Abandoned Mine Lands
California’s Abandoned Mines: The Golden State’s Environmental Legacy
Since the days of the gold rush of 1849, California’s mountains, valleys and deserts have been a source of precious metals and other minerals. California’s complex and diverse geology produces more than 700 mineral commodities, making California one of the nation’s most mineral-rich states. However, the mining and mineral-processing practices of the past were not subject to today’s environmental standards and have resulted in the discharge of millions of tons of waste rock and mill tailings to the land and waters of California. The unrecovered minerals and metals — most commonly arsenic, lead and mercury — in waste rock and mill tailings are released into the environment through natural processes over time, causing a threat to human health and the environment.
Abandoned Mine Lands Problem
More than a century and a half of mining in California has created an estimated 47,000 abandoned mine land (AML) sites. Historical mining and ore processing at these AML sites have resulted in the generation and disposal of millions of tons of mine wastes to the land and waters of California. Learn more about AML problems.
DTSC’s Abandoned Mine Lands Initiatives
DTSC addresses AML sites through a variety of programs and activities. Learn more about these initiatives.
DTSC’s Hazard Assessment and Remediation Process
Once an AML site has been identified and is under DTSC’s oversight, hazard assessment typically begins with a site investigation (a preliminary endangerment assessment) to determine the nature and extent of contamination resulting from past mining activities. Read more about the process here.
DTSC’s Abandoned Mine Lands Initiative Team
DTSC formed an AML Initiative Team in December 2008. The DTSC AML Initiative Team is composed of chemists, biologists, engineers, toxicologists and geologists who collaborate in a multidisciplinary effort to provide efficient, consistent oversight and technical support to landowners, cities and counties addressing AML issues. Learn more about the team here.
Examples of AML Sites
Outreach and Grants: Support to Communities and Abandoned Mine Land Stakeholders
DTSC is committed to developing and expanding relationships with AML stakeholders, providing assistance to local agencies and other stakeholders, and educating the general public about AML issues. Learn more about our outreach efforts.
Partnerships and Collaboration with Federal, State and Local Agencies
DTSC collaborates with federal, state and local agencies and other AML stakeholders to help pool resources for the investigation and cleanup of AML sites, as well as for other issues, such as area assessments, research efforts and community outreach. Learn more about our partners.
Through DTSC’s AML Initiatives, DTSC has implemented investigations and cleaned up sites affecting human health and the environment. Listed here is a brief summary of several success stories of DTSC at work.
Naturally Occurring Asbestos
DTSC is working in various areas of California to address concerns about potential effects of naturally occurring asbestos (NOA). Learn more here.
Library and Multimedia
- “Abandoned Mine Lands Preliminary Assessment Handbook”: This handbook provides basic information for conducting an initial investigation of AML sites and aids in the identification of mining features, constituents of concern and potential health risks.
- “Abandoned Mine Lands Site Discovery Process”: This document explains how AML sites are identified and brought under DTSC’s and the AML Initiative Team’s oversight.
- DTSC’s EnviroStor: DTSC’s database of regulated sites.
- Maps: Map of AML sites in California.
Guidance from agencies involved with AML issues:
- Abandoned Mine Land Inventory and Hazard Assessment (U.S. Department of the Interior, Bureau of Mines, May, 1994) Part A & Part B
- Risk Management Criteria for Metals at BLM Sites (U.S. Department of the Interior, Bureau of Land Management, October 2004)
- Abandoned Mine Site Characterization and Cleanup Handbook (U.S. Environmental Protection Agency, August 2000)
- California’s Abandoned Mines – A Report on the Magnitude and Scope of the Issue in the State (Department of Conservation, Office of Mine Reclamation, Abandoned Mine Lands Unit, June 2000)
- Mercury Contamination from Historic Gold Mining in California (U.S. Department of the Interior, Geological Survey, May 2000)
- Abandoned Mine Lands: A Decade of Progress Reclaiming Hardrock Mines (U.S. Department of the Interior, Bureau of Land Management and U.S. Department of Agriculture, Forest Service, September 2007)
Slide presentations and video presentations addressing AML issues.
- U.S. Environmental Protection Agency
- U.S. Geological Survey
- U.S. Department of Agriculture Forest Service
- U.S. Bureau of Land Management
- Abandoned Mine Lands Forum
- Sierra Nevada Conservancy
- State Water Resources Control Board
- California State Parks
- Sierra Fund
- California Indian Environmental Alliance
- Department of Conservation AML Unit