Consultant proposes early, systemic Sonar treatments and satellite cyanobacteria mapping for Ocean Shores waterways

Terry McNabb, the Aquatechnix consultant contracted for Ocean Shores’ freshwater program, told the Freshwater Advisory Board on Feb. 2 that survey work last summer found a dramatic expansion of curly leaf pondweed, a state-designated Class C noxious weed. McNabb said individual plants produce many turions (dormant propagules) that sink and sprout in fall, making late starts to treatment ineffective.

McNabb said Aquatechnix proposes starting systemic Sonar (chemical name given during the presentation) applications in April, with a granular controlled‑release pellet deployed across treatment polygons and a second application three to four weeks later. "One plant turns into 10 plants, which turns into hundreds of plants," McNabb said, explaining that Sonar must remain at low systemic concentrations for six to eight weeks for best effect and will translocate to roots for longer control.

The consultant described mapped priority areas—including about 20 acres north of the bridge on the Grand Canal, Bell canals and Bass Canal fingers—and recommended treating contiguous larger areas rather than isolated half‑acre patches because the pellets dilute if used in too small a footprint. McNabb said the pellet approach is designed to "bleed" product slowly so contact levels remain around target plants.

On pennywort, McNabb recommended spot treatments with tank mixes of Rodeo or triclopyr plus an aquatic surfactant; he warned pennywort often overwintered in a semi‑dormant state and is most effectively translocated later in the season (around June).

Board members asked whether the proposed chemicals would harm fish if the city stocks bass later; McNabb cited federal and state review processes and said Ecology and the EPA consider permitted uses safe at label rates, noting that one contact herbicide used last year, diquat, is used at higher rates in salmon and trout hatcheries.

McNabb also outlined a satellite chlorophyll‑mapping pilot using Planet Labs imagery to process five years of daily images for chlorophyll a as a complement to, and partial replacement for, routine boat sampling. "It could replace a lot of the sampling you have to do where you physically get in a boat," he said; the board asked that Aquatechnix and Herrera provide further details at a future meeting.

The board welcomed the briefing and asked Becky to include the consultant’s maps in the packet for council review. The board did not adopt a treatment authorization during the meeting; members agreed next steps include confirming polygons, local access logistics and boat safety protocols before applications begin.