CHAPTER 5

                          SUBPART E
                   GROUND-WATER MONITORING
                    AND CORRECTIVE ACTION


                      TABLE OF CONTENTS


5.1  INTRODUCTION

5.2  APPLICABILITY 40 CFR Section 258.50 (a) & (b)
     5.2.1     Statement of Regulation
     5.2.2     Applicability
     5.2.3     Technical Considerations

5.3  COMPLIANCE SCHEDULE 40 CFR Section  258.50 (c)
     5.3.1     Statement of Regulation
     5.3.2     Applicability
     5.3.3     Technical Considerations

5.4  ALTERNATIVE COMPLIANCE SCHEDULES 40 CFR 258.50 (d)(e) &
     (g)
     5.4.1     Statement of Regulation
     5.4.2     Applicability
     5.4.3     Technical Considerations

5.5  QUALIFICATIONS 40 CFR 258.50 (f)
     5.5.1     Statement of Regulation
     5.5.2     Applicability
     5.5.3     Technical Considerations

5.6  GROUND-WATER MONITORING SYSTEMS 40 CFR Section 258.51
     (a)(b)(d)
     5.6.1     Statement of Regulation
     5.6.2     Applicability
     5.6.3     Technical Considerations
                    Uppermost Aquifer
                    Determination of Background Ground-Water
                    Quality
                    Multi-Unit Monitoring Systems
                    Hydrogeological Characterization
                    Characterizing Site Geology
                    Monitoring Well Placement

5.7  GROUND-WATER MONITORING WELL DESIGN AND CONSTRUCTION 40
     CFR Section 258.51 (c)
     5.7.1     Statement of Regulation
     5.7.2     Applicability
     5.7.3     Technical Considerations
               Monitoring Well Design
                    Well Casing
                    Filter Pack Design
                    Surface Completion

5.8  GROUND-WATER SAMPLING AND ANALYSIS REQUIREMENTS 
     40 CFR Section 258.53
     5.8.1     Statement of Regulation
     5.8.2     Applicability
     5.8.3     Technical Considerations
               Sample Collection
                    Frequency
                    Water Level Measurements
                    Well Purging
                    Field Analyses
                    Sample Withdrawal and Collection
               Sample Preservation and Handling
                    Sample Containers
                    Sample Preservation
                    Sample Storage and Shipment
               Chain-of-Custody Record
                    Sample Labels
                    Sample Custody Seal
                    Field Logbook
                    Sample Analysis Request Sheet
                    Laboratory Records
               Analytical Procedures
               Quality Assurance/Quality Control
                    Field Quality Assurance/Quality Control
                    Validation
               Documentation
     
5.9  STATISTICAL ANALYSIS 40 CFR Section 258.53 (g)-(i)
     5.9.1     Statement of Regulation
     5.9.2     Applicability
     5.9.3     Technical Considerations
               Multiple Well Comparisons
               Tolerance and Prediction Intervals
               Individual Well Comparisons
               Intra-Well Comparisons
               Treatment of Non-Detects

5.10 DETECTION MONITORING PROGRAM 40 CFR Section 258.54
     5.10.1    Statement of Regulation
     5.10.2    Applicability
     5.10.3    Technical Considerations
               Independent Sampling for Background
               Alternative List/Removal of Parameters
               Alternative Frequency
               Notification
               Demonstrations of Other Reasons For
               Statistical Increase
               Demonstrations of Other Sources of Error

5.11 ASSESSMENT MONITORING PROGRAM 40 CFR Section
     258.55(a)-(f)
     5.11.1    Statement of Regulation
     5.11.2    Applicability
     5.11.3    Technical Considerations
               Alternative List
               Alternative Frequency

5.12 ASSESSMENT MONITORING PROGRAM 40 CFR Section 258.55(g)
     5.12.1    Statement of Regulation
     5.12.2    Applicability
     5.12.3    Technical Considerations
               Release Investigation
               Property Boundary Monitoring Well
               Notification of Adjoining Residents and 
               Property Owners
               Demonstrations of Other Sources of Error
               Return to Detection Monitoring

5.13 ASSESSMENT MONITORING PROGRAM 40 CFR Section
     258.55(h)-(j)
     5.13.1    Statement of Regulation
     5.13.2    Applicability
     5.13.3    Technical Considerations

5.14 ASSESSMENT OF CORRECTIVE MEASURES 40 CFR Section 258.56
     5.14.1    Statement of Regulation
     5.14.2    Applicability
     5.14.3    Technical Considerations
               Source Evaluation
                    Plume Delineation
               Ground-Water Assessment
               Corrective Measures Assessment
               Active Restoration
               Plume Containment
               Source Control
               Public Participation

5.15 SELECTION OF REMEDY 40 CFR Section 258.57 (a)-(b)
     5.15.1    Statement of Regulation
     5.15.2    Applicability
     5.15.3    Technical Considerations

5.16 SELECTION OF REMEDY 40 CFR Section 258.57 (c)
     5.16.1    Statement of Regulation
     5.16.2    Applicability
     5.16.3    Technical Considerations
               Effectiveness of Corrective Action
               Effectiveness of Source Reduction
               Implementation of Remedial Action
                    Practical Capability
               Community Concerns

5.17 SELECTION OF REMEDY 40 CFR Section 258.57 (d)
     5.17.1    Statement of Regulation
     5.17.2    Applicability
     5.17.3    Technical Considerations

5.18 SELECTION OF REMEDY 40 CFR Section 258.57 (e)-(f)
     5.18.1    Statement of Regulation
     5.18.2    Applicability
     5.18.3    Technical Considerations

5.19 IMPLEMENTATION OF THE CORRECTIVE ACTION PROGRAM 
     40 CFR Section 258.58 (a)
     5.19.1    Statement of Regulation
     5.19.2    Applicability
     5.19.3    Technical Considerations
               Monitoring Activities
               Interim Measures

5.20 IMPLEMENTATION OF THE CORRECTIVE ACTION PROGRAM 
     40 CFR Section 258.58 (b)-(d)
     5.20.1    Statement of Regulation
     5.20.2    Applicability
     5.20.3    Technical Considerations

5.21 IMPLEMENTATION OF THE CORRECTIVE ACTION PROGRAM 
     40 CFR Section 258.58 (e)-(g)
     5.21.1    Statement of Regulation
     5.21.2    Applicability
     5.21.3    Technical Considerations

5.22 FURTHER INFORMATION
     5.22.1    References
                              

5.1  INTRODUCTION 

     The Criteria establish ground-water monitoring and
corrective action requirements for all existing and new
MSWLF units and lateral expansions of existing units except
where the Director of an approved State suspends the
requirements because there is no potential for migration of
leachate constituents from the unit to the uppermost
aquifer.  The Criteria include requirements for the
location, design, and installation of ground-water
monitoring systems and set standards for ground-water
sampling and analysis.  They also provide specific
statistical methods and decision criteria for identifying a
significant change in ground-water quality.  If a
significant change in ground-water quality occurs, the
Criteria require an assessment of the nature and extent of
contamination followed by an evaluation and implementation
of remedial measures.

     Portions of this chapter are based on a draft technical
document developed for EPA's hazardous waste program.  This
document, "RCRA Ground-Water Monitoring:  Draft Technical
Guidance" (EPA/530-R-93-001), is undergoing internal review,
and may change.  EPA chose to incorporate the information
from the draft document into this chapter because the draft
contained the most recent information available.


5.2  APPLICABILITY 40 CFR Section 258.50 (a) & (b)

     5.2.1     Statement of Regulation

     (a)  The requirements in this Part apply to MSWLF
units, except as provided in paragraph (b) of this section.

     (b)  Ground-water monitoring requirements under Section
258.51 through Section 258.55 of this Part may be suspended
by the Director of an approved State for a MSWLF unit if the
owner or operator can demonstrate that there is no potential
for migration of hazardous constituents from that MSWLF unit
to the uppermost aquifer (as defined in Section 258.2)
during the active life of the unit and the post-closure care
period.  This demonstration must be 
certified by a qualified ground-water scientist and approved
by the Director of an approved State, and must be based
upon: 

     (1)  Site-specific field collected measurements,
sampling, and analysis of physical, chemical, and biological
processes affecting contaminant fate and transport, and 

     (2)  Contaminant fate and transport predictions that
maximize contaminant migration and consider impacts on human
health and environment.


     5.2.2     Applicability

     The ground-water monitoring requirements apply to all
existing MSWLF units, lateral expansions of existing units,
and new MSWLF units that receive waste after October 9,
1993.  The requirements for ground-water monitoring may be
suspended if the Director of an approved State finds that no
potential exists for migration of hazardous constituents
from the MSWLF unit to  the uppermost aquifer during the
active life of the unit, including closure or post-closure
care periods.

     The "no potential for migration" demonstration must be
based upon site-specific information relevant to the fate
and transport of any hazardous constituents that may be
expected to be released from the unit.  The predictions of
fate and transport must identify the maximum anticipated
concentrations of constituents migrating to the uppermost
aquifer so that a protective assessment of the potential
effects to human health and the environment can be made.  A
successful demonstration could exempt the MSWLF unit from
requirements of Sections 258.51 through 258.55, which
include installation of ground-water monitoring systems, and
sampling and analysis for both detection and assessment
monitoring constituents.  Preparing No-Migration 
Demonstrations for Municipal Solid Waste Disposal
Facilities-Screening Tool is a guidance document describing
a process owners/ operators can use to prepare a
no-migration demonstration (NMD) requesting suspension of
the ground-water monitoring requirements.


     5.2.3  Technical Considerations

     All MSWLF units that receive waste after the effective
date of Part 258 must comply with the ground-water
monitoring requirements.  
     
     The Director of an approved State may exempt an
owner/operator from the ground-water monitoring requirements
at Section 258.51 through Section 258.55 if the owner or
operator demonstrates that there is no potential for
hazardous constituent migration to the uppermost aquifer
throughout the operating, closure, and post-closure care
periods of the unit.  Owners and operators of MSWLFs not
located in approved States will not be eligible for this
waiver and will be required to comply with all ground-water
monitoring requirements.  The "no-migration" demonstration
must be certified by a qualified ground-water scientist and
approved by the Director of an approved State.  It must be
based on site-specific field measurements and sampling and
analyses to determine the physical, chemical, and biological
processes affecting the fate and transport of hazardous
constituents.  The demonstration must be supported by
site-specific data and predictions of the maximum con-
taminant migration.  Site-specific information must include,
at a minimum, the information necessary to evaluate or
interpret the effects of the following properties or
processes on contaminant fate and transport:


     Physical Properties or Processes:

     *    Aquifer Characteristics, including hydraulic
          conductivity, hydraulic gradient, effective
          porosity, aquifer thickness, degree of saturation,
          stratigraphy, degree of fracturing and secondary
          porosity of soils and bedrock, aquifer
          heterogeneity, ground-water discharge, and
          ground-water recharge areas;

     *    Waste Characteristics, including quantity, type,
          and origin (e.g., commercial, industrial, or small
          quantity generators of unregulated hazardous
          wastes);

     *    Climatic Conditions, including annual
          precipitation, leachate generation estimates, and
          effects on leachate quality;

     *    Leachate Characteristics, including leachate
          composition, solubility, density, the presence of
          immiscible constituents, Eh, and pH; and

     *    Engineered Controls, including liners, cover
          systems, and aquifer controls (e.g., lowering the
          water table).  These should be evaluated under
          design and failure conditions to estimate their
          long-term residual performance.


     Chemical Properties or Processes:

     *    Attenuation of contaminants in the subsurface,
          including adsorption/ desorption reactions, ion
          exchange, organic content of soil, soil water pH,
          and consideration of possible reactions causing
          chemical transformation or chelation.


     Biological Processes:

     *    Microbiological Degradation, which may attenuate
          target compounds or cause transformations of
          compounds, potentially forming more toxic chemical
          species.

     The alternative design section of Chapter 5.0 discusses
these and other processes that affect contaminant fate and
solute transport.

     When owners or operators prepare a no-migration
demonstration, they must use predictions that are based on
maximum contaminant  migration both from the unit and
through the subsurface media.  Assumptions about variables
affecting transport should be biased toward over-estimating
transport and the anticipated concentrations.  Assumptions
and site specific data that are used in the fate and
transport predictions should conform with transport
principles and processes, including adherence to
mass-balance and chemical equilibria limitations.  Within
these physicochemical limitations, assumptions should be
biased toward the objective of assessing the maximum
potential impact on human health and the environment.  The
evaluation of site-specific data and assumptions may include
some of the following approaches:

     *    Use of the upper bound of known aquifer parameters
          and conditions that will maximize contaminant
          transport (e.g., hydraulic conductivity, effective
          porosity, horizontal and vertical gradients),
          rather than average values

     *    Use of the lower range of known aquifer conditions
          and parameters that tend to attenuate or retard
          contaminant transport (e.g., dispersivities, decay
          coefficients, cation exchange capacities, organic
          carbon contents, and recharge conditions), rather
          than average values

     *    Consideration of the cumulative impacts on water
          quality, including both existing water quality
          data and cumulative health risks posed by
          hazardous constituents likely to migrate from the
          MSWLF unit and other potential or known sources.

     A discussion of mathematical approaches for evaluating
contaminant or solute transport is provided in Chapter 5. 


5.3  COMPLIANCE SCHEDULE 40 CFR Section  258.50 (c)

     5.3.1     Statement of Regulation*

     *[NOTE:  EPA finalized several revisions to 40 CFR Part
258 on October 1, 1993 (58 FR 51536), and these revisions
delay the effective date for some categories of landfills. 
More detail on the content of the revisions is included in
the introduction.]

     (c)  Owners and operators of MSWLF units must comply
with the ground-water monitoring requirements of this part
according to the following schedule unless an alternative
schedule is specified under paragraph (d):

     (1)  Existing MSWLF units and lateral expansions less
than one mile from a drinking water intake (surface or
subsurface) must be in compliance with the ground-water 
monitoring requirements specified in Sections 258.51 -
258.55 by October 9, 1994;

     (2)  Existing MSWLF units and lateral expansions
greater than one mile but less than two miles from a
drinking water intake (surface or subsurface) must be in
compliance with the ground-water monitoring requirements
specified in Sections 258.51 - 258.55 by October 9, 1995;

     (3)  Existing MSWLF units and lateral expansions
greater than two miles from a drinking water intake (surface
or subsurface) must be in compliance with the ground-water 
monitoring requirements specified in Sections 258.51 -
258.55 by October 9, 1996;

     (4)  New MSWLF units must be in compliance with the
ground-water monitoring requirements specified in Sections
258.51 - 258.55 before waste can be placed in the unit.


     5.3.2  Applicability

     The rule establishes a self-implementing schedule for
owners or operators in States with programs that are deemed
inadequate or not yet approved.  As indicated in the
Statement of Regulation, this schedule depends on the
distance of the MSWLF unit from drinking water sources. 
Approved States may specify an alternative schedule under
Section 258.50 (d), which is discussed in Section 5.4.  

     Existing units and lateral expansions less than one
mile from a drinking water intake must be in compliance with
the ground-water monitoring requirements by October 9, 1994. 
If the units are greater than one mile but less than two
miles from a drinking water intake, they must be in
compliance by October 9, 1995.  Those units located more
than two miles from a drinking water intake must be in
compliance by October 9, 1996 (see Table 5-1).


************************************************************
TABLE 5-1.
COMPLIANCE SCHEDULE FOR EXISTING UNITS AND LATERAL
EXPANSIONS IN STATES WITH UNAPPROVED PROGRAMS
     
Distance From Water Supply Intake       Time to Comply From 
                                        October 9, 1991

One mile or less                        3 Years

More than one mile but less than two    4 Years
miles

More than two miles                     5 Years
************************************************************


     New MSWLF units, defined as units that have not
received waste prior to October 9, 1993, must be in
compliance with these requirements before receiving waste
regardless of the proximity to a water supply intake.  


     5.3.3  Technical Considerations

     For most facilities, these requirements will become
applicable 3 to 5 years after the promulgation date of the
rule.  This period should provide sufficient time for the
owner or operator to conduct site investigation and
characterization studies to comply with the requirements of
40 CFR Section 258.51 through  Section 258.55.  For those
facilities closest to drinking water intakes, the period
provides 2 to 3 years to assess seasonal variability in
ground-water quality.  A drinking water intake includes
water supplied to a user from either a surface water or
ground-water source.

     
5.4  ALTERNATIVE COMPLIANCE SCHEDULES 40 CFR 258.50 (d)(e) &
     (g)

     5.4.1     Statement of Regulation

     (d)  The Director of an approved State may specify an
alternative schedule for the owners or operators of existing
MSWLF units and lateral expansions to comply with the
ground-water monitoring requirements specified in Sections
258.51 -258.55.  This schedule must ensure that 50 percent
of all existing MSWLF units are in compliance by October 9,
1994 and all existing MSWLF units are in compliance by
October 9, 1996.  In setting the compliance schedule, the
Director of an approved State must consider potential risks
posed by the unit to human health and the environment.  The
following factors should be considered in determining
potential risk:

     (1)  Proximity of human and environmental receptors;

     (2)  Design of the MSWLF unit;

     (3)  Age of the MSWLF unit;

     (4)  The size of the MSWLF unit;

     (5)  Types and quantities of wastes disposed, including
sewage sludge; and

     (6)  Resource value of the underlying aquifer,
including:

     (i)  Current and future uses;

     (ii) Proximity and withdrawal rate of users; and

     (iii)Ground-water quality and quantity.

     (e)  Once established at a MSWLF unit, ground-water
monitoring shall be conducted throughout the active life and
post-closure care period of that MSWLF unit as specified in
Section 258.61.

     (f)  (See Section 5.5 for technical guidance on
qualifications of a ground-water scientist.)

     (g)  The Director of an approved State may establish
alternative schedules for demonstrating compliance with 
Section 258.51(d)(2), pertaining to notification of
placement of certification in operating record; Section 
258.54(c)(1), pertaining to notification that statistically
significant increase (SSI) notice is in operating record;
Section  258.54(c)(2) and (3), pertaining to an assessment
monitoring program;  Section  258.55(b), pertaining to
sampling and analyzing Appendix II constituents; Section
258.55(d)(1), pertaining to placement of notice (Appendix II
constituents detected) in record and notification of notice
in record; Section  258.55(d)(2), pertaining to sampling for
Appendix I and II; Section  258.55(g), pertaining to
notification (and placement of notice in record) of SSI
above ground-water protection standard;  Section 
258.55(g)(1)(iv) and Section  258.56(a), pertaining to
assessment of corrective measures; Section  258.57(a),
pertaining to selection of remedy and notification of
placement in record; Section  258.58(c)(4), pertaining to
notification of placement in record (alternative corrective
action measures); and Section  258.58(f), pertaining to
notification of placement in record (certification of remedy
completed).


     5.4.2  Applicability

     The Director of an approved State may establish an
alternative schedule for requiring owners/operators of
existing units and lateral expansions to comply with the
ground-water monitoring requirements.  The alternative
schedule is to ensure that at least fifty percent of all
existing MSWLF units within a given State are in compliance
by October 9, 1994 and that all units are in compliance by
October 9, 1996.

     In establishing the alternative schedule, the Director
of an approved State may use site-specific information to
assess the relative risks posed by different waste
management units and will allow priorities to be developed
at the State level.  This site-specific information (e.g.,
proximity to receptors, proximity and withdrawal rate of
ground-water users, waste quantity, type, containment design
and age) should enable the Director to assess potential risk
to the uppermost aquifer.  The resource value of the aquifer
to be monitored (e.g., ground-water quality and quantity,
present and future uses, and withdrawal rate of ground-water
users) also may be considered.

     Once ground-water monitoring has been initiated, it
must continue throughout the active life, closure, and
post-closure care periods.  The post-closure period may last
up to 30 years or more after the MSWLF unit has received a
final cover.  

     In addition to establishing alternative schedules for
compliance with ground-water monitoring requirements, the
Director of an approved State may establish alternative
schedules for certain sampling and analysis requirements of
Sections 258.54 and 258.55, as well as corrective action
requirements of Sections 258.56, 258.57, and 258.58.  See
Table 5-2 for a summary of notification requirements for
which approved States may establish alternative schedules.


************************************************************
TABLE 5-2.
SUMMARY OF NOTIFICATION REQUIREMENTS

Section                            Description

258.51(d)(2)        14 day notification period after well
                    installation certification by a
                    qualified ground-water scientist (GWS)

258.54(c)(1)        14 day notification period after finding
                    a statistical increase over background
                    for detection parameter(s)

258.55(d)(1)        14 day notification period after
                    detection of Appendix II constituents

258.57(a)           14 day notification period after
                    selection of corrective measures

258.58(c)(4)        14 day notification period prior to
                    implementing alternative measures

258.58(f)           14 day notification period after remedy
                    has been completed and certified by GWS
************************************************************


     5.4.3  Technical Considerations

     The rule allows approved States flexibility in
establishing alternate ground-water monitoring compliance
schedules.  In setting an alternative schedule, the State
will consider potential impacts to human health and the
environment.  Approved States have the option to address
MSWLF units that have environmental problems immediately. 
In establishing alternative schedules for installing
ground-water monitoring systems at existing MSWLF units, the
Director of an approved State may consider information
including the age and design of existing facilities.  Using
this type of information, in conjunction with a knowledge of
the wastes disposed, the Director should be able to
qualitatively assess or rank facilities based on their risk
to local ground-water resources.


5.5  QUALIFICATIONS 40 CFR 258.50 (f)

     5.5.1     Statement of Regulation

     (f)  For the purposes of this Subpart, a qualified
ground-water scientist is a scientist or engineer who has
received a baccalaureate or post-graduate degree in the
natural sciences or engineering and has sufficient training
and experience in ground-water hydrology and related fields
as may be demonstrated by State registration, professional
certifications, or completion of accredited university
programs that enable that individual to make sound
professional judgements regarding ground-water monitoring,
contaminant fate and transport, and corrective action.


     5.5.2     Applicability

     The qualifications of a ground-water scientist are
defined to ensure that professionals of appropriate
capability and judgement are consulted when required by the
Criteria.  The ground-water scientist must possess the
fundamental education and experience necessary to evaluate
ground-water flow, ground-water monitoring systems, and
ground-water monitoring techniques and methods.  A
ground-water scientist must understand and be able to apply
methods to solve solute transport problems and evaluate
ground-water remedial technologies.  His or her education
may include undergraduate or graduate studies in
hydrogeology, ground-water hydrology, engineering hydrology,
water resource engineering, geotechnical engineering,
geology, ground-water modeling/ground-water computer
modeling, and other aspects of the natural sciences.  The
qualified ground-water scientist must have a college degree
but need not have professional certification, unless
required at the State or Tribal level.  Some States/Tribes
may have certification programs for ground-water scientists;
however, there are no recognized Federal certification
programs.


     5.5.3     Technical Considerations

     A qualified ground-water scientist must certify work
performed pursuant to the following provisions of the
ground-water monitoring and corrective action requirements:

     *    No potential for migration demonstration (Section
          258.50(b))

     *    Specifications concerning the number, spacing, and
          depths of monitoring wells (Section 258.51(d))

     *    Determination that contamination was caused by
          another source or that a statistically significant
          increase resulted from an error in sampling,
          analysis, or evaluation (Sections 258.54 (c)(3)
          and 258.55 (g)(2))

     *    Determination that compliance with a remedy
          requirement is not technically practicable
          (Section 258.58(c)(1))

     *    Completion of remedy (Section 258.58(f)).

     The owner or operator must determine that the
professional qualifications of the ground-water specialist
are in accordance with the regulatory definition.  In
general, a certification is a signed document that transmits
some finding (e.g., that monitoring wells were installed
according to acceptable practices and standards at locations
and depths appropriate for a given facility).  The
certification must be placed in the operating record of the
facility, and the State Director must be notified that the
certification has been made.  Specific details of these
certifications will be addressed in the order in which they
appear in this guidance document.

     Many State environmental regulatory agencies have
ground-water scientists on staff.  The owner or operator of
a MSWLF unit or facility is not necessarily required to
obtain certification from an independent (e.g., consulting)
ground-water scientist and may, if agreed to by the Director
in an approved State, obtain approval by the Director in
lieu of certification by an outside individual.
     

5.6  GROUND-WATER MONITORING SYSTEMS 40 CFR Section 258.51
     (a)(b)(d)

     5.6.1     Statement of Regulation

     (a)  A ground-water monitoring system must be installed
that consists of a sufficient number of wells, installed at
appropriate locations and depths, to yield ground-water
samples from the upper-most aquifer (as defined in Section
258.2) that:

     (1)  Represent the quality of background ground water
that has not been affected by leakage from a unit.  A
determination of background quality may include sampling of
wells that are not hydraulically upgradient of the waste
management area where:

     (i)  Hydrogeologic conditions do not allow the owner or
operator to determine what wells are hydraulically
upgradient; or

     (ii) Sampling at other wells will provide an indication
of background ground-water quality that is as representative
or more representative than that provided by the upgradient
wells; and

     (2)  Represent the quality of ground water passing the
relevant point of compliance specified by the Director of an
approved State under Section 258.40(d) or at the waste
management unit boundary in unapproved States.  The
downgradient monitoring system must be installed at the
relevant point of compliance specified by the Director of an
approved State under Section 258.40(d) or at the waste
management unit boundary in unapproved States that ensures
detection of ground-water contamination in the uppermost
aquifer.  When physical obstacles preclude installation of
ground-water monitoring wells at the relevant point of
compliance at existing units, the down-gradient monitoring
system may be installed at the closest practicable distance
hydraulically down-gradient  from the relevant point of
compliance or specified by the Director of an approved State
under Section 258.40 that ensures detection of ground-water
contamination in the uppermost aquifer. 

     (b)  The Director of an approved State may approve a
multi-unit ground-water monitoring system instead of
separate ground-water monitoring systems for each MSWLF unit
when the facility has several units, provided the multi-unit
ground-water monitoring system meets the requirement of
Section 258.51(a) and will be as protective of human health
and the environment as individual monitoring systems for
each MSWLF unit, based on the following factors: 

     (1)  Number, spacing, and orientation of the MSWLF
units; 
     
     (2)  Hydrogeologic setting; 

     (3)  Site history; 

     (4)  Engineering design of the MSWLF units; and 

     (5)  Type of waste accepted at the MSWLF units. 

     (c)  (See Section 5.7 for technical guidance on
monitoring well design and construction.)

     (d)  The number, spacing, and depths of monitoring
systems shall be:

     (1)  Determined based upon site-specific technical
information that must include thorough characterization of:

     (i)  Aquifer thickness, ground-water flow rate,
ground-water flow direction including seasonal and temporal
fluctuations in ground-water flow; and

     (ii)  Saturated and unsaturated geologic units and fill
materials overlying the uppermost aquifer, materials
comprising the uppermost aquifer, and materials comprising
the confining unit defining the lower boundary of the
uppermost aquifer; including, but not limited to:
thicknesses, stratigraphy, lithology, hydraulic
conductivities, porosities and effective porosities.

     (2)  Certified by a qualified ground-water scientist or
approved by the Director of an approved State.  Within 14
days of this certification, the owner or operator must
notify the State Director that the certification has been
placed in the operating record. 


     5.6.2     Applicability

     The requirements for establishing a ground-water
monitoring system pursuant to Section 258.51 apply to all
new units, existing units, and lateral expansions of
existing units according to the schedules identified in 40
CFR Section 258.50.  A ground-water monitoring system
consists of both background wells and wells located at the
point of compliance or waste management unit boundary (i.e.,
downgradient wells). The ground-water monitoring network
must be capable of detecting a release from the MSWLF unit. 
A sufficient number of monitoring wells must be located
downgradient of the unit and be screened at intervals in the
uppermost aquifer to ensure contaminant detection. 
Generally, upgradient wells are used to determine background
ground-water quality.

     The downgradient wells must be located at the relevant
point of compliance specified by the Director of an approved
State, or at the waste management unit boundary in States
that are not in compliance with regulations.  If existing
physical structures obstruct well placement, the
downgradient monitoring system should be placed as close to
the relevant point of compliance as possible.  Wells located
at the relevant point of compliance must be capable of
detecting contaminant releases from the MSWLF unit to the
uppermost aquifer.  As discussed earlier in the section
pertaining to the designation of a relevant point of
compliance (Section 4.4), the point of compliance must be no
greater than 150 meters from the unit boundary.

     The Director of an approved State/Tribe may allow the
use of a multi-unit ground-water monitoring system.  MSWLF
units in States/Tribes that are deemed not in compliance
with the regulations must have a monitoring system for each
unit.  

     A qualified ground-water scientist must certify that
the number, spacing, and depths of the monitoring wells are
appropriate for the MSWLF unit.  This certification must be
placed in the operating records.  The State Director must be
notified within 14 days that the certification was placed in
the operating record.


     5.6.3     Technical Considerations

     The objective of a ground-water monitoring system is to
intercept ground water that has been contaminated by
leachate from the MSWLF unit.  Early contaminant detection
is important to allow sufficient time for corrective
measures to be developed and implemented before sensitive
receptors are significantly affected.  To accomplish this
objective, the monitoring wells should be located to sample
ground water from the uppermost aquifer at the closest
practicable distance from the waste management unit
boundary.  An alternative distance that is protective of
human health and the environment may be granted by the
Director of an approved State.  Since the monitoring program
is intended to operate through the post-closure period, the
location, design, and installation of monitoring wells
should address both existing conditions and anticipated
facility development, as well as expected changes in
ground-water flow.


