Old Cascade Highway washout at Miller River Bridge
When a winter flood tore through the Skykomish Valley and changed the course of the Miller River in January 2011, it left behind millions of dollars in road and bridge damage -- a disaster that King County continues to struggle with today.
The flood destroyed a 100-foot section of the Old Cascade Highway in rural northeast King County and left the Miller River Bridge damaged and cut off from the roadway.
Since that federally declared disaster, the county's Road Services Division has been working with state and federal emergency management and transportation agencies to determine feasible options for next steps and has reached out to local residents for input on alternatives.
Four alternative projects have been approved by the Federal Emergency Management Agency (FEMA) for the Miller River and Skykomish community. FEMA has approved funding to repair the Skykomish River Bridge during the summer 2017, and for design of the west and east legs of the Old Cascade Highway roadway approaches. Additional King County budget authority needs to be approved to design for the Miller River Bridge removal.
What the county has learned
The Miller River continues to shift and move. The footings of the Miller River Bridge are not connected to the bedrock below. The island created by the migration of the river and the continuously moving river are now putting this bridge at risk. The Old Cascade Highway is a rural road that carries around 100 vehicles per day.
Even if a new bridge were to be built to span the washout, the new structure would be at risk, given the river's history of unpredictable migration.
The county has identified and analyzed 10 different options for a new bridge and reconstructed road. As part of that review, engineers looked at:
Rebuilding the damaged section of road and constructing a new bridge (including review of several different bridge lengths and alignments).
Construction methods to keep materials and other environmental impacts away from sensitive areas.
The need to accommodate potential future migration of the river.
Whether such a project could affordably be constructed with little available matching county funding.
The impacts on the community of closing the road altogether.
After careful analysis of these alternatives, the county has concluded that restoration of the Old Cascade Highway and construction of a new bridge will cost an estimated $19.1 million – far more than is available from federal emergency reimbursement dollars and other potential revenue sources.
Federal Emergency Management Agency (FEMA) rules do not allow federal aid dollars to be spent for enhancements or improvements beyond restoring the infrastructure that was in place before to the damage. These funds cannot be spent on improvements within the Town of Skykomish or on state roads. And given the continued decline of transportation revenues, King County is not likely to have resources for an investment of this size and magnitude any time soon.
There is some federal funding available for other transportation improvements in the Skykomish area. The county has identified possible projects for this funding, including rehabilitation or replacement of the Skykomish River Bridge just off of Highway 2 or of the Foss Bridge on Foss River Road.
King County's Flood Control District has purchased 28 acres under and around the Old Cascade Highway washout in order to get people and private property out of harm's way, given the Miller River's highly migratory pattern.
September 2012 – King County hosted a public meeting in September 2012 in Skykomish to talk with community members from Money Creek, Miller River, and Skykomish about the bridge and gather input on projects that could be funded as alternatives to repairing the Old Cascade Highway washout. The county also answered questions from residents about other steps that could be taken to help minimize the impacts of closing the Old Cascade Highway.
April 2013 – Skykomish community members met with county representatives to discuss responses to questions they had raised at the September meeting. Community members restated their preference for rebuilding the road to the existing bridge. County representatives described in more detail the options for using the FEMA funds. At the end of the meeting, community participants ranked the alternative projects, with a replacement bridge as their first choice.
June 2013 – King County hosted an open house for the Skykomish community where staff shared with the community a set of project options they could pursue for FEMA funding. View a list of potential Skykomish area FEMA projects that was shared. For more detail about this meeting and what was discussed, read the notes.
King County submitted four projects to FEMA for funding consideration. FEMA has approved funding to design the roadway approaches and make repairs to Skykomish River Bridge where construction was completed in October 2017, however additional funding needs to be approved in order to design the Miller River Bridge removal.
Have questions or comments about the Old Cascade Highway washout at Miller River? Send us an email or give us a call:
Community Relations Planner
King County Department of Transportation