At a former industrial site, the manufacturing buildings were removed in the 1990s, and a trichloroethylene (TCE) plume was discovered under one of the newly redeveloped buildings. Because two aging air-sparge remediation systems were expensive to operate and maintain and were not reducing source mass nor addressing potential vapor intrusion concerns, the responsible party hired Barr to conduct a remedial investigation and evaluate options for reducing the contamination.
Barr performed a subsurface investigation of one of the source areas, which was located under an existing building. We delineated a treatment zone and provided the necessary data for designing a remedy that would address movement of the source mass from under the building. We performed high-resolution characterization using membrane-interface/hydraulic profiling tool (MiHPT) boring and confirmed the results with soil samples and chemical and hydraulic analyses. Monitoring wells were installed to assess baseline geochemical conditions and contaminant concentrations in the groundwater.
We designed a “biobarrier” remedy with a multi-mechanism approach to reduce contaminant movement. The design included injection of four amendments—an adsorption mechanism, an abiotic mechanism, and a dual-amendment biological mechanism—and verification of proper distribution of the amendments using soil borings and piezometers in the vicinity of the injection locations.
Performance monitoring was conducted for three years after implementation, and the results indicate the biobarrier is performing as designed. Movement of TCE to the primary well downgradient of the biobarrier has been reduced by up to 99.5 percent. Lessons learned from the design investigation and implementation are currently being applied to a second source area at the site.