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Mr.Aragon November 21, 2008 Page 2 of 9 environmental controls employed to characterize a small area (93 feet by 22 feet) at the southeastern portion of the Site where the SPCC Containment Structure is currently being constructed. Additionally, this Report provides a delineation of the as-built excavation area, and the procedures necessary to complete the excavation/characterization of this material. 1.0 BACKGROUND The Site is located at 502 E. Grant Line Road, in Tracy, California. The Site occupies approximately 5.22 acres of property and is bound to the north by the existing PG&E substation which supplies electricity to a majority of the Tracy area; to the south by Hines Field, a vacant lot; to the east by a recently constructed industrial park; and to the west by railroad tracks owned by Southern Pacific (Figures 1 and 2). There are also residential properties located southwest of the Site just beyond the Southern Pacific Railroad right-of-way. The Site is currently owned by PG&E and is used as a Service Center and electrical substation. A review of historical records indicates that, from 1927 until 1930, an oil gas plant was operated at the Site. Natural gas was made available in the Tracy area in 1930, which was the reason for the abandonment of the MGP. Based on the description of the Site in the Preliminary Assessment conducted by PG&E in 1986, the plant equipment was retired in July 1930 and between 1930 and 1932 the plant was decommissioned. Equipment, including boilers and purifiers were dismantled and sent to other operational PG&E facilities. In 1934, the MGP was abandoned and according to records, the remainder of the plant was removed shortly thereafter. Since 1958, the Site has been owned and operated entirely by PG&E. Prior to 1958, portions of the Site were owned by others including the Tracy Gas Company, the Sierra & San Francisco Power Company, and Berverdor Incorporated. The SPCC Containment Structure will be constructed in an area of the Tracy Service Center that had potentially been impacted by former MGP operations. As such, PG&E contracted with Parsons to oversee the excavation work and to identify potentially impacted soil. At the time of the preparation of this Report, PG&E has begun construction on the SPCC Containment Structure in the southeastern portion of the Site near the existing sand and gravel storage area. When finished, the Structure will consist of a concrete containment that has a drain that runs down the middle of the Structure to the southern end where it empties into a sump. This Structure will be used to prevent the spill or leakage of oil-filled equipment (i.e., transformers) to surface water or other environmental media. 2.0 EXCAVATION ACTIVITIES In the period from October 20 through October 28, 2008, PSC conducted excavation activities for construction of the SPCC Containment Structure. The excavation is an area approximately 93 feet by 22 feet, the location of which is provided in the as built drawing (Figure 3). Excavation depths varied from two to four feet below ground surface (bgs) with an average excavation depth of approximately two and a half feet bgs. Originally, it was intended that the northernmost portion of the excavation extended to two feet bgs and slope gradually to the southern end of the excavation where it reached the maximum depth of four feet bgs. However, identification of MGP-related impacts resulted in nearly the entire SPCC footprint being excavated to a minimum of two feet bgs, with deeper excavations of three to four feet along the southern boundary. After the material was excavated to the appropriate depth, confirmation samples were collected and compared to the DTSC-approved preliminary screening criteria established in the Workplan (see Section 2.3.6). After review of the data and verification that concentrations were below the preliminary screening criteria, the Site was turned over to the