Quarry Management

The main objective of the quarry management program is to increase quarry production to provide a full range of uses and replace terrace sources as the primary supply for future construction aggregate. Meeting this objective recognizes that past production trends and use patterns need to change and that quarry products must be able to achieve a large market share. The approach chosen to achieve this objective is a combination of regulatory incentives, aggregate standards, and stricter limitations on competing alluvial sources with more severe environmental impacts.

Seven new quarry sites and expansion areas for most existing quarries are set forth on Figures 5-1 through 5-28, but this designation is not required to apply for or receive approval of a quarry operation nor does it signify automatic approval of all future mining proposals. All designated new quarry sites and potential expansion areas will be protected from incompatible uses by being considered in the review of all nearby development proposals. Uses which would be incompatible with future quarry development on designated sites shall not be permitted unless the public benefits of the proposed use outweigh the public benefits of the potential quarry development. The non-designated "Potential Quarry Resource Areas" mapped on Figure 5-29 are shown for informational purposes only and do not restrict other uses allowed by zoning in those areas or on adjacent lands nor will the development review process consider potential quarry resources in these undesignated areas.

Quarries are permitted in three resource and agricultural General Plan land use categories: RRD, DA and LEA. Approval of a use permit, reclamation plan and MR overlay zoning is required for all quarry development, except that, in the RRD, DA, and LEA zoning districts, a use permit and reclamation plan but the MR zoning overlay is not required for small isolated quarries that are less than 5 acres, produce less than 5,000 cubic yards or 7,500 tons per year, and do not include crushing or batching operations. Quarry operations are also allowed with approval of a use permit and reclamation plan in the PQP General Plan designation and PF zoning where such operations are compatible with allowed public uses.

Permit expiration dates will be set in each individual permit up to but no longer than 20 years. All quarry approvals will require environmental review to determine whether or not they are within the scope of the Program EIR. Some site-specific impacts which may result from development of the designated quarry sites are described in general terms in Chapter 9. Quarry mining and related uses are allowed on land under Williamson Act contract, provided that such sites are reclaimed to agricultural use as soon as mining has ceased and ancillary uses do not continue beyond the mining. 

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.

Post-mining uses are limited by the zoning and the General Plan designation applied to the site. Except on lands under Williamson Act contract, a use permit and reclamation plan can allow importation, processing, recycling, and sale of aggregate materials to continue beyond the end of mining. Reclamation plans for quarry sites under Williamson Act contract must provide for reclamation of the site to agricultural use. Native soils shall be stockpiled, maintained and used to the maximum extent feasible in site reclamation. A geotechnical analysis by a Certified Engineering Geologist or Registered Geotechnical Engineer, based on the requirements set forth in the State Reclamation Guidelines, is required to demonstrate the long-term stability of all final slopes and the slope configuration needed to ensure the safety and revegetation appropriate to the end use of the mined land. As the slopes are cut, periodic inspections shall be undertaken to observe the rock material exposed and adjust the final reclamation contours as needed.

Quarry sites shall be reclaimed and revegetated with planting grass mixtures approved by the SCS and with shrubs and trees native to the area. Mining activities shall be planned so that reclamation is an ongoing activity, thus shortening the duration of habitat loss. Slopes and benches shall be regraded and have soil added as necessary to the surface to restore pre-existing conditions as much as possible. The reclamation approach also needs to take into account the special qualities of each site. The change in topography and the requirement for reclamation offer the possibility that reclamation of some portions of the quarry sites could increase local biotic diversity as compared with the pre-mining condition. This potential exists because earth-moving equipment could create physical habitats that are unique or less common than those that existed on the site prior to mining or that exist in the vicinity of the quarry.