Which regulation outlines the definition of "Reportable Quantity" of hazardous substances?

The regulation that outlines the definition of "Reportable Quantity" of hazardous substances is found in 40 CFR 302.4. This section specifically defines what constitutes a reportable quantity for different hazardous substances, indicating the threshold amounts that trigger reporting requirements to federal authorities in case of releases into the environment. Understanding this regulation is essential for ensuring compliance with the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), which mandates reporting of hazardous substance releases that exceed these defined quantities.

While 40 CFR 117.3, 40 CFR 110.3, and 40 CFR 330.5 address various other aspects of pollution regulation and emergency planning, they do not provide the specific definition of reportable quantities related to hazardous substances. Each regulation serves a different purpose; for instance, 40 CFR 117.3 deals with the determination of reportable discharge of oil, and 40 CFR 110.3 focuses on the definition of "discharge of oil." Thus, the importance of 40 CFR 302.4 lies in its direct relevance to reporting requirements for hazardous substances, making it the correct choice for this question.