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Well Logs
What You Need to
Know
Owners of
new water wells should know that one of the most important
components of their household water well system can be kept
filed away—the well log. A well log is a document containing
vital information on the history of the well and the ground
surrounding it. Contractors must file well logs with their
respective states upon completion of all new wells. However,
well owners should have a copy, too, in case a need for
maintenance arises over the lifetime of the well. Quick
access to and understanding of the well log can be crucial
at such times.
Well logs
differ , some are called water well records or drilling
reports. Most, however, contain the same basic information.
Following is an explanation of the details contained in well
logs.
Well Log Layouts
A
reference number—unique to the well—will be at the top,
usually in the left corner, followed by areas that provide
the owner and location, construction and contractor details,
well testing information, and geologic formations
encountered by the contractor. Most well logs also will have
an area titled “comments,” where the contractor can provide
additional notes.
Construction and Contractor Details
The
construction section is essential if the owner has problems
with the water well system, as it describes the materials
found in the well. On some reports, this is where the
contractor information is listed.
Other items listed here on nearly all reports include the
reason for the well, the drilling method used, the depth of
the well, the amount and type of casing used, the size and
type of screen used, and the type of pump in the well. Some
reports also give information on the grout used in the
construction process.
Well owners should know the definitions of the items listed
in this area. A well’s casing is the tubular, watertight
structure that goes down the drilled hole to maintain the
well opening and prevent pollutants from entering the
waterway. The screen is a filtering device below the casing
that allows water, but not unwanted materials, to enter the
well. The grout is the material used to seal the casing in
place.
Well Testing Information
After constructing the well, contractors test it for an
extended period of time. Among the tests performed are those
for production rate, measured in gallons per minute; static
water level, the distance from the ground level to the top
of the water in the well; and drawdown, the difference
between the static water level and the level of water during
pumping. The information gathered from these tests forecasts
the long-term yield of the well. Most families will need a
yield of 6 to 12 gallons per minute. Storage tanks may be
needed for wells producing less than 6 gallons per minute.
Geologic Formations Encountered
This area is usually called the well log — just like the
name of the reports. It details what the contractor
encountered underground when drilling the well. It gives the
information in precise fashion. For instance, if the first
10 feet below the surface consists of yellow clay, followed
by 6 feet of sand and 20 feet of gray clay, the report will
list: 0-10, yellow clay;
10-16, sand; 16-26, gray clay. This information helps
identify the aquifer being used for the water supply and can
be beneficial if problems arise.
Spectrum Geotechnical Services Ltd.
Silvershares Place Suite 8 & 9 Km 15 Lagos-Epe Expressway,
Jakande, Lekki Phase 1,
Lagos, Nigeria.
Tel: (234) 482-4966,434-7585
Mobile: (234) 803-344-4404, 803-302-4953
E-Mail info@spectrumgeotech.com
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