Kolkata: Tunnel vision of city's underbelly
KMC engineers have undertaken de-silting and GRP lining of the sewerage system, which could make waterlogging in the city a thing of the pastkolkata Updated: Jun 27, 2013 11:40 IST
Underneath our roads, lanes and bylanes, a silent revolution is going on. It is likely to change Kolkata forever, particularly during the monsoon. For the past five years, Kolkata Municipal Corporation (KMC) engineers have started de-silting the massive network of sewerage lines, which date back to the British era.
Owing to their sheer age and brick construction, the sewerage lines were unable to drain out the voluminous garbage, silt and slush that got deposited each day. But a special coating is being given to the walls for a speedy and smooth transportation of water and solid materials.
After the project is complete, waterlogging in most areas would be a thing of the past. And, all this is because of the initiatives taken under the JNNURM project by Kolkata Municipal Corporation to upgrade and desilt man-entry and nonman entry brick sewer lines along with fixed Glass Reinforced Polymer (GRP) lining at major thoroughfares of the city. The Rs 508- crore project had started during the tenure of former city mayor Bikash Ranjan Bhattacharyya in 2006-07 and his successor Sovan Chatterjee would be completing the job.
According to a civic technocrat attached to the planning and development department and overseeing the JNNURM project, the present renovation work has resulted in a rise in the velocity of water underneath by 25%, which would significantly ensure less water retention on the streets of Kolkata this monsoon. “Take for example, the scene at Minto Park crossing or Rabindra Sadan or for that matter in front of Bagbazar Bata, the water retention would be almost nil even with heavy showers,” Nilangshu Bhusan Basu, chief municipal engineer (planning and development), told HT.
Earlier, there was around 60% to 90% silt filled in the man-entry brick sewers. “And after our work underground, the silt now is zero per cent and with GRP lining it has also become frictionless. This increases the velocity as well,” the chief engineer added.
The first phase of underground man-entry brick sewer lines includes major trunk roads like Acharya Prafulla Chandra (APC) Road, Acharya Jagadish Chandra (AJC) Bose Road, Kolutola Street, Rash Behari Avenue, Lenin Sarani, Canning Street, Beadon Street, Hazra Road and Nimtola Ghat Street. And, except for Rash Behari Avenue, work at all other major trunk roads had been completed and are expected to show results with almost no waterlogging this monsoon.
The incomplete 1.8 km stretch in Rashbehari Avenue, which includes one of the city’s busiest junctions – Gariahat-Rash Behari Avenue crossing – is yet to be completed. Even de-silting and repairing of non-man entry brick sewers at major waterlogging pockets like Sudder Street, Free School Street, Hungerford Street, Kyd Street, Gopalnagar Road, Gorachand Road, Shyambazar Street, Bagbazar Street, Hari Ghosh Street, Watgunge Street, Bakulbagan Road, Samsul Huda Road, Judges Court Road, Bidhan Sarani, Government Exchange Place, Council House Street (east), Rafi Ahmed Kidwai Road, BB Ganguly Street, Loudon Street and Rowdon Street would ensure fast receding of water level after every heavy shower this season. However, civic engineers are wary of the tall claims made by technocrats associated with the planning and development department on the success of the project.
“Without upgrading the town outfall (which is the biggest sewer line in the world with a dimension of 20 feet by 15 feet and connects to the trunk road sewer lines), the project would not be 100% successful,” a senior engineer attached to KMC’s drainage and sewerage department told HT.
The 1.75-km town outfall, which starts from Moulali crossing and ends in Palmer Bazar drainage pumping station is connected with major trunk roads like APC Road, AJC Bose Road and Lenin Sarani. And to get the best results, similar revolutionary upgrade of man-entry brick sewers should have been undertaken at this stretch too.
The most critical component is that the sewer system of the city has not been overhauled for more than a century. No maintenance and outdated design have led to solidification of deposits and reduction in hydraulic capacity of sewers. Silt has become stones, the channels have been constricted and roofs of the sewers are collapsing. In short, the city lives on a shaky foundation, says a retired civic engineer associated with the drainage and sewerage department.
City outfalls dating back to the Partition of India and refugee influx in 1947 and 1971 led to encroachments. Housing and Urban Development Corporation (Hudco) and Asian Development Bank funds have been utilised by the state irrigation and waterways department to overhaul the entire system. Again, acute crunch of funds did not allow the change to happen in whole of Kolkata. According to civic engineers, phase II would include major trunk roads like Park Street, Grey Street, Ballygunge, Raja Dinendra Street, Bidhan Sarani, Rabindra Sarani and Kaizer Street.
“Although we are ready with our proposals for phase II of the man-entry brick sewers, KMC bosses are not yet ready with matching grants for the JNNURM project and unless the whole of the underground revolution gets completed, 100% success would be a distant dream,” a senior civic engineer from the planning and development department asserted.
According to engineers, waterlogging at Chittaranjan Avenue is here to stay. “Underground Metro Rail had caused some re-settlement of sewer lines, which might be causing problems.”
According to the civic engineers, the British sewerage system of 1870s was designed in such a manner that in case of heavy rainfall there would be a maximum of 12 days of waterlogging in a year. “The force of water in the city’s sewerage system, that drains out both human waste and storm water, is 2.5 feet per second,” said an engineer.
In order to reduce the maximum permissible waterlogging from 12 days a year to just one day only in the city’s central business district, the authorities will have to spend about R1,205 crore. “It is not a viable project for Kolkata,” said a KMC engineer.
“To ensure full utilisation and structural stability of the brick sewers, we have started lining the sewer lines. This will give the 140-year-old sewers a life of another 50 years,” said a civic body technocrat.