Bridge 4
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GN's Bridge 4 by Greg Pierce





The Great Northern's Bridge at the Locks
By Greg Pierce
12/14/98

On a warm summer's day I, like many other Magnolia residents, stroll across the small wooden foot bridge that looks out over the double railroad tracks, pick a few blackberries, cross over West Commodore Way and pay a visit to the Hiram Chittenden Locks. Last year while enjoying a casual dinner, my lady friend and I watched the vessels move in and out of the locks and a procession of freight and passenger trains rumble over the massive double tracked deck of Bridge #4. She turned to me and asked "What kind of design is that old bridge?". In the early 1890's, Jim Hill's Seattle & Montana Railroad crossed through Ballard from Interbay Yard on a large curved wooden trestle located near 14th Ave West and ran along the north shore of Salmon Bay. This first wooden trestle also known as Bridge #4 would eventually have a swing span installed in the middle to accommodate water traffic. 1912 saw the Army Corps of Engineers began preparation for construction of the government locks and the ship canal. This work would necessitate the GN relocating its line over the bay (later the ship canal). Consequently, the GN began construction of the bascule bridge (costing $1,081,836 dollars) over Salmon Bay and the line that now passes through the deep cut under Emerson Street.

Salmon Bay Waterway, Bridge No. 4 was designed by The Strauss Bascule Bridge Co. of Chicago Illinois in 1912. Construction of the structure referred to as a "Strauss Heel-trunnion Bascule Bridge type" on GN blueprints began in 1913 by the Fort Pitt Bridge Works of Pittsburgh, Pennsylvania for the Great Northern Railway. The Bascule designed drawbridge provided a vital link for The Great Northern Railway's Cascade Division, thus connecting Seattle's gateway with Canada to the North and St. Paul to the East. GN records describe the railroad's requirements: "To secure double track on improved alignment, free from grade crossing and to comply with requirements of the U.S. engineers at the crossing of Salmon Bay Waterway, the level of which is to be raised in connection with the Lake Washington Ship Canal."

A 500 ton concrete counterweight is used to lift the 200 foot Bascule span. The counterweight itself was designed with doors located on the south side that open to its interior where heavy rail could be removed during the summer months to compensate for the ties that had dried out from the winter rains. The lift span, the 165 foot truss span to the south, and plate girder approaches on both ends give the bridge a total length of 1,145 feet. At extreme low tide the bridge sits about 50 feet above Salmon Bay's waters. The two towers located on the North and South ends of the superstructure were add ons for electric public utility and signal lines but are no longer used today. In the early 1920's passenger and railroad employees who lumbered across Bridge 4 on GN's "International", "Oriental Limited" or the "Empire Builder" could have looked up at the intimidating North face of the original counterweight and seen the huge "See America First, Glacier National Park" and the GN's "goat" trademark looking down as they passed underneath and paused at the Ballard depot (now a private residence and moved slightly west from its original location) for passengers to amble on/off.

On June 12th of 1948, Bridge 4's counterweight started showing signs of stress fatigue. Cracking sounds were heard and small portions of the concrete started coming off. An alert bridge tender notified the GN officials at King Street station who subsequently halted mainline operations over the bridge. The bridge was left in the upright position and trains were re-routed over the NP's Ballard line until repairs could re-open GN's mainline over Salmon Bay. On Sunday, June 13th, both the Seattle Times and Seattle Post-Intellgencer provided readers with the following reports: The Seattle P-I summary: "Service on the Great Northern Railway's main line between Seattle and Vancouver, B.C., was disrupted late yesterday when a 500-ton concrete counterbalance cracked on the north shore of the railroad's Lake Washington Ship Canal bridge. The severed counterbalance fractured a large steel girder and the span remained almost vertical. Louis Weaver, 3009 W. 58th St. the bridge tender, said the broken concrete tore out a steel stanchion. Workman were unable to effect repairs last night and the afternoon passenger train to Vancouver, B.C., was delayed more than one hour. Trains were being rerouted over Northern Pacific tracks to Snohomish. Rail crews are expected to complete repairs today."

