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1 Bev. CZRZZ� Ms Margaret Lagono ' October 1, 2004 Page 3 ' SP-1A, SP-2A and SP-3A were not operated during the third quarter 2004 since the sparge points were not submerged in groundwater 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 timer schedule is set to cycle through each operational 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 Microsparge System Status System operation began on August 14, 2002 System effectiveness is monitored by assessing ' periodic concentrations of dissolved oxygen (D O ) and monthly analysis of groundwater from monitoring wells MW-2, MW-10, and MW-11 and piezometer well NP-1 Wells MW-2, MW-10, 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 below ground surface (bgs) Wells MWA 0 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 3 Concentrations of TPHg and benzene versus time and TPHg versus depth to water in wells MW-2, MW-10, MW-11, and NP-1 are depicted graphically in Attachment D Effectiveness of Ozone Microsparge System Quarterly groundwater samples were submitted for analyses of BTEX by EPA Method 8021, TPHg by EPA Method 8015 Modified, and fuel oxygenate compounds MtBE, TAME, TBA, DIPE, and ETRE using EPA Method 8260B Additionally, groundwater samples were analyzed for lead scavengers, EDB, and 1,2-DCA, using EPA Method 8260B ' Periodic groundwater samples are collected from wells MW-2, MWA 0, MWA 1 and piezometer NP-1 to further assess the effectiveness of the system Periodic samples were collected on June 23, August 26, and September 14, 2004 The samples were submitted for analysis of BTEX by EPA Method 8021 and TPHg by EPA Method 8015M A summary of analytical results including the monthly sampling events is included in Attachment D as Table 1 ' Discussion Analytical results from wells MWA0 through MWA2 indicate that the ozone microsparge system appears to be effective as evidenced by the overall decreasing petroleum hydrocarbon concentrations Increases were observed in petroleum hydrocarbon concentrations in wells ' J Trojects10694012859 3571FinaftReportsl3rd Qtr 04-QMR RSM2859 3rd Qtr 04-QMR RSR doc ' Celebrahng 35 Years of Excellence in Environmental Services