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• Groundwater Gradient 0 0015 to 0 0030 fUft INTERIM REMEDIATION SYSTEM OPERATION AND PERFORMANCE Equipment Inventory Ozone Injection System (Manufactured by KVA) Operating Mode Operational Reporting Period October 11, 2004 through December 23, 2004 Historical Highest GRO Concentration 55,000 L�gIL(MW-6, 2002) Historical Highest Benzene Concentration 18,000 IL MW-8, 2001 Historical Highest MTBE Concentration 85,000µg/L(MW-6, 2002) _ Highest GRO Concentration this Period 13,000µglL(MW-4) Highest Benzene Concentration this Period 2,500 pg/L(MW-4) _ Highest MTBE Concentration this Period 23,000µg/L(MW-8) _ Number of System Shutdowns This Period 1 DISCUSSION At the time of the fourth quarter 2004 monitoring event, groundwater elevations had decreased between 0 74 and 0 92 feet since the previous sampling event (September 14, 2004) Depth-to-water measurements were corrected to mean sea level (MSL) and used to construct a groundwater elevation • contour map (Figure 3) Wells MW-9 and MW-10 are screened in a deeper portion of the water-bearing zone and were not used in contouring The groundwater flow direction on December 9, 2004, was radial away from groundwater highs that have developed around wells MW-4 and MW-5 Gradients ranged from 0 0015 to 0 0030 ft/ft Northeast flow has been observed at this site during previous quarters REMEDIATION SYSTEM STATUS System Description The C-Sparge7m system, manufactured by KVe, consists of a control panel (ozone generator, air compressor, and tubing manifold), and strategically located injection points (IW-1 through IW-5, see Figure 2) used to inject low concentrations of ozone into groundwater In addition, the control panel also has a programmable timer that limits the amount of ozone injected into each injection point The system injects a timed pulse of ozone at low flows and low pressures (10-30 psi) to each of the five injection points in a sequence The ozone dissolved in groundwater is expected to oxidize petroleum hydrocarbons into carbon dioxide and water, and any un-reacted ozone will degrade to dissolved oxygen, which is likely to enhance natural biodegradation of residual petroleum hydrocarbons System Operation Details The C-SpargeT"" system was started on December 26, 2002 The C-SpargeTM control panel was programmed and scheduled to inject ozone cyclically into each injection point for 14 minutes Based on this programming, each injection point will have ozone injection in 18 cycles for 4 2 hours every day During the fourth quarter 2004 (between October 11, 2004 and December 23, 2004), a Stratus technician conducted six site visits to collect field parameters and laboratory parameters and to conduct operation and maintenance of the ozone injection system The ozone injection system was shutdown between • October 11, 2004, and October 21, 2004, due to a compressor malfunction The ozone injection system was re-started on October 21, 2004, after replacing the compressor and the remediation system appears K\Bp-Arco for URS\5469\Quartcriy\2004\Arco_5469_4QO4 doc 5TRATUS