(1) Tepco estimates 1,000 tons of groundwater enters the area around reactors 1 to 4 at Fukushima No. 1 each day; 400 tons is believed to reach the reactor building basement levels.

(2) On Aug. 19, Tepco found 300 tons had leaked from a tank in this area. Of about 1,060 water tanks there, 350 are similar flange-type tanks, which are less durable than welded ones.

(3) Tepco believes a maximum of 300 tons of tainted water is seeping into the sea every day.

(4) Tepco plans to create a wall of frozen soil around the reactors by March 2015 to keep the groundwater out.