Explainer: What led to Sunkishala sidewall collapse?

The project was intended to draw water from the dead storage levels of the Nagarjuna Sagar Project even when its water levels are critically low

Hyderabad: The collapse of the sidewall of the under-construction Sunkishala project cannot be attributed purely to the technical reasons as it was caused by multiple factors including poor field level coordination among the agencies involved in the implementation of the project.

The project was intended to draw water from the dead storage levels of the Nagarjuna Sagar Project even when its water levels are critically low. But there was poor coordination between the dam authorities and the agency implementing the intake well pump house, according to Irrigation officials.

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Accurate inflow forecasting is crucial not only for dam monitoring staff for effective reservoir management but even the agency executing works on Sunkishala drinking water project.

The agency has gone on-record stating that flood was not expected so early to the reservoir. It was under the impression that flood may reach the level of the middle tunnel only by the end of August.

The NSP authorities were monitoring the flood levels in the river from the second week of July once the Almatti dam in the upper reach of the river basin received significant inflows and they started taking precautions accordingly for management of the project.

The middle tunnel gate of the tunnel at the pump house was completed less than a week before the incident. The flood water made its way to the tunnel when the construction of the tie-beam was in progress. The tie-beam is a horizontal link that serves to prevent parallel structures of the retainer wall from separating.

Collapse of the retainer wall was the fallout of the coordination failure at the agency end. Plans are underway to complete the work on all the tie beams planned by the end of August.

The installation of the gate of the middle tunnel should have been taken up in advance in anticipation of rise in the river level which is usual after the onset of monsoon so as to avoid the huge losses.

The reconstruction of the side wall was expected to cost Rs 20 crore additionally. It would add to the delay in the implementation of the project as well. The agency has decided to go ahead with the works on the middle tunnel to meet the deadline set for providing water by next summer.

Accordingly, they planned to set up the tunnel gate to block any flood flow towards the sump.

The gate work was executed for three days from July 29. The gate was very much a recent addition to the structure set up after the Congress party came to power in the state. With the inflows into the dam touching 3.50 lakh cusecs, the flood water made its way into the tunnel thus destroying the side wall connected to it.

All this happened in a short span of five minutes, submerging the entire structure including its sump. The water board officials said that the cost will be borne by the construction company, but the completion of the project would not be as scheduled, they said.