Consultancy services for feasibility study, preparation of (DPR), and providing of pre-construction activity for construction of highway tunnel in EPC mode for a tentative tunnel length of 5.00 km road along NH-310A in the State of Sikkim Consultancy services for feasibility study, preparation of (DPR), and providing of pre-construction activity for construction of highway tunnel in EPC mode for a tentative tunnel length of 5.00 km road along NH-310A in the State of Sikkim