Risk-Based Closure: Achieving Environmental Safety at a Former Telecomm Manufacturing Facility
Challenge
A 475,000 sq ft warehouse, previously used for telecommunication manufacturing, faced significant contamination from chlorinated solvents (TCE). The contamination was compounded by the presence of shallow bedrock, less than 3 feet below the building’s foundation, which facilitated the migration of TCE and created a widespread chlorinated solvent groundwater plume. This contamination had been documented over two decades of site assessments. Antea Group, in collaboration with our Canadian Inogen Alliance Associate Terrapex, worked with the Ontario Ministry of the Environment to discontinue the costly and ineffective operation of an outdated groundwater pump and treat system. The goal was to shift the site investigation to a more efficient, risk-based pathway toward site closure.
Solution
To refine the understanding of contamination levels, we conducted gap-filling investigations to delineate groundwater and soil vapor contamination. Following this, a Human Health Risk Assessment (HRRA) and an Ecological Risk Assessment (ERA) were performed to evaluate potential risks to both human and ecological receptors. Key areas of focus included groundwater, soil vapor concentrations, and sub-slab vapor samples. These assessments considered potential human receptors such as indoor, outdoor, and subsurface/construction workers who might be exposed to migrating soil vapors, as well as direct contact with contaminants. Ecological receptors included urban-adapted terrestrial wildlife and offsite aquatic environments.
Result
The HRRA and ERA findings indicated no significant risks to human health or ecological receptors. However, to mitigate any potential future risks to onsite commercial workers, we recommended a Risk Management Measure—installation of a sub-slab venting system in the source area. A comprehensive Risk Management Plan was developed to address the long-term maintenance, monitoring, and contingency requirements associated with this system. The implementation of this plan met the Ontario Ministry of the Environment’s goals for human health protection, while also reducing the frequency of groundwater monitoring well sampling, lowering operational costs and enhancing environmental safety.
