Damaged Portions of Block 7 at Medigadda Barrage May Have to Be Rebuilt
HYDERABAD: The news from Medigadda barrage — the lynchpin of the Kaleshwaram lift irrigation scheme (KLIS) – where tests are being done to determine weaknesses, cracks and other damage, is not very encouraging, with sources saying it is very likely that up to six piers, the gates between them, and the rest of the barrage structure in the worst-hit Block 7 may have to be taken down and rebuilt.
Ahead of the expected visit of a National Dam Safety Authority team next week, two crucial tests —electro resistivity tomography (ERT) and ground-penetrating radar (GPR) — have been completed on Block 7, according to sources in the irrigation department. A part of this block sank into the sandy floor of the Godavari river in October last year.
With worries that the adjacent Blocks 6 and 8 may also have developed cracks, the ERT and GPR tests will be conducted on these two blocks but this work on Block 6 may take some time as the recent release of around 2.5 tmc ft of water from the upstream Annaram barrage found its way through the gates on Medigadda barrage’s Block 5.
The sources said this led to flooding of Block 6 which was dewatered and cleaned and dried for the tests. The clean-up process has to be taken up again.
Making the testing further difficult is the daily flow of nearly 5,000 cusecs (cubic feet per second) of water from the Pranahita river joining the Godavari on which the Medigadda barrage has been built. Work on ensuring dewatering of the blocks to be tested while ensuring this incoming water flows through the barrage without causing any further problems is a task officials are keeping a close watch on.
On Block 7, the testing began at the worst hit piers 19, 20, and 21 and progressed sideways on both sides to determine how many of the piers in the block suffered cracks and damages. While four piers have clear damages and cracks, it may be possible to restore two more. Until the final report from the testing data is received, nothing can be said with certainty, an official said.
A team of officials from the State Dam Safety Organisation has visited Medigadda and Annaram and is reported to have suggested some preliminary steps that can be taken to arrest the damage. However, work can commence only after the NDSA team visits, inspects the Medigadda barrage and submits its findings and recommendations, the sources said.
Work is on to clear the sand from around Block 7, as well as Blocks 6 and 8 as sought by the NDSA for the team to study the sub-surface impact of the damage to the barrage so far, the sources said.
