Montana Department of Environmental Quality About Us Permitting & Operator Assistance Public Participation

Drinking Water Rules

Program Overview

Several online resources exist to help you find out about levels of regulated contaminants in your treated water for the preceding calendar year.

Consult your annual Consumer Confidence Report (CCR) through the U.S. Environmental Protection Agency (EPA), or search the Drinking Water Watch, which can be searched by county or several other parameters.

Water System Rule Summaries


The chemical contaminants were endorsed in phases collectively called the Phase II/V Rules or the Chemical Contaminant Rules. These rules regulate over 65 contaminants in three contaminant groups:

  • Inorganic Contaminants (IOCs) (including nitrate and arsenic),
  • Volatile  Organic Contaminants (VOCs), and
  • Synthetic Organic Contaminants (SOCs).
Inorganic Contaminants

Inorganic Contaminants (IOCs) are elements or compounds found in water systems and may be natural in the geology or caused by activities of man through mining, industry, or agriculture. It is common to have trace amounts of many Inorganic Contaminants in water systems. Amounts above the Maximum Contaminant Level (MCL) may cause a variety of damaging effects to the liver, kidney, nervous system, circulatory system, blood, gastrointestinal system, bones, or skin depending upon the inorganic contaminant and level of exposure. Some Inorganic Contaminants are more damaging to infants and pregnant women.

All community and non-transient non-community public water systems must monitor for regulated IOCs. Regulated Inorganic Contaminants include antimony, arsenic, asbestos, barium, beryllium, cadmium, chromium, fluoride, mercury, nickel, nitrate, selenium, and thallium. If a sample exceeds the MCL, quarterly monitoring is triggered for four quarters.  MCL’s are based upon a running annual average (RAA) for four quarters.  If the RAA is reliably and consistently below the MCL, the system will qualify for reduced monitoring.



Arsenic occurs naturally in soil and rock and can dissolve into groundwater. For most people, food and water are the biggest sources of exposure to arsenic. There are two forms of arsenic:

  • Inorganic arsenic is the type found in contaminated drinking water and is the most harmful type of arsenic. It is also found in rice, cereal grains, and other foods. 
  • Organic arsenic is the most common type of arsenic found in food. It is common in fish and shellfish and is less harmful to health than inorganic arsenic. Some arsenic in the environment comes from human activity. Arsenic was an ingredient in some pesticides and was used as a wood preservative for wood foundations, decks, and children's outdoor play structures.


Both community water systems (CWSs) and non-transient, non-community water systems (NTNC) are required to reduce the arsenic concentration in their drinking water systems to 10 µg/L.

Health Effects

Drinking water with low levels of arsenic over a long time is associated with diabetes and increased risk of cancers of the bladder, lungs, liver, and other organs. Arsenic can also contribute to cardiovascular and respiratory disease, reduced intelligence in children, and skin problems, such as lesions, discoloration, and the development of corns.  Health impacts of arsenic may take many years to develop, especially if you are in contact with arsenic at a low level over a long time.



Organic compounds are a type of chemical compounds where one or more than one carbon covalently bonded with each other and with other atom like nitrogen, oxygen, halogen etc.

Synthetic Organic Contaminants

Synthetic Organic Contaminants (SOCs) are man-made compounds used for a variety of industrial and agricultural purposes. This group of contaminants includes pesticides, PCBs, and dioxin. SOC health effects include damage to the nervous system, kidneys, and cancer risks.  The list of regulated SOC’s can be found at

  • Monitoring

Both community and non-transient non-community public water systems must monitor for these organic contaminants. Transient water systems do not have to test for these chemicals. If a sample exceeds the MCL, quarterly monitoring is triggered for four quarters.  MCL’s are based upon a running annual average (RAA) for four quarters.  If the RAA is reliably and consistently below the MCL, the system will qualify for reduced monitoring.

Volatile Organic Contaminants

Volatile Organic Contaminants (VOCs) are man-made compounds used for a variety of industrial and manufacturing purposes. VOCs are not readily dissolved in water and will tend to separate from the water forming gasses. VOCs have various effects on the liver, kidneys, nervous system, and some pose a cancer risk.  A list containing regulated volatile organic compounds can be found at

  • Monitoring

Community and non-transient non-community public water systems must test for these contaminants. Transient non-community water systems such as campgrounds are not required to test for VOC’s in their water supply.

 Maintaining Compliance

Compliance is achieved by monitoring quarterly, annually or one sample every three years. If a sample exceeds the MCL, quarterly monitoring is triggered for four quarters.  MCL’s are based upon a running annual average (RAA) for four quarters.  If the RAA is reliably and consistently below the MCL, the system will qualify for reduced monitoring.

Chemical Waivers

The United States Environmental Protection Agency (EPA) has authorized states to issue reduced monitoring waivers for inorganic and organic chemicals to PWSs that have completed an approved waiver application and review process. DEQ allows decreased monitoring of specific inorganics (IOC and asbestos) and organic (SOC and VOC) chemicals. Public Water Systems can apply for a waiver by completing the waiver application and submitting to DEQ.   Waivers for INO, SOC’s and VOC’s must be renewed in the first three years of a new compliance period after sample results are received by DEQ.  Sampling is required for asbestos in the first three years of a new compliance period if the PWS contains asbestos concrete pipe (AC) in the distribution system.  If no AC pipe is in the distribution system, the PWS must complete the waiver form and submit to DEQ in the first three years of the compliance period.

Waiver Applications


This rule applies to Public Water Systems that use ground water as a source and disinfect full time with chlorine.

What are the State Regulations Governing the Montana Chlorination Rule?

The Montana Chlorination Rule is referenced in the Administrative Rules of Montana

  • Reporting responsibilities are referenced in the control tests section of ARM 38.217
  • Sampling responsibilities are referenced in the control tests section ARM 38.225
  • Acceptable methods and levels of disinfection are referenced in the microbial treatment section of ARM 38.229

Which MDEQ standards apply to full time disinfection with chlorine?

