Site and soil evaluation for onsite wastewater management

The success of an onsite wastewater system depends largely upon site and soil characteristics, as well as system design, installation, and maintenance.

As such the site and soil evaluation is an important part of the land development permitting process for on-site wastewater systems. The site evaluation is used for the initial land development process to determine if site and soil conditions are suitable for installation of an on-site wastewater system, the size of the land application area and if any physical features such as lakes, creeks, drinking water bores, drainages, or wells that may require setbacks to prevent possible contamination.

The Government Sewerage Policy 2019 (external site) requires that the Site and Soil Evaluation (SSE) for onsite wastewater management is undertaken in accordance with Australian and New Zealand standard: Onsite Domestic Wastewater Management – AS/NZS 1547:2012 for majority of  unsewered subdivisions, density developments and rezoning proposals. Site and Soil Evaluation reports required under the Government Sewerage Policy 2019 also need to address the additional requirements under that Policy and its schedules. This can impact on the sizing of land application areas, groundwater clearances and setback requirements.

Where land has already been subdivided, and the lots are to be serviced by on-site wastewater systems, a SSE might be required to support an application to install an on-site wastewater system in accordance with the Health (Treatment of Sewage and Disposal of Effluent and Liquid Waste) Regulations 1974 (external site).

The Department of Health developed the following guidance material to assists the industry and enforcement agencies in preparation and assessment of the SSE reports:

Assessment of Site and Soil Evaluation Reports Workshops 

The assessment of SSE Reports workshops will be held in different locations throughout the State and information about the workshops will be updated on this web page. The key elements of the workshop will focus on the assessment of the Site and Soil Evaluation Reports prepared to determine site suitability for an on-site wastewater system installation in accordance with AS/NZS 1547:2012 and the Government Sewerage Policy 2019. The first workshop held on 24 February 2021 at the EHA conference was a success with lots of knowledge and experience sharing, view  the slides of the workshop presentations (PDF 2.5MB). The next workshops will be held in:

For any queries regarding the workshop please email WWApps

More information

Environmental Health Directorate
Department of Health
Telephone: 9222 2000
Email: WWapps@health.wa.gov.au

Last reviewed: 05-10-2021
Produced by

Environmental Health Directorate