This is almost universally known as Valleyfield, and is a small section of whitewater right in downtown Salaberry-de-Valleyfield. The town itself is on Grande-Ile, an island in the middle of the Saint Lawrence river. A channel cuts through the island and is named the Saint Charles river. At the upstream end of this channel is a control sluice that keeps a constant flow going through the short section of whitewater below. It has been enhanced by moving rocks around, and has slalom gates hung to give a great practice venue.
If you plan on being a regular user, there is a club here, Kayak Valleyfield that undertakes the maintenance of the site.
To get there; Head into Salaberry-de-Valleyfield on the QC-201, and turn South onto Rue de Grande-Ile. Park behind the Maxi Grocery store, right next to the course.