An Evaluation of the U.S. Highway 17 Underpass in Chesapeake, Virginia, as a Wildlife Crossing

About the report:

In November 2005, the Virginia Department of Transportation (VDOT) realigned and widened more than 10 miles of U.S. Highway 17 in Chesapeake, Virginia, to accommodate the growing volume of traffic and increase safety.  Through extensive coordination with regulatory and resource agencies, measures were designed to minimize impacts to the area’s natural resources and the neighboring Great Dismal Swamp National Wildlife Refuge (GDSNWR).  The primary mitigation included the construction of two parallel bridges, 984 ft long and approximately 8 ft high, that span a wetland within an important riparian corridor along the Paleo-Northwest River.  Two berms were constructed on the wetland beneath the bridges to serve as dry areas for wildlife crossings, and nearly 2 miles of 10-ft-high fencing extends from the underpass to help guide wildlife toward the underpass and prevent them from entering the roadway. 

A 29-month camera monitoring study was conducted to determine whether the structure facilitated wildlife passage.  Cameras documented 550 crossings by at least 12 species.  Thirteen black bear crossings occurred during the second year following underpass construction, evidence of the structure’s ability to provide safe passage for bears traveling to and from the GDSNWR.  Results suggest that the underpass connected important wildlife habitat.  In addition, as deer represented 30% of the crossings, the underpass also reduced the risk of deer-vehicle collisions, which is a significant issue for Virginia. 

The information gained from this project can assist with decisions regarding future investments in similar environmental mitigation projects.  It is reasonable to argue that the value of such measures increases over time in terms of ecological significance (i.e., facilitating wildlife movement and conserving important habitat); benefits to drivers from a reduction in the risk of animal-vehicle collisions; and cost savings to VDOT in carcass removal and disposal expenses. 

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