Managing water on site: tips for a wet spring

The Bureau of Meteorology’s long-range forecast for September to November predicts above-average rainfall across most of the eastern two-thirds of Australia, while western regions are expected to be drier than usual. For construction professionals working in eastern states, this means ongoing challenges like surface pooling, groundwater intrusion and even localised flooding.

Dewatering isn’t just a wet-season concern – it’s a critical process across a range of scenarios, including basement excavation; tunnelling, quarrying and mining; remediation projects to remove contaminated groundwater; and flood control, especially in low-lying or poorly drained areas.

“Whether it’s surface pooling or groundwater intrusion, effective dewatering is essential to maintain safety, protect excavation integrity and keep projects on track,” says Peter Chalmers Engineering Solutions Specialist at Coates.

Here’s what to consider when planning and executing dewatering on your site.

1. Assess ground conditions

Erosion can easily occur when water isn’t removed or discharged appropriately, so before you remove groundwater it’s important to understand your site soil profile and the local water table conditions. To ensure the safety and integrity of your excavation, carefully monitor ground conditions before, during and after dewatering.   

Weather can also affect the ground conditions on your site. “Excavating and dewatering during heavy rain can reduce the infiltration rate for dewatering, and in some cases prevent the process from working,” says Peter. For successful dewatering, keep an eye on the weather forecast and plan accordingly whenever possible.

2. Select the right dewatering technique

A range of different groundwater control and dewatering approaches – including exclusion, pumping and fluid counterpressure – can be used to safely and efficiently remove surface and groundwater from construction sites.

Common pumping-based methods include:

• Surface pumping: Pumps of various sizes can be placed near affected areas to remove surface water quickly and efficiently.
• Sump pumping: Groundwater is collected in sumps via drains and pumped out. It’s a straightforward and cost-effective method for shallow excavations in permeable soils and rocks.
• Wellpoint systems: A series of small-diameter wells (or spears) are installed around the excavation. Vacuum pumps draw groundwater to the surface, ideal for shallow, sandy soils and varied excavation geometries.
• Deepwells: Used for deeper excavations, submersible pumps are placed in wells to overcome suction lift limitations and manage higher water volumes. These are typically installed at wider spacing than wellpoints.

“Each method has its strengths, and selecting the right one depends on a combination of factors including soil type, excavation depth, flow rate and environmental constraints,” says Peter. “For specific advice on choosing the right dewatering technique, speak to a specialist.”

3. Treat and discharge water responsibly

To prevent environmental pollution, certain water quality standards must be met before water can leave construction sites. In most cases, this means that water removed through dewatering will require treatment before it can be discharged. 

“Dewatering systems work by removing the water from the ground and moving it to a holding tank where larger solids can settle. From here, pending on the contaminants in the water, a water treatment process will be implemented, including but not limited to chemical dosing, chemical reactions as well as physical filtrations,” says Peter.

Once treated, water can be discharged back to site to be used for dust suppression or ground infiltration purposes, or to a storm water or sewer inlet. Depending on the discharge location, the right permit must always be obtained before the discharge of any water.

4. Engage expert support early

Dewatering is more than just pumping water – it’s about protecting your site, your team and your timeline. Engaging experienced professionals can help avoid common pitfalls and ensure compliance with environmental and safety standards.

“Coates has a huge range of pumps for hire, from simple plug-and-play options you can operate yourself to fully engineered solutions for more complex dewatering and water treatment needs, says Peter. “Our team of geotechnical engineers, technicians, licensed drillers and solutions specialists can design, supply, install and monitor a dewatering system tailored to your site.”

Explore our pumps and accessories for hire and contact Coates Engineering Solutions for advice on your dewatering project