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June 23, 2008
Connecting downtown Seattle and downtown Bellevue by light rail sounds like a great idea. Whisking workers and shoppers between the state's two largest employment and retail centers is almost a no-brainer, right?
Wrong! A big body of water called Lake Washington creates technical and cost challenges that are risky, maybe too risky. No one in the world has put light rail on a floating bridge and Sound Transit should not be the first.
Some of the biggest questions raised by engineers who have studied the project are:
Will stray electrical currents corrode the Interstate 90 floating bridge?
How can the floating and fixed portions of the bridge be connected so trains run smoothly?
How can tracks be added to the bridge without poking a bunch of holes in it?
Sound Transit should avoid drilling holes in the bridge deck because that could undermine its structural integrity, according to an independent team of engineers hired by the state to assess the viability of adding rail to the I-90 bridge. As an alternative, the tracks could be attached with adhesives, the engineering team said.
The engineering team said the challenges could be overcome and that adding light rail to the I-90 bridge is doable.
Talented engineers and contractors would likely be able to place light rail on the floating bridge, but the cost may be too high. Add in the reduction of traffic lanes to accommodate rail and the project becomes even less appealing.
A comprehensive examination of cost, risk and traffic flow would likely show that light rail is not competitive with express bus service.
Sound Transit can be proud of its downtown to Sea-Tac route that is expected to operate next year. That segment can and should be expanded. The transit agency needs to look at making tracks around Lake Washington if it wants to bring light rail system to the Eastside.
Phil Brown can be reached by email or by phone at (206) 622-8272.
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