Project will make age-old above ground water mains carrying water to treatment plant redundant
In a bid to phase out above the ground British-era pipelines carrying water from Vaitarna, Upper Vaitarna, Middle Vaitarna and Tansa to Bhandup Water Treatment Plant, the Brihanmumbai Municipal Corporation (BMC) is all set to commission a massive tunnel which will collect all the water below the ground at a point and bring it to the plant at faster speed. This will help the transition loss due to leakages and tampering. However, the Rs2,000-crore project has missed its deadline of June 2016 and now it will see the light of the day in October.
The underground tunnel is in two parts, one is from Gundavali (near Bhiwandi) to Kapurbawdi (Thane) and the other from Kapurbawdi to Bhandup. Although the distance between Gundavali to Bhandup complex is more than 100 km, the aerial distance is close to 15 km. At least a kilometre of the 4,000 MLD capacity tunnel passes under the Thane creek.
"The commissioning is planned by the first week of October," said a senior official from Water Supply Projects.
The project will prove to be a boon for the city as water is brought from the source to Bhandup plant through a network of water mains, viz., Vaitarna, Upper Vaitarna, Tansa East and Tansa West. These mains, which have been carrying water, are more than 50 to 90 years old.
The thickness of these pipelines has reduced due to wear and tear, thereby causing frequent bursts. Hence it was necessary to replace them. The water supply network in the city is also old. Development works in the city as also encroachments have led to burial of water pipelines below roads and infrastructure at various locations. Due to old and dilapidated pipelines there have been frequent occurrences of bursts and leakages leading to frequent repairs. Sometimes, it becomes difficult even to approach such buried pipelines in case of repairs.
Considering all the above facts, BMC has undertaken various tunnel projects. It is the first civic body in India to undertake the tunnel projects with the use of Tunnel Boring Machine (TBM) in 1983. Till date more than 67km-long tunnels have been completed and commissioned. About 22 km tunneling is currently under progress and around 124 km of tunnels (15km in the city area and about 109 km outside city) are proposed to be undertaken in the future for augmentation of the water supply to Mumbai.
Benefits of tunnels
1) Tunnels are designed as earthquake resistant structures and have a life of 100 years. Need minimum maintenance
2) Tunnels begin 60 to 100 metre deep below the ground and avoid losses due to thefts, leakages. Thus they play a major role in reducing the percentage of Non Revenue Water (NRW) and help reduction in contamination. Also, they do not require expenses on account of land acquisition and rehabilitation
3) Tunnels operate on gravitational flow and thus do not require additional cost for pumping of water
4) Mumbai's dense population, heavy road traffic as well as the large network of underground utilities make it extremely difficult to lay new water mains of large diameters by open trench method. This makes tunnels the best option
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