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Foothill Sanitary Landfill 25 Department of Public Works/Solid Waste <br />First Semiannual 2025 Groundwater Monitoring ©2025 County of San Joaquin. All rights reserved. <br /> <br />The depth of liquid in the secondary sump is also monitored monthly using by a bubbler tube <br />installed into the sump. The minimum operational depth of liquid for pump operation is 2.5 <br />inches. <br />The record winter storms in early 2023 caused extreme quantities of leachate in all three sumps. <br />Sump depths exceeded permitted limits and the persistent heavy precipitation reduced or <br />eliminated viable disposal options. After discussion with Board staff, County staff implemented <br />emergency leachate removal procedures once conditions were acceptable. Emergency actions <br />included installing two elevated tanks, replacing the pump in Sump 1, and implementing daily <br />hauling of leachate via one to two water trucks. Some leachate was initially hauled off site, but <br />once the temperatures increased, most leachate was spread on lined areas of the landfill, <br />primarily module 2A. RWQCB Staff issued an NOV on June 27, 2023, requiring compliance by <br />August 15, 2023. Sumps 2A and 2B, as noted, were already in compliance but Sump 1 did not <br />come into compliance until July 25, 2023. Full documentation of the leachate removal effort was <br />reported previously to RWQCB staff. County staff also submitted a plan for long term <br />management of leachate that will result in a new leachate storage facility to be constructed in <br />2026. <br />On October 27, 2023, a leak from the LFG condensate line near the transformer of the flare <br />station was observed. During previous construction activity, the condensate line was damaged <br />by the contractor and not repaired properly, eventually causing the line to leak. Excavation <br />around the transformer station was completed and soil samples were collected on November 1, <br />2023. VOCs were detected in two of the three confirmation soil samples collected, so additional <br />excavation and soil sampling was completed on December 14, 2023. VOCs were detected in <br />one of the three additional soil confirmation samples. No additional action was required and the <br />excavated area was backfilled.