I'm helping out one of my favorite clients as a favor and essentially the driveway of their estate is covered in a very resilient growth of moss.I've tried taking a pressure washer to the driveway with a detergent mix and I'm actually pitting areas of the driveway before I actually take the moss off. The only way this moss comes off is if I hold the pressure washer almost right against the driveway but I'm running the risk of damaging areas of the driveway. I've tried using a mix of bleach and TSP, left if for 30 min, but still nothing. My client would be very appreciative if I could rid her driveway of this unsightly problem with a less forceful and intrusive method. Any help would be awesome, thanks!