ARCHIVED REPORTS_2003_4 - Laserfiche WebLink

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Soil Gas The soil is monitored for VOCs per the WDRs Order No. R5-2003-0020. Ten wells, SG-2 through SG-1 1, were installed surrounding modules "I" and 1 (Figure 5). Well depths range from 25 feet to 68 feet. Soil gas samples will be retrieved quarterly and tested by certified laboratory per EPA test method TO-14. MONITORING RESULTS Groundwater Well MW-2R was available for sampling during this semester. Monitoring and Field Parameters Chloride concentrations in LW-1 and MW-3 slightly exceeded the concentration limit. The sulfate concentration in LW-1 exceeded the concentration. The Nitrate as nitrogen concentration in MW-3 slightly exceeded the concentration limit. A release from the landfill is unlikely due to these indications. Although these concentrations are above the concentration limit,we note that they are below the drinking water standard (California DHS). The County will monitor concentrations of these constituents quarterly. Stiff Diagram Anal ' The stiff diagrams this semester indicate a calcium-bicarbonate water type since these ions have the highest concentrations in the four wells. The water type is similar in all wells as indicated by similarity in concentrations of the various constituents and the similarity in diagram shapes. These similarities point to groundwater uniformity beneath the landfill, which is an indication of lack of impact to groundwater by landfill leachate. VOCs ' All VOCs reported were also reported in quality control blanks and are therefore "false positives". These compounds included: • Acetone, Chloromethane and Methylene Chloride in wells MW-1 and MW-3 • Acetone was in well MW-2R • Acetone and Methylene Chloride in well LW-1. Foothill Sanitary Landfillartment of Public Works/Solid WasteDe p 2ND Semester/Annual 2003 Groundwater Monitoring County of San Joaquin-Revised June 29,2004