M. Malleswara Rao
Two leakages are existing since 1993, says Chief Engineer of Nagarjunasagar
‘Leakages pose no danger to the dam as the flow is within limits’
HYDERABAD: Even as the system is being readied to handle possible floods in the Krishna during monsoon, engineers have noticed four leakages in the Nagarjunasagar dam, with water gushing out from each of them.
They occurred on the glacis on the dam’s right side.
M. Ramachandraiah, Nagarjunasagar Chief Engineer, however, says “two leakages are existing since 1993”.
He ruled out the possibility of a flow from the reservoir which always, however, builds up pressure on the dam to escape seepage/leakage.
“The flow must be from any of the three drainage canals (galleries) provided at different heights to absorb seepage. The leakages pose no danger to the dam as the flow is within limits”.
“The 54-year-old dam can handle any flood, as it was designed to tackle a maximum flood of 15.3 lakh cusecs. It handled 8.5 lakh cusecs so far in 1998 when floods in the river submerged Srisailam right bank power house.
All its parameters, like uplift pressure and deflection, are within safe limits”, he added.
A special provision has been added afresh to the Rs 115-crore scheme taken up to ‘rehabilitate’ Nagarjunasagar, to plug leakages.
It will cover sinking of the right earthen dam at its foot. One of the five major works taken up originally under the scheme aims at filling patches of scouring caused on the dam’s slope by water released from the spillway. The tunnel excavated during the dam’s construction to divert the river course will be restored so that water can be drawn even when the reservoir level falls to 400 ft. The present minimum draw-down level is 510 ft. The other three works are construction of a foot-bridge connecting pinions of the 26 crest-gates to facilitate repairs of the gates, installation of three stop-log gates for use when crest-gates are taken out for repairs, construction of a road at the base of the dam to repair it when necessary, and modernisation of instrumentation by erecting a deflectometer and V-notches.