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C CORNERSTONE <br />EARTH GROUP <br />1.6 ENVIRONMENTAL SERVICES <br />Cornerstone Earth Group also provided environmental services for this project, including Phase <br />1 and 2 site assessments; environmental findings and conclusions are provided under separate <br />covers. <br />SECTION 2: REGIONAL SETTING <br />2.1 REGIONAL SEISMICITY <br />The San Francisco Bay area is one of the most seismically active areas in the Country. While <br />seismologists cannot predict earthquake events, the U.S. Geological Survey's Working Group <br />on California Earthquake Probabilities (2003) estimates there is a 62 percent chance of at least <br />one magnitude 6.7 earthquake occurring in the Bay Area region between 2003 and 2032. As <br />seen with damage in San Francisco and Oakland due to the 1989 Loma Prieta earthquake that <br />was centered about 50 miles south, significant damage can occur at considerable distances. <br />Higher levels of shaking and damage would be expected for earthquakes occurring at closer <br />distances. <br />The faults considered capable of generating significant earthquakes are generally associated <br />with the well-defined areas of crustal movement, which trend northwesterly. The table below <br />presents the State-considered active faults within 25 kilometers of the site (CDMG, 1998). <br />Table 1: Approximate Fault Distances <br /> <br />Fault Name Distance <br />(miles) Distance <br />(kilometers) <br />Calaveras 3'/, 5.2 <br />Greenville 9 14.5 <br />Hayward (Total Length) 9'/: 15.2 <br />A regional fault map is presented as Figure 3, illustrating the relative distances of the site to <br />significant fault zones. <br />SECTION 3: SITE CONDITIONS <br />3.1 SURFACE DESCRIPTION <br />The rectangular-shaped 23.1-acre parcel is located just east of the existing Ironwood residential <br />development near the eastern end of Mohr Avenue in Pleasanton, California. The site is also <br />bounded by an existing quarry pit to the north, undeveloped land to the east, and City of <br />Pleasanton Utility Maintenance Facility to the south. <br />The parcel is currently undeveloped, with the exception of iwo temporary construction trailers <br />that are located at the south end of the site. A 15-foot wide gravel construction access road <br />Ponderosa Active Adult Community Page 3 <br />132-2-1 <br />