United States
Environmental
Protection Agency
Solid Waste and
Emergency Response
(5305W)
EPA530-R-99-049
PB2000-101885
February 2000
RCRA, Superfund & EPCRA
Hotline Training Module
Introduction to:
Groundwater Monitoring
(40 CFR Parts 264/265, Subpart F)
Updated October 1999
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DISCLAIMER
This document was developed byBooz-Alien & Hamilton Inc. under contract 68-W 0-0039 to EPA. It is intended to
be used as a training tool for Hotline specialists and does not represent a statement ofEPA policy.
The information in this document is not by any means a complete representation ofEPA's regulations or policies.
This document is used only in the capacity of the Hotline train ing and is not used as a reference tool on Hotline calls.
The Hotline revises and updates this document as regulatory pro gram areas change.
The information in this docume nt may not necessarily reflect the current position ofthe Agency. This document is
not intended and cannot be relied upon to create any rights, subs tan live or procedural, enforceable by any party in
litigation with the United States.
RCRA, Superfund & EPCRA Hotline Phone Numbers
National toll-free (outside of DC area) (800) 424-9346
Loca I num ber (withi n DC a rea) (703) 412-9810
National toll-free for the hearing impaired (TDD) (800) 553-7672
The Hotline is open from 9 am to 6 pm Eastern Time,
Monday through Friday, except for federal holidays.
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GROUNDWATER MONITORING
CONTENTS
1. Introduction 1
2. Regulatory Summary 2
2.1 Permitted Facility Groundwater Monitoring 6
2.2 Interim Status Groundwater Monitoring 18
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Groundwater Monitoring -1
1. INTRODUCTION
This module presents the requirements for groundwater monitoring at interim status
and permitted treatment, storage, and disposal facilities (TSDFs) under the Resource
Conservation and Recovery Act (RCRA). The groundwater monitoring regulations are
found in 40 CFR Part 264/265, Subpart F. TSDFs managing hazardous waste in certain
land-based units are required to implement a groundwater monitoring program so that
releases of hazardous waste from these units to groundwater are detected and measures
are implemented to remediate the contamination as soon as possible.
The goal of this module is to explain the standards and specific requirements for
groundwater monitoring programs at interim status and permitted facilities. When you
have completed this module you will be able to:
• Describe the groundwater monitoring criteria for interim status and permitted
facilities
• Explain monitoring well placement
• Understand the three stages of the groundwater monitoring program for
permitted facilities.
Use this list of objectives to check your knowledge of this topic after you complete the
training session.
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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2 - Groundwater Monitoring
2. REGULATORY SUMMARY
The groundwater monitoring regulations in Part 264/265, Subpart F, are one part of an
overall strategy to reduce the likelihood of environmental contamination resulting from
hazardous waste treatment, storage, and disposal. This strategy includes restrictions on
disposal of untreated hazardous waste, unit-specific standards for land-based
hazardous waste management units, and monitoring groundwater below these units.
The land disposal restrictions program requires the treatment of hazardous wastes prior
to disposal to reduce the mobility or toxicity of hazardous constituents. The unit-
specific standards for land-based hazardous waste management units seek to prevent
the release of hazardous waste to the environment. Groundwater monitoring is the
final link in this strategy to prevent environmental contamination. Owners and
operators of all land-based units must institute a groundwater monitoring program that
is able to detect and characterize any releases of hazardous waste or hazardous
constituents to the groundwater underlying the facility. Should the other elements of
the strategy fail, groundwater monitoring will detect the release so it can be remedied.
The regulations in Subpart F of Part 264/265 are general requirements, establishing
performance-based standards that state what a successful groundwater monitoring
program must accomplish; they do not dictate specific technical standards. Each
facility's groundwater monitoring program is unique because no two TSDFs are exactly
the same. Individual groundwater monitoring programs are based on site-specific
conditions, including the underlying geology and hydrology, as well as the properties
of wastes managed on site.
The groundwater monitoring regulations for interim status facilities were promulgated
in the May 19,1980> Federal Register (45 FR 33232) and codified in Part 265, Subpart F.
These regulations were designed to supply background data on facilities before
permitting, as well as to act as a warning system to detect any releases to groundwater
prior to permit issuance.
The groundwater monitoring regulations for permitted facilities were promulgated in
the July 26,1982, Federal Register (47 FR 32350) and are found in Part 264, Subpart F.
These regulations pertain to any land-based facility seeking a Part B permit that
received waste after July 26,1982, or that certified closure after January 26,1983. Part
264, Subpart F, establishes a three-stage program designed to detect and remediate any
releases from regulated units.
