WJ Groundwater

A sump pump is used when groundwater is allowed to flow in to the excavation, it's then collected in sumps and then pumped away. Sump pumping is one of the simplest forms of dewatering and can be very reliable in a variety of different situations. Overpumping is the process of providing a temporary route to pump water from A to B often by-passing an existing structure such as a manhole or chamber, to ensure a vital continuation of services during construction. WJ have extensive experience in providing sump pump and overpumping solutions in the UK as part of a complete water control strategy for a project.

Ejector dewatering systems can dramatically improve ground conditions up to depths of 50m. WJ is the industry leader in the design, installation and maintenance of ejector systems, having installed then on some of the UK's largest infrastructure projects in recent decades including the Conway Crossing, Crossrail, and the installation of new drainage along the M3. Pictured right is our ejector dewatering system rigged for the Olympic Aquatic Centre, London. Ejector pumping stations, located centrally, feed high-pressure water to the base of the wells via an ejector body.

It is sometimes possible to control excess pore water pressures in a confined aquifer below the base of a proposed excavation by using passive relief well systems. The passive wells are drilled in the base of the excavation before the excavation has reached the piezometric level in the aquifer. As excavation continues below the piezometric surface, the wells will start to overflow, providing pressure relief. Water is then removed by sump pumping The effectiveness of the system is often proven with a pumping test carried out from a couple of passive wells that were lined during construction.