Hermiston hears PFAS update; staff recommends treating Well 5 and leaning on regional plant

Hermiston city staff and consulting engineers told the City Council July 27 that PFAS (per- and polyfluoroalkyl substances) have been detected above EPA limits at several local wells and outlined a multi-pronged strategy to bring the system into compliance.

Anderson Perry engineer Lucas Stengel summarized the federal regulatory framework and local sampling results. He said the EPA’s 2024 rule set maximum contaminant levels (MCLs) for several PFAS compounds — PFOA and PFOS at 4 parts per trillion, with other listed compounds at higher levels — and established an initial monitoring deadline of April 2027 and an implementation deadline of April 2029. “If PFAS levels exceed the MCL as part of the initial monitoring, there is an implementation compliance deadline of April 2029,” Stengel said.

Stengel and colleagues reviewed Hermiston’s testing and told councilors that PFOS exceeded the MCL at Wells 2, 4 and 5 during sampling. “For the hazard index, basically, if you have any of those compounds above the MCL, it’ll result in a hazard index of 1 or greater,” Stengel said.

City staffer Mark Morgan outlined the feasibility analysis Anderson Perry prepared for the city and explained the recommended baseload: install treatment at Well 5, fully utilize the regional water treatment plant, and mothball Wells 2 and 4. He said those steps would allow Hermiston to meet projected peak-day demand over the next 20 years without installing filtration at all affected wells. Morgan said the estimated capital cost for the filtration alternative was about $16.5 million, with annual operations and maintenance increases in the roughly $1.2–1.4 million range depending on the option selected.

“Installing filtration does remove PFAS from the water,” Morgan said, noting trade-offs. “But there’s significant capital costs and probably more importantly, expensive operational costs associated with that filtration process.” He emphasized that maximizing regional plant use would be immediately available and effective because PFAS is not detected in the regional system.

Engineers also described other options the study considered (building a new regional plant, a Columbia River collector well requiring ~7 miles of pipeline, and aquifer storage and recovery) and the technical and financial trade-offs for each. The Columbia River collector well, for example, was estimated at about $47 million in upfront capital primarily to construct pipeline and easements; the ASR approach was estimated at about $7 million capital with lower operating costs but more-limited capacity.

Staff identified near-term funding paths, including the Safe Drinking Water Revolving Loan Fund’s emerging contaminants program and federal infrastructure funding that states can allocate as forgivable loans or low-interest financing. Stengel said applications for the next funding round are due Aug. 15. Morgan told the council staff will return at the next meeting with an action item authorizing submission of grant/loan applications; he emphasized that applying does not obligate the city to implement a specific construction option.

Councilors pressed staff on treatment types (granular activated carbon, ion exchange, and PFAS-specific media such as Fluorozorb), pilot testing, why the city would not treat all wells, and demand-reduction measures such as greater irrigation-district use. Stengel said pilot testing is typical and that media removal produces handling costs because spent media cannot be regenerated and must be managed (hauled off or incinerated).

Next steps: staff will prepare an authorization for council consideration to apply for emerging-contaminant funding and continue refining cost estimates and implementation timetables.