SITE INFORMATION AND CORRESPONDENCE

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Soil and Groundwater Investigation Report Tracy Byron Road Project May 2008 ' 2.2 HISTORICAL AND EXISTING PIPELINE FACILITIES The site includes rights of way(ROWS)associated with the former Standard Oil of California(Standard; ' predecessor to Chevron)Wait-Mendota-Richmond pipeline(the OVP)and the TAOC pipelines. The OVP traversed the site immediately south and west of West Byron Road. The OVP was installed between 1902 and 1904 as a hot line(i.e.,the oil was heated to facilitate transmission)and carried San Joaquin Valley crude oil north from the Kern River Oil Fields(in and near Bakersfield)to Standard's Richmond Refinery. The pipeline and associated pump stations operated from 1903 until the early to mid 1930s. The pipelines were again used during the early 1940s to primarily transmit Bunker C fuel oil from the Richmond Refinery to railroad hubs in Tracy. The pipelines northwest of Tracy may have also been used to transport crude oil to various markets in the Bay Area until the late 1960s;they were reportedly abandoned in 1970. Where the OVP pipeline was not abandoned in place,it was removed and the trenches likely backfilled with native soil. ' The former TAOC pipelines ROW traversed the site immediately north and east of West Byron Road in the Union Pacific Railroad(UPRR)ROW. The TAOC pipeline system was constructed in 1907 and transmitted heated crude oil from Bakersfield to the Bay Area. The TAOC pipelines were abandoned in ' the 1970s. CEMC manages site investigations of TAOC facilities on behalf of Texaco Downstream Properties Inc. (Texaco),the successor-in-interest to TAOC. One active pipeline is also situated within the UPRR ROW:the Kinder Morgan Energy Partners,L.P. (KM)pipeline,which reportedly transports gasoline,jet fuel,and diesel. 2.3 HYDROGEOLOGIC SETTING The site is located within the San Joaquin Valley Groundwater Basin,which is divided into nine sub- basins. The site lies within the Tracy sub-basin(Groundwater Basin Number 5-22.15),which is defined by the aerial extent of unconsolidated to semi-consolidated sedimentary deposits bounded by the Diablo Range to the west,the Mokelumne and San Joaquin rivers to the north,the San Joaquin River to the east, ' and the San Joaquin-Stanislaus county line to the south. The Tracy sub-basin is located adjacent to the San Joaquin sub-basin to the east and the Delta-Mendota sub-basin to the south(California Department of Water Resources [DWR],2003). ' The Tracy sub-basin is comprised of continental deposits of late Tertiary to Quaternary age,which includes the Tulare Formation,Older Alluvium,Flood Basin Deposits,and Younger Alluvium. The thickness of these formations ranges from a few hundred feet in the western foothills to about 3,000 feet ' near the eastern margin of the basin. The Tulare Formation consists of semi-consolidated,poorly sorted, discontinuous deposits of clay,silt,and gravel. The Corcoran Clay is situated near the top of the Tulare Formation, separating groundwater in the basin in what has been reported as two primary aquifers. The upper aquifer is reported at 15 to 250 feet below ground surface(bgs)and the lower aquifer is reported at 600 feet bgs. Given the location of the site within the sub-basin,it is likely immediately underlain by Younger Alluvium,Older Alluvium, and/or Flood Basin Deposits. Groundwater near the site has been documented at approximately 15 to 20 feet bgs(DWR,2003). ' 2.4 EXISTING AND PLANNED DEVELOPMENT The City of Tracy installed two 60 inch-diameter,pre-cast concrete sewer lines in 2003 to carry storm ' water along the Byron Road corridor. A sanitary sewer and water main were also installed to service current and future development along Byron Road. The Interstate 205 (I-205)overpass at Byron Road is currently being widened. Affected soil on the ' Dividend Property(North Parcel)was encountered in July and August 2007 in two bridge-footing excavations(SAIC,2008). ' 2 `— �MR. From S�,'rCncc;�So�upo;�5