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1 <br /> Margaret Lagorio <br /> April 26, 2004 <br /> ' Page 3 <br /> ' VOC concentrations near the eastern property of the Unocal Site. Each sparge point has a <br /> dedicated line and is connected to the system by LDPE tubing. The tubing runs through <br /> Schedule 40 PVC. The system layout is shown in Figure 9. <br /> ' Ozone Micros ar e System Operation <br /> ' The schedule was initially set to cycle through each point 18 times per day, for nine minutes per <br /> point per cycle. There is an eight-minute rest period between cycles. The programmable <br /> timerlcontrollers are varied during the quarter to provide more treatment to selected areas. <br /> ' Ozone Microsparge System Status <br /> System effectiveness is monitored by assessing groundwater analytical data and concentrations <br /> ' of dissolved oxygen (D.O.) from single-completion wells U-3 and U-10 and nested piezometers <br /> NP-1 and NP-2 (Figure 2). Wells U-3, U-10 and NP-1, NP-2 are within the zone of influence of <br /> one or more sparge points. D.O. readings are collected monthly, with groundwater samples, <br /> ' from wells U-3, U-10, and piezometers NP-1 and NP-2. A summary of D.O. concentration data <br /> _is presented in Table 4. Well construction details and D.O. readings are summarized in Tables — <br /> 7 and 8, respectively. <br /> Concentrations of TPHg and benzene in wells U-3 and U-10 and piezometers NP-1 and NP-2 <br /> are depicted graphically in Attachment D. The ozone microsparge system was not operated <br /> ' continuously during the first quarter 2004 due to equipment malfunctions. <br /> Effectiveness of Ozone Microsparge System <br /> ' Groundwater samples were submitted for analyses of BTEX by EPA Method 8021, TPHg by <br /> EPA Method 8015 Modified, and fuel oxygenate compounds: MtBE, TAME, TBA, DIPE, and <br /> ETBE using EPA Method 82608, Copies of the groundwater sampling information sheets are <br /> included as Attachment B. Laboratory analytical results with chain-of-custody documentation <br /> are included as Attachment C. Graphs of concentrations of TPHg and benzene versus time in <br /> wells U-3 and U-10 and piezometers NP-1 and NP-2 are included as Attachment D. <br /> ' TPHg Concentration Trends <br /> ' TPHg concentrations decreased in piezometer NP-1-22 since the last sampling event. <br /> • TPHg concentrations in wells U-3 and U-10 and piezometers NP-1-65, NP-2-60, and <br /> NP-2-116 increased since the last sampling. event. All of these wells were sampled during ---- <br /> the last sampling event except for NP-1-65. <br /> • TPHg concentrations remained below laboratory reporting limits in piezometers NP-1-111 <br /> and NP-2-22. <br /> J:1Projects10694010187-3251FinallReportsllst Qtr 04-QMR RSRN0187 1st Qtr 04-QMR RSR.doc <br /> ' Q 5 35 Years of Excellence in Environmental Services <br />