What is a Contaminated Site?
A contaminated site is one at which levels of some contaminant, typically a chemical (e.g., benzene) or a mix of chemicals (e.g., diesel fuel), found in the soil, water or air at the site are potentially harmful to people or living organisms.
What is Remediation?
Remediation is the process of minimizing the harmful effects of contamination to people and the environment, by removing the contaminant (e.g., by excavating contaminated soil for off-site treatment/disposal) and/or by reducing contaminant levels (e.g., by chemical amendments) to an acceptable level that is safe for people and the environment.
How “Clean” is Clean?
An important aspect of remediation is reducing contaminant concentrations to levels below which the site is deemed “clean”, but the definition of what is meant by “clean” is not always straightforward.
In cases of common contaminants, regulators in many countries have developed their own standards for remediation; these may vary between countries and/or jurisdictions. These may include a range of standards or guideline values, based on factors such as soil matrix (e.g., coarse vs fine grained) and type of setting (e.g., industrial vs residential) and more. For mixtures of chemicals and less common contaminants, there may be no regulatory standards or guidelines; in those cases, the consultant may need to develop such criteria, for example, using toxicological data and risk assessment approaches (more on that later).
Phased Approach to Remediation
Most remediation projects are by necessity executed in a phased manner, generally with incremental increases in costs as we move through the phases of a typical remediation project:
1. Scoping Study
The first step for most remediation projects is to carry out some sort of scoping study, which uses already available information to provide an overview of site conditions, issues and a general plan for project phases. This may be done as a desktop study, or if more information is needed, with the addition of a site visit or meetings with key stakeholders. A typical scoping study can be completed in one to two weeks.
The main outcome here is a Scoping Report that summarizes available information, site conditions and sampling plan for site investigation.
