United States
Environmental
Protection Agency
Solid Waste and
Emergency Response
(5305W) 	
EPA530-R-99-055
PB2000-101 895
February 2000
RCRA, Superfund & EPCRA
Hotline Training Module
introduction to:		
Miscellaneous Units
(40 CFR Fart 264, Subpart X and
40 CFR Part 265, Subparts P, Q, and R)
Updated October 1999

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DISCLAIMER
This document was developed by Booz-Allen & Hamilton Inc. under contract 68-W0-0039 to EPA. It is intended to
be used as a training tool for Hotline specialists and does not represent a statement of EPA policy.
The information in this document is not by any means a complete representation of EPA's regulations or policies.
This document is used only in the capacity of the Hotline training and is not used as a reference tool on Hotline calls.
The Hotline revises and updates this document as regulatory program areas change.
The information in this docume nt may not necessarily reflect the current position of the Agency. This document is
not intended and cannot be relied upon to create any rights, substantive or procedural, enforceable by any party in
litigation with the United States.
RCRA, Superfund & EPCRA Hotline Phone Numbers:
National toll-free (outside of DC area)
Local number (within DC area)
National toll-free for the hearing impaired (TDD)
(800) 424-9346
(703) 412-9810
(800) 553-7672
The Hotline is open from 9 am to 6 pm Eastern Time,
Monday through Friday, except for federal holidays.

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MISCELLANEOUS AND OTHER UNITS
CONTENTS
1.	Introduction 	 1
2.	Regulatory Summary 										 3
2.1	Thermal Treatment Units (Subpart P)										3
2.2	Chemical, Physical, and Biological Treatment Units (Subpart Q) 		4
2.3	Underground Injection (Subpart R) 		5
2.4	Miscellaneous Units (Subpart X)								6
3.	Special Issues	10
3.1	Mobile Hazardous Waste Treatment Units	10
3.2	Land Disposal Restrictions 							 10
3.3	Air Emissions									10

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Miscellaneous and Other Units - 1
1. INTRODUCTION
Congress recognized that it would be impossible for EPA and authorized states to
issue permits to all hazardous waste management facilities before the Resource
Conservation and Recovery Act (RCRA) Subtitle C program became effective in
November 1980, RCRA §3005(e) provides for certain facilities to be treated as though
they had been issued a permit until final administrative action is taken on their permit
applications. This statutory permit is referred to as "interim status." EPA promulgated
interim status management standards in 40 CFR Part 265.
Part 265 contains both general facility standards applicable to all facilities and
requirements for specific hazardous waste management units and treatment processes.
EPA initially promulgated interim status standards for the most common hazardous
waste management units in existence at the inception of the RCRA program: containers,
tanks, surface impoundments, waste piles, land treatment units, landfills, and
incinerators (Part 265, Subparts I through O, respectively). EPA realized, however, that
certain hazardous waste treatment and disposal practices were conducted in other
types of units. As a result, the Agency also promulgated interim status standards for
broadly defined treatment processes that are not performed in any of the previously
listed units. These treatment processes include thermal treatment (Subpart P);
chemical, physical and biological treatment (Subpart Q); and underground injection
(Subpart R).
EPA promulgated final permit standards in Part 264 for all the specific hazardous
waste management units originally set forth in Part 265, Subparts I through O, as well
as both interim status and permit standards for boilers and industrial furnaces (BIFs),
drip pads, and containment buildings. The Agency, however, never established final
permit standards for thermal treatment units in Subpart P; chemical, physical, and
biological treatment units in Subpart Q; or underground injection control (UIC) wells in
Subpart R. As a consequence, facilities operating in interim status pursuant to these
subparts could never receive final permits. In addition, new thermal, chemical,
physical, and biological treatment facilities could not be constructed, since new
hazardous waste facilities need a permit before construction commences.
The promulgation of the Part 264, Subpart X, miscellaneous unit regulations in 1987
bridged the gap between Part 265 and Part 264. Subpart X allows for the construction
and permitting of units that do not meet the Part 264, Subparts I through W and DD,
and Part 266, Subpart H, unit descriptions. It also allows interim status facilities with
units that are not specified in these subparts to become fully permitted, to construct
new units, or to expand existing units.
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.