Plans and specifications meeting the requirements of DEQ-1, Chapters 1 and 2 for Community Water Systems and DEQ-3, Chapters 1 and 2 of Non Community systems must be provided and approved by MDEQ, prior to installation of full-time chlorination.

When did the changes to the MT Chlorination Rule take effect?

On October 16, 2009, the Board of Environmental Review, a rule-making board formed by the Montana legislature approved changes to the Montana Chlorination Rule that were proposed by the Montana Department of Environmental Quality (MDEQ).

How has the Montana Chlorination Rule changed?

Reporting of rotated distribution system residuals is generally no longer required.
Exception: The MDEQ Public Water Supply Section may still require individual systems to monitor and report in the distribution system.

Do I still have to sample and report the chlorine residual?

Yes, systems still must sample and report entry point residuals.

What is entry point sampling?

An entry point is a sample point after chlorine treatment and before or at the first user.

Chlorine residual sampling is required at the entry point, unless a specified sample point for meeting CT calculation is identified by MDEQ. The specified sample point pertains to systems that are complying with the Groundwater Rule.

How often do I have to sample at the entry point?

Community systems sample once per day.
Nontransient noncommunity (NTNC) and Noncommunity systems (NC) sample on days water is served to the public.

How should I report on days that my system is closed?

Noncommunity systems such as restaurants and schools may not be open every day. Please note this in the data form, for example: closed, weekend, vacation.

How frequently do I report chlorine levels?

Reports are due to MDEQ on the 10th of the month following sampling.

What residual level is required?

Systems that are subject to the Montana Chlorination Rule are required to maintain a residual level of 0.2 mg/L or ppm or greater at the point of entry.
MDEQ may require a system specific residual level - see the Groundwater Rule.

What should I do if the required residual level is not maintained?

If a Public Water System was not able to maintain the required residual level due to unforeseen circumstances, please explain the circumstances in the data form, for example: equipment malfunction, repairs to system.
If the well is not being used every day, please inform us that the pump was not on.

What are the requirements for compliance?

In order for a system to be in compliance, monitoring and reporting is required on all days water is served to the public.

A minimum chlorine level of 0.2 mg/L or ppm at the entry point must be maintained in order for a system to be in compliance.

System specific residual levels may apply – Groundwater Rule.

After a violation, how do I return to compliance?

One month of maintaining the required residual level and reporting returns a system to compliance.

How will the rule change effect consecutive connections?

Monitoring and reporting requirements depend on the monitoring and reporting requirements of the wholesaler.

The following flow chart provides entry point and distribution monitoring guidance for ground water, consecutive connections and surface water systems. Disinfection Flow Chart

Are the forms available online?

Yes, click here: PWS Monitoring Forms

How can data forms be submitted?

Internet: Use the link in the upper right corner of the above form. Receipt of the form is confirmed by us.


Fax: 444-1374

Mail: Permitting and Compliance Division
1520 East 6th Ave
What is a CCR?

The purpose of the Consumer Confidence Report (CCR) is to inform water consumers so they can make informed decisions about their and their families health. The CCR informs the public on the water supplied to their residence.  

 The CCR is a written report that summarizes information about a specific water system. Specifically, the report includes information about water source, water quality, treatment quality, treatment, and management of their drinking water, compliance, health effects, and educational information. The report is made available annually.  

Maintaining Compliance

The CCR Rule requires all community water systems to prepare and distribute an annual water quality report that includes the required information and language. The eight required elements of a CCR include:  

  1. Water system information with contact phone number 
  2. Source(s) of water 
  3. Required Definitions 
  4. Detected contaminant table 
  5. Information on monitoring for Cryptosporidium, radon and other contaminants if detected 
  6. Violations Accrued with explanation of resolution and health effects 
  7. Variances and exemptions 
  8. Required education and health effects language 

 In addition to drafting the report, the CCR must be distributed to customers. The population served determines the distribution requirements (see Distribution Guideline PDF below). The CCR is always available upon request; a copy of CCR must be provided to anyone who requests.  

The CCR includes information from the previous year, for example the 2020 CCR includes data from 01/01/2020 to 12/31/2020 and is due to the consumer and DEQ by June 30, 2021. The 2020 CCR Certification Form is due to DEQ by September 30, 2021. 

Notice that detected lead and copper results are required to be included in the CCR. In addition to including the lead and copper results and required language in the CCR the Lead and Copper Consumer Notice must also be completed to satisfy the Lead and Copper Rule.  


Certification Form - This DEQ required form is due by September 30, which certifies that the CCR was distributed and contains reliable information.

Additional Resources

Drinking Water Watch Is an online resource that will create the majority of the CCR by pulling in sample results, and the EPA required language. To complete the CCR several pieces of information must be added including: water system contact information, and if relevant, corrective actions taken for violations, for those water systems with chemical waivers the required language, and significant deficiencies and their current status.

Certified Laboratories - Several labs offer CCR drafting services. Check with your lab for this service and any associated fees.

CCR iWriter- Is an online resource that will generate a CCR from the information you provide. This site was developed by the EPA.

CCR Requirements- A summary document outlining the requirements for CCR. 

CCR Distribution Guidelines - A summary document that lays out the requirements and options for distributing the CCR to customers.

CCR Rule: A Quick Reference Guide - An EPA summary of the CCR rule.

Cross Connection and Backflow in Montana

This information applies to Public Water Systems in Montana and consists of definitions and frequently asked questions regarding cross connections and backflow.

What is cross connection?

A cross connection is a connection between a potable water system and any other liquid, or by Montana definition MCA 75-6-102-“Cross-connection” means a connection between a public water supply system and another water supply system, either public or private, or a wastewater or sewer line or other potential source of contamination…

What is a backflow?

