307-777-WELL (9355)

Common Contaminants

Well owners should be aware of the potential contaminants that could impact their drinking water. Groundwater can be contaminated by natural processes, land uses, waste disposal practices, and spills or leaks. A contaminated water supply is unsafe to use without treatment even though you may have used the same water for years without getting sick.

The following people are especially susceptible to illness caused by contaminents in water:

  • Infants
  • Young children
  • Pregnant women
  • Elderly
  • People with compromised immune systems

The contaminants listed below are the most common contaminants in Wyoming.  Any of them could cause long or short-term health problems.

For additional information, or constituents not listed above, the EPA Drinking Water Treatability Database has information on treatment options for numerous additional chemicals. 

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Find a Laboratory

The laboratory you choose should provide specific sampling instructions and clean bottles to collect the water sample. Carefully follow instructions for taking samples. Sampling is the most important part of testing. A carelessly collected sample can give you inaccurate results. Check with individual laboratories to get prices. Ask how soon you should expect results and about the information that will be provided with the test results. A good lab should help you interpret the results and make sense of the scientific data.

This information is provided to assist homeowners in finding an analytical laboratory for water analysis, inclusion on this list does not indicate WDEQ endorsement of the lab or the services provided.

Wyoming Department of Agriculture Analytical Lab
1174 Snowy Range Road
Laramie, WY 82070
Ph: (307) 742-2984

Combined Laboratories Facility
208 South College Drive
Cheyenne, WY 82002
(307) 777-7431  

460 East Pearl Ave.
PO Box 937
Jackson, WY 83001
Phone: 307-733-6401

Pace Analytical – Montana Laboratory
150 North 9th St
Billings, MT 59101
Ph: (406) 254-7226

Energy Labs
1120 South 27th St        2393 Salt Creek Hwy        400 West Boxelder Rd
Billings, MT 59101         Casper, WY 82601             Gillette, WY 82714
Ph: (800) 735-4489        Ph: (888) 235-0515            Ph: (866) 686-7175

Wyoming Analytical Laboratories, Inc.
1660 Harrison St             625 Center St
Laramie, WY 82070        Rock Springs, WY 82901
Ph: (307) 742-7995         Ph: (307) 362-3176

Intermountain Laboratory
1633 Terra Ave                 1701 Phillips Circle         541 Garden Dr., Unit O
Sheridan, WY 82801        Gillette, WY 82718          Windsor, CO 80550
Ph: (307) 672-8945           Ph: (307) 682-8945         Ph: (970) 460-0055

Town of Pinedale Microbiology Laboratory
55 Pinedale South Road
PO Box 709
Pinedale, WY 82941
Ph: (307) 367-2348

County and Local Resources
Under Construction
Wyoming Well Related Agencies
Protect Your Well

Know exactly where your well is located on your property, and keep well construction and maintenance records.  Remember to disinfect any equipment that will be used inside your well prior to use.

Keep potential contamination sources , such as fuel and chemical storage, septic tanks, or livestock away from your well.  To better understand how a contaminant source can impact your well water, review our Groundwater Contamination fact sheet

Know exactly where your septic system is located on your property, maintain it regularly, and keep maintenance records.

A big part of protecting your well from contamination is keeping surface water, which often carries contaminants, from entering your well.

  • To keep water from ponding around your well, make sure the soil slopes away from the well.
  • If you hear water freefalling into the well, find out where the water is entering your well.

Maintain the integrity of your water well. 

  • Check visible casing, sanitary seal and well cap for damage regularly.  Repair or replace missing or cracked components with commercially manufactured parts immediately. 
  • All vents should be covered with a fine mesh screen to prevent animals and debris from getting into the vent.

Properly plug and seal any unused or abandoned wells.

If you do need to drill a new well, be sure to review the DEQ fact sheet on locating new wells before you begin.

DEQ recommends sampling your well water annually. Water well owners in areas of potential oil and gas development should test for additional constituents.

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Understanding Your Results

DEQ recommends that you test your drinking water. As a private well owner, you are solely responsible for the quality of your drinking water. It is up to you to decide when and how to test your water.

Once you receive your lab results, the first question people usually ask is whether a detected chemical poses a health threat.  Lab results can be confusing and make it tough to understand if a detection is at a level that should be of a concern, or that could require treatment. Especially when labs may be reporting a concentration in one measurement, such as parts per billion (ppb or ug/L), and the comparison standards are listed in parts per million (ppm or mg/L), or visa-versa. If you are having trouble understanding your lab report contact the analytical lab for assistance. Ask the lab if there are any contaminants that present a health risk.

