COMPLIANCE INFO_JTD 9/3/2025 - Laserfiche WebLink

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Foothill Sanitary Landfill 6 Department of Public Works/Solid Waste First Semiannual 2025 Groundwater Monitoring ©2025 County of San Joaquin. All rights reserved. (GX-14, GX-15, GX-16, and GX-17) were installed by the County on LF-2, Module 1 to improve LFG recovery. The CVRWQCB issued a Notice of Violation (NOV) to the Second Semester and Annual 2017 Groundwater Monitoring Report on June 6, 2018. The NOV requested the County submit a Work Plan by July 16, 2018, to respond to the following three issues: 1) Install one groundwater monitoring well at the point of compliance of Module I, near gas probe SG-6A; 2) Re-install or re-construct background well MW-4; and 3) Provide reasoning why single completion gas probes SG-4, SG-7, and SG-9) have not been reconstructed as triple completion gas probes. The work plan was submitted in July 2018 and addressed the requested responses. Two new monitoring wells, one near SG-6A (MW-7) and one as a replacement for MW-4 (MW-4A), were installed in October and December 2018, respectively. The installation report for the new monitoring wells was submitted under separate cover on October 30, 2019. Monitoring well MW-7, installed in October 2018, was installed to a depth of 330 feet below ground surface and is deeper than the other monitoring wells at the site. During drilling, water was not observed at the depth consistent with the other monitoring wells at the site. In a September 20, 2021 submittal to the CVRWQCB, the County indicated its intent to install a replacement monitoring well for MW-7 in order to provide a point of compliance well for Module I. An alternate monitoring well location was proposed in the Monitoring Well MW-7 Replacement Location letter, submitted to the CVRWQCB on December 1, 2021. The alternate location was approved on December 9, 2021 and the well was installed in June and July 2022. Due to delays with pump procurement, 5 Year COC sampling was delayed until the pump could be installed in June 2023. The Regional Board expressed that the well installation report should also include the initial 5 Year COC sample results. The monitoring well installation report was submitted in August 2023 and included the initial 5 Year COC results. In 2021, three additional LFG extraction wells (GX-18, GX-19, and GX-20) were installed in Module “I” in proximity to MW-3 during the first semiannual 2021 monitoring period. These additional LFG extraction wells were installed as a corrective action measure to help reduce the release of VOCs from Module “I”. In 2022, eight additional LFG extraction wells were installed. Four were installed in Module “I” (GX-21 through GX-24) and four were installed in Module 2A (GX-30 through GX-33) (Figure 5). In 2023 Six additional LFG extraction wells and eight horizontal collectors were installed. LFG extraction wells GX-34 through GX-39 were installed in Module 2A. Horizontal collectors HC-13 through HC-17 were installed in Module 2B. Horizontal collectors HC-05 through HC-07 (previously installed in Module 2A) were connected to the LFG collection system. 2.2 Impermeable Barrier Placement – Potential Impact to Groundwater In examining the timeline of detections and corrective actions, a four to five-year lag between action at the surface of unlined LF-1 and changes in groundwater quality beneath LF-1 has been observed and concluded based on the following observations: