United States
Environmental
Protection Agency
Solid Waste and
Emergency Response
(5305W)
EPA530-R-99-054
 PB2000-101 894
  February 2000
     RCRA, Superfund & EPCRA
         Hotline Training Module
      Introduction to:
             Land Disposal Units
       (40 CFR Parts 264/265, Subparts K, L, M, N)
             Updated October 1999

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                                         DISCLAIMER

This document was developed by Booz-Allen & Hamilton Inc. under contract 68-WO-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,
                        RCRA, Superfund & EPCRA Hotline Phone Numbers:

           National toll-free (outside of DC area)                           (800) 424-9346
           Local number (within DC area)                                 (703) 412-9810
           National toll-free for the hearing impaired (TDD)                  (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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                      LAND DISPOSAL UNITS
                             CONTENTS
1.  Introduction	:	  1

2.  Regulatory Summary	  2
   2.1 Surface Impoundments	  2
   2.2 Waste Piles	  5
   2.3 Landfills	  7
   2.4 Land Treatment Units	  9

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                                                               Land Disposal Units -1
                           1.  INTRODUCTION
Subtitle C of the Resource Conservation Recovery Act (RCRA) creates a cradle-to-grave
management system for hazardous waste to ensure proper treatment, storage, and
disposal in a manner protective of human health and the environment. Under RCRA
3004(a), Congress authorized EPA to promulgate regulations establishing design and
operating requirements for land disposal units (LDUs).  The requirements are intended
to minimize pollution resulting from the disposal of hazardous waste in or on the land.
The statute lists nine types of LDUs.  RCRA 3004(k) defines land disposal as
placement of hazardous waste in any of the following:

     Landfill                              Salt dome formation
     Surface impoundment                 Salt bed formation
     Waste pile                           Underground mine
     Injection well                         Underground cave
     Land treatment facility

EPA has promulgated unit-specific technical standards for four of these LDUs within
the treatment, storage, and disposal facility (TSDF) requirements of Part 264/265. This
module provides an overview of the requirements for these four LDUs: landfills,
surface impoundments, waste piles, and land treatment units. LDUs that do not
qualify as one of these units are considered miscellaneous units (see the module
entitled Miscellaneous and Other Units for more details).

When you have completed this module, you will be able to summarize the land
disposal unit standards and list the relevant statutory and regulatory citations.
Specifically, you will be able to:

     Cite the statutory and regulatory minimum technological requirements

     Summarize the differences between interim status (Part 265)  and permitted (Part
      264) standards for land disposal units

     Find the definition of "surface  impoundment" and distinguish surface
      impoundments from tanks

     Describe surface impoundment retrofitting and retrofitting variance procedures

     Explain the connection between land disposal unit standards, post-closure, and
      groundwater monitoring.

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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 2 - Land Disposal Units
                      2.   REGULATORY SUMMARY
 Regulations governing surface impoundments, waste piles, land treatment units, and
 landfills appear under Subparts K through N of Part 264/265. The standards for
 permitted and interim status units address, among other things, design and operating
 requirements, including liners and leachate collection and removal systems (LCRS);
 closure and post-closure requirements; and special standards for ignitable, reactive,
 and dioxin-containing wastes. In addition to these unit-specific requirements, LDUs
 managing hazardous waste are subject to the general facility standards found in
 Subparts A through E of Part 264/265, as well as the appropriate groundwater
 monitoring, closure and post-closure, and financial assurance requirements.

 For each unit discussed, this module addresses five topic areas: design and operation,
 inspections, response actions, closure and post-closure, and special issues. This format
 will enable you to compare and contrast the regulations for each unit.
2.1   SURFACE IMPOUNDMENTS

Subpart K of Part 264/265 contains the design and operating standards for surface
impoundments used to treat, store, or dispose of hazardous waste. Surface
impoundments are very similar to landfills in that both units are either a natural
topographic depression, man-made excavation, or diked area formed primarily of
earthen materials, such as soil (although the unit may be lined with man-made
materials).  The units are, however, very different in their use. Surface impoundments
are generally used for temporary storage or treatment, whereas a landfill is an area
designated for final waste disposal.  Therefore, while the design and operating
standards are very similar, the closure and post-closure standards differ.

Most of the design, operating, and inspection requirements are, in fact, very similar for
surface impoundments, waste piles, and landfills. The requirements are discussed in
detail in this section, with successive sections referring to this section for specifics.

