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the south with a gradient of approximately 0.002 foot per foot. Groundwater flow <br /> velocity has been calculate to be 67 feet per year. <br /> Environmental Monitoring <br /> The current groundwater monitoring system is comprised of four monitoring wells, one <br /> upgradient well (MW-1) and three down gradient wells (MW-2, MW-3 and MW-3). <br /> Volatile organic compounds (VOCs)were first detected in 1991 in one groundwater <br /> monitoring well, MW-2. The cause of the impact was believed to be landfill gas <br /> migration. A landfill gas (LFG) collection system was installed in 1996 to mitigate <br /> groundwater impacts and control LFG migration. Three VOCs were reported <br /> consistently since first confirmed in 1991; however, recent monitoring data indicates one <br /> VOC remaining at very low concentration (tetrachloroethene below 1 ppb). <br /> An increasing chloride trend has been developing in MW-2, MW-3 and MW-4. <br /> Concentrations do not exceed the recommended secondary maximum contaminant level <br /> (MCL) for drinking water(25.0 mg/1) in wells MW-2 and MW-3 <br /> Run-off/Run-on facilities <br /> Harney Lane Sanitary Landfill utilizes several methods to control run-on and run-off. A. <br /> perimeter berm/road surrounds the site and prevents water from entering. The facility <br /> utilizes drainage ditches along the berm/road to handle storm water runoff from the <br /> landfill. The ditches discharge to a stormwater retention pond located at the south end of <br /> the site. <br /> HYPOTHETICAL RELEASE SCENARIO <br /> Based on the current impact to groundwater by LFG, and that this is an unlined site, the <br /> most reasonably foreseeable release that will require corrective action is an elevation in <br /> VOCs rather than an elevation of inorganics as follows: <br /> HYPOTHETICAL EVALUATION MONITORING PROGRAM <br /> An Evaluation Monitoring Program (EMP) will be conducted to investigate the lateral <br /> and vertical extent of a release from Harney Lane Sanitary Landfill. This EMP will <br /> consist of preparing a work plan for approval by the jurisdictional agencies, <br /> implementing the field investigation of this Plan, and reporting the findings. <br /> An EMP work plan will be submitted to the RWQCB in accordance with Section 20425 <br /> (a) and (b) of Title 27. The EMP will include a soil gas and groundwater step-out/step- <br /> Corrective Action Financial Assurance Cost Estimate 2 September 30,2008 <br /> Harney Lane Sanitary Landfill San Joaquin County Public Works Department <br />