Remediating Some of the World's Most Acidic Waters at the Iron Mountain Superfund Site-A Tough Challenge for Scientists
| Type |
- Site Characterization
- Feasibility Studies
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| Location |
Iron Mountain, Redding (Shasta County), CA |
| Partners |
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| Technology |
- Acid Neutralization Treatment Plan (lime/sulfide High Density
Sludge (HDS) treatment process)
- Capping of Selected Areas
- Surface-Water Diversions
- Mine Shaft Plugging (proposed but not implemented)
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| Contaminants |
- Metals (cadmium, copper, lead, mercury, zinc, and iron)
- Acidic Water
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| Description |
USGS scientists and their partners are studying the environmental
impact of copper mining at Iron Mountain, California, in conjunction
with stakeholders faced with cleaning up the site. Iron Mountain
is a massive sulfide ore deposit that has been extensively mined
for valuable metals, but has more recently earned the reputation
as the one of the Nation's largest point sources of extremely acidic
mine drainage containing large amounts of toxic metals. The total
concentration of metals has been reported as high as 200 grams per
liter. Iron Mountain has been a Superfund
site since 1983, and is home of the world's
most acidic water (negative 3.6 pH). In a word, remediating
the extensive mines in a mountain of rock with almost no acid neutralization
capacity is daunting. The scientists have conducted a variety of
studies in direct support of the federal and state agency plans
for remediation of the site. They include:
- Mine Shaft Plugging Assessment - Geochemical characterization
of Iron Mountain and geochemical modeling studies predicted that
if the mine portals were plugged, a pool of water would develop
with extremely acidic pH (near 1) and high metal concentrations
(grams of dissolved metals per liter). The flooded mine pool would
have a volume of about 600,000 cubic meters and would present
a high risk to the environment and to the local community because
of the potential of catastrophic plug failures, faulty plug seals
releasing mine water, and acid seeps developing in other locations.
Based on this information plugging of the mine was dropped from
consideration.
- Characterization and Assessment Studies - USGS scientists and
their partners have conducted a variety of geochemical and mineralogical
characterization studies to determine the acid-generating potential
of the mine sites, estimate the pre-mining water quality, and
determine the loads of metals discharging from the mine and transported
down the several creeks in the area as well as the Sacramento
River. They also developed methods to measure the extremely low
pH of the water in this harsh environment. This information has
been used to design the capacity of water treatment plants and
the scope of other remediation systems at the site.
- Sediment Characterization Studies - Metal-contaminated sediments
precipitated from the mine drainage have accumulated in the Spring
Creek Reservoir and the Keswick Reservoir on the Sacramento River.
USGS scientists and their partners participated in EPA's Remedial
Investigation by assessing the geochemistry, toxicity, and sorption
properties of the sediments in the two reservoirs. Their studies
showed the unexpected result that reduced iron in pore waters
caused much of the toxicity in the sediments. This new information
can be used to develop better mining regulations and to help resource
managers restore watersheds impacted by mining. The current focus
of their research is on the geochemistry, toxicity, and sorption
of metals in sediments formed by the neutralization of acid mine
waters that flow into the reservoirs.
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| More Information |
|
| Contact |
- Kirk Nordstrom, USGS, National Research Program, Denver, Colorado,
- Charles Alpers, USGS, California District, Sacramento, California,
|
| Publications |
- 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 from the National Academy of Sciences, v. 96, p. 3455-3462.
- Nordstrom, D.K., Alpers, C.N., Ptacek, C.J., and Blowes, D.W.,
2000,
- Negative
pH and extremely acidic mine waters at Iron Mountain Mine, California:
Environmental Science and Technology, v. 34, no. 2, p. 254-258.
- Nordstrom, D.K., Alpers, C.N., Coston, J.A., Taylor, H.E., McCleskey,
R.B., Ball, J.W., Ogle, S.A., Cotsifas, J.S., and Davis, J.A.,
1999,
- Geochemistry,
toxicity, and sorption properties of contaminated sediments and
pore waters from two reservoirs receiving acid mine drainage,
in Morganwalp, D.W., and Buxton, H.T., eds., U.S. Geological Survey
Toxic Substances Hydrology Program--Proceedings of the Technical
Meeting, Charleston, South Carolina, March 8-12, 1999--Volume
1 of 3--Contamination from Hardrock Mining: U.S. Geological Survey
Water-Resources Investigations Report 99-4018A, p. 289-296.
- Robbins, E.I., Rodgers, T.M., Alpers, C.N., and Nordstrom, D.K.,
2000,
- Ecogeochemistry
of the subsurface food web at pH 0-2.5 in Iron Mountain, California,
USA: Hydrobiologia, v. 433, no. 1-3, p. 15-23.
-
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| Links |
USGS Acid Mine Drainage Remediation Projects
- USGS
Abandoned Mine Lands Initiative
- Acidic
Plume Remediation Monitoring, Pinal Creek, AZ
- Evaluating
How Downstream Tailings Deposits Impact the Effectiveness of Remediation
Plans, Upper Arkansas River, Colorado
- Lake
Coeur d'Alene Remediation Assessment
- Summitville
Mine and its Downstream Effects
- Aquatic
Toxicology, Aquatic Physical Habitat, and Sediment Analysis in
Evaluating Land Mine Remediation Measures, Animas River, San
Juan County, Colorado
- Bear-Yuba
Watersheds Interagency Abandoned Mine Lands Project, Bear-Yuba
Watersheds, California
- Benthic
Macroinvertebrate Assessment of Abandoned Mine Lands Runoff and
the Development of Endpoints for the Determination of Ecological
Attainability in the Boulder River, Boulder River, Montana
- Effects
of Nutrients on the Formation of Acidic Mine Drainage
- Integration
of Geological and Ecological Indicators for Assessment of Impacts
on Stream and Riparian Resources, Boulder River, Montana,
and Upper Animas River, Colorado
- Restoration
of Stream Water Degraded by Acid Mine Drainage, Toby Creek
Mine Drainage Treatment Plant, Elk County, Pennsylvania
- Swatara Creek Basin, Schuylkill County, Pennsylvania
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