DESIGN AND OPERATION

In developing design and operation requirements for surface impoundments (as well
as landfills and waste piles), EPA adopted a regulatory goal of minimizing the
formation and migration of leachate to the adjacent subsurface soil, groundwater, and
surface water.

These comprehensive technical requirements for surface impoundments are the
minimum technological requirements (MTRs) mandated by RCRA 3004(o)(l)(A) and

 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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                                                                Land Disposal Units - 3
3004(o)(4).  These sections require a double liner, a LCRS, and a leak detection system
(264.221(c) and 265.221(a)). These MTRs apply to all new units, lateral expansions,
and replacement units for which construction (or reuse) commences after July 29,1992.
New, lateral expansion, and replacement units for which construction (or reuse) began
between July 15,1985, and July 29,1992, were required to have only the double liner
and LCRS.  Also, certain surface impoundments not subject to these MTRs are subject
only to single liner requirements (264.221 (a)).

The double liner system consists of a top liner to prevent migration of hazardous
constituents into the liner and a composite bottom liner consisting of a synthetic
geomembrane and three feet of compacted soil material. The unit must also be
equipped with an LCRS, which also serves as-the leak detection system. The LCRS,
along with the leak detection system drainage layers, must be designed with a  bottom
slope of at least one percent, be made of materials chemically resistant to the wastes
placed in the unit, and be able to remove the liquids at a specified minimum rate.  The
LCRS itself must be designed to collect liquids in a sump and subsequently pump out
those liquids. In addition to the performance and design requirements, the LCRS must
be located between the liners immediately above the bottom composite liner, enabling
the LCRS to collect the largest amount of leachate, while also representing the most
efficient place to identify leaks.

A surface impoundment must also be designed to prevent the flow of liquids over the
top of an impoundment (or overtopping) and ensure the structural integrity of  any
dikes.  Also, 264.222 requires that the owner or operator establish a site-specific
leachate flow rate, called the action leakage rate (ALR), to indicate when each regulated
unit's system is not functioning properly.

None of these technologies will be effective if the impoundment is installed improperly
or constructed of inferior materials. To ensure that a surface impoundment meets all
technical criteria, EPA requires a construction quality assurance (CQA)  program. The
CQA program requires a CQA  plan that identifies how construction materials and their
installation will be monitored and tested and how the results will be documented
(264.19). The CQA program is developed and implemented under the direction of a
registered professional engineer, who must also certify that the CQA plan has been
successfully carried out and that the unit meets all specifications before any waste may
be received in the unit.

INSPECTION

In addition to the general inspection requirements found at 264/265.15, there are two
types of specific inspections required at LDUs. The first inspection requirement
addresses the design and structural integrity of the unit (264/265.226). The owner
and operator must inspect liners and covers for any problems after construction or

  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 - Land Disposal Units
 installation, and continue inspections weekly and after storms to monitor for evidence
 of deterioration, malfunctions, improper operation of overtopping systems, sudden
 drops in the level of the impoundment contents, and severe erosions of dikes and other
 containment devices.

 In the second inspection requirement, owners/operators must monitor leak detection
 sumps at least weekly to measure the amount of liquid in the sump and determine
 whether the ALR has been exceeded. This is designed to verify both liner integrity and
 leachate pump efficiency. If a leak exceeds the ALR, the owner and operator must
 notify the Agency and respond in accordance with the response action plan
 (264/265.223).

 RESPONSE ACTIONS

 There are also two different types of response actions for the design and performance of
 the unit. The response action for the performance of the unit is determined by the
 terms of the response action plan, triggered when the ALR has been exceeded
 (264/265.223). If the action leakage rate has been exceeded, the owner and operator
 must notify the Regional Administrator; determine what short- term actions must be
 taken (e.g., shut down of the facility for repairs); determine the location, size, and cause
 of any leak; and send the assessments to the Region.

 There are also emergency repair provisions for unit design failure at permitted
 facilities only (264.227). If there is an indication of a failure  of the containment system
 (e.g., a sudden drop in the level of the contents not attributable to changes in the flow in
 or out of the impoundment), the surface impoundment must be removed from service.
 When this occurs, the owner and operator must follow the procedures in the
 contingency plan, including any necessary emergency repairs.

