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i a <br /> Remediation Progress <br /> The remediation system consists of two well pairs,a vapor monitoring well cluster(NP-2), <br /> a sparging blower,a vapor extraction blower,and a set of two granular-activated carbon <br /> vessels in series. <br /> AS/SVE Progress <br /> As reported in December 1995,the AS/SVE system was consuming carbon adsorption <br /> capacity at an excessive rate. The rate of carbon bed exhaustion was so rapid that <br /> hydrocarbon breakthrough was occurring within days after a carbon change out. To obtain <br /> better control of the operation,the system was taken out of service. We believe this <br /> excessive carbon exhaustion rate was driven by the formation of condensate during the <br /> cold winter months. The above-ground SVE system was reconfigured to minimize <br /> condensate formation,as the process flow diagram provided in Figure 3 shows.The SVE <br /> system reconfiguration is now complete,and the above-ground system is ready for <br /> reactivation. Unfortunately,the groundwater level has risen above the top of SVE well <br /> screens. We are unable to extract soil vapor until the water level drops back down by about <br /> 4 to 5 feet. <br /> AS/SVE Monitoring <br /> Soil and groundwater bacteria respiration and the influence of applied vacuum were last <br /> { measured in March 1995.We are planning to measure each of these parameters when the <br /> i AS/SVE system is back in service. <br /> Estimated Mass Removal by SVE <br /> With the SVE system out of service for reconfiguration,hydrocarbon mass removal has <br /> fbeen negligible since the last quarter. <br /> Intrinsic Bioremediation Demonstration <br /> Samples were collected from monitoring wells MW-DIS-2,3,4,9,8S,and 8D by the <br /> minimUm aeration protocol presented in the Appendix of the PAR/FRP(CH2M HILL, <br /> April 1995). In brief,the intent of this demonstration is to evaluate the geochemical <br /> indicators of natural biodegradation and assess the potential for self containment and <br /> abatement of the Disco site gasoline plume without the expense of more aggressive <br /> remedial measures. <br /> Analytical Results <br /> The geochemical indicators of intrinsic bioremediation are summarized in Table 3 for the <br /> current and all previous monitoring events. <br /> Figure 4 shows the ITB parameters associated with each of the wells monitored on 4/19/96. <br /> The dashed lines in the central lower third indicate the "zone of significant contamination" <br /> 1 SFOIC:IPROJECTSUELMONTE11QMO01—Doc <br />