Dewatering is the temporary lowering of the water table for the purpose of construction, compaction and drainage. This is achieved by draining ground water from soil with pumps. The main methods for dewatering are well-pointing, sump pumping and bore pumping.
Well-pointing lowers groundwater below the existing water table prior to excavation; It stabilises water-bearing soils during excavation. Well-pointing generally doesn’t require external support systems, increasing the speed of work.
Well-points are constructed with a slotted screen intake surrounded by a filter pack, drawing water from the ground by the vacuum generated by a pump.
Pumps United high-efficiency dewatering pump can operate approximately 50 metres of well-points drawing a maximum of 20 litres per second. For drawdowns in excess of six metres, further stages of well-points are installed at lower levels as excavation proceeds – Multi stage systems
Wellpoints are installed in stages, with the first stage reducing the water level by up to 5 meters.
Sump Pumping is used to remove accumulated water from a sump basin or pit. Commonly used in clay or rock based soils at the lowest point on building sites, water drains through the soil to a submersible pump or via hosing and a centrifugal pump.
Bore Pumping is used to remove large volumes of water, where the depth of excavation exceeds the lift capabilities of well-point dewatering.
It is executed with a deep well system consisting of one or more individual wells. A submersible pump is set at the bottom of each well, with its positioned determined by both a geotech report and required outcomes.
Centrifugal – Diesel and electric pumps – BA100, 150, 200
Submersible – Electric pumps – 2”, 3”, 4”, 6”, 8”
Sump Pump – Diesel pump or electric submersible
Bore Pumps – type of submersible
Flexi Drive Pumps – petrol or diesel
High Head Pumps – mine spec for the delivery of water at high head pressures
Piston Pumps – wellpoint dewatering pump
Pumps United uses several means of installation for well-point dewatering. Jet spearing by hand, sand Tubing with an excavator or drilling with a custom rig fitted with a single pendulum auger.
This depends on the water quality and the location of infiltration. Water quality needs to be within certain guidelines and may require a pH dosing unit (Chemical Dosing Unit: CDU) or a Metals Removal Module: MRM or a Hydrocarbon Removal Unit for treatment.
Yes, provided approval has been given from the local water authority and a one-off discharge form has been submitted and approved.
The time varies with ground conditions. On basic well-point dewatering systems we allow 24 hours to draw down the water table.
Depending on water quality, discharge restrictions and location a small system can be set up and running within one to two days.
Provided the flow rate does not exceed 10 litres per second over 30 days.
Water Licensing FAQs
The relevant government water department in each state is responsible for ensuring water resources meet community requirements.
Through proclamation of certain groundwater and surface water areas, the relevant government department can actively manage water resources by:
- Defining the volume of water available for licensing purposes from a resource
- Issue licences and permits under the relevant state legislation for the taking and use of water.
Most groundwater and surface water resources that are accessed by large or multiple users are proclaimed under the relevant state legislation.
To find out if your property is located within a proclaimed water resource area, refer to the proclaimed areas map located on the relevant state government website, or contact your local department office.
A licence is not required if:
- You intend to take surface water for domestic and non-intensive stock water purposes.
- Undertaking certain dewatering activities, examples may include: (always check with your relevant state government authority for exemptions).
- Domestic and ordinary use (i.e. water for your house)
- Fire-fighting purposes
- Watering of non-intensive stock
- Lawns and gardens of up to 0.2 hectares.
A licence/permit is required if:
- You intend to use water for purposes other than those listed as exemptions by your relevant local water authority
- You require water for intensive stock purposes
- You need to construct or alter a bore (well) in any area where a bore does not already exist (Note: licence exemptions for constructing or altering a bore may apply).
- You need to interfere with the bed and banks of a proclaimed watercourse. For example, if you are installing a pump or other structure to divert the flow of a proclaimed watercourse (including a dam).
- Note: There are certain areas where it is not possible to know beforehand whether artesian underground water will be intersected until the bore is drilled. It is recommended you seek advice from your local water authority before constructing a bore.
The collection of run-off of water on your property will not require a licence. That is provided the off-stream dam does not intercept the water table.
It is your responsibility to comply with any Commonwealth, state or local laws that relate to the construction or taking of water.
A licence or permit is required if you intend to take water from an artesian aquifer. These aquifers are licensed throughout your state regardless of location
In situations where work required under a permit may interfere with a public road or reserve, relevant approvals must be sought and provided by the authority responsible.