 CLOSURE

 Closure of a hazardous waste surface impoundment can take one of two forms.  The
 first option, called clean closure, requires the owner and operator to remove or
 decontaminate all wastes and unit components at closure  (264/265.228(a)(l)).  If the
 unit cannot be clean-closed, then the owner and operator must employ the second
 alternative.  Under this approach, wastes are left in place  and stabilized, free liquids are
 removed, and a cap or cover is placed on top of the waste. Since surface
 impoundments are generally used for storage, the second option is equivalent to
 closing as a landfill and requires the operator to take certain  precautions for a set time
period after closure (known as post-closure care (264/265.228(a)(2) and (b))).
 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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                                                               Land Disposal Units - 5
REGULATIONS FOR SPECIAL WASTES

The regulations place special requirements on surface impoundments that handle
ignitable or reactive wastes because these wastes require continuing protection from
conditions that could cause them to ignite or react (264/265.229).

Additionally, 264/265.230 prohibit the placement of incompatible waste or materials,
as described in Appendix V of Part 264/265, in the same surface impoundment unless
certain precautions are taken.

Further, if an owner/operator of a surface impoundment plans to manage dioxin-
containing waste (F020, F021, F022, F023, F026, and F027), they must employ a special
management plan approved by the Regional Administrator (264.231). These wastes
can only be disposed of in a permitted surface impoundment.

SURFACE IMPOUNDMENT RETROFITTING

Owners and operators of existing surface impoundments that become subject to RCRA
as the result of a new hazardous waste listing or characteristic must retrofit or cease
receipt of hazardous waste and begin the closure process within four years of the
promulgation of the listing or characteristic. For example, owners and operators of
surface impoundments which became subject to RCRA as the result of the
promulgation of the Toxicity Characteristic waste codes on March 29,1990, were
required to retrofit those units to meet the minimum technology requirements or cease
receipt of hazardous waste and begin the closure process by March 29,1994 (55 FR
11798; March 29,1990).

SURFACE IMPOUNDMENT VS. TANK

The definitions of surface impoundment and tank are very similar and tend to create
confusion. The major difference in the two definitions is what provides the structural
support to the unit. Surface impoundments are supported by earthen materials while
tanks are supported by non-earthen materials (e.g., wood, concrete, steel, plastic). In
determining whether a unit is supported by earthen or non-earthen material, it should
be evaluated as if it were free-standing and filled to its design capacity. If the unit can
maintain its structural integrity it is considered a tank. If the unit cannot retain its
structural integrity, it is considered a surface impoundment.

2.2   WASTE PILES

Regulations governing the management of hazardous waste in waste piles are found in
Part 264/265, Subpart L. Waste piles, which are essentially noncontainerized piles of
 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 - Land Disposal Units
solid, nonflowing hazardous waste, are temporary units, for storage or treatment only
(260.10). Because waste piles are temporary units, not intended for final disposal of
wastes, Subpart L does not contain post-closure care regulations for waste piles that are
closed with waste in place; such units are considered permanent or disposal units, and
are subject to post-closure regulation as landfills (see Section 2.4).

Owners and operators of permitted waste piles that meet special requirements are
subject to reduced regulation. Specifically, the waste pile must be located inside or
under a structure and not receive free liquid, protected from surface water run-on,
designed and operated to control dispersal of waste, and managed to prevent the
generation of leachate. If these standards are met, the owner/operator of the permitted
waste pile is exempt from groundwater monitoring requirements as well as the design
and operation requirements for waste piles (264.250(c)).

DESIGN AND OPERATION

Waste piles are subject to nearly the same MTRs as surface impoundments.
Specifically, new units, lateral expansions, and replacement units require a double liner
and LCRS (264.251(c) and 265.254). In addition, waste piles, with certain exceptions,
require a second leachate collection and removal system above the top liner.  If the
permitted waste pile is not subject to MTR (i.e., a unit, lateral expansion, or
replacement for which construction commenced before July 29,1992), then the unit is
subject to a single liner and basic LCRS requirements. Interim status waste piles that
are not subject to MTR are subject only to liner, run-on, and run^off controls if leachate
or run-off is found to be a hazardous waste.

Permitted waste piles  are subject to stormwater run-on and run-off controls to
minimize leachate generation during storms (264.251 (g),(h), and (i)). These
requirements are designed to keep stormwater from contacting the hazardous wastes
and to keep any contaminated stormwater from being released into the environment.

