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EPRIt® Ms Margaret Lagono April 12, 2004 Page 2 MW-21 and NP-1 were analyzed for fuel oxygenate compounds methyl tertiary butyl ether (MtBE), tertiary-amyl methyl ether (TAME), tert butanol (TBA), diisopropyl ether (DIPE), ethyl tertiary butyl ether (ETBE) using EPA Method 82608 Additionally, groundwater samples collected from wells ' MW-1 through MW-11, MW-20 and MW-21 were analyzed for lead scavengers 1,2 -dibromoethane (EDB), and 1,2-dichloroethane (1,2-DCA) using EPA Method 82608 Cumulative groundwater sampling analytical results are summarized in Tables 1 through 5 Dissolved concentrations of benzene, TPHg, MtBE, and 1,2-DCA in groundwater for first quarter 2004 are presented in Figure 5 Copies of the groundwater sampling information sheets are included in Attachment B Laboratory analytical results with chain-of-custody documentation are included in Attachment C Ozone Microsparcle System Description ' The C-SpargeTIA 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 to 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-1A, SP-1 B, SP-1 C, SP-2A, SP-213, SP-2C, SP-3A and SP-31B) 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 Micros ar e 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 Ozone Micros ar e System Status System operation began on August 14, 2002 System effectiveness is monitored by assessing monthly concentrations of dissolved oxygen (D O ) and quarterly analysis of groundwater from monitoring wells MW-2, MW-10, and MW-11 and piezometer well NP-1 Wells MW-2, MW-10, ' MW-11, 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 TPHg vs depth to water in wells MW-2, MW-10, MW-11, and NP-1 are depicted graphically in Attachment D J TrojecW06940059 357WinaRReportOst Qtr 2004-QMR-RSR doc 35 Years of Excellence,n Environmental Services