The 800-acre Carleton College arboretum underwent a long-term restoration of its woodland, prairie, savanna, and floodplain plant communities. When parking lots and a new recreation center were built adjacent to the arboretum, the college called on Barr to design a stormwater treatment facility in the arboretum.
The facility had to meet functional requirements—treating water before it reached the Cannon River and fitting into the arboretum’s natural landscape. Barr recommended a constructed wetland, which would be both effective and attractive in the arboretum setting.
Barr performed hydrologic and ecological analyses to determine the size of the new wetland and its potential fit with the natural topography and vegetation. Working with the college to site the wetland, Barr recommended reclaiming a former dumping area, where heaps of old blacktop were overgrown with invasive, exotic trees. By constructing the wetland there, the college lost an eyesore and an ecological liability while gaining valuable wildlife habitat and a visual amenity. Unlike typical stormwater-detention basins, this wetland system has gradual, natural-sided slopes; features a geosynthetic clay liner to allow for more permanent water storage in the basin; is shaped to resemble oxbow wetlands that occur naturally along rivers like the Cannon; and fosters a diverse wetland-plant community.