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A project of Volunteers

er Well
by : Ulric

in Asia

Manual
P. Gibson

and Rexford

D. Singer

Published
by:
United States Agency for International
Development
Washington,
DC 20532 USA
Paper copies

are $ 9-00.

Available
from:
Premier Press
P.G. Box 4428
Berkeley,
CA 94704

USA

Reproduction
of this microfiche
document in any
form is subject
to the same restrictions
as those
of the original
document.

A PRAGTICAL GUIDE FOR LOCATI
CONSTRUCTING WELLS FOR INDIVIDUAL
AND SMALL COMMUNITY WATER SUPPLIES

GROUND
WATER
IS ONE OF MAN’S
M’JST
IMPORTANT
NATURAL
RESOURCES.
ITS PROPER
UEVELOPMENT
BY MZ:ANS
OF WELLS
IS A MATTER
OF INCREASING
IMPORY’ANCE.
THIS
BOOK
DISCUSSE
5 THE
LOCATION,
DESIGN,
CONSTRUCTION,
OPERATI~JN,
AND
MAINTENANCE
OF SMALL
WELLS
USED
PI:,MARILY
FOR
lNDlVlDUAL
AND
SMALL
COMMUl’:ITY
WATER
SUPPLIES.

THE AUTvlORS,
WRITING
IN A Cy,EAR
AND
EASY-TOREAD
MANNER,
PRESENT
THE f’:lJNDAMENTALS
OF
WATER
WELLS
SO AS TO BE USEFUL
TO INDIVIDUAL
HOME
OWNERS,
FARMERS,
ANI.:) STUDENTS
AS WELL
AS TO THOSE
PRO’FESSIONALL
Y INVOLVED
SUCH
AS
WELL
DRILLING
CONTRACTD!ZS,
ENGINEERS,
AND
GEOLOGISTS.

MODERN
TECHNIQUES
FOR I.,EVELOPING
GROUND
WATER
ARE
COMPREHENSIVELY
DESCRIBED
WHETHER
THE WATER
SUPPkIES
ARE
FOR AGRICULTURAL,
INDUSTRIAL,
Of,! HUMAN
NEEDS.
TO
AID UNDERSTANDING
THE r”iUTHORS
HAVE
INCLUDED
MORE
THAN
100 ILLUSTRATIONS
THROUGHOUT THE
BOQK.
THIS
BOOK
WAS ORIGINALLY
PUBLISHED
BY
THE AGENCY
FOR INTERNATIONAL
DEVELOPMENT
OF THE
UNITED
STATES
GOVERNMENT
TO ASSIST
THE PEPPLE
LIVING
IN THE DEVELOPING
COUNTRIES
OF THE WORLD
WHO ARE WITHOUT
ADEQUATE
SUPPLIES
OF GOOD
QUALITY
WATER.
THIS NEW
EeblTlON
HAS SEEN PREPARED
SO THAT
ALL
PERSONS
INTERESTED
IN WATER
RESOURCES
MAY
BENEFIT
FROM
THIS VALWABLE
BOOK.

hmier

Pwss

Editorial Advisory Boani
for Water Resources
Harvey 0. Bat&T
Charles E Meyer
David K. Todd

A PRACTICAL

GUlDE

FOR lNDh/lDUAL

FOR LOCATING
AND SMALL

AND CONSTRUCTING

COMMUNITY

WATER

Uhic P. Gibson
Executive Engineer, Water Supply, Rural Areas
Ministry of Works & Hydraulics, Guyana

Rexford D. Singer
Associate Professor of Environmental Health
School of Public Health
University of Minnesota

PREMIER
Berkeley,

PRESS
California

WELLS

SUPPLIES

WATER
EL1
MANUAL

Covers Copyright @ by Premier Press 197 !

Published by the
Agency for International
Development of the U.S.
Department of State under
the title Small WellsMamai,
1969.

Text reprinted i971 by
PREMiER PRESS
P. 0. Box 4428
Berkeley, California 94704

Library of Congress
Catalog Card Number: 71-l 53696

Printed in the United States of America

Foul-t11Printing, May 1977

ii

The authors wkh to express their appreciation to the Health Service,
Oftlce of Wt?ron Hunger. United States :lgtfi~q t‘or International Development for making the publkation of this manual poss\lble.We art’ particularly
indebted to the UOP-JohnsonDivision, Universal Oil Products Company, St.
Paul. %Iinnesota for their advice and assistancein preparing the tnanuscript
and for their contribution of valuable inft)rmstion and illustrations and to Mr.
Arpad Rumy for the preparation of mani’ of the illustrations. We also wish to
express sincere gratitude to ail pcrs:ns who have offered comments,
suggestionsand assistanceor who havegiven their time to critically review the
manuscript.
In preparing this manual. an attempt h;ts been made to bring together
information and material from a variety of sources.We have endeavored to
give proper credit for the direct use of material from these sources, and any
omission of such credit is unintentional.

It has been estimated that nearly two-thirds of the one and a half billion
people living in the developing countries are without adequate supplies of
safe water. The consequencesof this deficiency are innumerable episodes of
the debilitating and incapacitating enteric diseaseswhrch annually affect an
estimated 500 million people and result in the deaths of as many as 10
million about half of whom are children.
Although there are many factors limiting the installation of small water
systems, the lack of know!edge in repdd to the availability of ground water
and effective means of extracting it fc-11use by rural communities is a major
element. It is anticipated that this manual will make a major contribution
toward fiiling this need by providing the man in the field, not necessarilyan
engineer or hydrologist, with the information needed to locate, construct and
operate a small well which can provide good quality water in adequate quantities for small communities.
The Agency for International Development takes great pride in cooperating with the University of Minnesota in making this manual available.

Arthur H. Holloway
Sanitary Engineer,
Health Service,Office of War on Hunger
Agency for International Development

...
111

Page
ii

ACKNOWLEDGEMENTS

.. .

FOREWORD

111

1. INTRODUCTION

1

PURPOSE

1

SCOPE

1

PUBLIC HEALTH AND RELATED FACTORS
Importance of Water Supplies. Ground-Water’s Importance. Need for Proper Development and Managementof
Ground Watt-bResources.

1

*L.ORIGiN,
WATER

OCCllRRENCE

AND

MOVEMENT

OF GROUND

4

THE HYDROLOGIC CYCLE

4

SUBSURFACE DISTRIBUTION OF WATER
Zone of Aeration. Zone of Saturation.

4

GEOLOGIC FORMATIONS AS AQUIFERS
Rock Classification. ‘Role nf Geologic Processes in
Aquifer Formation.

7

GROUND-WATER FLOW AND ELEMENTARY WELL HYDRAULICS
Types of Aquifers. A,quifer Functions. Factors Affecting
Permeability. Flow Toward Wells.
QUALITY OF GROUND WATER
Physical Quality. Microbiological Quality. Chemical Quality.

10

;72

28

3. GROUND-WATEREXPLORATION

EEOLOGIC DATA
Geologic Maps. Geologic Cross-Sections. Aerial Photographs.

28

INYENTORY OF EXISTING WELLS

30

SURFACE EVIDENCE

31
iv

Pi;ge
4. WATER WELL DESIGN

33

CASED SECTION

34

BUTARE SECTlON
Type and Construction of Screen.Screen Length, Size of
Openings and Diameter.

34

SELECTION OF CASING AND SCREEN MATERIALS
Water Quality. Strer&h Requirements. Cost. Miscellaneous.

47

GRAVELPACKING AND FORMATION STABILIZATION
Gravel Packing. Formation Stabilization.

50

SANITARY PROTECTION
Upper Terminal. Lower Terminal of the Casing.Grouting
and Sealing Casing.

52

55

5. -#ELL CONSTRUCTION
WELL DRILLING METHODS
Boring. Driving. Jetting. Hydraulic Percussion. Sludger.
Hydraulic Rotary. Cable-Tool Percussion.

55

INSTALLING WELL CASING

69

GROUTING AND SEALING CASING

70

WELL ALIGNMENT
Conditions Affecting Well Alignment. Measurement of
Well Alignment.

73

INSTALLATION OF WELL SCXEENS
Pull-back Method. Open Hole Methr?d.Wash-downMethod. Well Points. Artificially Gravel-Packed Wells. Recovering Well Screens.

75

FISHING OPERATIONS
Preventive Measures.Preparations for Fishing. Common
Fishing Jobs and Tools.

86

96

6. WELL COMPLETION
WELL DEVELOPMENT
Me&an&l Surging. Backwashing. Development of Gravel-Packed Wells. Dispersing Agents.

96

104

WELL DISINFECTION

V

114

S. PUMPING EQUIPMENT
CONSTANT DISPLACE>lE?ZT PLhlPS
Reciprocating Piston Pumps. Rotary Pumps. Helical
Rotor Pumps.

I17

VARIABLE DISPl.A(‘EMENl- PUMPS
C’entrlfugal Ptuqx. Jet Pumps.

120

DEEP WELL PUMPS
Lineshaft Pumps. Subrnersibk P!lrnps.

11-l

PRIMING OF PUMPS

I 10

PUMP SELECTION

137

SELECTION OF POWER SOLrRCE
Man Power. Wind. Electricity. Internal Combustion
Engine.

11x

4. SANITARY PROTECTION OF GROUND-WATER SUPPLIES

134

POLLUTION TRAVEL IN SOILS
WELL LOCATiON
SEALING ABANDONED WELLS
REFERENCES

138

CWEDI’i FOR ILLUSTRATIONS

139

APPENDICES
APPENDIX A.

MEASUREMENT OF PERMEABILITY

14(!

APPENDIX B.

USEFUL TABLES AND FORMULAS

111
151

INDEX
vi

C

PTER ‘I

I

CTI

PURPOSE

This manual is intended to serve as a basic introductory text book and to
provide instruction and guidance to field personnel engagedin the construction, operation and maintenance of small diameter, relatively shallow wells
used primarily for individual and small community water supplies.
it is aimed particularly at those persons who have had little or no
experience in the subject. An attempt has been made to treat the subject
matter as simply as possible in order that this manual may bF:of benefit not
only to the engineer or other technically trained individual (inexperienced in
this field) but also the individual home owner, farmer or non-technically
trained community development officer. This manual should also prove
useful in the training of water well drillers, providing the complementary
background material for their field experience. The reader who is interested
in pursuing the subject further, and with reference to larger and deeper wells,
is referred to the list of referencesto be found at the end of this manual.
SCOPE

This. manual covers the exploration and development of ground-water
sources in unconsolidated formations, primarily for the provision of small
potabie water supplies. Its scope has been limited to the consideration of
small tube wells up to 4 inches in diameter, a maximum of approximately
100 feet in depth and with yields of up to about 50 U.S.gallons per minute
(All references are to U.S. units. Conversion tables are to be found in
Appendix B). The location, design, construction, maintenance and rehabilitation of such wells are among the various aspects discussed. The above
limitation on well size (diameter) rules out the zonslderation of dug we!ls in
favor of the much more efficient and easierto protect bored, driven, jetted or
drilled tube wells. However, a method of converting existing dug wells to tube
wells is discussed.
PUBLIC HEALTH AND RELATED
hportance of Water Supplies

FACTORS

Water is, with the exception of ai?, the most important single substanceto
man’s survival. Man, like all other forms of biological life, is extremely
dependent upon water and can survive much longer without food than he can
without water. The quantities of water directly required for the proper
functioning of the body processesare relatively small but essential.
1

While man has always recognized ihe importance of water for his internal
bodily needs. his recognition of its importance to health is a more recent
development. dating back oniy a century or so. Since that time, much has
been learned about the role of inadequate and contaminated water supplies in
the spread of water-borne diseases.Among the first diseasesrecognized to be
water borne were cholera and typhoid fever. Later, dysentery, gastroenteritis
and other diarrhea1 diseaseswere added to the list. More recently, water has
also been shown to play an important role in the spread of certain viral
diseasessuch as infectious hepatitis.
Water is involved in the spreadof conznunicable diseasesin essentially two
ways. The first is the well known direct ingestion of the infectious agent
when drinking contaminated water (e.g. dysentery, typhoid and other
gastrointestinal diseases).The second is due to a lack of sufficient water for
personal hygiene purposes. Inadequate quantities of water for the maintenance of personal hygiene and environmental sanitation have been shown to
be major contributing factors in the spread of such diseasesas yaws and
typhus. Adequate supplies of water for personal hygiene also diminish the
probability of transmitting some of the gastrointestinal diseasesmentioned
above. The latter type of interaction between water and the spreadof disease
has been recognized by various public health organizations in developing
countries which have been trying to provide adequate quantities of water of
reasonable,though not entirely satisfactory, quality.
Health problems related to the inadequacy of water supplies are universal
but, generally, of greater magnitude and significance in the underdeveloped
and developing nations. It has been estimated that about two-thirds of the
population of the developing countries obtain their water from contaminated
?111!3rees.
The World Health Organization estimates that each year 500 million
people suffer from diseasesassociatedwith unsafe water supplies. Due largely
to poor water supplies, an estimated S,OOO,OOO
infants die each year from
diarrheal diseases.
In addition to the human consumption and health requirements, water is
a!so needed for agricultural, industrial and other purposes. Though all of
these needs are important, water for human consumption and sanitation is
considered to be of greater social and economic importance since the health
of the population influences all other activities.
Ground-Water’s Importance
It can generally be said that ground water has played a much less

imporatnt role in the solution of the world’s water supply problems than its
relative availability would indicate. Its outaf-sight location and the associated
lack of knowledge with respect to its occurrence, movement and development
have no doubt contributed greatly to this situation. The increasing acquisition
and dissemination of knowledge pertaining to ground-water development will
gradually allow the use of this source of water to approach its rightful’degree
of importance and usefulness.
More than 97 percent of the fresh wn:lteron our planet (excluding that in
the polar ice-caps and glaciers) is to be found underground. While it is not
2

practicable to extract all of this water becauseof economic tendother re;lsons.
the recoverable quantities would. no doubt, esceed the available supplies of
fresh surface water found in rivers and lakes.
Ground-water sources also represent water that is essentially irl ;iorage
while the water in rivers and lakes is generally i.n transit, being replaced
several times a year. The available quantity of surface water at any given
location is also more subject to seasonalfluctuations than is ground water. In
many areas, the extraction of ground water can be continued long after
droughts have completely depleteil rivers. Ground-water sources are, therefore, more rehable sourcesof water in many instances.
As will be seen in Chapter 2. ground waters are usually of much better
quality than surface waters. due to the benefits of percolation through the
ground. Oftener than not, ground water is also mctre readily available where
needed, requiring less transportation and, generally, costir?.gless to develop.
Greater emphasis should, therefore, be placed on the development and useof
the very extensive ground-water sourcesto be found throughout the world.
Need for Proper Development and Management of Ground-Water Resources
While some ground-water reservoirs are being repienished year after year
by infiltration from precipitation, rivers, canals and so on, others are being
replenished to much lesser degreesor not at all. Extraction of water from
these latter reservoirs results in the continued depletion or mining of the
water.
Ground water aiso often seepsinto streams, thus providing the low flow
(base flow) that is sustained through the driest period of the year. Conversely,
if the surface water levels in streams are higher than those in ground-water
reservoirs, then seepage takes place in the opposite direction, from the
streams into the ground-water reservoirs. Uncontrolled use of ground water
can, therefore, affect the levels of streams and Iakes and consequen.tly the
usesto which they are normally put.
Ground-water development presents special problems. The lack of solutions to these problems have, in the past, contributed to the mystery that
surrounded ground-water development and the limited use to which ground
water has been put. The proper development and management of groundwater resources requires a knowiedge of the extent of storage, the rates of
discharge from and recharge to underground reservoirs, and the use of
economical means of extraction. It may be necessary to devise artificial
means of recharging these reservoirs where no natural sources exist or to
supplement the natural recharge. Researchhas, in recent years, considerably
increased our knowledge of the processes involved in the origin and
movement of ground water and has provided us with better methods of
development and conservation of ground-water supplies. Evidence of this
increased knowledge is to be found in the greater emphasisbeing placed on
ground-water development.

An understanding of the processes and fxtors affecting the origin,
occurrence, and movement of ground water is essential to the proper
development and use of ground-water resources.Of importance in determining 2 satisfactory rate of extraction and suitable uses of the water are a
knowledge of the quantity of water present, its origin. the direction and rate
of movement to its poi:rt of discharge, the discharge rate and the rate at
which it is being replenished, and the quality of the water. These points are
considered in this chapter in as simplified and limited a form as the aims and
scope of this manual permit.
THE HYDROLQGIC CYCLE
The hydrologic cycle is the name given to the circulation of water in its
liquid, vapor, or solid state from the oceans to the air, air to land, over the
land surface or undergrountl, and back to the oceans(Fig. 2.1).
Evaporation, taking place at the water stirface of oceans and other open
bodies of water, results in the transfer of water vapor to the atmosphere.
Under certain conditions, this water vapor condensesto form clouds which
subsequently release their moisture as precipitation in the form of rain, hail.
sleet, or snow. Precipitation may xcur over the oceansretuning some of the
water directly to them or over land to which winds have previously
transported the moisture-laden air and clouds. Part of the rain falling to the
earth evaporates with immediate return of moisture to the atmosphere. Of
the remainder, some, upon reaching the ground surface, wets it and runs off
into surface streams finally discharging in the ocean while another part
infiltrates into the ground and then percolates to the ground-water flow
through which it later reaches the ocean. Evaporation returns some of the
water from the wet land surface to the atmosphere while plants extract some
of that portion in the soil through their roots and, by a processknown as
transpiration, return it through their leavesto the atmosphere.
SUBSURFACE DISTRIBUTION OF WATER
Subsurface water found in the interstices or pores of rocks may be divided
into two main zones (Fig . 2.2). These are the zvtle of aeration and the .zo/re
of saturation.
Zone of Aeration
The zone of aeration extends from the land surface to the level at which
all of the pores or open spacesin the earth’s materials are completely fiiled or
4

I

\ \I / /
- nSun -

t-%rcolarlon
V

--

_

7

-----

---_----

-

Fresh

_

---__

-;

..-_ IF --‘-- ---__ -c-__-_._-~.- -a.
--___

ground

- -

-

-

.--

--

.

.

water

~-1.w

1,.-1

-.

tmpermeable
-:
z - -- - -- - --- -~
-

--- -.-

formotionr
-

___

-

-

TJ
-z

----

Fig. 2.1 THE HYDROLOGIC CYCLE.

.--

-..

-.

--

nrnnn

saturated with water. A mixture of
air and water is to be found in the
Bsit of Soil Water
.
pores in this zone and hence its
name. It may be subdivided into
three belts. These are (1) the belt of
soil water, (3) the intermediate belt
tntermediate Belt
and (3) the capillary fringe.
The be/r of soil wafer lizs immediately below the surface and is
that region from which plants exCapillary Fringe
tract, by their roots, the moisture
necessary
for growth. The thickness
Water. Table
t
-of the belt differs greatly with the
type of soil and vegetation, ranging
from a few feet in grass-landsand
field crop areas to several feet in
forests and lands supporting deepGround Water
rooted plants.
The qdlary ftitlge occupies the
bottom portion of the zone of
aerh:ion and lies immediately above
the zone of saturation. Its name
comes from the fact that the water
in this belt is suspendedby capiliary
forces similar to those which
Fig. 2.2 DIVISIONS
OF SUBSURcause water to rise in a narrow or
FACE WATER.
capillary tube above the level of the
water in a larger vessel into which the tube has been placed upright. The
narrower the tube or the pores, the higher the water rises. Hence, the
thickness of the belt depends upon the texture of the rock or soil and may be
practically zero where the pores are large.
The intemrediute belt lies between the belt of soil water and the capillary
fringe. Most of its water reachesit by gravity drainage downward through the
belt of soil water. The wster in this belt is called intermediate (vadose)water.

