Enhancing Corridor Safety with Wildlife Crossings
When we think about roadway safety for wildlife, we may picture deer and other large mammals navigating rural roads to return to their forest habitats. Many of us might also take a moment to be a hero for a turtle, assisting them in safely crossing the asphalt and making sure they stay on their intended path. However, wildlife-vehicle collisions are not exclusive to rural areas; they occur in urban settings as well, creating significant safety risks for both motorists and animals alike.
In the heart of Dakota County, Minnesota, a transformative project took place to enhance both human and wildlife safety. The CSAH 32 Reconstruction project exemplifies innovative engineering and a commitment to environmental stewardship. One of the most unique features of this project is the implementation of wildlife crossings, specifically designed to protect the local fauna, including muskrats, squirrels, and the beloved turtles.
What are Wildlife Crossings?
Wildlife crossings, sometimes referred to as “turtle tunnels,” are essential in areas where roads intersect with natural habitats. Wildlife crossings can be designed in a variety of ways, including bridges, culverts, and underpasses, depending on the needs of the species impacted. These strategically placed structures provide safe passage for animals, reducing the risk of wildlife-vehicle collisions while simultaneously maintaining biodiversity of the site.
In the case of CSAH 32, the corridor bisects a highly biodiverse wetland complex near Lebanon Hills Regional Park. The existing roadway posed significant safety concerns for both commuters and animals, requiring an effective solution that balanced the needs of all stakeholders.
Overcoming Site Challenges
The CSAH 32 team had to navigate a complex landscape of utilities, drainage concerns, and sensitive environmental features. Grading was particularly challenging due to the numerous utilities that needed to be worked around. Furthermore, ensuring a traversable path for turtles while maintaining the integrity of the water bodies required innovative solutions, including the use of arch culverts, stormwater grating, and additional manholes.
Strategic Design and Implementation
Bolton & Menk, in collaboration with Dakota County and the City of Eagan, completed a comprehensive design process to address these challenges. A vehicle-centric, two-lane undivided rural corridor was converted into a two-lane divided urban section with multiuse trails. Perhaps the most transformative piece of the design includes wildlife crossings and animal fencing, ensuring animals can safely use the corridor without the threat of vehicular fatality.
One of the unique aspects of the wildlife tunnels is their design, which incorporates natural lighting to make the passage more inviting for animals. The tunnels are also strategically placed to keep road water out, ensuring water bodies that are crucial for the local ecosystem remain clean. This careful consideration of environmental factors highlights the project’s commitment to sustainability.
The design includes a 36-inch span reinforced concrete arch pipe, providing a safe passage for turtles beneath the roadway. Turtle fencing guides the animals toward the tunnel entrance, preventing them from crossing the road and risking vehicle collisions. A mountable curb is used to maintain existing drainage patterns, ensuring efficient water flow despite increased impervious surfaces and soils not conducive to infiltration. The project was developed in coordination with the Minnesota Zoo to address the specific needs of local turtle populations.
Dakota County and the Minnesota Zoo conducted wildlife mortality studies in the project area. Two areas along the project corridor met the MnDNRs recommendation of installing a turtle crossing as there were more than 10 turtle mortalities per year per 100 meters of road. One crossing area at Holland Lake had an especially high concentration of turtle mortalities. The project team worked closely with the Minnesota Zoo and MnDOT to identify the most ideal locations for the tunnels and appropriate treatment.
The tunnels were placed above the 100-year high water levels to ensure the pristine water quality of Holland Lake was preserved during large flood events. The tunnels have seen regular use from a variety of wildlife and, because of this, have been the subject of several local, regional, and national news stories and publications.
Community Involvement and Collaboration
A key element of the project’s success was the collaborative approach. Our team worked closely with Dakota County, the City of Eagan, and various stakeholders, including experts from the Minnesota Department of Transportation (MnDOT) and the Minnesota Zoo. Public involvement was also a critical component, with community input being sought through online platforms and public meetings, even during the challenges posed by COVID-19.
Implementing Wildlife Crossings in More Communities
Implementing wildlife tunnels in communities involves several crucial steps to ensure both wildlife safety and infrastructure effectiveness. The process begins with assessment and planning, where critical areas for wildlife crossings are identified through studies and stakeholder engagement. Feasibility studies are conducted to evaluate the practicality of constructing tunnels in these areas. The design and engineering phase focuses on creating tailored tunnel designs that cater to local wildlife needs, incorporating environmental considerations and safety features like fencing and barriers.
Securing project funding and resources is essential, with various sources such as government grants and public-private partnerships being explored. During construction, efforts are made to minimize disruption to both wildlife and human traffic, ensuring high-quality standards. Post-construction, regular monitoring and maintenance are crucial to track tunnel usage and maintain functionality. Community involvement and education through public awareness campaigns and volunteer programs are encouraged, along with collaboration and knowledge sharing with other communities to continuously improve the wildlife crossings initiatives.
Looking Ahead
The award-winning CSAH 32 Reconstruction project is an example of how thoughtful design and community collaboration create the most successful projects. The wildlife crossings enhance safety for animals and contribute to the overall goal of creating a safer, more sustainable corridor for all users. These tunnels have proven highly effective as documented by regional and national periodicals.
As the project moves forward, it serves as a model for future infrastructure projects that seek to balance motorists’ needs with environmental preservation by considering the well-being of all living beings frequently impacted by this corridor.
As the Northeast Minnesota work group leader, Josh Stier works closely with our staff to provide and expand our services in northern Minnesota. He is a principal engineer who began his engineering career with Bolton & Menk in 2012. He has an extensive background in stormwater management and is passionate about all things natural resources. Josh’s experience is not limited by his drainage expertise; he has a diverse project management background that includes leading numerous MnDOT and county highway projects, municipal reconstruction projects, complex drainage studies, and wetland restorations. This unique skillset engages him in some of Bolton & Menk’s largest and most complex projects. He enjoys the challenges presented by projects with highly sensitive environmental aspects and understands the correlation between strong communication and overall project success. In his free time, Josh enjoys traveling with his family and teaching his children about the great outdoors.
As a principal transportation engineer who began his career in 2009, Jacob Bongard works on a variety of projects ranging from high-level planning studies to in-depth final design projects. He uses the knowledge and experience obtained through his education and professional practice to identify project needs, work toward a solution, and communicate results to those in and outside the field of engineering. A transportation practice area leader at Bolton & Menk, Jacob loves to solve challenging problems and enjoys seeing the impact our work can have on improving the way people safely and efficiently get from one place to another. Outside of work, Jacob looks for ways to get outside including ice fishing in the winter, annual Boundary Waters trips in the spring, and slow pitch softball and golf in the summer and fall.
