Mumbai is in the midst of an epic infrastructure build with six metro lines being built simultaneously alongside new flyovers on the Eastern and Western Expressways and the most challenging project of them all – the $1.5bn Coastal Road. It is highly unlikely that any other city with 15 million people has seen so much digging & drilling & concrete in such a compressed period of time. One day the backstory of how all of this came to be will come to light. Until then we have a chance to understand the enormity of what is unfolding in front of us and this Indian Express helps us dig deeper – no pun intended – into the Coastal Road: “….an ambitious infrastructure project that is set to change the face of the Mumbai coast — a 10-km stretch of the Coastal Road, which, with its undersea tunnel and road built on reclaimed land, is expected to help cut down on travel time in one of the most congested cities in the world.”
The road has two parts to it. The northern part of the road links the Bandra-Worli Sealink with Versova. The southern part links Marine Drive with the Bandra-Worli Sealink using a tunnel and then a flyover to be built on reclaimed land. It is this build which is proving to be tricky and the Express article focuses on what promises to be an epic drama in the years to come: “This entire 10.58-km stretch from Marine Drive to the Worli Sea link will include, besides the road itself — much of it to be built on land reclaimed from the sea — complex interchanges, a road bridge, parks and promenades. But the most challenging segment is from Marine Drive to Girgaon Chowpatty, where the road will run a kilometre or so under the sea, through a set of twin tunnels. For the Shiv Sena-controlled Brihanmumbai Municipal Corporation (BMC), which is funding the project, this is as big as it gets — the tunnel, once ready, will be India’s first undersea road tunnel.”
The Indian Express article has maps of how this build in south Mumbai – which itself has been broken into 3 parts – is going to zip through some of the most congested streets on the planet and then dive under the sea. “…in October 2018, in what was billed as the formal start of construction of the Coastal Road, the BMC began work on reclaiming 111 hectares from the sea. So far, the civic body has completed about 80 hectares. Once completed, Mumbai’s sea coast will extend 100 metres into the sea.” Completion date, on paper at least, is 2023. However, court battles have already begun. “There are concerns being raised on the impact the road and its construction will have on marine life and livelihoods of fishing communities along the coast.”
Furthermore, drilling through the Mumbai subsoil is proving to be harder than expected. Deep underneath Nepean Sea Road, the tunnel boring machines (TBMs) are finding the going challenging. Says Vishal Thombre, executive engineer for the Coastal Road, ““If you are tunneling, there is always the risk of water seepage or a cave-in. While operating the machine, we have to maintain pressure equal to the surface.”
Thombre says the TBM could face some challenges as it moves ahead.
For one, the rock and soil strata below Malabar Hill can be highly unpredictable. “If the strata is rocky, then tunneling is easier but in case of loose strata, it can be challenging,” says an engineer from L&T.
Also, after Malabar Hill, the soil strata of the undersea segment is expected to be marine sand, which could slow down the speed of the TBM.”
Finally, there is one more powerful variable which deserves respect – Mumbai’s famous monsoons. “In 2019, during a cyclone in the city, a major portion of the reclaimed area at Worli and other sites were washed away in high tide. “Three years after the incident, we are still redoing that portion. Such events push back the entire project. When the monsoon arrives, all work mostly comes to a halt and the main focus shifts to securing whatever work has been done,” said a site engineer at Worli.”
So next time when visitors to Mumbai complain about the infrastructure in the city, you know what to tell them.
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