024401
Resource Conservation and Recovery Act
Subtitle C - Hazardous Waste Management
Section 3004 - Standards Applicable to Owners
and Operators of Hazardous Waste
Treatment, Storage, and Disposal
Facilities.
BACKGROUND DOCUMENT
Subpart F
Ground-Water Monitoring
U.S. Environmental Protection Agency
Office of Solid Waste
May 2, 1980
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TABLE OF CONTENTS
Page
I. INTRODUCTION 1
A. Legislative Mandate 1
B Key Definitions 2
II. RATIONALE FOR REGULATION 3
A. Importance of the Ground-Water Resources 3
B. Damage Case Summaries 3
C Federal and State Precedents 6
III. SYNOPSIS OF PROPOSED REGULATION 9
IV. COMMENT ANALYSIS AND RATIONALE FOR CHOSEN ACTION 12
A. Comments on Definitions 13
B. Specific Monitoring Requirements 22
1. Leachate Monitoring System 23
2. Applicability 31
3. Ground-Water Monitoring System 49"
4. Sampling and Analysis 75
5. Preparation, Evaluation and Response 98
6. Statistical Methods (Appendix IV) 109
7. Recordkeeping and Reporting 118
V. REFERENCES 125
Attachment No. 1 - Damage Cases 131
Attachment No. 2 - State Laws and Regulations 133
iii
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BACKGROUND DOCUMENT
GROUND-WATER MONITORING
I. INTRODUCTION
A. Legislative Mandate
Section 3004 of the Resource Conservation and Recovery Act of
1976 (RCRA) requires that the EPA Administrator promulgate regula-
tions establishing such performance standards, applicable to owners
and operators of facilities for the treatment, storage, or disposal
of hazardous wastes, as may be necessary to protect human health and
the environment. Section 3004(2) specifically requires that these
standards include requirements respecting satisfactory monitoring at
hazardous waste management facilities (HWMF).
The Agency interprets this provision to provide clear authority
for the RCRA Subtitle C regulations to require various types of moni-
toring at HWMFs. This document deals with regulations for ground-
water monitoring at hazardous waste management facilities.
The fundamental objective of ground-water monitoring at HWMF
sites is to serve as a continuing assessment of the quality of the
ground water in the uppermost aquifer which flows beneath the HWMF.
Introduction and transport of contaminants in such an aquifer could,
if undetected, result in a serious threat to human health and the
environment. The HWMF should be monitored in such a manner as to
detect, as early as possible, the movement of contaminants from the
HWMF into the ground water to allow prompt implementation of measures
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designed to correct any such contamination, if necessary. This con-
cept is implicit in the regulations discussed herein.
B. Key Definitions
The following definitions concerning ground-water monitoring
were the subject of substantial comment on the proposed rule and are
discussed in depth in Section IV below:
"Annular Space"
"Aquifer" (and "Usable Quantity")
"Endangerment"
"Ground Water"
"Hydraulic Gradient"
"Leachate Monitoring System"
"Monitoring Well"
"Unsaturated Zone"
"Water Table"
Other key definitions used in this document are:
"Facility" means all land and appurtenances, on it and to it,
used for the treatment, storage and/or disposal of hazardous waste.
A facility may consist of several treatment, storage, and/or disposal
operational units (e.g., one or more landfills, surface impoundments,
land treatment areas, or combinations of them). (See Part 260, Sub-
part B.)
"Leachate" means the liquid, including any suspended components
in the liquid, that has percolated through or drained from hazardous
waste. (See Part 265, Subpart N.)
"Saturated zone" or "zone of saturation" means that part of the
earth's crust in which all voids are filled with water. (NO com-
/
ments, proposed definition is retained.)
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II. RATIONALE FOR REGULATION
A. Importance of the Ground-Water Resource68
Almost one-half of the population (48%) of the United States de-
pends upon ground water as a source of drinking water. Of the total
population, 29% use ground water delivered by community systems and
another 19% have their own domestic wells (Figure 1). The rural
population dependent upon ground water is much higher (95%) than
the population served by public supplies (36%). The largest use of
ground water is irrigation which accounts for 67% of total ground-
water withdrawal. Public supplies are the second largest consumer
of ground water. Figure 2 illustrates the breakdown of ground-water
withdrawal by use.
B. Case Summaries
The potential for and existence of ground-water contamination
from hazardous waste land disposal facilities is well documented in
an EPA unpublished list of damage cases by Abby Howard.22 of the
two hundred forty-six cases surveyed in this document one hundred
twenty-six involved some form of ground-water contamination. The
following damage cases illustrate a few examples of the potential
for ground-water contamination.
(1) The Wisconsin Department of Natural Resources (DNR)
reported the existence of localized heavy ground-
water contamination in the vicinity of the Ansul
Company, which manufactures agricultural herbicides
in Marinette, Wisconsin. "
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SURFACE WAT5S -
PU3LJC SUPP
5! %
S-^^w'?**^?."•»VT//- i^*' •'-'"* -' -U. :TV.V^" ' '
^.".*_J=;'» >i-\ • ^*^*^»-*""*-^l-- — >"^_"-, ^
'SURFACE
RURAL DOMESTIC
SUPPLIES
o/
/o
Figure 1. Population served by source and supply, 1970
68
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SELF-SUPPLIED
INDUSTRY-
PUBLIC SUPPLIES
14 %
ELECTRIC
UTJL1TY-
2 %
RURAL DOMESTIC
. 4%
RURAL LIVESTOCK
2 %
« I CATION -87 %
Figure 2. Total ground-water withdrawal, by use, 1970.
68
5
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(2) An aluminum plant in Monroe County, Ohio, had grossly con-
taminated the ground water under its site. The source of
contamination was leachate from a used tailing pond and
used potline piles.44-
(3) A chemical plant in Hamilton County, Ohio, which utilizes
two infiltration lagoons for waste disposal had contami-
nated a very productive aquifer in the area. Discovery
of this occurred when new wells were installed on a nearby
property.43
(4) In 1972 shallow wells were installed near an arsenic pes-
ticide disposal site for the purpose of serving as a water
supply for a local construction company. Thirteen employ-
ees were stricken with what was later diagnosed to be ar-
senic poisoning.
(5) Contamination of ground water has occurred in Myers town,
Pennsylvania, as a result of disposal of arsenic wastes
from surface storage areas of a commercial laboratory.47
C. Federal and State Precedents
In developing these regulations, the Agency considered a number
of existing federal and state regulations and standards.
The following is a summary of these precedents as they relate to
ground-water monitoring:
1. EPA Recommendations for the Disposal of Pesticides and
Pesticide Containers(49)—
These guidelines recommend that, if appropriate incin-
eration facilities are not available, organic pesticides may
be disposed by burial in a "specially designated landfill."
Such landfills are those at which complete long term protec-
tion is provided for the quality of surface and subsurface
waters from pesticides and which are equipped with monitor-
ing wells, sampled and analyzed to detect any leakage.
2. EPA PCBs - Manufacturing, Processing, Distribution in Com-
merce, and Use Prohibitions^!)—
These regulations require disposal of certain PCB
wastes in chemical waste landfills which must be designed
and operated to provide containment of PCB wastes. Such
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landfills must be equipped with a ground-water monitoring
system described in the regulations. The monitoring system
installation, sampling and analysis requirements are very
similar to those described in these hazardous waste manage-
ment regulations.
3. EPA Land Disposal Facilities and Practices Criteria^^ —
While these regulations do not specifically require
ground-water monitoring at disposal facilities, they do,
however, require that complying facilities not discharge
certain substances to ground water. Similar to these
hazardous waste management regulations the ground water
quality standards of the criteria are to be applied at
the edge of the waste (i.e., the solid waste boundary).
4. Selected State Regulations and Standards —
A review of Agency files has yielded a list of 13
states which require some form and extent of ground-water
monitoring at hazardous waste management facilities.
These regulations and standards are summarized in Attach-
ment No. 2.
In addition, a survey conducted by the Minnesota
Pollution Control Agency has yielded information regarding
the status of State regulatory requirements for ground-water
monitoring at waste disposal facilities.12
In consideration of the Congressional mandate in RCRA, the
importance of protecting ground-water resources and the potential for
harm to these resources from hazardous waste management activities,
as evidenced by the preceding damage case summaries, the Agency has
determined that ground-water monitoring requirements need to be in-
cluded in these final rules. The concern for minimizing the extent
of ground-water contamination, caused by waste management activities,
through reliance upon ground-water monitoring systems, as demon-
strated in the summaries of state regulations, supports the Agency
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decision to require ground-water monitoring in these rules. Exami-
nation of damage cases and Federal/State monitoring requirements has
aided the Agency in better assessing the magnitude of ground-water
contamination attributed to disposal activities as well as yielding
valuable information on monitoring systems and technologies (e.g.,
well number and construction, etc.).
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III. SYNOPSIS OF PROPOSED REGULATION
RCRA Section 3004 Regulations for ground-water monitoring at
hazardous waste landfills and surface impoundments were proposed as
§250.43-8 in the Federal Register [43 FR 59005] on December 18, 1978.
Proposed §250.43-8 also dealt with leachate monitoring systems.
These systems have been deleted from the final rules for reasons
discussed in Section IV and will not be discussed here.
The proposed rule specified that a ground-water monitoring sys-
tem must consist of at least four monitoring wells. One well was to
i
be placed hydraulically upgradient from the facility to supply in-
formation on background quality of ground water. A minimum of three
wells were to be placed downgradient within the facility property
boundary at different depths to maximize the detection of any leach-
ate which had migrated into ground water. At least one downgradient
well was to' be placed immediately adjacent to the active portion of
the facility. All wells were to be cased and the annular space back-
filled. A "Note" allowed variances to the number and depth of wells
in certain cases.
All wells were to be sampled monthly for one year (beginning at
least three months before receiving wastes at a new facility) to pro-
vide background statistics on ground water quality. These samples
were to be subjected to a comprehensive analysis to quantify the con-
centrations of all parameters included in EPA's Interim Primary and
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Proposed Secondary Drinking Water Standards, beryllium, nickel, cya-
nide and phenols, and to detect the presence of organic constituents
by scanning by gas chromatography. In addition, these samples were
to be analyzed for specific conductivity, pH, chloride, total dis-
solved solids, dissolved organic carbon, and the principal hazardous
constituents of the hazardous waste handled at the facility. This
latter analysis was called a "minimum analysis," and was a sub-set of
the comprehensive analysis. A ""Note" allowed variances to the list
of these analyses in certain circumstances.
After the one-year period to establish background levels, sam-
ples were to be taken quarterly or semi-annual ly, depending upon the
ground-water flow rate, and subjected to the minimum analysis. How-
ever, at least annually, the wells were to be sampled and subjected
to the comprehensive analysis.
If the analyses of samples showed a significant difference in
any parameter from the background levels (as determined by the Stu-
dent's t, single-tailed test at the 95 percent confidence level),
the facility owner/operator was to discontinue facility operations,
notify EPA (within seven days), determine the cause of the discrep-
ancy, and determine the extent of ground-water contamination.
Otherwise the facility owner/operator was to keep records of
monitoring activities and analysis data for three years and send the
analytical data to EPA on a quarterly basis.
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During the interim status period, the proposed rules applied
only to owners/operators of facilities where a ground-water monitor-
ing system was already in place.
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IV. COMMENT ANALYSIS AND RATIONALE FOR CHOSEN ACTION
A few commenters specifically addressed these requirements as
they apply to facility owners and operators with interim status.
These commenters suggested that the proposed rules apply to all
facilities during the interim status period. Since these comments
dealt with the scope of the proposed rules, rather than their sub-
stance, the comments are discussed in the background document on
purpose, scope, and applicability. However, since the final interim
status regulations now do indeed require ground-water monitoring at
all facilities, not just those with a monitoring system already in
place, all substantive comments on the proposed rules are discussed,
below, except those relating specifically to permitted facilities.
Comments related to permit award will be addressed in the background
document for 40 CFR 264, Subpart F.
Similarly, comments which addressed the proposed ground water
human health and environmental standard (GWHHES) are not addressed
here. The GWHHES requirements were not proposed for facilities under
interim status and have not been included in these final interim
status regulations.
The remaining comments received can be grouped into those ad-
dressing (1) definitions concerning ground-water monitoring, and (2)
specific proposed monitoring requirements. In the following analy-
sis, the comments are addressed in that order.
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A. Comments on Definitions
1. "Annular Space"
The term "annular space" was defined to mean the space between
the bore hole and the casing. A bore hole is the man-made hole
in a geological formation for installation of a monitoring well.
Rationale for Final Definition
No comments were received on the proposed definition of this
term. The Agency feels that common English usage of this term is
generally understood. Therefore, this term has not been defined
in these final regulations. Use of the term in the regulations is
clarified where necessary.
2. "Aquifer" (and "Usable Quantity")
The term "aquifer" was defined in the proposed regulations as a
geologic formation that is capable of yielding usable quantities
of ground water to wells or springs.
Rationale for Proposed Definition
This definition is essentially that found in the dictionary,
for example: "aquifer - an underground layer of porous rock, sand,
etc., containing water, into which wells can be sunk" (Webster's New
World Dictionary, Second College Edition). In order to make this
definition somewhat more specific the Agency added language limiting
aquifers to those underground soils capable of yielding "usable quan-
tities" of ground water and specifically requested (in the preamble
to the proposed regulations) comments on this concept and suggestions
on defining "usable quantities." The Agency also suggested that 600
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gallons/day (an estimate of the needs of an urban family of 4 people)
could serve as a lower limit.
Comments Received
Since the term "usable quantity" is the key to the definition
of aquifer, virtually all comments on the definition related to this
term. In general, comments on the suggestion of 600 gallons/day
argued the impract icality of specifying such a number. It was stated
by one commenter that some aquifers in California serve as drinking
water supplies with yields only in the range of 50-200 gallons/day.
Other commenters, in less specific terms, explained that the minimum
acceptable yield of an aquifer for drinking water purposes depended
upon available alternative sources of drinking water. If no suitable
surface water supply or other ground-water source of drinking water
is available, and drinking water is necessary, then an aquifer yield-
ing any measurable quantity may be considered "usable." Another way
in which this opinion was expressed was that "usable quantity" should
be a case-by-case determination based upon local need and resources.
It was also suggested that the definition have an accompanying "Note"
explaining that "usable quantity" could only be determined on a local
basis.
Another suggestion attempting to avoid the problem of specifying
"usable quantity" would replace this term with for beneficial use
for a long period of time."
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Several comments discussed the issue of quantity vs. quality of
ground water. From one extreme, a commenter suggested protection of
all ground water regardless of current quality or potential yield in
order to assure underground sources of water for future generations.
Similarly, commenters suggested that any aquifer capable of yielding
water, or at least those yielding water containing less than 10,000
mg/1 total dissolved solids, be considered as "usable" in these regu-
lations. From the opposite extreme, a commenter suggested that the
regulations only address "potable subsurface water."
Comment Analysis/Rationale for Chosen Action
In general, the Agency agrees that it is infeasible to specify a
minimum yield for "usable quantity," in the definition of "aquifer,"
which could be applicable throughout the country. The Agency de-
sires, however, to protect even low yield ground-water aquifers,
which supply drinking water, from contamination from hazardous waste
management activities. Toward this end, the Agency has determined
that the suggested minimum of 600 gallons/day was too high. As in-
dicated, this consumption rate is the typical requirement for a sin-
gle family dwelling for 4 people in an urban area. In such an area,
this design consumption rate includes provision for such uses as fire
protection in addition to gardening and other non-human consumption
uses. In a rural area the actual water consumption rate for a family
of 4 people could be dramatically less. An EPA Water Supply Bulletin
suggests that 50 gallons/capita/day can satisfy most domestic water
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requirements.67 Even in Light of this discussion the Agency also
recognizes that 200 gallons/day (rural family of 4 people) may be
too high or too low in specifying a minimum yield to define "usable
quantity" in specific local situations. For these reasons the Agency
has decided to modify the proposed definition for "aquifer" in the
final regulations. No specification for "usable quantity" has been
included. However, the Agency does wish to draw attention to the
fact that the yield of an aquifer is an important factor in determin-
ing the degree of aquifer protection needed; therefore, it has used
the term "significant amount" in the definition. Only prevailing
local conditions determine whether an aquifer is capable of yielding
"significant amounts" of water.
The definition of "aquifer" in the final regulation reads:
"Aquifer" means a geologic formation, group of formations, or
part of a formation capable of yielding a significant amount
of ground water to wells or springs.
3. "Endangerment"
The term "endangerment" was defined to mean the introduction of
a substance into ground-water so as to:
(i) Cause the maximum allowable contaminant levels established
in the National Primary Drinking Water Standards in effect
as of the date of promulgation of this Subpart to be
exceeded in the ground-water; or
(ii) Require additional treatment of the ground water in order
not to exceed the maximum contaminant levels established in
any promulgated National Primary Drinking Water regulations
at the point such water is used for human consumption; or
(iii) Reserved (Note: Upon promulgation of revisions to the
Primary Drinking Water Standards and National Secondary
Drinking Water Standards under the Safe Drinking Water Act
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and/or standards for other specific pollutants as may be
appropriate.)
V
Rationale for Proposed Definition
The basis of this definition is a concept included in the Safe
Drinking Water Act which relates ground water protection to avoidance
of increased treatment. Any addition of substances to ground water
which would require additional treatment to render the water fit for
human consumption constitutes endangerment.
Comments Received
Commenters stated that application of the primary drinking water
standards, only, to ground water quality was unprotective and that
broader standards should be specified. Others commented that changes
in the primary standards may not always be incorporated in these RCRA
rules. Other comments argued that the endangerment concept was in-
consistent with objectives of RCRA Section 3004 which requires pro-
tection of human health and the environment, not only drinking water.
Response to Comments and Rationale for Final Definition
The term endangerment was used in the proposed regulations in
the §250.42-1 Ground-water Human Health and Environmental Standard.
This standard has been deleted from these final rules; therefore, the
term endangerment has also been deleted.
4. "Ground Water"
The term "ground water" was defined to mean water in the satur-
ated zone beneath the land surface.
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Rationale for Proposed Definition
This definition was derived and modified from two references,
the Webster's Collegiate Dictionary and the Glossary of Geology,
published by the American Geological Institute. The objective of
this definition was to emphasize that only the water beneath the land
surface that is contained in the saturated zone is considered ground
water.
Comments Received
The major comment received was that a clear distinction between
the terms "aquifer" and "ground water" should be made such that the
terms cannot be used interchangeably.
Response to Comments and Rationale for Final Definition
The term "ground water" is clearly defined to mean water in the
saturated zone and the term "aquifer" means a geologic formation ...
yielding ground water. In one case the water is defined and in the
other the formation which is capable of yielding ground water is de-
fined. The Agency does not use these terms interchangeably in the
final rule.
Final Definition
The proposed definition is retained for final regulations.
5. "Hydraulic Gradient"
The term "hydraulic gradient" was defined to mean the change in
hydraulic pressure per unit of distance in a given direction.
The proposed definition was derived from the understanding that
the pressure exerted by a column of water above a given datum
changes as a function of the height of that column of water. In
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an unconfined aquifer the hydraulic gradient is a change in
water Level (and thus a change in pressure exerted by that
water) per unit distance.
Comments Received
Commenters stated that the use of the phrase "change in hydrau-
lic pressure" is incorrect. They stated that a clearer, more widely
applicable definition would be "a change in hydraulic head per unit
of distance." Their rationale was that the slope of the water table
in an unconfined aquifer defines the hydraulic gradient, yet there
is no pressure change along the water table in either the up-or down-
gradient direction. It does represent a change in total head due to
change in water-table elevation.
Response to Comments and Rationale for Final Definition
The Agency agrees that the proposed wording of the definition is
not the generally accepted or understood definition. However, since
this term is no longer used in these final regulations, no definition
for this term is included.
6. "Leachate Monitoring System"
The term "leachate monitoring system" was defined to mean a
system beneath a facility used to monitor water quality in
the unsaturated zone (zone of aeration) as necessary to detect
leaks from landfills and surface impoundments* (For example, a
pressure-vacuum lysimeter may be used to monitor water quality
in the zone of aeration.)
Rationale for Proposed Definition
This definition was intended to convey the basic goal of a
system that would detect leachate from a facility in the underlying
unsaturated zone.
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Comments Received
The major comment was that the definition precludes the use of
leachate monitoring devices which do not rely on collection of
samples for quantitative anlay^is.
Response to Comments and Rationale for Final Definition
The final regulations have deleted leachate monitoring as a
requirement; therefore, a definition for this term has not been
included in these regulations.
7. "Monitoring Well"
The term "monitoring well" was defined to mean a well used to
obtain water samples for water quality analysis or to measure
ground-water levels.
Comments Received:
No comments were received on this definition.
Rationale for Final Definition
The Agency has decided not to specify a formal definition for
this term and instead to rely on normal English usage of the term.
8. "Unsaturated Zone"
The "unsaturated zone" ("zone of aeration") was defined to mean
the zone between the land surface and the nearest saturated
zone, in which the interstices are occupied partially by air.
