Building A Bridge


Federal stimulus money in the 2010 American Recovery and Reinvestment Act (ARRA) created an opportunity for financing. When the call went out for shovel-ready projects, the Idaho Dept of Transportation submitted a proposal to build a wildlife underpass at milepost 18.2 on Hwy 21. If funded, it would become a long-term solution for reducing vehicle-wildlife collisions on part of this road.

The Dept. of Transportation received $550,000 for the wildlife underpass. A few months later another $200,000 from the ARRA was applied toward building the wildlife fence, which is estimated to cost $450,000 to complete. The citizen-agency group is currently fundraising and writing grants to raise the remaining $250,000 needed to complete the fence.

Construction of the wildlife underpass begins July 2010. It will be the first road in Idaho retrofitted to protect people and to protect wildlife.

More road construction information can be found on the ITD web site.

The Design

Constructions plans for the wildlife underpass and fence incorporate countless details and interests. The design has to work for motorists, wildlife, the budget and for other people using the area, such as bicyclists and anglers. The Department of Transportation (ITD) staff drew up plans to accommodate these different and sometimes conflicting interests.

The plan calls for a 75-foot free span girder bridge at milepost 18.2. Motorists will drive over the bridge; wildlife will move under it through a 15 foot high and roughly 30 foot wide opening.

In addition, an 8 to12 foot high big game exclusion fence is to be built paralleling Hwy 21. Approximately 1.0 miles of fence on the west side and 1.65 miles on the eastside will help keep big game and other wildlife off Hwy 21 and guide those animals to safe crossing locations. The fence design includes one-way escape jump out ramps for deer, elk and other wildlife caught on the wrong side of the fence. Access gates for maintenance purposes and recreationists are also being installed in appropriate locations.

The fence crosses several popular routes used by bicyclists, anglers and hikers, especially around the turn-off for Spring Shores. Push/Swing gates are being installed in these locations to allow recreationists to continue to use these areas.


Road construction work will begin in early July 2010 though preliminary work is already underway, such as sighting the wildlife fence.

While the bridge is being built, the plan calls for two lanes to be kept open using a temporary shoe-fly. This would shift traffic away from the construction area and reduce traffic delays. Lanes constructed within the shoe-fly will be a minimum of 11 feet wide.

The bridge is to be completed by October 2010 and at least half of the fence finished in September. The wildlife underpass will be ready when elk and deer migrate into the area in the fall of 2010.

Preconstruction Items 05.18.2010
PS&E Submittal 5.18.2010
HQ Processing, Advertisement and Award 01.25.2010
Submittal and Approval of SWPPP/ESCP 05.18.2010
Construction Activities
Mob & Traffic Control Set-Up 07.09.2010
Detour Constructed 07.13.2010
Traffic Diverted to Detour 07.27.2010
Bridge Construction Begins 07.28.2010
Wildlife Fence (west side) Completed 08.26.2010
Bridge Construction Completed 09.24.2010
Traffic Switched to New Bridge 10.01.2010
Detour Demolished 10.02.2010
Wildlife Underpass Excavation Begins 10.02.2010
Underpass Excavation Completed 10.10.2010
Open Ground Stabilized, Fertilized, Seeded 10.10.2010
Most Traffic Control Signs Removed 10.10.2010
Seeding Completed / Last Traffic Signs Removed 10.15.2010
Project Complete 10.15.2010