SEELEY LAKE - The Lolo National Forest is proposing the North Fork Blackfoot Trail Bridges Project located in the Scapegoat Wilderness on the Hobnail Tom Trail #32 on the Seeley Lake Ranger District, Lolo National Forest. The project area is situated within the upper reaches of the North Fork Blackfoot River watershed and is located entirely on National Forest System Lands.
The Hobnail Tom Trail #32, located on the Seeley Lake Ranger District, is a highly developed mainline trail (Trail Class 4), approximately 27 miles in length, which provides access to the Scapegoat and Bob Marshall Wilderness areas and connects to the larger wilderness trail system that serves the entire Bob Marshall Wilderness Complex (BMWC). The trail serves as an important transportation corridor for administrative access as well as public access.
The primary season of public use is May through November. The trail is heavily used by outfitter/guides and other stock users (including hunters), as well as non-stock users, primarily backpackers. Administrative access to the Big Prairie administrative site in the Bob Marshall Wilderness, Spotted Bear Ranger District, Flathead National Forest, begins mid-May.
There are many substantial trail bridges in the BMWC. The Hobnail Tom Trail crosses the North Fork of the Blackfoot River via a pack bridge at milepost 3.1 (T16N, R11 W, Sec. 12), just inside the Scapegoat Wilderness, as well as milepost 6.3 (T17N, R10W, Sec. 29), just before the North Fork Cabin administrative site. Each bridge is a native log stringer bridge supported by native log crib abutments and two intermediate piers filled with rock ballast. The lower bridge is approximately 95 feet in length, and the upper bridge is approximately 89 feet.
A complete engineering bridge inspection was performed on each bridge in September 2013. Inspection of each bridge showed the native log crib abutments and piers to be in very poor condition with significant decay, settling and crushing, indicating the support structures are failing. If these conditions are not addressed, they will cause alignment issues and eventual collapse of the bridge superstructures. Bridge failure or closure would restrict access and disrupt established use patterns along the mainline trail system.
In their current design and placement, both bridges are undersized and encroach on the natural stream channel.
On the lower bridge, one support pier is located in the main river channel and the other pier is located in the floodplain. In addition, the eastern abutment of this bridge extends about 10 feet into the main channel, further obstructing it.
On the upper bridge, both support piers are located in the main river channel during high and low water flows. The river moves a significant amount of large wood due to the Canyon Creek Fire of 1988, and this large wood often collects on the bridge piers increasing the risk of failure.
The North Fork of the Blackfoot River supports the fluvial bull trout (listed Threatened Species under Endangered Species Act) in the upper Clark Fork River Basin. As these bridges “strain” the large wood from the system they are likely causing a negative impact in the creation of pool and spawning habitats for bull trout and other fisheries.
The proposed action is to replace the two existing bridges with a new bridge design that would span the river crossing from abutment to abutment and outside the ordinary high water level (Q2 level). The existing bridges would be deconstructed in the same field season the replacement bridges would be constructed.
Deconstruction would include removal of the existing superstructures, piers and abutments. At both bridge sites, wood from the bridges would be moved using rigging equipment, when necessary, to a nearby site to be sawed up and piled for burning. Nails, bolts, other metal and any treated bridge materials (decking and some posts) would be packed out using packstock. The work crew(s) would use traditional tools (non-motorized tools & non-mechanized transport) as much as feasible to deconstruct the bridges.
The replacement bridges would be built in the same location of the current bridges. Similar to bridge deconstruction, the work crew(s) would use traditional tools as much as feasible to build the replacement bridges. Due to the 1988 Canyon Creek Fire, native materials that would satisfy engineering standards for bridges of this type and span are not available in the local area. Thus, bridge materials would be comprised of treated wood and other man-made materials. Due to the size of the superstructure components, a combination of packstock and helicopter transportation would be used to transport bridge materials to each project site.
A Decision Guide has been drafted to analyze the minimum tools and transportation methods necessary to complete the project and corresponding effects to wilderness character. Bridge work will likely need to occur in two separate field seasons with work beginning as early as summer 2018. Bridge removal and replacement would be accomplished in an estimated 11 weeks per bridge (engineering estimate).
Work within the wetted stream channel would occur between July 15 – Sept. 1 to avoid westslope cutthroat and bull trout spawning. Seeley Lake Ranger District recreation staff do not anticipate that the trail would be closed to the public during the bridge work. While constructing the bridge, recreationists would be required to use the established fords at each location.
It is anticipated the proposed action would have an overall positive effect on the natural quality of wilderness character. Replacement bridges with a bridge design allowing for a full span and removal of the bridge piers would restore the natural stream dynamics, eliminate sediment sources, allow for effective transport of large woody debris and overall improvement of bull trout habitat.
The proposed action would also allow for continued historic, administrative and recreational use of the area as trail access across the North Fork Blackfoot River would be maintained and Trail #32 would continue to be used as the primary access route into the southern portion of the BMWC.
The deadline for comments is March 3, 2017. Please submit written comments to Rachel Feigley, District Ranger, Seeley Lake Ranger District, 3583 MT Hwy 83 North, Seeley Lake, Montana, 59868. The office business hours for those wishing to comment in person or by phone are: 8 a.m. - 4:30 p.m., Monday - Friday, excluding holidays (phone 406-677-2233). Comments may be faxed to 406-677-3902. Electronic comments should be submitted in rtf, MS Word, or Word Perfect format to comments-northern-lolo-seeley-lake@fs.fed.us. Please include the name of the project in the subject line.
Comments received in response to this solicitation, including names and addresses of those who comment, will be part of the public record for this proposed action. Comments submitted anonymously will be accepted and considered, but will not be eligible for objection per §218.5.
For more information, please contact Katie Knotek at the Seeley Lake Ranger Station 406-677-3924 or visit the Lolo National Forest website at fs.usda.gov/lolo.
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