     Uppermost Aquifer

     Monitoring wells must be placed to provide
representative ground-water samples from the uppermost
aquifer.  The uppermost aquifer is defined in Section 258.2
as "the geologic formation nearest to the natural ground
surface that is an aquifer, as well as lower aquifers that
are hydraulically interconnected with this aquifer within
the facility property boundary."  These lower aquifers may
be separated physically from the uppermost aquifer by less
permeable strata (having a lower hydraulic conductivity)
that are often termed aquitards.  An aquitard is a less
permeable geologic unit or series of closely layered units
(e.g., silt, clay, or shale) that in itself will not yield
significant quantities of water but will transmit water
through its thickness.  Aquitards may include thicker
stratigraphic sequences of clays, shales, and dense,
unfractured crystalline rocks (Freeze and Cherry, 1979).  

     To be considered part of the uppermost aquifer, a lower
zone of saturation must be hydraulically connected to the
uppermost aquifer within the facility property boundary. 
Generally, the degree of communication between aquifers is
evaluated by ground-water pumping tests.  Methods have been
devised for use in analyzing aquifer test data.  A summary
is presented in Handbook: Ground Water, Vol. II (USEPA,
1991).  The following discussions under this section (5.6.3)
should assist the owner or operator in characterizing the
uppermost aquifer and the hydrogeology of the site.


     Determination of Background Ground-Water Quality

     The goal of monitoring-well placement is to detect
changes in the quality of ground water resulting from a
release from the MSWLF unit.  The natural chemical
composition of ground water is controlled primarily by the
mineral composition of the geologic unit comprising the
aquifer.  As ground water moves from one geologic unit to
another, its chemical composition may change.  To reduce the
probability of detecting naturally occurring differences in
ground-water quality between background and downgradient
locations, only ground-water samples collected from the same
geologic unit should be compared.

     Ground-water quality in areas where the geology is
complex can be difficult to characterize.  As a result, the
rule allows the owner or operator flexibility in determining
where to locate wells that will be used to establish
background water quality.

     If the facility is new, ground-water samples collected
from both upgradient and downgradient locations prior to
waste disposal can be used to establish background water
quality.  The sampling should be conducted to account for
both seasonal and spatial variability in ground-water
quality.  

     Determining background ground-water quality by sampling
wells that are not hydraulically upgradient may be necessary
where hydrogeologic conditions do not allow the owner or
operator to determine which wells are hydraulically
upgradient.  Additionally, background ground-water quality
may be determined by sampling wells that provide
ground-water samples as representative or more
representative than those provided by upgradient wells. 
These conditions include the following:

     *    The facility is located above an aquifer in which
          ground-water flow directions change seasonally.

     *    The facility is located near production wells that
          influence the direction of ground-water flow.

     *    Upgradient ground-water quality is affected by a
          source of contamination other than the MSWLF unit.

     *    The proposed or existing landfill overlies a
          ground-water divide or local source of recharge.

     *    Geologic units present at downgradient locations
          are absent at upgradient locations.

     *    Karst terrain or fault zones modify flow.

     *    Nearby surface water influences ground-water flow
          directions.

     *    Waste management areas are located close to a
          property boundary that is upgradient of the
          facility.


     Multi-Unit Monitoring Systems 

     A multi-unit ground-water monitoring system does not
have wells at individual MSWLF unit boundaries.  Instead, an
imaginary line is drawn around all of the units at the
facility.  (See Figure 5-1 for a comparison of single unit
and multi-unit systems.)  This line constitutes the relevant
point of compliance.  The option to establish a multi-unit
monitoring system is restricted to facilities located in
approved States.  A multi-unit system must be approved by
the Director of an approved State after consideration has
been given to the:

     *    Number, spacing, and orientation of the MSWLF
          units

     *    Hydrogeologic setting

     *    Site history

     *    Engineering design of the MSWLF units

     *    Type of wastes accepted at the facility.


************************************************************
                        FIGURE 5-1
                             
              Comparison of Single Unit and 
               Multi-Unit Monitoring Systems
                         [Graphic]
************************************************************


     The purpose of a multi-unit system is to reduce the
number of monitoring wells that can provide the same
information.  The conceptual design of the multi-unit system
should consider the use and management of the facility with
respect to anticipated unit locations.  In some cases, it
may be possible to justify a reduction in the number of
wells if the waste management units are aligned along the
same flow path in the ground-water system.

     The multi-unit monitoring system must provide a level
of protection to human health and the environment that is
comparable to monitoring individual units.  The multi-unit
system should allow adequate time after detection of
contamination to develop and implement corrective measures
before sensitive receptors are adversely affected.


     Hydrogeological Characterization

     Adequate monitoring-well placement depends on
collecting and evaluating hydrogeological information that
can be used to form a conceptual model of the site.  The
goal of a hydrogeological investigation is to acquire
site-specific data concerning:

     *    The lateral and vertical extent of the uppermost
          aquifer

     *    The lateral and vertical extent of the upper and
          lower confining units/layers

     *    The geology at the owner's/operator's facility
          (e.g, stratigraphy, lithology, and structural
          setting)

     *    The chemical properties of the uppermost aquifer
          and its confining layers relative to local
          ground-water chemistry and wastes managed at the
          facility

     *  Ground-water flow, including:

          -    The vertical and horizontal directions of
               ground-water flow in the uppermost aquifer

          -    The vertical and horizontal components of the
               hydraulic gradient in the uppermost and any
               hydraulically connected aquifer

          -    The hydraulic conductivities of the materials
               that comprise the upper-most aquifer and its
               confining units/layers

          -    The average linear horizontal velocity of
               ground-water flow in the uppermost aquifer.

     The elements of a program to characterize the
hydrogeology of a site are discussed briefly in the sections
that follow and are addressed in more detail in "RCRA
Ground-Water Monitoring:  Draft Technical Guidance" (USEPA,
1992a).

     Prior to initiating a field investigation, the owner or
operator should perform a preliminary investigation.  The
preliminary investigation will involve reviewing all
available information about the site, which may consist of:

     *    Information on the waste management history of the
          site, including:

          -    A chronological history of the site,
               including descriptions of wastes managed
               on-site

          -    A summary of documented releases

          -    Details on the structural integrity of the
               MSWLF unit and physical controls on waste
               migration

     *    A literature review, including:

          -    Reports of research performed in the area of
               the site

          -    Journal articles

          -    Studies and reports available from local,
               regional, and State offices (e.g., geologic
               surveys, water boards, and environmental
               agencies)

          -    Studies available from Federal offices, such
               as USGS or USEPA

     *    Information from file searches, including:

          -    Reports of previous investigations at the
               site

          -    Geological and environmental assessment data
               from State and Federal reports.

     The documentation itemized above is by no means a
complete listing of information available for a preliminary
investigation.  Many other sources of hydrogeological
information may be available for review during the
preliminary investigation.


     Characterizing Site Geology

     After the preliminary investigation is complete, the
owner/operator will have information that he/she can use to
develop a plan to characterize site hydrogeology further.

     Nearly all hydrogeological investigations include a
subsurface boring program.  A boring program is necessary to
define site hydrogeology and the small-scale geology of the
area beneath the site.  The program usually requires more
than one iteration.  The objective of the initial boreholes
is to refine the conceptual model of the site derived from
the preliminary investigation.

     The subsurface boring program should be designed as
follows:

     *    The initial number of boreholes and their spacing
          is based on the information obtained during the
          preliminary investigation.

     *    Additional boreholes should be installed as needed
          to provide more information about the site.

     *    Samples should be collected from the borings at
          changes in lithology.  For boreholes that will be
          completed as monitoring wells, at least one sample
          should be collected from the interval that will be
          the screened interval.  Boreholes that will not be
          completed as monitoring wells must be properly
          decommissioned.

     Geophysical techniques, cone penetrometer surveys,
mapping programs, and laboratory analyses of borehole
samples can be used to plan and supplement the subsurface
boring program.  Downhole geophysical techniques include
electric, sonic, and nuclear logging.  Surface geophysical
techniques include seismic reflection and refraction, as
well as electromagnetic induction and resistivity. 

     The data obtained from the subsurface boring program
should enable the owner or operator to identify:

     *    Lithology, soil types, and stratigraphy

     *    Zones of potentially high hydraulic conductivity

     *    The presence of confining formations or layers

     *    Unpredicted geologic features, such as fault
          zones, cross-cutting structures, and pinch-out
          zones

     *    Continuity of petrographic features, such as
          sorting, grain size distribution, and cementation

     *    The potentiometric surface or water table.


     Characterizing Ground-Water Flow Beneath the Site

     In addition to characterizing site geology, the
owner/operator should characterize the hydrology of the
uppermost aquifer and its confining layer(s) at the site. 
The owner or operator should install wells and/or
piezometers to assist in characterizing site hydrology.  The
owner/operator should determine and assess:

     *    The direction(s) and rate(s) of ground-water flow
          (including both horizontal and vertical components
          of flow)

     *    Seasonal/temporal, natural, and artificially
          induced (e.g., off-site production well-pumping,
          agricultural use) short-term and long-term
          variations in ground-water elevations and flow
          patterns

     *    The hydraulic conductivities of the stratigraphic
          units at the site, including vertical hydraulic
          conductivity of the confining layer(s).


     Determining Ground-Water Flow Direction and Hydraulic
     Gradient

     Installing monitoring wells that will provide
representative background and downgradient water samples
requires a thorough understanding of how ground water flows
beneath a site.  Developing such an understanding requires
obtaining information regarding both ground-water flow
direction(s) and hydraulic gradient.  Ground-water flow
direction can be thought of as the idealized path that
ground-water follows as it passes through the subsurface. 
Hydraulic gradient (i) is the change in static head per unit
of distance in a given direction.  The static head is
defined as the height above a standard datum of the surface
of a column of water (or other liquid) that can be supported
by the static pressure at a given point (i.e., the sum of
the elevation head and pressure head).

     To determine ground-water flow directions and hydraulic
gradient, owners and operators should develop and implement
a water level-monitoring program.  This program should be
structured to provide precise water level measurements in a
sufficient number of piezometers or wells at a sufficient
frequency to gauge both seasonal average flow directions and
temporal fluctuations in ground-water flow directions. 
Ground-water flow direction(s) should be determined from
water levels measured in wells screened in the same
hydro-stratigraphic position.  In heterogeneous geologic
settings (i.e., settings in which the hydraulic
conductivities of the subsurface materials vary with
location in the subsurface), long well screens can intercept
stratigraphic horizons with different (e.g., contrasting)
ground-water flow directions and different heads.  In this
situation, the resulting water levels will not provide the
depth-discrete head measurements required for accurate
determination of the ground-water flow direction.

     In addition to evaluating the component of ground-water
flow in the horizontal direction, a program should be
undertaken to assess the vertical component of ground-water
flow.  Vertical ground-water flow information should be
based, at least in part, on field data from wells and
piezometers, such as multi-level wells, piezometer clusters,
or multi-level sampling devices, where appropriate.  The
following sections provide acceptable methods for assessing
the vertical and horizontal components of flow at a site.


     Ground-Water Level Measurements

     To determine ground-water flow directions and
ground-water flow rates, accurate water level measurements
(measured to the nearest 0.01 foot) should be obtained. 
Section 5.8 delineates procedures for obtaining water level
measurements.  At facilities where it is known or plausible
that immiscible contaminants (i.e., non-aqueous phase
liquids (NAPLs)) occur (or are determined to be potentially
present after considering the waste types managed at the
facility) in the subsurface at the facility, both the
depth(s) to the immiscible layer(s) and the thickness(es) of
the immiscible layer(s) in the well should be recorded.  

     For the purpose of measuring total head, piezometers
and wells should have as short a screened interval as
possible.  Specifically, the screens in piezometers or wells
that are used to measure head should generally be less than
10 feet long.  In circumstances including the following,
well screens longer than 10 feet may be warranted: 

     *    Natural water level fluctuations necessitate a
          longer screen length.

     *    The interval monitored is slightly greater than
          the appropriate screen length (e.g., the interval
          monitored is 12 feet thick).

     *    The aquifer monitored is homogeneous and extremely
          thick (e.g., greater than 300 feet); thus, a
          longer screen (e.g., a 20-foot screen) represents
          a fairly discrete interval.

     The head measured in a well with a long screened
interval is a function of all of the different heads over
the entire length of the screened interval.  Care should be
taken when interpreting water levels collected from wells
that have long screened intervals (e.g., greater than 10
feet).

     The water-level monitoring program should be structured
to provide precise water level measurements in a sufficient
number of piezometers or wells at a sufficient frequency to
gauge both seasonal average flow directions and temporal
fluctuations in ground-water flow directions. The
owner/operator should determine and assess
seasonal/temporal, natural, and artificially induced (e.g.,
off-site production well-pumping, agricultural use)
short-term and long-term variations in ground-water
elevations, ground-water flow patterns, and ground-water
quality.


     Establishing Horizontal Flow Direction and the
     Horizontal Component of Hydraulic Gradient

     After the water level data and measurement procedures
are reviewed to determine that they are accurate, the data
should be used to:

     *    Construct potentiometric surface maps and water
          table maps based on the distribution of total
          head.  The data used to develop water table maps
          should be from piezometers or wells screened
          across the water table.  The data used to develop
          potentiometric surface maps should be from
          piezometers or wells screened at approximately the
          same elevation in the same hydrostratigraphic
          unit;

     *    Determine the horizontal direction(s) of
          ground-water flow by drawing flow lines on the
          potentiometric surface map or water table map
          (i.e., construct a flow net);

     *    Calculate value(s) for the horizontal and vertical
          components of hydraulic gradient.

     Methods for constructing potentiometric surface and
water table maps, constructing flow nets, and determining
the direction(s) of ground-water flow are provided by USEPA
(1989c) and Freeze and Cherry (1979).  Methods for
calculating hydraulic gradient are provided by Heath (1982)
and USEPA (1989c). 

     A potentiometric surface or water table map will give
an approximate idea of general ground-water flow directions. 
However, to locate monitoring wells properly, ground-water
flow direction(s) and hydraulic gradient(s) should be
established in both the horizontal and vertical directions
and over time at regular intervals (e.g., over a 1-year
period at 3-month intervals).


     Establishing Vertical Flow Direction and the Vertical
     Component of Hydraulic Gradient

     To make an adequate determination of the ground-water
flow directions, the vertical component of ground-water flow
should be evaluated directly.  This generally requires the
installation of multiple piezometers or wells in clusters or
nests, or the installation of multi-level wells or sampling
devices.  A piezometer or well nest is a closely spaced
group of piezometers or wells screened at different depths,
whereas a multi-level well is a single device.  Both
piezometer/well nests and multi-level wells allow for the
measurement of vertical variations in hydraulic head.  

     When reviewing data obtained from multiple placement of
piezometers or wells in single boreholes, the construction
details of the well should be carefully evaluated.  Not only
is it extremely difficult to seal several piezometers/wells
at discrete depths within a single borehole, but sealant
materials may migrate from the seal of one piezometer/well
to the screened interval of another piezometer/well. 
Therefore, the design of a piezometer/well nest should be
considered carefully.  Placement of piezometers/wells in
closely spaced boreholes, where piezometers/wells have been
screened at different, discrete depth intervals, is likely
to produce more accurate information.  The primary concerns
with the installation of piezometers/wells in closely
spaced, separate boreholes are:  1) the disturbance of
geologic and soil materials that occurs when one piezometer
is installed may be reflected in the data obtained from
another piezometer located nearby, and 2) the analysis of
water levels measured in piezometers that are closely
spaced, but separated horizontally, may produce imprecise
information regarding the vertical component of ground-water
flow.  The limitations of installing multiple piezometers
either in single or separate boreholes may be overcome by
the installation of single multi-level monitoring wells or
sampling devices in single boreholes.  The advantages and
disadvantages of these types of devices are discussed by
USEPA (1989f).

     The owner or operator should determine the vertical
direction(s) of ground-water flow using the water levels
measured in multi-level wells or piezometer/well nests to
construct flow nets.  Flow nets should depict the
piezometer/well depth and length of the screened interval. 
It is important to portray the screened interval accurately
on the flow net to ensure that the piezometer/well is
actually monitoring the desired water-bearing unit.  A flow
net should be developed from information obtained from
piezometer/ well clusters or nests screened at different,
discrete depths.  Detailed guidance for the construction and
evaluation of flow nets in cross section (vertical flow
nets) is provided by USEPA (1989c).  Further information can
be obtained from Freeze and Cherry (1979). 


     Determining Hydraulic Conductivity

     Hydraulic conductivity is a measure of a material's
ability to transmit water.  Generally, poorly sorted silty
or clayey materials have low hydraulic conductivities,
whereas well-sorted sands and gravels have high hydraulic
conductivities.  An aquifer may be classified as either
homogeneous or heterogeneous and either isotropic or
anisotropic according to the way its hydraulic conductivity
varies in space.  An aquifer is homogeneous if the hydraulic
conductivity is independent of location within the aquifer;
it is heterogeneous if hydraulic conductivities are
dependent on location within the aquifer.  If the hydraulic
conductivity is independent of the direction of measurement
at a point in a geologic formation, the formation is
isotropic at that point.  If the hydraulic conductivity
varies with the direction of measurement at a point, the
formation is anisotropic at that point.  


     Determining Hydraulic Conductivity Using Field Methods

     Sufficient aquifer testing (i.e., field methods) should
be performed to provide representative estimates of
hydraulic conductivity.  Acceptable field methods include
conducting aquifer tests with single wells, conducting
aquifer tests with multiple wells, and using flowmeters. 
This section provides brief overviews of these methods,
including two methods for obtaining vertically discrete
measurements of hydraulic conductivity.  The identified
references provide detailed descriptions of the methods
summarized in this section.

     A commonly used test for determining horizontal
hydraulic conductivity with a single well is the slug test. 
A slug test is performed by suddenly adding, removing, or
displacing a known volume of water from a well and observing
the time that it takes for the water level to recover to its
original level (Freeze and Cherry, 1979).  Similar results
can be achieved by pressurizing the well casing, depressing
the water level, and suddenly releasing the pressure to
simulate the removal of water from the well.  In most cases,
EPA recommends that water not be introduced into wells
during aquifer tests to avoid altering ground-water
chemistry.  Single-well tests are limited in scope to the
area directly adjacent to the well screen.  The vertical
extent of the well screen generally defines the part of the
geologic formation that is being tested.  

     A modified version of the slug test, known as the
multilevel slug test, is capable of providing depth-discrete
measurements of hydraulic conductivity.  The drawback of the
multilevel slug test is that the test relies on the ability
of the investigator to isolate a portion of the aquifer
using a packer.  Nevertheless, multilevel slug tests, when
performed properly, can produce reliable measurements of
hydraulic conductivity.  

     Multiple-well tests involve withdrawing water from, or
injecting water into, one well, and obtaining water level
measurements over time in observation wells.  Multiple-well
tests are often performed as pumping tests in which water is
pumped from one well and drawdown is observed in nearby
wells.  A step-drawdown test should precede most pumping
tests to determine an appropriate discharge rate.  Aquifer
tests conducted with wells screened in the same
water-bearing zone can be used to provide hydraulic
conductivity data for that zone.  Multiple-well tests for
hydraulic conductivity characterize a greater proportion of
the subsurface than single-well tests and, thus, provide
average values of hydraulic conductivity.  Multiple-well
tests require measurement of parameters similar to those
required for single-well tests (e.g., time, drawdown).  When
using aquifer test data to determine aquifer parameters, it
is important that the solution assumptions can be applied to
site conditions.  Aquifer test solutions are available for a
wide variety of hydrogeologic settings, but are often
applied incorrectly by inexperienced persons.  Incorrect
assumptions regarding hydrogeology (e.g., aquifer
boundaries, aquifer lithology, and aquifer thickness) may
translate into incorrect estimations of hydraulic
conductivity.  A qualified ground-water scientist with
experience in designing and interpreting aquifer tests
should be consulted to ensure that aquifer test solution
methods fit the hydrogeologic setting.  Kruseman and
deRidder (1989) provide a comprehensive discussion of
aquifer tests.

     Multiple-well tests conducted with wells screened in
different water-bearing zones furnish information concerning
hydraulic communication among the zones.  Water levels in
these zones should be monitored during the aquifer test to
determine the type of aquifer system (e.g., confined,
unconfined, semi-confined, or semi-unconfined) beneath the
site, and their leakance (coefficient of leakage) and
drainage factors (Kruseman and deRidder, 1989).  A
multiple-well aquifer test should be considered at every
site as a method to establish the vertical extent of the
uppermost aquifer and to evaluate hydraulic connection
between aquifers.  

     Certain aquifer tests are inappropriate for use in
karst terrains characterized by a well-developed conduit
flow system, and they also may be inappropriate in fractured
bedrock.  When a well located in a karst conduit or a large
fracture is pumped, the water level in the conduit is
lowered.  This lowering produces a drawdown that is not
radial (as in a granular aquifer) but is instead a
trough-like depression parallel to the pumped conduit or
fracture.  Radial flow equations do not apply to drawdown
data collected during such a pump test.  This means that a
conventional semi-log plot of drawdown versus time is
inappropriate for the purpose of determining the aquifer's
transmissivity and storativity.  Aquifer tests in karst
aquifers can be useful, but valid determinations of
hydraulic conductivity, storativity, and transmissivity may
be impossible.  However, an aquifer test can provide
information on the presence of conduits, on storage
characteristics, and on the percentage of Darcian flow. 
McGlew and Thomas (1984) provide a more detailed discussion
of the appropriate use of aquifer tests in fractured bedrock
and on the suitable interpretation of test data.  Dye
tracing also is used to determine the rate and direction of
ground-water flow in karst settings (Section 5.2.4).

     Several additional factors should be considered when
planning an aquifer test:

     *    Owners and operators should provide for the proper
          storage and disposal of potentially contaminated
          ground water pumped from the well system.

     *    Owners and operators should consider the potential
          effects of pumping on existing plumes of
          contaminated ground water.

     *    In designing aquifer tests and interpreting
          aquifer test data, owners/operators should account
          and correct for seasonal, temporal, and
          anthropogenic effects on the potentiometric
          surface or water table.  This is usually done by
          installing piezometers outside the influence of
          the stressed aquifer.  These piezometers should be
          continuously monitored during the aquifer test.

     *    Owners and operators should be aware that, in a
          very high hydraulic conductivity aquifer, the
          screen size and/or filter pack used in the test
          well can affect an aquifer test.  If a very small
          screen size is used, and the pack is improperly
          graded, the test may reflect the characteristics
          of the filter pack, rather than the aquifer.

     *    EPA recommends the use of a step-drawdown test to
          provide a basis for selecting discharge rates
          prior to conducting a full-scale pumping test. 
          This will ensure that the pumping rate chosen for
          the subsequent pumping test(s) can be sustained
          without exceeding the available drawdown of the
          pumped wells.  In addition, this test will produce
          a measurable drawdown in the observation wells.

     Certain flowmeters recently have been recognized for
their ability to provide accurate and vertically discrete
measurements of hydraulic conductivity.  One of these, the
impeller flowmeter, is available commercially.  More
sensitive types of flowmeters (i.e., the heat-pulse
flowmeter and electromagnetic flowmeter) should be available
in the near future.  Use of the impeller flowmeter requires
running a caliper log to measure the uniformity of the
diameter of the well screen.  The well is then pumped with a
small pump operated at a constant flow rate.  The flowmeter
is lowered into the well, and the discharge rate is measured
every few feet by raising the flowmeter in the well. 
Hydraulic conductivity values can be calculated from the
recorded data using the Cooper-Jacob (1946) formula for
horizontal flow to a well.  Use of the impeller flowmeter is
limited at sites where the presence of low permeability
materials does not allow pumping of the wells at rates
sufficient to operate the flowmeter.  The application of
flowmeters in the measure of hydraulic conductivity is
described by Molz et al. (1990) and Molz et al. (1989).


     Determining Hydraulic Conductivity Using Laboratory
     Methods

     It may be beneficial to use laboratory measurements of
hydraulic conductivity to augment the results of field
tests.  However, field methods provide the best estimates of
hydraulic conductivity in most cases.  Because of the
limited sample size, laboratory tests can fail to account
for secondary porosity features, such as fractures and
joints, and hence, can greatly underestimate overall aquifer
hydraulic conductivities.  Laboratory tests may provide
valuable information about the vertical component of
hydraulic conductivity of aquifer materials.  However,
laboratory test results always should be confirmed by field
measurements, which sample a much larger portion of the
aquifer.  In addition, laboratory test results can be
profoundly affected by the test method selected and by the
manner in which the tests are carried out (e.g., the extent
to which sample collection and preparation have changed the
in situ hydraulic properties of the tested material). 
Special attention should be given to the selection of the
appropriate test method and test conditions and to quality
control of laboratory results.  McWhorter and Sunada (1977),
Freeze and Cherry (1979), and Sevee (1991) discuss
determining hydraulic conductivity in the laboratory. 
Laboratory tests may provide the best estimates of hydraulic
conductivity for materials in the unsaturated zone, but they
are likely to be less accurate than field methods for
materials in the saturated zone (Cantor et al., 1987).


     Determining Ground-Water Flow Rate 

     The calculation of the average ground-water flow rate
(average linear velocity of ground-water flow), or seepage
velocity, is discussed in detail in USEPA (1989c), in Freeze
and Cherry (1979), and in Kruseman and deRidder (1989).  The
average linear velocity of ground-water flow (v) is a
function of hydraulic conductivity (K), hydraulic gradient
(i), and effective porosity (n_e):

                         v = -  Ki 
                             n_e

     Methods for determining hydraulic gradient and
hydraulic conductivity have been presented previously. 
Effective porosity, the percentage of the total volume of a
given mass of soil, unconsolidated material, or rock that
consists of interconnected pores through which water can
flow, should be estimated from laboratory tests or from
values cited in the literature.  (Fetter (1980) provides a
good discussion of effective porosity.  Barari and Hedges
(1985) provide default values for effective porosity.) 
USEPA (1989c) provides methods for determining flow rates in
heterogeneous and/or anisotropic systems and should be
consulted prior to calculating flow rates.


     Interpreting and Presenting Data

     The following sections offer guidance on interpreting
and presenting hydrogeologic data collected during the site
characterization process.  Graphical representations of
data, such as cross sections and maps, are typically
extremely helpful both when evaluating data and when
presenting data to interested individuals.


     Interpreting Hydrogeologic Data

     Once the site characterization data have been
collected, the following tasks should be undertaken to
support and develop the interpretation of these data:

     *    Review borehole and well logs to identify major
          rock, unconsolidated material, and soil types and
          establish their horizontal and vertical extent and
          distribution.

     *    From borehole and well log (and outcrop, where
          available) data, construct representative
          cross-sections for each MSWLF unit, one in the
          direction of ground-water flow and one orthogonal
          to ground-water flow.

     *    Identify zones of suspected high hydraulic
          conductivity, or structures likely to influence
          contaminant migration through the unsaturated and
          saturated zones.

     *    Compare findings with other studies and
          information collected during the preliminary
          investigation to verify the collected information.

     *    Determine whether laboratory and field data
          corroborate and are sufficient to define
          petrology, effective porosity, hydraulic
          conductivity, lateral and vertical stratigraphic
          relationships, and ground-water flow directions
          and rates.

     After the hydrogeologic data are interpreted, the
findings should be reviewed to:

     *    Identify information gaps

     *    Determine whether the collection of additional
          data or reassessment of existing data is required
          to fill in the gaps

     *    Identify how information gaps are likely to affect
          the ability to design a RCRA monitoring system.

     Generally, lithologic data should correlate with
hydraulic properties (e.g., clean, well-sorted,
unconsolidated sands should exhibit high hydraulic
conductivity).  Additional boreholes should be drilled and
additional samples should be collected to describe the
hydrogeology of the site if the investigator is unable to 1)
correlate stratigraphic units between borings, 2) identify
zones of potentially high hydraulic conductivity and the
thickness and lateral extent of these zones, or 3) identify
confining formations/layers and the thickness and lateral
extent of these formation layers.

     When establishing the locations of wells that will be
used to monitor ground water in hydrogeologic settings
characterized by ground-water flow in porous media, the
following should be documented:

     *    The ground-water flow rate should be based on
          accurate measurements of hydraulic conductivity
          and hydraulic gradient and accurate measurements
          or estimates of effective porosity

     *    The horizontal and vertical components of flow
          should be accurately depicted in flow nets and
          based on valid data

     *    Any seasonal or temporal variations in the water
          table or potentiometric surface, and in vertical
          flow components, should be determined.

     Once an understanding of horizontal and vertical
ground-water flow has been established, it is possible to
estimate where monitoring wells will most likely intercept
contaminant flow. 


     Presenting Hydrogeologic Data

     Subsequent to the generation and interpretation of
site-specific geologic data, the data should be presented in
geologic cross-sections, topographic maps, geologic maps,
and soil maps.  The Agency suggests that owners/operators
obtain or prepare and review topographic, geologic, and soil
maps of the facility, in addition to site maps of the
facility and MSWLF units.  In cases where suitable maps are
not available, or where the information contained on
available maps is not complete or accurate, detailed mapping
of the site should be performed by qualified and experienced
individuals.  An aerial photograph and a topographic map of
the site should be included as part of the presentation of
hydrogeologic data.  The topographic map should be
constructed under the supervision of a qualified surveyor
and should provide contours at a maximum of 2-foot
intervals.

     Geologic and soil maps should be based on rock,
unconsolidated material, and soil identifications gathered
from borings and outcrops.  The maps should use colors or
symbols to represent each soil, unconsolidated material, and
rock type that outcrops on the surface.  The maps also
should show the locations of outcrops and all borings placed
during the site characterization.  Geologic and soil maps
are important because they can provide information
describing how site geology fits into the local and regional
geologic setting.

