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E11��t® Rog Ms Margaret Lagono ' February 5, 2004 Page 2 ' 1,2 -dibromoethane (EDB), and 1,2-dtchloroethane (1,2-DCA) using EPA Method 82608 Cumulative groundwater sampling analytical results are summarized in Table 1 through Table 5 Dissolved concentrations of benzene, TPHg, MTBE, and 1,2-DCA in groundwater for fourth quarter 2003 as presented on Figure 4 Copies of the groundwater sampling information sheets are included to Attachment B Laboratory analytical results with chain-of-custody documentation are included in Attachment C ' Ozone Microsparge System Description The ozone system consists of groundwater treatment via a C-SpargeTM system The C- SpargeT"" system includes an ozone generator, air compressor, and a programmable timer/controller The C-SpargeTM system utilizes ozone microsparging a process where ozone is entrained in air and introduced into groundwater The ozone is injected at low flow rates of 2- 6 cubic feet per minute through specially designed sparge points to create "microbubbles " As these microbubbles rise within the column of water, dissolved volatile organic compounds (VOCs) including petroleum hydrocarbons are oxidized The system cycles ozone/air injection between eight micro-sparge points (SP-1 A, SP-1 B, SP-1 C, SP-2A, SP-213, SP-2C, SP-3A and SP-313) Ozone sparge points introduce ozone into the areas of highest dissolved VOC concentrations near the eastern property boundary of the Unocal site Each sparge point has a dedicated line and is connected to the system by LDPE tubing The LDPE tubing runs through Schedule 40 PVC conveyance piping for added protection Ozone Microsparge System Operation The schedule was initially set to cycle through each sparge point 18 times per day, for nine ' minutes per point per cycle There is an eight-minute rest period between cycles The programmable timer/controller is varied during the quarter to provide more treatment to selected areas 1 Ozone Microsparge System Status ' System effectiveness is monitored by assessing monthly groundwater analytical data and concentrations of dissolved oxygen (D O) from monitoring wells MW-2, MW-10, and MW-11 and piezometer well NP-1 Wells MW-2, MWA 0, MWA 1, and NP-1 are located adjacent to the ' eastern property boundary of the site (Figure 2) and are within the zone of influence of one or more sparge points Well MW-2 is screened from 20 to 50 feet bgs Wells MW-10 and MW-11 are screened from 50 to 60 feet bgs Well NP-1 is screened from 85 to 90 feet bgs A summary of D O concentration data is presented in Table 6 Concentrations of TPH as gasoline vs depth ' to water in wells MW-2, MW-10, MWA 1, and NP-1 are depicted graphically in Attachment D The ozone micro sparge system was operated only intermittently during the fourth quarter 2003 due to equipment malfunctions and power outages ' J\Projectsk069401357-2859\FinaiNReports\4th Qtr 2003-QMR-RSR doc ' 35 Years of Excellence in Environmental Services