Risk Ranking Methodology for Contaminated Sites

Client: Ministry of Agriculture and Lands (MAL), Crown Land Restoration Branch (CLRB)

CLRB is responsible for managing contaminated sites on provincial lands in BC, sites of historic industrial activity where no responsible persons exist or can be identified and management has fallen to the province. For most of these sites there is limited information available regarding the extent of contamination or potential human health and ecological risks. CLRB is faced with the challenge of identifying those sites that present the highest potential for risks to human health and the environment. Funds can then be allocated to the highest risk sites for the best use of public funds. To classify sites based on risk, CLRB needed a scientifically based, defensible and systematic methodology to evaluate and rank Crown contaminated lands.

Azimuth was retained by MAL to develop a Risk Ranking Methodology (RRM) to meet this objective, focusing on historic mining sites because of their high potential for metal contaminant effects and the large number of sites where no identifiable owner or operator is taking responsibility. In partnership with Morrow Environmental (now SNC-Lavalin Environment), the RRM was first applied by MAL in 2007 to identify high priority sites (see page 10-11 of the 2008 CLRB Biennial Report). RRM uses a risk-based Preliminary Site Investigation (PSI) to gather key information about each site. This “modified” PSI was trialed by several contractors prior to finalization. The PSI information is then analyzed using a spreadsheet tool, and summarized according to a number of attributes aimed at characterizing potential risks. The summary information (more than 25 attributes) is used in a workshop attended by professional contaminated sites practitioners to evaluate and establish relative rankings of sites and also to recommend management actions to better understand and manage the identified risks.