Backflow means the undesirable reversal of water flow or the reversal of water flow containing other liquids gases or other substances from a connected source that flows into the distribution pipes of the public water supply system.

Why do public water suppliers need to control cross connections and protect their systems against backflow?

Backflow into a public water system can pollute or contaminate the water in that system resulting in water in that system that is unusable or unsafe to drink. Water suppliers have a responsibility to provide water that is safe to drink to their customers. Water suppliers should take reasonable precautions to protect their public water system against backflow and often times this means the use of backflow prevention.

What is backflow prevention?

Backflow prevention is using methods, assemblies or devices to prevent backflow. A basic method of preventing backflow is an air gap, which either eliminates a cross-connection or provides a barrier to backflow. The basic assemblies or devices for preventing backflow are mechanical backflow preventers which provide a physical barrier to backflow.

What is a method?

A method is a plumbing configuration or way to eliminate the cross connection hazard. This is normally accomplished by constructing an air gap which is considered the ultimate backflow protection. This is not always practical and is easily bypassed.

What is an assembly?

An assembly is a mechanism that is able to be tested and repaired in-line, has isolation valves and test ports provided. A list of approved backflow prevention assemblies is published by the FCCCHR (Foundation for Cross Connection Control and Hydraulic Research). The Department can assist with access.

What is a device

A device is generally a self contained mechanism designed to prevent backflow but it is not able to be tested and therefore has some limitations and may not be approved for use by the Department.

How does one choose the correct backflow prevention?

Correctly choosing backflow prevention depends on the degree of hazard of the cross connection. All states agree and adopt this classification of hazards. Low hazards are pollution risks and non-toxic connections, while high hazards are contamination risks and toxic connections. Other rules apply such as, direct or indirect connections, and is the connection subject to backpressure, or is the connection subject to backsiphonage, or is it under continuous use? It is best to contact the Department for help when choosing backflow prevention.

Do I have to test my backflow preventer and how often?

Backflow preventers are mechanical apparatus that are subject to failure due to age, wear, damage, corrosive water and manufacturing flaws therefore it is an industry standard to have all backflow prevention assemblies tested by a certified backflow prevention assembly tester after the initial installation, after repairs of any kind, and at least once annually.

Where can I find a certified backflow prevention assembly tester or how do I become certified?

The Department accepts a person who holds a current certificate issued by a certification program of any state authorizing the person to test backflow prevention assemblies or who holds a current certificate from the American Society of Sanitary Engineers or the American Backflow Prevention Association.  Both entities retain lists of certificate holders.

Does Montana have rules regarding cross connections and backflow?

Yes, Rules regarding Cross Connections and Backflow in Montana are referenced in the Administrative Rules of Montana, Title 17 Chapter 38 Subchapter 3.
Definitions and incorporated standards are referenced in the Definitions and Incorporation by Reference section of ARM 17.38.301 and 17.38.302.
Cross connections on public water supplies are referenced in the Cross Connection: Regulatory Requirements section of ARM 17.38.305.
Cross-Connection Control Programs are referenced in the Voluntary Cross-Connection Control Programs section of ARM 17.38.310.

How does the new Lead Free Law affect Backflow Prevention?

The Reduction of Lead in Drinking Water Act (42 USC 300G) requires that for manufacture, supply, new installs, and replacement, any valve, fitting, or fixture coming in contact with potable water must meet the requirement of having weighted average lead content of less than 0.25 percent.

Do I need to go out and find and replace all system components built before 2014 that allowed for up to 8% lead?” The answer is no, but when components fail and/or need replacement they need to be replaced with products meeting the new lead-free definition of 0.25%.


Air Gap

Atmospheric Vacuum Breaker

Double Check Valve

Hose Bibb Vacuum Breaker

Pressure Vacuum Breaker

Reduced Pressure Assembly


Health Concern

Some people who consume water with DBPs in excess of the Maximum Contaminant Level (MCL) over many years may experience problems with their liver, kidneys, or central nervous system, and may have an increased risk of getting cancer. The EPA has set the MCLs at 80 micrograms per liter (µg/L) for TTHMs and 60 µg/L for HAA5. These numbers are computed for your water system on a locational running annual average (LRAA). For water systems sampling quarterly, the LRAA is an average of the last 4 quarters of data at each sampling location. Because of this, your water system may have single detections above the MCL without having an MCL violation.

Contaminant Source

Chloroform diagramChlorine has been noted in numerous scientific and historical studies as being one of the most important health advances in modern human history. However, there is a balance between proper chlorine dosage as a microbial disinfectant versus the adverse effects of improper dosage. The Disinfection Byproducts Rule is the regulatory response to managing this balance.

Disinfection Byproducts (DBPs) are a group of contaminants that can form when disinfectants used to control microbial pathogens combine with naturally occurring organic matter in the source water. There are more than 500 DBPs that have been detected in treated drinking water and many more that continue to be identified and quantified.

Montana DEQ requires water systems that use chloramines or chlorine to monitor for the following DBPs*:

  • Total Trihalomethanes (TTHM)
  • Five Haloacetic acids (HAA5) *Water systems that use ozone as the primary disinfectant are required to monitor for Bromate DBPs
    Maximum Contaminant Level (MCL)

    The EPA has set the MCLs at 80 micrograms per liter (µg/L) for TTHMs and 60 µg/L for HAA5.

    Protecting Your Water/Health

    DBPs are mainly driven by source water quality and treatment effectiveness of the water system. Consumers should request information from their water supply on their specific results.

