Water Well Manual (USAID).pdf - The Water, Sanitation and Hygiene

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 MAINTE- 

NANCE OF SMALL WELLS USED PI:,MARILY FOR 

lNDlVlDUAL AND SMALL COMMUl’:ITY WATER 

SUPPLIES. 

THE AUTvlORS, WRITING IN A Cy,EAR AND EASY-TO- 

READ 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 AGRI- 

CULTURAL, INDUSTRIAL, Of,! HUMAN NEEDS. TO 

AID UNDERSTANDING THE r”iUTHORS HAVE IN- 

CLUDED MORE THAN 100 ILLUSTRATIONS THROUGH- 

OUT 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 LOCATING AND CONSTRUCTING WELLS 

FOR lNDh/lDUAL AND SMALL COMMUNITY WATER SUPPLIES 

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 PRESS 

Berkeley, California

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 Wells Mamai, 

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-t11 Printing, May 1977 

ii

The authors wkh to express their appreciation to the Health Service, 

Oftlce of Wt?r on Hunger. United States :lgtfi~q t‘or International Develop- 

ment for making the publkation of this manual poss\lble. We art’ particularly 

indebted to the UOP-Johnson Division, Universal Oil Products Company, St. 

Paul. %Iinnesota for their advice and assistance in preparing the tnanuscript 

and for their contribution of valuable inft)rmstion and illustrations and to Mr. 

Arpad Rumy for the preparation of man i’ of the illustrations. We also wish to 

express sincere gratitude to ail pcrs:ns who have offered comments, 

suggestions and assistance or who have given 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 consequences of this deficiency are innumerable episodes of 

the debilitating and incapacitating enteric diseases whrch 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-11 use 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 necessarily an 

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 

ACKNOWLEDGEMENTS ii 

FOREWORD 

1. INTRODUCTION 1 

PURPOSE 1 

SCOPE 1 

PUBLIC HEALTH AND RELATED FACTORS 1 

Importance of Water Supplies. Ground-Water’s Impor- 

tance. Need for Proper Development and Management of 

Ground Watt-b Resources. 

*L.ORIGiN, OCCllRRENCE AND MOVEMENT OF GROUND 

WATER 

THE HYDROLOGIC CYCLE 4 

SUBSURFACE DISTRIBUTION OF WATER 

Zone of Aeration. Zone of Saturation. 

GEOLOGIC FORMATIONS AS AQUIFERS 

Rock Classification. ‘Role nf Geologic Processes in 

Aquifer Formation. 

GROUND-WATER FLOW AND ELEMENTARY WELL HY- 

DRAULICS 10 

Types of Aquifers. A,quifer Functions. Factors Affecting 

Permeability. Flow Toward Wells. 

QUALITY OF GROUND WATER ;72 

Physical Quality. Microbiological Quality. Chemical Qual- 

ity. 

3. GROUND-WATEREXPLORATION 

EEOLOGIC DATA 

Geologic Maps. Geologic Cross-Sections. Aerial Photo- 

graphs. 

INYENTORY OF EXISTING WELLS 

SURFACE EVIDENCE 

iv 

. . . 

111 

4 

4 

7 

28 

28 

30 

31

4. WATER WELL DESIGN 

CASED SECTION 

BUTARE SECTlON 

Type and Construction of Screen. Screen Length, Size of 

Openings and Diameter. 

SELECTION OF CASING AND SCREEN MATERIALS 

Water Quality. Strer&h Requirements. Cost. Miscel- 

laneous. 

GRAVELPACKING AND FORMATION STABILIZATION 

Gravel Packing. Formation Stabilization. 

SANITARY PROTECTION 

Upper Terminal. Lower Terminal of the Casing. Grouting 

and Sealing Casing. 

5. -#ELL CONSTRUCTION 

WELL DRILLING METHODS 

Boring. Driving. Jetting. Hydraulic Percussion. Sludger. 

Hydraulic Rotary. Cable-Tool Percussion. 

INSTALLING WELL CASING 

GROUTING AND SEALING CASING 

WELL ALIGNMENT 

Conditions Affecting Well Alignment. Measurement of 

Well Alignment. 

INSTALLATION OF WELL SCXEENS 

Pull-back Method. Open Hole Methr?d. Wash-down Meth- 

od. Well Points. Artificially Gravel-Packed Wells. Re- 

covering Well Screens. 

FISHING OPERATIONS 

Preventive Measures. Preparations for Fishing. Common 

Fishing Jobs and Tools. 

6. WELL COMPLETION 

WELL DEVELOPMENT 

Me&an&l Surging. Backwashing. Development of Grav- 

el-Packed Wells. Dispersing Agents. 

WELL DISINFECTION 

V 

Pi;ge 

33 

34 

34 

47 

50 

52 

55 

55 

69 

70 

73 

75 

86 

96 

96 

104

S. PUMPING EQUIPMENT 114 

CONSTANT DISPLACE>lE?ZT PLhlPS I17 

Reciprocating Piston Pumps. Rotary Pumps. Helical 

Rotor Pumps. 

VARIABLE DISPl.A(‘EMENl- PUMPS 120 

C’en trlfugal Ptuqx. Jet Pumps. 

DEEP WELL PUMPS 11-l 

Lineshaft Pumps. Subrnersibk P!lrnps. 

PRIMING OF PUMPS I 10 

PUMP SELECTION 137 

SELECTION OF POWER SOLrRCE 11x 

Man Power. Wind. Electricity. Internal Combustion 

Engine. 

4. SANITARY PROTECTION OF GROUND-WATER SUPPLIES 134 

POLLUTION TRAVEL IN SOILS 

WELL LOCATiON 

SEALING ABANDONED WELLS 

REFERENCES 

CWEDI’i FOR ILLUSTRATIONS 

APPENDICES 

APPENDIX A. MEASUREMENT OF PERMEABILITY 

138 

139 

14(! 

APPENDIX B. USEFUL TABLES AND FORMULAS 111 

INDEX 151 

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 engaged in the construc- 

tion, 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 references to 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 rehabilita- 

tion 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 easier to 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 FACTORS 

hportance of Water Supplies 

Water is, with the exception of ai?, the most important single substance to 

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 processes are 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 diseases recognized to be 

water borne were cholera and typhoid fever. Later, dysentery, gastroenteritis 

and other diarrhea1 diseases were added to the list. More recently, water has 

also been shown to play an important role in the spread of certain viral 

diseases such as infectious hepatitis. 

Water is involved in the spread of conznunicable diseases in 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 diseases as yaws and 

typhus. Adequate supplies of water for personal hygiene also diminish the 

probability of transmitting some of the gastrointestinal diseases mentioned 

above. The latter type of interaction between water and the spread of 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 diseases associated with 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:lter on 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 because of economic tend other 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 seasonal fluctuations 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 sources of 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?.g less to develop. 

Greater emphasis should, therefore, be placed on the development and use of 

the very extensive ground-water sources to 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 degrees or not at all. Extraction of water from 

these latter reservoirs results in the continued depletion or mining of the 

water. 

Ground water aiso often seeps into 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 

uses to which they are normally put. 

Ground-water development presents special problems. The lack of solu- 

tions 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 ground- 

water 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. Research has, 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 emphasis being 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 determin- 

ing 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 condenses to form clouds which 

subsequently release their moisture as precipitation in the form of rain, hail. 

sleet, or snow. Precipitation may xcur over the oceans retuning 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 process known as 

transpiration, return it through their leaves to 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 spaces in the earth’s materials are completely fiiled or 

4

I 

-- 

---_- 

_ 

_ - -; _ - .-- 

. . 

t-%rcolarlon 

- - 

V Fresh ground water ~-1.w 

-- -. 

\ \I / / 

n 

- Sun - 

--- -.- - 

formotionr 

TJ .-- 

7 --- ..-_ IF --‘-- -- - -c-- - - 

__ __ - -: tmpermeable 

- -_._- z -- 

--- ___ - -z -.. 

- -- 

-- 

.- - - -. 

---_ --___ -a. - -~ - - ---- 

-- --- -~ 

Fig. 2.1 THE HYDROLOGIC CYCLE. 

-- 

1,.-1 nrnnn

Bsit of Soil Water 

tntermediate Belt 

Capillary Fringe 

Water. Table t 

-- - 

Ground Water 

Fig. 2.2 DIVISIONS OF SUBSUR- 

FACE WATER. 

. 

saturated with water. A mixture of 

air and water is to be found in the 

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 

and (3) the capillary fringe. 

The be/r of soil wafer lizs im- 

mediately below the surface and is 

that region from which plants ex- 

tract, by their roots, the moisture 

necessary for growth. The thickness 

of the belt differs greatly with the 

type of soil and vegetation, ranging 

from a few feet in grass-lands and 

field crop areas to several feet in 

forests and lands supporting deep- 

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 suspended by capil- 

iary forces similar to those which 

cause water to rise in a narrow or 

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 reaches it 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. 

5 

6

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~.,P sut!~ :ts granite. sandr’,>r-* e;\d limestone or 

rtrncomoiidated type (IL, .-:aterials) such as clay, sand Jnd gravel. The terms 

hml and soft are also usr,~: r.o describe 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 

categories cf 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 decom- 

position. 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 unconsoli- 

dated 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 forma- 

tions can also be expected. For example, the yield from wells in sand dunes 

7

and loess may be limited by both the fineness of the material and the limited 

areal extent and thickness of the deposits. 

Limestone, essentially calcium carbonate. and dolomite or calcium- 

magnesium 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 channels have developed. 

A 

Fig.2.3 A.FRACXJRESlNDENSELIMESTONETHROUGHWHICHFLOWMAY 

OCCUR. 

B. SOLUTION CHANNELS IN LIMESTONE CAUSED BY GROUND- 

WATERFLOWTHROUGHFRACTURES. 

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 

sandstones vary with the degree of cementation and fracturing. 

Shales and other similar compacted and cemented clays, such as mudstone 

or siltstone, are usually not considered to be aquifers but have been 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, because of 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 vesicles formed by the 

development of gas bubbles as the lava (magma flowing at or near the surface) 

cools. Basaltic aquifers may also contain water in crevices and broken up or 

brecciated tops and bottoms of successive layers. 

8 

B

Fragmental materials discharged by 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 gneiss from granite. Generally, these form poor aquifers with water 

obtained only from cracks and fractures. Marble, a metamorphosed lime- 

stone, 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 processes are 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 deepened and 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 sometimes buried 

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 streams produce the best glacial drift aquifers. 

Lake deposits are generally fine-textured, granular material deposited in 

quiet water. They vary considerably in thickness, extent, and shape and make 

good aquifers only when they are of substantial thickness. 

GROUND-WATER FLOW AND ELEMENTARY WELL HYDRAULICS 

Types of Aquifers 

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 pressure and 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 have been 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 because of 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 usage of the term artesian well 

referred only to the flowing type while current usage includes 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

Ground 

surfuce7 

Nonflowing 

artesian 

Woter- 

Fig. 2.4 TYPES OF AQUIFERS. 

Flowing 

. . 

artesian 

Recharge area 

at autc?opping 

of formation 

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 receive water underground from 

leakage through the confining layers and at intersections with other aquifers, 

the recharge areas of 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 areas of recharge to areas of 

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 as porosity 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 spaces is 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 represented by 

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:;~e of the 

aquifer material when allowed to drain freely by gravity (Fig. 7.5). TIK 

Static woter 

tese, - j’ 

Water drotned by 

growtty from 1.0 

cu ft of sand 

,f 

,,A!+-- 

. ’ ft 

,“ ., .~::.~~:.~~~:~: 

.‘.‘. _._.(. 1: 

‘C ..,.,., ::>:.:. 

Fig. 2.5 VISUAL REPRESENTATION 

OF SPECIFIC YIELD. ITS 

VALUE HERE IS 0.10 CU 

L’IXXCAFT OF AQUIFER 

. 

rennaining vulunte uf water not re- 

moved by gravity drainage is held by 

cupiktry forces sucl~ as found in 

the capillary fringe and by other 

forces of attraction. It is called 

the specific’reterttiott and. like 

the specific yield. may be ex- 

pressed as a decimal fraction or 

percentage. As defined, porosity is 

therefore equal to the sum of the 

specific yield and the specific reten- 

tion. 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~ 

of which 100,000 cubic feet would 

be yielded by gravity drainage. 

Conduit jim.ticm: The property 

of an aquifer related to its conduit 

function is known as the perttw- 

ubility. 

PL-meability is a measure of the 

capacity of an aquifer to transmit 

water. It is related to the pressure 

difference and velocity of flow be- 

tween 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). 

where V 

h, 

hz 

P 

P 

is the velocity of flow in feet per day, 

(2. I) 

is the pressure at the point of entrance to the section of 

conduit unlder consideration in feet of water, 

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

of water, 

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

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 

h1 - hz 

. where I = -, P 

c 

Slope equals hydmulic 

. . 

. . 

gradient 

.---. 

-7, 

‘. 

Direction of flow 

from I to 2 

v = PI 

and is called the hydraulic gradient. 

- 

‘.. ,, ,:. 

,, _, . . ,. ..,‘, ‘. 

:: 

. 

;. . ...,.,. “. 

,...;..~ :.-. . _ ‘.‘..‘...‘. ,: ‘:. . ) .;. ., ::: 

Fig 2.6 SECTiON THROUGH 

WATER-BEARING SAND 

SHOWING THE PRESSURE 

DIFFERENCE thl- hd 

CAUSING FLOW BETWEEN 

POINTS 1 AND 2. THE HY- 

DRAULIC GRADIEhTIS 

EQUAL TO TME PRESSURE 

DIFFERENCE DIVIDED BY 

THE DISTANCE, i!, BE- 

TWEEN THE POINTS. 

(2.2) 

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, 

Q=AV=PIA (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 co- 

efficient of perrneubility may, 

therefore, be defined as the quan- 

tity of hater that will flow through 

a unit cross-sectional area of porous 

material in unit time under a hy- 

draulic gradient of unity (or I = 1 .O) 

at a specified temperature, usually 

taken as 60°F. In ground-water 

problems, Q is usually expressed in 

gallons per day (gpd), A in square 

feet (sq ft) and P, therefore, in 

gallons per day per square foot 

(gpd/sq ft). The coefficient of per- 

meability 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-sectional area. 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 average coefficient of 

13

permeability, P, we see from equation (2.3) that the rate of flow, q, through 

this cross section is given by 

q=PmI (2.4) 

The product Pm of equation (2.4) is termed the coejficient of transntissi- 

bility 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-section of 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-section of an aquifer of unit width and whose height 

is the total thickness of the aquifer when the hydraulic gradient is unity. It is 

expressed in 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 forma- 

t 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 spheres were all of tennis ball size 

or all l/l000 inch in diameter. However, the smaller pores between the latter 

spheres would offer greater resistance to flow and, therefore, cause a decrease 

Fii. 2.7 UNIFORMLY SIZED 

SPHERES PACKED IN 

RHOMBOHEDRAL ARRAY. 

14 

Fig. 2.8 UNIFORMLY SIZED 

SPHERES PACKED IN CU- 

BICAL ARRAY.

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 spheres may also assume a 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 mix- 

ture. 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 

OF SAND AND GRAVEL in the material are interconnected, 

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 caused by 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 separates two 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 same as 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 ap y’ ied (Fig. 2.10). This means that the area 

across which t&e flow takes r also becomes successively smaller as the 

R, -2R, A, = 2A2 

v, ‘2V, 

Fig. 2.10 F L 0 W CONVERGES TO- 

WARD A WELL, PASSING 

THROUGH IMAGINARY 

CYLINDRKAL SURFACES 

THAT ARE SUCCESSIVELY 

SMALLER AS THE WELL IS 

APPROACHED. 

well is approached. With the same 

quantity of water flowing across 

these sections, it follows from equa- 

tion (2.3) that the velocity in- 

creases as the area becomes smaller. 

Darcy’s Law, equation (2.2), 

tells us that the hydraulic gradient 

varies in direct proportion to the 

velocity. The increasing velocity to- 

wards the well is, therefore, ac- 

companied by an increasing hy- 

draulic gradient. Stated in other 

terms, the water surface or the 

piezometric surface develops an in- 

creasingly steeper slope toward the 

well. In an aquifer of uniform shape 

and texture, the depression of the 

water table or piezonetric surface 

in the vicinity of a pumped or 

freely flowing well takes the form 

of an inverted cone. This cone, 

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 levels between the static 

water level and the surface of the cone of depression is known as the 

drawdown. Drawdown, therefore, increases from 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 shape of 

the cone of depression. The cone is deep, with steep sides, a large drawdown, 

16

-- Rodlus of Influence --+ 

Static water level 

_------ -- 

.-- 

T 

Drowdown 

in we8 

C--Well Screen 

Fig. 2.11 CONE OF DEPRESSION IN 

VICINITY OF PUMPED 

WELL. 

FRadius =IS,OCO ft-- 

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 in- 

creasing demand for water from the 

aquifer storage. The radius of in- 

fluence 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 

Transmissibility - IO.OCO gpd/ft 

Radius = 40,000 ft 

Transmissibi!ity - IOO.000 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 depression decreases with time. This 

is illustrated in Fig. 2.13 where C1 , C2 and C3 represent cones of 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. 

Fig. 2.13 CHANGES IN RADIUS AND 

DEWTH OF CONE OF DE- 

PRESSION AFTER EQUAL 

INTERVALS OF TIME, AS- 

~I$W&ONShUUT PUMP- 

. 

1. The cone enlarges until it in- 

tercepts 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 pump- 

ing rate. 

3. Recharge equal to the pump- 

ing rate is received from pre- 

cipitation and vertical infiltra- 

tion within the radius of in- 

fluence. 

4. Recharge equal to the pump- 

ing rate is obtained by leak- 

age through adjacent forma- 

tions. 

Where the recharge rate is the same from 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 

depressed in the direction of an imperrnea&le boundary intercepted by it (Fig. 

2.15). No recharge is obtained from such a boundary while that received from 

other directions maintains the higher levels in those directions. Recharge areas 

to aquifers, such as surface streams are, therefore, often referred to as positive 

boundaries while impermeable areas are 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

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 

Static water level I -_ a well affected by interference is 

greater fllA11 llit 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 

Fig. 2.16 INTERFERENCE BETWEEN subject to interference. 

ADJACENT WELLS TAi’- 

PING THE SAME AQUIFER. Ideally, the solution would be to 

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 reasons and the wells are spaced far enough apart. not 

to eliminate interference. but to reduce it to acceptable proportions. For 

wells use3 for water supply purposes, spacings of 115 to 50 feet between wells 

have bee11 found 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 screen lengths in excess of IO feet. 

There arc many patterns which may be used when grouping weils (Fig. 

2.17). Where the aquifer extends considerable distances in 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 recharge to 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

Fig. 2.17 LAI’OUT PATTERNS FOR MULTIPLE WELL SYSTEMS USED AS WATER 

SUPPLY SOURCES. CENTRALLY LOCATED PUhlP EQUAL.iZES SUCTION 

LIFT. 

I 

Well-point System 

Saturated sand A 

Sub-soil 

Water level 

while pumping 

Fig. 2.18 WELL-POINT DEWATERING SYSTEM. 

‘I 

ID) 

\ ‘\ \

Multiple well or well-point systems are also used OJI engineering construo- 

tion 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 process may 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 suspended matter 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 advantages of’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 sewage and 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 sands that 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 lessons of Nebraska City can be put 

to beneficiai use in many other areas of 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 am

10 ppm of iron means that in every million pounds (or kilograms) c,i‘ the 

water examined there will be found 10 pounds (or kilograms) of iron. 

Another very common form of expression is that of milligrams per liter (mg/l 

or mg per 1) which is the number of milligrams of the mineral found in one 

liter of water. This latter unit differs so little from the former that ihey are, 

for all practical purposes, considered equal and are ~on~n~only used 

interchangeably. 

The following are among the more important chemical substances and 

properties of ground waters which are of interest to the owners of small 

wells: iron, manganese, chloride, fluoride, nitrate, sulfate, hardness. total 

dissolved solids, pH, and dissolved gases such as oxygen, hydrogen sulfide, 

and carbon dioxide. 

Zrorz and nlarzgarlese are usually considered together because of their 

resemblances in chemical behavior and occurrence in ground water. It is 

important to note that iron and manganese, in the quantities usually found in 

ground water, are objectionable because of their nuisance values rather than 

as a threat to man’s health. They both cause staining (reddish brown in the 

case of iron and black in the case of manganese) of plumbing fixtures and 

clothes during laundering. Iron deposits may accumulate in well screens and 

pipes, restricting the flow oi water through them. Iron-containing waters also 

have a characteristic taste which some people find unpleasant. Such waters, 

when first drawn from a tap or pump, may be clear and colorless, but upon 

allowing the water to stand, the iron settles out of solution giving a cloudy 

appearance to the water and later accumulating in the bottom as a 

rust-colored deposit. 

Chlorides occur in very high concentrations in sea water, usually of the 

order of 20,000 mg/l. Rainwater, however, contains much less than I mg/l of 

chloride. Aquifers containing large chioride concentrations are usually coastal 

ones directly connected to the sea or which were so connected some time in 

the past. Excessive pumping of wells in aquifers directly connected to the sea 

or to brackish-water rivers will cause these high chloride-containing waters to 

move into the otherwise fresh water zones of the aquifers. Expert technical 

advice should be sought on the possibility of such an occurrence. 

Water with a high chloride content usually has an unpleasant taste and 

may be objectionable for some agricultural purposes. The level at which the 

taste is noticeable varies from person to person but is generally of the order 

of 350 mg/l. A great deal depends, however, on the extent to which people 

have been accustomed to using such waters. Animals usuaily can drink water 

with much more chloride than humans can tolerate. Cattle have, reportedly, 

been known to consume water with a chloride content ranging from 3000 

mg/l to 4000 mg/l. 

FZunride concentrations in ground water are usually small and mainly 

derived from the leaching of igneous rocks. Notable among the few cases of 

high concentrations is the reported 32 mg/l from a flowing well near San 

Simon, Arizona, U.S.A. High concentrations have also been reported in some 

parts of India, Pakistan and Africa. 

24

dissolved solids content would therefore be expected to present rhe taste, 

laxative and other problems associated with the individual minerals. Such 

waters are usually corrosive to well screens and other parts of the well 

structure. 

pH is a measure of the hydrogen ion ccncentration in water and indicates 

whether the water is acid or alkaline. It ranges in value from 0 to 14 with a 

value of 7 indicating a neutral water, values between 7 and 0 increasingly acid 

and between 7 and 14 increasingly alkaline waters. Most ground waters in the 

United States have pH values ranging fr0.m about 5.5 to 8. Determination of 

the pH value is important in the control of corrosion and many processes in 

water treatment. 

