What Is Interstitial Monitoring?
The hazardous substance UST must have a leak detection system that can indicate the presence of a leak in the confined space between the first and the second wall. Several devices are available to monitor this confined “interstitial” space. (“Interstitial” simply means “between the walls.”) The UST regulations describe these various methods and the requirements for their proper use. You can apply for an exception, called a variance, from the requirement for secondary containment and interstitial monitoring. To obtain a variance you must demonstrate to the regulatory authority that your alternative leak detection method will work effectively by providing detailed studies of your site, proposed leak detection method, and available methods for corrective action.
