Find out about the requirements for installing and maintaining an effluent disposal system, including approvals and soil reports.
Choosing an effluent disposal system
A number of factors can determine the type and location where a system can be installed, including:
- Soil type
- Available space
- Topography of the land including the slope
- Distance to water courses and bores
- Storm water management method.
Find out about the types of effluent disposal systems.
Approval of an effluent disposal system
Before installing any onsite system, an approval for the installation must be granted. It is an offence to install and use a wastewater system without an approval and ‘Permit to Use’ from the Shire.
Please note: Some areas are ‘sewage sensitive areas’ and secondary treatment may be required, For example, those properties close to the Margaret River or the Blackwood River. If you require planning approval for your development, contact a Shire Planning Officer on (08) 9780 5255 to ask if these special requirements apply to your proposal.
How to apply
Please complete the Application to Construct or Install Apparatus for the Treatment of Sewerage Form and submit with supporting documents outlined below. Application fees and charges will apply. The form can be submitted in person, by email or by post. Further details are provided in the form below
Please ensure your application includes the following:
- Details of the type of system that you are proposing to install, including the manufacturer and the size (check to ensure it is an approved wastewater system)
- Plan of the entire property showing the location of existing and proposed septic systems, contours, setbacks from buildings, boundaries and any bores or water courses
- Plan of the proposed system in relation to the house, showing setbacks and fixtures intending to discharge into the system
- Floor plan of the proposed building(s) that will be serviced by the system
- Soil report (see information below)
- If you are proposing to install an Aerobic Treatment Unit (ATU), a signed maintenance agreement is required with the person who will be servicing the unit.
What needs to be included in a soil report
All septic applications submitted to the Shire need to be accompanied by a soil report showing the suitability of the site for onsite wastewater disposal. The only exception is in areas where the soil conditions are consistent eg. Prevelly, Gracetown.
Site conditions and characteristics of soils are important for both the sizing and siting of septic systems. In poor draining soils, such as clay, larger disposal areas may be required to increase the area of soil into which the effluent can be absorbed. In contrast, some coarse sands can be so free draining they are not able to filter out pollutants. Shallow groundwater or thin layers of free draining soil over heavier soils also need to be considered.
As a minimum, the soil report must provide soil profile details at the septic disposal area (soil type and texture) to a depth of at least 1.2 meters and the depth to the winter water table.
The soil report used for the purposes of building foundations is not acceptable, as these reports are conducted according to a different Australian Standard. A suitably qualified and experienced person is required to undertake the soil assessment. See list of soil consultants below.
A sample soil report is available upon request.
The following consultants can assist with preparing your soil report.
|Civil/Structural Consulting Pty Ltd
|Environmental and Landscape Management
|Sand Tracks Consulting Pty Ltd
|Structerre Consulting Engineers
|Margaret River Structural Engineering
Please note: This list is provided as an information source for property owners residing in or having a property interest within the Shire of Augusta Margaret River. The information is provided with the consent of the consultants listed. The Shire does not accept any responsibility for the quality, business registration, capacity, insurances and or level of service provided by these consultants. It is the applicant’s responsibility to undertake their own due diligence before selecting a consultant to undertake a soil assessment. The Shire has provided this list in good faith, as a reference only.
Maintaining an effluent disposal system
Primary treatment systems
When a septic tank system is correctly installed and maintained, it should work effectively for many years.
If the septic tanks accumulate too much sludge and scum, the volume of the tank is reduced, which in turn reduces the time for separation to take place. This means not all the solids, grease and oils will separate and will pass out of the septic tanks and into the leach drains/soak wells. This will clog the soil surrounding the leach drains/soak wells. To prevent this from happening, the septic tanks should be pumped out (desludged) regularly and owners should minimise fat and grease getting into the system.
Do not dispose of non-biodegradable materials into your system, or old medicines, large amounts of disinfectant or other chemicals.
The frequency of desludging is dependent on the number of people contributing to the wastewater load. As a guide, every eight years for a two-person household, every four years for a four-person household, and more often for households with greater numbers, is recommended.
Most leach drains are fitted with a diverter which allows the occupier to alternate drains, effectively resting one drain and the surrounding soil. This should happen annually. The diverter box between the septic tanks and leach drains can be opened and the effluent flow handle turned.
Never drive over your septic system.
Each system will have its own maintenance requirements. Maintenance of secondary treatment systems can only be carried out by service persons authorised by the Department of Health.