UNICEF, Practica and Enterprise Works/VITA have developed a toolkit for African countries wishing to embark on the professionalisation of manual drilling. This toolkit includes Technical Notes, Technical Manuals, Advocacy Materials, Mapping of suitable areas for manual drilling, Case Studies, and Implementation and Traini ng 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. This Technical Note is …

When a borehole is drilled, different types of sediment and rock layers can be encountered. To drill through all these different layers a range of manual drilling techniques have been developed and are used around the globe. In each case the drilling technique must (a) break or cut the layers, (b) remove the cut material from the hole, and (c) if necessary provide support to the walls of the hole, to prevent collapse during drilling. Each drilling technique has been developed for either one or a range of specific sediment and rock types. In some situations, complementary drilling techniques can be used together for a single borehole. All existing drilling techniques can be classified in four main drilling principles: Hand Auger, Percussion, Sludging and Jetting. Hand Auger The hand auger consists of extendable steel rods, rotated by a handle. A number of different steel drill bits can be attached at the bottom end of the drill rods. The augers are rotated into the ground until they are filled, and then lifted out of the borehole to be emptied. A different drill bit can be used for each sediment type. Above the water table, the borehole generally stays open without the need for support. Below the water table a temporary PVC casing may be used to prevent the hole from collapsing, and can be emptied either with an auger or a bailer. The permanent well casing is then installed, while the temporary casing has to be removed. Augers can be used up to a depth of about 15-25 meters, depending on the geology. Sludging Sludging uses water circulation to bring the cuttings to the surface. The drill pipes are moved up and down. On the down stroke, the impact of the drill bit loosens the soil and on the up stroke, the top of the pipe is closed by hand, drawing up the water through the pipe and transporting the cuttings to the surface. On the next down stroke, the hand opens the top of the pipe and the water squirts into a pit, in front of the well. In this pit, the cuttings separate from the water and settle out, while the water flows back into the well. The borehole stays open by water pressure. To prevent the hole…

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