Hydro Vortex Drop™ Shaft Key to Undersea Sewage Access

Welsh Water’s challenge to upgrade the sewage infrastructure within the £multi-million brownfield Swansea Waterfront re-development has been facilitated with an innovative Hydro Vortex Drop™ shaft solution from Hydro International.

Raw sewage needed to be conveyed down a 14-metre drop in a constrained space within the former Prince of Wales Dock as part of an innovative and cost-saving solution, which enabled construction within a tight 14-week project window.

Part of a wider regeneration of the Swansea Docks, the £200 million brownfield development known as SA1 Swansea Waterfront in the former dock, required a 2-year sewage infrastructure redevelopment from Welsh Water.

“The solution recommended to Welsh Water involved installing the Hydro Vortex Drop™ Shaft in an existing 4-metre bore access shaft within the dock,” said Len Burgess, project engineer for Hyder Consulting . “The Drop™ Shaft takes the sewage 14 metres from street level down to the existing main sewage line below water level in the dock.

“The Drop™ Shaft uses a hydrodynamic vortex to throttle back the flow, dissipating the energy of the falling liquid and protecting the surrounding infrastructure from undue stresses. This solution was much more economical in terms of time, space and cost than trying to incorporate a new cascade or other alternative in the dock.”

The Hydro Vortex Drop™ Shaft is a single-shaft self-activating system with no moving parts, designed to quietly and safely drop water or sewage from heights in a space-saving design. By carefully controlling the flows, the system avoids noise and vibration which could damage the network infrastructure.

At Swansea, the 150mm bore Hydro Vortex Drop™ shaft is designed for a maximum flow volume of 20l/s. It is sited in a 4m bore foul access shaft which had been located in the dock structure to access the sewage outflow pipeline installed following renewal of the area’s sewage infrastructure in the 1990s.

Barry Louth, Contract Manager for Alun Griffiths added: “The main sewer is now around 8 metres below the mean tide level which complicated the overall installation. The Drop™ Shaft was installed during a 14 week window within the two year sewage infrastructure project. Meticulous planning between ourselves, Hyder Consulting and Hydro together enabled successful installation.”

To date, the Welsh Government has invested £50m in SA1, and the private sector £150m. SA1 aims to secure around 4000 jobs, and provide over 2000 new residential properties. With two new pedestrian and cycle bridges, the new SA1 Gateway road connection, and close proximity to motorway and air links, SA1 is a sustainable extension to Swansea City Centre.