Although the groundwater monitoring programs in Part 264 and Part 265 are different,
they do have some common technical and environmental performance standards. The
technical standards establish an engineering objective and allow a permit applicant to
develop a design or set of practices to achieve certain goals established in the
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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Groundwater Monitoring - 3
groundwater monitoring requirements under Subpart F. The environmental
performance standards specify limits on the levels of contamination that may be
released into the environment before remediation is required.
Groundwater is water found below the land surface in the zone of saturation, meaning
that part of the earth's crust in which all voids are filled with water. An important
source of groundwater is the aquifer, which is a geologic formation, group of
formations, or part of a formation capable of yielding a significant amount of
groundwater to wells or springs. There are two types of aquifers: confined and
unconfined. Confined aquifers are under pressure, unconfined aquifers are not
(Figure 1).
The Subpart F programs protect groundwater that is found in the uppermost aquifer,
which is the water-bearing geologic formation nearest the natural ground surface
(§260.10). Also included in this definition are any and all deeper aquifers that are
hydraulically interconnected with the uppermost aquifer within the facility's property
boundary. These interconnected aquifers are zones of saturation that present a
potential pathway for contamination to reach human beings (Figure 2).
Although the statute does not limit EPA's regulatory authority to only the uppermost
aquifer, the groundwater monitoring regulations only require that the uppermost
aquifer be monitored. The groundwater monitoring regulations of Subpart F do not
address other aquifers or any other groundwater resources which are not in or
connected to the uppermost aquifer (§§264.90-264.100 and §§265.90-265.94).
Contamination in such areas can be addressed by other mechanisms such as authority
under RCRA §§3004(u) and (v) (for facilities seeking a permit, codified in §264.101);
RCRA §3008(h) (for interim status facilities); RCRA §7003; the Comprehensive
Environmental Remediation, Compensation, and Liability Act (CERCLA); the Safe
Drinking Water Act (SDWA); or state or local enforcement authorities.
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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4 - Groundwater Monitoring
Figure 1
SCHEMATIC OF CONFINED AND UNCONFINED AQUIFERS
Confined
Aquifer
pressure
raises height
of water
column in well
low permeability
confining layer
permeable
layer
{impermeable
bedrock
confining layer
Unconfined
Aquifer
Water Table
Direction of
Groundwater
permeable
layer
impermeable
bedrock
layer
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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Groundwater Monitoring - 5
Figure 2
SCHEMATICS OF AN UPPERMOST AQUIFER
uppermost
aquifer
hydraulic
conductivity
along fault line
uppermost
aquifer
Water Table
Direction of
Groundwater
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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6 - Groundwater Monitoring
2.1 PERMITTED FACILITY GROUNDWATER MONITORING
EPA has the authority to require the owner and operator of a TSDF to remediate
releases of hazardous waste or hazardous constituents to the environment. All
permitted facilities must comply with Part 264, Subpart F, for releases from solid waste
management units (SWMUs). This module addresses the regulations pertaining to
releases to the uppermost aquifer from regulated units, a subset of SWMUs. See the
module entitled RCRA Corrective Action for a discussion of the regulations that apply
to other types of releases from SWMUs. Facilities with permitted regulated units —
landfills, surface impoundments, waste piles, or land treatment units — must conduct
groundwater monitoring to detect, characterize, and respond to releases of hazardous
waste or hazardous waste constituents into the uppermost aquifer. There are three
stages to the Part 264, Subpart F, groundwater monitoring and follow-up activities:
• Detection monitoring - to detect if a release has occurred
• Compliance monitoring - to determine if the Groundwater Protection Standard
(GWPS) has been exceeded once a release has occurred
• Corrective action - to remediate a release to the uppermost aquifer.
Section 264.97 sets out the basic requirements that apply to all groundwater monitoring
programs under Part 264, Subpart F. The specific requirements that apply to each of the
three phases of groundwater monitoring are found in §§264.98,264.99, and 264.100.
APPLICABILITY, WAIVERS, AND EXEMPTIONS
Owners and operators of TSDFs with regulated units must comply with the
groundwater monitoring requirements of Subpart F during the active life of the
regulated unit. There are, however, limitations to this applicability, expressed in the
regulations as waivers and exemptions. The owner/operator of a regulated unit is not
subject to Subpart F monitoring regulations if he or she can meet any of the conditions
for a waiver or exemption (§264.90(b)). These waivers or exemptions apply to units for
which any of the following apply:
• The unit is exempt from Part 264 under §264.1 (§264.90(b)(l))
• The unit does not receive free liquids, it is an engineered structure, the unit has
inner and outer containment layers, it has a leak detection system between
containment layers, and the design prevents run-on and run-off (§264.90(b)(2))
• The land treatment unit is not releasing hazardous constituents to the
environment as determined by the Regional Administrator (RA) (this exemption
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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Groundwater Monitoring - 7
applies only during the post-closure period) (§264.90(b)(3))
• The unit has no potential for migration of liquids from the regulated unit(s) as
certified by a qualified geologist or geotechnical engineer (§264.90(b)(4))
• The waste pile is designed and operated in accordance with §264.250(c)
(§264.90(b)(5)).
