COMPLIANCE INFO_JTD 9/3/2025 - Laserfiche WebLink

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Foothill Sanitary Landfill 3 Department of Public Works/Solid Waste First Semiannual 2025 Groundwater Monitoring ©2025 County of San Joaquin. All rights reserved. 2.0 COMPLIANCE HISTORY SUMMARY 2.1 History Prior to March 2000, no groundwater impacts had been determined due to landfill activities. From March 2000 to October 2001, volatile organic compounds (VOCs) were detected at a single groundwater monitoring well, MW-3, adjacent to unlined LF-1. These detections have been ascribed to ponding on refuse along a road immediately adjacent to that monitoring well during the previous five years. Impact to groundwater at other wells was not detected. In the spring of 1998, ponding in this area had been corrected by covering the refuse and grading the area to drain. However, penetration of water into the refuse below the ponding area apparently caused an increase in landfill gas (LFG) production in the years after ponding was corrected, sufficient to cause VOC impact to groundwater. Correction of the ponding allowed the LFG production to dissipate. In February 2002, approximately four years after correcting the surface ponding, water samples from MW-3 indicated that the VOC impact to groundwater had ceased. On November 6, 2002, nine months after the last detection of VOCs at MW-3, the County submitted an Evaluation Monitoring Plan at the request of CVRWQCB staff. This Plan proposed methods to delineate the nature and extent of groundwater impact previously seen at MW-3. The Plan included drilling and sampling from temporary borings, and a “step-out step-down” approach if groundwater contamination was detected at those borings. On January 30, 2003, eleven months after the last detection of VOCs at MW-3, the CVRWQCB issued new WDRs R5-2003-0020. These WDRs required the closure of unlined Module “I” (LF-1) and the monitoring of soil gas for VOCs as corrective actions. Groundwater contamination was not indicated at that time. In June 2003, one and one-half years after the last detection of VOCs at MW-3, the Evaluation Monitoring Program was completed. Groundwater samples from temporary borings were found free of contaminants, consistent with data from the permanent monitoring wells since February 2002. A deep soil gas probe, SG-1, was bored to sample soil gas above the water table near groundwater monitoring well MW-3. Four VOCs were detected at SG-1; however, these compounds were not detected in the water samples taken at MW-3 at that time. The County concluded that the corrective action of removing the ponding had prevented further groundwater impact at that time. On September 16, 2003, due to a delay in submitting the results of the Evaluation Monitoring Plan, the CVRWQCB issued a Water Code Section 13267 Order. This Order required that the County submit the results of the Evaluation Monitoring Program and an Engineering Feasibility Report (EFS) that includes closure of Module ‘I’. That Order did not require the submittal of a Closure Plan (the Preliminary Closure Plan was on file with CVRWQCB at that time).