600281160
Manual of Ground-Water Quality
Sampling Procedures
(U.S.) Robert S. Kerr Environmental
Research Lab., Ada, OK
Sep 81
PB82-103045
U.S. DEPARTMENT OF COMMERCE
National Technical Information Service
NTIS
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1 REPO
1^600/2-81-160
Applications Guide
3. RECIPIENT'S ACCESSION NO.
PB82-1030U5
. TITLE AND SUBTITLE
MANUAL OF GROUND-WATER QUALITY SAMPLING
PROCEDURES
5. REPORT DATE
September 1981
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Marion R.
Scalf, James F. McNabb, William J.
Dunlap, Roger L. Cosby, and John S. Fryberger
8. PERFORMING ORGANISATION REPORT NO
9 PERFORMING ORGANIZATION NAME AND ADDRESS
Robert S. Kerr Environmental
Post Office Box 1198
Ada, Oklahoma 74820
Research Laboratory
10. PROGRAM ELEMENT NO.
ABPC1A
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Robert S. Kerr Environmental Research Lab.
Office of Research and Development
U.S. Environmental Protection Agency
Ada, Oklahoma 74820
- Ada, OK
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA-600/15
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Recent environmental legislation has recognized the importance of ground water
quality protection and the stresses that man's activities, especially waste disposal,
place on this vital national resource. To provide a realistic assessment of current
and potential pollution problems and a rational basis for ground water quality protec-
tion, it is necessary to collect representative samples from this remote and relatival
inaccessible environment. This report presents some procedures currently utilized to
sample ground water and subsurface earth materials for microbial and inorganic and
organic chemical parameters.
In selecting a sampling procedure, a number of considerations are described
based on the objectives of the sampling program, characteristics of pollutants, nature
of pollution source, and hydrogeology of the area. Various techniques for constructin
sampling wells and for withdrawing samples are described with advantages and dis-
advantages of each method listed. For situations where samples of subsurface earth
materials are required to adequately assess ground-water quality threats, procedures
are described for collecting, handling, and processing core samples. Finally, sample
preservation, sample records, and chain of custody procedures are discussed.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Ground Water
Water Pollution
Monitoring
Samp!ing
Samples
Chemical Analysis
Microorganisms
48G
68D
. DISTRIBUTION STATEMENT
Release to the public,
19, SECURITY CLASS (This Report^
Unclassified.
21. NO. OF PAGES
105
20. SECURITY CLASS (Thispage)
Unclassified.
22. PRICE
EPA Form 2220-1 (9-73)
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PB82-1030U5
EPA-600/2-81-160
September 1981
MANUAL OF GROUND-WATER QUALITY
SAMPLING PROCEDURES
by
Marion R. Scalf, James F. McNabb,
William J. Dunlap, and Roger L. Cosby
Robert S. Kerr Environmental Research Laboratory
Ada, Oklahoma 74820
and
John S. Fryberger
Engineering Enterprises, Inc.
Norman, Oklahoma 73069
ROBERT S. KERR ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
ADA, OKLAHOMA 74820
REPRODUCED BY
NATIONAL TECHNICAL
INFORMATION SERVICE
US. DEPARTMENT OF COMMERCE
SPRINGFIELD. VA 22161
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NOTICE
THIS DOCUMENT HAS BEEN REPRODUCED
FROM THE BEST COPY FURNISHED US BY
THE SPONSORING AGENCY. ALTHOUGH IT
IS RECOGNIZED THAT CERTAIN PORTIONS
ARE ILLEGIBLE, IT IS BEING RELEASED
IN THE INTEREST OF MAKING AVAILABLE
AS MUCH INFORMATION AS POSSIBLE.
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DISCLAIMER
This report has been reviewed by the Robert S. Kerr Environmental Researx
Laboratory, U.S. Environmental Protection Agency, and approved for publication.
Mention of trade names or commercial products does not constitute endorsement
or recommendation for use.
11
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FOREWORD
A critical part of Environmental Protection Agency's research program is
the development of accurate and reliable scientific data on which to base the
Agency's environmental protection program. The Robert S. Kerr Environmental
Research Laboratory conducts research on the nature, transport, fate and
management of contaminants that may transverse the subsurface environment
and threaten ground water quality.
The technology upon which to base the protection of ground water quality
is perhaps a aecade or more behind that of surface water. This results from
a traditional lack of concern in the scientific and decision-making community
and the complexity of the subsurface environment relative to its surface
counterpart.
This report is a summary of several procedures currently used by the
ground water community to collect ground water quality data. Some of the
procedures described are in common usage while others are yet in the research
or developmental stage. These procedures plus the concepts noted should pro-
vide federal, state, and local agencies as well as industry with a sound
basis for the collection of reliable ground water data essential to the
protection of this valuable natural resource.
Clinton W. Hall
Director
Robert S. Kerr Environmental Research Laboratory
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ABSTRACT
Recent environmental legislation has recognized the importance of gru.
water quality protection and the stresses that man's activities, especially
waste disposal, place on this vital national resource. To provide a realistic
assessment of current and potential pollution problems and a rational basis
for ground water quality protection, it is necessary to collect representative
samples from this remote and relatively inaccessible environment. This report
presents some procedures currently utilized to sample ground water and subsur-
face earth materials for microbial and inorganic and organic chemical parameter:
In selecting a sampling procedure, a number of considerations are de-
scribed based on the objectives of the sampling program, characteristics of
pollutants, nature of pollution source and hydrogeology of the area. Var^u.
techniques for constructing sampling wells and for withdrawing samples are
described with advantages and disadvantages of each method listed. For sit-
uations where samples of subsurface earth materials are required to adequately
assess ground water quality threats, procedures are described for collecting,
handling, and processing core samples. Finally sample preservation, sample
records, and chain of custody procedures are discussed.
The procedures described provide a basic capability for sampling sub-
surface environments. Additional research is needed, however, to further
evaluate, improve and extend these capabilities, especially in sampling
related to organic chemical parameters.
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CONTENTS
Foreword iii
Abstract iv
Figures vii
Tables ix
Acknowledgements x
1. INTRODUCTION 1
2. OBJECTIVES OF SAMPLING 2
3. PRELIMINARY EVALUATIONS 3
A. Characteristics of Pollutant 3
B. Nature of Possible Pollution Source 5
C. Hydrogeologic Data . 5
4. HYDROGEOLOGIC CONSIDERATIONS 7
5. CONSTRUCTION OF MONITORING WELLS 17
A. General Requirements 17
1. Location 17
2. Diameter 17
3. Depth 18
4. Intake Portion of Sampling Wells 18
5. Well Casings 19
B. Drilling Methods 19
1. Mud Rotary 20
2. Air Rotary 22
3. Air Drilling with Casing Hammer 22
4. Cable Tool 24
5. Reverse Circulation 26
6. Special Reverse Circulation 26
7. Solid Stem Continuous-Flight Auger 26
8. Hollow-Stem, Continuous-Flight Auger 29
9. Keck Screened, Hollow-Stem, Continuous Flight Auger . . 31
10. Bucket Auger 31
11. Jetting 33
12. Use of Bore-Hole Geophysics 34
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C. Well Development 36
D. Multiple-Completion Sampling Wells 38
6. COLLECTION OF GROUND WATER SAMPLES 43
A. General Requirements 43
B. Withdrawing Samples
1. Bailers 45
2. Suction-Lift Pumps 45
3. Portable Submersible Pumps 48
4. Air-Lift Samplers 48
5. Nitrogen Powered, Continuous Delivery, Glass-Teflon . 48
6. Gas-Operated Squeeze Pump 50
7. Gas-Driven Piston Pump 53
8. Special Sampling Considerations for Organic Samples . 53
a. Grab Samples 53
b. Continuous Procedures ^~
c. Volatile Organics in the Unsaturated Zone ... 59
C. Field Tests and Preservation 61
1. Inorganic and Standardized Organic Chemical
Parameters 61
2. Organic Parameters . 62
3: Microbiological Parameters 62
7. SAMPLING SUBSURFACE SOLIDS 72
A. General Requirements 72
B. Acquisition of Core Samples 73
C. Handling and Processing of Core Materials 75
8. SAMPLE RECORDS AND CHAIN OF CUSTODY 80
References 83
Bibliography 85
Appendices 87
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FIGURES
Number Page
1 Permeable sand layer underlain by a clay layer 8
2 Two-aquifer system with opposite flow directions .... 9
3 Effect of permeability changes on shape of pollution plume . 10
4 Solution porosity aquifer - area! flow patterns 12
5 Solution porosity aquifer - vertical flow patterns. ... 13
6 Improperly constructed monitoring well in fractured
carbonate rock 14
7 Idealized monitoring network 15
8 Mud rotary drilling 21
9 Air drill with casing hammer 23
10 Cable tool drilling 25
11 Special reverse circulation 27
12 Continuous flight auger drilling 28
13 Hollow stem auger drilling 30
14 Keck screened, hollow-stem, continuous flight auger ... 32
15 Comparison of electric and radioactive bore hole logs. . . 35
16 Multiple completion well, for one-time sampling 39
17 Multiple completion well, for periodic sampling 40
18 Modified Kemmerer sampler 46
19 Teflon bailer 47
20 Air-lift sampler 49
vii
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FIGURES (continued)
Number Pf*2
21 Nitrogen powered, Glass-Teflon pump ........ 51
22 Gas-operated squeeze pump ',
23 Gas-driven piston pump .
24 System for grab sampling 55
25 Continuous sampling system for organics 57
26 Self-contained sampling unit for organics 58
27 Soil-water sampling device for volatile organics. ... 60
28 System for microbiological sampling of wells using a
suction-lift pump .
29 Thin wall tube sampler 74
30 Core sample extruding device 76
31 Subsampling a soil core 77
32 Typical locations for subsamples 79
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TABLES
Number Page
1 Recommendation for sampling and preservation of samples
according to measurement 63
2 Quantities of calcium hypochlorite, (70 percent) and
household laundry bleach (5 percent) required to make
100 gallons of disinfectant solution 69
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ACKNOWLEDGEMENTS
The authors are indebted to numerous ground-water professionals throus,
out the United States for providing information and for reviewing the manu-
script. Jerry Thornhill and Jack Keeley, EPA, Ada, Oklahoma were instrumental
in the early development of the project. James Gibb and Mike Barcelona of the
Illinois Water Survey, Don Signer of USGS, David Miller and Olin Braids of
Geraghty & Miller, Inc., Richard Tinlin of International Resource Consultants,
Wayne Pettyjohn, National Center for Ground Water Research, and Jay Lehr
and Dave Nielsen of NWWA all made contributions. Special appreciation is
extended to Robert C. Minning, President, Keck Consulting Services, Inc.,
Williamston, Michigan for his contribution on well construction.
Liberal use was also made of EPA Report 530/SW-611, "Procedures Manu<_, .„
Ground Water Monitoring at Solid Waste Disposal Facilities", and the authors
wish to express appreciation to EPA's Office of Solid Waste.
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SECTION 1
INTRODUCTION
Ground water accounts for the base flow of all perennial streams, over 90
percent of the world's fresh water resources, and one half the drinking water
in the United States, yet has traditionally received only token scientific
attention. Although surface and ground waters are inseparable parts of the
same hydrologic system with the waters of each flowing alternately between the
two components, water resource planners have often considered them as separate
enti ti es.
The Safe Drinking Water Act (PL 93-523) of 1974 has done much to rectify
this neglect by recognizing ground water as a major source of drinking water
and establishing standards of ground water quality protection. This Act plus
subsequent legislation, the Toxic Substances Control Act (PL 94-469) and the
Resource Conservation and Recovery Act (PL 94-580) further recognizes that
ground water quality is being increasingly threatened by various human activ-
ities, particularly the disposal of waste materials to the land.
In order to assess the impact of such activities on ground water quality
and, hence, to provide a rational basis for its protection, the behavior of
pollutants in the subsurface and the processes governing this behavior must be
evaluated. However, many water resource planners, inexperienced in ground
water investigations, are learning that techniques applicable to surface waters
do not necessarily apply to ground water.
Methods of collecting a representative ground water sample are much more
difficult and expensive in this often remote and relatively inaccessible
environment. The subsurface is an extremely complex system subject to exten-
sive physical, chemical and biological changes within small vertical and hori-
zontal distances.
Chemical and microbial parameters, such as BOD and coliforms traditionally
used to indicate pollution of surface waters, have limited, if any, value in
describing the water quality of a ground water aquifer.
The purpose of this manual is to provide guidance and suggested methods
of subsurface sampling for various typical ground water quality investigations.
Although the great variability of hydrogeological conditions precludes identi-
fication of typical sites, it is possible to identify some basic fundamentals
of subsurface sampling that may be used or modified to fit the unique con-
ditions involved.
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SECTION 2
OBJECTIVES OF SAMPLING
A monitoring well samples a very small part of an aquifer horizontally and
in many cases, vertically. Unlike its surface counterpart where a sample can
be arbitrarily taken at any point in the system, moving a ground water sampling
point implies the installation of additional monitoring wells. Because of the
difficulty and expense, it is essential that sampling objectives be firmly
established well in advance of field activities. These objectives will dictate
the parameters to be measured, the necessary reliability of the water quality
data, and analytical methodology and thence the sampling procedures necessary
to meet these objectives.
If the objective is simply to determine the presence or absence of a con-
servative pollutant in a particular water supply, it is simple and relatively
inexpensive to collect a sample at a water tap. However, if the objective is
to define the horizontal and vertical distribution of an organic pollutant or
pollutants and predict the eventual fate, then soil cores, monitoring wells
and special sampling equipment may increase efforts and cost several orders of
magnitude.
In the former case, the purpose of the sample collection activity is known
and limited in scope. In the latter case, there is a need to be concerned not
with point data as an end in itself, but as a component of a network approach
wherein information on the ground water system is developed as a basis for
extrapolating information to areas where samples were not collected and/or for
predicting the effects of natural and manmade stresses on the subsurface system
(1).
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SECTION 3
PRELIMINARY EVALUATIONS
CHARACTERISTICS OF POLLUTANT
The unstable nature of many chemical, physical, and microbial constituents
in ground water and subsurface materials limit the sample collection and
analysis options. Ground water normally moves very slowly. This results in
a slow rate of change in water quality parameters. However, the subsurface
is a unique heterogenous environment and maintaining the integrity of a
sample from the time of sampling to the time of analysis is often a very dif-
ficult process. Because the physical, chemical, and microbial aspects of the
environment are so closely interrelated it is very difficult to deal with one
aspect without affecting the others. However, in selecting ground water
sampling procedures, there are definite aspects of each that must be consid-
ered to maintain sample integrity.
Ground waters are usually well insulated, therefore temperature fluctu-
ations are minimal in their natural environment; however, once removed to the
surface, temperature may change very rapidly. Temperature may influence many
aspects of water quality. Kinetically slow processes such as gas exchange or
solid/solution reactions may be affected since many rates double with each
10°C rise in temperature. In an irreversible reaction, higher temperatures
will decrease the time required to produce the final products. In a
reversible reaction, temperature influences both the length of time required
to reach equilibrium, and the proportion of the reactants and products at
equilibrium conditions. Also, temperature affects microbial growth. In
general, microbial metabolic activity is approximately doubled for each 10°C
rise in temperature until a temperature is reached at which the rate of
thermal denaturation of enzyme proteins exceeds the rate of thermal stimulation
of enzyme reaction rates.
Many ions normally present in only trace amounts in normal waters may not
remain unchanged when sampled because of chemical and physical reactions
such as oxidation, precipitation, adsorption and ion exchange. Coprecipitation
may also reduce the concentrations of these constituents in solution. Iron
is a particularly troublesome component in natural waters because of its tend-
ency to precipitate from solution and to coprecipitate other ions. Precipi-
tation is generally enhanced in solutions where the pH is high and the
temperature is relatively low. Because iron is precipitated as the hydroxide,
it is seldom one of the major constituents in water. The metal, however,
occurs in water in both the ferrous and ferric states. Ferrous iron in
solution is unstable in the presence of oxygen.
+ 4HCO" + H?0 + JgO? ^^ Fe(OH)., + 4CO,
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If the sample is subjected to a strong reducing environment, the reaction
may reverse, and the resultant solution may contain large quantities of
ferrous iron. The solubility of iron in natural water is governed by pH, Eh,
and the concentration of organic ligands, as well as HC03" and S~ ions.
