LEVIATHAN MINE

Description and History

Leviathan Mine is an abandoned open-pit sulfur mine high on the eastern slope of the Sierra Nevada, in Alpine County CA. The mine, 24 miles southeast of Lake Tahoe, has been contaminating a nine-mile stretch of mountain creeks. The Toiyabe National Forest surrounds the site, and there are no permanent residents within several miles. The stream system drains into Nevada about five miles from the mine and enters the picturesque Carson Valley nine miles downstream from the mine. Although there had been some mining activities for copper minerals since the 1860s, major environmental problems originated during the open-pit sulfur mining that occurred from 1951 through 1962. During this period, Anaconda used Leviathan Mine as a source of sulfur to dissolve copper from relatively low-grade ore at a mine near Yerington, NV. In 1962 Anaconda ceased operations and sold the property to a local interest. No significant mining activities have taken place since.

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Contaminants and Risks

The high sulfur content in the waste rocks and fractures at the 250-acre mine site turns snowmelt, rain and groundwater into sulfuric acid, which leaches contaminants from the native minerals such as arsenic, copper, nickel, zinc, chromium along with aluminum and iron. This acid mine drainage then flows into the creek system at a number of points, devastating aquatic life until the creeks join the East Fork of the Carson River, a much larger flow. Since 1983, the State of California has invested millions of dollars to contour the pit and surrounding waste piles, channel Leviathan Creek around the major disturbed area and capture the most concentrated flow in a series of ponds. Except for high flow periods during the spring snowmelt, the acid rock drainage that has been identified produced roughly half of all the flow in Leviathan Creek. Until recent treatment activities, a thick layer of orange precipitate coated the streambed most of the year until it washed into the East Fork with the high spring runoff each year.

The investigation into impacts from the acid rock drainage will include contaminated sediment and soil along the stream system. The possibility exists that contaminants may be present in greater concentrations in these soils due to discharges from the mine and could pose an increased risk to plants and animals, and even to humans who might use these resources.

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Who is Involved

EPA closely coordinates cleanup plans and activities with all of the stakeholders including local and state agencies from California and Nevada, the U.S. Forest Service, the U.S. Fish and Wildlife Service and with the Potentially Responsible Parties (PRPs). In addition, the Washoe Tribe is strongly involved with the site to ensure that their unique traditional tribal uses of the area’s resources are protected.

By 1997, the Washoe Tribe of Nevada and California asked EPA to get involved to fully address the contamination from the mine. Local governments in California and Nevada also voiced their support for intervention. After a number of voluntary measures in 1997 and 1998 proved inadequate, the Leviathan Mine was listed on the NPL in May 2000.

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Investigation and Cleanup Activities

After listing the site on the National Priorities List, EPA ordered early cleanup activities and investigation of long-term remediation options. There has been significant progress over the last three years in implementation of several treatment approaches. In each of the past three years, an innovative two-phase lime treatment developed by the State of California with University of California-Davis has been very successful in eliminating the worst acid discharge, capturing millions of gallons throughout the year and treating it all during the summer months. Atlantic Richfield, the successor to Anaconda, is capturing and neutralizing most of the remaining acid rock drainage. So far, this system has only operated during the summer months. A full-scale biological treatment system designed by the University of Nevada-Reno has gained international attention for its remarkable success in treating one of the seeps year-round and has been expanded and redesigned with the aid of EPA researchers. In addition, EPA researchers tested a series of new mine treatment technologies at the Leviathan Site. During the summers of 2001 through 2005, the water quality of Leviathan and Bryant Creeks made remarkable improvements while the treatment systems were operating. However, none of the stakeholders are satisfied with only short-term successes. We are using these improvements to help better define long-term risks and feasible alternatives to clean up the site. In addition to careful monitoring of the treatment system operations, critical environmental data have been gathered to help characterize the site, including streamflow, water quality, sediment chemistry, meteorological data and stream biological measurements.

Since 2003, the biological treatment system captured and treated all the acidic drainage from the Aspen Seep, more than five million gallons per year. Atlantic Richfield has used various lime treatment systems to treat approximately six million gallons of acid mine drainage annually from the Delta Seep and Channel Underdrain, but only during the summer months. The California Regional Water Quality Control Board - Lahontan Region - continued to capture all the highly acidic waste from the Adit Seep and Pit Underdrain in the existing pond system then treat the entire year's accumulation during an intensive three-week period during the summer. Pond overflow, initially considered the most serious contaminant source, has been prevented for the past five years. In 2003, approximately 3.5 million gallons were treated using a two-phase lime neutralization system that left the ponds entirely empty for the third successive year. In the wet year of 2006, nearly 20 million gallons were treated during the Spring and Summer. In the very dry year of 2007, only 3 million gallons were treated to completely empty the ponds.

Another stage of early response actions is now underway (see April 2004 and 2005 Fact Sheets). All the known discharge sources were to be treated for the entire year to reduce environmental damage, allow a more thorough evaluation of remaining risks to the downstream area and to assess the effectiveness and reliability of potential long-term treatment options. Difficulties were encountered during 2006 which indicated that a lime treatment plant is not likely to be effective during the winter without very large investments in safe access and power at this remote mountain location. Improvements in the temporary lime treatment and biological systems are underway in 2007 and 2008. It is expected that the decision-making and design processes will continue for the next several years before a proposed plan for a long-term remedy is developed for public comment.

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Cleanup Results to Date

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Potentially Responsible Parties

Potentially responsible parties (PRPs) refers to companies that are potentially responsible for generating, transporting, or disposing of the hazardous waste found at the site.

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Documents and Reports

Administrative Records
		EARLY RESPONSE ACTION
Fact Sheets
	11/01/99	EPA Proposes Leviathan Mine for Superfund List
	05/01/00	Community Meeting Agenda
	05/01/00	Community Meeting Notice
	11/01/01	Update on Cleanup Activities
	04/01/04	Proposal for Year Round Treatment System
	06/01/05	YEAR-ROUND TREATMENT SYSTEM CHOSEN FOR ACID MINE DRAINAGE
	11/01/07	Update On Site Activities
Images
		SITE PHOTOS
Legal Documents
	09/26/08	Leviathan Modification to Removal Action Memo
	11/21/08	Leviathan Settlement Documents referenced in Federal Register Notice, Nov 21, 2008
	01/21/09	Administrative Settlement Agreement and Order on Consent for Removal Action
Technical Documents
	06/01/04	Community Involvement Plan
	10/22/08	Draft Data Quality Objectives Report for Leviathan Mine RI/FS

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Community Involvement

Public Meetings: 1) May 2000, Gardnerville, NV
2) November 2001, Washoe Tribe, Gardnerville, NV
3) May 2004, Gardnerville, NV

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Public Information Repositories

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Additional Links

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Contacts

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