February 26, 2021 1:58:05 am
TO COMPLETE the Veravali-Powai-Ghatkopar water supply tunnel project, which has been delayed after a tunnel boring machine (TBM) got stuck in the same tunnel it was drilling, the BMC now plans to bring in a new TBM.
According to BMC officials, after a series of meetings with experts from IIT-Mumbai and civic engineers, it has been decided to appoint a new contractor who will bring in a new TBM to complete the remaining tunneling works. To improve water supply in western and eastern parts of the city and strengthen the network, BMC’s water supply project (WSP) department is constructing a 6.6-km tunnel from Veravali to Ghatkopar.
In August 2019, a TBM – of German make and brought from Herrenknecht – got stuck near Powai while it was drilling a soil strata made of Pyroclastic Ash, which is very loose in nature. During monsoon, the tunnel was flooded and the TBM is now surrounded by slush.
BMC officials said that now, the new deadline is likely to be 2024 and the overall cost for the remaining work of tunnelling could be around Rs 300 crore, including the purchase of the new TBM. The work includes the purchase of a new TBM, construction of a new launching shaft to lower the TBM ahead of the location where the old one is stuck, completing the remaining excavation work and then removal of the stuck machine.
Additional Municipal Commissioner (Projects) P Velrasu said that the new contract will be based on the design, build and operate basis.
“Mumbai being a reclaimed city, the soil strata is unpredictable. Now, we have better information about the soil strata that exists at the alignment of the tunnel. BMC had conducted studies on the alignment and the soil strata, based on which contractors have executed the project. This has completely shifted the risk on the corporation.”
“We have had several discussions. Things will start taking shape in the next few days.”
According to BMC records, in January 2012, a contract of Rs 183 crore for constructing the Veravali-Powai-Ghatkopar water supply project was awarded to Patel Engineering Limited with a 48-month deadline. There are two arms of the tunnel and Powai is the centre point.
Officials said that one arm (2.2 km) from Powai to Veravali has been completed and commissioned. The other arm from Powai to Ghatkopar is of 4.4 km. On this stretch, during tunneling work from Powai towards Ghatkopar, the TBM got stuck after excavating 1.2 km at a depth of about 90 m. Officials said with the appointment of a new contractor, the project deadline will see a third extension. “The construction of the remaining tunnel and removal of the stuck machine is expected to be completed in three years. The original deadline for the project was 2016. Two extensions have been given to the contractor,” said an official from WSP department
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