Mitigating Public Health Risks During Low-Pressure Events

For professionals in the drinking water sector, whether you are a public health official, a field operator, a treatment plant manager, or a town council member, protecting community public health is the cornerstone of our daily work. Every infrastructure upgrade, daily monitoring check, and emergency response is driven by the commitment to deliver safe, reliable drinking water.

One of the key aspects of operations and maintenance planning is understanding and planning to prevent the potential public health risks of low-pressure events and main breaks. In order to support your response to these sometimes routine but crucial events, the Water Quality Control Division would like to present a review of recent epidemiological research and outline how our policies support your local response.

The Science: Recent CDC Findings on Low Pressure Events

The Centers for Disease Control and Prevention (CDC) recently published a cohort study investigating the health effects of low-pressure events in drinking water distribution systems across the United States. A low-pressure or pressure-loss event is when pressure in the water distribution system drops significantly below the normal operational pressure of 35 psi. For example, system operators may intentionally reduce pressure in the distribution system when they install, replace, or repair water lines. Broken water mains, failed pumping systems, power outages, leaking storage tanks, and high demand, such as fire flow, can cause unplanned pressure loss within part or all of the distribution system. Low pressure can cause drinking water contamination through backflow events, intrusion of groundwater or standing water around distribution pipes, disruption of distribution system biofilms, and other microbial or chemical contamination events leading to increased risk of widespread illness. 

Understanding the data helps us optimize our preventative and emergency response measures. Here are the key takeaways from the study:

• Gastrointestinal Risk: Households exposed to low-pressure events were found to be at a 20% higher risk for highly credible acute gastrointestinal illness (HCGI) compared to unexposed households.
• Respiratory Illness: The study detected no association between low-pressure events exposure and acute respiratory illness (ARI).
• Vulnerable Infrastructure: Event-level characteristics significantly impacted health risks. Households faced a higher risk of HCGI during low-pressure events involving older pipes (49–93 years), smaller pipe diameters (2–6 inches), iron pipes, or pipes submerged in trench water during repair.
• Mitigation Matters: Crucially, the risk of HCGI was higher when utilities did not disinfect the pipes and equipment before returning the water main to service. This highlights that adherence to standard distribution repair practices directly reduces community illness.

Colorado’s Culture of Protection: WQCD Policy and Guidance

At the WQCD, we view properly responding to main breaks and low-pressure events not just as operational hurdles, but as critical public health interventions. To help systems navigate these events, the Division utilizes Drinking Water Program Policy DW-1 and the Pressure Loss and Main Break Response Guidance.

When responding to an acute health threat or pressure loss, WQCD expects systems to follow these core protocols to safeguard public health:

• Swift Communication with the CDPHE: If greater than than 50% of the distribution system or greater than 100 service connections are affected by the low-pressure or no-pressure event, systems are required to notify the department as soon as possible via our 24-hour Incident Reporting Line at 1-877-518-5608. If the pressure loss is less than 50% or 100 service connections, the system can report the event via email to cdphe.wqacutes@state.co.us. See Pressure Loss Main Break Response Guidance for an email and door hanger template that can be used for smaller outages. 
• Swift communication with customers: 
• Outages Without an Advisory: For standard service interruptions that do not trigger a formal advisory, systems must notify all affected customers either verbally or by utilizing door hangers. This notice should inform residents of the expected duration of the outage and instruct them to flush their own plumbing by running cold water taps once service is restored. Be sure to warn customers that system flushing can stir up sediment and cause discolored water, and advise them to temporarily avoid using hot water or washing laundry. 
• Boil or Bottled Water Advisories: If the pressure loss poses an acute health threat that results in a boil or bottled water advisory, the situation requires a formal Tier 1 public notice. This notice must meet strict regulatory standards, and all steps in the process, from issuing the public notice to repairing the cause of the pressure loss and lifting the boil advisory, must be completed while in consultation with WQCD.
• Safe Excavation and Repair: Whenever possible, maintain pressure in the main during the entire repair process to prevent contamination. If pressure is lost, crews must keep the excavated pit water level below the break and plug all pipe openings when unattended.
• Rigorous Disinfection and Flushing: As supported by the CDC study, disinfection is non-negotiable. Crews must disinfect the interior of all repair pipes and fittings with a 1% chlorine solution. Once repaired, the affected areas must be flushed at a minimum velocity of 3 feet per second (ft/sec) until clear, and disinfected following AWWA C651 standards or Department-approved SOPs.
• Bacteriological Verification: Repair work is not complete until the water is proven safe. Systems must conduct bacteriological testing at representative locations. The number of required total coliform samples depends on your system's size and the scope of the outage. If any sample tests positive for total coliform, the flushing and disinfection procedures must be repeated until all results indicate safe conditions.

