Wetland restoration remediates chlorinated solvents in groundwater and protects surface water

Groundwater monitoring at a former manufacturing facility identified a slow-moving groundwater plume containing dissolved phase chlorinated volatile organic compounds (VOCs) - primarily trichloroethylene (TCE), dichloroethylene (DCE), and vinyl chloride (VCH) - discharging into a small dredged channel of a prominent local lake. Because this discharge could impact surface water quality, the State Pollution Control Agency required remediation. However, the slow-moving nature of the plume and the proximity to surface water made pump-and-treat or in situ chemical treatment technologies impractical, potentially detrimental to the surface water and adjacent wetlands, and unfavorable to local residents. After reviewing various remedial technologies an innovative wetland restoration was selected as the preferred treatment technology. Historical groundwater monitoring data suggests that anaerobic dechlorination processes have been the predominant attenuation method at the site. Restoring the wetland within the former channel is expected to reestablish a mixed anaerobic and aerobic environment similar to other freshwater wetlands, providing a natural groundwater treatment system for both TCE and its degradation by-products. This paper reports on the design, permitting, and construction activities for the restored wetland.