While the discussion for the tariff of the 720megawatt (MW) Mangdechhu Hydro Project Authority (MHPA) is still on-going, the project is committed to commission its four units on January 10, January 30, February 10 and February 28.

The project’s managing director, AK Mishra, shared the new dates on December 13 and said the overall physical progress of the project is 99.3 percent.

Inside the tunnels, workers were seen cleaning the areas, fixing pipes and cables running through the walls, scraping off debris and withdrawing the equipment.

“We are just doing the finishing works,” an engineer, Sonam Tobgyel, said. 

He was inside adit 5 (entrance) of the headrace tunnel (HRT), monitoring the ‘Butterfly Valve Chamber (BVC)’. Workers were testing it. “I spent most of my time here,” the engineer said.

The adit 5 is closed and the butterfly valve isolates the tunnel from the pressure shaft.

All physical erections of the hydro-mechanical works, officials say, are complete and they are testing the gates. The electro-mechanical machines are also being tested.

In adit 4, a section officer of the project, Sapna Ghalley, explained that they are in the last stage of plugging the diversion tunnels.

“We will close this wall and then the work is complete,” she said.

Workers were knee-deep in water, cleaning the area. “There was some flooding from the seepage water,” an official explained. “We have to ensure that it is drained well.”

Inside the powerhouse, of the four 180megawatt (MW) units, unit 1,2 and 3 have been boxed up. Works are ongoing to complete the fourth one. Four electrical engineers are setting up the control system for the generating units.

Executive engineer for the controls, Hareesh, explained that the units are connected to the computers, which would monitor the power generation.

The managing director said the transmission lines are charged from the Mangdechhu pothead yard to Alipur Daur via Jigmeling substation a month ago, using the Punatsangchhu II and I lines as of now.

“The Mangdechhu power line construction is struck in Assam because of wildlife clearance from Assam government, as it falls through the tiger reserve for 47kms and it is expected to be ready by March 2019,” he said.

He said the officials in Assam government granted the clearance and the first stage clearance is also accorded by the India government’s Ministry of Environment and Forest. “In the meantime, we will be using Punatsangchhu II and I transmission lines for power evacuation for now. We will shift to our lines once it is ready.”

The Druk Green Power Corporation (DGPC), which is about to take over the project once fully commissioned, is interviewing the employees.

It was learnt that 266 people have been interviewed. DGPC would be deploying about 350 employees once they take over.

There are however reports of a rush to complete the project. A rumour going around in Trongsa is that water was being stored to just spin the turbine for commissioning and that works would resume after the commissioning. Some even alleged that quality was compromised to complete the project.

AK Mishra, however, sounded confident.

He said the project would do everything systematically, as they had always done.

“My duty is to deliver this project to the Royal Government of Bhutan at the optimum cost and time,” he said. “I am sure I could fulfil this responsibility.”

He said that people could always visit the project and see the progress.

He said the project is trying to use the seepage water to fill the two-pressure shafts. “The water conductor system that is HRT and pressure shafts will consume some time, which could be partly saved if the pressure shafts are filled as above.”


The delay

Although not as bad as the Punatsangchu I and II, the Mangdechhu project also had some minor problems.

The project was initially expected to complete by mid-2017 and has revised the commissioning date about four times.

AK Mishra explained that he joined the project on August 27, 2010, and the detailed project report time is seven years, which means he should have delivered the project in September 2017.

He said the project lost 15 months and that was not because of the failure of the project management.

On March 9, 2011, the project signed the design and engineering agreement with NHPC, where it lost the initial six months in procedural formalities, three months each in 2016 and 2017 due to natural calamities like flooding in Phuentsholing, where BHEL equipment were washed away and Zomkhalum where the restoration of roads took some time. “The remaining six months was affected by the lack of cement supply.”

AK Mishra said the cost is Nu 60M per megawatt, which is the cheapest. “Once exported, it will earn good revenue and help the government in implementing its annual plan.”


Cost escalation

The project, which the government initially signed at Nu 29B on a 70:30 loan and grant ratio with India is now completing at about Nu 50B.

The managing director explained the cost escalation occurred because of inflation, deviation and extra work.

Plant details

The project comprises of 114m high concrete gravity dam from the deepest foundation level of 1,636m with two intake tunnels of 126m and 175m length, and an HRT capable of discharging 118cumec (cubic meters per second).

The 147.2m-high surge shaft will be 13.5m in diameter, and water will be fed to the underground powerhouse through two steel-lined pressure shafts measuring 1,873m long and 3.5m in diameter.

The underground powerhouse comprises of four 180MW Pelton turbines. The main cavern of the underground powerhouse will be 41m high and 155m long.

Meanwhile, the project was executed by 63 Bhutanese contractors, amounting to Nu 2.68B and five Indian contractors amounting to Nu 220M.

The project has 454 employees, of which six percent are non-Bhutanese. But all workers are non-Bhutanese inside the tunnels and main work areas.

The project claims to have spent more than Nu 398M on corporate social responsibility.

Tashi Dema| Trongsa