Nearly 7,500 workers and engineers work day and night to end Mumbai’s 60-year wait for a connection that would allow commuters to cross Thane Creek into Navi Mumbai.
The Mumbai Trans Harbor Link (MTHL) – a colossal pier that will connect Island City to Navi Mumbai and parts of the Raigad district – is finally beginning to climb one concrete segment at a time over one of the largest stretches of Thane Creek.
History of the project
The idea of a connector connecting the island city of Mumbai to the mainland was first proposed in 1962 in a study entitled “Planning the Road System for the Mumbai Metropolitan Area”. The idea was to build an infrastructure that would contribute to greater economic integration of the island of Mumbai with Navi Mumbai and the expanded regions of Pune, Goa, Panvel and Alibaug.
It took the Maharashtra government nearly 34 years to prepare a feasibility report of the project, which was produced in 1994. The project was bureaucratic for another decade before the study was updated in 2004 and calls for tenders were launched in 2006.
Corporate rivalry, litigation, and the state’s reluctance to move forward with the project – which would see 50,000 vehicles using the bridge from either end – resulted in the project being frozen for another decade.
In 2017, the project was revived with the Mumbai Metropolitan Region Development Authority (MMRDA) – the node agency responsible for building the project – which signed an agreement with the Japan International Cooperation Agency to provide development loan assistance for the Rs 18,000 billion project provides. Work on the project began in April 2018 and is expected to be completed by mid-2023.
Size of the project
The MTHL is a 21.8 km long bridge that will be India’s longest sea bridge and will connect Sewri in Mumbai to Chirle in Navi Mumbai. It will have six lanes, each 3.5 meters wide. A 16.11 km long section of the bridge will be built on water.
The MMRDA is also conducting a feasibility test as to whether the subway and its own bus corridor can be operated on the sea connection, which enables public transport in addition to passenger transport.
To make the work easier and to ensure a faster completion, the project has been divided into several packages, with all packages being worked on at the same time.
How the mid-lake segments are built
The hardest and most arduous part is building the project sections that are in the marine area. The proximity of the bridge to sensitive facilities such as ONGC, JNPT and BARC makes building these segments difficult, as engineers must be careful not to damage subsea installations such as pipelines or communication cables.
In order to support the enormous weight of the bridge, the engineers have to dig strong foundations, which in certain places lie at a depth of 47 meters.
These foundations support over 1,300 hollow pillars that are on average 26 meters high. It is these pillars that hold the massive girders that ultimately support the prefabricated deck of the bridge.
The 14.8 meter wide and 3.32 meter long precast elements are manufactured in two precast factories, one on the Mumbai side and the other on the Navi Mumbai side.
These precast segments are used with portal machines to manufacture the upper part of the bridge.
“With every foundation we have to determine how deep the ocean floor is. Only when we reach the hard rock bottom of the sea do we stop digging and then do the piling work. The piles are set down depending on the height. This is the most important task as this is the base of the entire bridge, ”said an official involved in the construction.
Challenges at work in the sea
The most demanding work is that which takes place at sea, in which a team of workers and engineers has to take a one-hour boat trip to their place of work every day.
Workers at sea work 24 hours a day in three separate batches, with fresh hands rotated every eight hours.
Workers say that changeable weather and gusty winds are the biggest challenges they face. “We continuously follow the weather reports to know when it will rain or how windy it will be in the coming weeks. We plan our work on the basis of these weather reports. The flood also plays a huge role in the type of work we can do, ”said one official.
“Daily work is also planned after the ebb and flow of the tide. Everything depends on the tides, such as when boats are transported, ”said a senior person on site.
During cyclones that hit the west coast in the past year and a half, the construction site’s ships had to be serviced and locked in the sea.
Officials say nearly 45 percent of the work is complete. They say the lockdown caused by the pandemic has affected construction to some extent, but they hope to meet the 2023 deadline.
“In addition to the complexity in terms of technology, methodology, location and sheer size, the project is extremely challenging. It will prove to be the engine of economic growth and a technical marvel. There are many novel methods and machines that were used for this project. I am sure that it will be in the service of the people in no time, ”said MMRDA commissioner SVR Srinivas.