Abandoned Mine lands iase Study
• Mining at Iron Mountain began in the mid 1890s and
ended in 1963
• The uncontrolled acid mine drainage from Iron
Mountain Mine was the largest source of surface
water pollution in the U.S. and accounted for
roughly one-fourth of the entire national discharge
of copper and zinc to surface waters from industrial
and municipal sources.
• EPA's cleanup and pollution control measures have
reduced the discharge of acidity, copper, cadmium,
and zinc by 95 percent.
• A financial settlement with the responsible parties
provides for the operation and maintenance of the
on-site treatment facilities far into the future.
Early in its history, Iron Mountain Mine was famous for being the
most productive copper mine in California and one of the largest
in the world. In recent years, the legacy of mining at Iron
Mountain turned its fame to infamy, as the site became known as the
largest source of surface water pollution in the United States and the
source of the world's most corrosive water. Even so, 40 years after the
cessation of mining activities, scientists seeking to understand how to
control the risks posed by the site made a valuable discovery of a
different kind at Iron Mountain: a new species of microbe that thrives
in the extreme conditions deep within the mountain. While pollution
from the site has not posed any great risk to the approximately 100,000
people living in the nearby City of Redding, the same can not be said
for the salmon, trout, and other aquatic organisms that have struggled
for survival downstream of Iron Mountain. More than 20 years of
work by EPA, other Federal and California State agencies, and
potentially responsible parties (PRPs)—much of it underwritten by
Superfund—is finally paying off in a big way. Remediation and
pollution control activities now neutralize almost all the acid mine
drainage and control 95 percent of the copper, cadmium, and zinc that
used to flow out of Iron Mountain into nearby streams and then into the
Sacramento River. Furthermore, EPA and the State of California
secured funding from one of the site's previous owners in one of the
largest settlements with a single private party in Superfund history.
The settlement terms should enable continuous operation and
maintenance of the treatment facilities for the foreseeable future.
March 07, 2006
-------
Iron Mountain Mine Case Study
Success Through Planning, Partnerships, and Perseverance
Site History
Iron Mountain is located in Shasta County, California, in
the southeastern foothills of the Klamath Mountains,
approximately 14 km (8.7 mi) northwest of the City of
Redding. The mineral deposits within Iron Mountain
define the southernmost end of the West Shasta mining
district.
The Superfund site known as Iron Mountain Mine
(1MM) encompasses approximately 1,800 hectares
(4,400 acres) and comprises many distinct mines, the
site of the former flotation mill at Minnesota Flats, the
Matheson Rail Loading Station site, and the Spring
Creek Arm of Keswick Reservoir. Between the mid
1890s, when the Old Mine was first excavated to extract
copper ore, and 1963, when mining activities ceased,
nearly ten separate mines were excavated at Iron
Mountain, including Old Mine, No. 8 Mine, Richmond
Mine, Hornet Mine, Confidence-Complex Mine, Mattie
Mine, and the open pit mine at Brick Flat near the
mountain's summit.
Geologists refer to formations like Iron Mountain as
massive sulfide deposits. The deposits in the West Shasta mining district formed 350 to 400 million years ago
in an island-arc setting in a marine environment as a result of geothermal hot springs on the sea floor expelling
sulfur-rich hydrothermal fluids.
Photo 1: Before cleanup began at the site, IMM
discharged, on average, five tons of iron, 650
pounds of copper, and 1,800 pounds of zinc per
day into Spring Creek and Kesnick Reservoir.
In the 1860s, surveyor William Magee and settler Charles Camden
noticed the striking red color of the rock outcrop on the south face
of Iron Mountain and deduced the presence of "an immense iron
deposit." In 1879, James Sallee discovered that the red rock—
known as gossan, rust-colored, oxidized iron ore—contained
silver as well as iron, and he, Magee, and Camden began mining
the gossan and extracting the silver. In the mid 1890s, the sulfide
deposits within the mountain were discovered, and copper mining
commenced. In subsequent years, Iron Mountain was also mined
for gold, iron, zinc, and pyrite (iron sulfide); pyrite, a source of
sulfur, was used to manufacture munitions and fertilizers and in
petroleum refining. California State records indicate that between
1888 and 1965, Iron Mountain yielded 313 million pounds of
copper, 265,314 ounces of gold, 24 million ounces of silver, 2.6
million pounds of sulfur, and sizeable quantities of zinc and iron.
At one time, IMM was the largest copper producer in California,
the sixth largest in the U.S., and the tenth largest in the world.
2 of 17
March 07, 2006
-------
Iron Mountain Mine Case Study
Success Through Planning, Partnerships, and Perseverance
Regulatory History
In 1976, the State of California adopted regulations making
owners of inactive mine sites responsible for meeting Federal
Clean Water Act standards for pollution. Between 1976 and
1982, the State fined IMM owners for unacceptable releases of
metals. In February 1982, the State of California initiated legal
action against the site owner, Iron Mountain Mines, Inc. (which
purchased the site from Stauffer Chemical Company in 1976).
The State's legal action resulted in a default judgment against the *
company and fines totaling $16.8 million. In June and July
1982, Iron Mountain Mines, Inc. filed motions to vacate the
default j udgments, which the Shasta County Superior Court Photo 2: Entrance to the refurbished Richmond
denied; the company appealed the denials on its motion in a(llt' showing the ventilation exhaust system.
