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indicated by soil color variation in aerial photos. No other buildings are visible in the western half of Parcel 24 or in Parcels 3 and 4, exclusive of two (2) buildings on the western central portion of Parcel 3. By 1993, the location of the railroad spurs in Parcels 24, 3 and 4 can be seen in the aerial photos. No buildings are visible in the western half of Parcel 24, or in Parcels 3 and 4. In 1998, the western half of Parcel 24, and Parcels 3 and 4 were also vacant. In 2004, redevelopment of Parcel 3 was initiated (Wallace Kuhl, 2005). Included in this redevelopment was construction of a two-story commercial building, with associated parking and landscaping. During on-site grading on 16 July 2004, hydrocarbon odors were observed. The Agency entered into a Voluntary Cleanup Agreement (VCA) with DTSC (Appendix D) and costs recovery reimbursement with the Regional Board (Appendix E) and subsequent soil sampling identified total petroleum hydrocarbons as diesel (TPHd), at concentrations ranging from 13 to 13,000 milligrams per kilogram (mg/kg) and total petroleum hydrocarbons as oil (TPHo) from 14 to 1,200 mg/kg. Trace concentrations of volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) were identified. Polychlorinated biphenyl's (PCBs) were not identified in the soil samples. Metals of concern included lead and arsenic. Excavation of TPH contaminated soil was initiated on 23 July 2004. Excavation was performed with DTSC and California Water Quality Control Board — Central Valley Region (RWQCB) oversight. The "Excavation stopped along the western sidewall because further excavation in this direction would have threatened the structural integrity of the compacted engineered fill material (compacted prior to excavation activities). Excavation was ceased to the east because results of laboratory analysis of sidewall samples revealed low residual concentrations of diesel. Excavation was stopped to the north because of the property boundary and to the south because of extensive underground utilities present in the former Market Street," as described in the Wallace Kuhl, 2005 report (Appendix F). 1.4 SITE SOILS AND RAILROAD BALLAST Soil beneath the Site consists of fill and native soil. Fill, located at the surface, varies in thickness from zero (0) to seven (7) feet, consisting of predominantly brick fragments; crushed rock; silt; sandy silt; gravelly silt; and light to dark brown, fine to medium sand. Native soil consists predominantly of interbedded dark brown clay; brown clayey silt to clayey sand with 2- inch cobbles; brown silty clay; light to dark brown silt (including high permeability silts) and clayey silt; and medium to dark brown, fine to coarse sand. A dark green, fine to medium sand was encountered in the southwest corner of Parcel 3 at a depth of between ten (10) and 19 feet bgs, having a thickness of a "thin lens" to approximately three (3) feet (Appendix F). A former railroad right-of-way was present, arching from the northwest corner to the center of the southern boundary of Parcel 24, then continuing south through the center of Parcels 3 and 4. This is a portion of the rail line that connects to the north into the wast-west tracks located on/adjacent to the north side of Weber Avenue and to the south of the Stockton UPRR Project area. Two (2) rail lines were present in the right-of-way, the track from those rail lines remaining after the lines were "abandoned." The side-by-side rail lines were placed on approximately two (2) feet of railroad ballast. Beneath the eastern line, and beneath the railroad ballast, a drain system was installed to a Golden State Environmental, Inc. - 4 - Los Angeles, San Diego and Houston Revised Work Plan — Soil and GW Characterization July 2006