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2024 ANNUAL GROUNDWATER MONITORING REPORT TEICHERT AGGREGATES AND GRANITE CONSTRUCTION VERNALIS AREA 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 variable3 prior to the well being replaced in 2019 with Granite#5. EC in Granite#5 ranged from 861 to 982 VS/cm since 2019,consistent with previous Granite #3 measurements. In fall 2022, Granite#5 could not be sampled because its pump had been removed. Therefore, Granite#4 was sampled as a replacement.The EC in Granite#4 was 914 VS/cm. Granite#4 was sampled again in fall 2023 because Granite#5 was not pumping on the day samples were retrieved. Groundwater samples were collected from Granite#5 for the entirety of the 2024 monitoring year. Groundwater quality data for 2024 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 16 to 25). 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 26). Calcium and sodium are the most prevalent cations in groundwater in both the shallow and deep zones. In the shallow zone(Hall and Faulkner wells), bicarbonate is the most prevalent anion,followed by chloride. Bicarbonate is also the most prevalent anion in the South Tracy#3 well, but it is closely followed by sulfate. Bicarbonate and sulfate are the most prevalent anions in the Brown's New well.Sulfate is the most prevalent anion at Granite#5 well,followed by bicarbonate.Shallow groundwater has greater chloride concentrations than deep groundwater and its hydrochemical facies is of Ca-Na/HCO3-CI (Faulkner)and Na-Ca/HCO3-CI (Hall) type. Deep groundwater has greater sulfate concentrations than shallow groundwater. South Tracy#3 and Brown's New well hydrochemical facies is of Ca-Na/HCO3-SO4 type. Groundwater retrieved from Granite#5 has proportionally more sulfate and is of Ca-Na/SO4-HCO3 type. Nitrate (as nitrate) concentrations in shallow groundwater samples retrieved from the Hall well increased from about 15 to 30 milligrams per liter(mg/L) between 1994 and 1996, decreased to about 20 mg/L in 1999, and remained relatively stable around 20 mg/L until between 2010 and 2013 when concentrations further decreased to 11.1 mg/L(Figure 27). Nitrate concentrations in the Faulkner well exhibit similar trends with an overall decline from 36 to 7.1 mg/L(1994-2013). Both the Hall and the Faulkner wells experienced concentration increases to 34.2 and 28.1 mg/L, respectively, in November 2014. From November 2014 to May 2017, concentrations fluctuated up to 16 mg/L. Since then, concentrations have declined to concentrations lower or similar to the mid-2000's (around 10 mg/L). z 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 8