Thurston County advances plan to buy TransAlta Water Bank shares to boost streamflow

Thurston County staff updated commissioners on the county’s Streamflow Restoration Program and a planned purchase from the TransAlta Water Bank intended to advance local compliance with the Streamflow Restoration Act.

Brian Benjamin of the county’s planning office described the 2024 application for TransAlta water. The bank contains about 26,631 acre-feet; the county’s Phase One request is for 800 acre-feet, of which 505 acre-feet would meet the minimum offset need for the watershed. County staff reported a current price estimate of about $3,150 per acre-foot and said they expect to close the transaction by the end of 2026.

Why it matters: the Hurst decision requires local jurisdictions to make independent determinations of water availability, and the Streamflow Restoration Act establishes a 20-year planning horizon and minimum offset targets for new permit‑exempt wells. Purchasing from a water bank is one of the more straightforward ways local governments can secure legally and physically available water rights to create instream benefits that address those requirements.

County presenters said the program aims to go beyond minimum compliance. In addition to the 505 acre-feet that would meet the watershed’s minimum offset, staff reported reserving an additional 295 acre-feet for aquatic habitat and climate resiliency. Benjamin explained a strategic procurement approach that targets purchases in low-flow months (June–September) to maximize ecological benefit per dollar and conserve bank supply for other users. Staff are developing a grant application to pursue month‑specific allocations rather than buying uniform shares across the year.

The presenters emphasized this kind of acquisition still requires substantial staff resources. They noted the county has identified 170 projects across four watersheds and 44 subbasins in its plans and that even relatively “low‑hanging fruit” like bank purchases involve multi‑year grant, review and closing processes. Benjamin said staff engaged the Chehalis-area tribe and nearby cities early; those jurisdictions provided letters of support for the application, which county staff expect will weigh favorably with the Department of Ecology’s grant review.

Next steps: CPED will complete the grant application for the month‑targeted purchase and return to the board with transaction details and a proposed close timeline. The county indicated the project would be resourced from existing program budgets and coordinated with partner jurisdictions.

“Buying during the low‑flow season maximizes the value of the purchase for our aquatic systems,” Benjamin said, describing the logic behind the timing and the outreach to bank stakeholders.

The board did not take a final purchase vote during the work session; staff said they would return with grant and closing details for formal approval.