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 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. Complicating this was the mandate from the bi-national owners that the bridge design and construction teams had to be equally represented by companies from both the United States and Canada.
The joint venture of bridge engineering firms Modjeski and Masters and Buckland & Taylor from British Columbia was formed and retained by the owners to develop studies and plans for the new long span bridge design. Working collaboratively with stakeholder groups, our creative bridge designers developed several bridge forms deemed suitable for the crossing, including cable-stayed, truss and arch bridge solutions. 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 two bridges represent very different structural systems, yet each reflects the era of their construction while sharing broadly similar geometry. 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.
The Second Blue Water Bridge went from concept to completion in just five years, an impressive feat considering the many challenges we were presented with: dual ownership, dual design and contracting firms, restrictions on construction from the channel, and the use of a new bridge design specification. Perhaps even more satisfying is the fact that the project was delivered on time and within budget. Since the bridge’s opening, Modjeski and Masters has continued to provide comprehensive life cycle bridge services. We completed the rehabilitation of the first crossing (with Buckland & Taylor) and provided ongoing bridge inspection services, load capacity rating, and gusset plate analysis for both the truss bridge and the continuous tied arch bridge. Our work will continue at least through 2011.