Categorized | Construction

Geotechnical Contractors Offer Water Extraction for Construction Projects

One of the problems with deep excavation during construction that can be anticipated without exception is that of excess water. The water table must be temporarily lowered below the construction area. This water must be removed in some manner to enable digging and construction to proceed unhampered. There are several ways this water can be removed.


Using this method to lower the water table involves digging deep wells and pumping at a particular rate until the water level is low enough to allow construction to proceed. This requires a lot of knowledge and expertise to be able to figure the size and depth of wells needed, their numbers, and the rate of pumping that must be maintained.

Care must be taken during the digging of the wells to disturb the ecosystem as little as possible. Several methods can be employed to keep mud and disturbance at a minimum. Geotechnical contractors make precise calculations to drill under optimum conditions to control this disturbance.

Extraction is not always possible or suggested as the best solution. Geotechnical techniques are then called for the get the results desired. There are a number of these techniques, each with its own pros specifications and benefits.

Extraction methods involve three main tools. These are:

  • Deep wells

These can go up to two feet in diameter and hundreds of feet deep. They have submersible pumps that operate to extract excess water and lower the water table. They are able to extract thousands of gallons of water per minute.

  • Well points

The major components in this system are the well points, shared pumps, and header pipes. They are best suited to shallow pumping situations. They can involve thousands of well points and hundreds of shared pumps. They are cost effective for their shallow capacity.

  • Ejector systems

These are comprised of jet pumps that power multiple wells. They are best for deeper extraction where close spacing is required. They have a lower unit cost that does deep wells.

Each of these extraction methods works in its own way to extract water without geotechnical requirements. They work before construction begins to lower the water level below the construction area.

Four Techniques When Extraction is not the Solution

  • Slurry trenches

This geotechnical method of slurry trenches involves trenches that are two to five feet wide, dug with slurries of a soil-bentonite to form a continuous cut-off. Other slurry substances can be used if needed to give even more cut-off.

  • Grouting systems

    • Jet grouting

This method can be used to fill in around conventional barrier walls, or can be used as the main barrier wall. It can be used as a horizontal, or bottom, barrier. It is cost effective when used as a thin panel.

    • Permeation grouting

This is usually used as perimeter cut-off and in situ containment of contaminants.

    • Structural grouting

This type of grouting involves introducing grout into cracks and gaps to seal off groundwater. The grouts are water-reactive to seal off quickly upon contact with any water.

  • Ground freezing

This method involves drilling holes and putting a chilled liquid, either brine or liquid nitrogen, into the soil and rock to freeze them and cause them to fuse together. This frozen material is impermeable and withstands stronger compression.

Author’s Bio

Ken is a geotechnical engineer who blogs frequently about news and developments in the industry. He keeps up with the latest developments and is eager to share with his readers when something new is on the front. He not only writes his field, but is involved in many charitable events as well, showing that there is more to life than just engineering, though engineering does have a significant place in the life of all people.