United States Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R09-93/101
September 1993
f/EPA Superfund
Record of Decision:
Iron Mountain Mine, CA
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50272.101
REPORTDOCUMENTA~ON 11. REPORT NO. 2. 3. Reclplenf8 Acc88a1on No.
PAGE ~PA/ROD/R09-93/101
4. Title and SUbtitle 5. Report Date
SUPERFUND RECORD OF DECISION 09/28/93
Iron Mountain Mine, CA 6.
Third Remedial Action
7. Author(a) 8. Performing Organization Rept. No.
9. Performing Organization Nama and Addr... 10 ProJact TaakIWorlc Unit No.
11. Contract(C) or Grant(G) No:
(C)
(G)
12. Sponaorlng Organization Name and Add....a ' 13. Type of Report .. Period Covered .
U.S. Environmental Protection Agency
401 M Street, S.W. 800/800
l Washington, D.C. 20460 14.
15. Supplemantary Notas
I
PB94-964511
16. Abstract (Limit: 200 words)
The 4,400-acre Iron Mountain Mine site is a commercial mining facility located 9 miles
northwest of Redding, Shasta County, California. Land use in the area is predominantly
recreational,' with largely undeveloped wilderness property. .. The site is bordered by
two heavily used national forests, and is located near the Sacramento River. The
estimated'70,000 people who reside in Redding use the ~iver as a major source of.
drinking water.- The Iron Mountain Mine site includes mining property on the
topograph-ic feature known .as Iron Mountain, the several inactive underground and open
pit mines, numerous waste piles, abandoned mining facilities, mine drainage treatment
facilities, and the downstr~am reaches of all creeks and rivers affected by drainage
from Iron Mountain Mine. In 1894, The Moun~ain Mining Co., Ltd. began operation of the
mine. Later, Mountain Copper Co. assumed ownership of the site. Under this company's
operation, high-grade copper ore was mined until 1907 in the Old Mine, and from 1907,
until as late as 1923, in Mine No. '8. In 1968, the mine was acquired by Stauffer
Chemical Co., and was operated there until 1976. In 1976, the State required the
abatement of the continuing pollution from the mountain. Iron Mountain Mines, Inc.
( IMMI) acquired a majority of the parcels to the mine in 1976 and currently operates
the facilities. IMMI constructed a copper cementation pl~nt on a nearby creek to
(See Attached Page)
17. Qocumant Analyala , a. Dasc:rlptors
Record of Decision - Iron Mountain Mine, CA
Third Remedial Action
Contaminated Medium: sw
Key Contaminants: metals (arsenic, copper,cadium, zinc), acids
b~ IdentlfieralOpan-Endad Terms
c. COSA TI FleldlGroup
18. Availability Statemant 19. Security Class (ThIs Report) 21. No. of Pegss
None 68
20. Security Class (ThIs Page) 22. Price
None
(See ANSI-Z39.18)
s.. Instructions on RellelSll
OPTIONAL FORM 272 (4:'77)
(Formerly NTI8-35) .
Department of Commarce
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EPA/ROD/R09-93/101
Iron Mountain Mine, CA
Third Remedial Action
Abstract (Continued)
recover copper from the acid mine drainage (AMD). Due to various fish kills and toxicity
problems, a number of investigations were conducted by the State which revealed high
concentrations of copper, cadmium, and zinc in the acidic discharges flowing from the Old
and No.8 mines into Slickrock Creek, a tributary of Spring Creek, which in turn .is a
tributary of the Sacramento River. A 1986 ROD addressed limited source control and water
management actions, which included constructing a partial .cap over a mineralized zone,
constructing diversions of various creeks to avoid an AMD-generating slide and to protect
cleaner waters, and enlarging the Spring Creek Debris Dam. A 1992 ROD addressed .
contaminants seeping from the two largest sources of AMD at the mine and from the numerous
waste rock piles, tailing piles, seeps, and contaminated sediment for the Boulder Creek
OU. This ROD addresses an interim .remedy for the Old/No.8 Mine Seep OU, the third largest
area ofAMD contami~ation at the site. Future RODs will address resource recovery and
additional source control. The primary contaminants of concern affecting the surface
water are metals, .includi~g arsenic, copper, cadmium, and zinc; and acids.
The selected remedial action for this site includes treating acid- and heavy
metal-contaminated surface water onsite using chemical neutralization/precipitation with
HDS process option; constructing collection structures, pipelines, and equalization
equipmerit to provide for delivery and onsite treatment of all base, sustained, and peak
AMD flows from the Old/No.8 Mine Seep to an elevated tank at the Minnesota Flats
treatment facility, located 24,000 feet from the discharge' area; and disposing of
residuals onsite in an inactive open pit mine. The estimated present worth cost for this
remedial action is $8,270,000, which includes an estimated total O&M cost of $3,920,000.
PERFORMANCE STANDARDS OR GOALS:
Not provided.
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Record of Decision
Old/No. 8 Seep
Iron Mountain Mine
Shasta County, California
September 24, 1993
U.S. Environmental Protection Agency
Region IX
75 Hawthorne Street
San Francisco, California 94105
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CONTENTS
The Declaration
1. Site Name and Location
II. Statement of Basis and Purpose
III. Assessment of the Site
IV. Description of the Selected Remedy
V. Statutory Determinations
The Decision Summary
I. Site Name, Location, and Description
II. Site History and Enforcement Activities
III. Highlights of Community Participation
IV. Scope and Role of the Operable Unit Within Site Strategy
V. Site Characteristics
VI. Summary of Site Risks
VII. Description of Alternatives
VIII. Alternative Comparisons
IX. The Selected Remedy
X. Statutory Determinations
XI. Documentation of Significant Changes
Tables
1 .
Summary of Water Quality and Flow Data for Old/No. 8. Mine
Seep, 1978 to 1990
2
Maximum Contaminant Levels Specified by Selected ARARs (~g/l)
3
Summary of Overall Protection of Human Health and the Environment
and Achievement of ARARs
4
Summary of Costs
5
Incremental Cost Summary for Alternative OJN8-1 ($ x 1,000)
6
Incremental Annual Operation and Maintenance Cost
Summary for Alternative O/N8-1 ($ x 1,000)
Page
1
1
1
2
3
4
7
7
13
17
19
20
21
25
34
44
47
54
20
39
40
42
47
48
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CONTENTS (continued)
Page
Figures
1
Location of Iron Mountain Site
8
2
Screening of Remedial Technologies for Mine Portals
28
3
Screening of Remedial Technologies for Waste Piles
29
4
HDS/Simple Mix Lime Neutralization
31
5
Generalized Flow Schematic-HDSfSimple Mix Treatment of
Acid Mine Drainage
32
6
Copper Cementation Facilities
35
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RECORD OF DECISION
IRON MOUNTAIN MINE
SHASTA COUNTY. CALIFORNIA
THE DECLARATION
I. SITE NAME AND WCATION
Iron Mountain Mine
Shasta County, California (near Redding, California)
II. STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected interim remedial action for control of
heavy-me tal-bearing acidic discharges, termed acid mine drainage, or AMD, from the
Old and No. 8 Mines into Slickrock Creek. These discharges are the third largest
source of AMD at the Iron Mountain Mine Superfund Site. Slickrock Creek is a
tributary of Spring Creek, which in turn is a tributary of the Sacramento River.
Slickrock Creek is on the south side of the Iron Mountain Mine (IMM) site. The IMM
site is located about 9 miles northwest of Redding, California. .
The selected interim remedial action is to collect and treat the AMD from Old/No. 8
Mine Seep. The selected interim remedial action was chosen in accordance with the
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA),
as amended by the Superfund Amendments and ReauthoriZation Act (SARA), and the
National Oil and Hazardous Substances Pollution Contingency Plan (NCP). This
decision is based upon the administrative record for this site.
The Natural Resource. Trustees Council, which includes both State and Federal
resource trustees for the. Site, concurs with the selection of treatment and the High
Density Sludge (HDS) process option as the interim remedial action for the Old/No.8
Mine Seep acid mine drainage discharges.
The California Department of Toxic Substances Control (DTSC) and Regional Water
Quality Control Board (RWQCB) concur with the selection of lime treatment and use
of a process option that will produce a dense sludge as the interim remedial action for
the Old/No.8 Mine Seep acid mine drainage discharges. However, DTSC and
RWQCB have encouraged EPA to fully evaluate the Aerated Simple Mix (ASM)
process proposed by Stauffer Management Company (SMC) as an alternative to the
HDS process. EP A has reviewed recently available treatability study data that indicate
that the ASM process will not produce the required dense sludges that DTSC and
RWQCB agree are necessary. EPA will review this information with the DTSC and
RWQCB and will continue to assess any subsequently developed information.
IMM Old/No.8 Record of Decision
1
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III. ASSESSMENT OF THE SITE
Heavy-metal-Iaden 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 ~304(l) inventory of impaired water bodies and the toxic point sources
affecting the water bodies, EP A 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 'un~er an agreement with EP A
IMM Old/No.8 Record of Decision
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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 ponal and the Lawson
ponal in the Boulder Creek Operable Unit. This action .addressed the two largest
sources of heavy-metal-Iaden 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,
EP A 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 Reser-
voir, and the Sacramento River; contaminated groundwater; and other sources of con-
tamination. The additional study will also gassess 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. EP A 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 TIlE SELECfED 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 necess~ 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 effiuent limitations of 40 C.F.R. ~~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. ~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 func-
tion as a disposal facility shall comply with the requirements of the Toxic
Pits Control Act and California requirements for disposal of mining
wastes.
IMM Old/No.8 Record of Decision
3
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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 Funher 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 EP A is relying on the ARARs waiver for "interim measures"
(40 C.F.R. ~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 contami-
nants "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.
EP A 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 bas considered the
quality of the data relied upon to characterize the site and the Old/No.8 Mine Seep
discharge. EP A 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. .
EP A has determined that the selected remedy represents the maximum extent to which
permanent solutions and treatment technologies can be utilized for the interim reme-
dial action for the OldINo. 8 Mine Seep Operable Unit at the IMM site. Alternatives
that might reduce or eliminate the AMD-fonning reactions have been developed and
evaluated in the Boulder Creek Operable Unit. EP A 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. EP A encourages
the continued development of those alternatives. that could r:educe 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.
IMM OldINo. 8 Record of Decision
4
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6
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. Sub-
sequent 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 EP A continues to develop final
remedial alternatives for the site.
~~1M-~:~1. m:LIr'-
Jonn Wise /.!
Acting Regional Admiiiistrator
t) -:2 L/ - 9:5
Date
IMM Old/No.8 Record of Decision
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RECORD OF DECISION
IRON MOUNTAIN MINE
SHASTA COUNTY, CALIFORNIA
THE DECISION SUMMARY
I. SITE NAME, LOCATION, AND DESCRIPTION
1.1 Site Name
Iron Mountain is located in Shasta County, California, approximately 9 miles nonhwest
of the City of Redding, see Figure 1. The collection of mines on Iron Mountain is
known today as Iron Mountain Mines. They are the southernmost mines in the West
Shasta Mining District. The District encompasses over a dozen sulfide mines that have
been worked for silver, gold, copper, zinc, and pyrite.
1.2 Site Location
The Iron Mountain Mine Superfund site is defined pursuant to the Comprehensive
Environmental Response, Compensation, and Liability Act (CERCLA) to include the
inactive mines on Iron Mountain and areas where hazardous substances released from
the mines are now located. The Iron Mountain Mine (IMM) site includes
approximately 4,400 acres of land that includes the mining property on the topographic
feature known as Iron Mountain, the several inactive underground and open pit mines,
numerous waste piles, abandoned mining facilities, mine drainage treatment facilities,
and the downstream reaches of Boulder Creek, Slickrock Creek, Spring Creek, Spring
Creek Reservoir, Keswick Reservoir, and the Sacramento River affected by drainage
from Iron Mountain Mine.
1.3 Site Description
The summit of Iron Mountain is 3,583 feet above mean sea level and is approximately
3,000 feet above the Sacramento River, 3 miles to the east. The terrain is very steep,
with slopes dropping 1 to 2 feet for every 2 feet horizontally, or steeper. The mountain
is predominantly forested with some areas of brush, and there are numerous unpaved
roads leading to various work locations.
Several, and possibly all, of the mines and the waste rock piles are discharging acidic
waters, typically with a high content of heavy metals. These discharges are herein
referred to collectively as acid mine drainage, or AMD. The largest sources of AMD
are located within the Iron Mountain Mine' property. The largest source of AMD is
the Richmond Mine, and the second largest is the Hornet Mine, both of which drain
into Boulder Creek. The third largest source and the subject of this ROD is the
Old/No. 8 Mine Seep, which drains into Slickrock Creek. Old/No. 8 Mine Seep is
7
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, SITE LOCATION
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FIGURE 1
LOCATION OF
IRON MOUNTAIN SITE
IRON MOUNTAIN MINE OL.DINO. 8 MINE SEEP ROD
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located on the south side of Iron Mountain at an elevation of approximately 2,500 feet.
The seep is located on the north slope of the Slickrock Creek valley proximate and
below the landslide-covered portals of Old Mine and No.8 Mine. The portals were
covered when a large mass of overburden soils and waste rock (largely from the Brick
Flat Pit open pit mining) slid into Slickrock Valley in 1955. The frequent small slides
are continuing to add to the landslide cover. The present condition of the tunnels and
stopes of the Old Mine and No.8 Mine is unknown, but the available reports and liter-
ature indicate that some of the mine openings were backfilled with sludge and waste
rock during mine operations. From observations of other underground mines at this
site, it is reasonable to assume that some of the unfilled mine openings have collapsed.
The proportion of drainage from the two mines is unknown.
EP A has identified control of the AMD sources in the Slickrock Creek drainage basin
as a major step in the ultimate control of the contaminant discharges from Iron Moun-
tain. EPA has designated the OldINo. 8 Mine Seep as an Operable Unit for a feasibil-
ity study of pollution sources and alternative approaches for AMD control. .
The IMM site contains a very large mass of nearly pure sulfide (massive deposit),
several small massive sulfide deposits, several zones of disseminated sulfides, and a
large gossan. The gossan is a zone of rock from which disseminated sulfides have been
almost completely removed by natural solution, leaving a residue of iron and ,other
metals. The gossan has been mined by open pit for residual metals. The disseminated
and massive sulfides have been mined in open pit and underground openings for cop-
per, cadmium, zinc, and pyrite. The main country rock at the IMM site is rhyolite.
Commercial mining at the IMM site started in 1879 and continued, with a few inter-
ruptions, until 1963. In the early- twentieth century, the site was one of the largest
copper mines in the United States. Mineral extraction objectives and methods varied
widely. In recent years, metal recovery activity at the site has been limited to extracting
copper from the AMD, using copper cementation and occasional sales of previously
mined material (such as hematite tailings).
1.4 Adjacent Land Uses
The adjacent land is largely undeveloped wilderness property that is currently infre-
quently visited because of the rugged topography and few roads. Off-road vehicles
have been known to visit these areas, and the U.S. Bureau of Land Management has
notified EP A with regard to potential acquisition of adjacent lands for preservation as
wilderness and enhancement for recreational use.
1.5 Natural Resources Uses
The natural resources on the mining property and in the surface waters which flow on
or adjacent to the mining property at one time included mature stands of timber, fish,
other aquatic populations, and sulfide minerals. The natural resources in the down-
gradient Sacramento River include the valuable Sacramento River fishery, recreational
use of the river and Keswick Reservoir, and the valuable water resources, which are a .
9
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major component of the U.S. Bureau of Reclamation's (USBR's) water distribution
system for the State of California.
The timber on the IMM site has been largely removed for the mine operations or sale.
The timber stands were also extensively damaged by historic smelter operations in the
early 19005. The portions of Boulder Creek, Slickrock Creek, and Spring Creek
impacted by AMD from IMM are essentially lifeless. A major portion of the sulfide
minerals remain in the mines and in undeveloped areas. The market for sulfide
minerals has not been attractive in recent years, and there is no verified proposal to
mine these deposits in the near future.
Spring Creek Reservoir was constructed in part as a mitigation measure for the AMD
discharges and does not support aquatic life. It is not used for any recreational
purpose.