August 1982. The company eventually reached a settlement with the State on the $16.8 million default
judgment. The State of California requested CERCLA funding for a remedial investigation/feasibility study to
determine the nature and extent of contamination at the site and to identify alternatives for remedial action. In
December 1982, the State of California requested that EPA propose Iron Mountain Mine for li sting on the
National Priorities List, and the site was listed in September 1983. In 1989, EPA issued an Administrative
Order requiring the PRPs (Rhone-Poulenc (Aventis CropSciences USA, Inc.); Iron Mountain Mines, Inc.; and
Mr. T. W. Arman) to implement emergency treatment of acid mine drainage discharges from the underground
mines to minimize the contamination of adjacent water bodies. In 1990, EPA ordered the PRPs to implement a
cleanup action in the Upper Spring Creek to divert clean water away from sources of contamination on the site.
One year later, EPA ordered the PRPs to assume responsibility for operation and maintenance of the completed
cleanup actions. In 1992, EPA ordered the PRPs to expand the existing emergency treatment operations and to
construct a full-scale permanent treatment system for the Boulder Creek Watershed. This was followed, in
1994, by an EPA Administrative Order requiring the PRPs to implement the collection and treatment system for
the acid mine drainage discharges at the Old Mine/No. 8 Mine. Finally, in 1997, EPA ordered the PRPs to
design and construct the Slickrock Creek Retention Reservoir to collect the area source acid mine drainage
discharges for treatment. In December 2000, the EPA, the U.S. Departments of Commerce and the Interior, and
several California State agencies reached a settlement with Aventis, the principal responsible party at IMM.
The total value of this settlement—for past costs and future
work—is over $950 million. (Terms of the settlement are
provided below in the Successes section.)
Photo 3: The view looking into the refurbished
Richmond adit. The pipe used to convey acid mine
drainage out of the mine is visible on the tunnel
floor at left.
Mining Impacts
Nearly 100 years of mining activity at Iron Mountain left
numerous waste rock and tailings piles, massive fracturing of the
bedrock overlying the extensive underground mine workings and
remaining sulfide deposits, sinkholes, seeps, and contaminated
sediments in nearby waterbodies. The underground mine
workings and the fractured bedrock above them provide an
effective means for both water and air to reach the enormous
sulfide deposits deep within the mountain, where water and
oxygen react with the sulfide ores (mostly pyrite), producing
3 of 17
March 07, 2006
-------
Iron Mountain Mine Case Study
Success Through Planning, Partnerships, and Perseverance
sulfuric acid and dissolving the heavy metals in the ore. This is a
classic recipe for acid mine drainage, which led one group of
researchers to call Iron Mountain "a 'worst-case scenario' with
respect to the formation of acid mine drainage." Most of the acid mine
drainage comes from the oxidizing sulfides within the three largest
sulfide ore bodies, the Brick Flat, Richmond, and Hornet deposits.
In 2000, microbiologists conducting research inside Iron Mountain announced the discovery of a new species of
iron-oxidizing Archaea (along with plants and animals, one of the three primary forms of life on Earth) that
thrives in the extreme conditions found in the mine. This organism (christened Ferroplasma acidarmanus)
grows on the surface of exposed pyrite ore in pools of water so acidic that they were previously thought to be
inhospitable to all forms of life. It greatly accelerates the rate of oxidative dissolution of pyrite, the process that
produces acid mine drainage by converting iron sulfide minerals to sulfuric acid. The discovery of
Ferroplasma acidarmanus helps explain why the acid mine drainage problem at Iron Mountain is so severe.
According to EPA, the uncontrolled discharge of copper and zinc from IMM is equal to about one-fourth of the
entire national discharge of these two metals to surface waters from industrial and municipal sources.
Members of the underground sampling
team had to contend with dangerous
conditions in the mine: temperatures over
120°F, humidity close to 100%, frequent
rock falls from the 40-foot ceiling, and hot
acidic water (more concentrated than
battery acid) dripping everywhere.
Groundwater
Ore Bodies
Whiskeytown Lake
— |—^
Spring Creek
Debris Dam
Spring Creek Reservoir
Sediments
Flat Creek
Keswick Reservoir
Shasta Dam
Spring Creek
Powerhouse
Sacramento River
./V ''A /"{/
/, Precipitation
Upstream (Clean) Creeks /GW
~ 2.
Slickrock Creek
y/t ///,/',//
Surface Water
^.Infiltration
Direct Groundwater
Discharge to Streams
V
Richmond Portal
> Groundwater ^
Seepage to Streams *-"LI JSj^Boulder
-^^^Creek
///•
Surface Water// / '
l 'LL!i Mi
Spring Creek
Runoff /_'//'/ Minnesota Flats Tailings Pile
Groundwater
Shasta Lake
Keswick Dam
Diagram of Acid Mine Drainage at Iron Mountain Mine
* Not to Scale
4 of 17
March 07, 2006
-------
Iron Mountain Mine Case Study
Success Through Planning, Partnerships, and Perseverance
Prior to EPA's cleanup of the site, most of the acidic effluent from Iron Mountain flowed or seeped out of the
mines into adjacent streams and eventually into Keswick Reservoir, a run-of-river reservoir on the Sacramento
River. Consequently, the creeks draining Iron Mountain are essentially devoid of aquatic life downstream
(though not upstream) of the mines. The stretch of the Sacramento River just below Keswick Dam is among the
river's most productive salmon spawning grounds and is also the location of the drinking water intake for the
City of Redding. Fortunately, acid mine drainage from Iron Mountain poses no imminent threat to Redding's
water supply due to the combination of dilution in the Sacramento River and removal of the metals in the city's
water treatment plant. The City of Redding does, however, have a contingency plan to switch its drinking water
supply to groundwater temporarily should a major release of metal-rich drainage from Iron Mountain occur.
