With an average annual rainfall around 450 mm and a landscape dominated by the Goulburn River floodplain, Shepparton sits on alluvial soils that vary laterally from sandy loam to heavy clay. Understanding how fast water moves through these layers is essential for septic system design, stormwater infiltration basins, and agricultural drainage. An infiltration test — using either a Porchet borehole or a double-ring infiltrometer — measures the saturated hydraulic conductivity of the soil profile in situ. The results guide the sizing of soakage trenches and retention basins across the region. Before interpreting permeability from ring data, engineers often cross-check soil classification with a granulometry analysis to confirm grain-size distribution, or they run a laboratory permeability test on undisturbed samples for comparison with field values.
Infiltration rates in Shepparton clays often fall below 5 mm/h, a value that drastically changes the sizing of any soakage system.
Method and coverage
Regional considerations
A common oversight in Shepparton is running infiltration tests after a dry spell without wetting the profile to field capacity first. This yields Ksat values that are too high, leading to undersized soakage trenches that fail during wet winters. Another risk comes from the region's dispersive clogs — sodic soils can collapse when water is introduced, causing the borehole wall to slake and plug the infiltration zone mid-test. To avoid misleading results, the team pre-wets the test location for at least 24 hours and monitors the soil's reaction to water. If dispersion is observed, a sulfate and organic content test is recommended to assess chemical instability before finalising drainage designs.
Standards that apply
AS 4678-2002: Earth-retaining structures (references for drainage design), AS/NZS 1547:2012 On-site domestic wastewater management (infiltration criteria), AS 1289.6.8.1: Standard test method for infiltration rate of soils in field using double-ring infiltrometer
Complementary services
Double-ring infiltrometer test
Two concentric rings driven into the ground, maintaining a constant water level in both. The inner-ring drop is measured to calculate vertical Ksat. Suitable for pervious pavements, retention basins, and large-scale drainage studies in Shepparton.
Porchet borehole infiltration test
A single auger hole is filled with water and the falling head is recorded. Best for shallow investigations where access is limited or the soil profile is uniform. Common for septic system designs and soakwell sizing in residential Shepparton developments.
Typical parameters
Top questions
How long does an infiltration test take in Shepparton clay soils?
A single double-ring test typically takes 2 to 4 hours to reach steady-state flow in clay-dominated profiles. In sandy loam, the test may finish in under 1 hour. Porchet boreholes usually require a longer pre-wetting phase, often 24 hours, to saturate the surrounding soil before the actual measurement begins.
What is the cost range for an infiltration test in Shepparton?
The cost of a field infiltration test in Shepparton ranges between AU$560 and AU$850 per test location. This includes setup, field measurements, data reduction, and a report with the calculated Ksat value. Additional boreholes or multiple ring positions can increase the price proportionally.
Can I use Porchet results for designing a stormwater infiltration basin?
Yes, but only if the borehole depth matches the planned basin depth and the soil profile is homogeneous. For layered profiles or basins deeper than 1.5 m, the double-ring infiltrometer is more representative because it tests the surface layer under ponded conditions. The engineer should apply a factor of safety of at least 2 to the measured Ksat for permanent basin design.