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A manual for hand drilling in developing countries by UNESCO

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UNDERSTANDING GROUNDWATER & WELLSin manual drilling

INSTRUCTION HANDBOOKfor manual drilling teams on hydro-geology for well drilling, well installation and well development

UNDERSTANDING GROUNDWATER & WELLSin manual drillingInstruction handbook for manual drilling teams on hydro-geology for well drilling, well installation and well developmentPublished by the PRACTICA Foundation Author Arjen van der WalPeer reading Richard C. Carter Structural support Wouter Jan Fellinga , Melanie Stallen French translation Julien Labas, Stphan Abric, Rgis Garandeau Swahili translation Walter Mgina, Ester Mgina-van Vugt Illustrations Franck Nederstigt Photos Arjen van der Wal Layout Marijke Kreikamp/ 4colour design First edition April 2008 Second edition June 2010

PRACTICA Foundation develops and disseminates low-cost appropriate technology in water and renewable energy in developing countries. We focus on technology that responds to local cultural contexts, can be locally produced and maintained, and supports existing markets.

PRACTICA foundation Oosteind 47 - NL-3356 AB Papendrecht - The Netherlands (t) +31(0)786150125 info@practicafoundation.nl www.practicafoundation.nlPRACTICA Foundation - Manual drilling series

DisclaimerThis manual is free of charge. Any parts of this instruction manual, including the illustrations and technical drawings may be copied to meet local needs, without permission from the author or publisher, provided the parts are distributed free, not for prot and reference to the source is made. The author would appreciate receiving notice and a copy of any materials in which original text or pictures have been used. For any reproduction with commercial ends, written permission must be obtained in advance from the PRACTICA Foundation. This instruction manual is available in English and in French and Swahili and has been developed for use in technical training courses organised for the intended users. In case you want to organize such training, you may contact the PRACTICA Foundation for further information and support. The first edition of this publication was made possible by a financial contribution from the Technical Training Programme of the ETC Foundation in the Netherlands and the United Nations Childrens Fund - UNICEF - office in Chad. An updated version of this publication (the second edition) was made possible by a financial contribution from the United States Agency for International Development (USAID) as part of the West Africa Water Initiative (WAWI). The United Nations International Childrens Fund (UNICEF), PRACTICA Foundation and Enterprise Works/Vita have developed a toolkit for African countries wishing to embark on the professionalization of manual drilling. This toolkit includes Technical Notes, Technical Manuals including this publication, Advocacy Materials, Mapping of suitable areas for manual drilling, Case Studies, and Implementation and Training Manuals. This initiative builds the capacity of the local private sector in order to respond to the ever increasing demand for safe water in rural areas. The Technical Training Program (TTP) of the ETC Foundation contributed with structural support in the educational aspects of this manual. While every care has been taken to ensure accuracy of the information given in this manual, neither the publisher(s) nor the author(s) can be held responsible for any damage resulting from the application of the described methods. Any liability in this respect is excluded.

Note to those considering translation or modication; before beginning any translation or modification and in order to avoid duplication of efforts and unintended mistakes, please contact the PRACTICA Foundation. This document or parts of this document may not be copied or published under a new name or author without permission from PRACTICA Foundation.

PRACTICA Foundation - Manual drilling series

ForewordContextOver the years much literature on geology, hydrogeology and hygienic aspects has been written and in a lot of countries this information is used by policy makers, project managers, engineers and technicians to construct machinedrilled wells in their countries. Machine-drilled wells are often very expensive and not affordable by large parts of the population in developing countries. Another option is to drill shallow water wells (up to about 35 meter depth) by hand, so reducing the price of a well by a factor 4 -10 compared to a machine-drilled borehole. This cost reduction not only enables NGOs and Governments to construct more water wells, but also opens the door to villagers, farmers, schools and small communities to have a well constructed independently through the private sector. Although most of the existing manual drilling enterprises are technically able to drill boreholes, mistakes are easily made during the construction and development of the wells. Furthermore good well construction alone does not ensure good water quality and sustained yield from the well over many years. In order to achieve that, know-how on geology and groundwater is important. However, many technical workers of manual drilling enterprises may have limited education. Much of the available literature on geology, hydrogeology and hygiene cannot easily be understood without an advanced education. Technical workers are used to learn through experience and repetition. Of course training could be given to these workers but classroom training alone is known to be insufficient for drilling teams. They need to relate theoretical information to the real practical problems which occur regularly while working on drilling sites. This book therefore only deals with those essential subjects which are relevant to manual drilling and well installation in practice, in simple and understandable language.*

