Green Lake Could be Algae-Free This Summer

December 15, 2015 6:15am
Photo by Dcoetzee

Photo by Dcoetzee

That’s right. Imagine a summer where Green Lake doesn’t have to shut down because of toxic algae. Thanks to the recent approval of the Capitol Improvement Program for 2016-2021, it looks like the summer of 2016 is the year. The approval includes $1.2 million for the study of and cleaning up of Green Lake with an alum treatment that is slated for next year.

If you are new to the Green Lake clean up, here’s some good background. The short version is that toxic algae blooms caused Green Lake closures for all water related activities for the past several years. In the past the lake has been treated with alum in 1991 and 2004 which helps to keep the Lake free of toxic algae.

This year the City spent $300,000 to research the best approach for treatment of the Lake. That includes the amount of alum that needs to be added for the lake to remain “clean” for the next 10 years.

While it may seem like there is substantial amount of waiting for this process to be done, the Parks Department works with multiple city, county and state departments to make sure they jump through all the necessary hoops for this process. That includes: Public Health of Seattle and King County, the King County Department of Natural Resources and Parks and the Washington State Departments of Health and Ecology.

So what’s next for Green Lake’s clean up?

Here’s the current timeline:

January 2016:  you will likely see signs around the park announcing the project and a public meeting that will likely occur in February.

Late March/early April: The application of the alum is slated to be applied to the lake at a time that is said to be most effective. Once it is “added” to the lake it is effective immediately according to Seattle Parks Department. Alum is applied via a barge that is placed in the lake for 10 days.

February 2016: Monitoring report will be complete and the lake should be algae free until 2026.

For more info about the alum, go to:

We will keep you posted about the details of the February public information meeting.