The 2000-MW Karun III hydroelectric project includes a 205-metre-high arch dam, a huge underground powerhouse complex, power and tailrace tunnels, and the world’s largest concrete-lined plunge pool, all built on a karstic limestone foundation in an area of high seismic activity.
The Karun III project provides 2000 MW of power, 1100 million cubic metres of irrigation water per year, clean drinking water, and a recreational lake. It features a 205-metre-high arch dam designed to withstand 7.0 magnitude earthquakes, a 2000-MW underground powerhouse complex, 1 million metres of grouting to seal the limestone bedrock foundation, and the world's largest concrete-lined plunge pool. To protect the limestone rock mass downstream of the spillways from the impact of discharge flows, Hatch designed the world’s largest concrete-lined plunge pool.
Hatch used state-of-the-art tools and modified software to analyze and overcome challenging geotechnical conditions, including a dam foundation on folded, jointed and karstic limestone bedrock in an area of high seismic activity.
Hatch was involved in the project definition and feasibility phases of the project which determined whether a single 300 m high dam at Karun II, either rock-fill or concrete arch, was technically and economically feasible. However, the alternative scheme using two lower dams, at Karun II and III, was selected. Hydrological and reservoir operation studies, geological investigations, power demand forecasts, transmission line routing studies, and dam and power facility layouts were all included in the work. The dams harness the power potential and provide storage and river regulation that permit the development of irrigation for more than 100000 ha.
The first phase of the work consisted of project definition studies which examined the various power and irrigation options and selected the preferred development scheme for optimal benefits. This was followed by a comprehensive feasibility study of the selected scheme, Karun III. Physical investigation work at the damsites upstream from Karun I included exploratory drilling, audits and topographic and geologic mapping.
In 1989, a Hatch and Mahab Ghodss joint venture provided final tender design engineering services for the Karun III hydroelectric development, supervised additional geotechnical investigations at the Karun II site, and prepared project definition studies for Karun II and Karun IV. In 1990 Hatch was also commissioned to provide project management services for a turnkey contract option for Karun III. Tender documents for a possible turnkey design, finance, construction, installation and commissioning contract were prepared for international tenders. The joint venture carried out tender evaluations and assisted in the contract negotiations. Finally, the contract for Karun III was awarded to Iranian contractors.
At the tender stage, the Karun III project comprised a 205-m high arch dam, a powerhouse and spillway facilities designed to handle flood flows of 22 350 m3/s. Flows for power generation were conveyed through power tunnels which are about 700-m long and vary in size from 12.6 m to 5 m in diameter. The underground powerhouse was planned to have a total installed capacity of 3000 MW. However, the initial development consisted of 2000 MW provided by eight units, each of 250 MW. An underground powerhouse was selected after comparison with a surface option. Flows from the powerhouse were conveyed to the river through two tailrace tunnels of 14 m maximum diameter.
The switchyard for the project was of the SF6 gas-insulated type, located within the underground complex. Station output was delivered by four 400-kV transmission lines to the Iranian national grid.
The joint venture’s services included
- Geotechnical investigations
- Seismic studies
- Hydraulic studies including physical modeling
- Detailed design
- Engineering drawings
- Scheduling and cost estimating
- Contract packaging and preparation of tender documents
- Procurement
- Project management
- Technology transfer and training. Supervision for the construction was completed under a separate contract.
Construction began in 1995 with impounding beginning on November 8, 2004. It took almost two years for the reservoir to reach full supply level on May 9, 2006. Power from the facility was delivered a year earlier in February 2005 with all eight units fully functioning as designed by the end of 2006.
- Award of Excellence from Canadian Consulting Engineer and Association of Canadian Engineering Companies, 2009
