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S E C ® R • Groundwater has been monitored on a quarterly basis since 1990 and sampled at the site on a quarterly or semi-annual basis since April 1993 Floating product or sheen has never been observed in any of the wells Historically, petroleum hydrocarbon concentrations in the t groundwater have ranged from not detected to 78,000 parts per billion (ppb) of TPHg (well VW- 2), not detected to 28,000 ppb of benzene (well MW-5), and not detected to 4,900 ppb of MtBE (well VW-3) Groundwater data for the third quarter 2001 sampling event on September 12 and 13, 2001 ranged from not detected to 34,000 parts per billion (ppb) of TPHg (well VW-7), not detected to 870 ppb of benzene (well VW-7), and not detected to 310 ppb of MtBE (well VW-4) Historically, depth to groundwater has risen from approximately 51 to 53 feet bgs in 1993 to 30 to 32 feet bgs in September 2001 Groundwater flow has been to the northeast with the hydraulic gradient ranging from 0 002 to 0 013 feet/feet In November 2001 Gettler Ryan install ten ozone wells SP-1 through SP-10 to approximately 65 feet bgs and three ozone wells SP-11 through SP-13 were installed to approximately 40 feet bgs The wells were connected to an ozone sparge system and the system was placed into operation on December 19, 2001 The system cycles ozone/air infection between ten sparge points (SP-1 through SP-10) Since the ozone microsparge panel can only supply ten points, wells SP-11 through SP-13 will be for future use The schedule is currently set to cycle through each point 16 times per day, for 5 to 10 minutes per point per cycle Sparge point selection and cycle times will be 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 The site has been monitored and sampled since 1" 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 REMEDATION STATUS The ozone infection systems consist of panel mounted KVA C-SpargeTM" Systems that produce 4 grams per hour (0 009 pounds per hour) of ozone The system infects ozone to ten ozone wells SP-2, SP-4 through SP-9, and SPA through SPA The system was placed into operation on December 19, 2001 During the first quarter of 2004 the system operated at 100% of the programmed runtime CHARACTERIZATION STATUS Contamination in soil and groundwater has been adequately delineated RECENT SUBMITTALS/CORRESPONDENCE April 27, 2004 —Quarterly Remedial Summary Report THIS QUARTER ACTIVITIES(First Quarter 2004) . 1 Prepared and submitted a quarterly summary report r