(a) An open pit excavation created by surface mining activities for the production of metallic minerals shall be backfilled to achieve not less than the original surface elevation, unless the circumstances under subsection (h) are determined by the lead agency to exist.

(b) Backfilling shall be engineered, and backfilled materials shall be treated, if necessary, to meet all of the provisions of Title 27, California Code of Regulations, Division 2, Chapter 7, Subchapter 1, Mining Waste Management, commencing with Section 22470, and the applicable Regional Water Quality Control Board's Water Quality Control Plan.

(c) Excavated materials remaining in overburden piles, waste rock piles, and processed or leached ore piles not used in the backfilling process and remaining on the mine site shall be graded and contoured to create a final surface that is consistent with the original topography of the area. Care shall be taken to avoid the creation of un-natural topographic features, impediments to natural drainage, or conditions hazardous to human life and wildlife.

(d) Backfilling, recontouring, and revegetation activities shall be performed in clearly defined phases to the engineering and geologic standards required for the end use of the site as stipulated in the approved reclamation plan. All fills and fill slopes shall be designed to protect groundwater quality, to prevent surface water ponding, to facilitate revegetation, to convey runoff in a non-erosive manner, and to account for long term settlement.

(e) The requirements of subsections (a), (b), (c), and (d) notwithstanding, no final reclaimed fill slopes shall exceed 2:1 (horizontal:vertical), nor shall the resultant topography exceed in height the pre-mining surface contour elevations by more than 25 feet. Final fill slopes shall have static and dynamic factors of safety, as determined by an engineer licensed in California, that are suitable for the proposed end use of the site and meet or exceed the requirements of applicable building or grading codes, ordinances, statutes, and regulations. Final slopes must be capable of being revegetated, and shall blend visually with the local topography. Surface soil shall be salvaged, stored, and reapplied to facilitate revegetation of recontoured material in accordance with the requirements of Section 3711 of this Article.

(f) For the purposes of this section, a metallic mine is defined as one where more than ten percent of the mining operation's gross annual revenues as averaged over the last five years are derived from the production of, or any combination of, the following metallic minerals by the open pit extraction method: Precious metals (gold, silver, platinum);

Iron;

Nickel;

Copper;

Lead;

Tin;

Ferro-alloy metals (tungsten, chromium, manganese);

Mercury;

Uranium and thorium;

Minor metals including rubidium, strontium, and cesium;

Niobium and tantalum;

(g) For the purposes of this regulation, an open pit mine is the same as an open pit quarry, opencast mine, or opencut mine, and is defined as a mine working or excavation that is open to the surface and in which the opening is approximately the full size of the excavation.

(h) The requirement to backfill an open pit excavation to the surface pursuant to this section using materials mined on site shall not apply if there remains on the mined lands at the conclusion of mining activities, in the form of overburden piles, waste rock piles, and processed or leached ore piles, an insufficient volume of materials to completely backfill the open pit excavation to the surface, and where, in addition, none of the mined materials has been removed from the mined lands in violation of the approved reclamation plan. In such case, the open pit excavation shall be backfilled in accordance with subsections (b) and (d) to an elevation that utilizes all of the available material remaining as overburden, waste rock, and processed or leached ore.

(i) This regulation does not apply to any surface mining operation as defined in Public Resources Code Section 2735(a) and (b) for which the lead agency has issued final approval of a reclamation plan and a financial assurance prior to December 18, 2002.