Swimmin' Stats

I am neither a meteorologist nor a mathematician, but I know a weather-related statistical problem when I see one.

Here’s what it is. So far, this week, Halifax’s harbour beaches have been closed every single day. That’s despite the renewed assurances from the mayor and Halifax Water that, thanks to the sewage treatment plant being back online, everything is A-Ok for swimming at Black Rock Beach and Dingle Park again.

This week’s closures have been due to this: any time there is a “heavy rain event” (and I take that term from a news release issued by the Mayor’s office in conjunction with Halifax Water) the wastewater discharged from the “combined sewer overflow chambers” will not receive full treatment, and will be discharged, after screening, directly into the harbour.

“Following the heavy rain events, swimmers should not swim in the harbour for three days,” says the Halifax Regional Municipality’s announcement.

Now, I’ve lived in Halifax for many, many years, and I happen to know that it tends to rain here fairly often during the summer months. Therefore, I have theorized that, if each time there is a heavy rainfall it means that the beaches will be closed for the next three days, the beaches are going to be closed...uh, a lot.

I am a Virgo, though, so not to go on gut instinct alone, I have collected some facts and figures to back up my hypothesis.

I called James Campbell at Halifax Water to ask what the municipality’s definition of “heavy rainfall” is, but he told me it was a difficult thing to put numbers on. “It all depends on the duration and the volume,” he said, indicating that short bursts of rainfall were more likely to overwhelm the system than an all-day rain.

Then I went to the Environment Canada website and started looking back at the climate data for the summer months in Halifax. Since we don’t really know what the tipping point for our sewage system is, I’ve looked at days with “greater than 5mm” of rain on a single day. Between 1971 and 2000, the number of days with that amount of rainfall breaks down as follows:

In the month of June, there have historically been 5.8 days with rainfall greater than or equal to 5 mm. In July, there are usually 4.5 days, and in August, we typically have 4.7 days with that much rain.

That means that, on average, 15 days out of 92 (in June, July and August) have a pretty good dump of rain. And that means that on 45 of those 92 days, the beaches (had they been subject to today’s conditions) might have been closed, depending on how intense the rainfall was. That’s not to mention the 15 days on which it actually rained, so there would most likely have been no one swimming, anyway.

My conclusion, then, is that, despite all the talk about the harbour being so swimmable, the likelihood is that even with the sewage treatment plant online, the water could still be un-swimmable for fully two-thirds of the summer.

So, I guess it might be best not to plan any beach parties at Black Rock or the Dingle this summer (or really, any summer), because the stats simply do not appear to be measuring up in your favour.

The Dirtiest Dirt

I’ll tell you a little-known fact about myself: when I was a toddler, I used to eat dirt.

You know how most children like to make mud pies?

Well, I guess I took that concept to the next level.

On a fairly regular basis, I would sit at the end of our driveway, or wherever my mother had plunked me down, and just chow down – or so I’m told. No harm every came to me because of my filthy habit, although my mother was concerned enough to have me examined by a doctor, who more or less shrugged it off, speculating that perhaps I was “missing something” in my diet.

Apparently, there’s a medical term for this particular propensity, but back then I think the word most commonly applied to my behaviour was simply, “weird.”

I tell you all this disturbing and deeply personal information to make the point that, even today, in my mind there’s “dirt” and then there’s “dirt.” And a nice, sandy beach has usually represented, for me, the good kind of dirt. You know – relatively harmless and probably delicious. If, uh, I still did that sort of thing.

But the Halifax Regional Municipality’s harbour beaches are obviously a different story, and that’s what I really wanted to talk about – because throughout the summer, I’ve seen a number of people beachcombing in the sand at Black Rock Beach in Point Pleasant Park.

I’m going to assume that these people are tourists, and therefore ignorant of the sorry state of our fetid harbour. Maybe their sense of smell has somehow become disabled, and they’re just not able to pick up on the signals that this may not be the ideal beach for picking up a periwinkle to bring back for the grandchildren.

When I see these folks walking, sometimes barefoot, on the soiled sand, and leaning over to pick up something with – argh! – their bare hands, I’m always tempted to scream “No!!” and run dramatically over to them, knocking whatever bacteria-laden object they’ve just discovered from their now-contaminated hands.

I don’t, of course. But recent research suggests that maybe I should. A study published last month by the United States Geological Survey showed that concentrations of E. coli bacteria are often much higher in beach sand than in the nearby water. It also showed that if 1,000 people played with beach sand for just one minute and then ingested what was on their fingertips, 11 would develop gastrointestinal illness.

And that’s just on a normal beach. Surely any shoreline that touches the waters of Halifax Harbour is considerably worse. The problem is, there’s no signage warning folks not to pick up objects or let their kids play in the sand at Black Rock Beach. The only indication that there’s any issue at all is a single small sign suggesting that the water “may” have bacterial contamination.

That hardly seems fair to unsuspecting visitors. A warning regarding the risk of contact with that sand might go a long way toward preventing a few days in the sick bay for the many cruise-ship passengers who think they’re just enjoying an innocent stroll on the beach.

I know my dirt, after all, and Halifax beach sand is some really dirty dirt.