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Tamakoshi-5, one of the strategic hydropower projects directly linked to Nepal’s energy security, has now reached a decisive stage of construction.

Built by reusing the water discharged after electricity generation from the 456 MW Upper Tamakoshi Hydropower Project, this project is simultaneously dealing with massive underground structures, a main water tunnel, and complex geotechnical conditions. On the other hand, it has also been racing against time due to forest approvals, tree felling, restrictions within protected areas, and administrative delays.

With a capacity of 99.8 MW, this project is considered one of Nepal’s important “cascade” hydropower projects. It is expected to generate around 495 GWh annually, which is approximately 495 million units of electricity.

A power purchase agreement (PPA) has already been signed with the Nepal Electricity Authority at Rs 8.40 per unit in the dry season and Rs 4.80 per unit during the wet season. If completed on time, the project is expected to significantly contribute to peak-hour supply in the national grid.

However, the project faced construction delays of around 8–9 months. Delays in forest clearance within the Gaurishankar Conservation Area, tree felling permits, environmental procedures, and right-of-way approvals disrupted the main construction schedule.

According to project chief Hemant Bhatt, engineering team member Prafulla Man Pradhan, and the company’s CEO, construction has now regained momentum, but managing the lost time has become the biggest challenge.

“There was no expected progress in work for about 8–9 months,” said project chief Bhatt. “That directly affected the overall construction schedule.”

Obstruction from the Gaurishankar Conservation Area

According to project management, the biggest setback in the construction of Tamakoshi-5 has come from forest and conservation-related procedures. Since some structures of the project fall within the Gaurishankar Conservation Area, processes related to forest land use rights, tree-felling permits, and environmental approvals were delayed for a long time.

In particular, construction activities in areas related to the main tunnel - Adits 2, 3, and 4 - were affected. In some locations, tunneling work could not even begin, according to the project side.

Officials working in the energy sector say that legal complexities related to infrastructure development inside protected areas, procedural uncertainties following a Supreme Court order, and a lack of coordination among different agencies slowed down the project. Later, construction resumed after the Cabinet approved the forest area “right of occupation.”

According to management, the disruption not only affected the construction schedule but also posed a significant risk to potential electricity generation and revenue.

A daily loss of Rs 20 million could occur

According to CEO Ram Kumar Yadav, if the project is not brought into operation on time, it could result in a potential loss of around Rs 20 million per day in electricity sales revenue.

“That could reach Rs 600–700 million per month,” he said. “So we are continuously motivating all sides to complete the work on time.”

Based on annual generation and PPA rates, the 9-month delay is estimated to have potentially affected electricity sales revenue of around Rs 2.45 billion.

Tamakoshi-5 is not just another hydropower project; it is also an important example of Nepal’s advancement in a “reuse-water cascade system.” The concept of reusing water discharged from Upper Tamakoshi is expected to improve water resource utilization efficiency.

Reuse of water from Upper Tamakoshi

The core concept of Tamakoshi-5 is to reuse the water discharged from the Upper Tamakoshi project.

According to project chief Bhatt, a large separate dam is not required for this. Water released from the tailrace of Upper Tamakoshi will be brought through a tunnel and reused for power generation in turbines.

“This project is based on the concept of maximizing water resource utilization,” he said. “Since electricity is generated by reusing available water, it is an important project both technically and economically.”

It is expected to play a key role in stabilizing the power system during periods of high energy demand, especially helping reduce electricity shortages during the dry season.

Large underground construction

The most complex aspect of Tamakoshi-5 is its underground structure. After traveling about 285 meters inside the main access tunnel, the project reaches the underground powerhouse area.

According to engineer Prafulla Man Pradhan, head of the Nepali technical team of contractor Sinohydro, both the powerhouse and transformer hall are being constructed underground. About 60% of the excavation work for the powerhouse has been completed, while excavation of the transformer hall has been fully completed. Work is now being prepared for earthing and concrete works there.

The project will install three main turbines with a capacity of 31.6 MW each and one auxiliary turbine with a capacity of 5 MW.

Electricity generated from the turbines will be transmitted to the transformer hall through three bus-duct tunnels. After voltage regulation there, the power will be taken out through a cable tunnel. It will then be connected to the national transmission system via the switchyard.

Target: 65%, Progress: 22%

According to the initial construction schedule, the physical progress of the project should have reached around 60–65 percent by now. However, the current overall progress is limited to only about 22 percent.

The project attributes this delay to forest clearance issues and construction disruptions, which have pushed progress far behind the target.

According to CEO Yadav, although the construction company is legally entitled to request an extension of time, the project is continuously pressuring it to complete the work within the original deadline.

“We have explained the importance of time to the contractor,” he said. “They are now also committed to completing the project within the scheduled period.”

Tunnel construction: the most difficult phase

The most challenging part of Tamakoshi-5 is considered to be the construction of the main water tunnel. Currently, tunneling work is being carried out through multiple adits.

So far, about 315 meters of the main tunnel has been excavated from Adit-2. The project consists of seven construction phases in total. While the seventh phase is relatively short, the remaining phases are long and complex.

According to the technical team, the target is to excavate about 3.5 to 4 meters of tunnel per day from each phase.

“If work continues at the current pace, the main tunnel could be completed within one and a half to two years,” said engineer Pradhan.

The project aims to complete the main tunnel by FY 2026/27, followed by equipment installation, testing, and commissioning, with electricity generation expected to begin by around April or May 2028.

Challenges in the MCT fault zone

One of the most sensitive geological structures in the project is the “Main Central Thrust (MCT)” fault zone. Technical teams estimate that around 1,100 meters of this section could pose serious challenges for tunnel construction.

Studies have also indicated that the geology around Adit-4, the surge tank, valve chamber, and the vertical pressure shaft may be weak and unstable.

However, the project management is confident that risks will be managed by using rock-support structures and other protective engineering measures.

Explosives and administrative hurdles

Although many forest-related issues have been resolved, the project still faces several administrative and procedural challenges.

In particular, delays in the timely availability of explosives required for tunnel excavation could pose risks to construction progress, according to management.

There are also delays in approval processes related to the import and re-export of equipment and materials brought from abroad, which has created additional operational difficulties.

According to CEO Yadav, if the concerned government agencies could make approval procedures faster and more coordinated, it would significantly help the project meet its deadline.

Improving relations with locals

The project has acknowledged that relations with the local community were not initially smooth. Some misunderstandings and local dissatisfaction even created situations that could have affected construction work.

However, the management claims that relations have now improved through direct dialogue, employment opportunities, and social programs. Currently, around 250 to 300 local people from Dolakha are directly employed in the project.

Certain construction works, such as gabion wall building, have also been assigned to local residents. Under its corporate social responsibility (CSR) activities, the project is also carrying out some work in education, health, and local infrastructure development.

Project cost: Rs 21.43 billion

The estimated cost of the Tamakoshi-5 project is Rs 21.43 billion. Although there could be some increase due to market price inflation and contract revisions, management says there will not be a significant cost escalation.

In particular, if the main tunnel construction proceeds smoothly, the project is expected to avoid major cost overruns.

According to management, Tamakoshi-5 is not just another hydropower project but a strategic project linked to Nepal’s energy security.

“We want to complete it on time and make it a model project,” said CEO Yadav. “The entire team is now focused on that goal.”

Jalasarokar