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First Quarter 2004, Quarterly Progress Report April 14, 2004 ' [ Page 3 t 3 2 Hydrocarbon Mass Estimate ' The hydrocarbon mass estimates presented below are an update of results presented within the Problem Assessment Report/Final Remediation Plan (PAR/FRP) Addendum, dated June 5, 2001 Methodology for determining the mass of hydrocarbons adsorbed to sod and dissolved in groundwater can be found ' within the PARIFRP Addendum l 3 2 1 Estimated Mass of Petroleum Hydrocarbons Dissolved in Groundwater ' The results presented below are based on the calculation presented within the PAR/FRP Addendum and cumulative 1Q04 GWE mass removal data To conservatively estimate analyte mass remaining, ' historical groundwater analytical data was used This information is summarized in the following table Constituent Estimated Mass Removed Mass Remaining in Percentage I Hydrocarbon Mass To Date(lbs)- Groundwater(lbs)- Removed (lbs)-July 24,2000 1Q04 1Q04 TPHg 55 97 453 176 ' Benzene 42 0 2 41 8 048 l MtBE 137 85 52 620 4.0 SUMMARY AND CONCLUSIONS I ( • The potential for groundwater flow in the A-zone near the site appears to be radially toward l extraction well EX-3, ' r . The groundwater gradient in the B-zone is variable IL • Concentrations of hydrocarbons offsite are below primary and secondary maximum contaminant levels (MCLs), • Concentrations of hydrocarbons dissolved in groundwater, in general, continue to decline, and GWET operational data indicates a decline in dissolved hydrocarbon mass removal from the ' subsurface • 5 0 RECOMMENDATIONS Based on the data presented above and historical data, SECOR recommends the following ' 51 Groundwater Extraction SECOR recommends the continued operation of the GWET system to maintain hydraulic control of II petroleum hydrocarbons remaining onsite I 11Chevron1957751Penodic Morrntonng\Q P R1200411st Quarter 2004 QPR doc