New wetland provides floodplain mitigation and habitat improvement

Posted in: Bridges, Construction, Environmental, Highways

Photo-5_wetland-mitigation-site-for-webThe primary benefits of wetlands are floodplain attenuation and a diverse natural habitat. Often, roadway construction projects affect wetlands, especially if the roadway is near a floodplain. So how can we mitigate or even correct damage to wetlands and the surrounding environment? Our project team took this task on during the recently completed Highway 29 project in Wausau, Wisconsin (Marathon County).

By incorporating environmental factors into the design, Mead & Hunt, along with Wisconsin Department of Transportation and the Wisconsin Department of Natural Resources, created new wetlands adjacent to a new highway interchange providing local habitats with an opportunity to thrive once again.

The new interchange provides safe access from the state highway to the local road network. Our team ran into a challenge when the optimum location of the interchange placed it within the floodplain of the Big Rib River, an area comprised primarily of wetlands. To determine the effects of the interchange on the floodplain, Mead & Hunt engineers modeled the floodplain characteristics of the Big Rib River. The initial analysis indicated that the interchange raised the upstream flood elevations by a marginal amount. Rather than raise flood elevations, the team opted to minimize floodplain impacts. By removing an area of high ground to the east of the proposed interchange, floodplain impacts were mitigated while also providing much-needed fill material for the interchange.

In addition, the dredged area became a prime location to improve the natural habitat while attenuating the flooding of the Big Rib River. The team decided to utilize this area to mitigate the wetland losses that would occur with the roadway and interchange construction. Mead & Hunt scientists and engineers collaborated with WisDOT and WDNR to convert this area to a wetland mitigation site. The wetland site was designed specifically to inhibit the spread of invasive species as well as promote the growth of native species.

By using our environmental resources thoughtfully, the team was able to construct new wetlands that accentuated the natural habitat. Adding wetlands to an environmentally-sensitive area benefits the local community as well. The wetlands act as a catch basin for flooding, which protects nearby property. These practices are just one way that we as engineers can take a step forward to reduce environmental damage and possibly give new life to a fading habitat.

John Rathke, PE, SE

About the Author

For John Rathke, P.E., S.E., it is more than managing more than 30 highway and bridge projects each year. It is about connecting with clients and listening to what is important. A leader in transportation engineering, John says that for him, the greatest reward is seeing the constructed product and sharing the pride and accomplishment with his clients, team and the public. According to John, “It’s all about teamwork.”

Read more posts by John Rathke, PE, SE

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