North Lakhimpur: Flood water has entered the powerhouse of NHPC's under-construction 2,000-MW Subansiri hydro project along the Assam-Arunachal Pradesh border, officials said on Monday. A portion of the temporary guard wall at the powerhouse collapsed on Sunday night after seepage started due to flooding of the Subansiri river, following heavy rain in upstream areas in Arunachal Pradesh, a company source told PTI.
"This was a temporary wall, which we would have removed after completion of the work at the powerhouse. However, the breach took place prematurely," he said.
The machines of one unit of the project, touted to be the biggest hydroelectric project undertaken in India so far, have been installed, while work on the second unit was underway when water entered the building.
"We will now have to dewater the premises. Then, cleaning will take place as the floor will be very slurry. Work at the powerhouse will be delayed by four-five months," another official said.
He also said that the damage is recognised as a threat to the ongoing last phase of construction work of the powerhouse.
On Friday, a diversion tunnel of the project was damaged due to landslides. No one was injured in the incident, the officials said.
The company had constructed five diversion tunnels as temporary measures to divert the river for construction of the dam foundation.
However, tunnel 5 was blocked at the outlet during 2020 and tunnel 2 was blocked near the entry point on September 16 this year due to landslides.
In June, one person was killed and another seriously injured when the roof of Intact Tunnel 2 collapsed.
The Assam government in March this year had informed the state Assembly that partial commissioning of the ambitious project has been further postponed till August 2022.
The project is likely to be completed in August 2023, as per information on NHPC website.
In December 2020, the company had set a target of March 2022 for commissioning the project at Gerukamukh along the Assam-Arunachal Pradesh border.
Construction work of the project on Subansiri river was stalled from December 2011 to October 2019 due to protests by locals and other groups, fearing safety and downstream impact.
According to a company estimate in January 2020, the cost of the mega project, which was scheduled to be commissioned in December 2012, had escalated to around Rs 20,000 crore from the initial sum of Rs 6,285 crore.
The Centre had allocated a total of Rs 11,000 crore as of December 2010 for construction of the dam.
(With PTI inputs)
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