To determine if water is generally safe to drink, water test results are compared to the US EPA National Primary Drinking Water Regulations table of contaminants and the Secondary Drinking Water Standards.  The EPA Drinking Water website also provides information on potential health effects associated with various drinking water contaminants.  Arsenic and You can help you understand arsenic in drinking water and how to minimize your exposure.  In addition, there is a table below to assist with understanding your lab results.

The Environmental Council of States has created an web application for well owners to get feedback about potential health concerns and water treatment options, Be Well Informed. Wyoming is a partner in the  web application, but please note that not all constituents that Wyoming utilizes as part of domestic classification of groundwaters are included. The Understanding Your Test Results document included on this page can provide information regarding additional constituents. 

It is a good idea to follow-up with a second test before you decide if any water treatment is needed. When considering a water treatment device, make sure its specifications match up to the substances and concentrations you wish to treat. Also, there are performance testing programs for treatment systems, such as the NSF International.

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Every March 13th is “Know Your Well Day”, but any day is a good day to learn moreabout your water well and drinking water supply.

If you live in a rural area, it is likely that your daily water supply comes from a well on your property. More than 75 percent of Wyoming’s population relies on groundwater for part, or all, of their drinking water supply. This water comes from more than 53,000 wells.

Your Well and Water, and Your Responsibility
You are solely responsible for the maintenance of your private water well, and are required to maintain it in such a condition that it does not contribute to contamination of groundwater. The Wyoming State Engineer’s Office regulates permitting and construction requirements for water wells. Properly maintained wells help to protect the groundwater that supplies your well. It’s a good idea to regularly inspect your well, and immediately correct any issues that you see.

Federal, state, and local government agencies provide education and technical assistance to private well owners through programs such as Know Your Well; however, private well owners are ultimately responsible for maintaining their wells and having their water tested. This means that the water quality of private water wells is not checked unless you take action to have your water sampled and tested. Knowing your water quality is the first step in protecting your family. Having your water tested regularly gives you an idea if there are issues with your well that may need to be addressed.

Testing your private well is an important step in ensuring the safety of your drinking water. Here are the steps to test your private well:

1. Determine what to test for: In Wyoming, it is recommended to test your well for bacteria (e. coli, total coliform) and nitrates every year. Additionally, it’s recommended to test for arsenic, lead, copper, iron, manganese, sulfate, and total dissolved solids (TDS) every five years. Uranium, radium, selenium, and methane are also common constituents in Wyoming groundwater.

2. Collect a water sample: Follow the instructions provided by the lab for collecting and handling the water sample. Typically, you will need to collect a certain amount of water in a sterile container provided by the lab. See our sampling instructions for more information or watch this Youtube Video ( for an example.

3. Send the sample to a testing lab: There are several options for testing labs, including state-certified labs and private labs. Make sure to choose a reputable lab that provides accurate and reliable results. Local laboratories are listed under our Find a Laboratory link.

4. Review the results: Once you receive the results from the lab, review them carefully to determine what was detected. Resources are available for help interpreting your lab results including our Be Well Informed tool ( and Understanding Your Results document (LINK). If there are any issues with the water quality, you may need to take corrective actions to improve it.

It’s recommended to test your well water at least once a year to ensure it remains safe to drink. If you notice any changes in the taste, color, or odor of your water, or if someone in your household experiences unexplained health issues, you should test your well water immediately.

In Wyoming, it is recommended to test your well for bacteria (e. coli, total coliform) and nitrates every year. Additionally, it’s recommended to test for arsenic, lead, copper, iron, manganese, sulfate, and total dissolved solids (TDS) every five years. Uranium, radium, selenium, and methane are also common contaminants in Wyoming.

It’s recommended to test your well every 12-14 months. You should also test your well when someone within the household has an unexplained illness or is a member of a sensitive population, such as during pregnancy, infants, elderly or has a health condition

If your well water tastes unusual or funny, it’s a good idea to test your well to determine the cause of the issue. Comparing results before and after the changes in taste are noticed can be helpful in identifying potential remedies.

