If your property or project is not connected to Council’s reticulated town sewer system, you will need or may already have an On-Site Sewage Management (OSSM) system. It provides efficient storage, treatment and disposal of household wastewater to minimise health risks and environmental hazards.
What is an on-site wastewater assessment?
An OSSM Assessment, also known as a Wastewater Management Report, is a technical document which determines how the sewage produced on-site will be managed, treated, and disposed. The assessment outlines the design of the OSSM system and is required by local councils as part of the approval process to have it altered or installed.
In rural and isolated properties where connection to a municipal sewerage system is not a viable option, the management of wastewater generated on these properties needs to be managed by an alternative method on-site.
Why are onsite wastewater assessments needed?
Landholders needing to install an on-site wastewater system need to first get approval from their local council.
A wastewater report is required in the following cases:
- Construction of a new residence or building in a non-sewered area.
- Modifications and alterations to existing houses or buildings (domestic or commercial).
- Rural subdivisions in areas not serviced by a reticulated town sewer system.
- Upgrades or alterations to an existing OSSM system.
- Construction of a secondary dwelling or building.
- Failing trenches or soil absorption systems
- Your local council has ordered that a OSSM Assessment be undertaken to recommend a new OSSM system.
An OSSM Assessment includes the information that needs to be provided with an application to the local council for approval. This includes
- scaled plan and specification of the system.
- a site assessment, including details of the following:
- climate
- geology
- hydrogeology
- topography
- soil composition
- vegetation
- statement of factors contributing to the hydraulic load.
- details on the operation and maintenance of the system.
How does the approval process work?
Following submission of the application, the local council will consider the proposal and its ability to:
- prevent the spread of disease;
- prevent the spread of foul odours;
- prevent the contamination of water;
- prevent the degradation of soil and vegetation;
- discourage insects and vermin;
- restrict human access and exposure to wastewater;
- re-use resources (including nutrients, organic matter, and water); and
- minimise any impacts on the amenity of the land and its surrounds.
Many councils may also need the proposed OSSM system to comply with relevant Australian Standards (AS/NZS 1546.1:2008, AS/NZS 1546.2:2008, and AS/NZS 1547:2012).
What do on-site wastewater assessments involve?
Wastewater assessments usually involve a desktop analysis, site assessment, and system design.
During a desktop analysis, background information about the site is gathered and analysed to better understand any environmental constraints of the surrounding land, as well as the applicable hydraulic loading rate.
The site assessment will include an assessment of drainage, vegetation, aspect, topography, surrounding land, and soils on the site. During the soil assessment, a minimum of three boreholes are excavated to determine the soils capability to assimilate and treat onsite wastewater. This involves an assessment of the soil’s texture, structure, hydraulic conductivity, pH, and electrical conductivity, as well as identifying the presence of waterlogged, dispersive, slaking, or slumping soils.
The information is then compiled to determine an appropriate OSSM system design for the site.
GeoLINK has the expertise to complete your OSSM assessments, with staff having completed relevant onsite wastewater management training courses to ensure you’ll get the best outcome for your onsite wastewater needs. Get in touch with our Environmental Science and Engineering team.