Carbonates and bicarbonates are particularly susceptible to an equilib-
rium shift if samples are taken in plastic bottles. Most plastics diffuse
CQo thereby creating an equilibrium shift.
C02(g) + H20 ^ H2C03 (aq.)
H2C03 (aq.) ^^ HC03" + H+
HC03'
A quick analysis is required to accurately determine these ionic species
before changes are made.
The percentage concentrations of the various components of the nitrogen
cycle may change rapidly as a result of biological activity which also greatly
influences the conversion of organic phosphates to ortho-phosphate.
Water containing dissolved sulfides readily loses hLS, particularly if
the pH of the sample is low. If the pH of the sample is high, sulfide ions
may be lost by oxidation.
Many water samples may contain solid colloidal particles showing a marked
tendency to lose certain components while retaining others. When this occurs,
the components that are lost are replaced with similar species from solution.
This phenomenon of ion-exchange is both cationic and anionic; however, cation
exchange is more prevalent in.ground water samples since most anions are very
water soluble (Cl , NCU , SO* ). Ion-exchange of sorbed species for hydrogen
ions is particularly enhanced by acid fixation before filtration, therefore,
care should be exercised in this regard.
Collection of ground water samples for the identification of specific
organic compounds is a relatively new, tedious and complex process and differs
substantially from routine methods used for inorganic compounds. Analyses
of organic compounds are both expensive and time consuming. Yet the thousands
of dollars spent for the evaluation of a suite of samples are completely
wasted if the samples are not properly collected and stored.
Organic compounds in the parts per billion range may be significant to
human health in contrast to the more innocuous inorganic compounds. Such
considerations combined with the great complexity of these compounds accentuate
the sampling problems associated with adsorption, contamination and volatility.
Materials from which pumps, samplers, discharge lines, storage containers and
well casings are constructed must receive careful consideration. Most of the
common metals and plastics either contaminate water samples or remove sub-
stances from them. Metals may strongly adsorb organic compounds and there is
the possibility of reactions catalyzed by metal surfaces. A compounding
problem is the presence of lubricants derived from pumps and joint compounds.
Many plastics adsorb organic contaminants and also bleed other compounds
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directly from their surfaces or, particularly, from the cementing agents
(solvent) used to join pipe sections. Cemented joints should be avoided in
any plastic materials used in sampling (3).
Sampling equipment should be constructed with materials that have the
least potential for affecting the sample. Chief among these is glass with
Teflon a close second and stainless steel probably third. The least desirable
material is rubber. Unfortunately, detailed experimental data on the potential
reactions between the materials and the wide range of organic compounds that
serve as real or potential ground-water contaminants are simply not available.
NATURE OF POSSIBLE POLLUTION SOURCE
The area of consideration, the time available for monitoring, and potential
concentration levels of pollutants all influence the sampling procedures se-
lected. A regional or large area monitoring program may permit the use of
existing wells, springs or even the baseflow of streams if these systems are
compatible with the parameters of interest. If time is critical, existing
sampling locations may be the only alternative. However, if the possible
pollution source is relatively small, such as a landfill or lagoon, or if
pollutant concentrations may be very low, such as with organics, special
monitoring wells will almost surely be necessary. The number and location of
additional wells needed depends on the purpose of monitoring, aquifer
characteristics, and mobility of pollutants in the aquifer.
If the potential contamination source is above the water table, it may be
necessary to sample the unsaturated zone to get a true picture of the threat
to ground water. With the exception of chlorides, and to a lesser extent
nitrates and sulfates, most pollutants can be sorbed to materials in the un-
saturated zone and removed to some extent under favorable conditions (2).
Therefore, it is possible to sample the ground water beneath a waste source
for years and observe no contamination. This can give a false sense of security
when actually pollutants are still moving very slowly through the unsaturated
profile toward the ground water.
Considerable future sampling of ground water will relate to pollution or
potential pollution resulting from hazardous waste disposal. Both soils and
ground water in many areas may be contaminated to the extent that construction
of monitoring wells and collection of samples may be hazardous to the health
of workers involved. Such considerations, where applicable, should be an
integral part of the process of selecting sampling procedures.
HYDROGEOLOGIC DATA
Geologic factors relate chiefly to geologic formations and their water-
bearing properties, and hydrologic factors relate to the movement of water in
the formations.
Knowledge of the hydrogeologic framework is important from two standpoints:
(1) prediction of ground-water movement, and (2) geochemical considerations
which affect the quality of ground water. The geologic framework includes
lithology, texture, structure, and mineralogy, and the distribution of the
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materials through which ground water flows. The hydraulic properties of the
earth materials depend upon their origin and lithology, as well as the sub-
sequent stresses to which the materials have been subjected. Ground-water
movement depends upon the effective permeability and the hydraulic gradient
within an aquifer. Permeability is related to the nature, size and degree
of interconnection of pores, fissures, joints, and other openings.
Prior to initiating any field work, all existing geologic and hydro!ogic
data should be collected, compiled and interpreted. Data that may be available
include: geologic maps, cross-sections, aerial photographs, and an array OT
water-well data including location, date drilled, depth, name of driller, water
level and date, well completion methods, use of well, electric or radioactivity
logs, or other geophysical data,formation samples, pumping test(s) and water-
quality data. After compiling and thoroughly reviewing the collected data,
the investigator can properly plan the type of investigation needed, including
the data necessary to fill the gaps and the sampling necessary (parameters,
frequency and locations(s)).
Water-level measurements are important basic preliminary data often used
in selecting ground-water sampling sites, equipment and procedures. Water-
level data can be obtained from wells, piezometers, or from surface-water
manifestations of the ground water system such as springs, lakes, and streams.
The depth to water may determine the type of pumps or samplers used and pro-
cedures and cost of constructing monitoring wells. Water-level contours drawn
from static levels in wells penetrating the same aquifer can be used to make
a preliminary determination of gross direction of flow. Note that nearby
pumping wells or other artificial discharges or recharges may alter the
natural gradient.
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SECTION 4
HYDROGEOLOGIC CONSIDERATIONS
A positive sample from a monitoring well may prove the presence of con-
tamination in the ground water, providing the integrity of the well and
sampling procedure are intact, but a negative sample does not necessarily
prove the absence of contamination in the aquifer. The heterogeneous nature
of subsurface environments makes the location of sampling points a complicated
and unpredictable science when trying to intercept a pollutant plume. Hydro-
geologic conditions are site specific and it is impossible to prescribe
standard locations for sampling points that would be applicable to all sites.
In an aquifer with intergranular porosity, such as sands, gravels, sandstones
and silts, water occurs in interconnected void spaces between individual
particles of aquifer material. Some simplified "typical" flow patterns are
illustrated in Figures 1 and 2. It is readily apparent that horizontal loca-
tion of a monitoring well in relation to the pollutant source determines
whether or not contaminated water is intercepted. Further, vertical location
of the well screen and other well construction aspects also affect the quality
of a sample collected from the well. Should the well screen be located above
or below the zone of contamination, and assuming proper seals are located
above and below the screen, samples from this well will very likely indicate
no contamination unless it is pumped sufficiently to change the ground water
flow pattern. On the other hand, if the well screen is not properly sealed
from other subsurface zones or if the entire saturated thickness is screened,
samples from the well may represent a composite of water from several different
zones and concentrations will not be representative of any. Furthermore,
such well construction may provide a conduit for the movement of contamination
from one zone to another.
As noted previously, gross ground water flow patterns can be developed
from water level contours. However, the actual movement of a plume may be
somewhat more complex. For example, in a geologic environment such as alluvium
or terrace deposits involving intergranular permeabilities, the shape of the
plume may be controlled by abrupt changes in permeabilities such as the channel
gravels as shown in Figure 3. Such changes in permeability are common in river-
deposited geologic formations and can greatly affect the shape and rate of
movement of pollution plumes.
The hydrogeology is further complicated by the different flow patterns of
different pollutants. Ground water contaminated with a dense pollutant such
as chloride creates a plume that tends to migrate to the base of the aquifer.
Conversely, lighter pollutants such as hydrocarbons tend to "float" near the
top of the saturated zone. In addition, different pollutants move through the
subsurface at different rates relative to the rate of water movement because
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CO
' •".-''" - ' • .:.- '""'• " '• "'•' '-' . :^,^^^^l^^^^^^^' >' -. PERCHED ,"..--•..- . •;. -';-
•SAND '•••'-.: ' ,r \':gj&rEi=^i AY^^ ^^^^^-^m- WATER TABLE . -• - ;•' . /.:;.;
Figure 1.
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<£>
fiaure 2 Two-Aquifer System with Opposite Flow Directions. Leachate first moves into and
' Tll^ithTh^hgToT^d-wTEiTTn the upper aquifer. Some of the leachate eventually
moves through the confining bed into the lower aquifer where it flows back beneath
the landfill and away in the other direction. (2)
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A
I
•BS
Pollution
Source
Plume
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of sorption, desorption, ion-exchange and biodegradation. Therefore, points
of maximum concentration of the different pollutants along the ground water
flow path will probably vary considerably.
Ground-water flow patterns are even less predictable in fractured rock
or solution porosity aquifers than in aquifers with intergranular porosity.
Flow patterns are generally controlled by fracture patterns such as those
illustrated in Figures 4 and 5. Obviously, the problem in locating monitoring
wells in such geology is to intercept fractures or solution channels that are
hydraulically connected to the source of contamination. It is possible in
many formations of this type to drill a well that is dry and move only a few
feet away and drill another that has plenty of water. However, neither well
may be hydraulically connected to a source of pollution only a few feet away.
In some fractured rock formations where caving is not a problem it is
possible to complete a monitoring well as open hole without using a well screen.
In most such wells it is advisable, however, to install casing (grouted in
place) to at least the depth planned to set the pump. Care must be exercised
especially in fractured rock formations such as limestone to maintain the
depth-specific factor for monitoring wells. Wells with much open hole may
intercept several fractured zones resulting in intercommunication between
layers and sampling of mixed waters. This potential problem is illustrated
in Figure 6.
In spite of the complexity, and in lieu of a detailed hydrogeologic study
there are some basic guidelines that can be used in locating monitoring wells
based on the considerations noted previously. A more detailed examination of
locating monitoring wells for a landfill is described in EPA Report EPA-530/
SW-611, "Procedures Manual for Ground Water Monitoring at Solid Waste Disposal
Facilities" (2).
A necessary component of any ground water monitoring program is background
sampling. Occasionally, it is possible to sample the ground-water quality of
an area before a source of contamination is introduced. This is desirable and
may become more common in the future as ground-water quality protection becomes
a greater part of normal operations. In most instances, however, a potential
source of contamination is already a reality and the objective is to collect a
sample for comparison that is out of the influence of that source. Another
consideration is that an analysis of an earlier sample may not have included a
parameter that is of current interest or that analytical capabilities may have
improved for certain parameters in the meantime.
One recommended monitoring method for detecting contamination at landfills
is location of a background well upgradient from the landfill and a minimum of
three wells downgradient and at an angle perpendicular to ground-water flow,
penetrating the entire saturated thickness of the aquifer. Such an arrangement
is illustrated in Figure 7 and is applicable to most potential point sources
of contamination.
If there is adequate reason to suggest that contamination has already
occurred and the objective is to define the pollutant plume, this remains a
reasonable initial approach. However, it is extremely important to locate
11
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LEGEND:
FLOW DIRECTION OF LEACHATE
ENRICHED GROUND WATER
LEACHATE ENRICHED
GROUND WATER
Figure 4. Solution Porosity Aquifer--Area1 Flow Patterns (2)
12
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Figure b.
. al
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.Pollution Source
Monitoring Well
Even in fractured carbonate formations there may be stratigrafic layers that,
although somewhat fractured, do not contain solution channels. Such layers form
barriers to ground water flow unless they are breached such as by an open hole of
a well. Such a monitoring well is not depth-specific and will not only lead to
erroneous conclusions regarding pollution concentrations and distribution, but also
will contribute to the spread of the pollution.
Figure 6. Improperly Constructed Monitoring
Well in Fractured Carbonate Rock
14
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LEGEND
A.B
- MONITORING
WELLS.
Figure 7. Idealized Monitoring Network (2)
-------
subsequent monitoring wells one at a time, sample, and base succeeding well
locations on results of previous sampling. Under no circumstances should the
entire drilling budget be expended on a series of monitoring wells based entirely
on the initial prediction of the direction of a pollutant plume. Even with the
best of background information, there is a high probability that a large per-
centage of these wells will miss the pollutant plume because of the heterogeneous
nature of subsurface permeabilities.
16
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SECTION 5
CONSTRUCTION OF MONITORING WELLS
The success of a ground-water monitoring program depends on numerous
factors; however, the location, design, and construction of the monitoring
wells is usually the most costly and non-repeatable factor. Hence, it is
extremely important that the well construction be accomplished properly at
the outset.
The primary objectives of monitoring wells are:
(a) to provide access to ground water
(b) to determine which pollutants are present in the ground water
and the concentrations.
(c) to determine the area! and vertical distribution of pollutants.
In order to accomplish these objectives in the most competent and cost-
effective manner, consideration must be given the proper well design and con-
struction method that will best fit the specific objectives and the hydro-
geologic conditions.
GENERAL REQUIREMENTS
Location
The general criteria for locating monitoring wells are discussed in the
preceding section. Occasionally a location which is highly desired from
groundwater flow criteria presents unusual problems in design and construction
of the monitoring well. The effect that the location may have on well design
and construction can best be appreciated following the detailed discussions
on drilling methods and design criteria.
Diameter
The diameter of the casing for monitoring wells should be just sufficient
to allow the sampling tool (bailer or pump) to be lowered into the well to the
desired depth. The diameter of the hole into which the casing is placed must
be at least sufficiently large for the casing to fit and in many cases must be
at least 2 inches larger to permit placement of a grout seal around the outside
of the casing.
Casings and/or holes drilled much larger than the necessary minimum can,
in fact, have undesired effects on the data. For example, in formations of
very low permeability the excessive storage in an unnecessarily large boring
can cause the water level inside the boring to be erroneously low for days or
17
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even weeks. Also, because it is usually necessary to remove water standing
in the well before taking a sample of the formation water, excessive storage
can complicate the water sampling procedure.
Depth
The intake part of a monitoring well should be depth-discrete. That part
of the well, the screen or other openings, through which water enters the well
or casing should be limited to a specific depth range.
Water supply wells that may exist in an area to be monitored are often
used as sampling points. Substantial care must be exercised when this is done
and the results are often questionable. Water-supply wells are constructed to
produce a given quantity of water, hence, they may be screened throughout a
thick aquifer, through several permeable layers of an aquifer, or sometimes
through two or more aquifers or discrete water-bearing layers. When this
situation exists, it is probable that the hydrostatic heads are different
between different layers. Under non-pumping conditions this interconnection
permits water from the layer with the higher head to flow through the well
and into the formation with the lower head. This can occur between layers
of different permeability separated by only a few feet of low permeability
material. This condition can, of course, have substantial effect on the con-
centration of a pollutant obtained by pumping for a short time before sampling.
Therefore, it is important that monitoring wells be constructed to be
depth-discrete and to sample only from one specific layer without intercon-
nection to other layers. In order to assure that this depth-discrete require-
ment is met, provisions for placing cement grout above and, if necessary, below
the well screen on the outside of the casing must be made in the design of
the wells.
Commonly (especially when sampling for contaminants lighter than water)
it is desirable to sample at the water table, or top of the saturated zone in
an unconfined aquifer. The screen or intake part of the well should then ex-
tend from a few feet above to a few feet below the anticipated position of
the water table to allow for future water-table fluctuations. Often, under
semi-confined aquifer conditions, the water will rise in the well above the
top of the more permeable layer and above the top of an improperly positioned
screen. Care must be exercised in these cases to extend the screen high enough
to be above the water level in the formation; otherwise, light organics or
other contaminants could be undetected or at least not properly quantified.
On the other hand, a contaminant can migrate along fairly restricted
pathways and go undetected by depth discrete wells which are not completed at
the proper depth. This danger is particularly present in a geologic environ-
ment of highly stratified formations, and in fractured rock formations.
Intake Portion of Monitoring Wells
That part of the well through which water enters the casing must be
properly constructed and developed to avoid subsequent sampling problems.
