NDSA interim report specifies measures to maintain status quo, prevent further damage to Medigadda

NDSA experts recommend interim measures for Kaleshwaram Lift Irrigation Project to prevent further structural distress before monsoon.

The National Dam Safety Authority (NDSA) experts’ team that made a physical inspection of the Medigadda, Annaram and Sundilla Barrages of Kaleshwaram Lift Irrigation Project (KLIP) on March 7 and 8 following sinking of piers in the 7th Block of Medigadda on October 21 last has not ruled out the possibility of any further unexpected movement/behaviour of the “structure in highly distressed condition”.

In its interim report sent to the State government, the experts committee has recommended several interim measures to be taken up before the onset of monsoon season to maintain the status quo of the distressed condition. In case of the Block-7 of Medigadda the panel suggested crack monitoring, bracing piers 16 to 22 adequately at appropriate locations to arrest any likely lateral movement and rectification/replacement of defective/damaged pressure release valves in the raft.

Also suggested was installation of optical targets — one each at upstream and downstream and at the middle on all piers in the Block for continuous monitoring and recording, assessment of upstream and downstream secant pile and parametric joint, removal of plinth slab which has been settled/displaced/damaged, compacting of river bed properly and placing of sand-filled bags against the vertical face of the plinth slab.

In order to avoid/minimise hydraulic force on gates as well as the structure, all gates of Block-7 are to be lifted to fully open position after proper checking of all their components. The report has suggested several steps in respect of radial gates from 15 to 22 in the Block which are not opening due to sinking of piers. Further, the panel has recommended separate measures in case of Blocks 1-6 and 8.

In the case of Annaram and Sundilla barrages too, the NDSA experts’ committee has recommended measures to avoid/minimise hydraulic force on all gates as well as the structures and also lift fully open all gates before the onset of monsoon. The panel wants the Irrigation Department to remove the first four rows of the downstream cement-concrete blocks on entire length of barrages and also compact the river bed. In case of the CC blocks beyond first four rows, it sought removal of settled/displaced/damaged ones.

Removal of sand heaps accumulated in front of the Annaram Barrage bay raft suitably by adhering to the Irrigation Department norms to clear the waterway and removal of all other obstructions including leftover debris, boulders, dead concrete, sheet piles and, sediment deposits to ensure smooth and even distribution of water flow through the barrage is also recommended.

In its 17-page report, the NDSA panel has also recommended further studies and investigation before the onset of monsoon to ascertain the reasons leading to the sinking of Medigadda Barrage piers, causes of other distresses in all the three barrages, certain geophysical and geotechnical tests in Medigadda area as well as some specific tests to assess the structural integrity.