TD367
.R37 °OOD82003 DRAFT
1982y
Vol. 3
RCRA GUIDANCE DOCUMENT
LAND TREATMENT tC" ^
'D
[to be used with Subpart M, Part 264
of the RCRA Regulations]
U.S. Environmental Protection Agency
fttgion 5, Library (PL-12J)
r> West Jecfcson eoufevard, 12th ftp*
C*kego,tt 60604-3590
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TABLE OF CONTENTS
Page
A. Purpose and Use 1
B. "Treatment" Demonstration [§264.272] 3
I. The Regulations
2. Guidance
3. Discussion
C. Design and Operating Requirements [§264.273] 9
I. Maximization of Treatment 9
1. The Regulations
2. Guidance
3. Discussion
II. Minimization of Run-off 18
1. The Regulations
2. Guidance
3. Discussion
III. Management of Collected Run-on/Run-off 23
1. The Regulations
2. Guidance
3. Discussion
IV. Wind Dispersal Control 27
1. The Regulations
2. Guidance
3. Discussion
Environments r-..-; ,:{;n Agency
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Page
D. Unsaturated Zone Monitoring [§264.278] 32
I. Selection of "Principal Hazardous Constituents" 32
1. The Regulations
2. Guidance
3. Discussion
II. Monitoring Procedure 35
1. The Regulations
2. Guidance
3. Discussion
III. Evaluation and Response 48
1. The Regulations
2. Guidance
3. Discussion
E. Closure and Post-Closure Care [§264.280] 51
1. The Regulations
2. Guidance
3. Discussion
References 60
Appendix I
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A. Purpose and Use
Under the authority of Subtitle C of the Resource Conservation
and Recovery Act (RCRA), EPA has promulgated interim-final
regulations for the treatment and disposal of hazardous waste in
land treatment units (40 CFR Part 264). This guidance
document presents land treatment unit design and operating
specifications which the Agency believes comply with the Treatment-
Demonstration Requirements (§264.272), the Design and Operating
Requirements (§264.273), the Unsaturated Zone Monitoring Requirements
(§264.278) and the Closure and Post-Closure Requirements (§264.280)
contained in these regulations.
Section 264.272 requires the owner or operator to demonstrate
that hazardous constituents in the applied wastes can be completely
degraded, transformed, or immobilized in the treatment zone. The
data used for the treatment demonstration must be generated under
conditions similar to those present in the treatment zone of the
facility.
Section 264.273 provides the design and many of the operating
requirements necessary at land treatment units. It focuses
particularly on requirements which are designed to maximize
treatment of hazardous constituents within the treatment zone and
minimize the escape of these constituents to ground water,
surface water, and air. Section 264.278 contains the unsaturated
zone monitoring requirements which are aimed at evaluating the
performance of the unit, while Section 264.280 delineates
the closure and post-closure care provisions.
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The requirements in all of the Sections mentioned above
consist of performance-oriented statements and rules, and, as
a result, are also general in nature. This provides maximum
flexibility to the owner or operator in locating, designing,
operating, and closing his unity. However, while this approach
provides flexibility, it lacks certainty because the permitting
official must render a value judgment on the acceptability of
the particular design, operation, and closure specifications proposed
for each given unit. As a result, there will be considerable
negotiation during permitting when this approach is used.
To provide additional certainty to this permitting
process, this document identifies specific designs and operational
procedures which the Agency believes accomplish the performance
requirements in Sections 264.272, 264.273, 264.278, and 264.280.
Permit applicants who design, construct, operate, and close
their units in accordance with the specifications contained
herein will be considered in compliance with these Sections.
The Agency wishes to emphasize that the specifications in
this document are guidance, not regulations. EPA is not
requiring, and does not intend, that all land treatment units be
designed and operated in this way. On the contrary, the Agency be-
lieves there are other designs and operating procedures which may be
acceptably used, depending on unit-specific factors. Detailed
discussions of various land treatment design and operational
approaches, including those recommended in this document,
are provided in the EPA technical resource document
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entitled Hazardous Waste Land Treatment (1). Owners or operators
who wish to utilize a very different design or operation than
those recommended herein may do so by providing sufficient data
to the permitting official which demonstrates compliance with
the various performance requirements.
This document is arranged according to the section of the
regulation to which it corresponds. EPA is particularly interested
in information and suggestions concerning the usefulness of this
document, expansion of it, and the effectiveness of the guidance
in ensuring compliance with the performance requirements in the
regulations. Those wishing to send technical information or
suggestions concerning this document should address them to:
Rod Jenkins, Chief, Land Disposal Branch, Office of Solid Waste
(WH-565E), U.S. Environmental Protection Agency, 401 M Street,
S.W., Washington, D.C. 20460.
B. "Treatment" Demonstration [§264.272]
1. The Regulations
Section 264.272 states that the owner or operator must
demonstrate with literature, experimental and/or operating data,
that hazardous constituents in the applied wastes can be completely
degraded, transformed, or immobilized in the treatment zone of
the unit. The demnstration must be based on conditions
similar to those in the treatment zone. "Treatment zone" is
defined as the portion of the unsaturated zone below and including
the land surface in which the owner or operator intends to maintain
the conditions necessary for effective degradation, transformation,
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immobilization. [The dimensions of this zone will be specified
in the permit. Section 264.271 specifies that the maximum depth
of the treatment zone must be (a) no more than 1.5 meters
(5 feet) from the initial soil surface, and (b) more than one meter
(3 feet) above the seasonal high water table.]
2. Guidance
a. Comprehensive waste analysis data should be used to
identify hazardous constituents present in the waste in significant
concentrations.
b. A thorough literature search should be conducted on each
hazardous constituent present in the waste. Available information
on (and factors affecting) the degradation, transformation,
immobilization, and toxicity of each hazardous constituent,
under conditions similar to those present in the treatment zone
of the facility, should be gathered.
c. If sufficient data to support the demonstration of
treatment is unavailable in the literature, the owner or operator
should conduct laboratory studies to examine the fate and effects
of hazardous constituents in the soil system and to determine
the impacts of various environmental factors or treatment processes.
Laboratory studies should include, at a minimum, studies addressing
degradation, transformation, mobility, and toxicity of hazardous
constituents. The environmental factors that should be examined
include at least soil pH, temperature, and moisture.
d. Field pilot studies should be conducted to verify certain
laboratory results, discover any unforeseen potential environmental
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problems, and investigate interactions which cannot be adequately
assessed in the laboratory.
e. The owner or operators of existing (interim status)
units should consider the use of actual monitoring
data, in lieu of laboratory and field studies, to make the
treatment demonstration. Such monitoring data should include
results from comprehensive soil core (including treatment zone)
soil pore-liquid, ground water, run-off, and air monitoring
generated over an extended period (i.e., several years) of unit
operation. This data should clearly demonstrate treatment with
no unacceptable release of hazardous constituents or hazardous
degradation products from the treatment zone.
f. All data used directly to support the treatment
demonstration should be generated under conditions which simulate
at least the following characteristics of the unit:
(i) characteristics of the land-treated waste;
(ii) characteristics of the treatment zone including the
soil texture, pH, cation exchange capacity, organic matter
content, moisture content, and depth of soil to the seasonal
high water table;
(iii) topography of the treatment zone including slope;
(iv) climate of the area including temperature, precipitation,
evaporation, and wind patterns; and
(v) operating practices including waste application method
and rate, tilling depth and frequency, and soil conditioning
practices (e.g., pH adjustment, fertilization, etc.).
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3. Discussion
The treatment demonstration required under §264.272 can be
accomplished using information derived from published literature,
laboratory studies, field studies and/or actual land treatment unit
operation experience (i.e., monitoring results). Successful demon-
strations will most often involve data obtained from several of the
above sources.
A literature search on each hazardous constituent in the
particular waste in question should first be conducted. Information
in the published literature may assist in the design of laboratory
or field experiments, or significantly reduce or eliminate the
need for additional experimentation. However, to completely
eliminate the need for additional testing, comprehensive literature
data on the degradation, transformation, mobility, and toxicity
of hazardous constituents under conditions similar to the treatment
zone must be clearly documented. Such literature data must also
have been subjected to a thorough peer review. However, the
Agency believes that for most land treated hazardous wastes, an
inadequate data base is available in the literature to conclusively
predict the fate of particular hazardous constituents under
particular site-specific conditions.
Therefore, a combination of laboratory and field studies
often will be necessary to provide the required treatability
data. Laboratory studies may be used as rapid screening techniques
for examining, within a reasonable time frame, the treatment of
hazardous constituents in a soil system, and the effects of
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various environmental factors on this treatment. These studies
should include tests directly addressing the degradation,
transformation, and mobility of the hazardous constituents in
the waste. The Agency suggests the use of soil respirometry
tests and/or organic constituent analysis and characterization
studies conducted over time to examine hazardous constituent
degradation and transformation. Soil thin-layer chromatography
tests or column leaching studies (using undisturbed soils
collected from the field) may be used to examine constituent
mobility. Discussion of the advantages and disadvantages of
each of these tests, and specific procedures for completing
them are provided in Hazardous Waste Land Treatment (1).
In addition, laboratory studies (and field studies) should
evaluate the potential toxicity of hazardous constituents in the
waste to microbes and plants. Prevention of microbial toxicity
is important to ensure successful biodegradation of degradable
waste constituents, while phytotoxicity must be limited in order
that an effective vegetative cover may be established. Suggested
procedures for completing these studies are also provided by EPA's
technical resource document on land treatment (1).
While laboratory tests provide valuable data, the
extrapolation of this data to field conditions is often difficult
because of the complex interactions that occur in the field.
Therefore, the Agency believes that field studies usually will
be necessary to verify certain lab-generated results. The extent
of verification required will depend on a number of factors
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including the variability in the laboratory test results, and
specific waste and land treatment unit characteristics. The Regional
Administrator will determine the extent of field verification
necessary.
Field pilot studies should be kept as small as possible.
Generally, plots should be no greater than 500 m^, unless
specialized equipment requires additional room for waste application
or incorporation. In general, waste application rates and treatment
zone conditions (e.g., pH maintenance) must be selected based on
the best available information obtained from the literature,
laboratory studies, and previous experience.
