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September 2021 – US EPA Publishes Draft CCL5 List

Sixty-six Culprits Drive US EPA Draft CCL5 List

On July 19, 2021, US EPA published the Draft Fifth Contaminant Candidate List (CCL5). US EPA had been seeking comment on the Draft CCL5 and the process used to select the contaminants; however, the comment period closed September 17, 2021. The original notice was included on the Federal Register site (Federal Register Notice: Drinking Water Contaminant Candidate List 5 – Draft (July 19, 2021).

The CCL is a list of drinking water contaminants that are currently not subject to proposed or promulgated national primary drinking water regulations but are known or anticipated to occur in public water systems. Contaminants listed on the CCL may require future regulation under the Safe Drinking Water Act (SDWA).

Prior CCLs (CCL1 through CCL4) have not resulted in any chemicals being added to the SDWA list of regulated chemicals; although in 2011, under the CCL3 list of chemicals, US EPA made a regulatory determination that perchlorate met the criteria for SDWA regulation. Ultimately, US EPA withdrew perchlorate from potential regulation on July 21, 2020. Even so, US EPA is reviewing that final determination under President Biden’s Executive Order No. 13990. 

The Draft CCL5 includes 66 chemicals, three chemical groups (per- and polyfluoroalkyl substances [PFAS], cyanotoxins, and disinfection byproducts [DBPs]), and 12 microbes. The CCL5 list of drinking water contaminants were selected from a universe of chemicals used in commerce, pesticides, biological toxins, disinfection byproducts, and waterborne pathogens.

Of particular significance is the listing of PFAS chemistries as a single group. In the Federal Register announcement, US EPA states that “Over 4,000 PFAS have been manufactured and used globally since the 1940s, which would make listing PFAS individually on the Draft CCL5 difficult and challenging.” We note here, as have many in the industry, that our clients could not cite “difficult and challenging” circumstances as an excuse to dismiss proper adherence to regulatory protocol on their US EPA-regulated projects.

A review of the detailed description of the process used to develop the Draft CCL5 of the chemicals can be found in the Technical Support Document for the Draft Fifth Contaminant Candidate List and the associated Contaminant Information Sheets. While most industry members are familiar with the CCL5 as published in the Federal Register, far fewer examine the underlying detail of the creation of the CCL5 itself.


Gerry Kirkpatrick, P.G.

Managing Partner