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US Fish & Wildlife Service FieldNotes

FWS Conservation Planning Assistance Program Protects Wetlands through Changes in Tollway Design

Region 3, November 5, 2012
Bioswale. - Photo Credit: n/a
Bioswale design.
Bioswale design. - Photo Credit: n/a
I-90 & Route 47 Interchange with bioswale area depicted and high-quality wetland complex to the west.
I-90 & Route 47 Interchange with bioswale area depicted and high-quality wetland complex to the west. - Photo Credit: n/a

The U.S. Fish and Wildlife Service Chicago Illinois Field Office worked with the U.S. Army Corps of Engineers-Chicago District and the Illinois Tollway to develop solutions that allow highway interchange improvements to be constructed without causing damage to downstream high-quality wetlands. As part of the I-90 and Route 47 interchange project, the Tollway proposed to add and widen lanes which would increase the amount of impervious cover from approximately three acres to approximately seven acres. To minimize indirect impacts to a high quality wetland complex downstream of the interchange, the Tollway proposed to divert some of the stormwater runoff to a ditch along I-90 with the remaining runoff being routed to a proposed vegetated swale. Service biologists were concerned that the proposed measures were not sufficient to protect the downstream wetlands: a 70-acre wetland complex possessing a very high floristic quality and providing habitat for numerous wetland and grassland birds. Increasing stormwater runoff from the expanded interchange threatened the high-quality wetlands through water level fluctuations which would lower biodiversity. To support our recommendation that a bioretention facility south of the interchange was required to reduce or eliminate the additional runoff from the interchange construction, the Service  provided a detailed assessment of the adverse impacts of runoff, information about the existing soils onsite, and designs for infiltration best management practices that should be used in those soils. Based on the information that we provided to protect aquatic and trust resources, the Corps agreed that incorporating a stormwater best management practice with soils conducive for the growth of native vegetation, and a storage zone or drainage layer below the soil planting zone, would be the best course of action and thus required the incorporation of the bioretention facility in the Tollway’s Clean Water Act permit.

Contact Info: Shawn Cirton, 847-381-2253xt.236, shawn_cirton@fws.gov