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In January 2008, Water Board staff approved the conceptual design for the method of closure of refuse outside the existing closure cap. This design included GCL overlain by two feet of soil. In December 2008, five new LFG extraction wells were installed, two more than originally proposed. The additional wells were located to control LFG impact to groundwater near MW-5. The vacuum at these wells was set at-0.1 in.wc. Vacuum applied to these wells has been gradually increased. Since October 2009, the vacuum of the wells has been set to -0.3 in. we. The concentration of methane from the wells remains below 2%. Continuing to collect low-methane gas from these wells reduces the methane content of the LFG reaching the flare station, inhibiting the ability of the flare to maintain proper temperature. On February 22, 2011, a meeting in a meeting at RWQCB offices Caltrans staff indicated willingness to participate with the closure of the landfill. Issuing a Section 13267 Order was discussed. On July 7, 2011,the County and Caltrans both received a Section 13267 Order to extend the closure cap over uncapped refuse. Task 1 of the order required that the Final Cover Expansion Design be submitted by October 10, 2011. The order also required the County to evaluate the extent of the groundwater release and to design corrective actions with the installation of three permanent groundwater monitoring wells. On August 30, 2011, the County and Caltrans signed a Memorandum of Understanding agreeing to allow the County access to Caltrans property to install groundwater monitoring wells required in the Order, and that the closure cap would be installed over both properties in a single project. On October 6, 2011, the County submitted the Final Cover Expansion Design, executing the design approved in January 2008,but providing two feet of soil over the GCL. A letter from RWQCB staff dated November 1, 2011 stated that Compliance and Enforcement staff concured that the plan satisfied the requirements of Task 1 of the Order. On October 10, 2011, the County drilled three wells in Caltrans property to assess the extent release of the plume as required by RWQCB order. VOC's related to LFG were discovered at each well. The extent of release could not be reliably assessed with these wells. To document this work, a"Well Completion Report"was submitted December 14, 2011, and an EMP report was submitted January 31, 2012. In February 2012 a second set of three wells were installed and sampled, again in Caltrans property. The results from these analyses allow confident estimate of the extent of release. County staff submitted a Well Completion Report on May 7, 2012. On March 15, 2012, the County and Caltrans received a Notice of Violation due to failure to submit a cover design that meets the performance standard of Title 27 for failure to submit an acceptable closure design,thereby rescinding the approval granted in 2008. • Corral Hollow Sanitary Landfill 5 Department of Public Works/Solid Waste 4"Quarter and Annual 2012 Groundwater Monitoring County of San Joaquin—January 15,2013