Officers said a double semi loaded with coal was straightening out from a curve near mile post 238 in Price when the driver went through a fence.
Authorities said the semi then traveled about 500 feet and hit a 30-foot deep wash.
The double trailers separated and went down the wash while the semi cab detached and continued another 75 yards before stopping in another deep wash.
Cranes will be needed to pull out the trailers and cab over the next few days.
The driver, 61-year-old Byron Adamson of Gunnison, Utah, died at the scene.