The portion of Keswick Reservoir impacted by Iron Mountain Mine AMD has reduced
recreational value. The resident trout fishery is impacted by the heavy metal contami-
nants in the water column of the mixing zones and the heavy sediment loadings caused
by the precipitation of iron and co-precipitation of heavy metals.
The upper Sacramento River salmon fishery is the most important fishery in the State.
The salmon fishery has experienced large population declines over the past 20 years
because of a number of factors, including Iron Mountain Mine AMD impacts. The
Sacramento River also supports a major steelhead trout and resident trout fishery.
The water resources held in Shasta Lake by the USBR as part of its Central Valley
Project (CVP) are an important component of the water distribution system for a grow-
ing California's municipal and agricultural interests. CVP operations are today
sometimes constrained by the Iron Mountain Mine AMD discharges in order that water
quality conditions in the Sacramento River can be maintained within. safe bounds for
fishery protection. On occasion, USBR has released water from Shasta to dilute AMD,
water which would otherwise have been used for beneficial purposes.
1.6 Location and Distance of Buman Populations
Iron Mountain Mine is mainly remote from human populations because of the rugged
terrain and the single-access roadway. The mine owner has provided heavy metal
gates, which are locked at most times to discourage casual entry to the site. Human
contact with the flows from Iron Mountain is mainly limited to the waters downstream
of Spring Creek Debris Dam, which include Keswick Reservoir and the Sacramento
River below Keswick Dam.
The closest community is Keswick, located just east of the site. Several isolated resi-
dences are between Keswick and the mine property. The City of Redding has a popu-
lation of approximately 70,000 people and is located approximately 9 miles from the
site.
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1.7 General Surface-Water and Groundwater Resources
Local surface drainage includes Boulder Creek, located northeast of the mountain, and
Slickrock Creek, located to the southwest. Boulder Creek and Slickrock Creek flow
into Spring Creek. Spring Creek flows south and east to the Spring Creek Debris Dam
(SCDD), from which the USBR releases flow into the Sacramento River. Flat Creek
drains an area to the east of Iron Mountain and enters the Sacramento River approxi-
mately 0.8 mile north of Spring Creek. Flat Creek also receives water from Upper
Spring Creek, as a result of a water diversion project constructed in 1990 as part of the
CERCLA response at Iron Mountain.
OldINo. 8 Mine Seep consists of several apparently separate discharges in an area of
about 130 square feet. The AMD discharging from the seep flows downhill and is
collected in an unlined basin about 12 feet long, 10 feet wide, and 2 feet deep. The
basin was constructed to measure flows from the seep. The AMD flows from the basin
to a copper cementation plant in a 140-foot-long stainless steel flume.
Slickrock Creek drains the south side of Iron Mountain and flows generally from the
northwest to the southeast. The headwaters of Slickrock Creek are at about Elevation
3200 feet. The creek flows about 3 miles to its confluence with Spring Creek at
Elevation 1350. The stream carries water from several small ephemeral tnoutaries as
well as discharges from OldINo. 8 Mine Seep and Big Seep, 200 to 300 feet upstream.
Slickrock Creek also receives drainage from Brick Flat Pit. The average daily flow of
Slickrock Creek at its confluence with Spring Creek is 9.4 cubic feet per second (4,200
gpm).
The rainfall-runoff responsiveness of the OldINo. 8 Mine Seep Operable Unit may vary
significantly throughout storm events. The amount of runoff is dependent on antece-
dent moisture conditions, storm intensity, the vegetative cover, ground slope, length of
distnouting area, and geology. Major storm events may cause a rapid rise in water
levels in the creek.
The rhyolite country rock is a dense rock with two to three sets of joints and a number
of faults. The rock blocks generally lack significant porosity, and the low porosity of
the rock mass is due to the joint/fault discontinuities. The presence of groundwater
and its movement within the rock are largely controlled by the discontinuities.
The massive sulfide deposits were largely isolated from the groundwater before mining
because the joints generally do not extend from the country rock into the mineralized
zone. Groundwater was present in the disseminated zones. Mine openings and crack-
ing caused by ground movements induced by mining have opened large volumes of
massive sulfide to groundwater and have increased groundwater access to the dissemi-
nated sulfide mineralization. The additional groundwater movement and increased
circulation of air within the rock mass has greatly accelerated the process of sulfide
dissolution and the formation of metal-rich acid mine drainage.
Surface water and groundwater at Iron Mountain were previously used for mining
operations and to provide water supply to the mine staff and their families. These
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resources are essentially unused today because the mines are inactive and surface
waters are being contaminated by AMD.
1.8 Surface and Subsurface Features
An open pit mine at Brick Flat, underground workings at Old Mine, No.8 Mine, the
Confidence-Complex Mine on the southern flank of the mountain, and the Richmond
and Hornet Mines on the nonhern flank are the large mines on Iron Mountain.
Four sulfide are bodies were mined in the Slickrock Creek drainage. They are Old
Mine, No.8 Mine, Confidence Mine, and Oskosh Mine. The Oskosh is a small mine
on the south side of the Slickrock Creek valley at a relatively low l~vel, and the
Confidence Mine is high on the nonh side of the valley. . Both mines appear to dis-
charge small to moderate volumes of AMD or secondary quantities of metal. The Old
Mine and No.8 Mine appear to have had more significant mining operations and to be
more significant so~rces of AMD.
Old Mine was developed to mine portions of a gossan deposit which could not be
reached by quarrying. The mine is under the north slope of Slickrock Creek valley with
the mine workings ranging from the elevation of the lower slope to well below the
elevation of the adjacent reach of Slickrock Creek. A method of underground mining
called slice stoping was used. The are was removed in 7-foot-high layers working from
the bottom toward the top of the deposit. A working surface was maintained by
progressively backfilling the mined opening with rock rubble returned to the mine
through dropholes from the ground surface. The extent of the backfilling is not clear
from the records available to EP A, but the volume of remaining voids in the mine at
the time of closure may have been .small compared with adjacent mines on the IMM
site. .
The are deposit of the No.8 Mine is at the level of the middle of the north slope of
Slickrock Creek valley. The intelVening 300 feet of rock has little or no sulfide miner-
alization. The are is a mass of rock with disseminated chalcopyrite mineralization in
veins as contrasted with the massive su1fide or massive disseminated ore bodies of the
other mines on the IMM site. The mine consists of three levels of tunnels and small to
moderate size openings which follow the veins. The mine is as high as Elevation 2400,
but portions are below the elevation of Slickrock Creek. Mining started in 1907 and
ended after World War II. Portions of the mine are reported to have been backfilled
with waste rock or tailings slime. -
The Brick Flat open pit mine was operated between 1929 and 1942 and from 1955 to
1962. Most of the overburden and waste rock was placed in a large waste pile south of
the pit and above the north slope of Slickrock Creek valley. In 1955, a large landslide
of these materials moved into the Slickrock Creek valley, covered the Old Mine and
No.8 Mine portals, and filled the valley bottom to a depth of 80 feet. A comparison of
old and recent topographic maps indicates that the present bed of Slickrock Creek is
about 40 feet south of the bed prior to the large slide. The slide surface is presently
almost devoid of vegetation, suggesting continued sliding.
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II. SITE HISTORY AND ENFORCEMENT ACTIVITIES
D.l History of Site Activities that Led to Current Problem
Iron Mountain Mine was first secured for mining purposes in 1865 and various individ-
uals held the property and conducted limited mining for the recovery of silver from the
gossan cap in the late 1800s. The waste-generating activities that created the surface
sources of AMD likely began in the 1880s when the gossan was first mined on a large
scale, and waste rock that was removed to reach the ore was apparently dumped into
ravines and eventually washed into the creeks.
Beginning in late 1894, Mountain Mining Co., Ltd., began operation of the mine. In
approximately 1896, Mountain Copper Co., Ltd., assumed ownership of the mine.
Under Mountain Copper, Ltd.'s, operation of the mines, Iron Mountain became the
largest producer of copper in California and the sixth largest producer in the country
during the first quaner of the twentieth century. The high-grade copper ore in Old
Mine was mined until 1907, No.8 mine from 1907 until as late as 1923, Hornet Mine
from 1907 to 1926, the Richmond Mine from 1926 through 1956, and Brick Flat Pit
from 1929 to 1942 and 1955 to 1962. '
In 1968, Stauffer Chemical Co. acquired Mountain Copper Co., Ltd., and thereby
acquired beneficial ownership of the Iron Mountain Mine. Stauffer transferred record
of ownership of most of the parcels comprising Iron Mountain Mine from its wholly
owned subsidiary to itself in 1969. Stauffer operated the copper cementation plant
during its ownership of the site and continued to investigate the commercial mining
potential of the property. In November 1976, the California Regional Water Quality
Control Board issued Stauffer an order requiring the abatement of the continuing
pollution from the mountain.
In December 1976, Stauffer transferred ownership of 31 parcels on Iron Mountain to
Iron Mountain Mines, Inc., (IMMI), and in December 1980, 5 additional parcels were
transferred to IMMI. IMMI, a California corporation, is the current owner of Iron
Mountain. IMMI constructed a copper cementation plant on Slickrock Creek in 1977.
IMMI has intermittently operated this plant and the copper cementation plant on
Boulder Creek to recover copper from the AMD.
D.2 Impacts of Mining Activity at Iron Mountain
Mountain Copper employed stoping, block caving, and room-and-pillar techniques in
the underground mines; side-hill and open-pit techniques were used at the ground sur-
face. These mining activities aDd subsequent collapse of some of the underground
mine workings have fractur~d the bedrock overlying the mine. The sulfides in the frac-
tured bedrock above the mine and the sulfides remaining in the mine are, in the post-
mining period, more exposed to water, air, and bacterial action. The potential for acid
drainage and metals contamination is greater than prior to mining and may have
increased since the mining ceased in response to deterioration of the ground over the
abandoned mines.
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The mined openings and the ground affected by mining activity now function as effec-
tive groundwater drains, drawing groundwater and unsaturated percolation to and
through the sulfide mineralization. The sulfides that were once largely below the water
table are now largely within the unsaturated zone, and oxygen is available for reaction.
The exothermic oxidation of the sulfide elevates the overall temperature in the sulfide
mineralized zone, induces convective airflow, and likely induces evaporation of some
subsurface ~ine waters. These processes contnoute to the intensity and pattern of
acidic discharges.
These mining-related characteristics, in combination with the natural occurrence at Iron
Mountain of nearly pure massive sulfide deposits surrounded by bedrock with very little
neutralizing capacity, result in a unique hydrogeochemical reactor that is nearly optimal
for maximum production of acid mine waters (Nordstrom and Alpers, 1990). Iron
Mountain produces mine waters that are among the most acidic in the world, contain-
ing extremely elevated concentrations of copper, cadmium, zinc, and other metals
known to be toxic to aquatic life.
TI.3 Central Valley Project Related Impacts
The use of Sacramento River water to serve a growing California has also increased the
significance of Iron Mountain AMD impacts in the Sacramento River. The USBR
constructed Shasta Dam in 1943 to control Sacramento River flows; Keswick Dam,
located downstream of Shasta Dam, was completed in 1950. Spring Creek and
Sacramento River flows mix in the lower third of Keswick Reservoir. Prior to the
USBR's construction of these dams on the Sacramento River, the AMD was often
diluted by large flows of water from farther upstream on the Sacramento River.
Although fish kills and toxicity problems were documented prior to the completion of
Shasta Dam in 1943, the dam compounded the toxicity problems by reducing the avail-
ability of dilution flows (Central Valley Regional Water Quality Control Board, 1976;
Wilson, 1977; Finlayson and Wilson, 1989).
Keswick Dam and Reservoir were completed in 1950. This dam restricted the salmon
and steelhead to spawning grounds in downstream areas. This restricted the naturally
spawning salmon and their early life stages to that area of the Sacramento River with
the greatest exposure to AMD discharges from Iron Mountain.
After construction of Keswick Dam in 1950, the sediment load from Spring Creek,
which previously had been wasted downstream, caused a delta to form in the Spring
Creek arm of Keswick Reservoir.
In response to the problems at Spring Creek, the USBR constructed SCDD in 1963 to
help control the toxic releases from Spring Creek and to prevent sediment from form-
ing a delta in the vicinity of the Spring Creek Powerplant tailrace.
The SCDD allows for the storage and controlled release of water from the Spring
Creek basin. Optimally, releases from Spring Creek Reservoir are timed to coincide
with releases from Shasta Reservoir to meet interim water quality criteria in the
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Sacramento River. However, because of the relatively limited capacity of Spring Creek
Reservoir with respect to peak discharges from the Spring Creek watershed, there have
been uncontrolled spills from the reservoir. Although the debris dam has helped to
reduce the incidence and severity of major fish kills, it has not eliminated them. In
addition, the gradual release of Iron Mountain AMD from SCDD increases the dura-
~ion of exposure of fish in the Sacramento River to chronic toxicity resulting from Iron
Mountain AMD (U.S. EP ~ 1992b). '
n.4 History of Federal and State Site Investigations
Remedial investigation (RI) activities at Iron Mountain began in September 1983, when
Iron Mountain was placed on the National Priorities List of the nation's most contami-
nated sites. In conjunction with EP A's Record of Decision for the first operable unit at
Iron Mountain, EPA issued an RI report in 1985 (U.S. EP~ 1985a). That report
characterizes the entire Iron Mountain sit~ with respect to the nature and extent of
contamination from information available at that time. Site characterization studies
have continued within the Boulder Creek watershed, and EP A has prepared a second
RI report (U.S. EP~ 19913) to present information developed in these additional
studies. An Endangerment Assessment (EA) has been prepared to characterize and
evaluate the current and potential threats to the environment that may be posed by
Iron Mountain contaminants migrating to the groundwater, surface water, and air (U.S.
EP~ 1992b), and EPA's public health risk assessment (U.S. EP~ 1991) has been up-
. dated. The RIIFS for the OldINo. 8 Mine Seep Operable Unit was completed in
December 1992.
The first ROD for the IMM site .was signed in October 1986 and addressed limited
source control and water management actions in an interim remedy. The Boulder
Creek OU ROD, signed in September 1992, addresses remedial actions for (1) AMD
from the Richmond and Lawson portals, the two largest sources of acidity and metals
contamination at Iron Mountain; and (2) the numerous waste rock piles, tailing piles,
seeps, and contaminated sediments that also affect contaminant levels in Boulder
Creek. The OldINo. 8 Mine Seep OU addresses the third largest source at IMM.
EP A has coordinated its site investigation and evaluation activities with those of
Zeneca, Inc., (Zeneca) in a cooperative RIlFS process. (Zeneca was formerly named
ICI Americas, Inc.) Zeneca represents Rhone-Poulenc Basic Chemicals Co. (formerly
named Stauffer Chemical Co.). Zeneca has performed investigation activities at the
site, predominantly related to the Boulder Creek OUFS.
n.s History of CERCLA Enforcement Activities and Remedial Action
EP A's Superfund program became involved with the Iron Mountain pollution problem
shortly after the enactment of the Superfund law in December 1980. On April 5, 1982,
EP A issued general notices of liability to Stauffer Chemical Co. and IMMI for the past
and continuing releases of hazardous substances from Iron Mountain and the resulting
damage to and destruction of natural resources.
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. .-- .
The Iron Mountain Mine site was listed on the National Priorities List in 1983. From
1983 through 1985, EPA conducted an RIfFS of the site and published its report in
1985. After public comment and publication of a Feasibility Study Addendum, EPA
signed the first Iron Mountain Mine Record of Decision in October 1986. That ROD
selected a partial remedy at the site, identifying a number of specific projects. These
projects included the construction of a partial cap over the Richmond mineralized zone,
including a cap of Brick Flat Pit; construction of a diversion in Slickrock Creek to avoid
an AMD-generating slide; construction of a diversion of the Upper Spring Creek to
avoid polluting its cleaner water and filling Spring Creek Reservoir; construction of a
diversion of the South Fork of Spring Creek for a similar purpose; a study of the
feasibility of filling mine passages with Low-Density Cellular Concrete; and an enlarge-
ment of Spring Creek Debris Dam, the exact size of which would be det~rmined after
implementation of other remedies.
. During 1987 and 1988, EPA sued the property owner to gain access to the site for the
purpose of constructing the first of these actions. The court granted EP A access and
ordered the property owner not to interfere with the remedial actions.
