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

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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 limitations of pipe-base screens also apply to this type of well point. Another type of well-point construction 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, particularly 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 handling 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 operations 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
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 37 and 38: ground waters in some parts of Arge
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: Fig. 4.3 THE Y-SHAPED OPENINGS OFTH
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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