South West Sydney is experiencing sustained population growth. New housing, subdivisions and rural-residential development are increasing across areas such as Camden, Campbelltown and Wollondilly.

Not all of this development is connected to sewer infrastructure.

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Wastewater assessments are required where sewer is not available, particularly for properties relying on on-site wastewater systems (OSSM) and effluent disposal.

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Growth and infrastructure

Greater Sydney is projected to grow significantly over the next two decades, with a large share of that growth in the south-west.

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While urban areas are typically serviced by sewer, parts of the growth corridor include land that is not fully connected to wastewater infrastructure.

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This is common in peri-urban and rural-residential areas on the edge of the metropolitan network, where on-site wastewater management is required.

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Use of on-site wastewater systems

In unsewered areas, properties rely on on-site wastewater systems.

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These systems are widely used across South West Sydney’s growth corridor, particularly in larger lot and rural-residential zones where connection to sewer is not available.

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For example, Wollondilly Shire has more than 8,000 on-site wastewater systems, one of the highest concentrations in NSW. This reflects the broader pattern across the region where wastewater treatment and effluent disposal must be managed on site.

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When a wastewater assessment is required

A wastewater assessment is required where a property is not connected to sewer.

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This commonly applies to:

• New dwellings in unsewered areas

• Secondary dwellings

• Subdivisions

• Changes to existing wastewater systems

• Some commercial developments.

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Council approval depends on demonstrating that wastewater can be treated and disposed of on site in accordance with local council and NSW regulatory requirements.

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What a wastewater assessment covers

A wastewater assessment evaluates whether a site can support an on-site wastewater system.

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This includes:

• Soil testing and permeability

• Slope and available land area

• Setbacks from boundaries, buildings and waterways

• Environmental constraints

• System selection and sizing

• Effluent disposal method and area

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The outcome is a council-ready wastewater report submitted with a development application (DA).

 

What makes South West Sydney unique when it comes to wastewater assessments

Across South West Sydney’s growth areas, site conditions vary and can affect wastewater system design.

 

Common factors include:

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• Clay soils or low permeability

• Sloping land

• Limited usable area on smaller lots

• Proximity to waterways, dams and the Sydney catchment

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On-site wastewater systems must be designed to suit these conditions and meet council requirements to ensure long-term performance and compliance.

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