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SEc0R ' Fourth Quarter 2003 Quarterly g P Progress Report January 14, 2004 Page 3 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 soil and dissolved in groundwater can be found within the PAR/FRP Addendum 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 4003 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 ' Hydrocarbon Mass To Date(lbs)- Groundwater(lbs)- Removed (lbs)- July 24, 2000 4003 4Q03 TPHg 55 94 456 171 Benzene 42 0 2 41 8 048 MtBE 137 85 52 620 �. 4.0 SUMMARY AND CONCLUSIONS The potential for groundwater flow in the A-zone near the site appears to be radially toward extraction well EX-3, • The groundwater gradient in the B-zone is variable ' • Concentrations of hydrocarbons offsite are below primary and secondary maximum contaminant levels (MCLs), • Concentrations of hydrocarbons dissolved in groundwater 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 5 1 Groundwater Extraction ' SECOR recommends the continued operation of the GWET system to maintain hydraulic control of petroleum hydrocarbons remaining onsite 5 2 Assessment Activities . SECOR recommends no additional assessment activities ' i%Chevron%957751Penodic MonitonnglQ P R1200314th Quarter 2003 QPR doe