Excess water in the wrong place at a construction site can derail a project and cause structural problems, schedule delays and safety hazards. That’s where dewatering comes in. Construction dewatering, where groundwater and surface water is removed from a site, is an important part of the process for any construction project. While the methods of dewatering may differ from location to location, finding the right technique is key to keeping operations on track. Read on for an overview of the construction dewatering process.
How Does a Dewatering System Work?
Dewatering on a construction site is typically done through the use of pumps. While pumps are the common denominator, there are many ways dewatering contractors can take advantage of them. Here are three common dewatering methods:
- Well points: With this technique, closely-spaced shallow wells (or well points) are drilled around the perimeter of a construction site to collect water. The well points connect to a common header pipe and the water is pumped out via a vacuum.
- Deep wells: These systems are typically used for deeper excavations with high volumes of water. In this method, contractors dig a system of deep wells around the construction site and place an electrical submersible pump into each well shaft before pumping the water out.
- Sump pumping: This method is widely used in construction dewatering and mine dewatering. It’s also useful for both groundwater and surface water control. Through sump pumping, groundwater is allowed to seep into the excavation site and directed to low basins called sumps. Sump pumps—powerful pumps with a high capacity to handle solids—then pump the water away.
What Happens to the Water?
A key decision that needs to be made on any construction site is where the excess water will be moved. No matter the method of dewatering, it’s important to properly discharge the water to the right location to avoid erosion and environmental concerns.
Contractors must take special care to regularly monitor both the construction site and the determined discharge site to prevent instability and other problems. The ultimate location of the disposed water depends on the qualities of the site and the water along with federal and state regulations and permitting requirements. Common discharge options include discharge to a sanitary sewer or nearby land, reuse on the construction site or use at a nearby facility.
If water has been contaminated with chemicals, oil or other contaminants, it may need to be treated before discharge. Neglecting to test a site's water and treat it when necessary can result in fines and adverse environmental impacts. And when it comes to discharges to a storm drain or body of water, permitting can be more difficult and treatment requirements more stringent given the potential impact on aquatic life.
Construction dewatering is a delicate process. Failing to properly remove and treat water on a site can result in erosion, instability and a host of problems that bring on delays and increased costs. Developing a comprehensive dewatering plan that includes quality water treatment systems and ensures responsible disposal of the wastewater is key to the success of a construction project.