AT MICROFICHE REFERENCE LIBRARY A project of Volunteers in Asia By: Sob Blankwaardt Published by: Rwegarulila Water Resources Institute P.O. Box 35059 Dar es Salaam, Tanzania Available from: TOOL Foundation Entrepotdok 68aI69a 1018 AD Amsterdam The Netherlands Reproduced with permission. Reproduction of this microfiche document in any form is subject to the same restrictions as those of the original document. I Hand Drilled Wells A Manual on Siting, Design, Construction anti Maintenance Hand Drilled Wells A Manual on Siting, Design, Construction and Maintenance Bob Blankwaardt Rwegaruli!a Water Resources Institute t The preparation and printing of this publication h;; been made possible by grants from the United P!ations Children’s Fund (UNICEF) and the Swedish International Development Agency (SIDA). 0 1984 Bob Blankwaardt ISBN 9976 936 01 X Published by the Rwegarulila Water Resources Institute, P-0. Box 35059, Dar es Salaam, Tanzania Layout and cover design by Lees Doikens, Illugrafika, Den Haag Drawings by the author Photography by Rwezaula J. Kabengula. Library Photographic Unit, University of Dar es Salaam Typeset and printed in the Netherlands by Roeland Foto-Offset B.V., Den Haag Distribution overseas by TOOL Foundation, Entrepbtdok 68A/69A, 1018 AD Amsterdam, the Netherlands. Copyright is reserved under Protocol 2 of the Universal Copyright Convention. Nevertheless, permission is hereby granted for reproduction of this material, in whole or part, for educational, scientific or development-related purposes, except those involving commercial sale, provided that a) full citation of the source is given and b) notiticaiion in writing is given to the Rwegarulila Water Resources Institute. Foreword We, at the Rwegarulila Water Resources Institute, are very happy with tlx publication of this handbook. In trying to opt for least cost altemstives in providing our people with clean drinking water and hygienic sanitation, the Ministry of Water, Energy and Minerals directed the Institute to give priority to local resources technology in its craft and technical curriculum. Training in Shallow Wells Technology has been included in our three year Full Technician Programme. While meaningful development in this direction has been achieved, lack of performance oriented instructional materials has been cur major setback. The publication of this handboek is timely. It is indeed an invalu&le input into our training system. For those involved in the construction and maintenance of tube wells at community level this handbook will be of much help. Washington Mutayoba Principal Rwegarulila Water Resource Institute Foreword We, at the Rwegarulila Water Resources Institute, are very happy with thz publication of this handbook. In trying to opt for least cost alternatives in providing our people with clean drinking water and hygienic sanitation, the Ministry of Water, Energy and Minerals directed the institute to give priority to local resources technology in its craft and technical curriculum. Training in Shallow Wells Technology has been included in our three year Full Technician Programme. While meaningful development in this direction has been achieved, lack of performance oriented instructional materials has bean Gur major setback. The publication of this handboek is timely. It is indeed an invalua’ole input into our training system. For those involved in the construction and maintenance of tube wells at community level this handbook will be of much help. , Washington Mutayoba Principal Rwegarulila Water Resource Institute Preface and Acknowledgements This Manual on Hand Driiled Wells is the product of 3 years’ field and classroom teaching experience, Brst at the Morogoro Wells Construction Project and later at the Rwegarulila Water Resources Institute. When I was asked to prepare the manual I accepted the task with enthusiasm, but I was imediately confronted with a problem. Although primarily meant for pre-service students at the Institute, the book should, at the same time, serve a much bwader public including craflsmen, technicians and practising engineers, and also project planners, 1 have tried to solve this problem by writing a kind of refewnce book with some features of a “true” manual in the sense that the most important operations have been described as step-by-step procedures and illustrated with many drawings and photographs. However, since I am convinced that practical skills can only be improved by theoretical knowledge. I have included more background information than strictly required for a manual. i reaiize that by writing in the English language, 1 will not reach the entire group o.