The dissolved ox-vgen content of ground wsters is usually low particularly 

in waters found at great depths. Oxygen speeds up the corrosive attack of 

water upon iron, steel, galvanized iron, and brass. The corrosive process is aLc, 

more rapid when the pH is low. 

Hydrogen sulfide is recognizable by its characteristic odor of rotten eggs. 

It is very often found in ground waters which also contain iron. In addition to 

the odor, which is noticeable at as low a concentration as 0.5 mg/l, hydrogen 

;r sulfide combines with oxygen to produce a corrosive condition in wells and 

also combines with iron to form a scale deposit of iron sulfide in pipes. Most 

of the hydrogen sulfide can be removed from ground water by spraying it 

into the air or allowing it to cascade in thin layers over a series of trays. 

Carbon dioxide enters water in appreciable quantities as the water 

percolates through soil in which plants are growing. Dissolved in water, it 

forms carbonic acid which, together with the carbonates and bicarbonates, 

controls the pH value of most ground waters. A reduction of pressure, such as 

caused by the pumping of a well, results in the escape of carbon dioxide and 

an increase in the pH value of the water. Testing of ground-water samples for 

carbon dioxide content and pH, therefore, requires the use of special 

techniques and should be done at the well site. The escape of carbon dioxide 

from a water may also he accompanied by the settling out of calcium 

carbonate deposits. 

While the above list includes those chemical substances that are likely to 

be of greatest general concern to owners of small wells, it is by no means an 

exhaustive one nor intended to be such. Conditions peculiar to specific areas 

may require analyses of ground waters for other substances. The group of 

elements often referred to as the trace elements because of the very low 

concentrations in which they are usually found in water are here worth 

mentioning. Among these are arsenic, barium, cadmium, chromium, lead and 

selenium, all of which are considered toxic to man at very low levels of intake 

(the order of a fraction of 1 mg/l). Since the rate of passage of some of these 

elements through the body is very slow, the effects of repeated doses are 

additive and chronic poisoning occurs. 

Trace elements generally are not present in objectionable concentrations in 

ground waters but may be so in a few specific areas. It has been reported for 

example, that arsenic has been found in sufficiently high concentrations in 

26

ground waters in some parts of Argentina and Mexico to be considered 

injurious to health. Problems are most likely to arise in areas where waste 

discharges from industries, such as electro-plating, and overland runoff 

containing high concentrations of pesticides (insecticides and herbicides) 

enter aquifers. 

‘The presence of these trace elements in drinking water are generally not 

detectable by taste or smell or physical appearance of the water. Proper 

chemical analyses are required for their detection. Health departments, 

laboratories, geological survey departments, and other competent agencies 

should be consulted in areas where waste disposal is likely to increase the 

natural content of these elements in ground water or where the natural levels 

are likely to be high because of the local geology. 

27

Water can be found almost anywhere under the earth’s surface. There is, 

however, much more to ground-water exploration than the mere location of 

subsurface water. The water must be in large quantities, capable of sustained 

flow to wells over long periods 7-t reasonable rates, and of good quality. To be 

reliable, ground-water explorat!on must combine scientific knowledge with 

experience and common sense. It cannot be achieved by the mere waving of a 

magic forked stick as may be claimed by those who practrce what is variously 

referred to as water witching, water dowsing, or water divining. 

Finding the right location for a well that produces a good, steady water 

supply all the year round is usually the job of scientists trained in hydrology. 

These scientists are called hydrologists. Their help may be sought from 

geological survey departments, governmental and private engineering organi- 

zations. and universities if and when available. These experts should always be 

consulted for large scale ground-water development schemes because of the 

great capital expenditures usually involved. However, it should be apparent 

from the remaining sections of this chapter that a sufficient number of the 

tools of the hydrologist is based upon. the application of common sense, 

intelligence and good judgement to permit their reasonably successful use by 

the average individual interested in the location of small wells. The 

interpretation of geologic data may present problems though, with some help, 

these need not be totally insurmountable to some of our readers. The use of 

well inventories and surface evidence of ground water location should be 

much less difficult and find greater general application. 

The following sections describe the simpler tools of the hydrologist and his 

use of them. The more sophisticated methods of exploration involving the use 

of geophysics are considered beyond the scope of this manual and, therefore, 

have been excluded. It is sufficient to note that they are available to the 

hydrologist to provide him with additional information on which to base his 

selection. 

GEOLOGIC DATA 

Before visiting the area to be investigated, the hydrologist seeks out and 

studies all available geologic data relating to it. These would include geologic 

maps, cross-sections and aerial photographs.

Geologic Maps 

Geologic maps, of which Fig. 3.1 is an example, show where the different 

rock formations, consolidated or unconsolidated, come to the land surface or 

outcrop, their strike or the direction in which they lie, and their dip or the 

angle at which they are inclined to the horizontal. Other useful information 

Legend 

Alluvwm, Includes 

unconsolidated sand, 

grovel, slit and cloy 

Char formotlon 

hmestone 

j-q 

Looml;bremotwx 

I 

Sontos formotlon 

shale 

I 

Osoge hmest0ne 

I 

hternom sandstone 

Strike and Dip 

. 

Test hole 

Fig. 3.1 EXAMPLE OF A GEOLOGIC MAP SHOWING TEST HOLE LOCATIONS. 

shown would include the location of faults and contour lines indicating depth 

to bedrock throughout the area. Faults are lines of fracture about which the 

rock formations are relatively dislocated. They are the result of forces acting 

in the earth to cause lateral thrust, slippage or uplift. The hydrologist can 

determine the location and area1 extent of aquifers from the type and 

location of rock outcrops and the location of faults. Faults are also likely 

sites for the occurrence of springs. The width of the outcrop and angle of dip 

indicate to him the approximate thickness of an aquifer and the depths to 

which it can be found. The combination of strike and dip tell him in which 

direction he should locate a well to obtain the maximum thickness of the 

aquifer. The surface outcrops also indicate the possible areas of recharge to an 

aquifer and, by deduction, the direction of flow in the aquifer. The bedrock 

contours indicate the maximum depth to which d well should be drilled in 

search of water. 

Geologic Cross-Sections 

Geologic cross-sections provide some of the main clues to the ground- 

water conditions of a locality. They indicate the character, thickness, and 

succession of underlying formations and, therefore, the depths and thick- 

nesses of existing aquifers. The main sources of information for the 

preparation of these sections are well records and natural exposures where the 

rock faces have not been greatly altered by weathering. Examples of the latter

may be seen in some river valleys and gorges. These sections may also indicate 

whether water-table or artesian conditions exist in an aquifer. The cross- 

sections of Fig. 3.2, drawn from the geologic map of Fig. 3.1, illustrate many 

of the important features mentioned above. 

Fig. 3.2 GEOLOGIC CROSSSECTIONS FROM THE MAP OF FIG. 3.1. 

Water surface 

Aerial Photographs 

Aerial photographs, skillfully interpreted, provide valuable information on 

terrain characteristics which have considerable bearing on the occurrences of 

ground water. Features which indicate subsurface conditions such as 

vegetation, land form and use, erosion, drainage patterns, terraces, alluvial 

plains, and gravel pits are apparent on aerial photographs. The skillful 

interpreter of aerial photographs can determine the most promising areas for 

ground-water development. 

INVENTORY OF EXISTING WELLS 

The hydrologist next makes a study of all available information on existing 

wells. 

Well logs which are records of information pertaining to the drilling and 

construction of wells would be the main sources of information. From these 

logs he may obtain such information as the location and depth of the well; 

30

depth. thickness. and description of rock fornrarions penetrated: water level 

variations as successive strata are penetrated; yields from water-bearing 

formations penetrated and the corresponding drawdowns; the form of well 

construction; and the vield and drawdown of the well upon completion. 

Many drilling orgsnizaiions also keep samples of rocks from the various 

formations penetrated. Associated with the well log should be a record of the 

water quality (physical and chemical characteristics) of water-bearing strata 

encountered. Of further interest to the hydrologist would be records of any 

tests making use of the well or materials from the well to determine the 

hydraulic characteristics such as permeability and transmissibility of the 

aquifer. To compiete the picture. he would be interested in records of the 

v&ations in yield and water quality and a history of any problems associated 

with the well since its completion. The hydrologist may wish to have new 

checks made on some aspecrs of ihese records sush as rhe water quality and 

yield. 

A!1 these records may not be available from any single source. In addition 

to the various agencies already mentioned. the hydrologist may have to 

consult well owners and drilling organizations. 

With records from a sufficient number of wells, the hydrologist would now 

be in 3 position to make a contour map of the water-table or upper surface of 

the zone of saturation. To do this. he uses the measured depths from Iihnd 

surface to the water table at wells and the height of the land surf’ace relative 

to sea level which he obtains front topographic maps or a site survey. He then 

connects ail points of equa! elevation of the water table on a map. This 

contour map shows the shape of the water surface. It is a very important map 

in tltat it shows not only the depth below which ground water is stored but 

also, from the slope of the water table, the direction in which the water 

moves. 

SURFACE EVIDENCE 

The hydrologist is now ready to visit the area and take a closer look at any 

surface evidence of ground-water occurrence. He will exantine in greater 

detail the important superficial features hc had noted on the topographic 

maps and aerial photographs. Among the features that would provide valuable 

clues would be land forms, stream patterns. springs, lakes, and vegetation. 

Ground water is likely to occur in larger quantities under valleys than 

under hills. Valley fills containing rock waste washed down from mountain 

sides are often found to be very productive aquifers. The material may have 

been deposited by streams or sheet floods with some of the finer material 

getting into lakes to form stratified lake beds. Some of these deposits may 

afso be found to have been transported by wind and redeposited as sand 

dunes. All these and other factors intluence the rate at which the valley fill 

will yield water. Coastal terraces, formed by the sinking and raising of coastal 

areas relative to sea level in the geologic past. and coastal and river plains are 

other land forms that wouid indicaie the presence of good aquifers. 

Any evidence of surface water such as streams. springs. seeps, swamps, or 

lakes is a good indication of the presence of some ground water, though not 

31

necessarily in usable quantity. The sand and gravel deposits found in river 

beds may very often ext .end laterally into the river bdanks which may be 

penetrated by shallow. highly product&e wells. 

Vegetation, particularly water-loving types when found in arid regions, 

provides good clues to shallow ground-water occurrence. Evidence of 

unusually thick overgrowth is generally a sure pointer to the presence of 

streams and other surface waters, the vicinities of which would be likely sites 

for ground-water investigations. Fig. 3.3 demonstrates the application of 

some of the principles outlined above in the selection of possible well sites. 

Fig. 3.3 SURFACE EVIDENCE OF GROUND-WATER OCCURRENCE. (Adapted 

from Fig. 4, Wafer Supply For Rural Areas And Small Communities. WHO 

Monograph Series No. 4.., 1959.) 

I - Dense vegetation indicating possible shallow water table and proximity 

to surface stream. 

2 - River plains: possible sites for wells in water-table aquifer. 

3 - Flowing spring where ground water outcrops. Springs may also be 

found at the foot of hills and river banks. 

4 - River beds cut into water-bearing sand formation. Indicate possibility 

of river banks as good well sites. 

In many areas, some of the records, maps, and other relevant information 

so far discussed will not be available to the hydrologist. Where the size of the 

project warrants it, he will arrange to fill in the information as far as is 

practicabie. in other situations, very likely the case for the size of weiis herein 

considered, he will simply use his best judgement based on the readily 

available information. 

32

CHAPTER 4 

Generally, the aim of engineering design is to achieve the best possible 

combination of performance, useful life and reasonable cost. The designer of 

small wells will often find that his optimum solutions involve a variety of 

compromises and that he must adopt a flexible approach to each problem. 

Among these compromises is the need to sacrifice performance or efficiency 

in order to reduce costs. For example, in the situation where a small yield is 

required from a very thick and permeable aquifer, a less efficient type of 

intake section such as slotted pipe may justifiably be used in a small well to 

save the extra cost of a more efficient factory-manufactured screen. Here, the 

limited yield relative to the highly productive nature of the aquifer makes 

cost and availability of funds assume a more important role than hydraulic 

efficiency. It may also be considered worthwhile to compromise the useful 

life of a small well with respect to its cost. With stainless steel and other 

non-corrosive materials costing two to three times as much as ordinary steel, a 

designer may use well casing of the latter mat,,rial under corrosive conditions, 

fully expecting to replace it, perhaps in one-half the time he would have had 

he used stainless steel. He may very well have based his decision on the fact 

that at the end of the shorter useful life, extra funds might be available for a 

replacement of the existing well. 

For design purposes, a well to be constructed in unconsolidated materials 

may be considered as consisting of two main parts. The upper part or cased 

section of the well serves as housing for the pumping equipment and as a 

vertical conduit through which water flows from the aquifer to the pump or 

to the discharge pipe of a flowing artesian well. It is usually of water-tight 

construction and extends downward from the surface to the impervious 

formation immediately above an artesian aquifer or to a safe depth below the 

anticipated pumping water level (see the later section of this chapter dealing 

with sanitary protection of wells). It is also referred IO as the well casing. 

The lower or intake section of the well is that part of the well st-ucture 

where water from the aquifer enters the well. The intake section may be 

simply the open lower end of the well casing, though this would be a most 

unsatisfactory arrangement in unconsolidated formations. The disadvantages 

are the large well diameters required for the natural seepage of water into the 

well and the tendency for aquifer material to heave into the well casing 

as the well is being pumped. A screening devze known as a well screen 

should be used instead. Such a screen permits the use of techniques aimed at 

increasing the natural seepage rate into the we!! (see later section on well 

33

development), thus making a much smaller well practicable. In addition to 

ensuring the relatively free entry of water into the well at low velocity, the 

screen must provide structural support against the collapse of the unconsoli- 

dated formation material and prevent the entry of this material with water 

into the well. 

CASED SECTION 

The selection of the well casing dimerer is usually controlled by the type 

and size of the pump that is expected to be required for the desired of 

potential yield of the well. The well casing must be large enough to 

accommodate the pump with s)lfficient clearance for easy installation and 

efficient opera?ion. For larger wells, such as those used for municipal and 

industrial suppiies, the casing diameter should be chosen as two nominal sizes 

(never :ess than one nominal size) larger than that of the pump bowls. For 

wells of 4 inches and less in diameter it is satisfactory to select a casing 

diameter which is one nominal size larger than that of the pump bowls, pump 

cylinder or pump body. The above assumes the use of a deep-well type of 

pump which is usually suspended by pipe column and/or shaft within the well 

casing. A pump having a bowl diameter (see Fig. 8.11) greater than 3 inches 

should not, according to this rule, be installed in a $-inch diameter casing. 

In small wells where pumping water levels below ground surface are known 

to be within the practical suction limits (15 feet or less) of most surface-type 

pumps, such pumps are either directly connected to the top of the well casing 

or connected to a suction pipe suspended inside the well casing. The well 

casing diameter may then be selected in relation to the diameter of the 

suction or inlet of the pump, bearing in mind that it is not good practice to 

restrict the suction capacity of the pump by using pipe of a smaller diameter 

than that of the suction side of the pump. 

In larger and deeper wells than those being considered, it is sometimes 

advantageous for economic and other reasons to reduce the casing diameter at 

levels below the lowest anticipated pumping depth. This is done by 

telescoping one or more smaller sized casing sections through the uppermost 

one. This saves the extra cost of extending the large diameter casing all the 

way down to the aquifer when a smaller size of pipe would be sufficient to 

accommodate the anticipated flow with reasonable head loss. However, there 

is little justification for this type of design in wells of 4 inches and less in 

diameter and not more than 100 feet deep. 

INTAKE SECTION 

Type and Construction of Screen 

The single factor with greatest influence on the efficient performance of a 

well is the design and construction of the well screen. A properly designed 

screen combines a high percentage of open area for relatively unobstructed 

flow into the well with sufficient strength to resist the forces to which the 

screen may be subjected both during and after installation in the well. The 

screen openings should preferably be shaped so as to facilitate flow into the 

well while making it difficult for small particles to become permanently 

34

lodged in them and thus restrict flow. A discussion of various types of WPII 

screens and their uses is presented in the following paragraphs. 

The corrtimmts-slot type of well screen shown in Fig. 4. I is made with 

cold-drawn wire, appro,ximately triangular in section, wound spirally around a 

circular array oflongitcldinal rods. The wire is welded to the rods at all points 

Fig.4.1 FABRICATION OF A CONTINUOUS-SLOT TYPE OF WELL SCREEN. 

at which they cross. The resulting cylindrical well screen becomes a one-peice. 

rigid unit. 

The stronger the material used in construction, the smaller would be the 

dimensions of the wire rods and hence the greater the ratio of open area to 

solid area of the screen surface. These screens are being made of metals such 

as galvanized iron, steel, stainless steel and various types of brass. Experi- 

.ments are also in progress with the use of plastic materials. 

The percentage of open area is the factor exerting the greatest influence on 

the efficiency of a screen. As will be shown later, the size of the well screen 

opening is determined from the size of the particles of the material 

composing the aquifer. With this size fixed, the aim of screen design is to 

obtain the maximum possible total open area in a given length of screen, The 

greater the total open area, the lesser is the resistance to flow into the well. 

The entrance velocity through the larger intake area is also lower and so is the 

resulting head loss for flow through the screen. Hence we have a more 

efficient well screen. The greater the percentage of open area in a screen, the 

greater is the total open area in a given length of screen. 

Looking at it in another way, the greater the percentage open area of a 

screen, the shorter is the length of screen required for a given rate of flow at a 

given velocity. This means that a saving in construction costs can be made 

throtigh the use of a shorter length of screen. The continuous-slot type of 

screen provides more intake area per square foot of screen surface or per unit 

length of screen than any other known type and, therefore, can result in 

savings when used.

Along with maximum open area in a well screen, the design must also be 

such that the openings do not become clogged by smd particles after the 

screen is placed in the aquifer. This is achieved by the use of V-shaped 

openings formed by the triangular shaped wire as shown in Fig. 4.2. III Fig. 

4.3 is shown a sand grain entering and passing through a V-shaped opening, 

never clogging it, while remaining in other known types of openings to clog 

them. This property of the V-shaped opening is of special importance when 

developing the well. as the developing process is based on passing the smaller 

sizes of sand particles through the screen and removing them from the well. 

This process, a necessary one for the completion 

in this chapter. 

of the well, is described later 

Fig. 4.2 SECTtON OF CONTLNSIOL6- 

SLOT TYPE SCREEN SHOW- 

ING V-SHAPED OPENINGS. 

Another notable feature of the 

continuous-slot type of screen is 

the fact that the slot openings can 

be easily varied in size even bvithin 

the same section of screen if the 

geologic conditions so require. This 

is done simply by altering the set 

spacing at which the adjacent wires 

are wrapped. Thus a single section 

of screen can be made with one or 

more different sizes of siot open- 

ings. The width oi‘ slot openings can 

also be held to close tolerances. 

Continuous-slot well screens are 

made with practically any width of 

(opening 0.006 inch and larger. The 

slot openings are designated by 

II umbers corresponding to the 

width of the opening in thou- 

sandths of 911 inch. Thus a screen 

with a No. IO slot has openings 0.0 IO inch wide. 

I,oI~I~= or sl2uttcr-type well screens have rows of openings in the form of 

shutter!; (Fig. 4.4). Manut’ucturers can and do arrange the optnings either at 

right arlgles or parallel to the axis ot’ the scrw1. ‘The openings arc produced in 

the wal,l of a welded tube by ;I stamping operation using a die. The range of 

sizes of openings is limited by the sizes of the set of dies used by each 

manufacturer. An unlimited range of die sizes would not be practical. This is 

one deficiency of this type of screen by comparison with the continuous-slot. 

Another important deficiency is the much lower percentage of open area in 

shutter-type screens. This is so because sizeable blank spaces must be left 

between adjacent openings if the metal is not to be torn In the stamping 

process. 

Yet another shortcoming of the shutter-type screen is the tendency of the 

openings to become blocked during the development of wells (Fig. 4.3) where 

the aquifer material contains an appreciable proportion of sand. This type of 

screen is. therefore, best used in artif‘ic;tlly gravel-packed wells. ;I description 

of which is presented later iI1 this &pter.

Fig. 4.3 THE Y-SHAPED OPENINGS 

OFTHECONTINUOUSSLOT 

TYPE OF SCREEN (RIGHT) 

ALLOWS SAN D GRAINS 

BARELY SMALLER THAN 

THE WIDTH OF THE OPEN- 

INGS TO PASS FREELY 

WITHOUT CLOGGING. 

OPENINGS WITHOUT THE 

TAPER TEND TO HOLD 

PARTICLES JUST SMALL 

ENOUGH TO ENTER THEM. 

- 

The pipe-base well screen is 

another type of screen in use. It 

consists of a jacket around a perfo- 

rated metal pipe. The jacket may be 

in the form of a trapezoidal-shaped 

wire wound directly onto and 

around the pipe (called a wrapped- 

on-pipe screen). Alternatively the 

wire may be wound over a series of 

longitudinal rods spaced at fixed 

intervals around the circumference 

of the pipe. The latter is a more 

efficient type of screen as the rods 

hold the wire away from the pipe 

surface to reduce the blocking of 

the screen openings. A stronger 

screen can be obtained by using a 

slip-on jacket made of an integral 

unit of welded well screen. 

The perforations or holes in the 

pipe and the spaces between adja- 

cent turns of the wrapping wire form two sets of openings in this type of 

screen. Usuahy the total open area of the holes in the pipe is less than that 

between the wrapping wire. It is, therefore, the holes in the pipe that control 

the performance of the screen. Tire percentage open area in the pipe is usually 

low and hence this type of screen is relatively inefficient. 

Very often this type of construction is used in order to avoid making a 

screen entirely of the costly noncorrosive alloys such as stainless steel, 

bronze or brass. Such alloys are then used only in the jacket while the pipe is 

of steel. A screen so constructed with two or more metals would be subject to 

failure from galvanic corrosion. Construction of the screen entirely of one of 

the noncorrosive alloys, while being more costly, will solve this problem and 

result in a more durable screen. 

Drive points or well points, as they are commonly known, are short 

lengths of well screen which are attached to successive lengths of pipe and 

driven by repeated blows to the desired position in an aquifer or in a 

formation to be dewatered. A forged steel point is usually attached to the 

lower end to facilitate penetration into the ground. 

Well points are made in a variety of types and sizes. Most commonly, they 

are designed for direct attachment to either l%inch or ‘L-inch pipe. They can 

be made of the continuous-slot type of well screen (Fig. 4.9, thus benefitting 

from all the desirable features of that type of screen. Such screens will 

withstand hard driving, but care should be taken to avoid twisting them while 

driving. 

