An acute water crisis could suck the city dry any day. With the regular buffer stock of Calcutta’s filtered water supply plummeting to a mere 30 hours’ requirement, households would have to go without water in the event of a major breakdown at the Palta waterworks. The culprit: Non-clearance of silt from the final settling tank.
The regular buffer stock of filtered water supply has dwindled alarmingly from three days’ stock to 30 hours’ requirement, as the Calcutta Municipal Corporation (CMC) has done precious little to remove silt from the huge final settling tank at Palta during the past two-and-a-half decades.
There are four primary settling tanks and one final settling tank, which, collectively, can hold over 500 million gallons of water. Palta produces 180 million gallons of filtered surface water every day for about 50 million Calcuttans.
The final settling tank, measuring about 100 acres, has a designed depth of 21 feet and is the mainstay of uninterrupted water supply to the city. But the continuous settling of silt has eaten up two-thirds of its actual depth, said engineers of the water supply department.
“I am worried about the situation. No thorough desilting operation has been undertaken on the settling tanks since 1977,” said member, mayor-in-council (water supply), Sovan Chatterjee. He feared that the city might go dry in the event of a major breakdown at Palta which would need more than a day to be repaired.
In 1977, a desilting operation was carried out through the suction-dredging method by the Calcutta Metropolitan Development Authority (CMDA).
However, since then, neither the former Left Front board, nor the present Trinamul Congress board of the CMC has allotted sufficient funds to remove silt from the final settling tank.
Civic engineers feel the total quantity of silt accumulated in the final settling tank over the past 25 years will be around 45 million cubic feet. Once removed from the tank, this huge quantity of fine-grained alluvial soil could be converted into 450 million pieces of brick and sold at a market price of Rs 135 crore, CMC officials feel.
A senior engineer at Palta pointed out that a thorough desilting operation will cost the CMC a little over Rs 5 crore and the expenses can easily be met by selling the bricks.
The civic authorities are now considering a proposal to allot Rs 50 lakh for undertaking desilting operations this year. But at this rate of annual allotment, it would take about 10 years for the CMC to clean up the final settling tank.