WJ News

Latest News and Updates from WJ Groundwater and across the Industry.

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Passive Relief Systems

Passive Relief Systems

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.

In practice passive relief wells are generally only used for shafts or excavations in stable soils, stiff clay or weak rock, where there is only a marginal risk of base heave caused by sand lenses, fissures or a confined aquifer.

Featured Pressure Relief Projects

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WJ Group AdminPassive Relief Systems
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Recharge Systems

Recharge Systems

Recharge Systems allow water to be returned to the ground usually from abstracted water from a groundwater control system to prevent groundwater levels falling outside prescribed limits.

Caution should be exercised when considering a recharge scheme to control groundwater levels or as a means of discharge disposal; such schemes are complex to operate and monitor and require careful planning. However, subject to obtaining necessary regulatory permissions recharge systems are a potential mitigation measure to control the impact on sensitive water dependant features such as wetlands, lakes, watercourses and water supply boreholes.

WJ have a huge wealth of knowledge in designing and operating these systems and with adequate early contractor involvement with customers this strategy can be a highly effective way in overcoming technical and regulatory constraints as well as providing potential cost savings for not having to provide physical groundwater cut-offs or costly off-site groundwater disposal charges.

Featured Recharge Projects

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WJ Group AdminRecharge Systems
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Sump Pumping and Overpumping

Sump Pumping and Overpumping

Sump pumping is one of the simplest forms of dewatering and can be very reliable in a variety of different situations. Groundwater is allowed to flow in to the excavation, is collected in sumps and then pumped away.

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 as part of a complete water control strategy for a project.

All WJ pumps are fully tested and serviced before being deployed to site to ensure each pump performs at its optimum efficiency and effectiveness.

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WJ Group AdminSump Pumping and Overpumping
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Wellpoint Systems

Wellpoint Dewatering

Wellpoints are used to lower groundwater levels and improve working conditions in shallow excavations, typically less that 6.0m in depth. For deeper excavations a number of strategies, such as staged and multi-tier wellpoint systems can be utilised.

 

 

 

 

Wellpoint systems consist of a series of small diameter wells, installed by water jetting, augering or rotary drilling techniques, connected by a header pipe connected to a centrally located suction pump. Groundwater is abstracted via the wellpoints from a vacuum generated by the pump. A wellpoint is capable of drawing water from the ground up to a depth of 6m and is idea for shallow excavations, basements, pipelines, confined spaces, underpasses and tunnel excavations.

Pumping options include surface electric or diesel suction pumps and super-silenced models for residential areas.

Wellpoint systems can be installed quickly in most ground conditions and are easy to maintain for the duration of the project.

WJ have one of the most extensive and modern fleets of wellpoint installation and pumping plant and equipment in the UK, and is well equipped to deal with all requirements. Our highly qualified team have worked on projects ranging all over the UK from as far south as the Channel Islands to the north coast of Scotland and from the west of Wales to the eastern tip of Norfolk.

Featured Wellpoint Projects

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WJ Group AdminWellpoint Systems
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Ejector Systems

Ejector Systems

Ejectors 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.

Ejector pumping stations, located centrally, feed high-pressure water to the base of the wells via an ejector body. The flow of water through the nozzle generates suction in the well, drawing in groundwater.

 

Featured Ejector Dewatering Projects

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WJ Group AdminEjector Systems
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Deepwell Systems

Deepwell Systems

Deepwell systems lower groundwater levels using a series of drilled wells, each fitted with its own electric submersible pump.

They are ideal for deep excavations with moderate to high soil permeabilities or where artesian conditions are present, and are capable of pumping hundreds of litres of water per minute, as the only limiting factors are well depth, pump performance and the prevailing ground conditions.

The flexibility on the well depth, spacing and pump capacities, mean they are suitable for for almost any project and location, and keep access restrictions to a minimum.

 

WJ carefully design and install deepwell systems to maximise drawdown and pump efficiency whilst ensuring a discharge free of suspended solids.

At the heart of each system an innovative electrical pump station is used to power and control multiple pumps from a central location. Control options include automatic mains failure (AMF) switchover to standby power, visual/audio/GSM test alarm systems, and a secure cloud based data logger for monitoring groundwater flows, pressures and levels.

 

Featured Deepwell Projects

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Neil.CoulterDeepwell Systems