Interpreting lab results can be challenging, particularly when comparing the results with established standards. Differences in units of measurement between the detected contaminants and comparison standards can lead to confusion, making it difficult to determine if the results pose a health risk. To help with understanding, resources such as the Be Well Informed tool (hyperlink: or the Understanding Your Results document (LINK) are available. If you need further assistance or have any questions, feel free to contact us

If your well is contaminated, there are several treatment options available for most types of contamination. To determine the best treatment option for your specific well and type of contaminant, it’s recommended to consult a licensed Water Treatment Specialist. They can recommend and install a treatment option that will work best for your situation.

For assistance interpreting your well water test results, you can contact the DEQ Know Your Well Program at or call 307-777-WELL(9355). You can also use the Wyoming-specific tool at to see if any detections exceed drinking water standards.

As a private well owner, you are responsible for ensuring the quality and safety of your drinking water. Unlike public water systems, the water quality from private wells is not regulated by government authorities. Therefore, it is essential to test your well water regularly to identify any potential contaminants that could pose a health risk to you and your family. Testing your well water can help detect any issues early and allow you to take necessary corrective actions to protect your health.

The only way to know for sure that your well water is safe to drink is through laboratory testing. Many common contaminants cannot be seen, tasted, or smelled and cannot be removed by boiling. Water quality can change naturally over time or as a result of activities in the area, which can affect the quality of your well water. Therefore, it is recommended to test your well water at least once a year to ensure it is safe to drink.

There are several steps you can take to protect your well and ensure the safety of your drinking water:

1. Conduct regular water testing: Testing your well water at least once a year is essential to identifying any potential contaminants that could pose a risk to your health.

2. Properly maintain your well: Regular maintenance, such as inspecting and repairing well equipment, can prevent well contamination and ensure the longevity of your well.

3. Properly dispose of hazardous materials: Do not dispose of hazardous materials, such as chemicals and pesticides, in your yard or near your well as they can seep into the groundwater.

4. Ensure proper well construction: Your well should be constructed by a licensed professional and meet all local codes and regulations.

5. Protect the area around your well: Prevent surface water from entering your well by properly grading and maintaining the area around the wellhead.

By following these steps, you can help protect your well and ensure the safety of your drinking water.

There are several resources available to well owners in Wyoming to help them manage and protect their well water. Here are some of the key resources:

Wyoming Department of Environmental Quality (DEQ): The DEQ is responsible for protecting Wyoming’s environment and public health. They provide information and resources to well owners, including information on well construction, water quality testing, and well abandonment. The WQD Groundwater Program works to protect and preserve Wyoming’s groundwater by permitting facilities to prevent contamination, and investigating and cleaning up known releases. Know Your Well is a program within DEQ to specifically assist Wyoming private well owners with questions regarding water quality. (

Wyoming State Engineers Office (SEO): The Wyoming State Engineer’s Office is charged with the regulation and administration of the water resources in Wyoming. In addition to processing and maintaining groundwater permits, the SEO Ground Water Division maintains a statewide observation well network, conducts interference investigations and water right adjudication inspections, reviews reports of water supply adequacy for subdivisions, and provides conflict resolution between groundwater and surface water appropriators. (

Wyoming Water Development Office (WDO): The Wyoming Water Development Commission is responsible for the coordination, development and planning of Wyoming’s water and related land resources. This agency contributes to the quality of life by addressing the water resources needs of our citizens through the construction of new water supply projects and the rehabilitation of existing water supply projects. (

Wyoming Well Drillers Association: The Wyoming Well Drillers Association is a professional organization that represents the interests of well drillers in the state. They provide information on well drilling, well construction, and well maintenance. (

Wyoming Association of Rural Water Systems: The Wyoming Association of Rural Water Systems provides training and technical assistance to rural water and wastewater systems, including private well owners. They offer workshops, webinars, and other resources on well maintenance, water quality testing, and well construction. (

University of Wyoming Extension: The University of Wyoming Extension provides education and outreach to communities throughout the state. They offer resources on well water management, including information on well construction, water quality testing, and well maintenance. (

Wyoming County Health Departments: Local health departments in Wyoming can provide information and guidance on well water quality testing and potential health effects from contaminated drinking water. They may also provide resources on well water treatment options. (LINK to Smartsheet –

Wyoming Association of Water Conservation Districts: Conservation districts are local units of government established under state law to carry out natural resource management programs at the local level. Districts work with landowners, counties, cities, towns and other community organizations to conserve land and water resources on private and public lands in the United States. (

These resources can provide valuable information and support to well owners in Wyoming. If you have questions or concerns about your well water, consider reaching out to these organizations for assistance.

