Roads, Bridges & Tunnels

Washington Governor Chris Gregoire yesterday announced she’d push back by two weeks a recommendation on how to best replace the aging, earthquake-prone Alaskan Way Viaduct on State Route 99 along Seattle’s downtown waterfront. But there’s more. A top Gregoire advisor tells the Seattle Times that the deep bored tunnel proposal – energetically advanced by Viaduct Stakeholders Advisory Committee members plus our Cascadia Center and the general public – is “probably the most viable option.” Deep bore tunneling technology has advanced greatly in recent years and the method is considered highly suitable for an inland downtown tunnel away from Seattle’s waterfront. (A tunnel boring machine used for Madrid’s M30 roadway project is pictured below, right.) The Times: OLYMPIA – A proposed Read More ›

A real consensus is emerging. Last night at the final Stakeholders Advisory Committee meeting on replacement of the earthquake-prone Alaskan Way Viaduct on State Route 99 along Seattle’s downtown waterfront, Seattle Deputy Mayor Tim Ceis and a top aide to King County Executive Ron Sims joined the near-unanimous majority in voicing clear support for more detailed study of the deep bore tunnel alternative in combination with surface and transit improvements. Meeting notes here. To minimize traffic and business disruption, the viaduct would stand until tunnel completion, and tolling the tunnel would close the funding gap. Tunnel boring technology has advanced greatly, as detailed a year ago at a Cascadia Center expert symposium on the topic. The downtown waterfront would be Read More ›

OK, another hot flash from your (currently) ”All Viaduct All The Time” news channel. Venerable Seattle Post-Intelligencer columnist Joel Connelly writes for tomorrow’s edition (online tonight), “What’s Needed Is A Third Option For The Viaduct.” The view here is we are not yet ready to swallow, and could gag on either viaduct option. What’s needed is tough, honest analysis of a third option, the combination of a deep-bored tunnel and surface transit. Speed is one factor: Could a tunnel get dug and be open for traffic before demolition of the existing Alaskan Way Viaduct? The city has to avoid, at all costs, the kind of prolonged mess that disrupted and degraded Third Avenue when the bus tunnel was built. The Read More ›

Advocates of the deep-bored tunnel option to replace the seismically vulnerable Alaskan Way Viaduct on State Route 99 along downtown Seattle’s waterfront, including business and neighborhood interests, rightly stress that the Viaduct serves some 110,000 daily vehicle trips and that the majority of that is “thru” traffic that neither starts nor finishes in downtown. According to p. AWV-5 of this report on the Viaduct, from Washington Governor Chris Gregoire, 60 percent of those 110,000 daily vehicle trips on SR 99 in the project area use the Viaduct as a route through, not to or from, downtown Seattle. This is crucial because if the Viaduct’s six total lanes are replaced with surface boulevards including 20-plus traffic signals, plus more transit and Read More ›

Since the recommendation came Thursday Dec. 11 from Washington State Department of Transportation, King County and Seattle officials that the wobbly Alaskan Way Viaduct through downtown Seattle on State Route 99 should be replaced with either a surface boulevard system and more transit, or another elevated roadway, the reaction has been remarkable. Remarkable because of how much support is being voiced for an option planners have essentially rejected for now, a deep-bored tunnel. Let’s survey some of the blowback, which is only likely to grow. The Seattle Post-Intelligencer’s editorial board today writes: …several troubling questions have arisen. Does a new, elevated structure really deserve to be one of just two finalists, with its massive commitment to autos and prospect of Read More ›

The last time anyone hazarded a report, it was estimated that a whopping four percent of daily trips in Puget Sound occurred on transit (second paragraph of p. E-6, here). That was in 2006. Let’s say that percentage has now more than doubled to ten percent. You’d still have nine out of every ten daily trips, occurring in vehicles – versus scheduled transit. Beating traffic congestion in the real world, that’s how leaders need to lead sometimes. Like now. With an historic decision for Puget Sound and Washington State partly unfolding later today on finalist options for replacement of the Alaskan Way Viaduct on State Route 99, an apropos reminder comes from our neighbor to the south, in Oregon. Editorial Read More ›

You don’t have to be in Seattle long to hear about the Alaskan Way Viaduct. Hugging the coastline, the aging structure carries north-south traffic through the city. It’s been the topic of debate for what seems like an eternity. Why? Because it has to come down or mother nature may take it down.
By the time the clock reaches midnight on New Year’s Eve, Governor Gregoire, King County Executive Sims and Mayor Nickels will have on their desks a list of final options for replacing the Alaskan Way Viaduct. They’ll make their decision in 2009.
Cascadia Center is at the heart of the debate and has long advocated construction of a deep-bored tunnel to carry traffic under the city.
Click below to see Cascadia’s most recent release and links to supplemental material.

Read More ›

Thursday, transportation officials from the State of Washington, King County and the City of Seattle are to choose two or three finalist options from a field of eight or nine, for replacement of the seismically vulnerable Alaskan Way Viaduct on Seattle’s downtown waterfront. Things are moving fast and furious and there is growing momentum for the deep-bored tunnel option – which compared to a new elevated viaduct or added surface street traffic would best minimize traffic congestion and environmental impacts, and open up the most public space on the waterfront. With some 110,000 vehicles traveling the elevated roadway on State Route 99 every day, and the bulk of that traffic bypassing downtown, simply expanding surface street capacity and adding transit Read More ›

To supplant the aging and seismically vulnerable Alaskan Way Viaduct on State Route 99, which blockades downtown Seattle from its waterfront, two elevated replacement options, three tunnel options and three surface/transit choices are under review. The state, King County and Seattle transportation department heads are to recommend a few semi-finalists as soon as the end of this week, with Governor Chris Gregoire, Seattle Mayor Gregoire, and King County Executive Ron Sims then to make a final choice to the legislature by the end of this month or the middle of next month at the latest. But Susan Gilmore of the Seattle Times reports today that some members of the Stakeholders Advisory Committee (SAC) for the viaduct replacement process are very Read More ›

A report titled “Large Diameter Soft Ground Bored Tunnel Review” has just been released by the transportation think tank Cascadia Center and global engineering and consulting firm Arup. It strongly suggests that a new state cost estimate for a deep bored tunnel of approximately two miles to replace the aging Alaskan Way Viaduct could be greatly inflated. The state’s Alaskan Way Viaduct Stakeholders Committee (SAC) pegs the cost of the one-mile tunnel at $3.5 billion, but the Cascadia-Arup report surveyed deep-bored vehicle tunnels worldwide and found costs typically fall in the range of $200 million-$700 million per mile, for large diameter soft ground bored tunnels, created with assistance of a tunnel boring machine (pictured below at right). A Nov. 20 Read More ›