Abstract

Ranganadi Hydro Electric Project (405 MW), Arunachal Pradesh, India is owned and operated by North Eastern Electric Power Corporation (NEEPCO), a Government of India Undertaking. The Project faced water leakage problem from water conductor system during 2001–2006 due to poor consolidation of rock. The problem was successfully tackled in 2006–07 with systematic grouting around the leakage zones. Pare Hydro Electric Project (110 MW) is another project of NEEPCO under construction located at 5.0 km downstream of Power House of RHEP. Rock in Pare is erodible and generally not groutable. Pre-construction groutability tests indicated poor groutability of rock and poor reliability of curtain grouting in dam foundation. Positive cut-off wall with plastic concrete was decided to be constructed. This paper presents an overview of the problems and the remedial measures undertaken in the face of the challenges to the projects vis-a-vis sustainability of hydraulic structures due to poor rock properties.

Introduction

Ranganadi Hydro Electric Project (RHEP), Arunachal Pradesh, India with an installed capacity of 405 MW is owned and operated by North Eastern Electric Power Corporation (NEEPCO), a Government of India Undertaking. The Project has been developed with creation of a reservoir by constructing a 67 m high concrete gravity dam across Ranganadi River and the reservoir water is diverted to Pare River through a 10.27 km long horse-shoe shaped tunnel of 6.8 m finished diameter. A surface power house is located at downstream of water conductor system with installation of three units of 135 MW each operating under a design head of 300 m. Pare Hydro Electric Project (PHEP) is another project of NEEPCO under construction located at 5.0 km downstream of Power House of RHEP (Figure 1). The project envisages utilization of water of both Pare River and water discharged through tailrace of RHEP through a gross head of 75 m for generation of a maximum of 110 MW of power. A 63.0 m high concrete dam across Pare River shall create a small reservoir for diversion. The water conductor system consists of a 2.81 km long concrete lined 7.5 m diameter horseshoe section headrace tunnel leading to a 58.0 m high surge shaft of 18.0 m diameter. Pressure shaft of 6.4 m diameter takes off from the surge shaft and is designed for a maximum discharge of 185.0 cumecs, 6.4 m diameter pressure shaft bifurcates into two penstock of 4.5 m diameter each leading to two vertical Francis turbines of 55 MW capacity installed in a surface power house on the right bank of the Pare River.

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