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Project No. 034-98081 Page No. 2 to the U.S. Geological Survey, 7.5 minute Stockton West, California topographic quadrangle map, the area of the subject site is relatively flat with an-approximate elevation of 15 feet above mean sea level. ' The subject site is currently occupied by a railroad construction contractor, H&H Engineering ' Construction. Two office/shop buildings and associated asphaltic-concrete pavements are located on the t i site(see Site Map, Figure 2). r 3.0 GEOLOGY/HYDROLOGY k The subject site is located within the northern San Joaquin'Valley portion of the Great Valley Geomorphic Province. The Great Valley is bordered to the north by the Cascade and Klamath Ranges, the west b the Coast Ranges, the east b the Sierra Nevada, and the south by the Transverse Ranges. Y g Y g Formation of the valley occurred by tectonic shifting of the Sierra Block; the western side dropping to form the valley and the eastern side being uplifted to form the Sierra Nevada. The valleyis characterized h + by a thick heterogeneous sequence of sediments derived from erosion of the adjacent Sierra Nevada to the east and the Coast Ranges to the west. The depth of the sediments vary from a thin veneer at the edges of the valley to depths in excess of 50,000 feet at the Valley structural axis. The surficial deposits in the area of the subject site are mapped as Quaternary alluvium"of the Modesto t Formation. The subsurface conditions encountered on the subject site are described in Section 5.0 of this I report. According to Groundwater Elevation Maps prepared by the San Joaquin County Flood Control and Water Conservation District, the depth to groundwater below the subject site is approximately 40 feet C below ground surface (bgs), with a regional gradient toward the east. We contacted officials with the 1 San Joaquin County Flood Control District to determine if specific groundwater depth information is i available for the area of the subject site. According to the officials contacted, groundwater depths ranging from about 30 to 60 feet were measured within about a anile of the site in the fall of 1997, and that based on the groundwater elevation contours developed by the District, groundwater would be � expected at an approximate depth of 40 feet bgs on the subject site. During Krazan's March, 1998 l i} groundwater sampling at the subject site, groundwater was encountered at a depth of approximately 42 j feet bgs. KRAZAN& ASSOCIATES,INC. ` Offices Serving the Western United States 3498081.WP