Historic preservation: what is "correct"? Its 1850 operational level, or its 1930 derelict status? A poster on another site suggested the C&O be returned to wilderness, which I guess meant tearing out the locks, filling in the canal and rewilding the area back to a game trail.
Their guidelines are to preserve the trail surface as it was during the canal operation. What that means by their rules, is that the soil used on the trail has to match the composition of the trail's soil at that time it was in operation. I spoke to a park service worker who was doing some maintenance one day as I was riding the trail.