Fish (especially young fish, known as fry) and other aquatic organisms are far more sensitive than humans to
metals like copper, zinc, and cadmium. These metals act as chemical asphyxiants by binding to gill surfaces
and interfering with the gills' ability to absorb oxygen. Even sub-lethal concentrations of toxic metals may
harm aquatic organisms. Thus, the water-quality criteria for copper, cadmium, and zinc are considerably more
stringent for aquatic life than for drinking water.
The diverse sources of acid mine drainage and the occasional
intense, high-runoff storm events characteristic of the area's
climate historically resulted in major releases of heavy metals.
During periods of heavy winter rain, high volumes of acid
mine drainage are produced because more water flows through
the mineralized zones and waste piles at IMM. Such high-
flow events result in elevated levels of metals in the discharges
of acid mine drainage: rather than diluting the base flows, the
higher flow during storms apparently increases pyrite
oxidation and dissolves soluble salts within the mine. In the past, heavy runoff from the Spring Creek drainage
occasionally caused the Spring Creek Reservoir to overflow. One consequence was an accumulation of heavy
metals in the sediments in Spring Creek and Keswick Reservoirs, downstream of the Spring Creek Debris Dam.
In addition, the Federal Bureau of Reclamation typically restricts the outflow from Shasta Lake during heavy
rains to prevent downstream flooding and to maximize water storage behind Shasta Dam. This reduces the
dilution of metal-rich effluent from IMM entering the Sacramento River, and the combination of these events
can raise dissolved copper concentrations in the
Sacramento River to 13 parts per billion (ppb) while
lowering the river's pH from its normal value of 7.5 to an
acidic 6. A concentration of 13 ppb copper is sufficient
to kill fish fry if the exposure lasts for several days, and
research indicates that copper's toxicity to fish increases
as pH decreases. In March 1992, at the height of the
second-worst drought in California history, the Bureau of
Reclamation was impelled to release 77,000 acre-feet of
water from Shasta Lake to dilute a spill from Spring
Creek Reservoir. At that time, Shasta Lake was only half
full, and the water released from the reservoir (valued at
$18 million) was badly needed by farmers in California's
Central Valley.
"When extraction of the ore was suspended
from the various stopes above the Lavvson, the
ground was in very bad shape, and the
conditions regarding heat and gas were so
terrible that it seemed advisable to abandon any
attempt to work from that level. In fact it was a
case of walking away and leaving the job for the
next generation" (William F. Kett, General
Manager, Mountain Copper Co., August 1944).
Photo 4: The lime neutralization/high-density sludge acid
mine drainage treatment facility at Minnesota Flats.
5 Of 17
March 07, 2006
-------
Iron Mountain Mine Case Study
Success Through Planning, Partnerships, and Perseverance
Photo 5: According to EPA documents,
workers once inadvertently left a shovel
standing in the green liquidflowing from one
of the mine portals. The next day half of the
shovel had been eaten away.
For decades, eroded tailings and waste rock (along with acid mine
drainage) have washed down Iron Mountain into Spring Creek,
especially during large winter storms. After the completion of the
Keswick Dam in 1950, the Spring Creek Arm of Keswick Reservoir
began to fill rapidly with the debris eroded off Iron Mountain and the
metals precipitating out of the acid mine drainage as it was
neutralized in the reservoir. Nearly all the acid mine drainage is now
collected and treated on-site, and movement of eroded tailings is
largely prevented by the remedial actions taken to date at both the
Slickrock Creek and the Spring Creek Debris Dams. Nevertheless, large quantities of contaminated sediments
now rest on the bottom of Spring Creek
and the Spring Creek Arm of Keswick
Reservoir. Studies by the U.S. Geological
Survey (USGS) and the California
Department of Fish and Game document
high concentrations of heavy metals in
these sediments. The sediments in the
Spring Creek Arm of Keswick Reservoir
are located directly downstream of the
discharge from the Spring Creek
Hydroelectric Power Plant. Consequently,
these sediments pose an ecological risk
because power plant operations or a major
storm event that causes Spring Creek
Reservoir to fill and spill could scour the
contaminated sediments in the reservoir,
,, . , , , , Photo 6: Part of the lime neutralization/high-density sludge acul mine
mixing them in the water column and , . . . . .... . .... ; , . , , ~.
p . . drainage treatment plant at Minnesota Flats. Ihe large tank at center-lejt is
exposing fish and other aquatic organisms one ()j fwo in w]t[c]t acid mine drainage is mixed with lime slurry.
downstream to the toxic metals.
