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I <br /> Mr Daniel K Barber, P E <br /> lie <br /> September 9, 2003 <br /> Page 9 of 17 <br /> regulatory agency screening-level criteria (and likely the site closure numerical criteria) are <br /> generally the same for volatile- and extractable-range hydrocarbons This report therefore <br /> ' evaluates hydrocarbon contamination as the sum of the volatile and extractable ranges (not <br /> including kerosene quantification) <br /> Soil Contamination <br /> Volatile- and diesel-range hydrocarbons, as well as BTEX, are present in residual soils at <br /> concentrations in excess of regulatory agency screening level criteria Onsite usage of both <br /> gasoline and diesel in USTs is docurnented These contaminants should be considered site <br /> contaminants of concern in soil (i e , their presence and concentrations should be confirmed if <br /> additional remedial measures are undertaken) Appendix A contains the tabulated soil data <br /> The fuel additive MTBE was analyzed for only in the initial (1999) subsurface investigation <br /> No MTBE was detected in any of 20 soil samples from five boreholes in the immediate <br /> vicinity of the former USTs, including boreholes with near maximum petroleum hydrocarbon <br /> concentrations This suggests that MTBE is not a contaminant of concern in site soil <br /> Groundwater <br /> Volatile-Range Hydrocarbons and BTEX <br /> Volatile-range hydrocarbons were detected in one of the two exploratory borehole "grab" <br /> groundwater samples (B-4) at 71 µg/L Of the nine groundwater monitoring well samples <br /> analyzed, volatile-range hydrocarbons have been detected only once---1n well MW-1 (March <br /> 2001) at 56 µg/L Both concentrations are well below the 100 µg/L RBSL While volatile- <br /> range hydrocarbons (and BTEX) were detected in soils in the immediate vicinity of the <br /> former USTs, historical groundwater monitoring data indicate that their impact to <br /> groundwater is negligible Therefore, in our opinion, these are not site contaminants of <br /> concern in groundwater, and further analysis for volatile hydrocarbons and BTEX is not <br /> technically warranted According to Mr Jeffery Wong of SJCPHS, MTBE is not considered <br /> a potential site contaminant of concern at this site, based on site history and early analytical <br /> results from the USF removal stage Appendix A contains the tabulated groundwater data <br /> Kerosene-Range Hydrocarbons <br /> As discussed previously, in our professional opinion, the reported kerosene contamination is a <br /> ' false-positive and total extractable-range hydrocarbons are appropriately quantified as diesel <br /> Therefore, kerosene is not a site contaminant of concern and further analysis for kerosene is <br /> ' technically unwarranted <br /> Stellar Environmental Solutions <br /> Z YNOIFF"191W3AcfivcN coSM0 DKDUEcF ClmweltcVm rl FqurtiREPDK'Y�ePmba 92W3dc <br />