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Table 5 Historical Groundwater Analytical Data South Shore Parcels-Parcel 2A and Adjacent Areas West Weber Avenue and North Lincoln Street Stockton,California Depth Ethyl- Sample (feet, Date TPHg TPHd TPHo Benzene Toluene benzene Xylenes MTBE TBA As ID bgs) Sampled (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) Explanations(cont.): 7=Sample exhibits unknown single peak or peaks. "=QA/QC samples collected by Clayton Group Services for Unocal:Lincoln/Weber. 9=The method reporting limit for TPHd is increased due to interference from gasoline-range hydrocarbons. '0=Repeated analysis yielded inconsistent results. The highest recovery value of has been reported,but should be considered an estimate. "=Matrix Spike/Matrix Spike Duplicate Results were affected by the analyte concentration already present in the un-spiked sample. "=Samples collected by Clayton Group Services for Unocal:Lincoln/Weber. '3=The silica gel extract for TPHd contained a slight contamination from the material in the extract vial cap. These compounds were subtracted from the TPH value. '4=Surrogate recovery for Method 8015 is above/outside the control limit(s). This may indicate a bias in the analysis due to the sample's matrix or an interference with the surrogate from compounds present in the sample. "=The original silica-gel-treated extract for sample MW-11 yielded results that did not appear consistent with the non-silica-gel-treated extract. The sample was re-prepared and re- analyzed. The second analysis was more consistent,and is the one that has been reported. It was extracted out of hold time,however. 6=Hydrocarbons reported as TPH as Motor Oil do not exhibit a typical Motor Oil chromatographic pattern. These hydrocarbons are higher boiling than typical diesel fuel,and/or have discrete peaks which may or may not be petroleum related. "=The sample was analyzed by EPA Method 82608 using a bottle that contained a headspace bubble greater than 1/4-inch in diameter. All of the HCI-preserved bottles for this sample contained headspace bubbles. This can happen with alkaline samples,because the Bicarbonate reacts with HCI to form Carbon Dioxide. 18=Hydrocarbons reported as TPH as Diesel do not exhibit a typical Diesel chromatographic pattern. These hydrocarbons are higher boiling than typical diesel fuel,and/or have discrete peaks which may or may not be petroleum related. 9=Surrogate recovery for Method 8015 was above the control limit(s). Since there were no Diesel or Motor-Oil range hydrocarbons detected in the sample,no data are flagged. 20=Samples were analyzed by EPA Method 82608 using a bottle that contained a headspace bubble greater than 1/4-inch in diameter. 21=Sample was re-analyzed to confirm the presence of compounds that were detected in the first analysis. 22=The Method Blank associated with sample MWA 8 contained 81 ug/L TPH as Motor Oil. 23=Samples collected by Wallace Kuhl for Unocal:Lincoln/Weber. 24=Hydrocarbons reported as TPH as motor oil do not exhibit a typical motor oil chromatographic pattern. 25=The Method Blank associated with samples MW-39 contained 88 ug/L TPH as Motor Oil. 26=Matrix Spike/Matrix Spike Duplicate Results for the analyte Toluene were affected by the analyte concentration already present in the un-spiked sample. 27=Hydrocarbons reported as TPH as Diesel do not exhibit a typical Diesel chromatographic pattern. There are discrete peaks which may or may not be petroleum related. 28=Hydrocarbons reported as TPH as Motor Oil do not exhibit a typical Motor Oil chromatographic pattern. These hydrocarbons are lower boiling than typical motor oil. 29=Hydrocarbons reported as TPH as Gasoline do not exhibit a typical Gasoline chromatographic pattern.These spikes are most likely due to the presence of tetrahydrafuran in the sample. 30=Results reported for P,M-Xylene that are below the method reporting limit should be considered estimates. The method detection limit for this compound is 0.37 ug/L. 3'=Hydrocarbons reported as TPH motor oil do not exhibit a typical Motor Oil chromatographic pattern. There are discrete peaks which may or may not be petroleum related. 32=Hydrocarbons reported as TPH as Motor Oil do not exhibit a typical Motor Oil chromatographic pattern.These hydrocarbons are lower boiling than typical motor oil. 33=TPHo results may be bias+/-47.0 ug/L. 34=Results reported for P,M-Xylene that are below the method reporting limit should be considered estimates. The method detection limit for this compound is 0.09 ug/L. 35=Hydrocarbons reported as TPH Diesel do not exhibit a typical diesel chromatographic pattern. These hydrocarbons are lower boiling than typical diesel fuel. 36=Discrete peaks present in motor oil range,atypical for motor oil. 37=Hydrocarbons are lower boiling than typical motor oil. 38=Analysis by Modified Method EPA 8015 yielded inconsistent results. The concentrations appear to vary between the bottles. The highest valid results are reported. 39=Surrogate Recovery for test method Mod.EPA 8015 was outside of control limits. This may indicate a bias in the analysis due to the sample's matrix or an interference from compounds present in the sample. 41=Gasoline hydrocarbons appeared to be present in much higher concentrations when measured via EPA Method 8015 as compared to EPA 82608. If there is undissolved product present in the bottle it will likely be included in the 8015 value but not the 8260B value. It is probable that the sample contains un-dissolved product. 41=Discrete peaks in Diesel range,atypical for Diesel fuel. 42=Discrete peaks,lower boiling hydrocarbons present,atypical for motor oil. 43=Lower boiling hydrocarbons present,atypical for diesel fuel. 44=Matrix Spike/Matrix Spike Duplicate results were outside of control limits. This may indicate a bias for the sample that was spiked. Since the LCS recoveries were within control limits, no data are flagged. 45=City of Stockton well;well not sampled this quarter. 46=Primarily compounds not found in typical gasoline. 4'=Discrete peaks,higher boiling hydrocarbons present,atypical for diesel fuel. 48=Method reporting limit increased due to interference from gasoline-range hydrocarbons. 41=Hydrocarbons reported as TPH as Diesel do not exhibit a typical Diesel chromatographic pattern. These hydrocarbons are higher boiling than typical diesel fuel. 60=Hydrocarbons reported as TPH Gasoline do not exhibit a typical Gasoline chromatographic pattern. The TPH Gasoline values are attributed to the presence of 2-ethyl-l-Hexanol which Kiff Analytical does not consider to be a typical gasoline constituent. Page 66 of 67