Well point dewatering system | Advantages and Disadvantages

What is well point dewatering system?

Dewatering is the process of removing water from the surface and underground of the construction site. The logging of water may delay the project’s progress and make the construction uneconomical.

Well point dewatering system | Advantages and Disadvantages
  • A well point dewatering system is mostly used for dewatering because it is easy to handle and operate in different groundwater situations.
  • Many pump sets for dewatering are fitted at a specific distance, depending on the needs and requirements of the site.
  • The well-point dewatering system will work more effectively or efficiently if the ground is permeable as much as possible to draw groundwater.

Purpose of Well-Point System

A well-point is usually located near an excavation, and it uses a vacuum to draw water roughly up to a height of about 6 meters.

To use stable working techniques, Well Point dewatering System is used to lower the groundwater level. Each small-diameter well in the system is connected by a header pipe to a well-point pump.

  • It assists in digging tunnels, basements and foundations.
  • Trenching for utilities and pipelines is done with it.
  • It is used in the construction of dams and embankments.
  • It facilitates the cleaning of contaminated sites.
  • It supports mining activities.

Types of the Well point dewatering system

There are two types of Well-Point System

  • Single Level Well-Point
  • Multilevel Well-Point

Single Level Well-Point

  • In Single Level Well-Point, the dimension of the pipe remains 50 mm in diameter and 1 m long. To prevent clogs, the pipe has perforations that are protected by a screen.
  • A jetting nozzle is available at the lower end. It also serves as the nozzle driving point.
  • During well-point installation, a ball valve is provided near the lower end, which limits the flow of water only downwards.
  • The lower end of the well point is connected to a riser pipe that roughly matches the diameter of the well point.
  • The riser pipes are connected to the header pipe, which is a horizontal pipe at ground level.
  • The distance between the well point and the header pipe is kept between 0.6 and 1.5 meters.
  • To sink the well-point to the required depth, water is forced down through the riser pipe.
  • After it is set up the pumping continues till all the excavation work is completed. Despite the shallow depth of excavation, a single-stage well point system is used.
  • They work well in granular soils. The single-stage well point stage method lowers the water table to 4.5 meters.

Multilevel Well-Point

  • These systems are used when the excavation depth exceeds 4.5 m and slope failure is possible. In this system, the fine-point installation occurs in stages.
  • The first phase involves establishing a well-point at a depth of about 4.5 m and operating it until the water table drops to about 4.5 m.
  • Then the area is dug to a depth of 4.5 meters. The second stage of well points are established in the already excavated area.
  • The water level has decreased by another 4.5 meters. This method of excavation is used up to a depth of about 15 meters.
  • A fine point system does not allow excavation deeper than 15 m.

installing well point dewatering systems

Well point dewatering system | Advantages and Disadvantages
  • There are three types of wells: driven, dug driven, and rugged/drilled. Well points are used by the types of wells operated.
  • How deep the well point should be depends on how deep the water table is.
  • Location is essential when using Well-Point. A moist soil level may be preferred for easy installation of the well-point system.
  • To ensure proper installation of your good point, the entire point must be below the water level; Otherwise, the pump will only draw air.
  • Please be aware that the water level will eventually drop during the operation of the pump, which may lead to a lower point connecting the water level below the pump’s capacity.

Advantages of Well point dewatering system

Most ground conditions can be quickly established with Well-Point.

They do not require much maintenance.

Steel self-jetting well-points, which are beneficial in environments with limited space for expansion and reusability, are another option.

During construction, confined layers can be quickly depressurized by establishing a well-point inside tunnels and cross-passages.

Using a small rotary drilling rig and either temporary casing or conventional and hollow-stemmed augers, the well-point can be embedded in locations with challenging soil properties, such as open gravel or overburdened firm soil.

Disadvantages of Well point dewatering system

Well-point dewatering systems are recommended to be used only at places with less than 5 to 6 meters of the water table. For deep excavation, it is recommended to use caisson foundation technology.

The operation of the well should continue until the required water level is reached.

In soils containing large boulders, clay, and gravel, well-point systems require the use of machine-drilled holes to operate, which will increase installation costs.

Applications of Well-Point System

  • It helps to build an underground water tank.
  • It is used for digging a tunnel work.
  • Wellpoint systems are important to make building stable foundations in areas with high groundwater levels.
  • Water can be efficiently drained from trenches to make the stability of the trench and create a safe environment for the workers.
  • It helps to control water levels close to shorelines, coastal projects, etc.
  • The well point system is used in mining to prevent the ingress of water during shaft sinking.

Q) Are there any alternatives to Well point dewatering system?

Ans:- Yes, alternatives include deep well dewatering, ejector systems, and sump pumping. The choice depends on factors like site conditions and project requirements.

Q) Can Well point dewatering system be used for emergency water control?

Ans:- While primarily designed for construction, well point systems can be adapted for emergency dewatering during flooding or water-related emergencies.

Q) To what extent can the water table be lowered by the well point dewatering system?

Answer: Depending on the permeability of the soil and the design of the system, well point dewatering systems can successfully lower the groundwater table to a depth of 15 to 20 feet.

Q) Is well point dewatering system applicable to all soil types?

Answer:  Yes, well point dewatering systems can be applied to all soil types in sandy, silt and clay soil.

Q) How long can a well point dewatering system last?

Answer:  Well point systems is operated as long as the construction project last. Generally Well point systems operation can take from 1 week to several months.

Read Also,

Water treatment process | Water treatment steps

Components of Water supply System | Source, Treatment, Pump

Relation between water content and dry density of soil

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"Structural Engineer" with over 5 years of experience in estimation, structural design, and surveying. I am passionate about using my skills to create safe and sustainable structures. I am also a keen writer, and I enjoy sharing my knowledge and experiences with others.