Rationale and Support for Proposed Definition
The proposed definition was taken from U.S. Geological Survey
Water-Supply Paper 1988, "Definitions of Selected Ground Water
Terms,"29 and modified considerably to accommodate the desired
environmental protection conveyed in the proposed regulations. In
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the proposed regulations leachate monitoring within the unsaturated
zone was required. Because of this it was important that the unsat-
urated zone be clearly defined.
Comments Received
Comments on the proposed definition suggested that the defini-
tion should be changed to read "... the zone between the land surface
and the nearest saturated zone," thus deleting the phrase "... in
which the interstices are occupied partially by air." No rationale
was submitted for this change.
Response to Comments and Rationale for Final Rule
The proposed definition attempted to describe the nature of the
unsaturated zone by adding the phrase "in which the interstices are
occupied by air." Reconsideration of the definition has revealed
that this clarification, describing the nature of the unsaturated
zone, is not necessary. A definition which merely describes the
unsaturated zone as that zone between the land surface and the water
table is adequate.
The definition in the final regulations reads:
•
"Unsaturated zone" or "zone of aeration" means the zone between
the land surface and the water table.
9. "Water Table"
The term "water table" was defined to mean the upper surface of
the zone of saturation in ground waters in which the hydrostatic
pressure is equal to atmospheric pressure.
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Rationale for Proposed Definition
The proposed definition was a modified dictionary definition.
The modification incorporating the concept of "hydrostatic pres«".re"
was intended to better convey the meaning of a water table with
regard to the proposed regulations.
Comments Received
One comment stated that as defined, "water table" refers to the
top of an aquifer. This is often the case but it does not hold true
in the case of a confined aquifer. Another comment suggested that
the definition be clarified with regard to hydraulic pressure, that
is, explain that pressure increases downward from the water table.
Response to Comments and Rationale for Final Definition
The Agency agrees that the proposed definition was not as clear
as it could have been. In the final regulations the term "water
table" has been deleted from the final regulations including the de-
finitions. Where necessary, the Agency is relying on normal English
usage.
B. Specific Monitoring Requirements
Proposed §250.43-8 addressed both ground-water and leachate mo-n-
itoring, and was organized as follows:
a. Ground-water monitoring system
b. Leachate monitoring system
c. Sampling and analysis
d. Recordkeeping and reporting.
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As mentioned earlier, the Agency has deleted leachate monitoring
at landfills and surface impoundments from the final rule. In this
section, the comments received on this issue, and the Agency's ratio-
nale for deleting the provision, are presented first.
The final interim status rule for ground-water monitoring has
been restructured as follows:
§265.90 Applicability
§265.91 Ground-water monitoring system
§265.92 Sampling and analysis
§265.93 Preparation, evaluation and response
§265.94 Recordkeeping and reporting.
The discussion of comments received on the proposed rule and the
Agency's rationale for the final rule are discussed in that order.
1. Leachate Monitoring System
Synopsis of Proposed Regulation
The proposed regulations required that a leachate monitoring
system be installed beneath a facility and above the ground water
in the zone of aeration. Drilling through the bottom or sides of a
facility to install the system was prohibited. The purpose of the
monitoring system was to collect samples in the zone of aeration.
The "Note" in the proposed regulations waived this monitoring
system requirement if the owner/operator could demonstrate that an
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alternative leachate monitoring technique would detect leaks as ef-
fectively as the prescribed system. The "Note" identified as accept-
able substitutes the Leachate Detection and Removal System described
in §250.45-2(b)(13) for landfills and the Leachate Detection System
described in §250.45-3(c)(3) for surface impoundments.
Sampling and analysis of the quality of water obtained from the
leachate monitoring system was required monthly for twelve (12)
months at existing facilities and at least three (3) months prior to
operation of new facilities to establish the background quality of
water in the zone of aeration. The proposed regulations specified
both a comprehensive analysis list, to be used for establishing back-
ground quality and annually thereafter, and a minimum analysis list
to be determined quarterly.
"Notes" included in the proposed regulations waived these re-
quirements if it could be demonstrated that an adequate volume of
water for analysis could not be obtained from the leachate monitoring
system.
Rationale for the Proposed Regulation
While recognizing that leachate monitoring technology was still
being refined, the Agency included these requirements for leachate
monitoring, using available equipment, to provide an "early warning
that ground-water contamination may occur." The Agency contended
that a "leak must move through and cause extensive contamination of
the zone of aeration before it reaches and contaminates the ground
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water," and that, therefore, ground-water monitoring alone was insuf-
ficient to protect the environment.
Comments Received
Many comments were received on the leachate monitoring require-
ments included in the proposed regulations. Only a few of these
comments supported the proposed requirements. These commenters sug-
i
gested leachate monitoring as a necessary complement to ground-water
monitoring. One commenter, however, suggested that ground-water
monitoring only need be initiated if the leachate monitoring system
indicated contamination in the zone of aeration. Other commenters
suggested deletion of the "Note" allowing variances to the require-
ment.
The majority of comments received recommended deletion of the
leachate monitoring requirements and reliance upon ground-water mon-
itoring to detect contamination for a variety of reasons discussed
below. A few commenters recommended that the leachate monitoring
requirement could be waived by the Regional Administrator depending
upon facility location and design. While no rationale was offered,
some commenters suggested waiving these requirements except at sur-
face impoundments or except at facilities using synthetic liners.
Waiving the leachate monitoring requirement at existing facili-
ties was the most frequently suggested comment. Commenters suggested
that leachate monitoring technology was poor, at best, and nearly
impossible at existing facilities especially since drilling through
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the bottom or sides of the facility liner was prohibited. Most cotn-
metiters agreed that the liner should not be penetrated, although a
few commenters stated that this was unnecessarily restrictive and
that drilling through a liner could be accomplished without creating
a pathway for contaminants to enter the ground water.
Three possible techniques for installing a leachate monitoring
system at existing facilities were identified and critiqued by com-
menters. The first involved digging a trench around the facility to
a depth greater than that of the wasta and then drilling or jacking
monitoring probes beneath the facility. Commenters stated that
equipment for drilling and jacking is scarce and expensive. Further-
more such equipment is limited to about a 200 foot maximum penetra-
tion which means that no facility greater than 400 feet in diameter
could be so equipped. One commenter included a cost analysis to
retro-fit a 200 foot square surface impoundment, which showed that
the cost of trenching and drilling would be about the same as the
cost of facility replacement. Another installation technique iden-
tified was angle drilling for monitoring probe placement but was
described as possible only at very small shallow facilities.
The final technique identified by coramenters involved removal
of the waste and installation of a leachate collection and removal
system. Commenters explained that this technique would also equal
or exceed the cost of facility replacement.
26
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The availability of leachate monitoring technology and equipment
was challenged by commenters. The only two monitoring techniques
identified by commenters were lysimeters (pressure/vacuum) for sam-
pling followed by analysis, and electrical conductivity measurements.
Electrical techniques were alleged to be capable of detecting the
presence of contaminated water but not quality. As with lysimeters,
electrical techniques increase in effectiveness with increasing mois-
ture. Regarding use of lysimeters, one commenter summarized the con-
cerns raised by other commenters by describing the experience at a
new New Jersey facility equipped with lysimeters in the aeration zone
as follows:
- lysimeters were subject to blinding (plugging) and did not
respond well to backflushing
- lysimeters were susceptible to damage, during and following
instal lation
- there was no way to know whether lysimeters were working or
not (i.e., no moisture present or plugged—result is the
same)
it was impossible to repair or replace defective lysimeters.
Other problems with lysimeters identified by commenters included:
lysimeters are sampled through small diameter tubes extending
from the lysimeter to the sampling point at the waste bound-
ary which could result in insufficient sample volume due to
loss of sample on the walls of the tube (one commenter sug-
gested a 20 foot limit)
lysimeters only sample the immediate surrounding soil volume
necessitating a very large number of lysimeters for complete
coverage beneath a large facility, with no guidance included
in the proposed regulations
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Commenters suggested that the only effective means of leachate
monitoring would be the use of a double liner equipped with a collec-
tion and removal system between the liners. They further asserted,
however, that this is not zone of aeration monitoring and that this
is impractical for existing facilities since this cannot be accom-
plished without removal of all the waste.
Some commenters rejected the entire concept of leachate moni-
toring because:
where natural in-place soils are used as a facility liner
there may be no zone of aeration above the water table
a saturated clay liner may be more effective in minimizing
leachate migration than an unsaturated soil
any samples obtained from a saturated liner may contain
leachate contaminants but this would not necessarily indi-
cate impending ground-water contamination
even where a zone of aeration exists it may be very difficult
to decide where to place a leachate monitoring system if
seasonal fluctuations of the ground-water table are large
detection of leachate in the zone of aeration may not sig-
nificantly precede detection in the ground-water monitoring
system.
Finally some commenters rejected the "Note" allowing reduced
monitoring and analysis if an insufficient volume of sample were ob-
tainable from the leachate monitoring system since a full leachate
monitoring system would have to be installed to demonstrate that it
was unnecessary.
Agency Response/Rationale for Chosen Action
As a result of these comments, the Agency undertook a reevalua-
tion of available information on leachate monitoring technology.
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Information available to EPA on the subject of aeration zone monitor-
ing is very limited. Both the EPA ground-water monitoring manual*8
and recent Office of Research and Development studies?3 discuss
various devices and techniques for obtaining water (leachate) samples
from the aeration zone beneath waste disposal facilities. In all re-
ported applications of aeration zone monitoring for the presence of
leachate in soil pore water, the investigations have been research-
oriented. In general, these investigations have attempted an assess-
ment of the impact of leachate on water present in the aeration zone
beneath landfills. EPA is unaware of any applications of aeration
zone monitoring to determine the integrity of containment design
waste disposal facilities.
Regarding reliance upon aeration zone monitoring for detection
of the failure of containment design waste disposal facilities, EPA
is forced to rely upon a common-sense evaluation of the available
technology in the absence of research or "real world" experience.
The most commonly, utilized aeration zone monitoring device has
been the suction (i.e., pressure-vacuum) lysimeter.1$ These de-
vices are porous, usually ceramic, cylinders emplaced in the soil.
By alternating application of vacuum and pressure, soil pore water is
drawn into the lysimeter from the soil immediately surrounding the
lysimeter. The volume of soil contributing pore water is dependent
upon the characteristics of the soil and the vacuum applied. In gen-
eral, the contributing soil volume is small as is the lysimeter.18
29
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In order, therefore, to sample (monitor) an entire horizon beneath
a waste management facility, the spacing of emplaced lysimeters must
be small. At large facilities, the number of needed lysimeters could
be several hundred if all possible leaks are to be detected. Even if
such large numbers of lysimeters were to be installed beneath a land-
fill or surface impoundment, the logistics of monitoring these de-
vices would be onerous because of the large number of plastic tubes
(two connected to each lysimeter) required for sampling. Other dis-
advantages of lysimeters include their reported tendency to deteri-
orate and/or plug over time.73 Research applications of these
devices have seldom exceeded two years. Once "fouled," these devices
are irreplaceable beneath a landfill or surface impoundment.
Deletion of the leachate monitoring requirements for landfills
and surface impoundments from the final regulations reflects the sug-
gestions of commenters. EPA considers the ground-water monitoring
provisions discussed below as the only suitable technique enabling
detection of leachate contamination of ground water as the leachate
migrates from the boundary of waste management.
In the case of land treatment facilities, however, the Agency
has realized the feasibility and appropriateness of aeration zone
monitoring. While aeration zone monitoring was not included in the
proposed regulations, these final regulations include this require-
ment. Both soil core analyses and lysimeter sample analyses are
requirements now contained in Subpart M of these regulations.
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While the Agency is aware that some of the same problems with
lysimeter monitoring beneath landfills and surface impoundments would
be encountered beneath a land treatment facility, most of these prob-
lems could be dealt with.
Two major differences exist when comparing the feasibility of
lysimeter monitoring beneath a land treatment facility versus a land-
fill or surface impoundment. At a land treatment facility there is
continued access to emplaced lysimeters for repair or replacement,
and moisture in the zone of aeration is expected, at least for a
short period of time following waste application or rainfall. Such
monitoring beneath a land treatment facility is not for the purpose
of detecting discrete leaks, but rather is to measure the progress of
applied waste through the soil. The monitoring objective is facility
effectiveness; a spacing of installed monitoring devices which pro-
vides representative indications of the movement of waste constitu-
ents through the facility can readily be achieved at land treatment
facilities.
A more complete discussion of zone of aeration monitoring at
land treatment facilities is included in the background document for
Subpart M.
2. Applicability
Synopsis of Proposed Regulation
The proposed regulations, §250.43-8, required the owner/operator
of a landfill or surface impoundment to install, maintain, and oper-
ate a ground-water monitoring system (GWMS) and a leachate monitoring
31
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system (LMS) and to comply with specified sampling and analysis and
recordkeeping and reporting requirements.
The proposed regulations also included a "Note" in §250.43-8(a)
with a provision to allow for no or a lesser degree of ground-water
monitoring if the owner/operator demonstrated that the geologic and
hydrologic conditions underlying the facility indicated no potential
for discharge to ground water.
The requirements for interim status in the proposed regulations
stated that both leachate and ground-water monitoring must be con-
ducted, where a facility has a ground water and/or leachate monitoring
system in place. Therefore, only those provisions under sampling and
analysis, and recordkeeping and reporting (250.43-8(c) and (d)) of
the proposed regulations were required for facilities under interim
status.
Rationale for the Proposed Regulation
The objective of the proposed leachate and ground-water moni-
toring requirements was to detect any discharge of contaminants from
hazardous waste management facilities as early as possible. The LMS
•
was intended to intercept leachate in the unsaturated zone. The GWMS
was required so as to detect contaminant migration from the facility
into ground water.
The proposed "Note" was intended to provide the owner/operator
an opportunity to demonstrate that lesser or no ground-water
32
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monitoring was appropriate at his facility based on geologic and
hydrologic conditions.
Comments Received/Rationale for Chosen Action
Ground-water and leachate monitoring. One commenter felt that
requiring the installation of both an LMS and a GWMS where "no prob-
lems have been detected" was too cautious and too expensive. The
commenter recommended choosing one monitoring system or the other on
a case-by-case basis depending on site geology, drainage, weather and
related site-specific factors.
The Agency does not agree that the proposed requirement for
an LMS and a GWMS at landfills and surface impoundments was either
too cautious or too expensive. The initial objective of subsurface-
facility monitoring was to detect ground-water contamination as early
as possible. Therefore, an LMS was a proposed requirement for land-
fills and surface impoundments. The LMS requirement was deleted for
landfills and surface impoundments for technical reasons only, as ex-
plained in the discussion on leachate monitoring. However, as fully
described in that discussion, leachate monitoring is both technically
feasible as well as useful at landfarms (now called land treatment
facilities) and is required in the final regulations for those facil-
ities.
The Agency believes that a GWMS alone is sufficient at landfills
and surface impoundments to detect ground-water contamination, since
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downgradient monitoring wells are required to be located and in-
stalled where they will be able to detect contaminant discharges as
early as possible, as described in the discussion of well location.
In contrast with landfills and surface impoundments, no ground-
water monitoring was proposed for land treatment facilities. How-
ever, comments on the desirability of ground-water monitoring at land
treatment facilities were requested in the preamble of the proposed
regulations for land treatment facilities, especially to seek reac-
tion to requiring only soil monitoring as the measure of environmen-
tal performance. The .Agency, in its rationale for proposing only
soil monitoring at land treatment facilities, suggested that soil
monitoring would detect waste constituents long before ground-water
monitoring. The Agency was not, and still is not, aware of any
documented case of ground-water contamination resulting from hazard-
ous waste land treatment.
Commenters presented opinions both for and against requiring
soil monitoring and/or ground-water monitoring at land treatment fa-
cilities. Commenters favoring inclusion of ground-water monitoring
suggested that soil monitoring was limited by its low reliability of
detecting highly mobile contaminants and should not be relied upon
alone to provide protection to ground water. Others favoring inclu-
sion of ground-water monitoring questioned the Agency's interpreta-
tion of when contaminants in the soil constitute a threat to the
environment. This criticism was based on the proposed requirement
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Commenters who opposed ground-water monitoring at land treatment
facilities pointed to a lack of data on adverse ground-water impacts
and also felt that the proposed siting and surface controls would
offer added protection of ground water.
The Agency believes that the human health and environmental
risks stemming from undetected ground-water contamination justify the
requirement of ground-water monitoring at land treatment facilities.
These final regulations for ground-water monitoring at hazardous
waste facilities under interim status are not applicable until one
year after the effective date of these regulations. One year has
been provided since the proper installation of a GWMS requires a
significant investment in time and money with careful planning by
experts (e.g., trained hydrogeologists) to determine appropriate well
locations, depths, etc. The anticipated demand for and possible
shortage of qualified hydrogeologists to perform such work was also
considered by the Agency in providing this time.
The final interim status rule states:
§265.90 (a) Within one year after the effective date of these
regulations, the owner or operator of a surface im-
poundment, landfill, or land treatment facility which
is used to manage hazardous waste must implement a
ground-water monitoring program capable of determining
the facility's impact on the quality of ground water
in the uppermost aquifer underlying the facility,
except as §265.1 and paragraph (c) of this Section
provide otherwise.
Demonstration of acceptability of a lesser degree of (or no)
ground-water monitoring. Several commenters favored less stringent
36
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or other conditions than those of the proposed "Note" for demonstrat-
ing that a lesser degree of (or no) ground-water monitoring would be
acceptable. Factors which commenters believed should be evaluated in
such a demonstration include: geologic and hydrologic conditions of
the facility area, status of the underlying ground water, nature of
the waste, expense of monitoring, facility design, and the state-of-
the-art of ground-water monitoring technology.
Commenters felt that lesser or no monitoring should be accept-
able if there was "no reasonable potential" or a "low potential" for
contamination of ground water (e.g., in dry areas with deep pressur-
ized aquifers).
In considering such comments, the Agency agrees that the provi-
sion in the "Note" of the proposed regulations which based acceptance
of no or a lesser degree of ground-water monitoring on "no potential
for discharge to ground water" is inappropriate and has revised this
requirement. Instead, in the revision, if the owner/operator can
demonstrate that hydrogeologic conditions underlying the facility and
other conditions indicate a low potential for migration of hazardous
waste or hazardous waste constituents from the facility via the up-
permost aquifer to water supply wells or to surface water, a lesser
degree of ground-water monitoring may be utilized (i.e., reduced
requirements from those specified in this Subpart). This revision
results from the basic technical problem that an owner/operator may
be unable to demonstrate conclusively that no potential for discharge
37
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exists. However, he may be able to demonstrate a low potential for
ground-water pollution.
The revised approach is not intended to weaken the objective
of these regulations. The Agency recognizes, however, that certain
hydrogeologic, climatic and other factors reduce the threat of leach-
ate being generated or ground water being impacted. In these situa-
tions reduced monitoring may be warranted. Examples of such cases
may be found in parts of southwestern United States where the water
table is very deep and geologic materials in the unsaturated zone are
of low hydraulic conductivity. However, in most other parts of the
United States, a facility will be expected to monitor ground-water as
described in this Subpart.
The demonstration that a lesser degree of monitoring is warran-
ted, now, must be certified by a qualified geologist or geotechnical
engineer. This is to provide an assurance that the complicated
issues involved in predicting the migration of constituents in ground
water will be addressed by experts in the field. The factors which
must be addressed in evaluating whether a lesser degree of ground-
water monitoring is warranted are described below. Each factor is
discussed with regard to its relevance in making such an evaluation.
There is no attempt in this section to develop a scheme for measuring
the potential for ground-water pollution or for contamination of
water supply wells.
38
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Geologic and hydrologic conditions of the facility area. A
thorough hydrogeologic investigation of the characteristics of both
the saturated zone and the unsaturated zone is required. The proper-
ties of both these zones influence the rate contaminants will mi-
grate and the degree to which contaminants will be attenuated in the
subsurface. Hydrogeologic factors must be considered through evalua-
tions of logs of test borings made by a geologist present during
drilling. Any other appropriate evidence such as geophysical data
may also be used in the evaluation. The Agency believes that a geol-
ogist should be .present during drilling since he is best qualified to
interpret the nature of the subsurface materials encountered in the
borings, especially since such materials often cannot be obtained in
such a manner (i.e., intact over the full core thickness) so as to
perform such observation at an off-site laboratory. Such interpreta-
tion is an active field procedure, in which a geologist observes and
records pertinent information about the earth materials being re-
moved. This information includes: general description of the mate-
rial (e.g., clay, sand, silt, — relating to particle size); abrupt
changes in materials (interfaces); or gradations from one material to
another. Several methods are available for evaluating and weighing
the potential for ground-water pollution based on the characteristics
of these zones.28,55 Also, review of these and other techniques,
their advantages and disadvantages, is given by Roy F. Weston,
Inc.71
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A water balance assessment should be made to establish if a
lesser degree of monitoring is warranted. Measurements of precipita-
tion, evapotranspiration, runoff and infiltration enable one to es-
tablish how much water infiltrates the waste. This in turn influ-
ences the amount of leachate that could be generated at the facility.
