Minister of Land, Infrastructure, Transport and Tourism Inspects Sewerage Construction Site / Tokyo’s Dual-Pipeline Project Aims to Reduce Functional Shutdown Risks
December 23, 2025 – Government & Organizations
Japan’s Minister of Land, Infrastructure, Transport and Tourism, Yasuyuki Kaneko, together with Vice-Minister Osamu Sasaki, inspected a sewerage construction site adjacent to the Shibaura Water Reclamation Center in Minato Ward, Tokyo, on December 20. The project involves constructing a new sewer pipeline using the shield tunneling method. By creating a dual-route system in combination with existing pipelines, the project aims to reduce the risk of sewer flow disruption in the event of an emergency.
Minister Kaneko and his delegation descended to a vertical shaft reaching a depth of 64 meters, where they received an explanation of the facility from officials of the Tokyo Metropolitan Government, the project owner. After the inspection, Minister Kaneko commented, “I hope sewerage operators across Japan will take this project as a reference.”
Tokyo is currently working on the construction of a new sewer pipeline known as the “Chiyoda Trunk Line.” Once completed, wastewater from multiple existing pipelines will be consolidated into this new trunk line. The existing pipelines, with reduced flow volumes, will be rehabilitated using methods such as the SPR technique, which involves lining the interior with band-shaped PVC materials to address aging infrastructure.
The Chiyoda Trunk Line is an underground tunnel approximately 8.7 kilometers long, connecting the area near Iidabashi Station in Chiyoda Ward to the Shibaura Water Reclamation Center. In terms of construction length per section, it is considered the longest sewer shield tunneling project in Japan.
The tunnel has an internal diameter of 4.9 meters and was excavated while avoiding 12 subway lines. To allow for gravity flow, a gradient of 0.5 millimeters per meter was applied. Construction was carried out by a joint venture between Okumura Corporation and Taiho Construction. The tunnel excavation has been completed, and the next phase will involve the installation of six intake manholes.
In January, a road collapse accident in Yashio City, Saitama Prefecture, forced approximately 1.2 million people to restrict sewer usage for about three weeks. In response to the incident, an expert panel established by MLIT released new recommendations on December 1, highlighting the importance of ensuring redundancy in sewer pipelines, strengthening inspection and survey efforts, and improving coordination between sewerage authorities and road administrators.
Following the site visit, Minister Kaneko stated, “In everyday life, we rarely consider the possibility of being unable to use toilets. However, when it happens, the impact is significant. Preparation is extremely important. I strongly encourage sewerage operators nationwide to conduct thorough investigations.”
Regarding funding, Minister Kaneko added, “Measures to address the aging of sewerage infrastructure are included in the First Mid-Term Implementation Plan for National Resilience. We must make effective use of the allocated budget to steadily advance these initiatives.”