    Maintaining Compliance

    Compliance with the Stage 2 Disinfection Byproduct (DBP) Rule is required by Community (C) and Non-Transient Non-Community (NTNC) Public Water Systems that use a disinfectant other than ultraviolet light. This rule complies with the Administrative Rules of Montana (ARM 17.38.213), which adopts the Code of Federal Regulations (40 CFR 141.130) and (40 CFR 141.620 for Stage_2 Subpart V). Sampling requirements depend on source water type (groundwater or surface water), population served, and historical concentrations. Since surface waters systems typically have significantly higher organic matter, the monitoring for surface water systems is weighted heavier than groundwater systems that don’t typically have high organic content. See below tables showing the routine and reduced monitoring requirements: Please keep in mind that the samples are due in the peak historical week and month - meaning the week of highest historical detections or the week with highest average temperature. Most reduced monitoring schedules are for the 2nd week of August due to temperature, which is a factor in DBP formation.. If you would like to access your online monitoring schedule, please follow this link: Public Water Supply Monitoring Schedule schedule

    Maximum Residual Disinfection Limit (MRDL)

    To ensure that your consumers are not consuming water with chlorine levels above the appropriate level (4.0 mg/L on a running annual average), public water systems are required to monitor their free chlorine residuals in the distribution system monthly (at same time and place as their total coliform sample). To fulfill this requirement, please fill out the form in the link below and send it to the email address on the form within 10 days after each quarter. Alternatively, simply provide the free residual chlorine level on the chain-of-custody you provide to the laboratory with each total coliform sample, and the lab will provide these values to DEQ. Quarterly DBP Reporting Form

    Understanding Your Samples

    DBPs represent a chronic risk, which means the adverse health effects are based on a lifetime exposure. Water systems and water consumers should look at long-term trends and keep an eye on long-term improvements for reduction of DBPs.

    More Information

    EPA website with many helpful links and documents

  •  EPA - Stage 1 and Stage 2 Disinfectants and Disinfection Byproducts Rules 

  • Quick Reference Guide for Disinfection

Montana depends on Groundwater for much of its drinking water supply from either public sources or private wells. It is important to understand how groundwater is protected and made safe for drinking.

Groundwater Quality Standards

Drinking water standards and guidelines place a ceiling on contaminant levels in the drinking water supplied by public water systems, regardless of whether the source is Groundwater or surface water.

There is no regulation for ensuring that private wells meet safe drinking water standards. However, private well owners can have their wells tested and use federal drinking water standards as a guide for assessing water quality.

Visit the Water Quality Standards Page for information on water quality standards.

When Groundwater Provides Your Drinking Water from a Public System

Water systems that have groundwater sources may be susceptible to fecal contamination. In many cases, fecal contamination can contain disease causing pathogens. The Groundwater Rule (GWR) applies to public water systems that use groundwater as a source of drinking water and that may be susceptible to fecal contamination. The rule also applies to any system that delivers surface and groundwater to consumers where the groundwater is added to the distribution system without treatment. The purpose of the Groundwater Rule is to reduce disease incidence associated with harmful microorganisms in drinking water.

Requirements of the Groundwater Rule
  1. Periodic sanitary surveys of groundwater systems require the evaluation of eight critical elements and the identification of significant deficiencies (e.g., a well located near a leaking septic system).
  2. Source water monitoring to test for the presence of E. coli, enterococci, or coliphage in the sample. There are two monitoring provisions: Triggered monitoring for systems that do not already provide treatment that achieves at least 99.99 percent (4-log) inactivation or removal of viruses and that have a total coliform-positive routine sample under Total Coliform Rule sampling in the distribution system. Assessment monitoring-As a complement to triggered monitoring, Montana has the option to require systems, at any time, to conduct source water assessment monitoring to help identify high risk systems.
  3. Assessment monitoring as a complement to triggered monitoring. Montana has the option to require systems, at any time, to conduct source water assessment monitoring to help identify high risk systems.
  4. Corrective actions required for any system with a significant deficiency or source water fecal contamination. The system must implement one or more of the following correction action options:
    • Correct all significant deficiencies;
    • Eliminate the source of contamination;
    • Provide an alternate source of water;
    • Provide treatment which reliably achieves 99.99 percent (4-log) inactivation or removal of viruses.
  5. Compliance monitoring to ensure that treatment technology installed to treat drinking water reliably achieves at least 99.99 percent (4-log) inactivation or removal of viruses.
Groundwater From a Private Well Used for Drinking:

Private well owners are responsible for the quality of their water, and no regulatory oversight exists to ensure water quality. However, there are numerous resources for private well owners to assist them in maintaining high quality drinking water.

For More Information:

Protecting Groundwater Quality in Montana

Montana Groundwater Rules

Montana Groundwater Quality Standards (DEQ-7)

Montana Water Quality Report

EPA Groundwater Rule Summary

EPA Groundwater Rule Quick Reference Guide

Health Concern

For the purposes of drinking water, there are two main water sources: surface water and groundwater. Surface water has been exposed to the atmosphere and is presumed to be contaminated with bacteria, viruses, and other pathogens. Groundwater is found below ground and therefore presumed to be naturally filtered, with no bacteria, viruses or pathogens.

However, in some cases subsurface drinking water sources (wells, springs, or infiltration galleries) may be close enough to surface water to be contaminated by that surface water. In this case the water needs to be treated to mitigate any risk to public health. The purpose of the groundwater under the direct influence of surface water (GWUDISW) rule is to identify those sources.

The health concern with GWUDISW is single-celled parasites such as Giardia lamblia and Cryptosporidium, which are not found in uncontaminated groundwater. Adequate distance between a surface water body and a public water source will provide some natural filtration. However, if a source is located close enough to nearby surface water, such as a river or lake, to receive immediate surface water recharge it may be directly influenced by surface water. Large diameter pathogens can then enter the source and be consumed by customers of the public water supply. These pathogens can cause extreme intestinal distress and may be difficult to treat. They are not inactivated by chlorine or chloramine disinfection and are therefore not controlled by normal groundwater treatment techniques.

