The first Tunnel Boring Machine (TBM) lowered for the construction of the underground Metro 3 corridor will not be pulled out till next year, although it will complete its 2.5-km journey by December this year, sources said. The machine is likely to stay under the ground till March next year. “The TBM from Nayanagar will complete its drive by December. But the retrieval depends on the availability of the shaft at Dadar, which is likely to be ready by March,” said S K Gupta, director (Projects), Mumbai Metro Rail Corporation Limited (MMRC).
The machine, named Krishna 1, was lowered into the shaft on September 21 last year and it started work on November 10. It was expected to complete the tunneling work by September this year. Gupta said, so far, there has been no delay in the tunneling work.
According to sources, the retrieval shaft, which is to be constructed near Sena Bhavan in Dadar, has seen a delay due to difficulty in getting right of way. “The retrieval shaft is on the road and it is in a congested area. It was difficult to get land there for the shaft. The arrangement for traffic diversions and utility shifting in the area also took some time. Usually, the construction of a retrieval shaft takes around six months,” said an official working on the project.
“Work on traffic diversion, decking, secant piles and other activities related to the shaft is going on. The shaft will be ready by March but the contractors are making efforts to expedite it,” said Gupta. Since September 2017, Krishna 1 has completed tunneling a distance of 1,574 m and it has to complete another 926 m. It has now reached the area below Paradise Cinema. Krishna 2, tunneling the parallel corridor, has reached near Shobha restaurant in Mahim covering a distance of 1,223 metres.
Vainganga 1, the TBM launched from the Pali shaft in Marol, will be the first of the 17 TBMs to complete tunneling. It will reach airport’s terminal 2 in September covering a distance of 1.26 km. Launched in January this year, it has covered 851m so far. “The TBM commissioned from Pali will be the first one to finish tunneling. It was commissioned from Pali and passing through Marol Naka station, it will reach the retrieval shaft at the International Airport in September,” Gupta said.
The MMRC has received 16 TBMs so far and with the 17th one set to reach this week, it will have all the TBMs in the city. Nine TBMs have started tunneling and completed a total distance of 6.5 km. “All the TBMs are set to be underground by next month. Twelve of them are already under the ground. Nine are tunneling and three more will be commissioned this month,” said Gupta.