet-closure alternatives,
it is likely that the ground water interception and pumping system (to Pond 3 for treatment)
can eventually be dismantled once the existing contaminated ground water has been
removed.
The dry-closure alternatives (Alternatives 3 and 6) will likely require that the ground water
pumping and treatment continue for longer than the other alternatives. This is because the
dry-closure, although effective at reducing infiltration from precipitation, would not
substantially change the chemistry of the high ground water table in the area below Pond 1.
Thus, the metals would continue to serve as a source for the ground water contamination
of the shallow aquifer.
The residual risk for all alternatives is low. The alternatives that include wet or dry closure
below Pond 1 (Alternatives 2, 3, 5, and 6) will have less risk of recontamination from floods
in Silver Bow Creek than the other alternatives. This is due to the nature of the flood
protection dike along the lower bypass below Pond 1. For Alternatives 2, 3, 5, and 6, this
dike would be designed to protect against the 0.5 PMF flood in the lower bypass. . For all
other alternatives, the required protection level for this dike would be considerably lower.
Since the contaminated materials would be either removed or capped, flood protection
would be needed only to protect the engineering structures associated with the ground water
cutoff and pumping system. This level has been established as the 100-year event. Flow in
excess of the 100-year event in the bypass channel could breach the protection dike and
spread into the area below Pond 1. Until the upstream reaches of Silver Bow Creek are
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cleaned up, these flows would likely contain transported tailings. The tailings could likely
settle out and recontaminate the area below Pond 1.
Residual risk differences among removal alternatives are related to repository site location.
Alternatives 1 and 4 would have very low residual risk because disposal of the excavated
materials could be within Pond 1 prior to capping or wet-closure. The Pond 1 area would
be protected to 0.5 PMF flood and the Maximum Credible Earthquake (MCE) under these
alternatives. The alternative utilizing the Opportunity Pond repository (Alternative 10) may
not be as protective as other alternatives. This is because this repository site is Within the
berms of the Opportunity Ponds, which may be subject to failure during a major earthquake
or major flood in Silver Bow Creek. A failure of the Opportunity Pond berms might lead
to a failure of the repository berms. However, the Opportunity Pond berms will be studied
as part of the Opportunity Pond feasibility study, and the area is likely to be remediated in
a manner that will achieve long-term stability of the berms. For similar reasons, the
Anaconda Pond repository (Alternative 11) may not be as protective as other repository
sites, but it is also likely to undergo remediation in the future, which would improve the
long-term stability of the berms.
Alternatives 8 through 11 have long-term effectiveness as a result of complete removal of
the tailings and contaminated soils. This removal eliminates the potential at the site for any
direct contact; however, those risks could be subsequently transferred to the repository site
where the contaminants would be placed. The direct contact risk could be minimized
through proper design of caps at the repository sites. '
The no-action alternative (Alternative 7) would have the lowest long-term effectiveness since
it would involve no remedial actions.
8.3
REDUCTION OF TOXICITY, MOBILITY, AND VOLUME
Alternatives 1, 4, and 9 would reduce the potential mobility of contaminants by removing
them 'from the historic flood plain below Pond 1 and depositing them in areas protected up
to the 0.5 PMF and the full MCE.
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Ii
Alternatives 2, 3, 5, and 6 would leave contaminants within the historic flood plain below
Pond 1 but would protect them up to the 0.5 PMF and the MCE through construction of
the flood protection dikes along the Mill-Willow Bypass. This would also effectively reduce
mobility.
The alternatives using the Opportunity and Anaconda repositories (Alternatives 10 and 11)
may be susceptible to contaminant mobility resulting from floods less than 0.5 PMF and
earthquakes less than the maximum credible earthquake since they are placed on waste
deposits not currently protected from these types of events. The Opportunity Ponds will be
studied as part of the Opportunity Ponds FS and this area will likely be remediated in a
manner that will achieve long-term stability of the berms. Similarly, it is likely that the
Anaconda Ponds will be remediated in the future to improve their stability.
The excavation and removal alternatives (Alternatives 1,4,8, 9, 10, and 11) would increase
waste volume during excavation. This is due to the natural tendency of soils to increase in
volume (bulking) during excavation. The greatest increase in volume would be for
Alternative 11 because the slurry option requires that water be added to transport the
materials.
N one of the alternatives would change the toxicity or persistence of contaminants associated
with solid materials. Metal contaminants are not amendable to being destroyed or easily
changed into relatively inert compounds through treatment. Alternatives 2, 4, 5, and 6,
which in part use wet closure (flooding/chemical fixation), would reduce the mobility of
most contaminants by placing them in a reducing environment. The chemical fixation
process involves the addition of lime, an alkaline material, into the wet closures. The
alkaline system prevents the oxidation of sulfide metals in the tailings and prevents the
formation of acid waters. At high pH conditions, most metals will not dissolve and therefore
are not transported into the ground water system. The dry-closure alternatives do not retard
the mobility of metals, particularly in a system such as this, where the tailings are generally
in contact with the ground water. Capping the tailings (dIy-closure) alone would not create
the' reducing condition needed to immobilize the metals. .
The potential for mobilizing the tailings and associated soils and pond bottom sediments
because of wind, flood, or earthquakes would be reduced to low levels for all action
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alternatives except 10 and 11. Once the Opportunity and Anaconda Pond berms are
stabilized and protected, the risk of this type of mobilization would be reduced to low levels.
The no-action alternative would not result in any reduction of toxicity, mobility, or volume.
8.5
SHORT-TERM EFFECTIVENESS
All alternatives will affect the nearby community of Warm Springs to some extent during
remediation. The generation of construction dust, noise, and traffic are the primary
impacts. The alternatives with the least impact include Alternatives 2, 3, 5, and 6 because
they would not require removal of materials. The minor amount of dust generated can be
controlled through proper dust control measures. The onsite excavation alternatives
(Alternatives 1 and 4) would have the potential for generation of considerably more
construction dust, but proper control techniques would minimize this impact. Alternatives 8
and 9 would have similar impacts to Alternatives 1 and 4. This is because the haul roads
for the excavated materials would be on the east side of the pond system, away from Warm
Springs. Alternatives 10 and 11 would have some impact because they would require
construction and operation of either a conveyor or slurry pipelines outside of the Warm
Springs Ponds.
None of the proposed action alternatives involves any activities that present significant
health risks to workers. Those alternatives that req~e the most handling of contaminated
materials obviously pose the highest risks relative to worker exposure. However, none of
the alternatives have unacceptably high risks associated with them. Workers will be
protected using appropriate protective equipment and will be required to have. 40-hour
health and safety training prior to beginning work on the site, and otherwise comply with
the Occupational Health and Safety Act.
The actual construction of Alternatives 1 through 6 can be accomplished over a 2-year
construction period. The alternatives that include dry closure of the eastern third of Pond 1
may require more time to fully implement. This is because the existing tailings and
contaminated soils in this area are saturated and may require considerable time (potentially
several years) to adequately drain prior to construction of a dry closure cap. The complete
removal alternatives (Alternatives 8 through 11) would require 3 to 4 years to implement
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because of the large quantity of materials involved. Alternative 11 (the slurry pipelines)
would likely require several additional years after actual removal operations are completed
to allow the deposited materials to drain and dry sufficiently to allow capping of the
repository.
The implementation of the complete removal alternatives may require additional time
beyond actual construction to obtain necessary permits. This could be significant for
Alternative 8 (East Hills repository) because of potential land use restrictions. Alter-
natives 10 and 11 (Opportunity and Anaconda repositories) could also encounter significant
delays because of permitting required to construct a conveyor or a ,pipeline across the 1-90
and railroad rights-of-way, and along e,xisting county roads.
All of the action alternatives will involve some alteration or disturbance of existing
wetlands. The alternatives involving wet closure below Pond 1 (Alternatives 2 and 5) would
have the least impacts to the existing wetlands below Pond 1. The raising of the water
surface in this area would alter and displace the existing wetlands, but over time the existing
functions and values would likely be reestablished in the shallow areas and on the edges of
the wet-closure ponds. Similarly, the alternatives including wet closure of the eastern third
of Pond 1 (Alternatives 4, 5, and 6) would result in altering and displacing the existing
wetlands in this area. Eventually, these wetlands could also be expected to reestablish
themselves.
The alternatives that include dry closure in the eastern third of Pond 1 or the area below
pond 1 (Alternatives 1, 2, 3, and 6) would result in permanent, irreversible loss of the
existing wetlands in the these areas.
The alternatives involving removal below Pond 1 (Alternatives 1, 4, and 8 through 11) would
result in removal and varying degrees of loss of wetlands because the existing high ground
water would be lowered by the ground water interception trench or trenches. Depending
upon the alternative, some of the functions and values of the existing wetlands could be
expected to become reestablished or improved over time.
All of the action alternatives would result in an increase in grassland habitat in the presently
unvegetated areas of exposed tailings in the dry areas within Pond 1.
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The no-action alternative (Alternative 7) would not result in any short-term impacts upon
the community or the existing environment.
8.6 IMPLEMENTABILITY
Most of the components proposed as part of the alternatives are well-developed
technologies, used to some extent in either the hazardous waste, materials handling, or
standard civil engineering disciplines. The technical feasibility of these components appears
to be good. Nevertheless, some alternatives are more easily implemented than others.
Alternative 5 is the most easily implemented. For the alternatives requiring dredging
(Alternatives 1,4, and 8 through 11), there are potential difficulties in implementation. The
most prevalent difficulty would involve operating a hydraulic dredge in areas containing logs
and other debris. Removing, or working around larger logs, brush, and debris may be
necessary by other methods such as clamshell, dragline, or backhoe. Another potential
difficulty could involve operating and transporting the mechanical dredging equipment in
the soft foundation conditions prevalent in the area. An additional concern would be
increased risk of turbid discharges to the bypass during dredging operations.
The alternatives requiring dry closure of the eastern portions of Pond 1 or the area below
Pond 1 (Alternatives 1, 2, and 3) would be difficult to implement because of saturated, soft,
soil conditions present. The tailings are completely saturated so that surface access and
trafficability by conventional construction equipmen~ will be impossible. Special equipment
will be required to undertake the excavation and redistribution of the excavated materials.
From an administrative feasibility standpoint, all of the alternatives are about equal except
for disposal and land acquisition considerations. The disposal of excavated tailings, pond
bottom sediments, and contaminated soil outside of the Ponds area may be difficult to
implement. The transport of approximately 3.4 million cubic yards of untreated waste is
administratively undesirable from both a transportation and disposal point of view. The
onsite disposal- option (Alternative 9) would likely be easier to implement because the
wastes would be transported to Pond 3 and thus remain within the operable unit. Alterna-
tive 8 would require the acquisition of approximately 180 acres in the east hills for
construction of the east hills repository. This could make Alternative 8 - difficult to
implement, depending upon the willingness of the existing landowners to sell their
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properties. Alternatives 9 and 10, involving disposal at the Anaconda and Opportunity
Ponds, would likely encounter public resistance.
