United States r- Offr i of Water &
Environmental Protection Waste Management
U6C. 1980
Agency Washington D.C. 20460
Solid Waste
v>EPA Procedures Manual
for Ground Water Monitoring
at Solid Waste Disposal
Facilities
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2d printing, December 1980, with new cover
An environmental protection publication (SW-611) in the solid
waste management series. Mention of commercial products does
not constitute endorsement by the U.S. Government. Editing
and technical content of this report were the responsibilities
of the Systems Management Division of the Office of Solid Waste,
Single copies of this publication are available from the
Solid Waste Information Distribution Office, U.S. Environmental
protection Agency, Cincinnati, Ohio 45268.
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ACKNOWLEDGMENT
This manual was prepared under Contract No. 68-01-3210 from the
U.S. Environmental Protection Agency, Office of Solid Waste, Washington,
D.C. Burnell Vincent, EPA Project Manager, played an active role in
the manual's preparation.
The manual was written by Dennis Fenn and Eugene Cocozza of Wehran
Engineering Corporation and John Isbister, Olin Braids, Bruce Yare, and
Paul Roux of Geraghty and Miller, Inc.
\ review panel consisting of solid waste representatives from state
regulatory agencies and other experts in the field was created especially
for this contract. The authors wish to recognize the valuable input
and guidance from the following members of the panel:
William Bentley
Joseph Boren
Gary Merritt
William Bucciarelli
Larry Burch
Herbert Iwahiro
Thomas Clark
Jack Moore
Bernhardt V. Lind
Charles Lynn
Jack McMillan
John Reinhardt
Thomas Tiesler
Avery Wells
Burnell Vincent
Dirk Brunner
Les McMillion
David Rickert
Jay Lehr
Warren Gregory
John Pacey
William Anderson
Nev York
Connecticut
Pennsylvania
Pennsylvania
California
California
Illinois
Illinois
New Jersey
Kansas
Mississippi
Wisconsin
Tennessee
Washington
U.S. Environmental Protection Agency
U.S. Environmental Protection Agency
Environmental Protection Agency,
Nevada
U.S. Geological Survey
National Water Well Association
National Solid Waste Management
Association
Emcon Associates
ASCE
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Special thanks are also extended to editor, Ms. Linda W. Barringer, B.A.
Houghton College; Stephini Vozza, Jean Fennessy, Lisa Schafer, and Mary
Ring for their typing assistance; and Alberto Funes and his assistant,
Edurne Hoppenstedt, for preparing all the graphics.
The assistance and cooperation extended by numerous other individuals
not mentioned above who were contacted on matters related to this manual
is gratefully acknowledged.
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CONTENTS
Chapter Page
ACKNOWLEDGEMENTS i
1 EXECUTIVE REVIEW 1
1.1 Introduction . 1
1.2 Purposes and Objectives of Monitoring 2
1.3 Types and Limitations of Monitoring 4
1.4 Fate of Indicators 6
1.4.1 Contaminants Not Usually Considered Toxic ... 6
1.4.2 Contaminants Usually Considered Toxic 1
1.4.3 Geohydrology 7
1.5 Cost of Monitoring
1.6 Implementation of an Effective Program 9
1.6.1 Assessment of Existing Land Disposal Sites .. 9
1.6.2 Review and Orientation of Present State
Program 10
1.6.3 Establish Monitoring Networks and Data
Needs for Land Disposal Sites H
1.7 Step Outline of Monitoring Procedures H
1.7.1 Step 1 — Initial Site Inspection H
1.7.1.1 Nature of the Solid Waste H
1.7.1.2 Areal Extent and Thickness of the Landfill .. 12
1.7.1.3 Pretreatment and In-Place Treatment of
Solid Waste 12
1.7.1.4 Landfilling Procedures , 12
1.7.1.5 Rate of Landfilling and Age of
Solid Waste 12
1.7.1.6 Liners and Covers 12
1.7.1.7 Visual Survey of Topography and Geology 1-*
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Chapter Paoe
1.7.1.8 Ground-Water Use (Preliminary) 13
1.7.2 Step 2 — Preliminary Investigations 13
1.7.2. \ Existing Data 13
1.7.2.2 Preliminary Site Investigation 13
1.7.3 Step 3 — Definition of the Hydrogeologic
Setting „ 14
1.7.3.1 Surficial Geology 14
1.7.3.2 Bedrock Geology 14
1.7.3.3 Ground Water „ 15
1.7.3.4 Determination of Existing Water Quality 16
1.7.3.5 Determination of the Rate of Leachate
Generation 16
1.7.4 Step 4 — Determination of the Pollution
Potential of the Landfill 16
1.7.5 Establish the Monitoring Program 17
1.7.5.1 Selection of the Monitoring S:' . s 17
1.7.5.2 Determination of Monitoring Objectives 17
1.7.5.3 Establishing the Monitoring Methods and
Procedures Necessary to Accomplish
Obj ectives , , 18
1.7.5.4 Establishing a Management Program , 19
1.8 Examples of Landfill Contamination
Problems 19
1.8.1 Scenario 1 — A Landfill Contamination
Study . . . 19
1.8.2 Scenario 2 — A Ground-Water Contamination
Problem 29
1.8.2.1 Landfill Investigations 35
1.8.2.2 Abatement Program I 36
1.8.2.3 Abatement Program II 37
MONITORING NETWORKS 39
2.1 Monitoring Approaches 39
2.1.1 Data Requisites for Monitoring
Network Design 40
2.1.2 Monitoring Networks ior Sanitary Lanatills .. 4C
2.1.3 The Effects of Aquifer Characteristics on
Monitoring Networks 43
2.2 Monitoring Network Types . . 44
2.2.1 Type I (Intergranular Porosity A^ui'.Vrs) .... 44
2.2.2 Type II (Fracture Porosity Aqt-ifers) 49
2.2.3 Type III (Solution Porosity Aquifers) 52
2.3 Leachate Movement in Differed '.ly'drogeclogic
Settings 52
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Chapter Page
MONITORING AND WELL TECHNOLOGY 71
3.1 Zone of Aeration 72
3.1.1 Soil Analysis 72
3.1.2 Pressure Vacuum Lysimeters 75
3.1.2.1 Methodology 75
3.1.2.2 Implementation 78
3.1.3 Trench Lysimeters 80
3.1.3.1 Methodology 80
3.1.3.2 Implementation 80
3.2 Zone of Saturation 82
3.2.1 Well Screened or Open Over a Single
Verticle Interval 82
3.2.1.1 Methodology 82
3.2.1.2 Implementation 84
3.2.2 Piezometers 86
3.2.2.1 Methodology 86
3.2.2.2 Implementation 88
3.2.3 Well Clusters 90
3.2.3.1 Methodology 91
3.2.3.2 Implementation 93
3.2.4 Single Well — Multiple Sample Points 97
3.2.4.1 Methodology 97
3.2.4.2 Implementation 100
3.2.5 Sampling During Drilling 103
3.2.5.1 Methodology 103
3.2.5.2 Implementation 104
3.2.6 Pore-Water Extraction from Core Samples .... 108
3.2.6.1 Methodology 108
3.2.5.2 Implementation 109
3.2.7 Summary of Cost Estimates 115
3.2.8 Selection of Well Size 115
3.3 Field Inspection 116
3.3.1 Seeps 117
3.3.2 Vegetation Stress 118
3.3.3 Specific Conductance and Temperature
Probes 119
3.3.4 Electrical Earth Resistivity 121
3.3.5 Seismic Surveys 124
3.4 Other Monitoring Techniques 126
3.4.1 Surface-Water Quality Measurements 126
3.4.2 Aerial Photography 127
3.4.3 Geophysical Well Logging 128
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Chapter Page
3.5 Well Technology 132
3.5.1 Drilling Methods 132
3.5.1.1 Drive Points 132
3.5.1.2 Augers 134
3.5.1.3 Wash Borings 137
3.5.1.4 Jet Percussion 139
3.5.1.5 Cable-Toll (Percussion) 139
3.5.1.6 Hydraulic Rotary 143
3.5.1.7 Air Rotary 145
3.5.2 Well Casing and Screen Materials 146
3.5.3 Well Security 147
INDICATORS OF LEACHATE 155
4.1 Introduction 155
4.2 Background Quality of the Ground Water ... 157
4.2.1 Chemical Quality of Natural Ground
Water 158
4.2.2 Other Sources of Ground-Water
Contamination 160
4.2.2.1 Highway Deicing 163
4.2.2.2 Leaky Sewers 163
4.2.2.3 Septic Tanks 165
4.2.2.4 Mining 165
4.2.2.5 Irrigation 166
4.2.2.6 Land Disposal of Sludge 166
4.2.2.7 Petroleum Exploration and Development .... 166
4.2.2.8 Feedlots 167
4.2.2.9 Waste Lagoons, Oxidation Ponds, and
Buried Pipelines 167
4.3 Chemical, Physical, and Biological
Indicators 167
4.4 Indicator Groups 168
4.4.1 Specific Conductance Measurements 171
4.4.2 Key Indicator Analyses Group 171
4.4.3 Extended Indicator Analyses Group 173
4.5 Guidelines for Using Indicators 175
4.5.1 Background-Water Quality Monitoring 175
4.5.1.1 New Land Disposal Site 175
4.5.1.2 Existing Land Disposal Sites 176
4.5.2 On-Going Monitoring 176
4.5.2.1 Key Indicator Program 176
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Chapter Page
4.5.5.2 Extended Indicator Program 178
4.6 Monitoring Frequency 179
4.6.1 Characteristics of Ground-Water Flow 180
4.6.2 Location and Purpose of the Monitoring
Well 181
4.6.3 Climatological Considerations 181
4.6.4 Trends in the Monitoring Data 182
4.6.5 Legal and Institutional Data Needs 182
4.6.6 Other Considerations 182
4.7 Cost Considerations 183
4.8 Data Management 184
4.8.1 General 184
4.8.2 Application of Statistics 188
4.8.3 Indicator Data Profiles 189
FUNDAMENTALS OF LEACHATE 194
5.1 Introduction 194
5.2 Origin, Composition, and Fate of
Leachate 194
5.2.1 Solid Waste Zone 195
5.2.2 Unsaturated Zone 193
5.2.3 Aquifer Zone 200
5.2.4 Measurement of Attenuation 203
5.3 Leachate Quantity 207
5.3.1 Water Balance Simplified 208
SAMPLE WITHDRAWAL, STORAGE AND PRESERVATION 220
6.1 Introduction 220
6.2 Sample Collection 220
6.2.1 Sample Withdrawal Methods 220
6.2.2 Records 228
6.2.3 Chain of Custody 229
6.3 Sample Containers 231
6.4 Preservation of Samples and Sample Volume
Requirements 231
6.5 Preservation of Samples in the Field 237
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Chapter Page
7 ANALYTICAL METHODS 239
7.1 Introduction 239
7.2 Alternate Analytical Methods 242
7.2.1 Method Comparability 242
7.2.2 Additional Analytical Methods 243
7.3 Specific Analytical Methods for the
Analysis of Relatively Concentrated
Leachate Samples 244
7.3.1 Introduction 244
7.3.2 Measurement of Interference Effects 245
7.4 Analytical Methods 246
7.5 Brief Description of Specific Analytical
Methods for Leachate Analysis 246
7.5.1 Additional Valuable Information 263
7.6 Field Testing Versus Testing in the
Laboratory 263
7.7 Mobile Laboratories 264
7.8 Automated Methods 265
7.9 Laboratory Quality Control 268
7.10 Manpower and Skill Requirements 268
7.11 Records, Data Handling and Reporting 269
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LIST OF FIGURES
Figijro Page
1. Scenario 1 - A-Site Conditions and Results of
Resistivity Survey 21
2. Water Table and Land Surface Contour Map with Test
Well Locations 24
3. Geologic Cross Section A-A' 26
4. Parallel - Ridge Grading Plan. 28
5, Scenario 2 - Geologic Cross-Section and Plan 31
6. Influence of Landfill Operations on Leachate Plumes 42
7. Monitoring Network For Aquifers With Intergranular
Porosity - Areal Flow Patterns 47
8. Monitoring Network For Aquifers With Intergranular 43
Porosity - Vertical Flow Patterns
9. Monitoring Network For Aquifers With Fracture
Porosity - Areal Flow 50
10. Monitoring Network For Aquifers With Fracture Porosity-
Vertical Flow Patterns 51
11. Monitoi ing Network For Aquifers With Solution Porosity-
Areal r ' ow Patterns 53
12 Monitor. '-'.'g Network For Aquifers With Solution Porosity-
^-i Flow Pattern 54
13. Sing!,- Vjuifer With A Deep Water Table 56
14. Ground- Water Discharge Areas 57
15. Fractured Rock Surface With A High Water Table 58
16. Fractured Rock Surface Wtih A Deep Water Table 59
17. Marsh Deposit Underlain By An Aquifer 60
18. Permeable Sand Layer Underlain By A Clay Layer 61
19. Perche^ Water Table Condition 52
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Figure Page
20. Abandoned Gravel Pit with a Clay Layer at its Base. 63
21 Marsh deposits bounded on either side by streams and
underlain by a shallow aquifer 54
22. Single Aquifer Interbedded with Clay Lenses. 65
23. Two-Aquifer System With Opposite Flow Directions 66
24. Three-Aquifer System With a Deep Water Table 57
25. Thick Clay Layer Underlain by an Aquifer 68
26. Single Aquifer Intersecting Landfill 69
27. Landfill is Located Near Large Salt-Water Body 70
28. Pressure - Vacuum Lysimeter Emplacement Beneath, A
Land Disposal Site 76
29. Modified Pressure - Vacuum Lysimeter Installation 77
30. Typical Monitoring Well Screened over a Single
Vertical Interval 83
31. Piezometer Well Installation For Shallow Ground-
Water Monitoring 87
32. Details of a Low Cost Piezometer Modified for
Collection of Water Samples 89
33. Typical Well Cluster Configurations 95
34. Use of a Sampling Pump to Isolate Casing Perforations 98
35. Construction Details of a Ground-Water Profile
Sampler Using a Well Point 99
36. The Casee Sampler 101
37. In-Situ Ground-Water Sampling Procedure 105
38. Procedure for Water Sampling During Drilling 107
39. Filter Press 111
40. Hydraulic Squeezer 114
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Figure Page
41. Specific Conductance - Temperature Probe 120
42. Interpretation of Resistivity Meausrements Using the
Empirical Cumulative Method 123
43. Detection of a Leachate Plume Using an Electric Well Log 130
44. Comparison of Geologic, Electric and Gamma - Ray Logs 131
45. Methods for Installing Well Points 133
46. Auger Equipment 135
47. Simplified Wash Boring Rig 133
48. Simplified Jet-Percussion Drilling Rig 140
49. Simplified Cable Tool Percussion Rig 141
50. Hydraulic Rotary Drilling Equipment 144
51. Generalized Method for Protecting a Well or Piezometer 148
52. Schematic Diagram of Leachate Characterization 156
53. Water Balance Profile 192
54. Cation Concentrations as a Percentage of Original
Concentration with Distance From a Landfill 206
55. Landfill Water Balance Simplified 209
56. Conditions Affecting Underflow 213
57. Estimating Rate of Landfill Underflow 214
58. Device for Direct Measurement of Landfill Infiltration 216
59. Structural Features of Modified Kemmerer Sampler 223
60. Air Lift Water Sampling Device 225
61. Schematic Diagram Showing The Construction & Mechanism
of an Airlift Pump 226
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LIST OF TABLES
Table Number Page
1. Well Construction Details, Water Levels and Water Quality
Data (Physical) 25
2. Typical Intergranular Porosities 45
3. Summary of Cost Estimates for Various Monitoring
Techniques and Construction Methods in the Zone of ,
Saturation 91
4. Relative Abundance of Dissolved Solids in Potable
Water 159
5. Analyses of Ground Water in which The Indicated Element
is a Major Constituent 161
6. Classification of Water 162
7. Contribution of Landfill Leachate Indicators to
Ground Water By other Sources 164
8. Probabilities of Landfill Leachate Indicators from
given sources Contaminanting Ground Water 169
9. Leachate Indicators 170
10. Comparative Costs of Indicator Analyses 185
11. Characteristics of Leachate and Domestic Waste Waters 1Q7
12. Susceptibility of Leachate Constituents to Differential
Attenuation 204
13. Percentages of Surface Runoff for a 2.5cm (1 inch)
rainfall 211
14. Recommendation for Sampling & Preservation of Samples
according to Measurement 233
15. Classification of Major Methods for Autoanalyzer I & II
systems 266
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1.0 EXECUTIVE REVIEW
1.1 INTRODUCTION
This manual brings into one volume, information valuable as a reference
source for those persons actively engaged in or planning ground water
monitoring programs at solid waste disposal facilities. It was completed
prior to passage of the Resource Conservation and Recovery Act of 1976,
which contains major provisions to move the country more rapidly toward
environmentally safe solid waste disposal practices. The implications
for monitoring activities are clearly great, and this manual should serve
as a particularly useful tool as State solid waste agencies proceed to
strengthen their land protection programs. The manual is primarily
addressed to the supervisory personnel of solid waste regulatory agencies,
although its contents can be readily used by engineers in the field.
It is offered as a guide to be used and tailored by the supervisory
personnel at their discretion and guidance to persons without prior
training or experience. It should prove helpful to the operators and
managers of solid waste disposal facilities who find a need for a
familiarity with and understanding of the fundamental principles involved
in ground water pollution and monitoring.
Generally, this manual includes fundamentals and provides guidance to
assist the user in:
* establishing the need for monitoring;
* assigning priorities for facilities to be monitored;
* implementing and directing cost-effective, on-going monitoring
program responsible to the purposes and data needs established.
The information, as presented, is offered as guidance and suggested methods
only. Site specificity is recognized throughout the manual.
The purpose of the Executive Review is to provide the reader with an
overview and summary of the contents of the manual. Background information
on the impact of waste disposal on ground water can be found in "The
Report to Congress: Waste Disposal Practices and Their Effects on
Ground Water" (January 1977, EPA Office of Water Supply and Office of
Solid Waste).
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1.2 PURPOSES AND OBJECTIVES OF MONITORING
The very fundamental objective of monitoring land disposal sites is to
serve as a check on potential leachate contamination. There are two
basic land disposal situations which require distinct approaches to
monitoring,existing sites and new sites. At existing sites where ground
water contamination has already begun, it is important to protect the
users (present and future) of the ground water. At new sites and at
existing sites where contamination has not occurred, protection of the
ground water resource may receive additional emphasis.
Where a potential for leachate generation exists, an assessment of the
leachate problem must be made to determine the control strategies for
a particular land disposal site. If the natural hydrogeological conditions
of the site cannot by themselves provide adequate control, artificial leachate
control techniques (e.g., plastic liners, clay liner) may be needed.
Ground water monitoring will play an all-important role in making such an
assessment and in providing long-term verification.
Several purposes of monitoring can be enumerated.
* Monitoring where the control strategy is the protection of
the ground water user.
* Monitoring where the control strategy emphasizes additionally
the protection of the ground water resource.
* Collection of evidential data for enforcement purposes.
* Demonstration of the presence or probable absence of leachate
contamination as may be done in a statewide evaluation of the
extent of the problem.
* Check on the effectiveness of an engineering design and site
preparation including such items as liners, berms, subsurface
diversionary measures, etc.
* Collection of prescriptive monitoring data in response to
descriptive monitoring to develop effective engineering remedies
for contamination problems.
* Performance of scientific investigations in developing and
validating design criteria, such as: rates of leachate movement,
attenuation, etc.
Monitoring for each purpose differs in both scientific and economic scope.
For example, a scientific investigation would attempt to quantify as
much as possible the amounts, movement, and attenuation of leachate
contaminants and their impact on the environment. Such a program requires
very extensive monitoring consisting of tens of monitoring wells and
the performance of extensive analysis with frequent sampling. It would
also involve extensive hydrogeologic and geophysical study with detailed
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field measurements of soils and ground water flows. On the other hand,
the simplest monitoring program for determining the presence or
probable absence of contamination, such as in a statewide survey, might
only require one or two wells. Perhaps a detailed site inspection by an
experienced hydrogeolegist familar with the geology would be sufficient.
Obviously, these extremes would differ in effort and cost by one or two
orders of magnitude ($100,000 vs. $1,000).
Generally, most monitoring programs will fall between these two extremes.
Monitoring programs may evolve in a sequential pursuit of the various
purposes listed above. For example, the presence/probable absence
monitoring will almost always be the starting point from which to build
a program. Once this has been satisfactorily addressed, the circumstances
specific to the site and State code will dictate the next step. If there
are nearby water supply wells which are potentially threatened by leachate
contamination, immediate steps would be taken to check their quality.
If there is no real threat to public health but the State's control
strategy is resource protection, immediate steps would be taken to
determine if leachate contamination is entering the groundwater. In
the former case, monitoring would initially focus on the nearby water
supply well; in the latter, monitoring would focus on the landfill.
This might logically lead in a much more comprehensive program to gather
evidential data for an enforcement case. In almost all cases, evidence
gathering will require a more intensive monitoring effort consisting of
additional sampling points and analyses to remove any doubt that the
landfill is the source of contamination.
Additional monitoring may be required to prescribe engineering design
criteria; and upon implementation, a check might be made of the effectiveness
of the said design. For example, several additional sampling points may
be established at the landfill in order to more accurately measure the
dimensions of the leachate plume (body of leachate-contaminated ground
water) as well as its movement, dispersion, and attenuation characteristics.
This data will provide valuable input into the engineering of the remedial
program.
An example of additional monitoring to check the effectiveness of a
remedial program would be the installation of sampling devices just
below an underliner or outside a cut-off wall to detect any pass-through
of contaminants.
Following is a brief summary of postulants, facts, and judgements gleaned
through the knowledge and experience of State solid waste management
officials which will put the manual into perspective.
* At the present time, extensive use of ground water monitoring
as a part of solid waste regulation is not being made.
* Where monitoring is required of landfill operators, seldom is
the data used in litigation for lesser enforcement actions.
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* State solid waste management administrators foresee extensive
use of ground water monitoring in the future and would welcome
guidelines for its use. Where ground water monitoring is now
required, it is almost exclusively for new sites.
* The statutes of many States would authorize ground water monitoring
by defining waters of the state to include ground water as well
as surface waters.
* Usually there are no regulations of specific applicability to
monitoring wells or specifications as to their construction.
Where wells are required, it is done on a case by case basis.
* Agreed upon standards defining leachate pollution do not exist;
some States use Public Health Service Potable Water Standards
while others use the guidelines of the National Water Well
Association and some operate under the statutory principle
of absolute nondegradation.
* The key to adequate control of landfills is a permit system.
Requirements for both existing and new landfills are imposed
as conditions of permits and monitoring results may be keyed to
permit conditions.
* Some express the opinion that rather than contaminate ground
water, discharge areas such as flood plains should be employed
for landfills on the theory that it is better to have the leachate
travel into the ocean then irrevocably into the ground water.
Others feel that if aquifers were contained and are not in use
for potable supplies, the site should be continued as a waste
sink with no necessity for monitoring.
* In some locations, ground water pollution cases or denial of
permits have been done exclusively on the basis of geological
information without any monitoring.
* There appears to be a general reluctance to impose ground water
monitoring requirements on publicly-operated landfills due to the
cost factors.
1.3 TYPES AND LIMITATIONS OF MONITORING
It is important for the administrator to have an understanding and
appreciation for what monitoring can and cannot do—the kinds of information
that it can provide as well as its limitations. Too often monitoring
is arbitrarily approached, producing insufficient, inaccurate, or unnecessary
information for the purpose intended. In order to avoid this and to
gain a fuller appreciation of monitoring, it is helpful to categorize
the process into two fundamental levels:
* detective monitoring, which establishes presence/absence
of contaminants and the need for further monitoring, and
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• interpretative monitoring, which determines extent of damage
and prescribes remedial action.
In the effective administration of a detective monitoring program, it
is important to have some appreciation of hydrogeology and its limiting
influences on monitoring. Monitoring ground water at a land disposal site
is completely different from monitoring a surface water, a waste discharge
pipe, or an air-pollution plume. The main differences are the unpredictability
and the difficulty and expense in obtaining representative data. For example,
modeling has been successfully used in predicting the impact of a waste
discharge on a stream or of a stack emission on the air. However, for
ground water, modeling is used in the sense of constructing a model of
the system as it exists, i.e., gathering enough data to enable a three-
dimentional image to be made of the plume. While modeling does not
necessarily imply the development of a mathematical simulation for use as
a predictive tool, it does require the collection of a considerable
amount of data over a long period of time—more than would be practical for
most land disposal sites or regulatory program needs. For example, the
following types of data that such modeling might include demonstrate this
point:
Geologic:
surface geology (topography and type/depth of overburden)
lithology of aquifer
type of geologic formation (local stratigraphy and struiture)
Hydrogeologic:
depth to water table
water-table contours
thickness of aquifer(s)
relative hydraulic heads, if more than one aquifer
annual precipitation
aquifer permeability and porosity
Geochemical:
background-water quality
chemistry of geologic formation
presence of other sources of chemical or biological contamination.
It is very difficult and expensive to obtain representative data necessary
to support math modeling which in its present pioneering state provides
limited reliability. While it may have application in highly critical
situations, such as detailed scientific investigations of hazardous or
toxic material threat to drinking supplies, it is not yet appropriate for
general use in State programs.
The many geohydrologic limitations inherent to ground water monitoring
require much interpolation and scientific estimation on its use. It is
difficult to obtain samples at many points. Unlike the situation found
in streams or in the air, ground water moves very slowly and there is little
mixing. Thus, there may be a wide range of unpredictable variations in
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contaminant concentrations within a plume of leachate-enriched ground
water. Several limitations as they relate to ground water monitoring,
are discussed below:
0 A monitoring well is sampling a very small part (point)
of the aquifer, thereby limiting its representiveness to the
quality of the ground water in the immediate area of that
well. Interpolation of the point data is compounded by the
hydrogeologic characteristics in leachate movement that produce
wide variations over short distances and time periods.
0 It is expensive to obtain reliable water-quality data at chosen
points in an aquifer. Unlike surface water where a sample can
be arbitrarily taken at any point, moving the sampling point
in ground water implies the installation of additional monitor-
ing wells.
0 Sample extraction may be made difficult due to the tightness
of a geological formation or the depth to the ground water.
0 Determination of the flow rate and direction of ground water
are prerequisites to monitoring well placement. Drilling will
be required and measurements must be made of the piezometric
surface.
0 Ground water flow rates are extremely slow resulting in a
correspondingly slow change in its quality at a particular
monitoring well. This phenomena will, in most cases, require
data collected over long periods of time (years or months) to
perform a comprehensive analysis of the landfill. There may
even be situations such as fractured rock conditions which are
so unpredictable as to frustrate a very intensive monitoring
effort.
1.4 FATE OF INDICATORS
Many of the chemical components of leachate are common to all municipal
waste sites. Other components such as certain heavy metals (Cr, Ni, Cd)
or synthetic organic compounds (pesticides, PCB's, solvents) may be
contributed by wastes specific to a site. The dissolved chemicals
leaving the bottom of the solid waste zone move with percolating water
with different degrees of interaction with each other arid with soil or
sediment components.
1.4.1 Contaminants Not Usually Considered Toxic
Inorganic components associated with leachate include the cations
(positive charge), sodium, potassium, calcium, magnesium, iron, manga-
nese, and ammonia. Anions (negative charge) include chloride, sulfate,
phosphate, and bicarbonate. Cations are subject to attenuation by
cation exchange reactions on adsorptive surfaces in soils and sediments.
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Anions, except for phosphate, are not appreciably affected by sorption
reactions. Thus, they move with percolating water with little change in
concentration. Ammonia is oxidized to nitrate under aerobic conditions.
Therefore, ammonia may be present; in leachate as it leaves the surface;
and by the time it reaches ground water, significant conversion to
nitrate would take place.
Bicarbonate, chloride, and sodium are rrequtntly the ions of cnoice for
tracing leachate in ground water. The choice of these, or others,
depends upon the quality of ambient ground water in the area. The ion
of choice must be clearly enriched in respect to background-water quality.
1.4.2 Co n t am inan t s Usually Con side red .To_xic_
The suite of heavy metals, boron, selenium, arsenic, and nitrate are the
inorganic chemical species identiLi'^d with varying degrees of toxicity.
These constituents are present in leachate in concentrations which more
directly reflect the specific landfill than do the v-oncentrations of the
preceding constituents.
Most of the heavy metals are subject to aLtenuation frora ion exhange or
precipitation reactions. Boron, selenium, arsenic, and nitrate occur as
anions slightly affected by sorption processes.
Since few organic constituents have been positively identified, the
toxicity is difficult to assess. From the usual odor associated with
leachate, organic constituents wouLl be considered decidedly undesirable
even if not proven clinically toxic. Organic constituents are the
decomposition products (largely anaerobic) of a variety of organic
wastes deposited in the landfill, if w.ner-soluble organic matter
is deposited, it may also be ptesen'- unaltered. Organic attenuation
occurs from a limited amount of adsorption and microbial degradation
occurring in the zone of aeration and possibly continuing in the aquifer.
Because of their virtual absence in ambient ground water, some of the
toxic components may make excellent leachate tracers. For example,
borate, a conservative ion and an unubiquitous component of ground
water, has been reported in leachate. These qualities make it a useful
tracer where present.
1.4.3 Geohydrology
A few hydrologic principles should be recognized in dealing with leachate
plumes in ground water:
Leachate is not diluted with the entire body of giovind water
but tends to remain as an intact body wirh only slight dispersion
and diffusion along the edges.
0 Leachate constituents actually move faster than the average
ground water velocity because of hydrodynamic dispersion.
0 The path of a leachate plume will follow the direction of
ground water flow. Diversions in flow direction from induced
changes in gradient (e.g., a pumping well) will also divert
the leachate plume.
7
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Hydraulic arid litnc logic cordit.'ons and lepchate density
determine the vertical depth to which ".eachate will migrate
into the aquifer. The thickness of the plume in the aquifer
will probably increase with disr:ar.ca downgraciient from the
source ,
The ex cent, and i.iovemen" of varou.-. constituents in the plume
will vary due to
1.5 COST OF MONITORING
f partial attentuction.
Costs will var\ direct, y with trt uurpos = ^r;d therefore the level of the
monitoring program. The more information aesired and the more quantitative
the site evaluation., trie higher-- f uie oos-tj vill oe . A faw examples will
serve to demonstrate r.'iis pcint:
If a .state solid waste ^rograr/ --ere to assess the extent of
leachate contamination in the si ic°. , th? emphasir would be on
iute"p "etnt i ve tnoritor i • •£ ,inimiz;* 1 ^c i d-ita gathering by drilling
borings, wells, etc. A->y sampling and analysis done would be
limited to existing wells (on or off site), leachate springs,
or surface waters and analyzed for key indicator parameters
only Such an as3es,.-,; a i i n... e
tial threat to public .ic?.1 th inc rif
sit>- i"d i.ts poten-
Another import an r purpose cf i.icritoripg is enfor.'ement. In
almost all cases cost? ••£ ent'ov't'emenr moid toeing will be much
higher than fcr assessnr-nt. nor.il oring as pi^e". in the first
example. Ouant ii;at: ve J,a..a wil1 be- nRra^saiy or the leachate
concaminac ion at tap v\t:e, Ti^e i^a^ : he sufficient data to
show a prepon-fe'-arve of evJc^-vi, o f- ,'rove h^yoi'd any
rea&cnabie doub*. that <. tm ^ proi-i :i* ion ^;";c;pt"3s tba applicable
standards and that The ••'.xc
J dnd dirpc-Kci1 nire, I: < >_i
gj'>'!urid w<=tt;i" .^ on rani r Hf ; '.•"--
th'msand do i. tars to , -?vr-ral
strength a.ia sper.i f i-,lt; o
F. caused by the
-:i; fleering for
v.Tji several
c-: dollars. The
protection laws
s '• n tawin =--.'; i in
t,r f. t=nf 01 ,:e r/j'
-j.;1'--: will rin^e1
tea.= PL rlic-.i^ari
the ground -'i^e
ana the s:tt? conditio-ty .are the T.ai.n causes of cost variations.
For example, iron L toeing for zi-iro-dlscharga ..avs would require
sampling devices beneath or immediately adjacent to the downgradient
landfill edge. More costly monitoring would be involved in
those areas where non-c c-gradation or "proper:, y line" laws
are in effect. In the?? cases, several monitoring wells at
various distances and depths dowigradtenr as well as compre-
hensive conditions, especially depth i.o ground water, will
directly affect the. installat .' on costs of sampling devices.
The. number of analytical parani:i. ers required by regulations
will have a direc/c effete on 1 he analytical cost?
-------
0 Another important purpose of monitoring is the performance of
scientific investigations to develop and verify design
criteria and standards. Such investigations involve comprehensive
surveillance of the disposal site including thorough analysis
of site conditions, blanketing the site with numerous sampling
devices along a horizontal and vertical profile, and the
running of frequent and extensive analyses. The entire program
will require a team of experts. Costs ranging from several
tens of thousands of dollars to a few hundred thousand dollars
would not be unusual.
General cost estimates are presented throughout the manual for order of
magnitude and comparative purposes only.
1.6 IMPLEMENTATION OF AN EFFECTIVE PROGRAM
In order to establish an effective state program, it must proceed
simultaneously on enforcement and locating alternatives with a systematic
approach and a good data base. The state must possess a working knowledge
of the hydrogeological setting and the probable extent of contaminant
transport at all existing landfill sites.
1.6.1 Assessment of Existing Land Disposal Sites
The assessment of existing sites must provide sufficient information
concerning the probable contamination profile at each major site. It
must be approached as a long-range continuing effort. It requires staff
geological talent (perhaps one experienced and two junior geologists for
a medium-sized northeastern state) and will commence with three to five
mandays per site including search of office files; U.S. Geological
Survey, SCS, and other files; and field visits for an initial assessment.
Maximum and minimum potential plumes should be sketched in cartoon form
(Chapter 2). Upon completion of a significant number of sites, geo-
physical and field analysis will begin at those more likely to pollute.
Well monitoring at existing sites will probably not be indicated prior
to this point in program maturity and only in a very few sites initially
upon completion of geophysical assessment. Pragmatic resource limitations
such as the size of the enforcement program staff will constrain the
rate of data collection. No administrator wants tf.n new major violations
reported all at once. The purposes for monitoring are not limited to
the support of enforcement actions. Other purposes include:
0 To assess empirically the state's facility standards on State
geology under local rainfall with local solid waste in place.
To provide justification for appropriate staffing and budgeting
in order to handle actual workload.
To provide sufficient information to make realistic estimates
of the best least cost exit from a site and the environmental
consequences of delays.
To provide bases for state-wide facility scheduling for optimal
disposal resource allocation.
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1.6.2. Review and Orientation of Present State Program
Simultaneously with the site assessment activity, the existing monitoring
program should be reviewed. This might include such tasks as the following:
0 Listing of all sites with established monitoring points
(surface or ground water), including sites presently being
studied for pollution abatement and/or permitting.
0 Continuing to require monitoring a new or potential serious
contaminating site with closer State input on location,
design, etc.
0 Revising organizational water analyses records to be more
consistent with future programs.
0 Establishing a monitoring station numbering system with field
markers.
0 Investigating organizational records and listing chemical and
physical indicators of leachate contamination from normal
solid waste and industrial waste. This should curtail lab
time per sample.
0 Running water analyses of discharges from existing special
waste sites to aid in identifying indicators representative of
these leachates.
0 Adopting recommended ground water and soils data-collection
methods and issuing a manual on the same.
0 Arranging interviews with major State drilling contractors/ground
water consultants to discuss proper sampling methods and
procedures. Contacting universities and research groups
regarding possible research projects on the environmental
effects of leachate and the development of design criteria and
standards.
0 Locating on up-dated topographic maps all existing sites,
monitoring locations, documented areas of contamination,
potential areas of contamination, etc.
0 Placing more emphasis on geophysical work, especially during
the subsurface investigative stage.
0 Purchasing of equipment such as pumps for shallow well sampling,
deep well sampling, conductivity meters, pH and temperature
probes, individual field kits, etc.
0 Determining priorities of monitoring at waste disposal sites.
0 Determining categories of enforcement action based upon monitoring
results.
10
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0 Investigating computerization of analyses and of sampling
requests
0 Correlating leachate quality and quantity to seasonal patterns.
1.6.3 Establish Monitoring Networks and Data Needs for Land Disposal
Sites
Utilizing the background assessment information obtained in Section
1.6.1, priorities should be assigned to sites relative to the need for
monitoring. The state will then work with the landfill operator in
establishing the number and placement of monitoring wells or other
sampling devices. Listing of analyses to be performed as well as sampling
schedules must also be agreed upon at this time.
1.7 STEP OUTLINE OF MONITORING PROCEDURES
For every landfill, both existing and proposed, the establishment of a
ground water monitoring program should be investigated. Although the
use of a "cookbook" approach cannot be justified, the establishment of a
monitoring program can be described in a logical sequence of individual
steps. However, as with any complex situation, the best possible solutions
will require incorporating original thought during each step.
Design and implementation of a monitoring program is usually accomplished
by the combined talents of a civil environmental engineer and hydro-
geologist. The hydrogeologist provides the expertise needed to inter-
pret the subsurface conditions and ground water flow patterns, and the
engineer applies the subsurface data in the landfill design and its
pollution control features.
The steps presented in this chapter are intended to indicate the logical
progression of required efforts and, therefore, are not accompanied by
detailed descriptions. Such descriptions can be found in other chapters
of this manual, or in the references cited at the end of the appropriate
chapter. The general approach consists of review of existing information
and employment of non-sampling field inspection techniques and sampling
techniques.
1.7.1 Step I—Initial Site Inspection
All information is gathered from an inspection of the landfill, examination
of landfill records and other existing information such as topographic
maps, and discussion with landfill-operating personnel. The purpose is
to define, with a minimum expenditure of time and money, the probable
magnitude of the ground water contamination problem. This will determine
the urgency for conducting a detailed study and establishing a monitoring
program.
1.7.1.1 Nature^ of the Solid Waste. The nature of solid waste disposal
varies widely from landfill to landfill depending largely on the types
of waste generated in the area, the regulatory agency for the area, the
landfill operator, and economics. A determination of the types of
wastes accepted at a particular landfill(both currently and historically)
11
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is critical to the monitoring evaluation.
The categories which are accepted at the landfill should be determined;
and in the case of industrial wastes, more detailed information should
be sought.
1.7.1.2 Aerial Extent and Thickness of the Landfill. The pollutant
application rate, represented by the size and thickness of a landfill is
an important factor in estimating the volume of leachate generated as
well as the concentration of contaminants in the leachate.
1.7.1.3 Pretreatment and In-Place Treatment of Solid Waste. In most
cases, solid waste is compacted using heavy equipment after it has been
placed in the landfill. The compaction should be determined to estimate
the density and field capacity of the landfill. Shredding and baling of
solid waste will increase its density. Incineration and resource
recovery operations will alter the composition of solid waste, and
consequently, the nature of the leachate generated.
1.7.1.4 Landfilling Procedures. The procedures used in placing and
covering the solid waste at the landfill site will influence the volumes
and characteristics of the leachate generated. Other important factors
to be considered are the different types of solid waste, the thickness
of the cover layers and the solid waste between them, and the type of
material used for the cover.
1.7.1.5 Rate of Landfilling and Age of Solid Waste. Since a thick
section of solid waste can absorb more water (field capacity), the rate
at which the thickness of a landfill increases will affect the volume of
leachate generated. If the landfill thickness increases at a sufficient
rate relative to precipitation and upon completion is covered to exclude
precipitation, very little leachate will be generated. Thus, the rate
of filling will influence the design of a monitoring system.
Solid waste layers of different ages produce leachates of different
chemical characteristics. This factor may be useful in designing a
monitoring program; however, other factors such as solid waste compo-
sition have a more noticeable influence on leachate than does age.
1.7.1.6 Liners and Covers. If a landfill is equipped with an under-
liner and a leachate collection system, ground water is assumed to be
uncontaminated. A monitoring system would then be designed only to test
the validity of this assumption. Similarly, if the landfill is completed
and covered to prevent the infiltration of precipitation, initial monitor-
ing would be necessary only to establish the absence of contamination.
If initial monitoring data show the liner or cover system to be ineffec-
tive, an expanded monitoring program would be designed to define the
extent of the problem and the necessary corrective measures.
If the bottom liner and collection system are effective, the volume of
leachate actually collected should be equal to the predicted volume of
leachate being generated. Relative to the effectiveness of covers and
12
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surface drainage systems, runotr -:u,c e'/apocrdnspi'/dt ion account for a
large percentage of prr-cipJ i^iJ j i. "ac^o.-, such ..i? covet permeability,
slopes, and vegetdticti-Lype would , " ..c'lpi.ier;-.! v>i this determination.
I./. 1.7 Visual Sur_v^&y_ of '^^'^^j-'^j-'i'J-' -^H/i .l^^A^-i" • J'^° pririiary purpose
of this effort is to establis.Ii -.-st im:;-,:es or .jifa-rr runoft ?no infiltration
patterns and to de terrain1-', the gc-iie: ^. Jlieou K :• ol ground water flow.
The topography of tae areas sun <. jiidinc the liiidfill vili establish the
direction of surface-witer flow, IT. ;hor '.ovu,:> or -.way frcir.i the landfill
surface. CHjce site itcharge -\\ic. f ^.i^.hc. ^f-,- ar<-is are determired, the
general dir = i.rion .>f th? fc/n,_-. : .,./.-.- !^A- --'- be "Pf^c'xi'i.iU'r1.
1.7.1.3 Ground Wajjar ')er' (_ii- j .). '.be rrogr^Ti' should be carefully
planned. I'r aceomp1 j'-.s _r. i; : ~i • .. f 1: . ; <--ut. _•, all '-xifsti'ig pj-rtinent
data are g,i:hc-:Leo du_ -,-.Him.e i . , t: •. ^ ii svt. Th i -, iata. includes all
informatiur. from Step 1 a.:d anv vsefui d.i a available, from outside
sources, Tn addition, inforiaat:\m which can be -e.adily obtained at the
landfill h.lr,-=: hiv: vac net ae^r'c-d r-;rlng S.cr • is gathered.
1-7,2.1 Exi_sj;ij..£, ''atjT:. ".P..-.;-,:•• ^ Lij j.'^.-itlo >L" -. -" "lia' L'naL gathered
in Step .1 in" l'i • ^s :
tf- "T. i nearby
;.Hs iMidtiil site;
tj'"t bo^ir-.^s at
-p-. nf the siTc ftom rfhich to
If p()tent[ij. ^ou.'e'-- ; f r.nii.a:ri.'>...-', 1.1 '.-"he'" thtr< r.:1'- ".'; nH f i i i are
located in the vi.iui:? , t- \ ,-JV -bK- "'nf ormal i V-P iegardln^ these
sources (typf -i"d vulune cf vi- . iu>tri.j' >,•" a :•••«:> .-<;!, itc.1 also
should be .:.^1 it'rtt-f; .-^^0 i-_.-.i > ,_,
1.7,2.2 _F'ft Lijuij^ar^ :_^ij-0 i'.r\ye^'.. ---Ll''1' 'l"!- '-^1pai data which will
improve the efficiency of .1 riydr... ;sooJ .'gj c vi;v- Htigorlon of -i landfill
(Step 3) i.ic:cap:
analycs of water :itl. .v/,, ~ t rcr, rutiaci. wate. boaie.,1.: and
exlstiig wells io^Jte. j ner.r i.rm iitp;
;--/ .- -,?••;? -r-:T si-r^ice seeps;
-------
0 examination of site vegetation by a botanist for signs of
stress;
° observations of surface drainage patterns during a rainfall;
0 a check of building basements and other subsurface structures
at the site for landfill gas accumulations.
Preliminary site investigation is not limited to supply wells. Surface-
water use in the area must also be considered. Nearby surface water may
be used for potable supply, fishing or shellfishing, swimming or other
recreation, or wildlife habitat. Since surface-water bodies are often
discharge areas, they are subject to contamination from leachate in the
ground water system. Information should be established as to the
location, use, and rate of flow for all surface-water bodies in the
vicinity of a landfill. Natural water quality, existing contamination,
and sources of contamination should be investigated. At discharge
points, ground-water contamination becomes most conspicuous. Therefore,
sampling of surface-water bodies may form an important part of a moni-
toring program.
1.7.3 J3tep _3_ — Definition o_f_ _the_ Hi^d£p_geo_log_i£ Setting
The hydrogeologic setting of the landfill is probably the most important
factor in establishing the need for and design of a landfill monitoring
system. Prior to selecting a landfill site, information as to surficial
and bedrock geology, depth to the water table, and direction and rate of
ground water flow should be determined, In the past, subsurface conditions
have not been well-defined; landfijls have been located on lands such as
swamps or abandoned gravel pits, traditionally considered useless and of
low economic value. Ground water pollution potential is present in
these areas; and in tha case of gravel pits, the potential is high. For
these reasons, the need for monitoring and abatement procedures is
acute.
1.7.3.1 Surficial Geology. The purpose of a surficial geology survey
is to establish the areal extent and thickness of the layers of the
various types of deposits under and adjacent to the landfill. Also, the
permeabilities and interconnections of these, layers should be determined.
The survey can be divided into three, sequential parts:
0 a review of geologic data gathered during Steps 1 and 2;
0 geophysical surveys designed to complete subsurface information;
0 test drilling to provide direct control for the geophysics,
obtain more precise data in critical areas, and allow detailed
analyses of the geologic samples.
1.7.3.2 Bedrock Geology. In some cases, bedrock will act as a barrier
to leachate movement; yet in others,, leachate may move into bedrock
14
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aquifers. The type of rock beneath the sites and the amount of fracturing
will determine the role of bedrock in the movement of leachate. Deter-
mination of bedrock geology essentially will follow the steps outlined
for surficial geology.
1.7.3.3 Ground Water. The ground water investigation should provide
information regarding the following:
0 depth to the water table;
0 the extent of ground water mounding caused by an existing
landfill;
0 the natural rate and direction of flow;
0 the degree of influence the landfill has on the rate and
direction of flow;
0 the locations of recharge and discharge areas;
0 the types and interconnection of aquifers;
0 the rate of site infiltration relative to the total ground
water flow.
Much of this information would be obtained during and immediately
following the geologic investigation previously outlined. During test
drilling, data regarding water levels and head differences with increasing
depth would be recorded. Test borings can be equipped with screens and
test pumped at various intervals while other borings could be implemented
as observation wells to establish aquifer characteristics and inter-
connection between aquifers.
Information relative to recharge at the site can be obtained from
historical precipitation records and estimation of the surface runoff
and evapotranspiration. These data are necessary to predict the probable
size and shape of the leachate plume. Ground water recharge and dis-
charge areas are determined by the results received from observing
surface features and the relative water levels in observation wells.
A monitoring program is dependent upon the information gained from
hydrogeologic investigations. The existing potential for a landfill to
contaminate an aquifer or surface-water body will require the construc-
tion of a monitoring program. Information regarding the actual con-
dition of threatened and contaminated aquifers (depth and extent) will
aid in determining the most favorable locations and depths of monitoring
wells. The size and complexity of a monitoring program will be based
partially on the calculated volume of recharge throughout the landfill
as well as the volume and rate of ground water flow. Subsequent steps
outlined in this chapter will provide the necessary data for the refine-
ment of the monitoring program initially outlined and for the elimina-
tion of its less important features.
15
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1.7.3.4 Determination of Existing Water Quality. An accurate and
complete record of existing ground and surface-water quality is neces-
sary as background water quality in a monitoring program. If previous
contamination has occurred, water samples should be collected from
uncontaminated areas and analyzed to establish natural water quality.
If sources of contamination are present (other than the landfill), the
effects of these sources should be determined. Since the objective of a
monitoring program is to determine change, historical data are indeed
vital.
