Dewatering

On this project, shown above, the skilled NCS Technicians were able to respond with a day’s notice, gathering necessary wellpoint dewatering (aka Sandpoint Dewatering) equipment and making it to site immediately to install a system that required total functionality with some flexibility of design. The flexibility of the NCS Fluid Handling Systems dewatering systems and the ingenuity of the team allowed custom built swing arms to reach specific zones of water specifically targeted, as well maintain the design specific vertical wells spaced closely together at Half a meter (18”) up to 1 meter (3’) and swing arms up to 3 meters (10’). The entire system was up and running within two days and water drawdown was immediate, with clean clear discharge water flowing off site and away from the excavation. Even with the heavy rains experienced the site will recover and dry up quicker allowing the contractor stay on budget and on time.

Additionally, when NCS uses the new “RAK ATTACK” augured installation method the elimination the use of high pressure pumps, on-site water storage, make sites less congested, cleaner, reduces heavy equipment support and add for a safe, fast and easy well point installation.

THE PROCESS EXPLAINED;

Wellpoint Dewatering is a process to remove surface and sub-surface water present during excavation and stabilize the soil on the location with low permeability with some silts or sandy silts.

A vacuum pump is used in most cases and in simple terms generates the vacuum and increases the hydraulic gradient casing flow to the well point, up to the header pipe and is then discharged to designed point off site. Generally, wellpoint dewatering is useful to drawdown more than 18 to 25 feet of ground water in low permeable soils.

But other than having an excavation with water in it why does “NCS Fluid Handling Systems” design, engineering and technicians focus on all the ground and site-specific conditions to stabilize soil and deliver a dry excavation.

In general, dewatering means modification of ground water by redirecting seepages, lowering the ground water table and simply reducing the water content in foundation soil to completely dry and stabilize the soil within an excavation ensuring the successful long-term use of assets such as water, gas or oil pipelines.

Any Professional Engineer who deals with soils should have good knowledge about the soil-water relationship. This is where “NCS Fluid Handling Systems” has gained superior customer trust and a solid reputation for delivering dry excavations, in a safe and timely manner. “NCS Fluid Handling Systems” Professional Engineers consider ground water hydrology with an emphasize on water flow characteristics in respect to directions and quantity as well as sub-surface soil conditions. “NCS Fluid Handling Systems” P Eng. and the skilled technical products representatives work to ensure that our customers are aware of benefits derived from reduction of pore water pressure and respective increase in soil stability and strength. The net results are improved in slope stability and the required increase in bearing capacity which is required for the long-term utilization of such assets as water and oil pipelines.

Well point dewatering is not only required for on civil engineered projects, but systems are also deployed / installed in other applications such as mining projects.

Other than getting it right first time save money and time, the benefits of a properly designed, installed and operating dewatering system are as follows:

• To reduce or prevent excavation and installation from frost heaving, this can be seasonal changes but not limited to. Heaves put additional stresses on piping installations.
• To stabilize natural or constructed slopes
• To reduce surface erosion
• To treat granular soils by reducing their compressibility
• To decrease lateral pressures on retaining walls or foundation, even when items such as sheet piles are installed reduced ground water pressure add benefits to safety and stability.
• To provide increased bearing strength and capacity of compacted foundation soils
• To keep working place dry like excavation for dams, building foundations and tunnels.
• To prevent piping a phenomenon of migration of soil particles in groundwater
• To improve the transportation characteristics and/or the workability of borrow pit materials

If we focus on a couple variables, then the techniques used to dewater soil vary. NCS Fluid Handling Systems PEng. use different techniques for coarse-grained soils versus that for fine grained soils. It may be that Coarse-grained soils can be dewatered through the simple use of gravity which allows drainage into ditches, slump and wells and then discharge of accumulated water using pumps to designated discharge location. Remember to consult with the “NCS Fluid Handling Systems” Professional Engineering department if additional filtration (such as discharge rule of dissolved iron, regulated in various parts of Canada) is required, this may also include holding water in storage tanks for sampling.

#dewatering