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4 Environmental Analysis <br /> 4.10 Hydrology/Water Quality <br /> feet per year (AFY). The relatively low amount of water used during this phase would be <br /> insufficient to generate significant runoff. <br /> As noted earlier in Section 4.9, Hazards and Hazardous Materials, the California Hazardous <br /> Materials Release Response Plans and Inventory Law requires any business handling hazardous <br /> materials at or above specified thresholds to prepare a Hazardous Materials Business Plan <br /> (HMBP). The thresholds include any site that stores hazardous materials in excess of 55 gallons <br /> (liquids), 500 pounds (solids), or 200 cubic feet for compressed gas. Any hazardous materials <br /> exceeding the established thresholds that would be stored onsite would be contained in <br /> designated areas in accordance with an HMBP, which would ensure that all handling, storage, <br /> and disposal of hazardous materials would be conducted in accordance with proven practices to <br /> prevent accidental release. <br /> For these reasons, the impacts on water quality during O&M would be temporary and less than <br /> significant. <br /> Decommissioning <br /> After the useful life of the Project is completed, decommissioning of the site would result in similar <br /> potential impacts as those described for construction, including the potential for erosion, <br /> sedimentation, and the release of pollutants. Activities anticipated during decommissioning also <br /> would be required to comply with the same applicable federal, state, and local water quality <br /> regulations. Ground disturbing activities during decommissioning would require coverage under <br /> the Construction General Permit, including the preparation and implementation of a SWPPP. <br /> Stormwater management measures would be required to be identified and implemented that <br /> would effectively control erosion and sedimentation and other construction-related pollutants <br /> during decommissioning. Therefore, the potential impact of Project decommissioning activities on <br /> water quality would be temporary and less than significant. <br /> Overall, the Project's impacts on water quality standards or waste discharge requirements would <br /> be temporary and less than significant. <br /> Mitigation: GEO-1. <br /> IMPACT 4.10-2: Would the project substantially decrease groundwater supplies or interfere <br /> substantially with groundwater recharge such that the project may impede sustainable <br /> groundwater management of the basin? (Less than Significant) <br /> The existing land use of the Project site is cattle grazing, and the disturbed Project area is <br /> approximately 32 acres, of which approximately 18.8 acres would be permanently disturbed with <br /> impervious surfaces. There are no public water systems or providers serving the Project area, <br /> with water supply provided by onsite wells. The existing vegetation onsite consumes water <br /> through evapotranspiration. Estimates for evapotranspiration from forage grass in the California <br /> Delta region range from 1 millimeter per day to 6 millimeters per day depending on the month <br /> (Medellin-Azuara et al. 2018). Using an average value of 3 millimeters per day over the 18.8 acres <br /> that would be permanently disturbed with impervious surfaces, the estimated evapotranspiration <br /> from the permanently disturbed portion of the Project site would be approximately 0.23 of per day, <br /> or approximately 83 AFY. <br /> Griffith Energy Storage Project 4.10-13 Tetra Tech/SCH 2022120675 <br /> Draft Environmental Impact Report August 2023 <br />