Primary Research Organization: Millennium EMS Solutions Ltd.
Start Date: June 2021
Anticipated End Date: Completed; Under review
Project Summary and Scope of Work
The Alberta Tier 1 Soil and Groundwater Remediation Guidelines (AEP, 2019a) for protection of Domestic Use Aquifer (DUA) are based on a groundwater model which assumes that shallow groundwater is a DUA. There is a process within the Tier 2 guidelines (AEP, 2019b) for the exclusion of the DUA pathway when there is a 5 m or greater isolating layer between the base of contamination and the top of any underlying DUA. However, in many cases the shallow groundwater does not qualify as a DUA but the requirements for excluding the pathway are not met (e.g., hydraulic conductivity does not meet the isolating layer criteria).
During the initial phase of this project (MEMS, 2018), a multi-layer groundwater model was proposed based on a modification of the existing Tier 1 groundwater model, adjusted to account for vertical transport through clean saturated (instead of unsaturated) soils and dilution within a deeper DUA. This proposed model was intended to align hydrogeological assessment with risk assessment particularly for use when the DUA is a critical pathway and shallow groundwater is not within a DUA, but the pathway cannot be unconditionally eliminated (i.e., insufficient data to demonstrate adequate isolating unit, isolating unit does not meet elimination requirements, or a specific substance is not eligible for elimination).