It may be possible to demonstrate the treatment of hazardous
constituents in a particular waste based solely on previous land
treatment unit monitoring data. This monitoring data, however, must
be comprehensive and clearly demonstrate degradation or transformation
of hazardous organic constituents within the treatment zone and
no unacceptable migration of any hazardous constituents to below
the treatment zone.
Finally, any data, regardless of the source, which is used to
support the demonstration of treatment must be generated under
conditions similar to those present in the land treatment unit.
Specific unit characteristics the owner or operator should consider
are outlined in the guidance section above. The Regional
Administrator may require the owner or operator to consider
additional characteristics which may be very important at a
specific unit. With regard to treatment zone characteristics,
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the Agency believes that the series classification will usually
adequately define the necessary similarities of soils; the soil
phase should also be considered in evaluating similarities in
surface soils.
C. Design and Operating Requirements [§264.273]
I. Maximization of Treatment [§264.273(a)]
1. The Regulations
The performance standard delineated in §264.273(a) requires
owners and operators to design, construct, operate, and maintain
the land treatment unit such that the treatment of hazardous
constituents by degradation, transformation, or immobilization,
is maximized within the treatment zone.
2. Guidance
a) A land treatment unit should be located, designed,
and constructed so that the treatment zone contains soils having
one or more of the following textures (USDA Classification):
loam, silt loam, sandy clay loam, sandy loam, silty clay loam,
or clay loam.
b) A land treatment unit should be designed and located
so that the treatment zone does not contain karst formations or
irregular terrain such as fissures, faults or bedrock outcrops.
c) The owner or operator should carefully determine the
proper waste application rate based on data on the properties of
the land treated waste and on the characteristics of the treatment
zone. The selected waste application rate must not exceed the
capacity of the treatment zone to degrade, transform, or immobilize
hazardous constituents.
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d) The pH of all portions of the treatment zone should be
maintained at greater than or equal to 6.0 and less than or equal
to 8.0.
e) Measures that affect microbial and chemical reactions
(e.g., fertilization, tilling, moisture control) should be
carefully evaluated and optimized to enhance the effectiveness
of treatment processes.
f) All design and operating recommendations specified in
other sections of this document should be followed.
3. Discussion
To meet the performance standard of Section 264.273(a),
each owner or operator should (a) properly locate, design, and
construct the land treatment unit such that the treatment zone
contains soils suitable for land treatment, and (b) then operate
the unit so that treatment occurs within the defined (in the
facility permit) boundaries of this zone.
Particular attention should be directed toward ensuring that
the treatment medium is adequate for the degradation, transformation,
or immobilization of the hazardous constituents of the waste.
The Agency recognizes that different soil characteristics and
depths will be acceptable under different unit-specific
conditions. Several general recommendations relating to soil
type, however, can be derived from experiences with currently
successful land treatment operations.
Each particular type of soil has certain advantages and
disadvantages with regard to use in a land treatment system.
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Coarse textured soils (e.g., sand) will remain aerated while
fine soils (e.g., clay) may often become reduced due to wetness.
The aeration state of the soil will play an important role in
determining how quickly, by what pathway, and in what form various
waste constituents will be degraded. In general, most waste
constituents are more rapidly degraded under aerobic conditions.
While the aeration conditions of fine textured soils may be less
desirable, the generally higher sorptive capacity of these soils
may be very effective in immobilizing various ions. The advantages
and disadvantages of various soil textures, as defined in the
1975 USDA soil classification system (2), are given in Table 1.
A more detailed discussion of each of the parameters in the
table is contained in Hazardous Waste Land Treatment (1). In
general, hazardous waste land treatment units should not be
established on extremely deep sandy soils having hydraulic connection
to underlying aquifers, due to the great potential for hazardous
constituents leaching to ground water. Similarly, silty soils
which have a severe problem with crusting should not be selected
due to the extreme potential for erosive transport of hazardous
constituents. Loam, silt loam, sandy clay loam, sandy loam,
silty clay loam, and clay loam soils generally provide the most
suitable medium for land treatment of hazardous wastes. However,
in all cases, soils having these textures will have to be properly
managed (e.g., maintenance of pH and fertility) to maintain
their treatment capabilities.
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TABLE 1 SUITABILITY OF VARIOUS SOIL TEXTURES FOR LAND
TREATMENT OF HAZARDOUS INDUSTRIAL- WASTES
Texture
Advantages
Disadvantages
sand
loamy sand
loam
silt loam
silt
silty clay
Loam
clay loam
very rapid infiltration
usually oxidized and .dry
low run-off potential
high infiltration
low to medium run-off
moderate infiltration'
fair oxidation
moderate run-off potential
generally accessible
good CEC
moderate infiltration
.fair oxidation
moderate run-off potential
generally accessible
good CEC
low infiltration
fair to poor oxidation
good CEC
good available water
medium-low percolation
fair structure
high CEC
medium-low percolation
good structure
med-poor aeration
high CEC
high available water
very low CEC
very high hydraulic
conductivity rate
low available water
little soil structure
low CEC
moderate to high
hydraulic conductivity
rate
low to medium
available water
fair structure
some crusting
high crusting potential
poor structure
high run-off
moderate run-off
often wet
fair oxidation
med-low infiltration
med-high run,-off
often wet
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'TABLE i (con't)
Texture
Advantages
Disadvantages
clay
sandy clay
sandy clay
loam
low percolation
high CEC
high available water
med-low percolation
med-high CEC
«•
med-high available water
good aeration
low infiltration
often massive structu:
high run-off
sometimes low aeratio
fair structure
moderate-high run-off
medium infiltration
From: K.W. Brown and Assoc., Inc. Hazardous Waste Land Treatment,
U.S.EPA publication SW-874, Contract No. 68-03-2940,
September, 1980 (1).
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In addition, special consideration in siting and designing a
land treatment unit should be given to avoiding karst formations
and broken or irregular terrain, such as bedrock outcrops, fissures,
and faults. Such formations often provide direct passages to
ground water.
Successful operation of a land treatment unit in compliance
with the §264.273(a) performance standard also depends upon properly
designing, operating, and constructing the unit such that the
treatment zone provides sufficient soil depth for treatment
of hazardous constituents sufficiently above the seasonal high
water table in order to minimize environmental impacts and optimize
treatment processes. As mentioned earlier in this document,
Section 264.271 of the regulations specifies that the boundaries
of the unit's treatment zone will be defined in the facility
permit. Treatment of hazardous constituents within these defined
treatment zone boundaries (i.e., the vertical and horizontal
dimensions) will then be the required goal of that unit.
Section 264.271 requires that the maximum depth of the treatment
zone must be 1.5 meters from the initial soil surface, or 1
meter above the seasonal high water table, whichever depth is
less. The Agency believes this maximum limit provides adequate
soil medium for acceptable treatment. The second part of this
requirement ensures a minimum buffer between the bottom of
the treatment zone and the seasonal high water table. Additional
rationale for this standard is provided in the preamble to the
regulation.
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Many operational controls are also .very important in ensuring
maximization of treatment within the treatment zone. Waste
application rate is one of the most important factors determining
the success of a land treatment unit. Overloading the system
can result in significant environmental impacts resulting from
hazardous constituent volatilization, run-off, or leaching to
ground water. The waste application rate should be carefully
determined so that the capacity of the soil to degrade, transform,
or immobilize hazardous constituents is not exceeded. In determining
the proper application rate, the owner or operator should consider
the characteristics of the waste and of the unit, particularly
soil properties, hydrogeology, climate and type of vegetative
cover, if any. Generally, one or only a few waste constituents
will limit application rates because of the constituent's concentratic
in the waste, or because the soil's assimilative capacity for
the constituent is very low. Further discussion on determining
the application rate limiting constituents is provided in the
EPA technical resource document entitled Hazardous Waste Land
Treatment (1).
Furthermore, because land treated wastes are often complex
mixtures of both inorganic and organic hazardous constituents,
the owner or operator should determine the application rate so that
adequate consideration is given not only to degradation and
transformation processes, but also to immobilization processes.
For instance, the application rate must not inhibit the physical,
chemical, and biological processes essential to the degradation
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of organic constituents. In addition, to attain treatment of
inorganics and persistent organics, the application rate must not
exceed the capacity of the treatment zone to immobilize these
constituents. In assessing the treatment zone's immobilization
capacity, particular attention should be given to the cation
exchange capacity, pH, and organic matter content of the soil.
Laboratory and pilot scale studies, as well as existing information
in the literature, which reflect the conditions present in the land
treatment unit should be used in determining the assimilative (degra-
dation, transformation, and immobilization) capacity of the treatment
zone. Some of this information should have been generated in the
treatment demonstration explained in Section B of this document.
Additional information on specific waste constituents can be
found in the literature (1, 3).
Maintenance of a soil pH in the treatment zone in the
range of 6-8 generally provides optimum soil pH conditions for
degradation, transformation, and immobilization processes. Data
has shown that the optimum soil pH for microorganisms lies in the
range of 6-8 (4,5,6); hence, waste biodegradation is greatest in
this pH range. In addition, most heavy metals are much less
mobile in soil and less available to plants at pH levels greater
than 6.0 (7,8,9). At pH levels greater than 8.0, however, the
mobility of certain metals increases, and the availability of
certain plant and microbial nutrients (e.g., phosphorus, iron)
decreases (4). This condition leads to leaching hazards and
less than optimum biological treatment of wastes. Maintenance
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of a neutral soil pH is a widely recommended practice for hazardous
and nonhazardous waste land treatment (6,10,11,12).
While the Agency generally recommends a soil pH in the range
of 6-8, it recognizes that there are a few exceptions to this
general rule. For instance, there are a limited number of
hazardous constituents (e.g., selenium) which are more available
to plants in neutral pH soils than in acid soils. Each owner or
operator should evaluate data on the mobility of the hazardous
constituents of the waste under various soil pH regimes prior to
land treating the waste.
