The Thao Long saltwater prevention and freshwater retention dam project located on the downstream of the Huong River (Hue City) started construction in August 2001 and was basically completed and put into operation in June 2006, with a total investment of 151 billion VND.
The scale of the project includes a saltwater prevention sluice designed with a water opening of 480.5m, including 15 compartments, each compartment is 31.5m wide and a boat lock compartment. The traffic bridge is designed with a 10m wide bridge deck. The lower shaft valve gate is made of CT3 steel, the valve gate opening and closing is done by a hydraulic cylinder system.
Since its inauguration, the project has played its main role in preventing salinity and keeping fresh water for the Huong and Bo River systems, ensuring adequate water supply for agricultural, industrial and residential production in the province. At the same time, it has contributed to improving the ecological environment and tourist landscape in the Huong River and Tam Giang lagoon.
However, there are still some shortcomings, CT3 steel gate valves, hydraulic equipment, electrical and electronic equipment installed outdoors, are subject to many adverse impacts of saline environment, humidity, and thunderstorms, so they are easily damaged over time.
According to the Provincial Irrigation Works Management and Exploitation Company (Irrigation Company) - the unit managing the Thao Long saltwater prevention and freshwater retention dam, the project is currently degraded and damaged. In particular, because it was not designed with a backup valve gate, in case of a valve gate failure, it cannot be closed or opened, causing very serious consequences.
The current status of the upstream and downstream of the salinity prevention sluice is silted up to a large volume, an average of thousands of cubic meters per year, causing gate jams and obstructing the flow. Every year, the Irrigation Company has organized dredging of a part of the downstream sluice to handle the jammed gate. The two abutments on the North and South banks of the sluice have also subsided, with locations ranging from elevation +1.2 to +0.8.
Most of the sluice gates have erosion under the bottom beam piles, the flow through is very large, affecting the work of preventing salt water, keeping fresh water and in the long term causing instability of the project. The part adjacent to the approach road and the traffic bridge abutment has sunk and cracked, affecting the traffic process, the protective roof of the pressure abutment on the South and North banks has sunk and damaged, although it has been temporarily repaired by the Provincial Road Management and Construction Joint Stock Company, it still faces many safety risks.
In addition, the gate with beam structure and gate face made of CT3 steel, is now rusted and corroded due to working in a salty environment, the face has many points of corrosion of 3 - 4mm, only 6-7mm remains. The shaft cluster system under the gate (12 shaft clusters/1 gate) has rusted, corroded, damaged, causing the shaft to slip out of position, through annual inspections by the Irrigation Company, there are gates that slide up to 3-4/12 shaft clusters, causing unsafety during the operation of the project.
Currently, the hydraulic system for closing and opening the valve doors has deteriorated and is damaged. Most doors open and close very slowly (the time to close or open some doors is up to 30 minutes instead of less than 10 minutes like in the first years of operation). Some doors sometimes cannot be opened or closed to regulate the water source, forcing the company to temporarily handle the situation by dismantling the hydraulic system of other doors to replace them, which is very unsafe...
Mr. Do Van Dinh, Chairman of the Irrigation Company, said that with the scale and tasks of the project being extremely important, the local budget is limited. Investing capital for maintenance and repair to prevent deterioration and ensure the project operates stably to meet its tasks is extremely necessary at present.
Recently, the Ministry of Agriculture and Rural Development has decided to approve Component Project No. 8: Urgent repair to ensure the safety of Thao Long Dam (under the Urgent repair project to ensure the safety of reservoir dams) and assigned the Provincial Management Board of Investment and Construction Projects of Agriculture and Rural Development as the investor with a total investment of more than 348 billion VND.
The urgent repair project to ensure the safety of Thao Long dam will handle the waterproofing of the dam foundation to prevent saltwater intrusion with Larsen IV steel sheet piles from compartment 1 to the end of compartment 15, with a length of 495m. Combine construction sheet piles as waterproofing piles with a depth of 13m. Treat the voids under the valve girder by high-pressure spraying of a mixture of sand and cement. Reinforce the scour hole, the downstream channel of the project with rubble, and a layer of stone gabions over a range of 24m for 6 compartments on the North bank and 44m for 9 compartments on the South bank.
Mechanical part, replace 6 valve doors and overhaul, repair 9 valve doors. Replace all bottom watertight assemblies and side watertight assemblies at 15 doors. Watertight assemblies are made of Sus304 steel, load-bearing bolts are made of stainless steel, watertight assemblies are made of sheet rubber and rubber bulbs. The arrangement of side and bottom watertight assemblies is convenient for repair, gasket replacement and valve door maintenance.
Lock compartment, replace the upper and lower lock doors with stainless steel; the shaft and bearing bolts are manufactured and replaced with high-strength stainless steel; watertight with rubber sheet and rubber bulb. Replace the cylinder system to close and open the main valve and the water supply and drainage valve of the lock chamber.
In addition, upgrade and repair the electrical system controlling the valves at the project and the management house. Repair and upgrade the management house, the embankment combined with the management road at both ends of Thao Long dam. Renovate the traffic bridge, lighting system, and signs. Build a monitoring system to serve the management and operation of the project.
| The Provincial People's Committee proposed the Ministry of Agriculture and Rural Development to support the implementation of a number of projects such as upgrading to ensure safety for 12 reservoirs in the province with a budget of 220 billion VND. Embankments to prevent riverbank erosion and dredging of waterways in the downstream of Huong River, Bo River, Truoi River, with a budget of about 300 billion VND. The project to upgrade the dyke system and sluices on the dyke along Tam Giang - Cau Hai Lagoon to increase flood drainage capacity, prevent waterlogging and flooding to ensure agricultural production, with a budget of about 500 billion VND. |
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