Saudi Arabia’s National Water Company has received expressions of interest from contractors to build a sewage conveyor from Monfouha in Riyadh to Al-Haer sewage treatment plant.

The winning bidder will build two tunnels, each with a length of 37 kilometres in Jurassic limestone. The tunnels will be 400 metres apart.

The project includes a wadi crossing and a cascade from the outfall of the northern tunnel. The southern tunnel will be 4.5km long.

The local Aziz Company won a contract in 2006 to design and build the Al-Haer sewage treatment plant that had an initial capacity of 400,000 cubic metres a day (cm/d) which was later stepped up to 640,000 cm/d.