Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:2:p2
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 2 (pt 2/3)
Character Range: 2019760–2022714

the GILs for protection of freshwater and marine water ecosystems were derived using a statistical distribution method and were calculated at four different protection levels, where the data permitted, and are applied according to the ecosystem condition. The aquatic ecosystem protection GILs presented in Table 1C of Schedule B1 are applicable to 'slightly  moderately disturbed' ecosystems. The AWQG should be consulted for additional values for protection of disturbed ecosystems and pristine ecosystems.

For guidance on the selection of relevant GILs—see Section 3.

Levels marginally in excess of the GILs do not imply unacceptability or that a significant human health or ecosystem impact is likely to be present. Subject to an appropriate investigation and assessment process, a decision not to take further action or to take further action may be justifiable based on the findings.

GILs are not intended to be clean-up levels. The decision on whether clean-up is required (and to what extent), should be based on site-specific assessment. Risk assessment is one aspect of making the decision; however, other considerations such as practicality, timescale, effectiveness, community acceptance, cost and durability are also important.

The referenced source documents should be consulted for information on how to develop site-specific criteria where generic guidelines are not available or applicable.

2.3              Conceptual site model
In order to commence an effective risk-based assessment of a site, a preliminary understanding of the potential site issues is necessary. The understanding of the site is referred to as a conceptual site model (CSM) and describes the source(s) of contamination, the pathway(s) by which contaminants may migrate through the various environmental media, and the populations (human and/or ecological) that may be exposed. For further information on the issues to be considered in the development of a CSM, refer to Schedules B2 (Sections 4 and 8) and B4.

2.4              The tiered approach
The risk assessment process for contaminated sites is usually undertaken in stages or 'tiers' involving progressively more detailed levels of data collection and analysis. In this guidance, the tiers are referred to as Tier 1, Tier 2 and Tier 3. The approach provides for assessment at a level of complexity that is appropriate for the problem under consideration. As the amount of data and assessment detail increases, and the CSM is refined and data gaps are filled, the level of uncertainty decreases. In turn, the level of uncertainty in the risk assessment process is reduced.

2.5              The basis for groundwater risk assessment
Groundwater should be assessed on the basis of its environmental values and the risk that the current (or realistic future) use may pose to human health and/or the environment. With regard to realistic future uses, consideration should be given to the quality and yield