The Karun III hydroelectric project is located on the Karun River in Khuzestan Province, Iran. It is about 120 km by river upstream from the existing Shahid Abbaspour (Karun I) dam and approximately 140 km by air northeast from Ahwaz. The Karun River starts in the Zagros Mountains and, after flowing through the mountains, enters the coastal plain at Gotvand. From there, it flows to the Persian Gulf entering the Arvandroud at Khorramshahr near Abadan. The Karun River is the largest river water resource in Iran.

The Karun III project is situated in folded sedimentary rocks in the Western Zagros Mountains. The project area consists of rugged, rocky terrain with local relief in the order of 1000 to 2000 m. The area is very seismically active. Project structures are founded mostly on limestone and marly limestone rock.

Karun III is designed to operate primarily as a hydroelectric plant providing peak power requirements to the Iranian national grid system. Karun III has an initial installed capacity of 2000 MW with the capability of delivering 4170 GWh of average annual energy.

Agricultural, irrigation and flood control benefits will also be available as a result of the project installations.
Diversion of the Karun River to allow dam construction was effected by two 13-m diameter, 613-m-long diversion tunnels, one concrete lined and the other partially concrete lined, and cofferdams upstream and downstream of the damsite designed to withstand overtopping. The diversion scheme was designed to pass a peak 3-yr return flood (1850 m3/s) without overtopping the cofferdams.

The Karun III dam is a double-curvature concrete arch dam designed for severe earthquake conditions. The dam, 205 m high, and 388 m in length at crest level, incorporates a crest weir spillway, two radial-gate equipped orifice spillways and flow compensation facilities.

A gated two-bay chute spillway with super-elevated flip buckets is provided adjacent to the dam on the right abutment. The total spillway facilities allow the passing of an inflow design flood of 15 000 m3/s without overtopping. All spillway flows are discharged into a 400-m-long, concrete lined plunge pool and over a 50-m-high mass concrete tail pond dam.

The power intake structure is located on the right bank adjacent to the chute spillway structure. Two intake tunnels (with provision for a third) lead via bifurcations to the intake gate gallery location. The four upper power tunnels then lead via power shafts to the four lower power tunnels which again bifurcate and form eight steel penstocks leading to the eight 250-MW units of the underground powerhouse.

Vertical shaft Francis turbines and associated generators, of conventional air-cooled, totally enclosed design, will operate at a speed of 167 r/min and generator voltage of 15.75 kV.

Mechanical equipment and station services underground include inlet butterfly valves, turbine draft tube gates and crane, inlet valve crane, two powerhouse cranes and various facilities dealing with cooling water supply, drainage, fire protection, oil storage, compressed air, air conditioning and ventilation, workshops, emergency power supplies and elevators.

Single-phase transformers, oil filled and water cooled, are located underground. High-voltage transformer output will be transmitted by SF6 bus ducts to an outdoor take-off yard and from there to the surface switchyard. Six 400-kV transmission lines lead from the switchyard to the national grid.

Impounding commenced in November 2004 and the reservoir reached full supply level for the first time during 2005. The construction of this project was completed by the end of 2006. More than 1 300 000 m3 of concrete had been placed in the arch dam and spillways and more than one million metres of grout-injection boreholes had been drilled for the grout curtain. A further 530 000 m3 of concrete had been poured in the world’s largest concrete-lined plunge pool and its associated tailpond dam. Five million cubic metres of overburden and rock had been excavated and disposed of related to the surface works and almost 2 000 000 m3 of underground excavation had been carried out in order to construct:

• The underground powerhouse – 251 m long x 25 m wide x 47 m long
• The transformer cavern – 251 m long x 21 m wide x 26 m high
• The inlet valve gallery – 244 m long x 10 m wide x 22 m high
• The intake gate gallery – 177 m long x 11.5 m wide x 30 m high, and
• More than five km of tunnels ranging in size up to 14 m in diameter.
• Also, electromechanical equipment associated with eight 250-MW generating units had been assembled and installed with commissioning taking place during 2005 and 2006.

Scope of Services
Following completion of the detailed design of the 2000-MW Karun III project, Hatch Energy predecessor company Acres, together with joint-venture partner Mahab Ghodss Consulting Engineering Company, provided engineering services for the multi-contract supervision of construction of the project. In general, the scope of work involved engineering design and supervision at the site and in manufacturers' workshops.

The scope of work included:

• Final design
• Review and approval of schedules prepared by the manufacturers and contractors for the contracts
• Supervision of quality and quantity of the work and work methodologies
• Preparing progress reports covering technical, financial and planning issues and quality assurance
• Reviewing the manufacturers' and contractors' monthly work progress
• Reviewing the technical, financial and contractual claims of the contractors and manufacturers and recommending action.

Detailed Components

Awards

• Award of Excellence from Canadian Consulting Engineer and Association of Canadian Engineering Companies, 2008