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Table 1 j Groundwater Monitoring Data and Analytical Results �r Tosco(Unocal)Service Station#5886 f 2701 West March Lane r '� Stockton,California F r I II� EXPLANATIONS Groundwater monitoring data and laboratory analytical results prior to March 25, 1998,were compiled from reports prepared by MPDS Services,Inc I1 h P (ppb)=Parts per billion TOC=Top of Casing B=Benzene 1 T=Toluene --W Not Measured/Not Analyzeld DTW=Depth to Water Feet ND = Not Detected (ft) I E= � S I =Screen interval X=Xylenes (ft bgs)=Feet Below Ground Surface MTBE=Methyl tertiary butyl ether � j I GWE=Groundwater Elevation (ms) 1 =Mean sea level 3 TPH-D=Total Petroleum Hydrocarbons as Diesel �I TPH-G=Tota]Petroleum Hydrocarbons as Gasoline t I The TOC elevations were surveyed relative to msl These well casing elevations were used pnor to the May 2, 1997 monitoring event * The TOC elevations of the well casings were resurveyed(except for wells MW-2 and MW-3)relative to msl on April 28, 1997 The well casing elevations are used beginning with the May 2, 1997 The new TOC elevations for wells MW-2 and MW-3 were calculated by using the previously surveyed {I, elevations for wells MW-1,MW-2 and MW-3(MW-1 =-0 84 feet msl, MW-2=0 30 feet msl,and MW 3= 0 14 feet ms])and the resurveyed 1i 1 elevation of well MW-1 (=-1 35 feet msl) ij ** Wells were re-surveyed on April 27 1999 by Morrow Surveying TOC elevations are based on City of Stockton Benchmark#226,top of 314"iron pin s in monument box at the intersection of the centerline of Feather River and the S ROW line of March Lane,(Elevation= 0 92 feet) 1r r Laboratory report indicates unidentified hydrocarbons unidentified hydrocarbons>Cl4 2 Laboratory report indicates unidentified hydrocarbons unidentified hydrocarbons>C 15 Laboratory report indicates unidentified hydrocarbons diesel and unidentified hydrocarbons>C20 I, a �I r Laboratory report indicates the hydrocarbons detected did not appear to be diesel f s Laboratory report indicates the hydrocarbons detected appeared to be a diesel non-diesel mixture TPH-D analysts with silica gel cleanup 7 MTBE by EPA Method 8260 ] ' e Detection limit raised Refer to analytical reports 9 Laboratory report indicates unidentified hydrocarbons C9-C24 10 Laboratory report indicates unidentified hydrocarbons C9-C24 and Discrete peak @ C24 11 Laboratory report indicates unidentified hydrocarbons C6-C12 ill 12 Laboratory report indicates unidentified hydrocarbons>C16 11 MTBE by EPA Method 8260 required reanalysis past hold time due to failing internal standard on first run First analysis was within hold time 1 isLaborator Y report indicates discrete peaks 1� it As 0008101 5886 x1s1#*7