The Environmental Cost Of A Tunnel Road

The fast-paced progress of Bengaluru’s Tunnel Road Project — from its announcement in early 2024 to cabinet approval a year later, and preparation of the detailed project report of the North-South corridor — has been in stark contrast to other public transport infrastructure projects in the city, such as the Bengaluru Suburban Rail Project (BSRP) and Namma Metro project, both of which have been mired in delays.

Envisioned by Deputy Chief Minister D.K. Shivakumar, the ambitious traffic decongestion project has two planned routes: the North-South corridor connecting Hebbal and Silk Board, and the East-West corridor connecting K.R.Puram to Nayandahalli.

The implementation of the project will initially focus on the North-South corridor, a 16.74 km-twin tunnel from Esteem Mall in Hebbal to Silk Board KSRP Junction, with intermediate ramps connecting to the main tunnel at Mekri Circle (Palace Ground), Race Course, and Lalbagh. It is expected to reduce travel time from about 90 minutes to 35 minutes, according to the detailed project report (DPR) by Rodic Consultants Pvt Ltd.

Bengaluru Smart Infrastructure Ltd (B-SMILE), a special purpose vehicle leading the project, will fund nearly half the project cost (₹8,476 crores), with the rest to be borne by a private party. The bidding process is ongoing, with the tender deadline revised twice already.

As the state government powers through delays, the Tunnel Road Project, designed primarily for car users, has faced severe backlash from mobility experts, environmentalists and citizens alike. Multiple public interest litigations (PILs) have been filed with the Karnataka High Court, and civic groups have moved the National Green Tribunal (NGT) seeking the cancellation of the project. Member of Parliament for Bengaluru South, Tejasvi Surya, has opposed the project, citing environmental concerns and the threat to Lalbagh Botanical Gardens, which the proposed tunnel road cuts through.

Can the Tunnel Road decongest Bengaluru?

According to independent mobility expert Satya Arikutharam, the foundational basis of the Tunnel Road Project is flawed. The Comprehensive Mobility Plan for Bengaluru, developed by the Directorate of Urban Land Transport (DULT) and accepted by the government in 2020, set a goal of 73% of every motorised trip in Bengaluru to be catered to by public transport. “So, the onus should be on strengthening the public transport spine of metro, suburban rail, and the complementing bus network,” he said. “There is no need for such an infrastructure from a transport planning perspective.”

Crucially, the Tunnel Road Project excludes 80% of the vehicles on Bengaluru roads, says activist Rajkumar Dugar, Convener of Citizens for Citizens (C4C). “No two-wheelers or three-wheelers will be allowed inside. Maybe 5-10% will be (other) four-wheelers or six-wheelers, but there are size restrictions. So it will almost exclusively be used by cars,” he said.

Another aspect is the project’s affordability and viability. According to the DPR, the toll for using the tunnel road will cost ₹19.42 per km. Mobility experts are urging authorities to conduct a ‘willingness to pay’ survey among vehicle users.

The focus should be on providing equity in transport bandwidth allocation, according to Sathyanarayanan Sankaran, Urban Strategy Lead at Rainmatter Foundation, Bengaluru. “All cities are going through the same crisis, where the per capita income is going up, and people are flooding the roads with motor vehicles,” he said. “Only because that is the only choice you are giving them. The choice of public transport, cycling and walking is deprioritised and underinvested.”

The proposed tunnel road has the same alignment as the proposed Namma Metro Phase 3A (Red Line), which means both projects are eating into each other’s viability, according to Arikutharam. “The 37 km-metro line that runs from Sarjapura to Hebbal; the tunnel road mimics the same alignment between Silkboard and Hebbal, roughly half of the metro line,” he said.

“The city has already chosen the metro, as featured in the comprehensive mobility plan. Twenty years from now, if after building the metro, there is still a need for the tunnel road which is unlikely, and we have the wherewithal to do it, so be it, but not now,” Arikutharam added. 

Tunnel Road Project deems Lalbagh dispensable

The Lalbagh Botanical Gardens, one of Bengaluru’s largest lung spaces, is the proposed location for one of the three intermodal hubs, where the surface road can connect to the tunnel road. Not only does the tunnel pass beneath Lalbagh, but the project has demarcated 23,806 sq. m. of parkland for the construction of two ramps and a multi-level intermodal hub.

The alignment of the tunnel will see it pass beneath the famous Lalbagh Rock — a typical exposure of Peninsular Gneiss (metamorphosed granitic rock) that is roughly 3,000 million years old. It was declared a National Geological Monument by the Geological Survey of India (GSI) in March 1975. “While there are similar outcrops elsewhere in the city, because of its age and extensive nature, we have called it a National Geological Monument,” said HSM Prakash, retired Deputy Director General of GSI.

While there have been concerns about the tunnelling impacts on the monument, Prakash notes that it should not be a problem. “The proposed tunnel road below the monument at a depth of 60 meters may not pose any problem to the monument as such. It is a compact, massive rock, made up of sodic feldspar,” he said.

The proposed built-up area in Lalbagh also includes the Western Ghats block on the eastern side of the park. Over five to six years, the horticulture department has recreated a slice of the Western Ghats on six acres of barren land, with rain guns (sprinklers atop tall poles) set up to imitate the precipitation in the region. “There are about 500 individual trees, around 180 species that I selected from the various parts of the Western Ghats, including 70 threatened species,” K.R. Keshava Murthy, the consulting chief botanist for the project, said.

