CORRESPONDENCE_2003-2004 - Laserfiche WebLink

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As of January 1995,statistically significant increasing trends were confirmed in Electrical Conductivity,Total Dissolved Solids, and Chloride. Consistent and repeated detections of Dichlorodifluoromethane and Tetrachloroethene were also observed. The County proposed the closure of the landfill in 1994 and subsequent installation of an LFG Collection System in 1996 (due to landfill gas migration)be considered corrective action measures. CORRECTIVE ACTION MEASURES Final Landfill Cover The final landfill cover was proposed as a corrective action measure based on the understanding that precipitation was creating leachate, and was possibly entering groundwater, as indicated by increasing trends in inorganic constituents and previous site investigations. The effectiveness of the final landfill cover is indicated by the lack of statistically increasing trends in all inorganic constituents and no concentrations of any inorganic constituent exceeding the limits established by the current WDRs. These results indicate that leachate is no longer entering the landfill and migrating to groundwater. A subsurface investigation performed in 1991 revealed no evidence of standing leachate beneath the landfill (Solid Waste Water Quality Assessment Test,Kleinfelder,June 1991). However, moist soils were encountered within 10 feet of the landfill bottom. Soil samples were taken and analyzed for VOCs, surrogates of metallic constituents, metals, and pH. No VOCs were detected in any of these samples,but high concentrations of Sulfate and Chloride indicated a possibility of impact to the groundwater from leachate migration. The closure of the landfill included placing a clay barrier layer as a component of the landfill cover. This is understood to be an effective measure to prevent water infiltration into the landfill and the resulting production of leachate. The integrity of the landfill cover is monitored by visual inspections for ponding and erosion and by surface emission scans of the landfill's top cover. The cover is graded and maintained to prevent ponding and soil erosion per Title 27, California Code of Regulations. Each winter, the landfill is monitored for ponding and erosion on the footprint of the landfill. Any ponding or erosion observed is noted and repaired when conditions allow,but prior to the next winter. The most recent repairs to the final cover were completed in November 2002. Reconditioning of the entire top surface of the landfill is planned for October 2003. Through Rule 4642 of the San Joaquin Valley Unified Air Pollution Control District(APCD), the County is required to regularly scan the top surface of the landfill for surface emissions. Surface scans are a means of checking the integrity of both the LFG collection system and the Progress of Corrective Action Measures 2 Hamey Lane Sanitary Landfill Revised-August 22,2003 County of San Joaquin