Swim Beach Monitoring Program
With the exception of Luther Burbank (use King County Link below) , swim Beaches are currently not being monitored.
The City of Mercer Island's water quality testing program has been in effect since 2003. For the past three years, the results from the testing program revealed very low quantities of bacteria in the water at our beaches. Water is tested weekly during the swim season and will be posted below.
Water Quality Testing Formula
The numbers we use to evaluate the swimming beaches were adopted by the EPA in 1976; a geometric mean of <200 cfu/100 ml, 90% of samples <400 cfu/100 ml. This program also uses the criteria of all samples <1000 cfu/100 ml.
- CFU’s (Colony Forming Units) are a unit of measure. After incubation, bluish colonies of bacteria should appear on the sample dish. It is then necessary to count all of the colonies that are in each dish. A calculation must be performed to determine the number of colony forming units per 100 milliliters of sample.
- E-Coli: One of hundreds of strains of the bacterium Escherichia coli. Although most strains are harmless and live in the intestines of healthy humans and animals, this strain produces a powerful toxin and can cause severe illness.
- Fecal Coliform: Bacteria from excrement, fecal coliform are not necessarily harmful by themselves, but are indicative of the presence of other disease-causing organisms that may cause diarrhea, vomiting, or a more serious illness.
Questions? email the Parks and Recreation Department.