The Alimineti Madhava Reddy Srisailam Left Bank Canal (AMR SLBC) project is in the news for collapse of the tunnel resulting in a serious human tragedy. This is not the first and certainly not the last such incident for major infrastructure projects anywhere in the world.
The gravity of this accident, hopefully, will make all the stakeholders go into the causes of the accident and learn appropriate lessons.
The impact of latest accident has to be fully assessed and it is too early to predict when the work will be resumed. As and when the work restarts, a clear-cut strategy needs to be in place to complete the project.
This is also an opportune time to take comprehensive measures instead of knee-jerk reactions to prevent further delay and cost escalations in the project.
The AMR SLBC project had been on the anvil since 1983, for transfer of water from the Krishna River at the Srisailam project to the erstwhile Nalgonda district for irrigating about 4 lakh acres, and to address fluoride-affected drinking water in Nalgonda and parts of present Nagarkurnool districts.
Topographically, Telangana is situated at a variable elevation of 100 m to 500 m to the river flow level of both Krishna and Godavari. Harnessing river water, therefore, requires a judicious mix of open canals and tunnels that can reduce the need for lifting river water for Telangana.
Sub-optimal design
In order to procure water through gravity, the SLBC project considered a tunnel in an ecologically sensitive zone from the left bank of Krishna River. The boundary conditions of the project site mandated minimisation of the disturbance to Amarabad Tiger reserve. The tunnel, therefore, was designed with only two openings, one at each end.
Balancing the concerns of protecting wildlife and pressing need for development, resulted in a somewhat sub-optimal design, making it the world’s longest tunnel (43.5 km) of its kind. Difficult geography and a tunnel without any intermediate adit (opening), led to enormous execution challenges.
Due to time taken for obtaining statutory clearances and procurement of tunnel boring machines (TBMs), the project could commence only in 2006. After on-site assembly of knocked down imported parts, two 10-metre diameter double shield TBMs were put into operation at each end.
It is a grim fact that after almost 18 years, it is reported that so far, a 20.5 km stretch of the tunnel had been drilled from one end, and another 14 km was completed from the other. The remaining 9.4 km work is still pending.
Challenging terrain
One of the main reasons for slow tunnelling is that the work has to be carried out in a geological challenging terrain, leading to frequent breakdown of TBMs including cutters. As a major portion of the tunnel passes through a shear zone with a strongly deformed crust, drilling hard rocks is a difficult task, resulting in abnormal wear and tear of cutters. Dewatering of seepage water also poses additional challenges.
One can visualise the difficult site conditions through the progress of work ( 10-50 metres a day) even when both TBMs are fully functional.
The project is in a catch-22 situation, both from financial viability point of view and on-ground completion. After several revisions, the latest project cost is estimated to be ₹4,658 crore, with ₹2,646 crore already spent. Insofar as technical issues are concerned, the choice is to go for new TBMs or continue to opt for repair. The productive life of the existing TBMs is nearly over and parts that require repair are not readily available.
In order to ensure completion of the project and financial viability, a de novo assessment is needed. In this regard, it is important to revisit all technical, financial and contractual issues. The latest deadline to complete the project, by June 2026, under the current situation has to be further pushed forward.
The writer is a retired IAS officer