In an effort to maximize treatment, the owner and operator
should also carefully manage any other additional operational
measures, such as method of waste application, fertilization,
tilling method and frequency, and moisture control, which influence
the effectiveness of treatment processes.
Finally, to ensure compliance with the Section 264.273(a)
performance standard, the owner or operator should follow the
additional guidance related to unit design, construction,
operation, and closure provided in other sections of this document.
Important sections include those pertaining to design and operating
conditions for minimizing run-off, wind dispersal control,
unsaturated zone monitoring, and closure and post-closure care
procedures. Run-on and run-off management systems must also be
developed and implemented, as required in Sections 264.273(c) and
264.273(d) of the regulations, respectively.
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11• Minimization of Run-off [§264.273(b)]
1. The Regulations
Section 264.273(b) requires the owner or operator to
design, construct, operate, and maintain the treatment zone to
minimize run-off of hazardous constituents during the active
life of the land treatment unit. [The regulations also
contain requirements pertaining to the control of run-off and run-
on. Section 264.273(c) specifies that the owner or operator must
design, construct, operate and maintain a run-on control system
to control flow onto or into the treatment zone during peak
discharge from at least a 25-year storm. Under Section 264.273(d)
the owner or operator must design, construct, operate and maintain
a run-off management system to collect and control at least the
water volume resulting from a 24-hour, 25-year storm. Guidance
related to run-on and run-off control systems is provided in
Hazardous Waste Land Treatment (1).]
2. Guidance
a) The treatment zone of the unit should not contain
soils (or soil-waste mixtures) having very low infiltration rates.
b) The surface slope of the active portion of a land
treatment unit should be greater than 0.2 - 0.5 percent and less
than five percent.
c) Waste should not be applied to the treatment zone
when the surface of the zone is frozen (less than or equal to 0°C)
d) Waste should not be applied during rainy weather or
when the treatment zone is saturated.
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e. A vegetative cover should be established on the
treatment zone whenever practicable.
3. Discussion
Run-off of hazardous constituents from land treatment
units may result in significant environmental contamination.
Therefore, the Agency believes that the goal of all land treatment
units should be to minimize the generation of run-off. This
can be achieved through proper unit siting, design, and
construction, particularly with regard to soil characteristics
and slope, as well as through proper management of unit operation,
including the scheduling, method and rate of waste application. .
Proper design of the treatment zone can greatly minimize run-
off potential. The treatment zone should not be composed of
soils or soil-waste mixtures which have very low infiltration
rates. (Infiltration is the entry of water into the soil, normally
measured as a rate having units of cm per sec. or cm per hour.)
In addition, soils subj/sct to crusting should be avoided. Soil
types recommended in Section C of this document generally provide
favorable infiltration properties.
The slope of the treatment zone is one of the most important
factors influencing the degree and rate of hazardous constituent
run-off. To minimize run-off, the surface slope of the active
portion should be less than 5 percent. However, a minimum slope
of 0.2-0.5 percent is recommended to provide adequate surface
drainage and to minimize water and waste ponding.
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Land treatment units may be equipped with terraces and
grass waterways to control the run-off of liquid and hazardous
constituents. This is particularly essential when significant
areas are rendered barren for one or several seasons by repeated
waste applications, as might occur for a sludge-type waste.
Proper conservation terracing is also important if the waste is
applied to a continuously vegetated surface. Terraces will slow
the flow of intensive storm water off the unit, allowing
optimal infiltration and putting less strain on retention basins.
Furthermore, by decreasing the slope length, less sediment will
erode from the slopes, and much less sediment will accumulate in
the retention structures. The run-off quality will also be
improved prior to the run-off entering retention structures.
Information on the design of terraces Is provided in Hazardous
Waste Land Treatment (1).
Proper management of unit operation also contributes
significantly to run-off control. Particular attention should be
given to the timing of waste applications. The Agency recommends
that waste applications be curtailed during periods when the
surface of the treatment zone is frozen, during rainy weather
and when the treatment zone is saturated. These conditions not
only significantly increase the potential for run-off, but also
generally inhibit treatment processes, which are essential to the
success of a land treatment unit.
The Agency believes that, in most cases, successful operation
of land treatment units will be limited to periods when
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surface soils are unfrozen. The incorporation of wastes into
frozen soils usually cannot be effectively accomplished. Kincannon
(12) found that at low temperatures (approximately 4.5°C), congealing
and solidification of oily waste sludges was a severe problem.
Inadequate waste incorporation results in increased risk of
run-off, volatilization, or wind erosion, as well as reduced
waste exposure to biological and chemical treatment mechanisms.
In addition, research data indicates that treatment processes
within a land treatment unit will be severely limited by low
temperatures. Powell (14) found that potential waste decomposition
in Arctic regions may be less than 15% of that in the southern U.S..
According to Harris (15), microbial activity slows during the
cool seasons and practically ceases when soils are frozen.
Studies by Dibble and Bartha (5) found negligible microbial
activity at 5°C, while Raymond et al (16) reported that results
from studies of two field locations showed little evidence of
degradation during the winter months. As a result of poor mixing
and negligible degradation at low temperatures, waste applied
during the winter may cause significant run-off contamination
problems during the spring thaw. Because of these problems,
existing land treatment units often discontinue or significantly
reduce waste application during the winter months (16, 17).
EPA also recommends that the application of wastes be
curtailed during heavy, rainy weather and when the treatment
zone is saturated with water. Rainy weather will obviously
increase the potential for contaminated run-off problems.
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Saturated soil conditions favor increased run-off, as well as
accelerated migration of waste constituents through the treatment
zone due to dissolution or physical removal, or as a result of
anaerobic conditions (18). Dissolution of waste constituents
will be a severe problem if the waste contains significant amounts
of water soluble substances such as the anions of carbonic,
sulfuric, hydrochloric, and nitric acids, and certain pesticides
such as carbaryl (18). Anaerobic conditions adversely affect
major (aerobic) degradation and immobilization processes, and
increase the potential for odor problems (19, 20). Aerobic
biodegradation of simple or complex organic material in soil is
commonly greatest at 50-70% of the soil water holding capacity
(5). Inhibition is observed at lower values due to inadequate
water, and at higher values due to the reduction in oxygen levels.
The solubility of most heavy metals is also increased under
more reducing conditions.
Saturated soil conditions also usually cause practical
operational problems. Plowing or tilling under these conditions
is usually very difficult. Attempts at manipulating saturated
soil, or even wet soil, usually aggravate problems because
plowing with heavy equipment often compacts soil and adversely
affects soil structure and porosity. Loss of pore space subsequently
enhances anaerobic conditions because pore spaces provide channels
through which oxygen diffuses into and through soils.
Finally, vegetative cover should be established in the
treatment zone whenever practicable. Vegetation will assist in
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minimizing run-off of hazardous constituents. Additional guidance
on vegetative covers is provided in Section C IV of this document.
III. Management of Collected Run-on/Run-off [§264.273(e)]
1. The Regulations
Section §264.273(e) specifies that collection and holding
facilities (e.g., tanks or basins) associated with run-on/run-
off control systems must be emptied or otherwise managed
expeditiously to maintain the capacity of the system. If the
collected run-on/run-off is a hazardous waste as defined in
Part 261, it must be handled as such.
Section 264.273(c) requires a run-on control system to
prevent flow onto the treatment zone during a peak discharge from
at least a 25-year storm, while Section 264.273(d) requires a run-off
management system to both control and collect run-off from at least a
24-hour, 25-year storm. Collection of run-on is not specifically
required by the regulations. However, if a collection facility
is associated with the run-on control system, it must be managed
such that the capacity of the system is maintained. Collection
facilities will usually be associated only with run-off management
fac ilities.
2. Guidance
a) A comprehensive analysis of the collected run-on/ run-
off should be conducted to determine if it is "hazardous".
b) The following options should be evaluated for the
disposal or treatment of hazardous and non-hazardous run-on/
run-off liquid:
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(i) Reapplication to the hazardous waste land treatment
unit to enhance treatment processes, promote growth of vegetation,
or provide control of wind dispersal of hazardous constituents;
(ii) Solar evaporation; and
(iii) Disposal or treatment in a hazardous waste disposal or
treatment unit, other than a land treatment unit.
c) The following additional options should be evaluated for
the disposal or treatment of nonhazardous run-on/run-off liquid:
(i) Treatment and disposal via a wastewater treatment plant;
and
(ii) Direct discharge under a NPDES (National Pollutant
Discharge Elimination System) permit.
3. Discussion
There are several available alternatives for rnanaging
collected run-on and run-off liquid. The first step in evaluating
these treatment or disposal alternatives is to determine the
characteristics of the collected liquid. If such liquid is
"hazardous", it must be treated or disposed of in a permitted
hazardous waste management unit. If it is non-hazardous,
other alternatives are available. Thus, a complete analysis
of the collected liquid must be conducted.
Hazardous (or nonhazardous) collected liquid may be disposed
of through (a) reapplication to the hazardous waste land treatment
unit, (b) solar evaporation, or (3) treatment or disposal in
a permitted hazardous waste management unit (other than a
land treatment unit).
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Reapplication of the collected liquid to the land treatment
unit may be the most practicable means of run-on/run-off
liquid treatment and disposal. This reapplied liquid may be used
to enhance microbial degradation of waste constituents, or
as an irrigation water source to promote vegetative crop growth.
In addition, the collected liquid may be used for surface
wetting in the control of wind dispersal of hazardous constituents.
If reapplication systems are used, care must be taken not to
saturate the treatment zone and thus, inhibit treatment processes.
When sprinkler irrigation systems are used, the systems should be
designed to apply water at a rate lower than the infiltration
rate to minimize run-off. The system should also be designed to
provide proper pressure at the nozzles to help spread the water
as uniformly as possible. Also, if the run-on/run-off liquid
contains hazardous constituents, irrigation systems should be run
only during periods of low wind velocity to minimize wind dispersal
problems. If the liquid contains significant levels of nutrients,
salts, or hazardous constituents, it will be necessary to keep a
record of water applications to monitor constituent accumulations.
