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What is a dug or bored well?

Discover how dug or bored wells work and why they are a reliable option for accessing water in areas with no traditional aquifer.

Updated over a year ago


Dug and bored wells are large diameter boreholes that extend from the surface to some shallow depth. They are usually three or more feet wide and

less than 100 feet deep. They store water that seeps in from the water table and near surface materials. They are typically installed where no traditional aquifer is available, leaving them as the only option. Dug and bored wells are generally found in areas with finer unconsolidated geology — like clay, silt, and loess — that may or may not have very thin sand lenses that can provide small amounts of water. These walls are built so large so they can provide storage and allow shallow groundwater to slowly seep into them.

How were hand dug wells constructed?

Before modern drilling methods were available, many wells were dug by hand. Though Figure 1 is a drawing, it is an accurate example of how hand-dug wells may be lined with stones or uncemented brick. Water, in this example, can seep into the well from nearly any depth between the bricks or stones, which makes it particularly vulnerable to surface contamination. Many people still use hand-dug wells for their water supply, though nearly every state now has construction standards for wells that wouldn't allow a modern well to be constructed this way.

Figure 1: Purdue University Cooperative Extension

How are bored wells constructed now?

Today, large diameter wells are constructed by a machine. The casing is generally four or five foot sections of precast concrete that are placed on top of each other and beveled to fit together. Water can seep into the well through the joints between these sections. In Figure 2, you can see the well has had the upper 10-plus feet around the well filled with clean earthfill, which is generally a clay and silt-based soil that reduces infiltration around the well. This helps protect the well from surface contamination and ensures that the joint openings that allow water to seep into the well are all below 10 feet.

Figure 2: Adapted from Illinois Department of Public Health

Why is concrete poured around a bored well, and is it required?

In Figure 3, the well — which has tile going all the way to the surface — shows that the upper two joints are protected by concrete filled into the annulus around the well, which serves the same purpose. Concrete isn't required in every state, though, and in some cases, the well annulus may not have been filled properly which could allow water to seep in at those first two joints. Check with your local well driller or health department to find out the regulations in your area.

Figure 3: Adapted from Illinois Department of Public Health

What kind of wells are the most vulnerable?

Dug and bored wells generally rely on shallow groundwater for their supply. Proper construction and protection from surface contamination are important for all kinds of wells. They are particularly critical for well owners with dug or bored wells or any other kinds of shallow wells.


The Private Well Class is a collaboration between the Rural Community Assistance Partnership and the University of Illinois through the Illinois State Water Survey and the Illinois Water Resource Center and funded by the United States Environmental Protection Agency. The views expressed here are solely from the class authors and not endorsed or reviewed by US EPA. For more information on private wells, sign up for our free 10-week email course at www.privatewellclass.org.

Want to learn more about your private well and how to care for it?

Sign up for the free 10-week email course from PrivateWellClass.org. The class is a project of RCAP and the University of Illinois, with funding from USEPA.

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