The Guide to Dewatering for Construction
Dewatering is an essential process in the construction industry. Job sites with wet soil can be dangerous and lead to mudslides and unstable structures.
Removing excess water helps keep projects on schedule and maintains job site safety. There are various methods for removing surface water or groundwater, depending on the construction zone’s soil and excavation.
Use this guide to learn more about the dewatering process and why it is so important for construction projects.
What Is Dewatering in Construction?
Dewatering refers to the process of intentionally removing surface or groundwater from a specific location. This practice is especially vital to construction because workers rely on dry and stable soil. Projects that involve excavation require dewatering to maintain worker safety and soil stability.
The dewatering process includes the following steps:
- Inspecting the water: The first step is examining the water to determine if it is surface or groundwater and looking to see if any sediments or contamination are present.
- Getting all necessary permits: Anytime you want to discharge water into a public drain, you’ll need a permit. Various federal, state and local government permits are necessary for legal dewatering.
- Choosing a dewatering method: There are various techniques for getting rid of water depending on the type of area you want to dewater and preparing accordingly.
- Treating the water: Some methods require you to treat the water before the dewatering process. Sediment removal and filtering is the most common way to prepare.
Dewatering improves work site conditions and serves multiple purposes. The following are the major reasons why this process is so important to the construction industry:
- Improving safety: Dewatering is a highly necessary practice for keeping workers safe on the job site. Runoff can make the ground slippery and unsafe. Any areas with sitting water, especially if it is contaminated, can pose health risks.
- Supporting soil stability: Stable soil is essential for a durable foundation for any building project. Groundwater can compromise the soil and cause dangerous mudslides on the job site.
- Maintaining productivity: Surface and groundwater can cause many problems for construction projects. They can lead to delays and unsafe working conditions, resulting in additional costs and scheduling issues.
- Protecting materials and equipment: Having excess water near your work site can cause issues with your raw materials over time. It also can make your site hazardous for your equipment since too much moisture can damage machinery.
- Reducing environmental impacts: Sitting water can cause soil erosion and attract mosquitos. Groundwater can contain pathogens and toxic waste that hurts the local environment so removing it is necessary.
Construction Dewatering Techniques
There are a few dewatering methods used in the construction industry, including the following:
The wellpoint method of dewatering utilizes a series of small wells situated evenly along an excavated area. Each wellpoint connects to the main pipe, where a high-efficiency pump carries the water away from the ground and to a specified discharge area.
Eductor Well Dewatering
Another technique for removing water is eductor well dewatering. This method involves a series of small-diameter wells that have a nozzle powered by a pumping station that the water flows through. Eductor well dewatering is a common choice for job sites with deep excavation because this system does not have suction lift limits.
Sump Pump Dewatering
Sump pump dewatering is the most common method for removing water from a job site. It involves sump pit excavation where workers create temporary pits to collect groundwater before routing it to a proper discharge area. This method is best suited for sites with a high sand or gravel content and shallow excavation. It is the simplest and most cost-effective dewatering solution.
Deep Well Dewatering
Deep well dewatering is slightly more complicated. It involves the removal of water from beneath an excavation and therefore requires a higher rate of pumping in to move the water to discharge sites efficiently. Each deep well has a submersible pump that propels water rather than pulling it like other vacuum-powered dewatering methods.
Common Dewatering Equipment
There are a few common construction dewatering tools that are responsible for filtering and moving water to discharge areas, including:
- Pumps: An efficient pump, such as submersible or centrifuge options, is an integral part of most dewatering techniques. These are arguably the most valuable piece of equipment for dewatering on a construction site.
- Vacuum filters: This equipment uses a vacuum to process sediment and slurry, then separates these materials from the water. A vacuum filter uses a rotating drum with valves to isolate and dry solids effectively.
- Centrifuges: Centrifuges utilize centrifugal force to filter sediments from the water using a fast-spinning bowl that separates the two. Then it sends the solids to their drying stages and discharges the liquid.
- Drying beds: Sludge drying beds allow water and liquid to drain through a permeable layer where the sludge sits. This dehydrates the sludge and makes the drying process easier.
Factors to Consider During the Dewatering Process
Anytime you pump water away from your work site, you’ll want to ensure the discharged water is not causing soil erosion. Pay attention to the following factors:
- Location: Finding the right place for discharging water is crucial. It should not be anywhere with downward slopes or in an area where the water is eroding the soil since these locations can result in additional safety concerns.
- Filtration: You’ll also want to ensure you properly filter out any surface water or groundwater sediments. You can use sediment bags or dewatering boxes to effectively remove anything that cannot go into public drainage systems.
- Exposure: As you pump the water, it is incredibly important to protect the collected water from exposure to any oils, grease or other chemicals.
You should carefully monitor the dewatering process to make job sites as safe as possible for construction workers and the environment alike.