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Wet, unstable soil makes the ground to be excavated difficult to work, difficult and expensive to remove from site and creates an unpleasant, sometimes dangerous environment in which to work.


The net result is usually lost time and added cost to the project.


The three photos below all show the same site, before, during and after dewatering.


Before Dewatering

During Dewatering

After Dewatering

The jetted wellpoints installed around the excavation perimeter combined with a suction pumping system stabilised the ground, giving it strength and making it easy to work. This considerably speeded up soil removal operations and enabled spoil to be transported and disposed of without problems.


The techniques used to achieve ground stabilisation dependent upon a number of factors including: level to which the water table is to be lowered, the flow volume of the water to be removed, the geology and topography at the site, the site layout and the construction programme constraints.


Ground strengthening techniques include the design and installation of:

  • wellpoint dewatering systems
  • deep well dewatering systems
  • perimeter drainage
  • land drainage within the excavation
  • structural stone drainage
  • sump systems with designed filtration
  • ground anchors with capillary drainage
  • combinations of the above


OGI is committed to providing our Clients with the most cost effective solutions available within the specific constraints of the project.  The sooner OGI is brought into the design process, the greater the potential for the design of the most effective and efficient way to control the groundwater issues on the site.


The following are examples:


Installation of ground anchors

Stone drainage layer protecting a steep batter face
Stabilise 3

Wellpoint dewatering combined with perimeter drainage
Stabilise 4

Land drainage machine installing from a level above water table to below formation level with bedrock at a relatively shallow depth
Stabilise 5

Drilled deep wells installed around the excavation perimeter to produce a dry excavation