City begins seasonal aquatic‑weed treatments at Logboom and parks; phosphorus and algaecide approach planned at lagoon

Kenmore staff began seasonal aquatic vegetation and algae treatments at city parks this month and outlined a multi‑pronged approach for the summer, including chemical treatment windows, phosphorus inactivation and mechanical skimming.

Environmental Services Director Richard Sawyer said the first round used a product identified as "Prosilocore," which can be applied earlier in the season and targets milfoil growth. At Logboom Park and other sites a second treatment window after mid‑July will target remaining milfoil and other invasive pond weeds; the city will alternate phosphorus inactivation with an algaecide at the lagoon at Takwadis Park to address cyanobacteria and algae.

Why it matters: neighbors have raised concerns about nuisance vegetation and algae blooms. Staff said phosphorus inactivation helps “remove excessive nutrients from the water column” and can reduce algal growth, while aeration and long‑term options will require further study and multi‑season monitoring. Operations crews will also perform periodic mechanical skimming to remove floating plant material.

City staff noted suction dredging—previously used in smaller areas—proved effective but is cost‑prohibitive for larger areas now targeted. Monitoring and consultant review will inform whether aeration systems or other longer‑term treatments are warranted.

No formal policy change was adopted; council received the operational update and asked staff to continue monitoring results and report findings and costs in follow‑up briefings.