Class A, which includes quantities of less than 55 gallons or 500 pounds.
Class B, which includes quantities of between 55 gallons to 550 gallons, and quantities of between 500 pounds and 5,000 pounds.
Class C, which includes quantities of between 550 gallons and 5500 gallons, and quantities between 5,000 pounds and 50,000 pounds.
Class D, which includes quantities of greater than 5500 gallons or 50,000 pounds.
N.C. Gen. Stat. § 95-191