None of the action alternatives presents any special operational problems. All of the
alternatives include ground water interception, which requires pumping the intercepted
water to Pond 3 for treatment. The pumping plant and pipeline would require regular
operation, inspection, and maintenance under all action alternatives to ensure that the
system functions as intended. Operation of the wet-closure cells under Alternatives 2, 4, 5,
and 6 would require control of flow through the cells to ensure that the ponds remain at the
proper operating level. The pH of the water in the wet-closure cells would have to be
monitored (and adjusted, if necessary) to assure that the pH remains elevated (above 8.5).
Regular inspection and periodic maintenance would be performed to ensure proper
operation.
Construction equipment and services required to implement any of the action alternatives
are readily available. The equipment required for the removal alternatives (Alternatives 1,
4, and 8 through 11) is somewhat specialized and may not be available locally. It is likely
that the hydraulic dredging and materials handling equipment (and potentially the skilled
operators) would have to be imported from outside the local area.
The no-action alternative (Alternative 7) would not require any implementation.
8.7
COSTS
The capital (construction), operation and maintenance, and present worth costs are
presented in Table 7. Alternative 5 is the most cost-effective, both in initial construction
costs and from a total present-worth standpoint.
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TABLE 7
COST SUMMARY TABLE
TOTAL CONSI'RUCTION OPERATION AND PROJECT PRESENT
cosr MAINTENANCE WORTH
Alternative No.1 $28,435,218 $ 671,800 $29,100,000
Alternative No.2 26,219,725 1,320,500 27,500,000
Alternative No.3 26,872,495 1,157,500 28,000,000
..
Alternative No.4 20,338,998 851,700 21,200,000
Alternative No.5 17,115,069 1,033,100 18,100,000
Alternative No.6 17,921,020 870,100 18,800,000
Alternative No.7 0 0 0
Alternative No.8 49,592,025 860,900 50,500,000
Alternative No.9 49,261,412 m,300 50,000,000
Alternative No. 10 48,769,448 m,300 49,500,000
Alternative No. 11 49,866,473 790,200 50,700,000
NOTE: Present worth is calculated by amortizing the Operation and Maintenance cost over 30 yeatS at a 5 percent discount ratc.
8.8 STATE ACCEPTANCE
The State of Montana, acting through the Department of Health and Environmental
Sciences, has been consulted throughout the process of evaluating potential remedies and
is in agreement with the EP A concerning the selected remedy. A copy of the State's letter
of concurrence with the selected remedy is attached to Part ill.
8.9
COMMUNITY ACCEPTANCE
The public, which includes citizens and elected officials from Silver Bow, Deer Lodge,
Granite, Powell, and Missoula counties, has been involved in the decision-making process
for the inactive area of the Warm Springs Ponds since the inception of the operable unit in
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1991. While many people have indicated reservations about the selected remedy, there are
others who fully support EP A's selection of Alternative 5. The majority of those who
expressed reservations are willing to accept the selected remedy as an interim solution.
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9.0 THE SELECTED REMEDY
9.1
INTRODUCTION
After evaluating alternatives with respect to each other and the nine required criteria, the
EP A and MDHES have identified Alternative 5 as the selected remedy for this Warm
Springs Pond Inactive Area Record of Decision (ROD). Alternative 5 provides
protectiveness that equals or exceeds the other alternatives considered, offers the potential
for being a permanent remedy, is supported by the public, is implementable, is cost-effective,
and provides the greatest environmental benefits that can be practically achieved. The
primary components of Alternative 5 involve measures to safely allow the contaminated
pond bottom sediments and tailings to remain in place. These measures include:
1.
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.
2.
Modify, or enlarge if necessary, the adjacent portion of the bypass channel to safely
route flood flows up to 70,000 cubic feet per second (ds) 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 benns.
3.
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 reconstruct~d berm
must 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.
4.
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
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13.
14.
15.
9.2
to
.
11.
Cover the dry tailings and contaminated soils within the western portion of Pond 1
with 2 inches of limestone, 12 inches of fill, and 6 inches of a suitable soil cap. This
dry-closed area will be contoured to control runoff and seeded with native vegetation.
12.
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 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 source discharge standards specified in
Attachment 5 to the Warm Springs Ponds Active Area Unilateral Administrative
Order.
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 conta.ct 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 institutional controls to prevent residential development, domestic well
construction, disruption of dry-closure caps, and swimming.
REMEDIATION AND PERFORMANCE STANDARDS
Alternative 5 will effectively meet the remediation goals established for the inactive area.
These remediation goals were established by EPA and MDHES as part of the Feasibility
Study (FS) process and the active area ROD selection, and were based primarily upon a
Public Health and Environmental Assessment prepared for the original Warm Springs Ponds
Operable Unit. A summary of the remediation goals and the measures that Alternative 5
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will employ to meet those goals is outlined below. The gQals are categorized according to
the media identified in the FS. A full description of required performance standards is
contained in Attachment 2 to this section.
9.2.1 Pond Bottom Sediments
The remediation goal for pond bottom sediments is to prevent release of contaminated
sediments during earthquakes and major floods. Alternative 5 will meet this goal by:
stabilizing and armoring the north-south berm, reinforcing the east~west Pond 1 berm and
other berms against the MCE; constructing an extension of the north-south flood control
berm to protect the wet-closed area below Pond 1 from up to a 0.5 PMF in the bypass
channel; and constructing a channel along the entire eastern side of Pond 1 and the area
below to protect against floods of up to the 0.5 PMF from the east hills.
9.2.2 Surface Water
There are two primary remediation goals dealing with surface water. The goals include:
o
Meet the State of Montana's ambient water quality standards for arsenic,
cadmium, lead, mercury, copper, iron, and zinc at the compliance point
Alternative 5 will have no discharge of water to the Clark Fork River.
Normal operation procedures for the . wet-closure cells will require a small
flow of water through the ponds to maintain high pH and prevent stagnation.
Since the source for this water will be Pond 2 effluent, and since the wet-
closure cells will provide additional treatment, any water that exits the wet-
closure cells is expecteq to meet ambient water quality standards, but in any
case, will not be discharged beyond the interception trench. All water in the
interception trench will be pumped back to the active area until such time as
it is demonstrated that a pump-back system here is no longer needed.
o
Prevent ingestion of water above the standards for arsenic, cadmium, lead,
mercury, copper, iron, and zinc, as specified by the Montana Public Water
Supply Act. Another goal is to prevent ingestion of water containing arsenic
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in concentrations that would increase cancer risks to greater than 1 in 10,000.
Alternative 5 will meet these goals through institutional controls that will
prevent use of the surface waters within the inactive area as a source for
drinking water, and operation of the interception trench and pump back
system.
9.2.3 Tailings Deposits and Contaminated Soils
The goal for remediation is to substantially reduce the potential for direct contact,
inhalation, and ingestion of contaminated soils and tailings. Alternative 5 will meet this goal
by isolating the contaminated soils and tailings, either through capping or covering in the
dry-closed areas or chemical fIxation and flooding by means of wet-closure.
9.2.4 Ground Water
The remediation goal for ground water is to prevent offsite migration of ground water with
contaminant concentrations in excess of Montana ground water maximum contaminant
levels. This goal will be met by means of chemical fixation and wet-closure, backed up by
construction of the ground water interception trench, which will prevent offsite migration
of all ground water from the shallow aquifer.
9.3
QUAN 1 fllliS AND COST ESTIMATE
The detailed listing of the components of Alternative 5, and their associated costs, are
included in Table 8. Annual operation and maintenance costs and present worth costs are
presented in Table 9.
It should be noted that these costs may change because of changes made during remedial
design and remedial construction. These changes are a result of modifications generally
required as more site-specific information is developed during detailed design.
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Table 8
Detailed Cost Estimates
Alternative S
Page 1 of 3
Unit Cost Amount
Description Quantity Units ($) ($)
Dike Improvements, East-West Dike of Pond I
Clearing and Stripping 12 AC 7,500.00 90,000
Foundation Excavation 10,000 CY 7.80 78,000
Gravel Fill 10,000 CY 9.00 90,000
Embankment 34,000 CY 4.50 153,000
Gravel Surfacing 3,400 CY 10.00 34,000
Subtotal 445,000
East Hills Flood Interceptor Channel-Pond I
Clearing and Stripping. 13 AC 7,600.00 98,800
Channel Excavation 80,000 CY 6.84 547,200
Geofabric 42,000 SY 4.50 189,000
Riprap 14,000 CY 30.00 420,000
Subtotal 1,255,000
Dry Closure of Pond I-Western Portion
Finish Grading 175 AC 1,520.00 266,000
Geogrid 847,000 SY 2.28 1,931,160
2" Limestone Cap 70,000 TONS 13.00 910,000
Random Fill 340,000 CY 6.00 2,040,000
6" Soil Cover 140,000 CY 5.00 700,000
Phosphate Fertilizer. 90 TONS 325.00 29,250
Seeding 175 AC 1,000.00 175,000
Riprap 600 CY 30.00 18,000
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Table 8
Detailed Cost Estimates
Alternative 5
Page 2 of 3
Unit Cost Amount
Description Quantity Units ($) ($)
Wet Closure/Chemical Fixation of Pond I-Eastern Portion
Lime Conditioning 115 AC 4,000.00 460,000
Wet Closure Dikes 20,000 CY 10.00 200,000
Geogrid Foundations 15,000 SY 4.00 60,000
Soil Cement Overflows 500 CY 50.00 25,000
Riprap 600 CY 30.00 18,000
Siphon From Pond 2 1 LS 20,000.00 20,000
Subtotal 783,000
Pond 1 Dike Extension-Area Below Pond 1
Embankment 75,000 CY 5.00 375,000
Foundation Excavation 20,000 CY 10.00 200,000
U nderdrain 2,400 LF 10.00 24,000
Soil Cement Erosion Protection 15,000 CY 30.00 450,000
Subtotal 1,049,00
East Hills Flood Interceptor Channel-Area Below Pond 1
Clearing and Stripping 5 AC 7,500.00 37,500
Channel Excavation 110,000 CY 6.84 752,400
Geofabric 15,000 SY 450 67,500
Riprap 5,000 CY 30.00 150,000
Subtotal 1,007,400
Wet Closure/Chemical Fixation-Area Below Pond 1
Lime Conditioning 74 AC 4,000.00 296,000
Wet-Closure D~es 20,000 CY 10.00 200,000
Geogrid 17,000 SY 4.00 68,000
Soil~Cement Overflows 1,000 CY 50.00 50,000
Riprap 1,000 CY 30.00 30,000
Siphon from Pond 2 1 LS 40,000.00 40,000
Tailings/Soils Removal 50,000 CY 12.00 6,00,000
Habitat Enhancement 30,000 CY 8.00 240,000
Subtotal 1,524,000
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Table 8
Detailed Cost Estimates
Alternative 5
Page 3 or 3
Unit Cost Amount
Description Quantity Units ($) ($)
Groundwater Interception and Pumpback System-Below Pond 1
Interceptor Excavation 55,000 CY 6.00 330,000
Tailings ReJ?oval 5,000 CY 7.00 35,000
Pump Station 1 LS 250,000.00 250,000
Pipeline 15,000 LF 35.00 525,000
Subtotal 1,140,000
Mill-Willow Bypass Channel Replacement
Channel Excavation 25,000 CY 4.00 100,000 .
