In Dewatering , what's the difference between well point system & deep well system ? and when each system can be used ?

Difference:

A deep well typically consists of a boreholes fitted with a slotted liner and an electric submersible pump. As water is pumped from a deep well, a hydraulic gradient is formed and water flows into the well forming a cone of depression around the well in which there is little or no water remaining in the pore spaces of the surrounding soil.

While, Wellpoints are small-diameter (about mm) tubes with slots near the bottom that are inserted into the ground from which water is drawn by a vacuum generated by a dewatering pump.

Use:

Deep wells can be installed in a ring around an excavation to lower the water level and maintain a safe, dry site and  Wellpoints are typically installed at close centers in a line along or around the edge of an excavation. As a vacuum is limited to0 bar, the height to which water can be drawn is limited to about6 meters (in practice).

Well point system is consisting of a number of well points along with trench excavation or around excavation site which are connected to a header line connected to a vacuum pump to release the air from header line and other to pump the water. Deep well system is a number of individual wells each have its own submersible pump and some times called as borehole. Deep well system are commonly used at high permeable soils such sand and rocks because its pumping capacity is larger than other dewatering system while well point system is commonly used to lower the ground water table within6-7m as maximum at excavated site to work in dry conditions.

WellPoint dewatering system consists of a series of well points, which are installed at a pre-determined depth (upto 6m) and appropriate spacing(1m-3m) around an excavation.

Usage

1) Suitable for depths upto 6 meter.

2) Cheap and flexible.Very rapid installation

3) Effective in sandy soils

Deep well systems consist of one or more individual wells, each of it has its own electric submersible pump at the bottom of the well shaft. Pumping from each well lowers the ground water level and creates a cone of depression around itself.

Usage

Effective in wide range of ground conditions- Sands, gravels , fissured rocks