A dewatering systems works as follows, dewatering involves controlling groundwater by pumping, to locally lower groundwater levels in the vicinity of the excavation. 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.
The most common methods for dewatering includes sumps, wells and well-points.
Sumps provide localized, very shallow dewatering and consists of pumping from perforated drums or casings in a gravel-filled backhoe pit. Sumps work best in tight, fine grained soils, or very coarse, boulder deposits.
Dewatering pumps are centrifugal pumps installed in a building that is situated below the groundwater level, to reduce the water level and then maintain it at this level.One example is in underground mining in which water penetrating into the audits is pumped up to the surface. In open-cast mining, the groundwater level is reduced through drainage well trenches until the pit is dry. The groundwater level in construction pits in civil engineering is reduced in a similar way.For dewatering or reducing groundwater on large building sites, protection is provided by drainage well trenches equipped with submersible motor pumps in excavations such as for underground railways, bridges or in open-cast mining. Portable submersible motor pumps are often used for pumping out heavily contaminated seepage water in such cases. With the latter type of pump, the motor is arranged above the pump.