HYDERABAD: The sinking of the piers (foundation) of the Medigadda barrage is due to a combination of various issues involving failure in planning, design, quality control and operation and maintenance, a report submitted by the National Dam Safety Authority (NDSA) to the Centre says.
After six piers of the Medigadda barrage suffered damage recently, an NDSA team visited the spot on October 24, met Irrigation officials and submitted its report which was made public on Friday.
The report mentions several shortcomings in the commissioning of the Medigadda barrage, which is an integral part of the State government’s prestigious Kaleshwaram Lift Irrigation Scheme (KLIS)
State government officials were yet to react to the report. However, it may be mentioned here that state irrigation department officials had announced recently that the sinking of piers was due to the washing away of the sand beneath the piers of the Medigadda barrage.
In its report, the NSDA cited transportation of the foundation material (sand) below the barrage foundation, inadequate bearing capacity of the foundation material, failure of upstream secant piles due to barrage load etc as the reasons for the sinking of the piers. This indicates failure in planning and designing the barrage, it said.
Barrage designed as floating structure, constructed as rigid one: NDSA
“These are deficiencies in the project planning & design. 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 behaviour from the designed,” the NDSA report said.
The NDSA said that it had regularly asked the Telangana State Dam Safety Organisation to get the pre and post-monsoon inspections done to check for any unusual behaviour or signs of distress. However, it appears that this has not been complied with.
The damaged Block No.7 has to be structurally restored (cannot be repaired and has to be removed and reconstructed from the foundation) to make it functional. Considering the commonalities, the likelihood of the failure of other blocks resulting in a similar mode exists. This would warrant rehabilitating (reconstructing) the whole barrage, the report said.
No to water storage
The filling of the reservoir in the present condition would worsen the barrage’s health and should not be resorted to. That is the barrage under the present condition cannot be functional until rehabilitation (reconstruction). The NDSA said, suggesting various precautionary measures to be taken.
Two barrages constructed upstream of Medigadda under the Kaleshwaram project --- Annaram and Sundilla barrages --- have similar designs and construction methodologies making them prone to similar failure modes. Signs of boiling already exist downstream of Annaram barrage, a precursor to failure. These barrages also should be examined urgently for signs of piping/ distress, the report says.
NON-COMPLIANCE WITH PROVISIONS OF THE DAM SAFETY ACT: NDSA