Subdivisions and town planning

Assessment of development, subdivision and rezoning proposals in unsewered areas

The Department of Health is responsible for providing public health advice relating to developments, subdivisions, and local government planning scheme amendments in unsewered areas.

The Western Australian Planning Commission (WAPC) consults the Department of Health on subdivision applications in unsewered areas of the state. Local Government authorities consult the Department for development applications and planning scheme amendments.

When assessing an application for development, subdivision or rezoning, the Department of Health may consider the following public health issues:

• The suitability of a lot for long-term on-site wastewater disposal
• The provision of safe drinking water
• Contaminated land sites
• Public health nuisances, e.g. mosquitoes, noise, vibration, odour, dust and particulates

Please refer to the Department of Planning, Lands and Heritage website (external site) for more information.

The Site and Soil Evaluation for onsite wastewater management for all unsewered subdivisions, density developments and rezoning proposals shall be prepared in accordance with Australian and New Zealand standard: Onsite Domestic Wastewater Management – AS/NZS 1547:2012 and the Government Sewerage Policy 2019 (external site). Where land has already been subdivided, and the lots are to be serviced by on-site wastewater systems, an installation of an on-site wastewater system must be undertaken in accordance with the Health (Treatment of Sewage and Disposal of Effluent and Liquid Waste) Regulations 1974 (external site).

Things to remember when applying the Government Sewerage Policy 2019

The Government Sewerage Policy (2019) (external site) (GSP) guides future planning, subdivision and development in relation to the disposal of sewage in Western Australia.

The GSP requires all new subdivision and development to be connected to reticulated sewerage where available or considered necessary on health, environment or planning grounds. However, the GSP also provides detailed site requirements for on-site sewage treatment and disposal where reticulated sewerage cannot be provided.

The following information is important to consider when applying the GSP:

How the GSP works:

• The GSP is administered by the Department of Planning, Lands and Heritage (DPLH)  in accordance with the planning legislative framework.
• The Department of Health (DOH), Local Government Authority (LGA) and Department of Water and Environmental and Regulation (DWER) are referral agencies who provide technical advice to the  DPLH on any WAPC submissions.
• The DPLH is the final decision making agency for any WAPC submission.

Requirement to connect to reticulated sewerage at rezoning stage:

• Section 5.1.1.7 of the policy requires connection to reticulated sewerage where land is being rezoned for the creation of lots less than one hectare and the highest groundwater level is less than 0.5 metres below the natural ground level. Land should not be rezoned for urban use if unsewered development is proposed that requires the use of engineered solutions (for example, fill or sub-soil drains) to achieve separation distances. 

Determination of highest groundwater level:

• Highest groundwater level should take into account the range of seasonal groundwater conditions.
• Information about highest groundwater level should be included in a Site and Soil Evaluation Report such as:

• At the desktop level investigation -  detailed information about existing groundwater bores that are located within the surrounding area. This information may be available from  Department of Water and Environmental Regulation (DWER) website and from the Interactive Maps of Geoscience Australia's geospatial services.
• At the field investigation during wettest time of the year - observation of any bores at the site or neighbouring properties, the height of standing water in the soil survey pits or holes should be recorded to at least 1.5m depth or 2.0m in PDWSAs. 
• Sites which are deemed wet and have very shallow groundwater (e.g. within 0.5m, in view of item 7 under Sect 5.1.1 of the GSP) should have observation bores installed and monitored during wettest time of the year to identify the peak level.

What does the GSP require for onsite wastewater disposal systems:

• Installation of a Secondary Treatment System (STS) with nutrient retentive capability in some instances. This is required by DWER and enforced by DPLH. Contact these agencies for further information and advice on whether Aerated Wastewater Treatment Systems (AWTS) can be used instead of STS. The list of approved STS and AWTS is updated regularly.
• A Site and Soil Evaluation on site suitability for an on-site wastewater disposal system is required to be provided to the DOH and LGA.

Approval of onsite wastewater systems:

• The Chief Health Officer approves on-site wastewater systems intended for domestic installation. A list of approved onsite wastewater systems is maintained by the DOH. Commercial installations are approved by the Chief Health Officer on a case-by-case basis.

The GSP does NOT apply to:

• a single house on a single lot development.
• a building application
• an onsite wastewater system installation application. However, if any conditions are imposed at early stage of development (e.g. subdivision, DA) it will be considered at this stage .

What LGA should be aware of when applying the GSP:

• Where a proposed development is located in a Sewage sensitive areas or Public drinking water source areas and no sewer connection is available it is likely that only nutrient retentive onsite wastewater systems can be used. If this is the case LGA should consider its ability to manage the ongoing supervision of the maintenance of nutrient retentive onsite wastewater system before supporting any subdivision.

• Government Sewerage Policy 2019 (external site)
• Government Sewerage Policy - Explanatory notes (external site)
• Site and Soil Evaluation for onsite wastewater management