This 2,11 miles cantilever motorway bridge which spans the St. Lawrence river in Canada is the busiest in the country. Built in 1962, the Manhattan bridge carries 120,000 vehicles per day, including heavy trucks. In addition to the heavy traffic, extreme weather conditions damage the bridge : exposition to de-icing salts, river ice and wide temperature variance (70°C in a yearly cycle). These conditions have lead to severe damages in particular penetration of salt and corroding cables. Since 2006, OSMOS has monitored the evolution of the pre-stressed concrete beams, especially during rehabilitation work. Thus, the client is able to continue the normal exploitation of the bridge with a full acknowledgement of the work impact on the structure.