Written by: Mark Taylor
So many reconstruction projects throughout New England are linked to the record-breaking floods brought by 2011’s Tropical Storm Irene. The latest installment in the Orvis/Trout Unlimited 1,000 Miles Campaign is one such project. The project began in August of 2014 and was completed in October.
The Hayes Brook road stream crossing project is located on Upper Michigan Road (Forest Road 35) in Chittenden, Vt. This crossing was formerly a 38-foot long, 6-by-8-foot corrugated squashed pipe located 4.2 miles upstream from the mainstem of the West Branch of the White River in Pittsfield, Vermont.
Although this structure did not wash out during the severe flooding from Tropical Storm Irene in August 2011, the roadway over the culvert sustained significant damage when water overtopped the pipe and eroded sediment and road gravel into the stream. This structure has been considered significantly undersized for the drainage area and is therefore extremely vulnerable to failure during these types of storm flows. After Tropical Storm Irene, the Green Mountain National Forest (GMNF) staff completed an emergency review of vulnerable crossings in this hard hit area and decided the structure was not adequate for large flood events like Irene or for protecting the aquatic resource within the stream channel. The final decision by the GMNF to install a properly-sized crossing at this location allowed engineers to restore stream channel functions that would result in the long-term protection of both the fisheries resource as well as the rural community immediately downstream of this crossing.
The ensuing partnership between the GMNF, TU, US Fish & Wildlife Service (USFWS), Orvis, and the Town of Chittenden was able to secure the necessary funds to hire the engineering firm of Vanasse Hangen Brustlin, Inc (VHB) to design a crossing that would easily pass the 100 year flood flows. The designed replacement structure would now be both flood-resilient as well as fish-friendly. In an effort to create the most cost-effective and functional stream crossing, project partners reviewed numerous options and decided on a prefabricated 50-foot steel stringer bridge spanning Hayes Brook’s 14-foot bank-full width. To support the bridge’s superstructure the partners choose to use cast-in-place concrete abutments placed well outside the high flow scour zone.
The Hayes Brook bridge installation was completed in October of 2014, opening up access to more than 1.5 miles of high-quality coldwater headwater habitat. In total, more than 6 miles of accessible spawning and rearing habitat were reopened to the White River’s mainstem channel. Post restoration monitoring will take place over the next few years to confirm that restoring fish passage at this site will improve both the density and diversity of the trout population. USFWS biologists will implement a fish-tagging project in the coming years to monitor the overall success of this reconnected tributary network.