Workers at Japan’s Fukushima Daiichi nuclear plant are preparing to freeze the ground around the plant’s crippled reactors.

Efforts started today to build a wall of frozen soil to stop groundwater from mixing with contaminated water inside the reactor buildings.

Workers began digging holes where they’ll insert equipment to freeze the soil.

Tokyo Electric says it hopes to begin cooling the ground next March.

Officials say if the wall works, it will cut the flow of water into the plant by a factor of ten.