The water balance, as developed in the soil and water conserva-
tion literature, is based upon the relationship among precipitation,
evapotranspiration, surface runoff, and soil moisture storage. Pre-
cipitation represents that amount of water added. Evapotranspira-
tion, the combined evaporation from the plant and soil surfaces and
transpiration from plants, represents the transport of water from the
earth back to the atmosphere, the reverse of precipitation. Su-face
runoff represents water which flows directly off the area of concern.
The soil moisture storage capacity represents water which can be held
in the soil.19
The 'location and proximity of water supply wells and the type of
water use in the vicinity of the facility should be known. Such
considerations are important if waste facilities are within the
sphere of influence of a pumping water supply well. In this case,
once contaminants have entered ground water, the likelihood of them
reaching the water supply is very high.
Status of the underlying ground water. Commenters felt that
facilities overlying certain aquifers should be exempted from the
ground-water monitoring requirements if the underlying aquifer is
40
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"not usable" and is in a "geologically isolated basin"; if the under-
lying aquifer has greater than 10,000 parts per million total dis-
solved solids or is not otherwise "safe for drinking or fresh-water
use"; if the underlying aquifer is "saline and non-useful"; if the
underlying aquifer is already "grossly contaminated" or used for
purposes other than drinking; if the ground water underlying the
facility area was not used for domestic or industrial purposes; or if
the underlying ground water was "perched" water with low quality and
quantity.
In responding to comments on ground-water quality underlying a
facility, the Agency believes it would not be in the interest of
human health and environmental protection to provide a "blanket" ex-
emption for a facility overlying an aquifer which is not a drinking
water supply. Such aquifers may be hydraulically connected with and
may serve as a path for contamination to migrate to a drinking water
supply at some distance from the facility. Furthermore, an aquifer
which is not usable because it is too contaminated may discharge
contaminants to surface waters or to water supply wells (not only
drinking-water wells), thereby limiting the use of these waters for
human purposes, as well as harming aquatic life or wildlife. In
order to prevent such adverse impacts, the final regulation requires
that the full monitoring requirements of this Subpart be implemented
at landfills, surface impoundments and land treatment facilities,
unless the owner/operator can demonstrate to the Regional
41
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Administrator that the facility overlies an uppermost aquifer in
which there is low potential for migration of contaminants into a
drinking water supply, to other water supply wells, or to surface
water via that uppermost aquifer. This provision will protect un-
derground sources of drinking water from indirect contamination via
an aquifer which is not a drinking water supply and will also protect
water supply wells and surface waters from such harmful ground-water
discharges.
Nature of the waste. Commenters also recommended that waste
characteristics (e.g., solubility and other chemical or physical
characteristics) should be used as a basis for determining lesser
(or no) ground-water monitoring requirements. A comment received on
"special wastes" stated that there is no evidence that special waste
disposal practices harm ground water and that any ground-water moni-
toring requirements for special waste should not be made unless the
results of a current EPA study so indicate.
The Agency believes that it is not appropriate, at this time, to
base ground-water monitoring requirements on the chemical or physical
characteristics of hazardous waste due to a lack of knowledge on the
several factors which affect the mobilities of these contaminants in
the subsurface environment, including: effects of density of differ-
ent contaminants in different subsurface earth materials; sorption
capacities of subsurface earth materials; and chemical reactions of
different contaminants with different subsurface earth materials.
42
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Regarding ground-water monitoring requiranents (§250.46 of the
proposed regulations) for "special wastes," there is no longer such a
category in the final regulations for special wastes pursuant to Sec-
tion 3004 of RCRA and thus the comment on this matter is irrelevant.
Expense of monitoring. Other conmenters felt that the expense
of ground-water monitoring offered sufficient justification for les-
ser monitoring requirements. Some stated that wells would be expen-
sive under certain conditions (e.g., where ground water is several
hundred feet deep). Other ccmmenters felt that the monitoring re-
quirements would be too expensive for their particular hazardous
waste management operations. As an alternative, one commenter sug-
gested sampling of the "closest drinking water supply" in lieu of
installing a GWMS.
The Agency believes that expense of ground-water monitoring
should not be a factor for determining the acceptability of a lesser
degree of (or no) monitoring. Reducing monitoring requirements based
on expense would seriously jeopardize the goal of RCRA to protect
w
human health and the environment. As discussed earlier, the owner
or operator is provided in the final regulations an opportunity to
demonstrate the acceptability of a lesser degree of (or no) ground-
water monitoring based on various factors (e.g., depth to ground
water as a hydrogeologic factor and not an expense factor). The
commenter's suggestion to use the closest drinking water supply
43
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instead of on-site monitoring wells is not appropriate since only
wells located at the limit of the waste management area could detect
a contaminant discharge as early as possible, thereby allowing the
maximum time to determine the extent of any ground-water contamina-
tion and to implement corrective action if appropriate.
Facility design. Facility design was suggested by some commen-
ters as a basis for a lesser degree of (or no) ground-water monitor-
ing, since properly designed facilities are frequently built to
retain hazardous wastes.
The Agency believes that for landfills, surface impoundments and
land treatment facilities, facility design (i.e., design intent)
should not be a basis at this time in determining the acceptability
of lesser monitoring requirements, since it has yet to be demon-
strated that any given design will positively prevent contaminant
discharges.
State-of-the-art of ground-water monitoring technology. One
commenter felt that the ground-water monitoring requirements should
be deferred pending further research and completion of a comprehen-
sive manual, since at present there is "limited knowledge and depen-
dability" for ground-water monitoring.
The Agency believes that ground-water monitoring requirements
should not be deferred since adequate monitoring methodology for
detecting contaminant migration has been demonstrated.2""/»->3,54
Deferring these requirements would result in undetected contaminant
44
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discharges, and thus a failure to meet the mandate of Congress to
protect human health and the environment. It is also important to
note that the Agency is continuously seeking to improve monitoring
methodology and will be providing further guidance on this subject in
the future.
Owners or operators who perform a lesser degree of (or no)
ground-water monitoring at their facilities during interim status
must have available for submission, at any time the Regional Admin-
istrator so requests, a demonstration that there is a low (or no)
potential for migration of hazardous waste constituents to a USDW,
to water supply wells, or to surface water via the uppermost aquifer,
during the active facility life and post-closure care period.
The final rule for interim status states:
§265.90 (b) Except as paragraphs (c) and (d) of this Section
provide otherwise, the owner or operator must install,
operate, and maintain a ground-water monitoring system
which meets the requirements of §265.91, and must com-
ply with §§265.92-265.94. This ground-water monitoring
program must be carried out during the active life of
the facility, and for disposal facilities, during the
post-closure care period as well.
(c) All or part of the ground-water monitoring requirements
of this Subpart may be waived if the owner or operator
can demonstrate that there is a low potential for mi-
gration of hazardous waste or hazardous waste consti-
tuents from the facility via the uppermost aquifer to
water supply wells (domestic, industrial, or agricul-
tural) or to surface water. This demonstration must
be in writing, and must be kept at the facility. This
demonstration must be certified by a qualified geolo-
gist or geotechnical engineer and must establish the
following:
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(1) The potential for migration of hazardous waste
or hazardous waste constituents from the
facility to the uppermost aquifer, by an
evaluation of:
(i) A water balance of precipitation,
evapotranspiration, runoff, and
infiltration; and
(ii) Unsaturated zone characteristics (i.e.,
geologic materials, physical properties,
and depth to ground water); and
(2) The potential for hazardous waste or hazardous
waste constituents which enter the uppermost
aquifer to migrate to a water supply well or
surface water, by an evaluation of:
(i) Saturated zone characteristics (i.e.,
geologic materials, physical properties,
and rate of ground-water flow); and
(ii) The proximity of the facility to water
supply wells or surface water.
Additional issues concerning applicability. One ccmmenter sug-
gested that the ground-water monitoring requirements should serve
only as a "guide" for reviewing agencies.
The Agency disagrees with the recommendation of this commenter,
since Congress mandated EPA to publish regulations to ensure safe
hazardous waste management, not "guides" for reviewing agencies.
A commenter suggested additional monitoring requirements for
"extraordinary" geologic or topographic conditions (e.g., Karst
areas).
The Agency feels that it is not necessary to specify in the
final regulations such additional monitoring requirements since such
46
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potential action is implicit in the final wording. Since these
regulations specify minimum monitoring requirements, additional
monitoring, e.g., more wells, may be required as deemed appropriate.
One commenter claimed that the "Note" of the proposed regulation
stipulating conditions for a lesser degree of (or no) monitoring
provided a loophole tt> escape regulation since conditions in ground
water can change after permit issuance.
The Agency recognizes that ground-water quality may change over
time. Conditions which must be demonstrated by the owner or operator
to justify the acceptability of a lesser degree of (or no) monitoring
are rigorous and consider not only hydrogeologic factors but
proximity to water supply wells and use of water as well. How-
ever, acceptance of lesser monitoring by the Regional Administrator
may be redetermined if information indicates that the basis for
demonstration is no longer valid. In addition, the "imminent hazard"
provisions of Section 7003 of RCRA may be employed in such situations
should a serious contamination threat arise.
An additional provision was included in these final interim
status regulations which allows for an alternate ground-water moni-
toring system (other than the one described in §§265.91 and 265.92)
to be installed if an owner or operator assumes (or knows) that
ground water has been contaminated. This provision enables the owner
or operator to bypass the monitoring of indicator parameters and
proceed with a more rigorous ground-water monitoring program which
would be more specific in its sampling of ground-water quality.
47
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As stated in the regulation, the owner or operator who elects to
utilize the alternate ground-water monitoring system will operate
under a slightly different monitoring schedule. No later than one
year after the effective date of these regulations, the owner or
operator will be required to initiate a ground-water quality assess-
ment plan and this more detailed plan (i.e., more detailed than the
indicator parameter sampling) will continue on a quarterly basis. The
rationale is that these more extensive assessments on a quarterly
basis allow for a more in-depth knowledge of the rate, direction and
concentration of subsurface contamination.
The final rule for interim status states:
§265.90(d) If an owner or operator assumes (or knows) that
ground-water monitoring of indicator parameters i-n
accordance with §§265.91 and 265.92 would show
statistically significant increases (or decreases in the
case of pH) when evaluated under §265.93(b), he may
install, operate, and maintain an alternate ground-water
monitoring system (other than the one described in
§§265.91 and 265.92). If the owner or operator decides
to use an alternate ground-water monitoring system he
must:
(1) Within one year after the effective date of these
regulations, submit to the Regional Administrator a
specific plan, certified by a qualified geologist or
geotechnical engineer, which satisfies the
requirements of §265.93(d)(3), for an alternate
ground-water monitoring system;
(2) Not later than one year after the effective date of
these regulations, initiate the determinations
specified in §265.93(d)(4);
(3) Prepare and submit a written report in accordance
with §265.93(d)(5);
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(4) Continue to make the determinations specified in
§265.93(d)(4) on a quarterly basis until final
closure of the facility; and
(5) Comply with the recordkeeping and reporting
requirements in §265.94(b).
3. Ground-Water Monitoring System
Synopsis of Proposed Regulation
The proposed regulations required the owner/operator of a land-
fill or surface impoundment to install, maintain and operate a
ground-water monitoring system (GWMS). This system was to consist of
a minimum of four monitoring wells with at least one well located
hydraulically upgradient from the active portion of the facility to
obtain representative background samples. A minimum of three wells
was required to be installed hydraulically downgradient of the active
portion of the facility. At least one of the downgradient wells was
to be located immediately adjacent to the active portion of the
facility, while the others were to be located within the facility
property, to provide the greatest opportunity for interception of any
leachate migrating from the facility into ground water. Downgradient
wells were to be drilled to different depths to detect any leachate
migration into ground water beneath the facility. Each well was to
be constructed to draw samples from those depths where the facility
owner/operator could demonstrate that contamination was most likely
to occur. In addition, a "Note" contained a provision to allow wells
to be drilled to a single depth if the owner/operator could demon-
49
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strate that this was the depth at which contamination was most likely
to occur.
All monitoring wells were required to be cased, and the annular
space backfilled with an impermeable material to prevent surface
water from entering the well bore and inter-aquifer water exchange.
This section of the ground-water monitoring requirements (i.e., well
number, location and construction) were not proposed for facilities
under interim status since only those facilities with monitoring
systems in place were required to comply. However, since these
requirements have been incorporated into these final rules, this
section of the proposed regulations is discussed.
Rationale for the Proposed Regulation
The objective of the proposed GWMS was to detect any ground-
water contamination caused by leachate migrating from a facility.
Wells would be strategically located relative to ground-water flow
direction and would be sampled at regular intervals to detect changes
in concentrations of chemical constituents in the ground water.
3a. Number of Monitoring Wells
Synopsis of Proposed Regulation
The proposed regulation required a GWMS consisting of a minimum
of four monitoring wells, with at least one well upgradient of the
active portion of the facility and at least three wells downgradient
of the active portion.
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Rationale for the Proposed Regulation
The number of monitoring wells required was site-specific with
large sites, or sites in complex hydrogeologic settings requiring a
greater number than a small site or a hydrogeologically simple site.
If the geologic setting of the facility area was not complex, and the
ground-water flow direction was accurately defined, the minimum re-
quirement of four wells was considered to be adequate.
The proposed four-well minimum requirement was determined
through review of available literature and through discussions with
knowledgeable organizations in ground-water monitoring.
Fenn et al., recommended a minimum monitoring system consisting
of: one upgradient well to sample background ground water, unaffec-
ted by the waste management activity; a line of three downgradient
wells between the waste management activity and facility property
boundary and perpendicular to ground-water flow; and another down-
gradient well located immediately adjacent to the waste management
activity.18
The system recommended by Mooij et al., called for wells both on
and off the facility property as follows: the wells within the
facility property would include one upgradient and two downgradient
of the waste management activity (with one downgradient well at the
facility property boundary and the other downgradient well between
the property boundary and the waste management activity); the "off-
site" wells, one upgradient and one downgradient, would be the
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nearest water supply wells (not necessarily hydraulically connected
to the wells within the facility property).36
The Texas Water Quality Board (TWQB), in its 1976 guidelines,
recommended one upgradient well and two downgradient wells (all
within the facility property), with one downgradient well closer to
the waste management activity than the other downgradient well.59
In discussions with the TWQB, EPA learned that the TWQB has issued a
draft of new guidelines which would recommend a minimum GWMS of four
we11s.58
After reviewing information on various GWMSs, the Agency felt
that four wells would be satisfactory for a minimum GWMS. All wells
would be located within the facility property boundary to ensure
early detection of any contaminant migration. One upgradient well
was considered by the Agency to be necessary to monitor uncontamin-
ated ground water as did those persons recommending other GWMSs.
Although other systems recommended two, three, or four downgradient
wells, the Agency felt that three would be an adequate minimum for
the simplest monitoring situations.
Comments Received/Rationale for Chosen Action
Commenters addressed the adequacy of the four-well minimum moni-
toring requirement, with some favoring more or fewer wells, while
others agreed with the proposed requirement. Commenters offered var-
ious rationales for determining an adequate number of monitoring
wells including: size of the facility area to be monitored; geology
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and hydrology of the facility area; use of pre-monitoring information
on the facility area; configuration of the waste management area;
number of waste management components in a facility; and waste char-
acteristics.
In regard to the size of the area to be monitored, some commen-
ters felt that the four-well minimum requirement was not adequate to
monitor large areas or was not functionally adequate with respect to
area (e.g., the number of wells should be in proportion to acres to
be monitored, such as one well per five acres). Commenters also
recommended spacing requirements for downgradient wells (e.g., one
well every 500 feet with variances due to site geology).
The Agency agrees with commenters in believing that the size of
the facility area to be monitored is an important factor in determin-
ing the number of monitoring wells necessary to adequately monitor
ground water at a facility. The proposed requirement did consider
concerns over this factor, since the requirement called for a minimum
of four wells. This minimum requirement is retained in the final
regulations. The Agency believes this to be a flexible approach.
Furthermore, the Regional Administrator may accept fewer than four
wells if the owner/operator can demonstrate that there is a low (or
no) potential for ground-water contamination as explained in the
discussion on applicability. The Agency does not agree with comments
concerning the determination of monitoring well number based on a
strict well to acre proportion or with specified equal spacings
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between downgradient wells. Such formulae do not provide the
flexibility to accommodate site-specific factors and may result in a
failure to detect a contaminant discharge through inappropriate well
location and number (e.g., a facility with multiple waste management
components may have distances between these components greater than
500 feet; or in a small site with complex hydrogeology, a prescribed
well per acre ratio may result in too few wells).
Some commenters felt that the number of monitoring wells should
be determined by site-specific geologic and hydrologic conditions,
such as ground-water flow direction, permeabilities of subsurface
materials, depth to ground water, and amount of precipitation. One
commenter felt that only one downgradient well was initially adequate
to detect leachate migration in dry areas with deep ground water,
maintaining that additional downgradiant wells could be required if
contamination appeared in the initial downgradient well. Another
contended that only one downgradient well would be needed in areas
having natural clay liners, allowing the Regional Administrator dis-
cretion in requiring more wells. Still another commenter believed
that an "absolute requirement" for four wells was arbitrary since the
purpose of the GWMS is to monitor each dominant flow direction and
this could be done by more or fewer than four wells.
The Agency agrees with commenters who believe that site-specific
hydrogeology is an important factor in determining an adequate number
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of monitoring wells. Concerning comments that one downgradient well
would be sufficient for dry areas with deep ground water or in sites
with natural clay liners, the final regulations provide the owner/
operator with the opportunity to demonstrate to the Regional Admin-
istrator that a lesser degree of monitoring would be acceptable.
The Agency is aware of no hydrogeological justification or pro-
tocol, either from public comments or any other information sources,
which adequately refutes the four-well minimum requirement. This
minimum has been determined by the Agency to be the least number of
wells needed to detect a contaminant discharge under the simplest of
conditions. The Agency, in maintaining the four-well minimum re-
quirement in these final regulations, still believes that at least
one well upgradient of the waste management area is needed to ensure
detection of a contaminant discharge. The final regulations require
that the downgradient wells be located at the limit of the waste
management area. One downgradient well located at the limit of the
waste management area may be sufficient to detect a contaminant dis-
charge which is in line with ground-water flow toward that well.
However, a discharge may occur to either side of this well and such
contamination may go undetected. Therefore, the final regulations
require at least two more wells at the limit of the waste management
area, installed such that they are on opposite sides of the first
well. The Agency anticipates that many facilities, because of hydro-
geologic and/or other factors such as large area, will be required to
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install more than three downgradient wells to ensure contaminant de-
tection. Based on this approach, the Agency disagrees with commen-
ters stating that the four-well minimum requirement is arbitrary. In
addition, the requirement is highly dependent on ground-water flow
direction, as further explained in the discussion on well location.
A commenter felt that "pre-monitoring" information on a facility
should also be a factor in determining the number of wells.
The Agency agrees with this commenter that any valid data about
the facility area should be used by the owner/operator in developing
a GWMS.
Commenters believed that the number of waste management compon-
ents within a facility and the configuration of the disposal area are
factors which should be considered in determining the number of moni-
toring wells. Some stressed that a common set of monitoring wells
should be allowed for a facility with multiple waste management com-
ponents, while one commenter stated that the four-well minimum re-
quirement could be inadequate at such a facility.
The four-well minimum requirement of these final regulations ap-
plies to facilities regardless of the number of waste management com-
ponents in the facility or the configuration of the waste management
area. In the case of a facility with multiple waste management com-
ponents, the monitoring-we11 system must ensure detection of a dis-
charge from any component. Thus, in some cases more than four wells
may be required.
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Commenters stated that waste characteristics, such as "degree of
hazardousness," should be considered in determining the number of
monitoring wells.
The Agency sees no valid reason for requiring well number to be
a function of waste characteristics, nor did ccmmenters provide a
rationale. Waste characteristics that would be relevant to a "degree
of hazard" scheme are not relevant to the number of wells in the
GWMS, where the key concern is the system's capacity to detect dis-
charges into ground water.
One commenter suggested replacing the four-well minimum require-
ment with a requirement for a "suitable number" of wells.
As previously stated, the Agency feels that the minimum require-
ment provided in the final regulations provides the flexibility
needed to meet the concern of this commenter.
Another commenter expressed concern that the proposed require-
ment that at least one of the downgradient wells be located imme-
diately adjacent to the active portion of the facility could result
in the installation of additional wells since the active portion of
a landfill constantly moves. The commenter also suggested deleting
reference to "active face."
In the proposed regulation it was not the Agency1s intention
to require monitoring wells at the edge of the active portions of a
landfill, with periodic relocation of these wells once the boundary
of the waste had been extended. It was assumed in the proposed
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regulations, and still is in these final interim status regulations,
that the wells would be located at the waste boundary which will
exist upon completion of the facility.
