Learning from earlier challenges encountered during the construction of Nagpur Metro Phase I, Maharashtra Metro Rail Corporation Ltd (Maha Metro) introduced a redesigned rainwater harvesting system for Nagpur Metro Phase II that is expected to improve groundwater recharge, reduce waterlogging on roads and minimise maintenance issues. The upgraded system is based on the rainwater harvesting arrangement first introduced during Phase I, where rainwater collected from the elevated metro viaduct deck was channelled through pipes into recharge bores around six to seven metres deep. While the system diverted rainwater from the viaduct, Maha Metro engineers observed issues such as clogging of recharge pits and downpipes, overflow during heavy rainfall and limited storage capacity. These operational experiences formed the basis for a comprehensive redesign in the Phase II.

 

Under the revised design, the depth of recharge bores will no longer follow a standard specification. Instead, engineers are determining the depth individually for every metro pier based on detailed geotechnical investigations. The bore will extend up to around two metres above the local groundwater table, enabling better recharge according to local soil and rock conditions rather than relying on a uniform depth. Another major change is the replacement of the earlier 1 metre by 1 metre collection pit with three circular precast collection chambers, each having a diameter of 1,200 mm. According to Maha Metro officials, the smaller pits used earlier became choked with silt and debris. This resulted in rainwater overflowing onto roads. The larger interconnected chambers increase storage capacity and are expected to prevent roadside spillage even during intense rainfall.