Photo/Illutration A sinkhole that formed on a road construction workers were tunneling under in October 2020 in Tokyo’s Chofu city (Asahi Shimbun file photo)

The Tokyo District Court is ordering a partial halt to the construction of an underground tunnel, which caused a large sinkhole to form in Chofu city, because it poses a danger to nearby residents.

Construction workers have been using heavy equipment called a shield machine to bore a 16-kilometer underground tunnel, which will stretch from underneath the Kan-etsu Expressway’s Oizumi Junction to the Tomei Expressway, for the Tokyo outer ring road. 

The project is meant to alleviate chronic congestion in the capital.

The court issued an injunction on Feb. 28 ordering the transport ministry, East Nippon Expressway Co., and other parties to stop the excavation work on a 9-km segment of the tunnel that stretches from the Tomei Junction in Tokyo’s Setagaya Ward to the area near Musashino city, which includes the part of the road that caved in.

“Even if we take into consideration the benefit the construction work would bring to the public, such as mitigating traffic congestion, the illegality of the work (on the 9-km segment) justifies the ban,” the ruling stated.

In May 2020, 13 residents living in the area where the construction work was taking place filed for a provisional order by the court to stop the drilling work, arguing that it would destabilize the ground.

Then, in October 2020, a cave-in occurred on a portion of a road in Chofu where the construction work was being done, creating a huge sinkhole about 3 meters long and around 5 meters wide. The excavation work was then suspended.

Mari Mokudai, a presiding judge, ruled that there is a risk of a dangerous repeat if the work resumes because the land that one of the plaintiffs lives on is in the same condition as the land that caved in.

“Another cave-in would completely disrupt the plaintiff’s daily life by making their house collapse and putting their body and life at risk,” she said in the ruling.

The construction operators maintained throughout the trial that another cave-in would not occur because they would take countermeasures, such as strengthening the ground.

However, the judge dismissed this argument, saying that no detailed measures to prevent a recurrence were produced.

A lawyer for the plaintiffs hailed the ruling as a landmark decision, but said it still falls short because it did not ban all further construction work in the project.

The operators resumed the excavation work on Feb. 25 in a different area than where the court ban applies.

One of the plaintiffs, Shigetake Maruyama, 80, said at a news conference after the ruling that the project should be re-examined in light of safety.

“I urge the operators to stop all the construction work and review the risk,” he said.

Following the ruling, the transport ministry and East Nippon Expressway commented, “We would like to deal with the issue appropriately.”

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