*NoteTechnical terms and the way in which subjects are explained are based on the average expected educational level of the intended users. Sometimes, the use of complicated geological and technical terms has been avoided to create better understanding. Some words (for example soil or gravel pack) have been used because they are known by the intended users, although these words are not always the terms that are used by geologists. Please keep in mind that the objective of the handbook is to create better understanding of well drilling in practice, aimed at technical workers of manual drilling teams who may have a limited educational background.

READERSHIPThis handbook can be used as a guide during training sessions for well drillers, local trainers and quality controllers. It also serves as a reference for drilling supervisors, NGOs, development agencies, manual drilling teams and enterprises during the entire drilling process. The handbook consists of three sections that can be read together, or used and printed separately for the various target groups.

PRACTICA Foundation - Manual drilling series

Colophon

AVAILABLE MANUALS IN THIS SERIES: Technical training handbooks on affordable manual well drilling.These practical handbooks create awareness of manual drilling for affordable water supply and a roadmap for implementation of manual drilling programs. The manuals provide an extensive and detailed guide for trainers and drilling teams in the use of various drilling techniques for making affordable boreholes. The techniques are explained in simple and understandable language, using clear illustrations and drawings.

JETTINGManual drilling series

1. Manual drilling series: JETTINGThis handbook describes in detail the various jetting techniques that can be used to drill wells in loose and soft soil formations. With this technique, wells are drilled in a number of hours rather than days.

TECHNICAL TRAINING HANDBOOK ON AFFORDABLE MANUAL WELL DRILLING

PERCUSSIONManual drilling series

2. Manual drilling series: PERCUSSIONThis handbook describes in detail the percussion technique. Although the technique is slower than other drilling techniques, it is the only manual drilling technique that is able to drill through consolidated rock layers.

TECHNICAL TRAINING HANDBOOK ON AFFORDABLE MANUAL WELL DRILLING

AUGERINGManual drilling series

3. Manual drilling series: HAND AUGERThis handbook describes the hand auger technique. This cheap and effective technique is very suitable for sinking shallow wells in soft soils and is excellent for soil surveys. Many drilling teams have this technique in their toolkit to complement other drilling techniques.

TECHNICAL TRAINING HANDBOOK ON AFFORDABLE MANUAL WELL DRILLING

SLUDGINGManual drilling series

4. Manual drilling series: SLUDGINGThis handbook describes the sludging technique, and in greater detail the ROTA-sludge technique. It is a combination of sludging and percussion and is particularly useful due to its versatile application for a range of soil formations.

TECHNICAL TRAINING HANDBOOK ON AFFORDABLE MANUAL WELL DRILLING

UNDERSTANDING GROUNDWATER & WELLSin manual drilling

5. Manual: Understanding Groundwater and Wells in manual drillingThe manual Understanding Groundwater & Wells in manual drilling complements the 4 technical training handbooks and highlights those essential subjects which are relevant to manual drilling, geo-hydrology, hygiene, well installation and well development in practice, in simple and understandable language.

INSTRUCTION HANDBOOKfor manual drilling teams on hydro-geology for well drilling, well installation and well development

PRACTICA Foundation - Manual drilling series

Table of contentsIntroductionMaking a well The Manual Additional information

22 2 2

4 DRILLING LOGS4.1 4.2 4.3 4.4 4.5 Why drilling logs Taking soil samples Drilling depths Filling in the drilling logs Determine the depth of the filter screen and backfilling Well-screen, position and length Sump Thickness of the gravel pack Thickness of the sanitary seal Cuttings Sanitary top-seal

1616 16 16 17 19 19 19 19 20 20 20

1 BASIC GEOLOGY1.1 Geology 1.2 Manual drilling techniques Hand augers Sludge / Rota sludge Jetting Percussion and bailer other techniques 1.3 Soil classification and determination Permeability Field tricks Porosity Turbidity