On July 19, 1988, EPA initiated construction of the partial cap over the Richmond
mineralized zone. As part of that construction, EP A used tailings materials from the
Minnesota Flat area, as well as selected other tailings piles that contained relatively
high concentrations of copper, cadmium, and zinc. EP A completed construction of the
partial cap in July 1989.
EP A, through the USBR, began construction of the Slickrock Creek diversion in July
1989 and completed construction in January 1990.
Under an EPA Order, ICIA (now known as Zeneca), on behalf of Stauffer Chemical
Company/Rhone-Poulenc Basic Chemicals Co., began construction of the upper Spring
Creek diversion in July 1990. Construction was substantially completed in December
1990.
In addition to the activities implemented pursuant to the ROD, EP A recognized the
need for additional actions in light of the drought conditions prevailing in California
during the late 19808. In the winter of 1988 through 1989, EP A operated an
emergency treatment plant at the site to reduce the toxicity of the AMD releases.
The following fall, the winter-run chinook salmon was listed as a threatened species
under the Endangered Species Act. In August 1989, in part due to the continuing
drought conditions, EP A issued an order requiring that potentially responsible parties
(PRPs) operate an emergency treatment plant at the site to reduce the toxicity of the
AMD discharges for the upcoming 1989 through 1990 winter wet season and to provide
for metals removal for future years until such time as remedial actions could be
selected and implemented. This plant was to be comparable in scope and operation to
the plant operated by EP A the previous winter. Pursuant to that order, Zeneca, on
behalf of Rhone-Poulenc Basic Chemicals, constructed the treatment plant and has
operated this treatment plant during the 1989 to 1990, 1990 to 1991, and 1991 to 1992
wet seasons. Because of the continuing drought in California and the critical fishery
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conditions, EPA issued an order on September 2, 1992, for the 1992 to 1993 wet season
requiring that additional emergency measures be implemented, including increasing
capacity of the treatment plant. .
EP A has also issued an order requiring the PRPs to operate and maintain all EP A-con-
structed remedial actions as well as the actions taken by the PRPs under other orders.
EP A has identified the following persons as potentially responsible parties, parties who
may be liable pursuant to CERCLA, for the cleanup of the site: the former owner and
operator, Rhone-Poulenc Basic Chemicals (the successor to Mountain Copper, Ltd. and
Stauffer Chemical Company), and the current owner and operator, Iron Mountain
Mines, Inc., and its president and primary owner, T. W. Arman. .
EPA and the State of California have brought a civil suit under CERCLA ~107 against
the potentially responsible parties to obtain reimbursement for government funds spent
in responding to the threat at IMM. The district court has held that the cost recovery
authorities of CERCLA do not allow actions against parties for response to mining
wastes and has dismissed the governments' action against Rhone-Poulenc Basic
Chemicals. EP A plans to appeal that ruling.
Subsequent to the ruling under CERCLA, EPA issued an amended order to the
responsible parties under the authority of RCRA ~7003, and the State of California
issued an order under the Health and Safety Code requiring the responsible parties to
continue with implementation of response actions, including construction of the treat-
ment plant selected in the September 1992 ROD., Rhone-Poulenc has agreed to con-
struct the simple mix peak plant and other portions of the selected remedy, and has
agreed to operate the emergency treatment plant under the same conditions as last
winter until the larger plant is on-line. The State of California has also filed an action
in Superior Court against the responsible parties.
m. IDGHLIGHTS OF COMMUNI1Y PARTICIPATION
EP A issued its first Record of Decision for the Iron Mountain Mine site in October
1986. EP A has issued factsheets regarding that decision and commencement of reme-
dial design (July 1987), commencement of remedial action (July 1988), implementation
of emergency response treatment actions (February 1989), and the performance of a
demonstration program under EPA's Superfund Innovative Technology Evaluation.
(SITE) program (August 1991). EPA also updated its Community Relations Plan,
which was finalized in May 1990.
EP A has regularly provided information to the local television news and the press re-
garding the ongoing study and cleanup actions, and this has resulted in significant local.
media coverage. Although the community has maintained interest in the progress of
cleanup at the site, community involvement had been moderate until the winter wet
seasons of 1991 to 1992. Due to the drought conditions facing California and the
occurrence of a March 1992 storm which required the special release of 95,000 acre-
feet of valuable. water resources from Shasta Lake, community interest and involvement
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in the IMM site, including OldlNo. 8 Mine Seep Operable Unit Feasibility Study and
Proposed Plan, was significant. Federal, state, and county officials expressed interest
and concern regarding cleanup progress and remedy selection.
EP A issued the Boulder Creek RI, FS, Environmental Endangerment Assessment, an
updated public health Risk Assessment, Administrative Record, and the Boulder Creek
Operable Unit Proposed Plan for public review on May 20, 1992. To fulfill the require-
ments of CERCLA Section 113(k)(2)(B)(i-v) and Section 117, EPA made these docu-
ments available to the public both at the EP A Records Center in San Francisco,
California, and at the official information repository at the Shasta County Library in
Redding, California. EP A also made the above documents and the large majority of
the Administrative Record available to the public at the Meriam Library of the
. California State University at Chico, California. A public comment period was held.
In addition, a public meeting attended by 200 people was held in Redding, California,
at the Red Lion Hotel on June 11, 1992. At this meeting, representatives from EP A,
the California Regional Water Quality Control Board, Department of Toxic Substances
Control, and Department of Fish and Game made presentations regarding the remedial
alternatives under consideration. EP A answered questions regarding the remedial
alternatives under consideration and problems at the site. EPA received 19 formal oral
comments at the meeting.
EP A received approximately 100 comment letters from the public during the public
comment period. EP A responded to these comments in a Responsiveness Summary,
which is part of the Record of Decision for the Boulder Creek OU, the second ROD
for the IMM site.
EP A issued the OldlNo. 8 Mine Seep RIIFS,. the Administrative Record, and the
OldlNo. 8 Mine Seep Operable Unit Proposed Plan for public review on February 11,
1993. To fulfill the requirements of CERCLA Sections 113(k)(2)(B)(i-v) and 117, EPA
made these documents available to the public both at the EP A Records Center in San
Francisco, California, and at the official information repository at the Shasta County
Library in Redding, California. EP A also made the above documents and the Adminis-
trative Record available to the public at the Meriam Library of the California State
University at Chico, California. The notice of availability of these documents was
published in the Redding Record Searchlight on February 11, 1993. A public comment
period was held from February 11, 1993 through April 15, 1993. In addition, a public
meeting attended by 100 people was held in Redding, California, at the Red Lion Hotel
on February 25, 1993. At this meeting, representatives from EP A made presentations
regarding the remedial alternatives under consideration. EP A answered questions
regarding the remedial alternatives under consideration and problems at the site. EP A
received three formal oral comments at the meeting.
. .
EP A received comment letters from the public during the pUQlic comment period.
EP A responded to, these comments in a Responsiveness Summary, which is part of the
Record of Decision for Old/No. 8 Mine Seep OU.
EPA has received an application for a Technical Assistance Grant (TAG) from the
Shasta Natural Science Association, which is associated with the Carter House Natural
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"$,~
Science Museum in Redding, California. The purpose of the TAG is to help interpret
for the layperson the scientific and engineering information developed as a part of the
Iron Mountain Mine Superfund cleanup action. The original application was received
in January 1992. The application was revised and resubmitted on July 22, 1993. EPA
expects to issue a decision on this grant in September 1993. If approved, the TAG will
provide $48,875, with the Shasta Natural Science Association contributing up to $29,900
in matching funds.
IV. SCOPE AND ROLE OF THE OPERABLE UNIT WITHIN SITE STRATEGY
IV.I Role of the Remedial Action
In accordance with the program management principles identified in the NCP and
40 C.F.R. ~300.439(a)(1)(ii)(A) and (B), EPA has designated the OldlNo. 8 Mine Seep
as an operable unit. .
EP A has determined, in conference with the California support agencies, that this
designation of the OldIN o. 8 Mine Seep Operable Unit will allow the EP A to focus its
RIJFS efforts on this large and complex Superfund site to more quicldy achieve a signif-
icant risk reduction and ultimately expedite the total site cleanup. To achieve the
greatest risk reduction in an expeditious manner, however, it has been necessary to
focus the FS further to take into account the following observations:
. The OldINo. 8 Mine Seep AMD discharges have been identified by
EP A's RI efforts as the third largest source of metal contamination on
Iron Mountain. The. seep discharges an estimated 30 percent of the
copper and 3 percent of the cadmium and zinc discharged from !MM.
Remediation of this source would provide an immediate significant
reduction in acid water and heavy metals loading to the environment.
The OldINo. 8 Mine Seep is drainage from at least one and probably
both of these mines. The portals of the two mines were covered by a
landslide in 1955 and are inaccessible. A part of the drainage may come
from landslide deposits adjacent to or above the mine portals.
Results from implementation of remedial actions for sources in the
OldINo. 8 Mine Seep Operable Unit will be important considerations in
setting remedial action objectives for an overall final site remedy. If, as
expected, water management capabilities remain a component of the
final site cleanup plan, the degree of success in halting or reducing the
AMD discharge will affect the ultimate design and cost of the water man-
agement system.
IV.2 Scope of the Problem Addressed by the Remedial Action Selected.
The OldINo.8 Mine Seep OUPS considers remedial alternatives for the largest
sources of acidity and metals contamination in the Slickrock Creek drainage. Because
this FS represents only an interim remedy for a portion of the site, consideration of
.
.
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alternatives for this source takes into account the need to be consistent with future
remedial action and the need to reduce significant risks as soon as possible.
EP A expects to require an additional study of the sources in the Slickrock Creek drain-
age; sediments in Slickrock Creek, Spring Creek, Spring Creek Reservoir, Keswick
Reservoir, and the Sacramento River; and other impacted areas and sources of contam-
ination. 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. EP A is currently developing a work plan for this additional RIIFS
activity.
V. SITE CHARACTERISTICS
V.l' Contamination
The AMD discharges from the Old/No. 8 Mine Seep at the base of the large debris
slide at !MM. This AMD is attributed to sources within the Old Mine and No.8 Mine
on the Slickrock Creek side of Iron Mountain because of its character and pattern of
discharge. These workings are, however, inaccessible due to the thick cover of debris
which has slid over these workings. The debris is side cast materials from the operation
of the Brick Flat Pit open pit mine. AMD flows year-round from the Old/No. 8 Mine
Seep. This flow has been monitored for flow rate and water quality on a regular basis
since 1978, as shown in Table 1. Flow from Old/No. 8 Mine Seep does not show sharp
peaks, although the flow rate will increase following a large winter storm. The
estimated average annual flow for Old/No.8 Mine Seep is 59 gpm. The pH is
commonly between 2 and 3.
Table 1
S1IDIJD8IY orWaler Quality and FI- Dala ror OldINo. 8 MIne Seep, 197810 1990
No. or Samples MeaDa MiD1mWD MaDmWD
Flow (gpm) 278 S9 15 231
pH 218 2.58 1.15 3.5
Copper, total (mglI) 286 133 S9 250
:Unc, total (mglI) 283 5S 19.3 140
Cadmium, total (mglI) 282 0.49 0.20 1.17
8Mean average calculated as sum of samples divided by number of samples.
V.2 Location of Contamination and Known or Potential Migration Routes
As discussed above, analytical data collected over 40 years indicate that Iron Mountain
is releasing large quantities of contariiinants to the environment (primarily surface
water) via AMD discharges. The AMD is characterized by low pH (1 to 3) and very
high concentrations of heavy metals. .
The water quality parameters of concern from a public health exposure perspective are
pH, cadmium, copper, and zinc. These parameters are selected because of potential
dermal contact effects caused by low pH and potential consumption of AMD (with
these three metals being of greatest concern from a water consumption perspective).
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l
~.
:P
The contaminants of concern from the perspective of fisheries (salmon and steelhead
trout) exposure are pH, cadmium, zinc, copper, and aluminum. These parameters are
selected because of their toxicity, primarily to salmonids, at low pH levels and concen-
trations ranging from 1 pg/J for cadmium to 100 pg/J for aluminum (copper toxicity
levels are in the range of 10 pgll, and zinc toxicity levels are in the range of 50 #Lg/J).
For comparison, 1 pg/J equals 0.001 mgll.
The contaminants of concern with respect to terrestrial wildlife include arsenic as well
as those listed above for aquatic species.
The major mechanism for onsite and offsite transport of contaminants is surface water.
The AMD enters Boulder and Slickrock. Creeks, and these two creeks discharge into
Spring Creek, which flows to the Sacramento River at Keswick Reservoir.
The major processes that appear to affect the fate of transported copper, cadmium,
and zinc are coprecipitation with iron hydroxides or precipitation as carbonates. Metals
concentrations are further reduced and surface-water pH is raised by dilution as Spring
Creek discharges into the main body of Keswick Reservoir (Figure 1).
AMD from the Old/No. 8 Mine Seep is physically transported by a short 9pen-topped
flume to a copper cementation plant located near the seep in Slickrock Creek valley.
The flume has, at times, overflowed and leaked at joints, which acidifies the receiving
soil and deposits highly concentrated metal salts into the terrestrial wildlife habitats.
The degree of consumption of these salts by deer and other animals is not presently
~~. .
The contaminants of concern can be biologically transported through the aquatic food
chain. For example, the initial uptake of contaminants would be by phytoplankton,
periphyton, and other aquatic vegetation. These food sources would be ingested by
benthic invertebrates and/or zooplankton. The plankton and benthos would be inges-
ted by fish at subsequently higher trophic levels and ultimately consumed by birds, ani-
mals, and humans.
VI. SUMMARY OF SITE RISKS
VI.I General
The Iron Mountain Mine Superfund site was placed on the National Priorities List on
September 8, 1983. The site was listed because of the impacts of metals-laden AMD
discharges on the Sacramento River, a major fishery and source of drinking water for
the City of Redding and other domestic water supplies. Th~ Iron Mountain site has
been associated with water quality degradation and impacts on aquatic resources in
nearby drainages during much of its history. Impacts include numerous fish kills in the
upper Sacramento River (39 documented fish kills since 1940), the primary salmon-pro-
ducing river in California (CDWR, 1985; CDFG, 1990). In addition, those portions of
Boulder Creek, Slickrock Creek, and Spring Creek that receive AMD from Iron Moun-
tain are essentially devoid of aquatic life. . -
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The rationale for the OldlNo. 8 Mine Seep Operable Unit is to address elevated metals
loadings emanating from Slickrock Creek into Spring Creek and subsequently entering
the Sacramento River. From the results of the RI, the Endangerment Assessment, and
the ARARs analysis, two problem areas are identified for remedial action - human
health risks and environmental risks. .
VI.2 Human Health Risks
The potential for direct human exposure to AMD is relatively small. The property
owner has posted the property to discourage trespassers who might become exposed.
The property is located between two heavily used national forests, however, and direct
exposure cannot be ruled out as a possibility.
Persons who might come into direct contact or consume concentrated AMD at Iron
Mountain could be at risk. Such persons include people working, living, or hiking at
the site. Individuals who enter the Iron Mountain site are at risk if they have direct
contact with or ingest the AMD. The risk of such exposure is limited by controlled
access to the minesite.
Persons who might come into direct contact with surface water downstream from Iron
Mountain include people working, living, hiking, or swimming near the site. Individuals
who come in direct contact with water or sediments from the main body of Keswick
Reservoir or Sacramento River are not currently at risk.
Persons who might consume surface water downstream from Iron Mountain include
people w~rking, living, or hiking near the site. Persons who might consume fish taken
from the Sacramento River downstream from Iron Mountain include the general pop-
ulation in the upper Sacramento River Valley. Risks from fish consumption are of
concern to the community. Individuals who consume fish from the main body of
Keswick Reservoir or Sacramento River may currently be at some risk; however the
uncertainties associated with this scenario are great and likely would result in the risk
being overestimated. EP A will continue to assess such impacts in its continuing studies
at the site.
Children are at somewhat greater risk than adults when considering noncancer toxicity
resulting from incidental ingestion of creek water downstream from Iron Mountain.
VI.3 Environmental Risks
The principal risks posed by the runoff of metals-bearing AMD from Iron Mountain
are the associated impacts on aquatic life in the Spring Creek drainage, Keswick Reser-
voir, and the Sacramento River downstream of Keswick Dam. Among these natural .
resources, the most important are the fishery resources in the Sacramento River down-
stream of Keswick Dam. Migratory populations of chinook salmon, steelhead trout,
resident trout, and numerous other aquatic and terrestrial species can be or are affec-
ted by AMD from Iron Mountain (U.S. EPA, 1992b).