Owners/operators of regulated units must also conduct groundwater monitoring in
accordance with Subpart F during the post-closure period. Post-closure is a period of
time after the active life of the facility during which certain maintenance and
monitoring activities must be conducted in order to ensure that no releases will occur
from the units and to remediate releases from these units. Certain units, however, are
exempt from the groundwater monitoring requirements after closure if they are able to
demonstrate clean closure, which involves removal or decontamination of all waste,
waste residues, contaminated containment system components, and contaminated
subsoils (§264.90(c)(l)). Subpart F cannot be waived during post-closure care if a
detection monitoring program is being conducted under §264.98, or if the facility is
conducting groundwater monitoring during the compliance period (§§264.90(c)(2) and
(3)). A summary of the §264.90, Subpart F, groundwater monitoring applicability
requirements is given in Figure 3.
GENERAL GROUNDWATER MONITORING REQUIREMENTS
The general requirements for groundwater monitoring programs at permitted facilities
are found in §264.97. These general requirements apply to all three phases of
groundwater monitoring: detection monitoring, compliance monitoring, and corrective
action. A groundwater monitoring program established pursuant to Part 264, Subpart
F, must have a sufficient number of monitoring wells, installed at appropriate locations
and depths, to yield water samples that:
• Represent the background conditions of the site (groundwater quality not
contaminated by leakage from an RU)
• Represent the quality of groundwater passing the point of compliance
• Detect any contamination of the uppermost aquifer at the point of compliance.
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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8 - Groundwater Monitoring
Figure 3
SUMMARY OF GROUNDWATER MONITORING
APPLICABILITY REQUIREMENTS
Do not have to comply
with Subpart F
NO
Regulated Unit =
Permitted SI, WP, LTU, or LF that
received waste after 7/26/82
§264.90(a)(2)
YES
YES
No liquids, engineered structure, inner/outer
containment, leak detection,
AND
no migration? §264.90(b)(2)
Do not have to comply
with Subpart F after
closure
YES
YES
YES
YES
Key
LF - Landfill
LTU - Land Treatment Unit
SI - Surface Impoundment
WP - Waste Pile
I
NO
LTU Treatment Zone "Clean?"
§264.90(b)(3)
I
NO
No migration?
§264.90(b)(4)
NO
Protected WP?
§264.90(b)(5)
NO
Clean Closure?
§264.90(c)
i
NO
Facility MUST comply with
Subpart F requirements
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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Ground water Monitoring - 9
If the facility has more than one regulated unit, the owner/operator has the option of
installing one groundwater monitoring system for the entire waste management area.
The groundwater monitoring system for the entire area can be thought of as an
imaginary line circumscribing the group of regulated units, including liners, dikes, or
barriers forming the containment area for such units, rather than for each individual
regulated unit within the waste management area, provided that contamination from
any of the regulated units can be detected at the point of compliance (§264.97(b)).
Figure 4 shows examples of groundwater monitoring systems for facilities with
multiple regulated units. Groundwater monitoring system configurations are
established on a site-specific basis and are detailed in the facility permit.
SAMPLING
Groundwater monitoring wells must be properly installed so that samples will yield
representative results. All monitoring wells must be lined, or cased, in a manner that
maintains the integrity of the monitoring well bore hole (§264.97(c)). Poorly installed
wells may give false results.
Consistent sampling and analytical procedures must be implemented to ensure an
accurate representation of the quality of groundwater below the waste management
area (§264.97(d)). At a minimum, there must be procedures and techniques for sample
collection, sample preservation and shipment, analytical procedures, and chain-of-
custody control. Sampling and analytical methods must be appropriate for
groundwater sampling and accurately measure the hazardous constituents being
analyzed. Each time that the groundwater is sampled, a determination of the surface
elevation of the uppermost aquifer needs to be made (§264.97(f)). The owner and
operator must develop an appropriate sampling procedure and interval for each
hazardous constituent identified in the facility's permit. This sampling procedure must
consist of a sequence of at least four samples taken at an interval that ensures each is an
independent sample. The owner and operator may use an alternate procedure if
approved by the RA. Requirements and procedures for obtaining and analyzing
samples are detailed in the facility permit, usually in a Sampling and Analysis Plan.
