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Table 4 Groundwater Analytical Data-Total Petroleum Hydrocarbons and BTEX South Shore Parcels-Parcel 2A and Adjacent Areas West Weber Avenue and North Lincoln Street Stockton,California Depth Ethyl- Sample (feet, Date TPHg TPHd TPHk TPHo Benzene Toluene benzene Xylenes ID bgs) Sampled (mg/1) (mg/1) (mg/1) (mg/1) (mg/1) (mg/1) (mg/1) (mg/1) Explanations: J=The reported value is below the Method Reportin Limit should be considered an estimate. 2=Sample ID also known as W-21-MW2 by Mobile Chem Labs Inc.analytical data and Applied GeoSystems'Subsurface Environmental Investigation Report dated October 31,1989. 3=Sample ID also known as W-25-MW3 by Chemwest Analytical Labs Inc.analytical data&within Applied GeoSystems'Subsurface Environmental Investigation Report dated October 31,1989. 4=Sample exhibits fuel pattern that does not resemble standard. 5=Lighter hydrocarbons contributed to the quantitation. 6=Heavier hydrocarbons contributed to the quantitation. 7=Sample exhibits unknown single peak or peaks. 8=QA/QC samples collected by Clayton Group Associates. 9=The method reporting limit for TPHd is increased due to interference from gasoline-range hydrocarbons. 10=Repeated analysis yielded inconsistent results for TPHg. The highest recovery value of has been reported,but should be considered an estimate. 11=Matrix Spike/Matrix Spike Duplicate Results for the analyte Benzene were affected by the analyte concentration already present in the un-spiked sample. 12=Samples collected by Clayton Group Services for Unocal:Lincoln/Weber. 13=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. 14=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. 15=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. 16=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. 17=The sample was analyzed by EPA Method 8260B 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 HCl 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. 19=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 8260B 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 MW-18 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 petroloeum 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. Stantec I:\Tidewater\TW Stockton(Parcel 2A-0415)\Tables\QMR Tables\2010\4Q10\20101117-Parcel2A(Tables 4,5,6,7)Historical GW Tables 4Q10.xls Page 66 of 67