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S E C ® R �g . 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) In November 2001 GR 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 injection 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 Sparge point selection and cycle times will be adjusted as petroleum hydrocarbon concentrations in groundwater change i 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 June 23, 2004 is included as Attachment A, including Tables 1- 3, Figures 1 - 5, and Graphs 1 - 8 plus field data sheets and groundwater analytical reports The site has been monitored and sampled since 1St 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 second quarter 2004 monitoring and sampling event (June 16, 2004) (Attachment A) the maximum TPHg, benzene, and MtBE concentration were 10,000 ppb (VW-7), 35 ppb (MW-16), and 38 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 Y Offsite wells MW-14 and MW-15 continue to report detections of MtBE ranging from 3 1 ppb to 38 ppb MtBE concentrations in both of these wells continue to decline 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 is included as Attachments B (including Tables B-1 - B-2, and Figures B-1 - B-3), Attachment C (Remediation Field Data Sheets), and ' Attachment D (Remediation Certified Laboratory Analytical Reports and Chain of Custody Documentation) The ozone injection systems consist 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, AS8, and AS10, and nested wells AS6SID and AS9S/D During the current quarter the system ran for 864 minutes before being shut down on May 19, 2004 due to ozone leaking out of the lines The lines will be replaced in the third quarter 2004 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 April 23, May r+ x