How feasible is it to launch a pontoon boat below Roza Dam on the Yakima? How close can I park and how long of a carry across the top of the dam is it? Is it hard to get down to the water on the other side. The fish passage crew there said they've seen it done, but they didn't think anyone gets to drive across the dam. Of course, it's closed water until you're 3500 ft. below Roza.