To the maximum extent feasible, all quarry sites shall be screened visually from public roads and uses with topographic features, berms, and shrubs and trees native to the area. The maximum allowable working slopes of the mine face are to be approved by a Certified Engineering Geologist or a Registered Geotechnical Engineer and specifically stated in the use permit. Any variation from the slope requirements of section 3502 (b)(3) of the State Reclamation Guidelines shall be specifically justified in the reclamation plan. Benches in slopes are required every 25 to 30 vertical feet for access and drainage control. Working slopes must eventually conform to final reclaimed slopes and topography. Drainage plans and facilities must minimize slope erosion and off-site sedimentation. Quarries in or near fault zones may be conditioned to incorporate additional geotechnical measures to insure worker and public safety.
Mining operations, stockpiles, and processing operations are to be set back a minimum of 25 feet from the MR zone boundary, the property boundary, and road easements and rights-of way, whichever is the most restrictive. The minimum allowed setback for quarry mining operations from stream banks and critical habitat areas designated in the General Plan is 100 feet. A minimum 200-foot setback is also required from General Plan residential designations. All quarry applications are to be reviewed to establish additional setback requirements as necessary to minimize environmental impacts and land use conflicts. If valuable wildlife habitat would be affected by a proposed quarry development, avoidance, replacement or other mitigation will be required to reduce habitat impacts to a less-than-significant level.
With approval of a use permit, quarry operations may include the manufacture of concrete and asphalt products and the processing and sales of raw, processed, or recycled earth materials and aggregate products. Importation of such materials may be included as ancillary uses allowed with the use permit. Existing quarries may import a maximum of 25 percent of the aggregate materials processed or sold in each calendar year without obtaining a new use permit. This limit does not apply to materials brought to quarries for recycling.
All quarry sites must have adequate water supplies to support the operation. Sites located in Sonoma County Water Zones III and IV will require analysis of the proposed water use, evaluation of the adequacy of the water supply, and mitigation of effects on water resources and nearby water users.
Each quarry operation shall be inspected by the County at least once every 90 days during the mining operations. As a condition of permit approval, quarry operators may be required to monitor, survey, or report on depth and grades of excavation, groundwater levels, water use, revegetation, and other subjects in addition to the annual reports to be submitted to the County and the State.