Mumbai Water Crisis: BMC Invites Bids for 7-km Underground Tunnel to Supply Desalinated Water to Suburbs

In a move aimed at strengthening Mumbai's water supply amid rising demand, the Brihanmumbai Municipal Corporation (BMC) has invited bids for a 7.05-kilometre underground tunnel that will carry treated water from the upcoming Manori desalination plant to Kandivali in the western suburbs.

The tender for the tunnel was floated last week, nearly a month after the civic body finalised the main contractor for constructing the desalination plant itself. Civic officials said the tunnel is a critical component of the project, as it will serve as the primary conduit to transport desalinated water into Mumbai's existing distribution network.

According to BMC officials, the tunnel will function as a water conveyance tunnel-an underground passage designed to move large volumes of water over long distances. Such tunnels are preferred over surface pipelines because their larger diameter allows smoother flow and minimises pressure losses. The proposed alignment will pass beneath the Gorai Creek and will be constructed using two Tunnel Boring Machines (TBMs) operating simultaneously.

An official associated with the project said the treated water from the Manori plant will be transported through the tunnel to Kandivali, where it will be connected to a shaft linked to the existing water supply system. From there, the water will be distributed to households and commercial establishments. Areas expected to benefit from the supply include Kandivali, Borivali, Malad and Goregaon.

Civic estimates show that the tunnel is being designed to carry 400 million litres per day (MLD) of treated water, along with a full 100 per cent standby capacity to manage emergencies or maintenance shutdowns. The tunnel will be integrated with the city's current distribution system through a dedicated shaft at Kandivali.

The BMC has pegged the cost of the tunnel at around ₹200 crore. As per the tender conditions, the selected contractor will be responsible not only for constructing the tunnel but also for operating and maintaining it for seven years after completion. Officials said floating the tunnel tender soon after awarding the desalination plant contract reflects the civic body's intent to push both components forward in parallel.

The Manori desalination project was first proposed in 2019 as a medium-term solution to Mumbai's growing water needs. The city's daily water demand is estimated at around 4,250 MLD, while the current supply stands at about 3,900 MLD. Once completed, the Manori plant will be the first desalination facility in Maharashtra and is expected to cost ₹11,166 crore for construction alone.

The plant is planned on a 12-hectare site at Manori village, a coastal fishing hamlet in northern Mumbai. The land belongs to the state government, and officials said the process of transferring it to the BMC is nearing completion. The facility will draw seawater from the Arabian Sea, treat it, and send the processed water to the suburbs through the new tunnel.

Mumbai currently depends on a network of lakes located in suburban Mumbai and neighbouring districts such as Thane, Palghar and Nashik for its water supply. Civic planners have said that these reservoirs, even when operating at full capacity, may not be sufficient to meet future demand driven by population growth and commercial expansion.

The desalination plant and the proposed tunnel are being developed as an additional water source to supplement existing supplies, with a particular focus on improving availability in the western suburbs, where consumption pressures continue to rise.