Dewatering is a term used to describe the removal, or control, of undesired water from a project, specific location or asset. The presence of such waters can lead to health and safety risks, impacts to programme and additional costs, so the correct technique and efficient management of water can be critical to success.

WELLPOINTING

A Wellpoint Dewatering System typically consists of a number of shallow wells (up to 6m deep), each connected to a header main. The main is then connected to a vacuum pump which will remove ground water and discharge it to a predetermined location.

For deeper excavations, a multi-stage system or the use of deep wells can be implemented.

DEEP WELLS

Deep well installations lower ground water levels for deep excavations and shafts. A series of drilled wells are installed around the perimeter of the excavation into which a multi-stage submersible borehole pump is installed. With the ability to operate off a level sensor, the borehole pumps deliver water into a collection main before discharging at a predetermined location.

EJECTOR WELLS

An ejector (or eductor) system uses high pressure water, pumped into the well to create a venturi within an ejector body. The vacuum condition created causes ground water to be discharged back up the well via a return line to a collection tank. Water within the collection tank is recirculated into the well to continue the cycle, with any excess abstracted water removed to a discharge location via a separate pump or weir and gravity pipe.

BYPASS DEWATERING

In order to facilitate repair or replacement of damaged pipelines, flows are stoppered or bunged upstream of the works area and a system of over pumping is installed to a suitable downstream location. This removes the need to work on a live asset and ensures a safe work environment and continuity of service.