Swimming standards & saltwater quality

The BEACH Program collects fecal bacteria data each year from Memorial Day through Labor Day, and at selected beaches throughout the winter.

Decisions to close saltwater beaches to swimming are based on the amount of enterococci bacteria in the water that indicates human or animal feces are present. Enterococci is usually nonpathogenic streptococcus that inhabits the intestine, but can cause inflammation and blood infection if introduced elsewhere in the body (e.g., by injury or surgery).  Learn more about the standards we use to protect people from illness-causing bacteria.

A rack with test tubes that glow blue and green. Tape labels on the tubes say

Testing for enterococci

Water quality criteria for decision making

Currently, the BEACH Program’s water quality decision criteria are based on EPA’s Ambient Water Quality Criteria for Bacteria - 1986, not the Washington State Water Quality Standard for fecal coliform.

The fecal indicator enterococci is used, because this indicator better correlates with swimming-related illness than other fecal indicators, like fecal coliform or E. coli.

The saltwater swimming criteria are in two parts:

  • The geometric mean* should not exceed 35 enterococcus/100 mL, based on results from a minimum of five weekly samples.
  • The statistical threshold value* should not exceed 276 enterococcus/100 mL.

If either of these criteria is exceeded, the beach should be CLOSED to swimming.

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

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