For beach samplers
Marine beaches are sampled weekly or every two weeks throughout the summer. Water samples are tested for illness-causing bacteria, known as enterococci. Because bacteria results can be highly variable, three sample results are averaged to ensure the level of risk at the beach is accurately represented. When the average exceeds 104 enterococci/100mL, a beach advisory is issued.
The instruction video and documents below providew more details about the process of collecting and testing beach water samples.
How to sample beaches for bacteria
- Our standard operating procedure contains step-by-step instructions for collecting marine samples for laboratory analysis.
- Our quality assurance project plan for the BEACH program describes program objectives and procedures to be followed.
Water quality criteria for decision-making
Our water quality decision criteria are based on EPA's National Beach Guidance and Required Performance Criteria for Grants. The fecal indicator enterococci is used, because this indicator better correlates with swimming-related illness. If enterococcus levels exceed 104 enterococci/100 mL, a beach advisory is issued by a local health jurisdiction.
The EPA's marine water (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.
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.
If either of these criteria is exceeded, a local health jurisdication may consider issuing a permenant advisory at a particular beach.