Hidden Lake

Managed by King County Department Natural Resources and Parks

Hidden Lake is a dammed section of Boeing Creek upstream of Innis Arden Way. This is a constructed open water feature designed to improve aquatic habitat; it contains a sediment forebay to trap sediment as it moves into the lake. In order to keep the lake as an open-water feature, the City maintains it by removing sediment on an annual or biannual basis.

It is part of Boeing Creek Park, a wooded park with trails and picnic areas.

Get directions to this beach

COVID-19

Keep your distance from other people.

Practicing social distancing is essential right now. Follow the advice of the health experts. If your community has asked that you remain indoors and away from others, do so. Heading to the beach should only be considered an option if social distancing practices can be followed. Spending a day in any crowded place is the worst thing we can do for our most vulnerable right now and will counter the efforts to curb the virus’ spread.

For more information, please visit the World Health Organization public resource on COVID-19.

Water Quality

Passed water quality tests 60-95% of the time
Historical Status
This status is based on the latest sample, taken on September 15th, 2020. King County Department Natural Resources and Parks updates the status of this beach as soon as test results become available. These results were posted to Swim Guide on September 17th, 2020 at 10:33 AM.

For water quality icon legend, click:

Report Pollution

Monitoring Frequency

Source Information

The King County Department of Natural Resources and Parks monitors water quality at designated swimming beaches in the county from May to September. Water quality data is collected weekly, usually on Mondays. Results are generally posted to the King County Swimming Beach Bacteria Monitoring page by noon on Wednesday.

During the sampling period, Puget Soundkeeper Alliance regularly updates the Swim Guide to reflect the most current information. Local health officials use the following protocol to make closure determinations – A day’s average E. coli value is over 1000 CFU/100 mL – OR - The average of the E. coli values for the three most recent sampling days is over 200 CFU/100 mL. The three-day average is calculated using the geometric mean (geomean). The unit of measure is a CFU which stands for Colony Forming Units.

A beach is marked Green (open) when both of these protocols are met.
A beach is marked Red (closed) when these criteria are not met and the public health officials have closed the beach.

A beach may also be marked Red if there is a Harmful Algal Bloom (HAB) reported at the beach. A beach is marked Grey when current water quality data is not available. The King County Water and Land Resources Division (WLRD) collects and analyzes the samples. Public Health Seattle & King County is alerted when bacteria or state algal toxin thresholds are exceeded and determines the health and safety implications of the bacteria and algal toxin data collected, and they work with King County WLRD and the local park manager to post an advisory.

For more information go to King County Swimming Beach Bacteria Monitoring website: kingcounty.gov/swimbeach.

Water Quality Graph