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Non-Water Release Corrective Action Plan North County Recycling Center and Sanitary Landfill AU24.1294.00 | Non-Water Release Corrective Action Plan Update 11 October 2024 same with only a few values that are 0.01 of an inch different. Since the difference is so slight, it will not be a significant change is the run-off amounts calculated. As such, the analyses presented in the original 2014 NWRCAP remains valid. This analysis is presented below. CalRecycle’s BMP’s indicate that 1,000-year, 24-hour storm events have occurred in California, and solid waste landfills that are Class II landfills are now required to be designed to withstand the 1,000-year, 24-hour storm event. Although the NCRCSL is a Class III landfill, CalRecycle’s proposed BMP for precipitation, as a causal event, is the 1,000-year, 24-hour storm event. From the NOAA Atlas 14 Precipitation Maps, the 1,000-year, 24-hour storm event is 5.17 inches (2019), 5.18 inches (2024) of rainfall; which is an additional 1.31 inches (2019), or 1.32 inches (2024) of rainfall over the 100-year, 24-hour storm event. This amounts to an increase in the depth of precipitation of 34%. Previous stormwater analyses at the site have used the rational method to calculate 100-year stormwater run-off for use in sizing the drainage system facilities (Preliminary Closure and Postclosure Maintenance Plan (PCPCMP) prepared by Shaw Environmental, Inc., January 7, 2010). This analysis used the rational method from the PCPCMP as a template to calculate stormwater runoff for the 1000-year event. It has been calculated that the top-deck berm, side-slope bench, and perimeter ditches have capacity to convey the run-off generated from a 1,000-year storm (see Appendix C). However, it has been calculated that seven locations of the down-drain pipes are insufficient in capacity. It is assumed that because the bench channels have sufficient capacity, additional run-off not able to be conveyed within the downdrains would overflow onto the bench. It is anticipated that localized erosion would be realized on the bench areas due to the channel overtopping. Therefore, erosion impacts to the channels are a reasonably foreseeable casual event and, therefore, mitigation measures were evaluated as part of this NWRCAP. 4.3 Fire Impacts Fires at landfills are either subsurface fires or surface fires (wildfires). The potential for these fires to occur are dependent on the location of the landfill relative to wildfires, management of waste that is still smoldering, accidents or arson, and availability of vegetation for fuel for a fire. 4.3.1 Subsurface Fires Subsurface landfill fires are most commonly caused by the intrusion of oxygen into the refuse prism from overdrawing of the gas collection system, which increases aerobic decomposition, resulting in increased temperatures. This can cause ignition of the organic material within the refuse fill. This underground combustion can cause damage to the landfill gas collection systems and potentially the intermediate and final cover. To assess if a subsurface fire exists, one must have visual confirmation or other conditions present. Generally a subsurface fire can be confirmed by: