Washington State Department of Transportation on Thursday announced a preferred alternative for how State Route 520 will be rebuilt, marking a major milestone in the environmental review process.

The preferred alternative designates that the aging and seismically vulnerable floating bridge and the Seattle side of the corridor will be rebuilt with two new lanes for carpools and buses in addition to four general purpose lanes. It will also include a new urban interchange at Montlake that reconnects the adjacent Seattle neighborhoods. The new bridge will be ready for light rail.

The preferred alternative was developed based on public and agency comments received on the supplemental draft environmental impact statement.

“This is a big deal for the Eastside as well as the entire region,” said Sen. Rodney Tom, D-Bellevue. [The] announcement puts us one big step closer to finally getting this bridge replaced.”

Tom added that while coming up with a preferred alternative hasn’t been easy, the debate over the project has gone on too long.

“Enough is enough,” Tom said. “Let’s start moving some dirt and get the region moving again.”

Gov. Chris Gregoire noted that the state has spent more than a decade working with neighborhoods, local governments, transit agencies and the public to replace this aging bridge.

“We … are ready to move forward to open the bridge in 2014,” Gregoire said.

The preferred alternative for the floating bridge and Seattle interchange includes:

· Four general purpose lanes and two new lanes dedicated to transit and carpools

· An urban interchange at Montlake Boulevard, with an extended lid to maximize open space and pedestrian/bicycle connections

· A second bridge and dedicated transit/carpool lanes across the Montlake Cut

· A path for bicyclists and pedestrians across the lake on the north side of the floating bridge

· Investments to treat stormwater and reduce traffic noise

In response to neighborhood, city and agency comments, WSDOT designed the preferred alternative to:

· Lower the floating bridge to approximately 20 feet above the water in the middle of the lake.

· Be ready for a future light rail connection to Sound Transit’s U-LINK station by creating a space between the bridge structures at the west end of the floating bridge.

· Reduce impacts to the Arboretum by providing access to Lake Washington Boulevard. at 24th Avenue East, eliminating the need for new ramps. Access through the Arboretum will be managed to reduce traffic volumes.

· Maintain transit priority using direct-access transit/carpool ramps with priority lanes on Montlake Boulevard.

· Narrow the Portage Bay Bridge to 105 feet, compared to 154 feet as previously proposed.

· Plan the Portage Bay Bridge as a boulevard, with a 6-foot-wide landscaped median, and operate at 45 miles per hour to reduce noise effects on the adjacent neighborhoods.

Since 1997, WSDOT and regional leaders analyzed design alternatives for a replacement SR 520 bridge and improved corridor. A draft environmental impact statement (EIS) released in 2006 drew more than 1,700 public comments. New designs were drafted and analyzed through a mediation process, and in January 2010 WSDOT released a supplemental draft EIS, which received more than 400 additional comments.

With the decision on a preferred alternative, WSDOT will finalize mitigation plans to address environmental and construction effects. A final EIS is scheduled for completion at the end of the year.

The legislature set the SR 520 program budget at $4.65 billion for improvements from I-5 in Seattle to SR 202 in Redmond. WSDOT continues to analyze the estimated cost of the preferred alternative for the floating bridge and Seattle interchange.

The cost is expected to be within the budget set by the Legislature. Toll revenue and state and federal funds provide about $2.37 billion in funding for a replacement six-lane floating bridge and SR 520 improvements on the Eastside.