Laserfiche WebLink
BACKGROUND <br /> The.Corral Hollow Sanitary Landfill(CHSL)is located in southern San Joaquin County at the <br /> intersection of Interstate 580 and Corral Hollow Road as shown on Figure 1. The County <br /> performs quarterly groundwater monitoring in accordance with Waste Discharge Requirements <br /> issued by the California Regional Water Quality Control Board. The groundwater well network <br /> consists of six total monitoring wells. Three of the wells monitor the deep water bearing zone, <br /> and three monitor the shallow,perched aquifer. MW-2 is an upgradient deep well, and MW-1 <br /> and MW-3 are downgradient deep wells. The flow in the shallow aquifer is historically bi- <br /> directional at the CHSL, so SB-1 is the upgradient well, and MW-4,MW-5 are downgradient <br /> shallow wells. The locations of all groundwater wells are shown on figure 2. <br /> VOC's were first detected in groundwater samples collected from MW-5 during the fourth <br /> quarter of 1991 (Trichlorofluoromethane(CFC 11) and tetrachloroethene (PCE)). Confirmation <br /> samples were collected February 12, 1992, and the presence of VOC's in the vicinity of <br /> monitoring well MW-5 was confirmed. The County continued to monitor VOC concentrations <br /> in MW-5 on a quarterly basis. A corrective action plan(CAP),which included the closure and <br /> capping of the landfill, has been implemented. As part of the CAP, a Mann-Kendall trend <br /> analysis of the VOC's for MW-5 is conducted quarterly. Tetrachloroethylene (PCE)has shown <br /> an increasing trend statistically over time. <br /> The California Regional Water Quality Control Board(CRWQCB)has requested a work plan <br /> including an evaluation of the lateral and vertical extent of VOC's in the shallow water bearing <br /> zone. The following is an analysis of the situation, and a proposal to determine the nature and <br /> extent of the contamination. <br /> ANALYSIS <br /> San Joaquin County conducts quarterly monitoring of seven landfill gas monitoring wells located <br /> around the perimeter of the landfill. Locations of the gas wells are shown on the attached figure <br /> 2. Gas monitoring results have indicated that landfill gas is migrating to the perimeter of the site <br /> along Corral Hollow Road. Gas well numbers 1,2,3 have shown the highest concentration of <br /> landfill gas while gas well numbers 4,5,6,7 have shown little or no landfill gas influence. It is <br /> 1 <br />