Committee forwards Edmonds Marsh filtration design amendment after WSDOT permitting and long-term maintenance discussion

Edmonds City Council Committee B on Oct. 21, 2025, forwarded a supplemental professional-services amendment for design work on the Edmonds Marsh water-quality improvements (agenda item 2.3) to the consent calendar after discussing permitting, funding and maintenance responsibilities.

Acting City Engineer Mike Dalila said the project combines two previously separate projects to retrofit catch basins along SR 104 (between West Dayton and Pine Street) with filter-cartridge systems intended to treat stormwater before it reaches Edmonds Marsh and to capture emerging pollutants such as 6PPD. Some work sits in WSDOT limited-access right-of-way, so WSDOT permits and approvals are required.

Dalila said the westbound/southbound and eastbound projects originated from separate funding streams (including a Department of Commerce appropriation), but that the projects were combined for design. During coordination WSDOT hydraulics added additional permitting and deviation requirements — in part because the roadway lacks a shoulder and the retrofit could encroach on the traveled way — which increased review and the scope for supplemental design work. The amendment before the committee reflects that additional permitting and design effort.

Committee members asked about the filtration media and long-term maintenance. Dalila said the media is more advanced than earlier oyster-shell demonstrators cited by council and that filter-cartridge media may need replacement once fouled; based on experience the replacement interval is uncertain but typically ranges from about one to three years depending on pollutant loads. Dalila said the city will sign an interlocal agreement with WSDOT that will allow the city to maintain the installed systems in perpetuity after permitting is finalized; the interlocal grants the city rights to access the limited-access area for maintenance with notice to WSDOT.

A council member noted a typographical error in the packet title ("amendment" misspelled); staff acknowledged the correction. Committee members indicated consensus to forward the supplemental-design-amendment item to the consent agenda. The amendment and interlocal maintenance approach will return to full council via the consent calendar; no roll-call vote was recorded at the committee meeting.