If not properly handled, groundwater on a jobsite can quickly turn a project into a nightmare, delaying the project and driving up costs.
An authority in dewatering, Water Movers Equipment Rental, with locations in Phoenix, Salt Lake City and Las Vegas, specializes in temporary portable pumping systems. “Often, we have found too little thought, time or budgetary consideration has been given to a dewatering system,” says Howard Nute. “Once problems are encountered, a piece-meal approach is taken until an adequate system is finally put in place. A more thorough and proactive approach may save time and money in the long run.”
In tough economic times, a dewatering plan makes even more sense. “In the current economy, most contractors have pricing squeezed, with material and labor costs increasing,” says Jarrod Williamson, Southeast region manager, Xylem Dewatering Solutions. “Any lost time for a contractor, such as a wet jobsite, could mean the difference between making a profit or losing money.
“Wet jobsites can also increase the potential for injuries from slippery conditions or unstable soil conditions,” he adds.
Tailor solutions to the site
Dewatering should not be an afterthought. “As with any part of construction, being prepared and having a plan is critical to success,” says Thomas Aldridge, Griffin Dewatering. “Factors that determine the options are typically a result of depth requirements and overall site limits. As with any construction project, each site has its own challenges. The dewatering solutions and equipment are tools to help overcome those challenges.”
The basic requirements that need to be understood before selecting a dewatering solution include flow requirements, head conditions and suction requirements.
“Along with those technical considerations, it is critical to understand the site itself — terrain, elevation changes throughout the site and access issues,” says Aldridge. “It is also important to know power requirements and discharge point and limits. If it is a groundwater dewatering system, the soils play a key part in both the volumes to pump and the installation methods that would be required.”
Other factors play a role in choosing a pumping system. “You would also want to consider the material to be pumped, the pH level and temperature — both ambient and of the fluid,” says Nute. “Desired flow, depth, discharge length, elevation change, footprint of the jobsite, available space and noise restrictions are all something that might need to be evaluated.”
Also consider the volume of fluid to be moved. “Pump manufacturers continue to build larger pumps that move larger volumes of water more efficiently,” says Williamson. “This reduces the number of pumps needed for bigger projects, saving the contractor money.”
Nute adds, “There are continuing improvements in pumps with solids-handling capacity, including sludge and no-clog type pumps. Many are also coming with more efficient engines for lower operating costs, in addition to pumps that are sound attenuated for better environmental conditions. Like everything, pumps are continuing to evolve and many new models with specific applications are coming into play.”
Give thought to the system
Almost any earthmoving contractor is familiar with setting up a pump.
“Pumps are common tools in the construction industry and the setup is usually not a problem,” says Aldridge. “Understanding the pump and its application tend to be more of a challenge. There are a number of methods that can be used, so each has to be evaluated based on the needs and cost.”
Most dewatering systems rely on trash pumps, wellpoint pumps and submersible pumps. Each has advantages and disadvantages depending upon the jobsite to be dewatered.
Trash pumps are by far the most widely used option found on construction sites. Most models will pass 3-in.-diameter solids without becoming clogged. They are widely used because of their versatility. A 6-in. trash pump is capable of pumping 1,500 gpm with 125 ft. of head.