‘Bengaluru's terrain suitable for tunnelling, 40 acres of additional land required': B-SMILE technical director addresses concerns about tunnel road project

Indian Express

18 hours ago

Brand Bengaluru's ambitious 16.75 km tunnel road project (TRP) connecting Hebbal and Silk Board junction is in the eye of a storm. From experts at the Indian Institute of Science (IISc) Bengaluru calling it unscientific to the government's own think tank Directorate of Urban Land Transport (DULT) observing that it does not align with city's Comprehensive Mobility Goal (CMP), the project, built at a cost of Rs 17,698 crore, is at the receiving end of severe criticism.
BS Prahallad, technical director of B-SMILE (Bengaluru Smart Infrastructure Limited), a special purpose vehicle executing critical infrastructure projects in Bengaluru, speaks to The Indian Express, breaking down the genesis of the tunnel road project, environmental impact, financial models, and addresses some of the key criticisms over the project.
Excerpts from an interview.
Q. What is the genesis of the tunnel project?
Prahallad: The tunnel project addresses the missing connectivity between Silk Board and Hebbal. Elevated corridors already exist on Hosur Road and Bellary Road, but the central NH stretch through the city was de-notified. Widening or building elevated roads here faced major challenges—land acquisition, displacement, and large-scale tree removal.
Geological studies, including those by Belgian experts, confirmed that Bengaluru's rocky terrain is suitable for tunnelling. Inspired also by Mumbai's coastal road tunnel, this project was chosen as a hazard-free solution to integrate the city's north–south and east–west corridors.
Q. IISc Bengaluru has called the project unscientific. What is your response?
Prahallad: IISc suggested that tunnels may only shift traffic. However, our detailed traffic study provides an end-to-end solution that disperses traffic rather than relocating it. The city's road space has remained constant while vehicles have grown exponentially.
Alongside the tunnel, multi-modal options like suburban rail, Metro, and pod taxis are being developed. With TOD encouraging vertical growth, private vehicle usage is expected to peak around 2035 and gradually decline. Bengaluru is not new to tunnelling—Metro has already executed 40–45 km successfully.
Q. How was the 40 per cent VGF figure arrived at?
Prahallad: Government policy caps VGF at 40 per cent for BOOT (Build-Own-Operate-Transfer) projects. Here, we are adopting a modified BOOT model—40 per cent fixed VGF with a flexible concession period. Financial analysis by BCG confirmed this as the most viable option.
The concessionaire brings 60 per cent investment, while the government's share is borrowed from HUDCO and repaid through Premium FAR fees collected by BBMP. It is not directly funded by Bengaluru's common taxpayers, instead indirectly. If the concessionaire recovers costs earlier, the project reverts to the government sooner.
Q. DPR indicates over 20 potential gridlock points. How will you address this?
Prahallad: We are acquiring about 40.6 acres for ramps and shafts—28.5 acres of government land and 11.5 acres of private land. This ensures we don't squeeze traffic into the existing road width. Most shaft sites are located on government lands, such as KIADB, Race Course, and Lalbagh, thereby minimising the impact on private land.
By planning entry and exit ramps with adequate space, we aim to prevent bottlenecks. We have also allocated Rs 800 crore for land acquisition, as against the initial estimation of Rs 600 crore.
Q. The DULT says the project doesn't align with the Comprehensive Mobility Plan. What do you have to say?
Prahallad: We studied the DULT's remarks carefully. The primary reason for proposing this tunnel is that the highest traffic density is along the north–south and the east–west corridors, which were once part of the National Highway network. The movement of people from the southern parts of the city to the north, and vice versa, cannot be avoided—it is indispensable. That is why this corridor has been identified as a principal proposal.
Q. Has the project received Section 19 BMLTA approval?
Prahallad: Yes, the government consulted the Bengaluru Metropolitan Land Transport Authority (BMLTA), but since rules are not fully framed, the agency directed us to take an appropriate decision at the government level. Following this, the Urban Development Department formed a committee headed by a BMRCL executive.
