Background/Objectives. A large-scale enhanced in situ bioremediation/reduction remedy was implemented at a coastal site in southern California with chlorinated solvent and hexavalent chromium impacts in groundwater. Beginning with a 100-point injection in 2006 across an area of approximately 1 acre, the treatment area was later expanded to other portions of the site with an additional 850+ injection locations over a total of approximately 4 acres. Since the initial injection in 2006, continuous monthly, followed by quarterly and semiannual sampling has tracked the long-term degradation trends, stability, and effectiveness of the single-injection passive bioremediation remedy. Although the emulsified vegetable oil (EVO) electron donor was likely exhausted in the first one to two years following the injection, active and effective biodegradation has continued to be observed throughout the treated area, possibly sustained by carbon contained within the biomass generated during the initial growth period.
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