100 Years and Counting at the W. Lake St. Bridge
The W. Lake St. bridge is the newest inductee to the “100 Club.” There are now ten CDOT bridges in the club. Of these ten, six are operated on a regular basis including three Loop Bridges. (In addition to Lake St., the other two are Washington and Jackson).
One hundred years ago the world's first double-decked trunnion bascule bridge opened at Lake St. The complex bridge was opened in stages in 1916. L-trains crossed the upper deck March 4th and street cars crossed the lower deck October 15th. Pedestrians and autos first crossed on November 6th completing the project.
The current bridge replaced a double-decked center pier swing bridge. All swing bridges in Chicago had been identified as obstructions to navigation and ordered removed by the U.S. War Department in the late 1800's. Replacing the swing bridges was a decades long process. The last Loop swing bridge was removed at Clark St. in 1929.
When it came time to replace the Lake St. swing bridge, the operators of the Chicago and Oak Park Elevated line which used the top deck of the bridge were concerned about delays in rail service due to construction of the replacement bridge. Chicago Public Works (CPW) engineers looked at various options to minimize the impact of construction on train service and determined the best approach was to continue rail traffic across the existing bridge while the new bridge was under construction.
Bids were opened in September of that year and all bids exceeded the amount appropriated for construction of the bridge. Citing the superiority and economy of their patented designs, Scherzer Rolling Lift Bridge Co., Strauss Bascule Bridge Co., and Strobel Steel Construction (Rall bascule lift) claimed that their bridges would be better and less expensive than the city's initial design.
In response to these claims, the Finance Committee of the Chicago City Council created a three engineer commission charged with evaluating competing bridge designs. The City Council appointed representatives from the city (John Ericson, City Engineer) and the elevated railway (J. E. Greiner, Consulting Engineer based in Baltimore). The third member, W.H. Finley (Chief Engineer of the Chicago & Northwestern RR), was selected by the appointed members.
Three competing designs emerged – a vertical lift bridge, a single leaf trunnion bascule, and a double leaf trunnion bascule. The vertical lift bridge was chosen by the engineer commission. As the double leaf trunnion bascule was more in tune with the aesthetic ideals of the 1909 Plan of Chicago, advocates favoring the more aesthetic bridge lobbied for their choice and won.
CPW engineers revised their earlier double leaf trunnion bascule design for cost savings. Construction contracts were awarded in March 1914. Substructure work began almost immediately.
The new bridge was built around the existing swing bridge with the bascule leaves in the vertical position. Once the leaves were complete, the swing bridge was rotated open, cut up, and floated away on the river. The bascule leaves were lowered into place and the railroad deck completed. The elevated rail traffic was stopped on the old bridge Sunday, February 27, 1916 and resumed on the new bridge March 4th (in 6 days, 14 hours). Street car traffic resumed on October 15th. Auto and pedestrian traffic was interrupted for the entire construction period and resumed on November 6th.
The staggered openings of the various traffic types using this bridge was due to the construction of the west approach to the lower deck of the bridge. The elevated railway and the surface line (Pennsylvania RR) had the shared responsibility to build the viaduct over the existing railroad tracks on the west bank but disagreed over the cost sharing thus delaying the project.
If maintaining traffic over an old bridge while a new bridge is being built isn't complicated enough, the swing bridge was operated 6132 times in 1914-15 during the construction project. In the hand-off year of 1916, both bridges were operated a total of 3321 times for river traffic.
The bridge house plaque summarizes the key players in the design and construction of this bridge. The steel was provided by the American Bridge Company, a subsidiary of U.S. Steel at the time.
This is the fifth bridge in approximately 165 years at this river crossing, yet it has been in place for most of that time. The longevity of this bridge is a testament to the Chicago engineering team that developed and refined the Chicago-type bascule trunnion bridge and the CDOT team that operates and maintains them. Today, this workhorse carries about 4,000 pedestrians, 14,500 cars, 526 trains every day and is operated about 40 times each year for seasonal sailboat runs.