Tailings Removal 5,000 CY 7.00 35,000
Subtotal 135,000
Basic Construction Cost 13,407,810
Division 1 Costs (11%) 1,472, 790
Contingency (15%) 2,186,400
Total Construction Cost 17,067,000
Operation and Maintenance. 1,033,000
Total Present Worth 18,100,000
.See Table 10-2 for details of Operation and Maintenance Costs.
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Table 9
Operation and Maintenance Cost
Alternative 5
Yearly Cost
Description. ($)
East- West Dike-Pond 1 2,200
East Hills-Flood Interceptor Channel-Pond 1 2,100
Dry Closure of Pond I-Western Portion 2,800
Wet Closure of Pond I-Eastern Portion 4,200
Pond 1 Dike Extension-Below Pond. 1 1,500
East Hills Flood Interceptor Channel-Below Pond 1 3,200
Wet Closure-Below Pond 1 4,200
Groundwater Interceptor System
Operation and Maintenance 10,600
Powe~ 12,800
Equipment Replacement Sinking Fund 7,000
Monitoring 12,600
5-Year Reviewb 4,000
Total Yearly Cost 67,200
Present Worth Factor 15.374
Total Present Worth 1,033,100
.Assumes power @ SO.07/kWh.
bAssumes S20,OOO every 5 years.
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10.0 STATUTORY DETERMINATIONS
Under its legal authorities, EPA's primary responsibility at Superfund sites is to undertake
remedial actions that achieve adequate protection of human health and the environment.
In addition, section 121 of CERCLA establishes several other statutory requirements and
preferences. These specify that when complete, the selected remedial action for this site
must comply with applicable or relevant and appropriate environmental standards (ARARs)
established under federal and state environmental laws unless a statutory waiver is justified.
These two criteria are threshold criteria that every remedy must meet. The selected remedy
also must be cost-effective and utilize permanent solutions and alternative treatment
. technologies or resource recovery technologies. to the maximum extent practicable. Finally,
the statute includes a preference for remedies that employ treatment that permanently and
significantly reduces the volume, toxicity, or mobility of hazardous wastes as their principal
element. The following sections discuss how the selected remedy meets these statutory
requirements.
10.1
PROTECTION OF HUMAN HEALTII AND TIlE ENVIRONMENT
The selected remedy will prevent direct exposure to contaminated soils and tailings within
the operable unit by covering those areas with lime and water in the case of wet closure
areas, or with limestone and a dry soil cap, in the case of dry closure areas. Institutional
controls to prevent residential development or disruption of the closures are also required,
and are described in Attachment 1 Part II. This will cause the current exposure risks to be
reduced to levels within EP A's range of acceptable exposure levels. Contamination within
the lower bypass area will be excavated and consolidated into the closure areas, which will
prevent unacceptable risks of on-site exposure or downstream migration.
Human and environmental exposure to contaminated ground water, either through further
'spread of the contamination in the aquifer or migration of the plume, will be controlled
through chemical fixation and wet-closure, backed up by the construction of an interception
trench at the waste unit boundary. ARAR requirements for ground water outside of the
waste unit boundary and the interception trench, described below and in Attachment 2 to
Part II, are established by this Record of Decision and must be met.
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Risks to human health and the environment from earthquake damage and floods, which may
cause migration of waste materials from the ponds, including the inactive area, will be
controlled by appropriate berm construction and strengthening. The construction of an
interception system along the east side of the inactive area, and the construction of adequate
capacity for the entire bypass channel will also ensure flood protection. ARARs related to
these requirements are explained and described below and in Attachment 2 to Part II.
.
Environmental risks other than those discussed in the previous paragraphs will be addressed
through the wet closure and dry closure cells, which will prevent significant' exposure
pathways to the environment. Ecological monitoring of the area will aid in EP A's continual
evaluation of environmental conditions at the site. Environmental enhancement will occur
through the reconstruction and restoration of the bypass channel, and creation of wetlands.
Surface water ARARs, described below and in Attachment 2 to Part II, must be met for.
instream ambient standards at the designated point of compliance. Compliance with those
ARARs will ensure environmental protection for surface waters downstream from the
inactive area, including the Clark Fork River.
Short term risks posed by the selected alternative can be controlled through effective site
safety plans and other means.
10.2
COMPUANCE WITH APPUCABLE OR RELEVANT AND APPROPRIATE
REQUIREMENTS
The selected remedy will comply with all applicable or relevant and appropriate
requirements (ARARs), except for those appropriately waived. A detailed description of
ARARs, appropriate waivers, and replacement standards is contained in Attachment 2 to
Part II. The most significant ARARs are highlighted and described in the section above.
10.3
COST-EFFEcrIVENESS
The selected alternative is the lowest cost alternative examined in the proposed plan, except
for the no action alternative. The selected remedy is cost-effective because it provides
overall protectiveness proportion31 to its costs. Alternatives involving ~otal removal of
contaminants (Alternatives 8 through 11) cost significantly more than the selected
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alternative, and yet did not provide significant additional overall protection of human health
and the environment than the selected alternative. In fact, alternatives involving total
removal presented unacceptable risks in terms of human safety because the removed
material would have to be transported by heavy equipment and placed at another location.
This type of activity has inherent safety risks.
10.4
UTIliZATION OF PERMANENT SOLUTIONS AND ALTERNATIVE
TREATMENT TECHNOLOGIES OR RESOURCE RECOVERY
TECHNOLOGIES TO THE MAXIMUM EXTENT PRAcrICABLE
Because the selected alternative will provide for extensive berming to prevent flood and
earthquake damage and release, it has a high degree of long term effectiveness and
permanence. To ensure this, clear operation and maintenance requirements will be invoked.
for the inactive area, to ensure that the berms remain protective and the wet closures and
ground water interception system work as designed.
Resource recovery technologies are not feasible for this site. Alternatives involving resource
recovery, examined in the original Warm Springs Ponds feasibility study, were high in cost
and would not remove all contaminants of concern from the waste material found at the
site. Use of chemical fixation and wet-closure cover is an alternative treatment technology,
and its effectiveness at this site will be monitored for possible use at other mining sites and
Clark Fork Basin operable units.
The selected alternative provides the best balance of tradeoffs in terms of long term
effectiveness and permanence, reduction in toxicity, mobility, or volume through treatment,
short term effectiveness, implementability, cost, and the statutory preference for treatment
as a principal element. Total removal options may be more permanent and effective over
the long term, but these factors do not outweigh the relatively high costs, implementability
problems, and human safety risks associated with them. Partial removal options also exhibit
implementability problems, and do not provide significantly higher overall protectiveness,
long term effectiveness, or cost reduction from the selected remedy.
The State of Montana concurs with EP A concerning the selected remedy for the inactive
area. While many community members have indicated reservations about the selected
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remedy, there are others who fully support EP A's selection of Alternative 5. The majority
of those who expressed reservations are willing to accept the selected remedy as an interim
solution.
10.5
PREFERENCE FOR 1REATMENT AS A PRINCIPAL ELEMENT
The selected remedy utilizes lime addition to many areas of contamination within the
inactive area. Lime addition, followed by wet-closure will reduce the mobility of the
contamination, and thus the remedy utilizes treatment as a principal part of the remedy.
. In addition, standard treatment of contaminated ground water will be accomplished through
. the pump-back system, which will return the contaminated ground water to the active area.
Therefore, the statutory preference for remedies that employ treatment as a principal
element is satisfied.
As explained above, other forms of treatment were examined in the feasibility study and
were determined to be infeasible and impracticable for the contamination found at the site.
The EPA is directed to follow the NCP (National Oil and Hazardous Substances Pollution
Contingency Plan, 55 Fed. Reg. 8665-8865, March 8, 1990) and is obligated to rely on
Superfund guidance in the selection of remedies. One major purpose of this section is to
layout provisions of the NCP and pertinent parts of guidance documents that played
important roles in the process of selecting this remedy.. In part, it is an attempt to trace the
rationale for selecting a remedy that will not remove the tailings and dispose of them
outside of the historic flood plain.
Although the majority of the basin's residents who participated in the remedy selection
process accept the remedy chosen, many residents of the lower basin feel strongly t~at the
tailings should be totally removed and they have presented strong arguments for their
position. Numerous scoping meetings and briefings were conducted prior to the EP A's
selection of the remedy. Most of the discussions focused on issues such as implementability,
permanence and costs. The EP A and State seldom paused to discuss what the NCP and
Superfund guidance have to say about situations of this sort.
The NCP directs the EP A to "use treatment to address the principal threat posed by a site,
whenever practicable" and to "use engineering controls, such as containment, for waste that
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poses a relatively low long term threat or where treatment is impracticable" (55 Fed. Reg.
8846).
Recent guidance (OSWER Pub!. 9380.3-06FS, November 1991) offers the follo\\-ing
definitions of principal threat and low level threat wastes:
Principal threat wastes are those materials considered to be highly toxic or highly
mobile and generally cannot be reliably contained or would present a significant risk
to human health or the environment should exposure occur. Where toxicity and
mobility of the source material combine to pose a risk of 1 X 10-3 (one excess cancer
per 1000 individuals) or greater, treatment alternatives should be evaluated.
Low level threat wastes are those source materials that generally can be reliably
. contained and would present only a low risk in the event of release. They include
source materials that exhibit low toxicity, low mobility in the environment, or are
near health-based levels.
Although NCP expectations are to use treatment technologies when there is a principal
threat, and containment or some other engineered solution when there is a low level threat,
categorizing the threat of waste at a site does not always render a perfect fit. Often it
becomes necessary to characterize the source material, which is the reservoir of hazardous
substances, pollutants, or contaminants from which ~ere is migration of the contamination
to ground water, surface water, or air, or from which there is a source of direct exposure.
In characterizing source materials, highly mobile or highly toxic materials, such as liquids
and volatile organic compounds, generally are regarded as principal threats. Relatively
immobile source materials of low to moderate toxicity generally are regarded as low level
threat wastes. It is important to note that contaminated ground water is not usually
considered to be a source material.
The NCP recognizes that in some situations the wastes will not be readily classifiable as
either a principal threat or low level threat waste. Thus, a combination of treatment and
containment methods may be appropriate to achieve protection of human health and the
environment. Additionally, institutional controls such as access restrictions, water use
restrictions, or deed limitations will be used to aid containment or treatment remedies.
