The Hood Canal Bridge draw spans are the two mechanically movable floating bridge pontoons that retract to allow marine traffic that can’t make it under the bridge’s transition spans to travel through Hood Canal. The draw spans are located between the bridge’s two control towers.
HOW DOES THE DRAW SPAN WORK?
The draw span is a complicated structure made up of hydraulic, electrical and mechanical systems and micro processors. There are over 200 control and time delay relays, switches, and sensors controlling and monitoring multiple large drive motors, hydraulic pumps, motor generators, gates, barriers, center, end locks and other parts that must be operated in a specific sequence. Each system plays an important role in opening and closing the Hood Canal Bridge.
Watch both sides of the draw span open:
Windows Media (14 seconds)
Real Video (14 seconds)
When the east-half draw span opens, this 300-foot floating pontoon is moved back into the “bulge” area between the roadway pontoons near the east control tower.
Watch the east-half draw span open:
Windows Media (15 seconds)
Real Video (15 seconds)
When the west-half draw span opens, this 300-foot floating pontoons is moved back into a space directly under a 300-foot section of the bridge road deck near the west control tower. The road deck is lifted about 6 feet into the air to allow for the west draw pontoon to slide under it.
Watch the west-half draw span open:
Windows Media (28 seconds)
Real Video (28 seconds)
NEW EAST-HALF DRAW SPAN
The new east-half draw span will be identical in design to the current west half draw span, making travel on the bridge safer by removing the “bulge” in the east side roadway.
The new east-half draw span will be made up of 10 different pontoons. Pontoons PA, PB, Q, NA and NB will be assembled together at Todd Shipyards in Seattle to form a “U” shape area around the location where the draw span retractable assembly units pull back. Then pontoons YD, YE and YF will be lowered under water, positioned underneath the other pontoons and connected.
When the third cycle of pontoon construction is completed, the two pontoons that make up the retracting section of the draw span will be connected together and assembled with the other eight draw span pontoons.
The new draw span will towed from Seattle and installed at Hood Canal Bridge during the east-half replacement process and bridge closure in May-June 2009.