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Underlying Hazardous Constituents

This is the waste designation decision matrix provided by the Small Business and Local Government Assistance Program to aid businesses in deciding how certain wastes must be handled.

Even when a waste is determined to be “hazardous” for a certain characteristic, other potential hazards to our environment may still exist. For that reason, the U.S. Environmental Protection Agency requires treatment of any underlying hazardous constituents that are “reasonably expected” to be present in a variety of characteristic wastes (this requirement extends to almost all characteristic wastes) unless:

  • treated waste is managed in a Clean Water Act system or equivalent; or
  • treated waste is managed in a Class 1 Safe Drinking Water Act system (underground injection wells).

“Underlying hazardous constituents” refers to any constituents “reasonably expected” to be present in the waste at the point of generation above the concentration-specific Universal Treatment Standard (except vanadium and zinc).

Generators must now identify—and treatment, storage, and disposal facilities must treat—all underlying hazardous constituents in most characteristic wastes (see table in 40 CFR 268.40   to verify).