Water Supply Wells

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Water Supply Well Basic Information

Owning and maintaining a safe drinking water supply doesn't happen automatically. It's the result of having a properly constructed well that accesses a known safe aquifer. It also takes well owners who are committed to operate and maintain a safe water supply.

The job is easier if you understand your role in developing a safe water supply. This includes understanding how local land use patterns may interact with the local geology and affect your well. It also means installing your well in a protected location away from sources of contamination.

Some of the most important steps in having a safe water supply include having your well constructed using high quality construction materials, only hiring DNR Certified Well Contractors to perform your well services, and requiring your contractor perform full depth grouting of the well casing.

In addition, as a well owner, you must take an active role in maintaining your water supply. This means protecting your well head area from sources of contamination, never dumping anything on the ground that is hazardous, inspecting and maintaining your well to minimize unnecessary problems, and routinely sampling your well water and sending it to a drinking water lab for analysis. After all, if you don't test your water, you won't know if its safe to consume.

In Iowa, water supplies fall into two categories: a private water supply or a public water supply. With a private water supply, all parts of the system are managed by the water user - things like the water supply well, the water distribution system, and all water treatment systems or devices. A private water supply connects to fewer than 15 individual connections (like homes, apartments, condo, camp spaces, etc.) and provides water for less than 25 individuals a day. Private supplies do not have a central administrator making water system related decisions for the water users. For private water supplies, well construction and reconstruction activities are issued private well construction permits through the local county health offices. Private well users are also responsible for testing their own water supply to confirm that water is safe to drink.

If your water supply has at least 15 service connections or regularly serves 25 or more individuals a day, the supply meets the definition of a public water supply. The definition of public water supply includes (1) any collection, treatment, storage, and distribution facilities under control of the supplier of water and used primarily in connection with the system; and (2) any collection (including wells) or pretreatment storage facilities not under the control of the supplier which are used primarily in connection with the system. Public water supply wells and systems can only be permitted through Iowa DNR Water Supply Engineering. Public water supplies operate under DNR Water Supply Operations permits. This requires the water system to undergo periodic testing to ensure the safety of the water, provide notice to water users when the water isn't safe to consume, and provide reports to DNR Water Supply Operation to verify and document the safety of the water system.

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Categories of Water Supply Wells

Water supply wells generally fall into four categories:

  1. Drilled or Cased Wells - Drilled wells for home, farm and light commercial use are generally 8" or less in diameter and draw their water from alluvial basins, inter-till sand or gravel deposits, or deeper bedrock that can hold and transmit water. Drilled wells are normally designed to obtain water from aquifers in geological settings that offer greater protection from surface water and shallow groundwater. In Iowa, it's common to find well depths ranging from 40' - 2000' deep depending on the quantity of water needed and the quality of water desired. Industrial well users and large drinking water suppliers use wells that can be as large as 30" in diameter and have a well depth that exceeds 2000'. Drilled wells make up the majority of the new well installations in Iowa and when placed, constructed and maintained properly, drilled wells are the most dependable and safe source of drinking water.
  2. Bored or Augered Wells - Bored wells are mainly found in areas with too little aquifer thickness to support normal household needs using a drilled well. Bored or augured wells are often called "seepage wells" because of the manner in which the well accumulates groundwater from shallow formations that "seep" water. They are also called "cistern wells" because their large diameter, up to 48", allows the well to hold a large volume of water when installed below the water table. The larger quantity of water can help sustain the peak water needs of a well user. Most bored wells are found in central, south central, and western Iowa where the ancient glaciers once rested. Often, bored wells cannot keep up with household or livestock water production needs, and many older bored wells have a difficult time providing safe drinking water. Bored wells installed prior to 1982 usually have few protective construction features, resulting in poorer general water quality when compared to wells installed after 1982. Newer bored wells can sometimes use materials similar to those used drilled or cased wells. When new construction methods are used and bored wells are placed, constructed, and maintained properly, they can provide a dependable and safe source of drinking water.
  3. Driven or Sandpoint Wells - These well are usually found in alluvial river basins and adjoining low laying areas nearby rivers or streams. These wells are generally 2" or less in diameter and are often less than 30' in depth. A sandpoint well is installed by joining a screened drive point (or sandpoint) to short lengths of pipe and physically driving the assembly into a shallow sand and gravel aquifer. Although a sandpoint well can provide safe drinking water when properly placed, maintained, and protected, the DNR does not recommend using a sandpoint well as a potable drinking water source due to the uncertainty of the water quality from the shallow groundwater sources they access.
  4. Hand Dug Wells - These wells are no longer allowed for new construction, but old hand dug wells can be found on old properties nearly anywhere in the state. They are most common in areas underlain by glacial till and nearby home sites that were originally built before 1940. Hand dug wells are generally 36" in diameter or larger. Some of the largest hand dug wells in the state are 36 feet in diameter. As the name implies, hand dug wells were constructed using hand labor (along with machine labor for extremely large diameters) to excavate a borehole. The borehole would be lined with brick, field stone, or even wood. Hand dug wells exhibit poor water quality due to the combination of using the most shallow groundwater and being constructed of materials that do not block out surface water or very shallow groundwater. They are also a safety hazard because the well top and opening is large and often poorly maintained and protected. Each year in the United States, individuals die or are severely injured due to falls into poorly protected hand dug wells. The DNR does not recommend the use of a hand dug well as a source for drinking water. If your property has a hand dug well, we urge you to properly plug the well to help reduce the liability that the well presents.
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Standards for Well Installation