If outside sources of contamination are present (determined in Step 2)
and if existing information is insufficient to define the problem,
additional investigation would be necessary. Such an investigation
would include:
° the rate of contaminant generation;
0 the nature of the contaminants;
0 the resulting degree of ground water degradation.
The monitoring system must then be designed to account for these "outside"
contaminants. If not accounted for, these contaminants might be inadvert-
ently attributed to the landfill.
Determination of the existing water quality is not limited to consider-
ation of the primary contamination directly introduced. When landfill
leachate reaches and blends with ground water, secondary reactions may
occur. For example, the oxidation potential of the leachate-enriched
ground water may be lowered by the mixing in of chemically-reduced
leachate. This, in turn, may reduce and dissolve iron or manganese
occurring as coatings in the aquifer materials. Cation exchange re-
actions releasing calcium and magnesium, changes in pH, or the precipi-
tation of some leachate constituents are other reactions which could
occur and change water quality.
1.7.3.5 Determination of the Rate of Leachate Generation. The leachate
generation rate is determined by a water-balance study of the landfill
and will influence the magnitude of the monitoring program. Necessary
data for water-balance determination include: precipitaton data, landfill
surface characteristics, vegetation-type and density, landfill site
topography, ground water underflow rate, the rate of landfilling, and
pretreatment and compaction of solid waste. A discussion of water-
balance calculations is given in Chapter 5 of this manual.
1.7.4 Step k_ — Determination of the Pollution Potential of the
Landfill
The extent and design of a monitoring system will be influenced greatly
by the pollution potential of the landfill. Estimation of the pollution
potential essentially is derived by consolidation of all data gathered
in Steps 1, 2, and 3. Determinations made would include:
16
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0 the location, size, and rate of the movement of the contami-
nated plume;
0 the aquifers now affected and those possibly affected in the
future;
° the types of contaminants present;
° and the degree of attenuation of those contaminants by the
subsurface sediments.
These data can then be used to predict the total pollution damage that
may be caused by the landfill if no action is taken. They also may be
used to estimate the influence of various possible abatement procedures.
Monitoring program data are then implemented in establishing the accuracy
of these predictions and provide a warning when abatement systems are
ineffective.
1.7.5 Establishing the Monitoring Program
The next step would be to compile the information gathered in the
previous steps into a detailed written report describing the investi-
gations and defining the ground water contamination problem at the
landfill site. The design of the monitoring system would be based on
this report. The methods and purposes for such a monitoring program are
outlined in this manual.
1.7.5.1 Selection of the Monitoring Sites. Using data from the
previous steps, all potential monitoring sites are ranked in order of
importance. High priority sites would include currently developed
aquifers and aquifers with good development potential and discharge
areas (such as marshland which could be damaged by the anticipated
leachate discharges). Monitoring sites should be selected to provide
early warning, allowing corrective action to be taken. Ideally, moni-,
toring should indicate the size and type of abatement program necessary'
in order to correct a problem once it has been detected. At the very
least, the monitoring program should insure that a health hazard does
not arise.
1.7.5.2 Determination of Monitoring Objectives. After selection of
the monitoring sites has been made, the specific objectives of the
monitoring program should be determined. In addition to the basic
monitoring purposes described earlier in this chapter, specific tech-
nical objectives might include:
0 defining the rate of leachate plume movement;
0 monitoring the concentration of a specific contaminant(s);
0 early warning of an unexpected change in direction or size of
the leachate plume;
17
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or unexpected interaquifer movement of the plume to a pre-
viously unpolluted aquifer.
Once the monitoring objectives have been determined, the data require-
ments must be defined to satisfy these objectives. Data requirements
would include:
o
specific chemical constituents to be included in analyses of
water samples;
0 physical measurements to be made at the site;
0 and the frequency of sampling or measurement.
For example, if an objective of a monitoring program is to insure that
leachate does not migrate into a particular aquifer, monthly measure-
ments of the specific conductance of water samples from that aquifer
might be selected to provide information which will protect the aquifer
at a minimal cost. A discussion of monitoring data requirements is
presented in Chapter 4.
1.7.5.3 Establishing the Monitoring Methods and Procedures Necessary
to Accomplish Objectives. To accomplish the specific monitoring program
objectives, certain monitoring devices would be required. For example:
At a specific point, a single well screened over a small section of an
aquifer may suffice. However, a cluster of several wells, screened over
different portions of the aquifer or in separate aquifers, may be re-
quired. Wells of a particular material may be necessary to avoid
interference with leachate 'sample chemistry, or devices other than wells
might be required. A discussion of monitoring and sampling techniques
is presented in Chapter 3.
To insure uniform results, a detailed sampling or measuring procedure
should be established; and, if possible, one person should be responsi-
ble for sampling. This would be especially important for complex
procedures, but less so for simpler tasks (such as conductance measure-
ments) . Proper handling and storage of water samples is extremely
important. For example, when nitrogen analyses are to be made, chilling
or acidification of the sample is required; when metals are to be
tested, acidification with nitric acid is necessary. A discussion of
sample preservation is given in Chapter 6 and analytical methods in
Chapter 7. The cost of monitoring will vary widely and will depend upon
the sampling procedures and analyses used. Therefore, the program
design should be properly operable within the available budget.
Budget allotments should be made for proper data reduction, record-
keeping, and periodic data review. Data records should be in three
forms; the original data as gathered and accompanied with explanatory
notes, continuous tabular form, and continuous graph form. Plotting
18
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data on near-uniform grids permits relative values and trends to be
easily recognized. Proper procedures for handling monitoring data
mandate the periodic review of all data by a qualified scientist followed
by a written summary and the distribution and review of the summary by
all involved parties.
1.7.5.4 Establishing a Management Program. Conditions under which
abatement procedures, other corrective measures, or additional moni-
toring steps that will be taken should be outlined at the outset of
monitoring. Such conditions might include; constituent limits, physical
parameter limits, or trend shifts. In the event the established conditions
are exceeded, possible steps which might be taken should be determined.
Responsibility should be assigned for all phases of the monitoring and
potential abatement programs.
1.8 EXAMPLES OF LANDFILL CONTAMINATION PROBLEMS
The following two scenarios depicting fictitious landfill investigations
leading to ground water monitoring programs are somewhat different.
The first begins with a landfill and defines the pollution problem;
whereas the second starts with a problem and searches for its probable
cause. The first scenario follows closely the preceding step outline;
however, the second is an example of a problem requiring a somewhat
different approach. The scenarios are intended as illustrative examples
and as such are necessarily simplified, i.e., some points included in
the step outline have been omitted. Since no attempt has been made to
include all possibilities, other approaches and conclusions may be
equally valid. These examples should prove beneficial if expanded upon
using the factual information presented in other chapters of this manual.
1.8.1 Senario _!_ — A^ Landfill Contamination Study. A large county-
maintained landfill is discovered to be allowing leachate to flow into
and contaminate an adjacent river violating the 1899 Harbors and Rivers
Act. As a result of a federal lawsuit, a court order is issued man-
dating county officials to take the necessary steps to remedy this
condition. A team having ground water and engineering expertise is
formed to investigate leachate conditions at the landfill site; deter-
mine if leachate is actually discharging into the river; and if so, what
steps should be taken to rectify this problem.
The team assigned to this project makes a visit to the landfill for a
preliminary inspection tour with the landfill operator. During this
tour, it is learned that the landfill receives approximately 1,000 tons
of solid waste per day. Approximately 90% is municipal waste; the
remaining 10% is of industrial origin. The solid waste receives no
pretreatment. However, after landfilling, it is spread into thin
layers by a bulldozer and compacted by a specially designed landfill
compactor. The layers of compacted solid waste are covered daily by
sandy cover material. Small amounts of industrial chemical waste are
19
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accepted at the landfill; but it is not separated from the other solid
waste. The rate and method of landfilling, the type of cover material
used, and local precipitation rates indicate that all the solid waste
has reached field capacity.
The landfill is 16.2 hectares (40 acres) in size, approximately 18.3
meters (60 feet) thick, and has a relatively flat top surface. Directly
north of the landfill is a hill with an elevation of approximately 24.4
meters (80 feet). South of the landfill is a tidal marsh separating the
landfill from the river. The distance between the landfill and the
river is approximately 305 meters (1,000 feet). The landfill is not
lined or covered with impermeable materials nor does it utilize any
other leachate prevention techniques.
In the opinion of the hydrogeologist, the topography of the site indicates
that ground water flow is from north to south. The hill and landfill
act as recharge areas and the marsh and river as discharge areas. The
nearest water-supply well serves an individual residence and is located
approximately one-half mile north of the landfill. No other wells or
borings are known in the landfill vicinity.
The landfill has been in existence for approximately 12 years. There
has been no special site preparation prior to landfilling; solid waste
has been dumped into the edge of the marsh. At present, there is little
or no vegetation on most of the landfill surface, and erosion channels
on the steeper slopes are apparent. Small leachate seeps are evident
along most of the toe of the landfill. These flow directly out into
the marsh and form leachate pools which are periodically flushed out
into the river during periods of heavy rainfall. A sketch map showing
important features of the landfill site is prepared by the study team
during the field inspection (Figure 1).
In a discussion with the landfill operator, the hydrogeologist learns
that the county is considering the construction of a berm, or dike,
around the southern toe of the landfill to prevent leachate from migrating
into the marsh area. County officials feel that leachate can be trapped
behind such a berm and pumped to an evaporation pit or back to the top
of the landfill for recirculation. The study team is asked to evaluate
the effectiveness of this scheme.
Further observations by the study team reveal the fact that the flat,
highly permeable top surface of the landfill would allow a large percentage
of precipitation to percolate into the solid waste. In addition, surface
runoff from the hilly area to the north is free to flow onto the top
surface of the landfill and infiltrate into the solid waste. The volume
of leachate likely to be generated from these two recharge sources would
be considerably greater than the volume discharged by the surface seeps.
Thus, a considerable volume of leachate must be moving with the ground-
water system beneath the landfill and discharging into the marsh or
20
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river. If this is the case, a surface berm would do little to abate the
problem. Final observations of the site inspection reveal the obvious
stress on vegetation in portions of the marsh directly south of the
landfill. However, there is no visible effect of discharging leachate
on the river.
Based on the preliminary investigation, the study team recommends a
detailed groundwater investigation to determine whether contaminated
groundwater is actually discharging directly into the river. If it is,
the nature of the contaminants and the rate of their discharge should be
determined. Further, it is stated that in this particular case, the
construction of a berm may do little to prevent leachate discharge to
the river. The results of the groundwater study, however, will suggest
other, more effective procedures.
The study team is advised to proceed with the groundwater investigation
and obtains the following information:
precipitation records for the past three years from
a weather station located 19.4 kilometers (12 miles)
from the landfill site;
0 A U.S. Geological Servey Map or State Geologic Survey map
showing bedrock and overburden materials in the vicinity of
the site;
0 soil conservation reports and maps indicating soil types
in the area;
0 information regarding the depth and construction
of the domestic supply well north of the landfill;
a sample from one of the leachate seeps;
0 a recent aerial photograph and topographic map of the
site.
Analysis of the data gathered indicates that precipitation on the
landfill surface averages approximately 1016 millimeters (40 inches) per
year. It is then estimated that a minimum of 50 percent of this precipi-
tation infiltrates the surface of the landfill. Since the landfill area
is 16.2 hectares (40 acres), at least 75.7 million liters (20 million
gallons) per year of leachate are generated from this source. The low-
permeability crystalline bedrock which underlies the site probably acts
as a barrier to leachate flow. Details regarding the nature of the
surficial materials at the landfill site are not available. The domes-
tic supply well north of the landfill was drilled to a depth of 30
meters (100 feet) and screened in a high-yielding coarse sand aquifer.
22
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Water from this well indicates no leachate contamination nor do any of
the water samples taken from the river. The seep sample, however, is
highly mineralized and contains contaminants typically found in muni-
cipal solid waste leachate. A base map of the landfill site is traced
from the aerial photograph.
To further define the location of contaminated groundwater at the
landfill site, an electrical resistivity survey is conducted. The
results of this survey (Figure 1) indicate that highly mineralized
groundwater is confined to an area of the marsh directly south of the
landfill. Some attenuation of contaminants in the groundwater appears
to be occurring in the direction of the river as indicated by the slight
increase in resistivity measurements from the landfill to the river.
While the results of the resistivity survey indicate that contaminated
groundwater is indeed flowing from the landfill to the river, additional
geologic and water-quality data are needed to define the problem further
and to suggest effective abatement procedures. To obtain this informa-
tion, a well drilling contractor is hired to install a series of test
borings and wells. Subsequently, five test borings are drilled on and
to the north of the landfill. Two casings with well points are installed
in each boring. The locations of these borings, designated A through E
for the deep wells and A' to E' for the shallow wells, are shown on
Figure 2. The drilling rig cannot be operated in the marsh area; there-
fore, ten additional test wells are installed in this area by hand. The
locations of these wells, designated 1 through 10, are also shown on
Figure 2.
Table 1 gives information concerning the construction details of the
wells and the elevations, temperature, and specific conductance of
groundwater for all the wells installed. Based on these data, a water
table contour map and geologic cross section are drawn (Figure 2 and 3
respectively). Also shown on Figure 2 is the groundwater head at each
well point. As groundwater follows the flowlines from areas of higher
head to areas of lower head, examinaton of the figures indicates that
highly contaminated groundwater from the landfill is flowing downward
into the deeper sediments beneath the landfill, flows upward, and
discharges directly into the river. This analysis is supported by the
specific conductances and temperature data.
While some attenuation of contaminants is occurring along the flow
path, the attenuation is by no means complete. Detailed chemical
analyses of water samples from all the test wells (not given here)
confirms this opinion. Contaminated ground water from portions of the
landfill is discharging directly into the marsh (Figure 3) and probably
is responsible for the observed vegetation stress. Figure 3 also shows
contaminated water discharging directly to the river. The dilution is
so great, however, that this source of contamination is not detectable
in river-water samples.
23
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Possible actions that night be considered with regard to this problem
are as follows:
0 do nothing;
0 remove the landfill to a more hydrologically acceptable site;
0 construct a shallow surface berm around the toe of the land-
fill;
0 install pumping wells directly beneath the landfill to reverse
the hydraulic gradient;
0 install a line of interceptor wells along the toe of the
landfill to restrict movement of leachate away from the
landfill toward the river;
0 reduce leachate generation by restricting recharge to the
landfill.
The severe stress placed on the marsh by the discharging leachate
renders the first possibility unacceptable. The second possibility is
prohibitively expensive; and due to the deep migration of the leachate,
the third possibility would do little or nothing to abate the problem.
The fourth and fifth possibilities may be technically feasible; however,
the low permeability of the sediments beneath the landfill would make
installation difficult to accomplish. Furthermore, these two solutions
would create the new problem of handling the large volume of contami-
nated water pumped from the wells. The final possibility appears to be
the best alternative and is recommended to the county.
The recommended procedures to reduce infiltration and leachate generation
are as follows:
A more environmentally sound alternate site should be sought
and prepared using the latest technology to reduce environ-
mental impact. Phase-out operations at the existing landfill
should continue to achieve an acceptable final grading plan
that minimizes infiltration and leachate generation. There-
after, the landfill should be closed as soon as the alternate
site is prepared.
A cutoff trench should be used to immediately eliminate
runoff onto the landfill surface; the collected uncontaminated
runoff should be drained directly into the marsh for its
beneficial flushing action.
When the landfill is closed to further dumping, the landfill
surface should be regraded to eliminate any flat or depressed
27
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areas. A continuous grade should be created from the hill
toward the marsh to encourage surface runoff. Use of a
"parallel-ridge" grading plan (Figure 4) is one technique used
to minimize infiltration and leachate by enhancing runoff and
controlling erosion.
0 The entire landfill surface should be covered with a compacted
soil of low permeability. This compacted material should be
covered with a layer of topsoil, and high-water use grass
species planted (e.g. alfalfa).
0 A series of swales and channels should be constructed on the
landfill side slopes to further increase surface runoff,
reduce erosion, and direct the surface runoff into the marsh
beyond the toe of the landfill.
In addition to the preceeding suggestions, the study team recommended
that the county institute a monitoring program to determine the effectiveness
of the abatement plan. It is recommended that the monitoring data
collection begin as soon as possible to obtain antecedent information
prior to making the abatement improvements on the completed landfill.
The recommended program is as follows:
0 Monitoring wells of the same design as Well No. 2 (well
cluster) should be installed at the two locations marked (^ on
Figure 2. These should be used as monitoring wells in addi-
tion to the 15 existing test wells.
0 The water level in each well should be measured once a month.
0 A yearly water sample should be taken from each well and an
expanded chemical analysis conducted of each sample taken.
0 If any well shows a marked change in specific conductance, an
immediate analysis should be done of a water sample taken from
that well for selected indicator analyses.
0 A rain gauge should be installed on the landfill surface and
the monthly precipitation recorded.
0 All data should be reduced to both tabular and graph form.
0 All data should be reviewed annually; if necessary, the
monitoring program should be adjusted as suggested by the data
analyses.
1.8.2 Scenario 2_ — A Ground Water Contamination Problem - Over a
period of two months, a growing number of complaints have been regis-
tered by residents of a housing development at the northern edge of a
29
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small city. Thus far, eight citizens from the development have visited
the Board of Health to complain that their drinking water suddenly has
become unsuitable.
The city sanitarian sends an inspector to investigate the eight com-
plaints. He returns with the following report: in two of the houses,
slightly reddish water comes from the faucets (even after running for
prolonged periods). In a third house, the water is slightly gray.
Although the remaining houses are not experiencing discoloration, the
water does have a peculiar taste and a slight odor.
Since none of the houses has a water softener, the inspector collects a
water sample directly from the kitchen sink from each house. The water
samples are sent to a laboratory for analysis. Meanwhile, the sani-
tarian maps the location for each of the affected houses. He notes that
each house is connected to the city sewer system, but each has its own
water-supply well. All of the houses where the problem has occurred are
in the northern half of the development and within an area a quarter-
mile wide. Dozens of other houses are interspersed with the ones
inspected, each having the same type of water supply and waste-disposal
system.
Apparently, there are only two possible causes for the water-quality
problems. The more likely of the two is that the 10-year old sewer
system may have suddenly developed several large leaks causing the raw
sewage to seep into the ground and contaminate the wells. The more
remote of the potential causes would be the 18.2 hectares (45-acre)
county landfill located more than 1.6 kilometers (1 mile) north of the
nearest affected house. When considering the topography of the area,
the landfill as a cause seems even more unlikely. North of the develop-
ment the terrain rises gently for several hundred yards and then is
broken by a steep, elongated hill blocking a view of the landfill from
the city. Beyond the hill, the ground slopes gently downward for more
than .8 kilometers (half a mile) to the edge of the landfill, located in
an old gravel quarry (Figure 5).
The sanitarian concludes that for contaminated water from the landfill
to reach the northern development it would have to travel in an uphill
direction for over a mile. If this were the case, the question arises
as to why the other houses were not affected sooner since both the
development and the landfill have existed for ten years. Furthermore,
why were only a few houses in the development affected? If the landfill
were the cause, why were the four houses located north of the hill
between the development and the landfill not affected? In an attempt to
define the problem, the sanitarian sends his inspector to obtain water
samples from several additional houses in the development where no
problem has been reported. Samples are also taken from two of the four
houses between the landfill and the development.
30
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In this case, the results of the water analyses did little to indicate
the source of the problem. Each of the original eight samples (taken
from the houses where the owners had complained) contain constituents
well above the recommended limits. However, the constituents in highest
concentrations are not the same for each house. Three of the houses
have water supplies with abnormally high iron content and low pH. In
all of the samples, chloride is well above normal for the area; but the
concentrations differ from sample to sample. Significantly, concen-
trations of calcium and sodium are abnormally high in two samples and
manganese in one. Ammonia is found to be above normal in five of the
samples. The analyses of the three samples from the houses in the
development whose owners had not complained and the two samples from
outside the development indicate that the wells at these locations are
producing high-quality water.
The levels of chloride and metals in several of the samples are too high
to have originated from the sanitary sewer. Furthermore, if large leaks
had developed in the sewer line, it is unlikely that the other houses in
the development would have high-quality water. The landfill is more
than a mile away and is downhill from the development. High-quality
water is being pumped from wells between the landfill and the develop-
ment; therefore, the landfill still seems an unlikely source. The
sanitarian now believes that some completely unknown source is respons-
ible and decides to hire a ground water expert to determine what it
might be.
A ground water consulting firm is retained by the city; presented with
the analyses of water samples from the 13 houses accompanied by a map
showing the location of those houses; and charged with locating the
source of the apparent contaminants in eight of the samples.
Assigned the task, the hydrogeologist first obtains topographic and
geologic maps of the area from the U.S. Geological Survey. He contacts
a company providing aerial photography services in a nearby city and is
able to obtain black and white aerial photographs of the city and the
region to the north. A visit to the local Health Department provides
well records for the houses in the affected development. These records
indicate the depth of each well, the geologic materials penetrated
during drilling, the static water level, and the yield of the well as
estimated by the driller. Calls to three local drilling firms produce
similar records for the wells serving the four houses between the develop-
ment and the landfill. A visit to the landfill site and discussions with
the operator discloses the age of the landfill, the methods of land-
filling used, and the surface conditions and drainage characteristics of
the landfill.
With these data available, the hydrogeologist is able to establish the
following:
32
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The houses in the development and the four houses north of
the development are resting on a layer of glacial till 3 to 9
meters (10 to 30 feet) thick.
Beneath this till layer is an extensive sand and gravel
aquifer, estimated to be approximately 15 to 30 meters (50 to
100 feet) thick. Underlying this aquifer is crystalline
bedrock.
The general direction of ground water flow is from the mountainous
area 16 kilometers (10 miles) north of the city.
The gradient of the water table in the vicintiy of the development
is low, but the permeability of the aquifer is relatively
high. The rate of ground water flow in the area is about .6
meters (2 feet) per day.
With the exception of the eight contaminated wells, the wells
belonging to the houses in the development are screened near
the top of the sand and gravel aquifer in an interval of about
15 to 18 meters (50 to 60 feet) below land surface.
With corrections for differences in elevation, the four wells
belonging to the houses north of the development are screened
at approximately the same depth in the aquifer as the majority
of the development houses.
The eight contaminated wells in the development are screened
substantially deeper than the other development wells. In
four of these, a 3-meter (10-foot) thick clay lens was penetrated
at the normal screening depth of 12 to 18 meters (40 to 60
feet); and the wells were drilled an additional 6 meters (20
feet) into the sand and gravel beneath the clay. The remaining
four wells were drilled at a later date by a different drilling
firm and were inexplicably deeper.
The landfill, located 1,830 meters (6,000 feet) upgradient of
the development, is situated in an abandoned gravel pit and
most likely directly connected to the aquifer serving the
development.
The landfill is roughly circular, covering an area of approximately
18.2 hectares (45 acres) and is about 488 meters (1,600 feet)
in diameter.
The contaminants of high concentrations fobnd in the eight
wells in the development are characteristic of typical munici-
pal landfall leachate.
The landfill and the sewer system are the only significantly
large sources of contamination located in the immediate
vicinity of the development or upgradient of the development
as far as the mountains 16 kilometers (10 miles) north.
33
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0 The landfill is 10 years old and has a broad, flat upper
surface. The deposited solid waste is covered daily with sand
taken from an unfilled portion of the old gravel bank.
0 Rainfall in the area averages 1,010 millimeters (40 inches)
per year.
Based on these findings, the hydrogeologist concludes that it not only
is possible but very probable that the landfill is the source of the
contamination found in the eight wells. Since the deeper wells had
become contaminated rather than the shallow ones, the sewer was no
longer considered the source of contamination.
Using the available geologic and hydrologic data, a cross section of the
area (including the landfill and the development) illustrates how only
the deeper wells could become contaminated (Figure 5). Since the
landfill most likely rests directly on top of the aquifer, leachate
generated in the landfill would flow into and move with the natural
ground water. From other landfill investigations, however, it is known
that leachate can flow as a distinct plume with relatively little
dispersal in the ground water system. Furthermore, this plume may tend
to sink toward the bottom of the aquifer as it moves. The plume might
be of sufficient thickness to enter the deeper wells; yet, it is still
possible for it to flow underneath the shallower ones (Figure 5). As
previously mentioned, both the landfill and the development have existed
for ten years. The reason for the 10-year delay in appearance of
contamination is the estimated flow rate of the ground water. If the
assumption is made that the leachate began to move into the aquifer
during the first year of landfilling, the approximate time lapsed before
reaching the vicinity of the first well would have been 3,000 days. The
distance from the landfill to the well is 1,830 meters (6,000 feet),
indicating a ground water velocity of .6 meters (2 feet.) per day and
correlating to established estimates of normal ground water flow. The
contamination then traveled 122 meters (400 feet) from the first well
affected to the last well affected in only 60 days. Normally, this
would have taken 200 days. This inconsistency can be explained by the
fact that the velocity of the ground water changes as it enters the cone
of influence created by a large number of pumping wells in a developed
area.
The width of the affected area, .4 kilometers (one-quarter mile) is
approximately equal to the width of the landfill. It is possible for a
leachate plume to migrate without substantial dispersion and remain at
approximately its original width for substantial distances. Thus, the
plume should be at least 488-meters (1,600-feet) wide (probably somewhat
wider) as it reaches the development.
34
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Along with the data and findings, the ground water consultants include
the following recommendations in their report to the city:
0 Immediately, the owner of the contaminated wells should be
advised to obtain their drinking water from other sources.
0 Water samples should be collected from all the unsampled wells
in the subdivision and analyzed for concentrations of chloride,
calcium, and iron. If any abnormalities exist, the owners of
those wells should be advised not to drink the water.
0 An immediate investigation should be instituted to positively
establish the landfill as the source of the problem and to
define the actual extent and rate of movement of the con-
taminants. Also, detailed water analyses should be performed
to determine what potential health hazards exist.
0 When the problem has been defined, effective abatement pro-
cedures should be established. The various possible proce-
dures should be evaluated and a determination made as to the
most effective.
The city Department of Health assumes the responsibility for the enforcement
of the first two recommendations. The consulting team with ground water
and engineering expertise is contracted to undertake the work necessary
to satisfy the third and fourth recommendations.
1.8.2.1 Landfill Investigations. The first phase of the consultant's
investigation, i.e., to establish the landfill as the actual cause of the
problem and to define the nature and extent of the leachate plume, is
undertaken as a series of tasks:
Task 1: Assemble and analyze all available background data
(already done during preliminary investigations).
Task 2: Conduct a field inspection of the landfill site (already
done during preliminary investigation).
Task 3: Conduct a resistivity survey in an attempt to define
the depth and lateral extent of the leachate p1ume.
Task 4: Drill a total of 6 wells to bedrock depth to verify
the results of the resistivity survey and to obtain
geologic and water samples. Conduct pumping test to
determine actual hydrologic characteristics of the
aquifer. These wells will also be used in a continual
monitoring program.
Task 5: Construct a water-balance model of the landfill to
accurately determine the contributions of precipitation
and underflow to the volume of leachate generation. This
task would be accomplished entirely with existing data.
35
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The results of the Phase I investigation indicate that the preliminary
analysis of the situation was essentially correct. Furthermore, the
leachate plume is found to contain hazardous constituents originating
from industrial waste traditionally accepted at the landfill. The
volume of leachate being generated by the landfill is calculated to be
approximately 303,000 liters (80,000 gallons) per day from precipitation
with no significant contribution from the underflow.
Based upon these results, two alternative abatement programs are presented
to the city. Both programs begin with the elimination of the pollution
source. The latter portion of each program deals with the handling of
the existing leachate. Monitoring recommendations are included in both
programs.
1.8.2.2 Abatement Program I. It is recommended that placement of
solid waste for the existing county landfill be stopped as soon as an
alternate disposal site can be located and prepared. The selection of a
new site should be based upon geologic and hydrologic considerations so
as not to create a new ground water contamination problem. Site preparation
and landfilling methods should be based upon the latest: technology to
minimize the possibility of leachate contamination of ground or surface
water.
The phase-out operations at the existing landfill should be planned to
eliminate the flat, top surface and depressions; provide adequately
sloped sides; and to promote precipitation runoff. The upper surface of
the landfill should be covered with a minimum .6 meters (2-foot) layer
of a low-permeability compacted soil to minimize infiltration. This
upper layer should be covered with a layer of top soil and then seeded.
A dense vegetation cover on the landfill surface should be maintained to
maximize evapotranspiration.
It has been determined by aquifer tests that the existing leachate in
the ground water system can be removed by a series of high-capacity
pumping wells. Three 245-millimeter (10-inch) diameter wells would be
installed at 122-meter (400-foot) intervals across the plume and 152
meters (500 feet) north of the development. In order to include the
entire thickness of the plume in the screened zone, the wells would be
drilled to bedrock and screened to a point 24.4 meters (80 feet) below
land surface to rock depth. The wells would be pumped continuously at a
rate of 126 liters per second-1/s (2,000 gallons per minute -gpm). This
will establish a hydraulic barrier, blocking leachate flowing south from
the landfill site toward the development. Also, leachate south of the
barrier wells will be drawn back toward the wells by the induced reversal
in gradient. When the polluted water has been removed from the aquifer
beneath the development, the pumping rate of the barrier wells can be
reduced to 44 1/s (700 gpm), and eight deep development: wells can be
returned to use—monitoring being continued for a period of time.
36
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1.8.2.3 Abatement Program II. Landfilling should be discontinued and
the existing landfill completed according to the description outlined in
Program I, The eight contaminated wells should not be used for water
supply., but kept intact as observation wells. Eight new wells should be
drilled to a depth of 15.2 meters (50 feet) below land surface. These
replacement wells would be screened above the contaminated zone at
approximately the same depth as the other wells in the development. The
contaminated plume should be allowed to flow along its natural course
toward the river. Since there are no city supply wells or other private
wells in its path, no additional effects will be apparent until the
plume reaches the river. The length of the leachate flow path from the
landfill to the river is approximately 4.8 kilometers (3 miles). During
the course of flow from the landfill to the river, sufficient attenuation
of contaminants may occur, rendering the leachate impotent. The progress
of the plume should be monitored by a series of observation wells placed
along its route. These monitoring wells will determine if attenuation
is actually occurring at a significant rate and if the plume is altering
its course. If at some time in the future it is determined that the
contaminants within the plume are not being sufficiently attenuated and
will be deleterious to the river, a series of barrier wells should be
installed to intercept the plume prior to its reaching the river.
The city should consider the possibility of connecting the northern
development to the city water supply. While this appears not to be
immediately necessary, continued close monitoring of the location of the
plume in the vicinity of the development may detect an enlargement of
the plume and all the wells would have to be abandoned.
37
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REFERENCES
1. Personal Communication. Ron Hoffer, State of Connecticut, Department
of Environmental Protection to Burnell Vincent, Project
Engineer, U.S. Environmental Protection Agency. 1976.
2. Office of Water Supply and Office of Solid Waste. U. S. Environmental
Protection Agency. The Report to Congress: Waste Disposal
Practices and Their Effects on Groundwater* January 1977
38
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2.0 MONITORING NETWORKS
2.1 MONITORING APPROACHES
One of the basic objectives of a landfill monitoring program is to
detect and evaluate potential or existing ground-water degradation
caused by landfill leachate. Monitoring may be either active or
passive. The former has a measurable, continuing impact on the
ground-water regime, i.e. considerably altering the flow system in
which the contaminant source is located. An active monitoring system
might consist of one or a series of pumping wells which intercept
ground water from the area that could be affected by the contaminant.
Theoretically, any contaminant entering the zone of intercepted
ground-water flow would eventually be detectable in the monitoring
well discharge. This approach is most suited for point-source,
"one-shot" contamination introduced into the ground water from such
events as spills or tank leaks. In its application to sanitary
landfills, this type of monitoring scheme unfortunately has several
drawbacks:
„ the larger (areally) the contaminant source, the
greater the number of pumping wells required to
intercept ground-water flow;
„ disposal of the pumped water can pose a problem,
especially when the water is contaminated;
o over a period of years, cumulative pumping costs
and well maintenance costs may be high;
„ pumping may accelerate the spread of leachate
through the aquifer, and tti'fe monitoring system
may eventually become a pumped withdrawal system;
o improper selection of screen depth could prevent
the well from intercepting the leachate plume.
On the other hand, passive monitoring is well-suited to monitoring
landfill leachate. In this approach, wells or other monitoring
devices strategically located with reference to ground-water flow
directions are sampled at regular intervals to determine changes in
concentrations of chemical constituents in the ground water. Flow
pattern disruptions are kept to a minimum. This system can be used
39
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to monitor continuous, long-term contaminant input from a source such
as a landfill. To monitor the area which might be affected by the
contaminant, a line of non-pumping wells is required.
The passive monitoring system will normally require a larger number
of wells than the active system. However, if these wells are small
diameter, sampling costs will be kept to a minimum; in the long run,
this approach should cost less than a major pump installation.
2.1ol Data Requisites for Monitoring Network Design
The basic data that should be carefully evaluated in designing a
monitoring network include:
o ground-water flow direction;
o distribution of permeable and impermeable ground
material;
o permeability and porosity ;
o present or future effects of pumping on the flow
system ;
„ background water quality .
Prior to commencing field investigations, the engineering/hydrogeologist
study team should first contact state and federal agencies for data
and publications concerning existing conditions of the landfill site
and its vicinity. State environmental departments and the U.S.
Geological Survey Offices are usually a valuable source of data
useful to site investigation. These data may save time, effort, and
expense. With this information, an engineering/hydrogeologist study
team familiar with the ground-water hydrology in the area may be able
to estimate conditions without actual field measurements. However,
every effort should be made to perform field measurements at the site,
including the installation of a series of low-cost wells, collecting
geologic samples during drillings, and measuring water levels in the
completed wells. Background-water quality can be determined from
chemical analysis of water samples from these wells. With good
statistical information, monitoring wells can be placed to most
effectively detect the contaminant plume spreading from the landfill.
2.1.2 Monitoring Networks for Sanitary Landfills
In order to detect and evaluate potential or existing ground-water
contamination at a landfill, a minimally acceptable monitoring well
network should be implemented and consist of the following:
„ one line of three wells downgradient fron the
landfill and situated at an angle perpendicular
to ground-water flow, penetrating the entire
saturated thickness of the aquifer;
40
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0 one well immediately adjacent to the downgradient edge
of the filled area, screened so that it intercepts the
water table.
0 a well completed in an area upgradient from the
landfill so that it will not be affected by potential
leachate migration.
The size of the landfill, hydrogeologic environment, and budgetary
restrictions are factors which will dictate the actual number of
wells used. However, every effort should be made to have a minimum
of five wells at each landfill and no less than one downgradient
well for every 76 meters (250 ft.) of landfill frontage.
Even if wells are sited according to the background information
previously described, there is a high probability that one or more
of them will not intercept the plume of leachate-enriched ground
water. This will be due to the heterogeneous and anisotrophic
elements in aquifer material. Also, the sequence of landfilling
operations has a significant effect on the shape of the leachate
plume—thus, the possibility of a well not detecting leachate
(Figure 6). For these reasons, if the budget allows, it is better
to have too many monitoring wells rather than too few.
Once contamination is detected, additional lines of wells can be
constructed farther downgradient to gauge dispersion and attenuation
of the leachate thereby providing the information necessary for
predicting the ultimate fate of the plume (assuming its veritcal
distribution can be delineated). This approach will be a time-
consuming and expensive process, the necessity for which will depend
on regulatory requirements.
Provided it is properly constructed, a single well adjacent to
or within the landfill can indicate whether or not leachate is
reaching the ground water and will give early warning of potential
aquifer degradation. Detection of leachate here should cause
the landfill operator to evaluate the observations of the down-
gradient wells with extreme caution. Installation of additional
downgradient wells at various distances from the landfill and/or
implementing remedial leachate control measures may also be justified
at this time. The actual course of action is dependent upon the
site conditions and on federal, State, and local statutes of en-
forcement agencies governing ground-water contamination.
There are potential problems associated with the use of a monitoring
well within the landfill which must be realized and appreciated.
First, the water monitored is skimmed only from the surface of the
41
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aquifer. If any density stratification is occurring, total reliance
on this well could give an unrealistic picture of actual leachate
concentration in the ground water. Secondly, elevated leachate
concentrations may be found in water samples due to improper well
construction. An improperly backfilled annulus can act as a conduit
for downward movement of leachate, introducing it into the aquifer
sooner than might have occurred naturally, (if at all). Proper
construction requires the placement of an impermeable seal of either
bentonite or cement grout in the annular space between the well casing
and the borehole wall. Because grout can shrink and bentonite can dry
and crack, their placement is not a complete guarantee of stopping
downward movement of leachate. However, neglecting to place this seal
during well installation is almost certain to speed and promote ground-
water contamination. The value of the information obtained from this
well will rarely be outweighed by the above problems, although
awareness of the problems and careful well construction are of extreme
importance.
The upgradient monitoring well provides water samples indicative of
background water quality. This well should be sampled at regular
intervals,and the analytical results used as a base line for comparison
with results from tne landfill and downgradient monitoring welis.
The background well can also provide information on contaminants in
the ground water not due to landfill leachate. When a constituent's
concentration rises, an outside source is indicated. Elevated
nitrates or sulfates from agricultural operations or low pH and high
iron due, to acid mine drainage are examples of contamination.
Therefore, proper water-quality base line data are necessary for the
correct interpretation of the chemical analyses of monitoring well
samples, both by the operator and the regulatory agencies involved.
2 = 1.3 The Effects of Aquifer Cha r a c t e r isti cs on Monitoring Networks
When considering the design of the monitoring system, aquifers can be
subdivided on the basis of permeability and porosity. Although the
design previously described could generally be applied to all aquifers,
aquifer parameters should dictate the following:
. monitoring well density, depth, construction, and
drilling methods;
o probability of successful detection of the contaminant
plume;
o sampling methods.
Thus, in order for the monitoring network to be effective, the basic
design at a particular site will require modification according to
geologic conditions. Some basic designs are presented here as
guidelines—not standards; they by no means will provide answers for
43
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all of the various hydrogeologic environments found in the United
States.
In an aquifer with intergranular porosity, water occurs in the void
spaces between individual particles of the aquifer material. In
order for the material to be considered an aquifer, these voids must
be interconnected and capable of transmitting water at a useful rate.
Typical aquifers are unconsolidated sands and gravels in river
valleys, coastal plains, intermontane valleys, alluvial plains, and
some sandstone formations. Sandstone porosity and permeability are
often lower than those of unconsolidated sands due to grain
cementation; cements such as iron oxide partially or completely
fill the pore spaces, binding the grains together. Clay and silts,
also composed of individual particles, can be highly porous; but
because clay and silt are relatively impermeable, they do not readily
transmit water. Typical porosity values are shown in Table 2.
Consolidated sediments and igneous and metamorphic rocks are fractured
to a greater or lesser degree, depending on the intensity and
frequency of the deformation and the rock type. If these fractures
are interconnected and capable of transmitting water, an aquifer can
form when they become filled with water. The ability of the aquifer
to transmit water (permeability) depends on fracture density and
interconnection; the greater the density of the fractures and the
degree of interconnection, the greater the ability to transmit water.
In some cases, the rocks can have both primary and secondary porosity;
i0e», primary porosity (intergranular porosity) produced during
sediment deposition or rock formation and secondary porosity caused
by the fracturing or solution activity which follows. Sandstone is
an example of both types of porosity since voids exist between the
sand grains, and sandstone formations are usually fractured0
Carbonate rocks are susceptible to solution by water moving through
fractures. With time, these openings are enlarged into cavities. If
the cavities are connected, ground water can move very rapidly through
the aquifer. In fact, carbonate aquifers can have extremely high
permeability. Solution openings and sinkholes provide open pathways
for leachate to reach the ground water and migrate through the
formation. Carbonate rocks can have both intergranular and fracture
porosity; but where solution cavities exist, ground water will move
through them preferentially.
2.2 MONITORING NETWORK TYPES
2.2.1 Type 1^ (Intergranular Porosity Aquifers)
Placement of monitoring wells in any hydrogeologic environment should
be done in relationship to ground-water flow paths. This manual
presents simplified diagrams to represent typica] flow patterns and
the positioning of monitoring wells for the type of aquifer discussed.
44
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TABLE 2
TYPICAL INTERGRANULAR POROSITIES
Porosity
Material Per Cent
Clay 45-55
Silt 40-50
Medium to coarse mixed sand 35-40
Uniform sand 30-40
Fine to medium mixed sand 30-35
Gravel 30-40
Gravel and sand 20-35
Sandstone 10-20
45
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Vertical and lateral flow distribution in a homogeneous, isotropic sand
aquifer are shown in Figures 7 and 8. Monitoring Wells A, B, and C
are the background, landfill, and downgradient wells, respectively.
The location of the background monitoring well ("A" well) is critical
if there is a ground-water mound associated with the landfill. This
mound, produced by increased infiltration due to landfilling, alters
flow patterns in the vicinity of the landfill as depicted on Figure 7.
If an "A" well is situated too close to the mound, sampling results
will indicate an anomalous water-quality base line. Since the extent
of flow toward the well will depend upon a variety of factors including
the amount of infiltration through the landfill and aquifer
characteristics, no rules of thumb can be given as to the separation
between this well and the landfill proper. The best policy would be
to locate the well at the most distant upgradient point of the
landfill site or, if permission of the owner can be obtained, on
adjacent upgradient property,, Assuming there are no apparent
contamination sources in the vicinity, well depth is not critical; but
better base line data would be provided if the well were screened
through the saturated thickness of the aquifer.
"B" wells should be constructed with great care and preferably located
in the first section to be filled^ Since "B" wells will detect
leachate entering the ground water, monitoring the zone of aeration
in hydrogeologic environments where r>p. water table is 1.5 to 3 meters
(5 - 10 feet) below the landfill is probably not necessary. However,
wuere the unsaturated zone is 3 meters (10 feet) or greater in
thickness, some monitoring device could be installed to detect
downward percolation of leachate before it reaches the water table.
Pressure-vacuum lysimeters can be used to trace downward movement of
leachate in the unsaturated zone and will also provide data on the
amount of attenuation and the likelihood of leachate reaching the
water table. At a new landfill, "B" wells and any lysimeters could
be installed just prior to landfilling, thus avoiding well installation
through the landfill. At most existing landfills, installationof "B"
wells will normally require drilling through the landfill itself.
The downgradient wells ("C" wells) should be in close proximity to
the landfill in order to detect the leachate plume as soon as possible.
Once leachate enters the ground water, it is difficult to control;
the sooner its presence is noted, the easier it will be to initiate
remedial action,, "C" wells are shown screened through the entire
saturated thickness of the aquifer. This procedure is recommended
because the actual flow path of the leachate plume is not known
unless previously defined by head relations in a number of observation
wellSo The flow path of leachate-enriched ground water as shown is
characteristic when the landfill is located in the aquifer recharge
area. If the landfill were closer to the point of discharge (in this
case, the river), the plume would probably be higher in the aquifer.
Since the physical behavior of contaminant bodies is not completely
46
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known, there is almost no way of anticipating where the plume of
contaminant will be within an aquifer. Therefore, the monitoring
device has to collect water over the entirp saturated thickness of
the aquifer; the simplest method is to screen the entire interval.
This type of construction could cause complications„ The primary
problem is that the well can contribute to the vertical spread of
contaminant by providing a conduit for ground-water movement. If the
aquifer is 15 meters (50 feet) or less in thickness, this is not a
major problem. Natural flow conditions would tend to distribute the
leachate uniformly throughout the aquifer, especially in recharge
areas. Thicker aquifers, 30 to 60 meters (100 to 200 feet), however,
tend to have more pronounced shallow and deep flow systems; there is
a chance the leachate plume would remain in the shallow flow system.
A well screened over the entire saturated thickness provides a path
from the shallow to deep flow systems. Of course, this is a gross
simplification and is intended as a guideline only, since actual
flow patterns will depend upon the hydrogeologic environment in which
the landfill is located.
The problem of vertical spread of contaminants can be overcome by
using the well-cluster technique as will be described in Chapter 3»
However, it will be necessary for the landfill investigator to'balance
the extra cost of a well cluster against the possibility of promoting
the vertical spread of contaminants.
Another problem with a well screened over the entire saturated
thickness is the dilution of leachate below limits of detection when
a sample is pumped from the wello This would result in a time lag
between the first arrival of contaminated ground water at the
monitoring well and its first detection in the sampled water. The
magnitude of this lag is difficult to predict. However, as the
contaminant travels in a definable plume with a small zone of
diffusion to uncontaminated water, only a minimal length of time
passes before the zone of diffusion moves past the well and the
contaminated ground water starts to enter. If detection is still a
problem, concentration or extraction techniques could then be used
for key leachate tracers to determine the presence or absence of
leachate in the sample. Since "C" wells are only designed to show
the presence or absence of leachate and not vertical distribution
once leachate is detected, a more sophisticated sampling devir» could
be used; e.g. well clusters, sampling during drilling, or other
methods discussed later in Chapter 3.
2.2.2 Type ll_ (Fracture Porosity Aquifers)
Ground-water flow patterns are not as predictable in fractured rock
aquifers as they are in aquifers with intergranular porosity. Unless
there is a primary porosity, as in a sandstone aquifer, ground-water
flow patterns will be controlled by the fracture pattern,, Flow
patterns are represented schematically in Figures 9 and 10. The
-------
GROUND-WATER FLOW
A,B,C MONITORING WELLS
FLOW DIRECTION OF
LEACHATE-ENRICHED
GROUND WATER
.LEACHATE ENRICHED
GROUND WATER
FIGURE 9, MONITORING NETWORK FOR AQUIFERS WITH FRACTURE
POROSITY - AREAL FLOW PATTERNS,
50
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same configuration of "A", "B", and "C" monitor!. _ /ells may be used
"in this hydtogeo3.ogic regime. However, the wells are open-hole
rather than screened with the exception of. cased-off surficial materials
to prevent them from caving into the open hole.
The major problem in fractured rock terranes is the interception of
the fractures that might contain contaminated ground water with a
monitoring wello A well can fail to intercept any fractures and will
be dry0 This will necessitate drilling another well nearby,, An even
more serious condition would be the interception by the monitoring
well of a set of fractures not connected to the landfill, failing
entirely to indicate leachate in the ground water. Without intensive
and expensive geologic analysis, it is impossible to predict more
than general ground-water flow direction at the site. Monitoring
wells cannot be located precisely; to compensate, a higher well
density is needed—perhaps one well for every 30 meters (100 feet) of
landfill frontage perpendicular to ground-water flow.
Specifying well depth presents another problem0 Because of the weight
of overlying material, fractures either were never formed or have been
squeezed shut with depth. If shut, these fractures can no longer be
considered an aquifer. A general rule of thumb is that fractures tend
to die out at depths of 90 meters (300 feet) or greater; monitoring
wells probably should not be drilled deeper unless there is geologic
or hydrologic information to the contrary.
2.2.3 Type III (Solution Porosity Aquifers)
Similar to fractured rock aquifers, ground-water flow patterns are
controlled by solution openings or fractures in carbonate rock
aquifers., The positioning of the "A", "B", and "c" monitoring wells in
this type of flow system is shown in Figures 11 and 12. The
monitoring network is the same as that for fractured rock, including
the same problems: i.e. intercepting the solution cavities and well
completion depth. Increased well density can solve the former; buc,
as in fractured rocks, there are no handy rules for the latter.
Sinkholes can be 30 meters (100 feet) or more deep; while the depth
at which solution cavities may exist is limited or.ly by trie thickness
of the carbonate rock,, Unless the solution cavities follow a well-
known regional fracture system, there is no way to predict their
position prior to locating a monitoring well. A trial-and-error
approach to placement is mandated by the hydrogeologic environment,
and there is no assurance that the wells will intercept the
contaminant plume.
