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S E C 0 R k� ei are not currently in operation Sparge point selection and cycle times are adjusted as petroleum hydrocarbon concentrations in groundwater change SENSTIVE RECEPTORS Based on a sensitive receptor survey a municipal well is present 1800 feet cross gradient from the site ° MONITORING AND SAMPLING TRC's Groundwater Monitoring Report dated October 15, 2004 is included as Attachment A, including Tables 1- 3, Figures 1 - 5, and field data sheets and groundwater analytical reports The site has been monitored and sampled since 15t quarter, 1990 From 1990 to the present the site has been monitored/sampled quarterly Currently, 18 wells (MW-1 through MW-2, MW-4 through MW-9, MW-11, MW-14 through MW-16, PTW-1, VW-1 through VW-4, and VW-7) are monitored and sampled quarterly each year Samples are analyzed for TPHg, TPPH, BTEX, and fuel oxygenates Based on the third quarter 2004 monitoring and sampling event (October 15, 2004) (Attachment A) the maximum TPHg, benzene, and MtBE concentration were 8,500 ppb (VW-7), 4 4 ppb (MW- 16), and 1 9 ppb (MW-15), respectively This represents an 87% decline in TPHg concentrations and over 99% decline in benzene and MtBE concentrations TPHg, benzene, and MtBE concentrations in groundwater continue to decline particularly in source area wells MW-2 and VW-7 • Based upon data collected during ongoing quarterly groundwater monitoring and sampling, dissolved hydrocarbons are effectively delineated both laterally and vertically in the vicinity of the site REMEDIATION STATUS SECOR's Quarterly Remedial Performance Summary which documents ozone sparging and SVE pulsing is included as Attachments B (including Tables B-1 - B-3, and Figures B-1 - B-2), Attachment C (Remediation Field Data Sheets), and Attachment D (Remediation Certified Laboratory Analytical Reports and Chain of Custody Documentation) The ozone injection system consists of panel mounted KVA C-SpargeTM Systems that produce 4 grams per hour (0 009 pounds per hour) of ozone The system injects to ten sparge points in eight wells AS1 through AS5, AS7, ASB, and AS10, and nested wells AS6SfD and AS9SID The ozone sparge system was off in July due to leaking ozone lines The system was repaired and restarted in August During the quarter the system ran for 560 hours System data is presented in Table B-1 (Attachment B) The performance of the ozone injection system is evaluated by groundwater sampling Monthly groundwater samples were collected from monitoring wells MW-16 and VW-7 on July 29, August 19, and September 16, 2004 and analyzed for total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, and total xylenes (BTEX compounds), and methyl tert-butyl ether (MtBE) Results of monthly groundwater sampling events are summarized in Table B-2 Concentration versus time graphs for dissolved TPHg, benzene, and MtBE in monitoring wells MW-16 and VW-7 are provided in Figures B-1 and B-2 • A VES utilizing a catox unit had been in continuous operation at the site between 1994 and 1998 Beginning in 1998 the system was operated in pulse mode due to low influent concentrations As of p the end of the second quarter of 2001, approximately 14,794 pounds of total petroleum s` I F� C �L