PB99-964404
EPA541-R99-072
1999
EPA Supei fund
Record of Decision:
California Gulch Site OU 2
Leadville, CO
9/28/1998
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1
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CALIFORNIA GULCH SUPERFUND SITE
OPERABLE UNIT 2
DECLARATION FOR THE RECORD OF DECISION FOR SOURCE
REMEDIATION AT OPERABLE UNIT 2 - SEPTEMBER 1999
SITE NAME AND LOCATION
CALIFORNIA GULCH NPL SITE ID # 29
CERCLISID COD980717938
OPERABLE UNIT-02
LEADVILLE, COLORADO
The California Gulch Superfund Site ("Site") is located in the Leadville,
Colorado mining district in Lake County approximately 10O miles southwest of
Denver. The California Gulch Site was listed on the National Priorities List on
September 8, 1983. The Site is in a mining area covering 16 % square miles of a
watershed that drains along California Gulch to the Arkansas River.
For ease of performance of remedial activities and administration of the Site
as a whole, the Site was divided into twelve Operable Units. These Operable
Units ("OUs") are depicted on a map entitled "Operable Units - Areas of
Responsibility," which is attached as Exhibit 2. The OUs are as follows:
1. Yak Tunnel/Water Treatment Plant
2. Malta Gulch Tailing Impoundments and
Lower Malta Gulch Fluvial Tailings
3. D&RG Slag piles and Railroad Yard/Easement
4. Upper California Gulch
5. Asarco Smelter sites/Slag/Mill sites
6. Starr Ditch/Stray Horse Gulch/Lower Evans Gulch/
Penrose Mine Waste Pile
7. Apache Tailing Impoundments
8. Lower California Gulch
9. Residential and Commercial Populated Areas
10. Oregon Gulch
11. Arkansas River Valley Floodplain
12. Site-wide Water Quality
This Record of Decision selects the remedial action for source remediation at
Operable Unit 2 of the Site. Operable Unit 2 includes the Malta Gulch Tailings
Impoundments, including Leadville Corporation Mill; the Malta Tailings, including
the Leadville Silver & Gold Mill facility; and the fluvial tailings in the area known as
the Lower Malta Gulch.
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STATEMENT OF BASIS AND PURPOSE
EPA selects "No Further Action" as the appropriate response action for OU
2 of the Site in accordance with the Comprehensive Environmental Response,
Compensation, and Liability Act of 1980 (CERCLA); the Superfund Amendments
and Reauthorization Act of 1986 (SARA); the National Contingency Plan (NCP);
EPA's "Interim Final Guidance on Preparing Superfund Decision Documents,"
OSWER Directive 9355.3-02 (June 1989); EPA's "Guide to Developing No Action,
Interim Action, and Contingency Remedy RODs," OSWER Publication 9355.3-
02FS-3 (April 1991); and the Administrative Record for the Site.
DESCRIPTION OF THE SELECTED REMEDY: NO FURTHER ACTION
Four (4) removal/response actions were performed at OU 2. In chronological
order, the fluvial tailings were excavated from Lower Malta Gulch and deposited in
the Malta Gulch Tailings Impoundment. The material in the Malta Gulch Tailings
Impoundment (Leadville Corporation) was consolidated, graded, capped and
revegetated. The material in the Malta Tailings Impoundment (Leadville Silver &
Gold) was graded, capped and revegetated. Forty-two drums, some very
corroded, were removed from the Leadville Corporation Mill and disposed of
appropriately.
These removal actions have served to prevent or control the release or
threatened release of hazardous substances from the sources of contamination
identified in OU 2 such that there are no unacceptable risks to human health and
the environment from these sources. Lead is the principal contaminant of
concern. However, the response actions performed will control all contaminants
of concern contained in the capped material.
This decision document makes no determination on whether surface water
or ground water within OU 2 requires remediation. Pursuant to the
August 25, 1994 Consent Decree at this Site, it was agreed that the decision on
remediation of surface and groundwater site-wide (Operable Unit 12) would be
made only after records of decision for source remediation were selected and
implemented at each operable unit. This decision document therefore determines
that for purposes of source remediation at OU 2 , no additional response actions,
either removal or remedial, are necessary beyond the removal actions already
performed at the component parts of OU 2. If additional response actions are
necessary to meet surface and/or ground water requirements, those actions will be
designated in the record of decision for Operable Unit 12. However, groundwater
in the area designated as OU 2 is not currently used as a drinking water source.
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No further response actions are necessary for the Malta Gulch Tailings
Impoundment and Malta Tailings Impoundment portions of OU 2, as long as the
present zoning. Industrial Mining, or similar zoning that does not allow residential
use is maintained. Procedures will be established to notify EPA of any proposed
zoning or land use changes. These procedures, and other measures, will be
established in coordination with the other Operable Units where waste is left in
place. In addition, the Malta Gulch Tailings Impoundment is presently covered
under a permit from the State Department of Minerals and Geology and the no
further action decision assumes that uses inconsistent with that permit shall be
prevented. The Lower Malta Gulch portion of OU 2 requires no institutional
controls.
Periodic monitoring will be conducted at the Malta Gulch Tailings
Impoundment and Malta Tailings Impoundment to assure that the response actions
conducted remain effective and to assure that the zoning has not changed.
DECLARATION STATEMENT
The Colorado Department of Public Health and Environment has been
consulted and does not concur with this "No Further Action" remedy. Our
response to the issues raised by the State in their decision not to concur is
available in the Record.
I have determined that the "No Further Action ROD" is a remedy that is
protective of human health and the environment and is cost effective.
Because this decision will result in hazardous substances remaining on site,
above health-based levels, reviews of the previous response actions. will be
required no less than five years after the initiation of the last response actions.
These reviews will also be conducted during site-wide five-year reviews.
The next five-year review is scheduled to be performed not later than
February 2001.
Date* Meix H. Dodsoh, Assistant Regional Administrator
Ecosystems Protection and Remediation
U.S. Environmental Protection Agency
Region VIII
111
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RECORD OF DECISION
CALIFORNIA GULCH
OPERABLE UNIT 2
SEPTEMBER 1999
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TABLE OF CONTENTS
DECISION SUMMARY Page
• Site Name and Location 3
• Scope and Role of Operable Unit
• Cultural Resources
Exhibit 1 through Exhibit 3
MALTA GULCH TAILINGS IMPOUNDMENTS
• Site Name and Location
• Site History
• Enforcement Activities
• Community Participation
• Site Risks & Characterization
• Response Actions
• Reclaiming Malta Gulch Tailings Impoundments
Drum Removal - Leadville Corporation Mill Building
• Monitoring
Exhibits MGTI -1 through MGTI -9
LOWER MALTA GULCH FLUVIAL TAILING 17
• Site Name and Location
• Site History
• Enforcement Activities
Community Participation
Site Risks & Characterization
• Response Action
• Monitoring
Exhibits LMG -1 & LMG -2
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MALTA TAILINGS IMPOUNDMENT 20
• Site Name and Location
• Site History
• Enforcement Activities
• Community Participation
• Site Risks & Characterization
• Response Action
• Monitoring
Exhibits MTI -1 through MTI -4
SELECTED REMEDY . 23
APPENDICES
A. REFERENCES
B. RESPONSIVENESS SUMMARY
TABLE
1. REMOVAL ACTIONS PERFORMED 6
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DECISION SUMMARY
Site Name and Location
The California Gulch Superfund Site ("Site") was listed on the National
Priorities List (NPL) on September 8, 1983. The Site, which is located in Lake
County, Colorado occupies 16 % square miles of watershed. (Exhibit 1). This
watershed drains along California Gulch to the Upper Arkansas River.
The Site includes the City of Leadville, various parts of the Leadville Historic
Mining District, and a section of the Arkansas River from the confluence of
California Gulch to the confluence of Lake Fork Creek. (Exhibit 2).
