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A Perth town councillor is speaking out against recent claims the Tay River may be unsafe for swimming.
Jim Graff was among the councillors who heard a March 8 presentation from Peggy Land, of the Canadian Federation of University Women. Land asked councillors to erect signs along the river, warning swimmers about the concentration of E. coli bacteria that she said “often exceeds safe swimming levels.”
But Graff says the water is safe, and the data presented to council proves it.
“If there was a chance there were real, serious health concerns, I’d be the first to be pounding up signs saying please protect your kids, don’t let them in the water,” Graff said in an interview.
“But when you considered the geometric means, they’re under 100.”
The provincial standard for safe swimming water is a maximum concentration of 100 E. coli bacteria per 100 ml of water. In her presentation, Land said testing done by the Rideau Valley Conservation Authority showed “that last year, on average, more than two out of three test results” exceeded this limit, with some results reaching “all-time high levels” of more than 600.
But Land is looking at the wrong numbers, according to Graff.
Citing a document that can be found on the website of Ontario’s health ministry, Graff said the geometric mean is the figure that’s supposed to be used to determine if water is safe for swimming.
That’s because it’s calculated with a formula that “tends to minimize the effect of very high or low values on the average,” the document states.
E. coli levels can be affected by factors such as water level, temperature or time of year, making very high readings possible on some occasions, Graff said.
In testing done at 17 sites between 2003 and 2010, RVCA data shows maximum readings as high as 1,000 bacteria per 100 ml, taken in the area where Grants Creek meets the Upper Scotch Line.
But, according to the health ministry document, it’s the geo-metric mean that best represents the results from the 50 to 60 samples taken at each site over the testing period.
By this standard, only two sites are over the limit, both of them on Grants Creek.
The three testing sites in downtown Perth – where the Tay River meets Rogers Road, Gore Street and Craig Street – were below the threshold, with geometric means of 78, 70 and 83 respectively.
Regardless of how the levels compare to the government’s safety standard, Land says there should still be signs warning of the bacteria’s presence.
“I think that no matter which mean you’re considering, you can see that the levels are rising, and that’s the main concern,” she said after being apprised of the health ministry document.
“There’s still a health concern.”
The RVCA’s only previous testing period was from 1998 to 2002, during which time they sampled the three spots in downtown Perth about 20 times each. Though there was a maximum reading of 200 at the Craig Street location, the three geometric means were between 38 and 64 bacteria per 100 ml.
The highest increase between testing periods was at Rogers Road, where the concentration more than doubled, jumping from 38 to 78.
Land is concerned at the lack of data – so far, the RVCA’s only testing periods were 1998-02 and 2003-10 – but maintains there is a trend of increasing E. coli concentrations.
She said the local health unit may have had data from previous years, but stopped testing Stewart Park’s outdoor pool on the river in 1995, when it ceased to qualify as a recreational swimming area.
After Land’s March 8 presentation, Perth committee of the whole recommended meeting with the local health unit to further discuss the issue of warning signs.
Land said she and the CFUW will be continuing the push for safer swimming conditions in the river with a discussion forum on April 18. The event is to include a panel discussion with representatives from the health unit, RVCA, the Stewart Park Festival, Eco-Perth, Friends of the Tay Watershed and, she hopes, town council.
Though there are currently signs prohibiting swimming in certain areas – a liability measure since there are no lifeguards on duty, according to Graff – Land said there should be signs explicitly stating the health risk, even if there isn’t one by government standards.
“If people knew there was E. coli in the water they could at least make an informed decision whether they wanted their kids exposed to it or not,” she said.
© Copyright Metroland 2011
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