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2 - Miscellaneous and Other Units
When you have completed this module, you will be able to describe the requirements
for and components of the miscellaneous unit permitting process. Specifically, you
will be able to:
•	Describe the basic requirements and types of units under Part 264, Subpart X,
and Part 265, Subparts P, Q, and R
•	Explain when corrective action applies to these subparts
•	Understand the relationship between Part 264, Subpart X, and Part 265, Subparts
P, Q, and R.
Use this list of objectives to check your knowledge of this topic after you complete the
training session.
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.

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Miscellaneous and Other Units - 3
2. REGULATORY SUMMARY
The RCRA regulations governing the management of hazardous waste at treatment,
storage, and disposal facilities (TSDFs) are divided into general standards that apply to
all facilities and unit- or process-specific standards. All thermal treatment units;
chemical, physical, and biological treatment units; UIC wells; and miscellaneous units
are subject to the general facility standards in Part 264/265, Subparts A through H (with
the partial exception of UIC wells). Accordingly, an owner/operator must comply with
personnel training; general waste analysis; preparedness and prevention procedures;
contingency plans; special requirements for the handling of ignitable, reactive, or
incompatible wastes; corrective action; closure; and any other applicable requirements.
In addition, each type of unit or process must comply with the relevant unit/treatment
process-specific subpart in Part 264/265. This module outlines the unit/treatment
process-specific design and operating requirements for the following types of
hazardous waste management units:
•	Part 265, Subpart P - Thermal Treatment
•	Part 265, Subpart Q - Chemical, Physical, and Biological Treatment
•	Part 265, Subpart R - Underground Injection
•	Part 264, Subpart X - Miscellaneous Units.
2.1 THERMAL TREATMENT UNITS (SUBPART P)
Since incineration was the most prevalent method used to thermally treat hazardous
waste in 1980, EPA established a subpart devoted specifically to this thermal waste
management technique (Subpart O). The Agency realized, however, that hazardous
waste may be thermally treated in units other than incinerators. So as not to discourage
the development and use of alternative thermal treatment processes, EPA also
promulgated interim status regulations for thermal treatment units that do not meet the
definition of an incinerator, boiler, or industrial furnace. Thermal treatment is defined
as the treatment of hazardous waste in a device that uses elevated temperatures as the
primary means to change the chemical, physical, or biological character or composition
of the hazardous waste (§260.10). Thermal treatment units include carbon regeneration
units and devices employing processes such as molten-salt pyrolysis, calcination, wet-
air oxidation, and microwave destruction. Since incinerators are a subset of thermal
treatment units, many of the Part 265, Subpart P, requirements are similar to the Part
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.

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4 - Miscellaneous and Other Units
265, Subpart O, standards.
OPERATING REQUIREMENTS
Before adding hazardous waste to a thermal treatment unit, the unit must be operating
under steady-state (normal) conditions of operation (§265.373). Owners/operators may
use auxiliary fuel or other means to bring the unit to operational readiness before
burning hazardous waste. The owner/operator must also perform waste analysis to
determine the heating value of the waste, the halogen and sulfur content of the waste,
and the concentrations of lead and mercury in the waste (§265.375). In addition,
owners/operators are required to conduct monitoring and inspections of the
temperature and emission control instruments, the stack plume, and all process and
ancillary equipment (§265.377). At closure, all hazardous waste and hazardous waste
residues must be removed from the thermal treatment unit. Finally, unless the thermal
treatment unit receives a special certification, the unit may not treat dioxin-bearing
hazardous wastes (F020, F021, F022, F023, F026, or F027) (§265.383).
OPEN BURNING AND OPEN DETONATION
Open burning and open detonation (OB/OD) of hazardous waste is prohibited in
interim status thermal treatment units, except for OB/OD of waste explosives. Waste
explosives include waste that has the potential to detonate and bulk military
propellants that cannot safely be disposed through other modes of treatment. OB/OD
must be performed in a manner that does not threaten human health or the
environment, such as following minimum distance requirements for treatment near
adjacent properties (§265.382).
2.2 CHEMICAL, PHYSICAL, AND BIOLOGICAL TREATMENT
UNITS (SUBPART Q)
Facilities may conduct chemical, physical, and biological treatment of hazardous waste
in units other than those specifically addressed in Part 265, Subparts I through O, W,
and DD. Examples of treatment processes that are often not performed in RCRA-
defined units include distillation, centrifugation, reverse osmosis, ion exchange, and
filtration. To accommodate these unique units, the Agency promulgated interim status
regulations for units that treat waste by chemical, physical, and biological treatment
technologies in Part 265, Subpart Q. The Agency's primary concern was the safe
containment of hazardous waste, hazardous waste constituents, and treatment by-
products. As a result, Subpart Q standards resemble the container and tank standards
in Part 265, Subparts I and J, respectively.
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.

