In the U.S., a series of tests were carried out under Project Plowshare. Some of the ideas considered included blasting a new Panama Canal, the use of underground explosions to create electricity, and a variety of geological studies. The largest of the excavation tests was carried out in the Sedan nuclear test in 1962, which released large amounts of radioactive gas into the air. By the late 1960s, public opposition to Plowshare was increasing, and a 1970s study of the economics of the concepts suggested they had no practical use. Plowshare saw decreasing interest from the 1960s, and was officially cancelled in 1977.