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"'---""
The salmon and steelhead trout populations have high commercial and/or recreational
value to the region (USFWS and USBR, 1984; USFWS and CDFG, 1987). The sus-
ceptibility of these populations to contaminants originating from Iron Mountain has
been documented (Wilson, 1982). One of the chinook salmon runs, the winter run, is
a species listed by the Federal Government as threatened with extinction and listed by
the State of California as a species endangered with extinction. .
Pollution from Iron Mountain is considered to be a major factor causing the decline in
Sacramento River fishery resources, and an impediment to achieving fishery resource
restoration goals. Other major factors contributing to the decline include loss of
spawning habitat, predation, habitat degradation, mortality at dams and diversions,
overfishing, and natural disasters (such as drought) (Vogel, 1989). FIsh migrating into
the uppermost river reach of the Sacramento River risk being killed by AMD from Iron
Mountain; offspring of adult fish spawning in that reach have reduced chances of sur-
vival due to the Iron Mountain AMD (Finlayson and Wilson, 1979). There is an indi-
cation that AMD from Iron Mountain has reduced the suitability of available spawning
grounds for salmon in the uppermost reaches of the Sacramento River and that fish
population reductions have occurred following uncontrolled spillage of Iron Mountain
AMD (Finlayson, 1979). The greatest decline in salmon-spawning populations has
occurred within the uppermost river reach from Balls Feny upstream to Redding, a dis-
tance of approximately 26 river miles (NOAA, 1989). i
Since the late 1960s, when fish counts were initiated at Red Bluff Diversion Dam
(RBDD), each of the anadromous salmonid runs has suffered major declines. A more
extensive data base is available specifically for fall-run chinook. This data base demon-
strates that recent levels of spawning escapement to the upper Sacramento River are
only about 50 percent of levels observed quring the late 19505. The greatest decline
among the salmon runs has occurred for the winter run, which has been reduced to less
than 5 percent of run sizes during the late 1960s. This serious decline prompted the
1989 listing of this fish as a threatened species by the Federal Government (NMFS,
1989) and an endangered species by the State of California (CDFG, 1989).
The primary potential exposed fisheries populations are the salmonids and steelhead
trout present in the Sacramento River; Boulder Creek, Slickrock Cr~ek, and Spring
Creek are devoid of fish and aquatic invertebrates below the mine drainage area. The
. upper Sacramento River chinook salmon runs, steelhead trout run, and resident pop-
ulations of rainbow trout have life history characteristics that make them wlnerable to
potential adverse effects from AMD originating from Iron Mountain. The probability
and magnitude of potential exposure depends on the releases of contaminated water
from SCDD, the releases of water from Shasta Dam, and the life stages present within
the zone of impact.
For spring- and fall-run chinook salmon, in a worst-case scenario, approximately half of
an entire year's fall spawning production could be at risk from contaminants released
from Iron Mountain. The impact of the release depends in large part on the pattern of
releases from Shasta Dam relative to when releases occur from !MM. For example,
flood control releases from Shasta Dam could cause most of the year's production to
23
-------
';;I':'
migrate downstream of the affected water quality zone, thereby reducing the AMD's
impact.
Winter-run chinook salmon could be at higher risk compared to other runs. They are
most likely to seek cooler water areas closest to Keswick Dam because of potentially
lethal water temperatures in lower reaches of the Sacramento River. Under drought-
type conditions, these fish are the most important to future runs because eggs laid
farther downstream are more likely. to be adversely affected by lethal warm water
temperatures. However, these same drought conditions are more likely to create condi-
tions (uncontrolled AMD release and low dilution in the Sacramento River) where
AMD from Iron Mountain could pose a high risk to juvenile rearing in the uppermost
reach of the river. .
The steelhead trout and resident rainbow trout populations that are potentially at risk
are not well-defined or understood. However, both the adult and yearling life phases
are potentially at risk because both are present in the river when fish kills have histori- .
cally occurred.
At present, a memorandum of understanding commits the USBR to operate SCDD in
a manner that (when considering releases .of dilution water from Shasta Dam) will
protect aquatic life in th,e Sacramento River downstream of Keswick Dam. The USBR
must also operate Shasta Dam to provide electric power, irrigation water, and flood
control. The USBR estimated that during an average year it may lose between $16
million and $168 million, depending on the level of protection required in the
Sacramento River, by supplying water to dilute Spring Creek flows. There is the poten-
tial that USBR's ability to supply adequate dilution water will be further reduced due
to conflicting priorities for water use, thereby increasing the potential risk to the.
aquatic community.
It is extremely difficult to quantify fish mortality in the Sacramento River as a result of
contamination from Iron Mountain Mine. This is due to a variety of factors, including
the general size of the Sacramento River downstream of Keswick Reservoir and diffi-
culty of visually observing dying or dead fish during periods when the water is turbid. .
However, there have been 39 documented fish kills near Redding since 1940, and there
have been observations of adult steelhead mortalities near Redding attnDutable to
metal contamination from Iron Mountain Mine since installation of the SCDD.
Boulder and Spring Creeks, downstream from Iron Mountain Mine discharges, do not
support aquatic populations, and the creeks may remain sterile following remediation at
Iron Mountain. Aquatic popUlations, water column and benthic, in Keswick Reservoir
downstream of Spring Creek are at risk because of sediment contamination, as well as
water column contamination. Below Keswick Dam, contaminant concentrations occa-
sionally exceed toxic concentrations for sensitive life stages and frequently exceed both
EP A and State of California criteria to protect aquatic life, indicating that these popu-
lations are also at risk. .
Any terrestrial wildlife onsite has the potential for direct exposure to AMD, such as
deer drinking from contaminated creeks or licking metals-laden salts along the flume
24
-------
r-.
ei.'
,
system, or consumirig contaminated plants, fish, or other organisms. More than 300
species of amphibians, reptiles, birds, and mammals can be expected to occur in the
Boulder Creek basin and downstream areas that may be directly exposed to AMD.
VII. DESCRIPTION OF ALTERNATIVES
VII.I General
Pursuant to 40 CFR ~300.430( e )(2)(i), in developing the remedial alternatives, the lead
agency shall establish remedial action objectives. The NCP requires that the remedial
action attain water quality criteria established under the Oean Water Act Sections 303
and 304 where relevant and appropriate under the circumstances of the release. The
remedial action objective at the site is to eliminate IMM site discharges that are harm-
ful to the environment. The contaminants of concern identified in the 1986 ROD (U.S.
EPA, 1986c) are acidity and toxic metals, which include copper, cadmium, and zinc.
An of these are present in AMD from Old/No. 8 Mine Seep.
VII.2 Screening Evaluation
In general, there are two principal steps in the development of a feasibility study. The
first step is a screening evaluation of all possible technologies that would apply, in this
case technologies to control AMD. The second step is a detailed analysis and com-
parison of selected and assembled technologies. EP A conducted a screening evaluation
similar to the Boulder Creek OU, which considered the concepts of mine plugging, air
sealing, groundwater control, capping, physical-chemical treatment/resource recovery,
biological treatment, passive treatment, fixation-stabilization treatment of sludge, land-
fill of sludge, surface-water discharge of treated water, and injection of treated water.
EP A has concluded that the site conditions in the Old/No. 8 Mine Seep OU restrict th~
number of alternatives to four general response actions:
.
No Action
.
Containment of the AMD and isolation of water and/or air from the
sulfide rock
.
Reduction in AMD discharge volume by reducing water infiltration into
the mine workings .
Treatment of the AMD, disposal of sludge, and discharge of the trecued
water
EP A performed a screening analysis of the general alternatives. EP A concluded that'
only three alternatives have potential applicability to the Old/No. 8 Mine Seep AMD
discharges. The Old/No. 8 Mine Seep FS includes detailed analysis and comparisons
of: .
.
.
No Action
25
-------
o
1-;" ,:
~.'
.
.
Copper Cementation
Treatment of the AMD, disposal of sludge, and discharge of the treated
water
Following is a brief summary of the screening evaluation.
Because the No-Action alternative is required by the NCP, it is automatically forwarded
to the detailed analysis. .
The containment alternatives of mine plugging and air sealing were eliminated in the
screening because the mine adits are not accessible, and it was concluded that construc-
tion activities to restore access would involve large costs and a great risk that access
would not be achieved. The containment alternatives of groundwater control and cap-
ping were eliminated because the surface of the landslide deposits over the mine por-
tals is too unstable to drill and maintain wells or to construct a permanent, impervious
cap.
Treatment was considered both as a stand-alone response action and in combination
with other technologies that would reduce the formation of AMD. Three technologies
were considered for AMD treatment in the Old/No. 8 Mine Seep OUF'S. The technol-
ogies are physical-chemical (resource recovery), biological, and passive.
The physical-chemical treatment systems considered were: . ion exchange, liquid-liquid
extraction, crystallization, and the membrane process. All of these treatment systems
were screened out because of uncertainty of achieving cleanup goals and high capital
and operating costs.
Copper cementation is currently being used to remove copper from the Old/No. 8 Mine
Seep. Cementation is effective in reducing the copper concentrations but the process
may not achieve the discharge standards for copper, and it does not reduce the concen-
trations of zinc and cadmium. Despite these limitations, copper cementation was
judged to be technically and economically effective to complement other measures and
for these reasons was retained for detailed analysis. .
Neutralization/precipitation is a process that is commonly used by the mining industry
for treatment of AMD and has been used successfully to reduce metals levels at the
IMM site. Under the Boulder Creek ROD, it is anticipated that the final design will
use a combination of high density sludge (HDS) treatment and a simple mix of AMD
. with soda/lime. EP A anticipates that the Richmond/Lawson treatment plant can be
expanded to accommodate flow from the Old/No.8 Mine Seep. EPA retained this
process for the detailed analysis.
Microbial decomposition of waste materials requires natural or manmade wetlands,
which are impractical in the Slickrock Creek valley. This innovative technology might
playa supporting role in the final solution for the IMM site.
Passive treatment by evaporation requires large ponds, which are impractical in the
Slickrock Creek valley. This technology is screened out.
26
-------
.- -,
. ;?::
The lime neutralization treatment processes generate sludge which can be conditioned
to make it more resistant to leaching and then disposed of in a RCRA landfill or a
municipal or mine waste disposal type landfill, depending on the sludge characteristics.
In addition, the landfIll could be onsite or offsite. These .options were evaluated in the
Boulder Creek OUFS. All of the disposal options are carried forward to the detailed
analysis.
Water disposal options are discharge to Spring Creek, Slickro.ck Creek, to the
Sacramento River, or injection of treated water into the mine or into the ground. Off-
site disposal is screened out because it is more expensive than onsite disposal and yields
the same resultant offsite water quality. .
Injection and onsite surface disposal are retained for further consideration in the FS.
The general characteristics of each general response are summarized in Figures 2 and
3.
The technologies and aptians that have been screened aut as infeasible are shawn by
baxes with cross-hatching. These aptians have been judged to. be infeasible because of
knawn technicallimitatians. It is unlikely that new informatian about the Iran Moun-
tain Mine site or applicatians elsewhere would justify further consideration af these
aptians.
The technolagies and aptions that have been screened out because af inadequate pre-
cedent ar inadequate information about their application to the Iran Mountain Mine
site are shown by boxes with dashed lines. This screening is based largely upen a judg-
ment that existing inferplatien dees nat pravide a streng er cemplete case far success-
ful applicatian af this aptian. There is a pessibility that additional infarmatian abaut
the site ar ather applicatiens may justify a future reexamination of these eptiens and
pessibly their inclusien as part af adopted remedial alternatives. The OldINa. 8 Mine
Seep OUFS relies in part upon the previeus Baulder Creek ROD information and
canclusians. .
The feasibility study addressed three basic alternatives fer cantral ef the OldINe. 8
Mine Seep AMD. They are Alternative OIN8-O-Na-Actian, a mandated baseline
alternative, Alternative OIN8-I-Treatment ef Flew frem Old/Na.8 Mine Seep, and
Alternative OIN8-2-Copper Cementatien ef Flew frem Old No.. 8 Mine Seep. The
main elements of these alternatives are descnbed belaw.
Vll.3 Alternative OIN8-0- No-ActioD
The "No-Actian" alternative, OIN8-0, is develeped and evaluated as required by the
NCP in 40 C.F.R. ~300.430(e)(6).
The ne-actien alternative is cemmenly used as a baseline alternative against which
ether alternatives are judged. As the name implies, this alternative dees net include
27
-------
GENERAL RESPONSE
ACl10NS
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FIGURE 2
SCREENING OF REMEDIAL
TECHNOLOGIES FOR MINE PORTALS
IRON MOUNTAIN MINE OLDINO. 8 MINE SEEP ROD
-------
"'.
~ENERAL RESPONSE
~ REMEmALTECHNOLOGY PROCESS OPTION DESCRIPTION SCREENING COMMENTS . to .
,
No Acllon I None I None No acllon Relalned per lhe NCP.
Pneumalically a~ied concrele 15 used E"ecllve at preventing or reducing erosion 01
10 limit surlal:e 11IIIII8Iion on wasllllJlles. tho wasle pilll. Reduces pllienliallor generalion
or AMI) by reducing IOltltrallonlmpiemenlalJlliIl
depnnds on localion 01 waste plio. Not relaml)( .
Capping Clay . Clay Is used 10 limil surface !nlillralion Similar to shOlcrele, bul less fIIsislani 10 orosion,
on waste pilos. and subjecllo desiccation Clackmg. Nol mtalOCtt.
Goosynlholic Membrano * Geosynltmlic cap is conslnJclod Similer 10 sholcrele, bul may require lOSS
, Conlalnment on wasl" "ilos. malllionance. flelainod
Mechanical OQuipmenlls used to reshape Not e"ecllve unless combined with
pilos 10 bnlll suriacfI.walor run.on. diversion syslom. Nol rolalnfJd.
Surface Controls
Diversion Syslems Ditches or benns are used 10 limit Should be eftedive al controlling erosion;
suriace.waler run.on to Ihe piles. Is mosl e"oclive in combinaluJII wllh
capping. flelmnod.
I"emoval , ExcBvation I Backhoes and 8ulldolers Mechanical equipment Is used 10 Commonly used; e"eclive and
romovo Iho pllos. Implomenlable. Relainnd.
Stabilization POllolonic Agents Materials are lidded 10 meet regulatory The need tor stabilill1l1on Is nol yet known;
requiremenls lor disposal. Ihe technology is implemenlahle and
e"eclive. Relained. >1'
TreRlment
- T -:
Resource recovery treatment processes The ImpIemenlebility and ""octiveness 01
Resource Recoveryl may be abln 10 recover melols. plus generate . reSOUlCR recovRry is unknown. allhough removal
SoIl Washing A nonhAlardous wasle producls. Some 01 e"iciencies probably will hn low. Nol rolained.
Physical.Chemicat Ihese lechmques welo usod previously 10
plOCOSS 010 al IMM.
Non-RCRA landlin
Halardous malerlals can be disposed
01 o"sile (3110 miles away) or al a .
new lacilily onsito.
Nonhalardous molorials can be disposed
01 o"sile (to m~8s away) or al a
now lacilily onsilo.
All options aro retained. oxcept Iho USB ot Ihe
mino wortr.ings. which cannol practicably bo
rohabililaled 10 comply wllh IIGIIA.
All options are relained.
HCRAlandlil
Disposal
landllft
NOTES
I. TECHNOLOGIES AND PROCESS OPTIONS
SCI1I:I=NEU OUT AilE SHOWN WITH HATCHING.
? . SElECTED REPRESENTATIVE PROCESS
OPTIONS FOil ALTEIINATIVE DEVELOPMENT.
0001181 03
5£ rl£MIIER 1993
RIJ0692O!1 0'.01
FIGURE 3
SCREENING OF REMEDIAL
TECHNOLOGIES FOR WASTE PILES
IRON MOUNTAIN MINE OLD/NO.8 MINE SEEP 1100
-------
..=.
