Construction dewatering refers to the methods used to remove accumulated groundwater or surface water by pumping or thru evaporation. When working on trenches, near a body of water, in areas with a high water table or an area filled because of rains and flooding it is important to understand proper methods for water removal. Proper Dewatering protocol should be included in a site SWPPP (Stormwater Pollution Prevention Plan) for a construction site. Methods may vary depending on municipality requirements, location of construction and proximity to waterways, lakes and streams.
IMPORTANT CONSIDERATIONS
When determining the type and scale of dewatering methods, some variables that need to be taken into consideration include the amount of water being relocated, how fast it will travel (pump or gravity?), and the amount and type of impurities in the water. Water that is pulled out of a ditch with a sump pump may have more sediment than water being removed from an area of a natural lake. Either way, the water will typically need to be filtered as it is relocated to minimize the effects of erosion and sedimentation. Water that is potentially polluted may need further treatment, such as using an oil and water separator to make sure that those impurities are not put back into natural waterways.DEWATERING AND FILTRATION OPTIONS
In almost every case, dewatering will require some kind of filtration to remove impurities from the water as it is removed and directed to a draining area or waterway. Some of these options include:
• Filter Sock, filter bag or tube: Filter Bags come in many shapes and sizes. As the name states – these bags are a filter that hold in silt and impurities while allowing water to pass thru and drain away.
• Dewatering Filter Pad – If needed, a dewatering pad allows for additional filtration beyond the sock or bag, using a combination of man-made and natural materials to clean the water.
• Drainage Ditch with lining (to prevent further erosion) and FLOC Logs. The Floc Logs are designed for use in flowing conditions for treating turbid water to remove suspended sediment
DEWATERING PRECAUTIONS
While the dewatering process is relatively simple, the reasons and methods are designed to protect our environment and require awareness and diligence to maintain the health of our natural waterways. When dewatering an area, it is always best to be aware of the amount of water, where it is traveling and look for ways to prevent damage to the existing natural landscape.
• Avoid overland routes that can cause further erosion
• Choose the best place for the discharge keeping in mind amount of water and flow rate
• Water leaving the construction site needs to be as clean as the water entering the site
• All dewatering protocols need to be monitored regularly to avoid filtration failure
Proper Dewatering and SWPPP protocols are important steps in Construction Best Management Practices (BMPs) and should be taken seriously. For more information contact our knowledgeable staff at 630-554-6655 or by email.
