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2021 ANNUAL GROUNDWATER MONITORING REPORT TEICHERT AGGREGATES AND GRANITE CONSTRUCTION VERNALIS AREA The calibration and maintenance of instrumentation is conducted following the manufacturers' instructions and guidelines using appropriate standard solutions and procedures and at manufacturer recommended intervals.The electrical sounder and temperature probe are factory calibrated and do not require calibration by the user. Samples are collected in laboratory-supplied bottles with no headspace. Bottles are labeled with laboratory-supplied labels, immediately placed on ice, and kept in a dark ice chest. 4 MONITORING RESULTS Quarterly groundwater level and quality monitoring commenced in March 1994 to characterize pre- mining groundwater conditions in the area and facilitate the continued evaluation of local groundwater conditions. Also,as part of Teichert and Granite's approved plan to dry-pit mine,groundwater level monitoring provides the necessary information to establish and maintain a buffer between the base of mining and groundwater. Mining of the Teichert Vernalis Central phases began in 1998 and has proceeded to varying depths up to 150 feet bgs through phase 4,with phases 2 through 4 currently used as siltation ponds. Currently,the mining of the Teichert Vernalis West and East phases has progressed to an approximate depth of 120 feet bgs in phase A5. Granite has completed mining of Phase 1 to a depth of 150 feet and has reclaimed Phase 1 with pond fines.The southern portion of Phase 2 is currently being mined. As of 2021, Phase 2 has been partially mined to a depth of 150 ft. 4.1 Groundwater Levels Long-term fluctuations of shallow groundwater levels in the area are depicted by the hydrograph for Well 4S/6E-5A1 (Figure 4),which has been monitored semi-annually by the California Department of Water Resources(DWR)from 1960 through 2020(typically in the winter, i.e.,January, February, or March;and in late summer/early fall, i.e., in September or October)and quarterly for Teichert's quarry excavation monitoring program since 1994.The lowest historic water level, i.e., 69 feet above mean sea level (msl),was recorded in early 1962,at the end of two consecutive critically dry years (DWR Water Year Hydrologic Classification Index for the San Joaquin Valley)'.Water levels recovered subsequently to a high of 90.9 feet(msl) in December 1969. During this early period,seasonally high-water levels ranged from approximately 86 to 89 feet(msl)and seasonally low elevations typically ranging from 81 to 85 feet (msl). Water levels declined about 5 feet during the 1976-77 drought and then recovered in the late 1970s and early 1980s to reach the highest water levels on record during the wet period of 1982-86(i.e., 94.2 feet, msl in October 1984). During the 1987-92 drought,water levels declined to levels below those observed during the 1976-77 drought and,since then, have not recovered to earlier elevations.The quarterly record,starting in 1994,shows that water levels recovered some,to a high of almost 81 feet (msl) in 1998(i.e., at the end of 4 consecutive wet years). Since then, seasonally high-water levels have steadily declined,and this corresponds with predominantly dry hydrologic conditions.The lowest recent water level, 62 feet above mean sea level (msl), occurred in October 2020. Prior to the 1987-92 drought, 1 http://cdec.water.ca.gov/reportapp/J`avareports?name=WSIHIST LUHDORFF He SCALMANINI CONSULTING ENGINEERS 4