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Miscellaneous and Other Units - 5
OPERATING REQUIREMENTS
The operating requirements for Subpart Q units specify that waste may not be placed in
the equipment if the waste could cause the process or equipment to rupture, leak,
corrode, or otherwise fail. In addition, where wastes are continuously fed into a
process, the units must be equipped with a feed cut-off system (§265.401).
Subpart Q units must also comply with special requirements for ignitable or reactive
wastes in addition to the general requirements for these wastes that apply to all RCRA
facilities (§265.405). These standards require the owner/operator to remove the
hazardous waste characteristic immediately before or after placement in the treatment
process or equipment. Likewise, Subpart Q units must comply with special
requirements for waste analysis in addition to the general waste analysis requirements
(§265.402). Whenever a waste is to be treated by a process that is substantially different
from any previous processes, the owner/operator must conduct waste analyses and
trial treatment tests or obtain written documentation showing that the treatment will
meet the applicable requirements.
Facilities must also inspect discharge control, safety equipment, and data gathered
from monitoring equipment at least once each operating day. In addition, facilities are
required to inspect the construction materials of the treatment process and confinement
structures at least weekly for corrosion, erosion, or leakage (§265.403). At closure, all
hazardous waste and hazardous waste residues must be removed from treatment
processes or equipment, discharge control equipment, and discharge confinement
structures (§265.404).
2.3 UNDERGROUND INJECTION (SUBPART R)
EPA originally intended to regulate UIC wells disposing of hazardous waste primarily
under the Safe Drinking Water Act (SDWA). At the inception of the RCRA program,
however, many states did not yet have a SDWA-approved UIC program. EPA
promulgated the interim status regulations for existing UIC wells to address the period
when UIC wells were used to dispose of hazardous waste but were not yet subject to
the SDWA. EPA never intended to promulgate Part 264 final permit standards for UIC
wells, since §270.60(b) allows a UIC permit to function as a RCRA permit-by-rule once
corrective action has been performed for all solid waste management units (SWMUs) at
the facility.
Class I and Class V wells used for injecting hazardous waste must have authorization
under both SDWA and RCRA. A well has SDWA authorization once it obtains a permit
issued under 40 CFR Part 144 or 145. A well is considered to have RCRA authorization
when it meets one of the following conditions: qualifies for and maintains RCRA
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.

