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feet below the top of the well casing (btoc). During the SSI, groundwater levels increased in elevation and ranged in depth from 7.75 to 8.84 feet btoc. Groundwater at the Site is flowing to the north-northeast at an approximate gradient of 0.003 ft/ft although there was a slight shift in the direction of groundwater flow to the east between the RI and the SSI. The depth-to-water measurements, along with the top of casing elevations and calculated groundwater elevations are presented on Table 1. The groundwater flow direction and gradient for the RI and SSI are presented in Figure 4. 2.2.4 Climatology The Site vicinity is located in an area of typical Mediterranean climate, characterized by warm dry summers and fairly mild winters. Temperature in the Site vicinity ranges from a minimum average of approximately 38 degrees Fahrenheit (°F) in the winter to a maximum average of approximately 93 OF in the summer. The average annual precipitation is approximately 12.7 inches per year(VWRCC, 2008). 2.3 CURRENT SITE OWNERSHIP AND HISTORICAL LAND USE 2.3.1 Property Ownership Since 1930, the Site has been owned and operated entirely by PG&E. Prior to 1958, portions of the property currently owned by PG&E (Parcels A, B, and C) were owned by others including the Tracy Gas Company (Parcel A from 1927-1930), the Sierra & San Francisco Power Company (Parcel B from 1929 to 1936) and Berverdor Incorporated (Parcel C prior to 1958). The following section provides a detailed description of the ownership of the Site. 2.3.2 Previous Facility Ownership/Operators The MGP was operated between 1927 and 1930 by various utilities, including Tracy Gas Company and PG&E. Little information is available on the site use prior to land acquisition for construction of the MGP. According to PG&E chain-of-title records, the Tracy MGP parcel was purchased from A. Grunauer et al on February 28, 1927, by the Tracy Gas Company. The location for this gas works was described by the local press as "...on the sugar beet factory spur on the north side of Lincoln Highway where the gas company purchased a number of acres from A. Grunauer" (Tracy Press, April 22, 1927). In the summer of 1930, MGP operations were discontinued due to the availability of natural gas in the Tracy area. In 1931 and 1932, the MGP was dismantled and then abandoned in 1934. The Site was divided into to three parcels; Parcel A, Parcel B and Parcel C, the locations of which are presented in Figure 5. In 1927, John F. Beals and Associates formed the Tracy Gas Company, purchased Parcel A and in October began the construction of a small oil-gas MGP. In February 1928, the MGP construction was completed and the first deliveries of gas were initiated. At that time, the MGP consisted of a gasholder, generators, scrubbers and purifying tanks. According to reports provided in the Preliminary Assessment (PA), the gasholder was approximately 50 feet in diameter and, when full, reached a height of about 50 feet (PG&E, 1986). Gas production operations were confined to Parcel A during the short life of the MGP. In 1929, the Sierra and San Francisco Power Company purchased Parcel B (Figure 5). In 1930, PG&E gained control of the MGP and Title to Parcel A was transferred to PG&E. Due to the arrival of natural gas into the Tracy area, the MGP was shut down in July 1930. In the period after the MGP was shut PARSONS 12 FINAL RI REPORT-FORMER TRACY MGP APRIL 2010