U.S. Environmental Protection Agency, 469 pp, 2016

In situ carbon dioxide (CO₂) sparging was designed and implemented to address a subsurface caustic brine pool (CBP) formed as a result of releases from historical chlor-alkali manufacturing operations at the LCP Chemicals Site. The remedial action objectives included reducing the pH of the CBP to between 10 and 10.5. Prior to the start of CO₂ sparging, the total mercury concentration in the CBP ranged from 35.7 to 2,530 µg/L (mean: 270 µg/L; median: 128 µg/L). By the end of Phase 3, almost every monitoring point (28 out of 30) in the deep Satilla aquifer had lower total Hg compared to pre-sparge levels. Most of the monitoring points (23 out of 30) had total Hg concentrations <20 µg/L. About one-third of all monitoring points had Hg concentrations <2 µg/L. At the end of Phase 3, the average total Hg concentration fell from 270 to 36 µg/L, and the median concentration fell from 128 to 4 µg/L. CO₂ sparging was extremely effective in lowering the mean pH in the deep Satilla aquifer from 11.32 (2011-2012) to 7.11. The median pH decreased from 11.44 to 6.57. https://www.epa.gov/foia/co2-sparging-phase-3-full-scale-implementation-and-monitoring-report-0