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r II� <br /> XWXW_ _ Al. HEAL! i <br /> 0 ;.�• ;s PVICE <br /> Science Applications International Corporation <br /> An Employee-Owned Company 03 AUG -1 PM 4. 32 <br /> 06-6102-00-2931-040 U <br /> July 31, 2003 <br /> Mr. M. Scott Mansholt <br /> Chevron Environmental Management Company <br /> P.O. Box 6012 <br /> San Ramon, Califomia-94583-2324 <br /> RE: Soils and Groundwater Investigation Work Plan <br /> Pombo Property(APN 232-170-07) <br /> 1755 West 11th St. <br /> Tracy, San Joaquin County, California <br /> Dear Mr. Mansholt: <br /> At the request of Chevron Environmental Management Company(ChevronTexaco), <br /> Science Applications International Corporation(SAIC)has prepared this Work Plan for <br /> soil and groundwater sampling at the Pombo Property(APN 232-170-07), 1755 West 11th <br /> St., Tracy, San Joaquin County, California. A generalized site location map is shown in <br /> Figure 1. <br /> BACKGROUND <br /> Previous investigations at the Pombo Property included soil sampling in support of a <br /> right-of-way relocation(July 1999); a soil and groundwater investigation with a human <br /> health screening risk assessment(January 2000); and additional soil and groundwater <br /> sampling with an updated human health screening risk assessment(May 2000). Figure 2 <br /> presents historical soil and groundwater sampling locations. <br /> Two of four soil borings advanced in June 1999 exhibited petroleum hydrocarbon <br /> affected soils. Total petroleum hydrocarbons quantified as crude (TPHc), toluene, <br /> xylenes, and polynuclear aromatic hydrocarbons (PNAs)were detected in soils from <br /> borings EB-7 and EB-9, at depths of 9.5 and 15 feet(ft)below ground surface(bgs), <br /> respectively. There were no observed impacts in the other two borings, so they were not <br /> sampled. <br /> Based on these findings, Geomatrix Consultants (Geomatrix) advanced 15 soil borings in <br /> late September 1999. Evidence of petroleum impacts was observed in eight of these <br /> borings, between depths of 7 and 19 ft bgs. Soil samples were collected from four of <br /> the eight impacted borings (GMX-2, GMX-6, GMX-7, and GMX-13), and analyzed for <br /> 3800 Watt Ave., Suite 210, Sacramento, CA 95821 (916)974-8800•Fax:(916)9748830 <br />