Wildlife and fisheries concerns, including those involving threatened or endangered species, should be taken into account when siting a bridge. For example, seasonal construction closures may be needed near salmon spawning habitat in Alaska (figure 37) or Indiana bat roosting trees in the Midwest.

Figure 37—Salmon habitat may need to be considered
when siting a bridge in the Northwest.

Carefully study the geologic and other hazards of the area where the proposed bridge will be located. Locations to avoid include:

• Avalanche chutes (figure 38)
• Springs/seeps
• Wetlands
• Areas with excessive snow loads
• Streams with problems of debris flow or that have high debris loading
• Areas on or below earthflows
• Areas low in flash flood channels
• Areas prone to rock fall
• Areas prone to wind throw or with many dead or dying trees
• Alluvial fans and other unstable areas

Figure 38—Avalanche chutes should be avoided when siting bridges.