Built within the framework of an overall wastewater treatment system, the tunnels will carry wastewater to the new treatment plant at Brightwater in King County, north of Seattle, before discharging treated wastewater into the sea.

The contract, worth $211 million (about €166 million), covers driving two tunnels of 6.1 kilometres and 3.6 kilometres respectively using two slurry tunnel boring machines (TBMs) with an external diameter of 5.30 metres and pressure of up to 7 bar. The technique, which is rarely used in the United States, is one VINCI Construction Grands Projets’ specific areas of expertise.

The two tunnels will form the central part (Brightwater central tunnel) of a wastewater collection system comprising 22 kilometres of tunnels. They will be made of prefabricated segments installed as the TBMs progress. VINCI Construction Grands Projets will also excavate two access shafts, one 28 metres deep and the other 63 metres. In addition, the company will trench a 1 kilometre pipeline between the new and existing systems. Of this, 0.5 km will be driven using microtunnelling.

Work will start on 28 August and take 51 months to complete.

VINCI Construction Grands Projets is one of the world’s leading specialists in tunnel construction, as illustrated by the numerous references it has in France and the rest of the world. These include the Hallandsas tunnel in Sweden, Mitholz tunnel in Switzerland, A86 motorway to the west of Paris, Terminal 5 tunnels at Heathrow Airport in the UK, and metro tunnels in Cairo, Algiers, Athens and Budapest. Over the past 15 years, VINCI Construction Grands Projets has driven 718 kilometres of tunnels.

The contract, worth $115 million (about €90 million), covers the construction of a main dam made of 600,000 cubic metres of roller-compacted concrete and a secondary dam made of 800,000 cubic metres of backfill. The Wadi Dayqah dams are part of the water supply scheme for the cities of Muscat and Quriyat.

VINCI Construction Grands Projets (leader) will execute the contract in a 50/50 consortium with Consolidated Contractors Company (CCC Oman).

Work will start on 1 August 2006 and is scheduled to take 36 months.

This success is attributable to the experience of CCC Oman and VINCI Construction Grands Projets: CCC Oman recently built four dams in Oman for the government, and VINCI Construction Grands Projets has prestigious contracts such as the Naga Hammadi dam, currently under construction on the Nile, the Yacyreta dams between Argentina and Paraguay, the Xiaolangdi and Ertan dams in China, Pangue dam in Chile, Zimapan dam in Mexico and the Petit Saut dam in French Guiana.