MUMBAI: The 33.5 km-long underground Metro 3 route stretches from the super-rich Cuffe Parade area to the business hub of SEEPZ at Andheri. En route, it also provides connectivity between the densely populated residential and commercial areas of the city and the political offices, newly developing business centers, railway stations, and the airport.
It certainly was not an easy task to have an underground metro in the busiest commercial capital of the city. Fifty per cent of tunneling has already been completed while 60% of tunneling work is likely to be completed by the year-end.
Heritage structures
As far as the issue of Heritage structures is concerned, Mumbai is a unique city. Unlike other cities that have some individual structures as Heritage Sites, the whole of the city Centre – the area of South Mumbai that has several Victorian structures as well as the Art Deco ensembles – is declared as the World Heritage Site by the UNESCO. Metro 3 passes under this largest heritage site of the country.
The other world heritage site in the city is the Chhatrapati Shivaji Maharaj Terminus (CSMT). The Heritage committee has asked the Metro administration to ensure that the construction of stations does not obstruct the view of this or any other heritage structures of the city.
Religious structures
Further, the owners of old buildings expressed apprehensions that the underground construction would damage the structures. Similar concerns were expressed by different communities about their religious structures.
Cases were filed and work was stalled by the courts temporarily. Inspections by the experts from premier institutions like IIT certified that the work won’t cause damage to the structures on ground after which the work could continue.
In the densely populated Kalbadevi and Girgaon area, the challenge was of a different nature. Some of the Mumbai’s iconic chawls needed to be demolished to make way for the Metro stations.
A detailed resettlement plan had to be chalked out for the residential as well as the commercial tenants and 734 of such tenants from 30 buildings have recently vacated their structures giving a boost to the work.
Under water
Before reaching the business district of Bandra-Kurla Complex (BKC) the Metro tunnel passes under the ill-famous Mithi river. The tunnels for the Metro route are being dug at the depth of around 15-20 m below the soil surface.
But challenges with tunneling below a water-body, was different. Unexpected behaviour of soil owing to pressure of the water column above and the possibility of mud and water rushing into a just-constructed tunnel section, was a scary thought.
Only other under-river tunnel for a mass transit project in India runs beneath the Hooghly in Kolkata, which was completed two years ago.
All the studies were done and in place of regular Tunnel Boring Machine (TBM) New Austrian Tunneling Method (NATM) was used. This slow process of tunneling causes minimal damage to the soil structure.
The tunneling has already started and is expected to be completed next year.For the 33.5 km route total tunneling required is of 52 km.
The route has 26 underground stations below the roads, which means the traffic above and buildings adjacent to the tunnel needs to be taken care of.