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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10 - Groundwater Monitoring
Figure 4
EXAMPLES OF GROUNDWATER MONITORING SYSTEMS FOR MULTIPLE
REGULATED UNITS
Hazardous Waste
Management Unit A
Hazardous Waste
Management Unit B
, .@ - 0. -0- -
V
Hazardous Waste
Management Unit A
'-©-
-I
Hazardous Waste
Management Unit B
0
©
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Groundwater Monitoring -11
STATISTICAL ANALYSIS
The owner/operator has a choice of five different statistical methods for evaluating
groundwater monitoring data. The method selected must be appropriate for the type
and distribution of chemical constituents detected or suspected to be present in the
groundwater. The five statistical method options (which are discussed in detail in
§264.97(h)) are:
• Parametric analysis of variance
• Nonparametric analysis of variance based on ranks
• Tolerance or prediction interval procedure
• A control chart approach
• Another statistical test method approved by the RA.
Any statistical method selected under §264.97(h) must comply with the performance
standards under §§264.97(i). These performance standards were established in order to
ensure that evidence of a statistically significant increase (SSI) in a hazardous
constituent is a true indication of a release and is not due to an error in data analysis.
All groundwater monitoring data collected pursuant to §264.97(g) must be maintained
in the facility operating record (§264.97(j)). The RA will specify in the facility's permit
when the data must be submitted for review.
STAGE I: DETECTION MONITORING PROGRAM
The goal of a detection monitoring program under §264.98 is to detect and characterize
any release of hazardous constituents from a regulated unit into the uppermost aquifer.
The detection monitoring system must be installed at the point of compliance and
adhere to the basic requirements applicable to all groundwater monitoring systems in
§§264.97(a)(2), (b), and (c) (§264.98(b)). The owner and operator must monitor for
certain indicator parameters and any other specific waste constituents or reaction
products that would provide a reliable indication of the presence of hazardous
constituents in groundwater at the point of compliance (§264.98(a)). The RA will
designate in the facility's permit what constituents or parameters must be monitored.
These constituents and parameters are monitored to detect potential changes in the
groundwater quality above background levels, which represent the quality of
groundwater not contaminated by hazardous waste management activity at the site. A
sequence of at least four samples from each well (both background and compliance
wells) must be collected semiannually and analyzed using the statistical methods
discussed above. The RA will specify the frequency for collecting samples and for
conducting statistical tests. Results from sampling wells at the point of compliance are
then compared to the data on background groundwater quality to determine if there is
any statistical evidence of an increase (increase or decrease in the case of pH) over
background. Statistically significant changes in indicator parameters may suggest that
a release has occurred.
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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12 - Ground water Monitoring
Using the statistical methods in §264.97(h), the owner and operator must determine if
there has been an SSI for any chemical or parameter specified in the permit within a
reasonable period of time after completion of sampling. The RA will specify in the
permit what is considered a reasonable period of time. Evidence of a release is probable
if an SSI has occurred. An SSI usually requires that compliance monitoring be initiated,
unless the owner and operator can demonstrate that the SSI was due to an error in
sampling or analysis, statistical evaluation, or natural variations in groundwater
chemistry.
If an SSI does occur, the owner and operator must:
• Notify the RA within 7 days indicating which parameter(s) or constituent(s)
triggered the SSI
• Immediately sample all wells for Part 264, Appendix IX, constituents (Appendix
IX is a list of compounds used to determine the presence of hazardous
constituents in groundwater)
• Determine which Appendix IX constituents are present and at what levels
• Submit an application for a permit modification within 90 days to establish a
compliance monitoring program meeting the requirements of §264.99
• Submit an engineering feasibility plan for a corrective action program within 180
days, and all data necessary to justify any alternate concentration limit sought
under §264.94(b).
If the owner and operator can prove, pursuant to §264.98(g)(6), that the contamination
did not result from his or her regulated unit, or that the SSI is due to an error in sample
analysis or natural variations in groundwater geochemistry, the owner and operator
will be released from the requirements to conduct compliance monitoring or to submit a
permit modification. The owner and operator must be able to provide adequate
supporting documentation to be released from these requirements. Figure 5 gives an
overview of the detection monitoring program.
STAGE II: COMPLIANCE MONITORING PROGRAM
Once it is established that a release has occurred, the owner and operator must institute
a compliance monitoring program. The goal of the compliance monitoring program is
to ensure that the amount of hazardous constituents released into the uppermost
aquifer does not exceed acceptable levels. Once those levels are exceeded, the owner
and operator must initiate corrective action. The compliance monitoring program
establishes routine monitoring (at least semiannually) to determine if the GWPS has
been exceeded.
