When a contractor or a client is to build in an area with a high water table – or needs room for a deep basement – it might be necessary to carry out groundwater lowering. The simplest form of dewatering is sump pumping, where groundwater is allowed to enter the excavation where it is then collected in a sump and pumped away by robust solids handling pumps. Sump pumping can be effective in many circumstances, but seepage into the excavation can create the risk of instability and other construction problems.
To prevent significant groundwater seepage into the excavation and to ensure stability of excavation side slopes and base it may be necessary to lower groundwater levels in advance of excavation. This is known as ‘pre-drainage’ and methods include:
- filter wells
- bleeding wells
- monitoring wells
- reinfiltration system
- well points
The selection of the dewatering technique at a particular site or country will depend on many factors and Aarsleff’s engineering team can provide a complete design and installation service to control the groundwater problems at a given site.