A former drycleaning operation resulted in releases of tetrachloroethene (PCE) to shallow soil and groundwater in an area with a complex network of subsurface urban infrastructure.
Our client retained Geosyntec to provide a site-wide remedy capable of achieving regulatory closure for groundwater and soil contamination under the Massachusetts Contingency Plan (MCP), the state's waste site cleanup program, despite technical, legal, public relations, and scheduling challenges. The client also wanted the remedy to incorporate green and sustainable design principles.
Geosyntec's Scope of Services
Geosyntec guided the delineation of nature and extent, optimized existing vapor intrusion mitigation systems and developed a Conceptual Site Model (CSM) for visualizing the complex interplay between dense subsurface infrastructure and complicated contaminant migration. This 3-dimensional CSM used Mining Visualization Software and served as the basis for developing the remediation plan early in the project's life.
Geosyntec designed interim measures to treat the PCE source area and prepared a feasibility study to address PCE in soil and groundwater. We performed remediation cost forecasting to estimate long-term cash flows and potential ranges of overall remediation costs. We conducted a human health risk assessment from exposure to PCE and its breakdown products. Geosyntec's remedy design included in situ bioremediation with performance monitoring of injection systems. Bioremediation is an effective and sustainable technology that requires substantially less energy, labor, and expense to implement and monitor than many traditional technologies for addressing chlorinated solvents. Geosyntec designed, installed, and operated a groundwater pump and treat system as a focused component of the remedy to hydraulically control the plume from advancing around a newly-constructed subsurface structure.
Geosyntec supported the client by providing a vision for site remediation and direction to the multi-consultant project team. As of 2019, the site is permanently closed with no activity and use limitations. PCE concentrations in the source area had begun greater than 100 parts per million (ppm) and are now non-detectable. Downgradient, concentrations had ranged up to 40 ppm and have decreased by over 99%.
Our careful planning and technical insight have provided the client with cost savings into the millions of dollars in life-of-project labor costs through improving project coordination and communication efficiency and lobbying with regulators for elimination of unnecessary treatment system components, justifying reductions in sampling frequency, and by developing an innovative in situ solution to treat nitrate in groundwater. We continue to receive thanks from our client for providing strategic and technical guidance on this multi-component and high profile project with the challenges of dealing with multiple stakeholders in an urban location.
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- Location: Massachusetts
- Client: Confidential
- Project Practice Areas: Contaminated Sites, Water & Wastewater
- Type of Facility: Former dry cleaner
- Services Provided: Conceptual site model development, Subsurface investigation, Human health risk assessment, Bioremediation system design and implementation, Vapor intrusion assessment and mitigation, Cost forecasting and financial risk analysis, Regulatory support
- Type of Work: Modeling/site remediation
- Governing Regulation: State regulations