Low Probability Receptor

Ian Terry, Millenium EMS Solutions Ltd.

In most cases, assessment, remediation and subsequent reclamation (herein referred to as remediation) of contaminated sites in Alberta are driven by the regulatory requirement that these sites meet guidelines that are protective of all receptors and exposure pathways which are linked, by definition, to a given land use. Unless exposure pathways can be excluded, thereby removing applicability of receptors on a site-specific basis where permitted under the Alberta Environment and Parks (AEP) Tier 2 process, the guidance requires that all receptors associated with the respective land use be considered as present. There is no explicit ability to adjust the remediation process to account for sites where the receptor does not exist and is unlikely to occur in the future (i.e., Low Probability Receptors [LPRs]) nor is there a defined process to modify receptor characteristics to be more reflective of site conditions. Thus, for a certain number of sites in Alberta, remediation criteria are driven to end-points that are disconnected from site receptors, either by non-existent receptors or pathways which may have a very low probability of future occurrence or by receptor profiles that are not appropriate for site circumstances. In relation to future receptors, examples of LPRs could include dugouts, residences, drinking water wells or absent ecological taxa. In relation to existing receptors, receptor profiles modification examples could include eco-site controlled vegetation, ecological communities vs individual species, characteristics of residential buildings.

The project is aimed at assessing the probability of certain receptors occurring in different areas of the province, and using this to develop a framework under which low probability receptors could be excluded when establishing remediation targets.

2018 Regulatory Precedent Report
2018 Current Precedent & Probability Derivation Report
2018 Presentation
2018 Update
2019 Event Presentation – May 2, 2019
2019 Net Benefits Analysis