TRH Guidance and Assessment Criteria
The 2013 NEPM for Contaminated Sites included a strong focus on Vapour Intrusion and Soil Vapour, with Health Screening Levels (HSLs) established for a range of contaminants, including volatile TRH bands. Within months of the NEPM being finalised, CRCCARE released their Technical Report 23 on Petroleum Vapour Intrusion (the ‘PVI guidance’), which contained additional advice and Action Levels for responding to TRH contamination in hydrocarbon Vapour Intrusion assessments.
A key difference between the NEPM and the PVI guidance is that the PVI guidance advocates the breakdown of TRH into its aliphatic and aromatic components. This approach, like the TPH-CWG, allows a more rigorous assessment of non-cancer risks against established fraction-specific toxicity values.
ALS now offers fully validated and NATA accredited TRH analysis from >C5 to C16 in the required fractions for direct comparison with the NEPM HSLs, the CRCCARE PVI threshold limits plus the TPHCWG risk-based screening levels (RBSLs) advocated by the US EPA.
ALS validation has proven that hydrocarbons to C and beyond (with sampling modifications) can be reliably analysed from canisters. Comparison of ‘>C10 to C12’ data with the NEPM HSLs for ‘>C10 to C16’ may underestimate risks from diesel and other heavy hydrocarbons as ‘>C10 to C12’ can omit some heavier components. When using ALS data a direct comparison with NEPM HSLs is now possible.