Commercially made well screens used in water-supply wells are recommended for
18
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most monitoring wells even though well efficiency is not a primary concern.
Other choices are sawed or torchcut slots in the well casing to let the water
flow in.
Design criteria for the intake part of the well are:
(a) The screen or intake part should have sufficient open area
to permit the easy inflow of water from the formation.
(b) The slot openings should be just small enough to keep most of
the natural formation out, but as large as possible to allow
easy flow of water.
(c) The well should be developed.
Well Casings
As noted earlier, sampling equipment, including well casings, should be
constructed of materials that have the least potential for affecting the
quality parameters of the sample. The usual dilemma for the field investigator
is the relation between cost and accuracy. Obviously, PVC is far less costly
than Teflon, a major consideration when contemplating well construction for a
major ground water monitoring effort. On the other hand, bleeding of organic
constituents from PVC cements, as well as adsorption, poses a significant
potential for affecting the quality of samples where the contaminants under
consideration may be in the parts per billion range.
In many situations, it may be realistic to compromise some accuracy with
cost, particularly in regard to casing materials used in well construction.
For example, if the major contaminants are already defined and they do not
include substances which might bleed from PVC or cemented joints, it might be
reasonable to use wells cased with the less expensive and readily obtainable
PVC. Or, wells constructed of less than optimum materials might be used with
a reasonable level of confidence for sampling if at least one identically-
constructed well was available in a nearby, uncontaminated part of the aquifer
to provide ground water samples for use as "blanks". Obviously, such a "blank"
will not address the problems of adsorption on the casing material nor leaching
of casing material induced by contaminants in the ground water. Careful con-
sideration is required in each individual case, and the analytical laboratory
should be fully aware of construction materials used.
Care must be given to preparation of the casing and well screens prior to
installation. As a minimum, both should be washed with a detergent and rinsed
thoroughly with clean water. Care should also be taken that these and other
sampling materials are protected from contamination by using some type of
ground cover such as plastic sheeting for temporary storage in the work area.
DRILLING METHODS
Selection of the drilling method best suited for a particular job is
based on the following factors in order of importance:
(1) Hydrogeologic Environment
(a) Type(s) of formation(s)
(b) Depth of drilling
(c) Depth of desired screen setting below water table
19
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(2) Types of pollutants expected
(3) Location of drilling site - dry land, or inside a lagoon
(4) Design of monitoring well desired
(5) Availability of drilling equipment
The principles of operation, advantages and disadvantages of the more
common types of drilling techniques suitable for constructing ground-water
monitoring wells are discussed as follows.
Mud Rotary
Principles of Operation: A drilling fluid is pumped down the inside of
the drill pipe, and then returns to the surface through the annulus between
the drill pipe and the borehole wall (Figure 8). This fluid cools the drill
bit, carries the cuttings to the surface, prevents excessive fluid loss into
the formation, and prevents the formation from caving. The rotating drill pipe
turns the bit which cuts the formation allowing the cuttings to be flushed out.
The drilling fluid may be clear water, water mixed with bentonite or
water mixed with a biodegradable organic "mud".
Mud rotary rigs are the most common rig available. Other types of drill-
ing rigs are, however, better suited for certain geologic environments and for
many water-quality sampling programs.
Advantages:
(1) Available throughout the U.S.
(2) Capable of drilling all formations, hard or soft.
(3) Capable of drilling to any depth desired for monitoring.
(4) Casing not required during drilling.
(5) Formation logging (sampling) is fairly reliable in most
formations.
(6) Relatively inexpensive.
Disadvantages:
(1) Drilling fluid mixes with formation fluid and is often
difficult to completely remove.
(2) Bentonite (if used to minimize fluid loss) will adsorb
metals and may interfere with some other parameters, thereby
making this drilling method (at least the use of bentonite
drilling mud) undesirable where metals are being sampled.
(3) Organic/biodegradable additives mixed with the water to
minimize fluid loss will interfere with bacterial analyses
and organic-related parameters.
(4) No information on the position of the water table, and only
limited information on water-producing zones is directly
available during drilling. Electric logging of rotary drilled
wells can substantially add to the accuracy of the driller's
log and to water-related information.
(5) Circulates contaminants.
20
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-Swivel
.Hose
Kelley
The drilling fluid (or water) is pumped through the swivel and down
through the kelley which is turned by the rotary table. The mud
then flows down through the drill pipe, out through the bit and
back up the hole carrying cuttings which settle out of the mud in
the first section(s) of the mud pit.
Figure 8. Mud Rotary Drilling
21
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Air Rotary
Principles of Operation: An air-rotary rig operates in the same manner
as a mud-rotary rig except that air is circulated down the drill pipe and
returns (bringing the cuttings) up the annulus. Some rotary rigs are equipped
to operate either with mud or air. Air rotary rigs are available throughout
much of the U.S. and are well suited for many ground-water quality programs.
Advantages:
(1) No drilling fluid is used, therefore, contamination or
dilution of the formation water is not a factor.
(2) Air-rotary rigs operate best in hard rock formations.
(3) Formation water is blown out of the hole along with the
cuttings, therefore, it is possible to readily determine
when the first water-bearing zone is encountered.
(4) Collection and field analysis (after filtering) of water
blown from the hole can provide enough information regarding
changes in water quality for some parameters such as
chlorides for which only large changes in concentration are
significant.
(5) Formation sampling ranges from excellent in hard, dry
formations to nothing when circulation is lost as in form-
ations such as some limestones or other formations with cavities.
(6) Air rotary rigs are common and readily available throughout
most of the U.S.
Disadvantages:
(1) Casing is required to keep the hole open when drilling in
soft, caving formations below the water table. This is often
a major disadvantage.
(2) When more than one water-bearing zone is encountered and
where the hydrostatic pressures are different, then flow
between the zones will occur between the time when the
drilling is done and the hole can be properly cased and one
zone grouted off.
Air Drilling with Casing Hammer
Principles of Operation: A top-head drive rotary rig can be modified to
accept a casing hammer. The method of drilling is the same as with air rotary
except that when caving formations are encountered the casing hammer drives the
casing down to prevent the hole from caving (Figure 9). The casing can be
driven without withdrawing the drill pipe. This drilling method is generally
excellent for constructing monitoring wells in unconsolidated formations.
Advantages:
(1) Same advantages as with standard air rotary drilling except that
soft, caving formations can be drilled.
(2) The use of casing minimizes flow into the hole from upper
water-bearing layers, therefore multiple layers can be
penetrated and sampled for rough field determinations of some
water quality parameters.
22
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Casing Hammer
in up (non-
driving)
position
Return Flow
(air and
formation
cuttings)
Power swivel
top-head drive
Drill Pipe
Casino
Casing Shoe
Drill Bit
An air drill with casing hammer operates like an air rotary drill except
that in caving formations the casing can be driven to hold the hole open.
The casing hammer is slipped down over the drill pipe and attached to the
top of the casing and by a hammering motion, drives the casing. Usually
the drill bit has drilled below the casing somewhat, but the casing shoe
cuts a larger hole than the drill bit and therefore has to be driven.
Figure 9. Air Drill with Casing Hammer
23
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Disadvantages:
(1) Air-rotary rigs with casing hc-mme'-" ?rs not in common use
throughout the Urn' tea States and ;r,3y be difficult to locate
in some areas.
(2) The cost per hour or per root is subst?ntir'ily hioher tha*'
other drilling methods,
(3) It is difficult to pull back the casing if it has been drivf
very deep - say deeper thar, 50 Teet I'M many formations,
Cable Tool
Principles of Operation: A CSCHP tool rig uses a heavy, solid- steel ,
chisel-type drill bit suspended on s. ';teei cable,, '.'hid1 when raised and
dropped chisels or pounds a hole tr.ro;, ;;r the soil? and rock (Figure 30).
drilling through the unsaturated -ar-:-f ' e--"-- v-t?r mvs-: be ad JOG to the he'c.
The cuttings are suspended in the water and then bailed out periodically,
After sufficient water is enteri'iq th- b^rfhole tn jppl^cc? tit? water :'?H;QW('
by bailing then no further water need b? added .
When soft caving formations are pncoMtaerea, it is necessary to drive
casing as the hole is advanced to prevent collaose of the hole. Often the
drilling can be only a few feet b<:-'kv/ in*- i'-jttom of the casing. Because the
drill bit is lowered through the casing, the hole created by the bit is
smaller than the casing. Therefore, the casing (with a sharp, hardened casing
shoe on the bottom) must be driven into the hole. The shoe in fact cuts a
slightly larger hole than the drill bit, TMs tioht- fitting drive shoe should
not, however, be relied upon to for,-! -< re-;i ' : fv.. ove- lying water-bearing zones
in water quality investigations,
Advantages:
(1) Formation samples can be exrel'Ierit with ;i skilled driller
using a sand-pump bailer1.
(2) Information regarding water-bearing zones is readily avail-
able during the drilling. Even relative permeabilities and
rough water quality o'atP fvorr; different /one? penetrated
can be obtained by ski fled --.petators.
(3) The cable- tool rig csn operat- satis fsctor-ily in all form-
ations, but is best suited fn; cavi'ig, large gravel type
formations or formatU"':; '^'n "r-re cavities above the wate>
table (such as limestones)
Disadvantages:
(1) Drilling is slow compared with rotary rigs.
(2) The necessity of driving the casing along with drilling in
unconsolidated formations reouires that the casing be
pulled back to expos? ^'-l-'L--" ^ter- bearing zones. This
process complicates the w:"!'i completion process and often
increases costs.
(3) The relatively large ;!'>?."::••••;?!•; >-eoi!ired (minimum of 4-inch
casing) plus the C^T; o. ..,:•." •• - -n '-e^ult in large costs
compared with rotsr;/ •. • '':'<.->,, ',;^ i/ivStiu tasing,
-------
Top Sheave
Stationary Sheave
Moving Sheave
Walking Beam
The cable tool (sometimes called churn drill or percussion drill)
operates as follows: Rotation of the crank gear causes the pitman
to raise and lower the walking beam which is anchored at the
stationary sheave end. The moving sheave end of the walking beam
moves up and down causing the wire rope passing over the top sheave
to alternately raise and lower the heavy drill stem and bit which
drills the hole. The bailer is used to remove cuttings, and the
casing is driven into the hole to prevent caving in soft formations.
Figure 10. Cable Tool Drilling
25
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(4) It is difficult to place a positive grout seal above the
drive shoe of the casing. Therefore, either the drive casing
must be totally removed and the seal placed around the
outside of an inner casing, or a seal must be placed above
the screen but below the drive shoe. Either procedure adds
to the cost and time of completion.
(5) Cable-tool rigs have largely been replaced by rotary rigs
in some parts of the U.S., hence availability may be
difficult.
Reverse Circulation
Principles of Operation: The common reverse-circulation rig is a water
or mud rotary rig with large diameter drill pipe and which circulates the
drilling water down the annulus and up the inside of the drill pipe (reverse
flow direction from direct mud rotary). This type of rig is used for the
construction of large-capacity production water wells and is not suited for
small, water-quality sampling wells.
Special Reverse Circulation
Principles of Operation: A few special reverse-circulation rotary rigs
are made with double-wall drill pipe. The drilling water or air is circulated
down the annulus between the drill pipes and up inside the inner pipe (Figure
11).
Advantages:
(1) The formation water is not contaminated by the drilling
water.
(2) Excellent formation samples can be obtained.
(3) When drilling with air, immediate information is available
regarding the water-bearing properties of formations pene-
trated.
(4) Caving of the hole in unconsolidated formations is not as
great a problem as when drilling with the normal air
rotary rig.
Disadvantages:
(1) Double-wall, reverse-circulation rigs are very rare and
expensive to operate.
(2) Placing cement grout around the outside of the casing above
the screen of the permanent well often is difficult -
especially when the screen and casing are placed down through
the inner drill pipe before the drill pipe is pulled out.
Solid-Stem Continuous-Flight Auger
Principles of Operation: Drilling is accomplished by rotating the solid
stem, continuous-flight augers into the soils. As the augers are "screwed"
into the soils, the cuttings are brought to the surface on the rotating
flights (Figure 12). Auger bits are essentially of two types: fish tail or
drag bits for use in unconsolidated materials, and claw or finger bits for
26
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DOUBLE WALL DRILL PIPE
FORMATION CUTTINGS
DRILL BIT
Air or drilling fluid is pumped down the annulus of the double-wall drill
pipe. Formation cuttings are brought up the inside of the inner pipe along
with the return air or fluid.
Figure 11. Special Reverse Circulation
27
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The continuous-flight auger bores into the soil and rotates the
cuttings upward along the flights. The uppermost cuttings are
discharged at the surface to make room for the space of the auger
as it penetrates additional soils.
Figure 12. Continuous Flight Auger Drilling
28
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use in more compacted, lithified or cemented soils. Once the desired depth
is reached, the augers are allowed to rotate to clean out the borehole. The
augers are then removed from the borehole and well screen and casing installed.
This method is best applied when installing monitor wells in shallow uncon-
solidated formations.
Advantages:
(1) The auger drilling rigs are generally mobile, fast and
inexpensive to operate in unconsolidated formations.
(2) No drilling fluid is used, therefore contamination problems
are minimized.
Disadvantages:
(1) Cannot be used in hard rock.
(2) Depth limitation varies with equipment and type of soils
but approximately 150 feet is maximum.
(3) Once the augers have been withdrawn, the degree to which
the borehole will remain open is dependent upon the degree
of soil consolidation and saturation. Most boreholes will
collapse below the water table.
(4) Formation samples may not be completely accurate.
(5) Depth to the water table may be difficult to determine
accurately in deep borings.
Hollow-Stem, Continuous-Flight Auger
Principles of Operation: This method differs from the solid stem augers
in that the stem is hollow. Upon reaching the desired depth, a small diameter
casing and screen can be set inside the hollow stem (Figure 13). The augers
are then pulled-out as the casing is held in place.
Advantages:
(1) The auger drilling rigs are generally mobile, fast, and
inexpensive to operate in unconsolidated formations.
(2) No drilling fluid is used, therefore contamination problems
are minimized.
(3) The problem of the hole caving in saturated, unconsolidated
material, as when the solid-stem, continuous-flight auger
is pulled out of the hole, is overcome by placing the
casing and screen down inside the hollow stem before the
augers are removed.
(4) Natural gamma-ray logging can be done inside the hollow
stem which permits defining the nature and thickness of the
formations penetrated.
(5) A grout seal can be placed around the permanent casing by
attaching a cement basket above the screen before setting
the assembly inside the hollow stem. Grout is placed in
the annul us between the casing and hollow stem and the
augers are pulled out. Grout is continuously injected or
placed until all augers are removed.
29
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rod inside hollow
stem for removing
plug
flight
removable plug
The hollow-stem, continuous-flight auger bores into soft soils carrying
the cuttings upward along the flights. When the desired depth is
reached, the plug is removed from the bit and withdrawn from inside the
hollow stem. A well point (1%-in. or 2-in.) can then be inserted to the
bottom of the hollow stem and the auger pulled out leaving the small-
diameter monitoring well in place.
Figure 13. Hollow Stem Auger Drilling
30
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Disadvantages:
(1) Cannot be used in hard rock.
(2) Depth limitation varies with equipment and type of soils but
approximately 150 feet is practical.
(3) Formation samples may not be completely accurate.
(4) Depth to the water table may be difficult to determine
accurately in deep borings.
Keck Screened, Hollow Stem, Continuous Flight AUger (14)
Principles of Operation: This method operates the same as the hollow-
stem augers except that the lead section incorporates a well screen (Figure
14).
Advantages:
(1) The auger drilling rigs are generally mobile, fast and
inexpensive to operate in unconsolidated formations.
(2) No drilling fluid is used, therefore contamination problems
are minimized.
(3) The problem of the hole caving in saturated, unconsolidated
material, as when the solid-stem, continuous-flight auger
is pulled out of the hole, is overcome by placing the
casing and screen down inside the hollow stem before the
augers are removed.
(4) Natural gamma-ray logging can be done inside the hollow
stem which permits defining the nature and thickness of the
formations penetrated.
(5) A grout seal can be placed around the permanent casing by
attaching a cement basket above the screen before setting
the assembly inside the hollow stem. Grout is placed in
the annul us between the casing and hollow stem and the
augers are pulled out. Grout is continuously injected or
placed until all augers are removed.
