Susan from Donahue Engineering told the commission on Dec. 2 that the granular activated carbon (GAC) system installed for PFAS treatment has been operational for more than a year and that most associated construction work is complete. She reported that leaking air‑release valves (24 total across the vessels) were replaced at no cost to the city, though a few valves remain under warranty work.

Susan said the contractor will coat the floor in Structure 120 to protect against damage from caustic rinses used during carbon reactivation and that one remaining construction item — the process waste tank — is still under negotiation.

On carbon management, staff said DNR guidance allows the city to use reactivated carbon from certified facilities, a process in which used carbon is thermally reprocessed and returned. Reactivation vendors named in the discussion are located in Oklahoma and Pennsylvania; staff said using reactivated carbon would yield an estimated roughly 20% cost savings compared with buying all new carbon. The GAC material changeout was discussed at an estimated cost of roughly $800,000–$1,000,000, with ongoing work to schedule staggered replacements and logistics.

Separately, staff reported receipt of a draft WPDES permit (received 2025-11-03) and said the city has until 2025-12-22 at 4:30 p.m. to submit factual comments. Staff said the draft includes PFAS monitoring requirements (effluent testing roughly every two months and biosolids testing annually) and that the DNR hopes to issue a final permit around 2026-01-01. Staff cautioned that an outlier result could trigger a pollutant‑minimization plan but said current testing to date suggests the plant is performing well relative to draft limits.

Next steps: staff will finish review comments on the draft WPDES permit before the Dec. 22 comment deadline; work on carbon reactivation scheduling and remaining construction punch‑list items will continue.