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Mr. M.Scott Mansholt--ChevronTexaco January 13,2005 Soil and Groundwater Investigation Report—Pombo Property Page 4 of 8 observed between 6.2 and 11 feet bgs in November 2003 and between 7.1 and 10.5 feet bgs in February 2004. Boring logs containing PID readings, USCS soil descriptions,and other pertinent drilling data are included in Appendix A, Visually affected soils were not encountered during the November 2003 and February 2004 field events. Based on these observations, soil samples were collected for laboratory analyses from immediately above first-encountered groundwater. Most soil samples were collected from a depth of less than 10 feet bgs for future health risk assessment purposes. All down-hole boring equipment was decontaminated between borings using a Liquinox solution and rinsed using potable water. All soil borings were properly abandoned by backfilling with cement grout to ground surface. SOIL SAMPLE ANALYTICAL RESULTS On November 5, 2003 and February 25, 2004, SAIC collected 12 soil samples from 1 1 soil borings for laboratory analysis. Soil samples were analyzed for TPHc using EPA Method 8015 (modified);BTEX using EPA Method 8260; and PAHs using EPA Method 8270C with selective ion monitoring(SI.M). Current soil sample analytical results for TPHc and BTEX are presented in Table 4,and analytical results for PAHs are presented in Table 5. Soil sample analyte concentrations are presented on Figure 6. Historical soil analytical results from previous investigations conducted at the Pombo Property are presented in Table 1 and TPHc concentrations are presented on Figure 3. Copies of the current laboratory analytical reports are included as Attachment B. TPI-Ic was only detected in one soil sample located on the WSID easement(5.6 mg/kg, SB-4 at 5 feet bgs). Toluene and total xylenes were detected at their respective detection limits in one soil sample located in the WSID easement(SB-3 at 8 feet bgs). TPHc and BTEX compounds were non-detect in all other soil samples. The detection of low concentrations of PAHs was fairly persistent across the area of the November 2003 .� and February 2004 investigation field events. PAHs were not detected in SB-9 and SB-6,both located on the eastern extent of the area of investigation. Four PAHs(benzo[b]fluoranthene,benzo[g,h,i]perylene, phenanthrene,and pyrene)were detected in SB-2 at or near their respective detection limits. Phenanthrene was detected in SB-1 to SB-5, SB-7, SB-8,SB-10, and SB-1 I at concentrations ranging from 0.0004 mg/kg(SB-4 at 8 feet and SB-5 at 8 feet)to 0.002 mg/kg(SB-10 at 7 feet). Pyrene was detected in SB-2, SB-4, SB-7, SB-8, SB-10,and SB-11 at concentrations ranging from 0.0004 mg/kg (SB4 at 5 feet)to 0.003 mg/kg(SB-10 at 7 feet). GRAB GROUNDWATER ANALYTICAL RESULTS Eleven grab groundwater samples collected on November 5,2003 and February 25,2004 were analyzed I for TPHd,with and without a silica-gel preparation using EPA Method 8015M; BTEX using EPA Method 8021 B; and PAHs by EPA Method 8270 SIM. Current groundwater analytical results are presented in Table 6 and groundwater analyte concentrations are presented on Figure 7. Historical groundwater results from previous investigations conducted at the Pombo Proprety are presented in Table 2 and TPIId concentrations are presented on Figure 4. A copy of the laboratory analytical report is included as Attachment B. Dissolved TPHd was detected in grab groundwater samples from all soil borings except SB-4 and SB-9, and ranged from 88 µg/L(SB-5)to 370 Etg/L(SB-1). TPHd was detected above the Water Quality Objective(WQO) for TPIId(100 ug/L)but below 370 ug/L in eight of 11 grab groundwater samples. Grab groundwater samples from borings furthest down gradient were detected in SB-8 at a concentration of 120µg/L and was non-detect in SB-9, furthest down gradient. Grab groundwater samples were reanalyzed for TPHd following silica-gel cleanup and detected in SB-1 through SB-3, SB-5, and SB-6 at concentrations ranging from 140 µg/l,(SB-3 and SB-5)to 210 µg/L