Construction of a cofferdam nearly 800 m long at the Eastmain-1-A intake was one of his biggest challenges, says Denis Groleau, Eastmain site manager. It had to be built out from the banks of the reservoir by dumping material off the end of the advancing dam into water up to 21 m deep.
The key issue was to determine the ideal distance between the advancing face of the crushed-aggregate core and the riprap of the lateral embankments. The solution, he found, was not fancy modeling software—no such program was available. Rather, it was an old-school, 3D, 1:60 scale model in a laboratory. LaSalle Consulting Group, LaSalle, Quebec, did the modeling.