Frequently Asked Questions

Q. Why are Cape Cod beaches tested?

Simply put, to protect the public health. The beach water samples are analyzed for “indicator” organisms, which of themselves are not harmful, but indicate the potential for the presence of human pathogens. A human pathogen is an organism or virus that is capable of producing an illness in a human host.

Q. What are these “indicator” organisms?

Indicator organisms, as their name implies, are used to “indicate” the presence of conditions which have the potential to cause illness. Through various studies conducted by Environmental Protection Agency (USEPA) and others, it has been determined that certain levels of some indicator organisms in bathing beach waters represent a threat to the public health. The indicator organisms assayed for in bathing beach samples that we collect are bacteria called enterococci and E. coli. Enterococcus has proven the most useful bacterial indicator for determining the extent of fecal contamination in marine recreational waters, while E. coli have proven most useful in freshwater situations. An important thing to remember regarding indicator organisms is that, of themselves, they may not be harmful. Rather, since these organisms are found in the intestine of many warm-blooded animals, their presence suggests that other harmful organisms and viruses also in the intestine of warm-blooded animals (including humans) may be present. If these harmful organisms and viruses (called pathogens) are present and are inadvertently ingested while swimming, they may cause a variety of diseases. The good news is that the most common illness is a mild gastroenteritis with flu-like symptomolgy. But even the milder diseases can be problematic to immune-compromised people.

Q. How do these organisms and pathogens get into the bathing water?

Runoff from rain events is the dominant cause for elevated indicator bacteria levels. Most of the closures in 2001 were related to storm water runoff. Runoff carries pollutants from roads and other paved surfaces directly to the surface water of beaches and ponds. Other possible causes are animal waste from pets as well as wild animals. Common waste observed on beaches can be from dogs, fox, seals, seagulls, ducks and geese. Most warm-blooded animals carry the same indicator bacterium used to classify recreational waters.

Q. Do boats affect samples taken at bathing beaches?

Sanitary wastes from marine craft has been increasingly eliminated as a potential threat to our bathing beaches for two reasons. Foremost, many marinas now have pumpout facilities for their visitors (often at no cost), and secondly, if a boat does discharge sanitary waste, it is required that it do so at least 3 miles offshore, where dilution rates are very high.

Q. How is it determined whether or not a beach is to be posted?

When a sample is taken for a marine(salt) beach, the water is brought back to the laboratory and tested for the presence of the indicator organism enterococci. It takes 24 hours to determine if enterococci are present in the sample. The maximum allowable number of enterococci colony forming units per 100ml sample are 104. If a sample exceeds this limit, the beach must be posted as closed to swimming and resampled.

When a sample is taken for a fresh water bathing beach, the water is brought back to the laboratory and tested for the presence of the indicator organism E. coli. It takes 24 hours to determine if E. coli are present in the sample. The maximum allowable E. coli colony forming units allowed per 100ml sample are 235. If a sample exceeds this limit the beach must be posted as closed to swimming and resampled.

Running averages (geometric means) are kept at all bathing beach sites as well. The geometric mean is calculated using the most recent 5 non-storm event samples in the bathing season. For marine beaches the geometric mean must not exceed 35 Enterococci CFU/100 ml., and for fresh water ponds the geometric mean must not exceed 126 E. coli CFU/100 ml.

Q. How long are beaches posted if high levels of bacteria are detected?

In the event a sample has a bacteria level above the standard listed above a resample of the bathing water will be conducted as soon as possible, and the beach will be reopened when test results show acceptable bacteria levels. The tides and currents in open waters act to disperse contaminants. Generally the level of the indicator bacteria is reduced within twenty four hours after the conclusion of the rainfall, typically after one full tide cycle. Unfortunately the laboratory analysis of a sample does not provide instantaneous results. There is a 24-hour incubation period for all samples. Therefore it is common for a bathing water closure to last for a day or two to ensure public health and safety.

Q. If a beach is posted closed to swimming can I still go to the beach?

Many safe activities can be enjoyed while the beach is closed to bathing and swimming. Examples include: walking on the beach, collecting seashells, building sand castles, and playing sport activities such as volleyball, paddleball, Frisbee, football, etc.

Q. Is there anything I can do to help?

  • Do not feed the birds.
  • Do not walk on the dunes: vegetation is a valuable filter of pollutants, and prevents erosion and reduces runoff.
  • Clean up after your pets.
  • Do not bury diapers or trash into the sand.