Utility staff monitor the water quality of Echo and Hidden Lakes. Staff monitor for potential health risks such as high bacteria levels and toxic algae as well as other water quality indicators such as temperature, dissolved oxygen and turbidity. The 2021 Lake sampling season is currently underway.

Swimming Beach Monitoring at Echo and Hidden Lake

• Echo and Hidden Lake swimming beaches are tested for fecal bacteria levels every week in summer, May through September.
• High fecal bacteria levels lead to swimming beach closures; beach closure signs are posted at the lake.
• More information on the King County Swimming Beach Program available here. 

Lake Stewardship: Long-term Trends Monitoring at Echo Lake

King County manages a monitoring program that evaluates long-term trends and changes in many King County lakes, including Echo Lakes. Every other week throughout the summer, a team of volunteer lake monitors gather data and water samples from the middle of Echo Lake.

• Water quality reports from the volunteer effort are available here.
• Interested in becoming a volunteer? Contact Chris Knutson, 206-477-4739. 

A big thanks to our dedicated Lake Stewardship volunteers! From the left: Teena Littleton, Marla Tullio, Paul Michel, Ann Michel, and Jon Polka (not pictured).  

Toxic Algae Monitoring at Echo Lake, Hidden Lake, Twin Ponds, and Ronald Bog

Harmful algal blooms are overgrowths of algae in water. Algae can appear in various forms and colors. Cyanobacteria, also known as blue-green algae, are bacteria that have some of the characteristics as plants and can pose a toxic threat. Cyanobacteria can look like a paint spill or like grass clippings, and it can cause a thin film along the shoreline or cover a large area of the lake. Green algae, on the other hand, can form thick mats of filaments that can be picked up - these are not cyanobacteria and do not pose a toxic threat.

If you see algae in a City lake, call the City immediately at 206-801-2700 to have it tested. There is no way to tell if an algae bloom is toxic by looking at it. For more information, visit https://www.nwtoxicalgae.org/.

• Toxic algae can lead to lake, pond, or bog closures; closure signs are posted near the waterbody.

Examples of algae observed in Shoreline lakes and ponds. 

The Utility collects and analyzes water quality data for six of the city's major streams. Samples are collected year-round on a monthly basis. Streams sampled include:

• Boeing Creek (east and west forks)
• Ballinger Creek
• Littles Creek
• McAleer Creek
• Storm Creek
• Thornton Creek

Annual reports are available on the King County Water Quality Index for Streams and Rivers webpage.

Photo: Water flowing through Boeing Creek

Surface Water Utility staff test Shoreline waterbodies for E. coli and DNA markers to help us better understand the impact of human, dog, and wildlife waste in our streams and lakes. The Utility focuses on waterways that fail state surface water quality standard for E.coli bacteria. 

Littles & Thornton Creek Fecal Source Tracking Project

Sampling results at Littles and Thornton Creeks indicate chronically high fecal bacteria pollution. To help locate the source of the waste, the Utility partnered with King County to conduct a series of DNA analyses. Preliminary results point to dog and human waste as the culprits. Dog and human waste can come from a number of activities, including failure to pick up pet waste in parks, streets, and even in one’s own backyard, leaky side sewers, and illegal dumping of waste in streams or storm drains. Local water quality data helps the Utility target and address high priority water quality issues.

Human Bacteroides Sampling & Analysis

In 2021, the Utility identified all City streams that exceeded safe fecal bacteria levels and began testing for the presence of human fecal bacteria. This data will help Utility staff better understand and potentially locate sources of human fecal bacteria. 

With the support of a Department of Ecology grant, the City developed the Echo Lake Cyanobacteria Management Plan to understand the causes of and reduce harmful algal blooms in Echo Lake. The plan identifies that excessive nutrients are the main cause of the blooms and suggest three long-term solutions: Oxygen Saturation Technology (OST), chemical treatments, and pollution prevention practices and programs.

• Fact sheet
• 2024 Echo Lake Cyanobacteria Management Plan 

2017 Monitoring Stormwater Retrofits in the Echo Lake Drainage Basin Report 

This report presents an evaluation of the effectiveness of a stormwater retrofit along the Aurora Corridor in the Echo Lake drainage basin. The study was designed to address data gaps by the Washington State Stormwater Work Group (SWG) in the effectiveness of stormwater treatment technologies used in the Puget Sound Region. For more information about this project, visit King County's project page.

2020 Freshwater Assessment Report. This report summarizes the results of water quality data collected between
the 2001 and 2020 water years and compares them to the results of the 2016 and 2009 Freshwater Assessment
Reports 2016. This data helps track long-term water quality in Shoreline.

2016 Freshwater Assessment Report This report summarizes water quality data collected over an 8 year period between 2009 through 2016. This data builds on the previous 2009 report in order to track long-term water quality in Shoreline.

2009 Fresh Water Assessment Report This report summarizes water quality data collected over an 8 year period between 2002 through 2009. Comparison of future data to the baseline data will help track long-term water quality trends and determine if current programs designed to improve water quality are effective.

2016 Echo Lake Aquatic Vegetation Report The Washington State Department of Ecology, in coordination with the City of Shoreline, conducted an aquatic vegetation survey at Echo Lake in June 2016. The survey revealed that Echo Lake contains nine native vegetation species and three non-native species.

2009 Bioassessment Report

A biological assessment of City streams was conducted in 2003 and 2007, using macroinvertebrates (stream bugs) as indicators of health in Thornton, McAleer, Boeing, and Storm creeks. The report found that all streams are severely or extremely impacted by urbanization.