Leak found in Adit tunnel during MHPA Commissioning

To delay Commissioning of project by around a month

The 720 MW Mangdechu Hydroelectric Project was supposed to spin its first turbine and export power from its first 180 MW turbine on 10th May 2019.

The second turbine was supposed to start from 24th May with the third turbine coming online in 9th June and the final turbine producing power on 24th June.

Test runs on two of the turbines had already been done in April 2019.

However, the power generation and export could not take place after the project noticed a leak in the Adit tunnel gate or access tunnel gate when the water was released from the dam to the Head Race Tunnel (HRT) that carries the water to the turbines.

This means that the fifth Adit tunnel gate that leads into the HRT was not plugged tightly enough.

Adit tunnels are used to access the main HRT tunnel from the sides during the construction of the HRT tunnel. It serves no purpose after that.

The MoEA Minister and Chairman of MHPA Lyonpo Loknath Sharma said that the given this development the commissioning of the project would be delayed by around a month.

The MHPA MD A.K Mishra said that the problem is not a major issue.

He said that the gate at the end of every Adit tunnel is held in place by an independent mechanism and is pressurized from the inside which means that it cannot open outwards and is further pressurized by the water in the HRT tunnel.

Mishra said that apart from the gate there is a rubber seal which is held in place by 134 bolts of which each bolt is 1.7 cm in diameter and 7 cm in length.

He said that only around four or five of these bolts came out and water started leaking from these places.

Mishra said that as part of the rectification measures the water from the dam to the HRT has been shut off and the water level in the HRT tunnel itself is being lowered.

He said the seal needs to be fixed and water put in the HRT tunnel again and so the whole process would lead to around a month of delay before power can be produced from the first turbine.

This means that the first two units will come online only in June 2019 and the rest two units will be commissioned by July 2019.

The Mangdechu project is supposed to generate around 3 billion units a year at a price of Nu 4.12 per unit.

Any considerable delay in the Mangdechu project will hit the revenue projections of the government. A large chunk of the civil service pay hike is being financed by the Mangdechu project.

The MHPA Project was initially supposed to be commissioned in June 2018 which was delayed to October 2018 and then January 2019.

After that the commissioning date was to spin all four turbines by April 2019.

This got shifted to May and June 2019 and now has been further shifted to June and July 2019.

However, compared to Punatsangchu I the MHPA project has done much better in terms of timeline and its completion cost.

Mr Mishra said that the project had been delayed only by nine months and its completion cost is projected at Nu 50.120 bn.