A common type of well point is the brass jacket type. It consists of a 

perforated pipe covered with bronze wire mesh which is, in turn, covered 

with a perforated brass sheet to protect it from damage. The pointed lower 

37

Fig.4.4 LOUVER- OR SHUTTER- 

TYPE WELL SCREEN, BEST 

USED IN ARTIFIClALLY 

GRAVEL-PACKED WELLS. 

(From Layne and Bowler, inc., 

Memphis, Tennessee.) 

end, made of forged steel, carries a 

wider shoulder to protect the 

screen from damage by gravel or 

stones while being driven. The lim- 

itations of pipe-base screens also 

apply to this type of well point. 

Another type of well-point con- 

struction is the brass tube type 

consisting of a slotted brass tube 

slipped over perforated pipe. It has 

an advantage over the wire-mesh 

jacket type in that it is not as easily 

ripped or damaged. 

The sizes of openings for the 

continuous-slot type of well points 

are designated as described for the 

continuous-slot well screens. Mesh- 

covered well point openings are 

designated by the mesh size in 

terms of the number of openings 

per linear inch. The common sizes 

are 40,50,60,70 ;rnd 80 mesh. 

Slotted pipe is sometimes used 

as a substitute for well screens 

particularly in the smaller sized 

wells under consideration in this 

manual. The openings or slots in 

the pipe are usually cut with a 

sharp saw, electrically operated if 

possible, to maintain accuracy and 

regularity in size. Several other 

methods have been used, however, 

such as cutting with an oxyacetylene torch and punching with a chisel and die 

or casing perforator. 

The method of construction immediately suggests a number of important 

limitations to the use of slotted pipe as well screens. These are: (1) structural 

strength requires wide spacing of slots, resulting in a low percentage of open 

area; (2) openings may be inaccurate, varying in size throughout the length of 

each slot; (3) openings narrow enough to control fine sands are difficult, if 

not impossible, to produce; (4) the lack of continuity of the openings reduces 

the efficiency of the process of well development; and (S) the slotting and 

perforation of steel pipe makes it more readily subject to corrosion, particu- 

larly at the jagged edges and surfaces. 

Slotted plastic pipe has been finding increasing use in small diameter wells 

in recent years. Its light weight and ease of handling make it suitable for use 

in remote areas not easily reached by motor driven vehicles. It is 

noncorrosive and less costly than steel pipe in sizes 4 inches in diameter and 

38

Fig. 45 CONTBNUOUSSLOT T Y P E 

OF WELL POINT AND EX- 

TENSION SECTION. 

smaller. In addition, the slots can 

be easily made on location with a 

sharp saw within reasonable limits 

of accuracy. Slots cut spirally 

around the circumference of the 

pipe in the manner shown in Fig. 

4.6 will result in less weakening of 

the pipe and closer spacing of the 

slots than if they were made at 

right angles to the axis. Conse- 

quently, the percentage of open 

area is greater. Slots made at right 

angles to the a-xis of plastic pipe are 

subject to tearing at both ends if 

the slotted pipe is bent when han- 

dling it during installation, This 

tendency is reduced by the use of 

the spiral design. 

The most convenient type of 

joint for use with small diameter 

plastic pipe in well construct ion is 

the spigotted joint. For these joints, 

the manufacturers supply a quick- 

setting cement which provides more 

than adequate and lasting strength. 

The slotted plastic-pipe screen can 

be lowered into a previously drilled 

hole on the end of casing of the 

same material. Steel clamps are 

used to suspend the string of pipes 

while adding new lengths. It may 

also be washed, open ended, with d jet of water into a previously drilled 

hole. Suitable drilling mud should be used during rotary drilling op- 

erations to prevent the open hole from collapsing while the string of 

plastic pipe is being placed in position. Cart should be taken to wash the 

hole clear of all cuttings before placing the pipe. Plastic pipe generally requires 

the use of greater care during handling and installation operations than do 

metal pipes. 

It cannot be contended that slotted plastic pipe will be as efficient a well 

screen as the continuous-slot type. However, when only small quantities of 

water are required from relatively thick (20 feet and greater) sand and gravel 

or gravel aquifers, efficiency loses some of its importance to economy and 

ease of construction. Under these conditions, together with the ones already 

mentioned, slotted plastic pipe is an attractive alternative to the continuous- 

dot or other manufactured type of well screen. it is particularly suited to the 

provision of individual water supplies in remote and inaccessible areas. 

39

Screen Length, Size of Openings and 

Diameter 

The length, size of openings and 

diameter of the well screen are the 

remaining design features which 

influence the efficiency of flow 

into a well. Together, they deter- 

mine the entrance velocity of flow 

through the screen into the well. 

This entrance velocity in turn in- 

fluences the head or pressure loss 

required for maintaining the flow 

and, as a consequence, also in- 

fluences the efficiency of the screen 

for that rate of flow. 

If designing a well to obtain the 

maximum yield from an aquifer, 

then the procedure would first be 

to select the screen length and size 

of openings based on the natural 

characteristics of the aquifer. The 

screen diameter would then be 

selected so as to provide enough 

total area of screen openings that 

the entrance velocity does not 

exceed the chosen design standard. 

Usua!ly, however, small wells are 

designed to provide a certain limited 

yield, well below the maximum 

possible yield, and the screen 

diameter is first chosen essentially 

with a view to keeping costs down 

to a minimum. The diameter se- 

Fig. 4.6 SLOTTED E’LASTIC PIPE. lected would then be the smallest 

practicable one, consistent with the 

expected yield and the diameter of the casing. Normally, it is not considered 

good practice to use a well screen of larger diameter than that of the casing. 

The size of the screen openings is, as before, fixed by the aquifer 

characteristics, but the screen length is, in this case, determined by the total 

area of screen openings required to keep the entrance velocity at or below the 

design standard. Should the screen length determined on this basis be greater 

than the thickness and other characteristics of the aquifer would permit, then 

the screen length is chosen as the maximum consistent with these limitations. 

Following this, a suitable diameter is chosen to be consistent with the design 

standard for entrance velocity into the screen. A more detailed discussion of 

the design standard for the entrance velocity follows discussions of the effects 

of aquifer characteristics on the selection of screen length and size of 

openings. 

40

Manufacturers make well screens in two series of sizes, the telescope-size 

and the pipe-size or ID-size. Telescope-size screens are designed to be 

“telescoped” or lowered through the well casing to the final position. The 

diameter of each screen is just sufficiently smaller than the inside diameter of 

the corresponding size of standard pipe to permit the screen to be freely 

lowered through the pipe. 

The pipe-size or ID-size series of well screens have the same inside diameter 

as the corresponding size of standard pipe. This type of screen is used when it 

is desired to maintain the same diameter throughout the full depth of the 

well. They are provided, in the small sizes under consideration, with either 

welded or threaded end connections. 

Screen length: The screen length selection can be influenced by the thickness 

of the aquifer. While definite rules may be set, based on this relationship, for 

large wells it would be unwise to do so for small ones. A farmer or home- 

owner should not be burdened with a long and costly well screen in a thick 

aquifer when his requirements are so small as not to warrant it. The screen 

length should be sufficient to meet his needs with a reasonable drawdown in 

the well. As already stated, a compromise must be made between well cost 

and well efficiency. The other ex.treme must also be avoided. Economization 

should not be taken to the point where the length of screen provided is such 

that the yield barely meets the owner’s present needs. A reasonable allowance 

should be made for his future ne:eds. Failure to do so may, in the long run, 

prove to be far more costly to the: owner. 

It is important to note that in a thick aquifer, well yield is much more 

effectively increased by increasing the screen length than by proportionately 

increasing the screen diameter. Doubling the screen diameter, for instance, 

will only result in an increase of 10 to 15 percent in the yield. In most cases, 

however, doubling the screen length will result in the yield being almost 

doubled. It is, therefore, much better to use screen length as a controlling 

factor on well yield rather than screen diameter in thick aquifers. 

The role played by aquifer characteristics in screen length selection is best 

demonstrated with the use of a few examples. Where a thick layer of coarse 

sand or gravel underlies a layer of fine sand as shown in Fig. 4.714, the screen 

length should be at least one-third the thickness of the coarse sand layer. For 

the sitatuions shown in Fig. 4.7B and Fig. 4.7C, almost the entire thickness of ., 

the lower layer of coarse sand should be screened. Should this prove 

inadequate for the desired yield, then it would be necessary to extend the 

screen a short distance into the overlying finer sand. Where a coarse sand 

overlies a fine sand as in Fig. 4.7D, it should normally be sufficient to place 

the screen in the coarse sand layer with the length being equal to about 

one-half the thickness of that layer. 

In thin aquifers confined by clays, particularly clays that tend to be easily 

eroded when exposed to water, screen lengths should be chosen so as to avoid 

the possibility of placing screen openings opposite these clays. Screening of 

clay layers could result in their collapse during the well development process 

with the well forever producing a muddy water. 

41

(A) Coarse port of form&ion is thick (8) Coarse pwt of formotion is thin 

(Cl Alternate kyere of coaree and fine s4md (0) Coarse material obova fine sond 

Fig. 4.7 RECOMMENDED POSITIONING OF WELL SCREENS IN VARIOUS STRA- 

TIFIED, WATER-BEARING SAND FORMATIONS. 

Screen slot operzirzg: An understanding of the method of selecting the size of 

screen slot openings first of all requires an understanding of the process and 

objectives of well development. As previously stated, fine material occupies 

part of the otherwise larger pore spaces of water-bearing formations, thus in- 

creasing the head losses due to friction and reducing the quantity of water 

yielded per unit of drawdown in a well (specific capacity). The object of well 

devehpment is to remove as much of this finer material as possible from a zone 

around the well to improve the specific capacity and efficiency of the well. 

There are a variety of methods that are used for inducing the flow of this fine 

material through the well screen and then extracting it by pumping or bailing. 

Some of these methods are described in Chapter 6. It is sufficient to note at 

this point that well development involves the removal of the finer aquifer 

material in the vicinity of a well and that this removal takes place through the 

screen and out of the casing. 

42

The limiting size of material to be removed, therelL)re, fixes the size of the 

screen slot openings. To determine this limiting size. ;I particlc sir.e ;tnalysis of 

the aquifer material must first be undertaken. About 3 cup ut‘ dry, thoroughly 

mixed aquifer material is passed through ;I st;indard set of sieves (Fig. 4.X) 

and the weight of the fractions retained OH each sieve is recorded. These 

wei&ts are then expressed as percerltages of the total weight of sample and a 

SAND AND GRAVEL 

--- 

.\Jl” t 6 mesh) 

093” ( Bmesh) 

,065” ( IO-mesh) 

046” (14 mesh) 

,033” I20 mesh) 

,023” (28.mesh) 

,016” (35 mesh1 

,012” (48.mesh1 

8ottom oan 

-- 

tl COARSt SAND 

,046” f 14 mesh) 

033” (20.mesh) 

.0X’ (28 mesh) 

,016” (35.mesh) 

,012” (48.mesh) 

.OOB” 165mesh) 

Bottom pan 

FOR FINE SAND 

.023” I 28.mesh) 

.016” I 35 mesh) 

,012” ( 48 mesh) 

.008” ( 65.mesh) 

.006” (100.mesh) 

Bottom p.m 

Fig.43 RECOMMENDED SETS OF 

STANDARD SlEVES FOR 

ANALYZING SAMPLES OF 

WATEK-BEARING SAND OR 

GRAVEL. 

graph is plot ted of the cumula: ive 

percent of tilt‘ sampk retained OII ;I 

given sieve and all the other sieves 

above it versus the size of the given 

sieve expressed in th~~usandths of 

an inch (Fig. 4.9). A smooth curve 

is drawn througil the points on the 

graph. This curve shows at a glance 

how much of the material is smaller 

or larger than 9 given particle size. 

For example, the curve in Fig. 4.9 

shws tiut 90 percent of the 

sample consists of sand grains larger 

than 0.010 inch or that 10 percent 

is smaller than this size. Expressed 

in another way, we may say that 

the 90 percent size of the sand is 

0.010 inch. 

Before describing the use of’ 

these sieve-analysis curves for the 

selection of screen slot openings it 

is desirable to point out another 

important use to which they are 

put. Reference here is to the use of 

the shape and location of the curve 

to determine the uniformity in size 

of the material and the ciassifica- 

tion of the material in such types as 

fine sands, coarse sands and gravels. 

For example, a narrowly spread, 

almost vertical type of curve indi- 

cates a uniform type of materia!. If 

such a curve occupies the left hand 

corner of the graph sheet (Fig. 4.10A) in the region of the small sieve sizes, 

then it represents a fine uniform sand. On the other hand, a curve widely 

spread across the graph sheet, as in Fig. 4.10D, indicates a sand and gravel 

mixture containing very little fine sand. An aquifer of such material would 

have a higher permeability and should be a much better producer of water 

than one containing the fine sand of Fig. 4.1 OA. 

Examinmg Fig. 4.1OD closely shows that removing all the material finer 

than the 40 percent size would leave only material coarser than 0.050 inch in 

43

100 

90 

‘p 

,ij 80 

0 

5 70 

E 60 

& 50 

CL 

em 

= 

; 30 

E 

a 20 

IO 

0 

102030405060708090100 

Grain size-in thousandths of an inch 

size of Sieve Cumulative Weights CumulotivePer 

Opening Retained Cent Retained 

0.046” 65 grams I 7% 

0.033” IO6 grams 28% 

0.023” 179 grams 47% 

0.0 16” 266 grams 70% 

0.0 12” 3 I2 grams 8 2 % 

0.008” 357 grams 94% 

Pan 380gran.s 100% 

Original weight = 382 grams 

Fig. 4.9 TYPICAL SIEVE-ANALYSIS CURVE SHOWS DISTRIBUTION OF GRAIN 

SIZES IN PER CENT BY WEIGHT. 

the formation. This relatively coarse material would have large pore spaces 

through which flow would be relatively free. A well constructed in aquifer 

material of this type with a screen carrying 0.050-inch slot openings or a No. 

50 slot screen would have a high efficiency after proper development to 

remove the fine material. 

Generally, well slot openings are designed to retain from 30 to SO percent 

of the formation material depending upon the aquifer conditions. The 

selection should tend toward the higher value for fine, uniform sands 

containing corrosive waters and toward the lower value for coarse sand and 

gravel formations. For e;:ample, the 40 percent size is recommended for a 

fine, uniform sand if the water is noncorrosive. If the water were corrosive, 

however, this would cause a gradual enlarging of the slot openings with time 

and a resulting steady flow of sand into the well. The designer must be more 

conservative under such circumstances and select the smaller opening that 

would be given by the use of the 50 percent size. In a coarse sand and gravel 

formation, however, the enlarging of the selected slot opening by a few 

thousandths of an inch would not create a perpetual sanding problem and the 

30 percent size may be chosen for the slot opening. 

The selection of a 30 percent size of opening means that 70 percent of the 

formation in the vicinity of the well will be removed in the developing 

process. Similarly, 60 percent of the formation is removed with a 40 percent 

size of slot opening. Selecting the 30 percent size as against the 50 percent 

size means that more material is removed, thus causing the development of a 

larger zone in the material surrounding the screen. This usually increases the 

specific capacity of the well and hence its efficiency in sufficient proportion to 

offset the extra cost of development. This is only permissible if the formation 

conditions are such as to indicate the use of the larger 30 percent size of slot 

opening. A more conservative selection of slot size is recommended whenever 

there is doubt about the reliability of the samples provided for analysis. 

44

too 

90 

E 60 

z 

t 50 

: 

.L 40 

2 30 

E 

(=j 20 

10 

0 

IO 203040 5060708090100 

Groin size, in thousondtns of on inch 

A. Fine, uniform sand that 

yields water at limited 

rates. 

lO2030405060708090100 

Grain size, in thousandths of an inch 

C. Fine sand with 10 to 20 

percent coarse particles 

” 

10203040506070809010(? 

Groin size.in thousondths of on inch 

B. Medium and coarse sand 

mixture with good per- 

meability. 

IO 20 30 40 50 60 70 80 90 100 

Grain size. in thousandths of on inch 

D. Sand aud gravel mixture 

with good permeability. 

Fig. 4.10 WICAL SIEVE-ANALYSIS CURVES FOR WATER-BEARING SANDS 

AND GRAVELS. 

45

Most geologic formations are stratified, having layers of varying particle 

size distribution. In such cases, slot size openings should be sejected for 

different sections of screen to suit the particle size distribution of the 

different strata. TWO more rules should be followed in aquifers where a fine 

sand overlies coarse material. 

1. The screen with the slot size designed for the finer material should be 

extended at least 2 feet into the coarse material. 

2. The slot size of the screen designed for the coarse material should never 

be greater than twice the slot size for the overlying finer material. 

These rules are aimed at reducing the possibility of the well perpetually 

producing sand from the fine upper layer. Fig. 4.11 illustrates how this 

possiiility may arise. It should also be remembered that depths to formation 

changes are not always accurately measured and it is not always possible to 

set screens at the exact levels intended. The observation of these rules Thor; 

assumes greater importance. 

The method of selecting screen slot openings so far outlined assumes 

Fig. 4.11 SEQUENCE ILLUSTR’iTES POSSIBILITY OF FINE SAND ENTER&NC UP- 

PERPARTOF LOWER :‘\ECI’ION OF SCREEN AFTER DEVELOPMENT OF 

WELL IF THE LARGLR OPENINGS OF THIS LOWER SECTION OF 

SCREEN EXTEND TO THE TOP OF THE COARSE MATERIAL. 

conditions that make it practicable to ;Irder well screens after doing sieve 

ma?yses of formation materials. In many countries and in the remote parts of 

~-xx others this procedure would result in costly delays while awaiting an 

imported screen. The desigxrer oi small wells under such conditions would be 

$tnfied jn seheciing a slot opening(s) based upon previous experience with 

existing roils in the same aquifer even before drilling operations begin. It 

WOU::J ~fi;lso be advisable to select a standyard size of slot opening for a 

multipk-well program in the same aquifer in order to benet from the 

resultjug xduced costs and time saving. This may, however, entail gravel 

packing of some of the wells to prevent them from producing fine sand. The 

efficiency of other wells may be less than optimum. This, however, is not a 

46

prime concern in small we!ls. Generally, the benefits of standardization of 

slot openings of small wells under the above stated conditions would offset 

the disadvantages. 

The entrance velocity is determined by dividing the expected or desired 

yield of the well expressed in cubic feet per second by the total area of the 

screen openings expressed in square feet. 

The total area of screen openings is the area of openings provided per foot 

of screen multiplied by the selected length of screen expressed in feet. Most 

manufacturers provide tables showing the open area per foot of screen for 

each size of screen diameter and for various widths of slot openings. Table 4.1 

is an example of one of these. From this table it is seen that a No. 40 slot, 

3-inch diameter telescope-size screen of this type contains 42 square inches of 

open area per foot of screen length. A IO-foot length of such a screen would, 

therefore, contain 420 square inches of total open area. 

The design standakd for the entrance velocity is chosen such that the 

friction losses in the screen openings will be negligible and the rate of 

incrustation and corrosion will be minimum. Laboratory tests and field 

TABLE 4.1 

INTAKE AREAS FOR SELECTED WIDTHS OF SLOT OPENINGS, (Square Inches per 

Lineal Foot of Screen). 

Nominal 

Screen 

Size 

2” TS 

I $4” PS 

2” Ps 

3” TS 

2w Ps 

3” Ps 

4” TS 

4” PS 

Actual Slot No. 10 

OD (0.010”) 

of Screen (0.25 mm) 

l-3/4” 10 

2-318” 13 

2-5 18” 14 

2-314” 15 

3-l 18” 17 

3-5 18” 20 

3-314” 21 

4-S IS” 25_ 

Slot No. 20 

(0.020”) 

(0.50 mm) 

16 

22 

25 

26 

30 

34 

35 

44 

- 

I 

Slot No. 40 

(0.040”) 

(1 .OO mm) 

26 

36 

41 

42 

48 

54 

56 

68 

- 

T 

-. 

Slot No. 60 

(0.060”) 

(1 SO mm) 

32’-. - 

45 

50 

52 

59 

68 

71 

I 86 

(Courtesy UOP-Johnson Division, Universal 

Oil Products Company, St. Paul, Minnesota) 

Notes: TS means telescope-size well screen 

PS means pipe-size well screen 

experience have shown that these objectives are achieved if the screen en- 

trance velocity is equal to or less than 0.1 ft per sec. The screen length 

preferably, or the diameter as is practicable, should be increased if this 

velocity is greater than 0.1 ft per sec. On the other hand, if the entrance 

velocity is appreciably less than 0.1 ft per set - say 0.05 ft per set - the 

screen length may be reduced until the entrance velocity more nearly 

approaches the standard of 0.1 ft per sec. 

SELECTION OF CASING AND SCREEN MATERIALS 

The choice of materials that go into the construction of a well is a very 

important aspect of water well design. A well constructed of materials with 

47

little or no resistance to corrosion can be destroyed beyond usefulness by Y 

highly corrosive water within a few months of completion. This will be the 

case no matter how cxceknt the other aspects of design. A poor seiec‘tion 1Jf 

materials can also result in collapse ot‘ the well due to inadequate strength. 

The above are factors which hrive considerable intluence urn what is cAled the 

useful life of a well. In addition to these influences, the selection of materials 

also has considerabie bearing on the cvst of a well. The corrusic!n resistant 

met& for example. are much mure costly than ordinary steel. The choice of 

a suitable metal or the provision of a greater thickness of the same metal to 

meet strength requirements invuriably results in higher costs. These considera- 

tions. therefore. indicate that the designer must exercise great cart’ in the 

selection of materials for a well. 

The designer usually makes his decision on the choice of materials after 

considering three main Factors. These are brtater qrtalirrr, strmgth reqrtirements 

and cyst. 

Water Quality 

Water quality. in this context, refers primarily to the mim~ral corltwt of 

the water that will be produced by the well. Its effects on metal may be of 

two basic types. It may cause wrrc~sim or iwmstatic~t~. Some waters cause 

both corrosion tend incrustaticln. Chemical analyses of water samples can 

indicate to the skilied interpreter whether a water is likely to be corrosive, 

incrusting, or both. Unless knowledge is already available on the nature of the 

water in the aquifer, it would be wise to seek the advice of a chemist with 

relevant experience before selecting materials for use in a welt. 

Grrusic~ is a process which results in the destruction of metals. Corrosive 

waters are usually acid and mdy contain relatively high concentrations of 

dissolved oxygen which is often necessary for and increases the rate of 

corrosion. Higll concentrations of carbon dioxide, total dissolved solids and 

hydrogen sulfid e with its characteristic odor of rotten eggs are other 

indications of a likely corrosive water. 

