Despite the most difficult challenges, such as the Covid-19 epidemic, the main project of Tan My Reservoir has been completed and will be operational by the end of 2021.
Ninh Thuan is the country’s driest region, though water still flows into the sea. Ninh Thuan currently has 21 reservoir with a capacity of 194 million m3, a subsurface flow of 1.94 billion m3, and an annual amount of water transferred from Da Nhim hydropower plant to Ninh Thuan province of 0.57 billion m3. The total amount of water available from all sources is approximately 2.51 billion m3/year. Cai River is the main river of Ninh Thuan province, with most of its flow concentrated during the flood season and many peaks exceeding 5,000m3/s.
Because the flow is very low during the dry season, fluctuating between 2 and 5 m3/s in early March, the Ministry of Agriculture and Rural Development and experts have decided to build Tan My reservoir in Phuoc Hoa commune, Bac Ai district. The reservoir with a capacity of 219 million m3 is responsible for regulating the flow, which is critical in ensuring water supply and socioeconomic development in Ninh Thuan province.
Tan My irrigation system has a total investment of 5,951 billion VND. As a multi-purpose and inter-provincial project, Tan My project is the heart of Ninh Thuan irrigation and is particularly interested and closely directed by the Ministry of Agriculture and Rural Development and the People’s Committee of Ninh Thuan province.
The main components of the Tan My Irrigation System Project are the Tan My rolling weir, the 29.6 km long pressure channel pipeline system, and the Song Cai Reservoir focal cluster of works. According to the Management Board of Irrigation Construction and Investment 7 (Board 7), the investor stated that the Tan My Irrigation System design survey began in August 2010 and had been ongoing since 2008. However, due to the project’s delay, it would not be restarted until 2015.
Tan My weir and channel system from location K0-K21.8 was completed and handed over for operation from February 2020. The focal cluster of Song Cai Reservoir, including 5 connected concrete dams with 2,770m in length, 66.7m in height. The focal cluster has a capacity of 219 million m3 and was constructed in early 2018. The Project’s main tasks include: irrigation and water supply for 7,480 ha; water supply for 12,800 ha of Nha Trinh – Lam Cam irrigation system; and water supply of 2.5 m3/s for irrigation areas of Cho Mo, Ba Rau, Song Trau, Ong Kinh, and others, as well as 2.56 m3/s of water for domestic, service, industrial, livestock, and aquaculture.
At the same time, it creates source for Bac Ai pumped-storage hydropower with a capacity of 1,200 MW and 2 hydropower plants with a capacity of 24 MW. In addition, the Tan My irrigation system also creates a source of water for the South Cam Ranh area (Khanh Hoa province); Mitigation of downstream floods and lake bed aquaculture.
Overcome difficulties to complete the construction on schedule
Due to the water shortage for production, daily lives of local residents in droughts, Ninh Thuan witnessed a heavy suffer from damages (the drought in 2015 to May 2016, the loss was about 700 billion VND; the drought in the dry season 2020 caused an economic loss of about 740 billion dong).
At the end of May 2020, leaders of Agriculture and Rural Development Department were assigned to work in Ninh Thuan Province in an attempt to help the locality overcome the drought. The leaders affirmed that the Tan My focal cluster of works would be ready for water storage by 2020 in order for overcoming drought, stabilizing the local livelihood and developing the socio-economic situation.
Under the closely direction and observation from the Leaders of Agriculture and Rural Development Department as well as the People’s Committee of Ninh Thuan province in recent years, the construction process was implemented in 3 continuous shifts, particularly in the 45-day emulation campaign to overcome the main flood in 2020.
To this point of time, the main project has completed 98 percent of the work volume, with many items was fully completed. As a result, 1.13 million m3 of various types of concrete were poured, 1.45 million m3 of soil and rock were dug and filled, 1,265 tons were processed and manufactured, and 1,513 tons of equipment were installed.
The work was inspected by the State Inspection Council on March 11, 2021, and it was agreed to allow blocking the flow and storing water; the expert group highly praised the project’s quality and management. According to the progress, after blocking the stream, it will be completed and put into use by the fourth quarter of 2021, contributing to the stabilization of people’s lives and the socio-economic development of Ninh Thuan province.
According to the leader of Board 7, the main project of Tan My Lake was built using roller compacted concrete technology. The Covid-19 epidemic broke out in many parts of the country recently, and the situation was very complicated; contractors faced many difficulties in mobilizing technical staff and workers to transport materials and equipment to the construction site, causing the project to be delayed.
“However, under the close observation of leaders from the Ministry of Agriculture and Rural Development, the People’s Committee of Ninh Thuan province, Tan My Lake has accumulated nearly 60 million m3, and will store water to a height of 181.3m with a capacity of nearly 112 million m3 after the main flood season and handed over to the locality for use by the end of 2021, contributing to the fight against drought in the following year’s dry season, as well as the socio-economic development.”
In terms of quality management, the works are built in accordance with the design process, technical instructions, and current construction standards and regulations. Material, construction product, component, and installation equipment testing and inspection results met design requirements. We conducted extensive product testing of roller compacted and reinforced concrete samples in the room with a total of 2,193 samples.
In addition, 11 experts from the construction industry, including leading scientists, industry managers, and the State Inspection Council, are participating in the construction process. The project has been inspected seven times, including one inspection and review of technical design, six site inspections, construction inspections, quality control, quality management, and acceptance work inspections.
In February 2021, the Council for State Inspection of Construction Works inspected and agreed to store water beginning March 15, 2021, two months ahead of schedule and in time to catch minor floods, contributing to participation against drought during the dry season in 2021; disbursement results in the first nine months of the year reached 66.6 percent of the assigned capital plan.
On October 7, the Construction Management Department and experts collaborated with Ninh Thuan province’s functional sectors to inspect flood and storm prevention, progress, and quality management of the works. As a result, the expert team evaluated the main construction work items meet the requirements specified in the design documents and the dam was stable.
After checking, Mr. Nguyen Tai Son, an expert from the Construction Management Department’s descriptor group, stated that the Song Cai dam was built with very good technique. The samples taken directly from the dam system met the technical requirements. The dam body’s infiltration system and drainage holes are functioning properly. The infiltration discharge rate is 24 liters/s, according to the design. The work’s current water storage height is 171 m, which corresponds to the allowable infiltration discharge rate of 14.18 liters/s, but the actual total infiltration discharge rate is 3 liters/s. As a result, the load acting on the dam is less than intended, increasing the dam’s safety margin.
Dr. Nguyen Duc Thang, a Descriptor Group expert, added that the dams in the Song Cai dam system are made of roller compacted concrete. The volume of concrete found in drilled samples from five dams exceeded the specified limit. The mass, compressive strength, tensile strength, and layer tensile strength criteria are all met. Furthermore, the coefficient of variation in dam concrete quality is between good and very good.
“The main project of Tan My is under construction, but the Tan My weir system has been effective for several years now, this system has directly and additionally supplied water to the Cho Mo, Thanh Son, Phuoc Trung irrigation reservoirs, etc. to participate in drought prevention in the dry season for the northern localities of the province with an area of over 2,000 hectares,” said Mr. Luu Anh Tuan, Deputy Director of Ninh Thuan Irrigation Works Single-member Limited Company.