About
By 1950 what was to become known as the Cold War was settling into place. The Soviet Union had detonated a nuclear device in the late 1940s, so the US nuclear monopoly was broken. In addition, both sides would successfully test thermonuclear weapons (a.k.a. hydrogen bombs) in the early 1950s.
So the sheer destructive power of nuclear weapons, even before operational thermonuclear devices, motivated the search for ways to "harden" (in current jargon) command and control centers to survive nuclear attack. Putting them underground was an obvious approach, but how deep and in what kind of rock?
The experiments here helped address these issues. Horizontal tunnels were dug in the Navajo Sandstone, a thick massive sandstone with relatively uniform mechanical properties. Explosions of various sizes were then detonated above these tunnels, while then-state-of-the-art instrumentation was installed in the tunnels to measure the effects. The investigations were carried out by Morrison-Knudsen (hence "MK tunnels"), at the time a well-known contractor.
Although the experiments were secret, and indeed remained classified till the 1980s, Morrison-Knudsen was remarkably open about the work. Test explosions would be announced and some were even photographed by people living around the area.
Testing wound down in 1952 and, presumably based on the test results, the Navajo Sandstone was deemed unsuitable for underground installations. Results from testing elsewhere presumably led to the construction of the underground installations in Cheyenne Mountain instead.
Know Before You Go
One of the tunnels is easily accessible from the Buckhorn Wash (or Draw) road, at 39.16418 N, 110.73599 W. As with the other tunnels, it is blocked off but with an open grate to give bats access. (Abandoned tunnels like this have become important habitats for bats.) An old shed-like structure, said to have been used for storing explosives, is not far away, across the road around 39.16778 N, 110.73785 W. There were also other structures around here during the construction, but nothing else is left.
The main tunneling site, however, is to the east on the bench above Buckhorn Draw, about 1.25 miles away. To get there, go up the Buckhorn Draw road to its junction with Green River Cutoff Road, at about 39.17081 N, 110.75135 W, and turn right. Go 3.5 miles to a junction at 36.16972 N, 110.70405 W and turn right onto BLM road 3432. Go 0.9 mile and bear right onto MK Tunnels Road at a junction around 39.16134 N, 110.71341 W. Continue about another 0.3 mile to where the edge of the bench drops off on the left. This overlooks the area where many of the explosions were set off, leaving obvious craters, some of which are fenced off. Use extreme caution in this area, especially with children and pets, because some of the craters have broken into the tunnels below. The area is also steep and covered with loose rock. Several interpretive signs describe the site. The portal to the main tunnel is at the base of the bluff to the west, about 39.15826 N, 110.71844 W. A steep trail leads down to this point.
The Green River Cutoff Road is graded and should be passable to passenger cars, at least in dry weather. Going down to the MK roads, however, will require high clearance. It's a straightforward hike, however, if an adequate vehicle is not available.
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Published
July 17, 2026