Zone of Saturation

Immediately below the zone of aeration lies the zone of saturation in
which the pores are completely fdled or saturated with water. The water in
the zone of saturation is known as ground water and is the only form of
subsurface water that will flow readiiy into 3 well. The object of well
construction is to penetrate the earth into this zone with a tube, the bottorn
section of which has openings which are sized such as to permit the inflow of
water from the zone of saturation but to exclude its rock particles.
Formations which contain ground water and will readily yield it to wells are
called aquifers.
6
5

IC FQRXA~NMIIS

AS AQUIFERS

For convenience, . :)iogists describe all earth materials as roclis. Rocks
may be of the ~~onti.J‘,-refl type (held firntiy together by compaction,
cementation and otLe:, K A~.,Psut!~ :ts granite. sandr’,>r-* e;\dlimestone or
rtrncomoiidated type (IL, .-:aterials)such as clay, sand Jnd gravel. The terms
hml and soft are also usr,~:r.odescribe consolidated and unconsolidated rocky
respectively.
Aquifers may be composed of consolidated or unconsolidated rocks. The
rock materiais must be sufficiently porous (contain a reasonably high
proportion of pores or other openings to solid material) and be sufficiently
permeable (the openings must be interconnected to permit the travei of water
through them).
Rock Classification

Rocks may be classified with respect to their or+;? into the three main
categoriescf sedimentary rocks, igneous rocks, and lxidmorphic rocks.
Sedimentary rocks are the deposits of material derived from the
weathering and erosion of other rocks. Though constituti;.; only about 5
percent of the earth’s crust they contain an estimated 95 percent of the
available ground water.
Sedimentary rocks may be consolidated or unconsolidated depending
upon a number of ?‘zctors such as the type of parent rock, mode of
weathering, means of transport, mode of deposition, and the extent to which
packing, compactiorl, and cementation have taken place. Harder rocks
generally produce sediments of coarser texture than softer ones. Web;>erin;
by mechanical disintegration (e.g. rock fracture due to temperature varlu
tions) produces coarser sediments than those produced by chemical decomposition. Deposition in water provides more sorting and better packing of
materials than does deposition directly onto land. Chemical constituents in
the parent rocks and the environment are responsible for the cemerltatioll of
unconsolidated rocks into hard, consolidated ones. These factors aiso
influence the water-bearing capacity of sedimentary rocks. Disintegrated shale
sediments are usually fine-grained and make poor aquifers while sediments
derived from granite or other crystalline rocks usually form good sand and
gravel aquifers, particularly when considerable water transportation has
resulted in well-rounded and sorted particles.
Sand, gravel, and mixtures of sand and gravel are among the unconsolidated sedimentary rocks that form aquifers. Granular and unconsolidated,
they va.ry in particle size and in the degree of sorting and rounding of the
particies. Consequently, their water-yielding capabilities vary considerably.
However, they consitute the best water-bearing formations. They are widely
distributed throughout the world and produce very significant proportions of
the water used in many countries.
Other unconsolidated sedimentary aquifers include marine deposits,
alluvial or stream deposits (including deltaic deposits and alluviai fans), glacial
drifts and wind-blown deposits such as dune sand and loess [very fine silty
deposits). Great variations in the water-yielding capabilities of these formations can also be expected. For example, the yield from wells in sand dunes
7

and loess may be limited by both the finenessof the material and the limited
areal extent and thickness of the deposits.
Limestone, essentially calcium carbonate. and dolomite or calciummagnesium carbonate are examples of consolidated sedimentary rocks known
to function as aquifers. Fractures and crevices caused by earth movement,
and later enlarged into solution channels by ground-water flow through them,
form the connected o:,enings through which flow takes place (Fig. 2.3).
Flows may be considerable where solution channelshave developed.

B

A
Fig.2.3

A.FRACXJRESlNDENSELIMESTONETHROUGHWHICHFLOWMAY
OCCUR.
B. SOLUTION CHANNELS IN LIMESTONE CAUSED BY GROUNDWATERFLOWTHROUGHFRACTURES.

Sandstone, usually formed by compactron of sand deposited by rivers near
existing sea shores, is another form of consolidated sedimentary rock that
performs as an aquifer. The cementing agents are responsible for the wide
range of colors seen in sandstones. The water-yielding capabilities of
sandstonesvary with the degreeof cementation and fracturing.
Shales and other similar compacted and cemented clays, such as mudstone
or siltstone, are usually not considered to be aquifers but havebeen known to
yield small quantities of water to wells in localized areas where earth
movements have substantially fractured such formations.
Igneous rocks are those resulting from the cooling and solidification of
hot, molten materials called magma which originate at great depths within the
earth. When solidification takes place at considerable depth, the rocks are
referred to as intrusive or plutonic while those solidifying at or near the
ground surface are called extrusive or volcanic.
Plutonic rocks such as granite are usually coarse-textured and non-porous
and are not considered to be aquifer;. However, water has occasionally been
found in crevices and fractures ol the upper, weathered portions of such
rocks.
Volcanic rocks, becauseof the relatively rapid cooling taking place at the
surface, are usually fine-textured and glassy in appearance. Basalt or trap
rock, one of tlze chief rocks of this type, can be highly porous and
permeable as a result of interconnected openings called vesiclesformed by the
development of gasbubbles as the lava (magma flowing at or near the surface)
cools. Basaltic aquifers may also contain water in crevicesand broken up or
brecciated tops and bottoms of successivelayers.
8

Fragmental materials dischargedby volcanos. such as ash and cinders, have
been known to form excellent aquifers where particle sizes are sufficiently
large. Their water-yielding capabilities vary considerably, depending on the
complexity of stratification, the range of particle sizes, and shape of the
particles. Examples of excellent aquifers of this type are to be found in
Central America.
Metanwrphic rock is the name given to rocks of all types, igneous or
sedimentary, which have been altered by beat and pressure. Examples of
these are quart&e or metamorphosed sandstone, slate and mica schist from
shale, and gneissfrom granite. Generally, these form poor aquifers with water
obtained only from cracks and fractures. Marble, a metamorphosed limestone, can be a good aquifer when fractured and containing solution channels.
With the above description of the three main rock types, it should now be
easier to understand why an estimated 95 percent of the available ground
water is to be found in sedimentary rocks which constitute only about 5
percent of the earth’s crust. The wells described in this manual will be those
constructed in unconsolidated sedimentary rocks which are undoubtedly the
most important sources of water for small community water supply systems.
Role of Geologic Processes in Aquifer Formation

Geologic processesare continually, though slowly, altering rocks and rock
formations. So slowly are these changes taking place that they are hardly
perceptible to the human eye and only barely measurable by the most
sensitive instruments now available. Undoubtedly, however, mountains are
being up-lifted and lowered, valleys filled or deepenedand new ones created,
sea shores advancing and retreating, and aquifers created and destroyed.
These changes are more obvious when referred to a geologic timetable with
units measured in thousands and ,millions of years and to which reference can
be made .in almost any book on geology.
Geologically old as well as young rocks may form aquifers but generally
the younger ones which have been subjected to less compression and
cementation are the better producers. Geologic processes determine the
shape, extent, and hydraulic or flow characteristics of aquifers. Aquifers in
sedimentary rock formations for example vary considerably depending upon
whether the sediments are terrestrial or marine in nature.
Terrestrial sediments, or materials deposited on land, include stream, lake,
glacial, and wind-blown deposits. With but few exceptions they are usually of
limited extent and discontinuous, much more so than are marine deposits.
Texture variations both laterally and vertically are characteristic of these
formations.
AZZMaI or stream deposits are generally long and narrow. Usually
SUbSUrface, or below the valley floor, they may also be in the form of terraces
indicating the existence of higher stream beds in the geologic past. The
material in such aquifers may range in size from fine sand to gravel
and
boulders. Abandoned stream courses and their deposits are sometimesburied
under wind-home or glacial depos,ts with no visible evidence of their
existence. Where a rapidly flowing stream such as a mountain stream
encounters a rapid reduction of slope, the decrease in velocity causes a

9

deposition of large aprons of material known as alluvial fans. These sediments
range from coarser to finer material as one proceeds away from the
mountains.
Glacial deposits found in North Central U.S.A., Southern Canada, and
Northern Europe and Asia may bc extensive where they result from
continental glaciers as compared to the more localized deposits of mountain
glaciers. These deposits vary in shape and thickness and exhibit a lack of
interconnection because of the clay and silt accumulations within the sand,
gravel and boulders. Outwash deposits swept out of the melting glacier by
melt-water streams are granular in nature and similar to alluvial sands.The
swifter melt-water streamsproduce the best glacial drift aquifers.
Lake deposits are generally fine-textured, granular material deposited in
quiet water. They vary considerably in thickness, extent, and shapeand make
good aquifers only when they are of substantial thickness.

GROUND-WATER
Types of Aquifers

FLOW AND ELEMENTARY

WELL HYDRAULICS

Ground-water aquifers may be classified as either water-table or artesian
aquifers.
A water-table aquifer is one which is not confined by an upper
impermeable layer. Hence, it is also called an unconfined aquifer. Water in
these aquifers is virtually at atmospheric pressureand the upper surface of the
zone of saturation is called the water table (Fig. 2.2). The water table marks
the highest level to which water will rise in a well constructed in a water-table
aquifer. The upper aquifer in Fig. 2.4 is an example of a water-table aquifer.
An artesian aquifer is one in which the water is confined under a pressure
greater than atmospheric by an overlying, relatively impermeable layer.
Hence, such aquifers are also called confined or pressure aquifers. The name
artesian owes its origin to Artois, the northernmost province of France, where
the first deep wells to tap confined aquifers were known to havebeen drilled.
Unlike water-table aquifers, water in artesian aquifers will rise in wells to
levels above the bottom of the upper confining layer. This is becauseof the
pressure created by that confining layer and is the distinguishing feature
between the two types of aquifers.
The imaginary surface to which water will rise in wells located throughout
an artesian aquifer is called the piezomettic surface. This surface may be
either above or below the ground surface at different parts of the same
aquifer as is shown in Fig. 2.4. Where the piezometric surface lies above the
ground surface, a well tapping the aquifer will flow at ground level and is
referred to as a flowing artesian well. Where the piezometric surface lies
below the ground surface, a non$owing artesiarl well results and some means
of lifting water, such as a pump, must be provided to obtain water from the
well. It is worthy of note here that the earlier usageof the term artesian well
referred only to the flowing type while current usageincludes both flowing
and non-flowing wells, provided the water level in the well rises above the
bottom of the confming layer or the top of the aquifer.
10

Nonflowing
artesian

WoterFlowing . .
artesian

Ground
surfuce7

Fig. 2.4

Recharge area
at autc?opping
of formation

TYPES OF AQUIFERS.

Water usually enters an artesian aquifer in an area where it rises to the
ground surface and is exposed (Fig. 2.4). Such an exposed area is called a

rechmge area and the aquifer in that area,being unconfined, would be of the
water-table type. Artesian aquifers may also receivewater underground from
leakage through the confining layers and at intersections with other aquifers,
the rechargeareasof which are at ground level.
Aquifer Functions

The openings and pores in a water-bearing formation may be considered as
a network of interconnected pipes through which water flows at very slow
rates, seldom more than a few feet per day, from areasof rechargeto areasof
discharge. This network of pipes, therefore, serves to provide both storage
and flow or conduit functions in an aquifer.
Stooge fin&on: Related to the storage function of an aquifer are two
important properties known asporosity and specific yieZd.
The porosiZy of a water-bearing formation is that percentage of the total
volume of the formation which consists of openings or pores. For example,
the porosity of one cubic foot of sand which contains 0.25 cubic foot of
open spacesis 25 percent. It is therefore evident that porosity is an index of
the amount of ground water that can be stored in a saturated formation.
The amount of water yielded by, or that may be taken from, a saturated
formation is less than that which it holds and is, therefore, not representedby
11

the pc>:ti,sity.This quautity is related tu the property known 9s t+e ::pec*ijk
yield and defined as the volume of water released front ;I unit volu:;~eof the
aquifer material when allowed to drain freely by gravity (Fig. 7.5). TIK
rennaining vulunte uf water not removed by gravity drainage is held by
cupiktry forces sucl~ as found in
’ ft
,,A!+-.
.
.
.
.
.
.
.
the capillary fringe and by other
,“
.,.~::.~~:.~~~:~:
Static woter
.‘.‘._._.(.
1:
forces of attraction. It is called
tese, j’ ,f ‘C ..,.,.,
::>:.:.
the specific’reterttiott
and. like
the specific yield. may be expressed as a decimal fraction or
percentage. As defined, porosity is
therefore equal to the sum of the
specific yield and the specific retention. An aquifer with a porosity of
0.25 or 25 percent and a specific
yield of 0.10 or 10 percent would,
therefore, have a specific retcnt ion
of 0.1 S or IS percent. One million
cubic feet of such an aquifel would
contain 250,000 cubic feet ofwate~
Water drotned by
of which 100,000 cubic feet would
growtty from 1.0
cu ft of sand
be yielded by gravity drainage.
Conduit jim.ticm: The property
of an aquifer related to its conduit
function is known as the perttwFig. 2.5 VISUAL REPRESENTATION
ubility.
OF SPECIFIC YIELD. ITS
PL-meability is a measure of the
VALUE HERE IS 0.10 CU
capacity
of an aquifer to transmit
L’IXXCAFT
OF AQUIFER
.
water. It is related to the pressure
difference and velocity of flow between two points under laminar or
non-turbulent canditions by the following equation known as Darcy’s Law
(after iierrry Darcy, the French engineer who developed it).
(2. I)
where V

is the velocity of flow in feet per day,

h,

is the pressure at the point of entrance to the section of
conduit unlder consideration in feet of water,

hz

is the pressure at the point of exit of the same section in feet
of water,

P

is the length of the section of conduit in feet, and

P

is a constant known as the coefficient of permeability but
often referred to simply as the permeability.

Equation (2.1) may be modified to read
v = PI

(2.2)

h1 - hz
and is called the hydraulic gradient.
. where I = -,
P

.

The quantity of flow per unit of
time through a given cross-sectional
area may be obtained from equation
(2.2) by multiplying the velocity of
flow by that area.Thus,

Slope equals hydmulic
.
gradient
. .
.---.
-7,

Q=AV=PIA

Direction of flow
from I to 2

(2.3)

where

Q

is the quanity of flow
per unit of time

and

A

is the cross-sectional
area.

Based on equation (2.3) the coefficient of perrneubility may,
,, _,. . ,.
.
;.
‘.
therefore, be defined as the quan,...;..~
‘:. .
) .;. ., :::
c
tity of hater that will flow through
a unit cross-sectionalarea of porous
THROUGH
Fig 2.6 SECTiON
WATER-BEARING
SAND
material in unit time under a hySHOWING THE PRESSURE
draulic gradient of unity (or I = 1.O)
DIFFERENCE
thl- hd
at
a specified temperature, usually
CAUSING FLOW BETWEEN
POINTS 1 AND 2. THE HYtaken as 60°F. In ground-water
DRAULIC
GRADIEhTIS
problems, Q is usually expressedin
EQUAL TO TME PRESSURE
gallons
per day (gpd), A in square
DIFFERENCE DIVIDED BY
THE DISTANCE,
i!, BEfeet (sq ft) and P, therefore, in
TWEEN THE POINTS.
gallons per day per square foot
(gpd/sq ft). The coefficient of permeability can also be expressed in
the metric system using units of liters per day per square meter under a
hydraulic gradient of unity and at a temperature of 15S”C.
-

‘..
..,‘, ‘.
::
....,.,.
“.
:.-.. _ ‘.‘..‘...‘. ,:

,,

,:.

It is important to note that Darcy’s Law in the form shown in equation
(2.3) states that the quantity of water flowing under iaminar or non-turbulent
conditions varies in direct proportion to the hydraulic gradient and,
therefore, the pressure difference (hI - h2) causing the flow. This means that
doubling the pressure difference will result in doubling the flow through the
same cross-sectionalarea. By definition, the hydraulic gradient is seen to be
equivalent to the slope of the water table for a water-table aquifer or of the
piezometric surface for an artesian aquifer.
Considering a vertical cross-section of an aquifer of unit width and having
a total thickness, m, a hydraulic gradient, I, and an averagecoefficient of

13

permeability, P, we see from equation (2.3) that the rate of flow, q, through
this crosssection is given by
(2.4)

q=PmI

The product Pm of equation (2.4) is termed the coejficient of transntissibility or transmissivity, T, OI the aquifer. By further considering that the total
width of the aquifer is W, then the rate of flow, Q, through a vertical
cross-sectionof the aquifer is given by
Q=qW=TIW

(2.5)
The coej@ient of trunsmissibility is, therefore, defined as the rate of flow
through a vertical cross-sectionof an aquifer of unit width and whose height
is the total thickness of the aquifer when the hydraulic gradient is unity. It is
expressedin gallons per day per foot (gpd/ft) and is equivalent to the product
of the coefficient of permeability and the thickness of the aquifer.
Factors Affecting Permeability

Porosity is an important factor affecting the permeability and, therefore,
the capacity of an aquifer for yielding water. This is clearly evident since an
aquifer can yield only a portion of the water that it contains and the higher
the porosity, the greater is the volume of water that can be stored. Porosity
must, however, be considered together with other related factors such as
particle size, arrangement and distribution, continuity of pores, and format ion stratification.
The volume of voids or pores associated with the closest packing of
uniformly&zed spheres (Fig. 2.7) will represent the same percentage of the
total volume (solids and voids) whether the sphereswere all of tennis ball size
or all l/l000 inch in diameter. However, the smaller pores between the latter
sphereswould offer greater resistanceto flow and, therefore, causea decrease

Fii. 2.7 UNIFORMLY
SIZED
SPHERES PACKED
IN
RHOMBOHEDRAL ARRAY.

Fig. 2.8 UNIFORMLY
SIZED
SPHERES PACKED IN CUBICAL ARRAY.

14

in permeability even though the porosity is the same.
The packing of tile spheres displajred in Fig. 2.7 is referred to as the
rhombohedral packing. The porosity for such a packing can be shown to be
0.26 or 26 percent. The spheresmay also assumea cubical array as shown in
Fig. 2.8 for which the porosity is 0.476 or 47.6 percent. These porosities
apply only to perfectly spherical particles and are included here to give the
order of magnitude of the porosities that naturally occurring uniform sands
and gravels may approach. A loose uniform sand may, for example. have a
porosity of 46 percent. Clays, on the other hand, exhibit much fligher
porosities ranging from about 37 percent for stiff glacial clays to as high as 84
percent for soft bentonite clays.
Consideration of the effects of particle size and arrangement on
permeability would be incomplete without simultaneously considering the
effect of particle distibution or grading. A uniformly graded sand, that is,
one in which all the particles are about the same size, wilt have a higher
porosity and permeability than a
less uniform sand and gravel mixture. This is so because the finer
sand fills the openings between the
gravel particles resulting in a more
compact arrangement and fess pore
volume (Fig. 2.9). Here, then, is an
example of a finer material having a
higher permeability than a coarser
one due to the modifying effect of
particle distribution.
Flow cannot take place through
porous material unless the passages
Fig. 2.9 NON-UNIFORM MI XT URE
in the material are interconnected,
OF SAND AND GRAVEL
WITH LOW POROSITY AND
that is to say, there is continuity of
PERh%tBII.ITY.
the pores. Since permeability is a
measure of the rate of flow under stated conditions through porous material,
then a reduction in the continuity of the pores would result in a reduction in
the permeability of the material. Such a reduction could be causedby silt,
clay, or other cementing materials partially or completely filiing the pores in
a sand, thus making it almost impervious.
An aquifer is said to be stratiflied when it consists of different layers of
fine sand, coarse sand, or sand and gravel. Most aquifers are stratified. While
some strata contain silt and clay, others are relatively free from these
cementing materials and are said to be clean. Where stratification is such that
even a thin layer of clay separatestwo layers of clean sand, this results in the
cutting off of the vertical movement of water between the sands. Permeability may also vary from layer to layer in a stratified aquifer.
A brief discussion on the measurement of permeability is to be found in
Appendix A.
15

Flow Toward Wells

Converging j&w: When a well is at rest, that is, when there is no flow
taking place from it, the water pressure within the well is the sameas that in
the formation outside the well. The level at which water stands within the
well is known as the static water level. This level coincides with the water
table for a water-table aquifer or the piezometric surface for an artesian
aquifer. Should the pressure be lowered within the well, by a pump for
example, then tire greater pressure in the aquifer on the outside of the well
would force water into the well and flak thereby results. This lowering of the
pressure within the well is also acz$ *nanied by a lowering of the water level
in and around the well. Water fl,j~ Through the aquifer to the well from all
directions in what is known as ~0 ergingflow. This flow may be considered
to take place through successit
lindrical sections which become smaller
and smaller as the we!1 is apy’
ied (Fig. 2.10). This means that the area
across which t&e flow takes r
also becomes successivelysmaller as the
well is approached. With the same
quantity of water flowing across
these sections, it follows from equation (2.3) that the velocity increasesas the areabecomessmaller.
Darcy’s Law, equation (2.2),
tells us that the hydraulic gradient
varies in direct proportion to the
velocity. The increasingvelocity towards the well is, therefore, accompanied by an increasing hydraulic gradient. Stated in other
terms, the water surface or the
R, -2R,
A, = 2A2
piezometric surface develops an inv, ‘2V,
creasingly steeper slope toward the
well. In an aquifer of uniform shape
Fig. 2.10 F L 0 W CONVERGES TOand texture, the depression of the
WARD A WELL, PASSING
water table or piezonetric surface
THROUGH IMAGINARY
CYLINDRKAL SURFACES
in the vicinity of a pumped or
THAT ARE SUCCESSIVELY
freely flowing well takes the form
SMALLER AS THE WELL IS
of
an inverted cone. This cone,
APPROACHED.
known as the cone of depression
(Fig. 2.1 l), has its apex at the water level in the well during pumping, and its
base at the static water level. The water level in the well during pumping is
known as the pumping water level. The difference in levelsbetween the static
water level and the surface of the cone of depression is known as the
drawdown. Drawdown, therefore, increasesfrom zero at the outer limits of
the cone of depression to a maximum in the pumped weft. The radius of
influence is the distance from the center of the well to the outer limit of the
cone of depression.
Fig. 2.12 shows how the transmissibility of an aquifer affects the shapeof
the cone of depression. The cone is deep, with steep sides,a large drawdown,
16

--

Rodlus of Influence

_------Static water level
.--

and a small radius ot‘ influence
when the aquifer transmissibility is
low. With a high transmissibility,
the cone is wide and shallow, rhe
drawdown being small, and the
radius of influence large.
Rechg~ md bortndar-y ejfects:
When pumping commences at ‘I
well. the initial quantity of water
discharged comes from the aquifer
storage immediately surrounding
the well. The cbne of depression is
then small. As pumping continues,
the cone expands to meet the increasing demand for water from the
aquifer storage. The radius of influence increases and, with it, the
drawdown in the well in order to
provide the additional pressure
head required to move the water
through correspondingly greater
distances. If the rate of pumping is
kept constant, then the rate of

--+
--

T
Drowdown
in we8

C--Well

Screen

Fig. 2.11 CONE OF DEPRESSION IN
VICINITY
OF PUMPED
WELL.

