SU0007720 - Laserfiche WebLink

Home Browse Search

2020 ANNUAL GROUNDWATER MONITORING REPORT TEICHERT AGGREGATES AND GRANITE CONSTRUCTION VERNALIS AREA water levels were observed in 1998. Since 1998, groundwater levels in all wells have decreased approximately 20 feet. Individual hydrographs for network wells are provided in Attachment 1. In 2020, the depth to groundwater in the shallow aquifer zone ranged from 96.75 to 125.23 feet in the Hall and Rustan wells, respectively (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 (Figure 6). 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 190 to approximately 400 feet(not including pumping water levels), with up to 40 to 60 feet of seasonal fluctuation (approximately 80 feet at Brown's#1 in 2012 and 2015). 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 2019, water levels in all wells remained relatively stable. In 2020, water levels in wells located furthest south remained relatively stable (Brown #1 and Granite#3), while water levels in the wells located in the central area (S.Tracy#1 and S. Tracy#9054) declined from about 25 to 65 feet. 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 tabulated in Attachment 2. Water levels in the South Tracy#3 production well were also monitored at a higher frequency. However, the sounding of water levels below a depth of approximately 271 feet has not been successful due to an obstruction at this depth. The Petz irrigation well, located west of the Teichert Vernalis plant, is completed in both the shallow and deep zones of the underlying aquifer system, and its water level hydrograph reflects a composite of these shallow and deep zones(see Attachment 1). The early water level record of this well (prior to 2000) shows groundwater level elevations between those observed in the discussed shallow and deep wells in the area. Similarly, seasonal fluctuations prior to 2000 appear to be a composite of observations made in the shallow and deep network wells. Specifically, seasonally high-water levels in this well rose from 72.46 to 86.58 feet(msl) between March 1994 and 1998, with seasonal fluctuations of almost 15 feet. Since then, water levels have been very similar to those observed in the shallow network wells. LUHDORFF&SCALMANINI CONSULTING ENGINEERS 5