According to
http://en.wikipedia.org/wiki/Gravel, crusher runs are basically the dense grade gravel that I've used before on top of #4 rock on the base? I don't understand how that small stuff could be used as a base, or am I missing something?
It sounds like the suggestion is filter cloth, then medium 4" recycled concrete, 12" of #4's, crusher screenings, then mixed washed gravel/sand/stone on top of that to keep it from washing? I think we could use the mixed gravel/sand/stone on the hill to keep it from washing. Some of the small #4's and dense grade that I've put on it previously has washed bad in places. Would agricultural lime be good on the top to seal it? I've heard it turns hard like asphalt when rain hits it.
