In the age of supersonic jets, the drainage department of the Calcutta Municipal Corporation (CMC) continues to depend on pumps belonging to the piston-engine bi-plane era to protect millions from waterlogging during monsoon. About 60 per cent of the pumps and motors in the drainage pumping stations date back to before World War II, when a four-seater De Havilland Fox Moth bi-plane was ferrying passengers in the country.

The result: pockets in Calcutta are inundated after rainfall at the rate of 6 mm per hour, even though the hourly drainage capacity of the 18 pumping stations is claimed to be 24 mm.

The reason is not far to seek. More than 60 per cent of the 95 pumps and motors in the pumping stations are 60 to 72 years old and their capacities have decreased by 20 to 25 per cent. Hence, the actual drainage capacity of the pumping stations is hardly 2.5 mm per hour. Most of the pumps in Palmer Bazar, Ballygunge and Maniktala pumping stations require immediate replacement.

A special technical team recently identified antique equipment as the cause of waterlogging in the city, prompting mayor Bikash Ranjan Bhattacharyya to direct the municipal commissioner to draw up a large-scale revamp scheme for drainage pumping stations.

According to municipal commissioner Alapan Bandyopadhyay, who is now holding regular meetings with engineers to prepare the scheme, about 60 pumps and motors need to be replaced immediately. The project involves an investment to the tune of Rs 200 crore. The CMC is planning to implement the scheme under the Jawaharlal Nehru National Urban Renewal Mission.

The revamp of the pumping stations is expected to take two years, stated CMC chief engineer Nilangshu Bose.

There are two primary systems — Town and Suburban — to drain out accumulated run off water after a heavy shower. While the Town system is mainly dependent on Palmer Bazar pumping station, the suburban system banks on Ballygunge pumping station.

The majority of the drainage pumping stations are equipped with British pumps and German motors, said a civic engineer. On an average, a pump delivers peak performance for 100,000 hours and its motor for 50,000 hours, the engineer added. The efficiency of the pumps and the motors thereafter starts to fall.

Civic deputy chief engineer (civil) P.K. Dhua, who looks after drainage and sewerage, said the pumps, barring one, were procured in 1934 and 1976. Only one pump was installed in 1996.