Tala powerplant restarted generating electricity on March 17 after completing major repairs to the 23km headrace tunnel (HRT) and other works.
The Tala powerhouse was shutdown on January 1 for inspection and rectification of the HRT and it was expected to restart operation on March 28.
Druk Green Power Corporation (DGPC) Managing Director, Dasho Chhewang Rinzin, said that a team of over 220 officers and support staff worked round the clock and the inspection and rectification works completed by the first week of March.
Issues and findings
DGPC MD said that there were voids and cracks in the sections of the tunnels and the debris on the tunnel floor. The robotic underwater inspection in March 2021 had shown the problems.
In the Padechhu area between Takti and Gedu, the damages to the tunnel were more severe. It was confirmed this section of the tunnel passed through poor geology. Even during construction, the then Tala project authority had faced difficulties in completing this section of the tunnel.
“It was timely that the inspection was undertaken,” the MD said.
Every meter of the tunnel was inspected and the findings were verified by an expert committee who also recommended the remedial measures. They were further reviewed by an international consultant online.
The rectification works involved chipping of the damaged sections of the tunnel and undertaking remedial measures like adding reinforcement and anchor bars, placement of high-performance concrete, chemical treatment and grouting based on site conditions and extent of damages.
The appearance of concrete debris at the generating units cannot be ruled out as several lengthy sections of the tunnel run through ‘very poor geological conditions’.
Even if there are no concrete debris at the generating units, periodical inspection of the tunnel should be done, he said.
The final cost of the exercise is about Nu 115M.
Of that, Nu 75M was to buy specialised construction equipment, which can be used in either maintenance of the existing power plants or transferred to projects under construction.
“Druk Holding and Investments and the DGPC board had given special dispensation for the procurement of specialised construction equipment and materials,” he said.
DGPC prioritised and mobilised workers from Tala hydropower plant and other power plants and its subsidiary companies. Expertise, manpower, materials and equipment support also came from underconstruction hydropower projects especially Punatsangchhu II and Nikachhu projects.
He said the Covid-19 task forces facilitated movement of workers and construction equipment. BPC and BT helped with the construction power and communication networking inside the tunnel.
“Experts visited the different sites in bubble mode while expert advice was availed through video linkages,” he said.
Import of electricity suspended
With Tala plant resuming power generation, import of electricity from India was immediately stopped. Bhutan would now be generating surplus power for export to India.
Dasho Chhewang Rinzin said, “However, the arrangement for imports from India will be kept as an option, in case of exigencies.
Starting January 1, 2022 to March 16, Bhutan imported a little over 240 million units of electricity from India through the energy exchange at a cost of Nu 798M.