*people involved in well construction. Particularly for the in-service training courses which are ma,~dy followed by craftsmen with primary education only, and in view of the strongly recommended village level operation and maintenance of water supply systems, a translation in due course of relevant parts of the book into Kiswahili remains a task of high priority. The manual is built up in six parts. The lirst part - Chapter 1 - is an introduction to the subject. In the second part - Chapters 2 and 3 - the nost necessary hydrogeological theory is given. Part three which includes Chapters 4 and 5, deals uith site investigation and the criteria for approving a site for construction of a well. In part four - Chapter 6 - the design of the well is discussed, and in part five - Chapters 7 to I I - the actual construction of the well including the installation of a hand pump. In the last part - Chapter I2 - a possible approach towards the maintenance of pumps and wells is indicated. In order to keep the siz.? of rhe chapters on site investigation and well drilling operations limited, the survey and well drilling equipment have been described in seperete appendices. In the course of reading this manual, the realization of a well can be followed with the help of an actual example from Chamazi village near Dar es Salaam. I am much indebted to the people of this village for their hospitality. In fact, this village has virtually become a permanent training ground for the Institute. Most of the photographs were taken here. Publication of this manual Nould not have been possible without the continuous encouragement of Washington Mutayoba. the Principal of the Institute, and the teaching statf: Elnathan M. Mundo. John T. Sambu. Juma M. Kaeje and Abdallah S. Bunga, who gave me good advice on the desired content of the book. 1 am very grateful to the following persons for their invaluable contributions. - My former colleagues in the Morogoro Wells Construction Project, especially Aat van der Wel who read an early version and made very helpful comments. - The Organization of Netherlands Volunteers for giving me the opportunity to finalize this work, - Abubakr Kigingi, executive engineer in the Morogoro Regional Water Engineer’s ofice, Frans van der Laak and Geert van den Honing of the Morogoro Wells Construction Project, Hartmut Floegel of the Tanga Integrated Rural Development i’roject and Jo Smet of the Community Health Department, Faculty of Medicine. University of Dar es Salaam, for their critical review of several chapters. - Daphne Beaton and Malcolm Norris of the Communication Skills Unit, University of Dar es Salaam, for their patient and undaunted correction of my English. - Helen Cramer, for typing the first version and large parts of the final manuscript. To Peter van der Werff, an old friend of mine, I owe special thanks for all his tireless work behind the scenes. Bob Blankwaardt VI Dar es Salaam, April 1984 VII Contents Chapter 1 Introduction I. 1 Comparison of water supply systems 1.2 Hand drilled wells: a short description I .3 Hand drilled wells versus dug wells I 2 3 Chapter 2 Groundwater 2.1 The hydrological cycle 2.2 Types of aquifers 2.3 Characteristics of aquifers 2.4 Basic well hydraulics 2.5 Groundwater level fluctuations Chapter 3 Origin and occurrence of unconsolidated sediments 3.1 The process of weathering 3.2 Slope erosion 3.3 Erosion and sedimentation by rivers 3.4 The search for aquifers Chapter 4 Site investigation 4.1 preparations in the offtce 4.2 Preparatory work in the village 4.3 Test urilling operations 4.4 Survey pump test 4.5 Description of soil samples 4.6 Drawing a section 4.7 Recording and storage of survey data Chapter 5 Criteria for borehole approval 5. I Test yield criterion 5.2 Water quality criteria 5.3 Hydrogeological criteria 5.4 Summary Chapter 6 The design of tube wells 6.1 Components of a tube well 6.2 Design principles 6.3 Example of a design Chapter 7 Well drilling operations 7.1 Preparations 72. Drilling without a casing 7.3 Installation of casing and bailing 7.4 Drilling inside the casing 7.5 Completion of the borehole 7.6 Telescopic drilling 7.7 Borehole description 12 13 13 17 21 22 23 26 27 29 31 33 34 35 36 37 37 40 41 42 44 46 46 47 48 VIII Chapter 8 Installation of filter pipe and gravel pack 8.1 The gravel 8.2 The filter pipe 8.3 Installation of the filter pipe 8.4 Installation of the gravel pack 8.5 Methods of removing the casing Chapter 9 Development, pump test and backfilling 9. I Objectives of development 9.2 Overpumping 9.3 Surging 9.4 Pump test 9.S What to do if the pump test fails 9.6 Clay seals and backfill Chapter 10 Construction of the slab 10.1 Design of the slab 10.2 Building materials IO.3 Building the slab Chapter 11 Hand pumps and their installation I I. I Choosing an appropriate pump l I .2 Pumps in Tanzania I I .3 Cylinder, rising main and pumprod 1 I .4 Installation of the pump Chapter 12 Maintenance of pumps and wells 12. I Towards village level operation and maintenance 12.2 Village maintenance tasks 12.3 The role of MAJI in well maintenance References Appendices A Prevention of