EPA ROD continued:
III. ASSESSMENT OF THE SITE
Heavy-metal-laden AMD is released from several, and possibly all, of the
inactive mine workings at IMM and from the numerous waste piles on the mine
property. The AMD drainage discharges to surface waters (which include
Boulder, Slickrock, and Spring Creeks, the Spring Creek Reservoir, Keswick
Reservoir, and the Sacramento River), causing severe environmental impacts
and posing a potential threat to human health. The Sacramento River is a
major fishery and source of drinking water for Redding. The National
Oceanic and Atmospheric Administration (NOAA) has identified the affected
area as the most important salmon habitat in California. Under the Clean
Water Act [Para]304(1) inventory of impaired water bodies and the toxic
point sources affecting the water bodies, EPA identified the IMM site as the
largest such discharger of toxic metals in the United States.
EPA has identified control of AMD sources in the Old/No. 8 Mine Seep
Operable Unit as a major step in the ultimate control of discharges of
contamination from the IMM site. The Old/No. 8 Mine Seep is the third
largest source of AMD at the site. Actual or threatened releases of AMD
from this site, if not addressed by implementing the response action
selected in the Record of Decision (ROD), may present an imminent and
substantial endangerment to public health, welfare, or the environment.
The Old/No. 8 Mine Seep Operable Unit (OU) includes the AMD discharges from
the seeps which emerge from the north slope of the Slickrock Creek valley in
the vicinity of several portals of the Old Mine and No. 8 Mine. The mine
portals are covered by landslides, and the mines are not accessible.
The AMD discharged to Slickrock Creek contains high concentrations of
copper, cadmium, and zinc and is the primary exposure pathway. The
principal threat posed by these releases is the creation of conditions toxic
to aquatic life in the receiving waters, most importantly, the Sacramento
River. The Sacramento River supports a valuable fishery that includes four
species of chinook salmon, steelhead, and resident trout. The Winter-Run
Chinook Salmon has been designated as a threatened species under the
Endangered Species Act.
The ROD for the Old/No. 8 Mine Seep Operable Unit (OU) is the third ROD for
the IMM site. The first ROD for the Site, signed in October 1986, provided
limited source control actions to begin lessening the AMD discharges and
provided water management capability to manage the ongoing AMD releases to
surface waters. Specific activities authorized by the 1986 ROD include a
diversion of Slickrock Creek around sulfide-bearing landslide debris,
diversion of Upper Spring Creek in the Boulder Creek drainage, and a partial
cap of Brick Flat Pit. All of these projects have been completed. The 1986
ROD also authorized the enlargement of the Spring Creek Debris Dam and the
diversion of the South Fork of Spring Creek. The enlargement of Spring
Creek Diversion Dam is currently being designed by the U.S. Bureau of
Reclamation under an agreement with EPA.
The second ROD for the IMM site was signed on September 30, 1992. It
provided for an interim remedial action to treat AMD from the Richmond
portal and the Lawson portal in the Boulder Creek Operable Unit. This
action addressed the two largest sources of heavy-metal-laden AMD at the
site. The design of the AMD collection and conveyance system, the treatment
system, and the sludge disposal in Brick Flat Pit is underway.
To achieve the remedial action objectives of the Superfund action at the IMM
site, EPA expects to require a further study or studies for the sources in
the Slickrock Creek drainage not addressed in today's Record of Decision;
other sources in the Boulder Creek drainage; sediments in Spring Creek,
Spring Creek Reservoir, Keswick Reservoir, and the Sacramento River;
contaminated groundwater; and other sources of contamination. The
additional study will also assess potential water management options,
including the need to coordinate releases of acidic waters with Central
Valley Project water releases. Any further study will also consider
resource recovery and source control. EPA is currently developing a work
plan for this additional Remedial Action/Feasibility Study (RI/FS) activity,
and this study will consider achieving all Applicable, or Relevant, and
Appropriate Requirements (ARARs) for the actions.