(6) Depth to water table can be accurately determined.
(7) Water samples can be collected at any desired depth below
the water table during the drilling operation without
removing the augers or setting a screen and casing.
Disadvantages:
(1) Cannot be used in hard rock.
(2) Depth limitation varies with equipment and type of soils
but approximately 150 feet is practical.
(3) Formation samples may not be completely accurate.
Bucket Auger
Principles of Operation: The bucket auger consists of a relatively large
(8-inch minimum diameter by 2 feet long) bucket with a cutting edge on the
bottom which is slowly rotated by a square, telescoping kelley or drill stem.
When the bucket fills with cuttings, it is brought to the surface and emptied.
This method is good for constructing shallow wells just into the water table
in unconsolidated formations.
31
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SCREEN
FLIGHT
KNOCK OUT PLUG
BIT
Figure 14. Keck Screened, Hollow Stem, Continuous Flight Auger
32
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Advantages:
(1) No drilling water is required when either drilling above the
saturated zone, or below the saturated zone in non-caving
formations.
(2) After the hole has been drilled, the setting of casing with
screen and grouting the outside of the casing to form a seal
is relatively easy.
(3) Formation sampling is excellent.
Disadvantages:
(1) The hole diameter is large, hence the annular space is large
when small diameter casing is used. This requires careful
grouting and backfilling to insure water sample integrity.
(2) In caving formations below the water table it is necessary to
continuously add water to prevent caving.
(3) Use of the bucket auger is restricted to soft formations and
depths less than about 50 feet.
(4) These rigs are not widely available.
Jetting
Principles of Operation: Jetting consists of pumping water or drilling
mud down through a small diameter (1% to 2-inch) standard pipe. The pipe
may be fitted with a chisel bit or a special jetting screen. Formation
materials dislodged by the bit and jetting action of the water are brought to
the surface through the annul us around the pipe. As the pipe is jetted
deeper, additional lengths of pipe may be added at the surface.
This method is acceptable in very soft formations, for shallow sampling,
and when introduction of drilling water to the formation is not a consider-
ation.
Advantages:
(1) Jetting is fast and very inexpensive.
(2) Because of the small amount of equipment required, jetting
can be accomplished in locations where it would be very dif-
ficult to get a normal drilling rig. For example, it would
be possible to jet down a well point in the center of a
lagoon at a fraction of the cost of using a drill rig.
(3) Jetting numerous well points just into a shallow water table
is an inexpensive method for determining the water table
contours, hence flow direction.
33
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Disadvantages:
(1) A large amount of foreign water or drilling mud is introduced
above and into the formation to be sampled.
(2) It is not possible to place a grout seal above the screen to
assure depth-discrete sampling.
(3) The diameter of the casing is usually limited to two inches
therefore, obtaining samples must be either by suction lift,
air lift, bailer, or other methods applicable to small diameter
casings.
(4) Jetting is only possible in very soft formations, and the
depth limitation is shallow - say 30 feet without special
equipment.
(5) Large quantities of water are often needed.
Use of Bore-Hole Geophysics
The use of geophysics can greatly enhance the amount of information
gained from a borehole (Figure 15). Each geophysical logging method is
designed to operate in specific borehole conditions, involves lowering a
sensing device into the borehole and can be interpreted to determine lithol-
ogy, geometry, resistivity, bulk density, porosity, permeability, moisture
content and to define the source, movement, chemical and physical character-
istics of ground water (5).
1. Spontaneous-Potential Log: These logs are records of the natural
potentials developed between the borehole fluid and the surrounding
rock/soil materials. The SP log is mainly used for geologic corre-
lation, determining bed thickness and separating non-porous from
porous rocks in shale-sandstone and shale-carbonate sequences. It
can be run only in open, uncased and fluid filled boreholes.
2. Normal Resistivity Logs: Normal logs measure the apparent resis-
tivity of a volume of rock/soil surrounding. The short normals
give good vertical detail and records the apparent resistivity of
the mud invaded zone. The long normals record the apparent
resistivity beyond the invaded zone. The radius of investigation
is generally equal to the distance between the borehole current
and measuring electrodes. These logs can be run only in open,
uncased and fluid filled boreholes.
3. Natural-Gamma Logs: Natural-gamma logs or gamma-ray logs are
records of the amount of natural-gamma radiation emitted by rocks/
soils. The main use of this logging method is for the identifi-
cation of lithology and stratigraphic correlation. These logs can
be run in open or cased, fluid or air filled boreholes. The radius
of investigation extends to about 6-12 inches of the borehole wall.
4. Gamma-gamma Logs: These logs record the intensity of gamma radiation
from a source in the probe after it is backscattered and attenuated
within the borehole and surrounding rocks/soil. The main uses of
gamma-gamma logs are for identification of lithology and measurement
of bulk density and porosity of rocks/soils. They are also used for
34
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I
SPONTANEOUS
POTENTIAL
RESISTIVITY
SHORT
LONG
GEOLOGIC
LOG
GAMMA
RAY
NEUTRON
CLAY
V SANO
FEW CLAY
LAYERS
(FRESH WATER)
SHALE
DENSE ROCK
LMS
SANDSTONE
SH LAYERS
(BRACKISH
WATER)
SHALE
FEW
SS LAYERS
SANDSTONE
(SALINE
WATER)
( WEATHERED)
DENSE
ROCK
PROBABLY
GRANITE
Figure 15. Comparison of Electric and
Radioactive Bore Hole Logs
35
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locating cavaties and cement outside the casing. The radius of
investigation is about 6 inches from the borehole wall. These logs
can be run in open or cased, fluid or air filled boreholes.
5. Caliper Log: A caliper log is the record of the average borehole
diameter. Its major use is to evaluate the environment in which
other logs are made in order to correct for hole-diameter effects.
They also provide information on lithology and borehole conditions.
Caliper logs can be run in fluid or air filled, cased or open bore-
holes.
6. Temperature Log: These logs provide a continuous record of the
fluid temperature immediately surrounding the probe. The data can
be interpreted to provide information on the source and movement
of ground water and the thermal conductivity of rocks/soils. Temp-
erature logs are best applied in fluid filled, open boreholes
although they can also be run in air filled and cased boreholes.
The zone of investigation is limited to that fluid immediately
surrounding the probe which may or may not be representative of the
temperature in the surrounding rocks/soils.
7. Fluid-Conductivity Logs: These logs provide a measurement of the
conductivity of the borehole fluid between the electrodes in the
probe. When properly corrected, they provide information on the
chemical quality of the borehole fluid. They are best applied in
open, fluid filled boreholes.
WELL DEVELOPMENT
Well development is the process of cleaning the face of the borehole and
the formation around the outside of the well screen to permit ground water to
flow easily into the monitoring well. During any drilling process the side
of the borehole becomes smeared with clays or other fines. This plugging
action substantially reduces the permeability and retards the movement of
water into the well screen. If these fines are not removed, especially in
formations having low permeability, it then becomes difficult and time con-
suming to remove sufficient water from the well before obtaining a fresh
ground-water sample because the water cannot flow easily into the well.
In the construction of high-capacity production type water wells, the
development process is an important step to assure maximum hydraulic efficiency.
Even though hydraulic efficiency is not a consideration in the construction
of monitoring wells, nevertheless, development should be performed.
Development is required for the following reasons:
(1) To restore the natural permeability of the formation adjacent
to the borehole to permit the water to flow into the screen
easily.
(2) To remove the clay, silt and other fines from the formation so
that during subsequent sampling the water will not be turbid or
contain suspended matter which can easily interfere with
chemical analysis.
36
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The development process is best accomplished for monitoring wells by
causing the natural formation water inside the well screen to move vigorously
in and out through the screen in order to agitate the clay and silt, and move
these fines into the screen. The use of water other than the natural forma-
tion water is not recommended.
Methods suitable for the development of monitoring wells are as follows:
(1) Surge block.
A surge block is around plunger with pliable edges such
as belting that will not catch on the well screen. Moving the
surge block forcefully up and down inside the well screen
causes the water to surge in and out through the screen accom-
plishing the desired cleaning action.
Surge blocks are commonly used with cable-tool drilling
rigs, but are not easily used by other types of drilling rigs.
(2) Air lift.
Compressed air pumped down a pipe inside the well casing
can be used to blow water out of the monitoring well. If air
is applied to the well intermittently and for short periods
then the water is only raised inside the casing rather than
blown out and will fall back down the casing causing the de-
sired back washing action. Finally, blowing the water out
will remove the fines brought into the screen by the agitating
action.
Considerable care must be exercised to avoid injecting
air into the well screen. Such air can become trapped in the
formation outside the well screen and alter subsequent chemical
analyses of water samples. For this reason, the bottom of the
air pipe should never be placed down inside the screen.
Another restriction on the use of air is the submergence
factor. Submergence is the feet of water above the bottom of
the air pipe while pumping (blowing water out) divided by the
total length of the air pipe. Submergence should be on the
order of at least 20 percent, which may be difficult to achieve
with many shallow monitoring wells.
(3) Bailer.
A bailer sufficiently heavy that it will sink rapidly
through the water can be raised and lowered through the well
screen. The resulting agitating action of the water is similar
to that caused by a surge block. The bailer, however, has the
added advantage of removing the fines each time it is brought
to the surface and dumped. Bailers can be custom-made for
small diameter wells, and can be hand-operated in shallow wells.
(4) Surging by pumping.
Starting and stopping a pump so that the water is alter-
nately pulled into the well through the screen and backflushed
through the screen is an effective development method. Periodi-
cally pumping to waste will remove the fines from the well and
permit checking the progress to assure that development is
complete.
37
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In conclusion, development of monitoring wells, although often overlooked,
is an important function of the well construction in order to facilitate
future sampling and to obtain samples free of turbidity,
MULTIPLE-COMPLETION SAMPLING WELLS
Most ground water pollution is relatively shallow and affects the first
and sometimes the second permeable layers. Conventional wells completed in
specific permeable layers are constructed so that each well is depth-specific.
Occasionally, it is desired to sample numerous permeable layers at con-
siderable depth, perhaps at a few hundred feet. If, for example, it is
desired to define the bottom of the pollution plume and then to periodically
sample the lower-most contaminated layer, a cemented and gun-perforated well
can be constructed. Or, if permanent monitoring in several deep layers is
required such as for underground injection wells, then the permanent type
multiple-completion well should be considered.
Figure 16 illustrates the construction of a gun-perforated well. This
type of well is commonly drilled and logged to define the depth of all the
permeable layers. Then casing is installed with centralizers and cement
grout is placed in the annulus from the bottom up to surround the casing.
The grout prevents intercommunication between permeable layers along the
outside of the casing.
The casing is then perforated opposite the bottom-most permeable layer.
Water from this layer is pumped out, sampled, and analyzed and the static
level is measured. If no contaminants are present, then cement grout is
pumped through a tremie pipe to fill the inside of the casing up past the
perforations thereby permanently sealing that zone. The second zone from
the bottom may then be perforated, sampled, and sealed if no contaminants
are found. This procedure may be repeated until contaminants are observed at
which time the well may be left to periodically monitor that layer, or plugged
and upper layers sampled.
Care must be exercised to assure that sufficient water is pumped from
the layer being sampled and that the sample is representative of the formation
water before that layer is plugged. This approach is not recommended when
the pollutants are reactive with cement.
Figure 17 depicts another alternative for constructing a multiple-
completion monitoring well. This approach provides for periodic sampling and
permanent monitoring of each permeable layer screened rather than one-time
sampling as shown in Figure 16. However, because of construction difficulties
it is rarely practical to monitor at more than three depths in a well. The
approach shown in Figure 16, on the other hand, permits sampling as many
layers as desired, but all layers cannot be permanently monitored.
The construction of a multiple-completion monitoring well as shown in
Figure 17 is difficult from the standpoint of lowering the various components
in the hole simultaneously. The drilling contractor must plan and execute
38
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orehoie
casing
cement grout
layer open for testing
layers perforated,
tested, and plugged
The entire casing is surrounded by cement grout to prevent interconnection
between permeable layers. Starting at the bottom, each layer is
perforated, sampled as often as warranted, then plugged on the inside
of the casing before the next layer is perforated. This procedure
permits vertical delineation of the contaminant plume in deep aquifer
systems at minimum cost.
Figure 16. Multiple Completion Well,
for One-Time Sampling
39
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Tremie pipe, withdrown
after use
Ci-'jfr-i
Permanent
casings
-Cement grout
'Sand Pack
Screened
Intervals
A.
B.
C.
Permanent casino and
screen sufficiently
large to accept
periodically installed
pump.
(3~ in. minimum for
submersible)
Permonent cosing for
air lift pumping.
i 2- inch minimum)
Permanent casing with
permanetly installed
submersible pump in
screen cage-
submersible pump
•well screen
A multiple completion sampling well may be completed with pumping arrangements
of A, B, or C. The sand pack material and cement grout are placed from the
bottom up through the tremie pipe as the pipe is pulled out.
Figure 17. Multiple Completion Well,
for Periodic Sampling
40
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this work carefully to be successful. The tremie pipe, commonly a 2-inch
pipe, is lowered into the hole along with the other pipes. Sand is pumped
through the tremie pipe to place the sand pack at the desired depths, and
cement grout is also pumped through the tremie to place the grout seals. A
wash plug and clear water can be pumped through to clean the grout out of
the pipe before the next layer of sand is placed. Or, in some cases, it may
be more feasible to use two tremie pipes, one for sand and one for cement
grout. In either case careful measurements are required to place the sand
and grout from the bottom up as the tremie pipe is withdrawn.
After the well is completed, each screened layer should be pumped thor-
oughly to remove the effects of foreign water in the formation due to
drilling, flushing, and placement of sand grout.
Several optional methods for constructing multiple-completion wells are
available. Option "A", Figure 17, utilizes two or three 3-inch or larger
casings from each screen depth all the way to ground surface. In addition
the temporary tremie pipe must be installed thereby requiring a hole diameter
of at least 11 to 12 inches. This option has the advantage of using one
pump, which is installed as required in each casing.
Option "B", Figure 17, is the least expensive. An 8-inch hole is probably
sufficient diameter for the installation of three permanent 2-inch casings
plus the tremie pipe. Conceivably it may be feasible to install more than
three permanent casings in a larger diameter hole, however, the difficulties
in handling the materials during installation become greater. The disadvan-
tage of the 2-inch casings is the limitation on pumping. If the layers to
be sampled are highly permeable then the time required to remove invaded water
from the formations becomes excessive due to the pumping limitation imposed
by the small casing. Also with 2-inch casings, specialized pumping systems
are required which may not be desirable considering either the aquifer char-
acteristics or the nature of the pollutants.
Option "C", Figure 17 utilizes a permanently-installed submersible pump
in a well-screen cage set at each layer to be sampled. Each pump discharges
through a 2-inch pipe to the surface. Foot valves are removed from the pumps
to permit static water levels to be measured. This approach has the advantage
of using submersible pumps for sampling highly permeable layers with deep
static levels, yet keeping the diameter of the hole smaller than that required
for Option "A". The maximum installed diameter would be the OD of the screen
(4-inches), plus two 2-inch discharge pipes, plus the 2-inch tremie pipe;
therefore, installation into a 9 or 10 inch hole should be feasible. Instal-
lation of this system is complicated, however, by the electric wiring that
must be installed to operate each pump. A disadvantage is the questionable
life-expectancy of the pumps; they cannot be replaced if they fail.
With any type of multiple completion well in which more than one discrete
depth can be sampled at any one time there is always the question of hydraulic
intercommunication between layers via the well. A possible test to evaluate
this potential is to measure the static levels in each casing, pump one of
the monitoring wells, and if the water levels in the other monitoring wells
41
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do not draw down, then intercommunication is probably not a factor.
Because of the intercommunication potential and because of the difficul-
ties in construction, the use of multiple completion wells should be avoided
except where this approach is significantly more cost-effective than individ-
ual wells.
42
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SECTION 6
COLLECTION OF GROUND WATER SAMPLES
GENERAL REQUIREMENTS
The importance of proper sampling of wells cannot be overemphasized.
Even though the well being sampled may be correctly located and constructed,
special precautions must be taken to ensure that the sample taken from that
well is representative of the ground water at that location and that the
sample is neither altered nor contaminated by the sampling and handling pro-
cedure.