A water main break tests the resilience of both our infrastructure and our response protocols. By utilizing data-driven practices and adhering to WQCD guidance, operators and municipal leaders can confidently mitigate risks and uphold our shared mission: protecting the health of every community in Colorado.

➽ Kyra Gregory Local Assistance Unit Manager, Acute Drinking Water Team Member 

➽ Chelsea Cotton, P.E. Lead Drinking Water Engineer, Acute Drinking Water Team Lead

PFAS Rule Updates: Extended Deadlines and What They Mean for Colorado Water Systems

The EPA is proposing revisions to the federal PFAS Drinking Water Rule, introducing significant changes that will provide Colorado drinking water systems with more flexibility and time to meet compliance standards. Here is what public water systems need to know about the upcoming changes and how the department is responding to keep Colorado aligned with federal standards.

What is changing for water systems?

Originally, the PFAS Rule required systems to comply with new maximum contaminant levels (MCLs) for six chemicals and a Hazard Index by April 1, 2029. Under the EPA’s proposed revisions announced in May 2026:

• Four chemicals and the Hazard Index may be dropped: The EPA plans to rescind the regulatory requirements for PFHxS, PFNA, HFPO-DA, PFBS, and the Hazard Index mixture.
• More time for PFOA and PFOS: The EPA is proposing a modified exemption process to give eligible water systems up to two additional years to meet PFOA and PFOS MCL requirements, pushing the compliance deadline to 2031. This extension framework is largely driven by the significant capital costs, supply chain constraints, and workforce limitations systems face when designing and installing new treatment facilities.
• Interim measures and public notice: An exemption gives systems more time, but requirements during that extension period are dependent on a system's specific PFOA or PFOS levels: 
• 12 parts per trillion (ppt) and above: If a system’s PFOA or PFOS levels equal or exceed 12 ppt, they must implement at least two interim control measures. These can include public education efforts and operational adjustments, like blending water sources, or providing point-of-use solutions directly to consumers, such as certified pitcher filters.
• Between 4 ppt and less than 12 ppt: If a system's PFOA or PFOS levels are above 4 ppt and less than 12 ppt, the proposed framework does not require them to implement interim control measures during the exemption period.
• Regardless of contamination levels, all exempted systems will be subject to public notice requirements to ensure their communities remain informed while long-term treatment solutions are built.

(Note: Without an approved exemption, suppliers will still be required to meet the original April 1, 2029 deadline).

What is the department doing?

Because the EPA signaled that these revisions would occur after the deadline for states to submit primacy applications, the EPA strongly encouraged states to request an extension. The department officially requested a six-month primacy extension this spring. This is an administrative step that provides us with the necessary time to review the EPA’s proposed changes and ensure Colorado’s exemption process aligns with the new federal framework. This extension does not impact public drinking water systems or alter the department’s enforcement oversight. It simply ensures our regulatory authority remains intact before the federal rule takes full effect in April 2027.

What are the next steps?

We will continue to update systems as the EPA finalizes these revisions. Currently, the department is communicating directly with the EPA regarding these drafts and the practical feasibility of implementing these PFAS exemptions at the state level.

