Bheri Babai Diversion Multipurpose Project
Bheri Babai Diversion Multipurpose Project (BBDMP) classified the Government of Nepal as "Project of National Pride" and about 562km far from Kathmandu, is aimed to transfer 40 m3/s water from Bheri-River to Babai River under a head of about 150m to provide round the year irrigation to 51,000 Ha cultivation land in Bardiya and Banke districts. Present mandate of BBDMP is to develop headworks, headrace tunnel and related infrastructures to divert the water from Bheri River to Babai River and also to utilize the head available. A power house on the bank of Babai River will be constructed that will generate power of about 48MW. BBDMP includes three major components, namely about 12.34 km long 4.2 m dia tunnel, headwork and desanding basin to be constructed in Bheri River end, and third components include fore bay, penstock, powerhouse and electro-mechanical parts of BBDMPP is located in Babai River end.
Geologically, the project area lies in the region occupied by the rocks of the Siwalik Group with the overburden above this. This Siwalik zone consists of sedimentary rocks of fluvial origin belonging to the Neocene age. These rocks are broadly classified into units namely the Lower Siwalik, Middle Siwalik and the Upper Siwalik. Construction of tunnel of this size in such geological formation itself is a challenging task. Considering the technical difficulties in the construction of tunnel with the application of prevailing technology of Drill and Blast Method, it has been decided to use Tunnel Boring Machine (TBM) to construct the tunnel which will also be lined with precast concrete segmental lining. It is going to be used first time in Nepal and first time in Siwalik geology that TBM technology is to be applied for tunnelling.