Friends of Cottage Lake

Toxic Algae results (10/27/25) – Toxic algae warning lifted – samples tested below the threshold, but could still be dangerous for pets. Details here

Toxic Algae again detected in Cottage Lake (sample from 09/01/25): We received lab results for the toxic algae sample collected in Cottage Lake, and it indicated above-threshold values for microcystin. Please avoid any algae scums you see and follow the guidelines the warning advisory

The toxic algae warning has been lifted (06/04/25) – We have received the results back from Monday’s sample and we now have two samples below State Recreational Guidelines – Public Health has lifted the lake advisory for toxic algae in Cottage Lake.

Phosphorus treatment – scheduled for Friday, May 30th – no irrigation or recreational restrictions – here is a presentation from Aquatechnex on phosphorus treatments and toxic algae – Aquatechnex_ Cottage Lake 2024 Results

Toxic Algae again detected in Cottage Lake (sample from May 4th): We received lab results for the toxic algae sample collected on 5/4/2025 in Cottage Lake, and it indicated above-threshold values for Anatoxin-a. Please avoid any algae scums you see and consider the lake closed for recreation.

Fundraiser: The annual FOCL fundraiser on Sunday, May 19th raised over $3500 for FOCL

State of the Lake 2024: Friends of Cottage Lake has been researching water treatments to remove phosphorus from the water and other treatments that might reduce harmful blue-green algae blooms. This year, we hope to try a treatment in partnership with Aquatechnex. Based on their analysis of the lake (they did additional lake and sediment sampling in 2023), the best treatment given our budget is to do two “water column stripping” treatments with Lanthanum (in May and July) to remove phosphorus from the water column with an estimated cost of about $56,000.00. We plan to have a community meeting in early May and then a spring fundraiser at Bassetti’s Crooked Arbor Gardens on Sunday, May 19, 2024. See the State of the Lake 2024 letter for more details.

Water Lilies – last treated in 2017 – watching the remaining lilies – no treatment currently planned.
See the water lily page for more info.

Fish Stocking information for 2024:
Cottage Lake Fish Stocking (waiting for 2024 update)

Join Friends of Cottage Lake on Facebook:
Click here to apply to join the private group or check out our public page here: https://www.facebook.com/FOCL.Woodinville

Who we are:

Friends of Cottage Lake (FOCL) is a non-profit, community-based group committed to improving and defending the health and continued enjoyment of Cottage Lake in Woodinville, WA.

We are currently working with King County to apply for grant money to help fund various lake improvement projects. In the summer of 2005, our lake was chosen as a recipient of a Centennial Clean Water Fund grant—this grant targets the phosphorus problem and funded water quality monitoring and community outreach programs for 5 years.

FOCL is also working with the community to deal with the water lily problem and the Eurasian Milfoil infestation on Cottage Lake. See the links for more information.