FRadius

=IS,OCO ft--

Transmissibility

- IO.OCO gpd/ft

Radius = 40,000

Transmissibi!ity

-

- IOO.000

ft

gpd/ft

-

Fig. 2.12 EFFECT OF DIFFERING COEFFICIENTS OF TRANSMISSIRILITY UPON
THE SHAPE, DEPTH AND EXTENT OF THE CONE c)F DEPRESSION,
PUMPING RATE AND OTHER FACTORS BEING THC SAME IN BOTH
CASES.

17

expansion and deepening of the cone of depressiondecreaseswith time. This
is illustrated in Fig. 2.13 where C1, C2 and C3 represent conesof depression
at hourly intervals. The hourly increases in radius of influence, R, and
drawdown, s, become smaller and smaller until the aquifer supplies a quantity
of water equal to the pumping rate. The cone no longer expands or deepens
and equilibrium is said to have been reached. This state may occur in any one
or more of the following situations.
1. The cone enlargesuntil it intercepts enough of the natural
discharge from the aquifer to
equal the pumping rate.
2. The cone intercepts a body of
surface water from which
water enters the aquifer at a
,rate equivalent to the pumping rate.
3. Recharge equal to the pumping rate is received from precipitation and vertical infiltration within the radius of influence.
4. Recharge equal to the pumping rate is obtained by leakage through adjacent formations.

Fig. 2.13 CHANGES IN RADIUS AND
DEWTH OF CONE OF DEPRESSION AFTER EQUAL
INTERVALS OF TIME, AS~I$W&ONShUUT
PUMP.

Where the recharge rate is the samefrom all directions around the well the
cone remains symmetrical (Fig. 2.12). If, however, it occurs main!y from one
direction, as may be the case with a surface stream, then the surface of the
cone is higher in the direction from which the recharge takes place than in
other directions (Fig. 2.14). Conversely, the surface of the cone is relatively
depressedin the direction of an imperrnea&leboundary intercepted by it (Fig.
2.15). No rechargeis obtained from such a boundary while that receivedfrom
other directions maintains the higher levels in those directions. Rechargeareas
to aquifers, such as surface streamsare, therefore, often referred to as positive
boundaries while impermeable areasare known as negative boundaries.
Mdtiple well system: Under some conditions the construction of a single
large well may be either impractical or very costly while the installation of a
group of small wells may be readily and economically accomplished. Factors
such as the inaccessibility of the area to the heavy equipment required for
drilling the large well and the high cost of transporting large diameter pipes to
the site may be among the important considerations in a situation such as
this. Small wells can be grouped in a proper pattern to give the equivalent
performance of a much larger single well.
The grouping of wells, however, presents problems due to interference
among them when operating simultaneously. Interference between two or
more wells occurs when their cones of depression overlap, thus reducing the
18

r

Discharging

well

Fig. 2.14 SYMMETRY OF CONE OF DEPRESSION AFFECJ.‘ED BY RECHARGE
FROM STREAM.

r

Discharging

well

Fig. 2.15 CONE OF DEPRESSION IN VICINITY OF IMPERMEABLE BOUNDARY.

19

yield of the individual wells (Fig . 2.16). The drawdowrl at any point on tile
composite cone of depression is equal to the sum of ihe drawdowns ai that
point due to each of the wells being pumped separately. In particular, the
drawdown for ;I specific disclltlrge ill
a well affected by interference is
Static water levelI -_
greater fllA11llit unaffected value b?
the amount of drawdown ait that
well contributed by the interfering
wells. In other words, the discharge
per unit of drawdown commonly
called the specific capacit), of the
well is reduced. This means that
pumping must take place from a
greater depth in the well, at a greater
cost, to produce the same qaan:ity
of water from the well if it were not
subject to interference.
Fig. 2.16 INTERFERENCE BETWEEN
ADJACENT WELLS TAi’Ideally, the solution would be to
PING THE SAME AQUIFER.
space the wells far enough apart to
avoid the mutual interference of one ok the other. Very often this is not
practic,tJ for economic reasonsand the wells are spacedfar enough apart. not
to eliminate interference. but to reduce it to acceptable proportions. For
wells use3 for water supply purposes, spacingsof 115to 50 feet between wells
have bee11found to be satisfactory. Spacings may be less in fine sand
formations, in thin aquifers or when the drawdowrt is not likely to exceed 5
feet. Greater spacings may be used where the depth and thickness of the
aquifer are such as to permit the use of screenlengths in excessof IO feet.
There arc many patterns which may be used when grouping weils (Fig.
2.17). Where the aquifer extends considerable distancesin all directions from
the site of a proposed wetI field, the most desirable arrangement is one in
which the wells are locaf!:d at equal distances on the circumference of a
circle. This pattern equalizes the amount of interference suffered by each
well. It should be obvious that a well placed in the center of such a ring of
wells would suffer greater interference than any of the others when all are
pumped simultaneously. Such centrally placed wells should be avoided in well
field layouts.
Where a known source of recharge exists near a proposed site the wells
may be located m a semi-circle or along a line roughly parallel to the source.
The latter arrangement is the one often used to induce rechargeto an aquifer
from an adjacent stream with which it is connected. This is a very useful
technique in providing an adequate water supply to a small community long
after the stream level becomes so low that only an inadequate quantity of
poor quality water can be obtained directly from the stream. This is possible
since the use of wells perrnirs the withdrawal of water from the permeable
river bed and the quality is enhanced by the filtering action of the aquifer
materials.
‘0

ID)

Fig. 2.17 LAI’OUT PATTERNS FOR MULTIPLE WELL SYSTEMSUSED AS WATER
SUPPLY SOURCES.CENTRALLY LOCATED PUhlP EQUAL.iZES SUCTION
LIFT.

Well-point

Saturated
sand
Sub-soil

System

Water level
while pumping

A

\

I

Fig. 2.18 WELL-POINT DEWATERING SYSTEM.

‘I

‘\

\

Multiple well or well-point systems are also used OJI engineering construotion sites for de-watering purposes, i.e. to extract water from an area to
provide dry working conditions (Fig. 2.18). The significant difference
between this use and that for water supplies is the fact that it is JIOW
important to create interference in order to lower water levels as much as
possible. Closer well spacings than those recommended for water supply
purposes are, therefore, necessary. Well spacings for de-watering systems
usually range from 2 to 5 feet depending upon the permeability of the
saturated sand, the depth to which the water table is to be lowered and the
depth to which the well points can be installed in the formation. It is
important to note that the de-watering processmay require as much as a day
of pumping before excavation can begin and must be continued throughout
the excavation. Nevertheless,de-watering has often proved more economical
than pumping from within a sheet pile surrounded working area.
QUALITY

OF GROUND WATER

Generally, the openings through which water flows in the ground are very
small. This considerably restricts the rate of flow while at the same time
providing a filtering action against particles originally in suspension in the
water. These properties, it will be seen, considerably affect the physical,
chemical, and microbiological qualities of ground water.
Physical Quality

Physically, ground water is generally clear, colorless, with little or no
suspended matter, and has a relatively constant temperature. This is
attributable to its history of slow percolation through the ground and the
resulting effects earlier mentioned. In direct contrast, surface waters are very
often turbid and contain considerable quantiiies of suspended matter,
particularly when these waters are found near populous areas.Surface walers
are also subject to wide variations of iemperature. From the physical point of
view, ground water is, therefore, more readily usable than surface water,
seldom requiring treatment before use. The exceptions are those ground
waters which are hydraulically connected to nearby surface waters through
large openings such as fissures and solution chamlels and the interstices of
some gravels. These openings may permit suspendedmatter to enter into the
aquifer. In such cases,tastes and odors from decaying vegetation may also be
noticeable.
Microbiological

Quality

Ground waters are generally free from the very minute organisms
(microbes) which cause disease and which are normally present in large
numbers in surface waters. This is another of the benefits that result from the
slow filtering action provided as the water flows through the ground. Also,
the lack of oxygen and nutrients in ground water makes it an unfavorable
environment for disease-producing organisms to grow and multiply. The
exceptions to this rule are again provided by the fissures and solution
channels found in some consolidated rocks and in those shallow sand and

73
--

gravel aquifers where water is extracted in close proximity to pollution
sources, such as privies and cesspools.This latter problem has been dealt with
in more detail in Chapter 9, where the sanitary protection of ground-water
supplies is discussed. Poor well construction can also result in the
contamination of ground waters. The reader is referred to the section in
Chapter 4 dealing with the sanitary protection of wells.
The solution of the potable water supply problems of Nebraska City,
Nebraska, U.S.A. in 1957 bears striking testimony to the benefits derived
from percolation of water through the ground and the general advantagesof’a
ground-water supply over one from a surface source. For more than 100 years
prior to 1957, Nebraska City depended upon the Missouri River for its
domestic water supply. The quality of the water in the river deteriorated as
the years went by due to the use of the river for sewageand other forms of
waste disposal. To the old problems of high concentrations of suspended
matter, dark coloration from decayed vegetation and highly variable
temperatures (too warn in summer and too cold in winter) was added
bacterial pollution. So bad was this sittration that the Missouri River, in this
region, soon beczrre recognized as a virtual open sewer and the water no
longer met the requirements of the United States Public Health Service
Drinking Watei- Standards for waters suitable to be treated for municipal use.
The search for a new source of supply for Nebraska City led to the use of
wells drilled into the sandsthat underlie the flood plain of the Missouri River
at depths up to 100 feet. Wells drilled a mere 75 feet from the river’s edge
and drawing a considerable percentage of their water from the river yielded a
very high quality, clear water that showed no evidence of bacterial pollution
or noticeable temperature variation. The lessonsof Nebraska City can be put
to beneficiai use in many other areasof the world.
Chemical Quality

The chemical quality of ground water is also considerably influenced by its
relatively slow rate of travel through the ground. Water has always been one
of the best solvents known to man. Its relatively slow rate of percolation
through the earth provides more than amfextra useful life
against lower initial cost, the cost of replacement at a later date and the
owner’s financial capacity.
h%scelianeous
Other miscellaneous factors also play important roles in the selection of
casing and screen materials. Chief among these, with reference to small wells,
would be site accessibility, ease of handling, availability, and on-site
fabrication. !n areasnot accessibleby motor vehiclesand necessitatingthe use
of air transportation, wei$t of materials could be the most decisive
consideration. The lighter plastic-type materials would then gain preference
over metals. Ease of handling, both for transportaiton and construction
purposes,would also favor the use of plastic-type material.
The above are on!y some of the major considerations in the selection of
materials, Solutions cannot be blindly transferred from one geographic area
to another. Each set of conditions, and the advantagesand disadvantagesof
each possible solution, must be carefully considered before making a final
selection.
GRAVEL PACKING AND FORMATION STABILIZATION
Both gravel packing and formation stabilization are aids to the processof
well development described earlier in this chapter. A further similarity is the
addition of gravel in the caseof gravel packing, and coarse sand 01 sand and
gravel in the case of fori,tirton stabilization to the annular spacebetween the
screen and water-bearing formation. This, however, is where the similarities
end. The differences between gravel packing and formation stabilization are
indeed very fundamental and should be thoroughly grasped.
It will be recalled that the development process in a naturally deveioped
well removes the finer material from the vicinity of the well screen,leaving a
zone of coarser graded material around the well. This cannot be achievedin a
formation consisting of a fine uniform sand due to the absenceof any coarser
material. The object of gravel packing a well is to artificially provide the
graded gravel or coarser sand that is missing from the natural formation. A
well treated in this manner is referred to as an artificially gravel-packedwell
to distinguish it from the natura!ly developed well.
Drilling by the rotary method through an unconsolidated water-bearing
formation of necessity results in a hole somewhat larger than the outside
diameter of the well screen. This provides the necessaryclearance to permit
the lowering of the screen to the bottom of the hole without interference.
50

The object of formation stabilization is to fill the annuiar space around the
screen(possibly 2 inches and more in width) at least partially, to prevent the
silt and clay materials above the aquifer from caving or slumping when the
development work is started. By avoiding such caving, proper development of
the well may be carried out with less time and effort. Note that the
development process here is a natural one, with the graded coarse material
coming from the aquifer itself and not from the added stabilizing material.
The objectives of gravel packing and formation stabilization, therefore,
provide the major difference between the two processes.These differences in
objectives also form the basis for the differences in the design features of the
two processes.
Gravel Packing
There are essentially two conditions in unconsolidated formations which
tend to favor artificial gravel-pack construction.
The first of these, fine uniform sand, has already been mentioned. Such a
sand would require a screen with very small slot openings and, even so, the
development processwould not be satisfactory becauseof the uniformity of
the sand particles. Also, screens with very small slot openings have low
percentagesof open area because of the relative thickness of the metal wires
that must be used to provide strength. By artificially gravel packing wells in
such formations, screens with larger slot openings may be used and the
improved development results in greater well efficiency. The use of artificial
gravel-pack construction is recommended in formations where the screenslot
opening, selected on the basis of.a naturally developed well, is smaller than
0.010 inch (No. 10 slot).
Extensively laminated for&ions provide the second set of conditions for
which gravel pack construction is recommended. This refers to those aquifers
that consist of thin, alternating layers of fine, medium, and coarse sand. In
such aquifers it is difficult to accurately determine the position and thickness
of each individual layer and to choose the proper length of each section of a
multiple-slot screen. The use of artificial gravel packing in such formations
reduces the chances of error that would result from natural development.
Selection of gravel-pack material: The selection of the grading of
gravel-pack material is usually based on the layer of finest material in an
aquifer. The gravel-pack material should be such that (1) its 70 percent size is
4 to 6 times the 70 percent size of the material in the finest layer of the
aquifer, and (2) its uniformity coefficient is lessthan 2.5, and the smaller the
better. Unifurmi@ coefficient is the number expressing the ratio of the 40
percent size of the material to its 90 percent size. it is well to recall here that
the sizesrefer to the percentageretained on a given sieve.
The first condition usually ensures that the gravel-pack material will not
restrict the flow from the layers of coarsestmaterial, the permeability of the
pack being several times that of the coarsest stratum. The second condition
ensures that the lossesof pack material during the development work will be
minimal. To achieve this goal. the screen openings are chosen so as to retain
90 percent or more of the gravel-pack material.
51

.

Gravel-pack material should consist of clean, well rounded, smooth grains.
Quartz and other silica-based materials are preferable. Lirnestorle and shale
are undesirable in gravel-pack material.
Tlzickrzessof gravel-pack ewelopes: Gravel-pack envelopes ltre usually 3 to
8 inches thick. This is not out of necessity as tests lime shown that ~1fraction
of an ~IX!I would satisfactorily retain and control the formation sand. The
greater thicknesses are used in order to ensure tllat the well screen is
completely surrounded by the gravel-pack material.
Forzdor.
Stabilization
The quantity of formation stabilizer should be sufficient to fill the annular
space around the screen and casin,u to a level about 30 feet. or as much as is
practicable, above the top of the screen. Ttlis would allow for settlement and
ItlIou~ the screen during development. If necessary,
losses of the materia! +hmore material should be added as development proceeds to prevent its top
level from falling below that of the screen. The settlement of the material is
beneficial in eroding the mud wall formed in boreholes drilled by the rotary
method, thus making well development much easier.
The typical concrete or mortar sand is widely used as a formation
stabilizer. The aquifer conditions under which it IS suitable range from those
requiring a No. 20 (0.020-inch) to those of a No. SO (O.OSO-incll) slot
opening. A specially graded material is not necessary.
SANITARY PROTECTION
It has been stated in Chapter 2 that ground waters are generally of good
sanitary quality and safe for drinking. Well design should be aimed at the
extraction of this high quality water without contaminating it or making it in
any way unsafe for human consumption. The penetration of a water-bearing
formation by a well provides two main routes for possible contamination of
the ground water. These are the open. top end of the casing and the annular
space between the casing and the borellole. The designer must concern
himself with the prevention of contamination througli tliese two routes.
Upper Terminal
Well casing should extend at least I foot above the general level of the
surrounding land surface. It sflould be surrounded at the ground surt’ace by a
4-inch thick concrete slab extending at least 2 feet in all directions. The upper
surface of this slab and its immediate surroundings should be gently sloping
so as to drain water away from the well. as shown in Fig. 4.12. It is also good
practice to place a drain around the outer edge of the sldb and extend it to a
discharge point at some distance from the well. A sanitary well seal should be
provided at the top of the well to prevent the entrance of contaminated
water or other objectionable material directly into the well. Examples of
these are shown in Fig. 4.13.
Lower Terminal of the Casing
For artesian aquifers. the water-tight
wards into tlie impermeable formation

casing should be extended down(sucl1 ;f~ a clay) which caps the

Pump unit

Sanitary
I/

well seal
,Relnfarced
concrete
‘Cover slab sloped away from pump

-%

----

. -1

-

-

--,r

L-I:

-

--

-L-F
I
-_

----

--

-

---

Fig.

4.12 S:\NlThKY

Drop pope

PKO’I‘ti”fION

OF l’PPt;.K ‘i‘ER31IN~\tL.Ok WCI.1..

Soft rubber expandlng gasket

I

OroDtme

-7

Soft rubber expanding gasket
\

\

Well casing

k.A

Well casing

In water-table aquifers the casing should be extended at least 5 feet below
the lowest expected pumping level. This limiting distance should be increased
to 10 feet where the pumping level is lessthan 25 feet from the surface.
The above are general rules which should be applied with some flexibility
where geologic conditions so require.
Grouting and Sealiug Casii

The drilled hole must of necessity be larger than the pipe used for the well
casing. This results in the creation of an ®ularly shaped annular space
around the casing after it has been placed in position. It is important to fill
this space in order to prevent the seepageof contaminated surface water
down along the outside of the casing into the well and also to seal out water
of unsuitable quality in strata above the desirable water-bearing formation.
In caving material, such as sand or sand and gravel, the annular spaceis
soon filled as a result of caving. In such cases, therefore, no special
arrangements need be made for filling the annular space.However, where the
material overlying the water-bearing formation is of the non-caving type, such
as clay or shale, then the annular space should be grouted with a cement or
clay slurry to a minimum depth of 10 feet below the sirface. Where the
thickness of the clayey materials permit it, increasing the depth of grout to
about 15 feet would provide added safety. The diameter of the drilled hole
should be 3 to 6 inches larger than the permanent well casingto facilitate the
placing of the grout. It is important to remove temporary casing when
grouting rather than simply filing the space between the two casings as
vertical seepagecan readily occur down the outside of any unsealed casing.
Methods of mixing and placing the grout are discussedin Chapter 5.