Contaminant Source

wellIf a public groundwater source is located close to a surface water body or is extremely shallow the source may be considered at risk of contamination. Sources most likely to be under the direct influence of surface water are:

  • Infiltration galleries and horizontal wells
  • Springs
  • Wells located close to surface water
  • Shallow wells

If a source is suspected of being GWUDISW, then it may be tested using microscopic particulate analysis (MPA) tests. This test identifies the number of primary surface water indicators trapped in a 1-micron filter after running water (1 gallon per minute) through the filter for about 18 hours, at not more than 10 pounds per square inch (about 1000 gallons).

Understanding Your Samples

If MPA samples are required for your source the interpretation of those results will be done by the lab and the GWUDISW rule manager at DEQ. The rule manager will help you understand your results.

Rather than looking for Giardia lamblia and Cryptosporidium directly the MPA test is designed to look for primary surface water indicators such as algae, diatoms, insect/larvae, plant debris, or rotifers. These particles would not be found in uncontaminated groundwater. They indicate that the water was exposed to sunlight within the last few weeks and that the pore spaces in the unsaturated zone and aquifer are allowing large particles to rapidly enter the drinking water source. Their presence indicates that the surrounding area does not provide adequate filtration of the water between the surface water and the public water source. This vulnerability requires that the water needs to be treated like surface water in order to be safely served to the public.


If two MPA results show that the source has a low risk of being under the direct influence of surface water (0-9 points), then that source can be determined to be groundwater. Any MPA score of 10 or higher (moderate or high risk) will result in the source being declared to be GWUDISW and subject to the surface water treatment rule (SWTR). The system will have 18 months to either modify the source or come into compliance with the SWTR and will work with DEQ to achieve that goal.

0-9 Low
10-19 Moderate
20+ High
Protecting Your Water/Health

The GWUDISW rule requires that groundwater sources in Montana must be either confirmed to be groundwater or determined to be GWUDISW. See DEQ circular PWS-5, for the complete GWUDISW rule. A source of subsurface water (well, spring, horizontal well, or infiltration gallery) is presumed to be groundwater at the start of the process. Only if evidence indicates that the source is under the direct influence of surface water will the determination change to GWUDISW.

The first step in determining if a source is under direct influence of surface water is for DEQ staff to complete a preliminary assessment form. Based on the results of the preliminary assessment, the source will either be characterized as groundwater or be required to undergo further assessment.

Once the determination has been made for each source, a record of decision letter will be written to the public water system and a copy will be retained in DEQ permanent records.

Maintaining Compliance

Once a source is determined to be groundwater it will only be revisited if there is some indication of a change in the status of the source. This may be from flooding, the movement of a surface water body closer to the PWS source, installation of a man-made surface water body, a sudden increase in bacteriological contamination, deterioration of the source construction, or some other cause. A new preliminary assessment can be completed any time a field staff person visits the source for a sanitary survey or other reason and observes a change that justifies reassessment.


Lead and Copper Webpage
Revised Lead and Copper Rule

The Environmental Protection Agency (EPA) has been working on long-term revisions to the Lead and Copper Rule for a number of years. The following is a statement from the Association of State Drinking Water Administrators (ASDWA) regarding the delays in the revisions:

In a Federal Register notice published June 16, 2021, EPA has delayed the effective date of the final Lead and Copper Rule Revisions (LCRR) originally published on January 15, 2021. The effective date of this rule is delayed until December 16, 2021. Additionally, the compliance date for the final rule is delayed until October 16, 2024. Extending the compliance deadline ensures states have the full three years provided by the Safe Drinking Water Act to adopt laws and regulations to obtain primacy for the rule and so water systems have adequate time to take any necessary actions to meet the compliance deadlines in the rule.

EPA explained that the further delay is needed to allow the agency adequate time to conduct a thorough review of the LCRR requirements and to assess whether the regulatory changes are needed. This action allows the agency to continue conducting virtual engagements to gather additional input from communities, national water associations, Tribes and Tribal communities, and EPA’s state co-regulators.

For more details regarding these updates, please see the EPA’s website at: Revised Lead and Copper Rule | Ground Water and Drinking Water | US EPA.

Health Concern

A small amount of copper is essential for good health. The Food and Drug Administration recommends a dietary allowance of 2 milligrams (mg) of copper a day. Major food sources of copper are shellfish, nuts, grains, leafy vegetables, mushrooms, chocolate, liver, and some fruits. Exposure to high doses of copper can cause health problems. Short-term exposure to high levels of copper can cause gastrointestinal distress. Long-term exposure and severe cases of copper poisoning can cause anemia and disrupt liver and kidney functions. While some of the copper you consume rapidly enters the bloodstream, your body is very good at preventing high levels of copper from entering the bloodstream; it will excrete excess copper after several days. Individuals with Wilson’s or Menke’s disease (genetic disorders resulting in abnormal copper absorption and metabolism) are at higher risk from copper exposure than the general public.


Lead is a toxic metal that can be harmful to human health even at low exposure levels. Lead is persistent, and it can bioaccumulate in the body over time.

Young children, infants, and fetuses are particularly vulnerable to lead because the physical and behavioral effects of lead occur at lower exposure levels in children than in adults. A dose of lead that would have little effect on an adult can have a significant effect on a child. In children, low levels of exposure have been linked to damage to the central and peripheral nervous system, learning disabilities, shorter stature, impaired hearing, and impaired formation and function of blood cells.

It is important to recognize all the ways a child can be exposed to lead. Children are exposed to lead in paint, dust, soil, air, and food, as well as drinking water. If the level of lead in a child's blood is at or above the CDC action level of 5 micrograms per deciliter, it may be due to lead exposures from a combination of sources. EPA estimates that drinking water can make up 20 percent or more of a person’s total exposure to lead. Infants who consume mostly mixed formula can receive 40 percent to 60 percent of their exposure to lead from drinking water.