203 LEACHATE MOVEMENT IN DIFFERENT HYDROGEOLOGIC SETTINGS
The rate, direction, and distance of leachate travel from a landfill
to an ultimate discharge point will be largely determined by the
hydrogeologic setting. The leachate plume may be confined to the
52
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i
LEGEND:
BO
MONITORING WELL
FLOW DIRECTION OF LEACHATE
'ENRICHED GROUND WATER
LEACHATE ENRICHED
GROUND WATER.
FIGURE 11, MONITORING NETWORK FOR AQUIFERS WITH SOLUTION
POROSITY - AREAL FLOW PATTERNS
53
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landfill site, or it may travel long distances; it may be divided into
multiple plumes, move into different aquifers, and reverse its
direction. If it is to be effective, a landfill monitoring program
must account for all possible routes of leachate movement.
Figures 13 to 27 illustrate a number of hypothetical hydrogeologic
landfill settings. These diagrams are schematic and are only intended
to illustrate general leachate flow principles. Although both the
geology and hydrology of the settings are necessarily somewhat
simplified over most actual conditions, the general principles
illustrated are still valid. In addition, such complicating factors
as differential attenuation of contaminants by subsurface sediments,
interference with leachate flow by production wells, and surface
emergence of leachate have been omitted. It is obvious that if all
factors influencing leachate migration from a landfill were considered,
the number of possibilities would be almost limitless. For this
reason, each individual landfill should be subjected to a hydrogeologic
investigation prior to the establishment of a monitoring system or
implementation of a pollution abatement program0
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3.0 MONITORING AND WELL TECHNOLOGY
This chapter discusses and evaluates various monitoring techniques
used in ground-water contamination studies relative to their use for
monitoring land disposal sites. An overview of well technology is
also presented to familiarize the reader with drilling methods and
equipment. Cost information is presented throughout the chapter
solely to demonstrate relative cost comparisons among the various
monitoring techniques. Costs will vary widely with location and
even with drilling contractors. Each project should establish its
own costs by carefully reviewing the site conditions, the monitoring
needs, and by contacting the local drilling contractors.
The monitoring techniques are divided into subsurface monitoring for
the aeration and saturation zones, field inspection techniques, and
other techniques such as surface-water quality measurements, aerial
photography, and geophysical well logging. The monitoring purposes
as well as the legal influences which are discussed in Chapter 1 will
determine which one or combination of techniques to utilize. For
example, if the purpose for monitoring is a state-wide evaluation of
the effects of the leachate problem, a presence/probable absence
determination using field inspection techniques would probably be
adequate in most cases. For some larger sites, verification with
some basic monitoring of the zone of saturation might also be
justified. If, however, the monitoring purpose is to obtain
enforcement evidence, extensive sub-surface monitoring in the zone
of aeration and/or saturation would be necessary, involving the
analysis of several monitoring wells.
Monitoring in the zone of aeration would not normally be part of a
routine monitoring program. However, monitoring this zone is
extremely useful for other than routine monitoring purposes. For
example, soil analysis and pressure-vacuum lysimeter techniques are
commonly used in scientific evaluations of sites; validation of
design criteria, such as the soil attenuation capabilities at a
site; and to check the effectiveness of an engineering design at a
site. Also, legal influences may require monitoring in the zone of
aeration. For example, in states where zero degradation laws are in
effect, monitoring the zone of aeration has significance as an
early-warning technique.
71
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3.1 ZONE OF AERATION
The zone of aeration is that part of the earth's crust where the voids
are filled with air and (usually) where some water is held by molecular
attraction. It is through this zone that percolating waters must pass
to recharge or contaminate the ground water. In most cases involving
landfill contamination, sampling in the zone of aeration would not
normally be carried out unless:
. scientific research such as measurement of attenuation
is involved;
. there are unusual geologic or hydrologic considerations;
. extremely toxic chemicals are suspected in the leachate
which would demand closer attention;
. sampling is to be used as an early-warning system to
check the effectiveness of engineering techniques.
Such sampling is difficult, and some of the methods are expensive.
However, when the decision has been made to monitor water quality
in the zone of aeration, the depth to water becomes an important
factor in placing the sampling devices.
Monitoring the zone of aeration is most appropriately done directly
beneath the landfill where the leachate is migrating downward toward
the water table. With this in mind, the monitoring devices should
be placed ahead of landfill wherever possible. This avoids drilling
through the landfill and the problems associated therewith.
3.1.1 Soil Analysis
Soil analysis can be valuable as a monitoring tool for tracing
leachate constituents, particularly those prone to cation exchange
or other adsorption reactions. Collecting soil cores beneath the
landfill can be done during well installation. Techniques for
core collecting are available, and methods for soil analysis are
documented. »'»' Soil analysis has had only limited use in leachate
monitoring programs for several practical reasons. Foremost is the
limited number of commercial soil-testing laboratories capable of
handling soil tests outside the scope of agricultural application.
For example, testing laboratories are established in each state for
soil fertility analysis (nitrogen, phosphorus, potassium, pH); but
heavy metals, organics, and exchangeable cations are not accommadated.
In many places, only noncommercial samples are accepted by these
labs.
Another restriction in soil analysis is inherent in the methodology.
The total soil is seldom analyzed; only a chemical extract is
considered. Fundamentally, a separation of the inorganic/organic
72
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matrix and chemical species in soil solution or "available" to soil
solution must be made. An analysis of the complete soil, including
the inorganic matrix,would be meaningless. The objective of the soil
analyst is to measure the chemical species: in solution, exchangeable
to solution, available to plants, or accumulated by adsorption or
precipitation on the inorganic matrix. To meet this objective, soils
must be treated with reagents of differing chemical reactivity under
a variety of physical conditions. The resulting solutions are then
analyzed for the chemical species of interest. Interpretation of
results is a function of soil characteristics and analytical
methodology. Although methods have been standardized to a degree,
the analyst must be able to adapt and interpret according to the
dictates of the soil sample. In contrast, water samples are usually
analyzed directly or with a minimum of pretreatment. This is not to
say that there are no analytical problems with water samples, but
bringing a soil sample to the same state as a collected water sample
involves an additional analytical step.
Soil samples yield information which cannot be obtained from water
samples. Therefore, soil sampling has a place in the leachate
monitoring program; its use should be expanded. Chemical species
associated with soil solution, as well as those on exchange sites, can
be traced downward in a soil profile or in the unsaturated zone.
Locations of accumulation or leaching can be identified.
Sulfate (SO^) , chloride (Cl), and nitrate (N03> are soluble and
unaffected by cation exchange reactions in soil. This results in
mobility impeded only by the restrictions of water percolation.
Soil samples can be analyzed for these anions in addition to cations
which are generally more strongly associated with the solid-soil matrix.
Because cations must be released from the soil matrix prior to
determination, analysis is more difficult. However, zone location ot
heavy metals or phosphorus accumulations can only be detected through
soil analysis.
In addition to the chemical information obtained from soil core
sampling, valuable information on grain type and size can be gained by
visual obsarvation. Organic matter layers, clays, or silts may be
encountered. Knowledge of their locations will aid in interpreting
flow patterns and chemical configuration in the plume. If verification
of the visual estimates is desired, a mechanical analysis can easily
be made by simply separating the soil into respective proportions of
sand, silt, and clay. Even more elaborate x-ray crystallographic
analysis of clays will identify the minerology. This latter degree
of sophistication is beyond the scope required for anything but a
research program on leachate production and movement.
Decisions regarding adoption of soil sampling in a monitoring program
should be made on the basis of the following criteria:
73
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applicability of information derived from the
monitoring program;
compliance with governmental regulations covering
monitoring programs;
relative cost of soil analysis and water analysis from
the zone of aeration;
availability of analytical facilities;
availability of analytical techniques for the
parameters of interest.
Advantages
1. Ease of soil sample
collection.
2. Accurate vertical and
areal sampling locations.
3. Best method to measure
leachate attenuation
through adsorption or
precipitation mechanisms.
4. Long interval between
sampling possible because
of intermittent leachate
production.
5. In situ conditions of
sample can be maintained
with proper handling.
6. Physical and chemical
condiitons throughout
unsaturated zone can
be observed.
7. Samples can be stored for
later comparison or
further analysis.
8. More representative
biological sampling
possible than with
water.
Disadvantages
1. Commercial laboratories
capable of non-agricultural
soil analyses are scarce.
2. Not a proven standardized
sampling method for
monitoring programs.
3. Cost of analysis likely
to be higher per sample
than water because of
2-step analytical procedure.
4. Applicable mainly in the
zone of aeration.
5. Requires special equipment
for each sample collection.
6. Analytical methods not
adaptable to high-rate
standard procedures as
available for water.
7. Wetting and drying cycles
and changes in redox
potential can change
chemical reactivity of
some soil constituents
after collection.
8. State-of-the-art not
documented in leachate
studies.
74
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3.1.2 Pressure Vacuum Lysimeters
3.1.2.1 Methodology. Pressure Vacuum lysimeters have been used
to obtain samples of in-situ soil moisture. They are used
predominantly in the zone of aeration but can easily be used to
sample ground water. In its most improved form, this device consists
of a porous ceramic cup capable of holding a vacuum, a small-diameter
sample accumulation chamber of PVC pipe, and two sampling tubes
leading to the surface. Once the lysimeter is emplaced, a vacuum
is applied to the cup. Soil moisture moves into the sampler under
this gradient, and a water sample gradually accumulates. Then, the
vacuum is released and pressure is applied, forcing the accumulated
water to the surface through the sampling tube. Construction,
installation, and sampling procedures are described by Grover and
Lamborn (1970)6, Parizek and Lane (1970)7, Wagner (1962)8, Wengel
and Griffen (1971)9, and Wood (1973)10.
The technology of lysimeter utilization is well established.
Lysimeters have been used to trace:
. pollution from septic tanks;
12
. pollution from cesspools;
. pollution from synthetic deter gents •,
14
. pollution from colliery spoil heaps*
Apgar and Langmuir (1971) used suction lysiraeters, wells, and soil
samples to study the movement and chemical characteristics of
leachate from a landfill in central Pennsylvania (Figure 2.8). At
that location, the water table is more than 61 meters (200 feet)
below ground surface; monitoring the unsaturated zone is of great
importance. To do this, the landfill excavation was graded and lined
to allow leachate to drain into a percolation trench along one side.
The lysimeters were installed underneath this trench. As many as
four lysimeters were emplaced at selected depths in a single borehole
to a maximum depth of 16.6 meters (54.5 feet)—each installation
separated from the next by a pelletized bentonite seal. Water samples
collected from the lysimeter network were analyzed for Eh, pH,
temperature, specific conductance, BOD. Cl~, SO^", total alkalinity,
NH3, NO^, NO^, P04, Ca"!"f, Mg"1"1", Na+, Y7, and total iron. Apgar and
Langmuir were able to define differences in leachate concentration
from upslope and downslope cells as well as from leachate attenuation
and rate of movement.
Wood (1973) suggested a modification of the lysimeters used by
Apgar and Langmuir so that water samples could be recovered from
any depth (Figure 29). Since a check valve prevents pressurization
75
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E.E
®w
TUBING TO SURFACE
CONNECTORS
PIPE-THREAD SEALANT
PVC PIPE CAP
P V C PIPE
PVC CEMENT
POLYETHYLENE TUBING
BRANCH "T"
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CONNECTORS
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POROUS CUP
FIGURE 29, MODIFIED PRESSURE-VACUUM LYSIMETER INSTALLATION
(After Wood, 1973)10
77
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of the porous cups, deep pressure-vacuum lysimeters appear to be the
best method of monitoring the zone of aeration. In deeply placed
lysimeters, pressure exceeding about one atmosphere in the sample
chamber would drive accumulated water back through the cup rather
than to the surface.
3.1.2.2 Implementation. Parizek and Lane (1970) have given a detailed
description of pressure-vacuum lysimeter installation and sampling
procedures:
A typical pressure-vacuum lysimeter installation is
shown in Figure 29 (sic.). Placement holes are first
drilled to the desired depth. They may be 101 to 152mm
(4-6 inches) (sic) in diameter depending upon the
number of lysimeters to be placed in eacn hole. A
plug of wet bentonite clay is placed in the bottom
of the hole to isolate the lysimeter from the
undisturbed soil below it. This plug is optional.
A layer of "Super Sil" at least six inches deep, is
placed on top of the bentonite. "Super Sil" is the
trade name for a commercially available, crushed,
pure silica-sand of almost talcum powder consistency.
This is used to provide a clean transmission medium
for soil moisture moving under capillary pressure,
to insure hydraulic contact of the adjacent soil
medium with the porous tip, to fill uneven voids
created during drilling, as well as to discourage
clogging of the ceramic tip by colloids, organic matter,
or soil particles. The lysimeter is placed in the
hole to the desired depth, and "Super Sil" is placed
around it until the lysimeter is half buried. Native
soil, free from pebbles and rocks, is backfilled and
tamped with long metal rods. After the lysimeter
is covered with about six inches of soil, a second
plug of bentonite is deposited to further isolate
the lysimeter and to guard against possible channeling
of water down the drill hole. Backfilling is continued
with native soil to the depth where it is desired to
set the next lysimeter, at which point the above
procedure is repeated.
It was found that three lysimeters were the maximum that could be
conveniently placed in a 152-mm(6-inch)diameter hole. If more
than three were installed, difficulties arose in proper depth
placement, proper tamping of backfill material was prevented, the
danger of crimping or tangling the copper tubing was increased, and
the risk of channeling soil water down the incompletely filled
hole became greater. Care was taken to accurately measure the depth
of placement of each lysimeter. It was possible to set the lysimetetfs
to within 152mm (6 inches) of the desired depth even in 9-meters
(30-foot) deep holes.
78
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After the lysimeters are placed, a short section of flexible Tygon
plastic tubing is secured over the end of each copper access tube with
PVC electrical tape. This procedure allows thumb-screw pinch clamps
to be used to seal the lysimeter between sampling periods, thereby
maintaining the vacuum within the lysimeter.
The pump used in conjunction with these pressure-vacuum lysimeters is
a two-way hand pump that can either deliver a back pressure or pull a
vacuum. It is similar to a tire pump and can be purchased from any
laboratory equipment supply house. A small vacuum gauge may be
installed on the pump by means of a tee union. This enables the
operator to consistently apply a desired vacuum (about 457mm—18 inches-
of mercury) to all lysimeters. A length of Tygon tubing is secured to
each of the pump's pressure and vacuum parts, allowing the pump to be
coupled to the access tubes of the lysimeters. The free ends of the
pump's tubing are slipped over a short length of copper tubing that is
secured to the pressure-vacuum tube of the lysimeter and is held
securely by a small spring-loaded clamp.
A typical pressure-vacuum lysimeter sampling sequence is as follows:
. The lysimeter's discharge tube is clamped shut and
the vacuum side of the two-way pump is attached to
the "in" tube.
. A vacuum of approximately 457mm (18 inches) of mercury
is drawn, and the "in" tubing is clamped shut.
. To recover soil-water samples, the pressure side of
the two-way pump is attached to the lysimeter's "in"
tube; and the pinch clamps are removed. A few
strokes of the hand pump generates enough pressure
to force the water out of the lysimeter and into
a collection bottle placed under the discharge
tube.
. After emptying the lysimeter, the vacuum side of the
pump is attached to the "in" tube, and the lysimeter
is evacuated again to gather another sample.
Advantages Disadvantages
1. Inexpensive sampling 1. Considerable care must be
device of great reliability. taken during operation. A
person with adequate training
2. Inexpensive installation. in the procedure is required.
3. Standard water analysis can 2. Sampling device failure is
be made. irreparable.
79
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4. Samples can be collected
at a central point.
3. Small volume of sample,
limiting number of analyses
that can be made.
4. Surface tubing subject to
tampering unless adequately
protected.
5. Use at depth greater than
33 meters (108 feet) not
documented.
6. Potential sample contamination
by porous cup if material is
not properly prepared.
7. Possible plugging of cup by
colloidal materials; cup
might exclude large molecules
and alter the quality of the
sample.
3.1.3 Trench Lysimeters
3.1.3.1 Methodology. Several investigators have used trench
lysimeters to sample water from irrigation or rainfall near the
surface of the zone of aeration. In normal practice, a wood-
reinforced trench or concrete-ring caisson is installed to a depth
of 3 to 9 meters (10-30 feet) below land surface. Pans, troughs,
or open end pipes, are forced out of the trench (caisson) through
access ports iato the subsoil. These collecting devices intercept
percolating water and conduct it to sample bottles inside the trench.
Only after irrigation or precipitation is there sufficient water
infiltrating the subsoil to collect a sample.
Due to the potential accumulation of hazardous gases generated by
decomposition of landfilled material, the use of an open trench or
caisson to collect leachate for sampling can be dangerous. Artificial
ventilation and gas monitoring devices are required to prevent injury
to personnel recovering samples collected inside the trench.
3.1.3.2 Implementation. A description of a typical trench lysimeter
is excerpted from Parizek and Lane (1970) . 7
A 1.2 meter (4-foot) wide, 3.6 meter (12-foot) long (sic)
trench was excavated to a depth of 3 meters (10 feet)
(sic) using a back hoe. The hoe was braced with timbers
and siding to allow safe access to the trench. The
trench was then hand-dug to a 5.2 meter (17-foot) (sic)
depth and braced. The entire seepage face was inclined
80
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1 to 5 degrees from the vertical and sloped toward a
hill down which soil water and interflow was
expected. The residual soil contained resistant
chert and quartzite cobble* and boulders and was
reasonably well cemented with iron oxide and clay.
As a result, the pans could not be inserted into
the soil profile without first providing an opening.
A sheet metal blade 102-wn (4-inches) (sic) wide a»d
.6-meters (2-feet) (sic) long was haaraered into the
overhanging bank with a sledge hawmer to provide
access for the pans. Pan lysimeters were tapped
into these openings and allowed to slope gently
toward the trench. Voids above and below the pans
were backfilled with soil, tanped into place. As
siding was added to the trench walls, holes were cut
to allow the copper tubings to project into the
sampling pit. Spaces between the original trench
faces and siding were filled with native soil an4
washed pea-gravel to allow water to flov freely
toward the pit floor. After the walls and braces
were etnplaced, plastic tubing was connected to the
copper tubing and inserted into plastic sampling
bottles. The sampling pit was covered with a sloping
roof and a half-round drain pipe was used to divert
roof water away from the installation. A ladder was
placed at one end of the house to allow access.
Alternate methods of construction are to place concrete manhole rings
in an open excavation or to sink them to a desired depth using
caisson construction techniques. The decision as to which method to
follow would depend upon soil stability.
Advantages
1. No apparent advantages.
Disadvantages
1. Collection procedure
dangerous because of
possible flamable gas
accumulation in trench.
2. Samples can be collected
only after rainfall.
3. Construction of trench or
caisson is expensive.
4. No documentation of
application to landfills.
81
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3.2 ZONE OF SATURATION
In the zone of saturation, leachate movement from a landfill will be
controlled by a combination of ground-water flow patterns and soil-
leachate interactions. Under shallow water-table conditions, only a
thin zone exists where unsaturated soil-leachate interactions can
reduce leachate concentrations. Therefore, careful collection of
representative ground-water samples from properly constructed wells
is necessary to trace leachate movement or to determine its
presence in the ground-water environment.
3.2.1 Well Screened or Open Over a_ Single Vertical Interval
3.2.1.1 Methodology. Wells screened over a single vertical section
of an aquifer are the most common construction method used to obtain
ground-water samples from unconsolidated sediments or semi-consolidated
rocks. Uncased wells (open hole) in consolidated rock can be used for
the same purpose. Although this type of well is routinely used in
monitoring leachate contamination of the ground water, a single well
is not effective in providing information on the vertical distribution
of a contaminant. '
In practice, a well is drilled to an arbitrary depth, usually just
below the water table in landfill studies. The screen is positioned
to intersect the water table as shown in Figure 30. The rationale for
this type of construction is that if leachate reaches the ground
water, it will be detected in water samples from this type of well.
The drawback of the construction is immediately apparent; only a
portion of the aquifer is sampled, and only the most recently
infiltrated leachate can be collected. In most cases, leachate will
be under partial control of a density gradient and will sink into
the ground-water body. This denser fluid body, sinking into fresher
water, cannot be sampled with a well that skims only the top of the
water body. However, great reliance has been placed on this type of
well construction to trace the extent of leachate movement into an
aquifer.
Although a well may be completed below the water table, 7t may not
provide water samples representative of leachate concentration at
that point. For example, the well casing may entirely seal off the
contaminated aquifer; or the screen may penetrate into another
aquifer system (if little is known about site geology). The
information gained from these water samples would be misleading.
This drawback can be counteracted in part when the well is screened
over the entire aquifer thickness. However, if the aquifer is thick
and the contaminated plume is thin, the composite ground-water sample
obtained provides no information on the vertical distribution of
leachate; sample dilution may mask the contamination.
82
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CAP
LAND SURFACE
BOREHOLE
SCHEDULE 40 PVC
CASING
SLOTTED SCHEDULE
40 PVC SCREEN
LOW PERMEABILITY
BACKFILL
GRAVEL PACK
WATER TABLE
FIGURE 30, TYPICAL MONITORING WELL SCREENED
OVER A SINGLE VERTICAL INTERVAL
33
-------
Taking everything into consideration, using a single-screen well
appears to be justified under two situations:
. when obtaining composite ground-water samples from
wells in which the entire saturated thickness of
the aquifer is screened;
. when the sampled area's depth to water is great,
and the major part of the sampling program is
aimed at the zone of aeration and the top of
the zone of saturation.
The latter case is probably the best use of this type well. The wells,
completed in the upper zone of the water body, would serve as an early-
warning system if any leachate were able to percolate to the ground
water. Once detected, other sampling techniques would be required to
trace the extent of leachate and movement in the aquifer.
3.2.1.2 Implementation. This type well can be drilled by a variety
of techniques, including:
mud-rotary,
. reverse-rotary,
. air-rotary,
. jetting,
. augering,
drive points.
Diameters range from 32mm (1% inches) to greater than, but rarely
exceeding, 914mm (36 inches). The drilling method chosen depends
upon factors such as:
the nature of the material to be penetrated;
. the diameter and depth of well desired;
site accessibility;
. availability of drilling water;
. budget and time constraints;
and a variety of other factors resulting from ind.> "idual site conditons.
Drilling methods are discussed in a later section. With the possible
84
-------
exception of hand augering and the installation of drive points, a
drilling contractor should be hired to install this type of well,
unless the investigator has access to a power auger, soil boring, or
Jetting rig.
A hypothetical water-table aquifer has been assumed for cost comparisons
of the various techniques described in this chapter. This aquifer
consists of sand, with a depth to water of 3 meters (10 feet) and a
saturated thickness of 30 meters (100 feet).
As mentioned in Chapter 2, the recommended type of construction for
monitoring purposes is to screen the well over the entire saturated
thickness of the aquifer. (The example is 30 meters—100 feet,)
The quickest and least expensive way to complete this type of
installation would be to:
. drill a 152- to 203-mm (6 to 8-inch) diameter borehole
with a hydraulic rotary rig to the bottom of the
aquifer;
. set 102-mm (4-inch) diameter slotted PVC well screen
and PVC casing;
backfill with a gravel pack or formation stabilizer;
. place a concrete collar around the well casing at
ground surface to prevent downward leakage of
rainwater or other fluids.
For the hypothetical example, the cost of this installation would be
in the range of $2,300 to $4,500 for drilling, materials, installation,
and development. A well screen is second only to drilling in terms of
cost, ranging from $1,000 to $1,500 for 30 meters (100 feet) of
102-mm(4-inch) slotted PVC. Construction cost could be reduced to a
total of $1,600 to $3,700 if 51-mm (2-inch) casing and screen are
used; but sampling can be more difficult and tedious in a well of
this diameter. On the other hand, using 152-mm (6-inch) casing and
screen facilitates development and water sampling but increases the
cost to the range of $6,400 to $7,500 per well. In wells of this
size, wire-wound or louvered metal well screens are more commonly
used than PVC, resulting in a substantial cost increase per
installation as compared to the 102-mm (4-inch) well.
If the investigator is interested in sampling only the top of the
aquifer with a well constructed so that a 3-meter (10-foot) long,
102-mm (4-inch) diameter screen intersects the water table, price
per installation would range from $700 to $1,200. This is a
substantial reduction in the expenditure required to monitor the
ground water; but as discussed above, it is not a completely
reliable technique for assessing ground-water contamination by
85
-------
leachate. Even greater reductions in expenditure per installation can
be obtained by installing a 51-mm (2-inch) diameter, 1.5-meter
(5-foot) long drive point by hand—the total cost of which would be
less than $200 per well including labor, materials, and development
with a pitcher pump.
Advantages
1. Small diameter, shallow
wells are quick and
easy to install.
2. Can provide composite
ground-water samples if
screen covers saturated
thickness of aquifer.
3. Can be drilled by a variety
of methods.
Disadvantages
1. No information is given on
the vertical distribution
of the contaminant.
2. Improper completion depth
can cause error in
determining leachate
distribution.
3. Screening over much of the
aquifer thickness can
contribute to vertical
movement of contaminant.
4. Leachate may become diluted
in the composite sample,
resulting in lower than
actual concentrations.
3.2.2 Piezometers
3.2.2.1 Methodology. The terms piezometer and observation well are
commonly used interchangeably; however, there is a significant
difference between them. As implied by its name, piezometer is a
pressure measuring device, frequently used for monitoring:
water pressure in earthen dams or under foundations;
water pressure in aquifers.
In the first instance, the piezometer resembles a porous tube or plate;
in the later, it resembles a screened well or open hole. A piezometer
is isolated from other pressure environments by an impermeable clay or
cement seal. Water samples representative of a specific horizon can
be obtained from well-type piezometers—a highly desirable factor in
designing a monitoring program (Figure 31). If the well screen is
properly isolated by an impermeable seal placed immediately above the
screen, a piezometer can also be used to measure vertical head
differences under unconfined conditions. Any well constructed
without this seal cannot be considered a piezometer. In application
to landfill leachate monitoring, there is a significant difference
-------
CEMENT OR
BENTONITE GROUT
SLOTTED SCHEDULE
40 PVC PIPE
REMOVABLE
'PVC CAP
-CONCRETE PLUG
SCHEDULE 40
PVC PIPE
SAND OR
GRAVEL PACK
FIGURE 31, PIEZOMETER WELL INSTALLATION FOR
SHALLOW GROUND-WATER MONITORING
(After Clark, 1975)19
37
-------
between a piezometer and a well screened over the entire vertical
interval. The relatively impermeable annular seal will prevent
downward movement of leachate into uncontaminated zones of the
aquifer.
A low-cost modification of a typical engineering piezometer will allow
collection of in-situ ground-water samples throughout the saturated
thickness of an aquifer. The piezometer, on modification, resembles
the deep pressure-vacuum lysimeter (Figure 32). Porous PVC is used
instead of a ceramic cup which in this instance is unnecessary and
would decrease the effectiveness of the sampler. With porous PVC,
a vacuum applied to the sampling chamber is immediately transmitted
to the aquifer, drawing water into the chamber; a porous ceramic cup
holds a vacuum and water slowly moves into it. Using porous PVC
(or even slotted PVC) should reduce the cost of the sampler below the
approximate $30 cost of commercially available deep pressure-vacuum
lysimeters. The surface sampling procedure can be the same as that
for the pressure-vacuum lysimeter described earlier.
3.2.2.2 Implementation. To place a grout or bentonite seal around
a well casing as required in piezometer construction, an annulus
between the casing and the borehole wall is needed. Drilling methods
are limited to:
. cable tool with inner and outer casing;
. one of the rotary techniques;
. hollow stem augering.
After casing and screen have been installed, a gravel pack is placed
around the screen. To seal the well casing, a neat cement grout or
bentonite slurry is poured or pumped into the annulus, preventing the
vertical leakage that might occur if the well were merely backfilled
with cuttings or fill. From a sampling standpoint, the seal is vital.
The sample withdrawn from the well is from a known vertical interval
of the aquifer. Without the seal, rainwater would infiltrate the
backfill, potentially diluting samples collected from the well; or
leachate could move downward, causing samples to be unrepresentative.
Another consideration is that the seal tends to prevent movement of
leachate in the annular material, which could act as a conduit to
uncontaminated zones of the aquifer. Constructing a monitoring
well that contributes to or hastens the spread of contamination is
obviously not a recommended procedure.
Since piezometers and wells screened over a single interval are
identical (except for an impermeable seal between the casing and
borehole wall), the only price difference is that incurred for
placing the impermeable seal and purchase of necessary sealing
88
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PRESSURE-VACUUM
LINE
DISCHARGE LINE
LAND SURFACE
LOW PERMEABILITY
MATERIAL
BOREHOLDE
POROUS OR SLOTTED
PVC PIPE
CHECK VALVE
SAND BACKFILL
POLYETHYLENE TUBING
"T"AND ELBOW FITTINGS
SAMPLE COLLECTION
CHAMBER
END CAP
FIGURE 32, DETAILS OF A LOW-COST PIEZOMETER MODIFIED
FOR COLLECTION OF WATER SAMPLES
89
-------
materials. In the hypothetical aquifer, only a 3-meter (10-foot) seal
is required. A two-man crew should be able to emplace it in half a
day to a day. This would increase installation cost about $500 to
$1,000 if grout were pumped into place and approximately $250 to $450
if bentonite were placed by hand. Total estimated cost per installation
can be found on Table 3.
Advantages
1. Sample is collected from a
selected vertical section
of the aquifer.
2. If properly constructed,
technique prevents downward
migration of leachate in
borehole.
3. Can be installed
inexpensively and rapidly if
casing diameter is small.
4. Modification of an
engineering piezometer will
allow vertical sampling of
contaminant.
Disadvantages
1. Restricted number of
drilling methods.
2. Improper completion depths
can cause error in
determination of leachate
distribution.
3. Improper construction can
contribute vertical migration
of contamination.
3.2.3 Well Clusters
3.2.3.1 Methodology. As previously discussed, the major drawback in
using individual wells or piezometers screened over a single vertical
interval of the aquifer is that they provide no inforaation on the
vertical distribution of the contaminant and only rudimentary
information on its area distribution. To overcome this, investigators
have used well clusters to define the vertical distribution of a
contaminant. Each cluster consists of a group of closely-spaced,
small-diameter wells completed at different depths. From these wells,
water samples that are representative of the different horizons
within the aquifer can be collected. Careful placement of well
clusters at a landfill site and the surrounding area will allow
reliable delineation of both vertical and areal leachate distribution.
Well clusters are by far the most common and successful technique to
date for delineating ground-water contamination. One shortcoming,
however, is that regardless of the selection of the completion
depth of each well in the cluster, there are unsampled intervals
through which leachate may pass undetected. Several approaches to
selecting depth have been made:
90
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. a pair of wells, one screened at the top of the
other at the bottom of the aquifer^20,21
. a 3-well cluster with screens set on the top, middle
and bottom of the aquifer under investigation,22
. clusters in which the screened intervals are
separated by preselected intervals, such as:
. the 3-, 6-, 9-, 12-, and 18-meter (10-. 20-,
30-, 40-, and 60-foot) screen depths;2*
. the 6-meter (20-foot) separation from
6 to 30 meters (20-100 feet) (Figure 33);24
. terminating 2 to 3 wells at 3 to 4.5 meters
(10-to-15-foot) intervals.25
The fixed sampling depth, whatever the screen placement selected,
limits to some degree the effectiveness of the well cluster.
Some uncertainty will always exist as to the actual vertical
distribution of the contaminant. Construction of more wells per cluster
is not the answer; only a limited number of wells can be constructed
close enough together to delineate vertical contaminant distribution
at one particular point. Also, construction costs and the time
required to complete the cluster would become prohibitive factors.
The only way to obtain the,most complete picture of leachate
distribution is to collect ground-water samples during drilling.
This procedure is described in section 3.2.5. However, this
technique provides only a one-time series of samples.
3.2.3.2 Implementation. Under certain conditions, well clusters are
easily installed—a major factor to be considered when designing a
leachate monitoring system. Normally, in unconsolidated sediments,
a small-diameter steel casing 51 to 63mm (2 - 2^ inches) is driven
by jet drilling to the desired depth; the screen is positioned by
casing pull-back or by augering a hole and forcing a well point to the
desired depth. Alternatively, a hole can be drilled or augered to a
predetermined depth and a well point driven out the bottom of the hole
into undisturbed sediments. Either installation technique is
relatively rapid and inexpensive. For shallow aquifers (6-9 meters—
20-30 feet), 32mm (1^-inch) well points can be driven by hand to
construct a cluster.
Another approach to well cluster construction is multiple well
completions in a single borehole. This involves drilling a large-
diameter hole, using rotary technique or a bucket auger and
installing small-diameter wells to selected depths with each
screened zone isolated from the others by an impermeable seal.
93
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Meyer (1973) completed as many as l&ree 102-mm (4-inch) PVC wells in
a single 559-mm (22-inch)borehole 27 and Huges et. al. (1971J
installed up to six 32 to 51-mm (lJs-to-2-inch) observation wells in
one boring.28 This technique for constructing well clusters is
feasible provided the cost of drilling large-diameter boreholes is not
prohibitive and care is taken in placing the impermeable seals between
screened zones (Figure 33). There is a great advantage in being able to
construct the wells sufficiently close to obtain samples that are truly
representative of a single point (areally) in the aquifer. This
increases the value of the water-quality data obtained. If the seals
between the individual wells are carefully constructed and
precautionary measures are taken, such as using a shrinkage-inhibitor in
the cement grout, reliable samples of ground water can be obtained. Of
course, the greater the number of casings in the borehole, the greater
the likelihood of imperfect seals between the casings. To insure that
the seals are effective, a check on water levels in wells not being
sampled should be made. An abrupt drop in water level would tend to
indicate a vertical connection between the screens.
A variety of drilling methods can be used to install a well cluster in
the hypothetical aquifer. One of the best methods is jet percussion;
the seal between casing and formation is tight, and drilling charges are
relatively low. This installation consists of a cluster of five wells
(51mm—2-inch diameter) with screens from 3 to 9, 9 to 15, 15 to 21,
21 to 27, 27 to 33 meters (10 to 30, 30 to 50, 50 to 70, 70 to 90,
90 to 110 feet) below ground surface. The cost ranges from $2,500 to
$3,800. Using screens only 15-meters (5-feet) long at depths of
9, 15, 21, 27, and 33 meters (30, 50, 70, 90, and 110 feet), the
installation cost of the well cluster would range from $1,700 to $2,300.
As previously discussed, however, the gaps between the screened
intervals could allow a thin plume of leachate-enriched water to pass
through undetected, rendering the latter type of construction less
satisfactory.
Another way to construct well clusters in this aquifer is to use a
power auger. In this method, sediment is loosened by a flight of
augers, and a well point and 51-mm (2-inch) casing are pushed through
the loosened material to the desired completion depth. This construction
is problematic in that there is a potential for vertical leakage of
water through the column of loosened soil around the well casing.
Also, well screens must be sturdy enough to withstand the stress of
being driven through the loosened sediments in the borehole. In
normal practice, relatively inexpensive drive points are used
(1.5 meters—5 feet—long or less). However, monitoring the entire
saturated thickness of the hypothetical aquifer would require five
6-meters (20-foot) long, stainless-steel, wire-wound screens with a
drive point. These would considerably increase the total cost of the
installation. An augered five-well cluster with 1.5-meters (5-foot)
long, inexpensive drive points should cost $1,800 to $2,600 while the
most effective installation from a sampling standpoint with five
94
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6-meters (20-foot) long, 51-mm (2-inch) diameter stainless-steel
screens would cost $4,600 to $5,300—significantly more.
More expensive alternatives are drilling with either the cable tool or
hydraulic rotary methods—the former costing about $9,850 to $14,150
per cluster of 152-mm (6-inch) diameter wells and the latter from
$13,800 to $19,400. The substantial difference in these figures is
due to the necessity of grouting the annulus between casing and
borehole wall in the rotary-drilled holes. Grout is necessary to
prevent vertical leakage of water through the annular material into the
screen, causing samples to be unrepresentative of formation water in
the screened zone. The presence of a seal between the casing and
borehole wall in a cable-tool well renders grouting unnecessary. No
substantial economies could be obtained by switching to 102-mm
(4-inch) diameter cable-tool holes. Drilling costs would be about the
same as for 152-mm (6-inch); the main savings would come from using
102-mm (4-inch) stainless-steel, wire-wound screens in Lieu of
152-mm (6-inch) screens.
An alternative method to a cluster constructed with five individual
well completions is to install multiple casings in a single borehole.
This type of installation would cost $8,200 to $11,000 for five
102-mm (4-inch) diameter wells installed in a 610-mm (24-inch)
diameter borehole, and in the range of $4,240 to $5,880 for five
51-mm (2-inch) wells installed in a 305-mm (12-inch) hole. The
formation of a good seal between each screen is vital; therefore,
screens 4.6 meters (15 feet) in length would have to be used in the
hypothetical aquifer, allowing for a 1.5-meter (5-foot) seal between
each screened interval. Again, this seal is critical; if not
properly constructed, an anomalous water-quality sample will result.
Advantages
1. Simple installation does not 1.
always require hiring a drilling
contractor.
2. Excellent vertical sampling
made possible if sufficient
number of wells are constructed.
2.
3. "Tried and true" methodology,
accepted and used in most
contamination studies where
vertical sampling is required.
4. Low cost if only a few wells 3.
per cluster are involved and
if the drilling contractor has
Disadvantages
If only a few wells are
installed, large vertical
sections of the aquifer are
unsampled. Artificial
constraint on data by
completion depths.
If jetting rigs or augers
are used, installations are
usually limited to total
depths of 38 to 46 meters
(125 to 150 feet).
Small diameter wells can be
used only for monitoring.
They cannot be used in
96
-------
equipment suitable for abatement schemes.
installation of small-diameter
wells. 4. In small-diameter wells,
development and sample
collection become tedious
and difficult if water
level is below suction lift.
3.2.4 Single Well—Multiple Sample Points
3.2.4.1 Methodology. Another method used to sample multiple horizons
in a single well is to set screens or casing perforations at regular
intervals in the well. Spacing will depend upon the sample density
required and construction expense; the greater the number of open
zones, the higher the well costs. The California Department of Water
Resources (1963) successfully obtained closely-spaced ground-water
samples by perforating steel casing with a mechanical perforator at
set intervals in the well, isolating each set of perforations with
inflatable packers and pumping the isolated casing segment with a
submersible pump (Figure 34).13 The attractiveness of this type
sampling operation is apparent. However, there are some pitfalls.
Care must be taken to insure that the packers isolate the sampled
section of screen and that no water from above or below leaks past the
packers, contaminating the sample. Pumping rates must be kept low to
insure that formation water is drawn only from opposite the screened
section. Higher and prolonged pumping rates may induce significant
flow from horizons above and below the level of the aquifer being
sampled, resulting in an unrepresentative sample. If the annulus
between the casing and borehole is not properly sealed, the influence
of the pumping gradient may cause vertical movement of leachate in the
annulus, resulting in non-representative samples. To adequately
protect against this type of sample contamination, an impermeable seal
of either bentonite or cement grout should be placed between every
screen or slotted interval. However, this may not be possible with
closely-spaced screens or casing perforations. A well constructed and
sampled according to these specifications will provide an excellent
opportunity to define the vertical distribution of a contaminant.
Another approach for shallow vertical sampling using a single well is
that described by Hansen and Harris (1974).^9 They isolated fiberglass
probes at regular spacings inside a 32-mm (1^-inch) diameter well point
(Figure 35). Samples were drawn to the surface through a tube
attached to the fiberglass probe after the well point was driven to
the desired depth. This type of construction is inexpensive and can
be "homemade" with little difficulty. However, collection of samples
can only be done from depths less than the suction limit—about
9 meters (30 feet) at sea level.
97
-------
SUSPENSION
CABLE
AIR LINE
WELL CASING
DISCHARGE LINE
SUBMERSIBLE PUMP
INFLATED RUBBER PACKER
CASING PERFORATION
PUMP INTAKE
INFLATED RUBBER PACKER
(After Department of
Water Resource*, Hie
Resources Agency of
California, 1963)13
FIGURE y\. USE OF A SAMPLING PUMP TO ISOLATE CASING PERFORATIONS
98
-------
GROUND SURFACE
////////////I
PIPE EXTENSIONS
WATER TABLE-
I/4"WELL POINT
1/4" 0 D TUBING
SAMPLE COLLECTION FLASKS
T7T777//////
SAND MATRIX
FIBERGLASS
TUBING FROM
LOWEST PROBE
CAULKING
FIGURE 35, CONSTRUCTION DETAILS OF A GROUND-WATER
PROFILE SAMPLER USING A WELL POINT
(After Hansen & Harris, 197M29
99
-------
3.2.4.2 Implementation. Unless the shallow well-point device as
described by Hansen and Harris (1974) is used, installing a multiple
sampling point well requires the services of a drilling contractor.
A large-diameter borehole is needed in which casing can be positioned,
necessitating the use of a cable tool or rotary rig. One hundred and
fifty-two mm (6-inch) diameter or larger casing should be used to
accommodate the packer-pump unit which in turn requires a tripod
winch, power, and air supply. If steel casing is not slotted before
installation, a special down-hole tool is required to make the slots.
The packer pump is not quite so formidable. Once a good-quality
submersible pump has been obtained, local investigators or machine
shop personnel can equip it with packers. Cherry (1965) has described
the design and operation of a rather elaborate packer pump (Figure 36).
...This sampler collects a pumped sample of water
from a specific zone in an uncased or multi-screened
well. Minor modification of the sampler permits
remote measurement of several chemical and
physical characteristics of the water in the zone
being sampled. The sampler can be used in wells
with diameters of 203 to 406mm (8-16 inches)
inclusive, which do not contain pumps, pipes, or
other obstructions. It is suspended on a cable
from an A-frame and is raised and lowered by an
electric motor that is powered by a 110-volt,
a-c portable generator. This generator also runs
the electric pump which is part of the sampler...(sic)
...The sampler consists of two inflatable packers
or boots—one mounted above the submersible pump
and the other below it. When the boots are inflated,
the zone between them is isolated from the remainder
of the well, and water can be pumped from this
isolated zone... (sic)
...The capacity of the pump is about 1 1/s (15 gpm).
The spacing of the boots can be varied by using
different lengths of connecting pipe between them.
The minimum spacing of the boots is 1.5 meters
(5 feet) (length of pump). The boots are inflated
by pumping water into them, from the well, through an
electrically controlled valve; they are deflated by
pumping the water out of them through another
electrically controlled valve. Advantages of this
sampler over other packer-type samplers are its
portability, the ease with which it can be
repositioned without removing it from the well, and
the fact that it is relatively inexpensive...(sic)
100
-------
Submersible
pump ^_
1 Metal plate
2 Pipe
3 Electric cable
4 Inflatable boot (rubber)
5 Pipe (to inflate boot)
6 Pipe (connects two boots)
7 Submersible-pump intake
8 Pressure sensor
9 Electric fill valve (normally closed)
10 Electric dram valve (normally open)
1 1 Pressure-relic* valve (optional)
NOT TO SCALE
1-6
SIDE VIEW
FIGURE 36, THE CASEE SAMPLER
(After Cherry, 1965)30
101
-------
...Instruments to measure temperature, specific
conductance, or other chemical or physical
characteristics of the water in the well can be
placed in the space between the boots.
Experience has shown,that continous measurement
of specific conductance, in this way, is very
useful in determining the proper time to
collect the water samples. It is desirable to
pump from the well a volume of water equal to at
least 3 times the capacity of the discharge line
and isolated section before collecting samples for
analysis, in order to ensure the collection of
representative samples ...
The packer/pump shown in Figure 34 is less elaborate and more
amenable to fabrication without the facilities of a machine shop.
Although actual construction is not described in the California
Department of Water Resources report, it seems that two rubber
diaphragms, possibly cut from tire inner tubes, were clamped
(probably with stainless-steel hose clamps) to the exterior of the
pump.13 An air line to the surface allows inflation or deflation of
the packers. If sampling is limited to shallow depths, "homemade"
diaphragms and valves should withstand the required inflation
pressures, greatly reducing fabrication costs of the packer/pump.
The use of 152-mm (6-inch) PVC casing, slotted PVC screen, and glued-
joint couplings will greatly facilitate construction of a well
capable of being sampled at set intervals within the casing. The
screen sections of set length can be separated by the appropriate
lengths of blank casing using only a handsaw to cut the lengths and
PVC cement to join them together. With the use of simple tools, this
construction can be done rapidly and requires little skill.
A well in the hypothetical aquifer with .3-meters (1-foot) long screen
sections separated by 1.2 meters (4 feet) of casing would cost
$3,000 to $4,700. Steel casing and screen would be considerably more
expensive. If casing perforation is done, its cost will depend upon
the availability of the necessary equipment. The pump/packer
assembly necessary for sample collection could be fabricated for
$1,000 to $2,000 or more depending upon the pump used and the
elaborateness of the packer system. Portable generators capable of
supplying the power necessary for the pump can be purchased for
several hundred dollars. Although these prices seem high, they are
one-time costs; with proper care and maintenance, the pump/
packer system should endure for years.
102
-------
Advantages Disadvantages
1. Excellent information is gained 1. Expensive.
on vertical distribution of the
contaminant. 2. Proper well construction
and sampling procedures are
2. If necessary, well diameter is critical to successful
large enough to use in a pumped- application.
withdrawal pollution abatement
problem. 3. Complicated sample collection
procedure involves a great
3. Sampling depths are limited deal of equipment.
only by the size of the sampling
pump.
4. Rapid installation possible.
3.2.5 Sampling During Drilling
3.2.5.1 Methodology. A major disadvantage of the previously-
discussed sample collection techniques is that a constraint is placed
on the data obtained from the ;ground-water samples by the fixed or
arbitrary point at which water samples are collected, i.e. "blind"
placement of wells can result in a false representation of contaminant
distribution if it is not uniformly dispersed throughout the aquifer
at the sampling point. Contaminants are often stratified: underlain,
overlain, or interfingering with uncontaminated ground water. To
define these relationships adequately, information on the vertical
distribution of contaminant must be obtained prior to installation of
the monitoring well. This information can be obtained by formation-
water sampling during drilling.
Several researchers have obtained satisfactory ground-water samples
during drilling using three basic techniques:
. driving a casing^ or well point^2 to the desired
depth, bailing or pumping a water sample from
that depth, and repeating the process to
completion depth or refusal;
. drilling a mud rotary hole to the sampling depth,
pulling the drilling string, setting and gravel
packing a temporary well screen, and pumping
a formation water sample,
. drilling a borehole to the desired horizon,
setting a packer and riser pipe, and pumping
a sample.
103
-------
?as true of the other techniques previously discussed, if proper
cautions are taken, formation-water samples collected using these
-echniques will be representative of water quality at a known vertical
interval of the aquifer. The critical factor in successful application
is the development of the temporary well to the point where all traces
of drilling fluid have disappeared from the pumped water before a
sample is collected. Dilution of the sample by the drilling fluid and
contributions of chemical constituents by clay particles in the mud
will produce erroneous data, and little information will be gained on
the actual vertical distribution of contamination.
The main advantage of the type of sampling is that the stratification of
the contaminated slug can be defined with reasonable accuracy prior to
setting a permanent casing and screen. With this information, the well
can be designed for the most advantageous sampling or withdrawal of the
contaminant at that point in the aquifer. Changes in the vertical
distribution can then be monitored very closely. »
3.2.5.2 Implementation. In the course of investigating a hexavalent
chromium contamination problem, Yare (1975) used ground-water-sampling-
while-drilling techniques. 24 A borehole was drilled using a hydraulic
rotary rig. Use was made of a drilling mud containing an organic-base
drilling fluid additive which minimizes the effect of drilling fluid
on the formation water. A slotted PVC screen attached to a riser pipe
was lowered to the bottom of the borehole; the screen zone was
packed with fine gravel, forming a well in the borehole. After the
gravel had settled through the drilling mud and around the screen, the
well was pumped clear. By this time, an effective filter cake had
formed on top of the gravel pack, isolating the screen from the fluid
in the borehole. Due to the hydrostatic force created when pumping the
well, the filter cake between the gravel and the borehole wall
disintegrated. To insure that formation water was collected, an
additional 379 liters (100 gallons) of water were pumped before sample
collection. It should be noted that the use of an organic-base drilling
fluid would be precluded if organic contaminants were to be determined.
