If I had to guess, the Corkscrew Pass will probably be the one this year as there are some massive structural cracks in the cave part that go all the way up to the walking surface above. Also with the water sluices being out of commission with the construction in Riverfront, this would be a good time to do this... and I'm not sure if it was related or not, but there were a few workers at the water lift for the sluice the final day of the season.