These important steps include siting, drilling and pump testing the well. Even though following the recommendations in this page will not guarantee all the clean water you may need or desire to have, it will greatly increase your chances of having a clean, reliable, productive well which is able to meet your needs.
Groundwater exploration is not a hit or miss (or random) proposition. Excess rainwater percolates into the soil and rock beneath the earth's surface accumulating in zones of saturation called aquifers. A well is a hole drilled into the aquifer from which a small portion of the groundwater can be pumped to the surface for man's use. It is true that any well penetrating an aquifer will yield water but the amount of water produced from a randomly sited well may be very small. Such low producing wells often provide adequate water for domestic or farmstead uses. If a well is to provide irrigation water a more highly productive well will usually be needed.
Scientific methods have been developed for locating wells where they will penetrate into zones of fractured rock buried beneath the soil surface. Wells located on a fractured rock zone will produce much larger quantities of water than wells drilled into zones where the rock is not fractured. Finding the fractured rock zones, or better yet, finding the intersection of two fractured rock zones can be a time consuming and expensive procedure. Only geologists and engineers with training in aerial photo interpretation and hydrogeology are qualified to locate wells by the fracture-trace technique. If a high producing well is desired, however, the consultants fee for siting the well is worth the extra benefit.
In addition to the siting considerations discussed above which pertain to finding adequate water, wells should be located at least 50 feet from sewers and septic tanks; at least 100 feet from pastures, on-lot sewage system absorption fields, cesspools and barnyards; and at least 25 feet from a silo. Areas where groundwater comes to within 10 feet of the soil surface should also be avoided.
Drilling a well is more than boring a hole into the earth. A finished well will consist of a borehole cut into the aquifer at a diameter large enough to accept the well casing (see Fig. 1) which will receive the pump. The decision on how large the pump must be to meet your intended demand must, therefore, be made before drilling starts. Table 1 relates the necessary well casing size to the size of pump needed to pump various quantities of water. For instance, a 6-inch casing will receive pumps which can pump up to 100 gallons per minute (gpm). If you desire to pump more than 100 gpm an 8-inch casing will be needed which will dictate at least a 10-inch borehole. Your well driller will actually make these decisions, but he must know your needs.
Figure 1. Well components.
The borehole itself can be drilled using any one of several types of drill rigs including impact, rotary, or various combinations. After the borehole has been drilled into or through the water bearing aquifer, the well screen should be installed in the producing zone. The zones above the producing aquifer must be cased to prevent cave-ins, and the annulus between the borehole and casing must be filled with grout to keep surface contaminates from entering the well.
Table 1. Well casing and borehole diameter for desired pumping rate. Borehole sizeDeveloping a well is the process of clearing the well of fines left by the drilling operation, and flushing these fine particles out of the gravel and aquifer between the well screen and the first few feet of the aquifer.
Development is accomplished by surge pumping, bailing or any operation which will force water through the development zone at high velocities. Developing a well is the responsibility of the well driller. Properly developed wells will yield more water than poorly developed wells.
With the well in place, the question remains "How much water can be pumped from the well on a sustained basis?" The sustained pump rate is determined by the aquifer rocks ability to move water toward the well under the influence of gravity while the well is being pumped. To determine the sustained pumping capacity of a well a pump test must be performed on the well. The pump test should be completed by the well drilling contractor as part of the contract to drill the well. The desire for a pump test must be made clear to the driller before drilling begins, since some drillers are not able to do pump testing. Be sure to use a driller who can complete the work including a pump test.
With the well in place, the question remains "How much water can be pumped from the well on a sustained basis?" The sustained pump rate is dependent upon the aquifers ability to move water toward the well under the influence of gravity while the well is being pumped. To determine the sustained pumping capacity of a well a pump test must be performed on the well. The pump test should be completed by the contractor as part of the well drilling contract. The desire for a pump test must be made clear to the driller before drilling begins because some drillers are not able to do the pump testing. Be sure to use a driller who can complete all drilling work including the pump test.
Several types of pump tests have been developed, but all are designed to establish the long term equilibrium rate at which water will flow towards and enter the well. The simplest, most straightforward pump test is to place a pump in the well, after the development phase is complete, and pump water from the well at a constant rate. The discharged water must be dumped some distance from the well so it can not recirculate back into the well during the pump test. The pump rate should be great enough to stress the well, but not so great as to cause the well to be pumped dry. During the pump test, the water level in the well must be measured and recorded at regular intervals starting at the time pumping begins and continuing until pumping stops. Pumping should continue for at least 24 hours (without interruption) or until the water level in the well remains at the same elevation for three consecutive half-hour readings.
