SU0004149 - Laserfiche WebLink

Home Browse Search

0 0 0 . Sec. 3704(c) Piles or dumps of mining waste shall be stockpiled in such a manner as to facilitate phased reclamation. They shall be segregated from topsoil . and topsoil substitutes or growth media salvaged for use in reclamation. The proposed reclamation plan specifies the segregation of topsoil (A-horizon) and undifferentiated overburden into separate stockpiles. The reclamation plan indicates that the topsoil would be used in construction of the landscape berm along Koster Road. Therefore the proposed reclamation appears to comply with this section. Sec. 3704(d) Final reclaimed fill slopes, including permanent piles or dumps of mine �J waste rock and overburden, shall not exceed 2:1 (horizontal to vertical), except when site-specific geologic and engineering analysis demonstrate that the proposed final slope will have a minimum slope stability factor of safety that is suitable for the proposed end use, and when proposed final slope can be successfully revegetated. The proposed project includes 1.5:1 final reclaimed slopes (steeper than the SMARA standard) but provides a slope stability analysis that indicates that the minimum static factor of safety for the final reclaimed slopes would be 1.5. This factor of safety is generally considered appropriate for an end use that does not involve potential threats to existing structures and conforms with the requirements of the County Development Title (see discussion below). The stockpiles for overburden would have slopes of 2:1 or less. The proposed project, therefore, appears to be in compliance with this section. Sec. 3704(e) At closure, all fill slopes shall conform with the surrounding topography and approved/or end use. The reclaimed fill slopes at the project site would be constructed below existing grade. The reclaimed agricultural fields would have steep slopes separating them from the surrounding lands but these slopes would be internally draining and would not be expected to cause erosion or other adverse impacts to the surrounding topography. The agricultural fields would have similar topography to the existing reclaimed field and they would conform with the proposed end use. Sec. 3704(f) Cut slopes shall have a minimum slope factor of safety that is suitable for proposed end use and conform with the surrounding topography and end use. The proposed project has maximum cut slopes of 113:1. The slope stability analysis (Kleinfelder, 1997) concluded that these slopes have acceptable minimum factors of safety for static and dynamic (seismic) conditions during mining. The analysis, based on site- specific testing of subsurface conditions and conventional slope stability modeling, indicate that the slopes are suitably stable and conform with the requirements of this section. The proposed end use following reclamation (i.e., agriculture) presents a low-risk condition relative to slope stability hazards. However, the factors of safety calculated for the temporary cut slopes do not meet, in all cases, the minimum requirements for mining s Draft Environmental Impact Report 2 ER-96-3 !