in reply to chattahochhee river deck surfaces- pressure cleaning is neccessary-however if the surface hasn't been sealed in a while with an epoxy binder- stones will be coming off- and mildew is possible. at this point if alot of stones are coming off and there is mildew growing in many of the open spaces, chances are that the deck can't be saved. if the pressure cleaning takes many more stones off then when it comes time to apply the epoxy sealer, the roller will make all the loose stones fly around everywhere and create a very sharp surface that will be hard to walk on. there are not many river rock contractors out there- but there are a few.