The land area needed for reapplication of collected run-on/
run-off will depend on the annual application rate and the annual
volume of collected run-on/run-off. The annual application rate
will be determined either by some limiting constituent in the run-off
or by the hydraulic loading of the land. The land area needed is
equal to the annual collected run-on/run-off volume divided by the
annual application rate. If the application rate is set on the
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basis of hydraulic loading, care must be taken to allow for
chronic wet periods which will increase the volume and reduce the
application rate when compared to the average annual values.
Hydraulic loading and run-off models have been developed which
utilize long-term weather information. Information regarding
these models can usually be obtained from local Soil Conservation
Service engineers or consulting firms. The spatial requirements
for systems of this type often include preapplication holding
ponds that are used to empty run-off retention structures and
hold the liquid for future application to the land, to avoid
application on soil that is already saturated, frozen, or covered
with snow.
Areas in the Western United States, where the moisture
deficit (evaporation minus precipitation) is greater than ten
inches, have a high potential for using evaporation for ultimate
disposal of collected liquid. The area needed for evaporation
ponds is a function of the annual run-off volumes held in the
pond plus the moisture that falls on the pond divided by the
evaporation rate in inches per acre for the climatic area under
consideration. The liquid may be sprayed in the air above the
pond to enhance evaporation if no volatile or aerosol hazard
will result. The use of nozzles that form large droplets is
encouraged to help minimize spray drift and any aerosol effects.
Another option for treatment or disposal of hazardous collected
liquid is disposal in a permitted hazardous waste management
unit. This option, however, is likely to be less economical
than the other alternatives suggested above.
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Collected liquid which is found to be nonhazardous may be
treated or disposed of by two additional methods. If the plant
or company owns and operates a wastewater treatment plant, the
run-on/run-off water can be pumped to the plant, treated, and
disposed via the wastewater treatment facility permit. Care must
be taken to ensure that this added volume of water does not
overwhelm the treatment plant. New facilities should have this
capacity designed into them. Where the option of using an existing
wastewater treatment facility is not a viable alternative, an
NPDES (National Pollutant Discharge Elimination System) permit
may be applied for. This would allow direct discharge of the run-
off liquid after collection if it meets the water quality standards
specified in the NPDES permit.
IV. Wind Dispersal Control [§264.273(f) ]
1. The Regulations
Section 264.273(f) states that if the treatment zone contains
particulate matter which may be subject to wind dispersal, the
owner or operator must manage the unit to control the wind
dispersal.
2. Guidance
a) Waste applications should be planned to correspond
with periods of low wind velocity and atmospheric stability.
b) The surface soil of the treatment zone should be
stabilized through surface wetting with water or use of chemical soil
stabilizing agents.
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c) A vegetative cover should be established on the
treatment zone.
d) The effectiveness of natural or man-made wind barriers
for wind dispesal control should be evaluated in unit design.
3. Discussion
Because large tracts of waste-treated land are often
exposed to wind erosion, wind dispersal of hazardous waste is one
of the most important environmental concerns at hazardous waste
land treatment units. The wind dispersal of hazardous
waste will be influenced by a number of factors including the
velocity and turbulence of the wind, the characteristics of the
surface soil-waste mixture (e.g., moisture content, texture), and
the nature and orientation of cover vegetation.
While wind velocity has a major influence, wind turbulence
probably has an even more significant impact. This results from
wind-carried particles exerting a large impact on particles not yet
disengaged.
Moisture content and texture of soils also significantly
influence the susceptibility of soil-waste particles to wind
erosion. The greater the moisture content, the greater the wind
velocity needed to induce particle movement. In addition,
moderately coarse particles (e.g., silt size) are more susceptible
to wind erosion than fine, less detachable particles (e.g.,
clay) or coarse, heavier, and less transportable particles (e.g.,
sand). Soils having a higher organic matter content will also
provide greater potential for particle aggregation.
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As a first step toward minimizing wind dispersal problems,
the Agency recommends that all waste applications be carefully
timed to avoid periods of excessive wind and atmospheric instability.
Waste application activities provide, in many cases, the most
significant opportunity for wind dispersal of hazardous constituents.
Second, the surface soil of the treatment zone should be
stabilized through surface wetting with water or use of chemical
soil stabilizing agents. Surface wetting with water is an
effective and economical means of increasing the resistance of
the soil-waste mixture to wind erosion by increasing the
cohesiveness of soil particles. Numerous types of surface
irrigation systems, commonly used in agricultural operations, are
available for water application. In certain cases, the waste
itself may provide the necessary moisture for limited periods of
time. Additional water application, however, may be necessary
between waste applications. Care should be taken to prevent
saturation of the treatment zone and inhibition of treatment
processes.
Chemical soil stabilizing compounds may be used in lieu of,
or in combination with, surface wetting with water. Many chemical
soil stabilizers, including organic polymers and other resin
emulsions, are currently available. These compounds vary in
their effectiveness and cost. Information on several chemical
soil stabilizers can be found in a recent report (21). In evaluating
these compounds, special attention should be given not only to
the compound's effectiveness and cost, but also to its effect on
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plant emergence and growth, and waste treatment. As in the case
of soil moisture, the waste itself may act as a stabilizer
against erosion.
Third, a vegetative cover should be established on the
treatment zone between waste applications, whenever practicable.
However, the vegetative cover crop should not be planted until
sufficient tilling and cultivation (when necessary) has allowed
adequate stabilization of the waste. An effective vegetative
cover may eliminate the need for continuation of surface soil
stabilization via water or chemical agents. In addition to
controlling wind dispersal of particulates, vegetation can minimize
run-off and water borne erosion by maximizing evapotranspiration
and infiltration, and can absorb excess nutrients such as nitrogen.
In situations where liquid hazardous wastes are surface spread
by irrigation, or where wastes are subsurface injected, it may
be possible to maintain a continuous vegetative cover. In instances
where solid hazardous wastes are surface spread only during the
warm season, a management schedule should be developed which will
allow enough time for the establishment of at least a temporary
cover crop after applications are complete. In situations where
waste is treated year round, the active portion of the unit
should be subdivided into plots or rows, so that the annual
application can be made within one or two short periods to given
plots or rows, followed by incorporation, surface contouring or
terracing as needed, and vegetation establishment on those plots
or rows. To maximize wind dispersal control, the rows of vegetation
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(between nonvegetated rows) should run perpendicular to the
prevailing wind direction.
Vegetation should be selected which is easily established
and maintained, and relatively tolerant of potentially phytotoxic
waste constituents, including organics, salts, metals, and excess
water where that is a factor. Disease and insect resistance
should also be considered. Information on the potential
phytotoxicity of various waste constituents has been reviewed by
several authors (1,3,7,22,23).
Grasses are often a good choice for vegetation because they
are relatively tolerant of many toxic waste constituents, and
can usually easily be established from seed. Perennial sod
crops native to the area are often the most desirable surface
cover, since they provide more protection against erosion, and a
longer period of active ground cover than annual grasses or
small grains. The most suitable or desirable plant species for a
vegetative cover, however, will vary depending upon the season
and the region of the country. Agronomists from the State
Agricultural Extension Service, USDA, or local university should
be consulted to provide information on varieties and cultural
practices best suited to the given region. Additional information
on the selection of vegetative covers for land treatment units
is available from several sources (1,3,24).
Regardless of the plant species selected, vegetation
establishment may require lime, fertilizer, the use of a mulch
and watering to ensure success. Information on the specific
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cultural practices required for successful establishment in a
particular region can also be obtained from the area agronomists
mentioned above.
Finally, each owner or operator should also evaluate the use
of natural (e.g., tree lines) or man-made (e.g., fences) wind
barriers in minimizing dispersal of hazardous waste. Since such
barriers will only temporarily redirect the wind, they will
often not be very effective at units having large fields.
There may be instances, however, particularly with small units,
when such measures may be effective and economically feasible.
Land treatment units having wind dispersal control measures which
include waste application timing, and a combination of surface
soil stabilization with water chemical agents, and/or vegetative
cover will be considered in compliance with Section 264.273(f) of
the RCRA regulations. Wind barriers may also fulfill part or
all of the wind dispersal control requirements depending on
unit-specific considerations. The acceptability of wind
barriers will be evaluated on a case-by-case basis.
D. Unsaturated Zone Monitoring [§264.278]
I. Selection of "Principal Hazardous Constituents"
1. The Regulations
Section 264.278(a) specifies that "principal hazardous
constituents" (PHCs) may be designated for unsaturated zone
monitoring purposes in lieu of monitoring for all hazardous
constituents. "Principal hazardous constituents" are
the most mobile hazardous constituents which are also
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relatively persistent and present in significant concentrations
in the waste. "Principal hazardous constituents" may be specified
in the permit by the Regional Administrator only after a review of
data from waste analyses, literature reviews, laboratory tests,
and field studies submitted by the owner or operator.
2. Guidance
a. The owner or operator should submit comprehensive waste
analysis data which identifies the hazardous constituents present
in the waste and their concentrations.
b. The owner or operator should gather and submit available
data in the literature pertaining to the relative mobility and
persistence of the various hazardous constituents in the waste.
This data should adequately address the conditions present in
the land treatment unit.
c. The owner or operator should evaluate the data generated
in performing the treatment demonstration (see Section B of this
document) and extract any pertinent information related to the
relative mobility and persistence of the hazardous constituents.
d. Data gleaned from the literature and treatment demonstration:
should, if necessary, be supplemented with additional laboratory
or field tests.
3. Discussion
A hazardous constituent, to be designated as a "principal hazard<
constituent" (PHC), must be one of the most mobile hazardous
constituents present in the waste. In addition, consideration
will also be given to the concentration and persistence of the
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constituent; a highly mobile hazardous constituent which is
present in insignificant concentrations, or which is quickly
degraded, would be an unacceptable PHC. The Regional Administrator
will usually elect to designate at least two PHCs because it is
likely, based on mobility, concentration, and persistence, that
no single hazardous constituent will clearly represent the "best"
principal hazardous constituent.