54

There are four basic operations involved in the construction of tubular
wells. These are the drilling operation, casing instailation, grouting of the
casingwhen necessaryand screen installation.
WELL DRILLING METHODS
The term well drilling methods is being used here to include ail methods
used in creating holes in the ground for well construction purposes.As such,
it includes methods such asboring and driving which are not drilling methods
in a pure sense.The classification is one of convenience in the absenceof a
better descriptive term. The limitations on well diameter (4 inches and less)
exclude the dug well from consideration. The sections that follow describe
the bored and driven, the percussion, hydraulic rotary and jet drilled wells.
Boring
Boring of small diameter wells is commonly undertaken with hand-turned
earth augers, though power-operated augers are sometimes used. Two common types of hand augers are shown in Fig. 5.1. They each consist of a shaft

Fig. 5.1

HAND AUGLRS.
Manual TM5297,

(From Fig. 6, Wello. Department
1957.)

of the Army Technical

with wooden handle at the top and a bit with curved blades at the bottom.
The blades are usually of the fixed type, but augers with blades that are
adaptabie to different diameters are also available. Shafts are usually made up
of S-ft sections with easy latching couplings.
The hole is started by forcing the blades of the bit into the soil with a
turning motion. Turning is continued until the auger bit is full of material.
The auger is then lifted from the hole, emptied and returned to use. Shaft
s5

extensions are added as needed to bore to the desired depth. Wells shallower
than 15 ft ordinarily require no other equipment than the auger. Deeper
wells. however. require the use of a light tripod with a pulley at the top, or a
raised platform, so that the auger shaft can be inserted and removed from the
hole without disconnecting all shaft sections.
The spiral auger shown in Fig. 5.2 is used in place of the normal cutting bit
to remove stones or boulders encountered during boring operations.
When turned in a clockwise direction, the spiral twists around a
stone so that it can be lifted to the
surface.
The method is used in boring to
depths of about 50 ft in clay, sift
and sand formations not subject to
caving. Boring in caving formations
may be done by lowering casing to
the bottom of the hole and boring
ahead little by little while forcing
the casingdown.
Driving
Driven wells are constructed by
driving into the ground a well point
fitted to the lower end of tightly
connected sections of pipe. The
well point must be sunk to some
depth within the aquifer and below
the water table. The riser pipe
above the well point functions as
the well casing.
Equipment used includes a drive
hammer, drive cap to protect the
top end of the riser pipe during
driving, tripod, pulley and strong
rope with or without a winch. A
light
drilling rig may be used inFig. 5.2 SPIRAL AUGER.
stead of the tripod assembly. Well
points can be driven either by hand
methods or with the aid of machines. Fig. 5.3 shows the assembly for a
purely hand-driven method. The drive-block assembliescommonly operated
by a drilling rig or by hand with the aid of a tripod and tackle are shown in
Fig. 5.4.
Whatever the method of drivin g, a starting hole is first made by boring or
digging to a depth of about Z feet or more. As driving is generally easierin a
saturated formation, the starting hole should be made deep enough to
penetrate the water table if the latter is sufficiently shallow. The starting hoie
should be vertical and slightly larger in diameter than the well point. The well

56

Ham? driver

point is inserted into this hole dnd
driven to the desired depth, S-ft
lengths of riser pipe being added as
necessary. Pipe couplings should
have recessed ends and tapered
threads to provide stronger connections than ordinary plumbing
couplings. The pipe and coupling
threads should be coated with pipe
thread compound to provide airtight joints. The well-point assembly should be guided asvertically as
possible and the driving tool, when
suspended,should be hung directly
over the center of the well. The
weight of the driving tool may
range from 75 to 300 pounds.
Heavier tools require the use of a
power hoist or light drilling rig. The
spudding action of a cable-tool
drilling machine (Fig. 5.14) is well
suited for rapid well point driving.
Slack joints should be periodically
tightened by turning the pipe lightiy with a wrench. Violent twisting
oi‘ the pipe mikes driving no easier
and can result in damage to the well
point. Thus must, therefore, be
avoided.
Dr%en wells can be installed
only ln unconsolidated formations
relatively
free of cobbles and
boulders. Hand driving can be
undertaken to depths up to about
30 feet; machine driving can
achieve depths of 50 feet and
greater.

----k-

Drive

cap

Htle backfilled
with pudd.ed clay

Fig. 5.3

SlMPLE TOOL FOR DRIVING WELL
POINTS
TO
DEPTHS OF 15 TO 30 FT.

Jetting

The jetting method of well drilling usesthe force of a high velocity stream
or jet of fluid to cui a hole into the grourrd. The jet of fluid loosens the
subsurface materials and transports them upward and out of the hole. The
rate of cutting can be improved with the use of a drill Si.t (Fig. 5.5) which can
be rotated as well as moved in an up-anddown chopping manner.
The fhrid circulation system is similar to that of conventional rotary drilling described later in this chapter. indeed the equipment can be identical with
that used for rotary drilling, with the exception of the drill bit. Simple
equipment for jet drilling is shown in Fig. 5%. A, tripod made of ‘I-inch
57

galvanized iron pipe is used to
suspend the galvanized iron drill
pipe and the bit by means of a Uhook (at the apex of the tripod),
single-pulley block and manila rope.
A pump having a capacity of approximately 150 gallons per minute
at a pressure of 50 to 70 pounds
per square inch is used to Li-;:e the
drilling tluid through suitable hose
and ;1 small swivel on through the
drill pipe and bit. The fluid, on
emsrging from the drilled hole,
tra:iels in a narrow ditch to a settling
pit where the drilled materials (cuttings) settle out and then to a storage pit where it is again picked up
by the pump and recirculated. The
important features of settling and
storage pits are described in the
later section of this chapter dealing
with hydraulic rotary drilling. A
piston-type
reciprocating pump
would be preferred to a centrifugal
one because of the greater maintenance required by the latter as a
result of! leaking seals and worn
impellers and other moving parts.
The ::pudding percussion action
can be imparted to the bit either by
means of a hoist or by workmen
alternately pulling and quickly releasing the free end of the manila
rope on the other side of the block
from’ the swivel. This may be done
while other workmen rotate the
drib pipe. The drilling fluid may be
and is very often plain water.
Depths of the order of 50 feet may
be achieved in some formations
using water asdrilling ff uid without
undue caving. When caving d3es
occur, then a drilling mud as
described in the later section on
hydraulic rotary drilling should be
used.
The jetting method is particular-

Fig. 5.4 DRIVE-BLOCK ASSEMBLIES
FOR
DRIVING
WELL
POINTS.

Fig.55

BITS FOR JET DRILLING.
(From Fig. 17, We&s,Department of the Army Technical
Manual TMS-297, 1957.)

58

single
:

Fig. 5.6

wlley

block

/Tripod

SIMPLE EQUIPMENT FOR JET OR ROTARY DRILLING.

ly successful in sandy formations. Under these conditions a high rate of
penetration is achieved. Hard clays and boulders dv present problems.
Hydraulic Percussion
The hydraulic percussion method uses a similar string of drill pipe to that
of the jelting method; The bit is also similar except for the ball check valve
placed between the bit and the lower end of the drill pipe. Water is introduced continuously into the borehole outside of the drill pipe. A reciprocating, up-and-clown motion applied to the drill pipe forces water with
suspended cuttings through the check vaPvc and into the drill pipe on the
down stroke. trapping it a~ the valve closes on the up stroke. Continuous
reciprocating motion produces a pumping action, lifting the fluid and cuttings
to the top of the drill pipe where they are discharged into a settling tank. The
cycle of circulation is then complete. Casing is usually driven as drilling
proceeds.
The method uses a minimum of equipment and provides accurstc samples
of formations penetrated. It is well suited for use in clay and sand formations that are relatively free of ccbbles or boulders.
Sludger
The sludger method is the name given to a forerunner of the hydraulic
percussion method described in the previous section. It is accomplished entirely with hand tools. makes use of locally available materials. such as

bamboo for scaffoiding, and is particularly suited to use in inaccessible areas
where labor is plentiful and cheap. The first description of the method is
believed to have come from East Pakistan where it has been used extensively.
In the sludger method, as used in East Pakistan. scaffolding is erected as
shown in Fig. 5.7. The reciprocating, up-anddown motion of the driil pipe is
provided by means of the manually
operated bamboo lever to which the
drill pipe is fastened with a chain. A
sharpened coupling is used as a bit
at the lower end of the drill pipe.
The man shown seated on the scaffolding uses his hand to perfortn
the functions of the check valve as
used in the hydraulic percussion
method, though. in this .case at the
top instead of the bottom of t!le
drill pipe. A pit, approximately 3
feet square and 2 feet deep, around
the drill pipe, is filled with water
which enters the borehole as drilling progresses. On the upstroke of
the drill pipe its top end is covered
by the hand. The. hand is removed
on
the downstroke (Fig. C.8), thus
Fig. 5.7 BAMBOO
SCAFFOLDING,
PIVOT AND LEVER USED
allowing some of the fluid and cutIN DRILLING BY THE SLUDtings sucked into the bottom of the
GER METHOD. (From “Jctdrill
pipe to rise and overflow. Conting S m a I 1 Tubewells By
Hand.” Wafer Supple and Santinuous repetition of the process
itaiion in Develop& Councauses
the penetration of the drill
fries. AID-LiNC/IPSED
Item
pipe
into
the formation and creates
No. IS. June 1967.)
a similar pumping action to that of
the hydraulic percussion method. New iengths of drill pipe are added as
necessary. The workman whose hand operates as the flap valve changes position up md down the scaffolding in accordance with the position of the top
of the drill pipe. Water is added to the pit around the drill pipe as the level
drops. When the hole has been drilled to the desired depth, the drill pipe is
extracted in sections;care being taken to prevent caving of the borehole. The
screen and casing are then lowered into position.
Wells up to250 feet deep have been drilled by this method in fine or sandy
formations. Reasonably accurate formation samples can be obtained during
drilling. Costs are confined to labor and the cost of pipe, and can therefore,
be very low. The method requires no great operating skills.
Hydraulic Rotary
Hydraulic rotary drilling combines the use of a rotating bit for cutting the
borehole with that of continuously circulated drilling fluid for removal of the
cuttings. The basic parts of a conventional rotary drilling machine or rig are a
derrick or mast and hoist: a power operllted revolving table rhat rotates the

drill stem and drill bit below it; a

pump for forcing drilling fluid via a
length of hose and a swivel on
through the drill stem and bit: and
a power unit or engine. The drill
stem is in effect a long tubular shaft
consisting of three parts: the kelly;
as many lengths of drill pipe as required by the drilling depth; and
one or more lengths of drill collar.
The kelly or the uppermost section of the drill stem is made a few
feet longer and of greater wall
Fig,..8
MAN ON SCAFFOLDING
thickness than a length of drill pipe.
RAISES HAND OFF PIPE
Its outer shape is usually square
ALLOWING
DRILL
FLUID
(sometimes six-sided or round with
AND CUTTINGS TO ESCAPE.
(From “Jetting
Small Tubelengthwise grooves), fitting into a
weiis By Hand,” Water Supply
similarly shaped opening in the
and Sanitation in Developing
rotary table such that the kelly can
Countries,
AID-UNC/IPSED
Item No. 15, June, 1957.)
be freely moved up or down in the
opening even while being rotated.
At the top end of the kelly is the swivel which is suspendedfrom the hook of
a traveling hoist block.
Below the kelly are the drill pipes, usually in joints about 20 feet long.
Extra heavy lengths of drill pipe called drill collars are connected immediately
above the bit. These add weight to the lower end of the drill stem and so help
the bit to cut a straight, vertical hole.
The bits best suited to use in unconsolidated clay and sand formations are
drag bits of either the fishtail or three-way design (Fig. 5.9). Drag bits have
short blades forged to thin cutting edgesand faced with hard-surfacing metal.
The body of the bit is hollow and carries outlet holes or nozzles which direct
the fluid flow toward the center of each cutting edge. This flow cleans and
cools the blades as drilling progresses.The three-way bit performs smoother
and faster than the fishtail bit in irregular and semi-consolidated formations
and has less tendency to be deflected. It cuts a little slower than the fishtail
bit, however, in truly unconsolidated clay and sand formations.
Coarse gravel formations and those containing boulders may require the
use of roller-type bits shown in Fig. 5.10. These bits exert a crushing and
chipping action as they are rotated, thus cutting harder formations effectively. Each roller is provided with a nozzle serving the samepurpose with respect
to the rollers as those on the drag bits with respect to their blades.
The pump forces the drilling fluid through the hose, swivel, rotating drill
stem and bit into the drilled hole. The drill fluid, as it flows up and out of the
drilled hole, lifts the cuttings to the ground surface. At the surface the fluid
flows in a suitable ditch to a settling pit where the cuttings settle out. From
here it overflows to a storage pit where it is again picked up by the pump and
recirculated. The settling pit should be of volume equal to at least three times

61

the volume of the hole being
drilled. 1t should be relatively shailow (a depth of 2 feet to 3 feet
usually proving satisfactory) and
About twice as long in the direction
of flow 3s it is wide and deep. In

Fishtail

Three-way

Fig. 5.9

ROTARY

DRILL BITS. (From

Fig. 41, Wells. Department of
the Army Technical Manual
TMS-297, 1957.)

accordance with fhe above rules a
settling pit 6 feet long, 3 feet wide
and 3 feet deep would be suitable
for the drilling of 4-inch wells (hole
diameter of’ 6 inches) 100 feet in
depih, A system of baffles may also
be used to provide extra travel time
in the pit and ih:ls improve the
settling.
The storage pit is inteilded
mainly to provide enough vo!ume
from which to pump. A pit 3 feet
square and 3 feet deep would be
satisfactory. It may either be combined with the settling pit to form a
single, larger pit or separated from
the settling pit by a connecti!lg
ditch. Drill hole cuttings should be
periodically removed from the pits
and ditches as is necessary.
The drilling fluid performs other
important functions in the drilled
hole besides those already mentioned. These are discussed later in
this chapter.

Fig. 5.10 ROLLER-TYPE
DRILL BIT.(From

ROTARY

Reed Drilling Tools. Houston, Texas.)

Fig. 5.1 I shows a number of the
component parts of a rotary drilling
rig. The ch,ain pulldowns shown are
used mainly for applying greater
do\,lnward force to the drill pipe
and bit but are not normally required for the drilling of small wells
in unconsolidated format ions.

Rotary drilling equipment for
small diameter shallow wells can be
much simpler and less sophisticated than that just described. The truck,.
trailer or skid mounted derrick or mast can be substituted by a tripod made
of Z-inch or 3-inch galvanized iron pipe. A small suitable swivel can be suspended by rope through a single-pulley block from a (J-hook fLved by a pin at
the apex of the tripod. Drill pipe and bits both made from galvanized iron

Galvanized
iron

pipe

collapse. In addition, tjle drilling
mud forms ;I mud cake or rubbery
sort of lining on the wail of the
borehoic. This mud aice holds the
loose part icies of the forma tioti in
place, protects the wail from being
eroded by the upward strem uf
fluid and scais the wall tu prevent
ic~ssc)f fluid into permeable formations such ;1s sands and gravels.
Drillers must be careful mt to increase the pumpirig rate to the
puint where it c;lcszs destruction ot
the mud czke and cming of the
hole.

Outlet for directing drill fluid onto
cutlmg edge

Cutting edges

The drilling rluid must aisv be
such that the clay doesn’t sett!e c~ut
of t he mixture when pumping
ce;mx but rcmins somewhat eiastic, thus keeping the Cuttings in suspensm. Ail rlaturul clays do nut
exhibit this property. k ncwtl ;is
gdirr:.
Beiitonitc clays do cxiiihit
satisfuctory gel strength and tire
added to uaturltl clays to improve
their gel properties to desired Icvcis.
The driller must 111so use his
good judgernerlt iu arrivilig tit ;i suitubie tluid thickness. TW thin ;I
tluid rc-suits in caving 01 tile hole
und loss of tluid into permeable i‘ormaths. 011 tilt‘ other hand. tluid

slmuid bc no rilickcr rhn is IICWSsary to nlairltrtin 3 .viousfy shown in Fig. 5.4. The drive block is raised
and dropped onto the drive head by means of manila rope wound on a cat head.
It is important that the first 40 to 60 feet of casing be driven vertically.
Proper aiignment of the string of tools centrally within the casing. when the
tools are allowed to hang freely. is a necessary precaution. Periodic checks

should be made with a plumb bob or carpenter’s level used along the pipe at
two positions approximately at right angles to each other to ensure that a
straight and vertical hole is being drilled.
Cable-tool percussion drilling can be used successfully in all types of formations. It is. however. better suited than other methods to drilling in unconsolidated formations containing large rocks and boulders.
The main disadvantages of the cable-tool percussion method are its slow
rate of drilling and the need to case the hole as drilling progresses. There are.
however, a number of advantages that account for its widespread use. Reasonably accurate sampling of formation material can be readily achieved. Rough
checks on the water quality and yield from each water-bearing stratum can
readily be made as drilling proceeds. Much less water is needed for drilling
than for the hydraulic rotary and jetting methods. This can be an important
consideration in arid regions. Any
encounter with water-bearing formations is readily noticed as the
water seeps into the hole. The
driller, therefore, need not be as
skilled as his rotary counterpart in
some respects.
INSTALLING WELL CASING
Some well drilling methods such
as the cable-tool percussion method
require that the casing closely follows the drill bit as drilling proceeds. In wells constructed by those
methods, the casing is usually driven
into position by any of the methods
already described. This section deals
with the setting of casing in an
open borehole drilled by the hydraulic rotary, jetting, hydraulic percussion or sludger methods.
It is first necessary to ensure
that the borehole is free from obstructions throughout its depth before attempting to set the casing. In
the hydraulic rotary and jetting
methods, the driller may ensure a
clean hole by maintaining the fluid
circulation with the bit near the
bottom of the hole for a long
enough period to bring all cuttings
to the surface. At times, the driller
may also drill the hole a little
deeper than necessary so that any
caving-material fills the extra depth

Fig. 5.17 SAND PUMP BAILER WITH
FLAT VALVE BOTTOM.

69

of the hole without affecting the
settirkg ui‘ the casing at the dcsircd
depth.
In setting casing. it may be suspended from witllin a coupling at
its top end by means of an adapter
called a sub which is attached to a
hoisting plug (Fig. 5.X), a casing
elevator (Fig. 5.2 1) or a pipe clamp
placed around the casing below the
.I
coupling. The first length of casing
is lowered until the coupling. casing
elevator or pipe clamp rests on the
rotary table or other support placed
Fig. 5.18 CAStbiG DRIVE SHOE.
on the ground around the casing. If
lifting by means of a sub. the sub on the first length of casing is unscrewed
and attached to the second length of casing. If lifting by elevators or pipe
clamps, then the elevator bails or their equivalent are released from the casing
in the hole and fixed to another elevator or pipe clamp on the second length
of casing. This length of casing is then lifted into position and screwed into
the coupling of the first length. The threads of the casing and coupling should
be lightly coated with a thin oil. Joints should be tightly screwed together to
prevent leakage. The elevator or otfler support for the casing is then removed
and the string of casing lowered and supported at its uppermost coupling. The
procedure is repeated for as many successive lengths of casing as are to bc
installed. Should caving be such as to prevent the lowering of the casing, the
swivel may be attached to the casing with a sub and by circulating tluid
through the casing wash it down. Alternatively, the c:~ing may be driven.
GROUTING

AND

SEALING

CASING
Grolitil2g is the name given to
the process by which a slurry or
watery mixture of cement or clay is
used to fill the annular space between the casing and the wall of the
borehole to seal out contaminated
waters from the surface and other
strata above the desirable aquifer.
Should the well be constructed
with both an inner and outer permanent casing, then the space between the casings as well as that between the wall of the borehole and
the outer casing should be grouted.
Puddled native cluy of the type
suitable for use as drilling fluid can

;#j$$
”
,,___,‘ ,/Y, _
Fig.219

DRIVING
CASING WITH
DRIVE CLAMPS AS HAMMER AEiD DRIVE HEAD AS
ANVIL.

70

be used for glcruting and may be
placed by pumicing with the mud
circulation pundit nvrmally used for
drifting purpose\ 1I should he used
at depths belt)\\ the first few feet
from the surtlli< where it would
not be subject to drying and shrinkage. It should 11kbthe used at depths
where water nncjc,ement is likely to
wash the clay p,;!iicfes away.
ctv?ltw t p-t )i l is the type most
commonly ust.~~ irld is the subject
of the renisind~ 01‘ this section. It
is made by rlxslng water and
cement in the I;I~IO of 5 to 6 gaitons
of water to a cU-tb sack of portland
cement. This mixture is usually
fluid enough to tlvw through grout
pipes. Quant ir Ic’\ ot‘ water 1nuc11in
excess of h gallons per sack of cenient result in the settling out ot
the cement. wll1~11is undesirable. It
is better toaim t‘or the drier mixture
based on the Io~ver quurltity of‘ 5
gallons of water peg-sack ot‘ c‘ement.
A better tloiving tnisture may be
obtained by uddtng 3 to 5 pounds
of bentonite cla>. per sack ot‘ cement. in which case about 6.5 gallons of water 1’;‘;’ sack should be
used. Where tl1.i ,!~ce to be filled is
large. sand 111.l he added to the
slurry to provli cstra bulk. This,
however. incrc.t \ the difficulty 01
placing and 11. iifirlg. The water
used in tfle m~\~l.~rcshould be free
of oil or other oIg2nic material sucfi
as plant leaves dnd bits of wood.
Cement of either the regular or
rapid-hardening r>.pe would be satisfactory. llse ot‘ r/12 latter perrnits an
of drilling operaearlier resump’
t ions.
Mi3iug of rl~ I out may be done
hxr, if available,
in a concietc
and batches stir’ _i temporarily until enough is nli ted for the job at
hand. The quanlit ies normally re-

Fig. 5.20 HOKTING PLUG. (From Fig.
5 1 Wk.
Dcpartmcnt of the
Army I cchnical Manual TM5297. 19.57.)

Fig. 5.2 I CASING ELEVATOR.