Besides water quality, there are other factors such as velocity offlow and 

dissirr&ritmv oj‘metn[s which contribute to the corrosion process. The greater 

the velocity of flow, the greater is the removal of the protective corrosion end 

products from the surface of’ the metal and hericc the cxposurc of that 

surf~e to further corrosion. This is another important reason for Xeeping the 

velocity through screen openings within acceptable limits. The use of two or 

more different types of metals such as stainless steel and ordinary steel, or 

steel and brass or bronze should be avoided whenever possible. Corrosion is 

usually greatest at the points of contact or closest proximity of the metals. 

Corrosion may occur in well screens as welt as casings. It can bc tnore 

critical in screens because it can reach damaging proportions much earlier 

than in casings. This is because only LI small enlargement of the screen 

openings is required for t!ie entry of sand through the screen, while the full 

thickness of the casing metal must be penetrated for failure of a well through 

corrosion of the casing. This is. however, no reason for ignoring the effect 01 

corrosion in casings. Casing frtiture by corrosion equally ruins a well as does 

failure of the screen. It c;tn cause the intrc~duction of clay and potjilted or

otherwise unsatisfactory water into the well. Corrosive well waters have been 

observed to destroy steel casings in less than c3 months in Guyana, thus 

ruining many wells. 

Ordinary stee! and iron are not corrosion resistant. There are. however, a 

number of metal alloys available with varying degrees of corrosion resistance. 

Among these are the stainless steels which combine nickel and chromium 

with steel and also the various copper-based alloys such as brass and bronze 

which combine traces of silicon, zinc and manganese with copper. Manufacturers, 

supplied with water analyses, can be expected to provide advice on 

the type of metal or metal alloys to be used. 

Plastic pipe of the polyvtilyl chloride (pvc) type is an attractive alternative 

to the use of metals in small wells, partickllarly under corrosive conditions. It 

combines corrosion resistance with adequate strength and economy. 

Irzcnrsration, unlike corrosion. results not in the destruction of metal, but 

in the deposition of minerals on it and in the aquifer immediately around a 

well. Physical and chemical changes in the water in the well and the adjacent 

formation cause dissolved minerals to change to their insoluble states and 

settle out as deposits. These deposits cause the blocking of screen openings 

and the formation pore spaces immediately around the screen with a resulting 

reduction in the yield of the well. 

Incrusting wsters are usually alkaline or the opposite to corrosive waters, 

which are acid. Excessive carbonate hardness is a common source of 

incrustation in wells. Scale deposits of calcium carbonate (lime scale) occur in 

pipes carrying hard waters. Iron and manganese, to a lesser extent, are other 

common sources of incrustation in wells. Iron causes characteristic reddishbrown 

deposits while those of manganese are black. 

Often associated with ironcontaining ground waters are iron bacteria. 

These minute ‘living organisms are non-injurious to health, but, while aiding 

the deposition of iron, produce accumulations of slimy, jelly-like material 

which block well screen openings and aquifer pore spaces. 

Strong solutions of hydrochloric acid are often used in treatment processes 

for the removal of all the above-mentioned incrusting deposits. The corrosive 

effect of this acid treatment, which must be repeated as the need. arises, 

makes it necessary to use screens made of corrosion-resistant materials. 

Unplasticized polyvinyl chioride pipe would &o withstand such treatment . 

Further discussion on rehabilitating incrusted wells is presented in Chapter 7. 

Strength Requirements 

Strength requirements are important in both casing and screens but are 

generally of mor e concern in screens. Screens must be strong enough to 

withstand the external radial pressures that could cause their collapse as well 

as the vertical loading due to the weight of the casing above them. 

Some metals have greater strength characteristics than others. Stainless 

steel, for example, can be twice as strong as some copper alloys. Screens and 

casings of adequate strength can be made from any of the metals and alloys 

commonly used in well construction. Manufacturers usually specify condi- 

tions under which their pipes and screens can be satisfactorily used. It is often 

49

helpful to consult with them on the selection of suitable materials for use in a 

well. 

cost 

Cost considerations may often be the deciding factor in the selection of 

construction materials used in small wells. The situation may arise, for 

instance, where stainless steel would be the most suitable material for use, 

combining corrosion resistance with excellent strength and a long, useful life. 

However, its cost may cause the designer to recommend the use of some 

other less suitable material after weighing the benefits *.>f extra 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 areas not accessible by motor vehicles and necessitating the 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 advantages and disadvantages of 

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 process of 

well development described earlier in this chapter. A further similarity is the 

addition of gravel in the case of gravel packing, and coarse sand 01 sand and 

gravel in the case of fori,tirton stabilization to the annular space between 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 achieved in a 

formation consisting of a fine uniform sand due to the absence of 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-packed well 

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 necessary clearance 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 process would not be satisfactory because of the uniformity of 

the sand particles. Also, screens with very small slot openings have low 

percentages of 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 screen slot 

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 less than 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 sizes refer to the percentage retained on a given sieve. 

The first condition usually ensures that the gravel-pack material will not 

restrict the flow from the layers of coarsest material, the permeability of the 

pack being several times that of the coarsest stratum. The second condition 

ensures that the losses of 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. 

are undesirable in gravel-pack material. 

Lirnestorle and shale 

Tlzickrzess of gravel-pack ewelopes: Gravel-pack envelopes ltre usually 3 to 

8 inches thick. This is not out of necessity as tests lime shown that ~1 fraction 

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 

losses of the materia! +h- ItlIou~ the screen during development. If necessary, 

more 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 casing should be extended down- 

wards into tlie impermeable formation (sucl1 ;f~ a clay) which caps the

Pump unit 

Sanitary well seal 

I 

/ 

,Relnfarced concrete 

‘Cover slab sloped away from pump 

-% 

--- - 

-- 

- 

. - 

-1 

- 

-- 

- 

--,r 

L-I: 

- ---- 

-L-F 

I 

- 

-_ 

-- 

- 

--- 

Fig. 4.12 S:\NlThKY PKO’I‘ti”fION OF l’PPt;.K ‘i‘ER31IN~\tL. Ok WCI.1.. 

Drop pope Soft rubber ex- 

pandlng gasket 

Well casing 

k.A 

\ 

I OroDtme -7 Soft rubber ex- 

panding gasket 

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 less than 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 &regularly 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 seepage of 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 space is 

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 casing to 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 seepage can readily occur down the outside of any unsealed casing. 

Methods of mixing and placing the grout are discussed in 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 

casing when necessary and 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 as boring and driving which are not drilling methods 

in a pure sense. The classification is one of convenience in the absence of 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 com- 

mon types of hand augers are shown in Fig. 5.1. They each consist of a shaft 

Fig. 5.1 HAND AUGLRS. (From Fig. 6, Wello. Department of the Army Technical 

Manual TM5297, 1957.) 

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 en- 

countered during boring operations. 

When turned in a clockwise direc- 

tion, 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 casing down. 

Fig. 5.2 SPIRAL AUGER. 

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 instead 

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 assemblies commonly 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 easier in 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 ----k- 

Htle backfilled 

with pudd.ed clay 

- Drive cap 

Fig. 5.3 SlMPLE TOOL FOR DRIV- 

ING WELL POINTS TO 

DEPTHS OF 15 TO 30 FT. 

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 connec- 

tions than ordinary plumbing 

couplings. The pipe and coupling 

threads should be coated with pipe 

thread compound to provide air- 

tight joints. The well-point assem- 

bly should be guided as vertically 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 light- 

iy 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. 

Jetting 

The jetting method of well drilling uses the 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

Fig. 5.4 DRIVE-BLOCK ASSEMBLIES 

FOR DRIVING WELL 

POINTS. 

Fig.55 BITS FOR JET DRILLING. 

(From Fig. 17, We&s, Depart- 

ment of the Army Technical 

Manual TMS-297, 1957.) 

58 

galvanized iron pipe is used to 

suspend the galvanized iron drill 

pipe and the bit by means of a U- 

hook (at the apex of the tripod), 

single-pulley block and manila rope. 

A pump having a capacity of ap- 

proximately 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 (cut- 

tings) settle out and then to a stor- 

age 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 mainte- 

nance required by the latter as a 

result of! leaking seals and worn 

impellers and other moving parts. 

The ::pudding percussion act ion 

can be imparted to the bit either by 

means of a hoist or by workmen 

alternately pulling and quickly re- 

leasing 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 as drilling 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-

single wlley block 

: /Tripod 

Fig. 5.6 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 intro- 

duced continuously into the borehole outside of the drill pipe. A recipro- 

cating, 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 forma- 

tions 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 en- 

tirely with hand tools. makes use of locally available materials. such as

amboo 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 

Fig. 5.7 BAMBOO SCAFFOLDING, 

PIVOT AND LEVER USED 

IN DRILLING BY THE SLUD- 

GER METHOD. (From “Jctting 

S m a I 1 Tubewells By 

Hand.” Wafer Supple and Sanitaiion 

in Develop& Counfeet 

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 

allowing some of the fluid and cuttings 

sucked into the bottom of the 

drill pipe to rise and overflow. Continuous 

repetition of the process 

fries. AID-LiNC/IPSED Item 

causes the penetration of the drill 

No. IS. June 1967.) pipe into the formation and creates 

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 posi- 

tion 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

Fig,..8 MAN ON SCAFFOLDING 

RAISES HAND OFF PIPE 

ALLOWING DRILL FLUID 

AND CUTTINGS TO ESCAPE. 

(From “Jetting Small Tube- 

weiis By Hand,” Water Supply 

and Sanitation in Developing 

Countries, AID-UNC/IPSED 

Item No. 15, June, 1957.) 

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 re- 

quired by the drilling depth; and 

one or more lengths of drill collar. 

The kelly or the uppermost sec- 

tion of the drill stem is made a few 

feet longer and of greater wall 

thickness than a length of drill pipe. 

Its outer shape is usually square 

(sometimes six-sided or round with 

lengthwise grooves), fitting into a 

similarly shaped opening in the 

rotary table such that the kelly can 

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 suspended from 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 edges and 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 effective- 

ly. Each roller is provided with a nozzle serving the same purpose 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

Three-way Fishtail 

Fig. 5.9 ROTARY DRILL BITS. (From 

Fig. 41, Wells. Department of 

the Army Technical Manual 

TMS-297, 1957.) 

Fig. 5.10 ROLLER-TYPE ROTARY 

DRILL BIT.(From Reed Drill- 

ing Tools. Houston, Texas.) 

the volume of the hole being 

drilled. 1 t should be relatively shai- 

low (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 

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 com- 

bined 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 men- 

tioned. These are discussed later in 

this chapter. 

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 re- 

quired 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

Cutting edges 

Galvanized iron pipe 

Outlet for direct- 

ing drill fluid onto 

cutlmg edge 

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~ss c)f fluid into permeable forma- 

tions such ;1s sands and gravels. 

Drillers must be careful mt to in- 

crease the pumpirig rate to the 

puint where it c;lcszs destruction ot 

the mud czke and cming of the 

hole. 

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 eias- 

tic, thus keeping the Cuttings in sus- 

pensm. 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 suit- 

ubie tluid thickness. TW thin ;I 

tluid rc-suits in caving 01 tile hole 

und loss of tluid into permeable i‘or- 

maths. 011 tilt‘ other hand. tluid 

slmuid bc no rilickcr rhn is IICWS- 

sary to nlairltrtin 3 .

-. 

- - 

-^ - - z-

inexperienced driller because of the differential rate of tr;insport 01‘ tht~ cuttings 

out of the borehole. The need for proper drilling mud c‘or\trcA ~1s~~ 

requires considertlbie experience on the part of the rotary driilcr. Ti~c training 

of rotary drillers can be more time consuming und dit‘tkult. lkspitc ~hcsc‘ 

disadvantages the method finds considtx~bic appiic;lt iorl in the coust ruct ioll 

of wells in al! types of formations 

t ions. 

Cable-Tool Percussion 

tend p;lrticuiarly url~ollsolidvttd t‘orma- 

Cable-tool percussion is one of the oldest methods used il: well construetion. 

It employs the pfincipie of 3 frtx-fulii:lg heavy bit delivering blows 

against the bottom of ri hole auci thus penetrating inttj the ground. C’uttings 

are periodically rerncved by rt bailer or s:md punlp. ‘I‘ool~ ti)r drillin:: aid 

bairing tire carried on separate fines or cttblcs spuoied cjn independent hoisting 

drums. 

The basic components of ;t cable-tool drilling rig are ;1 power unit for 

driving the bull reel (carrying the drilling csbie) and the sand reel (carrying 

the bailing cable). 2nd ;I spudding btxm tar impart in, (1 the drilling motiuu tu 

the drill tools. alf mounted on ;I t‘r;mx which carries ;I derrick or mat ut 

suitable height for the USC of ;I striug of drilling 

cable-tool drilling rig on ioctttiun. 

tools. Fig. 5.14 shahs ;I 

Fig. 5.14 STAR 7 1 CABLE-TOOL DRILLING RIG.

- Drill line 

.Rope et hzket 

Drilling jars 

- Drill s item 

-Drill bit 

Fig. 5.15 COMPONENTS OF A STRING 

OF DRILL TOOLS FOR 

CABLE-TOOL PERCUSSION 

METHOD. (-From Ac‘mt‘ Fib 

ing Tool Cornpan)-. Parkrr~ 

burg. We\t Virginia.) 

Four items comprise ;1 full string 

of drilling tools. These are the drill 

bit. drill stem. drilling jars and rope 

socket (Fig. 5.15 ). The chisel-shaped 

drill bit is used to loosen unconsolidated 

rock materials and with its 

reciprocating action mis these materials 

into a slurry which is later removed 

by baiimg. When drilling in 

dry formations water must be added 

to the hole to form the slurry. The 

water course on the bit permits the 

movement of the slurry relative to 

the bit and. therefore, aids in the 

free-failing reciprocating motion of 

the bit. The drill stem immediately 

above the bit merely gives additional 

weight to the bit and added length 

0 the ;tring of tools to help mainain 

a straight hole. 

The jars consist of a pair ot 

1 inked steel bars which can be moved 

il n avertical direction relative to each 

other. The gap or stroke of the drilling 

jars is 6 to 0 inches. Jars are used 

to provide upward blows when necessary 

to free a string of tools stuck 

or wedged in the drill hole. Drilling 

jars are to be differentiated t’rom 

similarly constructed fishing jars 

which have ;1 stroke of 18 to 36 

inches and art‘ used in fishing or recovering 

tools which have come 

loose from the string of drilling 

tools in Ihe hole. 

The rope socket connects the 

string of tools to the cable. its con- 

struction is such as to provide a 

slight clockwise rotation of the 

drilling tools relative to the cable. 

This rotation of the tools ensures 

the drilling of ;1 round hole. Another 

function of the rope socket is to 

provide. by its weight. part of the 

energy of the upward blows of the 

jars. 

The components of the tool

string are usually joined together by tool joints of the box and pin type with 

standard American Petroleum institute (API) designs and dimensions. 

The bailer is simply a length elf pipe with ;I check valve at the bottom. The 

v&e may be either the tlat-pattern or bell-and-tongue type called the dart 

valve. Fig. 5.16 shows a dart valve bailer being discharged by resting the 

tongue of the valve on a timber block. 

The sand pump (Fig. 5.17) is a 

bailer fitted with a plunger whicfl, 

when puiled upwards, creates a vac- 

uum that opens the check valve and 

sucks the slurried cuttings into the 

bailer. Sand pumps are always made 

with flat-pattern check valves. 

it is important that the drilling 

motion be kept in step with tile fail 

of the string of tools for good opera- 

tion. The driller must see to it that 

the engine speed has the same tim- 

ing as the I’41 of the tools and the 

stretch of the cable. This is a skill 

that can only be provided by an ex- 

perienced driller. 

Drilling by the cable-tool Fer- 

cussion method in unconsolidated 

format ions requires that the casing 

Fig.5.16 DISCHARGING DART cfosefy follows the drilling bit as tile 

VALVE BAILER. hole is deepened. This is necessary 

to prevent caving. The usual pro- 

cedure is to dig a starting hole into which is placed the first section of casing. 

The casing is driven one to several feet into the formation. water added and 

the material within the casing drilled to a slurry and removed by bailing. The 

casing is then driven again and the material within it watered if necessary. 

drifted and removed by b:tifing. The procedure is repeated, adding lengths ot 

casing until the desired depth is reached 

The pipe dliviug op i-iiiiiiiii iCcjLiiiCS ikit iI12 IoWcr C;:d of the first section 

of the casing be fitted wit11 a protective casing shoe (Fig. 5.18). Tile top of 

the casing is fitted with a drive head which serves as an anvil. Drive clamps 

made of two heavy steel forgings and clamped to the upper wrench square of 

the drill stem are used as the hammer (Fig. 5.19). The string of tools. which pro- 

vide the necessary weight for drivin g. is lifted and dropped repeatedly by the 

spudding action of the drilling machine. thus driving the casing into the 

ground. An alternative method of driving small diameter well casing uses a 

drive block assembly as prL>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 for- 

mations. It is. however. better suited than other methods to drilling in uncon- 

solidated 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. Reason- 

ably 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 

Fig. 5.17 SAND PUMP BAILER WITH 

FLAT VALVE BOTTOM. 

69 

consideration in arid regions. Any 

encounter with water-bearing for- 

mations 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 fol- 

lows the drill bit as drilling pro- 

ceeds. 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 hy- 

draulic rotary, jetting, hydraulic per- 

cussion or sludger methods. 

It is first necessary to ensure 

that the borehole is free from ob- 

structions throughout its depth be- 

fore 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

.I 

Fig. 5.18 CAStbiG DRIVE SHOE. 

of the hole without affecting the 

settirkg ui‘ the casing at the dcsircd 

depth. 

In setting casing. it may be sus- 

pended 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 

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 

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. 

;#j$$ 

” 

,,__ _,‘ ,/Y, _ 

Fig.219 DRIVING CASING WITH 

DRIVE CLAMPS AS HAM- 

MER AEiD DRIVE HEAD AS 

ANVIL. 

70 

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

Fig. 5.20 HOKTING PLUG. (From Fig. 

5 1 Wk. Dcpartmcnt of the 

Army I cchnical Manual TM5- 

297. 19.57.) 

Fig. 5.2 I CASING ELEVATOR. 

71 

be used for glcruting and may be 

placed by pumicing with the mud 

circulation pundit nvrmally used for 

drifting purpose\ 1 I 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 11kbt he 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 1nuc11 in 

excess of h gallons per sack of cenient 

result in the settling out ot 

the cement. wll1~11 is 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.~rc should 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 

earlier resump’ of drilling operat 

ions. 

Mi3iug of rl~ I out may be done 

in a concietc hxr, if available, 

and batches stir’ _i temporarily until 

enough is nli ted for the job at 

hand. The quanlit ies normally re-

Fig. 5.22 A GRAVITY PLACEMENT 

METHOD OF CEMENT 

GROUTING WELL CASING. 

PLUGGED CASING LOWER- 

ED INTO CEMENT SLURRY 

FORCES SLURRY lNT0 AN- 

NULAR SPACE. 

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 oper- 

ation 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 be- 

low. Suitable pumps. air or water 

pressure may be used to force the grout into the annular space. However, 

grout may also be placed in shallow 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 ;1 grout 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

Fig. 5.23 INSIDE-TUBING METHOD 

OF CEMENT GROUTING 

WELL CASING. 

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. 

The outside-tuhitzg method 

shown in Fig. 5.24 requires a bore- 

hole 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 

that used in the inside-tubing 

method, is initially extended to the 

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 sub- 

merging 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

Fig. 5.24 OUI’SIDE-TUBING METHOD 

OF CEMENT GROUTING 

WELL CASING. 

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 re- 

spect, straightness is the more im- 

portant fsctor. While 3 vertical 

pump can be installed in a reason- 

ably 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 con- 

trolled within reasonable limits. 

since the deviation tram the vertical 

can affect the operation and life of 

some pumps. Most well construc- 

tion codes and drilling contracts 

specify limits for the alignment of 

large diameter, deep wells. Gener- 

ally, these limits cannot be practi- 

cably applied to stnall diameter, 

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 can- 

not 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. peri- 

odic 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‘;lsin g. then any subsequent deviation ot‘ the cable 

from the center indicates 3 deviation of the hole from the vertical. The wear- 

irlg 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 ac- 

curately 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 ;1 pxficular well Inay be intluenced 

by the design of the well, the drillin g method and the tvpe of problems en- 

countered 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 percussion method, 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 sized just sufficiently 

smaller than the inside diameter of the casing to permit the telescoping 

of the screen through the casing. The top of the screen is fitted with a 

lead packer which is swedged out to make a sand-tight seal between the top 

of the screen and 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 casing is 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 

assembled screen may simpi,w _ he dropped in the casing. Having checked to 

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

Fig. 5.26 LOWERING HOOK. 

Fig. 5.27 B U M PI N G BLOCK BEING 

USED TO PULL WELL CAS- 

ING.(From Bergerson-Caswell, 

Inc. , Minneapolis, Minnesota.) 

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 screen to 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 pos- 

sible 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 pull- 

ing 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 swcdge block rests on 

the lead packer. The weight pro- 

vided by the pipe attached to the 

sliding bar is then lifted 6 to 8 

inches and dropped several times. 

The swedge block 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. 

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 line- 

.Cemsnt grout ,’ 

Exoanded .?:i 

leab pucker 

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. 

r

maintaining such 3 “dean” hole. ;1 short extension pipe may be attached to the 

bottom of 311 open-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 wa- 

ter 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 ;1 hole 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 

Fig. 5.32 WASH-DOWN METHOD OF 

SETTING WELL SCREEN. 

X0 

Well rcrrrn 

Coupling on uaah pipe 

fun18 In conkot aoat 

Combination back- 

Fig. 5.33 JETTING WELL SCREEN IN- 

TO POSITION.

to the surface with the return flow. Sand particles which inevitably accumu- 

late 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 re- 

turn flow of the jetting water in the space between the wash pipe and the 

screen. All the return flow from the washing OL jetting operation, therefore, 

takes place outside of the screen and casing. A little leakage of the jetting wa- 

ter 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 circu- 

lation 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 pos- 

sibie 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 driv- 

ing 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-Packed Wells 

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 

Fig.5.34 DRIVING WELL POINT 

WITH SELF-SEALING PACK- 

ER INTO WATER-BEARING 

FORMATION. 