3.b. Monitoring Well Location
Synoposis of Proposed Regulation ^
The ground-water monitoring system in the proposed regulations
required a minimum of four wells to assure detection of any contam-
inants entering ground water from the facility. The location of at
least one well was required to be hydraulically upgradient from the
active portion of the facility so as to yield samples representative
of the background quality of the ground water which flows under the
facility* A minimum of three wells were required to be located
hydraulically downgradient of the active portion of the facility.
The placement of the downgradient wells was further specified in the
regulation. One of these three wells was required to be located
immediately adjacent to the active portion of the facility and the
other wells were to be located within the property boundary of the
facility to provide the opportunity for interception of any leachate
that migrated into ground water underlying the facility.
Rationale for the Proposed Regulation
At least one well was required to be located hydraulically up-
gradient of the active portion of the facility so as to obtain back-
ground ground-water samples, i.e., unaffected by facility activities,
A minimum of three wells was required to be located hydraulically
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downgradient of the active portion of the facility. One of the
downgradient wells was required to be immediately adjacent to the
site in order to detect the leachate entering the ground water. The
other downgradient wells were required to be located within the pro-
perty boundary of the facility in order to detect the leachate plume
as soon as possible. The rationale was that once leachate enters the
ground water, it is difficult to control; the sooner its presence is
noted, the easier it will be to initate remedial action.
Comments Received and Agency Response
The comments as to the exact placement of the monitoring points
were varied. The most frequent comment received concerned the allow-
ance of a flexible approach to ground-water monitoring. The majority
of comments addessed the location of downgradient monitoring wells
only. Placement of the upgradient wells was not a major issue. With
regard to well placement specifically, the major comment was that
monitoring wells should not be located at the edge of the waste. One
rationale was that it was unnecessary because leachate monitoring was
also required in the proposed rule. The major contention was that
the leachate monitoring system will detect failures in the contain-
ment system prior to contaminants reaching the ground water at the
active edge of the waste, thus precluding the need for a monitoring
well at the active edge of the waste.
A major problem with this approach is that if leachate monitor-
ing failed to detect contamination migrating from the facility, the
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absence of monitoring wells would allow contamination to flow unde-
tected in ground water. The possibility of this occurring is dis-
cussed in the leachate monitoring section where the inadequacy of
leachate monitoring technology is established. Further since leach-
ate requirements have been deleted from the final regulations, this
comment is no longer valid.
A second rationale for not locating monitoring wells at the edge
of the waste was that such wells may promote leachate movement to
ground water, since leachate movement in active portions is lateral,
not vertical. The suggestion was to locate the monitoring point at
some meaningful distance between the active portion and the site
boundary.
The major reason for this commenter's suggestion is the asser-
tion that leachate movement in the active portions is lateral, not
vertical. These regulations require that the monitoring wells be
properly constructed so as to prevent surface water or water in the
unsaturated zone from migrating down the annular space of the moni-
toring well. Such prevention can be accomplished by backfilling the
space between the casing and the bore hole with material of very low
permeability. Because of this, and the fact that the wells will be
located at some reasonable distance from the boundary of the waste
management area, to allow installation, the likelihood of monitoring
wells located at the edge of the waste boundary being conduits for
contaminant migration to the ground water is very unlikely. However,
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these construction techniques should not be interpreted as being
suitable for installing monitoring wells through the facility. Such
practices, if applied to existing facilities, increase the possibil-
ity of contaminants entering the aquifer during drilling operations.
Technologies for new facilities do not resolve the problem of leach-
ate head buildup around wells installed through the facility. Such
head buildup increases the likelihood of contaminants migrating
through the annular space and into ground water. This head build
up should not be a factor for wells located at the edge of the waste
management area.
Commenters suggested that the proposed wording on well locations
be deleted and replaced with general wording which requires wells to
be. located so as to yield samples representative of the background
quality of the ground waters which flow under the facility and to
detect any leachate which has migrated into ground waters underlying
the facility property. The commenter's rationale for the change is
that it provides more flexibility. The recommended approach for well
location should be goal-oriented, allowing the owner/operator to pro-
vide monitoring data and to use his own discretion in choosing well
location. A similar comment recommended adding the statement that
"monitoring systems shall be designed and constructed to draw repre-
sentative samples from the zones in the ground-water system which
are representative of those zones most susceptible to endangerment,
and to detect contamination as soon as possible." The commenters
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contended that to use the proposed requirement could result in
ineffective ground-water monitoring.
These comments encourage more owner/operator discretion in
placement of the monitoring wells. In implementing the goal of
detecting contaminants as soon as possible after entering ground
water, there is little alternative but to place the monitoring well
at the boundary of the waste management area. Placing monitoring
wells through the facility is discouraged because this increases the
likelihood of contaminants entering ground water via migration down
the annular space between the well casing and the borehole. Any
approach that would allow for the possible location of the wells to
be some distance from the waste management area (as could happen when
left up to owner/opera tor discretion) would not allow for earliest
possible detection of contamination.
Rationale for Chosen Action
The required location of the upgradient well is unchanged
from the proposed rule. The required location of the downgradient
monitoring wells has been changed in the final regulations. Since
leachate monitoring of the unsaturated zone at landfills and surface
impoundments has been deleted from the final regulations because of
technical problems with such systems, the most protective alternative
is to monitor at the boundary of the waste management area.
This alternative is preferred over monitoring ground water
directly beneath the facility. Such monitoring would, in most cases,
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require the installation of monitoring wells through the waste and
into the underlying ground water. This practice is discouraged by
the Agency since the installation of such a system in existing fa-
cilities is likely to provide a direct conduit for migration of con-
taminants to the ground water. The nature of pollutant mobility and
ground-water flow is such that a facility which causes groundwater
contamination consistently beneath the facility will eventually cause
the ground water at the downgradient waste management area boundary
to be contaminated.
Placing monitoring wells at the edge of the waste management
area as opposed to some distance away (e.g., at the property
boundary) allows for early detection and possible remedy of the
problem.
For these reasons, in the final regulations ground-water moni-
toring wells must be located at the downgradient edge of the waste
management area. They must be located and completed such that they
will detect any contamination migrating from beneath the waste man-
agement area.
In the case of land treatment facilities, however, the Agency
believes that leachate monitoring (i.e. , soil pore water monitoring)
is both desirable and technically feasible, even at existing facil-
ities. Such monitoring can provide valuable information on the
effectiveness of the land treatment processes occurring in the soil
in retaining leachate constituents in the unsaturated zone material.
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Leachate monitoring at these facilities can also indicate if leachate
is migrating toward the saturated zone (i.e., toward ground-water).
This type of monitoring at land treatment facilities would be
accomplished through the emplacement of lysimeters in the unsaturated
zone directly beneath such facilities. Unlike placement of monitor-
ing wells, drilling and installation of lysimeters would not pene-
trate into the ground water, thus alleviating the concern that a
continuous boring from the land surface down to ground water could
act as a conduit for contamination. The Agency also believes it is
appropriate and requires monitoring wells at the perimeter of land
treatment areas, in the same manner as for landfills and surface
impoundments, to determine whether ground water is being impacted by
land treatment activities.
3.c. Well Depth
Synopsis of Proposed Regulation
The proposed regulations required that the upgradient well(s) be
installed so as to yield samples representative of background quality
of ground water which flows under the facility. The downgradient
wells were to be sunk to different depths to detect any leachate mi-
grating from the facility into ground water, with each well being
constructed to draw samples from depths where the facility owner or
operator could demonstrate that contamination is most likely to
occur.
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Furthermore, the proposed regulations contained a "Note" allow-
ing wells to be sunk to a single depth if the owner or operator could
demonstrate Chat this was the depth at which contamination was most
likely to occur.
Rationale for the Proposed Regulation
The proposed regulations required the upgradient well(s) to be
installed to obtain samples representative of ground water poten-
tially affected by a discharge from a facility. The requirement that
the downgradient wells be sunk to different depths where contamina-
tion is most likely to occur was based on the physical behavior
(e.g., density) of contaminants as related to sampling of different
vertical levels within an aquifer. For example, oily leachate would
float on top of ground water. If the physical behavior of a contami-
nant is not fully known, it is difficult to anticipate the depth at
which a contaminant will flow within an aquifer. Therefore, the pro-
posed requirement specified that the downgradient wells be installed
at different depths.
The "Note" gave the owner or operator an opportunity to install
wells at a single depth if he could demonstrate that contaminants
migrating from a facility would assume a specific depth within an
aquifer. Such an exception would require detailed knowledge by the
owner/operator of the aquifer and waste behavior within the aquifer.
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Comments Received and Agency Response
A commenter recommended that maximum depths for drilling into
bedrock and the minimum depth for drilling into ground water be
specified.
The Agency believes that it is not appropriate or feasible in
the requirement to specify well depths to ensure contaminant detec-
tion. Determining appropriate well depths is a site-specific process
and depends on various factors (e.g., depth to ground water and con-
taminant behavior in the aquifer). The Agency will offer, in the
future, guidance on monitoring well depths.
Concerning the single-depth provision of the "Note," one commen-
ter felt that such a provision was a regulatory loophole. The Agency
believes that the proposed provision did not constitute a regulatory
loophole since the owner or operator was required to demonstrate that
contamination was most likely to occur at that depth. However, the
single-depth provision has been deleted in the final regulations
since the final wording relates well depth to the performance goals
of the wells.
Commenters did not specifically address upgradient wells with
respect to depth. However, the Agency has revised the proposed word-
ing to more clearly express that depth and surface location must both
be considered in accomplishing the objective of the upgradient well.
Commenters addressed various aspects of downgradient wells with
respect to depth. One felt the requirement that downgradient wells
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be "sunk to different depths" should be changed to "drilled to appro-
priate depths" to reflect common terminology. The Agency agrees con-
ceptually and has rewritten the proposed requirement to more clearly
emphasize that depths of downgradient wells should be related to
their performance objective, that is, to ensure detection of contam-
inant migration from a facility.
Also, a commenter felt that it is not always necessary to moni-
tor at three different depths when the facility overlies a sole
source aquifer if one downgradient well is located immediately
adjacent to the active portion of the facility and is designed to
detect leachate in the shallowest aquifer. Furthermore, the com-
menter claimed that the single-depth provision of the proposed "Note"
supported his position.
The Agency believes that downgradient wells, whether in a sole
source or other aquifer, may be installed at the same or different
depths, depending on site-specific conditions. However, the Agency
disagrees with the commenter1s rationale that only one downgradient
well is sufficient to detect contamination, for reasons stated in the
discussion on well number. Furthermore, the single-depth provision
of the proposed "Note" did not imply that one downgradient well at
the depth where contamination was most likely to occur would be suf-
ficient to ensure contaminant detection.
Finally, a commenter felt that for downgradient wells, determin-
ation of the "subsurface elevation" at which contamination is most
likely to occur should be made by state or local authorities and the
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operator to prevent abuse by the operator. The Agency maintains that
the responsibility to determine well depths lies with the facility
owner/operator.
Rationale for Chosen Action
The Agency has revised the proposed wording on depth of monitor-
ing wells in order to reflect more common technical terminology and
to clarify the relationship between well depth and performance objec-
tives.
Therefore, the final interim status rule for monitoring well
number, location and depth states:
§265.91(a) A ground-water monitoring system must be capable of
yielding ground-water samples for analysis and must
consist of:
(1) Monitoring wells (at least one) installed hydrau-
lically upgradient (i.e., in the direction of
increasing static head) from the limit of the waste
management area. Their number, locations, and
depths must be sufficient to yield ground-water
samples that are:
(i) Representative of background ground-water
quality in the uppermost aquifer near the
facility; and
(ii) Not affected by the facility; and
(2) Monitoring wells (at least three) installed hydrau-
lically downgradient (i.e., in the direction of
decreasing static head) at the limit of the waste
management area. Their number, locations, and
depths must ensure that they immediately detect any
statistically significant amounts of hazardous waste
or hazardous waste constituents that migrate from
the waste management area to the uppermost aquifer.
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(b) Separate monitoring systems for each waste management
component of a facility are not required provided that
provisions for sampling upgradient and downgradient water
quality will detect any discharge from the waste
management area.
(1) In the case of a facility consisting of only one
surface impoundment, landfill, or land treatment
area, the waste management area is described by the
waste boundary (perimeter).
(2) In the case of a facility consisting of more than
one surface impoundment, landfill, or land treatment
area, the waste management area is described by an
imaginary boundary line which circumscribes the
several waste management components.
3.d. Buffer Zone for Ground-Water Protection
Synopsis of Proposed Regulation
The proposed regulation required that the active portions of
hazardous waste facilities be located a minimum of 60 meters from the
property line of the facility, unless it could be demonstrated that
unexpected releases or discharges of hazardous wastes could be con-
trolled before they cross the facility property boundary.
Rationale for the Proposed Regulation
The purpose of setting a minimum distance which the active por-
tion of a facility could be located from its boundary line was to
provide a buffer zone between the public and the facility. The
Agency believes that buffer zones reduce risks to public health and
the environment by allowing unexpected discharges resulting from
fires and explosions to dissipate, and for spills and underground
leaks to be contained or to dissipate before crossing the property
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boundary. In addition, buffer zones can be used for aesthetic pur-
poses, such as noise reduction or screening of facilities in order to
preserve natural appearances.
The section of 60 meters (200 feet) from the facility's boundary
line as the required width of the buffer zone was based on the
following:
The State of Oklahoma prohibits disposition of industrial
waste within 200 feet of the permit boundary, thus providing
a precedent of the proposed RCBA regulation. Although other
states have narrower width requirements for buffer zones
(e.g., Wisconsin-20 feet; Pennsylvania-25 feet; and New
York-50 feet), these regulations only pertain to municipal
solid waste. Since hazardous waste poses a greater risk to
public health and the environment than municipal solid
waste, Oklahoma's more stringent regulation for industrial
waste was adopted.
A fixed distance was specified in order to facilitate enforcement and
to provide a tangible point of reference.
Comments Received and Agency Response
Most commenters responded to the 60 meter buffer zone as it
applied categorically to all risks (i.e., fires, explosions, under-
ground leaks, etc.). Only a few singled out ground water when
commenting on the adequacy of the 60 meter buffer zone. Nearly all
of the comments regarding the buffer zone requirement were against
the specification of a discrete distance in the standard because of
the many factors (type and size of the facility, nature of waste
handled at the facility, type of land use surrounding the facility,
operating and safety procedures utilized at the facility, hydrogeo-
logic conditions beneath the facility) which influence the size of
the buffer zone that is needed at a facility.
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The few commenters who discussed the adequacy of the 60 meter
buffer zone with regard to ground-water protection were all in favor
of increasing the distance. Some commenters stated that facilities
should not be located in population centers because leachate from
chemical landfills may travel more than 200 feet in porous soil and
contaminate public or private wells.
Other commenters stated that the standard should require a 300
foot buffer zone. This suggestion was based on data derived from the
lateral subsurface migration of septic tank effluents.
While EPA believes that buffer zones may be an important com-
ponent of a ground-water protection strategy, the Agency is not
prepared to establish specific buffer zone requirements for such a
purpose at this time. This issue will be examined as part of the
Phase II regulations. This issue raises several key technical ques-
tions (e.g., transport and fate of contaminants in the subsurface)
which need further analysis.
3.e. Well Casing and Backfilling
Synopsis of Proposed Regulation
The proposed regulations required all monitoring wells to be
cased and the annular space backfilled with an impermeable material
to prevent surface water from entering the well bore and interaquifer
water exchange. "Annular space" was defined to mean the space
between the bore hole and the casing.
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Rationale for the Proposed Regulation
The objective of the proposed requirement for casing and back-
filling of monitoring wells was to ensure that representative samples
i
of ground water were obtained from the appropriate depths and that
the samples would not be contaminated by surface water infiltration
down the well bore or by interaquifer exchange of ground water.
Comments Received and Agency Response
A commenter felt that "casing" should be clarified to refer to a
well pipe to withdraw samples rather than an open hole. Furthermore,
this commenter believed that monitoring-well casing, as described in
the proposed requirement, could be confused with casing which is used
to prevent hole cave-in during drilling.
•
The Agency believes that it was clear in the proposed require-
ment that casing did not refer to an open hole, but to well pipe
installed to the appropriate depth to obtain ground-water samples.
Also, the Agency feels that it was clear in the proposal that casing
referred to monitoring-well casing and not to casing used to maintain
the structure of the bore hole during drilling. Monitoring-well
casing does, of course, assure the integrity of the well so that
monitoring in the future may continue. The final requirement makes
clear this purpose.
A commenter stated that monitoring-well construction as de-
scribed in the proposed requirements would probably not provide rep-
resentative samples, if any. The commenter further stated that well
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installation should include gravel pack and perforated casing at
levels to be sampled.
In response to the concerns of this commenter, the Agency has
clarified the wording of the proposed regulation to ensure that rep-
resentative ground-water samples will be obtained from appropriate
aquifer flow zones. A requirement that well casing be screened or
perforated where necessary is included in the final regulation since
not all well casings would require such a procedure. For example, a
casing with an open hole at the bottom may be sufficient in certain
types of aquifers, such as fracture and solution channels, provided
that the well was properly developed. In addition, gravel or sand
packing must be installed where necessary around the area of screened
or perforated casing in those situations where clogging by aquifer
materials would occur. The Agency believes this to be technology
which is common knowledge in well-drilling procedures.
Another commenter stated that the Agency should recognize that
certain wells drilled in bedrock formations should only be cased and
cemented into the top of the bedrock and that the remaining bore hole
is typically left uncased.
Although the Agency recognizes that ground-water samples may be
obtained with only partial casing in certain bedrock formations, the
final regulation requires casing to be installed throughout to enable
sample collection at depths where appropriate aquifer flow zones
exist, even in bedrock formations. This ensures that casing will
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extend to the desired sampling depth that will ensure detection of
contaminant migration from a facility, and enable cementing of the
annular space between the casing and bore hole.
Comments received also questioned the use of the word
"impermeable" in regard to the backfilling material requirement of
the proposed regulations, suggesting that no backfill material is
truly impermeable. Also, use of the term "highly impermeable" was
suggested as a remedy by one commenter.
The Agency agrees with commenters that the literal meaning of
the word "impermeable" is not accurate for backfill materials. Such
materials must, however, have very low permeabilities. Therefore,
the Agency has modified the requirement such that the final wording
emphasizes the intended performance goal of preventing contamination
of samples and the ground water by backfilling the annular space with
a suitable material.
Rationale for Chosen Action
The final regulations for well casing and backfilling have been
rewritten to clarify any misunderstanding created by the proposed
«
regulations. Terminology commonly used by well drillers, such as
"screened" and "sealed," has been incorporated. Emphasis of the goal
has been clarified.
The final interim status rule states:
§26/.91(c) All monitoring wells must be cased in a manner that
maintains the integrity of the monitoring well bore hole.
This casing must be screened or perforated, and packed
with gravel or sand where necessary, to enable sample
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collection at depths where appropriate aquifer flow zones
exist. The annular space (i.e., the space between the
bore hole and well casing) above the sampling depth must
be sealed with a suitable material (e.g., cement grout or
bentonite slurry) to prevent contamination of samples and
the ground water.
4. Sampling and Analysis
Synopsis of Proposed Regulation
The proposed regulations required periodic sampling and analysis
for both a comprehensive and a routine list of characteristics and
constituents following establishment of background ground-water qual-
ity. For an existing facility background quality was to be estab-
lished by monthly sampling and analysis for a period of one year. A
comprehensive analysis list was used to establish initial background
water quality, and to monitor any changes in background quality
annually. A shorter routine list of analyses was to be performed
semiannually if the ground-water flow rate was between 25 and 50
meters/year (82 and 164 ft/year) or quarterly if the ground-water
flow rate was greater than 50 meters/year (164 ft/year).
The comprehensive analysis list included at least 39 ground-
water quality characteristics including: the EPA Primary and
Secondary Drinking Water Regulations' constituents and character-
istics (except radioactivity); beryllium, nickel, cyanide, phenolic
compounds and organic constituents as determined by gas chromato-
graphy scanning; and the characteristics of the minimum or routine
analysis list. This routine analysis list included specific conduc-
tivity, chloride, total dissolved solids (TDS), dissolved organic
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carbon, and the principal hazardous constituents disposed in the
facility. A "Note" in the proposed regulations allowed deletion from
the comprehensive analysis list those characteristics that would not
result from hazardous waste managed at the facility, once background
levels had been established.
Rationale for the Proposed Regulation
The intent of the ground-water monitoring program as an integral
component of a hazardous waste management facility was to serve as a
backup system in the event of failure of the facility to adequately
contain the wastes. Both the frequency and types of analyses speci-
fied would provide failure so that remedial action could be taken to
eliminate or reduce environmental contamination.
The analyses made of samples taken from the monitoring system
should be sufficiently sensitive to determine statistically signifi-
cant changes in ground-water quality resulting from leakage from a
hazardous waste management facility. In addition, the selected
analyses should be sensitive to the levels of contamination associ-
ated with land disposal and should be capable of detection in a
reliable manner which minimizes the time required for sampling and
analysis.
