Utility staff told the Kennewick City Council the city must build treatment for per- and polyfluoroalkyl substances (PFAS) at Rainy Collector 5 (RC 5) to meet new federal drinking-water standards and that the project will require major capital investment and decisions about the treatment structure and appearance.

Caleb Shannon, Utility Services Manager, summarized the regulatory timeline and monitoring: "In April 2024, the EPA released the maximum contaminant levels, the MCLs, for several per and poly [fluoroalkyl] substances" and Rainy Collector 5 routinely exceeds the new PFOS MCL of 4 parts per trillion, with values the presentation showed generally between 8 and 15 parts per trillion and as high as 18 parts per trillion on some tests.

Staff said the city received a notice of $15,000,000 in DWSRF funding after applying in late 2024 and selected Hazen and Sawyer to design the PFAS treatment project in March 2025. Preliminary budgets developed earlier are in the roughly $33,000,000 range; staff told council that figure included an allowance for a treatment building at a high level but that an enclosure choice could raise or lower final costs.

Consultants described a likely treatment approach using granular activated carbon (GAC) vessels: a conceptual design includes about 14 GAC pressure vessels (roughly 25 feet tall and 12 feet wide each) and associated piping and a common electrical/mechanical room. Caleb Shannon said bench testing and further design work are underway to determine which media and exact configuration will yield the best lifecycle cost and replacement cadence.

Staff presented three enclosure options for the GAC vessels: (1) no enclosure (outdoor, exposed vessels), the lowest capital cost but with industrial appearance and maintenance challenges; (2) a metal/steel building offering speed and lower upfront cost than masonry, estimated to add roughly $3.8 million to the baseline; and (3) a masonry building matching existing RC 5 aesthetics, longest lifespan and lower maintenance but highest upfront cost, estimated to add roughly $5.5 million (about 16.7% of a $33 million baseline). Staff and council discussed combining options to achieve a hybrid approach — masonry at the base with metal siding above — to reduce cost while improving appearance.

Councilors asked about lifecycle and operational issues: staff said GAC change-out frequency is being defined through bench testing and that Hazen and Sawyer will present expected GAC service life; they also said both Rainy Collector 4 and 5 would be routed through the new treatment facility, and that the two collectors together supply about 60% of the city's annual water production (seasonal variation applies). The consultants noted ion-exchange treatment is an alternative but would increase pumping and electrical requirements and did not offer a clear lifecycle advantage over GAC for this application.

Staff recommended that Hazen and Sawyer proceed with a modified design that blends the metal-building approach with masonry or other architectural features to reduce visual impact, provide shelter for equipment (important for freeze protection), and allow for long-term operations and maintenance. Staff also said they will pursue site landscaping and value engineering to reduce costs and will continue bench testing to finalize the media selection and replacement schedule.

No formal council vote was recorded; staff sought council guidance on aesthetic preferences and on whether to proceed with a design that balances cost, longevity and park visibility. Council members generally indicated support for a blended building solution that provides enclosure and is cost-effective over the asset lifecycle.