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Osvaldo Cordero Forward, Inc. March 3, 2025 alternative final cover system has been constructed for the northern slopes of the northern portion of the landfill and is seeded with native grasses to minimize erosion. 2.2 Potential Vadose Zone Impacts The Forward Landfill site is in an area where the vadose zone is typically about 50 feet thick. LFG movement is likely the main way the vadose zone and subsequently groundwater may be impacted by a WMU. 2.3 Potential Groundwater Impacts The unlined sections of the landfill have the highest potential for additional groundwater impacts. If waste constituents reach groundwater, the natural groundwater flow gradients and the dispersive properties of the specific contaminants would determine how groundwater impacts will migrate from the site. Since groundwater typically flows in a northeasterly direction in accordance with the regional gradient, it is anticipated that potential groundwater impacts would be concentrated in the upper groundwater zone of the Victor Formation and would be detected by the existing DMP wells. 3 Anticipated Corrective Actions The following sections describe mitigation response measures for the purposes of establishing financial assurance for future corrective actions. 3.1 Surface Water Since creek waters are routed to not encounter wastes, and run-on and run-off will be controlled, the worst-case surface water release scenario involves transport of minor volumes of landfill constituents in run-off to Littlejohns Creek. However, considering that wastes will be covered by daily and interim cover soils, and since run-off will be controlled in a drainage system designed for the 1,000-year storm event and will be monitored as part of both WDR and NPDES permits, the risk and volume of impacted waterthat could potentially be released from the site is expected to be small. If run-off from the WMU impacts creek water, a program would be implemented to investigate how such impacts occur and to identify engineering measures (e.g., flow controls including cover soils or drains)to eliminate the source of impacts. The existing Forward Landfill operations financial reserve already provides funding for maintenance of the cover and drainage control. 3.2 Vadose Zone A network of soil-pore gas monitoring probes was constructed around the perimeter of the WMUs and are regularly monitored to verify the adequacy of the gas control measures. If methane concentrations exceed the regulatory limit(5%), then the existing GCCS well system of 249 gas extraction wells will be optimized or expanded to minimize the potential for gas migration and impacts to the vadose zone and groundwater, and a liner will be installed to minimize the potential for leachate to migrate to the vadose zone. Liner construction would be completed in accordance with a construction quality assurance plan to minimize liner defects. www.arcadis.com 5/8 FL Rev Financial Assurance 20250303