Flood of worries
Malad: 5 million litres/day lost since Feb 17……….Stuti Shukla
Malad: 5 million litres/day lost since Feb 17……….Stuti Shukla
Already reeling under an acute water crisis, Mumbai has been losing an additional 5 million litres everyday since February 17 when a borewell being dug without permission damaged an underground water tunnel in Malad.
After a month of grappling with a maze of technical difficulties in undertaking repairs, the BMC will now appoint a private firm. It will soon float tenders.
Though it has technical staff, the civic body does not have the advanced technology required to repair the tunnel, which is 250 feet below the road surface, a distance equivalent to the height of a 25-storey building.
An official of the hydraulic engineering department admitted engineers are still unaware of the precise nature and extent of the damage. It will be at least two more months before the leaking tunnel can be repaired.
The 12-km-long reinforced cement concrete tunnel, three metres in diameter and running east-west from Bhandup Complex to Liberty Garden in Malad, was damaged when a six-inch borewell was being dug illegally along the Malad-Marve Road. The tunnel supplies water to Malad, Goregaon, Kandivli and Jogeshwari.
Officials said to repair the rupture, workers will have to enter the tunnel through the vertical shaft connecting the tunnel to the dome opening in Liberty Garden, Malad, then walk one kilometre inside to the exact spot of the rupture. “For this we need to completely dewater that portion of the tunnel by isolating it and disconnecting supply,” said an official.
The BMC has not been able to achieve complete isolation as the valves to block supply don’t work. “The valves have been in the open position since 2004, when the tunnel was built. When we tried to close it, we realised the rubber sealing had cracked. So despite closing the valve, water is still gushing in through slits,” said the official.
Only after the BMC replaces the valves and the portion is completely dry can workers enter the tunnel. “Ladders won’t be any use for such a depth. So the firm that is appointed will have to build an electrically-operated gantry to act as a lift for men and machinery,” the official said.
Also, since oxygen cylinders are heavy and don’t last too long, a ventilation system will have be set up. The overall cost of the operation is expected to run into crores.
During this period, water supply will have to depend on an old network of pipelines in use prior to 2004. Unused for six years, these are worn out and rusted. Also, of the three reservoirs in Borivali connecting to the old pipelines, one is shut for repairs. “During the repair period citizens will face an extended water cut,” admitted the official.
The BMC had initially tried to insert a CCTV camera through the borewell to assess the damage but the plan failed because of muddy water around the rupture.
The BMC has installed two de-watering pumps at the site to prevent water from percolating into the ground. The pumps throw out water directly into the storm water drains.