8 TBMs, 3-year deadline for 16.75-km Hebbal–Silk Board tunnel

Bengaluru: Bengaluru Smart Infrastructure Ltd (B.SMILE), set to float a global tender for the tunnel road project, has proposed using eight tunnel boring machines (TBMs) and divided the 16.75-km stretch into two packages.

The agency aims to complete the work, covering Hebbal and Central Silk Board, in three years.

The detailed project report (DPR) had suggested three tunnelling options. The government opted for eight TBMs, each drilling 2 km a year. The three-lane underground twin tunnel road will have a tunnelling length of 33.49 km in both directions, with two-lane exit and entry ramps.

BS Prahallad, Technical Director of B.SMILE, said that TBMs would be lowered at Hebbal, Palace Grounds, Lalbagh, and the Silk Board Junction for tunnelling in multiple directions. "We have already identified the land. Tenders for both packages will be floated together," he said.

Earlier this month, B.SMILE secured government approval to invite two global tenders, allowing different firms to speed up construction.

The newly formed entity, carved out of the Bruhat Bengaluru Mahanagara Palike (BBMP), has also been authorised to borrow Rs 9,303 crore from the Housing and Urban Development Corporation (HUDCO) for the project.

The loan covers 40% of the project cost, including Rs 800 crore for property acquisition for ramps and related works. The interest rate offered is 8.95% per annum.

Though the DPR claims tunnelling can be finished in three years, the timeline could stretch, as seen with Namma Metro, which took around four years for two projects. With Bengaluru’s difficult geology and the need to tunnel beneath the metro’s upcoming Hebbal-Sarjapur line, the road faces several hurdles.

Mobility experts have opposed the project from the start, arguing that faster commute on a 16-km stretch means little if other roads remain clogged. They have urged the government to prioritise public transport and long-term decongestion measures.

The fine print 

Package 1 (North)

Hebbal near Esteem Mall Junction to Sheshadri Road (Freedom Park) 

BBMP share: Rs 3,508 cr

Private funding: Rs 5,262 cr

Package 2 (South)

Sheshadri Road to Silk Board Junction 

BBMP share: Rs 3,571.37 cr

Private funding: Rs 5,357 cr