Huron County Health Unit, Beach Testing 2007

E.coli bacteria per 100 mL of water

In accordance with Province of Ontario standards, samples are taken at five different spots at a beach, and the geometric mean of those five samples is computed. The Province considers that a geometric mean of 100 or less for the day's five samples is acceptable.

Note: The geometic mean (the nth root of the product of n values) minimizes the effect of large values that are present in the data. One of the international Blue Flag beach criteria is that no more than 20% of the samples may be above 100.

Summary statistics

Note: Camp Kintail and Bogies Beach are not public beaches. HCHU has historically sampled Bogies Beach so that it can compare its data to the samples taken by the Provincial Park.


Compared to recent years, the summer of 2007 experienced much less rainfall. Therefore, the run-off from farmland was less, and thus the lower statistics.

days/samples 24/120 24/120 10/50 23/115 14/70 14/70
minimum, all samples 10 10 10 10 10 10
geo.mean of daily geo.means 19 37 47 53 17 15
geo.mean of daily maximums 25 73 66 88 25 20
average, all samples 80 135 135 102 34 39
maximum, all samples 2000 1100 590 470 270 440
Blue Flag % of samples >100 10% 22% 32% 33% 11% 7%

ACLA gratefully acknowledges the cooperation of HCHU in providing its daily data so that we could compute these summary statistics. Compiled by Roger Watt. Last updated 2008-05-22.