The regulations or guidelines to follow are dependent on your site location, who has jurisdiction over the site, and the purpose for which the assessment or characterization is being completed.
Often times assigning of the applicable criteria may be a result of consultation with the regulators.
Most often, provincial regulations apply, unless the sites are owned by the federal government. However, provincial regulation may not provide standards or guidelines for all aspects of a site assessment project, at which point the regulator may request that federal guidelines be used.
Here is a quick link to the most common regulations and guidelines used in Canada: https://www.bvlabs.com/resources/regulations-guidelines