The Vernal Unit was established to provide a firm irrigation, municipal and industrial water supply to land in Ashley Valley. Historically, irrigators in Ashley Valley depended on direct flows from Ashley Creek for their water supply. During a dry year when there is little flow in the creek, or as flows in the creek diminished late in the irrigation season, the irrigator’s ability to adequately irrigate their land decreased. Preliminary investigation for a method to supply a firm water source to irrigators in Ashley Valley was initiated by Reclamation in 1939. In April of 1956, Congress authorized the Vernal Unit Project of the CUP as a participating project of the Colorado River Storage Project Act.
The purpose of the Vernal Unit is to store high spring runoff and winter flows in Ashley Creek to be used for supplemental irrigation, municipal and industrial purposes. The major features of the Vernal Unit include Steinaker Dam and Reservoir, Fort Thornburgh Diversion, Steinaker Feeder Canal and the Steinaker Service Canal. Construction on the Vernal Unit began in 1959. In the spring of 1961, the Fort Thornburgh Diversion and Steinaker Feeder Canal were completed, which allowed the diversion of Ashley Creek water to the new Steinaker Reservoir. Construction of Steinaker Dam was completed in 1962. The Steinaker Service Canal, which delivers stored irrigation water from Steinaker Reservoir to farmlands in Ashley Valley, was completed in late 1962. Steinaker Reservoir was filled to capacity for the first time on June 30, 1965.
The project serves approximately 14,000 acres of land with supplemental irrigation water either by direct delivery through the Steinaker Service Canal or by exchange through the existing canals above the Steinaker Service Canal. The project also delivers 1,600 acre-feet of water annually for municipal and industrial use by Maeser Water Improvement District, Ashley Valley Water & Sewer Improvement District, and Vernal City.
Reclamation transferred the operation and maintenance responsibilities for the Vernal Unit to the District in January 1967. The District continues the operation and maintenance of the project and administers the sale and delivery of project water.