Covia Holdings LLC

Tunnel City

Tomah, Wisconsin, United States

Certified Silver through 2023

Project Name
Project Type
Bat Tunnel
Karner Blue Butterfly
About the Program
The Covia Tunnel City site is in Tomah, central Wisconsin. Covia acquired the site in 2011, and it is used as a metallic mineral mine that utilizes open pit quarrying to produce industrial sand. Historically, a portion of the site was owned by Union Pacific Railroad, and the rest was a combination of residential homes, forest and farmland. The site is 1,900 acres in size, with 85 acres actively managed for wildlife. The program was first certified in 2013.

Practices and Impacts
  • The site is home to an abandoned and collapsed railroad tunnel that was considered to be a liability. After an initial survey in 2011, by the Wisconsin Department of Natural Resources (DNR), it was discovered that the tunnel was an important bat hibernaculum for several species. The team decided to take steps to allow the site to continue to serve as ideal bat habitat. The team installed a bat-friendly gate that allows bats to access the tunnel, while preventing human disturbance. Bat Conservation International helped design the gate.
  • The team also installed several bat boxes around the site to provide additional bat habitat. Local scouts help build the boxes.
  • The Wisconsin DNR helps monitor the bats for white nose syndrome, which is threatening many bat populations throughout the country.
  • Native plants were planted near the entrance of the tunnel to attract insects that are a food source for the bats. Plant species used include Canada wild rye, June grass and prairie dropseed.
  • The team is also providing more nesting options for bluebirds. The Wisconsin Bluebird Association helped the team identify ideal locations for nest boxes. The team then purchased boxes from the Wisconsin Bluebird Association and installed them in the locations they identified. The team regularly monitors nest box use and monitoring data is submitted to the Wisconsin Bluebird Association.
  • The team is making significant efforts to restore Karner blue butterfly habitat. The team worked closely with Wisconsin DNR to restore native plants on-site. They specifically focused on wild lupin, as this is the only food source of Karner blue butterfly caterpillars. Open corridors were also created between existing habitat and the restored habitat to allow migration of the butterflies. Regular monitoring of the butterflies takes place, and the results are reported annually.
  • The team also planted a pollinator garden near their office building in 2012. The garden is 5 acres in size and uses native species like lead plant and thimbleweed. In 2015, a beehive was installed near the garden. The team saw the potential to use the garden and beehive as educational tools and installed a nature trail in 2015 to allow easier access.