The definitions set forth in this section apply throughout this chapter.
(1) "Metals mining and milling operation" means a mining operation extracting from the earth precious or base metal ore and processing the ore by treatment or concentration in a milling facility. It also refers to an expansion of an existing operation or any new metals mining operation if the expansion or new mining operation is likely to result in a significant, adverse environmental impact pursuant to the provisions of chapter
43.21C RCW. The extraction of dolomite, sand, gravel, aggregate, limestone, magnesite, silica rock, and zeolite or other nonmetallic minerals; and placer mining; and the smelting of aluminum are not metals mining and milling operations regulated under this chapter.
(2) "Milling" means the process of grinding or crushing ore and extracting the base or precious metal by chemical solution, electro winning, or flotation processes.
(3) "Heap leach extraction process" means the process of extracting base or precious metal ore by percolating solutions through ore in an open system and includes reprocessing of previously milled ore. The heap leach extraction process does not include leaching in a vat or tank.
(4) "In situ extraction" means the process of dissolving base or precious metals from their natural place in the geological setting and retrieving the solutions from which metals can be recovered.
(5) "Regulated substances" means any materials regulated under a waste discharge permit pursuant to the requirements of chapter
90.48 RCW and/or a permit issued pursuant to chapter
70A.15 RCW.
(6) "To mitigate" means: (a) To avoid the adverse impact altogether by not taking a certain action or parts of an action; (b) to minimize adverse impacts by limiting the degree or magnitude of the action and its implementation, by using appropriate technology or by taking affirmative steps to avoid or reduce impacts; (c) to rectify adverse impacts by repairing, rehabilitating, or restoring the affected environment; (d) to reduce or eliminate adverse impacts over time by preservation and maintenance operations during the life of the action; (e) to compensate for the impact by replacing, enhancing, or providing substitute resources or environments; or (f) to monitor the adverse impact and take appropriate corrective measures.