Water Supply Wells

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 and gravel deposits, or deeper bedrock that can hold and transmit water - like porous or fractured limestone and sandstone. 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 drilled 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 that have too little aquifer thickness to support normal household needs through the use of a drilled well. These types of wells are commonly called "seepage wells" because of the manner the well accumulates groundwater from shallow formations that "seep" water. They are also called "cistern wells" because of the large diameter offers many gallons of water stored in every foot of casing below the water level. It's common to find bored wells up to 48" in diameter. This large diameter 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 the well user. In Iowa, most bored wells are found in the areas of central, south central, and western where the ancient glaciers once rested. It's common to find that bored wells can not keep up with the water production needed for household or livestock needs and many older bored wells have a difficult time providing safe drinking water. The bored wells installed prior to 1982 usually have fewer protective construction features which results in poorer general water quality when compared to those wells installed after 1982. Newer bored wells can sometimes use similar materials as used in drilled or cased wells. When newer construction methods are used and the bored well is placed, constructed and maintained properly, they can provide a dependable and safe source of drinking water.


3. Driven or Sandpoint Wells - This type of well is usually found in alluvial river basins and adjoining low laying areas nearby rivers, streams and waterways. 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 department 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 - This type of well is not permitted for new construction any more 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 and larger. Some of the largest hand dug wells in the state have been documented as large as 36 feet in diameter. As the name implies, these 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 utilizing 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. The Iowa DNR does not recommend that you use 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.

Standards Required 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 are used at each well location, it helps ensure the well will produce water that is safe to drink without extensive water treatment - plus it helps provide long-term protection to the aquifer, which helps ensure the resource is available for future generations. The most important fact to remember regarding this topic is 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 Iowa 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.

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.

Arsenic can be found in groundwater sources that supply water supply wells. Because of this, 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 testing except for coliform bacteria and nitrates - at any time a well is newly constructed or repaired. 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.

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. The map to the right provides a basic view of the test results. The red dots indicate arsenic levels above the maximum recommended levels and the blue dots indicate arsenic levels below the maximum recommended levels.

Because of the potential health risks that arsenic poses, public health and environmental health professionals encourage all private well owners to have their wells tested for arsenic at least one time. This testing will provide the well owner and water user(s) with important information on any health risks that arsenic may pose. In general, the cost for arsenic testing is approximately $20 per sample. Additional 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 from arsenic. Treatment systems designed to reduce or remove arsenic include reverse osmosis water treatment systems, water distillers, or one or more water filter beds that contain 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 a brochure from the State Hygienic Laboratory at the University of Iowa. The booklet is titled "Well Water Quality and Home Treatment Systems." Additional information on home water treatment devices can be obtained from a Water Systems Council information page titled "Drinking Water Treatments."

All water treatment systems advertised for sale or sold in Iowa must be registered with the Iowa Department of Public Health (IDPH). Please visit the IDPH website for more information. It's recommended that a licensed plumber install the system and that the water user understand the periodic maintenance and testing that the system requires. It's important to consult with a water treatment system sales professional to determine what types (species) of arsenic is present in the well water so that the correct system for arsenic removal is purchased.

When choosing a water treatment system to reduce or remove arsenic, it's important to consult with a water treatment system professional to determine what types (species) of arsenic your supply has and arsenic amount of arsenic that needs to be treated. 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. For more information or questions regarding home treatment systems that are registered in Iowa, contact Chelsea Stevens at the Iowa Department of Public Health, 515-281-5894,or by email at Chelsea.Stevens@idph.iowa.gov.