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E C 0 R Service Station #5469 QGM &RPR 2Q06 September 18, 2006 Page 4 A summary of the remediation system O&M and an evaluation of the effectiveness of the OS system is presented below OS System Description and Operation The OS system, manufactured by KVA", consists of a control panel (ozone generator, air compressor, and tubing manifold), and five OS wells (IW-1 through IW-5, Figure 2) The KVA C- SpargeT"" System produces up to two grams per hour of ozone The control panel has a programmable timer that cycles the ozone injection to the five OS wells at low pressures (10-30 pounds per square inch]) The ozone dissolved in the groundwater is anticipated to oxidize petroleum hydrocarbons into carbon dioxide and water, and any un-reacted ozone will degrade to dissolved oxygen (DO) The DO is likely to enhance natural biodegradation of residual petroleum hydrocarbons The OS system was started on December 26, 2002 The control panel was programmed and scheduled to inject ozone cyclically into infection points IW-1 through IW-5 for 14 minutes each Based on this programming, each infection point will have ozone infection in 18 cycles for 4 2 hours every day In April, Stratus replaced the fans in the ozone injection control panel In June, Stratus replaced the piston seals in the compressor Besides these O&M activities, the OS system was operated continuously with no unusual events during the second quarter 2006 OS Systema Monitoring Monitoring wells MW-3 through MW-10 are used as observation wells to monitor the performance of the OS system Monitoring wells MWA and MW-2 are used as background wells to evaluate and monitor for natural geo-chemical changes in groundwater During the second quarter 2006, groundwater parameters including depth to water, pH, DO concentration, specific conductivity, and oxygen reduction potential in the observation and background wells were measured and recorded in the field monthly Field-measured groundwater physical parameters are summarized in Table 4 Along with GRO, BTEX, MtBE, TAME, DIPE, EtBE, TBA, ethanol, 1,2-DCA and EDB, groundwater samples collected from wells MWA, and MW-4 through MWA 0 on May 30, 2006 were analyzed for chemical oxygen demand (COD) using EPA method 410 4, for total iron using EPA method 200 7, and for heterotrophic plate count using APHA standard method 9215B Additionally, samples collected from these wells are analyzed for total organic carbon (TOC), nitrates, sulfates, orthophosphates, and total dissolved solids (TDS) annually Groundwater analytical parameters are summarized in Table 5 The laboratory analytical report is included In Attachment C Evaluation of OS System Effectiveness The DO concentrations were measured in-situ with field instrumentation on April 7, May 5, and June 16, 2006 During these measurements, DO concentrations in observation wells (MW-3 through MW-10) ranged from 0 7 mg/L to 6 9 mg/L, with an average of 2 9 mg/L The DO concentrations in the background monitoring wells (MW-1 and MW-2) ranged from 1 9 mg/L to 5 7 mg/L, with an average of 3 3 mg/L The highest DO concentration (6 9 mg/L) was observed in observation well MW-7 (June 16), located approximately 10 feet from infection well IW-5 The DO concentrations in wells MW-1 through MW-10 versus time are shown on Figure 5 MW-7 and MW-9 are the only two monitoring wells within approximately 10 feet of an OS well 11BP-ARC0104 SP Valley Portfoho154691Reports\QMRs1200615469 2Q2006 doc SECOR International Incorporated