Over the next few days, a helicopter equipped with a 24-metre transmitter loop will fly over 200 km along the tunnel alignment
Published Nov 03, 2025 | 5:41 PM ⚊ Updated Nov 03, 2025 | 5:41 PM
Telangana Chief Minister A Revanth Reddy flagged off the helicopter operations at the SLBC outlet near Mannevalli in Nagarkurnool ditrict. (Credit: x.com/JacobBhoompag)
Synopsis: Telangana CM Revanth Reddy launched a helicopter-borne electromagnetic survey for the 43.93 km SLBC Tunnel-1 under AMRP on Nov 3, 2025. NGRI’s VTEM survey will map weak zones to complete the world’s longest shaft-less tunnel by mid-2028, irrigate 3 lakh acres, save Rs 500 crore annually, post deadly 2025 flood.
The Telangana state government on Monday, 3 November, launched a helicopter-borne electromagnetic geophysical survey for the Srisailam Left Bank Canal (SLBC) Tunnel-1 under the Alimineti Madhava Reddy Project (AMRP) — a major irrigation initiative aimed at transforming the drought-prone Nalgonda district.
Chief Minister A Revanth Reddy flagged off the helicopter operations at the SLBC outlet near Mannevalli in Nagarkurnool ditrict. Ministers N Utam Kumar Reddy (Irrigation) and Komatiredy Venkatareddy (Roads and Building) accompanied the chief minister. They flew in another helicopter and watched how the survey helicopter was doing its work.
Initiated in 1983, the AMRP seeks to irrigate about 3 lakh acres and provide drinking water to fluoride-affected villages using 3 TMC of Krishna River water. The SLBC’s Tunnel-1, extending 43.93 km, originates from the left bank of the Srisailam reservoir.
So far, 13.94 km has been excavated from the inlet side and 20.4 km from the outlet near Devarkonda, leaving about 9.8 km still to be completed.
Once finished, the tunnel will be the longest in the world excavated without any intermediate access shafts, a rare feat in global engineering. The alignment passes through dense reserve forest and challenging rock formations, making side access impossible.
Aerial Electromagnetic Survey Launched for SLBC Tunnel Works in Presence of Chief Minister Revanth Reddy
The Heliborne Aerial Electromagnetic Survey aimed at facilitating the continuation of Srisailam Left Bank Canal (SLBC) Project Tunnel works was launched in the presence of… pic.twitter.com/9ejlCQobcs
— Jacob Ross (@JacobBhoompag) November 3, 2025
In the tunnel’s absence, a lift irrigation scheme has been operational, costing the Telangana government over ₹500 crore annually in power bills to pump water that would otherwise flow by gravity once the tunnel is complete.
The project has seen multiple setbacks, including a massive flooding in October 2009 that submerged the Tunnel Boring Machine (TBM). Progress has been slow, averaging 75 metres per month per face, due to difficult geology marked by faults and shear zones.
Again, on 22 February, 2025, tragedy struck again when a sudden inflow of water, silt, and debris flooded 2.5 km of the tunnel, trapping and killing eight workers and burying a 130-metre TBM.
Following this, the state government constituted a high-level technical committee that recommended advanced tunnelling methods using scientific monitoring and observational techniques.
Acting on these recommendations, the Telangana Cabinet on 23 October 2025, approved a proposal to complete the tunnel by mid-2028, within the original budget, using cutting-edge technology.
The heli-borne VTEM Plus Magnetic Geophysical Survey, being conducted by the National Geophysical Research Institute (NGRI), forms a crucial part of this renewed strategy.
Over the next few days, a helicopter equipped with a 24-metre transmitter loop will fly over 200 km along the tunnel alignment, sending electromagnetic signals into the ground.
The data collected—covering depths up to 800–1,000 metres—will help identify weak zones, shear layers, and potential water bodies, enabling safer and more precise excavation.
To strengthen technical oversight, the state government has engaged Lt. Gen. Harpal Singh (Retd.), former Engineer-in-Chief of the Indian Army, as Special Advisor, and Col. Parikshit Mehra, a noted tunnel specialist, has been deputed for one year to assist in planning and execution.
Officials said the SLBC tunnel’s completion will not only bring substantial savings in power expenditure but also mark a historic engineering milestone, placing Telangana and India on the global map for world-class underground construction.
(Edited by Amit Vasudev)