The Seattle Times' report differed slightly with the following front page story: "The 500-ton concrete counterbalance on the Great Northern Railway bridge over the Lake Washington Ship Canal cracked at 5 o'clock yesterday afternoon, breaking a large steel support girder and putting the bridge out of service. The accident cut the railway's mainline between Seattle and Everett. The afternoon passenger and mail train to Vancouver B.C. , was delayed two hours and fifteen minutes while officials arranged to reroute GN trains over the Northern Pacific Railway's line to Snohomish, where they would return to GN tracks. The crack developed in the counterbalance while the bridge was raised. F. F. Van Tomme the bridge tender on duty, said the mishap made it impossible to lower the span until repairs could be made. The lower side of the counterbalance came to rest on the tracks. Engineers had to crawl underneath it, between the tracks, to get onto the bridge. Officials said they feared repairs could not be made until late today. Cause of the structural failure had not been determined last night".

The railroad conducted several examinations of the bridge at this time and found that the steel frame work inside the counterweight had suffered stress fatigue. As a result, GN's bridge gang and the Morrison-Knudsen company connected several large cables to the upright span and fastened the opposite ends to the bridge's piers on the north approach of the bridge. Once the span was anchored, jackhammers were brought to bear to remove the old counterweight, the steel frame was repaired and a new counterweight was poured and built in small sections. The bridge was finally repaired and back in service after a 6 month sabbatical. Several theories why the steel frame inside the counterweight became fatigued were put forth. Could vibration of the GN's steam Mallets have been the problem?

The most likely theory was put forth by retired GN/BN bridge engineer, Chuck Intlekofer: "Every time that bridge was placed in the upright position, the bridge's design is such that the burden of that weight was placed on that steel frame work inside of the concrete counterweight. "Well, after thousands of openings and closings, that steel became fatigued and it showed up in the form of those small chunks of concrete coming off".

Repairs have been relatively minor since 1948. April of 1992 saw BN spend $1.8 million on upgrades to the signal systems, electrical wiring, gears, and motor drives as well as the replacement of the original hand controlled levers and foot pedals with an automated control board. The Bascule designed drawbridge itself has remained largely unaltered for the past 84 years, averaging 30 trains in a 24 hr period and 250 lifts of the span a month. The electric motor and drive gears are housed in a structure located above the tracks and forward of the formidable counterweight, better known as the gear house. As a backup system, the bridge was designed with a small gas "donkey" engine in the event of a electrical power failure. GN bridge tenders were given instructions to start the small gas engine once a month to ensure that it would work properly if the need arose. Bridge operations are conducted out of "the Shed" adjacent to the bridge's superstructure where the bridge tender monitors both rail and marine band radios. To this day, the age old tradition of boat traffic sounding their horns to request a lift of the bridge is in use. On a side note, it is not uncommon in 1997 for the bridge tender to receive a radio message from boat captains requesting a lift of the "Great Northern Bridge". Per maritime law, boat traffic has the right of way over rail traffic.

Over the years, tall-masted pleasure craft have sometimes halted more than one freight train. I spoke with one former conductor who worked on GN's Empire Builder who reported that the span was always down several minutes ahead of time to accommodate GN's priority passenger train and never recalls a hold up for an open Bridge 4. During normal operations of the bridge when the span itself is in the raised position for water traffic, "derails" found on each set of approaching tracks are in the open position providing protection to train crew members and equipment, and boaters down beneath in the unlikely event that a train ever failed to stop. On either end of the bridge, signal lights are found which allow rail traffic onto the bridge. For this to happen, the bridge operator must have the bridge in the "Lined and Locked" position. When the bridge is in this position, the derails will be closed and ready for the approaching wheels of rail traffic. The Bridge tender must perform all phases of raising and lowering the span in a proper sequences of events that insures the fail-safe system.

The twilight years of the Great Northern Railway were well on their way by 1968. Big Sky blue was replacing Omaha Orange on equipment from F-7's to new SD-45's. Merger of the Northern Lines was being worked out with the ICC. A May 1968 Timetable gives the following instructions to GN train crews regarding Bridge No. 4:

"Interbay-Westward Dwarf Signal 5.5 of color light type located between Eastward and Westward main tracks East End Interbay Yard governing Westward train and engine movements is controlled from Interlocking Bridge No. 4, Ballard, Washington.

When train or engine is stopped by the stop Indication of this signal, a member of the crew must operate push button located on a cable post south side of Eastward track opposite the dwarf signal. This operation will inform Signalman on Bridge 4, and automatically clear signal 5.5 if there are no conflicting train movements. Train speeds are restricted on the bridge to 20 mph."