IV. DESCRIPTION OF THE SELECTED REMEDY
The remedy selected in this decision document addresses the principal threat
posed by contaminant releases from sources within the Slickrock Creek
watershed at the IMM site through collecting and treating the Old/No. 8 Mine
Seep discharge.
The major components of the selected remedy include:
. Construction of necessary structures, pipelines, pumping stations,
and equalization to provide for delivery of all AMD flows from the
Old/No. 8 Mine Seep to the treatment facility.
. Treatment facilities to perform chemical
neutralization/precipitation treatment of all of the Old/No. 8
Mine Seep AMD using the lime high density sludge (HDS)/simple mix
treatment process option to meet the performance standards of 40
C.F.R. Part 440, which have been determined to be relevant and
appropriate to this application. Discharges to lower Spring
Creek, Boulder Creek, and Slickrock Creek shall comply with the
effluent limitations of 40 C.F.R. [Para][Para]440.102(a) and
440.103(a), except for the limitation on pH and total suspended
solids (TSS). Discharges to Flat Creek shall also comply with the
pH and TSS requirements of 40 C.F.R. [Para]440.102(a).
. Disposal of treatment residuals onsite in the inactive open pit
mine, Brick Flat Pit. The design of the improvements to Brick
Flat Pit to function as a disposal facility shall comply with the
requirements of the Toxic Pits Control Act and California
requirements for disposal of mining wastes.
V. STATUTORY DETERMINATIONS
This interim action is protective of human health and the environment. The
selected remedy essentially eliminates the potential exposure and the
resultant threats to human health and the environment from the sources and
pathways addressed in this interim action. The Old/No. 8 Mine Seep Operable
Unit provides for an interim action that is not expected to be final and
does not address all of the sources of discharges from the IMM site. The
selected remedy, therefore, cannot be expected to be fully protective of
human health and the environment. Further remedial actions are required.
This interim action complies with (or waives) Federal and State ARARs for
this limited-scope action. The selected remedy is expected to comply with
most chemical-, action-, and location-specific ARARs. Because of the
environmental impacts of the sources not addressed in this ROD, EPA
anticipates that the Old/No. 8 Mine Seep Operable Unit remedial action will
not provide for compliance with all ARARs at all times, and consequently EPA
is relying on the ARARs waiver for "interim measures" (40 C.F.R.
[Para]300.430(f)(1)(ii)(C)(1)) for remedy selection with respect to sources
in the Old/No. 8 Mine Seep Operable Unit. The selected remedy does not
address all sources of contaminant discharges at the site and cannot provide
for compliance with the chemical-specific ARARs of the Central Valley
Regional Water Quality Control Board's Basin Plan water quality objectives
at all times or for full compliance with California Fish and Game Code
Section 5650, which prohibits discharge of contaminants "deleterious to
fish, plant life, or bird life." Accordingly, EPA is invoking the CERCLA
Section 121(d)(4)(A) waiver for "interim measures" for these ARARs.
EPA has determined that the selected remedy is cost-effective pursuant to
evaluations in accordance with Section 300.430(f)(1)(ii)(D) of the NCP. EPA
has considered the quality of the data relied upon to characterize the site
and the Old/No. 8 Mine Seep discharge. EPA has also considered the quality
of the data relied upon during the development and evaluation of potential
remedial alternatives, and the selection of the interim remedial action for
the Old/Mine 8 Mine Seep.
EPA has determined that the selected remedy represents the maximum extent to
which permanent solutions and treatment technologies can be utilized for the
interim remedial action for the Old/No. 8 Mine Seep Operable Unit at the IMM
site. Alternatives that might reduce or eliminate the AMD-forming reactions
have been developed and evaluated in the Boulder Creek Operable Unit. EPA
has concluded that significant additional development and evaluation of
these approaches is required, and this conclusion also applies to the
Old/No. 8 Mine Seep Operable Unit. EPA encourages the continued development
of those alternatives that could reduce or eliminate the AMD-forming
reactions for consideration in a subsequent action for the IMM site.
Treatment of the discharges will effectively eliminate the contaminant
discharges and is a component of all alternatives developed to date.
Treatment, therefore, is consistent with any anticipated subsequent actions.
