Chehalis approves interlocal with Centralia to use Newaukum diversion to bolster summer water supply

The Chehalis City Council on May 27 approved an interlocal agreement with Centralia to use Centralia’s diversion infrastructure on the Newaukum River to improve Chehalis’s water supply during low‑flow periods.

City staff explained Centralia’s intake sits in a deeper, better channel than Chehalis’s existing intake and has been unused since the mid‑1990s because Centralia lacked a treatment plant. Staff said the agreement would allow Chehalis to tie the diversion structure into its raw‑water line and lessen reliance on Chehalis’s shallower intake in summer.

Public works staff said the interlocal itself carries no immediate fiscal impact, but actual tie‑in work will require future design, an RFP and construction costs. The city recommended approval on first and final reading and to authorize the city manager to execute project documents. A councilmember described the measure as “a win‑win situation for Chehalis and Centralia,” citing the ability to pull more water when flows are low and preserving Centralia’s water rights.

Councilmembers asked whether Chehalis would maintain its existing intake; staff said both intakes could be used and that having the Centralia diversion would allow the city to clean sediment from its current structure without interrupting supply. Staff added that they would not be using Centralia’s traveling screen or its aging equipment — only the concrete diversion structure to tie into Chehalis’s raw‑water line.

Council approved the resolution on first and final reading; staff will return later with design details, cost estimates and procurement steps for the construction and tie‑in work.