Typhoon No. 19 two months disposal of a large amount of mud “Sealess Prefecture” Nagano's suffering December 12 21:19
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In Nagano City, where the Chikuma River embankment broke down due to the heavy rain of Typhoon No. 19, the removal of disaster waste and mud that had settled on the farmland is progressing, but the work is not expected to end, There are concerns about the future impact on agriculture. In addition, a problem unique to Nagano Prefecture where “the mud” should be disposed of has emerged.
A large amount of “mud” apple farmers…
Agricultural lands in Nagano City, where the Chikuma River embankment broke down due to the typhoon No. 19 disaster, and the surrounding farmland were filled with disaster waste such as furniture and a large amount of mud. It was.
On the 12th, two months after the disaster, volunteers gathered from inside and outside the prefecture picked up the fallen fruit to prepare for the removal of the mud from the apple fields.
According to JA, more than 5600 volunteers have participated in farmland so far, and in this area, removal of disaster waste and mud at the base of apple trees that have to be done manually is almost complete. It means that.
However, a large amount of mud still remains in a wide area of farmland, and in the future, the city etc. decides to remove it using heavy machinery, but the work is not expected to end, the future There are concerns about the impact on agriculture.
An apple farmer man said, “Volunteers helped me with the work, but now I am worried that I can start farming next year”
140,000 units of “mud” that flowed into disposal
On the ground along the Chikuma River in Yashima, Nagano City, which is a temporary storage area, we started accepting mud transported from the farmland in the city on the 10th, and on the 12th we started processing to mix the chemicals and remove moisture.
According to Nagano City, in Hoho and its surroundings, where the bank of the Chikuma River broke down, the amount of farmland such as apple fields and rice fields was 800,000 cubic meters. A lot of mud flowed.
The city and volunteers are removing mud from the fields, but there is no place to dispose of the removed mud, which is a major issue. According to the city, as a result of giving priority to the disposal of mud that flowed into houses and establishments, no contractor that can accept mud in farmland was found, and the only ground that could be secured as a temporary storage place is difficult to handle all mud in farmland That is.
The mud left along the river may flow out if heavy rains occur again, and the crops mixed in may rot and smell, which may affect the lives of neighboring residents.
Masanori Matsumoto section chief of the Nagano forest farmland Maintenance Division is you want to process quickly from the effects of the "safety and civic life, location and usage is limited, the prospect of disposal is not standing. Will continue to promote the coordination with relevant agencies ”
The circumstances unique to Nagano Prefecture where there is no sea
There are circumstances unique to Nagano Prefecture that make it difficult to dispose of the mud that flows into the farmland.
Disposal has been promoted by using a large amount of mud that has flowed out for land reclamation and land raising in areas affected by past heavy rain disasters, such as Hiroshima Prefecture, which suffered significant damage from the heavy rains of West Japan last year. However, Nagano Prefecture has no sea and cannot be used for landfill.
In addition, according to Nagano City, private companies entrusted by the city to use for raising the land were chased by the treatment of mud that flowed into houses and establishments, and no company that could accept mud from farmland was found. is.
In addition, it is difficult to secure a temporary storage area because the land is surrounded by mountains and the land is limited. For this reason, the city expected to be used for the restoration work of the embankment that had broken down as a powerful disposal method, but when the country investigated the components of the mud, the sand particles were fine, 0 points 075 mm or less, grass and It turned out that it contains a large amount of impurities such as plant roots and algae.
According to the country, if the sand particles are fine, they are easy to dissolve in water, and if there are many impurities, they may cause sinking or cracking, so it is not safe in terms of strength and durability and can not be used for dikes. .
According to geotechnical specialists, the place where the Chikuma River broke down was gentle and the environment was likely to accumulate grass and algae.
“The mud is not suitable for levee materials because the Chikugawa River Office of the Ministry of Land, Infrastructure, Transport and Tourism's Chikumagawa River Office,” says the city. ”
Expert: “Cannot be used for grass and other dikes, for new challenges”
Takashi Tsuchida, Director of the Disaster Prevention and Mitigation Research Center at Hiroshima University, who specializes in geotechnical engineering and is involved in the verification of heavy rain in western Japan, said “ Since the river was narrow and rapid, there were few cases where organic matter was accumulated at the bottom of the river.The Chikuma River is a very large river that flows slowly through the plains, so that decayed grass etc. is piled up at the bottom of the river, and it flows out This mud cannot be used for construction materials such as dikes because it will break down into microorganisms and form cavities over time. "
On top of that, regarding the problem of mud treatment, “I used to do landfilling at most ports, but now it is not just a problem for inland Nagano because demand is decreasing. First-class rivers are flooded to such a large scale. There have not been many cases so far, but it is an important new problem that mud containing organic matter carried by the river flows into a large volume and is difficult to dispose of it. It will be a new technical issue or how to use it. "