Because this action does not constitute the final remedy for the IMM site,
the statutory preference for remedies employing treatment that reduces
toxicity, mobility, or volume as a principal element will be further
addressed by the final response action. Subsequent actions are planned to
fully address the threats posed by the conditions at this site. Because
this remedy will result in hazardous substances remaining onsite above
health-based levels, a review will be conducted to ensure that the remedy
continues to provide adequate protection of human health and the environment
within 5 years after commencement of the remedial action. Because this is
an interim action ROD, review of this site and of this remedy will be
ongoing as EPA continues to develop final remedial alternatives for the
site.
9-24-93
John C. Wise Date
Acting Regional Administrator
Remedy:
Operable Unit:
ROD ID: EPA/ROD/R09-86/011 ROD Date: 10/03/86
Contaminant: ACIDS
CADMIUM
HEAVY METALS
INORGANICS
O&M Costs: Estimated Costs:
Keys: ACIDS
ALTERNATIVE TECHNOLOGY
CADMIUM
CAPPING
FUND BALANCING
GROUND WATER DIVERSION
HEAVY METALS
INORGANICS
MINING WASTES
O&M
SEDIMENTS
STATE CRITERIA
SURFACE WATER
Abstract:
IRON MOUNTAIN MINE (IMM) IS LOCATED IN THE SOUTHEASTERN FOOTHILLS
OF THE KLAMATH MOUNTAINS, APPROXIMATELY NINE MILES NORTHWEST OF THE CITY
OF REDDING, CALIFORNIA. BETWEEN THE 1860S AND 1962, IMM WAS
PERIODICALLY MINED FOR IRON, SILVER, GOLD, COPPER, ZINC. AND PYRITE.
THE MINE AREA, BELIEVED TO BE ONE OREBODY WHICH HAS BEEN SEGMENTED BY
FAULTING, IS LOCATED ON 4,400 ACRES OF PROPERTY THAT INCLUDES
UNDERGROUND WORKINGS, AN OPEN PIT MINING AREA, WASTE ROCK DUMPS, AND
TAILINGS PILES. RAINFALL, INFILTRATING INTO THE UNDERGROUND MINE
WORKINGS, MIXES WITH GROUND WATER AND THE ORE ZONE TO PRODUCE SULFURIC
ACID AND HIGH CONCENTRATIONS OF ZINC, CADMIUM, AND COPPER. THE
RESULTING HEAVY METAL-LADEN ACIDIC WATERS, REFERRED TO AS ACID MINE
DRAINAGE (AMD), EVENTUALLY DISCHARGE THROUGH MINE ADITS OR GROUND WATER
SEEPAGE INTO THE SPRING CREEK WATERSHED STREAMS, SPRING CREEK RESERVOIR,
AND THE SACRAMENTO RIVER. THE PRIMARY CONTAMINANTS OF CONCERN
INCLUDE; AMD, COPPER, CADMIUM, AND ZINC.
THE DESIRED REMEDIAL ACTION FOR THIS SITE WAS NOT SELECTED DUE TO
EXCESSIVE COST. INSTEAD, A FUND BALANCING WAIVER TO THE NCP WAS INVOKED
AND AN ALTERNATIVE THAT MOST CLOSELY APPROACHES ARARS WAS SELECTED. THE
ALTERNATIVE INCLUDES; CAPPING SELECTED CRACKED AND CARVED GROUND AREAS
USING A SOIL-CEMENT MIXTURE OR OTHER SUITABLE MATERIAL; DIVERTING CLEAN
SURFACE WATER IN UPPER SPRING CREEK TO FLAT CREEK, DIVERTING CLEAN
SURFACE WATER IN SOUTH FORK SPRING CREEK TO ROCK CREEK, AND DIVERTING
CLEAN UPPER SLICKROCK CREEK WATER AROUND WASTE ROCK AND TAILINGS PILES;
ENLARGING SPRING CREEK DEBRIS DAM FROM ITS PRESENT CAPACITY OF 5,800
ACRE FEET TO 9,000 ACRE FEET; IMPLEMENTING PERIMETER CONTROL AS NEEDED
TO MINIMIZE DIRECT CONTACT THREAT; AND PERFORMING HYDROGEOLOGIC STUDY
AND FIELD-SCALE PILOT DEMONSTRATION TO BETTER DEFINE THE FEASIBILITY OF
UTILIZING LOW-DENSITY CELLULAR CONCRETE TO ELIMINATE OR REDUCE ACID MINE
DRAINAGE FORMATION. THE ESTIMATED CAPITAL COSTS FOR THE FUND-BALANCED
ALTERNATIVE IS $68,100,000 WITH O&M PRESENT WORTH COSTS OF $4,100,000.
