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S ECOR <br />Second Quarter 2003, Quarterly Progress Report <br />July 14, 2003 <br />Page 4 <br />Constituent <br />Estimated <br />Hydrocarbon Mass <br />(lbs)- July 24, 2000 <br />Mass Removed <br />To Date (lbs)- <br />2Q03 <br />Mass Remaining in <br />Groundwater (lbs)- <br />2003 <br />Percentage <br />Removed <br />T PH g <br />55 <br />9 <br />46 <br />16.36 <br />Benzene <br />42 <br />0.2 <br />41.8 <br />0.48 <br />MtBE <br />137 <br />84.8 <br />52.2 <br />61.9 <br />3.3.2 Estimated Mass of Petroleum Hydrocarbons Adsorbed in Soil <br />The results presented below were previously presented within the first quarter 2003 (1 Q03) Quarterly <br />Progress Report. <br />Constituent <br />Estimated <br />Hydrocarbon Mass <br />(lbs) <br />Mass Removed <br />To Date (lbs)- <br />2Q03 <br />Mass Remaining <br />in Soil (lbs)- 2003 <br />Percentage <br />Removed <br />TPHg <br />1,450 <br />4,129.1 <br />-2,680.1 <br />284.8 <br />Benzene <br />1 370 <br />1 85.8 <br />1 284.2 <br />23.2 <br />MtBI* <br />167 <br />1 443.8 <br />1 -376.8 <br />662.4 <br />4.0 SUMMARY AND CONCLUSIONS <br />• Groundwater near the site appears to flow radially toward extraction well EX -3; <br />• Concentrations of hydrocarbons offsite are below primary maximum contaminant levels (MCLS); <br />• Vapor extraction mass removal has reached asymptotic levels; <br />• Concentrations of hydrocarbons dissolved in groundwater continue to decline, and; <br />• GWE operational data indicates a decline in dissolved hydrocarbon mass removal from the <br />subsurface. <br />5.0 RECOMMENDATIONS <br />Based on the data presented above and historical data, SECOR recommends the following: <br />5.1 Groundwater Monitoring and Sampling <br />Based on historical groundwater monitoring and sampling results, SECOR recommends that monitoring <br />wells MW -2, MW -11A, MW -11B, MW -12A, MW -12B, MW -13, MW -20A, and MW -20B be sampled on a <br />semi-annual basis and gauged quarterly. SECOR recommends quarterly groundwater monitoring and <br />sampling on the remaining wells. Additionally, SECOR recommends the removal of MW -5A from the <br />monitoring and sampling program. Monitoring well MW -5A is potentially screened across A and B -Zone <br />quarters and is used for contouring purposes. MW -5A is located in proximity to A -Zone well MW -6 and B - <br />Zone well MW -513. <br />1AChevron1957751Pedod1c MonitoringQuarterly Progress Reports1200312nd Quarter -2003 QPR.doc <br />