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What is an underlying hazardous characteristic?
During the mid-90s, EPA began regulating underlying hazardous constituents (UHCs) in characteristic wastes. This was in response to a court ruling that 1) land disposal restriction (LDR) treatment standards may apply to characteristic wastes after they are no longer characteristic and 2) EPA must address “underlying hazardous constituents” in the LDR standards for characteristic hazardous wastes. [Chemical Waste Management et al. vs. EPA et al.; U.S. Court of Appeals, D.C. Circuit; 976 F.2d 2; September, 25, 1992]
In order to effect this change to the regulations, EPA needed a way to identify UHCs in characteristic wastes. The agency had previously harmonized all of the concentration-based LDR standards by establishing universal treatment standards (UTS) in §268.48 that simplify LDR compliance when multiple waste codes apply. [September 19, 1994, 59 FR 47982] Realizing that the UTS could help the agency address UHCs, EPA defined a UHC in §268.2(i) as any UTS constituent in a hazardous waste that can reasonably be expected to be present in the waste above the UTS level at the point of generation. [April 8, 1996, 61 FR 15560]
In the LDR standards themselves [§268.40 table], EPA added a few words to the end of most standards for characteristic wastes: “and meet §268.48 standards.” When these words are present, in addition to meeting the standard for the characteristic itself, treatment to meet the UTS for any UHC is required before land disposal.
From an historical perspective, even though the UTS initially had nothing to do with UHCs, they presented a way to address this issue in characteristic wastes before land disposal. And now the two are inextricably linked by regulatory definition. For more compliance morsels, visit our website.
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