A temporary lake formed at river Rishi Ganga has started discharging water, reducing the risk of another flash flood in the region, while rescuers on Saturday began boring a wider and deeper hole into the tunnel at the flood-ravaged Tapovan-Vishnugad hydel project in an attempt to reach the over 30 people trapped inside for nearly a week.
“The Silt Flushing Tunnel (SFT) was punctured on Friday night itself by drilling a 75mm-diameter hole into it but now it is being widened to 300 mm so that a camera and a water flushing pipe could be inserted into the tunnel where the trapped are possibly located,” General Manager of the NTPC project R P Ahirwal said
The hole will have a depth of 12 metres, he said.
Ahirwal said muck removal from the intake Adit tunnel, below which the SFT is located, has been done up to 136 metres.
Rescuers said they were still hopeful of finding survivors, notwithstanding the numerous challenges like the muck and the water from Dhauli Ganga constantly flowing into the tunnels. The river had deviated from its path after the flash floods that have left 38 people dead and 166 missing.
The State Emergency Operation Centre here said scientists of the Indian Institute of Remote Sensing during an aerial survey of the Rishi Ganga found that the glacial lake formed due to the avalanche over it has begun to release water, which reduces chances of it breaching or causing a fresh flash flood during the rescue operations.
The lake is at the confluence of Raunthi Gad and Rishi Ganga.
According to Central Water Commission (CWC) chairman Saumitra Haldar, it is 400 metres in length, 25 metres wide and 60 metres deep.
The CWC is examining possibilities of what can be done if the water rises to a "critical" level. It is conducting simulation studies and also examining the possibility of carrying out a controlled blast to drain out the water.
"We are assessing what could be the impact if the water level rises following rains and snowfall as predicted by the IMD. We are also studying what volume of water would be released if the lake bursts and how much time it would take to reach downstream," Haldar told PTI.
Ahirwal said making an approach road to the desilting basin from downstream and diverting the course of the Dhauli Ganga river from left to right are also in progress.
P K Tiwari, Commandant of the National Disaster Response Force, said that based on their experience, they are optimistic about saving lives and mentioned the possible presence of air ducts and gaps in the tunnel.
He said the situation had seemed irretrievable initially as the whole project had been damaged, but since then a lot of progress has been made and they will continue their efforts to reach the trapped people.
When asked whether an attempt could also be made to send rescue personnel to the possible location of those trapped inside the tunnel through the hole, Ahirwal said it will need to be widened further for that and will be done if the need arises.
"More than 100 of our scientists are on the job. They are devising strategies and having them implemented," he said.
He said all resources and mechanical equipment required for the operations are available at the project site.
However, citing the conditions inside the tunnel, he said, "We can operate only with a few machines at a time. The rest of them have to be kept on standby because our strategy is to keep the operations underway round the clock."
If for some reason equipment stops working, there are alternatives on standby to ensure that the operations do not stop, he said.
He said many experienced workers of the project went missing in the calamity and those put on the job are new people. Still, they are working with total dedication.
Talking about the biggest challenge being faced by the rescue team, the NTPC official said, "The rescue personnel are going to the tunnel where the men are likely to be trapped via HCC Adit where muck is constantly coming down from the NTPC barrage and its desilting basin to hamper the rescue efforts.
"The water of Dhauli Ganga too is coming into our tunnels through the desilting basin as it has tilted to the left after the avalanche."
"Hence, restoring the flow of the Dhauli Ganga to the right is a big part of our strategy," Ahirwar said.
The sludge choked contours and conduits of the barrage's desilting basin can also be removed more effectively only if the flow is restored to its earlier position.
So far, 38 bodies have been recovered from the affected areas while 166 are still missing. DIG Nilesh Anand Bharne said 11 of the dead have been identified.
Eighteen body parts had also been recovered from the flood-hit areas, of which 10 have been cremated after taking their DNA samples so far, he said.
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