Gurgaon: A section of the slab over the Leg-1 master stormwater drain collapsed near Rotary Public School on Sushil Aima Marg after heavy rainfall on Tuesday afternoon, exposing the deteriorating condition of the three-decade-old drain.The collapse, spanning around 25 feet, also brought down part of the drain’s retaining wall, causing soil erosion beneath the adjoining service road and triggering a cave-in along its edge.The affected stretch doubles as a designated vending zone built over the drain slab. No injuries were reported as vendors who usually operate there were absent when the slab gave way, averting a major accident. Some vendors, however, claimed a kiosk was washed away by the strong flow of rainwater through the drain.Following the incident, GMDA barricaded the area and closed the affected portion of the service road to prevent accidents.Constructed more than three decades ago using brick masonry, the Leg-1 drain has weakened over the years due to continuous sewage flow and prolonged exposure to corrosive gases. Since its transfer from HSVP to GMDA in 2018, several sections have developed structural defects.In Sept 2023, a 10-15ft-deep cave-in developed outside Tau Devi Lal Park in Sector 23A after the drain weakened, with the collapse extending to part of the adjoining road. Earlier this year, TOI had also reported deterioration of the pavement above the drain as the structure beneath continued to weaken.GMDA is preparing to reconstruct the remaining stretch of the ageing drain. The project was first proposed in 2021 but was delayed after the alignment between Old Delhi-Gurgaon Road and Rezang La Chowk had to be redesigned because of trees along the corridor. The downstream section between Rezang La Chowk and Railway Culvert-47 was rebuilt in 2024, while work on the remaining stretch is yet to begin.In June, GMDA floated a Rs 32-crore tender to reconstruct the remaining 2.8km stretch between Old Delhi-Gurgaon Road and Rezang La Chowk using precast RCC box segments, which is scheduled for completion in 10 months. The project aims to remove a major bottleneck in the city’s stormwater network.Officials said the drain narrows from 4.25 metres upstream of Old Delhi-Gurgaon Road to 2.1 metres downstream, significantly reducing its carrying capacity and leading to frequent overflows in sectors 21, 22, 23 and Palam Vihar during heavy rain. The drain originates at Sikanderpur village and outfalls into the Najafgarh drain, making it a key stormwater channel for a large part of the city.The reconstruction has also gained urgency because the proposed Millennium City Centre-Cyber City metro corridor runs along the same stretch. GMDA has been asked to complete rebuilding the drain before construction of the elevated metro viaduct begins.“We have asked MCG to remove the vendors from the site as a precautionary measure. As a permanent solution, around 700 metres of the stretch from Old Delhi-Gurgaon Road to Tau Devi Lal Park will be reconstructed. We have also initiated the process to construct the new drain between Old Delhi-Gurgaon Road and Rezang La Chowk,” said GMDA executive engineer Vikram Singh.
