FUKUSHIMA — Tokyo Electric Power Company Holdings held a press viewing of the construction site of an underwater tunnel leading to the ocean for discharging treated water from the Fukushima No. 1 nuclear power plant in Fukushima Prefecture.

The treated water is to be piped to an offshore discharge site through the tunnel, which is about 1 kilometer long.

On the seaward side of reactor Nos. 5 and 6, there is a shaft about 18 meters deep that leads to a tunnel with a diameter of 3.1 meters that extends toward the sea.

The walls of the tunnel are covered with reinforced concrete to prevent leakage.

A shield machine with many pipes and cables has been used to dig about 80 meters since Aug. 4.

A worker was monitoring the excavation amid the loud sound of the motor.

"Once the tunnel is excavated to 150 meters, the pace of excavation will be several times faster from that point forward," said a TEPCO official. "We'll proceed with safety as our top priority."

The excavation is proceeding smoothly, but rough seas have prevented the installation of the discharge port at the end of the tunnel, which was scheduled to be done in August.

The ocean is expected to be even rougher in the winter. The failure to install the outlet before then could delay the construction work and possibly push back the start of water discharge, which is scheduled for the spring, to around summer.