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2020 ANNUAL GROUNDWATER MONITORING REPORT TEICHERT AGGREGATES AND GRANITE CONSTRUCTION VERNALIS AREA Contours of equal groundwater elevations prepared with data from the shallow network wells show that the general direction of groundwater flow during times of seasonally high-water levels was typically to the east-southeast and east.This includes the first monitoring event in spring 1994 with comparatively high-water levels (Figure 7)and the period of the highest historically recorded groundwater elevations in spring 1998 (Figure 8).The water level elevations in spring 2000 were relatively low compared to groundwater conditions observed in previous spring seasons, however, the predominant direction of flow was also to the east-southeast(Figure 9). In spring 2002, overall groundwater elevations were very similar to the spring 2000 elevations, but the groundwater flow direction was east-northeasterly as influenced by a relatively high groundwater level in the Koster irrigation well (Figure 10). The February 2020 (Figure 11) and November 2020 (Figure 12)groundwater elevation contour maps indicate easterly groundwater flow conditions. 3.2 Groundwater Quality The electrical conductivity(EC)of samples retrieved from the shallow network wells(Hall and Faulkner domestic wells) mostly ranged between 900 and 1,000 µS/cm between 1994 and the mid-2000's when EC values started to decrease until early 2014(Figure 13).The November 2014 EC measurement in the Faulkner well was the highest on record (1,130 µS/cm); Hall increased to 1,040 µS/cm. Since late 2015, EC decreased in both the Faulkner and Hall wells to values similar to early 2014. During 2020, EC in the Hall and Faulkner domestic wells were the lowest of the period of record (780 and 740 µS/cm, respectively).The EC of samples retrieved from the deep network wells South Tracy#1,#3, and Brown's New mainly range from 800 to 900µS/cm and have been very stable over the period of record.'The EC at Brown's#1 was more variable from 1994 until 2005 (when it was vandalized), and the EC at its replacement well (Granite#3; sampling commenced in 2006) was higher, but similarly variable prior to the well being replaced in 2019 with Granite#5. EC in Granite#5 ranged from 874 to 976 µS/cm in 2020, consistent with previous Granite#3 measurements. Groundwater quality data for 2020 are summarized in Table 3 and the complete water quality record is provided in Table 4. Laboratory reports and field notes are provided in Attachment 3. Time series plots of major cation concentrations (sodium, calcium, and magnesium) and anion concentrations(bicarbonate, chloride, and sulfate) prepared for the individual wells are consistent with the EC measurements and reflect stable hydrochemical groundwater conditions(Figures 14 to 22). Concentrations of major cations and anions were averaged over the period of record and plotted in milliequivalents per liter(meq/L) in a Schoeller Diagram (Figure 23). Calcium and sodium are the most prevalent cations in groundwater in both the shallow and deep zones. In the shallow zone (Hall and I The atypical electrical conductivity and associated elevated calcium,chloride,iron,and manganese concentrations in November 2017 are attributed to the rehabilitation work performed on this well in fall 2017,which included strong acid treatment. 3 In August 2009,a sample was retrieved from Granite#4 in lieu of Granite#3,where a sample could not be retrieved at the time. LUHDORFF&SCALMANINI CONSULTING ENGINEERS 6