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The final point that is pertinent with respect to principal threat wastes versus low level
threat wastes is that the NCP recognizes there are situations where wastes identified as a
principal threat simply cannot be treated (55 FR at 8703, March 8, 1990). Some situations
that may limit or preclude the use of treatment methods include:
a)
b)
c)
The extraordinary volume of materials or the complexity of the site .render
treatment technologies impracticable;
Implementation of a treatment-type remedy would result in greater overall
risk to human health or safety due to risks posed to workers or the
surrounding community during implementation; and
Implementation of a treatment-type remedy would result in severe effects
across environmental media (OSWER Pub!. 9380.3-06FS, November 1991).
With these directives and guidance in mind, where do the 3.4 million cubic yards of tailings,
sediments and soils within the inactive area of the Warm Springs Ponds fall out? In other
words, are the source materials a principal threat waste or a low level threat waste? Is
treatment the appropriate remedy? Or, is containment, removal, or some other engineered
solution the appropriate remedy? Is a combination of treatment and containment
appropriate? What is the primary threat? In light of the extraordinary volume of source
materials present in the inactive area, does this factor become the overriding consideration
and render treatment t~chnologies impracticable?
The EP A and State carefully considered all of these questions.
conclusions reached.
Following' are the
o
The source material at issue does not exhibit high mobility. Ground water
monitoring wells located between the Pond 1 berm and the Clark Fork River
show that the metals and arsenic meet drinking water standards just a few
hundred feet down gradient.
o
The source material can be reliably contained. Evidence of this is present
throughout the Warm Springs Ponds system, where less than adequate berms
and liming methods have for decades contained the source material rather
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effectively. Unquestionably, higher standards for dam safety and water
treatment are needed; however, these improvements are already components
of the remedy for the active area, and as components of the remedy for the
inactive area these improvements can reliably contain the source material.
o
The risks posed by the source material are above health-based levels. People
who work year around at the ponds (occupational scenario) face increased
cancer risks of 2 chances in 10,000. Direct contact with exposed tailings,
contaminated pond water and contaminated pond bottom sediments account
for this increased risk.
o
The source material is highly toxic to the aquatic environment. This is the
most controversial aspect of categorizing the threat of waste present in the
inactive area. On one hand, it can be argued that fish and wildlife already
live in contact with these materials throughout the pond system. On the other
hand, releases of wastes from the Mill-Willow Bypass into the upper Clark
Fork River, which are identical to the source materials at issue here, have in
past years caused massive, repeated fishkills.
o
There is an extraordinary volume of materials present. Often, this makes the
implementation of treatment technologies impracticable and limits the
possibilities. More significantly, however, the sheer volume of materials
makes one of the alternatives to treatment-specifica1ly removal-impracticable.
Attempting to remove the materials and dispose of them in another location,
outside of the pond system, would result in greater overall risks to the
environment and human safety during implementation. The EP A is not
willing to take these risks.
After carefully considering the questions raised by the NCP and guidance requirements, the
EP A and State believe that the 3.4 million cubic yards of tailings, contaminated sediments
and soils residing in the inactive area of the Warm Springs Ponds, and the contaminated
ground water underlying this area, are best suited to a combination of treatment
technologies, engineering controls, and institutional controls. Institutional controls are
expected to be needed to a very limited degree.
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By so concluding, a second tier of NCP requirements and guidance comes into play.
Whenever treatment is an element of the selected remedy, the NCP encourages the
development and implementation of innovative treatment technologies. (40 CFR Section
300.430( a)( 1 )(iii)(E»
Innovative treatment technologies are defined as new or emerging methods for reducing or
eliminating the toxicity, mobility or volume of waste; methods which have limited data in
support of their performance in terms of constructability, effectiveness and costs.
The EP A has taken steps nationwide to promote the implementation of innovative
technologies, particularly for contaminated soils and ground water. These steps include the
creation of incentives for participating potentially responsible parties (PRPs) and the
affected public. These steps also include a willingness to explore promising new
technologies with the recognition that there is some risk of failure, some risk of a false start,
or the need sometimes for a second attempt at solving the problems.
The EP A is willing to take the risks that come with applying innovative treatment
technologies because their potential for comparable or superior performance, less severe
impacts, and reduced costs is very promising as compared to the proven technologies
(OSWER Pub!. No. 9380.3-05FS, February 1991; OSWER Dir. 9380.0-17, June 1991).
Immobilization is one such innovative treatment technology that has shown promising
results. Immobilization is a term used in connection with any of the various technologies
that limit the solubility or mobility of contaminants. The term "fixation" is a synonym for
immobilization (OSWER Pub!. No. 9380.3-07FS, February 1991).
The various immobilization, or fixation technologies limit contaminant solubility or mobility
with or without a change in the physical characteristics of the matrix. Immobilization may
involve physical or chemical processes, or a combination of them, to accomplish the
objective. It is not a destructive technique; rather, it prohibits or impedes the mobility of
the contaminants.
Immobilization has proven effective for many inorganic contaminants, particularly metals.
Thus, immobilization will generally constitute treatment of wastes to reduce toxicity, mobility
or volume when metals are the contaminant of concern and there are compelling reasons
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for selecting this technology over removal, destructIon, or more conventional treatment
technologies (OSWER Pub!. No. 9380.3-07FS, February 1991).
The remedy selected for the inactive area includes, as a major component, the chemical
fixation (or immobilization) of metals contai~ed in the tailings, pond bottom sediments and
contaminated soils. Tailings, a by-product of milling processes, contain unrecovered
amounts of metals-principally metal sulfides. In the current environment, the metal sulfides
begin to oxidize due to contact with air and water. This oxidation process generates acid
waters and solubilizes the metals which then contaminate surface and ground waters. This
chemical fixation process involves the incorporation of lime, which is an alkaline material,
over and into the contaminated materials. In addition, a lime slurry (lime dissolved in
water) can also be added to the already dry materials to carry the lime deeper into the
contaminated soil horizon. Once the contaminated area is chemically fixed, it will be
flooded and the water level will be maintained.
By maintaining an alkaline dominant system over and within the tailings, the oxidation of
the metal sulfides can be prevented. Hence, the metals are immobilized since they cannot
dissolve and enter the underlying or overlying water. Any metals already dissolved in the
pore waters within the saturated tailings, will precipitate as insoluble metal hydroxides and
thus be immobilized. Excess lime will be added to exceed the acid generation potential of
the metal sulfides in the tailings so that the fixation process becomes permanent.
Wet closure and chemical fixation with lime is not a suitable mechanism for controlling
arsenic. In fact, addition of the lime enhances the mobility of arsenic. Fortunately, within
the inactive area, there is a relatively low concentration of arsenic available. Its release and
movement are not expected to be substantial; however, if that expectation proves to be
inaccurate, the interception trench will collect all contaminated water and a pump-back
system will prevent contaminants from entering the Clark Fork River and the ground water
beyond the interception trench.
The additional benefits associated with wet closure and chemical fixation are the wetlands
that will be formed and enhanced. The neutralized tailings will permit vegetative groWth,
the flooded areas will provide waterfowl habitat, and the ground water flowing from the
system is expected to improve to the point that interception, pumping and treatment will no
longer be necessary. The EPA expects such an improvement to occur over a period of a few
years, not decades.
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ATTACHMENT 1 TO PART II
INSTITUTIONAL CONTROLS
FOR THE
WARM SPRINGS PONDS INACTIVE AREA OPERABLE UNIT (OU U)
SILVER BOW CREEK/BUTTE AREA NPL SITE (original portion)
UPPER CLARK FORK RIVER BASIN, MONTANA
1.
Implementation of a conservation easement with restrictive covenants by ARCa for
the Inactive Area, to ensure that future development will not include residential use,
and will not cause disruption of disposal areas or waste ponds.
2.
Implementation of a permit development system, in cooperation with
Anaconda/Deer Lodge County and ARCa, which will prevent residential
development at the Warm Springs Ponds. The permit system includes the
development of a master plan, which will designate the ponds as a wildlife refuge.
3.
Implementation of a water well ban for the Inactive Area. The water well ban shall
prohibit water wells within the waste units at the Inactive Area permanently or until
such time as ARARs are achieved for the ground water.
4.
Implementation of a ban on swimming in the ponds of the Inactive Area, to be
accomplished through the posting of appropriate signs.
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ATTACHMENT 2 TO PART II
APPLICABLE OR RELEVANT AND APPROPRIATE
REQUIREMENTS, STANDARDS, CONTROLS, CRITERIA, OR LIMITATIONS
AND OTHER PERFORMANCE STANDARDS
FOR THE
WARM SPRINGS PONDS INACTIVE AREA OPERABLE UNIT
SILVER BOW CREEK/BUTIE AREA NPL SITE (original portion)
UPPER CLARK FORK RIVER BASIN, MONTANA
Section 121(d) of CERCLA, 42 D.S.C. Section 9621(d), certain provisions of the current
National Contingency Plan (the NCP), 40 CFR Part 300 (1990), and guidance and policy
issued by the Environmental Protection Agency (EP A) require that remedial actions taken
pursuant to Superfund authority shall require compliance with substantive provisions of
applicable or relevant and appropriate standards, requirements, criteria, or limitations from
State environmental and facility siting laws, and from federal environmental laws (commonly
referred to as ARARs) at the completion of the remedial action, and/or during the
implementation of the remedial action, unless a waiver is granted. These requirements are
threshold standards that any selected remedy must meet. The Feasibility Study for the
Warm Springs Ponds operable unit proposed a set of such requirements, and gave
justification for identifying the proposed requirements. After consideration of public
comments on the proposed requirements, and further review of applicable guidance and
standards including the NCP, ARARs for the Warm Springs Ponds area were further refined
in the Warm Springs Ponds Active Area Record of Decision (EPA, 1990) and its
Explanation of Significant Differences and Errata Sheet (EPA, 1991). The following list of
ARARs for the Warm Springs Ponds Inactive Area operable unit is based on the Active
Area ARARs and further refinements learned by EP A as it implements various cleanups
throughout the Oark Fork Basin Superfund Sites.
Each ARAR or group of related ARARs is identified by a specific statutory or regulatory
citation, and a compliance description which addresses how and when compliance with the
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ARAR will be measured (some ARARs will govern the conduct of the implementation of
the remedial action, some will govern the measure of success of the remedial action, and
some will do both). Contaminant specific ARARs are followed by a description of the point
of compliance, which describes where compliance with the ARAR will be measured.
Also contained in this list are references to lists of policies, guidances or other sources of
information which are "to be considered" during the selection and implementation of the
ROD. Although not enforceable requirements, these documents are important sources of
information which EP A and the State of Montana Department of Health and Environmental
Sciences (MDHES) referred to during selection of the remedy, especially in regard to the
evaluation of public health and environmental risks; or which will be referred to as
appropriate during evaluation and approval of various activities during the ROD
implementation.
