DEHRADUN: Two major tunnel projects in Uttarakhand have come under renewed safety scrutiny after an accident and unstable rock formations disrupted construction, underscoring the geological risks of building large infrastructure in the fragile Himalayas.
Work at the Vishnugad-Pipalkoti hydroelectric project in Chamoli remains suspended after water and debris entered an under-construction tunnel on August 13, trapping workers and prompting a multi-day rescue operation.
With the rescue completed, authorities are investigating the accident, examining the tunnel's structural stability and identifying safeguards required before excavation can resume. No date has been announced for restarting work.
Uttarakhand's Disaster Management, Rehabilitation and Panchayati Raj minister Madan Kaushik said normal construction had not resumed in the affected section.
“The immediate priority is to understand the reasons behind the accident and assess the technical condition and safety of the affected portion. We do not want to leave any shortcomings unaddressed,” Kaushik said.
“Tunnel experts will submit their report, and any further decision will be taken only after that,” the minister added.
Concerns have also surfaced at the Tapovan-Vishnugad project in Chamoli, where cavities and water seepage have reportedly hampered tunnelling. The recurring difficulties reinforce the need for continuous monitoring of underground conditions, rather than treating each disruption as an isolated event.
At the Silkyara-Barkot tunnel in Uttarkashi, however, excavation has been affected, but stabilisation and safety work is continuing, according to the National Highways and Infrastructure Development Corporation Limited (NHIDCL).
The project has recorded about 74% physical progress and 72% financial progress. Its scheduled completion date is March 31, 2027.
Three loose-rock zones were detected inside the tunnel during the final week of August, renewing concerns about worker safety. Rock bolting and cement grouting have been deployed to stabilise the vulnerable stretches.
The projects are thus at distinct stages: Chamoli awaits comprehensive technical clearance after a serious accident, while Silkyara is treating unstable formations before proceeding.
Speaking to TNIE, Colonel Deepak Patil (Retd), a Madras Sappers officer from the Corps of Engineers and a tunnel-engineering expert, said sections excavated from the Barkot side of the Silkyara tunnel had suffered primary lining deformation beyond permissible limits. Patil helped lead rescue operations after the tunnel's 2023 collapse.
He said some stretches already earmarked for final lining needed profile restoration to their designed dimensions before that work could begin.
“The Vishnugad project is a long-standing tunnelling project being executed by one of the country's highly competent companies,” Col Patil said.
“The tunnel has two Tail Race Tunnel sections. In a hydropower project, a Tail Race Tunnel, or TRT, carries water discharged from the powerhouse turbines back to the main river or reservoir after electricity generation. The incident occurred near the breakthrough point between the two TRT sections,” he added.
Patil said breakthrough zones were inherently sensitive because separately excavated sections meet there, concentrating geological uncertainty and stress. Surrounding rock behaviour must be assessed and controlled to protect workers and prevent deformation, water ingress or another collapse, he said.