Project completion date extended to July 2019 from April
Hydropower: The Punatsangchu-I dam would be the first major dam in the Himalayas to be constructed using the roller compacted concrete (RCC) technology, a shift from usual method of conventional vibrated concrete (CVC).
The project, however anticipates further delay.
The CVC methodology involves concreting blocks, aggregate, earth, sand and other common additives and it is time consuming because the cement takes more time to dry. While the RCC method uses fly ash and less water, thus saving time.
The RCC method is also cheaper because fly ash, one of the main ingredients, was a byproduct from thermal power plants available in India.
The project authority expected the Indian government’s approval to adopt the RCC technology in September or early October last year, but it was done so only in April this year. This has shifted the commissioning date from April 2019 to July 2019.
The project’s managing director, RN Khazanchi said the process itself was time consuming because it had to involve many stakeholders.
He said had the decision to adopt the RCC been cleared last year, works would have started in March this year and by June, the last 15 meters depth of the dam foundation would be concreted.
“But since the approval came at the last working season, we had to reverse our approach in the dam construction (from bottom up to top down),” he said.
The project authority then chose not to open up the last 15m of the dam foundation for the fear of making the sliding hill more fragile. “If we replaced the gap with concrete immediately, after excavation, then nothing could have happened,” he said. But then the decision for RCC was not cleared.
The treatment measures, RN Khazanchi said, from top of the disturbed area till the top of the dam has been completed. “The whole slope has been treated as per the design,” he said.
The second phase, he said comes as a part of dam foundation. The contractor LNT has hired Bauer, a German company, to drill the rocks on the unstable hill and replacing it with 180 piles on six different locations. “This is done for the first time in the sub-continent,” he said.
The managing director assured that quality would not be compromised as it was only a change in technology and dam strength would be same.
Research on RCC method has been carried out for last two years. However a full-scale trail is due early next year. This is also one of the limitations for Punatsangchu-I to expedite the works.
“Whatever unforeseen challenges and surprises in all the components of the project have been covered,” he said.
But the project is running low on budget since the original estimated cost of Nu 52.80B has been exhausted and the revised estimate is due for approval. It did not receive fund for the first quarter of the year.
RN Khazanchi said the revised cost of Nu 93.75B was checked by Public Investment Board of India and then the board has to present it to the Union Cabinet. “This should take place soon,” he said.
As a consequence, payment to major contractors like BHEL and BPC were withheld. This in turn led to slow down in non-critical works such as the headrace tunnel and powerhouse.
He also said that as soon as the contractors knew that funds were exhausted, they reduced their liabilities, for instance reducing the use of equipment and saving the corresponding bill on spare parts.
The project authority, he said did not put much stress in these non-critical parts, which were already on schedule. “But we have been very aggressive on strengthening measures.”
The Indian government, however has approved a total of Nu 14B for this year on Punatshanchu-I. The managing director said this was more than the requirement of about 10.50B.
The first dam using RCC in the Himalayas was recently completed in Sikkim but it is a relatively smaller dam consuming about 150,000 cubic meters of concrete. Punatshangchu-I would be consuming about 1M cubic meters.
Tshering Dorji