NHPC has said that concerns over the safety of India’s biggest hydroelectricity project in the northeast of the country are misplaced and adequate safeguards have been incorporated.
The recommendations of various committees have been implemented in the design and construction of the 2,000 MW Subansiri Lower Hydroelectric Project, which is expected to be commissioned in a few months, it said.
“All the technical issues regarding the seismic design parameters, dam safety and environmental impact assessment, release of minimum environmental flow during the lean season, etc, have been duly taken care,” the state-owned builder of hydroelectric projects said in response to queries by Moneycontrol on safeguards in the project.
India is gearing up for higher power demand this summer, with the met department saying the country is likely to experience heat waves between March and May. Peak demand for electricity is expected to climb to 229 gigawatts (GW) in April.
The Subansiri Lower project is the first among many dams planned by the government to harness the hydel potential in Arunachal Pradesh, which has an estimated capacity of 50,000 MW out of a total of 145,000 MW for the entire country. So far, 26 percent of the potential has been exploited nationwide.
As many as five panels reviewed the project – Technical Expert Committee, Joint Steering Committee, Dam Design Review Panel, Project Oversight Committee and Expert Committee – between 2011 and 2019.
The Subansiri Lower HE Project is the biggest hydroelectric project undertaken in India so far, NHPC said on its website. The project is likely to be completed in August 2023.
The project triggered controversies and agitations in Assam owing to fears over the safety and downstream impact of the dam. Construction work was stalled from 2011 to 2019 due to protests by civil society groups in the state whose concerns stemmed from the region’s vulnerability to earthquakes.
The National Green Tribunal’s approval of the project was challenged in the Supreme Court and was dismissed.
The delays have escalated the cost of the project to about Rs 20,000 crore from the initial estimate of Rs 6,285 crore.
Over the past three years, nine mishaps were reported from the construction site of the Subansiri project at Gerukamukh, which occurred during the monsoon and pre-monsoon months, including landslides, damage to diversion tunnels, breaches in the coffer dyke, and the collapse of a guard wall to protect the powerhouse.
Last March, three people were killed in separate incidents, which provoked a group of workers to burn an office at the site. Three months later, a worker lost his life when a steel rib fell on him from a headrace tunnel. NHPC’s plan to operationalise the first two units by August 2022 was postponed.
These episodes prompted the Central Electricity Authority, the highest technical body under the Union power ministry, to dispatch a team to the site. Their report raised disturbing questions on safeguards in the project.
It instructed NHPC to improve construction safety measures and re-evaluate the impact of river diversion on the slope stability of the surrounding mountains.
NHPC said the accidents at the diversion tunnel and the damage to the coffer wall would not recur as they are temporary structures built for the construction of the dam. They would be plugged after the construction of the project draws to a close.
“There is no damage to the permanent structure of the dam and powerhouse during the construction of the project in monsoon season,” NHPC said in its reply.
(Rajeev Bhattacharyya is a senior journalist in Assam)