Illustration:
When hot water is poured on frozen ground, the ground is defrosted but it also becomes muddy.
The mud can be prevented. If the frozen ground is surrounded by a low, waterproof fence and cold water is poured in, the water freezes. As the water changes to ice, heat is given off and the ground is warmed. A day or two later, the ice layer can be removed with an excavating machine and the unfrozen ground can be easily worked. Inclined, as well as level sites can be defrosted by this technique.