Digging A Water Well
Wells have traditionally been created by just hand digging. It’s the same method used in most rural areas in the developing world.
These kinds of wells are inexpensive and low-tech.
They require mostly manual labor (hands, a shovel, and a carrying bucket) and the well structure is usually lined with either stone or brick as the excavation proceeds.
The well would be excavated until incoming water exceeds the digger’s bailing rate. Even today, some wells are still sunk by hand.
Drilling A Water Well
More modern or automated drilling methods are, however, available to replace the manual labor methods. Most modern wells are usually drilled by drill rigs mounted on big trucks. They utilize several methods to advance the hole to the desired depth and also to remove the formation material loosened and suspended after the drilling and the fluid circulation or bailing system.
Different drill bits are used during the process including rotary (air rotary) drill bits which chew away at the rock and percussion bits which smash the rock. If the ground is soft, the larger auger bits (bucket augers) are used. There are other ways to sink a well like a cable tool, reverse circulation, and down-the-hole.
The depth of the well will vary based on factors like the groundwater depth and quality, as well as the geologic conditions at the chosen site. If a shallow hole is dug such that it only ends above the water table/aquifer, most of the underground water at this depth is still stuck to bits of rock and soil, and so only a little water empties out into the hole.
However, if the hole is dug deep enough such that it ends up below the water table, gravity pulls all the water out of the holes in the soil, rocks, and the entire surrounding saturated ground and into the empty space right at the bottom of the borehole thereby filling it up with fresh groundwater. The water only fills up the hole up to the bottom level of the aquifer/water table – just slightly lower.
In some instances, a layer of impermeable rock can sit above a layer of permeable rock that’s filled with water. Something interesting can happen in this case, especially when the impermeable rock slopes downward.
Water flowing in the bottom/lower level gets trapped by the upper layer of impermeable rock, creating a confined aquifer. As such, the water flows downward without any outlet causing pressure to build up.
Once a borehole is dug deep into the ground that it reaches the confined aquifer, the pressure alone can be great enough to shoot the water up the well all the way from the bottom with no help from a pump. These kinds of wells are known as flowing artesian wells.
Based on the specific makeup of the local geology, the well can contain water-soluble minerals and even contaminants, so it’s properly disinfected and capped in order to provide sanitary protection up until it’s connected to the home’s piping system.
If the water is of very poor quality, it can be sealed off by installing an additional liner or casing inside the original casing and then grouting it into place. In case the construction defects cannot be remedied or the water quality is really unsatisfactory, the well must be immediately abandoned and completely sealed so as to prevent possible cross-contamination between sites.