GSC deep marker stamped 69L029 on the sewer cover and sunk into the ground until refusal on the seaway property, on the east side of the St-Lambert lock , 14.0 m south of the centre line of the road leading to the office and observatory and 108.0 m east of the east end of the lift bridge. The marker is located 3.30 m from a beacon on a rod, 111.30 m from the St-Lambert lock, 4.0 m from a Frost fence and 21.65 m from the pavement of the entrance to the parking lot.