Hydro Disaster

Repeated Disasters at Subansiri Hydro project in 2022

(Feature Image: Massive landslide at Lower Subansiri hydro project dam site. Source North East Now 28 Oct. 2022)

Over the course of past two years, series of disasters and accidents have taken place at construction site of the controversial 2000 MW Lower Subansiri Hydro Power Project resulting in damages to project structure and death of construction workers thus raising questions over its safety and sustainability. Since 2005-06, the largest ever under-construction hydropower project is being developed by NHPLC Ltd (formerly known as the National Hydro Power Corporation Limited), a central government company in geologically fragile, seismically vulnerable and biodiversity rich area in the face of pending judicial case[i] and very strong opposition from people across the Assam.

The latest disaster in form of a massive landslide affected the project site on October 12, 2022 further delaying the repair works which were being carried to recover damages caused by the flash floods, landslips at dam site in last week of September 2022.

What is clear from the list of incident mentioned below is that in each of the last three years (2020, 2021 and 2022), both in monsoon and pre monsoon months, there has been series of disasters and accidents happening at the project. In fact in an unprecedented event, the Central Electricity Authority, the highest technical body under the Union Power Ministry had submitted a report dated April 2022, titled “Tour Report of Subansiri Lower Hydro Electric Project (8×250=2000 MW) in Arunachal Pradesh/ Assam being executed by NHPC Ltd” raising fundamental questions about the safety situation at the project.

Huge landslide at Lower Subansiri HEP dam site. Image Source: NET, 12 Oct. 2022

With this the worst fears of the critics are coming true and again shows how inadequate are our feasibility and appraisal studies and how little we understand the geology, ecology and geomorphology of northeast India. The project had been economically unviable[ii] long back with projected cost already over Rs 20000 crore and electricity production cost could be upwards of Rs 8 per unit while power is available at much cheaper rates from alternatives.

The Disasters & Accidents at Lower Subansiri HEP

October 2022: Incessant rain once again wreaked havoc at the Lower Subansiri hydropower project site in the Gerukamukh area of Assam’s Dhemaji. A large part of the hill is seen tumbling one by one near the main dam causing a landslide as per October 28, 2022 report. Earlier, on October 12, 2022, a large portion of the hill at location fell[iii] on the diversion course of the river causing panic among the workers and further affecting the repair work. The project site has been hit by landslides and water spills during the course of past several days has prompted the NHPC and its contractors to suspend work and evacuate its workers.

According to reports, the company executives of the NHPC are planning to construct an alternative route to reach the main dam (bundh). They are planning to develop concrete walls on the hillsides to prevent further landslides in the affected areas. The river’s wave also broke a portion of the guard wall of the power house constructed on the left bank, thereby damaging some machinery.

Union Power Minister Raj Kumar Singh, who visited the power house of the project in Gerukamukh on 14 June this year, had announced that the Subansiri project would be commissioned from early 2023. NHPC Chief Executive Director YK Subhe had also assured the people that the project would start generating power from Jan 2023. However, following the latest disaster, uncertainty is looming[iv] large over the much-hyped mega power project.

September 2022: Quoting some unnamed NHPC’s officials a PTI report revealed that the floodwater entered the powerhouse of the under-construction Subansiri hydro project leading to collapse of a portion of the temporary guard wall[v] on September 25, 2022. “We will now have to dewater the premises. Then, cleaning will take place as the floor will be very slippery. 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.

The machines of one unit of the project had been installed, while work on the second unit was underway when water entered the building when the guard wall collapsed[vi] during intervening night of September 24- 25, 2022. The incident took place due to the overflowing of the Subansiri river and the company had to evacuate all its workers[vii] from the powerhouse, where all the machinery are located. As per NHPC consultant AN Mohammed one of the tunnels at the project got damaged due to landslides[viii].

Before this, a diversion tunnel of the project was damaged due to landslides on September 23, 2022. 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. “The cavity above the diversion tunnel number two is being filled up and stabilised, though the works are being hampered due to rainfall in the project area during the last few days,” an official said in a statement.