The drilling and water-sampling procedure which evolved from this
investigation consists of the following steps (Figure 37):
. drilling an 203-mm (8-inch) diameter borehole to the
sampling horizon;
. pulling the drill string and replacing the bit
with a 1.5-meter (5-foot) long, 102-mm (4-inch)
diameter wire-wound well screen;
. lowering the screen and drill string to the
bottom of the hole and gravel packing the screen;
. attaching a gasoline-powered centrifugal pump
104
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105
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to the drill string, pumping until the drilling-
fluid level stabilizes in the hole, and the
discharge clears of drilling fluid—(In this
case, a centrifugal pump could be used as static
water levels ranged from 1.8 to 3.6 meters
(6-12 feet) below ground surface);
. pumping at least 379 liters (100 gallons) of
formation water before collecting the samples;
. pulling and removing the screen, lowering the
bit and drill string, and drilling to the next
sampling horizon.
Harden (1974) described a sampling-during-drilling technique useful for
deep holes in unconsolidated sediments. In this method, the first hole
drilled is 171mm (6 3/4 inches) in diameter. When the hole penetrates
approximately 4.6 to 9.2 meters (15-30 feet) into a sand from which a
water sample is desired, drilling is stopped (step 1, Figure 38).
The hole is reamed to a diameter of 251mm (9 7/8 inches) down to a
point just above the zone selected for water-sample collection. At
this point, the 171-mm (6 3/4-inch) hole is washed out to its original
depth (step 2, Figure 38); and a string of pipe with packer and screen
is positioned in the hole (step 3, Figure 38). The pipe is usually
102mm (4 inches) in diameter; the packer is a commercial rubber-cone
type with typical dimensions of 152 by 229 by 356mm (6x9x14 inches).
Often a canvas "shirt tail" is wrapped by the packer to assist sealing.
The packer is positioned on the shoulder at the junction of the
171-mm (6 3/4-inch) and the 251-mm (9 7/8-inch) portions of the hole.
Below the packer, a commercial 102-mm (4-inch) well screen 3 to 6
meters (10-20 feet) long is attached to the 102-mm (4-inch) pipe.
After the packer is seated, the temporary well is developed by airlift
for several hours until the water becomes clear. The air line is
removed from the 102-mm (4-inch) pipe; a small-diameter pump is
installed; and the temporary well is pumped once more until the water
becomes clear. The samples are then collected. When pumping comes to
a halt, the casing and screen are pulled from the hole; and drilling
of the 171-mm (6 3/4-inch hole)is resumed until a second water-bearing
zone is encountered from which a water sample is desired. At this time,
the entire water-sampling process is repeated.
In the case of the hypothetical aquifer previously described, the most
efficient sample-collection technique would probably be that described
by Yare (1975). if this method is used, samples can be obtained at
depths of 6, 9, 12, 15, 18, 21, 24, 27, 30, and 33 meters (20, 30, 40,
50, 60, 70, 80, 90, 100, and 110 feet) below ground surface. Five of
the most contaminated intervals of the aquifer can be screened with
1.5meters(5-foot) long, 102-mm (4-inch) plastic screens for a total
cost of $3,000 to $4,700. Additional sample points would cost $125
to $200 each. The samples from the screen segments could be collected
106
-------
STEP
6 3/4"'
HOLE
STEP 2
9 7/6" .
REAMED
HOLE
STEP 3
CLAY
'ilttt&S AND.-
6 CASING
-------
by using a packer/pump or by installing and isolating a deep pressure-
vacuum lysimeter in each screened interval. If a packer/pump is used,
152-mm C6-inch) casing is necessary; the total cost per installation
would be in the range of $3,300 to $5,200. Lysimeters could be placed
for approximately $100 each.
Advantages Disadvantages
1. The best technique currently 1. Considerably expensive.
available for defining vertical
distribution of contaminants 2. Careful supervision of
in thick aquifers. drilling and sampling is
necessary.
2. Completed well can be used for
water-quality monitoring and/or 3. Potential cross-
pumped withdrawal of contaminant. contamination of samples
exists.
3.2.6 Pore-Water Extraction From Core Samples
3.2.6.1 Methodology. An indirect method of obtaining ground-water
samples during drilling is to extract pore water from core samples
collected as the borehole is advanced. This is accomplished by
placing a segment of the core in a commercially available filter press,
hydraulic ram, or centrifuge^ and forcing interstitial water out of
the core. Standard analytical techniques can then be used on the
extracted water, typically electrical conductivity measurements and
titrametric analysis for chloride. 34, 35, 36
This technique is not infallable, however. During the process of
driving the coring device and bringing it to the surface, drilling-
fluid invasion into the core occurs. The greater the invasion, the
less reliable the water-quality data obtained. Sand and gravels are
more readily invaded than finer-grained sediments^
Luscynski (1961) overcame this problem by putting fluorescein dye
(green color) in the drilling mud.3^ Any penetration of drilling mud
into a core sample would be indicated by the dye. The uninvaded core
sections could be selected for extraction. In this way, dilution of
pore water by drilling fluids would not be a factorj and a
representative sample could be assured. Unfortunately, disposal of
the bright-green drilling mud upon completion of drilling becomes a
problem.^' Normally, drilling mud is dumped on the ground and is
eventually eroded away. Because of its natural gray or brown color,
it is not very obvious. The fluorescein in the bright-green mud,
although not believed toxic in dilute concentrations, is visible at
very low concentrations in water. If left at the site, its migration
to nearby wells could cause complaints from well owners.
108
-------
3.2.6.2 Implementation. Luscynski (1961) describes in detail the use
of a filter press to extract pore water:
...The filter press used is one of several types sold
commercially for use in determining filtration properties
of drilling muds. The unit consists of a chamber, a
filtering medium, a graduated tube for catching and
measuring the filtrate, and a pressure-source unit.
A cell, base cap, screen, rubber gaskets, and top cap
make up the chamber. The cell is 89*-inm(3*S-inches)
high and has inside and outside diameters of 76 and
89mm (3 and 3*5 inches), respectively. The filtering
medium is a sheet of filter paper which fits on the
screen over the base cap; it has a filtering area of
about 45cm^ (7 square inches). The filter paper used
is specially hardened to withstand the pressure in
the chamber. A graduated cylinder is used to catch
the filtrate... (sic)
...Uninvaded cores consisting of loose material such
as sand and gravel are transferred to the filter-
press chamber by spatula or spoon. Usually it is
not practical to remove much more than 25% to 50%
of the uninvaded material from the core barrel by
this method. Enough material is transferred to
fill the chamber about a quarter to half full.
It is then tamped lightly until an integrated unit
is formed in the chamber and a film of water is
formed on the surface of the material and along the
cylindrical wall...
...Usually less than 10 to 20 percent of a solid or
salty clay sample is invaded by the drilling fluid.
Plugs of the uninvaded material 25.4 to 51mm (!-'
2 inches) long are placed in the chamber to fill it
about a quarter full. Then they are molded and
tamped into an integrated unit. Difficulty can be
experienced in molding and ramping a relatively dry
solid clay—one having a water content of less than
15 to 20 percent of the dry weight of the clay... (sic)
...The total time between the opening of the split-
spoon core barrel and the placing of the chamber in
the frame is usually 60 to 120 seconds for the loose
material and 120 to 300 seconds for the tight
material. There is thus, very little opportunity for
evaporation...
109
-------
...After a sample is properly prepared for filtration,
the chamber is fully assembled, placed in the frame,
and made airtight by the T-screw (Figure 39). The
gas pressure is then applied.
...The pressure of the carbon dioxide gas in the
chamber moves some of the interstitial water through
the filter screen and filter tube into the graduated
cylinder. Pressures of 34.5 to 207 kN/m2 (5-30 psi)
suffice for the gravel, sand, and silt samples.
Pressures of about 690 kN/m2(100 psi) are usually sufficient
for silty and solid clay samples. The carbon dioxide
gas does not alter the chloride concentration of
water forced from the material into the filtrate
tube... (sic)
...Chloride determinations of the filtrate are made
in the field by the standard titration method using
silver nitrate solution. Relatively large amounts
of filtrate (25 to 50 ml) are needed when fresh
water is to be tested, and relatively small amounts
(1 -10 ml) when salt water or diffused water is to
be tested...
...Usually enough filtrate can be obtained from the
uncontaminated material of only one core if it is
taken in a diffused-water or salt-water zone. However,
more than one core may be necessary to obtain the
required amount of filtrate if the core is taken in
a fresh-water zone; this is particularly true for
solid-clay samples which yield only small amounts of
interstitial water...
An alternative to the mud filter press is to fabricate a core sample
squeezer which utilizes a hydraulic ram, as described by Manheim
(1965):38
...The squeezer utilizes a commercially available
cylinder and ram (made by the Carver, Co., Summit,
N.J.) to which a machined base with a filtering
element and fluid outlet is fitted. Construction
details are shown in Figure 40. The filter
unit consists of a stainless steel screen and a
perforated steel plate contained in a circular
recess in the steel filter holder. Alternatively,
a porous (sintered) metal plate may be used to replace
both screen and perforated plate. The top surface of
the filter should be flush with the other rim of the
holder so that it may support one or more paper
filter disks. Finegrained, hardened laboratory
filters give a visually clear effluent;, but
110
-------
r scRtw
PRESSURE INIET
MUO CUP
FRAME
SUPPORT ROD
GRADUATED CYLINDER
THUMB SCREW
SUPPORT
TOP CAP
RUBBER GASKE
BASE CAP WITH
FILTRATE TUBE
FILTRATE TUM
FIGURE 39,
FILTER PRESS
(As manufactured by Baroid Division, NL Industries,
Houston, Texas)
111
-------
membrane or microfilters may be used to assure
maximum freedom from suspended matter. The lower
part of the filtering assembly, fitted with a rubber
washer, protrudes into a recess in the steel base;
when pressure is applied, the gasket is squeezed
against the cylinder and prevents leakage of water
around the filter unit. The space in the recess
and the diameter of the outflow boring are kept
small so that little fluid can collect in the
squeezer itself. All metal parts in the filter
base are made of Iron and Steel Institute No. 303
stainless steel. Rubber and teflon disks just
below the piston prevent loss of fluid upward
when pressure is applied. The rubber, teflon, and
filter-paper disks are punched out with an arbor
punch and can be made as needed...(sic)
...The present design permits insertion of a disposable
syringe (preferably plastic) directly into the base of
the squeezer to receive fluid. The narrow effluent hole
is reamed out to permit fitting of the standard 'Luer'
taper of the syringe nose...
...A larger squeezer has also been constructed using
a 64-mm (2^-inch) Carver cylinder and piston. The
design is similar to that shown in Figure 39
except that the filter plate is increased in
thickness to give greater strength. The effluent line
remains small. Because the cross-sectional area of
the cylinder bore of the small squeezer is about 22-mm
(0.88-inch), a 10.16-tonne (10-ton) laboratory press
exerting its maximum load of 9,090kg (20,000 pounds)
will apply a pressure of about 151,724 kN/nr
(22,000 psi) to the sediment. However, a 9,090-kg
(20,000-pound) load will apply only about 34,482 kN/m2
(5,000 psi) in the large unit. The large squeezer
should therefore be used with a higher capacity press
when more compact sediments are to be squeezed...(sic)
...In sequence, the steps in squeezing a sample
are as follows: The filter holder with its gasket
is placed in the recess of the filter base. The
screen, perforated plate (or porous disk) and
2 or 3 filter-paper disks are positioned. The
cylinder is seated over the filter unit so that it
rests firmly on the base. Sediment is then quickly
transferred into the cylinder through the top,
followed by the teflon and rubber disks. The teflon
and rubber disks can be placed above the sample in
112
-------
either order to obtain a leak-free pressure transfer,
but placing the teflon disk below the rubber disk
gives a cleaner seal than the reverse order shown
in Figure 40. The .piston is depressed as
far as it will go into the cylinder, and the whole
unit put in the press for squeezing. Pressure is
applied gradually at firsts when the first
drop of interstitial fluid is seen, the syringe
is seated in its hole in the base (effluent
passage in Figure 40). The squeezed-out liquid
moves the plunger of the syringe back as the
liquid is expelled, and there is minimum
opportunity for evaporation. When the desired
amount of liquid has been obtained, the syringe is
removed and capped...(sic)
...After extraction of the liquid the parts of the
apparatus are rinsed with distilled water and
(except for rubber parts) with acetone. The
acetone helps dry the unit quickly in preparation
for the next sample. The squeezing and washing
operations together can be completed in 300 to
600 seconds (5 to 10 minutes) ../. (sic) „
The main expenditure in this type of sampling is the filter press. The
current price for this piece of equipment can be obtained from Baroid
Division, NL Industries, Houston, Texas. Current charges for cores
obtained by wire-line, 51-mm (2-inch) diameter split-barrel samplers
are $30 to $50 per core. A section of core can be taken from the
sampler, molded into the filter press, the fluid extracted and
analyzed for chloride concentration, and measured for specific
conductance in a half hour or less.
Advantages
1. Generally inexpensive.
2. Pore water extract is amenable
to field chemical analyses
such as: chloride concentration
and specific conductivity.
3. Excellent vertical sampling
when mud invasion into core
sample is monitored.
4. Samples can be obtained
from almost any depth when
wire-line coring apparatus is
used.
Disadvantages
1. Quantitative analysis
requires careful control
during sample collection.
2. Interstitial water can drain
from unconsolidated sand
and gravel reducing volume
of the collected water sample.
3. If dyed drilling mud is
used, it may be an eyesore.
4. Core recovery in coarse sand
and gravel can be difficult
and time consuming.
113
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TEFLON DISK-
STAINLESS STEEL-
WIRE SCREEN DISK
RUBBER (NEOPRENE)-
WASHER
BASE
EFFLUENT PASSAGE-
^
M^
RAM
RUBBER (NEOPRENE)DISK
-PERFORATED PLATE
(FILTER PAPER SUPPORT)
•FILTER HOLDER
EFFLUENT PASSAGE REAMED
TO FIT NOSE OF SYRINGE
SYRINGE
FIGURE 40, HYDRAULIC SQUEEZER
(After Manheim, }366) 38
-------
5. Qualitative use of pore water 5. Small sample volume available
extract allows for presence/ for chemical analysis.
absence determination.
6. Can be expensive.
6. Can be used with consolidated
rock as well as unconsolidated
sediment samples.
3.2.7 Summary of Cost Estimates
Table 3 presents a summary of cost estimates for the various monitoring
techniques used in the zone of saturation. The cost estimates are
based upon the hypothetical aquifer which was supposed to be composed
of unconsolidated sand with a depth to water of 3 meters (10 feet) and
a total saturated thickness of 30 meters (100 feet). It should be
realized that these cost estimates are based upon prevailing rates
(Fall, 1975) in the Northeast; consequently, actual costs will be
lower or higher, depending upon conditions in other areas. Also to
be considered are the rising costs of drilling and materials over the
past few years. Therefore, the costs presented here will soon be
outdated. However, these estimates indicate the relative cost
relationships that should remain fairly constant.
3.2.8 Selection of Well Size
The casing size required for a monitoring well is principally dependent
upon the particular sample-withdrawal technique to be utilized
(see Chapter 6). There is no justification establishing a blanket
well-size requirement resulting in additional cost especially when any
cost savings can be reinvested to establish additional monitoring
points and a more comprehensive program.
Where the ground-water sampling point is within suction lift (usually
less than 9 meters—30 feet), vacuum or pressure sampling methods can
be used with small diameter wells (51mm—2inch) . When samp-ling
beyond suction lift, bailers or submersible pumps are used which would
normally require a large well diameter '(102mm--4-inches). A
pressure sampling method can also be used, however, which would only
requite a 51-mm (2-inch) well.
The type of soils should also be considered. For example, in
extremely tight soils where recovery is slow (hours or days), a large
diameter may be desired so that one casing volume provides an adequate
sample quantity. Also, if the well will serve as a ground-water
pumping well to control contamination, this will affect the well size.
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3.3 FIELD INSPECTION
Field inspection is an extremely valuable tool in evaluating landfill
sites. Although an inspection by a trained observer would produce more
data, even an unskilled person can identify the presence of leachate in
springs, seeps, and streams by its color and odor. Frequently, vegetation
that has been exposed to leachate can be found in a dead or dying state.
The condition, surface configuration, and drainage away from a landfill
give insight into the amount of infiltration of precipitation that
might be taking place. A study of surface drainage, topography, and
nearby wells enables the inspector to make an estimate of ground-
water (and leachate) movement. Field observations increase in value
when combined with geohydrologic information and other pertinent
basic data contained in published reports and agency files.
Many of the monitoring techniques discussed in this chapter can be
combined with the field inspection to provide even more information.
The degree of success depends upon the ability of the inspector to
interpret the situation and the amount of time available for the study.
The inspector should have a detailed map or aerial photograph of the
landfill site (or at least a sketch map). While touring the landfill
and the surrounding acreage, the findings should be recorded on the
map, giving an overall picture that can be easily interpreted.
The cost of a landfill field inspection is variable according to the
operation size and the complexity of the surrounding terrain. In this
and all the following sections of this chapter, the probable expenditures
involved are estimated. Costs are based upon an estimated daily wage
rate for the required personnel, the approximate time required for the
various tasks (based upon an average situation), and other related
expenses such as laboratory fees and expense accounts. For a field
inspection of an average landfill (20.2 hectores—50 acres), one
hydrogeologist or engineer (or equivalent) would be required for
2 to 3 days at $200 per day. The estimated cost is $600.
Advantages Disadvantages
1. Can be carried out quickly and 1. Untrained inspector may
inexpensively. overlook subtle but valuable
data.
2. Helps place the overall problem
in perspective. 2. Findings are not always
conclusive in detecting
3. Establishes the extent of ground-water contamination.
additional investigations which
may be required. 3. Time factors are not
indicated relative to
condition changes.
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4. When combined with a literature 4. Few, if any, analyses or
survey on available data, actual physical measurements
inspection procedure may be are made.
used by an experienced hydrologist
to roughly establish the overall 5. Untrained inspector may be
situation. misled by visually impressive
but environmentally
5. Provides an opportunity for insignificant features.
personal communication with
landfill operator and other
personnel.
3.3.1 Seeps
Small springs of discolored, malodorous leachate which are frequently
found along the lower edges of many landfills are referred to as seeps.
These may be the only visible indication of landfill leachate and thus
often receive more than their share of attention. In fact, they may
represent only a very small fraction of the total leachate being
generated by the landfill. The few gallons per minute visible in
seeps are insignificant when compared with the possible hundreds or
even thousands of liters (gallons) of unseen leachate which may be
migrating downward to the water table. However, as indicators of
leachate, seeps do deserve consideration.
Seeps may represent the intersection of the water table and the land
surface, or they may be the discharge from a small perched water body
within a landfill. At times, a distinction between these two situations
can be made by inspection. For example, if the land surrounding the
landfill is dry, a seep discharging along the face of the solid waste
is not likely to represent the water table. Installation of a well
point near the landfill would establish the true water-table position
near the seep and provide a more definite distinction between the two
situations. Such well points have the added advantage of permitting
a sample of ground water to be collected and tested for leachate.
Seeps are valuable sources for the collection of concentrated leachate
samples—although it should be kept in mind that it is possible that
the seep may not always be representative of the large volume of
leachate generated in that particular landfill. In fact, the chemical
characteristics of any leachate sample, regardless of its source,
should not be considered representative of the total volume of leachate.
Landfill leachate has proven to be highly variable in relation to
location and the period of time. When there are substantial changes
in seep locations or flow rates or the sudden appearance of new ones,
a change in the flow system within the landfill is indicated. The
exact nature and cause of the change, however, must be investigated
by other means.
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Examination of seep would typically be included as a part of the field
inspection and, except for laboratory fees for analyses, would not
represent an additional expense.
Advantages
1. Where present, definite indication
of leachate generation.
2. Convenient point of collection
Disadvantages
1. May not indicate presence
of contaminated ground water.
2. Chemical quality not
necessarily representative
of bulk of leachate in the
landfill or entering the
ground water.
for leachate sample.
3. Changes in flow rates or
locations of seeps are
indicative of interval landfill
changes.
3.3.2 Vegetation Stress
Leachate contamination may result in stress and possible destruction of
vegetation on the surrounding area. Stressed species may include
agricultural crops, stands of trees, and marsh or meadow vegetation.
In marsh environments subject to leachate discharge, the condition of
vegetation serves as an excellent monitoring device to assess ecological
stress on the total system. Marsh vegetation is stationary and
sensitive and can be studied for signs of stress, either by using
aerial remote-sensing techniques or direct study by the field botanist.
Crops and trees generally grow in areas with a deeper water table than
is associated with the marsh environment and are more likely to be
stressed by landfill-generated gases than by leachate. Various types
of agricultural crops, including fruit orchards, have been destroyed
by migrating gases generated within a nearby landfill. Preliminary
stresses placed upon these species prior to their actual destruction
are often detectable by the botanist and by aerial remote sensing.
While identifying the precise cause and mechanisms of stress can be
prohibitively costly, it may be possible to relate the stress to a
general cause which may in turn be related to the presence of the
landfill. Mapping the extent of stressed vegetation may provide an
indication of the extent of the total impact of a landfill on its
surrounding environment. Also, early detection of stress may permit
the institution of corrective measures in sufficient time to prevent
irreparable damage.
A cursory investigation of vegetation stress would be included
in the field inspection and would not represent an additional expense.
A detailed survey of vegetation stress (including an assessment of
probable cause) would require 1 to 2 days of field work by a
botanist. Some laboratory work would also be involved. The estijnated
cost of such a survey is $1,000.
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If vegetation stress indications are to be used for monitoring or if
specific recommendations regarding the saving or replacement of
stressed species are to be made, the required program might cost
between $10,000 and $100,000, depending upon the extent, complexity,
and goals of the program.-
Advantages
1. Qualitative indicator of
leachate and gas contamination.
2. Mapping extent of stressed
vegetation may provide an
indication of the limits and
source of contamination.
3. Stressed vegetation can be
mapped remotely by aerial
photographic methods,
allowing wide coverage in a
short period of time.
4. Stress change is a good
indicator for monitoring
purposes. More effective if
selected species are planted,
then observed.
Disadvantages
1. Evidence of stressed
vegetation, especially in
ea^ly stages, is not always
evident except to a trained
botanist.
2. Stress may be caused by many
factors, some unrelated to
the presence of the landfill.
Determination of the responsible
factor or factors is usually
extemely difficult.
3. Certain stresses will not
occur unless physical or
chemical change occurs at the
surface or within the vadose
zone. Therefore, it provides
no indication of problems
at depth.
3.3.3 Specific Conductance and Temperature Probes
Two physical characteristics of ground water which can be readily
measured in the field are specific conductance and temperature. Since
landfill leachate generally has substantially higher temperature and
specific conductance than natural ground water, the presence of
leachate often can be detected by these two characteristics.
Typically, in-situ measurements of ground-water characteristics would
be made by lowering a remote-sensing probe into a well and recording
the results from surface instrumentation. In areas of high-water
table, however, the measurements can be made without installing a well.
The method involves the use of a self-contained conductance-temperature
probe. Construction details of such a device are shown in Figure 41.
The probe can be pushed directly into soft ground; where the ground is
harder, it can be inserted into a small-diameter, hand-augered hole.
During insertion, the perforations are protected from clogging by an
outside tube. When the probe is below the water table, the tube is
retracted, allowing the ground water to flow into it, Specific
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FIGURE 41, SPECIFIC CONDUCTANCE - TEMPERATURE PROBE
-------
conductance and temperature of the ground water can then be recorded.
After removal, the perforated end of the probe is washed in clean
water.
Another advantage of the specific conductance and temperature probe
method is inherent in the equipment required. Since the mechanisms
involved are not bulky or cumbersome, a two-man crew can easily carry
all necessary equipment into the field and make a series of probe
measurements over a typical landfill in 2 to 3 days. Also, swampy
areas not readily accessible to drilling rigs or resistivity survey
crews can be tested with little difficulty.
Although this method has distinct advantages, it is not an absolute.
The required equipment for probing is very delicate and is vulnerable
to physical abuse. Any malfunctioning of the equipment due to mechanical
failure or to pre-contamination before testing, can give erroneous
information. To prevent this development, the equipment should be
checked periodically for malfunctioning against a standard solution
such as potassium chloride.
Assuming the surface conditions were favorable for probe insertion, the
cost of a ground-water conductance and temperature survey using the type
probe discussed would be about $900. This estimate is based upon the
cost of a hydrogeologist or equivalent and a helper over a period of
three days. The survey may require more or less time depending upon
the size of the site to be investigated and its accessibility.
Advantages
1. Providing equipment is properly
calibrated and insertion
procedures carefully implemented,
positive determination as to
presence and degree of
contamination can be made.
2. Provides accessibility to
otherwise restricted areas,
such as marsh or swamplands.
3.3.4 Electrical Earth Resistivity
Disadvantages
1. Not an absolute method.
Equipment subject to
malfunctioning, causing
erroneous information.
Equipment must be checked
for malfunctioning against
a standard solution.
2. Requires hiring personnel
trained in the use and handling
of the equipment.
An electrical earth resistivity survey can be used to define subsurface
geology and the extent of leachate contamination of ground water. The
results of a resistivity survey, coupled with a minimal amount of direct
sampling, may provide a basis for decisions on the necessity of
remedial action or serve as a preliminary investigation from which a
detailed drilling and sampling program is designed. However, resistivity
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is an indirect method and is subject to possible error in interpretation;
final conclusions should not be based upon resistivity results alone.
The earth resistivity method depends upon the conduction of electric
current through the subsurface materials. The magnitude and distribution
of the current flow is a function of the effective resistivity (or its
reciprocal, conductivity) of the subsurface material. Since the vast
majority of the constituent minerals are poor electrical conductors,
the effective resistivity of saturated materials is dependent upon
moisture in interstices and pores. The pore spaces that contain water
also contain some dissolved salts; it is these ionic solutions that
allow the passage of current from the surface into the underlying
material. It has been found that materials such as moist clays and
silts have low resistivity; while in dry, loose soils, sand and gravel,
or sand and gravel saturated with high-quality water, the resistivity
is high. The electrical resistivity of a material is a function of the
actual resistance of the material and the length of the current flow.
Earth materials are not homogeneous; therefore, the measured resistivity
is actually termed apparent resistivity and is defined as the weighted
average of the actual resistivities of the individual subsurface
materials or strata within the depth of penetration of the resistivity
measurement.
To measure earth resistivity, a known current is introduced into the
earth through two current electrodes. The resulting potential drop is
measured between a second pair of potential electrodes. If the
electrodes are arranged in a straight line and the separations are
increased at constant increments, it is possible to make inferences
about the relations of variations in apparent resistivity, depth of
penetration, and electrode spacing.
Various procedures have been developed to interpret resistivity data.
The procedures are grouped into two basic types:
theoretical
. empirical.
Following the theoretical method, the field data are graphed and the
resulting curve compared with sets of master curves developed for
numbers of resistivity layers with definite ratios of resistivity and
thickness. By using this method, the value of resistivity for each
geologic unit as well as its thickness and depth can be determined.
The example given on Figure 42 illustrates the empirical method.
This procedure involves plotting the apparent resistivity and
accumulated apparent resistivity values on a graph. The first curve
indicates the type of material; the second shows the depth of the
interface between layers.
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Use of the resistivity method to define a leachate plume relies upon
the fact that the conductivity of the ground water is inversely
proportional to the resistivity measured in a section of earth
containing that ground water. Since the conductivity of landfill
leachate is generally much higher than that of natural fresh ground
water, a sharp decrease in apparent resistivity will occur if leachate
is present in the measured section. By running a series of resistivity
depth soundings on a grid over a landfill site, it is possible to define
the lateral extent of the leachate plume by contouring the values
obtained.
The estimated cost of a resistivity survey for a typical landfill
(20.2 hectojres—50 acres) site is $1,000 based upon 2 days of field
work by the crew along with data reduction and interpretation by a
geophysicist. For surveys encompassing substantially larger areas,
charges would increase proportionately. If access were difficult,
i.e. brush had to be cleared, costs would be greater.
Advantages
1. Definition of subsurface geology
and contaminated water bodies
can be derived at a faster and
cheaper rate than drilling.
2. Greatly reduces the number of
sampling wells required.
3. Surveys can be duplicated
periodically to provide
monitoring data.
Disadvantages
1. Indirect method. Requires
some substantiation by
drilling.
2. Many natural and man-made
field conditions preclude
resistivity surveys.
3. Data interpretation in
complex situations is often
questionable.
A. Background data on natural-
water quality are pre-
requisite.
3.3.5 Seismic Surveys
Seismic surveys are used to determine the depth to bedrock and the
thickness of the materials overlying the bedrock. The refraction
method of seismic exploration utilizes the principle that energy waves
can be propagated through earth materials. The velocity of propagation
is governed by the elastic properties of the earth materials through
which the waves are traveling. To determine their velocity, these
elastic waves can be timed from their initiation to arrival at a known
distance from the energy source. With known velocities and distances,
depths to the various geologic interfaces can be calculated. The
seismic reflection method of geophysical surveying may also be used.
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This system, in which the energy wave is reflected from the different
geologic horizons, can usually penetrate greater depths than the
refraction method. It is not generally applicable to landfill studies.
For more refined interpretations, well data are correlated with the
results of the seismic survey. Where well information is not
available, evaluation of seismic data is based upon interpretation of
the geologic environment and experience in geophysics.
In using the refraction method to determine depths and seismic
velocities of various materials, the reverse profile method is used.
A reverse profile is defined as the interchange of the most distant
energy source and the receiving unit (geophone); a second profile is
then recorded. The energy source is a hammer blow on a steel plate or
an explosive charge. With a single geophone seismic unit, a seismic
profile is conducted by implanting the geophone firmly into the ground
and moving the impact point away from the geophone at measured
distances. In a multi-geophone unit, the geophones are placed at
selected linear intervals; a single energy source, usually an
explosive device, is activated. By recording the energy arrivals for
different separations between the impact point and the receiver or
receivers, a curve can be plotted, correlating energy travel-time with
distance.
Data interpretation of a seismic survey requires a trained operator and
an experienced geophysicist. The complexity of the data-reduction
process generally requires the use of a computer. For these reasons,
seismic surveys should be contracted to a firm providing geophysical
services.
Though advantageous, seismic surveys are not without limitations. The
seismic method cannot provide information on the presence or absence
of leachate. For this reason, it cannot be considered a monitoring
method in itself. Unlike resistivity surveys, repetition is pointless
unless it is believed that the data are incorrect or insufficient.
The cost of a seismic survey would be essentially equal to a
resistivity survey, i.e. $1,800 for a typical small landfill site.
Advantages Disadvantages
1. Can provide subsurface geologic 1. Provides no direct information
information much faster and about leachate.
cheaper than drilling.
2. Requires more direct
2. Can be used to extend geologic substantiation such as
data over broad areas on a drilling.
limited budget.
3. In complex geologic formations,
3. Can be used in certain areas interpretation is difficult
where access for a drilling and substantial errors may
rig would be difficult. occur.
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4.
5.
Requires the hiring of a
trained person and the use
of a computer to reduce and
interpret data.
Subject to noise interference
in many field situations.
3.4 OTHER MONITORING TECHNIQUES
3.4.1 Surface-Water Quality Measurements
Surface-water bodies, such as ponds or streams, in close proximity to
landfills often have an orange color and an oily film on the surface.
These obviously polluted water bodies are usually discharge points for
contaminated ground water which originated within the landfill. Location
of these discharge points on a topographic map of the landfill site will
often help to provide a reasonable preliminary picture of the ground-
water flow patterns. Where surface-water bodies are large or rapidly
flowing, dilution of leachate as it discharges is often sufficient to
prevent detection by visual inspection. In such cases, water samples
should be taken and analyzed to establish the presence of typical
leachate constituents, although even here dilution may interfere.
prior to the collection of surface-water samples, in-situ measurements
should be made by performing a survey for:
. specific conductance,
. pH,
. Eh,
. dissolved oxygen.
Such a survey can provide much useful information in itself; it will
at least indicate the locations from which surface-water samples should
be taken. The importance of an analysis of surface-water quality at
a landfill site is twofold:
. determination of leachate discharge areas is
crucial to establishing an overall hydrogeologic
picture;
. surface-water quality degradation is an important
component of overall environmental degradation and
should be carefully examined.
Also, in a full investigation of surface-water bodies near a landfill,
the native biota should be studied for the effects of leachate.
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The estimated cost of a. surface-water quality survey as described is
$300, exclusive of laboratory fees. It is assumed that this program
would be part of a more extensive investigation and that analysis of
the results of the surface-water quality survey would be covered under
a more general data analysis phase.
Advantages Disadvantages
1. Useful in locating leachate 1. Surface water may be subject
discharge points. to contamination from other
sources not defined.
2. Can be a quick and inexpensive
means of estimating 2. Dilution may be too great to
environmental impact of the provide useful information.
landfill.
3.4.2 Aerial Photography
Aerial photography has several important uses in landfill studies.
Regardless of tone (black and white or color) , an aerial photograph in
its simplest form will show the landfill and drainage away from it.
For large areas, remote sensing of vegetation stress by the use of
aerial photography may be a justifiable undertaking. Advanced stress
may be visible on color photography; less advanced stress may be
distinguished by using infrared photography.
Another method which has been used in landfill investigations is the
taking of multispectral aerial photographs. This procedures involves
the use of special equipment to determine subtle differences in light
reflected at various wave lengths for stressed and unstressed species.
Photographic filters which emphasize this difference are used, and
several images of the same area are made simultaneously with the aid
of a multi-lens camera and the selected filters. Differences between
stressed and unstressed vegetation are further enhanced by projecting
the images through different color filters and superimposing them on a
projector screen.
The usefulness of aerial photography is not limited to the detection of
vegetation stress. Accurate contour maps of the landfill surface may
be constructed from aerial photographs and are important in determining
hydrologic characteristics of the landfill. As the surface changes,
stereo color photography is used to construct and update topographic
maps of the active landfill sites.
It is important that bench marks, wells, and other sampling points be
located on the map. The inclusion of these items will facilitate
problem interpretation.
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Aerial photographs of a landfill site may be readily available from a
local firm. If not available, it may be necessary to have the site
photographed. Available photographs generally cost about $10 to $30
each. A series of black and white photographs generally costs
approximately $100 to $300 for an overflight. Special photography
such as color infrared or multispectral photography along with the
necessary interpretation will cost up to $2,000 for a 20.2-hectores
(50-acre) landfill site. This sum would include a topographic map and
a map showing vegetation stress. A report of the result of the photo
interpretation also would be included.
Disadvantages
1. Availability of aerial
photographs and photographic
services is sometin.es limited.
2. Little information concerning
sub-surface conditions.
3. Little indication as to
precise causes of detected
surface changes.
Advantages
1. Frequently can detect stressed
vegetation which indicates
contamination.
2. Can be used to prepare contour
maps relatively inexpensively.
Also provides certain geologic
information.
3. Much less costly than a detailed
ground survey of vegetation
stress.
A. Yearly photographs can provide
unbiased and indisputable
evidence of surface changes
such as: landfill configuration,
vegetation conditions, and
surface-water body locations.
5. Can be used to precisely map
key wells and sampling points
of the landfill site.
6. Enables a quick familiarization
of the landfill site conditions
without visiting the site.
3.4.3 Geophysical Well Logging
Geophysical well logging provides indirect evidence of sub-surface
formations, indicating the relative permeabilities as well as the
depths of the formations. The most common borehole geophysical
operation is electric logging. This procedure consists of recording
the apparent resistivities of the sub-surface formations and the
spontaneous potentials generated in the borehole. This information
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is plotted against depth below the ground surface. The measurements
of apparent resistivity and spontaneous potential are related to the
electrical conductivity of the sediments—a partial function of the
size of the grains. Thus, fine-grained sediments containing silt and
clay will have a lower resistivity than clean, coarse sand and gravel.
In addition, a leachate plume may be detectable by an electric log as
illustrated schematically in Figure 43. Electric well logs can be run
only in uncased boreholes.
Gamma-ray logging is a borehole geophysical procedure based upon
measuring the natural gamma-ray radiation from certain radioactive
elements that occur in varying amounts in sub-surface formations.
The log is a diagram showing the relative emission of gamma-rays,
measured in counts per second, plotted against depth below land surface.
Since some formations contain a higher concentration of radioactive
elements than others, formation changes with depth often can be
accurately determined. For example, clay and shale contain more
radioactive elements (e.g. isotopes of uranium, potassium, phosphorous,
and thorium) than sand or sandstone. The relative amount of silt and
clay in the formations can be estimated by the deflections of the
gamma-ray log. Unlike electric logs, gamma-ray logs can be run in
single-cased wells.
Geophysical well logs are used to supplement the driller's and
geologist's logs of the materials penetrated by the borehole. An
example of the comparison between geologic, electric, and gamma-ray
logs is shown in Figure 44. An accurate evaluation of the sub-surface
geology at a landfill site is essential to the determination of the
direction and rate of movement of leachate from the landfill, and the
contaminant attenuation capacity of the materials through which the
leachate migrates. Geophysical well logs are helpful in evaluating
these characteristics.
Geophysical well logging generally is applicable only to those landfill
investigations which include test drilling and is therefore not an
independent tool. However, gamma-ray logging can be used to gain some
understanding of the sub-surface geology at a landfill site from
existing wells which may be in the vicinity and for which no geologic
logs are available.
Since geological well logging requires specialized equipment and the
knowledge of trained operators to implement, the task is normally
carried out by a firm offering geophysical services. In some instances,
larger well-drilling companies are so equipped in which case the logging
can be included as part of the well-drilling operation. The cost of
geophysical well logging would be $300 to $500 per day depending upon
the complexity of the equipment and size of the necessary crew.
Normally five or six shallow wells or two to three deep wells
(several hundred meters) can be logged in a day. Interpretation of
the logs by a geophysicist would cost about $400 for a landfill site
with six wells at a depth of 30 to 60 meters (100 - 200 feet).
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DESCRIPTIVE
LOG
ELECTRIC LOG
SP
APPARENT
RESISTIVITY
GAMMA -
RAY LOG
CASING
BRACKISH- :
WATER SAND
SALT-WATER-;
FIGURE
COMPARISON OF GEOLOGIC., ELECTRIC,
AND GAMMA-RAY LOGS
(After Johnson Division, UOP, 1972)
131
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Advantages
Disadvantages
Requires special equipment
and the hiring of trained
operators; thus, adding
considerable expense.
Is not an absolute for
quantitative hydrogeologic
determinations.
1. Provides back-up data to ".
substantiate driller's and
geologist's log of borehole.
2. Allows a more accurate
determination of depth to \
formation change than might be
achieved with routine sampling.
3. Allows a rough geological log
to be constructed from an
existing well that was not
logged when drilled.
4. May be useful in locating top
and bottom of a contaminated
ground-water body.
3.5 WELL TECHNOLOGY
This section presents a brief discussion of the various drilling methods
commonly used for installing monitoring wells. The drilling method and
equipment used are described, and the advantages and disadvantages of
the various methods are presented.
3.5.1 Drilling Methods
3.5.1.1 Drive Points. In this method of drilling, a 31.7- to 51-mm
(1^- or 2-inch) diameter drive point is attached to a 51-mm (2-inch)
pipe and driven to completion depth with a sledge hammer, drive weight,
mechanical vibrator, or pneumatic hammer. The point can be driven to
approximately 9 meters (30 feet) by hand and up to 30 meters (100 feet)
if a mechanical drive weight is used (but only if driving is done in
sands or finer-grained sediments that offer little resistance to
penetration). Boulders cannot be overcome. Powell et al. (1973)
report using a mechanical vibrator to drive points to depths of
20 meters (65 feet),39 Drive points, because of their small diameter,
are used in areas of high-water table from which water can be removed
by suction pumps (e.g., pitcher pumps or centrifugal pumps).
Reliance on a drilling contractor to install drive points may not be
necessary. Investigators can drive them with a minimal investment in
equipment and manpower. The first step is to bore a vertical hole as
deeply as possible with a hand auger slightly larger than the well
point (^Figure 45). The drive point is attached to a length of riser
pipe (1.5-meter—5-foot lengths are preferable) and placed in the
augered hole. A drive cap is placed on the top of the casing prior
to driving.
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Hand
driver
-Weight
.Drive
cap
HAND ASSEMBLY
HEAVIER ASSEMBLIES OPERATED BY
DRILLING RIG OR TACKLE
FIGURE 45. METHODS FOR INSTALLING WELL POINTS
(After Johnson Division, UOP, 1972)
133
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Casing can be driven with a tool similar to the type used for driving
steel fence posts or by a drive weight suspended from a tripod or
derrick. Drilling will be more efficient if there is a source of power
to lift the weight, as they can weigh from 34 to 204 kilograms (75 to
450 pounds). Drive points can also be driven with a sledge hammer,
but this procedure is difficult and tedious. As the casing and point
are driven, they are turned slightly to keep the threaded joint tight.
Advantages
2.
3.
4.
Easily installed by hand, to a
limited depth.
Water samples can be collected
at closely-spaced intervals
during drilling.
Can expect a good seal between
casing and formation. Little or
no vertical leakage.
Disadvantages
1 Hi f f i c-alt to deve] on and
sample if water table is
below 4^ to 6 meters
(15 to 20 feet).
2. Depth limitations. Applicable
to shallow work primarily less
than 9 meters (30 feet).
3. No formation samples, only
information on subsurface
material penetration rate.
4. Only certain types of pumping
equipment can be used.
5. Drive point screen may become
clogged with clay, if driven
through a clay unit.
6. 'Jan be used only in
unconsolidated sediments.
3.5.1.2 Augers. In auger boring, the hole is advanced by rotating and
pressing a soil auger into the soil and withdrawing and emptying the
auger when it is full. Since water tends to prevent accumulation of
soil in the auger, the borehole is kept dry as much as possible. Hand
augering can be easy or difficult depending upon whether clay, sand,
or gravel, respectively, is being removed. Small-diameter helical or
posthole augers can be used to advance 5- to 30-cm (12-inch) diameter
holes by hand to depths of 6 to 9 meters (20 to 30 feet) (Figure 46).
If a tripod and pulley are set up to aid in pulling the auger from
the hole, depths of 24 meters (80 feet) can be reached. If the hole
can be kept open below the water table (usually only in cohesive
material), screen and casing can be set, backfilledj and developed.
The process becomes much simpler and less time consuming if power
augers are used. Here, flights of spiral, hollow-stem augers are
forced into the ground while being rotated; the spiral action of the
augers conducts cuttings to the surface (Figure 46). On completion
134
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CAL AUG
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135
-------
of drilling, a small-diameter casing and well point are pushed to the
desired depth. When bucket augers are used, a large diameter barrel
(up to 122cm—48 inches) fitted with cutting blades is rotated into the
ground until it is full. The earth-laden bucket is then brought to the
surface, pulled to one side, and dumped. This process is repeated to
completion depth. CBucket augers would not normally be used in landfill
investigations, and they are not evaluated in this manual.)
Power augers can be used very effectively in cohesive soils. On the
other hand, they are not well suited for use in very hard or cemented
soils; they often fail to retain very soft soils and fully-saturated
cohesionless soils. However, if setting a drive point is the main
purpose of the hole, slumping or caving-in of the hole in cohesionless
sediment is not a major drawback.
Advantages
1. Inexpensive.
2. Small, high-mobility rigs can
reach most sites.
3. Can be used to quickly construct
shallow well clusters.
4. If borehole prematurely reaches
refusal depth, set-up time is
low and rig can be moved rapidly.
5. No drilling fluids introduced
into the borehole; no possibility
of diluting formation water.
Disadvantages
1. Limited penetration; normally
30 to 46 meters (LOO-150 feet)
maximum.
2. Vertical leakage through
sediircnt left in borehole
through which drive point is
forced to completion depth.
No method to isolate screened
zones of aquifer.
3. Careful attention during
drilling is required to
obtain correct log of
formation materials penetrated.
4. Unable to collect ground-
water samples during drilling.
5. Core sampling is possible only
if hollow-stemmed auger flights
are used.
6. Can be used in unconsolidated
sediments.
7. Borehole will collapse in
cohesionless sediment.
136
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3.5.1.3 Wash Borings. Awash boring is advanced partly by a chopping
and twisting action of a chisel-shaped bit and partly by the jetting
action of a stream of water pumped through the drill rod and out the
bit (Figure 47). As the bit penetrates the formations, the washing
action of the bit causes the casing to sink. Cuttings are carried to
the surface by the water circulating in the annular space between the
drill rod and casing. The drill string is lifted and dropped, while
the bit rotates, achieving a cutting action and producing a round hole.
These operations, as well as the pumping, may be performed entirely by
hand; but a small motor-driven winch and pump are generally used. A
closed system is implemented to recirculate the drilling water. Water
is pumped from a pit into the drill string and out the bit. After
circulating from the bottom to the top of the borehole, the water is
conducted back to the pit where the cuttings settle out.
The drill rod is generally 2.5- to 5-cm (1- to 2-inch) black-iron pipe.
Casing is required to keep the hole open in soft clays or sand and
gravel but is often unnecessary in stiff clays or similar cohesive
sediments. If. the borehole stays open by itself, casing and screen
are simply lowered and backfilled to construct a well. If casing is
required to drill, slip screens are set by the casing pull-back method.
Advantages
Inexpensive. Light equipment.
Drilling contractor not required.
Excellent for shallow bore holes
in unconsolidated sediments.
Can obtain vertically-spaced
ground-water sample if drive
point is forced ahead of borehole
and pumped.
Drilling equipment can reach
almost any site.
Core samples can be collected.
Disadvantages
1. Slow, especially at depth.
2. Maximum depth of 30 to 46
meters (100-150 feet).
3. Cannot penetrate boulders or
wash up coarse gravel.
4. Can be used only in
unconsolidated sediment.
5. Wash water can dilute formation
which must be taken into account
in vertical sampling.
6. Interpretation of geology from
wash samples requires skill.
7. Can set only short sections of
screen without difficulty.
137
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SUMLEOIOOUftLCCMMIMCAVt-HOOK TO*
UUITIPU BLOCK FOB WlUttG (XCA3IKO
THRU O* POUR- LEOOID DERRICK'
STANDARD PIPE OR TIMBER
FIGURE 47, SIMPLIFIED WASH BORING RIG
(After Hvorslev, 1965)1
133
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3.5.1.4 Jet Percussion. The drill tools and the drilling action of the
jet-percussion method are the same as those described for the wash-
boring method. One essential difference, however, is that during drilling
the casing is driven with a drive weight and not allowed to advance of
its own weight. Normally, this method is used to place 5-cm (2-inch)
diameter casing in shallow, unconsolidated sand formations but has been
used to install 7.6- to 10-cm (3- to 4-inch) diameter casings to
61 meters (200 feet). Screens should be set by the casing pull-back
method. Most jet-percussion rigs (Figure 48) are moderately-sized
units. Drilling contractors used to working in unconsolidated sediments
will probably be the best source for a rig.
1.
2.
3.
4.
Advantages
Relatively inexpensive.
Simple equipment and operation.
Good seal between casing and
formation prevents vertical
leakage of formation water.
Can obtain a reliable formation
water sample at completed depth.
Disadvantages
1.
2.
Slow.
Use of water during drilling
can dilute formation water.
