A team of experts from NDSA, CWC and CPWR said that the Srisailam dam on the Krishna River faces not only the serious problem of a large drop pool, which forms immediately after the dam's spillway, but also requires urgent attention to ensure its safety.
It may be remembered that Telangana had repeatedly urged the National Dam Safety Agency (NDSA) to ensure that the APs carry out the required repairs and on the day before NDSA Chairman Anil Jain inspected Hyderabad, the day before, after he inspected the dam the next day, reiterating the need for repairs.
The report said there were several issues that needed to be “attention immediately” and that the Plunge Pool conditions topped the list. It said the bottom layer of the plunge pool is much lower than the deepest base level of the dam. It further said that the depth wash in the fall pool is moving towards the dam, “if unattended, it creates a potential danger of dam stability.” The plummeting pool was first established after a major flood in 2009 and has grown every year since, with the deepest part exceeding 120 meters.
Telangana has been repeatedly urging NDSA to impress AP, at least starting to fill the pond with cement concrete tetrapods to reduce the water erosion effect before a full repair and final repair can be done. “There is just one month left before the monsoon sets in and work cannot be done then. AP must take up the repairs as any danger to the dam will result in severe cascading effects all the way downstream to Nagarjunasagar dam, and as well as will impact Vijayawada if there is a catastrophic dam failure,” Telangana engineer-in-chief (general) G Anil Kumar said.
The report also expressed serious concerns about the suffocation drainage holes in the dam foundation gallery, which would affect the dam’s ability to withstand lifting pressure. “The pressure in the foundation drainage hole has an effect on the uplift of the dam part, so the stability of the dam is.” The report called on the AP to call on the AP to clean the drainage hole, adding that this also caused a large amount of water to drain into the foundation gallery.
The expert's report also said there were two horizontal cracks in the dam's blocks 17 and 18, and called for an investigation into its causes and the reasons for monitoring, and repair them if stable is found.
Several other concerns that currently plague the structure are that exposed aggregates in the lower part of the dam are only adjacent to the spillway under the gates 4, 5, 9 and 10. “If these gates run during the next monsoon season, it may deteriorate at a faster rate,” the report said.
