Site Mitigation & Restoration Program

We protect and maintain California’s land and places
by setting strict standards for land restoration and cleanup

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

Listed and categorized here is a partial list of AML sites and projects that DTSC and the AML Initiative Team are working on. There may be more up-to-date information on the EnviroStor web site.

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.

Success Stories

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

Guidance Documents

Guidance from agencies involved with AML issues:


Slide presentations and video presentations addressing AML issues.