No formation water samples
can be taken during drilling.
Poor soil samples due to the
fact that fines are washed
out of sample.
Large number of wells is
required at one location to
obtain closely-spaced samples
throughout the contaminated
thickness of the aquifer.
Can only be used on
unconsolidated sediments
or weathered rock.
3.5.1.5 Cable-Tool (Percussion). In cable-tool or percussion drilling,
the hole is deepened by regularly lifting and dropping a heavy string
of drilling tools in the borehole (Figure 49). The drill bit breaks
or crushes hard rock into small fragments and in soft, unconsolidated
sediments loosens the material. The up and down action of the drill
string mixes the crushed or loosened particles with water to form a
slurry. If no water is present in the formation being penetrated,
water is added to the borehole. Cuttings are allowed to accumulate
until they start to lessen the impact of the bit and then are removed
with a bailer or sand pump.
A cable-tool drill string consists of three units:
139
-------
Cothtod
Air Chombtr
Pump
Suction Host
Stttllng Tank
Pulltyt
Derrick
Softty Hook
Wottr Swlvtl
Drill Rod
High Prtssurt
Host
Jar Staff
Drlvt Shot
Cross-Chopping Bit
FIGURE 48, SIMPLIFIED JET - PERCUSSION
(After Matlock, 1970)
HO
-------
-Sheave
Mast
Enclosed driving mechanism for spudder
Bit
FIGURE 49, SIMPLIFIED CABLE TOOL PERCUSSION RIG
(After Davis & De Wiest, 1966)
141
-------
. the drill bit,
. drill stem,
. rope socket.
The bit provides the cutting edge of the drill string, the action of
which is increased by the weight of the drill stem. This weight also
acts as a stabilizer, keeping the hole straight. The rope socket
connects the string of tools to the cable and allows the tools to
rotate slightly with respect to the cable.
Optional drilling jars are a pair of sliding, linked bars which provide
a slack of 15 to 23cm (6-9 inches) in the drill string. These are
used primarily in clay or caving formations. If the tools become stuck,
the jars permit successive upward blows in the attempt to free them
rather than a steady pull on a cable which might part. The shaking
and vibrations produced by the jars helps in freeing a stuck drill
string.
The bailer consists of a section of pipe with a check valve at the
bottom and is filled by an up-and-down motion in the bottom of the
hole. Each time the bailer is dipped, the valve opens, allowing the
cuttings slurry to move into it. The up-and-down motion is continued
until the bailer is full. At this point, it is brought to the
surface and the contents dumped on the ground. The sand pump is a
bailer that is fitted with a plunger so that an upward pull on the
plunger tends to produce a vacuum that opens the valve and sucks sand
or slurried cuttings into the tubing.
Casing is driven by attaching a drive clamp to the drill stem; the
reciprocal action of the rig hammers the casing into the ground as the
clamp makes contact with the drivehead on top of the casing. The
operation can be speeded by drilling ahead of the casing but only if
the hole will stay open by itself. If when drilling an open hole there
is a cave in, the drill string could be trapped. Cautious drillers,
therefore, rarely drill ahead of the casing unless they are going
through rock. Normal procedure in unconsolidated sediments is to drive
tne casing into the formation and then to clean out inside the casing
with the drill tools. This is slower but safer than drilling ahead
of the hole.
Advantages Disadvantages
1. Simple equipment and operation. 1. Slow.
2. Good seal between casing and 2. Use of water during drilling
formation if flush joint can dilute formation water.
casing is used.
142
-------
3. Good disturbed soil samples. 3.
Known depth from which cuttings
are bailed.
Potential difficulty in
pulling casing in order to
set screen.
4. Core samples can be collected.
5. If casing can be bailed dry
without sand heaves, a
formation-water sample can be
collected. 5.
6. Can be used in unconsolidated
sediments and consolidated rocks.
4. No formation water samples
can be taken during drilling
unless open-ended casing is
pumped, or a screen set.
Heavy steel drive pipe is used
and could be subject to
corrosion under adverse contaminant
characteristics.
7. Only small amounts of water are 6. Cannot run a complete suite
of geophysical well logs
because of casing.
required for drilling.
8. Once water is encountered,
changes in static or potentiometric
levels are readily observable.
3.5.1.6 Hydraulic Rotary. In drilling a hole by the hydraulic rotary
method, a rotating bit breaks up the formation and the cuttings are
brought to the surface by a recirculating drilling fluid (Figure 50).
Drilling mud is pumped from a settling basin, through a water swivel,
down the hollow interior of the drill rod, and through the bit. The
fluid then flows upward in the annulus, carrying the drill cuttings to
the surface. Here, it is discharged into the mud pit, and the cuttings
settle out. At the other end of the pit, the fluid is pumped out to
circulate down the drill rod again.
The drill string consists of the bit, a stabilizer, and the drill pipe.
Two basic types of bits are used:
. roller bits in rock,
. drag bits in unconsolidated materials.
Roller bits have conical rollers with hardened steel teeth of various
lengths, spacing and shape dependent upon the type of material to be
drilled. Some rollers have inset carbide buttons for drilling in
hard rock. As the rollers rotate, they crush and chip the formation
material. Drag bits have fixed blades, and the cutting edge is
surfaced with carbide or some other abrasion-resistant material.
The bit is attached to a heavy, weighted section of the drill string
called a drill collar or stabilizer. This weight, just above the
bit, tends to keep the borehole straight and vertical. The drill rod
connects the stabilizer to the kelly. The outside diameter ranges
from 6 to 11.4cm (2 3/8 - 4^ inches). The kelly is a fluted or square
143
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bar which passes through a rotary table and imparts a rotary motion
to the drill str-lng. When the length of the kelly has been drilled,
a new section of rod is added and drilling resumed.
Disadvantages
Expensive.
Requires complex equipment
and operation.
There is a potential for
vertical movement in
formation stabilizer material
placed between casing and
borehole wall after completion.
Advantages
1. Fast.
2. Dilution of formation water
is limited by formation of a
filter cake on borehole walls.
3. Formation water sample can be
obtained with a special technique.
4. Good disturbed soil samples from
known depths if travel time of
borehole cuttings is taken into
account, although sorting may
occur.
5. Flexibility in final well
construction.
6. Can run a complete suite of
geophysical well logs.
7. Core samples can be collected.
8. Can be used in unconsolidated
sediments and consolidated rocks.
3.5.1.7 Air Rotary. With this drilling method, a rotating down-hole
hammer may be used to break up formation material by percussion,
although conventional rotary bits are also used. However, rather than
carrying cuttings to the surface, high velocity compressed air is used.
Down-hole hammers are essentially the pneumatic hammer type, similar
in operation to those used by road repair crews to break up pavement.
Since the penetration rates of the air rotary drilling method are much
greater, this type of drilling is favored over the cable-tool or
hydraulic-rotary drilling. Drilling rates of 30 to 60cm (1-2 feet)
per minute are not unusual. One disadvantage, however, is that down-
hole hammers larger than 20cm (8 inches) are not readily available,
limiting the size of the borehole that can be drilled. Much of their
speed advantage is lost when conventional roller cone bits are used.
Most rigs are equipped with a small mud pump permitting a conventional
rotary hole to be drilled through unconsolidated overburden to
competent rock. When this hole is finished, casing is set into rock to
prevent caving, and drilling continues using the rotary method.
145
-------
Consequently, less water is required, thereby reducing a logistics
problem that can become difficult, especially in arid regions.
A minimum upward air velocity of 915 meters (3,000 feet) per minute is
required to lift cuttings to the surface. When drilling a 10-cm
(4-inch) diameter hole with 6-cm (2 3/8-inch) rod, at least
150 cubic feet per minute (CFM) of air are required to lift cuttings.
If a prolific aquifer is penetrated, the compressed air may be unable
to lift the volume of water entering the hole to the surface. At
915 meters (3,000 feet)perminute air velocity, this threshold is met
at about 3.15 liters/sec (50 gpm) in a 10-cm (4-inch) hole and at
about 9.5 liters/sec (150 gpm) in a 15-cm (6-inch) hole. When this
happens, a larger air compressor is required or drilling must be
changed to the hydraulic rotary method. Air rotary rigs are
available with compressors capable of supplying 31 cubic meters/minute
(1,100 CFM) at a pressure of 17.58 kg/cm2 (250 psi).
Advantages Disadvantages
(See section on Hydraulic Rotary
Drilling—Section 3.5.1.6)
3.5.2 Well Casing and Screen Materials
Landfill leachate can be characterized as a strong electrolyte which
may be corrosive. Specific characteristics of the leachate will depend
upon the type of material accepted by the operators. Therefore, some
thought, must be given to the materials used in monitoring well
construction to prolong the installation's operating life. Review of
comparison tables of various pipe materials to chemical attack indicates
that PVC pipe is resistant to most chemicals, with the exception of
ketones, esters, and arotnatics (among the more common chemicals) when
compared to steel well casing. PVC casing is a nonconductor and will
not be involved in electrochemical reactions as will a steel casing
and brass or iron well screen.
From a leachate sampling standpoint, PVC is very attractive. Because
of its chemical inertness, it will contribute little in the way of
chemical constituents to a leachate sample except in the parts-per-
billon range. Steel pipe can be expected to contribute at least iron
and probably other ions to a sample. Of course, this sample
contamination can probably be avoided by proper flushing of the well
before collection.
A major drawback to PVC casing is its lack of strength. PVC casing
projecting above ground surface can be easily broken by landfill
equipment or vandals. Therefore, special well-protection measures
(described in the Well Security section—3.5.3) must be taken. In
spite of this, PVC casing and screen appear to be the best materials
to use in constructing landfill monitoring wells.
146
-------
Actual well construction, however, will be dictated by a variety of
constraints, such as:
. contaminants being sampled for,
. drilling methods,
, aquifer type and formation materials,
. cost of well construction materials,
ease of installation.
Proper construction materials can be best evaluated for each situation
by a person familiar with landfill investigations, but a person not
familiar with them can fall back on a drilling method that will allow
PVC casing and screen to be installed and can be confident that the well
will last and not bias the samples.
3.5.3 Well Security
Once a well has been completed, some measures must be taken to protect
the installation from normal landfill operations (especially the use of
heavy equipment) and from vandals. In areas actively landfilled,
provisions should be made for extending the well casing and its
protection above the active level of the fill. An installation
capable of protecting the monitoring well and also capable of being
added on to the depth of the fill increases is illustrated in
Figure 51.
Construction of this protective installation is straightforward and
inexpensive with a reasonable likelihood of remaining undamaged by
landfill equipment or vandals. To accomplish this, a 3-meter
(10-foot) length of steel casing several centimeters (inches) larger
in diameter than the monitoring well is emplaced. This casing is
grouted and placed with a cement collar at least 1.2 to 1.5 meters
(4-5 feet) deep to hold it firmly in position. Although not
sufficiently rugged to withstand a run-in with a compactor or bulldozer,
it will withstand attempted vandalism. The casing should be threaded
so that a screw cap can be used to close the well. Two heavy-duty
hardened steel hasps welded on opposite sides of the cap and casing
will allow the well to be locked.
Unless the well is highly visible, the probabilities of it being
struck by equipment during normal landfill operations are great. To
avoid this, a simple tripod constructed of timbers (railroad ties or
equivalent) should be constructed over the well and crowned with a
brightly colored object such as a flag or painted tire. The well
could also be protected by brightly painted drums filled with soil.
147
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CEMENT COLLAR SLOPING
AWAY FROM WELL TO
PREVENT PERCOLATION
OF RAINWATER DOWN SIDE
OF CASING
CEMENT COLLAR PLACED
AS DEEP AS PRACTICAL
TIRE
BRIGHTLY COLORED
FLAG
3 Meter > TALL
TIMBER TRIPOD
SCREWED-ON
STEEL CAP
HARDENED STEEL HASP
-HARDENED STEEL
PADLOCK
3 Meter LENGTH OF
STEEL CASING PAINTED
A HIGHLY VISIBLE
COLOR.
PVC PLASTIC WELL CASING
PVC WELL SCREEN
FIGURE 51, GENERALIZED METHOD FOR PROTECTING
A WELL OR PIEZOMETER
148
-------
When landfilldng approaches the top of the installation, the tripod is
temporarily knocked down, additional casing added to the monitoring
well and protective shell, and placement of trash and cover is
continued around the well. If this procedure is followed, only a
slight interruption in the normal course of landfill operation will
be required to protect the monitoring well for future sampling.
149
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REFERENCES
1. Hyorsley, M.S. Subsurface exploration and sampling of soils
for civil engineering purposes. In Engineering foundation.
United Engineering Center. New York, 1965. 521p.
2. Black, C.A. ed. Physical and mineralogical properties including
statistics of measurement and sampling. In Methods of
soil analysis, part 1. Soil Science Society of America.
Madison, Wisconsin, 1965a. 770p.
3. Black, C.A. ed. Chemical and microbiological properties. In
Methods of soil analysis, part 2. Soil Science Society of
America, Madison, Wisconsin, 1965b. 802p.
4. Hanna, W.J. Methods for chemical analysis of soils. In Firman
E. Bear ed., Chemlscry of the soil. American Chemical
Society Mongraph Series No. 160. Reinhold Publishing Co.,
New York, 1964. pp. 474-502.
5. Instrumental methods for analysis of soils and plant tissue.
Soil Science Society of America. Madison, Wisconsin,
1971. 222p.
6. Grover, B.L., and R.E. Lamborn. Preparation of porous ceramic
cups to be used for extraction of soil water having low
solute concentrations. Soi^ Science Society of America:
Proceedings. 34(4);706-708. 1970.
7. Parizek, R.R., and B.E. Lane. Soil-water sampling using pan
and deep pressure-vacuum lysimeters. Journal of Hydrology,
11:1-21, 1970.
8. Wagner, G.H. Use of porous ceramic cups to sample soil water
within the profile. Soil Science, 94:379-386, 1962.
9. Wengel, R.W., and G.F. Griffen. Remote soil-water sampling
technique. Soil Science Society of America Proceedings,
35(4):661-664, 1971.
10. Wood, W.W, A technique using porous cups for water sampling at
any depth in the unsaturated zone. Water Resources Research,
9(2):486-488, 1973.
150
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11. Manbeck, D.M. Presence of nitrates around home disposal waste
sites. Annual meeting preprint, Paper No. 75-2066.
American Society of Agricultural Engineers, 1975.
12. Nassau-Suffolk Research Task Group. Final report of the Long
Island ground water pollution study. New York State
Department of Health. Albany, New York, 1969.
13. Annual report on dispersion and persistence of synthetic
detergents in ground water, San Bernadino and Riverside
Counties. Iji A report to the State Water Quality Control
Board, Interagency Agreement No. 12-17. Department of
Water Resources, The Resources Agency of California, 1963.
14. James, T.E. Colliery spoil heaps. I_n J.A. Cole, ed., Ground
water pollution in Europe. Water Information Center.
Port Washington, New York, 1974.
15. Apgar, M.A., and D. Langmuir. Ground water pollution potential of
a landfill above the water table. Ground Water, 9(6):76-94,
1971.
16. Personal Communication. Olin Braids, Geraghty & Miller, Inc.,
Port Washington, New York to Bruce S. Yare, Geraghty &
Miller, Inc., Port Washington, New York. September, 1975.
17. Anderson, J.R. and J.N. Dornbush. Investigation of the
influence of waste disposal practices on ground-water
quality. Technical completion report. Water Resources
Institute, South Dakota State University, 1968.
18. Fungaroli, A.A. Pollution of subsurface water by sanitary
landfills. U.S. Environmental Protection Agency Report
SW-12g, 1971.
19. Clark, T.P. Survey of ground-water protection methods for
Illinois landfills. Ground Water, 13(4):321-331, 1975.
20. Burt, E.M. The use, abuse, and recovery of a glacial aquifer.
Ground Water. 10(1);65-71. 1972.
21. Geraghty, J.J, and N.M. Perlmutter. Landfill leachate contamination
in Milford, Connecticut. Consultants report submitted to
General Electric-TEMPO, Center for Advanced Studies,
Santa Barbara, California, 1975.
151
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22. Weist, W.G., and R.A. Pettijohn. Investigation of ground-
water pollution from Indianapolis landfills—the lessons
learned. Ground Water. 13(2):191-196, 1975.
23. Pitt, W.A.J., Jr. Effects of septic tank effluent on ground
water quality, Dade County, Florida; An interim report.
Open File Report 74010. U.S. Geological Survey, 1974.
24. Yare, B.S. The use of a specialized drilling and ground-water
sampling technique for delineation of hexavalent chromium
contamination in an unconfined aquifer, Southern New
Jersey Coastal Plain. Ground Water, 13(2) .-151-154, 1975.
25. Palmquist, R., and L.V.A. Sendlein. The configuration of
contamination enclaves from refuse disposal sites on
floodplains. Ground Water. 13(2);167-181. 1975.
26. Aulenbach, D.B., and T.J. Tofflemire. Thirty-five years of
continuous discharge of secondary treated effluent onto
sand beds. Ground Water, 13(2):161-166, 1975.
27. Meyer, C.F., ed. Polluted ground water: some causes, effects,
controls, and monitoring. U.S. Environmental Protection
Agency 600/4-73-OOlb, 1973.
28. Hughes, G.M., Landon, R.A., and E.M. Farvolden. Hydrogeology
of solid waste disposal sites in northeastern Illinois.
U.S. Environmental Protection Agency, SW-12d, 1971.
29. Hansen, E.A., and A.R. Harris. A ground-water profile sampler.
Water Resources Research, 10(2):375, 1974.
30. Cherry, R.N. A portable sampler for collecting water samples
from specific zones in uncased or screened wells.
Professional paper 525-c. U.S. Geological Survey, 1965.
ppC214-216.
31. Fryberger, J.S. Rehabilitation of a brine-polluted aquifer.
U.S. Environmental Protection Agency. EPA-R2-72-014, 1972.
32. Childs, K.E., Upchurch, S. B., and B. Ellis. Sampling of variable
waste-migration patterns in ground water. Ground
Water, 12(6) :369-376, 1974.
33. Personal Communication. R.W. Harden, Denver, Colardo to
Bruce S. Yare, Geraghty & Miller, Inc., Port Washington,
New York. September, 1974.
152
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34. Lusczynski, N.J. Filter-press method of extracting water samples
for chloride analysis. U.S. Geological Survey water
supply paper 1544-A, 1961.
35. Swarenski, W.V. Determination of chloride in water from core
samples. American Association of Petroleum Geologists
Bulletin, 43(8):1995-1998, 1959.
36. Gill, H.E., et. al. Evaluation of geologic and hydrologic
data from the test drilling program at Island Beach State
Park, New Jersey. Water resources circular 12. New Jersey
Division of Water Policy and Supply, 1963.
37. Personal Communication. John Isbister, Geraghty & Miller, Inc.,
Port Washington, New York to Bruce S. Yare, Geraghty &
Miller Inc., Port Washington, New York. 1975.
38. Manheim, F.T. A hydraulic squeezer for obtaining interstitial
water from consolidated and unconsolidated sediment.
U.S. Geological Survey professional paper 550-C, 1966.
pp. C256-C261.
39. Powell, et. al. Water resources monitoring in Alabama. In
Information series 44. Geological Survey of Alabama.
University of Alabama, 1973.
ADDITIONAL REFERENCES
(not cited)
1. Beluche, R.A. et. al. Effective use of high water table areas
for sanitary landfills. Volumes I & II. U.S. Environmental
Protection Agency, 1973.
2. Campbell, M.D., and J.H. Lehr. Water well technology. McGraw-
Hill Book Co. New York, 1973. 681p.
3. Cartwright, K., and M.R. McComas. Geophysical surveys in the
vicinity of sanitary landfills. Ground Water, 6(5):23,
1968.
4. Environmental feasibility, proposed Silver Sands State Park,
Milford, Connecticut. Project Bi-T-55A. Report to the
State of Connecticut, Public Works Department. Department
of Environmental Protection. Geraghty & Miller, Inc.,
1973. (Section 3.3)
153
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5. Ground water and wells. Johnson Division, Universal Oil Products
Co., St. Paul, Minnesota, 1972.
6. Hem, John D. Study and interpretation of the chemical
characteristics of natural water. Geological survey
water-supply paper 1473. United States Government printing
office. Washington, B.C. 1970.
7. Hughes, G.M., Landon, R.A., and R.N. Farvolden. Hydrogeology
of solid waste disposal sites in Northeastern Illinois
Publication No. SW-12d. U.S. Environmental Protection
Agency, 1971. (Section 3.3).
8. In-situ investigation of movements of gases produced from
decomposing refuse. Final report prepared for California
State Water Quality Control Board. Publication No. 35.
April, 1967.
9. Kimmel, G.E., and O.C. Braids. Preliminary findings of a
leachate study on two landfills in Suffolk County,
New York. U.S. Geological Survey Journal of Research,
3(3):273-280, May-June, 1975.
10. Merz, R.C. Determination of the quantity and quality of gases
produced during refuse decomposition. Engineering quarterly
reports. U.S.C.E. Report: 83-3(September 30, 1962);
86-6(July 30, 1963); 87-7(September 30, 1963); 89-8
(December 31, 1963). University of Southern California,
Los Angeles.
11. Merz, R.C., and R. Stone. Gas production in a sanitary landfill.
Public Works, 95:84, February, 1964.
12. Parasnis, D.S, Principals of applied geophysics. John Wiley &
Sons, New York, 1962.
13. Stollar, R.L, and P. Roux. Earth resistivity surveys—a method
for defining ground-water contamination. Ground Water,
13(2):145-150, 1975.
14. Walker, W.H., Peck, T.R., and W.D. Lembke. Farm ground water
nitrate pollution—a case study. Meeting preprint.
American Society of Civil Engineers Annual and National
Environmental Engineering Meeting. October 16-22, 1972.
154
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4.0 INDICATORS OF LEACHATE
4.1 INTRODUCTION
Leachate represents an extremely complex system containing
soluble, insoluble, organic, Inorganic, ionic, nonionic, and
bacteriological constituents in an aqueous medium. Figure 52
schematically depicts an extensive characterization of leachate
by means of physical, inorganic, bacteriological, and organic
parameters. Chapter 5 presents additional information on leachate
characteristics.
In establishing a monitoring program, consideration should be
made of all the factors affecting the quality of the pure leachate
and leachate-enriched ground water and the resultant environmental
impact, including:
. purpose for monitoring;
« the background quality of ground water at the site;
. the other sources of ground-water pollution;
. the hydrologic conditions of the site and the resultant
monitoring network utilized;
, the climatologic influences;
. the costs and availability of manpower and laboratory
facilities;
. the site history.
A major item in any monitoring system will be the costs for the
analytical measurements. There are several ways these costs
may be minimized, yet meet regulatory requirements. The most
important of these is the proper selection of indicator parameters
to be monitored.
It will be the function of the regulatory agency to specify
monitoring requirements for land disposal sites. Some of the
necessary analyses will be time-consuming and relatively expensive.
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The regulatory agencies should maintain flexibility to consider
approval for substitution of a less expensive analytical indicator
if the parameter requiring the more expensive analysis can be
accurately inferred from the simpler, less expensive analytical
indicator. For example, the substitution of the COD (Chemical
Oxygen Demand) analysis for a portion of the BOD5 (5-day
Biochemical Oxygen Demand) analysis should be allowed in those states
where the latter is required if it can be shown that a satisfactory
correlation exists between the two parameters. Monitoring land
disposal sites can also be viewed in the sense of quality control.
A regulatory agency could allow (at least for frequent monitoring)
that the selection of indicators be subject only to the requirement
of quality-control comparisons between ground-water quality and
permit specifications. It is here that a strong effort should
be made to utilize inexpensive indicator analyses which can
provide quick, accurate, and correct information of those indicators
requiring more expensive analytical techniques. Promptness of
analysis is quite important since having the results for early
action will greatly simplify control requirements and sample
degradability effects will be minimized. As an example, conductivity
can sometimes be used as an indication of total dissolved solids.
This is a simple measurement and one which gives immediate
results for quality-control comparisons. However, for
quantitative extrapolations it is absolutely necessary to obtain
a correlation between the two indicator analyses for the particular
land disposal site being monitored.
This chapter will provide guidelines for selecting indicators
as well as scheduling and data management and' interpretation
resulting in a representative, valid, and cost/effective monitoring
program. The emphasis of this chapter is on monitoring of
ground-water sampling devices, strategically located in reference
to ground-water flow directions at regular intervals to determine
chemical constituents in the ground water at that point and time.
In addition, this chapter assumes that the landfill being monitored
disposes only normal municipal solid waste. Where special
wastes are involved, such as hazardous chemical and liquid wastes,
the indicator selection and sample scheduling would be modified
accordingly to be more waste specific.
4.2 BACKGROUND QUALITY OF THE GROUND WATER
The background-water quality at a land disposal site must be
considered in selecting the indicators for a monitoring program.
A ground water with a high background concentration of a particular
parameter would certainly lessen the value of that parameter
as a leachate indicator as it will require higher concentrations
to differentiate from background.
157
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No rule of thumb can be offered as to what background concentration
leyela render a parameter useless as a leachate indicator, Such,
a determination will be relative to the specific parameter. Its
limits of detection, the concentration difference observed
between the background and downgradient monitoring wells and
the standards of the regulatory agency juust be considered.
Phenols and total dissolved solids (IDS) are presented as two
extreme examples on this .matter. The drinking water standard for
phenols is 1 part per billion (pph) which is also its limit of
detection. Unless the downgradi.ent ^monitoring well contains a
very high concentration of phenols, even the slightest background
concentration of phenols would interfere with data interpretation.
However, the drinking water standards for IDS is 500 parts per
million (ppm) orders of magnitude higher than its limits of
detection. Therefore, high background concentrations of TDS
can be tolerated without interfering with data interpretation.
In a given landfill situation, it is necessary to obtain adequate
background data in order to draw reliable conclusions regarding
possible leachate contamination. Reliable data on background
quality of ground water will also be of critical importance
relative to regulatory and legal considerations. Therefore,
consideration must be given to both the ground-water quality
which occurs naturally, as well as other possible sources of
contamination which may affect the background quality,
4.2.1 Chemical Quality of Natural Ground Water
All ground water contains chemical constituents in solution. The
kinds and amounts of constituents depend upon the geologic
environment,movement, and source of the ground water. Typically,
concentrations of dissolved constituents in ground water exceed
those in surface waters. This is particularly true in arid
regions where recharge rates are low.
Dissolved constituents are primarily derived from minerals in
contact with ground water and percolating water going to ground-water
recharge. Common chemical constituents of ground water include:
Cations Anions Undissociated
Calcium Carbonate Silica
Magnesium Bicarbonate
Sodium Sulfate
Potassium Chloride
Nitrate
Table 4 lists relative abundances of these and other chemical
constituents in natural ground water. Minor and trace constituents
158
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TABLE 4
RELATIVE ABUNDANCE OF DISSOLVED SOLIDS IN
POTABLE WATER
Major Constituents (1.0 to 1000 ppm)
Sodium Bicarbonate
Calcium Sulfate
Magnesium Chloride
Silica
Secondary Constituents (0.01 to 10.0 ppm)
Iron Carbonate
Strontium Nitrate
Potassium Fluoride
Boron
Minor Constituents (0.001 to 0.1 ppm)
Antimony Lead
Aluminum Lithium
Arsenic Manganese
Barium Molybdenum
Bromide Nickel
Cadmium Phosphate
Chromium Rubidium
Cobalt Selenium
Copper Titanium
Germanium Uranium
Iodide Vanadium
Zinc
Trace Constituents (generally less than 0.0001 ppm)
Beryllium Silver
Bismuth Thallium
Cesium Thorium
Gallium Tin
Gold Tungsten
Indium Zirconium
Lanthanum
Platinum
*Davis, F. N., and R. J. M. De Wiest. Hydrogeology. John Wiley &
Sons, New York, 1966.
159
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are present selectively depending upon the mineralogy of the
region. Analyses of ground-^water samples enriched in silica,
iron, calcium, and sodium are giyen in Table 5. These elements
are frequently enriched in ground water. Brines and thermal
spring waters are not included in Table 5.
For convenience, ground-water quality is classified on a simplified
basis according to domestic and industrial use. Salinity, (the
concentration of total dissolved solids) and hardness (the combined
calcium and magnesium concentrations) are classificatory criteria.
The classification scheme is shown on Table 6. Water containing
a high, concentration of dissolved solids can build up scale in
boilers, be harmful to plants when used for irrigation, and
interfere with, quality of products in manufacturing. Hard water
also builds up scale deposits in boilers and forms scums with
soap in laundering.
Within a large body of ground water, the natural chemical composition
tends to be relatively consistent. Variation of ground water
relative to time is minor in comparison with surface-water
quality changes.
Under natural conditions, salinity of the ground water tends to
increase with depth. Most of the. geologic formations in the
United States are underlain by brackish to highly saline waters.
Density and permeability differences act to maintain a separation
between these waters and the overlying fresh ground water.
4.2.2 Other Sources o_f_ Ground-Water Contamination
Ground-water composition can vary widely under natural conditions.
Man's activities add another dimension to the complexity of
ground-water quality. The effect on ground-water quality of
point sources of contamination, such as: waste laggons, acid mine
spoils, and oil well brines are relatively easy to trace.
Diffuse sources of contamination, such as: regions of septic
tanks, irrigation, or farm chemical usage may affect bodies of
ground water, creating relatively uniform enrichment. Detection
of point-source contamination within a region of general
contamination will require relatively higher concentrations of
contaminants in comparison to comparable uncontaminated areas.
No estimate of background concentrations of leachate indicators
typical for a geohydrological setting could be used in lieu of
actual measurements. The only way to ascertain the ground<-water
quality at a given site is to measure it. As previously mentioned,
man's activities can influence ground-water quality. A description
of contaminants associated with certain of these activities
would be helpful as it points out those indicators which need to be
160
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TABLE 6
CLASSIFICATION OF WATER *
Concentration of total
Name dissolved solids ppro
Based on salinity
Fresh 0-1000
Brackish 100-10,000
Salty 10,000-100,000
Brine over 100,000
Slightly saline 1000-3000
Moderately saline 3,000-10,000
Very saline 10,000-35,000
Briny over 35,000
Based on hardness Hardness as CaC03 ppm
Soft 0-60
Moderately hard 61-120
Hard 121-180
Very hard over 180
*Hem, John D. Study and interpretation of the chemical characteristics
of natural water. In U.S. Geological survey water supply paper
No. 1473, 1970.
162
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delineated from unnaturally high background concentrations in
order to trace leachate-enriched ground water.
The following sources of ground-water contamination are listed in
Table 7 which, summarizes their potential contributions of
ground-water contaminants. Their similarities to and distinctions
from leachate should be carefully noted so that interferences
will be recognizable.
4.2.2.1 Highway Deicing, Over 6,567,000 tons (5,962,000 tonnes) of
deicing salts were used nationwide in 1966-67.^ The most common
salt in use is sodium chloride. Calcium chloride use amounts
to only 4 percent of that of sodium chloride.
Open storage of salt or salt/sand mixutres may result in leaching
of salt with rainwater. The leachate after reaching ground water
will form a pl-urne of salt-enriched ground water which could
contaminate wells in the vicinity. Howeyer, spreading of salt
on the road results in a -more diffuse salt-enrichment of ground
water. Wells located near major highways have been affected by
deicing salt.
4.2.2.2 Leaky Sewers. Sewer pipes which have been in service
over a period of years are likely to be leaky. Sewage gases form
acids which dissolve concrete and mortar, the usual substance of
older sewer pipes. When the pipes are located in the unsaturated
zone, raw sewage may leak and percolate to the ground water.
Sewage contains some inorganic salts, sulfur, nitrogen, trace
metals, and suspended and dissolved organic compounds. Sulfur and
nitrogen are generally present as sulfide and ammonia. After
entering the zone of aeration, these ions are oxidized to sulfate
and nitrate. Thus, sulfate and nitrate are associated with leaky
sewers in Table 7. The organic matter exerts a large BOD and
COD. Enteric organisms, bacteria and viruses, are present in large
numbers creating a potential for biological contamination. It
has been estimated that approximately 1.9 billion liters (500 million
gallons of sewage is lost annually in the U. S. through leakage. )
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4.2.2.3 Septic Tanks. Contaminants carried to ground water in
percolating septic tank effluent are similar to those from leaky
sewers. The major difference is that septic tanks have provided
an opportunity for some anaerobic decomposition. Thus, MBAS and
BOD levels are reduced from those of raw sewage. Again,
percolation of effluent through the zone of aeration converts
ammonium and sulfide to nitrate and sulfate. A reduction of
dissolved oxygen in the percolate or ground water by a high BOD
flow can cause dissolution of iron, hence the iron rating in
Table 7.
Unless the septic tank is within a few feet of the water table,
bacterial contamination should not be a problem. However, a
septic tank located in coarse-textured soil overlying a fractured
rock aquifer might cause considerable bacterial and viral
contamination.
Septic tanks in a density of approximately two per hectare
(one per acre) or less are not likely to significantly influence
regional ground-water quality. As density increases, these
point sources of contamination blend together and result in a
general degradation of regional ground water.
4.2.2.4 Mining. A variety of contaminants are generated in
leach-mining and ore benef iciation which are specific to the mineral
type and mine location. Locations generating these contaminants
would be obvious, thus it is unnecessary to deal with them here.
A more general contamination problem is generated by wastes from
strip and shaft mining, particularly as these methods pertain
to coal. In strip mining, overburden must be removed to expose
coal or ore seams. The coal is separated from waste rock and
is washed. The wastes produced in these processes are termed
spoils and gob piles.
Frequently, the waste rock and mineral contains pyrite
an iron sulfide mineral. When exposed to air, pyrite oxidizes with
the help of iron-oxidizing bacteria. The oxidation produces
sulfuric acid which keeps iron in solution and frequently dissolves
other heavy metals from waste minerals. Drainage water from
strip mine spoils or from mine shafts may have a pH of less than 2.
This acid mine drainage kills fish in surface waters and produces
an unsightly red-yellow scum.
The acid character of the spoils and gob piles prevents growth
of plant life on their surface.. The resulting erosion continuously
exposes new pyrite to oxidation. Acid mine drainage introduces
millions of tons of sulfuric acid into the environment each year.
Large regions of Pennsylvania, West Virginia, Ohio, Indiana, Illinois
have been contaminated from coal mining wastes. Abandoned
metal ore mines have produced a similar problem in Colorado.
165
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Acid water can contaminate ground water with a variety of heavy
metals which it dissolves. Reduction of the ground-water pH
also occurs creating a more corrosive medium. Iron and/or
manganese accompanying acidic water add a metallic taste, and
cause staining of plumbing fixtures and laundry.
4.2.2.5 Irrigation. Ground or surface water used for irrigation
becomes more mineralized as it percolates through soil and
dissolves mineral and fertilizer constituents. Irrigation water
going to recharge carries an enrichment of some or all of
the following ions: calcium, magnesium, sodium, potassium,
chloride, sulfate, and nitrate.
Continued irrigation increasingly mineralizes ground water.
This enrichment may become limiting to further ground water use.
In California, there are closed basins where ground water has
been recycled by irrigation and has become so mineralized it
is approaching the limit of usefulness.
4.2.2.6 Land Disposal of Sludge. The literature on sludge
chemistry has reported all of the indicators listed in Table 7
as being present in one sample or another. Concentrations range
from parts per billion to percentages.
Sludge is applied to the land surface. Therefore, its influence
on ground-water quality is determined by the transport of its
constituents through the top soil and underlying unsaturated
zone. The contribution of landfill leachate indicators to
ground water is calculated on the basis of sludge leachate
having undergone reactions in the top soil and unsaturated
zone.
Ammonium in sludge will nitrify, and the leaching portion will
migrate as nitrate. Most of the heavy metals and phosphate will
probably be retained in the soil and be in extremely low concentrations
in percolate.
Bacteria have been studied after sludge application to land.
Fecal coliforms exhibit a die-off rate which reduces their number
to a negligible population in a matter of 2-3 weeks. Bacterial
movement through soil is usually no more than a few centimeters.
Viruses have been shown to be more in soil but are not likely to
be a serious contaminant if digested sludge is used.
4.2.2.7 Petroleum Exploration and Development. Brines are almost
universally associated with oil deposits. They are sometimes
produced in greater quantities than crude oil, especially from
older fields. Brine pits are the most common waste disposal
facilities. In theory, water evaporates leaving salt accumulations.
In practice, brine frequently leaks from the pit and carries high
166
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concentrations of salt into underlying aquifers. Sodium and
calcium are the most common cations, with chloride, sulfate,
and nitrate as the most common anions. Some brines contain
enough, bromide for economic recovery. Brine may als,o be used as
a secondary recovery injectant. Indicative of the extent of
the problem, over 400 billion gallons of brine were produced in
the U. S. in 1974.3
4.2,2,8 Feedlots, Ground-crater contamination from feedlots occurs
principally from leaching of nitrate. Some.mineralization of
infiltrating water may also occur but not usually to an extent
that serious contamination results.
Phosphate from feedlot runoff is a serious pollution hazard to
surface water. However, phosphate is retained in soil and rarely
moves into ground water. Of the heavy metals, zinc is present in
the highest concentration in manure. None of the heavy metals
are in concentrations as high as those associated with municipal
sludges of mixed domestic and industrial origin. No appreciable
contribution to ground water of -manure-contaminated heavy metals
is anticipated.
4.2.2.9 Waste Lagoons, Oxidation Ponds»and Buried Pipelines.
Some sources of ground-water contamination are difficult to assign
specific chemical constituents. Waste lagoons and oxidation
ponds is one of these categories. Such facilities may contain a
wide range of varying inorganic or organic elements or organisms.
Therefore, in listing leachate indicators, probabilities are
given of their occurrence in lagooned and ponded waste leakage as
it enters the ground-water system (Table 8).
Buried pipelines and tanks are other sources of ground-water
contamination. Probably the most common contaminants from these
sources are petroleum products. Chemical storage tanks may also
be included in this category. Again, the probabilities shown
in Table 8 represent the probabilities of the given indicator
actually reaching ground-water.
4.3 CHEMICAL, PHYSICAL, AND BIOLOGICAL INDICATORS
A comprehensive listing of leachate indicator parameters has been
prepared and presented in Table 9. This listing reflects the most
widely used leachate indicators hy researchers in the field and
state regulatory agencies.^
The schematic diagram on Figure 52 and the list of leachate
indicator parameters in Table 9 represent the principal undesirable
characteristics of leachate from municipal solid wastes. Its
deleterious effects on ground and surface waters become apparent.
167
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Some of the effects include:
, Dissolved oxygen depletion in surface waters caused by
soluble organics and some inorganics;
, Objectionable tastes and odors in water supplies as a
result of the presence of soluble constituents;
, Health- hazards related to toxic materials and heavy metal
ions and microbiological contaminants present in excess
of drinking water standards;
, Limited use of ground and surface waters for drinking,
domestic, industrial, or recreational use as a result of
the effects of dissolved solids in excess concentrations.
These examples all point to the basic need for monitoring many
of these parameters. Further discussion and background information
regarding the undesirable nature and potential effects of the
various leachate indicator parameters can be found in the
Handbook for 'Monitoring Industrial Wastewater, U. S. EPA and
in the introductory remarks of Standard Methods.5>6
The actual selection and use of indicators for a particular
monitoring program will generally be decided from the indicators
on Table 9 and will depend upon a number of considerations:
. Type of monitoring 'network;
. Susceptability to attentuation;
, Background-water quality;
, Location of well being sampled;
, Purpose of monitoring;
, Other considerations including cost, regulatory standards
to be met, availability of laboratory equipment,
availability of manpower, and simplicity and precision of
determination;
, Type of solid waste handled and otner site-specific factors .
4.4 INDICATOR GROUPS
Indicators can be categorized into various groups or levels of
monitoring which vary in degree of information obtained in
relationship to the purpose for the monitoring. Three such levels
widely used are:
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TABLE 8
PROBABILITIES OF LANDFILL LEACHATE INDICATORS FROM
GIVEN SOURCES CONTAMINATING GROUND WATER
Indicator
Phosphate
Calcium
Magnesium
Sodium
Potassium
Ammonium
Chloride
Sulfate
Nitrate
Bicarbonate
Iron
Manganese
Boron
Selenium
Zinc
Copper
Lead
Other h.m.
MBAS
Phenols
PCB
Org N
PAH-HC
TOC
BOD
Colif orm
Virus
Waste lagoons
and ponds
II
III
III
I
III
II
I
I
I
III
I
I
II
II
II
II
II
II
III
I
II
II
III
II
II
III
III
Buried pipelines
and tanks
III
III
III
II
III
III
II
II
II
III
III
III
III
III
III
III
II
II
III
I
III
III
I
I
I
III
III
I=Highly probable
II=Probable
III=Unlikely
169
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170
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, Specific Conductance Measurements;
, Key Indicator Analyses;
, Extended Indicator Analysis
4.4.1 Specific Conductance Measurements
When-monitoring ground water and its temporal fluctuations,
specific conductance is a useful parameter for approximating the
total amount of inorganic dissolved solids. The real value of
specific conductance as an indicator is that it can be measured
quickly and easily, using inexpensive, accurate, and reliable
portable equipment and requires a low level of training.
Specific conductance has been successfully correlated with total
dissolved solids for monitoring leachate-enriched ground water.
It also has been used successfully to detect fluctuations and
trends for ionic impurities in the ground water. If conductivity
is used as a quantitative indicator of total dissolved solids,
it is absolutely essential that a valid correlation between the
two parameters be determined for the specific land disposal site
being-monitored. Otherwise, gross errors can result in data
interpretation. If however, specific conductance is used to
make quality control comparisons or to check for leachate presence
or absence, correlation with total dissolved solids is not as
critical. For purposes of quality control, availability of a
conductivity meter at a site would allow an operator to "spot
check" monitoring wells at very frequent intervals, i.e. weekly or
monthly. Where time and budget restrictions are a problem,
specific conductance measurements can also be used advantageously
during the sampling of a site to prioritize wells to be sampled.
4.4.2 Key Indicator Analyses Group
The intent of this monitoring group is to include highly sensitive
analytical parameters which can be performed rapidly and
accurately at a relatively low cost by personnel with a minimum
of training to yield reliable, useful data. A selection should
be made of a group of parameters which will provide information
regarding ionic, nonionic, inorganic, organic, and suspended
constituents of the ground-water sample. Most of the parameters
should lend themselves to field analyses using portable equipment.
Field -analyses have the advantage of eliminating the necessity for
low temperature and/or chemical preservation of the sample,
tfierehy minimizing labor and deterioration effects on the
analysis which can result from sample degradation due to aging.
This jnonitoring group can be performed at frequent intervals with
low cost, manpower, and equipment requirements.
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The final selection of analytical parameters must consider the
background-water quaHty, the pure leachate quality, as well as the
hydrogeologic influences. The group must, therefore, be site
specifi-c as well as remain flexible to change at a site as .may
be dictated by data interpretation.
For discussion purposes, the following list of key indicators
has been widely used in the field to determine the presence of
leachate:
, Specific Conductance
« Temperature
. Chloride
. Iron
, Color
. Turbidity
t COD
This group fits well the criteria for key indicators and, with
the exception of COD, can be performed rapidly using portable field
equipment .
It is not suggested that all of the indicator parameters
mentioned in this list must necessarily be used together to
determine the presence of leachate. Rather, this is to be left
to the judgment of the individual analyst. It is possible, for
instance, that results from just one of the analyses (e.g.,
Specific Conductance) could indicate the probable presence or
absence of leachate. A decision would then be made whether to run
some or all of the remaining parameters, or additional tests to
determine the reason for a high conductance value.
Data obtained from the key indicator analyses have value in and of
themselves, i.e. individual determinations will give valuable
information regarding the possible presence of leachate. In
addition, data obtained from several indicator analyses can be
cross-correlated and interpreted so that even .more insight can
be gained about the nature of the contamination, over and above
what is obtained from the individual tests.
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The following hypothetical examples serve to illustrate this
point;
Example 1. A sample of ground water is analyzed and yields
the following results: high levels of color
and COD; low levels of iron, turbidity, and
conductance. These results could he interpreted
as an indication of the presence of an appreciable
concentration of colored organic contamination
in a system which, is low in soluble and suspended
inorganic contaminant levels.
Example 2. A sample of ground water is analyzed and yields
the following results: high levels of conductance,
chloride, pH, and turbidity; low levels of COD,
color, and iron. These results could be interpreted
as an indication of the presence of an appreciable
concentration of inorganic materials, both
suspended and in solution, and a low concentration
level of organic materials.
Example 3. A sample of ground water is analyzed and yields
the following results: high levels of conductance,
chloride, iron, color, and COD; low levels of
turbidity and pH. These results could be
interpreted as an indication of the presence of
appreciable concentrations of both inorganic and
organic contaminants in acid solution and very
low levels of suspended materials.
For a more positive affirmation of the presence of leachate,
further interpretation of the indicator data must consider
background water quality, hydrogeology, attenuation, and other
pollution sources in the vicinity of the landfill.
4.4.3 Extended Indicator Analysis Group
This monitoring group is a much more comprehensive group of
analytical parameters. Table 9 presents a comprehensive extended
indicator analyses group which provides for a good characterization
of th£ water samples and represents indicators commonly used by
researchers and required by many regulatory agencies.^ Performance
of this joonitoring group will obviously be costly, requiring
trained personnel and an adequately equipped sanitary laboratory.
Very few of the parameters can be analyzed with portable field
equipment, thus requiring the utilization of acceptable storage and
preservation techniques.
There can be a number of reasons for performing extended indicator
analyses. The main reason to perform additional analyses is to
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provide jnore poaitive verification of contamination which has been
indicated by the key indicator analyses group.
Additional testing, whether instituted by a regulatory agency
or th£ landfill operator, should always be approached conservatively
from both, a technical and cost standpoint, Arbitrarily requiring
an extended program without reasonable technical justification
results in a very costly undertaking with, little or no regard to
its cost-benefit effectiveness.
An extended analysis program is justified when it can be demonstrated
that a key indicator program does not have the necessary and
sufficient capability to assure the absence of leachate contamination;
to yield required background quality information; or to provide
enough, information to solve a specific contamination problem. When
background quality information is being developed, a relatively
large number of analytical parameters should be investigated in
order to choose the few-most valuable ones which will constitute
the key indicator analysis program.
A sudden radical change in a key indicator may also point to the
necessity for extended analytical work. For example, an elevated
COD value might indicate contamination by a non-specific organic
material. In this case, the indication would be to perform a
number of analyses such as wet chemical tests or even infra-red
and gas chromatography (if equipment is available), in order to
determine which specific compound or compounds caused the change in
the COD. From a regulatory standpoint, the nature of an extended
analysis program would also be related to the standards which have
been set to assure the absence of leachate contamination. For
example, suppose that a state regulatory agency decides to adopt
as its enforcement standard the U. S. Public Health Service Drinking
Water Standards of 1962. This would result in an extended
analysis program which would at least require testing for 24
parameters—4 physical and 20 chemical. As another example, a
state regulatory agency may decide to adopt as its enforcement
standards a series of seven physical and chemical parameters
[eng.:pH., specific conductance, chemical oxygen demand (COD),
chloride, iron, color, and turbidity.]. This program would per se
constitute an adequate key indicator program, thereby eliminating
the need for an extended analysis program for regulatory purposes.
Thus, it can he seen that the concept of an extended analysis
program is a relative one. It is usually relative to regulatory
requirements, the need for data in addition to the key indicator
program, or the analysis of specific contamination problems. It
must, therefore, be the task of the responsible engineers and
analysts to determine what will constitute an extended analysis
program, if any, for a given landfill site.
