The following text wich is with the photo of the beach that was in LaSalle below the dam gives us new information such as the official name (Rocky Beach) and the year of the photo(1934):
Sunday afternoon at Rocky Beach in 1934. Adjacent to it was the Power House, wich before it closed down in 1931, used to blow a horn to warn people before opening its gates. Indeed, the strong current created by this opening would have been dangerous to the bathers. There were also restaurants on the beach (owned by Messrs. Dumas Lussier and Bélanger), when two hot-dogs sold for five cents and a soda for three. Policemen were especially hired to maintain order.
At one time I heard that there was question of re-constructing a dam at the same place. I am adding this new information to the photo in my Album no. 38 on my site.
Source: LaSalle Then and Now by Denis Gravel and Viviane Bouchard
Photo from Collection Conrad Poirier
Archives of the Société d'Histoire et de Généalogie de Verdun (SHGV)