The use of PHCs allows the owner or operator to significantly
reduce the analytical burden associated with monitoring. Thus,
the owner or operator should work closely with the Regional
Administrator in providing the necessary data to determine
acceptable PHCs. It is important that the data meet quality
assurance criteria and allow a clear understanding of the relative
mobility and persistence of the various hazardous constituents
in the waste under conditions similar to those present in the
unit. In evaluating literature data and designing experimental
tests, the owner or operater should consider the facility
characteristics outlined in the Treatment Demonstration
(Section B).
Because the selection of a principal hazardous constituent
will be very waste- and facility-specific, the Agency cannot define
a precise selection and testing protocol. The Regional Administrator
will determine the exact type and extent of data needed to support
the selection of one or more principal hazardous constituents for
a particular waste at a specific unit.
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II. Monitoring Procedure
1. The Regulations
Section 264.278 requires that all land treatment
units have an unsaturated zone monitoring program that is
capable of determining whether hazardous constituents have migrated
below the treatment zone. The monitoring program must include
momh soil-core and soil-pore liquid monitoring. Monitoring
for hazardous constituents must be performed on a background
plot (until background levels are established) and immediately
below the treatment zone (active portion). The number, location,
and depth of soil-core and soil-pore liquid samples taken must
allow an accurate indication of the quality of soil-pore liquid
and soil below the treatment zone and in the background area.
The frequency and timing of soil-core and soil-pore liquid
sampling must be based on the frequency, time and rate of waste
application, proximity of the treatment zone to ground water,
soil permeability, and amount of precipitation. The Regional
Administrator will specify in the facility permit the sampling
and analytical procedures to be used. The owner or operator
must also determine if statistical increases in hazardous
constituents (or PHCs) have occurred below the treatment zone.
[Ground-water monitoring is also required at hazardous waste
land treatment units. Requirements pertaining to ground-
water monitoring are provided under Subpart F of Part 264.
Run-off or air emission monitoring is not specifically required
at land treatment units under the Part 264 regulations.]
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2. Guidance
a) Soil-core monitoring - Background
Background concentrations of principal hazardous
constituents should be established using the following procedure.
(i) Take at least eight randomly selected soil
cores for each soil series present in the treatment zone from
similar soils where waste has not been applied. The cores should
penetrate to a depth below the treatment zone but no greater than
15 centimeters (6 inches) below the treatment zone.
(ii) After taking each soil core, backfill the core
hole with soil.
(iii) Obtain one sample from each soil-core portion
taken below the treatment zone.
(iv) Composite the soil-core samples from each soil
series to form a minimum of four composite samples for each soil
series (i.e., randomly composite two soil-core samples to form a
composite sample; since eight core samples per soil series were
taken, a total of four composite samples will be formed).
(v) Preserve and ship the composite samples according
to procedures specified in Test Methods for Evaluating Solid
Waste. (25).
(vi) Analyze each composite sample for the principal
hazardous constituents according to the methods included in
Test Methods for Evaluating Solid Waste (25).
(vii) For each soil series, a background arithmetic
mean and variance for each principal hazardous constituent should
be determined by pooling all composite sample measurements.
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b) Soil core monitoring - Active Portion
(i) The owner or operator should take at least six
randomly selected soil cores per uniform area, semi-annually.
However, if a uniform area is greater than 5 hectares (12 acres),
at least two randomly selected soil cores per 1.5 hectares (4
acres) should be taken semi-annually. The cores should penetrate
to a depth below the treatment zone but no greater than 15 centimeter
(6 inches) below the treatment zone.
(ii) After taking each soil core, backfill each core
hole with native soil or other material that will prevent direct
passage of waste constituents to below the treatment zone.
(iii) The pH of the treatment zone in each uniform
area should be determined using the following procedure:
(A) Obtain one representative sample from each soil-core
portion taken within the treatment zone.
(B) Composite the soil-core samples from each uniform area
to form a minimum of three composite samples for each uniform
area. However, if a uniform area is greater than 5 hectares
(12 acres), a minimum of one composite sample per 1.5 hectares
(4 acres) should be formed.
(C) Preserve and ship the composite samples according
to procedures provided in Test Methods for Evaluating Solid
Waste (25).
(D) Determine the pH of each composite sample according to
the method included in Test Methods for Evaluating Solid Waste
(25).
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(iv) The concentrations of principle hazardous constituents
below the treatment zone in each uniform area should be determined
using the following procedure:
(A) Obtain one sample from each soil-core portion taken
below the treatment zone.
(B) Composite the soil-core samples from each uniform area
to form a minimum of three composite samples for each uniform
area. However, if a uniform area is greater than 5 hectares
(12 acres), a minimum of one composite sample per 1.5 hectares
(4 acres) should be formed.
(C) Preserve and ship each composite sample according
to procedures provided in Test Methods for Evaluating Solid
Waste (25).
(D) Analyze each composite sample for the principal hazardous
constituents according to the methods included in Test Methods
for Evaluating Solid Waste (25).
(E) For each uniform area, an arithmetic mean and variance
for each principal hazardous constituent should be determined by
pooling all composite measurements.
c) Soil-pore liquid monitoring - Background
Background concentrations of principal hazardous constituents
should be established using the following procedure.
(i) For each soil series present in the treatment zone,
install two soil-pore liquid monitoring devices at randomly
selected locations (see Appendix I) in similar soils where waste
has not been applied. The sample collecting portions of the
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monitoring devices should be placed at a depth no greater than
30 centimeters (12 inches) below the actual treatment zone used
at the unit.
(ii) Collect and analyze samples from each of the soil-pore
liquid monitoring devices on at least a quarterly basis for at
least one year. If liquid is not present at a regularly scheduled
sampling event, a sample should be collected as soon as liquid
is present.
(iii) Sample preservation and shipment should be done in
accordance with the procedures provided in Test Methods for
Evaluating Solid Waste (25).
(iv) Samples should be analyzed for the principal hazardous
constituents according to the methods included in Test Methods
for Evaluating Solid Waste (25).
(v) For each soil series, a background arithmetic mean
and variance for each principal hazardous constituent should be
determined by pooling all measurements.
d) Soil Pore-liquid Monitoring - Active Portion
(i) The owner or operator should install three soil-pore
liquid monitoring devices at randomly selected locations (see
Appendix I) per uniform area, but no less than one device per 1.5 hec
tares (4 acres). The sample collecting portion of the monitoring
device should be placed at a depth no greater than 30 centimeters
(12 inches) below the treatment zone.
(ii) Samples from each of the soil-pore liquid monitoring
devices should be collected and analyzed at least quarterly unless
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the wastes are applied very infrequently. If liquid is not
present at a regularly scheduled sampling event, the monitoring
device should be checked within 24 hours of each following significant
waste application or rainfall event, and a sample drawn when
sufficient liquid is present.
(iii) Samples should be preserved and shipped according to
procedures provided in Test Methods for Evaluating Solid Waste (25).
(iv) Samples should be analyzed for the principal hazardous
constituents according to methods included in Test Methods for
Evaluating Solid Waste (25).
(v) For each uniform area, an arithmetic mean and variance
for each principal hazardous constituent should be determined by
pooling all measurements.
3. Discussion
The above guidance provides specific procedural protocols
for soil-core and soil-pore liquid monitoring in both background
plots and in the active portion of the unit. Guidance on the
installation of and equipment needs for these monitoring systems
is provided elsewhere (1, 26, 27). Guidance on ground-water
monitoring at hazardous waste disposal facilities is currently
being developed.
Although the regulations specify that the number of samples,
and the frequency and timing of unsaturated zone sampling must
be based upon a number of unit-specific factors, the guidance
delineated above provides the minimum elements of what the Agency
considers acceptable unsaturated zone monitoring protocols. EPA
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has attempted to develop soil-core and soil-pore liquid
monitoring protocols which would not only minimize sampling and
analytical costs, but also assure statistically reliable results.
To accomplish this, the Agency incorporated, in both monitoring
protocols, the essential elements of random sampling in given
"uniform areas" and sample compositing.
Soil characteristics, waste type, and waste application
rate are all important factors in determining the environmental
impact of a particular land treatment unit or part of a
unit on the environment. Therefore, areas of the land treatment
unit within which these characteristics are similar (i.e., uniform
areas) should be sampled as a single monitoring unit. As used
in the recommended protocols, a uniform area is an area of the
active portion of a land treatment unit which is composed of
soils of the same soil series (as defined in the 1975 USDA soil
classification system: Reference 24) and to which similar wastes
or waste mixtures are applied at similar application rates. If,
however, the texture of the surface soil differs significantly
among soils of the same series classification, the phase classificatic
of the soil should be considered in defining "uniform areas". A
certified professional soil scientist should be consulted in
designating uniform areas.
In addition, EPA recommends that the location of soil-core
sampling or soil-pore liquid monitoring devices within a given
uniform area be randomly selected. Random selection of samples
ensures a more accurate representation of conditions within a
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given uniform area. Procedures for randomly selecting sampling
locations are provided in Appendix I of this document.
Finally, the protocols specify that within a given uniform
area, samples should be composited to form a minimum number of
composite samples for analysis. The Agency believes that
compositing is an effective mechanism to increase statistical
reliability and to reduce analysis costs.
The soil-core and soil-pore liquid monitoring protocols for
both the active portion of the unit and a background area
[i.e., some other area where waste has not been applied and which
has soil characteristics similar to those present in the active
portion; for the purposes of this guidance, similar soil
characteristics means soils of the same soil series (and similar
surface soil texture)] are provided. Active portion samples
must be collected from uniform areas which are selected based
upon the soil series, waste type and application rate. The
appropriate background area is an untreated area having soil of
the same soil series. The determination of the appropriate
background area is based solely on soil series; waste type and
application rates are irrelevant in background area selection.
It is important that uniform areas and associated background
areas be selected under the supervision of a certified professional
soil scientist.
The Agency realizes that the owners or operators of certain
units will have background data on hazardous constituents
(in soil and soil-pore liquid) generated during the interim status
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period. This information may be submitted to the Regional
Administrator to fulfill some or all of the Part 264 requirements
related to the establishment of background values. This background
information should have been obtained using procedures which at
least generally conform with the guidance provided in this
document. The Regional Administrator will determine the validity
of the background data generated during the interim status period,
and the extent to which this data will fulfill the final Part 264
requirements.
