This fixed trunnion bascule bridge and its design is one of the finest and most impressive in the city of Chicago. Along with its near-twin on Wells Street, these are the only two movable bridges along the loop that carry the CTA "L" trains. These two bridges are also the only two double-deck bridges in Chicago that carry trains on one deck and vehicular traffic on the other deck. On both, the trains travel on the upper deck, allowed the already-elevated trains to seamlessly connect to the bridge at this level, while vehicular traffic travels on the lower deck. Sidewalks are also located on the lower deck. The double-deck configuration of the Lake Street Bridge makes for a very massive bridge. Because it is so massive, this bridge is very impressive to watch being raised or lowered. The Lake Street Bridge was built before Wells Street Bridge and as such the slight differences in the design and construction process of the Lake Street Bridge represent its prototypical nature, but overall the appearance of the two bridges is very similar. The Lake Street Bridge is technologically significant for its double-deck design, the first of its kind on the river when built.
Lake Street Bridge is the site of where Chicago's first crossing of the river was made, when a ferry was ordered at this location by the Commissioners of Peoria in 1829. Costs for crossing were listed in an Annual Report of the Department of Public Works as follows: Foot passenger: 6 1/4 cents, man and horse: 12 1/2 cents, horse and pleasure vehicle: 50 cents, one horse and wagon: 25 cents, two horse wagon: 37 1/2 cents, and each bushel of grain: 6 1/4 cents. The first documented bridge at Lake Street was built of wood in 1849. This bridge was rebuilt by N. Chapin in 1859, rebuilt by Fox and Howard as a wood/iron combination bridge. In 1885, an iron bridge was built by the Detroit Bridge Company. This bridge was converted into a double-deck bridge in 1893.
The design of the existing bascule bridge was not arrived at immediately. Early plans called for a vertical lift bridge at this location. The city had sought competitive plans and estimates for a bridge, and had those plans reviewed by City Engineer John Ericson, alongside J. E. Greiner (a noteworthy consulting engineer based out of Baltimore, Maryland) and Chicago and NorthWestern Railroad Acting Chief Engineer W. H. Finley. They arrived at the vertical lift design. However, the second choice, that of the bascule bridge was later decided upon for "reasons of public policy" according to the Annual Report of the Department of Public Works.
The Chicago Department of Transportation's Michelle Woods was kind enough to arrange a few moments out of her very busy schedule to give HistoricBridges.org a brief tour of the Lake Street Bridge's bridge tender house control room and machinery basement, following a similar tour provided to a school group. In addition, for comparison, a brief visit to the control room of the nearby modern Randolph Street Bridge provided a comparison to how the control rooms have changed from the era of the historic bridges to the modern bridges. Some of Chicago's bridge tender houses were documented in black-and-white photos by the Historic American Engineering Record in a minimal fashion, however HistoricBridges.org is proud to be the first bridge website to provide a complete set of full-color digital photos of a Chicago bridge tender house's interior. While there undoubtedly are variations between the bridge tender houses and associated operating equipment between Chicago's many historic movable bridges, the tour provided for this bridge is intended to not only document the Lake Street Bridge, but to provide an overview of the general type and design of equipment likely found in many other movable Chicago bridges. The Lake Street Bridge retains original design control house operating equipment, and the mechanics in the basement are largely unchanged from the original design as well. The only significant updates appear to have been changes to the sensor equipment in the basement, and the addition of a device that relays the status of the bridge locks to a nearby CTA control tower, so that the CTA knows when the stop or start running trains on the bridge.
A full tour of the bridge tender house control room and machinery is available as one of the photo galleries available for this bridge. Additionally, the below two diagrams are available.
The construction of this bridge was innovative in that City engineers designed a way to construct this bridge while maintaining traffic on the previous swing bridge at the location. The bascule leafs were constructed in the raised position around the old swing bridge, with the ends of the deck left off the bridge to allow traffic to pass through onto the old bridge during construction. Other considerations for accomodating the needs of both the old bridge and the new bridge construction were made, requiring such activities as temporary supports for sections of the old bridge. The practice of maintaining traffic on a former bridge, while constructing a replacement bridge on the same alignment was common among railroads, but uncommon for the city engineers, and the double-deck design undoubtedly introduced a unique level of complication to the project. As such, the construction of this bridge as well as the nearby Wells Street Bridge represent some of the most complex and creative engineering projects ever undertaken by the City of Chicago.
Above: These photos show the construction of the bridge. Because the former bridge was kept in service during construction, the design of the previous bridge can be discerned from these photographs.
Above: The above photos shows the process used to transfer traffic from the previous swing bridge to the bascule bridge with minimal disruption of traffic. This involved demolishing the center portion of of the swing bridge when in the open position, which allowed the bascule span to be lowered and opened to traffic quickly. Then, the rest of the swing span could be demolished without a rush.
In 1886, Volume 15 of the Engineering News-Record described the construction of the swing bridge that preceded the current bascule bridge. The text of the short paragraph follows.
Lake Street Bridge. --- The iron swing bridge over the Chicago river at Lake street, Chicago, is completed, but the viaduct and approaches are not yet finished The bridge is 220 feet long. 23 feet high in center, and 20 feet high at ends; it has a width of 60 feet, composed of two 21-feet roadways and two 7-feet sidewalks: the floor will carry a weight of 125 pounds per square foot: The drum on which the bridge turns is 48 feet in diameter, and rests on 74 solid iron wheel-, 18 inches diameter and 8 inches wide on face: the gearing is of phosphor bronze. The bridge will be turned by a steam engine with a pair of 8-in. by 12 in. cylinders, and a 7-inch cylinder engine will be used to drive the electric light plant: the engine-house is on top of the structure. The bridge will cost $145,000, divided equally between the city and the West Division Street R. R. Co.: the viaduct will cost $55,000. paid by the railroads interested: total cost, $200,000. Work was commenced in November last.
Above: Photos showing the newly constructed bridge.
Above: The Annual Report of the Public Works Department has a drawing of the bridge that showed several noteworthy details of the bridge, some of which were apparently not included in the final plans for the bridge, such as decorative details mounted on the trusses.
Main PlaqueBUILT 1916
WILLIAM HALE THOMPSON
THOMAS G. PIHLDELDT
ENGINEER OF BRIDGES
CHICAGO PLAN COMMISSION, E. H. BENNETT, ARCH'T.
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This bridge is tagged with the following special condition(s): Double-Deck
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