Finally, this list contains other legal provisions or requirements which should be complied
with during the implementation of this ROD.
The portions of the original" Warm Springs Ponds Feasibility Study (FS) which address
ARARs (primarily Chapter 3 and Appendix B), the portions of the Warm Springs Ponds
Active Area ROD, as amended, which address ARARs (primarily Part II, Section 5, and
Part ill, Subpart A, Section 2.3, and Subpart B, Section 3~O), and applicable EP A guidance,
policy, regulation, and statutory authority, form the basis for the final selection of ARARs
contained in this list. Responses to new comments on ARARs received during the Inactive
Area comment period are contained in Part ill of this Record of Decision.
ARARs are divided into contaminant specific, location specific, and action specific
requirements, as described in the new NCP and EP A guidance. Each category contains both
federal and State ARARs. For contaminant specific ARARs, ARARs are listed according
to the appropriate media.
Contaminant specific ARARs address chemical or physical characteristics of compounds or
substances on sites. Contaminant specific ARARs generally set health or risk based
ATTACHMENT 2 TO PART II
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numerical values or methodologies which, when applied to site-specific conditions, result in
the establishment of numerical values. These values establish the acceptable amount or
concentration of a chemical that may be found in, or discharged to, the ambient
environment.
Location specific ARARs are restrictions placed on the concentration of hazardous
substances or the conduct of cleanup activities because they are in specific locations.
Location speCific ARARs relate to the geographic or physical position of the site, rather
than to the nature of the contaminants at sites.
Action specific ARARs are usually technology or activity based requirements or limitations
on actions taken with respect to hazardous substances. For action specific ARARs, certain
provisions pertain to the entire cleanup action and are so indicated. Other ARARs pertain
to specific portions of the cleanup, and are so indicated.
Only substantive portions of the listed requirements are ARARs. Administrative and
procedural requirements are not ARARs, and need not be attained during or after site
cleanups. Administrative and procedural requirements are those which involve consultation,
issuance of permits, documentation, reporting, recordkeeping, and enforcement. The
CERCLA program has its own set of administrative procedures which assure proper
implementation of CERCLA. The application of additional 'or conflicting administrative or
procedure requirements could result in delay and .confusion. The only exception to this
involves the application of State of Montana water use law to activities contemplated at the
site. Because the substantive provisions of those laws are closely tied to procedural rights,
EP A has recommended that the potentially responsible party, ARCO, apply' for any
necessary water right permit or otherwise comply with State water right law, where water
rights are implicated by the cleanup activities contemplated by this ROD. This is a narrow
exception to the general principle described above, and EPA has reserved its right to review
this decision if significant delay is caused by separate water rights proceedings.
CERCLA authorized actions which are conducted on-site are exempt from permit
requirements, pursuant to section 121(e) of CERCLA, 42 U.S.c. ss~ 9621(e). This
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exemption applies to all activities contemplated by this Record of Decision. However, as
noted in the paragraph above, EP A has recommended to the potentially responsible party
that a narrow exception to this rule be observed for water rights issues.
Many requirements listed here are promulgated as identical or near identical requirements
in both federal and State law, usually pursuant to delegated environmental programs
administered by EPA and the States, such as the requirements of the federal Clean Water
Act and the Montana Water Quality Act. The preamble to the new NCP states that such
a situation results in citation to the State provision as the more stringent standard, but
treatment of the provision as a federal requirement.
The scope of this Interim Record of Decision
EP A guidance establishes that interim actio~, such as removal actions or interim remedial .
actions, need not meet all ARARs potentially implicated at an operable unit. Rather,
removals or interim actions must comply with ARARs which address the specific scope of
the removal or interim action.
The Warm Springs Ponds Inactive Area Remedial Action is an interim action, in that it will
be reviewed after implementation of upstream cleanup activities and cleanup activities at
the Ponds. Nevertheless, the action is meant to be a permanent action which addresses site
conditions comprehensively. Accordingly, all of the ARARs listed here are within the scope
of this interim action. .
Final action levels in soils and contaminated materials for protection of human health and
the environment for the various contaminants found at the Warm Springs Ponds Inactive
Area are not identified in this Record of Decision. Ongoing risk assessment work at other
operable units within the Oark Fork Basin will determine those action levels. Compliance
with a final action level is expected to be achieved with this cleanup (refer to Part II,
Section 6.7). This issue will be reviewed before a final cleanup is selected or declared for
the entire Warm Springs Ponds area.
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I.
A
1.
CONTAMINANT SPECIFIC ARARS AND PERFORMANCE STANDARDS
Groundwater
Maximum Contaminant Limits and nQn-zero Maximum Contaminant Limit Goals for
contaminants of concern at the site, promulgated pursuant to the Safe Drinking
Water Act, 42 U.S.c. sS~ss~ 300f et seq. and the Montana Public Water Supplies Act,
MCA sS~ss~ 75-6-100 et seq. Regulations establishing specific limits are found at 40
CFR sS~ss~ 141.11 - .16 and ARM sS~ss~ 16.20.203 - .205, .1002, .1003, and .1011.
These standards in part are also required by the Resource Conservation and
Recovery Act, 42 U.S.c. ~ 6901 et seq. and 40 CFR Sl~ 264.94, and corresponding
State of Montana statutes and regulations.
Specific limits are:
0.050 milligrams per liter (mgfl)
0.010 mgfl
0.050 mgfl
0.050 mgfl
0.002 mgfl
Arsenic
Cadmium
Chromium
Lead
Mercury
Nitrate
(as N) 10.000 mgfl
These standards must be met immediately north of the ground water interception trench,
outside of the wet closure cells below Pond 1, after implementation of the remedial action.
Compliance with these standards will also achieve compliance with the State of Montana
non-degradation standard for ground water, ARM Sl~ 16.20.1011.
B.
Ground water well construction criteria, certain provisions of MCA sS~ 85-2-505
which are described below (the Montana Water Use Act).
Additional contamination of ground water through construction of ground water wells
is prohIbited.. Ground water wells must be constructed and maintained so as to
prevent waste, contamination, or pollution of ground water. Activities cannot result
in the degradation of ground water, in accordance with ARM SI~SS~ 16.20.203, .204,
.206, .207, .1002, .1003, and .1011.
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TI.
Surface Water
A.
Ambient Standards
State of Montana surface water quality standards and federal water quality criteria,
or appropriate replacement values for those standards and criteria which are waived,
must be met for in-stream ambient water at or near the site (that is, water within the
reconstructed Lower Bypass, and the water entering the Clark Fork River). These
standards are enacted pursuant to the section 304 of the Clean Water Act, 42 D.S.C.
Sl~ 1314 and the "Gold Book" (aka Water Quality Criteria for Water. 1986); and the
Montana Water Quality Act, MCA SI~SI~ 75-5-101 et seq. and ARM S'gS'g
16.20.618(2) and 16.20.622(2). The Clark Fork River is a Class C-2 river and the
Mill and Willow creeks are Class B-1 streams - see ARM SI~S'~ 16.20.604, .618, and
.622.)
Specific limits are:
0.082 mg/lu
Chronic
0.19 mg/l
0.048 mg/l
0.02 mg/l*
0.0011 mg/l**
0.012 mg/l**
1.0. mg/l
0.0032 mg/l* *
0.2 ug/l *
0.11 mg/lu
Arsenic (Ill)
Arsenic (V)
Arsenic (Total)
Cadmium
Copper
Iron
Lead
Mercury
Zinc
Acute
0.36 mg/l
0.85 mg/l
0.0039 mg/l**
0.018 mg/l* *
0.12 mg/l**
* Indicates that the standard is a replacement standard for a standard which is waived,
pursuant to section 121(d)(4)(A) and (C) of CERCLA. See Warm Springs Ponds Active
Area Record of Decision (EPA, 1990).
n The value identified is based on an assumed hardness of 100 mg/l. The actual standard
will be based on measured hardness at the compliance point.
Dissolved Oxygen - Dissolved oxygen concentration may not be reduced below 7.0 mg/l.
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pH - Induced variation of pH within the range of 6.5 to 9.5 must be less than 0.5 pH unit.
Natural pH outside "this range must be maintained without change. Natural pH above 7.0
must be maintained above 7.0.
Turbidity - The maximum allowable increase above naturally occurring turbidity is 5
nephelometric turbidity units except for short-term construction or hydraulic projects, game
fish population restoration, as allowed in ARM sS~ 16.20.633.
TemperaJure - A 1 degree F maximum increase above naturally occurring water temperature
is allowed within the range of 32 degrees to 66 degrees F; within the naturally occurring
range of 66 "degrees F to 66.5 degrees F, no discharge is allowed which will cause the water
temperature to exceed 67 degrees F; and where the naturally occurring water temperature
is 66.5 degrees F or greater, the maximum allowable increase in water temperature is 0.5
degrees F. A 2 degree F-per-hour maximum decrease below naturally occurring water
temperature is allowed when the water temperature is above 55 degrees F, and a 2 degree
F maximum decrease below naturally occurring water temperature is allowed within the
range of 55 degrees F to 32 degrees F. "
Sediment, etc. - No increase is allowed above naturally occurring concentrations of sediment,
settleable solids, oils, or floating solids which will or are likely to create a nuisance or render
the waters harmful, detrimental, or injurious to public health, recreation, safety, welfare,
livestock, wild animals, birds, or other wildlife.
Color - True color must not be increased more than 5 units above naturally occurring color.
These standards must be met at the point of compliance, which will be within the
reconstructed bypass channel upstream of the confluence with Warm Springs Creek. This
point will be further defined in design documents developed for implementation of the
Warm Springs Ponds Inactive Area remedy. These standards must be met at the conclusion
of this remedial action implementation, or at the conclusion of the Active Area remediation
including the shakedown period, whichever comes later.
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Appropriate in-stream monitoring must be implemented to measure in-stream values, if such
monitoring is not already implemented as part of the Active Area remediation or the Clark
Fork Basin monitoring effort.
If exceedences of the in-stream standards can be demonstrated by the potentially responsible
party to be caused by contamination which is unrelated to the Warm Springs Ponds Active
and Inactive Area operable units, these ARARs and Performance Standards will not be
considered to be violated.
Compliance with these standards will constitute compliance with the State of Montana's
non-degradation standards, promulgated pursuant to the Montana Water Quality Act,
MCA sS~ 75-5-303, and ARM sS~ 16.20.702.
m. Air Standards
Standards related to air pollution are promulgated pursuant to the Clean Air Act, 42 U.S.c.
sS~ss~ 7401 et seq. and the Clean Air Act of Montana, MCA ss~ss~ 75-2-102 et seq., more
specifically the standards identified below.
A
B.
ARM sS~ 16.8.1401(2), (3), and (4). Airborne particulate matter. There shall be no
production, handling, transportation, or storage of any material, use of any street
road or parking lot, or operation of a construction site or demolition project unless
precautions are taken to control emissions of airborne particles. Emissions shall not
exhibit an opacity exceeding 20% or greater averaged over 6 consecutive minutes.
