Specialized road construction protects wildlife and people
copywrite 2011 by Joe EvanchoIn the Intermountain West, crashes between motor vehicles and wildlife are a threat to humans and animal safety costing hundreds of lives and more than $8 billion annually.
Rob Ament is the ecology program manager for the Western Transportation Institute (WTI) at Montana State University in Bozeman. He said studies show that wildlife-vehicle collisions have doubled in the past fifteen years and transportation agencies are looking to identify major corridors with increasing levels of wildlife movement, and then engineer solutions to prevent those kinds of accidents.
One solution involves wildlife crossings that connect habitats divided by highways thereby allowing animals to cross over or under roads safely. These crossings involve site-specific engineering and the construction of underpasses and overpasses for large or herd-type animals such as moose, elk and deer and tunnels for small mammals such as otters, skunks and badgers. There are even tunnels for amphibians and other little critters.
Some aquatic crossings allow for fish migration and may be used by smaller non-aquatic species.
Ament says the reasons for the collisions can vary from having high-quality habitat at the road’s edge to animals moving from winter to summer ranges with many other variables such as winding roads with poor visibility.
Other factors such as terrain and traffic determine the type of crossing needed for specific species, Ament says.
Gregg Servheen is the wildlife programs coordinator for the Idaho Department of Fish & Game. He said that new road development or improvements will address wildlife and public safety with engineered strategies for underpasses and overpasses. “Underpasses are probably the most common way of dealing with wildlife connectivity,” Servheen says. “It’s not only important to protect animals but it is also a public safety issue.”
Several wildlife mitigation programs across the West are addressing these issues.
The People’s Way, Montana
In northwestern Montana, The People’s Way is a 56.3-mile section of US-93 between Evaro and Polson south of Flathead Lake, with all but one mile on the Flathead Indian Reservation. This stretch of roadway represents the most extensive wildlife-sensitive highway design effort in North America to date Many uncommon native species occur within the project area, including grizzly bears and gray wolves, as well as more common species such as black bear, white-tailed and mule deer, bobcat, coyote, mountain lion, elk and many smaller species including the western painted turtle.
The Montana Department of Transportation has built 42 fish and wildlife crossing structures and nearly 17 miles of wildlife fencing.
These mitigation measures will improve safety for motorists by reducing wildlife-vehicle collisions. They will also function to maintain habitat connectivity and protect animal populations by providing safe passage through specially engineered overpasses and underpasses.
Great Western Engineering (GWE) of Helena designed the seven-mile long and southern most section of The People’s Way from Evaro to McClure Road. Their section was the most expensive, approximately $29 million, and includes a one and a half mile extension of a four-lane undivided roadway, a two-lane roadway with turn and alternating passing lanes for north and southbound traffic. The firm also engineered the relocation of one mile of Montana Rail Link line including a new railroad bridge in Evaro, three-and-a-half miles of wildlife fencing and ten wildlife crossing structures including an overcrossing designed for, but not limited to, grizzly bears.
Dan McCauley is president of GWE and he said a lot of biological study was involved before they started the design phase. “We coordinated with the tribes and various federal and state agencies to engineer the proper structures along with road engineering. After years of study it was determined that the overcrossing at the top of Evaro Hill is located in the best grizzly bear habitat on the entire stretch of US 93,” he says.
Of the 10 GWE designed undercrossings six are essentially big bottomless, oversized culverts over streams that include a path along the side where animals from mountain lions to turtles can get safe passage.
On the 56 miles of The People’s Way, more than 16 total miles of 8-foot high wildlife fencing on both side of the road keep the animals off the road and steer them into the passageways.
West Vail Pass, Colorado
In Colorado, the 18-mile section of Interstate 70 known as West Vail Pass has been chosen as the official site for the North American Wildlife Crossing Structure Design Competition, also known as ARC.
The location of the competition is in a unique habitat at 10,000 ft above sea level, about 70 miles west of Denver where man and wild things often collide.
ARC will bring together landscape architects, construction architects, engineers, ecologists, and other experts to create the next generation of wildlife crossing structures for North America’s roadways. Today, the cost of wildlife crossings prevents many of them from being built. The ARC competition will challenge entrants to design safe, efficient, cost-effective and ecologically responsive future wildlife crossings.
Togwotee Trail, Wyoming
The Togwotee Trail is a 38-mile section of U.S. Highway 26-287 between Dubois and Jackson along one of the country’s most scenic roadways. Today, a large wildlife crossing allows passage under the section known as Buried Bridge, so named because the bridge is literally buried under the highway and crosses over the wildlife crossing, making both undetectable to motorists.
Cody Beers, Wyoming Department of Transportation, Public Relations Specialist for District 5, says standard bridges have a tendency to become icy during the winter, causing hazardous traveling conditions. To avoid these conditions WYDOT chose to borrow a Canadian engineering idea.
The bridge was constructed near milepost 24 at more than 9,000 ft. along a known migration route for deer and elk. After the bridge was completed WYDOT crews covered it with five feet of dirt then built the road over the dirt. The dirt acts as insulation preventing icing of the road in the shadowy sections of the highway.
The underpass will be fenced to encourage wildlife use and it will be quieter under the structure as it has four to five feet of dirt on top of it, and then paved highway, says Beers.
I-15 Wild Cat, Utah
Monte Aldridge is Utah Department of Transportation Region 4 preconstruction engineer. He says that before they built the Wild Cat crossings on I-15 in Beaver County in 2004 there were on average 300 deer-car collisions per year. After the crossings and fencing were installed the incidents dropped to less than 10 per year.
Aldridge says that UDOT installed two massive culverts that were placed approximately two miles apart. “We also placed approximately 20 miles of wildlife fencing, 10 miles on each side of the highway, to funnel the deer to the crossings and keep them off the highway yet allow them travel their migration route,” he says.
Aldridge added that the location was critical to the deer’s ability to use the crossing. “We had to locate the crossings in areas that are naturally being used by wildlife, allowing them to have a good view of the facility so they can locate it and use it. And going from 300 incidents a year to 10 is truly sensational,” he says.