     Structure contour maps and isopach maps should be
prepared for each water-bearing zone that comprises the
uppermost aquifer and for each significant confining layer,
especially the one underlying the uppermost aquifer.  A
structure contour map depicts the configuration (i.e.,
elevations) of the upper or lower surface or boundary of a
particular geologic or soil formation, unit, or zone. 
Structure contour maps are especially important in
understanding dense non-aqueous phase liquid (DNAPL)
movement because DNAPLs (e.g., tetrachloroethylene) may
migrate in the direction of the dip of lower permeability
units.  Separate structure contour maps should be
constructed for the upper and lower surfaces (or contacts)
of each zone of interest.  Isopach maps should depict
contours that indicate the thickness of each zone.  These
maps are generated from borings and geologic logs and from
geophysical measurements.  In conjunction with
cross-sections, isopach maps may be used to help determine
monitoring well locations, depths, and screen lengths during
the design of the detection monitoring system.

     A potentiometric surface map or water table map should
be prepared for each water-bearing zone that comprises the
uppermost aquifer.  Potentiometric surface and water table
maps should show both the direction and rate of ground-water
flow and the locations of all piezometers and wells on which
they are based.  The water level measurements for all
piezometers and wells on which the potentiometric surface
map or water table map is based should be shown on the
potentiometric surface or water table map.  If seasonal or
temporal variations in ground-water flow occur at the site,
a sufficient number of potentiometric surface or water table
maps should be prepared to show these variations. 
Potentiometric surface and water table maps can be combined
with structure contour maps for a particular formation or
unit.  An adequate number of cross sections should be
prepared to depict significant stratigraphic and structural
trends and to reflect stratigraphic and structural features
in relation to local and regional ground-water flow.


     Hydrogeological Report

     The hydrogeological report should contain, at a
minimum:

     *    A description of field activities

     *    Drilling and/or well construction logs

     *    Analytical data

     *    A discussion and interpretation of the data

     *    Recommendations to address data gaps.

     The final output of the site characterization phase of
the hydrogeological investigation is a conceptual model. 
This model is the integrated picture of the hydrogeologic
system and the waste management setting.  The final
conceptual model must be a site-specific description of the
unsaturated zone, the uppermost aquifer, and its confining
units.  The model should contain all of the information
necessary to design a ground-water monitoring system.


     Monitoring Well Placement

     This section separately addresses the lateral placement
and the vertical sampling intervals of point of compliance
wells.  However, these two aspects of well placement should
be evaluated together in the design of the monitoring
system.  Site-specific hydrogeologic data obtained during
the site characterization should be used to determine the
lateral placement of detection monitoring wells and to
select the length and vertical position of monitoring well
intakes.  Potential pathways for contaminant migration are
three-dimensional.  Consequently, the design of a detection
monitoring network that intercepts these potential pathways
requires a three-dimensional approach.


     Lateral Placement of Point of Compliance Monitoring
     Wells

     Point of compliance monitoring wells should be as close
as physically possible to the edge of the MSWLF unit(s) and
should be screened in all transmissive zones that may act as
contaminant transport pathways.  The lateral placement of
monitoring wells should be based on the number and spatial
distribution of potential contaminant migration pathways and
on the depths and thicknesses of stratigraphic horizons that
can serve as contaminant migration pathways.

     Point of compliance monitoring wells should be placed
laterally along the downgradient edge of the MSWLF unit to
intercept potential pathways for contaminant migration.  The
local ground-water flow direction and gradient are the major
factors in determining the lateral placement of point of
compliance wells.  In a homogeneous, isotropic hydrogeologic
setting, well placement can be based on general aquifer
characteristics (e.g., direction and rate of ground-water
flow), and potential contaminant fate and transport
characteristics (e.g., advection, dispersion).  More
commonly, however, geology is variable and preferential
pathways exist that control the migration of contaminants. 
These types of heterogeneous, anisotropic geologic settings
can have numerous, discrete zones within which contaminants
may migrate.  

     Potential migration pathways include zones of
relatively high intrinsic (matrix) hydraulic conductivities,
fractured/faulted zones, and subsurface material that may
increase in hydraulic conductivity if the material is
exposed to waste(s) managed at the site (e.g., a limestone
layer that underlies an acidic waste).  In addition to
natural hydrogeologic features, human-made features may
influence the ground-water flow direction and, thus, the
lateral placement of point of compliance wells.  Such
human-made features include ditches, areas where fill
material has been placed, buried piping, buildings, leachate
collection systems, and adjacent disposal units.  The
lateral placement of monitoring wells should be based on the
number and spatial distribution of potential contaminant
migration pathways and on the depths and thicknesses of
stratigraphic horizons that can serve as contaminant
migration pathways.

     In some settings, the ground-water flow direction may
reverse seasonally (depending on precipitation), change as a
result of tidal influences or river and lake stage
fluctuations, or change temporally as a result of
well-pumping or changing land use patterns.  In other
settings, ground water may flow away from the waste
management area in all directions.  In such cases, EPA
recommends that monitoring wells be installed on all sides
(or in a circular pattern) around the waste management area
to allow for the detection of contamination.  In these
cases, certain wells may be downgradient only part of the
time, but such a configuration should ensure that releases
from the unit will be detected.

     The lateral placement of monitoring wells also should
be based on the physical/ chemical characteristics of the
contaminants of concern.  While the restriction of liquids
in MSWLFs may limit the introduction of hazardous
constituents into landfills, it is important to consider the
physical/chemical characteristics of contaminants when
designing the well system.  These characteristics include
solubility, Henry's Law constant, partition coefficients,
specific gravity, contaminant reaction or degradation
products, and the potential for contaminants to degrade
confining layers.  For example, contaminants with low
solubilities and high specific gravities that occur as
DNAPLs may migrate in the subsurface in directions different
from the direction of ground-water flow.  Therefore, in
situations where the release of DNAPLs is a concern, the
lateral placement of compliance point ground-water
monitoring wells should not necessarily only be along the
downgradient edge of the MSWLF unit.  Considering both
contaminant characteristics and hydrogeologic properties is
important when determining the lateral placement of
monitoring wells.  


     Vertical Placement and Screen Lengths

     Proper selection of the vertical sampling interval is
necessary to ensure that the monitoring system is capable of
detecting a release from the MSWLF unit.  The vertical
position and lengths of well intakes are functions of (1)
hydro-geologic factors that determine the distribution of,
and fluid/vapor phase transport within, potential pathways
of contaminant migration to and within the uppermost
aquifer, and (2) the chemical and physical characteristics
of contaminants that control their transport and
distribution in the subsurface.  Well intake length also is
determined by the need to obtain vertically discrete
ground-water samples.  Owners and operators should determine
the probable location, size, and geometry of potential
contaminant plumes when selecting well intake positions and
lengths.

     Site-specific hydrogeologic data obtained during the
site characterization should be used to select the length
and vertical position of monitoring well intakes.  The
vertical positions and lengths of monitoring well intakes
should be based on the number and spatial distribution of
potential contaminant migration pathways and on the depths
and thicknesses of stratigraphic horizons that can serve as
contaminant migration pathways.  Figure 5-2 illustrates
examples of complex stratigraphy that would require multiple
vertical monitoring intervals.

    
************************************************************
                        FIGURE 5-2
                             
Upgradient an Downgradient Designations for Idealized MSWLF
                         [Graphic]
************************************************************


     The depth and thickness of a potential contaminant
migration pathway can be determined from soil,
unconsolidated material, and rock samples collected during
the boring program, and from samples collected while
drilling the monitoring well.  Direct physical data can be
supplemented by geophysical data, available regional/local
hydrogeological data, and other data that provide the
vertical distribution of hydraulic conductivity.  The
vertical sampling interval is not necessarily synonymous
with aquifer thickness.  Monitoring wells are often screened
at intervals that represent a portion of the thickness of
the aquifer.  When monitoring an unconfined aquifer, the
well screen typically should be positioned so that a portion
of the well screen is in the saturated zone and a portion of
the well screen is in the unsaturated zone (i.e., the well
screen straddles the water table).  While the restriction of
liquids in MSWLFs may limit the introduction of hazardous
constituents into landfills, it is important to consider the
physical/chemical characteristics of contaminants when
designing the well system.

     The vertical positions and lengths of monitoring well
intakes should be based on the same physical/chemical
characteristics of the contaminants of concern that
influence the lateral placement of monitoring wells. 
Considering both contaminant characteristics and
hydrogeologic properties is important when choosing the
vertical position and length of the well intake.  Some
contaminants may migrate within very narrow zones.  Of
course, for well placement at a new site, it is unlikely
that the owner or operator will be able to assess
contaminant characteristics.

     Different transport processes control contaminant
migration depending on whether the contaminant dissolves or
is immiscible in water. Immiscible contaminants may occur as
light non aqueous phase liquids (LNAPLs), which are lighter
than water, and DNAPLs, which are denser than water.  LNAPLs
migrate in the capillary zone just above the water table. 
Wells installed to monitor LNAPLs should be screened at the
water table/capillary zone interface, and the screened
interval should intercept the water table at its minimum and
maximum elevation.  LNAPLs may become trapped in residual
form in the vadose zone and become periodically remobilized
and contribute further to aquifer contamination, either as
free phase or dissolved phase contaminants, as the water
table fluctuates and precipitation infiltrates the
subsurface.

     The migration of free-phase DNAPLs may be influenced
primarily by the geology, rather than the hydrogeology, of
the site.  That is, DNAPLs migrate downward through the
saturated zone due to density and then migrate by gravity
along less permeable geologic units (e.g., the slope of
confining units, the slope of clay lenses in more permeable
strata, bedrock troughs), even in aquifers with primarily
horizontal ground-water flow.  Consequently, if wastes
disposed at the site are anticipated to exist in the
subsurface as a DNAPL, the potential DNAPL should be
monitored:

     *    At the base of the aquifer (immediately above the
          confining layer)

     *    In structural depressions (e.g., bedrock troughs)
          in lower hydraulic conductivity geologic units
          that act as confining layers

     *    Along lower hydraulic conductivity lenses and
          units within units of higher hydraulic
          conductivity

     *    "Down-the-dip" of lower hydraulic conductivity
          units that act as confining layers, both
          upgradient and downgradient of the waste
          management area. 

     Because of the nature of DNAPL migration (i.e., along
structural, rather than hydraulic, gradients), wells
installed to monitor DNAPLs may need to be installed both
upgradient and downgradient of the waste management area. 
It may be useful to construct a structure contour map of
lower permeability strata and identify lower permeability
lenses upgradient and downgradient of the unit along which
DNAPLs may migrate.  The wells can then be located
accordingly.

     The lengths of well screens used in ground-water
monitoring wells can significantly affect their ability to
intercept releases of contaminants.  The complexity of the
hydrogeology of a site is an important consideration when
selecting the lengths of well screens.  Most hydrogeologic
settings are complex (heterogeneous and anisotropic) to a
certain degree.  Highly heterogeneous formations require
shorter well screens to allow sampling of discrete portions
of the formation that can serve as contaminant migration
pathways.  Well screens that span more than a single
saturated zone or a single contaminant migration pathway may
cause cross-contamination of transmissive units, thereby
increasing the extent of contamination.  Well intakes should
be installed in a single saturated zone.  Well intakes
(e.g., screens) and filter pack materials should not
interconnect, or promote the interconnection of, zones that
are separated by a confining layer. 

     Even in hydrologically simple formations, or within a
single potential pathway for contaminant migration, the use
of shorter well screens may be necessary to detect
contaminants concentrated at particular depths.  A
contaminant may be concentrated at a particular depth
because of its physical/chemical properties and/or because
of hydrogeologic properties.  In homogeneous formations, a
long well screen can permit excessive amounts of
uncontaminated formation water to dilute the contaminated
ground water entering the well.  At best, dilution can make
contaminant detection difficult; at worst, contaminant
detection is impossible if the concentrations of
contaminants are diluted to levels below the detection
limits for the prescribed analytical methods.  The use of
shorter well screens allows for contaminant detection by
reducing excessive dilution.  When placed at depths of
predicted preferential flow, shorter well screens are
effective in monitoring the aquifer or the portion of the
aquifer of concern.  

     Generally, screen lengths should not exceed 10 feet. 
However, certain hydrogeologic settings may warrant or
necessitate the use of longer well screens for adequate
detection monitoring.  Unconfined aquifers with widely
fluctuating water tables may require longer screens to
intercept the water table surface at both its maximum and
minimum elevations and to provide monitoring for the
presence of contaminants that are less dense than water. 
Saturated zones that are slightly greater in thickness than
the appropriate screen length (e.g., 12 feet thick) may
warrant monitoring with longer screen lengths.  Extremely
thick homogeneous aquifers (e.g., greater than 300 feet) may
be monitored with a longer screen (e.g., a 20-foot screen)
because a slightly longer screen would represent a fairly
discrete interval in a very thick formation.  Formations
with very low hydraulic conductivities also may require the
use of longer well screens to allow sufficient amounts of
formation water to enter the well for sampling.  The
importance of accurately identifying such conditions
highlights the need for a complete hydrogeologic site
investigation prior to the design and placement of detection
wells.

     Multiple monitoring wells (well clusters or multilevel
sampling devices) should be installed at a single location
when (1) a single well cannot adequately intercept and
monitor the vertical extent of a potential pathway of
contaminant migration, or (2) there is more than one
potential pathway of contaminant migration in the subsurface
at a single location, or (3) there is a thick saturated zone
and immiscible contaminants are present, or are determined
to be potentially present after considering waste types
managed at the facility. Conversely, at sites where ground
water may be contaminated by a single contaminant, where
there is a thin saturated zone, and where the site is
hydrogeologically homogeneous, the need for multiple wells
at each sampling location is reduced.  The number of wells
that should be installed at each sampling location increases
with site complexity.

     The following sources provided additional information
on monitoring well placement:  USEPA (1992a), USEPA (1990),
USEPA (1991), and USEPA (1986a).


5.7  GROUND-WATER MONITORING WELL DESIGN AND CONSTRUCTION 40
     CFR Section 258.51 (c)

     5.7.1     Statement of Regulation

     (c)  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 collection of
ground-water samples.  The annular space (i.e., the space
between the bore hole and well casing) above the sampling
depth must be sealed to prevent contamination of samples and
the ground water.

     (1)  The owner or operator must notify the State
Director that the design, installation, development, and
decommission of any monitoring wells, piezometers and other
measurement, sampling, and analytical devices documentation
has been placed in the operating record; and

     (2)  The monitoring wells, piezometers, and other
measurement, sampling, and analytical devices must be
operated and maintained so that they perform to design
specifications throughout the life of the monitoring
program.

     Section 258.52  [Reserved].


     5.7.2     Applicability

     The requirements for monitoring well design,
installation, and maintenance are applicable to all wells
installed at existing units, lateral expansions of units,
and new MSWLF units.  The design, installation, and
decommissioning of any monitoring well must be documented in
the operating record of the facility and certified by a
qualified ground-water scientist.  Documentation is required
for wells, piezometers, sampling devices, and water level
measurement instruments used in the monitoring program.

     The monitoring wells must be cased to protect the
integrity of the borehole.  The design and construction of
the well directly affects the quality and representativeness
of the samples collected.  The well casing must have a
screened or perforated interval to allow the entrance of
water into the well casing.  The annular space between the
well screen and the formation wall must be packed with
material to inhibit the migration of formation material into
the well.  The well screen must have openings sized
according to the packing material used.  The annular space
above the filter pack must be sealed to provide a discrete
sampling interval.  

     All monitoring wells, piezometers, and sampling and
analytical devices must be maintained in a manner that
ensures their continued performance according to design
specifications over the life of the monitoring program.  


     5.7.3     Technical Considerations

     The design, installation, and maintenance of monitoring
wells will affect the consistency and accuracy of samples
collected.  The design must be based on site-specific
information.  The formation material (lithology and grain
size distribution) will determine the selection of proper
packing and sealant materials, and the stratigraphy will
determine the screen length for the interval to be
monitored.  Installation practices should be specified and
overseen to ensure that the monitoring well is installed as
designed and will perform as intended.  This section will
discuss the factors that must be considered when designing
monitoring wells.  Each well must be tailored to suit the
hydrogeological setting, the contaminants to be monitored,
and other site-specific factors.  Figure 5-3 depicts the
components of a typical monitoring well installation.


************************************************************
                        FIGURE 5-3
                             
   Example of a Monitoring Well Design-Single Cased Well
                         [Graphic]
************************************************************


     The following sections provide a brief overview of
monitoring well design and construction.  More comprehensive
discussions are provided in USEPA (1989f) and USEPA (1992a).


     Selection of Drilling Method

     The method chosen for drilling a monitoring well
depends largely on the following factors (USEPA, 1989f):

     *    Versatility of the drilling method

     *    Relative drilling cost

     *    Sample reliability (ground-water, soil,
          unconsolidated material, or rock samples)

     *    Availability of drilling equipment

     *    Accessibility of the drilling site

     *    Relative time required for well installation and
          development

     *    Ability of the drilling technology to preserve
          natural conditions

     *    Ability to install a well of desired diameter and
          depth

     *    Relative ease of well completion and development,
          including the ability to install the well in the
          given hydrogeologic setting. 

     In addition to these factors, USEPA (1989f) includes
matrices to assist in selecting an appropriate drilling
method.  These matrices list the most commonly used drilling
techniques for monitoring well installation, taking into
consideration hydrogeologic settings and the objectives of
the monitoring program. 

     The following basic performance objectives should guide
the selection of drilling procedures for installing
monitoring wells:

     *    Drilling should be performed in a manner that
          preserves the natural properties of the subsurface
          materials.

     *    Contamination and/or cross-contamination of ground
          water and aquifer materials during drilling should
          be avoided.

     *    The drilling method should allow for the
          collection of representative samples of rock,
          unconsolidated materials, and soil.

     *    The drilling method should allow the
          owner/operator to determine when the appropriate
          location for the screened interval has been
          encountered.

     *    The drilling method should allow for proper
          placement of the filter pack and annular sealants. 
          The borehole should be at least 4 inches larger in
          diameter than the nominal diameter of the well
          casing  and  screen to  allow adequate space for
          placement of the filter pack and annular sealants.

     *    The drilling method should allow for the
          collection of representative ground-water samples. 
          Drilling fluids (including air) should be used
          only when minimal impact to the surrounding
          formation and ground water can be ensured.

     The following guidelines apply to the use of drilling
fluids, drilling fluid additives, and lubricants when
drilling ground-water monitoring wells:

     *    Drilling fluids, drilling fluid additives, or
          lubricants that affect the analysis of hazardous
          constituents in ground-water samples should not be
          used.

     *    The owner/operator should demonstrate the
          inertness of drilling fluids, drilling fluid
          additives, and lubricants by performing analytical
          testing of drilling fluids, drilling fluid
          additives, and lubricants and/or by providing
          information regarding the composition of drilling
          fluids, drilling fluid additives, or lubricants
          obtained from the manufacturer.

     *    The owner/operator should consider the potential
          impact of drilling fluids, drilling fluid
          additives, and lubricants on the physical and
          chemical characteristics of the subsurface and on
          ground-water quality.

     *    The volume of drilling fluids, drilling fluid
          additives, and lubricants used during the drilling
          of a monitoring well should be recorded.


     Monitoring Well Design

          Well Casing

          Well Casing and Screen Materials

     A casing and well screen are installed in a
ground-water monitoring well for several reasons:  to
provide access from the surface of the ground to some point
in the subsurface, to prevent borehole collapse, and to
prevent hydraulic communication between zones within the
subsurface.  In some cases, State or local regulations may
specify the casing and material that the owner or operator
should use.  A comprehensive discussion of well casing and
screen materials is provided in USEPA (1989f) and in USEPA
(1992a).  The following discussion briefly summarizes
information contained in these references.

     Monitoring well casing and screen materials may be
constructed of any of several types of materials, but should
meet the following performance specifications:  

     *    Monitoring well casing and screen materials should
          maintain their structural integrity and durability
          in the environment in which they are used over
          their operating life.

     *    Monitoring well casings and screens should be
          resistant to chemical and microbiological
          corrosion and degradation in contaminated and
          uncontaminated waters.

     *    Monitoring well casings and screens should be able
          to withstand the physical forces acting upon them
          during and following their installation and during
          their use -- including forces due to suspension in
          the borehole, grouting, development, purging,
          pumping, and sampling and forces exerted on them
          by the surrounding geologic materials.

     *    Monitoring well casing and screen materials should
          not chemically alter ground-water samples,
          especially with respect to the analytes of
          concern, as a result of their sorbing, desorbing,
          or leaching analytes.  For example, if chromium is
          an analyte of interest, the well casing or screen
          should not increase or decrease the amount of
          chromium in the ground water.  Any material
          leaching from the casing or screen should not be
          an analyte of interest or interfere in the
          analysis of an analyte of interest.
     
     In addition, monitoring well casing and screen
materials should be relatively easy to install into the
borehole during construction of the monitoring well.

     The selection of the most suitable well casing and
screen materials should consider site-specific factors,
including:

     *    Depth to the water-bearing zone(s) to be monitored
          and the anticipated well depth

     *    Geologic environment

     *    Geochemistry of soil, unconsolidated material, and
          rock over the entire interval in which the well is
          to be cased

     *    Geochemistry of the ground water at the site, as
          determined through an initial analysis of samples
          from both background wells and downgradient wells
          and including:

          -    Natural ground-water geochemistry

          -    Nature of suspected or known contaminants

          -    Concentration of suspected or known
               contaminants

     *    Design life of the monitoring well.  

     Casing materials widely available for use in
ground-water monitoring wells can be divided into three
categories:

     1)   Fluoropolymer materials, including
          polytetrafluoroethylene (PTFE),
          tetrafluoroethylene (TFE), fluorinated ethylene
          propylene (FEP), perfluoroalkoxy (PFA), and
          polyvinylidene fluoride (PVDF)

     2)   Metallic materials, including carbon steel,
          low-carbon steel, galvanized steel, and stainless
          steel (304 and 316)

     3)   Thermoplastic materials, including polyvinyl
          chloride (PVC) and acrylonitrile butadiene styrene
          (ABS).

     In addition to these three categories of materials,
fiberglass-reinforced plastic (FRP) has been used for
monitoring applications.  Because FRP has not yet been used
in general application across the country, very little data
are available on its characteristics and performance.  All
well construction materials possess strength-related
characteristics and chemical resistance/chemical
interference characteristics that influence their
performance in site-specific hydrogeologic and
contaminant-related monitoring situations.   

     The casing must be made of a material strong enough to
last for the life of the well.  Tensile strength is needed
primarily during well installation when the casing is
lowered into the hole.  The joint strength will determine
the maximum length of a section that can be suspended from
the surface in an air-filled borehole.

     Collapse strength is the capability of a casing to
resist collapse by any external loads to which it is
subjected both during and after installation.  A casing is
most susceptible to collapse during installation before
placement of the filter pack or annular seal materials
around the casing.  Once a casing is installed and
supported, collapse is seldom a concern.  Several steps that
can be taken to avoid casing collapse are:

     1)   Drilling a straight, clean borehole

     2)   Uniformly distributing filter pack materials at a
          slow, even rate

     3)   Avoiding use of quick-setting (high temperature)
          cements for thermoplastic casings installation.

     Compressive strength of the casing is a measure of the
greatest compressive stress that a casing can bear without
deformation.  Casing failure due to a compressive strength
limitation generally is not an important factor in a
properly installed well.  This type of failure results from
soil friction on unsupported casing.

     Chemical resistance/interference characteristics must
be evaluated before selecting monitoring well materials. 
Metallic casing materials are more subject to corrosion,
while thermoplastic casing materials are more susceptible to
chemical degradation.  The geochemistry of the formation
water influences the degree to which these processes occur. 
If ground-water chemistry affects the structural integrity
of the casing, then the samples collected from the well are
likely to be affected.

     Materials used for monitoring well casing must not
exhibit a tendency to sorb or leach chemical constituents
from, or into, water sampled from the well.  If a casing
material sorbs constituents from ground water, those
constituents may either not be detected during monitoring or
be detected at a lower concentration.  Chemical constituents
also can be leached from the casing materials by aggressive
aqueous solutions.  These constituents may be detected in
samples collected from the well.  The results may indicate
contamination that is due to the casing rather than the
formation water.  Casing materials must be selected with
care to avoid degradation of the well and to avoid erroneous
results.

     In certain situations it may be advantageous to design
a well using more than one material for well components. 
For example, where stainless steel or fluoropolymer
materials are preferred in a specific chemical environment,
costs may be saved by using PVC in non-critical portions of
the well.  These savings may be considerable, especially in
deep wells where only the lower portion of the well is in a
critical chemical environment and where tens of feet of
lower-cost PVC may be used in the upper portion of the well. 
In a composite well design, dissimilar metallic components
should not be used unless an electrically isolating design
is incorporated (i.e., a dielectric coupling) (USEPA, 1986).


          Coupling Procedures for Joining Casing

     Only a limited number of methods are available for
joining lengths of casing or casing and screen together. 
The joining method depends on the type of casing and type of
casing joint.  

     There are generally two options available for joining
metallic well casings:  welding via application of heat, or
threaded joints.  Threaded joints provide inexpensive, fast,
and convenient connections and greatly reduce potential
problems with chemical resistance or interference (due to
corrosion) and explosion potential.  Wrapping the male
threads with fluoropolymer tape prior to joining sections
improves the watertightness of the joint.  One disadvantage
to using threaded joints is that the tensile strength of the
casing string is reduced to approximately 70 percent of the
casing strength.  This reduction in strength does not
usually pose a problem because strength requirements for
small diameter wells (such as typical monitoring wells) are
not as critical and because metallic casing has a high
initial tensile strength.

     Joints should create a uniform inner and outer casing
diameter in monitoring well installations.  Solvent
cementing of thermoplastic pipe should never be used in the
construction of ground-water monitoring wells.  The cements
used in solvent welding, which are organic chemicals, have
been shown to adversely affect the integrity of ground-water
samples for more than 2 years after well installation; only
factory-threaded joints should be used on thermoplastic well
material.


          Well Casing Diameter

     Although the diameter of the casing for a monitoring
well depends on the purpose of the well, the casing size is
generally selected to accommodate downhole equipment. 
Additional casing diameter selection criteria include the 1)
drilling or well installation method used, 2) anticipated
depth of the well and associated strength requirements, 3)
anticipated method of well development, 4) volume of water
required to be purged prior to sampling, 5) rate of recovery
of the well after purging, and 6) anticipated aquifer
testing.


          Casing Cleaning Requirements

     Well casing and screen materials should be cleaned
prior to installation to remove any coatings or
manufacturing residues.  Prior to use, all casing and screen
materials should be washed with a mild, non-phosphate,
detergent/potable water solution and rinsed with potable
water.  Hot pressurized water, such as in steam cleaning,
should be used to remove organic solvents, oils, or
lubricants from casing and screens composed of materials
other than plastic.  At sites where volatile organic
contaminants may be monitored, the cleaning of well casing
and screen materials should include a final rinse with
deionized water or potable water that has not been
chlorinated.  Once cleaned, casings and screens should be
stored in an area that is free of potential contaminants. 
Plastic sheeting can generally be used to cover the ground
in the decontamination area to provide protection from
contamination.  USEPA (1989f) describes the procedures that
should be used to clean casing and screen materials. 


          Well Intake Design

     The owner/operator should design and construct the
intakes of monitoring wells to (1) accurately sample the
aquifer zone that the well is intended to sample, (2)
minimize the passage of formation materials (turbidity) into
the well, and (3) ensure sufficient structural integrity to
prevent the collapse of the intake structure.  The goal of a
properly completed monitoring well is to provide low
turbidity water that is representative of ground-water
quality in the vicinity of the well.  Close attention to
proper selection of packing materials and well development
procedures for wells installed in fine-grained formations
(e.g., clays and silty glacial tills) is important to
minimize sample turbidity from suspended and colloidal
solids.  There may be instances where wells completed in
rock do not require screens or filter packs; the State
regulatory agency should be consulted prior to completion of
unscreened wells.

     The selection of screen length usually depends on the
objective of the well.  Piezometers and wells where only a
discrete flow path is monitored (such as thin gravel
interbedded with clays) are generally completed using short
screens (2 feet or less).  To avoid dilution, the well
screens should be kept to the minimum length appropriate for
intercepting a contaminant plume, especially in a
high-yielding aquifer.  The screen length should generally
not exceed 10 feet.  If construction of a water table well
is the objective, either for defining gradient or detecting
floating phases, then a longer screen is acceptable because
the owner/operator will need to provide a margin of safety
that will guarantee that at least a portion of the screen
always contacts the water table regardless of its seasonal
fluctuations.  The owner or operator should not employ well
intake designs that cut across hydraulically separated
geologic units.  

     Well screen slot size should be selected to retain from
90 percent to 100 percent of the filter pack material
(discussed below) in artificially filter packed wells.  Well
screens should be factory-slotted.  Manual slotting of
screens in the field should not be performed under any
circumstances.


     Filter Pack Design

     The primary filter pack material should be a chemically
inert material and well rounded, with a high coefficient of
uniformity.  The best filter pack materials are made from
industrial grade glass (quartz) sand or beads.  The use of
other materials, such as local, naturally occurring clean
sand, is discouraged unless it can be shown that the
material is inert (e.g., low cation exchange capacity),
coarse-grained, permeable, and uniform in grain size. The
filter pack should extend at least 2 feet above the screened
interval in the well.

     Although design techniques for selecting filter pack
size vary, all use the filter pack ratio to establish size
differential between formation materials and filter pack
materials.  Generally, this ratio refers to either the
average (50 percent retained)  grain size of the formation
material or to the 70 percent retained size of the formation
material.  Barcelona et al. (1985b) recommend using a
uniform filter pack grain size that is three to five times
the size of the 50 percent retained size of the formation
material (USEPA, 1990).

     Filter pack material should be installed in a manner
that prevents bridging and particle-size segregation. 
Filter pack material installed below the water table should
generally be tremied into the annular space.  Allowing
filter pack material to fall by gravity (free fall) into the
annular space is only appropriate when wells are relatively
shallow, when the filter pack has a uniform grain size, and
when the filter pack material can be poured continuously
into the well without stopping.  

