Retake Zhengzhou Metro Line 5: Jishui District was on the “black list” ten years ago

Retake Zhengzhou Metro Line 5: Jishui District was on the "black list" ten years ago

“The roads are getting wider and wider, but getting into the water is getting harder and harder.” On July 23, 2021, Huang Bo, a citizen of Zhengzhou , looked at the pump when he passed the Wulongkou Parking Lot (hereinafter referred to as Wulongkou Parking Lot) of Metro Line 5 on July 23, 2021. The flood that the pipe keeps spitting out is so emotional.

On July 20, the Zhengzhou Metro Line 5 was forced to stop by floods, and more than 500 people were trapped. At least 12 people have been killed. The official report on the cause of the accident stated that on July 20, Zhengzhou City had a rare and extremely heavy rain, causing serious water accumulation in the Wulongkou parking lot of Zhengzhou Metro Line 5 and its surrounding areas. At about 18 o’clock, the stagnant water smashed the retaining wall of the entrance and exit line into the main line section, causing the first train of Zhengzhou Metro Line 5 to be forced to stop.

An investigation by Jiemian News shows that the occurrence of water accumulation in Wulongkou parking lot and surrounding areas is not accidental. Ten years ago, this area was already a “famous” water accumulation area, and it has improved after treatment. However, before the onset of the heavy rain, a cement cover of tens of meters was added to the drainage ditch more than 20 meters away from the Wulongkou parking lot, which caused poor flood discharge, or the cause of the accumulation of water in the subway tunnel. one.

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Huang Bo feels that flooding into Metro Line 5 may not be completely inevitable.

At about 17:00 on July 20, the stagnant water brought by the heavy rain had almost reached his knees, but Huang Bo decided to walk home from the company near the Wulongkou parking lot. He has lived in this area for nearly 40 years and is familiar with the roads and terrain here. He walked south along Lantian Road, and when he reached the first intersection, he turned to Songshan North Road.

“It’s not stagnant water. I can see the water flowing northward (in the direction of Wulongkou parking lot) with my naked eyes .” Huang Bo said. He walked in the direction of the incoming water, feeling that the water was getting deeper and deeper and the resistance encountered by his body was getting bigger and bigger. Although the Wulongkou parking lot has a low terrain, he was a little surprised by the speed of the flood.

From the company to the first crossroad less than 1,000 meters, Huang Bo walked for more than half an hour. This is an east-inclined crossroad. The four roads radiating from it have four names due to different construction times. They are Songshan North Road facing east, Wulongkou South Road facing west, and Tongbai North Road facing south. And the blue sky road facing north. Arriving at the crossroads, Huang Bo was surprised to find that the accumulated water on the other three roads all rushed to Lantian Road, heading north toward the Wulongkou parking lot.

Retake Zhengzhou Metro Line 5: Jishui District was on the "black list" ten years ago

The water from the three roads converges to Lantian Road and flows to the low-lying part of Wulongkou parking lot via Lantian Road. (The red arrow is the direction of water flow)

Huang Bo is 1.75 meters tall, and the flood has already submerged his waist at this time. He didn’t dare to wade through the water to move on, and chose to retreat to the company. He walked back carefully along the current.

At about the same time, Wang Chao, a worker near the parking lot of Line 5, came out of the work shed to check whether his car was flooded. He saw that the stagnant water on the environmental protection road in front of the Wulongkou parking lot office area was flowing in the direction of Lantian Road; not only that, the stagnant water in the northern section of Lantian Road was also flowing south. Floods from three directions rushed to the intersection of Lantian Road and Environmental Road. This is where the Wulongkou parking lot of Metro Line 5 faces the road side wall.

Retake Zhengzhou Metro Line 5: Jishui District was on the "black list" ten years ago

The water coming from Lantian Road arrives at the Wulongkou parking lot, where it merges with the water coming from the other two directions.