71

Fig. 5.22 A GRAVITY PLACEMENT
METHOD
OF CEMENT
GROUTING WELL CASING.
PLUGGED CASING LOWERED INTO CEMENT SLURRY
FORCES SLURRY lNT0 ANNULAR SPACE.

pressure may be used to force the
grout may also be placed in shallow

quired for small wells can, however,
be adequately mixed in a clean
SO-gallon oil drum. To 20 gallons of
water in the drum should be slowly
sifted 4 sacks of cetnent while the
water is being vigorously stirred
with a paddle.
Placirzg of the grout should be
carried out in one continuous operation before the initial set of the
cement occurs. Regardless of the
method of placing employed, the
grout should be introduced at the
bottom of the hole so that bY
working its way up the annular
space fil!s it completely without
leaving any gaps. Water or drilling
mud should be pumped through the
casing and up the annular space to
clear it of any obstructions before
placing the cement grout. To do
this. the top of the casing must be
suitably capped. If the borehole has
been drilled much deeper than the
depth to which the casing is being
set. then the extra depth below the
casing tnlty be back-filled with a
fine sand. There are several methods
of placing grout. of which ;1 few of
the simpler ones are described below. Suitable pumps. air or water
grout into the annular space. However,
boreholes by gravity.

A gruvit~~ p~accrmwt m~tiwd is indicated in Fig. 5.22. A quantity of slurry
in excess of that required to fill the annular space is introduced into the hole.
The casing with its lower end plugged with easily drillable material (soft wood
for example) and with centering guides is then lowered into the hole, forcing
the slurry upwards through the annular space and out at the surface. The
casing can be filled with water or weighted by other means to help it sink and
displace the slurry. If temporary outer casing is used. it should be withdrawn
while the grout is still fluid.
The imide-trrbir~g method for grouting well casing is shown in Fig. 5.23.
The grout is placed in the bottom of the hole through ;1grout pipe set inside
the casing and is forced up the annular space either by gravity. or preferably
by pumped pressure in order to complete the operation before the initial set
of the cement occurs. Grouting must be continued until the slurry overflows

the top of the borehole. A suitable
packer or cement plug fitted with a
ball valve is provided to the bottom
end of casing to prevent leakage of
the grout up the inside of the
casing. This packer too must be
made of easily drillable materials.
The grout pipe should be -%inch or
larger in diameter and the casing
filled with water to prevent it from
float in:. The diameter of the drilled
hole should be at least 2 inches
larger than that of the well casing.
method
The outside-tuhitzg
shown in Fig. 5.24 requires a borehole 4 to 6 inches larger in diameter
than the well casing. The casing
must be centered in the hole and
allowed to rest on the bottom of it.
The grout pipe, of similar size to
Fig. 5.23 INSIDE-TUBING METHOD
that used in the inside-tubing
OF CEMENT GROUTING
method,
is initially extended to the
WELL CASING.
bottom of the annular space and
should remain submerged in the slurry throughout the placing operations.
This pipe may be gradually withdrawn as the slurry rises in the annular space.
Should grouting operations be interrupted for any reason, the grout pipe
should be withdrawn above the placed grout. Before lowering the pipe into
the slurry again, grout should be used to displace any air and water in the
pipe. The slurry is best placed by pumping, though it can be done by gravity
flow. The casing may be plugged and weighted with water to prevent it from

floating. The we@ of the drilling tools may also be used to keep the casing
in place.
After cement grout has been placed, no further work should be done on
the weIl until the grout has hardened. The time required for hardening may
be determined by placing a sample of the grout in an open can and submerging it in a bucket of water. When the sample has firmly hardened, work
may proceed. Generally, a period of at least 72 hours should be allowed for
cement grout to harden. If rapid-hardening cement is used, the time may be
reduced to about 36 hours.
WELL ALIGNMENT
Alignment is being used here to include both the concepts of plumbness
and straightness of a well. It is important to understand these concepts and
how they differ. Plumbness refers to the variation with depth of the center
line of the well from the vertical line drawn through the center of the well at
the top of the casing. Straightness, however, melely considers whether the
center line of the weli is straight or otherwise. Thus, a well may be straight

73

but not plumb, since its alignment
is displaced in some direction or
other from the vertic;il.
Plumbness and straightness of a
well are important cr)nsiderations
of well construction because they
determine
whether
a vertical
turbine or subtnersible put~ip of a
givert size can be installed in the
well at a given depth. In this respect, straightness is the more important fsctor. While 3 vertical
pump can be installed in a reasonably straight well that is not plumb,
it cannot be insta!led in a well that
is crooked beyond a certain limit.
Plumbness must, however. be controlled within reasonable limits.
since the deviation tram the vertical
can affect the operation and life of
some pumps. Most well construction codes and drilling contracts
specify limits for the alignment of
large
diameter, deep wells. GenerFig. 5.24 OUI’SIDE-TUBING METHOD
ally,
these
limits cannot be practiOF CEMENT GROUTING
cably applied to stnall diameter,
WELL CASING.
shallow wells. These latter wells
should merely be required to be
sufficiently straight and piumb to permit the installation and operation of
the pumping equipment.
Conditions Affecting Well Alignment
While it is desirable that a well be absolutely straight and plumb, this ideal
is not usually achievable. Various conditions such as the character of the
subsurface material being drilled, the trueness or straightness of the drill pipe
and the well casing, and the pulldown force on the drill pipe in rotary drilling
combine to cause variations from true straightness and plutnbness. Varying
hardness of materials being penetrated can deflect the bit from the vertical.
So can boulders encountered in glacial drift formations. A straight hole cannot be drilled with crooked drill pipe. Too much force applied at the top end
of the rotary drill stem will bend the slender column of drill pipe and cause a
crooked hole. Weight. in the form of drill collars, placed at the lower end of
the drill stem just above the bit, however. will help to overcome the tendency
to drift away from the vertical. Even after the borehole is drilled, bent or
crooked casing pipes and badly aligned threads on them can result in a well
with appreciable variations from thz vertical and straight lines.

74

Measurement of Well .4lignment
hleasurement of alignment is usuall>~.dune in the cased b~~rehc~it;.Wll~r~
drilling has been b>, the rotary method these 1ne;1surc1nc1~ts sh~~uld be made
before the casing is grouted dl:d sealrd. For the txbl~-tool pcrcnssion and
orhcr methods in which the casing follows the bit as drilling progresses. periodic checks can be made on tfle plurnbrress and strsiglltness during drilling.
Whena cable-tool hole has been started with the pools suspended directly ovei
the center of the top of the c‘;lsing. then any subsequent deviation ot‘ the cable
from the center indicates 3 deviation of the hole from the vertical. The wearirlg of the.corners of the cable-tool percussion bit on one side only also serves
to indicate that 3 crooked hole is being drilled. These early indications help a
driller to take steps to correct the fault. He may find it necessary to change
the position of the drillilig rig or backfill ;t portion of the hole and redrill it.
A plumb bob suspended by wire cable from the derrick of the drilling rig
or from ;1 tripod is usually used to measure both straightness and plumbness
of ;L weit. The plumb bob should be in the form of 3 cvlinder 4 to h inches
long with outside diameter about ‘4 inc*h smaller than t-he inside dittmeter of
the casing. !t should be heave enough to stretch the wire cable taut. A guide
block is fixed to the derrick ;r tripod so that the center of its small sheave L)I
pulley is 10 feet above the top of the asin g and adjusted so that the plumb
bob hangs exactly in the center of tile casing. The wire cable should be accurately marked at IO-ft. intervals.
When the plumb bob is lowered to ;I particular IO-ft mark below the top
of the casing the measured deviation of the wire line from the center of the
top of the casing multiplied by 3 number that is one unit larger than that of
the number of IO-ft sections of able in the casing gives the deviation at the
depth 01‘ the plumb bob. For example. if the deviation from the center at the
lop c:t rhe casing is !/X inch when the plumb bob is 3C feet be!ow the top of
the casing. then the deviation from the vertical at 30 feet depth in the casing
is three plus one. or four. times l/S inch. that is I/J inch. Similarly. with the
plumb bob 40 feet in .the hole. the multiplier is five, and when 100 feet, the
multiplier is eleven.
7‘0 determine the straightness. the deviation is measured at I ‘3-ft intervals
in the wc1I. If the deviation from the vertical increases by the UIIIC amount
for each succeeding IO-ft interval. then the well is straight as CJr as the last
depth checked. The calculated deviation or drift from the vertical may be
plotted against depth to give a graph of the position of the axis or center line
of the well. Such a graph can be used to determine whether ;I pump of given
length and diameter can be placed at a given depth in the well. This can also
be checked on site by lowering inro rhe well a “dummy” length of pipe ot
the same dimensions ;IS the pump.

INSTALLATION

OF WELL SCREENS

There are several methods of installing well screens, some of which are
described below. The choice of method for ;1pxficular well Inay be intluenced
by the design of the well, the drillin g method and the tvpe of problems encountered in the drilling operrltion.

75

Pull-back Method

The pull-back method is by far the safest and simplest method used.While
it is commonly used in wells drilled by the cable-tool percussionmethod, it is
equally applicable in rotary drilled wells. The screen is lowered within the
casing, which is then pulled back a sufficient distance to expose the screen.
The screen must be the telescope type with outside diameter sizedjust sufficiently smaller than the inside diameter of the casing to permit the telescoping of the screen through the casing. The top of the screenis fitted with a
lead packer which is swedged out to make a sand-tight seal between the top
of the screenand the inside of the casing.
The basic operations in setting a well screen by the pull-back method are
indicated in the series of illustrations in Fig. 5.25. The casingis first sunk to
the depth at which the bottorn of the screen is to be set. Any sand or other
cuttings in the casing must be removed by bailing or washing. The screen is
then assembled. suspended within the casing, following which the hook
shown in Fig. 5.26 is caught in the bail handle at the bottom of the screen.
The whole assembly is then lowered on the hoist line to the bottom of the
hole. If the depth to water level in the hole is less than 30 feet, however, the
_ he dropped in the casing. Having checked to
assembled screen may simpi,w

Fig. 5.25 PULL-BACK METIIGD OF SETTING WELL SCREENS.
A. Casing is sunk to full depth of well.
B. Well screen is lowered inside casing.
C. Casing is pulied back to expose screen in water-bearing formation.

76

ascertain the exact positron of
screen, the hook is released and
withdrawn. A string of small pipe is
then run into and allowed to rest
on the bottom of the screento hold
it in place white the casing is being
pulled back to expose the screen.If
the casing has been driven by the
cable-tool percussion method, then
it may be pulled by jarring with the
drilling tools or with a bumping
block, the latter of which is shown
in Fig. 5.27. It may even be possible in some instances to pull the
casing with the casing line on the
drilling machine. I’vlechanicd or
hydraulic jacks (Fig. 5.38) may also
be used in combination with a pulling ring or spider with wedges or
slips. The casing should be pulled
back far enough to leave its bottom
end 6 inches to 1 foot below the
lead packer. The pipe holding the
screen in place is removed and a
swedge block (Fig. 5.29) used to
expand the lead packer and create a
sand-tight seal against the inside of
the casing. To do this. two or three
iengths of small diameter pipe are
screwed to the sliding bar which
passes through the swedge block.
The assembly is lowered into the
well until the swcdgeblock rests on
the lead packer. The weight provided by the pipe attached to the
sliding bar is then lifted 6 to 8
inches and dropped several times.
The swedgeblock itself should not
be lifted off the lead packer. It
should be simply forced down into
the packer by the repeated blows
of the weighted sliding bar.

Fig. 5.26 LOWERING HOOK.

Fig. 5.27 B U M PI N G BLOCK BEING
USED TO PULL WELL CASING.(From Bergerson-Caswell,
Inc. , Minneapolis, Minnesota.)

Open Hole Method

The open hole method illustrated in Fig. 5.30 involves the setting of the
screen in an open hole drilled below the previously installed casing. The
.
method is applicable to rotary drilled wells.
77

Wash liner

.Cemsnt

grout ,’

Exoanded
leab pucker

.?:i

Drilling mud
Wrtially
washing

L

Fig. 5.30 SETTING WELL SCREEN IN OPEN HOLE DRILLED BELOW THE WELL
CASING.

Fig. 5.31 LEAD SHOT AND LEAD WOOL FOR PLUGGING OPEN BOTTOM END OF
WELL SCREEN.

maintaining such 3 “dean” hole. ;1short extension pipe may be attached to the
bottom of 311open-ended screen to permit washing it down with drilling fluid.
The bottom of the extension pipt’ is then plugged with lead shot, lead wool
( Fig. 5.3 I ) or cement grout and the lead pucker expanded after circulating water to wash some of the drillins mud out of the hole. Lead wool or cement
grout should be tamped ifor comprtction. If lead shot is used. it is simply poured
in sufficient qu:tntity to form ;I 4 to ti-inch thick layer inside the extension pipe.

Wash&w

Method

The wash-down method of instttllation (Fig. 5.32) uses a high velocity jet
of Ii&t-weight
drilling mud or water issuing from a special washdown
bottom fit ted to the end of the screen to loosen the sand :md create ;1hole in
which the screen is lowered.
The washdown bottom is a self-closing ball valve. A string of wash pipe is
connected to it and used to lower the entire screen assembly through the
casing which has been previously cemented. As the screen is washed into
position. the loosened sand rises around the screen and up through the asing

Well

rcrrrn

Coupling on uaah pipe
fun18 In conkot aoat
Combination back-

Fig. 5.32 WASH-DOWN METHOD OF
SETTING WELL SCREEN.

Fig.

X0

5.33 JETTING WELL SCREEN INTO POSITION.

to the surface with the return flow. Sand particles which inevitably accumulate in the well screen must be washed out of it once the screen is in final
position. Water should later be circulated at a reduced rate to remove any
wall cake formed in the hole during the jetting operation. This causes the
formation to cave around the screen and grip it firmly enough for the wash
line to be disconnected.
it is common practice in jetted and rotary drilled small wells to set a
combined string of casing and screen, permanently attached. in one IJperation.
A jetting method for setting such a combined string is illustrated in Fig. 5.33.
The scheme employs the use of a temporary wash pipe assembled inside the
well screen before attaching the screen to the bottom length of casing. A
coupling attached to the lower end of the wash pipe rests in the conical seat
in the wash-down bottom. A close-fitting ring seal made of semi-rigid plastic
material or wood faced with rubber is fitted over the top end of the wash
pipe and kept in position by the coupling above it. The seal prevents any return flow of the jetting water in the space between the wash pipe and the
screen. All the return flow from the washing OLjetting operation, therefore,
takes place outside of the screen and casing. A little leakage of the jetting water takes place around the bottom of the wash-pipe and out through the
screen, thus preventing the entry of fine sand into the screen. Maintaining
this small outward flow through the screen is important, since it reduces the
possibility of sand-locking the wash pipe in the screen.
With the casing and screen assembly washed into final position, fluid circulation is stopped. The plastic ball then floats up into the seat, thus effectively
closing the valve opening in the washdown bottom. A tapered tap, overshot
or some other suitable fishing tool (see later section of this chapter on fishing
tools) is then used to fish the wash pipe and ring seal out of the screen. It
may also be possible to recover the wash pipe assembly by tapping the
coupling with pipe carrying regular pipe threads instead of a tapered tap. The
well is then ready for development.
Satisfactor> penetration by this method requires continuous circulation
when water is used as the jetting fluid. This may limit the use of the method
to the penetration of only as much screen and casing as it is physically possibie to assemble as a single string in an upright position with the available
drilling equipment. Subsequent additions of casing will require interruptions
of the circulation that can lead to the collapse of the drill hole (particularly
in water-bearing sands and gravels) around the combined string of screen and
casing thus preventing further penetration. This problem may be avoided by
the use of a suitable driIling mud. The method is very often used for washing
screens into position below previously drilled boreholes. If the borehole has
already been drilled into the aquifer to the full depth of the well, then the
wash-down bottom may be u3ed on the screen without the wash pipe.

Well Points
Well points can be and are often installed in drilled wells by some of the
methods just described in this section. The pull-back and open hole methods
would be particularly applicable. Where, because.of excessive friction on the
casing or a heaving sand formation. the pull-back method is impracticable, a

well point may be driven into the formation below the casing by either of the
methods shown in Fig. 5.34 or Fig. 5.35. In the method of Fig. 5.35 the driving force is transmitted through the driving pipe directly onto the solid poitlt
of the screen. This method is preferable, therefore, when driving relatively
long well points. In both cases the hole is kept full of water while the screen
is being set in heaving sand formations.

ttrtificially Gravel-PackedWells
The methods of screen installation so far described apply primarily to
wells to be completed by natural development of the sand formation. One
of &ese, the pull-back method, can, with little modification, be used in
artificiaiiy gravel-packed wells.
An artificidil!y gravel-packed well has an envelope of specially graded sand

Well

Fig.5.34

DRIVING
WELL
POINT
WITH SELF-SEALING PACKER INTO WATER-BEARING
FORMATION.

casing

-\

’ ‘Q/I

Drlvlng

pipe

Fig. 5.35 DRIVING BAR USED TO DELIVER
DRIVING
FORCE
DIRECTLY ON SOLID BOTTOM OF WELL POINTS 5 FiOR MORE IN LENGTH.

or gravel placed around the well
screen in a predetermined thickzess. This envelope takes the piace
of the hydraulically graded zone of
highly permeable material produced
by conventionti development precedures. Conditions that requil-c the
use of artificial gravel packing have
been described in the previous
chapter.
The modified pull-back method
known as the double-casing method
involves centering a string of casing
and screen of equal diameter within
an outer casing of a size corresponding to the outside diameter of
the gravel pack (Fig. 5.36). This
outer casing is first set to the full
depth of the well. The inner casing
and screen should be suspended
from the surface until the placement of the gravel pack is complcted. The selected gravel is put
in place in the annular space
around the screen in bax!?es of a
few feet. following each of which
the outer casing is pulled hack an
Fig. 5.36 DOUBLE-CASING
METHOD
OF ARTIFICIALLY
GRAVEL
appropriate distance and the proPACK!,% A WELL. GRAVEL
cedure repeated until the level of
IS ADDED AS THE OUTER
CASING IS PULLED BACK
the gravel is well above the top of
FRO:4 THE FULL DEPTH
the
screen. The well may then be
OF I-HE WELL;
developed to remove any fine sand
from the gravel and any mud cake that may have formed on the surface
between the gravel and the natural formation, The method can be used in both
cable-tool percussion and rotary drilled wells.
Care must be taken in placing the gravel to avoid separation of the coarse
and fine particles of the graded mixture. Failure to do so could result in a
well that continually produces fine sand even though properly graded material has been used in the gravel pack. This tendency towards separation of
particles of different sizes can be overcome by dropping the material in small
batches or slugs through the confined space of a small diameter conductor
pipe or tremie (Fig. 5.37). Under these confined conditions there is less tendency for the grains to fAl individually. Water is added with the gravel to avoid
bridging in the tremie. The tremie. usually about _’ inches in diameter. is raised
as the level of material builds up around the well screen. Water circulated in a
reverse direction to that of normal rotary drilling
that is down the annular
space between the casings, through the gra\A and screen and up through the
inner casing to the pump suction ~~ helps prevent bridging in the annular
-Inner

Carm~

space as the gravel is being deposited.
Some settlement of the gravel
will occur during the development
process. More gravel must, therefore. be added as is necessary to
keep the top level of the gravel
several feet above that of the
screen. The entire length of the
inner casing need not be le ‘t permanently in the well if the outer
one is intended to be permanent.
Towards this end, a convenient
joint in the inner casing can be
loosely made up while assembling
the string. After development of
the well the upper portion of casing
Fig. 5.37 PLACING GRAVEL-PACK
is
then unscrewed at this joint and
MATERiAL
THROUGH PIPE
USEDASTREMIE.
withdrawn, leaving enough pipe (at
least one length) attached to the
screen to provide an overlap of a
few feet within the outer CilSillg.
Another technique would be to
set the inner casing to the full
depth of the well and telescope the
screen and an appropriate length of
extension pipe attached to the top
of the screen into? that casing. The
entire string of inner casing nrrly
then be removed as ths gravel is
Fig.538
LEAD SLIP-PACKER IN PO!eaving the extension pipe
placed.
SITION
ON EXTENSION
overlapping inside the outer casing.
PIPE BEFORE EXPANSION
TO SEAL THE ANNULAR
Centering guides must be provided
SPACE.
on the temporary inner casing.
Cement grout, lead shot or pellets of lead wool can be llscd to seal the
annular space immediately above the top of the gravel. A mechanical type ot
seal known as a lead slip-packer (Fig. 5.38) is also often used. The packer. a
lead ring of similar shape to a casing shoe, sits on top of the extension pipe
and is of the proper diameter and wall thickness to form an effective seal
when expanded by a swedgeblock against the outer casing.
Recovering Well Screens

It may sometimes be necessary to recover an encrusted screen for cleaning
and return to the well, a badly corroded one for replacement or a good one
from an abandoned weil for reuse elsewhere. C‘onsiderableforce may have to
be applied to the screen to overcome the grip of the water-bearing sand
around it. The sand-joint method provides one of the best ways of transmitting
this force to the screen, dislodging and recovering it without daE,aging it. The

x4

method, however, cannot be used
in screens smaller than 4 inches in
diameter.
The sand-joint method uses sand
carefully placed in the annular
space between a pulling pipe and
the inside of the well screen +o
form a sand lock or sand joint
which serves ‘is the structural connection between the pulling pipe
and the screen (Fig. 5.39). The
necessary upward force may then
be applied to the pulling pipe by
means of jacks working against pipe
ciamps or a pulling ring with slips as
shown in Fig. 5 28.