~)
any additional remediation activities. The no-action alternative would include provi-
sions for limited monitoring, operation, and maintenance of the copper cementation
plants and operation and maintenance of the projects constructed pursuant to EPA's
1986 ROD. .
Without further remediation, the AMD production and discharge at Iron Mountain is
expected to continue for centuries, until such time as the sulfide-rich mineralization is
completely depleted. This geochemical process is expected to ,continue with the same
or similar pattern and intensity 'of the current discharges for the foreseeable future.
VII.4 Alternative OIN8-1-Treatment of Flow from Old/No. 8 Mine Seep
The 1992 ROD for the Boulder Creek OU selected treatment of the Richmond and
Lawson portal flows using lime neutralization. The lime/sulfide high density sludge
treatment process is specified for non-peak flows. (It is anticipated that the final design
will provide that the system is switched to the simple mix treatment process for peak
AMD flows.) All sludge disposal is in Brick Flat Pit. Detailed design of treatment
processes for AMD are underway. As part of this design, EP A has performed a
treatability study that indicates that the addition of sulfide during treatment may be
counterproductive. EP A may modify its treatment approach to delete the requirements
for the sulfide addition.
This alternative would entail collecting the OldlNo. 8 Mine Seep AMD and pumping it
to the treatment area at Minnesota Flats. The treatment facility under design includes
equalization tanks, an optional copper cementation plant, and an HDS/simple mix
treatment plant. Figure 4 is a conceptual schematic, and Figure 5 shows a block
schematic of this treatment system.
The capacity of the proposed treatment plant for the Boulder Creek OU would have to
be enlarged to treat the additional base flows with HDS and to provide for treatment
of peak flow from OldlNo. 8 Mine Seep of 250 gpm. The following additional improve-
ments would also' be required:
.
.
Access road to the OldlNo. 8 Mine Seep
Additional AMD and process water conveyance
Additional 300,000 gallons of equalization tank capacity
Additional electrical capacity for peak flows .
Additional sludge disposal capacity
.
,.
.
The concept for collection of the AMD at OldINo.8 Mine Seep is to provide both
surface and underground interception of the flows and closed piping to bring the flows
by gravity to a collection manhole and then to a measurement manhole near the pres-
ent Slickrock Creek copper cementation plant. The AMD would then be pumped
24,000 feet in a 6-inch pipeline to discharge into an elevated tank at the Minnesota
Flats treatment plant.
30
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RICHMOND
PORTAL
DRAINAGE
LAWSON
PORTAL
DRAINAGE
RDD12fj, 0'
SeP'"euBER '"3
RDD6&2~ 07 0'
PUMPED AND/OR
GRAVITY
CONVEYANCE'
,~,
~,'
EQUALIZATION
TANK(S)
HDS/SIMPLE MIX
TREATMENT
I
I
I
I
I
I
I
I
'----
TREATED
AMD RELEASE
NEuTRALIZATION
REAGENTS
PROCESS WATER
SLUDGE
DRYING BEDS
SLUDGE DISPOSAL
IN BRICK FLAT PIT
FILTRATE WATER
RGURE4 '
HDS/SIMPLE MIX LIME NEUTRALIZATION
IRON MOUNTAIN MINE OLDINO. 8 SEEP ROD
-------
. .
:13
OTHER REAGENTS
SLAKED LIME
t
I
I
I
I
I
I
I,
I
I
I
I
I I
I I
I I
I I
I I
I
I I
I ------
I I
L.------ I
I I
L.:Jj
SIMPLE MIX I
TANK I
I
I
I
I
I
I______-~
Q~..
ACID MINE
DRAINAGE
SLUDGE CONDITIONING
EQUALIZATION
TANK (S)
",!..r
g J(::.I
TANK .' .'
SPARGE AIR
REACTOR
FLOCCULATOR
'If
TREATED AMD
DISPOSAL TO
SPRING CREEK
RECIRCULATED
SLUDGE
SLUDGE
DRYING
BEDS
SLICK ROCK
CREEK
FILTRATE
BRICK
FLAT
PIT
- - - - - ~ ~ USED WITH HDS AND SIMPLE MIX
COMBINED TREATMENT OF PEAK FLOWS
RCO 126' C2
SE"EMB~I'I 1993
1'IC069205 07 C,
FIGURES
GENERALIZED FLOW SCHEMATIC
HDS/SIMPLE MIX TREATMENT
OF ACID MINE DRAINAGE
IRON MOUNTAIN MINE OLDINO, e MINE SeEP ROD
-------
e
The AMD flows from the three mines will be mixed in an equalization tank to make
the flows more uniform for treatment. The equalization capacity proposed for the flow
from OldINo. 8 Mine Seep would require approximately 300,000 gallons.
The treatment process is described in Appendix B of the 1992 Boulder Creek OU FS.
The HDS process will be used to treat normal flows, but a conversion to simple mix
treatment could be used to treat the peak storm flows t6 avoid equipping the plant with
large equalization and HDS treatment facilities to handle shon-term conditions. For
the Boulder Creek OU, the HDS and simple mix treatment systems were sized at
approximately 300 and 1,100 gpm, respectively. To incorporate treatment of OldINo. 8
Mine Seep AMD, the HDS and simple mix treatment system capacities will be
increased to 420 and 1,250 gpm, respectively.
Sludge from the treatment will be disposed in Brick Flat Pit. Sludge will be dewatered
at Minnesota Flats and hauled by truck to Brick Flat Pit for disposal.
This option does not rely upon copper cementation (Alternative OINS-2), but could be
designed to allow the continued operation of a copper cementation plant to remove
copper upstream of the lime treatment facility. Although copper cementation is
currently required for the AMD from Old MineINo. 8, this form of treatment/metals
recovery would no longer be necessary after construction of the treatment plant. After
construction of the lime treatment plant it is anticipated that the owner/operator will
operate the, copper cementation plant only when the price of copper justifies such
operation. This alternative would not preclude such operation.
Vll.5 Alternative O!N8-1-Copper Cementation
This alternative entails the collection of the Old/No. 8 Mine Seep AMD, treatment by
copper cementation, and effluent discharge to Slickrock Creek. This alternative would
replace the existing copper cementation plant to increase the efficiency of copper
removal. An observed peak flow of 250 gpm and an average flow of 60 gpm were used
to size the new plant and estimate capital and operating costs. The AMD collection
system is the same as for Alternative OINS-t. The new copper cementation plant will
be on the site of the present plant. Figure 6 shows the layout of these facilities.
The copper cementation treatment system relies on the electrochemical precipitation of
metal (copper in this case) by a more electropositive metal (such as iron). Copper
cementation involves passing copper-bearing AMD over scrap iron, where the copper
deposits and iron go into solution as ferrous iron. When the scrap iron is replaced by
copper, the copper is removed and sold for its scrap value. Two copper cementation
plants currently operate at the site. The process is passive, requiring. only periodic
manual or mechanized removal of the iron-depleted, copper-enriched scrap iron and
replacement with fresh scrap iron. .
33
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@
Cementation is carried out in acid-resistant chambers. The AMD flows through these
chambers by gravity.
As shown by the operational history or the existing onslte plant and experience with
more modem plants on other sites, it is assumed that the average removal efficiency
will be 90 percent. This is an increase of 20 percent over the performance of the
existing. plant. Based upon an average inflow of copper of 120 mg/l, the improved
plant efficiency would prevent an annual discharge of 6,000 pounds of copper. The
existing plant and the plant proposed in this alternative provide no removal of zinc or
cadmium.
vm. ALTERNATIVE COMPARISONS
The remedial alternatives developed in the OldINo. 8 Mine Seep OUFS were analyzed
in detail using the nine evaluation criteria specified by the NCP in 40 c.F.R.
~300.430( e )(9). The resulting strengths and weaknesses of the alternatives were then
weighed to identify the .alternative providing the best balance among the nine criteria.
These criteria are: (1) overall protection of human health and the environment;
(2) compliance with applicable or relevant and appropriate requirements (ARARs);
(3) reduction oftoxicity, mobility, or volume through treatment; (4) long-term effective-
ness and permanence; (5) short-term effectiveness; (6) implementability; (7) cost;.
(8) state acceptance; and (9) community acceptance. Each of these criteria is
descnbed below.
vm.l Criterion 1- Overall Protection of Human Health and the Environment
Overall protection of human health and the environment addresses whether a remedy
provides adequate protection and descnbes how risks posed through each pathway are
eliminated, reduced, or controlled through treatment, engineering controls, or institu- .
tional controls. .
The OldINo. 8 Mine Seep OU provides for an interim action that is not expected to be
final, and will not address all of the sources of contaminant discharges from the site.
Consequently, even though the remedial action will provide significant environmental
benefit, it is not expected to be fully protective of human health and the environment.
The remedial actions will address the third largest source of AMD at the site, the
OldINo. 8 Mine Seep, and will provide a significant contnbution toward the final site
cleanup. The remedial actions considered are intended to provide protection of human
health and the environment from the exposure pathway or threat posed by AMD from
Old1N0.8 Mine Seep. The comparative analysis of the alternatives is made on this
basis and on the basis of their contnbution toward meeting the final cleanup goal.
34
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EGEND
.
CONNECTION MANIIOLE
SUBSURFACE INTERCEPTOR DRAIN
- CONVEYANCE PIPELINE
FIGURE 6 "~'
COPPER CEMENTATION FACILITIES ::
IItnNM'IIINI""'''''1f1l flll""'1 !If-''III .~III'II'II\
~
!
f
r
f
I;
-------
/"""\
(2)1
Treatment of the AMD should contribute to protection of human health, although this
is not considered a major issue for either the no-action or the action alternatives. It is
. not considered a major issue because the concentrated acidic waters are mainly limited
. to remote and uninhabited areas, these source areas have restricted entry, and human
exposure to the dilute waters is limited.
The level of environmental protection among the alternatives considered ranges from
limited to good. The no-action alternative provides only a continuation of the controls
now in place, namely the existing flume for AMD conveyance, the cementation plant,
and the Slickrock Creek Diversion. Effluent from the cementation plants will continue
with undiminished zinc and cadmium, significantly reduced amounts of copper, and a
low pH. Present impacts are likely to continue. OldlNo. 8 Mine Seep degradation of
Slickrock Creek and downstream impacts would continue.
Alternative OIN8-1 would neutralize the acidity of the OldlNo. 8 Mine Seep AMD and
remove more than 99 percent of the metals from the seep flow.
From a comparison of case years 1978, 1980, 1981, and 1983, the water at the Slickrock
Creek confluence with Spring Creek, while considerably improved, would still not meet
the water quality criteria for copper, cadmium, or zinc at all times. These years have a
span of annual rainfall representative of all of' the years of record. Below the
confluence of the two creeks and below Keswick Dam, Alternative OIN8-1 would pro-
vide enough copper removal to allow the retention and controlled release of SCDD to
achieve compliance with water-quality criteria for all of the case years 1980 and 1983,
and greater compliance with the criteria than would occur under the no-action
alternative in other years.
Construction of pipelines shall be conducted primarily along roads, resulting in minimal
impact on vegetation. On the basis of this comparison, Alternative OIN8-1 would have
a very positive impact on achieVing the overall remedial action objectives for the site.
Alternative OIN8-2 would result in the removal of an additional 6,000 pounds of copper
per year when compared with the no-action alternative. This additional removal of
. copper could potentially reduce the days of non-compliance associated with copper.
However, copper cementation is not expected to reduce the amount of cadmium or
zinc, which individually and in combination appear to be the cause of non-compliance
at the confluence of Slickrock and Spring Creek.
In summary, the no-action alternative provides environmental protection that is limited
to the removal of most copper only; the treatment alternative, OIN8-1, provides for a
significant improvement in protection for aquatic resources in that it removes 99 per-
cent of all metals, and the improved copper cementation alternative, OIN8-2, would
improve copper removal but not provide protection from zinc or cadmium.
37
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..-
'-,.r
: -=-.'
VIII.2 Criterion 2 - Compliance with Applicable or Relevant and Appropriate Require-
ments
Applicable requirements are those cleanup standards, standards of control, and other
substantive requirements, criteria, or limitations promulgated under Federal or State
environmental or facility siting laws that specifically address a hazardous substance,
pollutant, contaminant, remedial action, location, or other circumstance at a CERCLA
site. Relevant and appropriate requirements are those cleanup standards, standards of
control, and other substantive requirements, criteria, or limitations promulgated under
Federal or State environmental siting law that, while not "applicable" to a hazardous
substance, pollutant, contaminant, remedial action, location, or other circumstance at a
CERCLA site, address problems or situations sufficiently similar to those encountered
at the CERCLA site that their use is well-suited to' the particular site.
Compliance with ARARs addresses whether a remedy will meet all Federal and State
environmental laws and/or provide a basis for a waiver from any of these laws. These
ARARs are divided into chemical-specific, action-specific, and location-specific groups. .
Iron Mountain Mine ARARs are discussed in greater detail in Chapter 3 of the
OldlNo. 8 Mine Seep RIIFS, and in the September 30, 1992, ROD in Section X.2.
Chemical-Specific ARARS. For the purpose of comparative analysis, the Old/No. 8
Mine Seep OUF'S considered compliance with three specific water quality goals at two
locations for each of the alternatives. The three goals were:
.
State of California water quality objectives in the Central Valley
Regional Water Quality Control Board Basin Plan (CVRWQCB Basin
Plan)-the most stringent water quality requirements.
.
Federal Oean . Water Act-ambient water quality criteria for protection
of human health.
.
Federal Oean Water Act-ambient water quality criteria for protection
of aquatic life in freshwater.
The maximum contaminant levels specified by selected ARARs are presented in
Table 2. The two points of compliance were:
.
Confluence of Slickrock Creek with Spring Creek
Sacramento River below Keswick Dam
.
The benefits of implementing the alternatives of Old/No. 8 Mine Seep OUF'S were
tested by estimating the water quality with each of the alternatives in operation under
the patterns of precipitation in 1978, 1980, 1981, and 1983. The results indicate that
Alternatives OIN8-1 and O/N8-2 would both reduce the days of non-compliance with
respect to the no-action alternative, but neither would eliminate non-compliance. The
modeling using the most stringent standard (CVRWQCB Basin Plan) for water quality
38
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/~-)
\...---
Table 2
Maximum Contaminant Levels Specified by Selected ARARs (J.cWI)
ARAR Copper Zinc Cadmium
California State Central Valley Water Quality 5.6 16 0.22
Control Board Basin Plan
Federal Clean Water Act water quality criteria for 1,300 none 10
protection of human health
Federal Clean Water Act ambient water quality 12.0 110 L1
criteria for protection of aquatic life in freshwateya
Safe Drinking Water Act 1,000 5,000 10
aBased on a water hardness of 100 mg/l. The values reponed are for a 4-day average
continuous concentration.
below Keswick Dam predicted 52 days of non-compliance per year for the no-action
alternative (O/N8-0) and copper cementation (O/N8-2) and 47 days for treatment of
flows (O/N8-1). The model using the Federal Clean Water Act Ambient Water Quality
Criteria below' Keswick Dam shows 12 days of noncompliance for ON8-0, 9 days for
ON8-1, and 11 days for ON8-2.
The Old/No. 8 Mine Seep OU provides for an interim action that it is not expected to
be final and does not address all of the sources of discharges from the site. Therefore,
it is not expected to fully comply with all ARARs with respect to water quality stan-
dards for metals concentrations in surface waters and State Fish and Game standards.
Although the remedial actions evaluated in the Old/No. 8 Mine Seep OUFS provide
for significant improvement by essentially eliminating the third "largest discharge from
the site, EP A is relying upon the ARARs waiver for "Interim Measures" (40 C.F.R. ~
300.430 (f)(l)(ii)(C)(i) for remedy selection with respect to the Old/No. 8 Mine Seep
OU and therefore is waiving the Regional Board's Basin Plan water quality objectives
and the Fish and Game ~5650 standards ARARsfor this operable unit. EP A's overall
goal at the site remains to achieve these water quality objectives and Fish and Game
standards. The alternatives for this Operable Unit otherwise will comply with ARARs,
including ARARs for sludge disposal. .
ARARs are discussed in greater detail in the feasibility study for the Old/No. 8 Mine
Seep Operable Unit (U.S. EPA, 1993).
The treatment of flow in an expanded treatment plant will make a significant contn'bu-
tion to the goal of complying with water quality standards. The no-action and O/N8-2
copper cementation alternatives are less effective because they do not remove cadmium
and zinc.
