DEQ outlines PFAS detections in Idaho drinking water; committee defers vote on adoption

BOISE, Idaho — The Idaho Department of Environmental Quality reported to the Senate Health and Welfare Committee on Feb. 7, 2025, that per- and polyfluoroalkyl substances (PFAS) have been detected at numerous public water system sources across the state and that the department is seeking to adopt the U.S. Environmental Protection Agency(EPA) drinking-water rule by reference.

The presentation, given by Tyler Fortunati, chief of the Drinking Water Bureau at the Department of Environmental Quality, summarized PFAS chemistry and health concerns, federal regulatory deadlines and what monitoring so far has revealed in Idaho. The committee did not vote on the pending state rule at the hearing; the chair said the committee will take that vote at a later meeting.

PFAS are a large family of man-made chemicals used for water-, grease- and stain-resistant properties in many industrial and consumer products, Fortunati told the committee. He said two compounds, PFOA and PFOS, have been the most studied, and that many PFAS compounds are persistent in the environment and bioaccumulate.

“The science is really emerging on this,” Fortunati said, summarizing uncertainties about the toxicity of newer PFAS compounds and the effects of exposure to chemical mixtures.

EPA finalized a drinking-water rule for PFAS in April 2024 that sets maximum contaminant levels (MCLs) for six PFAS analytes at concentrations measured in parts per trillion, Fortunati summarized. Under that federal rule, community and nontransient noncommunity public water systems must complete initial monitoring by April 2027; the initial results will determine routine monitoring frequency beginning May 2027. Systems must begin including PFAS information in consumer confidence reports starting April 2027, and public notification requirements and MCL compliance obligations take effect in 2029.

Fortunati described sampling efforts in Idaho. The Department of Defense monitoring detected PFAS at Mountain Home Air Force Base and at Gowen Field, with the Mountain Home detections affecting wells in that basepublic water system. Mountain Home installed treatment on one well in 2018; the well produced about 1,300 gallons per minute, the initial treatment installation cost was $1,360,000 and operating and maintenance cost at the time was about $100,000. The base took that source offline in 2020.

DEQ has run a voluntary PFAS sampling program since April 2021. Fortunati said Idaho has about 3,219 active public-water sources (wells, surface-water intakes or springs) and that DEQ had sampled 381 of those sources (about 12 percent). The state found 66 PFAS detections in those sampled sources (about a 17 percent detection rate by source). On the public-water-system level, DEQ has sampled about 203 systems (roughly 10 percent of the states systems) and reported detections at 58 systems (about 28 percent of sampled systems). Measured concentrations in the DEQ data ranged from about 1 part per trillion (ppt) up to a highest reported detection of 42.2 ppt.

“One of the primary compliance requirements is monitoring,” Fortunati said, explaining that systems found above the MCL will need to average multiple samples (the EPA MCL is determined by a running annual average) and then assess mitigation options. Fortunati listed treatment, developing a new source, or interconnecting with another system as possible responses.

Senator Michelle Wintrow (Senate Health and Welfare) asked how the public will be notified and how rural systems without large municipal infrastructure will be affected. Fortunati said the federal rule requires formal public notification beginning in 2029; before that, DEQ provides templates and encourages systems to communicate with users, and the department notifies local health districts and its regional offices when detections are found.

Fortunati also described funding available for mitigation: DEQs State Revolving Fund receives capitalization grants and related emerging-contaminant funding; he said the program has roughly $7.6 million annually available to assist public drinking-water systems (plus about $1 million for wastewater systems) through fiscal 2027, and that systems must submit a letter of interest documenting a PFAS issue to be considered for that funding.

The committee did not have the pending state rule before it for a final vote at the Feb. 7 hearing; the chair said the committee will vote on the docket at a subsequent meeting. Fortunati asked for the committee's support to adopt the state docket as final when it is next before the committee.

DEQ presentation materials and EPA monitoring results are publicly available on EPA and DEQ websites, Fortunati noted. He also said DEQ will provide follow-up information about soil remediation costs and options at the committee's request.