Groundwater Control Through Common Dewatering Methods
A common hurdle faced with construction projects is groundwater, which you encounter during ground excavation. Removing this water is not only necessary for the continuation of work, but it also helps make the working conditions safer by stabilizing the ground during construction.
While there are several methods to control groundwater, pumps are the most commonly used equipment to achieve this, through a process that’s called dewatering. The application of the right dewatering method, however, depends on parameters including ground conditions (soil permeability, stability, etc.), and water level.
These are the popular dewatering techniques used during excavations.
Sump pumping: This is a basic dewatering method that’s commonly used during minor excavation projects. The process involves digging a sump where groundwater collects, which is then simply drawn out using a pump. This method of groundwater removal is inexpensive, but can be time consuming.
Wellpoints: This method involves digging numerous, small-diameter wells (either vertical or horizontal) into the ground. These wells are referred to as wellpoints and they are connected to wellpoint pumps using header pipes. The water is drawn out using suction power and the method is suitable for clearing water that is deeper underground. Wellpoint systems can be quickly set up and made operational.
Deep wells: Like wellpoint systems, this method also involves boring numerous wells, but the similarity ends there. Deep wells utilize submersible pumps to extract water and while doing so, they create a cone of depression, which can get quite large.
Because the method uses submersibles and relies on creation of depressions, deep well systems are effective in removing large amounts of water from much deeper underground. The effectiveness of this method is affected by hydrological conditions.
Vacuum wells: A modified form of the deep well method, vacuum wells work the same way as deep wells, except for one crucial difference. While submersible pumps are utilized for drawing out groundwater, they are assisted by vacuum pumps that are placed above ground. The application of vacuum helps draw out water more efficiently from fine-grained soil, which a submersible pump alone cannot achieve.
Eductors/Ejectors: The effectiveness of a deep well system reduces when the soil has low permeability. In such conditions, educator systems are used. Once again, deep boreholes are used to draw out water, but instead of directly drawing out water using external or submersible pumps, high-pressure water is pumped down through a narrow nozzle from a supply tank above ground. This generates a powerful vacuum pressure at the level of the eductor, drawing out the water into the borewells and out into the supply tank. This cycle continues until the desired results are achieved. Eductor systems are also useful for stabilizing excavation sites with side slopes.
If you have any queries about groundwater control and want to determine the right pump type for the job, feel free to get in touch with us at www.visserssales.com or call us on our toll free number 1-800-367-4180. Our expertise extends to all types of liquid handling equipment and systems.