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11 Table 1 Groundwater Monitoring Data and Analytical Results Fortner Unocal Service Station#2859 1665 Pacific Avenue Stockton,California EXPLANATIONS Groundwater monitoring data and laboratory analytical results prior to Ma{h 6, 1998,1were compiled from reports prepared by MADS Services,Inc TQC=Top of Casing ji B E=Benzene (ppb)=Parts per billion (ft)=Feet 1� TIL Toluene ND=Not Detected DTW=Depth to Water j E��Ethylbenzene (D)=Duplicate GWE=Groundwater Elevation j X;=Xylenes --=Not Measured/Not Analyzed (ms])=Mean sea level MTBE=Methyl tertiary butyl ether QA=Quality Assurance/Trip Blank TPH-G=Total Petroleum Hydrocarbons as Gasoline EB=Equipment Blank * TOC elevations have been surveyed relative to mean sea level On February 10, 1999,TOC measurements were re-surveyed relative to City of Stockton BM#24, located in monument box at the northwest corner of Pacific Avenue and Har ing Way,(Benchmark Elevation=9 71 feet,NGVD29) On June 31,2001,the following wells were surveyed MW-4,MW-6 and MW-1 I through MW-14 using the previous benchmark. - r` Laboratory report indicates the hydrocarbons detected appeared to be{a gasoline and non-gasoline mixture z Laboratory report indicates the hydrocarbons detected did not appear'to be gasoline 3 Detection limit raised Refer to analytical reports MTBE by EPA Method 8260 5 Laboratory report indicates unidentified hydrocarbons C6-C12 6 Laboratory report indicates gasoline and unidentified hydrocarbons x8 r Well development only - a Laboratoryreport indicates gasoline and unidentified hydrocarbons C6-C121 9 Laboratory report indicates discrete peaks - 10 Laboratory report indicates gasoline C6-C12 " Laboratory report indicates weathered gasoline C6-C12 1 j iz Laboratory report indicates hydrocarbon pattern is present in the requested fuel quantitation range,but does not resemble the pattern of the requested fuel 13 11 Laboratory report indicates the result was reported with a high bias due to the continuing calibration verificcation falling outside acceptance criteria 14 !� Laboratory report indicates gasoline C6-C 10 'S Laboratory report indicates discrete peak @ C7 I E6Current laboratory analytical results to not coincide with historical data,and although the laboratory results were confirmed,it appears that the samples were switched ANALYTICAL METHODS EPA Method 8015 for TPH-G EPA Method 8020 for BTEX and MTBE(except where noted) EPA Method 8260 for MTBE(except where noted) A0/19/43 2859 x1054 11 .