As early as 1900, the California Fish Commission investigated fish
kills in the Sacramento River attributed to pollution from IMM, and
in 1939 the State of California began studying the relationship
between water quality and fish toxicity. State records document
more than 20 fish-kill events in the Sacramento River downstream of
IMM since 1963. Acid mine drainage from Iron Mountain killed
100,000 or more fish on separate occasions in 1955, 1963, and 1964;
and at least 47,000 trout died during a one-week period in 1967.
Among the aquatic organisms harmed by acid mine drainage from
Iron Mountain are four runs of Chinook salmon, steelhead and other
resident trout species, hundreds of species of aquatic insects, clams,
mussels, plants, and single-celled algae. The U.S. Fish and Wildlife
Service lists the winter-run and spring-run Chinook, which spawn in
the Sacramento River near Redding, as endangered and threatened,
respectively, pursuant to the Endangered Species Act.
6 of 17
March 07, 2006
-------
Iron Mountain Mine Case Study
Success Through Planning, Partnerships, and Perseverance
In addition to the abandoned mine
workings, mine tailings are another
source of acid mine drainage. The
Minnesota Flats area, on the east
flank of Iron Mountain, was the site
of a mill where ore was crushed and
processed. The legacy of that
refining process was a large tailings
pile. In 1989, EPA removed those
tailings to a disposal cell near the
top of Iron Mountain, and in 1994 a
water treatment plant was built at
Minnesota Flats. This facility,
which has been expanded and
upgraded since it was first
constructed, uses lime (calcium
oxide, CaO) to neutralize the acid
mine drainage collected from
several sources, including the
Richmond and Lawson portals, the
Old/No. 8 Mine seep, and the Slickrock Creek Reservoir. The acid mine drainage from these various sources is
transported to Minnesota Flats via more than three miles of pipeline. In the treatment plant, the acidic effluent
is thoroughly mixed with a lime slurry. The process not only neutralizes the acid, it also causes the metals to
precipitate out of solution, removing over 99% of the copper, zinc, cadmium, and other metals. The mixture is
then conveyed to a large sludge conditioning tank, where the resulting high-density sludge settles to the bottom.
Periodically, the sludge is removed from the tank and deposited in beds adjacent to the treatment facility, where
it is allowed to dry before being trucked to the disposal cell in the pit at Brick Flat.
Putting the IMM Problem in Perspective:
The acid mine drainage from IMM is among the most acidic and metal-laden anywhere on Earth. Prior to EPA's
cleanup, the heavily worked mines on Iron Mountain discharged, on average, 650 pounds of copper, 1,800
pounds of zinc, and 10,000 pounds of iron per day. For comparison:
1. The IMM discharge was at least equal to ail the combined industrial and municipal discharges to the San
Francisco Bay and Delta Estuary System.
2. The IMM discharge was more than twice the combined discharge from the 28 largest inactive mines in
Northern California. The next largest was less than one-tenth of the IMM discharge.
3. The IMM discharge was equal to about one-fourth of the entire national discharge of copper and zinc to
surface waters from industrial and municipal sources.
4. The IMM discharge was the largest discharge to surface waters in the nation identified under the Clean Water
Act (CWA) §304(1) program for cleanup of impaired waters of the United States.
Mining activities also left a large deposit of pyrite ore at the end of an aerial tram that used to move the ore
from the Richmond Mine and the open pit mine at Brick Flat to the Matheson Rail Loading Station, where the
ore was loaded onto trains for shipment. In addition to contributing to water pollution, the ore posed a risk of
direct human exposure to the arsenic, lead, cadmium, and other toxic metals contained in the ore. In response,
in 2005, EPA excavated and removed approximately 7,600 cubic meters (10,000 cubic yards) of soil
Photo 7: The sludge conditioning tank at Iron Mountain Mine is one of the largest in
the world. The sludge is periodically transferred to the drying beds visible behind the
tank before being placed in a disposal cell on the site.
7 Of 17
March 07, 2006
-------
Iron Mountain Mine Case Study
Success Through Planning, Partnerships, and Perseverance
contaminated with pyrite ore, along with old concrete bunkers and other debris from the three-acre site. The
material removed from the Matheson site was placed in a disposal cell on Iron Mountain. The site, located on
the shores of Keswick Reservoir, may now be enjoyed by the public.
At present, acid mine drainage still escapes untreated from waste piles and seepage on the north side of Iron
Mountain and flows into Boulder Creek. EPA continues to investigate and plan future actions to control acid
mine drainage in the Boulder Creek catchment.
EPA's Cleanup Objectives for Iron Mountain
EPA's primary objectives for IMM are to:
1. Reduce—and, if possible, eliminate—acid mine drainage and the mass discharge of toxic heavy metals
harmful to human health and the environment through application of best available control technologies.
2. Comply with water quality criteria established under the CWA in locations where species may be exposed to
the toxic metals and acid mine drainage.
3. Minimize the need to rely on California's scarce and valuable water resources to meet the water quality
criteria.
4. Encourage the continued development and evaluation of source control and resource recovery technologies
that may someday reduce or eliminate the discharges and the need to operate the treatment plant.
