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Catherine Quinn Page 3 June 27,2002 TPH-gas. In summary,as presented in the tables and figures in Attachment 1: • BTEX was not detected in any soil samples. • For the November 19,2001 excavation samples,TPH concentrations were low,ranging from non-detect up to only 5.8 mg/kg,which was for TPH-gas • For the November 21,2001 over-excavation samples,TPH concentrations were all non- detect,except for TPH-gas which was detected at a low concentration of only 3.0 mg/kg Soil sampling will not be performed for,analysis of lead because the results for the two composite samples (7.2 and 7 mg/Kg) are representative of background soil conditions. Lead is a naturally occurring metal that is present at some concentration in most if not all soils. In a study to define background concentrations in California,Bradford et al. (19961) sampled soils from 50 benchmark sites and analyzed these for 46:trace and major elements. Results of the study showed that lead ranged from 12.4 mg/kg to 97.1 mg/kg depending on location. The state-wide average lead concentration from this study was.23.9 mg/kg. San Joaquin county contained two of the benchmark soil sampling sites,which indicated that background lead concentrations ranged between 14.2 and 17.8 mg/kg. These background concentrations exceed the lead concentrations detected in the two composite soil samples. The results of Bradford et al. (1996)are consistent with other similar studies performed to assess background concentrations of metals in soil. Groundwater sampling will be performed for.analysis of TPH,BTEX,and MTBE to delineate the lateral extent of these constituents at the water table,which were detected in the November 19,2001 grab groundwater sample from the bottom of the excavation at the following concentrations: . • TPH-gas,TPH-diesel,and TPH-jet fuel at 0.26,23,and<0.05 mg/L,respectively • Benzene,toluene,ethylbenzene,and.xylenes at 1.6, 11,2.4,and 18.2 ug/L,respectively • MTBE at 82 ug/L Groundwater sampling will not be performed for analysis of lead because,as discussed above,lead detected for the two composite soil samples collected on November 19,2001 and November 21,2001 are representative of background soil conditions and likely not related to conveyance of petroleum products through the pipeline. 1 Bradford,G.R.,A.C:Chang,A.L.Page,D.Bakhar,J.A.Frampton,and H.Wright. 1996. Background Concentrations of Trace and Major Elements in California Soils. Kearney Foundation of Soil Science. Division of Agricultural and Natural Resources,University of California.