Hyderabad: One of the biggest challenges in starting the rescue operations in earnest in the collapsed SLBC tunnel has been the heavy seepage of water, which continued to rattle rescue planners as the flows continued to be at somewhat alarming high levels. Copious amounts of water fell with rocks and soil when a section of the tunnel caved in on the morning of February 17. “The seepage is constant, 365 days a year,” a senior irrigation department engineer said. During the rainy season, the flow can increase up to 7,000 litres per minute. “Before Covid struck, we encountered heavy flows of 10,000 litres a minute,” the official said when asked about the seepage. Former irrigation minister T Harish Rao too told reporters on Thursday that when all work was halted in the tunnel because of Covid, and the inflows were at 10,000 litres a minute. The irrigation engineer, asked if there was a possibility of the rocks above running out of their stored water, especially with a suspected gaping hole in the roof of the tunnel, said this would not be the case. “We get water every day. It is only during summer months that the flows go down. We do not know just how much water is stored in the rocks surrounding the tunnel, and to what extent in terms of area in the rocks the water is present,” he said. After the February 17 collapse, seepages varied between 3,200 and 5,000 litres per minute posing a challenge with the water column rising in the tunnel making it extremely difficult and hazardous for anyone to go to the 13.9 km marker in the tunnel where the collapse occurred. Typically, a bucket used in homes holds 20 litres of water. In other words, a rate of 3,200 litres per minute translates into a person filling 160 20-litre buckets a minute, and 5,000 litres translates into filling 250 buckets a minute. Since the seepage occurs round the clock, each day the tunnel was receiving anywhere between 2.3 lakh and 3.6 lakh buckets of water a day. An engineer from Jaiprakash Associates, who was tasked with running the dewatering pumps, said one of the biggest challenges was that the pumps were getting jammed because of the enormous amount of very fine silt that filled a large section of the tunnel. On Friday, government officials supervising the operations, said despite all the challenges, dewatering was going on smoothly with eight large pumps, and the seepage was now of clear water, and rescuers were able to move on the tunnel floor unlike over the past few days. “Abhi to paani jharna jaisi aa rahi hai (the water is clear like that from a natural spring),” Firoze Quereshi, one of the rat miners from Delhi, who went into the tunnel a few times, said. “Now that we are managing to pump out more water than that is coming in, we hope rescuers can make better progress in desilting. The more we can do this, the more the locomotive trolley can move forward and this in turn will help evacuate more debris and pieces of steel being cut from the mangled remains of the tunnel boring machine,” the official said.
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