Successes
Listing Iron Mountain Mine on the National Priorities List was key to the success of this project, as listing gave
EPA access to CERCLA funding (Superfund). EPA's Remedial Project Manager (RPM) at IMM for the past
17 years emphasizes the importance of Superfund monies in allowing the Agency to proceed with needed work
in a timely fashion and without having to wait for legal settlements or decisions. Because of Superfund, EPA
was able to step in and pay to do things "the right way" when work was delayed by negotiations or cleanup
decision disputes. Two illustrative examples cited by the RPM are the construction of the lime
neutralization/high-density sludge water treatment plant at Minnesota Flats and the reconstruction of a bridge
over Spring Creek that was washed out by extremely heavy rains on New Year's Day 1997, thereby preventing
access to the site.
Integral to the success of the cleanup was the relationship among EPA, other Federal agencies, and the State of
California. Specifically, the timely and effective support of California's Department of Toxic Substances
Control (DTSC) in mobilizing enforcement support resources was critical in the overall cleanup effort.
In December 2000, the EPA, Department of the Interior, Department of Commerce, and several California State
agencies reached a settlement with Aventis, the principal responsible party at IMM. The total value of this
settlement—for past costs and future work—is over $950 million. Under the terms of the settlement, Aventis
provided, through an insurance instrument held by American International Group, Inc. (AIG), $200 million for
the first thirty years of site activities, $100 million in cost overrun insurance, plus a balloon payment of $514
million in 2030, which the EPA or State of California may use to fund future activities. The settlement also
involved an $8 million payment to EPA for future site costs, a $10 million payment for natural resource
restoration projects, such as wetlands restoration, and an agreement by Aventis not to seek compensation for
$150 million in past project costs. This settlement is noteworthy for two principal reasons. First, it was one of
the largest settlements with a single private party in Superfund history. Second, the long time-horizon of the
settlement is crucial to the continued success of the Iron Mountain cleanup. Unless researchers eventually
8 of 17
March 07, 2006
-------
Iron Mountain Mine Case Study
Success Through Planning, Partnerships, and Perseverance
figure out an effective and reliable way to prevent the formation of
acid mine drainage at Iron Mountain, the lime-neutralization/HDS
water treatment plant will have to continue operating for a very
long time. USGS scientists estimate that at current erosion rates,
Iron Mountain will continue to produce acid mine drainage for
2,500 to 3,000 years, until the estimated 12 million tons of sulfide
deposits remaining within the mountain have weathered away.
A key factor in facilitating agreement to a settlement with Aventis
was making a convincing case that the observed damage to the
aquatic ecosystems downstream of the mines at Iron Mountain can
be causally linked to the mining activities at the site and that the
natural weathering of Iron Mountain did not result in similar effects
even before the advent of mining. There were two facets of this
case. The first was the observation that Spring Creek, Boulder
Creek, and Slickrock Creek support healthy ecosystems upstream
of the mines. The population of fish and other organisms would not
have been able to migrate upstream through the stretches of water affected by acid drainage to colonize the
upper reaches of these streams if Iron Mountain had been releasing recently-observed quantities of acid and
metals for millennia. The second facet of this case involves estimating the rate at which the sulfide deposits at
Iron Mountain have weathered naturally over time. This was accomplished by estimating the original quantity
of sulfide ore and the latest (i.e., most recent) date for which sulfide weathering could have begun. The
essential point here is that, for a given original quantity of sulfide ore, the later the onset of sulfide weathering,
the greater the rate of that weathering and consequently the higher the resulting acidity and concentrations of
metals in the adjacent streams. The gossan outcrop at Iron Mountain is the result of the weathering of exposed
sulfide deposits. The rust-red color of the gossan derives from the oxidized iron that makes up a large portion
of the material (the sulfide deposits within Iron Mountain are approximately 95% pyrite). By dating the start of
sulfide weathering (i.e., gossan formation), one obtains an estimate for the duration of sulfide weathering. And
by dividing that figure into the estimated total quantity of sulfide ore believed to have weathered during that
time, one obtains an estimate of the rate of
weathering and the rate of release of acid and
metals to adjacent streams. Because of the high
iron content of the gossan, USGS scientists were
able to use paleomagnetic techniques to establish
a minimum age for the gossan of 780,000 years.
This minimum age value means that, even
assuming a conservati vely large original quantity
of sulfide ore at Iron Mountain, the pre-mining
flux rates of metals at Iron Mountain were 25 to
300 times lower than those observed since Iron
Mountain was mined. The partnership between
EPA and USGS was essential to this bit of
geological detective work.
Cleanup partners
Bureau of Land Management
Bureau of Reclamation
National Oceanic and Atmospheric
Administration (NO A A)
U.S. Fish and Wildlife Service (FWS)
U.S. Geological Survey (USGS)
California Central Valley Regional
Water Quality Control Board
California Department of Fish and
Game
California Department of State Lands
California Department of Toxic
Substances Control (DTSC)
CalTrout
Photo 8: Gossan (rust-colored, oxidized iron ore) outcrop near the
summit of Iron Mountain.
