HYDERABAD: The interim report of the expert committee constituted by the National Dam Safety Authority (NDSA) stated that there would be no use, even if repairs were carried out to the damaged piers of Medigadda. “Under the given circumstances, any remedial measure for Block No-7 would be an interim measure only, primarily to maintain the status quo of distressed condition. However, it is pertinent to mention that the possibility of any further unexpected movement or behaviour of structure in such a highly distressed condition cannot be ruled out, despite interim measures,” the report stated.
“In order to ascertain the reasons leading to the sinking of Medigadda barrage and causes of other distresses in the three barrages, certain geophysical and geotechnical investigations in the barrage area, as well as certain tests to assess the structural integrity of the barrage structure and related appurtenances are necessary. These are to be carried out before the onset of the coming monsoon,” the NDSA interim report added.
Though the committee recommended certain interim measures on three barrages before the onset of monsoon, it might not be possible, as Godavari may start receiving floodwater in the next four weeks.
It may be mentioned here that the piers of Medigadda barrage in Block 7 were damaged in October 2023. The expert committee headed by Chandrasekhar Iyer had visited the state in March 2024, and submitted its interim report, as sought by the government, on May 1. The copy of the report was available on Tuesday.
The expert committee inspected the Medigadda barrage site on March 7.
Select approachable locations of the barrage from road bridge deck slab, walkway, river bed locations on the upstream and downstream of the barrage along block numbers 6 to 8, barrage raft at upstream and downstream including the gates, were inspected. As block numbers 1 to 5 were inaccessible due to the presence of water, the inspection of the upstream and downstream areas in these blocks could not be conducted.
In order to avoid/minimise hydraulic forces on gates as well as structure, all gates of Block 7 shall be lifted to fully opened position before onset of monsoon, the committee suggested and stated that the radial gates adjacent to pier No 20 (i.e. Gate No 20 & 21) of Medigadda barrage, which has suffered the maximum damage, shall be removed completely by dismantling and/or cutting the gate from trunnion assembly, and taken away.
NDSA suggests geographical survey
The Committee also suggested a geographical survey to assess the foundation of the Medigadda barrage.
“For carrying out geotechnical investigations for assessing the barrage foundation, two boreholes shall be drilled in each bay of Block-7. The depth of boreholes shall be 25 m. One borehole in each bay shall be located in the raft upstream of gate, whereas the second shall be located in the raft downstream of gate,” the report said.
Similar geotechnical investigations were suggested for Annaram and Sundilla barrages. The Committee recommended engaging organisations such as CSMRS, New Delhi / CWPRS, Pune / NGRI, Hyderabad for carrying out the investigations.
Medigadda
The committee noted that the Medigadda barrage reinforcements along the crack for full height of pier have failed. Cracks have developed in the piers downstream the radial gate as well. Structural cracks were noticed in the adjacent piers. Gantry girder and gantry rail alignment was distorted in horizontal direction in a few of the piers. Welding joints between the two gantry girders over pier are distorted.
Irrigation officials informed the Committee that 77 of the 85 radial gates in Medigadda barrage were successfully lifted. However, problems were encountered while lifting the remaining radial gates i.e. No. 15 to 22 in the distressed Block 7.
The panel was requested to suggest the way forward on the lifting of the remaining eight gates for carrying out the works before the onset of monsoon. It noticed that wide cracks developed at many other locations upstream and downstream the piers and raft of Block 7.
Annaram
On the Annaram barrage, the committee noted that the CC blocks and launching apron downstream were damaged for almost entire length of the barrage.
The wearing coat in the barrage sill / glacis / stilling basin was seen damaged and washed away in several bays. Huge sand heaps were seen accumulated upstream in front of the barrage bay raft, for almost the entire length of the barrage. Hence the areas upstream could not be inspected.
Sundilla
The CC blocks and launching apron at the downstream were seen damaged /settled / displaced for almost entire length of the barrage.