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Rationale for Considering Conditional - 5 - 25 March 2026 <br /> No Further Action <br /> Olin Chlor Alkali Facility <br /> Tracy, San Joaquin County, California <br /> - Concentrations exceeding the CC14 MCL of 0.50 fag/L are shown in bold. <br /> - Laboratory J flag indicates an estimated value. <br /> - Groundwater samples were analyzed for VOCs by USEPA Method 8260D. <br /> - Middle zone grab groundwater samples GGW-2 were collected at 37.5 and 51 feet <br /> bgs. <br /> - The primary and duplicate samples are separated by a forward slash. <br /> < = CC14 not detected above the method detection limit. <br /> CF: Recent analytical results for CF are shown in Figures 9 through 11. Time-series <br /> graphs for CF in the upper, middle, and lower groundwater zones are plotted in <br /> Figures 15 through 17. CF detections are localized off-Site, with detections below the <br /> MCL of 80 pg/L in all three zones. Concentrations are stable or decreasing and do <br /> not appear to be migrating farther downgradient. <br /> The table below presents the most recent concentrations of CF measured during the <br /> March 2025 groundwater monitoring event and the June 2024 grab-groundwater <br /> investigation: <br /> Identification Sample CF <br /> Number Month/Year Concentration Sample Type <br /> (pg/L) <br /> Upper Zone <br /> MW-5 March 2025 7.4 Well <br /> MW-9 March 2025 58 Well <br /> MW-11 March 2025 4.8 Well <br /> MW-13 March 2025 <0.030 Well <br /> GGW-1 June 2024 0.054 J Grab <br /> GGW-2 June 2024 15 J Grab <br /> Middle Zone <br /> MW-10 March 2025 55 Well <br /> MW-12 March 2025 76 / 75 Well <br /> MW-14 March 2025 <0.030 Well <br /> GGW-1 June 2024 0.031 J Grab <br /> GGW-2 (37.5) June 2024 13 / 12 Grab <br /> GGW-2 (51) June 2024 37 Grab <br /> Lower Zone <br />