Data shows E. coli presence in Whonnock Lake over past five years

photo of a lake
Whonnock Lake photographed by Carol Browne via Flickr

The Whonnock Lake swimming area is safe for swimming once again after E. coli reached normal levels, according to the announcement made by the City of Maple Ridge on Friday, July 14.

The closure of the beach area came after higher than normal level of E.Coli was found in the water sample on July 7.

The standard level of E. coli is 400/100 mL, however, the recent water sampling indicates the water currently contained 1,305 E. coli/100 mL.

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The cause of a higher level of E. coli is being attributed to algae blooms, geese and pet waste, according to a statement by the city.

However, this wasn’t the first time the swimming area was closed due to E.Coli.

Upon requesting data from Fraser Health Authority, The Ridge has learned that from January 2018 to July 2023 the Whonnock Lake water has been sampled 411 times.

Out of which, 293 samples have contained E.Coli, making it 71.29 per cent of the total water samples.

Sample results show that the highest level of E.Coli on the left side of the lake beach was 1,650/100 mL on 27 June 2023.

However, it is not uncommon for untreated, natural water to have E.Coli presence.

“There is always some level of risk when swimming in untreated recreational waters. Natural bodies of water are not treated to remove bacteria, not sampled daily and there is delay between the sampling time and the results. Other factors that can impact water quality include animal activity (e.g. geese), rainfall, hot temperatures and frequency of use,” said Dixon Tam, Senior Consultant of Public Affairs for Fraser Health.

Other reasons for E.Coli contamination include stormwater runoff into recreational water sites, recreational and sewer overflows, leaking septic tanks and discharge from boats, he added.

The water was also closed for swimming on July 18, 2019, when the E.Coli level was 1,450/100 mL.

The swimming area was closed in early July 2021 as well as on 18 July, 2019 when E.Coli level was 1,450/100 mL, according to information available online.


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