To obtain a representative sample of the ground water it must be under-
stood that the composition of the water within the well casing and in close
proximity to the well is probably not representative of the overall ground
water quality at that sampling site. This is due to the possible presence of
drilling contaminants near the well and because important environmental con-
ditions such as the oxidation-reduction potential may differ drastically near
the well from the conditions in the surrounding water bearing materials. For
these reasons it is highly desirable that a well be pumped or bailed until
the well is thoroughly flushed of standing water and contains fresh water
from the aquifer. The recommended length of time required to pump or bail a
well before sampling is dependent on many factors including the characteristics
of the well, the hydrogeological nature of the aquifer, the type of sampling
equipment being used, and the parameters being sampled. The time required
may range from the time needed to pump or bail one bore volume to the time
needed to pump several bore volumes. A common procedure is to pump or bail
the well until a minimum of four (4) to ten (10) bore-volumes have been re-
moved. '
Other factors which will influence the time required to flush out a well
before sampling include the pumping rate and the placement of the pumping
equipment within the column of water in the well bore. Care should be taken
to ensure that all of the water within the well bore is exchanged with fresh
water. For example, recent studies have shown that if a pump is lowered
immediately to the bottom of a well before pumping, it may take some time for
the column of water above it to be exchanged if the transmissivity of the
aquifer is high and the well screen is at the bottom of the casing (6) (7).
In such cases the pump will be pumping primarily water from the aquifer.
Gibb notes that removing all water from the well bore is only possible if the
well is pumped dry and suggests two alternative approaches: (a) monitor the
water level in the well while pumping. When the water level has "stabilized"
most if not all of the water being pumped is coming from the aquifer.
43
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(b) Monitor the temperature and pH of the water while pumping. When these
two parameters "stabilize" it is probable that little or no water from
casing storage is being pumped (7).
Specific details regarding the type of sampling equipment required for
specific chemical and biological parameters are discussed in detail in the
following sections. The sampling equipment used must not alter or contaminate
the sample. For example, if the sample is to be analyzed for trace organic
chemicals, special care must be taken since such sampling equipment as convc.-.
tional oil-lubricated pumps, tygon, and rubber tubing can be serious sources
of contamination. However, such equipment is usually satisfactory for sampling
for many other parameters. Sterile sampling gear may be essential for bio-
logical monitoring. In each case the selection of sampling equipment will be
dependent on the nature of the parameters of interest.
Interest in ground-water quality monitoring has recently been increasing
at an exponential rate and significant advances in the sampling state-of-the-
art will undoubtedly follow. For this reason and because the authors may
be unaware of some very effective alternatives, identification of equipment by
specific manufacturers has been avoided in most cases.
WITHDRAWING SAMPLES
This section is primarily concerned with the collection of water samples
from the saturated zone of the subsurface. The type of system used is a
function of the type and size of well construction, pumping level, type of
pollutant, analytical procedures and presence or absence of permanent pumping
fixtures. Ideally, sample withdrawal mechanisms should be completely inert;
economical to manufacture; easily cleaned, sterilized and reused; able to
operate at remote sites in the absence of external power sources; and capable
of delivering continuous but variable flow rates for well flushing and sample
collection.
Most water supply wells contain semi-permanently mounted pumps which limit
the options available for ground water sampling. Existing in-place pumps may
be line shaft turbines, commonly used for high capacity wells, submersible
pumps very commonly used in domestic wells for high-head, low capacity appli-
cations, and more recently for municipal and industrial uses, and jet pumps
commonly used for shallow, low capacity domestic water supplies. The advantage
of in-place pumps are that water samples are readily available and non-
representative stagnant water in the well bore is generally not a problem. The
disadvantages are that excessive pumping can dilute or increase the contaminant
concentrations from what is representative of the sampling point, that water
supply wells may produce water from more than one aquifer, and contamination
and/or adsorption may be a problem when sampling for organics.
The advantage to collecting water samples from monitoring wells without
in-place pumps is in the flexibility of selecting equipment and procedures.
The principal disadvantage is the possibility of a non-representative sample
either through collecting stagnant water that is in the well bore or introducing
contamination from the surface by the sampling equipment or procedures. Some
commonly used systems are described below:
44
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Bailers
One of the oldest and simplest methods of sampling water wells is the use
of bailers. A bailer may be in the form of a weighted bottle or capped length
of pipe on a rope or some modification thereof which is lowered and raised
generally by hand. Two examples are represented in Figures 18 and 19. The
modified Kemmerer Sampler is often used for sampling surface waters as well
as ground waters. The Teflon bailer was developed specifically for collecting
ground water samples for volatile organic analysis.
Advantages:
(1) It can be constructed from a wide variety of materials
compatible with the parameter of interest.
(2) Economical and convenient enough that a separate bailer may
be dedicated to each well to minimize cross contamination.
(3) No external power source required.
(4) Low surface to volume ratio reduces outgassing of volatile
organics
Disadvantages:
(1) Sometimes impractical to evacuate stagnant water in a well
bore with a bailer.
(2) Transfer of water sample from bailer to sample bottle can
result in aeration.
(3) Cross-contamination can be a problem if equipment is not
adequately cleaned after each use.
Suction Lift Pumps
There are a variety of pumps available that can be used when the water
table is within suction lift, i.e., less than about 20 feet. Centrifugal
pumps are the most commonly available, are highly portable and have pumping
rates from 5 to 40 gpm. Most of these require a foot-value on the end of the
suction pipe to aid in maintaining a prime.
Peristaltic pumps are generally low-volume suction pumps suitasle for
sampling shallow, small diameter wells. Pumping rates are generally low but
can be readily controlled within desirable limits. One significant limitation
is the low pumping rates used initially to flush out the well bore. Another
limitation is that electrical power is required. Hand operated diaphragm
pumps are available that can be operated over a wide range of pumping rates
which facilitates rapid evacuation of a well bore initially and lower con-
trolled pumping rates for subsequent sampling. One major advantage is
portability.
Advantages:
(1) Generally, suction lift pumps are readily available, relatively
portable, and inexpensive.
Disadvantages:
(1) Sampling is limited to ground water situations where water
levels are less than about 20 feet.
45
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Figure 18. Modified Kenmerer Sampler (2)
46
-------
4-4
_LL
NICKEL WIRE
CABLE
I-1/4" 0.0. x I 1.0. TEFLON
EXTRUDED TUBING,
18 TO 36" LONG
DIAMETER
GLASS MARBLE
l" DIAMETER TEFLON
EXTRUDED ROD
DIAMETER
HOLE
Figure 19. Teflon Bailer (14)
47
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(2) May result in degassing and loss of volatile compounds.
Portable Submersible Pumps
Ground water investigations routinely require the collection of samples
from depths which often exceed the limitations of conventional sampling equip-
ment. One such system consists of a submersible pump which can be lowered or
raised in an observation well, using 300 feet of hose that supports the weight
of the pump, conveys the water from the well, and houses the electrical cabl=
and an electrical winch and spool assembly. A portable generator provides
electricity for both the pump and the winch and the entire assembly can be
mounted in a pickup or van (8).
Advantages:
(1) Portable. Can be used to sample several monitoring wells in a
brief period of time.
(2) Dependent upon size of pump and pumping depths, relatively
large pumping rates are possible.
Di sadvantages:
(1) Submersible pumps currently available require a minimum well
casing inside diameter of three inches.
(2) Requires the services of a relatively large service-type
vehicle - either a van or truck.
(3) With conventional construction materials, it is not suitable
for sampling for organics.
Air-Li ft Samplers
There are a number of adaptations to the basic method of applying air
pressure to a water well to force a water sample out the discharge tube.
A high-pressure hand pump and any reasonably flexible tubing can be used as a
highly portable sampling unit. A small air compressor and somewhat more
elaborate piping arrangements may be required at greater depths as shown in
Figure 20. The primary limitation to this sampler is the potential alteration
of water quality parameters, the amount of air pressure that can be safely
applied to the tubing and finding a suitable source of compressed air.
Advantages:
(1) Can be used as portable or permanently installed sampling
system.
(2) Can be used to both pre-pump and sample.
Disadvantages:
(1) Not suitable for pH sensitive parameters such as metals.
(2) If air or oxygen is used, oxidation is a problem.
(3) Gas stripping of volatile compounds may occur.
Nitrogen Powered, Continuous Delivery, Glass-Teflon
With the interest in sampling ground water for trace organic pollutants
has come the need for a noncontaminating, nonadsorbing pump for collecting
48
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Discharge
Needle valve
Pressure gauge
Quick air hose
coupler
Ground surface
/8 non-collapsing tubing
iVor 11/2 plastic
Figure 20. Air-Lift Sampler (2)
49
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samples below the suction lift. Based on an initial design by Stanford
University, Rice University has developed a ground water sampling system con-
sisting of a two stage all-glass pump connected by Teflon tubing and powered
by nitrogen gas. The system contains four basic units as shown in Figure 21:
(1) a two-stage glass pump, (2) solenoid valve and electronic timer, (3)
nitrogen tank and regulator, and (4) columns for organic removal from the
ground water.
Advantages:
(1) Portable-ac power not required.
(2) Constructed of noncontaminating, nonadsorbing materials.
(3) Variable flow rates up to 45 gals/hr are obtainable.
(4) Can be used in well casings with minimum diameters of about
two inches.
Disadvantages:
(1) Requires high purity nitrogen gas.
(2) Glass construction is somewhat more fragile than other materials,
(3) Stripping of CCL from water may be a problem for pH sensitive
parameters.
(4) Gas stripping of volatile compounds may occur.
Gas-Operated Squeeze Pump
These systems consist principally of a collapsible membrane inside a
long, rigid housing, compressed gas supply and appropriate control valves.
When the pump is submerged, water enters the collapsible membrane through the
bottom check valve. After the membrane has filled, gas pressure is applied
to the annular space between the rigid housing and membrane, forcing the water
upward through a sampling tube. When the pressure is released, the top check
valve prevents the sample from flowing back down the discharge line, and water
from the well again enters the pump through the bottom check valve (10). A
diagram of the basic unit is shown in Figure 22.
Advantages:
(1) Wide range in pumping rates are possible.
(2) Wide variety of materials can be used to meet the needs of the
parameters of interest.
(3) Driving gas does not contact the water sample, eliminate
possible contamination or gas stripping.
(4) Can be constructed in diameters as small as one inch - permits
use of small economical monitoring wells.
(5) Highly portable.
Disadvantages:
(1) Large gas volumes and long cycles are necessary for deep
operation.
(2) Pumping rates cannot match rates of submersible, suction or
jet pumps.
(3) Commercial units relatively expensive - approximately $1000
for units currently available.
50
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H20|
Thick Wall Gloss
Diameter 1.5"
Length 17"
H,0
TOP
PUMP
BOTTOM
PUMP
t influent Wafer f
Figure 21. Nitrogen Powered, Glass-Teflon Pump (9)
51
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AIRLINE
CHECK VALVE
•1"PVC PIPE
FLEXIBLE
DIAPHRAM
CHECK VALVE
t
Figure 22. Gas-Operated Squeeze Pump (7) (10)
52
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Gas-Driven Piston Pump
A modification of pumps developed by Bianchi (11) and Smith (12) has been
reported by Signor (13) for collecting samples from wells of two-inch or
larger diameter. The pump is a double-acting piston type operated by com-
pressed gas (Figure 23). The driving gas enters and exhausts from the gas
chambers between the two pistons and the intermediate connector that joins
them. Built-in check valves at each end of the pump allow water to enter the
cylinders on the suction stroke and to be expelled to the surface on the
pressure stroke. Present designs are constructed basically of stainless steel,
brass and PVC. Pumping rates vary with the pumping head but pumping rates of
2.5 to 8 gallons/hour have been noted at 100 feet of pumping head.
Advantages:
(1) Isolates the sample from the operating gas.
(2) Requires no electrical power source.
(3) Operates continuously and reliably over extended periods of time.
(4) Uses compressed gas economically.
(5) Can be operated at pumping heads in excess of 500 meters.
Disadvantages:
(1) Relatively expensive - in excess of $3000 for the continuously
operating unit.
(2) Particulate material may damage or inactivate pump unless the
suction line is filtered.
(3) Low pumping rates.
Special Sampling Considerations For Organic Samples (3) (14)
Sampling for organic parameters is a new and in no way, a routine proce-
dure at this time. The equipment and methods in current use are largely in
the research state. The concepts are fundamental, however, and any particular
item can be modified to suit actual field needs. Furthermore, these rather
expensive and sophisticated procedures may not be necessary for sampling or
monitoring all areas. New techniques and materials are continuously being
examined, which in turn should lead to the development of more sophisticated
yet more economical sampling methods. The points that must be kept in mind
include the potential for sample contamination and the extremely fine detail,
subject to expert rebuttal, that may be necessary in a legal action.
Grab Samples--
Grab samples of ground water for non-volatile organic analysis may be
collected by utilizing the system shown in Figure 24 where the sampled water
contacts only sterile glass and Teflon, and the water table is within suction
lift. The sampled water is then carefully transferred to appropriate glass
sample containers for shipment to the laboratory.
For sampling at depths beyond suction lift, a noncontaminating submersible
pump should be used to pump the ground water to the surface, through scrupu-
lously cleaned Teflon tubing, directly into appropriate sample containers.
53
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Exhaust
Outflow
Piston
Pump
p'essure
from Surface
Viiot Operator
Normal Position
iroted Position
Pilot Volve
P'J, p.' " Pressure
- Exhaust
Needle Valve
Restriction
Switching Unit
P - Pressure
E - Exhaust
Switching
Unit Spindle
"o"-Ring seals
during up cycle
0 -Ring seals
during down cycle
T Needle Volve
^Restriction
Suctien
Figure 23. Gas-Driven Piston Pump (13)
54
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TEFLON CONNECTOR
6 MM 1.0.
.GLASS TUBING
6 M M 0.0.
TEFLON TUBING
6 MM OD.
WELLCASING
1-LITER ERLENMEYER
Figure 24. System for Grab Sampling (3)
TYGOH
TUBiNG
OUTLET
PERISTALTIC
PUMP
55
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The most commonly employed sample containers are 40 ml glass vials for
analyses requiring small sample volumes, such as total organic carbon, and
one-gallon jugs for analyses requiring relatively large volumes, such as
extractable organics. Both types of containers are equipped with Teflon-
lined screw caps. Like all glassware used in the sampling and analytical pro-
cedures, sample containers are thoroughly cleaned prior to use by washing
with detergent, rinsing extensively with tap water followed by high purity
deioniied water and heating to 560° for two hours.
Grab samples of ground water to be analyzed for highly volatile organics
by the Bellar-Lichtenberg volatile organic analysis (VOA) method (15) are
usually obtained by means of a Teflon bailer noted in Figure 18. Use of the
systems described previously is less desirable than bailers for VOA samples
because of possible stripping of highly volatile constituents from the sample
under the reduced or elevated pressure occurring in systems using pumps.
Continuous Procedures--
Continuous procedures, using selected adsorbents to concentrate and recover
organic constituents from relatively large volumes of ground water, may be
employed for sampling organic pollutants in situations where the analytical
sensitivity and sample uniformity attainable by grab sampling are inadequate.
These procedures are applicable for most organic pollutants except those of
very high volatility.
A special sampling system is shown in Figure 25 in which the water is
pumped directly from the well through Teflon tubing (6 mm O.D.) to two glass
columns of adsorbent in series. In this illustration, a peristaltic pump is
located on the outlet side of the columns for sampling with suction lift. A
noncontaminating submersible pump may be used at greater depths and may be
superior for practically all sampling uses. All components of the systems
that contact the water sample prior to emergence from the second column are,
with the exception of the adsorbent, glass or Teflon. Figure 26 shows a
typical sampling system installed in specially constructed housings to form
self-contained sampling units, which are easily transported and set up in the
field.
Columns prepared from macroreticular resins, activated carbon, and poly-
amide particles have been employed in sampling systems. Of these materials,
macroreticular resin (XAD-2, Rohm and Haas Company, Philadelphia, Pennsylvania)
has been the most convenient and generally useful and is the current adsorbent
of choice.
