Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:1:p2
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 1 (pt 2/4)
Character Range: 888564–891638

populations). This is achieved by modelling the dose that an individual may receive through incidental exposure to contaminated soil and/or water as a result of everyday activities. This estimated dose can then be compared against doses that are considered to result in no observable adverse impact to health, as published by authoritative bodies and health protection agencies.

The quantitative risk assessment process, in the context of this guidance, is primarily designed to evaluate the long-term or chronic risks to exposed populations from contamination in the environment. Short-term or acute risks can be dealt with using similar means though normally this is not necessary, because contamination that is severe enough to pose acute risks is sufficiently obvious that a complex assessment is not required.

There are two different approaches to risk assessment, which can be referred to as 'forward' and 'backward' assessments. In a forward assessment, the risks associated with a measured contaminant concentration are estimated by comparing an estimated dose that a receptor (i.e. a person) may receive with a dose considered to result in no significant observable impact to health. It is possible to undertake the modelling in reverse (a backward assessment), starting with the dose considered to result in no significant observable impact to health, and back-calculating 'tolerable' contaminant concentrations at the site. These concentrations can then be used to define management requirements or as remediation targets or site-specific clean-up criteria.

1.4              Site assessment process and terminology
The general site assessment process for contaminated land is described in Schedule A of this NEPM. Once the need for an assessment is triggered, a preliminary site investigation should be conducted using guidance outlined in Schedule B2. The objectives of the preliminary investigation are to identify the potential contaminants of concern, the areas of potential contamination and the potentially affected media (i.e. soil, water, sediment and air). The preliminary investigation report should clearly identify any significant data gaps and include an assessment of the accuracy of the information collected.

Where there is potential for soil and/or groundwater contamination to be present, then a detailed site investigation should be conducted. This involves the collection of soil, groundwater and soil vapour samples for field and laboratory analysis, and should be conducted using appropriate guidance such as that outlined in Schedule B2 and Schedule B3.

The sample analysis results are then compared against appropriate guidance values, such as HILs (after appropriate checking of the reliability of the data).

    1.4.1          Health investigation levels
HILs and health screening levels (HSLs) are defined as 'the concentration of a contaminant above which further appropriate investigation and evaluation will be required'. They are defined for specific land uses and will not necessarily be protective for other land uses. There