Well casing -\ ’ ‘Q/I 

Drlvlng pipe 

Fig. 5.35 DRIVING BAR USED TO DE- 

LIVER DRIVING FORCE 

DIRECTLY ON SOLID BOT- 

TOM OF WELL POINTS 5 Fi- 

OR MORE IN LENGTH.

-Inner Carm~ 

Fig. 5.36 DOUBLE-CASING METHOD 

OF ARTIFICIALLY GRAVEL 

PACK!,% A WELL. GRAVEL 

IS ADDED AS THE OUTER 

CASING IS PULLED BACK 

FRO:4 THE FULL DEPTH 

OF I-HE WELL; 

or gravel placed around the well 

screen in a predetermined thick- 

zess. This envelope takes the piace 

of the hydraulically graded zone of 

highly permeable material produced 

by conventionti development pre- 

cedures. 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 corre- 

sponding 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 place- 

ment of the gravel pack is com- 

plcted. 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 

appropriate distance and the pro- 

cedure repeated until the level of 

the gravel is well above the top of 

the screen. The well may then be 

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 ma- 

terial 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 ten- 

dency 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

Fig. 5.37 PLACING GRAVEL-PACK 

MATERiAL THROUGH PIPE 

USEDASTREMIE. 

Fig.538 LEAD SLIP-PACKER IN PO- 

SITION ON EXTENSION 

PIPE BEFORE EXPANSION 

TO SEAL THE ANNULAR 

SPACE. 

space as the gravel is being de- 

posited. 

Some settlement of the gravel 

will occur during the development 

process. More gravel must, there- 

fore. 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 per- 

manently 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 

is then unscrewed at this joint and 

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 

placed. !eaving the extension pipe 

overlapping inside the outer casing. 

Centering guides must be provided 

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 swedge block 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‘onsiderable force 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

Lead packer 

Pulhg pipe 

Sand join1 

Sacking 

wired on pipe 

Well screen 

Ball 

Fig. 5.39 ELEMENTS OF SAND-JOINT 

METHOD USED FOR PUL- 

LiNG WELL SCREENS. 

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 con- 

nection 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. 

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, how- 

ever, the size of pipe is chosen at 

one-half the nominal inside diam- 

eter of the screen. For example, a 

4-inch screen with nominal inside 

diameter of 3 inches would require 

1 ?&inch pipe. Extra heavy pipe 

should be used. The pipe couplings 

and threads should be of the 

highest quality in order to with- 

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 de- 

sirable. 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. 

I:$. 5.40 STRlPS OF SACKlNG BElNG 

TIED TO LOWER END OF 

THE PULLING PIPE USED 

IN THE SAND-JOINT 

METHOD. 

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

saving that sbandunmcnt ot‘ the borehole or well \vuuld altail. Only :tf’ter 

such careful cctnsidcrtlt ion should t’islljrl~ operations be undcrtakcn. For 

smttll dirimeter, rclativelv shallow wells it wtbuld often be t’wnd t’co~~o~~wd 

and othcxwise bexitci 11 tLj drill 3 I~CW ~vell rather than attempt fislling 

opcrtltions in OIW under construction. This is particul;lrly true prior to the 

placing and cement Eng of the permtlnent casing. It should also bc borne in 

mind that fishing operations require :I great deal of skill, rnucl~ more so than 

drilling operation s and the driller rnrty be inexperienced in such work. 

Preventive Measures 

As is the crtst’ with all other forms ofxcidents. prevention is always bc: ter 

than curt. Towards this end, the necessity to exercise the greatest care and 

attention at all times and throughout 

all stages of drilling operations 

cannot be over-stressed. While the 

utmost cat-e and attention will not 

completely eliminate the need for 

fishing. it will consider;rbly reduce 

the number and frequency of fishing 

optxrt ions. 

Among the precautions that 

should be undertaken is the propel 

care and use of drilling touls and 

equipment. This includes the propel 

cleuning und brtxking-in of new 

tool joints. the proper cleaning 

and setting of joints at all times, 

the correct dressing and hardening 

of bits. the regular maintenance and 

inspection of all wire rope. the regular 

inspection of all components 

of’ the drilling string for the development 

uf fatigue cracks and the 

discarding of worn out tools. Above 

all. cart! tnust be taken nevc’r tu 

overload equipment nor LLSC tools 

for purposes other than those for 

which they have been designed. 

The manut‘Hcturer’s limitations set 

UPPER END OF SACKING 

STRIPS ARRANGED EVEN- 

LY AROUND TOP OF WELL 

CASING AS THE PULLING 

PIPE IS LOWERED INTO 

THE. WELL. 

011 the use of equipment and tools 

should not be exceeded. 

The care of wire rope should be 

given special considerat ion. Many 

manufacturer’s catalogs contain detailed 

instructions. Among the most 

import ant of these is the need t,r 

regular lubrication with a good 

grade of lubricant. free from acid or 

x7

alkali and which will penetrate and adhere to the rope. The ust’ ot‘ crude 

oil or other material likely to be injurious to steel or ruse deterioratiorl 

or brittleness of the wires must be avoided. Failure to properly lubric’utt’ 

wire rope results in the wires becomm~ brittle. corroded, subject to excessive 

friction wear and ultimatt4y the sud& fracturmg of the rope. The rope 

should be tightly and evenly wound on winding drums and should not be 

allowed to stand in mud. dirt or other such medium which is h~rmt‘ul to steel. 

Only proper P&sterling clamps that do nut kink. flatten or crush the rope 

should be used. The fracturing CJf loaded wire rope, it should be remem- 

bered, can cause serious injury tu workmen as well as create fishing problems. 

lrnscrewed tool joints are ihe causes of many fishing operations. These can 

be avoided by the proper matirlg of the box and pin components of the 

joints. Both the pin shoulder and the box fi!ce should be thoroughly cleaned 

and free of imperfections that prevent a full and even contact. The threads 

and shoulders of the component parts should be thinly coated with a light 

machine oil before mttking up the joint. Joints should be firmly made up 

though not with excessive pressure as this cm result in broken boxes and 

pins. 

Tools. carelessly left on the rotary table or at some such point. nwy be 

accidentally tipped into a borehole. One half of 9 pipe clamp entering ;I well 

in this manner has been known to become wedged iu the well sc’recn 

just above a juint in the wash pipe being used in the development pr~xxss 

and result not only in the abandonment of the well but also the loss 

of several hundred feet of drill stern with it. All tools should be removed 

immediately after use to a convenient point of storage at ;I safe distance t’rom 

the borehole or well. 

Certain conditions such as slanting or caving formations. crooked holes 

and the presence of boulders often contribute to drilling troubles that may 

result in fishing operations. The utmost care must be exercised by drillers 

operating under these conditions. 

Prepmat ions for Fishing 

The nature of all operations (construction and maintenance) or1 wells is 

such that accidents do occur even under the supervision of the most capable 

and careful drillers. Therefore, the driller in anticipation of the inevitable 

fishing job should record or have access to the exact dimensions of everything 

used in or around the well. This facilitates the selection and design of a 

suitable fishing tooi when necessary. All tools brought to the site should be 

accurately measured and the measurements properly recorded. Some of the 

important measurements are: the outside diameter and length of the rope 

socket; the diameter, length and stroke of the drill jars; the diameter and 

length of the drill stem; the size of tool joints and the outside diameter and 

length of the pin and box collars; the body size and length of bits; the length 

of pin collars on the bits. A careful record of the depth or the hole and the 

ovemil length of the drilling string is also essential for successful fishing 

operations. 

The drill hole must of necessity be larger than any tools placed in it. As a

esult, tools lost in a hole do not often remain in the vertical or upright 

position but become wedged in sloping positions across the hole. In addition, 

material from a caving formation may fall onto and cover the tool. No 

amount of measurement at the surface could teli the driller exactly what 

position the lost tool has assumed in the hole or. in some cases, whether the 

top portion of it is free from obstruction. It is, therefore. considered good 

practice to use what is known as a n impression block to obtain an impression 

of the top of the tool before at- 

- Drill pipe tempting any fishing operations. 

This is particularly necessary in 

rotary drilled, uncased holes. Impression 

blocks are of many forms 

and designs, one of which is shown 

in Fig. 5.32. A short block of wood 

(preferably soft wood) turned on a 

f-- Box pin 

lathe to a diameter about one inch 

less than that of the drilled hole and 

with the upper portion shaped in 

the form of a pin, is driven to fit 

tightly into a drill pipe box collar. 

For added security. the wooden 

block should be wired or pinned 

securely to the collar. The wooden 

block may aiternative!y be bolted 

to the dart of a dart valve bailer. A 

quantity of small headed nails is 

driven into the bottom of the circular 

block, leaving an extension of 

about */4 inch. Sheet metal ir temporarily 

nailed around the block 

with a protrusion of a few inches 

over the lower end of the block. 

Warm paraffin wax, yellow soap or 

other plastic material is poured to 

fill thus protrusion and then left to 

cool and solidify. The nail heads 

help to hold the plastic material 

onto the block. After the sheet 

metal is removed and the lower end 

of the plastic material carefully 

smoothed, the impression block is 

ready for use. The block should be 

lowered carefully and slowly into 

Fig. 5.42 IMPRESSION BLOCK. 

the hole until the object is reached. 

It is then raised to the surface where 

the impression made in the wax or 

soap can be examined. By careful 

89

interpretation of the impression, a driller can determine fhc’ position of the 

fish and the best means of retrieving it. 

Common Fishing Jobs and Tools 

It is often said, with considerable justificatiun. that no IIVO fishing jobs are 

alike. While fishing jobs may be classified into various type-\, individual jobs 

within these types are usually quite different. Fishing jobs. ;IS ;L result. test the 

skill and ingenuity of the driller to the fullest extent. The driller relies on a 

number of basic principles in his attack on fishing problemh. A great variety 

of special tools have been devised to assist him in this work. Many of these 

toois are used very infrequently and it is not uncommon to i‘ind a tvol made 

for a particular job and never used again. Only large-scale drilling operators 

can afford to have more than a limited stock of fishing tooI>. Whenever pos- 

sible. small operators usually rent took as the>, are needed Q‘rum suppliers. 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 drill- 

ing 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 up- 

per formation material onto the top of the pipe or whether the pipe has be- 

come embedded into the wall of the hole. If the top of rhe pipe is unob- 

structed. 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 cut- 

tings 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~Z UT merai cu~ti~~gs. Circuiation cannot be corn- 

pleted 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

e 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 cable- 

tool 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 project- 

ing 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 bc- 

come stuck in the hole. Far the 

range of boreholc sizes being con- 

sidered, 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 ab- 

sence of a hitch it is lowered below 

t!le first point and again tested f

If the hold is secure, continue 

lifting the tools out of the hole until 

the broken wiresappear. Stop lifting 

and tie the wires together and then 

to the prongs of the grab to prevent 

the loose ends from unfolding and 

causing the hold to break. The tie 

itself does not carry the load but 

holds the broken lines in position. 

Continue lifting until the lost tools 

are recovered. 

If the string of lost tools is not 

free, then sufficient line should be 

let out to bring the jars into use. 

Jarring should be continued until 

the lost tools come loose or the 

broken cable parts. 

(3) Fishing for the neck of a 

rope 

object 

socket, 0 t her cy Iindrical 

or the pin of a tool: The 

combination socket (Fig. 5.46) is 

one of several tools used to catch 

the neck of a wire-line socket after 

broken line has been cleared away, 

or the pin of a bit or drill stem that 

has become unscrewed in the hole. 

The tool can also be used to fish for 

any cyhndrical object such as a drill 

stem or tubing standing upright in 

the hole, providing the bore of the 

socket is at least l/8 inch larger 

than the diameter of the fish. The 

fishing string should consist of a 

rope socket, stem, long-stroke 

fishing jars and combination socket. 

Combination sockets are pro 

vided with two sets of slips, one set 

of which is used to engage the 

threads of the pin on a bit, stem or 

other tool and the second set to 

take hold of the neck of the rope 

socket. The proper set of slips must 

be selected for the particular fishing 

Fig. 5.45 CENTER SPEAR. 

job in accordance with knowledge of 

the exact size of the fish. It is also 

good practice to determine if the socket can go over the fish by first running 

the socket with its inner parts removed. The re-loaded combination socket is 

93

then slowly iowered on the fishing string with the fishing jars adjusted for 

shortest stroke. Upon contact with the-fish. a light downward jar is used to 

secure a hitch. Tension is then taken on the line and the fishing job completed 

if the tools are not stuck. 

If the tools are stuck, then a slow spudding action should first be tried to 

release them. Should this fail. then sufficient line is let out to bring the jars ill- 

to use. Short and rapid jarring should cause the freeing of the tools and is pre- 

ferabie to hard long-stroke jarring even ihoaug!~ several hours of work my be 

necessary-. Long-stroke jarring could result in break.ing of the hitch on the lost 

tools or in broken fishing tools. Alternate up-jarring and down-jarring would 

release the hitch on the lost tools, should it become obvious that they cannot 

be freed and recovered. 

After successful completion of a fishing job. the hitch is broken by remov- 

ing the wooden block above the spring in the combination socket and so re- 

lieving the pressure on the spring and slips. 

(4) Releasijrg locked jars: Jars sometimes becorxe stuck or tools above the 

jars wedged in the hole by a piece of rock or other material. A jar bumper (Fig. 

5.47) is the tool normally used under such circumstances. The following pro- 

cedure should be followed. A strain is first taken on the drilling cable. The jar 

bumper is then lowered on the sand line, using the drilling cable as a guide, 

until the bumper reaches the string of tools. The bumper is then raised IO or 

12 feet and dropped. repeating this as often as necessary to loosen the jars or 

string of tools. A few blows are usually sufficient for this purpose. Too many 

blows might batter the neck of the rope socket and should be avoided. Should 

the bumper fail to release the tools, cut the cable and use a combination 

socket. 

95

CHAPTER 6 

WE11 C6MPLETION 

Well completion is the term u\ed to describe the two basic processes which 

are undertaken after a well has been constructed in order to ensure a good 

yield of water that is clear and relatively free of suspended matter and dis- 

ease-producing organisms. These processes are called well development and 

well disinfection. 

WELLDEVELOPMENT 

The object of well development is the removal of silt, fine sand and other 

such materials from a zone immediately around the well screen, thereby 

creating larger passages in the formation through which water can tlow more 

freely towards the well. 

In addition to the above, well development produces two other beneficial 

results. Firstly, it corrects any clogging or compacting of the water-bearing 

formation which has occurred during drilling. Clogging is particularly evident 

in wells drilled by the, rotary method where the drilling mud effectively seals 

the face of the borehole. Driving casing in the cable-tool percussion method 

vibrates the unconsolidated particles, thus compacting them. These are not 

the only drilling methods that damage the formation in one way or the other. 

All drilling methods do to different degrees of magnitude, and well develop- 

ment is needed to correct this damage. 

Secondly, well development grades the material in the water-bearing for- 

mation immediately around the screen in such a way that a stable condition 

in which the welt yields sand-free water at maximum capacity is achieved. In 

a zone just outside the screen, ail particles smaller than tl-:e size of the screen 

openings are removed by development, thus leaving only ihe coarsest material 

in place. A little farther away some medium-sized grains remain mixed with 

the coarser ones. This grading of coarse through successively less coarse ma- 

terial continues as distance from the screen increases until material of the 

original character of the water-bearing formation is reached. This marks the 

end of the developed zone around the well. The succession of graded zones of 

material around the screen stabilizes the formstion so that no further sand 

movement will take place. Tlie extent of the envelope depends upon the 

formation characteristics, the well screen design and the skill of the well 

driller. Fig. 6.1 illustrates the principle of well development described above 

and which applies to naturally developed wells. Gravel-packed wells present a 

somewhat different problem which is discussed later in the chapter. 

96 

4

Fig.6.t HIGHLY YEIEMEABLE DEVELOPED ZONE AROUND WELL SCREEN. 

ALL !~IATERL(AL I-1kk.K IHAN Ikit SCKttN Wk’tl\rlNbS HAS BLkl\r 

REMOVED. REMAINING MATERiAL GRADED FROM COARSER TO 

FINER SIZES WITH DISTANCE FROM THE SCREEN. 

The development operation, to be effective. must cause reversais ot‘ tlow 

t!trough the screen openings and the furmatiun immediately around the well 

(Fig. 6.2). This is necessary to rtvuid the bridgirig of openings by groups of

‘N 

E 

L 

VI 

E 

L

A solid-fj*pe surge plwger is shown in Fig. 0.4. it is of simple WIIstrut 

ion. consisting ut‘ two Icather 

or rubber-belt discs sandwiched between 

wooden discs. all assembled 

3ver ;L pipe nipple with steel plates 

selxing ;IS washers under the end 

couplings. The leather or rubber 

discs shuuld fc)rm :J reasc,nubly 

close fit in the well casing. This is 

by no means the only way of 

making ;t s4id-type surge plunger. 

It is only one of several ways of so 

doing but serves to illustrate the 

essential features of this tool. Vuristions 

could include the use of 

cupped leather or rubber fazing on 

the wooden discs instead of the flat 

leuther or rubber-belt discs. A 

simple form of plunger can also be 

made for use in small diameter 

fW”l]< . . . . b;, -. securely tying enough 

Fig.6.4 TYPICAL SOLID-TYPE 

SURGE PLUNGER. 

strips of sacking around the drill 

pipe (preferably at ;I joint) to ob- 

tain ;1 close fit in the well casing. 

Before surging. the weI1 should bc washed with ;I jet of water and bailed or 

pumped to remove some of the mud cake w the face of the borehoic and any 

sand that may have settled in the screen. This ensures that ;I sufficiently free 

flow of water will take place from the aquifer into the well to permit the 

plunger to run smoothly and freely. The surge plunger is then lowered into 

the well (Fig. (3.5) to 3 depth It) tu I4 feet under the water but zbuve the top 

of the screen. A spudding motion is then applied. repeatedly raising and 

dropping the plunger through ;I distance of 2 to 3 feet. If ;t cable-tool drilling 

rig is used. it should be oper:,ted on tk Ion, (I-stroke spudding motion. It is 

important that enough weight bc at txhcd to the surge plunger to make it 

drop readily on the downstroke . A drill stem or hc~y string of pipe is usu;~IIy 

found adequate for this purpose. 

Surging should be started s!owly. gradually increasing the s,eed but 

keeping within the limit at which the plunger will rise and fill smoothly. 

Surge for several minutes. noting the speed. stroke and time for this initial 

operation. Withdraw the plunger. lower the bailer or sand pump into the well 

and after checking the depth of sand xxumulatcd in the screen. bail the sand 

out. Repeat the surging operation. compxin, u the quantity of sand with that 

hr,\,.nirt 

v.\tui;l., in ini:ial!y. Bail W: the sand and repeat the surging and bdiling 

operaitons until little or IIU sand is pulled into the well. The time should be 

increased for each successive period of surging as the rate of entry ~)t‘ sand 

into the well decreases. The sand-pump typt‘ of bailer dcscribcd earlier in Chapter 

5 is generally Pdvored fix rt‘movin, ~1 sand _ during dcvrtopment work.

Static water :evel 

-m----.-e 

Solid surge plunger 

+- Well casing 

+- Well screen 

- Sand and silt 

in water 

Fig. 6.5 SOLID-TYPE SURGE PLUNG 

ER READY FOR USE IN DE- 

VELOPING A -gELi.. D&X 

STROKE FORCES WATER 

OUTWARD INTO SAND FOR- 

MATION. UPSTROKE PULLS 

IN WATER, SILT AND FINE 

SAND THROUGH SCREEN. 

100 

T he valve-type surge phryer 

differs from the solid-type surge 

plunger in that the former carries 2 

number of small portholes through 

the plunger which are covered by 

soft valve leather. In Fig. 6.6 the 

valve leather is raised to indicate 

one of the six portholes which are 

spaced at equal distances around 

the circumference of the plunger. 

Valve-type surge plungers are op 

erated in a similar manner to solid 

plungers. They pull water frum the 

aquifer ;,lto the well on the up- 

stroke and, by allowing some of the 

water in the well to press upward 

through the valves on the down- 

stroke. produce a smaller reverse 

flow in the aquifer. This creation of 

a greater in-rush of water to the 

well than out-rush during the 

surging operation is the principal 

and most important feature of this 

type of plunger. The valve-type 

surge plunger. because of this fea- 

ture, is particularly suited to use in 

developing wells in formations with 

low permeabilities, since it ensures 

a net flow of water into the well 

rather than out of it. A net outward 

flow can result in the water moving 

upwards to wash around the out- 

side of the casing since the low 

permeability of the aquifer will not 

permit flow read.ily into it. Washing 

around the outside of the casing 

could cause caving of the upper 

formations and thus create very dif- 

ficult problems. 

An incidental benefit gained 

from the use of this type of plunger 

is the accumulation of water above 

the plunger ;;:ith the eventual dis- 

charge of some water, silt and sand 

over the top of the well. The valves 

in effect produce a sort of pumping 

action in addition to the surging of

the well and thus reduce the 

number of times it is necessary to 

remove the plunger to bail sand out 

of the well. 

Surge plungers can also be op 

erated within the screen. This may 

be desirable in developing wells with 

long screens. By operating the phmger 

within the screen, the surging 

action can be concentrated at chosen 

levels until the well is fully developed 

throughout the entire length 

of the screen. The surge plungers 

should. for iuch use, be sized to pass 

freely through the screen and its 

Fig. 6.6 TYPICAL ?!!!z!~-T~!$ 

SURGE PL! JNtiEK WIIH 

VALVE LEATHER RAISED 

TO SHOW ONE OF SIX PORT- 

HOLES. 

fittings and not form a close fit in 

them, as is the case when operating 

within the well casing. Special care 

must be exercised when surging 

within the screen to prevent the 

plunger from becoming sand-locked 

by the settling of sand above it. For 

this reason the use of plungers within 

experienced drillers. 

screens should only be attempted by 

Care must also be exercised when using surge plungers to develop wells in 

aquifers containing many clay streaks or clay balls. The action of the plunger 

can, under such conditions, cause the clay to plaster over the screen surface 

with a consequent reduction rather than increase in yield. In addition, surging 

of the part]y or wholly plugged screen can produce high differential 

with a resulting collapse of the screen. 

pressures, 

Backwashing 

Hjg~-ve/~city jetting or the backwashing of an aquifer with high velocity 

jets of water directed horizontally through the screen openings is generally 

the most effective method of well development. The principal items of equipment 

required are a simple jetting tool . a high pressure pump, the necessary 

hose, piping, swivel and water tank or other source of water supply. 

