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Shallow Water Wells
(also known as: Dug well, Driven well, Bored well )

A shallow well is used when the water table (top surface of the ground water) is high - anywhere from 10 feet to 100 feet below the surface.

Shallow wells are less expensive to dig, but rapid or large changes in water levels can be expected during periods of heavy rains. The well may go dry during a drought when the ground water table drops. They are also more likely to be contaminated from surface contaminants.

There are three types of shallow wells - dug, driven, and bored.

Dug Wells

A "dug well" is the oldest type of water well. A hole is dug in the ground using a shovel or backhoe until incoming water exceeds the digger’s bailing rate.

Typically dug wells are found next to older homes, dug before drilling equipment was readily available or when drilling was considered too expensive.

Most hand-dug wells are from 3 to 6 feet in diameter (large enough for a person to work in), and shallow, usually 10 to 30 feet deep.

Brick tile, stones or other material are used to line the well, to prevent collapse while allowing water to enter. Then the hole is covered with a cap of wood, stone, or concrete.

If you have a dug well on your property and are using it for drinking water, check to make sure it is properly covered and sealed.

 
Being so shallow, dug wells have the highest risk of becoming contaminated.
To minimize the likelihood of contamination, a dug well should have features to prevent contaminants from traveling along the outside of the casing or through the casing and into the well.

1. The well should be cased (lined) with a watertight material
   (for example, tongue-and-groove precast concrete) and a cement grout or bentonite clay sealant poured along the outside of the casing to the top of the well.
   
   
2. The well should be covered by a concrete curband cap that stands about a foot above the ground.
   
   
3. The land surface around the well should be mounded so that surface water runs away from the well and is not allowed to pond around the outside of the wellhead.
   
   
4. Ideally, the pump for your well should be inside your home or in a separate pump house, rather than in a pit next to the well.
   
   

Driven Wells
Like dug wells, driven wells pull water from the water-saturated zone above the bedrock.

Driven wells are generally deeper than dug wells - 30 to 50 feet deep, where the ground water table is within 15 feet of the ground’s surface.

In the proper geologic setting (areas with thick sand and gravel deposits), driven wells can be easy and relatively inexpensive to install.

Lengths of metal pipes of 2" -3" in diameter are assembled and driven into the ground.

A screened "well point" located at the end of the pipe helps drive the pipe through the sand and gravel. This screen allows water to enter the well and filters out sediment.

The pump for the well can be located in one of two places - on top of the well or in the house.

An access pit is usually dug around the well down to the frost line. A water discharge pipe to the house is joined to the well pipe with a fitting.

The well and pit are capped with the same kind of large-diameter concrete tile used for a dug well. The access pit may be cased with pre-cast concrete.

 
Although deeper than dug wells, driven wells are still relatively shallow and have a moderate-to-high risk of contamination from nearby land activities.

To minimize this risk, the following steps should be taken:

1. The well cover should be a tight-fitting concrete curb and cap with no cracks and should sit about a foot above the ground
   
   
2. Slope the ground away from the well so that surface water will not pond around the well
   
   
3. If there’s a pit above the well, either to hold the pump or to access the fitting, you may also be able to pour a grout sealant along the outside of the well pipe.
   
   
4. Protecting the water quality requires that you maintain proper well construction and monitor your activities around the well.
   
   

Bored Wells
Bored wells are the modern equivalent of hand dug wells. These wells are dug using an auger, scoop, dragline, or some similar machine, and are relatively large in diameter (2 to 4 feet).

Bored wells are typically constructed where aquifers (water bearing geologic formations) are both shallow and low-yielding, 20 to 100 feet deep.

To compensate for these low-yielding aquifers, large diameter bored wells serve as storage reservoirs to provide water during periods of high demand.

Older bored wells are commonly lined with sections of clay pipe; newer bored wells are usually lined with concrete pipe.

If properly constructed and covered, they can provide a satisfactory water supply and present no special hazard. Abandoned, they are as dangerous as dug wells and cisterns, and should be plugged.




 
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