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1 • BACKGROUND INFORMATION <br /> Proposed ELDORADO APARTMENTS <br />' 2450 South El Dorado Street, Stockton, California <br />' REGIONAL GEOLOGIC SETTING <br /> The property is situated within the Great Valley Geomorphic Province of California, a large, <br /> elongate, northwest trending, asymmetric structural trough The Great Valley Province has been <br /> filled with thick sequences of sediment ranging in age from Jurassic to Recent,creating a nearly flat- <br /> lying alluvial plain,extending from the Tehachapi Mountains in the south to the Klamath Mountains <br />' in the north The western and eastern boundaries of this province are comprised of the California <br /> Coast Range and the Sierra Nevada, respectively Rocks composing the basement complex of the <br />' province have not been completely defined but are believed to be metamorphic and igneous in origin <br /> The northern and southern portions of the Great Valley Province have been designated the <br /> Sacramento and San Joaquin Valleys, respectively <br />' Based on the General Soil Map from the San Joaquin County Soil Survey,published by the United <br /> States Department of Agriculture Soil Conservation Service in 1992, the site area is within the <br /> Jackson-Hallenbeck-Stockton (JHS) association The JHS soils are located within basins, and <br /> generally consist of moderate to poorly drained fine textured soils The soils are generally derived <br /> from both manne and non-manne sediment, and are generally formed in alluvium derived from <br /> liemixed rock sources <br /> The Modesto,Riverbank, Turlock Lake Formations and overlying recent alluvium are the principal <br /> I sources of domestic groundwaterin the 13,500-square-mile San Joaquin Valley Ground Water Basin <br /> (Basin 5-22) This basin is drained primarily by the San Joaquin River The nearest surface water <br /> feature in the vicinity of the property is the Old River,approximately 2 5 miles west of the property <br /> PREVIOUS SITE ASSESSMENT <br /> Previous site assessments on thero ert include <br /> P P Y <br /> - February 2002 - A geotechnical investigation was conducted at the site by Raney <br /> Geotechnical Inc(RGI) During the course of the investigation, soil samples collected from <br /> two borings (B4 and B5)were noted as having a"gasoline odor" <br /> May 2002 - Five soil borings (B-1 through B-5) were advanced at the site by Construction <br /> Testing & Engineering, Inc (CTE) to determine the nature and extent of soil possibly <br /> impacted by petroleum hydrocarbons Soil samples collected from three of the five soil <br /> borings (B-1, B-2 and B-5) contained concentrations of total petroleum hydrocarbons <br /> quantified as gasoline (TPH-g), diesel (TPH-d) and/or motor oil (TPH-mo) The highest <br /> detected concentrations were found in soil samples collected from borings B-2 and B-5 at <br /> . depths of 10 and 15 feet below surface grade (bsg), respectively, however, additional <br /> laboratory analysis of the 15-foot sample from boring B-5 did not detect volatile organic <br />