I have a Player Magus whose CrIg Casting total is +11, He's currently in a fertile oasis in a glacier in Iceland. They need to melt a channel through the glacier to allow a small boat to float down a river. how long should I make the channel be so that this takes a season?
He also know Pilum of Fire, but even adding in +3 from ceremonial casting and philosophy, his casting total is only +14.
but they can scout before they try this, and I don't want it too obvious that I am using Handwavium (although that is exactly what I was intending) If it sounds plausible on first try.