Mumbai pins hopes on Rs 2,000-crore twin projects to cut Mithi River pollution

Mumbai has committed close to Rs 2,000 crore to two large infrastructure projects aimed at tackling long-standing pollution in the Mithi River. The initiative is being positioned as the most comprehensive effort so far, targeting the river’s biggest problem—continuous discharge of untreated sewage—while also addressing flooding in the tidal stretch that affects several dense neighbourhoods every monsoon.

A key component of the plan is an underground diversion tunnel built to reroute dry-weather sewage from major feeder drains before it enters the Mithi. By intercepting wastewater upstream, civic authorities aim to prevent sewage from flowing directly into the river channel, a practice that has continued unchecked for decades.

The tunnel runs for 6.63 km between Bapat Nalla near the airport and Safed Pul Nalla at Saki Naka, and is designed to transport sewage to the upcoming Dharavi wastewater treatment facility. Once operational, the system will shift sewage management away from open drains to a closed, controlled network.

Officials estimate that the diversion system will capture around 168 million litres of sewage per day from the two nallas, accounting for more than half of the Mithi’s total estimated sewage load. This level of interception has not been attempted in earlier river-cleaning projects in the city..

Although tunnelling and shaft construction are nearing completion, authorities say the project’s impact on water quality will not be visible until the Dharavi wastewater treatment plant becomes functional. Until treated discharge begins, the intercepted sewage cannot be fully diverted away from the river.

The Rs 1,700-crore second phase targets the tidal portion of the Mithi, stretching from CST Bridge in Kurla to Mahim Causeway. This section of the river is affected by both sewage inflow and seawater ingress, leading to stagnant water, foul conditions and repeated flooding in adjacent areas.

To prevent backflow during high tide, the project includes gate-and-pump mechanisms at 18 discharge points along the river. These systems are expected to block tidal water from entering the city’s drainage lines and help evacuate stormwater during periods of intense rainfall.

The tidal stretch upgrade includes construction of new sewer lines, retaining walls along vulnerable banks, service roads for maintenance access, a pumping station at Machchimaar Colony and an interceptor at Vakola. Together, these works aim to stabilise the river corridor and improve flow management.

Nearly 2,000 structures have been identified within the project zone, with large clusters along Kurla, Vakola and near Maharashtra Nature Park. Officials acknowledge that encroachment removal and rehabilitation will be the most difficult aspect of the project, as delays could affect wall construction, pipe-laying and access to work sites.

Environmental specialists caution that while sewage diversion is essential, it will not be enough on its own to restore the Mithi. They stress that unless dumping of solid waste, industrial discharge and unregulated riverbank activity are consistently monitored and controlled, improvements may not be sustained despite heavy public spending.