Because the proposed facility standards prohibited "endanger-
ment" (causing the ground water to require increased treatment), the
monitoring requirement included many contaminants for which treatment
is required when their concentrations exceed Agency-specified levels.
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Thirty-one of the listed characteristics came from the EPA drinking
water regulations (40 CFR 141 and 143). The Agency realized that the
list was not inclusive of all contaminants for which treatment would
be required. A variable frequency of monitoring was included in the
proposal in recognition of differing rates of ground-water flow in
different areas. More frequent monitoring was required in high
ground-water flow rate areas to better assure early detection of
contamination.
Comments Received and Agency Response
Sampling Frequency. Only a few comments were received regarding
the specified frequencies of routine monitoring after establishing
background water quality. Most agreed that monitoring frequency
should be related to ground—water flow rates but also urged Agency
flexibility. The Agency now, for facilities in interim status, re-
quires at least semi-annual ground-water sampling for certain "indi-
cator" parameters and at least annual sampling for other specified
water quality parameters, as described later. The Agency believes
that these frequencies will provide adequate data to evaluate any
significant changes in ground-water quality over time.
Background Water Quality. Every commenter who addressed the
issue of obtaining 12 samples at monthly intervals to determine back-
ground water quality felt that this requirement should be relaxed.
The Agency agrees that in many cases this frequency is unnecessary,
but it also feels that obtaining representative background data at a
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reasonably frequent interval during the first year is critical to the
success of the overall monitoring program. Thus, the Agency is re-
vising the proposed regulation to require quarterly samples during
the first year and feels that this interval is sufficient to obtain
statistically valid data, incorporating seasonal and other unpredict-
able variations.
Representative background water quality data is essential to the
success of the ground-water monitoring program. The list of back-
ground water quality parameters must provide a reasonably broad base
for comparing current water quality in the event of a need to perform
a further assessment of facility impact on ground water; yet, it
cannot be so extensive that it is neither reasonable nor cost
effective. It is in the best interest of the owner or operator to
accurately assess background water quality because overstating it
would unnecessarily trigger the need for a much more extensive
ground-water quality assessment, while understating background
quality would unduly delay the triggering of a ground-water quality
assessment which, in turn, could be more costly to clean up.
Sampling and Analysis Protocol. Two commenters recommended that
specific protocols should be included for ground-water sampling,
sample preservation and methods of analysis. The Agency had intended
in the proposed regulation that the guidelines for these methods and
others would be provided by guidance documents rather than formaliz-
ing them into the regulatory framework. This would give the owner or
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operator the latitude of choosing a particular method from several
generally accepted or equivalent methods. In deference to these
comments, however, the final regulations have been revised to include
reference to the Agency's suggested publications: "Methods for
Chemical Analysis of Water and Wastes," EPA-600/4-79-020, March i979,
and "Procedures Manual for Ground-Water Monitoring at Solid Waste
Disposal Facilities," EPA-530/SW-611, August 1977, for sample collec-
tion, sample preservation and shipment, analytical procedures, and
chain of custody control. This specification provides guidance while
at the same time allowing the originally intended latitude in those
cases where several methods may be acceptable. The final interim
status regulation now requires the facility owner or operator to
develop and follow a ground-water sampling and analysis plan which
must include procedures and techniques for sample collection, sample
preservation and shipment, analytical procedures, and chain of
custody control. This plan must be kept at the facility so it will
be available for inspection by the Regional Administrator or facility
inspector.
List of Parameters. The proposed parameters listed for analysis
received considerable attention during the comment period. Several
alternatives were recommended, including suggested additions and
deletions to the list, tailoring the list to the facility wastes, and
using a variable list in which subsequent analyses are based on pre-
vious results. Many commenters believed that there is no need to
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analyze for substances which are not supposed to be handled at the
facility. One commenter felt that the abbreviated list was inade-
quate to detect the migration of hazardous waste and that the annual
sampling and analysis frequency was insufficient. Another stated
that the comprehensive list should be periodically Lengthened to
include new constituents from the waste manifest. Many commenters
objected to the number and expense of the proposed parameters on the
comprehensive analysis list. Commenters also pointed out that the
large number of comparisons required in the proposal would cause a
high probability of detecting significant differences when no real
ground-water quality change had occurred (false significance). For
further details, see the discussion of statistical methods in the
section on preparation, evaluation and response.
The Agency believes that the disadvantages of most of the sug-
gested alternative schemes outweigh their merit. It was frequent-
ly suggested that the list of characteristics for comprehensive
analyses contain only those substances or characteristics which were
the cause of the wastes being labeled hazardous. However, rather
than limiting the numbers of analyses to anticipated waste con-
stituents, the Agency has chosen to limit the analyses to parameters
in Appendix III reflecting the aquifer's suitability as a drinking
water supply (analyzed quarterly for first year only); six parameters
which are commonly used to characterize ground-water quality
(analyzed annually); and four indicator parameters used to determine
80
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if a facility is leaking (analyzed semi-annually). While limiting
the routine analyses to the anticipated constituents may have merit
in a few cases, in general the Agency feels that this approach is not
prudent. In specifying parameters which are indicators of the broad
range of anticipated constituents, the Agency believes that the need
to analyze for specific waste constituents may be deferred until
facility leakage to the ground water has been detected. Since the
owner or operator will seldom if ever be advised of all the toxic
components of a particular waste and since it would not be feasible
to make this determination on a load-by-load basis, many of the toxic
substances not on the manifest would go undetected. Even if all of
the toxic components were inventoried, many would still go undetected
because of the likely possibility that many of the waste components
could be chemically or biologically transformed into other toxic
substances. A great many facilities may be used for a wide variety
of wastes. The Agency takes the position that many owners or
operators will have no way of estimating what environmental or health
damage could result from discharge of leachate from the nonhazardous
portion of wastes. A program to routinely determine the absence of
particular contaminants from each shipment of wastes would be
prohibitively expensive, yet faulty assumptions about waste content
or decomposition products could result in widespread undetected
contamination. In the event that a ground-water quality assessment
is required, the owner or operator will need to determine the
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presence of and concentration of hazardous waste and hazardous waste
constituents in the ground water. The Agency believes that techniques
such as gas chromatography will be used to determine which hazardous
waste constituents are in the ground water.
As previously discussed, the Agency proposed monitoring regula-
tions designed to assure detection of unacceptable performance under
a standard prohibiting "endangerment." Many commenters suggested
that a list of 10 or fewer indicators be selected for routine analy-
sis representing broad classes of contaminants which may be present
in the waste and capable of endangering ground water. Others sug-
gested that the minimum list of analyses serve as a guide to make a
more comprehensive investigation when the levels established in back-
ground analyses are exceeded. Two commenters suggested ways of
allowing the Regional Administrator to shorten the list when appro-
priate, either by substituting a Regional Administrator-approved list
where equivalent protection could be demonstrated, and/or by allowing
the Regional Administrator to delete specified parameters at facili-
ties where there is clearly no possibility of their occurrence, such
as certain on-site facilities. These concerns are largely satisfied
in the final regulation, where the objective of routine monitoring is
now the detection of leakage into ground water using indicator para-
meters, not the identification of specific harmful emitted constitu-
ents. Since monitoring does not have to result in a determination
regarding endangerment, the parameters listed for monitoring no
longer need to be associated with "increased treatment" requirements.
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With this monitoring objective in mind, primary consideration
was given to selecting those parameters which would most likely indi-
cate leachate movement at the widest variety of sites, be generally
accepted by the scientific community as those which would be most
representative of ground-water quality, and be readily quantifiable.
Specific comments pertaining to the proposed comprehensive anal-
ysis list are noted below:
• Several commenters noted the redundancy of total dissolved
solids, specific conductivity, chloride, and other charac-
teristics. The Agency agrees and has deleted redundancies
from the final revised regulations.
• Dissolved organic carbon, BOD, COD, and other gross organic
indicators were attacked by reviewers as being insufficiently
sensitive to detect some highly toxic organics which are
dangerous at very low levels. The Agency agrees that these
indicators should not be used specifically to detect such
contaminants. Their use will be restricted to indicate the
presence of gross organic emissions as part of a set of
indicators that discharge has occurred. Low level toxics
will be investigated only after determination that ground
water has been contaminated (see discussion of ground-water
quality assessment below).
• Several commenters suggested that there are procedural
reasons that the list of contaminants contained in the
National Secondary Drinking Water Regulations should not be
used. Whether the contaminants have regulatory status in
another EPA program should not affect their use in these
regulations. The Agency feels that each characteristic
should be evaluated on its individual merits, and points out
that no arguments were presented during the comment period
that any of the characteristics in that list would be in-
appropriate for determining a facility discharge. The
argument that the secondary contaminant levels are not
enforceable, or that they are suggestions which the states
may revise or disregard, does not apply to a discussion of
the lists of analyses. The recommended numerical limit is
immaterial for routine monitoring, under the final regula-
tions. The list of parameters should comprise useful
characteristics which indicate whether or not the facility is
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in compliance with regulations, the list's origin and other
uses notwithstanding.
The Agency agrees with the commenter who suggested that
ground-water quality standards should not be adopted from the
proposed or final editions of the Water Quality Criteria
published in accordance with Section 304(a) of the C.W.A! (33
U.S.C. 131f(a)) without formally proposing them for applica-
tion in these regulations.
The Agency agrees with the comment that the phrase "principal
hazardous constituents" is vague. It has been deleted from
the monitoring requirements in these regulations.
Upon obtaining consecutive analytical results showing the
absence or very low concentrations of a particular background
characteristic, some commenters recommended deleting that
characteristic from subsequent analyses for background deter-
minations. In view of the importance of establishing repre-
sentative background water quality data on a continuing
basis, the Agency takes the position that background values
will probably be variable and, therefore, it would be inap-
propriate to delete a particular characteristic based on the
historical absence of it. Determination of background water
quality is in the operator's best interest in order to demon-
strate whenever water quality degradation has been caused by
other sources. Therefore, the Agency is requiring continued
determinations even of those characteristics which initially
were absent.
The comment was made that water level should be recorded with
each sample. The Agency agrees that the water table gradient
is indeed essential information without which system integ-
rity cannot be assured. Sampling and analysis requirements
have been revised to require water level monitoring to detect
shifts in water table gradient.
Gas chromatographic scans were roundly criticized as being
too nonspecific for regulatory purposes, too expensive, too
easy to distort the conclusions for some waste types, and too
sophisticated and time consuming. No commenters favored
regular use of gas chromatography. The Agency agrees and
will not require the test on a routine basis. However, when
a ground-water quality assessment is required or when an
owner or operator chooses to implement an alternative
monitoring system rather than indicator monitoring, methods
such as gas chromatography/mass spectrometry (GC/MS) would be
needed to successfully identify specific hazardous wastes and
hazardous waste constituents.
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Rationale for Chosen Action
As a result of the many comments received on this topic the
Agency has thoroughly reevaluated various sampling and analysis
protocols for effective ground-water monitoring. This reevalution
has convinced the Agency that various sampling and analysis require-
ments for several different objectives are appropriate. These final
regulations include a threestage approach. The first stage involves
establishment of initial background ground-water quality for those
parameters listed in Primary Drinking Water Regulations as well as
ten other useful ground-water quality parameters and indicators of
ground-water contamination. Seasonal water table gradients will also
be determined. From this stage the Agency, first, will be fully
aware of the initial suitability of the ground water as a drinking
water supply; second, will initiate a baseline for in-depth analyses
of suspected ground-water contamination if a ground-water quality
assessment is required; and third, will establish the baseline for
later comparison of routinely monitored indicator parameters. For
upgradient wells, the mean and variance of each indicator parameter
concentration or value must be determined by pooling of all replicate
measurements for the respective parameters for all quarterly samples
obtained during the first year. At least four replicate measurements
must be obtained for each indicator parameter concentration or value
to provide statistically valid data for future comparisons. Pooling
will also account for seasonal fluctuations in the upgradient
ground-water quality.
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The second stage, following establishment of initial background
water quality, involves routine water quality measurement, discharge
detection, and water table gradient monitoring. Facilities not im-
pacting ground water will continue this stage throughout the monitor-
ing period. If the results of analyses in this stage indicate that
the facility is impacting ground water, the owner or operator is re-
quired to implement a thorough ground-water quality assessment, the
third stage.
Procedures for sampling and analysis. The facility owner or
operator is required to develop and follow a sampling and analysis
plan which must be kept at the facility. Techniques for sample
collection, preservation and shipment, and the laboratory procedures
are influenced by the installed system, site-specific geology, and
available laboratory capabilities, to some extent. A comment
accompanies the regulation which suggests use of the procedures
contained in two EPA manuals, "Procedures Manual for Monitoring at
Solid Waste Disposal Facilities," EPA-530/SW-611, August 1977, and
"Methods for Chemical Analysis of Water and Wastes," EPA-600/4-
79-020, March 1979. Variations of these suggested procedures may
also be used. Control over the chain-of-custody of the samples,
analyses and data should be the responsibility of the owner or
operator to assure EPA that only the owner or operator or his agents
have custody.
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The final interim status rule states:
§265.92 (a) The- owner or operator must obtain and analyze samples
from the installed ground-water monitoring system. The
owner or operator must develop and follow a ground-water
sampling and analysis plan. He must keep this plan at
the facility. The plan must include procedures and
techniques for:
(1) Sample collection;
(2) Sample preservation and shipment;
(3) Analytical procedures; and
(4) Chain of custody control.
[Comment: See "Procedures Manual For Ground-water Monitoring At
Solid Waste Disposal Facilities," EPA-530/SW-611, August 1977
and "Methods for Chemical Analysis of Water and Wastes,"
EPA-600/4-79-020, March 1979 for discussions of sampling and
analysis procedures.]
Selection of Parameters. The Agency has decided that the most
effective method to determine the presence of contaminants in ground
water due to leachate from of a hazardous waste management facility
is to select a small number of reliable, readily quantifiable
indicators of organic and inorganic contamination to be used
routinely. If such indicators are found to rise significantly over
established background levels, ground-water contamination may be
suspected, requiring more in-depth analysis and evaluation. Use of a
small number of indicators will also minimize the number of false
positive determinations when the statistical test is applied to the
data. For further details, see the discussion of statistical
methods.
The Agency is requiring that gross indicators of both the organ-
ic and inorganic content of ground water be monitored at least
semiannually. In choosing a small select group of reliable
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indicators the Agency is reducing the number of analyses that must be
performed on ground-water samples by the owner or operator of a
facility, thus reducing his burden while maintaining assurance that
any ground-water quality change resulting from a facility discharge
will be readily detected.
The lists of parameters in the final regulation have been tail-
ored for three separate ground-water monitoring objectives: charac-
terizing initial background water quality in terms of suitability as
a source of drinking water; determining general trends in localized
ground-water quality beneath the site; and detecting facility dis-
charges. Initial suitability is expressed in terms of the concen-
trations of the contaminants listed for ground water in the National
Interim Primary Drinking Water Regulations (Appendix III). These
twenty contaminants (a twenty-first contaminant, turbidity, is
applicable only to surface water supplies) have been identified by
the Agency as substances for which all public water supply systems in
the U.S. should be routinely analyzed. Contaminant limits have been
established for these substances based upon their known effects on
man when consumed in drinking water. Initial determination of their
levels in the ground water beneath the site is needed to fully char-
acterize the suitability of the aquifer as a source of drinking water
for human consumption.
The second list of parameters contains six selected substances
which are sensitive to a wide variety of influences and ground-water
-------
changes. The Agency believes that any ground-water quality change
due to other sources of contamination or to regional influences will
be reflected in the levels of these six parameters. General trends
in regional ground-water quality, such as oxygen depletion, acidity
or alkalinity changes, and organic and ionic enrichment, will influ-
ence these parameters. This water quality data will be collected
annually so that in the event contamination is detected by the
indicator parameters, comparative data will be available on which to
base a more extensive ground-water quality assessment. Since there
is no a priori information available as to the type or extent of
background data needed, the Agency has elected to require a set of
six parameters (sodium, sulfate, iron, manganese, chloride, and
phenols) which it feels is representative of the data that will be
needed in the event such an assessment becomes necessary. In
selecting these parameters, primary consideration was given to those
water quality criteria that are routinely used in characterizing
drinking water and water for other purposes.^ 13,37,52,65 ^Q
Agency expects that if a ground-water quality assessment is ever
required, these six parameters will not, by themselves, be adequate
to establish a basis for an in-depth comparison but rather will form
a nucleus of a more extensive set of background data to be determined
if such a situation arises. By virtue of their widespread use and
generally accepted value as water quality parameters the procedures
for analysis have been standardizedll and thoroughly tested.57
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There is no provision in the present regulations for dealing
with specific wastes on a case-by-case basis, and even if there were
so little is known in regard to the transport and ultimate fate in
the subsurface of the types of compounds that will result from haz-
ardous waste, it would be of little value in predicting precisely
which parameters should be monitored. This being the case, the
Agency must devise a monitoring protocol that will be responsive to a
large, undefined set of chemical compounds at unspecified concentra-
tion levels which can only be classed in general terms as ionic,
non-ionic, organic, inorganic, or suspended in the ground water. An
appropriate monitoring scheme must, therefore, measure and be indica-
tive of those general properties associated with leachate contamina-
tion. Within these constraints and those set out by Gage™ for
acceptable test procedures, the Agency has chosen pH, specific
conductance, total organic carbon (TOG), and total organic halogen
(TOX) to be used as indicators of leachate contamination of ground
water and will be determined at least semiannually. Statistically
significant changes in these parameters over established background
»
levels will trigger the requirement for more detailed analysis and
evaluation.
Specific conductance, pH and TOG are widely used by both re-
searchers in the field and various regulatory agencies and are
considered to be among the most useful in detecting leachate con-
11,62,64,68 Lik the
tamination in a wide variety of situations.
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ground-water quality parameters discussed earlier, methods for these
three indicators have been standardized and thoroughly tested.57
Use of TOX as an indicator is gaining increasing acceptance as
demonstrated by its use by several universities and government
agencies.27 standardization of TOX procedures is being conducted
by a committee of the American Society of Testing and Materials
(ASTM) for inclusion in the Annual Book of ASTM Standards.16
Expanded use of the TOX procedure is expected as the accessibility to
users of existing instrumentation is increased.
The Agency is aware of another method of determining organic
halogen content in water samples (i.e., gas chromatography/mass
spectrometry (GC/MS)). GC/MS can yield an additive value for organic
halogen content of a sample through summing the concentrations of
individually identified organic halogens. Compared to the TOX
analysis required in these regulations, the GC/MS procedure is more
complex to perform, is more expensive with respect to cost of the
instrumentation and is unable to readily serve the function of an
"indicator."
The monitoring protocol of the final regulation effectively
reduces the number of analyses compared to that required in the
proposed regulation but at the same time maintains a high degree of
assurance that changes in ground-water quality due to leachate
contamination will readily be detected.
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It has been recently pointed out that an acceptable test proce-
dure must possess many different qualities.20 Important among
these are that it must be generally accepted by the scientific com-
munity as indicative of the particular characteristic to be measured;
must be thoroughly tested and evaluated; and it must give precise and
accurate results. Other qualities include: the capability of meas-
uring the parameter in the presence of interferences; relative
simplicity, so as to minimize time requirements; the availability of
necessary instrumentation on the open market at a reasonable cost;
the utilization of standard laboratory methods; and finally that
there be sufficient analysts available having the necessary skills
and training to carry out the test procedure. These factors and
others formed the basis for selecting both the water quality para-
meters and the contamination indicators contained in the final reg-
ulations.
Specific conductance and pH were chosen for monitoring the
inorganic constituents because they satisfy virtually every require-
ment for being acceptable test procedures, and there are no alterna-
tive inorganic indicators which can provide equivalent informational
value. Aside from its importance as an absolute measure of hydrogen
ion activity, pH is valuable as an indicator to detect if a partic-
ular water is being altered by other waters with a different pH. pH
affects the solubility and mobility of many of the toxic constituents
of wastes, and it determines the rate and outcome of many of the
chemical reactions the pollutants will undergo. Specific conductance
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on the other hand is a numerical expression of the summation of con-
tributions from all ions present in a solution. Since conductance is
an additive property, it is useful as an indicator parameter because
it can effectively determine all ions simultaneously. It has
successfully been used to check for the presence or absence of
leachate in ground-water and also to detect fluctuations and trends
of the total ionic properties of groundwater.2»3,4,5,6,7,61,66
While pH and specific conductance are somewhat redundant and
while a change in pH is generally accompanied by a change in specific
conductance, or vice versa, this is not always' the case. At least
one EPA report shows unexplained changes in one without a correspond-
ing change in the other.
TOG was chosen as an indicator parameter for organics because
of its widespread use, acceptability as an effective test pro-
cedure, and general applicability to all types of organic con-
tamination. 11»61»62,68 xt is one of the few parameters that will
provide a broad description of the organic content of water and is
gradually replacing chemical oxygen demand (COD) for this purpose,
especially in ground-water analysis. TOG provides a more direct
expression of organic content than COD, is more sensitive, and is a
less difficult procedure.
