A slow-moving plume of chlorinated solvents extends from a former manufacturing facility northward to a channel connected to Lake Minnetonka in the western Twin Cities area. This plume had been in the subsurface for many years and was being slowly degraded into environmentally safe compounds by natural processes, but the Minnesota Pollution Control Agency (MPCA) was concerned that even a small flow could affect the surface water.
Because a pump-and-treat system would be resource-intensive and alter existing mechanisms, Barr designed a constructed wetland that enhances the already occurring natural attenuation and developed a plan that generated public and MPCA support. Our design included a barrier to passively control and direct groundwater flow through the reconstructed wetland, where mechanisms bio-stimulate the attenuation process.
To address the MPCA’s requirement of four years of wetland performance monitoring to evaluate the effectiveness of the wetland treatment system’s operation and maintenance, Barr developed an innovative performance monitoring program. This included maintaining the wetland’s operation by promoting growth of desired plant species and monitoring the wetland hydraulics, chemicals of concern, wetland geochemistry, and surface water immediately downgradient of the wetland. After four years of performance monitoring, the data showed the wetland operates as designed and provides a permanent, successful, low-cost treatment system while also serving as a park area for the community.
Vice President Senior Environmental Engineer
Vice President Senior Civil Engineer
Vice President Senior Engineer