Environmental Restoration

Document Type

Report

Publication Date

3-2022

Abstract

To test an active remedy for treating the groundwater contamination at the Technical Area-V (TA-V) Groundwater (TAVG) Area of Concern (AOC), the U.S. Department of Energy/National Nuclear Security Administration (DOE/NNSA) and Sandia National Laboratories, New Mexico (SNL/NM) personnel implemented a Treatability Study of In-Situ Bioremediation (ISB) to remediate the two constituents of concern, trichloroethene (TCE) and nitrate. Both contaminants were detected in the groundwater at TA-V at concentrations above their respective U.S. Environmental Protection Agency (EPA) maximum contaminant levels (MCLs). The EPA MCLsare the cleanup goals for groundwater remediation at the TAVG AOC as specified in the Compliance Order on Consent.

The Treatability Study was planned in two Phases. Phase I Treatability Study started in November 2017 and concluded in May 2021, and delivered bioremediation solution using injection well TAV-INJ1 followed by performance monitoring in the treatment zone. Phase I Treatability Study results showed limited success of ISB. The injected treatment solution only affected a small, localized area near the injection well.

Several key factors contributed to the limited success of ISB at this site, including aquifer characteristics and restrictions of infrastructure on installing multiple injection wells. More importantly, the TCE concentration at this site was too low to sustain the dechlorinating microbial community, even though microbial metagenome data showed that bioaugmentation and biostimulation implemented had the capability to establish a bioremediation treatment zone for reductive dechlorination of TCE at the site.

Based on Phase I results, DOE/NNSA and SNL/NM personnel do not recommend proceeding with Phase II of the Treatability Study. Phase I results have proven that ISB is not a feasible technology for such low concentrations of chlorinated compounds contamination (e.g., TCE concentration below 10-20 μg/L) with the existing aquifer characteristics. Also, DOE/NNSA and SNL/NM personnel recommend proceeding with updating the Current Conceptual Model and Corrective Measure Evaluation Report for the TAVG AOC. Data obtained during the Phase I Treatability Study will provide input on recommending a final remedy for Corrective Action at the TAVG AOC. 524 pages

Language (ISO)

English

Publisher

Sandia National Laboratories/NM

Keywords

Technical Area-V Groundwater Area of Concern TA-V Groundwater Investigation TAVG AOC Treatability Study In-Situ Bioremediation

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