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Phelan Development Holly Master Plan - Buildings H & 1 15188.000.006 Geotechnical Exploration The test pit logs (Appendix A) present descriptions and graphically depict the subsurface conditions encountered.We used the field logs to develop the report logs in Appendix A. The logs depict subsurface conditions at the exploration locations for the date of exploration; however, subsurface conditions may vary with time. 2.2 GEOLOGY AND SEISMICITY 2.2.1 Geology We present the following discussion of site geology based on our field reconnaissance, subsurface exploration, and review of the CGS Geologic Map of the San Francisco-San Jose Quadrangle (Wagner, Bortugno, and McJunkin 1991). The site is located in the Great Valley geomorphic province. The Great Valley is an elongated, northwest-trending structural trough bound by the Coast Ranges on the west and the Sierra Nevada on the east. The Great Valley has been and is presently being filled with sediments primarily derived from the Sierra Nevada. Based on our review of the referenced geologic map shown on Figure 4, the subject site is underlain by Holocene-aged Alluvial Fan Deposits; just north of the site is a mapped contact with Pleistocene-aged deposits of the Dos Palos alluvium formation (Qdp) generally consisting of interbedded clay, silt, sand, and gravel. 2.2.1 Seismicity The site is located in an area of moderate seismicity. No known active faults cross the site and the property is not located within an Alquist-Priolo Earthquake Fault Zone; however, large (>Mw7) earthquakes have historically occurred in the Bay Area to the west and along the margins of the Central Valley and many earthquakes of low magnitude occur every year. The two nearest earthquake faults zoned as active by the State of California Geological Survey 2008 National Seismic Hazard Maps are the Great Valley fault, located approximately 5% miles west, and the Greenville fault, located approximately 141/2 miles west. The Great Valley fault is a blind thrust fault with no known surface expression; the postulated fault location was based on historical regional seismic activity and isolated subsurface information. Portions of the Great Valley fault are considered seismically active thrust faults; however, since the Great Valley fault segments are not known to extend to the ground surface, the State of California has not defined Earthquake Fault Zones around postulated traces. The Great Valley fault is considered capable of causing significant ground shaking at the site, but the recurrence interval is believed longer than for more distant, strike-slip faults. Recent studies suggest that this boundary fault may have been the cause of the Vacaville-Winters earthquake sequence of April 1892 (Eaton, 1986; Wong and Biggar, 1989; Moores and others, 1991). Other active faults capable of producing significant ground shaking at the site include the Mount Diablo thrust fault, 22 miles northwest; the Calaveras fault, 28 miles west; the Hayward fault, 32 miles southwest; and the San Andreas Fault, 51 miles southwest of the site. Any one of these faults could generate an earthquake capable of causing strong ground shaking at the subject site. ENGEO December 13, 2021 Expect Exceltence