King County wastewater director warns MDCSO cost revisions push out‑year sewer rates sharply higher

King County’s Regional Water Quality Committee heard March 5 that the county is proposing a 7.5% sewer rate increase for 2026, but that revised cost estimates for a large combined‑sewer‑overflow control project and concurrent capital needs mean much larger increases are likely in later years.

Director Cameron Gural, director of the Wastewater Treatment Division (WTD), told the committee that "the proposed rate for 2026 is a 7.5 increase over 2025, fairly close to the 7% increase that we forecasted last year." He said the primary driver of the higher out‑year forecast is an updated, higher‑class cost estimate for the mouth‑of‑Duwamish CSO project (MDCSO), a regulatory‑mandated CSO control project in South Seattle. Gural said the MDCSO class‑5 estimate now…