39
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..' '.
Location-Specific ARARs. The 01d/No.8 Mine Seep OUFS provides a detailed
description of possible location-specific ARAR's. All of the alternatives are expected
to meet location-specific ARARs, some of which ensure that wetlands, historical, or
archaeological sites are not damaged or disturbed.
Action-Specific ARARS. Significant action-specific ARARs include'those that address
the need to protect species and those that relate to the safe disposal of wastes. All
three alternatives are consistent with statutes such as the Federal and California
Endangered Species Acts and the Fish and Wildlife Coordination Acts and Fish and
Game Code Section 1505. Alternatives D/N8-1 and O/N8-2 improve , habitat and will
therefore provide greater compliance.
Alternative O/N8-1 is the only alternative that would require disposal of sludge. The
disposal unit at Brick Flat Pit is being designed by EP A to comply with the provisions
of California Water Code Section 13172 and Health and Safety Code Section 25208, et
seq. (Toxic Pit Control Act). These ARARs are applicable to the disposal of the
sludge.
Table 3 is a summary of the alternatives' ability to meet objectives of protecting human
health and the environment and achieving ARARs.
Table 3
Summary or Overall Protection or Human Health and the Environment
and Achievement of ARARs
OveraU Protection of Human Health
Alternatives' and the Environment and Achievement or ARARs
O/N8-0 No-Action . Human health risk likely to be low.
. Present environmental impacts are likely to continue and may
increase in severity with prolonged exposure to contaminated
water and increased volume of contaminated sediments.
. Cementation removes about 70 percent of the copper, but does
not remove other metals or reduce acidity.
. Will not meet ARARs.
O/N8-1 Treatment of Flow . Human health risk likely to be low.
. Significant reduction in environmental impacts with up to 99 per-
cent reduction in metals and acidity.
. This interim action will not provide full compliance with ARARs.
. The large anticipated reduction in metals in the disCharges is a
significant contribution to final cleanup standards
O/N8-2 Copper Cementa- . Similar to O/N8-0, with an additional removal of copper
tion of Flow .' This interim action will not provide full compliance with ARARs.
40
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8
VllI.3 Criterion 3 - Long- Term Effectiveness and Permanence
Long-term effectiveness and permanence refers to the ability of a remedy to maintain
reliable protection of human health and the environment over time. This criterion
includes the consideration of residual risk and the adequacy and reliability of controls.
All of the alternatives considered control the contaminated flow and have no effect on
the geochemical reactions that generate the AMD. The alternatives will remain effec-
tive as long as the conveyance systems and treatment plant operations are maintained.
For AlteI1)ative OIN8-1, assuring adequate disposal capacity is part of the long-term
remedy. The current pit disposal has a capacity for at least 60 to 100 years.
VllI.4 Criterion 4-Reduction of Toxicity, Mobility, or Volume Through Treatment
Reduction of toxicity, mobility, or volume through treatment refers to the preference
for a remedy that uses treatment to reduce health hazards, contaminant migration, or
the quantity of contaminants at the site.
Geochemical reactions are anticipated to continue for hundreds of years unless alterna-
tive technologies are developed, adequately tested, and applied to the site. The no-
action alternative will continue to reduce flow toxicity associated with copper, and the
copper cementation will improve on this reduction by removing additional copper.
Alternative OIN8-1 will reduce flow toxicity associated with copper, zinc, cadmium, and
low pH. Alternatives OIN8-0 and OIN8-2 do not reduce the mobility, toxicity, or vol-
ume of zinc and cadmium, but will reduce the volume of copper without requiring dis-
posal. All metals treated at Minnesota Flat (OIN8-1) will have reduced mobility and
will be appropriately disposed of in Brick Flat Pit. Brick Flat will be equipped with an
underdrain system further limiting any future remobilization of metals.
In summary, the comparison is essentially between not addressing the actual AMD tox-
icity and mobility for zinc, cadmium, and pH in Alternative O/N8-0 and O/N8-2 and the
potential mobility of 99 percent of all metals treated and disposed of as a sludge in
compliance with disposal standards. O/N8-1 will provide a greater overall reduction in
AMD toxicity, mobility, and volume through treatment.
VllI.S Criterion 5 - Short-Term Effectiveness
Short-term effectiveness refers to the period of time required to complete the remedy
and any adverse impacts on human health and the environment that may be posed dur-
ing the construction and implementation of the remedy.
Alternative O/N8-1 ranks first in short-term effectiveness as it provides the greatest
improvement in surface-water quality and does not involve unusual worker or environ-
mental risks. Alternative OIN8-2 is less effective than O/N8-1, but it is better than
O/N8-0. It also has no unusual worker or environmental risks.
41
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."
VIII.6 Criterion 6- Implementability
Implementability refers to the technical and administrative feasibility of a remedy,
including the availability of materials and services needed to implement the chosen
solution. It also includes coordination of Federal, State, and local governments to clean,
up the site.
Alternatives OIN8-1 and OIN8-2 are also fairly simple to implement in that they involve
established technologies with known costs, effectiveness, and reliability. Alternative
OIN8-1 is somewhat more complex than OIN8-2 because it requires sludge disposal. All
of the alternatives are easily reversible in the event other technologies become avail-
able.
VIII.7 Criterion 7 - Cost
This criterion examines the estimated costs for each remedial alternative. For compari-
son, capital and annual O&M costs are used to calculate a 3D-year present worth cost
for each alternative. . .
Table 4 presents estimates of the 3D-year present worth for the alternatives. The table
shows the present worth of the initial capital investment, 30 years of operation, and the
total 3D-year cost. The 3D-year basis is selected merely to compare the early costs of all
alternatives. Unless another remedial action is subsequently developed which obviates
the need for continued treatment, treatment of the seep is expected to be required
beyond the 3D-year costing period. The total present worth costs range from $8.3
million for OIN8-1 to $1.7 million for Alternative OIN8-2. It is commonly assumed that
actual cost may vaI)' from the stated amounts by as much as plus 50 percent to minus
30 percent.
Table 4
Summary or Costs
Present Worth Basis
Alternatives Capital Costs ($) Operating Costs (S) Total Costs (S)
OIN8-0 No-Action -0- 446,000 446,000
O1N8-1 Treat seep flow at a treat- 4,350,000 3,920,000 8,270,000
ment plant co-located with
the Boulder Creek operable
unit plant -
OIN8-2 Treat seep flow with a, new 905,000 753,000 1,658,000
copper cementation plant
located near the seep
42
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('is)
~
VIII.8 Criterion 8-State Acceptance
State acceptance refers to the State's position and key concerns related to the pre-
ferred alternative and other alternatives, and State comments on ARARs or the pro-
posed use of waivers.
EPA has worked closely throughout the Old/No. 8 Mine Seep OU with the California
Department of Toxic Substances Control (DTSC) (the State lead agency), the Regional
Water Quality Control Board (RWQCB), and the Department of Fish and Game. All
three agencies support the selection of EP A's preferred alternative, treatment of the
Old/No. 8 Mine Seep AMD flows.
In an April 15, 1993, letter, DTSC supported the selection and implementation of treat-
ment. The Department urged EP A to implement this remedy as soon as possible to
allow for its integration with ongoing design and construction of the Boulder Creek OU
treatment plant. DTSC views treatment as an interim remedy and encourages the
further development and consideration of an alternative that could reduce or eliminate
the need for treatment at the site, including capping, plugging, and resource recovery
approaches. DTSC expressed concern that the disposal facility for the treatment
residuals be properly designed. EP A has agreed that the disposal facility must meet
the appropriate design criteria.
The Department of Fish and Game signed an April 14, 1993, letter along with the
other Natural Resource Trustees for the site, supporting the selection of treatment of
the Old/No. 8 Mine Seep AMD discharges. These agencies recommend that EPA
proceed expeditiously with additional site investigations and cleanup actions.
VID.9 Criterion 9-Community Acceptance
This criterion refers to the community's stated preferences through verbal and written
comments on EP A's Proposed Plan regarding which components of the alternatives
interested persons in the community support, have reservations about, or oppose.
There was significant community interest in EPA's Proposed Plan for the Old/No. 8
Mine Seep OU at !MM. EP A's public meeting was attended by approximately 100
people. EP A received three oral comments at the meeting. EP A received letters com-
menting on the Proposed Plan. In general, the community expressed interest in select-
ing a remedy that would safely protect the water and fishery resources that could be
implemented quickly, and that could remediate permanently the long-standing site
problems.
There was overwhelming support from the community to take immediate action at. the
site. The community supported treatment of the AMD discharges as a logical
43
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."",\
iL ..:
'-
extension of EPA's September 1992 ROD. The community supports the use' of the
inactive open pit mine, Brick Flat Pit, for sludge disposal.
Zeneca, on behalf of Rhone-Poulenc Basic Chemicals, submitted detailed comments in
support of its conclusion that operation of the existing copper cementation plant, the
no-action alternative (OIN8-0), was the preferred approach and could be safely imple-
mented, would be effective, and was the lowest-cost option. '
Jron Mountain Mines, Inc., (IMMI) submitted detailed comments in support of its pre-
ferred approach, in situ mining of the mineralized zones. IMMI opposed EPA's
reliance upon Brick Flat Pit for sludge disposal. IMMI stated its interest in mining the
remaining sulfide deposit in Brick Flat Pit.
Responses to the above comments are presented in the attached Responsiveness Sum-
mary.
IX. THE SELECTED REMEDY
EP A is selecting collection and treatment of the OldINo. 8 Mine Seep AMD flows.
Treatment sludges will be disposed of onsite in the inactive open pit mine, Brick FIat
Pit.
the selected remedy differs in one minor respect from the preferred alternative in
EPA's February 11, 1993, Proposed Plan. EPA is selecting the preferred alternative of
the Proposed Plan, treatment by chemical neutralization/precipitation with HDS pro-
- cess option. EP A is not requiring use of sulfide based upon treatability study results
from the design work for the Boulder Creek treatment plant. Peak AMD flows could
be treated with a simple mix treatment plant, consistent with the process configuration
selected for the Boulder Creek treatment plant.
The major components of the selected remedy include:
.
Collection structures, pipelines, and equalization to provide for delivery'
of all AMD flows from the Old/No. 8 Mine Seep to the treatment facility
for treatment. ' '
.
Additional or expanded treatment facilities to perform chemical neutral-
ization/precipitation treatment of the OldINo. 8 Mine Seep AMD flows at
the Minnesota Flats plant site. The treatment plant effluent shall meet
the effluent limitations of 40 C.F.R. ~~440.102(a) and 44O.103(a). Except
for pH and TSS levels for discharges into Boulder Creek, Slickrock
Creek, or contaminated parts of Spring Creek, EP A has determined that
these standards are relevant and appropriate in. this application. H the
discharge is made to one of these creeks, it will not be possible to adjust
the pH due to the expected acidity in the creeks. Treatment for TSS
levels would not be practicable due to the high levels of
44
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'.
',. ,
''7'\
:'l' '., ,I
TSS already in the creeks. IT the discharge is made to Flat Creek, which
is not expected to be acidic from other sources, the pH and TSS stan-
dards would be relevant and appropriate.
EP A has selected treatment Alternative OIN8-1, the HDS process option,
as the required treatment technology option. The HDS process option,
as discussed in the Boulder Creek OUFS, relies upon simple mix treat-
ment and equalization for peak flows beyond the capacity of the HDS
plant. The HDS plant shall be designed to provide capacity to treat
sustained elevated flows from the OldINo. 8 Mine Seep. In conducting
design studies for the plant, EP A has concluded that the HDS plant may
be designed with a simple mix peaking plant.
.
Disposal of treatment residuals onsite in the inactive open pit mine, Brick
Flat Pit. Brick Flat Pit shall be modified to comply with the applicable
requirements of the Toxic Pits Control Act, Health and Safety Code
~25208, et seq., and California requirements for disposal of mining wastes
promulgated under Water Code Section 13172. .
The collection and conveyance systems shall provide for delivery of all base, sustained,
and peak AMD discharges from the Richmond and Lawson adits. The treatment plant
shall provide equalization capacity, treatment capacity, or a combination of both to
ensure that all of the AMD flows are treated in compliance with the performance stan-
dards. The conveyance and treatment facility design shall provide for excess capacity
and redundancy of elements necessary to assure reliability of performance.
The routing of pipelines and siting of tankage and treatment facilities is expected to
have minimal impacts on the undisturbed habitat. The historic mining-related distur-
bance is significant, caused by collapse of the underground workings, surface mining,
and establishment of roadways and cleared work areas. Pipeline routing and design
and siting of facilities shall minimize impacts on undisturbed habitat by use of existing
cleared work areas and roadways to the maximum extent practicable and by avoidance
of siting of any facilities in areas of riparian or wetland habitat.
EP A has selected the HDSprocess option (O/N8-1) for the following reasons:
.
The HDS process produces treatment sludges with superior characteris-
tics with respect to dewatering and leachability. 'The smaller volumes of
denser sludge are expected to significantly increase the life of Brick Flat
Pit for use as an onsite sludge disposal facility. The superior leaching
characteristics may allow for reduced regulatory requirements on the
design of the modifications' to Brick Flat Pit for sludge disposal.
.
The sludge from an HDS plant could be placed in Brick Flat Pit dry.
Although Brick Flat Pit modification designs must address several signifi-
cant issues such as storm runoff, the design for placement of HDS
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sludges is significantly less complicated, and its operation is more within
conventional engineering practice.
.
EP A has chosen to site the treatment plant downgradient of the AMD
discharges. The reliance upon HDS for treatment of base flows will
reduce the annual O&M cost for hauling sludges to Brick FIat Pit for
disposal by a significant amount. EPA has concluded that siting at a
downgradient location could be more easily engineered to assure reliable
operations. The use of the HDS process option may make this alterna-
tive site cost-effective by significantly reducing the volumes of sludge that
must be trucked to Brick Flat Pit for disposal.
, .
Use of the same treatment plant as the Boulder Creek OU will save additional
construction and operation costs.
For the HDS process treatment facility located at the Minnesota Flats site, the treat-
ment plant would discharge to lower Spring Creek and shall meet the requirements of
40 CPR ~440.102(a) and ~440.103(a), except pH and TSS standards. Because lower
Spring Creek will not attain ambient water quality criteria pursuant to remedial actions
being performed in the OldINo. 8 Mine Seep OU, EPA is invoking the ARARs waiver
for "interim measures" provided by the NCP at 40 CPR 300.430(t)(1)(ii)(C)(1). EPA is
not requiring that the discharge from the treatment plant meet the ambient water qual-
ity criteria in lower Spring Creek for this interim action.
For the HDS treatment facility located at Minnesota FIats, it is relevant and appropri-
ate to provide protection of the FIat Creek drainage, including meeting the effluent
limitation for pH and TSS at 40 CPR ~440.102(a). FIat Creek does not currently meet
all ambient water quality criteria (A WQC) and Basin Plan water quality standards due
to a pollution source on Upper Spring Creek, the Stowell Mine. . Once this source is
remediated by RWQCB, EPA expects that FIat Creek could meet AWQC and water
quality standards. Therefore, discharges from the dewatering of sludge that do not
meet A WQC must be prevented from entering FIat Creek. Proper design of the de-
watering ponds is an economically viable option, although mechanical dewatering can
also be considered.
Brick Flat Pit must be modified to function as a safe, long-term disposal site for treat-
ment plant sludges. The remedial design of the disposal facility in Brick Flat Pit shall
address and comply with the requirements of the Toxic Pits Control Act and the.
California mining waste requirements. The discharge from Brick Flat Pit shall comply
with California mining waste requirements. Because Boulder Creek and Sliclcrock
Creek do not currently comply with ambient water quality criteria, and remediation of
sources in the interim action pursuant to the OldINo. 8 Mine Seep OU will not allow
for compliance with these standards without further actions, EP A is relying upon a
waiver for "interim measures" and is not requiring that the discharge from Brick Flat
Pit meet ambient water quality criteria in surface waters r~ceiviitg the discharge.
