Soil disposal mound in Atami disaster was made of surplus from construction sites

An artificial mound of soil at the apparent starting point of a mudslide that hit Atami, Shizuoka Prefecture, on Saturday had been reported to the city government as surplus soil from construction sites, The Yomiuri Shimbun has learned.

Accidents involving the collapse of soil disposal sites have occurred across the nation, and thus the Atami city government, the Land, Infrastructure, Transport and Tourism Ministry and other concerned authorities will examine whether such a collapse was a causal factor in the mudslide disaster in the city.

According to the city government and other sources, the land at the starting point of the mudslide was purchased by a real estate company based in Kanagawa Prefecture.

In 2007, based on the Shizuoka prefectural government’s ordinance about rules on collecting soil, the company reported that soil would be brought into the site with the aim of disposing of it.

The ordinance states that municipal governments should take charge of administrative procedures, and the Atami city government confirmed the transportation of the soil into the site at the time.

The ordinance stipulates that the height of artificial mounds on slopes should be limited to 15 meters, primarily with the aim of preventing disasters.

The city government continues to examine whether the work conditions for constructing the mound were confirmed at the time.

Under the Law on Regulation of Residential Land Development, strict safety measures and municipal government inspections on the completion of residential land development work are required.

However, because the purpose of the work was not residential land development, the work at the site was not regulated by the law.

Soil from construction sites is regarded as a reusable resource. Unlike waste substances, there is no law that directly regulates how soil disposal should be handled.

There have been cases in which surplus soil was piled up in mountainous areas or used for landfill work.

According to the ministry, 14 accidents involving collapses of soil disposal sites occurred in 11 prefectures including Osaka and Yamanashi from 2001 to 2014. In one of them, a house was hit by the collapsing soil and one person died.

The Shizuoka prefectural government estimates that about 100,000 cubic meters of earth collapsed in Saturday’s disaster in Atami, including at least 50,000 cubic meters from the artificial mound.