"Bridge that can't be fixed" Japan's best Why in Niigata Prefecture?
When I looked it up, it was December 23rd at 19:16.
There are prefectures that have an outstanding number of bridges that cannot be repaired.
I realized this when I was covering the issue of aging infrastructure.
Analyzing the open data of more than 700,000 bridges, one tenth of all bridges were concentrated.
That prefecture is Niigata Prefecture.
Why?
I looked it up.
(NHK aging infrastructure coverage group)
*Details of the data are at the end of the article.
Data analysis of bridges Why is Niigata so popular?
"There are many in Niigata"
I noticed that at a glance of the data map.
This is a map that visualizes the inspection data of more than 700,000 road infrastructures nationwide, created to convey the problem of aging infrastructure.
Aging infrastructure Click here for a detailed analysis article on the whole country
The yellow dots are bridges that have not been repaired despite being deemed “need to take measures” due to aging (as of March 2022).
There are more than 32,000 of them nationwide.
A large area of Niigata Prefecture appears to be filled with yellow.
Its number 3168.
Analysis revealed that one-tenth of the country's population was concentrated in Niigata Prefecture.
Even by prefecture, the number is outstanding.
Are there many bridges in "agricultural prefectures"?
I started researching to find out why.
Looking at the data, there are more than 23,000 bridges in Niigata Prefecture.
It ranks ninth in the nation.
When I interviewed the person in charge of the local government about the reason, they said that the reason is that Niigata has a long coastline with many rivers flowing into it, and that it is an "agricultural prefecture".
I understand that "many rivers" = "many bridges", but in agricultural prefectures, will there be many bridges?
Arata Tanabe (79) answered this question.
He has long been involved in the maintenance of farmland as a staff member of the former Makimachi (now Nishikan Ward, Niigata City).
Mr. Tanabe says, "Bridges are indispensable for improving farmland."
In farmland, waterways are often arranged at the same time, and bridges are necessary.
And many small bridges were built.
During the 1970s and 1980s, when Mr. Tanabe was involved in farmland maintenance, he received requests from many farmers to build bridges.
Mr. Arata Tanabe `
`At the time, farmers were also making money and there were countless requests for projects to expand farmland. It was an era where 'making is the first thing', when things were becoming richer.
Looking at the years when bridges were built in Niigata, many bridges were built in the 1970s and 1980s.
A perishable environment?
The fight against "salt damage"
There are many bridges that cannot be fixed because there are many bridges.
Is that all?
The keyword "salt damage" came up when I searched for that question.
We headed for the Urahama Bridge along the coast in Nishikan Ward, Niigata City, in the snow.
It is a 60-meter-long bridge that was built nearly 50 years ago.
From a distance, it looked fine, but when I went under the bridge, I found here and there where the iron parts were blackened.
According to the city, in addition to deterioration over time, it is "rust" due to "salt".
Bridges near the coast, where there is a lot of salt coming in from the sea, deteriorate particularly quickly.
Influence of "anti-freezing agent"
And it turns out that this "salt damage" is another factor that is unique to Niigata, which is deep in the snow.
That is the "anti-freezing agent" that is sprinkled to prevent road freezing.
What do you mean?
"Anti-freezing agent", which is sprinkled when roads are expected to freeze due to snow accumulation, is actually mostly made of salt.
Niigata Prefecture is known as one of the most snowy regions in Japan.
I had repeatedly seen how the antifreeze was sprayed, and it was said that the "salt" contained in it was leading to the deterioration of the bridge.
Even if repaired once, "re-deterioration" ...
"Salt damage" was creating further problems.
One of the sites is the "Yukiyoshi Overpass" in Gangnam Ward.
When I went under the bridge, the melted snow on the road was dripping onto the concrete that formed the bridge.
This water contains a lot of antifreeze "salt", which causes "rust" in the reinforcing bars inside the concrete.
The rusty iron inside expands and appears as "cracks" on the surface.
Eiji Kosugi of the Niigata City Civil Engineering and General Affairs Division says that this bridge was actually just repaired seven years ago.
However, the place where I repaired it, cracked again.
This phenomenon is called “re-degradation”.
At this location, after cracks were confirmed, the concrete was removed, the rust on the internal reinforcing bars was removed, and new concrete was hardened for repair.
Construction was completed in 2015, seven years ago.
However, four years ago in 2018, a crack was found in the same place.
Eiji Kosugi, Civil Engineering General Affairs Division, Niigata City
"During repair work, we tried to prevent the rebar from rusting, but it deteriorated again. Once the rebar had rusted due to the salt content, it continued to rust even after the rust was removed. In the city, we have not confirmed this type of 're-deterioration' other than on this bridge, but I am concerned that it will occur on other bridges if the conditions are met."
Although the Urahama Ohashi and Yukiyoshi overpasses have been judged to be in need of repair at an early stage, Niigata City says there are no safety issues at this stage.
"I don't have the money to fix it"
In addition to deterioration over time, salt damage is one of the factors, and the deterioration of bridges progresses rapidly.
The situation can be seen from the settlement of accounts of Niigata City.
This is the "bridge maintenance cost" that indicates the cost of repairing and inspecting the bridge.
It has increased rapidly since around 2008, and has reached about 2 billion in the last three years.
The city estimates that the cost of repairing and inspecting the bridge will be at least 13 billion yen by fiscal 2028.
The amount is expected to increase further in the future.
The city has introduced its own inspection system and is working to cut costs, such as reducing inspection costs, which used to be 400 million yen, by 90%.
However, it is said that maintenance will become even more difficult in the future.
