City staff updated the Mercer Island Utility Board on a proposed replacement and realignment of the island’s water supply line, options to transfer Seattle Public Utilities (SPU) assets to city ownership, and next steps on a wholesale contract amendment with SPU.

Jason (city staff) said the new proposed alignment would still receive water at the East Mercer Channel bridge but would follow a route around Southeast 36th/30th and up Gallagher to Southeast 40th to reduce reliance on a 24-inch section of pipe that experienced a leak last year. He said the city has hired RH2 as design and engineering team for the project and is near the final stages of selecting a contractor under a heavy civil GCCM (general contractor/construction manager) delivery model to bring a contractor in early in the design process.

Jason described a staff recommendation that Shorewood — currently a direct customer of SPU — be permanently connected to Mercer Island’s water system when the new supply line is constructed. He said staff has discussed the proposal with SPU and did not expect opposition. "By transferring ownership of this segment of pipe or this section, it would once water comes onto the island, everything would be city owned, operated, controlled moving forward," he said.

Board members asked whether Shorewood drew from Mercer Island’s reservoir during previous emergencies; staff said Shorewood had been supplied via an emergency intertie in past events and that the city’s water modeler indicates the island could absorb Shorewood demand. Staff said Shorewood’s internal private distribution system would remain the owner’s responsibility, and any detailed condition assessments of Shorewood infrastructure would be part of further information requests to SPU and Shorewood management.

Jason said council direction was to pursue a permanent connection for Shorewood, to abandon the remaining SPU 24-inch line once the new supply line is in place, and to pursue transfer of ownership for the remaining SPU assets along the island so that, from the East Channel Bridge onward, the system would be city-owned. He also said the city is exploring expanding well capacity and other resiliency measures; those options and the Confluence draft action plan will be folded into the city’s water system plan and future capital improvement programs.

Staff described timing and next steps: a contract reopener/amendment with SPU will be discussed with council (a May meeting was flagged for further details); the GCCM contractor selection may be finished within a month; and staff will bring a draft contract amendment for board review prior to council consideration. Staff also noted recruitment work for open utility-board seats and the planned May in-person/hybrid meeting.

No formal action was taken; the board requested continued updates and forthcoming council materials.