The Effectiveness of Vertebrate Passage and Prevention Structures: a Study of Boeckman Road in Wilsonville

Focus Area

Wildlife & Ecosystems


Natural Resources






1-2 years

Research Idea Scope

TERI Administrator Update (Jan 2009) – Research Underway – The Effectiveness of Vertebrate Passage and Prevention Structures: a Study of Boeckman Road in Wilsonville (completion date: Sept. 2009)

Wildlife collisions are a serious issue resulting in extreme costs from property damage, including injury and possible death, as well as typically fatal results for the wildlife. Given the impacts to both the driver and wildlife, which may include at-risk or endangered animals, more recent attention has been given to modifying or retrofitting roads to facilitate wildlife passage.  In the city of Wilsonville, Oregon a road project known as the Boeckman Road Extension will be concluding construction in the summer of 2008. Wildlife passage was taken into great consideration in the construction of this road and as a result it includes a bridge, three large box culverts, and eleven small round culverts to facilitate wildlife passage as well as an amphibian wall and deer fence to prevent wildlife access to the road surface. Two large culverts and three small culverts include elements that will allow natural light to penetrate the culvert.

This road provides a unique opportunity to examine the efficacy of multiple types of passage and prevention structures in a given area where no road existed previously.  A mammal wildlife survey was conducted at the Boeckman road site prior to construction in March of 2004 and found evidence of black tailed deer, raccoon and coyote, nutria, beaver, mink and river otter. Adjacent lands are considered prime red legged frog habitat and the presence of a pond as well as an upland island could someday provide essential habitat for the threatened western pond turtle. Using motion detection cameras coupled with road kill surveys, the types, frequency and preferences of animal (mammals and amphibians) passage will be determined. We will also use cameras to monitor locations at two transects one parallel and one perpendicular to the road. These transects will provide general information on the volume and species of animals utilizing this general location as well as provide a comparison to usage rates of the passage structures. Pit traps will be used at strategic locations along the amphibian/reptile wall to verify its use and effectiveness and to determine species present.

Urgency and Payoff

Determining the species-specific use of the different passage types and the efficacy of fencing will help identify best environmental practices for future projects and retrofits. This information should help match structure type to species of most concern, improving animal use and avoiding costs of less effective passages and fencing. The results of this study will also provide information valuable to assessing the proper passage structures in sensitive habitats, aiding transportation planners and wildlife biologists in working together to make the best assessment for the given area. The proposed project will be an important first step in a broader study that will include comparisons of other roadways, with and without culverts and fencing, and additional types of passage structures.

Suggested By

Leslie Bliss-Ketchum, Graduate Student - Portland State University Environmental Science & Management Department, Telephone: 503-481-6753

[email protected]