Dewatering design

AGT is specialised in dewatering and reinjection design. Dewatering is a temporary or permanent decrease of the natural groundwater level by pumping of groundwater. The pumped water is either discharged in surface water systems (for example ditches, sewers) of reinjected in the aquifer at a distance from the pumping installation.

Need for a dewatering design

Dewatering has many applications in utility construction (sewers, gas pipes…), office buildings and appartment blocks, large infrastructural works or port development. In many countries, more a more regulations are put in practice for dewatering, concerning environmental hazards (pollution), safety control, discharge costs, liabilities… In many cases, a thorough investigation before the works is required to meet these regulations, including a follow-up of the dewatering during construction.

AGT applies the most advanced software to model the groundwater system of complex sites, using all available data (borehole logs, cone penetration tests, pumping tests, geophysical measurements, expert judgement…).

Proof of concept

A dewatering design start with a concept, in which the dewatering installation is proposed according to the boundary conditions (excavation level, surface area, cut-off structures, local hydrogeology). This concept is then adjusted and verified by a numerical groundwater model. The results of the model simulations are maps of the groundwater level at different instances, graphs of drawdown in function of time and dewatering discharges. Finally, a detailled bill of quantities is of the dewatering installation is formulated, which can be used to contract dewatering firms.

Impact reduction

In the dewatering design, a lot of attention is paid to reduce all possible (negative) impacts of the dewatering to the environment. Ground subsidence due to the lowering of the groundwater, which is particulary dangerous for buildings on clay or peat layers,  is estimated and if necessary reduced by cut-off structures or reinjection. The mobilization of contaminants or salt water can be modelled with specific transport models. In an excavation, the geotechnical stability of walls and slopes is checked and bottom collapse is avoided.