I agree with moving the GraCouDam waypoint to the visitor center entrance.
Looking into this issue reveals some other issues in the vicinity. First off, the IndAve point just south of the GraCouDam waypoint is shown as a private service road on OSM, so I'm going to convert that to a shaping point. (nobody is using that point so it won't affect any list files) I'm guessing that this point was just chosen for shaping, but anyway...
Also, it seems like WA155 could use a point at Roosevelt Avenue, since that is the main street of Coulee Dam and it's a point that many including myself would find useful since that's where you turn off to watch the light show in the evenings. And of course, some of the other waypoints need to be recentered.
Anyway, I'll be making these changes along with the things in Idaho over the next few days.