Appears to have happened at the start of the Canyon in the Triple Drop/Nokomis sequence.

For those who don't know him, Rada was one of the legends of creek boating on the Lake Superior shore and pioneered many of the runs in the 1970's. He probably had more runs on the Presque Isle than just about anyone and he did it at all levels. His unpublished guidebook manuscript--"Rada's Book"--is still recognized as the best guide for class IV and V paddlers in the region. Looking at it this morning I note that his description of the Presque Isle is the most detailed of any in the book. It's clear that it was one of his personal favorites.

http://www.paddleguides.com/rivers/midwest/michigan_west_up/presque_isle/presque_isle.html