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Prospectus Blog Viaduct A Key Thru Traffic Route; Tunnel Best Replacement

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 an added lane in each direction on the shoulder of Interstate 5 for several miles, Viaduct thru traffic will nonetheless spill onto surface streets and I-5 and worsen congestion severely. More and more so as Puget Sound’s population grows by half again in the next 30 years, and total vehicle miles travelled in Washington State rise a projected 54 percent from 2007 to 2030.
Thus the argument, in part, for a deep-bored tunnel which could handle the SR 99 traffic load without obstructing the waterfront like either the envisioned wide, heavily-used boulevards or another elevated viaduct. These are the two options currently recommended for further study.
Some non-governmental advocates of the surface-transit option to replace the Viaduct have been saying that “only 15 percent of the trips are regional trips.” This can be misleading if it is understood to refer to SR 99’s thru traffic bypassing downtown Seattle, because that is not the case. As this Washington State Department of Transportation document shows (p. 4), 85 percent of person trips through Center City (essentially the downtown Seattle core plus several adjacent neighborhoods) begin or end within a somewhat larger zone known as the “study area,” including North and South Seattle. These person trips are on a wide range of streets and roads, on transit and in vehicles, and could be described as more local than regional. Fifteen percent of these person trips don’t begin or end in the study area, and are thus considered longer-range, or more regional in nature.
That’s all nice to know, and certainly of some use for transportation planning – along with such tidbits as the four percent market-share of scheduled transit for daily trips in the region, last any survey was done (see 2nd paragraph of p. E-6 here). But we’re looking at tearing down a crucial portion of a specific state highway that carries 110,000 vehicle trips a day, 60 percent of which are thru traffic bypassing downtown entirely. Sixty percent of 110,000 is 66,000 vehicles a day.
There’s a better way. The deep-bored downtown bypass inland tunnel can be built for
$2 billion or less
. Nonetheless, to safeguard taxpayers from possible financial risk, a method strongly recommended for greater use by the Washington State Transportation Commission (see p. 9 here) should be employed. This is so-called “alliance contracting,” in which highly competitive bidding delivers a stringent agreement between the public sector and a private consortium of contractors, who must perform project design and construction for a set price within a given timeline or suffer reduced payments.
Facility operations and maintenance can also be included in such an agreement, which is then termed a “DBOM” or “design-build-operate-maintain” project. British Columbia has used DBOM or related approaches successfully to control costs on several new infrastructure projects including a new rail line to the Vancouver airport, a tolled bridge across the Fraser River in metro Vancouver, and the rebuilt Sea-To-Sky Highway connecting Vancouver and Whistler.
Cost controls are one thing, capital is another. If additional financing beyond the remaining $1.7 billion in public monies is determined to be necessary to build the deep-bored bypass tunnel on SR 99, then several approaches should be considered. One is formation of a local improvement district (LID) where property owners who benefit from the project can approve a special levy. A similar approach is formation of a transportation benefit district (TBD) in which a $20 per vehicle license tab renewal fee surcharge can be levied without a vote and a higher amount with a public vote. In either case, electronic tolling of the tunnel could be integrated into the finance plan.
Another strategy that is likely to be viewed as daunting but which holds real promise, is investment from public employee union or building trade union pension funds, provided adoption of a north-south corridor tolling plan covering I-5 and SR 99 in Seattle. With respect to additional financing, we should heed the stated intention of the Washington State Investment Board, which manages numerous state employee pension funds, to invest 5 percent of its substantial capital in infrastructure projects. Jurisdictions across the U.S. are beginning to grasp what Europe, Canada and Australia have long realized: in some instances, innovative approaches to infrastructure contracting and financing are essential to getting road and transit projects built on time and on budget, and built sooner rather than later or not at all.
There is every reason for Washington State to take a leadership role here, not only on SR 99, but also urgently needed improvements to SR 520, I-5, SR 167, SR 705, SR 509, and US 2. Whether through LIDs, TBDs or union pension funds – and while deploying cost-control best practices – Washington State can and must move forward on major roadway projects required for public safety and improved mobility.
Cascadia Center commends the Viaduct project team and the state for all their hard work to date, and hopes that the ongoing dialog around further consideration of the deep-bored tunnel proves fruitful.
RELATED: “Port Of Seattle Urges More Study Of Viaduct Tunnel Hybrid,” Seattle Times, Dec. 16, 2008.