Local Roads Feature Timber Bridges
LANSING, MI Bridge construction is going back to nature in some areas of Michigan, as bridges made of timber are appearing on local road systems. Timber bridges are equipped with current safety features including crash-tested guardrails and modern load requirements. The bridges are an economically efficient method for county road commissions to replace culverts, promote fish ecosystems and beautify the area across the state of Michigan.
Timber bridges in use by Michigan's county road commissions are highlighted in the summer 2017 edition of Crossroads, the quarterly journal of the County Road Association of Michigan.
The Emmet County Road Commission (ECRC) in northwest Michigan has recently adopted timber bridges as an alternative to replace aging culverts and conserve wildlife. ECRC used the bridges along Minnehaha Creek, a trout stream once traveled by author Earnest Hemingway, to replace inefficient culverts.
The ECRC timber bridges were built with public and private funds, including from the Huron Pines Nature Conservancy (HPNC), as part of a larger road project.
"Huron Pines came to us with a plan and $280,000 to build the timber bridge," said Brian Gutowski, PE, Engineer-Manager for ECRC. "Their sources are grants from the U.S. Fish and Wildlife, the USDA Natural Resources Conservation Service and private grants from several foundations."
Timber bridges are equipped with features that prolong the life of the bridge such as erosion resistance and improved strength tolerances. Construction of timber bridges allows for a significant savings of 25-50 percent compared to traditional concrete bridges. Low manufacturing costs are associated with the construction of a timber bridge, as it requires only a small number of workers and a pilings contractor.
Since 2006, ECRC has built eight timber bridgesreplacing undersized culverts and improving the ecosystem. The timber bridges match the look of the natural environment, which makes them popular among the residents and the Native American community.
Barry County Road Commission (BCRC) has also adopted the use of timber bridges and in 2016 installed the longest single-span timber bridge currently possible, stretching 42 feet across Cedar Creek.
"Our work on this project has slowed down the flow of water, and improved the ecosystem for the fish. It was a win-win for us," said Bradley Lamberg, PE, BCRC Managing Director.
The 83 members of the County Road Association of Michigan represent the unified voice for a safe and efficient county transportation infrastructure system in Michigan, including appropriate stewardship of the public's right-of-way in rural and urban Michigan. Collectively, Michigan's county road agencies manage 75 percent of all roads in the state, including 90,000 miles of roads and 5,700 bridges. County road agencies also maintain the state's highway system in 64 counties. Michigan has the nation's fourth-largest local road system.