The Assam government in March 2022 had informed the state assembly that partial commissioning of the project has been further postponed till August 2022. The project is likely to be completed in August 2023, as per information on the NHPC website.   In December 2020, the company had set a target of March 2022 for commissioning the project. According to a company estimate in January 2020, the cost of the mega project, which was scheduled to be commissioned in December 2012, has 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 project.

Meanwhile, NHPC, in a filing before the stock exchange, has claimed[ix] that the “partial” flooding of the powerhouse on September 25, 2022 will not “significantly” affect its planned commissioning schedule of the project and it will only need some extra time to dewater and clean the powerhouse. It claimed the flooding happened due to incessant rain and heavy discharge, but no figures are given about the rainfall or discharge or the design capacity of the guard wall. It is also not clear why the construction work was going on during the monsoon months, when normally, as a safety measure, no construction work is undertaken.

Amid incessant rain, sinkhole appears on left bank of Lower Subansiri project. ITNE, 16 Sept. 2022

On September 16, 2022, amid torrential rains a major cave-in[x] (sink hole) occurred at the dam site resulting in breaking off[xi] a part of tunnel number 2. It is worth remembering that experts had long warned that the soil and stone of the region are too soft to support a mega dam.  

The cave-in was reported on the left bank of the project and said to be large enough[xii] for full-sized 16-wheeler trucks to fall in. With the hole being formed, the upper parts of tunnel number 2 were reported to be damaged. The sinkhole appeared during the recent rains. Many people have started to protest against the project citing that the dam might bring more risks to the people living near it.

In the wake of flash flood, landslides damaging the dam site, the Krishak Mukti Sangram Samiti (KMSS) and All Assam Students’ Union (AASU) on September 27, 2022 staged a protest[xiii] against construction of the project citing its downstream impacts. The construction work of the controversial project at Gerukamukh along the Assam-Arunachal border was stalled from December 2011 to 14 October, 2019, due to protests by locals and many groups, fearing safety and downstream impacts.

August 2022: Exposing unsecured working condition at the project site, one more worker died[xiv] on the spot at the Block No. 2 of the main dam on August 22, 2022 due to electrocution. The worker identified as Rajesh Saikia (38), son of Mitheswar Saikia, resident of village Moharicamp Chapori had been working at the project site under Soma Enterprise and a contractor for a couple of years as a contract worker. It is alleged that shot-circuit is a common phenomenon at the Block No. 2 of the main dam of the project. It is also alleged that the NHPC authority and other contractor organizations of the project have never paid any attention to secure the work places to check untimely death of the workers but made them work in an unsafe environment.

June 2022: A worker lost his life[xv] on June 6, 2022 when a steel rib being fixed on to the roof of second headrace tunnel at Subansiri dam site fell on him. As per an official the deceased worker, Jitu Hatibarua, resident of Parbatipur was first rushed to the hospital at the project site and died on the way while being taken to the district hospital from there.

The company was expecting to operationalize the first two units of 250 MW each by August 2022 but the date could be postponed, the official said. The North East Now report claims that the incident happened due to a landslip inside one of the tunnels at the project site killing one and injuring two workers[xvi] employed by Patel Engineering.

In the same month, blaming the heavy rains since April 2022, NHPC again shifted the commissioning[xvii] of four units of the project from August 2022 to March 2023. In Dec 2020, the NHPC had claimed that it would commission be project by March 2021. Again in November 2021, it claimed[xviii] that two units would be project would be operational by August 2022.

In this June 2022 report Rajeev Bhattacharyya a senior journalist in Assam details some reason why the dam is a disaster[xix] in the making.

