Opportunities exist to use crossings as learning tools and bipartisan healing

By Kevin Hetrick, PE

Earlier this year, construction began on the world’s largest wildlife crossing. The $87 million Wallis Annenberg Wildlife Crossing in Agoura Hills, California will eventually be a superhighway for animals residing and migrating in Southern California. The crossing will span 10 lanes of Highway 101 and allow animals safe passage into important migratory habitats for mountain lions, coyotes, deer, snakes, and other species. The project is hailed as an endeavor that will create a new era of environmentalism and conservation, which will establish an interconnectedness of human and animal infrastructure. 

Further, the Bipartisan Infrastructure Deal has established $350 million in federal funding for wildlife infrastructure, an unprecedented investment in wildlife crossings across the country. It’s estimated that there are only 1,000 wildlife crossings in America’s 4 million mile roadway network, or about one crossing every 4,000 miles. 

Animals’ lives and species survival are altered by the infrastructure that we rely on for our daily commutes. While it is encouraging to see high-profile projects like the Wallis Annenberg Wildlife Crossing achieving global recognition, we recognize the necessity of establishing a better understanding of the needs across all regions of the US that are affected by human transportation infrastructure. Engineering efforts are already underway in small towns across the Midwest; while we may not host larger animals like bears and bobcats, racoons and frogs among a myriad of other species deserve our attention and protection as well.  

A Mutually Beneficial Solution

The impact of infrastructure on wildlife is undeniable: our footprint has eliminated habitats, disrupted migratory patterns, and isolated animal subsets from larger breeding pools with genetic implications. 

However, the impact isn’t confined to the animal world. The Federal Highway Administration has estimated that between 1 and 2 million vehicle-animal strikes occur every year, causing over $8.3 billion in cost associated with damage, injuries, and fatalities. 

Engineers, with public and governmental support, are positioned to lead the charge. Engineers bear responsibility to offer solutions when designing new roadways, bridges, and structures that allow for the safe passage of animals in their natural environments. In a time of increasingly divided politics, wildlife crossings have been identified as a non-partisan, mutually beneficial initiative to improve conservation and safety. 

With the help of interviews from Brian Boszor of the Indiana Department of Natural Resources, Katy Duffield, children’s author of Crossings, as well Clark Dietz’s staff of Professional Engineers, we explored how to make wildlife crossings and conservation approachable in the context of engineering design.

What is Road Ecology?

Kevin Hetrick—Clark Dietz: How exactly does infrastructure affect nature?

Brian Boszor—Central Region Environmental Biologist, Indiana Department of Natural Resources: Road, bridge, trail, and utility line construction have been shown to impact fish, wildlife, and botanical resources in seven major ways: mortality from construction activities, mortality from maintenance activities or collision with vehicles, modification of animal behavior, alteration and fragmentation of the physical environment, alteration of the chemical environment, spread of invasive plant species, and increased human use and disturbance of natural areas. The evidence from well-designed studies suggests that well-connected habitat corridors are valuable conservation areas for fish, wildlife, and botanical resources.

KH: What should the public understand about the importance of wildlife passage in their communities? 

BB: Most municipalities in Indiana have at least one major waterway that bisects their town or city. Wildlife species use waterways in much the same way that humans use a roadway. The number of different wildlife species that can pass through an urban area is directly related to the number of passable bridge or culvert structures. Wildlife passage is critical to maintaining healthy wildlife populations, which benefits people that hunt and fish as well as those who just enjoy seeing or knowing that wildlife is present around them.

KH: Clark Dietz submits permit applications for review by the Department of Natural Resources on behalf of municipalities that include wildlife crossing designs. What key features are you looking for when providing solutions for safe wildlife passage?

BB: The key features of a crossing detail that should be considered for any wildlife crossing are the inclusion of a flat level pathway across a 2:1 spill slope, the ability to back fill the area with smaller substrate that is passable to a wider variety of wildlife species, the placement of the pathway above the ordinary high-water mark, and the ability to tie the pathway into existing elevations upstream and downstream of the bridge or culvert.

KH: How can the DNR and engineers continue to prioritize wildlife conservation as it relates to infrastructure?

BB: With four Environmental Biologists recommending roughly seven to 10 wildlife crossings per month, we can potentially help improve roughly 100 bridges and culverts per year for wildlife passage. Many engineering firms here in Indiana, including Clark Dietz, are coming up with great solutions to improve wildlife passage as a part of their bridge and culvert designs in coordination with the Division of Fish and Wildlife Environmental Unit.

KH: Why is now the right time to push for adoption of wildlife conservation solutions?

BB: The Bipartisan Infrastructure Bill has outlined roughly 9 new and expanded Federal and State funding mechanisms for the analysis, design, and implementation of wildlife crossings related to infrastructure projects. There has literally never been a better time to work on improving the permeability of our linear infrastructure for fish and wildlife passage as well as human safety.

