The unusual (but successful) path to replacing the viaduct’s southern mile

At first glance, the curvy temporary stretch of State Route 99 that opened last fall to the west of Seattle’s stadiums seems like an unusual path for a highway to take. Certainly it’s not the straightest line between two points. But viewed in a broader context – keeping the highway open during SR 99 tunnel construction – it’s most certainly the right path. It saves everyone in the long run by maintaining a vital route to and through downtown Seattle as we continue replacing the Alaskan Way Viaduct.

Fittingly, the path to completion of that circuitous section of highway, and the permanent section immediately to its south, was unconventional. Yes, we always weigh risks and look for opportunities to save time and money. But this time our vigilance resulted in big changes – most notably swapping an underpass for an overpass at the eleventh hour – made with an eye toward big savings. The history behind that decision is a complicated one. The result is not: We replaced the southern mile of the Alaskan Way Viaduct one year early and under budget. And our last-minute design changes saved more than $50 million.

Of course, making big changes complicated an already challenging project. We knew that we would have to make minor adjustments along the way, and even re-do work in some cases. But the cost of those minor re-dos was well worth it given the overall cost savings and the safety benefit of removing half of the seismically vulnerable viaduct. Here’s the brief history of how it all went down:

  • The contract to build the viaduct’s south-end replacement went to bid in early 2010.
  • Our original construction budget for this project was $152.6 million, plus an additional $38 million to manage construction, and minimize risk and impacts to the public. Altogether, the total budget for the project was $190 million.
  • An important component of the contract was an underpass that would allow drivers to bypass a busy train track that crosses South Atlantic Street, near the entrance to the Port of Seattle’s busiest freight terminal.
  • As contractors prepared bids, a value engineering study of the program yielded the potential for major savings if we changed from the underpass to an overpass.
  • Recognizing the value, and being confident in our ability to deliver the project while minimizing impacts to the public, we chose to make the switch. We removed the underpass from the contract and told bidders the overpass would be put out to bid later in a separate contract. We remained in close contact with interested bidders to ensure they understood the changes as they prepared their bids.
  • Skanska USA Civil was announced as the low-bidder on the main south-end project in May 2010. Thanks to a highly competitive bidding climate, their bid of $114.6 million was 25 percent under our construction estimate. As a result of the low bid, the overall project budget was adjusted from $190 million to $152 million.
  • Skanska completed their work in September 2012, one year early, at a final construction cost of $121 million. A portion of the additional cost was due to changes that were made necessary by the switch to an overcrossing. Add in the risk and construction management costs and you end up with $150 million – $2 million less than our adjusted budget.
  • In May 2012, the overcrossing contract was awarded to Atkinson Construction for $29.4 million, $6.2 million under our estimate. The estimated cost for building the underpass was $90 million.
  • All contracts associated with the viaduct’s south-end replacement are scheduled to be completed by the end of 2013, as originally planned.

What all of this really adds up to is this: our job is to deliver transportation projects safely, on time and on budget, while minimizing impacts to the public. With the viaduct’s south-end replacement, we did that and more. It just so happened the best way there was the road less traveled.