Central Electricity Authority (CEA) apprehensive about Subansiri project's guard walls

Officials of the National Hydro-Electric Power Corporation Limited (NHPC) are averring that two units (Unit-1 and Unit-2 each of 250 MW) of the 2,000 MW (8x250MW)
Central Electricity Authority (CEA) apprehensive about Subansiri project's guard walls

STAFF REPORTER

GUWAHATI: Officials of the National Hydro-Electric Power Corporation Limited (NHPC) are averring that two units (Unit-1 and Unit-2 each of 250 MW) of the 2,000 MW (8x250MW) Subansiri Lower Hydro Electric Project are scheduled to be commissioned in August 2022 and the remaining six units (Unit # 3-8 each of 250 MW) are scheduled to be commissioned in August 2023, but a team of the Central Electricity Authority (CEA) has observed after visiting the project site recently that scheduled commissioning of Unit-1 & Unit-2 can be achieved in the year 2022-23 only if substantial concreting works can be carried out in the monsoon months.

Significantly, the CEA officials have raised fears over the strength of the guard walls of the project. A portion of the powerhouse protection wall collapsed partially on April 1 this year. The CEA noted that protection measures have been undertaken on the riverside as well as the powerhouse side for protection of the powerhouse from any ingress of water from the riverside. However, a higher flow of river water during the monsoons would result in higher pressure on the protection wall. As such, the CEA has advised that the adequacy of the powerhouse protection wall's strength and its capacity to bear maximum water pressure during monsoons should be vetted by a specialized agency before the ensuing monsoons. During the visit to the dam site, the CEA team observed that some workers were working without safety helmets and without proper safety harnesses. The matter was pointed to the NHPC officials for redressal.

The CEA team further suggested that the contractors may be advised to submit the details of the accidents mentioned in their monthly Accident Reports submitted to NHPC so that NHPC is able to assess the exact cause behind the accident(s) and take appropriate measures/issue necessary directions for prevention of such incidents in future. The CEA team also noted on the basis of audit reports that Safety Committee meetings were not held periodically in the recent past. Further, NHPC has been advised to engage adequate resources for ensuring the safety of the workmen on the project premises and to ensure that the Safety Officers are not required or permitted to do any work which is unconnected to, inconsistent with, or detrimental to the performance of the duties prescribed to them.

Moreover, the CEA team found that due to a left bank slide earlier, one of the Diversion Tunnels (DTs) got blocked and currently only four DTs are diverting the river. The DTs are temporary structures which are designed for 100 years. The continuous water flow through DTs for such a long time in the case of the Subansiri Lower Hydro Electric Project might have the effect of eroding its walls, the CEA team noted. The team advised that the NHPC should carry out a reassessment of the impact of river diversion through DTs for such a long period on the slope stability of the surrounding mountains.

The CEA team, which visited the project site on April 21, was led by Balwan Kumar, Director, HPPI Division of CEA and Faraz, Deputy Director, HPM Division of CEA.

The project is designed as Run-of-River (with diurnal storage) facility on the River Subansiri/ Brahmaputra. The Techno-Economic Clearance for the project was accorded on January 13, 2003, by CEA at an estimated cost of Rs 6,608.68 crore with an expected commissioning date of September 2010. However, in reality, an expenditure of Rs 15,506.40 crore has been incurred till March 2022. The revised cost of the project is Rs 19,992.43 crore. The project was delayed due to various reasons like agitations by local people, proceedings in the National Green Tribunal, etc.

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