The background soil-core monitoring protocol recommends a
minimum of eight soil cores from each background area. Background
soil cores should penetrate to the same depth as the cores taken
from the active portion. (Soil cores from the active portion
should be taken at a depth below the depth of the treatment zone
but no deeper than 15 centimeters (6 inches) below the treatment
zone depth.) The limit on the depth of the soil cores enables a
valid and accurate comparison of the levels of principal hazardous
constituents immediately below the treatment zone (active portion)
to background levels at the same depth. One sample should be
taken from each soil core portion taken below the depth of the
treatment zone. These samples should then be composited to
form at least four composite samples for analysis of principal
hazardous constituents. The Agency believes that four samples
are the minimum number of samples necessary to ensure the
establishment of accurate background data. The arithmetic mean
and variance for each principal hazardous constituent should then
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be determined by pooling all composite sample measurements from
each background area representing a specific soil series.
The soil-core monitoring protocol for the active portion of
a land treatment unit is similar to the background protocol
with the following exceptions: (a) soil cores are collected from
uniform areas; (b) a minimum of six soil cores per sampling area
(uniform area) is recommended; and (c) sampling within the treatment
zone is recommended for the determination of soil pH, and (d)
monitoring frequency is semi-annual, rather than a one-time event.
Sampling from uniform areas is included for the active portion
to allow the selection of sampling areas to be based not only on
soil series, but also on waste type and application rates. The
active portion protocol also specifies that if a given uniform
area is greater than 5 hectares (12 acres), at least two randomly
selected soil cores per 1.5 hectares (4 acres) should be taken
semi-annually. This provision is included to ensure that an
adequate number of cores are taken from very large uniform areas.
A minimum of six cores (which are composited to form three
samples for analysis) per sampling area is suggested for the
active portion, rather than eight (as in background), in order
to minimize the burden of the active portion sampling and analysis.
Active portion monitoring must be carried out throughout the
unit operating life, closure, and post-closure, whereas
background monitorng is a one-time event.
Finally, it is recommended in the soil-core monitoring protocol
for the active portion that the pH of the treatment zone in each uniform
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area be determined by taking a representative sample from each
soil-core portion within the treatment zone. A "representative
sample" of soil within the treatment zone may be obtained by
collecting subsamples from each 30 cm (12 inch) depth interval
(within the treatment zone), and then compositing and mixing
these subsamples to form a composite sample.
The regulations only require analysis for principal hazardous
constituents be conducted on soil-core samples taken below the
treatment zone. However, analysis for these constituents of
samples taken within the treatment zone may provide important
information on the success of degradation and transformation, if
such mechanisms are used to attain treatment. All analyses
should be conducted according to the methods provided in Test
Methods for Evaluating Solid Waste (25).
A specific protocol for soil-pore liquid monitoring (background
and active portion) is also provided in this guidance. Background
areas are selected according to the same criteria (i.e., soil
series) as specified for soil-core monitoring. In order to
minimize costs and to adequately account for changes in soil-pore
liquid quality over time, the Agency is recommending that background
levels be established using quarterly monitoring of two soil-
pore monitoring devices per soil series over a period of one
year. The sample collection portions of the background soil-
pore liquid monitoring devices should be placed at the depth
corresponding to the depth of active portion devices (i.e., no
greater than 30 cm below treatment zone).
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Although the elements of the protocol for soil-pore liquid
monitoring on the active portion of the unit are generally
similar to those for soil-core monitoring on the active portion,
there are several notable differences. First, only one half as
many soil-pore liquid monitoring devices are specified per unit of
area in order to limit the costs associated with installation of
numerous monitoring devices. Second, compositing of soil-pore
liquid samples is not recommended because only the minimum number
of samples are specified in the protocol to minimize the cost of
lysimeter installation and management. If the number of samples
is significantly increased, compositing of samples may be
considered. Third, the maximum depth for sampling below the
treatment zone is somewhat greater than that provided for soil
core samples (30 centimeters instead of 15 centimeters). This
provides flexibility to the owner or operator for site-specific
variations in the installation of soil-pore liquid monitoring
devices.
Finally, the frequency for the sampling and analysis of
soil-pore liquid is greater than that for soil cores (i.e.,
quarterly versus semi-annually). This is because information
on fast-moving principal hazardous constituents is needed on a
more frequent basis. The Agency believes that at least quarterly
sampling and analysis is necessary for soil-pore liquid monitoring
at units at which waste is applied on a relatively frequent
basis (i.e., at least 3 times per year). More frequent sampling
may be necessary, for example, at units located in areas
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with highly permeable soils or high rainfall, or at which wastes
are applied very frequently. The timing of sampling should be
geared to the waste application schedule as much as possible.
At land treatment units at which wastes are applied
infrequently (i.e., only once or twice a year), quarterly sampling
and analysis of soil-pore liquid may be unnecessary. Because
soil-pore liquid is instituted primarily to detect fast-moving princi-
pal hazardous constituents, monitoring for these constituents many
months after waste application would be useless. The Agency believes
that if fast-moving principal hazardous constituents are to migrate out
of the treatment zone, they will migrate at least within 90 days follow-
ing waste application (assuming normal climatic conditions). There-
fore, owners or operators of land treatment units at which wastes
are applied infrequently may monitor soil-pore liquid less
frequently (semi-annually or annually). The Regional Administrator
will determine the frequency of sampling and analysis necessary
based on the frequency and rate of waste application, and on the
characteristics of the waste and unit treatment zone.
If sufficient liquid is not present in the soil-pore liquid
monitoring devices during a scheduled sampling, the owner or operator
should obtain a sample immediately after liquid is present. Following
an unsuccessful sampling, the owner or operator should check the
monitoring devices for liquid within 24 hours following any significant
rainfall or waste application event.
Existing land treatment units covered under the interim
status regulations, promulgated on May 19, 1980, were required to
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have implemented unsaturated zone monitoring systems, including
soil-pore liquid monitoring devices. EPA realizes that many of
these devices were not installed according to the exact specifications
(e.g., located randomly in "uniform" areas) provided in this guidance.
The Regional Administrator will evaluate the design and location
of these existing systems and determine the extent of system
modification necessary. In many cases, the Agency believes no
relocation or modification will be necessary; in certain cases,
however, additional devices will have to be installed.
Finally, although the Part 264 regulations do not require
run-off or air emission monitoring, the Agency believes that such
monitoring is good management practice at all hazardous waste land
treatment units. At least periodic monitoring of run-off
quality will be necessary during the active life to determine the
management and ultimate disposal of collected run-off. For
example, if the collected run-off is a hazardous waste, it must
be treated or disposed of in a permitted hazardous waste management
unit. (See Section C III of this document for a discussion
of management of collected run-off.) In addition, periodic air
monitoring should be conducted to evaluate the success of controls
geared toward minimizing wind dispersal and volatilization of
hazardous constituents.
Ill. Evaluation and Response
1. The Regulations
Under Section 264.278(f), the owner or operator must
compare the results for each hazardous constituent (or PHC)
48
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obtained in soil-core and soil-pore liquid monitoring, to
its respective background value to determine if statistically
significant increases have occurred. Section 264.278(g) specifies
that if statistically significant increases are observed, the
owner or operator must notify the Regional Administrator of this
finding within 7 days. The owner or operator must then, within
90 days, submit to the Regional Administrator a request for
permit modification to incorporate modifications to unit
operations which will maximize treatment of hazardous
constituents within the treatment zone.
Under Section 264.278(h), however, the owner or operator
may demonstrate that a source other than the regulated unit
caused the increase or that the increase resulted from error in
sampling, analysis or evaluation. In making this demonstration,
the owner or operator must (1) within 7 days notify the Regional
Administrator in writing that he intends to make a demonstration,
(2) within 90 days, submit a report to the Regional Administrator demon-
strating that a source other than the regulated land treatment unit
caused the increase or that the increase resulted from error in samplinc
analysis or evaluation, (3) within 90 days, submit to the Regional Ad-
ministrator an application for a permit modification to make any appro-
priate changes to the unsaturated zone monitoring program at the unit,
and (4) continue to monitor in accordance with the established
unsaturated zone monitoring program.
2. Guidance
a) If statistically significant increases in
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hazardous constituents (or PHCs) are observed, the following
modifications to unit operations should be considered to
maximize treatment within the treatment zone:
(i) modifications of waste characteristics;
(ii) reduction of waste application rate;
(iii) modification in method or timing of waste application;
(iv) cessation of the application of one or more particular
wastes at the unit;
(v) modifications to treatment zone cultivation or management
practices; and
(vi) modification of characteristics of the treatment zone,
particularly soil pH or organic matter.
3. Discussion
Hazardous constituent movement to below the treatment zone
may result from improper unit design, operation, or location.
Problems related to unit design and operation can often be
corrected, while serious problems resulting from poor unit
siting are more difficult to rectify. Certain locational
"imperfections" may be compensated for through careful unit
design, construction, and operation.
If statistically significant increases of hazardous
constituents are detected below the treatment zone via unsaturated
zone monitoring, the owner or operator should closely evaluate
the unit's operation, design and location to determine the
source of the problem. The characteristics of the waste should
be evaluated for possible effects on treatment effectiveness.
50
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The rate, method, and timing of waste application should be
examined. Management of the treatment zone including maintenance
of physical, chemical and biological characteristics necessary
for effective treatment, should also be reevaluated. Soil pH
and organic matter content of the treatment zone are two important
parameters which should be assessed. Finally, the owner or
operator should determine if the design or location of the unit
is causing failure of the system. Topographic, hydrogeologic,
pedalogic and climatic factors all play a role in determining
the success of the .Land treatment system. In certain cases, the
necessary unit modifications will be very minor, while in
other cases they will be major. Numerous unit-specific
factors must be considered to make this determination. The
Regional Administrator will make the final determination of the
modifications necessary based on the seriousness of the problem.