Wang Chao noticed that across the Lantian Road, a yellow plastic baffle was erected on the opposite side of the Wulongkou parking lot. Behind the baffle is a small river, but the flood cannot pass the baffle for a while, and it accumulates higher and higher in this area. Wang Chao had never seen such a flood before and hurried back to the work shed. It didn’t take long for him to hear “a sound like a waterfall falling”. This bursting sound continued for a while and turned into a steady sound of falling water.

As Huang Bo walked back, he felt that the flood was on a downward trend. He waited until he walked back to the Wulongkou parking lot, only to discover the whole story: the wall on the side of the Wulongkou parking lot near Lantian Road was washed away, and the flood leaned down like a dam and entered the subway tens of meters deep. In the parking lot.

Afterwards, Zhengzhou officials reported that on July 20, Zhengzhou City had a rare and extremely heavy rain, causing serious water accumulation in the Wulongkou parking lot of Zhengzhou Metro Line 5 and its surrounding areas. At 18:00, the stagnant water broke the retaining wall of the entry line and entered the main line section, causing a train of Zhengzhou Metro Line 5 to stop in the section between Shakou Road Station and Haitansi Station, and more than 500 passengers were trapped.

Zhengzhou Metro Line 5 started construction in December 2014 and opened to traffic on May 20, 2019. This line is a loop line, with a total of 32 stations, 1 depot and 1 parking lot-Wulongkou Parking Lot. It is the busiest line in Zhengzhou Metro.

The subway parking lot is mainly responsible for the inspection and cleaning of subway trains. The train passes through the entrance and exit lines and enters the main line. This is also the route through which flood water enters the subway car tunnel. Although the Wulongkou parking lot is a ground parking lot, there is still a few meters of height difference between the train parking area and the ground. On the periphery of the parking lot, there is a brick structure with a base and a steel tube wall above it.

A tender information for the parking lot published in 2017 shows that the Wulongkou parking lot is in the shape of a knife handle, with a length of about 900m from east to west and a width of about 220m from north to south. The total planned area of ​​the parking lot is about 18.3 hectares, of which the subway area is about 11.3 hectares.

At this time, Huang Bo noticed that on the opposite side of the wall of the parking lot of Metro Line 5 that was washed out, some gaps were also opened in the yellow building baffle, but on the other side of the gap, the flood did not drain into the river smoothly. Instead, it stays on a section of the river course that is tens of meters long.

He believes that torrential rain is not the entire cause of the disaster. “The torrential rain is very heavy, but if the drainage ditches can work, it will not necessarily flood the subway.”

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On July 23, Jiemian reporters came to the Wulongkou parking lot of Metro Line 5. The area that was washed out seemed to have opened a gap. The fence and steel fence fell into the parking lot with messy garbage hanging on it. Several pumps are working, draining water to the road a few meters away. The discharged water does not flow apart, but is deposited here and enters the underground pipeline through the strainer. “Everyone knows that the terrain is the lowest here.” Huang Bo said.

On the opposite side of Lantian Road, more than 20 meters away is a small river named Wulongkou Minggou, which flows from south to north. Huang Bo said that when the Lantian Road was not built, Wulongkou Minggou belonged to the Minghe River, and nearby villagers often set up slab houses to do business along the river. Later, Lantian Road passed through the small river, and a section of the small river became an underground river.

Retake Zhengzhou Metro Line 5: Jishui District was on the "black list" ten years ago

There is a 20-meter-wide Lantian Road between the edge of the parking lot of Line 5 and Wulongkou Minggou, but the Wulongkou Minggou is covered with a cover.

The natural landform of Zhengzhou is high in the southwest and low in the northeast, with a natural slope of 3.4‰, and the natural height difference between the west and east of the city is more than 30 meters. Wulongkou Parking Lot is located in the northwest of Zhengzhou City, between the Second Ring Road and the Third Ring Road. Relative to the entire city, the terrain here is not low, but in the Wulongkou area, this is a well-known depression. Standing near the washed-out wall of the subway parking lot, you can see by visual inspection that the road pavement in three directions is obviously higher than here.

