Redundancy in planning of dam complex: Plugging of diversion tunnels for baglihar hep- A case study

Planning and design of diversion system for any hydropower project is very important and critical aspect, which needs in-depth understanding, experience and consideration of construction aspects in addition to time and cost. Apart from contemplation of heterogeneity and anisotropy of the founding medium, it is always desired to have redundancy in system needed during construction/operation stages. For large hydropower projects, considering the required time horizon to complete the construction and number of uncertainties involved in various systems, it might happen that at some juncture ‘the solution’ will be needed regardless of its cost and time implications. After collapse of both diversion tunnels of Baglihar HEP, a sluice was made in block-11 of the dam to facilitate the dam construction. After, dam construction, plugging of diversion tunnel for which inlet was totally buried, outlet was fully submerged and there was no approach in between, became a big challenge. An outrageous innovative way relied on and diversion tunnel was blocked with utmost accuracy. This paper deals with design and construction methodology of plugging of the diversion tunnels after dewatering, construction of temporary barrier upstream of plug and near outlet and construction of main concrete plug in 20 m length.