Owners and operators of waste piles must also cover or manage their wastes  to prevent
any wind dispersal. Interim status  waste piles are not subject to the stormwater
controls, but are subject to wind dispersal provisions (265.251).

INSPECTION AND RELEASE RESPONSE

Waste piles are subject to the same  inspection and release response requirements as
surface impoundments. Specifically, waste piles are required to establish an  ALR
(264.252 and 265.255), a response  action plan (264.253 and 265.259), monitoring and
inspection schedule (264.254), and a CQA plan (264/265.19). The interim status
monitoring and inspection provision only requires the owner and operator of a waste
pile meeting MTR to record the amount of liquids removed from the leak detection

 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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                                                               Land Disposal Units - 7
system sump at least once a week (265.260). Note that waste piles are not subject to
the emergency repair provisions for surface impoundments.

CLOSURE

Since waste piles are storage units, as opposed to disposal units, all waste residues and
contaminated subsoils and equipment must be removed or decontaminated at closure
(264/265.258(a)). This requirement is identical to clean closure of a surface
impoundment. If the owner or operator removes or decontaminates all waste residues
and makes all reasonable efforts to remove or decontaminate all structures and soils
and finds that some contamination remains, the waste pile will then be subject to the
closure requirements for landfills, including post-closure care (264/265.258(b)).

SPECIAL REQUIREMENTS FOR CERTAIN WASTES

Waste piles are subject to the same specialized standards for ignitable, reactive,
incompatible, and dioxin-containing waste as surface impoundments. These
requirements are discussed in Section 2.1.

WASTE PILE VS. CONTAINMENT BUILDING

Containment buildings, sometimes characterized as "indoor waste piles," are units
used to hold noncontainerized piles of hazardous waste.  The difference between waste
piles and containment buildings, from a regulatory standpoint, is that containment
buildings are not land disposal units. For this reason, containment buildings are
designed with a containment system rather than a liner and leak detection system (Part
264/265, Subpart DD). The module entitled Containment Buildings provides more
information about the standards that apply to containment buildings.
2.3   LANDFILLS

Since landfills are used as final disposal sites for a large portion of the nation's
hazardous waste, it is critical that they are monitored during the entire active life
(which includes closure) and the post-closure period.  The regulations concerning
hazardous waste landfills are promulgated as Subpart N of Part 264/265.

DESIGN AND OPERATION

Landfills are subject to virtually the same MTRs as surface impoundments and waste
piles. They must have a double-liner, LCRSs, leak detection (264/265.301), and an
ALR (264/265.302). Like waste piles, landfills require the second LCRS above the
top liner. In addition, landfills must have stormwater  run-on and run-off controls to

 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 - Land Disposal Units
 prevent migration of hazardous constituents for at least a 25-year storm, and a cover to
 prevent wind dispersal.

 INSPECTION AND RESPONSE ACTIONS

 Once again, the inspection and response action plans are almost identical to the
 requirements for surface impoundments, including a response action plan if the ALR is
 exceeded (264.304 and 265.303), and a CQA program (264/265.19).  In addition, the
 owner and operator of a hazardous waste landfill must perform monitoring and
 inspections (264.303 and 265.304).  As with surface impoundments and waste piles,
 these requirements ensure that the unit is maintained in good working condition and
 that any problems are promptly detected.

 CLOSURE

 Since landfills typically serve as permanent disposal sites, the closure and post-closure
 requirements for landfills are somewhat different from those for other land-based units.
 One example is the requirement for a final cover over the landfill that can provide long-
 term minimization of liquid migration through the closed landfill, promote drainage,
 accommodate settling, and function with a minimum amount of maintenance
 (264/265.310(a)). After closure, the owner or operator must comply with the post-
 closure requirements of 264/265.117 through 264/265.120 covering such actions as
 monitoring and maintenance (see the module entitled Closure  and Post-Closure). In
 addition, the owner and operator must maintain the final cover, leak detection system,
 and groundwater monitoring system, as well as prevent run-on and run-off from
 damaging the final cover, and protect the surveyed benchmarks (i.e., location and
 characteristics) of the landfill.