In order to make the demonstration provided for under §264.278(h),
the owner or operator should carefully investigate activities
occurring near the unit to confirm the source of the
contamination, and also closely examine the procedures used in
completing unsaturated zone monitoring. Resampling of the unit
may be required to determine errors in sampling, analysis, or
evaluation. The exact elements of the demonstration will be
determined on a case-by-case basis.
E. Closure and Post-Closure Care [§264.280]
1. The Regulations
The regulations specify that, during the closure period, the
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owner or operator must continue all operations necessary to maximize
degradation, transformation, or immobilization of hazardous
constituents within the treatment zone except to the extent that
such operations are inconsistent with the vegetative cover requirement
specified in Section 264.280(a)(8). These operations are simply
extensions of those required under §264.273(a). The closure
requirements also specifically require (a) minimization of run-off,
(b) maintenance of run-on control and run-off management systems,
(c) control of wind dispersal of hazardous waste, (d) food-chain
crop growth restrictions, (e) continuation of unsaturated zone
monitoring, and (f) establishment of vegetative cover at such time
that the cover will not substantially impede degradation, transformation,
or immobilization of hazardous constituents within the treatment zone.
Soil-pore liquid monitoring may be terminated 90 days after the
last waste application.
The post-closure care requirements state that the owner or
operator must (a) continue all operations necessary to enhance
degradation and transformation, and sustain immobilization of
hazardous constituents, (b) maintain the vegetative cover,
(c) maintain run-on control and run-off management systems,
(d) control wind dispersal of hazardous waste,(e) assure that the
growth of food chain crops complies with §264.276, and (f) continue
unsaturated zone monitoring (except soil-pore liquid monitoring
which may be terminated 90 days after last waste application).
An owner or operator may be exempted from the vegetative
cover requirement under closure, and all of the post-closure care
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requirements if he demonstrates to the Regional Administrator
that the entire treatment zone contains no statistically significant
increases in hazardous constituents over background. In addition,
Subpart F of the regulations states that if the above successful
demonstration is made and if the unsaturated zone monitoring
(§264.278) has not shown statistically significant increases of
hazardous constituents (or PHCs) over background below the treatment
zone at any time during the active life of the unit, then the
the owner or operator is exempt from ground-water monitoring during
the post-closure period.
Owners or operators of land treatment faciities must also
comply with the general closure requirements provided under
Subpart G. These requirements address the closure performance
standard (§264.111), the closure plan (§264.112), time allowed
for closure (§264.113), disposal or decontamination of equipment
(§264.114), certification of closure (§264.115), post-closure care
period (§264.117), post-closure plan (§264.118), and notices
(§264.119 and §264.120).
2. Guidance
(a) To meet the above closure and post-closure care requirements
under §264.280 the owner or operator should follow the applicable
recommendations provided in Section C of this document.
(b) Unsaturated zone monitoring during the closure care
period should be carried out in accordance with the protocol
outlined in Section D of this document.
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(c) In enhancing degradation and transformation, and in
sustaining the immobilization of hazardous constituents during
the post-closure care period, the owner or operator should,
at a minimum, consider the effects of soil pH, soil moisture
content, nutrient levels, and physical, chemical, or biological
disturbances of the treatment zone.
(d) Unsaturated zone monitoring during the post-closure care
period should be carried out in accordance with the protocol outlined
in Section D of this document except that the minimum frequency
of sampling should follow a geometrically progressive schedule
(i.e., 1/2, 1, 2, 4, 8, 16 and 30 years after the post-closure care
period begins). If not already terminated during the closure period,
soil-pore liquid monitoring may be terminated 90 days after the
last waste application.
(e) To demonstrate that the entire treatment zone contains
no statistically significant increases in hazardous constituents
over background, the owner or operator should use the following
procedure:
i. Background
A. Take at least eight randomly selected (see Appendix I)
soil cores for each soil series present in the treatment zone from
similar soils where waste has not been applied. The soil cores
must penetrate to a depth equal to the depth of the treatment zone.
B. From each soil core, obtain one sample of every 30
centimeter (12 inch) depth increment so that the sample increments
correspond for all soil cores within a soil series.
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C. Composite all soil-core samples for each depth increment
of a soil series, to form at least four composite samples (for
each depth increment of a soil series) for analysis. Analyze each
composite sample for the hazardous constituents of the waste according
to methods provided in Test Methods for Evaluating Solid Waste (25).
(D) For each depth increment in each soil series, a background
arithmetic mean and variance for each hazardous constituent
should be determined by pooling all measurements.
i i. Active Portion
(A) Take at least six randomly selected soil cores per
uniform area. However, if a uniform area is greater than (12
acres) at least two randomly selected soil cores per 1.5 hectares
(4 acres) should be taken. The soil cores must penetrate to the
bottom of the treatment zone.
(B) From each soil core, obtain one sample of every 30
centimeter (12 inch) depth increment, so that the sample increments
correspond for all soil cores within a uniform area.
(C) Composite all soil-core samples for each depth increment
of a uniform area to form a minimum of three composite samples
(for each depth increment of a uniform area). However, if a
uniform area is greater than 5 hectares (12 acres), the minimum
for each depth increment is one composite sample per 1.5 hectares
(4 acres) .
(D) Analyze each composite sample for the hazardous
constituents of the waste according to methods provided in
Test Methods for Evaluating Solid Waste (25).
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(E) For each depth increment in each uniform area, an
arithmetic mean and variance for each hazardous constituent
should be determined by pooling all measurements.
iii. Comparison
Compare the arithmetic mean results for each hazardous
constituent determined in paragraph (e)(ii)(E) of this Section to
its respective background arithmetic mean determined in paragraph
(e)(i)(D) of this Section, using the statistical test or procedure
specified in the facility permit to determine statistically
significant changes.
3. Discussion
"Closure" of a land treatment unit begins after the last
load of waste is accepted for treatment. The initial phases of
closure include management practices which are simply extensions
of those carried out during active unit operation. All practices
designed to maximize the degradation, transformation, and immobilization
of hazardous constituents must be continued throughout the closure
period, except those practices that will prevent the establishment
of a vegetative cover (after sufficient treatment has occurred).
Such activities (e.g., tilling of soil) must be terminated when the
establishment of the vegetative cover commences according to the
provisions specified in Section 264.280(a)(8).
In addition, unsaturated zone monitoring should be continued
as specified in Section D of this document. Soil pore liquid
monitoring may be terminated 90 days after the last waste
application.
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During the closure period, the owner or operator must also
establish a vegetative cover over the closed portion of the
unit. This vegetative cover must not be established until
sufficient treatment has occurred so that the termination of
certain management practices (e.g., tilling) and the establishment
of a vegetative cover will not substantially impede treatment
processes. This vegetative cover must be capable of sustaining
growth without requiring extensive maintenance (e.g., frequent
fertilization, liming, watering). Specific guidance on potential
vegetative covers is contained in Hazardous Waste Land Treatment (1).
The Agency recognizes that degradation and transformation
processes at land treatment units are, in many cases, long
term processes. Complete degradation and transformation of certain
degradable waste constituents may take several years. The
accomplishment of sufficient treatment (after which certain
active treatment management activities may be reduced and a
vegetative cover established), however, usually may be possible
within a shorter time frame. Therefore, during the closure period,
the Agency requires the completion of certain active practices
(e.g., tilling) which promote sufficient treatment and allow
establishment of a vegetative cover. The Agency does believe
that, in general, sufficient treatment will have been achieved
when it is determined that certain active treatment management
activities (e.g., tilling) are no longer necessary to maintain
continued degradation of residual organic constituents, and
continued effective immobilization of inorganic constituents.
57
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Also, the vegetative cover must not be established until it is
determined that the cover will not substantially inhibit degradation,
transformation, or immobilization of hazardous constituents.
Results from unsaturated zone monitoring, treatment zone analyses,
and data on run-off liquid quality, should be used in judging the
degree of treatment achieved.
The Agency believes that, in many cases, the closure activities
at land treatment units (i.e., sufficient treatment (via tilling, etc.)
and establishment of vegetative cover) may be accomplished within
180 days (as specified in Subpart G), assuming the last waste
applications occur at the early stages of closure. Additional
time, however, may be required by a number of other land treatment
units due to one or more factors.
The post-closure care requirements include activities for
enhancing and sustaining treatment, and precautions for managing
and monitoring for unacceptable releases (e.g., run-on/run-off
controls, unsaturated zone monitoring). Therefore, treatment
may be completed during the post-closure care period without
increased environmental risk. Soil pH, soil moisture content,
nutrient levels, and significant physical, chemical, or biological
disturbances of the treatment zone may all play a major role in
enhancing sustaining the degradation, transformation and
immobilization of hazardous constituents. These factors should
be carefully examined and corrected periodically, if necessary,
throughout the post-closure care period to ensure maintenance of
treatment processes.
58
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Soil-core monitoring during the post-closure care period should
continue as recommended in Section H of this document, except
that the frequency of monitoring may follow a progressive geometric
schedule of 1/2, 1, 2, 4, 8, 16, and 30 years after post-closure care
begins. The reduced frequency of this monitoring is suggested
because EPA believes that the risk of hazardous constituent
migration will be reduced over time in closed land treatment
units where waste applications have ceased and treatment is
nearing completion.
Soil-pore liquid monitoring during the closure and post-
closure care periods will only have to continue for 90 days after the
last waste application. Thus, depending on when wastes are applied
during the closure period, soil-pore liquid monitoring may or may
not have to be conducted during the post-closure care period. At
least two sampling events should occur during that 90 days
following the last waste application.
Finally, the Agency has provided a sampling protocol for use
in demonstrating that the entire treatment zone contains no
statistically significant increases in hazardous constituents
over background. This soil-core monitoring protocol differs from
the one provided in Section D of this document in that samples
are taken of various depth increments within the treatment zone,
rather than just below the treatment zone. Samples from respective
depths within each uniform area may be composited to form a
minimum of four samples for analysis. Background and active-
portion samples at each depth should then be compared using an
appropriate statistical procedure.
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If a successful demonstration is made under §264.280(d), the
owner or operator is not required to establish a vegetative cover
or comply with the post-closure care requirements. However, the
Agency still believes that it is good management practice to
establish a vegetative cover, even if hazardous constituents are
not present, in order to minimize soil erosion.
