Second tunnel borer digs into Howrah Maidan

Kolkata: The second tunnel borer for the East-West Metro was launched for excavation on Tuesday. This tunnel will cover 2.9km underground for the grand under-the-river connectivity.
TOI was witness to the commissioning at Howrah Maidan as the eastbound tunnel boring machine (TBM), Rachna (S639), took off to build the down-tunnel in the presence of N K Goel, chairman of Kolkata Metro Railway Corporation (KMRCL), the agency implementing the city's biggest infrastructure project, around 3 pm on Tuesday.Puja was performed before the machine started moving towards river Hooghly from Howrah Maidan. Prerna, the west-bound (S640) TBM, was moving on the other tunnel.
The TBMs, manufactured by German firm Herrenknecht, were gathering dust at Shibpur ever since work got stalled in July 2012. The first TBM, which started digging in March, has already progressed 225m towards the river, crossing an 88-year-old railway quarters to reach the tracks at Howrah station.
The other TBM, Rachna, was stationed near the starting point of the tunnel through which trains will run from Howrah Maidan towards Kolkata via the river Hooghly.
The twin East-West Metro tunnels will connect the proposed Mahakaran station on the Kolkata side to the terminating station at Howrah Maidan. The current cost of the 8.5m-long TBMs is Rs 70 crore each. Afcons Infrastructure, the joint venture company laying tracks and building stations for the second phase of the East-West Metro between Howrah Maidan and Sealdah on behalf of KMRCL, had bought them for Rs 20 crore each when they were first brought in at Howrah Maidan in June 2011.
In January this year, work on digging the tunnel on the Howrah Maidan-Sealdah stretch resumed after being stuck for more than three-and-a-half years. The first TBM started drilling work in March.
A KMRCL engineer said, "The second TBM will cover 700m to reach Howrah Station in four months. It's expected to reach river Hooghly in the next six months and Kolkata in another year from then." The west-bound TBM is likely to reach Howrah station by the first week of August. It will reach the river in October and cross it to reach the other end (proposed Mahakaran station) in June next year. The depth of the tunnel, with an inner diameter of 18ft, from the Hooghly riverbed will be 66ft. At Howrah Maidan, the tunnel's depth is 59ft from the surface. The TBM, an alternative to the drill-and-blast method of building a tunnel, creates minimum disturbance to surroundings. The machine is fitted with several cutting and drilling tools."
Parallel tunnels are being dug through Howrah Maidan en route to the river. Pre-caste concrete segments are placed to lay the shaft the moment the boring machine drills underground and removes mud to create a portion of the pass.
Work on boring the tunnel got stalled in July 2012 after the Mamata Banerjee government refused to shift encroachers from Bowbazar and Brabourne Road and proposed a realignment. The alignment had to be fixed before the TBM would function. The railways agreed to the realignment proposal in October last year.