Operation Plowshare

 Crater from the 1962 "Sedan" nuclear test as part of Operation Plowshare. The 104 kiloton blast displaced 12 million tons of earth and created a crater 320 feet deep and 1,280 feet wide. (Look to the size of the roads in the bottom-right of the picture, and the observation deck at the lower-right edge of the crater, for a sense of scale)

Let's see, what can we use nuclear weapons for:

Project Plowshare was the overall United States term for the development of techniques to use nuclear explosives for peaceful construction purposes. The phrase was coined in 1961, taken from Isaiah 2:3–5 ("And he shall judge among the nations, and shall rebuke many people: and they shall beat their swords into plowshares, and their spears into pruning hooks: nation shall not lift up sword against nation, neither shall they learn war any more"). It was the US portion of what are called Peaceful Nuclear Explosions (PNE).
There were many negative impacts from Project Plowshare’s 27 nuclear projects. Consequences included blighted land, relocated communities, tritium-contaminated water, radioactivity, and fallout from debris being hurled high into the atmosphere. These were ignored and downplayed until the program was terminated in 1977, due in large part to public opposition, after $770 million had been spent.Proposed uses included widening the Panama Canal, constructing a new sea-level waterway through Nicaragua nicknamed the Pan-Atomic Canal, cutting paths through mountainous areas for highways, and connecting inland river systems. Other proposals involved blasting underground caverns for water, natural gas, and petroleum storage. Serious consideration was also given to using these explosives for various mining operations. One proposal suggested using nuclear blasts to connect underground aquifers in Arizona. Another plan involved surface blasting on the western slope of California's Sacramento Valley for a water transport project.
Project Carryall, proposed in 1963 by the Atomic Energy Commission, the California Division of Highways (now Caltrans), and the Santa Fe Railway, would have used 22 nuclear explosions to excavate a massive roadcut through the Bristol Mountains in the Mojave Desert, to accommodate construction of Interstate 40 and a new rail line. At the end of the program, a major objective was to develop nuclear explosives, and blast techniques, for stimulating the flow of natural gas in "tight" underground reservoir formations. In the 1960s, a proposal was suggested for a modified in situ shale oil extraction process which involved creation of a rubble chimney (a zone in the oil shale formation created by breaking the rock into fragments) using a nuclear explosive.  However, this approach was abandoned for a number of technical reasons.

 I came across this bit of history in the book, The Big Roads.  Wow, what a crazy and terrible idea.