NDSA Slams AP Over Srisailam Dam Safety

Hyderabad: The National Dam Safety Authority (NDSA) has expressed serious concern over safety of the Srisailam dam in Andhra Pradesh, making it clear that scouring of the river bed and rock profile on the downstream side of the dam had the “potential to compromise the dam’s safety.”

In a letter to the AP government, NDSA chairman Anil Jain, who led an inspection of the dam on April 29 and 30, pointed out the apparent lackadaisical approach to the dam’s safety and said: “Its regular monitoring was in the recommendations of all expert groups formed for the safety of Srisailam dam. However, the same has not been complied with and as on date no one is aware about the conditions of the measures taken earlier to protect the rock face against the scouring.”

The level of concern over the damages to the dam structure, and temporary protection measures in the form of installed steel cylinders to stop further damage immediately after the spillway, the NDSA asked the AP government to “minimise” the operations of Gates 5 and 6 (in the middle of the dam which has 12 gates. Typically when dam gates are opened, this process starts from the middle and extends to the sides) “in view of the severe damaged condition of the cylinders and possible scour of the old cofferdam.”

It may be recalled that the problems at the Srisailam dam began to emerge once efforts began to understand the damage resulting from the formation of a huge plunge pool downstream in the area where water from the spill way falls. It may also be recalled that Telangana had been urging the AP government and the NDSA to take up immediate repairs to the plunge pool, and to the rest of the damaged dam structures, warning that the dam may even face catastrophic failure in the event of a large flood.

With respect to the plunge pool, the NDSA said it required immediate short term work that must be completed before the onset of the monsoon, which likely leaves the AP government with just about two weeks to complete all given tasks, especially in the wake of the Indian Meteorological Department predicting early onset of monsoon this year.

As part of the short-term measures, the NDSA called for immediate geophysical and topographical studies to determine the damages, and take up rehabilitation measures to the damaged cylinders installed to prevent dam-bound scouring of the river bed from the cascading water from the spillway.

With respect to long-term measures, the NDSA advised the AP government to seek help from the Central Water Commission for designing rehabilitation measures, for attending to the plunge pool which could cause further problems if left unattended to. It further called for ‘stability analysis’ of the dam’s Block 8 and Block 12, “as a minimum.

Infograph

NDSA worried over Srisailam dam safety

Despite clear recommendations, no bathymetry survey of the plunge area and under water videography of the cylinders have been carried out by the state government.

Operation of Gate 1 appears restricted in view of possible damage and scouring of left abutment downstream;

Reduce use of Gates 5 and 6 in view of severe damaged conditions in view of possible scour of old cofferdam.

Immediate rehabilitation of steel cylinders installed to protect the dam from scouring in plunge pool;

Short-term solutions must be implemented before onset of this year’s monsoon