Winning bid for 520 bridge pontoons is lower than estimate

A partnership led by Kiewit Construction has submitted the winning bid to build 33 pontoons for the future Highway 520 floating bridge — for $180 million less than expected, the state Department of Transportation (DOT) announced Wednesday.

The Kiewit-General Joint Venture rebuilt the Hood Canal floating bridge this year, and each company has worked on Interstate 90 floating-bridge rebuilds.

Its bid for Highway 520, one of three, totaled $367 million. A DOT engineer had estimated the cost at $547 million, said Mike Cottenstate design-build manager for the project.

Pontoons will be built at one of two sites on the banks of Grays Harbor, one a log-sorting yard and the other a former log yard.

The project offers up to 800 jobs in a place that has long been economically depressed.

Construction of a casting facility starts next year, followed by pontoon fabrication in 2012.

The pontoons would be towed around the Olympic Peninsula and fastened across Lake Washington by early 2014. Most will measure 360 feet by 75 feet, barely able to pass through the Ballard Locks.

Rebuilding the corridor from Interstate 5 to Interstate 405 is expected to cost $4.65 billion.

The state has neither a tolling strategy to fill a $2 billion shortfall nor an agreed-upon design for fixed bridge sections on the Seattle shore.

Regardless of how those controversies play out, the pontoon work needs to begin now, said program director Julie Meredith.

The existing 46-year-old bridge is deteriorating and could sink in a severe windstorm.

Mike Lindblom: 206-515-5631 or mlindblom@seattletimes.com