June 2019 Vol. 27, No. 2

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Culvert designs allow fish passage

drainage pipe

Mounds of RAP at a gravel pit in Carlton County offer road agencies an alternative to
natural gravel and crushed aggregate for gravel roads. But RAP has to be used in the
right proportion with gravel. Photo: MnDOT

Minnesota transportation practitioners now have access to a comprehensive culvert design guide to help preserve stream connectivity and promote the safe passage of fish and other aquatic organisms through culverts.

“Minnesota’s 140,000 miles of road and 92,000 miles of streams and rivers meet at tens of thousands of places,” says Matt Hernick, an associate engineer with the U of M’s St. Anthony Falls Laboratory. “Because of the variety of ecological regions in the state, the range of culvert geometries, and other factors, no single solution can work for culverts statewide. The new guide fills this information void.”

Culverts are a cost-effective solution to allow traffic to cross over smaller waterways, but they have historically been designed with only flood flows and the safe passage of vehicles in mind, and not the health of streams and the organisms that depend on them.

The 221-page guide is amply illustrated with photos, charts, and more. Sections include culvert design, the current regulatory context, site assessment, analysis and tools, best practices, and a design method selection chart.

Benefits for users may include more-efficient design and permitting processes and lower construction costs. The project was sponsored by MnDOT and the LRRB.

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