A decade long study conducted by the Wildlife Conservation Society (WCS), the Wyoming Cooperative Fish and Wildlife Research Unit and the Wyoming Department of Game and Fish (WDGF) — and supported in part by the National Fish and Wildlife Foundation (NFWF) — found that the pronghorn antelope’s habitat and 6,000-year-old migration route across Wyoming had been severely affected by factors including development, natural resource extraction and an increase in traffic along U.S. Highway 191 in the area of Trapper’s Point. The 90-mile biannual journey between Grand Teton National Park and the Upper Green River Basin is known as the “Path of the Pronghorn” and, over the last five years, 702 pronghorn antelope and mule deer were killed while trying to cross the 27-mile stretch of Highways 189 and 191. With approximately 75 percent of the migration routes already lost in the Greater Yellowstone Ecosystem, it was imperative that this route remained intact. In order to allow pronghorn antelope as well as mule deer, elk and moose safe passage across busy U.S. Highway 191, the Wyoming Department of Transportation (WYDOT) searched for a solution.
In addition to preserving the wildlife, the cost benefit to reducing the number of animal-vehicle collisions was staggering. According to state figures, roughly 1,800 vehicles collide with wildlife each year, resulting in two killed and 140 injured people. In this area alone, drivers spend approximately $350,000 per year in vehicle repair and doctor bills due to collisions with wildlife.
As the solution and way to minimize these accidents, the WYDOT chose two BEBO® Bridge Concrete Arch Systems — 66’ x 24’ x 150’ and 78’ x 27’-10” x 150’ in size — to serve highway traffic below and wildlife corridors above. These structures were chosen for their ability to be installed rapidly with minimal disruption to highway traffic and the migration of the animals.
The challenge of limiting traffic interruption during construction was solved by the quick installation of the structures over the active highway. It took six days to install the 66’ span BEBO structure with traffic going through the structure at 20-minute intervals. The 78’ span BEBO was installed in seven days with traffic also going through at 20-minute intervals. As required by the WYDOT, the roadway remained open at all times throughout the installation.
In order to channel thousands of pronghorn and mule deer towards the safe overpasses, WYDOT installed 31 miles of 8’ high fencing along the highways. Pronghorn antelope are found only in North America and are the fastest hoofed animal on the continent, with speeds up to 60 mph. They once numbered an estimated 35 million in the early 19th century. About 700,000 remain today and more than half of those are in Wyoming. Due to the pronghorn antelope’s fondness for the open range, the ability to see well at long distances and their preference for a good line of sight, overpass — rather than underpass — structures were deemed critical to the success of this project.
“They eliminate the danger of collisions and will help to preserve a spectacular element of our natural heritage — the longest mammal migration in the 48 contiguous United States,” said Joel Berger, a scientist with the WCS. “This is an accomplishment that all Americans can celebrate.”
“Through the use of trail cameras, early monitoring results from October 1 to December 15, 2012 have documented that nearly 9,000 big game animals have successfully used the overpasses and underpasses,” stated John Eddins, District 3 Engineer with the WYDOT. “Over 2,000 pronghorn antelope and 1,000 mule deer crossed the overpass located at Trapper’s Point. This means that 9,000 big game animals were not exposed to vehicle collisions crossing US 191 at grade. This indicates that the estimated 80 percent reduction in wildlifevehicle collisions this project promises, may hold true. There are not very many treatments a department of transportation can do to a highway to reduce crashes by 80 percent.”
Along with the 80 percent reduction in collisions, it is estimated that this project will save approximately $27.9 million in wildlife losses, vehicle damages and injury to property or people over the next 50 years.
In October 2012, while watching 100 pronghorn antelope cross the newly-completed structure in just 15 minutes, Jeff Burrell, Northern Rockies Program Coordinator at the WCS commented, “As conservationists, it seems sometimes that we are spending our time trying to keep things from getting worse. Today was different. While the structures are only necessary because of a human-created problem, at least humans came together and designed a solution … and one that if today is any indication, will work better than we hoped. Now we just need more of these overpasses, a lot more!”
This project was named Wyoming Engineer Society’s 2012 President’s Project of the Year.