Canadian Pacific Railroad Bridge Over Black River, LaCrosse, WI

Project Engineer: Jeremy May.  This project involved monitoring the existing swing span structure during construction of the new substructure.  The existing structure, a Swing Span Truss built in 1902, was being replaced with a segmental bascule structure.  This structure is part of Canadian Pacific’s mainline from the Twin Cities to Chicago and averages approximately 50 trains a day.  This structure also swings open to allow up to approximately 20 boats and barges to pass.

Westbrook received the 2005 State Finalist Award in the Engineering Excellence Competition for this project.

Project Background

During construction of the east approach substructures the existing piers experienced settlement reaching up to 14 inches.  The settlement was due to shallow wooden piling supporting the existing piers, the close location of the new substructure to the existing piers, and consolidation of the surrounding loose granular soil due to the vibratory and hydraulic hammer used to drive the piling. 

To complete the substructure portion of the project, two piers remained to be constructed within 30 feet of the existing swing span pier.  The 14 inches of settlement encountered at the approach piers would not be acceptable at the swing span pier.  The swing span pier had an allowable settlement of 5 inches controlled by the elevations of the approach piers and the mechanical components of the swing span structure required to keep the structure operational.

Due to the high amount of barge and train traffic it was important to keep the swing span operational during construction of the two remaining piers.  Due to the loose soil conditions the contractor used jetting to drive the piling.  Jetting consists of using air and water, at high pressures, to drive the piling.  The jetting process would confine vibrations felt at the existing swing span pier and reduce settlement. 

Westbrook Associated Engineers, Inc. Services

The contractor needed a way to monitor the settlement and provide real time on-site data to multiple parties involved in the project.  Westbrook provided on-site real time data on Westbrook’s website that would be used to correlate with settlement readings recorded by SOL Data, a highly accurate and sensitive survey system based from France.  Westbrook recorded train-crossing times, swing opening and closing times for barge traffic, along with sheeting and pile driving records.  Westbrook was also responsible for monitoring settlement recorded by the SOL Data system.  The substructure work was completed with minimal disruption to train and barge traffic.  The existing swing span pier experienced only 1-¹/₂ inches of settlement. 

Additionally, Westbrook designed and developed an innovative system using barges and jacking towers to float-out the old bridge and float-in the new one million pound bridge.
 

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