New 520 bridge? Expect to pay at least $4.5 billion

  • BY Wire Service
  • Monday, November 24, 2008 11:48am
  • News
A view of the I-520 bridge.

A view of the I-520 bridge.

It will cost about at least $4.5 billion to build a new 520 bridge complete with an interchange for the Montlake/University of Washington area, state officials said Thursday. However, the total could rise another $500 million to $2 billion if other options are picked.

Mediation has resulted in three options that now have cost estimates, according to Paula Hammond, Washington Transportation Secretary.

“We will need to make sure that we choose an option which is affordable and within the means of our region, while considering the effects on neighborhoods, quality of life, traffic and the environment,” Hammond said.

The three west side options are the product of a mediation process directed by the Washington Legislature in the 2007 legislative session in Engrossed Substitute Senate Bill 6099.

“SR 520 is an essential regional facility that needs to be replaced,” Hammond said. “Decision makers and the public now have realistic projections of the probable costs for this critical regional project.”

Hammond also noted that the Tolling Implementation Committee has been analyzing tolling options to fill the SR 520 funding gap, and reviewing the toll scenarios with the public. Earlier in 2008 the funding gap was estimated at $2 billion. The updated cost estimates would increase the funding level required from tolling or other sources.

The costs for the Eastside Transit and HOV Project, the pontoon construction and the floating bridge itself represent the latest in design configurations. The most significant factors in cost increases from 2006 can be attributed to:

· Cost increases in construction materials such as steel, concrete and asphalt.

· Increases in quantities of construction materials as a result of additional design information.

· New regulations that require changes in wetland mitigation and stormwater treatment.

· Accommodations for future high capacity transit.

· Updated geotechnical information resulting in a complex design for the pontoon construction site.

The cost estimates have been adjusted to account for risk and inflation and are shown in year of expenditure dollars, state officials say. The estimates by segment of the corridor program are as follows:

· $776 million for Eastside Transit and HOV Project. Rebuilds corridor from Evergreen Point Road to 108th Avenue NE, including continuous HOV lane, two transit stops, three lids over the roadway, bicycle/pedestrian path, and environmental mitigation. Re-configures HOV lane to SR 202.

· $1.728 billion for pontoon construction and the floating bridge. Includes pontoon construction site, primary and supporting pontoons, and floating bridge road deck.

· $2.022 billion to $2.298 billion for west side Option A (interchange similar to today). Includes interchange in current location, second bascule bridge, and transit only ramp.

· $4.070 billion to $4.168 billion for west side Option K (tunnel under Montlake Cut). Includes a new interchange below grade east of Montlake Boulevard and a tunnel under the Montlake Cut to connect to Pacific Street.

· $2.562 billion to $2.642 billion for west side Option L (bridge across Montlake Cut). Includes a new interchange over SR 520 east of Montlake Boulevard and a new bridge crossing over the Montlake Cut to Pacific Street.

Additional information on the cost estimates and the mediation options can be found at

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