IN AN OFFICIAL OPENING ceremony, King Abdullah of Jordan inaugurated the Tannur dam, and unveiled a monument commemorating the contribution made by the consultants and the various contractors involved in the landmark project.

The US$30M dam has been constructed for the Jordan Valley Authority and is the country’s first RCC dam. It will form part of a water supply and irrigation project serving 800ha of farmland in the Southern Ghors area.

Situated 150km south of Amman on one of Jordan’s largest wadis, Wadi Hasa, the 60m high, 250m long concrete gravity dam has a reservoir capacity of 17M m3 and stores flash flood water for much needed domestic supplies and irrigation. As the dam is located in a highly seismic area – founded on interbedded marls and limestone of only moderate strength and near the Dead Sea Fault – the design is at the forefront of RCC technology. A high paste RCC was adopted with a relatively high total cementitious content of 175kg/m3. In addition, grout enriched RCC was used for the upstream and downstream facings of the dam wall rather than conventional mass concrete.

Tannur dam’s spillway discharges a maximum of 3080m3/sec. It has a crest length of 180m with a stepped downstream face terminating in a cascade structure and stilling basin. Other major elements include drawoff and bottom outlet works with a capacity of 90m3/sec, and extensive foundation grouting.

Throughout the two-year construction period, Mott MacDonald led the supervision team which included Australian consultant Gutteridge, Haskins and Davey advising on the RCC, and local Jordanian practice Consulting Engineering Centre.

Mott MacDonald also undertook the design review and prepared construction drawings. The dam was completed to programme and budget, despite difficult geological conditions dictating some design adjustments in the early stages.