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Site Background Information RALPH'S SQUARE 2122 South Airport Way, Stockton, California The site is bounded on the west by Airport Way, on the south and east by a vacant lot, and on the south by a commercial property. A single structure housing a mini -mart presently occupies the eastern portion of the site. REGIONAL GEOLOGIC SETTING The site is situated within the southern portion of the Great Valley Geomorphic Province of California, a large, elongate, northwest trending, asymmetric structural trough; the northern and southern portions of the Province have been designated the Sacramento and San Joaquin Valleys, respectively. The Province is bordered by the Coast Ranges to the west, the Klamath Mountains and Cascade Range to the north, and the Sierra Nevada to the east. The Great Valley has been filled with sediments derived from both marine and continental sources. Thickness of the sedimentary fill ranges from thin veneers along the valley edges to more than 20,000 feet in the south central portion of the valley. The sedimentary formations range in age from Jurassic to Recent, with the older deposits being primarily marine in origin and the younger deposits being primarily continental. Continental -derived sediments were primarily deposited in lacustrine, fluvial, and alluvial environments with sediment sources being the mountain ranges surrounding the valley (Olmsted and Davis, 1961); the site itself is located on unconsolidated and semi -consolidated alluvium, lake, playa and terrace deposits of Quaternary age (California Division of Mines and Geology, 1977). Rocks composing the basement complex of the Province have not been completely defined but are believed to be metamorphic and igneous in origin. Based on a General Soil Map from the San Joaquin County Soil Survey, published by the United States Department of Agriculture Soil Conservation Service in 1992, the site area is described as within the Jacktone-Hollenbeck-Stockton (JHS) association. The JHS soils are located on basin rims and within basins, and generally consist of somewhat poorly drained and moderately well drained, fine -textured soils that are moderately deep and deep to a cemented hardpan. The JHS soils generally formed in alluvium from mixed rock sources. The Modesto, Riverbank and Turlock Lake Formations and overlying Recent alluvium are the principal sources of domestic ground water in the 13,500 -square mile San Joaquin Valley Ground Water Basin (Basin 5-22). SITE HYDROGEOLOGIC CONDITIONS The closest surface water feature to the site is Duck Creek, located approximately 1,000 feet south of the site. Water from creek drains into the San Joaquin River Deep Water Channel and is primarily Advanced GeoEnvlronmental, Inc.