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<br /> <br /> <br />1810 East Hazelton Avenue | Stockton, California 95205 | T 209 468 3000 | F 209 468 2999 <br />Follow us on Facebook @ PublicWorksSJC Visit our website: www.sjgov.org/pubworks <br />Department of Public Works <br /> <br />Fritz Buchman, Director <br />Alex Chetley, Deputy Director - Development <br />Kristi Rhea, Deputy Director - Administration <br />David Tolliver, Deputy Director - Operations <br /> Najee Zarif, Deputy Director - Engineering <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> July 31, 2025 <br /> <br />Mr. Todd Del Frate, PG <br />Engineering Geologist <br />Central Valley California Regional Water Quality Control Board <br />11020 Sun Center Drive, #200 <br />Rancho Cordova, California 95670-6114 <br /> <br />SUBJECT: First Semiannual 2025 Groundwater and Surface Water Monitoring <br />Report, Foothill Sanitary Landfill <br /> <br />Mr. Del Frate, <br />Enclosed is the First Semiannual 2025 Groundwater and Surface Water Monitoring Report for <br />the Foothill Sanitary Landfill, submitted in accordance with WDR No. R5-2015-0058. <br />Wells MW-3, MW-5, MW-7R, and surface water locations were either dry or had insufficient <br />water present and therefore no sampling took place at these locations during the first <br />semiannual period. County staff will be submitting a work plan to replace these wells this <br />quarter. Sampling in the remaining six wells was conducted during January 2025 and a <br />summary of the findings are provided below. <br />• MW-1A – The CL for turbidity was exceeded however, the concentration remained <br />within historical range. <br />• MW-2R – The CL for turbidity was exceeded and bicarbonate alkalinity was at the <br />CL, however, the concentrations remained within historical range. <br />• MW-4A – The CL for turbidity was exceeded and bicarbonate alkalinity was at the <br />CL, however, the concentrations remained within historical range. <br />• MW-6 – No CL’s were exceeded; all concentrations were within historical ranges. <br />• MW-7 – The CLs for turbidity, sodium, potassium, and sulfate were exceeded. The <br />concentrations of sodium and potassium were reported within historical range. <br />The concentrations of turbidity and sulfate exceeded the historical maximums. <br />Although some concentrations exceeded the CLs, most were still within the range of historical <br />data. Monitoring constituents were consistent with previous monitoring periods. <br />VOCs were not detected in the groundwater monitoring wells during the 2025 first semiannual <br />period.