Dewatering Systems

Excavations made as part of a Civils or Construction project sometimes need to go below the natural water table. When this happens there is a risk of soil instability and/or flooding. The impact of not dealing with groundwater problems can be enormous both in economic and engineering terms, if not dealt with professionally.

Project Dewatering Ltd can offer a wide range of effective and innovative pumping solutions through design, installation and management of Dewatering Systems to:

• Artificially lower the groundwater level around and beneath a dig, and create dry, stable and safe working conditions. 
  

• Preventing base heave of excavations.
  

• Lowering the hydrostatic pressure against sheet or scant piles and diaphragm walls.
  

• Increasing the effective stress of soils to improve gradients and stability of battered slopes.
  

• Proficiently extracting groundwater without the risk of removing fines and inducing settlement to nearby structures.

The choice of the Dewatering System, is dependant on principally the soil and groundwater characteristics (Hydrogeology), target drawdown levels and spatial parameters. Commonly, the solution will involve the use of, or combination of, the following methods:

Groundwater is simply water found within the earth. It forms part of the hydrologic cycle, which is the natural and continuous movement of water around the planet.

In the UK precipitation through rain, snow and sleet falls to the ground. Natural evaporation and bio-transpiration remove the majority, but some flows in surface run-off into rivers, lakes and the sea. Depending of localised conditions some of this will seep into the soil, i.e. an effluent stream or river. If the right conditions apply, the remainder will slowly seep downwards through the ground towards into an aquifer.

An aquifer is a zone of soil or rock in which groundwater is stored and moves from. A confined aquifer is one that is sandwiched between two impermeable zones (aquicludes), and is feed by a source at distance. The measurable water level, that is what is recorded if a well is sunk, is known as the piezometric level, and sometimes is above ground level (artesian head). A water table aquifer has no upper confining zone, with its water level or phreatic head equal to the point of zero pore water pressure, relative to atmospheric pressure. A perched water table occurs when an impermeable layer, such as Clay laminae within Sand aquifers impedes downward seepage.