Sampling is conducted by continuously pumping ground water through the
sampling systems at flow rates usually ranging from 10 to 30 ml/min. The
volumes sampled are dependent on the desired sensitivity of analysis. For
analysis by modern gas chromatographic techniques, sampling of 50 liters of
water is sufficient to provide a sensitivity of at least one yg/liter (1 ppb)
for almost all compounds of interest. Volumes sampled are determined by
measuring the water leaving the sampling systems in calibrated waste receivers.
56
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GLASS TUBING
6 M M 0.
TEFLON
CONNECTO
"TEFLON TUBING
6MM O.D.
WELL
CASING
TO WASTE
RECEIVER
PERISTALTIC
PUMP
Figure 25. Continuous Sampling System for Organics (3)
57
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Figure 26. Self-Contained Sampling Unit
for Organics (14)
58
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Volatile Organics In The Unsaturated Zone (3)--
For investigations pertaining to organic pollution of ground water, it is
often desirable to sample water in the unsaturated zone to detect and follow
the movement of pollutants that are migrating toward the water table. This
is a particularly difficult task in the case of highly volatile compounds,
including the low molecular weight chlorinated hydrocarbons such as trichloro-
ethylene. A number of these compounds are widely used and released into the
environment in significant quantities, exhibit some form of toxicity, partic-
ularly carcinogenicity, and are being increasingly implicated in cases of
ground water pollution.
Soil-water samples may be collected using the device depicted in Figure
27, which consists of a sampler, a purging apparatus, and a trap connected to
sources of nitrogen gas and vacuum. The soil-solution sampler consists of a
7/8 in. O.D. (2.2 cm) porous ceramic cup, a length of 3/4 in. O.D. Teflon or
PVC pipe and a Teflon stopper fitted with 3 mm O.D. Teflon exhaust and col-
lection tubes. The length of the pipe is dictated by the depth of sampling
desired, which is limited to a maximum of about 20 feet. The device is
basically a suction lysimeter and, consequently, suffers from the limitations
of such equipment.
The purging apparatus and trap are parts of the Tekmar LSC-1 liquid-sample
concentrator to which have been added Teflon valves and "Tape-Tite" connectors.
The purging apparatus is borosilicate glass, while the trap consists of Tenax-
GC porous polymer (60/80 mesh), packed in a 2 mm x 28 cm stainless steel tube
plugged with si lane-treated glass wool. The purge gas is ultra high purity,
oxygen-free nitrogen. Vacuum is provided by a peristaltic pump.
Prior to sample collection, the purging apparatus is cleaned with acetone
and distilled water and then baked at 105 to 108° for at least an hour. In
the field, it is rinsed thoroughly with distilled water between samples with
special care being exercised to force the rinse water through the glass frit.
The soil-solution sampler is driven to the bottom of a pre-augered 19 mm
(0.75 in) diameter hole. This is done very carefully to insure intimate con-
tact between the ceramic cup and the soil.
Prior to collection of a sample, the exhaust tube is opened to the atmos-
phere and the collection tube disconnected and pumped to remove any solution
tnat Tiay have leaked into the tube through the porous cup. Then, the collection
tube is reconnected to the purging aparatus, the exhaust tube closed with a
pinch clamp, and 5 to 10 ml of solution is collected by closing valve C and
ooening valves A and B (Figure 27). After sample collection, the exhaust tube
is opened to remove from the sampler and collect on the trap any of the com-
pounds that may have volatilized in the sampler. Following this procedure, A
is closed and C opened. Nitrogen gas is then bubbled through the solution at
a rate of 40 ml/min for ten minutes to purge volatile organics from solution.
iraos are capped and returned to the laboratory for analysis within six hours
of collection or for storage at -20°C for later analysis. Chemical concentra-
tions are determined according to procedures based on the method of Bellar
and Lichtenberg.
59
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TRAP
CD
o
EXHAUST
TUBE
SOIL SOLUTION
SAMPLER
PURGING
APPARATUS
TO Na
SUPPLY
i=^s—VAC u UM
Figure 27. Soil-Water Sampling Device for Volatile Organics (3)
-------
:IELD TESTS AND PRESERVATION
Type of information required and its intended use determines the field
analyses and sample preservation necessary. Because of the slow rate of change
in many parameters, it is often possible to establish ground water quality by
collecting samples in the field and transporting to a laboratory for subsequent
analyses. As noted earlier, other parameters may change very rapidly when the
sample is removed from its natural subsurface environment into another environ-
ment of different temperature, pressure, light, substrate or oxygen conditions.
Samples should be preserved at low temperatures in the dark during trans-
port to the laboratory for analysis. Appropriate chemical preservation should
be performed in the field for various analytical parameters at the time of
sampling. Regardless of the method of preservation, analyses should be per-
formed as soon after sampling as is practicably possible in accordance with
EPA and Standard Methods holding times.
Inorganic and Routine Organic Chemical Parameters (16)
Complete and unequivocal preservation of samples is a practical impossi-
bility. 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.
Methods of preservation are generally limited to pH control, chemical
addition, refrigeration, and freezing and are intended generally to (1) retard
biological action, (2) retard hydrolysis of chemical compounds and complexes
and (3) reduce volatility of constituents. Various preservatives that may be
used to retard changes in samples are as follows:
Preservative
Acid (HNCL)
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, phos-
phorus forms
Metals
Organic samples
(COD, oil and
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.)
61
-------
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, sample volumes required, type of
sample container, and holding time for various constituents is given in Table
1 which is taken from USEPA recommended methods for chemical analysis (2).
Organic Parameters
Because organic analyses are tedious, time-consuming and require sophis-
ticated laboratory equipment, all ground water samples should be transported
to a laboratory for analysis. Small grab samples should be quick-frozen on dry
ice, with care being exercised to allow adequate space in the container for
expansion during freezing. For large samples, containers should be topped-off
to exclude air, packed in ice, and shipped to the laboratory as soon as possible.
Frozen samples can be stored at -40°C until analyzed; analysis of unfrozen
samples should be initiated immediately upon arrival at the laboratory.
Grab samples to be analyzed for highly volatile organics and collected by
the sterilized Teflon bailer, should be carefully poured from the bailer into
clean serum bottles or screw-cap vials of appropriate size (usually 40 - 125 ml),
avoiding turbulence, which might result in the loss of volatile organics and/or
excessive oxygenation of the samples. The containers should be topped-off to
avoid gas space and tightly closed with Teflon-lined septums held in place by
aluminum crimp-on seals or open top screw caps. The sealed VOA samples are
packed in ice and returned to the laboratory for analysis at the earliest con-
venient time.
When sampling is completed with resin columns, the columns should be
sealed while completely filled with sample water and the sampling units should
be immediately returned to the laboratory for disassembly and elution of the
accumulated organic pollutants from the adsorbent. Similarly prepared columns
should be processed along with the sampling columns to provide blank extracts
for quality control. Although not absolutely necessary, columns should be kept
cool by refrigeration or icing during transit when possible (3).
Microbiological Parameters
Collection of ground water samples for microbiological analyses involves
the same general considerations as for obtaining samples for chemical analyses,
but also involves the special considerations to ensure representative, uncon-
taminated samples.
The proper collection, preservation, storage and analysis of water samples
for microbiological parameters is explained in other publications (15), (16),
(17), (18) which should also be consulted. For bacteriological analyses sample
bottles must be at least 125 ml volume for adequate sampling and for good
mixing, must be sterilized and must be chemically clean. Wide-mouth boro-
silicate glass bottles with screw-cap or ground-glass stoppers or heat-resistant
plastic bottles are recommended if they do not produce toxic or nutritive
62
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TABLE 1. RECOMMENDATION FOR SAMPLING AND PRESERVATION
OF SAMPLES ACCORDING TO MEASUREMENT ia/
Measurement
Physical
Properties
Color
Conductance
Hardness
Odor
pH
Residue
Fi ° ierable
Non-
mtarable
" C.1 1 3 ]
'/ '• i o t i 1 e
.'."sttleabl e Matter
Temperature
Turbidity
ft-cals
u~: ssc'ived
jiisperded
T i •• i T
Vol.
Req.
(ml)
50
100
100
200
25
100
100
100
100
1000
1000
100
200
200
100
(b)
Container v ' Preservative
P,G Cool, 4°C
P,G Cool, 4°C
P,G Cool, 4°C
HN03 to pH<2
G only Cool, 4°C
P,G Det. on site
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 Det. on site
P,6 Cool, 4°C
P,G Filter on site
HN03 to pH<2
Filter on site
P,G HN03 to pH<2
Holdina »
Timetcj
24 Hrs.
t*i * .1 \ G /
t$ Hrs. '
6 Mos. ^
24 Hrs.
6 Hrs.
7 Days
7 Days
7 Days
7 Days
24 Hrs.
No Holding
7 Days
6 Mos. ^e'
6 Mos.
6 Mos>!
(continued)
63
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TABLE 1. (continued)
Measurement
Mercury Dissolved
Total
Inorganics, Non-Metal
Acidity
Alkalinity
Bromide
Chloride
Chlorine
Cyanides
Fluoride
Iodide
Nitrogen
Ammonia
Kjeldahl, Total
Nitrate plus Nitrite
Nitrate
Nitrite
Vol.
Req.
(ml)
100
100
lies
100
100
100
50
200
500
300
100
400
500
100
100
50
Container^ '
P,G
P,G
P,G
P,G
P,G
P,G
P,G
P,G
P,G
P,G
P,G
P,G
P,G
P,G
P,G
Preservative
Filter on site
HN03 to pH<2
HN03 to pH<2
None Req.
Cool, 4°C
Cool, 4°C
None Req.
Det. on site
Cool , 4°C
NaOH to pH 12
None Req.
Cool, 4°C
Cool, 4°C
H2S04 to pH<2
Cool, 4°C
H2S04 to pH<2
Cool , 4°C
H2S04 to pH<2
Cool, 4°C
Cool, 4°C
Holding >
Timetcj
38 Days
(Glass)
13 Days
(Hard
Plastic)
38 Days
(Glass)
13 Days
(Hard
Plastic)
24 Hrs.
24 Hrs.
24 Hrs.
7 Days
No Holding
24 Hrs.
7 Days
24 Hrs.
24 Hrs.
24 Hrs/f'
24 Hrs/f'
24 Hrs.
48 Hrs.
(continued)
64
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TABLE 1. (continued)
Vol.
Req.
Measurement (ml)
Dissolved Oxvaen
°r>ve " 300
Winklc-r 300
Phosphorus
Ortho-phospnate, 50
HKsO'Ved
riycrci;/;ab;f' 50
lets': 50
Fetal , 50
Disseised
Sili ca 50
%:-V,Le 50
M-lfirie 500
S.sfite 50
•.,D 1000
50
''i^ >' ^re^e 1000
ivg^rr;; Carbon 25
;;nenoi ics 500
, _
Container Preservative
G only Det. on site
G only Fix on site
P,G Filter on site
Cool, 4°C
P,G Cool, 4°C
H2S04 to pH<2
P,G Cool, 4°C
H2S04 to pH<2
P,G Filter on site
Cool, 4°C
H2S04 to pH<2
P only Cool, 4°C
P,G Cool, 4°C
P,G 2 ml zinc
acetate
PSG Det. on site
P,6 Cool, 4°C
PSG H2S04 to pH<2
G only Cool , 4°C
H-SO. or HCL to
pH<2
P,G Cool, 4°C
H?SOd or HCL to
pH<2
G only Cool , 4°C
HjPO^ to pH<4
1.0 g CuSC,/l
Holding »
Time^ '
No Holding
4-8 Hrs.
24 Hrs.
24rirs.(f)
24 Hrs.(f)
24Hrs.(f)
7 Days
7 Days
24 Hrs.
No Holding
24 Hrs.
7 Days(f)
24 Hrs.
24 Hrs.
24 Hrs.
65
[continued)
-------
TABLE 1. (continued)
Measurement
MBAS
NTA
Vol.
Req.
(ml)
250
50
Container^ '
P,G
P,G
Preservative
Cool ,
Cool ,
4°C
4°C
Holding %
Timetcj
24 Hrs.
24 Hrs.
a. A general discussion on sampling water and industrial wastewater may be
found in ASTM, Part 31, p. 72-82 (1976) Method D-3370.
b. Plastic (P) or Glass (G). For metals polyethylene with a polypropylene
cap (no liner) is preferred.
c. It should be pointed out that holding times listed above are recommended
for properly preserved samples based on currently available data. It is
recognized that for some sample types, extension of these times may be
possible while for other types, these times may be too long. Where
shipping regulations prevent the use of the proper preservation technique
or the holding time is exceeded, such as the case of a 24-hour composite,
the final reported data for these samples should indicate the specific
variance.
d. If the sample is stabilized by cooling, it should be warmed to 25°C for
reading, or temperature correction made and results reported at 25°C.
e. Where HN07 cannot be used because of shipping restrictions, the sample may
be initially preserved by icing and immediately shipped to the laboratory.
Upon receipt in the laboratory, the sample must be acidified to a pH < 2
with HN03 (normally 3 ml 1:1 HN03/liter is sufficient). At the time of
analysis, the sample container snould be thoroughly rinsed with 1:1 HNO,
and the washings added to the sample (volume correction may be required).
f. Data obtained from National Enforcement Investigations Center-Denver,
Colorado, support a four-week holding time for this parameter in Sewerage
Systems. (SIC 4952).
66
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'•M ferial s when sterilized. If ground waters are suspected of containing >0.01
me/liter concentrations of toxic heavy metals such as copper, nickel, or zinc,
etc-, 0.3 ml of a 15 percent solution of ethylendiaminetetracetic acid (EDTA)
cecrasodium salt, should be added for each 125 ml sample column prior to steril-
ization. Sample bottles should be protected from contamination during transit
-V <:•. .erlng the tops and necks with aluminum foil or kraft paper before steril-
'latlon, Sterilization may be accomplished by autoclaving at 121°C for 15
nnnutes or heating in a hot air oven at 170°C for not less than two hours.
1 here are several different methods for obtaining a ground water sample.
Each of these methods differ in their advantages and disadvantages for obtain-
ing samples for microbiological analyses.
The majority of ground water samples are obtained using preexisting wells
w'mc1-1 have existing in-place pumps. This limits the precautions the sampler
•.i:i l.r^ r.o ensure a non-contaminated sample. Samples should be obtained from
eiiM-'t'j as close as possible to the pump and should not be collected from leaky
or fault- spigots or spigots that contain screens or aeration devices. The
cu;.;p should be pumped to waste for 5-10 minutes before the sample is col-
"et'-c'd. A steady-flowing water stream at moderate pressure is desirable in
::, .ier to prevent splashing and dislodging particles in the faucet or water
line.
TO collect the sample, remove the cap or stopper carefully from the sample
bottle. Do not lay the bottle closure down or touch the inside of the closure.
Avoid touching the inside of the bottle with your hands or the spigot. The
scrnp'ie bottle should not be rinsed out and it is not necessary to flame the
spigot. The bottle should be filled directly to within 2.5 cm (1 inch) from
•:he '.op. The bottle closure and closure-covering should be replaced carefully
j.ii.! the bottle should be placed in a cooler (4 - 10°C) unless the sample is
going to bf, processed immediately in the field.
If a well does not have an existing in-place pump, samples can be obtained
by either using a portable surface or submersible pump or by using a bailer.
Eden .r.ethod presents special problems in obtaining an uncontaminated sample.
;'^£ i".1'" problem in using a sterilized bailer is obtaining a representa-
'.''- " .:;v'ie of the aquifer water without pumping or bailing the well beforehand
the water in the bore for fresh formation water. This is difficult
pre-sampling activities must be carried out in sucn a way as to not
e the well. Care must also be taken with bailers to not contaminate
with any scum on the surface of the water in the well. This is
:.:;v done by using a weighted, sterilized sample bottle suspended by a
: • "'\.._> ,"d lowering the bottle rapidly to the bottom of the well.
he use of portable pumps provides a way of pumping-out a well before
st-.p.q and thus providing a more representative sample, but presents a
"•rial source of contamination if the pumping apparatus cannot be sterilized
:-?ir.rc!. The method of sterilization will depend on what other samples are
;.' i rcm the well since the use of many disinfectants may not be feasible if
well is also sampled for chemical analyses. If disinfection is not ruled
67
-------
out by other considerations, a method of sterilizing a submersible pump system
is to submerge the pump, and any portion of the pump tubing which will be in
contact with the well water, into a disinfectant solution and circulating the
disinfectant through the pump and tubing for a recommended period of time.
