Cutting congestion on roads should help to reduce air pollution
Solved the problem
It aims to reduce traffic congestion by providing a metro line between two major cities
Used engineering skill
Build a railway in twin underground tunnels under a river, and above ground on viaducts
Build a metro line to connect Kolkata, formerly known as Calcutta, to Salt Lake City, India.
The Kolkata East-West Metro – also known as Line 2 of the Kolkata Metro - is a 17km-long railway currently under construction in Kolkata, the capital of West Bengal, in India.
The scheme will connect the state capital to the satellite town of Bidhannagar, popularly known as Salt Lake City.
Around 65% of the railway will run in twin tunnels underground, with the rest above the surface – some of it on specially-constructed viaducts.
The route will include a 520m tunnel under the river Hooghly – the first transportation tunnel constructed under a river in India. Engineers view this section of the line as a major challenge of the project.
The line will connect the two mammoth railway terminals of Howrah and Sealdah – both built in the 19th century.
The scheme is a response to Kolkata’s increasing importance as a business and cultural centre. With a rapidly growing population, the 300-year old city suffers from overpopulation and widespread traffic congestion.
The railway aims to take commuters out of cars and buses and onto the new mass transit system – cutting road traffic and easing congestion. Train bosses estimate 1m people a day will use the scheme by 2035.
Under construction since 2009, the line is set to open in phases from late 2018 to 2020.
Aaron Matthew, Civil Engineer for Transport for London, talks to us about the East-West project in Kolkata, India. The East-West Metro connects Howrah to the East of the city and is India's first under water metro crossing.
Did you know …
The idea for a local railway network in Kolkata was first proposed by Bengal-born British engineer Sir Harley Hugh Dalrymple-Hay in 1921.
Construction of the current scheme has been stalled several times – mainly through problems buying land for the route. The delays have seen project costs rocket to 80% over original estimates.
As with trains on other Kolkata metro lines, seats in every compartment on the east-west line will be reserved for women and senior citizens.
Difference the project will make
The Kolkata East-West Metro aims to change the daily habits of hundreds of thousands of commuters – ditching their cars and the city’s overloaded bus network for a train ride into work.
The scheme should cut traffic on the roads and ease congestion – as well as reducing air pollution from private vehicles.
The scheme will connect Kolkata’s central business district with the fast-developing IT industry hub of Salt Lake City.
How the work was done
Work on the project has seen engineers excavating over 5,400 metres of tunnel for the first phase of the scheme. The project team used two tunnel boring machines (TBMs) to excavate the tunnels.
TBMs come in different sizes, but they’re mostly large and cylinder-shaped. TBMs used for London’s Crossrail project were each 150m long and weighed 1,000 tonnes. A rotating cutterhead dug out earth which was transported back behind the machine by a moving conveyor belt.
Underground stations on the first phase of the Kolkata scheme used the ‘cut and cover’ method of construction.
The technique sees workers dig a trench which is then lined with concrete. A concrete roof is added and sealed, with soil piled on top.
Engineers constructing the tunnel under the river Hooghly used 2 TBMs to dig the structure 13m under the river bed. The machines – named Rachna and Prerna – started on opposite sides and met under the river after 36 days.
The tunnel route was close to a number of old buildings, leading to concerns that some could collapse. Residents in the area were temporarily moved out and some of the buildings reinforced with concrete before digging started.