However, the project’s managing director says there will be no delay or extra expenses incurred

Flood: A swollen Punatsangchhu spilled over the Punatsangchhu Hydropower Project Authority (PHPA)-II coffer dam and flooded the main dam construction site yesterday.

The river began flowing past the project’s diversion tunnel and over the coffer dam by around 9am.

While sources said that it could take more than a month for the project to pump out the water from the construction site, PHPA managing director, RN Khazanchi, said that the overflow or spillover is expected during the monsoon season for PHPA-II, and it would result in no delay or extra expenses.

However, sources said that the already delayed construction of the dam is likely to face more delay as it could take more than a month to pump out the water from the dam-construction site. Further more, this process can begin only after the water level goes down.

However, RN Khazanchi said that each spillover could be addressed within seven-ten days.

He said unlike PHPA-I, the PHPA-II diversion tunnel is not designed for the monsoon season. It is designed to adjust only half the discharge as that of PHPA-I, which has two diversion tunnels.

The PHPA-II was designed to have only one diversion tunnel because of costs, said the managing director. “In our time schedules the spillover of cofferdam is allowed,” RN Khazanchi said.

The top of the cofferdam is 811 metres above sea level and when the water level reaches 808.5 metres, all heavy machinery is relocated to safer grounds, he said.

The height of the cofferdam was increased following a spillover, last year, sources said.

In an earlier interview with Kuensel, RN Khazanchi said concreting of the dam’s foundation would be complete by mid-June. However, this is yet to be completed. The managing director said the “share zone” excavation is still in progress at the dam site.

Prime Minister Tshering Tobgay also pointed out on social media, that the coffer dam is designed to withstand “over topping” or spill over, and therefore, no damage had occurred to the coffer dam, diversion tunnel or dam site.

Meanwhile, the river broke its banks in some areas along the Wangdue valley, flooding roads and fields surrounding a hotel, located 1km away from Bajo town. The river also submerged an area used for mining sand.

The river also washed away embankment walls at Kamichu opposite the small temporary town, leaving families in fear of being flooded.

Sonam Choden, a Kamichu resident who has started constructing a two-storey house opposite the Kamichu bazaar said she is worried about a flood.

She was one of the seven residents of Kamichu bazaar who were provided with substitute land by PHPA-II, last year.

The retaining walls have been washed away and the water level is rising with every rainfall, she said. “This is leaving us sleepless and concerned about the  danger it might bring to us.”

Dawa Gyelmo | Wangdue