This provision must be complied with at the site during remedial action
implementation activities.
ARM sS~ 16.8.1404(2). Visible Air Contaminants. Emissions into the outdoor
atmosphere shall not exhibit an opacity of 20% or greater averaged over 6
consecutive minutes. This provision must be complied with at the site during
remedial action implementation activities.
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C.
D.
E.
F.
G.
ARM s'~ 16.8.1427. Nuisance or odor bearing gases. Certain gases (excluding diesel
gases from vehicles), vapors, and dusts must be controlled such that no public
nuisance is caused. This provision must be complied with at the site during remedial
action implementation activities. Compliance with this provision at the site will assure
that no public nuisance occurs.
ARM sS~ 26.4.761. Fugitive dust control. Practicable fugitive dust control measures
must" be planned, through description of appropriate measures in design documents
subject to EP A approval, and implemented during excavation activities.
ARM sS~ 16.8.815. Lead. The concentration of lead in ambient air shall not exceed
a 90 day average of 1.5 micrograms per cubic meter of air. This provision must be
complied with at the conclusion of the remedial action implementation.
ARM s'~ 16.8.818. Settled particulate. Settled particulate shall not exceed a 30 day
average of 10 grams per square meter. This provision must be complied with at the
conclusion of the remedial action implementation.
ARM sS~ 16.8.821. PM-10. The concentration of PM-10 in ambient air shall not
exceed a 24 hour average of 150 micrograms per cubic meter of air and an annual
average of 50 micrograms per cubic meter of air. This provision must be complied
with at the conclusion of the remedial action implementation.
IV. Soils and Contaminated Material and Mining Waste
Contaminated soils and other mining waste found within the Warm Springs Ponds Inactive
Area will be remediated through dry closure and capping, excavation, and chemical fixation
and wet closure, as described in the ROD text. All such material which meets or exceeds
the following criteria shall be addressed through the Warm Springs Pond Inactive Area
remediation, in a manner consistent with the Warm Springs Ponds Inactive Area ROD and
as approved by EP A
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Color shall be used as the primary criterion. Discolored materials shall be remediated.
Discolored materials are readily identified visually by discoloration compared to the natural
color of adjacent materials.
Texture shall be used as a secondary criterion for remediation. Soils or waste materials
which are fine grained shall be remediated. Fine grained materials can be distinguished
from coarse grained materials by identifying coarse sand, gravel, or cobbles (Refer to section
2.1 of the Mill-Willow Bypass Removal Work Plan).
Following remediation of the above identified materials, the contaminant concentrations of
soils and waste material remaining after remediation are expected to exhibit the range of
concentrations shown in the table addressing this issue in Part II, Section 6.7. H this range
is not exhibited, remediation shall continue until the range is exhibited, in a manner to be
approved by EP A
2.
LOCATION SPECIFIC ARARS AND PERFORMANCE STANDARDS
1. Floodplain and Floodway Management Act Standards
A.
Structures such as parks and wildlife management areas are permitted within
floodplains, in accordance with the substantive provisions of MCA s'~ 76-5-402.
B.
Flood control works are permitted in the floodplain and floodway, if they are
protective to the 100 year flood frequency flow, in accordance with the substantive
provisions of ARM s'~ 36.15.606.
c.
Construction and remediation activities must minimi7.e potential harm to the
floodplain and improve natural and beneficial values of the floodplain, in accordance
with the substantive provisions of 40. CFR s'~ 6.302(b) and Executive Order No.
11,988.
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D.
The Inactive Area facilities must be designed, constructed, operated, and maintained
to avoid washout to the 100 year floodplain, in accordance with ARM s'~16.44.702,
as that section incorporates 40 CFR Sl~ 264.18( a) and (b).
ll. Natural Streambed and Land Preservation Act Standards
A.
Soil erosion and sedimentation to Montana rivers must be kept to a minimum, in
accordance with MCA SI~SS~ 75-7-102, -104, -105, and -111, and ARM sS~36.2.404.
This ARAR is particularly important during construction activities, and must be met
through adequate design and implementation practices.
III. Historic Preservation Standards
A.
B.
Identified or eligible cultural resources shall be identified and the impact of the
Warm Springs Ponds Inactive Area remediation on those resources must be avoided
or mitigated. Performance Standards for notification and documentation of cultural
and historic resources are those procedures established by the Programmatic
Agreement, in accordance with the substantive provisions of 40 CFR Sl~ 6.301(b) and
36 CFR Part 800.
If significant scientific, prehistorical, historic, or archaeologic data is found at the
Warm Springs Ponds Inactive area, it must be preserved in an appropriate manner,
in accordance with the substantive provisions of 40 CFR Sl~ 6.301( c).
IV. Wetlands Protection Standards
An inventory of wetlands at the Warm Springs Ponds Inactive area as they existed prior to
any cleanup activities must be compiled and approved. Activities must be conducted so as
to avoid or minimize destruction of wetlands. If destruction is not avoidable, wetlands must
be replaced and} or restored to ensure that no net loss of wetlands will occur as a result of
the cleanup activities (past and present) at the Warm Springs Ponds Inactive area, in
accordance with the substantive provisions of 40 CFR Sl~ 6.302(a) and 40 CFR Part 6,
Appendix A and Executive Order No. 11,990.
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It has been noted by EP A and the consulting agencies that cleanup activities within the Mill
Willow Bypass and other areas of the Warm Springs Ponds Active Area, have exhibited
adverse impacts on wetlands habitat. Therefore, all efforts directed toward reconstruction,
reclamation and restoration, or other similar activities planned by the potentially responsible
party must be done as part of the remedial action implementation process, to ensure
compliance with this standard.
v. Endangered Species Protection Standards
Bald eagles and peregrine falcons have been identified as users of the Warm Springs Ponds
Inactive Area. Appropriate mitigative measures during construction activities must be
followed, and additional biological surveys or other studies may be required, in accordance
with the substantive provisions of the Endangered Species Act, 16 V.S.C. Sl~ 1531 et seq., .
and 50 CFR Parts 17 and 402, and 40 CFR Sl~ 6.302(h).
VI. Fish and Wildlife Coordination
In accordance with the Fish and Wildlife Coordination Act, 16 V.S.C. Sl~ 1531 et seq.. and
40 CFR Sl~ 6.302(g), remediation activities at the Warm Springs Ponds Inactive Area shall
provide adequate protection of fish and wildlife resources. This requirement must be met
during implementation of the remedial activities and at. the conclusion of the remedial
action activities. EPA will consult with the V.S. Fish and Wildlife Service and the Montana'
Department of Fish, Wildlife and Parks to ensure that design plan and remedial activities
comply with this ARAR.
VII.
Waste Disposal Siting Restrictions
Relevant and appropriate RCRA siting requirements, found at ARM Sl~ 16.44.702, which
incorporates by reference 40 CFR Sl~ 264.18(a) and (b), prohibit disposal of wastes within
200 feet of a fault, and impose certain conditions on waste disposed of within a flood plain.
Relevant and appropriate solid waste siting requiremerits, found at ARM SI~SI~ 16.14.505
and .523, prohibit disposal of solid waste within the 100 year flood plain. Because the
ATIACHMENT 2 TO PART II
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berming and other remedial activities will ensure that the Pond 1 area and the wetlands
closure area below Pond 1 will be outside of a re-engineered flood plain, these ARARs are
satisfied through implementation of the Record of Decision activities, and through
appropriate design, construction, operation, and maintenance of the remediated area. If it
is determined that the remediated areas are within the flood plain, EP A invokes an ARAR
waiver pursuant to section 121(d)(4)(A) of CERCLA, 42 U.S.c. Sl~ 9621(d)(4)(A) which
applies to ARM sl~16.14.505(c).
3.
ACTION SPECIFIC ARARS AND PERFORMANCE STANDARDS
The remedy for the Warm Springs Ponds Inactive Area requires the excavation and
reconstruction, reclamation, and restoration of the Lower Bypass Channel, which includes
creation of a new channel in the lower portion of the bypass, creation of wet closure cells'
which will function as wetlands within Pond 1 and below Pond 1, creation of a dry closure
cell for the western portion of Pond 1, strengthening of existing pond berms and
construction of a new berm, development of a ground water interception system at the
northern boundary of the area below Pond 1, and implementation of necessary surface water
and ground water monitoring. Following are ARARs and Performance Standards for these
aspects of the remedial action.
1.
Reconstruction/Reclamation/Restoration of the Lower Bypass Channel
The Warm Springs Ponds Inactive Area remediation will include the excavation and
reconstruction, reclamation, and restoration of the bypass channel from the Pond 2 discharge
point to the current northern end of the bypass. (The bypass from its southern. boundary
to Pond 2 discharge point is addressed in the Warm Springs Ponds Active Area action). In
addition to the contaminant specific and location specific standards identified above, further
cleanup work in the Bypass and any following reconstruction, restoration, and/or
reclamation work must comply with the following requirements:
A
Substantive provisions of the dredge and fill requirements must. be met, in
accordance with 40 CFR Parts 230 and 231 and 33 CFR Parts 323 and 330.
ATTACHMENT 2 TO PART II
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B.
"c.
D.
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Reclaimed drainages must be designed to emphasize channel and floodplain
dimensions that will blend with the undisturbed drainage above and below the area
to be reclaimed. The channel must be restored to a more natural configuration with
geomorphically acceptable gradient. Reclamation must provide for long-term
stability of the landscape, establishment or restoration of the stream to include a
diversity of aquatic habitats (generally a meandering series of riffles and pools), and
restoration enhancements, or maintenance of natural riparian vegetation, in
accordance with the substantive provisions of ARM s'~ 26.4.634.
Temporary diversion structures at the Bypass or nearby creeks must be constructed
to safely pass the peak run-off from a precipitation event with a lO-year, 24-hour
recurrence interval. Channel lining must be designed using standard engineering
practices such as riprap, to safely pass designed velocity. Free board must be no less"
than 0.3 feet, all in accordance with the substantive provisions of ARM s'~ 26.4.636.
Reclamation and revegetation requirements described below in Section m. must be
met.
As noted above, reconstruction, reclamation, and restoration measures are required for the
Lower Bypass area pursuant to this action, in part to ensure compliance with the standards
regarding no net loss of wetlands at the Warm Springs Ponds.
II. General Reclamation and Revegetation Standards
The Warm Springs Ponds Inactive Area remediation requires excavation of contaminated
areas at the existing Lower Bypass channel and possibly in the area below Pond 1, and the
consolidation and dry capping of contaminated areas, which will result in the creation and
maintenance of a disposal area within the Pond 1 berm. All of these areas must be
reclaimed and revegetated. For those activities, the following standards apply:
A
The disposal "unit and other reclaimed areas must be covered with clean soil and
revegetated in an appropriate manner, consistent with the Timber Butte removal
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B.
ill.
action and work plan, in accordance with the substantive provisions of 30 CFR ss~
816.111.
