Wildlife crossings and fish-passage improvements are becoming an increasingly visible component of transportation infrastructure investments. Federal officials estimate that more than one million wildlife-vehicle collisions occur annually in the United States. The crashes result in tens of thousands of serious injuries, hundreds of fatalities and billions of dollars in economic losses each year. Transportation agencies are responding with wildlife overpasses and underpasses, exclusion fencing and other infrastructure designed to keep animals and motorists safely separated.
A similar effort is underway where highways, railroads and waterways intersect. Aging or undersized culverts can restrict fish migration, alter stream flow and contribute to flooding and roadway damage. In June, the Federal Highway Administration announced the availability of up to $800 million in federal funding for culvert removal, replacement and restoration projects that improve passage for fish and other aquatic organisms. The result is an expanding pipeline of transportation projects that combine public safety, environmental restoration and infrastructure resilience. Most upcoming projects that are currently being designed are very similar to the ones that follow.
Design work is underway on the first two phases of a four-phase wildlife-crossing program along U.S. Highway 550 in Sandoval County, N.M. The New Mexico Department of Transportation has identified the corridor north of Cuba as the state’s most severe wildlife-vehicle collision hotspot. The current design effort covers Phases 1 and 2 of a broader 16-mile corridor improvement program and includes the state’s first dedicated wildlife overpass structures.
Phase 1 will include a 150-foot-wide, single-span wildlife overpass with 17 feet of vertical clearance, a 54-foot-wide precast arch underpass and an eight-foot-tall woven-wire game fence extending just over four miles along both sides of the highway. Phase 2 will add a second overpass and underpass several miles from the initial crossing locations, along with approximately four additional miles of wildlife fencing. Fencing will also extend approximately one-half mile along NM 96 near its intersection with U.S. 550.
Supporting work will include vegetated approaches, graded fill slopes, drainage improvements, wildlife escape ramps and game guards. Both phases are currently in design, with final plans expected by the end of 2026. New Mexico has appropriated $50 million to its Wildlife Corridors Fund to advance wildlife-crossing projects identified in the state’s Wildlife Corridors Action Plan, with the U.S. 550 corridor designated as the highest priority.
A major wildlife-crossing project is also advancing along U.S. 395 near Mammoth Lakes in Mono County, Calif. Caltrans is developing improvements along a corridor that averages 57 wildlife-vehicle collisions annually. Deer and automobile collisions account for the overwhelming majority of recorded wildlife collisions in the area, so plans focus heavily on protecting the region’s migrating mule deer herds.
Construction plans include a vegetated wildlife overcrossing near McGee Creek and a separate undercrossing at Convict Creek. The overcrossing will measure approximately 140 feet wide and between 142 and 153 feet long. At Convict Creek, existing culverts will be removed and replaced with a three-span bridge. Work will also include creek-channel and bank reconstruction, rock slope protection and native landscaping.
Eight-foot wildlife-exclusion fencing will extend along both sides of the highway, accompanied by cattle guards and approximately 26 wildlife escape ramps. Temporary roadway modifications, construction easements and right-of-way acquisition are also included. Environmental work has advanced significantly, and the California Department of Fish and Wildlife issued its concurrence with the project’s environmental determination in March. Current state documentation anticipates project implementation beginning in summer 2029.
A $22 million fish-passage replacement project is scheduled along State Route 202 just east of Fall City in King County, Washington. The Washington State Department of Transportation is preparing the Mud Creek crossing for replacement. The existing crossing is classified as a chronic environmental deficiency because sediment regularly blocks the culvert, contributing to roadway flooding and repeated emergency maintenance.
The project will remove an existing fish-passage barrier beneath SR 202 and reroute approximately 325 feet of Mud Creek east of its current crossing. Work will include replacing the undersized four-foot culvert with a new bridge that will improve stream flow and provide fish access to upstream habitat. Crews will reconstruct portions of the stream channel and address sediment buildup and drainage problems that contribute to roadway flooding.
Additional work will include roadway reconstruction, connections to the new bridge, construction staging areas and a temporary bypass to maintain two lanes of traffic during construction. The project is currently in the pre-construction phase. The agency plans to advertise the project for competitive bidding in 2028, select a contractor that summer and begin construction soon thereafter.
A $16.9 million culvert and fish-passage replacement project is also planned along U.S. 101 at Nedonna Creek in Tillamook County, Ore. The Oregon Department of Transportation is designing new crossing structures where the creek currently passes beneath both the highway and the adjacent Port of Tillamook Bay railroad. The existing culverts are in poor condition and must be replaced.
The structures will be removed and replaced with new crossings beneath U.S. 101 and the railroad to improve drainage and allow Nedonna Creek to flow more effectively through the corridor. Related work will address the highway and railroad crossing areas as well as fish passage. Design work is scheduled to continue through 2027, with construction planned for 2028 and 2029.
Six road-stream crossing projects across Maine’s Midcoastal region and Downeast region will be the focus of an approximately $19 million culvert replacement initiative. The Maine Department of Transportation, working with the state’s Department of Marine Resources, will oversee improvements intended to restore aquatic connectivity in watersheds used by Atlantic salmon, river herring and other sea-run fish species.
Plans call for replacing undersized, perched or poorly aligned culverts and other small crossing structures that restrict fish movement during normal and high-water conditions. Replacement structures will be designed around natural stream dimensions and profiles and will incorporate stable, nature-like streambeds and increased hydraulic capacity. The objective is to improve channel alignment and flow while eliminating barriers caused by elevation differences and narrow openings. Collectively, the six sites are associated with approximately 35,700 square meters of modeled Atlantic salmon spawning and rearing habitat and 1,644 acres of alewife habitat.
Maine transportation officials plan to coordinate work across the six locations so that design, environmental review and construction can advance as part of a broader aquatic-passage initiative rather than as isolated improvements. Construction is anticipated to begin in 2028.
For contractors, engineering firms and environmental specialists, projects such as these represent a growing niche within the transportation marketplace. Wildlife crossing projects require structural engineering, bridge and roadway construction, fencing, earthwork, drainage, landscaping, environmental monitoring and habitat restoration. Fish-passage projects call for a combination of bridge and culvert replacement expertise, hydraulic engineering, stream reconstruction, erosion control and environmental services. As transportation agencies replace aging infrastructure and address safety and resilience simultaneously, environmental considerations are becoming part of the infrastructure itself. That shift will continue to generate contracting opportunities well beyond traditional highway construction.
