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1 2.0 Site Description F1 1 t Ll Descriptions of the former and current uses of the site property and the environmental setting are provided in the following subsections. A brief narrative of site investigation activities conducted to date is also presented. 2.1 Site Use The site property consists of two commercial buildings that, in aggregate, are approximately 4,310 square feet, and about 2,650 square feet of paved area. There are two active businesses on the property: a transmission repair shop and a drapery delivery business. The site was formerly used as a retail service station with gasoline dispensing activities ceasing sometime in the 1950s according to information provided by the San Joaquin County Public Health Services (SJCPHS). It is believed that two gasoline USTs and possibly one waste oil UST were present at the site (Figure 2). SanbornTM Maps for the property depict a UST present in 1950, but not present in 1917 or 1972. It is presumed that one gasoline UST and the waste oil UST were removed during the 1950s; however, little information is available regarding the extent of removal, findings, or vadose zone residue. In February 1996, one 550 -gallon UST was removed from the site by Thorpe Oil of Lodi, California (Shaw, 2006a). 2.2 Geology and Hydrogeology This section provides an overview of the local geology and hydrogeology at the site. Most of the soil lithology information described herein was based on observations previously gathered from soil boring and well installation at the site. 2.2.1 Geology Lithologic features at the site are best represented by an approximate 30- to 40 -foot -thick layer of clayey silt overlaying interbedded layers of poorly to well graded sand, silty sand, silty clay, and clayey silt. A representation of the site stratigraphy, based upon lithologic descriptions from borings DP -9, MW -1R -D, MW -6, VW -1, VW -2, VW -3, and VW -4, is presented on Figure 3. Locations of the borings/wells are shown on Figure 4. A more detailed description of the varying lithologic layers and approximate depths is as follows: • 0 to 30 feet — Clayey silt to silty clay with discontinuous lenses, less than 5 feet thick, of poorly to well graded sand existing at depths of 15 to 18 feet below ground surface (bgs). 1 FS_OnsdePetroleum Hydrocarbon Remediation.doc 2-1 Shaw Environmental, Inc.