TOX was selected to measure only those organic compounds con-
taining halogens. It has been used successfully in recent years and
its use is expanding in this country, Canada, and
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Europe.17,21,25,26,32,45,46,71 Degpite
use of TOX, the Agency feels that in view of the relatively large
amount of hazardous waste which may contain halogenated hydrocarbons
and the higher degree of toxicity usually associated with these com-
pounds, it should be included as an indicator. The TOG test alone
will not reliably detect the minor TOG fluctuations due to signifi-
cant levels of halogenated hydrocarbons, and the TOX test alone will
not provide the broad range of organic coverage necessary.
Gas chromatography (GC) was originally part of the comprehensive
analysis list in the proposed regulations. Its use in the final reg-
ulation was seriously considered in spite of the several serious dis-
advantages which were identified by commenters. Neither GCM or GC/MS
is readily adaptable as an indicator. Several commenters correctly
noted that GC would probably be too confusing to be used as an in-
dicator parameter. On the other hand, GC/MS would enjoy the distinct
advantage of providing a unique means of identifying the individual
components of a complex mixture of many different organic compounds.
In spite of this unique advantage and its substantially higher sen-
sitivity, GC/MS was rejected for routine analyses because it fails to
meet many other requirements for being an acceptable test procedure.
It requires extremely expensive instrumentation that is difficult to
operate and not readily available. Including sample preparation,
GC/MS requires substantial amounts of time to carry out, and there
are relatively few analysts capable of running the equipment or
interpreting the results.
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The final interim status rule states:
§265.92(b) The owner or operator must determine the concentration or
value of the following parameters in ground-water samples
in accordance with paragraphs (c) and (d) of this
Section:
(1) Parameters characterizing the suitability of the
ground water as a drinking water supply, as
specified in AppendixIII.
(2) Parameters establishing ground-water quality:
(i) Chloride
(ii) Iron
(iii) Manganese
(iv) Phenols
(v) Sodium
(vi) Sulfate
[Comment: These parameters are to be used as a basis for
comparison in the event a ground-water quality assessment is
required under §265.93(d).]
(3) Parameters used as indicators of ground-water
contamination:
(i) pH
(ii) Specific Conductance
(iii) Total Organic Carbon
(iv) Total Organic Halogen
Monitoring Frequency. The Agency has selected a monitoring
schedule for routine monitoring which is both reasonable and protec-
tive. Quarterly background sampling and analysis for the first year,
annual ground-water quality determinations and semiannual contamina-
tion-indicator samples are required at all wells. The Agency
believes that the required schedule is environmentally safe, prudent
and readily achievable at all facilities.
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APPENDIX III
EPA INTERIM PRIMARY DRINKING WATER STANDARDS65
Parameter Maximum Level
(mg/1)
Arsenic 0.05
Barium 1.0
Cadmium 0.01
Chromium ........ 0.05
Flouride 1.4-2.4
Lead 0.05
Mercury 0.002
Nitrate (as N) 10
Selenium . 0.01
Silver 0.05
Endrin 0.0002
Lindane 0.004
Methoxychlor 0.1
Toxaphene 0.005
2, 4-D 0.1
2, 4, 5-TP Silvex 0.01
Radium 5 pCi/1
Gross Alpha 15 pCi/1
Gross Beta 4 millirem/yr
Turbidity 1/TU
Coliform Bacteria 1/1°° ml
NOTE:
Turbidity is applicable only to surface water supplies (see ref. 65).
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The final interim status rule states:
§265.92(c) (1) For all monitoring wells, the owner or operator must
establish initial background concentrations or
values of all parameters specified in paragraph (b)
of this Section. He must do this quarterly for one
year*
(2) For each of the indicator parameters specified in
paragraph (b)(3) of this Section, at least four
replicate measurements must be obtained for each
sample and the initial background arithmetic mean
and variance must be determined by pooling the
replicate measurements for the respective parameter
concentrations or values in samples obtained from
upgradient wells during the first year.
(d) After the first year, all monitoring wells must be
sampled and the samples analyzed with the following
frequencies:
(1) Samples collected to establish ground-water quality
must be obtained and analyzed for the parameters
specified in paragraph (b)(2) of this Section at
least annually.
(2) Samples collected to indicate ground-water
contamination must be obtained and analyzed for the
parameters specified in paragraph (b)(3) of this
Section at least semi-annually.
Water Table Gradient. The velocity and direction of the flow of
ground water beneath a site are dependent upon both natural and man-
induced influences. Nearby well extractions, surface water dis-
charges and recharges, flood control measures and other hydrogeologic
modifications, as well as natural and seasonal influences, can change
the direction and velocity such that a properly installed monitoring
system becomes obsolete. The final regulations require the owner or
operator to determine the water surface elevation in each well
quarterly for the first year and semiannually thereafter. These
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elevations will be used as an indication of water table gradient and,
when change is observed, the well location requirements must be
reevaluated, as described in preparation, evaluation and response,
below.
The final interim status rule states:
§265.92 (e) Elevation of the ground-water surface at each monitoring
well must be determined each time a sample is obtained.
5. Preparation, Evaluation and Response
Synopsis of Proposed Regulation
As proposed, the regulations required the owner/operator, upon
observing statistically significant differences between background
quality and subsequent ground-water quality analyses to: notify the
Regional Administrator of the observance; determine the cause of the
observance; determine the extent of ground-water contamination; and
discontinue facility operations while awaiting instructions from the
Regional Administrator.
Rationale for the Proposed Regulation
While selection of many of the ground-water quality parameters
was based on the proposed human health and environmental standard,
the emergency response was keyed to the facility standards which
required that facilities be designed, constructed and operated so
that discharges are minimized or do not occur. The regulatory intent
was that the owner/operator and the Regional Administrator be in
communication, so that there would be a common understanding of the
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background water quality and the specific analytic results which con-
stituted a significant difference, and that upon notification, the
Regional Administrator would commence an immediate review of evidence
at the facility and determine with the operator any necessary
actions. It was expected that the contingency plan established under
§250.43-3 would contain facility-specific sets of conditions upon
which appropriate response would be made contingent. While these
plans would be examined during the permit application and review pro-
cess and cover the forseeable conditions of discharge or failure at
the facility, it is conceivable that the actually occurring situation
could differ from the anticipated. It was review of these differ-
ences by the Regional Administrator that the owner or operator would
await after reporting the statistically significant difference pur-
suant to §250.43-8(c)(4).
Comments Received and Agency Response
Commenters on the proposed emergency response procedures stated
that the automatic response of discontinuing operation immediately
after observing a statistically significant difference was seldom
likely to be warranted. They also point out that the language was
not precise; it even required shutdown when upgradient wells were
affected. It was made clear that the intended relationship between
the emergency response and the contingency plan was not adequately
developed in the proposed regulation.
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Commenters recommended that the operator's response to analyti-
cal results be related to the magnitude and nature of the change in
ground-water quality. Facility closure, it was indicated, should
automatically result only from the most drastic indications for
alarm. Normal aberrations in data should be expected, and the more
appropriate response would be accelerated sampling and analysis
schedules. Closure of the facility, even for a few days, could cause
severe hardship to haulers and generators as well as to facility
operators, often with only undetectably small environmental benefit.
The Agency agrees that automatic shutdown may be unwarranted in many
situations before an actual determination of the extent of the
problem.
Several commenters pointed out that the proposed regulations
would require the notification and shutdown procedures upon observing
a statistically significant improvement in the quality of the
background water. This was not the Agency intent.
Several commenters suggested that the regulations establish a
time limit for the Agency's response to notification. As proposed,
the facility would be shut until the Regional Administrator deter-
mined what actions should be taken. They feared that, with confusing
data, indecisive officials could unduly procrastinate, delaying both
a positive remedy and the resumption of operation. The Agency agrees
that delays and indecision are to be avoided following observance of
a water quality change.
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Rationale for Chosen Action
The final regulations have been developed to facilitate a
sequential response to detected changes in ground-water quality.
Following detection of a statistically significant increase (or pH
decrease) over background in the concentration of one of the indi-
cator parameters at a downgradient monitoring well, this sequence
will be followed:
1) verification of laboratory results
2) notification of the Regional Administrator
3) submission of a ground water quality assessment plan
4) performance of a ground water quality assessment
5) preparation and submission of an assessment report to the
Regional Administrator, and
6) Continuance of ground-water quality assessments on a
quarterly basis until closure (if contamination first
appears during post-closure, only a single assessment need
be performed).
The final regulations require the owner/operator to prepare an
outline of a ground water quality assessment program to determine the
extent and severity of suspected ground-water contamination. This
outline is intended to serve as a basis for a comprehensive assess-
ment plan which is to be developed and submitted to the Regional
Administrator following detection of a significant increase in the
concentration of an indicator parameter in a downgradient well.
The Agency recognizes that it is difficult to specify details of
a comprehensive ground-water quality assessment in advance of the
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event. However, the Agency believes that an outline of a program
should be available at a hazardous waste management facility to guide
more detailed plan development, if ever required, without delay.
The final interim status rule states:
§26^.93(a) Within one year after the effective date of these
regulations, the owner or operator must prepare an
outline of a ground-water quality assessment program.
The outline must describe a more comprehensive
ground-water monitoring program (than that described in
§§265.91 and 265.92) capable of determining:
(1) Whether hazardous waste or hazardous waste
constituents have entered the ground water;
(2) The rate and extent of migration of hazardous waste
or hazardous waste constituents in the ground water;
and
(3) The concentrations of hazardous waste or hazardous
waste constituents in the ground water.
The final regulations specify the procedures for determining
when a statistically significant increase (or pH decrease) in the
concentration of the indicator parameters in ground-water samples has
occurred. The arithmetic mean and variance, based on at least four
replicate measurements for each parameter, for samples from each well
in the ground-water monitoring system are to be statistically com-
pared with the initial (historic) background water quality for these
parameters, using a Student's t-test. The statistical requirements
t
in this Subpart are discussed^the next section of this document. If
a significant difference is detected, one of two actions is trig-
gered. If the significant difference is detected in an upgradient
monitoring well the owner/operator is required to include a discus-
sion of this occurrence in his annual report submission to the
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Regional Administrator. If, however, a significant difference is
detected in a downgradient well, the facility is immediately sus-
pected of contaminating ground water.
If suspected, the owner/operator is required to obtain addition-
al samples for analysis from those downgradient wells showing a sta-
tistically significant increase (or pH decrease). Each of the addi-
tional samples is to be split into two samples and submitted to the
lab for analysis. This step is included in the regulations to reduce
the possibility of a laboratory error causing the significant
difference. Unless the owner/operator is able to demonstrate
laboratory error, he must, within seven days, notify the Regional
Administrator, state and local officials that his facility may be
affecting ground water.
The final interim status rule states:
§265.93(b) For each indicator parameter specified in §265.92(b)(3),
the owner or operator must calculate the arithmetic mean
and variance, based on at least four replicate
measurements on each sample, for each well monitored in
accordance with §265.92(d)(2), and compare these results
with its initial background arithmetic mean. The
comparison must consider individually each of the wells
in the monitoring system, and must use the Student's
t-test at the 0.01 level of significance (see Appendix
IV) to determine statistically significant increases (and
decreases, in the case of pH) over initial background.
(c) (1) If the comparisons for the upgradient wells made
under paragraph (b) of this Section show a
significant increase (or pH decrease), the owner or
operator must submit this information in accordance
with §265.94(a)(2)(ii).
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(2) If the comparisons for downgradient wells made under
paragraph (b) of this Section show a significant
increase (or pH decrease), the owner or operator
must then immediately obtain additional ground-water
samples from those downgradient wells where a
significant difference was detected, split the
samples in two, and obtain analyses of all
additional samples to determine whether the
significant difference was a result of laboratory
error.
In the event that an owner/operator is required to notify the
Regional Administrator concerning possible ground-water contamina-
tion, the regulations allow a two week period during which he must
develop a detailed plan for performance of a ground-water quality
assessment, based upon the previously prepared ground-water quality
assessment program outline, and submit it to the Regional Adminis-
trator. The regulations indicate that the plan must specify well
number, location and depths, and sampling, analysis and evaluation
procedures to be used to determine the cause, extent and severity of
ground-water contamination and a schedule for implementing the plan.
While not specifically required in the regulations the Agency
anticipates that an assessment plan will incorporate comprehensive
analytical techniques, such as gas chromatography/mass spectrometry,
in order to accomplish a thorough assessment; such techniques will be
necessary to determine the rate and extent of migration, as well as
the concentration, of hazardous waste constituents in the ground
water.
The regulations also incorporate a provision for the owner/
operator to submit information obtained from previous facility
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ground-water monitoring activities which demonstrate that the de-
tected significant differences in the indicator parameters were not
caused by the facility. EPA anticipates that the data collected on
the ground-water quality parameters (i.e., chloride, iron, manganese,
phenols, sodium and sulfate) will be used for this purpose.
The final interim status rule states:
§265.93(d) (1) If the analyses performed under paragraph (c)(2) of
this Section confirm the significant increase (or pH
decrease), the owner or operator must provide
written notice to the Regional Administrator—within
seven days of the date of such confirmation—that
the facility may be affecting ground water quality.
(2) Within 15 days after the notification under
paragraph (d)(l) of this Section, the owner or
operator must develop and submit to the Regional
Administrator a specific plan, based on the outline
required under paragraph (a) of this Section and
certified by a qualified geologist or geotechnical
engineer, for a ground-water quality assessment
program at the facility.
(3) The plan to be submitted under §265.90(d)(1) or
paragraph (d)(2) of this Section must specify:
(i) The number, location, and depth of wells;
(ii) Sampling and analytical methods for those
hazardous wastes or hazardous waste
constituents in the facility;
(iii) Evaluation procedures, including any use of
previously-gathered ground-water quality
information; and
(iv) A schedule of implementation.
After submitting the plan to the Regional Administrator the
owner or operator must implement the plan. In order to evaluate the
potential danger, the plan must determine at a minimum the rate and
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extent of migration of the hazardous waste constituents in the ground
water. In addition, it must determine what concentrations of these
constituents are present in the ground water. The initial assessment
must be performed as quickly as is technically feasible. The entry
of hazardous waste constituents into ground water may be presenting a
serious health risk. It is therefore important that the assessment
be initiated quickly once contamination is discovered. The owner or
operator must submit a written report to the Regional Administrator,
within fifteen days after completing the determination, containing
the results of the assessment.
Depending upon the results of the assessment, the indicator
evaluation program may be reinstated if it is demonstrated that no
hazardous waste or hazardous waste constituents from the facility
have entered ground water* However, if ground water has been
impacted the owner or operator is required to continue the assess-
ment on a quarterly basis until closure. If the determination that
ground water is impacted occurs during the post-closure period the
assessment program may cease.
The rationale for the above-stated process is described in the
preamble. The main reason for increasing the assessment to quarterly
during the active life is to allow the Regional Administrator to
evaluate more frequent analyses of the contamination problem once it
has occurred.
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During the post-closure period it is assumed that adequate
closure procedures have been carried out, that surface drainage has
been diverted, cover material installed and the amount of leachate
production significantly reduced. Moreover, no additional waste is
being applied to the facility. With these controls in place, the
amount of ground-water contamination can be expected to reduce, if
not cease. Because of this the Agency felt that a single ground-
water quality assessment during post closure would be adequate. It
should be kept in mind that monitoring of the indicator parameters
will continue through post closure until contaminants are detected
and the problem is assessed.
Within seven days of shifting from an indicator evaluation
program to a ground-water quality assessment program, the owner or
operator must notify the Regional Administrator. A similar notice
must be given when the owner or operator shifts back to an indicator
program after conducting a ground-water quality assessment program.
These provisions assure that the Regional Administrator will know
which program the owner or operator is implementing. In setting
priorities for permitting it will be particularly important to know
which set of facilities are introducing hazardous waste constituents
into ground water.
The final interim status rule states:
§263.93(d) (4) The owner or operator must implement the ground-
water quality assessment plan which satisfies the
requirements of paragraph (d)(3) of this Section,
and, at a minimum, determine:
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(i) The rate and extent of migration of the
hazardous waste or hazardous waste
constituents in the ground water; and
(ii) The concentrations of the hazardous waste or
hazardous waste constituents in the ground
water.
(5) The owner or operator must make his first deter-
mination under paragraph (d)(4) of this Section as
soon as technically feasible, and, within 15 days
after that determination, submit to the Regional
Administrator a written report containing an
assessment of the ground-water quality.
(6) If the owner or operator determines, based on the
results of the first determination under paragraph
(d)(4) of this Section, that no hazardous waste or
hazardous waste constituents from the facility have
entered the ground water, then he may reinstate the
indicator evaluation program described in §265.92
and paragraph (b) of this Section. If the owner or
operator reinstates the indicator evaluation pro-
gram, he must so notify the Regional Administrator
in the report submitted under paragraph (d)(5) of
this section.
(7) If the owner or operator determines, based on the
first determination under paragraph (d)(4) of this
Section, that hazardous waste or hazardous waste
constituents from the facility have entered the
ground water, then he:
(i) Must continue to make the determinations
required under paragraph (d)(4) of this
Section on a quarterly basis until final
closure of the facility, if the ground-water
quality assessment plan was implemented prior
to final closure of the facility; or
(ii) May cease to make the determinations required
under paragraph (d)(4) of this Section, if the
ground-water quality assessment plan was
implemented during the post-closure care
period.
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(e) Notwithstanding any other provision of this Subpart, any
ground-water quality assessment to satisfy the require-
ments of §265.93(d)(4) which is initiated prior to final
closure of the facility must be completed and reported in
accordance with §265.93(d)(5).
The final regulations now include a requirement that the facili-
ty owner/operator, at least annually, evaluate the water table ele-
vation data which is to be gathered for each ground-water sampling
interval. This water level data will be used to calculate the direc-
tion of ground-water flow to determine whether or not his downgradi-
ent wells are still downgradient, as required in §265.91(a)(2), such
that these wells will continue to detect discharges from the waste
management area. If this evaluation shows that the direction of
ground-water flow has appreciably changed, the owner/operator must
modify his ground-water monitoring system accordingly.
The final interim status rule states:
§265.93(f) Unless the ground water is monitored to satisfy the
requirements of §265.93(d)(4), at least annually the
owner or operator must evaluate the data on ground-water
surface elevations obtained under §265.92(e) to determine
whether the requirements under §265.91(a) for locating
the monitoring wells continues to be satisfied. If the
evaluation shows that §265.91(a) is no longer satisfied,
the owner or operator must immediately modify the number,
location, or depth of the monitoring wells to bring the
ground-water monitoring system into compliance with this
requirement.
6. Statistical Methods (Appendix IV)
Synopsis of Proposed Regulations
The proposed regulation required that the results of sampling
and analysis of ground-water monitoring wells be statistically com-
pared to established background ground-water quality using the
1Q9
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Student's t, single-tailed test at the 5 percent level of signifi-
cance. As a result of the analysis of comments received, the Agency
re-proposed the statistical test for ground-water monitoring data
evaluation. On September 19, 1979, the Agency proposed the use of
the Mann-Whitney U-test at the 5 percent level of significance.
Rationale for the Proposed Regulations
The Agency's initial selection of the Student's t-test was an
attempt to require use of a familiar statistical testing procedure
which was generally well suited for evaluation of ground-water moni-
toring data. The Agency's reproposal of the Mann-Whitney U-test was
an attempt to overcome the suggested major weakness of the Student's
t-test, namely its underlying assumption of "normality."
Comments Received and Agency Response
Comments received can be classified into four groups:
statistical model and the underlying assumptions; type I ( ) error
rate resulting from multiple comparisons; spacial and temporal
variations in ground-water quality; and the number of replicate
measurements to be taken on each monitoring sample of ground water.
/
s>
Statistical model and the underlying assumptions: The major-
ity of commenters felt that the Student's t-test was the better test
even though there is some question regarding the assumption of
normality. The Student's t-test assumes that both sets of samples
(i.e., initial background and periodic) are random samples drawn from
normal populations with equal variances. Numerous studies have shown
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that the t-test is robust (i.e., tolerant) to considerable departures
from underlying assumptions.8 The Agency has reconsidered use of
the Student's t-test in light of the comments received.
Type I (a) error rate resulting from multiple comparisons: Many
commenters were concerned about the compounding of type I error
(detection of false significance) due to multiple comparisons of
several variables between the upgradient and downgradient wells. The
Agency recognizes that this is a serious concern and has incorporated
changes in the methodology to control for this compounding (see next
section).
Spacial and temporal variation in ground-water quality: Commen-
ters were concerned that the proposed method of comparing samples,
without considering variations related to time and space, would
result in the detection of significant difference attributable to
natural variability in ground-water quality and not to facility
contributions to ground water. The Agency agrees that these concerns
are valid and has modified the proposed methodology to incorporate
estimates of these components of variability by establishment of
background data for a period of one year prior to actual "compli-
ance" monitoring.
The number of replicate measurements to be taken on each ground-
water sample: Several commenters were concerned about the number of
replicates to be obtained on each sample. While the number of
replicates was not specified in the originally proposed regulations,
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seven replicate measurements were suggested as providing a minimum
level of power for the Mann-Whitney U-test. In response to comments,
however, the final required methodology establishes a minimum number
of replicates based upon a more appropriate approach.
