A guard wall at the powerhouse of the NHPC’s much-delayed 2,000 MW Subansiri hydro project along the Assam-Arunachal Pradesh border collapsed due to rising water level in Subansiri river, officials said on Sunday.
The incident took place on Saturday night due to the overflowing of the Subansiri river and the company has evacuated all its workers from the powerhouse, where all the machinery is located, they said.
"Heavy rainfall in the foothills of Arunachal Pradesh increased water volume at the Subansiri Lower Hydro Electric Project. As a consequence, a portion of the guard wall of the powerhouse collapsed," an NHPC official said.
Another NHPC official said that the damage is recognised as a threat to the ongoing last phase of construction work of the powerhouse, which is almost ready.
On Friday, one of the diversion tunnels at the project got damaged due to landslides. No person was injured in the incident, a senior official said. According to NHPC Consultant AN Mohammed, the landslides at the tunnel had no effect on the main Subansiri project.
"The cavity above the diversion tunnel no 2 is being filled up and stabilised though the works are being hampered due to rainfall in the project area during the last few days," he said in a statement.
The company had constructed five diversion tunnels as temporary measures to divert the river for the construction of the dam foundation.
However, two diversion tunnels — tunnel no 5 was blocked in the outlet in 2020 and tunnel no 2 was blocked near the entry point on September 16 — due to landslides.
"As the dam construction is nearing completion with 88 per cent progress, the necessity of the diversion tunnels is over and NHPC is planning to plug all the diversion tunnels after this monsoon," Mohammed said.
The construction work of the ambitious project at Gerukamukh along the Assam-Arunachal Pradesh border was stalled from December 2011 to October 14, 2019 due to protests by locals and many 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 worth of Rs 6,285 crore.
