Laserfiche WebLink
Foothill Sanitary Landfill 8 Department of Public Works/Solid Waste <br />First Semiannual 2025 Groundwater Monitoring ©2025 County of San Joaquin. All rights reserved. <br /> <br />3.0 MONITORING PROGRAM <br />3.1 Groundwater <br />The groundwater well network consists of up-gradient wells MW-4 and MW-4A and down- <br />gradient wells MW-2R, MW-3, MW-5, MW-6, MW-7, and MW-7R. Well MW-1, which had <br />previously been considered up-gradient, was later found to be cross-gradient from the landfill, <br />and not down-gradient of any portion of the landfill. Groundwater monitoring wells MW-4 and <br />MW-5 were installed during the fall of 2006. Deeper well MW-1A was installed in 2013 due to <br />decreasing water levels in MW-1. MW-6 was installed during the spring of 2015. Replacement <br />background well MW-4A was installed in December 2018. MW-7 was installed in October 2018. <br />Monitoring well MW-7R installation was completed in July 2022. These new wells were installed <br />in accordance with a work plan approved by the CVRWQCB. A copy of the Sampling and <br />Analysis Procedures is in Appendix A. <br />All monitoring wells are equipped with dedicated purge and sampling pumps. Information on the <br />type of pump and the pumping characteristics of each well during the sampling event is <br />contained on the field sheets in Appendix B <br />Groundwater samples are analyzed semiannually for the following field parameters: <br /> Elevation (Quarterly)  pH <br /> Temperature  Turbidity <br /> Electrical Conductivity <br />Groundwater samples are analyzed semiannually for the following monitoring parameters: <br /> Total Dissolved Solids  Chloride <br /> Carbonate Alkalinity  Bicarbonate Alkalinity <br /> Nitrate-Nitrogen  Sulfate <br /> Calcium  Magnesium <br /> Potassium  Sodium <br /> Volatile Organic Compounds <br />(VOC) <br /> <br />Groundwater samples are analyzed every 5 years for the following additional constituents of <br />concern (COC): <br /> VOC (extended list)  Semi-volatile Organic Compounds <br /> Dissolved Metals  Organophosphorus Compounds <br /> Chlorophenoxy Herbicides <br />The previous 5-year COCs were collected during the first semiannual period of 2019. During the <br />second semiannual period of 2024, the 5-year COC monitoring event took place. Three wells <br />were dry during the first semiannual period of 2025 (MW-3, MW-5, and MW-7R). A second <br />attempt will be made to collect the 5-year COCs for these wells during the second semiannual <br />period of 2025. The next 5-year COC sampling event is scheduled for 2029.