Wadi Dayqah Dam, near Quriyat in Oman, was completed in 2009. With very few significant dam sites, Wadi Dayqah is not only the largest dam yet to be constructed, but the largest ever likely to be built in the country.

The dam comprises a 77 m high RCC structure, over which the spillway is routed, and a 40 m high rockfill saddle embankment. The 600 000 m³ of concrete comprising the RCC dam was placed between January 2008 and May 2009, with the bulk of the dam body completed by December 2008.

Due to the high temperatures to which the site is exposed, RCC placement was generally undertaken at night and high capacity water chillers were used to drop the RCC temperature at placement to 15°C below ambient.

Despite being hit by the Cyclone Gonu flood, with a recurrence interval in excess of
10 000 years, just 1 year after construction was initiated, the project was completed early, allowing impoundment to commence in August 2009. The design team comprised Black and Veatch of the UK, Su-Yapi of Turkey and Nespak of Pakistan, with ARQ filling the role of RCC Specialists and providing design assistance for the dam structure and the spillway.

During early June 2010, Tropical Cyclone Phet dropped approximately 450 mm of rainfall on the Wadi Dayqah catchment and the reservoir rose very rapidly, causing the discharge over the spillway to peak at 5200 m³/s, with a head over the crest of 5,25 m.

Inspections after the flood demonstrated that the dam performed in an exemplary manner and Wadi Dayqah Dam must, in fact, be one of the most impermeable RCC dams yet constructed.

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