EPA Extends Schedule for Revised M/DBP Regulations

The Association of Metropolitan Water Agencies (AMWA) posted a notice that the Environmental Protection Agency (EPA) has announced “…..an extension of the deadlines for proposed revisions to the National Primary Drinking Water Regulations (NPDWRs) regarding microbial and disinfection byproduct (MDBP) rules. Originally set for July 31, 2024, the proposal deadline has been extended to July 31, 2025, while the final action deadline, initially scheduled for September 30, 2027, has been moved to October 2, 2028.”


The SDWA requires that every six years, EPA review primary drinking water regulations to determine whether they should be revised. In January 2017 EPA published the results from the third six-year review of contaminants.  The outcome of that review was that EPA considered eight NPDWRs as candidates for regulatory revision (chlorite, Cryptosporidium, haloacetic acids, heterotrophic bacteria, Giardia lamblia, Legionella, total trihalomethanes, and viruses). These constituents are currently regulated under the Long-term 2 Enhanced Surface Water Treatment Rule and the Stage 2 Disinfection Byproduct Rule and are referred to as M/DBP regulations.

In 2022 EPA formed an M/DBP Rule Revisions Working Group under the National Drinking Water Advisory Council (NDWAC) to develop recommendations for revisions to the M/DBP regulations. The first meeting of the NDWAC M/DBP Working Group was held in May 2022. The M/DBP Working Group met through November 2023 and prepared a final report with recommendations that was submitted to EPA on December 14, 2023.  The M/DBP Working Group report presented recommendations to EPA on 13 topics.

The 12 month extension of the schedule to publish proposed and final M/DBP regulations, is consistent with the language in the May 2020 signed Consent Decree between EPA and the Waterkeeper Alliance and California Coastkeeper Alliance (the lawsuit was filed in January 2019 regarding EPA’s missing statutory deadlines).