Construction dewatering hose in the GCC: wellpoints, deep wells and the discharge line

Dig a basement almost anywhere along the Gulf coast and you meet water within a few metres. Studies of coastal sabkha find the water table close to 2 m below ground, sometimes much less. In Doha a rising water table — blamed on rapid development, leaking older networks and seawater intrusion — flooded key projects and halted tunnelling on the Metro Red Line in 2015. Jeddah’s groundwater rose for decades with seepage from cesspools and irrigation, damaging roads and foundations, and Kuwait City has seen similar rises from over-irrigation and leaking networks. Dewatering is not a special case on GCC sites; it is part of the programme.

/01The three methods.

Ground conditions drive the choice. Research on Jeddah’s highly permeable coralline limestone, for example, recommends wellpoints in the coastal zone and ditches and sumps further inland, and warns that deep wells there would draw enormous volumes and wash fines out of the ground. Dubai’s own drainage regulation refers to deep-well dewatering. Your dewatering designer sets the method; the hose has to match it.

/02A wellpoint system, end to end.

A line of wellpoints — small-diameter screened tubes jetted into the ground at close centres — is joined to a header pipe along the edge of the excavation by short flexible connections. A vacuum-assisted wellpoint pump draws water from the whole header. Every one of those connections works under vacuum, so they must be suction hose with a rigid helix; a lay flat hose there would collapse. On the pump’s outlet the pressure is positive, and that is where lay flat hose takes over, carrying the water to the settlement tank and outfall. Our article on suction hose vs lay flat hose explains the split.

/03Sizing the discharge line.

Add up the flow of every pump that feeds the line, then choose a bore that keeps friction loss well within the pump’s head at that flow. Discharge lines on GCC sites are often long, because the settlement tank, lagoon or approved outfall is at the site boundary or beyond it. As a rough guide from our friction loss guide, 6" lay flat carries 150 m³/h for several hundred metres at modest loss; at 400 m³/h and above, 8" to 10" is the usual starting point. Most site dewatering runs at low pressure, so the NBR discharge hose (10 bar) or TPU dewatering hose (14 to 21 bar by size) both have ample margin.

/04Settlement tank and outfall.

Pumped groundwater carries sand and silt. Dubai’s drainage regulation requires a sand trap, kept clean, before dewatering water enters the public network, and Qatar’s authorities expect sedimentation tanks or filters and regular water-quality reporting. The hose layout should bring every pump’s discharge into the tank inlet, take clear water from the outlet to the approved discharge point, and make the line easy to inspect for leaks. See our guide to dewatering discharge permits in Dubai, Abu Dhabi and Qatar for what the permit will ask for.

/05Choosing the hose.