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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Groundwater Monitoring -13
Figure 5
SUMMARY: DETECTION MONITORING PROGRAM (§264.98)
Has monitoring revealed
contamination?
NO
Compliance Monitoring
YES
§264.91(a)(4)
§270.14(c)(6)(l)
Detected levels >
GWPS?
Establish background values for parameters or
constituents specified by the RA in the permit
to be used in Detection Monitoring
§264.97(g)
T
NO
YES
Implement a Detection Monitoring Program:
Indicator parameters and/or constituents are
measured semiannually
GW Flow Rate and Direction must be
determined annually
§§264.98(a),(c),(d),(e)
YES
§264.98(g)(6)
Trigger SSI?
NO
YES
§264.98(f)
_ Demonstrate SSI not from RU
NO
Detected levels >
GWPS?
Key
CM = Compliance Monitoring
CA = Corrective Action
GW = Groundwater
GWPS = Groundwater Protection Standards
RU = Regulated Unit
SSI = Statistically Significant Increase
YES
NO
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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14 - Groundwater Monitoring
Groundwater Protection Standard
The GWPS is used to indicate when corrective action is necessary to control plumes of
contamination from regulated units (§264.92). When a facility submits an application
for a permit modification to establish compliance monitoring, the RA specifies the
GWPS in the permit. The GWPS consists of four elements:
• A list of hazardous constituents (§264.93)
• The concentration limits for each of the hazardous constituents (§264.94)
• The point of compliance (§264.95)
• The compliance period during which the GWPS applies (§264.96).
The hazardous constituents identified in the GWPS are those constituents from Part 261,
Appendix VIII, which have been detected in the uppermost aquifer and are reasonably
expected to be in or derived from the waste contained in a regulated unit.
Concentration limits are the levels of hazardous waste or hazardous waste constituents
allowed to be present in the groundwater. The concentration levels can be drawn from
one of three sources:
• Background levels
• Maximum concentration limits (MCLs) identified in Table 1 of §264.94(a)(2) if the
background level of the constituent is below the value given in Table 1
• Alternate concentration levels (ACLs) established by the RA under §264.94(b).
The RA will also identify in the permit the compliance period (§264.96) and the point at
which the GWPS applies, known as the point of compliance (§264.95). The point of
compliance is the vertical surface at which the owner and operator must monitor the
uppermost aquifer to determine if the GWPS has been exceeded (Figure 6). A proposed
point of compliance is incorporated into the Part B permit as required by §270.14(c)(3).
The compliance period is the length of time during which the owner and operator must
conduct compliance or corrective action monitoring, equal to the active life of the waste
management area, including any waste management activity prior to permitting and
the closure period. This period begins when a permitted facility begins compliance
monitoring, rr: 0 liance monitoring, the owner and operator must determine whether
the regulated units are in compliance with the GWPS at the point of compliance during
the compliance period.
The owner and operator must determine whether there is any evidence of increased
contamination for any of the hazardous constituents specified in the permit. This is
accomplished by comparing data on samples collected at the point of compliance to the
concentration limits set in the GWPS. The owner and operator must collect a minimum
of four samples from the background and compliance wells at least semiannually
during the compliance period. The RA will specify the frequency for collecting samples
and the statistical method appropriate to determine if an SSI has occurred. The
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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Groundwater Monitoring -15
Figure 6
SCHEMATIC OF POINT OF COMPLIANCE
LIMIT OF THE WASTE MANAGEMENT AREA
I TWO-DIMENSIONAL POINT OF COMPLIANCE I
UPPERMOST AQUIFER
Direction of Groundwater Flow
uppermost aquifer flow rate and direction must also be determined at least annually
(§§264.99(d)-(f)).
The owner and operator must analyze samples from compliance wells for all Part 264,
Appendix IX constituents at least annually to determine-if any additional constituents
are present that are not specified in the permit. If additional constituents are found,
they must be added to the list of constituents to be monitored.
Appendix IX constituents which are not contained in Appendix VIII of Part 261, may be
included as hazardous constituents into the GWPS of a facility's permit by the Regional
Administrator using the omnibus authority of §270.32(b)(2) and RCRA §3005(c)(3). For
further information on the omnibus authority, see the module entitled Permits and
Interim Status.