9 Of 17
March 07, 2006
-------
Iron Mountain Mine Case Study
Success Through Planning, Partnerships, and Perseverance
As two USGS scientists working at Iron Mountain put it, "the
effectiveness of a remedial alternative usually cannot be easily
quantified or predicted. Hence, we must admit that remediation is
experimental " Cleanup activities on the scale of Iron Mountain
typically comprise both short-term and long-term objectives, and while it
is ideal if short-term solutions also contribute to achieving long-term
ends, that is not always possible. In the case of Iron Mountain,
achieving the short-term goal of protecting human and ecosystem health
by collecting and treating the acid mine drainage does nothing to achieve the long-term goal of eliminating the
source of the acid mine drainage, whereas removing tailings piles and contaminated sediments and capping
subsidence areas on the mountain may serve long-term ends. But despite years of investigation and
consideration of many possible alternatives (e.g., strip mining Iron Mountain in its entirety, mining out the
remaining sulfide ore, or sealing the mine portals and flooding Iron Mountain with water or an inert gas), it
remains unclear whether there is a good, permanent solution to the problem. As such, one of the great successes
of the efforts to date has been the application of an iterative approach: implementing low-risk and low-cost
options while studying the options and planning next steps.
Applying IMM Achievements to Other Sites
EPA's plan for Iron Mountain
encourages the continued
development and evaluation of
source control and resource recovery
technologies that may someday
reduce or eliminate the discharges
and the need to operate the
treatment plant.
Over the past 25 years, there have been truly
dramatic improvements in the conditions at the
IMM site, in the creeks that drain the mountain
and in the Keswick Reservoir and Sacramento
River farther downstream. Site cleanup and
pollution control measures—in particular, the
acid mine drainage collection and treatment
systems—now intercept 95 percent of the
historic quantities of copper, cadmium, and
zinc discharged from Iron Mountain and
neutralize the associated acidity. Further, the
Slickrock Creek Dam and other engineered
structures should prevent the uncontrolled
release of acid mine drainage from Iron
Mountain in all but the most severe storms.
This success not only helps guarantee the
protection of a safe drinking water supply for
the City of Redding, it goes a long way toward
safeguarding the viability of threatened and endangered salmon and trout species in the Sacramento River and
the river's aquatic ecosystem as a whole. The achievements at Iron Mountain are the result of a number of
important factors, including:
Photo 9: The recently completed Slickrock Creek Dam captures acid
mine drainage escaping from fractured bedrock and buried mine portals
along the south side of Iron Mountain. The water in the reservoir is
transported by pipeline to the treatment plant at Minnesota Flats.
1. The use of Superfund monies to implement pollution control measures in a timely manner while making
efficacy—not low price—the paramount criterion;
2. A financial settlement with the PRPs that provides for the operation and maintenance of the on-site
treatment facilities far into the future;
10 of 17
March 07, 2006
-------
Iron Mountain Mine Case Study
Success Through Planning, Partnerships, and Perseverance
3. Effective partnerships among Federal, State, and local stakeholder groups;
4. A highly skilled and motivated technical team comprising experts from within EPA, other Federal agencies,
State agencies, and contractors with mastery of the full range of technical issues posed by complex
Superfund sites;
5. An iterative approach to site cleanup that involved starting simply and implementing low-cost, low-risk
controls while studying and preparing next steps;
6. The effective use of a combination of Superfund and enforcement tools; and
7. Valuable research on the causes of acid mine drainage—including the discovery of a new species of iron-
oxidizing microorganism.
Many, if not all, of these success factors are potentially applicable to other Superfund sites and to other metal
sulfide mine and mineral processing sites around the country and the world.
11 of 17
March 07, 2006
-------
Iron Mountain Mine Case Study
Success Through Planning, Partnerships, and Perseverance
Site Timeline
1860s
1879
1894
1895 - 1896
1899- 1900
1902
1904
1907
1907
1914
1920- 1943
1928 - 1942
1931
1928
1939
1943
1944
1950
1955
Land surveyor William Magee discovers massive iron ore deposit (gossan outcropping) in the
Spring Creek basin.
Silver is discovered in gossan and mining begins.
Mountain Mines Ltd. of London, England buys the property; name subsequently changes to
Mountain Copper Co.
Underground mining begins with the discovery of copper sulfide ore below gossan in Old Mine
workings; ore is shipped to smelter built at Keswick (on the site now occupied by the Spring
Creek Powerhouse adjacent to the Keswick Reservoir) via an 18 km, narrow-gauge railway
California Fish Commission investigates periodic fish kills in the Sacramento River attributed to
pollution from Iron Mountain Mine.
U.S. Forest Reserve sues company for vegetation damage from smelting activities.
Keswick smelter hits peak operation, processing 1,000 tons of ore daily.
Local smelting at Keswick is phased out and ore is henceforth transported to Martinez,
California for processing.
No. 8 ore body is discovered below Old Mine; Hornet Mine opens on Boulder Creek.
Minnesota Flats flotation mill is constructed—first flotation plant in California.
Crushing and screening plant operates near Hornet Mine.
Gossan is mined by open pit method at Brick Flat; 600 tons of ore treated daily at cyanide plant
on Slickrock Creek to extract gold and silver.
Minnesota Flats mill closes.
California Fish and Game Commission files complaint regarding tailings dam.
State initiates studies of water quality and fish toxicity.
Construction of Shasta Dam, upstream from Iron Mountain outflows, is complete, reducing
dilution of polluted discharges from Iron Mountain to the Sacramento River.
Copper cementation plant is built on Boulder Creek to remove copper from water discharged
from Richmond and Lawson (Hornet Mine) portals.