The most widely used method of disinfection due to its simplicity is
chlorination. Chlorine solutions may be easily prepared by dissolving either
calcium or sodium hypochlorite in water. Calcium hypochlorite, (CaOCl)-, is
available in a granular or tablet form usually containing about 70 percent of
available chlorine by weight and should be stored under dry and cool conditions.
Sodium hypochlorite, NaOCl, is available only in liquid form and can be bought
in strengths up to 20% available chlorine. In its most available form, house-
hold laundry bleach, it has strength of about 5 percent available chlorine,
but should not be considered to be full strength if it is more than 60 days
old. The original percentage of available chlorine will be on the label.
Table 2 gives the quantities of either calcium hypochlorite or laundry
bleach required to make 100 gallons of disinfectant solution of various con-
centrations. Fresh chlorine solutions should frequently be prepared because
the strength will diminish with time. The proper strength to use in disin-
fection is dependent upon many factors including pH and temperature. As a rule
of thumb, hypochlorite solutions of 50-200 ppm available chlorine and a contact
time of 30 minutes should be effective at pH ranges of 6-8 and temperatures
of greater than 20CC. After disinfection the pump should be carefully placed
in the well and then pumped to waste until the chlorine is thoroughly rinsed
from the pump system.
If the pump cannot be disinfected, then the pump and tubing should be
carefully handled to avoid gross surface contamination and the well should be
pumped for 3-10 bore volumes before taking a sample. It may be desirable
after pumping to pull the pump and take the sample with a sterile bailer.
In those cases where the water level in the well is less than 20 to 30
feet below the surface, a surface vacuum-pumping system can be used for flush-
ing out the well and withdrawing a sample. An ideal apparatus for this is
depicted in Figure 28. This apparatus consists of two lengths of tubing which
are sterilizable by autoclaving and a portable vacuum system. The two tubing
lengths which are attached side-by-side to each other, are sterilized in the
laboratory in large covered containers. In the field they are lowered into
a well using sterile gloves, attached to a vacuum system, and the well is
pumped to waste for 3-10 bore volumes with the bypass system. Then the well
is sampled by drawing water into a sterile vacuum flask on the inlet side of
the pump. Large volume sampling for viruses or pathogenic bacteria can be
accomplished by substituting filters or columns with various absorbents in
place of the vacuum flask.
Standing water is prevented from entering the sampling tubing upon inser-
tion into the well by making the sampling tube a few feet shorter than the
flushing tubing and turning on the pump to the flushing system as the tubing
is put into the well.
68
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TABLE 2. QUANTITIES OF CALCIUM HYPOCHLORITE, (70 PERCENT)
AND HOUSEHOLD LAUNDRY BLEACH (5 PERCENT) REQUIRED
TO MAKE 100 GALLONS OF DISINFECTANT SOLUTION
Desired Chlorine Dry Calcium 5C/, Household
Strength Hypochlorite, Ib. Bleach, Quarts
ifO PO-H 0.07 0.4
a)0 pom .14 0.8
150 pum .20 1.2
200 ppm .30 1.6
69
-------
To sample wells using this type of system requires a relatively large
autoclave, several sets of sampling tubing, and of course, relatively shallow
ground water.
Springs are unlikely to yield representative samples of an aquifer due to
surface contamination close to a spring's discharge unless the spring has an
extremely fast flow and the outlet is protected from surface contamination.
Lastly, interpretation of analytic results may be difficult in some cases
since surface contamination of wells due to poor drilling and completion prac-
tices is common. In cases where drinking water supplies are involved, a
thorough inspection of the well is required to eliminate surface contamination
down the well bore as a source of contaminants. Disinfection of the well by
approved methods (21), (22) and resampling may be advisable, if disinfection
will not affect the well for other sampling purposes.
70
-------
Autodavsbie ^=^^
Tubing for flushing
weii
Bypass system for
for flushing well
/
GLASS/TUBING
Autoclavable Tubing
-,>for sampling wsl!
1 foot shorter than
flushing tubing
.WELL CASING
I-LITER ERLENMEYER
(Sterile)
System for Microbiological
-:-r,-,,j" ;<-,r: of Wells Using a
Sucuicr, •[ ::"t Pump (6)
71
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SECTION 7
SAMPLING SUBSURFACE SOLIDS
GENERAL REQUIREMENTS
A common misconception regarding ground-water monitoring is that absence
of contaminants in tne ground water precludes a contamination problem. In
many cases, ar; effective evaluation cf the potential impact on ground water
quality of activities releasing pollutants into the earth's crust, requires
samples of subsurface earth materials, both saturated and unsaturated, as well
as ground wster samples. There are several principal reasons for this require-
ment. (I) Only by analysis of earth solids from the unsaturated zone under-
lying pollutant-releasing activities can those pollutants which are moving
very slowly toward the water table because of sorption and/or physical impediment
be detected and their rates of movement and degradation measured. Almost all
pollutants are attenuated to some degree in the subsurface, especially in the
unsaturated zone. The degree of attenuation and rate of movement varies greatly
between different pollutants and different subsurface conditions but many of
the mobile pollutants may not be detected in ground water until the activities
releasing them have been in operation for protracted periods. Because of their
potential for long-term pollution of ground water, it is imperative that the
behavior of these pollutants in the subsurface be established at the earliest
practicable time. (2) Analyses of pollutants in subsurface solid samples from
the zone of saturation are needed for a realistic evaluation of the total
extent and probable longivity of pollution in an aquifer. Such analyses provide
a measure cf the quantity of pollutants which are sorbed on aquifer solids and
which are in equilibrium with, and in essence serve as a reservoir for, pollut-
ants in solution in the adjacent ground water. (3) Microbial populations
which may be involved in the biological alteration of pollutants in subsurface
formations are likely to be in such close association with subsurface solids
that they will not be present in well waters in numbers which are quantitatively
indicative of their presence in the formations; hence, analysis of subsurface
solids are needed for accurate evaluation of such populations. (4) Even when
the best well construction and ground-water sampling procedures are used, it
is difficult to completely eliminate the possibility that contaminating surface
microbes may be present in ground-water samples. Solids taken from the interior
of cores carefully obtained from the zone of saturation probably provide the
most autheric samples of aquifer microorganisms that can be obtained.
As witn ground water samples, successful sampling of subsurface earth
solids reauires both acquisition of cores of subsurface solids at desired depths
in a manner minimizing potential contamination and proper handling and proces-
sing of the core material obtained to insure its integrity and produce samples
suitable for determinative analytical procedures.
72
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Although tools for collecting soil or core samples have been used for a
nunber of years in the foundation engineering and geology professions, core
sampling for around water quality investigations has received relatively little
'Ut.er^ion. r,'..^e rjre undoubtedly many procedures developed for the foundation
engineer-;-^, ?'j~ic'jl ;:ure and petroleum industries that can be used or modified
tor orouna Kit? • quality applications. This section of the manual presents
sorrc- o* t!,e pr.icediires that; are currently being used.
AC:AJHT~"ON .'F CCr?£ SAMPLES
rhere are a variety of procedures and equipment that have been used to
coliect earth materials for classification and identification of physical
cha^act-f:.'.>cs. Tools a: simple as a shovel or backhoe can and have been used
and a ndrw.- •*? .:ertgned samplers have also been used for this purpose. Because
of -.-"- \\.; : •' :;, to penetrate greater deoths and to maintain the physical integrity
'~>f tr-; : v •'• •• , most designed samplers employ some type of coring mechanism.
The tr.os* TH:1, ion p-rcedures use a thin-wall steel tube (core barrel) which is
forceo if-; :.pp undisturbed soil at the bottom of a bore hole. This is some-
time-;, v-c-fe^^d to cs drive sampling. Core barrels ara generally from one inch
to tn:"ee irche^ ir diameter and 12 to 24 inches long. When the core barrel is
rct'i •:•!'j/-., friction will usually retain the sample inside, at least in most un-
saturated T:?Aerials.
The Oar- nole can be made witn a continuous flight or hollow stem auger,
rcUir,, ror>3 u-"P. 1 cr othe^ drilling method. For water quality analyses, it is
genera TO/ rpconmen-'.ed that the drilling method employed avoid the use of drilling
f«ui'.:,o •;?.',cc these greatly increase the potential for sample contamination.
Similarly, it is also recommended that core sampling equipment avoid the use of
c'H 1 ' in..) "i• ,;••, ice corsets principally of a head unit threaded 10 fit
;• ' .•..•"' i- , " ''^ c.m a reo i jcccj'le thin v.all seamless steel tube (23). The
'• j^r, ;),3.:'/'dr- tu":e size is 3 inches O.D. although sizes f^cm 2 inches to 5 inches
"r • "'••••- .''•••' -:- I" rone subsurface materials, drag on the inner wall of the
"it '"j- '. e ^ .-• ccns idcrcble compression of the sample in unsaturated materials.
"t ••--•:')•."• "'•' s distortion ^nd aid in keeping the sample in the tube during with-
' .::•'•< ''••'.'" .<•'- ')ore hc^e, some i.nvettigators use a drive shoe en the bottom of
*-•- -;-'- •: - n-iS an ir,sic,i diameter slightly less than that of the tube.
Aricu cr ,ne',hod of irinimizing compression of the sample during coring is to
wet -.he inside c* tf:e coring tuoe with distilled water immediately preceding the
•>--
-------
BALL CHECK
THIN-WALL TUBE
Figure 29. Thin Wall Tube Sampler (23)
74
-------
sample is extremely difficult, especially in fine sand aquifers. Use of a
hollow-stem auger can alleviate this problem in many situations but in extreme
situations, removal of th? auger plug may permit sand to flow up the interior
of the auger before the core sample can be taken.
Sampling in a saturated zone also increases problems of contamination.
The coring tube must travel through water in the bore hole and this water will
almost surely contaminate at least the outside of the core sample. It is
necessary, especially for mlcrobial analyses, that the outside of the cores be
discarded and that only tk- i^cer-.or oe used for sample analyses.
For deeotr sanipl •'no. beyond the practical capability of augers, methods
for collecting uncontanv,nated samples have not been proven. Air drilling with
casing harmer offers the potential for opening a bore hole at the greater depths
without a'']"'-'! fluids. Hoover., data is lacking at this time concerning the
depth c:,:~ trie 'rrristiirhad t>oi~om of tie bore hole that is affected by the air
drilling, jm^ -v~y, limited use has been made of a piston sampler for deeper
sampling. Th& piston sampler employs a sample tube identical to the thin-wall
core barrel but drilling fli^'d pressure is used as the driving force. The
sampler sits or, tne Bottom cf the borehole at the end of the drill stem. A
snear pin irairitains the sample tube in an "up" position until a vent plug is
cropped down the drillstem tc the sampler. Pressure of the drilling fluid then
shears the pir-, forcing the tube through the bottom of the hole into the undis-
turbed material below the borehole, Considerable additional work is needed,
however, to evaluate the extent cf core contamination and to develop optimum
methods for avoiding juch contamination.
HANDLING AND PROCESSING OF CORE MATERIALS
The .vGcaiures to follow i;* frocessing a sample will depend on the type of
analyses end the ntuition ir trie- field. Regardless of the types of analyses to
be per^orircd, processing s,;,uul: ^e as soon as possible. When dealing with
cores, the core ray be processec ";n the field or if necessary the core may be
retained ";il chiit '.-Ur:'" the con? barrel. Recommendations on storage
of sar,:p'es before processing ^ary widely from maintaining samples at the temper-
atures at wr.ich they a^e sampled tc r?friaerating them.
^pl">t tjb-3s cr sectioned tubes are sometimes used to collect cores so as to
permit Dcc.'iss to the core material with minimal disturbance. Dunlap, et al.
reconvene!? a single niece coring tubo and the use of a hydraulic extruding de-
vice when s-j/inline subsurface solids for orcanics or microorganisms (12). As
sooo *? rv,-. r-^re i? --.b^dinsd, th= drive shoe, if used, is removed and the sample
tube is placed into fie extruding device (Figure 30). As the core sample is
foread out o'r tne tuoc, the first 5 to 8 cm (2 - 3 in) are cut off with a sterile
seal Del and discarded, or used ~o- analyses of chemical or physical parameters.
The center of the rr.r,-?s i i ^en s;,j3~.:;pl'".;: to obtain material suitable for
microbial analysis by pushing a sterile 1.3 cm ()-5 in) I.D. stainless steel tube
into the core for a^out 15 cm (6 in), as shown in Figure 31. The subsarr.ple is
extruded w;t* 3 sterile rod ir/o aoorcDr-iatc containers.
-------
..SAMPLE
HYDRAULIC CYLINDER
Figure 30. Core Sample Extruding Device (14)
-------
i-
o
a
CT
c-
3
CO
77
-------
The type of sample container which is used is dependent on the type of
analysis to be performed. For culturing of aerobic organisms any sterile con-
tainer is suitable if analyses are to be performed within a few hours. If
there is to be a significant delay before the sample is used, care is exercised
to keep the sample in a manner that prevents major changes in the microbial
content. Polyethylene bags, which allow the passage of air but not water vapor,
are good sample containers because the samples have access to air and yet are
kept from drying.
Since subsurface environments of any depth are usually reducing in nature,
the enumeration and identification of anaerobic microorganisms is essential if
the total microbial composition of the system is to be known. Because many
anaerobic bacteria are known to be extremely sensitive to oxygen, it is impor-
tant that samples which will be used in anaerobic culturing procedures be
handled in a manner that minimizes exposure to air. This can be accomplished
by extruding subsamples into sterile glass tubes from which the air is re-
placed quickly with an oxygen-free gas.
Two methods have been utilized for air removal and replacement. In one
method the sample tube is closed with a cotton plug and placed in an anaerobic
jar from which the oxygen is removed either by catalytic means or by the use of
a vacuum pump-replacement gas system (usually oxygen-free nitrogen). In the
second method, the sterile glass tube containing the subsample is fitted with
a gas-tight rubber septum stopper. A needle is pushed through the septum and
the tube is evacuated with a vacuum pump and filled with a sterile, oxygen-
free gas such as nitrogen. This process of evacuation and gas replacement
should be repeated at least three times.
Samples to be analyzed for parameters such as biomass or viruses require
specialized processing procedures which are continually changing as the state
of art develops. Because such procedures are rapidly being improved, recom-
mendations of any specific procedure are beyond the scope of this manual.
After a sub-core for microbial analysis has been removed from the parent
core, a 10 cm (4 in) length of core material for chemical analysis is obtained.
For organic analyses, the sample is extruded directly into a thoroughly cleaned
disposable aluminum baking pan, covered tightly with clean aluminum foil, and
placed in an insulated polystyrene box containing liquid nitrogen to quick-
freeze the sample material. Typical locations for microbial and organic samples
in a parent core are shown in Figure 32.
The frozen samples are returned to the laboratory on dry ice, stored
temporarily at -45°C in a low-temperature freezer, and freeze-dried as soon as
possible in a bulk type freeze dryer. Each sample of dried solids is carefully
crushed and mixed to obtain a better degree of homogeneity. These samples are
then transferred to thoroughly cleaned 475 ml (16 oz) wide-mouth jars with
Teflon lined caps and stored at -45°C until subjected to further processing or
analysis.
Samples of dried core material may be subjected to gross organic analysis,
such as total organic carbon, without further processing. Samples suitable for
more definitive analysis, including identification of individual compounds, are
prepared by solvent extraction of the solid samples.
78
-------
N-
in
I —
MICROBIAL SAMPLE
I.3X 15.2 cm
ORGANIC SAMPLE
7.6 X 10.2 cm
MICROBIAL SAMPLE
1.3 X 15.2 cm
ORGANIC SAMPLE
7.6 X 10.2 cm
Figure 32. Typical Locations for Subsarnples (14)
79
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SECTION 8
SAMPLE RECORDS AND CHAIN OF CUSTODY
It is obvious from the foregoing discussions that the collection and
analysis of a ground water sample ordinarily requires a substantial investment
of resources in terms of equipment facilities and manpower. However, inadequate
information regarding the circumstances of collection and subsequent disposition
of the sample, i.e., chain of custody, may render any resulting data useless.