Rationale for Chosen Action
Based on the comments received, the Agency is again specifying
the use of the Student's t-test to detect leaching of hazardous waste
or hazardous waste constituents into the ground water.
The Student's t-test is intended to detect differences in the
sample mean values between periodic and initial background indicator
parameter concentrations or values. As indicated, the Student's
t-test is robust (i.e., relatively insensitive) to the underlying
assumption of normality and therefore can be successfully used in
situations where the underlying distribution deviates from normal-
ity. ° The methodology required in these final regulations involves
comparison of periodically determined concentrations of four
indicator parameters with their initial background concentrations.
The initial background concentrations are established by quarterly
sampling and analysis of the upgradient well for a period of one
year. Initial background, therefore, incorporates both measurement
error and usual fluctuations of ground-water quality over time into
the estimates of means and variance used in the statistical testing.
The Student's t-test involves the calculation of a t-statistic,
using sample means and variances of measurements on the indicator
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parameters. The t-test allows the comparisons to the background
means. Critical values for the t-statistic at a given level of
significance can be found in most introductory statistics texts.
The t-statistic is calculated as follows:69
X - X
P
where:
(n - 1)S + (n. - 1)S,
2 P p D b
t n + n, - 2
P D
and where: t - the calculated t-statistic with k degrees of freedom;
the calculated arithmetic mean of the replicate
measurements for a single indicator parameter for
a given periodic sampling event.
the calculated arithmetic mean of all the
replicate measurements for single indicator
parameter obtained during establishment of initial
background.
the calculated variance of the replicate
measurements for a single indicator parameter for
a given periodic sampling event.
the calculated variance of all the replicate
measurements for a single indicator parameter
obtained during establishment of initial
background.
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n_ • the numbers of replicate measurements for a
single indicator parameter for a given periodic
sampling event (no fewer than four replicates).
n^ = the total number of replicate measurements
for a single indicator parameter obtained during
establishment of initial background (no fewer than
16 rep-licates).
For three of the four indicator parameters (specific conduct-
ance, total organic carbon, and total organic halogen) only increases
over initial background levels are of interest; therefore, for these
indicators single-tailed tests are to be made at the 0.01 level of
significance. For the remaining indicator, pH, increases or decreas-
es over background are of interest; therefore, a two-tailed test at
the overall 0.01 level of significance is required.
These final regulations specify a minimum number of replicate
analyses for each sample to ensure the use of accurate data in the
statistical comparisons. Typical analytical apparatus and techniques
can achieve an estimate of the actual concentration or value of the
indicator parameters in ground-water samples that is within 5% of the
actual concentration or value. That is to say, typical analytical
procedures and care can achieve relative accuracy of 5% or .
better.1'27'57
Similarly, the literature indicates that typical apparatus and
techniques used for analysis of the concentration or value of the
indicator parameters can achieve relative precision of 5% or better
(as low as US).1'27*57
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In light of these capabilities for accuracy and precision the
Agency determined that the 95% confidence level should be specified
because it provides a high degree of assurance that the mean of the
sample replicates is within _+ 5% of the value being estimated. That
is, if the measurement process was repeated a large number of times,
roughly 95% of the means of the replicates would be within _+_ 5% of
the actual mean value.
Under the usual assumption that measurement or laboratory error
is normally distributed, the number of replicate measurements (sample
size) is related to the error (the difference between the estimate
and the actual quantity it is supposed to estimate) and the standard
1 69
deviation of the measurement process in the following manner: '
N =
where: N = number of replicate measurement,
z = the standard normal deviate,
s = the standard deviation of the measurement process,
and
e = the error in estimating the actual value.
Then, since: (1) relative precision is equal to the standard
deviation divided by the actual value, and
(2) relative accuracy is equal to the error
divided by the actual value,
the equation for estimating N can be rewritten as:
N * (relative precision)^ (standard normal deviate)2
(relative accuracy)^"
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where: N - minimum number of replicate measurements
Using a value of 2 for the standard normal deviate to correspond
to an approximate 95% confidence level (the exact value is 1.96), the
relationship, in this case, is:
N = (0.05)2 (2)2
= 4
(0.05)2
A minimum of four replicate measurements is, therefore, required
for each indicator analysis of a ground-water sample.
In order to control for compounding of type I error due to
multiple comparisons the Agency examined several univariate (e.g.,
Student's t vs. Mann-Whitney, sign test ANOVA, etc.) and multivariate
techniques (Hotelling's T, multivariate ANOVA, etc.) and concluded
that the Student's t-test provided the best overall solution given
the large variability in owner or operator statistical expertise and
computing capabilities. This method allows for direct paired compar-
isons using the Student's t-test; however, recognizing the compound-
ing effect of multiple comparisons: the number of parameters to be
compared has been reduced to four; tests for significant difference
are set at the 0.01 level of significance; and, significant differ-
ences are to be confirmed by additional analysis of split samples
before initiating a potentially costly ground water quality
assessment.
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APPENDIX IV
TESTS FOR SIGNIFICANCE
As required in §265.93(b) the owner or operator must use the
Student's t-test to determine statistically significant changes in
the concentration or value of an indicator parameter in periodic
ground-water samples when compared to the initial background concen-
tration or value of that indicator parameter. The comparison must
consider individually each of the wells in the monitoring system.
For three of the indicator parameters (specific conductance, total
organic carbon, and total organic halogen) a single-tailed Student's
t-test must be used to test at the 0.01 level of significance for
significant increases over background. The difference test for pH
must be a two-tailed Student's t-test at the overall 0.01 level of
significance.
The Student's t-test involves calculation of the value of a t-
statistic for each comparison of the mean (average) concentration or
value (based on a minimum of four replicate measurements) of an indi-
cator parameter with its initial background concentration or value.
The calculated value of the t-statistic must then be compared to the
value of the t-statistic found in a table for t-test of significance
at the specified level of significance. A calculated value of t
which exceeds the value of t found in the table indicates a statis-
tically significant change in the concentration or value of the indi-
cator parameter.
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Formulae for calculation of the t-statistic and tables for t-
test of significance can be found in most introductory statistics
texts.
7. Recordkeeping and Reporting
Synopsis of Proposed Regulation
The proposed regulation required that the owner or operator of a
facility report on a quarterly basis the results of sampling and an-
alysis of the ground-water and leachate monitoring systems. Records
of "monitoring and analytical activities and data, including all
original strip chart recordings and instrumentation, calibration, and
maintenance records," were to be maintained by the owner or operator
for at least three years.
Rationale for the Proposed Regulation
The general rationale for requiring the owner or operator of a
facility to maintain records of the ground-water monitoring system
and to periodically report such information to the Regional Admini-
strator was to enable the Agency to have an opportunity to review the
performance of a facility whether or not an indication of ground-
water contamination had been reported. By specifying quarterly
reporting the Agency would obtain this ground-water monitoring infor-
mation within three months of sampling and analysis regardless of the
frequency of sampling and analysis. In this way there would be mini-
mal time lapse before the Agency would become aware of any unreported
increase in contaminants in ground water. By requiring that records
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of such monitoring be retained for a period of three years or more,
the Agency would be afforded the opportunity of reviewing virtually
all information and data related to the monitoring system during
routine inspections or if the need arose following interpretation of
monitoring data.
Comments Received and Agency Response
Reporting frequency. Very few comments were received which ad-
dressed the recordkeeping and reporting requirements of the ground-
water monitoring section. No comments addressed the recordkeeping
requirements of the section and nearly all comments on reporting re-
quirements urged a reduced frequency. Since the proposed regulations
permitted sampling and analysis of the monitoring system as infre-
quently as annually, under some circumstances, commenters stated that
semiannual or annual reporting should be sufficient and permissible
especially in light of the fact that within seven days of detecting a
significant increase of a contaminant over established background
levels the Regional Administrator was to be notified.
The Agency agrees that quarterly reporting of the ground-water
monitoring system data should not be required for routine monitoring.
For owners or operators performing an indicator monitoring program,
annual reporting supplemented by notification within seven days of
the confirmation of significant differences in indicator parameter
concentrations should be sufficient to keep the Agency informed on
facility performance. The Agency does, however, require quarterly
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reporting of the concentrations of those parameters which character-
ize the suitability of the ground water as a drinking water supply,
which are listed in Appendix III in the section on sampling and
analysis, duriisg the initial year when background water quality is
being established. In addition, the owner or operator must identify
in these quarterly reports any such primary drinking water parameter
which is detected in the ground water at a concentration higher than
the maximum contaminant level (MCL) for that parameter. By way of
this requirement the Regional Administrator will promptly become
aware of any contaminated ground-water conditions during that year
which may necessitate Agency notification of nearby users of the
ground water as a drinking water source. This requirement is
especially important for existing facilities where ground water may
have become contaminated as a result of previous waste management or
other practices.
For facility owners or operators performing a ground-water qual-
ity assessment monitoring program, records of all analyses and evalu-
ations specified in the ground-water quality assessment plan must be
kept and submitted annually in a report to the Regional Administra-
tor.
Report distribution. One commenter, who agreed with the quar-
terly reporting requirement, suggested that reports be provided not
only to the Regional Administrator but also to both state and local
authorities. The Agency believes that such distribution might
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constitute an unnecessary burden on the owner or operator and on the
state and local authorities who must process and review such data.
Review by three or more agencies would be needlessly duplicative.
Those State and local authorities that are interested in examining
the reports may obtain copies from EPA or the authorized State agen-
cies responsible for receiving such information.
Rationale for the Chosen Action
Although no comments on recordkeeping requirements were re-
ceived, the Agency has included requirements in the final regulations
which differ from the proposed. Whereas the proposed regulations re-
quired that records of ground-water quality be maintained for a mini-
mum of three years, these final regulations require that ground-water
quality information be maintained throughout the active life of the
facility and, for disposal facilities, throughout the post-closure
care period as well. Since ground-water changes may occur slowly, it
will be useful to have a history of the facility that is longer than
three years. This information will be invaluable in determining the
significance of increases or decreases in indicator parameters and
for successful completion of a ground-water quality assessment
program. The proposed requirement that the records include original
strip charts and other analytic information has been deleted. These
final regulations only require that water quality data and appropri-
ate evaluations for each monitoring well be maintained. (For
121
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recordkeeping and reporting requirements for land treatment facili-
ties, see the background document for Subpart M, Land Treatment.)
For an indicator monitoring program, with the exception of noti-
fication within seven days of significant changes in the concentra-
tion of any indicator parameter from background water quality, the
Agency requires submission of ground-water quality data and evalua-
tions only annually along with the annual report for the facility.
During the first year, however, when background quality is being
established, monitoring information for those parameters which char-
acterize the suitability of the ground water as a drinking water
supply must be reported quarterly. This information will be useful
in identifying those aquifers which are in greatest jeopardy and to
set priorities for consideration of permits. In keeping with this
goal, the owner or operator must indicate in his report any such
parameter which exceeds its MCL.
If a facility owner or operator initially chooses to implement a
ground-water quality assessment program rather than the indicator
monitoring program, or when the results of an indicator program re-
quire the owner or operator to perform a ground-water quality assess-
ment, the recordkeeping and reporting requirements are slightly
different. For a ground-water quality assessment program, the owner
or operator must keep records of all analyses and evaluations speci-
fied in his ground-water quality assessment plan and submit an ini-
tial assessment as soon as is technically feasible. Thereafter
annual reporting of the quarterly assessments is required.
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The final regulations for indicator monitoring programs have a
requirement that water surface elevations be measured and recorded
during sample collection to determine changes in water table gradient
(velocity or direction). The recordkeeping and reporting section in
the final regulation now provides that records of gradient evalua-
tions be submitted in the annual report along with a description of
the response to such evaluations, where applicable.
The final interim status rule states:
§265.94(a) Unless the ground water is monitored to satisfy the
requirements of §265.93(d)(4), the owner or operator
must:
(1) Keep records of the analyses required in §265.92(c)
and (d), the associated ground-water surface
elevations required in §265.92(e), and the
evaluations required in §265.93(b) throughout the
active life of the facility, and, for disposal
facilities, throughout the post-closure care period
as well; and
(2) Report the following ground-water monitoring
information to the Regional Administrator:
(i) During the first year when initial background
concentrations are being established for the
facility: concentrations or values of the
parameters listed in §265.92(b)(1) for each
ground-water monitoring well within 15 days
after completing each quarterly analysis.
The owner or operator must separately
identify for each monitoring well any
parameters whose concentration or value has
been found to exceed the maximum contaminant
levels listed in Appendix III.
(ii) Annually: concentrations or values of the
parameters listed in §265.92(b)(3) for each
ground-water monitoring well, along with the
required evaluations for these parameters
under §265.93(b). The owner or operator must
123
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separately identify any significant
differences from initial background found in
the upgradient wells, in accordance with
§265.93(c)(l). During the active life of the
facility, this information must be submitted
as part of the annual report required under
§265.75.
(iii) As a part of the annual report required under
§265.75: results of the evaluation of
ground-water surface elevations under
§265.93(f), and a description of the response
to that evaluation, where applicable.
(b) If the ground water is monitored to satisfy the require-
ments of §265.93(d)(4), the owner or operator must:
(1) Keep records of the analyses and evaluations
specified in the plan, which satisfies the
requirements of §265.93(d)(3), throughout the active
life of the facility, and, for disposal facilities,
throughout the post-closure care period as well; and
(2) Annually, until final closure of the facility,
submit to the Regional Administrator a report
containing the results of his ground-water quality
assessment program which includes, but is not
limited to, the calculated (or measured) rate of
migration of hazardous waste or hazardous waste
constituents in the ground water during the
reporting period. This report must be submitted as
part of the annual report required under §265.75.
124
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REFERENCES
1. Annual Book of ASTM. 1976. Part 31, Water, Standard D1125-77
through D 2579.
2. A.W. Martin Associates, Inc. 1975. Evaluation of the effect of
the Lafayette, Louisiana Sanitary Landfill on ground and surface
water resources. EPA contract No. 68-01-3135. 55 pages.
3. A.W. Martin Associates, Inc. 1975. Evaluation of the effect of
the Lexington Co., South Carolina Landfill on ground and surface
water resources. EPA contract No. 68-01-2993. 59 pages.
4. A.W. Martin Associates Inc. 1975. Evaluation of the effect of
the Yates County, New York Landfill #1 on ground and surface
water. EPA contract No. 68-01-2993. 55 pages.
5. A.W. Martin Associates, Inc. 1975. Evaluation of the City of
Cheyenne, Wyoming Landfill on ground and surface water re-
sources. EPA contract No. 68-01-3135. 47 pages.
6. A.W. Martin Associates, Inc. 1975. Evaluation of the effect of
the Anderson Township, Ohio Fill on ground and surface water re-
sources. EPA contract No. 68-01-3136. 51 pages.
7. A.W. Martin Associates, Inc. 1976. Evaluation of the effect of
the Town of Enfield, Connecticut Sanitary Landfill on ground and
surface water resources, EPA contract No. AW-464. 78 pages.
8. Boneau, C.A. 1960. "The effects of violations of assumptions
underlying the t-test." Psychological Bulletin, 57:49-64.
9. Bouwer, H. 1978. Ground Water Hydrology, McGraw-Hill, New
York, Chapter 10, Groundwater Quality.
10. California State Water Resources Control Board. 1978. Waste
discharge requirements for nonsewerable waste disposal to land
(Part E).
11. Chian, E.S.K. and F.B. DeWalle. 1975. Compilation of method-
ology for measuring pollution parameters of landfill leachate.
U.S. Environmental Protection Agency, Cincinnati, Ohio.
EPA-600/3-75-011.
12. Clark, J.P. and V.S. Gretchen. 1980. "Requirements of State
regulatory agencies for monitoring ground-water quality at waste
disposal sites." Ground Water, vol. 18, no. 2, pages 168-174.
125
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REFERENCES (Continued)
13. Cox, C.R. 1964. "Operation and control of water treatment pro-
cesses," Monograph Series No. 49, World Health Organization,
Geneva, Switzerland. 390 pages.
14. Criteria for classification of solid waste disposal facilities
and practices. 5^44 (179), September 13, 1979.
15. Dixon, W.J. and F.J. Massey. 1969. Introduction to Statistical
Analysis. McGraw-Hill, New York, pages 270-273.
16. Dressman, Ronald (MERL, EPA, Cincinnati). Personal telephone
communication. Subject: "TOX standardization status."
17. Dressman, R.C.; Najar, B.A. and Redzikowski, R. (Drinking Water
Research Division, U.S. E.P.A., Cincinnati, Ohio 45268). Un-
dated. "The Analysis of organohalides (OX) in water as a group
parameter."
18. Fenn, D.; et al. 1977. Procedures manual for ground water mon-
itoring at solid waste disposal facilities. EPA/530/SW-611.
269 pages.
19. Fenn, Dennis G. , Keith J. Hanley, and Truett V. DeGeare. 1975.
Use of the water balance method for predicting leachate genera-
tion from solid waste disposal sites. EPA/530/SW-168.
20. Gage, S.J. 1979. "The Role of Research and Development in the
Environmental Protection Agency1s Approach to the Toxic Pol-
lutants Problem," Measurement of Organic Pollutants in Water and
Wastewater, C.E. Van Hall, ed., American Society for Testing and
Materials, STP 686. Philadelphia. 3 pages.
21. Glaze, W.H. and Peyton, G.R. 1977. "Total organic halogen as
water quality parameter: adsorption/microcoulometric method."
Environmental Science and Technology, Volume 11, No. 7, pages
685-690.
22. Howard, Abby. 1978. Personal injury, economic damage, of
fatalities from hazardous wastes. Unpublished list of reports,
catalogues and damage cases on file at the USEPA.
23. Illinois Environmental Protection Agency. 1977. Special-Waste
Land Disposal Permits Criteria.
24. Illinois Environmental Protection Agency. 1977. Special and/or
Hazardous waste permit information, Module E.
126
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REFERENCES (Continued)
25. Jekel, Martin and Reinhard, Martin. October 1979. "Total^
specific compound analysis in advanced treated wastewaters"
(paper presented at the Pacific Conference on Chemistry and
Spectroscopy, Pasadena, California).
26. Jekel, M.R. Undated. "The determination of total organic
halogen (TOX) as practiced at the Stanford Water Quality Control
Research Laboratory, Department of Civil Engineering, Stanford
University, Stanford, CA 94305."
27. Joyce, Robert (Dohrmann/Envirotech). Personal telephone com-
munication. Subject: "Users of TOX instrumentation." April 2,
1980.
28. LeGrand, Harry. 1979. Evaluation of ground-water contamination
potential from waste disposal sources. EPA contract No.
68-01-4405.
29. Lohman, S.W. et al. 1972. Definitions of selected ground-water
terms - revisions and conceptual refinements. USGS Water Supply
Paper 1988.
30. Lohman, S.W. 1972. Ground-water hydraulics. U.S. Geological
Survey Professional Paper 708.
31. Louisiana Department of Natural Resources Regulations, Sections
5.5.2 and 8.4.10. August 1979.
32. Martin, R. Jekel, and Paul Roberts. 1979. Total organic halo-
gen measurements for the characterization of reclaimed water.
Submitted to Environmental Science and Technology.
33. Maryland Natural Resources Code. March 1977 (as amended).
Title 8, Section 1413.2(c), Chapter 618.
34. Maryland Water Resources Administration Regulation 08.05.05.
Amended through July 1978.
35. Minnesota Regulations for Hazardous Waste Management. June
1979-
36. Mooij, H.; et al. 1977. Recommended procedures for landfill
monitoring program design and implementation. Environment
Canada. EPS 4-EC-77-3. 25 pages.
127
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REFERENCES (Continued)
37. National Academy of Sciences and National Academy of Engineer-
ing, 1972. Water Quality Criteria 1972, Report prepared by
Committee of Water Quality Criteria at request of U.S. Environ-
mental Protection Agency, Washington, D.C., 594 pages.
38. New Jersey Department of Environmental Protection. 1977 (as
amended). New Jersey Administrative Code 7:26-1 et seq.
39. New York Department of Environmental Conservation. August 1977.
Rules and Regulations, Part 703 et seq.
40. New York Department of Environmental Conservation. August 1977.
Part 360.8 et seq.
41. Ohio Environmental Protection Agency, Division of Hazardous
Wastes. June 1976. Criteria for Landfill Disposal of Hazardous
Wastes in Ohio.
42. Ohio Environmental Protection Agency. June 1976. Draft
criteria for the disposal of very hazardous wastes in Ohio.
43. Ohio Environmental Protection Agency. Investigations by Ohio
EPA ground water group - specific contamination cases. Hamilton
County.
44. Ohio Environmental Protection Agency. Investigations by Ohio
Environmental Protection Agency ground water group - specific
contamination cases. Monroe County. Unpublished list.
45. Oliver, B.C. 1979. Chlorinated nonvolatile organics produced
by reaction of chloride with humic material. Canadian Research,
11 (6):21-22.
