Counting America's Abandoned Mines: The USGS National Inventory

The problem

Mining has supplied essential materials to the United States since its founding. Today's mines are regulated to protect communities and the environment, but many historic mines ran before modern environmental laws and were simply abandoned when production stopped.

• A mine can have dozens of workings — shafts, open pits, tunnels — called mine features, so the country has hundreds of thousands of abandoned ones.
• Physical hazards: open shafts people can fall into, tunnels that can collapse. Closures such as bat grates can make these safe while still letting wildlife in and out.
• Environmental hazards: for example acid mine drainage — highly acidic water carrying heavy metals.
• As of 2025, there is no complete national inventory of abandoned mine features and their hazards, so the total risk and liability they pose is unknown.

A new national database

The 2021 Bipartisan Infrastructure Law — the Infrastructure Investment and Jobs Act — requires the Secretary of the Interior to set up a program to inventory abandoned hard-rock mines (Sec. 40704). Interior's Office of Environmental Policy and Compliance asked the U.S. Geological Survey's Mineral Deposit Database project (USMIN) to build, from existing data, an inventory of every abandoned mine feature in the country — metals, industrial minerals and coal alike.

Beyond locations, it records the land management agency, the physical and environmental hazards, and any cleanup already done, supporting risk assessment, hazard mitigation, ecosystem restoration and reclamation.

Why nothing like it existed

• Coal: the Surface Mining Control and Reclamation Act of 1977 charges coal mines a per-ton fee to pay for reclaiming abandoned coal mines. The Office of Surface Mining Reclamation and Enforcement sends that money to state and tribal agencies each year and keeps an inventory of abandoned coal mine lands.
• Everything else: there is little federal funding to inventory or reclaim abandoned metal and industrial mineral mines.
• Scattered records: local knowledge is often rich, and some agencies keep databases — but others have none, keep paper files, or have incomplete records. What's needed is one digital, nationwide database covering coal, metals and industrial minerals.

How it's built

In 2022, USMIN worked with state, federal and tribal agencies to design a structure based on individual features that works nationwide, holding the essential information most agencies share, as simply as possible:

Filling it: USMIN takes data from agencies willing to share, translates it into the common structure, and reviews records with each provider — an independent quality check many agencies value. One feature often needs data from several agencies, since different ones may track safety and environmental hazards, or coal and non-coal mines. The goal is a living database, maintained by USMIN and updated as new data arrive.

What will — and won't — be public

Many agencies don't want exact locations published, because they could be used to explore dangerous underground workings or vandalize historic mine buildings. So USMIN won't publish feature locations, and the detailed database won't be public. Instead it will publish summaries at broader scales — for example, maps of the number and type of features in each congressional district or county, or in watersheds at risk from acid mine drainage.

Sources

Based on "The abandoned mine inventory of the United States—A brief summary," fact sheet, U.S. Geological Survey; a work of the United States government in the public domain. Its photographs, supplied by Environmental Protection Services (Nevada) and the California Department of Conservation, are not reproduced.