Topic Area: 2d. Biobarrier Implementation and Management

Formatted Title:

Optimizing In Situ Treatment Barriers: An Adaptive Strategy for a Superfund Site

Background/Objectives:

The remedial design (RD) for this site incorporates in situ treatment barriers using in situ bioremediation (ISB) or zero-valent iron (ZVI) emplaced in trenches where TCE is greater than 500 µg/L and MNA where TCE is less than 500 µg/L. The RD includes two hotspot ISB barriers and three downgradient treatment barriers.

Approach/Activities:

Six years after pre-RD characterization and a field pilot ISB injection program, an intensive pre-remedial action (RA) characterization was conducted to provide an updated extent of contamination and inform treatment barrier installation. This effort was enhanced with 3-D visualization to update the CSM in real time to guide subsequent portions of the characterization. This work resulted in significant changes to the barrier alignments and recommended application of ZVI or ISB barriers. A pre-RA field-scale ISB injection test was also conducted to refine injection well spacing, evaluate the use of shear thinning fluid, and adjust amendment mixture composition for full-scale implementation. In 2024, full-scale injection of the two hotspot ISB barriers was completed, delivering emulsified vegetable oil, sodium bicarbonate for pH buffering, and bioaugmentation culture through pre-packed wells.

Kimberly Caldwell

Affiliation

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Optimizing In Situ Treatment Barriers: An Adaptive Strategy for a Superfund Site