6 Colo. Code Regs. § 1007-3-100.3.30
For the purposes of these sections, hazardous waste treatment, storage, and disposal units are classified according to the method or methods used to manage hazardous wastes. These classes are ranked from I- IV with class I being the highest class.
Class I includes those unit(s) of a facility which manage hazardous wastes in landfills, disposal corrective action management units ("CAMUs"), or underground injection wells pursuant to Parts 264, 265, and 100 of these regulations.
Class II includes those unit(s) of a facility which manage hazardous wastes in surface impoundments, land treatment facilities, waste piles, or treatment/storage CAMUs, or which incinerate hazardous waste or burn hazardous waste in boilers or industrial furnaces, or which are research, pilot, or RD&D units pursuant to Parts 264, 265, and 100 of these regulations.
Class III includes those unit(s) of a facility used to manage hazardous wastes in tanks or containers, waste piles, containment buildings, or any unit used for physical, chemical, biological, or thermal treatment of hazardous waste pursuant to Parts 264, 265, and 100 of these regulations, except those units listed in Classes I or II.
Class III also includes hazardous waste management units associated with resource recovery, namely, treatment or storage of the hazardous waste residues generated from a resource recovery facility. Such units associated with resource recovery are subject to the reduced fee requirements described further in § 100.31.
Class IV includes those hazardous waste management facilities that qualify for a permit by rule under § 100.21.
6 CCR 1007-3-100.3.30