| Wells construction: hand dug and hand drilled |
|Section two: Hand dug wells|
Rural communities have frequently employed hand-dug wells to increase the supply of water available for individual use. Using simple construction techniques and suitable materials, hand-dug wells can provide reliable sources of water and offer the following advantages:
• Because the community can be involved in the actual construction, it is "their" well, which they are more likely to maintain.
• The equipment needed is light and simple and thus suitable for use in remote areas.
• The construction techniques are easily taught to unskilled workers, thus cutting supervision time.
• With the exceptions of cement and reinforcing rods, the necessary materials are usually locally available, making it one of the cheapest methods of wells construction in a rural community.
• A completed well provides a reservoir at the source which will accumulate and store water from aquifers that would otherwise be too weak to use.
On the other hand, hand-dug wells present certain limitations:
• 60 meters is usually the practical limit to the depth that can be reached, although most dug wells are less than 20 meters deep.
• Construction is slow.
• Extracting large quantities of water with motorized pumps is not feasible.
• Hard rock is very difficult to penetrate and often can only be accomplished by blasting, which is slow, hard work.
• Because it is difficult to penetrate very far into the aquifer, slight fluctuations in the water table often make hand-dug wells unpredictable and unreliable.
The hand-dug well is the only method of well construction where people actually go into the well to work educational campaign to demonstrate and explain what each part of the well is and how it works might help villagers understand and then want to work with and maintain it more. In so doing, proper maintenance necessary in keeping the well functioning might be better carried out, particularly in communities using a well or an improved water source for the first time.
For sanitation reasons a pump is desirable. If installed on a hand-dug well with a full cover, a pump will help reduce chances of contamination significantly. In rural areas where pump maintenance and repair can be a real problem, large diameter wells are often the best solution to water supply problems. Pumps can be installed while leaving an accessway through which water can be drawn by rope and bucket if the pump should break down. (See Pumps Appendix).
Compared to other well sinking methods, digging a well by hand takes a long time. An organized and experienced construction team consisting of five workers plus enough people to lower and raise loads in the well can dig and line 1 meter per day in relatively loose soil that does not cave in. However, the bottom section is likely to take 2 or 3 days per meter because of the difficulty in working while water continually enters the well. Depending on how you plan to develop the well, the top section can take anywhere from a day or two to several weeks. An experienced team sinking a 20 meter well and installing pulleys on the top structure could easily take 5 weeks, including occasional days off (this, of course, assumes no major delays). A new or inexperienced group would be expected to take twice that time.
Hand-dug wells should be dug during the dry season when the water table is likely to be at or near its lowest point. The well can be sunk deeper with less interference from water flowing into it. The greater depth should also ensure a year-round supply of water.
If the well cannot be dug during the dry season, plan to go back to it at the end of the dry season to deepen it.
B. Work Outline
Outlined below are the major steps involved in digging a well. The appropriate community leaders, health committee, public works committee, and others who are interested should be involved in all the planning decisions.
• Begin community education and awareness activities to enable the people to understand what is happening and how they can benefit.
• Choose a well site based on geological factors, user preference, sanitary conditions, and accessibility.
• Determine available expertise - people (including yourself) with well or general construction experience.
• Assess materials available - tools, cement, reinforcement rods (re-rods), sand, gravel, wood.
• Select methods of construction that are most suitable for the use and available materials, considering shape, size, depth, lining, bottom, and top.
• Plan and begin any training that will be necessary for workers.
• Before construction begins, put down in writing the workplan for the construction of the entire well.
• Gather all equipment and materials needed for construction of the well at the well site. Arrange these at the site so as to facilitate construction as much as possible.
• If concrete lining rings are to be used, begin constructing them in advance. Each ring must be cured for at least 4 days before it is put in place at the well head.
• Lay out the hole with provisions for checking diameter and plumb (see p. 53).
• Arrange for people and materials to get in and out of the well.
• Dig and line the middle section.
• Continue the digging and lining procedure until
(1) you reach water, or
(2) some obstruction causes you to
(a) change digging/lining procedure
(b) abandon this well and pick a new site.
• Dig and line the bottom section as far as possible into the aquifer. The method used to dig and line the bottom section will often be different from the digging and lining method used in the middle section. This may be necessary because you are not only concerned with digging, lining, and possible hole collapse (as in the middle section), but also with removing enough water from the well to permit work to continue.
• Install a simple sand and gravel filter or porous concrete plug across the bottom of hole.
• Extend the lining up above ground to form the head wall.
• Build and install the well cover.
• Install the pump in the cover on the well.
• Disinfect the well.
• Build the apron (platform) around the head wall to channel the run-off to one particular place.
• Build a drainage pit or other device for removal of standing water.*
• Build an animal trough.*
• Build a wash-basin platform.*
*These items are not always necessary but should be considered.