Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:3:p4
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 3 (pt 4/5)
Character Range: 2032989–2035942

hardness (ANZECC & ARMCANZ 2000). The AWQG are conservatively presented on the basis of low hardness (30 mg/L CaCO3) and the relevant GILs may be modified for increased levels of hardness according to the algorithm presented in ANZECC & ARMCANZ 2000.

Exceedence of Tier 2 criteria may result in a need for a Tier 3 assessment. As with Tier 1 exceedences, an assessment of the significance of exceedences may be necessary where they are marginal or present over a limited area. If Tier 2 criteria are exceeded, but further assessment (or action) is not proposed, the information and logic used to inform the decision should be documented clearly and transparently.

If no modification of the Tier 1 criteria is applicable, then the risk assessor may decide to proceed directly to Tier 3.

    3.4.3         Tier 3
A Tier 3 assessment may be required where exceedence of Tier 2 site-specific target levels is judged to represent a potentially unacceptable risk to human health and/or the environment. The Tier 3 assessment typically focuses on the risk-driving contaminants in more detail and generally requires additional site investigation to reduce critical uncertainties in the risk assessment.

Tier 3 risk assessments compare groundwater contaminant concentrations at the point of exposure (point of use) with existing generic GILs or can incorporate additional information such as ecosystem/environmental variability and exposure to derive modified, site-specific response levels.

The relevant jurisdictional policy should be consulted when modifying GILs at the point of use. For example, when determining criteria for groundwater discharging to a surface water body, these should be determined on a site-specific basis, as some jurisdictions allow for a mixing zone or water treatment, whereas others apply the GILs at the point of discharge without mixing in order to protect benthic organisms.

Further information is available in Schedule B2 and ANZECC & ARMCANZ (2000).
Example Tier 3 activities include:
    * contaminant fate and transport modelling to predict groundwater quality at existing (and realistic future) receptors using a range of aquifer conditions to assess the significance of the site contamination at the point of exposure/use  refer Schedule B2
    *  consideration of metal speciation (speciation modelling or chemical measurement) – refer AWQG
    * biological effects testing (for example direct toxicity testing) – refer AWQG.

3.5              Risk management
At the point of use or exposure, GILs may be considered as response levels: the response may include further investigation or management as appropriate.

Contaminant levels marginally in excess of the GILs do not imply unacceptability or that a significant human health or ecosystem risk is likely to be present. The decision on whether clean-up is required (and, if so, to what extent) should be based on site-specific assessment. Risk assessment is one