The Palensky Wildlife Underpass

Northern red-legged frogs (Rana aurora) are a Federal Species of Concern and a State Sensitive Species facing a variety of threats in urban landscapes. The Oregon Department of Fish and Wildlife (ODFW) partnered with Columbia River Estuary Study Taskforce to coordinate the design and construction of the Palensky Wildlife Underpass on U.S. Highway 30 in Portland. The project is the first of its kind in Oregon and aims to provide safe passage for Northern red-legged frogs during biannual migration between upland forested habitat and wetland habitat in the Palensky Wildlife Area. ODFW identified crossing hotspots and selected the location with the greatest potential for reducing road mortalities. Staff selected specific design features that allow the interior of the underpass to mimic ambient conditions. Multiple light box grates allow both light and moisture to enter the underpass, a white interior increases light reflection, a thick layer of local substrate creates a natural base and predator protection, and altered hydrology ensures the underpass will not pass water. 600ft of directional wall directs wildlife toward the underpass entrances. Construction was completed in December 2024 and ODFW is implementing the first phase of monitoring. One month of monitoring documented Northern red-legged frogs, Pacific treefrogs, multiple species of salamanders, and small mammals in the underpass. Long-term monitoring will provide valuable data about the effectiveness of this model of underpass for the conservation of Northern red-legged frogs and will provide information for two amphibian underpass projects in development within 5 miles of the Palensky Wildlife Underpass.