Operators of Japan’s crippled power plant say they will release more than 10,000 tons of contaminated water into the ocean to make room in their storage tanks for water that is even more radioactive.

Chief Cabinet Secretary Yukio Edano confirmed the plan at a press conference Monday, saying the step is “unavoidable” to ensure safety. He said the water to be released is much less radioactive than the water that will be pumped into the storage tanks, mainly from the Fukushima plant’s number two reactor.