Hand-Dug Wells

Technical brief Hand-dug wells Part of a series of Introduction WaterAid technology briefs. The traditional method of obtaining groundwater in rural areas of the developing world, and still the most common, is by means of hand‑dug wells. Available online at However, because they are dug by hand, their use is restricted to suitable www.wateraid.org/ types of ground such as clays, sands, gravels and mixed soils where only small technologies boulders are encountered. Some communities use the skill and knowledge of January 2013 local well‑diggers, but often the excavation is carried out, under supervision, by the villagers themselves. The volume of the water in the well below the standing water table acts as a reservoir which can meet demands on it during the day and should replenish itself during periods when there is no abstraction. Fig 1: A hand‑dug well Technical brief Hand-dug wells Dimensions of hand-dug wells excavate a well which is less than a metre in diameter; an excavation of Hand‑dug wells can range in depth about 1.5 metres in diameter provides from about five metres deep, to deep adequate working space for the wells over 20 metres deep. Wells diggers and will allow a final internal with depths of over 30 metres are diameter of about 1.2 metres after the sometimes constructed to exploit well has been lined. a known aquifer. It is impractical to Fig 2: A safe well‑digging operation Air line Air compressor unit to pump placed so that fumes Water cannot reach the well discharging Safety equipment and first aid kit Brake post Dewatering pump Bosuns chair Air control valve 2 Technical brief Hand-dug wells Digging with the sides of the excavation supported There are several methods of always be used in unstable ground. supporting the sides of the excavation When construction has finished, while digging proceeds: the joints between the rings which are above the water table should be Pre-cast concrete rings sealed with cement mortar. The safest method is to excavate In situ lining within pre‑cast concrete rings which later become the permanent lining In suitable ground, excavation may to the sides of the well. The first ring proceed for a short distance without has a cutting edge, and additional support to the sides; these are then rings are placed on it as excavation supported by means of concrete proceeds. As material is excavated poured in situ from the top, between within the ring, it sinks progressively the sides of the excavation and under its own weight and that of the temporary formwork, which becomes rings on top of it. This method should the permanent lining to the well. This process is repeated until the water table is reached. Supported excavation (the ‘Chicago’ method) In suitably stable ground, excavation may proceed within the protection of vertical close-fitting timber boards, supported by horizontal steel rings (the Chicago method). The timbers are hammered down as excavation proceeds and additional timbers are added progressively at ground level. The steel rings must be hinged, or in two parts bolted together, so that lower ones can be added as the excavation progresses. The vertical spacing between the rings will depend on the instability of the ground. The well is lined with bricks or concrete blocks, from the water table upwards, within the timbers as they are withdrawn. A wide-diameter well being constructed in Uganda using the Chicago method of safe well construction. The photo illustrates the use of a temporary support system for safe digging in open holes. Steel rings, WaterAid/Jim Holmes wedges and timber boards ensure the safety of workers at any depth. 3 Technical brief Hand-dug wells Digging with the sides of the excavation unsupported In stable ground, wells are often In firm and stable ground, wells may excavated down to water level without be safely excavated without support a lining, and are lined with in situ and may give satisfactory service, concrete, or with pre‑cast concrete although it is strongly recommended rings, from this level upwards. that a permanent supporting lining be installed. This will support the sides of Wells safely dug during the dry season the excavation, preventing them from may become unstable when the water collapse and preventing pollution by level rises in the wet season and surface water. Suitable lining materials therefore must be lined before this have been shown in the following occurs to prevent a collapse. sketches and include concrete, pre‑ cast concrete, masonry and brickwork. Fig3: Different ways of lining a well Method 1 Method 2 Method 3 Method 4 Sinking pre‑cast Reinforced concrete Masonry lining of burnt Galvanised iron rings concrete rings. or ferrocement cast in bricks above water line, bolted together as situ above water line, caisson made of blocks