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Since the accident, highly contaminated water has been accumulating inside the seawater piping trench; a underground tunnel originally designed to store pipes and cables, connected to the seaside of Unit 2 to Unit 4 turbine buildings. TEPCO has been trying to reduce the risks of soil/ocean contamination by removing this accumulated water and filling the inside of trench. Considering the conditions or the quality/quantity of water contained in the tunnels or vertical shafts of the trench, the contaminated water is carefully transferred to the turbine buildings. The inside of trench is also filled with materials selected considering the individual structure or length, combining several materials where needed.

Please refer to the following materials for more details since the structure of the seawater piping trench differs for each unit.

Progress of Seawater Piping Trench Measures
(as of March 2017)

Progress of Contaminated Water Removal: 100%

Unit 2 Unit 3 Unit 4
Conditions
  • Tunnel filling: Completed on December 18, 2014
  • Vertical shaft filling: Completed on March 9, 2017
  • Transfer of water retained in trench: Completed on June 30, 2015
  • Tunnel filling: Completed on April 8, 2015
  • Vertical shaft filling: Completed on Aug. 27, 2015 (except upper part of vertical shaft D)
  • Transfer of water retained in trench: Completed on July 30, 2015
  • Tunnel filling: Completed on March 21, 2015
  • Filling of openings II and III: Completed on April 28, 2015
  • Transfer of water retained in trench: Completed on December 11, 2015
  • Tunnel above water discharge channels: Completed on December 21, 2015
Amount of
remaining
retained water
0 m³ 0 m³ 0 m³
Filling amount Approx. 4,910 m³ Approx. 5,980 m³ Approx. 780 m³

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