Dewatering Contractor
Dewatering is the work of lowering the groundwater table during construction so the excavation stays dry and stable. Without it, water enters the excavation, the base softens, and the substructure works below cannot be executed properly.
This is not standalone work. Dewatering almost always runs alongside earth retention — the wall holds the soil, dewatering holds the water. The two must be planned together, not in sequence.
How It Works
Lower it, then hold itDeep wellss are bored around the excavation and fitted with submersible pumps. These wells lower the water table across the whole area, rather than merely removing water that has already entered.
The water level is drawn down in stages until it sits below the excavation base — not all at once, so the surrounding ground does not settle abruptly.
Water that still seeps into the excavation collects in a sump pit and is pumped out. This complements the deep wells; it does not replace them.
Pumps run continuously through the substructure works. Stop too early and the water rises again before the structure is strong enough to resist it.
Applied Example
AIS Tunnel, JakartaOn the Australian Independent School tunnel works, the groundwater table sat at elevation +7.500 while the excavation base lay well below it. The method statement called for drawing the water down to around +1.000 to +1.500 — one to one and a half metres below the excavation base.
Two deep wells with submersible pumps were installed for this, together with two to four surface pumps and a sump pit keeping the water from rising again while excavation and structural works proceeded.
Service Area
Greater Jakarta and beyond JavaWe are based in Bekasi Regency and work from Greater Jakarta through to islands beyond Java. Dewatering is most often carried out alongside foundation and retaining wall works on the same project, so the water plan and the excavation plan are drawn up together rather than separately.
How We Work Together
From soil data to demobilisationA boring log with groundwater readings, the planned excavation depth, a site layout, and the distance to neighbouring buildings. Those four decide the method.
Expected flow and the required drawdown are calculated from that data, then the method is chosen: sump pit, wellpoint, deep well, or a combination. The number of points follows the calculation rather than being fixed in advance.
The scope is stated openly: number of points, pump capacity, the operating duration assumed, power source, and who carries the generator and fuel.
Wells and pumps are installed together with piezometers and settlement markers. The initial water level is recorded before the first pump starts.
Pumps run continuously through the substructure works. Water levels and running hours are logged daily; if the drawdown falls short of the plan, the method is adjusted.
Pumping is stopped in stages rather than all at once, so the water table rises slowly and the finished structure is not hit by sudden uplift.
What You Receive
Water that is measured, not estimatedAccountable dewatering always leaves numbers behind: the water level before work started, the drawdown day by day, running hours for each pump, and readings from the settlement markers. Those same records are what show when pumping can safely stop — without guessing.
Questions and Answers
The ones we are asked mostHow long does dewatering have to run?
For as long as the substructure works last, until the structure is heavy enough to resist uplift. The duration follows the structural schedule rather than ours — which is why changes to that schedule feed straight into operating cost.
Can dewatering cause neighbouring buildings to settle?
There is a risk, particularly in soft ground. That is why drawdown is staged, settlement markers are installed from the start, and where the risk is high the solution shifts towards a cut-off wall such as secant piles, so that far less water has to be pumped.
Where does the water go?
Into the municipal drain through a settling tank, so that silt is not carried along. Discharge permits differ between regions and are best confirmed before work begins.
Where does the power come from?
Ideally from the project supply, with a generator as backup. Dewatering pumps cannot stay off for long — a dry excavation can be flooded again within hours. Who provides the generator and fuel is stated plainly in the quotation.
What is the difference between deep wells, wellpoints and sump pits?
A sump pit only removes water that has already entered the excavation, which suits shallow digs in cohesive soil. Wellpoints lower the water table by roughly four to six metres per stage in sandy ground. Deep wells handle deep excavations and high flows.
Can dewatering be carried out separately from the piling works?
Yes, and often it is. But when the foundation and retaining wall are handled by the same team, the sequence of excavation, pumping and concreting is far easier to align — and that is usually where time is saved on site.
Discuss your requirements
Not sure which foundation method suits your site? Just describe the conditions — our engineering team is glad to help, with no obligation.
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