Significance Of Dewatering Can’t Be Overlooked

By Jeff Griffin, Senior Editor | February 2011, Vol. 66 No. 2

Dewatering is a necessary aspect of many underground construction projects. Construction sites near coastlines, rivers, other bodies of water and in other situations may require 24-hour dewatering every day. Heavy rains may fill work areas during storms.

Whatever the source of water in pits and other excavations, no work can be done until the water is removed.

“My father was a contractor for 42 years, and I grew up in the construction business,” said John J. Struzziery, P.E., principal engineer, Kleinfelder/SEA, Cambridge, MA. “I’ve always remembered something he told me: ‘If you control the groundwater, you can do anything.’ ”

Throughout his career as an engineer, Struzziery frequently has had projects that require dewatering. It may simply require pumping water and redirecting or “recharging” it into to the ground at another location or can require deep wells with pumps placed to remove water.

“Different conditions require different methods,” Struzziery said. “For our company’s projects, we specify dewatering criteria and the methods to accomplish the task.”

Pumps
No matter the source, pumps are the heart of most dewatering applications.

Ron Askin, Godwin Pumps vice president and director of sales, said if the dewatering system requires lifting the water to a higher elevation, it will require pumping.

“There are a wide variety of pumps available depending on the application, water level and permeability of the soil and required pumping distance,” said Askin. “The most common are automatic self priming pumps, centrifugal and rotary lobe well point pumps and submersible dewatering pumps. A dewatering system becomes necessary when the construction conditions require the work be done in a dry condition. This may be for a variety of reasons including soil compaction, sealing joints and structures, or just to increase productivity.”

In addition to pumps, said Askin, dewatering systems generally require diesel or electric power sources for the pumps and a piping system -- hoses, valves, fittings, etc. -- to get the water to the disposal location.

“Also important with dewatering systems,” he added, “are controls that automatically stop and start pumps, dependent upon the fluid level, and will also adjust the speed to match the water infiltration conditions.”

Simple dewatering needs often are accomplished by the general contractor or subcontractor responsible for underground construction portions of a project. Dewatering pumps are widely available for rent from pump companies and their distributors and equipment rental specialists.