BRS leaders have been insisting that the sinking of piers was an issue of no consequence and that the barrage was in fine condition.
Medigadda Barrage (X)
In a major blow to the image of the BRS ahead of the Telangana Assembly elections, the Central Water Commission (CWC) has written to the state government that the Medigadda Barrage, whose piers had sunk recently, was “useless” in the current condition until fully rehabilitated.
Medigadda, which is part of the Kaleshwaram Lift Irrigation Scheme (KLIS), is billed as the world’s largest in its class of projects.
The adverse verdict of the CWC on the failure of Medigadda could not have come at a worse time for the BRS.
After all, its leaders have been exhausting their lung power in trying to project the sinking of the piers as an issue of no consequence and claiming that the barrage was in fine condition.
In a letter to Irrigation Special Chief Secretary Rajat Kumar, CWC Member (Design and Research) Sanjay Kumar Sibal said that the National Dam Safety Authority (NDSA), whose team inspected the Medigadda Barrage between 23 and 25 October, said in its report that the distress condition that developed in one block of the Medigadda barrage was adversely affecting the functionality of the barrage.
He also sounded a caution that the damaged block of Medigadda may have to be structurally restored to make it functional.
He said that considering the commonalities, the likelihood of the failure of other blocks existed. This would warrant rehabilitating the entire barrage.
He advised a detailed investigation to determine the causes of the failure and NDSA may be informed of the outcome of such investigation and the proposed rehabilitation process. Similar action may also be taken for the other two upstream barrages, he said.
He sent a copy of his letter to the Union Jal Shakti minister and the chairman of the CWC.
In his letter, he referred extensively to the report submitted by the NDSA, to explain the damage caused to the project and how the state government had ignored its statutory responsibility of undertaking operation and periodic maintenance in accordance with the laid down norms.
He also pointed out that the NDSA had regularly asked the Telangana State Dam Safety Organisation (TSDSO) to conduct pre and post-monsoon inspections to check for any unusual behaviour or signs of distress.
But it appears that this was not complied with, he said, thus attracting the provisions of Section 41 (b) of Chapter X of the Dam Safety Act of 2021.
“There appear to be many areas where compliance with the DSA, 2021, was missing, which is a serious matter as the barrage has a high-risk potential for life and the economy,” he said.
The CWC member, expressing concern over the condition of the two barrages constructed upstream from Medigadda under the Kaleshwaram project — Annaram and Sundilla — have similar designs and construction methodologies, making them prone to similar failure modes.
Signs of “boiling” already exist downstream of the Annaram barrage, a precursor to failure. These barrages also should be examined urgently for signs of piping or distress, he said.
He also sounded caution that filling the reservoir of Medigadda in the present condition would worsen the barrage’s health and should not be resorted to.
Sibal said that the NDSA committee, in its report submitted to its chairman, said that as per its findings, the piers had sunk due to a combination of issues involving planning, design, quality control, and Operation and Maintenance (O&M).
The committee felt 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 possible reasons — piping, where transportation of foundation material has occurred; inadequate bearing capacity of foundation material (sand); or failure of upstream secant piles due to the barrage load.
The committee pointed out that there appeared to be a construction deficiency due to the lack of stringent quality control during the construction of sub-surface contiguous secant piles and plinth connection between the raft and cut-offs.
Gaps might have been created in the secant pile formation, making the barrier permeable, leading to piping and subsequent progressive failure.
There are deficiencies in the project planning and design as well. 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.
Taking the downstream cut-off up to the impermeable strata alters the uplift pressure due to blocking the sub-surface flow. The construction methodology adopted for transverse cut-offs has imposed different conditions than what was assumed in the design.
The alignment of the flared-out wall provided upstream of the barrage makes the barrage hydraulic-deficient.
The dam owner is supposed to undertake sounding and probing in the apron area every year immediately after the monsoon to assess the scours and launching of aprons in the vicinity of structures.
The non-launching portion should also be carefully examined, particularly downstream, to ensure the effectiveness of the inverted filter.
The upstream floor should be inspected every year early in the fair-weather season by probing and using underwater lamps. A careful inspection of joints is also to be carried out.
The dam owners have not inspected or maintained the cement concrete blocks or launching aprons since the commissioning of the barrage in 2019-20.
In this regard, this maintenance deficiency of the dam owners has progressively weakened the barrage, leading to its failure.
“This is a significant lapse on the operation and maintenance front,” said Sibal.
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