Protecting Your Groundwater Through Farmstead
Assessment:
Assessing the Condition of Your Water Well and Its
Location
AE-1074, July 1998
John Nowatzki, Water Quality Associate
Bruce Seelig, Water Quality Specialist
Thomas Scherer, Agricultural Engineer
The condition of your well is an important
factor to consider when looking at the potential for groundwater
contamination. Specifically, you should be concerned about well
depth, well construction and activities around the well.
Planning for New Wells
When planning a new well, take some time to assess future
farmstead activities. Locate your new well so that it will not be
in jeopardy of ever being contaminated. Locate your well on high
ground, so that if a spill occurs, contaminated water will flow
away from the well. Make the well accessible for repairs,
cleaning, testing and inspection. Hire a competent, licensed well
driller to dig your new well. The licensing process for well
drillers ensures that wells will be constructed according to the
most recent codes that protect your health.
Water Testing
Water testing is the only sure way to know what
substances are present in your drinking water. Some contaminants
may be purely aesthetic and not harmful to your health, while
some contaminants such as bacteria and nitrates can be quite
serious, or even fatal. A list of certified laboratories that
perform water testing in North Dakota is listed in Appendix I of
this circular.
This circular contains a brief discussion of each question on
the Farmstead Assessment checklist, and a section discussing what
you can do and who to call if you answered "Yes" to any
of the questions.
1. Is your well shallow (less than50 feet deep)?
The depth of your well is an important factor to consider
when looking at the potential for groundwater contamination.
Contaminants which infiltrate from the surface are more
likely to reach a shallow well than a deep well. Also, wells
screened in the lower part of an aquifer have less potential
for contamination than those screened in the upper part of an
aquifer. For deep or shallow wells, they should be screened
to draw water from the deeper part of the aquifer where less
contamination is likely to occur.
2. Do you have a driven or dug well?
Different types of wells include dug, driven, and drilled.
A dug well is a large-diameter hole more than two feet in
diameter often constructed by hand. Of the different types of
wells, dug wells have the greatest risk of being contaminated
because they are usually shallow and often poorly protected
from surface water.
Driven wells are usually 2 inches or less in diameter,
less than 50 feet deep, and typically installed only in areas
of relatively loose materials such as sand. Because driven
wells are usually shallow and not grouted between the casing
and earth, their risk of being contaminated is also higher
than other types of wells.
Drilled wells are usually the least susceptible to
contamination and usually the safest. Drilled wells are
deeper than most wells and have grout surrounding the casing
to prevent contamination.
3. Was your well constructed more than 50 years ago?
The age of your well is a factor to consider when
assessing the potential for groundwater contamination. The
older your well, the more likely it is improperly located,
downhill from possible pollution sources. Older wells are
generally shallow and likely to have structural problems such
as collapsed casing or casing with holes.
4. Is there a depression around the casing of your well?
Direction of surface flow can affect the risk of your
drinking water supply being contaminated. Possible pollution
sources on your farmstead should be situated downslope from
your well. If contaminants do get into the surface water
flow, they will flow away from the well.
If a depression exists around your well casing, it
provides a sink for surface water to accumulate in.
Contaminants in the accumulated surface water can either leak
down along the well casing or penetrate through cracks in the
well casing.
The top of the well casing cannot, by law, terminate in
the basement of any building or in a pit, room, or other
space which is below ground level.
Minimum distances of specific possible contamination
sources from your well include:
- At least 50 feet from privy pits, cesspools, septic
tanks, absorption fields, barnyards, feedlots, high
water marks of lakes, streams, sloughs, and ponds.
- At least 30 feet from sewer-lines.
- At least 10 feet from basements or pits.
- At least 20 feet from overhead powerlines.
Greater distances are always preferable and often
necessary, depending on soil conditions.
5. Does the casing of your well extend less than 12 inches
above the ground level?
In looking at potential groundwater contamination, you
need to consider casing height. Currently, in North Dakota,
the well casing or cap (if the well has one) is required to
project not less than 12 inches above final ground elevation.
In addition, in areas subject to flooding, the top of the
casing, cap, or well cover shall be at least 2 feet above the
highest known flood elevation and be surrounded with earth
fill (Section 33-18-01-06 of the North Dakota Century Code).
The purpose of these standards is to ensure that surface
water cannot run into the well through the top. If your well
does not meet these standards, the risk of your drinking
water being contaminated is higher.
6. Is your wellhead located in a pit?
Wellheads located in well pits are more easily flooded
during periods of excessive surface water or when the
groundwater level rises above normal levels. Flooding of well
pits increases the likelihood of well contamination by
surface water and accompanying contaminants. Wellheads ending
in pits should be modified to extend the top of the well at
least 12" above ground level and the pit should be
properly filled.
