The deep inner channel, which includes "the Dalles", that forms the modern St. Croix River valley was excavated by a second drainage event. This inner channel is incised as a narrower valley cut into, and hence younger than, the Chengwatana surface. This demonstrates that the St. Croix valley is slightly younger than the Kettle River valley and Moose Lake outlet and was cut by water flowing out of the lower and younger Brule outlet of the Duluth level of glacial Lake Duluth. Because the trace of the Chengwatana surface grades to a terrace level higher than the potholes in International State Park, they were eroded by spillway water from Duluth level of glacial Lake Duluth. The association of the Duluth level of glacial Lake Duluth with the second discharge event and creation of the St. Croix valley and the potholes indicates that they were created between 10,800 and 10,600 BP calibrated.