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OPERATION AND MAINTENANCE LAN LANDFILL GAS MIGRATION MONITORING AND CONTROL SYSTEM CORRAL HOLLOW SANITARY LANDFILL i 1.0 BACKGROUND 1.1 GENERAL Corral Hollow Sanitary Landfill (CHSL)is a closed, unlined Class III landfill located at 31130 South Corral Hollow Road, in southern San Joaquin County, approximately 5 miles south of the City of Tracy, at the intersection of Interstate 580 and Corral Hollow Road. The landfill covers approximately 58 acres, of which 43 acres was permitted disposal area. The remaining area is comprised of access roads, storm water retention ponds, setbacks for environmental monitoring, and firebreaks. Land within 1,000 feet of the facility is used for grazing and agriculture In 1996, CHSL was certified closed with the installation of the closure cap, Landfill gas (LFG) migration monitoring wells and groundwater monitoring wells. The cap consists of a 2-to 6-foot foundation layer under a 1-foot minimum thick, low-permeability soil layer,with a 1-foot thick vegetative surface layer. 1.2 LFG MIGRATION MONITORING 3 CHSL has seven triple-probe perimeter monitoring wells (Figure 2). All wells are labeled and locked. Well logs of the perimeter probes are available upon request. Each perimeter well monitors the shallow, intermediate and deep sub-surface soil layers for off-site migration. Each probe is color coded to represent its depth. Color red identifies shallow probe, color blue identifies the intermediate probe, and gold color identifies the deepest probe. 1 1.3 LFG COLLECTION AND CONTROLLED SYSTEM In 2001, a LFG collection and controlled system (LFGCCS)was installed to control subsurface LFG migration and to mitigate impact of volatile organic compounds on the shallow aquifer. The LFG system includes a flare station and 39 LFG extraction wells installed in refuse. The landfill gas wells vary from approximately 25 to 92 feet in depth. A typical vertical LFG extraction well casing consists of of 6-inch diameter high density polyethelene (HDPE)pipe. Each well is provided with an adjustment valve and sampling port. The flow rate from each well is adjusted based on the concentration of methane in the gas collected at the well. The piping serving the wells is comprised of HDPE, and is buried in the vegetative layer of the landfill. Each well is connected through a lateral pipe to the main header pipes. LFG condensate collects at low points in the piping,from where the condensate is pumped to LFG Operation And Maintenance Pan San Joaquin County Corral Hollow Sanitary Landfill 7 Public Works Department March 31,2008 Solid Waste Division