A simple form ofjetting tool for use in small Web is shown in Fig. 6.7, An 

appropriately sized coupling with a steel plate welded over one end is screwed 

to a I-, l-1/2- or 2-inch pipe. Two to four 3/ 16- or l/4-inch diameter holes, 

equally spaced around the circumference are drilled through the full thicknesses 

of the coupling and the jetting pipe at a fixed distance along the 

coupling 

i,;iir:,lp~ -c.,---from 

the near surface of the steel plate. Better results would be 

_- $I ‘~ nn,LJerl-b~ ‘ + =ixy- -‘---gd nozzles are used instep,’ + .’ .I_*.: ‘.I::...: 

* “. l ..W “.Laih.,L u.v,ru 

ho& shown but the latter are acceptably effective. Any of the above mentioned 

sizes -would be suitable for use in a 4-inch well but the 2-inch or 

T-T/2$rch tooi would be preferable. The I-l/Zinch tool can also be used in a 

3~mch web while the l-inch tool is recommended for use in a 2-inch well. 

101

The procedure is to lower the tool on the jetting pipe to a poini near the 

botrom of the screen. The upper end of the pipe is c’onnt’cttxl through a 

swivel and host to the dis&ttrge end of a high prtxure pump such 2s the mud 

pump used for hydrtmlic rotary drilling. The pump should hc capable of 

opsratin~ at 3 pressure of at least IW pounds per squart‘ inch (psi) and 

preferably at about 150 psi while delivering II) to 12 gallons per minute 

(gpm) for each Z/ 1 h-inch nozr.te or lh tu 20 gpm for each I /it-inch nuzzle on 

the tool. For example. :L tool with two .S/ I Gnch diamttter nozzles would 

require a pumping rate of about 20 to 24 gprn. while ;i tr;ol with three 

l/4-inch diameter nozzles would require ;i pumping rate of 4X to hO gpm. 

While pumpin, u water through the nozzles and screen into the formation, t hc 

jetting tiara is slowly rotttted. thus washing ;mcl developing the formation near 

the bottum of the well screen. The jet tin, 0 tool is then raised at intervals of a 

few inches and the process repeated ur?til the entire length of screen has been 

backwashed and fully developed. 

Where possible. it is very desirable to pump the well at the same time as 

the jetting operation is in progress. This may be done in a 4-inch well if ;I 

/ 

Jetting pipe 

Coupling 

sja!i” or IA” 

holes 

. Steel plate, 

welded to 

coupling 

i-g* 6:7 SIMPLE TOOL FOR DEVEL- 

OPING WELL BY HICH- 

VELOCITY JETTING METH- 

I-I/_‘-inch jetting pipe is used. thus 

permitting 9 small suet ion pipe to 

be lowered alc:ng side of it in the 

well. The static water level must bc 

near enough :o the surface to per- 

mit pumping by suction lift. By 

pumping more water out ~1‘ the 

well than is added by jetting. flow 

will bt induced into the well from 

the aquifer, thus bringing the for- 

marion material. loosened by the 

jetting, into the well and out of it 

with the discharged water. This 

speeds up the development process 

and makes it more efficient. 

The high-velocity jetting method 

is more effective in wells con- 

structcd with continuous-slol type 

well screens. The greater percentage 

of open area of tl;is type of screen 

permits a more effective use of the 

energy of the jet in disturbing and 

loosening formation material rather 

than in being dissipated by merely 

impinging upon the solid areas of 

slotted pipe (Fig. 6.X). 

Jetting is the inoFt cl‘l‘t&ive of 

development methods because the 

energy of the jets is concentrated 

over small areas at any particular

Fig.6.8 GREATER PERCENTAGE OF OPEN AREA IN CONTINUOUS-SLOT 

SCREENS PERMIT3 BETTER DEVELOPMENT BY HIGH-VELOCITY JET- 

TING THAN IS POSSIBLE WITH SLO’ITED PIPE. 

time and every part of the screen can be selectively treated. Thus uniform and 

complete development is achieved throughout the length of the screen. The 

method is also relatively simple to apply and not too likely to cause trouble 

as a result of over-application. 

Another backwashing method ojf deveiopment suitable for use in small 

wells is one which uses a centrifugal pump with the suction hose connected 

directly to the top of the well casing and carrying a gate valve on the dis- 

charge end. The procedure simply involves the periodic opening and closing 

of the discharge valve while the pump is in operation. This creates a surging 

effect on the well. The process is continued until the discharge is clear and 

sand-free. The method is only applicable where static water levels are such as 

to permit pumping by suction lift. Some damage can be caused to the pump 

through the wearing of its parts by the sand pumped through it. particularly 

if in large quantities. The use of the pump to be pe:manently installed at the 

well is, therefore, not recommended for use in development of a well by this 

method. 

Development of Gravel-Packed Wells 

Development of gravel-packed wells is aimed at removing the thin skin of 

relatively impervious material which is plastered on the wall of the hole and 

sandwiched between the natural water-bearing formation and the artificially 

placed gravel. 

The presence of the gravel envelope creates some difficulty in accom- 

plishing the job. Success depends upon the grading of the gravel, the method 

of development and the avoidance of an excess thickness of gravel pack. The 

jetting method, because of its concentration of energy over smaller areas, is 

usually more effective than the other methods in developing gravel-packed 

I03

wells. The thinner the gratlel pack, the more likely is the removal of all of the 

undesirable material, including any fine sand and silt. The use of dispersing 

agents (described immediately below) such as polyphosphates effectively 

assist in loosening sift and clay. 

Dispersing Agents 

Dispersing agents, mainly polyphosphates, are added to the drilling fluid, 

backwashing or jetting water, or water standing in the well to counteract the 

tendency of mud to stick to sand grams. These agents act by destroying the 

gel-like properties of the drilling mud and dispersing the clay particles, thus 

making their removal easier. Sodium hexametaphosphate is probably the best 

known of these chemical agents. though tetra sodium pyrophosphate, sodium 

tripolyphosphate and sodium septaphosphate are also effectively used in 

well development. These agents work effectively when applied at the rate of 

half a pound of the chemical to every LOO gallons of water in the well. The 

mixture should be allowed to stand for about one hour before starting devel- 

opment operations. 

WELL DISINFEC-HON 

Disinfection is the fmal step in the completion of a well. Its aim is the 

destruction of ah disease-producing organisms introduced into the well during 

the variotis construction operations. Entry of these organisms into the well 

can occur through contaminated drilling water, on equipment, materials or 

through surface drainage into the well. All newly constructed wells with the 

possible exception uf flowing artesian wells should. therefore, be disinfected. 

WeIls should also be disinfected after repair and before being returned to use. 

The water from flowing artesian wells is generally free from contamination by 

disease-producing organisms after being allowed to flow to waste for a short 

while. If. however, analyses show persistent contamination, then the well 

should be disinfected as described later in this chapter. 

Because of the problems of testmb for specific disease-producing orga- 

nisms, of which there may be several types present in water, coliform bacteria 

are used as indicators of the possible presence of disease-producing organisms 

of human or animal origin in water. Disinfection is, therefore, considered 

complete when sampling :tnd testing of water show the presence of no 

coliform bacteria. Sampling and testing should be undertaken by experienced 

personnel from a health agency or recognized laboratory. 

The well should be cleaned. as thoroughly as possible, of foreign sub- 

stances such as soil, grease and oi! before disinfection. Disinfection is most 

conveniently achieved by the addition of a strong solution of chlorine to the 

well. The contents of the weLl should then be thoroughly agitated and al- 

lowed to stand for several hours and preferably overnight. Care should also be 

taken io wash all surfaces above the water level in the well with the disin- 

fecting solution. Foliowing this. the well zhould be pumped icrtg enough to 

change its contents several times and so flush the excess chlorine out of it. 

Calcium hypochlorite is the most popular source of chlorine used in the 

disinfection of wells. It is sold in chemical supply and some hardware stores 

in the granular and tablet form containing 70 percent of available chlorine by 

104

weight. It is fairiy siable when dry, retaining 90 percent of its original 

chlorine content after one year’s storage. When moist, it loses its strength and 

becomes quite corrosive. It should, therefore, be stored under cool, dry con- 

ditions. Enough calcium hypochlorite should be added to the water standing 

in the well to produce a solution of strength ranging from 50 to 200 parts per 

million (ppmj by weight and usually about 100 ppm. A solution of approx- 

imately 100 ppm chlorine can bc obtained by adding 2 ounces or 4 heaped 

tablespoons of calcium hypochlorite (containing 70 percent of available 

chlorine) to every 100 gallons of water standing in the well. Usually for 

convenience of application, a stock solution is made by mixing the caicium 

hypochlorite with a small amount of water to form a smooth paste and then 

adding the remainder of 2 quarts of water for every ounce of the chemical. 

Stir the mixture thoroughly for 10 to 15 minutes before allowing to settle. 

The clearer liquid is then poured off for use in the well. A gallon of this 

solution. when added to 100 gallons of water in the well, produces a solution 

of strength approximately equal to 100 ppm of chlorine. The stock solution 

should be prepared i!~ a thoroughly cleaned glass, crockery or rubber lined 

container. Metd containers become corroded and should be avoided. Stock 

solutions should be prepared to meet immediate needs only since they lose 

strength rapidly unless properly stored in tightly covered dark glass or plastic 

containers. Storage of the chemical in the dry form is much more desirable. 

Sodium hypochlorite may be used in the absence of calcium hypochlorite. 

This chemical is available only in liquid form and can be bought in strengths 

of up to about 20 percent available chlorine. In its most common form, 

household laundry bleach, it has a stJ-c?ngth of about 5 percent of available 

chlorine. A stock solution of equivalent strengh to that made from calcium 

hypochlorite and described in the previous paragraph can be made by dilcting 

commercial bleach with twice as much water. This stock solution should also 

be added to the well at the rate of one gallon to every 100 gallons of water in 

the well. 

Flowing artesian wells are disinfected, when necc;zT, hy !cJwering a per- 

forated container, such as a short length of tubing capped at both ends, Zlzi? 

with an adequate quantity of dry calcium hypochlorite to the bottom of the 

well. The natural up flow of water in the well will distribute the dissolved 

chlorine throughout the full depth of the well. A stuf’ig box can be used at 

the top of the well to partially or completely restrict the flow and so reduce 

the chiorine losses. 

105

Wells, like all other engineering structures. need regular, routine main- 

tenance in the interest of a continuous high level of performance and a 

maximum useful life. The general tendency towards the maintenance of wells 

is one that can best be described as “out of sight - out of mind.” Con- 

sequently, very little or no attention is paid to wells after completion until 

problems reach crisis levels, often resulting in the complete loss of the well. 

The importance of a routine maintenance program to the prevention, early 

detection and correction of problems that reduce well performance and use- 

ful life cannot be overemphasized. A routine maintenance program can pay 

handsome dividends to a well owner and will certainly result in long-term 

benefits that exceed its cost of implementation. 

FACTORS AFFECTING THE MAINTENANCE OF WELL PERFORMANCE 

The factors affecting the maintenance of well performance or yield are 

numerous. Care should be taken to differentiate between those factors asso- 

ciated with the normal wearing of pump parts and those directly associated 

with changing conditions in and around the well. A perfectly functioning 

well, for example, can show a reduced yield because of a reduction in the 

capacity of the pump due to excessively worn parts. On the other hand, the 

excessive wearing of pump parts may be due to the pumping of sand entering 

the weII through a corroded weli screen. It is also possible for corrosion to 

affect only the pump, reducing its capacity, but to have little or no effect on 

a properly designed well. 

The hydrologic conditions of some aquifers are such that the static water 

level drops graduaIly when. wells are pumped continuously. While this results 

in reduced yields unless pumping levels are also correspondingly lowered, it is 

not an indication of a failure of the well itself, necessitating repairs or treat- 

ment of any forin. 

Most commonIy, a decrease in the capacity of a well results from the 

clogging of the well screen openings and the water-bearing formation imme- 

diately xound the well screen by incrusting deposits. These incrusting depos- 

its (Fig. 7.1) may be of the hard cement-like form typical of the carbonates 

and sulfates of calcium and magnesium, the soft sludge-like forms of the iron 

and manganese hydroxides or the geIatinous slimes of iron bacteria. Iron may 

also be deposited in the form of ferric oxide with a reddish-brown, scale-like 

appearance. Less common is the deposition of soil materials such as silt and 

cIay. 

106

A B C 

Fig. 7.1 FORMS OF INCRUSTATION. 

__ L 

A. Hard cement-like deposits of calcium and magnesium carbonates. 

B. Gelatinous slime deposits typical of iron b~t4~ 

C. Scale-like deposits of iron oxide completely plugging screen openings. 

The deposition ot ctlrbomrtes and the compounds of iron and munganese 

can often be traced to the release of carbon dioxide from the water. The 

capacity of water to frofd carbon dioxide varies directly with the pressure 

the higher the pressure. the greater tfre quantity of carbon dioxide fleld. 

Pumping of a we11 reduces the pressure in and near the well. thus allowing the 

escape of carbon dioxide to the atmosphere and altering tire chemical quality 

of the water in such ;t manner as to cause the precipitation of carbonate and 

iron deposits. 

A change in velocity is another factor that can result in the precipitation 

of iron and manganese hydroxides. This too occurs at 2nd near the well 

screen where the velocity of the slowly flowing water is suddenly increased 

on entry to the well. 

PLANNING 

The pianning of well maintenance procedures should be based on a system 

of good record keeping. The preceding paragraphs have indicated that the 

problems that result in reduced well yields occur at and around the well 

screen and very much out of sight. The analysis of good records must, therefore, 

be relied upon as the source of problem detection in weflc. There can be 

no substitute for the keeping of good records. 

Among the records kept sfroufd be pumping rates. drawdown. total hours 

-_-._ 

d opcrztion, puwt~r consumption and water quafity analyses. Pumping rates 

and drawdown are particularly useful in determining the specific capacity (discharge 

per foot of drawdown) which is the best indicator of existing problems 

in a well. The specific capacities of wells should be checked periodically and 

compared with previous values including those immediately after completion 

107

of the wells to determine whether significant reductions have taken place. A 

significant reduction in the specific capacity of a well could often be traced to 

blockage of the well screen and the formation around it, most likely by 

incrusting deposits. As stated earlier. a reduction in the pump discharge 

would not by itself be evidence of a reduced capacity of the well. If, however, 

the drawdown in the well does not show an equal reduction, then the specific 

capacity will be reduced, thus indicating the probability of an incrustation 

problem. 

Power consumption records also provide valuable evidence of the existence 

of problems in wells. Should there be an increase in power consumption, not 

accompanied by a corresponding increase in the quantity of water pumped, 

then a problem is possible in either the pump or the well. Should an mvesti- 

gation show no problems in the pump nor appreciable increase in the dynam- 

ic head against which the pump has been operating, then it is most likely that 

a problem exists in the well and that the problem is causing an increased 

drawdown. A check on the drawdown should then be undertaken to verify 

the deduction and the well checked for incrustation. 

Since there would be no incrustation in the absence of incrusting chem- 

icals in the water. the value of chemical analyses of well water is self-evident. 

Such analyses are more useful as problem indicators if undertaken regularly. 

They indicate the type of incrustation that might occur and the expected rate 

of deposition in the well and its vicinity. The quality of some well waters 

changes slowly with time and orl!y regular routine analyses would indicate 

such changes. 

In wells, the waters of which are known to be incrusting, the frequency of 

observations of all types should be as high as possible and consistent with the 

use to which the water is being put. Observations should be made muzh more 

frequently at wells serving a community than at a private home-owner’s well, 

since more people are dependent on the community wells. Power con- 

sumption. well discharge, drawdown, operating hours and other such observa- 

tions are often made daily on community wells and may even be done on a 

continuous basis. Chemical analyses on such wells may be done on an annual, 

semi-annual or quarterly basis, as conditions warrant them. Observations on 

home-owner’s weils are usually much less frequent but should, nevertheless, 

be undertaken regularly. 

MAINTENANCEOPERATIONS 

Maintenance operations should not be deferred until problems assume 

major proportions as rehabilitation then becomes more difficult and some- 

times impossible or impracticable. incrustation not treated early enough can 

so clog the well screeri and the formation around it that it becomes extremely 

difficult and even impossible to diffuse a chemical solution to all affected 

points in the formation. Any attempts at rehabilitation would then prove 

unsuccessful. 

No methods have yet tzen developed for the complete prevention of 

incrustation in wells. Various steps 2zn be taken to delay the process and 

reduce the magnitude of its effects. Among these are the proper design of

well screens and the reduction of pumping rates, both aimed at reducing 

entrance velocities into screens and drawdown in wells. For example, it may 

be worthwhile to share the pumping load among a larger number of wells in 

order to reduce the rate of incrustation. Howel:er, the ultimate or fmal solu- 

tion will be in a regular cleaning program. incrusting wells are usually treated 

with chemicals which either dissolve the incrusting deposits or loosen them 

from the surfaces of the well screen and formation materials so that the 

deposits may be easily removed by bailing. 

Acid Treatment 

Acid treatment refers to the treatment of a well with an acid, usually 

hydrochloric (muriatic) acid or sulfamic acid for the removal of incrusting 

deposits. Both of these acids readily dissolve calcium and magnesium carbon- 

ate, though hydrochloric acid does so at a faster rate. Strong hydrochloric 

acid solutions also dissolve iron and manganese hydroxides. The simultaneous 

use of an inhiiitor serves to slow up the tendency of the acid to attack steel 

casing. 

Wells are sometimes treated with acid in preparation for the withdrawal of 

a screen either for re-use elsewhere or in the same well. For example, it may 

be desirable to recover a screen that is in good condition from a well whose 

casing has been corroded beyond usefulness. Or, a screen may be recovered 

for more effective treatment against incrustation thBn can be achieved in the 

well. In either case, a preliminary acid treatment to dissolve some of the 

incrusting deposits will make it much easier to pull the screen. 

Hydrochloric acid is usually available in three grades from chemical supply 

shops. The strongest grade, designated as the 27.92 percent grade, should be 

used. It is sold in either glass or plastic carboys containing about 12 gallons 

each. If inhibited acid cannot be obtained, unflavored gelatin added at the 

rate of 5 to 6 pound? ?o every 100 gallons of acid will prevent serious damage 

to steel casing. 

Hydrochloric acid should be used at full strength. Each treatment us&&y 

requires l-112 to 2 times the volume of water in the screen. This provides 

enough acid to fill the screen and additional acid to maintain adequate 

strength as the chemical reacts with the incrusting materials. Fig. 7.2 illus- 

trates a method of placing acid in a well. Acid is introduced within the screen 

by means of a wide-mouthed funnel and 3/4- or l-inch black iron or plastic 

pipe. Acid is heavier than water which it tends to displace but with which it 

also mixes readily to become diluted. When used in long screens, acid should 

be added in quantities sufficient to fill 5 feet of the screen and the conductor 

pipe raised 5 feet after pouring each quantity. 

The acid solution in the well should be agitated by means of a surge 

plunger or other suitable means for 1 to 2 hours following which the well 

should be bailed until the water is relatively clear. The driller usually can 

detect an improvement in the yield of the well while running the bailer. The 

well may, however, be pumped to determine the extent of improvement. If 

this is not as expected, then the treatment may be repeated using a longer 

period of agitation before bailing. A third treatment may even be undertaken. 

The procedure is sometimes varied to alternate acid treatment and chlorine 

109

Black iron or plastic 

pipe 


Acid placed inslde 

well screen 

Fig.7.2 ARRANGEMENT FOR 

INTRODUCING ACID IN- 

SIDE WELL SCREEN FROM 

BOTTOM UPWARDS. 

treatment (described later in this 

chapter,), repeating the alternate 

treatments as many times as it 

appears that beneficial results are 

being obtained. The chlorine helps 

to remove the slime deposited by 

iron bacteria. 

Sulj~mk acid can be obtained as 

a dry granular material which pro- 

duces a strong acid solution when 

dissolved in water. It offers a num- 

ber of advantages over hydrochloric 

acid as a means of treating incrusta- 

tion in wells. It can be added to a 

well in either its original granular 

form or as an acid solution mixed on 

site. Granular sulfamic acid is non- 

irritating to dry skin and its solution 

gives off no fumes except when 

reacting with incrusting materials. 

Spillage, therefore, presents no haz- 

ards and handling is easier, cheaper, 

and safer. It also has a markedly 

less corrosive effect on well casing 

and pumping equipment and is safe 

for use on Everdur and type 304 

stainless steel well screens. These 

advantages tend to offset its higher 

cost than inhibited hydrochloric 

acid. Sulfamic acid dissolves calcium 

and magnesium carbonates to pro- 

duce very soluble products. The 

reaction is, however, slower than 

that using hydrochloric acid and a 

somewhat longer contact period 

in the well is required. 

Sulfamic acid is usually added to 

wells in solution form using a black 

iron or plastic pipe as described for 

the application of hydrochloric acid. 

Ten gallons of water dissolve 14 to 

20 pounds of the granules depending 

upon the temperature of the water. 

The granular material itself can, 

however, be poured into and mixed 

with the water standing in the well. 

The water must be agitated to en-

sure complete solution of the acid. The quantity of acid added in this case 

should be based on the total volume of-water standing in the well and not on 

that in the screen only. as is the case if the acid is applied in solution form. An 

excess of the granular material may be added to keep the solution up to 

maximum strength while it is being used up through reaction with the tncrust- 

mg material. The addition of a low-foaming, non-ionic wetting agent im- 

proves the cleansing action to some extent. 

A number of precatctims must be exercised in using any strong acid solu- 

tion. Goggles and water-proof gloves should be worn by all persons handling 

the acid. When preparing an acid solution, always pour the acid slowly into 

the water. In view of the variety of gases, some of them very to.xic, produced 

by the reaction of acid with incrusting materials, adequate ventilation should 

be provided in pump houses or other confined spaces around treated wells. 

Personnel should not be allowed to stand in a pit or depression around the 

well during treatment because some of the toxic gases such as hydrogen 

sulfide are heavier than air and will tend to settle in the lowest areas. ,Zfter a 

well has been treated, it should be pumped to waste to ensure the complete 

removal of all acid before it is returned to normal service. 

Chlorine Treatment 

Chlorine treatment of wells has been found more effective tha:: acid treat- 

ment in loosening bacterial growths and slime deposits which often 

accompany the deposition of iron oxide. Because of the very high concen- 

trations required. 100 to 200 ppm of available chlorine, the process is often 

referred to as shock treatmetrt with chlorine. Calcium or sodium hypochlorite 

may be used as the source of cfllorine as described for the disinfection of 

wells in Chapter 6. The chlorin e soltuion in the well must be agitated. This 

may be done by using the high-velocity jetting technique (see “Well Develop 

ment,” Chapter 6) or by surging with a surge plunger or other suitable 

techniques. The recirculation provided with the use of the jetting technique 

greatly Improves the effectiveness of the treatment. 

