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Abdelwahed Facility, Ultramar Site No. 13792 May 9, 2013 Stockton California NFAR Request and Well Destruction Work Plan through the bottom of the hand-augered borings to the target depth. All soil gas locations (SG -1 through SG -4) were advanced to approximately 5.5 feet bsg. Soil gas flow conditions were favorable at all locations as vacuum was less than 10 inches of mercury. At each soil gas location, the soil gas purging assembly (filter and tubing) were inserted down the center of the drive rod. The drive rod was retracted approximately 6 inches off the bottom of the bore hole to approximately 5 feet bsg. As the drive rod was retracted, sand was installed in the annulus around the filter. The annulus around the tubing was backfilled to within one foot of the surface with granular bentonite and hydrated. Subsurface conditions were allowed to equilibrate for approximately 2 hours at each location prior to soil gas sampling. Purge testing was conducted at soil gas sampling location SG -1. Purge test soil gas samples were collected after purging one, three and ten apparatus volumes. The single apparatus - volume purge yielded the highest analyte concentrations. Thereafter, soil gas samples SG -2, SG -3 and SG -4 were collected after purging one apparatus volume. A shut-in test was conducted at the SG -3 location to test for leaks in the above -ground sampling apparatus. Leak testing with a shroud was conducted at each soil gas location during purge testing and soil gas .sampling. The compound 1,1-difluoroethane (DFA) was utilized as a leak check tracer gas. Soil gas purging and sampling was conducted with lab -sterilized 50 -cubic -centimeter syringes at flow rates ranging from 100 to 200 milliliter per minute (ml/min), as determined by the elapsed time to fill the sampling syringes. The QA/QC protocol of the mobile lab included one duplicate soil gas sample, SG -2 (DUP). A duplicate soil gas sample was collected at sampling location SG -3 [SG -3 (DUP)] to confirm the results of the mobile laboratory utilizing a 250-m1 Summa canister fitted with a 180 ml/min flow regulator. After completion of the sampling, purge tubing was removed from the ground and the bore holes were backfilled with neat cement, and capped with concrete. Soil gas samples collected from locations SG -1 through SG -4 were analyzed in the TEG mobile lab for. TPHd by EPA Method 8015m; TPHg, BTEX, MTBE, DCA, EDB, DFA by EPA Method 826013, oxygen and carbon dioxide. The Summa canister duplicate soil gas sample SG -3 DUP was transported to the ATL lab and analyzed for TPHg, BTEX, MTBE, DCA, EDB and DFA by EPA Method TQ -15. Results of Soil Gas Investigation Soil gas analytical results are summarized in Table 3. The TEG and ATL analytical reports are contained in Attachment F. The analytical results of soil gas sampling are summarized below: • the probe blank contained 20% oxygen; no hydrocarbon concentrations were detected in the probe blank; • soil gas sample S,G-1 contained 240 micrograms per cubic meter (µg/m3) toluene and 17% oxygen; no other analyte concentrations were detected in sample SG -1; • soil gas samples SG -2 and SG -2 (DUP) contained the following maximum concentrations: 13,000 µg/m3 TPHg; 300 µg/m3 toluene; 170 gg/m3 ethylbenzene; 850 µg/m3 xylenes; and 16% oxygen; no concentrations of TPHd, benzene, MTBE, DCA, EDB or carbon dioxide were detected in samples SG -2 and SG -2 (DUP); 1792 NFAR rpt.doc Project No. 1792.26 5 HORIZON ENVIRONMENTAL INC.