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e County investigated to determine if refuse was resent below the drainage In September 2005, th ty g p g ditch, the access road, and east of the road at the eastern edge of the landfill. This investigation found refuse below the ditch and that the final closure cover did not extend to the ditch. In early 2006, improving trends in water quality (nitrate) at MW -4 were noted, apparently beginning in late 2004. The County believes that this is the result of removing ponding from the drainage ditch along the east side of the landfill completed in late 2003. In February 2006, the California Department of Resources, Recycling, and Recovery (CDRRR — previously CIWMB) required additional investigation of the closure cap and refuse on the eastern edge of the landfill footprint. ' In March 2006, the County formally submitted the results of the investigation and a proposed plan to upgrade and extend the closure cap adjacent to the access road to the Local Enforcement ' Agency (LEA) and CDRRR. The closure cap would be extended using geo-composite clay liner (GCL) I In August 2006, CVRWQCB staff issued a violation for "insufficient groundwater monitoring" of the shallow aquifer on the western side of the landfill; however, a shallow aquifer does not exist on the western side of the landfill. This violation has not been rescinded. In October of 2006, the County proposed a Phase 2 investigation of the extent of closure cap, incorporating comments from the LEA and CDRRR staff received since February 2006. In December 2006, CVRWQCB staff issued a violation for VOCs in groundwater at monitoring well MW -5, and directed the County to perform evaluation monitoring. In mid-January 2007, the County submitted a revised Phase 2 plan to further define the edge of closure cap and refuse along the eastern footprint edge, incorporating further comments from CDRRR and CVRWQCB staff. In late January 2007, the County submitted a proposal to increase corrective action along the eastern edge of the landfill footprint in response to the violation received in December 2006. On March 9, 2007, CVRWQCB staff issued a second violation for the VOCs present in groundwater since 1991 at monitoring well MW -5. In March 2007, the County submitted an Evaluation Monitoring Program (EMP) work plan in response to the directive by RWQCB staff to further assess the nature and extent of potential off- site migration of landfill gas in the vadose zone, and VOCs and chloride in the shallow aquifer. The EMP included the installation of two permanent groundwater monitoring wells, and groundwater and vadose zone soil gas sampling at nine temporary borings in the shallow aquifer outside County property. On August 17, 2007, the County fully delineated the extent of refuse within County property, allowing design of the closure cap over the refuse not now provided with a closure cap. This investigation also indicated the possibility of refuse in the adjacent Caltrans property. Corral Hollow Sanitary Landfill 5 Department of Public Works/Solid Waste 3rd Quarter 2013 Groundwater Monitoring County of San Joaquin — October 15, 2013