3.3 Other Well Types
Other common domestic well types include bored, driven, and jetted wells. All of these methods are used to install relatively shallow wells (ranging from about 15 to 60 m deep) in unconsolidated (or weakly consolidated) aquifers.
- Bored wells are constructed by boring a hole in the ground with an auger and installing a casing. There are several types of augers that can be used, including large-diameter bucket augers (usually < 900 mm diameter), solid-stem augers (usually 350 to 600 mm diameter), and hollow-stem augers (usually 160 to 330 mm diameter). The auger can be hand operated for smaller diameter wells or machine operated for larger diameter wells and deeper boreholes (i.e., power augers or truck-mounted auger drill rigs). Bored wells are typically less than 45 m deep but can be deeper.
- Driven wells are constructed by using a downward force to drive a small diameter casing (typically 50 mm or less) into shallow sand and gravel aquifers. A well screen is placed at the bottom of the casing to allow water to enter the well. They are also commonly referred to as well-points, sand-points, or driven-point wells. Driven wells may use downward force and jetting methods simultaneously to install the well. They can be driven by machine or by hand, using a weighted pipe (similar to how a metal fence post is driven into the ground). Driven wells are usually less than 15 m deep.
- Jetted wells use a high-velocity stream of water to create a hole in the ground. This method is most suitable for installing small diameter wells (50 to 100 mm diameter) in unconsolidated sand aquifers. The construction of jetted wells can involve installing a permanent casing and screen while the hole is jetted down. Alternatively, a temporary casing is jetted down that allows a permanent casing and screen to be installed before removing the temporary casing. The casing is either jetted, or simultaneously jetted and driven, into the ground. Jetted wells usually range in depth from about 6 to 60 m.