Revegetation of any excavated, capped in place area, disposal area, or other land
area disturbed or addressed by this action must comply with the substantive standards
of ARM sS~s.~ 26.4.501(3)(a), .501(A)(1)(a), .520(4), .631, .638, .640(1), .644(1), and
.761, and MCA sS~ss~ 82-4-231 and -233.
Dry Disposal Area within Pond 1 Standards.
The Warm Springs Ponds Inactive Area remediation requires the creation and maintenance
of a dry disposal area within the Pond 1 berm. The construction and maintenance of these
areas must comply with the following standards:
A
B.
All waste placed within the disposal areas must be drained of free liquids, and
stabilized appropriately, in accordance with the substantive provisions of 40 CFR sS~
264.228(a)(2)(i), which is incorporated by reference into ARM s'~ 16.44.702.
Closure of the disposal areas must be done in such a manner as to minimize the
need for further maintenance and to control, minimize, or eliminate, to the extent
necessary to protect public health and the environment, post-closure escape of
hazardous substances, hazardous constitue~ts, leachate, contaminated run-off or
hazardous substance decomposition products to the ground water or surface waters
or to the atmosphere, all in accordance with the substantive provisions of 40 CFR sS~
264.111, which is incorporated by reference into ARM s'~ 16.44.702. This standard
does not require an impermeable cap or liners.
c.
Disposal facility covers for the unit must function with minimum maintenance,
promote drainage, and minimize erosion or abrasion of the final cover, and
accommodate. settling and subsidence, in accordance with 40 CFR sS~
264.228(a)(2)(iii)(B), (C), and (D), and 40 CFR ss~ 264.251(c),(d), and (f) which are
incorporated by reference into ARM s'~ 16.44.702.
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D.
.'
The potentially responsible party must submit to the local land use or zoning
authority a survey plat indicating the location and dimensions of waste disposed of
in each unit. Additionally, the Respondent must record a deed restriction, in
accordance with State law, that will in perpetuity notify potential purchasers that the
property has been used for waste disposal and that its use is restricted, in accordance
with the substantive provisions of 40 CFR SI~SI~ 264.116 and .119, which is
incorporated by reference into ARM Sl~ 16.44.702.
E.
The disposal area must be constructed in such a manner so as to comply with the
general handling, st~rage, and disposal requirements of 40 CFR SI~SI~ 257.3-1(a),
257.3-2, 257.3-3, and 257.3-4, which are incorporated by reference into ARM ss~
16.44.702..
F.
The potentially responsible party's waste can be disposed of on its own property, but
the disposal areas must not create a nuisance or a public hazard. Additionally, the
waste must be disposed of outside of the 100 year flood plain, must be disposed of
in a manner which prevents pollution of the ground or surface water, must contain
adequate drainage structures, and must prevent run-off from entering disposal areas;
and waste must be transported to the disposal areas in such a manner as to prevent
its discharge, dumping, spillage, or leaking, in accordance with the substantive
provisions of ARM SI~SI~ 16.14.505 and .523, and MCA Sl~ 75-10-214.
IV. Wet closure cell standards
A
B.
The wet closure cells must be designed and operated so as to comply ,with the
structural integrity requirements of 40 CPR Sl~ 264.221(g), which are incorporated
by reference into ARM Sl~ 16.44.702.
The potentially responsible party must submit to the local land use or zonmg
authority a survey plat indicating the location and dimensions of waste disposed of
in each unit. Additionally, the Respondent must record a deed restriction, in
accordance with State law, that will in perpetuity notify potential purchasers that the
ATIACHMENT 2 TO PART II
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D.
v.
property has been used for waste disposal and that its use is restricted, in accordance
with the substantive provisions of 40 CFR S'~S'~ 264.116 and .119, which is
incorporated by reference into ARM S'~ 16.44.702.
c.
The disposal area must be constructed in such a manner so as to comply with the
general handling, storage, and disposal requirements of 40 CFR S'~S'~ 257.3-1(a),
257.3-2, 257.3-3, and 257.3-4.
The potentially responsible party's waste can be disposed of on its own property~ but
the disposal areas must not create a nuisance or a public hazard. Additionally, the
waste must be disposed of outside of the 100 year flood plain, must be disposed of
in a manner which prevents pollution of the ground or surface water, must contain
adequate drainage structures, and must prevent run-off from entering disposal areas;
and waste must be transported to the disposal areas in such a manner as to prevent
its discharge, dumping, spillage, or leaking, in accordance with the substantive
provisions of ARM S'~S'~ 16.14.505 and .523, and MCA S'~ 75-10-214.
Berm Strengthening Standards
The berms within the Warm Springs Ponds Inactive Area will be remediated by
strengthening the berms against floods and earthquakes. The berm strengthening actions
must comply with the following standards:
A
The North South berm adjacent to Pond 1 and the new berm extension.
1.
The berm, which is an integral element of a high hazard dam syste,m, must
comply with the criteria given in ARM S'~ 36.14.501, including compliance
with the Maximum Credible Earthquake standards.
2.
The berm, which is an integral element of a high hazard dam system, must be
able to withstand the calculated design flood (0.5 Probable Maximum Flood)
in accordance with the substantive provisions of ARM S'~ 36.14.502. The
ATIACHMENT 2 TO PART II
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reconstructed lower bypass channel adjacent to this berm must be designed
to safely pass the design flood.
B.
The Existing East-West aspect of the Pond 1 Berm
1.
The berm must store water and contaminated sediments in a secure, thorough,
and substantial and safe manner, in accordance with the substantive provisions
of MCA sS~ss~ 85-15-207 and 208.
2.
The berm, which is an integral element of a high hazard dam system, must
comply with the criteria given in ARM Sl~ 36.14.501, including compliance
with the Maximum Credible Earthquake standards.
VI.
- Ground Water -Monitoring Standards
The Warm Springs Ponds Inactive Area remediation requires the monitoring of ground
water at the ground water interception trench, to ensure compliance with the ground water
standards described in the Contaminant Specific ARARs and Performance Standards
Section. Such activities must comply with the following standards:
A
Standards established in 40 CFR Sl~ 264.97, which is incorporated by reference into
ARM Sl~ 16.44.702, must be complied with. Only contaminants for ground water
identified in this -ROD must be monitored.
VII. Surface Water Monitoring Standards
Ambient surface water standards are required to be met by this remedial action, in the
manner described above. Adequate surface water monitoring, to the extent such monitoring
does not exist as part of the Active Area monitoring program or the Oark Fork Basin
monitoring program; must be implemented to measure compliance with those standards.
ATIACHMENT 2 TO PART II
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4.
OTHER LAWS
In addition to the environmental or siting standards identified above, the State of Montana
has identified a list of other State laws which should be complied with during the conduct
of site remediation and maintenance activities. These are:
1.
TI.
ill.
IV.
To the extent applicable, noise levels for protection of on-site workers must be met,
as described in ARM s'~ 16.42.101.
The Occupational Health and Safety Act, 20 D.S.C. S'~S'~ 651 - 678, and
implementing regulations must be complied with. Particularly, 29 CFR Part 1926 and
29 CFR S'~S'~ 1910.120 and .132 must be complied with. The Respondent is required
to submit and follow a site specific Health and Safety Plan for conduct of activities
at the Warm Springs Ponds Inactive Area.
To the extent it is applicable, substantive provisions of the Montana Safety Act, MCA
S'~ 50-71-201 must be complied with.
To the extent applicable, the Employee and Community Hazardous Chemical
Information Act must be complied with, in accordance with the substantive provisions
of MCA S'~S'~ 50-78--202, -203, -204, and -305. .
Ground Water Well Drilling and Monitoring
v.
VI.
H ground water w~lls are determined to be necessary, well drillers must be licensed
and registered as stated in ARM S'~s'~ 36.21.402, .403, .405, .406, .411, .701, and .703.
Ground water wells must be logged and reported to the Department of Natural
Resources Conversation, as stated in MCA S'~ 85-2-516.
ATIACHMENT 2 TO PART II
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Water use rights
VII.
To the extent applicable, any remedial activities at the Warm Springs Ponds Inactive
Area must comply with the substantive provisions of MCA SI~SS~ 85-2-301, -306, -311,
and -402, and MCA ss~ss~ 75-7-104 and.87-5-506, and implementing regulations found
at ARM SI~SS~ 36.16.104 - .106, and 26.4.648.
5.
TO BE CONSIDERED
A list of documents which EP A, in consultation with the State,. relied on in assessing
potential risk at the Warm Springs Ponds area, or which may be relied on in reviewing and
approving Warm Springs Ponds Inactive Area actions is included in the Warm Springs Ponds
Active Area Record of Decision, and is incorporated by reference. EP A reserves the right
to supplement this list at any time.
A'ITACHMENT 2 TO PART II
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1
June 17, 1992
DEPARTMENT OF
HEALTH AND ENVIRONMENTAL SCIENCES
ITA" snpHZHS. GOVU"OR
'AX' (4Ot) 443.7312
STATE OF MONTANA
omcz
LOCATJON.
8\.8...bo.' Dl_1<
818 H.l.... "".11"., R.... )02
Talephon.: (4OG) 4411.4087
MAIUNG
ADDIUS..
COG.W.U a..III1I1111
H.leu. NT 111820
ENV:FI(INME~T 1\1.
prK>TECJ'nON AGI:NCY
JUN ? 3 w~,
MONTAN,A, OFFICE
Mr. John F. Warden
U.S. Bnvironmental Protection Agency
,Drawer 10096, Federal Bui1ding
301 South Park
Helena, Montana 59626-0096
Dear Mr. WardeD:
MDHES ConcurTence with Selccted Remedy, Silver Bow Creek/Butte Area NPL
Site, Warm Springs Ponds Inactive Area '
By this letter, the' State of Montana, acting through the Department of Health and
Environmenta1 Sciences (MDHES), indicates its concurrence with BPA's selected remedy for
the Inactive Area of the Wann Springs Ponds Operable Unit, Silver Bow Creek/Butte Area NPL
Site. We expect to be able to provide concurrence with the Wann Springs Ponds Inactive Area
Record of Decision, but have not to date received a full draft document to review. We wjJ1
need to review the final published document prior to concurrence with the ROD.
Subject: '
At this time we are specifica11y cencumng with the selection of Alternative 5, as described in
the Wann Springs Ponds Inactive Area Proposed Plan (March 1992), as the selected remedy
for this site. The components .of the selected remedy include:
.
.