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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16 - Groundwater Monitoring
If the GWPS is exceeded, the owner and operator must notify the RA in writing within
seven days. The owner and operator must indicate which concentration limits have
been exceeded, submit a permit modification within 180 days to establish a corrective
action program, and continue to monitor in accordance with the compliance monitoring
program (§264.99(h)).
If the owner and operator can prove contamination resulted from a source other than
the regulated unit, or that the SSI is due to an error in sample analysis or natural
variations in groundwater geochemistry, he or she must notify the RA in writing within
seven days. The owner and operator must also submit documentation proving the
claim to the RA within 90 days and submit a permit modification within 90 days to
make appropriate changes to the compliance monitoring program. If the contamination
is found to have resulted from a regulated unit, the owner and operator must initiate
corrective action. Figure 7 presents an overview of the compliance monitoring
program.
STAGE III: CORRECTIVE ACTION PROGRAM
The goal of the Subpart F corrective action program is to bring regulated units back into
compliance with the GWPS at the point of compliance (§264.100(a)). The Subpart F
corrective action program seeks to accomplish this goal by requiring that the owner and
operator either remove the hazardous constituents or treat them in place (§264.100(b)).
The RA determines the time period by which the owner and operator must begin
corrective action after the GWPS is exceeded (§264.100(c)). The specific measures
undertaken to achieve corrective action are also specified by the RA and will vary with
each facility. Examples of corrective measures include excavation, stabilization,
solidification, and source control. The owner and operator must also conduct corrective
action to remove or treat in place any hazardous constituents that exceed the GWPS
between the point of compliance and the downgradient property boundary, and
beyond the facility boundary where necessary to protect human health and the
environment (§§264.100(e)(l) and (2)).
Effectiveness of Program
In addition to corrective action; the owner and operator must establish and implement a
groundwater monitoring program to demonstrate the eocess anness of the corrective
action program. This program may be based on the requirements for a compliance
monitoring program under §264.99 (§264.100(d)). A semiannual report on the
effectiveness of the corrective action program is required under §264.100(g).
Duration
Corrective action must commence within a reasonable time period after the GWPS is
exceeded. During the compliance period, corrective action measures must be continued
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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Groundwater Monitoring -17
Figure 7
COMPLIANCE MONITORING PROGRAM SUMMARY (§264.99)
• Notify RA
• Monitor and establish concentrations for all
Appendix DC constituents which are detected
• Submit permit modification & engineering
feasibility plan for CA
§264.98(g)
Detection Monitoring
• Establish GWPS (§264.92)
l.ListofHC
2. Concentration Limits of HC
3. Point of Compliance
4. Compliance Period
§264.99(a)
• Implement Compliance Monitoring Program
1. Semiannual monitoring
2. Flow rate and direction annually
3. Appendix IX analysis annually
Exceed GWPS?
YES l§264.99(h)
Demonstrate the release
is NOT from a Regulated
Unit?
NO
YES
§§264.99(e)-(g)
§264.99(i)
Key
CA - Corrective Action
GWPS - Groundwater Protection Standards
HC - Hazardous Constituents
NO
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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18 - Groundwater Monitoring
to the extent necessary to achieve compliance with the GWPS. Once compliance with
the GWPS has been achieved, the owner and operator may reinstitute a compliance
monitoring program. During the compliance period, facilities might move from
compliance monitoring to corrective action, and back again. If the compliance period
ends and corrective action is still being conducted, corrective action must continue as
long as necessary to achieve the GWPS. The owner and operator can only terminate the
corrective action program when the GWPS has not been exceeded for three consecutive
years (§264.100(f)). If the regulated unit is still in the post-closure period, the owner and
operator may then reinstate a detection monitoring program.
A facility may move from one phase of groundwater monitoring to another depending
on the status of the groundwater quality. This means a facility may move from:
• Detection to compliance monitoring
• Detection monitoring to corrective action
• Compliance monitoring to corrective action
• Corrective action to compliance monitoring
• Compliance to detection monitoring (a facility can reinstate a detection
monitoring program if it is still in the post-closure period and the compliance
period has ended).
For an overview of the corrective action program and the sequences of the groundwater
monitoring program, refer to Figure 8.
2.2 INTERIM STATUS GROUNDWATER MONITORING
The requirements for groundwater monitoring programs for interim status TSDFs with
regulated units are found in Part 265, Subpart F. This program is designed to determine
the facility's impact on the quality of groundwater in the uppermost aquifer underlying
the facility (§265.90(a)). Part 265, Subpart F, however, does not contain any provisions
for corrective action when a release has occurred. If corrective action is required at an
interim status facility, it will be addressed under RCRA §3008(h), other cleanup
authorities such as RCRA §7003, or in the facility permit when issued. The interim
status groundwater monitoring program requires the owner and operator of a surface
impoundment, landfill, or land treatment facility used to manage hazardous waste to
implement a groundwater monitoring program pursuant to Part 265, Subpart F. These
requirements apply to all interim status facilities which have land-based units (except
waste piles), unless the units qualify for an exemption under §265.1. Interim status
waste piles are not subject to Part 265, Subpart F. The owner and operator can also be
exempted by demonstrating that there is a low potential for migration of hazardous
waste or hazardous waste constituents to drinking water supply wells (§265.90(c)).
