I just saw your blog that you went out and visited the Green River Complex. I also visited the area and was determined to find the supposed large open tunnel system [that you alluded to on your mailing list in 1997]...I don't recall anything about the 1997 posting, but apparently someone sent it to me as an email and asked that their name not be used. Their actual name and email address is long lost (since I've been through many computer crashes since then).
The River Complex has a real intriguing ghost town atmosphere. You almost feel the ghosts of the past in each building. For me the trip out there was well worth it; however I felt that I never really had a chance to explore the entire complex (lack of time, sunlight, and directions). Given your recent photos and trip to the complex do you have anything further to add regarding the rumor of a large open tunnel system somewhere on the base?
While I spent only two hours superficially exploring the area near the freeway, the chance of anything especially secret near Green River is remote.
This is essentially public land now. There are still a few fenced-in compounds where no one has broken the lock yet, but the public has had the run of this place for three decades. There are no end of idle males with 4WDs who have explored every road-accessible corner of the American desert. (I was one of them once!) Any "open tunnel" would have been found and publicized long ago. There are no secrets on public land. That's not to say there aren't hidden gems out there, like these abandoned buildings of the missile complex, but nothing "big."
Heck, there could be secret tunnels anywhere, right below your feet even, but where the tunnels come to the surface, there have to be signs. If there's dirt, you have to haul it away and put it someplace, and if there are human workers, you have to have some reliable way to keep them quiet. That pretty much limits the prospects to actively guarded military installations, and at Green River there aren't any.
The West, in fact, is riddled with tunnels. They are called "mines" and there are abandoned ones everywhere. If you search hard enough, you can usually find some old timer who remembers working at any specific mine. There is never any significant secrecy attached to these facilities, so news of anything interesting would certainly spread to the wider community.
The community of Green River is miles from anywhere with NOTHING TO DO. What people in towns like this do for amusement is explore every corner of the desert around them. If there were anything remotely interesting in the hills, I am sure that someone from Green River itself would have found it and posted it on the internet.