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Highway Quality Compendium

Teaming Up to Accelerate Lake Washington's Floating Bridge Project

Washington State Route 520 (SR 520) is one of only two major State highways running east-west between Seattle on the west side of Lake Washington and the communities of Bellevue, Redmond, and Kirkland on the east side of the lake. Designed for an average daily traffic of 65,000 vehicles, the road now carries between 110,000 and 120,000 vehicles daily and is often congested for 13 hours on weekdays. A March 2004 workshop in Seattle looked at ways to accelerate the replacement of SR 520's 40-year-old Evergreen Point floating bridge across Lake Washington. The workshop was held by the Washington State Department of Transportation (WSDOT) and the Accelerated Construction Technology Transfer (ACTT) team sponsored by the Federal Highway Administration (FHWA) and the American Association of State Highway and Transportation Officials.

One of the oldest floating bridges in the world, the Evergreen Point Bridge is reaching the end of its useful life. Not only is its capacity inadequate, but it is vulnerable to storms and seismic events. The bridge's pontoons are subject to cracking and leaking and its low position in the water makes it susceptible to high, crashing waves during storms. With an estimated cost of between $1.5 and $3.4 billion, depending on the number of lanes selected for the new bridge, funding for the project is a challenge. There has also been concern expressed by communities on both sides of the bridge about the proposed construction and its impact. Three project alternatives-a four-lane, six-lane, and eight-lane bridge-are currently being evaluated by WSDOT. Also being evaluated are the use of tolls to help fund the project.

The ACTT workshop brought together local and national transportation experts from State highway agencies, industry, academia, and FHWA. These experts' skill areas included design, construction, structures, traffic/safety/intelligent transportation systems, innovative contracting and financing, environment, and right-of-way. Dan Mathis, Division Administrator for FHWA's Washington State Division Office, noted that, "This workshop is about meeting the customers' needs during and after construction. It's about being creative. Our role is ‘To get in there, do the work and do it right, and then get out of the way.'" Building on these concepts, the goals of the workshop included:

  • Shorten construction time
  • Minimize construction impacts
  • Identify options for construction staging
  • Develop creative financing strategies
  • Maximize maintenance of traffic flow
  • Encourage contractor innovation and involvement.

Rick Smith, WSDOT's Innovative Project Delivery Director, and other WSDOT staff introduced workshop participants to the complicated urban project and gave them a tour of the project site. Participants met in smaller skill set groups to brainstorm ideas and develop recommendations for meeting the project goals. These recommendations included using a design-build contract to shorten the overall project delivery time by overlapping design with construction. Also suggested was segmenting contracts, such as replacing the bridge in four separate segments. In addition, employing prefabricated bridge construction was recommended as a means of accelerating the project, including the use of precast substructures, deck panels, and superstructures. In the area of materials, it was suggested that self-consolidating concrete (SCC) be used, particularly for the construction of the bridge's pontoons. Because of the large quantity of concrete necessary and the anticipated depths of the pontoons, the use of conventional concrete would be very labor intensive. SCC flows easily and can completely fill intricate and complex forms under its own weight, eliminating the need for vibration.

Other workshop recommendations included breaking the pontoon fabrication into separate contracts, depending on the type of work; designing the bridge's simple pontoons first so that they can be constructed while the more complex pontoons are still being designed; and building "lids" over the roadway first and then using them for construction access and traffic staging. Also stressed was the importance of coordinating with other regional projects, as there are several other mega projects being proposed in the area. Among the financing options, participants recommended looking at the benefits of starting toll collection on SR 520 earlier than originally planned to raise additional funds.

"Participants were fully engaged and creative and brought new information and ideas to the table," noted Maureen Sullivan, Project Director in WSDOT's Urban Corridors Office. "The recommendations present a great opportunity for saving 1-2 years in construction time." Depending on the availability of funding, WSDOT tentatively plans to begin construction on the new bridge in 2008.

To learn more about the SR 520 Bridge Replacement Project, visit www.wsdot.wa.gov/projects/SR520Bridge, or contact Maureen Sullivan at WSDOT, 206-381-6436 (email: SullivM@wsdot.wa.gov), or Julie Meredith at WSDOT, 206-381-6406 (email: MeredJL@wsdot.wa.gov). For more information on ACTT, contact Dan Sanayi at FHWA, 202-493-0551 (email: dan.sanayi@fhwa.dot.gov). Information is also available online at www.fhwa.dot.gov/construction/accelerated or through your local FHWA Division Office. An ACTT workshop will be held this month in Oklahoma, with workshops also scheduled in Minnesota (June), Wyoming (September), Rhode Island (October), New Jersey (November), and Nevada (March 2005).

Reprinted from Focus, May 2004.

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Updated: 07/26/2018
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