33 3 4 4 5 5 5 6 6 7 7 8

5 WATER PRESSURE AND DRILLING FLUIDS5.1 Drilling with water pressure Temporary casing Water pressure Borehole 5.2 Drill fluid additives Bentonite Other natural clays Polymers Fresh cow-dung Fibers and other solids 5.3 Removal of additives from the borehole

2121 21 21 22 23 23 23 23 24 24 24

2 HYDROLOGY2.1 2.2 2.3 2.4 2.5 Hydrology Groundwater flow Aquifers Sea water intrusion Salt, iron and minerals

99 9 10 11 11

3 HYGIENE IN RELATION TO GEOLOGY3.1 Site selection Latrines Waste (dump) areas, fire places and fuel stations Sun or shade 3.2 Migration of pathogens (bacteria) Different aquifers One aquifer 3.3 Sanitary seal

1313 13 13 13 14 14 14 14

6 WELL CONSTRUCTION6.1 Well design Borehole diameter Borehole depth Completion of the borehole Measuring tools

2525 25 25 25 25

PRACTICA Foundation - Manual drilling series

6.2 Materials: PVC well-screen and casing 26 Diameter and wall thickness of well casing 26 Slots 26 Sump 27 Pipe joints 27

APPENDIXA Country specific regulations B Country specific geological conditions C Drilling logs D Test pumping form E Chlorination

4141 41 41 41 41

6.3 Materials: Gravel pack 6.4 Materials: Sanitary seal 6.5 Well construction

27 28 28

7 WELL DEVELOPMENT AND TESTING 317.1 Welldevelopment Surge block or plunger Discontinuous pumping (start-stop cycle pumping) Pumps for well development Re-development 7.2 Pumping test Well yield Dip tape Yield test with motorized or deep well pumps Yield test with hand pumps Water level measuring tape or measuring rope 7.3 Water quality testing Representative water samples Well disinfection chlorination 31 31 32 32 32 33 33 33 34 34 35 35 35

8 FINALIZATION8.1 Concrete slab/apron 8.2 Soak pit 8.3 Pump choice

3636 36 36

GLOSSARY OF TERMS ACKNOWLEDGEMENTS

37 40

PRACTICA Foundation - Manual drilling series

PRACTICA Foundation - Manual drilling series

Understanding Groundwater & Wells in manual drilling

INTRODUCTIONMAKING A WELLThe construction of a well, using manual drilling techniques is a complicated process. Before drilling starts a good drilling site has to be selected, where experience suggests that there will be an adequate quantity of good quality groundwater. During the drilling process there are a lot of different aspects which require attention to prevent things from going wrong. Besides the practical drilling skills which are executed at ground level, at the same time attention has to be paid to important processes which are happening below ground level during drilling. Water used in drilling (working water) could flow away or worse; the borehole could collapse, burying part of the drilling equipment. And finally, once the hole has been drilled, the well casing, screen and sanitary seals have to be installed at the right depth, preventing contaminated water from entering, and ensuring a sufficient yield.

In many countries manual drilling teams experience problems with site selection, loss of working water, soil determination, logging, well installation, well development, water quality and well yield (flow rate of the well). These problems may occur when the drilling process is not completely understood and important steps are missed.

This instruction manual describes many of the subjects and problems which you may come across during drilling. The manual will help you to understand the drilling process at ground level and far below ground level in the drilled hole. With the information provided you will be able to understand what is taking place in the hole during drilling, and perform a professional job as you construct high quality water wells.

THE MANUALHow does this instruction manual work? In the table of contents (see previous page) an overview is given of the subjects and where to find them.

Chapter 1 to chapter 8 contains all the information needed for a good understanding of the drilling process and correct well installation. In the Appendix you will find country specific regulations. These are regulations designed for communal wells and defined by the government or NGO you are working for. In the Appendix you will also find some specific geological conditions, which are unique for the area or country you work in. Furthermore, simple blank drilling logs are included, which can be copied for use in the field.

ADDITIONAL INFORMATIONFor more detailed background information for policy makers, project managers, implementing NGOs, trainers and supervisors, some useful titles of existing books and manuals are given at the end of this instruction manual.

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PRACTICA Foundation - Manual drilling series

Understanding Groundwater & Wells in manual drilling

1 BASIC GEOL...