     At least 2 inches of filter pack material should be
installed between the well screen and the borehole wall. 
The filter pack should extend at least 2 feet above the top
of the well screen.  In deep wells, the filter pack may not
compress when initially installed.  Consequently, when the
annular and surface seals are placed on the filter pack, the
filter pack compresses sufficiently to allow grout into, or
very close to, the screen.  Consequently, filter packs may
need to be installed as high as 5 feet above the screened
interval in monitoring wells that are deep (i.e., greater
than 200 feet).  The precise volume of filter pack material
required should be calculated and recorded before placement,
and the actual volume used should be determined and recorded
during well construction.  Any significant discrepancy
between the calculated volume and the actual volume should
be explained.

     Prior to installing the annular seal, a 1- to 2-foot
layer of chemically inert fine sand may be placed over the
filter pack to prevent the intrusion of annular or surface
sealants into the filter pack.  When designing monitoring
wells, owners and operators should remember that the entire
length of the annular space filled with filter pack material
or sand is effectively the monitored zone.  Moreover, if the
filter pack/sand extends from the screened zone into an
overlying zone, a conduit for hydraulic connection is
created between the two zones.  

          Annular Sealants

     Proper sealing of the annular space between the well
casing and the borehole wall is required to prevent
contamination of samples and the ground water.  Adequate
sealing will prevent hydraulic connection within the well
annulus.  The materials used for annular sealants should be
chemically inert with the highest anticipated concentration
of chemical constituents expected in the ground water at the
facility.  In general, the permeability of the sealing
material should be one to two orders of magnitude lower than
the least permeable part of the formation in contact with
the well.  The precise volume of annular sealants required
should be calculated and recorded before placement, and the
actual volume used should be determined and recorded during
well construction.  Any significant discrepancy between the
calculated volume and the actual volume should be explained.

     When the screened interval is within the saturated
zone, a minimum of 2 feet of sealant material, such as raw
(more than 10 percent solids) bentonite, should be placed
immediately over the protective sand layer overlying the
filter pack.  Granular bentonite, bentonite pellets, and
bentonite chips may be placed around the casing by means of
a tremie pipe in deep wells (greater than approximately 30
feet deep), or by dropping them directly down the annulus in
shallow wells (less than approximately 30 feet deep). 
Dropping the bentonite pellets down the annulus presents a
potential for bridging (from premature hydration of the
bentonite), leading to gaps in the seal below the bridge. 
In shallow monitoring wells, a tamping device should be used
to prevent bridging from occurring.

     A neat cement or shrinkage-compensated neat cement
grout seal should be installed on top of the bentonite seal
and extend vertically up the annular space between the well
casing and the borehole wall to within a few feet of land
surface.  Annular sealants in slurry form (e.g., cement
grout, bentonite slurry) should be placed by the tremie/pump
(from the bottom up) method.  The bottom of the placement
pipe should be equipped with a side discharge deflector to
prevent the slurry from jetting a hole through the
protective sand layer, filter pack, or bentonite seal.  The
bentonite seal should be allowed to completely hydrate, set,
or cure in conformance with the manufacturer's
specifications prior to installing the grout seal in the
annular space.  The time required for the bentonite seal to
completely hydrate, set, or cure will differ with the
materials used and the specific conditions encountered, but
is generally a minimum of 4 to 24 hours.  Allowing the
bentonite seal to hydrate, set, or cure prevents the
invasion of the more viscous and more chemically reactive
grout seal into the screened area.

     When using bentonite as an annular sealant, the
appropriate clay should be selected on the basis of the
environment in which it is to be used, such as the
ion-exchange potential of the sediments, sediment
permeability, and compatibility with expected contaminants. 
Sodium bentonite is usually acceptable.  

     When the annular sealant must be installed in the
unsaturated zone, neat cement or shrinkage-compensated neat
cement mixtures should be used for the annular sealant. 
Bentonite is not recommended as an annular sealant in the
unsaturated zone because the moisture available is
insufficient to fully hydrate bentonite.


     Surface Completion

     Monitoring wells are commonly either above-ground
completions or flush-to-ground completions.  The design of
both types must consider the prevention of infiltration of
surface runoff into the well annulus and the possibility of
accidental damage or vandalism.  Completing a monitoring
well involves installing the following components:

     *    Surface seal

     *    Protective casing

     *    Ventilation hole

     *    Drain hole

     *    Cap and lock

     *    Guard posts when wells are completed above grade.

     A surface seal, installed on top of the grout seal,
extends vertically up the well annulus to the land surface. 
To protect against frost heave, the seal should extend at
least 1 foot below the frost line.  The composition of the
surface seal should be neat cement or concrete.  In an
above-ground completion, the surface seal should form at
least a 2-foot wide, 4-inch thick apron.

     A locking protective casing should be installed around
the well casing to prevent damage or unauthorized entry. 
The protective casing should be anchored below the frost
line (where applicable) into the surface seal and extend at
least 18 inches above the surface of the ground.  A 1/4-inch
vent hole pipe is recommended to allow the escape of any
potentially explosive gases that may accumulate within the
well.  In addition, a drain hole should be installed in the
protective casing to prevent water from accumulating and, in
freezing climates, freezing around the well casing.  The
space between the protective casing and the well casing may
be filled with gravel to allow the retrieval of tools and to
prevent small animal/insect entrance through the drain.  A
suitable cap should be placed on the well to prevent
tampering or the entry of any foreign materials.  A lock
should be installed on the cap to provide security.  To
prevent corrosion or jamming of the lock, a protective cover
should be used.  Care should be taken when using such
lubricants as graphite or petroleum-based sprays to
lubricate the lock, as lubricants may introduce a potential
for sample contamination.

     To guard against accidental damage to the well from
facility traffic, the owner/operator should install concrete
or steel bumper guards around the edge of the concrete
apron.  These should be located within 3 or 4 feet of the
well and should be painted orange or fitted with reflectors
to reduce the possibility of vehicular damage. 

     The use of flush-to-ground surface completions should
be avoided because this design increases the potential for
surface water infiltration into the well.  In cases where
flush-to-ground completions are unavoidable, such as in
active roadways, a protective structure, such as a utility
vault or meter box, should be installed around the well
casing.  In addition, measures should be taken to prevent
the accumulation of surface water in the protective
structure and around the well intake.  These measures should
include outfitting the protective structure with a steel lid
or manhole cover that has a rubber seal or gasket and
ensuring that the bond between the cement surface seal and
the protective structure is watertight.  


          Well Surveying

     The location of all wells should be surveyed by a
licensed professional surveyor (or equivalent) to determine
their X-and coordinates as well as their distances from the
units being monitored and their distances from each other. 
A State Plane Coordinate System, Universal Transverse
Mercator System, or Latitude/Longitude should be used, as
approved by the Regional Administrator.  The survey should
also note the coordinates of any temporary benchmarks.  A
surveyed reference mark should be placed on the top of the
well casing, not on the protective casing or the well apron,
for use as a measuring point because the well casing is more
stable than the protective casing or well apron (both the
protective casing and the well apron are more susceptible to
frost heave and spalling).  The height of the reference
survey datum, permanently marked on top of the inner well
casing, should be determined within plus or minus 0.01 foot
in relation to mean sea level, which in turn is determined
by reference to an established National Geodetic Vertical
Datum.  The reference marked on top of inner well casings
should be resurveyed at least once every 5 years, unless
changes in ground-water flow patterns/direction, or damage
caused by freeze/thaw or desiccation processes, are noted. 
In such cases, the Regional Administrator may require that
well casings be resurveyed on a more frequent basis.


          Well Development

     All monitoring wells should be developed to create an
effective filter pack around the well screen, to rectify
damage to the formation caused by drilling, to remove fine
particles from the formation near the borehole, and to
assist in restoring the natural water quality of the aquifer
in the vicinity of the well.  Development stresses the
formation around the screen, as well as the filter pack, so
that mobile fines, silts, and clays are pulled into the well
and removed.  The process of developing a well creates a
graded filter pack around the well screen.  Development is
also used to remove any foreign materials (drilling water,
muds, etc.) that may have been introduced into the well
borehole during drilling and well installation and to aid in
the equilibration that will occur between the filter pack,
well casing, and the formation water.  

     The development of a well is extremely important to
ensuring the collection of representative ground-water
samples.  If the well has been properly completed, then
adequate development should remove fines that may enter the
well either from the filter pack or the formation.  This
improves the yield, but more importantly it creates a
monitoring well capable of producing samples of acceptably
low turbidity.  Turbid samples from an improperly
constructed and developed well may interfere with subsequent
analyses.

     When development is initiated, a wide range of grain
sizes of the natural material is drawn into the well, and
the well typically produces very turbid water.  However, as
development continues and the natural materials are drawn
into the filter pack, an effective filter will form through
a sorting process.  Inducing movement of ground water into
the well (i.e., in one direction) generally results in
bridging of the particles.  A means of inducing flow
reversal is necessary to break down bridges and produce a
stable filter.

     The commonly accepted methods for developing wells are
described in USEPA (1989f) and Driscoll (1986) and include:

     *    Pumping and overpumping

     *    Surging with a surge block

     *    Bailing.

     USEPA (1989f) provides a detailed overview of well
development and should be consulted when evaluating well
development methods.


          Documentation of Well Design, Construction, and
          Development

     Information on the design, construction, and
development of each well should be compiled.  Such
information should include (1) a boring log that documents
well drilling and associated formation sampling and (2) a
well construction log and well construction diagram ("as
built").  


     Decommissioning Ground-Water Monitoring Wells and
     Boreholes

     Ground-water contamination resulting from improperly
decommissioned wells and boreholes is a serious concern. 
Any borehole that will not be completed as a monitoring well
should be properly decommissioned.  The USEPA (1975) and the
American Water Works Association (1985) provide the
following reasons, summarized by USEPA (1989f), as to why
improperly constructed or unused wells should be properly
decommissioned:

     *    To eliminate physical hazards

     *    To prevent ground-water contamination

     *    To conserve aquifer yield and hydrostatic head

     *    To prevent intermixing of subsurface water.

     Should an owner or operator have a borehole or an
improperly constructed or unused well at his or her
facility, the well or borehole should be decommissioned in
accordance with specific guidelines.  USEPA (1989f) provides
comprehensive guidance on performing well decommissioning
that can be applied to boreholes.  In addition, any
State/Tribal regulatory guidance should be consulted prior
to decommissioning monitoring wells, piezometers, or
boreholes.  Lamb and Kinney (1989) also provide information
on decommissioning ground-water monitoring wells.

     Many States require that specific procedures be
followed and certain paperwork be filed when decommissioning
water supply wells.  In some States, similar regulations may
apply to the decommissioning of monitoring wells and
boreholes.  The EPA and other involved regulatory agencies,
as well as experienced geologists, geotechnical engineers,
and drillers, should be consulted prior to decommissioning a
well or borehole to ensure that decommissioning is performed
properly and to ensure compliance with State law.  If a well
to be decommissioned is contaminated, the safe removal and
proper disposal of the well materials should be ensured by
the owner/operator.  Appropriate measures should be taken to
protect the health and safety of individuals when
decommissioning a well or borehole.

     
5.8  GROUND-WATER  SAMPLING AND ANALYSIS REQUIREMENTS 40 CFR
     Section 258.53

     5.8.1     Statement of Regulation

     (a)  The ground-water monitoring program must include
consistent sampling and analysis procedures that are
designed to ensure monitoring results that provide an
accurate representation of ground-water quality at the
background and downgradient wells installed in compliance
with Section 258.51(a) of this Part.  The owner or operator
must notify the State Director that the sampling and
analysis program documentation has been placed in the
operating record and the program must include procedures and
techniques for:

     (1)  Sample collection;

     (2)  Sample preservation and shipment;

     (3)  Analytical procedures;

     (4)  Chain of custody control; and

     (5)  Quality assurance and quality control.

     (b)  The ground-water monitoring program must include
sampling and analytical methods that are appropriate for
ground-water sampling and that accurately measure hazardous
constituents and other monitoring parameters in ground-water
samples.  Ground-water samples shall not be field-filtered
prior to laboratory analysis.

     (c)  The sampling procedures and frequency must be
protective of human health and the environment.

     (d)  Ground-water elevations must be measured in each
well immediately prior to purging, each time ground water is
sampled.  The owner or operator must determine the rate and
direction of ground-water  flow each time ground water is
sampled.  Ground-water elevations in wells which monitor the
same waste management area must be measured within a period
of time short enough to avoid temporal variations in
ground-water flow which could preclude accurate
determination of ground-water flow rate and direction.

     (e)  The owner or operator must establish background
ground-water quality in a hydraulically upgradient or
background well(s) for each of the monitoring parameters or
constituents required in the particular ground-water
monitoring program that applies to the MSWLF unit, as
determined under Section 258.54(a), or Section 258.55(a) of
this Part.  Background ground-water quality may be
established at wells that are not located hydraulically
upgradient from the MSWLF unit if it meets the requirements
of Section 258.51(a)(1).

     (f)  The number of samples collected to establish
ground-water quality data must be consistent with the
appropriate statistical procedures determined pursuant to
paragraph (g) of this section.  The sampling procedures
shall be those specified under Section 258.54(b) for
detection monitoring, Section 258.55(b) and (d) for
assessment monitoring, and Section 258.56(b) of corrective
action.


     5.8.2  Applicability

     The requirements for sampling and analysis apply to all
facilities required to conduct ground-water monitoring
throughout the active life, closure, and post-closure
periods of operation.  Quality assurance and quality control
measures for both field and laboratory activities must be
implemented.  The methods and procedures constituting the
program must be placed in the operating record of the
facility.

     For the sampling and analysis program to be technically
sound, the sampling procedures and analytical methods used
should provide adequate accuracy, precision, and detection
limits for the analyte determinations.  Prior to sampling,
the static ground-water elevations in the wells must be
measured to allow determination of the direction of
ground-water flow and estimates of rate of flow.  The time
interval between measurements at different wells must be
minimized so that temporal changes in ground-water
elevations do not cause an incorrect determination of
ground-water flow direction.  

     Background ground-water quality must be established at
all upgradient or background wells.  The background water
quality may be determined from wells that are not upgradient
of the MSWLF unit, provided that the wells yield
representative ground-water samples.

     The sampling program must be designed in consideration
of the anticipated statistical method applied by the owner
or operator.  The data objectives of the monitoring program,
in terms of the number of samples collected and the
frequency of collection, should be appropriate for the
statistical method selected for data comparison.  


     5.8.3  Technical Considerations

     The purpose of a ground-water sampling and analysis
program is to establish a protocol that can be followed
throughout the monitoring period of the site (operating,
closure, and post-closure).  The protocol is necessary so
that data acquired can be compared over time and accurately
represent ground-water quality.  Sample collection,
preservation, shipment, storage, and analyses should always
be performed in a consistent manner, even as monitoring
staff change during the monitoring period.

     The owner's/operator's ground-water monitoring program
must include a description of procedures for the following: 

     *    Sample collection

     *    Sample preservation and shipment

     *    Analytical procedures

     *    Chain of custody control

     *    Quality assurance and quality control.

     The ground-water monitoring program must be documented
in the operating record of the facility.

     The objectives of the monitoring program should clearly
define the quality of the data required to detect
significant changes in ground-water chemistry due to the
operation of the solid waste disposal facility.  These data
quality objectives should address:

     *    Accuracy and precision of methods used in the
          analysis of samples, including field measurements

     *    Quality control and quality assurance procedures
          used to ensure the validity of the results (e.g.,
          use of blank samples, record keeping, and data
          validation)

     *    Number of samples required to obtain a certain
          degree of statistical confidence

     *    Location and number of monitoring wells required.  


     Sample Collection

     Frequency

     The frequency of sample collection under detection
monitoring should be evaluated for each site according to
hydrogeologic conditions and landfill design.  In States,
the minimum sampling frequency should be semiannual.  The
background characterization should include four independent
samples at each monitoring location during the first
semi-annual event (i.e., during the first 6 months of
monitoring).  (See the discussion under Section 5.10.3 on
collecting independent samples to determine background.) 
More frequent sampling may be selected.  For example,
quarterly sampling may be conducted to evaluate seasonal
effects on ground-water quality.

     The frequency of sample collection during assessment
monitoring activities will depend on site-specific
hydrogeologic conditions and contaminant properties.  The
frequency of sampling is intended to obtain a data set that
is statistically independent of the previous set.  Guidance
to estimate this minimum time to obtain independent samples
is provided in "Statistical Analysis of Ground-water
Monitoring Data at RCRA Facilities - Interim Final Guidance"
(USEPA, 1989).


     Water Level Measurements

     The ground-water monitoring program must include
provisions for measuring static water level elevations in
each well prior to purging the well for sampling. 
Measurements of ground-water elevations are used for
determining horizontal and vertical hydraulic gradients for
estimation of flow rates and direction.

     Field measurements may include the following:

     *    Depth to standing water from a surveyed datum on
          the top of the well riser (static water level)

     *    Total depth of well from the top of the riser (to
          verify condition of well)

     *    Thickness of immiscible layers, if present.

     Measurements of the static water level and the depth to
the well bottom can be made with a wetted steel tape. 
Electronic water level measuring devices may also be used. 
Accepted standard operating procedures call for the static
water level to be accurately measured to within 0.01 foot
(USEPA, 1992a).  Water level measurements should be made at
all monitoring wells and well clusters in a time frame that
avoids changes that may occur as a result of barometric
pressure changes, significant infiltration events, or
aquifer pumping.  To prevent possible cross contamination of
wells, water level measurement devices must be
decontaminated prior to use at each well. 

     The ground-water monitoring program should include
provisions for detecting immiscible fluids (i.e., LNAPLs or
DNAPLs).  LNAPLs are relatively immiscible liquids that are
less dense than water and that spread across the water table
surface.  DNAPLs are relatively immiscible liquids that are
more dense than the ground water and tend to migrate
vertically downward in aquifers.  The detection of an
immiscible layer may require specialized equipment and
should be performed before the well is evacuated for
conventional sampling.  The ground-water monitoring program
should specify how DNAPLs and LNAPLs will be detected.  The
program also should include a contingency plan describing
procedures for sampling and analyzing these liquids. 
Guidance for detecting the presence of immiscible layers can
be found in USEPA (1992a).


     Well Purging

     Because the water standing in a well prior to sampling
may not represent in-situ ground-water quality, stagnant
water should be purged from the well and filter pack prior
to sampling.  The QAPjP should include detailed,
step-by-step procedures for purging wells, including the
parameters that will be monitored during purging and the
equipment that will be used for well purging. 

     Purging should be accomplished by removing ground water
from the well at low flow rates using a pump.  The use of
bailers to purge monitoring wells generally should be
avoided.  Research has shown that the "plunger" effect
created by continually raising and lowering the bailer into
the well can result in continual development or
overdevelopment of the well.  Moreover, the velocities at
which ground water enters a bailer can actually correspond
to unacceptably high purging rates (Puls and Powell, 1992;
Barcelona et al., 1990).   

     The rate at which ground water is removed from the well
during purging ideally should be approximately 0.2 to 0.3
L/min or less (Puls and Powell, 1992; Puls et al., 1991;
Puls and Barcelona, 1989a; Barcelona, et al., 1990).  Wells
should be purged at rates below those used to develop the
well to prevent further development of the well, to prevent
damage to the well, and to avoid disturbing accumulated
corrosion or reaction products in the well (Kearl et al.,
1992; Puls et al., 1990; Puls and Barcelona, 1989a; Puls and
Barcelona, 1989b; Barcelona, 1985b).  Wells also should be
purged at or below their recovery rate so that migration of
water in the formation above the well screen does not occur. 
A low purge rate also will reduce the possibility of
stripping VOCs from the water, and will reduce the
likelihood of mobilizing colloids in the subsurface that are
immobile under natural flow conditions.  The owner/operator
should ensure that purging does not cause formation water to
cascade down the sides of the well screen.  At no time
should a well be purged to dryness if recharge causes the
formation water to cascade down the sides of the screen, as
this will cause an accelerated loss of volatiles.  This
problem should be anticipated; water should be purged from
the well at a rate that does not cause recharge water to be
excessively agitated.  Laboratory experiments have shown
that unless cascading is prevented, up to 70 percent of the
volatiles present could be lost before sampling.

     To eliminate the need to dispose of large volumes of
purge water, and to reduce the amount of time required for
purging, wells may be purged with the pump intake just above
or just within the screened interval.  This procedure
eliminates the need to purge the column of stagnant water
located above the well screen (Barcelona et al., 1985b;
Robin and Gillham, 1987; Barcelona, 1985b; Kearl et al.,
1992).  Purging the well at the top of the well screen
should ensure that fresh water from the aquifer moves
through the well screen and upward within the screened
interval.  Pumping rates below the recharge capability of
the aquifer must be maintained if purging is performed with
the pump placed at the top of the well screen, below the
stagnant water column above the top of the well screen
(Kearl et al., 1992).  The Agency suggests that a packer be
placed above the screened interval to ensure that "stagnant"
casing water is not drawn into the pump.  The packer should
be kept inflated in the well until after ground-water
samples are collected.  

     In certain situations, purging must be performed with
the pump placed at, or immediately below, the air/water
interface.  If a bailer must be used to sample the well, the
well should be purged by placing the pump intake immediately
below the air/water interface.  This will ensure that all of
the water in the casing and filter pack is purged, and it
will minimize the possibility of mixing and/or sampling
stagnant water when the bailer is lowered down into the well
and subsequently retrieved (Keeley and Boateng, 1987). 
Similarly, purging should be performed at the air/water
interface if sampling is not performed immediately after the
well is purged without removing the pump.  Pumping at the
air/water interface will prevent the mixing of stagnant and
fresh water when the pump used to purge the well is removed
and then lowered back down into the well for the purpose of
sampling.  

     In cases where an LNAPL has been detected in the
monitoring well, special procedures should be used to purge
the well.  These procedures are described in USEPA (1992a).

     For most wells, the Agency recommends that purging
continue until measurements of turbidity, redox potential,
and dissolved oxygen in in-line or downhole analyses of
ground water have stabilized within approximately 10% over
at least two measurements (Puls and Powell, 1992; Puls and
Eychaner, 1990; Puls et al., 1990; Puls and Barcelona,
1989a; Puls and Barcelona, 1989b; USEPA, 1991; Barcelona et
al., 1988b).  If a well is purged to dryness or is purged
such that full recovery exceeds two hours, the well should
be sampled as soon as a sufficient volume of ground water
has entered the well to enable the collection of the
necessary ground-water samples.

     All purging equipment that has been or will be in
contact with ground water should be decontaminated prior to
use.  If the purged water or the decontamination water is
contaminated (e.g., based on analytical results), the water
should be stored in appropriate containers until analytical
results are available, at which time proper arrangements for
disposal or treatment should be made (i.e., contaminated
purge water may be a hazardous waste).


     Field Analyses

     Several constituents or parameters that owners or
operators may choose to include in a ground-water monitoring
program may be physically or chemically unstable and should
be tested after well purging and before the collection of
samples for laboratory analysis.  Examples of unstable
parameters include pH, redox (oxidation-reduction)
potential, dissolved oxygen, temperature, and specific
conductance.  

     Field analyses should not be performed on samples
designated for laboratory analysis.  Any field monitoring
equipment or field-test kits should be calibrated at the
beginning of each use, according to the manufacturers'
specifications and consistent with methods in SW-846 (USEPA,
1986b).


     Sample Withdrawal and Collection 

     The equipment used to withdraw a ground-water sample
from a well must be selected based on consideration of the
parameters to be analyzed in the sample.  To ensure the
sample is representative of ground water in the formation,
it is important to keep physical or chemical alterations of
the sample to a minimum.  USEPA (1992a) provides an overview
of the issues involved in selecting ground-water sampling
equipment, and a summary of the application and limitations
of various sampling mechanisms.  Sampling materials and
equipment should be selected to preserve sample integrity. 
Sampling equipment should be constructed of inert material. 
Sample collection equipment should not alter analyte
concentrations, cause loss of analytes via sorption, or
cause gain of analytes via desorption, degradation, or
corrosion.  Sampling equipment should be designed such that
Viton, Tygon, silicone, or neoprene components do not come
into contact with the ground-water sample.  These materials
have been demonstrated to cause sorptive losses of
contaminants (Barcelona et al., 1983; Barcelona et al.,
1985b; Barcelona et al., 1988b; Barcelona et al., 1990). 
Barcelona (1988b) suggests that sorption of volatile organic
compounds on silicone, polyethylene, and PVC tubing may
result in gross errors when determining concentrations of
trace organics in ground-water samples.  Barcelona (1985b)
discourages the use of PVC sampling equipment when sampling
for organic contaminants.  Fluorocarbon resin (e.g., Teflon)
or stainless steel sampling devices which can be easily
disassembled for thorough decontamination are widely used. 
Dedicating sampling equipment to each monitoring well will
help prevent cross-contamination problems that could arise
from improper decontamination procedures.

     Sampling equipment should cause minimal sample
agitation and should be selected to reduce/eliminate sample
contact with the atmosphere during sample transfer. 
Sampling equipment should not allow volatilization or
aeration of samples to the extent that analyte
concentrations are altered.

     Bladder pumps are generally recognized as the best
overall sampling device for both organic and inorganic
constituents, although other types of pumps (e.g., low-rate
submersible centrifugal pumps, helical rotor electric
submersible pumps) have been found suitable in some
applications.  Bailers, although inexpensive and simple to
use, have been found to cause volatilization of samples,
mobilization of particulates in wells and imprecise results
(USEPA, 1992a).

     The following recommendations apply to the use and
operation of ground-water sampling equipment:

     *    Check valves should be designed and inspected to
          ensure that fouling problems do not reduce
          delivery capabilities or result in aeration of
          samples.

     *    Sampling equipment should never be dropped into
          the well, as this will cause degassing of the
          water upon impact.

     *    Contents of the sampling device should be
          transferred to sample containers in a controlled
          manner that will minimize sample agitation and
          aeration.

     *    Decontaminated sampling equipment should not be
          allowed to come into contact with the ground or
          other contaminated surfaces prior to insertion
          into the well.

     *    Ground-water samples should be collected as soon
          as possible after the well is purged.  Water that
          has remained in the well casing for more than
          about 2 hours has had the opportunity to exchange
          gases with the atmosphere and to interact with the
          well casing material (USEPA, 1991b).

     *    The rate at which a well is sampled should not
          exceed the rate at which the well was purged.  Low
          sampling rates, approximately 0.1 L/min, are
          suggested.  Low sampling rates will help to ensure
          that particulates, immobile in the subsurface
          under ambient conditions, are not entrained in the
          sample and that volatile compounds are not
          stripped from the sample (Puls and Barcelona,
          1989b; Barcelona, et al., 1990; Puls et al., 1991;
          Kearl et al., 1992; USEPA, 1991b).  Pumps should
          be operated at rates less than 0.1 L/min when
          collecting samples for volatile organics analysis. 

     *    Pump lines should be cleared at a rate of 0.1
          L/min or less before collecting samples for
          volatiles analysis so that the samples collected
          will not be from the period of time when the pump
          was operating more rapidly.  

     *    Pumps should be operated in a continuous manner so
          that they do not produce samples that are aerated
          in the return tube or upon discharge.

     *    When sampling wells that contain LNAPLs, a
          stilling tube should be inserted in the well. 
          Ground-water samples should be collected from the
          screened interval of the well below the base of
          the tube.

     *    Ground-water samples collected for analysis for
          organic constituents or parameters should not be
          filtered in the field.

     Once appropriate sampling equipment has been selected
and operating procedures established, samples should be
collected and containerized in the order of the
volatilization sensitivity of the parameter.  The preferred
collection order for some of the more common ground-water
analytes is depicted on the flow chart shown in Figure 5-4.


************************************************************
                        FIGURE 5-4
                             
  Generalized Flow Diagram of Ground-Water Sampling Steps
                         [Graphic]
************************************************************


     The ground-water monitoring program documentation
should include explicit procedures for disassembly and
decontamination of sampling equipment before each use. 
Improperly decontaminated equipment can affect samples in
several ways.  For example, residual contamination from the
previous well may remain on equipment, or improper
decontamination may not remove all of the detergents or
solvents used during decontamination.  Specific guidance
regarding decontamination of the sampling equipment is
available (USEPA  1992a).  To keep sample
cross-contamination to a minimum, sampling should proceed
from upgradient or background locations to downgradient
locations that would contain higher concentrations of
contaminants.


     Sample Preservation and Handling

     The procedures for preserving and handling samples are
nearly as important for ensuring the integrity of the
samples as the collection device itself.  Detailed
procedures for sample preservation must be provided in the
Quality Assurance Project Plan (QAPjP) that is included in
the sampling and analysis program description.


     Sample Containers

     To avoid altering sample quality, the samples should be
transferred from the sampling equipment directly into a
prepared container.  Proper sample containers for each
constituent or group of constituents are identified in
SW-846 (USEPA, 1986b).  Samples should never be composited
in a common container in the field and then split.  Sample
containers should be cleaned in a manner that is appropriate
for the constituents to be analyzed.  Cleaning procedures
are provided by USEPA (1986b).  Sample containers that have
been cleaned according to these procedures can be procured
commercially. 

     Most vendors will provide a certification of
cleanliness.


     Sample Preservation

     During ground-water sampling, every attempt should be
made to minimize changes in the chemistry of the samples. 
To assist in maintaining the natural chemistry of the
samples, it is necessary to preserve the sample.  The owner
or operator should refer to SW-846 (USEPA, 1986b) for the
specific preservation method and holding times for each
constituent to be analyzed.  Methods of sample preservation
are relatively limited and are intended to retard chemical
reactions, such as oxidation, retard, biodegradation, and to
reduce the effects of sorption.  Preservation methods are
generally limited to pH control, refrigeration, and
protection from light.


