The city’s sewer network has been clogged with silt that would take more than Rs 1,000 crore to flush out.
Mayor Bikash Ranjan Bhattacharyya has blamed years of neglect and petty politics in the civic body, continuing since the “pre-Independence era”, for the situation.
“The accumulated silt — the cause of extensive waterlogging across the city — has imposed a financial burden of Rs 1,000 crore on the civic body. The present board has inherited this liability,” the mayor pointed out.
“We have convinced the Centre about the need to clear the blockages in the sewers and a detailed project report of Rs 500 crore has been submitted to the Union urban development ministry,” said municipal commissioner Alapan Bandyopadhyay.
The Calcutta Municipal Corporation has decided on twin measures as part of its drainage revamp initiative — desilting brick sewers and trunk sewers (big-diameter pipes under main roads) using “a micro-tunnelling technique” and removing encroachments over surface drains.
Several firms in Europe and Singapore have expressed interest in undertaking the micro-tunnelling (trenchless) work.
A survey in the late-1990s had revealed that over 55 per cent of the space within brick and trunk sewers has been filled up with “solidified silt”. The blockage is as much as 70 per cent in places like Sealdah, Gariahat and Mechhua.
In some pockets, the silt is so solidified that any attempt at extraction would result in a collapse of the network.
In 2006-07, the sewers under AJC Bose Road, APC Road and Camac Street yielded around 2.25 lakh metric tonnes of silt, which was even less than one per cent of the deposit in the entire network.
A civic official pointed out that if the silt extracted from under the three arteries was dumped in Mohammad Ali Park, the three-bigha plot would attain the height of a 15-storeyed building.
The civic authorities are also planning to remove illegal, makeshift shops that have sprouted up by covering at least 500 km of the 900-km-long surface drains.
Thank to these shops, the drains have not been be cleaned for years, reducing their water-bearing capacity.