temporary measure for concrete rings sunk with cutting ring below emergencies. below the water line. water line. Concrete Bricks or apron blocks 1m 0.9m 50mm Chicken wire Backfill thick reinforcement with gravel Concrete Ferrocement Galvanised rings cast in situ iron rusts quickly in acidic waters Water line Sunk caissons Cutting Each circle of galvanised ring iron is composed of three curved sections bolted together 4 Technical brief Hand-dug wells Excavation below the water table Fig 4: Example of excavation below water table using concrete caisson Regardless of which method has been rings used to excavate the well to the water table, excavation below this level should never be attempted until the sides of the excavation have received the support of their permanent lining, from water table to ground level. Excavation below the water table Cast in situ should be carried out within pre‑cast or pre‑cast concrete caisson rings of a smaller Clay concrete diameter than the rest of the well. To caisson rings facilitate the ingress of water, these lower rings are often constructed with porous, or no-fines, concrete and their joints are left unpointed. See the Porous diagram (right): concrete caisson rings Water table Sand aquifer Cutting ring Fig 5: Hand-dug well fitted with Completion handpump After construction of the well shaft has been completed, the bottom is plugged with gravel. This helps to prevent silty material from clay Concrete surround soils, or fines from sandy materials, being drawn into the well. Any annular space between the pre‑cast Clay – to caisson well rings and the side of the seal the excavation should also be filled with wall 1m gravel; such filling behind the rings Concrete which are below the water helps to layer increase water storage and to prevent the passage of fine silts and sands into the well. Aquifer The space behind the top three metres, or so, of the well rings should Gravel or be backfilled to ground level with sand to act puddled clay, or concrete, and the well as filter rings should project about one metre. An apron and a drain should then be constructed. This apron should be wide enough for people to stand on. 1.25m It should be made of concrete that is between 75 and 100mm thick, 5 Technical brief Hand-dug wells preferably reinforced by steel rods or an access hole, or a handpump, mesh. This apron provides a sanitary depending upon the yield of seal to prevent polluted water seeping water available and the ability of into the well. It should have a smooth the benefiting community to pay surface sloping down to the drain for ongoing maintenance for the and a rim to prevent water going handpump, spare parts, etc. A hand‑ over the edge. The drain should be a dug well fitted with a handpump can cement‑lined channel, at least four serve the needs of about 300 people. metres long, that takes spilled water to a soakage pit, an animal‑watering References trough or a vegetable garden. Watt S B and Wood W E (2007) Hand- Abstraction dug wells and their construction. IT Publications Water is abstracted by means of WaterAid (2000) WaterAid’s health either a bucket and windlass above and safety policy Advantages of hand-dug wells ✓ Cheap materials can be used ✓ Can be constructed by local artisans so communities can build themselves ✓ Generally good yields Disadvantages of hand-dug wells ✗ Can be time‑consuming to construct ✗ Risk of collapse if not supported properly ✗ Depth of well is limited ✗ Unless capped or protected, hand‑dug wells can be open to contamination An example of a handpump operated hand-dug well with an apron and drain surrounding the well head in Adi-awna- waza village in the Hintalo-Wajarat WaterAid/Marco Betti region of Ethiopia 6 Technical brief Hand-dug wells Case study Example of the hand-dug well method WaterAid/Jon Spaull The well being pumped out, Woriziehi, Tamale, Northern Region, Ghana Hand‑dug wells have been constructed for thousands of years but in the past this water supply often consisted of unlined holes (prone to collapse), that were unprotected from contamination, leading to health risks. In order to avoid these problems it is advisable to use the method outlined below: Materials required Construction methodology: for construction: • Excavate to depth of first pre-cast concrete ring and to diameter of • Shovel and approximately 1.5metres pickaxe • Add additional concrete rings as excavation deepens – de-watering • Concrete rings, will need to take place to keep excavating after water table depth is the first one with reached a cutting edge • Use smaller diameter rings to continue excavating from water table to and smaller desired depth diameter ones to continue past the • Plug bottom of well with gravel after construction water table depth

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