Environmental Division
ENVIROMAIL # 34
November 2008
RTA Foreign Materials Testing and
Particle Sizing in Soils & Sediments
RTA Method T276 is a requirement of the Excavated Natural Material
Exemption 2008, under the NSW POEO (Waste) Regulation.
The determination of Particle Size Distribution in soils and sediments is an
essential requirement for many engineering, construction and environmental
projects. ALS is pleased to announce that these services are now NATA
accredited through ALS Newcastle.
Background – RTA Foreign Material Content
Classification of soil as Natural Excavated Material (NEM) allows disposal as engineering fill or use in
earthworks. To be classified as NEM soil must be excavated, with at least 98% natural content (i.e. less than
2% total foreign material) and shown to comply with maximum contaminant levels by a range of chemical and
physical tests. These tests include determining percentages of rubber, plastic, bitumen, paper, cloth, paint
and wood using RTA Test Method T276.
Samples for Foreign Material Content analysis require air drying prior to analysis, which can impact
turnaround for wet samples. Samples do not need to be chilled during transit to the laboratory and can be
shipped in sturdy plastic bags. RTA Test Method T276 specifies that 6kg of air dried sample is required.
Results are reported on the standard ALS Environmental Certificate of Analysis (COA) and can be provided in
a variety of export formats. These results can also be previewed or downloaded through WebTrieveTM.
The following is an example of reported analytes and formats.
Right solutions….
….Right partner
Background – Sizings
Australian Standards prescribe the use of sieving for determining particle sizes of 75 µm or larger (large
stones, gravel and sand), and hydrometer for clay and silt. The larger particles are mechanically
separated on the calibrated sieves recommended in the Australian Standard AS1289.3.6.1 or
alternatively, using sieve apertures selected by the client. Hydrometer analysis is carried out according
to Australian Standard AS1289.3.6.3, which is based on an application of Stokes Law that relates
sedimentation rate to particle size. Hydrometer analysis allows estimation of the percentage clay and
silt.
Samples for particle size distribution should be air dried prior to analysis and do not require chilling while
in transit to the laboratory. The amount of soil/sediment required for this test is specified in AS1289.1.1
and depends on the maximum size of the particles present in the sample (See Table 1 below). If
insufficient sample is received the test can still be carried out, however there is a greater uncertainty in
the results for the coarse fractions and consequently, the report will contain a note that “The sample size
submitted does not meet the Australian Standard requirement”.
Table 1. Sample Sizes Required by AS1289.1.1-2001 Preparation of Disturbed Soils.
Minimum Mass of Sample Required for PSD
Maximum Particle Size (mm)
0.425
2.36
3.35
4.75
6.7
9.5
13.2
19.0
Mass of Sample Required (kg)
0.05
0.20
0.25
0.50
0.60
1.0
2.5
5
Notes
•
•
PSD results can be reported as numerical data on the standard ALS NATA endorsed report, and/or in a graphical
presentation as recommended in the Australian Standard (see below).
Some sample types may require pre-treatment to remove salts, organics or carbonates. If the purpose for testing
precludes pre-treatment, please indicate this requirement on the Chain of Custody.
Standard Sieve Sizes (mm)
Fine:
0.075, 0.150, 0.300, 0.425, 0.600, 1.18
Intermediate:
2.36, 4.75, 9.5
Coarse:
19.0, 37.5, 75, 150
Soil Classification - Particle Size Limits
Clay:
Less than 2 µm
Silt:
2 µm to 60 µm
Sand:
60 µm to 2 mm
Gravel:
2 mm to 60 mm
Cobbles:
60 mm to 200 mm
ALS Sizing Graphical Reporting
Logistics
Samples for particle size distribution should be packed to
avoid any leakage and can be submitted via the ALS
Environmental National network.
For further information please contact newcastle@alsenviro.com or your local ALS team.
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