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Table I Water Level Data and Groundwater Analytical Results - Chevron Service Station #9-6171, 6633 Pacific Avenue, Stockton, California (continued) EXPLANATION NOTES (continued) DTW = Depth to water ' Monitoring well abandoned on July 31, 1992 TOC = Top of casing elevation ' EDB was also analyzed and not detected at detection limits of 0 2 ppb GWE= Groundwater elevation ' TOG was also analyzed and not detected at detection limits of 5,000 ppb msl = Measurements referenced relative to mean sea level ' Gasoline range concentration reported Peaks not associated with gasoline are TPH(G) = Total Purgeable Petroleum Hydrocarbons as Gasoline observed early in the chromatogram B = Benzene ° Both gasoline and multiple solvent peaks were observed to the chromatogram T = Toluene ° Uncategonzed compound is not included in the gasoline hydrocarbon E = Ethylbenzene concentration X = Xylenes ' Detection limit raised due to surfactants EDB = Ethylene dibromide ' Typical gasoline pattern not present Peak at 7 2 minutes subtracted from TOG = Total Oil and Grease gasoline range before calculating gasoline concentration VOC = Volatile Organic Compound ' Non-gasoline components which were not identified by the laboratory present to MTBE = Methyl t-Butyl Ether sample at 150 ppb, 11/29190 Non-gasoline components which were not — = Not analyzed/not applicable identified by the laboratory present lin sample at 300 ppb,3114/91 ppb = Parts per billion tO Gasoline range concentration reported, peaks are representative of tetrachloroethane and trace amount of gasoline ANALYTICAL METHODS " Gasoline range concentration reported The chromatogram shows only a single peak TPH(G) = EPA Method 5030/8015 `= Both gasoline and a single solvent peak (chlorinated) were observed in the BTEX = EPA Method 602/EPA Method 8020 chromatogram EDB = EPA Method 504 i3 Both gasoline and a single solvent peak are observed in the chromatogram TOG = Standard Method 503E " Detection limit raised due to foaming sample matnx VOC = EPA Method 8240 t3 TOC elevation for well MW-7 was surveyed by Ron Miller, Licensed Land Surveyor, PE#15816 on September 13, 1993 NOTES 16 Carryover from previous sample in tun sequence made it necessary to analyze backup sample Back-up sample foamed,therefore,no data is available TOC elevations were surveyed by Ron Miller, Licensed Land Surveyor,CE#15816 on ° The sample was diluted due to high concentration of non-target compounds September 5, 1990 Hydrocarbons in the gasoline sample do not match the gasoline standard pattern The sample was diluted due to high concentrations of non-target compounds Water level elevation data and laboratory analytic results prior to May 30, 1995 were " MTBE was also analyzed and not detected at detection limit of 2 5 ppb compiled from Quarterly Monitonng Reports prepared for Chevron by Sierra Environmental m Laboratory reported discrete peak C8-C9 Services 21 Laboratory reported unidentified hydrocabron <C9 Laboratory report indicates discrete peals C7-C8 * Product thickness was measured with an MMC tlexi-dip interface probe =' Laboratory report indicates discrete peaks C6-C8 5121 TQM 6