NDSA Report: The Medigadda Barrage Is Useless Unless Fully Rehabilitated

Delhi/Hyderabad, Nov 4 (Hydnow): The National Dam Safety Authority (NDSA) ripped into the Telangana government on the issue of the sinking of pillars of the Medigadda (Lakshmi) Barrage, which diverts rather than storing water into the Godavari River.  The report of NDSA said the incident had made the structure ‘useless’ unless fully rehabilitated. 

The Medigadda barrage is part of the Kaleshwaram, the flagship project of the state government costing Rs. 80,000 crore and is touted to be the world’s largest lift irrigation scheme. 

NDSA chairman Sanjay Kumar Sibbal, in his letter to Telangana State Special Chief Secretary (Irrigation) Dr. Rajat Kumar, said that according to the committee findings, piers had sunk due to a combination of issues involving planning, design, quality control, and operation and maintenance (O&M)

The report said that the primary reason for the failure was the settlement of the barrage raft.  The piers, being monolith with it, have also settled, moved, and cracked.  This could occur due to several reasons, viz, piping, wherein transportation of foundation material has occurred, inadequate bearing capacity of foundation material (sand), and failure of upstream secant piles due to barrage load.  

There appears to be construction deficiency due to a lack of stringent quality control during the construction of sub-surface contiguous secant piles and plinth connection between the raft and cut-offs, it said.

The 43-page report further said that the gaps might have been created in the scant pile formation, making the barrier permeable, leading to piping and subsequent progressive failure.  there are deficiencies in the project planning & design as well, it said.  The barrage has been designed as a floating structure but constructed as a rigid structure.  The contiguous secant pile type cut-offs adopted by the project authorities were taken up to rock both upstream and downstream of the barrage. this has changed the structure behavior from the design, it said.  

The report also found fault with the construction methodology adopted for transverse cut-offs have imposed different conditions than what was assumed in the design. The alignment of the flared-out wall provided upstream of the barrage making it hydraulic deficient.

The NDSA felt that the dam managers had not inspected or maintained the cement concrete blocks or launching aprons since the commissioning of the barrage in 2019-20.  The maintenance deficiency has progressively weakened the barrage, leading to its failure.  This is a significant lapse on the operation and maintenance front, it added. 

The report said the NDSA had regularly asked the Telangana State Dam Safety Organisation to get pre and post-monsoon inspections done to check for any unusual behavior or signs of distress but this was not done, it added.  (Hydnow) 

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