Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:3:p5
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 3 (pt 5/9)
Character Range: 931564–934474

resulting in a much lower result in many cases. Further information is provided in Section 2.4.4 of Schedule B1. Guidance on analytical methods and their selection is given in Schedule B3.

     3.4.1.2         Data quality objectives
Data collection is a vital and integral part of the risk assessment process. All data should be collected to meet pre-determined data quality objectives. In many instances, data from a preliminary or detailed site investigation may be available prior to commencing the risk assessment. In such cases, the assessor should determine whether the data quality objectives of any previous investigations are compatible with the objectives of the risk assessment and whether the original data quality objectives have been satisfactorily met. Guidance on the development of data quality objectives is given in Schedule B2.

     3.4.1.3         Limits of detection
The detection limit of the analytical method used must be lower than the level at which the contaminant might become a concern (that is, lower than the HIL or Tier 1 screening level).

     3.4.1.4         Density and distribution of samples
Under most circumstances, the data should adequately characterise the contamination at the location where the population is likely to be exposed to it. Where sampling density guidelines cannot be followed, the effects of the lack of data on the risk assessment should be considered. Guidance on the development of sampling programs is given in Schedule B2.

    3.4.2          Three dimensional source definition
Understanding the source is a critical part of risk assessment. There are many factors that control the risk to health—the contaminant concentration is only one of them. The CSM should include a detailed description of the source, bringing together information from the site history, soil and geological information, the depth and extent of the source, and the chemical data. Guidance on developing CSMs can be found in Schedule B2.

Site history should provide information on how the contaminants were released to the soil, and the form in which they were likely to have been released. It may also provide information on the length of time the contaminants have been on the site. This information permits judgements to be made on the likely form and mobility of the contaminants and, together with geological and hydrogeological information, on whether groundwater may be impacted. Site history should also allow judgements to be made on where the contamination is likely to be located.

Contaminants may not be uniformly distributed through the soil profile; they may be associated with a particular soil stratum, such as a layer of imported fill material, or a layer of clay that preferentially adsorbs a contaminant. If the distribution or depth of the contamination is not characterised correctly, the risk can be overestimated or underestimated. The risk of