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| In Da Woods |
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by Melanie B. Fullman, US Forest Service
If you build it, they will come! The stream is fairly narrow at this spot; our biologists wondered if trout would ever return? Perhaps there was a waterfall, low-water, or other barrier downstream? If we built a better crossing, would they come? |
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A New Old Idea An unexpected answer arose from the neighboring Chequamegon-Nicolet National Forest when our head road engineer happened to be talking to their engineers about timber bridges. Timber bridges are an old idea, updated for modern times. As the name implies, they are made entirely from wood. No concrete or steel is used for the framing. The treated glu-lam beams are easier to install, have the same lifespan (approx. 30 years), and a comparable load rating (log trucks) as steel bridges. They cost about the same, too. Built from native, natural materials, timber bridges blend with the forest surroundings and don’t require specialized equipment or training to construct. There’s a lot less logistics as well – no coordinating cement deliveries, for instance. A long time ago, timber bridges were the only bridges. So, this summer, the Ottawa Forest decided to replace those dark, scary culverts. Funding specifically for aquatic habitat restoration would be used. The goal was to provide better passage for vehicular traffic and hopefully, proper habitat for brook trout. A contractor drove 20’ pilings ten feet into the ground. Each piling is a 12” diameter southern yellow pine log, treated with a compound that doesn’t leach into the water (like creosote did). SEVEN massive glue-laminated beams, each 12” wide, 30” deep, and 30’ long, were placed across the stream; they were built by a manufacturer in northern Wisconsin. The new structure is 26’ wide, sufficient for 2 lanes of traffic, but only half the width of the old culvert crossing. Because it’s a bridge, high off the water, a lot more sunlight extends beneath the structure. Sunlight that is, apparently, like the light at the end of a tunnel. |
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News Travels Fast The day after the old culverts were removed – the very day that free-flowing conditions were restored to this little stream – our project manager spotted brook trout exploring new-found territory. Even as the contractor placed boulders in the stream to mimic natural habitat conditions, creating resting areas and hunting holes, curious brook trout swam forth. The next morning, when the shallow water had cleared from its muddied disturbance, lovely little brook trout faces poked through and around the bridge. Safe to say, the engineer and contractors were thrilled! During construction, a temporary bridge allowed local traffic to cross. The new bridge is now complete. There’s a bit more road work to finish, which we intend to have done by mid-November (something about the start of deer season and all our employees taking leave…?). Our project manager has had lots of experience overseeing construction of steel and concrete bridges; this was his first timber bridge. He liked it a lot – said it was interesting and that he was impressed with how fast it was built. He learned a few things, too, which will make overseeing the next one easier and more efficient. Since I know he’s also an avid fisherman, I asked if he had any thoughts on fishing for his new ‘friends’. “Nah”, he said with a laugh, “I get enough crawling through tag alder at work that I don’t do that on my weekends!” They All Lived Happily Ever After |