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6 - Miscellaneous arid Other Units
interim status; obtains a UIC permit and meets the requirements for a RCRA permit-by-
rule; or obtains a RCRA Part B permit for all units, including the operating well.
The first option would allow the well to obtain RCRA interim status. The RCRA
interim status regulations specify that UIC wells injecting hazardous waste are subject
to all the Part 265 general facility standards, except closure (Subpart G) and financial
assurance (Subpart H). The second option allows a well to qualify for a RCRA permit-
by-rule. To obtain a RCRA permit-by-rule, the well must obtain a SDWA underground
injection permit pursuant to Parts 144 and 145 and comply with §144.14 for wells
managing hazardous waste (§270.60(b)). Finally, the UIC well may obtain a final RCRA
permit. UIC wells may receive RCRA permits as miscellaneous units.
Because all Class I and Class V wells used for injecting hazardous waste require
permits or permits-by-rule under RCRA Subtitle C, certain RCRA standards apply to
these wells even if they have a permit-by-rule. Most significantly, they must comply
with corrective action requirements. Likewise, any associated hazardous waste storage
units at the UIC well facility must be permitted and would also be subject to corrective
action.
2.4 MISCELLANEOUS UNITS (SUBPART X)
On December 10,1987, EPA promulgated standards regulating miscellaneous units in
Part 264, Subpart X (52 FR 46946). The promulgation of Subpart X extended RCRA
permit eligibility to UIC wells and to interim status units performing thermal, chemical,
biological, or physical treatment under Part 265, Subparts P, Q, and R. Additionally,
new and innovative technologies managing hazardous waste in units not previously
regulated under RCRA became eligible for RCRA permits as miscellaneous units.
In developing the Subpart X regulations, the Agency wanted to promulgate a new set
of general standards that would cover the diverse technologies and units not yet
covered in Part 264. To accomplish this goal, the Subpart X regulations are general, not
technology-specific. In sum, miscellaneous units are required to be located, designed,
constructed, operated, maintained, and closed in a manner that will prevent any unsafe
releases into the groundwater, subsurface environment, surface water, wetlands, soil
surface, or air. This media-based or pathway-based approach ensures that any
potential problems arising from units are addressed.
The Agency regards the Subpart X regulations as environmentally more protective than
the corresponding interim status regulations found in Part 265, Subparts P, Q, and R.
Since the site-specific Part 264 permit provisions are tailored to specific facilities, these
standards provide better environmental protection. Subpart X is also more flexible, as
it allows new and innovative technologies to receive RCRA permits. In addition, these
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.

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Miscellaneous and Other Units - 7
regulations give the implementing agency the flexibility to develop permit standards
on a case-by-case basis when considering the technology-specific data required to be
submitted by the applicant.
The following portion of the module describes and presents an overview of the types of
units regulated by Part 264, Subpart X, and outlines the types of performance standards
specified in the regulations. In addition, the section summarizes the monitoring,
analysis, inspection, response, reporting, corrective action, and closure requirements
for miscellaneous units.
TYPES OF UNITS COVERED BY SUBPART X
Miscellaneous units are defined as hazardous waste management units where
hazardous waste is managed in a unit other than a container, tank, surface
impoundment, pile, land treatment unit, landfill, incinerator, boiler, industrial furnace,
UIC well, containment building, or unit eligible for a research, development, and
demonstration (RD&D) permit (§260.10). Since Subpart X is intended to serve as a
"catch all" category, the Agency did not develop an all-inclusive list of units designated
as miscellaneous units. The Agency, however, felt it would be helpful to identify
several types of units that may receive permits under Subpart X. The types of units
subject to Subpart X include, but are not limited to:
•	Placement of hazardous waste in geologic repositories other than injection wells
•	Placement of hazardous waste in deactivated missile silos other than injection
wells or tanks
•	Thermal treatment units other than incinerators, boilers, or industrial furnaces
•	OB / OD of waste explosives
•	Chemical, physical, biological treatment units.
The Subpart X regulations do not regulate:
•	Units regulated under other portions of Parts 264 or 266
•	Units excluded from permitting under Parts 264 and 270
•	Underground injection wells (Part 146)
•	RD&D units covered under Part 270.
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.