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6)
Some modifications and refinements may be made to the remedy during remedial
design and construction. Such modifications or refinements, in general, would reflect
the results of the engineering design process. Estimated cost for the remedy is $10.4
million. Details of the costs for the treatment component are shown in Table 5, and
capital costs and O&M costs are shown in Table 6.
x. STATUTORY DETERMINATIONS
EP A's primary responsibility at Superfund sites is to select remedial actions that are
protective of human health and the environment. CERCLA also requires that the
selected remedial action for the site comply with applicable or relevant and appropriate
environmental standards establish~d under Federal and State environmental laws,
unless a waiver is granted. The selected remedy must also be cost-effective and use
permanent treatment technologies or resource recovery technologies to the maximum
extent practicable~ The statute also contains a preference for remedies that include
treatment as a principal element. The following sections discuss how the selected
remedy for the OldINo. 8 Mine Seep OU at the Iron Mountain Mine site meets these
statutory requirements. .
Table 5
Incremental Cost Summary for Alternative O/N8.1 ($ x 1,000)
' Component Incremental Cost
Site Preparation and Access Roads 56
AMD and Process Water Conveyance System 1,362
Treatment Plant (Including Equalization and Copper Cementation) 677
Brick FIat Pit Improvements 200
Construction Subtotal 2,295
Bid Contingencies (10 percent) 230
Scope Contingencies (30 percent) 689
neral Contingencies (8 percent) 184
Construction Total 3,398
Permitting and Legal (3 percent) 102
Services During Construction (10 percent) 340
Total Implementation Cost 3,840
Engineering Design Cost (15 percent of Construction Total) 510
Total Incremental Capital Cost 4,350
30- Year Present Worth of Incremental O&M Costs (Interest = 5 percent) 3,920
Total 30- Year Incremental Present Wo.rth (Interest = 5 percent) 8,270
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. "--"
Table 6
Incremental Annual Operation and Maintenance Cost
Summary for Alternative OIN8-1 ($ x 1,(00)
Component Incremental O&M Cost
Access Roads 9
AMD and Process Water Conveyance 75
Treatment Plant (Including Equalization and Copper Cementation) 147
Sludge Disposal at Brick Rat Pit 24
Total Yearly Incremental O&M 255
Total Incremental Present Wonh of 30-year O&M (Interest = 5 percent) 3,920
X.I Protection of Human Health and the Environment
The selected remedy protects human health and the environment from the exposure
pathways that are being addressed in this interim action. The selected remedy
addresses the AMD discharges from th~ OldINo. 8 Mine Seep. The human health
threat posed by this source is small and related to direct contact or ingestion of the
AMD, which is unlikely due tp the remote location, rugged topography, and restriction
of access to the property. The environmental threats posed by this source are the very
significant releases of copper, cadmium, zinc, and acidity into surface waters. The
selected remedy will essentially eliminate the discharges from the source being
addressed in this interim action. The OldINo. 8 Mine Seep is a very effective collector
of the AMD that is believed to originate in the Old Mine and No.8 Mine workings.
Treatment of the discharges is expected to reduce the copper, cadmium, and zinc by
greater than 99 percent. . .
The OldINo. 8 Mine Seep OU provides for an interim .actionthat is not expected to be
final and does not address all of the sources of discharges from the site. The selected
remedy therefore cannot be expected to be fully protective of the environment in those
areas affected by other discharges.
X.2 Compliance with ARARs
The selected remedy for the OldINo. 8 Mine Seep OU provides for an interim
remedial action for a specific source at the site. The selected remedy provides for
48
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c)
~
significant progress toward meeting the objectives of the Superfund cleanup action at
Iron Mountain Mine by providing for significant reductions in the discharges of copper,
cadmium, zinc, and acidity from the site. In panicular, the remedy will result in better
water quality in the Sacramento River and reduce the number of days each year that
the Sacramento River exceeds State Basin Plan standards due to discharges of copper,
cadmium and zinc from !MM. This section discusses the ARARs which the action shall
meet and identifies the ARARs which are being waived.
The Old/No. 8 Mine Seep AMD discharge is similar in its nature and characteristics to
the Richmond. and Lawson portal AMD discharges which were addressed in the
September 30, 1992, Record of Decision (ROD) for the Boulder Creek Operable Unit
at !MM. The September 30, 1992, ROD thoroughly discusses the ARARs for this type
of source, AMD containing high concentrations of copper, cadmium, and zinc, and also
discusses the ARARs for the selected remedy, treatment with onsite sludge disposal or
discharge of the treated effluent to lower Spring Creek. The September 30, 1992,
ROD discussion regarding ARARs in Section X.2 is incorporated fully by reference.
The discussion below summarizes the compliance of the selected remedy for the'
Old/No. 8 Mine Seep OU with ARARs. . .
X.2.1 AMD Discharge. The components of the selected remedy to address the
Old/No. 8 Mine Seep AMD discharge are collection, treatment, and disposal of treat-
ment residues onsite. This action shall comply with the following ARARs in the man-
ner described:
X.2.1.1 Chemical-Specific ARARs. Chemical-specific ARARs for the selected treatment
remedy include the Clean Water Act effluent limitations for discharges of mine drain-
age from copper mines, exerCise of best professional judgment under the Clean Water
Act, Safe Drinking Water Act Maximum Contaminant Levels (MCLs), and non-zero
Maximum Contaminant Level Goals (MCLGs) at the water" intake to the City of
Redding, and the Basin Plan water quality objectives.
The primary adverse environmental impact from the IMM discharges is the impact on
surface waters arid the species which live in those waters. CERCLA provisions
respecting water quality criteria and the requirements of the Clean Water Act and
California Water Code are ARARs for the Site.
In the final remedy, any discharge from the mine to surface waters should comply with
the water quality objectives in the Central Valley Regional Water Quality Control
Board's Basin Plan. In determining the manner in which the mine discharges should be
controlled to achieve these levels, EPA may use best professional judgment (BPJ) to
determine the level of control. In addition to the use of BP J to achieve the water qual-
ity objectives in the receiving waters, EP A considers effluent limitations on related
mining activities as relevant and appropriate.
The selected treatment remedy for the Old/No. 8 Mine Seep OU will comply with the
following chemical-specific ARARs:
49
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, "'-;:,
\-.::;/
.
Substantive requirements of - NPDES permitting or substantive require-
ments regarding Waste Discharge Requirements
Use of BPJ to establish effluent limitations where there is no 'regulation
of the specific discharge
.
.
The BPT and best available technology (BAT) limits for point sources at
copper and zinc mines (40 CFR ~~440.102(a) and 440.103(a) (for treat-
ment plant discharges to lower Spring Creek, EP A has determined that
the limits for pH and TSS are not "relevant and appropriate")
.
MCLs and non-zero MCLGs established under the Safe Drinking Water
Act for the Sacramento River near Redding's Jewel Creek intake
The selected treatment remedy for the Old/No. 8 Mine Seep is an interim remedy and
does not address all of the sources of contamination at the site. Treatment of the
Old/No. 8 Mine Seep AMD discharge, in combination with other remedies already
selected for the ,site, cannot assure compliance with all ARARs. Further actions will be '
required. The selected remedy will comply with all ARARs to the extent practicable in
the context of the interim remedial action. However, EP A expects that it is necessary
to waive the following ARARs for the interim remedial action:
.
The water quality objectives of California's Central Valley Basin Plan for
the Sacramento River and its tnbutaries above the State Highway 32
bridge '
.
Water quality objectives of the California Inland Surface Waters Plan
X.2.1.2 Action-Specific ARABs. The selected remedy shall address and comply with all
action-specific ARARs. Significant action-specific ARARs include those relating to
disposal of the treatment sludge and ARARs directing activity to protect affected fish-
eries and habitat.
Selection of this alternative is consistent with statutes such as the Federal and
California Endangered Species Act and the Fish and Wildlife Coordination Acts
because the remedial alternative is being developed pursuant to a process_of consulta-
tion like that required by the Acts. The alternative would also comply with Fish and
Game Code Section 1505, since the improved water quality should result in greater
protection of fishery habitat in the Sacramento River below Keswick Dam.
The disposal unit used for the treatment residue should comply with the applicable
provisions of California Water Code Section 13172 and Health and Safety Code Sec-
tion 25208, et seq. (Toxic Pits Control Act, or TPCA). The Regional Board mining
waste requirements are ARARs which are applicable to the disposal of the treatment
residue. It is expected that chemical analysis of the treatment residues from the HDS
plant will indicate that the wastes are properly categorized as Group B wastes.
50
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f)
Although the HDS sludge will be less aqueous than the simple mix sludge, it may still
contain free liquids subject to TPCA provisions.
Consequently, the unit must not be located in a Holocene fault; shall be located outside
areas of rapid geologic change; shall require flood-plain protection from a lOO-year
peak streamflow; shall have liners and a filtrate collection system; shall have precipita-
tion and drainage controls for a 10-year, 24-hour storm; and shall comply with specific
monitoring requirements. .
Insofar as. the sludge contains free liquids, the disposal unit must also comply with
TPCA, which prohibits discharge of free liquids into a surface impoundment unless the
surface impoundment does not pollute or threaten to pollute the waters of the State.
If the treatment sludge contains free liquids, the design of the disposal unit must be
such that the unit does not pose a threat to pollute the waters of the State.
X.2.1.3 Loctltion-Speci.fic ARABs. The selected remedy shall address' and is expected to
comply with all location-specific ARARs. EP A has determined that the RCRA
requirements for management of hazardous wastes, including siting and .construction
criteria, are not relevant and appropriate to the management and disposal of residuals
from treatment of the AMD discharges or the waste piles. EP A is employing a
variance from Hazardous Waste Control Law requirements for disposal of the non-
RCRA waste. Accordingly, the selected remedy shall comply with requirements of the
Toxic Pits Control Act and California requirements for management and disposal of
mining wastes, including siting and technology requirements for disposal facilities.
The action shall comply with the following location-specific ARARs:
.
.
Archeological and Historic Preservation Act
National Historic Preservation Act
Oean Water Act (Section 404)
. Executive Order on Floodplain Management
Executive Order on Protection of Wetlands
.
.
.
X.2.2 ARAR Waivers For this Operable Unit. This section summarizes which ARARs
are subject to ARAR waivers. Because the Old/No.8 Mine Seep Operable Unit is an
interim remedy, it can qualify for the ARAR waiver for such actions. CERCLA
~121(d)(4)(A), 42 U.S.C. ~9621(d)(4)(A), provides that ARARs may be waived if "the
. remedial action selected is only part of a total remedial action that will attain such level
or standards of control when completed."
The ARARs which are being waived for purposes of this operable unit are:
.
The Basin Plan water quality objectives, discussed in detail below.
Because the treatment plant does not address all sources that are con-
tributing to. the exceedances of the water quality objectives, it is not pos
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\:::;J
sible to fully comply with ARARs until funher response actions are
selected and implemented.
.
Fish and Game Code Section 5650, which prohibits "permit[ ting] to pass
into...the waters of this State...substance or material deleterious to fish,
plant .life, or bird life." Because the treatment plant would not address
all sources at this site, this alternative would not eliminate all releases. It
would, however, eliminate 99 percent of the material passing into the
waters from the two ponal sources.
The overall remedy, including the activities in the 1986 Record of Decision, the 1992
Boulder Creek Record of Decision, this Operable Unit, and subsequent operable units
are expected to achieve compliance with these ARARs (at least in those ponions of the
site immediately below Keswick Dam). .
EPA has previously stated that the Old/No. 8 Mine Seep Operable .Unit will be
followed by other studies ,and remedial actions to address matters such as releases from
Slickrock Creek nonpoint sources and the sediments in the Spring Creek arm of
Keswick Reservoir. Those activities are not a pan of this OU~ The Old/No. 8 Mine '
Seep Operable Unit, however, is not expected to achieve this ARAR in all years with-
out the planned funher remedial action. As such, it is an interim remedy. In the event
of an interim remedy, EP A may elect to invoke an interim remedial action waiver as
provided in CERCLA f121(d)(4)(A), 42 U.S.c. f9621(d)(4)(A).
There is also some question regarding the technical practicability of meeting water
quality objectives in cenain segments of Boulder, Slickroc~ and Spring Creeks. In par-
ticular, it may not be technically practiCable to meet the water quality objectives in
cenain portions of these creeks. In such a case; EP A may consider the use of a waiver
under CERCLA f121(d)(4)(C), 42 U.S.C. f9621(d)(4)(C). The preamble to the NCP
discusses the use of the technical impracticability waiver at 55 Fed. Reg. 8748 (March
8, 1990). The main criteria for invoking this ARARwaiver are engineering feasibility
and reliability. EP A explained in the preamble that cost plays a "subordinate role" in
determining whether a remedial action is "practicable from an engineering perspective."
Id. Because this action is an interim remedial action, EP A is not today reaching any
conclusions regarding the technical impracticability of achieving ARAR compliance in
Boulder, Slickrock, and Spring Creeks, but is invoking the interim remedy waiver for all
stream segments.
The selected remedy will not provide for compliance with the applicable chemical-
specific ARARs of the Central Valley Regional Water Quality Control Basin Plan
water quality objectives, as discussed above. The selected remedy will allow for
compliance with these water quality objectives most of the time and represents a signifi-
cant improvement compared to the no-action alternative, O/NS-O. The selected remedy
will not provide for meeting water quality objectives in Slickrock Creek.
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~)
Subsequent remedial measures will address other sources of contamination that prevent
achievement of the water quality objectives in the Sacramento River. A subsequent
study will also address whether or not a wai~er for technological impracticability is
appropriate for water quality objectives in the creeks adjacent to Iron Mountain Mine.
X.3 Cost-Effectiveness
EP A has concluded that the selected remedy is cost-effective in mitigating the risk
posed by the discharge of heavy-metal-laden AMD from the Old/No. 8 Mine Seep to
surface waters. Section 300.430(f)(ii)(D) of the NCP requires EPA to evaluate cost-
effectiveness by comparing all the alternatives against three additional balancing cri-
teria: . long-term effectiveness and permanence; reduction of toxicity" mobility, or vol-
ume through treatment; and short-term effectiveness. The selected remedy meets these
criteria and provides for effectiveness in proportion to its cost. The estimated cost for
the selected HDS treatment remedy is $8.3 million.
X.4 Utilization of Permanent Solutions and AlterDative Technologies or Resource
Recovery Technologies to the Maximum Extent Practicable
EP A has determined that the selected remedy represents the maximum extent to which
permanent solutions and treatment technologies can be employed in a cost-effective
manner for the interim remedial action for the Old/No. 8 Mine Seep OU at Iron
Mountain Mine.
EP A recognizes that the mineralization at Iron Mountain Mine will continue to gener-
ate AMD unless additional remedial actions are developed, evaluated, and selected for
implementation to reduce or eliminate the AMD-forming reactions. Treatment does
not address the reactions themselves. Treatment effectively addresses the resultant
discharges. EP A has developed and evaluated alternatives as part of the ongoing
remedial investigation and feasibility study activities at IMM that could reduce or elimi-
nate the AMD-forming reactions. Resource recovery alternatives have also been pro-
posed and evaluated. EP A has concluded that further information is required to be
developed and evaluated before one of these approaches could be selected for imple-
mentation. The needed further information would address technical feasibility, implem-
entability, effectiveness, and cost-effectiveness concerns and risk factors with respect to
these approaches. EP A encourages the further development of alternatives that could
control the AMD-forming reactions and resource recovery alternatives for future evalu-
ation and potential selection in a subsequent action.
The selected remedy will provide for a significant reduction in the copper, cadmium,
zinc, and acidity discharges from the site. The current water supply and fishery condi-
tions are critical. There is a critical need to implement controls on these discharges as
soon as possible, while studies are ongoing' with respect to ~er source control or
resource recovery approaches. Treatment is effective, a part of each approach devel-
oped to date, and is consistent with implementation of a subsequent action.
53
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X.4.1 Preference for Treatment as a Principal Element. Although EP A is not selecting
a remedy which treats the source such that no funher AMD is formed, EP A is using
treatment to reduce the toxicity and mobility of the AMD which is being generated. By
selecting'the HDS treatment process instead of the simple mix treatment process, the
AMD treatment will also reduce the expected volume of the sludge. HDS sludge will
also be less toxic than the simple mix sludge.
Mine sealing or plugging alternatives present the potential to completely stop the
AMD-forming reactions and the discharge if the surrounding rock mass can contain a
mine pool at elevations sufficient to inundate all mineralization. The plugging alter-
natives might (with innovative approaches) address acidic metal-laden salts that dissolve
in the flooding mine pool and thus are mobilized and create a discharge pathway
through fractures or mining-related openings. A partially successful plugging alternative
would reduce the AMD-forming reactions, but not eliminate them. A partially success-
ful program presents risks of release of contaminants to the environment.
