Dewatering NSW: The Groundwater Approval That Stops Excavation

PUMPING GROUNDWATER MAY NEED ITS OWN APPROVAL.NSW: test dewatering requirements before scheduling excavation.

You find a site with a real story: a sloping block a few streets from the water, room for the homes the numbers need, and a design your planner likes. Then the geotechnical report comes back with groundwater at two metres and the designer starts talking about a drained basement or a deeper footing system.

That is usually treated as a construction problem. In New South Wales it is also a water licensing problem, and it can stop the site before anyone lifts a spade.

The deal question: will your dig take water from a water source?

NSW Water's page on managing groundwater in NSW identifies which activities fall within the scope of aquifer interference, and construction dewatering for buildings, transport projects or civil works is named among the high risk activities. An aquifer interference activity is described there as an activity that penetrates an aquifer, interferes with groundwater in an aquifer, changes or obstructs groundwater flow in an aquifer, takes groundwater from an aquifer, or disposes of water taken from an aquifer.

So the feasibility question is not "is there water in the hole". It is this: does the excavation or the ongoing drainage of the finished structure take water from a water source, and how much?

The trap: development consent is not permission to take groundwater

This is the misconception that causes the damage, and it is worth reading the department's own words. The minimum requirements for building site groundwater investigations and reporting states that developers, or their agents, must seek appropriate licences and approvals for a building project before construction starts, and that the licensing of a volume of water is independent of the planning process, even in integrated or state significant development. It then states plainly that developers should be aware that getting development consent does not automatically include permission to take groundwater.

Read that against a normal consent. Your conditions of consent may require a dewatering management plan, and that plan may read as though it authorises the take. It does not. The plan is one document in a separate licensing pathway.

What actually needs to be obtained

The departmental page records that works used in the taking of groundwater by an aquifer interference activity need an approval unless an exemption applies, and lists the possibilities as one or more of a water access licence, a water supply work approval, a water use approval or a controlled activity approval. It also records that aquifer interference activity approvals are not available at this time, which is why the pathway in practice runs through the other instruments rather than the one named after the activity.

The NSW Aquifer Interference Policy explains why the volume matters even when the water is never used. It records that water is taken incidentally where the take is required to allow the effective and safe operation of the activity, giving dewatering to allow mining or coal seam gas extraction as the example, and that in all cases the activity is taking water from a water source. It also states that dewatering of groundwater during building construction requires a water licence unless an exemption applies, even where that water is not being used consumptively.

The exemption that saves some sites, and what it does not cover

There is a genuine and useful exemption. The dewatering exemptions page states that a dewatering licence exemption applies if you take 3 megalitres or less of groundwater per year from any water source, and describes a separate exemption for groundwater taken in connection with the construction of buildings and infrastructure in designated coastal areas, where the construction occurs within the coastal water sharing plan areas and all water taken is recorded and reported.

The page then puts the boundary around it. It states that these exemptions only apply to water access licences, and that even if you are eligible for an exemption from a water access licence you must still obtain any other relevant approvals, such as a water supply work approval.

Three megalitres is not a large allowance on a deep dig with a long programme. The exemption is a screening question at feasibility, not a conclusion.

The no more than minimal harm test shapes your design

The same departmental material and the minimum requirements document both turn on the no more than minimal harm test. The minimum requirements document states that approvals can only be granted if the approval body is satisfied that no more than minimal harm will result, and that where insufficient site-specific evidence is provided to characterise the ground and groundwater conditions beneath the property, the department may not be able to determine that no more than minimal harm will result. It states the department will adopt a precautionary approach in those cases and require the take of groundwater to be limited to the building construction period only, and that applications for drained basements that cannot demonstrate no more than minimal harm will not be supported without further detailed information.

That is a design instruction disguised as a regulatory test. A tanked basement that keeps groundwater out permanently is a different application from a drained basement that pumps for the life of the building, and the difference is decided by the groundwater evidence you commission early.

The site test a student would run, in order

1. Check the depth to groundwater on the geotechnical and hydrogeological evidence, not on the architect's assumption about footing depth.
2. Decide whether the design takes groundwater. Any excavation receiving inflows or seepage, and any basement that is drained rather than tanked, is a candidate.
3. Estimate the volume the excavation and the construction period will take, and compare it with the exemption thresholds.
4. Screen the exemption position. Volume alone is not enough; the work approval question survives the licence exemption.
5. Check whether the work is on waterfront land or otherwise needs a separate water approval, because the same framework governs controlled activities near waterways.
6. Price the licence, the investigation reports, the dewatering management plan and the monitoring into the feasibility as a line item, with contingency.
7. Start the enquiry before the development application is lodged, which is what the department recommends.

What this does to the offer

Run the feasibility twice: the basement design you want, and a shallow design that stays above the watertable. If the second version is materially more profitable once the water approvals, reports, pumping, treatment and monitoring are costed, then the water is the deal, and your offer should reflect the cost of the first version rather than the optimism of the second.

Also test a timing shock. If the licence takes months rather than weeks, what happens to your holding costs, your builder's programme and your presale obligations? An approval that arrives after the machine is booked is a delay you are paying for twice.

Practical next steps

You are not expected to solve this yourself. A geotechnical engineer or hydrogeologist characterises the ground and the groundwater beneath the site and defines the volume of take. A town planner confirms how the water approval sits inside the development application and whether the proposal is integrated development. A water licensing consultant, or the department's own water licensing team, confirms which authorisations are required for this site and which exemptions genuinely apply. Confirm the current in-force Act text, policy and exemption position before you commit to a basement, a programme or a price.

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