According to Murthy, the Deputy CM visited their herbarium during a site visit and assured that nothing would happen to that particular piece of land. “We planted the saplings in August 2023, and now the trees have grown to huge sizes. If destroyed, I will be devastated,” he said.

One of the recommendations by the Expert Committee appointed to review the DPR, was to re-examine and relocate the vertical shaft and intermodal hub outside Lalbagh. However, the Deputy CM has suggested that Lalbagh will not be affected; that “a small area will be used temporarily during construction and restored afterwards.”

“Nobody returns an inch of land in Bengaluru,” activist Dugar replied. He recalls a similar situation in 2017 when he had actively fought to save the Bamboo Bazaar playground during the development of the Bangalore Cantonment metro station. BMRCL had publicly promised to return 80% of the playground after the construction, but now there is nothing left.

Mobility expert Arikutharam sees Lalbagh as a red herring. “Today, Lalbagh has got more attention than the tunnel road itself. Now it’s easy for the state government to say, ‘Okay, we will shift the alignment, but we’ll go ahead with the project.’ The public will see it as a victory; at the same time, the government will get to push the project through,” he said.

Tree loss, aquifer risk and geological competence

While the DPR has estimated ₹65 crores for tree cutting and relocation as part of the project costing, the tree enumeration remains a mystery. “Till today, there is no information out in the public domain,” Dugar said, regarding the number of trees that will be cut down.

At the recent PIL hearing, the Karnataka High Court bench directed the government to provide details regarding tree cutting in relation to the project. Though the 16.74 km-tunnel runs underground, the intermodal hub facilities at five shaft locations and 13 intermediate ramps (averaging 1.1 km long) require vast land acquisition, which will result in tree loss.

However, it is possible to reduce tree loss, according to Ajay Kumar Naithani, Head of the Engineering Geology Department at the National Institute of Rock Mechanics, Bengaluru. “In Bengaluru, our top priority is saving trees. When building ramps to connect surface roads to tunnels, a steeper slope angle reduces the required site area, thereby minimising tree loss,” he said. “A vertical ramp will require additional structural support, but we must prioritise trees over economic optimisation.”

Arikutharam considers the government’s decision to pursue an underground tunnel road over surface or elevated infrastructure as cavalier. “It is scandalous to mess with the groundwater situation in Bengaluru,” he said.

Naithani, however, favours underground structures. “Compared to elevated options, tunnels are cheaper to construct, have a longer lifespan, and require less maintenance,” he said. “We should prioritise underground structures, but always with great caution.”

“During excavation, you encounter varied zones — hard, competent rock masses alongside weak ones — altering stress distribution,” said Naithani. Geological weak zones serve as recharge areas for water, he explains. “In Bengaluru’s geological setting, we cannot expect large aquifers. The hard granitic rock mass has only secondary permeability, meaning water flows solely through pre-existing faults or fractures, not the rock itself,” he said. “Yet fractures can be extensive, perhaps a kilometre long, potentially connecting to a reservoir.”

In Bengaluru, the primary concern is lakes, he stresses. “There is no question of routing a tunnel beneath a waterbody.”

Yet the proposed alignment passes near Hebbal lake and Lalbagh lake. The latest design change also includes an exit ramp near Sankey Tank, an artificial lake built in 1882 spanning 37 acres.

Retired GSI geologist Prakash emphasises that it is crucial to prepare a detailed geological map for the project. “All along the proposed tunnel, for about half a kilometre on either side, a geological map should be prepared, detailing the type of rock, if there are discontinuities, fractures, faults, shear zones, or old stream beds,” he said. “In the present scenario, in a highly developed city like Bengaluru, there will be little to no surface geological information available. We will have to refer to pre-1971 or pre-1991 geological maps and topography sheets to understand the surface and subsurface.”

“There will be so many restrictions during the investigation period, but we have to leave no stone unturned,” Naithani said. He estimates that it will take at least a year to conduct a complete geological analysis for a massive project like the Tunnel Road. However, the DPR for the North-South corridor was completed in four months, leaving one to question the geological competence of the report.

According to Prakash, upon the request of MP Tejsawi Surya, the sitting deputy general of the GSI has directed the local office to conduct a detailed study of all geological aspects of the project. The Karnataka High Court bench has also sought the opinion of the GSI regarding the environmental implications of the project.

The best and worst case scenario

Dugar and Arikutharam say that the public is largely unaware of the actual contours of the tunnel road project. Many do not even know that their two-wheelers won’t be allowed in the tunnel, Arikutharam said. “Those who know, they are worried that if they oppose something like this, they will be seen as anti-development.”

Arikutharam foresees three outcomes for the tunnel road project. “The worst case is they go ahead and do it, which means you can kiss goodbye to the Metro Red Line. The other scenario is that it stays in limbo, as a distraction from other problems afflicting the city. The best case is they drop the project, but whether they do it gracefully or not will have to be seen,” he said.

“The tunnel road is a microcosm of the lens in which governing bodies make transport decisions,” Sankaran at Rainmatter said. “Instead, they should focus on making the city more liveable.”

(Published under Creative Commons from Mongabay India)