If you are unsure if the aquifer you intend to take water from is artesian or non-artesian, or if a permit is required, contact your local water authority office or call Pumps United.
The right to take water for any purpose can be restricted by local by-laws.
The department prepares water allocation plans to guide the allocation of water in proclaimed areas.
In certain circumstances the local water authority may issue directions that may restrict someone from taking or using water.
Where a landholder’s use of surface water is impacted by another user in an unproclaimed area, a landholder may use ‘civil remedy’ under common law.
Pumps United Environmental Services can complete all soil testing from basic geotechnical testing right through to full chemical analysis. We complete testing on sites of all sizes from residential through commercial and mining.
Our primary laboratory, ALS Environmental provides results in a seven to 10-day period. However, turnaround of results can be altered to suit client requirements.
There are visual indicators of ASS as well as a potential hydrogen sulfide odour, however these are only indicators. Initial field-testing is required and then ASS must be confirmed via laboratory analysis.
This is determined based on specific project requirements, but all are calculated on a site by site basis based on excavation depths, dewatering timeframes and sub-surface soil conditions. Call Pumps United and discussed with our expert team, obligation free.
Approximately 8 to 12 weeks from submission, depending on your local water authority.
Environmental regulators - Approximately 45-day turn around. Applications are requested to have priority to prevent construction hold ups.
Typical turnaround time is seven business days. Fast turnaround may be requested for an additional fee
Many stormwater drains discharge into the local waterways. Years of unregulated discharge have caused degradation to water quality. Some discharge points are in low-flushing bays and environmentally sensitive areas. Environmental regulators have a maximum contaminant level, which determines when discharge is allowed.
Groundwater is finite. The Department of Water regulates how much water is abstracted so excessive abstraction is prevented.
Yes, but only at a discharge rate allocated by your state’s regulator. Sewer pipe diameters were not made with dewatering rates in mind. Excessive discharge rates can cause pipe breakage and overflow of pumps stations into the environment. This can result in significant fines.
We can provide clients with geotechnical services through a strategic partnership with a leading geotechnical firm.
An environmental auditor is not necessarily required on each site investigated. An environmental auditor may be required on a site-by-site basis particularly if the site has been classified as a known or potential contaminated site.
Regulations do not permit environmental consultants to make recommendations. The client is responsible for engaging an auditor independently of Pumps United. For a detailed list of accredited auditors contact Pumps United and our environmental experts will point you in the right direction.
Pumps United has years of experience dealing with regulators so on a schedule of rates that suits your budget we can review and offer advice on how to proceed.
Pumps United places the highest emphasis on Quality, Health, Safety and Environmental (QHSE) management when conducting our daily business. Legal compliance is our minimum standard, our objective is to ensure our activities exceed minimum statutory regulations.
At Pumps United we know that this key objective will only be achieved through the constant promotion of best practice procedures and encouraging commitment to improved work practices.
Our commitment is to ensure all plant and equipment hazards are identified, assessed and controlled.
To achieve our objective we perform risk assessments with staff consultation, on all new equipment prior to commencing work.
Personnel are trained to operate plant and equipment to manufacturer specifications. All planned and responsive maintenance on plant and equipment are completed to manufacturer specification. Plant and equipment modifications are made in accordance with manufacturer guidelines and plant, equipment and parts are purchased from reputable providers.
Full service, testing and tagging, calibration and lifting records are maintained and readily accessed for review.
All plant and equipment is maintained to the highest specifications. Where applicable all gear is fitted with emergency stops, battery isolators, reflective tape and fire extinguishers.
Environmental controls include self-bunded systems, noise reducing canopies and the choice of electric pumps for use in confined spaces. Should a site require additional items, they will be implemented where practicable.
Staff development needs are constantly assessed and reviewed. Training requirements are identified through skills matrices and notification in advance of expiring licences and qualifications via a cloud based HR management system.
This ensures our personnel are always suitably skilled, compliant with legislative requirements. Training is conducted both internally and externally by reputable and established RTO’s.
Rolling workplace inspections and internal and external audits monitor the effectiveness of our integrated management system.
External audits have been conducted by Rio Tinto, John Holland and Georgiou. Results were of a high standard with positive feedback being provided.
Any areas of improvement identified are always discussed at management and floor level to ensure all stakeholders are involved prior to implementing change. Pumps United welcomes customers to undertake external audits.