Educations Is Paramount to Future Success

Kevin Hetrick—Clark Dietz: You wrote Crossings, a children’s book that describes different types of wildlife crossings that exist globally. What do you want children and families to learn about wildlife crossings?

Katy Duffield—Author of Crossings: First, and foremost: Animals are important. I firmly believe that everything in nature is interconnected—from the tiniest insect to the largest mammal. Every creature plays a distinct role, and we need every single species. Secondly, thinking outside the box is a great way to come up with viable solutions to problems. Thirdly, putting our hearts and our minds together, we can solve problems. Everyone can contribute. Everyone can make a difference.

KH: Do you think there is an opportunity to use wildlife crossings as a STEM learning opportunity? We hope to inspire future generations of engineering professionals.

KD: I’ve connected with many teachers and librarians since Crossings came out and I’ve been honored and thrilled to see how they are using my book in their classrooms. Many educators have shared with me how they’ve had their students design and build their own crossings in the classrooms using cardboard tubes, blocks, Legos, magnet tiles, etc. Once their creation is complete, many have used plastic animals to demonstrate how their inventions work. So many wonderful, imaginative solutions! 

I also wanted to highlight the creators of the crossings—the “animal lovers” like the scientists who study where the crossings will be most effective, the architects and engineers who draw up the actual structures, the construction workers who complete the on-site building of the structures, and others who are instrumental in making these crossings happen.

KH: Projects like Wallis Annenberg Wildlife Crossing can be quite expensive, but we’ve shown that local municipalities can support crossings within limited budgets. How can both large and small-scale projects be used to further public education?

KD: I think larger projects that get a lot of press can be a great way to raise awareness for crossings in general. They may prompt the public and other governmental bodies to look at ways to protect the animals in their areas—even if it is not on such a grand scale. It comes down to doing what we can to raise awareness across the board; look to see where the problems arise and figure out ways to remedy them.

Quality Of Life Extends to All Living Things

As infrastructure engineers, we are trained to design solutions to human-centric problems, and yet we run the risk of being shortsighted about the interconnectedness of humans and wild animals. 

Project Manager and Clark Dietz Civil Engineer Katherine Kreienkamp, PE says, “Many times, I think that people can become hyper focused on ‘How does this affect me?’. By teaching about crossings, we can introduce effects on the environment and the ecosystem in a project area. This also helps people to realize that choices made in a project are not made only to benefit one party, but a system as a whole.”

Safer infrastructure is a byproduct of conservation-focused engineering design. While many municipalities Clark Dietz serves in Indiana are incorporating wildlife crossings as a requirement of the permitting process on new projects, they are recognizing the ancillary benefits. 

“While the design detail helps to protect wildlife, the safe passage of animals under a bridge or structure also means that less wildlife will try to cross a corridor with vehicular traffic.  As a result, there are less potential roadway obstructions and drivers will experience safer passage,” says Sandra Bowman, Manager, Ecology and Waterway Permitting Office of the Indiana Department of Transportation.

Brian Powers, PE, CFM, ENV SP, who spearheaded Clark Dietz’s wildlife crossing design as approved by the Indiana Department of Natural Resources encourages a more symbiotic relationship with the environment. 

“I love wildlife focused designs. In my opinion, humans can’t occupy every square inch of this planet; we need to set aside space for the other species as well. I find it incredibly satisfying to know that we’re doing our part to improve both design and education as it relates to road ecology.”

With unprecedented levels of public support, we are on the precipice of a major shift in conservation and safety led by engineering-based solutions. Wildlife crossings both large and small have the opportunity to transform our nation’s vast infrastructure network. 

“I feel optimistic about benefits that come from implementation of design features that take conservation strategies into account. Because the construction of infrastructure can be a disruptor to an environment, finding a way to mitigate the impact to surrounding wildlife is always a net positive,” says Kreienkamp.  


Kevin Hetrick, PE is Clark Dietz’s Central Indiana Area Manager and serves as Project Executive for Transportation projects State-wide. At Clark Dietz, he has been involved with roadway, path, and bridge design and construction, as well as small structure inspections. He previously worked for 14 years at INDOT, first as a Project Engineer in Greenfield District Construction, then in the Central Office Project Management section.
Clark Dietz, Inc. a multi-disciplined infrastructure engineering firm operating from offices in Illinois, Indiana, Kentucky, and Wisconsin. Our primary areas of service include civil and environmental infrastructure, transportation, structural, mechanical, and electrical engineering. Clark Dietz’s mission is engineering quality of life that provides a positive impact on people, the natural environment, and the economic well-being of communities. www.clarkdietz.com