Dewatering risk evaluation-discreption page

Dewatering of shallow subsurface water-bearing media is commonly essential in engineering support of a variety of projects, particularly to complement construction activities. There are different aspects of dewatering design that should be considered. Dewatering risk is an important consideration that may be overlooked in many projects, which can result in sub-optimal to deleterious outcomes.
There have been attempts to evaluate the risks associated with dewatering based on site-specific variables that have an influential bearing on the dewatering component of projects. The main site-specific variables that have the potential to pose risk in association with dewatering are listed as below:

1- Depth of excavation
2- Groundwater level versus planned final depth of excavation
3- Soil and sub-soil type where excavation is happening
4- Duration of dewatering/lowering of groundwater-surface elevation
5- Cost of project components which may be influenced by dewatering
6- Potential effects on adjacent infrastructure, services and/or activities, buildings, and private properties (e.g. owing to possible induced subsidence).

A few examples/scenarios of dewatering and their possible deleterious outcomes are illustrated in Figures A through C.

Figure A presents a typical desirable dewatering effect by lowering the water level compared to pre-dewatering water table conditions.

In contrast, Figure B shows an undesirable outcome as represented by induced land subsidence phenomena caused by the use of a risk-tolerant dewatering design.

Figure C illustrates how the removal of overburden material for excavation purposes also removes the counterbalancing weight that offsets the uplift pressure from the deeper of the two aquifers.
To have a quick risk evaluation of your dewatering project, simply click the dewatering toolkit button.

Figure A: Typical Lowered Groundwater Level as a Result of a Dewatering Operation
Figure B: Cracked/Land Subsidence Phenomena Caused by Inappropriate Dewatering
Figure C: Critical Role of the Saturated Unit weight and Submerged Unit Weight in Possible Uplift from Artesian Pressure
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