Hidden Lake

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.

WATER QUALITY

Passed water quality tests 60-95% of the time
Historical Status
This status is based on the latest sample, taken on June 10th, 2019. Puget Soundkeeper Alliance updates the status of this beach as soon as test results become available. These results were posted to Swim Guide on at

For water quality icon legend, click:

Report Pollution

MONITORING FREQUENCY

SOURCE INFORMATION

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

Hidden Lake

Shoreline, Washington

Managed by Puget Soundkeeper Alliance

WATER QUALITY

Passed water quality tests 60-95% of the time
Historical Status
This status is based on the latest sample, taken on June 10th, 2019. Puget Soundkeeper Alliance updates the status of this beach as soon as test results become available. These results were posted to Swim Guide on at

For water quality icon legend, click:

MONITORING FREQUENCY

SOURCE INFORMATION

WATER QUALITY GRAPH

Beach	Location	Water Quality
Richmond Beach Saltwater Park Shoreline, Washington	Shoreline, Washington	Historical Status
Echo Lake Shoreline, Washington	Shoreline, Washington	Historical Status
Carkeek Park Seattle, Washington	Seattle, Washington	Historical Status
Edmonds Marina Beach Park Edmonds, Washington	Edmonds, Washington	Historical Status

Other Beaches Near This One

Beach	Location	Water Quality
Richmond Beach Saltwater Park Shoreline, Washington	Shoreline, Washington	Historical Status
Echo Lake Shoreline, Washington	Shoreline, Washington	Historical Status
Carkeek Park Seattle, Washington	Seattle, Washington	Historical Status
Edmonds Marina Beach Park Edmonds, Washington	Edmonds, Washington	Historical Status

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	Green means the beach’s most recent test results met relevant water quality standards.

	Red means the beach’s most recent test results failed to meet water quality standards.

	Grey means water quality information for the beach is too old (more than 7 days old) to be considered current, or that info is unavailable, or unreliable.

	Green means the beach passed water quality tests 95% of the time or more.

	Yellow means the beach passed water quality tests 60-95% of the time.

	Red means the beach failed water quality tests 40% of the time or more.

	Green means the beach has historically excellent or pristine water quality, but there is no current data.

	Red means the water at the site has water quality issues or there is an emergency.

	Grey means there is no current water quality information, the beach is under construction, there has been an event that has rendered water quality information unreliable or unavailable.