The replacement culvert on Little Shanley Creek. This was to allow for aquatic organism passage and to reduce the risk of culvert failure. This is one example of the 43 stream crossing improvements implemented through the Southwestern Crown Collaborative; part of the national Collaborative Forest Landscape.
The undersized culvert on the Little Shanley Creek was replaced in 2015 with a new culvert.
OVANDO - The Lolo National Forest (LNF) just completed the fourth culvert replacement on streams in the Seeley Lake Ranger District (SLRD). Culverts for Spring, Cottonwood, McCabe and most recently Little Shanley Creeks have been replaced in the north Ovando landscape. These culvert replacements are just one example of the ongoing efforts made possible by the Southwestern Crown Collaborative (SWCC) and the Collaborative Landscape Restoration Program. Two more culverts down the road from Little Shanley Creek will be replaced next year.
In 2010, the SWCC received funding devoted to restoration work and monitoring within the Southwestern Crown of the Continent. Eighteen goals were set in the Collaborative's 10-Year Restoration Strategy to move the landscape toward resiliency and sustainability. One of these goals was to improve or mitigate effects where roads cross streams. Restoration efforts include improving or replacing culverts, bridges or fords or removing these structures.
According to U.S. Forest Service (USFS) Fisheries Biologist Shane Hendrickson, stream crossing are prioritized based on several factors. First a transportation assessment is done on an area, identifying all the roads that need to be maintained. After a road is identified to be kept, USFS employees prioritize the culverts, bridges or fords based on species present in the streams and the constriction ratio (diameter of the culvert/width of the stream). Those streams that are more constricted due to the road, culvert or other structure are at a higher risk of failure.
The final priority is given to those streams that open up the most habitat and are the most cost-effective for the restoration efforts.
"There are a lot of undersized stream crossings in the area," said Hendrickson. "The Southwest Crown Collaborative funding has allowed us to reach deeper down the priority list and we have greater capacity to do more work"
According to Hendrickson, undersized culverts cannot accommodate large velocity flows during high water runoff, restrict fish passage and create stream channel and maintenance issues. Small culverts tend to plug more readily and are more prone to failure.
"From the standpoint of the watershed the [old standard] 36 inch [diameter] culverts were barriers. They were not doing their job," said USFS Region 1 Engineer Rod Blessing.
In 2013 LNF employees surveyed a road crossing on Little Shanley Creek and designed a project to improve the site. In 2014 a local contractor, Schlegel Enterprises from Kalispell, Mont., was awarded the contract to replace the undersized culvert. This past summer the new culvert was installed on Little Shanley Creek. The original 36-inch diameter culvert was replaced with a bottomless arch culvert that has a nine-foot span, five-foot rise and is 45 feet long.
"The original culvert [in Little Shanley Creek] was undersized by a third. This new culvert will accommodate the bank full width and reduce the long term maintenance," said Hendrickson. It will also allow for upstream passage of Westslope Cutthroat Trout.
USFS Region 1 Watershed Coordinator Traci Sylte said that as a result of the 1995 mandate to prepare for flood events, all culvert replacements are required to accommodate a 100-year design flow.
"We have more rain on snow events, increased discharge rates and higher pulses," said Sylte. "We need to be prepared for higher flows in the future."
The new culvert on Little Shanley Creek opens up two miles of the Cottonwood Watershed. The Forest Service owns the headwaters in the Cottonwood Watershed but the lower half is owned by private and other land managers. Hendrickson said that this work will help the rest of the restoration work downstream be more successful.
Blessing said that the cost to replace the culvert on Little Shanley Creek was around $130,000. If the culvert were to fail, culvert replacement and rebuilding the road would cost an estimated $300,000-$400,000.
"Many people look at these projects as a cost. It is also an industry in preventative maintenance and ecological restoration," said Sylte. Sylte said that based on an economic study on the Ninemile Ranger District for similar projects, between 75–95 percent of the project cost is returned to the local economy by hiring local contractors. For the four culvert replacements on the SLRD, contractors from Missoula, Mont. and Kalispell have been used that were on the list of qualified contractors and had the lowest bid. According to Liaison Officer Sandy Mack, in addition to using local contractors, the SWCC has invested more than $6.4 million in partnership agreements to complete restoration implementation work and an additional $1.7 million to local groups for monitoring.
The culvert replacement projects are monitored annually with photo points. Hendrickson said if biologists visually recognize something that needs further attention, they will initiate more detailed surveys of the streams.
For additional highlights of the SWCC's restoration and monitoring work visit the Collaborative's website at http://www.swcrown.org. For more information about the Collaborative Forest Landscape Restoration Program visit http://www.fs.fed.us/restoration/CFLRP/
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