Tokyo Electric Power Company has unveiled plans to construct an undersea tunnel to release more than one million tonnes of treated water from the Fukushima-Daiichi nuclear power station site into the Pacific Ocean.

Plans for the 1 km tunnel were announced after the Japanese government decided in April that it would go ahead with plans to release the accumulated water into the ocean in about two years’ time.

Tepco said it will start building the tunnel by March 2022 after carrying out feasibility studies and obtaining approval from authorities. It will have a diameter of about 2.5 metres and will stretch east into the Pacific from tanks at the plant containing around 1.27 million tonnes of treated water.