ARCHIVED REPORTS SOIL AND GROUNDWATER INVESTIGATION REPORT

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' Soil and Groundwater Investigation Report Tracy Byron Road Project May 2008 are included as Appendix D.2. Section 5.1 compares soil results to the PRGs and ESLs to assess the ' extent of affected soil and whether any further soil characterization is appropriate. 4.3 GROUNDWATER ANALYTICAL RESULTS ' Groundwater analytical results, ESLs, and WQOs are summarized in Tables 3 and 4. Table 5 summarizes the General Minerals analytical results. A data usability discussion is included in Appendix D as Appendix D.1, and copies of the groundwater laboratory reports are included as Appendix D.2. Section ' 5.2 compares the groundwater results to the ESLs and WQOs to assess the extent of affected groundwater and whether any further groundwater characterization is appropriate. 4.4 DATA USABLITY SUMMARY ' SAIC performed a data usability evaluation in order to determine whether the data could be used for the intended purposes (i.e., delineation and risk evaluation). The evaluation determined that all analytical ' data are usable. See the Data Usability Summary in Appendix D.1 for more information. Qualified data with reason codes are provided in Table D-1 and are summarized in Appendix D.1. 5. DISCUSSION OF PETROLEUM DISTRIBUTION ' 5.1 EXTENT OF AFFECTED SOIL Soil analytical results from this and previous investigations along the West Byron Road corridor were ' compared to the lowest, most conservative PRG and ESL concentrations for delineation purposes. Soil sample analytical results were at non-detect levels and less than PRGs and ESLs. Soil results from previous investigations along the West Byron Road corridor that exceeded the PRGs and/or ESLs are ' presented on Figures 3a through 3f. 5.2 EXTENT OF AFFECTED GROUNDWATER ' Groundwater analytical results were compared to the lowest,most conservative ESL and WQO concentrations for delineation purposes. Groundwater sample analytical results were less than WQOs and ESLs, with the following exceptions: ' • TPHd: SB-37 (100 micrograms per liter[[tg/L]), SB-38 (140 Itg/L), SB-39 (160 pg/L), SB-40(330 µg/L),and SB-41 (330 ttg/L); and • Benzo(g,h,i)perylene: SB-39 (0.40 µg/L). ' The extent of crude-oil affected groundwater, based on evaluation of the groundwater data of this and previous site investigations along the West Byron Road corridor,is delineated on Figures 3a through 3f. Past experience at HPP project sites indicates that attenuation of TPHd in groundwater from the reported concentrations in borings SB-37 through SB-41 to concentrations below the WQO/ESL of 100 pg/L is likely to occur a very short distance from the OVP and TAOC pipelines. ' 5.2.1 Suitability of the Groundwater for Drinking Total dissolved solids (TDS) concentrations in groundwater samples collected from SB-37 and SB-38 ' were 1,980 milligrams per liter(mg/L) and 2,180 mg(L,respectively. The criteria of the Water Quality Control Plan for the Sacramento River Basin and the San Joaquin River Basin, for which an aquifer is considered a potential source of drinking water, are as follows: ' • TDS in groundwater less than or equal to 3,000 mg/L; and • Groundwater yield greater than 200 gallons per day. ' The TDS levels in the shallow groundwater of the site therefore indicate that the groundwater is a potential drinking water source. However, it is important to note that TDS in site groundwater is above ' 6 QA Ir �,rq From Science to Solutions 1