On sites where groundwater will be encountered during the construction works, it is essential to understand and manage this issue to ensure your project stays on budget and on schedule.
As a leading UK construction dewatering subcontractor, the Project Dewatering Team can understand your project requirements to allow the design, installation, and monitoring of a tailor-made dewatering system for your site. We have the experience and expertise needed to provide professional, cost-effective, bespoke dewatering and groundwater remediation solutions for groundwater control in construction projects.
We have an extensive range of modern dewatering solutions, such as horizontal dewatering, deepwells, wellpoints, ejectors and pressure relief wells. We’re part of Europe’s largest dewatering and water management contractor.
Horizontal dewatering is used where shallow dewatering is required, i.e. to less than 6.5m bgl and where long linear configurations are required such as pipelines and drainage. The method is considerably more cost effective where long linear distances are involved and has the advantage that minimal surface equipment is required, i.e. no well points and header pipe running on the surface, with only the pumps and discharge pipe present. Also because the pipework remains below ground, this method has the advantage that the infrastructure can be put in at the beginning of the works when the site is less constricted, and then accessed when required. In addition, if further works are needed later in the project the pipework can simply be reconnected, there is no need for installation of a second dewatering system as would be the case with a well point system.
Deepwells are used for site dewatering of excavations below 6m in depth and the permeability of the targeted soil is moderate to high. A deep well system uses bored wells, typically pumped by submersible pumps. This method involves applying the drilling and pumping technologies used in water supply wells and using them in dewatering systems.
A wellpoint is a small-diameter, closely-spaced shallow well, which offers a quick installation and versatile method of groundwater control where site drawdown is less than 5-6m in depth. Wellpoints are pumped using specialist surface vacuum pumps and are particularly effective in stratified and fine-graded soils.
Where groundwater needs to be lowered more than six metres below ground in lower permeability soils, such as silt or fine sand, ejectors offer one of the best dewatering solutions. Ejector systems require both a high pressure supply and low pressure return header and require a greater level of experience to successfully operate than traditional deepwell and wellpoint systems.
Pressure relief wells (sometimes called bleed wells) are used to reduce water pressures in confined aquifers or in stratified ground conditions. Waste water flowing from the relief wells is typically disposed of by sump pumping. A granular drainage blanket and network of drains can be used to direct water to the sumps and prevent ‘ponding’ in the excavation.