NPDWR Initial Monitoring Deadline May Be Closer Than You Think

The U.S. EPA’s National Primary Drinking Water Regulation (NPDWR) for PFAS was made final in 2024. Although the agency has signaled its intent to extend the final compliance deadline, every covered water system must complete Initial Monitoring by April 26, 2027. EPA has not proposed to change the Initial Monitoring deadline. If you already have more than enough on your plate, you may be wondering how long you can realistically wait to fit PFAS sampling into the mix. In this post, we walk through the math, using the Initial Monitoring requirements and the deadline to highlight when water systems MUST begin sampling to stay on track.

PFAS Initial Monitoring Requirements

Under the PFAS NPDWR, all monitoring is done at each entry point to the distribution system. Initial Monitoring requirements depend on system size and source water:

• Surface water and Ground Water Under the Direct Influence (GWUDI) of surface water systems (all sizes): Four samples per entry point in a single 12‑month period, with each sample 2–4 months apart.
• Groundwater systems serving more than 10,000 people: Same as surface water—four samples per entry point, 2–4 months apart within 12 months.
• Groundwater systems serving 10,000 or fewer people: Two samples per entry point in a 12‑month period, 5–7 months apart.

Again, all systems must complete Initial Monitoring by April 26, 2027, regardless of whether the ultimate compliance deadline is changed.

Doing the Math: The Deadline to Begin Sampling

One confusing aspect of the regulation is that the four samples per year are often referred to as “quarterly” samples. The rule defines quarterly Initial Monitoring as four consecutive samples taken 2–4 months apart within a 12‑month period—not necessarily one per calendar quarter. With that in mind, figuring out the latest date you can start sampling is a two‑step process. 

The first step is to work backward from the Initial Monitoring deadline to determine when sampling must begin. 

Surface water, GWUDI systems, and groundwater systems serving more than 10,000 people: To complete four samples 2–4 months apart in 12 months, the first sample must be collected at least six months before the last sample. Therefore, if your last (fourth) sample is on April 26, 2027, October 26, 2026 (six months earlier) becomes your “working deadline” for sampling to begin.  

Groundwater systems serving 10,000 or fewer people: To collect two samples within a single 12‑month period, spaced 5–7 months apart, and finish by April 26, 2027, the “working deadline” is November 26, 2026 (five months earlier). 

However, the calculation does not stop there, because the entire process—including sample collection, laboratory testing, and data uploads—must all be completed by the Initial Monitoring deadline. Therefore, step two is to work with your laboratory partner to determine lead times for sample collection and analysis. Given the demands on commercial testing capacity, this timing is likely to become even more of a critical constraint as the deadlines draw nearer. 

When UCMR 5 Data Can be Used—and When it Can’t

EPA has indicated that previously collected PFAS data, including UCMR 5, may be used to satisfy some PFAS NPDWR Initial Monitoring requirements, but only when certain conditions are met. Using eligible UCMR 5 data can save water systems time and cost, but there are situations where UCMR 5 data may not be acceptable for Initial Monitoring. For example, groundwater systems serving more than 10,000 people only had to sample twice under UCMR 5 and will require additional sampling under the PFAS NPDWR.

One of the most common challenges involves how UCMR 5 sampling results were reported. The PFAS NPDWR builds on the analytical performance established under UCMR 5 but under UCMR 5, laboratories only had to report results at or above the minimum reporting levels (MRLs). An MRL is the lowest allowable reporting concentration and is based on what multiple laboratories could reliably quantify using specified methods. For the regulated PFAS, this was typically in the low single digit ng/L range, and anything below the MRL was reported simply as “<MRL.”

The PFAS NPDWR introduced Trigger Levels set at one‑half of each PFAS MCL and one‑half of the Hazard Index MCL. Trigger Levels are used to determine whether monitoring frequency can be reduced (for example, from quarterly to triennial). Because Trigger Levels are below the MCLs and, in some cases, near or below historic reporting limits, laboratories must be able to detect and numerically report results low enough to determine whether Trigger Levels are exceeded.