The Site is situated in a highly mineralized area of the Colorado Rocky
Mountains. Mining, mineral processing, and smelting activities have produced .
gold, silver, copper, lead, zinc, and manganese for more than 130 years:
California Gulch collects the runoff from numerous abandoned mines and
tailings piles with the largest single source of metallic loading coming from the Yak
Tunnel. This tunnel was built to drain water from the underground mine workings
and to make mineral exploration and development easier. This tunnel drained
hundreds of miles of underground mine workings and, prior to the installation and
operation of the Yak Tunnel Wastewater Treatment facility, discharged 210 tons
yearly of various metals into California Gulch.
The Phase I Remedial Investigation issued in January 1987 determined that
surface water in California Gulch contained cadmium and lead exceeding primary
drinking water standards. The Phase I Rl also determined that Site surface water
contained cadmium, copper, lead, and zinc exceeding water quality criteria. Soils,
which were highly disturbed in many portions of the Site, were found, to contain
significant concentrations of arsenic, zinc, lead, copper, and cadmium.
From this report, the main mining-related features that were identified as
potentially requiring some removal or remedial response included:
• Acid mine drainage from the Yak Tunnel;
• Seven major tailings impoundments;
• More than two thousand waste rock piles;
• Abandoned mine, milling, and reprocessing operations;
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• Smelter wastes, slag and debris; and
• Fluvial tailings.
• Residential Soils
Scope and Role of Operable Unit
For ease of performance of remedial activities and administration of the Site
as a whole, the Site was divided into twelve Operable Units. These Operable
Units ("OUs") are depicted on a map entitled "Operable Units - Areas of
Responsibility," which is attached as Exhibit 2. The OUs are as follows:
1. Yak Tunnel/Water Treatment Plant
2. Malta Gulch Tailing Impoundments and
Lower Malta Gulch Fluvial Tailings
3. D&RG Slag piles and Railroad Yard/Easement
4. Upper California Gulch
5. Asarco Smelter sites/Slag/Mill sites
6. Starr Ditch/Stray Horse Gulch/Lower Evans Gulch/
Pen rose Mine Waste Pile
7. Apache Tailing Impoundments
8. Lower California Gulch
9. Residential and Commercial Populated Areas
10. Oregon Gulch
11. Arkansas River Valley Floodplain
12. Site-wide Water Quality
This Record of Decision selects the remedial action for Operable Unit 2 of
the Site. Operable Unit 2 includes the Malta Gulch Tailings Impoundments,
including Leadville Corporation Mill; the Malta Tailings, including the Leadville
Silver & Gold Mill facility; and the fluvial tailings in the area known as the Lower
Malta Gulch, specifically Fluvial Site 7. (See map attached as Exhibit 3).
Table 1 provides an outline of the background and response actions at each of the
locations listed.
Cultural Resources
EPA has conducted a Cultural Resources Survey for each of the removal
actions performed within OU 2 of the Site. In consultation with the State Historic
Preservation Office (SHPO), it was determined that there were no cultural
resources within OU 2 that were considered contributing to the National Historic
Landmark District. However, at the request of the Lake County Historic
Preservation Advisory Board, the remnants of the Ore & Chemical Mill were
preserved. Further information regarding cultural resource concerns is available in
4-
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the Cultural Resources Report, California Gulch Superfund Site, Operable Units 1
thru 12. The report is dated July 1998 and addressees Removal Actions
performed at all Operable Units from July 24, 1994 thru June 30, 1998.
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C O D\0 R] A DO
CALIFORNIA
SUPERFUND SITE
Source: SMI/TerraMalrlx. 18B8a
EXHIBIT
California Gulch
SuperfundSlle
General Location Map
Leadville, Colorado
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MALTA QUtCH TAIUNOS IMPOUNDMENT
MALTA TARINGS IMPOUNDMENT
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REMOVAL ACTIONS PERFORMED AT CALIFORNIA GULCH OPERABLE UNIT 2
Location
Lower Malta Gulch
Fluvial Tailing
Malta Gulch Tailings
Impoundment &
Leadville Corporation
Mill
Malta Tailings
Impoundment -
Malta Gulch Tailings
Impoundment &
Leadville Corporation
Mill-
Start/
Complete
Dates
9/5/95
to
3/17/97
10/5/95
to
3/17/97
8/9/96
to
3/31/97
5/26/98
to
7/2/98
Contaminants
of Concern '
Metals, Sulfate,
Cyanide
Metals, Sulfate,
Cyanide
Metals, Sulfate,
Cyanide
Drums (42) 2
Description of Response Action
Fluvial tailing contamination was
excavated and hauled to the Malta
Gulch Tailing Impoundment for
disposal. No Monitoring required.
Consolidation, Grading, Capping
and Reclamation
Grading, Capping, and Revegetation
Removal from site and appropriate
disposal. No. monitoring required.
Cleanup
Standard
6,700 ppm
Total Lead
Must support
vegetation.
Must support
vegetation
None
1) Principally, Arsenic, Cadmium, Copper, Lead and Zinc
2) 36 x 55 Gallon, 6x5 Gallon, containing acids, bases, flammable liquids
TABLE 1
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MALTA GULCH TAILINGS IMPOUNDMENT
LEADVILLE CORPORATION
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MALTA GULCH TAILINGS IMPOUNDMENTS - LEADVILLE CORP. (MGTI)
RECLAIMING MGTI
Site Name and Location (MGTI)
The Malta Gulch Tailings Impoundment - Leadvilie Corporation (MGTI) is
located at the upper end of Malta Gulch about two miles west of the City of
Leadvilie. Its general location is shown on the Operable Units and Areas of
Responsibility Map which is attached as Exhibit 2. It is shown, in more detail, on
the Maps which are attached as Exhibits MGTI-1 and MGTI-2. Ponds #1, #2, #3
& #5 are tailings impoundments. Ponds #4 & #6 are clarification ponds.
Site History (MGTI)
The Stringtown portion of the Leadvilie Mining Area District, which includes
the Malta Gulch Tailings Impoundments ("MCTI"), was developed between 1879
and 1882 as a large group of placer claims.
It appears that the earliest use of this area for tailings disposal was from the
fall of 1943 through August 1946 by the Ore & Chemical Company ("OCC").
OCC constructed a large tonnage sink-float mill near the site of the present day
Leadvilie Corporation Mill. OCC deposited approximately 800,000 tons of tailings
behind low profile berms. These berms appear to have been unsuccessful in
completely containing the tailings and there appears to have been periodic releases
of OCC tailings into the Lower Malta Gulch. The OCC tailings berms became the
pre-cursors to the current basins known as Impoundments # 1 and # 2.
From the period of 1945 to 1973, there was no activity at this portion of
the Site although ownership of the property changed hands numerous times. The
property was purchased by its current owner, Leadvilie Corporation, in 1968. In
1974, the Hecla Mining Company (Hecla), in conjunction with Day Mines, leased
the property as a site for disposal of tailings generated from its milling of ores from
the Sherman Mine which was a silver mine in a dolomite formation. The Malta
Gulch Tailings Impoundments, in their present configuration, were constructed in
1974 by Hecla/Day. Hecla/Day also constructed 4 tailings impoundments
(#1, #2, #3 & #5) and two clarification ponds (#4 and #6). The entire facility
occupies approximately 23 acres. Additional information regarding the six
structures is shown on the attached maps/cross sections which are identified as
Exhibits MGTI-3, MGTI-4 and MGT1-5. Full size drawings of the exhibits are
available in the Administrative Record.
These milling operations were permitted and bonded by the State of
Colorado's Division of Minerals & Geology, and the permit remains in effect.
