Centre refutes theory linking Joshimath subsidence with NTPC tunnelling in draft letter
The Centre has dismissed allegations by environmentalists and geologists that tunnelling associated with the National Thermal Power Corporation’s 520 MW Tapovan Vishnugad hydropower project in Uttarakhand’s Joshimath town may have triggered land subsidence in the region.
In a letter drafted to be sent to the Uttarakhand government, the Union power ministry said the NTPC tunnel does not pass under the town and that sub-surface seepage erosion caused by natural drainage, occasional heavy rainfall, periodic seismic activities and increased construction activities appear to be the main causes of subsidence.
“The letter has not been sent yet. It is correct that we have drafted a letter but we are sharing it first with the home ministry, and then will share it with the Uttarakhand government,” a senior official in the power ministry said, seeking anonymity.
According to the power ministry, the tunnel is at a horizontal distance of around 1.1 km away from the outer boundary of Joshimath town and vertically around 1.1 km below the ground level. The construction of the tunnel along this stretch has been carried out using a Tunnel Boring Machine (TBM) that causes no disturbance to the surrounding rock mass, it said.
“The land subsidence in Joshimath is a very old issue… the construction of the tunnel in rock mass at a depth of around 1 km causes no impact on the surface ground, including flora and fauna. There are no signs of sinking around the tunnel alignment at the overground surface,” the letter said.
Local residents alleged the NTPC’s project is the key reason behind land subsidence in Joshimath due to its “non-stop digging and underground blasting to dig a tunnel.”
A senior environment ministry official corroborated the power ministry’s claims and said “the (Joshimath) crisis has no links with the NTPC hydropower project.”
“We have absolutely no doubt that NTPC’s tunnelling has suddenly exacerbated land subsidence… Restoration work in the tunnel started after the Rishiganga deluge… This (crisis) is certainly linked to the restoration works,” said Mallika Bhanot, member of Ganga Ahvaan.