Brownfield Development - Featured Articles

Risk Assessment in Brownfield Redevelopment

Barenco Site Remediation Services

Some Brownfields have unique environmental issues that make them difficult to redevelop. What if the cost to excavate and dispose contaminated soil exceeds the redevelopment value of the land? What if the property's value lies in an existing building, but the contaminants are beneath that building? Or what if the contaminants are in the ground water and remediation in any reasonable timeframe is uncertain?

A very useful tool in Brownfield redevelopment is the Ministry of Environment's Standards development process via Risk Assessment. The objective of a Risk Assessment is to develop site specific remediation Standards that represent environmentally safe levels for soil and ground water contaminants on a property.

Risk Assessment procedures were first developed by the United States Environmental Protection Agency (EPA) and adopted by the Canadian Council of the Ministers of Environment (CCME) and are now used in several provinces. Site specific details, including the geological and hydrogeological setting and future use of the land, are considered when developing the soil and ground water remediation Standards.

The ecological and human health risks posed by the contaminants are determined by the types of chemicals, their concentrations and toxicities, and the extent to which various receptors might be exposed. In simple terms, a Risk Assessment evaluates the source (contaminant), the pathway (e.g. ground water ingestion) and the receptor (e.g. human) to determine acceptable levels for each contaminant.

When the MOE developed the generic Standards found in Tables 2 to 5, these same Risk Assessment procedures were used. However, in the absence of any site specific characteristics, a worst case set of assumptions regarding receptors and pathways was employed in order to derive remediation Standards that would be protective of all receptors on all properties. By the very nature of the process of setting broadly applicable clean up Standards, the most stringent Standards are found in the generic tables.

The advantage of a site specific Risk Assessment is that it creates less stringent Standards than those in the generic Tables, but is equally protective of the environment. The end result is re-defining "contamination" at the property, resulting in lower remediation costs.

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