ARCHIVED REPORTS_2006_1 - Laserfiche WebLink

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Previous Corrective Action A landfill gas system was installed in 2001 as corrective action against volatile organic compounds (VOCs) in shallow aquifer monitoring well MW-5. Ponding along the west side of the eastern landfill road was corrected in December 2004. Closure construction in 1996 initially included installation of a half-round(open) corrugated metal culvert ' to conduct water along the western side of the eastern road. Significant erosion had occurred beneath this culvert since closure. Although not observed directly, the roughness of the erosion beneath the culvert provided numerous small ponding areas. These ponding areas were eliminated by removing the culvert, regrading the invert of the ditch, and placing anti-erosion mesh in the invert. Recent water quality data(presented in the 2006 Fourth Quarter and Annual Groundwater Report), indicates an improvement in water quality at the shallow aquifer monitoring wells. It is possible that regrading the drainage ditch in 2004 to prevent ponding reduced infiltration along the alignment of the ditch such that impact by leachate is now dissipating. INVESTIGATION Purpose The purpose of this investigation was to determine if refuse and/or the closure cap was adjacent to the road. This investigation was conducted in September 2005 in accordance with the Plan to Evaluate Impacts to Groundwater, submitted to the RWQCB on February 10, 2005. Procedure This investigation was by excavation with a backhoe, and included excavating on both sides of the eastern landfill road(Figure 3). Excavation was from the road east to near the perimeter fence, and from the road west across the drainage ditch. The excavations were dug to six feet if refuse was not encountered, up to 12 feet to determine the depth to refuse if refuse was encountered(see Field Record). Excavated refuse was either replaced in the excavation or removed to an active County-owned landfill. Four excavations were originally planned; however,a fifth excavation was added during the investigation to further define the refuse limits. Of special concern was the presence of the petroleum pipeline near the center of the road. Prior to excavating, a representative of Shell Oil visited the site and marked the location of the pipeline in the vicinity of the planned excavations. During investigations, special care was taken to ensure that we did not excavate near the pipeline. Investigation of Groundwater Impact 2 San Joaquin County Public Works/Solid Waste Corral Hollow Sanitary Landfill March 3,2006