Rush to Fill Gaps Under KLIS Barrages likely Complicated Repair Plans
Hyderabad: Evidence is emerging that possible over-enthusiasm by officials in the irrigation department may have queered the pitch for the National Dam Safety Authority (NDSA) that is tasked with preparing a final report on the repairs needed at the Medigadda barrage.
It is learnt that the NDSA has expressed unhappiness over how the gaps and voids under the foundations of Medigadda barrage, as well as those at Annaram and Sundilla, were grouted though the NDSA itself did not specify any such action in its interim report.
The NDSA had limited itself to mandating a series of studies whose results would assist its experts in preparing plans for the way forward to stabilise the barrages and protect them from possible future disasters.
“The grouting has meant that the geotechnical conditions in the foundations of the barrages have been irrevocably changed though introduction of foreign material which in turn means that the original conditions of the riverbed sections on which the barrages have been built were modified. This means going back to the drawing board all over again and the NDSA has expressed its displeasure over this development,” sources said.
Sources said the idea of grouting of the voids was enthusiastically adopted by the irrigation department based on ‘recommendations’ by a technical committee of experts constituted specifically to assist the Justice P.C. Ghose commission of inquiry on the technicalities and engineering aspects with respect to planning, design, and construction of the Kaleshwaram project’s barrages.
“The committee had no business to make any recommendation, despite being asked by the commission to visit the barrages which it did on June 1 this year. The irrigation department, ‘based on the site observations interim suggestions’ in a memo, in an act of overreach, asked its field officials to ensure the grouting was done,” the sources said.
In its memo dated June 3, the irrigation department said, among others, “the voids blow the blocks of raft foundations at the three barrages that are under notice of seepage are to be backfilled using sand + cement + admixture.”
It further said close grouting with cement-bentonite mix along the upstream side secant piling up to its bottom of all three barrages is suggested to be taken up with the blocks under the notice of seepage.
“For this purpose, the calculated amount of grout mix based on the porosity of sand bed can be injected to cover a width of 3 metres away from the secant piles,” the memo said.
The directions also suggested that the “conspicuously disturbed secant piles and raft slab junctions on upstream and downstream sides” of Block 7 of Medigadda barrage – which experienced subsidence – “are to be sealed in order not to allow the direct entry of surface water into the space below the raft.”
“All these actions have played havoc with the original sand and soil bed conditions under the barrages, particularly at Medigadda. By these actions, irrigation department officials have made it that much harder for designing proper measures for rectification of the problems as the river bed structure has been changed. This should not have happened as the NDSA had made it clear that by keeping all the gates open at the barrages, no new harm will come to the barrages,” a source with knowledge of the issue said.
