BMC to construct 7 km underground tunnel to supply water to western suburbs from proposed desalination plant

A month after finalising the contractor for constructing its ambitious desalination plant, the Brihanmumbai Municipal Corporation (BMC) last week floated a fresh tender for constructing an underground water conveyance tunnel that will link the plant with Kandivali in the western suburbs.

A water conveyance tunnel is an underground channel that is used for supplying large quantities of water over a longer distance. Civic officials said that tunnels are preferred over conventional pipelines since the former provides improved water flow due to their larger diameter.

According to the BMC’s latest plan, the new tunnel will be 7.05 km long and will originate from Manori. The tunnel will pass underneath the Gorai Creek and will be excavated by using two Tunnel Boring Machines (TBM) simultaneously.

“The treated water from the desalination plant will be transported through this tunnel to Kandivali, where we will link the tunnel with a shaft of the existing water supply network, from where the water could be further supplied in households and commercial establishments,” said an official privy to the development.

The civic authorities said that the treated water from the plant will be supplied in pockets of western suburbs like Kandivali, Borivali, Malad and Goregaon.

“The tunnel will be equipped to transfer 400 MLD (million litre per day) of water every day with a standby 100 per cent capacity,” said the official.

According to the authorities, the cost of the tunnel has been pegged at Rs 200 crore, and the tender document states that besides construction of the tunnel, the contractor will also be responsible for its operation and maintenance over a period of seven years.

The proposal of constructing a desalination plant was first mooted in 2019 as a solution to counter the issue of growing water demand in Mumbai, which requires 4,250 MLD of water daily, while the civic body can serve only 3,900 MLD. This will be the first desalination plant in Maharashtra.

A desalination plant is a facility where saline water from the sea is scientifically treated by removing salt and minerals to make it fit for consumption. Desalination plants are popular in countries like Israel that have minimal access to natural consumable water, like rivers and lakes, but are close to the sea.

The plant will come up on a 12-hectare plot at Manori village, which is a fishing hamlet in northern Mumbai. The plot is owned by the state government, and civic officials said that the process of transferring the land to the BMC is in the final stage. The civic body will shell out Rs 11,166 crore to construct the desalination plant.

At present, Mumbai is dependent on seven lakes – Tulsi, Vihar, Tansa, Bhatsa, Modak Sagar, Upper Vaitarna, and Middle Vaitarna – located in suburban Mumbai, Thane, Palghar and Nashik for water supply. The catchment area of these lakes gets filled during the monsoon, following which water is transferred through pipelines and tunnels.