Boulder Road Project Location, Problem, and Project Purpose

Location

The proposed trail improvement project is in Park and Sweet Grass County south of Big Timber, Montana, in the Main Boulder River Valley.  The town of Big Timber is in the Yellowstone River Valley in south central Montana, at the confluence of the Boulder and Yellowstone Rivers, 60 miles east of Bozeman, Montana and 85 miles west of Billings, Montana.  State Secondary Highway 298 begins in Big Timber, running southward through the Boulder River Valley.  The secondary highway is paved to the national forest boundary, at mile 28 south of Big Timber.  The snowmobile trail begins at mile 38 on the County road.  The proposed project begins at mile 40, at the intersection with the Hells Canyon Campground Road in Sweet Grass County.  This route is unplowed and is a groomed snowmobile trail from late December until April.   The proposed trail improvement project spans about eight miles on the narrow, gravel-surfaced county road ending south (upstream) of the Box Canyon Trailhead at mile 49.  The proposed trail improvements for this project span about eight of 16 total miles of groomed snowmobile trail, with seven of those miles in Park County.

Problem

The harsh conditions of spring snowmelt and runoff and heavy forest visitation have caused damage to the underlying road infrastructure, causing increasingly difficult conditions to groom and maintain the snowmobile trail in the winter months.  Record runoff from the snowpack in 2022 (a 500-year event) caused heavy damage to the trail and caused two bridges crossing the Boulder River south of Box Canyon Trailhead to fail.  Due to the bridge failures, Park County closed the trail south of Box Canyon to ATVs and UTVs in September of 2023.   The Main Boulder South (reference map on the left) portion is mostly in Park County where the snowmobile trail begins during the winter. 

Park County has historically considered the county-owned route south of Box Canyon as a primitive trail or two track road, which results in repairs and maintenance being performed by users of the corridor.  The condition of the road infrastructure has gradually declined to point of near impassability even by high clearance vehicles. With the loss of two bridges, the County closure prevents ATV and UTV access to the public facilities and private lands within the Gallatin National Forest.

Project Purpose

This project, proposed for Trails Stewardship Program funding, aims to repair a severely damaged trail segment with safety issues affecting winter maintenance and snowmobile use. A major project goal is construction of a temporary low water crossing around the bridge damaged by the historic flood in 2022 and subsequently closed to wheeled traffic.  The 800-foot-long crossing detour joins the primitive two-track upstream of the closed bridge and is the end of the project.  Other planned work includes installing drainage infrastructure – ditches, culverts, water bars – to direct snowmelt runoff away from the road.  These betterments will support Park County's future project to construct two new structures replacing the two closed bridges south of Box Canyon.  The Montana Department of Transportation has allocated $280,000 for materials for the new bridges, and Park County Commission plans to apply for a grant to supplement this funding for bridge construction and trail reopening.  

If the proposed project is funded by the Trails Stewardship Program, drainage and roadway improvements will greatly improve the safety and resiliency of the snowmobile trail that is groomed by Sweet Grass County Recreation Association volunteers.  Open water from perennial springs poses hazardous conditions along the trail to groomer operators and snowmobilers.  The project will eliminate spring water from encroaching on the road, and reduce the sediment washed from the road into the Boulder River.  Completion of the proposed project enables the Park County planned bridge replacement project to start sooner and ultimately reopening the trail by 2028 – after five years of the trail being closed to ATV and UTV traffic. 

Park County has also allocated $18,000 of County funds toward repairing a critical area on the trail about mile 44, south of the Fourmile Parking Area. High water flows in the Boulder River from snow melt over the last four springs has eroded the riverbank to a point that the edge of the two-track path is less than a foot from the river’s edge.  This is an unseen hazard to users and, if not fixed, could result in another closure of the road/trail next spring.

If funded by the Trails Stewardship Program, this project will improve winter trail safety for grooming volunteers by repairing trail segments, fixing dips, and adding drainage feature to prevent water issues and halting erosion. The temporary detour and low water crossing of the Main Boulder River will also restore ATV, UTV, and four-wheel vehicle access for part of the summer after high waters recede.  With the corridor reopened to wheeled vehicles, private landowners and public facility managers can resume stewardship activities.