Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:4:p7
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 4 (pt 7/11)
Character Range: 135068–138025

surface of the site. In these circumstances the assessment can proceed directly to remediation (removal of bonded ACM fragments and ensuring that the soil surface is free of visible asbestos) and validation.

4.10          Determining asbestos in soil concentrations
Bonded ACM is the most common and the most readily quantifiable form of asbestos soil contamination due to its ease of visual detection. Where site circumstances are favourable, bonded ACM in sound condition can be used as the primary means of estimating contamination by subjecting soil samples to on-site sieving and gravimetric procedures as described below.

Assessment of bonded ACM is the recommended measure for total asbestos contamination where FA and AF (derived from bonded ACM only) are not likely to be significant as established by the PSI including the site inspection (as a guide, this may be taken to be where FA and AF are likely to make up less than 10% of the total amount of asbestos present).

Important considerations in determining asbestos concentrations in soil include:
    * observations and calculations of surface asbestos occurrence/distribution should be recorded on a grid system (a grid of up to 10 m x 10 m is generally reasonable when large surface areas are impacted, however, non-impacted soils should be excluded from calculations to avoid dilution effects)
    * where more than one distinct fill unit or soil stratum/unit is impacted by asbestos materials, separate asbestos determinations should be made for each stratum/unit
    * averaging asbestos concentrations across all soils at a site is not appropriate
    * for sub-surface samples, (e.g. boreholes and trenches) the calculation should be carried out per sample (i.e. not averaged over a grid square)
    * the statistical procedures outlined in Section 3.2 (such as comparing mean concentrations with the screening level and no individual sample concentration exceeding 250% of the screening level) are not appropriate for asbestos
    * a weight-of-evidence approach (refer 4.11), which takes into account field observations and methodology and relevant site history findings (e.g. location and nature of fill and demolished buildings etc.)' is recommended for determining whether individual or adjacent samples exceeding the relevant screening levels are of concern.
Asbestos in soil concentration by gravimetric approach
Guidance on recommended sampling methods is given in Schedule B2 and is based on the WA DoH guidelines (2009).

The asbestos concentration calculations are based on the amount of asbestos equivalent (i.e. asbestos in asbestos-containing-materials) in a measured/estimated amount of soil, expressed as a % weight for weight. The soil volume may be one or more individual 10 L samples from specific soil units or the area of a grid square multiplied by the investigation depth for raking and tilling methods (refer Schedule B2).

As outlined in enHealth (2005), the