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References
1. Brown, K.W. and Assoc., Inc., Hazardous Waste Land Treatment,
U.S. EPA publication, SW-874, Contract No. 68-03-2940 (9/80).
2. Soil Survey Staff, Soil Conservation Service, USDA, Soil
Taxonomy; A Basic System of Soil Classification for Making
and Interpreting Soil Surveys, Agriculture Handbook No. 436,
U.S. Government Printing Office, Washington, DC, 12/75.
3. Overcash, M.R. and D. Pal, Design of Land Treatment Systems
for Industrial Wastes - Theory and Practices. Ann Arbor
Science, Ann Arbor, Michigan, 1978.
4. Brady, N.C., The Nature and Properties of Soils - 8th Ed.
McMillan Publ. Co., N.Y., 1974.
5. Dibble, J.T. and R. Bartha, "Effect of Environmental
Parameters on Biodegradation of Oil Sludge," App. Env.
Microbiology 37: 729-38, 1979.
6. SCS Engineers, Land Cultivation of Industrial Wastes
and Municipal Solid Wastes; State of the Art Study.
Volume I. Contract No. 68-01-2435, U.S. Environmental
Protection Agency, August, 1978.
7. Page, A.L., Fate and Effects of Trace Elements in Sewage
Sludge When Applied to Agricultural Lands. A Literature
Review Study. EPA-670/2-74-005, U.S. Environmental
Protection Agency, January 1974.
8. Dowdy, R.H., and W.E. Larson. "The Availability of
Sludge-born Metals to Various Vegetable Crops." J. of
Env.Quality 4: 278-282, 1975.
9. Chaney, R.L., P.T. Hundemann, W.T. Palmer, R.J. Small,
M.C.White and A.M. Decker, "Plant Accumulation of Heavy
Metals and Phytotoxicity Resulting from Utilization of
Sewage Sludge and Sludge Composts on Cropland," pp 86-97. In
Proc. Nat'l Conf, Composting Municipal Residues and Sludges.
Information Transfer Inc., Rockville, Md., 1978.
10. Huddleston, R.L., "Treatment of Oily Wastes by Land
Farming," Presented at the RSMA Meeting, "Disposal of
Industrial and Oily Sludges by Land Cultivaton," Houston,
Texas, January 18-19, 1978.
11,
CONCAWE, Sludge Farming: A Technique for the Disposal of Oily
Refinery Wastes, Report No. 3/80, 1980.
61
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12. U.S. Environmental Protection Agency, "Principles and
Design Criteria for Sewage Sludge Application on
Agricultural Land.", Chapter 9 in Sludge Treatment and
Disposal - Vol. 2., 1978.
13. Kincannon, C.B., Oily Waste Disposal by Soil Cultivation
Process., EPA - R2-72-100, U.S. EPA, 12/72.
14. Rowell, Michael J., "Land Cultivation in Cold Regions"
In: Disposal of Industrial and Oily Sludges by Land
Cultivation, Resource Systems & Mgmt Assoc., 1980.
15. Harris, J.O., "Petroleum Wastes in Soil" In: Land
Application of Waste Materials, Soil Conservation
Society of America, Akeny, Iowa, 1976.
16. Raymond, R.L., J.O. Hudson, and J.W. Jamison, "Oil
Degradation in Soil." Applied and Environmental
Microbiology, 31:4 522-535, 1976.
17. Lewis, R.S., Sludge Farming of Refinery Wastes as Practiced
at Exxon's Bayway Refinery and Chemical Plant. Presented
at the National Conference on Disposal of Residues on Land,
St. Louis, Missouri, Sept. 13-16, 1976.
18. Fuller, W.H., Movement of Selected Metals, Asbestos,
and Cyanide in Soil; Applications to Waste Disposal.
EPA - 600/2-77-020, U.S. EPA, April, 1977.
19. Lytle, Paul E., Site Visit: Gulf Coast Waste Disposal
Authority, Houston, Texas; Trip report. U.S. EPA, Office
of Solid Waste, Wash., D.C., Jan. 1, 1978.
20. Lennon, James V., Site Visit: IT Corporations, Martines,
Calif., Trip Report, U.S. EPA, Office of Solid Waste,
Washington, D.C., Oct. 24, 197. Slide Presentation.
21. Versar, Inc. Technical Assistance in the Coal BAT Review-II;
Special Report; Revegetation of Coal Strip Mines, U.S.EPA
Contract No. 68-01-5149, November 26, 1979.
22. Allaway, W.H. Agronomic Control over Environmental Cycling
of Trace Elements. Adv. Agron. 20:235-274, 1968.
23. Chaney, R.L. and P.M. Giordano. Microelements as related to
plant deficiencies at toxicities. pp 234-279. In: L.F. Elliott
and R.J. Stevenson (ed.) Soils for Management of Organic Wastes
and Waste Waters. American Socity of Agronomy, Madison, WI. , 1977.
24. Lutton, R.J. Evaluating Cover Systems for Solid and Hazardous
Waste. U.S. EPA publication no. SW-867. EPA-IAG-D7-01097, 9/80.
25. U.S. Environmental Protection Agency, Test Methods for
Evaluating Solid Waste, Publication No. SW-846, 1982.
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26. Wilson, L.G., Monitoring in the Vadose Zone; A Review of
Technical Element and Methods, EPA-600/7-80-134, Contract
No. V-0591-NALX, 6/80.
27. Fenn, D., E. Cocozza, 0. Braids, B. Yare, and P. Roux,
Manual for Ground Water Monitoring at Solid Waste Disposal
Facilities, EPA publication SW-611, Contract. No. 68-01-3210
12/80.
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Appendix I
Random Sampling
If n units are to be selected from the population, a simple
random sample is defined as a sample obtained in such a manner
that each possible combination of n units has an equal chance of
being selected (1). In practice, each unit is selected separately,
randomly, and independently of any units previously drawn. For
unsaturated zone monitoring, each unit to be included in the
"sample" is either a volume of soil (soil core) or a volume of
liquid (soil-pore liquid).
It is convenient to spot the field location for soil-coring
and soil-pore liquid devices by selecting random distances on a
coordinate system and using the intersection of the two random
distances as the location at which a soil core should be taken or
a soil-pore liquid monitoring device installed. This system
works well for fields of both regular and irregular shape, since
the points outside the area of interest are merely discarded, and
only the points inside the area are used in the sample.
The location, within a given uniform area of a land treatment unit
(i.e., active portion monitoring), at which a soil core should be
taken or a soil-pore liquid monitoring device installed should be
determined using the following procedure:
(1) Divide the land treatment unit into uniform areas,
as defined in Section H of this document. A certified professional
soil scientist should be consulted in completing this step;
1-1
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(2) Map each uniform area by establishing two base lines at
right angles to each other which intersect at an arbitrarily
selected origin, for example, the southwest corner. Each baseline
should extend to the boundary of the uniform area.
(3) Establish a scale interval along each base line. The
units of this scale may be feet, yards, miles, or other units
depending on the size of the uniform area. Both base lines must
have the same scale.
(4) Draw two random numbers from a random numbers table
(usually available in any basic statistics book). Use these
numbers to locate one point along each of the base lines.
(5) Locate the intersection of two lines drawn perpendicular
to these two base line points. This intersection represents one
randomly selected location for collection of one soil core, or
for installation of one soil-pore liquid device. If this location
at the intersection is outside the uniform area, disregard and
repeat the above procedure.
(6) For soil-core monitoring, repeat the above procedure as
many times as necessary to obtain six soil coring locations within
each uniform area of the land treatment unit. If a uniform area is
greater than twelve acres, repeat the above procedure as necessary
to provide at least two soil coring locations per four acres.
[If the same location is selected twice, disregard the second
selection and repeat as necessary to obtain different locations]
This procedure for randomly selecting soil coring locations must
be repeated at each sampling event (i.e., semi-annually).
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DATE DUE.
(7) For soil-pore liquid monitoring, repeat the above
procedure as many times as necessary to obtain three locations for
installation of soil-pore liquid monitoring devices within each
uniform area. In addition, there should be no less than one
soil-pore liquid monitoring device (location) per four acres of
uniform area. Monitoring at these same randomly selected locations
will continue throughout land treatment unit life (i.e., devices do
not have to be relocated at every sampling event).
One point should be made regarding randomly locating soil-
pore liquid monitoring devices according to the procedure specified
above. In many cases, this procedure will result in the selection
of a sampling location situated in the middle of the active
portion. In order to prevent operational inconvenience and
sampling bias, the monitoring system should be designed and
installed so that the above-ground portion of the device is
located at least 10 meters from the sampling location. If the
above-ground portion of the device is located immediately above
the sampling device, the sampling location will often be avoided
because of operational difficulties. Thus, samples collected at
this location will be biased and not representative of the treated
area.
Locations for monitoring on background areas should be randomly
determined using the following procedure:
(1) Consult a certified professional soil scientist in
determining an acceptable background area. The background area
must have characteristics (i.e., at least soil series classification)
1-3
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similar to those present in the uniform area of the land treatment
unit it is representing.
(2) Map an arbitrarily selected portion of the background
area by establishing two base lines at right angles to each other
which intersect at an arbitrarily selected origin.
(3) Complete steps 3, 4, and 5 as defined above.
(4) For soil-core monitoring, repeat this procedure as
necessary to obtain eight soil coring locations within each
background area.
(5) For soil-pore liquid monitoring, repeat the above
procedure as necessary to obtain two locations for soil-pore liquid
monitoring devices within each background area.
Referencees
(1) Petersen, R.G., and L.D. Calvin. Sampling. In Methods of
Soil Analysis, Part 1^, Physical and Mineralogical Properties,
Including Statistics of Measurement and Sampling. C.A. Black, ed,
American Society of Agronomy, Inc., 1965. p. 57-59.
(2) N.C-118. Sampling and Analysis of Soils, Plants, Waste Waters
and Sludges: Suggested Standardization and Methodology. N.C.
Regional Publication 230. Kansas State University Agricultural
Experiment Station, 1975.
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