Protecting Your Water Source: What’s the Condition of Your Water Well?
(AE1951, April 2020)Water wells can become contaminated over time, and usually, the source of contamination is within 100 feet of the well. Testing the water is the only way to know what substances are present, if your well tests positive for bacteria and/or elevated nitrates, there are several questions to ask. This publication goes over testing your well water, and what questions to ask if it is contaminated.
Contact your county NDSU Extension office to request a printed copy.
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1. Are potential sources of pollution near the well?
Ideally, your household well should be uphill from any potential contamination source. Your well should be at least 100 feet from any of these common sources of contamination: septic tanks and drainfields, barnyards, feedlots, manure piles, silage piles, outhouses and cesspools. Other possible contamination sources are garbage disposal sites and excavations. All of these can produce bacteria and/or nitrates.
Water from these sources can get into the groundwater near the well and flow to the well from normal daily pumping.
2. Is the depth of your well less than 50 feet?
Well depth has a significant effect on potential water contamination. Contaminants that infiltrate from the surface
are more likely to reach the groundwater of a shallow well than
a deep well.
Through the years, wells often were constructed with one of these methods:
- Hand dug or bored (larger diameter)
- Driven, commonly called “sand points”
- Drilled using the rotary or cable-tool method
Dug or bored wells are easy to identify because their diameter can
vary from 18 inches to more than 3 feet. These wells have been shown to have the greatest risk of contamination because they are shallow and generally have porous casing materials.
The well casing is the material that keeps the well hole from collapsing. Dug or bored wells can have cylindrical metal or concrete sections, wood staves and sometimes rocks mixed with concrete as casing materials.
Because dug wells have porous casings, shallow water can get into the well and roots can create openings in the casing that allow rodents and other creatures to get into the well. Dead rodents and snakes have been found in dug wells and become the source for a positive bacterial test.
Driven wells are usually 2 inches in diameter, less than 50 feet deep and typically installed in sandy areas. Their contamination risk is generally not as high as in a dug well.
Drilled wells are the most common and generally the least susceptible to contamination. They are typically 4 or 5 inches in diameter with a metal or plastic casing. The casing will extent to the surface and a cap that may be red, black or have a galvanized color (gray). Because they are usually more than 50 feet deep, they are less susceptible to contaminated water from the surface.
4. Does the casing or cover of the well have any cracks or holes?
The well casing keeps soil out of the well so the water can be pumped. Checking the casing annually for cracks or holes on the outside and the inside is advisable.
To prevent contaminants from entering the well, a vermin-proof cap or cover must be on the well. If the well has a pump mounted on the cover, it usually has a pipe extending into the well. The annulus (ring-shaped piece) around the pipe should be sealed and covered with a protective flashing.
The cover should be watertight and sealed to the casing to prevent rodents and other animals from entering the well casing. On large-diameter wells, the cover should have a sealed and locked access hole.
To see the inside of the well casing, remove the cap (drilled and driven wells) or the cover of the access hole. Use a powerful flashlight to inspect the condition of the casing inside the well. If you hear water running when the pump is not operating, it could be entering through a crack or hole lower in the well. In large-diameter wells, look for roots or other accumulated debris.
5. Is the top of the well casing less than 12 inches above ground level?
In North Dakota, the well casing or cap (if the well has one) is required to project not less than 12 inches above the final ground elevation. In areas subject to flooding, the top of the casing, cap or well cover must be at least 2 feet above the highest known floodwaters elevation and surrounded with earth fill (North Dakota Administrative Code Section 33-18).
The purpose of these requirements is to ensure that surface water doesn’t flow into the well through the top. If your well does not meet these requirements, the contamination risk to your drinking water is higher.
7. Are any open abandoned wells within 100 feet?
Abandoned wells can be a safety hazard. Plus, they provide a direct route for contaminants to enter the groundwater. Abandoned wells within 200 feet of the operational well should be plugged as soon as possible.
For information on how to fill an abandoned well, obtain a copy of NDSU Extension publication AE966, “A Guide to Plugging Abandoned Wells,” online at https://tinyurl.com/PluggingAbandonedWells-NDSU or from the Extension office in your county. Also, the Natural Resources Conservation Service (NRCS) has information and may provide assistance for plugging wells.
According to the North Dakota Century Code, a naturally flowing well (artesian well) must to be plugged by a licensed well driller. Check with the North Dakota State Water Commission at www.bwwc.nd.gov/index.html.
