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site in 100 years. The probability of a magnitude 6 or larger earthquake within 50 km of the site in 100 years is 0.05% to 3%. Although the Foothills fault system represents the closest active faults to the site, an earthquake with magnitude 5 or larger located within 30 km or magnitude 6 or larger located within 50 km is not likely to occur in 100 years. Therefore, the Foothills fault system does not impact the MPE at the site. Central Valley Coast RangeFault The Coast Range/Central Valley Thrust (CRCV) fault zone (also called the Coast Range Sierran Block Boundary Zone) is characterized by thrust faulting due to crustal shortening in the direction normal to the San Andreas fault. This shortening accommodates some of the convergence between the Pacific and North American plates in this region. The thrust fault generally does not reach the surface and is considered a "blind thrust" fault. The CRCV extends about 600 km along the western edge of the Central Valley in central and Northern California (Wong, 1988), but the faulting is discontinuous. Most of the segment lengths are 5 to 20 km with a maximum segment length of about 35 km (Geomatrix,1992). The O'neil and San Joaquin faults (Jennings, 1994) can be considered part of the CRCV system. There have been several earthquakes over magnitude 6 that have occurred along the CRCV fault zone. The 1983 Coalinga earthquake (M=6.4) and the 1985 Kettleman Hills earthquake (M=6.1) occurred on the CRCV. The 1892 Winters -Vacaville earthquake (M=6.4) may also have occurred on the CRCV, but its location is not well constrained (Toppozada, Real, and Parke, 1981). A recent study by Unruh (written communication, 1998) suggests that the CRCV is not present in the Delta region. According to this study, the CRCV begins to decrease in activity north of the San Luis Reservoir and south of Lake Berryessa. The Foothills Landfill site is located northeast of the San Luis Reservoir in the proposed region of decreased activity rate. Although the site is located in the middle of this zone, the CRCV is assumed to exist near the site based on the uncertainty in the location of the CRCV fault system.