Second Blue Water Bridge Design

When it opened in 1938, the Blue Water Bridge successfully met the needs of two countries. But traffic and trade volume steadily increased, and by the early 1990s the structure was carrying about four million cars and one million trucks annually, 17 times the volume it handled in its inaugural year. As the fourth busiest border crossing between Canada and the United States, that volume is expected to double in the next 25 years. The need for additional capacity necessitated a new crossing at the site. But that wasn’t the only challenge Modjeski and Masters (M&M) faced. The existing bridge had become an integral part of the local heritage - any new bridge should neither detract from nor overtake the existing view shed.

The joint venture of M&M and Buckland & Taylor (now COWI) from British Columbia was formed and retained by the owners to develop studies and plans for the new long span bridge design. The owners and stakeholders decided that the Second Blue Water Bridge, located parallel to and less than 200 feet south of the original crossing, was to be developed as a continuous tied arch bridge. We designed the arch bridge to compliment the lines of the original structure, a famous landmark in the area. The new structure was the first major bridge to be designed and constructed using SI units and in accordance with the AASHTO LRFD Bridge Design Specifications. With the Coast Guard’s ban of erection from the river, we developed an innovative construction scheme: the continuous tied arch bridge was erected by cantilevering over the channel using stays and temporary falsework towers, which were erected over the main piers.