Appendix E - Geology and Soils Geotechnical Supporting Information COMBINED

LESTER-SHRINER PROPERTY 132-8-2 Page 4 unnamed Cretaceous sandstone (Kp). Locally overlying these geologic formations within low lying areas and the valley bottom are Quaternary Alluvium (Qa). The following unit descriptions are from Dibblee and Minch, (2005). The Tmc unit is described as “Clay shale and siltstone, gray, vaguely to moderately bedded, includes fine grained sandy facies.” The Clairmont Shale (Tm) is described as “Siliceous shale, white-weathered, thin bedded, platy, porcallenous to cherty, brittle.” The Tms unit is described as “Sobrante Sandstone: local lens at base of the Tmc Clairmont Shale member which is similar to the Briones Sandstone.” 2.2 REGIONAL SEISMICITY The San Francisco Bay area is one of the most seismically active areas in the Country. While seismologists cannot predict earthquake events, the U.S. Geological Survey’s Working Group on California Earthquake Probabilities 2007 estimates there is a 63 percent chance of at least one magnitude 6.7 or greater earthquake occurring in the Bay Area region between 2007 and 2036. As seen with damage in San Francisco and Oakland due to the 1989 Loma Prieta earthquake that was centered about 50 miles south of San Francisco, significant damage can occur at considerable distances. Higher levels of shaking and damage would be expected for earthquakes occurring at closer distances. The two major active strike-slip faults in the study area are the Hayward Fault, located west of the site, and the Calaveras Fault, located approximately 3,800 feet east of the site. Other significant faults in the study area include the Pleasanton Fault and the Verona Fault. These faults, as well as several other faults that juxtapose Cretaceous and Tertiary age geologic units in the East Bay Hills, appear to have a compressional component of slip. Neither of these faults is included in an Alquist-Priolo Earthquake Fault Zone Map for the Dublin Quadrangle (CDMG, 1982) More locally, the Dublin Fault trends southerly through the hills located north of Highway 580 but the map by Dibblee (1980) and Dibblee and Minch (2005) show it as terminating within Tertiary geologic units located just on the north side of Hwy 580. Our review of historical aerial photography (see references) confirms a general alignment of drainages and topographic saddles along the mapped surface trace of this fault. Crane (1988) shows an unnamed “detachment fault” projecting through the far southwest corner of the site from the southeast but he depicts it terminated near (south of) the south property line. The earlier site investigation on the adjacent Lester property mistakenly projected this detachment fault through the site with a northwesterly trend. This fault truncates some but not all of the Tertiary age units southeast of the site but does not offset and Quaternary age geologic units and therefore is a Pre-Quaternary fault and not active. During our recent updated site reconnaissance, we noted a zone of deformation within the Tertiary geologic units located just east of the Crane fault projection within the creek channel. This zone of deformation may represent a subsidiary fault. The faults considered capable of generating significant earthquakes are generally associated with the well-defined areas of crustal movement, which trend northwesterly. The table below presents the State-considered active faults within 25 kilometers of the site. Ii! CORNERSTONE EARTH GROUP