In 1948 the Federal Government sent some military officials to the San Rafael Swell to build a series of tunnels over a 300 acre area. Morrison Knudsen Corporation (MK) won the construction contract to blast the tunnels in the solid rock. It was a top secret mission; not even local employees were infomed about the reason behind the work they were doing. Over a period of four years, blasting was done to create tunnels in three different areas. Once the tunnels were made, varying amounts of trinitroluene (TNT) or C-2 explosives were set off on top of the rock structure. Most supposed it was to test the sandstone to see if it could withstand a nuclear blast. This tunnel is the largest of the tunnels. The shaft itself is nearly 1000 feet long. The surface disturbance seen in the aerial photograph opened up the top of this tunnel.
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