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. State Water Resources Control Board as required by AS2886 The electronic delivery receipt Is attached
<br /> in Appendix C
<br /> Ozone In ection Mondorinci Plan
<br /> Monitoring wells MW-3 through MW-10 are used as observation wells to monitor the performance of the
<br /> ozone infection system Monitoring wells MW-1 and MW-2 are used as background wells to evaluate and
<br /> monitor for natural geo-chemical changes in the groundwater
<br /> During the third quarter 2004, field parameters were collected on a monthly basis and select laboratory
<br /> parameters were collected on a quarterly basis During the third quarter 2004 monitoring event, all
<br /> samples were collected after purging three volumes of well casing The modified ozone injection
<br /> monitoring plan is listed below and a summary of frequency and significance of field and laboratory
<br /> parameters is presented in Table 3
<br /> Field Parameters (Monthly) pH, Dissolved Oxygen (DO), and Specific Conductivity
<br /> Laboratory Parameters (Quarterly) GRO, BTEX, five oxygenates, Chemical Oxygen Demand (COD),
<br /> Ferrous Iron, Total Iron, and Heterotrophic Plate Count
<br /> Laboratory Parameters (Annually) Total Organic Carbon (TOC), Nitrates, Sulfates, Phosphates, and Total
<br /> Dissolved Solids
<br /> Results
<br /> Results of field and analytical parameters collected to date to evaluate and optimize the performance of
<br /> • the ozone infection system are presented in Tables 4 and 5 The GRO, benzene, and MTBE
<br /> concentrations observed in all the groundwater monitoring wells during the third quarter 2004 are
<br /> presented in Figure 4 Change In DO concentrations for select observation and background monitoring
<br /> wells are presented in Figure 5 The historical GRO, benzene, and MTBE concentration variation over
<br /> time at select monitoring wells (MW-4 through MW-8) are illustrated graphically in Figures 6 through 10
<br /> During the third quarter 2004, GRO concentrations appeared to have generally increased in wells MW4
<br /> and MW-8, with the highest increase observed in well MW-8 (from 180 pg/L. to 25,000 pg/L) Historically
<br /> GRO was not reported in wells MW-5 or MW-6, however, the laboratory reporting limits in these wells
<br /> were raised to 500 pg/L and 25,000 pg/L, respectively
<br /> During the third quarter 2004, benzene was reported In wells, MW-4 and MW-8 Benzene concentrations
<br /> had decreased (from 990 pg/L. to 420 pg/L) In well MW-8, and had increased (from 1,900 pg/L to 2,500
<br /> pg/L) in well MW-4, since the previous sampling event (June 8, 2004) Benzene concentrations in other
<br /> monitoring wells were below the laboratory reporting limit of 0 5 pg/L
<br /> Since the previous sampling event (June 8, 2004), MTBE concentrations had decreased in groundwater
<br /> samples collected from wells MW-1, MW-3, MW-5, MW-6, MW-8, and MW-9, and had increased in well
<br /> MW-10 The greatest decrease in MTBE (from 32,000 pg/L to 20,000 pg/L) was observed in well MW-8,
<br /> while the only increase (from 85 pg/L to 100 pg/L)was observed in well MW-10
<br /> DIPE (0 74 pg/L) was reported In well MW-9 1,2-DCA was reported in wells MW-7 (1 3 pg/L) and MW-9
<br /> (3 8 pg/L) TBA, ETRE, TAME, EDB, or ethanol were not reported In any of the wells Analytical data
<br /> were submitted to the State Water Resources Control Board as required by AB2886 The electronic
<br /> delivery receipt is attached in Appendix C
<br /> . During the third quarter 2004, the average DO levels in observation wells (MW-3 through MW-10) varied
<br /> In the range of 0 80 mg/L to 8 7 mg/L, while the average DO levels in background monitoring wells (MW-1
<br /> P\BP-Arco for UR5154691Quarterly120041Arco_5469_3Q04 doc 3TRAW5
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