MumbaiTo prevent waterlogging in south Mumbai, the Brihanmumbai Municipal Corporation (BMC) will soon take up a mammoth task to replace and widen the British-era closed pipe drains called dhapas.The Rs24-crore project will focus on flood-prone areas. The BMC has, however, not mapped dhapa drains in the island city. The BMC floated tenders on Friday to overhaul dhapa drains and reconstruct nullahs in Zone II of the city, which comprises Byculla, Mumbai Central, Chinchpokli, Elphinstone, Mahalaxmi, Worli, and Lower Parel.It proposes to start replacing these drains, which have gone through wear and tear over the years, within 12 to 14 months after finalising a contractor, which usually takes three to four months.For that, a civic official said the BMC will have to dig several patches of roads, six to eight metres below the ground. This is likely to inconvenience motorists. An official from the storm water drains (SWD) department said, “We do not have an underground map of the drains. But we are mapping roads in flood-prone areas where dhapa drains can be repaired or replaced.” The civic official said, “There are at least five areas in each ward in Zone II, where old drains will be replaced with wider ones. It will ensure that rain water is completely drained during the monsoon. Officials from each ward were asked to monitor flood-prone areas three month ago. Work on drains in these areas will start on a priority basis.” The official quoted above said, “We have marked spots prone to waterlogging. We will start work by widening drains here.” In 2009, two consecutive accidents happened on Peddar road, where the surface of the road caved in after an underground dhapa drain collapsed. Following this, a survey of underground British-era drains was conducted in the Peddar road area which revealed an extensive SWD system, most of which was dilapidated. Estimating that the condition of the rest of the old drains in the city will be similar to this one, BMC has been planning to repair, and replace dhapa drains.