A large proportion of rural-residential and semi-rural properties in the Southern Highlands rely on on-site wastewater management systems (septic, aerated treatment units, or other on-site systems) and bore or rainwater supplies rather than mains water and sewer. When pool removal involves excavation near these systems, setback requirements and potential for cross-contamination or system disturbance must be carefully considered.
This guide addresses the specific issues that arise when pool removal works are near an on-site wastewater system or bore water supply in the Southern Highlands.
Quick Answer (BLUF)
Pool removal excavation near a septic system or bore water supply must respect required separation distances and must avoid disturbing or damaging these systems. Minimum separation distances in NSW range from 3m to 15m+ depending on the system type and the nature of the works. If your pool is within these distances, your certifier, WSC’s plumbing compliance team and potentially an environmental health officer need to be involved in the approval planning. In most cases, careful methodology can manage the works safely.
Why This Matters on Highlands Rural Properties
Rural-residential properties in the Southern Highlands, particularly in Bundanoon, Exeter, Robertson, Burrawang and rural parts of Bowral, Moss Vale and Mittagong, are frequently not connected to reticulated sewer. These properties have:
On-site wastewater systems. These include:
- Conventional septic tanks with absorption trenches (soil dispersal)
- Aerated Wastewater Treatment Systems (AWTS), more sophisticated, producing higher-quality effluent
- Composting toilets with greywater systems
- Combined treatment and disposal systems
Bore water. Many rural properties have a bore (drilled well) that supplies water for irrigation, stock or (sometimes) household use. Bore casings extend to aquifer depths that vary across the Highlands geology.
Rainwater tanks. While not subject to setback requirements in the same way, buried or surface-mounted tanks should be identified before excavation.
When pool removal involves excavation, any of these systems could potentially be affected if they’re in close proximity to the pool.
Key Setback Requirements in NSW
The NSW requirements for on-site wastewater systems are set out in:
- NSW Government’s Environment & Health Protection Guidelines: On-site sewage management (2004)
- Local Government (General) Regulation 2021
- Wingecarribee Shire Council’s On-site Sewage Management Development Control Plan
Typical minimum separation distances from septic absorption trenches and AWTS disposal areas:
- From any structure: 1.5m minimum
- From property boundaries: 3m minimum
- From bores, wells and water supply: 20m minimum (for absorption trenches), 50m in some circumstances
- From waterways: 10m minimum
For the pool removal works themselves, the concern is twofold:
- Physical disturbance, excavator operations near absorption trenches, tank lids or bore casings could damage these systems
- Groundwater management, pool removal involves significant ground disturbance; if this alters drainage patterns, it could affect the performance of nearby absorption systems
Identifying Your On-Site Systems Before the Quote
Before seeking a pool removal quote or lodging for approval, confirm:
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Location of the septic tank(s) and absorption trenches. Older properties may not have accurate plans. Visual inspection (look for raised or different vegetation over trenches, visible inspection ports, pump-out access covers) can identify approximate locations. WSC’s environment and health team may have records of approved septic installations for older systems.
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Location of any bore or well. The bore casing typically protrudes at the surface (a 100-150mm diameter pipe capped at ground level). The bore driller’s log (if available) will show depth and casing details.
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Location of any irrigation lines or control boxes associated with an AWTS.
Provide these locations to your pool removal contractor at the site inspection stage. Marking them with stakes or spray paint before the inspection helps.
The Approval Process When Systems Are Nearby
If your pool is within the setback distances of an on-site wastewater system or bore:
WSC’s Environmental Health team. Pool removal near on-site wastewater systems may need to be referred to WSC’s environmental health team as part of the approval process. They may impose conditions on the works, methodology requirements, inspection hold points, or restrictions on when excavation near the absorption area can occur.
Plumbing compliance. Any modification to the pool’s plumbing (capping connections) must be done by a licensed plumber. If this plumbing connects to systems that also serve the on-site wastewater system, the licensed plumber must ensure separation is maintained.
Bore management. NSW groundwater management requirements may apply if the excavation is near a bore. The NSW Natural Resources Access Regulator (NRAR) administers bore and groundwater licensing; your certifier can advise on any notification or approval requirements.
Risk Management During Works
For pool removal near sensitive systems, the contractor should:
- Mark exclusion zones around bore casings, tank access points and known absorption trench areas before work begins
- Use directional excavation, approaching the pool from the side away from sensitive systems and working methodically to maintain separation
- Hand-dig near systems if the excavation must get close to any marked system
- Inspect visually for signs of disturbance during and after works, a damaged absorption trench or disturbed bore casing must be reported and addressed immediately
Post-Removal: Impact on Drainage
Pool removal significantly alters the drainage pattern of the property in the pool area. The pool previously acted as a collection point for roof water and surface drainage directed to it. After removal:
- The filled pool area will drain differently, water will permeate through the backfill material rather than collecting at the hard surface
- This changed drainage pattern must not direct increased water flow toward absorption trenches or bore water
- If the pool’s drainage lines previously connected to a surface drainage system, the post-removal drainage configuration should be designed to maintain appropriate flow paths away from on-site wastewater systems
In some cases, a simple graded surface on the filled area (sloping away from the absorption trenches) is sufficient. In others, a stormwater drain or French drain may be needed to manage post-removal drainage.
FAQs
How do I find out where my septic absorption trenches are?
Check with WSC’s Environmental Health team, they hold approval records for on-site wastewater systems (though older pre-council records may be incomplete). Your plumber may know if they’ve serviced the system. On-site, look for: areas of unusually lush, green grass (absorption trenches encourage plant growth over them); inspection ports or concrete access lids; and any drainage depressions or mounds in the garden.
Can pool removal work proceed while a septic inspection is pending?
Ideally, confirm the position and condition of your septic system before pool removal commences. If the systems are clearly well-separated from the pool area (more than 10-15m), pool removal can typically proceed without special measures. If you’re uncertain about locations, it’s worth delaying the start until you have clarity, damaging a septic absorption trench requires expensive repair.
My pool is only 5 metres from my bore water, can I still remove it?
Yes, in most circumstances, pool removal doesn’t require excavation to bore depth (bores are typically 20-50m+ deep in the Highlands). The concern is protecting the bore casing at surface level and ensuring excavation doesn’t destabilise the ground around the casing. Your contractor should hand-dig within 2-3 metres of the bore casing and ensure the casing is protected from machine contact. Discuss this specifically with your contractor and certifier.
Will removing the pool affect my septic absorption system’s performance?
If the systems are appropriately separated and the post-removal drainage is managed to maintain the same or better separation, removal should not affect septic performance. In fact, removing the pool’s water supply (which added to the water balance on the property) may slightly reduce the total water load on the absorption system.