LAHORE: High water flows in Indus River at Tarbela Dam threaten the completion scheduled of the 4th Extension Hydroelectric project, a spokesman of the Water and Power Development Authority (Wapda) said on Friday.
In a meeting, presided over by Wapda chairman and attended by member (water), member (power) and member (finance), the situation was discussed and decisions taken, including to expedite the work and inform the World Bank – financier of the project – of the possible delay.
The Tarbela 4th Extension Hydropower Project (T4) would add 1,419 megawatt of electricity to the grid, and earlier, was scheduled for completion in February 2018, the Wapda spokesman said; however, the financier of the project devised an acceleration programme for early completion. The accelerated construction programme was devised with the approval of the World Bank, financier, to complete the project by mid 2017 to benefit from the high water flow season of the year.
To execute the T4, intake structure of tunnel four was redesigned to fit generating machines. With a view to carrying out construction work to modify the intake tunnel in accordance with its new design, a concrete coffer dam was built in the reservoir.
Height of the coffer dam (1,512 feet above mean sea level) was ascertained in consultation with the Indus River System Authority (IRSA). This was determined, keeping in view the water inflow pattern to the reservoir, where construction work could be continued until the reservoir reached the level of 1,483 feet.
As per the estimates the water level in the reservoir would have increased to 1,483 by mid July 2016, and subsequently over flow the coffer dam. Once the water attains the 1,505 feet level in the reservoir, it could have been released through spillways. Prior to this level, the water flows out of the reservoir from tunnels one, two, three, and five.
The spokesman explained that due to the pre-monsoon rains and abnormal increase in temperature in the catchment areas, Indus River average inflows were 27,000 cusecs and 53,000 cusecs higher than the last five years average during May and June, respectively. Maximum capacity to release water from the tunnels one, two, three, and five was 190,000 cusecs, whereas current inflows were in the range of more than 250,000 cusecs.
“The water level in the reservoir will reach 1,483 feet by June 19 instead of the earlier prediction of mid July 2016. Resultantly, the work on intake of tunnel 4 will have to be stopped due to overlapping of the coffer dam,” the spokesman added.
This eventuality would adversely affect the on-going works on T4. It is worth mentioning that the works on the project also suffered last year for about four-six weeks due to erratic flows and early increase in reservoir level and its late depletion in accordance with IRSA indent.
IRSA wrote a letter to the project authorities that in view of the existing trend of inflows in the river Indus, it was expected that Tarbela may touch to 1,490SPD level by June 30, 2016, despite the maximum release from the dam. This eventuality was likely to adversely affect the ongoing works on Tarbela 4th Extension Hydropower Project.
The meeting has decided to immediately send a high level technical team for Tarbela, headed by Member (Water), to coordinate with the contractor for expediting the construction work on intake of tunnel four to the maximum in the remaining days till the water attains the level of 1,483 feet.
The World Bank would also be immediately informed of the phenomena, as accelerated construction work was also approved and was being monitored by the bank.
The meeting further decided to pursue the contractor for carrying out the work round-the-clock to attain maximum progress in the intake area, before overlapping the coffer dam.
Since the coffer dam has been constructed in concrete, it would again be utilised without additional cost following the pumping out of water from the construction area of intake tunnel four, scheduled after depletion of the reservoir level in December.