At its completion, the 5.8-mile Gunnison Tunnel under western Colorado's Vernal Mesa was the longest irrigation tunnel in America. It carried water from the Gunnison River to the Uncompahgre Valley to irrigate 146,000 acres of cropland.
Work on the 30,582-foot tunnel was first performed manually. Adverse geological conditions provided great challenge for this pioneering project. The drilling crews had to deal with clay, sand, shale, and a badly fractured fault zone.
