There are three main types of private drinking water wells and it’s important to know what type your drinking water is coming from.
Dug, or bored, wells are often dug right into the ground by a shovel or backhoe. To prevent collapse, these types of wells are lined with stones, brick, tile, or other materials, and are covered with a cap of wood, stone, or concrete. Dug wells have a large diameter and are generally the shallowest type, typically between 10 and 30 feet deep. With their big diameter, a large area is exposed to the aquifer and are able to obtain water from less-permeable materials like sand, silt, or clay. One disadvantage is that the well can go dry during periods of drought if the water table drops below the well’s bottom.
Driven wells are constructed by driving a small diameter pipe into soft ground, such as sand or gravel, where it draws water from the saturated zone. A screen is usually attached to the bottom of the pipe to filter out sand and other particles. These well types are slightly deeper than dug wells, usually between 30 and 50 feet.
Last, there are drilled wells. Most modern wells are drilled using a rotary-drilling machine that chews through rock to reach water deep underground. These are the deepest of the three well types and are often times hundreds of feet deep. At the bottom of drilled wells, often a pump is placed to help push the water up to the surface. Finally, a plastic or metal casing is placed around the well to prevent collapse. While drilled wells do have the lowest risk of contamination because of its protective casing, as with all wells, it cannot be assumed that it is contamination free.
