Looking to treat a gravel driveway that's approximately 3/4 of a mile long. As it is right now, there's a menagerie of weeds and grasses that are encroaching on the gravel. I've read that Sahara and Pramitol will accomplish what I'm looking for, but the threat of it leeching into the surrounding grass is somewhat troubling. I can't afford to have the nice grass in the ditches killed. Any thoughts on a product that will provide long term prevention of undesired growth without damaging the surrounding foliage?