Construction crews are removing trees in Medina and prepping to install anchors in Lake Washington for a new State Route 520 floating bridge. With more work in the water, drivers on SR 520 could see occasional intermittent closures of the highway for boat traffic.

Crews are removing trees and brush to create a work zone north of the highway – a necessary move that allows construction of an access road, the future highway alignment and a new bridge maintenance facility. Most of the trees and brush removed will be mulched and reused. Full landscaping is planned around the future maintenance facility, which eventually will be tucked under the new SR 520 highrise.

Now that SR 520 construction barges are stationed within the eastern navigation channel, updated Coast Guard rules require the Washington State Department of Transportation to occasionally close the SR 520 floating bridge to allow taller boats to pass through the bridge’s movable drawspan – a process that can take up to 30 minutes.

Under the new rules, taller vessels must give 12 hours notice if they wish to pass through the floating bridge drawspan on weekdays between 5 a.m. and 9 p.m. Vessel pilots need only give two hours notice to pass through the SR 520 drawspan between 9 p.m. and 5 a.m. on weekdays and anytime on weekends when traffic volumes are typically lower. Previous Coast Guard rules prohibited drawspan openings from 5 a.m. to 9 p.m. on weekdays.

Until now, boaters had a few options besides the movable drawspan. Before construction barges were in place, the SR 520 eastern highrise has accommodated boats up to 64 feet tall. Boaters with vessels less than 45 feet tall – or lowered to meet that height – still can pass beneath the SR 520 45-foot-tall west highrise.

The new drawspan opening rules are expected to be in place until August 2015. To the extent possible, WSDOT will work with vessel pilots and the boating community to minimize possible traffic disruptions for drivers.

“Our goal is to strike a balance that keeps traffic flowing on the bridge, helps boaters navigate the lake and maintains progress on SR 520 bridge construction,” said Dave Becher, WSDOT SR 520 floating bridge construction engineering manager.

WSDOT will use several tools to give the public as much advance notice as possible when the bridge is scheduled to close to traffic for a drawspan opening.

• Electronic message signs on highways approaching SR 520 will list the scheduled time for the closure, allowing drivers to plan for delays or choose an alternate route.
• On weekdays and when possible after hours and on weekends, updated information will be posted on the WSDOT What’s Happening Now construction page.
• Updated information will be posted on the WSDOT traffic and travel alert Web pages.
• Follow WSDOT on Twitter: @wsdot_traffic for Puget Sound traffic.
• Updated information via WSDOT’s 511 information line in advance on weekdays and during a closure at night and on weekends.

Each year, up to 20 vessels taller than 64 feet pass through the SR 520 drawspan after hours and on weekends. With construction under way in the eastern navigation channel, it’s possible that additional boats between 45 feet tall and 64 feet tall will request daytime closures of the floating bridge and passage through the drawspan.

Also according to updated Coast Guard rules and the construction contract, the contractor will take steps to assure that both the west and east navigation channels will be open on several major events and holidays when boat traffic is heaviest. Those dates include opening day of boating season, Memorial Day weekend, Fourth of July weekend, Seafair weekend and Labor Day weekend.

The target for opening the new floating bridge to traffic is the end of 2014. The completed floating bridge will not have a movable drawspan and will have an eastern navigation channel able to accommodate vessels 70 feet tall.