There is a water cellar, the street is still flooded
In order to reduce flooding in some areas of the city, in 2019 Hanoi Sewerage One Member Limited Liability Company (Water Drainage Company) proposed the City People’s Committee to deploy 3 locations of underground tanks to collect and regulate rain water. . The locations proposed by the Drainage Company are located in heavily flooded areas when it rains, including: Nguyen Khuyen Street, Thanh Duong Street and Ly Thuong Kiet – Phan Boi Chau Street junction. Up to now, after 3 years of implementation, as noted by reporter Tien Phong, only the underground rainwater collection tank in Nguyen Khuyen street has been built, the remaining 2 underground tanks are still on paper.
Flooding city and river in Hanoi
On June 3, present on Nguyen Khuyen street, reporter Tien Phong Note that the rainwater collection tunnel was built underground under the yard of Ly Thuong Kiet Secondary School. The underground tank has a reinforced concrete construction design, 34 m long, 9 m wide, 6.6 m deep, with a storage capacity of 2,000 m3. In the middle of the tunnel there is a reinforced concrete column to support the ceiling (school yard). The tunnel is operated in the form, when it rains and there is water floating on the road, the water collection manholes are located on Nguyen Khuyen street, the mouth has a protective iron net to collect water through the pipe to the tunnel. When rainwater on the sewer network has withdrawn, 3 pumps of the tunnel project with a capacity of 750 m3 of water/h will operate to pump water out.
Evaluation of the operation of the underground tank, Mr. Bui Ngoc Uyen, Deputy Head of the Department of Communication and External Relations, Hanoi Sewerage and Drainage Company, said that the underground tank was handed over to the company for management and operation from the end of 2021, through the end of 2021. some rains in late 2021 and early 2022, the station has been operating effectively when reducing the level of flooding on Nguyen Khuyen street by up to 70%.
For example, Mr. Uyen said that before, with rain up to 50mm, Nguyen Khuyen street was flooded, but now with such rainfall, there is no longer any flooding. When there is no underground tank, with rains from over 50-100mm, Nguyen Khuyen street will be flooded from about 0.5 to 0.7m, but now the level of flooding, if any, is only about 0.2 to 0.3. m.
In fact, reported by reporters, the first rain of this year on May 23, the area of Nguyen Khuyen street was flooded by 0.2 to 0.3m. By the second rain after that, this street was flooded to 0.5m. Thus, the underground tank at Nguyen Khuyen street is only responding to the average rainfall of less than 50mm. During the first two rains of the past month (with a flow rate of 180 – 300mm), the drainage system and underground tanks were overloaded.
Flooding due to the filling of lakes, ponds and rivers
Many urban experts, water supply and drainage experts believe that the construction of underground tunnels to prevent flooding only happens in cities that do not have many rivers and lakes, specifically Japan. In Hanoi in particular and Vietnam in general, the system of ponds and lakes is very numerous, the terrain is very favorable for building a natural flood drainage system and zoning for drainage. “But over the years, Hanoi city has not taken advantage of this terrain to implement drainage planning, instead focusing on building underground culverts, pumping stations located far away from rivers and then having to build canals. Meanwhile, rivers, ponds and lakes are being filled and narrowed,” said Assoc.
The location of building a water tank and a manhole to collect rain water is located at the gate of Ly Thuong Kiet Secondary School on Nguyen Khuyen Street, Hanoi.
In fact, reported by reporters, the first rain of this year on May 23, the area of Nguyen Khuyen street was flooded by 0.2 to 0.3m. By the second rain after that, this street was flooded to 0.5m. Thus, the underground tank at Nguyen Khuyen street is only responding to the average rainfall of less than 50mm. During the first two rains of the past month (with a flow rate of 180-300mm), the drainage system and underground tanks were overloaded.
Assoc. Prof. Dr. Tran Duc Ha said that an urban area will have a good natural drainage system when ponds, lakes and rivers account for 5% of the urban land fund. 20 years ago, Hanoi used to have a land fund for ponds, lakes and rivers up to 10%, but now the city has allowed high urbanization, so this land fund is only 2%.
Going against the plan?
Vice Chairman of the Vietnam Water Supply and Sewerage Association – Assoc. Prof. Dr. Ung Quoc Dung commented that Hanoi is building a drainage system that goes against the contents of the master plan approved by the Prime Minister. Specifically, building a pumping station must be associated with regulating lakes or making a conditioning reservoir for the pumping station.
According to Vice Chairman of the Vietnam Water Supply and Sewerage Association – Assoc. Prof. Dr. Ung Quoc Dung, currently the Yen Nghia, Dong Bong 1, Dong Bong 2 and Co Nhue pumping stations are built with a huge amount of money but are not operating efficiently due to There is no air conditioner. Meanwhile, the Prime Minister’s plan clearly states that, along with the construction of pumping stations in Hanoi, it is necessary to arrange a conditioning reservoir for the pumping stations.
Because the conditioning reservoir at the pumping station will meet two goals, both ensuring the landscape, a mild climate, and regulating flood water and collecting water for the pumping station. When preparing for rain, the pumping stations will work to lower the water level at the lake, when it rains, the conditioning reservoir will receive all the rainwater pouring down quickly, then if it’s full, the pump will work to pump it out. .
According to Mr. Dung, currently the pumping stations Yen Nghia, Dong Bong 1, Dong Bong 2 and Co Nhue were built with a huge amount of money but operate inefficiently due to the lack of a conditioning reservoir. Meanwhile, the Prime Minister’s plan stated that, along with the construction of pumping stations in Hanoi city, it is necessary to arrange a conditioning reservoir for these pumping stations.
at Blogtuan.info – Source: Soha.vn – Read the original article here