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8 - Miscellaneous and Other Units
PERFORMANCE OBJECTIVES
The Agency concluded that it would be impossible to set technology-based design and
operating standards for the enormous diversity of technologies eligible for a permit as
a miscellaneous unit. Instead, EPA provided a set of objectives designed to protect
groundwater, surface water (including wetlands), air, and soil from the migration of
hazardous constituents. The performance objectives require permit applicants to
evaluate the potential environmental impacts of the unit or facility and to demonstrate
that the unit will not adversely affect human health and the environment (§264.601).
This performance-based regulatory approach offers several advantages. First, it allows
the Agency the flexibility to address a full range of environmental issues raised by any
waste management situation without the need to develop specific design and operation
conditions. Second, for those Subpart X units resembling conventional units, the
permit may incorporate appropriate requirements from Subparts I through O, W, and
DD, and Part 266, Subpart H. For example, a miscellaneous unit that is similar to a
surface impoundment may be required to have liners and a leachate collection system.
Third, this approach allows the implementing Agency the flexibility to tailor each
permit to meet the particular issues and circumstances based on the technology used,
the types of waste, the site location, and the regional meteorological, climatic, and
hydrogeologic characteristics.
PERMIT REQUIREMENTS
All owners and operators of miscellaneous units must obtain a permit to treat, store,
and/or dispose of hazardous waste. The Subpart X permitting standards require
permit applicants to describe the unit and evaluate the potential environmental
impacts of the unit or facility (§270.23).
The permit application must include information that clarifies and defines the type of
unit for which the owner and operator is seeking a permit. The applicant must
describe the unit, its physical characteristics, construction materials, and dimensions.
The bulk of the application is expected to contain detailed plans and engineering
reports describing the unit location, design, construction, operation, maintenance,
monitoring, inspection, and closure.
In addition, each of the environmental performance standards must be assessed. The
permit application must contain information on the potential pathways of human or
environmental exposure to hazardous waste or hazardous constituents. Where this
assessment indicates that releases to air, surface water, or groundwater are possible,
the applicant is expected to provide details on the potential magnitude and nature of
such
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.

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Miscellaneous and Other Units - 9
exposures, as well as detailed hydrologic, geologic, and meteorologic assessments and
maps for the region surrounding the site (§270.23).
MONITORING, ANALYSIS, INSPECTION, RESPONSE, REPORTING, AND
CORRECTIVE ACTION
Each miscellaneous unit must have monitoring, testing, analytical data, inspections,
response, and reporting procedures. These procedures ensure that a unit is in
compliance with the general performance standards. The required activities are
included in the unit's permit. At a minimum, the monitoring program must be capable
of determining the unit's impact on groundwater, air quality, surface and subsurface
contaminant migration; although in many cases, monitoring of a specific medium will
not be necessary. It should also ensure compliance with the general inspection
requirements, testing and maintenance of equipment schedules, reporting
requirements, and corrective action (§264.602),
CLOSURE
Units that cannot clean-close require post-closure care. The unit must meet all of the
environmental performance standards, as well as the appropriate post-closure
standards of Part 264, Subpart G, during the post-closure care period (§264.603).
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.

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10 - Miscellaneous and Other Units
3. SPECIAL ISSUES
Keep in mind the following points about how miscellaneous units relate to other
RCRA issues.
3.1	MOBILE HAZARDOUS WASTE TREATMENT UNITS
Mobile treatment units (MTUs) are designed to move from facility to facility treating
waste on site. These units must comply with the applicable interim status or permitted
unit standards. If the MTU does not meet the description of any of the units regulated
under Subparts I through O, W, and DD of Part 264 or Subpart H of Part 266, then
permitting under Part 264, Subpart X, is required. Current regulations require MTUs to
undergo RCRA permit procedures at each site of operation. See the module entitled
Permits and Interim Status for more information on permitting MTUs.
3.2	LAND DISPOSAL RESTRICTIONS (LDR)
Many units permitted under Subpart X also meet the definition of a land disposal unit
under RCRA (i.e., underground mines or caves). Therefore, any hazardous waste
prohibited from land disposal must be treated to meet applicable Part 268 treatment
standards prior to placement in the unit.
The Part 268 land disposal restrictions' applicability to OB/OD units requires further
clarification. When waste explosives are detonated in RCRA OB/OD units, wastes are
typically managed on the ground. The Agency has concluded that OB/OD of waste
explosives does not constitute land disposal because it is treatment rather than
disposal. This may not be true, however, in cases where the residues from the OB/OD
operation remain a hazardous waste. In these cases, the practice of allowing the
remaining wastes to remain on the ground or to seep into the ground may be
considered land disposal.
3.3	AIR EMISSIONS
When appropriate, a miscellaneous unit's permit must include the air emission control
requirements of Subparts AA, BB, and CC. Subpart X miscellaneous units are
permitted on a case-by-case basis with terms and provisions as needed to protect
human health and the environment. Appropriate portions of the existing technical
standards for other waste management units, such as the air emission standards, will
be incorporated into a permit as necessary.
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.

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