Pregnant Women

Lead can accumulate in our bodies over time, where it is stored in bones along with calcium. During pregnancy, lead is released from bones as maternal calcium and is used to help form the bones of the fetus. This is particularly true if a woman does not have enough dietary calcium. Lead can also cross the placental barrier exposing the fetus to lead. This can result in serious effects to the mother and her developing fetus, including:

  • Reduced growth of the fetus
  • Premature birth

Find out more about lead's effects on pregnancy:

Lead can also be transmitted through breast milk. Read more on lead exposure in pregnancy and lactating women (PDF) (302 pp, 4.3 MB, About PDF).


Lead is also harmful to adults. Adults exposed to lead can suffer from:

  • Cardiovascular effects, increased blood pressure and incidence of hypertension
  • Decreased kidney function
  • Reproductive problems (in both men and women)

Related Information

Can I shower in lead-contaminated water?
Yes. Bathing and showering should be safe for you and your children, even if the water contains lead over EPA’s action level. Human skin does not absorb lead in water.

This information applies to most situations and to a large majority of the population, but individual circumstances may vary. Some situations, such as cases involving highly corrosive water, may require additional recommendations or more stringent actions. Your local water authority is a valuable resource for testing and identifying lead contamination in your tap water. Many public water authorities have websites that include data on drinking water quality, including results of lead testing. Links to such data can be found on the EPA Consumer Confidence Report website.

Contaminant Source

Lead and copper are unusual among drinking water contaminants in that they seldom occur naturally in water supplies like rivers and lakes. Lead and copper enter drinking water primarily as a result of the corrosion, or wearing away, of materials containing lead and/or copper in the water distribution system and facility/residential plumbing. These materials include lead-based solder used to join copper pipe, brass and chrome-plated brass faucets, and in some cases, pipes made of lead that connect facilities to water mains (service lines). In 1986, Congress banned the use of lead solder containing greater than 0.2% lead, and restricted the lead content of faucets, pipes and other plumbing materials to 8.0%. In 2011, the Reduction of Lead in Drinking Water Act further reduced the allowable lead content in water-bearing materials with a new definition of “lead-free” products. The new definition of “lead-free” is a weighted average of 0.25% lead calculated across the wetted surfaces of a pipe, pipe fitting, and fixture and 0.2% lead for solder and flux.

When water is stagnant in lead pipes or plumbing systems containing lead and copper for several hours or more, the lead and copper may leach into the drinking water. Facilities that are seasonal such as schools can be particular susceptible to higher lead concentrations due to their extended periods of no water use (e.g. holidays, weekends, and winter/spring/summer breaks).

Action Level (AL)

In 1991, EPA published a regulation to control lead and copper in drinking water. This regulation is known as the Lead and Copper Rule (also referred to as the LCR). Since 1991 the LCR has undergone various revisions, see the Rule History section below.

The treatment technique for the rule requires systems to monitor drinking water at customer taps. If lead concentrations exceed an action level of 0.015 milligrams per Liter (mg/L) or copper concentrations exceed an action level of 1.3 mg/L in more than 10% of customer taps sampled, the system must undertake a number of additional actions to control corrosion

Protecting Your Water/Health

For Public Water Systems (PWS)

PWSs should have an understanding of their water chemistry and how it will interact the distribution system plumbing.


Customers should learn about the water they are receiving from their local water supply utility. This can be done by reading the annual consumer confidence report (CCR) which is prepared by all community water systems. Customers can also perform the following activities which will minimize your potential exposure to lead and copper in your drinking water.

  • Use only cold water for drinking and cooking. Hot water can be more corrosive than cold water.
  • Flushing your water system after any extended period of non-use like vacations. Flushing is an easy and effective way of reducing the potential of lead and copper exposure in your drinking water. Flush each faucet or fixture that is used for drinking and food preparation for a couple minutes prior to use.
  • Routine inspection of your plumbing system for signs of corrosion. Corrosion can be caused by a number of things such as dissimilar materials (copper pipe connected to brass fitting) and electrical grounding (electrical system being ground to copper pipe).
  • Routine inspection of faucet aerators. Check your aerators on a regular basis. The aerator is located at the end of the faucet and should be able to unscrew. Particulates can collect in the aerator, reducing your flow and increasing potential for lead and copper exposure.
Maintaining Compliance

For detailed information for how to maintain compliance with the Lead & Copper Rule see the EPA document Lead and Copper Monitoring and Reporting Guidance for Public Water Systems.

The Lead & Copper Rule applies to Community and Non Transient/Non Community Public Water Systems. Systems must have a site sampling plan that indicates the sample locations as well as backup locations. The number of sample locations is dependent on the system’s population.

Table 1
>100,000 100 50
10,001 to 100,000 60 30
3,301 to 10,000 40 20
501 to 3,300 20 10
101 to 500 10 5
100 or less 5 5

The lead and copper regulations require you to sample at locations that may be particularly susceptible to high lead or copper concentrations. The LCR establishes a tiering system for prioritizing sampling sites. A materials evaluation is required to help classify sampling sites into tiers. You must perform a materials evaluation before you begin lead and copper tap monitoring. Table 2 below, defines the tiering system for prioritizing sampling sites.

