Tri An was the first hydropower plant in southern Vietnam after 1975 and has been part of PSC’s journey since the company was founded in 1981.
Tri An Hydropower Plant
- Capacity: 400 MW
- Location: On the Dong Nai River, Dong Nai Province
- Design consultant: PECC2 in cooperation with Soviet experts
- Owner: EVN
- Total reservoir capacity: About 2.765 billion m³
Tri An was the first hydropower plant in southern Vietnam after 1975 and has been part of PSC’s journey since 1981. The plant is the result of Vietnam–Soviet friendship and the valuable contributions of people from provinces across the country. Its construction was of great importance for economic development, for meeting the needs of residents in the Ho Chi Minh City – Bien Hoa area and the Dong Nai River delta, and for maintaining political and social stability after the country’s reunification:
- Securing energy for the socio-economic development of 16 southern provinces and cities;
- Securing industrial and domestic water supply for more than 5 million people;
- Providing irrigation water for more than 20,000 hectares of downstream farmland.
Main project components
- Main dam: earth-rockfill, 420 m long, 40 m high, 10 m wide crest.
- Spillway dam: concrete gravity, 150 m long, with 8 bays, each 15 m wide.
- Suoi Rop Dam: homogeneous earth, 2,750 m long, 45 m high, 10 m wide crest.
- Auxiliary dams: homogeneous earth, total length 6,263 m.
- Intake: approach channel, trash racks, maintenance gates and 4 emergency gates.
- Penstocks: reinforced concrete, 4 conduits with a 6.5 × 7 m cross-section.
- Powerhouse: 4 Francis units of 100 MW each.
- Switchyard: 220/110 kV.
Topographic and geological conditions
Tri An lies at the lower end of the Dong Nai River’s middle reach, where hills and rapids give way to the low-lying downstream area. The wide reservoir with many islands, together with the main and auxiliary dams, creates a large area to survey and monitor. A notable hydrogeological feature is the interaction between reservoir water and nearby aquifers, including basalt aquifers south of the reservoir. Surveys and assessments must focus on seepage through the dam body and foundation, groundwater fluctuations and the distribution of reservoir sedimentation over time.
PSC’s work on the project (1981 to date)
- Surveys for planning, pre-feasibility, feasibility, technical design and construction drawings.
- Geotechnical construction: grouting of the main dam, and foundation reinforcement and treatment during operation.
- Surveys for downstream flood inundation mapping for flood prevention.
- Surveys for hydraulic calculations used in downstream inundation maps for flood releases.
- Safety inspection of the dam and reservoir.
- Surveys for erosion treatment on the left bank of the intake approach channel.
- Followed by surveys for the Tri An expansion project.
Tri An Expansion Hydropower Project
- Capacity: 200 MW from 2 units of 100 MW each, raising the combined capacity of the existing plant and the expansion to 600 MW
- Location: On the Dong Nai River in Tri An Ward, Dong Nai City (formerly Hieu Liem Commune, Vinh Cuu District, Dong Nai Province)
- Total investment: VND 3,965 billion
- Design consultant: The PECC2 – Institute of Energy consortium provided survey consultancy, technical design, construction drawings and tender documents
- Owner: EVN; Power Project Management Board 3 manages the project on the owner’s behalf
- Land acquired for the project: 92.09 ha; the project shares the existing Tri An reservoir
The Tri An expansion shares the existing reservoir and adds a new powerhouse and waterway to make better use of the hydropower resource. It adds peak-load capacity, improves frequency regulation and uses surplus flood-season water to generate power:
- Increasing peak-hour power supply, especially for the Southeast region.
- Adding an expected average output of about 113 million kWh per year.
- Improving water use efficiency and helping reduce dependence on fossil fuels.
- Reducing the workload of the existing units, extending equipment life and saving maintenance and repair costs.
- Applying Building Information Modelling (BIM) from the feasibility stage to support design coordination and project information management.
Main project components
- Approach channel: connects to the auxiliary reservoir of the existing plant and conveys water to the intake.
- Intake: receives and controls water entering the expansion plant’s waterway.
- Penstocks: convey water from the intake to the units.
- Powerhouse: 2 units of 100 MW each.
- Tailrace channel: returns water downstream after generation.
- Grid connection: links the expansion plant to the existing power system.
- Operation roads and auxiliary facilities: for construction, management and operation.
- Hieu Liem Bridge: 249.5 m long and 9 m wide, used to transport materials and equipment during construction and to connect local traffic.
Topographic and geological conditions
The Tri An expansion sits within the existing Tri An site, with components extending from the approach channel, intake and penstocks to the powerhouse and tailrace. EVN reported complex geological conditions during construction; the site used anchors to reinforce excavated slopes and curtain grouting at the intake. Surveys therefore had to focus on soil and rock structure, the degree of weathering and fracturing, seepage conditions, excavated slope stability and consistent topographic data across all components. The rainy season also required control of surface water and seepage and strict site safety.
PSC’s work on the project: surveys and testing for the pre-feasibility, feasibility, technical design and construction drawing stages.
