Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:1:p4
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 1 (pt 4/6)
Character Range: 2906755–2909688

(refer to Schedule B2, Section 4). The preferred approach is to examine a range of summary statistics including the contaminant range, median, arithmetic/geometric mean, standard deviation and 95% UCL. Further information is provided in Section 11 of Schedule B2.

The application of interim HILs also needs to take into consideration soil vapour data. This data should be evaluated in order for it to be used in the appropriate exposure scenario at a site. The relevance of conducting statistical tests (other than the arithmetic mean) should be evaluated for soil vapour data. Where data is limited or it is not relevant (for the purpose of assessing exposure) to conduct statistical analysis, the maximum soil vapour concentration can be compared against the interim HIL.

Exceedence of the HILs does not automatically imply that quantitative modelling at Tier 2 risk assessment stage is warranted. Similarly, concentrations less than that of the HILs do not necessarily imply that a Tier 2 risk assessment stage is not warranted. As already mentioned, HILs are not intended to indicate a clear demarcation between 'acceptable' and 'unacceptable' soil contaminant levels.

The decision to proceed or not to proceed with additional data collection and risk assessment should always be considered with reference to the site-specific exposure pathways, the consequences of exposure, and the characteristics of the exposed population (i.e. site-users).

1.4              Principles and methodology for generating the HILs
The derivation of HILs follows the same five-step process central to Australian risk assessment practice as outlined in Schedule B4 and enHealth (2012a).

Fundamentally, the HILs have been derived as scientifically-based, generic criteria designed to be used in the first stage of an assessment of potential risks to human health from chronic exposures to contaminants. The underlying principles/considerations adopted in deriving the HILs are as follows:
    * each HIL should embody a margin of safety such that there is no appreciable risk for exposures for the relevant scenarios, A–D. This has been undertaken on the basis of available scientific information to March 2012 (including toxicity reference values that are generally based on the known most sensitive significant toxicological effects).
    * where an HIL has been formerly established (NEPC 1999) and scientific information is available that supports the revision of the HIL (to a higher or lower value), then the HIL has been revised. However a policy decision has been applied such that where the scientific information only supports a minor revision of the HIL by less than approximately 20%, or the new scientific data is not adequately robust, the existing HIL has been retained (with no change). Where this decision has been made, this is documented in Appendix A of this Schedule. The calculated values, before and after rounding, can be