ARCHIVED REPORTS - OZONE PILOT TEST & SEMI-ANNUAL GROUNDWATER MONITORING REPORT - THIRD QUARTER 2014

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' 20 March 2015 AGE Project No. 00-0769 Page 15 of 19 water. Ozone injection appears to be the cause for the increased concentrations of barium; however, concentrations of barium did not greatly exceed the MCL (Table 4). • At the conclusion of the ozone pilot test, dissolved concentrations of aluminum had increased in wells MW-2A, MW-5A, MW-6B, MW-8A and decreased in wells MW-1, MW-3A, MW-7B, and MW-10 compared to baseline concentrations detected in June 2013. Aluminum concentrations fluctuated significantly in well MW-9A during the pilot test, increasing to concentrations as high as 2.03 mg/1 in January 2014 and then decreasing to below baseline levels during the final sampling event in October 2014. The aluminum concentrations detected in well MW-9A during the January 2014 and June 2014 sampling events were above the State of California Primary MCL of 1.0 mg/l for drinking water. However, at the conclusion of the ozone pilot test, aluminum concentrations were all below the MCL of 1.0 mg/1 (Table 4). • During the ozone pilot test, dissolved concentrations of Cu, Fe, Zn, B, Ca, Mg, Mn, Na, and K all fluctuated, but remained below their respective State of California Primary MCLs (Table 4). i • Hexavalent chromium, chromium, mercury, and nickel were not detected above their respective laboratory reporting limits in groundwater samples collected from any of the wells during the baseline and four subsequent sampling events (Table 4). • At the conclusion of the ozone pilot test, dissolved concentrations of bromate had 1 increased in wells MW-1, MW-5A, MW-6B, MW-7B, MW-8A, and MW-10 and decreased in wells MW-2A, MW-3A, and MW-9A compared to baseline concentrations detected in June 2013. With the exception of well MW-8A, ' baseline bromate concentrations detected in June 2013 at the site ranged from 1.08 mg/1 (MW-3A) to 6.13 mg/I (MW-1); final bromate concentrations detected in October 2014 at the site ranged from 1.06 mg/I (MW-3A) to 6.63 mg/1 (MW-1). A slight increase in bromate concentrations was observed in the majority of the wells sampled during the ozone injection pilot test. Bromate concentrations were ' significantly above the State of California Primary MCL of 0.01 mg/1 for drinking water. However, bromate concentrations exceeded the Primary MCL of 0.01 mg/1 in each well prior to ozone infection based on sampling performed in June 2013. Based on the data collected prior to ozone injection and at the conclusion of ozone injection, it does not appear that ozone injection is the cause of the high levels of bromate (Table 5). • At the conclusion of the ozone pilot test, COD, pH, electrical conductivity, TDS, chlorine, sulfate, and total alkalinity were all detected at low to normal background concentrations and had not changed significantly compared to ' baseline concentrations (Table 5). Advanced GcoEnvironmental Inc.