Abandoned Mine Remediation & Solid Mineral Extraction

California is famous for its mineral wealth dating back to the discovery of gold at Sutter’s Mill in 1848. This mineral wealth resulted in the exploration and development of gold mines throughout California. In 1975, the Legislature enacted the Surface Mining and Reclamation Act (SMARA), creating a comprehensive surface mining and reclamation policy and regulation of surface mining operations to ensure that adverse environmental impacts are minimized and mined lands are reclaimed to a usable condition.

Tens of thousands of mines were abandoned before SMARA was enacted, some of which date back to before the Commission was created and before the federal government transferred certain federal lands, known as school lands, to California. While abandoned mines can pose a public safety or environmental hazard to the public and wildlife, they also provide habitat for wildlife species such as bats, owls, desert tortoises, and bighorn sheep. Abandoned mines sometimes possess historical and cultural features important to our history.

Most abandoned mines are located on public lands managed by the federal Bureau of Land Management, but some are located on private lands and state lands under the jurisdiction of various state agencies, including the Commission.  In 2009, the Department of Conservation’s Division of Mine Reclamation inventoried abandoned mines on state lands which revealed that 100  school land parcels have abandoned mine features on them. Public Resources Code 6201.5 authorizes the Commission to rehabilitate abandoned mines.

The Abandoned Mine Remediation Program

Commission staff, in the course of its field inspection work, has noted various mine features that could pose a hazard to the public and wildlife, such as vertical mine shafts and horizontal adits. The Commission partnered with the Department of Conservation’s Division of Mine Reclamation to inventory and remediate abandoned mine features on state lands. The partnership was formalized through a Memorandum of Understanding that is effective through 2023. The Memorandum of Understanding describes the responsibility of both agencies, funding, and remediation measures to be employed.

• Staff Report: 02/09/2016 (74)
• Memorandum of Understanding

The Abandoned Mine Remediation Process

Addressing the physical hazards associated with abandoned mines is a complex process. Remedies range from simple signage to permanent closure and are determined on a case-by-case basis depending on the severity of the public hazard. If staff determines that a mine feature is sufficiently hazardous to warrant a permanent closure, staff surveys the mine feature’s biological, historical, and physical characteristics to determine which closure technique is appropriate.

When surveys find that significant resources exist at a mine, bat gates or cupolas are built to protect the public and wildlife. Bat gates are constructed at the portal or front of horizontal mine openings, known as adits, that allow bats, owls, desert tortoises, and other wildlife to use the mine for habitat while safeguarding the public. For vertical shafts, a cupola (a box made of steel angle iron) is installed over the shaft to allow wildlife access. These techniques protect and preserve historic resources and are designed to give biologists, archeologists, or geologists survey access.

Mine shafts that are relatively shallow and have no horizontal workings generally have little historical value and provide poor wildlife habitat but may still pose a fall hazard to the public. When these shafts have the original waste rock dump adjacent to them, staff contracts for a small front-end loader to backfill the shaft using the original waste rock. When waste rock is unavailable, staff uses a polyurethane foam plug covered with native rock that protects the foam from sunlight and hides the original location.

Certain mine features may not be suitable for bat gates, cupolas, or foam plugs. In these instances, wire fences are often used, either permanently or as a temporary measure until a permanent solution is found. Cable netting is occasionally used on complex mine structures with large or irregular shaft openings that are not amenable to cupolas or foam plugs.

Commission staff consults with the California Department of Fish and Wildlife and the State Office of Historic Preservation on all closures to ensure that sensitive resources are preserved.