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4.5 GUIDELINES FOR USING INDICATORS
For a given land disposal site, the selection and use of indicators
will vary with, the background-water quality, the differential
attentuation that may occur and the monitoring well being sampled,
4.5.1 Background Water Quality Monitoring
4,5,1,1 New Land Disposal Site. For a new land disposal site, the
background monitoring will define the naturally occurring constituents
in thfi ground water and contaminants from other possible pollution
sources that may be in the area, Section 4.2 presents a comprehensive
Summary of a variety of oth.er pollution sources and related
contaminants. Usually, the background quality at a new site can
be satisfactorily defined by performing an extended indicator
analysis group on an "A" well(s) that has been installed at the
site for this purpose. Chapter 2 discusses various types of "A"
wells in the different monitoring networks. It may be desirable
to have additional "A" wells if other significant pollution sources
are suspected or where more than one water-bearing zone is to be
monitored.
For the initial sampling, the extended indicator analyse? group
should be comprehensive, such as the list of parameters of Table 9.
Additional parameters may be deemed desirable where applicable to
define "other pollution sources" in the area. In the case of the
latter, the characteristics of other pollution sources should be
investigated in selecting any additional parameters for monitoring.
If possible, it is desirable to perform a few samplings (3 or 4)
to obtain a statistically reliable data base for the long-term
monitoring prior to commencement of operations. As is usually the
case, time and economic considerations prohibit this pre-sampling
procedure. Therefore, it is suggested that additional data be
collected on a few selected key indicators which will likely be
used in the long-term monitoring. These can be done quickly
and cheaply and will provide valuable data in developing a
statistically reliable data profile, as will be discussed later in
this chapter.
While the "A" wells will establish, the background water quality
for the site, it is also important to develop background quality
data for each "fi" and "C" well. This is more important for larger
landfills where the "A", "B", and "C" wells are relatively far
apart in respect to changes in geology and other pollution
sources which may influence their quality. Therefore it is
recommended that an initial extended indicator analysis group be
performed on all monitoring wells as soon as possible after their
installation.
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4.5.1.2 Existing Land Disposal Sites. For an existing land disposal
site where solid waste has already been landfilled, the background-
quality monitoring should acknowledge possible leachate contamination
that may have already occurred on the site, Monitoring in this
casejnuat then involve the "A", "B", and "C" wells installed at
th£ site. The "A" well will define the upgradient background
quality while th.e "B" and "C" wells define the downgradient
quality and any existing leachate contamination.
Here, the quality of the "B" well becomes especially significant
in selecting the. key and extended indicators for the monitoring
program. This monitoring well will detect the leachate contaminants
that are entering the saturated zone. The analysis of this well
will also provide valuable information about the unknown past
history of a site. For example, an old site -may have previously
disposed of hazardous wastes which could result in significant
concentrations of exotic contaminants not normally attributed
to municipal solid waste (e.g., certain heavy-metals or pesticides).
Depending upon the extent of the problem and the degree of potential
hazard to the public, a decision can then be made as to the
inclusion of additional parameters into the monitoring program
for use as key or extended indicators. In any event, analysis
of the "B" well will represent the "worse case" in terms of
leachate contamination at a particular site and can provide a
basis for including or excluding indicator parameters in the
on-going monitoring program.
4.5.2 On-Going Monitoring. The on-going monitoring program should
consist of the judicious use of representative key and extended
indicator analyses groups—the former run at more frequent intervals
and the latter run less frequently for verification purposes. The
key indicator group is designed for the primary purpose of
determining the presence or absence of leachate contamination and
as a "check" on quality fluctuations. The extended indicator
group is designed to provide verification of non-specific key
indicators (e.g. COD or specific conductance) as may be required
for purposes of enforcement, design, or scientific investigation.
4.5.2.1 Key Indicator Program, The on-going program will, of
course, involve the monitoring of the "A", "B", and "C" wells.
After establishing some background-quality data for the various
wells (whether it be one or a series of samplings), the most
representative indicators for the site would be selected. In
doing this, one must consider the background-quality data, the
constituents of th.e leachate, and the potential influence of
attenuation. The information presented earlier in this chapter on
background-water quality and in Chapter 5 on attenuation provides
some valuable guidelines for selecting indicators.
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As an example, suppose the natural background quality is high in iron or
total dissolved solids. In this case, the high concentrations required
to distinguish leachate from background water quality lessens the value of
iron and specific conductance as key indicators of learhatp contamination.
Or, there may be another pollution source in the vicinity that is affecting
the background quality of ttie ground water, such as: deicing of adjacent
highways, seepage from local septic tanks, or leaky sewers0 These, too,
might serve to lessen the value of various parameters as leachate indicators.
Susceptibility of attentuation in different soils would also affect the
value of the various parameters as incidators of leachate. The information
presented in Section 502 and Table 12 can be used as a guide in indicator
selection for a particular disposal site. Because of its freedom from
attenuation, chloride is noted as a popular and useful indicator. As long
as no presence of leachate is detected or no significant fluctuations in the
data are observed where leachate is already present, the key indicator
program should be followed,, Another consideration, however, would be the
regulatory agency's requirements. Some states do require a periodic
(e.gu, semi-annual or annual) testing for an extended analysis group
regardless of the monitoring trends being observed.
In most cases, all "A", "B", and "C" wells at the site should be included
in the key indicator program. However, this is not to be considered an
ironclad rule. Many large acreage land disposal sites may have a large
number of wells (20 to 30). In these cases, one may elect not to sample all
wells at each sampling, but to rotate sampling to include a small number
of wells each sampling date. Therefore, in the case of quarterly sampling,
each well would be sampled once per year. Generally, each sampling should
include at least one of each well type, i.e., an "A", "B", and "C" well.
The convenience of the specific conductance test can be a valuable asset in
this case0 The ability to be tested quickly with a field instrument may
allow at least a specific conductance reading on all wells at each sampling
date. The specific conductance reading provides the added dimension of
making on-the-spot decisions as to which wells should receive sampling
priority,, Having the specific conductance data profile on hand for quick
reference, the field technician can compare the most recent reading with the
profile. A significant change worthy of further investigation may be
indicated. A combination of a routine rotational sampling schedule that is
subject to possible modification due to significant changes in specific
conductance would comprise a sound rationale to the use of the
indicator group„
If a significant change is observed in a key indicator parameter or
parameters (e.g., increase in specific conductance), the possibility of
leachate contamination should be suspected and a plan for further
investigative and corrective action should be instituted immediately. This
plan should include additional sampling and analytical work as determined
by the key indicator data obtained. This data should serve as a base for
developing a satisfactory corrective action to eliminate the cause of the
contamination problem and to monitor the effect of implementing the same«
Assuming that a leachate contamination problem has been discovered by the
key indicator program and corrective action implemented, sampling and key
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indicator testing should be instituted on an increased level of frequency,
with the possible inclusion of additional parameters. This should be
continued until there is reasonable certitude that conditions have
returned to normal and will probably remain so. At this point, a
re-assessment of the key indicator analytical program should be made,, It
should then be decided whether to reinstitute the program in its original
form or to initiate it in a modified form based upon experience gained
in solving the contamination problem.
The following hypothetical example will serve to illustrate this approach:
Sulfate was found to be a principal contributing
contaminant and had caused a high specific conductance
reading. It was then decided to test for sulfate, for
a limited time, in addition to the other parameters of
the key indicator program. In this manner, valuable
data was collected that showed sulfate/conductance
ratios which could be used as a guide in monitoring
for future problems.
4.5.5.2 Extended Indicator Program0 Obtaining background-quality data
and further investigating a particular problem are the principal technical
reasons for implementing an extended indicator analyses group„ In the
legal sense, enforcement data needs may require extended indicator
analyses data. Administratively, many regulatory agencies will require
sampling for an extended indicator analyses group0 The extended indicator
program should be used judiciously due to the relatively excessive costs
and manpower requirements associated with their performance.
The fact that the extended indicator parameters are basically serving
to verify the results of the key indicator parameters should provide a
basis of a rationale for selecting and ranking the former. In other
words, a significant fluctuation in a particular key indicator would
"trigger" further investigation by a select group of extended parameters
and not automatically the entire extended indicator analyses group.
The implementation of the extended indicator analyses group should also
be a monitoring well specific decision. For example, a quality change
in one "C" well should not immediately require the testing for extended
indicators in all of the "C" well.
The following examples of relationships between key and extended indicators
serve to illustrate thje point:
, A significant change in specific conductance would be
an indicator of possible changes in levels of one or more
of the following extended indicator parameters: pH, total
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dissolved solids, chloride, sulfate, phosphate, alkalinity,
acidity, nitrogen series, sodium, potassium, calcium,
magnesium, hardness, heavy metals, cyanide, fluoride, and
COD.
. A significant change in chloride concentration would be
an indicator of possible changes in levels of one or more
of the following extended indicator parameters: specific
conductance, total dissolved solids, pH, acidity, and
metal ions.
. A significant change in iron (total) concentration would
be an indicator of possible changes in levels of one or
more of the following extended indicator parameters:
specific conductance, pH, total dissolved solids, chloride,
sulfate, phosphate, manganese, and fluoride.
• A significant change in color would be an indicator of
possible changes in levels of one or more of the following
extended indicator parameters: COD, TOC, tannins,
lignins, organic N, total dissolved solids, pH, iron,
BOD, and conductance.
. A significant change in turbidity would be an indicator
of possible changes in levels of one or more of the
following extended indicator parameters: pH, conductance,
COD, TOC, tannins, lignins, total suspended solids,
phosphate, alkalinity, acidity, calcium, magnesium,
hardness, heavy metals, fluoride, and BOD.
• A significant change in COD would be an indicator of
possible changes in levels of one or more of the following
extended parameters: BOD, pH, conductance, TOC, volatile
acids, tannins, lignins, organic N, total dissolved solids,
total suspended solids, volatile solids.
In a practical situation, several of the key indicators will most
probably show variations at the same time. Therefore, looking
at combinations of key indicators will provide additional information
for the analyst to define the chemistry of the system involved
and further assist in specifying additional extended indicators
for analysis.
4.6 MONITORING FREQENCY
The sampling schedule for a land disposal site should be flexible,
allowing for modification. Monitoring frequency is greatly
influenced by many factors, such as:
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. Characteristics of ground-water flow;
. The location and purpose of the particular monitoring
well;
* Trends in the monitoring data;
• Legal and institutional data needs;
. Climatological characteristics;
. Other considerations.
The hazardous nature of the leachate in relationship to the
threatened water resource (e.g., a single domestic well or an
entire municipal water supply) will to a large degree dictate
the monitoring effort.
4.6.1 Characteristics of Ground-Water Flow
The principal characteristics of concern in selecting a sampling
frequency is the rate of ground-water flow at the land disposal
site. The flow rate will be primarily dependent upon the aquifer
porosity and permeability as well as the hydraulic gradient
existing at the site. Aquifers are generally categorized by
porosity into intergranular porosity, fracture porosity, and
solution porosity. Ground-water flow rates ranging in orders
of magnitude from a few meters (feet) per year in an impervious
intergranular porosity aquifer to tens of meters (feet) per day
in the more unpredictable fracture and solution porosity aquifers
(Chapter 2).
The higher the rate of ground-water flow, the greater the monitoring
frequency needed. Two extreme examples would be an intergranular
porosity aquifer with impervious clay soils vs. a fracture or
solution porosity aquifer with unpredictable and high flow rates
likely. Hypothetically then, if the closest "C" well is
30 meters (100 feet) from the landfill and the closest downgradient
property line or domestic well is 90 meters (300 feet) away, at
the site with clay soils it would be senseless to do frequent
sampling since, theoretically, it would take ten to twenty years
fcr any leachate-enriched ground water to even reach the well. In
this instance after establishing background quality, a semi-annual^.
or annual monitoring of the well with select key indicator
parameters would suffice. In the case of a fracture or solution
porosity aquifer, it is possible that contaminants could migrate
from the property in a matter of days, weeks, or months. Here, a
quarterly monitoring with key indicators and a more frequent
spot-checking with specific conductance would be warranted. As
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was previously discussed, the extended indicator group would be
utilized as needed. Most landfills will fall between these two
extremes; however, careful consideration must be given to the flow
rate and the distance involved to select a frequency which will
not miss an environmental occurence.
In a similar sense, the monitoring well would be influenced by
the vertical flow rate of leachate-enriched ground water. For
example, if a disposal site is underlain by a sand aquifer with a
relatively high ground-water flow rate and is separated from the
landfill by a thick layer of impervious clay, a concentrated
monitoring effort of the "C" wells in the aquifer would not be
justified until the "B" well detected that contaminants have
traveled through the clay layer and reached the aquifer.
4.6.2 Location and Purpose of the Monitoring Well
The distance that a monitoring well is located from the land
disposal site as well as its depth will influence monitoring
frequency. For example, there may be a case where a line of "C"
wells are placed along the property line for legal and administrative
reasons due to ground-water protection laws. There is little
need to concentrate on monitoring these wells until the monitoring
results of closer "C" wells present some reason to believe that
leachate contaminants may be approaching close to the property
line. Only minimum monitoring of these wells to establish
background quality and meet regulatory requirements would be
justified.
Another example might be a well located in deep water bearing
zones separated from the disposal site by other aquifers and
aquicludes. Chapter 2 depicts examples of areas (e.g., coastal plain)
where there are a series of alternating aquifers and aquicludes.
For institutional reasons or regional water planning purposes, a
monitoring well may be placed in a deep aquifer which has almost
no chance of being contaminated by the land disposal site. After
an initial monitoring for background purposes such wells would
only deserve less frequent attention—unless, of course, other
monitoring results cause reason for concern.
4.6.3 Climatological Characteristics
In setting up the initial monitoring schedule for a particular site,
the fluctuations in leachate generation that occur over the year
should be analyzed. The water balance method (Chapter 5) is a
very useful tool for this purpose. As an example, it may be
desired to perform quarterly sampling. Instead of arbitrarily
assigning a sampling date every third month, the monitoring
schedule should be correlated with ground-water recharge periods in
the year when leachate generation is greatest. Selection of the
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actual sampling dates should also take into account the well
location and depth, ground-water flow rate, saturation condition
of the landfill, and other factors to project approximate lag
times that may occur between first appearance of leachate and
its impact on the monitoring well.
4.6.4 Trends in the Monitoring Data
The three factors presented above (ground-water flow rate, well
purpose and location, and climate) will be used at the outset in
establishing monitoring frequencies. However, monitoring frequencies
should never be considered ironclad. They should maintain
flexibility for modification to respond to trends in the monitoring
data.
As an example, if a spot check with a specific conductance meter
indicates a significant change in the water quality at a particular
well, further investigation with additional key and extended
indicators would be desired immediately, regardless of the next
sampling schedule. Concentration on this well might also reduce
the frequency at another well where recent data has shown no
significant changes in water quality.
4.6.5 Legal and Institutional Data Needs
Monitoring frequencies at a site may also be altered for legal
and institutional reasons. As an example, if an enforcement
action is initiated against a landfill, to strengthen their case,
attorneys for both the State and the disposal site may request
that all of the monitoring wells be monitored for an extended
indicator analyses group.
4.6.6 Other Considerations.
Other reasons for modifying the monitoring frequencies at a site
would include:
. Complaints from neighboring residents;
. An unusually severe climatological event such as
a hurricane, with large amounts of rain in a short
time period;
A sudden change in or addition of an "other
pollution source", such as an oil spill adjacent
to the property;
. An unusual operational occurence, such as the
illegal and/or improper dumping of a large volume
of liquids at a site.
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A properly planned monitoring program will allow for modification
in sampling schedules to respond to the above-mentioned occurrences.
4.7 COST 'CONSIDERATIONS
In selecting indicator parameters and sampling frequencies,
it is important to be mindful of relative costs for performing
the monitoring. The three basic levels of indicators used for
monitoring presented earlier vary not only in the depth of
analytical data provided but also in the costs for sampling and
analysis.
Specific conductance is valuable because it is so inexpensive to
perform. By using a portable field meter, the analytical cost
is merely the few extra minutes required by the technician to
perform the test at the site. The meter itself is relatively
inexpensive, costing approximately $300.00 (1976 prices). The
sampling costs are also low, primarily because it is not necessary
to collect and preserve samples for the laboratory. This lessens
the amount of bottles to be carried and the time for adding sample
preservatives. This advantage would be somewhat limited where
pre-pumping of the wells is done. There is no way of estimating
sampling costs and time requirements since they are site specific
depending upon accessibility and number of wells as well as the
pre-pumping and sample withdrawal method used. For order of
magnitude comparison purposes only, a typical commercial laboratory
would charge approximately $3.00 per sample for a specific conductance
analysis (New York Area, 1976 prices), exclusive of sampling.
A typical key indicator analysis group, i.e. specific conductance,
pH, temperature, chloride, iron, color, turbidity, and COD would
be more expensive for sampling and analysis. With the exception
of COD, all the analyses can be run in the field with portable
equipment. Sampling time will be increased, however, by the
additional equipment and analyses required and the time to collect,
store, and preserve the COD sample. Where one man could manage
nicely with specific conductance measurements, an assistant may be
desirable in monitoring for all the key indicators depending
upon the number and accessibility of wells to be sampled and the
sample withdrawl method used. Adverse weather conditions may also
necessitate transporting samples back to the laboratory for
analyses where as specific conductance could still be done
in the field. For order of magnitude comparison purposes, a
typical commercial laboratory would charge approximately $50.00 per
sample for the key indicator analyses listed (New York Area, 1976
prices), exclusive of sampling.
A typical extended indicator analysis group, such as listed in
Table 9, would be the most expensive level of monitoring for both
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sampling and analysis. With the exception of some key indicators
which might be run in the field, all the indicators require
proper storage, preservation, and transport of samples to the
laboratory for analysis. This would require additional sampling
time and possibly additional manpower to sample properly and
efficiently in the field. Of course, adverse weather conditions
may further complicate sampling efforts.
Again, for order of magnitude comparison purposes, a typical
commercial laboratory would charge approximately $600 - $700 per
sample for the extended indicator parameters listed in Table 9,
exclusive of sampling.
Table 10 summarizes the cost of analysis for the various monitoring
groups discussed above. As noted, no comparisons of sampling
costs have been made due to its extreme site specificity.
4.8 DATA MANAGEMENT
4.8.1 General
At a given land disposal site, appreciable quantities of data
relative to ground-water quality will be generated over a period
of time. Several factors govern the amount of data produced,
including the number of monitoring wells, the number of parameters
to be tested, and the frequency of testing (both scheduled and
unscheduled).
As a hypothetical case, assume that there are 20 monitoring wells
at a given landfill and that the following tests are performed
in a given year:
Testing Category No. of Parameters No. of Wells No. of Tests
Annual-Extended 30 20 600
Quarterly-Indicator 10 20 600 (200 x 3)
Problem-Unscheduled 30 20 600
Total 1,800
The total number of tests performed in the landfill over a period
of one year will be 1,800. This figure could approach 20,000 over
a 10-year period. This amount of raw data must be processed,
interrelated, statistically analyzed, and stored in readily
retrievable form so that it will be of maximum value for quality
control, engineering, and legal purposes.
The use of digital computer treatment would appear to be an
excellent tool; it is both rapid and cost-effective as a management
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TABLE 10
COMPARATIVE COSTS OF
INDICATOR ANALYSES*
Approximate Cost of Analysis
Monitoring Group Per Sample ($)
Specific Conductance $ 3,00
Key Indicators $50.00
Extended Indicators $600.00-$700.00
Note: It should be noted that there is an economy of numbers
relative to both sampling and analysis. Appreciable quantity
discounts are usually available for different levels of sampling
and analysis. Additional savings can usually be realized through
the use of a long-term sampling and analysis contract.
*A comparison of sampling costs has not been made due to its
extreme site specificity - such a comparison should consider the
number and accessibility of wells, weather conditions, whether or
not the wells will be pre-pumped prior to sampling, and the
pre-pumping and sample withdrawal methods used.
-f-Based on January 1976, rates of a typical commercial
laboratory in the New York Area. Refer to Chapter 7 for laboratory
manpower requirements for analyses.
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information system in the handling of this type of data. Other
approaches to data management could entail manual processing,
storage, and retrieval of the data in the form of tables, charts,
and graphs which can show parameter levels and trends relative to
standard values. In both cases, the statistical handling and use
of analytical data for quality control purposes in the form of
ranges, means, standard deviations, parameter ratios (e. g., specif ic
conductance/TDS ratio), and control charts will be important.
The technological state of the art of land disposal is still
relatively young and is highly dependent upon monitoring for its
development. Even if a particular design and operational strategy
is successful at one site, it cannot be automatically assumed
acceptable for all sites due to the extreme site specificity
which is fundamental to land disposal of solid waste. Again,
monitoring becomes critically important. Thus, the parameters
monitored and the significant results obtained from the monitoring
program will be critically evaluated in assessing a site and
related design and operational approaches and in deciding upon
modification. Because of the significance which may be placed
on the results of the monitoring program, it should be the desire
of the landfill management to understand and attempt to identify
the causes of fluctuations in monitoring data obtained. Incorrect
interpretation of monitoring data may result in unnecessary
expenditures or in a false sense of security.
The variability of the indicator parameters measured in a
monitoring program may result from various phenomena, some of which
are:
. Natural fluctuations in the background-water quality;
. Occurrence of another pollution source which might
cause the background-water quality to fluctuate;
. Attenuation taking place in the subsurface environment;
. Climatological variations;
Operational deficiencies, incidents, and modifications;
. Experimental errors in the analyses of measured
parameters;
. The sampling method utilized.
Variations in the background-water quality will occur with location
and time. Such variations recorded in the "A" wells should be
fingerprinted statistically to allow for more accurate interpretation
of the data fluctuations recorded at the "B" and "C" wells. In
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the same vein, fluctuations in background quality may be artificially
induced by another pollution source. As was stressed earlier,
such occurrences must be carefully recorded because of their
effect on monitoring data interpretation. Differential attentuation
(Chapter 5) and climatological variations (Section 4.6.3) will have a
definite influence on temporal and distance variations in monitoring
data.
Operational factors will have a definite influence on the monitoring
data and its evaluation and should be carefully documented. For
example, operation changes, such as: type of wastes, a sudden
disposal of a large quantity of liquid wastes, a deficiency in cover,
or construction of the dikes, diversion ditches etc...could all
significantly affect monitoring results and should be carefully
described with dates recorded.
The results of the analysis of a sample by the same or different
technicians using the same laboratory techniques often fluctuate
widely. Even very accurate laboratory analysis cannot prevent a
relatively wide range in determined values of parameters such as
BOD, which may experience experimental error as high as 20%.
Variations will also exist with alternate analytical methods,
especially field versus"laboratory methods. This becomes even
more significant for concentrated leachate samples where interferences
further complicate analysis. Because of its significance in
data interpretation, all of this information must be carefully
recorded.
Because of the variations that can be created, differences in
the sampling withdrawl method utilized is important for monitoring
data evaluation. Questions that should be asked are:
. Was the well flushed out prior to obtaining a
sample?
. Was the sample collected aerobically or anaerobically?
Was the sample properly preserved?
. How much time ellapsed between sample collection
and analysis?
. Who did the sampling?
It is important that these questions be answered and their implications
understood when evaluating the monitoring results.
Therefore, all of the possible causes in variations should be
carefully recorded and identified for proper evaluation of the
monitoring results. It will be important that the monitoring
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program distinguish between fluctuations which are significant and
attributable to the landfill requiring some form of remedial action
versus those variations which are insignificant or not attributable
to deficiencies at the landfill. A complicating feature for a
land disposal site, unlike water and air pollution, is the time lag
which inherently exists between cause and effect,. For example, it
may take months or years for a fluctuation observed in an "A" or
"B" well to reach a. distant "C" well thus often further complicating
data interpretation.
4„8 o2 Application of Statis tics
In the Handbook for Monitoring Industrial Wastewater, the value of
statistics in" monitoring is discussed:5
Statistics aid in the development of general laws
resulting from numerous individual determinations
which, by themselves may be meaningless. The
resulting relationships are part of the fundamental
function of statistics which expresses the data
obtained from an investigative process in a condensed
and meaningful form,, Thus, the average or mean is
often used as a single value to represent a group of
data,, The variability of the group of observations
is expressed by the value of the standard deviation
and trends in concentrations during the monitoring
process are expressed in the form of regression
coefficients„
In general, the concern is with the treatment of the
collected data0 The accuracy or usefulness of these
data is greatly enchanced if a full understanding
was involved in generating the facts,, The balance
between use of statistical methods and evaluation
based upon physical understanding is extremely
important. The use and value of statistics decreases
as physical understanding increases. Specifically,
the difficulty lies in separating chance effects from
valid occurrenceso With the knowledge of basic
probability theory and the use of statistical techniques,
such as Least Squares Curve Fitting, Analysis of
Variance, Regressive and Correlation Analysis,
Chi-Squared Goodness of Fit, and others, it is possible
to construct mathematical models and curves of almost
any level of precision desired. Such techniques
help to evaluate in information having wide variations,
so that an estimate of the best value of the parameter
being measured can be assigned; and also to assess the
precision of that estimate^ Statistical procedures may
also help in identifying errors and mistakes and are
helpful in comparing sampling methods and procedures and in
evaluating waste loadings from different process schemes.
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Because of the extreme site specificity of the various phenomena
involved, evaluation based upon physical understanding (Section 40801)
is especially significant for monitoring a land disposal site,,
Probably, the major use of statistics in a monitoring program
is to correlate the data for the proper choice of statistical parameters
(mean, range, and standard deviation) for the specific indicators for
evaluation and comparison purposes„
Statistics and data analyses are very broad topics and are beyond
the scope of this manualo The aforementioned EPA publication,
Handbook for Monitoring Industrial jtostewater, cites several good
references on statistics„ It should be emphasized that rules and
formulas for data analyses are many. To be of value, they must be
:hosen wisely and applied correctly.
'4.8o3 Indicator Data Profiles
3nce a monitoring program has been in operation for an appreciable period
}f time, the data obtained from it can be used to provide specific
analytical profiles for ground water and/or surface water for a given
Land disposal site. These profiles will be characterized by data from
a number of sampling points within the landfill and will reflect the
influence of the various phenomena that result in fluctuations in the
indicator parameters„ Statistical analyses of the profiles will provide
such important statistical values as normal ranges, means, and standard
deviations for each of the indicator parameters„
Quality control data of the landfill site can be obtained from the
profile data. This could take the form of control charts for the
various parameters which would indicate whether the operation was "in
control" or "out of control" relative to upper and lower control limits
provided by the control chart.
Statistics can play an important role in the correlation of specific
parameters, especially in the case of specific conductance to other
parameters such as total dissolved solidso The Handbook for Monitqring
Indus trial Was tewa ter,^ presents an excellent discussion on the
statistics for correlation of specific parameters,, The data profile
will also provide an insight into the interrelationships of the various
key indicator parameters in the form of normal ratios, (e.g., specific
conductance to total dissolved solids) which should be developed for a
cost effective monitoring program» When enough data are obtained on
indicator parameter ratios for a given landfill site, statistical values
of range, mean, and standard deviation can be developed as is done for
the individual indicator parameters themselves. This information can
be used as a valuable statistical tool for quality control of the
landfill and as an aid in the diagnosis of leachate contamination
problems and their probable causes«
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In a monitoring program, data profiles can be used in a variety
of ways, some of which are:
. Concentration of the various indicator parameters
vs. time for each monitoring well. This is
perhaps the most common use of a data profile in
monitoring programs. It provides an immediate
visual picture of the trends in quality and is
nicely defined with the basic statistical values
(mean, range, and standard deviation). It provides
a valuable tool in comparing monitoring results
of the "A", "B", and "C" wells for operational and
enforcement purposes. It provides a readily
available and convenient tool for comparing water
quality trends to trends and occurrences in the
various phenomena that influence the ground-water
quality which were discussed earlier.
. Concentration of the various indicator parameters
versus distance from the landfill. This type of
profile would be constructed by plotting the data
for selected indicator parameters which are obtained
on a particular date for the various "C" wells
located at different distances from the landfill.
The quality of the "B" well would represent the
concentration at zero distance from the landfill.
Chapter 5 discusses the use of this type of profile
in the measurement of attentuation at a land disposal
site. Figure 54 shows an example of this profile.
. Maps with contour lines of equal concentration for
key indicators can be prepared for the land disposal
site. This technique is often used to present
the results of resistivity surveys. Such a map
has a value in outlining the aerial dimensions of a
leachate plume and, if done periodically, trace
the movement of contaminants. The U. S. Geologic
Survey has prepared an excellent paper on this and
other methods of ground-water data interpretation
and presentation.7
. Other profiles providing "physical understanding"
information. In the evaluation of the monitoring
data obtained at a land disposal site, it would
be of value to be readily accessible to information
on the phenomena which may be the potential cause
of fluctuations and trends in the monitoring data.
This might include a water-balance profile showing
ground-water recharge periods of a "chronological
events" profile of important occurrences. A water
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balance profile, such as shown in Figure 53 could
be developed for each site as part of the permit
applications or for several representative
"typical sites" throughout the state. The actual
quantities are not as important as the trends they
would depict. A profile of "chronological events"
could be kept on file and easily up-dated by the
inspection and monitoring personnel. Reference
to such a profile would be of value, providing
physical understanding in evaluating monitoring
results, consideration should be made for the
time lag between cause and effect that is inherent
at land disposal sites.
An indicator program based upon sufficient background quality data
and on-going statistical information should provide a basic,
cost-effective, reliable monitoring tool for the quality control of
a landfill.
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120 '
100-
Month
LEGEND
PERCOLATION INTO LANDFILL
SOIL MOISTURE RECHARGE
SOIL MOISTURE UTILIZATION
INFILTRATION
£ & ACTUAL EVAPOTRANSPIRATION
FIGURE 53, WATER BALANCE PROFILE
(Fenn, et. al., 1975)6
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REFERENCES
1. Field, Richard, Strugeski, E.J., H.E. Masters, et. al. Water
pollution and associated effects from street salting. Jernell,
W.J. and Rita Swan, eds. I_n Water pollution control
in low density areas. University Press of New England,
Hanover, New Hampshire, 1975. pp.317-340.
2. Personal Communication. Paul Roux. Geraghty & Miller, Inc.,
Port Washington, New York, to Olin Braids. Geraghty &
Miller, Inc., Port Washington, New York.
3. Personal Communication. Douglas R. MacCallum. Geraghty & Miller,
Inc., Port Washington, New York, to Olin Braids. Geraghty
& Miller, Inc., Port Washington, New York.
4. Chian, and DeWalle. Compilation of methodology for measuring
pollution parameters of landfill leachate. University of
Illinois, U.S. Environmental Protection Agency. Cincinatti,
Ohio, 1975.
5. Handbook for monitoring industrial wastewater. U.S. Environmental
Protection Agency, Technology Transfer, August, 1973.
6. Standard methods for the examination of water and wastewater,
13th Edition. American Public Health Association, 1970.
7. Hem, John D. Study and interpretation of the chemical characteristics
of natural water. In U.S. Geological Survey water supply
paper No. 1473, 1970.
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5.0 FUNDAMENTALS OF LEACHATE
5.1 INTRODUCTION
As discussed in Chapter 1, it is important to understand and assess
the potential for leachate contamination at a land disposal site
in order to properly design, implement, and interpret a monitoring
program and its data. Of concern here is leachate production: its
quality, quantity, and its fate in the hydrogeologic environment.
A clear understanding of each of these concepts, their underlying
theories, causes, and results should be prerequisite to the design
and implementation of a monitoring program.
An overview of the fundamentals of leachate is presented in this
chapter for use in assessing the potential for leachate contamination
at a land disposal site. If properly applied, the resultant information
will be useful in the design and implementation of a monitoring program
and interpretation of the resultant data. Further, the information
presented may be useful to regulatory officials in preparing
background and reference material for enforcement actions.
In approaching the monitoring of a land disposal site, the following
questions should be asked:
For what kind of contamination is the landfill
being monitored?
. How much contamination in terms of concentration
and quantity can be expected?
Where, how fast, and how far will the contamination
travel?
What is the best monitoring method for the contamination?
Addressing these questions inquires a clear understanding of leach&te
production and its fate in the landfill and surrounding environment.
5.2 ORIGIN, COMPOSITION, AND FATE OF LEACHATE
In understanding the quality of leachate contaminants and the
concentrations that may be encountered by monitoring, consideration
should be made as to changes in its quality as it emanates from the
compacted solid waste and travels in the subsurface environment.
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The former would be the quality of pure leachate, while the latter
deals with the quality of leachate-enriched ground water.
Where precipitation is greater than runoff and evapotranspiration
combined, leachate moves downward through solid waste and underlying
soil and sediment until it reaches an impermeable layer or ground
water. In its journey leachate traverses three zones of geochemical
activity with certain characteristics which are shared and others
which are unique. This section describes some of the characteristics
in each of the zones and explores the ways they affect the mobility
of leachate.
5.2.1. Solid Waste Zone
Solid waste deposited in municipal landfills is a heterogeneous
mixture of organic and inorganic materials and living organisms.
Upon deposition, and frequently before, microbial activity begins
the degradative process on organic matter. The microbial decomposition
of organic matter is encouraged by moisture and warm temperatures.
Microbial activity soon depletes the oxygen supply and causes the
solid waste beyond the zone of rapid air diffusion to go anaerobic
(absence of oxygen). Ananerobic conditions cause the end products
of decomposition to be somewhat different from carbon dioxide and
water (the products of complete oxidation), notably methane gas.
Other organic anaerobic decomposition products such as alcohols,
aldehydes, and thiols tend to be more odoriferous than their
aerobic counterparts. Of particular importance with regard to
leachate are the anaerobic forms of sulfur, nitrogen, iron and
manganese.
The percolate flows downward through the solid waste which is in
progressively advanced stages of decomposition. It then passes
through layers of buried cover material. Percolate shows a net
gain in dissolved constituents as it progresses downward but may
lose some individual ions from cation exchange or other reactions
encountered en route.
Nitrogen present in solid waste organic matter is released in
soluble form with microbial decomposition. In organic substances,
nitrogen is in a chemically reduced state. With aerobic decomposition,
the nitrogen is oxidized to nitrate ion. Under anaerobic conditions,
nitrogen is released as the ammonium ion. Since anaerobic conditions
are predominant in landfills, most nitrogen in leachate is present
as ammonium. The relatively small amount of nitrate produced,
coupled with its probable denitrification, explains the typically
low nitrate concentrations in leachate.
Aerobic decomposition of the organic matter in solid waste releases
carbon dioxide in larger amounts than under anaerobic conditions.
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The enrichment of the interstitial gas in solid waste by carbon
dioxide results in production of bicarbonate ion which is frequently
a major anion in leachate. Because of the reversibility of the
reaction producing bicarbonate, it acts as a pH buffer.
Heavy metals in landfills are primarily in their metallic state
and are not soluble. The exception is with deposition of soluble
heavy metal salts either as solids or in solution. These may come
from certain industrial activities such as electroplating or metal
pickling. Most heavy metals occur in solution as cations, but a
few are usually present as anions. Anionic heavy metals include
vanadium, chromium, and molybdenum. Phosphorus is released to
percolating water by decomposition of organic matter. Soils have
a high capacity for phosphate attenuation as oppossed to solid waste
material which does not. Phosphate can be, and frequently is,
produced in substantial amounts of leachate. Were leachate to
enter ground water directly, it would almost certainly contribute
more phosphate than would leachate which has passed through soil.
Water quality parameters which do not measure individual chemical
species include biochemical oxygen .demand (BOD), chemical oxygen
demand (COD), total organic carbon (TOC), color, conductance, and
turbidity. The solid waste zone provides little, if any, attenuation
of these parameters—instead it usually contributes to them.
Fecal coliform and fecal streptococci have been observed in leachate,
and poliovirus was reported in leachate from a simulated landfill.
The recent trend in the use of disposable diapers has increased the
source of enteric bacteria and viruses in solid waste. Sewage
sludge and septic tank pumpings, a principal source of bacteria,
are also frequently disposed of in municipal landfills.
Movement of bacteria and viruses within the landfill and through
the unsaturated zone is dependent upon the porosity of solid waste
and underlying geologic formations. Solid waste may offer many
paths through which water can travel relatively unimpeded. If
coarse sand and gravel or fractured rock underlie the solid waste,
percolating water may carry microorganisms with little or no
attenuation except for natural die off. The latter conditions,
judging from locations which have been studied, are the exception
rather than the rule.
Much data on leachate quality has been reported in literature and
is worthy of note. The U.S. Environmental Protection Agency has
prepared Table 11 which illustrates some of the chemical and
biological characteristics found in leachate and compares fresh
leachate to a typical domestic waste water. The quality of leachate
depends upon many variables which are specific to each land disposal
site. Therefore, a recent Environmental Protection Agency report
emphasizes the cautious interpretation of reported leachate data: 1
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197
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The compositions of leachates reported in the literature
are quite diverse... The breadth of reported data are
also typical for individual studies over a long period
of time. The many factors that contribute to the spread
of data are time since deposition of the solid waste;
the moisture regimen, such as total volume, distribution,
intensity, and duration; solid waste characteristics;
temperature; and sampling and analytical methods. Other
factors such as landfill geometry and interaction of
leachate with its environment prior to sample collection
also contribute to the spread of data. Most of these
factors are rarely defined in the literature, making
interpretation and comparison with other studies
difficult, if not rather arbitrary, (sic)
In this same report, the Environmental Protection Agency has
prepared a comprehensive summary of quality data for both pure
leachate and leachate-enriched ground water as has been observed
and reported by many researchers. In addition, the report
addresses the significance of microbiological organisms in solid
waste.
5.2.2 Unsaturated Zone.
Pertaining to this chapter, the unsaturated zone is defined as
the area in soil or sediments between the bottom of the landfill
deposits and the water table. The distance can vary between zero
(solid waste contacting ground water) to hundreds of meters (feet).
The zone is below what is usually considered "topsoil" or weathered,
organic-matter-rich upper horizons of most soils. At most
landfill sites, topsoil has been removed (sometimes much
subsoil, also) prior to deposition of solid waste. The porous
materials comprising the subsoil are likely to be low in organic
matter, have a sparse microbial population, and may vary widely
in permeability. For purposes of discussion, the unsaturated
zone will be considered at 6 to 60 meters (20 to 200 feet) thick.
This range allows percolating water an opportunity to react
chemically with its environment before reaching ground water.
Percolating water has four options in passing through the unsaturated
zone. It can move virtually unchanged, can show a net gain of
solute, show a net loss of solute, or keep the same total ionic
concentration with a net exchange of ions. Since few soils or
sediments are chemically inert, changes in transported solute
are to be expected.
Chemical activity in the unsaturated zone is primarily located at
the surfaces of clay minerals and hydrous oxide coating. Limited
microbial activity may take place either from the indigenous
population or that transported from solid waste.
198
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Cations will be removed from solution until either the cation
exchange capacity is reached, or the limit of displacement reactions
is reached. The limit of cation exchange capacity (CEC) can
range from nearly zero to probably not more than 60 milliequivalents
per 100 grams of soil. Solution concentrations, pH, and percolation
rate quantitatively affect the reactions. It should be noted
that adsorption is not a permanent fixation. Cations may be
desorbed with changes in solution composition, pH, or oxidation-
reduction (redox) potential.
In soils and sediments underlying landfills, the cation exchange
capacity will immobilize a certain amount of the leached cations.
When the capapcity has been reached, further percolaton of cations
will not be affected. Adding cover material of a heavier texture
than sand should help attenuation by providing exchange capability
between solid waste cells.
Divalent and trivalent cations include most of the heavy metals.
These are held more strongly than sodium, potassium, or ammonium
on the cation exchange complex. Divalent and trivalent cations
will displace monovalent cations which are adsorbed.
Heavy metals are prone to adsorption on hydrous oxide coatings in
the soil. The hydrous oxides are frequently cited as so limiting
metal solubility that agricultural deficiencies of copper, zinc,
and cobalt occur.2 Attenuation of heavy metals present in leachate
is desirable. In locations virtually free of clay minerals,
these coatings may be present on sand grains giving the sandy
formation some ability to attenuate metallic ions.
Adsorption, is only one mechanism for removing dissolved ions from
solution. Changes in the geochemical environment can also affect
solution equilibria. A transition from reducing conditions in the
landfill to oxidizing condition in the unsaturated zone can reduce
the concentration of some redoxsensitive species in solution and
change the chemical form of others. For example, iron and manganese
will oxidize and precipitate from solution.
If porosity will allow bacterial movement, biochemical reactions
involving leachate constituents can proceed. Sulfide and ammonium
can be oxidized to sulfate and nitrate. Dissolved organic matter
measured in terms of BOD and COD can be reduced through microbial
decompostion. Some nutrient elements in the. course of these
reactions will be incorporated in bacterial cells and thereby be
removed from solution until the bacterial cells die off. Conversion
of ammonium to nitrate changes nitrogen from a form subject to
attenuation to a form which is not. Sulfide to sulfate oxidation
is not expected to be as significant. Sulfide can form insoluble
precipitates with many of the heavy metals. For this reason, it
may not be present in more than trace amounts in leachate.
19Q
-------
Microorganisms may also attack the organic ligands associated with
chelated and complexed metals. Decomposition or absorption by
microorganisms would remove the metals from leachate.
Phosphate reacts with a variety of soil components forming insoluble
products. Calcium and phosphate react in solution to form hydroxypapite,
the least soluble phosphate compound known. Iron, alumninum, and
manganese can also form virtually insoluble precipitates with phosphate.
These reactions lead to a strong attenuation of phosphate when these
metal ions are present in the unsaturated zone.3
Carbonate also reacts with calcium, magnesium, and some heavy metals
forming relatively insoluble compounds. Calcareous deposits in the
unsaturated zone can be valuable in attenuating phosphate and heavy
metals from leachate. Because carbonate neutralizes acids, BOD and
COD as expressed in organic acid concentration may also be reduced.
Carbonate induced alkalinity may change solubilities of heavy metal
chelates and lead to a deposition of heavy metals.
The unsaturated zone has a reciprocal influence on the leachate
which percolates into it. Water of low oxidation potential first
infiltrating into the unsaturated zone of high oxidation potential
will become more oxidized while simultaneously reducing substances
in the unsaturated zone. A continued percolation of reduced water
may convert what had been an oxidized system into a reduced one.
Or, the percolate may become oxidized if that capacity in the
unsaturated zone is greater. The degree of influence of reduced
leachate on the oxidized unsaturated zone and vice versa depends
upon the reserves of material capable of oxidizing or reducing in
the unsaturated zone and leachate. The greater the distance
leachate travels between solid waste and ground water, the better the
chance that the entire path through the unsaturated zone will not
become reduced. Raising the oxidation potential of leachate will tend
to attenuate some components in solution at the point of exit from
the solid waste.
5.2.3 Aquifer Zone.
Concepts useful for describing surface-water pollution are generally
not valid for ground water. Ground-water movement is described by
Darcy's Law which states that velocity is directly proportional to
the permeability of the aquifer and the hydraulic gradient and
inversely proportional to the porosity. Ground-water flow velocities
vary over a wide range, 1.5 meters/year to 1.5 meters/day, typically
5 feet/year to 5 feet/day). Highly permeable glacial outwash deposits,
fractured basalts and granites, and cavernous limestone aquifers allow
much greater velocities.
The relatively slow velocity of ground water results in laminar flow
which exhibits different characteristics of mixing than does
turbulent flow usually associated with surface streams. A water of
200
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different chemcial composition from ground water injected or
percolated into ground water tends to maintain its integrity and
is not diluted with the entire body of ground water. Instead, it
moves with the ground-water flow as a plume undergoing minimal mixing.
The plume shape is determined by the physical characteristics of
the aquifer. Porous media give somewhat different shaped plumes
from fractured rock or cavernous limestone. Chapter 2 illustrates
the paths of ground-water movement in various hydrologic regimes.
Differential attenuation is defined as a reduction in concentration
of a dissolved constituent, with distance along the direction of
water flow which is disproportional to changes in concentration of
other constituents. Differential attenuation may result from chemical
or biochemical reations which remove the constituent from solution.
Apparent attenuation occurs from dilution by mixing with water of
lower constituent concentration.
Dilution may take place in ground water in two ways. One is hydrodynamic
dispersion, and the other is molecular diffusion. Microscopic
dispersion describes mixing caused by the tortuous flow of water
around individual grains and through pores of various sizes in a
porous aquifer. Macroscopic dispersion describes mixing as water
flows in and around heterogeneous geologic formations. Molecular
diffusion is the diffusion of solute across a concentration gradient
from stronger to weaker concentration. It is seldom possible to measure
in the field. On the other hand, there are mathematical equations
which describe dispersion. By measuring enough physical and chemical
parameters at a site over a sufficient length of time, an approximaate
calculation can be made for dispersion.
Chemical interactions provide the greatest amount of differential
attenuation in the aquifer zone. Hydrous oxides of iron, aluminum,
and manganese or clay minerals present in aquifers attenuate cations
in the same way that they do in soils or in the unsaturated zone.
Since hydrous oxide and clay colloids are in constant contact with
water in the aquifer, it can be assumed that the exchange sites are
saturated and essentailly in -equilibrium with the ambient ground
water. When contacting these colloids, leachate-enriched ground
water will initiate cation exchange resulting in desorption of
cations which are less strongly held than those replacing them. In
this way, hydrogen, sodium, calcium and magnesium may be released
into the aqueous phase by exchange with heavy metals and other cations
in leachate. High hardness values associated with leachate plumes
be due, in part, to this ion exchange phenomenon.
Chemical precipitation in the aquifer is possible if the natural
ground-water composition includes ions which form insoluble compounds
with constituents in leachate. An example would be formation of
hydroxyapatite with leachate phosphate and calcium in ground water.
201
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Changes in redox potential, buffering reactions, or changes in
lithology may produce other attenuation reactions.
The third means of attenuation in aquifers is that termed decay.
Oxidation of organic compounds reduced them to carbon dioxide and
water. Microorganisms carried into the aquifer zone are deprived of
a good nutrient supply and are subjected to a cooler temperature
than in the solid waste zone. This results in a lowering of biochemical
activity, frequently to the point of cessation. The inactivation
coupled with natural die off tends to reduce bacterial numbers rather
rapidly.
There are two additional complications in the interpretation of
ground-water quality in leachate plumes. One is the variation in
leachate concentration with time, and the other is the discontinuous
recharge of leachate which occurs in most geographical regions.
Leachate production begins as soon as deposited solid waste attains
field capacity; this can occur locally in channelized patterns or
integrally. The lag time depends upon local climatic conditions
and rate of solid waste deposition. In an active landfill, older
organic matter is stabilizing while simultaneously new organic
matter is beginning to ferment and produce stronger leachate. The
net effect is an increasing leachate concentration from a given
area and/or increasing areal contamination as long as the landfill
is active.
Leachate produced at the initiation of percolation through the
landfill is less concentrated than that produced after several years'
solid waste accumulation. This leachate will be found at the distal
end of the plume of leachate-contaminated ground water. The closer
£he sampling .point to the landfill, a more concentrated contaminated
ground-water would be expected. An increasingly concentrated
leachate source in addition to the factors of dilution and
attenuation must be considered in interpreting the results of
sampling the plume. If the variation in source strength is ignored,
an erroneously high value for attenuation or dilution may be given.
The intermittent recharge occurring from most landfills also
complicates interpretation of leachate-plume configuration. During
summer months when evaporation frequently exceeds rainfall, little
or no leachate may be produced. Repeated infiltration of precipitation
from summer showers into solid wastes should produce a zone of
leached and deposited contaminants. When evaporative losses are
reduced in the fall, percolating water will then re-dissolve these
materials. They will then travel as a relatively highly concentrated
slug to the ground-water reservoir. Ground water, however, moves
under the landfill at a relatively steady rate. Thus, there will be
temporal variations in the volume and strength of leachate reaching
ground water. These variations will show in the leachate plume as
202
-------
variations in total solute concentration. A sample taken from the
plume at any given time may represent a "high" or "low" in the
intermittent recharge pattern. One way to visualize this phenomenon
would be to observe the response of a conductivity probe in a
monitoring well over a period of time. As leachate-enriched ground
water move past the well, conductivity will vary with changes in
dissolved solids concentration. The variations may be noticeable
only in time spans of weeks to months. Since concentrations may
vary from factors other than aquifer characteristics, calculations
of values for dispersivitiy in dilution may not be accurate.