The problem of stagnant water near Wulongkou has been around for a long time. As early as 2009, a person in charge of the Zhengzhou municipal department introduced in an official document that the roads of Funiu Road, Tongbai Road and other road sections are mainly drained to the Wulongkou Minggou and discharged into the urban area through the Wulongkou Minggou. However, before the stagnant water in these sections enters Wulongkou Minggou, it needs to “climb” a high slope of 80 cm to enter the river.

In July 2010, Zhengzhou City was hit by heavy rains and a large amount of roads were flooded. The citizens complained. In this context, the Zhengzhou Municipal Government has sorted out 62 stagnant water spots in the city, and the responsible persons of multiple units have subcontracted to transform them within a limited time. According to the materials seen by Jiemian reporters, the water accumulation problem in Minggou area of ​​Wulongkou is “a place on the list.”

After this renovation and subsequent dredging, the drainage function of the Wulongkou open ditch has been improved, and the water accumulation problem in the vicinity has been relieved to a certain extent. Huang Bo remembers that about 3 years ago, Zhengzhou also encountered a heavy rain. At that time, the accumulation of water in the vicinity was almost to the knees, but the excessive accumulation of water eventually flowed into the Wulongkou Minggou without serious damage.

Many nearby citizens said that this small river has decades of history. Later, when the Wulongkou sewage treatment plant was built nearby, the small river became a drainage river for the plant. After the construction of Lantian Road, a small river flows out from under the road, and the river can be seen standing on the sidewalk on the side of the road. In the event of heavy rain, the excessive stagnant water crosses the roadbed and drains directly into the Wulongkou Minggou. It flows for about 5 kilometers and flows into the famous Jialu River in Zhengzhou and finally into the Huai River.

Jiemian News reporter noticed that the height of the base of the brick wall of the Wulongkou parking lot was significantly higher than the entrance of the Minggou Wulongkou on the opposite side of the road. This means that when the flood reaches this area, it should first overflow into the Wulongkou open ditch and be discharged under normal circumstances.

A number of nearby citizens said that about a few months ago, the river section here was covered with a cement cover, and the original open ditch was turned into a culvert, which caused the excessive drainage of water to be unsmooth. Jiemian reporters saw on the scene that the cover plate was about 8 meters wide and nearly 50 meters long. It was spliced ​​by a single white reinforced concrete beam. A large amount of domestic garbage shed in the gap between the two cover plates.

Retake Zhengzhou Metro Line 5: Jishui District was on the "black list" ten years ago

The cover plate turns the open ditch into a culvert. Photography: Zhao Meng

Several excavators were parked by the small river. The yellow baffles had been disassembled, some were squashed, and some of the mounds on the side were shoveled away. From the sidewalk into the upper cover, to the end, you can see the whole picture of Wulongkou Minggou. The river is about ten meters wide and five or six meters deep. There are a lot of weeds and garbage scattered on both sides of the river. Wastewater flows out of the river channel under the cover, exuding a foul smell.

There are long precedents due to poor flood discharge after the river is covered with slabs. On July 18, 2007, Jinan was hit by a super heavy rain, and many covered sheds were congested. Flood drainage was not smooth, causing a lot of losses to the lives of citizens. Later, Jinan took this as an opportunity to demolish some of the buildings covered by the shed.

On July 23, a staff member of Shifo Sub-district Office of Zhengzhou High-tech Zone responded to the interface news that Wulongkou Minggou was managed and protected by the office. Due to the height difference between the river and Lantian Road, there was a safety hazard, so there was an increase in the river. The cover plate, which will be developed into a green belt, “is approved by the municipal government and the (High-tech Zone) Management Committee.” Regarding the impact of increasing the cover plate on flood discharge, she said that “this situation should have been considered.”