     Sample Storage and Shipment

     The storage and transport of ground-water samples must
be performed in a manner that maintains sample quality. 
Samples should be cooled to 4 degrees C as soon as possible
after they are collected.  These conditions should be
maintained until the samples are received at the laboratory. 
Sample containers generally are packed in picnic coolers or
special containers for shipment. 

     Polystyrene foam, vermiculite, and "bubble pack" are
frequently used to pack sample containers to prevent
breakage.  Ice is placed in sealed plastic bags and added to
the cooler.  All related paperwork is sealed in a plastic
bag and taped to the inside top of the cooler.  The cooler
top is then taped shut.  Custody seals should be placed
across the hinges and latches on the outside of the cooler.

     Transportation arrangements should maintain proper
storage conditions and provide for effective sample pickup
and delivery to the laboratory.  Sampling plans should be
coordinated with the laboratory so that appropriate sample
receipt, storage, analysis, and custody arrangements can be
provided.  

     Most analyses must be performed within a specified
period (holding time) from sample collection.  Holding time
refers to the period that begins when the sample is
collected from the well and ends with its extraction or
analysis.  Data from samples not analyzed within the
recommended holding times should be considered suspect. 
Some holding times for Appendix I constituents are as short
as 7 days.  To provide the laboratory with operational
flexibility in meeting these holding times, samples usually
are shipped via overnight courier.  Laboratory capacity or
operating hours may influence sampling schedules. 
Coordination with laboratory staff during planning and
sampling activities is important in maintaining sample and
analysis quality.

     The documentation that accompanies samples during
shipment to the laboratory usually includes chain-of-custody
(including a listing of all sample containers), requested
analyses, and full identification of the origin of samples
(including contact names, phone numbers, and addresses). 
Copies of all documents shipped with the samples should be
retained by the sampler.


     Chain-of-Custody Record

     To document sample possession from the time of
collection, a chain-of-custody record should be filled out
to accompany every sample shipment.  The record should
contain the following types of information:

     *    Sample number

     *    Signature of collector

     *    Date and time of collection

     *    Media sampled (e.g., ground water)

     *    Sample type (e.g., grab)

     *    Identification of sampling location/well

     *    Number of containers

     *    Parameters requested for analysis

     *    Signatures of persons involved in the chain of
          possession

     *    Inclusive dates of possession with time in 24-hour
          notation

     *    Internal temperature of shipping container when
          samples were sealed into the container for
          shipping

     *    Internal temperature of container when opened at
          the laboratory

     *    Any remarks regarding potential hazards or other
          information the laboratory may need.

     An adequate chain-of-custody program allows for tracing
the possession and handling of individual samples from the
time of collection through completion of laboratory
analysis.  A chain-of-custody program should include:

     *    Sample labels to prevent misidentification of
          samples

     *    Sample custody seals to preserve the integrity of
          the samples from the time they are collected until
          they are opened in the laboratory

     *    Field notes to record information about each
          sample collected during the ground-water
          monitoring program

     *    Chain-of-custody record to document sample
          possession from the time of collection to analysis

     *    Laboratory storage and analysis records, which are
          maintained at the laboratory and which record
          pertinent information about the sample.


     Sample Labels

     Each sample's identification should be marked clearly
in waterproof ink on the sample container.  To aid in
labeling, the information should be written on each
container prior to filling with a sample.  The labels should
be sufficiently durable to remain legible even when wet and
should contain the following information: 

     *    Sample identification number

     *    Name and signature of the sampler

     *    Date and time of collection

     *    Sample location

     *    Analyses requested.


     Sample Custody Seal

     Sample custody seals should be placed on the shipping
container and/or individual sample bottle in a manner that
will break the seal if the container or sample is tampered
with.


     Field Logbook

     To provide an account of all activities involved in
sample collection, all sampling activities, measurements,
and observations should be noted in a field log.  The
information should include visual appearance (e.g., color,
turbidity, degassing, surface film), odor (type, strength),
and field measurements and calibration results.  Ambient
conditions (temperature, humidity, wind, precipitation) and
well purging and sampling activities should also be recorded
as an aid in evaluating sample analysis results.

     The field logbook should document the following:

     *    Well identification

     *    Well depth

     *    Static water level depth and measurement technique

     *    Presence and thickness of immiscible layers and
          the detection method

     *    Well yield (high or low) and well recovery after
          purging (slow, fast)

     *    Well purging procedure and equipment

     *    Purge volume and pumping rate

     *    Time well purged

     *    Collection method for immiscible layers

     *    Sample withdrawal procedure and equipment

     *    Date and time of sample collection

     *    Results of field analysis

     *    Well sampling sequence

     *    Types of sample bottles used and sample
          identification numbers

     *    Preservatives used

     *    Parameters requested for analysis

     *    Field observations of sampling event

     *    Name of collector

     *    Weather conditions, including air temperature

     *    Internal temperature of field and shipping
          containers.  


     Sample Analysis Request Sheet

     A sample analysis request sheet should accompany the
sample(s) to the laboratory and clearly identify which
sample containers have been designated for each requested
parameter and the preservation methods used.  The record
should include the following types of information:

     *    Name of person receiving the sample

     *    Laboratory sample number (if different from field
          number)

     *    Date of sample receipt

     *    Analyses to be performed (including desired
          analytical method)

     *    Information that may be useful to the laboratory
          (e.g., type and quantity of preservatives added,
          unusual conditions).


     Laboratory Records

     Once the sample has been received in the laboratory,
the sample custodian and/or laboratory personnel should
clearly document the processing steps that are applied to
the sample.  All sample preparation (e.g., extraction) and
determinative steps should be identified in the laboratory
records.  Deviations from established methods or standard
operating procedures (SOPs), such as the use of specific
reagents (e.g., solvents, acids), temperatures, reaction
times, and instrument settings, should be noted.  The
results of the analyses of all quality control samples
should be identified for each batch of ground-water samples
analyzed.  The laboratory logbook should include the time,
date, and name of the person who performed each processing
step.


     Analytical Procedures

     The requirements of 40 CFR Part 258 include detection
and assessment monitoring activities.  Under detection
monitoring, the constituents listed in 40 CFR Part 258,
Appendix I are to be analyzed for.  This list includes
volatile organic compounds (VOCs) and selected inorganic
constituents.  No specific analytical methods are cited in
the regulations, but there is a requirement (40 CFR Section
258.53(h)(5)) that any practical quantitation limit (PQL)
used in subsequent statistical analysis "be the lowest
concentration level that can be reliably achieved within
specified limits of precision and accuracy during routine
laboratory operating conditions that are available to the
facility."  Suggested test methods are listed in Appendix II
of Part 258 for informational purposes only.  Method 8240
(gas chromatography with packed column; mass spectrometry)
and Method 8260 (gas chromatography with capillary column;
mass spectrometry) are typical methods used for all Appendix
I VOCs.  The inorganic analyses can be performed using
inductively coupled plasma atomic emission spectroscopy
(ICP) Method 6010.  These methods, as well as other methods
appropriate to these analyses, are presented in Tests
Methods for Evaluating Solid Waste, Physical/Chemical
Methods, SW-846 (USEPA, 1986), and are routinely performed
by numerous analytical testing laboratories.  These methods
typically provide PQLs in the 1 to 50 ug/L range.  The
ground-water monitoring plan must specify the analytical
method to be used.

     Evaluation and documentation of analytical performance
requires that quality control samples be collected and
analyzed along with the ground-water monitoring samples. 
Chapter One of SW-846 (Quality Assurance) describes the
types of quality control samples necessary, as well as the
frequency at which they must be collected and analyzed.  In
general, these quality control samples may include trip
blanks, equipment rinsate samples, field duplicates, method
blanks, matrix spikes and duplicates, and laboratory control
samples.

     Other mechanisms, including sample holding times,
surrogate constituents, and standard additions,  are also
used to control and document data quality.  The
specification of and adherence to sample holding times
minimizes the sample degradation that occurs over time. 
Evaluating the recovery of surrogate constituents spiked
into organic samples allows the analyst and data user to
monitor the efficiency of sample extraction and analysis. 
The method of standard additions is used to eliminate the
effects of matrix interferences in inorganic analyses.


     Quality Assurance/Quality Control

     One of the fundamental responsibilities of the owner or
operator is to establish a continuing program to ensure the
reliability and validity of field and analytical laboratory
data gathered as part of the overall ground-water monitoring
program.  The owner or operator must explicitly describe the
QA/QC program that will be used in the  laboratory.  Most
owners or operators will use commercial laboratories to
conduct analyses of ground-water samples.  In these cases,
the owner or operator is responsible for ensuring that the
laboratory of choice is exercising an appropriate QA/QC
program.  

     The owner or operator should provide for the use of
standards, laboratory blanks, duplicates, and spiked samples
for calibration and identification of potential matrix
interferences, especially for metal determinants.  Refer to
Chapter One of SW-846 for guidance.  The owner or operator
should use adequate statistical procedures (e.g., QC charts)
to monitor and document performance and to implement an
effective program to resolve testing problems (e.g.,
instrument maintenance, operator training).  Data from QC
samples (e.g., blanks, spiked samples) should be used as a
measure of performance or as an indicator of potential
sources of cross-contamination, but should not be used by
the laboratory to alter or correct analytical data.  All
laboratory QC data should be submitted with the ground-water
monitoring sample results.   


     Field Quality Assurance/Quality Control

     To verify the precision of field sampling procedures,
field QC samples, such as trip blanks, equipment blanks, and
duplicates, should be collected.  Additional volumes of
sample also should be collected for laboratory QC samples.

     All field QC samples should be prepared exactly as
regular investigation samples with regard to sample volume,
containers, and preservation.  The concentrations of any
contaminants found in blank samples should not be used to
correct the ground-water data.  The contaminant
concentrations in blanks should be documented, and if the
concentrations are more than an order of magnitude greater
than the field sample results, the owner/operator should
resample the ground water.  The owner/operator should
prepare the QC samples as recommended in Chapter One of
SW-846 and at the frequency recommended by Chapter One of
SW-846 and should analyze them for all of the required
monitoring parameters.  Other QA/QC practices, such as
sampling equipment calibration, equipment decontamination
procedures, and chain-of-custody procedures, are discussed
in other sections of this chapter and should be described in
the owner/operator's QAPjP.


     Validation

     The analytical data report provided by the laboratory
will present all data measured by the laboratory but will
not adjust those data for field or laboratory quality
control indicators.  This means that just because data have
been reported, they are not necessarily an accurate
representation of the quality of the ground water.  For
example, acetone and methylene chloride are often used in
laboratories as cleaning and extraction solvents and,
consequently, are often laboratory contaminants, transmitted
through the ambient air into samples.  Method blanks are
analyzed to evaluate the extent of laboratory contamination. 
Constituents found as contaminants in the method blanks are
"flagged" in the sample data.  The sample data are not,
however, adjusted for the contaminant concentration.

     Other kinds of samples are analyzed to assess other
data quality indicators.  Trip blanks are used to assess
contamination by volatile organic constituents during sample
shipment and storage.  Matrix spike/matrix spike duplicate
sample pairs are used to evaluate analytical bias and
precision.  Equipment rinsate samples are used to assess the
efficacy of sampling equipment decontamination procedures. 
The data validation process uses the results from all of
these QC samples to determine if the reported analytical
data accurately describe the samples.  All reported data
must be evaluated -- a reported value of "non-detect" is a
quantitative report just like a numerical value and must be
validated.

     The data validation process must also consider the
presence and quality of other kinds of data used to ensure
data quality (e.g., calibration frequency and descriptors,
matrix specific detection limits).  All of the criteria for
data quality are described in the quality assurance project
plan (QAPjP) or sampling and analysis plan (SAP).  These
documents may reference criteria from some other source,
(e.g., the USEPA Contract Laboratory Program).  The
performance criteria must be correctly specified and must be
used for data validation.  It is a waste of time and money
to evaluate data against standards other than those used to
generate them.  Several documents are available to assist
the reviewer in validation of data by different criteria
(i.e., Chapter One of Test Methods for Evaluating Solid
Waste, Physical/Chemical Methods, USEPA CLP Functional
Guidelines for Evaluating Organics Analyses, USEPA CLP
Functional Guidelines for Evaluating Pesticides/PCBs
Analyses, etc.).

     In addition to specific data that describe data
quality, the validator may consider other information that
may have an impact on the end-use of the data, such as
background concentrations of the constituent in the
environment.  In any event, the QAPjP or SAP also should
describe the validation procedures that will be used.  The
result of this validation should be the classification of
data as acceptable or unacceptable for the purposes of the
project.  In some cases, data may be further qualified,
based either on insufficient data or marginal performance
(i.e., qualitative uses only, estimated concentration,
etc.).


     Documentation

     The ground-water monitoring program required by Section
258.50 through Section 258.55 relies on documentation to
demonstrate compliance.  The operating record of the MSWLF
should include a complete description of the program as well
as periodic implementation reports.

     At a minimum, the following aspects of the ground-water
monitoring program should be described or included in the
operating record:

     *    The Sampling and Analysis plan that details sample
          parameters, sampling frequency, sample collection,
          preservation, and analytical methods to be used,
          shipping procedures, and chain-of-custody
          procedures;

     *    The Quality Assurance Project Plan (QAPjP) and
          Data Quality Objectives (DQOs);

     *    The locations of monitoring wells;

     *    The design, installation, development, and
          decommission of monitoring wells, piezometers, and
          other measurement, sampling, and analytical
          devices;

     *    Site hydrogeology;

     *    Statistical methods to be used to evaluate
          ground-water monitoring data and demonstrate
          compliance with the performance standard;

     *    Approved demonstration that monitoring
          requirements are suspended (if applicable);

     *    Boring logs;

     *    Piezometer and well construction logs for the
          ground-water monitoring system.

     
5.9  STATISTICAL ANALYSIS 40 CFR Section 258.53 (g)-(i)

     5.9.1  Statement of Regulation

     (g)  The owner or operator must specify in the
operating record one of the following statistical methods to
be used in evaluating ground-water monitoring data for each
hazardous constituent.  The statistical test chosen shall be
conducted separately for each hazardous constituent in each
well.

     (1)  A parametric analysis of variance (ANOVA) followed
by multiple comparisons procedures to identify statistically
significant evidence of contamination.  The method must
include estimation and testing of the contrasts between each
compliance well's mean and the background mean levels for
each constituent. 

     (2)  An analysis of variance (ANOVA) based on ranks
followed by multiple comparisons procedures to identify
statistically significant evidence of contamination.  The
method must include estimation and testing of the contrasts
between each compliance well's median and the background
median levels for each constituent.

     (3)  A tolerance or prediction interval procedure in
which an interval for each constituent is established from
the distribution of the background data, and the level of
each constituent in each compliance well is compared to the
upper tolerance or prediction limit.

     (4)  A control chart approach that gives control limits
for each constituent.    

     (5)  Another statistical test method that meets the
performance standards of Section 258.53(h).  The owner or
operator must place a justification for this alternative in
the operating record and notify the State Director of the
use of this alternative test.  The justification must
demonstrate that the alternative method meets the
performance standards of Section 258.53(h).  

     (h)  Any statistical method chosen under Section
258.53(g) shall comply with the following performance
standards, as appropriate:

     (1)  The statistical method used to evaluate
ground-water monitoring data shall be appropriate for the
distribution of chemical parameters or hazardous
constituents.  If the distribution of the chemical
parameters or hazardous constituents is shown by the owner
or operator to be inappropriate for a normal theory test,
then the data should be transformed or a distribution-free
theory test should be used.  If the distributions for the
constituents differ, more than one statistical method may be
needed.

     (2)  If an individual well comparison procedure is used
to compare an individual compliance well constituent
concentration with background constituent concentrations or
a ground-water protection standard, the test shall be done
at a Type I error level of no less than 0.01 for each
testing period.  If a multiple comparisons procedure is
used, the Type I experiment wise error rate for each testing
period shall be no less than 0.05; however, the Type I error
of no less than 0.01 for individual well comparisons must be
maintained.  This performance standard does not apply to
tolerance intervals, prediction intervals, or control
charts.

     (3)  If a control chart approach is used to evaluate
ground-water monitoring data, the specific type of control
chart and its associated parameter values shall be
protective of human health and the environment.  The
parameters shall be determined after considering the number
of samples in the background data base, the data
distribution, and the range of the concentration values for
each constituent of concern.

     (4)  If a tolerance interval or a predictional interval
is used to evaluate ground-water monitoring data, the levels
of confidence and, for tolerance intervals, the percentage
of the population that the interval must contain, shall be
protective of human health and the environment.  These
parameters shall be determined after considering the number
of samples in the background data base, the data
distribution, and the range of the concentration values for
each constituent of concern.

     (5)  The statistical method shall account for data
below the limit of detection with one or more statistical
procedures that are protective of human health and the
environment.  Any practical quantitation limit (PQL) that is
used in the statistical method shall be the lowest
concentration level that can be reliably achieved within
specified limits of precision and accuracy during routine
laboratory operating conditions that are available to the
facility.

     (6)  If necessary, the statistical method shall include
procedures to control or correct for seasonal and spatial
variability as well as temporal correlation in the data.

     (i)  The owner or operator must determine whether or
not there is a statistically significant increase over
background values for each parameter or constituent required
in the particular ground-water monitoring program that
applies to the MSWLF unit, as determined under Sections
258.54(a) or 258.55(a) of this part.

     (1)  In determining whether a statistically significant
increase has occurred, the owner or operator must compare
the ground-water quality of each parameter or constituent at
each monitoring well designated pursuant to Section
258.51(a)(2) to the background value of that constituent,
according to the statistical procedures and performance
standards specified under paragraphs (g) and (h) of this
section. 

     (2)  Within a reasonable period of time after
completing sampling and analysis, the owner or operator must
determine whether there has been a statistically significant
increase over background at each monitoring well.


     5.9.2  Applicability

     The statistical analysis requirements are applicable to
all existing units, new units, and lateral expansions of
existing units for which ground-water monitoring is
required.  The use of statistical procedures to evaluate
monitoring data shall be used for the duration of the
monitoring program, including the post-closure care period.

     The owner or operator must indicate in the operating
record the statistical method that will be used in the
analysis of ground-water monitoring results.  The data
objectives of the monitoring, in terms of the number of
samples collected and the frequency of collection, must be
consistent with the statistical method selected.

     Several options for analysis of ground-water data are
provided in the criteria.  Other methods may be used if they
can be shown to meet the performance standards.  The
approved methods include both parametric and nonparametric
procedures, which differ primarily in constraints placed by
the statistical distribution of the data.  Control chart,
tolerance interval, and prediction interval approaches also
may be applied.

     The owner or operator must conduct  the statistical
comparisons between upgradient and downgradient wells after
completion of each sampling event and receipt of validated
data.  The statistical procedure must conform to the
performance standard of a Type I error level of no less than
0.01 for inter-well comparisons.  Control chart, tolerance
interval, and prediction interval approaches must
incorporate decision values that are protective of human
health and the environment.  Generally, this is meant to
include a significance level of a least 0.05.  Procedures to
treat data below analytical method detection levels and
seasonality effects must be part of the statistical
analysis.  


     5.9.3     Technical Considerations

     The MSWLF rule requires facilities to evaluate
ground-water monitoring data using a statistical method
provided in Section 258.53(g) that meets the performance
standard of Section 258.53(h).  Section 258.53(g) contains a
provision allowing for the use of an alternative statistical
method as long as the performance standards of Section
258.53(h) are met.

     The requirements of Section 258.53(g) specify that one
of five possible statistical methods be used for evaluating
ground-water monitoring data.  One method should be
specified for each constituent.  Although different methods
may be selected for each constituent at new facilities, use
of a method must be substantiated by demonstrating that the
distribution of data  obtained on that constituent is
appropriate for that method (Section 258.53(h)).  Selection
of a specific method is described in Statistical Analysis of
Ground-Water Monitoring Data at RCRA Facilities - Interim
Final Guidance" (USEPA, 1989) and in Statistical Analysis of
Ground-Water Monitoring Data at RCRA Facilities - Addendum
to Interim Final Guidance (USEPA, 1992b).  EPA also offers
software, entitled User Documentation of the Ground-Water
Information Tracking System (GRITS) with Statistical
Analysis Capability, GRITSTAT Version 4.2.  In addition to
the statistical guidance provided by EPA, the following
references may be useful for selecting other methods (Dixon
and Massey, 1969; Gibbons, 1976; Aitchison and Brown, 1969;
and Gilbert, 1987).  The statistical methods that may be
used in evaluating ground-water monitoring data include the
following:

     *    Parametric analysis of variance (ANOVA) with
          multiple comparisons

     *    Rank-based (nonparametric) ANOVA with multiple
          comparisons

     *    Tolerance interval or prediction interval

     *    Control chart

     *    An alternative statistical method (e.g., CABF
          t-test or confidence intervals).

     If an alternative method is used, then the State
Director must be notified, and a justification for its use
must be placed in the operating record.

     The statistical analysis methods chosen must meet
performance standards specified under Section 258.53(h),
which include the following:  

     1)   The method must be appropriate for the observed
          distribution of the data

     2)   Individual well comparisons to background
          ground-water quality or a ground-water protection
          standard shall be done at a Type I error level of
          no less than 0.01 or, if the multiple comparisons
          procedure is used, the experiment-wise error rate
          for each testing period shall be no less than 0.05

     3)   If a control chart is used, the type of chart and
          associated parameter values shall be protective of
          human health and the environment

     4)   The level of confidence and percentage of the
          population contained in an interval shall be
          protective of human health and the environment

     5)   The method must account for data below the limit
          of detection (less than the PQL) in a manner that
          is protective of human health and the environment

     6)   The method must account for seasonal and spatial
          variability and temporal correlation of the data,
          if necessary.

     These statistical analysis methods shall be used to
determine whether a significant increase over background
values has occurred.  Monitoring data must be statistically
analyzed after validated results from each sampling and
analysis event are received.

     The statistical performance standards provide a means
to limit the possibility of making false conclusions from
the monitoring data.  The specified error level of 0.01 for
individual well comparisons for probability of Type I error
(indication of contamination when it is not present or false
positive) essentially means that the analysis is predicting
with 99-percent confidence that no significant increase in
contaminant levels is evident when in fact no increase is
present.  Non-detect results must be treated in an
appropriate manner or their influence on the statistical
method may invalidate the statistical conclusion. 
Non-detect results are discussed in greater detail later in
this section.

     
     Multiple Well Comparisons

     If more than two wells (background and downgradient
combined) are screened in the same stratigraphic unit, then
the appropriate statistical comparison method is a multiple
well comparison using the ANOVA procedure.  The parametric
ANOVA procedure assumes that the data from each well group
come from the same type (e.g., Normal) of distribution with
possibly different mean concentrations.  The ANOVA tests for
a difference in means.  If there are multiple background
wells, one should consider the possibility of trying to pool
these background data into one group.  Such an increase in
sample size often allows for more accurate statistical
comparisons, primarily because better information is known
about the background concentrations as a whole. 
Downgradient wells should not be pooled, as stated in the
regulations.  Ground-water monitoring data tend to follow a
log normal distribution (USEPA, 1989), and usually need to
be transformed prior to applying a parametric ANOVA
procedure.  By conducting a log transformation, ground-water
monitoring data will generally be converted to a normal
distribution.  By applying a Shapiro-Wilk test, probability
plots, or other normality tests on the residuals (errors)
from the ANOVA procedure, the normality of the transformed
data can be determined.  In addition, data variance for each
well in the comparison must be approximately equivalent;
this condition can be checked using Levene's or Bartlett's
test.  These tests are provided in USEPA (1992b) and USEPA
(1989).

     If the transformed data do not conform to the normality
assumption, a nonparametric ANOVA procedure may be used. 
The nonparametric statistical procedures do not depend as
much on the mathematical properties of a specified
distribution.  The nonparametric equivalent to the
parametric ANOVA is the Kruskal-Wallis test, which analyzes
variability of the average ranks of the data instead of the
measurements themselves.

     If the data display seasonality (regular, periodic, and
time-dependent increases or decreases in parameter values),
a two-way ANOVA procedure should be used.  If the
seasonality can be corrected, a one-way ANOVA procedure may
still be appropriate.  Methods to treat seasonality are
described in USEPA (1989).  

     ANOVA procedures attempt to determine whether different
wells have significantly different average concentrations of
constituents.  If a difference is indicated, the ANOVA test
is followed by a multiple comparisons procedure to
investigate which specific wells are different among those
tested.  The overall experiment-wise significance level of
the ANOVA must be kept to a minimum of 0.05, while the
minimum significance level of each individual comparison
must be set at 0.01.  USEPA (1992b) provides alternative
methods that can be used when the number of individual
contrasts to be tested is very high.


     Tolerance and Prediction Intervals

     Two types of statistical intervals are often
constructed from data:  tolerance intervals and prediction
intervals.  A comprehensive discussion of these intervals is
provided in USEPA 1992b.  Though often confused, the
interpretations and uses of these intervals are quite
distinct.  A tolerance interval is designed to contain a
designated proportion of the population (e.g., 95 percent of
all possible sample measurements).  Because the interval is
constructed from sample data, it also is a random interval. 
And because of sampling fluctuations, a tolerance interval
can contain the specified proportion of the population only
with a certain confidence level.

     Tolerance intervals are very useful for ground-water
data analysis because in many situations one wants to ensure
that at most a small fraction of the compliance well sample
measurements exceed a specific concentration level (chosen
to be protective of human health and the environment).

     Prediction intervals are constructed to contain the
next sample value(s) from a population or distribution with
a specified probability.  That is, after sampling a
background well for some time and measuring the
concentration of an analyte, the data can be used to
construct an interval that will contain the next analyte
sample or samples (assuming the distribution has not
changed).  Therefore, a prediction interval will contain a
future value or values with specified probability. 
Prediction intervals can also be constructed to contain the
average of several future observations.

     In summary, a tolerance interval contains a proportion
of the population, and a prediction interval contains one or
more future observations.  Each has a probability statement
or "confidence coefficient" associated with it.  It should
be noted that these intervals assume that the sample data
used to construct the intervals are normally distributed.

     
     Individual Well Comparisons

     When only two wells (e.g., a single background and a
single compliance point well) are being compared, owners or
operators should not perform the parametric or nonparametric
ANOVA.  Instead, a parametric t-test, such as Cochran's
Approximation to the Behrens-Fisher Students' t-test, or a
nonparametric test should be performed.  When a single
compliance well group is being compared to background data
and a nonparametric test is needed, the Wilcoxin Rank-Sum
test should be performed.  These tests are discussed in more
detail in standard statistical references and in USEPA
(1992b).


     Intra-Well Comparisons

     Intra-well comparisons, where data of one well are
evaluated over time, are useful in evaluating trends in
individual wells and for identifying seasonal effects in the
data.  The intra-well comparison methods do not compare
background data to compliance data.  Where some existing
facilities may not have valid background data, however,
intra-well comparisons may represent the only valid
comparison available.  In the absence of a true background
well, several monitoring events may be required to determine
trends and seasonal fluctuations in ground-water quality.  

     Control charts may be used for intra-well comparisons
but are only appropriate for uncontaminated wells.  If a
well is intercepting a release, then it is already in an
"out-of-control" state, which violates the principal
assumption underlying control chart procedures.  Time series
analysis (i.e., plotting concentrations over time) is
extremely useful for identifying trends in monitoring data. 
Such data may be adjusted for seasonal effects to aid in
assessing the degree of change over time.  Guidance for and
limitations of intra-well comparison techniques are provided
in USEPA (1989) and USEPA (1992b).


     Treatment of Non-Detects

     The treatment of data below the detection limit of the
analytical method (non-detects) used depends on the number
or percentage of non-detects and the statistical method
employed.  Guidance on how to treat non-detects is provided
in USEPA (1992b).

     
5.10 DETECTION MONITORING PROGRAM 40 CFR Section 258.54

     5.10.1    Statement of Regulation

     (a)  Detection  monitoring is required at MSWLF units
at all ground-water monitoring wells defined under Sections
258.51(a)(1) and (a)(2) of this part.  At a minimum, a
detection monitoring program must include the monitoring for
the constituents listed in Appendix I of this part.  

     1)   The Director of an approved State may delete any
          of the Appendix I monitoring parameters for a
          MSWLF unit if it can be shown that the removed
          constituents are not reasonably expected to be in
          or derived from the waste contained in the unit.

     2)   The Director of an approved State may establish an
          alternative list of inorganic indicator parameters
          for a MSWLF unit, in lieu of some or all of the
          heavy metals (constituents 1-15 in Appendix I), if
          the alternative parameters provide a reliable
          indication of inorganic releases from the MSWLF
          unit to the ground water.  In determining
          alternative parameters, the Director shall
          consider the following factors:  

     (i)  The types, quantities, and concentrations of
constituents in wastes managed at the MSWLF unit;

     (ii)  The mobility, stability, and persistence of waste
constituents or their reaction products in the unsaturated
zone beneath the MSWLF unit;

     (iii)  The detectability of indicator parameters, waste
constituents, and reaction products in the ground water; and

     (iv)  The concentration or values and coefficients of
variation of monitoring parameters or constituents in the
background ground-water.

