The Washington Department of Ecology BEACH program tests water quality at salt water swimming beaches every week from Memorial Day to Labor Day for enterococcus bacteria. During the sampling period, Puget Soundkeeper regularly updates the Swim Guide to reflect the most current information. The saltwater swimming criteria are in two parts:

The geometric mean* should not exceed 30 enterococci/100 mL, based on results from a minimum of five weekly samples and a maximum of 12 weekly samples. The statistical threshold value* should not exceed 110 enterococci/100 mL, based on results from a minimum of five weekly samples and a maximum of 12 weekly samples. If either of these criteria is exceeded, a beach advisory should be issued at the beach.

To protect swimmers' health, BEACH also uses a Beach Action Value. If enterococcus levels exceed 104 enterococci/100 mL, a beach advisory is issued.

A beach is marked green if it meets all of the above criteria.
A beach is marked red if it exceeds any one of the above criteria.
A beach is marked grey if no current data is available.

Sample results are also shared on the Department of Ecology BEACH program website: https://fortress.wa.gov/ecy/coastalatlas/Tools/BeachClosure.aspx

More information about sampling protocols is available here: http://www.ecy.wa.gov/programs/eap/beach/program.html

* The geometric mean and statistical threshold value concentrations are based on the arithmetic average of the three samples collected at a single beach for the day