Public comment is being sought on a draft environmental assessment that outlines alternatives to address the Eurasian watermilfoil discovered last fall in Beaver Lake.

The Montana Fish, Wildlife and Parks office in Kalispell is preparing the assessment.

For the last several months, a working group with members from Fish, Wildlife and Parks, the county weed department, the state agriculture department, Flathead Basin Commission and the Montana Department of Natural Resources and Conservation has been meeting to discuss how to deal with the aquatic invasive species discovered in the county.

Some confusion has arisen about which agency should oversee any treatment plan regarding the weed and which agency can close the lake to any users to avoid spreading the weed.

According to Dave Burch, state weed coordinator at the Montana Department of Agriculture, the lake is leased by Montana Fish, Wildlife and Parks from the DNRC and those two agencies have authority for decisions related to treating the weeds.

Beaver Lake was closed by Fish, Wildlife and Parks last October and remained closed until it iced over. It was reopened this spring when the ice came off the lake, but the area where the weed was found was marked off with buoys and posted as closed.

A 40-by-50-foot patch of the weed was found near the public boat ramp at the edge of the lake. Last Oct. 31, a diver attempted to pull up some of the weeds, but after county weed department employees realized the patch was larger than originally believed, they instead opted to place barrier mats on top of it. The goal was for the barriers to contain the weeds to that small area and prevent sunlight from reaching the weeds. Without sun, the weeds die. The mats remain in place today.

BEAVER LAKE is the only place Eurasian watermilfoil is known to exist in the Flathead system, according to Jim Satterfield, regional supervisor for Montana Fish, Wildlife and Parks. That’s why Satterfield supports an aggressive approach to destroying the weed in Beaver Lake.

“My position is if this is so important we are considering closing the lake, why not throw the kitchen sink at it to get it out of there,” Satterfield said. “If this is the only place it exists in Northwest Montana, let’s stop it.”

He clarified that position is his and not shared by all members of the working group.

Satterfield says a multipronged approach is needed to destroy the weed in Beaver Lake — using barrier mats to prevent spread and slow or stop growth, applying a chemical to kill the weed and pulling individual weeds before they spread.

His goal regarding any chemical treatment is that it be a one-time effort. He’s optimistic one treatment over the barriers would kill the patch.

“You don’t have to remove the barriers to apply a chemical,” Satterfield said. “You can treat on top of the barrier. That double effort would be good in this instance.”

That is the preferred alternative in the draft environmental assessment. It identifies two options for dealing with the milfoil. Alternative A calls for taking no action. Under that scenario, the draft document says the Eurasian watermilfoil would likely spread in Beaver Lake and to other nearby water bodies.

Alternative B, the proposed management action, calls for using barrier mats, pulling weeds and applying herbicides as deemed necessary. Use of an herbicide and manually pulling weeds out of the lake bottom are both permitted by Montana’s 2011 strategic plan for invasive aquatic plant management and resource protection.

Herbicide treatments of aquatic species have been commonplace in the United States for 50 years, Satterfield said. The practice hasn’t occurred in the Flathead Valley because aquatic invasive species haven’t been discovered in many places in the area.

“You plan for it carefully,” Satterfield acknowledged. “But there is a lot of experience in doing this work around the U.S.

“There’s been apprehension about using a herbicide; we need to get over it,” Satterfield said at a recent meeting of the county weed board. “It is appropriate in this case.”

If an herbicide is used at Beaver Lake, the lake would have to be closed for several weeks, he said.

“We’re vulnerable to having weeds come up as they are dying and they could get attached” to watercraft or fishing equipment, Satterfield said. The most common way aquatic weeds are transferred to other bodies of water is via boats or other equipment taken into an infested lake. If the weeds or other invasive species aren’t washed off a boat and that boat is put into a healthy body of water, the invasive species takes off and infects the second body of water.

Boat inspection stations are operating this summer at Eureka, Ronan and Clearwater Junction, manned by Fish, Wildlife and Parks employees. Any boats found carrying any invasive species are quarantined. All boats entering Glacier National Park are inspected for invasive species and boaters are required to obtain permits to launch in the park.

Eurasian watermilfoil spreads by stem fragments and seed, according to Fish, Wildlife and Parks Fisheries Biologist Mark Deleray. Milfoil displaces native aquatic plants. The weed grows quickly and creates dense canopies that shade surrounding vegetation, killing the native vegetation. It also causes the death of invertebrates and organisms that serve as fish food, Deleray wrote in the draft environmental analysis.

Because it grows in a dense mat, it can clog water intakes and damage boat motors. Its decaying mats foul lakeside beaches, he wrote.

THE ABSENCE of much sun this spring and early summer has kept the temperature of Beaver Lake low enough that the milfoil hasn’t emerged from its dormant phase, Satterfield said. Because of that, it’s not yet possible to determine if the mats killed the weeds over the winter, he said.

A survey of the lake is planned for next week to make that determination.

But Satterfield is proceeding with the environmental assessment because if the weed resurfaces this summer, he wants to have a decision made about how it will be dealt with.

“We want to get the EA done so if we decide at some point this summer we need to use chemicals, we’re ready to go,” he said.

Satterfield and other members of the working group all agree a plan needs to be developed to deal with future discoveries of invasive species.

“We need to have a plan, not a reactionary approach,” Satterfield said.

At last month’s weed meeting, Flathead County weed department Director Jed Fisher said it’s not the county’s goal “to get into aquatic applications. It’s a huge liability for taxpayers.”

Property owners are expected to spray terrestrial weeds on their land in the county, he said.

“We have to have bigger plans in place to prevent the spread” of aquatic invasive species, Fisher said.

Reporter Shelley Ridenour may be reached at 758-4439 or sridenour@dailyinterlake.com.