The well point dewatering system is an effective method of controlling groundwater in shallow excavations. This system works effectively in sandy and silty soil conditions. The approach is to create a vacuum to draw out water so that the water table can be lowered. This is one of the most cost-effective dewatering methods. However, it comes with its own unique set of challenges. These limitations and challenges can be worked out if you source the system from the right supplier or service provider.
Here is a rundown of the common problems associated with the well point dewatering system and their solutions for smoother operations.
Challenge 1 # Inadequate Lowering of Water Table
The common complaint about this system is that it is unable to sufficiently lower the water table. The reason – the spacing of wellpoints is not done properly or the right pump has not been selected or there are not enough wellpoints.
Solution:
- Keep wellpoints at the right spacing, about 1 to 2 meters apart.
- The soil permeability should be evaluated and more wellpoints added, if required.
- You can use a vacuum pump system or a submersible dewatering pump for additional support. This is applicable if the water table remains high.
Challenge 2 # Air Leaks in the System
Often the well point dewatering system stops performing effectively due to air leaks in the header pipes, fittings, or wellpoint connection.These can reduce suction power leading to inefficient dewatering.
Solution:
- Pressure tests should be conducted regularly for leak detection and fixing.
- All clamps, joints, and hoses should be regularly inspected for signs of leakage.
- High-quality sealing compounds or gaskets should be used during installation.
Challenge 3 # Clogged Wellpoints or Filters
With constant use, the well point dewatering system can get clogged in the presence of fine particles, sediments, and organic debris. Clogged wellpoints or their strainers can decrease flow and efficiency.
Solution:
- Use mesh filters will wellpoints to block finer particles.
- Methods like periodic backflushing can be used for clearing clogged points.
- Pre-treating with a gravel filter or installing temporary drainage mats can also be considered.
Challenge 4 # Pump Failures and Inefficiency
The well point dewatering system often fails to work at its best due to various reasons. These include – overloading, air binding, wear and tear from abrasive materials, improper priming, etc.
Solution:
- Make sure the pump has the right capacity, else the expected flow rate can be affected.
- Integrate a submersible dewatering pump for deeper or isolated wells. This works as a supplement to the vacuum system.
- Investing in preventive maintenance is the ideal way to make the pumps work effectively. Routine maintenance cover aspects like impeller inspection and motor checks.
- Reduce downtime by storing spare parts and a backup pump on-site.
Challenge 5 # Soil Instability Around Wellpoints
If the soil around the well point dewatering system is destabilised due to excessive drawdown or incorrect installation, the pump could collapse.
Solution:
- If the soil is sensitive, limit drawdown.
- The installation of wellpoints should be done gradually. Simultaneously, the soil behaviour of the surrounding area should be monitored.
- If instability is detected, reinforce the area with geotextiles or shoring.
Challenge 6 # Environmental and Regulatory Concerns
The dewatered water disposal is a challenge as if it is not properly discharged or treated, there could be environmental issues.
Solution:
- Before discharge, filter or treat the water
- It is important to understand and comply with local regulations for water disposal.
The right well point dewatering system helps control shallow groundwater. However, there could be challenges but by continuous monitoring and maintenance, these issues can be effectively handled.