Construction of Keswick Dam, downstream from Iron Mountain outflows, is complete.
Large landslide from mine waste pile fills Slickrock Creek canyon to a depth of 24 m, covering
portals to Old Mine and No. 8 Mine.
12 of 17
March 07, 2006
-------
Iron Mountain Mine Case Study
Success Through Planning, Partnerships, and Perseverance
1955 - 1962 Open pit mining of pyrite occurs at Brick Flat for sulfuric acid production.
1963 Construction of Spring Creek Debris Dam is complete, regulating outflow of acid mine waters to
the Sacramento River and preventing sediment from filling Keswick Reservoir.
1967 Stauffer Chemical Company acquires property.
1976 State of California adopts regulations making owners of inactive mine sites responsible for
meeting Federal Clean Water Act standards for pollution; Iron Mountain Mines, Inc. acquires
property.
1976 - 1982 State of California fines owners for unacceptable releases of metals.
1977 Copper cementation plant is constructed on Slickrock Creek to remove copper from water
discharge and Old and No. 8 Mines seep.
1983 IMM is listed on National Priorities List (NPL) for EPA Superfund, ranking as the third largest
polluter in the State of California.
1986 - 1997 Four Records of Decision (RODs) by EPA require several remedial activities, including partial
capping; surface-water diversions; tailings removal; and lime neutralization treatment of the
most acidic, metal-rich flows, reducing copper and zinc loads by 80 to 90%.
1988 - 1994 Operation of an emergency treatment plant through the wet season of each year significantly
reduces the discharge of heavy metals from Iron Mountain by partially treating the discharges
from the Richmond and Lawson portals, the most concentrated acid mine drainage discharges at
the site.
1989 EPA completes a series of remedial actions authorized in the 1986 ROD: removal of tailings
from the Minnesota Flats area, capping in Brick Flat pit, and capping of several subsidence areas.
1990 EPA completes the diversion of uncontaminated flow in upper Slickrock Creek around a large
waste pile.
1991 EPA completes the diversion of clean water in upper Spring Creek, which now flows to Keswick
Reservoir via Flat Creek.
1994 Rhone-Poulenc (one of the responsible parties at the site) completes construction of a lime
neutralization treatment plant at Minnesota Flats for the acid mine drainage collected from the
Richmond and Lawson portals. The treatment process neutralizes the acid mine drainage and
traps the toxic metals in a high-density sludge (HDS). Completion of the consolidation and
capping of seven pyritic waste piles that were discharging acid mine drainage and eroding into
Boulder Creek. Completion of a system to collect and convey the Old and No. 8 Mines seep
flow to the lime neutralization/HDS treatment plant at Minnesota Flats.
1996 EPA completes construction of the onsite HDS landfill in Brick Flat pit.
13 of 17
March 07, 2006
-------
Iron Mountain Mine Case Study
Success Through Planning, Partnerships, and Perseverance
2000 EPA, the State of California, Aventis CropSciences USA, Inc. (corporate successor to Mountain
Copper Ltd. and Stauffer Chemical Co.) and Stauffer Management Co. (indemnitor to Aventis)
reach a settlement agreement. Under the settlement, the PRPs provide funding to ensure that the
treatment plant, "the heart of the IMM remedy," will continue to operate in perpetuity.
2002 EPA implements additional remedial activities, including diverting and treating water from
Slickrock Creek, bringing overall load reduction of copper and zinc to 95%.
2004 Construction of the Slickrock Creek Dam is complete, resulting in 95% overall load reduction of
historic copper, cadmium, and zinc discharges.
2005 Mine wastes (pyrite ore) are removed from the Matheson Rail Loading Station site on the banks
of Keswick Reservoir.
2007 Dredging of contaminated sediments to occur in the Spring Creek Arm of Keswick Reservoir.
14 of 17
March 07, 2006
-------
Iron Mountain Mine Case Study
Success Through Planning, Partnerships, and Perseverance
References
"Lake flows reduced, but supervisors upset." Redding (CA) Record Searchlight. 18 March 1992.
"Iron Mountain Mine history." Redding (CA) Record Searchlight. 6 July 1994. p. A4.
"Superfund Site AMD Cleanup Continues." Engineering and Mining Journal. June 2004. p. 10.
Interview with EPA Region 9, California Department of Toxic Substances Control, and CH2M Hill staff.
Redding, CA. 31 August 2005.
Alpers, C. N. and Nordstrom, D. K. (1997). "Timing of gossan formation at Iron Mountain and implications
for natural background metal fluxes." Sacramento, CA: Water Resources Division, U.S. Geological
Survey.
Alpers, C. N.; Nordstrom, D. K.; and Spitzley, J. (2003). "Extreme acid mine drainage from a pyritic massive
sulfide deposit: The Iron Mountain end-member." Environmental Aspects of Mine Wastes. Edited by J.
L. Jambor, D. W. Blowes, and A. I. M. Ritchie. Vancouver: Mineralogical Association of Canada. 31:
407-430.
Bowman, C. "Dam completes system for huge cleanup at mine." Sacramento Bee. 7 May 2004.
Breitler, A. "EPA will remove toxic dirt." Redding (CA) Record Searchlight. 9 April 2005. pp. Bl-2.
