Water and Power Development Authority (WAPDA) is planning to shut down tunnel 3 and 4 of the Tarbela Hydropower Project’s 4th extension for 85 days. Ministry of Water Resources has taken up the matter with Power Division for approval of shut down as being demanded by National Power Control Centre (NPCC) and as per previous practice.
According to WAPDA the shutdown of tunnels is being considered for removing rock barriers in front of both tunnels. The operation of the units depends on water level above the rock barriers. The partial operation of single intake starts at 6 meters (20 feet) above rock barrier level and full operation of both the tunnels is at 10 meters (33 feet) above rock barrier level.
During 2021 the rock barrier removal up to E1 1417 ft was achieved and the tunnels were made operational and units started on June 10, 2021 .This year with the lowering of rock barrier from El.1417 ft. to 1398 ft., the SOP’s regarding operations of units remain the same except that units will be able to be operated at lower levels.
Considering the rate of rock removal during 2021 it is estimated that it will take around 85 days for the completion of work during which time both the tunnels will remain closed.