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Construction Dewatering 101

To dewater means to remove water from an area. Dewatering is usually done at a construction site to remove surface water or groundwater from it, and the process is normally done either by letting the water evaporate or through the use of a dewatering pump. Dewatering is necessary before any excavation is done so that the construction crew can have dry land to step on and also to lower an area’s water table that may cause problems when the excavation work is begun.

Where does water accumulate?
The most top two reasons for water accumulation are rain and a high water table. In construction sites, water can accumulate in excavations and trenches, in sloped areas, or if the site is notlocated within an area with a low water table. If these areas are not dewatered, construction work may not continue as scheduled, and the project will lag. Accumulated water can also be a threat to the safety of workers who may slip and injure themselves.

Methods of dewatering
The simplest way to remove water from a construction trench or open excavation is by letting gravity do its work. Drainage channels are created from the affected area to the designated discharge point. To protect the channels, ditch linings can be used. This is feasible for elevated construction sites. If the site is lower than the designated discharge area, submersible dewatering pumps are necessary. It is also possible to remove water through siphoning it or using construction machinery to scoop up water.

Precautions during dewatering
The quickest way to remove accumulated water from a construction site is through the use of pumps. However, dewatering is not simply submerging the pump in the affected area and letting the water out somewhere else; there are precautions that must be followed to ensure that soil erosion and other problems are avoided. One of the considerations that builders have to keep in mind is that the location for the discharged water must be carefully selected.

As a precaution against erosion, builders should avoid discharging water onto a slope directly. As much as possible, the water should be channeled to wooded area, or through channels surrounded by grass and vegetation. If the site starts to show erosion or if the ground shows signs of being unstable, the dewatering activities should be discontinued.

Dewatering at a construction site also involves the risk of water being contaminated with grease and oil. Water contaminated with industrial grease must never be discharged into the environment because it may damage the soil and the surrounding areas that have vegetation. If the accumulated water is contaminated, an oil and water separator must first be used. Once separated, the water can be discharged and the oil can be disposed of properly following the regulations.

Other applications
Aside from building construction sites, dewatering is also done in mining excavations, particularly in rock mines and borrow pits. It is also conducted in lake excavations for making stormwater management systems. Installation of utility lines such as sewers, water, telephone, and electricity also requires dewatering.

Wherever dewatering is done, builders and contractors must always make sure that the best management practices are followed to ensure that erosion is prevented and that no harm is done to the environment.