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From construction methods to water sources to permits, here’s everything you need to know about a drilled well.
A drilled well is a well built by drilling a hole into an underground water source using machinery such as rotary drills, cable tools, or jet drills.
Drilled wells are made with specialized machines. Rotary drilling and percussion drilling are the main methods used. In rotary drilling, a bit turns in the soil to cut through the ground. Percussion drilling uses a heavy weight that strikes down to break the soil. Both methods use machines that create a borehole for the well.
The depth of a drilled well depends on the local geology. Drilled wells may range from a few dozen feet to several hundred feet. Most wells go deep enough to reach an aquifer that holds water beneath the ground.
Drilled wells need a casing. This is a pipe installed in the well’s upper part. It prevents surface water and subsurface contaminants from entering the well. The casing helps the structure stay stable and keeps the water inside clean.
Drilled wells have a lower risk of contamination than shallow wells. This is due to their depth and the use of a casing that runs for a continuous length. The casing helps keep surface and subsurface pollutants out of the well water.
A drilled well reaches groundwater by cutting through layers of soil, sand, and rock until it finds an aquifer. The aquifer stores the water the well will provide.
People choose drilled wells in places where the water table is deep. Sometimes, many layers of different materials must be drilled through before reaching the groundwater.
When a drilled well taps into a pressurized, confined aquifer, water may rise in the well and flow out freely. This type is called an artesian well. Water continues to flow as long as the pressure in the aquifer is higher than the ground surface.
Well construction must follow local rules and standards. For example, in Alberta, contractors must follow the Water (Ministerial) Regulation of the Water Act. The rules cover well design, building, cleaning, testing the water flow, installing pumping equipment, and proper closure of unused wells.
In some places, a professional engineer must inspect the grouting. Grouting is the material that seals space around the casing to stop leaks. The inspection helps confirm the well has been sealed correctly.
A record must be kept when the well is built. After construction, the builder completes a Well Record Form. This form is given to the province’s environmental office.
Regulations require setbacks. These are the minimum distances between the well and other structures such as septic systems. The setback helps protect the well from possible contamination.
Drilled wells are made with special machines. These machines use drill bits that cut through soil, rock, and other underground materials.
The way a drilled well is built depends on the underground conditions. No single drilling method works for all soil or rock types. The ground conditions and local geology determine how the well is drilled and how deep it must go.
The drillers design each well based on the type of aquifer they reach. The geology found during drilling decides how the well is finished, including the depth and any extra protection.
