|Wells Construction: Hand Dug and Hand Drilled (Peace Corps, 1980, 282 p.)|
|Section two: Hand dug wells|
Supplies include the materials, tools, and equipment necessary for construction of the well.
The following supplies will be needed for construction of any hand dug well:
· digging fools - shovel, pick, mattock;
· equipment to lower and lift people and supplies in and out of the well;
· construction material and the tools needed to work with it.
Tools that may be used with the various materials include the following:
· reinforced concrete - cement, sand, gravel, forms, reinforcing-rod, tie wire, re-rod cutter, re-rod bender, wire cutters, pliers, buckets, 1 trowel (2 would be better), mixing hoes, aggregate gauge box;
· concrete - cement, sand, brick or rock, mixing area, buckets, trowel, mixing hoes, aggregate gauge box;
· wood - wood, saw, nails, hammer.
B. Tools and Equipment
· lowering equipment - tripod, headframe or pulley support with pulley;
· cable or rope - 12 mm steel or 25 mm hemp;
· buckets - 1 large, 2 small;
· square nosed shovel (mixing);
· round nosed shovel (digging);
· hard hat for each worker in well;
· spare shovel and hammer handles'
· plumb bob and plumb line; · level.
Most of the lining methods discussed here rely on the use of cement in one form or another, including concrete, mortar, and porous concrete. For the construction of permanent, sanitary hand-dug wells, cement compounds are the only materials in common use around the world. There is no other material so readily available worldwide that combines the strength, workability, and adaptability of cement compounds. Without cement it will be very difficult to build a permanent, sanitary water source. (See Cement Appendix, p. 221.)
a. Limited amount of cement available
Where there is a limited supply of cement available which will not permit you to pour linings or build masonry, you might consider building a loose rock or brick wall. Simply mortar the inside layer to prevent it from falling into the well. This should only be attempted in very stable ground not subject to collapse.
In some areas only the top 3 meters of the well needs to be lined. This reinforces the area of the well which is most likely to cave-in and uses a minimum of material, and it can be attempted only where a mortar or concrete lining is built in place in a well which is being sunk in firm soil.
Wells lined like this are rarely more than 10 meters deep.
b. Cement Substitutes
Cement substitutes are sometimes commercially available or can be manufactured locally. Lime, for example, can be mixed with sand and water to form a mortar-like paste which can be used in laying brick or rock walls. Like other cement substitutes, it does not have anywhere near the bonding strength of cement mortar.
2. Other Materials
If you cannot get cement in a reasonable length of time and at a reasonable cost, you should consider building the well with other materials such as wood or unmortared rock. These other materials will not last as long as cement but they will enable you to make water available where it is needed now.
· Unmortared brick or rock
Many wells have been built of unmortared rock and have lasted for hundreds of years. This, however, is only where highly skilled stone masons and suitable rock are both available.
Normally unmortared brick or rock is only a temporary solution which will collapse in time. Where the ground is very stable, you might consider such a lining, although the well may stand unharmed without a lining for a long time in this case.
This also is only a temporary solution. It will rot soon (in 1-3 years), tainting the water and allowing caveins.
D. Organization of supplies at the well site
In your planning consider:
· the space needed for each operation;
· the arrangement of supplies within each operation space;
· which operations must be performed at the same time so that their respective spaces do not conflict or cross;
· that a different lining method may be used for the bottom section which will require space for working and materials.
There are 3 different types of operations which must be performed during the sinking of a well:
· removing excavated soil and rock and dumping it;
· lowering and lifting people and supplies in and out of the well;
· preparation and placement of lining materials.
The purpose of organizing the supplies around the well is to provide comfortable working spaces for each of these operations where they will not conflict with each other but are still close enough to be coordinated and efficient. (See Fig. 4-1)
FIG. 4-1. LAYOUT OF MATERIALS AND SUPPLIES
1. Removing excavated soil and rock and dumping it.
A great deal of time will be spent performing this same basic operation over and over again. As a result workers will be tempted to do the least amount of work necessary to get by. It is important that the dumping area be:
· far enough away from the well to not subject the well to danger of caving in;
· not so far away as to slow well sinking because excavated material is not being dumped fast enough;
· located so that rain will not wash material back into the well;
· located in order that water pulled from the well for sinking the bottom section will run off and not collect near the well;
· large enough to hold all the material taken from the well.
2. Lowering and lifting _people and supplies in and out of the well.
This operation is critical for the whole well sinking process but is also so flexible in its placement that too often it is simply assumed that space can be found after everything is set up. Unnecessary delays and possibly dangerous situations can be avoided in later work by simply arranging the supplies so that nothing ever obstructs the lane the pullers must use to raise and lower supplies in the well. Also avoid placing supplies so that they must cross the pulling lane to be used.
3. The preparation and placement of lining materials.
Most hand dug wells need space to store and later mix sand, water, gravel, and cement to form concrete. The actual mixing area should be close to the well and next to the pulling lane to permit easy movement of concrete into the well. The materials necessary for concrete should be stored near the mixing area but far enough from the well to prevent danger of cave-ins.
Sand and gravel storage will take up a large amount of space, which should preferably be easily accessible from the mixing area and from the opposite side to allow for replenishment if necessary. Also, if you plan to use pre-cast Lining rings, you will have to allow space for their construction.
The importance a few minutes worth of planning can have is demonstrated in the following example.
Assume that we have a well with a 1.3m interior finish diameter, a 7.5cm thick reinforced concrete lining, and a depth of 20m - an average sized well. This well will require about fifty 50kg bags of cement for construction of the middle and bottom section. If only complete bags of cement are mixed at a time that will require:
· 50 trips to and from the cement storage area;
· 50 wheelbarrow trips of sand;
· 100 wheelbarrow trips of gravel;
· some multiple of 50 trips to and from the water supply;
· about 500 trips with concrete from the mixing area to the well, depending on the size of the concrete buckets.
Obviously the shorter all these trips can be, the less time and energy will be consumed by them. Remember too that as you take sand and gravel from the near side of the storage piles you have to walk farther and farther.