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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
