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Floating Bridge Changes Cost DOT $81M

Thursday, August 1, 2013

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After owning up to its mistakes, the Washington Department of Transportation will pay the price: about $81 million in change orders to the multibillion-dollar SR 520 bridge replacement project, officials have announced.

The 7,500-foot-long floating bridge project, which will connect Seattle and Medina, has been plagued with problems since May 2012, when crews found cracking and spalling after completing post-tensioning on a longitudinal pontoon that is designed to keep the bridge afloat.

SR520 floating bridge
Photos: WSDOT

WSDOT plans to pony up $81.1 million in change orders for cracked concrete, ballast water leaks, and other problems on its 7,500-foot-long floating bridge project.

WSDOT recently admitted that its own design mistakes were to blame for the cracked concrete in the initial cycle of pontoons, which also required modifications to the second construction cycle. Soon after, Jugesh Kapur—the state’s top bridge engineer, who lead the Bridge and Structures Office—was fired and a second, unidentified employee was reportedly demoted.

3 Change Orders

WSDOT and its contractors have reached agreement on the cost of repairing four pontoons from the first construction cycle and modifying another four pontoons from the second cycle, officials announced Tuesday (July 30).

The repairs were recommended by an engineering firm specializing in the repair of concrete structures and were endorsed by an expert review panel.

Also Tuesday, WSDOT announced three change orders totaling $81.1 million to be paid from the SR 520 risk reserve, which was developed to address “unforeseen project issues.” The remaining risk reserve now sits at $100 million.

Washington DOT

Several problems with the pontoons were discovered last year. WSDOT later accepted the blame for its design mistakes and fired its top bridge engineer a short time later.

The first change order cost the agency $9.9 million for repairs to four pontoons from cycle one, which included de-tensioning one pontoon, removing spalled concrete, modifying the post-tensioning profile, and reinforcing a bolt beam.

For the second change order, WSDOT will pay $48.8 million to repair cycle one pontoon cracks to the bridge contractor, Kiewit-General-Mason Joint Venture, which was awarded the original $586 million design-build contract in January 2011.

The repairs for cycle one have been underway since June to keep bridge construction moving along.

The repairs include:

  • Leasing and towing pontoons to drydock facilities in Portland and Seattle;
  • Building a coffer cell in Tacoma and towing it to Seattle for repairs on the other two pontoons; and
  • Implementing repair procedures on all four pontoons, including epoxy injections, transverse post-tensioning and carbon-fiber wrap application.

For the third change order, WSDOT will pay $22.4 million to pontoon construction contractor Kiewit-General for previously completed transverse post-tensioning to four pontoons.

Additional change orders that have yet to be finalized include:

  • Adding transverse post-tensioning to pontoons built in cycles 3-6; and
  • Schedule effects to the pontoon construction project and the floating bridge and landings project.

“These repairs are important to ensure we are building a safe bridge that meets the needs of the traveling public and supports the regional transportation system for many years,” said Lynn Peterson, WSDOT Secretary.

“We are committed to following the recommendations of the expert review panel and moving forward,” Peterson said.

History of Problems

In August 2012, an inspection of pontoons already floated out of the casting basin found ballast water leaking between two cells in one pontoon and moisture on the inside of an end wall in another.

Inspectors discovered in October 2012 that one of the 58-foot-tall concrete columns for the bridge had too little buffer between the concrete and reinforcing steel, causing project managers to remove and replace the column.

floating bridge pontoons

A total of 77 pontoons will be used in the bridge's construction. Pictured is one of the 21 longitudinal pontoons that will be connected end-to-end to support the floating bridge.

While removing a tube from one column, some of the concrete peeled off with it, and workers discovered that the rebar cage had shifted during the pour, leaving less than the normal 1.5-inch concrete thickness around the rebar.

Also in the fall of 2012, inspectors rejected several of the 345 pre-cast concrete wall panels for either exceeding contractual limits for cracking or duct alignment issues.

In the winter, divers examined four large pontoons on the lake and found cracks on the undersides that had been concealed when the pontoons were in the casting basin.

Current Progress

The third construction cycle, out of six total, recently wrapped up, culminating in eight completed bridge pontoons being floated out to the bridge location.

These eight pontoons bring the number of completed pontoons to 32. Overall, 77 total pontoons will be needed to construct the world’s longest floating bridge, including:

  • Two cross pontoons, each weighing over 10,000 tons, mark the ends of the floating section of the bridge;
  • 21 longitudinal pontoons, each about 360 feet long and 11,000 tons, form the backbone of the bridge and support the roadway superstructure; and
  • 54 supplemental pontoons, each weighing over 2,500 tons, stabilize and support the weight of the floating bridge.

About the Bridge

Originally scheduled for completion in December 2014, the new bridge is now estimated to open in late 2015 or early 2016.

The current bridge will be 50 years old this month and is nearing the end of its original service life. The bridge carries 115,000 vehicles per day and has only two lanes in each direction. The pontoons have become vulnerable to windstorms, and the support columns have become vulnerable to earthquakes.

The new pontoons are designed for a 75-year service life to withstand windstorms up to 89 mph and a 1,000-year earthquake event.

The project is the first construction phase of the SR 520—I-5 to Medina: Bridge Replacement and HOV Project, for which the Washington State Legislature has set a program budget of $4.65 billion.


Tagged categories: Bridges; Concrete; Concrete defects; Construction; Contractors; Cracks; Department of Transportation (DOT); Design; Federal Highway Administration (FHWA); Government contracts; Inspection; Program/Project Management; Quality control

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