wildlife underpasses effectiveness specifications surrounding terrain implementation cost...

Wildlife Underpasses

•Effectiveness•Specifications•Surrounding Terrain•Implementation•Cost•Maintenance

Effectiveness87 percent (average) when used in

combination with large-mammal fencing

Specifications. Dimensions of the three different types of

crossing structures.

Crossing Structure Type

Dimensions (as seen by the animals)

Large-mammal underpass

7.6–8.7 yd wide, 4.4–5.5 yd high

Medium-mammal underpass

2.6–9.8 ft wide, 1.6–8.2 ft high

Small- or medium-mammal pipe

1.0–2.0 ft in diameter

Open-span bridge

Large-mammal underpass

Medium-mammal

underpass

Small- to medium-mammal pipe

Ungulates

Deer sp.

Elk

Moose

Mountain goat

Bighorn sheep

Pronghorn

Open-span bridge

Large-mammal underpass

Medium-mammal

underpass

Small- to medium-mammal pipe

Weasel Pine marten Fisher Striped skunk Badger ? ?

Wolverine ? ? Bobcat Canada lynx ? ? Cougar Fox1 Fox2 ? ?

Coyote Wolf Black bear Grizzly bear

Surrounding TerrainRoadway is relatively higher than the surrounding terrain

The roadbed does not have to be : raised the approaches lowered reduces the overall excavation

It is advisable:To allow animals to see to the other sideAvoid flooding of underpasses and the associated soil erosion

Wildlife fencing alongside the road corridor typically ties into the wing walls of the underpass or the structure itself ( above for smaller culverts)

Noise and light disturbance from the road need to be minimized (e.g., employing sound-attenuating walls above the entrances).

Impementation

At-Grade Animal “Sidewalks”

At-Grade Animal “Sidewalks”

CostsType Size Cost

Open-span Bridge (Hwy 93)

32.8 yd in w and 13.1 yd in length

$423,483 in 2006

Open –span Bridge (Baniff)*

13.1 yd in w and about 5.5 yd in height

$700,000–1 million (1995–1997) Can

Open span Bridge (Baniff )*

17.4- to 27.3 yd-wide $2.5 million (2007) Can

Large Mammal Underpass (Canada)

7.7 yd) in w and 4.4 yd in height ( across a 4 lane road

$225,000 - $250,000 (1995-1997) Can

Large Mammal Underpass

(Netherlands)

7.7–10.9 yd wide and about 4.4 yd high and 21.9 yard wide

€600,000–€1,000,000.

Large Mammal Underpass

(Montana) arched culverts (3)

7.7–8.7 yd in w and 5.5 yd in height (road width) varies between 20–24 yd

$217,000 in 2006 each ( for 3)

CostsMedium Mammal Underpassbox or elliptical culvert

9.8–13.1 ft) wide and high

$180,000 (1995–1997) CAN

Medium Mammal Underpassbox culverts (Montana)

3.9–5.9 ft wide and high and 30.1 yd long 6.6 ft wide, 4.9 ft high and 30.1 yd long

$69,000 each in 2006

Medium Mammal Underpassbox culverts (Netherlands)

2.6–4.3 ft wide, 1.6–2.5 ft high and a road width of 21.9 yd

€24,000-50,000.

Small and Medium Pipes

2.0 ft in diameter/ 21.9 yds long

€14,000–€24,000 (2005)

Maintenance