Owners and operators of surface impoundments that are used only to neutralize
corrosive wastes, and contain no other hazardous waste, may also qualify for an
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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Groundwater Monitoring -19
Figure 8
OVERVIEW OF THE CORRECTIVE ACTION PROGRAM (§264.100)
• Notify RA
• Submit Permit Modification and
Corrective Action Plan
Implement CA
1. Bring RU into compliance
2. Prevent HC from exceeding GWPS
3. Remove or treat HC in place
1
Establish and implement
program to demonstrate
effectiveness of CA program
Report effectiveness to RA
semiannually
§264.99(h)
Compliance Monitoring
Corrective Action
§§264.100(a) and (b)
§264.99(d)
§264.99(g)
YES
Achieve GWPS?
Key
CA - Corrective Action
CM - Compliance Monitoring
GWPS - Groundwater Protection Standards
HC - Hazardous Constituents
RA - Regional Administrator
RU - Regulated Units
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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20 - Groundwater Monitoring
exemption. The owner and operator must demonstrate that there is no potential for
migration of hazardous wastes from the impoundment (§265.90(e)).
To comply with Part 265, Subpart F, the owner/operator must install, operate, and
maintain a groundwater monitoring system capable of representing the background
groundwater quality and detecting any hazardous constituents that have migrated from
the waste management area to the uppermost aquifer. Under Part 265, Subpart F, there
are two types of groundwater monitoring programs: an indicator evaluation program
designed to detect the presence of a release, and a groundwater quality assessment
program that evaluates the nature and extent of contamination. Figure 9 illustrates
groundwater monitoring applicability for interim status facilities.
GROUNDWATER MONITORING SYSTEM
To determine existing groundwater conditions at an interim status facility, the owner
and operator must install at least one well hydraulically upgradient from the waste
management area. The well(s) must be able to accurately represent the background
quality of groundwater in the uppermost aquifer. The owner and operator must install
at least three wells hydraulically downgradient at the limit of the waste management
area, which are able to immediately detect any statistically significant evidence of a
release.
A separate monitoring system for each management unit is not required as long as the
criteria in §265.91(a) are met and the system is able to detect any release at the edge of
the waste management area.
SAMPLING AND ANALYSIS
Section 265.92 establishes the requirements for the development and implementation of
a groundwater sampling and analysis plan to be followed for all groundwater
monitoring activities. The plan must specify procedures for sample collection, sample
preservation, analytical procedures, and chain-of-custody control (i.e., point of
generation to the lab) (§265.92(a)).
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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Groundwater Monitoring - 21
Figure 9
APPLICABILITY OF GROUNDWATER MONITORING FOR INTERIM STATUS
FACILITIES
Part 265, Subpart F
Not Required
NO
YES
Alternative
groundwater
monitoring program
(Assessment)
YES
§265.93(d)
Interim status surface
impoundment,
landfill, or land
treatment unit?
YES
Low Migration
Waiver?
I
NO
Statistically significant
increase (SSI) of
indicator parameters
assumed?
NO
YES
Neutralization in
surface impoundment
exemption?
I
§265.90(a)
§265.90(c)
§265.90(d)
§265.90(e)
NO
Facility must comply with
Part 265, Subpart F
§265.91
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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22 - Groundwater Monitoring
Owners and operators must establish concentrations for the three sets of parameters
listed in §265.92(b) in both upgradient and downgradient wells. Sampling for these
parameters must be conducted at the following frequencies:
TYPE TESTING FREQUENCY
first year only after first year
Appendix III Constituents* quarterly no further
sampling required
Groundwater Quality Parameters quarterly annually
(Chloride, Iron, Manganese, Phenols,
Sodium, Sulfate)
Groundwater Contamination quarterly semi-annually
Indicator Parameters
(pH, Specific Conductance, Total Organic
Carbon, Total Organic Halogen)
Part 265, Appendix III is a list of EPA Interim Primary Drinking Water Standards taken from the Safe Drinking Water Act.
Appendix III is used to determine the suitability of an aquifer as a drinking water supply.
