40 CFR Appendix V to Part 265 - Examples of Potentially Incompatible Waste

Appendix V to Part 265 - Examples of Potentially Incompatible Waste

Many hazardous wastes, when mixed with other waste or materials at a hazardous waste facility, can produce effects which are harmful to human health and the environment, such as (1) heat or pressure, (2) fire or explosion, (3) violent reaction, (4) toxic dusts, mists, fumes, or gases, or (5) flammable fumes or gases.

Below are examples of potentially incompatible wastes, waste components, and materials, along with the harmful consequences which result from mixing materials in one group with materials in another group. The list is intended as a guide to owners or operators of treatment, storage, and disposal facilities, and to enforcement and permit granting officials, to indicate the need for special precautions when managing these potentially incompatible waste materials or components.

This list is not intended to be exhaustive. An owner or operator must, as the regulations require, adequately analyze his wastes so that he can avoid creating uncontrolled substances or reactions of the type listed below, whether they are listed below or not.

It is possible for potentially incompatible wastes to be mixed in a way that precludes a reaction (e.g., adding acid to water rather than water to acid) or that neutralizes them (e.g., a strong acid mixed with a strong base), or that controls substances produced (e.g., by generating flammable gases in a closed tank equipped so that ignition cannot occur, and burning the gases in an incinerator).

In the lists below, the mixing of a Group A material with a Group B material may have the potential consequence as noted.

Group 1-A Group 1-B
Acetylene sludge Acid sludge
Alkaline caustic liquids Acid and water
Alkaline cleaner Battery acid
Alkaline corrosive liquids Chemical cleaners
Alkaline corrosive battery fluid Electrolyte, acid
Caustic wastewater Etching acid liquid or solvent
Lime sludge and other corrosive alkalies
Lime wastewater Pickling liquor and other corrosive acids
Lime and water Spent acid
Spent caustic Spent mixed acid
Spent sulfuric acid

Potential consequences: Heat generation; violent reaction.

Group 2-A Group 2-B
Aluminum Any waste in Group 1-A or 1-B
Zinc powder
Other reactive metals and metal hydrides

Potential consequences: Fire or explosion; generation of flammable hydrogen gas.

Group 3-A Group 3-B
Alcohols Any concentrated waste in Groups 1-A or 1-B
Water Calcium
Metal hydrides
SO2Cl2, SOCl2, PCl3, CH3SiCl3
Other water-reactive waste

Potential consequences: Fire, explosion, or heat generation; generation of flammable or toxic gases.

Group 4-A Group 4-B
Alcohols Concentrated Group 1-A or 1-B wastes
Aldehydes Group 2-A wastes
Halogenated hydrocarbons
Nitrated hydrocarbons
Unsaturated hydrocarbons
Other reactive organic compounds and solvents

Potential consequences: Fire, explosion, or violent reaction.

Group 5-A Group 5-B
Spent cyanide and sulfide solutions Group 1-B wastes

Potential consequences: Generation of toxic hydrogen cyanide or hydrogen sulfide gas.

Group 6-A Group 6-B
Chlorates Acetic acid and other organic acids
Chlorine Concentrated mineral acids
Chlorites Group 2-A wastes
Chromic acid Group 4-A wastes
Hyphochlorites Other flammable and combustible wastes
Nitric acid, fuming
Other strong oxidizers

Potential consequences: Fire, explosion, or violent reaction.

Source: “Law, Regulations, and Guidelines for Handling of Hazardous Waste.” California Department of Health, February 1975.

[45 FR 33232, May 19, 1980, as amended at 71 FR 40276, July 14, 2006]