55    APPLYING THE MIXTURE AND DERIVED-FROM RULES
TO OLD LANDFILL SITES
David V. Kalet, Environmental Engineer
Amoco Oil Company
Whiting, Indiana 46394
PURPOSE AND SCOPE
This paper is intended to assist facilities in their interpretation of the mixture and derived-from
rules as they specifically apply to listed wastes contained in old landfill sites, and will address the
following issues:
1. What is the regulatory status of:
a. wastes disposed of prior to the effective listing date?
b. disposal units that contain newly listed wastes?
c. rainwater runoff from these sites?
d. leachate that has been produced from these disposal units?
2. How can a facility determine if rainwater runoff and groundwater has been mixed with
leachate so as to become regulated as a listed waste?
3. What compliance options are available to facilities based on past agency rulings and
interpretations of this rule?
BACKGROUND
Prior to the enactment of the Resource Conservation and Recovery Act (RCRA) and subsequent
regulations, process residues were routinely managed in onsite impoundments and landfills. Many of
these units received materials that have since become regulated as hazardous wastes. The regulatory
status of the site components are of critical importance when assessing site liabilities or developing
plans for project work at sites that contain wastes currently listed in 40 CFR part 261, subpart D.
The basis for the regulatory authority at these affected sites begins with two hazardous waste
definitions collectively referred to as the "Mixture and Derived-From Rules." EPA stated these definitions were essential to regulate waste mixtures to prevent generators from evading Subtitle C requirements by simply commingling listed wastes with nonhazardous wastes to dilute rather than treat the
wastes.
Mixture Rule
"A solid waste is a hazardous waste if it is a mixture of solid waste and one or more
hazardous wastes listed in Subpart D. . ."
Derived-From Rule
"any solid waste generated from the treatment, storage, or disposal of a hazardous waste,
including any sludge, spill residues, ash, emission control dust or leachate is a hazardous
waste."
••I
REGULATORY STATUS OF WASTES, LANDFILLS, RAINWATER RUNOFF,
AND LEACHATE
In the preamble to the Land Disposal Regulations (LDRs), USEPA clarified its authority over
wastes disposed prior to the effective date by stating:
". . . hazardous waste listings are retroactive, so that once a particular waste is listed, all
wastes meeting that description are hazardous wastes no matter when disposed."2
USEPA has made an important distinction over its authority in regulating surface impoundments
containing these wastes:
47th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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