The Australian Standard AS 4678:2002 for earth retaining structures and AS/NZS 1547:2012 for on-site wastewater management both require reliable infiltration data, and that is exactly what our team delivers through the Porchet and double-ring infiltrometer methods in Rockhampton. This city sits on the Fitzroy River floodplain, where alluvial silts and clays alternate with sandy lenses – a setting that demands site-specific hydraulic conductivity values rather than default tables. We perform each infiltration test according to AS 1289.6.8.1 procedures, measuring steady-state flow under a constant head to characterise the soil profile for septic soakage, stormwater basins, and permeable pavement subgrades. The combination of seasonal rainfall exceeding 800 mm per year and expansive clay layers near the surface makes the infiltration test a critical first step before any groundwater recharge design or detention system sizing. Before the infiltration test, we often recommend a complementary density test with sand cone to verify compaction levels in the near-surface zone, as loose fills can produce artificially high infiltration rates that mislead designers.
A single dry-season infiltration test in Rockhampton may underestimate long-term percolation by a factor of two without wet-season verification.
Scope of work
Area-specific notes
Rockhampton has a population of approximately 80,000 and lies within a moderate rainfall zone, but the real risk lies in its soil variability – one block may have permeable sandy loam while the adjacent lot sits on dense clay with K values below 0.01 m/day. Designing a soakage trench or a retention basin without site-specific infiltration test results in this context can lead to surface ponding, foundation moisture problems, and regulatory non-compliance under the Plumbing and Drainage Act 2018. Our infiltration test identifies these contrasts before construction begins, allowing engineers to adjust drainage layouts or specify subsoil drains where natural percolation is insufficient. For sites where expansive clay is present, we also cross-check results with the Atterberg limits test to quantify shrink-swell potential and its effect on long-term permeability.
Watch how it works
This service complements our laboratory testing work for a complete project analysis.
Standards used
AS 1289.6.8.1 (Standard Test Method for Infiltration Rate of Soils in Field Using Double-Ring Infiltrometer), AS/NZS 1547:2012 (On-site domestic wastewater management), AS 4678:2002 (Earth retaining structures – drainage design)
Linked services
Porchet Infiltration Test
Single-ring method suitable for narrow test pits or boreholes. We auger a 150 mm diameter hole to the required depth, pre-soak the soil for 24 hours, then measure the falling head at regular intervals. Results are reported as percolation rate (min/mm) and hydraulic conductivity (m/day). Recommended for residential septic systems and small-scale drainage assessments.
Double-Ring Infiltrometer Test
Two concentric rings driven 100 mm into the soil, maintaining a constant head in both. This method eliminates lateral flow error and gives a true vertical infiltration rate. Ideal for stormwater infiltration basins, rain gardens, and large-scale commercial developments where precise K values are required for design.
Typical parameters
FAQ
How long does an infiltration test take in Rockhampton?
The field measurement itself takes 90 to 120 minutes per test location, but we require a 24-hour pre-soaking period for dry soils to reach natural moisture conditions. Total turnaround including reporting is typically 3 to 5 business days.
What is the cost of a Porchet or double-ring infiltration test?
The typical range for a standard infiltration test in Rockhampton is between AU$530 and AU$620 per location, including equipment setup, field measurement, and a certified report with K values. Volume discounts apply for multiple test points on the same site.
Do I need an infiltration test for a retaining wall in Rockhampton?
Yes – AS 4678 requires drainage design behind retaining walls to prevent hydrostatic pressure build-up. An infiltration test determines whether the backfill will drain freely or require a geocomposite drainage layer. We often recommend the double-ring method for this application because of its higher accuracy.