At the end of June 2007, Alberta Environment released new guidelines for the remediation of contaminated sites: Alberta Tier 1 Soil and Groundwater Remediation Guidelines and Alberta Tier 2 Soil and Groundwater Remediation Guidelines. The framework for the management of contaminated sites is designed to achieve three policy outcomes: pollution prevention, health protection and productive use. Under this framework, three management options are provided: Tier 1, Tier 2 and Exposure Control.
Within a given land use, sites will fall into a range of sensitivities because of differences in receptors and site conditions. For example, workers on a construction site experience a different exposure than a baby living on a residential property. Tier 1 remediation guidelines are generic. They are developed to protect the more sensitive end of the range and can be used at most sites without modification. The Tier 1 approach is based on the assumption that all exposure pathways and receptors relevant to a particular land use are actually present. Tier 2 remediation guidelines allow the consideration of site-specific conditions through the modification of Tier 1 guidelines and/or removal of exposure pathways that may not be applicable to the site. Exposure Control involves risk management through exposure barriers or administrative controls based on site-specific risk assessment.
The Tier 1 remediation guidelines are simple tabular values that require minimal site information. Conservative assumptions about soil and groundwater characteristics have been used to develop Tier 1 guidelines to protect sites likely to be sensitive to contamination. Sites that may be more sensitive than conditions assumed in the Tier 1 guidelines are better dealt with under the Tier 2 guidelines.
The Tier 2 guidelines usually require more information from the site than the Tier 1 guidelines, resulting in a more tailored approach. Tier 2 guidelines may be more restrictive or less restrictive than Tier 1 values depending on the sensitivity of the site. Less sensitive sites may have Tier 2 guidelines that are less restrictive than Tier 1 values, however the same level of human and ecological health protection would be delivered because they are tailored to that specific site.
The same level of human or ecological protection, human health and ecological endpoints must be maintained at all management Tiers. Changes to endpoints require ongoing administrative controls or site management and therefore would be considered under Exposure Control. When adverse effects are evident, contaminants must be managed to alleviate adverse effects, regardless of whether a site meets Tier 1 or Tier 2 remediation guidelines.
The Tier 1 and 2 guidelines replace the Alberta Soil and Water Quality Guidelines for Hydrocarbons at Upstream Oil and Gas Facilities (2001 Upstream Guidelines). Also, soil monitoring and management programs at approved facilities will adopt the new guidelines as outlined in their operating approval and Soil Monitoring Directive.