Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:2:p6
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 2 (pt 6/21)
Character Range: 54875–57981

subject to international peer review during its development.

Copies of the technical reports can be found in the ASC NEPM Toolbox. Additional information on the development phases of the project, including responses to peer review comments, can be found on the CRC CARE website:
 http://www.crccare.com/publications/technical_reports/hsl_tech_report.html
Assessment of vapour risks is a specialist area. It is the responsibility of contaminated land professionals to become familiar with the limitations of the HSLs and their correct application in site assessment (Friebel & Nadebaum 2011a, 2011b, 2011c).

    2.4.2          HSL methodology
The HSLs were developed to be protective of human health by determining the reasonable maximum exposure from site sources for a range of situations commonly encountered on contaminated sites. As there are many parameter inputs to the methodology, very conservative assumptions have not been made for every parameter as this would result in an unrealistic result arising from the compounding of conservatism. Typically the parameter values selected correspond to the mean or median of the available information, with some parameters corresponding to the 95th percentile. For further information on the rationale for each parameter selected, refer to Friebel and Nadebaum (2011a).

The HSLs apply to the same land use settings as for the interim HILs for VOCCs and include  additional consideration of soil texture and depth to source to determine the appropriate soil, groundwater and soil vapour criteria for the exposure scenario. As with all modelling approaches, the assumptions made regarding the exposure scenario limit the extent of their reasonable application. The main limitations for the HSLs are summarised in Section 2.4.13.

HSLs for soil (Table 1A(3)), groundwater  (Table  1A(4)) and soil vapour (Table 1A(5)) apply to exposure to petroleum hydrocarbons through the dominant vapour inhalation exposure pathway only. Direct contact HSLs have been developed for the incidental soil ingestion, dermal and inhalation exposure pathways. The direct contact HSLs are generally not the risk drivers for further site assessment for the same contamination source as the HSLs for vapour intrusion.  Direct contact exposure should be considered where relevant to the site-specific scenario e.g. an external source in near-surface soils in a residential or recreational setting. Further details can be found in Friebel and Nadebaum (2011a, 2011b, and 2011c).

There are many site-specific, soil-specific and building-specific variables that affect the level of the HSLs and these factors should be considered in the site assessment. Detailed information on the model inputs and assumptions (for example, soil properties, sub-slab attenuation factor, organic carbon content, chemical properties, building parameters) and overall limitations are provided in Friebel and Nadebaum (2011a). A sensitivity analysis was used to evaluate the effect that these parameters have on the derived HSLs (Friebel & Nadebaum 2011c).

A review of vapour models was undertaken by