Photo courtesy: CEA/AT

May 2022 Notably the Central Electric Authority (CEA) has asked NHPC to improve its construction safety measures, including reassessment of slope stability of surrounding mountains, strength of the protection wall, and workers’ safety at Subansiri dam site. The CEA team during site visit to review the physical progress of various works for the project, has also suggested that reassessment of the impact of river diversion through diversion tunnel (DT) on the slope stability of surrounding mountains may be carried out by the NHPC.

In its report, it said that, due to “left bank slide earlier, one of the diversion tunnels had got blocked and currently, only four DTs are diverting the river. The continuous water flow through diversion for such a long time might have the effect of eroding its walls.” This revelation is in contradiction to the MoEF&CC’s misleading claim in its June 2019 letter, in which it had said that there was no significant instability.

Under construction power station flooded after collapse of guard wall at Lower Subansiri HEP. NE Now, 28 Sept. 2022

As per the report, the powerhouse protection wall had collapsed[xx] on April 1, 2022 because of the tail race channel construction activities of Units 1 and 2. Following the collapse of the wall, the CEA team advised that the adequacy of powerhouse protection wall’s strength to bear maximum water pressure during monsoons be “vetted by a specialised agency before the coming monsoons.” It also suggested that the contractors submit the details of the accidents mentioned in their monthly accident reports.

Further, it asked the NHPC to engage adequate resources for ensuring safety of the workers in the project premises. The CEA had noted that a few workers were without safety helmets and safety harnesses. The team, citing audit report, said that safety committee meetings were not held periodically in the recent past.

March 2022: As per this report, at least three workers were killed[xxi] in separate accidents at dam site in third week of March 2022. Following these incidents a group of workers burnt an office housed in a container where two other workers were praying. The attackers suspected that those praying were performing some black magic. The attack led to injury to two workers near the main dam of the project.

August 2021: The guard wall that was built to protect the project’s main dam reportedly collapsed[xxii] in on August 26, 2021 due to the rapid surge of overflowing water. The flood water toppled over the main dam for three consecutive days wreaking havoc in the downstream area. This incident raised suspicion on its capacity to withstand the natural disasters thought one of the main goals of the mega project was to control the massive flood and erosion problems caused by the Subansiri river.

The overflowing water of the Subansiri inundated the powerhouse[xxiii] of the project by breaching the guard wall.  Moreover, a landslide occurred at Tunnel Road triggered by the heavy downpour. Earlier in July 2020,  two guard walls of the dam collapsed at the dam site.

Flood causes major damages to NHPC’s Subansiri Lower Dam Project. Time 8, 22 July 2020.

July 2020: The guard wall of the power house of the dam had collapsed[xxiv] in the third week of July 2020 too following heavy rainfall and a flood spate. As a result the entire powerhouse was flooded within no time and the water was flowing over the main. The downstream areas were also affected by the flood incident. In earlier months also the flood had caused major damages to the project inviting stiff protest and criticism from locals and experts. The NHPC authority, as usual, were not available for comment. 

June 2020: The dam site faced a series of natural disasters[xxv] since May 27, 2020 with landslides and damages to claddings of the diversion tunnel. The overflowing Subansiri also inundated many installed machineries and other infrastructure at the project site. The flood water continued to flow over the main dam causing fear in downstream villages.

The river on June 19, 2020 breached the coffer dyke[xxvi] at project site. Landslides in the area close to the dam site damaged the cladding of the diversion tunnels of the river.

Landslide near Subansiri dam. NE Now, 29 May 2020

May 2020: There were landslides[xxvii] around 200 meters away on the right side from dam site on May 27, 2020. Cracks were also developed on the hills near the construction site following week long rains. Landslides also took away a portion of an abandoned road leading to the view point of the dam 300 meters away from the construction site.

