What is Construction Dewatering?
Dewatering is the process of removing water from solid material or soil by wet classification, centrifugation, filtration, or similar solid-liquid separation processes. This process is often used in the construction industry to remove water from hardened concrete, soil, or other materials and enable the reuse of construction materials. It’s also used to assess soil suitability for construction purposes.
The latter is referred to as “slurry,” a mixture of water and solids that cannot be separated by filtration or centrifugation. The water content of the slurry is typically very high, and as such, it is often transported by the pump.
The dewatering process is important in many industries apart from construction, including mining and wastewater treatment. Dewatering often takes place after a period of rain or flooding, and it can also be used to remove water from a structure that is being demolished.
What is the Purpose of the Dewatering Process?
The purpose of dewatering is to remove water from a material or structure so that it can be reused or disposed of in a safe manner. Without this process, many materials would be unusable or pose a safety hazard.
Dewatering can be used for a variety of purposes, including:
- Lowering the water content of slurry prior to transport
- Enabling the dewatering of construction materials for reuse
- Assessing the suitability of soil for construction purposes
Dewatering is a critical step in many processes and can significantly impact the environment.
Which Methods are Used for Dewatering?
There are a variety of methods that can be used for dewatering, each with its own advantages and disadvantages. The most common methods are:
Channeling
This method involves excavating a trench in the ground and then lining it with filter fabric. A pump is used to remove water from the trench, and the water is discharged into a drainage system.
Sump Pumping
Sump pumping is one of the most common and economical methods for dewatering. It works by allowing the groundwater to seep into the excavation area. Once it is collected in the sumps, it will be then pumped out.
Wellpoint Method
The wellpoint approach involves aligning a number of wells along the excavated area. The riser pipes that the well points are attached to are secured to a single vacuum pipe and header pump.
After receiving the necessary treatment to eliminate contaminants and unwanted materials, water is released from the site.
Deep Wellpoint
With the deep wellpoint method, the groundwater level is lowered below the excavation level by using boreholes and submersible pumps.
The excavated region is surrounded by wells that have a diameter of 15 to 20 cm, where groundwater naturally flows downward. As a result, the groundwater level in the excavated region drops, thus reducing the water.
Eductor Wells
Like the wellpoint method, the eductor wells also use a well. Eductor wells differ primarily in that they pull water using high-pressure water rather than a vacuum to draw it out.
Factors to Consider for Dewatering Process
There are several factors to consider when planning for construction dewatering, including:
- The type of soil
- The depth of the water table
- The length of time needed for dewatering
- The volume of water to be removed
With careful planning and execution, construction dewatering can be a successful and effective way to ensure a construction project proceeds as planned.
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Benefits of Construction Dewatering on a Site
There are many benefits to dewatering on a construction site. Below are some:
- Promotes worker safety – Dewatering helps promote worker safety as it eliminates various health risks, such as the removal of potentially contaminated waters, and lessens slips and falls.
- Ensures a stable soil and work area – The process prevents unstable working conditions on the site like mudslides, unstable foundations, and bogging, which causes equipment failure. It also prepares it for excavation and cement footing.
- Prevents unnecessary delays – Implementing an effective dewatering process averts unnecessary delays on the site caused by flooding, equipment failures, and many more.
- Enhances longevity of work equipment – The dewatering process removes excess moisture that can affect the construction equipment on your site.
- Environmentally friendly -Effective dewatering methods helps lessens the impact on the environment because it removes contaminated waters and prevents soil erosion and any site hazards in the area.
What are the Risks Involved in Dewatering During Construction?
While dewatering can be a useful tool, there are also risks involved. If not done properly, dewatering can lead to instability of the ground and soil. This, in turn, can lead to sinkholes and other problems. There is also the potential for groundwater contamination if the water removed is not properly treated.
Proper planning and execution of dewatering are essential to avoid these risks. If you are planning a construction project that will require dewatering, be sure to consult with an expert to ensure that it is done correctly.
FAQs for Construction Dewatering
Though every method has its own purpose and advantages, dewatering by open sump pumping is one of the most reliable and common methods used for dewatering. This method applies to a variety of use cases and can easily be carried out by those running on a tighter budget.
The three main reasons to dewater a construction site are to:
- lower the water table;
- remove any standing water that can pollute the area; and
- install any needed drainage facilities.
Permanent dewatering is a process that removes water from a solid material and prevents it from reabsorbing water. This can be accomplished through the use of chemicals, freezing, or evaporation.
Dewatering pumps are equipment used to remove water from an area. They vary depending on the material you are trying to use for the process. For example, a dewatering sludge pump works best if you want to dewater using a solid medium.
SafetyCulture Content Team
