Pakistan Tarbela Dam Phase I
Unleashing Hydropower Potential, Energizing a Nation
Pakistan Tarbela Dam
The Tarbela Dam was build in the late 60’2 early 70’s. The Tarbela Dam is one of the largest earth-fill dam constructions in the world. The dam is situated on the Indus River in the province of Khyber Pakhtunkhwa (KP) at a distance of about 70 kilometers (km) NW of Islamabad. The reservoir behind the dam is almost 100 km long and measures 260 km2 when completely filled. The live storage capacity of the reservoir was initially 11.9 billion m3, but this has been reduced due to siltation during 35 years of operation to 6.8 billion m3. The Tarbela Dam is 2,743 m long, 143 m high above the river bed and has two spillways cutting through the left bank and discharging into a side valley.
Pakistan Dam Project Phase I
Tarbela Dam is an earth-filled dam along the Indus River in Pakistan’s Khyber Pakhtunkhwa province. Located in the Swabi and Haripur Districts of the province, the dam is about 30 km (20 mi) from the city of Swabi, 105 km (65 mi) northwest of Islamabad, and 125 km (80 mi) east of Peshawar. It is the largest earth-filled dam in the world, and also the largest dam by structural volume.
History
The dam was completed in 1976 and was designed to store water from the Indus River for irrigation, flood control, and the generation of hydroelectric power.The dam is 143 metres (470 ft) high above the riverbed. The dam’s reservoir, Tarbela Lake, has a surface area of approximately 250 square kilometres (97 sq mi).
Because the source of the Indus River is glacial meltwater from the Himalayas, the river carries huge amounts of sediment, with an annual suspended sediment load of 200 million tons. Live storage capacity of Tarbela reservoir had declined more than 33.5 per cent to 6.434 million acre feet (MAF) against its original capacity of 9.679 MAF because of sedimentation over the past 38 years. The useful life of the dam and reservoir was estimated to be approximately 50 years. However, sedimentation has been much lower than predicted, and it is now estimated that the useful lifespan of the dam will be 85 years, to about 2060.
EXTENSION IV FINANCED BY ASIAN INFRASTRUCTURE INVESTMENT BANK AND THE WORLD BANK.
Tarbela dam extension-IV was planned in June, 2012, and PC-1 was developed for the project . In September 2013, Pakistan’s Water and Power Development Authority signed a contract with Chinese firm Sinohydro and Germany’s Voith Hydro for executing civil works on the 1,410 MW Tarbela-IV Extension Project. Construction commenced in February 2014, and was completed in February 2018. This project was constructed on Tunnel No. 4 of Tarbela Dam. It consists of three turbine-generator units, each with a capacity of 470 MW. The project is expected to provide an average of 3.84 billion units of electricity annually to the National Grid. It is intended to help supplement electricity supply during the high-demand summer months.
The final inspection dives and main gate opening of Tunnel number 4 was contracted and executed by ACET.
Acet Projects
1st Mission: Installation of 72 Trash-racks for Tunnel 4 intake (160feet max depth)
2nd Mission: removal of wedges and 8 main gates for Tunnel 4 intake (300Feet max depth)
The time expected for the 2 objectives was 15 weeks. Storm, satellite issues and equipment failure set us back a week. The project was nevertheless finished in 10 weeks with the maximum depth of 310 feet reached by the divers, the deepest stop log installation by divers ever. Special adjustments had to be made to dive computers, rebreathers and diveplans as the lake sits roughly 1800feet above sealevel.
ACET was contracted in April 2017. ACETS first job was to install trash racks into the tunnel number 4’s intake. Which has been converted from a irrigation tunnel to a electricity producing tunnel.
Acet 1st Project
Due to the circumstances, out of the control of everyone the entire project was delayed 3 months as the rising water levels made diving and working at depth a serious safety concern for all those involved. As the dam is used for irrigation and the production of hydroelectricity, the high water levels meant it was perfect for producing electricity and to lose any output would have follow on consequences for the entire Pakistan. ACETS first job was to install trash racks into the tunnel number 4’s intake. Which has been converted from a irrigation tunnel to a electricity producing tunnel.
With enough checked and carry on luggage to keep any an entire football team running for months 7 members of ACET met up in the Islamabad to begin operations. With the project being delayed the same team members made the return trip back on the 4th of October. A quick sleep and grab last minute supplies on the Thursday morning before the four-and-a-half-hour drive to the dam. Tarbela Dam is well protected and surrounded by many armed military and Water and Power Distribution Authority guards, to gain access numerous check points must be cleared and you must be a part of an official convoy as a vast part of the journey is on military roads.
Eagerness quickly took over and the next day we all begain the process of setting up the equipment up, a relative easy process in most places but not here. All our equipment that could not be hand carried onto a boat had to be first loaded (by hand) onto the container that would be then lowered by crane onto the barge working deck. Once again a relative east task…but this being Pakistan. The dams water levels at the moment are falling just shy of 1 m a day, positioning the barge then all of a sudden becomes very important as getting it stuck aground would cause delays, the disappearing water also caused crane issues as the crane used a 75 tonne, was on full reach ad power to lower the containers onto the barge from its limited access point. With a bit of Pakistan/Chinese injunity all went according to plan and very smoothly.
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