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• During the first quarter 2006, TBA, DIPS, ETBE, TAME, EDB, or ethanol were not reported in any of the upper zone ARCO wells GRO (640 �Lg/L) and benzene (5 5 pg/L) were reported in well MW-4 MTBE was reported in wells MW-1, MW-3 through MW-6, MW-8, MW-11, and MW-13, at concentrations ranging from 0 80 µg/L (MW-3) to 5,700 µg& (MW-6) 1,2-DCA was reported in wells MW-7 (1 0 Pg1L), MW-12 (0 74 µg/L), and MW-13 (7 4 pg/L) GRO, benzene, and MTBE analytical data for the first quarter 2006 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 (2000-2004) are included in Appendix D Lower Zone Wells At the time of the first quarter 2006 monitoring event, groundwater had increased 1 22 and 1 60 feet in wells MW-9 and MW-10, respectively, since the previous monitoring event (December 8, 2005) Depth to water measurements were corrected to mean sea level (MSL) and used to construct a groundwater elevation contour map (Figure 4) East-southeast groundwater flows, at average gradients ranging from 0 0012 ft/ft offsite to 0 0093 ft/ft onsite, were generally observed During the first quarter 2006, GRO, BTEX, TBA, ETBE, TAME, EDB, or ethanol were not reported in any of the lower zone ARCO wells MTBE was reported in wells MW-9 (8 4 pg/L) and MWA 0 (23 µg/L) 1,2-DCA was reported in wells MW-9 (1 8 pg/L) and MW-10 (6 7 µg/L) DIPE (2 1 µg/L) was reported in well MW-10 GRO, benzene, and MTBE analytical data for the first quarter 2006 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 (2000-2004) are included in Appendix D REMEDIATION SYSTEM STATUS • System Description The C-SpargeTM system, manufactured by KVA®, consists of a control panel (ozone generator, air compressor, and tubing manifold), and 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-Sparge m system was started on December 26, 2002 The C-SpargJm 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 The bearings on the compressor appear to have worn out and a new compressor was installed on February 1, 2006 During the first quarter 2006 (from January 10, 2006 to March 21, 2006), 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 K IBp-Arco for URS154691Quarteriy120061Arco_5469_1Q06 docPage 4 of 6 57"RA7"u5