Project Rio Blanco is the first phase of a three-phase program to demonstrate the potential of commercial development of I a natural-gas field by nuclear stimulation techniques in the Piceance Basin in Rio Blanco County~ Colorado. Because the gas is tightly held within the surrounding rock, this field cannot be developed by conventional stimulation methods. The first phase will consist of simultaneously detonating three nuclear explosives at different depths within the Fort Union and Mesaverde formations. The detonation is designed to stimulate a 1,350-foot vertical section of the Fort Union and Mesaverde formations. After a 3-month waiting period, a reentry well will be drilled into the gas-filled chimney, and the reservoir testing and evaluation will start.