Other alternatives such as intercepting groundwater flow and capping areas which chan-
nel infiltrating water toward mineralization would likely reduce the rate of reaction o~
the AMD formation, but not eliminate them. These alternatives provide less risk of
creating new discharge pathways and rely on conventional engineering approaches.
Resource recovery approaches merely treat the discharge, recovering economic values.
Conventional treatment is effective at eliminating the discharge, but does not treat the
sources of the discharge. .
ErA encourages the continued development and evaluation of alternatives that may
partially satisfy the preference for treatment as a principal element, and this issue will
be addressed in the final decision document for the site. EP A has concluded that fur-
ther development and evaluation of the. above approaches is necessary to address
uncertainties with respect to technical feasibility, implementability, effectiveness, cost-
effectiveness concerns, and risk factors. .
XI. DOCUMENTATION OF SIGNIFICANT CHANGES
EP A is today approving the Proposed Plan. There are no significant changes.
EP A will locate the Old/No. 8 Mine Seep treatment plant at Minnesota Flat. As EP A
proposed in its February 11, 1993, Proposed Plan for the Old/No. 8 Mine Seep OU,
EPA will co-locate the Old/No. 8 Mine Seep treatment plant with the Boulder Creek
treatment plant to take advantage of cost savings that can be realized from this
approach. EP A has selected Minnesota Flat for the plant site based upon cost and
reliability considerations developed and evaluated in detail during design of the Boulder
Creek treatment plant. In conducting treatability studies for the plant, EP A has
concluded that it is not necessary to require that sulfide be used in the treatment
process. Treatability studies have shown that the addition of sulfide hinders the
formation of the HDS sludges. Since the same plant and process will be used for the
discharges from this OU, sulfide will not be required for treatment.
54
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,
STATE OF CALIFORNIA - ENVIRONMENTAL PROTECTION AGENCY
PETE WILSON. GDllernor
DEPARTMENT OF TOXIC SUBSTANCES CONTROL
REGION 1
10151 CROYDON WAY. SUITE 3
SACRAMENTO. CA 95827.2106
(916) 255-3545
September 9, 1993
Mr. Dave Jones
U.S. Environmental Protection Agency
Region IX
75 Hawthorne Street
San Francisco, California 94105
IRON MOUNTAIN MINE; AGENCY REVIEW DRAFT, OLD/NUMBER 8 MINE RECORD
OF DECISION
Dear Mr. Jones:
We have received ~he agency review draft. of the Old/Number 8
operable unit Record of Decision (ROD) for the Iron Mountain Mine
Superfund Project. We concur with the U. S. Environmental
Protection Agency's (EPA) interim remedy selection of treatment
for the acid mine drainage flows emanating from the Old/Number 8
Mine Seep. We agree that Minnesota Flats appears to be a
suitable location for the treatment plant and that Brick Flat
Pit, after modification to comply with the Toxic Pits Control
Act, California Water Code, Section 13172 and the regulations
adopted thereunder, appears to be a suitable location for
permanent disposal of sludges.
At this point in time, however, we are unable to concur with
the selection of the high density sludge (HDS) treatment method.
In principle, we agree.that HDS is a preferable treatment
methodology due to its reputably superior sludge characteristics.
Those characteristics, when compared to the sludge generated by
the simple mix process, include higher solids content (lower
resultant sludge volume), superior handling and disposal
characteristics and superior dewatering/leachate characteristics.
But in light of Stauffer Management Company's (SMC)
representations and plans with regard to the construction of a
300 gallon per minute aerated simple mix plant (which doubles as
a 1400 gallon per minute partially aerated simple mix plant), we
have insufficient information upon which to base a conclusion
that HDS is. necessary.
.,
. .
...
p',n'eG or. R«, ,/:..,,: .
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Mr. Dave Jones
September 9, 1993
Page Two
We envision the following actions at the site:
1.
SMC should construct the plant as required by EPA Order 93-1
(as proposed to be amended in EPA's July 15, 1993 letter to
SMC and SMC's July 27, 1993 letter to EPA) and the state's
Order I/&SE 93/94 002 (as proposed to be amended in our
August 10, 1993 letter to SMC).
Facilities to convey the Old/Number 8 Mine Seep Acid Mine
Drainage flows to the treatment plant be constructed in the
summer of 1994 as required by the State's Order I/&SE
93/94 002. ' ,
2.
3.
Performance of the treatment plant will be monitored in
accordance with an approved monitoring plan during the rainy
season of 1994/1995. optimal operational parameters will be
determined during this time frame. '
If conditions warrant, i.e., the quantities arid quality of
the sludge generated by the SMC plant prove to be
unmanageable, the HDS plant is then constructed.
4.
If you have any questions or concerns, please call me or
Mr. Duncan Austin at (916) 255-3706.
cc:
Sincerely,
/;.-,..~,~ /., j-.I' .
/ ...... ""'-:-- a .., '"
:.. ~ 1" I''.' (.;.-....':"':'"
- ./
Anthony J. Landis, P.E., Chief
Site Mitigation Branch
Mr. James Pedri
Regional Water Quality Control Board
415 Knollcrest Drive
Redding, California 96002
Mr. Harry Rectenwald
Ca'lifornia Department of Fish and Game
601 Locust Street
. Redding, California 96001
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~.
United States Department of the Interior
.
-
IS REPL\" REF'ER TO:
OFFICE OF TIIE SECRETARY
. Office of Environmental Affairs
600 Harrison Street, Suite 515
San Francisco, California 94107-1376
.-
-
-
.
Mr. Rick Sugarek
Region IX
Environmental Protection
75 Hawthorne st.
San Francisco, CA 94105
August 31, 1993
Agency H-6-2
Dear Mr. Sugarek:
Thank you for the opportunity to review the Record of Decision
presenting interim remedial actions for discharges from the
Old/No.8 Mines. While we agree with the selection of treatment
technology as the interim remedy, we are concerned that by
concentrating on the single seep, other discharge points are
escaping capture by the system. Each such discharge in .
Slickrock Creek that escapes capture and treatment is eventually
collected at spring Creek Debris Dam and increases the need for
dilution water.
We suggest that if such a remedy is selected, that it include
efforts to collect more of the discharge. Alternatives include
placement of the treatment facility downstream or collection at
the seep site itself (in much the same way as a spring would be
developed) .
. sincerely, - I ~
D~-V f'/Dp
~~~ Sanderson Port
Regional Environmental Officer
cc:
Kris Doebbler, BR
Roger Helm, FWS
Denise Klimas, NOAA
Harry Rectinwald, CA
Fish and Game
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1'4) ""'IS 0' ".~
~D
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Ser/ice
Office 0' Ocean Resources Ccnservation arid ASiOessmer.t
Hazardous Materia!s Response and Assessmer.: DiviSion
Coastal Resources Coordination Branch
September 7, 1993
Mr. Rick Sugarek (H-6-2)
U.S. Environmental Protection Agency
Region IX
75 Hawthorne Stteet
San Francisco, CA 94105
Subject:
Review of the Iron Mountain Mine 01d/No. 8 Mine Operable Unit Draft Record of
Decision.
Dear Mr. Sugarek:
The Natural Resources Trustee Council for the Iron Mountain Mine Superfund site, comprised of
the National Oceanic and Atmospheric Administration, the National Marine Fisheries Service, the
Department of Interior Office of Environmental Affairs, the U.S. Fish and Wildlife Service, the
U.S. Bureau of Reclamation, and the California Department ofFish and Game, has reviewed the
August 6, 1993 Agency Review Draft Record of Decision (ROD) for the 01d/No. 8 Seep at Iron
Mountain Mine (IMM). The Natural Resources Trustees previously commented on the agency
review draft of the Remedial Investigation/Feasibility Study for the Operable Unit The alternative
selected in the ROD is consistent with the tteatment alternative recommended by the Natural
Resource Trustee Council in the April 8, 19931etter. However, we believe that the details on the
amount of contamination that is collected for tteatment is not consistent with our earlier
recommendation. We also have some commentS on the details of implementing the selected
alternative and some commentS on technical discussions contained in the document
The Operable Unit is defined as the Old and No.8 Mines. We believe that because these mines are
buried by tens of feet of loosely consolidated landslide material, there is more contamination
coming from the mines than is accounted for by the most obvious seep that is the focus of the
remedial action. The ROD should disclose how the releases from this buried, leaking, flooded ore
body travel through several known or potential migration routes to surface waters. The amount of
contamination from the source (OldINo. 8 Mine Operable Unit) that will be treated by remedial
action will depend upon the efficiency of the collection system for the discharge from the buried
mines. We recommend developing the most effective design possible for collecting acid mine
discharge (AMD) from the buried and flooded mine workings..
We believe that maximizing the collection of the contaminants from this flooded mine pool
(Operable Unit) is consistent with the National Contingency Plan (NCP). Reducing the
contamination better satisfies the evaluation criteria, including protection of the environment, long-
and shon-term effectiveness, and compliance with Applicable or Relevant and Appropriate
Requirements. .
Specific Comments:
Page 2, 2nd Paragraph, 1st Sentence: The subject seeps are emerging from the north slope of
Slickrock Valley or the south facing slope of Iron Mountain.
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Page 2, 3rd Paragraph: The.ROD correctly describes the Sacramento River winter-run chinook
salmon as listed Threatened by the National Marine Fisheries Service under the Federal
Endangered Species Act; you should include also that the species has been listed as. Endangered by
the State of California, under the California Endangered Species Act.
Page 2, Paragraph 5, Second Sentence: The diversion of upper Spring Creek is into Flat Creek
and is not in the Boulder Creek drainage.
Page 18, 2nd Paragraph: This discussion should disclose that contamination from the OldINo. 8
Mine workings Ope~ble Unit has many known and potential migration routes to the surface waters
in the Slickrock Creek drainage. We believe this is the case, considering the fact that the releases
from this mine pool must first flow through several tens of feet of loosely consolidated landslide
material before reaching the surface. After AMD from the flooded mine pool emerges through the
buried mine portal, it can diffuse throughout the landslide fonnation. There is evidence that seeps
down-gradient from the main identified seep have a chemical characteristic and flow pattern similar
to the main seep, indicating a common source (Old/No. 8 Mine Operable Unit).
We believe that the selected remedy for this Operable Unit should be designed to abate as much of
the contamination originating from this source that is possible. It appears that the site would lend
itself to designs that would pass the implementability evaluation criteria in the NCP. It would be
most prudent to establish collection systems at an elevation at least as deep as the buried mine
portals. .
Page 19. 1st Paragraph. 2nd Sentence: The fish toxicity should be described as ~ toxicity, .
rather than just toxicity, because cm-onic toxicity levels are much lower than the values specified
here. Acute toxicity also occurs at concentrations lower than those specified in this discussion.
especially if the concentrations referred to are in the form of dissolved metals.
Page 21. 4th Paragraph, 3rd Sentence: Fishery data in this discussion is outdated. During and
prior to the recent, extended drought, the salmon and steelhead were undergoing a decline that at
that time produced a population that was only 50 percent the size of the earlier populations. The
drought greatly accelerated this ongoing decline, producing escapementS of salmon in the upper
Sacramento River during the 1990's that are now only 20 percent of the levels observed during the
late 1950's.
Page 22, 1 st Paragraph, 3rd Sentence: The flood control releases from Shasta Reservoir described
here should be qualified as high volume flood control releases. This qualification will avoid
. confusion with other flood control operations at Shasta Dam that produce a very low volume
release to prevent compounding ongoing flooding of downstream areas in the Central Valley. This
low volume release operation has produced catastrophic fish kills in the past, because it does not
encourage downstream migration and reduces dilution of toxicant.
Page 22. 2nd Paragraph, I st Sentence: Spring-run chinook and early spawning fall-run chinook
have also exhibited this panern of concentrating spawning activity in the cooler uppermost river
reaches that are more susceptible to metal toxicity.
Page 22. 3rd Paragraph: The risk to resident trout and steelhead is overall less than that-for salmon
due to the fact that the sensitive early life stages of trout and steelhead are predominantly located in
tributaries to the Sacramento River that do not receive the toxicant
Page 31. 1st Paragraph, 1st Sentence: The concept for collection of AMD at the OldINo. 8 Seep is
intended to provide both surface and underground interception of the flows. We believe it is
important to collect the AMD emanating from these ore bodies to the maximum extent
possible, in order to comply with the nine evaluation criteria specified by the National
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Contingency Plan (40 CFR ~300.430 (e)(9»., See also above comment concerning Page 18, 2nd
Paragraph.
Page 52, 1st Paragraph, last sentence: The Natural Resource Trustees have previously commented
on the failure ~f a mine plugging program similar to that described in this section. One of the
greatest risks to biological resources in general, and the ESA listed winter-run chinook salmon in
particular, is the likelihood that contaminants from the leaking mine pool would be released in a
manner that would be uncollectible or only fractionally collectable for treatment This, in our
opinion, represents a severe risk. This risk should be included in this discussion.
If you have any questions regarding these comments, please contact one of the following:
1)
Ms. Patricia Pon, Office of Environmental Affairs, U.S. Department of the Interior, San
Francisco, CA (415) 744-4090
2)
Ms. Denise Klimas, National Oceanic and Atmospheric Administration, San Francisco CA
(415) 744-3126
3)
4)
5)
6)
Mr. Roger Wolcott, National Marine Fisheries Service, Santa Rosa, CA (7CJ7) 578-7513
Mr. Jim Haas, U.S. Fish and Wildlife Service, Sacramento, CA (916) 978-4866
Ms. Kris Doebbler, U.S. Bureau of Reclamation, Sacramento, CA (916) 978-5046
Mr. Richard Elliott, Regional Manager, California Department of Fish and Game, Redding,
CA (916) 225-2364
Sincerely,
NATIONAL OCEANIC AND A 1MOSPHERIC ADMINISTRATION
BY: ({)~)t.~
. Denise M. Klimas, Coastal Resources Coordinator
National Oceanic and Atmospheric Administration
Hazardous Materials Response and Assessment Division
75 Hawthorne Street (H-1-2)
San Francisco, CA 94105
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6
NATIONAL RINE FISHE~ S~VlCE .
BY: -".--£!. ~
L Matlock, Ph.D., Actin~Onal Director
{-. ',- ational Marine Fisheries Service
501 West Ocean Blvd., Suite 4200
Long Beach, CA 90802-4213
u.S. FISH AND WILDLIFE SERVICE
BY: U
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S'jATE OF CALIFORNIA - Environmental Protection Agency '----"
CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD
CENTRAL VALLEY REGION
4 1 5 Knollcrest Drive. Suite 100
Redding. CA 96002
PHONE: (916) 224-4845
FAX: (916) 224-4857
PETE WILSON. Governor
17 September 1993
Mr. David Jones
U. S. Environmental Protection Agency
Region 9
75 Hawthorne Street
San Francisco, CA 94105
DRAFT ROD - OLDINO. 8 SEEP
We have reviewed the agency draft of the Record of Decision (ROD) for the Old/No.8 mine seep.
. .
We concur with the selection of neutralization treatment as an interim remedy for control of acid
and metals emanating from the Old/No.8 mine seep. As discussed in the DTSC response letter (9
September 1993), we are not at this time recommending a specific treatment process. We concur
with the DTSC proposal to evaluate sludge characteristics from the aerated simple mix plant and
then determine if HDS is warranted. Given the relatively high cost of treatment and the problems
with sludge disposal, efforts should be made to replace treatment technology at the earliest possible
date with remedial action which prevents or reduces the formation of acid mine drainage.
The Slickrock Creek basin in the vicinity of OldINo. 8 mine has been shown to be a significant
source of additional Cu loading from Iron Mt. Mine. We request that there be a continued effort to
identify the actual source of this additional Cu load and an evaluation of feasible control actions.
ave any questions, please contact Dennis Heiman of my staff at (916) 224-4851, or the
mes:. {!~- . f-
James C. Pedri, P.E.
Supervising Engineer
DRH:tch
cc:
Mr. Anthony Landis, DTSC, Sacramento
Mr. Harry Rectenwald, Department of Fish and Game, Region 1, Redding
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