Nuclear explosives were once considered for use in large-scale excavation. A nuclear explosion could be used to create a harbor, or a mountain pass, or possibly large underground cavities for use as storage space. It was thought that detonating a nuclear explosive in oil-rich rock could make it possible to extract more from the deposit, e.g. note the Canadian Project Oilsand. From 1958 to 1973 the U.S. government exploded 28 nuclear test-shots in a project called Operation Plowshare. The purpose of the operation was to use peaceful nuclear explosions for moving and lifting enormous amounts of earth and rock during construction projects such as building reservoirs. The Soviet Union conducted a much more vigorous program of 122 nuclear tests, some with multiple devices, between 1965 and 1989 under the auspices of Program No. 7 – Nuclear Explosions for the National Economy.