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• MW-8 1,2-DCA (1 0 pg/L) was reported in well MW-7 GRO, benzene, and MTBE analytical data for the fourth quarter 2005 are presented in Figure 5 Analytical data were submitted to the State Water Resources Control Board as required by AB2886 The electronic delivery receipt is attached in Appendix C Historical groundwater monitoring and chemical analytical data dating back to 2000 are included in Appendix D Lower Zone Wells At the time of the fourth quarter 2005 monitoring event, groundwater had decreased 0 15 and 0 55 feet in wells MW-9 and MW-10 since the previous monitoring event (September 8, 2005) Depth-to-water measurements were corrected to mean sea level (MSL) and used to construct a groundwater elevation contour map (Figure 4) The groundwater flow direction was generally to the northeast at an average gradient of 0 016 ft/ft During the fourth quarter 2005, GRO, BTEX, TBA, ETBE, TAME, EDB, or ethanol were not reported in any of the lower zone wells MTBE was reported in wells MW-9 (1 6 pg/L) and MW-10 (54 pg/L) 1,2-DCA was reported in wells MW-9 (2 2 pg/L) and MW-10 (7 0 pg/L) DIPE (1 8 pg/L) was reported in well MW-10 GRO, benzene, and MTBE analytical data for the fourth quarter 2005 are presented in Figure 6 Analytical data were submitted to the State Water Resources Control Board as required by AB2886 The electronic delivery receipt is attached in Appendix C Historical groundwater monitoring and chemical analytical data dating back to 2000 are included in Appendix D REMEDIATION SYSTEM STATUS System Description The C-SpargeTM 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-SpargeTM 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 2005 (from October 6, 2005 to December 29, 2005), a Stratus technician conducted six site visits to collect field and laboratory parameters, and to conduct operation and maintenance of the ozone injection system Field data sheets presenting field parameters collected during the fourth quarter 2005 are included in Appendix A Certified analytical reports with chain-of-custody documentation are included in Appendix C Analytical data were submitted to the State Water Resources Control Board as required by AB2886 The electronic delivery receipt is attached in Appendix C Ozone In ection Monitoring Plan Monitoring wells MW-3 through MW-10 are used as observation wells to monitor the performance of the ozone injection system Monitoring wells MW-1 and MW-2 are used as background wells K 1Bp-Arca for URS154691Quarterly120051Arco_5469_4Q05 docPage 4 of 6 5TRaTU5