All wells need to be planned and constructed to adapt to the geologic and groundwater protection needs of the actual well site. When proper construction standards help ensure a well will produce water that is safe to drink without extensive water treatment, and it helps provide long-term protection of the aquifer, which helps ensure the resource is available for future generations. However, it is important to remember that the statewide minimum construction standards used in price quotes by some contractors may not be enough to protect your well from local contamination. This is why it is important for you - as a well owner - to choose your contractor carefully and understand that the lowest cost to construct a well may not provide the best water quality and aquifer protection. Please consult with local DNR Certified Well Contractors to learn more about what role well construction has in protecting your resource.

Below are five areas that are covered by statewide private well rules.

  • Certified Well Contractors - The installation of all water supply wells in Iowa requires that the homeowner hire an individual Iowa DNR Certified Well Driller to perform the well construction or perform the actual work themselves. All well construction must meet the minimum construction standards for the area of installation. The Iowa DNR does not recommend that you undertake any well services yourself. This is because well services are specialized work that requires knowledge, skill and specialized tools. Plus, this type of work can be dangerous to your personal safety and the groundwater. In addition, should you complete part of the job and then require a certified well contractor to finish the work, it may cost you more than if the contractor solved your well problem from the start. When you hire a well contractor, make sure that they are currently certified with Iowa DNR Well Contractor Certification in the proper well service disciplines.
  • Construction Standards in 567 IAC Chapter 49 - Statewide well construction standards offer minimum levels of well protection but some areas of the state may require greater protections to be used for well construction. Increasing the amount and depth of casing to avoid poor quality groundwater and/or grouting the well to a deeper level will help ensure long term protection to the well and aquifer, specific to the region the well is located. In addition, ll well service work and repair must meet Chapter 49 standards including well disinfection and water testing.
  • Water Testing - All water supply wells must be tested to determine if the water is safe to drink when the well is newly constructed or when the well is serviced or repaired. It is the responsibility of the well owner to insure that the testing is completed and that the well users are informed of the outcome of the testing.
  • Well Plugging- When a well is no longer needed or is in a state of repair that eliminates the possibility of repairing the well for use, the well must be abandoned and properly plugged.
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Special Considerations for Drinking Water Wells Located in Karst Bedrock Conditions

The term "Karst" refers to terrain characterized by the presence of easily dissolved bedrock near the ground surface. Because carbonate rocks can be dissolved by groundwater, karst areas are often characterized by sinkholes, springs, and losing streams. The shallow groundwater located in or near Karst areas can be highly vulnerable to contamination because contaminants can travel quickly from surface water to the local shallow aquifers.

Because of the prevalence of agriculture and livestock in Karst regions of our state, localized contamination of karst aquifers with nutrients, pesticides, and bacteria can be a concern. Contaminated aquifers should not be used for drinking water purposes unless proper water treatment is used and maintained.

Although Karst features can be found in a number of locations across Iowa, they are most abundant in the NE corner our state. The NE Iowa Karst map can help you determine if your property is located on or nearby Karst bedrock features. 

