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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 4 October 2024 4.1 Seismically-Induced Impacts Seismically-induced impacts are those that result from a large earthquake that occurs within a distance of engineering significance to the site, and could theoretically include one or a combination of the following: ground rupture, slope failure, dynamic settlement, liquefaction, seiche, or tsunami. To determine which, if any, of these seismically-induced phenomena could be reasonably foreseen to affect the NCRCSL, a site-specific seismic hazard assessment was conducted for this report to identify faults within a 100-mile radius of the site to estimate the peak ground acceleration associated with the Maximum Credible Earthquake (MCE) as required by CalRecycle’s BMPs. The site is in an active seismic area of the California Central Valley near the Sierra Nevada Foothills. The site is situated between the Sierra Nevada foothill faults and the Bay Area faults (see Figure 3). The Stockton Fault is mapped approximately 10 km south of the landfill site (Figure 3). However, the fault has no evidence of surface rupture and its position has only been estimated from oil well data. Subsurface data indicates that no appreciable movement has occurred on this fault for greater than 3 million years (County of San Joaquin Public Health and Safety, 1992). Accordingly, the seismic hazard of this fault will not cause a reasonably foreseeable impact at this site. The western edge of the Foothills Fault System is located about 30 km east of the NCRCSL site (Figure 3). The Jennings (2010) state fault map shows these faults as being pre-Quaternary except for a few small isolated sub-segments (3 to 7 km long) that were thought to be active in the Pleistocene. Analysis of the Foothills Fault System by Lettis Associates (1994) found that parts of the Foothills faults are active but that they have very low activity rates. The small segments of the Foothills faulting along the east edge of the Sierran Block have slip-rates of about 0.001 to 0.03 mm/yr resulting in recurrence intervals of 20,000 years for earthquakes with magnitude greater than 6 (for the individual segments). Abrahamson, (2007), Cao (2003), and the USGS website do not consider the Foothill faults to be active. Accordingly, based on the activity rate of the Foothills faults, these faults will not be considered to contribute to the MCE ground motions, and therefore, do not constitute a reasonably foreseeable impact at the NCRCSL. Based on a deterministic approach, potential significant seismic events that could be produced by the MCE events within the region are presented in Table 1. The MCE is defined as the largest anticipated magnitude earthquake the fault is capable of producing based on the known tectonic framework. Site-specific seismic parameters included are the distances to the nearest, active causative faults, MCE magnitudes, and expected peak ground accelerations based on attenuation relationships for sites with similar soil conditions. A list of all known active faults with 100 miles of the site is presented in Appendix A based on USGS, 2008 and USGS, 2019. The Great Valley 6-7 Fault is considered to have the most significant effect on the site from a design standpoint (Table 1). From a deterministic approach (which calculates the maximum site