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MALTA GULCH
TAILINGS IMPOUNDMENT
! MALTA TAILINGS
IMPOUNDMENT
EXHIBIT MGTI-1
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EXHIBIT MGTI-2
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BORING LOCATIONS
MALTA GULCH TAILINGS
MM ^-- flBurt 4
EXHIBIT MGTI-3
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WCST
B
£AST
B*
•-WC-MW-OJ
•-MO-MW-04 IMW-J
i-HC-HW-U
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IMPOUNDMENT IMPOUNDMENT
f«
NOTE:
I pftcuccTWN or Bust or MY/MCCM TMUNCS.
MPOUMDUCNT f I
7 pmuccnofi or BASE or wtt-nteu TWUNCS,
WPOUNOmMT ft
* °*Y/HCCW MUH8S-
4 mojccnon or BASC or ntc-HcetA TMUNCS.
MPOUNIHICHT |f
5 MKMCCnON Or MWnMMI OEPIH TO 6W£ or
PAY/HCCU WUNOS, UPOWOUCHT f j
(MO PMC-HCCU TMJNCS)
AtHtlKH BUOWN eOM»m.TAMT«. inc.
EAST-WEST
CROSS SECTION
THROUGH MALTA GULCH SITE
MAY,
EXHIBIT MGTI-4
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SOUTH
IMPOUNDMENT
15
B-MG-MW-IA
vtmui.
SCAIC
HOMOMTAI.
sou
* NOWttttU WtU l-Me-HW-S moJtCTTO
MV oatmum.tr ICCI»N
v ronxnounnic rw/ict
WHTH
A'.
AOHIAN BFIOWN CON8ULTANT3, INC.
NORTH-SOUTH CROSS SECTION
THROUGH
MALTA GULCH SITE
MAY, 1992
Figure 10
EXHIBIT MGTI-5
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Hecla leased the MGTI from Leadville Corporation until 1987. During its
leasehold, Hecla/Day operated an on-site flotation mill that generated
approximately 680,000 tons of tailings. No cyanide was used in the processing
during this time.
The Leadville Corp. refitted the mill to use a cyanide leaching process and
approximately 50,000 tons of dolomitic tailings were added to the impoundments
in 1988.
Enforcement Activities (MGTI)
In September 1991, EPA and Hecla signed an Administrative Order on
Consent for the performance of an Engineering Evaluation/Cost Analysis (EE/CA)
at the Malta Gulch Tailings impoundments. The purpose of the EE/CA was to
determine the nature and extent of any releases at and from the MGTI and to
determine an appropriate response action. In August 1993, the EE/CA was
approved as final. An Action Memorandum, officially selecting the EE/CA's
preferred alternative, was issued by EPA on September 10, 1993.
In January 1993, the United States and Hecla Mining Company entered into
a partial consent decree which settled Hecla's "Sitewide Liabilities." According to
this decree, Hecla reimbursed the United States for costs incurred to respond to
releases of hazardous substances at portions of the Site other than areas where
the Malta Gulch Tailings had come to be located. The United States and Hecla
settled Hecla's liabilities for release of Malta Gulch Tailings in a "Remaining
Liabilities" partial consent decree, entered by the United States District Court for
the District of Colorado on August 17,1994. Under the terms of this latter
consent decree, $688,000 were set aside to perform the cleanup of the MGTI.
In January 1993, the United States and Leadville Corporation entered into a
partial consent decree which settled Leadville Corporations "Sitewide Liabilities".
According to this decree, Leadville Corporation agreed to a payment schedule to
reimburse the United States for costs incurred to respond to potential releases of
hazardous substances, for which Leadville Corporation had potential liabilities.
*
Community Participation (MGTI)
At Leadville, Colorado, the public interest in the clean up of this Superfund
Site has been intensive; many public meetings have been held. Numerous Fact
Sheets have been released to the public. On August 2, 1993, the public was
notified in the local newspaper that the Final Engineering Evaluation/Cost Analysis
(EE/CA), Malta Gulch Tailings, Leadville, Colorado, dated July 29, 1993 was
8
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available for review and comment. EPA held a public meeting in Leadville on
August 12, 1993. The comment period continued through September 1, 1993.
EPA responded to all comments on the EE/CA in a Responsiveness Summary
which was prepared in September 1993 prior to the issuance of the Action
Memorandum on September 10, 1993.
Site Risks & Characterization (MGTI)
The July, 1993 (EE/CA) concluded that the principal threats were: (1) the
potential for ingestion by individuals, during casual use, through direct contact
with the tailings material which is contaminated with heavy metals; and (2) the
potential release of heavy metals, cyanide, and sulfates to groundwater as a result
of precipitation events.
The six impoundments comprising MGTI were sampled from surface to a
depth of 4 feet or to the total depth of tailings whichever was smaller and from 4
feet to the depth of the natural ground. The principal purpose of this effort was to
determine the extent and chemical characteristics of the Hecla and Pre-Hecla
tailings. The boring locations are shown on Exhibit MGTI-2. Seventeen shallow
soil samples and seven deep soil samples were collected. The results of this
sampling event are contained in the EE/CA. Tables summarizing the data are
produced below:
Parameter
Arsenic
Cadmium
Lead
Mercury
Zinc
Range (mg/Kg)
8- 600
25- 69
800 - 5600
0.3 - 2.3
2600 - 9400
Mean (mg/Kg)
99
46
2058
0.9
5941
Median (mg/Kg)
21
43
1800
0.8
5710
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Summary of Deeper Tailings Solids - Pre Hecia ( Abstracted from Table 8 in EE/CA)
Parameter
Arsenic
Cadmium
Lead
Mercury
Zinc
Cyanide
Concentration
(mg/Kg)
90
32.9
3,400
0.55
7,150
10.0
Summary of Deeper Tailings Solids - Pre Hecia ( Abstracted from Table 8 in EE/CA)
Impoundment #2- Depth Interval = 24.0 - 27.1 Feet
Parameter
Arsenic
Cadmium
Lead
Mercury
Zinc
Cyanide
Concentration
(mg/Kg)
152
87.3
4,680
0.81
14,400
8.6
Prior to implementation of the Removal Action, surface soils samples were
collected and analyzed by XRF for lead, by the U.S. BOB in August, 1996. The
impoundment was marked off in 100 foot grids. Sixty-four (64) samples had a
range of lead concentrations from 1,700 to 57,600 parts per million (ppm). Sample
locations are shown on Exhibit MGTl-6 which is attached. Source: Final
Construction Report to the Environmental Protection Agency on 1996 OU2/OU7
Construction Activities, California Gulch NPL Site, Leadville, Colorado,
March 1997.} Lead was used as the indicator contaminant of concern because for
the alternative response actions being considered, the control of lead would also
control any other contaminant of concern.
Surface runoff is ephemera! and of low volume. Its impact on the main
reach of Malta Gulch appears to be very low.
Groundwater samples from upstream and downstream monitoring wells in
Malta Gulch were collected by the U.S. BOB on June 26, 1996. The up stream
well is identified as B-MGMW-02 East; the down stream well is identified as
10
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X
C3
•••*
u_2
2
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B-MGMW-05 South. The locations of the wells and groundwater elevation
contours are shown on MGTI Exhibit 7, attached. Water quality data for the
contaminants of concern for these wells from samples collected on
June 26, 1996, are summarized below:
U.S. BOR Groundwater Data - Malta Gulch Tailinas lmnn,,nrimo«*e i..«/i i
Arsenic
Cadmium
HHMWMMHU.H.^^.^^M.