 SPECIAL REQUIREMENTS FOR CERTAIN WASTES

 Like surface impoundments and waste piles, landfills are subject to certain restrictions
 on the management of ignitable, reactive, incompatible, and dioxin-containing wastes.
Unlike other units, though, the placement of bulk or noncontainerized liquid
hazardous waste or hazardous waste containing free liquids in any landfill is
prohibited (264/265.314(b)).  The placement of nonhazardous liquids in a landfill is
 also essentially prohibited (264.314(e) and 265.314(f)).  There are only certain
 situations when containers holding free liquids can be placed in a landfill (e.g.,  small
containers such as ampules, containers that are products such as batteries, or lab packs)
 (264.314(d) and 265.314(c)). If sorbents are used to treat hazardous wastes so that the
waste no longer contains free liquids, the owner and operator must use
nonbiodegradable sorbents.
 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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                                                               Land Disposal Units - 9
SPECIAL REQUIREMENTS FOR CERTAIN CONTAINERS

To prevent significant voids that could cause collapse of final covers when containers
erode, and to maintain and extend available capacity in hazardous waste landfills,
containers placed in a landfill must be either at least 90 percent full or crushed,
shredded, or in some other way reduced in volume, unless the containers are very
small, such as ampules (264/265.315).

Finally, there are special standards for lab packs or overpacked drums being placed in
a landfill (264/265.316). Lab packs generally contain small containers of a wide
variety of hazardous wastes in relatively small volumes that are packed in sorbent
material to prevent leaking. This sorbent material must be nonbiodegradable.
2.4   LAND TREATMENT UNITS

While surface impoundments, waste piles, and landfills share many regulatory
standards, land treatment units (LTUs) are significantly different both in purpose and
in management.  Land treatment involves the application of waste on the soil surface or
the incorporation of waste into the upper layers of the soil in order to degrade,
transform, or immobilize hazardous constituents present in hazardous waste.
Essentially, the waste is treated within the matrix of the surface soil, whereas the major
goal of the other units is to prevent migration to the surface soil. Specifically, the waste
must be placed only in the unsaturated zone, which is the portion of the surface soil
above the water table (or the highest point of the ground water flow). Based on the
proximity to the  groundwater, the success of land treatment is highly dependent on the
operational management of the unit.

Because the goal of land treatment is to let the soil microbes and sunlight degrade the
hazardous waste, the design and operating standards are significantly different from
those imposed on the three types of units already covered.  Land treatment units
generally do not use impermeable liners to contain  wastes. Instead, units rely on the
physical, chemical, and biological processes occurring in the topsoil layers. In a sense,
these units can be viewed as an open system.

Maintenance of proper soil pH, careful management of waste application rate, and
control of surface water run-off are all key to the operation of a land  treatment unit.
The regulations concerning hazardous waste land treatment units are promulgated in
Subpart M of Part 264/265.

Because placement of hazardous waste in a land treatment unit is considered land
disposal, land disposal restrictions (LDR) standards must be considered. If the
hazardous waste does not meet the applicable treatment standard prior to placement in

 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 - Land Disposal Units
the land treatment unit, the unit owner or operator must obtain a no-migration variance
before applying any hazardous waste to the unit.  (See the Land Disposal Restrictions
module for more details concerning the LDR standards and no-migration variances.)

DESIGN AND OPERATION

Land treatment units must devise a program and demonstrate its effectiveness given
the design of the unit and characteristics of the area. In addition, the regulations set out
specific operating requirements that must be met in the treatment program. The
following discussion details these requirements.

Treatment Program and Demonstration

The requirements outlined in the treatment program, including design and operating
criteria and unsaturated zone monitoring, stem from a treatment demonstration. The
purpose of the treatment demonstration is to show that hazardous constituents in the
waste can be completely degraded or immobilized in the treatment unit. A treatment
demonstration may involve field testing on a sample soil plot or laboratory testing.
The Regional Administrator uses information provided by the treatment demonstration
to set permit standards. Interim status units are not required to establish a  treatment
program because the interim status regulations are self-implementing. Owners and
operators can only place hazardous waste in the LTU, however, if the waste will be
rendered nonhazardous or less hazardous (265.272(a)).

During the treatment demonstration, the owner and operator must establish the
following parameters:

     Specify the wastes that may be handled at the unit. In general, land treatment is
      confined to wastes that are primarily organic and that can be greatly reduced in
      volume by physical, chemical, and biological decomposition in surface soils.
      The owner and operator must be able to account for smaller fractions of heavy
      metals and persistent organic compounds by immobilizing those constituents
      (264.271(a)(l)).