Importantly, the proposed extensions and revisions do not change immediate testing deadlines. Suppliers must still comply with the initial monitoring requirements for the six PFAS chemicals by April 1, 2027. To satisfy this requirement, systems must complete monitoring and report the results of either two or four samples (depending on system size and source water type) per entry point. If a supplier has completed all required initial monitoring, they should check their monitoring schedule and AIMS Tool to ensure initial monitoring results have been accepted and marked complete. 

For more information, visit the department’s PFAS rule webpage, sign up for future PFAS Rule email notifications, or email cdphe_wqcd_DWrules@state.co.us.

➽ Bryan Pilson Technical, Regulatory Implementation and Coordination Unit Manager

Grant Opportunity - Emerging Contaminants for Small or Disadvantaged Communities

The Water Quality Control Division has been awarded funds from the EPA to implement the EPA Emerging Contaminants for Small or Disadvantaged Communities (EC-SDC) Grant Program. The EC-SDC Grant Program awards grants to public water systems in small or disadvantaged communities to address emerging contaminants in drinking water. Eligible emerging contaminant projects include PFAS, manganese, and any other contaminants on the EPA Drinking Water Contaminant Candidate List. The program has two categories available for grant applications:

• Tier 1 Planning & Design projects to address emerging contaminants:
• Project duration up to 24 months
• Maximum grant of $300,000
  
  
• Tier 2 Infrastructure projects to address emerging contaminants:
• Project duration up to three years
• Maximum grant of $30 million at $10 million per year

Important Summer Dates:

The next request for Applications opens July 6th and the division will be accepting applications through August 4th on the EC-SDC website. 

A series of webinars will be hosted the week of June 22nd:

• Join us for Office Hours June 24, 2026 4 - 5 p.m.
• Sign up for the June 25 Webinar 10:30 - 11:30 a.m.

Questions?

• Learn more on the program website here.
• Stay informed and subscribe here: Stay Informed - Water Quality. 
• If you would like to discuss a potential project email cdphe_wqcd_ec_sdc_grants@state.co.us

➽ Laura Leonard, Ph.D. Lead Testing and EC-SDC Project Manager

EPA Security Advisory

CDPHE is sending you the following information in partnership with EPA: 

Stay connected with the Office of Water Emergency Response & Cybersecurity at EPA

EPA Advisory: Protecting Sensitive Operational Information in Water and Wastewater Systems

cyber alert

The U.S. Environmental Protection Agency (EPA) is advising water and wastewater systems to consider the risks of disclosing sensitive operational information following multiple public records requests from artificial intelligence (AI) service providers, as reported by the WaterISAC and the American Water Works Association (AWWA).

In at least one instance, an AI service provider requested “all SCADA logs for 2026 for all treatment, distribution and wastewater management systems.” The requestor also indicated they were seeking “daily or hourly historical logs” for specific environmental and physical process indicators, including inflow and outflow water volumes and flow rates, aggregate water quality baseline metrics, historical reservoir and tank storage levels, and aggregate daily energy consumption or equipment run-times.

This type of information carries significant operational sensitivity given the insight it provides to a utility’s operations. EPA concurs with the WaterISAC’s and AWWA’s recommendation that water and wastewater utilities recognize that the aggregation of operational data across multiple utilities has the potential to reveal patterns, vulnerabilities, and system behaviors in the water sector. Such data, if obtained with malicious intent, could be used to jeopardize continuity of service, endangering public health and national security.

EPA encourages water sector utilities to evaluate the potential sensitivity of information requests and to make risk‑informed decisions about whether—and under what conditions—to respond, consistent with applicable state information protection laws.