Copper
Lead
Zinc
Suffate
B-MGMW-O2
(Up Stream)
Total Metals
June 1996
<1.00
<0.10
<5.00
<1.00
6.34
68 mg/L
B-MGMW-02
(Up Stream)
Diss. Metals
June 1996
<1.00
<0.10
<5.00
<1.00
<4.00
Not Applicable
B-MGMW-05
(Down Stream)
Total Metals
June 1996
1.87
9.31
<5.00
1.43
1,160
368 mg/L
— i-st — :
B-MGMW-05
(Down Stream)
Diss. Metals
June 1996
<1.00
9.10
Not Analyzed
1.38
1,143
Not Applicable
Potential pathways of exposure can be found in the EE/CA. A copy of the
Conceptual Site Models for the Current Conditions and the Post-Closure Phase of
this response action are attached as Exhibits MGTI-8 and MGTI-9.
The EE/CA also found that the MGTI is geotechnically stable. The EE/CA
references an earlier report prepared by Dames and Moore in 1985 entitled
Additional Geotechnical Studies for Hecta Mining Company, Leadville Unit
Colorado. This report was prepared for submission to the Division of Mines and
Geology under the Mined Land Reclamation Permit for MGTI. However
subsequent inspections conducted in 1995 by EPA found fractures in the north
berm along ponds 2 & 3 requiring stabilization.
Alternatives for addressing the principal threats from the MGTI were
developed in the EE/CA. The Alternatives considered were: 1) No Action-
2) Institutional Controls; 3) Regrade and Reclaim; and, 4) Site Consolidation and
Reclamation Based on the findings of the EE/CA, EPA determined that the risk to
human health and the environment posed by the material in the MGTI would be
substant,ally reduced or eliminated by implementation of capping and closure
measures. The alternative selected by EPA for the MGTI was set out in a
September 10, 1993 Action Memorandum.
11
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HICU noontime *tu
HCCU JUKI Moi(-nueeti
(• we- in I
«(iu (iuw)
0 f '« «OHfTO«"M(! «ttlt {n, W»)
». W1IM NUWKIlQ]
AOHIAH •ROWH CON1UI.T»KT». IMC.
QROUNDWATER ELEVATION
MALTA QULCH TAILINGS
MAY. 1992
rijuri
EXHIBIT MGTI-7
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PRIMARY SOURCE
RELEASE
MECHANISM
SECONDARY SOURCE
EXPOSURE
ROUTE
POTENTIAL
RECEPTOR
COMMENTS
HUMAN BIOTA
TAILINGS
DIRECT
INGESTION
INHALATION
DERMAL
X
X
X
INFILTRATION
PERCOLATION
GROUNDWATER
INGESTION
RUNOFF
SURFACE WATER
SEDIMENT
WIND/AIR
DUST
PATH LEGEND:
ACCtSS • PHOCCSS CON1ROLUO AND PCKUintO
UHCONTBOtltO
PATHWAY
X COUPUTl CATMWAV
X
X
X
—*-o o
OWNED AND
CONTROLLED
BY LEADVILLC
CORPORA TION
NO ON-SITE
DRINKING WELLS
CMLRD PERMIT
MAIN IMPOUNOUENT
COVERIO
CMLRD PERWT
. xe.
CONCEPTUAL SITE PLAN
MALTA TAILINGS
Current Conditions
EXHIBIiMGTF-8
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PRIMARY SOURCE
RELEASE
MECHANISM
SECONDARY SOURCE
EXPOSURE
ROUTE
POTENTIAL
RECEPTOR
COMMENTS
TAILINGS
DIRECT
INFILTRATION
PERCOLATION
GROUNDWATER
INGESTION
INHALATION
DERMAL
INGESTION
RUNOFF
SURFACE WATER
INGESTION
DERMAL
WIND/AIR
INGESTION
HUUAH BIOTA
} O
~ -. SURFACE
<-> vl COVERED
) O
o o
o o
O
Q
SlTE-\
INSTITUTIONAL
CONTROL
SURFACE WATER
CONTROLLED
SURFACE
COVERED
PATH LEGEND:
ACCCSS k MOCCSS CONTdOUCO AND PMMITTtD
UNCONTROUCD
Q INCOUPltn PATHWAY
X COUPUU PATHWAY
COMIUI.TA*/T*.
CONCEPTUAL SITE PLAN
MALTA TAILINGS
Post-Closure Phase
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Response Action (MGTI) - Reclaiming MGTI
The MGTI consists of four tailings impoundments and two clarification
ponds which cover about 23 acres. The Removal Action included: consolidation,
grading, capping, and revegetating the impoundments. Prior to the EPA Removal
Actions, the property owner, Leadville Corp. under direction from the Division of
Minerals and Geology, placed a 6" to 12" dolomite and soil cover over the tailings
to minimize fugitive dust from blowing from the site.
The work conducted by EPA at the MGTI was performed in two field
seasons. The work commenced on October 5, 1995 and was completed on
October 15, 1996. The selected removal action required that the MGTI be graded,
its slopes stabilized, capped with "borrow material" to a depth of 18", and
revegetated. The "borrow material" was obtained from an existing borrow pit
located north of the tailings impoundments, and consisted of native glacial deposit
soils found in the area. Before this action was completed, EPA consolidated about
30,000 cubic yards of contaminated material from Lower Malta Gulch and
transported them to MGTI.
The 1995 construction activities included stripping the vegetation from the
borrow area and production of rip-rap. Between October 5, 1995 and
November 3, 1995, approximately 6,800 cubic yards of pit run borrow material
were placed and compacted in the new 2:1 slope face along the northern side of
Impoundments #2 & #3 where recent subsidence of the embankment had
occurred subsequent to the 1985 Dames & Moore site inspection and report. This
borrow material was in addition to 2,O33 cubic yards of original slope material
which was excavated and recompacted in place. 1995 activities also included
construction of a rip-rap geotextile spillway from impoundment # 2 to control
runoff; and, reestablishment of the local drainage and fencing. In the fall of 1999
impoundment #3 was regraded to promote drainage and revegetated.
In 1995, Clarification Ponds #4, and #6 and Tailings Impoundment #5 were
to be covered with borrow material in barren areas where tailings were subject to
wind erosion to enhance the work previously conducted by Leadville Corp. This
was accomplished at Pond #5 which was covered with approximately one foot of
unprocessed borrow material. A notch was cut and rip-rapped in the downstream
berm of Pond #5 to provide high inflow release capacity. However, soft ground
conditions and snow cover forced postponement of the work at Ponds #4 and #6
until 1996.
The complete details of the 1995 construction work at MGTI can be found
in the referenced report (Hecla Impoundment Slope Re-construction/Malta Gulch
Final Removal Action Construction Report for OU-02) by the Bureau of
Reclamation dated January 1996.
12
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The work remaining after the 1895 construction season required to
complete the removal action selected in the August 1995 Action Memorandum
was performed in 1996. A small, bare area in Impoundment #1 was covered with
approximately two feet of native glacial till cover material from the adjacent south
slope distributed by dozer. The tailings in Clarification Pond #4 were removed
from the upper portion of the pond, down to the original grade, and consolidated
into Tailings Impoundment #3. The excavated area was then re vegetated. The
bare areas in Impoundments #4 & #6 were covered with approximately two feet of
compacted cover from the borrow pit. The final site grading insures that all
precipitation runoff flows into Impoundments #1, #2 or #3. The covered areas,
including the north slopes of Impoundments #2 and #3, were hydro-seeded. The
revegetation work was based on the Field Revegetation Studies In Selected Malta
Gulch Test Pits, Leadville, Colorado, dated October 8, 1996, which is included as
Appendix E of the March 1997 BOR Report. The seed mixture is shown in Figure
2 of the Field Revegetation Studies Report.
The complete details of the 1996 construction work at MGTI can be found
in the referenced report {Final Construction Report for 1996 Construction Activities
at OU2/OU7) by the Bureau of Reclamation dated March 1997.
Confirmation samples of the cover material were not needed because the
"borrow material" was from a vegetated area and therefore should not contain
elevated levels of metals.
