How can a facility determine if they must report a release of a mixture containing hazardous substances under CERCLA section 103?

If the quantity of all of the hazardous constituents of the mixture or solution is known, a person in charge of a vessel or facility must report a release of a mixture of hazardous substances when an RQ or more of a hazardous constituent is released; or, if the quantity of one or more of the hazardous constituents of the mixture or solution is unknown, notification is required where the total amount of the mixture or the solution released equals or exceeds the RQ for the constituent with the lowest RQ (40 CFR 302.6(b)(1)).

For most hazardous wastes, the waste streams should be treated like any other mixture and the person in charge should apply the mixture rule. If the concentrations of all of the hazardous substances in the waste are known, reporting is required when an RQ or more of a hazardous constituent is released. If the concentrations of the substances are unknown, the RQ of the waste stream or unlisted waste applies.

For hazardous waste streams K169, K170, K171, K172, K174, and K175, the concentration of the hazardous constituents may be assumed based on the table in 40 CFR 302.6(b)(1)(iii). A November 8, 2000 (65 FR 67132) final rule inadvertently removed the maximum observed constituent concentrations for K169, K170, K171, and K172 from the table in that section when it was amended to include the maximum observed constituent concentrations for listed hazardous wastes K174 and K175. On February 22, 2012 (77 FR 10387), EPA took direct final action to reinstate the observed constituent concentrations for K169, K170, K171, and K172 that were inadvertently removed. The final rule became effective April 23, 2012.