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

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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
Page 1 and 2: A PRAGTICAL GUIDE FOR LOCATI CONSTR
Page 4 and 5: hmier Pwss Editorial Advisory Boani
Page 6 and 7: WATER EL1 MANUAL Covers Copyright @
Page 8 and 9: Page ACKNOWLEDGEMENTS ii FOREWORD 1
Page 10 and 11: S. PUMPING EQUIPMENT 114 CONSTANT D
Page 12 and 13: While man has always recognized ihe
Page 14 and 15: An understanding of the processes a
Page 16 and 17: Bsit of Soil Water tntermediate Bel
Page 18 and 19: and loess may be limited by both th
Page 20 and 21: deposition of large aprons of mater
Page 22 and 23: the pc>:ti,sity. This quautity is r
Page 24 and 25: permeability, P, we see from equati
Page 26 and 27: Flow Toward Wells Converging j&w: W
Page 28 and 29: expansion and deepening of the cone
Page 30 and 31: yield of the individual wells (Fig
Page 32 and 33: Multiple well or well-point systems
Page 34: 10 ppm of iron means that in every
Page 39 and 40: Geologic Maps Geologic maps, of whi
Page 41 and 42: depth. thickness. and description o
Page 43 and 44: CHAPTER 4 Generally, the aim of eng
Page 45 and 46: lodged in them and thus restrict fl
Page 47 and 48: Fig. 4.3 THE Y-SHAPED OPENINGS OFTH
Page 49 and 50: Fig. 45 CONTBNUOUSSLOT T Y P E OF W
Page 51 and 52: Manufacturers make well screens in
Page 53 and 54: The limiting size of material to be
Page 55 and 56: too 90 E 60 z t 50 : .L 40 2 30 E (
Page 57 and 58: prime concern in small we!ls. Gener
Page 59 and 60: otherwise unsatisfactory water into
Page 61 and 62: The object of formation stabilizati
Page 63 and 64: Pump unit Sanitary well seal I / ,R
Page 65 and 66: There are four basic operations inv
Page 67 and 68: Ham? driver ----k- Htle backfilled
Page 69 and 70: single wlley block : /Tripod Fig. 5
Page 71 and 72: Fig,..8 MAN ON SCAFFOLDING RAISES H
Page 74 and 75: Cutting edges Galvanized iron pipe
Page 76 and 77: inexperienced driller because of th
Page 78 and 79: string are usually joined together
Page 80 and 81: .I Fig. 5.18 CAStbiG DRIVE SHOE. of
Page 82 and 83: Fig. 5.22 A GRAVITY PLACEMENT METHO
Page 84 and 85: Fig. 5.24 OUI’SIDE-TUBING METHOD
Page 86 and 87:
Pull-back Method The pull-back meth
Page 89 and 90:
Wash line- .Cemsnt grout ,’ Exoan
Page 91 and 92:
to the surface with the return flow
Page 93 and 94:
-Inner Carm~ Fig. 5.36 DOUBLE-CASIN
Page 95 and 96:
Lead packer Pulhg pipe Sand join1 S
Page 97 and 98:
saving that sbandunmcnt ot‘ the b
Page 99 and 100:
esult, tools lost in a hole do not
Page 101 and 102:
Tapered Tap Die Overshot Circulatin
Page 103:
If the hold is secure, continue lif
Page 106 and 107:
CHAPTER 6 WE11 C6MPLETION Well comp
Page 108 and 109:
‘N E L VI E L
Page 110 and 111:
Static water :evel -m----.-e Solid
Page 112 and 113:
The procedure is to lower the tool
Page 114 and 115:
wells. The thinner the gratlel pack
Page 116 and 117:
Wells, like all other engineering s
Page 118 and 119:
of the wells to determine whether s
Page 120 and 121:
Black iron or plastic pipe Well scr
Page 122 and 123:
,&ting technique is used to agitate
Page 124 and 125:
Drilling and completing a well form
Page 126 and 127:
container is termed the srrctiorl h
Page 128 and 129:
plunger on the tijrward stroke p~~s
Page 130 and 131:
or deep well type and are usually d
Page 132 and 133:
Fig. 8.9 VOLUTE-TYPE C’ENTRIFU- C
Page 134 and 135:
pre y.,,:~ 1; +-.b to, rourT the no
Page 136 and 137:
Check valve Radial bearing lmpetfer
Page 138 and 139:
To storage ha I 3 Power unit - Stat
Page 140 and 141:
Provision may also be made for pump
Page 142 and 143:
132
Page 144 and 145:
OF Too great stress can never be pl
Page 146 and 147:
feet before final disappearance at
Page 148 and 149:
REFERENCES Acme Fishing Tool Compan
Page 150 and 151:
T OF PE ICITY The coefficient of pe
Page 152 and 153:
Unit TABLE B.3 VOLUME Equivalents o
Page 154 and 155:
- B-8 PRESSURE 1 Atmosphere = 760 m
Page 156 and 157:
TABLE B-14 ESTIMATING DISCHARGE FRO
Page 158 and 159:
-z- TABLE B.16 DRILLING CABLE ROPE
Page 160 and 161:
A Abandoned well, I37 Acid. hydroch
Page 162 and 163:
Gelling, 64 Geologic cross-sections
Page 164 and 165:
s Sand, 7,9? 119, 126, 129, 137 --
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