The capping, revegetation, and fencing installed by the property owner
around the perimeter of the site all serve to substantially reduce or eliminate the
risks from direct contact with the contaminated materials. Potential releases of
contaminants to groundwater are reduced or eliminated by the capping,
revegetation, and reconstruction of the slopes. These measures serve to keep
water from precipitation events from directly contacting the contaminated
materials, which serves to reduce or prevent metals from potentially affecting
groundwater. Lead is the principal contaminant of concern. However, the
response action performed will address all contaminants of concern in the waste
material.
13
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Monitoring (Reclaiming MGTI)
in order to ensure continued protectiveness of the remedy, long-term
monitoring will be required to assure that the cover material and vegetation remain
effective. A revegetation monitoring plan will be developed to monitor the
condition of the revegetated areas. In addition, present zoning of the MGTI is
Industrial Mining which will not allow uses inconsistent with the remedy, hence
periodic monitoring and review is necessary to verify that zoning of the MGTI has
not been changed to allow uses inconsistent with the remedy. Procedures will be
established to notify EPA of any proposed zoning or land use changes. These
procedures and other measures will be established in coordination with the other
Operable Units where wastes are left in place. EPA will then make a determination
on whether the proposed change is consistent with the remedy. Further, the
MGTI is covered by a DMG permit that would allow the present owner of this
facility to use this property as a mine waste impoundment. Thus, monitoring is
also necessary by EPA, to periodically review the status of this DMG permit and
use of the mill and impoundments. Upon termination of the permit, and after final
reclamation activities have been implemented under the bond held by DMG, EPA
will review the site conditions to assure that final construction of the remedy is
consistent with performance standards for the other Operable Units. EPA will
conduct additional work if necessary to address any identified adverse impacts to
surface and ground water resulting from contaminant releases from the tailings.
14
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MALTA GULCH TAILEVGS IMPOUNDMENT
LEADVILLE CORPORATION
DRUM REMOVAL
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MALTA GULCH TAILINGS IMPOUNDMENT -
DRUM REMOVAL (MGTI) - LEADVILLE CORPORATION MILL
Site Name and Location (Drum Removal - MGTI Mill)
The Leadviile Corporation mill is located at the southern boundary of MGTI.
The mill area is shown on a map of OU 2 which is attached as Exhibit 3.
Site History (Drum Removal - MGTI Mill)
In 1997, officials of the State's Division of Minerals & Geology conducted a
mine permit inspection and discovered that forty-two (42)drums, in one of the
buildings at the Leadviile Corporation mill, were corroding and beginning to leak as
evidenced by moisture on the drum surfaces. No leakage from any of the drums
was found on the ground surface. Since Leadviile Corporation did not have the
resources to dispose of the drums, the State's Division of Minerals and Geology
requested EPA's Emergency Response Team to dispose of them. Thirty-six (36) x
55 gallon drums and 6x5 gallon drums were involved. The drums contained
hazardous substances which represented a threat to human health and the
environment. The drums contained acids, bases and flammable liquids.
Enforcement Actions (Drum Removal - MGTI Mill)
Prior to commencing this removal action, EPA notified Leadviile Corporation
of the problem and offered it the opportunity to conduct this removal action.
Leadviile Corporation declined the opportunity.
Community Participation (Drum Removal MGTI Mill)
This action was performed as a Time-Critical Removal. No public meeting
was held. Information regarding this action is available in the U.S. EPA, Region
VIII, Superfund Record Center.
She Risks and Characterization (Drum Removal - MGTI Mill)
The forty-two (42) drums located on the site contajned acids, bases and
flammable liquids. The Action Memorandum dated April 15, 1998 determined that
these drums represented an immediate threat of exposure to hazardous substances
through direct contact or ingestion by trespassers, vagrants or nearby residents.
15
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Response Action (Drum Removal - MGTI Mill)
This Removal Action addressed the need to mitigate the threats to the
environment and health posed by thirty-six 55-galion drums and six 5-gallon
containers which contained acids, bases and flammable liquids. The
drums/containers found at the site were in various conditions from slightly to
severely corroded. The Removal Action was performed under an Action
Memorandum dated April 15, 1998. All hazardous materials were removed from
the site and were, disposed of appropriately. This response action started on May
26, 1998 and was completed on July 2, 1998.
Monitoring (Drum removal - MGTI Mill)
This was a complete removal, no future monitoring is required.
16
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LOWER MALTA GULCH
FLUVIAL TAILINGS
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LOWER MALTA GULCH FLUVIAL TAILINGS (LMG)
She Name and Location (LMG)
The Lower Malta Gulch Fluvial Tailings (Fluvial Tailings #7) lie directly
downstream of the Malta Gulch Tailings Impoundments. Malta Gulch runs in a
southwesterly direction for about three miles where it joins California Gulch. (See
Exhibit LMG-1 attached)
Site History (LMG)
According to the July 1993 EE/CA for the Malta Gulch Tailings
Impoundment removal action, the fluvial tailings in Lower Malta Gulch originated
from the milling operations conducted by the Ore & Chemical Company (OCC)
from the fall of 1943 through August 1946. This was prior to the Leadvilie
Corporation (Hecla) operation which began in 1974. OCC had constructed a large
tonnage sink-float mill near the site of the present day Leadvilie Corporation Mill.
OCC deposited approximately 800,000 tons of tailings behind low profile berms.
These berms appear to have been unsuccessful in completely containing the
tailings and there appears to have been periodic releases of OCC tailings into the
Lower Malta Gulch. Tailings and waste material from these operations remain near
Malta Gulch.
Enforcement Activities (LMG)
EPA performed the removal action at LMG using Fund monies.
The United States, as a successor to the Ore & Chemical Company (OCC),
has settled its liabilities for the OU 2 area in the August 25, 1994 Consent Decree.
These settlement amounts were based on the proportionate share of liability the
United States had as the Successor to the Alien Property Custodian or OCC's
successor corporation.
Community Participation (LMG)
This action was performed as a Time-Critical Removal. No public meeting
was held. Information regarding this action is available in the U.S. EPA, Region
VIII, Superfund Record Center.
Site Risks and Characterization (LMG)
According to the Tailings Disposal Area Remedial Investigation Report,
California Gulch site, Leadvilie, Colorado, January 1994, by Woodward-Clyde,
LMG Fluvial Tailings Site #7 consists of a single contiguous area and can be
accessed from the west of the Malta Gulch Tailings Impoundments area and
across Malta Gulch. A railroad grade exists on the west side and parallel to the
Malta Gulch. The Malta Gulch is approximately 500 feet wide and 2500 feet long
and slopes at an estimated three percent to the southwest. The closest home is
17
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approximately 300 feet to the southwest.
The Tailings Disposal Rl Report states that Fluvial Tailings Site #7 covers an
area of approximately 26 acres. Eighteen (18) soil samples at nine (9) locations
(surface and at depth) were collected in Lower Malta Gulch and analyzed for lead
by XRF. The sample locations are shown on Exhibit LMG-1. The lead content
found in the fluvial tailings ranged from 20 to 47,800 parts per million (ppm).
Based on data from previous remedial investigations, it was thought that the site
contained an estimated volume of 10,000 cubic yards with an estimated average
tailings depth of one-fourth foot. Additional samples were collected to improve
the efficiency of the response action by more precisely defining the area! extent
and depth of contamination in the Lower Malta Gulch. Thirty-five (35) test pits on
approximately 200 foot centers across the valley were excavated and the soil was
sampled and analyzed to determine the lead concentration, the physical soil
characteristics and what revegetative soil amendments might be required.
Samples were also analyzed for lead, arsenic, copper, cadmium and zinc. The lead
concentrations ranged from 5.5 to 16,152 ppm. Estimates of the amount of
material to be removed increased to 30,000 cubic yards.