SANDRP (ht.sandrp@gmail.com)


[i] https://indianexpress.com/article/india/subansiri-dam-work-on-despite-assurance-to-ngt-that-it-wont-5831255/

[ii] https://timesofindia.indiatimes.com/india/northeast-diary-why-experts-still-not-convinced-about-safety-of-this-mega-project/articleshow/94872377.cms  

[iii] https://nenow.in/north-east-news/assam/assam-landslides-subansiri-project-gerukamukh-disaster.html

[iv] https://arunachaltimes.in/index.php/2022/10/14/uncertainty-looms-over-2000-mw-slhep-subansiri-river-triggers-massive-landslides-in-gerukamukh/ 

[v] https://arunachaltimes.in/index.php/2022/09/27/floodwater-inundates-powerhouse-of-nhpcs-subansirihydro-project/ 

[vi] https://www.eastmojo.com/assam/2022/09/26/flood-water-inundates-powerhouse-of-nhpcs-mega-project-along-assam-arunachal-border/    

[vii] https://arunachaltimes.in/index.php/2022/09/26/nhpcs-2000-mw-subansiri-dam-partially-damaged-in-flooding/ 

[viii] https://nenow.in/north-east-news/arunachal-pradesh/arunachal-pradesh-subansiri-dam-nhpc-damaged-floods.html

[ix] https://energy.economictimes.indiatimes.com/news/power/power-house-at-nhpcs-under-construction-subansiri-lower-he-project-partially-flooded-statement/94494032

[x] https://twitter.com/anuraag05/status/1570986093448929281?s=20&t=mLpsxNxJuECvhsGn5EMrng 

[xi] https://www.facebook.com/northeastlivetv/videos/1464542017347520/?extid=CL-UNK-UNK-UNK-AN_GK0T-GK1C&ref=sharing  

[xii] https://nenow.in/north-east-news/assam/assam-massive-sinkhole-near-nhpcs-subansiri-hydro-project.html

[xiii] https://www.guwahatiplus.com/exclusive-news/protests-erupt-after-parts-of-subansiri-lower-dam-damaged-in-assam 

[xiv] https://www.sentinelassam.com/north-east-india-news/assam-news/worker-dies-due-to-electrocution-at-subansiri-project-under-dhemaji-district-608883    

[xv] https://timesofindia.indiatimes.com/city/guwahati/assam-subansiri-dam-accident-claims-workers-life/articleshow/92049000.cms  

[xvi] https://nenow.in/north-east-news/assam/assam-landslide-kills-worker-at-lower-subansiri-hydropower-project-site-at-gerukamukh.html 

[xvii] https://www.livemint.com/companies/people/urgent-need-to-develop-our-hydropower-capacity-nhpc-11654541267808.html    

[xviii] https://projectstoday.com/News/Two-units-of-Subansiri-Lower-Hydel-Power-Project-to-be-ready-by-August-2022

[xix] https://theprobe.in/subansiri-dam-is-a-disaster-waiting-to-happen-in-eastern-assam/

[xx] https://arunachaltimes.in/index.php/2022/05/14/cea-asks-nhpc-to-reassess-slope-stability-protection-wall-improvement-in-safety-measures-in-subansiri-lower-hep/ 

[xxi] https://nenow.in/north-east-news/assam/assam-clash-among-workers-in-lower-subansiri-dam-two-severely-injured.html 

[xxii] https://www.eastnews.in/latest-north-east-news/latest-breaking-news-of-assam/subansiri-flood-affected-97-villages-in-lakhimpur-district/

[xxiii] https://www.pratidintime.com/latest-assam-news-breaking-news-assam/assam-subansiri-dams-guard-wall-collapses-fuels-flood-fear

[xxiv] https://www.time8.in/flood-causes-major-damages-to-nhpcs-subansiri-lower-dam-project/

[xxv] https://nenow.in/north-east-news/assam/panic-grips-residents-of-north-assam-as-subansiri-river-flows-over-gerukamukh-dam.html

[xxvi] https://nenow.in/north-east-news/assam/coffer-dyke-breached-as-landslide-continues-in-lshep-site-in-gerukamukh.html

[xxvii] https://nenow.in/north-east-news/assam/landslide-near-subansiri-dam-triggers-panic-along-assam-arunachal-boundary.html

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