If any off-channel excavation proposes to extend below the level of seasonal high groundwater, then six (6) months prior to the commencement of excavation below the average high groundwater level, the operator shall identify and locate all off-site municipal wells within one thousand (1,000) feet and all domestic wells within five hundred (500) feet of the proposed wet pit mining boundary. If active wells are identified, well characteristics (pumping rate, depth, and locations of screens) shall be determined. If wells are not located within one thousand (1,000) feet, the pre- mining impact evaluation shall be considered complete.
If wet pit mining is proposed within one thousand (1,000) feet of a municipal water supply or within five hundred (500) feet of a domestic water supply well, a capture zone analysis shall be conducted using the U.S. Environmental Protection Agency model WHPA (or a similar model of equal capability and proven reliability, as approved by the Director). The simulation shall assume thirty (30) days of continuous pumping of the water supply well (at its maximum probable yield) under analysis. A mining setback shall be established so that the capture zone and the pit do not coincide. Alternatively, the operator shall submit a written agreement that the well owner has agreed to relocate or redesign the well, or accept the potential impact (at no expense to the County). The analysis shall be prepared and signed by a Registered Civil Engineer or Certified Hydrogeologist and submitted to the County for review and approved at least six (6) months prior to the commencement of excavation below the seasonal high groundwater level.
Any new drinking water wells proposed for installation within one thousand (1,000) feet of an approved wet pit mining area shall be subject to review by the Yolo County Environmental Health Department. The County shall determine, based on site-specific hydrogeology and available water quality data, whether to approve the proposed well installation. Analysis of environmental impact for projects in the vicinity of the wet pits shall include consideration of potential water quality impacts on the open water bodies.
The County may retain appropriate staff or a contract consultant to provide third party critical review of all hydrogeologic reports related to mining applications.
(§ 1, Ord. 1190, eff. September 5, 1996; as amended by Ord. 1518, eff. February 13, 2020)