Response Action (LMG)
The Removal Action for the LMG, Fluvial Tailings # 7 was performed in the
1995 and 1996 construction seasons. This removal action was performed a.s a
Time Critical Removal Action, in accordance with an Action Memorandum dated
August 14, 1995. The materials excavated from LMG were disposed at the Malta
Gulch Tailings Impoundment (MGTI) prior to the Non-Time Critical Removal Action
which was planned for MGTI in 1996.
During the 1995 construction season, approximately 34,000 cubic yards of
contaminated material was removed from LMG and deposited in MGTI Pond #3.
Four check dams in the site drainage, and a diversion berm above LMG were
constructed to manage surface runoff by runoff passing surface water through the
upper portion of the site from the Hecla Impoundment site (MGTI). These
structures also act as a deterrent to unauthorized use by vehicles.
After excavation of the fluvial tailings, the soil was analyzed to confirm that
the removal achieved the clean-up level of 6,700 ppm total lead, the
concentrations for lead exposure identified as protective for worker exposure as
identified in the Baseline Human Health Risk Assessment Part C, dated April 1995.
Approximately 45 samples were collected on 200 foot centers. However, all field
confirmation sampling results concluded that the lead levels were below the
residential clean-up level of 3,500 ppm total lead as finalized in the September 2,
1999 Record of Decision for OU9. A map showing the post removal lead
concentrations is attached as Exhibit LMG-2. This lead concentration is also more
conducive to revegetation. U.S. Bureau of Reclamation determined that soils with
a concentration of lead at or below 3,500 ppm, contained zinc at a satisfactory
level for supporting vegetation.
18
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ICBEHfi
• sunrAct SUWAMPU
n
OAIt Of MAPPIMC - AUCOSr 27 « 28. U90
WATER
tVASTE
& UNO
FIGURE 8-6
APPROXIMATE SURFACE TAILINGS
SAMPLE LOCATIONS
TAILINGS SITES No. 7 AND Mo.
EXHIBrr LMG-l
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LEGEND
(UNDISTURBED)
CONSTRUCTION 80UNDRT
MALTA GULCH FLUVIAL TAILINGS
FINAL CLEAN UP LEAD LEVELS (pprrV
EXHIBIT LMG-2
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The complete details of the 1995 construction work at Lower California
Gulch can be found in the referenced report (Hecla Impoundment Slope Re-
construction/Malta Gulch Final Removal Action Construction Report for OU-02) by
the Bureau of Reclamation dated January 1996.
Revegetation work in Malta Gulch was performed in 1996. Malta Gulch
was hydro-seeded at a rate of 20 to 30 Ibs/acre, with a recommended seed
mixture and Biosot Plus, an organic fertilizer, following ripping and incorporation
into the soil of the recommended lime equivalent amounts of local dolomite gravel.
The complete details of the 1996 construction work at Lower Malta Gulch
fluvial tailings can be found in the referenced report {Final Construction Report for
1996 Construction Activities at OU2/OU7) by the Bureau of Reclamation dated
March 1997. The revegetation work was based on the Field Revegetation Studies
In Selected Malta Gulch Test Pits, Leadvillet Colorado, dated October 6, 1996,
which is included as Appendix E of the March 1997 BOR Report. The seed
mixture is shown in Figure 2 of the Field Revegetation Studies Report.
Monitoring (LMG)
This removal action addressed potential risks by the complete removal of
the tails from LMG and disposal of these tailings in the MGTI where the tailings
have been capped. This was a total removal of the contaminated fluvial tailings.
Subsequent monitoring in 1997 and 1998 have verified that the revegetation was
successful and no long term monitoring is required. Confirmatory sampling
demonstrated that residual contamination levels after the removal were below the
residential action levels, thus no institutional controls are necessary at this portion
of OU 2.
19
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MALTA TAILINGS IMPOUNDMENT
LEADVILLE SILVER & GOLD
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MALTA TAILINGS IMPOUNDMENT (MTI)
Site Name and Location (MTI)
The Malta Tailings Impoundment (Leadville Silver & Gold Mill facility) is
located 1.5 miles west of Leadville, 0.8 miles north of Stringtown and
0.6 miles north of California Gulch. (See Exhibit MTI-I attached)
Site-History (MTI)
The Leadville Silver & Gold, Inc. constructed a mill to recover pyritic
materials from various tailings and waste materials from nearby properties which
had been obtained under leasehold arrangements. This pyritic materials recovery
process operated from 1983 through 1988.
Approximately 2,000 tons of pyrite were shipped to various off-site smelters
for use as a flux. As a result of this operation, approximately 10,000 cubic yards
of tailings was generated or disposed of at the Malta Tailings Impoundment.
Enforcement Activities (MTI)
On September 3, 1993, a Consent Decree between the United States and
Leadville Silver & Gold (LSG) was entered by the U.S. District Court for the District
of Colorado. In accordance with that Consent Decree, LSG must perform the
response action contained herein unless it can demonstrate that it does not have
the financial ability to pay or perform the cleanup. LSG has agreed that it has the
financial ability to conduct the monitoring to assure the long-term stability of the
consolidated cap.
Community Participation (MTI)
This action was performed as a Time-Critical Removal. No public meeting
was held. Information regarding this action is available in the U.S. EPA, Region
VIII, Superfund Record Center.
Site Risks & Characterization (MTI)
The Malta Tailings Impoundment consists of three small impoundments
surrounded by berms and occupies 4.6 acres of nearly flat land at the top of a
ridge. The total volume of tailings is estimated to be slightly in excess of 10,000
cubic yards.
Areas within the immediate vicinity of the tailings impoundments are littered
with scrap metal, concrete slabs, and other mining/processing material. There
was also a stockpile of mine waste, including drums of product, nearby.
20
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MALTA GULCH
TAILINGS IMPOUNDMENT
'MALTA TAILINGS
IMPOUNDMENT
EXHIBIT MTI-1
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The berms have retained their structural integrity. Surface water flow is
ephemeral and occurs near the impoundments only during periods of extended
and/or intense precipitation. There are no signs of water overflowing these berms.
Sampling of the surficial soils reveals elevated concentrations of cadmium,
copper, lead, silver, and zinc and in the subsurface tailings elevated levels of
arsenic, cadmium, lead, and zinc. Composite sample locations are shown on
Exhibit MTI-2.
A number of metals from the subsurface soils were tested by Method 1312,
Toxic Characteristic Leaching Process (TCLP). The results of the TCLP tests were
within regulatory requirements.
According to the Tailings Disposal Area Remedial Investigation Report,
California Gulch Site, Leadville, Colorado, January, 1994, by Woodward-Clyde
(Table 5-6) the surface soils in the Malta Tailings Impoundment (MTI) contain the
following concentrations of the contaminants of concern:
CONTAMINANT CONCENTRATION (mg/Kg)
Arsenic 64.7 J
Cadmium 60.8
Copper 428
Lead 3,850
Zinc 7,250
Similarly, one soil sample which was collected from the Malta Tailings
Impoundment, at the 4-5 foot interval, on September 19, 1991, contained the
following:
CONTAMINANT CONCENTRATION (mg/Kg)
Arsenic 8.2
Cadmium 132
Copper Not analyzed
Lead 7,250j
Zinc 14,700
One sample of ponded water at the MTI was collected on
September 19, 1991 and analyzed. The principal contaminants are: arsenic
63,300 ug/L; cadmium 21,200 ug/L; lead 2,200 ug/L and zinc 3,120,000 ug/L.
The June 1996 groundwater monitoring performed by the U.S. BOR
provided analytical data for the contaminants of concern, from up-gradient and
down-gradient monitoring wells around the Malta Tailings Pile (See Exhibit MTI-3
attached). Only dissolved metals were determined. The report is attached to the
U.S. BOR, March 1997 Report as Appendix A. The data are summarized below:
21
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WATER
LAND
we.
