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r■ r r rr r r rr rr r r r r r■■ r ■r r r r r i i • Table 1 Groundwater Monitoring Data and Analytical Results Former Unocal Service Station No. 0187 437 East Miner Avenue Stockton, California EXPLANATIONS: Groundwater monitoring data and laboratory analytical results prior to November 29,2003,were compiled from reports prepared by Gettler-Ryan, Inc. TOC=Top of Casing TPHg =Total Petroleum Hydrocarbons as Gasoline (ug/L)= micrograms per liter (ft)= Feet B= Benzene —= Not Measured/Not Analyzed DTW = Depth to Water T=Toluene (D)= Duplicate S.I. =Screen Interval E= Ethylbenzene QA=Quality Assurance/Trip Blank (ft. bgs)= Feet Below Ground Surface X=Xylenes GWE= Groundwater Elevation MTBE = Methyl tertiary butyl ether (msl)= Mean sea level TOC elevations have been surveyed relative to Benchmark marked"IS-9"in monument box at San Joaquin and Oak Streets, (Elevation= 10.523 feet, msl). Site re-surveyed on February 10, 1999 by Field Designs. TOC elevations were surveyed on November 16, 2000, by Virgil Chavez Land Surveying using the previous Benchmark. GWE corrected due to the presence of free product; correction factor: I(DTW-TOC)+(Product Thickness x 0.75)]. ' Laboratory reported the hydrocarbons detected appeared to be a gasoline and non-gasoline mixture. Z Laboratory reported the hydrocarbons detected did not appear to be gasoline. 3 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. 4 MTBE by EPA Method 8260B. 5 Laboratory report indicates gas and unidentified hydrocarbons DC7. 6 Laboratory report indicates discrete peak C6. 7 Laboratory report indicates unidentified hydrocarbons C6-C12. a Laboratory report indicates gasoline and unidentified hydrocarbons C6-C12. 9 Well development performed. 10 Laboratory report indicates gasoline C6-C12. 11 Laboratory report indicates weathered gasoline C6-C12. 12 Detection limit raised. Refer to analytical reports. 13 Laboratory report indicates gasoline C6-C12 +unidentified hydrocarbons<C6. 14 Laboratory report indicates gasoline C6-C12 +unidentified hydrocarbons C6-C12. 15 Detection limit raised due to high levels of non-target compounds. Refer to analytical reports. 16 Sample collected from bottom of well using discrete bomb sampler at 114 feet. 17 Sample collected from bottom of well using discrete bomb sampler at 69 feet. 16 Well development not completed. DTW only. 06940-325 37 of 38 ENSR Corporation