COMPLIANCE INFO_1997-2002 - Laserfiche WebLink

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4.0 REGIONAL GEOTECHNICAL /1 The subject site is located in the San Joaquin River region of the Great Central Valley geomorphic province, a region characterized by a 50 -mile wide and a 400 -mile long sediment -filled basin drained by the Sacramento River at the north half and the San Joaquin River to the south, and interior drainages at the southern edge of the basin. The site vicinity is situated on dissected Pleistocene Age stream deposits of the San Joaquin River Valley. These deposits consist primarily of sand with some gravel, silt and clay (CDMG,1966). Review of the -United Stated Geologic Survey (USGS) 7.54minute topographic maps for the Tracy and Union City quadrangles indicate that the site is at an elevation of approximately 22 feet above mean sea level (msl). The topography in the vicinity of the subject site is generally flat, sloping gently north. Site drainage is complex, but generally flows north towards the San Joaquin River. The closest water bodies include unnamed aqueducts in the immediate site vicinity. The closest river is the Old River, located approximately 23.3 miles to the north. :► / 1 : � � a7c�� Review of local groundwater records indicate that the site is underlain by two separate groundwater zones. The upper groundwater zone which was encountered during the field exploration at a depth of 9.5 to 11 feet below the existing ground surface is referred to as the Upper Telary Aquifer. This aquifer is apparently not used for either for drinking or agricultural purposes. The apparent gradient of the shallow groundwater is in a northerly direction. The second groundwater zone is referred to as the Lower Tebuy Aquifer. The upper surface of this lower aquifer, according to records, is at a depth of approximately 250 feet below ground surface. This aquifer is used for both domestic and agricultural purposes. 4.3 SEISMICITY The site is situated, as is all of Northem California, in a seismically active area. The closest known active fault is the Midway Fault which is located approximately 4.8 miles southwesterly of the site. An aerial summary of faults that may adversely affect the site is presented below. IN 40007-095-01 ftp—w197-06j—\a-n-.d0r 4-1