Remedy:
- CAP SELECTED CRACKED AND CAVED GROUND AREAS ON IRON MOUNTAIN
ABOVE THE RICHMOND ORE BODY USING A SOIL-CEMENT MIXTURE OR
OTHER SUITABLE MATERIAL *;
- DIVERT CLEAN SURFACE WATER IN UPPER SPRING CREEK TO FLAT
CREEK, DIVERT CLEAN SURFACE WATER IN SOUTH FORK SPRING
CREEK TO ROCK CREEK, AND DIVERT CLEAN UPPER SLICKROCK CREEK
WATER AROUND WASTE ROCK AND TAILINGS PILES;
- ENLARGE SPRING CREEK DEBRIS DAM (SCDD) FROM ITS PRESENT
CAPACITY OF 5,800 ACRE FEET TO 9,000 ACRE FEET;
- IMPLEMENT PERIMETER CONTROL AS NEEDED TO MINIMIZE DIRECT
CONTACT THREAT; AND
- PERFORM HYDROGEOLOGIC STUDY AND FIELD-SCALE PILOT DEMONSTRATION
TO BETTER DEFINE THE FEASIBILITY OF UTILIZING LOW-DENSITY
CELLULAR CONCRETE TO ELIMINATE OR REDUCE ACID MINE DRAINAGE
FORMATION.
* (BASED ON THE PRESENT RECORD, I BELIEVE THAT CONSTRUCTION
OF A PARTIAL CAP OVER THE RICHMOND ORE BODY IS A NECESSARY SOURCE
CONTROL COMPONENT OF THE OVERALL REMEDY AS ENVISIONED BY EPA.
HOWEVER, THE POTENTIALLY RESPONSIBLE PARTIES ARE PROPOSING TO
IMPLEMENT A SOLUTION MINING OPERATION THAT MAY BE ABLE TO
EFFECTIVELY EXPLOIT THE ORE BODY AS A RESOURCE AND CONTROL THE
DISCHARGE OF ACID MINE DRAINAGE FROM THE MOUNTAIN. CONSTRUCTION
OF THE PARTIAL CAP COULD ADVERSELY AFFECT THE SOLUTION MINING
OPERATION. EPA INTENDS TO FURTHER EXPLORE THE IMPLEMENTATION
AND ENVIRONMENTAL RESULTS ASSOCIATED WITH A SOLUTION MINING
OPERATION DURING THE NEXT 60 DAYS. THEREFORE, NO ACTION WILL BE
TAKEN TO IMPLEMENT THE CAPPING COMPONENT FOR A PERIOD OF AT
LEAST 60 DAYS FROM THE SIGNATURE DATE ON THIS RECORD OF DECISION.
TO THE EXTENT THAT NEW INFORMATION CAUSES EPA TO MODIFY ITS
PRESENT OPINION THAT THE MOUNTAIN SHOULD BE PARTIALLY CAPPED,
EPA WOULD PROVIDE TO THE PUBLIC AN OPPORTUNITY TO COMMENT PRIOR
TO MAKING ANY FINAL DECISION. I WILL MAKE A DECISION REGARDING
THE IMPLEMENTATION OF THE CAPPING COMPONENT AFTER THE 60-DAY
PERIOD HAS ENDED.).
It's my understanding that the mining solution is the solution that is currently blessed by the EPA.
Regards,
Gary |
