Designing a Passing Lane for Wildlife

For people who routinely drive over Snoqualmie Pass in the scenic Cascade Mountains, the jarring sight of an animal carcass on the side of the road is an all too common experience.

It could be a deer or elk, a black bear or cougar, or any of 70 species that populate this forested wilderness an hour east of Seattle.

On a 15-mile stretch of Interstate 90, between here and Hyak, road crews clear an average of 50 deer and elk carcasses a year. They don’t keep track of the smaller roadkills, such as raccoons and foxes, because there are too many.

“What’s going on there is really a massacre,” said Marcel Huijser, a road ecologist from Montana State University who has taken an interest in an ambitious plan being considered by Washington state transportation officials.

The proposal calls for building a system of wildlife pathways that would allow animals to safely cross that section of I-90. The plan could cost as much as $100 million, making it one of the largest roadkill-prevention projects in the United States.

The project would be part of a larger plan to improve and widen that section of I-90, which is routinely congested. The freeway is the main artery connecting rural Eastern Washington to the heavily populated Puget Sound area. An average of 27,000 vehicles a day pass through this stretch, many of them long-haul trucks.

The state is still soliciting public comments, but the Legislature has already committed $387 million to the overall proposal, which could reach $980 million. If all goes according to plan, construction would begin in 2011 and last seven years.

“This is on the forefront of road ecology,” said Huijser, who works at MSU’s Western Transportation Institute, which is advising Washington state on the proposal. “There are not many projects in North America that approach this scale.”

Other states, such as Arizona and Montana, have built smaller wildlife corridors.

Outside Barstow, California and federal crews worked together to build a system of fences and culverts that allows endangered desert tortoise to safely cross Route 58. The culverts, made of corrugated steel pipe, run underneath the highway like small tunnels.

In Florida’s Everglades, road workers constructed a series of narrow bridges over a 40-mile stretch of what is now Interstate 75, allowing safe passage of alligators, Florida panthers, armadillos and foxes. That stretch of road has come to be called Alligator Alley.

One of the only animal-crossing projects in North America that approaches the Snoqualmie Pass plan in scope is the system in Canada’s Banff National Park, made of two grass-covered 150-foot-wide overpasses and 22 smaller underpasses that cross the Trans-Canada Highway.

The Snoqualmie Pass project would include up to 14 crossings. Some would resemble large tunnels or culverts, and some would be bridges, including one that would span 1,200 feet -- the length of four football fields -- and be planted with dense, natural vegetation.

The tunnels would be designed for more secretive animals, such as cougars. Deer, elk, moose and bear would be more likely to use the land bridges. A system of fences would funnel wildlife toward the crossings, which would be located where specific species are known to cross.

Paul Wagner, senior biologist for the transportation department, said it could take as long as two years for the animals to grow accustomed to the structures. Wagner said the generation of animals that grows up around the crossings would be more likely to use them.

A coalition of 30 environmental groups has hailed the proposal.

Charlie Raines, a leader of the I-90 Wildlife Bridges Coalition, said it reflects a more “progressive and enlightened approach” to building and improving roads. Said Raines: “It’s not the old approach of ‘We just do concrete.’ ”

Some people required more convincing.

State Senate Minority Leader Bill Finkbeiner, a Republican from Kirkland, initially voiced reservations about the plan, questioning the “cost-benefit,” and asking whether there were cheaper alternatives. He also wondered whether the price tag was justified.

“I was concerned with how it looked to be spending this kind of money during a time when we’re considering a gas tax,” Finkbeiner said. But the senator said he’s had “a change of heart.” After discussing the proposal with a number of people, Finkbeiner said he saw long-term benefits for the region.

The science of road ecology involves a great deal more than just trying to get animals across a road. Its goals have to do with building roads while also preserving animals and habitat and the intricate connections between them.

In many ways, the Cascade range, which runs north and south, is a single ecosystem, and I-90, which runs east and west, bisects this ecosystem and hinders or prevents animals from access to their home range.

The interstate acts “like a brick wall in the middle of the wilderness,” Finkbeiner said.

Animals that try to cross risk being hit and killed by vehicles, and animals that don’t cross are often isolated and forced to inbreed. Inbreeding creates genetic problems that weaken an animal population, making it more vulnerable to disease, which affects the entire food chain of the ecosystem.

Another benefit to helping animals cross safely is fewer collisions with cars and trucks. Wagner, the state biologist, said four people were killed near here in June 2004 when their vehicle hit an elk and hurtled over an embankment.

The state has no statistics on human fatalities caused by animal-vehicle collisions on I-90, but Huijser, from Montana State, said nationally at least 29,000 people are injured and more than 200 killed each year in such accidents.