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Vital Statistics

Watershed Area 254 acres
Lake surface area 46 acres
Maximum depth 24 feet
Mean depth feet
Public Park Yes
Boat Ramp Yes, no gas engines
Fish Present stocked rainbow


Volunteer monitoring began at Steel Lake in the 1980s and continued through 2004, when it was discontinued. Federal Way has resumed monitoring in 2014. In 2004, the data indicated that the lake was relatively low in primary productivity (low mesotrophic) with very good water quality. No strong trends were identified.

Profile data indicated that thermal stratification may be unstable through summer, but the sediments do release a small amount of phosphorus into the deep water. Nitrogen to phosphorus ratios were generally above 20:1 through the summer, which favors other species of algae over bluegreens, but the ratio was closer to 20:1 in the fall.

Steel Lake has a public access boat launch, and the lake has been treated for a Eurasian milfoil several times, with a long-term plan adopted for control, including funding through the formation of a Lake Management District.

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This bathymetric map shows contour lines of equal depth, similar to a topographic map would for mountains and valleys. The red 'X' marks the location where water quality samples are taken.
This map shows the area of the watershed relative to the area of the lake. Generally speaking, the larger a watershed is relative to a lake, the greater the influence land use practices on lake water quality.

Click image to enlarge

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Water Quality Data  

Through a combination of efforts by volunteer lake monitors and King County staff, data relating to physical, chemical, and biological aspects of the lake have been collected for most lakes. The King County Lake Stewardship Program analyzes data to track long-term water quality trends in small lakes in western King County.

View or Download Data
Use this tool to view or download data from the lake in tabular format. You can define date ranges and select which parameters to view or download.

Chart Data
Use the charting tool to look at graphs showing single parameters for a single water year at a time.

Water quality over time
A common method of tracking water quality trends in lakes is by calculating the “trophic state index” (TSI) (Carlson, 1977) and testing the values for positive or negative trends over time. TSI indicators predict the biological productivity of the lake based on water clarity (Secchi) and concentrations of total phosphorus (TP) and chlorophyll a (Chlor). Generally at least 8 years of data without major lake management activities are needed to have confidence in a significant trend.

The average of these three TSI indicators during the growing season can be used to place lakes in one of three broad categories:
<40 = oligotrophic (low productivity),
40 to 50 = mesotrophic (moderate productivity)
>50 = eutrophic (highly productive).

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Reports and Related Links

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For questions about lakes in King County, please contact lakes@kingcounty.gov or call the Water and Land Resources Division front desk at 206-477-4800.