Rs 12,700-crore Mumbai coastal project taps new state-of-the-art technology

The massive project will involve digging a kilometre-long tunnel under the Arabian Sea - a first for India

For the last 18 months, bystanders, fitness enthusiasts and passersby around the Worli area have been witness to massive earthmoving mach­ines, spaceship-size drills and other such heavy-duty industrial equipment working at a frenetic pace — morning, noon and night. Along with an army of men and women, the machines are on the job to reclaim land from the Arabian Sea to execute one of the most ambitious infrastructure projects — the Mumbai Coastal Road Project — in what is today among the world’s most congested cities.

The massive project will also involve digging a kilometre-long tunnel under the Arabian Sea — a first for India.

The project is envisioned as a solution to the constant traffic jams and bottlenecks that Mumbai’s 20-odd million people deal with day in, day out. In a bid to make the city move faster, the Mumbai Coastal Project, a 29.2-km-long freeway, was proposed alongside the western coast — from the Princess Street Flyover at Marine Drive to Kandivali. 

And now, some 1,500 people are on the job at or near several of Mumbai’s landmarks such as Haji Ali, Breach Candy, Napean Sea Road and Marine Lines giving shape to that vision.   

The project, which has a deadline of 2023, is divided into two phases. Phase 1, to be executed by Municipal Corporation of Greater Mumbai (MCGM), is the South End — a 9.98 km stretch from Princess Street Flyover to the Worli end of the Bandra-Worli Sea Link. Phase 2 (the North End) — from the Bandra end of the Bandra-Worli Sea Link to Kandivali — will be handled by the Maharashtra State Road Development Corporation, or MSRDC.

The total project cost is pegged at around Rs 12,700 crore. Package 2, worth Rs 2,126 crore, has been awarded to the joint venture of Hindustan Construction Company (HCC) and Hyundai Development Corporation (HDC). The other contractors include L&T.

Pulling off something of this scale is no easy feat and calls for novel state-of-the-art technologies. 

Foremost amongst the methods being deployed is the use of “Mono Pile Foundation systems”. Used in Dutch windfarm turbines but a first in India, this involves a single structure that reduces time of installation, cost and speed for setting up bridges and highway foundations, explains an MCGM official who does not wish to be named. “The substructure of the Marine area bridge and interchanges is constructed using the mono pile method," he says. 

The other challenging part of the project is the tunnel, 12.20 metre or 40 feet in diameter, being constructed 20 metre below the sea. Starting some 70 metres under the upscale Malabar Hill, the tunnel would overall be some 2 km long, half of which will be under the sea. It will have three lanes for transportation, one of which is proposed for emergency use.

The Tunnel Boring Machine (TBM) tasked with the job is India’s biggest and has been named “Mavala” — a term drawn from the “soldiers of Shivaji”.

After the tunnel is complete, it will be integrated with the help of a supervisory control and data acquisition (SCADA) system, which allows for ongoing collection of information and monitoring of structures.

Given that most of the coastal highway structures are executed with construction in water, geotextiles (which are permeable fabrics) are being leveraged. So how does this work?

The MCGM official says approach roads or dykes are created to reach the sea wall locations by filling the area with multiple layers of rocks. A final layer of non-woven geotextile is laid over the sea wall bedding layer to prevent the fine matter from the reclamation from getting washed out into the sea. 

Officials say that 5.5 lakh cubic metres of concrete has been poured in for the project and the overall structure, which uses non-corrosive steel rods, has been designed to withstand wear and tear and to remain functional for at least a hundred years.

Work on the coastal road started in November 2018 and about 25 per cent of it has been completed to date. This includes 100 metres of the tunnel, officials say. 

The grand project will provide an alternative North-South Trunk route to Mumbai. It will help reduce traffic congestion on the Western Express Highway, Swami Vivekananda (SV) Road and Link Road. It will also reduce the journey time between South Mumbai to Worli from 45 minutes in peak traffic to 10 minutes flat. And that, ask any Mumbaikar, is worth all the trouble.