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Nothing like getting your hands dirty

Great start to the year being able to get out in the field, taking samples and classifying soil types. I was collecting data to develop a MEDLI model, to estimate the optimum irrigation regime for sustainable wastewater effluent disposal to land.


For this project, we are working with industry expert Bernie Powell, who led the soil classification and sample collection and gave us what was really a master class in soil science.

Disposal of wastewater effluent to land is designated as an environmentally relevant activity (ERA), which are licenced by the QLD Department of Environment and Science (DES). To demonstrate that the activity can be undertaken sustainably, there is a requirement to model the effects of the irrigation on the water, salt and nutrient balance, and understand the potential for leaching and impacts to soil, vegetation and groundwater. It is so important to have site-specific data on the soil, to make sure that the model is as relevant to the site as possible.


This particular project is a QLD Government site that is not yet connected to sewer. There are many sites across the state like this, that require all effluent to be managed within the site boundaries and the responsibility can fall to a grounds person, the school principal, a business manager or even a P & C group.


To expose the soil horizons, a pit was excavated, revealing a face of about 1 metre wide and 1.6 metres deep. Excavating a pit was important because bulk density is best collected via rings that are inserted horizontally, as opposed to drilling vertical cores with a rig.


This pit gave excellent access for taking samples and understanding the characteristics of the horizons and seeing how the soil is structured in situ. Engaging a really capable excavator operator was key to this work, to make sure the site is fully restored. Once he had worked his magic, you could barely tell we had been there.


In addition to working with industry partners like Bernie Powell, Viridis now has engaged a Soil Scientist, David Manning, to give us more resources to undertake these types of projects that have become more frequent, as ERA licences are updated across QLD. This methodology can be applied in other states including:

  • to support works approvals in Victoria as part of a development proposal (s. 1J of the Environment Protection Act 1970)

  • to support an application to NSW DoI Water under section 60 of Local Government Act 1993 or section 292 of the Water Management Act 2000

  • to support an application to NSW IPART under the Water Industry Competition Act 2006

  • to support an application to local council under section 68 of Local Government Act 1993 in NSW.