Lacey V. Murrow Memorial Bridge

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Coordinates: 47 ° 35 ′ 23 "  N , 122 ° 16 ′ 6"  W.

I-90.svg Lacey V. Murrow Memorial Bridge
Lacey V. Murrow Memorial Bridge
Looking east towards Mercer Island ,
right the Lacey V. Murrow Memorial Bridge,
left the Homer M. Hadley Memorial Bridge
use Interstate 90 eastbound
Crossing of Lake Washington
place Seattle , Washington
Entertained by Washington State Department of Transportation
Building number 90 / 25S
construction Pontoon bridge
overall length 2019 m
building-costs 8,854,000 USD
completion 1940, 1993
opening 2nd July 1940
location
Lacey V. Murrow Memorial Bridge (Washington)
Lacey V. Murrow Memorial Bridge

The Lacey V. Murrow Memorial Bridge , originally Lake Washington Floating Bridge or Mercer Island Bridge , is a floating bridge in the US state of Washington . It is used by the eastbound directional lane of Interstate 90 to cross Lake Washington between Seattle and Mercer Island ; the directional lane for traffic to the west is used by the Homer M. Hadley Memorial Bridge , which runs parallel to the Lacey V. Murrow Memorial Bridge to the north .

The Lacey V. Murrow Memorial Bridge is named after Lacey V. Murrow , the former head of the Washington Roads Department and was the longest floating bridge in the world with a length of 2019 meters when it opened in 1940. It was only exceeded in 1963 by the 2310 meter long Governor Albert D. Rosellini Bridge — Evergreen Point , a few kilometers to the north .

Together with the eastern portals of the Mount Baker Ridge Tunnel , the Lacey V. Murrow Memorial Bridge is an official monument of the City of Seattle and a National Monument of the American Association of Civil Engineers ASCE .

history

At the beginning of the 20th century, ways of better developing the east coast of Lake Washington from Seattle were sought. Lake Washington has an average depth of 30 m, which made building a bridge with piers complex or even impossible. Engineer Homer M. Hadley , who was involved in the construction of concrete ships during the First World War , therefore proposed the construction of a floating bridge. The authorities were skeptical of the idea; Even a construction as a privately financed toll bridge did not seem possible because the banks were not receptive to the proposal and called it Hadley's Folly , German "Hadley's Narretei". Only George Lightfoot and the politically active publisher Miller Freeman , both living on Mercer Island, supported the idea of ​​a bridge to better develop their place of residence. During the Great Depression , when government funds were available for construction projects, Hadley presented the proposal to the then director of the Washington State Highway Department, Lacey V. Murrow, who was intrigued by the proposal and had it implemented.

The bridge was henceforth known as the Lake Washington Floating Bridge . Hadley's design was for a reinforced concrete floating bridge with two-way and four lanes. The bridge was part of the Lake Washington Bridge Project , which, in addition to the floating bridge , also included the twin-tube Mount Baker Ridge Tunnel and the East Channel Bridge to the west , and US Highway 10 , which later became Interstate 90, from Bellevue via Mercer Island to Seattle leads. The Lake Washington Floating Bridge consisted of the floating bridge with 25 concrete pontoons anchored in the lake bed and the two front bridges designed as tied arch bridges. These were mounted on both sides so that they could follow the movements of the floating bridge. The superstructure of the floating bridge was a hollow box girder made of reinforced concrete. On the east side, a field of the floating bridge was designed as a push bridge , the movable part of which could be retracted into a pocket in the middle of the adjacent fixed field to allow larger ships to pass through. The lanes were swiveled sideways around the bag.

Construction began in December 1938 and was opened on July 2, 1940. Until 1946, the bridge was subject to tolls. Already at the beginning there was a lot more traffic over the bridge than expected. She made a major contribution to the development of Mercer Island from a summer resort to a suburb of Seattle, and the once agricultural Bellevue to become the fourth largest city in the state.

In 1967 the bridge was renamed Lacey V. Murrow Memorial Bridge in honor of Murrow, who had died the year before .

In 1981 the 60 m long push bridge contained in the structure was expanded and the field with the pivoted lanes replaced by a normal straight field. This made it possible to eliminate the point which often leads to traffic accidents and which could only be driven on at reduced speed. The spot was particularly dangerous because, depending on the time of day, the direction of the middle two lanes with variable message signs was changed to increase the capacity in the main traffic direction . This meant that the vehicle drivers had to drive around the obstacle on the left or right, depending on which lane they chose. In addition, a metal joint ran at a shallow angle over the roadways. Therefore, at this point, which was referred to as the bulge , there were always serious accidents.