FIGURE 5-2
APPROXIMATE LOCATION OF SU8SAMPLES
COLLECTED FOR SURFACE TAILINGS SAMPLING
Do»«:
NOV 1992
Project:
22S09C
EXHIBIT MTI-2
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Impoundments (ug/U
Arsenic
Cadmium
Copper
Lead
Zinc
MAITMW-04
(Up-Gradient)
Total Metals
June 1996
NOT TAKEN
NOT TAKEN
NOT TAKEN
NOT TAKEN
NOT TAKEN
MAITMW-04
(Up-Gradient)
Diss. Metals
June 1996
<1.00
0.12
<5.00
1.46
8.33
MAITMW-02
(Down Gradient)
Total Metals
June 1996
NOT TAKEN
NOT TAKEN
NOT TAKEN
NOT TAKEN
NOT TAKEN
MAITMW-02
(Down Gradient)
Diss. Metals
June 1996
1.12
<0.10
<5.00
<1.00
5.37
A complete description of the site characteristics may be found in the
Remedial Investigation Report by Woodward-Clyde cited above.
Response Action (MTI)
The native soils in this area are not disturbed and are not phy to toxic.
Accordingly, the native soils pose no risk to human health or the environment and
no response action was deemed necessary.
The tailings and pyritic material, however, do present a risk to human health
and the environment, since they are a source of acid mine drainage. The acid
mine drainage generated by these materials may present a potential threat for
contamination of ground water, since such a pathway of exposure does exist at
this portion of the Site.
The removal action selected in the August 1996 Action Memorandum was
to consolidate the acid-generating materials, neutralize the acidic leachate, cap and
revegetate. These removal action goals were achieved by grading the
impoundments to eliminate ponding and then applying dolomitic limestone to a
depth of eight inches. Following the application of the dolomite, an 18 inch layer
of borrow material (local soils from the berms of MTI) was added to provide a base
for the revegetation. Twelve (12) confirmation soil samples were collected from
the soil surface to be revegetated. The samples were analyzed for lead using XRF.
The clean-up level for the response actions is 6,700 ppm lead, the concentrations
for lead exposure identified as protective for worker exposure as identified in the
Baseline Human Health Risk Assessment Part C, dated April 1995. The lead
concentration of the twelve samples confirmation samples ranged from 700 to
5400 ppm. The sample locations are shown on Exhibit MTI-4. Table 2 of the
1997 BOR Report provides the analytical data. The seed mixture used on Lower
Malta Gulch was also used for the MTI revegetation.
The piles of pyrite concentrate, and drums were removed during the 1996
construction season, for use as a product.
22
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CM
I
D)
il
6
A
B
AKCM
1 u I
EXHIBIT MTI-4
-------
The complete details of the 1996 construction work at the Malta Tailings
Impoundment can be found in the referenced report (Final Construction Report for
1996 Construction Activities at OU2/OU7) by the Bureau of Reclamation dated
March 1997. The revegetation work was based on the Field Revegetation Studies
In Selected Malta Gulch Test Pits, Leadviile, Colorado, dated October 6. 1996,
which is included as Appendix E of the March 1997 BOR Report. The seed
mixture is shown in Figure 2 of the Field Revegetation Studies Report.
Monitoring (MTI)
In order to ensure continued protectiveness of the remedy, long-term
monitoring will be required to assure that the cover material and vegetation remain
effective. In addition, present zoning of the MTI is Industrial Mining which will not
allow uses inconsistent with the remedy, periodic monitoring and review is
necessary to verify that zoning of the MTI has not been changed to allow uses
inconsistent with the remedy. EPA will negotiate with LSG to provide for long-
term monitoring and financial assurance.
SELECTED REMEDY - NO FURTHER ACTION
Performance of the removal actions outlined above have greatly reduced or
eliminated any potential risk posed to human health or the environment from
releases of hazardous substances found at the Malta Gulch Tailings
Impoundments, Lower Malta Gulch and Malta Tailings Impoundment portions of
OU 2 of the Site. Accordingly, EPA has determined that further removal or
remedial actions are not necessary, since there are no unacceptable risks to
human health or the environment at or from OU 2 of the Site.
EPA and the Colorado Department of Public Health and Environment have
selected a "NO FURTHER ACTION" Remedy for OU 2 because removal actions
which have been completed for the Malta Gulch Tailings Impoundments, Leadviile
Corporation Mill, Lower Malta Gulch and the Malta Tailings Impoundment have
eliminated or significantly reduced the risk to human health or the environment
from hazardous substances that may remain at OU 2 of the Site.
Periodic monitoring of the MGTI and the MTI are necessary to assure the
effectiveness of the caps placed on these impoundments and to assure that the
present institutional controls, zoning and DMG permit for the MGTI and zoning for
the MTI, have not substantially been altered such that inconsistent uses may be
allowed on these portions of OU 2.
Because this decision results in hazardous substances remaining on site,
above health-based levels, five-year reviews of the previous response actions will
be required. These reviews will be conducted in conjunction with site-wide five-
23
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year reviews.
This decision document makes no determination on whether surface water
or ground water within OU 2 requires remediation. Pursuant to the
August 25, 1994 Consent Decree at this Site, it was agreed that the decision on
remediation of surface and groundwater site-wide (Operable Unit 12) would be
made only after records of decision for source remediation were selected and
implemented at each operable unit. This decision document therefore determines
that for purposes of source remediation at OU 2 , no additional response actions,
either removal or remedial, are necessary beyond the removal actions already
performed at the component parts of OU 2. If additional response actions are
necessary to meet surface and/or ground water requirements, those actions will be
designated in the record of decision for operable unit 12.
EPA announced its preferred alternative in a Proposed Plan for California
Gulch, Operable Unit 2 in a Fact Sheet dated March 1997. The Colorado
Department of Public Health and Environment concurred in selection of this
alternative. A Public Meeting was held on March 19, 1997 and public comments
relative to the Proposed Plan were accepted from March 19, 1997 through
April 18, 1997. EPA's responses to all comments are included in the
Responsiveness Summary attached as Appendix B.
24
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APPENDIX A - REFERENCES
Phase I Remedial Investigation (Rl). Dated May 1987. Prepared by
CH2M Hill.
Tailings Disposal Area Remedial Investigation Report, California Gulch Site,
Leadville, Colorado. Dated January 1994. Prepared by Woodward-Clyde for
ASARCO, Inc.
Malta Gulch Tailings-Final EE/CA. Dated June 25, 1993,. Prepared
by Adrian Brown Associates for Hecla Mining.
Final Screening Feasibility Study for Remediation Alternatives at the California
Gulch NPL Site-Leadville, CO. Dated September 1993. Prepared by U.S. EPA,
Region VIII.
Additional Geotechnical Studies for Hecla Mining Company, Leadville Unit,
Colorado, dated December 1985. Prepared for Hecla Mining Company
Final Baseline Aquatic Ecology Risk Assessment (BAERA) dated 1995. Prepared by
Roy F. Weston for EPA.
EPA Action Memorandum (AM) dated September 10. 1993. Action Memorandum
for PRP Financed Removal Action at the Malta Gulch Tailings Impoundment Site.
EPA Action Memo dated August 1995. Action Memorandum for a Time Critical
Removal Action for the Lower Malta Gulch portion of Operable
Unit-02.
EPA Action Memo dated August 9, 1996. Action Memorandum for a Time Critical
Removal Action for the Malta Tailings Impoundment of OU-02.
Baseline Human Health Risk Assessment Part A, Risks to Residents from
Lead/California Gulch Superfund Site dated November 1995. Prepared by Roy F.
Weston for EPA.
