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Non-Water Release Corrective Action Plan Corral Hollow Sanitary Landfill • Since the landfill will be in a state of closure with no personnel onsite daily, it is assumed that a subsurface fire will begin around a single malfunctioning landfill gas extraction well and will be identified and controlled after spreading approximately 150-feet. It is also assumed that the fire will reach a depth of 20-feet and will be suppressed by excavation and soil burial. It is assumed that the fire and excavation would damage a single vertical landfill gas extraction wells. The cost for excavating and replacing waste, soil suppression, final cover placement, erosion control, and construction of the replacement landfill gas extraction well is estimated to be $373,634 (see Table F-2, Appendix F). 5.3.2 Wildfires Wildfires are discussed in Section 4.3.2. Due to the location of the CHSL within a moderate fire hazard severity zone, wildfires are a reasonably-foreseeable casual event. The BMP for moderate fire hazard severity is to assume that 25% of the combustible surface structures within a zone of 200-feet at or near the landfill cell boundary would be destroyed. It is anticipated that a wildfire would cause damage to the landfill gas extraction system well-heads and surface vegetation. The removal and replacement costs for the extraction wells and the re-seeding the landfill is estimated to be $79,274 (see Table F-3, Appendix F). 5.4 MITIGATION OF FLOOD-RELATED IMPACTS As discussed in Section 4.4, it is likely that a 500-year flooding event will impact the CHSL due the southern side slope being near the limits of the 100-year flood plain. Based on being in a "Zone X, shaded" flood zone, it is assumed that a 500-year flood would be an additional 1-foot in elevation above that of the 100-year flood. At a 5:1 (horizontal to vertical) side slope, this would result in an affected area of approximately 8,500 square feet. It is anticipated that flood impacts would require reconstruction of the final cover system and re-seeding the slopes in the impacted area and is estimated to cost$165,606 (see Table F-4,Appendix F). 6.0 ESTIMATED NON-WATER RELEASE MITIGATION COST ESTIMATE SUMMARY Damage associated with the design precipitation event, wildfires, subsurface fires, and flooding does appear to be reasonably foreseeable, and costs to mitigate hypothetical damage from these events were estimated to range between $79,274 and $373,634 (see Table F-5, Appendix F). 17 Geo-Logic ASSOCIATES