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Non-Water Release Corrective Action Plan Corral Hollow Sanitary Landfill • A search of historic earthquake events by the program EQSEARCH (Blake, 2000) indicates that the largest calculated historic peak ground acceleration (PGA) at the site in the last 200+ years was 0.11g from a Magnitude 8.25 earthquake approximately 56.9 miles from the site in 1906 (San Francisco EQ). That earthquake was also the largest recorded earthquake magnitude within 100 miles of the site. For purposes of this evaluation, seismic impacts to the landfill will use a PGA of 0.568. The results of the seismic analysis are presented in Appendix A and were used to determine the potential for seismically-induced impacts in the following sections. 4.1.1 Impacts from Ground Rupture Seismically-induced ground rupture occurs when a fault moves during an earthquake. The nearest active fault is at least 0.7 miles from the site at a depth of 7 km. Accordingly, there is no reasonable expectation that ground rupture could occur at the landfill site because of the distance and depth of the nearest active fault. 4.1.2 Impacts from Seiches • A seiche is a seismically-induced wave on a restricted water body such as a bay, harbor, lagoon, or lake. The nearest large body of water (Bethany Reservoir) is approximately 10 miles northwest of the site and is at the same approximate elevation as the landfill. At this distance and configuration, an impact from a seiche is extremely unlikely, and outside the definition of a reasonably foreseeable impact. 4.1.3 Impacts from Tsunamis A tsunami is an oceanic wave or series of waves produced by an undersea or near-shore earthquake, landslide, or volcanic eruption. The CHSL is located approximately 35 miles from the Pacific Ocean (San Francisco Bay) at an elevation of 250 feet above mean sea level. As a result, impact from a tsunami is considered extremely unlikely, and outside the definition of a reasonably foreseeable impact. 4.1.4 Impacts from Liquefaction and Associated Dynamic Settlement Liquefaction and dynamic settlement of soils can be caused by strong vibratory motions that occur during an earthquake resulting in a total loss of shear strength in the affected soil layer, • thereby causing the soil to flow as a liquid, sometimes causing excessive settlement and sand boils at the ground surface. Both research and historical data indicate that loose, saturated, Geo-Logic ASS 0C I A T E S