Baseline Human Health Risk Assessment Part B, Risks to Residents from
Contaminants Other than Lead/California Gulch Superfund Site dated January
1996. Prepared by Roy F. Weston for EPA.
Baseline Human Health Risk Assessment Pan C, Evaluation of Worker
Scenario/California Gulch Superfund Site dated April 1995. Prepared by Roy F.
Weston for EPA.
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Ecological Risk Assessment for the Terrestrial Ecosystem, California Gulch A/PL
site, Leadville, Colorado dated January 1997. Prepared by Roy F. Weston for
EPA.
Final Construction Report for 1995 Construction Activities at OU 2, dated
January 1996. Prepared by the Bureau of Reclamation for EPA.
Final Construction Report for 1996 Construction Activities at OU2/OU7, dated
March 1997. Prepared by the Bureau of Reclamation for EPA.
Proposed Plan for Operable Unit 2, California Gulch Superfund Site ,
Leadville, Colorado, March 1997.
Cultural Resources Report, California Gulch Superfund Site, Operable Units 1
thru 12, for the period July 22, 1994 through July 1, 1998. The report is
dated July 1998 and was prepared by EPA.
Final Pollution Report, California Gulch, Operable Unit 2, Non-Time Critical
Removal Action at the Malta Gulch Tailings Impoundment Site, 1995 &
1996 construction seasons, July 7, 1998
Final Pollution Report, California Gulch, Operable Unit 2, Time Critical
Removal Action at the Lower Malta Gulch portion of Operable Unit 2 (OU2),
July 7, 1998
Final Pollution Report, California Gulch, Operable Unit 2, Time Critical
Removal Action at the Malta Tailings Impoundment portion of Operable Unit
2 (OU2), July 7, 1 998
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Appendix B - Responsiveness Summary
During the 30 day public comment period for the Proposed Plan for the California Gulch site,
Operable Unit 2 Record of Decision, EPA received written comments from Resurrection Mining
Company. No verbal comments were received during the public meeting held on March 19,1997.
The following are EPA's responses to Resurrection's comments:
General Comments (EPA should conduct a RI/FS for OU2)
The Tailing Disposal Area Remedial Investigation, California Gulch site, Leadville, Colorado,
January 1994 includes an assessment of the lower Malta Gulch fluvial tailing, and the Malta
Tailings Impoundment. Since the Removal action hi Lower Malta Gulch completely removed the
tailings and was verified with confirmation sampling, no further studies or assessments are
necessary. The Engineering Evaluation/Cost Analysis (EE/CA) for the Malta Gulch Tailings
Impoundment (July 29, 1993) provides the equivalent of a Remedial Investigation/Feasibility .
Study and thoroughly assesses site conditions and a detailed analysis of the different alternatives
or response actions. The Action Memorandums for the three Removal actions conducted in OU2
provide further discussions of the threats to health and environment and discuss the work to be
preformed to mitigate the threats. Consequently, a RI/FS is not necessary for OU2. In addition
any additional studies and subsequent response actions will be addressed under OU12 when site
wide surface and ground water will be assessed upon completion of the response actions at all
Operable Units 1-11. Further assessment of the effectiveness of the OU2 remedies will be
conducted under a five-year review that is required for any of the Operable Units where wastes
have been left in place.
Work at the Malta Gulch Tailings Impoundment did not address all the actions identified
in the September 10,1993 Action Memorandum
The Proposed Action section of the September 10, 1993 Action Memorandum identified the
following actions to mitigate the potential release and subsequent threats to health and
environment: a) Consolidation of the tailings: EPA response contractors consolidated tailing and
high metal soils found outside the impoundments into tailings impoundments 2 and 3;
b) Regrade and reclaim the disturbed areas: EPA response contractors regraded all disturbed area
to assure adequate storm water management and the disturbed areas were revegetated; c)
Regrade and reclaim tailings impoundments, including the retention of the existing structures
where appropriate: After consolidating tailings and soils outside of the impoundments into the
impoundment, the impoundments were regraded to assure proper drainage and the areas were
revegetated. Tailings located in the retention pounds were also consolidated in the impoundment;
d) Install a single layer cap: After consolidation of tailings and high metal soils into the
impoundment, a single layer cap was placed over the newly placed material as well as existing
areas where tailings were exposed to the surface; e) Provide for long-term maintenance and
monitoring. As discussed in the Record of Decision, periodic monitoring will be necessary to
assess whether the remedy is effective and to verify that zoning of the property has not changed.
Further, the property is subject to a Colorado Division of Minerals and Geology permit, that also
requires long-term monitoring of the property.
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EPA conducted an investigation of the stability of the tailings embankment and found failures in
the north embankments along ponds 2 & 3. A total of 6,800 cubic yards of soil was compacted in
the new 2:1 slopes in addition to the 2,033 cubic yards of original slope material that was
recompacted in place. A rip-rap spillway was then constructed to improve run-off conditions
from the impoundments. The embankments were then successfully revegetated. These actions
have adequately addressed the stability of the impoundments and as discussed above periodic
monitoring will continue to assure that the stability is maintained.
Dolomite rock from the Sherman Mine was used for cover material at the site and laboratory
analysis of 10 samples confirmed that lead was found to be between 16 mg/kg to 5,840 mg/kg in
9 of the samples with one sample having 23,900 mg/kg, for an average of 5000 mg/kg for all 10
samples. This is well below the 6,700 mg/kg for lead that was established in the human health
risk assessment for commercial and industrial workers that would be consistent with current land
uses and zoning. The dolomite has a high amount of available calcium carbonate making the
metals low in availability and will immobilize metal migration minimizing infiltration into the
groundwater.
Erosion Stability of the Lower Malta Gulch (Evaluation of stream channel during floods)
Drainage within lower Malta Gulch where the fluvial tailings were removed does not flow within
an existing channel, but fans out covering the entire gulch. Accordingly, the area was successfully
revegetated and graded to maintain a stable condition during the maximum probable precipitation
event and run-off and access control berms were placed in coordination with the property owner.
Malta Tailings Impoundment (Revegetation status and pyrite disposal)
The revegetation of the Malta Tailings Impoundment was done according to the Malta Gulch
Revegetation Statement of Work and included incorporating 10 tons/acre of limestone. The
vegetation has been established for three growing seasons and is successful.
Pyrite concentrates from the Apache Energy and Minerals property were consolidated into the
impoundment prior to placement of the soil cap. The tailings in the impoundment were from the
Leadville Silver and Gold Mill that also produced a pyrite concentrate and thus the material from
the Apache Energy and Minerals site was chemically and physically the same as the existing
tailings. Less than 1,000 cubic yards of Apache concentrates were consolidated into the Malta
Tailings Impoundment.
Specific Comment No. 1 (Incorrect OU Boundaries)
The Operable Unit boundary map from the Consent Decree has been incorporated into the ROD
showing the correct OU boundaries.
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Specific Comment No. 2 (Additional Disposal in Malta Gulch Tailings Impoundment)
The disposal of additional material from OU2 or any other Operable Units is not being considered
at this time. However, use of this site for disposal in the future is not being ruled out.
Specific Comment No. 3 (Final Closure)
As stated in the Record of Decision, as long as the present zoning, Industrial Mining, or similar
zoning'that does not allow residential use is maintained, no further response actions are necessary.
Thus, local zoning will have to be considered for all long-term land uses for the site.
Specific Comment No. 4 (Ground water concern)
Resurrection as a party to the Site-wide Consent Decree dated May 17, 1,994, agreed that
decisions on remediation of surface and ground water would be made only after records of
decision for source remediation were selected and implemented at each operable unit. If
additional response actions are necessary to meet surface or ground water requirements, those
actions will be designated in the Record of Decision for Operable Unit 12.
Specific Comment No. 5 (Ground water monitoring)
The specific program for monitoring site-wide ground water which will include OU2 will be
developed in the future.
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