Dry closure' of the presently dry western portion of Pond 1;
Wet closure of the presently wet eastern portion of Pond 1;
Stabilization of the east-west benn of Pond 1 for maximum credible earthquake
(MCB) protection;
Upgrade of the north-south benn of Pond 1 for MCB protection and 0.5 probable
maximum flood (PMF) protection;
Wet c]osure of the tailings ]ocatcd below Pond 1, by construction of a series of
low dikes, lime addition, and flooding;
Groundwater interception by use of a trench in the existing MiU-Wi11ow Bypass
channel at the lower end of the wet closed area, with associated pumping
equipment to return intercepted groundwater to Pond 3 for treatment;
Extension of the O.S PMF flood-protection dike along the Mm- WiJJowBypass;
Construction of a new Mm- Wi110w Bypass channel to the west of tbe extended
flood-protection dike; ,
Construction of a new channel to intercept flood ronoff from the hiUs east of
Pond 1 and the area below Pond 1; and
Implementation of a bjological monitoring program to establish a means to
ev~uatc long-tenn recovery of the pond ecosystem.
.
.
.
.
.
.
.
.
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Mr. John F. Warden
June I', .1992
Page 2
MDHBS has made this concurrence after careful consideration of al1 11 alternatives that were
evaluated in detail. Several key considerations were weighed jn our evaluation and dedsion.
They included environmental impacts associated with removal of saturated taiJings, the abiHty
of wet closure to prevent metals mobiJity in groundwater, specific site conditions, such as the
volume and quality of groundwater discharge to lower Snver Bow Creek, and the potential
ilnpact of wet closure on residen~ and migrant species using the ponds.
r.
Based on our review, the following conclusions were drawn. First, those alternatives involving
total removal of both Pond 1 and the area below Pond J were rejected as causing short-tenn
environmental damage, having considerable uncertainties associated with the implementabiHty
and the effectiveness of removal of contamination, and being excessively expensive. A decision
regarding total removal of Pond I and below is more appropriately tIed to the final decision
regarding ultimate disposition of the entire Wanl1 Springs Ponds system. Second, those
alternatives involving dry closure of presently-wet areas of Pond I jp1d below were rejected
because of Joss of wetlands habitat, the difficulty of constnlcting that portion of the remedy,
and uncertainties related to the resulting mobi1ity of mctals in the saturated tailings to be dry
closed. Third, the two alternatives utilizing wet and dry closure of Pond 1 and either removal
(Alternative 4)' or wet closure (Alternative 5) were considered to be relatively equaJ in tenns
of overal1 protectiveness and compliance with ARARs. The final seJection of Alternative 5 was
based on the foUowing rationale.
We concur with BFA and its consultants that, in this specific situation, wet closure offers an
equal reduction in contaminant mobility in comparison with removal. Although we beJievc that
certain uncertainties attach to either the wet-closure or the removal option, we are convinced
that, in this instance, wet closure involves less uncertainty than removal. Uncertainties
associated with the removal option include the difficulty of construction in the saturated
materials, the degree to which contaminated materials can be cleaned out of tbe system using
dredging approac11cs, the manner in which cleanup would be confinncd once the remova1 is
complete, the oxidation of presently-reduced acid-generating materials and potential associated
increase in metals mobility m the groundwatcr, the type of surface conditions that would remain
at the site once the removal was complcte, and the extent of short-tenn destruction of cxisting
wetlands habitat..
Wet dosure of the area below Pond 1 also has some uncertainties attached to it. Although we
arc relatively sure that copper and zinc mobility can be effectively controned by maintenance
of high pH water in the wet-c]osure system, considerable question remains as to the reaction
of arsemc to this new system. Data from OUT Streambank TaiJings and Revegetation Studies
(STARS) indicate that the more toxic fonn of arsenic (Arsenic V) can become quite. mobile at
pH in the range of 7.S to 8. As the remedy is implemented we will need to observe cJoscJy
both the pathway for transport and potential ~eploTs of arsenic contamination within the
Inactive Area. Wet closure is also thought to be a lcss irreversible aJtemative than removal;
jf future monitoring indicates that wet closure is not working adequately, then another approach
may be possible at that time.. . . .
MDHES' belief that wet closure can be an effective remediation in this instance is largeJy
dependent on thc specific site conditions of the Inactive Area. These conditions incJudc the
fa~ts that a very limited amount of groundwater appears to be. discharging 1.0 the lowcr Mi1J-
Willow Bypass (and therefore the upper Clark Fork River) in this area, minor amounts of
groundwater contamination are found be10w Pond I relative to what might be expected beneath
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2.
Mr. John F. Wardell
June 17, 1992
Page 3 .
interception trench downgradient from the wet closures. MDHES specifically emphasizes that
the acceptance of wet.closure approaches in this instance should not be considered precedent
setting. Other sites may exhibit larger or more direct connection between the groundwater and
surface water, greater groundwater contarnin;ition, or other site.-specific ccnditions that may
require other remediation approaches for satUJdted tai)jngs, including removal.
MDHBS concurrence on this selected remedy is contingent upon satisfactory adherence to
conditions identified in the Proposed Plan and to be placed 011 ARCO by EP A in the Record
of Decision and subsequent RD/RA orders. These ccnditions include the foJJowing:
J.
Biological monitoring of the site needs to continue whiJe the wel closures are in place
until presentJy-unanswered questions about the long-tenn effect of contamination on the
ecology of the resident wetlands' species can be answered. MDHES supports the
development of a monitoring program that is directed to answer specific research and
decision-making objectives and is wen coordinated with simUar efforts undelWay on the.
Clark Fork River and at other basin Superfund sites. We insist tl1at both MDHBS and
the Department of Fish, Wildlife and Parks be fuJly involved in the development and
implementation of that biological monitoring program.
The reconstruction of the lower portion of the Mill-Willow Bypass should be undertaken
in a manner to enhance fishery habitat. That effol1 should be consistent with what wjJI
be undertaken tbis summer in the upper Bypass, and should be coordinated with both
MDHES and DFWP. We'd like to reiterate our comment on the Active Area Pinal
Remedial Design document noting that indiyjduals with appropriate expertise should be
on site during channel reconstruction to assure that appropriate fisheries habitat features
are incorporated.
3.
The evaluation of alternatives and the Proposed Plan were based, in part, on the
proyjsion that the existing east-west benn of Pond 1 will be strengthened to provide
protection from the maximum credib]e earthquake. The ARAR for earthquake protection
in the initial WSP ROD requires MCE protection for aU Pond system oonns. ARCO
apparently now questions the need to upgrade the Pond 1 cast-west benn and proposes
to rely on the new berm below Pond 1 to provide the required earthquake protection for
the tailings contained within Pond 1. MDHBS believes it essentia1 to retain the MCE
'protectiveness requirement for the Pond 1 east-west berm, so that the buffer zone
between the tailings in Pond J and the Clark Fork River can be maintained. That
buffer, including \he groundwater inte~tion trench downgradient of the wet closures I
would be ]ost in the event of earthquake faUure of the Pond 1 benn. The groundwater
interceptiontn:nch is critical to \he success of Alternative 5 in handling groundwater
contamination. MDHBS would likely evaluate differently the effectiveness of Alternative
5 relative to Alternative 4 if the probabiUty for faiJure of the Pond 1 east-we.~t hem} and
migration of Pond) tailings to the north were increased.
MDHES concurrence with the selected remedy is additionally contin¥ent up'0n EP A
satisfactorily addressing the concerns of MDHBS and the Department of FJsh, WJldJife and
Parks jn its final issuance of the Inactive Area ROD and the development of the RD/RA consent
or unilateral order. These concerns include the fonowing: . .
1.
Sincc the remedy seJected in this action wm require long-tenn maintenance to assure that
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Mr. John P. Warde11
June 17, 1992
Page 4
f!
2.
include conditions in the implementing orders that win assure that adequate financial
resources are avai1ab1e faT any future monitoring and maintenance necessary, for as long
as the remedy remains in place.
The design, construction, and operation of the new Mi1I- WH10w Bypass and the east hi11s
flood interception channel should be done in such a manner as to minimize sedimcnt
deposition in the upper Clark Fork River. Sediment loading due to construction over
the East two years has been considerable. To minimize future sediment 10ading, every
feasJbJe, prudent sediment reduction construction technique should be empJoyed.
3.
The draft Inactive Area ~rd of Decision that we have reviewed does not discus~
compliance monitoring for the ambient surface water quality ARAR. EP A technical stAff
has suggested that compliance cannot be required because upstream sources from Mi11
and WnIow Creek surface waters or Opportunity Ponds groundwater may be the cause
of noncompliance. BFA has indicated that the only monitoring required wouJd be for
the Pond 2 discharge and the Inactive Area groundwater. MDHBS disagrees with that
approach. Compliance with the ambient surface water quality ARAR, presumably after
completion of the Active Area shakedown period, is fundamental to implementation of
both the Active Area and the Inactive Area RODs. It was our understanding that
monitoring for ambient water quality ARAR compliance was deferred in accordance with
the Active Area ESD, but would be picked up under the Inactive Area action. We
bcJieve it essentiaJ that compliance monitoring for ambient surface water quality, at the
downstream boundary of the operabJe unit, be required at the conclusion of the
shakedown period. To understand the reasons for any exceedences of the aJnbicnt
surface water quality ARAR, it would a150 be prudent to monitor potential pertinent
source inputs to the system. These include MiU and Wi110w Creeks, the Pond 2
discharge, groundwater from the Opportunity Ponds, groundwater from the Inactive
Area, and groundwater from the Active Area. Without monitoring for ambient surface
water quality compliance, we have no way of knowing for sure whether surface water
leaving the operable unit meets the ARAR. Without monitoring the additional inputs
listed above, especia11y the three potential grouridwater inputs, we wm not know the
sources of exceedcJ1ccs. .
Although ARCO has committed verbally to some sort of demonstration remediation work
in the area between the Inactive Area and the Governor's Clark Fork Rivcr
Demonstration Project, the draft ROD is silent on tbis matter. As we have consistently
stated in our comments regarding the Inactive Area, acceptance of Alternative 5 as the
selected remedy is contingent upon implementation of demonstration remediation work
downstream of the newly defined operable unit boundary, in a timely manner, to avoid
impacts from sl.onn-event ronoff on the upper Clark Fork River near the Govemor's
project. We believe that such a commitment should be made in writing by both BPA
and ARCa and an appropriate mechanism set up to design, approve, conduct and
oversee the selected project.
MDHES concurrence in the selected remedy will not extend to a1terations or modifications that
may be made in the Record of Decision without consultation with and the ~nsent of MDHES.
MDHES concurrence a1so does not extend to EPA decisions during the design, implementation,
enforcement and review phases of subsequent remedial actions at the Warm Springs Ponds
Inactive Area unless such decisions are made with :MDHES consent.
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Mr. John F. Wardell
June 17, 1992
Page S
MDHES appreciates the opportunity to work with EPA in the development and implementation
of a remedy for the Wann Springs Ponds Inactive Area. We look forward to workjng with YOll
during remedjal design and remedial action. If YOll have any questions regarding this letter,
please feel free to call me. .
Sincerely,
Dennis Iverson, Director
cc:
Glenn Phillips, DFWP
Duane Robertson, SHWB
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