Soil and Groundwater Treatment System Optimization
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Project Objective

Releases of chlorinated solvents from a manufacturing facility resulted in a groundwater plume extending offsite. Multiple treatment systems were installed over time by various consultants to attempt to halt plume growth and treat impacted groundwater and protect downgradient surface water. In 2015, Geosyntec was retained to optimize the various treatment systems and develop an in situ remediation strategy for eventual project closure. Implementation of the closure strategy began in 2016.

Geosyntec’s Scope of Services

While the treatment systems were in compliance, Geosyntec’s immediate task was to repair and optimize existing treatment systems, which included an onsite groundwater capture system, onsite soil vapor extraction (SVE) systems in three source areas, a downgradient groundwater extraction system with air stripper treatment and reinjection well system, and wellhead treatment systems on downgradient water supply wells. Optimization efforts included replacement and repairs to existing equipment and infrastructure, development of scheduled preventative maintenance plans, and rehabilitation of treated groundwater injection wells.

In addition to O&M, Geosyntec led the development of a project closure strategy; conducted additional source zone investigations; conducted routine groundwater sampling and compliance monitoring and reporting; assessed remedial alternatives to expedite mass removal, including the completion of an in situ biological and chemical reduction treatability study; and led regulatory negotiations to transition the groundwater remedy from pump-and-treat to in situ biological remediation. Transition to in situ biological reduction began in 2017, with completion of three pilot studies to treat source mass, concentrations at the property boundary, and concentrations offsite. The pilot studies were successful and, with regulatory approval, were expanded to full-scale in 2018.

Notable Accomplishments

Geosyntec successfully transitioned a site that was in perpetual care remediation system operation towards regulatory closure. As an immediate benefit to the client, Geosyntec instituted substantial cost savings for the client through optimization of the existing treatment systems. Furthermore, Geosyntec gained regulatory approval for the decommissioning of SVE, air sparge systems onsite and offsite, and the implementation of in situ biological reduction interim remedial measures. Geosyntec’s work to date has not only enhanced mass removal and the clean-up timeframe, but also resulted in significant long-term remediation cost savings.