The trail to Mosca (Fly) Pass starts where the Wellington Ditch once picked up its water. This was once a horse trail and then later an early wagon and auto road. Long washed out, it is now a pleasant walk along a creek in the woods.
Today, Mosca Pass can still be reached by auto from the east. There are some seldom visited camp sites at the end of the dirt road at the pass. Carbonate Peak is a strenuous hike from here.