| Wells construction: hand dug and hand drilled |
|Section one: Planning|
|Chapter 1: Introduction to wells planning|
1. Availability of Materials
Even as you are beginning site selection and community awareness activities, you should determine the availability of construction materials and the difficulty in obtaining them. Later you will need to assess in greater detail the specific tools and supplies needed, and the quantities of each.
First of all, can you get cement or pipe? If cement is available, it should be fresh and powdery, and not congealed in hard clumps. Cement, sand, gravel, and water can be mixed to make concrete which when it hardens is very strong and long lasting especially when reinforced with steel reinforcing rod (rerod). If neither cement nor pipe is available, you will need to find a local material that can serve as the lining. (See p. 38.)
Metal, plastic, or concrete pipe can be used. Metal pipe, usually galvanized iron or steel, is more durable for well sinking but is subject to corrosion and rusting over time. Plastic pipe, on the other hand, has less strength and is not easy to use in the sinking process. Nevertheless, it is virtually unaffected by ground water quality. Large diameter concrete pipe can be used to line dug wells.
If you can get these basic materials, you will probably be able to find the other related tools, equipment, or adapt local equipment. A local metal worker (welder or blacksmith) can probably make any special tools you may need. For a list of these, see page 37 of the next section.
2. Use of Local Materials
Construction of a well is cheaper, more easily understood, and more likely to be incorporated into the culture if the builders use local materials whenever possible.
The materials required to construct the bottom section, lining, well head, and pump (see Figs. A and B) should be sufficiently strong to withstand the stress of installation and the wear and tear of daily use. They should also be able to support the weight of the column where necessary and not contaminate the water, as a result of natural wear, during the lifespan of the well.
In emergency situations, when the best water available is immediately needed, a number of substitute materials and techniques can be used. For example, wood lining can be used instead of cement. Wells built with wood or other substitute materials and techniques will supply acceptable water for a short period of time. However, they cannot now or in the future be converted into permanent sources of clean water without rebuilding major portions of the structure.
3. Materials for Well Parts
The two most important sections of the well are the lining (or casing), and the bottom (or intake) section. While it is not necessary that both be built of the same material, it is often cheaper and more convenient to do so. Almost all modern well linings are made of either concrete or pipe (metal or plastic).
Nowadays, concrete is used most often in the lining of hand-dug wells. It can be easily mixed and cast in place in the well. Reinforcing bars can be added to either mortar or concrete to make a much stronger and more durable lining. (See Appendix IV, Concrete.)
Metal pipe is normally used in the construction of drilled wells. It can easily be shaped to make the necessary tools with which to sink the well and can also serve as the permanent casing and bottom section.
Plastic pipe is too soft to use during drilling but is in many situations a better casing than metal pipe, because it will not rust or corrode.
Cement and pipe are available in most countries and usually in all but the most remote regions. When both materials are available, consider such factors as transportation, type of well, depth, ease of construction, and adaptability to local practices before deciding which is the more appropriate.