Deep Well Dewatering System in Construction

Deep well dewatering system is a method of dewatering used to perform deep excavation as a part of construction project. 

Image Credits: vertexenvironmental.ca

When the excavation performed is deep, that it exceeds the well point system ( water table level) and water tremendously interfere the excavation process, we need to dewater and perform further excavation. Thus the process gives a dry site for excavation.

Deep Well System

Deep well dewatering system make use of a series of drilled wells, each connected to its own submersible pump to pump the water out. Deep well system can drawdown water as much as 40 m.

Features of Deep Well Dewatering System

1. Deep well dewatering system uses a series of drilled wells, to lower the groundwater level.
2. The system is flexible that can be used for any well depth, spacing and different pump capacities. This can vary based on the site conditions.
3. This method is ideal for deep excavations with moderate to high soil permeability soils like granular soil and rocks. 
4. It is best suitable where the artesian groundwater pressures threaten the base stability.
5. It is best used where small drawdowns are required over large areas.

Components of Deep Well Dewatering System

As mentioned before, the system consists of an array of widely spaced bored well connected to multi-stage electric submersible pumps. It consists of vertical or inclined bore holes ( 200 mm to 300 mm diameter casings) that is placed through the strata that requires dewatering. Into which a uPVC deep well casing is placed that have screened and case sections.

A filter pack is installed to maximize the well yield and inhibit the movement of fines. After the arrangement, before pumping water, airlifting is performed. 

Deep well dewatering can be performed on periphery of the excavation area, and therefore require adequate access area. It requires proper planning and site investigation before its commencement. It is a highly flexible method but the cost of well installation is high.