rhodedendron alongside of highway

A project to construct needed improvements to a stretch of mountain highway in Washington State will provide new opportunities for moving people through the corridor and reconnecting wildlife habitat and natural systems, which for years have been fragmented by the roadway.

Solutions for I-90

Washington State DOT and partner agencies worked to develop innovative solutions for the I-90 Snoqualmie Pass East project, to achieve needed safety and mobility improvements for drivers, provide safe passage for wildlife, and reestablish vegetation and hydrologic connections across the roadway.

The solutions were developed by a unique partnership of agencies – including state and federal transportation agencies and the U.S. Forest Service, which manages the surrounding land – as well as other agencies, nonprofit conservation and public advocacy groups, universities, and citizens.

The 15-mile project area is on National Forest land and must be compatible with the U.S. Forest Service’s adaptive management plan for the area.

The DOT agreed to include wildlife connectivity along with transportation improvements as a part of the project purpose and need statement.  The environmental impact statement specifies that the project is intended to meet traffic demands and improve public safety by addressing avalanches and slope instability, repairing structural deficiencies in the existing roadway, and expanding capacity, while also providing for ecological connectivity.

Regarding highway improvements, the project will:

  • expand the roadway from two lanes to three lanes;
  • replace the concrete pavement, straighten dangerous curves, and provide additional chain-up areas for trucks,
  • construct a new six-lane snow shed for protection from avalanches, and
  • stabilize dangerous slopes to reduce rock fall hazards.

In addition, wildlife passing structures are planned at 14 major wildlife crossing areas as part of the project. Structures include replacing narrow bridges and culverts with longer and wider structures to facilitate wildlife passage; adding wildlife exclusion fences to keep animals off the highway; and adding wildlife overcrossings at strategic locations.

A key aspect of the project was the identification of 14 separate “connectivity emphasis areas” – locations near streams or upland that can benefit fish, wildlife and hydrologic functions through restoring or enhancing a connection to habitat on both sides of the road. The areas were identified by a multi-agency mitigation development team.

Gold Creek Bridges and Wildlife Crossing

Gold Creek is one example of a connectivity emphasis area on the project, with improvements planned to achieve wildlife passage, hydrological connectivity, and re-establishment of vegetation.

The existing bridge structures at Gold Creek are 138-feet and 126 feet long, with a large quantity of imported fill within the floodplains and wetlands – a situation that has allowed little connectivity for aquatic or terrestrial species. Roadway improvements will replace the existing structures with wider and longer spans – two 1100-foot structures – and add a new wildlife undercrossing, all designed to improve connectivity and restore ecological functions.

Gold Creek was among the project areas that also benefited from partnerships among agencies and conservation groups to acquire private land to protect and contribute to the effectiveness of the conservation emphasis areas.

Over the last 15 years, a coalition including the Cascades Conservation Partnership, the Mountains-to-Sound Greenway Trust, the U.S. Fish and Wildlife Service and U.S. Forest Service have invested more than $100 million to protect land in the I-90 project area. Through combinations of land purchases and exchanges, the partnership has added 75,000 acres of conservation land and National Forest land within the area.

The Gold Creek improvements will allow multiple benefits – connecting wildlife habitat for small and large species while also helping to restore achieve hydrologic connectivity and providing mitigation for wetlands impacts.

Other noteworthy aspects of the project’s environmental commitments include creative solutions that combine benefits for wildlife connectivity and wetland mitigation and efforts to test and reestablish native vegetation in ecologically challenging environments.

In addition, the project includes extensive efforts to monitor wildlife occurrences – both before and after construction of wildlife crossings – to determine the effectiveness of the structures.

The monitoring program includes a unique public involvement effort, I-90 Wildlife Watch, in which citizens are encouraged to help gather data on wildlife in the area and to report wildlife sightings – including live animals or victims of collisions with vehicles.

The many environmental commitments of the project were in part the result of the extensive collaborative effort of the environmental review process itself, which was led by an interdisciplinary team including FHWA, WSDOT, USFS, USFWS, and Washington Department of Fish and Game. In addition, a range of other advisory committees, consultations, and partnerships with agencies, organizations, and the public helped to streamline the process of developing the Environmental Impact Statement. The project received FHWA’s 2011 Environmental Excellence Award in the category of Environmental Streamlining.

For more information, visit the project website at www.wsdot.wa.gov/projects/i90/SnoqualmiePassEast.