King County tells Mercer Island board repairs on sewer intertie are complete; finish date pushed to October 2026

King County project manager Meredith Redmond told the Mercer Island Utility Board on March 10 that the North Mercer sewer intertie project — a multi‑work‑zone effort that includes a triple‑barrel siphon across Lake Washington and pump station upgrades — remains on track for a coordinated system start this year but now targets substantial completion in October 2026.

Redmond said the single capital effort is being delivered through two construction contracts (conveyance and pump station), both awarded to Walsh Construction in January 2022. She described the work on Mercer Island as roughly four miles of new conveyance divided into 12 work zones, including 7,000 linear feet of 16‑ and 18‑inch force mains in the north zones and a 3,400‑foot transition to 24–30‑inch gravity sewer in the middle sections.

The project schedule has been extended, Redmond said, primarily because contractor‑installed force mains in work zones 1–4 failed pressure testing and required…