On January 22, information from the Ministry of Transport said that this agency has just issued a document responding to a petition from voters in Ba Ria - Vung Tau province reflecting on the flooding of the Phan Thiet - Dau Giay expressway.
“The Phan Thiet - Dau Giay Expressway is flooded, this proves the weakness of the design consulting company and the design appraisal level of the appraisal agency and the project investor. Voters request that the authorities let them know who is responsible for the flooding of the Phan Thiet - Dau Giay Expressway, which agency? How to handle the responsibility?”, voters reflected.
Regarding the above-mentioned voters' petition, the Ministry of Transport said that the Phan Thiet - Dau Giay expressway project was assigned by the Ministry of Transport to the Thang Long Project Management Board as the investor, and the main route was put into operation in May 2023, meeting the travel needs of people and contributing to promoting the socio-economic development of localities in the region. Since its operation, the expressway has basically met quality standards.
At 4:30 a.m. on July 29, 2023, the project area experienced prolonged heavy rain, causing localized flooding at the section Km25+369 - Km25+469. Immediately after receiving the information, the Ministry of Transport issued a document requesting the investor to be present at the scene with construction and operation units to coordinate with the police force and local authorities to regulate traffic to National Highway 1A, arrange specialized vehicles to rescue affected vehicles, guide and operate to ensure traffic; by 6:30 a.m. on the same day, the water receded and vehicles were able to circulate normally.
To determine the cause, responsibility and propose solutions in an objective, scientific and careful manner, the Ministry of Transport has assigned specialized agencies to review survey and design documents; on August 2 and 3, 2023, the Ministry of Transport sent a working group including specialized agencies, consulting units, contractors, and experienced hydrologists to organize field inspections, assess in detail the terrain and hydrological conditions upstream and downstream of the flooded area, and review survey and design documents.
Based on the investor's report, the results of the actual inspection, review and assessment by experts show that the construction process and units have followed the approved design documents, ensuring quality requirements.
Regarding the culvert aperture at the flooded location: the design consultant has conducted a survey of the water level and calculated the culvert aperture. The results of reviewing the basin and input parameters show that the culvert was designed to meet the drainage requirements of the upstream natural basin. At the time of the flood, although the rainfall had not yet reached the calculated frequency, the height was higher than the historical flood peak, which is an unusual factor that needs to be studied and clarified.
Regarding the cause of flooding: the section is located close to the Phan River, upstream there is the Phan River dam about 8.6km from the flooded location. In general, after being put into operation, the downstream of the dams, the riverbed and streams all change, sediment, and invasive vegetation increases the roughness and narrows the flow, leading to a very complex hydrological regime, causing local congestion, causing the water level in the culvert area to rise, causing flooding.
Regarding responsibility: this is a new route, at the time of the survey, the area the route passes through was sparsely populated, the investigation of hydrological data was difficult, the consultant had not fully anticipated the narrowing of the flow downstream of the culvert leading to stagnation, so the hydrological calculation file determined the design elevation at a frequency of 1% at the culvert location without considering the stagnation water level. The responsibility belongs to the consulting unit although it was not an intentional error.
The Ministry of Transport has requested the investor to urgently coordinate with the locality to organize the clearance of riverbed obstacles from the culvert location to the downstream of the Phan River bridge to increase drainage capacity and lower the water level on the Phan River, reducing the impact of water on the construction area; clarify the responsibilities of the units to handle according to the provisions of the contract, including the costs of remedying the errors of the relevant parties.
Implementing the direction of the Ministry of Transport, up to now, the investor has organized the clearance of riverbed obstacles (without using project capital), at the same time, the independent consulting unit is conducting surveys, calculations, and mathematical modeling for the entire area, thereby determining the water level corresponding to the design frequency of the project, as a basis for proposing a thorough treatment plan (if necessary). After the independent consultant has reported the results, the investor will organize an assessment, review the responsibility of the relevant collective and individuals and handle it according to regulations.
TM
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