The committee reviewed feasibility, alignment, cost estimates, and even the number of geotechnical surveys done (18 instead of 14). Their final recommendation was clear—the project is feasible, but to allow a 10–15 per cent cushion for unforeseen conditions.
Q. Will tunnel congestion worsen with more cars in the future?
Prahallad: Our projections show vehicle growth at 7 per cent annually for the first six years, 5 per cent for the next seven years, and 4 per cent from year 15 onwards. Private vehicle use will peak by 2035 but then decline with better public transport and TOD. By 2040, the traffic growth rate is expected to stabilise at just 4 per cent, making tunnel congestion manageable.
Q. Are autos and two-wheelers permitted?
Prahallad: No. This is an NHAI directive, not a state decision. Two-wheelers are barred from tunnels across India, including Mumbai, for safety, speed, and security reasons.
Q. What about buses?
Prahallad: Yes, buses will be allowed. Early financial models excluded them from revenue calculations, which caused confusion. The final DPR makes it clear—public buses, mini-buses, and electric buses will use the tunnel.
Q. Will buses get a dedicated lane?
Prahallad: The design provides a 10.5m-wide, 3-lane carriageway with footpaths and refuge bays. If bus demand grows significantly, a dedicated bus lane can be introduced. The design leaves this flexibility open.
Q. Why retail and commercial spaces at shafts?
Prahallad: Shaft areas would remain underutilised if used only for ventilation. By adding retail, we encourage transit-oriented development and create commuter-friendly hubs. It's similar to multiplexes in malls—mobility combined with amenities attracts more users and prevents these spaces from going to waste.
Q. How will you avoid risks to Metro structures?
Prahallad: The tunnel is 120 feet deep, while Metro tunnels are only about 60 feet. Our alignment ensures at least '2D' clearance below Metro lines, and additional engineering care will be taken at critical crossings. Such points will receive additional engineering care during the construction phase. So there is no reason for apprehension.
Q. Why is there no Environment Impact Assessment (EIA), especially after the Silkyara tunnel collapse in Uttarakhand?
Prahallad: Under the Centre's 2006 notification, no EIA is required. More importantly, Bengaluru's hard granite rock is stable and conducive for tunnelling, unlike the fragile geology in Uttarakhand, which is one of the rarest of the rare cases. Nevertheless, safety precautions are being built into the project.
Q. What about environmental concerns at Lalbagh?
Prahallad: The tunnel runs deep underground and won't disturb surface ecology or groundwater. Precautions will be taken, but similar Metro tunnelling of 40–45 km in Bengaluru faced no objections.
Q. The consultants selected for DPR and feasibility are under scrutiny. Why was such a company chosen?
Prahallad: As per the law of the land, any party has the right to defend themselves. In this case, the companies in question have obtained stay orders from courts against blacklisting from various entities and defended themselves legally. Until the final judgment, we are bound by the law to allow their participation.
Q: How was the response to the pre-bid meeting with construction companies?
Prahallad: Very positive. All leading Indian infrastructure companies participated, along with interest from international players through Indian partnerships. No major objections were raised—only requests for more time to study details, for which we have extended the tender receipt bids till August 21.
Q. The toll of Rs 330 (around Rs 20/km) is being criticised. Is it justified?
Prahallad: First, tolling will start only after project completion—around 2030–31, not today. Second, only tunnel users will pay; surface roads remain toll-free. The rates follow the formula under the state government's 2008 notification, which is applied across the state. This is not unique to our project—similar tolls are already collected on elevated corridors in Electronic City and NICE infrastructure corridors.
Q. The DPR mentions a 51-month deadline. Is that realistic?
Prahallad: Yes. With six tunnel boring machines (TBMs), the pace is about 100m/month, which gives a 48–63 month timeline. If we use eight high-speed TBMs, the progress could double to 200m/month, reducing the timeline to 36 months for boring, plus finishing work. Tunnelling is now standard technology worldwide, and costs and timelines improve with every project.