There are several potential sources of groundwater contamination in Wyoming, including:

1. Agriculture: The use of fertilizers and pesticides in agriculture can lead to contamination of groundwater with nitrates and other chemicals.

2. Industrial Runoff: Industrial activities such as mining and manufacturing can lead to groundwater contamination from runoff and discharge of wastewater.

3. Landfills and Waste Disposal Sites: Improperly constructed or managed landfills and waste disposal sites can leach chemicals and other contaminants into groundwater.

4. Livestock and Animal Waste: Manure and other animal waste can contain pathogens, bacteria, and other contaminants that can leach into groundwater if not managed properly.

5. Natural Contamination: Natural sources such as radon, arsenic, and uranium can also contribute to groundwater contamination in some areas of Wyoming.

6. Oil and Gas Development: Exploration, drilling, and production activities in the oil and gas industry can lead to groundwater contamination from spills, leaks, and disposal of wastewater.

7. Septic Systems: Failing or improperly designed septic systems can release bacteria, viruses, and other contaminants into groundwater.

8. Stormwater Runoff: Runoff from rain and snowmelt can carry pollutants from roads, rooftops, and other surfaces into groundwater.

It’s important for well owners to regularly test their water and properly maintain their wells to reduce the risk of contamination.

Geology can have a significant impact on groundwater quality. The type of rock and soil that the groundwater flows through can affect the concentration and types of contaminants present in the water. For example, groundwater that flows through limestone can be naturally high in calcium and magnesium, which can contribute to hard water. Conversely, groundwater that flows through shale or sandstone can be naturally high in arsenic or radon.

Geologic features such as fractures, faults, and karst formations can also affect groundwater quality. These features can provide pathways for contaminants to enter groundwater, or they can serve as barriers that prevent contaminants from moving through the subsurface.

Human activities such as land use changes, waste disposal, and mining can also affect groundwater quality by introducing contaminants into the subsurface. The geologic properties of the area can influence the extent to which these contaminants are able to move through the subsurface.

Overall, the geology of an area plays a crucial role in determining groundwater quality and can affect the types and concentrations of contaminants present in the water.

Private wells are typically drilled into the ground to access groundwater, which is stored in an aquifer below the surface. The well is typically made up of a casing, which is a long pipe that is inserted into the ground and sealed to prevent surface water and contaminants from entering the well. The casing is typically made of steel, PVC, or concrete.

A pump is installed in the well casing to draw water up from the aquifer and into the house or property. The pump may be a submersible pump, which is installed at the bottom of the well and pushes water up through pipes to the surface, or a jet pump, which sits above ground and uses suction to draw water up from the well and into the home.

Private wells require regular maintenance and monitoring to ensure that they are functioning properly and providing safe drinking water. This may include regular water testing for contaminants, regular well inspections to check for damage or wear and tear, and periodic cleaning or disinfection of the well and pump system.

Public water supply and private wells both have their advantages and disadvantages.

Public water supply:

  • Consistent quality: Public water supplies are regulated by the EPA and are required to meet strict water quality standards. This means that the water you receive from your tap is consistent and generally safe to drink.
  • Convenience: You don’t have to worry about maintaining or repairing the water system, as this is the responsibility of the public water provider.
  • Access to emergency services: If there is a water-related emergency or contamination event, public water suppliers typically have emergency response plans in place to quickly address the issue.
  • Higher costs: Public water supplies typically come with a monthly water bill, which can be higher than the cost of maintaining a private well.
  • Limited control: You have limited control over the quality and source of your water, as the public water provider is responsible for making decisions about water treatment and supply.

Private well:

  • Cost-effective: Private wells are typically less expensive in the long run, as the cost of drilling and maintaining the well is spread out over many years.
  • Control: You have the responsibility to know and understand the quality of your water. You can choose to install water treatment on your well, or not, and the type of treatment.
  • Access: Private wells are often the only option for properties located in rural areas or far from a public water source, providing access to a reliable source of drinking water.
  • No monthly water bill: With a private well, there is no monthly water bill to worry about.
  • Maintenance and repair: You are responsible for the maintenance and repair of your well system, which can be costly and time-consuming.
  • Water quality concerns: There is no government agency that regulates the quality of groundwater supplied to domestic private wells, like there is for public systems. Therefore if there is a concern with your water quality, as a private well owner, you are responsible for determining if there is an issue and how to treat it.

Contact Information

For more information, please contact our Groundwater Program:

307-777-WELL (9355)