A generalized summary of the susceptibility of leachate to differential
attenuation is provided in Table 12. The mechanism of attenuation
which affects each constituent is listed for the zones through
which leachate may pass. When data are summarized in this fashion,
only the principal mechanisms can be cited. For example, "no
attenuation" is listed for all of the constituents in the solid
waste zone. However, this is not always valid. Quantification is
impossible, and there is a net release of most of the constituents.
Sulfate, nitrate, and ammonium are given biochemical conversion
alternatives. These ions are subject to oxidation and reduction
reactions which may convert or eliminate them. Heavy metals are
also prone to one or more of the attenuation mechanisms and may not
be universally present in leachate. Biochemical reactions for the
aquifer zone are not listed as biological activity is inhibited.
In places, biological activity may be significant in the aquifer;
but the amount and type cannot be predicted.
5.2.4 Measurement of Attenuation.
From the previous discussion, it is evident that attenuation
describes two phenomena associated with the transportation of solute.
One is dilution resulting from dispersion and diffusion; the other
is dilution resulting from chemical or biochemical removal of
solute from ground water. The former type of dilution is referred
to as apparent attenuation since no active chemical processes are
operating to reduce the concentration of dissolved constituents.
Since the prediction of the future conditions depends upon the extent
of active attenuation, it is important to distinguish between apparent
and active attenuation in the field. To accomplish this, several
samples of leachate-enriched ground water must be collected along the
leachate plume's path of travel. Chemical constituents measured in
these samples are then chosen on the basis of their susceptibility
to attentuation. Relative changes in concentration with distance
from the source are noted. Providing background levels are not
influenced by other sources of chloride contamination (e.g. road
salting, brine dumping, etc.), chloride is the best constituent to
measure as an indicator of dilution. Since it carries a negative
charge and does not form precipitates with the common cations in
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water, chloride is unaffected by ambient conditions. Reductions in
chloride concentration can then be attributed to dispersion and
diffusion. If ground-water equations were used in an attempt to
calculate dispersion coefficients for leachate-enriched ground water,
chloride concentration data would be a good first choice for use in
the calculations. Nitrate reacts in virtually the same way, but
nitrate is less frequently present in leachate in comparable
concentrations.
Concentrations of other constituents sampled simultaneously with
chloride should represent equal dilution. If they are observed in
lower than expected concentrations, this indicates that active
attenuation has taken place. Conversely, if their concentrations
are greater than those calculated on the basis of chloride, desorption
from ion exchange sites or contributions from other sources may
account for the nontheoretical results.
An example which is calculated from data obtained in a landfill
study is presented below.^ The cations calcium, sodium plus
potassium, ammonium, and iron in leachate-enriched ground water are
plotted in percentage of original concentration vs. distance from
the landfill. (Figure 54). If all of the cations were diluted
equally, they would plot on the same curve. Reference points for
chloride are included to facilitate a comparison of the theoretical
dilution-only curve with the actual cation concentration curves.
The plume of leachate-enriched ground water represented by Figure 54
is produced by a landfill that has been active for 28 years. The
leachate plume can be traced about 3231 meter (10,600 feet)
downgradient from the landfill and vertically throughout the thickness
of the aquifer (about 24 meters—80 feet) with the most concentrated
contamination near the bottom.
Calcium remains above the chloride curve throughout the length of the
plume in agreement with other reports indicating that calcium is
desorbed from clays as a result of cation exchange with leachate
components.5 In this specific situation, there may also be a
contribution of calcium from septic tank effluent.
Ammonium remains above the chloride curve for about half the length
of the plume. It also may be desorbed and is a component of septic
tank effluent. The loss of ammonium at more distant points of the
plume may be due, in part, to more aerobic ground-water conditions
that will permit nitrification of ammonium.
Sodium and potassium generally plot below the chloride points, and
iron is even more attenuated. Probably the iron is removed largely
through solubility changes resulting from increases in Eh as distance
from the landfill increases.
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The geohydrologic environment is characterized by soft, rather acid
native ground water in a highly silicaceous, unconsolidated sand
and gravel aquifer. Uncontaminated ground water contains iron in
concentrations which frequently exceed the recommended drinking
water limit of 0.05 mg/1. No significant amounts of clay or silt
are present in the path of the leachate plume. Sand grains are
coated with iron oxide which probably exhibits a small amount of
cation exchange capacity. Septic tanks used in the area and
intermittent recharge of leachate as influenced by the climate
complicate the interpretation of chemical data along purely
theoretical principles.
5.3 LEACHATE QUANTITY
Estimating the leachate quantity being generated at a land disposal
site is important in the environmental assessment of the site and
the relative need for monitoring the site. Knowledge of leachate
quantity and generation rates will also be useful in determining
which monitoring scheme and pollution abatement programs should be
most effective.
The water-balance or water-budget method has been presented in th£
literature as a useful, tool in estimating leachate quantities
and generation rates at land disposal sites.
In two U. S. Environmental Protection Agency reports, ' excellent
summaries of the water balance method and its application to land
disposal sites are presented. The reports discuss the theories
and principal factors involved in leachate generation including
useful information and data on the following:
. The influence of slope, surface condition, and soil
type of the quantity of runoff and the potential for
leachage production;.
. The dependency of infiltration on the storm frequency,
duration, intensity, and soil moisture conditions;
. The influence of vegetation on evapotranspiration and
infiltration;
. The relationship of soil permeabilities to infiltration
rates and volumes;
. The moisture retention capabilities of various types
of solids as well as compacted municipal solid waste.
207
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Caution must be exercised in applying the water-balance method to
land disposal sites. Review of the above-referenced information
clearly shows the extreme sensitivity of leachate quantity estimates
to the many variables used in the water-balance calculations. For
example, slight changes in runoff coefficients, evapotranspiration,
or moisture retention figures can result in a significant change
in the leachate quantity estimate. In addition, unless extensive
on-site measurements are performed, the many parameters in the
water-balance calculations are purely theoretical estimates.
Therefore, this manual presents the water balance method as a
useful tool for planning, design, and assessment purposes. The
leachate quantity estimates generated should be viewed with this
qualification in mind.
5.3.1 Water Balance Simplified
The water-balance or water-budget method is the measurement of the
continuity of flow of water for any given time interval and can be
applied to any drainage basin.7 Here, the drainage basin being
considered is a land disposal site together with the land immediately
surrounding it. The calculation of the water balance for a landfill
requires the measurement of numerous physical parameters and can
be a relatively difficult and expensive task. For most landfill
investigation and monitoring work, however, a reasonable approximation
of the magnitude of the various water-balance components will be
sufficient. Methods of estimating each of these components, using
as much available information and as few field measurements
as possible, are given below.
The seven principal water-balance components of a hypothetical
landfill are shown in Figure 55. These are: precipitation.and
irrigation, surface runoff onto the landfill, surface runoff from
the landfill, evapotranspiration, underflow (in and out), and'
infiltration.
Precipitation and Irrigation. In most cases, precipitation and
irrigation will be the principal source of water into the landfill.
This may not be true for landfills placed in the water table;
landfills not diverting runoff from adjacent property; or landfills
accepting large quantities of liquid wastes. Significant variations
in precipitation may occur in certain localized areas, especially in
mountainous regions requiring cautious use of generalized rainfall
maps. Significant variations may also occur with time, an abnormally
wet year (for example); such abnormalities cannot be shown on
a general map. For these reasons it is advisable to seek precipitation
data specific to the landfill site and for a number of years
preceeding the investigation. Historical precipitation records for
weather stations can be obtained from the U. S. Department of
Commerce, National Oceanic and Atmospheric Administration,
Fjivironmental Data Service, Asheville, North Carolina. The locations
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of weather stations for which data are available are shown on maps
obtainable from the above address. Interpolation of the data from
two or more stations can be made to more closely approximate the
precipitation at the landfill site. For extended investigations or
monitoring programs, it may be desirable to determine the precise
volume of precipitation reaching the landfill surface. For this
purpose, a rain guage would be Installed in a suitable location on or
near the landfill. There are many types of rain gauges available,
and the selection of one would be based upon the particular conditions
of the monitoring program and the available budget.
Irrigation may be applied to the landfill surface to maintain a desired
vegetation growth, particularly when the landfill is completed and
its surface is being used as a golf course or other recreational
facility. The volume of water used for irrigation should be measured
with a flow meter and added to the precipitation.
Surface Runoff. The percentage of precipitation which flows onto
the landfill from adjoining higher ground and off the landfill
surface to adjoining lower ground can be calculated by the rational
runoff formula described by Ven Te Chow. A reasonable estimation
of runoff can also be made from the data presented in Table 13,
where the rational runoff formula was applied to a series of typical
situations. Areas and slopes are measured by a survey, and surface
conditions are determined by inspection.
Evapotranspiration. Evapotranspiration is the sum of water loss by
evaporation and transpiration (plant water consumption). Methods of
calculating evapotranspiration are given in the hydrologic literature.
However, the large number of variables that must be measured to perform
the calculations make it a difficult process.
Estimation of evapotranspiration from available generalized data, such
as "potential" evapotranspiration maps or annual water consumption
figures for different plant species, may be misleading. This
approach cannot account for numerous specific variables such as soil
type, soil water available, and vegetation density. Since
evapotranspiration from a landfill surface may be anywhere from
insignificant to the single most important mechanism for the removal
of water, an accurate estimate of "actual" evapotranspiration from
the specific site should be made. (The "actual" becomes less than
the "potential" as soil moisture is depleted.) Thornthwaite and
Mather^ have developed a method for estimating the actual
evapotranspiration accounting for soil moisture effects and an
Environmental Protection Agency report^ applies this method to
hypothetical landfills for estimating leachate generation.
Because of the difficulties in arriving at an accurate figure for
actual evapotranspiration, it is suggested that professional
assistance be obtained. If a hydrologic consultant is retained
210
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TABLE 13
PERCENTAGES OF SURFACE RUNOFF
FOR A 2.5 cm RAINFALL (8)
Surface
Condition
Percent
Slope
Percent Surface Runoff
Sandy
Loam
Clay or
Silt Loam
Clay
Pasture or
meadow cover
crop
Flat
Rolling
Hilly
No vegetation-
not compacted
Flat
Rolling
Hilly
0-5
5-10
10 - 30
10
16
22
30
36
42
40
55
60
0-5
5-10
10 - 30
30
40
52
50
60
72
60
70
82
211
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for the landfill study, he will be able to estimate actual
evapotranspiration for the specific case involved. If such a
consultant is not used, information on evapotranspiration rates for
an area will often be available from a local agricultural research
station, a nearby U.S. Geological Survey field office, or possibly
the agriculture department of a nearby university.
Underflow Underflow is defined here as the rate of
ground-water flow from adjoining areas directly into the landfill.
This condition will occur only if the base of the landfill is below
the water table. A second necessary condition, however, is that the
landfill adjoins or is situated near an area of elevation substantially
higher than its base—that is, there is a significant water-table
gradient beneath the landfill. If the landfill is situated on
level ground and substantial percolation of water through the
landfill is occuring, leachate being generated by the percolation
will move away from the landfill and underflow, as defined above,
will not occur (Figure 56).
Precise measurement of underflow, if it is occuring is not feasible.
A determination of the occurrence of underflow, and a reasonable
approximation of its rate can be made, however, by means of a
relatively straightforward hydrologic investigation. Figure 57
presents a schematic diagram and method for estimating the rate of
underflow. This process requires the drilling and testing of at
least two wells, which could also be used as monitoring wells as
part of the on-going monitoring program.
Percolation. Infiltration is generally defined as that
portion of surface water which penetrates the land surface. ' Some of
this water may then be taken up by plants and some may be directly
evaporated from the first few centimeters (inches) of soil. That
portion of water which migrates below the root zone and into the
solid waste and thus contributes to the volume of leachate generated
is the percolate. However, solid waste placed in a landfill is capable
of absorbing a certain volume of water and holding it against the
force of gravity. The volume of water so absorbed by the solid waste
is termed its field capacity. Generally, municipal solid waste field
capacity is about 25.4 millimeters 0 1 inch) of water for each .3
meters ( 1 foot) of solid waste. Leachate will not be generated
in any significant volume until almost all of the solid waste has
reached field capacity. Channeling^may occur resulting in some
leachate generating prior to reaching field capacity.
Percolation can be calculated as follows:
Percolation = precipitation + runoff onto landfill - runoff
from landfill - actual evapotranspiration.
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Direct measurement of percolation is possible using a sub-surface
water trap such as the one shown on Figure 58.
Leachate Generation. Having estimated all of the pertinent
parameters, leachate generation can be simply estimated with the
following water balance formula:
Leachate generation • percolation + Underflow
215
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^ACCESS FOR MEASURING WATER LEVEL
AND PUMPING OUT BOX WHEN FULL.
CAP
I'/2P1PE
STEEL RODS
FIBERGLASS SCREEN
STRIP TO FASTEN
SCREEN
METAL OR
PLASTIC BOX
FIGURE 58,
DEVICE FOR DIRECT MEASUREMENT
OF LANDFILL INFILTRATION
216
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REFERENCES
1. Summary report: gas and leachate from land disposal of municipal
solid waste. U.S. Environmental Protection Agency.
Cincinnati, Ohio. (In press.)
2. Jenne, E.A. Controls on Mn, Fe, Co, Ni, Cu, and Zn concentrations
in soils and water: the significant role of hydrous Mn and
Fe oxides. In Robert F. Gould, ed. Trace inorganics in
water. Advances in chemistry series no. 73. American
Chemical Society. Washington, D.C., 1968. pp.337-387.
3. Bouer, H., Lance, J.C., and M.S. Riggs. High-rate land treatment II:
water quality and economic aspects of the Flushing Meadows
project. Journal of Water Pollution Control Federation,
46(5):844-859, 1974.
4. Kimmel, G.E., and O.C. Braids. Preliminary findings of a leachate
study on two landfills in Suffolk County, New York. Journal
of Research. U.S. Geological Survey, 3(3);273-280, 1975.
5. Griffin, R.A., and N.F. Shimp. Interaction of clay minerals and
pollutants in municipal leachate. Preprint for wateruse.
Proceedings of the second national conference on complete
wateruse. American Institute of Chemical Engineers, Chicago,
May 4-8, 1975.
6. Fenn, D.G., et. al. Use of the water balance method for predicting
leachate from sanitary landfills. Office of the Solid Waste
Management Program, U.S. Environmental Protection Agency,
1975. Unpublished manuscript. 55p.
7. Chow, Ven. Handbook of applied hydrology. McGraw-Hill Book Co.,
New York, 1964.
8. Salvato, J.A., Wilkie, W.G., and B.E. Mead. Sanitary landfill
leachate prevention and control. Journal of Water Pollution
Control Federation, 43(10);20-84, 1971.
9. Thormthwaite, C.W., and J.R. Mather. Instructions and tables for
computing potential evapotranspiration and the water balance.
Publications in Climatology, 10(3), 1957.
217
-------
ADDITIONAL REFERENCES
(not cited)
1. Burrows, W.D., and R.S. Lowe. Ether soluble constituents of
landfill leachate. Journal of Water Pollution Control
Federation, 47(5):921-923. 1975.
2. Davis, S.N., and R.J.M. DeWiest. Hydrogeology. John Wiley & Sons,
Inc., New York, 1966.
3. Fungaroli, A.A. Pollution of subsurface water by sanitary landfills.
Volume 1. Report No. Sw-12rg. U.S. Environmental Protection
Agency, 1971.
4. Geraghty, J.J., et. al. Water atlas of the United States. Water
Information Center, 1973.
5. Hall, E.S. Some chemical principles of groundwater pollution.
In John A. Cole, ed. Groundwater pollution in Europe. Water
Information Center. Port Washington, New York, 1974.
pp96-115.
6. Hem, J.D. Study and interpretation of the chemical characteristics
of natural water. Water supply paper #1473. U.S. Geological
Survey, 1970.
7. Ho, S., Boyle, W.C., and R.K. Ham. Chemical treatment of leachates
from sanitary landfills. Journal of Water Pollution Control
Federation. 46(7):1776-1791.
8. Hughes, G.M., Landon, R.A., and R.N. Farvolden. Hydrogeology of
solid waste disposal sites in Northeastern Illinois.
Publication No. SW-12d. U.S. Environmental Protection Agency,
1971. 154p.
9. Marr, H.E., Law, S.L., and O.L. Neylan. Trace elements in the
combustible fraction of urban refuse. Preprint, international
conference on environmental sensing and assessment. Las Vegas,
Nevada. September 14-19. U.S. Environmental Protection Agency,
1975.
10. McCarty, P.L. Energetics and kinetics of anaerobic treatment.
In_ Robert F. Gould, e_d_._ Anaerobic biological treatment
processes. Advances in chemistry series 105. American
Chemical Society, Washington, D.C., 1971. pp.91-107.
11. Merz, R.C., and R. Stone. Quantitative study of gas produced by
decomposing refuse. Public Works, 99(11);86, 1968.
218
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12. Robertson, J.M., Toussaint, C.R,, and M.A. Jerque. Organic
compounds entering ground water from a landfill. EPA-660/2-74-077.
Environmental Protection Agency, 1974.
13. Stevenson, F.J., and M.S. Ardakani. Organic matter reactions
involving micronutrients in soils. In J.J. Mortvedt, P.M.
Giordano, and W.L. Lindsay, eds. Micronutrients in agriculture.
Soil Science Society of America. Madison, Wisconsin, 1972.
pp.79-114.
14. Stone, R., Conrad, E.T., and C. Melville. Land conservation by
aerobic landfill stabilization. Public Works. 99(12):95,
1968.
219
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6.6 SAMPLE WITHDRAWAL, STORAGE, AND PRESERVATION
6.1 INTRODUCTION
The sampling of ground and surface waters associated with the
monitoring of land disposal sites is a critically important operation.
The analytical results obtained from the samples and the subsequent
decisions based upon the analytical data are vitally dependent upon
the validity of the samples obtained.
Every effort must b« made to assure that the sample is representative
of the particular body of water being sampled. A detailed sampling
plan, acceptable to all interested parties, should b« developed prior
to any sampling operations.
The physical, chemical, and bacteriological integrity of the sample
must be maintained fron the time of sampling to the time of testing
in order to keep any changes at a minimum. The time between sampling
and testing should be kept at the absolute minimum.
6.2 SAMPLE COLLECTION
6.2.1 Sample Withdrawal Methods
Sample withdrawal methods include the use of pumps, compressed air,
bailings, and samplers. The primary consideration is to obtain a
representative sample of the ground-water body by guarding against
mixing the sample with stagnant (standing) water in the well casing.
In a non-pumping well, there will be little or no vertical mixing of
the water; and stratification will occur. The well water in the
screened section will mix with the ground water due to normal flow
patterns, but th« wall water above the screened section will remain
isolated and become stagnant. Persons sampling should realize that
stagnant water may contain foreign material inadvertently or
deliberately introduced from the surface, resulting in unrepresentative
data and misleading interpretation of the same.
To safeguard against collecting non-representative stagnant water in
a sample, the following guidelines and techniques should be adhered
to during sample withdrawal:
As a general rule, all monitoring wells should be
pumped or bail«d prior to withdrawing a sample.
Evacuation of a minimum of one volume of water in
220
-------
the well casing and preferably three to five volumes
is recommended for a representative sample. In a
high-yielding ground-water formation and where
there is no stagnant water in the well above the
screened section, evacuation prior to sample
withdrawal is not as critical. However, in all
cases where the monitoring data is to be used for
enforcement actions, evacuation is recommended.
For wells that can be pumped or bailed to dryness
with the sampling equipment being used, the well
should be evacuated and allowed to recover prior
to sample withdrawal. If the recovery rate is
fairly rapid and time allows, evacuation of more
than one volume of water is preferred.
For high-yielding monitoring wells which cannot be
evacuated to dryness, bailing without pre-pumping
the well is not recommended; there is no absolute
safeguard against contaminating the sample with
stagnant water. The following procedures should
be used:
a. The inlet line of the sampling pump should be
placed just below the surface of the well
water and three to five volumes of water pumped
at a rate equal to the well's recovery rate.
This provides reasonable assurance that all
stagnant water has been evacuated and that the
sample will be representative of the ground-
water body at that time. The sample can then
be collected directly from the pump discharge
line.
b. The inlet line of the sampling pump (or the
submersible pump itself) should be placed
near the bottom of the screen section, pumped
approximately one well volume of water at the
well's recovery rate, and the sample collected
directly from the discharge line.
A non-representative sample can also result from
excessive pre-pumping of the monitoring well.
Stratification of the leachate concentrations in
the ground-water formation may occur, and excessive
pumping can dilute or increase the contaminant
concentrations from what is representative of the
sampling point of interest.
221
-------
In light of this discussion, bailing by hand is not a recommended
well-sampling method unless adequate precautions are taken. Bailing
is accomplished in small diameter wells by lowering and raising a
weighted bottle or capped length of pipe on a length of rope. Rarely
can a sufficient quantity of water be removed to adequately eliminate
stagnant water from the sample unless many time-consuming trips in
and out with the bailer are made. Persons sampling a well often will
use the first bailer full of water as the sample because of the ease
with which the sample can be colledted. The reliability of this
sample is nul, and this fact must be impressed upon the sample
collector. Of course, in situations where the well can be bailed
dry or there is only about a meter of water in the bottom of a well
representative samples can be obtained with a bailer as the casing
can readily'be emptied.
A Kemmerer water bottle sampler, as shown on Figure 59, is a commonly
used bailer. In transferring the sample from the sampler to the
sample bottle, contact with air and agitation of the sample should
be minimized; slow and careful transfer, placing the tip of the
sampler's exit tube to the side of the sample bottle, is recommended.
To minimize cross-contamination, the bailers should be thoroughly
flushed out with tap water and the first sample from the next well
to be sampled prior to collecting the sample for analysis.
Where the water table is within suction lift, small-diameter wells
can be sampled with peristaltic, centrifugal, or pitcher pumps.
Peristaltic pumps have rather low pumping capacities. The sample is
conducted through inert silicone rubber tubing, thereby reducing the
possibility of sample contamination by constituents from the sampling
apparatus. For this reason, the procedure is attractive. Small,
highly portable centrifugal pumps are available with pumping rates
from .3 to 2.5 1/s (5 to 40 gpm). Removing stagnant water and
flushing the discharge set-up clean will pose little difficulty,
allowing collection of representative samples. If concentrations of
less than one ppm are being investigated, extra care must be taken in
sampling; in the extreme ppb range, the peristaltic pump would
have to be used.
Pitcher pumps can be easily carried to a site, screwed onto a well,
and used to pump a sample. No power source is required other than
the investigator, and equipment costs are low. A typical vacuum
sampling technique would involve the use of a vacuum or suction pump
and a portable generator as a power source. Vacuum can also be supplied
from an automobile or truck engine manifold or from a hand pump,
replacing the vacuum pump. In Orange County Florida^, such a
vacuum pump was used to collect ground-water samples under anaerobic
conditions. At that location, a 1.27-cm (1/2-inch) tube is
permanently installed in the monitoring well thereby eliminating the
possibility of cross-contamination between wells.
222
-------
D510
ch—chain which anchors upper valve to upper intenor guide
dh—rubber drain tube.
dt—brass drain tube.
g—interior guide fastened to inner surface of sampler.
h—rubber tube.
j—jaw of release.
js—jaw spring.
Iv—lower valve.
m—messenger.
o—opening interior of drain tube.
p—pinch cock.
i—upper release spring operating on horizontal pin. one end of which Tits into groove on centre! rod
spr—spring fastened to lower internal guide and operating in groote on central rod to provide !o»er release.
st—stop on central rod.
uv—upper valve.
Left—View of complete sampler with valves open.
Top right—Another t\pe of construction of upper valve and tripping device.
Bottom right—Another tvpe oT construct ion of lo»er »ahr ?nd c1-; n tune
FIGURE 59, STRUCTURAL FEATURES OF MODIFIED KEMMERER SAMPLER
(P.S. Welch, Limnological Methods, p. 200. Figure 59.)
223
-------
As an alternative to these pumps, an inexpensive bailer pump can be
constructed from readily available materials. This pump consists of
a length of garden hose with a foot valve at its bottom end and
fittings at its top end that allows a vacuum to be applied to the base.
A water sample is collected by moving the hose up and down and
activating the foot valve, causing the partial vacuum to assist in
bringing water to the surface. Vacuum is obtained from an automobile
engine. It should be remembered, however, that this sampler should be
used where the well contains only a small volume of water in order that
clearing stagnant water from the casing does not become an inordinately
time-consuming process.
An inexpensive air lift sampler can be constructed from polyethylene
or any reasonably flexible tubing, as shown in Figure 60. Since the
tubing is flexible, it can be readily coiled and moved conveniently
from well to well. Primary limitations on the sampler are the
amount of air pressure that can be safely applied to the tubing and
finding a suitable source of compressed air. A high-pressure hand
pump would serve nicely for a shallow water table, but a small air
compressor may be required for lift greater than 9 meters (30 feet).
The advantage of this sampler is that the apparatus can be designed
for permanent installation in the monitoring well. The smaller the
tubing used, the less that can be pumped; this can be compensated for
by pumping longer to obtain the minimum sample volume required for
analysis.
With a pressure-type sampling method, the sample is obtained by
connecting the sample bottle directly to the 1.27cm (ij-inch) water
discharge outlet. To prevent contact with oxygen, the sample bottle
could be flushed out with an inert gas prior to collecting a sample.
The built-in feature of this method used to both pre-pump and sample
the well can effect considerable savings on labor and also eliminate
the possibility of cross-contamination between wells as can occur
with portable pumping and sampling devices. This method is also of
notable value in obtaining bacteriological samples where external
sources of contamination must be avoided.
Somewhat more elaborate pumping equipment is required in small-diameter
wells where the water level is below suction lift. The easiest, but
not the driest, way to collect a sample is to install an airline in
the well and blow the water out. However, trying to adjust airflow
so that water flows smoothly over the top of the casing instead of
blowing violently into the air is a difficult task. The addition of
some simple, relatively inexpensive hardware to cap the well can make
sampling a straightforward and easy process. Sommerfelt and Campbell
(1975) have described such an installation (Figure 61), and Trescott
and Finder (1970) have pumped water from as deep as 58 meters
(190 feet) with this type of installation. Air pressure can be
supplied from a gasoline-powered air compressor, an engine air pump,
224
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12.7mm.(1/2 inch) CAP
12.7mm. (1/2 inch) TEE
50.8mm.(2 inch) CAP
50.8mm. (2 inch) CASING
12.7mm (1/2 inch) DISCHARGE-
PIPE
I78mm.(7 inch)BORE HOLE
SLOTTED PVC
WELL CASING
12.7mm (1/2 inch)PIPE
12 7mm.(l/2inch)CAP
VENT HOLE
SHRADER VALVE
76 mm. ( 3 inch )
BENTONITE SLURRY
6.4mm.(1/4 inchlAIRLINE
152 mm. (6 inch) SAND
305mrn.(l2 inch)
GRAVEL
FIGURE 60, AIRLIFT WATER SAMPLING DEVICE*
"Walker, William. Field verification of industrial hazardous
material migration from land disposal sites in humid regions
U.S. Environmental Protection Agency, July,
225
-------
Dischorgi
Electrical
cord gr ip
conneclor
Needle valve
Jj^Lyv p'p* *eldt
-------
or a compressed air cylinder. The source of air pressure selected
will depend upon well site accessibility and budgetary constraints.
Where a well is not accessible to vehicle transportation, a good-
quality hand pump (available in stores handling racing bicycles) can
be used as an air supply.
The best, but most expensive, method of collecting water samples is
with a small submersible pump. McMillion and Keeley (1968) have
designed a truck portable submersible pump capable of being set at
depths up to 91.4 meters (300 feet) inside a casing as small as ,
114 mm (44 inches) ID with a capacity of .44 to .88 1/s (7 to 14 gpm).
With this equipment, a pump can be set as desired in the well and
operated until a representative sample can be obtained. Cross-
contamination between wells from the sampling equipment will be
virtually eliminated by the flushing action during pre-pumping.
Provided there are no air leaks in the pumping system, samples could
also be collected for dissolved gas analyses.
Samples for bacteriological examination must be collected in sterile
containers. Detailed sampling procedures for bacteriological samples
are given in:
. Standard Methods, 13th Ed., pp. 657-660;
. Biological Analysis of_ Water and Wastewater, AM 302,
Millipore Corp., 1974, pp. 4-6.
Samples can be taken directly from wells with a sterile bottle in a
weighted frame which can be lowered below the water surface and
opened below surface. Samples can also be obtained by means of
various pumping devices as previously described. However, great care
must be taken to minimize sample contamination by the sampling
equipment. Sample volumes of approximately 250 ml are usually
satisfactory for bacteriological testing.
Sampling and preservation of samples are addressed in:
. 1973 Annual Book of_ ASTM Standards, Part 23, Water and
Atmospheric Analysis—
pp. 72-75, "Standard Methods of Sampling Homogeneous
Industrial Wastewater";
pp. 76-91, "Standard Methods of Sampling Water".
227
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6.2.2 Records
Adequate records should be maintained on each sample that is taken.
Record information should include:
sample description — type (ground water, surface water),
volume ;
sample source — well number, location;
. sampler's identity — chain of evidence should be
maintained; each time transfer of a sample occurs,
a record including signatures of parties involved in
transfer should be made. (This procedure can have
legal significance.);
time and date of sampling;
. significant weather conditions;
sample laboratory number;
pertinent well data — depth, depth to water surface,
pumping schedule, and method;
sampling method — vacuum, bailer, pressure;
preservatives, (if any) — type and number (e.g., NaOH
for cyanide, ^PO and CuSO^ for phenols, etc.);
sample containers — type, size, and number (e.g., three
liter glass stoppered bottles, one gallon screw-cap
bottle, etc. ) ;
reason for sampling — initial sampling of new landfill,
annual sampling, quarterly sampling, special problem
sampling in conjunction with contaminant discovered in
nearby domestic well, etc.;
appearance of sample — color, turbidity, sediment,
oil on surface, etc.;
any other information which appears to be significant —
(e.g., sampled in conjunction with state, county, local
regulatory authorities; samples for specific conductance
value only; sampled for key indicator analysis; sampled
for extended analysis; resampled following engineering
corrective action, etc.);
name and location of laboratory performing analysis;
223
-------
. sample temperature upon sampling;
. thermal preservation—(e.g., transportation in ice
chest);
. analytical determinations (if any) performed in
the field at the time of sampling and results
obtained—(e.g., pH, temperature, dissolved
oxygen, and specific conductance, etc.);
. analyst's identity and affiliation.
6.2.3 Chain of Custody
Proper chain of custody procedures play a crucial role in enforcement
cases. The following are some basic guidelines which have legal
significance:
. As few people as possible should handle the sample.
, Stream and ground-water samples should be obtained
by using standard field sampling techniques as
discussed in this manual.
. The chain of custody records should be attached to
the sample container at the time the sample is
collected, and should contain the following
information: sample number, date and time taken,
source of the sample (include type of sample and
name of firm), the preservative and analysis
required, name of person taking sample, and the
name of witness. The prefilled side of the card
should be signed, timed, and dated by the person
sampling. The sample container should then be
sealed, containing the regulatory agency's
designation, date, and sampler's signature. The
seal should cover the string or wire tie of the
chain of custody record, so that the record or tag
cannot be removed and the container cannot be
opened without breaking the seal. The tags and
seals should be filled out in legible handwriting.
When transferring the possession of samples, the
transferee should sign and record the date and
time on the chain of custody record. Custody
transfers, if made to a sample custodian in the
field, should be recorded for each individual
sample. To prevent undue proliferation of
custody records, the number of custodians in the
chain of possession should be as few as possible.
229
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If samples are delivered to the laboratory when
appropriate personnel are not there to receive them,
the samples should be locked in a designated area
within the laboratory so that no one can tamper
with them.
Blank samples should be collected in containers,
with and without preservatives, so that the
laboratory analysis can be performed to show that
there was no container contamination.
A field book or log should be used to record field
measurements and other pertinent information necessary
to refresh the sampler's memory in the event he later
becomes a witness in an enforcement proceeding. A
separate set of field notebooks should be maintained
for each survey and stored in a safe place where they
can be protected and accounted for at all times. A
standard format should be established to minimize field
entries and should include the types of information
listed in Section 6.2.2. The entries should then be
signed by the field sampler. The responsibility
for preparing and retaining field notebooks during
and after the survey should be assigned to a survey
coordinator or his designated representative.
The field sampler is responsible for the care and
custody of the samples collected until properly
dispatched to the receiving laboratory or turned
over to an assigned custodian. He must assure that
each container is in his physical possession or in
his view at all times or stored in a locked place
where no one can tamper with it.
Photographs can be taken to set forth exactly where
the particular samples were obtained. Written
documentation on the back of the photograph should
include the signature of the photographer, the time,
date, and site location. Photographs of this
nature, which may be used as evidence, should be
handled according to the established chain of
custody procedures.
Each laboratory should have a sample custodian to
maintain a permanent log book in which he records
for each sample the person delivering the sample,
the person receiving the sample, date and time
received, source of sample, sample number, how
transmitted to the lab, and a number assigned to
each sample by the laboratory. A standardized
230
-------
format should be established for log-book entries.
The custodian should insure that heat-sensitive
or light-sensitive samples or other sample materials
having unusual physical characteristics or requiring
special handling are properly stored and maintained.
Distribution of samples to laboratory personnel who
are to perform analyses should be made only by the
custodian. The custodian should enter into the
log the laboratory sample number, time, date, and
the signature of the person to whom the samples were
given. Laboratory personnel should examine the
seal on the container prior to opening and should
be prepared to testify that their examination of
the container indicated that it had not been
tampered with or opened.
6.3 SAMPLE CONTAINERS
For most samples and analytical parameters, either glass or plastic
containers are satisfactory. Some exceptions are encountered such
as the use of plastic for silica determinations and glass for
phenols or oil and grease determination. Containers should be kept
full until samples are analyzed to maintain anaerobic conditions.
As a general guide in choosing a sample container, the ideal
material of construction should be non-reactive with the sample
and especially the particular analytical parameter to be tested.
Table 14 lists the recommended containers for various analyses.
Cleanliness of containers is of utmost importance. An effective
procedure for cleaning containers is to wash with detergent,
sequentially followed by: tap water rinse, nitric acid rinse, tap
water rinse, hydrochloric acid rinse, tap water rinse, and finally
a rinse with deionized or distilled water. In addition, the
containers should be rinsed at least once with the sample at the
time of sampling.
6.4 PRESERVATION OF SAMPLES AND SAMPLE VOLUME REQUIREMENTS
The following excerpt, including the tables, is a useful guide for ,-
sample preservation, sample volume requirements, and sample containers:
Complete and unequivocal preservation of samples, either
domestic sewage, industrial wastes, or natural waters,
is a practical impossibility. Regardless of the nature
of the sample, complete stability for every constituent
can never be achieved. At best, preservation techniques
can only retard the chemical and biological changes that
inevitably continue after the sample is removed from the
parent source. The changes that take place in a sample
231
-------
are either chemical or biological. In the former case,
certain changes occur in the chemical structure of the
constituents that are a function of physical conditions.
Metal cations may precipitate as hydroxides or form
complexes with other constituents; cations or anions
may change valence states under certain reducing or
oxidizing conditions; other constituents may dissolve
or volatilize with the passage of time. Metal cations
may also adsorb onto surfaces (glass, plastic, quartz,
etc.) such as, iron and lead. Biological changes
taking place in a sample may change the valence of
an element or a radical to a different valence.
soluble constituents may be converted to organically
bound materials in cell structures, or cell lysis may
result in release of cellular material into solution.
The well-known nitrogen and phosphorus cycles are
examples of biological influence on sample compositions.
Methods of preservation are relatively limited and are
intended generally to (1) retard biological action,
(2) retard hydrolysis of chemical compounds and
complexes and (3) reduce volatility of constituents.
Preservation methods are generally limited to pH
control, chemical addition, refrigeration, and freezing.
Various preservatives that may be used to retard changes
in samples are as follows:
Preservative
HgCl2
Acid (HN03)
Acid (H2S04)
Alkali (NaOH)
Refrigeration
Action
Bacterial Inhibitor
Metals solvent, prevents
precipitation
Bacterial Inhibitor
Salt formation with
organic bases
Salt formation with
volatile compounds
Bacterial Inhibitor
Applicable to:
Nitrogen forms,
phosphorus forms
Metals
Organic samples
(COD, oil &
grease, organic
carbon)
Ammonia, amines
Cyanides, organic
acids
Acidity-alkalinity,
organic materials,
BOD, color, odor,
organic P,
organic N, carbon,
etc. ,
biological
organism
(coliform, etc.)
232
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In summary, refrigeration at temperatures near freezing
or below is the best preservation technique available,
but it is not applicable to all types of samples.
The recommended choice of preservatives for various
constituents is given in Table 14 Csic). These
choices are based upon the accompanying references
and on information supplied by various Regional
Analytical Quality Control Coordinators.
TABLE 14
RECOMMENDATION FOR SAMPLING AND PRESERVATION
OF SAMPLES ACCORDING TO MEASUREMENT1
Measurement
Acidity
Alkalinity
Arsenic
BOD
Bromide
COD
Chloride
Chlorine Req.
Color
Cyanides
Dissolved Oxygen
Probe
Winkler
Fluoride
Hardness
Vol.
Req.
(ml)
100
100
100
1,000
100
50
50
50
50
500
300
300
300
100
Container
P,G<2>
P,G
P,G
P,G
P,G
P,G
P,G
P,G
P,G
P,G
G, only
G, only
P.G
P,G
Preservative
Cool, 4°C
Cool, 4°C
HN03 to pH<2
Cool, 4°C
Cool, 4°C
H2S04 to pH<2
None Req.
Cool, 4°C
Cool, 4°C
Cool, 4°C
NaOH to pH 12
Det. on site
Fix. on site
•:Cool, 4°C
Cool, 4°C
Holding
Time (6)
24 Hrs.
24 Hrs.
6 Mos.
6 Hrs. ^
24 Hrs.
7 Days
7 Days
24 Hrs.
24 Hrs.
24 Hrs.
None
None
7 Days
7 Days
233
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TABLE 14 (continued)
Measurement
Iodide
MB AS
Metals
Dissolved
Suspended
Total
Mercury
Dissolved
Total
Nitrogen
Ammonia
Kjeldahl
Nitrate
Nitrite
Vol.
Req.
(ml)
100
250
200
100
100
100
400
500
100
50
Container Preservative
P,G Cool, 4°C
P,G Cool, 4°C
P,G Filter on site
HN03 to pH<2
Filter on site
HN03 to pH<2
P,G Filter
HN03 to pH^2
P,G HN03 to pH<2
P.G Cool, 4°C
H2S04 to pl<2
P,G Cool, 4°C
H2S04 to pH<2
P,G Cool, 4°C
H2S04 to pH<2
P,G Cool, 4°C
Holding
Time (6)
24 Hrs.
24 Hi's.
6 Mos.
6 Mos.
6 Mos.
38 Days
(Glass)
13 Days
(Hard
Plastic)
38 Days
(Glass)
13 Days
(Hard
Plastic)
24Hrs.<4)
24 Hrs.<4)
24 Hrs.(4)
24 Hrs. (4>
234
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TABLE 14 (continued)
Measurement
NTA
Oil & Grease
Organic Carbon
PH
Phenolics
Phosphorus
Ortho-
phosphate,
Dissolved
Hydrolyzable
Total
Total,
Dissolved
Residue
Filterable
Non-filterable
Total
Volatile
Setteable Matter
Selenium
Vol
Req.
(ml)
50
1,000
25
25
500
50
50
50
50
100
100
100
100
1,000
50
Container Preservative
P,G Cool, 4°C
G only Cool, 4°C
H2S04 to pH<2
P,G Cool, 4°C
H2S04 to pH<2
P,G Cool, 4°C
Det. on site
G only Cool, 4°C
H3P04 to pH<4
1.0 g CuS04/l-
P,G Filter on site
Cool, 4°C
P,G Cool, 4°C
H2S04 to pH<2
P,G Cool, 4°C
P,G Filter on site
Cool, 4°C
P,G Cool, 4°C
P,G Cool, 4°C
P,G Cool, 4°C
P,G Cool, 4°C
P,G, None Req.
P,G HN03 to pH<2
Holding
Time (6)
24 Hrs.
24 Hrs.
24 Hrs.
6 Hr*. <3>
24 Hrs.
24 „„. M)
24 Hrs. (^
24 Hrs.<4>
24 Hrs. (4)
7 Days
7 Days
7 Days
7 Days
24 Hrs.
6 Mos.
235
-------
TABLE 14 (^continued)
Measurement
Silica
Specific
Conductance
Sulfate
Sulfide
Sulfite
Temperature
Threshold
odor
Turbidity
Vol
Req.
(ml)
50
100
50
50
50
1,000
200
100
Container
P only
P,G
P,G
P,G
P,G
P,G
G only
P,G
Preservative
Cool, 4°C
Cool, 4°C
Cool, 4°C
2 ml zinc
acetate
Cool, 4°C
Det . on site
Cool, 4°C
Cool, 4°C
Holding
Time (6)
7 Days
24 Hrs.<5)
7 Days
24 Hrs.
24 Hrs.
None
24 Hrs.
7 Days
1. More specific instructions for preservation and sampling are found
with each procedure as detailed in this manual. A general
discussion on sampling water and industrial wastewater may be found
in ASTM, Part 23, p. 72-91 (1973).
2. Plastic or Glass
3. If samples cannot be returned to the laboratory in less than
6 hours and holding time exceeds this limit, the final reported
data should indicate the actual holding time.
4. Mercuric chloride may be used as an alternate preservative at a
concentration of 40 mg/1, especially if a longer holding time is
required. However, the use of mercuric chloride is discouraged
whenever possible.
5. If uhe sample is stabilized by cooling, it should be warmed to
25°C for reading or temperature correction made and results
reported at 25°C.
6. It has been shown that samples properly preserved may be held for
extended periods beyond the recommended holding time.
236
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Additional useful information relative to preservation of polluted
waters, wastewaters. etc., is available in Standard Methods, 13th Ed.
1971, pp. 368-369.5
Furthermore, Standard Methods provides a very useful "Sampling and
Storage" section for many of the analytical methods, offered.
6.5 PRESERVATION OF SAMPLES IN THE FIELD
Samples should be preserved at low temperatures during transport to
the laboratory for analysis. A convenient method is to use an
insulated cooler containing ice so that a temperature of 0° to 10°C
is maintained.
If possible, appropriate chemical preservation should be performed
in the field for various analytical parameters at the time of
sampling. In this case, separate bottles and chemical preservatives
are required for particular parameters. As an example, for the
extended analyses group in Chapter 4, proper preservative techniques
would require splitting the sample into approximately 10 bottles.
For this reason, sampling a large number of wells for several
analyses can become a cumbersome exercise. Regardless of the
method of preservation, analyses should be performed as soon after
sampling as is practicably possible.
237
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REFERENCES
1. Effective use of high water table areas for sanitary landfill.
Final report (SW-57d.l). U.S. Environmental Protection
Agency, 1973.
2. Sommerfeldt, T.G., and D.E. Campbell. A pneumatic system to pump
water from piezometers. Ground Water, 13(3):293, 1975.
3. Trescott, P.C., and G.F. Finder. Air pump for small-diameter
piezometers. Ground Water, 8(3);10-15, 1970.
4. McMillon, L.G. and J.W. Keeley. Sampling equipment for ground-
water investigations. Ground Water, 6(2);9-ll, 1968.
5. Methods for chemical analysis of water and waste. Report No.
625/6-74-003. Environmental Protection Agency, pp. vi-xii.
6. Standard methods for the examination of water and wastewater,
13th Edition. American Public Health Association, 1970.
238
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7.0 ANALYTICAL METHODS
7.1 INTRODUCTION
Reliable, cost-effective analytical methods must be selected and
applied in order to successfully implement Basic Indicator, and
Extended Analysis programs.
The parameters of interest in the analytical characterizations of
leachate are usually physical, chemical, and biological. Normally,
the desired information is quantitative rather than qualitative,
although qualitative data may be required at times for special
problems. For purposes of this manual, consideration will be given
only to the quantitative aspects of the analytical data.
As stated previously in Chapter 6, "Leachate represents an extremely
complex system containing soluble, insoluble, organic, inorganic,
ionic, nonionic, and bacteriological constituents in an aqueous
medium. Actual types, numbers, and levels of constituents are widely
variable..."
When dealing with a complex material of variable composition, such as
leachate, it is recognized that there is a serious potential for
numerous interferences in the determination of a given parameter.
The physical measurements, such as specific conductance and pH, are not
normally subject to appreciable interference; but many of the chemical
and biological determinations are readily affected by matrix
interferences.
When an analyst wishes to perform a quantitative determination on a
particular parameter, he must decide which analytical method will be
used. There is usually a choice among several standard methods which
can be applied to a given determination. Among the many factors which
must be considered in the choice of an analytical .method are the
following:
. sensitivity, precision, and accuracy required;
nature of the matrix and its effect upon the
determination (interferences);
available equipment, manpower and instrumentation;
239
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quantity of sample available;
level of expertise of the analyst;
number of samples to be analyzed;
turn-around time;
history and available information regarding the
sample;
reason for performing the analysis;
. how the analytical data will be applied;
other parameters, if any, to be determined on the
sample;
cost factors.
When all pertinent considerations of this nature have been carefully
weighed, the decision is then made to apply a particular standard
method to the problem. There are several literature sources of
standard analytical methods which can be applied, either directly or
with modification, to the analysis of leachate samples. Because of
their importance in analytical procedures, the following three
publications are herein referenced as the "rule books" for the analysis
of leachate samples:
• Standard Methods for the Examination of_ Water and
Wastewater, 13th Ed., APHA, 1971.
. Manual of Methods for Chemical Analysis of Water and
Wastes, U. S. Environmental Protection Agency (EPA),
1974.
. 1973 Annual Book of ASTM Standards, Part 23, Water;
Atmospheric Analysis.
The following quotation is relative to the analysis of polluted waters
and other similar samples in Standard Methods for the Examination of
Water and Wastewater, P. 367:*
These procedures described in Part 200 of this manual are
intended for the physical and chemical examination of
wastewaters of both domestic and industrial origin,
treatment plant effluents, polluted waters, sludges and
bottom sediments. An effort has been made to present
*Due to the magnitude of importance of quoted material within this
chapter, references are cited with the text rather than at the end of
the chapter.
240
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methods which apply as generally as possible and to
indicate modifications which are required for samples of
unusual composition, such as certain industrial wastes.
However, because of the wide variety of industrial wastes,
the procedures given here cannot cover all possibilities
and may not be suitable for all wastes and combinations
of wastes. Hence, some modification of a procedure may
be necessary in specific instances. Whenever a procedure
is modified, the nature of the modifications must be
plainly stated in the report of results. The procedures
which are indicated as being intended for the examination
of sludges and bottom sediments may not apply without
modification to chemical sludges or slurries.
In this same vein, the following comments are made in Handbook, for
Analytical Quality Control in Water and Wastewater Laboratories, U. S.
EPA, 1972, p. 1-3:
Regardless of the analytical method used in the laboratory,
the specific methodology should be carefully documented.
In some water pollution reports it is customary to state
that Standard Methods have been used throughout. Close
examination indicates, however, that this is not strictly
true. In many laboratories, the standard method has been
modified because of recent research or personal preferences
of the laboratory staff. In other cases, the standard
method has been replaced with a better one. Statements
concerning the methods used in arriving at laboratory data
should be clearly and honestly stated. The methods used
should be adequately referenced and the procedures applied
exactly as directed.
