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Additional Phase II Environmental Site Assessment Report Buena Vista Storm Drain,Stockton,CA August 15,2005 Page 3 containers were labeled, stored in a cooler chilled with Blue Ice®, and delivered, under chain-of-custody procedures, to Argon Laboratories in Ceres, California, for analyses. Borings GP-13 through GP-16 were advanced to 20 feet below ground surface (bgs). One groundwater sample was collected from each of the borings after all four of the borings were advanced. Upon completion of the boring and sampling, the boreholes were backfilled with a grout consisting of neat cement. The grout was tremied into the boreholes. 4.0 LABORATORY ANALYSES The groundwater samples collected from the borings were analyzed for total petroleum hydrocarbons quantified as gasoline (TPH-G) by EPA Method 8015M, and for benzene, toluene, ethyl benzene, total xylenes (BTEX), and selected gasoline oxygenates/additives by EPA Method 8260B. The gasoline oxygenates/additives include MTBE, tertiary-butanol (TBA), di-isopropyl ether (DIPE), ethyl tertiary- butyl ether(ETBE), and tertiary-amyl methyl ether(TAME). 5.0 INVESTIGATION RESULTS The results of the groundwater investigation include field observations and laboratory analytical results for the groundwater samples. 5.1 FIELD OBSERVATIONS No discoloration of the groundwater was noted in the samples collected from the borings. 5.2 RESULTS OF LABORATORY ANALYSES The groundwater sample laboratory analytical results are presented in Table 1, below. Copies of laboratory analytical reports and chain-of-custody records for the samples are included in Appendix B. Laboratory analytical results indicate that TPH-G, BTEX, and the selected gasoline oxygenates/additives were not detected at or above the laboratory reported detection limits in any of the groundwater samples collected from borings GP-13 through GP-16. Table 1 Groundwater Sample Laborator Analytical Results Sample I.D. Sample Date B T E X TPH-G Oxygenates/ (119/L) (µg/L) (gg/L) (gg/L) (mg/L) Additives(gg/L) 4038D-GP-13-7/26/05 7/26/05 <0.5 <0.5 <0.5 <1.0 <0.05 <0.5-<5.0 4038D-GP-14-7/26/05 7/26/05 <0.5 <0.5 <0.5 <1.0 <0.05 <0.5-<5.0 4038D-GP-15-7/26/05 7/26/05 <0.5 <0.5 <0.5 <1.0 <0.05 <0.5-<5.0 4038D-GP-16-7/26/05 7/26/05 <0.5 <0.5 <0.5 <1.0 <0.05 <0.5-<5.0 Unit Conversions: Analytical gg/L=micrograms per liter(ppb). B,T,EA=benzene,toluene,ethyl benzene,total xylenes. mg/L=milligrams per liter TPH-G=total petroleum hydrocarbons,quantified as gasoline. Oxygenates/additives = tertiary-butanol (TBA), methyl tertiary-butyl ether (MTBE),di-isopropyl ether(RIPE),ethyl tertiary-butyl ether(ETBE),and tertiary- amyl methyl ether(TAME). t4k.A �.,� CONDOR