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Combining transportation improvements and wildlife connectivity on freeway rebuild in Washington’s Cascade Mountains


Interstate 90 over the Cascades is a significant barrier to over 250 species of wildlife, including cougar, elk, deer, mustelids (otters, fishers, badgers, etc.), amphibians, and reptiles. In the vicinity of Snoqualmie Pass, urban development to the west and agriculture and resort development on the east has shrunk the forest connecting the north and south Cascades to less than 64.6 kilometers wide. The Washington State Department of Transportation (WSDOT) is proposing to expand a 24.15-kilometer stretch of Interstate 90 just east of Snoqualmie Pass through a particularly critical zone for north-south wildlife corridors. Absent effective wildlife-crossing structures, the expansion would worsen the barrier by increasing roadkill and further isolating populations, thus inhibiting genetic exchange. However, the state has made ecological connectivity a project goal, along with increasing capacity, straightening curves, and repaving. The I-90 Wildlife Bridges Coalition has been working with WSDOT, other public officials, transportation interests, and the public to promote high-quality wildlife-crossing structures. Such structures can also improve safety for motorists by reducing collisions that are sometimes fatal to humans, as well as wildlife. Good data is available to inform where to build crossing structures. WSDOT and the US Forest Service collaborated on a study entitled I-90 Snoqualmie Pass Wildlife Habitat Linkage Assessment (Singleton and Lehmkuhl 2000) that used tracking and road-kill counts to map existing crossing activity. Additional relevant information comes from analysis leading to the Snoqualmie Pass Adaptive Management Area Plan and I-90 Land Exchange (US Forest Service, 1997 and 1999) and Washington State Dept. of Fish and Wildlife studies of cougar movements using radio collars. Recent land acquisitions and national forest-management changes have dramatically improved the outlook for habitat quality near the project. In recent years, purchases, donations, and exchanges have brought more than 50,000 acres of land valued at $200 million into public ownership and protection. The Forest Service is committing to additional habitat restoration, such as road removal. Two of the distinguishing features of the I-90 project are the prevalence of wetlands associated with the Yakima River and the variation in habitat as precipitation and elevation decline from west to east. A variety of structure types—from extended vehicle bridges, to box culverts, to overpasses specifically for wildlife—is required to allow both hydrological connectivity and connections for a diverse array of species. Preferred habitat conditions and existing movement patterns are balanced with site-specific design considerations, including cost, to establish a range of possible solutions to be presented in a draft environmental-impact statement due in spring 2005. Given the intense competition for transportation funds, particularly big-ticket projects near urban areas, the I-90 Snoqualmie Pass East project will need broad-based support to obtain funding. To overcome the environmental community’s general opposition to expanded freeways, the project will need to provide a high level of wildlife connectivity. Project proponents will also need to navigate anti-tax politics by joining in a diverse coalition of agencies, conservation groups, and shipping interests. The recent partnership to acquire habitat north and south of the project points the way. The coalition has grown out of a history of grassroots activism and collaboration around the Central Cascades region. Citizen involvement has played a critical role in the management policies of this area. The I-90 project will be a greater success due to the high level of attention and input received from the public. Public involvement will have peaked in the spring of 2005 with the release of the Draft Environmental Impact Statement followed by five public comment hearings throughout Washington State. This input will be considered throughout the summer of 2005 and (hopefully) brought to a successful completion in the fall/winter of the same year.

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