# What is dewatering?
**Dewatering (Dutch: bronbemaling) is the process of lowering the groundwater table around a construction site by extracting water from a series of wells or well-points. This allows excavation and foundation work to proceed in dry conditions, preventing soil instability and flooding of the work area.**
## How well-point dewatering works
A ring of well-points — small-diameter perforated pipes — is installed around the perimeter of the excavation. These are connected via a header pipe to a vacuum pump that draws water from the soil. As water is extracted, the local water table drops below the excavation depth, creating a dry working zone.
### Common dewatering methods
– **Well-point system:** Shallow wells (up to about 6 m depth) connected to a vacuum pump. Multiple stages can increase the achievable drawdown.
– **Deep-well dewatering:** Submersible pumps installed in bored wells for deeper excavations (6–30 m or more).
– **Eductor wells:** Jet-pump systems for fine-grained soils with low permeability.
– **Open sump pumping:** Simple pumping from a sump pit within the excavation for minor seepage.
## Design considerations
Engineers must assess soil permeability, required drawdown depth, influence radius, and potential settlement of surrounding structures. Environmental regulations often require monitoring of groundwater levels and, in some jurisdictions, reinjection of extracted water to prevent subsidence.
## Applications
– Deep basement and underground car park excavations
– Pipeline and sewer trench construction below water table
– Bridge foundation and caisson work
– Tunnel entry and exit shafts
– Remediation of contaminated groundwater
## Related terms
– Groundwater table
– Permeability
– Excavation support
– Sheet piling
– Soil settlement
– Piezometer
– Reinjection (retourlozing)
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