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Mr.M. Scott Mansholt—CEMC O 41 Soil and Groundwater Investigation Work Plan Addendum November 30,2009 Tracy Byron Road Page 2 of 3 in May 20084. The RWQCB reviewed the results of previous investigations and the recommendations presented in the May 2008 report, and concurred that additional lateral delineation of affected soil and groundwater was necessary to the south (see Attachment A)5. The RWQCB also concurred that the up-gradient extent of soil and groundwater was defined during a site investigation on the Calderon's General Store property (Geological Audit Services, 1995)6; therefore, proposed step-out boring SB-44 located on this property was not necessary and has been removed from the scope of work. PROPOSED BORING OBJECTIVES Investigation startup was deferred for the remaining borings because site access to the majority of the planned boring locations could not be obtained. However, with the recent signing of access agreements to adjacent properties, SAIC will advance the remaining three proposed borings at alternate locations on properties that have granted access. The proposed boring locations are shown on Figure 3. Samples will be analyzed for the constituents of potential concern (COPCs) as originally proposed in the 2004 work plan. Analysis of benzene, toluene, ethylbenzene, and total xylenes (BTEX), and polynuclear aromatic hydrocarbons (PAHs) in groundwater will be performed using the methods described in the 2007 work plan. Boring objectives are outlined as follows: • To fully delineate the extent of affected soil and groundwater to the south and up gradient of SB-19, proposed boring SB-42 will be moved to and advanced on Assessor's Parcel Number (APN) 238-050-01 (Figure 3). • To fully delineate the extent of affected soil and groundwater to the south and up gradient of SB-23, proposed boring SB-43 will be advanced on APN 238-050-09 (Figure 3). • To fully delineate the extent of affected soil and groundwater to the southeast and up gradient of SB-33,proposed boring SB-45 will be moved to and advanced on APN 238- 050-22 (Figure 3). In accordance with Chevron's Consistent Technical Approach, should SAIC encounter affected soils, or observe a sheen and/or separate-phase oil (SPO) in groundwater in a boring, additional contingency step-out borings will be advanced as part of the same field investigation effort to the extent allowed by site access agreements. Note that step-out borings are not shown on Figure 3, as their actual locations will depend on field conditions. SAMPLE COLLECTION If SPO and/or sheen are observed, a soil and/or groundwater sample(s) will be collected for fuel fingerprinting. The sample(s) will be submitted to Chevron Energy Technology Company for fuel-fingerprint analysis using gas chromatography/mass spectrometry. If no affected soil or groundwater is found, then no fuel-fingerprint sample will be collected. 4. SAIC,2008. Soil and Groundwater Investigation Report, Tracy Byron Road Project, Tracy,San Joaquin County, California. May. 5. RWQCB,2008. Review-Soil and Groundwater Investigation Report,Tracy Byron Road Project,Tracy,California. July 8. 6. Geological Audit Services, 1995. Site Summary Report, Calderon's General Store, 12750 West Byron,Road, Tracy, California. March. 7. Geomatrix Consultants,Inc. 2005, Technical Approach to Site Evaluation and Decision Making,Historical Pipeline Portfolio, Central Valley Region. February.