Hand Dug Wells – The Basics

Rural communities have frequently employed hand-dug wells to provide a supply of water for individual use. Using simple construction techniques and suitable materials, hand-dug wells can provide reliable sources of water and offer the following advantages:

·         The equipment needed is light and simple and thus suitable for use in remote areas.

·         The construction techniques are easy for an unskilled worker to learn.

·         With the exceptions of cement and reinforcing rods, the necessary materials are usually locally available, making it one of the cheapest methods of well construction.

On the other hand, hand-dug wells present certain limitations:

·         200 feet is usually the practical limit of depth that can be reached, although most dug wells are less than 65 – 70 feet deep.

·         Construction is slow.

·         Extracting large quantities of water with motorized pumps is not always feasible due to lack of electricity.

·         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.

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 access way through which water can be drawn by rope and bucket if the pump should break down.

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 3 feet per day in relatively loose soil that does not cave in. However, the bottom section is likely to take 2 or 3 days per foot because of the difficulty 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 70 foot 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.

Plan your work - Below are the major steps involved in digging a well.

·        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), pre-cast liners, sand, gravel, and wood.

·        Select methods of construction that are most suitable for the use and available materials, considering shape, size, depth, lining, bottom, and top.

·        Before construction begins, put down in writing the work plan 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.

·        Lay out the hole with provisions for checking diameter and plumb.

·        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 you reach water, or some obstruction causes you to change digging/lining procedure or 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.

Design your well - To design a well, it is necessary to decide what materials will be used and how they will be put together. This includes determining:

·         The size and shape of the hole.

·         Preferred digging and lining methods.

·         How much water needs to be available, and, therefore, how deep the bottom section should go into the aquifer.

·         How the top section should be constructed to best protect the well from contamination, while allowing easy access to the water.

·         The anticipated well depth.

Decisions to make?

Well Shape - The shape of the well is what it would look like if you were looking straight down into it.

 

Well Size - The size of the well is a measure of how wide it is. Some holes are very large, and some are very small. The size will be largely determined by: (1) the way it is excavated, (2) the materials used to line it, and (3) the purpose of the well.

The size of the round hole is usually expressed by its diameter, a measurement from one edge of the hole through the midpoint of the well to the other side of the circle.

Diameter is the longest measurement across the hole.

Although wells can be dug in any shape, almost all wells are round. The reason for this is that a round well produces the greatest amount of water for the least amount of work. Also, a round lining is the strongest that can be built for the smallest quantity of materials. Thus, while other well shapes have been used without problems, a round shape enables the builder to get the most from available time, money, and materials.

Square or rectangular wells are usually dug where materials to be used in lining the well necessitate such a shape. This is most often the case when flat wood boards are the only lining materials available. Wood, however, is not recommended.

Many factors could determine which diameter should be used.

·         Pre-cast lining sections come in specific diameters.  Choose your well diameter based on the available size of Pre-cast lining sections.

·         Generally, the choice of diameter will be based on two considerations. The well should have (a) the smallest diameter which still provides (b) a comfortable working space for the number of people that will be working in the well at one time.

The smaller the diameter of the well, the less soil and rock will have to be dug and fewer materials will be required to line the well. Remember, if you double the diameter of the well, you increase the amount of soil and rock that must be dug by four times. The workers will need enough space so that they are not hampered in their work. There must be enough space for them to use their tools and for the bucket which will remove excavated materials from the well. Without enough space, they will continually bump into each other and the wall.

During stages of its construction, a well may have two or sometimes three different diameters.

(i.e. The hole is dug to the diameter decided upon.  When a lining is installed, the diameter is reduced along with the available working space.  You may be installing the bottom section lining inside the existing lining. This will further reduce the diameter.)

Ground Conditions and Lining - It is very difficult to anticipate what the final depth of a well will be before it is begun. However, if there are other wells in the area, it is possible to get an idea of the approximate depth of the water table. This can be a great help when gathering the materials needed for the lining construction.