If historical UCMR 5 data exist only as “<MRL” and cannot be reprocessed to produce validated numeric values low enough to evaluate against the Trigger Levels, the state may require new NPDWR‑compliant sampling. Where laboratories can re‑evaluate UCMR 5 data and generate results that satisfy the NPDWR data‑quality objectives, some or all of those results may be accepted in place of resampling. Pace® has the capability to perform this type of data reprocessing, but not all UCMR 5 laboratories do.

Working through these questions early is essential. Utilities should coordinate with their primacy agency and, where needed, their laboratory partner well in advance. Together, they should review available UCMR 5 and other PFAS data and confirm whether the methods and reporting limits meet PFAS NPDWR expectations. This review will determine whether those data can substitute for some or all Initial Monitoring requirements or whether new sampling will still be required.

Pace® can help review your existing UCMR 5 submittals and coordinate with your state to determine whether the format and content of your data qualify, or whether additional sampling or data reformatting will be needed. Contact us for assistance.

Don’t Wait: De-Risk NPDWR Compliance by Finalizing Your Sampling Program Now

Waiting until the last moment to begin PFAS sampling exposes you to several avoidable risks. If you wait, you may also discover that your UCMR 5 data do not fully qualify, forcing you into rushed, back‑to‑back sampling events with limited flexibility.

Starting Initial Monitoring now lets you spread sampling over time, confirm that your historic data are sufficient, and ensure you have room to respond if early results show PFAS above MCLs or Trigger Levels. Getting an early start preserves valuable time for pilot testing, treatment design, and funding applications ahead of the compliance date, reducing the risk of last‑minute surprises as 2027 approaches.

This is also a good time to think about how you’re going to get samples from the field to the lab reliably and on schedule. Pace field sampling and courier services are designed to take a lot of that uncertainty off your plate by making sure the right bottles, preservatives, and documentation are in place from day one. With a consistent pickup schedule and trained field teams, you can reduce the risk of missed holding times, shipping delays, and other last‑minute issues that can derail a carefully planned PFAS sampling program—especially as more systems ramp up testing and capacity tightens.

New PFAS Cost Recovery Opportunity Now Open

Before I wrap up, I also want to point you to a page that may be useful as you finalize your Initial Monitoring plans. Phase 2 of the National Rural Water Association (NRWA) PFAS Cost Recovery Program is now open. This program is an opportunity for public water systems that first detected PFAS after the Phase 2 June 22, 2023 deadline, to seek cost recovery for testing, treatment, and compliance efforts. The NRWA is encouraging eligible systems to register at no cost so they do not miss upcoming settlement deadlines and can secure much-needed funding to help protect their customers and communities.

Over the past few years, I’ve had the privilege of speaking with many water professionals all over the country. This Spring, our team and I will be attending and presenting at several water conferences over the next several weeks:

• Virginia Rural Water Association Conference and Technical Expo, Roanoke, VA, April 20-22.
  Presentation: PFAS Considerations for Wastewater Professionals, April 22, 10:00 – 11:00 AM.

• Wyoming Association of Rural Water Systems, Virtual Conference, April 21.
  Presentation: Navigating the Next Drinking Water Regulatory Era: UCMR 5 Insights, UCMR 6 Predictions, and Perchlorate Considerations.
  Presentation: Biosolids Analysis for PFAS: Challenges, Considerations, and Options.

• Georgia Rural Water Association Spring Conference, Jekyll Island, GA, May 5 – 6.
  Presentation: GA EPD PFAS Sampling Program Ins and Outs, May 6, 1:00 – 1:30 PM.
  Presentation: Biosolids Analysis for PFAS: Challenges, Considerations, and Options, May 7, 2:00 – 2:30 PM

If you’re planning to attend any of these events and would like to sit down and talk through your PFAS projects in more detail, we’d be glad to connect. Just reach out to me ahead of time, and we can set up a time to meet that works with your conference schedule.

Contact Pace® for Help

Staying ahead on PFAS and the evolving NPDWR requirements is not easy, especially with everything else on your plate. Pace® has supported thousands of water systems with UCMR analysis, NPDWR compliance, and many other types of PFAS projects. If you have questions about PFAS sampling, biosolids, or how these new rules may affect your system, feel free to reach out—I’d be happy to talk through your specific situation and next steps.