Karun III Hydroelectric Development

The Karun III hydroelectric development in the Zagros Mountains of Khuzestan, Iran, fulfils a two-fold need. Though Iran is a country rich in oil reserves, it actually suffers from a shortage of electrical energy. In addition, irrigation is crucial to maintaining the agricultural sector. The project provides power at an installed capacity of 2,000 MW with the capability to expand to 3,000 MW. It also provides 1,100 million cubic metres of irrigation water per year, is a supply of clean drinking water, and provides a new lake for recreation.

The project was begun in the late 1970s and was completed at the end of 2006. The major components are a 205-metre high arch dam, a huge underground powerhouse complex, power and tailrace tunnels, and the largest concrete-lined plunge pool ever built. All these were constructed in very difficult geotechnical conditions, with a folded, jointed and karstic limestone foundation, located in an area of high seismic activity. The foundation was sealed with one of the largest grout curtains in the world.

From the beginning, Hatch Energy of Niagara Falls, Ontario (formerly Acres International) has assisted the Iranian authorities in managing and designing the project.

Hatch Energy was involved from the initial conceptual development and geotechnical investigations, to detailed design, construction and final commissioning. Hatch Energy experts worked with their Iranian counterparts from their joint venture partner Mahab Ghodss. The relation- ship between the two firms spanned decades and involved more than 100 man-years of Canadian consulting engineering leadership and management skills.

Building on highly permeable limestone

Aside from the magnitude of the project, the challenges lay in the extremely complex foundation conditions. The presence of highly permeable limestone formations in Iran have a history of causing problems for impoundment projects.

For this reason, Hatch Energy undertook detailed geological investigations over a decade. The results showed that the project could be constructed on the downstream limb of the Keyf Malek anticline. However, this formation had many adverse features such as joints, some solutioned, some filled with weak clays, well defined discontinuities up to 300 metres long, and cavities to depths of 200 metres below the river bed. In the dam abutments these features formed large wedges which could become unstable following impoundment.

Using state-of-the-art tools and software designed to simulate the stresses on the foundation and seismic load- ings, detailed designs were formulated to deal with each potential problem. For example, Hatch Energy modified available software to produce an appropriate dynamic analysis of the effects of large earthquakes.

The project represented one of the largest undertaken in Iran. Besides the 205-m high arch dam and spillway facilities, the underground excavations involved nearly 2,000,000 cu. m and involved carving out a power house 251 m long x 25 m wide x 47 m high. There is also a transformer cavern more than 250 m long, an inlet valve gallery, 244 m long, and an intake gallery, 177 m long, as well as 5 kilometres of tunnels up to 14 m in diameter.

The main dam is a double-curvature concrete arch dam designed for earthquakes up to 7.0 in magnitude. It is 388 m long at the crest level, 29 m wide at its base, and 5.5 m wide at the crest. The advanced “thin-arch” design transmits loads from the reservoir pressure directly to the limestone bedrock foundation.

Construction began in 1995, and by 2006 the reservoir reached full supply level and all eight generating units were functioning. The plant is generating the expected quantities of electricity, and post construction seepage from the dam is within 10% of the quantities estimated.

Name of project: Karun III Development Project, Khuzestan, Iran

Award-winning firms: Hatch Energy, Niagara Falls, Ontario (Michael H. Boase, P. Eng., A. Zak Erzinclioglu, P. Eng., Robert R. Steele, P. Eng. (deceased), Allen L. Mee, P. Eng., Dan D. Curtis, P. Eng.) Joint venture partner: Mahab Ghodss Consulting Engineers, Iran (Nasser Kamjoo)

Owner: Iran Water and Power Resources Development Company