Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:1850:p25
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 1850 (pt 25/117)
Character Range: 415501–418507

soil sampling program informed by site history, inspection and contaminant form is the preferred approach for site assessment. On occasions it is necessary to stockpile soils that have not been assessed or only partially assessed in situ, and to devise a thorough stockpile sampling plan.

    7.5.1          Excavation and inspection of the stockpile
Excavation may result in mixing of low-level or uncontaminated soil with smaller quantities of contaminated soil, having the effect of diluting higher concentrations. It is preferable for assessors to supervise excavation and, as far as practicable, segregate stockpiles according to soil and contaminant types and to avoid dilution.

The process of excavating material often results in mixing of strata and different fill and soil types. Stockpiling may cause some segregation of grain sizes particularly on the exterior slopes. Specific grain sizes may contain the contaminant source and concentrate in some stockpile locations; for example, finer material may tend to accumulate at the toe of batters and coarser material towards the crest. Sticky clay material may be distributed into a different part of the stockpile than loose soils. The age and surface condition of the stockpile should be assessed, particularly if it has been weathered and subjected to leaching.

The composition of the stockpile should be documented by inspection of its external appearance and excavations into the stockpile by shovel (for small stockpiles) or excavator bucket where a shovel cannot reach the centre of the stockpile. The stockpile dimensions should be determined noting its regular or irregular shape and a 3-D plan prepared. The volume of material present should be estimated.

    7.5.2          Number of samples
Table 4 below provides the minimum number of samples recommended for characterisation of stockpiles up to 200 m3 comprising similar materials. A greater number of samples may be required when there is a large range in contaminant concentrations or soil types. If only the minimum number of samples is collected and there is a large range in contaminant concentration, then either the maximum concentration should be assumed for disposal purposes or additional samples collected and analysed and the situation re-evaluated. In situ samples taken prior to excavation may be helpful for informing the decision on the number of samples required for adequate characterisation of stockpiles.

Table 4. Minimum number of samples recommended for initial assessment of stockpiles
Stockpile volume, (m3)  No. of samples
<75                     3
75  <100               4
100  <125              5
125  <150              6
150  <175              7
175  <200              8

The recommended sampling frequency (Table 4) applies to the characterisation of homogenous soils suspected of contamination. Lower sampling rates may be derived for soil quantities greater than 200 m3 by applying statistical analysis. Worked examples of applying 95% UCLave