Bengaluru: After the post-rain havoc last week, the Banglore Water Supply and Sewerage Board(BWSSB) has speeded up the work of desilting drains and clearing manholes. In a massive drive  employing 12 jetting machines, the BWSSB is clearing underground drains across the city.

To tackle flash floods and sewage overflowing from manholes this monsoon, the BWSSB has bought 48 new jetting machines (high pressure machines to clean underground drains) in the last financial year, taking the fleet strength to 120. This number, however, is not sufficient to clean the huge underground drain network in the city.

The core areas of the city have a drain network of 3,600 km and Rs1.2 lakh manholes. With the BWSSB’s services extending to the new BBMP areas, and out of the 3,000 km UGD planned in the erstwhile CMC/ TMC areas, about 1,600 km have already been laid. This makes the city’s drain network 5,200 km long. Considering an average of one manhole every 30 m of the drain line, the total number of manholes in the entire city (core and peripheral areas) are Rs1.7 lakh.

“We have begun a massive drive of desilting UGD and clearing manholes. Most important, it is a continuous drive. We carry on desilting work throughout the year except on Sundays. Out of the 120, six are small machines, which will facilitate easy movement on narrow roads in the core city.

One jetting machine can clean two-three manholes in a day and cleaning two manholes automatically desilts another 4-5 manholes downstream,” said T Venkataraju, Engineer-in-Chief, BWSSB.In the experts’ opinion, desilting all the drains just before the monsoon is crucial to avoid flash floods and the BWSSB must finish all the desilting work before the monsoon arrives.

According  to the Indian Meteorological Department, the months between November and  March are a good time to take up desilting of drains as the city receives no rainfall during this season.

“Desilting during the rains is not a good idea. Due to abundance of water, no silt but only water comes out during desilting. This makes the manholes look clean, which might not be the case,” former irrigation secretary Captain S Raja Rao said.