Site assessment and wastewater design for houses in Tasmania is specified in Australian New Zealand Standard 1547. The latest version is AS/NZS1547:2012.
Accreditation of Wastewater Designers
Designers of domestic wastewater systems in Tasmania must be accredited as a building practitioner under the Building Act 2000.
Bill Cromer is an experienced Accredited Designer for wastewater systems in Tasmania. He has been a practitioner in this field since the early 1980s. He is and was a member of Environmental Health Australia (EHA) and its predecessors, and was awarded its Environmental Health Industry Award in the late 1980s for compiling the Code of Practice: Site Assessment for Septic Tank Absorption Trenches (1988) for site assessors. A decade later, he was on an EHA Tasmanian subcommittee which upgraded the 1988 document to produce a draft Code of Practice for On-site Wastewater Disposal (1998). This later Code introduced Bill’s software package Trench®3.0 — highly regarded and an industry standard — which assists practitioners throughout Australia assess sites for domestic wastewater management. Bill holds training sessions across eastern Australia in its use, and in Tasmania has demonstrated its applications at workshops conducted by the Centre for Environmental Training.
Are you an owner/buyer wanting to build on land in an un-sewered area?
Your local council may require a Site and Soil Assessment of the property to assess its suitability to dispose of domestic wastewater. If wastewater cannot be disposed of in an acceptable manner, you may not be able to build a house on your land. If wastewater can be disposed of acceptably, the local council will issue you with a Special Plumbing Permit. See my flowchart setting out the process in Tasmania (PDF Document 13kB).
It is wise to determine site suitability before you buy. Relying on a previous council approval for domestic wastewater disposal for your land may not be sufficient. Times and regulations change. A good example is the new Tasmanian On-site Wastewater Management Code introduced in 2015 to all state interim planning schemes. This is yet another bureaucratic hurdle you might have to jump over. See my post about the Code, and my flowchart to assess whether or not your land might be exempt from it (PDF Document 33kB).
Site investigations for domestic wastewater surveys might need to include inspection, mapping, test pitting by an excavator, hand or mechanical augering, soil sampling and testing of soils.
In Australia, AS/NZS1547:2012 recognises six classes of soils, from Category 1 gravel and sand, through loams, to heavy clay (Category 6). Your soil type and available land area may significantly affect the way you manage your wastewater.
There are many ways to manage domestic wastewater:
- Septic tank and absorption/evapotranspiration trenches
- Septic tank and absorption/evapotranspiration (conventional, in-ground) beds
- Nonconventional (above ground) beds
- Aerated Wastewater Treatment Systems (AWTSs)
- Bottomless sand filters
- Wisconsin (above ground) Mounds
- Composting toilet and separate greywater disposal
- Chemical toilet and separate greywater disposal
- Other methods
Are you an owner wanting to extend your existing home?
Your local council may require a statement from an accredited wastewater designer that your existing wastewater system will be able to cope with any additional loading as a result of your extension. At the very least, the designer will need to establish where and what system you have. A Site and Soil Assessment of the property may need to be done. If wastewater cannot be disposed of in an acceptable manner, you may not be able to extend your home.
Do you have no wastewater disposal system, or a non-approved system?
Best to do something about it now.
Are you a developer proposing to subdivide land in an un-sewered area?
Your local council may require a wastewater assessment of the subdivision, or (if you have already submitted a proposal plan) an assessment of the suitability of each lot to treat wastewater. A wastewater assessment may recommend changes to the number, location, or size of lots.
It makes sense to do the wastewater assessment (and perhaps a full geotechnical assessment) before preparing a proposal plan.