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Broken Bridge to Cost $170M Extra

Wednesday, January 15, 2014

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Design mistakes on a floating bridge megaproject in Washington State are sucking every last cent out of the project’s risk reserve fund, and the state says it will need an additional $170 million to finish the bridge.

The surprise nine-figure tab is the latest glitch in the troubled multibillion-dollar SR 520 bridge replacement project, which will provide a seamless transition from the floating bridge over Lake Washington to fixed bridges offshore and on land, connecting Seattle and Medina.

Construction of the 7,500-foot-long floating structure has been problematic since May 2012, when Washington State Department of Transportation crews found cracking and spalling after completing post-tensioning on a longitudinal pontoon.

WSDOT design mistakes
Photos: WSDOT

After admitting that its own design errors caused problems with giant floating pontoons, WSDOT says change orders will use up the remaining risk reserve fund, and an extra $170 million is needed.

A few months later, ballast water was found leaking between two cells in one pontoon and moisture on the inside of an end wall in another.

The project is the first construction phase of the $4.65 billion SR 520 - I-5 to Medina: Bridge Replacement and HOV Project. In January 2011, WSDOT awarded a $586 million design-build contract to Kiewit-General Joint Venture to build the concrete pontoons and a six-lane bridge, among other things.

Depleting the Reserve

Last week, Washington Transportation Secretary Lynn Peterson and SR 520 Program Director Julie Meredith announced that WSDOT's pontoon design error was consuming much of the program's $250 million risk reserve.

The agency has proposed funding the $170 million shortfall with existing revenue sources, and Peterson said those sources had been identified.

"While the error discovered in 2012 is depleting most of the contingency reserve, we are proactively managing the remaining risks and don't foresee the need for new funding sources to complete the work at hand and move our region closer to a safer, high-capacity, multimodal 520 corridor," Peterson said.

WSDOT says it has reached agreement with its pontoon contractor for added costs associated with building pontoons. The agency is working with the state legislature to approve an increase in its budget for the project.

'Unfortunate and Costly Mistake'

In February 2013, WSDOT admitted that the agency's own design mistakes were to blame for the problems. Designing the pontoons itself was the agency's strategy to attract lower bids and get the floating section built by 2014. The winning bid to build the pontoons was $180 million less than the state expected to pay.

SR 520 foating bridge

At 50 years old, the SR 520 bridge is vulnerable to windstorms and earthquakes.

The current SR 520 bridge recently turned 50 years old and is nearing the end of its service life. Carrying 115,000 cars per day with only two lanes in each direction, the bridge's pontoons have become vulnerable to windstorms, and its support columns are vulnerable to earthquakes.

After owning up to its missteps (and firing the state's top bridge engineer), WSDOT announced in August that it had reached agreement with its contractors for change orders totaling $81.1 million. Now, that total will reach $208.2 million with new change orders announced by WSDOT in December.

"The original pontoon design included an unfortunate and costly mistake," Peterson said.

Peeling Concrete

The ill-designed pontoons haven't been the only issue with the floating bridge's construction.

SR 520 change orders

The new bridge is expected to open in late 2015 or early '16.

In October 2012, crews began construction on 10 58-foot-tall concrete columns to put on top of one of the two cross pontoons. KGM inspectors then discovered that one of the concrete columns had too little buffer between the concrete and reinforcing steel. KGM decided to remove and replace the column.

"KGM's decision to replace this column at their expense is the appropriate action," Meredith said at the time.

The columns were formed by pouring concrete around a cylindrical cage or reinforcing bar contained in a temporary steel tube. When the tube was removed from the one column, some of the concrete peeled off with it, and workers found that the rebar cage had shifted during the pour, leaving less than the normal 1.5-inch concrete thickness around the rebar.

The new roadway deck will be installed on top of bridge piers before sloping down onto the columns being constructed on the pontoons.

The new bridge is now expected to open to traffic in late 2015 or early 2016.


Tagged categories: Bridges; Concrete; Construction; Cracking; Department of Transportation (DOT); Design

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