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Table 1 Groundwater Monitoring Data and Analytical Results Former Tosco(Unocal)Service Station##6981 ?I 4707 Pacific Avenue p Stockton,California I EXPLANATIONS l� Groundwater monitoring data and laboratory analytical results prior to March 5,1998,were compiled from reports prepared by MPDS Services,inc TQC=Top of Casing TPH-G=Total Petroleum Hydrocarbons as Gasoline (ppb)=Parts per billion (It)=Feet B=Benzene ND=Not Detected I P DTW=Depth to Water T=Toluene -=Not Measured /Not Analyzed S i =Screen Interval E=Ethylbenzene NA = Not Avail 0 able X=Xylenes QA=Quality Assurancerfnp Blank (ft bgs)=Feet Below Ground Surface y GWE=Groundwater Elevation MTBE=Methyl tertiary butyl ether * TOC elevations have been surveyed relative to the City of Stockton Datum On September 9, 1999 and on September 30,2000,TOC elevations were re-surveyed based on City of Stockton Benchmark,a brass cap in monument well on the east side of Pacific Avenue approximately fifty feet south i of March Lane,(Elevation= 11 56)City of Stockton datum Laboratory report indicates the hydrocarbons detected did not appear to be gasoline it 2 The analytical results of the groundwater samples collected from monitoring wells MW-8 through MW-13 on January 17 and 18, 1994,were inconsistent with the previous analytical results for these wells Therefore,MPDS Services,inc resampled these wells on February 28, 1994 i Laboratory has identified the presence of MTBE at a level above or equal to the taste and odor threshold of 40 ppb in the sample collected from this well ; IItt II ° Covered by a new sidewalk 'I S The positive result for gasoline does not appear to have a typical gasoline pattern 6 � 1 MTBE by EPA Method 8260 7 Field Blank II I ,I s Well was obstructed 9 Laboratory report indicates gasoline and unidentified hydrocarbons>C8 la Laboratory report indicates gasoline and unidentified hydrocarbons C6-C8 ?I i I Laboratory report indicates gasoline and unidentified hydrocarbons DC7 12 Laboratory report indicates unidentified hydrocarbon-;>C7 s 17 I Laboratory report indicates gasoline C6-C12 14 Laboratory report indicates weathered gasoline C6-C12 it 15 Laboratory report indicates discrete peaks 16 Laboratoryreport indicates unidentified hydrocarbons C6-C12 it TPH-G and BTEX by EPA Method 8260 1 is TPH-G,BTEX and MTBE by EPA Method 8260 19 � Laboratory report indicates a hydrocarbon pattern is present in the requested fuel quantitation range but does not resemble the pattern of the requested fuel `° Laboratory report indicates that sample vials for MW-9 were not received,although documentation of the sample arriving at the laboratory is presented on the Chain of Custody I i! 6981 x1c038 a AJO(26103