The International Atomic Energy Agency has agreed to monitor the release of radioactive water from the Fukushima nuclear power plant into the ocean under an agreement announced on Aug. 25. Tokyo Electric Power Company Holdings plans to build a concrete undersea tunnel to hold a pipeline carrying treated but still radioactive water from the plant, damaged by a 2011 earthquake and tsunami. It will be discharged at a depth of about 40 feet below the ocean’s surface in an effort to minimize its impact on marine life off the coast and avoid interference with local fishing.