California Department of Toxic Substances Control. "Profile Report - ID: 45100001 - Iron Mountain Mine."
Site Mitigation and Brownfields Reuse Program Database, ID# 45100001.
http://www.dtsc.ca.gov/database/Calsites/CALP001.CFM?IDNUM=45100001 (Accessed on 5 October
2005).
Chui, G. "Acid Mountain." San Jose Mercury News. 28 March 2000. p. IF.
Coleman, J. "North state mine's water called world's worst." Chico (CA) Enterprise-Record. 27 March 2000.
Edwards, K. J.; Bond, P. L.; Gihring, T. M.; and Banfield, J. F. (2000). "An Archaeal Iron-Oxidizing Extreme
Acidophile Important in Acid Mine Drainage." Science 287: 1796-1799.
Hazle, M. "Toxic microbe found in Iron Mountain Mine." Redding (CA) Record Searchlight. 11 March 2000.
Jorgenson, P. "World's Most Acidic Waters are Found Near Redding, California." U.S. Geological Survey. 17
March 2000. http://ca.water.usgs.gov/water_quality/acid/ (Accessed on 29 July 2005).
Kay, J. "Iron Mountain's toxic legacy: Endless pollution from deep within a mountainside." San Francisco
Examiner. 2 November 1997. p. A12.
Landers, J. (2004). "Retention Reservoir Caps Remediation Efforts at California Mine." Civil Engineering
74(7): 28-29.
15 of 17
March 07, 2006
-------
Iron Mountain Mine Case Study
Success Through Planning, Partnerships, and Perseverance
Lawson, J. "Mining venture helped write local history." Redding (CA) Record Searchlight. 24 June 1986. pp.
Al, A7.
Martin, G. "Water Released at Shasta Lake to Dilute Pollution from Mine." San Francisco Chronicle. 21
March 1992.
Nordstrom, D. K. and Alpers, C. N. (1999). "Negative pH, efflorescent mineralogy, and consequences for
environmental restoration at the Iron Mountain Superfund site, California." Proceedings of the National
Academy of Sciences USA. 96(7): 3455-3462.
Nordstrom, D. K.; Alpers, C. N.; Ptacek, C. J.; and Blowes, D. W. (2000). "Negative pH and Extremely Acidic
Mine Wastes from Iron Mountain, California." Environmental Science & Technology. 34(2): 254-258.
Reiterman, T. "Goal: Mining His Own Business." Los Angeles Times. 10 May 2005.
Reiterman, T. "Test of Mettle: Iron Mountain owner locked in battle over toxic mine." Redding (CA) Record
Searchlight. 27 June 2005. pp. Al, A6.
SHN Consulting Engineers and Geologists (1996). "Iron Mountain Mine." Redding, CA: Shasta Natural
Science Association.
Spitzley, J. "Iron Mountain Mine: Challenges and Successes." Geo-Strata, January 2002, pp. 7-11.
U.S. Environmental Protection Agency (2004). "Iron Mountain Mine Superfund Site: Iron Mountain Mine
cleanup controls 95% of the copper, cadmium and zinc discharges." San Francisco, CA.
U.S. Environmental Protection Agency (2004). "Iron Mountain Mine Superfund Site: opportunity for public
comment on proposed plan to clean up contaminated sediments." San Francisco, CA.
U.S. Department of Justice (2000). "U.S., California Announce Settlement to Clean up One of the Country's
Most Toxic Waste Sites." Washington, DC.
U.S. Environmental Protection Agency. "Iron Mountain Mine, California." ID# CAD980498612.
http://yosemite.epa.gov/r9/sfund/overview.nsf/507c94f730e0ebf488256958005cda5f/7a8166ef29880480
8825660b007ee658?OpenDocument (Accessed on 18 October 2005).
U.S. Environmental Protection Agency (1987). "Iron Mountain Mine Superfund Site: EPA begins design of
interim remedial action program and initiates a source control pilot study." San Francisco, CA.
U.S. Environmental Protection Agency (1988). "Iron Mountain Mine Superfund Site: EPA completes design
and begins construction of partial cap." San Francisco, CA.
U.S. Environmental Protection Agency (1992). "Iron Mountain Mine Superfund Site: EPA announces proposed
plan for cleanup of Boulder Creek contaminant sources." San Francisco, CA.
U.S. Environmental Protection Agency (1993). "Iron Mountain Mine Superfund Site: EPA announces proposed
plan for additional cleanup action: 01d/#8 Mine seep." San Francisco, CA.
16 of 17
March 07, 2006
-------
Iron Mountain Mine Case Study
Success Through Planning, Partnerships, and Perseverance
U.S. Environmental Protection Agency (1994). "Iron Mountain Mine Superfund Site: EPA announces proposed
plan for treatment of Slickrock Creek base flows and enlargement of Spring Creek Reservoir." San
Francisco, CA.
U.S. Environmental Protection Agency (1996). "Iron Mountain Mine Superfund Site: EPA announces proposed
plan for collection and treatment of contaminated Slickrock Creek flows." San Francisco, CA.
U.S. Geological Survey. "Iron Mountain Superfund Site - EPA Technical Support." ID# CA527.
http://ca.water.usgs.gov/projects00/ca527.html (Accessed on 29 July 2005).
17 of 17
March 07, 2006
------- |