The pre-commissioning testing of the four generating units and testing of auxiliary equipment in the powerhouse of the Mangdechhu will begin in October this year, according to project officials.

Each unit is capable of generating 180 MW of power. While three unites have been readied, the installation of one is expected to complete by next month.

This is being done to save time, MHPA officials said as the balance works for headrace tunnel (HRT) including plugging of tunnel is expected to complete between September and October this year.

The testing of generating units would be done by diverting the water from a nearby stream to the pressure shaft, which is just above the powerhouse, and without filling the water in the HRT.  In reality the water discharge from the dam is being taken into the intake tunnel followed by the HRT and then to the pressure shaft. The discharge from the pressure shaft spins the turbines.

The MHPA, in its June’s progress report stated that contact and consolidation grouting works of the HRT is also being done in parallel so that plugging of the tunnel is achieved, soon after completion of overt and invert lining of the remaining portion of the HRT.

Out of 13,505.19m of proposed contact grouting in HRT, 5617.7m has been completed. About 1,208m of consolidation grouting has been completed.

As for the dam components, including intake tunnel and desilting chambers, all works have been completed and currently cleaning works are going on, according to the report.

The Diversion Tunnel and Head race Tunnel of Mangdechhu Project shall be plugged by the end of October this year, meaning that by this time, filling the dam with water would begin. This the MHPA management said is being done because managing the water discharge would be easier post-monsoon.

Data reveals that Mangdechhu reveals a discharge of 100 cumecs (cubic meters per second) during monsoon. By mid September, he said it drops to 58 cumecs, which is more manageable to control the water discharge in a channelised manner.

As of May 31 this year, 96.5 percent of the works have been completed including the transmission lines.

“After filling the pressure shaft and surge shaft with water, each turbine would be tested, one by one,” A K Mishra, said. “Similarly each machine will have to be synchronised with the Indian grid.”

The whole process will consume about a month. If everything goes smooth, commissioning date of November is achievable, project officials said.

The first revised cost estimate of Rs 40.2B at 2014 price level was approved by the Government of India, which is an increase of Rs. 11,24B from the initial approved cost of Rs. 28.96B at March 2008 price level.

The second revised cost estimate at 2016 price level was Rs 46.72B. As on June 30, 2018, the MHPA has received a total amount of Rs 45.67B, of which Rs 44.69B has been spent.

Tshering Dorji