the Rio Blanco massive hydraulic fracturing demonstration has been undertaken by the Bureau of Mines, Atomic Energy Commission, and a group of 15 industry participants. CER Geonuclear Corp. has been retained as program manager to evaluate the stimulation effects of very long fractures , suitably propped open in thick sections containing multiple intervals of low permeability gas-bearing sands. The zone of interest for this demonstration includes Fort Union and Mesaverde sands from about 5,800 to 8,200 feet deep in Rio Blanco County, Colo., about 1 mile from the site of the May 1973 triple nuclear detonation aimed a t stimulating production from the same reservoirs .