Figure 2 is a schematic of the water levels within the geologic structure while a pump is drawing water from a well. The cone of depression is produced when water is removed from the well bore by the pump, causing the water level in the well to drop. This drop in the well water level means the water surrounding the well is at a higher elevation and the gravitational water in the rock begins to flow into the well bore. As this continues, the distance between the original water table and the water level in the well, or drawdown, increases forming a large cone of depression. At some point, the drawdown reaches a point of equilibrium, where the water flows to the well at the same rate as it is being pumped from the well. This equilibrium usually occurs after 24 to 48 hours of continuous pumping at a constant flowrate.
Figure 2. Well hydraulics.
The capacity of a well can be estimated by first determining the specific capacity of the well. Specific capacity Sc of a well is the pump rate, Q in gallons per minute during the pump test, divided by the drawdown, s (in feet) after 24 hours or at equilibrium. In other words, the specific capacity is the flowrate per foot of drawdown.
Sc = Q(gpm)/s(ft)
Knowing the depth of the well and where the permanent pump will be placed, the maximum permissible depth to water in the well can be taken to be 10 feet above the permanent pump intake location. The difference in elevation between the original water table and the maximum permissible depth to water is the maximum drawdown, Smax. The maximum sustainable discharge for the well is then the specific capacity times the maximum drawdown.
Qmax = Sc (Smax)
After the pump test is completed, you will have developed knowledge about how much water the well can be expected to produce. You are now ready to proceed with your irrigation design.
Approximately 15 percent of Americans (or, around 45 million people), rely on private wells for their water. While they were once only dug for homes far out in rural areas where municipal services didn't reach, today, more homeowners in populated areas are considering having their own private well. If you're building a home or you're simply looking for alternative ways to become self-sustaining, we are breaking down the benefits of well drilling in Raleigh.
City water can be unreliable, especially as infrastructure ages and deteriorates. When a water main breaks, it can take days to get it fixed, leaving you and your family relying on bottled water for drinking and cooking and having to go without showering and laundry. Also, contamination is often a problem with municipal water as a pipe can break, there can be a failure at a water treatment plant, or a chemical spill can contaminate the water requiring lengthy boil water advisories (and that's assuming the problem is discovered and shared with the public!).
By having your own well drilled, you have a continuous, steady source of fresh water that's readily available and reliable.
Have you ever gone to drink tap water and notice it smells or tastes faintly of chlorine or even just a "chemical" taste? In order to make it safer to drink, tap water is treated with salts and chemicals to remove bacteria and impurities, but in doing so, this affects the taste and odor. Well water is pulled from deep within the ground water where it has been naturally filtered through layers of rock and mineral deposits. This gives it a cleaner, more pure taste.
When you're connected to a city water, you're paying every month for water and sewer services, plus any taxes and fees. Most households in North Carolina pay well over $100 a month for water service, and over time that adds up to a lot of money.
While well digging is an investment, once it's in place, the only costs involved are annual testing for impurities and contamination and occasional maintenance. The average well pump will last around 10 years so large costs tend to be rare and far between.
Municipal water is drawn from surface water replenished by rain and run-off that is then treated with chemicals and additives. Well water is naturally filtered through layers of rocks and rests in underground aquifers where it is infused with minerals, such as calcium and magnesium. These minerals are essential to the body, and by getting them through our ground water, we're getting an extra boost that isn't found in tap water, generally. Children can especially benefit from the extra minerals in ground water.
As we mentioned, ground water is naturally filtered through layers of rock and is stored in underground aquifers. There are no chemicals needed to treat or clean the water, and the only energy required is a well pump to pull water up and into your home. Well water is sustainable, even in the worst droughts, ground water is rarely exhausted and is continually refreshed.
Municipal water is much harder on the environment. Chemicals used to treat the water end up back in the earth. Massive amounts of power and energy are needed to work with the amounts of water necessary to meet the needs of most homeowners. Plus, surface water is not as sustainable and is more easily affected by the short-term weather changes like seasonal droughts.
Often, digging a well can improve your property value. Homeowners are becoming more aware of the benefits of having a private well, especially if it's already in place, saving them the investment of having to dig it themselves. The sustainability and eco-friendly aspects, paired with cost-saving functionality makes this feature attractive to many prospective buyers.
If you're ready to experience the benefits of well water for yourself, speak to a well specialist today for a quote! We have decades of experience in well drilling, well pump repair and installation, and other comprehensive well services. To learn more about our services or get an estimate, give us a call at 919-291-4063 or fill out our contact form below to get started.
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