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After the disaster, Zhengzhou officials notified the public that from 20:00 on July 17 to 20:20 on July 20, the rainfall in the course of three days was 617.1mm. Among them, hourly precipitation and single-day precipitation have broken through the historical record of 60 years since Zhengzhou was established in 1951. The average annual rainfall in Zhengzhou is 640.8mm, which is equivalent to the previous year’s rainfall in these three days. At the same time, talks about the rainstorm “once in a hundred years” and “once in a thousand years” began to spread.

On July 21, Chen Tao, the chief forecaster of the Central Meteorological Observatory, introduced that from the perspective of atmospheric science research, China formed a rigorously recorded meteorological record only after 1950, when there was a relatively accurate and complete scientific record of rainfall. . Up to now, the entire rainfall record has been around 70 years. He said that the so-called “once in a hundred years” and “once in a millennium” are “difficult to talk about this issue” until there is currently no reliable, long-term, and effective rainfall record.

Public information shows that, on July 19, @郑天气 released multiple pieces of information about heavy rainfall in the area. At 12:28 on July 19, the Zhengzhou Meteorological Observatory issued a yellow warning signal of heavy rain. The nowcasts issued at 13:00, 14:00, 14:28, 16:00, 18:00, and 18:13 on the same day are still rainstorm yellow warning, or rainstorm yellow, thunder yellow warning.

At 19:13 that day, the Zhengzhou City Meteorological Observatory issued the first orange warning signal of the rainstorm. At 21:59, the Zhengzhou Meteorological Observatory issued the first red warning signal of rainstorm in this round. At 06:02 on July 20, the station once again issued a red warning signal for heavy rain. On the same day, the Zhengzhou Meteorological Observatory issued a total of 10 red warnings of heavy rain.

The rainstorm warning signal is divided into four levels: blue, yellow, orange, and red. In mainland China, the red rainstorm warning signal is the highest level. The corresponding defense guidelines include: the government and relevant departments do a good job in anti-storm emergency and rescue work in accordance with their responsibilities; stop gatherings, suspension of classes, and business suspension (except for special industries) ; do a good job in defense and rescue work against disasters such as mountain torrents, landslides, and mudslides, etc. .

On July 23, Jiemian News reporter interviewed a number of surrounding citizens along the spillway of Changzhuang Reservoir in Zhengzhou City. Many people said that they had not received reminders of work suspension, class suspension, evacuation, etc. before the occurrence of the flooding, and many people were still as usual. Commute.

Retake Zhengzhou Metro Line 5: Jishui District was on the "black list" ten years ago

The scene of a washed-out subway parking lot. Photography: Zhao Meng

A person from the meteorological department introduced to Jiemian News that it is rare to issue nearly 10 red warnings of heavy rain in one day, and emergency management departments should pay enough attention.

According to the requirements of the “Emergency Plan for Urban Flood Control in Zhengzhou”, before the flood season, you should be responsible for inspecting district-managed roads and bridges; dredging open ditches and rainwater harvesting wells in the jurisdiction; timely cleaning up water blocking objects such as branches and leaves on the grate of the harvesting well; managing roads in the district Control and disposal of stagnant water areas. Rivers and municipal departments should open the drainage gates of river channels and open ditches in advance according to the rainfall conditions and when there is a three-level warning or more, lower the various dams of the river channels, and strictly monitor them.

However, the workers said that they had been working here more than 20 days before the rainstorm, and no personnel from relevant departments came to check the drainage of the river.

On July 24, Jiemian reporters came to the Wulongkou parking lot again. The gap opened by the flood was blocked, but the messy scene in the parking lot was still there. On the Wulongkou Minggou on the opposite side of the road, many workers are working. Except for some building baffles that have been removed, the cover on the river has been covered with a layer of green cloth. The workers said that concrete will be put on the cover next, “no one asked us to stop.”

Posted by:CoinYuppie,Reprinted with attribution to:https://coinyuppie.com/retake-zhengzhou-metro-line-5-jishui-district-was-on-the-black-list-ten-years-ago/
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