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i <br /> T 1 z <br /> Groundwater Monitorin to and Analytical Results <br /> Former Tosco(Unocal)Service Station#4409 - <br /> 1502 North El Dorado Street <br /> Stockton,California <br /> EXPLANATIONS <br /> TOC=Top of Casing TPH-G=Total Petroleum Hydrocarbons as Gasoline ND=Not Detected <br /> OTW=Depth to Water B=Benzene --=Not Measured/Not Analyzed <br /> (ft)=Feet T=Toluene <br /> S I =Screen Interval E=Ethylbenzene <br /> (ft bgs)=Feet Below Ground Surface X=Xylenes <br /> GWE=Groundwater Elevation MTBE=Methyl tertiary butyl ether <br /> (msl)=Mean sea level (ppb)=Parts per billion <br /> * TOC elevations were re-surveyed in November of 2001,by Siegfried Engineering,using the previous benchmark <br /> Previously,TOC elevations were surveyed relative to msl, per the City of Stockton Benchmark No 23,(Elevation=11 14 feet,ms])NGVD 29 <br /> i MTBE by EPA Method 8260 <br /> 2 Laboratory report indicates gasoline C6-C12 <br /> 3 Laboratory report indicates weathered gasoline C6-C12 <br /> 4 Well development performed <br /> 5 Detection limit raised Refer to analytical reports <br /> 6 Laboratory report indicates sample has a reported value of 100 ppb by EPA 8021B,however,the EPA 8260B MTBE result on this sample is ND All of <br /> the data has been reviewed and no laboratory discrepancies were noted Based upon the data review,there was co-elution of MTBE with 3-methyl-pentane <br /> on the EPA 8021B analysis and the reported value of 100 ppb is a false positive The 8260B chromatogram and spectra have been reviewed for sample MW-10 and the <br /> MTBE result for this sample is ND <br /> 4409 xis/#180238 5 As of 04/18/02 <br />