The Metals Mining and Milling Operations Act (chapter 78.56 RCW), passed in 1994, established a regulatory scheme that is specific to metal mining. Mines included under the Metals Mining and Milling Operations Act are defined as operations mining base or precious metals and processing the ore by treatment or concentration in a milling facility. Milling is defined as the process of grinding or crushing ore and extracting base or precious metals by chemical solution, electrowinning, or flotation processes. The Act includes new or expanding mines and mills, but excludes existing mines and mills. DNR's responsibilities are carried out through its Geology and Earth Resources Division.
Some of the main points of the Metals Mining and Milling Operations Act are:
- Department of Natural Resources regulates reclamation of the disturbed areas of the metal mine.
- Agencies with regulatory authority are required to inspect mines four times a year.
- Department of Ecology and Department of Natural Resources will hold all performance securities for the site.
- Criteria for tailings impoundment control and siting including site geology, liner design, and leak detection and collection are established.
- A waste-rock management plan must be developed and approved by the Departments of Ecology and Natural Resources.
- Citizens can observe and verify water sampling taken by either the mine operator or the Department of Ecology.
Any new cyanide heap leach operations regardless of the size would be regulated under the Metal Mining and Milling Operations Act because of the use of cyanide.
Pouring gold doré bars at Republic
Head frame at the Hecla gold mine at Republic, prior to closure