Category: Structure & materials
Prepared by Eng. Ahmed Fathy, Projects Manager ·
Definition
Dewatering is temporarily lowering groundwater in and around the excavation with wells or wellpoints and pumps, so foundations and waterproofing are built dry. It is common in Jeddah, the Eastern Province and sites near the sea.
Why it matters on a project
Without it concrete cannot be placed or waterproofing installed properly. It can run for weeks, affecting programme, cost and neighbouring buildings if not designed.
Measurement and pricing
Per day or month of operation, wells and pumps by number, or a lump sum from a specialist.
Common mistake
Stopping dewatering before the building's weight or basement backfill is in place, so groundwater lifts the slab or leaks in.
Frequently asked questions
How do I know my site needs dewatering?
From the groundwater level in the soil report compared with the excavation depth.
Where does the pumped water go?
It is discharged with the authority's approval to a network or approved location, never randomly into the street.
Related terms
- ExcavationRemoving soil down to the required foundation level.
- Raft foundationA single reinforced concrete slab foundation under the whole building.
- WaterproofingLayers preventing water ingress into structural elements or spaces, such as bituminous membranes and cementitious coatings.
- Soil investigation reportThe borehole study on which the foundations are designed.
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