Continued Monitoring of Stormwater Effluents from Filter Media in Two Bioslope Sites

  • A technical drawing of the design for the infiltratoin study plots shows 6 inches of engineerred media atop a gravel and sand layer. A PVC underdrain pipe at the bottom of the installation directs filtered liquid away.
  • A map of northeastern Minnesota includes locations and photographs of the project's two bioslopes one large bioslope installation along highway 169 at Eagles Nest and a set of bioslope test plots at the National Resources Research Institute at the University of Minnesota Duluth. A western portion of Lake Superior is visible.
Status:  Complete
Report Date:  07/13/2021


Bioslopes are among the methods MnDOT uses to control roadway stormwater runoff. Engineered bioslopes slope down from the roadway and mimic the natural landscape. They use special filtration media such as new compost and sand, which is trucked into road construction sites. This filter media holds and slowly filters rainwater, and retains nutrients and other pollutants. In a previous study, researchers investigated salvaging local materials such as project excavated peat or mucky soils for the organic component in filter media or slope dressing, which would ordinarily be discarded as waste. This could save time and money, and be environmentally sound. One large highway bioslope and a set of test plots with recycled media in northeastern Minnesota were monitored for absorption, infiltration, filtration and pollution capture. The results were promising. This research represents the second two-year monitoring study of the sites.

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