Wells Essay ⋆ Environment Essay Examples ⋆ EssayEmpire

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Wells are holes dug, punched, or drilled into the ground to access water or some other liquid such as oil or brine, or gas such as methane. The technology for digging wells has developed from shallow wells dug with hand tools to wells that are drilled thousands of feet into the surface of the earth. Water wells are dug because there is no surface or groundwater available, or because the supply of groundwater is insufficient for the needs of people, livestock, or industry. Shallow wells dug by hand were the primary source of water for people for thousands of years. Wells are considered shallow if they descend to less than 50 feet. Shallow wells reach either the water table (water table wells), which is the level at which the soil is saturated with water, or a well may be dug through an impermeable layer of clay or rock to an aquifer, which is a permeable layer of either soil or rock through which water flows, but which is capped by at least one impermeable layer (aquifer wells).

In many third world countries, shallow wells are still being dug and used by people as a substitute for sharing a waterhole with wild animals. Typically, a shallow well is dug using hand tools and local labor. The well is dug during the dry season to the local water table and then a little deeper. Digging during the dry season insures that the lowest point the local water level descends to below ground will be the lowest level for water in the well at any time. The bottom of the well is covered with sand and gravel to inhibit mud incursions. This will keep the water freer from particles of dirt. If suitable rock is unavailable, then mud bricks are made on site. After the mud bricks have been fired and cooled they are solid enough to not dissolve in the water and will last for a long time. The bricks are then used to line the well from bottom to top and are joined together with cement.

Wells such as those built in some African countries are usually covered with a locally made cement top that has a hole in it. PVC pipe is put through the hole in the well top, which may be called a cap. Then a locally made pump, which is like a bicycle pump, is attached to the PVC pipe. When the pump is propelled water flows out of the lip in the top of the well. Wells of this type can cost $300 or less to build. They then provide water for a whole village that may number 100-200 people or more. Wells that are properly dug will be located well away from possible sources of pollution or from runoff that may carry pollution. In addition, a good well will have a sanitary seal made of cement grout or bentonite clay and its pump will be designed to protect the wellhead.

Wells can be drilled with machinery as well as dug with hand tools. The drilling of wells began in the mid 1800s. The well diggers of that time adopted a machine that drove or “pounded” a bit into a hole into the ground. The bit was attached to a cable and was dropped repeatedly into the drill hole. The cable tool drilling method was slow and inefficient. The rotary drilling method replaced it in the 1900s. The rotary drill bit is made of tungsten steel or other tough metals. Attached to a drill pipe, it is rotated to grind up rock that it encounters in drilling the well. It operates inside of a larger pipe that is regularly flushed with water to cool the drill bit and to wash out the cuttings, dirt, gravel, and sand. The outer pipe acts as a wall and prevents the drill hole from collapsing, which would block the drill hole. As the drilling progresses the well driller keeps an accurate log of the depths of the drilling and the levels at which water is encountered.

Many drillers use a “down-hole air hammer” when drilling in hard rock. The compressed air blows the crushed rock debris out of the well hole along with any water that has entered the hole. After the well is drilled the hole has to be finished to prevent collapse and contamination by pollutants. Lining it with well casing usually made of steel or plastic seals a well. The casing is smaller than the well hole. The space between the well hole and the casing will be filled with a “grout” to prevent contamination. The “grout” is either cement or volcanic clay called bentonite. The space may also be filled with a special kind of fine rock. Usually, only the top 20 feet are grouted. Well drilling equipment is commercially available in units for individuals who wish to drill wells of depths less than 300 feet that can be used for irrigating lawns, gardens, or other farm or home operations. Proper drilling and maintenance of water wells is needed to ensure that the well’s water remains safe. In many locations the accelerating exploitation of well water has had a negative impact on aquifers.

Bibliography:

Michael D. Campbell and Jay H. Lehr, Water Well Technology: Field Principles of Exploration, Drilling, and Development of Ground Water and Other Selected Minerals (McGraw-Hill, 1973);
Michael Detay, Water Wells: Implementation, Maintenance and Restoration (John Wiley & Sons, 1997);
Ulric P. Gibson and Rexford D. Singer, Water Well Manual: A Practical Guide for Locating and Constructing Wells for Individual and Small Community Water Supplies (Premier Press, 1971);
P. Howsam, Water Wells-Monitoring, Maintenance, Rehabilitation: Proceedings of the International Groundwater Engineering Conference Cranfield Institute of Technology (Taylor & Francis, 1990).