Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:2:p12
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 2 (pt 12/21)
Character Range: 71122–74139

land use but which may not be acceptable for protection of the environment or water resources or from an aesthetics perspective. Site results should be considered with reference to relevant ecological and 'management levels'(refer Sections 2.5 and 2.9) which may become the predominant risk driver. Management levels should be applied after human health, ecological risks and risks to groundwater resources have been assessed.

    2.4.11      Direct contact HSLs
Direct contact HSLs have been developed for exposure through dermal contact, incidental oral ingestion and dust inhalation and then combined as a single HSL for direct contact with soil (Friebel & Nadebaum, 2011a).  For most site assessments, the direct contact HSLs are unlikely to become drivers for further investigation or site management as the values are significantly higher than most other soil screening levels and consequently have not been included here.  There are situations where the combined vapour and direct contact pathways can make a difference to the outcome of the assessment. For further information on considering combined vapour and direct contact exposure, refer to Section 3.3 of Friebel and Nadebaum (2011b). The combined HSLs for direct contact can be found in Appendix A of Friebel & Nadebaum (2011a).

Contamination at the levels of the direct contact HSLs are likely to present unacceptable aesthetic considerations which should be addressed in accordance with the discussion in Section 3.6.  Exposure to a contaminated surface (other than of short and temporary duration) at the levels of the direct contact HSLs may also cause an unacceptable short-term vapour exposure risk.

    2.4.12      HSLs and multiple-lines-of-evidence approach
For an assessor to conclude that the vapour intrusion/emission pathways are unlikely to be active or to present a significant risk, the assessor should undertake a multiple-lines-of-evidence approach. This requires the assessor to present several reasoned lines of evidence as to why the pathway is considered inactive or is unlikely to present a significant risk.

The soil and groundwater HSLs provide the principal assessment criteria for open excavations (such as tank removal operations) while greater emphasis is placed on soil vapour HSLs in assessing potential vapour intrusion risks from hydrocarbon sources and groundwater plumes adjacent to or under buildings. In general, evaluating all contaminant phases will provide greater confidence in the outcomes of the site assessment.

Soil vapour measurements can provide a more accurate representation of vapour risks (compared with the soil and groundwater HSLs), depending on site-specific conditions e.g. where soil vapour can be measured directly under conditions that are relevant to the future or continuing use of the site. In high moisture conditions, however, such as occur within the capillary fringe or as a result of seasonal watertable fluctuations, it is not possible to obtain reliable soil vapour readings. In