I think the biggest concern is having the arches fall down. The stone is not the most solid stuff around and other arches there (such as the great arch) are expected to break and fall down. The idea is to minimize the impact so others can see them in the future.
I am interested in heading up to Darrington, however I am not sure what the conditions would be like at this time of year. I assume lots of snow on the approach, but will the rock be dry?
I also heard a rumor that there were some access issues?