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r 3 - Geminl Petrographic Investiclations Regional Water Resources Maps,which indicate a groundwater flow direction varying,according to seasons, from southwest to south-south east. Mean seasonal precipitation for the site is from 10-15 Inches according to the National Weather Service. IV, RESULTS A. LABORATORY RESULTS Ten samples were collected with six samples(with concurrence of Ms,Darlene Reuss,SJCPHD) representing upper and lower sections of the borehole were submitted for laboratory confirmation for Total Petroleum Hydrocarbon (as gasoline ) and BTX&E on 9 November 1990. The samples were submitted under chain-of-custody protocol to Superior Analytical Laboratories,Inc.,of Martinez.The laboratory data Indicates that all samples have concentrations below the analytical detection limits for TPH (as gasoline). BTX&E constituents were detected (ppb range) In five of six samples with concentration ranging for Benzene from NO to 5 ppb,Toulene from NO to 15 ppb,Xylene from NO to 37 ppb and Ethylbenzene from NO to 10 ppb. Sample 90481-1-9 at 44.5.45.0' exhibited the highest concentrations of BTX&E constituents. Sample 90481-1.2,at 9.5.10.0'(approximately 2.3 fe6t below the bottom of the former tank),was non-detected for all 13TX&E constituents. BTX&E constituent concentrations appear to Increase with depth,peaking at 45.0',and then decllning to below or at detection Ilmit levels at 50.0'.It should noted that Superlor Analytical Laboratory's quantitation reporting limits (3 ug/kg vs.5 ug/kg)are lower than those proposed by the Tri-Valley Regional Guidelines for Practical Ouantltatlon Reporting Limits. The results of the laboratory analyses Is summarized In Table 1 below. Laboratory analysis and _. chain-of-custody documentation Is located in Appendix B. TABLE 1 Analytical Test Results-Soil Samples Cozad Trailers-4907 East Waterloo Road,Stockton Ethyl Sample. TPH(G) Benzene Toluene Xylene benzene Num)era _ Depth _(ppm) fppb (ppb) bb1__. 90481.1-2 9.5-10.0' NO NO NO ND NO 90481-1-3 14.5-15.0' ND NO 7 7 NO 90481.1-4 19.5-20.0' ND NO 7 8 NO 90481.1-8 39.5-40.0' NO NO 7 22 9 _ 90481-1-9 44.5-45.0' N D 5 15 37 10 90481-1 A 0 49.5-50.0' N D NO 3 9 4 - --. - MDL 1.0 3 3 3 3 5