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Idaho SH-21 Wildlife Management Linkage Project

Project #: 99875  –   Updated: April 12, 2012

Project Summary

More mule deer are killed by vehicles on a 22-mile stretch of roadway east of Boise than on any other stretch of road in southwest Idaho.

This stretch includes 8 miles of Warm Springs Avenue, which runs along the base of the Boise Foothills and parallels the Boise River. It moves east through city neighborhoods and then suburban developments that are scattered across the valley.

This checkerboard of houses and bare land gives way to open space along 14 miles of State Highway 21. Much of it is public land or part of the Idaho Fish and Game’s Boise River Wildlife Management Area (BRWMA...

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Location (by county):
Ada County (ID), Boise County (ID)

Watersheds:
Middle Snake-Succor, Boise-Mores

Congressional Districts:
ID District 01, ID District 02

Bird Conservation Regions:
Great Basin

USFWS Regions:
Pacific Region

Project size:
1.74 miles

Public Access

Site Name Publicly Accessible
Idaho State Highway 21, Boise Idaho Yes
Wildlife Exclusion Fence Yes
Wildlife Underpass Yes

Full Project Description

More mule deer are killed by vehicles on a 22-mile stretch of roadway east of Boise than on any other stretch of road in southwest Idaho.

This stretch includes 8 miles of Warm Springs Avenue, which runs along the base of the Boise Foothills and parallels the Boise River. It moves east through city neighborhoods and then suburban developments that are scattered across the valley.

This checkerboard of houses and bare land gives way to open space along 14 miles of State Highway 21. Much of it is public land or part of the Idaho Fish and Game’s Boise River Wildlife Management Area (BRWMA.) The road continues into the mountains traversing rocky and steep mountainous features of the Boise Front.

What was once a laid-back country road used by local residents, loggers and sportsmen, is now a busy well-paved two-lane road. It has occasional passing lanes and numerous curves planked by long stretches of concrete guardrail paralleling the highway. The alignment of the road and surrounding terrain further limits a driver’s visibility.

For generations deer herds have migrated from as far away as the Sawtooth Mountains to as far south as the Deer Flat Wildlife Refuge. Their off-spring continue to follow the same routes with one exception. Deer and elk now stop short and winter in the Boise Foothills. When the snow flies in the mountains, upwards to 8.000 mule deer and a thousand elk move toward the Boise Foothills They follow the ridgelines and draws, steadily moving down hill and down river. Come spring deer and elk use the same trails to return to their summer range in the mountains.

During both migrations, elk and deer cross Highway 21 at least once. When bad winters drive wildlife down to the Boise River, they will frequently cross Warm Springs Avenue, as well. Up to 200 mule deer and 10 elk are killed on this stretch of road every year.

Separating wildlife and vehicles is the best way to protect both the traveling public and wildlife.

From the beginning, the Boise River Wildlife Linkage Partnership (BRWLP) has imagined long-term fixes for Hwy 21’s vehicle-wildlife conflicts. Working toward this end, the group identified locations frequently used by deer and elk and hot spots where most accidents occurred. They had professional knowledge of the roadway and what was needed for a permanent structure to provide safe passage for wildlife and motorists. What BRWLP didn’t have was money to pursue this alternative.

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. This underpass became a long-term solution for reducing vehicle-wildlife collisions on part of this road.

Construction of the wildlife underpass began in July 2010 and was completed in October 2010. It is the first road in Idaho retrofitted to protect people and to protect wildlife.

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

In addition, a portion of a 8 foot high big game exclusion fence was built paralleling Hwy 21 to guide those animals to the wildlife underpass. 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 were also installed in appropriate locations.

A variety of wildlife (deer, elk, fox, coyote, cougar) have been using the underpass on a daily basis, fences are the key to guiding more animals to the crossing so they can pass safely under the highway.

Although $756,000 of federal stimulus funds were used to build the bridge, underpass and part of the wildlife fence within the Hwy 21 right of way, additional money needs to be raised to build the largest portion of the fence on the east side of the highway.

The Boise River Wildlife Linkage Partnership has completed raising the money for and built 2400' of the 7400' of fencing that still needs to be completed. The Partnetship plans to raise the final $150,000 necessary to build the remaining 4000' of wildlife fence. This includes three jump outs, 4 pedestrian gates and one ATV gate as well.

Project Assistance & Partnership Opportunities

Volunteers

We will need volunteers to help build Jump outs in spring of 2012

Funding

We are currently trying to raise an additional funds to complete the fencing.

Goals and Targets

Primary motivations:

Conservation Mission
To conserve big game populations and habitat connectivity
Public Benefit
To reduce the number of wildlife-vehicle collisions on SH-21 and Warm Springs Ave.

Consistent with plans:

Habitat Conservation Plan
This project is consistent with the Boise River Wildlife Management Area Habitat Plan

Targeted habitats:

    • Shrublands and Grasslands
      • Shrublands and Steppe
        • Sagebrush Shrubland and Steppe

Targeted species:

  • Mule Deer Odocoileus hemionus
  • Elk Cervus canadensis

Actions

Project Actions
Other: Reduce Wildlife-Vehicle Collisions Show/Hide details

Outcomes

Is the success of this project's actions being monitored?   Yes

Please describe your monitoring activity.

We have wildlife cameras that take photographs of animals using the underpass.

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Organization

Boise River Wildlife Linkage Partnership
(Other)

Primary Contact

Edward Bottum  (Wildlife Habitat Manager)
Idaho Department of Fish and Game
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Partners

  • Idaho Department of Fish and Game
  • Idaho Transportation Department - R3
  • City of Boise
  • Ada County
  • Ada County Highway District
  • County of Boise
  • Rocky Mountain Elk Foundation
  • Mule Deer Foundation
  • U.S. Forest Service

Project Photos

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