Table 2
Tier 1 sampling sites are single family structures with copper pipes with lead solder installed after 1982 (but before the effective date of your State’s lead ban) or contain lead pipes; and/or that are served by a lead service line. Note: When multiple-family residences (MFRs) comprise at least 20% of the structures served by a water system, the system may count them as Tier 1 sites. Tier 1 sampling sites consist of buildings: with copper pipes with lead solder installed after 1982 (but before the effective date of your State’s lead ban) or contain lead pipes; and/or that are served by a lead service line.
Tier 2 sampling sites consist of buildings, including MFRs: with copper pipes with lead solder installed after 1982 (but before effective date of your State’s lead ban) or contain lead pipes; and/or that are served by a lead service line. Tier 2 sampling sites consist of buildings with copper pipes with lead solder installed before 1983. Tier 2 sites shall complete its sampling pool with representative sites throughout the distribution system.
Tier 3 sampling sites are single family structures w/ copper pipes having lead solder installed before 1983. Used if all Tier 1 and Tier 2 sites have been exhausted. Tier 3 sites shall complete its sampling pool with representative sites throughout the distribution system. Tier 3 Not applicable.
Note: All States were required to ban the use of lead solder in all public water systems, and all homes and buildings connected to such systems by June 1988 (most States adopted the ban in 1987 or 1988). Contact the Drinking Water Program in your State to find out the effective date. Note: 40 CFR 141.86(8) Any water system whose distribution system contains lead service lines shall draw 50% of the samples it collects during each monitoring period from sites that contain lead pipes, or copper pipes with lead solder, and 50 % percent of the samples from sites served by a lead service line.

Once monitoring begins, you must use the same sites, unless a site is no longer accessible to you or no longer fits the requirements of a priority site (e.g., the lead service lines that served the site have been replaced ).

Monitoring frequency is determined by a number of factors and are generally in two categories (Standard and Reduced).

Standard Monitoring- Samples are collected within a 6-month window (January-June and July-December). Systems will need 2 consecutive rounds of 6-month data with results less than the action level for lead and copper. All new systems and systems that have a change in source or treatment must be on standard monitoring. Systems that have an action level exceedance will also have to go to standard monitoring.

Reduced Monitoring- If a system has 2 consecutive rounds of 6-month data with results less than the action level for lead and copper, the system would be a candidate for reduced monitoring of either annual or triennial sampling. Systems would also have the number of samples reduced. Refer to Table 1.

Understanding Your Samples

Calculate the 90th Percentile Concentration

  • 90th Percentile Calculator: The following external link was created by the state of Colorado and is an easy to use tool for operators to calculate the 90th percentile for compliance with the Lead & Copper Rule. The state of Montana is currently working on our own adaptation of the tool, but in the meantime please use the above link.
  • For systems that collect 5 samples, take the average of the 2 highest concentrations.
  • For systems that collect 10 samples, take the 2nd highest sample

Compare the 90th Percentile Concentration with the Action Levels

  • Copper – 1.3 mg/L
  • Lead – 0.015 mg/L

If your 90th percentile concentration for both Lead and Copper meets or is lower than the AL than continue with monitoring schedule.

If one or both exceed the AL than requirements for an Action Level Exceedance (ALE) need to be completed.

When an ALE occurs for Lead and/or Copper following tasks are required.

  • Collection of Water Quality Parameters (WQPs) from entry point and distribution system.
    • WQPs include temperature (field), pH (field), calcium (lab), Alkalinity (lab), and conductivity (lab)
    • WQPs are to be collected in the same monitoring period that the ALE occurred
  • Collection of a source water sample from entry point for lead and copper.
    • Source water sample will help determine if concentrations are from source or not.
    • Must be collected within 6 months of end of monitoring period
  • Submit recommendations for Optimal Corrosion Control Treatment (OCCT)
  • Implementation of the OCCT recommendations within 24 months after the approval by the DEQ
  • Deliver Lead Public Education (PE) (Lead only)
    • Deliver PE to your customers to inform them of:
      • The health effects for lead
      • Measures you are taking to correct the problem
      • What they can do to minimize their exposure to lead
  • Must be distributed within 10 days of receipt of data.
  • Must be re-distributed annually for as long as you exceed the ALE
  • DEQ has templates that can be used

An ALE is not a violation but if required tasks are not followed, a violation can be issued.

Health Concern

Infants less than 6 months old are the most vulnerable population where consumption of high levels of nitrates in drinking water have caused serious illness and sometimes death. Symptoms of this condition, called Methemoglobinema or blue baby syndrome, are shortness of breath and blueness of the skin.  

 For children and adults, long term exposure of nitrate above Maximum Contaminant Level (MCL) can lead to development of diuresis, increased starchy deposits, and hemorrhaging of the spleen.  

Contaminant Source

Nitrate (NO3) and nitrite (NO2) are inorganic chemicals that are composed of nitrogen and oxygen. They are naturally found in soil, human and animal feces, and as natural deposits. Because nitrogen is a critical element for plant growth, nitrate is major component of synthetic fertilizer.

Maximum Contaminant Level (MCL)
  • The MCL for nitrate is 10 mg/L.
  • The MCL for nitrite is 1 mg/L.
  • The MCL for Nitrate+Nitrite is 10 mg/L.
Protecting Your Water/Health

Nitrate is a water-soluble molecule that can be carried with surface runoff into creeks, rivers, and lakes along with infiltrating into the soil and groundwater. Through these pathways both surface and groundwater can become contaminated with nitrate. Groundwater with elevated nitrate levels indicates that some contamination has reached the groundwater.   

Preventing nitrate contamination of groundwater is an important element of source water protection. Blocking surface runoff into the well near the well can be done by ensuring the well casing and sanitary seal are secure and providing a 100 feet buffer around the well. The source of nitrate contamination is often found locally (e.g., onsite leaking septic tank or neighboring agriculture field).  

For those PWS that remove nitrate through a treatment process, ensuring the treatment system is functioning is vital for serving safe drinking water. Nitrates can be removed from water through reverse osmosis, ion exchange, and electrodialysis processes. All these treatment processes require engineering design and persistent operations and maintenance to guarantee continual functionality.  

