Most King County offices will be closed on Monday, May 28, for Memorial Day.  
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When values lower than the minimum analytical detection level (MDL) are reported, the MDL value for that analysis will be substituted on the chart. A data download will show for which dates the substitutions were made. Please select a sample location.

Due to revisions to the monitoring program in 2009, bacteria samples are no longer collected in Lake Washington or Lake Sammamish as part of the routine lake monitoring. However, fecal coliform bacteria is monitored seasonally at selected King County swimming beaches. (Visit the Swimming Beach web page for more information.)