A west metro lake that’s become the testing ground for local agencies and the state of Minnesota to see if new measures will work at killing zebra mussels is holding off the invasive species.

As the boating season has come to a close, Christmas Lake hasn’t let up its efforts to keep the small lake next to Lake Minnetonka free of the aquatic invasive species after costly and groundbreaking efforts to rid the lake of mussels over the last year.

Since then, boat inspections were expanded, a security camera was installed at the boat launch that streams online and to local police and each month, scuba divers surveyed the lake’s bottom to scan for the water pests — with no sign of them yet.

“Obviously, the more years that go by, the more confident you can be,” said Eric Fieldseth, AIS program manager for the Minnehaha Creek Watershed District.

More than 200 Minnesota waterways are listed as infested by the state Department of Natural Resources but few lakes in the state or the nation have accomplished what Christmas Lake has done so far. In August 2014, zebra mussels were discovered near the public boat launch thanks to the watershed district’s early detection program, which monitored the lake and closed off the area.

The lake was the first in the nation to use Zequanox, a biological pesticide. Then crews used a copper treatment, followed by potash to treat the nearly 1-acre area of the lake, which is next to mussel-infested Lake Minnetonka.

In the small area of Christmas Lake, the zebra mussels were killed off — the first time mussels were eliminated from an area of a Minnesota waterway. However, last May, more zebra mussels were found outside that area. Crews treated the area with potash in June and a 10-acre area in July. Since then, Fieldseth said monthly scuba dives of the area have turned up no mussels.

But the work isn’t over yet. Volunteers will check zebra mussel samplers weekly through October. And next May, crews will resume lakewide scuba dives in search for the invasive species after ice-out. It will take another year or two before officials can say for certain that zebra mussels were eradicated from the lake.

But the success story could provide lessons for other lakes and rivers infested with the fingernail-sized pest, which can damage boat motors, slice swimmers’ feet and threaten fish.

“We’re confident we’re doing everything we can to protect the lake,” said Joe Shneider, president of the Christmas Lake Homeowner’s Association.

The lake also expanded its inspection program this year, checking every boat entering the 267-acre lake when the boat launch is open, and will continue to do so until Oct. 31.

The inspections and treatments are funded by the watershed district, city of Shorewood, state DNR and the homeowners group. They’ve also gotten help from the Minnesota Aquatic Invasive Species Research Center.