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2024 ANNUAL GROUNDWATER MONITORING REPORT TEICHERT AGGREGATES AND GRANITE CONSTRUCTION VERNALIS AREA 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, seasonal water levels fluctuated commonly 5-8 feet.Since 1994, seasonal water level fluctuations have mostly ranged between 2-3 feet. DWR's semi-annual record indicates that seasonally high-water levels are most typically observed in late summer and early fall, not during the wet season in winter and early spring. Quarterly groundwater level measurements in the five shallow wells (including 4S/6E-5A1)since 1994 show very similar seasonal and long-term water level fluctuations across the area (Figure 5).The highest water levels were observed in 1998. Since 1998,groundwater levels in all wells have decreased approximately 25 feet. Individual hydrographs for network wells are provided in Attachment 1. In 2024,the depth to groundwater in the shallow aquifer zone ranged from 100.89 feet(Hall, 2n1 quarter)to 178.41 feet(Blewett,4th quarter) (Table 1). Corresponding groundwater elevations are shown in Table 2. Groundwater levels observed in the deep wells are generally significantly lower,and they exhibit greater seasonal and annual fluctuation than the shallow wells due to increased aquifer confinement(Figures 6- 9). Also,the deep wells target the primary water production zone and are,therefore,subject to greater pumping stresses. Water levels in the deep zone have ranged in depth from about 208 to approximately 460 feet(not including pumping water levels),with up to 40 to 60 feet of seasonal fluctuation (approximately 90 feet at Brown's#1 in 2015 and S.Tracy#3 in 2021). Like groundwater levels in the shallow wells, deep water levels are subject to regional hydrologic conditions as expressed by DWR's Water Year Hydrologic Classification Index.The highest water levels were observed in the late 1990s and in 2000.This was followed by steep declines of approximately 60 to 80 feet, incomplete recovery during the 2005-2006 wet period, relatively stable water levels through the winter 2012-2013, and additional substantial water level declines associated with the extensive dry period through 2016. 2017 was a wet water year and this is reflected by some water level recovery. From 2017 to spring 2020,water levels in all wells remained relatively stable. Since spring 2020,water levels in wells located furthest south declined approximately 25 to 40 ft (Brown#1 and Granite#3, respectively),while water levels in the wells located in the central area (S.Tracy#1 and S.Tracy#9054)declined about 17 to 72 feet, respectively. Water levels in the South Tracy#1 production well typically recovered to an elevation between 20 and 40 feet(msl)each winter until 2001,when increased pump operation made the measurement of static water levels difficult. Upon Teichert's initiative, plant staff measured static and pumping water levels in the South Tracy#1 well more frequently from late 2001 to 2008,and these supplemental data are LUHDORFF&SCALMANINI CONSULTING ENGINEERS 6