Initial background concentrations are established during the first year by monitoring all
wells (upgradient and downgradient) for the three groups of constituents listed in
§265.92(b). After the first year, the owner and operator must continue to monitor all
wells for the groundwater quality parameters and groundwater contamination
indicator parameters. This is known as the indicator evaluation program. The data on
the groundwater contamination parameters collected from downgradient wells are
compared to data on background water quality to determine if any contamination of
the uppermost aquifer has occurred. As discussed earlier, statistically insignificant
changes in the indicator parameters indicate a potential release. Groundwater elevation
must also be determined each time a sample is taken.
If an owner/operator assumes or already knows that contamination of the uppermost
aquifer has occurred, he or she may initiate an assessment monitoring program as
described below in lieu of an indicator evaluation program (§265.90(d)).
GROUNDWATER ASSESSMENT PROGRAM
In addition to the basic program of at least one upgradient and three downgradient
wells under §265.91, owners and operators must prepare an outline of a more detailed
groundwater monitoring program (§265.93). This program must be able to determine
whether hazardous waste or hazardous waste constituents have leached into the
uppermost aquifer in a quantity that would cause a significant change in groundwater
quality. This additional program is often referred to as a groundwater assessment
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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Groundwater Monitoring - 23
program. The groundwater assessment program must be implemented when there has
been an SSI (increase or decrease for pH) of an indicator parameter over background
levels. The groundwater assessment program is designed to determine whether
hazardous constituents have entered the groundwater. Once the owner and operator
make this determination, they have to establish the rate, extent of migration, and the
concentrations of constituents in the plume.
Statistically Significant Increase (SSI)
If variations in groundwater quality are detected by evidence of statistically significant
differences in concentrations of any of the indicator parameters between the
downgradient wells and background data, the regulations require the owner and
operator to obtain additional samples (§265.93(c)(2)). If the assessment monitoring
indicates that no hazardous constituents have entered the groundwater, then the owner
and operator may reinstate the basic indicator evaluation program. If the analyses
performed on the second round of samples confirms an SSI, the owner and operator
must notify the RA within seven days. Examples of variations that would require
additional sampling include a significant increase or decrease in pH or a significant
increase in any of the groundwater contamination parameters (e.g., total organic
carbon) being monitored. Within 15 days after the initial notification, a written
monitoring assessment plan must be developed by the owner and operator and
submitted to the RA. The assessment plan must include the number of groundwater
monitoring wells, the intended sampling, analytical, and evaluation procedures, and an
implementation schedule. The plan must be designed to determine the rate and extent
of migration of hazardous waste constituents and their concentration (§265.93(d)(4)).
Information gathered from assessment monitoring must be submitted within 15 days
after it is collected. The owner and operator must repeat the groundwater assessment
at least quarterly until final closure of the facility (§265.93(d)(7)).
An interim status facility's groundwater monitoring program can move from:
• Indicator evaluation to assessment monitoring
• Assessment to indicator evaluation monitoring
• Assessment monitoring through final closure.
To meet the requirements of the groundwater assessment program, the owner and
operator may need to install additional wells at various locations and depths.
Additionally, wells are required to pinpoint the exact location of a contaminated plume.
Schematic examples of the placement of wells for meeting the requirements of the
interim status groundwater monitoring assessment program are given in Figure 10.
Notice that wells of various depths are sometimes placed in "clusters" at a single
location, thereby allowing for an assessment of the groundwater at various depths.
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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24 - Groundwater Monitoring
Figure 10
SAMPLE OF ASSESSMENT PHASE MONITORING WELL PLACEMENT
CONFINING LAYER
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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Groundwater Monitoring - 25
Recordkeeping and Reporting Requirements
Owners and operators of interim status TSDFs conducting groundwater monitoring
must comply with the recordkeeping and reporting requirements of §265.94.
At a facility in the indicator evaluation phase (i.e., no release has occurred), the owner
and operator must keep all records of analyses required by §§265.92(c), (d), and (e), and
§265.93(b). The owner and operator must also report the results of the following to the
RA (§265.94(a)(2)).
What When
• Background concentrations in all Quarterly for first year
monitoring wells for parameters
under §265.92(b)(l)
• Concentrations of parameters under Annually
§265.92(b)(3)
• Groundwater surface evaluation Annually
under §265.93(f)
When a release has occurred and the uppermost aquifer is monitored pursuant to
§265.93(d)(4), the owner and operator must keep all records of analyses and evaluations
required under §265.93(d)(3) on-site and submit an annual report to the RA on the
status of the groundwater quality assessment program.
The information in this document is not by any means a complete representation of EPA's regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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