Maintaining Compliance

The only way to know the nitrate level in water is to measure it. The foundation of the Safe Drinking Water Act is for PWS to sample their water as this is the most reliable way to know contaminate levels.  

The level of nitrate concentration determines the frequency of nitrate (and nitrite) monitoring. PWS that have nitrate levels below the action level (<5 mg/L) are required to sample once per year. Whereas PWS that have historic nitrate samples above the action level (>5mg/L) are required to sample quarterly for at least four consequent quarters.  

Understanding Nitrate Samples

The required nitrate sample results are useful information for managing a PWS. It is recommended to graph all nitrate samples over time. This will highlight trends in nitrate levels. Nitrate levels can change over time in the same well. This can occur between wet and dry seasons, wet and dry years, and with changes in land use.  

 The Nitrate Concentration Guide provides recommended action that PWS can take to proactively tackle nitrate contamination.  

Nitrate Concentration Guide
Nitrate Concentration


Protecting Your Water/Health

One of the best ways water systems can contribute to community health is to make sure as many people as possible within a service area know about water quality issues and how to protect themselves from potential risks. Public notification of drinking water violations and other situations provides a way to educate the public, protect public health, build trust with consumers through open and honest sharing of information, and establish an ongoing, positive relationship with your community.  

Maintaining Compliance

Tier 1 (Immediate Notice, Within 24 Hours)

Notice as soon as practical or within 24 hours via radio, TV, hand delivery, posting, or other method specified by primacy agency, along with other methods if needed, to reach persons served. Public Water Supply Systems must also initiate consultation with primacy agency within 24 hours. Primacy agency may establish additional requirements during consultation.

Tier 2 (Notice as Soon as Possible, Within 30 Days)

Notice as soon as practical or within 30 days. Repeat notice every three months until violation is resolved. Community Water Systems: Notice via mail or direct delivery. Non-Community Water Systems: Notice via posting, direct delivery, or mail. Primacy agencies may permit alternate methods. All Public Water Systems must use additional delivery methods reasonably calculated to reach other consumers not notified by the first method.

Tier 3 (Annual Notice)

Notice within 12 months, repeated annually for unresolved violations. Notices for individual violations can be combined into an annual notice (including the Consumer Confidence Report, if public notification requirements can still be met). Community Water Systems: Notice via mail or direct delivery. Non-Community Water Systems: Notice via posting, direct delivery, or mail. Primacy agencies may permit alternate methods. All PWSs must use additional delivery methods reasonably calculated to reach other consumers not notified by the first method.

Reporting (10 Days) and Record Keeping (3 Years)

Public Water Systems have ten days to send a certification of compliance and a copy of the completed notice to the primacy agency. Public Water Systems must keep notices on file for three years.


Additional Resources

Public Notification Tools


What are radionuclides?

Radioactive materials, also called radionuclides, are both naturally occurring and human-made. Radionuclides from naturally occurring sources can get into groundwater and surface waters in Montana. When radionuclides break down (decay), they create radiation. Radionuclides are a natural part of our environment, and small amounts of radiation are common in the air, water and soil.

How do radionuclides get into groundwater?

Most of the radionuclides found in Montana’s ground water occur naturally from the weathering and dissolution of rocks and minerals. The amount and type of radiation released during the decay process depends on the radionuclides present.  Radioactive materials are also used in medical diagnostics and treatments, electricity production, commercial products, research and nuclear weapons. Human activities, such as disposal of radioactive wastes, may increase the levels of radioactive materials in groundwater. 

What are safe levels of radionuclides in drinking water?

The US Environmental Protection Agency (EPA) has set maximum contaminant levels (MCLs), for radioactive substances in public drinking water systems. EPA defines an MCL as the maximum allowable level of a contaminant that may be present in drinking water without a high risk of causing health problems. DEQ uses these standards for public water systems. The table below shows the MCLs for radionuclides:



MCL’s in Drinking Water

Radium (-226 and -228) 5 pCi/L (combined)
Gross Alpha 15 pCi/L

30 µg/L

Elevated radionuclides in Montana

Montana’s community water systems are required to sample for radionuclides. The map below shows the concentrations of radionuclides that are above the MCL.

Health effects of radionuclides

Exposure to radiation can cause different types of health effects depending on the source of radioactivity, how much radiation you are exposed to (total dose), and how long you are exposed to the radiation. Drinking water that has radionuclide levels near the federal drinking water standards puts you in contact with very low doses of radiation every day. This exposure, when combined with other sources of radiation exposure, can slightly increase your lifetime risk of developing cancer or kidney problems.


Total coliforms are a group of related bacteria that are (with few exceptions) not harmful to humans. A variety of bacteria, parasites, and viruses, known as pathogens, can potentially cause health problems if humans ingest them. EPA considers total coliforms a useful indicator of other pathogens for drinking water.

All public water systems, including seasonal water systems, are required to collect total coliform samples at sites which are representative of water quality throughout the distribution. For seasonal systems, the startup procedure must be completed and sent in to DEQ before operating the public water system for the season.

The purpose of the Surface Water Treatment Rules (SWTRs) is to reduce illnesses caused by pathogens in drinking water. The disease-causing pathogens include Legion, Giardia lamblia, and Cryptosporidium. The SWTRs requires water systems to filter and disinfect surface water sources. Some water systems are allowed to use disinfection only for surface water sources that meet criteria for water quality and watershed protection.

Surface Water Rule Summary-DEQ

Emerging Contaminants


Montana has developed health-based guidance values for Manganese in drinking water. Information on the health effects of Manganese is an evolving science, and Montana is using a guidance value approach to help Montana families take voluntary steps to ensure that their drinking water is safe. Because they are guidance values, there are no new or additional regulatory requirements for homeowners or public water systems.


Please follow the link to DEQ's Cleanup PFAS webpage for more information on PFAS in drinking water.

PFAS in Drinking Water