NEW DELHI: In the wake of recent tunnel collapse incidents, such as the Silkyara tunnel collapse in Uttarakhand, the Ministry of Road Transport and Highways has developed a Standard Operating Procedure (SoP) for tunnel alignment studies and approval on national highways.
The new SoP mandates that at least three alternative alignments, such as the shortest path, geologically or geotechnically favourable routes, and options with minimal social or cost impact must be evaluated before finalising the alignment.
The guidelines caution against routes passing through eco-sensitive zones, heritage sites, fault lines, steep slopes, or dense urban settlements. They prescribe a step-by-step methodology: identifying preliminary corridors, reviewing past investigation reports, collecting high-resolution baseline data across multiple disciplines, developing technically viable alignments, consulting stakeholders, and comparing alternatives to ensure robust planning.
The SoP further states that the portal location should be optimised for access, gradient, drainage, and minimal land acquisition. For tunnel portals, the document stresses optimisation for access, gradient, drainage, and land acquisition, while also factoring in slope stability, drainage channels, and land cover.
The under-construction Silkyara Bend–Barkot tunnel in Uttarakhand collapsed in November 2023, trapping 41 workers for 16 days. In May, to enhance tunnel safety across India, the National Disaster Management Authority (NDMA) initiated the development of national guidelines for tunnel construction and operation.
The tragic Silkyara incident highlighted gaps in India’s tunnel safety mechanisms, particularly the lack of dedicated codes and disaster response protocols. Currently, tunnel construction relies on general engineering standards and international practices, which do not comprehensively address disaster preparedness and rescue operations specific to tunnels.
According to officials, tunnel alignments longer than 1.5 km will henceforth be finalised in line with the new SoP and submitted to the Alignment Approval Committee for sanction after review.
The document also highlights the use of Geographic Information System (GIS) and Digital Elevation Model (DEM) tools for mapping elevation profiles, and mandates the preparation of a Geotechnical Investigation.
“Planning tunnel infrastructure is inherently complex and multi-disciplinary. It requires harmonisation of topographical, geological, geotechnical, geophysical, hydrological, environmental, social, and financial dimensions. Without rigorous, standardised studies and data-backed alignment evaluations, tunnel projects may face delays, cost escalations, and stakeholder conflicts,” the SoP reads.
It has also been mandated to develop a Geotechnical Investigation Interpretative Report (GIR), synthesising and interpreting the geological, geotechnical, and hydrogeological data collected during field investigations.