Why Are Beaches Posted?

It can be a disappointment. You arrive at a beach on a hot summer day looking forward to a cool swim. Then you find signs posted that warn bathers to stay out of the water.

What’s polluting our beaches

Several sources of water pollution can result in beach postings. These include:

Guidelines for beach postings

Beach Posting Sign
Health Department
Beach Posting Sign

Ontario beaches are posted with warnings when E.coli bacteria measure more than 100 E.coli per 100 millilitres of water. Generally it’s up to the local Medical Officer of Health to judge when a beach should be posted. If bacterial counts exceed the provincial standard, the Health Department will arrange to have signage posted at the beach warning the public that the water is unsafe for swimming.

Beaches are usually reopened when E.coli levels have fallen to an acceptable level of 100 E.coli per 100 mL or less for two or three days.

What are the risks of going into the water?

A beach may be posted because the water has levels of bacteria that increase your risk of developing an infection. The most common are minor infections of the skin, eye, nose, throat and stomach disorders. Those most susceptible to these infections are young children, the elderly and those with depressed immune systems. It is recommended that you do not go into the water if you have an infection or open wound.

Based on health risk data, the chances are less than 1.5 per cent that you will contract a disease such as gastrointestinal illness when swimming in waters that contain as much as 200 EC per 100 mL of water.

In special circumstances a beach will be closed if there are indications of hazardous or infectious materials present in the water or in the event of a blue-green algae bloom.

Watch out for rainstorms

Beach Posting Sign
Health Department
Heavy Rainfall Warning Sign

Beach postings often occur after heavy rains. In urban areas, stormwater washes fecal material from dogs, cats, birds and other wildlife into storm sewers that flow directly into nearby rivers and lakes. In rural areas, stormwater washes fecal matter from livestock operations into nearby streams and lakes. Additionally, high wave action may stir up bacteria settled on the lake bottom.

Many older cities have combined sewers that convey both sanitary sewage and stormwater to a sewage treatment plant. During heavy rains, however, overflows from these combined sewers are discharged untreated directly into rivers and lakes.

In Durham Region all beaches have permanent yellow signs (June - September) posted in one or more locations reminding the public not to swim in beach water for at least 48 hours after heavy rainfall as bacteria levels can increase due to run-off.

How can you help to keep our beaches clean and safe for swimming?

Adapted and reprinted with permission of Ontario Ministry of the Environment.