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Ploughshare scientists believe that if they are careful about atmospheric and wind conditions when shots are fired, shock waves in the air will do no serious damage, but scientists are not so sure about ground shock waves. If 50 megatons must be exploded to cut a hole in a mountain ridge, ground shock may shake down buildings many miles away. Luckily, at least three of the most promising canal routes go through almost uninhabited country, with little but jungle and a few huts to be damaged. Another possible danger is radioactivity that may seep up through the bottom of the canal. There is no way to estimate how much will do so, but the strong current that will run through the canal should carry most of it away.
The strongest point in the Ploughshare pitch is the low cost of nuclear digging. If employed on a very large scale, atoms are the world's cheapest workers, and they are getting cheaper year by year. Dr. Gerald W. Johnson, scientific director of Ploughshare, believes that a sea-level canal at the Sasardi-Morti route in eastern Panama could be completed, ready for use, for $500 million, using only 170 megatons of explosive. This is hardly more than the present Panama Canal cost when it was completed 50 years ago.