Lake weeds reduced by 18K pounds

SANDPOINT — Aquatic Weed Solutions, Inc., in Sandpoint removed more than 18,000 pounds of noxious weeds from the Lake Pend Oreille this year.

"It went highly successful for how late we started in the year," Mat Lawrence of AWS told Sandpoint City Council members Wednesday.

AWS was contracted by the city of Sandpoint last summer to manage aquatic invasive species of noxious weeds through diver-assisted suction harvesting. Beginning in August, the divers removed 335 totes, for a total of 18,425 pounds, of wet biomass from the waters around Windbag Marina and the City Beach swim area.

The divers also spent one day at the Memorial Field boat launch removing eurasian milfoil and flowering rush in the boat traffic areas, as well as a few scattered rush plants from Third Street Pier.

Lawrence said 120 of the 233 hours were focused on mature eurasian milfoil within three feet of the water surface. The divers focused on the top three feet for boat traffic clearance, and Lawrence said removing root systems could cause sediment issues.

"Ideally we want to tackle that well before it gets to that height, that way we can basically get the most bang for our buck with the suction harvesting," he said.

During the pre-treatment survey by AWS, Lawrence said they identified 700 flowering rush plants, which they eliminated successfully during the remaining 113 hours. During that time, the divers discovered an additional 100 rush plants.

Jared Yost, Sandpoint city forester, said even with efforts by AWS, volunteer organizations and private citizens groups, the flowering rush is getting worse in the boating and swimming areas.

"It's a very difficult battle to try and win against that flowering rush," Yost said. "It's the one battle that we are hoping we could try to remove from that area."

Lawrence said AWS is "definitely making progress" on the flowering rush, but agreed it is a "never-ending battle."

Moving forward, Lawrence said AWS plans to continue the suction harvesting. In past years, a biodegradable bottom barrier was used, but over the years began to float up with the plant mass and risked getting tangled in boat propellers.

"That is one of the reasons I didn't necessarily like the biodegradable barriers as a control method," he said. "They seem like they have a two- to three-year window from the date I'm looking at where they were pretty effective, but I think suction harvesting is the definite answer moving forward as far as I can see right now."

Also, with suction harvesting, Lawrence said the divers can be selective in order to leave most of the native plants in place.

In 2017, Lawrence said AWS plans to get into Lake Pend Oreille earlier in the summer, possibly May or June, to gain better control over the eurasian milfoil and flowering rush.