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<br />North County Recycling Center & Sanitary Landfill Public Works/Solid Waste <br />First Semiannual 2024 Groundwater Monitoring 9 ©2024 COUNTY of San Joaquin. All Rights Reserved. <br /> <br />during the first quarter., except for turbidity in wells G-11, and G-14. General chemistry results <br />did not exceed the CLs during the first quarter, with the exception of bicarbonate in G-12. <br />As recommended in the DMP Evaluation submitted in November 2021, new background well <br />G-12 located in the northwest portion of the facility was installed in the first semiannual 2022 <br />period and will be used to update concentration limits after a sufficient number of data points <br />have been collected. Therefore, the current concentration limits calculated from G-1A and <br />provided in the WDR will be used in the interim. <br />VOCs <br />No VOCs were reported in any of the monitoring wells (G-7 through G-14) that surround the <br />landfill during the first semiannual 2024 period. <br /> <br />VOCs have not been detected above the laboratory reporting limits at the North County Sanitary <br />Landfill since 2008, when short-term detections were reported in wells G-3D and G-5A. Due to <br />the continued drop in groundwater levels at the site, neither of these wells have been sampled <br />since 2016. <br />Storm Water <br />During the first semiannual 2024 period, storm water samples were not collected during the <br />monitoring period as no significant storm events were reported. Storm water is monitored <br />according to the site Industrial General Permit. <br /> <br />Surface Water <br />Surface water sampling locations were dry during the January 23, 2024 and April 2, 2024 <br />monitoring events and could not be sampled during the first semiannual 2024 period. <br /> <br />Unsaturated Zone (Lysimeters) <br />Three lysimeters were sampled during the first semiannual 2024 period. VZ-01 and VZ-03A/B <br />were each sampled in February and March 2024. Both were dry in April 2024. VZ-06 was <br />sampled in February but was dry in March 2024. All other lysimeters were reported as dry during <br />the reporting period, indicating no detectable leaks from the liner in those areas during the first <br />semiannual 2024 period. Unsaturated zone monitoring will continue in accordance with the <br />WDRs. The results of the sampling are provided in Table 8. <br />Soil Gas <br />Soil gas samples were collected on May 24, 2024. VOCs were detected in soil gas monitoring <br />wells SG-1D (2 VOCs) and SG-6 (15 VOCs), as shown in Appendix G. Methane was detected <br />at 0.0% in soil gas probes SG-1D and SG-3D, and at 20.30 % in soil gas probe SG-6, as shown <br />in Table 6. See Appendix G, Unsaturated Zone Soil Pore Gas Tabular Summary of Historical <br />Monitoring Data.