Percolation testing and wastewater land application assessment, AS 1547

Before a council will approve an on-site wastewater system, somebody has to prove the ground can take the effluent. We run the percolation and permeability testing, assess the land application area to AS/NZS 1547, and give your designer the soil category and design loading rate they need, reported so it can be lodged with your plumbing application.

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When you need a percolation test

Any development on a block that isn't connected to town sewer. That covers most rural and semi-rural land across Moreton Bay, the Sunshine Coast hinterland and Northern New South Wales.

New houses going on septic or an aerated system

Rural and acreage subdivisions, assessed lot by lot

Replacing or upgrading a failing septic system

Secondary dwellings, granny flats and sheds with amenities adding load

Commercial and tourism development outside the sewer network

Buying acreage and needing to know it will take a system before you commit

Council requesting a land application report as a condition of approval

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What we test, and why it matters

Soil profile. Test pits or bores across the proposed land application area, logged to AS 1726. The profile tells you what the effluent has to travel through and where it stops.

Percolation and permeability. Falling head percolation testing in the field, and hydraulic conductivity testing where the design calls for a measured permeability.

Soil category and design loading rate. The profile and the test results assign the soil category under AS/NZS 1547, which sets the design loading rate, or the design irrigation rate where the system applies effluent to the surface. That number sizes the trench, the bed or the irrigation area.

Site constraints. Slope, buffer distances to boundaries, bores and watercourses, groundwater, rock, seasonal wetness, flood-prone land and existing structures, all of which affect whether the proposed area can be approved, and whether the required reserve area fits on the block.

The loading rate sets the size of the land application area, so it is measured, not assumed.

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What you get

Soil profile logs across the land application area

Percolation and permeability results, with the methods stated

Soil category and design loading rate under AS/NZS 1547

Site and constraint assessment, including buffer distances and slope

Recommended land application area and system type

A report formatted for council lodgement

RPEQ certification arranged where the approval requires it

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Wastewater system design

We assess the land and produce the data the wastewater system designer works from, in the format they need for the design.

We assess the land and determine the correct locations for the system. That information goes to our plumbing contractor, and together we correlate it to provide a wastewater design report.

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Where we work

Moreton Bay, the Sunshine Coast and hinterland, Brisbane rural fringe, Ipswich, the Lockyer Valley, the Gold Coast hinterland and Northern New South Wales.

Reports lodged with Moreton Bay, Sunshine Coast, Brisbane, Ipswich, Logan and Gold Coast councils.


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Get a fixed quote

Send the site address, the lot and plan, and any drawings you have.

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or Call 0408 861 788

Common questions


How much does a wastewater investigation cost?

It depends on lot size, access, how many test locations the land application area needs and whether the design calls for laboratory permeability testing. Send the site address and any plans and we will come back with a fixed price.

Can you do the percolation test and the site classification in one visit?

Yes. On an unsewered residential lot both can be scoped in one mobilisation, with the soil profile logged once.

How long does it take?

Falling head percolation testing needs the ground pre-soaked, so allow more than a single visit on most sites. We give you the programme with the quote.

My existing septic has failed. Do I need a new assessment?

Usually yes. Councils treat a replacement as a new application, so the land application area has to be assessed against current requirements, and those have changed since most older systems went in. A failure often means the original area was undersized or has simply worn out, which means the new one may need to go somewhere else on the block. We test, size the new area and report it so your plumber can lodge the application.

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Coastal Geo Consulting Licensee: Luke James Whittaker Licensed under the QBCC Act · QBCC Licence No: 1534 8305


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