Lacey V. Murrow Memorial Bridge

The Lacey V. Murrow Memorial Bridge is a floating bridge in the Seattle metropolitan area of the U.S. state of Washington. It is one of the Interstate 90 floating bridges that carries the eastbound lanes of Interstate 90 across Lake Washington from Seattle to Mercer Island. Westbound traffic is carried by the adjacent Homer M. Hadley Memorial Bridge.
The Murrow Bridge is the second-longest floating bridge in the world, at (the longest is the Governor Albert D. Rosellini Bridge—Evergreen Point, a few miles north on the same lake). The original Murrow Bridge opened in 1940, and was named the Lake Washington Floating Bridge. It was renamed the Lacey V. Murrow bridge in 1967. The original bridge closed with the current bridge opening 
Along with the east portals of the Mount Baker Ridge Tunnel, the bridge is an official City of Seattle landmark. While the bridge originally had an opening span at the center of the bridge to allow a horizontal opening of for major waterborne traffic, the only boat passages currently are elevated fixed spans at the termini with of vertical clearance.
History.
The bridge was the brainchild of engineer Homer Hadley, who had made the first proposal in 1921. The bridge came about after intensive lobbying, particularly by George Lightfoot, who came to be called the "father of the bridge." Lightfoot began campaigning for the bridge in 1930, enlisting the support of Miller Freeman. Construction began January 1, 1939 and was completed in 1940. The construction cost for the project, including approaches, was approximately $9 million. It was partially financed by a bond issue of $4.184 million. Opened July 2, 1940, the bridge carried US 10 (later decommissioned and renamed Interstate 90). Tolls were removed in 1949. The bridge sank in a storm on November 25, 1990 while it was undergoing refurbishing and repair. The current bridge was built in 1993. The eponymous Lacey V. Murrow was the second director of the Washington State Highway Department and a highly decorated U.S. Air Force officer who served as a bomber pilot in World War II and rose to the rank of graduate of Washington State College in Pullman, he was the oldest brother of CBS commentator Edward R. Murrow.
The original bridge was built under a -year contract awarded to the Puget Sound Bridge and Dredging Company (the project was led by engineer Peter John Jensen) in the amount of $3.254 million. It included a movable span that could be retracted into a pocket in the center of the fixed span to permit large boats to pass. This design resulted in a roadway "bulge" that required vehicles to swerve twice across polished steel joints as they passed the bulge. A reversible lane system, indicated by lighted overhead lane control signals with arrow and 'X' signs, compounded the hazard by putting one lane of traffic on the "wrong" side of the bulge at different times of day in an effort to alleviate rush-hour traffic into or out of Seattle. There were many serious collisions on the bridge. The problems grew worse as the traffic load increased over the years and far outstripped the designed capacity. Renovation or replacement was essential and a parallel bridge, the Homer M. Hadley Memorial Bridge, was completed in 1989, and named for Hadley in 1993.
With the opening of the new bridge, the 49-year-old Murrow Bridge closed on June 23, 1989, for renovation work that was originally projected to take 
In 1979, Stacy Sparks drowned after driving off the bridge.
1990 disaster.
On November 25, 1990, while under re-construction, the original bridge sank because of a series of human errors and decisions. The process started because the bridge needed resurfacing and was to be widened by means of cantilevered additions in order to meet the necessary lane-width specifications of the Interstate Highway System. The Washington State Department of Transportation (WSDOT) decided to use hydrodemolition (high-pressure water) to remove unwanted material (the sidewalks on the bridge deck). Water from this hydrodemolition was considered contaminated under environmental law and could not be allowed to flow into Lake Washington. Engineers then analyzed the pontoons of the bridge, and realized that they were over-engineered and the water could be stored temporarily in the pontoons. The watertight doors for the pontoons were therefore removed.
A large storm on November 22–24 (the Thanksgiving holiday weekend), filled some of the pontoons with rain and lake water. On Saturday, November 24, workers noticed that the bridge was about to sink, and started pumping out some of the pontoons; on Sunday, November 25, a section of the bridge sank, dumping the contaminated water into the lake along with tons of bridge material. It sank when one pontoon filled and dragged the rest down, because they were cabled together and there was no way to separate the sections under load. No one was hurt or killed, since the bridge was closed for renovation and the sinking took All of the sinking was captured on film and shown on live TV. The cost of the disaster was $69 million in damages. A dozen anchoring cables for the new Hadley bridge were and it was closed for a short time afterward. Westbound traffic was allowed and eastbound traffic was resumed in early December.
The disaster delayed the bridge's reopening by 14 months, to September 12, 1993.
Precedents and lessons learned.
WSDOT had lost another floating bridge, the Hood Canal Bridge, in February 1979 under similar circumstances. It is now known that the other major floating bridge in Washington, the Evergreen Point Floating Bridge, was under-engineered for local environmental conditions; that 1963 bridge was replaced with a new floating span 