     (b)  The monitoring frequency for all constituents
listed in Appendix I, or the alternative list approved in
accordance with paragraph (a)(2), shall be at least
semiannual during the active life of the facility (including
closure) and the post-closure period.  A minimum of four
independent samples from each well (background and
downgradient) must be collected and analyzed for the
Appendix I constituents, or the alternative list approved in
accordance with paragraph (a)(2), during the first
semiannual sampling event.  At least one sample from each
well (background and downgradient) must be collected and
analyzed during subsequent semiannual sampling events.  The
Director of an approved State may specify an appropriate
alternative frequency for repeated sampling and analysis for
Appendix I constituents, or the alternative list approved in
accordance with paragraph (a)(2), during the active life
(including closure) and the post-closure care period.  The
alternative frequency during the active life (including
closure) shall be no less than annual.  The alternative
frequency shall be based on consideration of the following
factors:

     1)   Lithology of the aquifer and unsaturated zone;

     2)   Hydraulic conductivity of the aquifer and
          unsaturated zone;

     3)   Ground-water flow rates;

     4)   Minimum distance between upgradient edge of the
          MSWLF unit and downgradient monitoring well screen
          (minimum distance of travel); and

     5)   Resource value of the aquifer.

          (c)  If the owner or operator determines, pursuant
to Section 258.53(g) of this part, that there is a
statistically significant increase over background for one
or more of the constituents listed in Appendix I or the
alternative list approved in accordance with paragraph
(a)(2), at any monitoring well at the boundary specified
under Section 258.51(a)(2), the owner or operator:

     (1)  Must, within 14 days of this finding, place a
notice in the operating record indicating which constituents
have shown statistically significant changes from background
levels, and notify the State Director that this notice was
placed in the operating record; and

     (2)  Must establish an assessment monitoring program
meeting the requirements of Section 258.55 of this part
within 90 days, except as provided for in paragraph (3)
below.

     (3)  The owner/operator may demonstrate that a source
other than a MSWLF unit caused the contamination or that the
statistically significant increase resulted from error in
sampling, analysis, statistical evaluation, or natural
variation in ground-water quality.  A report documenting
this demonstration must be certified by a qualified
ground-water scientist or approved by the Director of an
approved State and be placed in the operating record.  If a
successful demonstration is made and documented, the owner
or operator may continue detection monitoring as specified
in this section.  If after 90 days, a successful
demonstration is not made, the owner or operator must
initiate an assessment monitoring program as required in
Section 258.55.


     5.10.2  Applicability

     Except for the small landfill exemption and the no
migration demonstration, detection monitoring is required at
existing MSWLF units, lateral expansions of units, and new
MSWLF units.  Monitoring must occur at least semiannually at
both background wells and downgradient well locations.  The
Director of an approved State may specify an alternative
sampling frequency.  Monitoring parameters must include all
Appendix I constituents unless an alternative list has been
established by the Director of an approved State.

     During the first semiannual monitoring event, the owner
or operator must collect at least four independent
ground-water samples from each well and analyze the samples
for all constituents in the Appendix I or alternative list. 
Each subsequent semiannual event must include, at a minimum,
the collection and analysis of one sample from all wells. 
The monitoring requirement continues throughout the active
life of the landfill and the post-closure care period.

     If an owner or operator determines that a statistically
significant increase over background has occurred for one or
more Appendix I constituents (or constituents on an
alternative list), a notice must be placed in the facility
operating record (see Table 5-2).  The owner or operator
must notify the State Director within 14 days of the
finding.  Within 90 days, the owner or operator must
establish an assessment monitoring program conforming to the
requirements of Section 258.55.  

     If evidence exists that a statistically significant
increase is due to factors unrelated to the unit, the owner
or operator may make a demonstration to this effect to the
Director of an approved State or place a certified
demonstration in the operating record.  The potential
reasons for an apparent statistical increase may include:

     *    A contaminant source other than the landfill unit

     *    A natural variation in ground-water quality

     *    An analytical error

     *    A statistical error

     *    A sampling error.  

     The demonstration that one of these reasons is
responsible for the statistically significant increase over
background must be certified by a qualified ground-water
scientist or approved by the Director of an approved State. 
If a successful demonstration is made and documented, the
owner or operator may continue detection monitoring.

     If a successful demonstration is not made within 90
days, the owner or operator must initiate an assessment
monitoring program.  A flow chart for a detection monitoring
program in a State whose program has not been approved by
EPA is provided in Figure 5-5.


***********************************************************
                         FIGURE 5-5

                Detection Monitoring Program
                          [Graphic]
***********************************************************


     5.10.3    Technical Considerations

     If there is a statistically significant increase over
background during detection monitoring for one or more
constituents listed in Appendix I of Part 258 (or an
alternative list of parameters in an approved State), the
owner or operator is required to begin assessment
monitoring.  The requirement to conduct assessment
monitoring will not change, even if the Director of an
approved State allows the monitoring of geochemical
parameters in lieu of some or all of the metals listed in
Appendix I.  If an owner or operator suspects that a
statistically significant increase in a geochemical
parameter is caused by natural variation in ground-water
quality or a source other than a MSWLF unit, a demonstration
to this effect must be documented in a report to avoid
proceeding to assessment monitoring.

     
     Independent Sampling for Background

     The ground-water monitoring requirements specify that
four independent samples be collected from each well to
establish background during the first semiannual monitoring
event.  This is because almost all statistical procedures
are based on the assumption that samples are independent of
each other.  In other words, independent samples more
accurately reflect the true range of natural variability in
the ground water, and statistical analyses based on
independent samples are more accurate.  Replicate samples,
whether field replicates or lab splits, are not
statistically independent measurements.

     It may be necessary to gather the independent samples
over a range of time sufficient to account for seasonal
differences.  If seasonal differences are not taken into
account, the chance for false positives increases
(monitoring results indicate a release, when a release has
not occurred).  The sampling interval chosen must ensure
that sampling is being done on different volumes of ground
water.  To determine the appropriate interval between sample
collection events that will ensure independence, the owner
or operator can determine the site's effective porosity,
hydraulic conductivity, and hydraulic gradient and use this
information to calculate ground-water velocity (USEPA,
1989).  Knowing the velocity of the ground water should
enable an owner/operator to establish an interval that
ensures the four samples are being collected from four
different volumes of water.  For additional information on
establishing sampling interval, see Statistical Analysis of
Groundwater  Monitoring  Data  at RCRA Facilities - Interim
Final Guidance, (USEPA, 1989).


     Alternative List/Removal of Parameters

     An alternative list of Appendix I constituents may be
allowed by the Director of an approved State.  The
alternative list may use geochemical parameters, such as pH
and specific conductance, in place of some or all of the
metals (Parameters 1 through 15) in Appendix I.  These
alternative parameters must provide a reliable indication of
inorganic releases from the MSWLF unit to ground water.  The
option of establishing an alternative list applies only to
Parameters 1 through 15 of Appendix I.  The list of
ground-water monitoring parameters must include all of the
volatile organic compounds (Appendix I, Parameters 16
through 62).

     A potential problem in substituting geochemical
parameters for metals on the alternative list is that many
of the geochemical parameters are naturally occurring. 
However, these parameters have been used to indicate
releases from MSWLF units.  Using alternative geochemical
parameters is reasonable in cases where natural background
levels are not high enough to mask the detection of a
release from a MSWLF unit.  The decision to use alternative
parameters also should consider natural spatial and temporal
variability in the geochemical parameters.

     The types, quantities, and concentrations of wastes
managed at the MSWLF unit play an important role in
determining whether removal of parameters from Appendix I is
appropriate.  If an owner or operator has definite knowledge
of the nature of wastes accepted at the facility, then
removal of constituents from Appendix I may be acceptable. 
Usually, a waste would have to be homogeneous to allow for
this kind of determination.  The owner or operator may
submit a demonstration that documents the presence or
absence of certain constituents in the waste.  The owner or
operator also would have to demonstrate that constituents
proposed for deletion from Appendix I are not degradation or
reaction products of constituents potentially present in the
waste.


     Alternative Frequency

     In approved States, 40 CFR Section 258.54(b) allows the
Director to specify an alternative frequency for
ground-water monitoring.  The alternative frequency is
applicable during the active life, including the closure and
the post-closure periods.  The alternative frequency can be
no less than annual.

     The need to vary monitoring frequency must be evaluated
on a site-specific basis.  For example, for MSWLF units
located in areas with low ground-water flow rates, it may be
acceptable to monitor ground water less frequently.  The
sampling frequency chosen must be sufficient to protect
human health and the environment.  Depending on the
ground-water flow rate and the resource value of the
aquifer, less frequent monitoring may be allowable or more
frequent monitoring may be necessary.  An approved State may
specify an alternative frequency for repeated sampling and
analysis of Appendix I constituents based on the following
factors:

     1)   Lithology of the aquifer and the unsaturated zone

     2)   Hydraulic conductivity of the aquifer and the
          unsaturated zone

     3)   Ground-water flow rates

     4)   Minimum distance between the upgradient edge of
          the MSWLF unit and the downgradient well screen

     5)   The resource value of the aquifer.

     Approved States also can set alternative frequencies
for monitoring during the post-closure care period based on
the same factors.


     Notification

     The notification requirement under 40 CFR Section
258.54(c) requires an owner or operator to 1) place a notice
in the operating record that indicates which constituents
have shown statistically significant increases and 2) notify
the State Director that the notice was placed in the
operating record.  The constituents can be from either
Appendix I or from an alternative list.


     Demonstrations of Other Reasons For Statistical
     Increase

     An owner or operator is allowed 90 days to demonstrate
that the statistically significant increase of a
contaminant/constituent was caused by statistical, sampling,
or analytical errors or by a source other than the landfill
unit.  The demonstration allowed in Section 258.54(c)(3) may
include:

     1)   A demonstration that the increase resulted from
          another contaminant source

     2)   A comprehensive audit of sampling, laboratory, and
          data evaluation procedures

     3)   Resampling and analysis to verify the presence and
          concentration of the constituents for which the
          increase was reported.

     A demonstration that the increase in constituent
concentration is the result of a source other than the MSWLF
unit should document that:

     *    An alternative source exists.

     *    Hydraulic connection exists between the
          alternative source and the well with the
          significant increase.

     *    Constituent(s) (or precursor constituents) are
          present at the alternative source or along the
          flow path from the alternative source prior to
          possible release from the MSWLF unit.

     *    The relative concentration and distribution of
          constituents in the zone of contamination are more
          strongly linked to the alternative source than to
          the MSWLF unit when the fate and transport
          characteristics of the constituents are
          considered.

     *    The concentration observed in ground water could
          not have resulted from the MSWLF unit given the
          waste constituents and concentrations in the MSWLF
          unit leachate and wastes, and site hydrogeologic
          conditions.

     *    The data supporting conclusions regarding the
          alternative source are historically consistent
          with hydrogeologic conditions and findings of the
          monitoring program.

     The demonstration must be documented, certified by a
qualified ground-water scientist, and placed in the
operating record of the facility.


     Demonstrations of Other Sources of Error

     A successful demonstration that the statistically
significant change is the result of an error in sampling,
analysis, or data evaluation may include the following:

     *    Clear indication of a transcription or calculation
          error

     *    Clear indication of a systematic error in analysis
          or data reduction

     *    Resampling, analysis, and evaluation of results

     *    Corrective measures to prevent the recurrence of
          the error and incorporation of these measures into
          the ground-water monitoring program.

     If resampling is necessary, the sample(s) taken must be
independent of the previous sample.  More than one sample
may be required to substantiate the contention that the
original sample was not representative of the ground-water
quality in the affected well(s).


5.11 ASSESSMENT MONITORING PROGRAM 40 CFR Section
     258.55(a)-(f)

     5.11.1    Statement of Regulation

     (a)  Assessment  monitoring is required whenever a
statistically significant increase over background has been
detected for one or more of the constituents listed in
Appendix I or in the alternate list approved in accordance
with Section 258.54(a)(2).

     (b)  Within 90 days of triggering an assessment
monitoring program, and annually thereafter, the owner or
operator must sample and analyze the ground water for all
constituents identified in Appendix II of this part.  A
minimum of one sample from each downgradient well must be
collected and analyzed during each sampling event.  For any
new constituent detected in the downgradient wells as a
result of the complete Appendix II analysis, a minimum of
four independent samples from each well (background and
downgradient) must be collected and analyzed to establish
background for the new constituents.  The Director of an
approved State may specify an appropriate subset of wells to
be sampled and analyzed for Appendix II constituents during
assessment monitoring.  The Director of an approved State
may delete any of the Appendix II monitoring parameters for
a MSWLF unit if it can be shown that the removed
constituents are not reasonably expected to be contained in
or derived from the waste contained in the unit.

     (c)  The Director of an approved State may specify an
appropriate alternate frequency for repeated sampling and
analysis for the full set of Appendix II constituents
required by Section 258.55(b) of this part, during the
active life (including closure) and post-closure care of the
unit considering the following factors:

     (1)  Lithology of the aquifer and unsaturated zone;

     (2)  Hydraulic conductivity of the aquifer and
unsaturated zone;

     (3)  Ground-water flow rates;

     (4)  Minimum distance between upgradient edge of the
MSWLF unit and downgradient monitoring well screen (minimum
distance of travel);

     (5)  Resource value of the aquifer; and

     (6)  Nature (fate and transport) of any constituents
detected in response to this section.

     (d)  After obtaining the results from the initial or
subsequent sampling events required in paragraph (b) of this
section, the owner or operator must:

     (1)  Within 14 days, place a notice in the operating
record identifying the Appendix II constituents that have
been detected and notify the State Director that this notice
has been placed in the operating record;

     (2)  Within 90 days, and on at least a semiannual basis
thereafter, resample all wells specified by Section 
258.51(a), conduct analyses for all constituents in Appendix
I to this Part or in the alternative list approved in
accordance with Section 258.54(a)(2), and for those
constituents in Appendix II that are detected in response to
paragraph (b) of this section, and record their
concentrations in the facility operating record.  At least
one sample from each well (background and downgradient) must
be collected and analyzed during these sampling events.  The
Director of an approved State may specify an alternative
monitoring frequency during the active life (including
closure) and the post closure period for the constituents
referred to in this paragraph.  The alternative frequency
for Appendix I constituents or the alternate list approved
in accordance with Section 258.54(a)(2) during the active
life (including closure) shall be no less than annual.  The
alternative frequency shall be based on consideration of the
factors specified in paragraph (c) of this section; 

     (3)  Establish background concentrations for any
constituents detected pursuant to paragraphs (b) or (d)(2)
of this section; and  

     (4)  Establish ground-water protection standards for
all constituents detected pursuant to paragraph (b) or
(d)(2) of this section.  The ground-water protection
standards shall be established in accordance with paragraphs
(h) or (i) of this section.

     (e)  If the concentrations of all Appendix II
constituents are shown to be at or below background values,
using the statistical procedures in Section 258.53(g), for 
two consecutive sampling events, the owner or operator must
notify the State Director of this finding and may return to
detection monitoring.

     (f)  If the concentrations of any Appendix II
constituents are above background values, but all
concentrations are below the ground-water protection
standard established under paragraphs (h) or (i) of this
section, using the statistical procedures in Section
258.53(g), the owner or operator must continue assessment
monitoring in accordance with this section.


     5.11.2    Applicability

     Assessment monitoring is required at all existing
units, lateral expansions, and new facilities whenever any
of the constituents listed in Appendix I are detected at a
concentration that is a statistically significant increase
over background values.  Figure 5-6 presents a flow chart
pertaining to applicability requirements.


************************************************************
                         FIGURE 5-6

                    Assessment Monitoring
                          [Graphic]
************************************************************


     Within 90 days of beginning assessment monitoring, the
owner or operator must resample all downgradient wells and
analyze the samples for all Appendix II constituents.  If
any new constituents are identified in this process, four
independent samples must be collected from all upgradient
and downgradient wells and analyzed for those new
constituents to establish background concentrations.  The
complete list of Appendix II constituents must be monitored
in each well annually for the duration of the assessment
monitoring program.  In an approved State, the Director may
reduce the number of Appendix II constituents to be analyzed
if it can be reasonably shown that those constituents are
not present in or derived from the wastes.  The Director of
an approved State may specify an appropriate subset of wells
to be included in the assessment monitoring program.  The
Director of an approved State also may specify an
alternative frequency for repeated sampling and analysis of
Appendix II constituents.  This frequency may be decreased
or increased based upon consideration of the factors in
Section 258.55(c)(1)-(6).  These options for assessment
monitoring programs are available only with the approval of
the Director of an approved State.

     Within 14 days of receiving the results of the initial
sampling for Appendix II constituents under assessment
monitoring,  the owner or operator must place the results in
the operating record and notify the State Director that this
notice has been placed in the operating record. 

     Within 90 days of receiving these initial results, the
owner or operator must resample all wells for all Appendix I
and detected Appendix II constituents.  This combined list
of constituents must be sampled at least semiannually
thereafter, and the list must be updated annually to include
any newly detected Appendix II constituents.

     Within the 90-day period, the owner or operator must
establish background values and ground-water protection
standards (GWPSs) for all Appendix II constituents detected. 
The requirements for determining GWPSs are provided in
Section 258.55(h).  If the concentrations of all Appendix II
constituents are at or below the background values after two
independent, consecutive sampling events, the owner or
operator may return to detection monitoring after
notification has been made to the State  Director.   If,
after  these two sampling events, any detected Appendix II
constituent is statistically above background but below the
GWPSs, the assessment monitoring program must be continued.  


     5.11.3    Technical Considerations

     The purpose of assessment monitoring is to evaluate the
nature and extent of contamination.  The assessment
monitoring program is phased.  The first phase assesses the
presence of additional assessment monitoring constituents
(Appendix II or a revised list designated by an approved
State) in all downgradient wells or in a subset of
ground-water monitoring wells specified by the Director of
an approved State.  If concentrations of all Appendix II
constituents are at or below background values using the
statistical procedures in Section 258.53(g) for two
consecutive sampling periods, then the owner or operator can
return to detection monitoring.  

     Following notification of a statistically significant
increase of any Appendix I constituent above background, the
owner or operator has 90 days to develop and implement the
assessment monitoring program.  Implementation of the
program involves sampling downgradient monitoring wells for
ground water passing the relevant point of compliance for
the unit (i.e., the waste management unit boundary or
alternative boundary specified by the Director of an
approved State).  Downgradient wells are identified in
Section 258.51(a)(2).  Initiation of assessment monitoring
does not stop the detection monitoring program.  Section
258.55(d)(2) specifies that analyses must continue for all
Appendix I constituents on at least a semiannual basis. 
Within the 90-day period, the owner or operator must collect
at least one sample from each downgradient well and analyze
the samples for the Appendix II parameters.  If a
downgradient well has detectable quantities of a new
Appendix II constituent, four independent samples must be
collected from all background and downgradient wells to
establish background for the new constituent(s).  The date,
well locations, parameters detected, and their
concentrations must be documented in the operating record of
the facility, and the State Director must be notified within
14 days of the initial detection of Appendix II parameters. 
On a semiannual basis thereafter, both background and
downgradient wells must be sampled for all Appendix II
constituents.


     Alternative List

     In an approved State, the Director may delete Appendix
II parameters that the owner or operator can demonstrate
would not be anticipated at the facility.  A demonstration
would be based on a characterization of the wastes contained
in the unit and an assessment of the leachate constituents. 
Additional information on the alternative list can be found
in Section 5.10.3.


     Alternative Frequency

     The Director of an approved State may specify an
alternate sampling frequency for the entire Appendix II list
for both the active and post-closure periods of the
facility.  The decision to change the monitoring frequency
must consider: 

     1)   Lithology of the aquifer and unsaturated zone;

     2)   Hydraulic conductivity of the aquifer and
          unsaturated zone;

     3)   Ground-water flow rates;

     4)   Minimum distance of travel (between the MSWLF unit
          edge to downgradient monitoring wells); and

     5)   Nature (fate and transport) of the detected
          constituents.

     The Director of an approved State also may allow an
alternate frequency, other than semiannual, for the
monitoring of Appendix I and detected Appendix II
constituents.

     The monitoring frequency must be sufficient to allow
detection of ground-water contamination.  If contamination
is detected early, the volume of ground water contaminated
will be smaller and the required remedial response will be
less burdensome.  Additional information on the alternate
frequency can be found in Section 5.10.3.  

     In an approved State, the Director may specify a subset
of wells that can be monitored for Appendix II constituents
to confirm a release and track the plume of contamination
during assessment monitoring.  The owner or operator should
work closely with the State in developing a monitoring plan
that targets the specific areas of concern, if possible. 
This may represent a substantial cost savings, especially at
large facilities for which only a very small percentage of
wells showed exceedances above background.  The use of a
subset of wells likely will be feasible only in cases where
the direction and rate of flow are relatively constant.


5.12 ASSESSMENT MONITORING PROGRAM 40 CFR Section 258.55(g)

     5.12.1    Statement of Regulation

     (g)  If one or more Appendix II constituents are
detected at statistically significant levels above the
ground-water protection standard established under
paragraphs (h) or (i) of this section in any sampling event,
the owner or operator must, within 14 days of this finding,
place a notice in the operating record identifying the
Appendix II constituents that have exceeded the ground-water
protection standard and, notify the State Director and all
appropriate local government officials that the notice has
been placed in the operating record.  The owner or operator
also:

     (1) (i)  Must characterize the nature and extent of the
release by installing additional monitoring wells as
necessary;

     (ii)  Must install at least one additional monitoring
well at the facility boundary in the direction of
contaminant migration and sample this well in accordance
with Section 258.55(d)(2);

     (iii)  Must notify all persons who own the land or
reside on the land that directly overlies any part of the
plume of contamination if contaminants have migrated
off-site if indicated by sampling of wells in accordance
with Section 258.55(g)(i); and

     (iv)  Must initiate an assessment of corrective
measures as required by Section 255.56 of this part within
90 days; or

     (2)  May demonstrate that a source other than a MSWLF
unit caused the contamination, or that the statistically
significant increase resulted from error in sampling,
analysis, statistical evaluation, or natural variation in
ground-water quality.  A report documenting this
demonstration must be certified by a qualified ground-water
scientist or approved by the Director of an approved State
and placed in the operating record.  If a successful
demonstration is made the owner or operator must continue
monitoring in accordance with the assessment monitoring
program pursuant to Section 258.55, and may return to
detection monitoring if the Appendix II constituents are
below background as specified in Section 258.55(e).  Until a
successful demonstration is made, the owner or operator must
comply with Section 258.55(g) including initiating an
assessment of corrective measures. 


     5.12.2    Applicability

     This requirement applies to facilities in assessment
monitoring and is applicable during the active life,
closure, and post-closure care periods.

     5.12.3    Technical Considerations

     If an Appendix II constituent(s) exceeds a GWPS in any
sampling event, the owner or operator must notify the State
Director within 14 days and place a notice of these findings
in the operating record of the MSWLF facility.  In addition,
the owner or operator must:

     1)   Characterize the lateral and vertical extent of
          the release or plume by installing and sampling an
          appropriate number of additional monitoring wells

     2)   Install at least one additional downgradient well
          at the facility property boundary in the direction
          of migration of the contaminant plume and sample
          that well for all Appendix II compounds initially
          and thereafter, in conformance with the assessment
          monitoring program

     3)   Notify all property owners whose land overlies the
          suspected plume, if the sampling of any property
          boundary well(s) indicates that contaminants have
          migrated offsite

     4)   Initiate an assessment of corrective measures, as
          required by Section 258.56, within 90 days.

     In assessment monitoring, the owner or operator may
demonstrate that a source other than the MSWLF unit caused
the contamination or that the statistically significant
increase was the result of an error in sampling, analysis,
statistical evaluation, or natural variation in ground-water
quality.  The demonstration must be certified by a qualified
ground-water scientist or approved by the Director of an
approved State.  Until a successful demonstration is made,
the owner or operator must comply with Section 258.55(g) and
initiate assessment of corrective measures.  If the
demonstration is successful, the owner or operator must
return to assessment monitoring and may return to the
detection program provided that all Appendix II constituents
are at or below background for two consecutive sampling
periods.

     
     Release Investigation

     If the GWPS is exceeded, a series of actions must be
taken.  These actions are described in the next several
paragraphs.  The owner or operator must investigate the
extent of the release by installing additional monitoring
wells and obtaining additional ground-water samples.  The
investigation should identify plume geometry, both laterally
and vertically.  Prior to such field activities, records of
site operation and maintenance activities should be reviewed
to identify possible release locations within the landfill
and whether such releases are expected to be transient
(e.g., one time release due to repaired liner) or long-term. 
Due to the presence of dissolved ionic constituents, such as
iron, magnesium, calcium, sodium, potassium, chloride,
sulfate, and carbonate, typically associated with MSWLF unit
leachates, geophysical techniques, including resistivity and
terrain conductivity, may be useful in defining the plume. 
Characterizing the nature of the release should include a
description of the rate and direction of contaminant
migration and the chemical and physical characteristics of
the contaminants.


     Property Boundary Monitoring Well

     At least one monitoring well must be installed at the
facility boundary in the direction of contaminant migration.
Additional wells may be required to delineate the plume. 
Monitoring wells at the facility boundary should be screened
to monitor all stratigraphic units that could be
preferential pathways for contaminant migration in the
uppermost aquifer.  In some cases, this may require
installation of nested wells or individual wells screened at
several discrete intervals.  The well installed at the
facility boundary must be sampled semiannually or at an
alternative frequency determined by the Director of an
approved State.  The initial sample must be analyzed for all
Appendix II constituents.


     Notification of Adjoining Residents and  Property
     Owners

     If ground-water monitoring indicates that contamination
has migrated offsite, the owner or operator must notify
property owners or residents whose land surface overlies any
part of the contaminant release.  Although the requirement
does not describe the contents of the notice, it is expected
that the notice could include the following items:

     *    Date of detected release

     *    Chemical composition of release

     *    Reference to the constituent(s), reported
          concentration(s), and the GWPS

     *    Representatives of the MSWLF facility with whom to
          discuss the finding, including their telephone
          numbers

     *    Plans and schedules for future activities

     *    Interim recommendations or remedies to protect
          human health and the environment.


     Demonstrations of Other Sources of Error

     The owner or operator may demonstrate that the source
of contamination was not the MSWLF unit.  This demonstration
is discussed in Section 5.10.3.
     

     Return to Detection Monitoring

     A facility conducting assessment monitoring may return
to detection monitoring if the concentrations of all
Appendix II constituents are at or below background levels
for two consecutive sampling periods using the statistical
procedures in Section 258.53(g).  The requirement that
background concentrations must be maintained for two
consecutive sampling events will reduce the possibility that
the owner or operator will fail to detect contamination or
an increase in a concentration of a hazardous constituent
when one actually exists.  The Director of an approved State
can establish an alternative time period (Section 258.54(b).

     
5.13 ASSESSMENT MONITORING PROGRAM 40 CFR Section
     258.55(h)-(j)

     5.13.1    Statement of Regulation

     (h)  The owner or operator must establish a
ground-water protection standard for each Appendix II
constituent detected in the ground water.  The ground-water
protection standard shall be:

     (1)  For constituents for which a maximum contaminant
level (MCL) has been promulgated under Section 1412 of the
Safe Drinking Water Act (codified) under 40 CFR Part 141,
the MCL for that constituent; 

     (2)  For constituents for which MCLs have not been
promulgated, the background concentration for the
constituent established from wells in accordance with
Section 258.51(a)(1); or

     (3)  For constituents for which the background level is
higher than the MCL identified under subparagraph (1) above 
or health based levels identified under Section
258.55(i)(1), the background concentration.

     (i)  The Director of an approved State may establish an
alternative ground-water protection standard for
constituents for which MCLs have not been established. 
These ground-water protection standards shall be appropriate
health based levels that satisfy the following criteria:

     (1)  The level is derived in a manner consistent with
Agency guidelines for assessing the health risks of
environmental pollutants (51 FR 33992, 34006, 34014, 34028);

     (2)  The level is based on scientifically valid studies
conducted in accordance with the Toxic Substances Control
Act Good Laboratory Practice Standards (40 CFR Part 792) or
equivalent;

     (3)  For carcinogens, the level represents a
concentration associated with an excess lifetime cancer risk
level (due to continuous lifetime exposure) with the 1 x
10^-4 to 1 x 10^-6 range; and

     (4)  For systemic toxicants, the level represents a
concentration to which the human population (including
sensitive subgroups) could be exposed to on a daily basis
that is likely to be without appreciable risk of deleterious
effects during a lifetime.  For purposes of this subpart,
systemic toxicants include toxic chemicals that cause
effects other than cancer or mutation.

     (j)  In establishing ground-water protection standards
under paragraph (i), the Director of an approved State may
consider the following:

     (1)  Multiple contaminants in the ground water;

     (2)  Exposure threats to sensitive environmental
receptors; and

     (3)  Other site-specific exposure or potential exposure
to ground water. 


     5.13.2    Applicability

     The criteria for establishing GWPSs are applicable to
all facilities conducting assessment monitoring where any
Appendix II constituents have been detected.  The owner or
operator must establish a GWPS for each Appendix II
constituent detected.

     If the constituent has a promulgated  maximum
contaminant level (MCL), then the GWPS is the MCL.  If no
MCL has been published for a given Appendix II constituent,
the background concentration of the constituent becomes the
GWPS.  In cases where the background concentration is higher
than a promulgated MCL, the GWPS is set at the background
level.

     In approved States, the Director may establish an
alternative GWPS for constituents for which MCLs have not
been established.  Any alternative GWPS must be health-based
levels that satisfy the criteria in Section 258.55(i).  The
Director may also consider any of the criteria identified in
Section 258.55(j).  In cases where the background
concentration is higher than the health-based levels, the
GWPS is set at the background level.


     5.13.3    Technical Considerations

     For each Appendix II constituent detected, a GWPS must
be established.  The GWPS is to be set at either the MCL or
background.  Where the background concentration is higher
than the MCL, then the GWPS is established at background.

     Directors of approved States have the option of
establishing an alternative GWPS for constituents without
MCLs.  This alternative GWPS must be an appropriate
health-based level, based on specific criteria.  These
levels must:

     *    Be consistent with EPA health risk assessment
          guidelines

     *    Be based on scientifically valid studies

     *    Be within a risk range of 1x10^-4 to 1x10^-6 for
          carcinogens

     *    For systemic toxicants (causing effects other than
          cancer or mutations), be a concentration to which
          the human population could be exposed on a daily
          basis without appreciable risk of deleterious
          effects during a lifetime.