All wells, except those drilled through rock, can be expected to cave in with time unless a lining is installed to support the well. The lining thus helps to keep the well open. There are certain acts of nature, such as earthquakes or even gradual ground shifts, which will break even the strongest linings, but these cannot be planned for or anticipated.

Occasionally slight ground shifts can put pressure on linings causing them to split and separate if not strongly built. If no such information is available, it is recommended that you build the lining strong enough to withstand normal earth stresses.

Depending on ground conditions, you may or may not be able to dig the complete hole and then line it. In very loose sandy soil, for example, the sand from the walls of the hole will frequently cave into the hole, seriously hampering efforts to deepen the hole. There are often relatively simple methods of dealing with such problems.  Designing the lining for the middle section is largely a matter of assessing the ground conditions and materials availability to determine the lining materials and method most appropriate for the situation.

Ground Conditions

·         Very loose soil (example: dry sand) - the hole is as wide as the hole is deep because its sides continually collapse and cave in.

·         Loose soil (example: damp sand) - a relatively shallow (3 to 15 foot) hole can be dug before its sides may cave in.

·         Firm soil (example: compacted clay and sand mix) a hole can be dug to the water table with minimal danger of collapse and cave in.

Unless you have had substantial experience digging in the area and this particular type of soil, or have been trained in the identification of soils and their properties do not leave the hole unlined for more than 15 feet.

The only possible advantage to digging the entire hole first is that you can then be certain that water can be reached before you start using your often expensive materials to line the well. However, if there is any question about the safety of working in an unlined section of the well, it is not worth the gamble to leave it unlined.

Dig a short section and line - One source has suggested that for safety reasons, no more than 15 feet of a well should be dug and left unlined. More commonly, this cautious method is used in loose soil. This means of construction is also recommended in all soils when workers are inexperienced. Using this method, wells are dug in 2 to 15 foot sections, and then lined.

Dig to water table and line - This method is commonly used in firm soil, especially where the water table is not very deep. It has the previously mentioned advantage of not using any expensive materials in a well until a good supply of water can be assured. However, this method should not be attempted by workers inexperienced with well work.

Dig complete well and then line - This method is not recommended because of the danger of cave-ins beneath the water table which would undermine the entire well shaft. The only situation in which this method might be justified is where the middle section lining must rest on the bottom section lining for support, but there are many ways of avoiding that necessity.

Design the top section - The purpose of the top section is to provide safe and easy access to well water and to prevent as much contaminated surface materials as possible from entering the well.

The design of the top section is strongly influenced by two aspects of well usage: (1) access to water or how water is drawn from the well and (2) preventing surface contaminants from entering the water.

These two functions are not always compatible. It is often necessary to compromise sanitation for the sake of water access. A top section, in fact, is not absolutely necessary for the function of a well. However, the different design of the parts of the top section is intended to make the well safer, cleaner, and more convenient for users.

Major components of the top section:

·         Head wall

·         Drainage apron (platform)

·         Cover

Head wall - A head wall should be built on all wells which will not be fitted with a permanent cover and a pump as a simple inexpensive safety feature which will prevent people and animals from accidentally falling in.

This is simply a wall which extends above the surface of the ground far enough to prevent most accidental entry of people, particularly children, and animals. Its external dimension is dependent on how thick you want the head wall to be.

The easiest and best way to construct the head wall is as an extension of the lining. In most cases it will be convenient to build the head wall as an extension of the lining above ground. You will already have the equipment and supplies on site with which to do this.

Drainage apron (platform) - A drainage apron is most often a reinforced concrete slab 3 to 4 feet wide which surrounds a well and, because of its slight slope, channels surface water away from the well. Wire mesh reinforcing may be used if it is available.

By forcing water to flow away from the well, the apron serves two functions:

·         It prevents contaminated surface water from following the outside of the lining and flowing back down into the well before it has had a chance to be sufficiently filtered by the earth.

