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' Corral Hollow LFG System Audit and Upgrade Report MrqQV4ffVMra�_01111111 extraction wells to maintain minimum vacuum at all points while reducing flows at those wells ' with poor methane quality, and increasing vacuum and flow rate wells with higher methane content. ' Appendix B provides an Operational Procedures Document with details on the County's current program and recommended future operation, monitoring and maintenance provisions to be implemented to ensure to the extent possible that LFG extraction is continuously optimized. ' Repairs or Upgrades to GCCS System Piping. Based on SCS' Operations Review, it appears the GCCS collection piping system is not experiencing any restriction issues, and that ' the LFG extraction wells are getting ample vacuum. Based on our flow testing, we saw no evidence that main header velocities exceed this value. Thus, there is no need for any major repairs or significant upgrades to the existing piping network at this time. ' Some minor maintenance items were noted during our field inspection. We recommend the following: • Replacement of test ports on the extraction wellheads to improve monitoring capabilities of each LFG Well. These upgrades should be performed for in-fill extraction wells (EW- ' 1 through EW-34) at a minimum. • Add soil cover around well EW-21, to prevent the potential of air intrusion between the annular spacing of the well and the adjacent soil cover ' Repairs or Upgrades to Gas Condensate Collection and Handling Systems. The condensate management system is properly functioning and no repairs or upgrades are necessary at this time. This conclusion is based on results of our operations review (Appendix A), which ' showed that vacuum is available at accessible locations along the LFG header. Given that this system utilizes mechanical components (i.e., condensate pumps, ' regulators/controllers, etc.), all affiliated system components will require periodic inspection and maintenance in order to maintain steady, effective operation. Details on ongoing condensate system maintenance to ensure LFG extraction is continuously optimized are provided in ' Appendix B, Operational Procedures Document. Installation of Additional In-fill or Vadose Zone Extraction Wells. Our review of GCCS extraction well spacing and design indicates a reasonably comprehensive system is already in place. Therefore,the installation of additional wells is not recommended at this time. ' The installation and subsequent activation of extraction wells EW-40 through EW-42, which are located adjacent to the latest 1.6-acre closure area and collect LFG from the waste mass, were found to exhibit methane concentrations in the range of 0 to 4% v/v in October 2013. The most ' recent extraction wells within the latest closure area (EW-48 and EW-49) monitored during the October 2013 event were found to have methane concentrations of 0 and 0.1% v/v, respectively, indicating that the closure and ongoing GCCS operation have proven effective for source control. 1 1 December 2013