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 Dug
Wells
Dug wells are holes in the ground dug by shovel or backhoe. Historically,
a dug well was excavated below the groundwater table until incoming water
exceeded the digger’s bailing rate. The well was then lined (cased)
with stones, brick, tile, or other material to prevent collapse. It was
covered with a cap of wood, stone, or concrete. Since it is so difficult
to dig beneath the ground water table, dug wells are not very deep. Typically,
they are only 10 to 30 feet deep. Being so shallow, dug wells have the
highest risk of becoming contaminated.To minimize the likelihood of contamination,
your dug well should have certain features. These features help to prevent
contaminants from traveling along the outside of the casing or through
the casing and into the well.
Dug Well Construction Features
- The well should be cased with a watertight material (for example,
tongue-and-groove precast concrete) and a cement grout or bentoniteclay
sealant poured along the outside of the casing to the top of the well.
- The well should be covered by a concrete curband cap that stands about
a foot above the ground.
- 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.
- 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.
Land activities around a dug well can also contaminate it. (see
our chart of activites that may contaminate a drinking water well)
While dug wells have been used as a household water supply source for
many years, most are “relics” of older homes, dug before drilling
equipment was readily available or when drilling was considered too expensive.
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. Another problem
relating to the shallowness of a dug well is that it may go dry during
a drought when the ground water table drops.
Other types of wells:
The information contained on this page, as well
as the above graphic was provided by The Rhode Island Department of Environmental
Management from their document: Health
Drinking Water for Rhode Islanders: Private Drinking Water Wells
(644KB PDF FILE, 4 pgs)
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