46. Oxidation Techniques in Drinking Water Treatment. 1978. In:
Proceedings of Karlsruhe Conference, F.R.G., held Sept. 11-13.
H. Sontheimer, ed., EPA-570/9-79-020, 39 pages.
47. Pennsylvania Department of Environmental Resources. 1975.
Water quality management and solid waste management. Supple-
mentary Geology and Ground Water Information, Module 5A - Phase
1.
48. Pennsylvania Department of Environmental Resources. June 1977.
Pennsylvania Administrative Code, Section 75.38 et seq.
128
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REFERENCES (Continued)
49. Pesticides and Pesticide Containers, Regulations for Acceptance
and Recommended Procedures for Disposal and Storage, FR 39 (86),
May 1, 1974.
50. Piskin, R. July 1976. Suitability of landfills for disposal
of hazardous wastes in Illinois. Waste Age.
51. Polychlorinated biphenyls; criteria modification, hearings FR 44
(106), May 31, 1979.
52. Public Health Service. 1962. Drinking Water Standards, U.S.
Department of Health, Education and Welfare, Washington, D.C.,
61 pp.
53. Shuster, K.A. 1976. Leachate damage assessment - case study of
the Sayville solid waste disposal site in Islip (Long Island),
New York. EPA/530/SW-509. 18 pages.
54. Shuster, K.A. 1976. Leachate damage assessment - case study of
the Fox Valley solid waste disposal site in Aurora, Illinois.
EPA/530/SW-514. 34 pages.
55. Silka, Lyle R. and Ted L. Swearingen. 1978. A manual for eval-
uating contamination potential of surface impoundments. EPA
570/9-78-003.
56. South Carolina Proposed Hazardous Waste Management Regulations,
Sections R61-79.4.
f
57. Standard Methods for the Examination of Water and Wastewater.
1976. APHA, AWWA, WPCF, 14th ed. Washington, D.C.
58. Texas Department of Water Resources. January 1979. Technical
Guideline No. 6 (draft revision) - Monitoring Systems and Leach-
ate Collection.
59. Texas Water Quality Board. May 1976. Technical Guideline No.
6, Monitoring/Leachate Collection Systems.
60. Texas Water Quality Board. 1977 (as amended). Industrial solid
waste management regulation, Section 3-07.
61. U.S. Environmental Protection Agency. 1973. The effective use
of high water table areas for sanitary landfill. EPA-SW75d.l.
62. U.S. Environmental Protection Agency. 1973. Handbook for Moni-
toring Industrial Wastewater, Technology Transfer.
129
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REFERENCES (Concluded)
63. U.S. Environmental Protection Agency. 1973. Manual of Indivi-
dual Water Supply Systems, Office of Water Programs. 164 pages.
64. U.S. Environmental Protection Agency. March 1979. Methods for
Chemical Analysis of Water and Wastes. EPA-600/4-79-020.
65. U.S. Environmental Protection Agency. National Interim Primary
Drinking Water Regulations, 40 CFR 141.
66. U.S. Environmental Protection Agency. 1977. The prevalence of
subsurface migration of hazardous chemical substances at
selected industrial waste land disposal sites. EPA/530/SW-634.
67. U.S. Environmental Protection Agency. 1974. Report to con-
gress: disposal of hazardous wastes. EPA SW-115.
68. U.S. Environmental Protection Agency. January 1977. Report to
congress - waste disposal practices and their effects on ground
water. 531 pages.
69. Walpole, Ronald E. and Raymond H. Myers. 1972. Probability and
statistics for engineers and scientists. Macmillan Co., New
York. Pages 187-192, 242-245.
70. Washington State Administrative Code - Hazardous Waste Regula-
tions, Chapter 173. 302.280. January 1978.
71. Wegman, R.C. and Greve, P.A. 1977. "The microcoulometric
determination of extractable organic halogen in surface water;
application to surface waters of the Netherlands." The Science
of the Total Environment, Volume 7, pages 235-245.
72. Weston, Roy F., Inc. 1979- Pollution prediction techniques for
waste disposal siting - a state-of-the-art assessment. U.S.
Environmental Protection Agency Report SW-162c.
73. Wilson, L.G. August 1979. Monitoring in the vadose zone: a
review of technical elements and methods. Unpublished Report,
EPA Contract No. V-0591-NALX.
74. Wisconsin Department of Natural Resources. 1977. Hazardous
waste management guidelines and procedures.
75. Wisconsin. 1977. Assembly Bill 880, Section 17 (144441).
76. Wisconsin Department of Natural Resources. 1974. News release
copy on file at EPA.
130
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Attachment No. 1
Damage Cases
The following is a detailed description of the documented damage
cases illustrating the potential for groundwater contamination from
hazardous waste land disposal sites :
1. The Ansul Company manufactures agricultural herbicides in
Marinette, Wisconsin, which resulted in the production of
salt wastes containing arsenic. The company had accumulated
many tons of these salts at their plant location. Surveys
by Ansul and the Wisconsin Department of Natural Resources
(DNR) had indicated localized heavy groundwater contamina-
tion. Contamination of the Menominie River, adjacent to the
plant, had occurred with maximum levels in the sediment
found to be 35 ppm of arsenic (USPHS standard is 0.05 ppm) .
The river contamination had been attributed to 7,500 tons of
the salt wastes which has been stored on a loading dock
within 10 feet of the river. A well at the dock had been
found to yield water containing about 1.0 mg/1 arsenic. The
DNR had ordered the Ansul Company to construct new storage
facilities for the salt wastes. Two new storage facilities
were to be built, the first for the daily salt waste produc-
tion and the second for the wastes currently stored on
site.
2. An aluminum plant in Monroe County, Ohio had grossly contam-
inated the ground water under its site with flourides, high
pH, and other trace chemicals. The water was also dis-
colored. The source of contamination was leachate from a
used tailing pond and used potline piles. As a partial so-
lution the firm was treating the pollution source with acid.
They have also developed interceptor wells between their
source of pollution and their main production well. The
OEPA did recognize that these actions were beneficial in
containing the pollution within the aquifer under the firms
site. However, if the firm were to discontinue operations
and thus discontinue the use of the main production well,
the use of the inceptor well, and the use of acid treatment,
the site would be a major source of pollution for many years
after the plant closed.
131
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3. A chemical plant in Hamilton County, Ohio which utilizes two
infiltration lagoons for waste disposal had contaminated a
very productive aquifer. This was discovered recently when
a new well was developed on a nearby property. Follow up
studies revealed that several other wells in the area were
also contaminated. Abnormally high values of sodium, potas-
sium, nitrogen, sulfates, phenols and high TOC values were
found. A few of these constituents in several of the con-
taminated wells exceeded standards for drinking water.
4. An arsenic pesticide was used to control a grasshopper
infestation near Perham, Minnesota in 1934. After the
infestation was under control, the unused pesticide was
buried in an unmarked shallow trench far from any urbanized
areas. In 1972 a shallow well was installed near the pesti-
cide disposal area to serve as a water supply for a local
construction company. Soon after the well was placed in
service, thirteen employees were stricken with what was
later diagnosed to be arsenic poisoning. All of the thir-
teen employees required medical treatment and two had to be
hospitalized. One employee was hospitalized for more than a
month and still suffers from nerve damage.
5. Since August 1968, a commercial laboratory in Myers town,
Pennsylvania, has disposed of its arsenic waste by surface
storage within the plant area (some of waste materials not
known). This practice apparently has led to contamination
of the ground and subsequent migrations into groundwaters
.through leaching, ionic migration actions, etc., abetted by
the geologic and edaphic character of the plant site. In
order to meet discharge requirements and/or eliminate the
waste hazard, the company has had to design and construct a
system of recovery wells to collect the arsenic effluent
from groundwaters in the area. Recovered arsenic and cur-
rent arsenic waste (previously stored on the land) are now
retained in storage lagoons. Presumably, the sludge from
these lagoons was periodically reclaimed in some way.
Lagoons of this type are generally not well attended and may
result in environmental catastrophes.
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Attachment No. 2
State Laws and Regulations
A survey of various state hazardous waste regulatory programs
yielded the following information:
California
The California State Water Resources Control Board is the agency
regulating disposal sites and monitoring of hazardous wastes. Moni-
toring plans are developed case-by-case, based upon the detailed geo-
logic and hydrologic requirements of the permit.10 The monitoring
programs for hazardous waste disposal facilities may include any or
all of the following components:
1. Monitoring of local ground and surface water from locations
considered to be within the radius of influence of a dis-
posal site; and from a background location. These data may
be compared. The regulations observe that collection of
baseline data is important because it may offer a basis to
discount claims of degradation of water quality which may be
filed later by other parties.
2. Periodic site inspection, sampling, and analysis of wastes
performed by agency personnel. The operator is allowed to
collect samples for replicate analysis.
3. Installation of piezometers or monitoring wells at critical
locations.
4. Operation of continuous fluid level measuring instruments at
seepage collection drains and dumps.
5. Monitoring wells, located on the basis of local ground and
surface-water hydrology, from which the disposer may be re-
quired to collect samples.
The selection of constituents for analysis and evaluation is re-
lated to the type of waste being disposed. The basic program in-
cludes testing for pH, electrical conductivity or total dissolved
solids, chloride, hardness, and total alkalinity. Specialized moni-
toring of hazardous waste disposal may require sample analyses for
toxic materials, heavy metals, organics, color, BOD, tannins and
lignins, with field tests for carbon dioxide.
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At sites receiving up to 200 tons of wastes daily, monitoring
reports are generally required on a quarterly basis. Sites receiving
more than 200 tons daily must submit monthly reports".
JH. lino is
The Division of Land and Noise in the Illinois Environmental
Protection Agency (IEPA) is responsible for the State's hazardous
waste management program. Criteria developed for land disposal of
hazardous wastes place considerable emphasis upon the origin and
composition of the materials to be disposed of.23 The waste
generator is required to list the standard industrial classification
(S.I.C.) number for the industrial activity from which waste is
derived. IEPA has assigned a number to each of the subgroups in the
S.I.C. table. These numbers are used to determine the minimal scope
of chemical analyses required with the permit application; this waste
characterization provides a guide for future ground-water monitoring.
IEPA uses a landfill simulation- leaching test to determine the
environmental impact of the was-te material.^ This test is applied
to hazardous wastes for which a disposal permit is required, accord-
ing to the previously mentioned grouping of wastes by S.I.C. numbers.
Theoretically, waste characterization should permit design of a waste
constituent-oriented monitoring program at each site.
The agency usually requires installation of at least one moni-
toring well hydraulically upgradient and one down-gradient, placed as
close as possible to the deposition area. The monitoring wells may
penetrate shallow perched water zones which are widespread in Illi-
nois. If contamination is detected, IEPA interprets this as an
"early warning signal" indicating possible later contamination of the
underlying water-table aquifer.*0
Louisiana
The Department of Natural Resource's hazardous waste management
regulations include provisions for surveillance and monitoring of
facilities, requiring a systematic program to conduct investigations
and recording of ground-water monitoring systems.31 Specific
requirements of the ground-water monitoring system address well
number and location; sampling frequency and parameters; evaluation of
and response to analytical results; and recordkeeping and reporting.
Maryland
The program to monitor storage and disposal of hazardous wastes
in Maryland is in the early stages of implementation, following the
1976 enactment of a law entitled "Safe Disposal of Designated Hazard-
ous Substances,11" and promulgation of applicable regulations by the
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Maryland Department of Natural Resources (DNR). The law requires
that the DNR "establish procedures for monitoring of hazardous and
industrial substances from the time of generation to the time of
final disposal."33 it specifically directs the DNR to set minimum
requirements for ground-water monitoring.
The DNR's regulations require detailed hydrogeological informa-
tion (e.g. soils, rock formations, boring results) to be submitted by
the permit applicant.34 xhe applicant must also present informa-
tion on the ground-water monitoring system design, including back-
ground ground-water analyses and sampling procedures.
Minnesota
Hazardous waste management regulations were promulgated in 1979
by the Minnesota Pollution Control Agency.35 These regulations
require the owner/operator of a hazardous waste disposal facility,
before accepting hazardous waste, to construct a monitoring system.
This system would be used to determine effects in soil, ground water
and air attributable to the disposal facility operations. In
addition, for closure of a hazardous waste land disposal facility,
ground water and surface water monitoring systems must be constructed
if not already installed. The monitoring system must also be
employed in the long-term maintenance of a facility after closure.
New Jersey
Regulations promulgated by the New Jersey Department of Environ-
mental Protection (DEP) in 1975 (as amended in 1977) prohibit opening
of a new solid waste facility without prior installation of a ground-
water monitoring system.38 Background water-quality data must also
be obtained and recorded before any waste is deposited at the site.
The DEP may also require installation of monitoring systems at the
sites in operation prior to September 1975. All monitoring system ap-
provals are made on a case-by-case basis. Each disposal facility
receiving hazardous wastes must have interception, collection, and
treatment systems for any leachate generated at the site.
The submission of the required monitoring data must be made an-
nually, at which time the registrant is required to provide a state-
ment updating the information contained in the initial registration
statement. The registrant must notify the DEP within 30 days of any
change in status of the operation covered by the original statement.
The regulations require an extensive list of parameters to be in-
cluded in the annual analyses of samples collected as part of the
monitoring program.
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New York
At the present time, New York State is in the process of imple-
menting a program designed to upgrade hazardous waste disposal and
monitoring practices. The program will be managed by the Hazardous
Waste Bureau of the Department of Environmental Conservation (DEC).
Regulations classifying ground water and establishing water-
quality effluent standards have been proposed by the DEC. The stan-
dards, if approved, will be applicable to industrial waste treatment,
including hazardous waste management facilities designed both for
treatment and storage.39
Effective solid waste management regulations set specific re-
quirements for ground-water protection and monitoring with special
precautionary measures required at land burial facilities used for
hazardous waste disposal.40 At these sites, monitoring programs
will be established by the DEC on a case-by-case basis. A minimum of
three monitoring wells, with two located hydraulically downgradient
from the solid waste fill area, is required. Ground-water sampling
frequency is set as part of the operating permit. Baseline water
quality must be established prior to use of the site. The regula-
tions are applicable to both new and modified secure land burial
facilities, which are defined as "a disposal facility meeting the de-
sign and operation requirements (. ) for the proper disposal of
hazardous wastes so that such wastes are immobilized or otherwise
prevented from release to the environment or rendered harmless or de-
composed into harmless materials within the facility."
Ohio
In 1976, the Ohio EPA promulgated new solid waste regulations
which gave the Agency's Office of Land Pollution Control (OLPC),
Division of Hazardous Wastes, more authority.41 These regulations
influence future monitoring of hazardous waste storage and disposal
facilities two ways. They provide a specific definition for ground-
water pollution, and stipulate that sites must be located in geologic
formations where permeability of the clay is such that the time re-
quired for the movement of leachate through the walls or bottom of
the landfill to ground water or surface water must be 1,000 years
under a "hydraulic gradient of 1.2."42 Pollution of ground water
is defined as the "entrance of any substance into such waters in such
quantities as to prevent or materially interfere, either immediately
or cumulatively, with any use of such waters otherwise possible, or
in such quantities as would require such waters to be treated prior
to use." This policy of long-term protection of existing ground-
water quality is further reinforced by the site data and monitoring
requirements of the regulations.
1.36
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The permitting procedure requires submission of a complete geo-
logic and hydrologic report on existing conditions, including the
"ground-water development potential" of the aquifer(s) beneath the
disposal site. Chemical analyses of ground-water samples for 17 con-
stituents must be submitted, with the agency entitled to request a
sampling program involving "analysis of such a number of samples from
such a number of wells as deemed necessary." The applicant must also
provide data on the "location, surface elevation, depths, con-
struction details, materials penetrated, water levels, available re-
ports on future plans for, chemical sampling, and other relevant
characteristics of all monitor wells to be used for ground-water sam-
pling, and detection of leachate production and migration."
Provision is to be made for the collection, containment, treat-
ment or disposal of leachate. The permittee is responsible for the
maintenance of monitoring wells for sampling until three years after
the landfill is completed.
Pennsylvania
The Division of Solid Waste Management in Pennsylvania's Depart-
ment of Environmental Resources (DER) is responsible for the permit-
ting and surveillance of monitoring programs associated with the
disposal of hazardous waste throughout the State. At present, there
are no facilities designed specifically for this purpose. However,
since passage of RCRA, the Division has received inquiries from waste
disposal firms interested in establishing facilities.
The Division's monitoring authority was strengthened consider-
ably by a 1977 revision of State Solid Waste Management Rules and
Regulations applicable to industrial waste disposal sites. The per-
mitting procedures are designed to promote full disclosure of site
and waste characteristics through a two-phase permitting procedure.
Data solicited from the applicant include complete coverage of per-
tinent geologic and ground-water conditions.^ Phase I requires
the applicant to describe monitoring proposed as part of the project,
and to delineate specific monitoring points. However, the permit
application advises that "wells are not to be drilled until the
Department approves the design, location, and specifications." The
regulations stipulate that "monitoring points should not be located
more than 500 feet from the permitted area, in order to obtain
ground-water samples capable of being analyzed for contaminants as
close as possible to the actual place of deposition."48
One monitoring well must be installed hydraulically downgradient
and one monitoring well upgradient from the deposition area. This is
considered to be the minimum requirement for each project. However,
DER approval of hazardous waste monitoring projects is to be on a
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case-by-case basis with provision for additional monitoring wells at
the discretion of the agency. Design of the monitoring wells and
sampling procedure are dictated by the terms of the project permit.
The regulations stipulate that each monitoring well must be
purged prior to obtaining water samples. Chemical analyses of water
samples from the monitoring well and other hydrologic data must be
submitted quarterly. Constituents included in the analyses are de-
termined on a case-by-case basis, according to the chemical and phys-
ical properties and the volume of the materials disposal of.
South Carolina^6
South Carolina's proposed regulations for hazardous waste man-
agement facilities include requirements for ground-water monitoring,
addressing well number and location; sampling frequency and para-
meters; evaluation of and response to analytical results; and record-
keeping and reporting.
Texas
The Texas Water Quality Board (Board) is actively involved in a
program to insure that ground-water monitoring requirements are sat-
isfactory at both on-site and off-site hazardous waste management
facilities. Owner/operators are required to install ground-water
monitoring systems meeting the specifications of the Board's May 1976
guidelines (draft revision, January 1979) or institute other equiva-
lent procedures acceptable to the Board.53,59 Long-term post-
operational surveillance is required in order to minimize possible
damage to ground or surface water beyond the site.^0
The guidelines establish a three-phase monitoring program.
Phase I involves sampling to establish background water quality at
the site. Phase II consists of a periodic sampling of monitoring
points, the initial results of which must be reported to the Board
monthly during the first year of site operation, and quarterly there-
after. Phase III of the monitoring program extends sampling and an-
alysis of ground water for a period of time after the site is closed.
The sampling frequency and time period of monitoring after closure is
established by the agency at the time of permitting. Registration of
hazardous waste disposal operations is on a case-by-case basis with
the number of monitoring points set by the agency. The registration
procedure was initiated as a means of obtaining information on exist-
ing waste disposal sites.
Sampling point distribution and monitoring procedures are deter-
mined by hydrogeologic conditions and types of waste likely to be
encountered. The proposed revised guidelines developed by the Board
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recommend a minimum of four monitoring wells under ideal conditions,
that is, where the underlying earth materials are fairly homogeneous,
relatively permeable, and uniformly sloping in one direction. The
monitoring wells should be located upgradient and downgradient of the
waste management activity with respect to ground-water flow. ^ In
cases of multiple aquifer systems, each water-bearing formation
should be monitored.
All monitoring wells should be cased, with the annular space be-
tween the zone of saturation and the surface completely backfilled or
plugged with cement or packed with clay, to prevent percolation of
surface water into the well bore. The well casing must be fitted
with a removable cap to prevent entrance of runoff and rainfall.
If contamination is noted by the owner/operator, a report must
be submitted to the Board, as well as a plan to determine the con-
tamination source. If the facility is the source, a corrective ac-
tion plan must be submitted to the Board.
Washington
Washington's hazardous waste regulations require monitoring
wells under each "burial trench" and "evaporation pond" to be checked
at least quarterly.70
Wisconsin
The Wisconsin Department of Natural Resources (DNR) views moni-
toring as one portion of the total hazardous waste management pro-
gram, required principally as a surveillance tool with the data
generated to be used in enforcement procedures.
Under a proposed law, facilities approved by DNR would not be
required to obtain any local permits or authorizations which may
otherwise be necessary to operate the facility.75 Licensing would
involve three steps, with monitoring and closure plans to be
submitted as part of the first step for the feasibility report. A
waste classification plan incorporated in the law would assign all
waste to classes, based upon the relative degree of hazard posed by
the waste. The principal emphasis on monitoring devices is related to
the long-term care provisions of the proposed law. In the original
plan of operation, the DNR can require up to 10 years of long-term
care, unless the licensee agrees to a longer period of time. After
this time period expires, a decision on termination is to be made by
the DNR.
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