The Making of Atal Setu – India’s Longest Sea Bridge

The 12th longest sea bridge in the world and the longest sea bridge in India was recently inaugurated by PM Modi. Are you aware of that?

The construction of this bridge has been nothing short of extraordinary, given the complex challenges posed by its marine location. In this blog, we will unravel the making of the Atal Setu and understand what makes it one of India’s most remarkable infrastructure projects.

But first, it’s crucial to understand why it was required in the first place.

The Need for Atal Setu

Mumbai is home to over 12.5 million people and handles over 40% of India’s sea-borne cargo. The existing routes connecting Mumbai Island City to the mainland get severely congested, with average traffic speeds reduced to 10–15 kmph during peak hours.

The construction of the Mumbai Trans Harbour Link project connecting Sewri on the Mumbai mainland to Chirle on Nhava Island will help redirect traffic away from the congested routes and can handle over 70,000 vehicles per day. This sea bridge cuts down travel time between the two points from over 90 minutes to just 20 minutes.

The sea link will also give a fillip to the development of the lesser-developed areas of Navi Mumbai, Panvel, Kharghar, etc. The connectivity and reduced travel time it provides are expected to attract more commercial and residential development in these areas.

Characteristics of Atal Setu

• Design – McElhanney Consulting Service Limited
• Total length – 21.8 kilometres 
• Width – 27 metres 
• Height – 25 metres
• Water depth – 47 metres 
• Traversable? – Yes
• Longest span – 180 metres 
• Piers in water – 1,089
• Design life – 100+ years
• Construction cost – ₹17,083 crore

Unparalleled Scale and Complexity of Construction

The scale of design and construction has been unprecedented, consuming 165,000 tonnes of steel reinforcement, 96,250 tonnes of structural steel sheets and plates, and 830,000 cubic meters of concrete. 70 specialized orthotropic steel decks were pre-fabricated to enable the long spans over water, using over 96,250 tonnes of speciality steel. The longest span extends 180 meters between piers, setting a record for India’s longest bridge span constructed over water.

A key highlight has been the extensive use of precast segments, minimizing work over water. Around 12,000 concrete boxes were precast in a facility and then joined to form 60-metre spans weighing up to 1050 tons each. Likewise, steel spans were assembled on land before being launched over piers using advanced techniques. Construction also involved highly complex activities like lifting and placing 2,600-tonne steel decks atop piers in tidal waters using precision-engineered self-propelled jack-up/jack-down systems.

Over 14,000 skilled personnel, including engineers and technicians, worked around the clock, braving the middle of the sea. The Mumbai Metropolitan Region Development Authority (MMRDA) set up casting yards at multiple locations where segment casting was done using specialized formwork systems. The segments were then launched with precision using segment-carrying girders.

Advanced engineering techniques like full-span launching, reverse circulation drilling, and customized barge-mounted cranes have been used for the first time in the country. Construction progressed rapidly after initial delays, with 95% completion by June 2023, followed by integration with road links, testing, and inspections before the January 2024 opening.

Features of the Atal Setu

1. Noise Barriers and Vision Barriers

A 6 km stretch of the sea link has noise barriers installed on both sides to minimize noise pollution and disturbance to residential zones. It also has vision barriers on stretches near sensitive sites like the Bhabha Atomic Research Centre to prevent visual access. Together, these aid in the conservation of migratory birds that feed and breed in the adjoining Sewri Mudflats Wildlife Sanctuary. Silent zones with no honking have also been enforced near habitat areas.

2. Intelligent Traffic Management

The bridge boasts state-of-the-art traffic management systems for safety and congestion control. An Intelligent Transport System (ITS) enables real-time monitoring of traffic, immediate incident detection, and centralized coordination of emergency responses. Along with speed limits, surveillance systems, and speed violation detection cameras, it facilitates the rapid dispatch of rescue resources.

3. Disaster Resilience

Built to withstand disasters, the irreversible box girder sections can resist earthquakes of magnitude 6.5 and cyclonic winds up to 270 kmph. It can also handle ship collision loads. Warning systems linked to structural health monitoring immediately identify any damage or deterioration for timely repairs. Thus, the bridge offers over 100 years of resilient and disruption-free service.

4. Sustainability

With sustainability in mind, the bridge construction utilized industrial byproducts like copper slag and ground-granulated blast furnace slag. Special stone mastic asphalt has been used for its ability to reduce noise, improve vehicle grip, enhance durability, and enable easier repairs through recycling. Energy-efficient lighting reduces electricity consumption, while specialized light fixtures prevent spillage into the sea that would disturb marine habitats.

Thus, Atal Setu sets global benchmarks in sustainable construction using industrial waste while prioritizing the conservation of ecosystems in surrounding areas.

Conclusion

The inauguration of the Atal Setu Bridge represents a new era of ambitious infrastructure for India. As the nation’s longest sea bridge, it demonstrates India’s exceptional engineering capabilities and commitment to enhancing connectivity for its citizens. Constructed using an advanced TMT bar for strength and endurance, the Atal Setu stands as proof of what India can achieve through vision and tenacity.

As the country continues investing in critical infrastructure projects, innovative building materials and techniques will be key driving forces. Companies like Jumbo TMX are developing cutting-edge TMT bar solutions that leverage technology to improve strength, corrosion resistance, and ease of construction. With homegrown innovation from Indian companies, the nation is poised to catalyze even greater infrastructure achievements moving forward.