Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:2:p1
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 2 (pt 1/4)
Character Range: 1502144–1505055

2                   Overview of the method for deriving soil quality guidelines
Soil quality guidelines can have various purposes. The National Environment Protection (Assessment of Site Contamination) Measure (NEPM) contains a specific type of SQG, the ecological investigation level (EIL), to guide the assessment of contaminated sites in Australia. The EILs were derived in such a manner that when they are exceeded it indicates that terrestrial ecosystems may experience harmful effects due to the presence of contaminants. The EILs are thus used to indicate when further investigation is necessary.

However, SQGs with other purposes can and have been developed. For example, the Dutch have three sets of SQGs, each with a different purpose. These are target levels (their purpose is to indicate the long-term goals for the concentration of contaminants), maximum permissible levels (their purpose is to define the maximum level of contamination that is considered acceptable), and intervention levels (their purpose is to define the maximum permitted concentration before some immediate action is required).

As a result of consultation conducted in developing the Australian methodology in November 2008, three different sets of ecotoxicity data were used to derive SQGs. The three sets of SQGs are termed SQG(NOEC & EC10), SQG(LOEC & EC30) and SQG(EC50) reflecting the type of ecotoxicity data that was used in their generation. A summary of the three types of SQGs, the data used and likely ecotoxicological effects that would be expected to occur if these are met is presented in Table 1. A combination of lowest observed effect concentration (LOEC) and 30% effect concentration data (EC30) has been adopted in the NEPM for the derivation of EILs.
Table 1. The relationship between the three types of soil quality guidelines (SQGs), the data that is used to derive the SQGs and the type of toxic effects that would be experienced if the SQGs are met.
Type of SQG        Toxicity data used to calculate the SQGs  Expected toxic effects if the SQG is not exceeded
SQG(NOEC & EC10)   NOEC and EC10                             slight toxic effects
SQG(LOEC & EC30)   LOEC and EC30                             moderate toxic effects
SQG(EC50)          EC50                                      significant toxic effects

An overview of the SQG derivation methodology (detailed in Schedule B5b) is presented in Figure 1. One of the key aims in developing the methodology was to account for the availability and toxicity of the contaminant in the soil being studied. To do this, key soil and site-specific factors that are known to modify the toxicity of contaminants had to be accounted for. One factor that was incorporated into the methodology was the background concentration. In order to do this, the data used to derive the SQGs was expressed in terms of the amount of contaminant that had to be added