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SW - all populations: For entry points served by surface water,
4 consecutive quarters of samples per entry point within a 12-month period with samples collected 2 to 4 months apart.
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GW greater than 10,000 people: For entry points to the distribution system only served by groundwater and population greater than 10,000,
4 consecutive quarters of samples per entry point within a 12-month period with samples collected 2 to 4 months apart.
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GW 10,000 people or fewer: For entry points to the distribution system only served by groundwater and population of 10,000 or fewer,
2 consecutive samples per entry point within a 12-month period with samples collected 5 to 7 months apart.
Purchasing water systems
C and NTNC systems that have entry points served by purchased water are subject to the rule but do not have to monitor for PFAS at purchased water entry points. Finished drinking water that is provided through a system interconnection is only required to be monitored for by the seller or wholesaler.
Seasonal water systems or seasonal entry points
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For systems required to monitor 4 consecutive quarters within a 12-month period:
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Systems should monitor in the quarters when the entry point is in use and providing water to users within a 12-month period, with samples 2 to 4 months apart.
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For systems required to collect 2 consecutive samples within a 12-month period:
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For entry points in use and providing water to users 4 months or less a year, collect 1 sample anytime within the 4-month operating period.
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For entry points in use and providing water to users 5 or more months a year, collect 2 samples 5 months apart.
Previously acquired PFAS data
Water systems can use previously acquired PFAS monitoring data to satisfy some or all of the initial monitoring requirements (for example, UCMR5 data) if it meets
all of the following criteria:
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Samples were collected on or after January 1, 2019.
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Samples were collected from the entry point. Note: samples collected from other locations may be acceptable in some cases; contact your regulator if questions.
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Samples must have been analyzed using EPA method 533 or EPA method 537.1 (version 1 or 2).
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Results were reported using minimum reporting levels (MRLs) that were at or below the MCLs. Note: The results from the 2021/2022 OHA PFAS sampling project that are currently in Data Online do not meet this criteria so cannot be used to help meet the initial monitoring requirements.
For samples collected on or after June 25, 2024:
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Labs performing the analysis must be accredited by EPA or ORELAP. See below for a list of ORELAP-accredited labs.
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Results must be reported using minimum reporting levels (MRLs) that are at or below the “trigger levels” in the rule (½ the MCLs).
If a water system has some previously collected results meeting the above criteria, but fewer than necessary to meet the initial monitoring requirements, the system can supplement with additional monitoring such that all required calendar periods are represented, regardless of the year.
Important information about UCMR5 data
To be considered for reduced compliance monitoring after April 26, 2027, all initial monitoring results must be at or below the “trigger levels,” which are ½ the MCLs. UCMR5 results for PFOA and PFOS were reported to the MCLs (4.0 ppt each), not the trigger levels (2.0 ppt each).
Water systems serving more than 10,000 will need to ask their UCMR5 lab to reprocess the PFOA and PFOS data down to at or below the trigger levels of 2.0 ppt prior to submitting the data to OHA for initial monitoring if they want to be considered for reduced compliance monitoring after April 26, 2027.
EPA has indicated they will request UCMR5 labs used by water systems serving 10,000 or fewer to automatically reprocess the data and report it to the water system and OHA. For more information, see the “UCMR5 Monitoring Data” section on page 3 of
this EPA memo.
Compliance Monitoring Requirements
Ongoing compliance monitoring begins on April 26, 2027. Compliance monitoring frequency is determined by initial monitoring results:
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Quarterly if any initial monitoring results are at or above the trigger levels (½ the MCLs), or
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Triennially (every 3 years) if all initial monitoring results are below the trigger levels (½ the MCLs)
Systems with multiple entry points may have different compliance monitoring schedules for each entry point depending on their initial monitoring results.
Labs for PFAS Analysis in Drinking Water
Public water systems must use a lab approved by the EPA or the state to analyze PFAS samples needed to meet the initial monitoring requirements. Samples for initial monitoring must be analyzed using EPA method 533 or EPA method 537.1 (Version 1 or 2). See below for a list of ORELAP-accredited labs for the analysis of PFAS in drinking water:
OHA PFAS Sampling Project
OHA-DWS is conducting a PFAS drinking water sampling project at small public water systems in Oregon that have not already sampled for PFAS. The purpose of the project is to identify water systems with PFAS detections so the systems can access currently available funding to address the issue. The analysis is being paid for with federal funding and will be done at no cost to the water system. The Oregon Department of Environmental Quality (DEQ) lab will be collecting and analyzing the drinking water samples for 25 PFAS compounds using EPA method 533.
Samples will be collected at all Community (C) and non-profit Non-Transient Non-Community (NTNC) water systems serving fewer than 3,300 people that have not already sampled for PFAS. Sampling will also occur at water systems where previous sampling by OHA was not able to report results down to the new regulatory levels.
Sampling is scheduled to begin in late summer 2025 and continue through spring 2026. DEQ staff will contact water systems directly to arrange a time for sample collection (DEQ staff will collect the samples). One sample will be collected from each active entry point (EP) to the distribution system during normal operating conditions.
The sample will count toward meeting some of the initial monitoring requirements under the new national PFAS drinking water regulations. Public water systems are responsible for collecting any additional PFAS samples needed to meet the initial monitoring requirements under the rule by April 2027. Make sure additional samples you collect are either 5 to 7 months apart (groundwater serving 10,000 or fewer) or 2 to 4 months apart (surface water or groundwater serving more than 10,000) from the sample collected by DEQ. For more information, see the PFAS sampling project FAQ below:
Rule Resources