The traffic load had by far exceeded the planned capacity over the years, so that the operation of the bridge became increasingly difficult. A renovation was urgently needed. However, it could only be tackled after the opening of the Homer M. Hadley Memorial Bridge, completed in 1989 and running parallel to the existing bridge . In the course of this repair work, the Lacey V. Murrow Memorial Bridge sank in a storm on November 25, 1990 and had to be replaced by a new structure, which was completed in 1993. Since then, only traffic to the east has passed over the Lacey V. Murrow Memorial Bridge, while traffic to the west uses the Homer M. Hadley Memorial Bridge.

Sink of the bridge in 1990

Looking northeast of the bridge, western approach and Mount Baker Tunnel

The Lacey V. Murrow Memorial Bridge sank on November 25, 1990 due to several human errors . The trigger was the plan to renew the road surface and widen the bridge by adding lateral cantilever beams so that the width of the lanes would again meet the requirements of the Interstate Highway System. The Washington State Department of Transportation (WSDOT) decided to use high-pressure water jets to separate the components that were no longer required, such as the sidewalks on both sides of the carriageway . The water used was considered polluted according to environmental law and was not allowed to get into Lake Washington.

Engineers analyzed the bridge pontoons used in the original bridge construction and found that they were oversized. It was therefore decided to temporarily store the polluted water in the pontoons, which is why the watertight doors to the cavity inside the pontoons were removed.

On Thanksgiving weekend in 1990 (November 22-24), rain and seawater penetrated some of the unlocked pontoons during a strong storm. When construction workers discovered the damage on November 24th, they immediately began pumping out the pontoons. Nevertheless, on November 25, an 850 meter long section of the bridge with the dirty water stored in it and several tons of construction material sank in the lake. After one of the pontoons had filled with water, further pontoons were gradually pulled into the depth in a chain reaction. The steel cables connecting the pontoons could no longer be loosened under load. Since the bridge was completely closed due to the construction work and only slowly sank, no one was injured. The process was recorded by cameras and broadcast live on television. The damage amounted to $ 69 million.

Ten years before the Lacey V. Murrow Memorial Bridge sank, the Hood Canal Bridge had sunk under similar circumstances. Meanwhile, it has also been announced that Governor Albert D. Rosellini Bridge — Evergreen Point is undersized for the local environmental conditions.

Individual evidence

  1. ^ NRHP Washington State Historic Highway Bridges. (PDF; 77 kB) (No longer available online.) WSDOT, March 21, 2013, archived from the original on December 2, 2013 ; accessed on November 26, 2013 (English). Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.wsdot.wa.gov
  2. ↑ a b c d Alyssa Burrows: Homer Hadley formally proposes a concrete pontoon floating bridge across Lake Washington on October 1, 1921. HistoryLink.org, January 18, 2005, accessed November 16, 2013 .
  3. ↑ Lacey V. Murrow becomes Director of Highways on March 20, 1933. HistoryLink.org, March 16, 2005, accessed November 12, 2013 .
  4. ↑ Landmarks Alphabetical Listing for L. In: Individual Landmarks. Department of Neighborhoods, City of Seattle, accessed November 16, 2013 .
  5. ^ Lacey V. Murrow Bridge and Mount Baker Ridge Tunnels. (No longer available online.) In: ASCE Site. Archived from the original on October 31, 2013 ; accessed on November 16, 2013 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.asce.org
  6. ^ Lacey V. Murrow Memorial Bridge. Seattle-Mercer Island, Washington. Historical background. (PDF; 549 kB) Retrieved November 16, 2013 (English).
  7. ↑ Alan J. Stein: Lacey V. Murrow Memorial Bridge (Lake Washington Floating Bridge) sinks on November 25, 1990. HistoryLink.org, January 1, 2000, accessed November 16, 2013 .
  8. ↑ Floating Bridge Drawspan of Concrete Pontoon Floating Structure on Lake Washington, Entering East Portal of Seattle. In: Engineering Department Photographic Negatives. June 5, 1959, accessed on November 17, 2013 (English, picture of the bulge).
  9. ^ "WSDOT Projects: SR 520 - Bridge Replacement and HOV Project" , Washington State Department of Transportation

Web links

Commons : Interstate 90 Lake Washington bridges  - Collection of pictures, videos and audio files

Descriptions of the bridge:

Descriptions of the 1990 collapse:

Traffic situation: