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Draft Supplemental Environmental Impact Report Page IV.E-11 Forward Inc.Landfill 2014 Expansion Project The Forward Landfill has standard operating procedures in place to address subsurface landfill oxidation events. If physical indications of a subsurface oxidation event are noted, the environmental manager and landfill manager are immediately notified. An initial investigation is performed and a physical inspection conducted that includes visual observation, infrared thermometer surveys, and measurements at nearby landfill gas wells. The data is then analyzed and a course of action is developed. The actions include removing oxygen from the subsurface oxidation area by shutting down wells that may have caused the subsurface oxidation, shutting down wells in the surrounding area, capping or repairing any items that may have contributed to the oxygen intrusion, and replacing cover materials where necessary. Following the corrections and repairs, the subsurface oxidation area is monitored until the indicators of subsurface oxidation are no longer noted. The Forward Landfill had one subsurface oxidization event in 2007 and six in 2008. In • consultation with representatives of Cal Recycle and the San Joaquin County Health Department--Local Enforcement Agency, Forward Landfill made improvements to its landfill gas collection system and placed additional intermediate cover in the areas that had experienced these events. Forward Landfill has not had any subsurface oxidization events since the improvements were implemented and the consent decree (2:11-cv-00590 EFB) specifying the LFG Collection System improvements has been completed and terminated. (Lewis, pers. com). The subsurface oxidation events in 2007 and 2008 did not occur because of too much landfill gas or uncontrolled landfill gas, they occurred for a completely different reason;in fact, for almost the opposite reason.In certain areas of the landfill that either had low gas production or were very near to the surface or to the edge of waste (landfill perimeter), putting vacuum on the refuse to control emissions and migration can also draw in excess air. It is a delicate balance to try to place proper vacuum (pull hard enough) to meet regularly requirements while preventing air intrusion. Some air intrusion is inevitable on all landfill gas systems, and the situation is more of an issue in the low production areas (where the amount of available gas is low, so it is easy to over pull) or perimeter areas where the source of air is close by and thus affected by the system vacuum. s.. When air is pulled into the landfill gas system(and into the refuse prism), the oxygen can react under conditions of heat and in the presence of combustible material (certain wastes) and start surface oxidation events as occurred in 2007 and 2008 at Forward. Every landfill with a landfill gas system will ultimately exhibit subsurface oxidation events over its history, and every site is different, so the conditions that cause these events are highly variable from site to site. The typical solution to preventing or extinguishing a subsurface oxidation event is to turn off or turn down gas collection in the affected area (stop pulling in air/oxygen). However, doing this is contrary to the regulatory requirements to control surface emissions and migration of landfill gas. As such, subsurface oxidation is not a problem of gas accumulation, rather it is an issue with not enough gas in a specific area resulting in an excess of air being pulled into the system. During the 2007 and 2008, all required landfill gas monitoring was being conducted for both the landfill gas wells as well as the landfill surface.It is this monitoring that detected the subsurface oxidation events, and triggered additional monitoring beyond the regulatory requirements. It was also this monitoring that was used to gauge the progress of corrective actions conducted to 4 reduce or eliminate this problem.More monitoring would not have solved or avoided this problem.The problem was driven by the need to control surface emissions and gas migration, and it took an extended period of time to get to the right balance of adequate gas collection while avoiding air intrusion. The site ultimately solved this problem through a combination of i0v actions,including better cover practices beyond industry standard (to prevent air intrusion through the surface), repairs and upgrades to landfill gas wells (to prevent air being pulled in