     Formulate a set of operating measures.  The LTU must be operated in a manner
      that will maximize degradation, transformation, and immobilization of
      hazardous waste constituents. The specifics of the operation are discussed in the
      following section of this module (264.271(a)(2)).

     Establish unsaturated zone monitoring. The purpose of this program is to make
      sure that treatment is occurring within the treatment zone, and that all hazardous
      constituents are being adequately treated. The information provided from the
      monitoring can help the owner and operator "fine tune" the treatment process to

 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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                                                               Land Disposal Units -11
      maximize the success of the treatment. Unsaturated zone monitoring involves
      soil monitoring (e.g., obtaining soil samples) immediately below the treatment
      zone (264.271(a)(3)).

     Define the treatment zone. This zone comprises the horizontal and vertical
      dimensions of the unsaturated zone in which the owner and operator intend to
      perform the actual treatment. The zone can be no deeper than 1.5 meters (5 feet)
      and the bottom of the zone must be at least one meter (3.2 feet) above the
      seasonal high water table (264.271(c)).

Operation

Basic design and operating requirements are outlined in 264.273 and 265.272.  These
sections require the Regional Administrator to specify certain parameters in the facility
permit:

     Rate and method of waste application
     Measures to control soil pH
     Measures to enhance microbial and chemical reactions
     Measures to control the moisture content of the treatment zone.

In addition, land treatment units are subject to requirements for stormwater run-on and
run-off controls. Management to control wind dispersal and weekly inspections is also
required.

Food Chain Crops

In some cases, the owner and operator may grow food-chain crops on a land treatment
unit (264/265.276). The Agency believes that  this can be done safely if certain
conditions are met that require the owner or operator to demonstrate that hazardous
constituents are not present in the crop in abnormally high concentrations.
Additionally, if cadmium is present in the unit,  the owner and operator must comply
with additional management standards specified under 264.276(b) and 264.276(c).

INSPECTIONS AND RESPONSE ACTIONS

Although there are no requirements to inspect the unit,  the owner and operator must
maintain unsaturated zone monitoring to assure that the unit is meeting its
performance standards (264/265.278).

As discussed earlier, the purpose of unsaturated zone monitoring is to provide
feedback on the success of treatment in the treatment zone and to determine if
hazardous constituents are migrating out of the  treatment zone (i.e., the monitoring

 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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 12 - Land Disposal Units
program must be designed to determine the presence of hazardous constituents below
the treatment zone). Generally this means that the owner and operator would monitor
for the most stable hazardous constituents found in the wastes placed in or on the
treatment zone.  Keep in mind that unsaturated zone monitoring is not a substitute for
groundwater monitoring.  Both are required for land treatment units.

To perform unsaturated zone monitoring, the owner and operator must first establish
which constituents must be monitored and the background levels of those constituents
in the soil. The frequency of the monitoring is based on the elements of the operation
of the LTU, such as the frequency, timing, and rate of application of the waste. Once
the samples have been taken, the owner and operator must determine whether there is
a statistically significant change over the background values (i.e., the natural
constituent levels in the soil) for any hazardous constituent. If there is a statistically
significant increase in the hazardous constituents of concern, the owner and operator
must notify the Regional Administrator within seven days, and submit a permit
modification within 90 days to change the operating practices at the facility to
sufficiently treat hazardous constituents within the treatment zone.

CLOSURE

When a land treatment unit is being closed, the owner and operator maintain all
operating parameters to continue the treatment processes, and continues run-on and
run-off controls and unsaturated zone monitoring. The major element of the closure
procedure is placing a vegetative cover over the closing unit that is capable of
maintaining growth without extensive maintenance.  At completion of closure the
owner or operator may submit the closure certification by an independent qualified
soil scientist in lieu of an independent registered professional engineer. Closure and
post-closure are waived if the hazardous constituents in the treatment zone no longer
exceed background levels.

SPECIAL REQUIREMENTS FOR CERTAIN WASTES

Like other LDUs, land treatment units are subject to limitations regarding ignitable,
reactive, incompatible, and dioxin-containing wastes (264/265.281-282 and 264.283).
 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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