Beach Water

Why is public beach water tested?

Beaches are monitored to protect swimmers from illnesses that may be linked to unacceptable bacteria levels. Swimming in water with unacceptable bacteria levels can result in an increased risk of infection of the ears, eyes, nose and throat or gastrointestinal or stomach illnesses if the water is swallowed.

What are the water samples analyzed for?

The Provincial Laboratory analyzes each sample for E.coli bacteria. E. coli is used because it is the most specific indicator of fecal pollution. (It should be remembered that there are thousands of different kinds of E.coli bacteria, but only a few of them cause illness in humans.) The results of the laboratory analysis indicate the bacterial quality of the beach water at the specific time the beach was sampled. To get an accurate assessment of water quality, a number of samples across the beach area must be taken.

The health unit does not routinely monitor chemical quality of water at beaches. However, if there is reason to believe chemical contamination may exist at a beach, the health unit and the provincial Ministry of the Environment will investigate.

When are beaches posted?

When there is evidence that bacterial levels exceed Provincial guidelines and there may be a higher than normal risk of infection, a warning is posted advising the public that the water may be unsafe for swimming. Before a beach is posted, results from several samples are required. A type of average of the sample results, called a 'geometric mean', is calculated. The geometric mean is used rather than a normal arithmetic average because it reduces the biasing effect of occasional extreme readings. When the geometric mean of the sampling results exceeds 100 E.coli bacteria per 100 ml of water, beach posting is considered. If posting is needed, the owner of the beach (usually the municipality) will post signs in prominent positions to warn swimmers of the potential risk. The signs will normally remain posted at the beach until sample testing shows the risk to swimmers is once again within acceptable limits.

What else is done when samples are taken?

At the time of sampling, the weather conditions, any rain during the previous two days, the wind direction (onshore, offshore, cross-shore), the degree of wave action (calm, light, medium, heavy), the number of bathers, waterfowl or animals (i.e.dogs) in the immediate beach area and the clarity of the water are also recorded. This field data is gathered so that historical data on factors influencing a particular beach is available for assessment by the health unit to predict water quality deterioration.

How are sampling sites selected?

The locations of sampling sites at a beach are fixed for the season and should be representative of the complete beach area. A minimum of five sampling sites per beach is normally established. For large beaches that are more than one kilometre in length more sampling sites are required. They would normally be spaced 200 metres apart.

How often are the beaches sampled?

Based on past sampling data and the beach sampling protocol produced by the Ministry of Health, the health unit determines how often beaches should be sampled. Normally beaches are sampled once per week during July and August, but might be sampled more often under some circumstances.