Why The Mumbai-Pune 'Missing Link' Is Making Engineers Uncomfortable
By Manu Shrivastava
I did not grow up believing that infrastructure was meant to impress. In the US, at Johns Hopkins University, where I trained, and, in Maryland, where I worked as an environmental engineer, the grammar drilled into me as a professional was different. Build only what can endure, disturb as little as possible and respect the geology before you attempt to conquer it.
Years later, now as a qualified legal counsel and journalist, standing in the Western Ghats in Maharashtra watching traffic slip almost casually through a mountain that refused to move, I realised India had internalised that grammar long before it was theorised in classrooms.
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| The writer at the newly-inaugurated 'Missing Link' stretch of the expressway |
The Mumbai-Pune Expressway is now described in superlatives. Also known as the 'Missing Link', India’s first six-lane controlled-access highway housing the world’s widest underground road tunnel is a feat of speed and connectivity. Those are convenient labels but they are not the truth I see. What I observed, every time I traversed that stretch, are two decisions that defy the orthodoxy I was trained in: a cable-stayed flyover at Khopoli and a twin-tube tunnel driven beneath Lonavala Lake. One announces itself against the valley skyline, the other hides under water, doing its work in silence. Both, in their own ways, challenge the limits of what engineers are supposed to attempt.
I remember my first passage through that tunnel. I did not know there was a lake above me. When I learned of it later, I reacted not with wonder, but with discomfort. Because every environmental instinct tells you that a water body is not something you interfere with lightly. A freshwater lake is a living system as it breathes through its bed, negotiates pressure through its geology and punishes intrusion with seepage, collapse, or slow, irreversible degradation. To place a road tunnel beneath it is not merely ambitious but borders on reckless, unless you understand every variable you are disturbing.
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| The project is an engineering marvel |
The Sahyadri basalt does not make that understanding easy. It fractures unpredictably, allows water to percolate where you least expect it and resists the kind of precision that tunnelling demands. In academic settings, we spoke of such combinations as Case Studies in constraint. High hydrostatic pressure above, uncertain rock behaviour around and zero tolerance for leakage over decades. Most projects would be redesigned to avoid that equation altogether. Here, the equation was accepted.
What followed, I now recognise, was not bravado but discipline. Pre-grouting fissures before excavation. Controlling blast sequences so the rock was persuaded, not shattered. Designing a lining system that behaved less like a road tunnel and more like a submerged structure. The waterproofing philosophy itself felt closer to submarine engineering than highway construction. It was not about stopping water once it entered. It was about ensuring it never found a pathway in the first place.
Two decades on, that restraint has held as the tunnel beneath Lonavala Lake has not betrayed the ecosystem above it. It has not leaked through monsoons that would overwhelm infrastructure in far more temperate geographies. As someone trained to expect failure modes, I find that absence of failure more instructive than any design document. It tells me the intervention respected the system it entered.
The Khopoli flyover, by contrast, is visible theatre. A cable-stayed structure stepping lightly across a valley that would not tolerate a conventional road. But even here, what appears dramatic is, in truth, minimalism. The gradients, the seismic classification of the Ghats, the instability driven by monsoon-soaked soils all combine into a problem of load distribution. You do not solve that by adding more concrete, you solve it by rethinking how forces travel.
The cable-stayed design does exactly that. It redistributes weight through tension rather than mass, allowing the structure to adapt rather than resist. When I look at it, I do not see an aesthetic flourish, I see an engineer’s refusal to overbuild. The pylons are anchored with an understanding of the rock beneath, not in defiance of it. The cables meet the deck at angles that absorb asymmetry instead of amplifying it. Expansion, contraction, seismic movement, all are negotiated through geometry rather than brute reinforcement.
This is where my training and what I witness here converge. Sustainable infrastructure is often reduced to materials and emissions, which is an incomplete reading. True sustainability lies in precision ... in using exactly what is needed and nothing more. In designing systems that cooperate with their environment rather than constantly correcting for it.
What strikes me most about the Mumbai-Pune Expressway is not that it was ambitious for its time. It is that it remains instructive for ours. In an era where infrastructure across the world is frequently overengineered to compensate for uncertainty, these interventions demonstrate the opposite approach. They show what happens when uncertainty is studied, reduced and then engaged with clarity.
I have sat in rooms where projects far less complex are debated into paralysis. Here, the mountain did not move. The lake was not drained. The valley was not filled. The solutions were inserted with a kind of calibrated humility that I was taught to admire but rarely see executed at scale.
As an environmental engineer, I am conditioned to ask what was disturbed, what was lost, what might fail. On this corridor, the more compelling question is different. How did something so intrusive leave so little visible scar? How did a tunnel pass beneath a living lake without announcing its presence to the ecosystem above?
The answers are not rhetorical. They are technical, deliberate, and, in their quiet way, radical. They remind me that the future of infrastructure will not be decided by how loudly we build, but by how precisely we do.
The lake remains where it always was. The road moves beneath it, almost apologetically. And, somewhere between those two layers lies a lesson I suspect the world is only beginning to understand.
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