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Appendix A: Summary of Previous Environmental Activities I SAIC 2010 SOIL ANDR 5 G OiJrNDWATER INVESTIGATION 1 SAIC supervised the advancement of three soil borings (SB-42, SB-43, and SB-45)to 25 feet bgs on January 25 and 26,and February 4, 2010, to define the extent of affected soil and groundwater at the site. Hydrocarbon-affected soil and groundwater were not observed during the investigation. SAIC compared soil analytical results to the lowest, most conservative Regional Screening Level (RSL) and ESL values for delineation purposes. Constituents were not detected above screening levels with the exception of benzene. Benzene was detected at levels slightly above the RSL,but below the ESL, in three of the six soil samples analyzed during the current investigation;these levels are not considered significant_ ' SAIC collected groundwater samples from the three borings. Total petroleum hydrocarbons (TPH)quantified as diesel (TPHd),and benzene, toluene, ethylbenzene, and total xylenes (BTEX)were not detected in any of the groundwater samples submitted for analysis. Polynuclear aromatic hydrocarbons(PAHs)were detected in groundwater samples collected from the three borings with only benzo(a)pyrene in SB-43 exceeding screening levels at a concentration of 0.0032 pg//L. In a sample collected from SB-41,total dissolved solids(TDS) were detected at 1,500 milligrams per liter(mg/L), which did not exceed the W QO of 3,000 mg/L. ' SAIC evaluated the results of the investigations and concluded the following regarding the nature and extent of affected soil and groundwater at the site: • Thirteen areas of affected soil and/or groundwater at the site have been identified. • The vertical extent of affected soil has been delineated and does not exceed an approximate depth of 20 to 25 feet bgs. ' • The lateral extent of affected soil has been delineated. • The extent of affected groundwater has been delineated. Due to the age of Historical ' Pipeline Portfolio—Bakersfield to Richmond releases,the extent of affected groundwater is stable or decreasing and concentrations of dissolved constituents will gradually decrease as the petroleum-hydrocarbon mass is depleted. The lack of BTEX and PAHs in groundwater samples indicates that intrinsic biodegradation has been and continues to be active at this site. The northern boundary of the Tracy Byron Road site is shared with the Catellus property. The boundary was shifted south so that borings SB-I through SB-4 and SB-37 that were advanced during previous Tracy Byron Road investigations became part of the Catellus property for reporting purposes. ' Soil and groundwater have been effectively delineated at the site, and SAIC recommended performing a human health screening evaluation as a further step in the process of moving the site toward no further action required status. ' S. SAIC,2010. Soil and Groundwater hivestigation Report-Tracy Byron Road August. A-3 SAIC