Now, geological study a must for tunnels

Bhanu P Lohumi

Tribune News Service

Shimla, October 28

The National Safety Council’s safety norms should be followed while constructing tunnels for hydro-electric projects or carving out roads.

This was stated by the State Disaster Management Authority in its advisory issued to the Public Works Department, State Electricity Board and other hydro and road project authorities, Deputy Commissioners in the wake of tunnel collapse while carrying out the four-laning of Kiratpur-Nerchowk on September 12. The advisory states that topographical, geological and hydrological parameters will be kept in mind before selecting tunnel sites.

“The construction of all tunnels shall be done as per the standard, norms and practices of Himalayan geology which is young and fragile and if any geological changes are observed or encountered during construction, necessary innovative and remedial measures will be incorporated in the design,” the advisory read.

Government agencies will be mandated to check the ongoing tunnel construction works periodically and the designs will be vetted by them.

“Mobile seismographs to record vibrations while blasting will be used to ensure controlled blasting in the tunneling process, the date of blasting will be submitted to the state PWD, state geologist and respective Deputy Commissioners,” said DD Sharma, special secretary, Disaster Management.

Intermediate adits and vertical shafts be constructed at low hill points for ensuring air draft for safety of workers while the lateral side tunnels will be constructed for rescue, day lighting and communication facilities.

The tunnel alignment surface shall have to be drained during construction and post-construction to ensure that no damage is caused by seepage and safety norms such as provision of drinking water, oxygen supply, food and emergency evacuation shall be properly followed.

The guidelines will go a long way in ensuring safety as over two dozen tunnel projects are under execution or in the pipeline.

While the Larji tunnel is complete, 8.8 km Rohtang tunnel is under construction and six tunnels are proposed to be constructed under the Kiratpur-Nerchowk and three under Shimla-Parwanoo four-laning projects.

The pre-feasibility study of Chamnuda-Holi, Tissa-Kilar and Jalori Jot has been conducted and some other transport tunnels, including Lift-Himfed petrol pump, Lakkar Bazar-Sanjauli, Khara-Pathar, Ranital, Swarghat-Bilaspur, Bangana-Dhaneta and Karsehar-Telang, have been proposed.