Reasons for Exemption
Mapping resources indicate the property to the west (APN 026-040-088) has a well on the north end of the property which appears to be over 4000’ from the proposed well. According to Environmental Health records, the well on the property directly to the north (APN 026-040-009) is approximately 3000’ from the proposed well. Based on a review of the State Water Resources Control Board’s Low-Threat Underground Storage Tank Case Closure Policy, a 1,000-foot separation from active production wells to contamination plumes is considered to be sufficient separation to pose a low threat to human health, safety or the environment, and appropriate for no further action determination based on the groundwater-specific criteria specified. Further, this proposed well is within the key assumptions of modeling work by Santa Barbara County demonstrating that a new or replacement well located more than 1,000 feet from an existing well is not likely to interfere with the production of that well. The
modeling is based on hypothetical water well drawdown using conservative yet anticipated values for transmissivity, storage coefficient, and anticipated pumping yields to support field grown agriculture commodities.
According to the Owens Valley Groundwater Basin Final Groundwater Sustainability Plan of Dec. 9, 2021 (see Appendix A, p. 7): The hydrogeologic setting in the Fish Slough and Tri-Valley management area is dominated by volcanics and alluvial fan sediments which are typically not susceptible to subsidence. Groundwater levels in this area are showing chronic declines with rates observed to be about 0.15 feet/year (Fish Slough) and 0.49 – 1.86 feet/year (Tri-Valley) and are thought to be historic lows for this management area. The groundwater extractions in this management area are distributed throughout the area rather than being concentrated in small zones, so the effects of subsidence, if any, may be more area-wide. Despite one of the necessary factors being present, there is no direct instrumental evidence of subsidence in the management area. Consequently, the potential for subsidence is considered low.