The following is from a news release from the U.S. Geological Survey (USGS):
There are three basic styles of modern well construction:
Drilled Bedrock Wells or Fractured Rock Wells, Sand and Gravel Wells, Large
Diameter Dug and Bored Wells. How you should build a well is determined by type
of well (dug or drilled), the local geology (sand, gravel, fractured rock, bed
rock, etc.) local precipitation and environmental conditions.
The drilled bedrock or fractured rock wells have become the
dominant well in most of the country. Dug and bored wells are generally around
three foot in diameter and are less frequently used today because they are very
susceptible to contamination.
According to the U.S. Geological Survey (USGS): Dug wells
typically have problems with well yield (having enough water for a modern
household) and bacteria (contamination). “Traditional dug wells did not produce
a lot of water and often ran dry in the summer or in drought, leaving the owner
without water. Also, because the older dug wells had many joints in them,
bacteria were able to get into the water, and people sometimes got sick. The
new drilled wells that went deeper to the bedrock aquifer didn’t have these
problems, so people switched (to drilled wells).”
Joe Ayotte , the Chief of the Environmental Hydrology
Section at the USGS New England Water Science Center and his team have patented a new design for a dug
well to solve these problems with supply and contamination. They call their new
design a “Novel Dug Well.” The USGS was not trying to revive a quant old well,
instead they were trying to solve a newly discovered problem.
Joe Ayotte, the Chief of the Environmental Hydrology Section
at the USGS New England Water Science Center has been studying groundwater
throughout New England for much of his career. He has found that certain
contaminants, like arsenic and uranium, is in the groundwater that many New
Englanders use for drinking water purposes. Turns out, the bedrock in much of
New England has naturally occurring arsenic and uranium, both of which are
elements that are linked to negative health conditions like kidney disease and
cancer and negative birth outcomes. I am interested in his work because in many
areas Virginia bedrock has naturally occurring uranium and the Virginia Rural
Household Water Quality Program has been collecting data looking for arsenic in
our groundwater.
Since the problems with the shallow aquifer stemmed from the
lack of water in traditional dug wells and the bacteria introduced by the older
design, the team from the USGS lead by Mr. Ayotte set out to redesign the dug
well to solve these issues.
With colleagues throughout the USGS, Mr. Ayotte came up with
a design for a “Novel Dug Well,” as he
called it, that successfully combined a large area of inflow with ample storage
to provide sufficient water yield needed by well owners. The well has even
proven to be drought resilient. Furthermore, the casing he uses has no joints
and is sealed with a sanitary cap to prevent bacteria from gaining access. This
enables well owners to access shallow aquifers that avoid the arsenic and
uranium problems from the bedrock aquifer.
Once the redesign tested successful, the USGS team received
a patent for their new well design. The technology is available for licensing
to entities or persons who can manufacture and make use of the research. This could
enable well users to reduce exposure to potential deep aquifer contaminants and
providing an alternative water supply.
Depending on geology there are other designs available today
for shallow wells. More traditional large diameter shallow wells are constructed
by machine and are generally of one of two varieties; a bored well with concrete
collar or a bored well with a buried slab. In the concrete collar construction
the casing is generally 4 or 5 foot sections of precast concrete that are
placed on top of each other and allows water to seep into the well through the
joints between these sections. Because of the possibility of surface
infiltration near the well, the upper 10+ feet around the well is grouted with
concrete or has a bentonite seal, but frankly the USGS design seen below appears
to be a better option.
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| from USGS public domain |
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