     The health-based GWPS may be established considering
the presence of more than one constituent, exposure to
sensitive environmental receptors, and other site-specific
exposure to ground water.  Risk assessments to establish the
GWPS must consider cumulative effects of multiple pathways
to receptors and cumulative effects on exposure risk of
multiple contaminants.  Guidance and procedures for
establishing a health-based risk assessment may be found in
Guidance on Remedial Actions for Contaminated Groundwater at
Superfund Sites, (USEPA, 1988).

     
5.14 ASSESSMENT OF CORRECTIVE MEASURES 40 CFR Section 258.56

     5.14.1    Statement of Regulation

     (a)  Within 90 days of finding that any of the
constituents listed in Appendix II have been detected at a
statistically significant level exceeding the ground-water
protection standards defined under Section 258.55(h) and (i)
of this part, the owner or operator must initiate an
assessment of corrective measures. Such an assessment must
be completed within a reasonable period of time.

     (b)  The owner or operator must continue to monitor in
accordance with the assessment monitoring program as
specified in Section 258.55.

     (c)  The assessment shall include an analysis of the
effectiveness of potential corrective measures in meeting
all of the requirements and objectives of the remedy as
described under Section 258.57, addressing at least the
following:

     (1)  The performance, reliability, ease of
implementation, and potential impacts of appropriate
potential remedies, including safety impacts, cross-media
impacts, and control of exposure to any residual
contamination;

     (2)  The time required to begin and complete the
remedy;

     (3)  The costs of remedy implementation; and

     (4)  The institutional requirements such as State or
local permit requirements or other environmental or public
health requirements that may substantially affect
implementation of the remedy(s).

     (d)  The owner or operator must discuss the results of
the corrective measures assessment, prior to the selection
of remedy, in a public meeting with interested and affected
parties.


     5.14.2    Applicability

     An assessment of corrective measures must be conducted
whenever any Appendix II constituents are detected at
statistically significant levels exceeding the GWPS.  The
assessment of corrective measures must be initiated within
90 days of the finding.  During the initiation of an
assessment of corrective measures, assessment monitoring
must be continued.  The assessment of corrective measures
must consider performance (including potential impacts),
time, and cost aspects of the remedies.  If implementation
requires additional State or local permits, such
requirements should be identified.  Finally, the results of
the corrective measures assessment must be discussed in a
public meeting with interested and affected parties.


     5.14.3    Technical Considerations

     An assessment of corrective measures is site-specific
and will vary significantly depending on the design and age
of the facility, the completeness of the facility's
historical records, the nature and concentration of the
contaminants found in the ground water, the complexity of
the site hydrogeology, and the facility's proximity to
sensitive receptors.  Corrective measures are generally
approached from two directions: 1) identify and remediate
the source of contamination and 2) identify and remediate
the known contamination.  Because each case will be
site-specific, the owner or operator should be prepared to
document that, to the best of his or her technical and
financial abilities, a diligent effort has been made to
complete the assessment in the shortest time practicable.

     The factors listed in Section 258.56(c)(1) must be
considered in assessing corrective measures.  These general
factors are discussed below in terms of source evaluation,
plume delineation, ground-water assessment, and corrective
measures assessment.


     Source Evaluation

     As part of the assessment of corrective measures, the
owner or operator will need to identify the nature of the
source of the release.  The first step in this
identification is a review of all available site information
regarding facility design, wastes received, and onsite
management practices.  For newer facilities, this may be a
relatively simple task.  However, at some older facilities,
detailed records of the facility's history may not be as
well documented, making source definition more difficult. 
Design, climatological, and waste-type information should be
used to evaluate the duration of the release, potential
seasonal effects due to precipitation (increased
infiltration and leachate generation), and possible
constituent concentrations.  If source evaluation is able to
identify a repairable engineering condition that likely
contributed to the cause of contamination (e.g., unlined
leachate storage ponds, failed cover system, leaky leachate
transport pipes, past conditions of contaminated storm
overflow), such information should be considered as part of
the assessment of corrective measures.  

     Existing site geology and hydrogeology information,
ground-water monitoring results, and topographic and
cultural information must be documented clearly and
accurately.  This information may include soil boring logs,
test pit and monitoring well logs, geophysical data, water
level elevation data, and other information collected during
facility design or operation.  The information should be
expressed in a manner that will aid interpretation of data. 
Such data may include isopach maps of the thickness of the
upper aquifer and important strata, isoconcentration maps of
contaminants, flow nets, cross-sections, and contour maps. 
Additional guidance on data interpretation that may be
useful in a source evaluation is presented in RCRA Facility
Investigation Guidance:  Volume I -Development of an RFI
Work Plan and General Considerations for RCRA Facility
Investigations, (USEPA 1989a), RCRA Facility Investigation
Guidance:  Volume IV - Case Study Examples, (USEPA 1989d),
and Practical Guide For Assessing and Remediating
Contaminated Sites (USEPA 1989e).


     Plume Delineation

     To effectively assess corrective measures, the lateral
and vertical extent of contamination must be known.  When it
is determined that a GWPS is exceeded during the assessment
monitoring program, it may be necessary to install
additional wells to characterize the contaminant plume(s). 
At least one additional well must be added at the property
boundary in the direction of contaminant migration to allow
timely notification to potentially affected parties if
contamination migrates offsite.

     The following circumstances may require additional
monitoring wells:

     *    Facilities that have not determined the horizontal
          and vertical extent of the contaminant plume

     *    Locations where the subsurface is heterogeneous or
          where ground-water flow patterns are difficult to
          establish

     *    Mounding associated with MSWLF units.

     Because the requirements for additional monitoring are
site-specific, the regulation does not specifically
establish cases where additional wells are necessary or
establish the number of additional wells that must be
installed.

     During the plume delineation process, the owner or
operator is not relieved from continuing the assessment
monitoring program.

     The rate of plume migration and the change in
contaminant concentrations with time must be monitored to
allow prediction of the extent and timing of impact to
sensitive receptors.  The receptors may include users of
both ground-water and surface water bodies where
contaminated ground water may be discharged.  In some cases,
transfer of volatile compounds from ground water to the soil
and to the air may provide an additional migration pathway. 
Information regarding the aquifer characteristics (e.g.,
hydraulic conductivity, storage coefficients, and effective
porosity) should be developed for modeling contaminant
transport if sufficient data are not available.  Anisotropy
and heterogeneity of the aquifer must be evaluated, as well
as magnitude and duration of source inputs, to help explain
present and predicted plume configuration.

     Currently, most treatment options for ground-water
contamination at MSWLF units involve pump and treat or
in-situ biological technologies (bio-remediation).  The cost
and duration of treatment depends on the size of the plume,
the pumping characteristics of the aquifer, and the chemical
transport phenomena.  Source control and ground-water flow
control measures to reduce the rate of contaminant migration
should be included in the costs of any remedial activity
undertaken.  Ground-water modeling of the plume may be
initiated to establish the following:

     *    The locations and pumping rates of withdrawal
          and/or injection wells

     *    Predictions of contaminant concentrations at
          exposure points

     *    Locations of additional monitoring wells

     *    The effect that source control options may have on
          ground-water remediation

     *    The effects of advection and dispersion,
          retardation, adsorption, and other attenuation
          processes on the plume dimensions and contaminant
          concentrations.

     Any modeling effort must consider that simulations of
remedial response measures and contaminant transport are
based on many necessary simplifying assumptions, which
affect the accuracy of the model.  These assumptions include
boundary conditions, the degree and spatial variability of
anisotropy, dispersivity, effective porosity, stratigraphy,
and the algorithms used to solve contaminant transport
equations.  Model selection should be appropriate for the
amount of data available, and the technical uncertainty of
the model results must be documented by a sensitivity
analysis on the input parameters.  A sensitivity analysis is
generally done after model calibration by varying one input
parameter at a time over a realistic range and then
evaluating changes in model output.  For additional
information on modeling, refer to the Further Information
Section of Chapter 5.0 and the RCRA Facility Investigation
Guidance:  Volume II - Soil, Groundwater and Subsurface Gas
Releases (USEPA, 1989b).


     Ground-Water Assessment

     To assess the potential effectiveness of corrective
measures for ground-water contamination, the following
information is needed:

     *    Plume definition (includes the types,
          concentration, and spatial distribution of the
          contaminants)

     *    The amenability of the contaminants to specific
          treatment and potential for contaminants to
          interfere with treatability

     *    Fate of the contaminants (whether chemical
          transformations have, are, or may be occurring,
          and the degree to which the species are sorbed to
          the geologic matrix)

     *    Stratigraphy and hydraulic properties of the
          aquifer

     *    Treatment concentration goals and objectives.

     The owner or operator should consider whether immediate
measures to limit further plume migration (e.g., containment
options) or measures to minimize further introduction of
contaminants to ground water are necessary.

     The process by which a remedial action is undertaken
will generally include the following activities:

     *    Hydrogeologic investigation, which may include
          additional well installations, detailed vertical
          and lateral sampling to characterize the plume,
          and core sampling to determine the degree of
          sorption of constituents on the geologic matrix

     *    Risk assessment, to determine the impact on
          sensitive receptors, which may include
          identification of the need to develop treatment
          goals other than GWPSs

     *    Literature and technical review of treatment
          technologies considered for further study or
          implementation

     *    Evaluation of costs of different treatment options

     *    Estimation of the time required for completion of
          remediation under the different treatment options

     *    Bench-scale treatability studies conducted to
          assess potential effectiveness of options

     *    Selection of technology(ies) and proposal
          preparation for regulatory and public review and
          comment

     *    Full-scale pilot study for verification of
          treatability and optimization of the selected
          technology

     *    Initiation of full-scale treatment technology with
          adjustments, as necessary

     *    Continuation of remedial action until treatment
          goals are achieved.


     Corrective Measures Assessment

     To compare different treatment options, substantial
amounts of technical information must be assembled and
assessed.  The objective of this information-gathering task
is to identify the following items for each treatment
technology:

     *    The expected performance of individual approaches

     *    The time frame when individual approaches can
          realistically be implemented

     *    The technical feasibility of the remediation,
          including new and innovative technologies,
          performance, reliability and ease of
          implementation, safety and cross media impacts

     *    The anticipated time frame when remediation should
          be complete

     *    The anticipated cost of the remediation, including
          capital expenditures, design, ongoing engineering,
          and monitoring of results

     *    Technical and financial capability of the owner or
          operator to successfully complete the remediation

     *    Disposal requirements for treatment residuals

     *    Other regulatory or institutional requirements,
          including State and local permits, prohibitions,
          or environmental restrictions that may affect the
          implementation of the proposed remedial activity.

     The performance objectives of the corrective measures
should be considered in terms of source reduction, cleanup
goals, and cleanup time frame.  Source reduction would
include measures to reduce or stop further releases and may
include the repair of existing facility components (liner
systems, leachate storage pond liners, piping systems, cover
systems), upgrading of components (liners and cover
systems), or premature closure in extreme cases.  The
technology proposed as a cleanup measure should be the best
available technology, given the practicable capability of
the owner or operator.

     The technologies identified should be reliable, based
on their previous performance; however, new innovative
technologies are not discouraged if they can be shown, with
a reasonable degree of confidence, to be reliable.  

     Because most treatment processes, including
biorestoration, potentially produce byproducts or release
contaminants to different media (e.g., air stripping of
volatile compounds), the impacts of such potential releases
must be evaluated.  Releases to air may constitute a worker
health and safety concern and must be addressed as part of
the alternatives assessment process.  Other cross media
impacts, including transfer of contaminants from soils to
ground water, surface water, or air, should be assessed and
addressed in the assessment of corrective actions.  Guidance
for addressing air and soil transport and contamination is
provided in USEPA (1989b) and USEPA (1989c).

     Analyses should be conducted on treatment options to
determine whether or not they are protective of human health
and the environment.  Environmental monitoring of exposure
routes (air and water) may necessitate health monitoring for
personnel involved in treatment activities if unacceptable
levels of exposure are possible.  On a case-by-case basis,
implementation plans may require both forms of monitoring.

     The development and screening of individual corrective
measures requires an understanding of the physio-chemical
relationships and interferences between the constituents and
the sequence of treatment measures that must be implemented. 
Proper sequencing of treatment methods to produce a feasible
remedial program must be evaluated to avoid interference
between the presence of some constituents and the effective
removal of the targeted compound.  In addition, screening
and design parameters of potential treatment options should
be evaluated in the early stages of conceptual development
and planning to eliminate technically unsuitable treatment
methods.  In general, selection of an appropriate treatment
method will require the experience of a qualified
professional and will necessitate a literature review of the
best available treatment technologies.  

     Numerous case studies and published papers from
scientific and engineering technical journals exist on
treatability of specific compounds and groups of related
compounds.  Development of new technologies and refinements
of technologies have been rapid.  A compendium of available
literature that includes treatment technologies for organic
and inorganic contaminants, technology selection, and other
sources of information (e.g., literature search data bases
pertinent to ground-water extraction, treatment, and
responses) is included in Practical Guide for Assessing and
Remediating Contaminated Sites (USEPA, 1989e).

     The general approach to remediation typically includes
active restoration, plume containment, and source control as
discussed below.  The selection of a particular approach or
combination of approaches must be based on the corrective
action objectives.  These general approaches are outlined in
Table 5-3.  It should be emphasized that the objective of a
treatment program should be to restore ground water to
pre-existing conditions or to levels below applicable
ground-water protection standards while simultaneously
restricting further releases of contaminants to ground
water.  Once treatment objectives are met, the chance of
further contamination should be mitigated to the extent
practicable.  


************************************************************
TABLE 5-3

MISSING
************************************************************


     Active Restoration

     Active restoration generally includes ground-water
extraction, followed by onsite or offsite wastewater
treatment.  Offsite wastewater treatment may include sending
the contaminated water to a local publicly owned treatment
works (POTW) or to a facility designed to treat the
contaminants of concern.  Treated ground water may be
re-injected, sent to a local POTW, or discharged to a local
body of surface water, depending on local, State, and
Federal requirements.  Typical treatment practices that may
be implemented include coagulation and precipitation of
metals, chemical oxidation of a number of organic compounds,
air stripping to remove volatile organic compounds, and
biological degradation of other organics.  

     The rate of contaminant removal from ground water will
depend on the rate of ground-water removal, the cation
exchange capacity of the soil, and partition coefficients of
the constituents sorbed to the soil (USEPA, 1988).  As the
concentration of contaminants in the ground water is
reduced, the rate at which constituents become partitioned
from the soil to the aqueous phase may also be reduced.  The
amount of flushing of the aquifer material required to
remove the contaminants to an acceptable level will
generally determine the time frame required for restoration. 
This time frame is site-specific and may last indefinitely.

     In-situ methods may be appropriate for some sites,
particularly where pump and treat technologies create
serious adverse effects or where it may be financially
prohibitive.  In-situ methods may include biological
restoration requiring pH control, addition of specific
micro-organisms, and/or addition of nutrients and substrate
to augment and encourage degradation by indigenous microbial
populations.  Bioremediation requires laboratory
treatability studies and pilot field studies to determine
the feasibility and the reliability of full-scale treatment. 
It must be demonstrated that the treatment techniques will
not cause degradation of a target chemical to another
compound that has unacceptable health risks and that is
subject to further degradation.  Alternative in-situ methods
may also be designed to increase the effectiveness of
desorption or removal of contaminants from the aquifer
matrix.  Such methodologies may include steam stripping,
soil flushing, vapor extraction, thermal desorption, and
solvent washing, and extraction for removal of strongly
sorbed organic compounds.  These methods also may be used in
unsaturated zones where residual contaminants may be sorbed
to the geologic matrix during periodic fluctuations of the
water table.  Details of in-situ methods may be found in
several sources: USEPA (1988); USEPA (1985); and Eckenfelder
(1989).


     Plume Containment

     The purpose of plume containment is to limit the spread
of the contaminants.  Methods to contain plume movement
include passive hydraulic barriers, such as grout curtains
and slurry walls, and active gradient control systems
involving pumping wells and french drains.  The types of
aquifer characteristics that favor plume containment
include:

     *    Water naturally unsuited for human consumption 

     *    Contaminants present in low concentration with low
          mobility

     *    Low potential for exposure to contaminants and low
          risk associated with exposure

     *    Low transmissivity and low future user demand.

     Often, it may be advantageous for the owner or operator
to consider implementing ground-water controls to inhibit
further contamination or the spread of contamination.  If
ground-water pumping is considered for capturing the leading
edge of the contaminant plume, the contaminated water must
be managed in conformance with all applicable Federal and
State requirements.  Under most conditions, it is necessary
to consult with the regulatory agencies prior to initiating
an interim remedial action.


     Source Control

     Source control measures should be evaluated to limit
the migration of the plume.  The regulation does not limit
the definition of source control to exclude any specific
type of remediation.  Remedies must control the source to
reduce or eliminate further releases by identifying and
locating the cause of the release (e.g., torn geomembrane,
excessive head due to blocked leachate collection system,
leaking leachate collection well or pipe).  Source control
measures may include the following:

     *    Modifying the operational procedures (e.g.,
          banning specific wastes or lowering the head over
          the leachate collection system through more
          frequent leachate removal)

     *    Undertaking more extensive and effective
          maintenance activities (e.g., excavate waste to
          repair a liner failure or a clogged leachate
          collection system)

     *    Preventing additional leachate generation that may
          reach a liner failure (e.g., using a portable or
          temporary rain shelter during operations or
          capping landfill areas that contribute to leachate
          migrating from identified failure areas).

     In extreme cases, excavation of deposited wastes for
treatment and/or offsite disposal may be considered.


     Public Participation

     The owner or operator is required to hold a public
meeting to discuss the results of the corrective action
assessment and to identify proposed remedies. 
Notifications, such as contacting local public agencies,
town governments, and State/Tribal governments, posting a
notice in prominent local newspapers, and making radio
announcements are effective.  The public meeting should
provide a detailed discussion of how the owner or operator
has addressed the factors at Section 258.56(c)(1)-(4).

     
5.15 SELECTION OF REMEDY 40 CFR Section 258.57 (a)-(b)

     5.15.1    Statement of Regulation

     (a)  Based on the results of the corrective measure
assessment conducted under Section 258.56, the owner or
operator must select a remedy that, at a minimum, meets the
standards listed in paragraph (b) below.  The owner or
operator must notify the State Director, within 14 days of
selecting a remedy, that a report describing the selected
remedy has been placed in the operating record and how it
meets the standards in paragraph (b) of this section.

     (b)  Remedies must:

     (1)  Be protective of human health and the environment;

     (2)  Attain the ground-water protection standard as
specified pursuant to Sections 258.55(h) or (i);

     (3)  Control the source(s) of releases so as to reduce
or eliminate, to the maximum extent practicable, further
releases of Appendix II constituents into the environment
that may pose a threat to human health or the environment;
and

     (4)  Comply with standards for management of wastes as
specified in Section 258.58(d).


     5.15.2    Applicability

     These provisions apply to facilities that have been
required to perform corrective measures.  The selection of a
remedy is closely related to the assessment process and
cannot be accomplished unless a sufficiently thorough
evaluation of alternatives has been completed.  The process
of documenting the rationale for selecting a remedy requires
that a report be placed in the facility operating record
that clearly defines the corrective action objectives and
demonstrates why the selected remedy is anticipated to meet
those objectives.  The State Director must be notified
within 14 days of the placement of the report in the
operating records of the facility.  The study must identify
how the remedy will be protective of human health and the
environment, attain the GWPS (either background, MCLs, or,
in approved States, health-based standards, if applicable),
attain source control objectives, and comply with waste
management standards.


     5.15.3    Technical Considerations

     The final method selected for implementation must
satisfy the criteria in Section 258.57(b)(1)-(4).  The
report documenting the capability of the selected method to
meet these four criteria should include such information as:

     *    Theoretical calculations

     *    Comparison to existing studies and results of
          similar treatment case histories

     *    Bench-scale or pilot-scale treatability test
          results

     *    Waste management practices.

     The demonstration presented in the report must document
the alternative option selection process.

     
5.16 SELECTION OF REMEDY 40 CFR Section 258.57 (c)

     5.16.1    Statement of Regulation

     (c)  In selecting a remedy that meets the standards of
Section 258.57(b), the owner or operator shall consider the
following evaluation factors:

     (1)  The long- and short-term effectiveness and
protectiveness of the potential remedy(s), along with the
degree of certainty that the remedy will prove successful
based on consideration of the following:

     (i)  Magnitude of reduction of existing risks;

     (ii) Magnitude of residual risks in terms of likelihood
of further releases due to waste remaining following
implementation of a remedy;

     (iii) The type and degree of long-term management
required, including monitoring, operation, and maintenance;

     (iv) Short-term risks that might be posed to the
community, workers, or the environment during implementation
of such a remedy, including potential threats to human
health and the environment associated with excavation,
transportation, and redisposal or containment;

     (v)  Time until full protection is achieved;

     (vi) Potential for exposure of humans and environmental
receptors to remaining wastes, considering the potential
threat to human health and the environment associated with
excavation, transportation, redisposal, or containment;

     (vii)     Long-term reliability of the engineering and
institutional controls; and

     (viii) Potential need for replacement of the remedy.

     (2)  The effectiveness of the remedy in controlling the
source to reduce further releases based on consideration of
the following factors:

     (i)  The extent to which containment practices will
reduce further releases;

     (ii) The extent to which treatment technologies may be
used.

     (3)  The ease or difficulty of implementing a potential
remedy(s) based on consideration of the following types of
factors:

     (i)  Degree of difficulty associated with constructing
the technology;

     (ii) Expected operational reliability of the
technologies;

     (iii)  Need to coordinate with and obtain necessary
approvals and permits from other agencies;

     (iv) Availability of necessary equipment and
specialists; and

     (v)  Available capacity and location of needed
treatment, storage, and disposal services.

     (4)  Practicable capability of the owner or operator,
including a consideration of the technical and economic
capability.

     (5)  The degree to which community concerns are
addressed by a potential remedy(s).


     5.16.2    Applicability

     These provisions apply to facilities that are selecting
a remedy for corrective action.  The rule presents the
considerations and factors that the owner or operator must
evaluate when selecting the appropriate corrective measure.

     
     5.16.3    Technical Considerations

     The owner or operator must consider specific topics to
satisfy the performance criteria under selection of the
final corrective measure.  These topics must be addressed in
the report documenting the selection of a particular
corrective action. The general topic areas that must be
considered include the following:

     *    The anticipated long- and short-term effectiveness
          of the corrective action

     *    The anticipated effectiveness of source reduction
          efforts

     *    The ease or difficulty of implementing the
          corrective measure

     *    The technical and economic practicable capability
          of the owner or operator

     *    The degree to which the selected remedy will
          address concerns raised by the community.


     Effectiveness of Corrective Action

     In selecting the remedial action, the anticipated
long-term and short-term effectiveness should be evaluated. 
Long-term effectiveness focuses on the risks remaining after
corrective measures have been taken.  Short-term
effectiveness addresses the risks during construction and
implementation of the corrective measure.  Review of case
studies where similar technologies have been applied provide
the best measures to judge technical uncertainty, especially
when relatively new technologies are applied.  The
long-term, post-cleanup effectiveness may be judged on the
ability of the proposed remedy to mitigate further releases
of contaminants to the environment, as well as on the
feasibility of the proposed remedy to meet or exceed the
GWPSs.  The owner or operator must make a reasonable effort
to estimate and quantify risks, based on exposure pathways
and estimates of exposure levels and durations.  These
estimates include risks for both ground-water and
cross-media contamination.  

     The source control measures that will be implemented,
including excavation, transportation, re-disposal, and
containment, should be evaluated with respect to potential
exposure and risk to human health and the environment.  The
source control measures should be viewed as an integral
component of the overall corrective action.  Health
considerations must address monitoring risks to workers and
the general public and provide contingency plans should an
unanticipated exposure occur.  Potential exposure should
consider both long- and short-term cases before, during, and
after implementation of corrective actions.

     The time to complete the remedial activity must be
estimated, because it will have direct financial impacts on
the project management needs and financial capability of the
owner or operator to meet the remedial objectives.  The
long-term costs of the remedial alternatives and the
long-term financial condition of the owner or operator
should be reviewed carefully.  The implementation schedule
should indicate quality control measures to assess the
progress of the corrective measure.  

     The operational reliability of the corrective measures
should be considered.  In addition, the institutional
controls and management practices developed to assess the
reliability should be identified.  


     Effectiveness of Source Reduction

     Source control measures identified in previous sections
should be discussed in terms of their expected
effectiveness.  If source control consists of the removal
and re-disposal of wastes, the residual materials, such as
contaminated soils above the water table, should be
quantified and their potential to cause further
contamination evaluated.  Engineering controls intended to
upgrade or repair deficient conditions in landfill component
systems, including cover systems, should be quantified in
terms of anticipated effectiveness according to current and
future conditions.  This assessment may indicate to what
extent it is technically and financially practicable to make
use of existing technologies.  The decision against using a
certain technology may be based on health considerations and
the potential for unacceptable exposure(s) to both workers
and the public.


     Implementation of Remedial Action

     The ease of implementing the proposed remedial action
will affect the schedule and startup success of the remedial
action.  The following key factors need to be assessed:

     *    The availability of technical expertise

     *    Construction of equipment or technology

     *    The ability to properly manage and dispose of
          wastes generated by treatment

     *    The likelihood of obtaining local permits and
          public support for the proposed project.

     Technical considerations, including pH control,
ground-water extraction feasibility, or the ability to
inject nutrients, may need to be considered, depending on
the proposed treatment method.  Potential impacts, such as
potential cross-media contamination, need to be reviewed as
part of the overall feasibility of the project.

     The schedule of remedial activities should identify the
start and end points of the following periods:

     *    Permitting phase

     *    Construction and startup period, during which
          initial implementation success will be evaluated,
          including time to correct any unexpected problems

     *    Time when full-scale treatment will be initiated
          and duration of treatment period

     *    Implementation and completion of source control
          measures, including the time-frame for solving
          problems associated 
          with interim management and disposal of waste
          materials or treatment residuals.

     Items that require long lead times should be identified
early in the process and those tasks should be initiated
early to ensure that implementation occurs in the shortest
practicable period.  


     Practical Capability

     The owner or operator must be technically and
financially capable of implementing the chosen remedial
alternative and ensuring project completion, including
provisions for future changes to the remedial plan after
progress is reviewed.  If either technical or financial
capability is inadequate for a particular alternative, then
other alternatives with similar levels of protectiveness
should be considered for implementation.


     Community Concerns

     The public meetings held during assessment of
alternative measures are intended to elicit public comment
and response.  The owner or operator must, by means of
meeting minutes and a record of written comments, identify
which public concerns have been expressed and addressed by
corrective measure options.  In reality, the final remedy
selected and implemented will be one that the State
regulatory agency, the public, and the owner or operator
agree to.

     
5.17 SELECTION OF REMEDY 40 CFR Section 258.57 (d)

     5.17.1    Statement of Regulation

     (d)  The owner or operator shall specify as part of the
selected remedy a schedule(s) for initiating and completing
remedial activities.  Such a schedule must require the
initiation of remedial activities within a reasonable period
of time taking into consideration the factors set forth in
paragraphs (d) (1-8). The owner or operator must consider
the following factors in determining the schedule of
remedial activities:

     (1)  Extent and nature of contamination;

     (2)  Practical capabilities of remedial technologies in
achieving compliance with ground-water protection standards
established under Sections 258.55(g) or (h) and other
objectives of the remedy;

     (3)  Availability of treatment or disposal capacity for
wastes managed during implementation of the remedy;

     (4)  Desirability of utilizing technologies that are
not currently available, but which may offer significant
advantages over already available technologies in terms of
effectiveness, reliability, safety, or ability to achieve
remedial objectives;

     (5)  Potential risks to human health and the
environment from exposure to contamination prior to
completion of the remedy; 

     (6)  Resource value of the aquifer including:

     (i)  Current and future uses;

     (ii) Proximity and withdrawal rate of users;

     (iii)  Ground-water quantity and quality;

     (iv) The potential damage to wildlife, crops,
vegetation, and physical structures caused by exposure to
waste constituent;

     (v)  The hydrogeologic characteristic of the facility
and surrounding land;

     (vi) Ground-water removal and treatment costs; and

     (vii)  The cost and availability of alternative water
supplies.

     (7)  Practicable capability of the owner or operator.

     (8)  Other relevant factors.


     5.17.2    Applicability

     The requirements of Section 258.57(d) apply to owners
or operators of all new units, existing units, and laterally
expanded units at all facilities required to implement
corrective actions.  The requirements must be complied with
prior to implementing corrective measures. The owner or
operator must specify the schedule for remedial activities
based on the following considerations:

     *    The size and nature of the contaminated area at
          the time the corrective measure is to be
          implemented

     *    The practicable capabilities of the remedial
          technology selected

     *    Available treatment and disposal capacity

     *    Potential use of alternative innovative
          technologies not currently available

     *    Potential risks to human health and the
          environment existing prior to completion of the
          remedy

     *    Resource value of the aquifer

     *    The practicable capability of the owner/operator

     *    Other relevant factors.


     5.17.3    Technical Considerations

     The time schedule for implementing and completing the
remedial activity is influenced by many factors that should
be considered by the owner or operator.  The most critical
factor is the nature and extent of the contamination, which
significantly affects the ultimate treatment rate.  The size
of the treatment facility and the ground-water extraction
and injection rates must be balanced for system
optimization, capital resources, and remedial timeframe
objectives.  The nature of the contamination will influence
the degree to which the aquifer must be flushed to remove
adsorbed species.  These factors, which in part define the
practicable capability of the alternative (treatment
efficiency, treatment rate, and replenishment of
contaminants by natural processes), should be considered
when selecting the remedy.