Lead packer

Pulhg

pipe

Sand join1

The size of the pulling pipe
varies with the diameter of the
scrl:en and the force wnich may be
required. As a general rule, howSacking
wired on pipe
ever, the size of pipe is chosen at
one-half the nominal inside diameter of the screen. For example, a
Well screen
4-inch screen with nominal inside
diameter of 3 inches would require
Ball
1?&inch pipe. Extra heavy pipe
should be used. The pipe couplings
and threads should be of the
Fig. 5.39 ELEMENTS OF SAND-JOINT
highest
quality in order to withMETHOD USED FOR PULLiNG WELL SCREENS.
stand the pullin, 0 force. The sand
should be clean, sharp and uniform
material of medium to moderately tine size.
The first step in the preparation of the sand joint is the tying of Z-inch
strips of sacking to the lower end of the pulling pipe immediately above
a coupling or ring welded to the pipe (Fig. 5.40). The sacking forms a socket
to retain the sand fill around the pulling pipe. The pipe and sacking with both
ends tied to the pipe are then lowered into the casing until only the upper
ends of the strips remain above the top of the casing. The string which holds
the upper ends of the sacking to the pipe is then cut and the strips of sacking
arranged evenly around the top of the casing as shown in Fig. 5.41.
Next the pulling pipe is towered to a point near the botttim of the screen,
care being taken to keep it as well centered as possible. The sand is then
poured slowly into the annular space between the pulling pipe and the casing.
An even distribution of the sand around the circumference of the pipe is desirable. The pulling pipe should be moved gently backward and forward at the
top while pouring the sand to avoid bridging above couplings. A small stream
of water playing onto the sand would also help in preventing bridging. Enough

85

sand sflould be used to fill at least two-thirds bur not the entire IcIlgth oft hi\
screen. The level of the sand in the screen an he ,hxked with ;I string ot‘
small dismcter pipe used as a sounding rod.
The proper clu;intity of sdnd
having been piaced, tt:e pulling pipe
is then gradually lifted to a~rnpaut
the sand and develop ;I fit-t*: + it, ~)II
the inside surface of the screen.
Additi!mal tension is applied until
the screen begins tu mc)ve.
The
screen may then he pulled steadily
without difficulty until it is out ot
the well. The sand joint can be
broken at the surfxc by washing
out the sand with a stream ot
waler.
Prc-fwatrtwt!t
01‘ the szrt‘cn with
hydrochluric or muriut ic acid serves
to loosen encrusting materials and
thus reduce the force rcctuired to
obtain initial movement of the
screen. Fur this purpose the sc‘reen
is filled with a mixture of cqual
amounts of acid ard water which is
left IO stand for several hours, eve. Whenever possible. small operators usually rent took as the>, are needed Q‘rumsuppliers. It
would be impractical to attempt a discussion of all types ot‘ fishing jobs and
the too!5 used on them. Instead, the discussion that follows centers on some
of the more common types of fishing jobs and tools.
t I ) Parted &ill pipe: One of the most frequent fishingjc&s in rotary drilling is that for the recovery of drill pipe twisted off in the hole. The break
may either be due to shearing of the pipe or failure of a threaded joint.
An impression block should first be used to determine the exact depth and
position of the top of the pipe. whether there has been any caving of the upper formation material onto the top of the pipe or whether the pipe has become embedded into the wall of the hole. If the top of rhe pipe is unobstructed. then either the rapereclfishiqg tap or die o~~slzor could be effective
if used before the cuttings in the hole settle and “freeze” the drill pipe. The
kwlatitg-slip
overshot. which permits the circulation of drilling fluid, would
be the best tooi to use after the pipe has been frozen by the settling of cuttings around it. These tools dre all illustrated in Fig. 5.43.
The tapered fishing rap, made of heat-treated steel, tapers approximately 1
inch per foot from a diameter somewhat smaller than the inside diameter of
the coupling to a diameter equal to the outside diameter of the drill stem.
The tapered portion is threaded and fluted the full length of the taper to
permit the escape of chips cut by the tap. The tap is lowered slowly on the
drill stem until it engages the lost pipe. the circulation being maintained at a
low rate through the hole in the tap during this period. Having engaged the
lost pipe, the circulation is stopped and the tap turned sltiwly by the rotary
mechanism or by hand until the tap is threaded inio the pipe. An attempt
should then be made to reestablish the circulation through the entire drill
string before pulling the lost pipe.
The de over&t is a long-tapered die of heat-treated steel designed to fit
over the top end of the lost drill pipe and cut its own thread as it is rotated. It
is fluted to permit iiIr: ~SLL~ZUT merai cu~ti~~gs.Circuiation cannot be cornpleted to the bottom of the hole through the lost pipe since the flutes also
allow the fluid to escape. The upper end of the tool has a box thread designed
to fit the drill pipe.
The circrdatirzg-slip overshot is a tubular tool approximately 3 feet long
with inside diameter slightly larger than the outside diameter of the drill pipe.

Tapered

Tap

Die Overshot

Circulating

Slip Overshot

The belled+ut lower portinjn ot‘ the tool helps to icntruliz and guide the top
of the lost drill pipe into the slip shown fitted in tllc tapcrcd slcevc. The slot
cut through one side ot‘ the slip cnahlcs it to ~syarld ;IS the tucrl is II)wered
over the drill pipe. As the tol,l is raised the slip is pu!M rlowtl into the
tapered sleeve, thus tightening tllc slop against the pipe. i’iruulatiorl ot’ tluid
can then be established through
~he pipe. freeing it for recovery.
A wall Izooli shown in Fig. 5.44 cm be used to set the lost drill pipe erect
in the hole in preparation for the trip or overshot tools. Tile wall ho~~k is ;I
simple tool that can be made from 2 suitable size of steel casing cut to shape
with a cutting torch. A reducing sub must then be used to connect the top
end of the tool to the drill stem. To operate the wall h~\jk, it is lowered until
it engages the pipe. ,then slowly rotated until the pipe is fully within the
hook. The hook is then raised slowly to set the pipe in art uptight positicjn.
later disengaging itself from the pipe.
It is also possible to pin a tapered fishing tap into the upper portion of 3
wall hook made from steel casing. With such a combined tool. the hook may

be used to realign the lost drill pipe and then. while being lowered, guide the
tap into the drill pipe to cunlpkte both operations in tine run ot‘ tools into
the hole. This method is particularly desirable when the drill pipe ttm&
to
fall
over against the wall of a much Larger hole rather than remain erect.
(1) &chken wire Ike: Wheli the
drilling line or sand line of ;i cabletool drilling rig breaks, leaving the
drilling tools or bailer in the hole
with a substantial amount of wire
line on top of the t00is, the wire
live cerrter spew ( Fig. 5.4.5 ) is the
recommended fishing tool. This tool
consists of a single prong with a
number of upturned spikes projecting from it. The spikes have sharp
inside corners that permit the spear
to catch even a single strand of wire.
If the lost tools are stuck in the
ide md cltnrwt be pulled, the sharp
spikes will shear the win! line.
The shoulder of the spear should
be about the same sire as the bore!lole in order to prevent the broken
wiie line from getting past the spear
as it is lowered and causing it to bccome stuck in the hole. Far the
range of boreholc sizes being considered, center spears are tnade for
specific siLes of hole.
The spear is used with a set of
fishing jars. short sinker and wire
line socket above it. It should be
carefully eased down the Me to the
point where it is expected to cngagc
the broken cable. It is then pulled
to see if it has a hitch. In the absence of a hitch it is lowered below
t!le first point and again tested fc+type piston pump is c~~rnnnc~nlyknown ;1s ;I
pitcher pump.

Fig. 8.5

DEEP WELL SINGLE-ACTING PISTON PUMP.

The basic principle of the single-acting piston pump can be modified to
cause water to be pumped on both the forward and the reverse strokes.
Pumps thus modified are known a:$ double-acting piston pumps. 0 ther

Helical Rotor Pumps
Tilt

helical

purup

is

rotary

type

;I

or screw-type

rcjtor

Itlc~~it’i~a~i~~Il
i)t’

cotlslaII

01’
t

tilt2

dispiscc-

111cntpurrlp. The Iil;iitl clcllIctIls
01’
tllc purllp ;trc lllc IIiglIly
!~~~iisitcd
nletlli rotor or screw it1 the fort11 ot
3 Ileiicai. sin& thread worr11 and
the outer stritor nlade of rubber.
Flexible 171ountinps
allow
tile rotor
to

rotate

eccentrically

within

the

st:ltor. prthng ;I corltitluc)us !;trel,r:I
01 water forward alo~lg rhc cavities
jr1 tilt2 stator. The water ;1iso acts as
3 lubricant bctwecn the ti:‘;) clc-

I I‘)

melItS

of

puIllpS

cm

tile
hc

pump.
citficr

Hclic;;!
01’ tllc

rotor
surt’licc

or deep well type and are usually driven by engines or electric motors. Fig. 8.8
illustrates a deep well, helical rotor pump.
VARIABLE DISPLACEMENT PUMPS
The distinguishing characteristic of variable displacement pumps is the inverse relationship between their discharge rates and the pressure heads against
which they pump. That is to say, the pumping rate decreases as the pressure
head increases. The opposite is also true, the pumping rate increases as the
pressure head reduces. The two main types ot’ variable displacemer:t pumps
used in small wells .arecentrif~rlgal and@ pumps.

Discharge
Discharga
1

Fig. 8.7

DOUBLE-ACTING,

SEMI-ROTARY

of Crane Company. Salem. Ohio.)

HAND PUMP. (From Deming Division

Centrifugal Pumps
Centrifugal pumps are the most common types of pumps in general
The basic principles of their operation can be illustrated by considering
effect of swinging a pail of water around in a circle at the end of a rope.
force that causes the water to press outward against the bottom of the
rather than run out at the open end is known as the centrifugal force.

use.
the
The
pail
If a

hole were cut in the bottom of the pail. water would be discharged through
the opening at a velocity which is related to the centrifugal force. Further,
should an intake pipe be connected to an air-tight cover on the pail, a partial
vacuum would be created inside the pail as waier is discharged. This vacuum
could bring additional water into the pail from ;! supply placed at the other
end of the intake Flpe within the 1imii of the suction lift created by the
vacuum. Thus a continuous ilow of water could be maintained in a manner
similar to that operating in a centrifugal pump. The pail and cover
correspond to ihe casing of the
pump, the discharge hole and intake pipe correspond to the pump
outlet
and intake respective&,
while the rope and arm perform the
functions of the pump impeller.
Centrifugal pumps used on small
weUs can be subdivided into two
r,;ain types based on their design
statwbmldod
features. These are volute pumps
and tttrbirte or diffuser pumps. The
impellers of volute pumps are
housed in spirally shaped casings
(Fig. X.9) in which the velocity of
the water is reduced upon leaving
the impeller with a resulting increase in pressure. In turbine pumps
the impellers are surrounded by
diffuser vanes (Fig. 8. IO). These
vanes provide gradually enlarging
passages through whic!l the velocity
of the water leaving the impeller is
gradually
reduced, thus transforming the velocity head into pressure head.
The conditions of use dcterminc
Fig.8.8 BEEP WELL ttEL.lc ;$?.
the
choice between volute and tur‘ROTOR PUMP.
bine pumps. The volute design is
very commonly x+ed in surface-Lype pumps where pump size is not a limiting
factor and design heads are low to medium. Deep wetl centrifugal pumps are,
however, of the turbine type of design which is better suited to use where the
diameter of the pump must be limited, in this case by the diameter of the
well casing.
The performance of a centrifugal pump depends greatly upon the design of
its impeller. For example. the pump discharge against a given head can be
increased by enlarging the diameter of the inlet eye agd the width of the
impe%x. it is also customary to use a larger number of guide vanes (up to 12)
in turbine pumps when a higher pressure head is desired. The extent to which

Dtffuser

Fig. 8.9

VOLUTE-TYPE
CAL PUMP.

C’ENTRIFU-

vane

k:ig. 8.10 TURBINE-TYPE
C’ENTRIFUCAL PlJMP SHOWING (‘HARA~TERISTIC
D I F 1; I! SE R
VANES.

operation. however. increase in direct proportion to the number of stages or
impellers. For fxampte. the pressure tied uf 3 4-stage pump, me stage ot
which devztops a pressure ot. 40 feet head of water, would be 4 times 40 or
IhO feet of water. Fig. X.1 I shows a section through a Sstage deep well
turbine pump which is, in effect. three pumps assembled in series with flow
passing from one to the next and the head being increased with passage
throug!i each stage.
Jet Pumps
Jet pumps, in reality. combine centrifugal pumps and ejectors to lift water
from greater depths in wells than is possible through the use of surface-type
centrifugal pumps when acting alone. The basic components of ejectors are a
nozzle 2nd a venturi tube shown in Fig. S.l 2. The operating principles are as
follows. Water under pressure is delivered by the centrifugal pump (mounted
at ground level) through the nozzle of the ejector. The sudden increase in the
velocity of the water as it passes through the tapered nozzle causes a reduction in pressure as the water leaves the nozzle and enters the venturi tube. The
higher the water velocit y through the nozzle, the greater is the reduction in
pressure at the entrance to the venturi tube. This reduction in pressure can,
therefore, be made great enough to create a partial vacuum and so suck water
from the welt through the intake pipe of the ejector and into the venturi tube.
The gradual enlargement of the venturi tube reduces the velocity of flow with
a minimum of turbulence and so causes a recovery of almost all of the water

Sboft

I-

Grout

-Return

seal

pipe

Venturi -

Stage

Impeller

Strainer

-

Ejector

~

Foot

valve

Screent------Well

casing

Fig. 8.1 I THREE-STAGE LINESHAFT
DEEP WELL TURBINE
PUMP.

Fig. 8.12 JFT PUMP. (Adapted from
Fig. 13. MQFZUQ~ of Individual
Water Supply Systems. Publit

Health Service Publication No.
24. 1962.)

I 23

pre y.,,:~ 1; +-.b

to,rourT the nozzle. The centrifugal pump then picks up the

flow,sendirlgpart ot’i! :1,-:: 25

> 25

so-150

Advantages

--

Disadvantages

-

Remarks

1. Same as surface-type
turbine.
2. Short pump shaft to
motor.
3. Plumbness and alignment of well less critical than for lineshaft type.
4. Less maintenance
problems due to wearing of moving parts
than for lineshaft
type.
5. Lower installation and
housing costs than for
lineshaft type.
6. Lower noise levels
during operation than
for lineshaft type.

I. Repair to motor or
pump requires removal
from well.
2. Repair to motor may
require shipment to
manufacturer or his
agent.
3. Subject to abrasion
from sand.

I. Relatively recent
design improvements for
sealing of electrical
equipment make long
p%ciods of troubletree service possible.

1. Simple in operation.
2. Does not have to be
installed over the
well.
3. No moving parts in the
well.
4. Low purchase price and
maintenance costs.

I. Generally inefficient.
!. Capacity reduces as
lift increases.
3. Air in suction or return line will stop
pumping.

I. The amount of water
returned to the
ejector mcreases
with
_..
Increased lit t 5 I)“:
of total water pumped
at 51)ft lift and 7S?G
at 100 ti lift.
2. Generally rimitzd to
discharge of about 20
gpm against 159 ft
maximum head.

*Practical suction lift at sea level. Reduce lift 1 foot for each 1000 ft above level.

2. Motor should be protected by suitable
device against power
failures.

OF

Too great stress can never be placed on the need to provide sanitary
protection for all known ground-water sources, whether in immediate use or
not, since such sourcesmay some time in the future be of great importance to
the development of their 1o;alities.
Small wells, of the type being considered in this manual, very often have
relatively shallow aquifers as their sources of water. These sources, in many
cases, are merely a few feet below the ground surface and can often be
reached without great difficulty by pollution from privies, cesspools,septic
tanks, barnyard manure. and industrial and agricultural waste disposal. It also
very often happens that privies and septic tanks are the only economically
practicable means of sewagedisposal in a small and sparsecommunity which
must for various reasonsdepend entirely upon a shallow ground-water source
for its potable water supply. Such dependence may be due to the inability of
a small community to meet the costs of 3 sophisticated treatment plant for
available surface water. Many rural areas are also subjected to annual
extended periods of drought when strearrs become completely dry and
shallow ground-water aquifers provide the only reliable sources of potable
water. It is, therefore, of great importance that such sources be adequately
protected.
POLLUTION TRAVEL IN SOILS
The sanitary protection of ground-water supplies must be based on an
understanding of the basic facts relating to the travel of polluted substances
thiough soils and water-bearing formations. It must be remembered that all
water seeping into the ground is polluted to some degree, yet this water can
later be retrieved in 3 completely satisfactory condition for domestic and
other human uses.Some purifying processesmust be taking place within the
soil 3s the water travels through il. Several studies have been made of
“nature’s purifying action” by researchworkers in many parts of the world,
particularly in Europe, India and the United States of America. These studies
have contributed very much to our knowledge of the processesinvolved in
the natural purification of ground waters and the patterns and extent of flow
of pollution in them. The basic findings are summarized in the succeeding
paragraphs.
The natural processesoccurring in soils to purify water travelling through
them are essentially three in number. The first two of these are the
134

I
mechanical removal of microorganisms (including disease-producingbacteria)
and other suspended matter by fi‘ltration and sedimentation or settling.
Filtration depends upon the relative sizes of the pore spacesof the soil
particles and those of the microorganisms and other filterable material. The
finer the soil particles and the smaller the pore spacesbetween them, the
more effective is the filtration process.Filtered material also tends to clog the
pore spacesand thus help to improve the filtration process.Sedimentatron
depends upon the size of the suspended material and the rate of flow of the
water through the pore spaces.The larger the particles of suspendedmatter
and the slower the rate of flow through the soil, the more efficient would be
the sedimentation process. It is, therefore, seen that the porosity and
permeability of the soil are very important factors in the operation of the
fdtration and sedimentation processesand, 3s 3 result, in the extent of travel
of bacterial pollution in soils.
The third factor is what is often termed the natural die-away of bacteria in
soils. Bacteria which produce diseasein man live for only limited periods of
time outside of their natural host which is generally man or animals. Their life
spans are usually short in the unfavorable conditions found in soils. This
property contributes considerably to the self-purification of ground water
during its movement and storagein sand and gravel aquifers.
The effect of filtration is, of course, completely lost and sedimentation
somewhat reduced in ground waters travelling through large crevices and
solution channels in limestone and other such consolidated rocks, This
explains the generally better microbiological quality of ground water
obtained from sands, gravels and other unconsolidated formations 3s against
those obtained from the larger crevices, fissures and solution channels in
consolidated rocks.
While the above mentioned processesare effective against the travel of
bacterial pollution in ground water and usually within short distances and
periods of time, they are not nearly 3s effective against the travel of chemical
pollution. Chemical pollution, it will be seen later, persists much longer and
travels much faster in ground waters than does bacterial pollution. Chemical
reactions with soil material do play some part in restricting the travel of
chemical pollution but require more time than the other processesdo in
controlling bacterial pollution.
Pollution (bacterial and chemical) in soils usually moves downward from
the source until it reaches the water table and then along with the
ground-water flow in a path which first gradually increasesin width to 3
limited extent and then reduces to final disappearance.Downward travel of
bacteria through homogeneous soil above the water table has seldom been
found to be more than about 5 feet. Upon reaching the water table, no
pollution travel takes place against the natural direction of ground-water flow
unlessinduced by the pumping of a well upstream of the pollution source and
with a circle of influence (upper surface of the cone of depression) that
includes the pollution source. The horizontal path of the flow of bacterial
pollution in sand formations from a point source, such as 3 well used to
recharge an aquifer, has been found to reach 3 maximum width of about 6

feet before final disappearance at a distance \jf about 101) feet from the
source. The corresponding distances for pit latrine sources have per~rally
been smaller. The maximum distance of bacterial po:iution tlow is ot‘tcn
reached several !lours (often less than 2 days) after ihe introduction of the
pollution. Filtration and the natural die-aw:jy processes then cause a rapid
reduction in the numbers of bacteria found and the extent of the path until
eventually only the immediate vic-nity of the pollution source is found to be
affected.
Chemical poliutkrn follows a similar but much b;ider and longer path than
that of bacterial pollution. Maximum widths of about 25 to XI feet and
lengths of about 300 feet flave been observed. Investigations have indicated
that chemicsl pollution travels twice as fast as bacterial pollution.
The above fmdings serve to emphasize the importance of the proper
location of wells with respect to sources of pollution if contamination is to be
avoided. They also form the basis for the general rules which are applied in
well location and construction and the siting of pit latrines. cesspools and
other such means of waste disposal in relation to ground-water sources.
WELL LOCATION
Wells should be located on the highest practicable sites and certainly on
ground higher than nearby sources of pollution. The ground surface in the
immediate vicinity of the well should slope away from it and be well drained.
If necessary, the site should be built up to achieve this end. A special drainage
system should be provided for waste water from public weils. It is good
practice, whenever practicable, to off-set the pump installation and discharge
pipe as far as possible from 3 public well. This. together with a good drainage
system, ensures that no waste water accumulates in the immediate vicinity of
the well to become 3 possible source of pollution or unsightly pools and
mosquito breeding grounds. if a well must be located down-hill from 3
pollution source, then it should be placed at a reasonably safe distance away,
depending upon the source and the soil conditions. Recommended minimum
distances from various types of pollution sources are listed in Table 9.1.
TABLE 9.1
Pollution Source

I

Cast iron sewer with leaded or
mechanical joints

I

Recommended Minimum Distance
10 ft.