Especially in sampling programs related to legal actions, proper chain of cus-
tody procedures are crucial. The following are some basic guidelines for sample
records and chain of custody procedures (2):
Sample Records
• 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,
H3PO 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.;
80
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• 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;
• 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., pHs temperature, dissolved
oxygen, and specific conductance, etc.);
• analyst's identity and affiliation.
Chain of Custody
• As few people as possible should handle the sample.
• Samples should be obtained by using standard field sampling techniques,
i f available.
• 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 s^C'jld cover the string or wire tie of the chain of custody record,
so tnat 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
Prcliferction of custody records, the number of custodians in the chain
of possession should be as few as possible. 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 pre-
servatives, 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
31
-------
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 aoove.
The entries should then be signed by the field sampler. The responsi-
bility 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 photo-
graph 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 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.
82
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REFERENCES
1. National Handbook of Recommended Methods for Water-Data Acquisition.
Interagency Advisory Committee on Water Data, Office of Water Data
Coordination, USGS, Reston, Virginia, 1977.
2. Procedures Manual for Ground Water Monitoring at Solid Waste Disposal
Facilities. U.S. Environmental Protection Agency, EPA/530/SW-611,
August 1977, 269 p.
3. Pettyjohn, W.A., W.J. Dunlap, R.L. Cosby, and J.W. Keeley. Sampling
Ground Water for Organic Contaminants. Ground Water Journal (In Press).
4. Winning, R.C. Keck Consulting Services, Inc., Private Communication, 1980.
5. Keys, W. Scott and L.M. MacCary. Application of Borehole Geophysics
to Water-Resources Investigations, U.S. Geological Survey Techniques of
Water-Resources Investigations. Book 2, Chapter E-l, pp. 1-126, 1971.
6. McNabb, J.F., and G.E. Mallard, Introduction to Subsurface Microbiology
and Sampling Problems. Presented at American Society for Microbiology
Annual Meeting, Miami Beach, Florida, May 13, 1980.
7. Gibb, J.R., R.M. Schuller, and R.A. Griffin. Monitoring Well Sampling
and Sample Preservation Techniques. U.S. EPA (In Press).
8. McMillion, L.G. and J.W. Keeley. Sampling Equipment for Ground Water
Investigations. Ground Water Journal, Vol. 6, No. 2, March-April 1968.
9. To.r.son, M.B., S. Hutchins, J.M. King, and C.H. Ward. A Nitrogen Powered
Continuous Delivery, Bell-Glass-Teflon Pumping System for Ground Water
Sampling from below 10 meters. Ground Water (In Press).
10. Middelburg, Robert F. Methods for Sampling Small-Diameter Wells for
Chemical Quality Analysis. Presented at National Conference on Quality
Assurance of Environmental Measurements, Denver, Colorado, November 27-
29, 1978.
II. Bianchi, W.C., Johnson, C.E., and Haskell, E.E, A Positive Action Pump
for Sampling Small Bore Wells. Soil Science Society of America Pro-
ceedings, Vol. 26, No. 1, 1962.
12. Smith, A.J. Water Sampling made Easier with New Device. The Johnson
Drillers Journal, July-August, 1976.
13. Signer, Donald C. Gas-Driven Pump for Ground Water Samples. USGS
Water Resources Investigation 78-72, Open-File Report, July 1978.
83
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14. Qunlap, W.J., J.F. McNabb, M.R. Scalf, and R.L. Cosby, Sampling for
Organic Chemicals and Microorganisms in the Subsurface. EPA-6QO/2-77-176,
August 1977.
15. Bellar, T.A. and J.J. Lichtenberg. Determining Volatile Organics at
Microqrams per Litre Levels by Gas Chromatography. Journal American
Waterworks Association. 66:739-744, 1974.
16. Methods for Chemical Analysis of Water and Wastes. EPA-600/4-79-020,
March, 1979.
17. Winter, J.A., R. Bordner, and P. Scarpino. Microbiological Methods for
Monitoring the Environment, Part I "Water and Wastes" EPA-600/8-78-017,
USEPA, EMSL, Cincinnati, 1978.
18. Handbook for Analytical Quality Control in Water and Wastewater Laborato-
ries. EPA-600/4-79-019, USEPA, EMSL, Cincinnati, 1979.
19. Geldreich, E.E. Handbook for Evaluating Water Bacteriological Laborato-
ries. EPA-670/9-75-006, USEPA, MERL, Cincinnati, 1975.
20. Standard Methods for the Examination of Water and Wastewater, 14th Edition.
American Public Health Association, Washington, D.C., 1976.
21. Campbell, M.D. and J.H. Lehr. Water Well Technology, McGraw-Hill Book
Company, New York, 1973.
22. Manual of Individual Water Supply Systems. EPA-430/9-74-007, USEPA, OWP,
Washington, 1974.
23. Acker, W.L. Basic Procedures for Soil Sampling and Core Drilling. Acker
Drill Company, Incorporated, 1974.
84
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BIBLIOGRAPHY
Benfall, Ray. Methods of Collecting and Interpreting Ground Water Data.
U.S. Geological Water Supply Paper 1544-H. 1963. p. 41-497.
Black, C.A. (Editor) Methods of Soil Analysis, Vol. 2. American Society
of Agronomy, Inc. Madison, Wisconsin, 1965.
Brown, E., M.W. Skougstad, and M.J. Fishman. Methods for Collection and
Analysis of Water Samples for Dissolved Minerals and Gases. U.S.
Geological Survey Techniques of Water Resources Investigations.
Book 5, Chapter A-l. 1970. p. 1-160.
Crouch, R.L., R.D. Eckert, and D.D. Rugg. Monitoring Ground Water Quality:
Economic Framework and Principles. U.S. Environmental Protection
Agency, EPA-600/4-76-045. September 1976. 104 pp.
DeVera, E.R., B.P. Summons, R.D. Stephens, and D.L. Storm. U.S. Environmental
Protection Agency, EPA-600/2-80-018. January, 1980. 78 pp.
Everett, L.G., K.D. Schmidt, R.M. Tinlin, and O.K. Todd. Monitoring Ground
Water Quality: Methods and Costs. U.S. Environmental Protection
Agency, EPA-600/4-76-023. May, 1976. 152 pp.
Gilmore, A.E. A Soil Sampling Tube for Soil Microbiology. Soil Science, 87.
1959. p. 95-99.
Ground Water, Section 18, SCS National Engineering Handbook. U.S. Department
of Agriculture, Soil Conservation Service. April, 1969.
Hampton, N.F. Monitoring Ground Water Quality: Data Management. U.S.
Environmental Protection Agency, EPA-600/4-76-019. April, 1975.
70 pp.
Hatheway, A.W., J. Humphrey, and B.K. Thacker. Characterization and Environ-
mental Monitoring of Full Scale Utility Waste Disposal Sites;
Appendix A, Hydrogeologic and Geotechnical Procedures Manual. U.S.
Environmental Protection Agency (In Press).
Heath, Ralph C. "Basic Elements of Ground Water Hydrology With Reference to
Conditions in North Carolina." U.S. Geological Survey Water Resources
Investigations Open-File Report 80-44. 1980.
Hem, John D. Study and Interpretation of the Chemical Characteristics of
Natural Water. U.S. Geological Survey Water-Supply Paper 1473. 1959.
85
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Kill, D.L. Pumping Water by the Air-Lift Method has Practical Applications:
Johnson Drillers Journal. November-December 1973.
Lindorff, D.E. and K. Cartwright. Ground Water Contaminations: Problems
and Remedial Actions. Environmental Geology Notes, No. 81. Illinois
State Geological Survey, Urbana, Illinois. May, 1977.
Nogg, J.L. Factors Affecting Design, Development, and Cost of Wells. Johnson
Drillers Journal. May-June, 1973.
Rainwater, F.H. and L.L. Thatcher. Methods for Collection and Analyses of
Water Samples. U.S. Geological Survey Water-Supply Paper 1454. 1960.
Sampling and Analysis of Soils, Plants, Wastewaters, and Sludge. Research
Publication 170. Agricultural Experiment Station. Kansas State
University, Manhattan, Kansas.
Silka, L.R, and T.L. Swearingen. A Manual for Evaluating Contamination
Potential of Surface Impoundments. EPA-570/9-78-003. June, 1978.
Tinlin, R.M. (Editor) Monitoring Ground Water Quality: Illustrative Examples.
U.S. Environmental Protection Agency, EPA-600/4-76-036. July, 1976.
92 pp.
Todd, O.K., R.M. Tinlin, K.D. Schmidt, and L.G. Everett. Monitoring Ground
Water Quality: Monitoring Methodology. U.S. Environmental
Protection Agency, EPA-600/4-76-026. June, 1976. 172 pp..
Walton, W.C. Ground Water Resource Evaluation. McGraw-Hill Book Company,
New York, 1970.
Warner, D.L. Rationale and Methodology for Monitoring Ground Water Polluted
by Mining Activity. U.S. Environmental Protection Agency, EPA-680/
4-74-003. July, 1974. 84 pp.
Warner, D.L. Monitoring Disposal Well Systems. U.S. Environmental Protection
Agency, EPA-680/4-74-008. July, 1975. 109 pp.
Wilson, L.G. Monitoring in the Vadose Zone: A Review of Technical Elements
and Methods. GE79TMP-55. General Electric Company-TEMPO, Center
for Advanced Studies. 1979.
Wood, W.W. Guidelines for Collection and Field Analyses of Ground Water
Samples for Selected Unstable Constituents. U.S. Geological Survey
Techniques of Water Resources Investigations, Book 1, Chapter D-2.
1974.
86
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APPENDIX A
SUMMARY OF PROCEDURES BASED ON PARAMETER OF INTEREST
The nature of the pollutant being sampled for is the primary factor
determining the type of well and the sampling method recommended for monitoring
and investigative sampling. This summary section offers guidelines for sampling
procedures to be used for various categories of pollutants. For specific
details of each sampling procedure and recommended sample-handling procedures
consult the appropriate section in the text, references, and bibliography.
87
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Measurement
Well-Construction
Sampling Method
Physical Properties
Color
Conductance
Hardness
Odor
PH
Residue
Filterable
Non-
filterable
Total
Volatile
Settleable Matter
Temperature
Turbidity
All of the drilling
and construction
methods described in
the test are accept-
able. The use of
water or drilling
mud will not signi-
ficantly affect the
samples if the well
is pumped prior to
sampling for a suf-
ficient time to
clear the well of
drilling fluids.
This can be deter-
mined in the field
using a conductivity
meter.
All of the methods
described in the
text are acceptable.
The easiest method
should be used pro-
viding the sampling
device is rinsed
thoroughly between
sampling events.
Devices which affect
the gas composition
of the sample will
affect the pH.
-------
Measurement
Well-Construction
Sampling Method
Metals
Dissolved
Suspended
Total
Mercury
Dissolved
Total
All of the drilling
and construction
methods described in
the text are accept-
able except benton-
ite clays or other
clay-based drilling
muds should not be
used if possible.
Plastic casing is
preferable to metal
casing.
All of the methods
described in the
text are acceptable
provided the ground
water is not aerated
during the sampling.
The sampling device
should be metal-free
and should be rinsed
thoroughly between
sampling events.
Inorganics, Non-Metallics
Acidity
Alkalinity
Bromide
Chloride
Chlorine
Cyanides
Fluoride
Iodide
Nitrogen
Ammonia
Kjeldahl, Total
Nitrate plus Nitrite
Nitrate
Nitrite
All of the drilling
and construction
methods described in
the text are accept-
able. The use of
water or drilling
mud will not signi-
ficantly affect the
samples if the well
is pumped prior to
sampling for a suf-
ficient time to
clear the well of
drilling fluids.
This can be deter-
mined in the field
using a conductivity
meter.
All of the methods
described in the
text are acceptable
although methods
such as bailers,
squeeze pumps, and
piston pumps which
minimize changes in
dissolved gas compo-
sition of the sample
are preferable if
the parameters being
measured are affect-
ed by pH or dissol-
ved gas changes.
89
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Measurement
Well-Construct!on
Sampling Method
Dissolved Oxygen
Probe
Winkler
Phosphorus
Ortho-
phosphate,
Dissolved
Hydro!yzable
Total
Total,
Dissolved
Silica
Sulfate
Sulfide
Sulfite
Organics - Routine Analyses
COD
Oil & Grease
Organic Carbon
MBAS
All of the drilling
and construction
methods described in
the text are accept-
able, with except-
ions noted below.
All of the methods
described in the
text are acceptable
provided the samp-
ling device is
rinsed thoroughly
between sampling
events, with except-
ions noted below.
Exceptions: Methods of Appendix B should be used
for "Oil and Grease" when a separate organic phase
is present in the aquifer. For high sensitivity
"Organic Carbon" analyses methods for "Organics"
by chromatographic methods, presented below, are
preferable.
90
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Measurement
Well-Construct!on
Sampling Method
Organics - To be determined using high sensitivity analyses by chromatographic
methods
Purgeable (VOA)
Non-Purgeable
Mi croorganjjms^
Bacteria
Fungi
Protozoa
Viruses
Desirable for wells
to be constructed
without the use of
contaminating dril-
ling fluids and cas-
ings. Casing in
order of preference
should be Teflon,
stainless steel,
steel. If possible,
plastic casing
should not be used.
All of the methods
described in the
text are acceptable
with the exception
that biodegradable
drilling muds such
as Revert should not
be used. All compo-
nents of a well-
casing, sandpack
pump-should be
chlorinated after
completion and then
thoroughly pumped to
remove any residual
chlorine.
Samples to be ana-
lyzed for purgeable
volatile organics
(VOA) should be
collected by a
glass or Teflon
bailer after the
well is thoroughly
flushed with non-
aerating pump.
Vacuum and air-lift
pumps should not be
used. Samples to
be analyzed for
trace levels of
organics should be
collected with
Teflon or glass
systems.
All of the methods
described in the
text are acceptable
if the sampling
device can be
sterilized before
use.
91
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APPENDIX B
SAMPLING FOR LOW DENSITY, IMMISCIBLE ORGANICS
Low-density, immiscible organics include gasoline and other chemicals and
petrochemicals which have specific gravities less than water and which are
likely to be present in aquifers as a separate phase because of low solubility
in water. These chemicals tend to float on the water surface in a water table
environment and corrmonly occupy the capillary fringe zone above the water table.
In a confined aquifer these chemicals are found along the upper surface of the
permeable material and also within the overlying confining layer.
WELL CONSTRUCTION
Care must be exercised to insure that the well screen extends significantly
into both the water saturated zone and the overlying formation. This design
will insure that contaminants in the capillary fringe or overlying aquitard,
as well as ground water, enter the well to be observed. A well screen with
abundant open area such as a wire-wrapped screen is important in allowing free
flow of the petrochemicals into the well.
With the above considerations in mind, nearly any of the drilling methods
previously discussed which permits a well of at least 3 inches ID to be con-
structed is satisfactory.
SAMPLING PROCEDURES
Sampling procedures for low density, immiscible organics differ substan-
tially from those for other pollutants. It is necessary to sample at least two
and sometimes three distinct layers or depths within the sampling well.
After the well is initially constructed it should be developed and pumped
to remove invaded water, then, it should sit idle for at least several days to
allow the water level to fully stabilize and the floating layer of petrochemicals
to stabilize.
Measurement of the thickness of the petrochemical layer may then be
accomplished by using a water-level indicator gel with a steel tape to determine
the depth to the water surface. A weighted float may be used to determine the
depth to the top of the petrochemical layer. The difference between these two
readings is the thickness of the petrochemical layer. Electric water-level
sounders will not work properly for these determinations.
A sample of the floating petrochemicals may then be taken using a bailer
which fills from the bottom. Care should be taken to lower the bailer just
through the petrochemical layer, but not significantly down into the under-
lying ground water.
92
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Samples of the ground water at the bottom of the screen and at some inter-
mediate location, such as the mid point of the screen, may also be obtained
with a bailer. However, in order to avoid mixing the waters, a separate casing
is temporarily lowered inside the permanent well casing. This casing is
equipped with an easily removed cap on the bottom so that no fluid enters the
casing until it has reached the desired depth for sampling. The cap is then
knocked free of the bottom of the casing, allowing water to enter from that
specific depth to be sampled by bailer. At significant depths below the
petrochemicals several full bailers of water may be withdrawn and discarded
before the sample is taken to obtain a fresh formation sample.
Thorough cleaning of the bailer, as previously discussed, is required
between sampling events.
93
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