HOW DEEP SHOULD MY WELL BE?
If the driller has drilled several wells in the area, he may be able to estimate the approximate depth. Most of the time, however, the depth needed to find the required well yield cannot be determined prior to drilling. Deeper wells may cost more than a shallow well to construct, but not drilling deep enough can result in later problems. Listed below are some of the factors that may influence decisions about the depth of a water well.
Seasonal Rise And Fall Of The Water Table
During the year, the water in the well fluctuates up and down in response to seasonal precipitation in the area and local ground water use. The well must therefore be drilled deeper than the lowest expected elevation of the water table. Water level fluctuations may occur over several years if there have been drought conditions.
Surface Contamination Risks
Deeper wells that are properly constructed including grout, casing, well cap, and a pitless adaptor (in freezing climates) usually provide guaranteed protection from bacterial contamination sources originating at the surface.
Low Yielding Rock Formations
In low yielding rock formations the well may have to be drilled deep enough to serve as a storage cavity for ground water. To ensure the well will have ample supply and a long life, the drilling company will continue to drill below the water table. Once a well is drilled, depth to the top of the ground water table (static level) and diameter of the well determine how much water will be stored within the well cavity.