Septic tank or sewer of tightly
join ted tile

so ft.

Earth-blit privy, seepage pit or
drain field

75 ft.

Cesspool receiving

r3w

100 ft.

sewage

136

These minimum distances are meant to be no more than guides to good
practice and may be varied its soil and other conditions require. They should
be applied only where the soil has filtering capacity equal to, or better than
that of sand.
WeiS location should also take into consideration accessibility for pump
repair. cleanin g. treatment, testing and inspection. Wells located adjacent to
buildings should be at least 2 feet clear of any projections such as
over-hanging eaves.
Chapters 4: 5 and 6 should be consulted for information concerning the
design, construction and compietion aspects, respectively. of the sanitary
protection of wells.
SEALING ABANDONED WELLS
The objectives of sealing abandoned wells are ( i) the prevention of the
contamination of the aquifer by the entry of poor quality water and other
foreign substances through the well, (2) the conservation of the aquifer yield
and artisean head where there is one, and (3j the elimination of physical
hazard.
The basic concept of proper seaiing of an abandoned well is the
restoration, as far as practicable, of the exis5ng geologic conditions. IJnder
water-table conditions sealing must be effective to prevent the percolation of
surface water through the well bore or along the outside of the casing to the
water table. Sealing under artesian conditions must be effective in confining
water to the aquifer in which it occurs.
Sealing is usually achieved by grouting with puddled clay, cement or
concrete. When grouting under water, the grouting material should be placed
from the bottom 11p by methods that would avoid segregation or excessive
dilution of the material. Grouting methods have been described in Chapter 5.
It may be necessary; in some cases, to remove well casing opposite
water-bearing zones to assure an effective seal. Where the upper 15 or 20 feet
of the well casing was not carefully cemented during the original construction, this portion of the casing should be removed before final grouting
for abandonment.

137

REFERENCES

Acme Fishing Tool Company. Ac772e. Greutest IVUl?li’ irl Cubltj ‘Tools Sirm
IYOU. Catalog. Parkersburg, West Virginia.
American Water Works Association. National Water Well Association. .4 Ct’lt’A
Standard j&- Deep Wells. AWWA AIOO-hh. New York: AWA
111~~.lC)hb.
Anderson. Keith E. (ed.). Water lt’e11 Harrdhook.
Water Well Drillers Association. 1966.

Rolla, Missouri: Missouri

Baldwin. Helene L.. and C. L. McGuinness. A Primer ml Grourlti Water.
United States De artment of the Interior, Geological Survey. Washington:
Government Prin Ping Office. 1963.
Bowman, Isaiah. Well-Driliitlg Methods. Geological Survey Water-Supply Paper
257. Washington: Government Printing Office. 191 1.
Decker. Merle G. Cable Tool FiMzg. Water Well Journal. Series of articles
commencing Vol . 21,No. l.(Jan., 1967). pp. 14-lh,S9.
Departments of the Army and the Air Force. Wells. TMS-297. AFM X5-23.
Washington: Government Printing Office, 1957.
Edward E. Johnson, Inc. Ground Water and Weils. St. Paul. Minnesota. 1906.
Gordon, Raymond W. Water Well Drillirlg \tYth Cuhle Tools. Sourly Milwaukee, Wisconsin: Bucyrus-El-ie Company, 195X.
Harr, M. E. Groundwater
Company Inc., 1962.

aHd Seepage. New York:

McGraw-Hill

Book

Livingston, Vern. Frown: Too-Thin-to-Plough Missouri. To: Just-Right-toDrink Well Water, Water Works Engineering (May, 1957), pp. 493495,
521.
McJunkin, Frederick E. (ed.). International Program in Sanitary Engineering
Design. Jetting Small Tubewells b-y Hand. AID-UNC/IPSED Series Item
No. 15. University of North Carolina, 1967.
Meinzer, 0. E. Occurrence of Ground Water in the United States. Geological
Survey Water-Supply Paper 4S9. Washington: Government Printing Office,
1959.
Outline of Ground-Water Hydrology. Geological Survey WaterSupply Paper 494. Washington: Government Printing Office, 1965.
Miller, Arthur P. Water and Man’s Health. Washington: Department of State,
Agency for International Development, 1962.
New York State Department
York, 1966.

of Health. Rural Water Supply. Albany, New

13s

f

State of Illinois. Department of Public Health, Division of Sanitary
Engineering. I,‘lirmis li’afer WcN Cousfnrc-tiorl Cih. Springfield, Illinois,
19h7.
Todd, David Keith. Crort~lci I4’~rrr H_rxi~o/o~~. New York: John Wiley & S,ms,
Inc., 1960.
U. S. Department of Health. Education, and Welt‘tlre. Dri~lkiug h’arer
Standards. Public Health Service Publication No. 956. Washington:
Government Printing Office. 19h2.
. hlarrual of htlividual
Water Supp[v LSystenls. Public Health
Service Publication No. J-1. Washington: Government Printing Office.
1963.
U. S. Department of the Interior. lnterdepartmenlal Committee on Water for
Peace. Water fur Peace. A Report of Backgrotmd Consideratiorzs and
Recol?lr)ZelldatiOtls on the Water for Peace Program Washington : Government Printing Office. 1967.
Wagner, E. G., and J. N. Lanoix. Water Supp[v jiu Rural Areas and Small
C~mtwmities. Geneva: World Health Organkation. 19s~).
Wisconsin State Board of Health. Wisconsitl Well Corastntctiorl ami Pump
tnsrallatim C&e. Madison, Wisconsin, I95 1.

CREDIT FOR ILLUSTRATIObJS

The authors wish to give credit to UOP-Johnson Division, Universal Oil
Products Company. St. Paul, Minnesota for the use and adaptation of the following illustrations: Figures 2.3.2.5,2.9,2.10,~.12.2.13,2.17.3.1.3.2.4.1.
4.2, 4.3, 4.5, 4.7, 4.8, 4.10, 4.1 1, 5.16, 5.22, 5.23, 5.24, 5.25, 5.26. 5.29,
5.30, 5.31, 5.32, 5.33, 5.34, 5.35, 5.36, 5.37, 5.38, 5.39, 5.40, 5.41, 6.1, 6.2,
6.4, 6.5, 6.6,6.8, 7.1, 7.2, 8.2, and A.l.

139

ICITY

T OF PE

The coefficient of permeability, or permeability as it is usually referred to
in practice, can be determined by both laboratory and fie!d experiments.
The field experiments, or pumping tests as they are called, have the advantage
over laboratory experiments in that they are performed on the aquifer
matcrlals in their natural, undisturbed state. They are, however, more
complicated, time consuming, costly and beyond iLe scope of this book.
Permeameters are used for laboratory determinations of permeability. The
simplest laboratory method for the determination of permeability uses a
constant head permeameter iiS
follows. Flow under constant head
or pressure is maintained through a
chosen length, C, of the sample of
-1oaquifer material placed between
porous plates !.n a tube of cross
ir:z
sectiona! area. A (Fig. A.l). The
-Idevice at the upper left of the
-sfigure is used to provide the flow
-57
under constant head. The rate of
-.:,-L
flow, Q, through ibe sample is
fz-.
obtained by measu.;. ,:, .he volume,
-aV, of water discharged I:iio a grad-0
uated cylinder in a given time. t.
.i
The
manometer tubes to the riglIt
-of the figure are used to measure
the head loss, hI- h2, as the water
flows through the length, f, of the
sample. Care must be taken to
expel any air trapped in the satnple
before taking measurements.

f”’
;
.e
r=.*

Fig. A.1

Then

CONSTANT-HEAD
PERMEAMETER FOR LABORATORY
DETERMINATlON
OF COEFFECIENTS QF PERMEABILITY.

V

P(hl -h2)A

t

II

Qz-=

VV
Giving

\

P=
(h, -h2) A t

To obtain P in units of gallons per day per square foot (gpd/sq ft), V must
be expressed in gallons, II, hl , and h2 in feet, A in square feet, and t in days.

140

USEFUL TABLES A

Unit

T

TABLE B.l LENGTH
I

Centimeters

1 Centimeter
1 hleter
1 Kilometer
1 Inch
1 Foot
1 Yard
1 Mile

Unit

Meters
1

100
100,000

2.54
30.48
91.44
160,935

.3937
39.37
39,370
1
12
.9144 .00091-?
36
1,609.3 1.6093 63,360

r
Square
Zentimeters

Equivaleuts of First Column
-*KiloFeet
Inches
meters

TABLE

.0328
.u109
3.2808
1.0936
3,280.8 1,093.6
.c)833
.0278
1
.3333
3
1
5,280
1,7&o

.(
:
1Miles

DO00062
.000621

.621
.05)0016
.000189
.0010568
1

B-2 AREA

Equivdents
Square
Meters

Yards

of First Column

Square
Inches

Square
Feet

Square
Yards

Acres

Square
Miles

-

-

1 sq.

centimeter
1
1 sq.
Meter
10,000
1 sq.
Inch
6.452
1 sq.
Foot
929
1 sq.
Yard
8,361
1 Acre 40,465,284
1 sq.
Mile
-

I
I-

.OOOl

.155

1

1,550

.000645

1

.0929

144

.00108
10.76
.!I0694
1

.00012

1.196 .000247
.00077 2

-

.I1 1 .000023

-

.836
1 .000207
1,296
‘9
4,047 5,272,640
1 30156
4,840
43,560
27,878,400 3,097.600
640
!,5 89,998

141

TABLE

B.3 VOLUME
Equivalents of First Column

Unit
Cubic
Centimeters

1 Cu. Centimeter
1 Cu. Meter

I Liter
1 U.S. Gallon
1 Imperial Gallon
1 cu. Inch

1 Cu. 12oot

Cubic
Meters

U.S.
Gallons

Liters

Cubic
Inches

.000264

.00022

.061

264.17

220.083

61.0:!3

35.314

.264

.220

61.023

.0353

1
1,ooo.ooo
1,000

.000001
1
.OOl

3.785.4

.00379

3.785

I

4,542.5

.00454

4.542

1.2

16.39
28,317

.0000164
.0283

.OOl
1,000
1

Imperial
Gallons

.833

.0164

.00433

.00361

7.48

6.232

TABLE B.4 FLOW

.0000353

231

1

28.317

Cubic
Feet

.I34

277.274

.I60
I

.000579

1,728

1

-.

-

Equivalents of First Column

1 Cu. Foot per Day
1 U.S. Gallon per Min.
1 Imp. Gallon per Min.
1 U.S. Gallon per Day
1 Imp. Gallon per Day

U.S. Gallons
Per Minute

Imp. Gallons
Per Minute

U.S. Gallons
Per Day

448.83

374.03

646,323

.00519

.00433

1
1.2

7.48

.833

1

.000694

.000579

.000833

.0006”3

226.28

188.57

:
’
j

538.860

1.983

6.233

.00002 3

1,440

1,200

.00442

1,728

1,440

.oos3

1
!.2
125,850
.ci.C:-~~

.833

1
271,542

.00000307
.0000036,8

I

TABLE B.5 WEIGHT
Equivalents of I‘izst Column
Unit

Ounces

Kilograms

Grams

/

Pounds

/

(Avoirdupois)

I
1
1000

1 Gram

1 Kilogram

.oo 1
1

1Ounce
28.349
(Avoirdupois)
1 Pound
453.592
(Avoirdupois)
907.184.8
1 Ton (Short)
1 Ton (Long) 1.016.046.98

.0283
.454
907.185

1.016.047

TABLEB.6

POWER

=i=
Equivalents of First Column

!

Unit
Kilowatts

Watts
1 Watt

1

1 Kilowatt
1 Horsepower
1 Foot Pound
Per Minute
1 Joule
Per Second

TABLEB.7

Foot Pounds
Per Minute

Horsepower

Joules
Per Second

1000

1
1,000

746

746
.0226

1

VOLUMESANDWEIGHT

1=

EQUIVALENTS(Waterat39.2"F)

Equivalents of First ::olumn

I-

Unit

Cubic
Meters

Liters

UIS.
Gallons

Imp.
Gallons
-.-

264.17

220.083

I

1 Cu. Meter
1 Liter
1 U.S. Gallon
1 Imp. Gallon
1 Cu. inch
1 Cu. Foot
1 Pound

1
.OOl

1,000
1

.264

1
I’.-

.00379

3.785

.00454

4.542

.0000164

.0164

.00433

.0183

28.317

7.48

.00045

.154

. 17
-

Cubic
Inches

61.033
61.023
‘31

143

Pounds

' 700.83
35.314 -..035 3
’ ‘01
.--“0
-..833
.I34
8.333
1 177.774
.I60
IO
.00361
.0361
1 .000579
6.232
1,728
1
62.32
17.72
.016
1
.I

-

-

Cubic
Feet

B-8 PRESSURE
1 Atmosphere = 760 mibreters of mercury at 32°F.
29.921 inches of mercury at 32°F.
14.7 pounds per square inch.
2,116 pounds per square foot.
1.033 kilograms per square centimeter.
33.947 feet of water at 6:!“F.
B.9 TEMPERATURE
Degrees C = 5/9 x (F - 32)

Degrees F = 9/5 C t 32

TABLE B-10 FRICTION LOSS IN SMOOTH PIPE
(approximate head loss in feet per 1000 feet of pipe1
I
Nominal Pipe Size in Inches

Flow Rate in
Gallons per Miwte

2%

1%

10
15

20
44

20
25

79
123

30
40

178

4
6
9
16
25

50
-

2
I

TABLE

B-11

PIPE, CYLINDER

Diameter (Inches)

OR HOLE CAPACITY
Gallons Per Foot

1%

0.09

2

0.16

2%
3
4

0.25
0.37

6

0.67
1.47

8

2.61

10

4.08

12

5.86

16

10.45

18

12.20

20

16.35

24

23.42

144

B-1 2 DISCHARGE

MEASUREMENT

USING SMALL CONTAINER

(Oil Drums. Stock Tanks. etc.)

Discharge (Gallons per minute) =

TABLE B.13

ESTIMATING DISCHARGE FROM A HORIZONTAL
PIPE FLOWING FULL

DISCHARGE

-

Volume of container (Gallons) x 60
Time (Seconds) to fill container

RATE (Gallons Per Minute)
Nominal Pipe Diameter (Inches)

Horizontal
Distance, x
(Inches)

1

1%

1‘h

2

2Y2

4

5.7

9.8

13.3

22.0

31.3

5

7.1

12.2

16.6

27.5

39.0

6

8.5

14.7

20.0

33.0

47.0

7

10.0

17.1

23.2

38.5

55.0

8

11.3

19.6

26.5

44.0

62.5

9

12.8

22.0

29.8

49.5

70.0

10

14.2

24.5

33.2

55.5

78.2

11

15.6

27.0

36.5

60.5

86.0

12

17.0

29.0

40.0

66.0

94.0

13

18.5

31.5

43.0

71.5

102.0

14

20.0

34.0

46.5

77.0

109.0

15

21.3

36.3

50.0

82.5

117.0

22.7

39.0

53.0

88.0

16

4

145

-

125.0

TABLE B-14

ESTIMATING DISCHARGE
PIPE OR CASING

DISCHARGE
Height, H
(Inches)

FROM VERTICAL

RATE (Gallons Per Minute)
Nominal Pipe Diameter, D (Inches)

2

3

4

1%

23

43

68

2

26

55

9?

3

33

74

130

4

38

88

155

5

44

99

175

6

48

110

190

8

56

125

225

10

62

140

255

12

69

160

280

78

175

315

18

85

195

350

21

93

210

380

24

100

230

400

15

.

146

TABLE

B.15

ROPE CAPACITY

OF DRUM OR REEL

(Wire Rope Evenly Spooled)
Outer layer of rope

Rope Capacity (feet) = K (A+B)AxC

where A,B,C are in inches and K
has. values in table below

Nominal Rope Diarnet er
(IncheyF

Nominal Rope Diameter
(Inches)
4.4

i/4

I

9116

2.8
2.0
1.4

i/2

1.1

147

-K
.9

TABLE B.16

DRILLING

CABLE ROPE CAPACITIES

(Left Laid - Mild Plow Steel - 6x19 Hemp Center)
Recommended
Working Load
(Pounds)

Approximate

Rope
Diameter
(Inches)
112

3,200

9/16

4,200
.66

5,000

.95

7,200

713

1.29

9,800

1

1.68

513
-314
;

TABLE

B.17

12,600

-

SAND LINE CABLE ROPE CAPACITIES

(Coarse Laid - Plow Steel - 6x7 Hemp Center)
Rope
Diameter
(Inches)

Approximate
Weight Per Foot
(Pounds)

114

.09

800

S/l6

.15

1,200

313

.21

1,800

7/16

.29

2,400

112

.38

3,200

-z-

148

Recommended
Working Load
(Pounds)

TABLE

B.18

CASING LINE CABLE ROPE CAPACITIES

(Non Rotating - Plow Steel - 18 x 7 Hemp Center)
Rope
Diameter

Approximate
Weight Per Foot

(Pounds)

(Inches)

Recommended

Working Load
(Pounds)

513

.hS

5,400

314

1;

7,600
10,200

713

TABLE B. 19 MANILA

ROPE CAPACITIES (3-STRAND)

Rope
Diameter
(Inches)

Approximate
Weight Per Foot
(Pounds)

Recommended

318

.04

270

7116

.05

350

1:‘2

.08

530

!a/16

.lO

690

518

.13

880

314

.17

1,080

7/3

.23

1,540

1

.27

1,800

149

Working Load
(Pounds)

A

Carbon dioxide. 26, 48, 107
Carbonate. 106, 109
Casing, (see Well casing)
- elevator, 70
-shoe
68
Cementation, 7, 1S
Cementing agents, 8. 1S
Cesspools, 23. 25, 134, 136
Chemical analysis, 48, 108
- constituents, 7
- decomposition, 7
- treatment of wells, (see Well maintenance operations)
Chloride, 24
Chlorination, (see Well disinfection)
Chlorine treatment, (see Well maintenance operations)
Circle of influence, 135
Clay, 7, 106, 11 1
-, bentonite, 7 1
cemented, 8
=: grouting with, 7Of.. I 13, I37
-, screening of, 41
Compaction, 7f.
Concrete, 52, 137
Conduit functiou of aquifers, I I ff.
Cone of depression, 16ff., 135
--composite, 20
--: definition, 16
Confined aquifer, 10
Contaminated sources, 2
- water, 2.70, 104
Contamination, 23. 104, 136f.
-+ routes of, through wells, 52
Contour lines, 29
- map of water table, 31
Corrosion. 26, 37f.. 48f.
-, control of, 26
-, dissimilarity of metals, 48
-., galvanic, 37
- resistant materials, 33, 48ff.
Corrosive waters, 26, 44, 48
Cost, effects on pump selection, 126
-selection of power source,
-2 8ff.
- - well design, 33, 35. 40, so
=: fishing operations, 86
Crevices, 8. 135
Cyanosis. 25

Abandoned well, I37
Acid. hydrochloric. 49, 86, 109f.
-, precautions in using, I I 1
-, sulfamic, 109ff.
- treatment, (see Well maintenance
operations)
Aerial photographs. 28. 30
Agricultural wastes. effects on groundwater quality. 25. I34
- water needs. 2
- - use. 24
Alignment. (see Well alignment)
Alluvial plains, 30
Altitude, effect on suction lift, I I s
Aquifer, coastal, 24
-, definition, 6
-, depth of, 29
-. extent of. 9
- functions. I Ift’.
-. hydrltulic cnnracteristics, 9
-. shape of. 9
-. stratified, definition, IS
-. thickness of, IO. 13, 20. 29, 41
-, t,ypes of. I Of.. (also see Artesian
aquifer and Water-table aquifer)
-m. width of, I4
Area. cross-sectional. I3
Artesian aquifer. 10. 13. 16. 30, 33. 52
- head. I37
- well, flowing, IO, 33. IO4
- -.. non-flowing, IO
Auger. hand, SS
-, spiral. 56
B
Bacteria, coliform. 104
-. disease-producing, I 35
-. iron, 49, 106. I IOf.
bacterial growths, I I 1
Bailers, 66. 68, 89, 99, 104
Barnyard, 2S
- manure, 134
Basalt, 8
-, breociated. 8
Belt. intermediate. 6
--, soil water, 6
bits. (see Drilling methods)
borehole. depth of, 88
boring. (see Drilling methods)
boulders. 9. 74, 88
Boundary. effects. I7
-, impermeable. 18
-, negative. 18
-. positive, 18
Brackish-water rivers, 2-1

D

Darcy’s Law, 12. 16
Dental fluorosis, 25
Deposition, 7
Deposits, alluvial, 7, 9f.
-, area1 extent of, 8
-, deltaic. 7
-, glacial, 7, 10
-, lake, 9f.
-, marine, 7, 9
-, scale, 2Sf., 49
-, slime, 11 I
-, stream, 7,9
-, thickness of, 8
-, w%d-blown, 7, 9
Design, well, 33ff., 75
Development of wells, 36, 38, 42, SOf.,
96ff.

