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s Science Applications International Corporation An Employee-Owned Company June 16, 2003 Mr.M. Scott Mansholt ChevronTexaco Chevron Environmental Management Company 6001 Bollinger Canyon Road, Room K2050 'I San Ramon, California 94583-2324 Aloe Subject: Byron Road Characterization Work Plan` Final Draft West Byron Road Tracy, California Dear Mr. Mansholt: At the request of Chevron Environmental Management Company (ChevronTexaco), Science Applications International Corporation (SAIC) has prepared this work plan for characterization of affected soil and groundwater contiguous with West Byron Road in Tracy, California (Figure 1). This document was written in response to the Regional Water Quality Control Board — Central Valley Region (RWQCB) letter dated April 17, 2003, requesting characterization of the extent of soil and groundwater impacts identified in conjunction with the City of Tracy's Westside Channel Outfall project. A copy of the RWQCB letter is included in Appendix A. Site Description The study area encompasses an approximate 7,000-foot long corridor that trends southeast to northwest, along Byron Road from Corral Hollow Road to just northwest of the I-205 overpass in Tracy, California (Figure 1 and Figure 2). The study area contained the former Standard Oil of California Wait-Mendota- Richmond(OVP) and Tidewater Associated Oil Company (TAOC) Pipelines. The OVP was operated as a hot oil line from 1903 until the early to mid 1930s. The OVP lines north of Tracy were operated until the late 1960s. The TAOC pipeline system was constructed in 1907 and also operated as a hot line; it was operated until the 1970s. In the area of study,the OVP pipeline right of way is on the south side of Byron Road and the TAOC pipeline is on the north side of Byron Road in the Union Pacific Railroad right of way(ROW). The former old valley pipelines(hereinafter, "OVP"shall collectively refer to both the OVP and TAOC pipelines unless otherwise stated) carried crude oil and Bunker C fuel oil. Currently, north and south of Byron Road are mainly residential properties and small businesses. Presently, the length of the study area (Figure 2) is under construction at the direction of the City of Tracy. During the construction phase, the City of Tracy will increase the capacity of their storm water sewer by installing two 60-inch diameter pre-cast concrete pipes along the Byron Road corridor. During the initial phase of construction, concrete pipes were installed beneath a railroad ROW. In order to accomplish installing the two 60-inch diameter pipes, an excavation approximately 7,000-feet in length will be dug to a depth between 11 and 16 feet below ground surface (bgs) to accommodate the pre-cast concrete pipe. Depth to groundwater is approximately 5 to 10 feet bgs. A total of 132 dewatering wells were installed to an approximate depth of 35 feet bgs and 27 dewatering wells were installed to an approximate depth of 50 feet bgs. The well borings were drilled using a 24-inch diameter flight auger and a bucket auger once groundwater was encountered. The wells were installed with 8-inch diameter 3800 Watt Ave., Suite 210, Sacramento, CA 95821 (916)974-8800•Fax.(916)974-8830