The treatment shotild be repeated 3 or 4 times in order to reach every part 

of the formation thet may be affected, and it may also be alternated with 

acid treatmeni, the latter being performed first. 

Dispersing Agents 

Polyphosphates, or glassy phosphates as they are commonly called, effec- 

tively disperse silts, clays and the oxides and hydroxides of iron and man- 

ganese. The dispersed materials can be easily removed by pumping. In addi- 

tion, the polyphosphates are safe to handle. They find considerable applica- 

tion, therefore, in the chemical treatment of wells. 

For effective treatment, 15 to 30 pounds of polyphosphate are added lo 

every 100 gallons of water in the well. A solution is usually made by SUJ- 

pending a wire basket or burlap bag containing the polyphosphate in a tank 

of water. Abo,ut a pound of calcium h; pochlorite should be added for every 

IOU gallons of water in the well in order to facilitate the removal of iron 

bacteria and their slimes and also for disinfection purposes. After pouring this 

polyphosphate and Eypochlorite solution into the well, a surge plunger or the

,&ting technique is used to agitate the water in the well. The recirculation of 

the solution with the use of the high-velocity jetting technique greatly im- 

proves the effectiveness of the treatment. Two or more successive treatments 

may be used for better results. 

WELLPOINTINSTALLATPONINDUGWELLS 

Dug wells are holes or pits dug by hand or machine tools into the ground 

to tap the water table. They are ususclly 3 to 20 feet in diameter, IO to 40 

/ 

Asphaltic seal 

Fig. 7.3 DUG WELL. Fig. 7.4 DUG WELL OF FIG. 7.3 

CONVERTED TO SAFER 

AND MORE PRODUCTIVE 

TUBULAR WELL WlTH 

DRIVEN WELL POINT AS 

SCREEN. 

feet deep and lined with brick, jiune, tile. wood cribbing or steel rings to pre- 

vent the walls from caving (Fig. 7.3). They depend entirely on natural seepage 

from the penetrated portion of water-bearing formations for their yield of 

water.

This type of well is at a disadvantage on two scores when compared with 

tubular wells of the type so far described. Firstly, dug wells are much more 

diffcu!t to maintain in a sanitary condition. Secondly, their yields are very 

low, because they do not penetrate very far into the water-bearing formation 

and cannot be developed in a similar manner to screened wells. 

Dug wells usually can be made much safer and more productive by driving 

well points into the water-bearing formation and thus converting them into 

tubular wells. A properly developed well with a short length of 2” drive- 

point screen will usually produce water at 3 much higher rate than can be had 

from a dug well several feet in diameter. The annular space between the casing 

of the driven well and the wall of the existing well shouid be back-filled with 

a puddled clay or other suitable material. The sanitary precautions with re- 

spect to the completion of the upper terminal of 3 well (described in Chapter 

4) should be observed. The wall of the existing dug well may be cemented 

prior to back-filling. A converted dug well is illustrated in Fig. 7.4. 

113

Drilling and completing a well form only part of a solution to the 

problem of getting water in sufficient quantity where it is desired for use. 

Small wells are generally used for supplying water to a horn&:, a group of 

homes or other such limited consumers of water as a small factory. The water 

is usually required for use at elevations somewhat higher than tkose at which 

the water is found in the well and, often, some appreciable distance from the 

well. Therefore, some means must be found of lifting the water from a well 

and forcing it through pipes at suitable velocities to the points and elevations 

of use. Tfke exception to this general statement is the case of the flowing 

artesian well, which has a sufficiently high discharge at an adequate pressure 

to meet the limited demands of one or a few small holmes without any 

external help. Generally, however, help is needed, and this is provided in the 

form of a suitable pump. It is important that the pump be a suitable cjne, 

selected on the basis of the demand to be fulfilled and the capacity of the 

well to yield water. It cannot and must not be just any pump, as it is then 

unlikely that the needs will be met. Pump selection is discussed later in this 

chapter. 

Pumps do not develop power of their own. Some ex!ernal source of power 

must be provided to drive a pump and so cause it to lift and force water from 

one point to another. The source of power may be the man who uses his hand 

to operate 3 lever upward and downward or forward and backward or who 

turns a wheel connected to the pump. In this case, the pump is said to be 

manually operated or hand driven. The power source may also be a windmill, 

an electric motor or an engine which burns a fuel such as gasoline or diesel 

oil. A very common error is not being able to distinguish between a pump and 

its motive or driving force, particularly when that force is an engine or motor 

directly coupled to the pump. Care should be taken to avoid this, 3s the 

problems of pumps, engines and motors are very different and need different 

approaches to solve them. 

The action of most pumps can be divided into two parts. The first is the 

lifting of the water from some lower level to the pump intake or suction side 

of the pump. The second is concerned with applying pressure to the water in 

the pump to force the water to its destination, 

SU&MZ lift: Consider an openended tube which is suspended vertically in 

a large container of water (Fig. 8.IA). Since the water both within and 

without the tube is exposed to the atmosphere, the only external force acting 

114

Atmospheric 

pressure 

?- 

A 

Atmospheric 

Zero pressure 

(absolute) 

Fig. 8.1 A. ATMOSPHERIC PRESSURE THROUGHOUT. NO DIFFERENCE IN 

WATER LEVELS. 

B. PRESSURE IN TUBE REDUCED TO ZERO ATMOSPHERES (TOTAL 

VACUUM). WATER LEVEL W TUBE RISES TO APPROXIMATELY 

34 FT. 

on both surfaces is that due to atmospheric pressure. The pressure on the 

water surface being the same within and without the tube, there will be no 

difference in the water levels (assuming a wide enough tube that capil!ary 

forces may be neglected). if, however, the pressure on the water surface 

within the tube is reduced below atmospheric pressure while that outside of 

the tube remains at atmospheric pressure, then water will rise in the tube 

until th,? weight of the column of water inside the tube exerts a pressure 

equal to the original pressure difference on the water surfaces within and 

without the tube. The maximum height to which this column wilt rise occurs 

when the pressure on the water surface within the tube is reduced to zero 

atmospheres (absolute). The water column will then be exerting a downward 

pressure equal to the atmospheric pressure (Fig. 8.1B). Atmospheric pressure 

at sea level is approximately equivalent to a column of water 34 feet high, 

and this is the height to which the water will rise in the tube. Atmospheric 

pressure decreases as the altitude or height above sea level increases. 

Accordingly, the maximum height to which the water column can be made to 

rise also decreases with increase of altitude. 

The term SUCY~M is used to describe ihc amount by which the pressure in 

the tube is reduced below atmospheric pressure. Suction can be applied to the 

tube by operating a pump attached to the top end of the tube. The level to 

which the water rises within the tube above the water surface in the large

container is termed the srrctiorl hji. AL pump. in order to pump water. must be 

able to create enough suction to lift the water in the tube to the level of the 

suction end of the pump. In Fig. 8.2, t!le well casing represents the larger 

container while the suction pipe of the pump takes the place of the tube. 

I- 

Pump 

/ 4 I 

Atmospheric w 

PI I 

./ Wall casing 

water bfsl 


Fig.8.2 PRINCIPLES OF PL'MPINC 

AWATERWELL. 

Note- that the lifting of the water in 

the suet ion pipe must be ;ICCOII~- 

parlied by ;1 lowering of the water 

level in the well casing. The water 

level within the casing :lild the 

suction pipe before the pump 

created the suction lift is called the 

stuck rryater IwA The level in the 

well txing during pumping is the 

privrpirlg bvater level. 

In theory then, a pump, by 

creating zero pressure (absolute) or 

9 total vacuum within its suction 

pipe. should be capable of ;1 suction 

lift of ~ppruximately 34 feet of 

water at sea level and somewhat less 

3t higher altitudes. In practice, 

however. this is not achieved. as 

pumps are not 101) percent efficient. 

and other fxtors such ;LS 

water temperature and friction or 

resistance to flow in the suction 

pipe reduce the suction lift. At sea 

level. the best designed pu171ps usually 

achieve ;I suction lift of about 

-- ‘5 feet. while the suction lift of an 

average pump varies from 15 to 

about IX feet. Should it be neces- 

sary to lift water in ;t well from a 

level 25 feet or more below ground 

surfxe. some mc;ms must bc found 

of lowering the pump into the well 

and ::ither completely submerging 

the pump in the water or taking it 

near enough to the water surface to 

pertnit suction lifting of the water. 

This iimitiq suction lift is used to classify pumps into surface-type or shalPow 

well pumps and deep well pumps. SurjIzce-type pumps are those pumps which 

are placed at or above ground jurfrtce rind are iimited to lifting water by 

suction fronl a dzpth . . ..-...II-. -.. .--- l L . .._. . . 

uxkmy IIU ;;lvdtCi iihui LL b iiiit 25 fe?i belo’* the ground 

surface. Deep \treI! prmps are those pumps which arc placed within the well 

and are used for extracting 

I.elow the ground surface. 

water frotn depths generally in L’XWSS of 25 feet

.4nother very common classification of pumps divides them into two main 

types based on the mechanical principles involved. These two types are 

comtant dispkemertt tend wriable displacemerlt pumps. 

CONSTANT DISPLACEMENT PUMPS 

Constant displacement pumps are so designed that they deliver substan- 

tially the same quantity of water regardless of the pressure head against which 

they are operating. That is to say. the rate of discharge is essentially the same 

at low or high pressures. However, the input power or driving force varies 

directly in proportion to the pressure in the system and must be doubled ii 

the pressure is doubled. There are three main designs of this type of pump 

which are commonly used in water wells. These are reciprocatirlg piston 

pumps, rotaop pumps and helical rotor pumps. 

Reciprocating Piston Pumps 

Reciprocating piston pumps, the most common type of constant displace- 

mcnt pump. use the up and down or forward and backward (reciprocating) 

movement of a piston or plunger to displace water in a cylinder. The flow in 

and out of the cylinder is controlled by valves. The basic principles and steps 

in the operation of a single-acting piston pump are illustrated in Fig. 8.3. The 

Forward Stroke 

Reverse Stroke 

Closed 

II 

Dischargei 

‘Open 

Forward Stroke 

Fig. 8.3 PRlNCIPLES OF A SINGLE-ACTING RECIPROCATING PISTON PUMP. 

(Adapted from Fig. 38, Water Supply For Rural Areas And Small Communi- 

fies, WHO !+Ionograph Series No. 42, 1959.)

plunger on the tijrward stroke p~~shes writer t‘rw~~ the c‘ylittdcr through tllc 

open dischye vltlve into the dischxge pipt‘ u tlilc at 111~ suw timt’ crcatins ;I 

suction behind it thttr ~~p~nj the foot valw ;md pc’rmits water to tlobv tllrou$1 

the suction pipe into the cylinder. ‘l‘hc ~‘t’vt’rst St:-ohc ctwtes ;I prcssurt2 

behind the piston in the cylinder. thus chin, 11 the foot valve and opcnilig the 

bucket vrtlves in the piston tu let water through to ttlt‘ discharge side ot‘ tllc 

piston. Continuous repetition of the for\i,xd and rcvc’lsc strokes of the piston 

results in 9 steady tlow at watt‘r out of the dishargc pipe. ‘fhc amount 01’ 

pressure developed by such ;t pump depetlds upw the power applied in 

operating the piston. Tht~se pumps art‘ manufxtured irl both the surt’vce (Fig. 

S-4) and deep well (Fig. S.5) typ t‘s and may be manually or enpinc operated. 

.4 m;~nutllly operated. 

pitcher pump. 

surP>c+type piston pump is c~~rnnnc~nly known ;1s ;I 

Fig. 8.5 DEEP WELL SINGLE-ACT- 

ING 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

I I‘) 

Helical Rotor Pumps 

Tilt helical rcjtor or screw-type 

purup is ;I Itlc~~it’i~a~i~~Il 01’ tilt2 

rotary type i)t’ cotlslaII t dispiscc- 

111cnt purrlp. 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- 

melItS of tile pump. Hclic;;! rotor 

puIllpS cm hc citficr 01’ tllc 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 in- 

verse 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 .are centrif~rlgal and@ pumps. 

Discharge 

Discharga 1 

Fig. 8.7 DOUBLE-ACTING, SEMI-ROTARY HAND PUMP. (From Deming Division 

of Crane Company. Salem. Ohio.) 

Centrifugal Pumps 

Centrifugal pumps are the most common types of pumps in general use. 

The basic principles of their operation can be illustrated by considering the 

effect of swinging a pail of water around in a circle at the end of a rope. The 

force that causes the water to press outward against the bottom of the pail 

rather than run out at the open end is known as the centrifugal force. 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 cen- 

trifugal pump. The pail and cover 

correspond to ihe casing of the 

pump, the discharge hole and in- 

take 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 

statw bmldod 

Fig.8.8 BEEP WELL ttEL.lc ;$?. 

‘ROTOR PUMP. 

weUs can be subdivided into two 

r,;ain types based on their design 

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 in- 

crease 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 trans- 

forming the velocity head into pres- 

sure head. 

The conditions of use dcterminc 

the choice between volute and tur- 

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

Fig. 8.9 VOLUTE-TYPE C’ENTRIFU- 

CAL PUMP. 

Dtffuser vane 

k:ig. 8.10 TURBINE-TYPE C’ENTRIFU- 

CAL PlJMP SHOWING (‘HAR- 

A~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 reduc- 

tion 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 

Stage 

Impeller 

Strainer 

Fig. 8.1 I THREE-STAGE LINESHAFT 

DEEP WELL TURBINE 

PUMP. 

I 23 

Venturi - 

Screen- 

- 

I- Grout 

seal 

-Return pipe 

- Ejector 

~ Foot valve 

t------Well casing 

Fig. 8.12 JFT PUMP. (Adapted from 

Fig. 13. MQFZUQ~ of Individual 

Water Supply Systems. Pub lit 

Health Service Publication No. 

24. 1962.)

pre y.,,:~ 1; +-.b to, rourT the nozzle. The centrifugal pump then picks up the 

flow,sendirlgpart ot’i! :1,-::

epas possible without removing the whole pump assembly from the well. 

Greater flexibility can also be achieved by the use of a dual right-angle drive 

head to which two engines, two electric motors or one engine and an electric 

motor can be coupled. This arrangement permits the use of a stand-by power 

/ 

Drive head assembly 

\ 

, Gasoline engine 

\ 

Flexible shaft coupling 

Prelubricatiori tube connected I 

to dimharoa aim \ 

Pipe column assembly 

Air line 

Pump bowl assembly 

Stages 

u 

Filler gage 

Discharge 

pipe 

Fig. 8.13 ENGINE DRIalEN, LINESHAFT DEEP WELL TURBINE PUMP. (Adapted 

y;5..Pig. 116, Wells, Deptiment of the Army Technical Manual TMS-297, 

source and continuous operation of the pump by one source while the other 

is being serviced or repaired. 

Lineshaft pump installations must, however, be enclosed in pump houses 

and, partly as a result of this, are usually more costly than submersible pump 

installations. The shafts and bearings of lineshaft pumps also provide many more 

125

Check valve 

Radial bearing 

lmpetfers 

Pump intake 

Seat 

Electric motor 

Pressure equal- 

izing tube 

Thrust and radial 

bearing 

Fluid chamber 

Fig.8.14 CLJT-AWAYVIEWOFASUB- 

MERSIBLE PUMP. Wrorn F. 

E. Myers & Bra. Company. 

Ashland, Ohio.) 

moving parts which are subject to 

both normal wear and that xcelera- 

ted by corrosion and abrasive sand 

particles. 

Submersible Pumps 

Submersible pumps, though 

built during the past SO yetus. have 

only been extensively used over the 

last IS years. The increase in use 

coincided with design impLove- 

ments in the submersible motors, 

electric cables and water-tight seals. 

These improvements made it possi- 

ble to achieve efficiencies compara- 

ble with those obtained from hne- 

shaft pumps and also long periods 

of trouble-free operation. The elin- 

ination of the long drive shaft (and 

multip!e bearings with it) has not 

only eliminated the wearing and 

maintenance problems associated 

with lineshaft pumps but has also 

reduced the problems created by 

deviations in the vertical alignment 

of a well. The use of submersible 

pumps also results in savings in in- 

stallation costs since pump houses 

are not usualiy required. The opera- 

tion of the motor at a depth of sev- 

eral feet in the well also considerably 

reduces noise levels. The entire pump 

and motor must, however, be with- 

drawn to effect repairs and to ser- 

vice the motor. The riced to do so, 

however, arises very infmquently. 

PRIMING OF PUMPS 

Friming is the name given to the process by which water is added to a 

pump in order to displace any air trapped in the pump and its suction pipe 

during shutdown periods. In other words, priming results in a continuous 

body of water from the inlet eye of the pump impeller downward through 

the suction pipe. Without this continuous body of water a centrifugal pump 

will not deliver water after the engine or motor has been started. Positive displacement 

types of pumps are less affected and need priming only to the extent 

necessary to seal Ieakage past pistons, valves and other working parts. 

The many devices and procedures used in obtaining and maintaining, a 

primed condition in pumps generally involve one or a combinaticn of the 

126

following: ( I) a foot-valve to retair water in the pump during shut-down 

periods, (2) a vent to perntit the t~aptt tit‘ trapped air. (-3) an ausilialy pump 

or other devics( pipe front an overhead tank) to fill the pump with water. (-I) 

use of a self-primin g tj,pe o1‘ construction ill the pump. Self-pl’inlirlg pumps 

usually have an ausiliary chamber integrated itlt~ the pump structure in selctt 

a way that the trapped air is exhausted as flte pump circulates the priming 

water. 

PUMP SELECTION 

The proper selection of a pump for installation ai a well involves the con- 

sideration of several factors. The followittg discusslon presents some c,f the 

more important factorsand particularly those which are very often overlooked 

ahd need to be emphasized. 

The first factor to be considered must of necessity be the yield of the well. 

So logical as this may seem. it is a Factor that is often overlooked in pbntp 

selection for small wells. Tltere is no way ot’ extracting more M2ter fiOlll a 

well than that determined by its maximum yield. It is, therefore. foolhardy 

to select a pump of greater discharge capacity t!tatl the w:ll will yield. Maxi- 

mum we/i yields are usually determined by test pumping. For small wells, 

test pumping need not involve more than tlte pumping of the well at a specific 

rate or series of rates for a period of time in excess of :lte likely service re- 

quirements. The records of the test catt then be used :u determine the specific 

capacity. 

With the knowledge of the specific capacity and tlie estimated water de- 

mands a suitable pumping rate can then be selected taking into consideration 

the provision of storage. Consideration may be given to the use of several hours 

of storage capacity and a high pumping rate in order to keep the number of 

pumping hours as low as possible. The advantages of so doing should be 

weighed against the use of a lower pumping rate for extended hours of pump- 

ing and the provision of lower storage capacity. The availability of electric 

power only for limited periods of the day or night would also influettce the 

decision. Having chosen a pumping rate, the expected drawdowtt in the well 

for that rate can then be estimated by dividing it by the specific capacit;l of the 

well. For example, a pumping rate of 30 gpm in a well with a specific capacity 

of 5 gpm/ft would create a drawdown of 30 divided by 5, that is. 6 feet. Adding 

the drawdown to the depth of the static water level below the ground surface 

gives the depth to the expected pumping water level. This dey:h to the pump 

ing water level is then used to choose between a surface-type ;Tump and a deep 

well pump. In so doing, it must be remembered Ihat :*easr)r-?; vari:ltions in the 

water table, extended pumping and interference from orher welis could cause 

the lowering of the pumping water level. Allowances should, therefore, be 

made for such possibilities where they are likely to occur. The use oi‘ deep 

well pumps would be indicated where the depth to the ptimping water level 

is 25 feet or more and the well is deep enough and large enough in diameter 

to accommodate a suitable pump. Surface-type pumps would otherwise be 

used with limited pumping rates if necessary. 

197

To storage 

ha 

I 

3 Power unit 

- Static udtkt level 

- Water kvel when 

pumping 

Submerged-intake 

installation 

Fig. 8.15 TOTAL PUMPING HEAD OF 

WATER WELL PUMP IN- 

CLUDES VERTICAL LIFT, 

h , PLUS FRICTION LOSSES 

IIt PIPE, hf, AND VELOCITY 

HIAD (may usually be neglect- 

. 

The next logical step is the 

estimation of the total pumping 

head which, with the pumping rate, 

determines the capaciry of the 

pump to be selected. The total 

pumping head, ht, can be estimated 

by adding the total vertical lift, he, 

from the pumping water level to 

the point of delivery of the water 

(Fig. 8.15) and the total friction 

losses, hf, occurring in the suction 

and delivery pipe. This estimate 

ignores the velocity head or head 

required to produce the flow 

through the system since this head 

can be expected to be negligible in 

most installations using small wells. 

The total vertical lift, he, includes 

the suction lift and the delivery 

head or head above the pump 

impeller when a surface-type pump 

is used (Fig. 8.2). The total friction 

losses, h , can be estimated with the 

use of f able B.10 in Appendix B. 

Pump manufacturers or their 

agents can then be consulted on the 

selection of a suitable pump to 

meet the estimated pumping capac- 

ity and suction conditions, where 

applicable. A number of other 

factors would affect the final selec- 

tion. Among these are the purchase 

price and cost of operating the 

pump; the extent of maintenance 

required and reliability of the main- 

tenance service available; the availability of spare parts; the ease with which 

repairs can be effected; the sanitary features of the pump; and the desirability 

to standardize on the use of a particular type and make of pump in order to 

reduce the diversity of spare parts. A guide to pump selection is provided in 

Table 8.1. In it is summarized the conditions under which the various types 

of pumps discussed in this chapter would normally be used and the 

advantages and disadvantages of each type. It must be emphasized that the 

table is designed for use only as a general guide to pump selection. 

SELECTION OF POWER SOURCE 

The zest of power can and often does constitute a major part of the cost 

of pumping. In view of the limited economic resources usually available to 

128

Fin. 8.16 W I N D M I L L . (Manual 

operation of pump also pos- 

sible.) 

those persoIls and communities 

using small wells, it is very important 

that careful considerutioll be 

given to the selection of a power 

source. The type of power available 

will, in many cases, be the determining 

factor in the design of a 

small pumping installation. There is 

normally a choice of four sources 

of power for operating Puntps on 

small wells. These sources are man 

power, wind. electric motors and 

internal combustion engines. 