Hand-Pumped Wells Disinfection Updates Underway

Did you know that Colorado has over 100 hand-pumped wells that provide drinking water to transient public water systems throughout the state at areas such as campgrounds? These hand-pumped wells are regulated by CDPHE and have very specific procedures and guidelines must be followed to ensure that they are providing potable water. Hand-pumped wells are, as the name implies, water sources that are pumped by hand and do not have continuous disinfection treatment. For seasonally operated hand-pumped wells, the well water, pump and piping must be disinfected within 30 days of opening for the season. The hand-pumped wells typically have a removable plug that can be removed and a chlorine solution can then be poured into the well to disinfect the well. However, operators have reached out to the Division with concerns about disinfecting hand-pumped wells where there is no removable plug or the plug is seized and cannot be removed. In 2024, the Division worked with hand-pumped systems to update the department’s “Hand-pumped wells operational guidance and handbook” and develop an alternative disinfection procedure. Based on communications with operators and hand-pumped systems, the current configuration on disinfecting hand-pumped wells was not the most conducive method. In close collaboration with operators, an alternative disinfection procedure (below) was developed to utilize for situations where there is no removable plug or if the plug is seized. 

Gallon Chlorine Solution Method – Utilizing the hand-pump’s weep hole, chlorine solution is applied via the spout and into the pump base. One (1) gallon of chlorine solution is added to the hand-pump according to the standing water height in the well casing. A chlorine solution of 3 tablespoons of 8 ¼ percent bleach will be added to a 1 gallon jug of water for every 10 feet of standing water. For example, 18 tablespoons of 8 ¼ percent bleach will be added to the 1 gallon water jug and inserted into the hand-pump base for 60 feet of standing water. A table showing the amount of bleach used per gallon jug of water is presented below for different chlorine bleach strengths. To ensure that the chlorine solution entered the well casing, wait a few minutes for all the chlorine solution to drain from the weep hole. Pump the well one to two times to ensure no solution is pumped out and that all the chlorine solution enters the well casing.  After completely pouring the 1 gallon chlorine concentrate into the well, operate the hand pump until the distinct odor of chlorine is detected in the discharge. Remove the pump handle and allow the chlorine solution to remain in the well for a minimum of 6 hours. Reinstall the pump handle and flush the well until the free chlorine residual is below 0.2 mg/L. Chlorine residual must be measured with an approved chlorine test kit. After successfully completing the disinfection process please continue to follow the “Hand-pumped wells operational guidance and handbook” on completing the necessary steps to bring the well online.

Disinfection of hand-pumped wells is an important step in ensuring safe drinking water and the division appreciates the coordination with operators on this issue. The Field Services Section will be working on an update to the “Hand-pumped wells operational guidance and handbook” in the future. If you have questions regarding hand-pump disinfection, please email the Field Services Section at cdphe_wqcd_fss_questions@state.co.us. The department, operators and the supplier share the same goal – “Always Safe Drinking Water.” 

➽ Thomas Valenta, Field Services Work Group Lead

Asset Management - A Resource for Now

For years, the water sector has been preparing for a dynamic future—navigating evolving regulations, economic shifts, and changing climate conditions. Today, that future has arrived, giving us the opportunity to put our planning into action. Following the scarce winter with little snow to recharge our source waters, Colorado communities are already stepping up to wisely manage our vital water supplies. Now is the time to implement or improve upon a good Asset Management program. It is necessary now more than ever. 

Free Asset Management training!
The Local Assistance Unit (LAU) is now offering Asset management on a quarterly basis as part of their regular training courses. The Asset Management (AM) course curriculum will review the 5 core criteria of asset management and demonstrate how to apply each of them to your system. You will learn how to get started and review some tools to assist you in developing an asset management plan. No need to reinvent the wheel when it comes to AM, there are many tools and templates available that fit the needs of every sized system. 

Can’t make a workshop and need assistance with asset management or capacity development?
The Colorado Department of Public Health (CDPHE) Water Quality Control Division (WQCD) has capacity coaching available for free through the Local Assistance Unit (LAU). A Public Water System can request assistance by filling out the Coaching Assistance Form. 

Join us for an Asset Management course and learn how to begin your asset management program and earn 0.2 TU’s for attending. 

