DavidMac: Unfortunately I have to archive this one, because the national park has taken over the hiding area!
Several months ago I was at the park headquarters to attend a meeting, when I came across a very new map that showed the land surrounding the cache as park property. After a little investigation, I have found out that the park recently acquired several plots of Tapoco property, one being between the highway and the powerline which runs northwest from the 129 overlook toward Calderwood Lake and another one west of the highway and north of the Calderwood development. At this point, none of these new holdings are on any publicly released maps, but NPS signs have recently been installed along the new boundary. The problem is that the cache is clearly within one of these areas.
At the time that I hid this cache I knew someone whose father worked at one of the dams in this area. He was able to confirm which lands were national park, which were open to the public (and caching), and which were closed. The cache was in an area that was open to visitors and caching. Unfortunately I no longer have this contact and I have been told that there's no chance of the GRSM ever allowing physical caches in the park.
If any reviewers need more specifics on which lands in this area are NPS property, I might be able to get a copy of the latest map.