Man Power 

Man power is. in many places, 

not only a cheap source, but, sometimes, 

the only one available for 

operating pumps on wells. It is, of 

course, the oldest known source. Its 

use is suited to individual water 

supply systems with small, intermittent 

demands. Sometimes elevated 

storage is provided to maintain 

a continuous supply. The use 

of man power would, normally, be 

restricted to pumping rates not 

exceeding about 10 gpm and suction 

lifts of no more than about 20 

feet. Hand pumps, subject to repeated 

use by the general public, 

can often have abnormal maintenance 

problems due to the fracturing 

of thP !:and lever and cylinder, 

and 1:~ .,,,.,:,ive wear of the 

inner wall s.: i i ! !e cylinder, particularly 

when the water contains sand. The most sturdy Lypes of pumps should 

be used under such conditions. Manufacturers have been experimenting with 

various types of nletal construction of the levers, cylinders and cylinder 

linings in order to mlr;;mize the maintenance problems. 

Wind 

Wind is another very cheap source of power worthy of careful consideration 

in individual and small community water supply systems. Windmills (Fig. 

8.16) usually require the availability of winds at sustained speeds of more 

than 5 miles per hour. Towers are normally used to raise the windmills 15 to 

20 feet above the surrounding obstacles in order to provide a clear sweep of 

wind to the mills. Windmills usually drive reciprocating pumps through a 

connection of the pump rod from the mill to the piston rod of the pump.

Provision may also be made for pumping by hand during long periods of relti- 

tive calm. It is good prsctice to provide adequate clevrtted storage tu maintain 

the water supply during periods when there is insufficient wind. Windmills 

are normally manufxtured in siLes expressed in terms ot‘ the diameters ot 

their wheels. When ordering a windmill t‘wrn ;f mnut‘tlcturer. he must be 

supplied with information on the average wind velocity in addition to the 

required capacity and other relevant informut ion NI the pump. The operation 

and maintenance costs of windmills ;Lre usutllly very negiigible and strongly 

influence their use in communities wiiose financitil resources are inadequate 

to operate and maintain motor or engine driven pumps. 

Electricity 

Electricity. where available from a central supply at reasonable cost. 

is to be preferred over other sources of power. It would, however, be unwise 

tb mstall electric generators simply to provide a supply for operating a small 

pump. Electricity‘s great advantage is the fact that it can be used to provide a 

continuous. automatically controlled supply of water. The power source must 

be reliable and not subject to significant vol;age variations. Small electric 

motors are usually low in initial cost. require little maintenance and are cheap 

to operate. 

lnternd Combustion Engine 

Internal combustion engines (gasoline, diesel or kerosene) are o!‘ten used in 

areas where electric power is not available and winds are Infrequent or 

inadequate to meet the water supply demands. Qiesel engines, though usually 

the most costly to purchas c, are generally the best from the point of view of 

operation and maintenance. Internal combustion engines require more 

maintenance than electric motors and must always be attended by an 

operator. Good service is obtained if a regular routine tnaintenancc program is 

followed and a supply of spare parts always available. 

130

Type of Pump 

Reciprocating: 

1. Surface 

2. Deep Well 

Rotary: 

1. Surface 

(gear or 

vane) 


(helical 

zotor) 

TABLE8.1~GUIDE TO PUMP SELECTION 

(Adapted from Table 7hforrnation on Pumps. Manual of Individual Water Supply Systems, U.S. Dept. of Health, 

Education & Welfare, Public Health Service Pub. No. 24, Revised 1962 j 

Practical 

Suction 

lift* (CO 

21 

L~suallv 

submerged 

Usual 

Pumpin 

lcpth I P t) 

Usual Pressure 

Heads .!ft of 

water) 

50-200 

Up to 600 

above the 

cylinder. 

50-150 

100-500 

Advantages 

1. Positive action. 

2. Discharge constam un- 

der variahlc hcadr. 

3. &cat fltxbility in 

mecling variable de- 

mands. 

1. Pumps wlter containing 

sand and silt.. 

5. Especially adapted to 

low capacity and high 

lifts. 

I. Positive action. 

2. Discharge constant un- 

der variable heads. 

3. Efficient operation. 

I. Same as surface-type 

rotary. 

2. Only one moving pump 

part in the well. 

Disadvantages 

I. Pulsating discharge. 

! Subject I ibration 

;rllJlloirc. 

I. Maintenance cost5 may 

be high. 

I. Llay cause destructive 

pressure if operated 

againht a closed valve. 

I. Subject to rapid \vear 

if wat:r contains sand 

or silt. 

1. Wear of gears reduces 

efficiency. 

1. Subject to rapid wear 

if waler contains sand 

or silt. 

Remarks 

. Best suited for capacities 

of S-25 gpni against 

modcratc to high head\. 

. AdaptablL to IlllIld 

operation. 

Best stnled for ION 

sprtd operation. 

. Semi-rotary type 

adaptahlc to hand 

operation. 

. A cutless rubber 

stator incrcastis life 

of pump. 

I. Best suited for IOH, 

capacity and high hcadr. 

,-

132

Type of Pump 

b. Submersible 

turbine 

(multi-stage) 

Jet: 


Practical 

sue tion 

Lift* (ft) 

Pump and 

motor sub. 

merged. 

20-I 00 

below the 

ground. 

(Ejector 

submerged 

5 t-t). 

usual 

Pumpin 

Depth ( B t) 

> 25 

> 25 

Usual Pressure 

Heads (ft of 

water) 

so-150 

Advantages -- 

1. Same as surface-type 

turbine. 

2. Short pump shaft to 

motor. 

3. Plumbness and align- 

ment of well less cri- 

tical than for line- 

shaft type. 

4. Less maintenance 

problems due to wear- 

ing 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. 

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. 

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

Disadvantages 

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. Generally inefficient. 

!. Capacity reduces as 

lift increases. 

3. Air in suction or re- 

turn line will stop 

pumping. 

- 

Remarks 

I. Relatively recent 

design improvements for 

sealing of electrical 

equipment make long 

p% ciods of troubletree 

service possible. 

2. Motor should be pro- 

tected by suitable 

device against power 

failures. 

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.

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 sources may 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 sewage disposal in a small and sparse community which 

must for various reasons depend 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 processes must be taking place within the 

soil 3s the water travels through il. Several studies have been made of 

“nature’s purifying action” by research workers 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 processes involved 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 processes occurring 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-producing bacteria) 

and other suspended matter by fi‘ltration and sedimentation or settling. 

Filtration depends upon the relative sizes of the pore spaces of the soil 

particles and those of the microorganisms and other filterable material. The 

finer the soil particles and the smaller the pore spaces between them, the 

more effective is the filtration process. Filtered material also tends to clog the 

pore spaces and 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 suspended matter 

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 processes and, 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 disease in 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 storage in 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 processes are 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 processes do 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 increases in 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 

unless induced 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 Recommended Minimum Distance 

Cast iron sewer with leaded or I 10 ft. 

mechanical joints 

Septic tank or sewer of tightly 

join ted tile 

Earth-blit privy, seepage pit or 

drain field 

so ft. 

75 ft. 

Cesspool receiving r3w sewage 100 ft. 

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 con- 

struction, 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. Rolla, Missouri: Missouri 

Water Well Drillers Association. 1966. 

Baldwin. Helene L.. and C. L. McGuinness. A Primer ml Grourlti Water. 

United States De artment of the Interior, Geological Survey. Washington: 

Government Prin P ing 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 Milwau- 

kee, Wisconsin: Bucyrus-El-ie Company, 195X. 

Harr, M. E. Groundwater aHd Seepage. New York: McGraw-Hill Book 

Company Inc., 1962. 

Livingston, Vern. Frown: Too-Thin-to-Plough Missouri. To: Just-Right-to- 

Drink 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 Water- 

Supply 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 of Health. Rural Water Supply. Albany, New 

York, 1966. 

13s

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 : Govern- 

ment 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 fol- 

lowing 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 

f

T OF PE ICITY 

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 

Fig. A.1 

-1o- 

ir:z 

-I- 

-s- 

-57 

-.- 

:,-L 

fz-. 

-a- 

-0 

.i 

-- 

f”’ 

.e ; 

r=.* 

constant head permeameter iiS 

follows. Flow under constant head 

or pressure is maintained through a 

chosen length, C, of the sample of 

aquifer material placed between 

porous plates !.n a tube of cross 

sectiona! area. A (Fig. A.l). The 

device at the upper left of the 

figure is used to provide the flow 

under constant head. The rate of 

flow, Q, through ibe sample is 

obtained by measu.;. ,:, .he volume, 

V, of water discharged I:iio a grad- 

uated cylinder in a given time. t. 

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. 

Then Qz-= 

V P(hl -h2)A 

CONSTANT-HEAD PERMEA- 

METER FOR LABORATORY 

DETERMINATlON OF COEFt 

II 

FECIENTS 

ITY. 

QF PERMEABIL- 

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

Unit 

USEFUL TABLES A 

- 

1 Centimeter 1 

1 hleter 100 

1 Kilometer 100,000 

1 Inch 2.54 

1 Foot 30.48 

1 Yard 91.44 

1 Mile 160,935 

Unit 

1 sq. 

centimeter 

1 sq. 

Meter 

1 sq. 

Inch 

1 sq. 

Foot 

1 sq. 

Yard 

1 Acre 

1 sq. 

Mile 

- 

- 

r Equivdents 

Square 

Zentimeters 

10,000 

TABLE B.l LENGTH 

Equivaleuts of First Column 

T -*- 

I 

Centi- 

Kilo- 

Meters 

Inches Feet Yards 

meters 

meters 

1 

6.452 

929 

8,361 

40,465,284 

- 

.9144 .00091-? 

1,609.3 1.6093 

Square Square 

Meters Inches 

.OOOl 

1 

.000645 

.0929 

.836 

4,047 

!,5 89,998 

TABLE B-2 AREA 

of First Column 

I 

.155 

1,550 

1 

144 

1,296 

5,272,640 

- 

I 

- 

141 

.3937 .0328 .u109 

39.37 3.2808 1.0936 

39,370 3,280.8 1,093.6 

1 .c)833 .0278 

12 1 .3333 

36 3 1 

63,360 5,280 1,7&o 

Square 

Feet 

.00108 

10.76 

.!I0694 

1 

‘9 

43,560 

27,878,400 

Square 

Yards 

.00012 

1.196 

.00077 2 

.I1 1 

1 

4,840 

3,097.600 

Acres 

: .( 

Miles 

DO00062 

.000621 

.621 

.05)0016 

.000189 

.0010568 

1 

1 

- 

Square 

Miles 

- - 

.000247 

- 

- - 

.000023 

.000207 - 

1 30156 

640 

-

Unit 

TABLE B.3 VOLUME 

Equivalents of First Column 

Cubic Cubic U.S. Imperial Cubic Cubic 

Centimeters Meters Liters Gallons Gallons Inches Feet 

1 Cu. Centimeter 1 .000001 .OOl .000264 .00022 .061 .0000353 

1 Cu. Meter 1 ,ooo.ooo 1 1,000 264.17 220.083 61.0:!3 35.314 

I Liter 1,000 .OOl 1 .264 .220 61.023 .0353 

1 U.S. Gallon 3.785.4 .00379 3.785 I .833 231 .I34 

1 Imperial Gallon 4,542.5 .00454 4.542 1.2 1 277.274 .I60 

1 cu. Inch 16.39 .0000164 .0164 .00433 .00361 I .000579 

1 Cu. 12oot 28,317 .0283 28.317 7.48 6.232 1,728 1 

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 

TABLE B.4 FLOW 

U.S. Gallons 

Per Minute 

448.83 

.00519 

1 

1.2 

.000694 

.000833 

226.28 


Imp. Gallons U.S. Gallons 

Per Minute Per Day 

374.03 646,323 

.00433 7.48 

.833 1,440 

1 1,728 

.000579 : 1 

.0006”3 ’ !.2 

188.57 j 125,850 

.c i.C:-~~ 

-. - 

538.860 1.983 

6.233 .00002 3 

1,200 .00442 

1,440 .oos3 

.833 .00000307 

1 .0000036,8 

271,542 I

Unit 

Grams Kilograms 

1 Gram 1 .oo 1 

1 Kilogram 1000 1 

1Ounce 

(Avoirdupois) 28.349 .0283 

1 Pound 

(Avoirdupois) 453.592 .454 

1 Ton (Short) 907.184.8 907.185 

1 Ton (Long) 1.016.046.98 1.016.047 

Unit 

1 Watt 

1 Kilowatt 

1 Horsepower 

1 Foot Pound 

Per Minute 

1 Joule 

Per Second 

=i= 

Watts 

1 

1000 

746 

TABLE B.5 WEIGHT 

Equivalents of I‘izst Column 

Ounces / Pounds / 

(Avoir- 

dupois) 

I 

TABLEB.6 POWER 


! 

Kilowatts Horsepower 

Foot Pounds Joules 

Per Minute Per Second 

TABLEB.7 VOLUMESANDWEIGHT EQUIVALENTS(Waterat39.2"F) 

Unit 

1 Cu. Meter 1 1,000 

1 Liter .OOl 1 

1 U.S. Gallon .00379 3.785 

1 Imp. Gallon .00454 4.542 

1 Cu. inch .0000164 .0164 

1 Cu. Foot .0183 28.317 

1 Pound .00045 .154 

- 

1= 

I- 

Cubic 

Meters 

I 

Liters 

Equivalents of First ::olumn 

UIS. 

Gallons 

264.17 

.264 

1 

I’ .- 

.00433 

7.48 

. 17 - 

143 

Imp. 

Gallons 

-.- 

220.083 

.-- “0 

.833 

1 

.00361 

6.232 

.I 

- 

Cubic Cubic 

Inches Feet 

61.033 35.314 

61.023 .035 3 

‘31 .I34 

177.774 .I60 

1 .000579 

1,728 1 

17.72 .016 

1 

1,000 

746 

.0226 

1 

Pounds 

-.- ' 700.83 

-.- ’ ‘01 

8.333 

IO 

.0361 

62.32 

1

- 

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 

Flow Rate in 

Gallons per Miwte 

TABLE B-10 FRICTION LOSS IN SMOOTH PIPE 

(approximate 

I 

head loss in feet per 1000 feet of pipe1 

1% 

10 20 

15 44 

20 79 

25 123 

30 178 

40 

50 

Nominal Pipe Size in Inches 

TABLE B-11 PIPE, CYLINDER OR HOLE CAPACITY 

Diameter (Inches) Gallons Per Foot 

2% 

1% 0.09 

2 0.16 

2% 0.25 

3 0.37 

4 0.67 

6 1.47 

8 2.61 

10 4.08 

12 5.86 

16 10.45 

18 12.20 

20 16.35 

24 23.42 

144 

4 

6 

9 

16 

25 

I 

2

B-1 2 DISCHARGE MEASUREMENT USING SMALL CONTAINER 

Discharge (Gallons per minute) = 

(Oil Drums. Stock Tanks. etc.) 

Volume of container (Gallons) x 60 

Time (Seconds) to fill container 

TABLE B.13 ESTIMATING DISCHARGE FROM A HORIZONTAL 

PIPE FLOWING FULL 

Horizontal 

Distance, x 

(Inches) 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

- 4 

DISCHARGE RATE (Gallons Per Minute) 

Nominal Pipe Diameter (Inches) 

1 1% 1 ‘h 2 

5.7 9.8 13.3 22.0 

7.1 12.2 16.6 27.5 

8.5 14.7 20.0 33.0 

10.0 17.1 23.2 38.5 

11.3 19.6 26.5 44.0 

12.8 22.0 29.8 49.5 

14.2 24.5 33.2 55.5 

15.6 27.0 36.5 60.5 

17.0 29.0 40.0 66.0 

18.5 31.5 43.0 71.5 

20.0 34.0 46.5 77.0 

21.3 36.3 50.0 82.5 

22.7 39.0 53.0 88.0 

145 

- 

2Y2 

31.3 

39.0 

47.0 

55.0 

62.5 

70.0 

78.2 

86.0 

94.0 

102.0 

109.0 

117.0 

125.0

TABLE B-14 ESTIMATING DISCHARGE FROM VERTICAL 

PIPE OR CASING 

Height, H 

(Inches) 

1% 

2 

3 

4 

5 

6 

8 

10 

12 

15 . 

18 

21 

24 

DISCHARGE RATE (Gallons Per Minute) 

Nominal Pipe Diameter, D (Inches) 

2 3 4 

23 43 68 

26 55 9? 

33 74 130 

38 88 155 

44 99 175 

48 110 190 

56 125 225 

62 140 255 

69 160 280 

78 175 315 

85 195 350 

93 210 380 

100 230 400 

146

TABLE B.15 ROPE CAPACITY OF DRUM OR REEL 

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

Nominal Rope Diarnet er 

(IncheyF 

i/4 4.4 

I 2.8 

(Wire Rope Evenly Spooled) 

Outer layer of rope 

2.0 

1.4 

i/2 1.1 

147 

where A,B,C are in inches 

-- 

and K 

has. values in table below 

Nominal Rope Diameter 

(Inches) 

K 

9116 .9

-z- 

TABLE B.16 DRILLING CABLE ROPE CAPACITIES 

Rope 

Diameter 

(Inches) 

(Left Laid - Mild Plow Steel - 6x19 Hemp Center) 

112 

9/16 

Approximate Recommended 

Working Load 

(Pounds) 

3,200 

4,200 

513 .66 5,000 

-314 .95 7,200 

; 

713 1.29 9,800 

1 1.68 - 12,600 

TABLE B.17 SAND LINE CABLE ROPE CAPACITIES 

Rope 

Diameter 

(Inches) 

(Coarse Laid - Plow Steel - 6x7 Hemp Center) 

Approximate 

Weight Per Foot 

(Pounds) 

Recommended 

Working Load 

(Pounds) 

114 .09 800 

S/l6 .15 1,200 

313 .21 1,800 

7/16 .29 2,400 

112 .38 3,200 

148

TABLE B.18 CASING LINE CABLE ROPE CAPACITIES 

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

Rope Approximate 

Diameter Weight Per Foot 

(Inches) (Pounds) 

Recommended 

Working Load 

(Pounds) 

513 .hS 5,400 

314 1; 7,600 

713 

10,200 

TABLE B. 19 MANILA ROPE CAPACITIES (3-STRAND) 

Rope 

Diameter 

(Inches) 

318 

7116 

1:‘2 

!a/16 

518 

314 

7/3 

1 

Approximate Recommended 

Weight Per Foot 

(Pounds) 

Working Load 

(Pounds) 

.04 270 

.05 350 

.08 530 

.lO 690 

.13 880 

.17 1,080 

.23 1,540 

.27 1,800 

149

A 

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 ground- 

water 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 

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 

Cable. (see Wire rope) 

- -tool percussion drilling, (see Drill- 

ing methods) 

Calcium hypochlorite, l04f., I1 I 

- -. stock solution, POS 

- -. storage of. 105 

Capillary forces, 6 

- fringe, 6 

- tube, 6 

B 

C 

151 

Carbon dioxide. 26, 48, 107 

Carbonate. 106, 109 

Casing, (see Well casing) 

- elevator, 70 

-shoe 68 

Cementation, 7, 1 S 

Cementing agents, 8. 1 S 

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 

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. 

D

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 

--.-.--- 9 drilling jr&r,, 67 

-- -_- - rig, 66, 99 

c- ---- 

l : fishing jars, 67 

- -, - - --. rope socket, 67, 93, 

(also see Wire line socket) 

--t---- 

string of drilling 

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 1 f. 

- --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. 

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. 

Electric motor, I 14, 120. 124 

- -, submersible, 126 

Engine. 114. 120, 124 

-, diesel. 130 

-, gasoline, 130 

-, kerosene, 130 

Equilibrium, definition. IS 

Erosion, 30 

Faults. 29 

Filtration, effects on ground-water qual- 

ity, 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 

E 

F

Gelling, 64 

Geologic cross-sections. 2aff. 

- data, 28ff. 

- formations, 7ff. 

- maps, 29 

- processes, 9f. 

Geology, effect on water quality, 27 

Geo hysics, 28 

c,:“,, -g. 12% formation stabilization mate- 

-, haveI-pack material, Slf., 103 

-, uniform, of particles. definition, 1 s 

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 move- 

ment, 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 1 f. 

-. -, 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 

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 

c 

I 

Impermeable layer, 10 

Incrustation, 48f., 108 

153 

Incrustation, reduction of, 1 osf. 

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 

.I 

Jars, drilling, (see Drilling met hods) 

-, fishing, (see Fishing tools) 

Jetting, (see Drilling methods) 

-, high-velocity, well development, 

10 1 ff. 

-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. 

N 

Natural purification processes in soils, 

134f. 

Nitrate, 25 

Nozzle, jetting tool, 10lf. 

Odors in ground water., 22, 26f. 

Organisms, disease-producmg, 22, 104, 

135 

Outcrop, 29 

Oxygen, dissolved, 26, 48 

0

P 

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 

&cent size, definition, 43 

Percolation, benefits of, 3, 2 3 

Percussion drilling, (see Drilling Met h- 

P%?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 


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, 1 o, 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. 

-, --s-- discharge rate, 119 

- -,rotary,‘ll7 119 131 

=: deep well, 116, 1 18: 1 Zdff., 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 

154 

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. 

- --9 internal combustion engine, 

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 1 Sff., 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, 

- test., 127 

Q 

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

54 

_- 7 - -, chemical, 23ff., 48f. 

-- compared with surface 

Gter, 22f. 

--9 - -> microbiological, 22f., 135 

-1 - -, physical, 22 

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 


-, 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, (see Drilling methods)

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 

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 

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 

U 

Unconfined aquifer, 10 

Uniform grading of particles, IS 

Uniformity coefficient, definition, 5 1 

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. 

W 

Wash-down bottom, 80f. 

Wastes, effects on ground-water quality, 

agricultural, 25, 134 

-, ----- , animal. 25, 134 

-9 - - - - -, human, 25 

-9 ----- , industrial, 27, 

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 

- ‘-1-P definition, 16 

- -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, 

Well development, (see Development of 

wells) 

- disinfection. 96. 104f.. 1 11 

-- --I chlorine solution for, 104f. 

- -, 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 observations, 

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 

-- -9 -9 pull-back method,‘81 

- -, 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 

156 

Well screen, entrance velocity, 35, 40, 

47f.. 109 

-- l, installina. 75ff. 

- -9 -- in gr&el-packed wells, pull- 

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. 

Windmill, 114, 129f. 

-, wind speed requirement, 129 

Wire line socket, 9 2 (also see RcJpe 

socket) 

- rope, care of, 87f. 

Y 

Y;::“; 8i X&, 31, 40f., 49, 106, 109, 113, 

.I 

-, specific: 1 If. 

-9 -, definition, 12 

Z 

Zone of aeration, 4ff. 

- - saturation, 4ff. 

a

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