Viaduct Bypass, I-5 Expansion Should Be Linked

Original Article

The shocking collapse of the Minneapolis Interstate 35W bridge will no doubt aid the campaign for the multibillion-dollar roads-and-transit package facing central Puget Sound voters in November. Yet two crucial transportation projects relevant to the Minnesota tragedy are partially on hold — replacement of the central waterfront section of Alaska Way Viaduct on State Route 99, and full funding for reconstruction of the 40-year-old stretch of Interstate 5 from Northgate to Tukwila.

Earlier this year, Seattle voters rejected two ideas for replacement of the viaduct — a larger aerial structure and a cut-and-cover four-lane waterfront tunnel. State transportation leaders have approved nearly $1 billion in improvements to the north and south ends of the viaduct to fix about 55 percent of the seismically vulnerable structure. Yet only the so-called “surface transit” option for the central waterfront is under continuing study by the city of Seattle and the state.

At Discovery Institute’s Cascadia Center, we support tearing down the aerial viaduct and have endorsed several aspects of the surface transit option, including bus rapid transit, a circular streetcar network emanating from the waterfront, and return of the “Mosquito Fleet” to expand water taxi and passenger-only ferry options.

However, any notion that the viaduct’s 110,000 daily vehicle trips can be replaced by a series of transit enhancements fails to comprehend the complexity of moving freight in a constricted north-south corridor. Simply put, I-5 can’t take any more traffic and freight can’t take a bus.

Solutions so far have been piecemeal and money is scarce. The Washington state Legislature allotted $21 million in its construction budget to begin repaving sections of I-5 between Federal Way and Northgate, initially around Spokane Street. Repaving I-5 is an important first step, but alone will not eliminate bottlenecks and poorly designed ramps, for which much of the funding has been pushed to 2017 and beyond.

We can’t look to the federal government for help. The Highway Trust Fund will have a $4 billion deficit in 2009, and Congress has shown no willingness to raise the 18.3-cent per gallon federal gas tax. I-5 in central Seattle carries 260,000 vehicles a day, rivaling sections in Los Angeles. The absence of the I-5 rebuild/reconstruction on the regional transportation ballot is a head-scratcher at best. Indeed, I-5 was completed around 1967 — roughly the same time as I-35W in Minnesota.

So we propose a bold — some would say radical — rethink. Our plan would consider both I-5 reconstruction and added capacity and replacement of the central section of the Alaskan Way Viaduct, within the context of regionwide tolling and partnerships for private capital.

A deep-bored tunnel through downtown to replace the viaduct, beginning at Sodo and splitting to either State Route 99 east of the Seattle Center or continuing to the Mercer/I-5 ramp, would segregate local traffic from through traffic, and would avoid the construction disruptions on the central waterfront that threaten businesses.

Obayashi Corp. is building a deep twin-bore tunnel in Seattle right now for Sound Transit’s light rail line. The 21-foot-wide twin tunnels are about a mile long and cost about $300 million total. As a replacement for the viaduct, twin bores would need to be 35-40 feet wide to accommodate three lanes of traffic in each direction, including trucks. Recently in the Swiss Alps, a 21-mile deep bore tunnel was completed at a cost of $3.2 billion — evidence of major advances in bored tunneling since the state rejected it as an option in 2001.

In addition to accelerating the reconstruction of I-5, our plan would redesign the reversible express lanes from Northgate to downtown. We would eliminate the notorious backup caused when the lanes “switch” from north to south by designing an additional “contra flow lane” in the opposite direction.

This would allow the express lanes to operate 24 hours a day in each direction and provide an additional through lane in the difficult downtown area, which currently has only two through lanes. Overpasses and ramps would have to be modified or removed, but a bottleneck of gigantic proportions would be eliminated, and it could be done on the existing footprint. For this premium service, a variable toll would be charged for the express lanes only; drivers could still access the regular lanes free. We’d dedicate a portion of the toll to expand bus rapid transit options as a supplement to current transit investments on I-5 and Highway 99.

How do we pay for such a feat of engineering without added taxpayer exposure? Answer: In addition to tolls, union and public employee pension funds could be invested in these projects and would pay back a return over many years.

Earlier this year, Cascadia and the Gallatin Group hosted former U.S. House of Representatives Majority Leader Dick Gephardt, now with Goldman Sachs, who said the $7 billion building trades’ pension funds were “patient funds looking for infrastructure investments in America and the Northwest.” In fact, union pension funds were used in Seattle recently to construct the Pacific Place garage. Calpers, the major California pension fund, is also considering joint investments with public agencies in infrastructure.

Gov. Chris Gregoire and the Legislature should consider modifying state law to allow this partnership with union pension funds. And if the November ballot measure fails, the State Route 520 bridge should be added to the I-5/Highway 99 pilot project.

Our failure to think big in the past is one reason we’re in today’s transportation mess. Let’s start now to change that.

Bruce Agnew is director of Discovery Institute’s Cascadia Center For Regional Development. Visit

Bruce Agnew

Director, Cascadia Center
Since 2017, Bruce has served as Director of the ACES NW Network based in Seattle and Bellevue, Washington. The Network is dedicated to the acceleration of ACES (Autonomous-Connected-Electric-Shared) technology in Northwest transportation for the movement of people and goods. ACES is co-chaired by Tom Alberg, Co-Founder and managing partner of Madrona Venture Group in Seattle and Bryan Mistele, CEO/Co-Founder of INRIX global technology in Kirkland. In 2022, Bruce became the director of the newly created Pacific Northwest Economic Region (PNWER) Regional Infrastructure Accelerator. Initial funding for the Accelerator has come from the Build America Bureau of the USDOT. PNWER is a statutory public/private nonprofit created in 1991 by the U.S. states of Alaska, Idaho, Oregon, Montana, and Washington and the Canadian provinces of Alberta, British Columbia, and Saskatchewan and the territories of the Northwest Territories and the Yukon. PNWER has 16 cross-border working groups for common economic and environmental initiatives.