Mr. Eiji Kosugi, Civil Engineering General Affairs Division, Niigata City,
"The amount of 13 billion yen is a budget for repairing bridges that are currently known to be deteriorated, and there is a possibility that repair costs will increase further in the future. Prioritize the bridges to be repaired. We are working to reduce the cost of maintenance and inspections, but we feel that there is a limit.We are worried that it will be difficult to maintain and manage all the bridges, but we have no choice but to continue doing what we can.”
On the other hand, Mr. Hoyasu Kaneko, General Manager of the Civil Engineering Department of Niigata Prefecture, commented on the fact that there are many bridges that cannot be repaired in municipalities in Niigata Prefecture.
“The impact of salt damage is significant, and the budget is limited. I want to continue
"Influence of 'Kado-san'"
As I proceeded with the interview, I still had a question: Why does Niigata have so many bridges when there are many other "agricultural prefectures"?
I met someone who said that one of the factors was "politics."
Tadashi Takahashi (86), former member of the Niigata Prefectural Assembly.
Since he was first elected in 1974, he has served seven terms as a prefectural assembly member, and has successively held positions such as secretary-general of the Liberal Democratic Party's prefectural federation.
Mr. Takahashi looks back on the 1970s and 1980s, when bridges were being built one after another, as "an era of hope in politics."
Tadashi Takahashi, a former member of the Niigata Prefectural Assembly:
“At the time, Japan as a whole had momentum, and as the economy continued to grow, each region came to petition the bridge as if they were competing with each other to make their lives better. (Former Prime Minister Kakuei Tanaka, from Niigata Prefecture.) I think that Niigata Prefecture's residents and politics were close to each other, and many of the requests were met. It was an era when there was hope for people, and the number one goal was to build bridges and roads to make people's lives better."
Then, how do you see the current situation where the bridges built at that time are aging?
Tadashi Takahashi, former member of the Niigata Prefectural Assembly:
“Looking back now, it was important to think about the cost of maintenance, but one of the roles of politicians at the time was to prepare infrastructure, and people wanted that. The times have changed, and how to maintain the roads and bridges we built and how to protect people's livelihoods will be an important political issue in the future, and even though I've stepped back from the front line, I still have to think about it."
Expert "Consider downsizing as necessary"
How should maintenance be managed in the future?
We asked an expert.
Professor Tatsuhiko Saeki of Niigata University, who specializes in concrete engineering.
It is also necessary to change the way of thinking about social infrastructure, as the problems facing Niigata will become problems faced by more regions in the future.
Professor Tatsuhiko Saeki , Niigata University
: “Niigata is in a particularly difficult situation, but local governments across the country are facing the issue of aging infrastructure. Infrastructure is the foundation of society, and in order to maintain it, society as a whole needs to pay more attention to management.”
On top of that, we should use data such as "derailment" and proceed with "removal" of bridges as necessary.
Professor Tatsuhiko Saeki of Niigata University
“It is not realistic to maintain everything when considering the finances and manpower of the local government. We need to seriously consider how to size it in the future.”
Interview postscript
Yamada, a member of the interview team, has lived in Niigata Prefecture for over four years.
In my interviews so far, I have heard many times that "Niigata Prefecture has always fought against snow. Many people have worked to improve roads in order to eliminate people who cannot go to the hospital due to heavy snow."
On the other hand, I feel that there is no time to wait to deal with the reality that the infrastructure that has enriched our lives is now aging and has become an issue.
I would like to continue reporting on what we can do to protect the infrastructure that supports our lives.
Analysis result details
Based on the "National Road Facility Inspection Database" published by the Ministry of Land, Infrastructure, Transport and Tourism, NHK analyzed the status of measures as of March 2022 by road bridge location.
(not a number for each administrator)
1. By prefecture
・Number of
bridges The number of bridges is considered to be due to geographical factors such as the number of rivers, the extent of farmland and reclaimed land, in addition to the area of the prefecture.
Okayama prefecture had the most.
・Number of bridges in need of
repair Next is the number and percentage of bridges that were judged to require repair by inspection.
Hokkaido had the most.
・The number of bridges
that have not been repaired The number and percentage of bridges that have not been repaired as of March 2022.
Niigata prefecture had the most.
2. In Niigata Prefecture By municipality
We also summarized the repair status of bridges for each municipality in Niigata Prefecture.
The number is increasing in proportion to the size of the municipality.
3. When the bridge was built
Based on the data for the year in which the bridge was built, we analyzed the period in which new bridges were built.
The construction of bridges increased rapidly during the high economic growth period, peaking in the 1970s according to the data for which the year of construction is known.
After that, after the collapse of the bubble, the number of constructions will decrease greatly.
4. “Aging” Bridges 50 Years Old
It is the number of bridges that have passed 50 years since construction.
The construction of new bridges has decreased significantly in recent years, but on the other hand, the “aging” of bridges is a serious situation.
By 2037, it is expected to double from the current level of 2022.
(Interview)
Reporter
Hiroki Uchiyama Joined the Bureau
in 2011
After being in charge of disasters, he will be in charge of the Ministry of Land, Infrastructure, Transport and Tourism from 2021 Covering
housing issues and infrastructure measures
(Interview)
Niigata station reporter
Takeshi Yamada
Joined in 2018
Born in Kumamoto
Niigata Prefectural Government
Coverage on recovery from the Niigata Chuetsu Earthquake
(Analysis)
Reporter
Keijiro Saito
Joined in 2010 Taking
up the challenge of data analysis when raising children
Currently studying programming in addition to GIS
(Analysis)
Reporter, Network News Department
Eiji Akioka
After working at the News Bureau and the Otsu Bureau, he is currently
in charge of data analysis in the data visualization team "NMAPS".