EPA released Method 1633A on December 5, 2024, and the agency’s Clean Water Act Methods Update Rule 22, published January 21, 2025, brought PFAS methods into 40 CFR Part 136 — the list of approved methods for NPDES permits.

What changed

• Method 1633A covers 40 PFAS compounds across wastewater, surface water, groundwater, soil, sediment, biosolids and tissue.
• It replaces the earlier release of Method 1633 with clarifications that came out of multi-lab validation.
• Permit writers now have an approved method to cite, so PFAS monitoring conditions are showing up in NPDES renewals.

What it means in the field

The method’s material restrictions apply to your sampling train, not just the laboratory. Wetted parts need to be free of PTFE and other fluoropolymers, aqueous samples go into HDPE or polypropylene bottles with unlined caps, and equipment blanks are expected. Our PFAS sampling collection lists the pumps, bailers, tubing and filters selected on that basis, alongside the low-flow sampling equipment used on the groundwater side of the work.

Confirm materials, containers and hold times against your project QAPP and the current revision of the method before you mobilize.

Sources: EPA — CWA analytical methods for PFAS; Federal Register — Methods Update Rule 22.