water-related diseases B Surveying equipment C Water quality standards D Well drilling equipment E Topographical maps F Checklist for pump maintenance G Disinfection of a well Annexes 1 Village Sketchmap 2 Situation Sketchmap 3 Survey Borehole Description Form 4 Well Description Form 5 Maintenance report 6 Educational posters Index 49 50 51 52 54 56 56 57 58 58 59 61 63 64 68 68 70 72 76 79 80 82 85 87 96 99 107 114 116 117 119 121 123 12.5 127 129 Chapter 1 Introduction For the development of rural water supply the Tanzanian Government started the National Rural Water Supply Programme in 197 I I and has adopted the United Nations’ Water and Sanitation Decade target: “To provide a reliable water supply by the year 1991, whereby all people have ease of access (at a distance of 400 m or less) to a pubiic domestic water point”. The ministry responsible for the planning, preparation and execution of this programme is the Ministry of Water, Energy acd Minerals (MAJI). The Government’s optimistic claim that currently 40 % of the rural population of 15 million people has access to clean drinking water, might hold true if it were based on the installed capacity. However, taking into account the water supply schemes that are out of order, probably not more than 3 million people at present have access to a reliable supply. The remainder of the population is still (or again!) entirely dependent on the use of water from hand dug holes, unprotected wells, rivers, pools, etc. The traditional picture of women fetching water of dubious quality at places many miles from their homes is still the rule in the rural areas. Long walking distances also imply a low rate of consumption. B& Aa poor quality and the small quantity of water (often less than 10 litres per person per day) are responsible tbr the spread i;f water-related diseases. Assuming a growth rate of 3 96 per year, the total rural population will have grown to about 20 million people by the year 1991. Consequently new water supply systems will have to be constructed, and old ones rehabilitaled. for 17 million people in 7 years’ time: that is to say, for around 2.5 million people per year, provided that none of the existing or new supplies breaks down. In the present economic situation it is entirely beyond the country’s capabilities (even with donor assistance) to provide every household with a tap inside the house. The country has to resort to low cost technology which requires the least capital expenditure per head of population for investment, operation and maintenance and at the same time guarantees a reliable and safe supply. 1.1 Comparison of water supply systems Supply systems of the following types are commonly constructed in the country: - gravity-fed or pumped surface water; - deep boreholes with motor-driven pumps: - wells with hand pumps. The features of these systems can briefly be described as follows. a) Surface water - pumped or gravity-fed - is generally polluted. bacteriologically unsafe and carries a high seasonal sediment load. Very often it needs treatment which results in high investment and operational costs and in a demand for skilled manpower. b) For the construction of deep boreholes machine- powered equipment is required. Even the simplest drill rig requires skilled operators and high investment, and its operation depends on the availability of fuel and spare parts. Moreover, the exploration of deep ground- water requires expensive geophysical investigations. Both surface water and borehole supplies require capital intensive distribution systems. These include pipelines, break-pressure tanks. storage tanks and dcmestic water points. The cost depends, of course, on the location of the river intake or borehole and the size of the sillage to be supplied. cl Tube wells and ring wells of shallow to medium depth (often not quite correctly called “shallow wells”) can be made hy hand drilling and digging respectively. This leads to comparatively low investment costs. Construction failures (lower yield than anticipated) seldom occur if the location and the design of the wells are based on the results of proper test drilling and pumping. Operational costs are low because these wells can be equipped with hand pumps, which do nor require any fuel or highly skilled personnel. Moreover, if maintenance is made the responsibility of the village, mamtenance costs can be limited. In fact, centralized maintenance may well be beyond the country’s financial and organizational capabilities. A comparison of estimated investment, operational and maintenance costs of the various systems is given in Table 1.1. 1 HAND DRILLED WELLS Table 1.1 Cost of water supply systems per head of popuiation in T.Shs. Type of supply Investment 0 & M”)/year .-- Gravity 600- 1200 10 Pumped surface water 600- 900 20 Deep borehole 600- 900 15 Concrete ring wellb) loo- 150 5 Hand drilled tube