7. Can you see any cracks or holes in the casing of your
well?
Condition of the well casing and cap need to be assessed
when looking at the potential for groundwater contamination.
Wells are commonly cased with steel, plastic, or concrete to
prevent the collapse of the borehole. The space between the
casing and the sides of the borehole is filled with grout,
usually cement, concrete, or bentonite, depending on the
geologic materials encountered. Both the casing and the grout
prevent pollutants from seeping down into the well.
To prevent contaminants from flowing into the well casing,
a tight-fitting, vermin-proof cap must be installed on the
well when it is constructed. Not all wells are capped; some
wells have pumps mounted on top of the casing. The cap should
have a screened vent which is turned downward so air can
enter the well. The vent should be high enough so it will not
allow surface water to enter the well.
It is possible for the well casing to corrode or crack and
the well cap to become damaged. You should visually inspect
the above-ground portion of your well for holes or cracks and
make sure the cap is secure. You can also check the inside of
the casing by removing the well cap and shining a light
around the inside of the casing. If you have a shallow well,
you may also be able to assess the condition of the well
casing underground. If you hear water running when the pump
is not operating, there could be a crack or hole in the well
casing. Also, make sure the casing is still firmly in place.
If you can move the casing, a channel probably exists between
it and the surrounding materials. That channel can conduct
contaminants quickly, below the surface and possibly directly
to the aquifer.
8. Are there abandoned wells on your farmstead that have not
been properly plugged?
Besides being a safety hazard, abandoned wells are a
direct pathway for contaminants to enter the groundwater. The
NDSU Extensive Service in cooperation with several other
agencies has developed guidelines for the plugging of
abandoned wells in North Dakota. If you decide to plug an
abandoned well on your farm, the guidelines should be
followed as closely as possible.
Assessing the Condition of Your Well
------------------------------------------------------------------------
If you
answered
"Yes" to the
following What you Other
questions should do Who to call references
------------------------------------------------------------------------
Questions Have your water Water testing can be Please refer
1,2,3,7. tested annually for obtained through the to Appendix I
the most common con- North Dakota State for other cer-
taminents, nitrate Department of Health, tified labs
and bacteria, to 701/221-5262 (micro- available for
see if a problem biology), and 701/ water testing.
actually exists. 221-6142 (chemistry).
------------------------------------------------------------------------
Question 4. Relocate sources of State Dept. of Health North Dakota
contaminants down- Water Quality Divi- State Dept. of
slope from well. sion about contam- Health "Water
inent distances from Well Construct-
Fill in Depression wells. 701/221-5210. ion and Water
and mound. Well Pump
Installation,"
Test water annually. Article 33-18.
------------------------------------------------------------------------
Question 5. Measure well casing Local certified well "Water Well
to make sure it is driller for well Construction
at least 12 inches modifications. and Water Well
above the ground Pump Installation,"
surface. State Dept. of Health ND State Dept.
for construction of Health,
codes and inspections Article 33-18.
701/221-5210.
------------------------------------------------------------------------
Question 6. Extend the top of Local certified well "Water Well
the well to at least driller for well Construction
12' above the ground modifications. and Water Well
surface. Fill in the Pump Installation,"
well pit. North Dakota State
Dept. of Health,
Article 33-18.
------------------------------------------------------------------------
Question 8. Assess number of County SCS for tech- NDSU publication
abandoned wells nical assistance. AE-996; Plugging
located on your Abandoned Wells.
farmstead. County Extension for
information. County
SCD or Water Board
for possible cost-share.
------------------------------------------------------------------------
Appendix 1
List of certified laboratories that perform water testing:
All of these laboratories are certified by the State of North
Dakota. Please contact the laboratory to determine if they will
accept your sample.
---------------------------------------------------------------
North Dakota State Department Minnesota Valley Testing Lab
of Health and Consolidated 1411 South 12th Street
Laboratories Bismarck, ND 58501
1205 Avenue A West Telephone: 701-258-9720
Bismarck, ND 58501 or 1-800-279-6885
Telephone: 701-221-5262
or 701-328-6140 Southwest Dist. Health Unit
2869 3rd Avenue West
Diagnostic Laboratory Dickinson, ND 58691
Vet Science Department Telephone: 701-227-0171
North Dakota State Univ.
Van Es Hall
Fargo, ND 58105
Telephone: 701-231-7527
First District Health Unit
801 11th Ave. SW
Minot, ND 58701
Telephone: 701-852-1376
Fargo Cass Public Health Center
401 Third Ave. North
Fargo, ND 58105
Telephone: 701-241-1360
Astro-Chem Service and Lab
4102 Second Avenue West
Williston, ND 58801
Telephone: 701-572-7355
---------------------------------------------------------------
AE-1074, July 1998
|