·         It prevents the formation of a mucky area immediately around the well which can be a source of contaminants to the well water.

A sloping platform will simply move the mucky area from direct contact with the head wall to the edge of the platform.

By installing a shallow channel,

   or a very short wall

around the edge of the platform, the water can be funneled off to one specific area away from the well where people and animals will not have to track through it to get to the well.

The apron should be strongly and carefully constructed as it will receive a lot of wear, and any cracks or chips which develop will decrease the effectiveness of the apron.

An apron can be built of stone with mortared joints. If for some reason it is not feasible to build an apron, dirt should be built up around the well so that water spilled will tend to run off away from the well rather than collect around it.

The Cover - A cover can improve the sanitary quality of the water in the well by preventing the dust and dirt normally carried in the air from entering and contaminating the water. It also prevents people from dropping things into the well.

There are two basic variations of well covers, temporary (removable) and permanent (fixed in place).

·         A temporary cover is one that covers the well between the times it is being used, but must be removed to pull water from the well. For example, a temporary cover would be a wooden cover that rests on top of the well but must be removed to throw a bucket, tied to a rope, into the well. This is a limited step toward protecting the well water from surface contamination.

·         A permanent cover is usually made of reinforced concrete. It can be poured in place on the well or pre-cast in one or more pieces and later set over the well.  Pump mounting bolts and an access door can be cast into the concrete. Pre-casting the cover in one or two pieces may be easier because of the difficulty of building a form which is both strong enough to support the weight of the concrete over the open well and which can then be removed after the concrete has set.

Design The Bottom Section - There are two basic methods for constructing the bottom section – sink the lining and dig-and-line.

1. Sink lining into place. Advantages include:

·         The method protects workers from cave-ins during sinking;

·         Workers in the well can put all their effort into removing soil and water, presumably allowing greater well penetration into the aquifer.

A disadvantage is the possibility that workers may have difficulty in firmly attaching the rings together.

2. Dig and then line. Advantages include:

·         The method requires less special preparation;

·         The bottom section lining attaches directly to the lower part of the middle section lining, thus producing a stronger, continuous structure.

The disadvantages include:

·         Workers probably cannot get as far into the aquifer as in the other method because of the necessity for workers to remove soil and water and place reinforcing rod and concrete at the same time;

The purpose of the bottom section is to allow as much water as possible into the well without permitting any of the fine soil particles from the surrounding aquifer to enter the well.

There are three commonly used methods of allowing water to enter the well.

·         Through porous concrete linings - Lining rings sunk into the bottom section can be made of porous concrete which acts as a filter to prevent soil particles from entering the well.

·         Through angled holes in the lining - Holes can be punched in a freshly poured concrete ring which, when cured, can be sunk into the bottom section. These holes are more effective at preventing soil entry if they are slanted up toward the middle of the well.

·         Through the bottom - The bottom of the well should always be constructed to allow water to come up through it. Often the bottom is simply left open and uncovered but it is preferable to prevent soil entry and the gradual filling up of the well.

The final step – is to disinfect your well in order to kill harmful bacteria or other organisms that may have been introduced during the construction process. Disinfecting is necessary after well completion, pump installation, and at any time the system is opened for repair or maintenance.

FYI:

Deeper Wells are generally less vulnerable to contaminations from local surface activities. The water in deep wells probably traveled a considerable distance underground.

Shallow Wells usually draw from the groundwater nearest the land surface, which may be directly affected by farmstead activities. Rain and surface water soak into the soil and can carry pollutants with it.

Local Geology determines the length of time for pollutants to contaminate well water. In some places, this process happens quickly - less than one year. Areas with thin, sandy soil cover or cracked and exposed bedrock are particularly vulnerable. On the other hand, thick clay soils absorb some pollutants. This may delay - but not prevent - the day when a well "turns bad".

If you want to learn about ALL of it - pumps, wells, and so on...

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