     In addition, the rate at which treatment may occur may
be restricted by the availability or capacity to handle
treatment residues and the normal flow of wastes during
remediation.  Alternative residue treatment or disposal
capacity must be identified as part of the implementation
plan schedule.

     If contaminant migration is slow due to low transport
properties of the aquifer, additional time may be available
to evaluate the value of emerging and promising innovative
technologies.  The use of such technologies is not excluded
as part of the requirement to implement a remedial action as
soon as practicable.  Delaying implementation to increase
the availability of new technologies must be evaluated in
terms of achievable cleanup levels, ultimate cost,
additional environmental impact, and potential for increased
risk to sensitive receptors.  If a new technology clearly is
superior to existing options in attaining remediation
objectives, it may be appropriate to delay implementation. 
This may require that existing risks be controlled through
interim measures.

     In setting the implementation schedule, the owner or
operator should assess the risk to human health and the
environment within the timeframe of reaching treatment
objectives.  If the risk is unacceptable, considering
health-based assessments of exposure paths and exposure
limits, the implementation time schedule must be accelerated
or the selected remedy altered to provide an acceptable risk
level in a timely manner.

     Establishment of the schedule also may include
consideration of the resource value of the aquifer, as it
pertains to current and future use, proximity to users,
quality and quantity of ground water, agricultural value and
uses (irrigation water source or impact on adjacent
agricultural lands), and the availability of alternative
supplies of water of similar quantity and quality.  Based on
these factors, a relative assessment of the aquifer's
resource value to the local community can be established. 
Impacts to the resource and the degree of financial or
health-related distress by users should be considered.  The
implementation timeframe should attempt to minimize the loss
of value of the resource to users.  The possibility that
alternative water supplies will have to be developed as part
of the remedial activities may need to be considered.

     Because owners or operators may not be knowledgeable in
remediation activities, reliance on the owner or operator to
devise the schedule for remediation may be impracticable. 
In these instances, use of an outside firm to coordinate
remediation scheduling may be necessary.  Similarly,
development of a schedule for which the owner or operator
cannot finance, when other options exist that do allow for
owner or operator financing, should be prevented.


5.18 SELECTION OF REMEDY 40 CFR Section 258.57 (e)-(f)

     5.18.1    Statement of Regulation

     (e) The Director of an approved State may determine
that remediation of a release of an Appendix II constituent
from a MSWLF unit is not necessary if the owner or operator
demonstrates to the satisfaction of the Director of an
approved State that:

     (1)  The ground water is additionally contaminated by
substances that have originated from a source other than a
MSWLF unit and those substances are present in
concentrations such that cleanup of the release from the
MSWLF unit would provide no significant reduction in risk to
actual or potential receptors; or 

     (2)  The constituent(s) is present in ground water
that:

     (i)  Is not currently or reasonably expected to be a
potential source of drinking water; and

     (ii)  Is not hydraulically connected with waters to
which the hazardous constituents are migrating or are likely
to migrate in a concentration(s) that would exceed the
ground-water protection standards established under Section
258.55(h) or (i); or
     
     (3)  Remediation of the release(s) is technically
impracticable; or

     (4)  Remediation results in unacceptable cross-media
impacts.

     (f)  A determination by the Director of an approved
State pursuant to paragraph (e) above shall not affect the
authority of the State to require the owner or operator to
undertake source control measures or other measures that may
be necessary to eliminate or minimize further releases to
the ground water, to prevent exposure to the ground water,
or to remediate the ground water to concentrations that are
technically practicable and significantly reduce threats to
human health or the environment.


     5.18.2    Applicability

     The criteria under Section 258.57(e) and (f) apply in
approved States only.  Remediation of the release of an
Appendix II constituent may not be necessary if 1) a source
other than the MSWLF unit is partly responsible for the
ground-water contamination, 2) the resource value of the
aquifer is extremely limited, 3) remediation is not
technically feasible, or 4) remediation will result in
unacceptable cross-media impacts.  The Director may
determine that while total remediation is not required,
source control measures or partial remediation of ground
water to concentrations that are technically practicable and
significantly reduce risks is required.


     5.18.3    Technical Considerations

     There are four situations where an approved State may
not require cleanup of hazardous constituents released to
ground water from a MSWLF unit.  If sufficient evidence
exists to document that the ground water is contaminated by
a source other than the MSWLF unit, the Director of an
approved State may grant a waiver from implementing some or
all of the corrective measure requirements.  The owner or
operator must demonstrate that cleanup of a release from its
MSWLF unit would provide no significant reduction in risk to
receptors due to concentrations of constituents from the
other source.  

     A waiver from corrective measures also may be granted
if the contaminated ground water is not a current or
reasonably expected potential future drinking water source,
and it is unlikely that the hazardous constituents would
migrate to waters causing an exceedance of GWPS.  The owner
or operator must demonstrate that the uppermost aquifer is
not hydraulically connected with a lower aquifer.  The owner
or operator may seek an exemption if it can be demonstrated
that attenuation, advection/dispersion or other natural
processes can remove the threat to interconnected aquifers. 
The owner or operator may seek the latter exemption if the
contaminated zone is not a drinking water resource.  

     The Director of an approved State may waive cleanup
requirements if remediation is not technically feasible.  In
addition, the Director may wave requirements if remediation
results in unacceptable cross-media impacts.  A successful
demonstration that remediation is not technically feasible
must document specific facts that attribute to this
demonstration.  Technical impracticabilities may be related
to the accessibility of the ground water to treatment, as
well as the treatability of the ground water using
practicable treatment technologies.  If the owner or
operator can demonstrate that unacceptable cross-media
impacts are uncontrollable under a given remedial option
(e.g., movement in response to ground-water pumping or
release of volatile organics to the atmosphere) and that the
no action option is a less risky alternative, then the
Director of an approved State may determine that remediation
is not necessary.

     A waiver of remedial obligation does not necessarily
release the owner or operator from the responsibility of
conducting source control measures or minimal ground-water
remediation.  The State may require that source control be
implemented to the maximum extent practicable to minimize
future risk of releases of contaminants to ground water or
that ground water be treated to the extent technically
feasible.

     
5.19 IMPLEMENTATION OF THE CORRECTIVE  ACTION PROGRAM 40 CFR
     Section 258.58 (a)

     5.19.1    Statement of Regulation

     (a)  Based on the schedule established under Section
258.57(d) for initiation and completion of remedial
activities the owner/operator must:

     (1)  Establish and implement a corrective action
ground-water monitoring program that:

     (i)  At a minimum, meets the requirements of an
assessment monitoring program under Section 258.55;

     (ii) Indicates the effectiveness of the corrective
action remedy; and

     (iii)  Demonstrates compliance with ground-water
protection standard pursuant to paragraph (e) of this
section.

     (2)  Implement the corrective action remedy selected
under Section 258.57; and

     (3)  Take any interim measures necessary to ensure the
protection of human health and the environment.  Interim
measures should, to the greatest extent practicable, be
consistent with the objectives of and contribute to the
performance of any remedy that may be required pursuant to
Section 258.57.  The following factors must be considered by
an owner or operator in determining whether interim measures
are necessary:

     (i)  Time required to develop and implement a final
remedy;

     (ii) Actual or potential exposure of nearby populations
or environmental receptors to hazardous constituents;

     (iii)  Actual or potential contamination of drinking
water supplies or sensitive ecosystems;

     (iv) Further degradation of the ground water that may
occur if remedial action is not initiated expeditiously;

     (v)  Weather conditions that may cause hazardous
constituents to migrate or be released;

     (vi) Risks of fire or explosion, or potential for
exposure to hazardous constituents as a result of an
accident or failure of a container or handling system; and

     (vii) Other situations that may pose threats to human
health and the environment.


     5.19.2    Applicability

     These provisions apply to facilities that are required
to initiate and complete corrective actions.  

     The owner or operator is required to continue to
implement its ground water assessment monitoring program to
evaluate the effectiveness of remedial actions and to
demonstrate that the remedial objectives have been attained
at the completion of remedial activities.

     Additionally, the owner or operator must take any
interim actions to protect human health and the environment. 
The interim measures must serve to mitigate actual threats
and prevent potential threats from being realized while a
long-term comprehensive response is being developed.


     5.19.3    Technical Considerations

     Implementation of the corrective measures encompass all
activities necessary to initiate and continue remediation. 
The owner or operator must continue assessment monitoring to
anticipate whether interim measures are necessary, and to
determine whether the corrective action is meeting stated
objectives.  


     Monitoring Activities

     During the implementation period, ground-water
monitoring must be conducted to demonstrate the
effectiveness of the corrective action remedy.  If the
remedial action is not effectively curtailing further ground
water degradation or the spread of the contaminant plume,
replacement of the system with an alternative measure may be
warranted.  The improvement rate of the condition of the
aquifer must be monitored and compared to the cleanup
objectives.  It may be necessary to install additional
monitoring wells to more clearly evaluate remediation
progress.  Also, if it becomes apparent that the GWPS will
not be achievable technically, in a realistic time-frame,
the performance objectives of the corrective measure must be
reviewed and amended as necessary.


     Interim Measures

     If unacceptable potential risks to human health and the
environment exist prior to or during implementation of the
corrective action, the owner or operator is required to take
interim measures to protect receptors.  These interim
measures are typically short-term solutions to address
immediate concerns and do not necessarily address long-term
remediation objectives.  Interim measures may include
activities such as control of ground-water migration through
high-volume withdrawal of ground water or response to
equipment failures that occur during remediation (e.g.,
leaking drums). If contamination migrates offsite, interim
measures may include providing an alternative water supply
for human, livestock, or irrigation needs.  Interim measures
also pertain to source control activities that may be
implemented as part of the overall corrective action.  This
may include activities such as excavation of the source
material or in-situ treatment of the contaminated source. 
Interim measures should be developed with consideration
given to maintaining conformity with the objectives of the
final corrective action.  


5.20 IMPLEMENTATION OF THE CORRECTIVE ACTION PROGRAM 40 CFR
     Section 258.58 (b)-(d)

     5.20.1    Statement of Regulation

     (b)  An owner or operator may determine, based on
information developed after implementation of the remedy has
begun or other information, that compliance with
requirements of Section 258.57(b) are not being achieved
through the remedy selected.  In such cases, the owner or
operator must implement other methods or techniques that
could practicably achieve compliance with the requirements,
unless the owner or operator makes the determination under
Section 258.58(c).

     (c)  If the owner or operator determines that
compliance with requirements under Section 258.57(b) cannot
be practically achieved with any currently available
methods, the owner or operator must:

     (1)  Obtain certification of a qualified ground-water
specialist or approval by the Director of an approved State
that compliance with requirements under Section 258.57(b)
cannot be practically achieved with any currently available
methods;

     (2)  Implement alternate measures to control exposure
of humans or the environment to residual contamination, as
necessary to protect human health and the environment; and

     (3)  Implement alternate measures for control of the
sources of contamination, or for removal or decontamination
of equipment, units, devices, or structures that are:

     (i)  Technically practicable; and

     (ii) Consistent with the overall objective of the
remedy.

     (4)  Notify the State Director within 14 days that a
report justifying the alternative measures prior to
implementing the alternative measures has been placed in the
operating record.

     (d)  All solid wastes that are managed pursuant to a
remedy required under Section 258.57, or an interim measure
required under Section 258.58(a)(3), shall be managed in a
manner:

     (1)  That is protective of human health and the
environment; and

     (2)  That complies with applicable RCRA requirements.


     5.20.2    Applicability

     The requirements of the alternative measures are
applicable when it becomes apparent that the remedy selected
will not achieve the GWPSs or other significant objectives
of the remedial program (e.g., protection of sensitive
receptors).  In determining that the selected corrective
action approach will not achieve desired results, the owner
or operator must implement alternate corrective measures to
achieve the GWPSs.  If it becomes evident that the cleanup
goals are not technically obtainable by existing practicable
technology, the owner or operator must implement actions to
control exposure of humans or the environment from residual
contamination and to control the sources of contamination. 
Prior to implementing alternative measures, the owner or
operator must notify the Director of an approved State
within 14 days that a report justifying the alternative
measures has been placed in the operating record.  

     All wastes that are managed by the MSWLF unit during
corrective action, including interim and alternative
measures, must be managed according to applicable RCRA
requirements in a manner that is protective of human health
and the environment.


     5.20.3    Technical Considerations

     An owner or operator is required to continue the
assessment monitoring program during the remedial action. 
Through monitoring, the short and long term success of the
remedial action can be gauged against expected progress. 
During the remedial action, it may be necessary to install
additional ground-water monitoring wells or pumping or
injection wells to adjust to conditions that vary from
initial assessments of the ground-water flow system.  As
remediation progresses and data are compiled, it may become
evident that the remediation activities will not protect
human health and the environment, meet GWPSs, control
sources of contamination, or comply with waste management
standards.  The reasons for unsatisfactory results may
include:

     *    Refractory compounds that are not amenable to
          removal or destruction (detoxification)

     *    The presence of compounds that interfere with
          treatment methods identified for target compounds

     *    Inappropriately applied technology

     *    Failure of source control measures to achieve
          desired results

     *    Failure of ground-water control systems to achieve
          adequate containment or removal of contaminated
          ground water

     *    Residual concentrations above GWPSs that cannot be
          effectively reduced further because treatment
          efficiencies are too low

     *    Transformation or degradation of target compounds
          to different forms that are not amenable to
          further treatment by present or alternative
          technologies.

     The owner or operator should compare treatment
assumptions with existing conditions to determine if
assumptions adequately depict site conditions.  If
implementation occurred as designed, the owner or operator
should attempt to modify or upgrade existing remedial
technology to optimize performance and to improve treatment
effectiveness.  If the existing technology is found to be
unable to meet remediation objectives, alternative
approaches must be evaluated that could meet these
objectives while the present remediation is continued. 
During this re-evaluation period, the owner or operator may
suspend treatment only if continuation of remedial
activities clearly increases the threat to human health and
the environment.

     

5.21 IMPLEMENTATION OF THE CORRECTIVE ACTION PROGRAM 40 CFR
     Section 258.58 (e)-(g)

     5.21.1    Statement of Regulation

     (e)  Remedies selected pursuant to Section 258.57 shall
be considered complete when:

     (1)  The owner or operator complies with the
ground-water protection standards established under Sections
258.55(h) or (i) at all points within the plume of
contamination that lie beyond the ground-water monitoring
well system established under Section 258.51(a).

     (2)  Compliance with the ground-water protection
standards established under Sections 258.55(h) or (i) has
been achieved by demonstrating that concentrations of
Appendix II constituents have not exceeded the ground-water
protection standard(s) for a period of three consecutive
years using the statistical procedures and performance
standards in Section 258.53(g) and (h).  The Director of an
approved State may specify an alternative length of time
during which the owner or operator must demonstrate that
concentrations of Appendix II constituents have not exceeded
the ground-water protection standard(s) taking into
consideration:

     (i)  Extent and concentration of the release(s);

     (ii) Behavior characteristics of the hazardous
constituents in the ground water;

     (iii)  Accuracy of monitoring or modeling techniques,
including any seasonal, meteorological, or other
environmental variabilities that may affect the accuracy;
and

     (iv) Characteristics of the ground water.

     (3)  All actions required to complete the remedy have
been satisfied.

     (f)  Upon completion of the remedy, the owner or
operator must notify the State Director within 14 days that
a certification that the remedy has been completed in
compliance with the requirements of Section 258.58(e) has
been placed in the operating record.  The certification must
be signed by the owner or operator and by a qualified
ground-water specialist or approved by the Director of an
approved State.

     (g)  When, upon completion of the certification, the
owner or operator determines that the corrective action
remedy has been completed in accordance with the
requirements under paragraph (e) of this section, the owner
or operator shall be released from the requirements for
financial assurance for corrective action under Section
258.73.

     Section 258.59  [Reserved].


     5.21.2    Applicability

     These criteria apply to facilities conducting
corrective action.  Remedies are considered complete when,
after 3 consecutive years of monitoring (or an alternative
length of time as identified by the Director), the results
show significant statistical evidence that Appendix II
constituent concentrations are below the GWPSs.  Upon
completion of all remedial actions, the owner or operator
must certify to such, at which point the owner or operator
is released from financial assurance requirements.


     5.21.3  Technical Considerations

     The regulatory period of compliance is 3 consecutive
years at all points within the contaminant plume that lie
beyond the ground-water monitoring system unless the
Director of an approved State specifies an alternative
length of time.  Compliance is achieved when the
concentrations of Appendix II constituents do not exceed the
GWPSs for a predetermined length of time.  Statistical
procedures in Section 258.53 must be used to demonstrate
compliance with the GWPSs.

     The preferred statistical method for comparison is to
construct a 99 percent confidence interval around the mean
of the last 3 years of data and compare the upper limit of
the confidence interval to the GWPS.  An upper limit less
than the GWPS is considered significant evidence that the
standard is no longer being exceeded.  The confidence
interval must be based on the appropriate model describing
the distribution of the data.  

     Upon completion of the remedy, including meeting the
GWPS at all points within the contaminant plume, the owner
or operator must notify the State Director within fourteen
days that a certification that the remedy has been completed
has been placed in the operating record.  The certification
must be signed by the owner or operator and a qualified
ground-water scientist or approved by the Director of an
approved State.  Upon completion of the remedial action, in
accordance with Section 258.58(e), the owner or operator is
released from the financial assurance requirements
pertaining to corrective actions.

     The Director of an approved State may require an
alternate time period (other than 3 years) to demonstrate
compliance.  In determining an alternate period the Director
must consider the following:

     *    The extent and concentration of the release(s)

     *    The behavior characteristics (fate and transport)
          of the hazardous constituents in the ground water
          (e.g., mobility, persistence, toxicity, etc.)

     *    Accuracy of monitoring or modeling techniques,
          including any seasonal, meteorological or other
          environmental variabilities that may affect
          accuracy

     *    The characteristics of the ground water (e.g.,
          flow rate, pH, etc.).

     Consideration of these factors may result in an
extension or shortening of the time required to show
compliance with remediation objectives.


5.22 FURTHER INFORMATION

     5.22.1    References

     Aitchison, J., and J.A.C. Brown (1969).  "The Lognormal
Distribution"; Cambridge University Press; Cambridge.

     American Water Works Association (1984).  "Abandonment
of Test Holes, Partially Completed Wells and Completed
Wells."  Appendix I.  American Water Works Association
Standard for Water Wells, American Water Works Association,
Denver, CO, pp 45-47.

     Barari, A., and L.S. Hedges (1985).  "Movement of Water
in Glacial Till."  Proceedings of the 17th International
Congress of International Association of Hydrogeologists.

     Barcelona, M.J., J.A. Helfrich and E.E. Garske, (1985). 
"Sampling Tube Effects on Groundwater Samples"; Analytical
Chemistry 47(2):  460-464.

     Barcelona, M.J., J.P. Gibb, J.A. Helfrich, and E.E.
Garske, (1985b).  "Practical Guide for Ground-Water
Sampling," USEPA, Cooperative Agreement #CR-809966-01,
EPA/600/2-85/104, 169 pp.

     Barcelona, M.J., et al.  1990.  Contamination of Ground
Water:  Prevention, Assessment, Restoration.  Pollution
Technology Review No. 184, Noyes Data Corporation, Park
Ridge, NJ, 213 pp.

     Cantor, L.W., R.C. Knox, and D.M. Fairchild (1987). 
Ground-Water Quality Protection. Lewis Publishers, Inc.,
Chelsea, MI.

     Cooper, H.H., Jr., and C.E. Jacob (1946).  "A
Generalized Graphical Method for Evaluating Formation
Constants and Summarizing Well-Field History."  American
Geophys. Union Trans., V. 27, No. 4.

     Daniel, D.E., H.M. Liljestrand, G.P. Broderick, and
J.J. Bounders, Jr. (1988).  "Interaction of Earthen Linear
Materials with Industrial Waste Leachate in Hazardous Waste
and Hazardous Materials," Vol. 5, No. 2.

     Dixon, W.J. and F.J. Massey, Jr. (1969).  "Introduction
to Statistical Analysis"; 3rd Edition; McGraw-Hill Book Co.;
New York, New York.

     Driscoll, F.G., (1986).  "Groundwater and Wells";
Johnson and Johnson; St. Paul, Minnesota.

     Eckenfelder, W.W., Jr., (1989).  Industrial Water
Pollution Control.  McGraw-Hill, Inc., Second Edition.

     Fetter, C.W., Jr. (1980). Applied Hydrogeology. Charles
E. Merrill Publishing Co., Columbus, OH.

     Freeze, R.A. and J.A. Cherry, (1979).  Groundwater;
Prentice-Hall, Inc.; Englewood Cliffs, New Jersey.

     Gibbons, J.D., (1976).  "Nonparametric Methods for
Quantitative Analysis"; Holt, Rinehart, and Winston
Publishing Co.; New York, New York.

     Gilbert, R.O., (1987).  Statistical Methods for
Environmental Pollution Monitoring; Van Nostrand Reinhold
Co.; New York, New York.

     Heath, R.C. (1982). Basic Ground-Water Hydrology. U.S.
Geological Survey Water Supply Paper 2220, 84 pp.

     Hsieh, P.A., and S.P. Neuman (1985). "Field
Determination of the Three - Dimensional Hydraulic
Conductivity Teasor of Anisotropic Media." Water Resources
Research, V. 21, No. 11.

     Kearl, P.M., N.E. Korte, and T.A. Cronk.  1992. 
"Suggested Modifications to Ground Water Sampling Procedures
Based on Observations from the Colloidal Borescope." 
Ground-Water Monitoring Review, Spring, pp. 155-160.

     Kruseman, G.P., and N.A. de Ridder (1989). "Analysis
and Evaluation of Pumping Test Data," International
Institute for Land Reclamation and Improvement/ILRI,
Bulletin II, 4th Edition.

     Lamb, B. and T. Kinney (1989). "Decommissioning Wells -
Techniques and Pitfalls." Proceedings of the Third National
Outdoor Action Conference on Aquifer Restoration,
Ground-Water Monitoring and Geophysical Methods, NWWA, May
22-25, 1989, pp 217-228.

     McGlew, P.J. and J.E. Thomas (1984). "Determining
Contaminant Migration Pathways in Fractured Bedrock."
Proceedings of the Fifth National Conference on Management
of Uncontrolled Hazardous Waste Sites.

     McWhorter, D.B., and D.K. Sunada (1977). Ground-Water
Hydrology and Hydraulics. Water Resources Publications, Fort
Collins, CO.

     Miller, J.C. and J.N. Miller, (1986).  Statistics for
Analytical Chemistry; John Wiley and Sons; New York, New
York.

     Molz, F.J., O. Guven and J.G. Melville (1990). "A New
Approach and Methodologies for Characterizing the
Hydrogeologic Properties of Aquifers." EPA Project Summary. 
EPA 600/52-90/002.

     Molz, F.J., R.H. Norin, A.E. Hess, J.G. Melville, and
O. Guven (1989) "The Impeller Meter for Measuring Aquifer
Permeability Variations:  Evaluation and Comparison with
Other Tests." Water Resources Research, V 25, No. 7, pp
1677-1683.

     Puls, R.W. and R.M. Powell.  1992.  "Acquisition of
Representative Ground Water Quality Samples for Metals." 
Ground-Water Monitoring Review, Summer, pp. 167-176.

     Puls, R.W., R.M. Powell, D.A. Clark, and C.J. Paul. 
1991.  "Facilitated Transport of Inorganic Contaminants in
Ground Water:  Part II."  Colloidal Transport,
EPA/600/M-91/040, 12 pp.

     Puls, R.W., and M.J. Barcelona.  1989a.  "Filtration of
Ground Water Samples for Metals Analysis."  Hazardous Waste
and Hazardous Materials, v. 6, No. 4.

     Puls, R.W., and M.J. Barcelona.  1989b.  "Ground Water
Sampling for Metals Analysis."  USEPA Superfund Ground Water
Issue, EPA/504/4-89/001, 6 pp.

     Sevee, J. (1991). "Methods and Procedures for Defining
Aquifer Parameters," in D.M. Nielsen, ed., Practical
Handbook of Ground-Water Monitoring. Lewis Publishers,
Chelsea, MI.

     USEPA (1975).  Manual of Water Well Construction
Practices. USEPA Office of Water Supply, Report No.
EPA-570/9-75-001, 156 pp.

     USEPA, (1985).  "Handbook:  Remedial Action at Waste
Disposal Sites"; EPA/540/G-88/003; U.S. EPA; Office of
Emergency and Remedial Response; Washington, D.C.

     USEPA, (1986a).  "RCRA Groundwater Monitoring Technical
Enforcement Guidance Document"; Office of Solid Waste and
Emergency Response - 9950.1.
Note:  Office of Solid Waste, OSW, was renamed Office of Resource Conservation and Recovery, ORCR, on January 18, 2009

     USEPA, (1986b).  "Test Methods for Evaluating Solid
Waste - Physical/Chemical Methods"; EPA SW-846, 3rd edition;
PB88-239-233; U.S. EPA; Office of Solid Waste and Emergency
Response; Washington, D.C.

     USEPA, (1986c).  "Superfund Public Health Evaluation
Manual"; PB87-183-125; U.S. EPA; Office of Emergency and
Remedial Response; Washington, D.C. 20460.

     USEPA, (1986d).  "Superfund Risk Assessment Information
Directory"; PB87-188-918; U.S. EPA; Office of Emergency and
Remedial Response; Washington, D.C. 20460.

     USEPA, (1988).  "Guidance on Remedial Actions for
Contaminated Groundwater at Superfund Sites";  PB89-184-618;
U.S. EPA; Office of Emergency and Remedial Response;
Washington, D.C. 20460.

     USEPA, (1989).  "Statistical Analysis of Groundwater
Monitoring Data at RCRA Facilities-Interim Final Guidance";
EPA/530-SW-89-026; U.S. EPA; Office of Solid Waste;
Washington, D.C.
Note:  Office of Solid Waste, OSW, was renamed Office of Resource Conservation and Recovery, ORCR, on January 18, 2009

     USEPA, (1989a).  "RCRA Facility Investigation (RFI)
Guidance; Interim Final; Vol. I Development of an RFI Work
Plan and General Considerations for RCRA Facility
Investigations"; PB89-200-299;  U.S. EPA; Office of Solid
Waste; Washington, D.C.
Note:  Office of Solid Waste, OSW, was renamed Office of Resource Conservation and Recovery, ORCR, on January 18, 2009

     USEPA, (1989b).  "RCRA Facility Investigation (RFI)
Guidance; Interim Final; Vol. II - Soil, Ground Water and
Subsurface Gas Releases"; PB89-200-299;  U.S. EPA; Office of
Solid Waste; Washington, D.C.
Note:  Office of Solid Waste, OSW, was renamed Office of Resource Conservation and Recovery, ORCR, on January 18, 2009

     USEPA, (1989c).  "Criteria for Identifying Areas of
Vulnerable Hydrogeology Under the Resource Conservation and
Recovery Act, Interim Final. Appendix B -Ground-Water Flow
Net/Flow Line Construction and Analysis."

     USEPA, (1989d).  "RCRA Facility Investigation (RFI)
Guidance; Vol IV: Case Study Examples;" PB89-200-299;  U.S.
EPA; Office of Solid Waste; Washington, D.C.
Note:  Office of Solid Waste, OSW, was renamed Office of Resource Conservation and Recovery, ORCR, on January 18, 2009

     USEPA, (1989e).  "Practical Guide for Assessing and
Remediating Contaminated Sites - Draft"; U.S. EPA; Waste
Management Division, Office of Solid Waste, 401 M Street,
S.W.; Washington, D.C.  May 1989.
Note:  Office of Solid Waste, OSW, was renamed Office of Resource Conservation and Recovery, ORCR, on January 18, 2009

     USEPA, (1989f).  "Handbook of Suggested Practices for
the Design and Installation of Ground-Water Monitoring
Wells"; PB90-159-807; U.S EPA; Office of Research and
Development; Washington, D.C.

     USEPA, (1990).  "Handbook:  Groundwater Vol I;"
EPA/625/6-90/016a; U.S. EPA; Office of Research and
Development; Cincinnati, Ohio.

     USEPA, (1991).  "Handbook:  Groundwater Vol II";
EPA/625/6-90/016b; U.S. EPA; Office of Research and
Development; Cincinnati, Ohio.

     USEPA, (1992a).  "RCRA Ground-Water Monitoring:  Draft
Technical Guidance"; EPA/530-R-93-001; U.S. EPA; Office of
Solid Waste; Washington, D.C. PB93-139-350.
Note:  Office of Solid Waste, OSW, was renamed Office of Resource Conservation and Recovery, ORCR, on January 18, 2009

     USEPA, (1992b).  "Statistical Training Course for
Ground-Water Monitoring Data Analysis", EPA/530-R-93-003;
U.S. EPA; Office of Solid Waste; Washington, D.C.
Note:  Office of Solid Waste, OSW, was renamed Office of Resource Conservation and Recovery, ORCR, on January 18, 2009

     USEPA, (1992c).  "User Documentation of the
Ground-Water Information Tracking System (GRITS) with
Statistical Analysis Capability, GRITSTAT Version 4.2;"
EPA/625/11-91/002; USEPA Office of Research and Development,
Center for Environmental Research, ORD Publications.

     USGS, (1989).  "Chapter C2, Computer Model of
Two-Dimensional Solute Transport and Dispersion in
Groundwater";  L.F. Konikow and J.D. Bredehoeft; Book 7;
U.S. Geological Survey; U.S. Department of Interior.

     Way, S.C., and C.R. McKee (1982).  "In-Situ
Determination of Three-Dimensional Aquifer Permeabilities."
Ground Water, V. 20, No. 5.