A generator that accumulates hazardous waste on-site in a tank (read: What is a hazardous waste tank?) must comply with regulations applicable to their generator status.

• A large quantity generator (LQG) must manage its hazardous waste tank in compliance with 40 CFR 265, subpart J.
• A small quantity generator (SQG) must manage its hazardous waste tank in compliance with 40 CFR 262.17(b)(3).  Prior to May 30, 2017 and the implementation of the Generator Improvements Rule these regulations were found at 40 CFR 265.201.

Both of the above regulations require the generator to conduct inspections of various parts of the tank system at one of two frequencies: “at least weekly” or, “at least once each operating day”.

While, “at least weekly” has been widely – though not universally – interpreted to mean one inspection every seven (7) days, and “at least once…” is clear, what is meant by “…each operating day”?

EPA has clarified that “each operating day” has been defined as “every day the tank is in operation (i.e., storing or treating
hazardous waste) and not necessarily just on days the facility is open for business.”

The above is from the EPA document: Introduction to Tanks

By this EPA interpretation, every day hazardous waste is present in a tank is an “operating day”.  This would include weekends and holidays even when the facility is not in operation.