When you live in a Karst area and use a water supply well for your drinking water needs, it's important to understand how protected your water source is based on your specific location, the land use practices in your area, your well's construction, and frequent sampling and analysis of your well water. If your well is located in a Karst area, please refer to our Karst guidance document for additional information.

Most modern water supply wells include protective construction features designed to exclude the shallow groundwater associated with Karst terrain. If you live in a Karst area and are considering a new well, make sure that you hire only Iowa DNR Certified Well Drillers and ask them to document what construction features they will use to help protect your well and drinking water quality.

Older water supply wells may not have adequate protections in place to ensure that the well obtains its water from deeper, protected aquifers. If you have an older well, or if you don't know the depth and construction details of your well, you should have your well water sampled at least yearly so that you know if you should consume the water. You should also consider hiring an DNR Certified Well Contractor to perform a thorough well inspection to determine if your well only accesses water from known safe aquifers and that your well provides safe drinking water.

If you live in a Karst area and your well obtains its water from shallow groundwater sources that have been proven to be unsafe to drink and renovating or replacing your well is not an option, you should use a known safe alternative source for your drinking water or consider the use of reverse osmosis water treatment. Properly designed, installed, and maintained, reverse osmosis systems can provide you with a safe source of drinking water under Karst conditions.

For more information on Karst areas, refer to the DNR's Kast Bedrock & Well Contamination webpage.

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Natural Arsenic in Drinking Water Supplies

Arsenic is a naturally occurring element that can be found at some level in groundwater in many locations around our state. It usually occurs in conjunction with certain sulfide minerals that are deposited as part of our soil and bedrock formations. The environment that created the arsenic deposits is a result of millions of years of accumulation, sedimentation, and erosion.

Traces of arsenic can be found in water sources including groundwater, lakes, rivers, and oceans. Foods like fruits, vegetables, and seafood can also contain trace amounts of arsenic. Since arsenic is a natural part of our environment, everyone is exposed to small amounts of this element during their lifetime.

Because arsenic can be found in groundwater sources that supply water supply wells, it's important for all well users to understand if their water supply contains any arsenic. Neither state nor federal governments have set minimum drinking water quality standards for private wells and there are no requirements for mandatory arsenic testing. This means that it's the responsibility of the well owner and the water users to perform testing on their own private sources so that they understand the quality of their drinking water and any adverse health effects the water may pose.

Refer to the Water Systems Council Arsenic & Well Water fact sheet for more information.

A recent study by the University of Iowa tested 475 private wells for various contaminants. Out of this group, eight percent (8%) of the wells were found to have arsenic levels above the health threshold. 

Because of the potential health risks that arsenic poses, all private well owners are encouraged to have their wells tested for arsenic every 5 years, or more frequently if arsenic is detected. This testing can be provided free of charge through your local county environmental health department using Iowa's Grants-to-Counties (GTC) Program. Additional information on the GTC Program can be found here. More information on arsenic testing can be obtained by viewing the State Hygienic Laboratory arsenic information web page.

If a private well user discovers that arsenic is present in their water supply and the levels pose a health risk, there are water treatment options that help reduce or eliminate the risk. Treatment systems designed to reduce or remove arsenic include reverse osmosis, water distillers, or one or more water filter beds containing activated alumina. Because in many cases it's only necessary to treat the drinking water in a home, the treatment may be as simple as installing a “point of use” treatment system at a convenient location like the kitchen sink, or the water tap on the refrigerator and ice maker.

Information about arsenic treatment options is available in the Well Water Quality and Home Treatment Systems brochure from the State Hygienic Laboratory at the University of Iowa. Additional information on home water treatment devices can be obtained from the Water Systems Council Water Treatments factsheet.

It's important to consult with a water treatment system sales professional to determine what types (species) of arsenic are present in the well water and the amount of arsenic that needs to be treated so that the correct system for arsenic removal is purchased. In some cases, arsenic removal is a multi-step process and requires additional treatment equipment. Understanding the arsenic in your water supply will help ensure that the water treatment system that you consider will perform properly and provide you with safe drinking water. 

Once you have chosen the treatment system, we recommended that a licensed professional install the system and that the water user be trained on system operation, periodic maintenance, and the need for water testing to confirm that the system is working properly. 

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Additional Resources

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