 maybe some pea gravel and sand down to absorb things. Or you could buy one of the new artificial turf systems made just for that purpose. It looks and feels just like real grass. It's not rough like the old sports turf from the 70s. It also includes underlying drain holes to facilitate percolation, and it'll keep your dog's paws cleaner for the return trip to the house. So the bottom line here, there's no substitute for good training.