What is Asset Management?
Asset Management is a proactive approach to managing a public drinking water system’s infrastructure and capital assets. It gives systems tools to optimize output at the lowest possible operating cost. By prioritizing assets, estimating useful life, and improving decisions about asset rehabilitation, repair, and replacement, it enables more accurate budgeting. Budgeting will continue to become more critical as systems face continued and potentially worse drought conditions. Water restrictions mean less revenue for systems which means doing more with less and making strategic long term planning even more necessary. Asset Management is a tool to help with this critical next step. 

➽ Angela Green Garcia, Drinking Water Training Specialist

Upcoming Perchlorate Rule

Program Manager message:

Colorado’s Safe Drinking Water Program is not the only such program in the United States with a newsletter. Over the years, I have subscribed to a few of these newsletters, and sometimes we have reprinted or used articles from them with permission. In this case, I recently read an excellent article in the Arkansas Drinking Water Update newsletter regarding EPA’s proposed perchlorate rule. I reached out to my counterpart in Arkansas, Lance Jones, who authored the article and gained his permission to reprint it here. We are also adding a Colorado perspective regarding likely perchlorate rule impacts on Colorado’s public water systems. 

➽ Ron Falco, P.E., Safe Drinking Water Program Manager

EPA Proposes Perchlorate Rule

On January 2, 2026, the Environmental Protection Agency (EPA) issued a proposed Rule under the Safe Drinking Water Act to regulate perchlorate (ClO4-) in drinking water as part of the National Primary Drinking Water Standards.

The proposed Rule includes a Maximum Contaminant Level Goal (MCLG) of 20 micrograms per liter (ug/L). EPA is also co-proposing enforceable Maximum Contaminant Levels (MCLs) of 20 ug/L, 40 ug/L, or 80 ug/L for perchlorate and will apply to community and non-transient public water systems.

Initial monitoring consists of quarterly monitoring or semi-annual for small ground water systems, for a 12-month period, with routine monitoring determined by those results. Systems with a running annual average above the MCL require quarterly monitoring, systems less than the MCL but greater than or equal to 4 ug/L require annual monitoring (surface water) or triennial (ground water) monitoring, and every 9 years for systems less than 4 ug/L. 

Perchlorate has had a back-and-forth regulatory history for the past 25+ years. Starting with including perchlorate levels in drinking water systems under the 1999 Unregulated Contaminant Monitoring Rule (UCMR). The results led to a 2011 decision by EPA to regulate perchlorate in drinking water. EPA proposed a Rule to regulate perchlorate in drinking water in 2019. In July 2020, EPA withdrew the determination to regulate perchlorate. A legal challenge of the decision to withdraw was filed and led to a 2023 court decision to vacate the withdrawal. EPA entered into a consent decree to sign and issue a final Rule to regulate perchlorate in drinking water by May 21, 2027.

Perchlorate is commonly used in solid rocket propellants, munitions, fireworks, matches, signal flares, and vehicle airbag initiators. It has also been associated with some imported fertilizers and trace amounts can result from improper handling and degradation of hypochlorite solutions.

Perchlorate can potentially interfere with the thyroid gland hormone production. Changes in thyroid hormone production in pregnant women are associated with adverse neurodevelopmental effects in their children. Thyroid hormone level changes at other life stages can lead to hyperthyroidism, developmental outcomes, and cardiovascular system impacts.

EPA’s data show that perchlorate is not widespread in drinking water systems and EPA expects less than 1,300 of the over 135,000 regulated water systems nationwide to find perchlorate levels above the proposed limits. For systems that do find elevated levels of perchlorate, treatment options include ion exchange, biological reduction, reverse osmosis, and blending with another source.

The sampling of several Arkansas water systems in 2001 and 2002 found no detects of perchlorate. ASD will add sampling of perchlorate to the current compliance monitoring efforts upon EPA promulgating a final Rule.

More information about perchlorate in drinking water can be found on the EPA website at:

https://www.epa.gov/sdwa/perchlorate-drinking-water#proposed-perchlorate

➽ Lance Jones, P.E. Health Program Administrator, Arkansas DPHP Environmental Health Engineering