The objective of dewatering is to lower the groundwater table to prevent significant groundwater flow into an excavation, and/or to ensure slope stability. The preferred dewatering system will depend on hydrogeological conditions and construction requirements.
The deep well system forms a large number of bored wells in the site area where the water is excavated by submersible pumps. Whenever the water is pumped out it creates a dry patch in the well making it level and creates a cone of depression or drawdown around itself.
Sump pumping is the most common method for dewatering, since it basically works by gravity.
Groundwater is allowed to seep into the excavation area, where it is collected in sumps to be pumped out. This method is used in shallow excavation areas, where the soil has a high content of sand or gravel. If the excavation area is large, this method can use a ditch – a long and narrow sump along the excavation.