Knowing the specific method which has been -used, the
reviewer can apply the associated precision and accuracy
of the method when interpreting the laboratory results.
If the analytical methodology is in doubt, the data uaer
-may honestly inquire as to the reliability of the result
he is to interpret.
The advantages of strict adherence to accepted methods
should not stifle investigations leading to improvements
in analytical procedures. In spite of the value of
accepted and documented methods, occasions do arise when
a procedure must be modified to eliminate unusual
interference, or to yield increased sensitivity. When
modification is necessary, the revision should be carefully
worked out to accomplish the desired result. It is
advisable to assemble data using both the regular and
the modified procedure to show the superiority of the
latter. This useful information can be brought to the
241
-------
attention of the individuals and groups responsible for
methods standardization. For maximum benefit, the modified
procedure should be rewritten in the standard format so
that the substituted procedure may be used throughout the
laboratory for routine examination of samples. Responsibility
for the use of a non-standard procedure rests with the
analyst and his supervisor, since such use represents a
departure from accepted practice.
7.2 ALTERNATE ANALYTICAL METHODS
7.2.1 Method Comparability
Relative to the use of alternate analytical methods for the National
Pollution Discharge Elimination System, the EPA has published
guidelines in the Federal Register, October 16, 1973, as follows;
Typical Comparability Testing Procedure, (sic)
This procedure is designed to provide data on the
comparability (equivalence of two dissimilar analytical
methods for measurement of the same property or
constituent.
In making the comparison, one method is assumed to be
satisfactory (standard) and the second or alternate
method is compared for equivalency. To provide sufficient
data to apply statistical measurements of significance,
the following determinations are required:
1. Using an effluent sample representative of normal
operating processes, well-mixed between aliquot
withdrawal, run seven replicate determinations by
each method.
Report val-ues in the following manner:
TABLE 1
Effluent Sample Representative of Normal Operating Conditions
Aliquot Standard Method* Alternate Method*
List 1 through 7
*Cite .method reference
2. If variations occur in the concentration of the
measured constituent in the plant eFfluerit, repeat
the above testing on two more samples, one collected
242
-------
at the highest level of constituent normally
encountered in the waste samples examined by the
laboratory and one having a concentration at or
near the lowest level usually examined. Report
values in the following manner:
TABLE 2^
Effluent Samples of Varying Composition
Aliquot Low Level High Level
List 1 through 7
3. Using the sample from 1, add a small volume of
standard solution sufficient to double the
concentration. Run 7 replicate determinations
by each method. Report values as Table 3:
Effluent Samples Plus Standard Solution, in the same
way as Table 1. Cite source and amount of standard
solution; it should be proportioned to the original
concentration. The above procedure must be followed
on each outfall for which a permit is issued, unless
it can be shown that the outfalls in question are
comparable.
A comparability test procedure for analytical methods used on landfill
leachate samples can be modelled after the above-cited EPA procedure.
Samples, instead of representing plant effluents, will represent
potentially leachate-enriched ground and/or surface waters. The
results of the standard and alternate methods should be compared for
statistically significant differences. If the alternate method proves
to be equal to or better than the standard method, it should be
considered an acceptable analytical method for the determination of
the particular parameter in the leachate sample.
7.2.2 Additional Analytical Methods
A considerable amount of valuable pertinent information on analytical
methodology and data is available in Standard Methods for the
Examination of Water and Wastewater, 13th Edition, 1971. The
particular subjects of interest in the analysis of leachate samples
are:
. Other (instrumental) methods of analysis, including
Atomic Absorption Spectroscopy, Flame Photometry,
Emission Spectroscopy, Polarography, Potentiometric
Titration, Specific Ion Electrodes and Probes, Gas
Chromatography, and Automated Analytical Instrumentation.
(pp. 12-15)
243
-------
• Interferences and methods used for their
elimination. (pp. 15-18)
o Expression of Results. (pp. 18-20)
o Significant Figures. (pp. 20-21)
• Precision and Accuracy, Statistical Approach, Standard
Deviation, Range, Rejection of Experimental Data,
Presentation of Precision and Accuracy Data, Quality
Controlo (pp. 22-25)
, Graphical Representation of Data, Method of Least
Squares. (pp. 25-27)
o Self-evaluation (desirable philosophy for the analyst)
(Po 27)
o Methods Evaluation by the Committee on Standard Methods
of the Water Pollution Control Federation. (pp. 369-370)
7.3 SPECIFIC ANALYTICAL METHODS FOR THE ANALYSIS OF RELATIVELY
CONCENTRATED LEACHATE SAMPLES
7-3.1 Introduction
Specific analytical methods for the analysis of relatively
concentrated leachate samples were investigated in the report
"Compilation of Methodology for Measuring Pollution Parameters
of Landfill Leachate" by E0S.K. Chian and F.B. DeWalle, University
of Illinois, EPA Program Element No. 1DB0640 It is stated in
the abstract, P. IV of the subject report:
Since different analytical methods can be used to
determine a specific parameter, a preliminary
laboratory evaluation was made of those methods least
subject to interferences. All analyses were conducted
with a relatively concentrated leachate sample obtained
from a lysimeter filled with milled solid waste. The
results indicate that strong interferences are sometimes
encountered when using colorimetric tests due
principally to the color and suspended solids present in
leachate. In such instances, alternative methods were
evaluated or recommendations were made to reduce the
interfering effects. Automated chemical analysis using
•jcolorimetric'methods can sometimes experience significant
interferences.
Further research is necessary to evaluate additional
methods using leachate samples of different strengths
and collected from landfills of different ages» The
precision and sensitivity of each method will also
244
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have to be determined. The interfering parameter
should be quantified to allow predictions of its
magnitude with leachate samples of different strengths.
Also in the above-cited report, Introduction, p. 3, it is stated:
It is the purpose of the present study to review the
analytical methods to determine contaminants as
reported in the literature. The methods compiled and
evaluated in this study were generally reported in
the literature; additional information was obtained
by contacting the principal investigators. Interferences
in the chemical analysis due to the complex nature of
the leachate as enumerated in the reported studies are
listed in this report.
The compilation showed that different methods subject
to different interferences are used to determine a
certain parameter. For each parameter, only that
method was evaluated in this laboratory which was
found to have the smallest interference. The
laboratory evaluation tested the method for its
susceptibility to certain interferences commonly
found in leachate. In addition, the accuracy of the
method was tested. All laboratory analyses were
performed using a high strength leachate sample
obtained from a recently installed lysimeter filled
with milled refuse. Recommendations made in this
report, therefore, only apply to leachate of similar
strength. No evaluation was made of precision and
sensitivity of each method since this was beyond the
scope of the work. Realizing the above restrictions,
recommendations were made in the present study for
the selection of those methods least subject to
interference. Further recommendations were made
concerning modifications of the selected methods.
7.3.2 Measurement of Interference Effects
Two general procedures were used by Chian and DeWalle to deal with
interference effects in the evaluation of specific analytical methods.
These procedures were the Standard Addition Method and Dilution Method.
These methods are discussed in this report in pp. 12-15.
In general, it would be expected that interferences encountered in
concentrated leachates would be relatively severe and constitute
"worst case" effects when compared with more dilute leachates.
Leachates obtained in the field (landfills) for analysis may vary
greatly in total concentration; i.e., from total concentration of
minimum detectability to a highly concentrated product. The ratios of
245
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the individual contaminants present in the leachate are also variable
and must be considered when evaluating interference effects in a giyen
analytical method.
The analyst, therefore, must always evaluate a specific analytical
method relative to a specific leachate sample. General guidelines
for handling interferences are of great value. The judgment of the
analyst is of prime importance in applying the guidelines to the
specific problems at hand. Experience with a given leachate is
obviously of practical value. The degree of accuracy, sensitivity,
and precision required in a specific analytical problem will constitute
foremost considerations in the final selection of the method and
possible modifications.
7.4 ANALYTICAL METHODS
In discussing individual analytical methods in their aforementioned
report (pp. 16-121) Chian and DeWalle address the following aspects in
each case: Principle, Interferences, Previous Studies, Evaluation of
the Method, Recommendations, and Procedures.
The methods discussed in the report are as follows:
. Physical Parameters: pH, Oxidation Reduction
Potential (ORP), Specific Conductance, and
Residue.
. Organic Chemical Parameters: C.O.D., T.O.C.,
Volatile Acids, Tannin and Lignin, Organic
Nitrogen.
Inorganic Chemical Parameters: Chloride,
Sulfate, Phosphate, Alkalinity and Acidity,
Nitrate, Nitrite, Ammonia, Sodium and Potassium,
Calcium and Magnesium, Hardness, Heavy Metals.
Biological Parameters: B.O.D., Coliform Bacteria
(Total and Fecal).
. Miscellaneous Determinations.
The report also contains a useful appendix of parameters and methods
used by various investigators. (Appendix A, p. 125 - Survey of
physical, chemical and biological methods used by various
investigators).
7.5 BRIEF DESCRIPTION OF SPECIFIC ANALYTICAL METHODS FOR LEACHATE
ANALYSIS
Following is a brief description of the analytical methods as
246
-------
recommended by Chian and DeWalle for the analysis of concentrated
leachate. Information on interferences and methods of minimizing them,
is included.
1. Physical Parameters:
A. pH Determination:
Method: Electrometric determination using a
glass indicating electrode and calomel reference
electrode or a combination electrode. The
procedure is according to Standard Methods,
p. 279.
Interference: The glass electrode is relatively
immune to interference from color, turbidity,
colloidal matter, free chlorine, oxidants, or
reductants as well as from high saline content,
except for a sodium error at high pH. The error
caused by high sodium ion concentrations at a pH
above 10 may be reduced by using special "low-
sodium error" electrodes.
B. Oxidation Reduction Potential (ORP) Determination:
Method: The measurement is made with a pH meter,
using a platinum indicating electrode and a calomel
reference electrode. The pH determination is
made concurrently.
Interference: Oxidation of the sample and
presence of foreign matter on electrodes can
cause erroneous results.
C. Specific Conductance Determination:
Method: The determination is performed with a
commercially available meter and an electrode
with a cell constant of 1.0. Both temperature
and pH are determined concurrently as they affect
the results. Reference is made to Standard
Methods, pp. 326-327.
Interference: Fouling of the electrode surfaces
may occur and checks of the indicated conductance
using another cell or standard solution may be
necessary. A chromium-sulfuric acid mixture is
effective in cleaning the electrodes.
D. Residue Determination:
247
-------
Total solids is determined after drying to
constant weight at 103-105°C and the volatile
solids is determined from the weight loss at
550°C for one hour. The suspended solids
(filterable residue) is determined using a
glass fiber filter and drying to constant weight
at 103-105°. The following reference is given:
Standard Methods, pp. 289, 292, 293»
Interference: The determination of the total
solids can vary due to volatilization of part
of the organic matter, loss of occluded water
and gases from heat-induced chemical decomposition.
The suspended solids determination is affected
by the physical nature of the material in
suspension, the pore size of the filter, and the
area and thickness of the mat.
2. Organic Chemical Parameters:
A0 Chemical Oxygen Demand (C.O.D.)
Method: The C.O.D. determination is performed
by the dichromate reflux method, according to
Standard Methods, pp0 496-499« If the C.O.D0 is
less than 100 mg/liter, more accurate results
may be obtained by using the low-level C.O.D.
procedure cited in the same reference.
Interference: Straight-chain aliphatic compounds,
aromatic hydrocarbons, and pyridine are not
oxidized to any appreciable extent, although this
method gives more nearly complete oxidation than
the permanganate method. The straight-chain
compounds are more effectively oxidized when silver
sulfate is added as a catalyst; however, silver
sulfate reacts with chlorides, bromides, or
iodides to produce precipitates which are only
partially oxidized by the procedure. There is no
advantage in using the catalyst in the oxidation of
aromatic hydrocarbons, but it is essential to the
oxidation of straight-chain alcohols and acids0
The oxidation and other difficulties caused
by the presence of chlorides in the sample may
be overcome by employing the following method
which is a complexing technique for the elimination
of chlorides from the reaction. This is
accomplished by adding mercuric sulfate to the
248
-------
samples before refluxing. This ties up the
chloride ion as a soluble mercuric chloride
complex, which greatly reduces its ability
to react further.
B. Total Organic Carbon (XO.C.)
Method: The T.O.C. analysis is performed by
the combustion-infrared method according to
Standard Methods, pp» 257-259.
Interference: The removal of carbonate and
bicarbonate by means of acidification and
purging with nitrogen gas can result in the
loss of very volatile organic substances.
Another important loss can occur from the
failure of large carbon-containing particles
in the sample to enter the hypodermic needle
used for injection.
C. Volatile Acids (Total Organic Acids)
Method: Volatile acids are determined by the
column-partition chromatographic method
involving extraction from the column with
chloroform-butanol solvent and titration with
0.02N standard sodium hydroxide titrant, as
given in Standard Methods, pp. 577-580.
Standard amounts of acetic acid are added to
determine the recovery of the method.
Interference: The chloroform-butanol solvent
system employed in the method is capable of
eluting organic acids other than the volatile
acids and some synthetic detergents as well.
Crotonic, adipic, pyruvic, phthalic, fumaric,
lactic, succinic, malonic, gallic, aconitic,
and oxalic acids, alkyl sulfates and alkyl-
aryl sulfonates are all adsorbed by silicic
acid and eluted when present.
D. Tannin and Lignin
Method: Aromatic hydroxyl groups reduce
tungstophosphoric and molybdophosphoric acids
to form a blue color which is measured
spectrophotometrically at a wavelength of 700nm.
Interference: Other easily oxidizable substances
such as reduced metal ions, sulfides, and nitrite
249
-------
may give a similar reaction in this test and
caution should therefore be exercised in
evaluating the results. The largest
interference is caused by ferrous iron and
2 mg/liter will give a color equivalent to
1 mg/liter tannic acid.
E. Organic Nitrogen
Method: In the presence of sulfuric acid,
potassium sulfate and mercuric sulfate
catalyst, the amino nitrogen of many organic
materials is converted to ammonium bisulfate.
After the mercury ammonium complex in the
digestate has been decomposed by sodium
thiosulfate, the ammonia is distilled from an
alkaline medium and absorbed in boric acid.
The ammonia is determined colorimetrically or,
if preferred, by titration with a standard
mineral acid. The sensitivity of the colorimetric
methods makes them useful for the determination
of organic nitrogen levels below 1 mg/liter.
The titrimetric method of measuring the ammonia
in the distillate is suitable for the
determination of a wide range of organic
nitrogen concentrations depending upon the
volume of boric acid absorbent used and the
concentration of the standard acid titrant.
Should the total kjeldahl nitrogen and ammonia
nitrogen be determined individually, the "organic
nitrogen" can then be obtained by difference.
Interference: The only interferences which are
encountered may be due to the incomplete
oxidation of the organic nitrogen to ammonia.
The organic nitrogen determination is according
to Standard Methods, pp. 244-248.
3. Inorganic Chemical Parameters:
A. Chloride:
Method: In biologically stabilized leachate
samples in which color does not cause any
interference, the chloride determination is
conducted with the mercuric nitrate titration
method given in Standard Methods, pp. 97-99.
Interference: Bromide and iodide are titrated
with mercuric nitrate in the same manner as
250
-------
chloride. Chromate, ferric, and sulfite ions
interfere when present in excess of 10 mg/liter.
Alternate Method: In strongly polluted leachate,
chloride ion is determined by the potentiometric
titration method with silver nitrate solution
using a glass and silver-silver chloride electrode
system according to Standard Methods, pp. 377-380.
Interference: Iodide and bromide also are
titrated as chloride. Ferricyanide causes high
results and must be removed. Chromate and
dichromate interfere and should be reduced to the
chromic state or removed. Ferric iron interferes
if present in an amount that is substantially
higher than the amount of chloride. Chromic ion,
ferrous iron, and phosphate do not interfere.
Grossly contaminated samples usually require
pre-treatment. Where contamination is minor,
some contaminants can be destroyed simply by
the addition of nitric acid.
B. Sulfate:
Method: Sulfate is precipitated in a
hydrochloric acid medium as barium sulfate
by the addition of barium chloride. The
precipitation is carried out near the boiling
temperature; and after a period of digestion,
the precipitate is filtered, washed with water
until free of chlorides, dried at 105°C, and
weighed as BaS04 according to Standard Methods,
pp. 331-333.
Interferences leading to high results: Suspended
matter, silica, barium chloride precipitant,
nitrate, sulfite, and water are the principal
factors in positive errors. Suspended matter
may be present in both the sample and the
precipitating solution; soluble silicate may
be rendered insoluble and sulfite may be oxidized
to sulfate during processing of the sample.
Barium nitrate, barium chloride and water are
occluded to some extent with the barium sulfate.
Interferences leading to low results: Alkali
and metal sulfates frequently yield low results.
This is especially true of alkali hydrogen
sulfates. Occlusion of alkali sulfate with
251
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barium sulfate causes the substitution of
an element of lower atomic weight than
barium in the precipitate. Hydrogen sulfates
of alkali metals act similarly and, in
addition, decompose on being heated. Heavy
metals, such as chromium and iron, cause low
results by interfering with the complete
precipitation of sulfate and by formation of
heavy metal sulfates. Barium sulfate has
small but significant solubility, which is
increased in the presence of acid. Although
an acid medium is necessary to prevent
precipitation of barium carbonate and phosphate,
it is important to limit its concentration to
minimize the solution effect.
C. Phosphate:
Method: The total phosphorus content of the
sample includes all of the orthophosphates and
condensed phosphates, both soluble and insoluble,
and organic and inorganic species. To release
phosphate from combination with organic matter,
a digestion or oxidation technic is called for.
The rigor of the digestion required depends upon
the type of sample. Three digestion technics,
in order of decreasing rigor, are perchloric
acid digestion, sulfuric acid digestion, and
persulfate digestion. Following digestion, the
liberated orthophosphate is determined
colorimetrically. The colorimetric method used,
rather than the digestion procedure, governs in
matters of interference and minimum detectable
concentration.
The ascorbic acid colorimetric method is used
to measure total phosphorus concentration in
leachate, using the persulfate digestion. The
amount of recommended persulfate digestion
reagent is 400 mg/100 ml sample, while the
digestion time recommended by Standard Methods
is sufficient to hydrolyze the phosphorus. The
ortho-phosphate test as determined by the
ascorbic acid method does not experience
significant interference and should be run on
the anaerobically stored leachate after as
little dilution as possible. In order to obtain
reliable results, a standard addition or
progressive dilution curve should be established
for the total phosphorus determination. Such
252
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steps are not necessary for the ortho-
phosphate determination. References for
the total phosphate and ascorbic acid
methods are in Standard Methods, pp. 524-
526 and 532-534.
Interference: Arsenates react with the
molybdate reagent to produce a blue color
similar to that formed with phosphate.
Concentrations as low as 0.10 mg/liter
arsenic interfere with the phosphate
determination. Hexavalent chromium and
nitrite interfere to give results about 3%
low at concentrations of 1.0 mg/liter and
10-15% low at concentrations of 10 mg/liter
chromium and nitrite. Sulfide (Na2S) and
silicate do not interfere in concentrations
of 1.0 and 10.0 mg/liter.
D. Alkalinity and Acidity:
Method: The alkalinity of a water is the
capacity to accept protons and is determined
by titrating the sample with strong mineral
acid to a specified endpoint. The acidity
of a water is the capacity to donate protons
and is determined by titrating the sample
using strong mineral base to a specified
endpoint. In unpolluted waters, Standard
Methods recommends titration endpoints at
pH 8.3 and between 5.1 and 4.5, depending
upon the magnitude of the alkalinity. In
polluted waters, it recommends an arbitrary
endpoint of 8.3 (phenolphthalein endpoint)
and 3.7 (methyl orange endpoint) unless a
potentiometric titration curve indicates a
distinct inflection point which can be
employed, and the endpoint should then be
specified with the analysis. From the
titration curve, the inflection point can be
determined, whereafter the amount of acid or
base, expressed as CaC03 equivalent, can be
calculated. The potentiometric titration is
also to be used for colored or turbid waters
where difficulties arise in determining a
color indicator endpoint.
It is recommended that alkalinity and acidity
determinations be made potentiometrically on
the undiluted samples and that the endpoints
253
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be used as determined from the titration
curve. These endpoints should be specified
in reporting the results of the analysis.
Standard Methods references; pp. 54-56 and
370-375.
Interference: Standard Methods indicates
that the acidity and alkalinity determination
is not restricted only to bicarbonate species
but is also contributed by other weak acids
or bases and hydroxides. The test, therefore,
only indicates general properties of the
leachate and cannot be used for the quantitative
determination of specific species.
E. Nitrate:
Method: Nitrate is determined with the specific
ion electrode or by the brucine-sulfanilic acid
colorimetric method. Standard Methods reference
for the colorimetric method is pp. 461-464.
Interference: It is preferable to use an
undiluted sample when measuring nitrates with
the specific ion electrode. Standard amounts
of nitrate should be added to the sample to
determine the recovery of the method.
In the brucine colorimetric method, all strong
oxidizing or reducing agents interfere. The
presence of oxidizing agents may be determined
by the addition of orthotolidine reagent, as in
the measurement of residual chlorine. Ferrous
and ferric iron and quadrivalent manganese give
slight positive interferences; but in
concentrations less than 1 mg/liter, these
are negligible. The interference due to
nitrite up to 0.5 mg N02-N/1 is eliminated
by the use of sulfanilic acid. Chloride
interference is masked by the addition af
excess Nad. High concentrations of organic
matter, such as in undiluted raw wastewater
will usually interfere. Suspended solids and
color may be removed with a massive lime dosage
of 5,000 to 10,000 mg/liter Ca(DH)2. Aluminum
hydroxide is not as effective as a coagulant.
F. Nitrite:
Method: Nitrite is determined colorimetrically
254
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at 520 ran through the formation of a reddish-
purple azo dye produced at pH 2.0 to 2.5 by
the coupling of diazotized sulfanilic acid
with naphthylamine hydrochloride. The procedure
is given in Standard Methods, pp. 240-243. The
naphthylamine is replaced by n-(naphthyl)
ethylenediamine dihydrochloride. Standard
amounts of nitrite nitrogen are added to the
filtered sample.
Interference: The following ions interfere
due to precipitation under the conditions of
the test and, therefore, should be absent:
antimonous, auric, bismuth, ferric, lead,
mercurous, silver, chloroplatinate, and
metavanadate. Cupric ion may cause low results
by catalyzing the decompositon of the diazonium
salt. Colored ions which alter the color system
should likewise be absent. When small amounts
of suspended solids seriously impair nitrite
recovery, a sample may be passed through a
membrane filter (0.45^ pore size) to achieve
the necessary clarification before color
development is undertaken. The determination
should be made promptly on fresh samples to
prevent bacterial conversion of the nitrite to
nitrate or ammonia.
G. Ammonia:
Method: Two methods are recommended for
determination of ammonia. One uses the
selective ion ammonia electrode with sufficient
sample dilution to reduce matrix interference
of the leachate (Ref.: U. S. EPA Methods for
Chemical Analysis of Water and Wastes, 1974,
pp. 165-167). The other method uses distillation
followed by titration of the ammonia in the
distillate with standard 0.02N I^SO^ with mixed
methyl red-methylene blue as the indicator.
For this method, a maximum concentration of
75 mg/liter ammonia in the diluted sample is
recommended, unless additional buffer is used.
A pH of 7.4 is sufficiently high to distill
off the ammonia. A pH of 9.4 is too high,
causing partial destruction of the organic
nitrogen. (Ref.: Standard Methods, pp. 224-
226 and 246-247)
Interference:
255
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Selective ion electrode method: Color and
turbidity have no effect on the measurements
and distillation is not necessary. Volatile
amines act as a positive interference.
Mercury interferes by forming a strong complex
with ammonia. Thus, the samples cannot be
preserved with mercuric chloride.
Distillation-titration method: The largest
difficulty in the distillation step is
-maintaining the pH of 7.4. When the pH of
the distillation mixture is too high, certain
organic nitrogen compounds are converted to
ammonia, thus increasing the apparent
concentration, and when the pH is too low,
the recovery of ammonia is too low. Ammonia
recovery from preliminary distillation will
be low on water samples containing more than
250 mg/liter calcium unless the pH is properly
adjusted before distillation is undertaken.
The calcium, and the.phosphate buffer react to
precipitate calcium phosphate, releasing
hydrogen ions and lowering the pH. The
titrimetric procedure is also subject to amine
interference because the standard acid can
react with such alkaline bodies. However, the
titration procedure is free of interference
from neutral organic compounds.
H. Sodium and Potassium:
Method: The most rapid and sensitive method
uses flame emission photometry to determine
sodium and potassium concentrations at
wavelengths of 589.0 nm and 766.5 nm, respectively
(Ref.: Standard Methods, Sodium: pp. 316-320
and Potassium: pp. 283-284).
Sodium and potassium may also be determined by
atomic absorption spectroscopy (Ref.: U. S.
EPA Methods for Chemical Analysis, etc.,
Sodium: pp. 147-148 and Potassium pp. 143-144).
Interferences:
Flame photometry: Particulate matter can cause
burner clogging and should be removed by
filtration through a medium pore-sized filter
paper.
256
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Potassium and calcium have been reported
to interfere with the sodium determination
by the internals-standard method if the
potassium-to-sodium ratio is 5:1 or greater
and the calcium-to-sodium ratio is 10:1 or
higher. When these ratios are exceeded,
the calcium and potassium should be
determined first so that the approximate
concentration of interfering ions may be
added, if necessary, to the sodium calibration
standards. Magnesium interference does not
appear until the magnesium-to-sodium ratio
exceeds 100, a rare occurrence. Among the
common anions capable of causing radiation
interference are chloride, sulfate and
bicarbonate in relatively large amounts.
Atomic absorption spectroscopy: An extensive
evaluation of the method showed the necessity
to add the easily ionizable cesium ion to the
sample at a concentration of 1,000 mg/liter
in the final dilution, to suppress ionization
of the analyte ion in the determination of
sodium and potassium. Sodium may interfere
in the potassium determination if present at
much higher levels than the potassium. This
effect can be compensated by approximately
matching the sodium content of the potassium
standards with that of the sample.
I. Calcium and Magnesium:
Method: Calcium and magnesium are determined
by atomic absorption spectroscopy, using
10,000 mg/liter lanthanum to reduce interference,
(Ref.: Standard Methods, pp. 212-213 and U. S.
EPA Methods for Chemical Analysis, Calcium pp.
103-104 and Magnesium pp. 114-115).
Interference: Phosphate and sulfate interfere
in the calcium atomic absorption determination
and 200 mg/liter of each caused a 35% and a
30% depression, respectively (Ref.: Parker,
C. R., "Water Analysis by Atomic Absorption
Spectroscopy", Varian Techtron, Palo Alto,
California, 78 P., 1972) Both effects are
masked by the addition of lanthanum chloride.
Concentrations of more than 1,000 jug/liter
magnesium and 500 mg/liter each of sodium and
potassium cause a 5-10% enhancement due to
257
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suppression of the calcium ionization (Ref.:
Brown, E., et al., Methods for Collection and
Analysis of Water samples for Dissolved
Minerals and Gases in Techniques of Water
Resources Investigations of the U. S.
Geological Survey, Chapter 1, U. S. Geological
Survey, Washington, D. C., 1970, 160 P.). The
magnesium determination is interfered with by
more than 400 nig/liter each of sodium, potassium,
and calcium, while phosphates and sulfates also
cause interferences. Silicates and carbonates
at 200 mg/liter each caused a 42% and 17%
depression, respectively (Parker, 1972).
Phosphate, for example, will bind the magnesium
and prevent the magnesium atomic absorption
when the light passes through the flame.
Interferences in the calcium and magnesium
determination are reduced by addition of an
inorganic "releasing" agent, lanthanum, in a
concentration of 10,000 -mg/liter in the sample.
This prevents the binding of calcium and
magnesium by anions. The interferences are
also reduced by using a nitrous oxide-acetylene
flame instead of the lower temperature air-
acetylene flame.
J. Hardness:
Method: The hardness reflects the total
concentration of polyvalent metals, mainly
calcium and magnesium; but will include iron,
zinc, and copper when present in significant
quantities. The most accurate method is by
summation of the individual polyvalent metals,
as measured by atomic absorption spectroscopy,
which are then expressed as CaC03 equivalents.
A more rapid method is based upon ethylenediamine
tetraacetic acid (EDTA) titration, using
Eriochrome Balck T as indicator (Ref.: Standard
Methods, pp. 178-184). This method measures
the calcium and magnesium ions.
Interference:
Calculation from determination of individual
cations: This method is subject to the usual
interferences encountered in the atomic absorption
determinations of the individual cations.
EDTA titration: Some metal ions interfere with
258
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this procedure by causing fading or
indistinct endpoints. This interference
is reduced by the addition of certain
inhibitors to the water sample before
titration with EDTA. The maximum
concentrations of interfering substances
which may be present in the original
sample and still permit titration with
EDTA are shown in Table 122(1), p. 180 of
Standard Methods. Suspended or colloidal
organic matter in the sample may also
interfere with, the endpoint but may be
overcome by evaporating the aliquot to
dryness on a steam bath, followed by heating
in a muffle furnace at 550°C until the
organic matter is completely oxidized.
K. Heavy Metals:
Sample pretreatment for Metal Analysis:
In the EPA Manual, Methods for Chemical
Analysis ojE Water and Wastes, 1974, metal
content of a sample is divided into four
categories as follows:
Dissolved metals: those constituents
(metals) which, will pass through a 0.45
memb rane f ilt er.
. Suspended metals: those constituents
(metals) which are retained by a 0.45
membrane filter.
Total metals: the concentration of metals
determined on an unfiltered sample
following vigorous digestion or the sum
of the concentrations of metals in both
the dissolved and suspended fractions.
. Extractable metals: the concentration of
metals in an unfiltered sample following
treatment with hot dilute mineral acid.
Procedures are given for sample treatment
prior to the determination of metals in the
four categories described. This information
is found in pp. 81-83 of the above reference.
A decision should be made, prior to sampling
and analysis, relative to what type of metal
content information is required; i.e.,
259
-------
dissolved, suspended, total or extractable,
and the sample should be handled accordingly.
Method: Most heavy metals are determined
by atomic absorption spectroscopy methods
(EPA Manual, pp. 78-157).. .Standard additions
are used for leachatee of high strength to
determine the magnitude of the interference.
Standard additions should be used for the
elements lead, copper, nickel, and chromium,
but may be omitted for zinc and cadmium.
For total metal analysis, the sample should
be collected in a polyethylene bottle and
acidified to pH 2 with 1:1 redistilled nitric
acid. When the dissolved metals, those
filterable through a 0,45-*** filter, are
determined, the suspended metals should be
determined concurrently. Mercury is determined
by atomic absorption with the cold vapor
technique (EPA, pp. 118-122).
Colorimetric methods are recommended for
arsenic and selenium. Arsenic is determined
with silver diethyldithipcarbamate (EPA pp.
9-10) and selenium is determined by the
diaminobenzidine method (Standard Methods,
pp. 296-298).
Interference: Several interferences are
reported for the. atamic absorption determination
and can be classified as chemical, non-atomic,
ionization and spectral (EPA, p. 84). Chemical
interference occurs when heavy metals are not
available in the atomic form because of molecular
combination with anions present in the solution.
This interference can sometimes be overcome
by addition of a releasing agent such as
lanthanum. The presence of a high concentration
of dissolved solids may cause a non-atomic
interference such as by light scattering.
This effect is partially corrected by measuring
absorbance of a nearby non-absorbing wavelength..
lonization interferences occur when the atom
ionizes in the flame, after which it is not
available for atomic absorption. This
interference is reduced by addition of an easily
ionized element such as cesium to suppress the
ionization of the analyte atom. Spectral
interference can occur when the absorbing
wavelength of another element falls within the
260
-------
width of the absorption line of the analyte
atom. Such interference is partially reduced
by narrowing the slit width- of the instrument.
Th.e analysis of .mercury by atomic absorption
with the cold vapor technique depends on the
reduction of the sample with SnS04 or SnCl2,
which may not he complete when other oxidants
in high concentrations are present. Interference
from certain volatile organic materials which
will absorb at the wavelength of mercury
C253.7mn) is also possible. A preliminary run
without reagents should determine if this type
of interference is present.
The determination of arsenic and selenium by
atomic absorption spectrescopy using the
gaseous hydride method anay not be satisfactory,
since reduction to the trivalent form with
SnCl2 may not be complete. Th.e conversion to
gaseous arsine after addition of zinc metal
may also not be complete.
In the colorimetric determination of arsenic
with silver diethyldithiocarbamate, chromium,
cobalt, copper, mercury, molybdenum, nickel,
platinum, and silver may interfere in the
generation of arsine. High sulfur content of
a sample may exceed removal capacity of the
lead acetate scrubber. Samples shonild be
spiked with a known amount of arsenic to
establish adequate recovery.
For the colorimetric determination of selenium
with diaminobenzidine, no inorganic compounds
give a positive interference. Negative
interference results from compounds that lower
the concentration of diaminobenzidine by
oxidizing this reagent. Iodide and, to a
lesser extent, bromide, cause low results.
4 . Biological Parameters:
A. Biochemical Oxygen Demand (B.O.D.)
Method: The biochemical oxygen demand
determination is a bioassay-type procedure
and measures the oxygen demand exerted by
microorganisms during uptake of degradable
substrates and by chemical oxidation reactions.
The sample is incubated under aerobic conditions
261
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in the dark at 20°G during a five-day
period.
The B.O.D. determination is run according
to Standard Methods, pp. 489-495, using
dilution water which is seeded with settled
domestic sewage. B.O.D. values obtained
should be judged carefully and be determined
parallel with comparable chemical tests, such
as free volatile fatty acids, C.O.D. or T.O.C.
Interference: Relatively low results are
obtained with the test when toxic compounds
are present that inhibit the bacterial
population or when a biomass is -used that is
not adapted to the specific substrate.
B. Coliform Bacteria (Total and Fecal)
Method: The most probable number (MPN) technique
should be selected for leachate monitoring
purposes, as opposed to the membrane filter
(MF) technique, since it is able to detect
bacteria at lower concentrations and is less
subject to suspended solids interference.
Inactivation studies, however, in which a
certain amount of bacteria is added to a
sample to study its subsequent reduction with
time, should be conducted if the MF technique
is used. Presumptive and confirmed tests are
run for total coliforms and ..he completed
coliform test is run in those instances where
leachate causes pollution of drinking water
supplies. (Ref.: Standard Methods, pp. 664-
668)
The fecal coliform MPN procedure is used as a
confirmatory test procedure in conjunction
with prior enrichment in a presumptive test
medium for optimum recovery of fecal coliforms.
(Ref.: Standard Methods, pp. 669-672)
Interference: The results of the examination
with the multiple tube technique are expressed
in terms of a statistical Most Probable Number
(MPN) and the estimate generally tends to be
greater than the actual numbers. An observed
limitation of the membrane filter technique
is. its reduced ability to detect bacteria in
turbid samples or in the presence of high
concentrations of noncoliform bacteria.
262
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5. Miscellaneous Determinations:
Some of the miscellaneous leachate parameters
which, haye been given attention in various studies
are: Methylene blue active substances, cyanide,
fluoride, sulfide, silica, h.exane solubles, ether
solubles, color, visual appearance, and odor.
7.5.1 Additional Valuable Information
Additional valuable information on specific analytical methods is
available in "Procedures for the Analysis of Landfill Leachate", in
Proceedings of an International Seminar, Environmental Conservation
Directorate, Ottawa, Ontario, Report EPS-4EC-75-2, October 1975.
7.6 FIELD TESTING VERSUS TESTING IN THE LABORATORY
The majority of tests performed on leachate samples are run in the
analytical laboratory on samples which have been preserved by
refrigeration or chemical means. A limited number of tests, however,
can be performed at the sampling site on a freshly drawn sample. There
are a number of advantages in field testing in which sample degradation
is practically eliminated, along with the need for sample preservation,
transportation, and handling. An added advantage is the ability to
re-sample and re-analyze immediately, on site, if it is suspected that
a particular sample is not representative or valid. There are also
disadvantages encountered in field testing and these usually relate to
the reliability of the particular method and equipment used for the test.
Some tests can be run in the field with the same -methods and equipment
which would be used in the laboratory and yield the same reliability.
Among such tests are those involving the measurements of pH, oxidation
reduction potential, specific conductance, turbidity, dissolved oxygen,
and specific ions by means of specific ion electrodes. The equipment
used in these tests is available in portable models which are of equal
applicability in the field and laboratory.
Other tests are sometimes performed exclusively in the field using
methods and equipment specifically designed for field use. A number of
commercial kits are available for such purposes.
While offering distinct advantages, there are also disadvantages
inherent in the use of field kits. The following evaluation of field
kit useage is given in Handbook for Monitoring Industrial Wastewater,
s. S. EPA, Technology Transfer, August 1973, p. 5-14:
Estimating the Amount £f Pollutants Present b_y_ Use o_f_ "Kits"
Companies, such as the Hach Chemical Company, Delta
Scientific, Inc., and Koslow Scientific Company have
263
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manufactured "Kits" for the analysis of various
constituents of wastewater. The kits consist of a
small portable container in which all the necessary
equipment and instructions are conveniently packaged
and arranged to perform a variety of tests. No
previous laboratory training is required and, within
minutes, an indication of the chemical constituents
in wastewater can be determined.
Koslow Scientific and the Hach Company provide kits
for determining the presence of heavy .metals, such as.
Cd, Hg, and Pb, and includes reagents for masking
interferences.
The major disadvantage in using kits is the inability
of the pre-packaged devices and reagents to effectively
cope with interferences. Reference 2 (Standard Methods
for the Examination of Water and Was t ewa t er, 13th Edition,
American Public Health Association, 1971) outlines
procedures for the removal of interferences by
pretreatment techniques and the reagents necessary for
masking these interferences that are usually not available
in the kits. The accuracy of the tests performed with
kits is usually less than that obtainable with precise
laboratory techniques. Kits give good results in
relatively clean water but pose problems when used to
analyze wastewaters. They are nevertheless useful in
preliminary surveys performed to determine overall
characteristics of a wastewater.
This evaluation of the use of field kits for the analysis of industrial
wastewater is equally applicable in the case of leachate analysis. Due
to their limited accuracy, the use of kits may not be acceptable for
juost enforcement cases.
7.7 MOBILE LABORATORIES
Although not in widespread usage, mobile analytical laboratories have
the potential of providing a combination of laboratory capability and
field-testing convenience. The instrumentation and general capability
of a mobile laboratory can vary over a wide range, depending upon its
application, manpower, and the capital investment involved. By using
normal laboratory equipment and methods, the mobile laboratory can
obtain results equivalent to those of a conventional analytical
laboratory, while incorporating all of the advantages of field kits.
Limitations imposed by sample degradability and work load will be
encountered by the mobile laboratory in much the same way as experienced
by the conventional laboratory under certain conditions. If a sample
or samples presented to a mobile laboratory must be analyzed for a
large number of parameters (i.e., 20 or 30), then sample degradation
264
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versus work load will have to be addressed. The sample will have to be
preserved and the analyses prioritized relative to order of degradability.
In this respect, the mobile laboratory shares the disadvantages of the
conventional laboratory, along with its advantages.
7,8 AUTOMATED METHODS
Automated wet chemistry methods offer many advantages, among which are
economy, increased precision, and accuracy when applied to repetitive
analytical work loads of significant volumes. Federal, state and local
regulatory agencies, industry, educational institutions, and independent
testing laboratories (among others) use automated methods to handle
large, demanding repetitive analytical work loads .
Automated wet chemistry is addressed in the Handbook for Ifonitoring
Industrial Wast ewa t er, U. S. EPA, August 19737~p7~lPl4 as follows:
Automated wet chemistry is frequently used in analysis of
wastewaters and for automated monitoring of waste effluents.
When used, the system consists of a sampler to.select air,
reagents, diluents, and filtered samples. From the sampler,
the fluids pass through a proportioning pump and manifold
where the fluids are aspirated, proportioned,' and mixed.
The samples are then ready for separation by passing through
any one of the following units: a dialyzer (continuously
separates interfering materials in the reaction mixture);
a digester (used for digestion, distillation, or solvent
evaporation); a. continuous filter (for on-stream separation
of particulate onatter by a moving belt of filter paper),
or a distillation head (separates high vapor pressure
components).
After separation, the samples can be conditioned in a
constant temperature heating bath. After conditioning,
the samples pass through a detection system which may be
a colorimeter, a flame photometer, a fluorometer, a UV
spectrophotometer, an IR spectrophotometer, an atomic
absorption spectrophotometer, or a dual differential
colorimeter. The signals from the detection system are
sent to a recorder or a computer system.
In the May 1975 issue of Environmental Newsletter, a publication of
Technicon Industrial Systems, a list of water quality juajor automated
methods is presented (Table 15). It should be noted that ten of the
methods are Federal Register approved and eleven of the methods are
presented in the U. S. EPA Manual, ^Methods jror_ Chemical Analysis £f_
Water and Wastes, 1974.
Automated -methods are discussed in Standard Methods j[or^ the Examination
of Water and Wastewater, 13th Edition, 1971, pp. 14-15, as follows:
265
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PiniMttr
Technicon
oc
Other Method
Federal
Register
Approved
Individual
Viriince
Approval!
1974 EPA
Methods Book
Reference (D
Practical
Method<2>
Usual
Method
R.n,.(3)
Acidity (Thymol Blue)
Alkalinity (Methyl Orange)
Aluminum
Ammonia (Dialysis)
Boron
164-71W
111-71W
(•
270-73W
202-7 2W
P. 5
(4)
0-500mg/l
0-500mg/l
0-1mg/l
0-1mg/l
'£*#
W-70W
t«2-7tW
137-7 W
181-7JW
211-72W
P. 31
X
X
X
X
0-10mg/l
-------
Automated analytical instrumentation: Automated analytical
instruments are now available and in use to run individual
samples at rates of 10 to 60 samples per hour. The same
instruments can be modified to perform analyses for two to
twelve constituents simultaneously from one sample. The
instruments are composed of a group of interchangeable
modules joined together in series by a tubing system.
Each module performs the individual operations of
filtering, heating, digesting, time delay, color sensing,
etc. that the procedure requires.
The read-out system employs sensing elements with indicators,
alarms, and/or recorders. For monitoring applications,
automatic standardization-compensation, electrical and
chemical, is done by a self-adjusting recorder when known
chemical standards are sent periodically through the same
analysis train. Such instrument systems are presently
available.
Appropriate methodology is supplied by the manufacturer for
many of the common constituents of water and wastewater.
Some methods are based on procedures described in this
manual while others originate from the manufacturer's
adaptation of published research. Since a number of
methods of varying reliability may be available for a
single constituent of water and wastewater, a critical
appraisal of the method adopted is obviously mandatory.
Automated methodology is susceptible to the same
interferences as the original method from which it
derives. For this reason, new methods developed for
automated analysis must be subjected to the exacting
tests for accuracy and freedom from adverse response
already met by the accepted standard methods.
Off color and turbidity produced during the course of an
analysis will be visible to an analyst manually performing
a given determination and the result will be properly
discarded. Such abnormal effects caused by unsuspected
interferences might escape notice in an automated
analysis. Calibration of the instrument system at least
once each day with standards containing interferences of
known concentration could help to expose such difficulties.
Routine practice is to check instrument action and guard
against questionable results by the insertion of
standards and blanks at regular intervals—perhaps after
every 10 samples in the train. Another important
precaution is proper sample identification by arrangement
into convenient groups .
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In brief, a fair degree of operator skill and knowledge,
together with adequately detailed instructions, is
required for successful automated analysis.
In the report "Compilation of Methodology for Measuring Pollution
Parameters of Landfill Leachate" by E. S. K. Chian and F. B. DeWalle,
the following comments are made concerning automated methods:
All automated methods as recommended by EPA (1974) for
water and wastewater and Technicon (1973) for industrial
waste should be evaluated for possible interferences
since most tests are based on colorimetric analyses
which are generally subject to strong interferences by
the color and suspended solids present in leachate.
Such evaluation is necessary since increasing amounts
of leachate samples will be analyzed by automated
methods at a future date.
7.9 LABORATORY QUALITY CONTROL
The subject of laboratory quality control is treated in detail
in Handbook for Analytical Quality Control in Water and Wastewater
Laboratories, U. S. EPA Technology Transfer, June, 1972. The various
topics covered include: Importance of Quality Control, Laboratory
Services, Instrumental Quality Control, Glassware, Reagents,
Solvents and Gases, Control of Analytical Performance, Data
Handling and Reporting, Special Requirements for Trace Organic
Analysis, and Skills and Training. A number of valuable references
are provided in each section.
The technical and legal aspects of an adequate quality control
program are of prime importance in the analysis of sanitary
landfill leachate samples. The investment of time and effort
needed for a quality control program are well compensated in the
resultant reliability of and confidence in the data obtained.
The economics of quality control is greatly favored in the use
of automated analysis systems as compared to manual systems, In
a recent issue of U. S. EPA's Analytical Quality Control Newsletter
(October, 1975, p. 5), it is stated that for a particular automated
system, the additional personnel work load required to provide
an analytical quality assurance overhead of 40% is estimated to be
about 1%. The 40 to 1 advantage is most impressive.
7.10 MANPOWER AND SKILL REQUIREMENTS
Manpower and skill requirements for analytical work are dependent
upon a number of factors, including nature of the sample, work
load, analytical parameter to be tested, method used, sensitivity,
precision and accuracy desired, and equipment and facilities
268
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available. A consideration of major importance, of course, is
whether the analyses will be performed by manual or automated
methods.
In Handbook For Analytical Quality Control In Water and Wastewater
Laboratories. U. S. EPA. June 1972, pp. 9-2, 9-3, 9-4, skills
and skill-time ratings for standard manual analytical operations
are discussed in detail.
Manpower and skill requirements are reduced dramatically when
automated methods are used. The usual skill requirements are those
of a technician for preparation of samples, solutions, calibration,
and glassware handling. Automated data processing affords
additional manpower savings.
A comparison of manual versus automated analytical methods for
throughput, space, and personnel requirements is given in "Automated
Methods For Assessing Water Quality Come of Age", by M. J. F. Du Cros
and J. Salpeter, In Environmental Science and Technology, Vol. 9,
Number 10, October 1975, p. 932.
Data are presented in tabular form for the analysis of 12 water
quality parameters. For the manual methods, 12 personnel and
114-feet of bench space are required to perform 100 to 126
determinations per hour. For the automated methods, 3 personnel
and 45-feet of bench space are required to perform 370 determinations
per hour. In addition to an appreciable savings of space, the
automated throughput is approximately 12 times that achieved with
manual methods.
.7.11 RECORDS, DATA HANDLING, AND REPORTING
A significant amount of analytical data are generated in a leachate
testing program. The data must be handled, interpreted, checked
for validity, recorded, and reported. This is an important aspect
of the testing program and should be given appropriate attention.
If the data are not properly handled, the considerable effort and
expense involved in sampling and analysis can be lost or erroneously
applied. It should be noted that legal as well as technical
considerations can be associated with records, data handling, and
reporting.
A detailed discussion on data handling can be found in "Data
Handling and Reporting", in Handbook for Analytical Ouality Control in
Water and Wastewater Laboratories, U. S. EPA, June 1972, pp. 7-1 to
7-11. Amoung the topics treated in this chapter are: Significant
Figures, Accuracy Data, Precision Data, Report Forms, Digital
Read -Out, Key Punch Cards and Paper Tape, STORET- Computerized Storage
and Retrieval of Water Quality Data, and SHAVES- a Consolidated
Data Reporting and Evaluation System.
269
*U.S. GOVERNMENT PRINTING OFFICE; 1980-0-722-523/438
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