NTPC denies project link to Joshimath subsidence, records show a long history of breaches

What the company did not mention is that its TBM has a history of breaches. In fact, official records accessed by The Indian Express show that since December 2009, there have been a string of “aquifer ingress” events — incidents where TBM breaks into rock that holds groundwater — along the tunnel of the Tapovan Vishnugad hydel project.

Indeed, in December 2009, the TBM triggered “massive surges of high pressure subsurface water” in the tunnel. And in summer of 2010, NTPC had to agree to local residents’ demands for funding a long-term solution to an unprecedented drinking water problem in Joshimath caused by that surge.

A man shows the cracks that appeared at his house in Joshimath. (PTI)

That year, geologists MPS Bisht and Piyoosh Rautela of H.N.B. Garhwal University had red-flagged in Current Science how this could have a lasting impact: “This sudden and large-scale dewatering of the strata has the potential of initiating ground subsidence in the region.”

When contacted Sunday, Rautela, who is now executive director of the Uttarakhand government’s Disaster Management and Mitigation Centre, told The Indian Express said that the latest land subsidence is “likely caused by aquifer breaches as we see muddy waters pouring out.”

People affected by the gradual ‘sinking’ of the houses wait with their belongings for evacuation at Joshimath. (PTI)

On whether this time, too, there was a link with the tunnel, he said there “no evidence yet to link or delink it with the hydel tunnel.”

Others are more forthright.

“When the aquifer ingress caused by NTPC’s TBM in December 2009 impacted the water situation in Joshimath, how can the company claim that the project tunnel cannot be linked to the land subsidence we are witnessing now? Only a water test can tell if the streams erupting in the town are from the hydel tunnel,” said Dr Hemant Dhyani who was a member of the High-powered Committee appointed by the Supreme Court on the Chardham Project.

When contacted, an NTPC spokesperson declined to comment saying a public statement will be made soon.

Two hotels have been closed after one building was found to have tilted towards the other, in Joshimath. (Express photo by Avaneesh Mishra)

Originally scheduled to be commissioned in 2012-13, the Tapovan Vishnugad hydel project has been delayed by nearly a decade due to a series of “mishaps” experts blame primarily on “inadequate geological assessment”.

NTPC began work on the project in late 2006, commissioning a joint venture of Larsen & Toubro (India) and Alpine Mayreder Bau (Austria) for civil work and Geoconsult (Austria) as an advisor to assist with the TBM work.

In December 2009, records show, the TBM got trapped at a depth of 900 m as “massive surges of high pressure subsurface water, containing faulted rock material, broke two crown segments of the segmental lining (of the machine) immediately… with the initial flow rates reaching” 700 litres per second.

A building tilts following landslides at Joshimath in Chamoli district, Sunday, Jan. 8, 2023. (PTI Photo)

The work was called off for more than 10 months before a bypass tunnel was dug to free the machine. However, records show, the TBM was again trapped in February and October 2012 in the same 20-m-wide fault zone at a depth of some 700 m.

“The water rapidly eroded the water sensitive fault gouge and breccia causing further cavity development, ground creep and ground in-flow through the cutter head and shield openings trapping the TBM,” said a Geoconsult document in March 2014.

A building tilts following landslides in the Joshimath of Chamoli district of Uttarakhand. Cracks have started appearing in the houses causing panic in the whole city. Administration is shifting residents. (PTI Photo)

Geoconsult noted that tender documents had mentioned faults and possible water-inflow and the contractor needed to make their own assessment about the geological conditions. “More rigorous efforts,” said the Geoconsult document, were recommended “to stop geological surprises…and allow for preventive measures to be established… during the feasibility and design and tendering phases.”

Water oozes out after cracks appeared in the houses due to landslides at Vishnupuram Marwari Colony, in the Joshimath of Uttarakhand, Friday, Jan. 6, 2023. (PTI Photo)

Given these adverse conditions, excavation was halted pending a renegotiation of the contract which was eventually terminated in 2014. In 2016, NTPC hired Hindustan Construction Co (HCC) which, in turn, hired Seli Overseas to rescue the TBM and complete the head race tunnel.

The TBM was rescued, refurbished and relaunched in 2019. But it could advance only 55 m before it became trapped yet again, with less than 2 km remaining to be excavated. The glacial flood hit the project in February 2021. Since then, work on the tunnel has been on hold.