What Is A Dewatering System in Construction?
What Is A Dewatering System in Construction?
Dewatering is the process of removing water from a specific location. This can be achieved through various methods such as wet classification, filtration, centrifugation, and other solid-liquid separation techniques.
In the context of construction, dewatering refers to the removal of groundwater or surface water from a construction site, riverbed, mine shaft, or caisson by pumping or evaporation.
This is often done before foundation excavation, shoring, or the creation of cellar space in order to lower the water table. Submersible pumps, centrifugal pumps, eductors, or vacuum-assisted well points are commonly used for dewatering during construction.
The goal of dewatering on a construction site is to create a safer work environment by removing excess water that may compromise the stability of the structure being built. It is important for builders to follow proper safety measures when using dewatering pumps.
There are four main types of dewatering systems that can be used for construction projects; wellpoints, sump pumping, eductor wells and deep wells. Each method is best suited for certain soil types and excavations.
Wellpoints involve using small-diameter tubes with slots near the bottom which are inserted into the ground and used to draw water out using a vacuum created by a pump. They are typically used in sandy soil conditions and are installed in a line along or around the edge of an excavation. However, they have a limited suction lift and are not as effective in clay or rock soil.
Sump pumping involves digging pits, called sumps, in the drainage area to collect water, which is then removed using pumps. This method is simple and cost-effective but it is best for shallow excavations, minimal surface water and low-permeability soils. It can increase the risk of erosion or collapse and produce water with high total suspended solids.
Eductor wells involve using an at-grade pumping station with a series of small wells equipped with nozzles to create a vacuum and draw groundwater in through a piping system. This method is low-maintenance, cost-effective and works well for deep excavations, but it cannot handle a high volume of water.
Deep wells consist of a borehole with a slotted liner and an electric submersible pump. As water is pumped out, it creates a cone of depression around the well in which there is little or no water remaining in the surrounding soil. They work best in soils with a certain permeability and can be used to lower the water level around an excavation and maintain a dry site.
Designing a successful dewatering system involves a firm understanding of the underlying principles, practice and experience. Some dewatering situations are so common that they can be designed almost by rule of thumb. Additionally, Deep wells are also used for aquifer testing and groundwater drainage by wells.
Factors To Consider When Choosing A Dewatering Method
When determining the appropriate dewatering method for your construction project, several factors must be taken into account including soil type, budget, volume of water to be removed, and the depth of the excavation.
Soil permeability or the rate at which water flows through the soil, plays a crucial role in determining the suitable dewatering method. Methods such as sump pumping and eductor wells are effective in soil with low permeability, while deep well dewatering is better suited for soil with high permeability. Wellpoint dewatering can be used in both types of soil.
Cost also plays a role in selecting the dewatering method, with sump pumping being the most economical option. Wellpoint and eductor wells are also relatively affordable. Though deep well dewatering is generally more expensive it may be necessary if it is the best fit for the project.
The amount of water to be removed, whether it is surface water or groundwater also plays a role in selecting the dewatering method. Sump pumping and eductor wells are suitable for removing small volumes of water while wellpoint dewatering is effective in shallow aquifers of 50 feet or less. Of the options, only deep well dewatering can handle large volumes of water.
Finally, the depth of the excavation also has an impact on the dewatering process. Eductor wells and deep wells are suitable for deep excavations, while wellpoint and sump pumping are better for shallow excavations.
Benefits Of Dewatering
Dewatering is an essential process for many industries. Not only does it help to control flooding, but it can also reduce pollution and preserve the environment. The benefits of dewatering include the removal of suspended solids and biological contaminants from water, resulting in improved water quality.
In addition, dewatering can reduce the load on downstream water treatment facilities, making it more efficient and cost effective. Furthermore, dewatering can improve the efficiency of operations in areas with high-water tables or where space is limited due to urbanization or saturated soils.
Finally, well-managed dewatering processes can help to protect groundwater systems by reducing impacts on aquatic life and ecosystems.
Methods For Water Redistribution
Dewatering, or the process of removing water from a construction site, is closely regulated by local, state, and federal guidelines. The water cannot typically be allowed to leave the site without first being cleaned of sediment or chemicals.
The methods used to remove the water and where it is redistributed will depend on the soil type at the site. For example, in the case of porous or gravelly soils, the water may be able to be pumped to another area on the site and allowed to percolate back into the ground, but this may not be possible with less porous soils like clay.
One way to redistribute the water is by using detention ponds or basins, which are man-made bodies of water created to store runoff.
This can be beneficial for the environment by reducing the transfer of pollutants and contaminants to other bodies of water. If this method is chosen, it is important to follow federal and state requirements for regularly checking the ponds and basins.
Another option is to use tanks or boxes to transport the dewatered water from the construction site to another location. These tanks or boxes can also be used for drainage, filtering out solids, sediments, and sludge, and reducing wastewater. It is important to check with federal and state regulations about the water being moved or drained.
Lastly, the water can be released or redistributed to rivers, wetlands, or lakes. However, it is important to ensure the wastewater undergoes filtration or is treated prior to release and to secure permission from federal and state environmental authorities.