C
Cable. (see Wire rope)
- -tool percussion drilling, (see Drilling methods)
Calcium hypochlorite, l04f., I1 I
- -. stock solution, POS
- -. storage of. 105
Capillary forces, 6
- fringe, 6
- tube, 6

151

Development, artificially gravel-pazked
wells, 103f.
-, backwashing, high-vehxif”
jetting,
10lff.
---. -,
jetting tool, IOlf.
-7 object of, 96 ’
-, surging, 98ff.
De-watering, well-point systems for,
22
Diameter, casing, 34, ~4
-, driiled hole. 1, 54. 7 3
Dip of formation. 29
Discharge, natural, of aquifer. 18
f&eases, communicable, 2
-, diarrheal, 2
-. gastrointestinal, 2
-, viral. 2
-, water-borne. 2
Disinfection, (see Well disinfection)
Disintegration. mechanical, 7
Dispersing agents, 164, 1 11 f.
Dolomite, 8
Drawdown, 16f.. 31. 41, 107ff.
-. definition, 16
Drill bits, (see Drilling methods)
- col!ar. 6 1. 74
- stem. 61
Drilling equipment, (see Drilling methods)
- -, care and use of. 87ff.
- fluid, functions of, blff., 78, 80
- methods, SSff., 75
- -, boring, SSf.
- -. cable-tool percussion. 66ff.. 76
--_-advantages and disadvantages. 69 ’
--_, drill bit, 67
.
--.-.--9drilling jr&r,, 67
--_- rig, 66, 99
c---: fishing jars, 67
- -, - - --. rope socket, 67, 93,
(also see Wire line socket)
string of drilling
--t---tools. 66f.
’
-, driving, SSf.
--. equipment, 56
- ---I hydraulic percussion, ~9
-, - rotary, 39, SO, 60ff.
--.-advantages and disadvantages, 65f.’
-%- -, drill bit (simple), 63
- -* -- -, - ms, 61
--. - collar. 6 I, 74
- -, - -. - stem, 61
--.-, drilling equipment,
simule. 62f.
---- fluid, functions of,
61ff:
’
-_
-- mud, properties of,
63ff.’
’
- -. - - rig, 6Off.
-7 -_
: mud pump. 61, 102
-, - -, settling pit, 61f.
--storage pit. 6 1f.
- --I jetting,’ 57ff.
-, -, drill bit, 57f.
--,--equipment, S7f.
- -, sludger, 59f.
-- mud, 58,78. 81,96, 104
- -, gelling property. 64, 104
- -, properties of, 63ff.
- -. thickness of, 64
- string, length of, record keeping. 88
- tools, (see Drilling methods)
- -, care and use of, g?ff.
l

Drilling tools, record of dimensions, 88
- ---, storage, 88
- -. tool joints, making up, 88
Dti*:king water standards, United States
Pu3lic Health Service. 2 3
Dri;,e head, right-angle, 124f.
- point, (see Well point)
- shoe, (see Casing shoe)
Driven wells, (see Drilling methods)
Driving well casing, 68
- - point, 56f., 82
Drought, 3
Dug well, 1 l2f.

E

Electric motor, I 14, 120. 124
- -, submersible, 126
Engine. 114. 120, 124
-, diesel. 130
-, gasoline, 130
-, kerosene, 130
Equilibrium, definition. IS
Erosion, 30

F

Faults. 29
Filtration, effects on ground-water quality, 22, r35ff.
Fish, definition, 85
-. position of, 90
Fishing jobs, 90ff.
- -. broken wire line, 92f.
- -, cylindrical objects, 93ff.
- -, neck of rope socket. 93ff.
- -, parted drill pipe, 90ff.
- -, pin of tool, 93ff.
-, releasing locked jars, 95
- operations, 86ff.
- --, preparations for. 88ff.
- --.-preventive
measures, 87f.
- tools, circulating-slip overshot, 90f.
- -, combination socket, 93ff.
- - , die overshot. 81, 90
- -, fishing jars, 67, 92ff.
- -, imoression block. 89f.
- -, jar’bumper. 95
- -, sinker, 92
- -. tapered fishing tap, 8 I, 9 I f.
- --. wall hook, 9 I f.
- -, wire line center spear. 92f.
Fissures, 22, I35
Flow, base, 3
-, converging. I6f.
-, direction of, 29
-, rate of, 13f., 22f., 135
-. resistance to, 14
- toward wells. I6ff.
Fluoride, 24f.
Formation. consolidated, 7
-, impermeable, 52
-, laminated, 5 1
-. penetrated, record of. 3 I, 6Sf.
-. samples of. 59, 65f.
- stabilization, 50ff.
- -, material used, Slf.
-, unconsolidated. I, 7, 34. 57, 66. I35
Fractures, 8f.
Friction, I I6
-

lossrs,

I 28

Incrustation, reduction of, 1osf.
Incrusting deposits. I06ff.
- waters, 49
Industrial water heeds, 2
Infiltration,
4. 18
Insecticides, 27
Interference, 18ff.. 127
- , defimtion, 18
Intermediate water, 6
Interstices, 22
Iron. 24, 26, 49
- bacteria, 49, 106, I 10f.
- hydroxide, 106f., 100, 11 I

c

Gelling, 64
Geologic cross-sections. 2aff.
- data, 28ff.
- formations, 7ff.
- maps, 29
- processes, 9f.
Geology, effect on water quality, 27
Geo hysics, 28
-g. 12% formation stabilization matec,:“,,
-, haveI-pack material, Slf., 103
-, uniform, of particles. definition, 1s
Granite, 7f.
Gravel, 7, 9, 78
--pack envelope, thickness of, 52,
103f.
- - material. grading of, Slf., 103
--, selection of, 5 1
- packing of wells, soff., szff.
- pits, 30
Ground water, availability of, 3. 7
- -, definition, 6
-- -, depletion of, 3
- -, discharge rate, 3,4
- -, flow of, 4, 1Off.
- -. importance of, 2f.
- -, mining of, 3
- -, natural purification process,
134f.
- -, origin, occurrence and movement, 2. 4ff.
- -. quality of, 3. 4
- -, rate of extraction, 4
- -. rate of recharge (replenishment),
3.4
Ground-water development. 2, 2 8
- --, exploration, 28ff.
- - resources, development of, 3, 4
- - --I management of, 3
- - sources, 3. 134, 136
-- - sapplies. sanitary protection of.
134ff.
Grout, cement, 7lff.. do, 84
-7 -7 mixing, 7 1f.
-. -, placing, 54, I2f.
-,--,
time to hari;en, 73
-. clay, puddled, /Of., 113. 137
- pipe, 72f.
Grouimg methods, 72f.
- -, gravity placement, 72
- -, inside-tubing, 72f.
- -, outside-tubing, 73

.I
Jars, drilling, (see Drilling met hods)
-, fishing, (see Fishing tools)
Jetting, (see Drilling methods)
-, high-velocity, well development,
10 1ff.
-3 - -, with chlorine treatment. I 11
-7 - -, with dispersing agents, 104

L
Lakes, 31
Laminar flow, 13
Land forms, 30f.
- use. 30
Lava. 8’
Laxative effects. causative chemicals in
water, 25f.
Lead packer, 76
- shot, 80, 84
- slip-packer, 84
- wool, 80, 84
Leakage, 18
Limestone, 7f.
Location of wells. 2Off.. 25, 28, 30.
136f.
Loess. 7
M
Magma, 8
Maintenance of wells, (see Well maintenance)
Manganese, 24,49
- hydroxide, 107. 109, 11 1
Marble I 9
Marsh funnel, 64f.
- - viscosity, 65
Methemoglobinemia,
25
Mineral content of water, 23ff.. 48
Minerals, solution in water, 23
Mud balance. 64
- cake, 64, 83. 99
- wall, in boreholes, 52
Mudstone, 8
Multiple well systems, 18ff.

H
Hardness, 2 5
Herbicides. 27
Hoisting p&, 70
Hydraulic characteristics of aquifers,
IOff.. 31
- gradient, 13f., 16
- percussion drilling, (see Drilling
met hods)
- rotary drilling, (see Drilling methods)
Hydrogen sulfide, 26, 48
Hydrologic cycle, 4
Hydrologist, 28

N
Natural purification processes in soils,
134f.
Nitrate, 25
Nozzle, jetting tool, 10lf.

0
Odors in ground water., 22, 26f.
Organisms, disease-producmg, 22, 104,
135
Outcrop, 29
Oxygen, dissolved, 26, 48

I
Impermeable layer, 10
Incrustation, 48f., 108

153

P

Pump impeller, 12 If., 126, 128
-, jet, 120, 122ff., 133
-, Iineshaft., 124ff., 132
-, manually-operated, 114, 118
-, multi-stage, l22ff.
-, pitcher, 118
-, positive displacement, 124, 126,
131, (also see constant displacement)
-, power so:uce, electricity, 127, 129f.
internal combustion engine,
-¶ --9
129f.
-9 - -, man power, 129
-9 - -, selection of, 128ff.
-1 - -, wind, 129f.
-, priming of? 126f.
-, reduction m capacity, 106
-, selection of, 127f.
-, self-priming, 127
-, standardization, 128
-, submersible, 74, 124, 126, 133
---I surface-type, 1 16, l 1Sff., 127f.,
13lf.
--, variable displacement, 117, 1 ZOff.,
132f.
-1 - -, centrifugal, 1 ZOff., 132f.
-, jet, 120, 122ff., 133
-,--, vertical turbine, 74
Pumping equipment, 33f., 114ff.
-, hours of operation, record keeping,
107
- water level, 54, 116, 127
Tif;;es
of, 107, 109, 119f., 124,

Particle classification, 43
size analysis, (see Sieve analysis)
Gicles,
arrangement of, 14f.
-, distribution of, 14f., 46
-, packing of, 7, 14f.
-, rounding of, 7
-9 shape of, 9
-, size of, 9, 14f.
sorting of, 7
¢ size, definition, 43
Percolation, benefits of, 3, 2 3
Percussion drilling, (see Drilling Met hP%?eabiIity
12ff 31 43, 100. 135
-, coefficiem of,“1 2ff.
-. factors affecting. 14f.
Permeable, 7f.
Pesticides. 27
pII,
PyTmetric
surface, definition, 10, 13,
Pipe, black iron, l09f.
- clamp, 70, 85
- joints, spigoted, 39
-, plastic, 38f., 49f., 109f.
-, polyvinyl chloride (PVC), 49
- , slotted, 33, 38f.. 102
Pit latrine, 136
Pl.ains, coast al, 3 1
-, river, 31
Pollution, bacterial, 23, 135f.
-, chemical, 135f.
-. rate of travel, 136
-, sources of, 23, 134ff.
- travel in soils, 134ff.
Polyphosphates, 104, 111
Pore, 4ff., 11, 135
Pores, continuity of, 14f.
-, volume of, 14
Porosity, 14f., 135
-, definition, 11
Porous, 7f.
Power consumption, 107f.
Precipitation, 4, 18
Pressure, 12f., 16f., 26, 40, 101, 107,
114ff., 121
- aquifer, 10
-. atmospheric, 1 15
- differences, 13
Privies, 23, 25, 134
Public health, l
Pulling ring, 77, 85
Pump, 1o, 114ff.
-, capacity of, 127f., 13lff.
-, centrifugal, 120ff.. 132f.
-, -, turbine, l?lf., 132
-, volute, 12l. 132
=I constant displacement, 117ff., 131
- -, helical rotor, 117, 1 19f.,
TS4.131
- -, reciprocating piston, 117,
li4,
129f.
discharge rate, 119
-, --s-- -,rotary,‘ll7
119 131
=: deep well, 116, 1 18: 1Zdff., 127,
132f.
-1 - -$ lineshaft, 124ff., 132
-3 - -, submersrble, 74, 124, 126,
133
-. driving force, 114, 117
-) hand-driven, 114, 119, 13 1, (also see
manually-operated)
- house, 125

-

test., 127

Q
Quality,
54
_- 7 -Gter,
--9 -1 -

ground water, 3f., 20, 22ff., 31,
-,

chemical, 23ff., 48f.
compared with surface

22f.
-> microbiological,
-, physical, 22

22f., 135

R
Radius of influence, 16
Recharge. 17f.. 20
-area,
il, 18, 29
- -, definition, 11
- effects, 17f.
River beds, 32
Rocks, classification, 7ff.
-, consolidated, 7, 22, 29, 135
-, definition, 7
-, deposition of, 7
-, erosion of, 7
-, extrusive, 8
-, hard, 7
-, igneous, 7ff., 24
-, intrusive, 8
-, metamorphic, 7, 9
-, plutonic, 8
--, sedimentary, 7ff.
-, soft, 7
-, transport of, 7
-,
unconsolidated,
1, 7, 29
-, volcanic, 8f.
-, weathermg of, 7
Rope socket, 67, 93, (also see Wire line
socket)

Rotary drilling,

154

(see Drilling

methods)

U
Unconfined aquifer, 10
Uniform grading of particles, IS
Uniformity coefficient, definition,

s

Sand, 7,9? 119, 126, 129, 137
-- anaylsn, (see Sieve analysis)
- dune, 7, 31
- pump, 68
- pumping from a well, 46
Sandstone, 7f.
Sanitary protection, ground-water
supplies, 134ff.
-- -, wells, S2ff.. 136f.
- well seal, 52
Screen, (see Well screen)
Sediments, terrestrial, 9
!%$II tganks, I34

51

V
Vacuum, 116, 121f.
Vadose water, 6
Valley fill, 31
Valleys, 9, 30f.
Vegetation, 6, 30ff.
Velocity, 12f., 16, 34,48, 107, 114,
121f.
- head, 128
Vesicles, 8
Volcanic rocks, 8f.

Sieve inalysis, 43, 46
Sieve-analysis curves, 43ff.
Sieves, standard sets of, 43
Silt, 106, 111
Siltstone, 8
Site accessibility, effect on selection
of well materials, 50
Slotted pipe, 33, 38f., 102
Sludger, drilling method, 59f.
Sodium hypochlorite, 105, 111
Solution channels, 8f., 22, 135
Solvent, water as, 2 3
Spacing of wells, 20ff.
Specific capacity, 20, 42, 44, 107f., 127
- retention, 12
- yield, 12
Spring, 29, 31
Static water level, 16, 103, 106, 116
Storage, aquifer, 3, 17
- function of aquifers, 1 If.
Stratification, 9, 14f., 46
Stream patterns, 31f.
Strike of formation, 29
Subsurface water, 4ff.
Suction, 11 Sf., 128
- lift, 103, 114ff., 121, 128
- -, definition, 114ff.
Sulfate, 25, 106
Surface drainage, contamination of
wells, 104
- evidence, ground-water exploration,
28, 31f.
- water, 3, 18, 134
Surge block, 98
- plunger, 98ff.. 109, 111
- -. operation within well screen,
101
- -. solid-type, 99
- -. valve-type, lOOf.
Surging, chlorine treatment, 11 1
-, well development, 98ff.
Suspended matter in ground water, 22
Swamps, 31
Swedge block, 77, 84

W
Wash-down bottom, 80f.
Wastes, effects on ground-water quality,
agricultural, 25, 134
, animal. 25, 134
-, -----9 - - - - -, human, 25
----, industrial, 27,
-9
134
Water analysis, 48
--bearing
capacity, 7
- - formation, clogging of, 96, 106
-- - -9 compaction of, 96
- - -9 pollution travel in, 134ff.
- - -, stabilization by well development, 96
- level, pumpirg, 54, 116, I27
definition, 16
- ‘-1-P
- -1 -I estimation of, 127
- -, static, 16, 103, 106, 116
- -9 ,, definition, 16
- quahty, (see Quality)
- supplies, importance of, If.
- table, 13, 16, 56, 112, 127, 135,
137
- - contour map, 31
- 2, definition, 10
---table aquifer, 1 Of.., 13, 16, 30, 54
--yielding
capabilittes of rocks, 7ff.
Weat hering of rocks, 2 9f.
Well alignment, 73ff., 126
- -9 checks on, 75
- -, conditions affecting, 74
- --, measurement of, 71
- -, plumbness, 73ff.
- -, straightness, 73ff.
artificially gravel-packed, 36, 46,
<;ff.,
82ff.
-, - - --9 conditions favoring use,
51
--development of, 103f.
E’capacity,
1i 4, 127
- -, decrease in, 106
--9 cased section of, 33f.
-- casing, diameter of, 34, 40
- -, grouting and sealing, 54, 70ff.
- -9 installing, 69f.
- -, lower terminal of, 52ff.
- -, pulling, 77
- -, sealing abandoned wells, 137
-. --, shoe, 68
- -, temporary, 54
- completion, 96ff.
- construction, 6, 23, 31, 55ff.
-, depth of, 1, 30
- design, 33ff., 75

T
Tastes in ground water, 22, 24, 26f.
Temperature, 13, 2 2f., 116
Terraces, 9, 30f.
Texture of rocks, 7f.
Total dissolved solids, 25f., 48
Toxic chemicals in water, 26f.
Trace elements, 26f.
Transmissibility-, 14, 16f., 31
coefficient of, definition
14
Tra;lsmissivity, coefficient of: 14
Transport, rock, 7
Treatment, water, 22f., 26

155

Well screen, entrance velocity, 35, 40,
47f.. 109
-- l, installina. 75ff.
-- in gr&el-packed wells, pull-9
back mtr hod. 82ff.
-. -‘etting method for setting
COT
’ , .. ,.i :dsing and screen, 8 1
- -,
- iowering hook, 76f.
- -, -, open hole method, 77ff.
- -, -, pull-back method. 76f.. 81f.
- -* -, wash-down met hod, SO’f.
- -, length of, 4Of., 47
- -, louver- or shutter-type, 36
- -, open area, 34ff., 47
- - openings, clogging of, 106
- - -9 shape of, 34ff.
- - -9 size of, 42ff.
- - -9 standardization of sizes, 46
- --, pipe-base, 37
- -, pipe-size, 41, 47
- -, recovering, sand-joint method,
84ff.
- - slots, plastic pipe, 38f.
- -, telescope-size, 41, 47, 76
- spacing, 20ff.
-, upper terminal of, 52, 113
-, useful life of, 33, 106
Wells, arrangement of, 20ff.
Wetting agent, 111
Wind, 31, 129f.
a
Windmill, 114, 129f.
-, wind speed requirement, 129
Wire line socket, 9 2 (also see RcJpe
socket)
- rope, care of, 87f.

Well development, (see Development of
wells)
- disinfection. 96. 104f.. 1 11
chlorine solution for, 104f.
---I
- -, flowing artesian wells, 105
- drilling methods, (see Drilling
rret hods)
1: %%ia~~~of, 42. 44, 46, 51
- hydraulics, IOff.
-, intake section of, 33ff.
- inventories, 28, 30f.
- location, 2Off., 25, 28, 30
relative to pollution sources,
--,
136f.
- logs, 30f.
- maintenance, 106ff.
- - operations, 108ff.
- - -, acid treatment, 109ff.
- - -3 - -, placing acid, 109
--- -, precautions, 111
- - -% ’ chlorine treatment, 109ff.
--dispersing agents, I 1 lf.
- -, plrLning of, 107f.
- -, record keeping, 107f.
- -, frequency of observa--.
tions, 108
- materials, corrosion resistant, 33,
48ff.
- -. selection of, J7ff.
- -, strength requirements, 48, 49f.
- performance, 33, 106
- -, maintenance of, 106f.
- point, installing. driving, 56f.. 82
- -9 - in dug well, 112f.
. open hole method. 81
--.pull-back method,‘81
--9
-9
- -, types of, 37f.
- pumd,-(see Pump)
- rehabilitation, 106ff.
-, sand producmg, 46
screen, 33ff., 102f.
- -, continuous-slot type, 35f., 102f.
- ---, design, influence of aquifer charactertstics, 40ff.
- - -9 - on well development, 96,
102
- -, oiameter of, 4Of., 47

Y

Y;::“;

8i X&, 31, 40f., 49, 106, 109, 113,
.I
-, specific: 1 If.
-9 -, definition, 12
Z

Zone of aeration, 4ff.
- - saturation, 4ff.

156



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