Unexpected weather condition
At 5am, Da Nhim Hydropower Plant Extension Project site was flooded with bustling working atmostphere.
Mr. Luu Huu Phi - Head of the Supervision Team, Da Nhim Hydropower Plant Extension Project Management Board said that the project is being expedited by the project owner, suppliers and contractors. At the water intake site, the contractor pours reinforced concrete which is scheduled to complete in July 2017, prepares for installation of inlet valve in late August 2017, early September.
Pressure tunnel is one of the most important and difficult construction items of the project. Although the contractor uses the most modern TBM (Tunnel Boring Machine) in Vietnam, they still face many difficulties due to the incompatible transmission and positioning system, etc. In addition, due to terrain and geological conditions of the project which is based on some areas of weak soil, further reinforcement is thus needed and consequently the project implementation progress is negatively affected. Suppliers and contractors have made every effort to ensure the overall progress of the project.
As for the penstock item, only some of the shaddles and pipes near the Plant area have been completed. The penstock is constructed in areas having complicated topographic condition, steep slopes up to 46 degrees, therefore the grooving, mounting of shaddles and pipes are difficult, requiring the contractor to study and do detailed calculations for each construction position.
Construction of penstock using TBM technology - Photo: Thanh An
The greatest impact on the general progress of the project is imposed by the weather in the Central Highlands, when in the midday, temperature may climb up 35 degrees Celsius, but in the afternoon, it may drop to around 20 degrees Celsius, and rains may drop heavily. Mr. Nguyen Mien - Head of the Construction Team of Enterprise 19, Construction 47 JSC said that a working day of workers usually starts at 5am and ends at 14pm. Although during midday noon, they are usually arranged to work outdoors less, but sunny weather, unusual rain also makes the project construction difficult.
Therefore, the contractor together with the Project Management Board, the supervision consultant have put out reasonable construction solutions in the rainy season, such as division of labor into several groups, each of which works in a construction position. In order to secure safety and health of workers, contractors make protective fences in areas of steep slope, some locations may be equipped with safety shields. On heavy rainy days, to prevent water from overflowing into working positions, contractors may use rain covers, operate pumps at full capacity, all to serve the sole objective that the project implementation schedule will be on track.
All for the project’s progress and quality
Mr. Le Van Quang - General Director of Da Nhim - Ham Thuan - Da Mi (DHD) Hydropower Joint Stock Company, which is assigned by the Vietnam Electricity as the project owner said: To complete construction of a hydropower project needs about 4 years (from 45 to 60 months), in which construction of reservoir and dam occupies the most time. However, Da Nhim Hydropower Plant Extension Project takes only about 27 - 28 months, due to "reuse" the existing reservoir and dam of Da Nhim Hydropower Plant.
Therefore, from June 2016 at the beginning of the project, DHD actively asked suppliers, contractors and the supervision consultant to immediately execute construction items. However, from October 2016 to August 2017, due to abnormal changes in the weather, the outdoor construction items have been affected considerably. Although the project progress fundamentally meets the overall project schedule, the time reserve for each project item is almost no longer available. Therefore, the project owner, suppliers, contractors and the supervision consultant are urgently accelerating their works, taking advantage of every hour and minute, ensuring both progress and quality of the project.
Mr. Nguyen Trung Tinh - Director of Enterprise 5, in charge of TBM construction, said that this is the first time that Vietnam has been transferred and applied the new tunneling technology, so many difficulties still persist and machines have not operated stably yet.
During the construction process, when drilling more than 300m, contractors have encountered geologically complex areas, requiring much time for handling. However, based on experiences accumulated from more than 2 working months, Enterprise 5 will enhance their manpower for maintenance and operation. Some deficiencies relating to electricity and conveyor of the construction line have also been remedied. With guidance of German experts, the Japanese supervision consultant, suppliers and contractors will try their best to put the penstock construction item on schedule.
Although there are a lot of pending works, the weather is not favourable, the important items of the Da Nhim Hydropower Plant Extension Project are implemented with satisfactory quality and on schedule. The target of putting the project into operation in December 2018, adding more power supply to the southern provinces and cities from 2019, has been gradually come into reality.